Nanocrystal engineered superlattices are a new type of material, differing from either a single particle or the corresponding bulk material, explains Z. L. Wang. He briefly outlines what is meant by a self-assembled nanocrystal lattice—the Figure shows an example consisting of faceted particles—before reviewing their structural analysis, concentrating on transmission electron microscopy and related techniques.
Wireless sensor networks will be responsible for a majority of the fast growth in intelligent systems in the next decade. However, most of the wireless smart sensor nodes require an external power source such as a Li-ion battery, where the labor cost and environmental waste issues of replacing batteries have largely limited the practical applications. Instead of using a Li-ion battery, we report an ultrastable, highly efficient, and superhydrophobic-surface-based triboelectric nanogenerator (TENG) to scavenge wind energy for sustainably powering a wireless smart temperature sensor node. There is no decrease in the output voltage and current of the TENG after continuous working for about 14 h at a wind speed of 12 m/s. Through a power management circuit, the TENG can deliver a constant output voltage of 3.3 V and a pulsed output current of about 100 mA to achieve highly efficient energy storage in a capacitor. A wireless smart temperature sensor node can be sustainably powered by the TENG for sending the real-time temperature data to an iPhone under a working distance of 26 m, demonstrating the feasibility of the self-powered wireless smart sensor networks.
A classical switch or router determines which of several inputs to the device passes through the output. In analogy, a quantum switch that coherently links the input to a superposition of several outputs plays an important role in quantum information processing, especially when operating at the fundamental limit where a single photon can be controlled. The controllable path superposition of propagating photonic qubits enabled by the quantum switch provides the basis for numerous quantum applications, including entanglement generation and distribution, enhanced quantum communication, and quantum random access memory. In this work, we realize such a quantum switch for microwave single photons with superconducting quantum circuits. We use a superconducting qubit to coherently switch the output path of single microwave photons and confirm quantum entanglement between the control qubit and the photons' propagation path. We further showcase the generation of quantum entanglement between a time-bin-encoded propagating photonic qubit and a superconducting qubit with the quantum switch, thus providing a versatile approach to generate reconfigurable multinode entanglement in one step. As such, our work provides a prime building block for microwave quantum networks and modular superconducting quantum computing.
Abstract : In this project, intensive research effort has been invested in the development of self-powered MNSs, and various prototypes have been built up. Flexible piezotronic device based on RF-sputtered piezoelectric ZnO thin film is a great UV sensor. A nanogenerator based on the hydrothermal growth of a ZnO nanowire film on a spring shows a stable output and both the output voltage and current, displaying a linear relationship with the weight loaded on the spring. Thus, the nanogenerator can be utilized as an active mechanical sensor for measuring the weight applied onto the spring. A flexible thermoelectric nanogenerator (TENG) can be used as a wearable energy harvester by using human body temperature as the energy source. At the same time, the TENG can work as a self-powered temperature sensor with a response time of 17 s and a reset time of 9 s. The detection sensitivity of the sensor can reach 0.15 K in ambient atmosphere. The single output peak from a pyroelectric nanogenerator (PENG) based on a lead zirconate titanate (PZT) film can be used to directly drive a LCD. Further, a homemade Li-ion battery can be charged by the PENG under different working frequencies from 0.005 to 0.02 Hz, which can be used to drive a green LED. An integrated module in the form of a combination of a nanoparticle-WO3 film electrochromic device and a nanogenerator demonstrates the potential of monochrome self-powered displays. This self-powered electrochromic device showed desirable electrochromic response times and high coloration efficiency values. A transparent flexible nanogenerators made by growing ZnO nanowires on flexible polydimethylsiloxane (PDMS) substrate is a self-powered sensor for monitoring vehicle speed and detecting vehicle weight. Using two kinds of piezoelectric material, ZnO and poly-(vinylidene fluoride) (PVDF), we fabricate a composite structure for a nanogenerator (NG) or active-sensor for mechanical energy harvesting and vortex-based gas/liquid flow measurements.
