Self-Gating Effect Induced Large Performance Improvement of ZnO Nanocomb Gas Sensors

Much greater surface-to-volume ratio of hierarchical nanostructures renders them with promising potential for high performance chemical sensing. In this work, crystalline nanocombs were synthesized <i>via</i> chemical vapor deposition and fabricated into resistive gas sensors. Particularly, NO₂ sensing performance of these devices has been systematically characterized, showing higher sensitivity as compared to their nanobelt counterparts. Through device simulation, it was discovered that the teeth part of a nanocomb could serve as a “negative-potential gate” after accumulating electrons captured by surface adsorbed NO₂ molecules. This self-gating effect eventually results in a greater reduction of nanocomb device channel conductance upon NO₂ exposure, as compared to a nanobelt device, leading to a much higher NO₂ detection sensitivity. This study not only sheds light on the mechanism of performance enhancement with hierarchical nanostructures, but also proposes a rational approach and a simulation platform to design nanostructure based chemical sensors with desirable performance

Organic Halides and Nanocone Plastic Structures Enhance the Energy Conversion Efficiency and Self-Cleaning Ability of Colloidal Quantum Dot Photovoltaic Devices

This paper presents solid-state ligand exchange of spin-coated colloidal lead sulfide quantum dot (PbS QD) films by methylammonium iodide (MAI) and integration of them in depleted heterojunction solar (DHS) devices having an antireflecting (AR) nanocone plastic structure. Time-resolved photoluminescence measurements determine a shorter lifetime of the charge carries on a semiconductor (TiO₂) electron transfer layer for the MAI-passivated QD films as compared with those with long-chain aliphatic or short thiol ligands. Consequently, the DHS device yields improved power conversion efficiency (>125%) relative to oleic-acid-passivated PbS QD films. Using anodized aluminum oxide templates, an inverted nanocone polydimethylsiloxane structure was also prepared and utilized as an AR layer in the DHS device. The solar cells exhibit an energy conversion efficiency of 7.5% with enhanced water-repellant ability

ZnO Quantum Dot Decorated Zn₂SnO₄ Nanowire Heterojunction Photodetectors with Drastic Performance Enhancement and Flexible Ultraviolet Image Sensors

Here we report the fabrication of high-performance ultraviolet photodetectors based on a heterojunction device structure in which ZnO quantum dots were used to decorate Zn₂SnO₄ nanowires. Systematic investigations have shown their ultrahigh light-to-dark current ratio (up to 6.8 × 10⁴), specific detectivity (up to 9.0 × 10¹⁷ Jones), photoconductive gain (up to 1.1 × 10⁷), fast response, and excellent stability. Compared with a pristine Zn₂SnO₄ nanowire, a quantum dot decorated nanowire demonstrated about 10 times higher photocurrent and responsivity. Device physics modeling showed that their high performance originates from the rational energy band engineering, which allows efficient separation of electron–hole pairs at the interfaces between ZnO quantum dots and a Zn₂SnO₄ nanowire. As a result of band engineering, holes migrate to ZnO quantum dots, which increases electron concentration and lifetime in the nanowire conduction channel, leading to significantly improved photoresponse. The enhancement mechanism found in this work can also be used to guide the design of high-performance photodetectors based on other nanomaterials. Furthermore, flexible ultraviolet photodetectors were fabricated and integrated into a 10 × 10 device array, which constitutes a high-performance flexible ultraviolet image sensor. These intriguing results suggest that the band alignment engineering on nanowires can be rationally achieved using compound semiconductor quantum dots. This can lead to largely improved device performance. Particularly for ZnO quantum dot decorated Zn₂SnO₄ nanowires, these decorated nanowires may find broad applications in future flexible and wearable electronics

Integrated Flexible, Waterproof, Transparent, and Self-Powered Tactile Sensing Panel

Portable and wearable electronic devices are human-centered devices; therefore, many unique attributes are highly desirable, such as flexibility, being self-powered, and waterproof. These properties render devices excellent adaptivity in harsh operation environments. In this work, we report an integrated triboelectric tactile sensor array with flexible, transparent, self-powered, and waterproof features. Each tactile sensor is a surface nano/microtexture enhanced triboelectric nanogenerator. The sensor array can serve as a touch panel for electronic devices. Owing to a unique design of a built-in triboelectric contact pair and an electrical shielding layer, an individual pixel of the fabricated tactile sensor array can generate an open circuit voltage up to 1.613 V and a short circuit current density of 47.308 mA/m² under 612.5 kPa. The tactile sensors can produce stable voltage signals regardless of the materials of the touching objects, and work stably both in ambient and aqueous environments. To examine the touch panel function of a sensor array, a matrix of 10 × 10 individually addressable 4 mm × 4 mm triboelectric sensors has been integrated into a thin, transparent, and flexible film, and the 2-D touch mapping has been successfully demonstrated. The unique triboelectric tactile sensor array reported here is robust and highly versatile, and it may find broad applications in display, wearable electronics, artificial skins, Internet of Things (IoT), <i>etc</i>

Integrated Flexible, Waterproof, Transparent, and Self-Powered Tactile Sensing Panel

