National Center for Nanoscience and Technology

We have converted nanoscale mechanical energy into electrical energy by means of piezoelectric zinc oxide nanowire (NW) arrays. The aligned NWs are deflected with a conductive atomic force microscope tip in contact mode. The coupling of piezoelectric and semiconducting properties in zinc oxide creates a strain field and charge separation across the NW as a result of its bending. The rectifying characteristic of the Schottky barrier formed between the metal tip and the NW leads to electrical current generation. The efficiency of the NW-based piezoelectric power generator is estimated to be 17 to 30%. This approach has the potential of converting mechanical, vibrational, and/or hydraulic energy into electricity for powering nanodevices.

autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Although organic photovoltaic (OPV) cells have many advantages, their performance still lags far behind that of other photovoltaic platforms. A fundamental reason for their low performance is the low charge mobility of organic materials, leading to a limit on the active-layer thickness and efficient light absorption. In this work, guided by a semi-empirical model analysis and using the tandem cell strategy to overcome such issues, and taking advantage of the high diversity and easily tunable band structure of organic materials, a record and certified 17.29% power conversion efficiency for a two-terminal monolithic solution-processed tandem OPV is achieved.

The production of clean and renewable hydrogen through water splitting using photocatalysts has received much attention due to the increasing global energy crises. In this study, a high efficiency of the photocatalytic H(2) production was achieved using graphene nanosheets decorated with CdS clusters as visible-light-driven photocatalysts. The materials were prepared by a solvothermal method in which graphene oxide (GO) served as the support and cadmium acetate (Cd(Ac)(2)) as the CdS precursor. These nanosized composites reach a high H(2)-production rate of 1.12 mmol h(-1) (about 4.87 times higher than that of pure CdS nanoparticles) at graphene content of 1.0 wt % and Pt 0.5 wt % under visible-light irradiation and an apparent quantum efficiency (QE) of 22.5% at wavelength of 420 nm. This high photocatalytic H(2)-production activity is attributed predominantly to the presence of graphene, which serves as an electron collector and transporter to efficiently lengthen the lifetime of the photogenerated charge carriers from CdS nanoparticles. This work highlights the potential application of graphene-based materials in the field of energy conversion.

Abstract Recent achievements in the construction of surfaces with special wettabilities, such as superhydrophobicity, superhydrophilicity, superoleophobicity, superoleophilicity, superamphiphilicity, superamphiphobicity, superhydrophobicity/superoleophilicity, and reversible switching between superhydrophobicity and superhydrophilicity, are presented. Particular attention is paid to superhydrophobic surfaces created via various methods and surfaces with reversible superhydrophobicity and superhydrophilicity that are driven by various kinds of external stimuli. The control of the surface micro‐/nanostructure and the chemical composition is critical for these special properties. These surfaces with controllable wettability are of great importance for both fundamental research and practical applications.

Particularly uniform: Monodisperse ferrite microspheres can be synthesized to have diameters of about 200–800 nm (TEM image, left). High-resolution TEM analysis (image, right and inset) shows that each microsphere is a single crystal. Their hydrophilic and magnetic properties impart to the microparticles many potential uses in electronics and biomedicine.

Abstract Hierarchical flowerlike nickel hydroxide decorated on graphene sheets has been prepared by a facile and cost‐effective microwave‐assisted method. In order to achieve high energy and power densities, a high‐voltage asymmetric supercapacitor is successfully fabricated using Ni(OH) 2 /graphene and porous graphene as the positive and negative electrodes, respectively. Because of their unique structure, both of these materials exhibit excellent electrochemical performances. The optimized asymmetric supercapacitor could be cycled reversibly in the high‐voltage region of 0–1.6 V and displays intriguing performances with a maximum specific capacitance of 218.4 F g −1 and high energy density of 77.8 Wh kg −1 . Furthermore, the Ni(OH) 2 /graphene//porous graphene supercapacitor device exhibits an excellent long cycle life along with 94.3% specific capacitance retained after 3000 cycles. These fascinating performances can be attributed to the high capacitance and the positive synergistic effects of the two electrodes. The impressive results presented here may pave the way for promising applications in high energy density storage systems.

Abstract Asymmetric supercapacitor with high energy density has been developed successfully using graphene/MnO 2 composite as positive electrode and activated carbon nanofibers (ACN) as negative electrode in a neutral aqueous Na 2 SO 4 electrolyte. Due to the high capacitances and excellent rate performances of graphene/MnO 2 and ACN, as well as the synergistic effects of the two electrodes, such asymmetric cell exhibits superior electrochemical performances. An optimized asymmetric supercapacitor can be cycled reversibly in the voltage range of 0–1.8 V, and exhibits maximum energy density of 51.1 Wh kg −1 , which is much higher than that of MnO 2 //DWNT cell (29.1 Wh kg −1 ). Additionally, graphene/MnO 2 //ACN asymmetric supercapacitor exhibits excellent cycling durability, with 97% specific capacitance retained even after 1000 cycles. These encouraging results show great potential in developing energy storage devices with high energy and power densities for practical applications.

