Green approach for in-situ growth of highly-ordered 3D flower-like CuS hollow nanospheres decorated on nitrogen and sulfur co-doped graphene bionanocomposite with enhanced peroxidase-like catalytic activity performance for colorimetric biosensing of glucose.

We describe a green and facile hydrothermal route to synthesize highly ordered 3D flower-like hierarchical CuS hollow nanospheres@N-S-rGO bionanocomposite used to detect glucose. After synthesis and comprehensive characterization of all potential catalysts, the peroxidase-like activity of 3D CuS NSs@N-S-rGO is compared extensively with pure 3D CuS NSs, N-S-rGO, N-rGO, and GO to monitor the effect of each modification and treatment on their catalytic properties. The results indicate promising peroxidase activity of 3D CuS NSs@N-S-rGO by possessing the highest catalytic activity and the Michaelis constant of ~93.5 times lower and 9.7 times higher than that of reported for HRP, respectively. The bionanocomposite is used to detect glucose in serum with and without light. The results show a remarkable enhancement in the limit of detection for glucose from 0.3 µM to 0.075 µM (40 folds) with visible light that can be attributed to the fast electron transfer on the surface of 3D CuS NSs@N-S-rGO and the synergistic interaction of 3D CuS NSs and N-S-rGO. The method was further applied to the colorimetric detection of glucose in human serum and showed high selectivity. Our result also show that this method based on 3D CuS NSs@N-S-rGO is economical, reliable, feasible, and highly efficient.

Cr(OH)3-NPs-CNC hybrid nanocomposite: a sorbent for adsorptive removal of methylene blue and malachite green from solutions.

In this article, Cr(OH)3 nanoparticle-modified cellulose nanocrystal (CNC) as a novel hybrid nanocomposite (Cr(OH)3-NPs-CNC) was prepared by a simple procedure and used as a sorbent for adsorptive removal of methylene blue (MB) and malachite green (MG) from aqueous solution. Different kinetic models were tested, and the pseudo-second-order kinetic model was found more suitable for the MB and MG adsorption processes. The BET and Langmuir models were more suitable for the adsorption processes of MB and MG. Thermodynamic studies suggested that the adsorption of MB and MG onto Cr(OH)3-NPs-CNC nanocomposite was a spontaneous and endothermic process. The maximum adsorption capacities for MB and MG were reached 106 and 104 mg/g, respectively, which were almost two times higher than unmodified CNC. The chemical stability and leaching tests of the Cr(OH)3-NPs-CNC hybrid nanocomposite showed that only small amounts of chromium were leached into the solution.

Comparative study of photocatalytic activities of Zn5(OH)8Cl2·H2O and ZnO nanostructures in ciprofloxacin degradation: Response surface methodology and kinetic studies.

Zinc hydroxide chloride monohydrate (Zn5(OH)8Cl2·H2O) and zinc oxide (ZnO) nanostructures were synthesized by simple precipitation and pyrolysis methods, respectively and characterized by means of various instrumental methods. Their photocatalytic efficiencies as two potential photocatalysts for photodegradation of a clinical wastewater, ciprofloxacin (CIP), were probed and compared. The results indicated that in comparison with Zn5(OH)8Cl2·H2O nanoplates, the photodegradation was 1.4 times faster when using ZnO nanoparticles as well as higher removal percentage. The optimum pH obtained was 8 that it is typically found for hospital wastewater. Analysis of variance (ANOVA) exhibited high R2 values, high F-values, very low P-values, and non-significant lack of fit values demonstrating good correlation between experimental and predicted values of the response for both catalysts. Kinetic studies identified first order model as a suitable model for description of photodegradation processes for both nanosized Zn5(OH)8Cl2·H2O and ZnO. The chemical oxygen demand (COD) removal of 43.30 and 56.30% were obtained after 24h for Zn5(OH)8Cl2·H2O nanoplates and ZnO nanoparticles, respectively. Ultra-performance liquid chromatography method coupled with tandem mass spectrometry (UPLC-MS/MS) for the determination of CIP degradation products has been used. Taken together, ZnO nanoparticles were more efficient in CIP removal due to some properties as in higher surface area and lower band gap.

Comments on the paper "Adsorptive removal of methylene blue by rhamnolipid-functionalized graphene oxide from wastewater".

Hereby, two mistakes of writing and applying pseudo-first order kinetic and Brunauer-Emmett-Teller (BET) isotherm models for adsorption systems have been pointed out. In this discussion, it is recommended and suggested to cite any kind of model e.g. kinetic, thermodynamic, isotherm, and so on from original papers of the mentioned models as well as a careful writing in order to prevent from repeating such inadvertent mistakes to publish more valuable and readable papers.

Efficient method for determination of methylene blue dye in water samples based on a combined dispersive solid phase and cloud point extraction using Cu(OH)2 nanoflakes: central composite design optimization.

A new method was developed for the efficient spectrophotometric determination of methylene blue (MB) dye in solutions. The method is based on a combined dispersive solid phase and cloud point extraction using Cu(OH)2 nanoflakes (as an adsorbent). Cu(OH)2 nanoflakes were synthesized by facile and fast methods and characterized using various techniques. The developed method is based on the adsorption of MB on the Cu(OH)2 nanoflakes and transfer into a surfactant-rich phase using Triton X-114 as a nonionic surfactant. Subsequently, MB dye is desorbed from Cu(OH)2 nanoflakes using a mixture of nitric acid and methanol solution and determined by UV-Vis spectrophotometry. The effects of pH, amount of Cu(OH)2 nanoflakes, volume (concentration of Triton X-114), and temperature were investigated by designing experiments using response surface methodology (RSM). A quadratic model was utilized to predict the variables. Analysis of variance (ANOVA) was applied for the analysis of variables and their interactions, and optimal conditions were established. The results demonstrated logical agreement between experimental and predicted values of the response owing to high F value, low P value, and low lack-of-fit. The calibration graph was linear in the range of 2.0-350.0 µg L-1 of MB dye with a correlation coefficient (R) of 0.9996. The limits of detection and quantification were found to be 0.65 and 2.05 µg L-1, respectively. The developed method was successfully applied to different water samples, thereby confirming the applicability of the approach. Graphical Abstract Proposed procedure.