Abstract

Here, the quenching process of Rhodamine B fluorophores coupled with Titanium dioxide (TiO2) nanoparticles (NPs) and Graphene oxide (GO) nano structures is empirically investigated during the laser induced fluorescence (LIF) events in various detection angles. According to Stern-Volmer formalism, the slope of Stern-Volmer graph is strongly dependent on the angular orientation of the detector, mainly because of the alteration in active volume. The corresponding spectral shift lucidly changes due to the anisotropy of the re-absorption events while the single and multiple scattering simultaneously take place, particularly at dense suspensions. The fluorescence Stokes shift of RdB molecules, as well as the effect of non-homogeneous population of the exited/unexcited molecules are taken into account as dominant factors during the measurements. However, the fluorescence trapping becomes more effective in dense suspension and larger detection angles.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

1. Introduction

Fluorescence quenching of fluorophores at the attendance of nanoparticles and nano structures is an attractive topic in biotechnology and biophotonics which offers an authentic method to determine the optical properties of random media. This is also beneficial in the field of tumor diagnosis, biosensors and cancer therapy [13]. In this way, 2D carbon nanostructures such as GO, have attracted the substantial regards due to their surface functionality and tendency to form chemical bonds with biological species and active molecules [46]. Among the various organic and inorganic materials, NPs and GO exhibit some favorable properties in dye solutions [7]. Recently, GO-based fluorescence quenching has shown to be a desirable sensing mechanism for quantitative DNA detection [8]. The fluorescence quenching of dye molecules is demonstrated in the vicinity of the gold nanoparticles [9]. Furthermore, the fluorescence quenching of Rhodamine 6G (Rd6G) by graphene oxide (GO) was investigated [10]. However, those reports do not deal with the angle of detection and the correlation to the corresponding spectral properties of the hybrid media of interest. The re-absorption effects on the fluorescence signal reduction was reviewed in order to determine the intensity of scattered fluorescent photons and the quantum yield of fluorophores as well [11,12].

On the other hand, it was shown that some chemo-drugs, such as doxorubicin, paclitaxel and bleomycin, act as fluorophores too. The chemo-drugs and some biocompatible dyes have been used extensively to imprint the tissues for diagnostic purposes in imaging and therapeutic applications. The LIF properties of several chemo-drugs are studied accordingly [1316]. The red/blue spectral shifts of LIF emissions are obtained in a diversity of dye doped scattering media [17]. The spectral analysis of the fluorescence emission from the laser pumped colloidal suspension of nanoparticles (NPs) in dye solutions has been widely investigated [1,18]. A notable red shift of the fluorescence emission has been reported by additive TiO2 NPs in Rhodamine 6G (Rd6G) ethanolic solutions [19]. The effect of carbon nanostructures such as graphene (G), graphene oxide (GO) and nano diamond (ND) on the spectral properties of Rd6G emission due to LIF spectroscopy has been examined [20]. Furthermore, GO/ND Nano quenchers in Doxorubicin (DOX) solution attests linearity of the fluorescence ratio versus the quencher density according to Stern- Volmer formalism [21]. The angular distribution of laser induced fluorescence emission of active fluorophores in scattering media was reported too [22]. The quenching coefficient K was measured according to the linear Stern-Volmer formalism in a methylene blue (MB) fluorophores loaded on TiO2 nanoparticles and it was shown that the quenching effect in the (TiO2+MB) suspension is much stronger than that of other metal oxide nanoparticles [23]. Moreover, the Stern-Volmer slope was obtained in (GO + MB) suspension indicating a strong quenching due to the hydrogen bonding and π-π staking [24].

Here, the laser induced fluorescence emissions of the RdB molecules in typical hybrid media of interest, e.g. (RdB + TiO2) and (RdB + GO) are measured in different angular orientation θ to attest the angular dependence of Stern-Volmer slope. In fact, θ is defined as the detection sight relative to the laser direction. In this work, we have shown that the Stern-Vomer slope varies as a function of sight angle. Despite the linear fluorescence ratio is obtained at small angles for RdB, however a notable nonlinearity takes place at large angles. This effect arises from the nature of the small Stokes shift of RdB molecules as well as strong re-absorption events at different angles regarding the change of laser excitation volume and fluorescence trapping. In the case of TiO2 nanoparticles dispersed in the RdB solution, we have shown here that the Stern-Volmer slope non-linearly depends on the detection angle; however, a linear relationship of the red shift takes place against the detection angle θ. On the other hand, the Stern-Volmer slope linearly depends on the detection angle θ for (RdB + GO) colloidal suspensions following a lucid red shift that in turn linearly varies versus θ. This undergoes much larger values for GO than TiO2 in comparison.

2. Fluorescence quenching

The fluorescence quenching process is classified into static and dynamic regimes. In the case of static quenching, a non-fluorescent complex is formed including a fluorophore and a quencher. Static quenching follows the well-known Stern-Volmer equation, given by:

$$\frac{{{I_ \circ }}}{I} = 1 + {K_S}[Q ],$$
where Io and I ascertain the fluorescence intensity in the absence and presence of quencher, [Q] is the quencher concentration. One believes that Io/I ratio versus [Q] obeys a linear behavior having a slope as a characteristic constant KS for static quenching.

The dynamic quenching deals with the collisional events between the fluorophores and quenchers. The collision of quencher with an excited unbound fluorophore leads to the dissipation of radiative energy. The dynamic quenching characterizing with KD features by

$$\frac{{{I_ \circ }}}{I} = 1 + {k_q}{\tau _ \circ }[Q ]= 1 + {K_D}[Q ],$$
where, kq and τ0 are the bimolecular quenching constant and the lifetime of the fluorophores in the absence of quencher respectively. Here, KS is replaced by KD according to the linear dependence of Io/I ratio with [Q] [25]. The Stern-Volmer equation does not express the effects of detection angle such that the dynamic quenching coefficient resembles to be independent of the angle of detection that is not always true as discussed later in this work where K(θ) is not invariant.

In the well-known fluorescence trapping effect, the photons are emitted from excited molecules would be trapped by the unexcited molecules due to re-absorption effects. Furthermore, fluorescence trapping is taken into account as a significant effect because of the large overlap of the fluorescence and absorption spectra [2628]. Moreover, a theoretical method has been developed regarding LIF signal attenuation due to both absorption of the laser and trapping of the fluorescence [29].

Here, it was shown that Stern-Volmer slope does not necessarily address the quenching coefficient for complex hybrid media, including nano quenchers and fluorophores, mainly due to heterogeneity of excited and unexcited molecules in the active volume. In other words, the angular dependence of K(θ) i.e., Stern-Volmer slopes in hybrid media, undergoing various active volumes, resemble not to be a measure of quenching coefficient in this case.

3. Materials and methods

Steady state fluorescence measurement of the colloidal suspension of TiO2 nanoparticles (mixed anatase and rutile crystal structure, with an average diameter of 21 nm, Purity 99.5%) in ethanolic solutions of Rhodamine B (C28H31N2O3Cl, ACROS ORGANICS, 99% Pure, MW=479.01 gr/mol) are prepared. The second harmonic generation (SHG) of CW-Nd:YAG laser 150 mW at 532 nm is utilized to excite Rhodamine molecules in a thick cylindrical glass cell with 1.3cm diameter and 4cm height. The glass cell with 1.3cm diameter and 4cm height was chosen regarding the laser beam diameter (2mm). Note that the diameter of laser beam should be adequately smaller than cuvette dimension (2 mm < 13 mm). Emission spectra are measured in different detection angles of 30°, 45°, 65° and 90°. The spectrophotometer (Avantes Ava Spect, wavelength resolution 0.4 nm) is employed to detect the fluorescence emission. The GO nanostructure is supplied from Sigma-Aldrich Co. with 5-100 µm lateral size and the thickness of 0.7-1.4 nm. All the suspensions are homogenized using ultrasonic bath in order to assure that nanoparticles would homogeneously diffuse through the suspension. Figure 1 illustrates the schematic arrangement of the angular measurement setup.

 

Fig. 1. Schematic of LIF setup for angular measurement of the fluorescence spectra in order to measure angular dependence of the Stern-Volmer slopes K(θ). The laser direction and the angle of detection are shown above.

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4. Results and discussion

4.1 A) Rhodamine B

One of the distinct characteristics of each fluorophore is the spectral separation between the excitation and emission spectra, known as the Stokes shift as shown in Fig. 2. The Stokes shift arises from the shift of the potential energy surfaces of the ground and excited states in equilibrium condition due to the harmonic electron-photon interactions in the course of the electron transitions. The strength of electron-photon coupling is determined by Huang-Rhys factor S parameter to be proportional to the Stokes shift.

 

Fig. 2. Normalized absorption and emission spectra for RdB solution. Inset depicts the maximum fluorescence intensity in terms of RdB concentration at various detection angles.

