Tunable Contacts of Bi2 O2 Se Nanosheets MSM Photodetectors by Metal-Assisted Transfer Approach for Self-Powered Near-Infrared Photodetection.

Owing to the Fermi pinning effect arose in the metal electrodes deposition process, metal-semiconductor contact is always independent on the work function, which challenges the next-generation optoelectronic devices. In this work, a metal-assisted transfer approach is developed to transfer Bi2 O2 Se nanosheets onto the pre-deposited metal electrodes, benefiting to the tunable metal-semiconductor contact. The success in Bi2 O2 Se nanosheets transfer is contributed to the stronger van der Waals adhesion of metal electrodes than that of growth substrates. With the pre-deposited asymmetric electrodes, the self-powered near-infrared photodetectors are realized, demonstrating low dark current of 0.04 pA, high Ilight /Idark ratio of 380, fast rise and decay times of 4 and 6 ms, respectively, under the illumination of 1310 nm laser. By pre-depositing the metal electrodes on polyimide and glass, high-performance flexible and omnidirectional self-powered near-infrared photodetectors are achieved successfully. This study opens up new opportunities for low-dimensional semiconductors in next-generation high-performance optoelectronic devices.

Time trends and endoscopic management of foreign body ingestion in the upper GI tract: a retrospective analysis of 1,152 cases in China.

OBJECTIVES: foreign body ingestions are encountered in the clinical practice and sometimes require endoscopic management. However, time trends and epidemiology of these cases have not been fully clarified. Whether seasons and festivals have an effect on the occurrence has been poorly described. METHOD: from 2009 to 2020, 1,152 consecutive foreign body ingestion cases were enrolled in our endoscopic center. Case records were reviewed for demographic data, foreign body type and location, outpatient or hospitalization, adverse events and dates. Annual time trends and seasonal variation were analyzed as well as the influence of Chinese legal festivals on the incidence. The impact of SARS-CoV-2 pandemic on the potential delay for clinical consultation of these cases was preliminarily explored. Clinical features of these cases were demonstrated. RESULTS: the overall success rate was 99.7 % and the adverse events rate was 2.4 %. There was an uptrend in the annual frequency of food foreign body ingestion endoscopic extraction from 0.65 in 2009 to 8.86 in 2020 per 1,000 esophagogastroduodenoscopy patients (r = 0.902, p < 0.001). Furthermore, the frequency of endoscopic extraction significantly increased in winter (p < 0.001) and during Chinese New Year celebratory season (p = 0.003). The duration of hospitalization may be longer in the pandemic period (p = 0.0049). CONCLUSION: considering the uptrend of the annual frequency of food related foreign body endoscopic extraction, the publicity about the danger of foreign body ingestion should be enhanced. Arrangement of endoscopic physicians and assistants during the high-incidence season should be emphasized.

Toward High-Performance Self-Powered Near-Ultraviolet Photodetection by Constructing a Unipolar Heterojunction.

Constructing a unipolar heterojunction is an effective energy band engineering strategy to improve the performance of photoelectric devices, which could suppress dark current and enhance detectivity by modulating the transfer of carriers. In this work, unipolar heterojunctions of Si/PbI2 and GaSb/PbI2 are constructed successfully for high-performance self-powered near-ultraviolet photodetection. Owing to the unique band offset of unipolar heterojunctions, the transport of holes is blocked, and only photogenerated electrons in PbI2 can flow unimpeded under the driving force of the built-in electric field. Thus, the recombination of photogenerated electron-hole pairs is suppressed, contributing to high-performance near-ultraviolet photodetection. The as-fabricated Si/PbI2 self-powered near-ultraviolet photodetector exhibits a low dark current of 10-13 A, a high Ilight/Idark ratio of 104, and fast response times of 26/24 ms, which are much better than those of the PbI2 metal-semiconductor-metal photodetector. Furthermore, the as-fabricated GaSb/PbI2 unipolar heterojunction photodetector also exhibits impressive self-powered near-ultraviolet photodetection behaviors. Evidently, this work shows the potential of unipolar heterojunctions for next-generation Si-based and GaSb-based high-performance photodetection.

Tunable synaptic behaviors of solution-processed InGaO films for artificial visual systems.

Due to their persistent photoconductivity, amorphous metal oxide thin films are promising for construction of artificial visual systems. In this work, large-scale, uniformly distributed amorphous InGaO thin films with an adjustable In/Ga ratio and thickness are prepared successfully by a low-cost environmentally friendly and easy-to-handle solution process for constructing artificial visual systems. With the increase of the In/Ga ratio and film thickness, the number of oxygen vacancies increases, along with the increase of post-synaptic current triggered by illumination, benefiting the transition of short-term plasticity to long-term plasticity. With an optimal In/Ga ratio and film thickness, the conductance response difference at a decay of 0 s between the 1st and the 10th views of a 5 × 5 array InGaO thin film transistor is up to 2.88 µA, along with an increase in the Idecay 30s/Idecay 0s ratio from 45.24% to 53.24%, resulting in a high image clarity and non-volatile artificial visual memory. Furthermore, a three-layer artificial vision network is constructed to evaluate the image recognition capability, exhibiting an accuracy of up to 91.32%. All results promise low-cost and easy-to-handle amorphous InGaO thin films for future visual information processing and image recognition.

Time trends and endoscopic management of foreign body ingestion in the upper GI tract: a retrospective analysis of 1152 cases in China

Objectives: foreign body ingestions are encountered in the clinical practice and sometimes require endoscopic management. However, time trends and epidemiology of these cases have not been fully clarified. Whether seasons and festivals have an effect on the occurrence has been poorly described. Method: from 2009 to 2020, 1,152 consecutive foreign body ingestion cases were enrolled in our endoscopic center. Case records were reviewed for demographic data, foreign body type and location, outpatient or hospitalization, adverse events and dates. Annual time trends and seasonal variation were analyzed as well as the influence of Chinese legal festivals on the incidence. The impact of SARS-CoV-2 pandemic on the potential delay for clinical consultation of these cases was preliminarily explored. Clinical features of these cases were demonstrated. Results: the overall success rate was 99.7 % and the adverse events rate was 2.4 %. There was an uptrend in the annual frequency of food foreign body ingestion endoscopic extraction from 0.65 in 2009 to 8.86 in 2020 per 1,000 esophagogastroduodenoscopy patients (r = 0.902, p < 0.001). Furthermore, the frequency of endoscopic extraction significantly increased in winter (p < 0.001) and during Chinese New Year celebratory season (p = 0.003). The duration of hospitalization may be longer in the pandemic period (p = 0.0049). Conclusion: considering the uptrend of the annual frequency of food related foreign body endoscopic extraction, the publicity about the danger of foreign body ingestion should be enhanced. Arrangement of endoscopic physicians and assistants during the high-incidence season should be emphasized. (AU)