How Graphene Oxide Quenches Fluorescence of Rhodamine 6G

We investigate the fluorescence quenching of Rhodamine 6G （R6G）, a well known laser dye with a high fluorescence quantum yield, by as-synthesized graphene oxide （GO） in aqueous solution, which is found to be rather efficient. By means of steady-state and time-resolved fluorescence spectroscopy combined with detailed analysis about the linear absorption vari- ation for this R6G-GO system, the pertinent quenching mechanism has been elucidated to be a combination of dynamic and static quenching. Possible ground-state complexes be- tween R6G and GO during the static quenching have also been suggested. Furthermore, the direction of photoindueed electron transfer between R6G and GO has been discussed.

Simultaneous Determination of Fluorescein, Rhodamine 6G and Rhodamine B in Turbid Solution by Polarization Variable-Angle Synchronous Fluorescence Spectrometry

Polarization variable-angle synchronous fluorescence spectrometry was proposed to determine samples in turbid solution. A mixture of fluorescein, rhodamine 6G and rhodamine B was used to evaluate the technique. The background caused by scattering light was decreased remarkably. The limits of detection were 0.6 ng/ml for fluorescein, 2.3 ng/ml for rhodamine 6G and 4.1 ng/ml for rhodamine B, respectively.

A Transparent Thin Film with Hexagonal Mesostructure Containing Rhodamine 6G

A transparent thin film was prepared by depositing the sol-gel mixture for the synthesis of MCM-41 mesoporous molecular sieve doped with rhodamine 6G (R6G) dye on glass substrates. The film of silica-surfactant-R6G materials, which was identified to possess hexagonally ordered mesostructure, was composed of nanocrystallites about 35 nm in diameter and 1-10 mm in thickness. Cleanness of the substrates, concentration of the sol-gel mixture and rate of evaporation of the solvent were the key factors affecting transparency and homogeneity of the film. Moreover, optical change and lack in dye aggregation were observed to the R6G-functionalized MCM-41 thin film in contrast with that in ethanol solution.

Fe_(3)O_(4)-rhodamine 6G nanoparticles:An iron enhanced pH sensitive multimodal probe for fluorescence and magnetic resonance imaging of tumor cell

The accurate diagnosis of tumor at the early stage depends on efficient medical imaging methods using probes with high sensitivity to the environment of tumor cells.For this purpose,we design the Fe_(3)O_(4)-rhodamine 6 G(Rh6G)nanoparticles(NPs)as a kind of dual-mode probe for fluorescence and magnetic resonance imaging(MRI).The Fe_(3)O_(4)-Rh6G NPs are demonstrated to be Fe^(3+)enhanced and pH-sensitive fluorescent agents,and the strongest fluorescence performance occurs under the pH value of 3.Cyto-toxicity assessment in HeLa cells proves the good biocompatibility and low toxicity of the Fe_(3)O_(4)-Rh6G NPs.The consequent fluorescence experiments in tumor cells show good imaging contrast,which is con-tributed by both the Fe^(3+)released from Fe_(3)O_(4)and the acid environment of tumor cells.Moreover,the Fe_(3)O_(4)-Rh6G NPs are superparamagnetic and have a strong MRI T 2 contrast effect.According to the per-formance in fluorescence and MRI tests,the Fe_(3)O_(4)-Rh6G NPs are potential dual-mode probes for MRI contrast agents and fluorescence probes with high biocompatibility for early-stage tumor detection.

