Reversible Colorimetric Sensor for Moisture Detection in Organic Solvents and Application in Inkless Writing

Colorimetric sensors based on Sudan-III (<b>1</b>) and Alizarin red S (<b>2</b>) have been developed for the detection of a trace amount of water in organic solvents such as THF, acetone, acetonitrile, and DMSO. The deprotonated (anionic) forms of <b>1</b> and <b>2</b> namely <b>1.F</b> and <b>2.F</b> are reprotonated by using a trace amount of water. Deprotonation of <b>1</b> and <b>2</b> was obtained by using fluoride anion. Test papers of <b>1.F</b> and <b>2.F</b> in organic solvents with and without moisture showed dramatic changes in color. Receptor <b>1.F</b> exhibits high sensitivity for water in acetone and THF with the detection limit as low as 0.0042 and 0.0058 wt %. Remarkably, probes <b>1.F</b> and <b>2.F</b> are reversible in nature both in solution and in test strips. <b>1.F</b> and <b>2.F</b> are reversible and reusable for sensing moisture in the organic solvents with high selectivity, high sensitivity, and fast response. The reversible moisture sensor <b>1.F</b> has also been used for application in inkless writing

Selective Detection of Cyanide in Water and Biological Samples by an Off-the-Shelf Compound

The simple off-the-shelf chemical 6,7-dihydroxycoumarin (<b>1</b>) based copper complex (<b>1·Cu</b>^<b>2+</b>) has been used for the selective detection of toxic cyanide in aqueous medium. The DFT calculation confirms the binding behavior between <b>1</b> and Cu²⁺ (2:1) and the red shift in the UV–vis spectrum with copper ion was confirmed by the decrease in energy between HOMO–LUMO band gaps. The cyanide sensing in water was confirmed by both absorption and emission spectral studies. Cyanide ion showed 13-fold increments in fluorescent intensity in emission spectrum via displacement of copper from <b>1·Cu</b>^<b>2+</b>. The limit of detection of CN^– in water is 5.77 μM; <b>1·Cu</b>^<b>2+</b> also applicable for the detection of cyanide in fresh mouse serum with detection limit of 14.4 μM. The cell images showed that <b>1·Cu</b>^<b>2+</b> could be used to detect intracellular CN^–

Selective Detection of H₂S by Copper Complex Embedded in Vesicles through Metal Indicator Displacement Approach

A new approach for the detection of hydrogen sulfide (H₂S) was constructed within vesicles comprising phospholipids and amphiphilic copper complex as receptor. 1,2-Distearoyl-<i>sn</i>-glycero-3-phosphocholine (DSPC) vesicles with embedded metal complex receptor (<b>1.Cu</b>) sites have been prepared. The vesicles selectively respond to H₂S in a buffered solution and show colorimetric as well as spectral transformation. Other analytes such as reactive sulfur species, reactive nitrogen species, biological phosphates, and other anions failed to induce changes. The H₂S detection is established through a metal indicator displacement (MIDA) process, where Eosin-Y (EY) was employed as an indicator. Fluorescence, UV–vis spectroscopy, and the naked eye as the signal readout studies confirm the high selectivity, sensitivity, and lower detection limit of the vesicular receptor. The application of vesicular receptors for real sample analysis was also confirmed by fluorescence live cell imaging

Investigation of the Role of 3<i>d</i>‑4<i>d</i> Elements in a Disordered Double Perovskite toward Efficient Photocatalytic Energy Conversion and Electrochemical Energy-Storage Behaviors

Toward the goal of achieving green and sustainable energy conversion and storage behaviors, double perovskite oxide materials are always pronounced not only due to their exciting properties but also for their advanced catalytic and electroactive nature. In order to understand the factual role of either 3d or 4d metal ions in double perovskites toward energy conversion and storage applications, herein we have demonstrated three ruthenium-based disordered double perovskites, namely, Ca2MnRuO6 (CMRO), Ca2Mn1.25Ru0.75O6 (CMRO-1), and Ca2Mn0.75Ru1.25O6 (CMRO-2), by varying the Mn/Ru stoichiometry. The well-characterized phase-pure polycrystalline oxides are employed as efficient photocatalysts for visible light-driven water oxidation in a neutral pH medium. Even a small quantity of the present catalyst can evolve larger amounts of oxygen compared to reported photocatalysts. Furthermore, electrochemical supercapacitor performance has been accomplished by the CMRO compounds and reduced graphene oxide (rGO) composite electrodes. The electrochemical measurement reveals that the as-fabricated CMRO-2 oxide-rGO composite electrode possesses much higher capacitance of 598.8 F/g at a scan rate of 2 mV/s in 0.5 M H3PO4 electrolyte solution compared to 0.5 M H2SO4 common electrolyte medium. Remarkably, the CMRO-2 and rGO composite electrode exhibited a maximum energy density of 431.1 Wh/kg at a power density of 14.4 W/kg in 0.5 M H3PO4 electrolyte. Notably, the slight variation of Mn/Ru concentration in title perovskite structures commendably affects the photocatalytic water oxidation and electrochemical supercapacitor performances. Such exciting structure–activity phenomena of 3d-4d transition metal-based oxide materials are also validated through density functional theory calculations