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Nowadays, broadband photodetectors are gaining popularity among optoelectronic applications. However, 2-D materials-based Van der Waals heterostructures (vdWHs) photodetectors have a narrow photodetection scope. To broaden the detection bandwidth, a photodetector based on GaSe/WSe2 and WSe2/BP parallel-mode heterojunctions is presented in this work. For convenience, the parallel-mode structure of the GaSe/WSe2 and WSe2/BP heterojunctions are denoted as “GaSe/WSe2//WSe2/BP.” GaSe/WSe2 and WSe2/BP heterojunctions show high detection performances in the ultraviolet–visible (UV-Vis) and visible-near infrared (Vis-NIR) spectra, respectively. Using the photoresponse complementary characteristics of GaSe/WSe2 and WSe2/BP heterojunctions, the GaSe/WSe2//WSe2/BP heterojunction photodetector demonstrates self-powered multicolor broadband photodetection cover UV-Vis-NIR spectra. Besides, the photodetector has an on-/off-ratio of $\approx 10^{4}$ , $\approx 0.1$ pA dark current, and a short response time ( $\sim 40~\mu \text{s}$ ). Our work paves the way for developing 2-D materials-based high-performance broadband photodetectors.

Numerous molecular ferroelectrics having excellent properties even comparable to inorganic ones, which usually contain heavy or toxic metals, have been developed recently. Hopefully, they can be used as substitutes for the well-known organic ferroelectric polymers (P(VDF-TrFE)) with huge coercive fields and poor spontaneous polarization for various applications. However, the bottleneck for practical applications, i.e., the preparation of high-quality thin films and high resolution device arrays with a desired crystallographic orientation for memory switching, still remains. In this study, large-area micro device arrays of molecular ferroelectrics with highly-crystalline or even single-crystalline films are intentionally self-assembled on electrodes or within electrode gaps using a solution processing technique, including the molecular ferroelectrics for which it is usually difficult to make thin films. The as-grown air-stable memory micro arrays with an optimum crystallographic orientation can exhibit excellent non-volatile memory performance with a smaller operation voltage of

Monolayer MoS2 is a direct bandgap semiconductor which is believed to be one of the most promising candidates for optoelectronic devices. Chemical vapor deposition (CVD) is the most popular method to synthesize monolayer MoS2 with a large area. However, many defects are always found in monolayer MoS2 grown by CVD, such as sulfur vacancies, which severely degrade the performance of devices. This work demonstrates a concise and effective method for direct growth of high quality monolayer MoS2 by using SiO2/Si substrates pretreated with sulfur vapor. The MoS2 monolayer obtained using this method shows about 20 times PL intensity enhancement and a much narrower PL peak width than that grown on untreated substrates. Detailed characterization studies reveal that MoS2 grown on sulfur vapor pretreated SiO2/Si substrates has a much lower density of sulfur vacancies. The synthesis of monolayer MoS2 with high optical quality and low defect concentration is critical for both fundamental physics studies and potential practical device applications in the atomically thin limit.

Electron transport chain (ETC) dysfunction or hypoxia causes toxic NADH accumulation. How cells regenerate NAD

We investigate the growth of ( 2 ˉ 01 ) β-Ga2O3 nanowires with a GaN seed crystal in detail. Growth of ( 2 ˉ 01 ) β-Ga2O3 nanowires starts with the formation of (001) Ga(II)–O chains of octahedral Ga2O6 structures, indicating the initial formation of ( 2 ˉ 01 ) and (001) atomic facets of β-Ga2O3 nanowires. Subsequent growth of Ga2O3 leads to the formation of (100) Ga(I)–O chains and energetically stable (100) and (010) sidewalls and octahedral Ga2O6 structures in the β-Ga2O3 nanowires. Energetically stable tetrahedral GaO4 structures are eventually formed in the β-Ga2O3 nanowires. High-quality N-doped ( 2 ˉ 01 ) β-Ga2O3 nanowires are synthesized and growth kinetics is clarified. The β-Ga2O3 nanowires deep-ultraviolet photodetectors show superior performance with high photoresponsivity (3.5 × 103 A W−1) and detectivity (9.6 × 1015 Jones) at −10 V bias.

Monolayer MoS2 is a direct bandgap semiconductor which is believed to be one of the most promising candidates for optoelectronic devices. Chemical vapor deposition (CVD) is the most popular method to synthesize monolayer MoS2 with a large area. However, many defects are always found in monolayer MoS2 grown by CVD, such as sulfur vacancies, which severely degrade the performance of devices. This work demonstrates a concise and effective method for direct growth of high quality monolayer MoS2 by using SiO2/Si substrates pretreated with sulfur vapor. The MoS2 monolayer obtained using this method shows about 20 times PL intensity enhancement and a much narrower PL peak width than that grown on untreated substrates. Detailed characterization studies reveal that MoS2 grown on sulfur vapor pretreated SiO2/Si substrates has a much lower density of sulfur vacancies. The synthesis of monolayer MoS2 with high optical quality and low defect concentration is critical for both fundamental physics studies and potential practical device applications in the atomically thin limit.

