Electrochemical monitoring of photoelectrocatalytic degradation of rhodamine B using TiO2 thin film modified graphite electrode

A commercially available TiO₂ powder (Degussa P25) has been used to prepare thin films on graphite plates. The photoelectrochemical degradation of rhodamine B was investigated using this photoelectrode. The effects of applied potential, pH, and initial rhodamine B concentration on the photoelectrocatalytic (PEC) degradation of rhodamine B using ultraviolet illuminated TiO₂/graphite (TiO₂/C) thin film electrode were examined and discussed. Also, direct photolysis, electrochemical oxidation, photocatalytic, and PEC degradation of rhodamine B were compared. Results show that the best responses for PEC are obtained at applied potential of 1.2?V vs. reference electrode, pH?4.0, and initial rhodamine B concentration of 4.2?mg?L^?1.     

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.     

Rhodamine 101 Conjugates of Triterpenoic Amides Are of Comparable Cytotoxicity as Their Rhodamine B Analogs

Pentacyclic triterpenoic acids (betulinic, oleanolic, ursolic, and platanic acid) were selected and subjected to acetylation followed by the formation of amides derived from either piperazine or homopiperazine. These amides were coupled with either rhodamine B or rhodamine 101. All of these compounds were screened for their cytotoxic activity in SRB assays. As a result, the cytotoxicity of the parent acids was low but increased slightly upon their acetylation while a significant increase in cytotoxicity was observed for piperazinyl and homopiperazinyl amides. A tremendous improvement in cytotoxicity was observed; however, for the rhodamine B and rhodamine 101 conjugates, and compound 27, an ursolic acid derived homopiperazinyl amide holding a rhodamine 101 residue showed an EC₅₀ = 0.05 µM for A2780 ovarian cancer cells while being less cytotoxic for non-malignant fibroblasts. To date, the rhodamine 101 derivatives presented here are the first examples of triterpene derivatives holding a rhodamine residue different from rhodamine B.     

A novel and selective spectral method for the determination of trace chlorine in water basing on the resonance scattering effect of rhodamine B-I(3) association nanoparticles

In Na₂HPO₄-citric acid buffer solution, Cl₂ can oxidize I⁻ to form I₂ and then it reacts with excess I⁻ to form I₃⁻. The I₃⁻ combines respectively with rhodamine dyes, including rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG) and rhodamine S (RhS), to form association particles which give stronger resonance scattering (RS) effect at 400 nm. The RS intensity of the RhB, b-RhB, RhG and RhS systems is proportional to chlorine concentrations in the range of 0.008-1.74, 0.019-1.33, 0.021-2.11 and 0.019-2.04 μg/mL Cl₂, respectively. The detection limits of the systems were 0.0020, 0.0048, 0.0063 and 0.0017 μg/mL, respectively. In them, the RhB system has good stability and high sensitivity, and has been applied to the analysis of chlorine in drinking water, with satisfactory results which is in agreement with that of the methyl orange (MO) spectrophotometry.     

Co3O4-Bi2O3 heterojunction: An effective photocatalyst for photodegradation of rhodamine B dye

Recently, the research on the remediation of aqueous organic pollutants over visible-light-active photocatalysts has got much attention. Therefore, this study reports the fabrication of visible-light-active Co₃O₄-Bi₂O₃ heterojunction photocatalyst for the photodegradation of rhodamine B dye. The Co₃O₄-Bi₂O₃ heterojunction was synthesized by the coprecipitation method and characterized by XRD, EDS, SEM, TEM, TGA, and FTIR. The as-prepared Co₃O₄-Bi₂O₃ heterojunction was utilized as a photocatalyst for the abatement of rhodamine B dye. It was observed that Co₃O₄-Bi₂O₃ showed the best catalytic performance with ～92% degradation of rhodamine B dye than Co₃O₄ and Bi₂O₃ with 14 and 34% removal of rhodamine B dye, respectively. The rate constant for Co₃O₄-Bi₂O₃ catalyzed photodegradation of rhodamine B was 6 times and 3 times higher than the rate constant for Co₃O₄ catalyzed and Bi₂O₃ catalyzed photodegradation of rhodamine B, respectively. The as-prepared Co₃O₄-Bi₂O₃ exhibited the highest catalytic performance at pH 8.     

