Yousong Gu

Highly transparent triboelectric nanogenerator for harvesting water-related energy reinforced by antireflection coating

Water-related energy is an inexhaustible and renewable energy resource in our environment, which has huge amount of energy and is not largely dictated by daytime and sunlight. The transparent characteristic plays a key role in practical applications for some devices designed for harvesting water-related energy. In this paper, a highly transparent triboelectric nanogenerator (T-TENG) was designed to harvest the electrostatic energy from flowing water. The instantaneous output power density of the T-TENG is 11.56 mW/m2. Moreover, with the PTFE film acting as an antireflection coating, the maximum transmittance of the fabricated T-TENG is 87.4%, which is larger than that of individual glass substrate. The T-TENG can be integrated with silicon-based solar cell, building glass and car glass, which demonstrates its potential applications for harvesting waste water energy in our living environment and on smart home system and smart car system.

Enhanced photoelectrochemical property of ZnO nanorods array synthesized on reduced graphene oxide for self-powered biosensing application

We have realized the direct synthesis of ZnO nanorods (ZnO NRs) array on reduced graphene layer (rGO), and demonstrated the enhanced photoelectrochemical (PEC) property of the rGO/ZnO based photoanode under UV irradiation compared with the pristine ZnO NRs array. The introduction of the rGO layer resulted in a favorable energy band structure for electron migration, which finally led to the efficient photoinduced charge separation. Such nanostructure was subsequently employed for self-powered PEC biosensing of glutathione in the condition of 0 V bias, with a linear range from 10 to 200 µM, a detection limit of 2.17 µM, as well as excellent selectivity, reproducibility and stability. The results indicated the rGO/ZnO nanostructure is a competitive candidate in the PEC biosensing field.

Self-Powered Photoelectrochemical Biosensor Based on CdS/RGO/ZnO Nanowire Array Heterostructure.

A CdS/reduced graphene oxide (RGO)/ZnO nanowire array (NWAs) heterostructure is designed, which exhibits enhanced photoelectrochemical (PEC) activity compared to pure ZnO, RGO/ZnO, and CdS/ZnO. The enhancement can be attributed to the synergistic effect of the high electron mobility of ordered 1D ZnO NWAs, extended visible-light absorption of CdS nanocrystals, and the formed type II band alignment between them. Moreover, the incorporation of RGO further promotes the charge carrier separation and transfer process due to its excellent charge collection and shuttling characteristics. Subsequently, the CdS/RGO/ZnO heterostructure is successfully utilized for the PEC bioanalysis of glutathione at 0 V (vs Ag/AgCl). The self-powered device demonstrates satisfactory sensing performance with rapid response, a wide detection range from 0.05 mm to 1 mm, an acceptable detection limit of 10 μm, as well as certain selectivity, reproducibility, and stability. Therefore, the CdS/RGO/ZnO heterostructure has opened up a promising channel for the development of PEC biosensors.

Design of sandwich-structured ZnO/ZnS/Au photoanode for enhanced efficiency of photoelectrochemical water splitting

We developed and demonstrated a ZnO/ZnS/Au composite photoanode with significantly enhanced photoelectrochemical water-splitting performance, containing a ZnS interlayer and Au nanoparticles. The solar-to-hydrogen conversion efficiency of this ZnO/ZnS/Au heterostructure reached 0.21%, 3.5 times that of pristine ZnO. The comparison of the incident photon-to-current efficiency (IPCE) and the photoresponse in the white and visible light regions further verified that the enhancement resulted from contributions of both UV and visible light. The modification of the Au NPs was shown to improve the photoelectrochemical (PEC) performance to both UV and visible light, as modification encouraged effective surface passivation and surface-plasmonresonance effects. The ZnS interlayer favored the movement of photogenerated electrons under UV light and hot electrons under visible light, causing their injection into ZnO; this simultaneously suppressed the electron-hole recombination at the photoanode-electrolyte interface. The optimized design of the interlayer within plasmonic metal/semiconductor composite systems, as reported here, provided a facile and compatible photoelectrode configuration, enhancing the utilization efficiency of incident light for photoelectrochemical applications.

Synthesis of crystalline C3N4 by MPCVD

In this study, carbon nitride thin films are synthesized on Si and Pt substrates by microwave plasma chemical vapor deposition (MPCVD). The major part of the films is composed of alpha-C3N4 and beta-C3N4. XPS and FT-IR spectra strongly support the existence of C-N covalent bonds in C3N4. Raman spectra also support the existence of beta-C3N4. The carbon nitride films on Pt substrates have a high bulk modulus of 349 GPa

Gold nanoparticles coated zinc oxide nanorods as the matrix for enhanced L-lactate sensing.

