Photolysis Dynamics Laser Chemistry Lab

This study discusses the prospect of using biomass waste material, such as Cassia fistula (golden shower) fruit, as a carbon precursor in the development of new carbon material for the sustainable electrochemical sensor application. We successfully synthesized platinum-rhenium nanoparticles decorated on a porous activated carbon (Pt-Re NP/PAC) nanocomposite through the incorporation of metal precursors such as platinum(II) acetylacetonate (Pt(acac)2) and dirhenium decacarbonyl (Re2(CO)10) via a facile thermal reduction process. A variety of physicochemical and electrochemical methods were employed to characterize the morphology, structural, and electrochemical properties of the Pt-Re NP/PAC material. We then looked into the analytical behavior and applications of GCE modified with Pt-Re NP/PAC (Pt-Re NP/PAC/GCE) for the determination of furazolidone (chemotherapy drug) by employing different voltammetric techniques. The influence of experimental conditions such as scan rate, pH, accumulation time, amount of the modifier, and sample concentration on the peak current of the furazolidone was studied. The proposed drug sensor exhibited a wide linear range (WLR) for furazolidone in 0.05 M phosphate-buffered saline (PBS, pH 7.0) from 1.0 to 299 μM with a limit of detection (LOD) of 75.5 nM and appreciable sensitivity (5.52 μA μM-1 cm-2) which were calculated from linear sweep voltammetry (LSV). In addition, these analytical parameters including WLR, sensitivity, and LOD were estimated to be 0.2-117.7 μM, 19.20 μA μM-1 cm-2, and 20.8 nM and were obtained using differential pulse voltammetry (DPV). Therefore, the prepared Pt-Re NP/PAC modified sensor could be a potential candidate for the determination of furazolidone in pharmaceutical formulation, human urine, and blood serum samples, and the results are appreciable. Copyright © 2020 American Chemical Society.

Rotational energy transfer (RET) by Ar collisions within the v′ = 0 level of the SH A2Σ+ state is probed using a laser-induced dispersed fluorescence technique, following photodissociation of H2S at 248 nm. The Ar pressure is adjusted appropriately to allow for significant observation of the single-collision induced RET process. The spin-resolved and spin-averaged rate constants are then evaluated with the aid of a kinetic model under single-collision conditions. The theoretical counterparts are calculated using a quantum scattering method, in which a newly fitted potential energy function is based on ab initio potential energy surface reported previously. The experimental and theoretical kinetic data are essentially consistent in the trend of N and ΔN dependence. Several propensity rules are found in the RET collisions. For instance, for ΔN = 1, 2, and 3, the rate constants decrease with increasing N or ΔN. Given a fixed ΔN, the rate constants of the same initial N in the downward transition appear to be larger than those in the upward transitions. In ΔN = 0, the F2 → F1 transitions prevail over the F 1 → F2 transitions (F1 = N + 1/2, F 2 = N - 1/2), whereas in ΔN ≠ 0, the fine-structure- conserving collisions are more favored than the fine-structure-changing collisions. The principle of microscopic reversibility is also examined for both experimental and theoretical kinetic data, showing that translational energies of the RET collisions are close to thermal equilibrium at room temperature. The propensity rules may be rationalized according to this principle. © 2010 the Owner Societies.

The multiple sensing capabilities of molybdenum disulfide quantum dots (MoS2 QDs) towards metal ions were scrutinized by tuning their surface functional groups. The MoS2 QDs surface was individually modified with thiol-containing capping agents to form carboxylic-, amine- and thiol-functionalized MoS2 QDs (MoS2/COOH, MoS2/NH2 and MoS2/SH) by the facile hydrothermal method. Each as-prepared QDs exhibits strong excitation wavelength dependent fluorescence behavior. The design of MoS2 QDs based metal ion sensor was implemented based on the fluorescence turn-on mechanism. These MoS2/COOH, MoS2/NH2 and MoS2/SH QDs sensors exhibit superior performance towards the highly selective detection of Co2+, Cd2+ and Pb2+ ions, respectively, due to the varied association of each functional group towards metal ions. The resultant detection limit of Co2+, Cd2+ and Pb2+ was evaluated to be 54.5, 99.6 and 0.84 nM, respectively, and the related fluorescence turn-on mechanism is verified unambiguously. The binding energies were calculated for QDs with metal ions pairs and the results lent support to the determined sensitivity. The as-prepared QDs were also successfully demonstrated to detect the above metal ions in real water samples. While becoming potential candidates in the chemosensors based on the fluorescence probe, these surface modified MoS2 QDs can offer an excellent sensing capability for specific metal ions with extremely high selectivity.

Acid-functionalized mesoporous carbons (AF-MPCs) have been synthesized and used as adsorbents for removal of an azo dye, Eriochrome Black-T (EBT), from aqueous solution. To generate acid surface functionalities, mesoporous carbons (MPCs) were treated with sulfuric acid. Characterization of the samples was analyzed by XRD, Raman spectra, N 2 adsorption-desorption, FE-TEM, TGA, and FT-IR studies. The adsorption studies were carried out under various parameters, such as pH, adsorbent dosage, contact time, initial dye concentration solution temperature, and salt concentration. The results showed that the EBT adsorption onto samples was affected by the pH of solution; the maximum EBT ion adsorption took place at pH 1; and the adsorption uptake was increased with an increase in the initial dye concentration. Moreover, the mechanism of adsorption was investigated using kinetic, diffusion, and isotherm models. The best fit was obtained by the Langmuir model with high correlation coefficients (R 2 = 0.9463) with a maximum monolayer adsorption capacity of 117.0 mg·g -1 . The adsorbed anionic EBT dye molecules were eluted by ethanol solvent with the recovery percentage of 98%. Moreover, this study demonstrates that AF-MPCs can be successfully used as a low-cost adsorbent for the removal of EBT from aqueous solutions. © 2019 American Chemical Society.