Flexible photodetectors have attracted a great deal of research interest in recent years due to their great possibilities for application in a variety of emerging areas such as flexible, stretchable, ...implantable, portable, wearable and printed electronics and optoelectronics. Novel functional materials, including materials with zero‐dimensional (0D) and one‐dimensional (1D) inorganic nanostructures, two‐dimensional (2D) layered materials, organic semiconductors and perovskite materials, exhibit appealing electrical and optoelectrical properties, as well as outstanding mechanical flexibility, and have been widely studied as building blocks in cost‐effective flexible photodetection. Here, we comprehensively review the outstanding performance of flexible photodetectors made from these novel functional materials reported in recent years. The photoresponse characteristics and flexibility of the devices will be discussed systematically. Summaries and challenges are provided to guide future directions of this vital research field.
Flexible photodetectors are of great importance in next‐generation optoelectronics and can provide a number of new functionalities towards some practical applications. The development of flexible photodetectors based on various novel functional materials are reviewed. Their photoresponse properties and mechanical flexibility are systematically discussed. Conclusions on the current techniques and future challenges are presented.
Following a significant number of graphene studies, other two‐dimensional (2D) layered materials have attracted more and more interest for their unique structures and distinct physical properties, ...which has opened a window for realizing novel electronic or optoelectronic devices. Here, we present a comprehensive review on the applications of 2D‐layered semiconductors as photodetectors, including photoconductors, phototransistors, and photodiodes, reported in the past five years. The device designs, mechanisms, and performances of the photodetectors are introduced and discussed systematically. Emerging techniques to improve device performances by enhancing light‐matter interactions are addressed as well. Finally, we deliver a summary and outlook to provide a guideline of the future development of this rapidly growing field.
2D layered semiconductors beyond graphene are successfully used in various high‐performance photodetectors, including photoconductors, phototransistors, and photodiodes. Here, a comprehensive review on the emerging 2D photodetectors is presented, focusing on the device designs, mechanisms, and performances. Various approaches for the optimization of device performance are introduced. In the end, a summary and an outlook of this field are delivered.
The number of catalytically reactive sites and their intrinsic electrocatalytic activity strongly affect the performance of electrocatalysts. Recently, there are growing concerns about layered double ...hydroxides (LDHs) for oxygen evolution reaction (OER). Exfoliating LDHs is an effective method to increase the reactive sites, however, a traditional liquid phase exfoliation method is usually very labor‐intensive and time‐consuming. On the other hand, proper heteroelement doping and edge engineering are helpful to tune the intrinsic activity of reactive sites. In this work, bulk CoFe LDHs are successfully exfoliated into ultrathin CoFe LDHs nanosheets by nitrogen plasma. Meanwhile, nitrogen doping and defects are introduced into exfoliated ultrathin CoFe LDHs nanosheets. The number of reactive sites can be increased efficiently by the formation of ultrathin CoFe LDHs nanosheets, the nitrogen dopant alters the surrounding electronic arrangement of reactive site facilitating the adsorption of OER intermediates, and the electrocatalytic activity of reactive sites can be further tuned efficiently by introducing defects which increase the number of dangling bonds neighboring reactive sites and decrease the coordination number of reactive sites. With these advantages, this electrocatalyst shows excellent OER activity with an ultralow overpotential of 233 mV at 10 mA cm−2.
Engineering the edge and corner active sites and realizing nitrogen incorporation in ultrathin N‐CoFe layered double hydroxides (LDHs) are implemented and synthesized simultaneously using N2 plasma to treat bulk CoFe LDHs nanosheets. With these unique features, the ultrathin N‐CoFe LDHs nanosheets as electrocatalyst show excellent oxygen evolution reaction properties.
The reasonable design of electrode materials for rechargeable batteries plays an important role in promoting the development of renewable energy technology. With the in‐depth understanding of the ...mechanisms underlying electrode reactions and the rapid development of advanced technology, the performance of batteries has significantly been optimized through the introduction of defect engineering on electrode materials. A large number of coordination unsaturated sites can be exposed by defect construction in electrode materials, which play a crucial role in electrochemical reactions. Herein, recent advances regarding defect engineering in electrode materials for rechargeable batteries are systematically summarized, with a special focus on the application of metal‐ion batteries, lithium–sulfur batteries, and metal–air batteries. The defects can not only effectively promote ion diffusion and charge transfer but also provide more storage/adsorption/active sites for guest ions and intermediate species, thus improving the performance of batteries. Moreover, the existing challenges and future development prospects are forecast, and the electrode materials are further optimized through defect engineering to promote the development of the battery industry.
Recent advances regarding defect engineering on electrode materials for rechargeable batteries are systematically summarized, with a special focus on application in metal‐ion batteries, lithium–sulfur batteries, and metal–air batteries. The defects can not only promote diffusion of ions and charge transfer, but also maintain structural stability and provide more energy storage/adsorption/active sites, thus improving the performance of the batteries.
When COVID-19 emerged in China in late 2019, most citizens were home-quarantined to prevent the spread of the virus. This study explored the prevalence of post-traumatic stress disorder (PTSD) and ...depression in a sample of home-quarantined college students to identify the psychological distress risk factors.