A new and sensitive resonance-scattering method for determination of trace nitrite in water with rhodamine 6G

In the medium HCl–KI–rhodamine dye, NO₂^– reacts with excess I^– to form I₃^– and the I₃^– and rhodamine dye combine to form an association particle which gives three resonance-scattering (RS) peaks at 320 nm, 400 nm, and 595 nm. In systems containing rhodamine 6G (Rh6G), rhodamine B (RhB), rhodamine S (RhS), and butyl rhodamine B (BRhB) the resonance scattering intensity at 400 nm is proportional to nitrite concentrations in the range 2.3–276 ng mL^–1, 9.2–184 ng mL^–1, 9.2–184 ng mL^–1, and 9.2–92 ng mL^–1, respectively. Because of the high sensitivity, wide linear range, and good stability of the Rh6G system, it has been used for determination of nitrite in water samples, with satisfactory results. The spectral results have been used to verify that the formation of (Rh6G·I₃)_n association particles and their interface with the system are main factors that cause the RS enhancement.     

A new sensitive and selective fluorescence method for determination of chlorine dioxide in water using rhodamine S

A new simple, selective and sensitive method for the determination of trace chlorine dioxide in water has been developed, based on the oxidation by chlorine dioxide to reduction the fluorescence of rhodamine dyes in ammonia-ammonium chloride buffer solution. Four rhodamine dyes systems such as rhodamine S, rhodamine G, rhodamine B and butyl-rhodamine B were tested. The rhodamine S system is the best, with a linear range of 0.0060-0.450 μg mL⁻¹ and a detection limit of 0.0030 μg mL⁻¹ ClO₂. It was applied to the determination of chlorine dioxide in synthetic samples and real samples, with satisfactory results. This method has good selectivity, especially, other chlorine species such as chlorine, hypochlorite, chlorite and chlorate do not interfere the determination. The mechanism of fluorescence reduction was also considered.     

Raman spectra in the electronic excited state: CARS spectra of lasing rhodamine 6G

By choosing ω₂ (4880 Å) preresonant with the S₁S₀ transition of rhodamine 6G, and ω₁ (4537 Å) resonant with the S₂S₁ absorption, the resonant CARS spectra for lasing rhodamine 6G in methanol, ethanol and acetonitrile have been observed in the 1500–1650 cm^?1 range. Strong positive bands, attributed to CARS from the S₁ state, replace the negative ground state preresonant bands as the S₀ state saturates at high laser beam power densities. A water solution behaves quite differently, possibly as a result of strong association of water with rhodamine in the excited state.     

Highly selective coextraction of rhodamine B and dibenzyl phthalate based on high‐density dual‐template imprinted shells on silica microparticles

A simple one‐pot approach based on molecularly imprinted polymer shells dispersed on the surface of silica for simultaneous determination of rhodamine B and dibenzyl phthalate (DBzP) has been developed. Highly dense molecularly imprinted polymer shells were formed in the mixture of acetonitrile and toluene by the copolymerization of methacrylic acid and ethylene glycol dimethacrylate, as well as two templates, rhodamine B and dibenzyl phthalate, directed by the vinyl end groups functional monolayer at surface silica microspheres after 3‐methacryloxypropyl trimethoxysilane modification. The obtained imprinted polymer shells showed large average pore diameter (102.5 nm) and about 100 nm shell thickness. The imprinted particles also showed high imprinting factor (α_RhB = 3.52 and α_DBzP = 3.94), rapid binding kinetics, and excellent selective affinity capacity for rhodamine B and dibenzyl phthalate containing another three competitors in mixed solution. Moreover, the imprinted particles coupled with ultra high performance liquid chromatography was successfully applied to simultaneous analysis of rhodamine B and dibenzyl phthalate in two spiked beverage samples with average recoveries in the range of 88.0−93.0% for rhodamine B and 84.0–92.0% for dibenzyl phthalate with the relative standard deviation lower than 5.1%.     

