Rhodamine 6G Dye Molecules Research Articles

Flower-like Ag-decked non-stoichiometric Bi2O3-x/rGO hybrid nanocomposite SERS substrates for an effective detection of Rhodamine 6G dye molecules.

In early years, SERS-active substrates were generally noble metals. However, their practical applications were limited due to their poor biocompatibility, low uniformity and high cost. Recently, the utilization of semiconductor SERS-active substrates has greatly expanded the applications of SERS in many fields. However, metal-free SERS-active substrates have a low enhancement factor (EF), which can be overcome by adjusting their oxygen deficiency or through the effective preparation of non-stoichiometric semiconducting oxide materials. This is the key strategy and may work as an efficient and simple way to achieve high sensitivity and obtain an enhancement factor (G-factor) comparable to that of noble metals. Here, we report the preparation of flower-like rGO-Bi2O3/Bi2O2.75 and rGO-Ag-Bi2O3/Bi2O2.75 hybrid thin film nanocomposites using a liquid/liquid interface method (LLI) for the first time. In addition to the synergic effect of different enhancement mechanisms, the 3-D flower-like morphology of the substrate shows more favourable properties to improve the G-factor due to the existence of more hotspots. The rGO-Ag-Bi2O3/Bi2O2.75 hybrid thin-film nanocomposites show an EF of 1.8 × 109 with a detection ability of up to 1 nM towards Rhodamine 6G (R6G), which is highly toxic to humans and the aquatic environment.

Structural and Optical Properties of R6G Doped Nanotitania Thin Films Deposited via Sol–Gel Dip-coating Meth

Pure and rhodamine 6G (R6G) doped titanium dioxide (TiO2) nanostructure thin films with different concentrations (310-4 , 310-5 , 310-6 , and 310-7 ) M of doped TiO2 sol were deposited on glass substrate via dip-coated sol-gel method. Amorphous structure of the pure and doped TiO2 thin films was identified by X-ray diffraction (XRD) technique. UV-Visible (UV-vis) and fluorescence spectrophotometry techniques were used to study optical and spectroscopic characterization of the samples, respectively. The absorption spectra for all pure and doped TiO2 films indicate a strong absorbance in the UV region which open the possible application of these films for UV filter optical element. 50 nm blue shift of the absorption edge for the TiO2 films with respect to the sol was observed which proves the nanostructure texture of TiO2 thin films. Upon increasing dye concentration, a red shift in the maximum fluorescence emission peaks of R6G ethanolic solution and doped TiO2 sol was observed. The presence of R6G dye molecules in the matrix of TiO2 films is demonstrated by the appearance of two distinct intensity fluorescence peaks at 540 and 600 nm. Various fluorescence peaks of R6G doped TiO2 thin films were observed in UV-vis region under 300 nm pumping wavelength.

Optical characterization of DNA origami-shaped silver nanoparticles created through biotemplated lithography.

Here, we study optically resonant substrates fabricated using the previously reported BLIN (biotemplated lithography of inorganic nanostructures) technique with single triangle and bowtie DNA origami as templates. We present the first optical characterization of BLIN-fabricated origami-shaped silver nanoparticle patterns on glass surfaces, comprising optical transmission measurements and surface-enhanced Raman spectroscopy. The formed nanoparticle patterns are examined by optical transmission measurements and used for surface enhanced Raman spectroscopy (SERS) of Rhodamine 6G (R6G) dye molecules. Polarization-resolved simulations reveal that the higher SERS enhancement observed for the bowties is primarily due to spectral overlap of the optical resonances with the Raman transitions of R6G. The results manifest the applicability of the BLIN method and substantiate its potential in parallel and high-throughput substrate manufacturing with engineered optical properties. While the results demonstrate the crucial role of the formed nanogaps for SERS, the DNA origami may enable even more complex nanopatterns for various optical applications.

Effect of Silver Modification on the Photoactivity of Titania Coatings with Different Pore Structures.