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At first, the ethanolic solution of RdB fluorophores was examined without nanoparticles. Inset of Fig. 2 Depicts the maximum fluorescence intensity in terms of RdB concentration at various detection angles. In the absence of nanoscatterer, Fluorescence signal ratio Io/I for a given dye concentration is defined as the highest intensity dividend by the intensity of that concentration. Furthermore, Fig. 3(a) and (b), depicts Io/I ratio versus RdB concentration at the small 30°, 45° and the large 65°, 90°detection angles respectively to attest the linearity intensity ratio versus fluorophore concentration according to the self-quenching. The latter usually takes place at large fluorophore concentration mainly due to RET (Resonance Energy Transfer) leading to the reduction of the emission intensity. This arises from the de-activation of the excited fluorophores regarding the other non-exited dye molecules in the active volume [17].

 

Fig. 3. (a) and (b) Fluorescence signal ratio Io/I as a function of RdB concentration [Q] at the smaller and the larger angles of detection respectively. (c) Spectral shift in terms of RdB concentration due to the re-absorption and self-quenching events at various angles of detection. Note that the high abundance of non-excited molecules give rise to higher re-absorption rates leading to larger red shift.

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Figure 3(a) depicts the fluorescence signal ratio versus RdB concentration at small angles that lucidly attests the linearity of signal ratio versus fluorophore concentration. Though the fluorescence intensity usually increases in terms of RdB concentration, however, a couple of mechanisms may attenuate the fluorescence signal. The effect becomes dominant at the higher concentration where the mean molecular distance (r) decreases, leading to a larger rate of dipole-dipole energy transfer according to the Forster equation, given by:

$${k_T}(r) = \frac{1}{{{\tau _D}}}{\left( {\frac{{{R_ \circ }}}{r}} \right)^6}$$

Where kT is the fluorophore dipole-dipole energy transfer rate, r is the mean distance between the donor (D) and acceptor (A), τD is the lifetime of the donor in the absence of energy transfer, and Ro is the Forster distance [30]. When the dye concentration is increased, the distance between molecules reduces, which promotes resonance energy transfer (RET) between molecules leading to decrease the fluorescence intensity. This phenomenon notably enhances where the excited molecular population is large and the fluorescence signal decreases due to the quenching. The apparent ­population of unexcited molecules is relatively larger at 45° sight of detection against 30° mainly due to inhomogeneous excitation from Gaussian profile of laser beam.

In addition, the reduction of the fluorescence signal arises from the formation of dimers and polymers in dense concentrations. Dimerization mainly takes place at dense dye solutions and in turn alter the corresponding absorption/emission spectra leading to the sensible spectral shift. However, it is worthy to note that the molar fraction of dimer to monomer in ethanolic solutions of Rhodamine is usually small for concentrations up to 100 mM indicating a negligible effect [31].

Figure 3(b) illustrates the fluorescence signal ratio versus RdB concentration at large angles that lucidly does follow nonlinearity (saturation) at large populations. In fact, the appreciable overlap of the absorption/emission spectra is taken into account as the significant factor of the re-absorption of emitted photons by the adjacent molecules. According to Beer-Lambert law, the signal reduces along a certain distance l experiencing the successive scattering events, as below:

$$I(\lambda ,l) = {I_0}(\lambda )\exp \left( { - \int\limits_0^l {{\sigma_{reabs}}(\lambda )N_{dye}^G({l^{\prime}})d{l^{\prime}}} } \right)$$

Where Io(λ), σreabs(λ) and $N_{dye}^G({l^{\prime}})$ denote to be the initial fluorescence intensity, the re-absorption cross section of dye molecules at wavelength λ and density of the non-excited (ground state) fluorophores respectively. The value of σreabs(λ) is determined by Huang–Rhys factor S of dye molecule which is proportional to the Stokes shift [22]. Note that in the absence of nanoparticles (as scatterers), l is determined by the medium thickness. At the larger angles, the intensity reduces because of the congestion of the unexcited RdB molecules then the light travels a longer optical path length (OPL). Those certainly demonstrate that the re-absorption effect is further enhanced at larger angles because of the abundance of non-excited molecules. Hence, both excessive unexcited molecules at the sight of detection as well as higher re-absorption rate give rise to the saturation. Furthermore, photon trapping may take place at dense suspensions.

Figure 3(c) demonstrates the emission wavelength versus RdB concentration at the detection angles of interest. In all directions, the dense dye suspension linearly lead to the larger red shift of the fluorescence emission as expected. Notice that the rate of this spectral shift enhances at larger angles. This arises from the fact that at larger lines of sight relative to the laser direction, the number of excited molecules decreases and consequently the re-absorption events by non-excited molecules notably increase, that is why the elevation of re-absorption rate gives rise to the larger red shift.

Angular anisotropy obviously appears in both the intensity ratio plots and the emissive wavelength. In general, this is linear for a couple of typical angles 30° and 45° but a significant changeover to the saturation takes place at larger angles 65° and 90°. According to Fig. 3(c), the greater red shift occurs at large angles (typically 30 and 20 nm for 90° and 65° respectively) due to the nonlinear re-absorption. It is supposed the saturation of re-absorption due to the small overlapping area at high concentrations gives rise to the decrease of the re-absorption events. This significantly takes place outside of the excitation population area mainly at larger detection angles. The saturation is beforehand occurred in 90° related to 65° as depicted in Fig. 3(b).

For convenience, Fig. 4 depicts the schematic of RdB suspension and different active volumes in various angles of detection. This lucidly demonstrates when the detection angle varies from 30° to 90°, then the excited active volume becomes smaller and the observing unexcited volume resembles to be enlarged, which emphasize the change of active apparent volume along detection sight. Here, two parameters are effective namely laser beam divergence and numerical aperture of optical fiber denote to be 0.3 mrad and 0.22 respectively.

 

Fig. 4. Schematic of different active apparent volumes at various detection angles (a) θ=30°, (b) θ=45°, (c) θ=65° and (d) θ=90°. Note that the volume of excited and unexcited regions notably change with detection angles.

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4.2 B) RdB+ TiO2 NPs

Various densities of TiO2 nanoparticles as scatterer guests are added to certain dye solution host CRdB=40 µM in order to investigate the effect of TiO2 nanoparticles on the spectral shift of LIF spectra and the slope in Stern-Volmer lines. This dye concentration (40 µM) lies in the linear part of the self-quenching area according to Fig. 3(b) as to the self-quenching effect is negligible. In fact, the quenching events lead to the formation of chemical complexes where the spectral shift and subsequent reduction of the fluorescence signal takes place.

Furthermore, it is essential to consider the quenching events due to chemical interaction between fluorophores and nanoscatterers. Previously, we have shown that in the case of Rd6G, the chemical interaction of fluorophores with very low density of TiO2 NPs are identified via the UV-Vis spectra. Slight blue shift reveals the presence of the (TiO2 + Rd6G) complexes [17] that is further enhanced at higher concentrations according to the Eq. (3). Here, the RdB molecule is examined as the fluorophore of interest.

Figure 5(a) illustrates fluorescence signal ratio Io/I versus TiO2 densities (Stern-Volmer plot) for several observation angles. TiO2 nanoparticles considerably deactivate the excited RdB molecules via the dynamic quenching process. The reduction of the emission intensity is further enhanced by the re-absorption events especially at larger angles. Far from the laser direction, due to the presence of plentiful non-excited molecules, and the occurrence of the re-absorption events, the emission intensity is reduced in the course of further TiO2 additives. Therefore, the Stern-Volmer linear plot shows a greater slope at larger θ. The further reduction of the intensity signal happens at larger angles of detection due to the both dynamic quenching (by TiO2 molecules) and the re-absorption events (due to non-excited fluorophores) according to Fig. 8.

 

Fig. 5. (a) Fluorescence signal ratio Io/I versus TiO2 densities for several observation angles, Stern-Volmer plot (b) Spectral shift of (RdB + TiO2) in terms of various observation angles at CRdB = 40 µM in ethanolic solution; TiO2 NP additives ranging 200-15000 µg/ml (c) Spectral shift in terms of detection angle at different TiO2 densities (typically 1000, 5000 and 10000 µg/ml)

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Besides, for a system of dimension L containing nanoscatterers that satisfy condition of Rayleigh scattering, the excessive of nanoscatterers gives rise to a changeover in the photon propagation. The photon trajectory enlarges due to the excessive scattering events. This follows the diffusion theory criteria that states L >> ls >> λ, where λ and ls ascertain the photon wavelength and mean scattering length. The excessive nanoscatteres dispersed in the medium causes more multiple scattering events. This enhances the re-absorption rate leading to much stronger red shift [20].