Rhodamine 6G-based Chemosensor for the Visual Detection of Cu2＋ and Fluorescent Detection of Hg2＋ in Water

A novel water soluble chemosensor 1 based on rhodamine 6G spirolactam scaffold has been synthesized and characterized.Upon addition of a wide range of the environmentally and biologically relevant metal ions,chemosensor 1 shows a colorimetric selective Cu2＋ recognition from colorless to pink confirmed by UV-Vis absorption spectral changes,while it also exhibits a fluorometric selective Hg2＋ recognition by fluorescence spectrometry.An absorption enhancement factor over 17-fold with 1-Cu2＋ complex and a fluorescent enhancement factor over 45-fold with 1-Hg2＋ complex were observed.Their recognition mechanisms were assumed to be a 1：1 stoichiometry for 1-Cu2＋ complex and a 1：2 stoichiometry for 1-Hg2＋ complex,respectively,which were proposed to be different ligation leading to the ring-opening of rhodarnine 6G spirolactam.Furthermore,the detection limits for CU2＋ or Hg2＋ were 3.3 × 10-8 or 1.7x 10-7 mol/L,respectively.

Direct measurement of the Raman enhancement factor of rhodamine 6G on graphene under resonant excitation

Graphene substrates have recently been found to generate Raman enhancement. Systematic studies using different Raman probes have been implemented, but one of the most commonly used Raman probes, rhodamine 6G （R6G）, has yielded controversial results for the enhancement effect on graphene. Indeed, the Raman enhancement factor of R6G induced by graphene has never been measured directly under resonant excitation because of the presence of intense fluorescence backgrounds. In this study, a polarization-difference technique is used to suppress the fluorescence background by subtracting two spectra collected using different excitation laser polarizations. As a result, enhancement factors are obtained ranging between 1.7 and 5.6 for the four Raman modes of R6G at 611, 1,183, 1,361, and 1,647 cm-~ under resonant excitation by a 514.5 nm laser. By comparing these results with the results obtained under non-resonant excitation （632.8 nm） and pre-resonant excitation （593 nm）, the enhancement can be attributed to static chemical enhancement （CHEM） and tuning of the molecular resonance. Density functional theory simulations reveal that the orbital energies and densities for R6G are modified bv ~raphene dots.

Manipulation of interfacial thermal conductance via Rhodamine 6G

Interfacial thermal conductance plays a sig- nificant role in the heat transfer efficiency of nanoscale systems. The thermal conductance across Al/SiO_2 inter- faces, which is subjected to the change in concentration of sandwiched Rhodamine 6G solution, is measured with time domain transient thermoreflectance technique. The thermal conductance of the interface between Al and SiO_2 logarithmically decreases with an increase in the concen- tration of the Rhodamine 6G solution. This study reveals that heat transport efficiency across an interface can be conveniently manipulated according to the demand of thermal engineering by introducing organic moleculars between both sides of the interface.

Green Synthesis, Characterization and Photophysical Properties of Rhodamine Derivatives

Rhodamine 6G-chromone-derived compounds RD1 - RD4 have been synthesized by condensation of rhodamine 6G hydrazide and substituted chromone aldehydes in ethanol using microwave-assisted reaction. The structures of these synthesized rhodamine 6G derivatives were confirmed by proton nuclear magnetic resonance (1H-NMR), carbon nuclear magnetic resonance (13C-NMR), and high-resolution mass spectra data (HRMS). Colorimetric and photophysical studies show the synthesized compounds selectively detect copper (II) ion in aqueous acetonitrile solution.

Preparation of nano-structured Ag solid materials and application to surface-enhanced Raman scattering

Silver nano-particles with average diameter of about 60 nm were compacted in a high-strength mold under different pressures at 523 K to produce nano-structured Ag solid materials. The structure and characteristic of the nano-structured Ag solid materials (NSS-Ag) were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectrometer. The NSS-Ag could be used as highly efficient surface-enhanced Raman scattering (SERS) active substrates. The common probe molecules Rhodamine 6G (R6G, 1×10-10 mol/L) were used to test the SERS activity on these substrates at very low concentrations. It is found that the SERS enhancement ability is dependent on the density of NSS-Ag. When the relative density of NSS-Ag is 83.87%, the materials reveal great SERS signal.

