Rhodamine 6G Dye Solution Research Articles

Observing Variation in Whispering Gallery Mode Resonance of a Trapped and Levitated Dye Doped Microdrop.

Whispering gallery mode (WGM) resonance was created in a spherical micro drop. A gradual shift in the resonance were observed. For a 600 nm droplet radius, the blue shift were 1.5, 0.7, 3.7 nm. It was estimated that such a shift corresponds to a reduction in optical radius of the droplet by 1.3, 0.6, 3.3 nm respectively. The droplet was created from a solution of glycerol, methanol and rhodamine 6G dye, and was trapped and levitated in a modified Paul trap. The WGMs were created by optically exciting the dye material from an external 532 nm cw laser beam. A shift in the WGM was observed during a gradual increase in power of the excitation laser, and a reason for such a shift was thought to be thermal evaporation of the liquid. For a larger droplet an initial 0.1 nm thermal expansion was also estimated, preceding the volume contraction. Such an expansion was negligible for a smaller droplet. The rate of change of the blue shift depends upon initial radius of the droplet. For the smaller droplet the estimated rate of change of WGM with a change in optical radius, was 0.771. For larger droplet, this rate is lower.

Impact of ion-specific interactions on laser-induced liquid microjet generation

Jet velocity and jet power are the crucial parameters that govern the release profile of drugs/vaccines in needle-free injection systems, where salts are considered as one of the essential constituents of drugs/vaccines as adjuvants. However, the impact of salts on the generation of laser-induced liquid microjets that have shown tremendous potential for drug delivery has remained unexplored. Here, we have investigated the influence of Hofmeister ions on the velocity of laser-induced liquid jets in rhodamine 6G (Rh6G) dye solution. A comprehensive experimental approach is adopted to find out the values of the liquid microjet velocity by varying the parameters, such as input energy of the laser beam, concentrations of the dye, and specific Hofmeister ions in the aqueous solution. From our experimental findings, it is observed that the presence of ions significantly influences the jet velocity that follows the Hofmeister series: SO42−>I−>SCN−. This, in turn, governs the ion-specific penetration depth of liquid jets as simulated for the model soft tissues. The observed Hofmeister trend in the jet velocity values showcases the possible specific-ion interactions between anions and Rh6G molecules in the aqueous solution. Our detailed experimental findings on ion-specific jet velocity and jet power could be beneficial in designing needle-free drug delivery systems with controlled penetration depths.

Narrow-band random Raman lasing from Rhodamine 6G assisted by cascaded stimulated Raman scattering effect

This study reports the first experimental observation of cascaded stimulated Raman scattering (SRS) generation in a colloidal disordered medium. Generation of the cascaded effect requires both a high Raman gain and pump power in the disordered medium. Here, to extend effective path lengths of photons into the Raman gain medium for producing additional SRS processes, ZnO microspheres with abundant nano-protrusions as suitable scattering centers are proposed. It is explained that nano-protrusions on the surface of the spheres can act as nano reflectors and significantly provide potent feedback in the disordered system. This provided feedback via nano-protrusions boosts cascaded SRS generation to allow the appearance of higher Raman signals of Rhodamine 6G dye solution at a low scatterer concentration of 5 mg/ml. The threshold for the formation of the first Raman signal is measured at about 60 mJ/pulse. Also, the evolution of Raman signals under several fixed pump pulses is examined to investigate the stability from pulse to pulse. Our findings provide promising perspectives for achieving the single-frequency laser sources and generate desirable wavelengths for specific applications.