Figure 5(b) depicts the spectral shift in terms of TiO2 density at different angles of detection. The fluorescence emission wavelength reaches a plateau at relatively large amounts of TiO2 nanoparticles due to the gradual reduction of the overlapping area of the absorption and the emission spectra after sufficient re-absorption events. The saturation of the spectral red shift takes place for less populated TiO2 NPs at small detection angles. In fact, at detection angles close to the laser beam direction (θ=30°), the active volume is occupied by the plenty of excited fluorophores that cannot reabsorb the photons. Therefore, the re-absorption effect would not be dominant. As detection angle increases, the population of the excited molecules decreases. Then, the nanoparticle population enlarges within the excitation volume via scattering of the laser photons to further distances from the laser direction. This arises mainly from high refractive index of TiO2 nanoparticles. Consequently, the shrinkage of the overlapping area does not happen, then the re-absorption events would not be enhanced due to the larger TiO2 NPs density and the further elongation of the photonic random walk takes place.

In fact, quenching process at dilute NP densities reduces the signal intensity and increases the red shift due to the notable re-absorption events, whereas at dense NP populations, the quenching process is accompanied by dominant complex formations, which gives rise to induce an excessive blue shift to create a plateau region eventually. Red shift at dilute NP densities (re-absorption) will compensate with blue shift (complex formation) at dense NP population. The complex formation corresponds to less fluorophore concentration to induce a blue shift against the red shift to balance each other leading to a plateau. Figure 5(c) illustrates the spectral shift in terms of detection angle at different TiO2 densities that elucidates a linear red shift versus observation angle.

4.3 C) RdB+ GO (sp2) nanostructures

Graphene oxide is taken in to account as sp2 2D-carbon structure. GO, having oxygen-containing groups such as –COOH, -CO and –OH at the surface, benefits several advantageous properties such as hydrophilicity, high surface activity and significant fluorescence quenching [32]. Figure 6(a) depicts Io/I ratio in terms of GO density at a certain dye concentration (CRdB=40µM) for various angles of detection. It lucidly emphasizes that Stern-Volmer plot is linear having slight slopes for all angles. In comparison, the origin of static quenching for GO, as previously reported, is based on the formation of (Rd6G+ GO) complexes [20]. Furthermore, it has been shown that GO flakes can dynamically quench the RdB molecules as reported which is dominated over static quenching at low densities of GO. It gives rise to the reduction of fluorophore concentration associated with slight blue shift [8]. There is small differences between the Stern-Volmer slopes at different detection angles, which arises from the fact that GO nanostructures are strong quenchers, homogeneously dispersed in the medium. It resembles that the Stern-Volmer slope does not lucidly change against the detection angle. However, the slope of Stern-Vomer may not directly address quenching coefficient at various detection angles because the apparent active volume lucidly changes according Fig. 8.

 

Fig. 6. (a) Io/I ratio versus GO density at certain CRdB = 40 µM. Invariant Stern-Volmer slope of RdB + GO (0-18 µg/ml) takes place at different observation angles θ. (b) Spectral shift in terms of GO density for various detection angles. (c) Spectral shift in terms of detection angle at different GO densities (typically 2, 4, 8 and 10 µg/ml) at certain CRdB = 40 µM. Note that a notable red shift linearly appears at various observation angles and a plateau takes place at higher GO densities.

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On the other hand, Fig. 6(b) illustrates the emission wavelength versus GO densities ranging 0-18 µg/ml for various detection angles. Just after an initial red shift at low GO densities, then a plateau appears where no spectral shift takes place at larger GO densities. It is mainly due to the competition of red/blue shift mechanism leading to a plateau. Notice that the maximum value of the red shift at largest angle (90°) in Fig. 5(b) (∼ 30 nm) is notably larger than that of Fig. 6(b) (∼ 8 nm) to reveal the homogeneity of the excited population in (RdB + GO) suspension against that of (RdB + TiO2) colloidal suspension. Moreover, GO nanosheets limit the random walk to reduce red shift whereas TiO2 NPs allow the elongation of optical path that gives rise to more re-absorption events and subsequently the larger red shift.

The result obtained for GO is similar to that was reported for the TiO2 NP additives. However, here the amount of GO nanostructures is considerably smaller than that of TiO2 NPs and the plateau in the spectral shift occurs at relatively very small densities of GO. The GO nano sheets effectively deactivate the excited RdB molecules via dynamic quenching process and photon trapping leading to the reduction of the fluorescence intensity such that relatively smaller re-absorption events take place in comparison with TiO2 NPs. This strongly becomes dominant by increasing the GO density. According to Fig. 5(b) and Fig. 6(b), the competition of the re-absorption/dynamic quenching (red shift) and aggregation/static quenching (blue shift) gives rise to a plateau at larger densities of nano quenchers. The plateau certainly appears when the competition mechanisms balance at larger quencher densities. Note that in the case of GO, the strength of quenching is obviously strong to induce adequate blue shift to compensate the red shift leading to perfect plateau, whereas this plateau still undergoes slight red shift even at large values of TiO2. Figure 6(c) demonstrates the spectral shift in terms of detection angle at different densities of GO which indicates the linear red shift enhancement at large observation angles. The involved mechanisms are more or less similar to what elucidated for Fig. 5(c).

Despite the Stern-Volmer slopes (KTiO2 and KGO) may be proportional to quenching coefficient; however, we have been very cautious not to claim this fact mainly due to the complexity of the events. As a consequence, Fig. 7(a) and (b) depict the experimental values of slopes from linear Stern-Volmer at different observation angles for (RdB + TiO2) and (RdB + GO) suspensions respectively. The former shows non-linear dependence of KTiO2 on the detection angle, while the latter emphasizes that the Stern-Volmer slopes follow a linear function versus θ.

 

Fig. 7. (a) Slope KTiO2 in terms of detection angle θ for (RdB + TiO2) and (b) KGO versus observation angle in (RdB + GO) hybrid suspension respectively. Note that slope K increment for TiO2 is much larger than that of GO while K for GO is much larger than that of TiO2.

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Furthermore, the value of slopes for GO nanostructures, 1-2×10−3 (µg/ml)-1, is one order of magnitude larger than that of TiO2 NPs, 0.2-7×10−4 (µg/ml)-1, emphasizing GO is a strong quencher in suspension.

Eventually, we conclude that the large Stern-Volmer slope is obtainable in (RdB + GO) suspension due to the strong chemical bond coupling between fluorophore molecules and GO nano structures which gives rise to the relative reduction of the RdB molecular abundance consequently. On the other hand, the Stern-Volmer slopes for (RdB + TiO2) suspension are dependent on the observation angles mainly due to the non-homogenous distribution of the excited molecules in the bulk scattering media such that KTiO2 significantly increases in terms of detection angle. However, KTiO2 does not necessarily correlate quenching coefficient mainly due to the complexity of involved parameters. In both cases, the angular dependence of spectral shift attests the dominant re-absorption events as well as static quenching at moderate nanoparticle densities. Figure 8(a), (b) and (c) display the graphical representation to envisage the involved mechanisms. The apparent active and unexcited volumes obviously change in terms of the detection angle and due to the Gaussian profile of provoking laser, photon trapping and other events, the Stern-Volmer slope and corresponding spectral shifts, vary with NP density and observation angle. Moreover, Fig. 8(d), (e) and (f) illustrate the typical chemical structures (RdB: TiO2), (RdB: GO) complex compounds and the typical SEM (Scanning Electron Microscopy) image of (RdB: GO).

 

Fig. 8. (a), (b) and (c) schematics of RdB, (RdB + TiO2) and (RdB + GO) suspension respectively. (d) and (e) chemical interaction between (RdB + TiO2) and (RdB + GO) respectively [33,34] and (f) Typical SEM image of (RdB:GO). Note that π-π stacking and hydrogen bounding are dominant effects to form complex compounds.

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5. Conclusion

This is a continuation of our previous works on the investigation of Stern-Volmer formalism and the measurement of quenching coefficients of hybrid scattering media. The angular dependence of spectral shift and the fluorescence signal on (Rd6G + TiO2) has been vastly investigated and the quenching coefficient of a typical DOX chemodrug coupled with GO and ND were formerly reported [15,19].

Here, LIF spectroscopy is carried out for a laser pumped colloidal suspension of TiO2-NPs in RdB solution as well as (RdB + GO) suspension. We have shown that the Stern-Volmer slope of fluorophore molecules increases in terms of the observation angle. This demonstrates that the spectral shifts are angularly asymmetric due to the non-homogenous distribution of the excited/unexcited volume around the provoking laser in the bulk scattering media.

