Publications

The Beijing Institute of Nanoenergy and Nanosystems (BINN), Chinese Academy of Sciences, was founded in 2012 by Wang. The mission of BINN is to carry out fundamental research related to nanoenergy and nanosensors as well as train future scientists. The two major areas of BINN's research are nanogenerators for self-powered systems and blue energy and piezotronics and piezo-phototronics for third-generation semiconductors. After 7 years of development starting from scratch, BINN now has about 400 members including graduate students. This special issue published in Advanced Functional Materials showcases a group of selected papers submitted by colleagues at the BINN to represent some of the on-going research in the institute. Based on piezoelectric and triboelectric effects, nanogenerators represent a new approach that converts tiny mechanical energy into electric power, which now has attracted worldwide attention, particularly in the era of Internet-of-things, sensor networks, artificial intelligence, and robotics. Piezoelectric nanogenerators (PENGs) were first invented in 2006 using the piezoelectric effect obtained from nanowire materials. The triboelectric nanogenerator (TENG) was first invented in Wang's group in 2012 by using a conjunction of contact-electrification and electrostatic induction effects. TENGs have quickly gained worldwide attention and now comprise a new field of research that involves fundamental physics, chemistry, materials, electric engineering, and mechanical engineering. Nanogenerators have shown very broad applications in different fields. Firstly, they serve as the micro-power source for wireless distributed mobile/wearable electronics, Internet-of-things, sensor networks, and implantable medical electronics, which require a tremendous amount of mobile power sources, and in many cases, the batteries could not completely satisfy the practical requirements in terms of size, capacity, flexibility, or non-replaceable in vivo. Secondly, nanogenerators can serve as a self-powered sensor (or active sensor) for detecting mechanical triggering, pressure fluctuation, and environmental stimulation without requiring external power being supplied to the sensor tip, which thus possesses great potential for human-machine interfacing, security systems, physiological characterization, and infrastructure monitoring. They also have applications in smart skin, robotics, MEMS, and biomedical science among other fields. Lastly, nanogenerators can be a possible approach for harvesting large-scale energy from ocean waves. By constructing units that are the size of a baseball, inside which the TENGs are installed, millions or even billions of such units can be interconnected into a “fishing net,” which can float on the water surface for harvesting the kinetic energy. This technology has the merits of low cost, light weight, high efficiency, high output power density, and easy scaling, leading towards the dream of “blue energy”, the energy from the ocean. Piezotronics is a term coined by Wang in 2007, which involves using the piezoelectric effect to control electronics via mechanical stimuli. For wurtzite structures that have non-central symmetry, such as ZnO, GaN, and InN, piezoelectric polarization charges are created at the interface/surface by applying a strain. The strain created inner-crystal piezopotential can serve as a “gate voltage” that can effectively tune/control the charge transport across an interface/junction. This mechanism is termed the piezotronic effect and the electronics fabricated based on such a mechanism is coined as piezotronics, with applications in force controlled electronic devices, sensors, logic units, memories, and catalysts. Analogically, new electronic components can be fabricated as well by using the electric potential created by contact-electrification as a gating voltage, which is called tribotronics. The presence of polarization charges at a p-n junction can effectively distort the local band structure and consequently affect carrier transport, separation, or recombination. Applying either a compressive or tensile strain depending on the polarization of the piezoelectric material, the efficiency for charge carrier separation or recombination can be effectively enhanced. The combination of photon excitation, coupling among semiconductors, photon excitation, and piezoelectricity represents a new field of research called piezo-phototronics. The piezo-phototronic effect is the tuning and controlling of charge carrier generation, separation or recombination at a heterojunction by the strain induced piezoelectric polarization charge. This effect could lead to tremendous performance gain in LEDs, laser diodes, photodetectors, photovoltatic devices, and catalysis by applying static or quasi-static mechanical strains. The fields of research conducted at BINN can be summarized using a “science tree” (Figure 1) to project its main “trunk”, major fields, and applications. The main trunk is based on functional materials and fundamental physics effects, which leads to new and innovative fields. The major fields of research are self-powered systems, triboelectric nanogenerators, hybridized nanogenerators, blue energy, tribotronics, piezotronics, and piezo-phototronics, which are in the middle of the tree. The small branches are the potential applications, as well as future perspectives. We anticipate this tree will grow fast and expand quickly with abundant fruits in the near future.