The PTSD and depressive symptoms in the 2485 participants from 6 universities were investigated using online survey versions of the PTSD Checklist Civilian Version and the 9-question Patient Health Questionnaires (PHQ-9), and data on sleep durations, exposure, home-quarantine time and socio-demographic variables were also collected.
The PTSD and depression prevalence were found to be 2.7% and 9.0%. Subjectively, feeling extreme fear was the most significant risk factor for psychological distress, followed by short sleep durations, being in their graduating year (4th year) and living in severely afflicted areas. Sleep durations was a mediator between exposures and mental health problems.
The results suggested that the psychological consequences of the COVID-19 could be serious. Psychological interventions that reduce fear and improve sleep durations need to be made available to the home-quarantined university students, and graduating students and those in the worst-hit areas should be given priority focus.
The pandemic of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global crisis. Replication of SARS-CoV-2 requires the viral ...RNA-dependent RNA polymerase (RdRp) enzyme, a target of the antiviral drug remdesivir. Here we report the cryo-electron microscopy structure of the SARS-CoV-2 RdRp, both in the apo form at 2.8-angstrom resolution and in complex with a 50-base template-primer RNA and remdesivir at 2.5-angstrom resolution. The complex structure reveals that the partial double-stranded RNA template is inserted into the central channel of the RdRp, where remdesivir is covalently incorporated into the primer strand at the first replicated base pair, and terminates chain elongation. Our structures provide insights into the mechanism of viral RNA replication and a rational template for drug design to combat the viral infection.
DNA copy number variation (CNV) has been recognized as an important source of genetic variation. Array comparative genomic hybridization (aCGH) is commonly used for CNV detection, but the microarray ...platform has a number of inherent limitations.
Here, we describe a method to detect copy number variation using shotgun sequencing, CNV-seq. The method is based on a robust statistical model that describes the complete analysis procedure and allows the computation of essential confidence values for detection of CNV. Our results show that the number of reads, not the length of the reads is the key factor determining the resolution of detection. This favors the next-generation sequencing methods that rapidly produce large amount of short reads.
Simulation of various sequencing methods with coverage between 0.1x to 8x show overall specificity between 91.7 - 99.9%, and sensitivity between 72.2 - 96.5%. We also show the results for assessment of CNV between two individual human genomes.
In the past several years, organic–inorganic hybrid perovskites and all inorganic perovskites have attracted enormous research interest in a variety of optoelectronic applications including solar ...cells, light‐emitting diodes, semiconductor lasers, and photodetectors for their plenty of appealing electrical and optoelectrical properties. Benefiting from the inherent amplification function of transistors and the pronounced photogating effect, perovskite‐based phototransistors and hybrid photodetectors can provide very high photoresponsivity and gain, rendering them highly promising for some specific applications especially ultrasensitive light detection. A review on the recent progress of phototransistors and hybrid photodetectors using perovskites as light‐sensitive materials is presented. The efforts and development in 3D and 2D perovskite‐based phototransistors, and perovskite/functional material (e.g., graphene, 2D semiconductors, organic semiconductors, and other semiconductors) heterojunction‐based hybrid photodetectors are introduced and discussed systematically. Some processing techniques for optimizing device performance are also addressed. In the final section, a conclusion of the research achievements is presented and possible challenges as well as outlook are provided to guide future activity in this research field.
Organic–inorganic hybrid perovskites and all inorganic perovskites are successfully used in phototransistors and hybrid photodetectors with very high photoresponsivity and gain. Herein, a review of the recent progress in phototransistors and hybrid photodetectors based on pure 3D and 2D perovskites, and perovskite/functional material heterojunctions is presented. A summary and outlook of this research field are also delivered.
Nanoparticle-stacked porous Ni3FeN nanosheets were synthesized through a simple nitridation reaction of the corresponding LDHs. The nanosheet is composed of stacked nanoparticles with more active ...sites exposed for electrocatalytic reactions. Thus, it exhibited excellent oxygen evolution reaction performance having an extremely low overpotential of 223 mV at 10 mA/cm2 and hydrogen evolution reaction property with a very low overpotential of 45 mV at 10 mA/cm2. This electrocatalyst as bifunctional electrodes is used to overall water splitting in alkaline media, showing a high performance with 10 mA/cm2 at a cell voltage of 1.495 V.
Hierarchical porous structures are highly desired for various applications. However, it is still challenging to obtain such materials with tunable architectures. Here, this paper reports hierarchical ...nanomaterials with oriented 2D pores by taking advantages of thermally instable bonds in vanadium‐based metal–organic frameworks (MOFs). High‐temperature calcination of these MOFs accompanied by the loss of coordinated water molecules and other components enables the formation of orderly slit‐like 2D pores in vanadium oxide/porous carbon nanorods (VOx/PCs). This unique combination leads to an increase of the reactive surface area. In addition, optimized VOx/PCs demonstrate high‐rate capability and ultralong cycling life for sodium storage. The assembled full cells also show high capacity and cycling stability. This report provides an effective strategy for producing MOFs‐derived composites with hierarchical porous architectures for energy storage.
A unique bonding guidance in vanadium‐based metal–organic frameworks is investigated for achieving oriented 2D pores. Benefiting from its typical loose morphology, the hierarchical vanadium oxide/porous carbon composite with oriented pores endows sodium‐ion anode with superior electrochemical performance.
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