The effect arises from the small Stokes shift of RdB molecules as well as various re-absorption rates at different angles due to the nonhomogeneous excitation of the medium regarding the laser direction. Both re-absorption rate and the non-homogeneity of the excited population of fluorophores are modified by adding excessive TiO2-NPs. As a consequence, the re-absorption events are reduced in front detection due to the saturation of the excited molecules within the active volume, whereas at large detection angles, the elevated population of non-excited fluorophores are dominant leading to more red shift and the larger quenching coefficient.

Furthermore, we have demonstrated that the Stern-Volmer slope KTiO2 are strongly dependent of the detection angles ranging 0.2×10−4- 7×10−4 in the (RdB + TiO2) suspension that nonlinearly varies with the detection angle θ. Similarly, (RdB + GO) demonstrates a linear KGO versus θ, to be one order of magnitude higher ranging 1×10−3- 2×10−3 that attests GO is notably stronger nano quencher. In addition, both nano quenchers exhibit a lucid linear spectral shift versus sight of detection. The hybrid suspensions undergo a sharp linear red shift and then a plateau over large NP densities. The plateau arises from the competition of re-absorption events (leading to red shift) and the conjugate formation and aggregation (giving rise to blue shift) at dense nano quencher additives. In comparison, GO nano quencher is efficiently able to balance the competitive effects of re-absorption events over plateau region most likely due to its surface functionality to form the compounds of interest.

This suggests a novel method to identify the hybrid suspensions based on the spectral shift of fluorescence signals and the corresponding Stern-Volmer formalism. For instance, despite GO nanosheets restrict the random walk to reduce red shift (∼ 8 nm), however TiO2 NPs can elongate the optical path that gives rise to larger red shift (∼ 30 nm) to discriminate those suspensions via spectral shift measurements.

Eventually, the linear correlation of emission wavelength versus detection angle is highlighted. The angular dependence of the Stern-Volmer slope is reported here to emphasize that the nonlinearly varies with detection angle in (RdB + TiO2) suspension, whereas a linear correlation appears for (RdB + GO), mainly due to high affinity of bonding between fluorophore-nanoparticle coupling such as hydrogen bonding and π-π interaction and the formation of chemical complex at large additive densities. This attests angular dependent slope K(θ) is not invariant and strongly varies against detection angle because the apparent active excited and unexcited volumes lucidly change with the observation angle.

It is supposed that the Slope of linear Stern-Volmer may undergo deviation from quenching coefficient due to complexity of hybrid media including re-absorption, photon trapping, conjugate formation and non-uniform laser irradiation.

Acknowledgements

Hereby, we thank Dr. Fatemeh Pahang for her constructive pieces of advice to clarify the chemical concepts of the manuscript and Dr. Najmeh Hosseini Motlagh for her contribution and interpretation.

Disclosures

The authors declare that there are no conflicts of interest.

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12. M. Enoki and R. Katoh, “Estimation of quantum yields of weak fluorescence from eosin Y dimers formed in aqueous solutions,” Photochemical & Photobiological Sciences, 2018.

13. N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, and F. Atyabi, “Fluorescence properties of several chemotherapy drugs: doxorubicin, paclitaxel and bleomycin,” Biomed. Opt. Express 7(6), 2400–2406 (2016). [CrossRef]  

14. N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, F. Atyabi, S. Jelvani, and S. Abdolhosseini, “Laser induced fluorescence spectroscopy of chemo-drugs as biocompatible fluorophores: irinotecan, gemcitabine and navelbine,” Laser Phys. Lett. 13(7), 075604 (2016). [CrossRef]  

15. F. Ghasemi, P. Parvin, N. S. Hoseini Motlagh, A. Amjadi, and S. Abachi, “Laser induced bearkdown spectroscopy and acoustic response techniques to discriminate healthy and cancerous breast tissues,” Appl. Opt. 55(29), 8227–8235 (2016). [CrossRef]  

16. F. Ghasemi, P. Parvin, N. S. Hoseini Motlagh, and S. Abachi, “LIF spectroscopy of stained malignant breast tissues,” Biomed. Opt. Express 8(2), 512–523 (2017). [CrossRef]  

17. A. Bavali, P. Parvin, S. Z. Mortazavi, M. Mohammadian, and M. R. Mousavi Pour, “Red/blue spectral shifts of laser-induced fluorescence emission due to different nanoparticle suspensions in various dye solutions,” Appl. Opt. 53(24), 5398–5409 (2014). [CrossRef]  

18. H. Z. Wang, F. L. Zhao, Y. J. He, X. G. Zheng, X. G. Huang, and M. M. Wu, “Low-threshold lasing of a rhodamine dye solution embedded with nanoparticle fractal aggregates,” Opt. Lett. 23(10), 777–779 (1998). [CrossRef]  

19. S. A. Ahmed, Z.-W. Zang, K. M. Yoo, M. A. Ali, and R. R. Alfano, “Effect of multiple light scattering and self-absorption on the fluorescence and excitation spectra of dyes in random media,” Appl. Opt. 33(13), 2746–2750 (1994). [CrossRef]  

20. A. Bavali, P. Parvin, S. Z. Mortazavi, and S. S. Nourazar, “Laser induced fluorescence spectroscopy of various carbon nanostructures (GO, G and nanodiamond) in Rd6G solution,” Biomed. Opt. Express 6(5), 1679–1693 (2015). [CrossRef]  

21. N. S. Hoseini Motlagh, P. Parvin, M. Refahizadeh, and A. Bavali, “Fluorescence properties of doxorubicin coupled carbon nanocarriers,” Appl. Opt. 56(26), 7498–7503 (2017). [CrossRef]  

22. A. Bavali, P. Parvin, M. Tavassoli, and M. R. Mohebbifar, “Angular distribution of laser-induced fluorescence emission of active dyes in scattering media,” Appl. Opt. 57(7), B32–B38 (2018). [CrossRef]  

23. F. Pahang, P. Parvin, H. Ghafoori-Fard, A. Bavali, and A. Moafi, “Fluorescence properties of methylene blue molecules coupled with metal oxide nanoparticles,” OSA Continuum 3(3), 688–697 (2020). [CrossRef]  

24. F. Pahang, P. Parvin, and A. Bavali, “Fluorescence quenching effects of carbon nano-structures (Graphene Oxide and Nano Diamond) coupled with Methylene Blue,” Spectrochim. Acta, Part A 229, 117888 (2020). [CrossRef]  

25. . J.R. Lakowicz, “Quenching of fluorescence, in Principles of fluorescence spectroscopy”, 1983, Springer. p. 257–301.

26. D. Sumida and T. Fan, “Effect of radiation trapping on fluorescence lifetime and emission cross section measurements in solid-state laser media,” Opt. Lett. 19(17), 1343–1345 (1994). [CrossRef]  

27. K. Xu, “Silicon MOS optoelectronic micro-nano structure based on reverse-biased PN junction,” Phys. Status Solidi A 216(7), 1800868 (2019). [CrossRef]  

28. H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

29. P. Desgroux, L. Gasnot, J. Pauwels, and L. Sochet, “Correction of LIF temperature measurements for laser absorption and fluorescence trapping in a flame,” Appl. Phys. B 61(4), 401–407 (1995). [CrossRef]  

30. C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009). [CrossRef]  

31. A. Penzkofer and W. Leupacher, “Fluorescence behaviour of highly concentrated rhodamine 6G solutions,” J. Lumin. 37(2), 61–72 (1987). [CrossRef]  

32. H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014). [CrossRef]  

33. R. Zhang, M. Hummelgard, G. Lv, and H. Olin, “Real time monitoring of the drug release of rhodamine B on graphene oxide,” Carbon 49(4), 1126–1132 (2011). [CrossRef]  

34. C. Pérez León, L. Kador, B. Peng, and M. Thelakkat, “Characterization of the Adsorption of Ru-bpy Dyes on Mesoporous TiO2 Films with UV-Vis, Raman and FTIR Spectroscopies,” J. Phys. Chem. B 110(17), 8723–8730 (2006). [CrossRef]  