Hierarchical micropapillae and nanofolds are known to exist on the petals' surfaces of red roses. These micro- and nanostructures provide a sufficient roughness for superhydrophobicity and yet at the same time a high adhesive force with water. A water droplet on the surface of the petal appears spherical in shape, which cannot roll off even when the petal is turned upside down. We define this phenomenon as the "petal effect" as compared with the popular "lotus effect". Artificial fabrication of biomimic polymer films, with well-defined nanoembossed structures obtained by duplicating the petal's surface, indicates that the superhydrophobic surface and the adhesive petal are in Cassie impregnating wetting state.

Optimizing the molecular structures of organic photovoltaic (OPV) materials is one of the most effective methods to boost power conversion efficiencies (PCEs). For an excellent molecular system with a certain conjugated skeleton, fine tuning the alky chains is of considerable significance to fully explore its photovoltaic potential. In this work, the optimization of alkyl chains is performed on a chlorinated nonfullerene acceptor (NFA) named BTP-4Cl-BO (a Y6 derivative) and very impressive photovoltaic parameters in OPV cells are obtained. To get more ordered intermolecular packing, the n-undecyl is shortened at the edge of BTP-eC11 to n-nonyl and n-heptyl. As a result, the NFAs of BTP-eC9 and BTP-eC7 are synthesized. The BTP-eC7 shows relatively poor solubility and thus limits its application in device fabrication. Fortunately, the BTP-eC9 possesses good solubility and, at the same time, enhanced electron transport property than BTP-eC11. Significantly, due to the simultaneously enhanced short-circuit current density and fill factor, the BTP-eC9-based single-junction OPV cells record a maximum PCE of 17.8% and get a certified value of 17.3%. These results demonstrate that minimizing the alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.

Broadening the optical absorption of organic photovoltaic (OPV) materials by enhancing the intramolecular push-pull effect is a general and effective method to improve the power conversion efficiencies of OPV cells. However, in terms of the electron acceptors, the most common molecular design strategy of halogenation usually results in down-shifted molecular energy levels, thereby leading to decreased open-circuit voltages in the devices. Herein, we report a chlorinated non-fullerene acceptor, which exhibits an extended optical absorption and meanwhile displays a higher voltage than its fluorinated counterpart in the devices. This unexpected phenomenon can be ascribed to the reduced non-radiative energy loss (0.206 eV). Due to the simultaneously improved short-circuit current density and open-circuit voltage, a high efficiency of 16.5% is achieved. This study demonstrates that finely tuning the OPV materials to reduce the bandgap-voltage offset has great potential for boosting the efficiency.

Y Artificial intelligence (AI) coupled with promising machine learning (ML) techniques well known from computer science is broadly affecting many aspects of various fields including science and technology, industry, and even our day-to-day life. The ML techniques have been developed to analyze high-throughput data with a view to obtaining useful insights, categorizing, predicting, and making evidence-based decisions in novel ways, which will promote the growth of novel applications and fuel the sustainable booming of AI. This paper undertakes a comprehensive survey on the development and application of AI in different aspects of fundamental sciences, including information science, mathematics, medical science, materials science, geoscience, life science, physics, and chemistry. The challenges that each discipline of science meets, and the potentials of AI techniques to handle these challenges, are discussed in detail. Moreover, we shed light on new research trends entailing the integration of AI into each scientific discipline. The aim of this paper is to provide a broad research guideline on fundamental sciences with potential infusion of AI, to help motivate researchers to deeply understand the state-of-the-art applications of AI-based fundamental sciences, and thereby to help promote the continuous development of these fundamental sciences.

Multiple biological structures have demonstrated fog collection abilities, such as beetle backs with bumps and spider silks with periodic spindle-knots and joints. Many Cactaceae species live in arid environments and are extremely drought-tolerant. Here we report that one of the survival systems of the cactus Opuntia microdasys lies in its efficient fog collection system. This unique system is composed of well-distributed clusters of conical spines and trichomes on the cactus stem; each spine contains three integrated parts that have different roles in the fog collection process according to their surface structural features. The gradient of the Laplace pressure, the gradient of the surface-free energy and multi-function integration endow the cactus with an efficient fog collection system. Investigations of the structure–function relationship in this system may help us to design novel materials and devices to collect water from fog with high efficiencies. Biological structures such as the backs of beetles and spider silk have fog-collecting properties. Here, clusters of conical spines and trichomes on the stem of the cactus O. microdasysare found to be responsible for its fog-collecting abilities.

Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10(13) cm(-2) is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

ABSTRACT RNA interference (RNAi) is an ancient biological mechanism used to defend against external invasion. It theoretically can silence any disease-related genes in a sequence-specific manner, making small interfering RNA (siRNA) a promising therapeutic modality. After a two-decade journey from its discovery, two approvals of siRNA therapeutics, ONPATTRO ® (patisiran) and GIVLAARI™ (givosiran), have been achieved by Alnylam Pharmaceuticals. Reviewing the long-term pharmaceutical history of human beings, siRNA therapy currently has set up an extraordinary milestone, as it has already changed and will continue to change the treatment and management of human diseases. It can be administered quarterly, even twice-yearly, to achieve therapeutic effects, which is not the case for small molecules and antibodies. The drug development process was extremely hard, aiming to surmount complex obstacles, such as how to efficiently and safely deliver siRNAs to desired tissues and cells and how to enhance the performance of siRNAs with respect to their activity, stability, specificity and potential off-target effects. In this review, the evolution of siRNA chemical modifications and their biomedical performance are comprehensively reviewed. All clinically explored and commercialized siRNA delivery platforms, including the GalNAc ( N -acetylgalactosamine)–siRNA conjugate, and their fundamental design principles are thoroughly discussed. The latest progress in siRNA therapeutic development is also summarized. This review provides a comprehensive view and roadmap for general readers working in the field.

Abstract Improving power conversion efficiency (PCE) is important for broadening the applications of organic photovoltaic (OPV) cells. Here, a maximum PCE of 19.0% (certified value of 18.7%) is achieved in single‐junction OPV cells by combining material design with a ternary blending strategy. An active layer comprising a new wide‐bandgap polymer donor named PBQx‐TF and a new low‐bandgap non‐fullerene acceptor (NFA) named eC9‐2Cl is rationally designed. With optimized light utilization, the resulting binary cell exhibits a good PCE of 17.7%. An NFA F‐BTA3 is then added to the active layer as a third component to simultaneously improve the photovoltaic parameters. The improved light unitization, cascaded energy level alignment, and enhanced intermolecular packing result in open‐circuit voltage of 0.879 V, short‐circuit current density of 26.7 mA cm −2 , and fill factor of 0.809. This study demonstrates that further improvement of PCEs of high‐performance OPV cells requires fine tuning of the electronic structures and morphologies of the active layers.

We introduced a facile method to construct hierarchical nanocomposites by combining one-dimensional (1D) conducting polyaniline (PANI) nanowires with 2D graphene oxide (GO) nanosheets. PANI nanowire arrays are aligned vertically on GO substrate. The morphologies of PANI nanowires can be controlled by adjusting the ratios of aniline to GO, which are attributed to different nucleation processes. The hierarchical nanocomposite structures of PANI-GO were further proved by UV-vis, FTIR, and XRD measurements. The hierarchical nanocomposite possessed higher electrochemical capacitance and better stability than each individual component as supercapacitor electrode materials, showing a synergistic effect of PANI and GO. This study will further guide the preparation of functional nanocomposites by combining different dimensional nanomaterials.

The design and use of materials in the nanoscale size range for addressing medical and health-related issues continues to receive increasing interest. Research in nanomedicine spans a multitude of areas, including drug delivery, vaccine development, antibacterial, diagnosis and imaging tools, wearable devices, implants, high-throughput screening platforms, etc. using biological, nonbiological, biomimetic, or hybrid materials. Many of these developments are starting to be translated into viable clinical products. Here, we provide an overview of recent developments in nanomedicine and highlight the current challenges and upcoming opportunities for the field and translation to the clinic.

Abstract Heteroatom (N or S)‐doped graphene with high surface area is successfully synthesized via thermal reaction between graphene oxide and guest gases (NH 3 or H 2 S) on the basis of ultrathin graphene oxide‐porous silica sheets at high temperatures. It is found that both N and S‐doping can occur at annealing temperatures from 500 to 1000 °C to form the different binding configurations at the edges or on the planes of the graphene, such as pyridinic‐N, pyrrolic‐N, and graphitic‐N for N‐doped graphene, thiophene‐like S, and oxidized S for S‐doped graphene. Moreover, the resulting N and S‐doped graphene sheets exhibit good electrocatalytic activity, long durability, and high selectivity when they are employed as metal‐free catalysts for oxygen reduction reactions. This approach may provide an efficient platform for the synthesis of a series of heteroatom‐doped graphenes for different applications.

The wetting/antiwetting behavior of liquid droplets on a solid surface is not an apparent or simple contact between two phases, but among three phases. Inspired by the antiwetting behavior of oil droplets on fish scales in water, a superoleophobic and low-adhesive interface is created on a solid substrate with micro/nanohierarchical structures, using oil/water/solid three-phase systems.