Bharat Sharma

Electrospinning is a prominent technique for micro/nanofiber production and has received significant attention in the 21^st century. It enables the production of ultrafine fibers using a variety of polymers, including synthetic, natural, and hybrid materials. Electrospun nanofibers (NFs) possess unique properties such as a high surface‐to‐volume ratio, tunable pore structures, and customizable composition, making them highly desirable in various fields such as biomedical science, textiles, sensors, filters, energy, and packaging. Herein, particular attention will be given to the application of NFs in biomedical fields. The use of NFs for the delivery of drugs, growth factors, proteins, nanoparticles, etc., holds significant promise in the field of biomedical science. To combine these compounds with NFs, various electrospinning techniques have been developed with outstanding improvements, and based on the requirements of the application type, different electrospinning processes are favored. In this review, the most common drug loading methods into NFs, generally used synthetic/natural polymers for NF production, and their application in drug delivery systems, tissue engineering, and wound dressing will be mentioned. Finally, challenges and future perspectives for above mentioned biomedical applications are discussed.

Synergistically increased oxygen evolution reaction (OER) of manganese oxide (MnO2) catalyst is introduced with surface-modified halloysite nanotube (Fe3O4-HNTs) structure. The flake shaped MnO2 catalyst is attached on the nanotube template (Fe3O4-HNTs) by series of wet chemical and hydrothermal method. The strong interaction between MnO2 and Fe3O4-HNTs maximized active surface area and inter-connectivity for festinate charge transfer reaction for OER. The synergistical effect between Fe3O4 layer and MnO2 catalyst enhance the Mn3+/Mn4+ ratio by partial replacement of Mn ions with Fe. The relatively increased Mn3+/Mn4+ ratio on MnO2@FHNTs induced σ* orbital (eg) occupation close to single electron, improving the OER performances. The MnO2@FHNTs catalyst exhibited the reduced overpotential of 0.42 V (E vs. RHE) at 10 mA/cm2 and Tafel slope of (99 mV/dec), compared with that of MnO2 with unmodified HNTs (0.65 V, 219 mV/dec) and pristine MnO2 (0.53 V, 205 mV/dec). The present study provides simple and innovative method to fabricate nano fiberized OER catalyst for a broad application of energy conversion and storage systems.

Hydrogen as a source of clean and future alternative to fossil fuels demands a class of powerful gas sensor technologies. To this end, we have developed unique bi-stacked heterogeneous layers based on 2D Pnictogens and graphene sheets via photolithography and pattern transfer methods. The nanoengineered heterostructure morphology consists of truncated/hexagonal antimonene flakes dispersed on graphene sheets. Amongst the Pnictogen class, the hybrid antimonene-graphenes (Sb/G) demonstrated excellent sensing behavior characterized by a large gas response to H2 (~4-fold improvement), high selectivity, fast response/recovery times (>3 fold reduction), and ultra-low limit of detection (LOD: 0.05 ppm) in comparison to pristine sensors. The microstructural and density functional theory (DFT) calculations demonstrated a Bader charge transfer mechanism from Sb/G heterojunction to the H2 gas, which modulated the Schottky barrier and improved gas response. The outstanding performance of the Sb/G sensor places it amongst the highly selective and fast hydrogen sensors based on the Pnictogen-graphene family.

Although they are not as favorable as other influential gas sensors, metal-oxide semiconductor-based chemiresistors ensure minimal surface reactivity, restricting their gas selectivity, gas response, and reaction kinetics, particularly when functioning at room temperature (RT). A hybrid design, which includes metal-oxide/carbon nanostructures and passivation with specific gas filtration layers, can address the concerns of surface reactivity. We present a novel hierarchical nanostructured zinc oxide (ZnO), decorated with graphitic carbon (GC) and synthesized via a wet-chemical strategy, which is then followed by the self-assembly of a zeolitic imidazolate framework (ZIF-8). Because of its large surface area, high porosity, and efficient inspection of other analyte (interfering) gases, the ZnO@GC can provide intensified surface reactivity at RT. In the present study, such a hybrid sensor confirmed extraordinary gas sensing properties, which was characterized by excellent H₂ selectivity, fast response, rapid recovery kinetics, and high gas response (ΔR/R₀ ∼ 124.6%@10 ppm), particularly in extremely humid environments. The results reveal that adsorption sites provided by the ZIF-8 template-based ZnO@GC frameworks facilitate the adsorption and desorption of H₂.