Visible light photocatalysis promoted by homogenously doped (non-metals) anatase from a chelated titanium precursor

The anion-modified titania finds extensive application in many solar energy-mediated processes. The current study addresses the generation of anatase homogeneously co-doped with carbon and nitrogen with the help of the polyaminocarboxylate backbone of EDTA complexed with titanium. Various physicochemical techniques were used to characterize the sample from the hydrothermally hydrolyzed product of Ti-EDTA. The anatase polymorph formed from this reaction was yellow in color and suggested a defective one. The crystallites had an average size of 12 nm. The tetragonal lattice dimensions showed deviation from the pure anatase, confirming the presence of oxygen vacancies. The electron microscopy experiments demonstrated the homogeneity and its tetragonal symmetry. The XPS analysis confirmed 9.5 and 1.5 % of carbon and nitrogen-doped in the anatase as Ti–O–C/N species. Raman spectrum indicated lattice disorder caused by the co-doping carbon and nitrogen. The oxygen vacancies showed paramagnetic signal in the EPR spectrum both at room temperature and at 77 K. Emission in the blue region in the photoluminescence spectrum confirmed the existence of oxygen vacancies. The sample showed absorption in the entire UV region extending up to the visible region and had an optical bandgap of 2.8 eV. The sample exhibited excellent catalytic activity in the visible light, promoted decolorization of crystal violet, rhodamine 6G dye solutions following pseudo-first-order kinetics. The sample also catalyzed 85 % of bisphenol (BPA) degradation under visible radiation, from which salicylaldehyde was identified as the major product by the GC-MS analysis. The catalyst retained its ability up to three times its reuse without undergoing any structural change. OH● radicals have been identified as the reactive oxidation species (ROS) involved in these experiments with scavenger experiments.

Fabrication of ZnO–TiO2 nanohybrids for rapid sunlight driven photodegradation of textile dyes and antibiotic residue molecules

Abstract Semiconductor nanohybrids garner huge interest among environmentalists for the various applications owing to their efficiency, cost-effectiveness and benignity. We report the fabrication of TiO2 nanoparticles (TNPs) functionalized ZnO nanoflakes (ZNFs) and their outstanding detoxification ability towards the methylene blue (MB), rhodamine 6G (R6G) and Oxytetracycline (OTC) molecules solution in water. TEM studies confirm the formation of 3D architecture of ZnO–TiO2 nanohybrids while high-resolution transmission electron microscopy assures the uniform functionalization of TNPs over ZNFs. Scanning electron microscopy studies reveal the modulation in the surface morphology with the tenability in volume ratios of Zn and Ti sources. Significant PL quenching in ZnO–TiO2 nanohybrids spectrum as compared to ZNFs confirms the improvement in the charge separation which is highly favorable for the enhancement in the photodegradation efficiency. The 3D architecture of ZnO–TiO2 with volume ratio (Zn: Ti: 4:1) showed superior photodegradation activity and decompose OTC, MB and R6G dye solution within 8 min, 6 min and 30 min respectively under natural solar light (~862 W/cm2). Most efficient ZnO–TiO2 nanohybrid exhibits extremely high rate constant values for MB, R6G and OTC molecules which are 7, 5 and 4.8 times of the rate constant value of pure ZNFs. Extremely superior photodegradation performance of 3D architecture of ZnO–TiO2 nanohybrid could be ascribed to the charge separation and synergistic effect between the TNPs and ZNFs which is responsible for the high density of electrons in the conduction band of ZnO–TiO2 nanohybrids. ZnO–TiO2 nanohybrids reveal the extremely high photodegradation rate for the decomposition of azo dyes and pharmaceutical residue which has not been reported till now.

Spectral and energy characteristics of resonatorless lasing in solutions of Rhodamine 6G with nanoparticles of various nature with femtosecond pumping

The results of measurements of the spectral and energy characteristics of cavity-free lasing in Rhodamine 6G dye solutions with Al nanoparticles irradiated with femtosecond laser pulses are presented. A comparison is made of the threshold generation values in a pure dye solution and in a dye solution with nanoparticles upon irradiation with femtosecond pulses.