Nanostructured photoactive systems are promising for applications such as air and water purification, including self-cleaning coatings. In this study, mesoporous TiO2 sol-gel coatings with different pore structures were prepared and modified with silver by two methods: the “mixing” method by adding AgNO3 to the precursor sol, and the “impregnation” method by immersing the samples in AgNO3 solution (0.03 and 1 M) followed by heat treatment. Our aim was to investigate the effects that silver modification has on the functional properties (e.g., those that are important for self-cleaning coatings). Transmittance, band gap energy, refractive index, porosity and thickness values were determined from UV-Vis spectroscopy measurements. Silver content and structure of the silver modified samples were characterized by X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, High-resolution transmission electron microscopy and Energy Dispersive X-ray Spectrometry elemental mapping measurements. Wettability properties, including photoinduced wettability conversion behavior were investigated by water contact angle measurements. Photoactivity was studied under both UV and visible light with rhodamine 6G and methylene blue dye molecules, at the liquid–solid and air–solid interfaces modeling the operating conditions of self-cleaning coatings. Samples made with “impregnation” method showed better functional properties, in spite of their significantly lower silver content. The pore structure influenced the Ag content achieved by the “impregnation” method, and consequently affected their photoactivity.

Novel synthesis method and microstructure evolution of Ti3C2(OH)2/K2Ti8O17 nanocomposites as an effective surface enhanced Raman scattering substrate

In this paper, we have developed a mild and facile approach using KOH solution as etchants to corrode Ti3SiC2 at room temperature, fabricating novel Ti3C2(OH)2/K2Ti8O17 nanocomposites with open network structures and abundant surface functional groups. The as-produced products obtain the excellent surface enhanced Raman scattering (SERS) performance in the determination of crystal violet (CV), rhodamine 6G (R6G) and methylene blue (MB) dye molecules. The enhancement factors of the three can be calculated to be 3.98 × 105, 1.78 × 105 and 5.27 × 105, and the Raman signals can be detected at the concentrations as low as 10−6 M, 10−8 M and 10−6 M, respectively, suggesting the potential for reliable SERS substrates. In this regard, this work provides a new strategy for exploring and synthesizing MAX phase-derived nanomaterials as promising SERS substrates for high-sensitive molecular detection.

Rapid and sensitive label-free SERS determination of fucoxanthin in algae using gold nanoparticles

In this paper, we explored a rapid and ultra-sensitive detection method of fucoxanthin in algae by surface-enhanced Raman scattering. Gold nanoparticles (Au NPs) were prepared by the reduction of chloroauric acid with citric acid. An effective Raman indicator molecule, Rhodamine 6G(R6G) dye molecule, was used to characterize Au NPs that were used in SERS analysis to detect fucoxanthin. It was found that the detection limit of fucoxanthin could reach 10−6 mol·L−1. The characteristic peak of fucoxanthin at a wave number of 1520 cm−1was selected as the working curve, and it presents good linearity of fucoxanthin concentration with R2 = 0.932 in the range from 5×10−4∼1×10−7 M. We first proposed the rapid detection of fucoxanthin by surface-enhanced Raman scattering, which took only one minute to detect. In addition, the Raman strength of the pure algae or kelp and the addition of fucoxanthin was compared under the gold nanoparticle substrate, so as to verify the application value of SERS technology in the rapid determination of fucoxanthin.

Strong exciton-plasmon coupling in dye-doped film on a planar hyperbolic metamaterial.

We experimentally demonstrate the direct strong coupling between the S0→S1 absorption transition of rhodamine 6G (R6G) dye molecules and the surface plasmon polaritons of a hyperbolic metamaterial (HMM) substrate. The surface plasmon mode was excited by a guided mode of the R6G-doped polymer thin film on the HMM. The coupling strengths of the interactions between the surface plasmon and two molecular exciton modes are greater than the average linewidths of the individual modes indicating a strong coupling regime. This is the first, to the best of our knowledge, experimental demonstration of the direct strong coupling between the resonance mode supported by the HMM and the dye molecules on the HMM surface, not embedded in the HMM structure. The study may provide the foundation for the development of novel planar photonic or electronic devices.