Journal Article Dual-Mode Elecromechanical Resonance of Nanobelts Observed by In-situ TEM Get access Z L Wang, Z L Wang School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 + e-mail: zhong.wang@mse.gatech.edu Search for other works by this author on: Oxford Academic Google Scholar X D Bai, X D Bai School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245International Center for Quantum Structures and State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China Search for other works by this author on: Oxford Academic Google Scholar P X Gao, P X Gao School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 Search for other works by this author on: Oxford Academic Google Scholar E G Wang E G Wang International Center for Quantum Structures and State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 9, Issue S02, 1 August 2003, Pages 338–339, https://doi.org/10.1017/S143192760344169X Published: 19 July 2003

Piezo-phototronic effect is a fundamental effect of semiconductors lacking of central symmetry with geometries from one-dimensional (1D) nanowire to 3D bulk. Here, we present that the piezo-phototronic effect can even tune a spin–orbit coupled photoluminescence (PL) based on all-inorganic perovskite CsPbBr3 quantum dots (QDs). Although the cubic structure of CsPbBr3 QDs is nonpiezoelectric, a cooling treatment can change it to an orthorhombic structure, which is proven to possess a piezoelectric property. The spin–orbit coupled PL intensity is demonstrated to be dependent on the polarization of the excited light. Because of the manipulation of the spin-split energy levels via the piezo-phototronic effect, the spin–orbit coupled PL intensities under a −0.9% compressive strain for linearly and circularly polarized light excitations can be enhanced by 136% and 146%, respectively. These findings reveal fundamental understandings of the spin–orbit coupled PL dynamics and demonstrate promising optoelectronic applications of the piezo-phototronic effect in these QDs.

Abstract The selectivity and activities of platinum (Pt) particles strongly depend on their sizes and shapes. A technique has been recently reported for controlling the shapes and sizes of Pt particles [1]. Pt particles were prepared by bubbling Ar gas through the solution of K2PtCl4, and the Pt ions were reduced by flowing H2 gas through the solution. The shape control was performed by changing the ratio of the concentration of the capping polymer material to that of the platinum cations used in the reductive synthesis of colloidal particles in solution at room temperature [2]. High percentage of cubic, tetrahedral and octahedral particles have been prepared at room temperature, making it possible for studying the chemical activities of particles with different shapes and facets. This paper aims to study the surface structures of Pt particles prepared by the shape-controlling synthesis technique using high-resolution transmission electron microscopy (HRTEM).

Abstract To investigate the situation of antibiotic consumption and to assess the inappropriate use on pediatric inpatients of different types hospitals in Sichuan, China. A cross-sectional survey of antibiotic prescriptions among hospitalized children aged 1month -14years were conducted from April 2018 to June 2018 in southwestern China. Antibiotic prescriptions were extracted from electronic records during hospitalization of each inpatient in five different types hospitals. In this study, the antibiotic prescription rate of hospitalized children was 66.9% (1176/1758). Compared with tertiary children hospital (TC) (46.1%), general hospitals and non-tertiary children hospitals has higher rate of antibiotic prescription (almost 85%) (P < .001 ) . 93.4% of inpatients received parenteral antibiotic. Overall, the most common antibiotics were Cefoperazone and enzyme inhibitor, Cefixime and Azithromycin . Lower respiratory tract infection (LRTI) was the leading reason for antibiotic consumption in pediatric wards (56.8%), followed by upper respiratory tract infection (URTI) (22.2%). For children with LRTI, Cephalosporins were heavy prescribed, especially broad-spectrum third-generation Cephalosporins (60.3%). The antibiotic prescription proportion of URTI in general hospitals and non-tertiary children hospitals (more than 18%) was higher than TC (8.1%) ( P < .001). There was inappropriate use of antibiotic in hospitalized children including overuse of parenteral administration, overprescribing of antibiotic on URTI and misuse of third-generation Cephalosporins in pediatric inpatients with LRTI. Compared with tertiary freestanding children hospital, the irrational antibiotic prescription of general hospitals and non-tertiary children hospitals were more serious. Management strategy should be implementer on quality improvement of antibiotic use.

Nanobelt is a quasi-one-dimensional structurally controlled nanomaterial that has well-defined chemical composition, crystallographic structure, and surfaces (e.g., growth direction, top/bottom surface, and side surfaces). This article reviews the nanobelt family of functional oxides, including ZnO, SnO2, In2O3, Ga2O3, CdO, and PbO2 and the relevant hierarchical and complex nanorods and nanowires that have been synthesized by a solid-vapor process. The nanobelts are single crystalline and dislocation free, and their surfaces are atomically flat. The oxides are semiconductors that have been used for fabrication of nanosize functional devices of key importance for nanosystems and biotechnology, such as field-effect transistors, gas sensors, nanoresonators, and nanocantilevers. The structurally controlled ZnO nanobelts that exhibit piezoelectric properties are also reviewed. By controlling growth kinetics, we show the success of growing nanobelt-based novel structures whose surfaces are dominated by the polarized +-(0001) facets. Owing to the positive and negative ionic charges on the zinc- and oxygen-terminated +-(0001) surfaces, respectively, a spontaneous polarization is induced across the nanobelt thickness. As a result, helical nanostructures and nanorings are formed by rolling up single-crystal nanobelts; this phenomenon is a consequence of minimizing the total energy contributed by spontaneous polarization and elasticity. The polar surface-dominated ZnO nanobelts are likely to be an ideal system for understanding piezoelectricity and polarization-induced ferroelectricity at nano-scale and they could have applications as one-dimensional nano-scale sensors, transducers, and resonators.