Harnessing Environmental Sensitivity in SnSe-Based Metal-Semiconductor-Metal Devices: Unveiling Negative Photoconductivity for Enhanced Photodetector Performance and Humidity Sensing.

The extreme sensitivity of 2D-layered materials to environmental adsorbates, which is typically seen as a challenge, is harnessed in this study to fine-tune the material properties. This work investigates the impact of environmental adsorbates on electrical properties by studying metal-semiconductor-metal (MSM) devices fabricated on CVD-synthesized SnSe flakes. The freshly prepared devices exhibit positive photoconductivity (PPC), whereas they gradually develop negative photoconductivity (NPC) after being exposed to an ambient environment for ∼1 day. While the photodetectors based on positive photoconductivity exhibit a responsivity and detectivity of 6.1 A/W and 5.06 × 108 Jones, the same for the negative photoconductivity-based photodetector reaches up to 36.3 A/W and 1.49 × 109 Jones, respectively. In addition, the noise-equivalent power of the NPC photodetector decreases by 300 times as compared to the PPC device, which implies a prominent detection capability of the NPC device against weak photo signals. To substantiate the hypothesis that negative photoconductivity stems from the photodesorption of water and oxygen molecules on the dangling bonds of SnSe flakes, the flakes are etched along the most active planes (010) with a focused laser beam in an inert environment, which enhances responsivity by 43%, supporting negative photoconductivity linked to photodesorption. Furthermore, the humidity-dependent dark current variation of the NPC photodetectors is used to design a humidity sensor for human respiration monitoring with faster response and recovery times of 0.72 and 0.68 s, respectively. These findings open up the possibility of tuning the photoelectrical response of layered materials in a facile manner to develop future sensors and optoelectronic multifunctional devices.

Phosphorus-Doped Nickel Oxide Micro-Supercapacitor: Unleashing the Power of Energy Storage for Miniaturized Electronic Devices.

For an uninterrupted self-powered network, the requirement of miniaturized energy storage device is of utmost importance. This study explores the potential utilization of phosphorus-doped nickel oxide (P-NiO) to design highly efficient durable micro-supercapacitors. The introduction of P as a dopant serves to enhance the electrical conductivity of bare NiO, leading to 11-fold augmentation in volumetric capacitance to 841.92 Fcm-3 followed by significant enhancement of energy and power density from 6.71 to 42.096 mWhcm-3 and 0.47 to 1.046 Wcm-3, respectively. Theoretical calculations used to determine the adsorption energy of OH- ions, revealing higher in case of bare NiO (1.52 eV) as compared to phosphorus-doped NiO (0.64 eV) leading to high electrochemical energy storage performance. The as-designed micro-supercapacitor (MSC) device demonstrates a facile integration with the photovoltaic system for renewable energy storage and smooth transfer to external loads for enlightening the blue LED for ≈1 min. The choice of P-NiO/Ni not only contributes to cost reduction but also ensures minimal lattice mismatch at the interface facilitating high durability up to 15 K cycles along with capacitive retention of ≈100% and coulombic efficiency of 93%. Thus, the heterostructure unveils the possibilities of exploring miniaturized energy storage devices for portable electronics.

Porous Carbon Template Decorated with MOF-Driven Bimetallic Phosphide: A Suitable Heterostructure for the Production of Uninterrupted Green Hydrogen via Renewable Energy Storage Device.

Water splitting via an uninterrupted electrochemical process through hybrid energy storage devices generating continuous hydrogen is cost-effective and green approach to address the looming energy and environmental crisis toward constant supply of hydrogen fuel in fuel cell driven automobile sector. The high surface area metal-organic framework (MOF) driven bimetallic phosphides (ZnP2 @CoP) on top of CNT-carbon cloth matrix is utilized as positive and negative electrodes in energy storage devices and overall water splitting. The as-prepared positive electrode exhibits excellent specific capacitances/capacity of 1600 F g-1 /800 C g-1 @ 1A g-1 and the corresponding hybrid device reveals an energy density of 83.03 Wh kg-1 at power density of 749.9 W kg-1 . Simultaneously, the electrocatalytic performance of heterostructure shows overpotentials of 90 mV@HER and 204 mV@OER at current density of 10 and 20 mA cm-2 , respectively in alkaline electrocatalyzer. Undoubtedly, it shows overall water splitting with low cell voltage of 1.53 V@10 mA cm-2 having faradic and solar-to-hydrogen conversion efficiency of 98.81% and 9.94%, respectively. In addition, the real phase demonstration of the overall water-splitting is performed where the electrocatalyzer is connected with a series of hybrid supercapacitor devices powered up by the 6 V standard silicon solar panel to produce uninterrupted green H2 .

Electron deficient nonplanar ß-octachlorovanadylporphyrin as a highly efficient and selective epoxidation catalyst for olefins.