In this study, an enzymatic electrochemical biosensor for L-lactate detection was proposed. The device was developed based on gold nanoparticles (Au NPs) modified zinc oxide nanorods (ZnO NRs). The sensing performance of the device was examined by cyclic voltammetry and amperometry. Compared with pristine ZnO based biosensor, Au/ZnO based sensor exhibited higher sensitivity of 24.56 μA cm(-2) mM(-1), smaller K(M)(app) of 1.58 mM, lower detection limit of 6 μM and wider linear range of 10 μM-0.6 mM for L-lactate detection. The introduction of Au NPs enhances electro-catalytic ability and electron migration, which contributes to the improvement of the sensing performance. Hence, the results confirm the essential character of Au NPs in such semiconductor based electrochemical biosensing system.

Dark current characteristics of GaAs-based 2.6 µm InGaAs photodetectors on different types of InAlAs buffer layers

GaAs-based In0.83Ga0.17As photodetectors (PDs) with cut-off wavelengths up to 2.6 µm are demonstrated. The effects of continuously-graded or fixed-composition InAlAs buffers on the device performances are investigated. The dark current characteristics of the PDs at various temperatures are analysed in detail. The photocurrents are also measured at 300 K; the detectivity of the PDs is extracted. The two GaAs-based PDs with different buffer schemes show different temperature-dependent dark current behaviours. The around room temperature performances of the GaAs-based device on the fixed-composition buffer are not as good, but comparable to those of InP-based devices, revealing a promising candidate for the GaAs-based PDs and focal plane arrays for many low-end applications.

Self-powered ultraviolet photodetector based on a single ZnO tetrapod/PEDOT:PSS heterostructure

A new ultraviolet (UV) photodetector based on a single ZnO tetrapod and PEDOT:PSS heterostructure was constructed and investigated. At zero bias, the detector showed an on/off ratio of ~1100, a rise time of ~3.5 s and a decay time of ~4.5 s when the 325 nm UV (0.16 mW) illuminated the p–n heterojunction. The self-powered properties were driven by the photovoltaic effect, with a short-circuit current of ~1.1 nA, an open-circuit voltage of ~0.2 V and a fill factor of ~25%. Furthermore, self-powered properties were also found when the UV irradiated the ZnO tetrapod only, and the short-circuit current and the open-circuit voltage decreased with the increasing distance between the illuminated spot at the ZnO tetrapod and the heterojunction. The mechanisms for the performances of the detector were examined and discussed. In consideration of the multiterminal feature of ZnO tetrapods, our work provides a possible new approach to developing independent and multifunctional nanodevices.

Size dependence and UV irradiation tuning of the surface potential in single conical ZnO nanowires

Investigating and tailoring surface potential changes of a system at the interfaces is of significance in the fundamental understanding and application of semiconductor devices. Thus the surface potential of zinc oxide (ZnO) nanowires is a vital factor to tune the performance of devices. In this paper, Kelvin probe force microscopy (KPFM) is used to measure the surface potential of single conical ZnO nanowires with different diameters. A size dependence of the surface potential in single conical ZnO nanowires is experimentally revealed. As the diameter decreases, the surface potential of the ZnO nanowires is found to decrease linearly under 400 nm. At large diameters (≥400 nm), the surface potential remains almost constant. The contact potential difference of the ZnO–PtIr tip increases to saturation after 40 min UV illumination and remains stable. An energy band theory is introduced to explore the surface potential change of ZnO nanowires under UV illumination. This study provides an understanding of the surface electrical properties of semiconductors at the nanoscale, which is valuable for optimizing functional nanodevices based on semiconductor nanowires.

First-principles studies on the structural transition of ZnO nanowires at high pressure

The structural transition of ZnO nanowires at high pressures from wurtzite to rocksalt structure has been studied by first-principles density functional calculations using the SIESTA code. The size effect was studied by calculating a series of nanowires with different diameters, and the doping effect was studied by ion substitution. It is found that the critical pressure of structural transition for nanowires is lower than that of the bulk, and it decreases as the diameter of the nanowire decreases. It is also found thatMn doping can reduce the transition pressure. The size effect and doping effect are discussed in terms of the chemical bonding and energies of the nanowires.