References

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  1. M. Siddique, L. Yang, Q. Z. Wang, and R. R. Alfano, “Mirrorless laser action from optically pumped dye-treated animal tissues,” Opt. Commun. 117(5-6), 475–479 (1995).
    [Crossref]
  2. K. Xu, Y. Chen, T. A. Okhai, and L. Snyman, “Micro optical sensors based on avalanching silicon light-emitting devices monolithically integrated on chips,” Opt. Mater. Express 9(10), 3985–3997 (2019).
    [Crossref]
  3. S. Diaz, S. Foaleng Mafang, M. Lopez-Amo, and L. Thevenaz, “A High-Performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
    [Crossref]
  4. J.-L. Li, B. Tang, B. Yuan, L. Sun, and X.-G. Wang, “A review of optical imaging and therapy using nanosized graphene and graphene oxide,” Biomaterials 34(37), 9519–9534 (2013).
    [Crossref]
  5. J. Liu, L. Cui, and D. Losic, “Graphene and graphene oxide as new nanocarriers for drug delivery applications,” Acta Biomater. 9(12), 9243–9257 (2013).
    [Crossref]
  6. T. K. Das and S. Prusty, “Recent advances in applications of graphene,” Int. J. Chem. Sci. Appl. 4, 39–55 (2013).
  7. M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
    [Crossref]
  8. S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
    [Crossref]
  9. E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
    [Crossref]
  10. K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
    [Crossref]
  11. A. V. Fonin, A. I. Sulatskaya, I. M. Kuznetsova, and K. K. Turoverov, “Fluorescence of dyes in solutions with high absorbance Inner filter effect correction,” PLoS One 9(7), e103878 (2014).
    [Crossref]
  12. M. Enoki and R. Katoh, “Estimation of quantum yields of weak fluorescence from eosin Y dimers formed in aqueous solutions,” Photochemical & Photobiological Sciences, 2018.
  13. N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, and F. Atyabi, “Fluorescence properties of several chemotherapy drugs: doxorubicin, paclitaxel and bleomycin,” Biomed. Opt. Express 7(6), 2400–2406 (2016).
    [Crossref]
  14. N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, F. Atyabi, S. Jelvani, and S. Abdolhosseini, “Laser induced fluorescence spectroscopy of chemo-drugs as biocompatible fluorophores: irinotecan, gemcitabine and navelbine,” Laser Phys. Lett. 13(7), 075604 (2016).
    [Crossref]
  15. F. Ghasemi, P. Parvin, N. S. Hoseini Motlagh, A. Amjadi, and S. Abachi, “Laser induced bearkdown spectroscopy and acoustic response techniques to discriminate healthy and cancerous breast tissues,” Appl. Opt. 55(29), 8227–8235 (2016).
    [Crossref]
  16. F. Ghasemi, P. Parvin, N. S. Hoseini Motlagh, and S. Abachi, “LIF spectroscopy of stained malignant breast tissues,” Biomed. Opt. Express 8(2), 512–523 (2017).
    [Crossref]
  17. A. Bavali, P. Parvin, S. Z. Mortazavi, M. Mohammadian, and M. R. Mousavi Pour, “Red/blue spectral shifts of laser-induced fluorescence emission due to different nanoparticle suspensions in various dye solutions,” Appl. Opt. 53(24), 5398–5409 (2014).
    [Crossref]
  18. H. Z. Wang, F. L. Zhao, Y. J. He, X. G. Zheng, X. G. Huang, and M. M. Wu, “Low-threshold lasing of a rhodamine dye solution embedded with nanoparticle fractal aggregates,” Opt. Lett. 23(10), 777–779 (1998).
    [Crossref]
  19. S. A. Ahmed, Z.-W. Zang, K. M. Yoo, M. A. Ali, and R. R. Alfano, “Effect of multiple light scattering and self-absorption on the fluorescence and excitation spectra of dyes in random media,” Appl. Opt. 33(13), 2746–2750 (1994).
    [Crossref]
  20. A. Bavali, P. Parvin, S. Z. Mortazavi, and S. S. Nourazar, “Laser induced fluorescence spectroscopy of various carbon nanostructures (GO, G and nanodiamond) in Rd6G solution,” Biomed. Opt. Express 6(5), 1679–1693 (2015).
    [Crossref]
  21. N. S. Hoseini Motlagh, P. Parvin, M. Refahizadeh, and A. Bavali, “Fluorescence properties of doxorubicin coupled carbon nanocarriers,” Appl. Opt. 56(26), 7498–7503 (2017).
    [Crossref]
  22. A. Bavali, P. Parvin, M. Tavassoli, and M. R. Mohebbifar, “Angular distribution of laser-induced fluorescence emission of active dyes in scattering media,” Appl. Opt. 57(7), B32–B38 (2018).
    [Crossref]
  23. F. Pahang, P. Parvin, H. Ghafoori-Fard, A. Bavali, and A. Moafi, “Fluorescence properties of methylene blue molecules coupled with metal oxide nanoparticles,” OSA Continuum 3(3), 688–697 (2020).
    [Crossref]
  24. F. Pahang, P. Parvin, and A. Bavali, “Fluorescence quenching effects of carbon nano-structures (Graphene Oxide and Nano Diamond) coupled with Methylene Blue,” Spectrochim. Acta, Part A 229, 117888 (2020).
    [Crossref]
  25. . J.R. Lakowicz, “Quenching of fluorescence, in Principles of fluorescence spectroscopy”, 1983, Springer. p. 257–301.
  26. D. Sumida and T. Fan, “Effect of radiation trapping on fluorescence lifetime and emission cross section measurements in solid-state laser media,” Opt. Lett. 19(17), 1343–1345 (1994).
    [Crossref]
  27. K. Xu, “Silicon MOS optoelectronic micro-nano structure based on reverse-biased PN junction,” Phys. Status Solidi A 216(7), 1800868 (2019).
    [Crossref]
  28. H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.
  29. P. Desgroux, L. Gasnot, J. Pauwels, and L. Sochet, “Correction of LIF temperature measurements for laser absorption and fluorescence trapping in a flame,” Appl. Phys. B 61(4), 401–407 (1995).
    [Crossref]
  30. C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009).
    [Crossref]
  31. A. Penzkofer and W. Leupacher, “Fluorescence behaviour of highly concentrated rhodamine 6G solutions,” J. Lumin. 37(2), 61–72 (1987).
    [Crossref]
  32. H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
    [Crossref]
  33. R. Zhang, M. Hummelgard, G. Lv, and H. Olin, “Real time monitoring of the drug release of rhodamine B on graphene oxide,” Carbon 49(4), 1126–1132 (2011).
    [Crossref]
  34. C. Pérez León, L. Kador, B. Peng, and M. Thelakkat, “Characterization of the Adsorption of Ru-bpy Dyes on Mesoporous TiO2 Films with UV-Vis, Raman and FTIR Spectroscopies,” J. Phys. Chem. B 110(17), 8723–8730 (2006).
    [Crossref]

2020 (2)

F. Pahang, P. Parvin, H. Ghafoori-Fard, A. Bavali, and A. Moafi, “Fluorescence properties of methylene blue molecules coupled with metal oxide nanoparticles,” OSA Continuum 3(3), 688–697 (2020).
[Crossref]

F. Pahang, P. Parvin, and A. Bavali, “Fluorescence quenching effects of carbon nano-structures (Graphene Oxide and Nano Diamond) coupled with Methylene Blue,” Spectrochim. Acta, Part A 229, 117888 (2020).
[Crossref]

2019 (2)

2018 (1)

2017 (2)

2016 (3)

2015 (1)

2014 (3)

A. V. Fonin, A. I. Sulatskaya, I. M. Kuznetsova, and K. K. Turoverov, “Fluorescence of dyes in solutions with high absorbance Inner filter effect correction,” PLoS One 9(7), e103878 (2014).
[Crossref]

A. Bavali, P. Parvin, S. Z. Mortazavi, M. Mohammadian, and M. R. Mousavi Pour, “Red/blue spectral shifts of laser-induced fluorescence emission due to different nanoparticle suspensions in various dye solutions,” Appl. Opt. 53(24), 5398–5409 (2014).
[Crossref]

H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
[Crossref]

2013 (4)

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

J.-L. Li, B. Tang, B. Yuan, L. Sun, and X.-G. Wang, “A review of optical imaging and therapy using nanosized graphene and graphene oxide,” Biomaterials 34(37), 9519–9534 (2013).
[Crossref]

J. Liu, L. Cui, and D. Losic, “Graphene and graphene oxide as new nanocarriers for drug delivery applications,” Acta Biomater. 9(12), 9243–9257 (2013).
[Crossref]

T. K. Das and S. Prusty, “Recent advances in applications of graphene,” Int. J. Chem. Sci. Appl. 4, 39–55 (2013).

2011 (1)

R. Zhang, M. Hummelgard, G. Lv, and H. Olin, “Real time monitoring of the drug release of rhodamine B on graphene oxide,” Carbon 49(4), 1126–1132 (2011).
[Crossref]

2010 (2)

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

2009 (1)

C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009).
[Crossref]

2008 (1)

S. Diaz, S. Foaleng Mafang, M. Lopez-Amo, and L. Thevenaz, “A High-Performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[Crossref]

2006 (1)

C. Pérez León, L. Kador, B. Peng, and M. Thelakkat, “Characterization of the Adsorption of Ru-bpy Dyes on Mesoporous TiO2 Films with UV-Vis, Raman and FTIR Spectroscopies,” J. Phys. Chem. B 110(17), 8723–8730 (2006).
[Crossref]

2002 (1)

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

1998 (1)

1995 (2)

M. Siddique, L. Yang, Q. Z. Wang, and R. R. Alfano, “Mirrorless laser action from optically pumped dye-treated animal tissues,” Opt. Commun. 117(5-6), 475–479 (1995).
[Crossref]

P. Desgroux, L. Gasnot, J. Pauwels, and L. Sochet, “Correction of LIF temperature measurements for laser absorption and fluorescence trapping in a flame,” Appl. Phys. B 61(4), 401–407 (1995).
[Crossref]

1994 (2)

1987 (1)

A. Penzkofer and W. Leupacher, “Fluorescence behaviour of highly concentrated rhodamine 6G solutions,” J. Lumin. 37(2), 61–72 (1987).
[Crossref]

Abachi, S.