Portable and wearable electronic devices are human-centered devices; therefore, many unique attributes are highly desirable, such as flexibility, being self-powered, and waterproof. These properties render devices excellent adaptivity in harsh operation environments. In this work, we report an integrated triboelectric tactile sensor array with flexible, transparent, self-powered, and waterproof features. Each tactile sensor is a surface nano/microtexture enhanced triboelectric nanogenerator. The sensor array can serve as a touch panel for electronic devices. Owing to a unique design of a built-in triboelectric contact pair and an electrical shielding layer, an individual pixel of the fabricated tactile sensor array can generate an open circuit voltage up to 1.613 V and a short circuit current density of 47.308 mA/m² under 612.5 kPa. The tactile sensors can produce stable voltage signals regardless of the materials of the touching objects, and work stably both in ambient and aqueous environments. To examine the touch panel function of a sensor array, a matrix of 10 × 10 individually addressable 4 mm × 4 mm triboelectric sensors has been integrated into a thin, transparent, and flexible film, and the 2-D touch mapping has been successfully demonstrated. The unique triboelectric tactile sensor array reported here is robust and highly versatile, and it may find broad applications in display, wearable electronics, artificial skins, Internet of Things (IoT), <i>etc</i>

Efficient Light Absorption with Integrated Nanopillar/Nanowell Arrays for Three-Dimensional Thin-Film Photovoltaic Applications

Efficient light absorption in thin-film photovoltaic (PV) devices is crucial for improving their efficiency and reducing cost. Here we have not only developed a low-cost and scalable method to fabricate a unique type of integrated-nanopillar-nanowell (i-NPW) structure by integrating nanopillar and nanowell arrays together vertically, but also demonstrated the attractive optical property of the i-NPW arrays by leveraging the advantages of “positive” and “negative” nanostructures for photon harvesting. Impressively, the 2 μm thick i-NPW arrays with only 40 nm a-Si coating obtained a day-integrated absorption of 89.27%, as opposed to only 33.45% for the planar control sample. These results suggest the feasibility and clear advantage of vertical integration of three-dimensional (3-D) nanophotonic structures, and meanwhile also pave a viable and convenient way toward a 3-D ultrathin film PV module with potency for high energy conversion efficiency

Quasi Core/Shell Lead Sulfide/Graphene Quantum Dots for Bulk Heterojunction Solar Cells

Hybrid nanostructures combining semiconductor quantum dots and graphene are attracting increasing attention because of their optoelectronic properties promising for photovoltaic applications. We present a hot-injection synthesis of a colloidal nanostructure which we define as quasi core/shell PbS/graphene quantum dots due to the incomplete passivation of PbS surfaces with an ultrathin layer of graphene. Simulation by density functional theory of a prototypical model of a nonstoichiometric Pb-rich core (400 atoms) coated by graphene (20 atoms for each graphene sheet) indicates the possibility of surface passivation of (111) planes of PbS with graphene resulting in a decrease in trap states and recombination sites. The graphene coating of the PbS quantum dots decreases the exciton lifetime up to 0.78 μs as compared to 1.2 μs for the oleic acid passivated PbS quantum dots due to the fast extraction of carriers. We have employed PbS/graphene as well as Cd-doped PbS/graphene quantum dots as active layers of bulk heterojunction solar cells, and we achieved solar power conversion efficiencies of 3.6 and 4.1%, respectively

Data_Sheet_1_Using AGREE II reporting checklist to evaluate the quality of Tuina clinical practice guidelines.pdf

ObjectiveThe objective of this study is to evaluate the methodological quality of Tuina clinical practice guidelines (CPGs).MethodsComputer searches of China National Knowledge Infrastructure (CNKI), Chinese Technical Periodicals (VIP), Wanfang Data Knowledge Service Platform, PubMed, Cochrane Library, Embase, and other databases were conducted to search for published guidelines on Tuina, with a search time frame from database creation to March 2021. Four evaluators independently used the Appraisal of Guidelines for Research and Evaluation II instrument to evaluate the quality of the included guidelines.ResultsA total of eight guidelines related to Tuina were included in this study. The quality of reporting was low in all included guidelines. The highest quality report had a total score of 404 and was rated as “highly recommended.” The worst guideline had a final score of 241 and was rated as “not recommended.” Overall, 25% of the included guidelines were recommended for clinical use, 37.5% were recommended after revision, and 37.5% were not recommended.ConclusionThe number of existing Tuina clinical practice guidelines is limited. The methodological quality is low, far from the internationally accepted clinical practice guideline development and reporting norms. In the future, reporting specifications of guidelines and the methodology of guideline development, including the rigor of the guideline development process, the clarity, application, and independence of reporting, should be emphasized in the development of the Tuina guidelines. These initiatives could improve the quality and applicability of clinical practice guidelines to guide and standardize the clinical practice of Tuina.</p

Highly Efficient Flexible Perovskite Solar Cells with Antireflection and Self-Cleaning Nanostructures

Flexible thin film solar cells have attracted a great deal of attention as mobile power sources and key components for building-integrated photovoltaics, due to their light weight and flexible features in addition to compatibility with low-cost roll-to-roll fabrication processes. Among many thin film materials, organometallic perovskite materials are emerging as highly promising candidates for high efficiency thin film photovoltaics; however, the performance, scalability, and reliability of the flexible perovskite solar cells still have large room to improve. Herein, we report highly efficient, flexible perovskite solar cells fabricated on ultrathin flexible glasses. In such a device structure, the flexible glass substrate is highly transparent and robust, with low thermal expansion coefficient, and perovskite thin film was deposited with a thermal evaporation method that showed large-scale uniformity. In addition, a nanocone array antireflection film was attached to the front side of the glass substrate in order to improve the optical transmittance and to achieve a water-repelling effect at the same time. It was found that the fabricated solar cells have reasonable bendability, with 96% of the initial value remaining after 200 bending cycles, and the power conversion efficiency was improved from 12.06 to 13.14% by using the antireflection film, which also demonstrated excellent superhydrophobicity

Additional file 1: Figure S1. of A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes

Linear correlation between AAO pore depth and integrated charge density in a large voltage range (a) 20–200 V; (b) 346–600 V