Quantum chemical studies on structural, vibrational, nonlinear optical properties and chemical reactivity of indigo carmine dye

Synthesis of azole-functionalized microspheres and their adsorption properties for gold(I) thiosulfate complex

Gold is an essential precious metal with exceptional properties. Thus, azole-functionalized microspheres (PS-3-AT) were prepared by grafting 3-amino-1,2,4-triazole (3-AT) into chloromethyl polystyrene beans (PS-Cl) and used as a novel adsorbent for the gold(I)-thiosulfate complex. The effects of initial gold concentration, thiosulfate concentration, temperature, and pH on the Au(S₂O₃)₂^3- adsorption process over PS-3-AT were investigated. In this study, PS-3-AT was considered an effective adsorbent for Au(I) recovery from a thiosulfate solution, demonstrating that PS-3-AT completely adsorbed Au(S₂O₃)₂^3- with an adsorption capacity of 39.8 kg t^-1 achieved during multistage adsorption testing. Through adsorption kinetics and isotherm studies, the pseudo-second-order and Freundlich models well describe the adsorption process of PS-3-AT for Au(I), also suggesting the exothermic nature. Furthermore, SEM, FT-IR spectroscopy, BET, and XPS techniques were used to characterize the surface and structural properties of the samples. Notably, a reliable adsorption mechanism was developed that proposed the formation of the -NH⁺Cl^- group during the grafting process and Cl^- exchange with Au(S₂O₃)₂^3- to achieve Au(I) capture. Moreover, quantum chemistry calculations and the independent gradient model (IGM) were adopted to visualize the interaction between PS-3-AT and Au(S₂O₃)₂^3- at an atomic level. The desorption ratio was 97.9% while 2 M NaCl was used as the desorbent, and regeneration with PS-3-AT was achieved after five cycles. Therefore, the facile synthetic method and adsorption properties of PS-3-AT for the gold(I)-thiosulfate complex are satisfactory, which is valuable for the development of thiosulfate gold leaching technologies.

Estimating hydroxyl/epoxy ratio in graphene oxide through adsorption experiment and semiempirical GFN2-xTB quantum method

CONTEXT

The reactivity of graphene oxide (GO) with amines is related to the ring-opening of the epoxy groups in its basal surface, as addressed experimentally. Therefore, discussing the hydroxyl/epoxy ratio for GO is relevant to improve the characterization of such material. As the adsorption of Methylene Blue into GO is related to a graphene derivative's oxidation degree (OD), we combined adsorption experimental information and theoretical data to estimate the hydroxyl/epoxy ratio. The theoretical data were compared to the experimental adsorption of Methylene Blue and Indigo Carmine into GO synthesized in our department. Our results show GO systems with hydroxyl/epoxy ratios equal to 0.7, 0.8, and 0.9 are the most representative in which the most coherent model corresponds to OH/EP=0.8 for our GO previously synthesized.

METHODS

The GO-MODEL software was developed in the present work to obtain cartesian coordinates of GO systems. We investigated 204 systems comprising models with 486 carbon atoms with the GFN2-xTB semiempirical quantum method. The supramolecular arrangements were constructed with the recently developed UD-APARM program.

A new 1,2,3-triazole and its rhodamine B derivatives as a fluorescence probe for mercury ions

A newly synthesized compound, 5-methyl-1-phenyl-1H-1,2,3-triazole-4- carboxylic acid (MPC) was analyzed for its quantum chemical parameters and theoretical spectrum by computational chemistry. The calculated spectrum was in accord with the experimental measurements in a great degree. Then MPC was successfully designed and synthesized to a novel rhodamine B derivative RMPC. The RMPC exhibited about a 4000-fold increase in fluorescence intensity in the presence of Hg²⁺ ions over most other competitive metal ions. The triazole appended colorless chemodosimeter RMPC turns to pink upon the complex formation only with Hg²⁺ ions as a 1: 2 M ratio and enables naked-eye detection. The coordination mechanism of turning on/off fluorescence for Hg²⁺ ions were well proposed by explaining Hg²⁺ inducing the ring-opened rhodamine B moiety. The fluorescence imaging experiments of Hg²⁺ in HeLa cell demonstrated that the probe was labeled and it could be used in biological systems.

A triazole-based fluorescence probe for detecting Hg2+ ions and its biological application

A new compound, ethyl 5-phenyl-2-(p-tolyl)-2H-1,2,3-triazole-4-carboxylate was successfully introduced and synthesized as a novel rhodamine B derivative named REPPC, and characterized by ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, and high resolution mass spectrometry (HRMS). It showed an obvious fluorescence and UV-visible light absorption enhancement towards Hg²⁺ ion without interference from common metal ions in N,N-dimethylformamide-H₂ O (pH 7.4). The spirolactam ring moiety of rhodamine in REPPC was converted to the open-ring form generating a 1:1 complex with the intervention of a mercury ion, verified by electrospray ionization-mass spectroscopy testing and density functional theory calculation. REPPC was used to visualize the level of mercury ions in living HeLa cells with encouraging results.

The computational and experimental studies on a 1, 2, 3-triazole compound and its special binding to three kinds of blood proteins

A newly synthesized compound, ethyl 5-phenyl-2-(p-tolyl)-2H-1, 2, 3-triazole-4-carboxylate (EPPC) may be considered as a drug candidate and was exploited to study the structural and spectral properties by using quantum chemical calculation and multiple spectroscopic techniques. The results on theoretical spectrum of EPPC were consistent with experimental spectrum in great degree. In addition, EPPC has been as a special probe and investigated on the interactions with three kinds of blood proteins including human serum albumin (HSA), human immunoglobulin (HIgG) and bovine hemoglobin (BHb) by using UV-Vis, fluorescence spectroscopy and molecular modeling, respectively. Changes in various fluorescence and UV-Vis spectra were observed upon ligand binding along with a remarkable degree of fluorescence enhancement on complex formation under physiological condition with binding constant about 10⁵ order of magnitudes, which caused the variations of conformation and microenvironment of these proteins in aqueous solution. The obtained results from the thermodynamic parameters calculated according to the van't Hoff equation indicated that the entropy change ΔS° and enthalpy change ΔH° were found to be 0.168 KJ/mol K and 22.154 KJ/mol for EPPC-HSA system, 0.284 KJ/mol K and 54.408 KJ/mol for EPPC-HIgG system, and 0.228 KJ/mol K and 37.548 KJ/mol for EPPC-BHb system, respectively, which demonstrated that the primary binding pattern is determined by hydrophobic interaction. The results of docking and molecular dynamics simulation using three proteins crystal models revealed that EPPC could bind to three proteins well into hydrophobic cavity, which showed good consistence with the spectroscopic measurements.Communicated by Ramaswamy H. Sarma.