Abdolhosseini, S.

N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, F. Atyabi, S. Jelvani, and S. Abdolhosseini, “Laser induced fluorescence spectroscopy of chemo-drugs as biocompatible fluorophores: irinotecan, gemcitabine and navelbine,” Laser Phys. Lett. 13(7), 075604 (2016).
[Crossref]

Ahmed, S. A.

Alfano, R. R.

M. Siddique, L. Yang, Q. Z. Wang, and R. R. Alfano, “Mirrorless laser action from optically pumped dye-treated animal tissues,” Opt. Commun. 117(5-6), 475–479 (1995).
[Crossref]

S. A. Ahmed, Z.-W. Zang, K. M. Yoo, M. A. Ali, and R. R. Alfano, “Effect of multiple light scattering and self-absorption on the fluorescence and excitation spectra of dyes in random media,” Appl. Opt. 33(13), 2746–2750 (1994).
[Crossref]

Ali, M. A.

Amjadi, A.

Atwater, H.

H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

Atyabi, F.

N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, F. Atyabi, S. Jelvani, and S. Abdolhosseini, “Laser induced fluorescence spectroscopy of chemo-drugs as biocompatible fluorophores: irinotecan, gemcitabine and navelbine,” Laser Phys. Lett. 13(7), 075604 (2016).
[Crossref]

N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, and F. Atyabi, “Fluorescence properties of several chemotherapy drugs: doxorubicin, paclitaxel and bleomycin,” Biomed. Opt. Express 7(6), 2400–2406 (2016).
[Crossref]

Bavali, A.

Bibette, J.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Chen, G. N.

C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009).
[Crossref]

Chen, X.

C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009).
[Crossref]

Chen, Y.

Choi, I.

H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
[Crossref]

Coll, J.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Cui, L.

J. Liu, L. Cui, and D. Losic, “Graphene and graphene oxide as new nanocarriers for drug delivery applications,” Acta Biomater. 9(12), 9243–9257 (2013).
[Crossref]

Das, T. K.

T. K. Das and S. Prusty, “Recent advances in applications of graphene,” Int. J. Chem. Sci. Appl. 4, 39–55 (2013).

Desgroux, P.

P. Desgroux, L. Gasnot, J. Pauwels, and L. Sochet, “Correction of LIF temperature measurements for laser absorption and fluorescence trapping in a flame,” Appl. Phys. B 61(4), 401–407 (1995).
[Crossref]

Diaz, S.

S. Diaz, S. Foaleng Mafang, M. Lopez-Amo, and L. Thevenaz, “A High-Performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[Crossref]

Dufort, S.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Dulkeith, E.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Enoki, M.

M. Enoki and R. Katoh, “Estimation of quantum yields of weak fluorescence from eosin Y dimers formed in aqueous solutions,” Photochemical & Photobiological Sciences, 2018.

Fan, C.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Fan, K. L.

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

Fan, T.

Fang, H.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Feldmann, J.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Foaleng Mafang, S.

S. Diaz, S. Foaleng Mafang, M. Lopez-Amo, and L. Thevenaz, “A High-Performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[Crossref]

Fonin, A. V.

A. V. Fonin, A. I. Sulatskaya, I. M. Kuznetsova, and K. K. Turoverov, “Fluorescence of dyes in solutions with high absorbance Inner filter effect correction,” PLoS One 9(7), e103878 (2014).
[Crossref]

Gasnot, L.

P. Desgroux, L. Gasnot, J. Pauwels, and L. Sochet, “Correction of LIF temperature measurements for laser absorption and fluorescence trapping in a flame,” Appl. Phys. B 61(4), 401–407 (1995).
[Crossref]

Ge, J.

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

Geng, Z.-G.

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

Ghafoori-Fard, H.

Ghasemi, F.

Gittins, D. I.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Goutayer, M.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Guo, Z.-K.

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

He, S.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

He, Y. J.

Heinrich, E.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Hoseini Motlagh, N. S.

Hu, J.-H.

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

Huang, X. G.

Huang, Y-W.

H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

Hummelgard, M.

R. Zhang, M. Hummelgard, G. Lv, and H. Olin, “Real time monitoring of the drug release of rhodamine B on graphene oxide,” Carbon 49(4), 1126–1132 (2011).
[Crossref]

Jelvani, S.

N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, F. Atyabi, S. Jelvani, and S. Abdolhosseini, “Laser induced fluorescence spectroscopy of chemo-drugs as biocompatible fluorophores: irinotecan, gemcitabine and navelbine,” Laser Phys. Lett. 13(7), 075604 (2016).
[Crossref]

Jiang, S.-L.

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

Josserand, V.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Kador, L.

C. Pérez León, L. Kador, B. Peng, and M. Thelakkat, “Characterization of the Adsorption of Ru-bpy Dyes on Mesoporous TiO2 Films with UV-Vis, Raman and FTIR Spectroscopies,” J. Phys. Chem. B 110(17), 8723–8730 (2006).
[Crossref]

Katoh, R.

M. Enoki and R. Katoh, “Estimation of quantum yields of weak fluorescence from eosin Y dimers formed in aqueous solutions,” Photochemical & Photobiological Sciences, 2018.

Klar, T.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Kodiyath, R.

H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
[Crossref]

Kulkarni, D. D.

H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
[Crossref]

Kuznetsova, I. M.

A. V. Fonin, A. I. Sulatskaya, I. M. Kuznetsova, and K. K. Turoverov, “Fluorescence of dyes in solutions with high absorbance Inner filter effect correction,” PLoS One 9(7), e103878 (2014).
[Crossref]

Lee, H.W.

H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

Leupacher, W.

A. Penzkofer and W. Leupacher, “Fluorescence behaviour of highly concentrated rhodamine 6G solutions,” J. Lumin. 37(2), 61–72 (1987).
[Crossref]

Levi, S. A.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Li, D.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Li, J.-L.

J.-L. Li, B. Tang, B. Yuan, L. Sun, and X.-G. Wang, “A review of optical imaging and therapy using nanosized graphene and graphene oxide,” Biomaterials 34(37), 9519–9534 (2013).
[Crossref]

Liu, J.

J. Liu, L. Cui, and D. Losic, “Graphene and graphene oxide as new nanocarriers for drug delivery applications,” Acta Biomater. 9(12), 9243–9257 (2013).
[Crossref]

Lopez-Amo, M.

S. Diaz, S. Foaleng Mafang, M. Lopez-Amo, and L. Thevenaz, “A High-Performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[Crossref]

Losic, D.

J. Liu, L. Cui, and D. Losic, “Graphene and graphene oxide as new nanocarriers for drug delivery applications,” Acta Biomater. 9(12), 9243–9257 (2013).
[Crossref]

Lu, C. H.

C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009).
[Crossref]

Lv, G.

R. Zhang, M. Hummelgard, G. Lv, and H. Olin, “Real time monitoring of the drug release of rhodamine B on graphene oxide,” Carbon 49(4), 1126–1132 (2011).
[Crossref]

Moafi, A.

Mohammadian, M.

Mohebbifar, M. R.

Möller, M.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Mortazavi, S. Z.

Morteani, A. C.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Mousavi Pour, M. R.

Niedereichholz, T.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Nourazar, S. S.

Okhai, T. A.

Olin, H.

R. Zhang, M. Hummelgard, G. Lv, and H. Olin, “Real time monitoring of the drug release of rhodamine B on graphene oxide,” Carbon 49(4), 1126–1132 (2011).
[Crossref]

Pahang, F.

F. Pahang, P. Parvin, H. Ghafoori-Fard, A. Bavali, and A. Moafi, “Fluorescence properties of methylene blue molecules coupled with metal oxide nanoparticles,” OSA Continuum 3(3), 688–697 (2020).
[Crossref]

F. Pahang, P. Parvin, and A. Bavali, “Fluorescence quenching effects of carbon nano-structures (Graphene Oxide and Nano Diamond) coupled with Methylene Blue,” Spectrochim. Acta, Part A 229, 117888 (2020).
[Crossref]

Papadakis, G.

H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

Parvin, P.

