ABSTRACT
ZnO-based heterojunctions have found applications as self-powered ultraviolet photodetectors (PDs). However, high doping levels are not compatible with high mobility for metallic doped ZnO-based PDs so further development has been inhibited. This study demonstrates a method to increase the open-circuit voltage (V oc) that allows keeping a sufficiently high level of mobility of ZnO, using a ZnO nanorod/GaN heterojunction that incorporates graphene nanosheets as the active layer. These hybrid PDs have triple the value for V oc of PDs that have only pure ZnO and better exhibit photo-response characteristics. The results of surface Kelvin probe microscopy and x-ray photoelectron spectrometer show that the complex defects that occur because Zn interstitials form a shallow donor in ZnO are mainly responsible for the increase in the value of V oc. Using this functional nanostructure as an active layer represents a new method for the manufacture of high-performance self-powered PDs.
ABSTRACT
Deep learning and analysis of heavy metal concentration are very crucial to our life, for it plays an essential role in both environmental and human health. In this paper, we developed a new Cu (II) ions sensor made by all organic material with bending and stretching properties. The new sensor consists of chlorophyll-a extracted from fresh leaves of Common Garcinia, plant fiber and with the use of PDMS as a substrate. Fluorescence spectra study shows that chlorophyll-a is significantly much more sensitive to Cu (II) ions than any other heavy metal ions and the device sensitivity outperforms all the Cu (II) ions sensors ever reported. The result fully shows the selectivity of chlorophyll-a toward Cu (II) ions. Bending and stretching tests show that the sensor has an outstanding durability, which can be used to develop accompanying applications, such as real-time sampling and the analysis of Cu (II) concentration specified in athlete's sweat or patients with brain death and Parkinson's disease.
