Samrat Devaramani

Herein, we report a non-enzymatic paper-based device for selective electrochemical detection of creatinine. This work demonstrates three modification strategies adopted for the paper-based electrochemical sensing device (PESD) for the detection of creatinine. Copper, a non-enzymatic metal electrode, was fabricated on the Whatman paper without sophisticated instrumentation. The fabricated pristine non-enzymatic PESD could detect creatinine in the linear range 10 µM to 90 µM with a detection limit of 6.6 µM. Further, the electrode and Whatman paper were modified with silver to improve the sensitivity of PESD towards creatinine. Firstly, the working electrodes were modified by the Scotch tape strategy via galvanic displacement of Ag on Cu. The Ag-modified Cu electrodes were stuck on the Whatman paper, which sensitized the creatinine in the linear range 10 nM to 240 nM with a detection limit of 0.089 nM. Secondly, the Whatman paper was modified by mussel-inspired soak, polymerize, and then reduction of silver on the paper. The modified paper works similarly to the modified electrode with Ag in the linear range 10 nM to 90 nM with a detection limit of 2.5 nM. Further, the fabricated pristine PESD was tested for Jaffe’s inspired indirect electrochemical detection of creatinine in the linear range 10 µM to 100 µM with a detection limit of 6.4 µM. The sensitivity of the fabricated pristine PESD was improved from µM to nM by adopting modification strategies. The reported PESD with the least interference from the co-existing biomolecules has the potential applicability of monitoring creatinine in urine sample analysis. Graphical Abstract

Metal sulphides combined with graphene/reduced graphene oxide (rGO) represent a unique class of materials for hydrogen generation either through electrocatalytic or photo(electro) catalytic methods. Herein, we report a solvothermal synthesis of Cu₃SnS₄ decorated rGO resulting in a highly active electrocatalyst for hydrogen evolution reaction (HER) compared to its native Cu₃SnS₄. The Cu₃SnS₄‐rGO exhibited very low overpotential of 190 mV versus reversible hydrogen electrode (RHE), whereas Cu₃SnS₄ requires 250 mV versus RHE at a current density of 10 mA/cm². Tafel slope of Cu₃SnS₄‐rGO and Cu₃SnS₄ is about 64 and 76 mV/dec, respectively. This suggests that Cu₃SnS₄‐rGO is a better electrocatalyst when compared to Cu₃SnS₄ and follows mixed Volmer and Heyrovsky mechanism for HER.

The elimination of volatile organic solvents in organic synthesis is the most important goal in “Green” chemistry. We report a simple, efficient and facile method for the addition of progargyl bromide to carbonyl compounds using Mg metal as a mediator under solvent-free conditions which could regioselectively generate homopropargyl alcohols efficiently in good to excellent yields. The procedure has advantages such as short reaction time, operationally simple, excellent product yields, high regioselectivity and organic solvent-free.

The novel membrane test strip of phenolphthalein hydrazide (PH)‐polysulfone has been designed and demonstrated for Cu²⁺ ions detection. Before finding performance of membrane the studies with PH alone has been performed. Aqueous solutions of PH are colorless, but upon interaction with Cu²⁺ ions become pink (when 8.2 ≤ pH ≥ 12). The colorimetric change is initiated by the coordination of Cu²⁺ with PH as a polydentate ligand, opening the spirolactam ring that subsequently hydrolyses releasing phenolphthalein (P). Further membrane was preloaded with PH that could be used as a simple, low cost, and portable sensor for Cu²⁺ ions in environmental water samples. Given the detection limits of this sensor, a maximum response would warn the tester that Cu²⁺ concentrations were above safe drinking regulation values. Approximate concentrations can be determined via a color comparison chart.Different metal ions were tested in order to determine the chemodosimeters specificity, of the 12 tested ions only Hg²⁺ induced a similar molecular transformation (i.e., PH to P). The chemodosimeter allows the quantification of Cu²⁺ ions in the linear dynamic range of 0–22 μM. The Sandell sensitivity, limit of detection, limit of quantification, and relative standard deviation were found to be 0.276 μg/mL/cm², 0.279 μM, 1.674 μM, and 0.682% respectively. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

How to improve the accuracy of target detection substance in low-abundance and complex of real sample, which is still a major challenge in the analysis field. There is no doubt that the internal standard method is the best choice in the analysis methods. The internal standard method of ECL strategy can furnish more accurate detection results in the changeable complex environment, and it can dispel the primary vaguest interference in the system through the self-calibration of two emission spectrums. Herein, we effectually explored a strong and stable bimodal ECL system based on g-CNQDs as single luminophore in the presence of double co-reactants potassium persulfate (K2S2O8) and tetrabutylammonium bromide (TBAB) under the optimized conditions. ECL-1 at 2.82 V and ECL-2 at 1.73 V were observed when the potential was scanned between -3 and 3 V at the scan rate of 0.2 V•s-1. The ECL-1 was responding to the analyte i.e. ascorbic acid (AA) and the ECL-2 was not for a certain concentration of AA, hence, the developed bimodal ECL system was used as internal standard method for quantitative AA in human serum due to the different sensitivity of the double-peak ECL signals to the target analytes. The linear relationships was obtained based on the lnI (ECL-1/ECL-2) against the concentration of AA in the concentration range of 3.5 to 330 nM with a detection limit of 110 pM (S/N=3).

Recombination of photogenerated electron–hole pairs is extremely limited in the practical application of photocatalysis toward solving the energy crisis and environmental pollution. A rational design of the cascade system (i.e., rGO/Bi₂WO₆/Au, and ternary composites) with highly efficient charge carrier separation is successfully constructed. As expected, the integrated system (rGO/Bi₂WO₆/Au) shows enhanced photocatalytic activity compared to bare Bi₂WO₆ and other binary composites, and it is proved in multiple electron transfer (MET) behavior, namely a cooperative electron transfer (ET) cascade effect. Simultaneously, UV–vis/scanning electrochemical microscopy is used to directly identify MET kinetic information through an in situ probe scanning technique, where the “fast” and “slow” heterogeneous ET rate constants (K_eff) of corresponding photocatalysts on the different interfaces are found, which further reveals that the MET behavior is the prime source for enhanced photocatalytic activity. This work not only offers a new insight to study catalytic performance during photocatalysis and electrocatalysis systems, but also opens up a new avenue to design highly efficient catalysts in photocatalytic CO₂ conversion to useful chemicals and photovoltaic devices.