<p indent=0mm>Compared with the first-generation semiconductors (such as silicon, germanium) and the second-generation semiconductors (such as gallium arsenide, indium antimonide), the third-generation semiconductor materials represented by silicon carbide (SiC), zinc oxide (ZnO), gallium nitride (GaN) and cadmium sulfide (CdS) usually possess wider band gap, higher thermal conductivity, bigger electron saturation rate and better radiation resistance properties, and thus draw intensive attentions in high temperature and high frequency applications in recent years. Most of the third-generation semiconductors are wurtzite structures, which have piezoelectric effects due to their lack of symmetry in certain directions. This feature serves as a good bridge of transferring mechanical stress signals between the flexible semiconductor electronic devices and the surrounding environment or the host (e.g., the human body). Conventional piezoelectric effects are mainly found in barium titanate and lead zirconate titanate type perovskite materials, but such materials do not have semiconductor properties, thus limiting their use in electronics and optoelectronic devices. Our group has pioneered a new research field, i.e., piezoelectric nanogenerator, by utilizing third-generation semiconductor nanowires (such as ZnO nanowires) under a dynamic force. The piezoelectric potential generated by the dynamic strain on the nanowire can drive electrons to flow in the external load circuit, which is the basic principle of the piezoelectric nanogenerator. Piezoelectric nanogenerator based on ZnO nanowires was firstly proposed in 2006. When a uniform strain is applied on a non-centrosymmetric semiconductor, a piezo-potential will be induced in the semiconductor, accompanied with static piezoelectric charges distributed on the surfaces. This piezoelectric effect is commonly existed in the third generation semiconductors. The strain-induced piezo-potential and piezoelectric polarization charges can also statically and/or dynamically tune the transportation and photoelectric processes of carriers at the interfaces or junctions. The three ways coupling among piezoelectric, photoexcitation and semiconducting properties coined two new research fields, that is, the piezotronics and piezo-phototronics. In order to systematically explain the coupling properties of piezoelectric and semiconductor transport properties in such materials, our group first coined the term piezotronics in a paper published in 2007. The piezotronics is about the modulation of the metal-semiconductor interface barrier via piezoelectric potential acting as a “gate” voltage, which has been used to explain the transistor behavior observed in metal-ZnO-metal structures and the strain-gated diode effect of metal-ZnO structures. The basic core of piezo-phototronics is to regulate the generation, separation, transport and/or recombination of photogenerated carriers at interfaces or heterojunctions by piezoelectric polarization charges, which was first proposed by our group in 2010. The performance of many optoelectronic devices can be effectively enhanced by piezo-phototronic effect. Over the past decade, these two areas have received extensive attentions and made great progresses in basic science and device applications. The combinations of piezotronics and piezo-phototronics with the current popular electronics, optoelectronics and spintronics have great significances, which will bring in revolutionized impacts for future sensor networks, artificial intelligence, micro-nano energy and human-machine interaction applications. This paper gives a brief review of the experimental progress in device application in these two fields in recent years, and looks forward to the future development of these two subjects.
Triboelectric nanogenerators (TENGs) as an avant-garde technology that transforms mechanical energy into electrical energy, offering a new direction for green energy and sustainable development. By means of high-efficiency TENGs, conventional materials as new triboelectric materials have exhibited multi-attribute characteristics, achieving innovative applications in the field of micro-nano energy harvesting and self-powered sensing. The progress of TENGs technology with the triboelectric materials is complementary and mutually promoting. On the one hand, one of the cruxes of TENGs lies in the triboelectric materials, which have a decisive impact on their performance. On the other hand, as the research and application of TENGs continue to deepen, higher demands are placed on triboelectric materials, which in turn promotes the advancement of the entire material system as well as the fields of materials science and physics. This work aims to delve into the characteristics, types, preferred choices, and modification treatments of triboelectric materials on the performances of TENGs, hoping to provide guidance and insights for future research and applications.
