Sabri Alpaydin

Kinetic Study of Hg(II) Transport Through a Bulk Liquid Membrane Containing Ester Derivative of bis‐Calix[4]arene

Abstract A kinetic study of Hg(II) transport from an aqueous donor solution into an aqueous acceptor solution through a bulk liquid membrane containing N,N′‐bis[carbonylmethoxy(5,11,17,23‐tetra‐tert‐butyl‐25,26,27‐tris‐(ethoxycarbonyl‐methoxy)calix(4)arenyl)]‐1,2‐diaminoethane as a carrier was studied. The kinetic parameters (k 1d, k 2m, k 2a, t max, R m max, J d max, J a max) for the transport were investigated in terms of the effect of temperature, the stirring rate, the carrier concentration, and the type of solvent. In this study, the pseudo‐first‐order apparent rate constant of the interfacial transport of the Hg(II) is determined by using the spectrophotometric method. The kinetics of the transport was analyzed in the formalism of two consecutive irreversible first‐order reactions. The membrane entrance and exit rate constants were increased with increasing of temperature, stirring rate, and carrier concentration. The membrane entrance and exit rate constants depended on the type of solvent and was found to be in the order of CH2Cl2 > CHCl3 > CCl4. The activation energy values are calculated as 25.50 ± 2.20 and 45.62 ± 4.38 kJ mol−1 for extraction and reextraction, respectively. The values of the calculated activation energy indicate that the process is diffusionally controlled by species.

Graphene-based hybrid for enantioselective sensing applications

Chirality is a major field of research of chemical biology and is essential in pharmacology. Accordingly, approaches for distinguishing between different chiral forms of a compound are of great interest. We report on an efficient and generic enantioselective sensor that is achieved by coupling reduced graphene oxide with γ-cyclodextrin (rGO/γ-CD). The enantioselective sensing capability of the resulting structure was operated in both electrical and optical mode for of tryptophan enantiomers (D-/L-Trp). In this sense, voltammetric and photoluminescence measurements were conducted and the experimental results were compared to molecular docking method. We gain insight into the occurring recognition mechanism with selectivity toward D- and L-Trp as shown in voltammetric, photoluminescence and molecular docking responses. As an enantioselective solid phase on an electrochemical transducer, thanks to the different dimensional interaction of enantiomers with hybrid material, a discrepancy occurs in the Gibbs free energy leading to a difference in oxidation peak potential as observed in electrochemical measurements. The optical sensing principle is based on the energy transfer phenomenon that occurs between photoexcited D-/L-Trp enantiomers and rGO/γ-CD giving rise to an enantioselective photoluminescence quenching due to the tendency of chiral enantiomers to form complexes with γ-CD in different molecular orientations as demonstrated by molecular docking studies. The approach, which is the first demonstration of applicability of molecular docking to show both enantioselective electrochemical and photoluminescence quenching capabilities of a graphene-related hybrid material, is truly new and may have broad interest in combination of experimental and computational methods for enantiosensing of chiral molecules.