We have synthesized 2,3,7,8,12,13,17,18-octachloro-meso-tetraphenylporphyrinatooxidovanadium(iv) (VOTPPCl8) and characterized by various spectroscopic (UV-Vis, IR and EPR) techniques, MALDI-TOF mass spectrometry and elemental analysis. The DFT optimized structure of VOTPPCl8 in CH3CN exhibited a highly nonplanar saddle shape conformation of the porphyrin macrocycle. The cyclic voltammogram of VOTPPCl8 showed a 500 mV anodic shift in the first ring reduction potential and 220 mV in the first ring oxidation potential compared to VOTPP indicating the electron deficient nature of the porphyrin π-system and further proving the existence of a nonplanar conformation of the macrocycle in solution. Further, VOTPPCl8 exhibited very high thermal stability till 390 °C as indicated in its thermogram. The oxidation state of the metal ion (V(IV)) was confirmed by EPR spectroscopy and VOTPPCl8 exhibited an axial spectrum which corresponds to the axially compressed dxy(1) configuration. VOTPPCl8 was utilised for the selective epoxidation of various olefins in good yields with very high TOF numbers (6566-9650 h(-1)) in the presence of H2O2 as an oxidant and NaHCO3 as a promoter in a CH3CN/H2O mixture. The oxidoperoxidovanadium(v) species is expected to be the intermediate during the catalytic reaction which is probed by (51)V NMR spectroscopy and MALDI-TOF mass analysis. Notably, VOTPPCl8 is stable after the catalytic reaction and doesn't form a µ-oxo dimer due to the highly electron deficient nonplanar porphyrin core and can be reused for several cycles.

Mimicking peroxidase activity by a polymer-supported oxidovanadium(IV) Schiff base complex derived from salicylaldehyde and 1,3-diamino-2-hydroxypropane.

The polymer-supported oxidovanadium(IV) complex PS-[V(IV)O(sal-dahp)] (2) (PS=chloromethylated polystyrene crosslinked with 5% divinylbenzene, and H3sal-dahp=dibasic pentadentate ligand derived from salicylaldehyde and 1,3-diamino-2-hydroxypropane) was prepared from the corresponding monomeric oxidovanadium(IV) complex [V(IV)O(Hsal-dahp)(DMSO)] (1), characterized and successfully used as catalyst for the peroxidase-like oxidation of pyrogallol. The oxidation of pyrogallol to purpurogallin with PS-[V(IV)O(sal-dahp)] (2) was achieved under mild conditions at pH7 buffered solution. Plausible intermediate species formed during peroxidase mimicking experiments are proposed, by studying the model complex [V(IV)O(Hsal-dahp)(DMSO)] (1) by UV-visible and (51)V NMR spectroscopies. The high peroxidase mimicking ability of polymer-supported complex 2, its stability in a wide pH range, the easy separation from the reaction media, and the reusability without considerable decrease in activity, suggest that this heterogeneous catalyst has high potential for application in sustainable industrial catalysis.

Oxidovanadium(IV) and dioxidovanadium(V) complexes of hydrazones of 2-benzoylpyridine and their catalytic applications.

Reactions between the tridentate ONN donor ligands, Hbzpy-tch () and Hbzpy-inh (), with [V(IV)O(acac)2] in dry methanol give two different types of complexes, [V(IV)O(acac)(bzpy-tch)] () and [V(IV)O(OMe)(bzpy-inh)] (), respectively. Irrespective of their nature in methanol upon aerial oxidation and precipitation both yield dinuclear [{V(V)O(bzpy-tch)}2(µ-O)2] () and [{V(V)O(bzpy-inh)}2(µ-O)2] (). Treatment of or in methanol with H2O2 yields the oxidomonoperoxidovanadium(v) complexes [{V(V)O(bzpy-tch)}2(µ-O2)2] () and [V(V)O(O2)(bzpy-inh)] (). Reactions of and with imidazolomethylpolystyrene cross-linked with 5% divinylbenzene (PS-im) in DMF give the polymer-supported PS-im[V(V)O2(bzpy-inh)] () and PS-im[V(V)O2(bzpy-tch)] (). The compounds are characterized by various spectroscopic techniques and compounds and were also analyzed by thermal, atomic force microscopy (AFM), field-emission scanning electron micrographs (FE-SEM) as well as energy dispersive X-ray (EDAX) studies. The molecular structures of and of [V(V)O(O2)(bzpy-inh)(H2O)]·0.5MeOH () were determined by single-crystal X-ray diffraction, confirming the µ-bis(O) and ONN binding mode in the dinuclear complexes and , as well as the side-on coordination of the peroxido ligand in and . The polymer-grafted compounds and were used for the catalytic oxidation of isoeugenol using aqueous H2O2 as an oxidant. The intermediate peroxido species, expected to be involved during catalytic action, were also generated from solutions of and studied by UV-Vis and (51)V NMR. The catalytic activity of the several systems was tested and the polymer-supported versions showed higher conversions than their neat counterparts. The polymer-supported complexes allow for recyclable catalytic systems, thus providing additional advantages over their homogeneous counterparts in terms of increased catalyst lifetime and easier separation from the reaction mixture.