2D Hybrid Perovskite Sensors for Environmental and Healthcare Monitoring.

Layered perovskites, a novel class of two-dimensional (2D) layered materials, exhibit versatile photophysical properties of great interest in photovoltaics and optoelectronics. However, their instability to environmental factors, particularly water, has limited their utility. In this study, we introduce an innovative solution to the problem by leveraging the unique properties of natural beeswax as a protective coating of 2D-fluorinated phenylethylammonium lead iodide perovskite. These photodetectors show outstanding figures of merit, such as a responsivity of >2200 A/W and a detectivity of 2.4 × 1018 Jones. The hydrophobic nature of beeswax endows the 2D perovskite sensors with an unprecedented resilience to prolonged immersion in contaminated water, and it increases the lifespan of devices to a period longer than one year. At the same time, the biocompatibility of the beeswax and its self-cleaning properties make it possible to use the very same turbidity sensors for healthcare in photoplethysmography and monitor the human heartbeat with clear systolic and diastolic signatures. Beeswax-enabled multipurpose optoelectronics paves the way to sustainable electronics by ultimately reducing the need for multiple components.

Temperature-Dependent Conduction and Photoresponse in Few-Layer ReS2.

The electrical behavior and the photoresponse of rhenium disulfide field-effect transistors (FETs) have been widely studied; however, only a few works have investigated the photocurrent as a function of temperature. In this paper, we perform the electrical characterization of few-layer ReS2-based FETs with Cr-Au contacts over a wide temperature range. We exploit the temperature-dependent transfer and output characteristics to estimate the effective Schottky barrier at the Cr-Au/ReS2 interface and to investigate the temperature behavior of parameters, such as the threshold voltage, carrier concentration, mobility, and subthreshold swing. Through time-resolved photocurrent measurements, we show that the photocurrent increases with temperature and exhibits a linear dependence on the incident light power at both low and room temperatures and a longer rise/decay time at higher temperatures. We surmise that the photocurrent is affected by the photobolometric effect and light-induced desorption of adsorbates which are facilitated by the high temperature and the low pressure.

Electric Transport in Few-Layer ReSe2 Transistors Modulated by Air Pressure and Light.

We report the fabrication and optoelectronic characterization of field-effect transistors (FETs) based on few-layer ReSe2. The devices show n-type conduction due to the Cr contacts that form low Schottky barriers with the ReSe2 nanosheet. We show that the optoelectronic performance of these FETs is strongly affected by air pressure, and it undergoes a dramatic increase in conductivity when the pressure is lowered below the atmospheric one. Surface-adsorbed oxygen and water molecules are very effective in doping ReSe2; hence, FETs based on this two-dimensional (2D) semiconductor can be used as an effective air pressure gauge. Finally, we report negative photoconductivity in the ReSe2 channel that we attribute to a back-gate-dependent trapping of the photo-excited charges.

Evidence for Cerebral Embolic Prevention in Transcatheter Aortic Valve Implantation and Thoracic Endovascular Aortic Repair.

BACKGROUND: Embolic stroke is a formidable complication of transcatheter aortic valve implantation (TAVI) and thoracic endovascular aortic repair (TEVAR). Mechanical strategies to reduce the risk of ischemic embolic lesions include embolic protection devices (EPDs) and carbon dioxide flushing (CDF). This study aims to assess the efficacy for EPD and CDF uses in TAVI and TEVAR. METHODS: A literature review was performed according to the Preferred Reporting Items for Systematic reviews and Meta-Analysis. All searches were performed via PubMed, OvidSP, MEDLINE, Web of Science Core Collection, and Cochrane Library. Conference abstracts and proceedings were included. Those that were out of scope of interest and review articles were excluded. RESULTS: Eighteen studies fulfilled the inclusion criteria of the 456 articles searched. Regarding EPD use in TAVI, systematic review comparing EPD with no-EPD showed smaller total volume of cerebral lesions and smaller volume per lesion in patients with EPD in all studies. They also performed better in postoperative neurocognitive assessments but could not demonstrate clinical prevention of embolic stroke in all studies. While for EPD use in TEVAR, capture of embolic debris and absence of early postoperative neurocognitive deficit were demonstrated in all cases of 2 prospective pilot studies. Concerning CDF in TEVAR, significant reduction in gaseous emboli released during stent-graft deployment was shown by 1 in vitro study. Successful CDF application in all patients, with only 1 case of postoperative nondisabling stroke, was also demonstrated by 1 cohort study. CONCLUSIONS: This systematic review of medical literature has demonstrated the safety and feasibility of EPD use in TAVI. Although improvements in clinical outcomes have yet been demonstrated, there was level I evidence showing reduced embolic lesions in imaging. The use of EPD and CDF in TEVAR was suggested, but evidence remained inadequate to support routine clinical use.