Influence of Refractive Index on Lasing Coupling Efficiency and Emission Spectrum

An optical fiber with a diameter of $125~\mu \text{m}$ is integrated in a polydimethylsiloxane (PDMS) microfluidic channel. The lasing gain medium is consisted of a lower refractive index (RI) rhodamine 6G (Rh6G) dye solution. With this configuration, we have presented the study on the lasing coupling efficiency and lasing emission spectrum affected by the RI of the dye solution under different polarization states of the pump light. When the fiber is pumped by a linearly ${s}$ - or ${p}$ -polarized light, the intensity of the emitted whispering gallery modes (WGMs) lasing, i.e., transverse magnetic (TM) or transverse electric (TE) mode, decreases by approximately two-fold as the RI of the dye solution increases from 1.325 to 1.419, meaning a significant difference on the lasing coupling efficiency is achieved under different RI of the dye solution. When the fiber is excited by a ${s}$ - and ${p}$ -mixed polarized light, the mode separation between the adjacent TM and TE mode decreases with the increase of the RI of the dye solution, providing a simple and effective method for applications, such as RI sensing.

Using ZnO nanosheets grown by electrodeposition in random lasers as scattering centers: the effects of sheet size and presence of mode competition

In this paper, a random laser is fabricated based on zinc oxide (ZnO) nanosheets, which are grown on a fluorine-doped tin oxide glass substrate using an electrodeposition technique. ZnO nanosheets act as scattering centers, while optical gain in the random laser is provided by Rhodamine 6G dye solution. It is found that there is only a single emission peak in the random laser spectrum. It is also observed that changing the electrolyte concentration used in electrodeposition leads to the generation of ZnO nanosheets with different sizes, thicknesses, and shapes. The effects of changing the sheet geometry on the random laser characteristics are studied. Our results reveal that by increasing the size of nanosheets and decreasing their thickness, first the lasing threshold decreases and then two peaks appear in the emission spectrum, which are called random laser modes. These effects arise from the dependence of optical absorption and scattering strength of ZnO nanosheets on their sizes and thicknesses. Because of mode competition and cross gain saturation effects between the excited modes, an increase in their threshold and a decrease in their intensity are observed. Furthermore, our results show that the double mode random lasing emission from ZnO nanosheets strongly depends on the region of the sample illuminated by the pump laser.

Investigation the concentration effect on the absorption and fluorescence properties of Rhodamine 6G dye

Concentration dependence of the optical absorption and fluorescence spectra of Rhodamine 6G dye solution have been investigated. Shift the absorption and the fluorescence peaks with an increase the dye concentration, from 0.1 to 250 μM, is studied. By measuring the absorbed and the fluorescence spectra of Rhodamin 6G dye, enhancement of the absorbance and quenching of the fluorescence intensity are obtained. Observed fluorescence quenching of Rhodamine 6G after 60 μM is caused by the collisional mechanism. From 0.1 to 30 μM, the absorbance obeys the Beer-Lambert law. While, beyond 30 μM, due to contributions of the dimers and aggregation of dye molecules, the absorbance deviates from the Beer-Lambert law.

Photodegradation of Rhodamine 6G by Amorphous TiO2 Films Grown on Polymethylmethacrylate by Magnetron Sputtering

Titanium dioxide (TiO2) was deposited on polymethylmethacrylate (PMMA) substrates by magnetron sputtering using a Compact Planar Magnetron sputtering device at different flow rate ratios of O2/Ar. The deposited TiO2 on PMMA substrates were characterized using X-ray Diffraction analysis, X-ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy, UV-Visible Spectroscopy, and Scanning Electron Microscopy (SEM). These techniques confirm the deposition of a chemically stable amorphous TiO2 layer on the PMMA surface. Photocatalytic activity of the amorphous TiO2 layers were tested via photodegradation of Rhodamine 6G (Rh6G) dye solution. The samples were able to degrade 18–27% of the Rh6G solution after the initial 25 minutes of UV irradiation and complete degradation of Rh6G was observed after 7 hours of UV irradiation.

Sol-Gel Synthesis of High-Purity Actinide Oxide ThO2 and Its Solid Solutions with Technologically Important Tin and Zinc Ions.

