Traditional gas sensors are facing the challenge of low power consumption for future application in smart phones and wireless sensor platforms. To solve this problem, self-powered gas sensors are rapidly developed in recent years. However, all reported self-powered gas sensors are suffering from high limit of detection (LOD) toward NO 2 gas. In this work, a photovoltaic self-powered NO 2 gas sensor based on n-MoS 2 /p-GaSe heterojunction is successfully prepared by mechanical exfoliation and all-dry transfer method. Under 405 nm visible light illumination, the fabricated photovoltaic self-powered gas sensors show a significant response toward ppb-level NO 2 with short response and recovery time and high selectivity at room temperature (25°C). It is worth mentioning that the LOD toward NO 2 of this device is 20 ppb, which is the lowest of the reported self-powered room-temperature gas sensors so far. The discussed devices can be used as building blocks to fabricate more functional Internet of things devices.

Our meta-analysis suggests that the combined application of IV and topical TXA for patients undergoing THA may reduce the total blood loss compared with IV use alone without increasing the risk of postoperative complications. However, due to the quality and number of included studies, more studies were need to further identify the optimal dose for combine IV-TXA.

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to 2000 ppm acetone environment will suffer from nausea and vomiting symptoms. [2] In addition, public health studies have shown that human exhaled breath mainly contains carbon dioxide, oxygen, nitrogen, water, and inert gases. The remaining tiny fraction consists of more than a thousand trace VOCs with concentrations in the range of parts per million (ppm) to parts per trillion by volume. [3] Some common VOCs in exhaled breath for all humans are products of core metabolic processes and partly informative for clinical diagnostics such as isoprene, methanol, ethane, and acetone. [4] In particular, breath acetone has been related to diabetes, promoting the analysis of exhaled acetone to be a noninvasive diagnosis for related disease. [3c,5] In general, breath acetone analysis is mostly carried out by gas chromatography followed by flame ionization detection, [6] ion mobility spectrometry, [6a] or mass spectrometry. [7] These methods generally require bulky instrumentation, skilled operators and long test time, thus leading to considerable difficulty in detecting breath acetone in real time. [3c] Hence, developing useful tools for noninvasive, real-time and low-cost diagnosis is urgently demanded. In the past few years, chemiresistive gas sensors have attracted much attention owing to the facile operation, good reversibility and possibility of integration in Internet of Things related devices. [8] Metal oxide semiconductors, such as WO 3 , [8b,c] In 2 O 3 , [8a] and SnO 2 , [8d,9] have been maintained a dominant presence as sensitive materials for acetone sensing owing to high sensitivity and low cost. However, their high operating temperature requirements (generally over 200 °C) may cause high power consumption and potential safety hazard. On the other hand, the long response/recovery time and relatively poor selectivity also limit their practical applications. 2D materials (such as graphene and black phosphorus), with high carrier mobility and large surfaceto-volume ratio, have been considered as alternative materials to metal oxides for room-temperature acetone gas sensors. [10] For example, Robinson et al. fabricated a reduced graphene oxidebased acetone sensor for the first time, showing high sensitivity toward 250 ppm acetone, but displaying a poor recovery, which limits its practical applications. [11] Yang et al. reported a gasThe analysis of exhaled acetone is used as a noninvasive diagnosis for diabetes. Compared with traditional breath analysis tools, chemiresistive gas sensors have attracted more attention for real-time monitoring, owing to the possibility of integration and facile operation. However, most reported room-temperature acetone gas sensors suffer from complicated preparation, costly raw materials, or relatively long response and recovery time. In this work, naturally occurring layered mineral stibnite is used to prepare Sb 2 S 3 by a one-step method of electrochemical cathodic exfoliation. As-prepared Sb 2 S 3 displays an amorphous feature with porous, hierarchical nanostructure...

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