Influence of water on molecular forms of rhodamine B in dip-coated thin films

Dip-coated thin films including rhodamine B have been prepared using the sol-gel reaction of tetraethyl orthosilicate under relative humidity of 30% and 60%. They have been aged under relative humidity of 20%, 60%, and 95% for 5 days. According to the absorption spectra, just after the preparation of the films and under higher humidity, a larger amount of the dimers (H-and J-types) were formed in the films. Five days after the preparation of the films and aged under higher humidity, the H-dimer increased. On the other hand, the J-dimer increased, regardless of humidity under which the films were aged.     

Photophysics and photochemistry of nalidixic acid

The photophysics and photochemistry of nalidixic acid (NA) were studied as function of pH and solvent properties. The ground state of NA exhibits different protonated forms in the range of pH 1.8-10.0. Fluorescence studies showed that the same species exist at the lowest singlet excited state. Absorption experiments were carried out with NA and with the methylated analog of nalidixic acid (MNE) in different organic solvents and water pH 3, where the main species corresponds to that protonated at the carboxylic group. These studies and the DFT calculation of torsional potential energy profiles suggest that the most stable conformation of the NA in nonprotic solvents corresponds to a closed structure caused by the existence of intramolecular hydrogen bond. Absorption and fluorescence spectra were studied in sulfuric acid solution. The pK value (Ho -1.0) found in these conditions was attributed to the protonation of the 4' keto oxygen atom of the heterocyclic ring. Theoretical calculations (DFT/B3LYP/6-311G*) of the energies of the different monoprotonated forms of the NA and Fukui indexes (f(x)-) showed that the species with the proton attached to 4' keto oxygen atom is the most stable of all the cationic forms. MNE and enoxacin also showed the protonation of the 4' keto oxygen atom with similar pK values. The photodecomposition of NA is dependent on the medium properties. Faster decomposition rates were obtained in strong acid solution. In nonprotic solvents, a very slow decomposition rate was observed.     

Surface-bound humic acid increased rhodamine B adsorption on nanosized hydroxyapatite

In this study, humic acid-bound nanosized hydroxyapatite (HA-nHAP) was developed as a novel adsorbent, and the potential of using HA-nHAP for the adsorption of rhodamine B (RhB) from aqueous solution as functions of pH, adsorbent dosage, contact time, ionic strength, and temperature was investigated. The results indicated that the HA binding significantly increased the adsorption of RhB due to the introduction of abundant negatively charged functional groups. The adsorption capacity of HA-nHAP for RhB was found to be pH-dependent, and the optimal pH value was found to be 6.0. The adsorption equilibrium data obeyed Sips and Freundlich isotherms and the kinetic data were well described by the Elovich kinetic model. According to the Sips equation, the maximum adsorption capacity for RhB was 24.12 mg/g. The temperature and ionic strength experiment showed that they both had an effect on the adsorption capacity of HA-nHAP. Thermodynamic study confirmed that the adsorption was a spontaneous, endothermic, and more random arrangement process. The present investigation showed that HA-nHAP is a promising adsorbent for the removal of RhB from aqueous solution.     

Dimeric states of rhodamine B

Aggregation of the coloured neutral and cationic forms of rhodamine β in aqueous solution has been studied. The formation constants and absorption of the dimers were determined. The geometric disposition of monomers in both aggregates and the nature of the association forces are discussed. Trimers are not formed.     

Fluorescence of the lactone form of rhodamine B

A quantum-chemical investigation of spectral fluorescent properties of the lactone form of rhodamine B molecule is conducted with allowance for its interaction with polar solvent. It is shown that within the model, two emitting states emerge that can be attributed to the zwitterion and lactone forms of the rhodamine molecule based on their nature and energy. A lack of interaction between the emitting states is observed in the internal conversion channel. The rate constants of photophysical processes are estimated. The quantum yields of dual fluorescence are calculated.     