Thermal behavior of rhodamine 6G-TiO2 microspherical particles

An aerosol procedure was used for the preparation at room temperature of rhodamine 6G-doped TiO₂ spherical particles. The luminescence properties and in particular the lifetime of the trapped rhodamine 6G were studied by analysis of fluorescence decay kinetics which yields information about the entrapping medium. Lifetimes were resolved using variable-frequency (0.01–120 MHz) phase and modulation data. This information is important to understand the identity of the different rhodamine 6G emitting species, and the mechanism of interaction of the molecules with the surface. The evolution of the excitation and fluorescence spectra of rhodamine 6G-doped particles with thermal treatment at 70°C, and drying time was also evaluated.     

Chemiluminescence behavior of sodium hydrogen carbonate in the potassium permanganate-hydrogen peroxide reaction

Chemiluminescence (CL) phenomenon of hydrogen peroxide with potassium permanganate in the presence of sodium hydrogen carbonate was reported. Effects of the surfactant on the CL system were investigated. Nonionic surfactants could effectively increase the CL signal. Radical scavengers and organic reagents such as nitro blue tetrazolium chloride (NBT), cytochrome c, sodium azide, ascorbic acid, thiourea, tert-butanol and dimethyl sulphoxide were used to study the emitting species. CL emission spectrum was recorded and the results showed that the maximal emission wavelengths of NaHCO₃-H₂O₂-KMnO₄ system were 440 and 634 nm. The mechanism was discussed based on electron spin resonance (ESR) spectra, fluorescence spectra and UV-vis absorption spectra. The addition of rhodamine B or uranine into this CL system enhanced the CL signal. It was due to part of the energy transfer from singlet oxygen and excited triplet dimers of two CO₂ molecules to rhodamine B or uranine. The CL could be induced by excited rhodamine B or uranine.     

Resonance CARS spectra of the lowest excited singlet states of rhodamines

The resonance CARS spectra of the S₁ states of rhodamine 6G, rhodamine B and sulforhodamine were obtained by choosing ω₁ resonant with the S₁ ← S₀ and S₃ ← S₁ transitions simultaneously and by varying the laser beam power density of ω₁ or ω₂. The vibrational frequencies for the S₀ and S₁ states are similar, implying that the structure of the S₁ state is not distorted significantly.     

A simple and sensitive resonance scattering spectral method for determination of hydroxyl radical in Fenton system using rhodamine S and its application to screening the antioxidant

Based on resonance scattering (RS) effect of rhodamine dye association particles, a new resonance scattering method for the determination of hydroxyl free radical from Fenton reaction was developed. In HCl-NaAc buffer solution, the OH of Fenton reaction oxidized the excess I⁻ to I₃⁻. The I₃⁻ combined, respectively, with rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG) and rhodamine S (RhS) to form association particles that exhibit stronger resonance scattering effect at 420 nm and 610 nm. However, the RS peak at about 610 nm was interfered with its synchronous fluorescence peak at 580 nm for RhB, 580 nm for b-RhB, 560 nm for RhG and 560 nm for RhS, respectively. The concentration of H₂O₂ in the range of 0.648-21.6 μmol/L, 0.423-13.0 μmol/L, 0.216-13.0 μmol/L and 0.092-13.0 μmol/L was linear to its resonance scattering intensity at 420 nm. Its detection limit was 0.15 μmol/L, 0.10 μmol/L, 0.092 μmol/L and 0.044 μmol/L, H₂O₂, respectively. This RhS RS method was applied to selection of the antioxidant, with satisfactory results.     

Synthesis,chemical reactivity,and photophysical properties of 2′,7′ phenylated rhodamine dyes

While exploring water soluble rhodamine based fluorescent polymeric systems for biological imaging applications we came across new rhodamine derivatives that possess interesting optical properties. We report the synthesis of three different 2′,7′-diphenylated rhodamine derivatives (1–3) with distinct photophysical properties. The three rhodamine derivatives differ by the number of methyl groups present on the nitrogens and their absorption maxima are red-shifted on increased methylation. We observed an unusual inertness of these compounds toward traditional DCC–DMAP esterification conditions, which we attribute to the ease of lactonization in the presence of even minute amounts of the nucleophile/base DMAP (pK_a = 9.2). Synthesis of acrylate esters was successfully accomplished using MSNT (1-(Mesitylene-2-sulfonyl)-3-nitro-1,2,4-triazole) coupling conditions using a much milder nucleophile/base, for example, N-methyl imidazole (pK_a = 6.95).     