The applicability of epoxide-based sol-gel synthesis for actinide oxide (thoria) starting from air-stable salt, Th(NO3)4, has been examined. The homogeneous gel formed from Th(NO3)4 when calcined at 400 °C yielded nanostructured thoria, and with increasing tempeartures (600, 700, and 800 °C), the average crystallite size increased. Successful Rietveld refinement of the powder X-ray diffraction pattern of ThO2 in Fm3̅m space group was carried out with a = 5.6030(35) Å. The fingerprint vibrational mode of the fluorite structure of ThO2 was noticed as a sharp band in the Raman spectrum at 457 cm-1. In the SEM image, a near spherical morphology of thoria was noticed. Samples showed blue emission on exciting with λ = 380 nm in the photoluminescence spectrum indicative of the presence of defects. Following this approach, 50 mol % of Sn4+ could be substituted for Th4+, retaining the fluorite structure as evidenced by the PXRD, Raman spectroscopy, electron microscopy, EDAX, and XPS measurements. Randomization of the lattice was observed for the tin-substituted samples. A significant blue shift in the absorption threshold along with a persistent blue emission in the photoluminesence spectra were evident for the tin-substituted samples. The concentration of Zn2+ ion in thoria was limited to 15 mol % as revealed by PXRD and XPS measurements. The Raman peak shifted to higher values for Zn2+-substituted samples. A change in the optical absorbance characteristics was observed for the zinc-substituted thoria. A 50 mol % Sn4+-substituted thoria degraded aqueous Rhodamine 6G dye solutions in the presence of UV-vis radiation following pseudo-first-order kinetics.

Properties of lasing in Rhodamine 6G solutions with nanoparticles free of plasmon resonance

The threshold characteristics of lasing in a 20-μm layer of colloidal solution of Rhodamine 6G dye with plasmon-resonance Au nanoparticles and non-plasmon-resonance Pt nanoparticles excited by 532-nm radiation are experimentally studied. The spectral dependence of the scattering and absorption cross sections of gold and platinum nanoparticles are calculated within the Mie theory. It is found experimentally that the addition of nanoparticles to the active medium decreases the lasing thresholds by two orders of magnitude. It is shown that the lasing thresholds are 1.5–2 times lower when adding gold nanoparticles than when adding platinum nanoparticles of the same concentration.

Demonstration of polarization mode selection and coupling efficiency of optofluidic ring resonator lasers.

We demonstrate the polarization mode selection and the dependence of coupling efficiency on polarization state of pump light for an optofluidic ring resonator (OFRR) laser. An optical fiber is chosen to serve as the ring resonator and surrounded by rhodamine 6G dye solution of lower refractive index as the fluidic gain medium. When the ring resonator is pumped by a linearly s-polarized laser, the emitted whispering gallery mode (WGM) lasing is of parallel polarization (TM mode), while p-polarized laser excitation generates a vertically polarized lasing emission (TE mode), both TM and TE mode lasing emission coexist simultaneously if the ring resonator is pumped by the s- and p-mixed polarized light. Further investigation reveals that the lasing intensity of the TM mode is approximately twice that of the TE mode for the same pump energy density, meaning an obvious difference of coupling efficiency on the polarization state of pump light; the experimental results of coupling efficiency are well explained by an induced dipole model.

Soft chemical synthesis of Ag3SbS3 with efficient and recyclable visible light photocatalytic properties

Application of Ag3SbS3, obtained by soft chemical approach involving rapid reaction of air stable metal–thiourea complexes in ethylene glycol medium, as visible light photocatalyst for the degradation of dye solutions was investigated. Ag3SbS3 was confirmed by high resolution powder X-ray diffraction pattern and its no defined morphology was present in SEM images. From UV–vis spectroscopy measurements, optical band gap of 1.77eV was deduced for Ag3SbS3. Rapid degradation kinetics and recyclability was exhibited by Ag3SbS3 towards Methylene Blue, Methyl Orange, Malachite Green, and Rhodamine 6G dye solutions under visible radiation. All these processes followed pseudo first order kinetics. High surface area (6.39m2/g), with mesopores (3.81nm), arising from solvent mediated synthesis of Ag3SbS3 has been correlated to its catalytic activity.

Observation of two-photon fluorescence for Rhodamine 6G in microbubble resonators.