Cation–π Interaction Assisted Molecule Attachment and Photocarrier Transfer in Rhodamine/Graphene Heterostructures

AbstractCation–π interactions between molecules and graphene are known to have a profound effect on the properties of the molecule/graphene nanohybrids and motivate this study to quantify the attachment of the rhodamine 6G (R6G) dye molecules on graphene and the photocarrier transfer channel formed across the R6G/graphene interface. By increasing the R6G areal density of the R6G on graphene field‐effect transistor (GFET) from 0 up to ≈3.6 × 1013 cm−2, a linear shift of the Dirac point of the graphene from originally 1.2 V (p‐doped) to −1 V (n‐doped) is revealed with increasing number of R6G molecules. This indicates that the attachment of the R6G molecules on graphene is determined by the cation–π interaction between the NH+ in R6G and π electrons in graphene. Furthermore, a linear dependence of the photoresponse on the R6G molecule concentration to 550 nm illumination is observed on the R6G/graphene nanohybrid, suggesting that the cation–π interaction controls the R6G attachment configuration to graphene to allow formation of identical photocarrier transfer channels. On R6G/graphene nanohybrid with 7.2 × 107 R6G molecules, high responsivity up to 5.15 × 102 A W−1 is obtained, suggesting molecule/graphene nanohybrids are promising for high‐performance optoelectronics.

Plasmon-assisted random lasing from a single-mode fiber tip.

Random lasing occurs as the result of a coherent optical feedback from multiple scattering centers. Here, we demonstrate that plasmonic gold nanostars are efficient light scattering centers, exhibiting strong field enhancement at their nanotips, which assists a very narrow bandwidth and highly amplified coherent random lasing with a low lasing threshold. First, by embedding plasmonic gold nanostars in a rhodamine 6G dye gain medium, we observe a series of very narrow random lasing peaks with full-width at half-maximum ∼ 0.8 nm. In contrast, free rhodamine 6G dye molecules exhibit only a single amplified spontaneous emission peak with a broader linewidth of 6 nm. The lasing threshold for the dye with gold nanostars is two times lower than that for a free dye. Furthermore, by coating the tip of a single-mode optical fiber with gold nanostars, we demonstrate a collection of random lasing signal through the fiber that can be easily guided and analyzed. Time-resolved measurements show a significant increase in the emission rate above the lasing threshold, indicating a stimulated emission process. Our study provides a method for generating random lasing in the nanoscale with low threshold values that can be easily collected and guided, which promise a range of potential applications in remote sensing, information processing, and on-chip coherent light sources.

A Study of Plasmon-Coupled Fluorescence of Rhodamine 6G on Thin Nickel Films

Plasmon-coupled luminescence of rhodamine 6G dye molecules on a thin nickel film has been studied experimentally and theoretically. The spatial distribution of fluorescence of dye molecules, which is calculated using the transfer matrix method for describing flat-layered media, is in good agreement with the experimental diagrams obtained for the spatial distribution of radiation with different polarization. The coupling efficiency between the luminophore and nickel film plasmons is experimentally determined.

Effect of Adsorption Characteristics of Rhodamine 6G Dye Solution in Fe3O4 Magnetic Nanoparticles on Fluorescence Quantum Yield

In this work, the use of Fe3O4 magnetic nanoparticles in the adsorption of rhodamine 6G solution was evaluated via absorbance and fluorescence spectroscopy using the UV-Vis spectrometer. The adsorption mechanism of rhodamine 6G on Fe3O4 was determined with respect to the adsorbent dosage (2.5–10 mg/L) and treatment time (0–150 min). The experimental data revealed that the fluorescence quantum yield of rhodamine 6G was inversely proportional to the percentage of dye removal. The highest efficiency of dye removal was obtained at 10 mg/L Fe3O4, and the adsorption capacity was about 150 mg/g, together with a reduced treatment time of 30 min, owing to active adsorption of Fe3O4. We believe that our study makes a significant contribution to the literature because Fe3O4 magnetic nanoparticles were found to be able to quench rhodamine 6G dye molecules, which will aid in eliminating toxic and hazardous pollutants from dye wastewater, which are otherwise detrimental to the environment and human health.