The rhodamine B intercalation of montmorillonite

Using photometric methods the dissociation constants and weight fractions of rhodamine B dimer in water solutions at different concentrations were determined. The montmorillonite (SWy) samples were fully intercalated with rhodamine B (RhB) solutions at various monomer/dimer ratios. The amount of rhodamine B in fully intercalated montmorillonite (RhB-SWy) increases with increasing concentration of dye in water solutions, i.e., with increasing dimer/monomer ratio. The sum of exchangeable guest cations in RhB-SWy is approximately constant (0.900 meq g(-1)) for all samples, because RhB-SWy samples with prevailing dye monomer also contain higher amounts of non-exchanged alkali elements. The experimental data are supported by calculated structure models that illustrate the changes in RhB-SWy structure depending on monomeric and/or dimeric arrangement of guests. The analysis of the calculated structure models confirmed the existence of two phases with different basal spacings, d approximately 1.8 and approximately 2.3 nm, revealed by X-ray diffraction.     

About the microdetermination of thallium with rhodamine B

Summary The spectrophotometric determination of thallium with Rhodamine B as Rhodamine B-thallium(III) tetrabromide using extraction of the complex into benzene was investigated. For the oxidation of thallium(I) ceric sulphate was used. The optimum conditions and interferences of some ions for the determination of microgram amounts of Tl are described. The sensitivity is 0.0028 g of Tl per 1 ml of benzene. 5 g of Tl can be determined with a precision of ±2.4%. The method described may be applied in trace analyses of thallium, where sulphuric-nitric acid is used for the decomposition of the sample.

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Zusammenfassung Ein spektrophotometrisches Verfahren zur Thalliumbestimmung mit Rhodamin B wird beschrieben, bei dem der gebildete Thallium(III)-komplex mit Benzol extrahiert wird. Zur Oxydation von einwertigem Thallium wird Cer(IV)-sulfat verwendet. Die optimalen Bedingungen sowie Störungen durch Fremdionen bei der Bestimmung von g-Mengen Thallium werden beschrieben. Die Empfindlichkeit betrÄgt 0,0028 g Tl/1 ml Benzol. 5 g Tl können mit einer Genauigkeit von±2,4% bestimmt werden. Das beschriebene Verfahren kann bei der Spurenanalyse von Thallium in solchen Proben benutzt werden, die mit Schwefel- und SalpetersÄure aufgeschlossen worden sind.

     

Sensitive flotation-spectrophotometric method for the determination of vanadium (IV) with 3,5-dinitrosalicylic acid and rhodamine B

Vanadium(IV) is determined by reaction with 3,5-dinitrosalicylic acid and rhodamine B in weakly acidic medium. The flotation of the ternary ion-association complex is carried out with cyclohexane followed by dissolution in acetone for subsequent spectrophotometric determination. The molar absorptivity is 5.91×10⁵ l mole^–1 cm^–1 at 555 nm. Beer's law is obeyed in the range 0.05–1.5 g vanadium(IV) in 25 ml. The method is selective for vanadium(IV) in the presence of sodium fluoride and has been applied to standard reference materials.     

Photophysics and Photochemical Studies of the Vitamin B6 Group and Related Derivatives

The photophysics and photochemical properties of vitamin B6 constituents and analogs were studied as function of pH and solvent. The p K of the phenolic oxygen and the pyridine ring nitrogen depends on the electron donor-acceptor ability of the 4-substituent, and agrees with the calculated proton affinity. For all studied compounds, the fluorescence properties showed that the phenolic oxygen is 8 units more acidic in the lowest singlet excited state than in the ground state. The pyridine N-atom is slightly more basic in the excited state. At pH of biological significance, pH 6–8, pyridoxamine and 4-pyridoxic acid are the more efficient chromophores with higher fluorescence yield and longer lifetime. Spectroscopic studies showed that the tautomeric equilibrium depends on the nature of the 4-substituent. The quenching of the singlet excited state of pyridoxamine and 4-pyridoxic acid by amino acids, free or in a peptide, and DNA bases at pH 7 was studied by time-resolved fluorescence techniques. The quenching rate constants are well correlated with the redox properties of the pyridoxinic compound and amino acids, and are related to the free energy change in the electron transfer process. Guanosine and pyrimidine bases also are efficient quenchers, involving an electron transfer reaction.     

