238 wileyonlinelibrary.com COMMUNICATION available highly purifi ed CNTs, with reported purity of up to 99.9% or even higher. [ 22 ] Another factor leads to the slow progress on the development of high-performance CNT IR detectors is that device structure and operation mode have not been optimized for solution-processed CNTs to achieve performance comparable with that of state-of-the-art commercial IR detectors. [ 23,24 ] In this letter, we show that high-performance photodiodes can be constructed using solution-processed CNTs via a dopingfree technique. In contrast to other photodetectors that use photocurrent as the signal, [ 8,[11][12][13][14][15][16][17][18][19][20] here we exploit using photovoltage as the signal. The major benefi t of using photovoltage is that the commonly occurring shot noise and 1/ f noise can be signifi cantly suppressed. In addition, signal can be multiplied via introducing virtual contacts, which leads to further improvement on signal-to-noise ratio. A prototype CNT IR detector is demonstrated, which works at room temperature and shows broadband response, high responsivity and detectivity that are comparable to that of state-of-the-art room temperature semiconductor IR detectors. It is also demonstrated that our CNT IR detectors have excellent stability, as a result of the dopingfabrication process used here, with time, under high power illumination and at rigorous temperature conditions. An array of 150 × 150 photodetectors on a single chip is fabricated, with tested yield of 100% and high device uniformity, showing the potential for large-scale fabrication capability and imager applications.In a typical photovoltaic device, a built-in fi eld is essential for the effi cient separation of photoinduced electron-hole pairs. For CNT-based diodes, ideal rectifi cation behavior has been realized by using split gates or asymmetric contacts on individual CNTs. [ 9,10,13 ] However, light absorption in these devices is usually very weak. It is thus advantageous to construct a photodiode using CNT fi lm with more CNTs in the device channel. However, solution-processed CNT-fi lm-based diodes showing excellent rectifi cation effect have not been realized. [ 23,24 ] Here, we show that such high-performance diode based on solutionprocessed CNT fi lm can be realized by using a doping-free technique in a barrier-free-bipolar diode (BFBD) device geometry as depicted in Figure 1 a. In this device geometry, Sc and Pd are asymmetrically contacted to a CNT fi lm made by a liquidphase deposition technique on an n + silicon/SiO 2 substrate (see Figure S1a,b, Supporting Information). Thus, p-region and n-region are automatically formed adjacent to the contacts by charge transfer from the contacts. This process involves no intentionally introduced dopants, no extra defects on CNTs,

Environment‐related degradation and lead leakage in perovskite solar cells have posed a big challenge for their commercialization. Here, design of superhydrophobic surfaces is demonstrated as an effective strategy toward these issues, in which thiol‐functionalized perfluoroalkyl molecules are employed to chemically modify the lead halide perovskite film and metal electrode via a vapor‐assisted self‐assembly process. Due to the van der Waals forces, the generation of self‐assembly monolayer prefers to pack in a dense way, resulting in the formation of a closest‐packed, crystalline‐like molecular array. This dense array is endowed with a low‐surface‐energy chemistry that can not only enhance the water and oxygen resistance of the completed device but also reduce the defect density on the perovskite surfaces. These merits eventually boost the efficiency of inverted perovskite solar cells up to 21.79% along with a substantially improved long‐term stability. More importantly, the thiol‐functionalized superhydrophobic array can immobilize most of the undercoordinated lead ions on the perovskite surfaces by metal‐thiol coordination effect, which results in suppressing the lead leakage from the water‐soluble lead halide perovskites. Therefore, an avenue is pointed out here to fabricate stable perovskite solar cells with reducing lead leakage, representing a substantial step toward practical applications.

With the development of tissue engineering, the required biomaterials need to have the ability to promote cell adhesion and proliferation in vitro and in vivo. Especially, surface modification of the scaffold material has a great influence on biocompatibility and functionality of materials. The small intestine submucosa (SIS) is an extracellular matrix isolated from the submucosal layer of porcine jejunum, which has good tissue mechanical properties and regenerative activity, and is suitable for cell adhesion, proliferation and differentiation. In recent years, SIS is widely used in different areas of tissue reconstruction, such as blood vessels, bone, cartilage, bladder and ureter, etc. This paper discusses the main methods for surface modification of SIS to improve and optimize the performance of SIS bioscaffolds, including functional group bonding, protein adsorption, mineral coating, topography and formatting modification and drug combination. In addition, the reasonable combination of these methods also offers great improvement on SIS surface modification. This article makes a shallow review of the surface modification of SIS and its application in tissue engineering.