Effect of metal–dielectric substrates on chemiluminescence kinetics

We studied chemiluminescence of rhodamine 6G (R6G) dye in a series of R6G:DNPO:PMMA films deposited onto a variety of metallic, metal–dielectric, and dielectric substrates. We found that chemiluminescence kinetics on top of Ag and Au films covered by an insulating MgF2 layer had longer decay times than those on top of purely dielectric substrates, MgF2 films on glass. We infer that Ag- and Au-based substrates with an insulating MgF2 layer on top affected the reaction rates by influencing polarization energies of reactants and surrounding molecular dipoles. At the same time, the chemiluminescence kinetics on top of Ag and Au surfaces (without an insulating MgF2 spacer) were substantially shorter than those on top of dielectric substrates, probably because of conventional chemical catalysis. The peak emission intensities on top of metallic substrates (with and without the MgF2 layer on top) were lower than those on top of purely dielectric substrates, likely due to inhibition of the energy transfer to acceptors (R6G dye molecules) known in the vicinity of metals. The further reduction of chemiluminescence intensity on top of lamellar metal–dielectric stacks could be due to preferential emission of light inside the volume of the metamaterial rather than outside.

Determination of concentration of adsorbed molecules by Raman spectroscopy and optical imaging

In this paper, solution soaking is used to deposit Rhodamine 6G (R6G+) dye molecules on two-dimensional materials, i.e., graphene and molybdenum disulfide (MoS2), which concentrate the solution-phase R6G+ molecules into a solid thin film. The concentration of adsorbed molecules on graphene/MoS2 can be calculated using graphene 2D/MoS2 A1g peak as an internal standard. It is found that optical imaging also provides a quantitative way to determine the concentration of adsorbed molecules whose results are further confirmed by atomic force microscopy. The obtained results will facilitate the fabrication of surface-enhanced Raman scattering substrates using two-dimensional materials. Adsorptive removal of various dyes to lighten effluent pollution from industries is a basic and applied research area. Carbon-based materials are well-known adsorbents for dyes. Using optical imaging, the dynamic processes of solution-dependent R6G+ sorption and desorption onto graphene are monitored. Our results also shed light on potentially using graphene materials as adsorbents for toxic and carcinogenic molecules.

Enhancement of the spontaneous emission rate of Rhodamine 6G molecules coupled into transverse Anderson localized modes in a wedge-type optical waveguide.

In this paper, the dynamics of the spontaneous emission rate of Rhodamine 6G dye molecules, coupled into disorder-induced optical cavities in a scattering medium, is investigated by a time-resolved spectroscopic technique. The system is a wedge-type wave-guiding system formed by a polymer with randomly positioned air inclusions. The scattering of light in the medium induces transverse Anderson localization, which gives rise to quasi-optical modes or Anderson-localized cavities. The presence of these modes strongly enhances the decay emission of the emitters. The waveguide is fabricated by a conventional fiber drawing technique inside a fused silica micro-rod. Localized optical modes are observed to appear in the form of sharp spectral resonance peaks at various frequencies throughout the photoluminescence spectrum of the dye molecules. The spontaneous emission rate of the molecules on resonance with the localized modes is measured to enhance by a factor of up to 6.8, which elucidates that the transverse Anderson localization enables an efficient way to alter the spontaneous emission rate of quantum emitters in an optically asymmetric simple wedge-type photonic waveguide, offering a moderate alternative to highly engineered sophisticated light-wave devices.

Gold nanoworms: Optical properties and simultaneous SERS and fluorescence enhancement.

Fabrication of platforms for efficient Raman and fluorescence enhancement is very attractive for plasmon-based molecular sensing. For superior sensitivity, the plasmonic constituents of such platforms should be effective electromagnetic field enhancers. Furthermore, nanoparticles having plasmon peak in the spectral range of therapeutic window are superior for biomedical application. Herein, we show that worm-shaped Au nanoparticles can be used for simultaneous surface enhanced Raman scattering (SERS) and metal enhanced fluorescence (MEF). Gold nanoworms (Au-NWs) with an intense plasmon absorption in the therapeutic window were synthesized using a facile single-stepped recipe. Electron microscopy imaging revealed that Au-NWs have a non-uniform surface. Owing to their special morphology, three distinct plasmon bands were seen in the experimental spectrum. The presence of three plasmon peaks was also verified by finite element based simulations. The simulation results further show that Au-NWs can provide intense near field enhancement for multiple excitation wavelengths. As a proof of concept, we have used Au-NWs based platforms for simultaneous enhancement of fluorescence and Raman signal of rhodamine 6G (R6G) dye molecule.

