Fluorescence Spectral Study on the Rhodamine B-I_3^- Association Nanoparticle System and Its Analytical Applications

In acid medium, rhodamine B（RhB）, rhodamine S（RhS）, rhodamine 6G（RhG） and butyl rhodamine B（b-RhB） have a fluorescence peak at 580, 549, 553 and 580nm, respectively. BrO^-3 oxidizes excess I^- into I^-3 Rhodamine dyes combine I^-3 to form ion association nanoparticles, resulting in fluorescence quenching at 580, 549, 553 and 580 rim, respectively. The fluorescence quenching intensity is proportional to the concentration of BrO^-3 in the range of 0.020 4 - 0.710 μg/mL for RhB, 0.025 - 0. 512μg/mL for RhS, 0.025 - 0.260 μg/mL for RhG, 0.025 - 1.28μg/mL for b-RhB, respectively. In the four systems, RhB system has good stability and high sensitivity. Thus, a simple, sensitive fluorescence method was proposed for the determination of BrO^-3 in commercial bread additives and flours, with satisfactory results. The results of the fluorescence spectra and scan electron microscopy show that the formation of about 60 ran （RhB - I^-3） n association nanoparticles and the interface between the nanoparticles and solution are main factors that cause the fluorescence quenching.

A novel, simple and sensitive resonance scattering spectral method for the determination of chlorite in water by means of rhodamine B

A new resonance scattering method was proposed for the determination of chlorite, basing on the resonance scattering effect of rhodamine dye. In HCl-sodium acetate buffer solution, chlorite oxidizes 1- into 12 and the reaction of 12 and excess 1- results in If. It is respectively combined with rhodaminc dyes, including rhodamine B （RhB）, butyl rhodamine B （b-RhB）, rhodamine G （RhG） and rhodamine S （RhS）, to form association complex particles, which exhibit stronger resonance scattering （RS） effect at 400 nm. The chlorite concentration of ClO2 in the range of 0.00726-0.218 μg/ml, 0.0102-0.292 μg/ml, 0.00726-0.145 μg/ml and 0.0290- 0.174 μg/ml is respectively linear to the RS intensity of association complex particle systems at 400 nm for the RhB, b-RhB, RhG and RhS. The detection limits of the four systems were respectively 0.00436, 0.00652, 0.00580 and 0.01450μg/ml ClO2^-. In the four systems, the RhB system possesses good stability and high sensitivity. It has been applied to the analysis of chlorite in wastewater with satisfactory results.

Real-time in situ visualization of internal relative humidity in fluorescence embedded cement-based materials

The transmission and distribution of moisture in cement-based materials are of great significance to the properties and durability of materials. Traditional macro-humidity monitoring equipment in civil engineering cannot capture the microscale humidity inside cement-based materials in situ. In this paper, a method of using rhodamine 6G fluorescence to characterize the change in relative humidity in cement-based materials is proposed. Two kinds of moulding processes are designed, which are premixed and smeared after moulding, and the optimal preparation concentration is explored. The results showed that rhodamine 6G can reflect the relative humidity of cement-based materials in situ by its fluorescence intensity and had little effect on the hydration heat release and hydration products of cement-based materials;the fluorescence intensity was much higher when the internal relative humidity was 63% and 75%. The research results lead the application of polymer materials in the field of traditional building materials, help to explore the performance evolution law of cement-based materials in micro scale, and have important significance for the evolution from single discipline to interdisciplinary.

Synthesis and characterization of rare earth metal doped tungsten trioxide photocatalyst for degradation of Rhodamine B dye

Nowadays,it is concern for researchers that due to high recombination rate of photogenerated charge carriers in tungsten trioxide(WO_(3)) nanoparticles,the future applications are limited in the field of photocatalysis.Herein we attempt to synthesize tungsten trioxide nanoparticles with different doping concentrations of lanthanum i.e.2 wt%,4 wt%,6 wt% and 8 wt%.The synthesized samples were characterized by using various characterization techniques:X-ray diffraction(XRD),Raman spectroscopy,Fourier transform infrared spectroscopy(FTIR),photoluminescence spectra(PL),transmission electron microscopy(TEM),energy dispersive X-ray(EDX) and UV-Vis spectroscopy.WO_(3) retains its monoclinic structure even after doping which was confirmed by XRD analysis.FTIR helps to descry functional groups present in the samples.The size of nanoparticles was calculated by using TEM.EDX confirms the absence of any impurity in the synthesized samples.Raman spectroscopy confirms the presence of a large number of imperfections induced in the lattice of WO_(3).The rate of recombination was analyzed by photoluminescence(PL) spectroscopy and is minimum in 4 wt% doping of lanthanum.The optical bandgap was calculated using UV-Vis spectroscopy and becomes narrow along with the doping concentrations.Intriguingly,it is found that doping of La in WO_(3) has considerably ameliorate the photocatalytic activity by reducing rate of recombination due to the trapping of electrons by defects introduced in the lattice.Photocatalytic decolorization of Rhodamine B(RhB) dye was performed and the values of c/c_0 and rate constant(k) confirm that the 4 wt% doping shows maximum degradation efficiency.The kinetic study for photodegradation of Rhodamine B was done by using various kinetic models and results show that the reaction follows first order kinetics very well.Therefore,optimum doping of lanthanum increases the decolorization ability of WO_(3) towards RhB dye.

Detection of Gain Enhancement in Laser-Induced Fluorescence of Rhodamine B Lasing Dye by Silicon Dioxide Nanostructures-Coated Cavity

In this work, nanostructured silicon dioxide films are deposited by closed-field unbalanced direct-current （DC） reactive magnetron sputterin technique on two sides of quartz cells containing rhodamine B dye dissolved in ethanol with 10-5 M concentration as a random gain medium. The preparation conditions are optimized to prepare highly pure SiO2 nanostructures with a minimum particle size of about 20nm. The effect of SiO2 films as external cavity for the random gain medium is determined by the laser-induced fluorescence of this medium, and an increase of about 200% in intensity is observed after the deposition of nanostructured SiO2 thin films on two sides of the dye cell.

The ion transfer of the basic dye rhodamine B across the liquid-liquid interface of two immiscible solvents

The ion transfer of the basic dye rhodamine B at the interface between water and nitro- benzene,water and 1,2-dichloroethane,as well as water and nitrobenzene-chlorobenzene mixtures has been studied by cyclic voltammetry and chronopotentiometry with linear current scanning.A transfer mechanism of rhodamine B is proposed in terms of its electrochemical behavior,dissociation and distribution equilibria,and is ascribed as diffusion-controlled reversible process of rhodamine B.The ex- perimental data obtained for the relationship between interfacial half-wave potential ° and pH are in agreement with the theoretical equation based on the mechanism,and the standard interracial potential differences °and standard Gibbs energies G°are calculated by extrapolation.The effect of the nature of solvent on the transfer behavior and the stability of the interface have been dis- cussed.