Social media streams, such as Twitter, Facebook, and Sina Weibo, have become essential real-time information resources with a wide range of users and applications. The rapidly increasing amount of live information in social media streams has important societal and marketing values for large corporations and government organizations. There is a strong need for effective techniques for data gathering and content analysis. This problem is particularly challenging due to the short and conversational nature of posts, the huge data volume, and the increasing heterogeneous multimedia content in social media streams. Moreover, as the focus of "conversation" often shifts quickly in social media space, the traditional keywords based approach to gather data with respect to a target brand is grossly inadequate. To address these problems, we propose a multi-faceted brand tracking method that gathers relevant data based on not just evolving keywords, but also social factors (users, relations and locations) as well as visual contents as increasing number of social media posts are in multimedia form. For evaluation, we set up a large scale microblog dataset (Brand-Social-Net) on brand/product information, containing 3 million microblogs with over 1.2 million images for 100 famous brands. Experiments on this dataset have demonstrated that the proposed framework is able to gather a more complete set of relevant brand-related data from live social media streams. We have released this dataset to promote social media research.

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Conversion efficiency (CE) is the most important figure of merit for photodetectors. For carbon nanotubes (CNT) based photodetectors, the CE is mainly determined by excitons dissociation and transport of free carriers toward contacts. While phonon-assisted exciton dissociation mechanism is effective in split-gate CNT p-n diodes, the CE is typically low in these devices, approximately 1-5%. Here, we evaluate the performance of a barrier-free bipolar diode (BFBD), which is basically a semiconducting CNT asymmetrically contacted by perfect n-type ohmic contact (Sc) and p-type ohmic contact (Pd) at the two ends of the diode. We show that the CE in short channel BFBD devices (e.g., 60 nm) is over 60%, and it reduces rapidly with increasing channel length. We find that the electric-field-assisted mechanism dominates the dissociation rate of excitons in BFBD devices at zero bias and thus the photocurrent generation process. By performing a time-resolved and spatial-resolved Monte Carlo simulation, we find that there exists an effective electron (hole)-rich region near the n-type (p-type) electrode in the asymmetrically contacted BFBD device, where the electric-field strength is larger than 17 V/μm and exciton dissociation is extremely fast (<0.1 ps), leading to very high CE in the BFBD devices.

Partitioning gaseous water-soluble organic compounds (WSOC) to the aerosol phase is a major formation pathway of atmospheric secondary organic aerosols (SOA). However, the fundamental mechanism of the WSOC-partitioning process remains elusive. By simultaneous measurements of both gas-phase WSOC (WSOCg) and aerosol-phase WSOC (WSOCp) and formic and acetic acids at a rural site in the Yangtze River Delta (YRD) region of China during winter 2019, we showed that WSOCg during the campaign dominantly partitioned to the organic phase in the dry period (relative humidity (RH) < 80%) but to aerosol liquid water (ALW) in the humid period (RH > 80%), suggesting two distinct SOA formation processes in the region. In the dry period, temperature was the driving factor for the uptake of WSOCg. In contrast, in the humid period, the factors controlling WSOCg absorption were ALW content and pH, both of which were significantly elevated by NH3 through the formation of NH4NO3 and neutralization with organic acids. Additionally, we found that the relative abundances of WSOCp and NH4NO3 showed a strong linear correlation throughout China with a spatial distribution consistent with that of NH3, further indicating a key role of NH3 in WSOCp formation at a national scale. Since WSOCp constitutes the major part of SOA, such a promoting effect of NH3 on SOA production by elevating ALW formation and WSOCg partitioning suggests that emission control of NH3 is necessary for mitigating haze pollution, especially SOA, in China.

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