Visible light induced photocatalytic reaction of rhodamine B dye via 12-tungstosilicic acid in water

Using 12-tungstosilicic acid (SiW124-) as the catalyst, rhodamine B (RhB) dye in an aerated aqueous solution can undergo an effective photocatalytic stepwise N-deethylation process under visible light irradiation, and dioxygen is reduced to hydrogen peroxide by the reducedSiW12 4-. This provides the potential for moving polyoxometalate-based photocatalytic processes from the near-UV into the visible region of the spectrum.     

罗丹明B共振光散射法测定马丙共聚物

建立了共振光散射法测定马丙共聚物的新方法.在B-R缓冲溶液中,罗丹明B与马丙共聚物结合形成离子缔合物并产生强烈共振光散射增强效应,其最大散射峰位于372 nm.研究了pH、罗丹明B浓度、反应时间和温度对散射峰的影响,结果表明在pH1.5～2.0的B-R缓冲体系中,1.0×10-3 mol /L罗丹明B用量为1.5 mL...     

Significant improved selectivity of a fluorescent sensor for Al3+ made from a fluorinated rhodamine B Schiff base

Research on Chemical Intermediates - Two rhodamine B-based Schiff bases (RBF, RBC) with different substituent groups (–F and –COOH) have been synthesized. In order to study the sensing...     

Controllable size, shape and morphology of molybdic acid self-aggregated with rhodamine B to construct functional material

Controllable size, shape and morphology of rhodamine B/molybdic acid (RBMA) aggregates were prepared from a self-aggregation reaction in a molybdic acid and rhodamine B (RhB) coexisting solution. Nanodisks, as well as microcrystal rods and polyhexagonal microcrystal rods, have been obtained in conventional bulk solutions at different temperatures. Large-sized network microcrystal rods and branched fractal aggregates constructed with nanosubunits after the nucleation duration of an ice-water-cooled process have also been achieved under the evaporation-enhanced conditions on glass substrates. The factors affecting the size, shape and morphology of RBMA aggregates including temperature, nucleation and growth, and processing conditions are discussed. The results show that photofunctional molecules (RhB) modified the surface of the molybdic acid particles and influenced their self-aggregation. The temperature and nucleation play key roles in the formation of RBMA aggregates. The structures of RBMA aggregates were characterized by X-ray diffraction, infrared spectra and elemental dispersive spectroscopy. The results indicate that the aggregates show the characteristics of RhB-mediated hydrated ammonium molybdenum bronze with the metastable hexagonal phase. Visible-light-induced electrons transfer reactions in the RBMA aggregates from rhodamine B molecules to MoO3 matrixes were measured by UV-vis spectra and X-ray photoelectron spectra, and the fluorescent image was observed by laser scanning confocal microscopy.     

Level decay and orientational kinetics of the rhodamine B monomer and dimer

The population kinetics and the rotational diffusion of the rhodamine B monomer and dimer were measured by using picosecond pulses from a mode-locked Nd : YAG laser to induce and time resolve the concentration-dependent transient absorption saturation of various aqueous solutions of this organic dye.     

电化学法研究罗丹明B与壳聚糖的相互作用

用电化学方法研究了罗丹明B与壳聚糖(CS)的相互作用,在pH 3.0的NaAc-HAc缓冲溶液中,罗丹明B在-0.67 V(vs.SCE)处有一个灵敏的线性扫描二阶导数极谱波,当加入一定量的CS后,反应体系的电化学信号发生变化,结果表明,罗丹明B与壳聚糖可形成结合物,结合物的峰电流在一定范围内与壳聚糖的浓度成正比,因而可用于测定壳聚糖的含量.此外,实验还探讨了罗丹明B与壳聚糖的最大结合数,为进一步研究有机染料与多糖的结合提供了理论基础.     

罗丹明B内酯单晶的生长及晶体结构

从含有罗丹明B的溶胶-凝胶中首次水热合成了罗丹明B内酯的单晶,并测定了其晶体结构。每个不对称单位含有两个独立分子。     

Behaviour of rhodamine B in aqueous LiCl solution

Absorption, pH and electric conductance of rhodamine BLiClH₂O solutions are examined. The obtained results show that aqueous rhodamine B has a tendency to dimerize by the addition of LiCl. Other features on the structural properties of rhodamine B in aqueous LiCl solutions are discussed briefly.