F. Pahang, P. Parvin, and A. Bavali, “Fluorescence quenching effects of carbon nano-structures (Graphene Oxide and Nano Diamond) coupled with Methylene Blue,” Spectrochim. Acta, Part A 229, 117888 (2020).
[Crossref]

F. Pahang, P. Parvin, H. Ghafoori-Fard, A. Bavali, and A. Moafi, “Fluorescence properties of methylene blue molecules coupled with metal oxide nanoparticles,” OSA Continuum 3(3), 688–697 (2020).
[Crossref]

A. Bavali, P. Parvin, M. Tavassoli, and M. R. Mohebbifar, “Angular distribution of laser-induced fluorescence emission of active dyes in scattering media,” Appl. Opt. 57(7), B32–B38 (2018).
[Crossref]

N. S. Hoseini Motlagh, P. Parvin, M. Refahizadeh, and A. Bavali, “Fluorescence properties of doxorubicin coupled carbon nanocarriers,” Appl. Opt. 56(26), 7498–7503 (2017).
[Crossref]

F. Ghasemi, P. Parvin, N. S. Hoseini Motlagh, and S. Abachi, “LIF spectroscopy of stained malignant breast tissues,” Biomed. Opt. Express 8(2), 512–523 (2017).
[Crossref]

F. Ghasemi, P. Parvin, N. S. Hoseini Motlagh, A. Amjadi, and S. Abachi, “Laser induced bearkdown spectroscopy and acoustic response techniques to discriminate healthy and cancerous breast tissues,” Appl. Opt. 55(29), 8227–8235 (2016).
[Crossref]

N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, and F. Atyabi, “Fluorescence properties of several chemotherapy drugs: doxorubicin, paclitaxel and bleomycin,” Biomed. Opt. Express 7(6), 2400–2406 (2016).
[Crossref]

N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, F. Atyabi, S. Jelvani, and S. Abdolhosseini, “Laser induced fluorescence spectroscopy of chemo-drugs as biocompatible fluorophores: irinotecan, gemcitabine and navelbine,” Laser Phys. Lett. 13(7), 075604 (2016).
[Crossref]

A. Bavali, P. Parvin, S. Z. Mortazavi, and S. S. Nourazar, “Laser induced fluorescence spectroscopy of various carbon nanostructures (GO, G and nanodiamond) in Rd6G solution,” Biomed. Opt. Express 6(5), 1679–1693 (2015).
[Crossref]

A. Bavali, P. Parvin, S. Z. Mortazavi, M. Mohammadian, and M. R. Mousavi Pour, “Red/blue spectral shifts of laser-induced fluorescence emission due to different nanoparticle suspensions in various dye solutions,” Appl. Opt. 53(24), 5398–5409 (2014).
[Crossref]

Pauwels, J.

P. Desgroux, L. Gasnot, J. Pauwels, and L. Sochet, “Correction of LIF temperature measurements for laser absorption and fluorescence trapping in a flame,” Appl. Phys. B 61(4), 401–407 (1995).
[Crossref]

Peng, B.

C. Pérez León, L. Kador, B. Peng, and M. Thelakkat, “Characterization of the Adsorption of Ru-bpy Dyes on Mesoporous TiO2 Films with UV-Vis, Raman and FTIR Spectroscopies,” J. Phys. Chem. B 110(17), 8723–8730 (2006).
[Crossref]

Penzkofer, A.

A. Penzkofer and W. Leupacher, “Fluorescence behaviour of highly concentrated rhodamine 6G solutions,” J. Lumin. 37(2), 61–72 (1987).
[Crossref]

Pérez León, C.

C. Pérez León, L. Kador, B. Peng, and M. Thelakkat, “Characterization of the Adsorption of Ru-bpy Dyes on Mesoporous TiO2 Films with UV-Vis, Raman and FTIR Spectroscopies,” J. Phys. Chem. B 110(17), 8723–8730 (2006).
[Crossref]

Prusty, S.

T. K. Das and S. Prusty, “Recent advances in applications of graphene,” Int. J. Chem. Sci. Appl. 4, 39–55 (2013).

Qi, W.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Refahizadeh, M.

Reinhoudt, D. N.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Ren, H.

H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
[Crossref]

Royère, A.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Seunghoon, H.

H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

Siddique, M.

M. Siddique, L. Yang, Q. Z. Wang, and R. R. Alfano, “Mirrorless laser action from optically pumped dye-treated animal tissues,” Opt. Commun. 117(5-6), 475–479 (1995).
[Crossref]

Snyman, L.

Sochet, L.

P. Desgroux, L. Gasnot, J. Pauwels, and L. Sochet, “Correction of LIF temperature measurements for laser absorption and fluorescence trapping in a flame,” Appl. Phys. B 61(4), 401–407 (1995).
[Crossref]

Sohkoyan, R.

H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

Song, B.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Song, S.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Sulatskaya, A. I.

A. V. Fonin, A. I. Sulatskaya, I. M. Kuznetsova, and K. K. Turoverov, “Fluorescence of dyes in solutions with high absorbance Inner filter effect correction,” PLoS One 9(7), e103878 (2014).
[Crossref]

Sumida, D.

Sun, L.

J.-L. Li, B. Tang, B. Yuan, L. Sun, and X.-G. Wang, “A review of optical imaging and therapy using nanosized graphene and graphene oxide,” Biomaterials 34(37), 9519–9534 (2013).
[Crossref]

Tang, B.

J.-L. Li, B. Tang, B. Yuan, L. Sun, and X.-G. Wang, “A review of optical imaging and therapy using nanosized graphene and graphene oxide,” Biomaterials 34(37), 9519–9534 (2013).
[Crossref]

Tavassoli, M.

Texier, I.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Thelakkat, M.

C. Pérez León, L. Kador, B. Peng, and M. Thelakkat, “Characterization of the Adsorption of Ru-bpy Dyes on Mesoporous TiO2 Films with UV-Vis, Raman and FTIR Spectroscopies,” J. Phys. Chem. B 110(17), 8723–8730 (2006).
[Crossref]

Thevenaz, L.

S. Diaz, S. Foaleng Mafang, M. Lopez-Amo, and L. Thevenaz, “A High-Performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[Crossref]

Thyagarajan, K.

H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

Tsukruk, V. V.

H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
[Crossref]

Turoverov, K. K.

A. V. Fonin, A. I. Sulatskaya, I. M. Kuznetsova, and K. K. Turoverov, “Fluorescence of dyes in solutions with high absorbance Inner filter effect correction,” PLoS One 9(7), e103878 (2014).
[Crossref]

Van Veggel, F.

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
[Crossref]

Vinet, F.

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

Wang, H. Z.

Wang, L.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Wang, Q. Z.

M. Siddique, L. Yang, Q. Z. Wang, and R. R. Alfano, “Mirrorless laser action from optically pumped dye-treated animal tissues,” Opt. Commun. 117(5-6), 475–479 (1995).
[Crossref]

Wang, X.-G.

J.-L. Li, B. Tang, B. Yuan, L. Sun, and X.-G. Wang, “A review of optical imaging and therapy using nanosized graphene and graphene oxide,” Biomaterials 34(37), 9519–9534 (2013).
[Crossref]

Wen, Y.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Wu, M. M.

Xu, K.

Xu, W.

H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
[Crossref]

Yang, H. H.

C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009).
[Crossref]

Yang, L.

M. Siddique, L. Yang, Q. Z. Wang, and R. R. Alfano, “Mirrorless laser action from optically pumped dye-treated animal tissues,” Opt. Commun. 117(5-6), 475–479 (1995).
[Crossref]

Yoo, K. M.

Yuan, B.

J.-L. Li, B. Tang, B. Yuan, L. Sun, and X.-G. Wang, “A review of optical imaging and therapy using nanosized graphene and graphene oxide,” Biomaterials 34(37), 9519–9534 (2013).
[Crossref]

Zang, Z.-W.

Zhang, Q.

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

Zhang, R.

R. Zhang, M. Hummelgard, G. Lv, and H. Olin, “Real time monitoring of the drug release of rhodamine B on graphene oxide,” Carbon 49(4), 1126–1132 (2011).
[Crossref]

Zhao, F. L.

Zheng, X. G.

Zhu, C.

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Zhu, C. L.