Lasing dynamics study by femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy

Femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy （FNOPAS） is a versatile technique with advantages of high sensitivity, broad detection bandwidth, and intrinsic spectrum correction func- tion. These advantages should benefit the study of coherent emission, such as measurement oflasing dynamics. In this letter, the FNOPAS was used to trace the lasing process in Rhodamine 6G （R6G） solution and organic semiconductor nano-wires. High-quality transient emission spectra and lasing dynamic traces were acquired, which demonstrates the applicability of FNOPAS in the study of lasing dynamics. Our work extends the application scope of the FNOPAS technique.

Determination of heavy metal ion in landfill leachate with solvent extracting ＆ fluorescence quenching method

Add the masking agent and biscyclohexanoneoxalyldihydraone into the diluted clarificd liquid of the landfill leachate which was treatmented by digestion and centrifugal filtration to complexate all heavy metal ion in the trcatmented liquid, and extracted using CHCl3 many time, then it were demasking and decomposing respectively, and adjusted different pH and formed Me^n＋-PAN coordination compound when these metal ion reaction with PAN. The Fluoresence quenching of Rh6G （λex/λem=543mn/558nm） when the metal ion coordination compound was add into the Rh6G solution step by step, the quenching intensity was directly proportional to the concentration of the metal ion in the certain range. So a new method of fast and simple for determination of trace metal ion in landfill lcachate was established to determine metal ion in sample of different landfill leachate in Three Gorge Water Reservoir, and comparison the classic assay method with satisfactory results.

Molecular interactions induced collapse of charge density wave quantum states in 2H tantalum disulfide nanosheets

2H-tantalum disulfide(2H-TaS_(2))is a layered metallic transition metal dichalcogenide(TMD)that has recently been studied from the perspective of new physics phenomena,including simultaneous lattice distortion and charge density modulation known as the charge density wave(CDW)phase.Here we explored the collapse of CDW states in few-layer 2H-TaS_(2)induced by molecular interactions using Raman spectroscopy.Our results indicate that the CDW states disappear in few-layer 2H-TaS_(2)with rhodamine 6G(R6G)adsorbed due to the charge transfer,which is reflected by the change of behaviors of lattice vibrational modes in 2HTaS_(2).We observed the 2-phonon mode that signifies the CDW formation in 2H-TaS_(2),becomes a phonon-hardened mode when R6G molecules are absorbed on its surface.R6G adsorption further induces the breakdown of the Raman polarization selection rule in 2H-TaS_(2),which results in the alteration of the A_(1g)phonon mode polarization state of 2H-TaS_(2).This study can shed light not only on the underlying mechanisms of CDW states but also on controlling the CDW states under a variety of environmental conditions.

Silver nanocubes monolayers as a SERS substrate for quantitative analysis

Surface-enhanced Raman scattering(SERS)is a powerful spectroscopic tool in quantitative analysis of molecules,where the substrate plays a critical role in determining the detection performance.Herein,a silver nanocubes/polyelectrolyte/gold film sandwich structure was prepared as a reproducible,highperformance SERS substrate by the wate r/oil inte rfacial assembly method.In addition to the hot spots on the nanocubes surface,the edge-to-edge interspace of the Ag nanocubes led to marked enhancement of the SERS intensity,with a limit of detection of 10~(11)mol/L and limit of quantitation of 10~(10)mol/L for crystal violet.When rhodamine 6 G and crystal violet were co-adsorbed on the Ag nanocube surfaces,the characteristic SERS peaks of the two molecules remained well resolved and separated,and the peak intensities varied with the respective concentration,which could be exploited for concurrent detection of dual molecules.Results from this work indicate that organized ensembles of Ag nanocubes can serve as effective SERS substrate can for sensitive analysis for complex molecular systems.

