4,218 publications from this institution
The authors report on the synthesis of two graphitic nanoribbons from the readily available tetrachloro-perylene bisimide. By utilizing sequential Ullmann coupling reactions, the bisimide could be dimerized twice to afford the tetramer. Spectroscopic analyses of the two tetramer products show that 2C as well as either 2A or 2B are formed. Both tetramers show good solubility in common organic solvents.
Zinc oxide is a unique material that exhibits exceptional semiconducting, piezoelectric, and pyroelectric properties. Nanostructures of ZnO are equally as important as carbon nanotubes and silicon nanowires for nanotechnology and have great potential applications in nanoelectronics, optoelectronics, sensors, field emission, light-emitting diodes, photocatalysis, nanogenerators, and nanopiezotronics. Fundamental understanding about the growth of ZnO nanowires is of critical importance for controlling their size, composition, structure, and corresponding physical and chemical properties. The papers by She et al. and Ito et al. in this issue describe the controlled growth and field-emission properties of individual nanostructures, respectively. These studies provide new approaches and insight into the controlled growth and electrical properties of ZnO nanostructures.
This review focuses on the growth, properties and novel applications of aligned arrays of ZnO nanowires (NWs) and nanobelts (NBs) for nanogenerators and nano-piezotronics. Owing to the semiconducting and piezoelectric dual properties of ZnO crystals, novel applications are introduced using aligned ZnO NWs, such as nanogenerators. These unique properties and applications will have profound impacts in many areas, such as self-powered nanodevices and nanosystems for in situ, real-time and implantable biosensing and biodetection, self-powering for defence and commercial applications, and remote sensing for space technology. The article provides detailed illustrations about the synthesis method, mechanical, electrical and optical properties, as well as the underlying mechanism for piezoelectronic devices and systems.
As a potential next generation mechanical‐to‐electricity power generator, the triboelectric nanogenerator (TENG) has drawn considerable attention in recent years. Its mechanical‐to‐electrical signal control properties also gave rise to the original idea of “tribotronics”, which utilize triboelectric output to drive/control electronic devices. Using a TENG as input for gate voltage for a field effect transistor, a tribotronic device has potential application in mainly two areas (i) mechanically controlled electronics and (ii) motion/displacement sensing. An experimental study has already been recently reported and therefore a theoretical study is strongly desired as the theoretical basis and optimization strategy for designing such circuits. Here, both analytical calculations and numerical simulations are used to study the tribotronic device, both on the logic operation and on mechanical sensing. The static charge and inherent capacitance of TENG are determined by the structure design of the TENG and have strong coupling with the field effect transistor. Such coupling effect is taken into consideration, thus developing a methodology to effectively optimize the tribotronic device design according to such a coupling effect.
Scalability enhancement in Multi-agent Reinforcement Learning (MARL) is essential for tackling large-scale multi-agent challenges. Parameter sharing serves as an efficient mechanism to alleviate computational complexity during training, promoting improved learning efficiency and system stability. However, full parameter sharing often overlooks the differences between agents, leading to policy homogenization, slower convergence and difficulties in adapting to diverse decision-making tasks. In this paper, we propose a method called Attention Parameter Sharing (AtPS). AtPS incorporates multi-head self-attention into the value network, allowing agents to selectively focus on other agents with high similarity to themselves, which reduces model parameters while maintaining effective coordination. Moreover, we employ hierarchical clustering using the attention weights of each agent to form multi-agent groups, facilitating targeted parameter sharing within each group. Numerical results demonstrate that AtPS outperforms existing methods across various tasks in the six environments of SMAC, particularly in heterogeneous multi-agent scenarios. As the agent count grows, the performance gains of our method become increasingly evident, underscoring its effectiveness and practicality in scaling MARL.
Abstract Due to polarization of ions in crystals with noncentral symmetry, such as ZnO, GaN, and InN, a piezoelectric potential (piezopotential) is created in the crystal when stress is applied. Electronics fabricated using the inner‐crystal piezopotential as a gate voltage to tune or control the charge transport behavior across a metal/semiconductor interface or a p–n junction are called piezotronics. This is different from the basic design of complimentary metal oxide semiconductor (CMOS) field‐effect transistors and has applications in force and pressure triggered or controlled electronic devices, sensors, microelectromechanical systems (MEMS), human‐computer interfacing, nanorobotics, and touch‐pad technologies. Here, the theory of charge transport in piezotronic devices is investigated. In addition to presenting the formal theoretical frame work, analytical solutions are presented for cases including metal–semiconductor contact and p–n junctions under simplified conditions. Numerical calculations are given for predicting the current–voltage characteristics of a general piezotronic transistor: metal–ZnO nanowire–metal device. This study provides important insight into the working principles and characteristics of piezotronic devices, as well as providing guidance for device design.
Orientational ordering of faceted nanocrystals in nanocrystal arrays has been directly observed for the first time, by use of transmission electron microscopy imaging and diffraction to resolve the structure of thin molecular-crystalline films of silver nanocrystals passivated by alkylthiolate self-assembled monolayers. The type of ordering found is determined by the nanocrystal's faceted morphology, as mediated by the interactions of surfactant groups tethered to the facets on neighboring nanocrystals. Orientational ordering is crucial for the understanding of the fundamental properties of quantum-dot arrays, as well as for their optimal utilization in optical and electronic applications.