C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009).
[Crossref]

ACS Appl. Mater. Interfaces (1)

H. Ren, D. D. Kulkarni, R. Kodiyath, W. Xu, I. Choi, and V. V. Tsukruk, “Competitive adsorption of dopamine and rhodamine 6G on the surface of graphene oxide,” ACS Appl. Mater. Interfaces 6(4), 2459–2470 (2014).
[Crossref]

Acta Biomater. (1)

J. Liu, L. Cui, and D. Losic, “Graphene and graphene oxide as new nanocarriers for drug delivery applications,” Acta Biomater. 9(12), 9243–9257 (2013).
[Crossref]

Adv. Funct. Mater. (1)

S. He, B. Song, D. Li, C. Zhu, W. Qi, Y. Wen, L. Wang, S. Song, H. Fang, and C. Fan, “A graphene nanoprobe for rapid, sensitive, and multicolor fluorescent DNA analysis,” Adv. Funct. Mater. 20(3), 453–459 (2010).
[Crossref]

Angew. Chem. (1)

C. H. Lu, H. H. Yang, C. L. Zhu, X. Chen, and G. N. Chen, “A graphene platform for sensing biomolecules,” Angew. Chem. 121(26), 4879–4881 (2009).
[Crossref]

Appl. Opt. (5)

Appl. Phys. B (1)

P. Desgroux, L. Gasnot, J. Pauwels, and L. Sochet, “Correction of LIF temperature measurements for laser absorption and fluorescence trapping in a flame,” Appl. Phys. B 61(4), 401–407 (1995).
[Crossref]

Biomaterials (1)

J.-L. Li, B. Tang, B. Yuan, L. Sun, and X.-G. Wang, “A review of optical imaging and therapy using nanosized graphene and graphene oxide,” Biomaterials 34(37), 9519–9534 (2013).
[Crossref]

Biomed. Opt. Express (3)

Carbon (1)

R. Zhang, M. Hummelgard, G. Lv, and H. Olin, “Real time monitoring of the drug release of rhodamine B on graphene oxide,” Carbon 49(4), 1126–1132 (2011).
[Crossref]

Chin. J. Chem. Phys. (1)

K. L. Fan, Z.-K. Guo, Z.-G. Geng, J. Ge, S.-L. Jiang, J.-H. Hu, and Q. Zhang, “How Graphene Oxide Quenches Fluorescence of Rhodamine 6G,” Chin. J. Chem. Phys. 26(3), 252–258 (2013).
[Crossref]

Eur. J. Pharm. Biopharm. (1)

M. Goutayer, S. Dufort, V. Josserand, A. Royère, E. Heinrich, F. Vinet, J. Bibette, J. Coll, and I. Texier, “Tumor targeting of functionalized lipid nanoparticles: assessment by in vivo fluorescence imaging,” Eur. J. Pharm. Biopharm. 75(2), 137–147 (2010).
[Crossref]

IEEE Sens. J. (1)

S. Diaz, S. Foaleng Mafang, M. Lopez-Amo, and L. Thevenaz, “A High-Performance Optical Time-Domain Brillouin Distributed Fiber Sensor,” IEEE Sens. J. 8(7), 1268–1272 (2008).
[Crossref]

Int. J. Chem. Sci. Appl. (1)

T. K. Das and S. Prusty, “Recent advances in applications of graphene,” Int. J. Chem. Sci. Appl. 4, 39–55 (2013).

J. Lumin. (1)

A. Penzkofer and W. Leupacher, “Fluorescence behaviour of highly concentrated rhodamine 6G solutions,” J. Lumin. 37(2), 61–72 (1987).
[Crossref]

J. Phys. Chem. B (1)

C. Pérez León, L. Kador, B. Peng, and M. Thelakkat, “Characterization of the Adsorption of Ru-bpy Dyes on Mesoporous TiO2 Films with UV-Vis, Raman and FTIR Spectroscopies,” J. Phys. Chem. B 110(17), 8723–8730 (2006).
[Crossref]

Laser Phys. Lett. (1)

N. S. Hoseini Motlagh, P. Parvin, F. Ghasemi, F. Atyabi, S. Jelvani, and S. Abdolhosseini, “Laser induced fluorescence spectroscopy of chemo-drugs as biocompatible fluorophores: irinotecan, gemcitabine and navelbine,” Laser Phys. Lett. 13(7), 075604 (2016).
[Crossref]

Opt. Commun. (1)

M. Siddique, L. Yang, Q. Z. Wang, and R. R. Alfano, “Mirrorless laser action from optically pumped dye-treated animal tissues,” Opt. Commun. 117(5-6), 475–479 (1995).
[Crossref]

Opt. Lett. (2)

Opt. Mater. Express (1)

OSA Continuum (1)

Phys. Rev. Lett. (1)

E. Dulkeith, A. C. Morteani, T. Niedereichholz, T. Klar, J. Feldmann, S. A. Levi, F. Van Veggel, D. N. Reinhoudt, M. Möller, and D. I. Gittins, “Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects,” Phys. Rev. Lett. 89(20), 203002 (2002).
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Phys. Status Solidi A (1)

K. Xu, “Silicon MOS optoelectronic micro-nano structure based on reverse-biased PN junction,” Phys. Status Solidi A 216(7), 1800868 (2019).
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PLoS One (1)

A. V. Fonin, A. I. Sulatskaya, I. M. Kuznetsova, and K. K. Turoverov, “Fluorescence of dyes in solutions with high absorbance Inner filter effect correction,” PLoS One 9(7), e103878 (2014).
[Crossref]

Spectrochim. Acta, Part A (1)

F. Pahang, P. Parvin, and A. Bavali, “Fluorescence quenching effects of carbon nano-structures (Graphene Oxide and Nano Diamond) coupled with Methylene Blue,” Spectrochim. Acta, Part A 229, 117888 (2020).
[Crossref]

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. J.R. Lakowicz, “Quenching of fluorescence, in Principles of fluorescence spectroscopy”, 1983, Springer. p. 257–301.

H. Seunghoon, Y-W. Huang, H. Atwater, H.W. Lee, R. Sohkoyan, G. Papadakis, and K. Thyagarajan, “Optical modulating device having gate structure,” 2017, Google Patents.

M. Enoki and R. Katoh, “Estimation of quantum yields of weak fluorescence from eosin Y dimers formed in aqueous solutions,” Photochemical & Photobiological Sciences, 2018.

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Figures (8)

Fig. 1.
Fig. 1. Schematic of LIF setup for angular measurement of the fluorescence spectra in order to measure angular dependence of the Stern-Volmer slopes K(θ). The laser direction and the angle of detection are shown above.
Fig. 2.
Fig. 2. Normalized absorption and emission spectra for RdB solution. Inset depicts the maximum fluorescence intensity in terms of RdB concentration at various detection angles.
Fig. 3.
Fig. 3. (a) and (b) Fluorescence signal ratio Io/I as a function of RdB concentration [Q] at the smaller and the larger angles of detection respectively. (c) Spectral shift in terms of RdB concentration due to the re-absorption and self-quenching events at various angles of detection. Note that the high abundance of non-excited molecules give rise to higher re-absorption rates leading to larger red shift.
Fig. 4.
Fig. 4. Schematic of different active apparent volumes at various detection angles (a) θ=30°, (b) θ=45°, (c) θ=65° and (d) θ=90°. Note that the volume of excited and unexcited regions notably change with detection angles.
Fig. 5.
Fig. 5. (a) Fluorescence signal ratio Io/I versus TiO2 densities for several observation angles, Stern-Volmer plot (b) Spectral shift of (RdB + TiO2) in terms of various observation angles at CRdB = 40 µM in ethanolic solution; TiO2 NP additives ranging 200-15000 µg/ml (c) Spectral shift in terms of detection angle at different TiO2 densities (typically 1000, 5000 and 10000 µg/ml)
Fig. 6.
Fig. 6. (a) Io/I ratio versus GO density at certain CRdB = 40 µM. Invariant Stern-Volmer slope of RdB + GO (0-18 µg/ml) takes place at different observation angles θ. (b) Spectral shift in terms of GO density for various detection angles. (c) Spectral shift in terms of detection angle at different GO densities (typically 2, 4, 8 and 10 µg/ml) at certain CRdB = 40 µM. Note that a notable red shift linearly appears at various observation angles and a plateau takes place at higher GO densities.
Fig. 7.
Fig. 7. (a) Slope KTiO2 in terms of detection angle θ for (RdB + TiO2) and (b) KGO versus observation angle in (RdB + GO) hybrid suspension respectively. Note that slope K increment for TiO2 is much larger than that of GO while K for GO is much larger than that of TiO2.
Fig. 8.
Fig. 8. (a), (b) and (c) schematics of RdB, (RdB + TiO2) and (RdB + GO) suspension respectively. (d) and (e) chemical interaction between (RdB + TiO2) and (RdB + GO) respectively [33,34] and (f) Typical SEM image of (RdB:GO). Note that π-π stacking and hydrogen bounding are dominant effects to form complex compounds.

Equations (4)

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I I = 1 + K S [ Q ] ,
I I = 1 + k q τ [ Q ] = 1 + K D [ Q ] ,
k T ( r ) = 1 τ D ( R r ) 6
I ( λ , l ) = I 0 ( λ ) exp ( 0 l σ r e a b s ( λ ) N d y e G ( l ) d l )

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