Enhanced photodegradation activity of ZnO:Eu3+and ZnO:Eu3+@Au 3D hierarchical structures

In this work the flower-like hierarchical structures(HS) based on 3 D pristine ZnO,ZnO:Eu^3+ and ZnO:Eu^3+ @Au were successfully obtained by a template-free solvothermal and deposition-precipitation method.The decolorization/photodegradation of these structures towards model organic dye(rhodamine 6 G) was studied.The synthesized ZnO-based HS were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),UV-vis and photoluminescence(PL) spectroscopies.The proposed synthesis approaches allow to obtain highly crystalline 3 D ZnO,ZnO:Eu^3+ and ZnO:Eu^3+ @Au composites.Results of scanning microscopy show that ZnO flower-like HS are assemblies from smaller components,forming larger ones,the whole ZnO structure was approximately 3 μm.Au nanoparticles(size^10 nm)are successfully deposited on ZnO HS surface.Luminescent studies show that ZnO is an ideal matrix for incorporation of Eu^3+ ions in broad concentration range(Eu^3+=1.0 at%-5.0 at%) with an efficient red luminescence.The strong UV emission in ZnO,as well as ZnO;Eu^3+HS is observed under 325 nm excitation.Doping of ZnO HS matrix by Eu^3+ions leads to the red shift of deep level emission peak(DLE).The PL intensity reaches the maximum up to 5 at% Eu^3+.The photocatalytic properties of ZnO and ZnO:Eu^3+ @Au HS were investigated under UV-Vis light irradiation towards rhodamine 6 G.The obtained results demonstrate the synergetic effect of the deposited gold nanoparticles and Eu3^+ doping on photocatalytic activity of ZnO:Eu^3+@Au HS in comparison to pristine ZnO and ZnO:Eu^3+ HS.

A Highly Selective and Sensitive Ratiometric Fluorescent Probe for pH Measurement Based on Fluorescence Resonance Energy Transfer

Fluorescein-rhodamine 6G（Flu-Rh） was synthesized and used as the fluorescence probe for pH measurement based on fluorescence resonance energy transfer（FRET）. In the probe, fluorescein fluorophore and pH-sensitive rhodamine 6G hydrazide were used as FRET donor and acceptor, respectively. The values of acidity constant（pKa） and fluorescence quantum yield（Ф） of Flu-Rh were 3.71 and 0.72, respectively. The fluorescence efficiency of Flu-Rh remains almost constant when the pH value of the sample solution changed 10 times in a range of 4.78-7.03 continuously. The present probe is simple and easy-to-use for the pH measurement in acidic media.

Synthesis and application of highly sensitive fluorescent probe for Hg2＋ regulated by sulfur

Rhodamine-based fluorescent probe is widely used in chemical analysis, environmental analysis and life sciences area due to their excellent optical properties. Based on the thiophilic property of Hg2＋, using C = S structural motif as the core segment, our group have designed and synthesized three novel probes containing cinnamyl aldehyde with different substituents, exhibiting high selectivity and excellent sensitivity. The structure-property relationships of these probes have been investigated that the optical change caused by electron withdrawing effect and heavy atom effect. Furthermore, these Hg2＋ probes could be applied in living mice imaging, which provide a promising tool for quantitative mercury（Ⅱ） ion imaging in living organism.

A simple strategy for constructing acylhydrazone photochromic system with visible color/emission change and its application in photo-patterning

As a potential photochromic system,acylhydrazones exhibit many outstanding adva ntages including low cost,simple synthesis and high modifiability compared with some classic photochromic systems.However,the absorption wavelengths of acylhydrazones usually locate in ultraviolet regio n,which makes the band separation between the absorbance maxima of its irradiated and unirradiated forms cannot be observed by naked eyes and greatly limits their practical applications.In this work,a simple strategy for constructing acylhydrazone photochromic system with visible color/emission change is provided.Rhodamine 6 G hydrazine-2-aldehyde-pyridine Schiff base(compound 3)is designed and synthesized by combining acylhydrazone with Rhodamine 6 G structure.The introduction of Rhodamine 6 G moiety to 3 not only makes it remain all the advantages of acylhydrazone photochromic system but also exhibits visible photo-induced color/emission changes both in solution and in a solid matrix.Moreover,3 exhibits reversible photochromic property with good fatigue re sistance,which makes it an excellent candidate for p hoto-patterning.