ABSTRACT
Herein, we introduce an eco-friendly electrochemical sensor based on melamine-enriched nitrogen-doped carbon nanosheets decorated with gold nanoparticles (Au-CNSm) for arsenic sensing. An extremely facile, low-toxicity, biocompatible, and affordable hydrothermal technique was adopted for the synthesis of the Au-CNSm nanocomposite. The Au-CNSm-integrated sensing platform was optimized for electrode composition by cyclic voltammetry (CV). Owing to the synergistic effects of melamine-enriched carbon nanosheets (CNSm) and gold nanoparticles (AuNPs), the anodic peak current increased in the Au-CNSm-modified sensing electrode as compared to the CNSm-decorated platform. A wide linear range of 0.0001-100 µM and a low detection limit of 0.0001 µM were obtained. The visual signals can be measured at a very minute concentration of 0.0001 µM (0.1 ppb) on a screen-printed carbon electrode (SPCE) modified with Au-CNSm. Hence, this electrode system clearly outperformed the previously reported studies in terms of linear range, limit of detection (LOD), and electrocatalytic activity for arsenic sensing. Interestingly, the fabricated biosensor can be developed as a point-of-care device for real-time environmental monitoring for public safety. Henceforth, owing to exceptional attributes such as portability, selectivity, and sensitivity, this device offers great promise in modeling a revolutionary new class of electrochemical sensing platforms for an ultrasensitive and reliable detection strategy for arsenite (As(III)).
ABSTRACT
Highly transparent resistive-switching (RS) devices were fabricated by growing amorphous tantalum pentoxide (a-Ta2O5) and indium tin oxide (a-ITO) thin films on barium-borosilicate glass (7059) substrates, using electron beam evaporation. These layers exhibited the transmittance greater than ~ 85% in the full visible region and showed RS behavior and battery-like IV characteristics. The overall characteristics of RS can be tuned using the top electrode and the thickness of a-Ta2O5. Thinner films showed a conventional RS behavior, while thicker films with metal electrodes showed a battery-like characteristic, which could be explained by additional redox reactions and non-Faradaic capacitive effects. Devices having battery-like IV characteristics showed higher enhanced, retention and low-operation current.
ABSTRACT
Thin films of ß-W are the most interesting for manipulating magnetic moments using spin-orbit torques, and a clear understanding of α to ß phase transition in W by doping impurity, especially oxygen, is needed. Here we present a combined experimental and theoretical study using grazing incidence X-ray diffraction, photoelectron spectroscopy, electron microscopy, and ab initio calculations to explore atomic structure, bonding, and oxygen content for understanding the formation of ß-W. It is found that the W films on SiO2/Si have 13-22 at.% oxygen in A15 ß structure. Ab initio calculations show higher solution energy of oxygen in ß-W, and a tendency to transform locally from α to ß phase with increasing oxygen concentration. X-ray absorption spectroscopy also revealed local geometry of oxygen in ß-W, in agreement with the simulated one. These results offer an opportunity for a fundamental understanding of the structural transition in α-W and further development of ß-W phase for device applications.
ABSTRACT
Unlike graphene nanostructures, various physical properties of nanostructured MoS2 have remained unexplored due to the lack of established fabrication routes. Herein, we have reported unique electrostatic properties of MoS2 nanostructures, fabricated in a controlled manner of different geometries on 2D flake by using focused laser irradiation technique. Electrostatic force microscopy has been carried out on MoS2 nanostructures by varying tip bias voltage and lift height. The analysis depicts no contrast flip in phase image of the patterned nanostructure due to the absence of free surface charges. However, prominent change in phase shift at the patterned area is observed. Such contrast changes signify the capacitive interaction between tip and nanostructures at varying tip bias voltage and lift height, irrespective of their shape and size. Such unperturbed capacitive behavior of the MoS2 nanostructures offer modulation of capacitance in periodic array on 2D MoS2 flake for potential application in capacitive devices.