We report an observation of multi-photon excitation of organic chromophores in microbubble whispering gallery mode resonators. High-Q microbubble resonators were formed by heating a pressurized fused silica capillary to form a hollow bubble that was then filled with liquid. In this work, the microbubble was filled with a solution of Rhodamine 6G dye. The resonator and dye were excited by evanescently coupling continuous wave (CW) light from a 980nm laser diode using a tapered optical fiber. The two-photon fluorescence of the dye can be seen with pump powers as low as 700μW.

Degenerate polarization multiwave mixing between light beams in a solution of rhodamine 6G dye

The characteristics of diffracted waves derived from four- and six-wave mixing in a solution of Rhodamine 6G dye are studied in different combinations ofthe polarization states of waves that participate in wave interaction.

Fiber-based tunable microcavity fluidic dye laser

We investigate a tunable fluidic dye laser formed by a microcavity filled with a dye solution. We achieve a wide 18nm tunability of the laser wavelength by controlling the cavity length for the first time. The microcavity is made of a silica capillary and two aligned fibers with end faces Au-coated. The Rhodamine 6G dye solution flowing through the microcavity is pumped by 532nm wavelength laser pulses. Laser emission around 570nm in the form of TE mode with a threshold of about 58 μJ/pulse is obtained. This work suggests a fiber-based convenient approach to achieve wavelength tunability and integration with lab-on-a-chip systems.

Deformation properties between fluid and periodic circular obstacles in polydimethylsiloxane microchannels: Experimental and numerical investigations under various conditions

Understanding the mechanical properties of optically transparent polydimethylsiloxane (PDMS) microchannels was essential to the design of polymer-based microdevices. In this experiment, PDMS microchannels were filled with a 100 μM solution of rhodamine 6G dye at very low Reynolds numbers (∼10(-3)). The deformation of PDMS microchannels created by pressure-driven flow was investigated by fluorescence microscopy and quantified the deformation by the linear relationship between dye layer thickness and intensity. A line scan across the channel determined the microchannel deformation at several channel positions. Scaling analysis widely used to justify PDMS bulging approximation was allowed when the applied flow rate was as high as 2.0 μl/min. The three physical parameters (i.e., flow rate, PDMS wall thickness, and mixing ratio) and the design parameter (i.e., channel aspect ratio = channel height/channel width) were considered as critical parameters and provided the different features of pressure distributions within polymer-based microchannel devices. The investigations of the four parameters performed on flexible materials were carried out by comparison of experiment and finite element method (FEM) results. The measured Young's modulus from PDMS tensile test specimens at various circumstances provided reliable results for the finite element method. A thin channel wall, less cross-linker, high flow rate, and low aspect ratio microchannel were inclined to have a significant PDMS bulging. Among them, various mixing ratios related to material property and aspect ratios were one of the significant factors to determine PDMS bulging properties. The measured deformations were larger than the numerical simulation but were within corresponding values predicted by the finite element method in most cases.

Photostability of lasing process from water solution of Rhodamine 6G with gold nanoparticles

We report the lasing performance and photobleaching of gain material containing a water solution of Rhodamine 6G dye and gold nanoparticles (NPs). In comparison to a pure dye solution, the investigated material demonstrated both enhancement and quenching of the lasing output, depending on the relative concentration of the gold NPs. Although the presence of NPs with an optimized concentration looks preferable in terms of the lasing output enhancement, such additives deteriorate the operational resource of the gain material; i.e., the photobleaching rate speeds up.

Inflection point of the spectral shifts of the random lasing in dye solution with TiO2 nanoscatterers

We report the inflection point of the spectral shift of random lasing, from blue shift to red shift, in Rhodamine 6G dye solution with TiO2 nanoscatterers under picosecond pulses pumping, on increasing the scatterer density for certain dye concentrations. The red shift, resulting from the re-absorption and re-emission of the dye, indicates a longer optical path length of the emitted laser travelling inside the media. The diffusion theory is provided to show the discrepancy in the theory and the experimental results, which show that the light stays in the medium longer than the theory predicts. So this inflection point shows that the system changes from a diffusion system to a weakly localized one. The spectral width shows similar behaviour, for a longer optical path length results in a broader spectral width.