Yanbing Guo

Light-Controlled Organic/Inorganic P−N Junction Nanowires

P-N junctions are of great importance both in modern electronic applications and in understanding other semiconductor devices. Organic/inorganic P-N junction nanowires composed of functional organic molecules and inorganic molecules may be able to realize new or improved chemical and physical properties that were not observed in the individual component on nanosize and their bulk materials. We report herein the fabrication of the organic/inorganic semiconductor P-N junction nanowire and the remarkable performance on the light-controlled diode within a single hybrid P-N junction nanowire. Controlling the conductivity of the P-N junction nanowire by the light irradiation simply to achieve diode work indicates a new way to realize the photoelectric integration in a single nanowire device.

Self‐Assembly of Functional Molecules into 1D Crystalline Nanostructures

Self-assembled functional nanoarchitectures are employed as important nanoscale building blocks for advanced materials and smart miniature devices to fulfill the increasing needs of high materials usage efficiency, low energy consumption, and high-performance devices. One-dimensional (1D) crystalline nanostructures, especially molecule-composed crystalline nanostructures, attract significant attention due to their fascinating infusion structure and functionality which enables the easy tailoring of organic molecules with excellent carrier mobility and crystal stability. In this review, we discuss the recent progress of 1D crystalline self-assembled nanostructures of functional molecules, which include both a small molecule-derived and a polymer-based crystalline nanostructure. The basic principles of the molecular structure design and the process engineering of 1D crystalline nanostructures are also discussed. The molecular building blocks, self-assembly structures, and their applications in optical, electrical, and photoelectrical devices are overviewed and we give a brief outlook on crucial issues that need to be addressed in future research endeavors.

Effect of Aspect Ratio on Field Emission Properties of ZnO Nanorod Arrays

ZnO nanorod arrays are prepared on a silicon wafer through a multi-step hydrothermal process. The aspect ratios and densities of the ZnO nanorod arrays are controlled by adjusting the reaction times and concentrations of solution. The investigation of field emission properties of ZnO nanorod arrays revealed a strong dependency on the aspect ratio and their density. The aspect ratio and spacing of ZnO nanorod arrays are 39 and 167 nm (sample C), respectively, to exhibit the best field emission properties. The turn-on field and threshold field of the nanorod arrays are 3.83 V/μm and 5.65 V/μm, respectively. Importantly, the sample C shows a highest enhancement of factorβ, which is 2612. The result shows that an optimum density and aspect ratio of ZnO nanorod arrays have high efficiency of field emission.

Organic−Inorganic Nanohybrids via Directly Grafting Gold Nanoparticles onto Conjugated Copolymers through the Diels−Alder Reaction

Nanocomposites of poly- p-phenyleneethynylene gold nanoparticles (PPE-Au) were synthesized via directly grafting maleimide functionalized gold nanoparticles (MA-Au) onto PPE chains by a mild Diels-Alder reaction. The Diels-Alder reaction between copolymers and MA-Au leads to self-assembly of the MA-Au as well as enhances electronic communication between the copolymers and inorganic particles. The as-prepared hybrid nanoassemblies show homogeneous status and well-defined interfaces, which facilitate the electronic interaction between conjugated polymers and gold nanoparticles. Moreover, dramatic photophysical properties and an influence on the assembly behavior of gold nanoparticles are also exhibited, which allows this procedure to be performed as a smart assay for monitoring the process of the Diels-Alder reaction.

Fabrication of large-area hybrid nanowires arrays as novel field emitters

A hybrid nanomaterial composed of ZnO nanoparticles (NPs) and CuTCNQ (copper 7,7,8,8-tetracyanoquinodimethane) nanowires (NWs) was successfully fabricated in a simple solution method. The electron field emission properties of the hybrid NWs were dramatically improved over those of raw CuTCNQ NWs. The maximum current density of ZnO-CuTCNQ NWs was six times that of the CuTCNQ NWs array. Importantly for ZnO-CuTCNQ NWs, no obvious degradation of current density was observed and the emission current fluctuation was less than 10% during a period of over 4000 seconds. It is of significance that the coating layer of ZnO NPs produced by our approach makes a great contribution to stabilization of organic field emitters and enhancement of their field emission properties. The high emission stability can be also observed for In2O3-CuTCNQ NWs which are fabricated by the same method. It is confirmed that the moderate approach presented herein is of practical significance in stabilization of organic field emitters avoiding decomposition of the core organic materials.

Thermoreversible Covalent Self-Assembly of Oligo(p-phenylenevinylene) Bridged Gold Nanoparticles

Organic-inorganic hybrids have been fabricated through mild Diels-Alder cross-linking between maleimide bearing oligo(p-phenylenevinylene) (OPV) and furan functionalized gold nanoparticles with diameter smaller than 2 nm. The OPV ligands afford strong reaction ability toward furan group due to their maleimide moieties. These small gold nanoparticles form close-packed homogeneous hybrids with well-defined interfaces by incorporating OPV ligands in solutions. Covalent assembly and disassembly of gold nanoparticles can be achieved by repeated thermal stimuli on as-obtained hybrids, which can be monitored by fluorescence changes of OPVs and surface plasmon resonance absorption. Moreover, the dramatic photophysical properties and assembly behavior of these hybrids allow this procedure to be performed as a smart assay for monitoring the process of the Diels-Alder reaction.

Determination of InN/Diamond Heterojunction Band Offset by X-ray Photoelectron Spectroscopy

Diamond is not only a free standing highly transparent window but also a promising carrier confinement layer for InN based devices, yet little is known of the band offsets in InN/diamond system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band offset (VBO) of InN/diamond heterostructure. The value of VBO was determined to be 0.39 ± 0.08 eV and a type-I heterojunction with a conduction band offset (CBO) of 4.42 ± 0.08 eV was obtained. The accurate determination of VBO and CBO is important for the application of III-N alloys based electronic devices.

Field Emission Properties and Fabrication of CdS Nanotube Arrays.

A large area arrays (ca. 40 cm2) of CdS nanotube on silicon wafer are successfully fabricated by the method of layer-by-layer deposition cycle. The wall thicknesses of CdS nanotubes are tuned by controlling the times of layer-by-layer deposition cycle. The field emission (FE) properties of CdS nanotube arrays are investigated for the first time. The arrays of CdS nanotube with thin wall exhibit better FE properties, a lower turn-on field, and a higher field enhancement factor than that of the arrays of CdS nanotube with thick wall, for which the ratio of length to the wall thickness of the CdS nanotubes have played an important role. With increasing the wall thickness of CdS nanotube, the enhancement factorβ decreases and the values of turn-on field and threshold field increase.

Construction of heterojunction nanowires from polythiophene/polypyrrole for applications as efficient switches.

The design and fabrication of PTh-PPY heterojunction nanowires that exhibits smart responses to electrochemical redox potentials is described. In their oxidized state, PTh-PPY nanowires act as resistors, whilst in their reduced state, they acts as diodes. Furthermore, the electrical transport mode can be reversibly changed by alternately exposing the nanowires to negative and positive potentials. Constructing full-organic heterojunction nanowires with smart, controllable properties will contribute to the development of intelligent organic devices and organic-electronic circuits on the nanoscale.