Solvent Dependence of the Fluorescence Lifetimes of Xanthene Dyes

Fluorescence lifetimes of Ave representative xanthene dye species-the rhodamine B zwitterion (RB⁼), the rhoda-mine B cation (RB⁺), the rhodamine 6G cation (R6G⁺), the rhodamine 101 zwitterion (R101) and the fluorescein dianion (F^2-)-were measured in H₂O, D₂O and in a series of alcohol solvents ranging from methanol to octanol. The lifetimes of both RB⁼ and RB⁺ increased markedly as the solvent was varied from water to octanol. In contrast, the lifetimes of R6G⁺ and R101± decreased slightly over the alcohol series and that of F^2- increased only slightly in the same series. For all the dyes studied the fluorescence lifetimes observed in D₂O were slightly longer than those in H₂O. Possible causes for the variations observed are discussed.     

TiO2-石墨烯光催化剂：制备及引入石墨烯的方法对光催化性能的影响

利用溶胶-凝胶法原位制备了二氧化钛/石墨烯(TiO2-GE)复合光催化剂,研究了纯TiO2以及不同方法制备的TiO2-GE复合光催化剂对亚甲基蓝及罗丹明B光催化降解性能。结果表明:石墨烯的引入提高了TiO2的光催活性,这主要是得益于石墨烯优异的电子传输性能及较好吸附特性。不同方法制备TiO2-GE复合催化剂的光催化活性也存在较大差别。原位制备的TiO2-GE复合光催化剂表现出最佳的光催化活性。     

Preparation of mesoporous TiO2/CNT nanocomposites by synthesis of mesoporous titania via EISA and their photocatalytic degradation under visible light irradiation

Stabilized mesoporous TiO₂ was synthesized by evaporation induced self assembly (EISA) method and mechanically incorporated into single-walled carbon nanotubes (SWCNT) with different ratios. The physicochemical properties of the nanocomposites (mesoporous TiO₂/SWCNT) materials were investigated by Brunauer–Emmett–Teller (BET) measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), photoluminescence (PL) and ultraviolet–visible (UV–Vis) spectroscopy measurements. The catalytic activity of mesoporous TiO₂ and nanocomposites were assessed by examining the degradation of rhodamine B as model aqueous solution under visible light. CNTs are facilitating the photocatalytic activity of mesoporous TiO₂ in the degradation of rhodamine B efficiently.     

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 nitrobenzene, 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 experimental data obtained for the relationship between interracial half-wave potential Δ^W_oφ° and pH are in agreement with the theoretical equation based on the mechanism, and the standard interfacial potential differences Δ^W_oφ° and standard Gibbs energies Δ^W_oG° are calculated by extrapolation. The effect of the nature of solvent on the transfer behavior and the stability of the interface have been discussed.     

Synthesis and spectral properties of perylene–rhodamine dyads with lipophilic dendritic auxiliaries

The present publication reports a new entry of perylene–rhodamine dyads, whose solubilities in organic solvents are enhanced by the lipophilic dendritic auxiliaries. Spectroscopic studies on these dyad systems have demonstrated that the intramolecular Förster resonance energy transfer (FRET) from the perylene donor to the rhodamine acceptor was activated upon protonation with either H₂SO₄ or TFA to result in drastic colour change of the fluorescence emissions. This phenomenon can be reasonably accounted for in terms of the switching behaviour of the FRET interactions, which is suppressed by disruptive interference from lone pair electrons of the amino moieties.     

Positively charged liposomes consisting of the KTTKS pentapeptide conjugated with rhodamine increase rhodamine toxicity in E. coli and zebrafish embryo

Liposomes composed of cell‐penetrating peptide derivatives increased transport across the cell membrane. Conjugating rhodamine to a cell‐penetrating peptide increased the toxicity of rhodamine in E. coli and zebrafish embryos. A similar total protein inhibition pattern with different intensities, indicating that the interaction pathways of the rho‐KTTKS‐CONH₂ monomer and liposomes were the same. It suggests that the rho‐KTTKS‐CONH₂ liposomes showed higher toxicity because better transport across the cell membrane increased the effective concentration inside cells. The staining of zebrafish embryos using rho‐KTTKS‐CONH₂ liposomes showed a longer retention time, suggesting that it can penetrate deeper tissues or organs in zebrafish.