The production of oxygenated polycrystalline graphene by one-step ethanol-chemical vapor deposition

Large-area mono- and bilayer graphene films were synthesized on Cu foil (∼1 in.²) in about 1 min by a simple ethanol-chemical vapor deposition (CVD) technique. Raman spectroscopy and high resolution transmission electron microscopy revealed the synthesized graphene films to have polycrystalline structures with 2–5 nm individual crystallite size which is a function of temperature up to 1000 °C. X-ray photoelectron spectroscopy investigations showed about 3 at.% carboxylic (COOH) functional groups were formed during growth. The field-effect transistor devices fabricated using polycrystalline graphene as conducting channel (L_c = 10 μm; W_c = 50 μm) demonstrated a p-type semiconducting behavior with high drive current and Dirac point at ∼35 V. This simple one-step method of growing large area polycrystalline graphene films with semiconductor properties and easily functionalizable groups should assist in the realization of potential of polycrystalline graphene for nanoelectronics, sensors and energy storage devices.     

Three-dimensional nitrogen rich bubbled porous carbon sponge for supercapacitor & pressure sensing applications

Three-dimensional (3D) porous carbonaceous materials offer numerous merits such as light-weight, high surface area, flexibility, and thus hold immense potential in energy storage applications. In this work, we report preparation of nitrogen-rich free-standing compressible porous neuron-like carbon sponge using commercially available kitchen sponge by a facile, cost-effective, and scalable synthetic strategy. The unique neuron-like bubbled interconnected carbon structure with enhanced N/O functionalities improves the electrochemical performance by providing sufficient space for ion transport and large accessible surface-active sites. This material also delivers high current response under compressive stress acting as a pressure sensor. This bubbled carbon material achieves an improved specific capacitance of 268.5 F g⁻¹ at 0.5 A g⁻¹. As a self-supporting electrode in a symmetrical supercapacitor cell, it still delivers a good specific capacitance of 167 F g⁻¹ at 0.35 A g⁻¹, retaining 92.5% of capacitance over 7000 charge/discharge cycles. Furthermore, the device delivers a maximum energy density of 14.8 Wh Kg⁻¹, demonstrating its immense potential for multi-functional applications owing to its unique features.     

Large‐Area,Flexible Broadband Photodetector Based on ZnS–MoS2 Hybrid on Paper Substrate

Flexible broadband photodetectors based on 2D MoS₂ have gained significant attention due to their superior light absorption and increased light sensitivity. However, pristine MoS₂ has absorption only in visible and near IR spectrum. This paper reports a paper‐based broadband photodetector having ZnS–MoS₂ hybrids as active sensing material fabricated using a simple, cost effective two‐step hydrothermal method wherein trilayer MoS₂ is grown on cellulose paper followed by the growth of ZnS on MoS₂. Optimization in terms of process parameters is done to yield uniform trilayer MoS₂ on cellulose paper. UV sensing property of ZnS and broadband absorption of MoS₂ in visible and IR, broadens the range from UV to near IR. ZnS plays the dual role for absorption in UV and in the generation of local electric fields, thereby increasing the sensitivity of the sensor. The fabricated photodetector exhibits a higher responsivity toward the visible light when compared to UV and IR light. Detailed studies in terms of energy band diagram are presented to understand the charge transport mechanism. This represents the first demonstration of a paper‐based flexible broadband photodetector with excellent photoresponsivity and high bending capability that can be used for wearable electronics, flexible security, and surveillance systems, etc.     

Nickel Metal-Organic Framework/PVDF Composite Nanofibers-based Self-Powered Wireless Sensor for Pulse Monitoring of Underwater Divers via Triboelectrically Generated Maxwell's Displacement Current

With the increasing need for underwater exploration to monitor environment, collect data or recreation, underwater diving and its associated technologies have drawn significant attention. So, a single-electrode triboelectric nanogenerator (STENG) as self-powered wireless sensor based on Maxwell displacement current concept for underwater usages to monitor arterial pulse and body movements of diver is demonstrated. The STENG is fabricated with an optimized 7.5 wt.% of hydrothermally synthesized Ni-MOF and PVDF based composite nanofibers (Ni-MOF/PVDF CNF) on copper foil as electronegative tribo-material and electrospun nylon 66 nanofibers as electropositive tribo-material. The PDMS encapsulation of STENG exhibits water-proof properties with V_oc, I_sc, and charge output at 45 V, 0.77 µA, and 0.169 µC/cycle, respectively under single-finger tapping. As pulse sensor, STENG monitors arterial pulse and wirelessly transmits information underwater (without external power), wherein STENG generated current creates polarized field in water to get transmitted within a certain distance. Additionally, STENG is demonstrated as a strain sensor to monitor joint movements like ‘elbow, shoulder, knee, etc. Detailed reliability studies reveal that the device is robust against multiple cycles of bending, retains its performance in saline/muddy water, and in the presence of obstacles in the transmission path, which confirms its potential in real life conditions for pulse monitoring of underwater divers.