Near-Infrared Surface-Enhanced Raman Scattering on Silver-Coated Porous Silicon Photonic Crystals.

Surface-enhanced Raman scattering (SERS) with near-infrared (NIR) excitation offers a safe way for the detection and study of fragile biomolecules. In this work, we present the possibility of using silver-coated porous silicon photonic crystals as SERS substrates for near-infrared (1064 nm) excitation. Due to the deep penetration of NIR light inside silicon, the fabrication of photonic crystals was necessary to quench the band gap photoluminescence of silicon crystal, which acts as mechanical support for the porous layer. Optimal parameters of the immersion plating process that gave maximum enhancement were found and the activity of SERS substrates was tested using rhodamine 6G and crystal violet dye molecules, yielding significant SERS enhancement for off-resonant conditions. To our knowledge, this is the first time that the 1064 nm NIR laser excitation is used for obtaining the SERS effect on porous silicon as a substrate.

Исследование плазмонно-связанной флуоресценции родамина 6Ж на тонких никелевых пленках

The plasmon-coupled luminescence of rhodamine 6G dye molecules on a thin nickel film was experimentally and theoretically studied. The spatial distribution of the fluorescence of dye molecules, calculated using the transfer matrix method for the description of plane-layered media, agrees well with the experimental diagrams obtained for the spatial distribution of radiation of different polarization. The efficiency of the coupling of the fluorophor with the plasmons of a nickel film has been experimentally established.

Sensing at terahertz frequency domain using a sapphire whispering gallery mode resonator.

In this Letter, we experimentally demonstrate a terahertz (THz) whispering gallery mode (WGM) sensor based on a sapphire WGM resonator. The fundamental mode at 129.49GHz with a Q-factor of 4.63×103 is used to study its sensitivity to adsorbed molecules. The efficiency of our sensor to detect rhodamine 6G dye molecules in a polyvinyl alcohol matrix at room temperature has been manifested, and a detection sensitivity of 25 parts per million has been achieved. Also, we report an analytical approach based on coupled-mode theory between the waveguide mode and the spherical resonator mode to evaluate the absorption coefficient of the adsorbed molecule on the resonator. The model is modified to evaluate optical constants of materials. The results obtained have been verified by continuous-wave THz transmission results. The results are of importance in sensing, metrology, and material characterization.

Study of organic pollutant removal capacity for magnetite@ graphene oxide nanocomposites

In the present work, magnetite (Fe3O4) nanoparticles decorated graphene oxide (GO) sheets were synthesized using the chemical method. Graphene based nanocomposites show an effective adsorbent property, and therefore can be used as an organic pollutant remover from the aqueous medium. The X-ray diffraction analysis was done to investigate the crystallinity and particle size of Fe3O4 decorated GO sheets and the particle size was found to be 28 nm. Surface morphology of Fe3O4@GO nanocomposites was studied using transmission electron microscopy and the obtained inter planer spacing in Fe3O4@GO nanocomposites was 0.246 nm. For the applications point of view, these nanocomposites have been used for the removal of Rhodamine 6G dye molecules from the aqueous medium. The removal capacity was found to increase as the concentration of the nanocomposite increases. In Fe3O4@GO nanocomposites the GO sheets provide large surface area due to different functional groups like epoxide (C-O-C), carboxylic acid (-COOH), hydroxyl (-OH) to adsorb dye molecules. This study provides a new platform for the use of Fe3O4@GO nanocomposites in a water clean-up process.

Spectroscopic studies of dye-doped porous alumina membranes

We have studied the spectroscopic properties of nanoporous alumina membranes impregnated with rhodamine 6G (R6G) dye molecules. At small dye concentrations, the reflectance spectra feature one minimum, corresponding to the absorption band of R6G. With increase of the dye concentration, the reflectance dip splits in two and the energy difference between the two minima increases. A similar behavior is shared by the emission spectral band. We explain these observations in terms of strong coupling of closely situated dye molecules inside the channels. At the same time, the experimentally observed angular dependence of the reflectance spectrum is consistent with a long-range collective behavior of dye molecules across an array of dye-impregnated channels.