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An ultrasound-assisted dispersive liquid-liquid microextraction by solidifying floating organic droplets, coupled to a form of temperature-programmed gas chromatography flame ionization detection, has been developed for the extraction and determination of thymol and carvacrol. This method utilizes undecanol as the extraction solvent, offering advantages such as facilitating phase transfer through solidification and enhancing solvent-focusing efficiency. The optimal gas chromatography conditions include a sample injection volume of 0.2 µL, a split ratio of 1:10, and a flow rate of 0.7 mL min -1 . The extraction conditions entail an extraction solvent volume of 20 µL, a disperser solvent (acetone) volume of 500 µL, pH 7.0, 7.0% NaCl (3.5 M), a sample volume of 5.0 mL, an ultrasound duration of 10 min, and a centrifuge time of 7.5 min (800 rpm). These conditions enable the achievement of a high and reasonable linear range of 3.5 to 70. 0 μg mL -1 for both thymol and carvacrol. The detection limits are found to be 0.95 and 0.89 μg mL -1 , respectively, for thymol and carvacrol. The obtained relative standard deviations, 2.7% for thymol and 2.6% for carvacrol, demonstrate acceptable precision for the purpose of quantitative analysis.

Amino-functional silica-coated N-doped carbon dots (NH 2 -SiO 2 -CDs) were covalently modified by l-tryptophan (chiral selector) by producing an amide bond between carboxyl groups of L-try and amino groups of NH 2 -SiO 2 -CDs to develop a novel high throughput chiral nanoprobes (L-try-CONH-SiO 2 -CDs) for highly sensitive and enantioselective quantification of S-/R-mandelic acid (S-/R-Man). The method showed a great difference between S- and R-isomers (enantioselectivity coefficient = 4.17) due to the ultra-stability of the Meisenheimer complex that was formed between S-isomer and nanoprobe (K S-Man /K R-man  = 2122.7, where K is the binding-constant). At optimal experimental conditions, two linear ranges of 0.5-25.0 (LOD of 0.05 μM) and 0.5-22.0 μM (LOD of 0.27 μM) for S- and R-Man, respectively, along with an enhanced sensitivity toward S-isomer (about 5.7-fold higher than R-isomer) were attained. High selectivity for the determination of mandelic acid was achieved compared to metal ions, amino acids, and sugars that commonly coexist with it. Intra-day as well as inter-day assays, respectively, showed RSD values of about 3.2 and 3.9%. The mechanistic studies were performed for proving the enantioselective behavior of the developed nanoprobe. The method was then used for S-/R-mandelic acid determination in bio-samples. The figures of merit for the method were found to be better than those already reported for enantioselective detection of R-/S-Man., Competing Interests: Declaration of competing interest The Authors declare that there are no known conflict of interest., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Nanocubic MoS 2 -FeS 2 , as a photocatalyst, was synthesized with high catalytic active edges and high specific surface areas with the capability of absorbing visible light. The results showed that the photocatalytic efficiency of nanocubic MoS 2 -FeS 2 for adsorption/degradation of methylene blue (MB) as well as the reduction of Cr(VI) was high. The adsorption process was found to follow a kinetic model of a pseudo-second-order kind ( Q = 464 mg g e.cal = 464 mg g -1 = 340 mg g Q e.cal = 340 mg g -1 . The photodegradation process was achieved by holes. It was found that the photodegradation rate constant of MB by MoS 2 -FeS 2 (0.203 min -1 ) was about 22 times higher than that of MoS 2 (0.0091 min -1 ). The percent apparent quantum yield for photoreduction of Cr(VI) to Cr(III) using MoS 2 -FeS 2 (5.7%) was about 33 times higher than utilizing MoS 2 (0.1709%). Therefore, the synergistically prolonged visible-light harvesting as well as the photocarrier diffusion length proved that MoS 2 -FeS 2 nanotubes can effectively be utilized in environmental pollutant's remediation.