This chapter introduces the optical characterization of two-dimensional (2D) semiconductors by Raman spectroscopy, photoluminescence (PL) spectroscopy, and absorption spectroscopy. It starts by presenting how Raman spectroscopy can be utilized to characterize the properties of 2D semiconductors such as crystal structures, strain, doping, defects, thermal conductivity, electronic band structures, and so on. Then basic exciton properties of 2D semiconductors including neutral excitons, charged excitons, bounded excitons, biexcitons and the effects of electrostatic gating, chemical doping, strain, magnetic field, circular polarized light, and substrate on these excitonic structures explored by PL spectroscopy are elaborated. Besides basic excitonic emission, single-photon emission, stimulated emission, and dark excitons of 2D semiconductors are reviewed. Moreover, absorption investigations on 2D semiconductors are also discussed where steady-state absorption features and transient absorption properties of 2D semiconductors are included.

High-resolution temperature records spanning the last deglaciation from low latitudes are scarce; however, they are important for understanding the rapid propagation of abrupt climate events throughout the Northern Hemisphere and the tropics. Here, we present a branched GDGTs-based temperature reconstruction from the sediments of Maar Lake Huguangyan in tropical China. The record reveals that the mean temperature during the Oldest Dryas was 17.8 °C, which was followed by a two-step increase of 2-3 °C to the Bolling-Allerod, a decrease to 19.8 °C during the Younger Dryas, and a rapid warming at the onset of the Holocene. The Oldest Dryas was about 2 °C warmer than the Younger Dryas. The reconstructed temperature was weighted towards the wintertime since the lake is monomictic and the mixing process in winter supplies nutrients from the lake bottom to the entire water column, greatly promoting biological productivity. In addition, the winter-biased temperature changes observed in the study are more distinctive than the summer-biased temperature records from extra-tropical regions of East Asia. This implies that the temperature decreases during abrupt climatic events were mainly a winter phenomenon. Within the limits of the dating uncertainties, the broadly similar pattern of winter-weighted temperature change observed in both tropical Lake Huguangyan and in Greenland ice cores indicates the occurrence of tightly-coupled interactions between high latitude ice sheets and land areas in the tropics. We suggest that the winter monsoon (especially cold surges) could play an important role in the rapid transmission of the temperature signal from the Arctic to the tropics.

Stroke is a major cause of mortality and long-term disability worldwide. The study of biomarkers and pathogenesis is vital for early diagnosis and treatment of stroke. In the present study, a continuous-flow normal-phase/reversed-phase two-dimensional liquid chromatography-quadrupole time-of-flight mass spectrometry (NP/RP 2D LC-QToF/MS) method was employed to measure lipid species in human plasma, including healthy controls and lacunar infarction (LI) patients. As a result, 13 lipid species were demonstrated with significant difference between the two groups, and a "plasma biomarker model" including glucosylceramide (38:2), phosphatidylethanolamine (35:2), free fatty acid (16:1), and triacylglycerol (56:5) was finally established. This model was evaluated as an effective tool in that area under the receiver operating characteristic curve reached 1.000 in the discovery set and 0.947 in the validation set for diagnosing LI patients from healthy controls. Besides, the sensitivity and specificity of disease diagnosis in validation set were 93.3% and 96.6% at the best cutoff value, respectively. This study demonstrates the promising potential of NP/RP 2D LC-QToF/MS-based lipidomics approach in finding bio-markers for disease diagnosis and providing special insights into the metabolism of stroke induced by small vessel disease. Graphical abstract Flow-chart of the plasma biomarker model establishment through biomarker screening and validation.

Two-dimensional heterojunctions exhibit many unique features in nanoelectronic and optoelectronic devices. However, heterojunction engineering requires a complicated alignment process and some defects are inevitably introduced during material preparation. In this work, a laser scanning technique is used to construct a lateral WSe

Glycerolipid is a main component of membranes in oxygenic photosynthetic organisms. Up to now, the majority of publication in this area has focused on the physiological functions of glycerolipids and lipoprotein complexes in photosynthesis, but the study on the separation and identification of glycerolipids in thylakoid membrane in cyanobacteria is relatively rare. Here we report a new method to separate and identify five photosynthetic glycerolipid classes, including monoglucosyl diacylglycerol, monogalactosyl diacylglycerol, digalactosyl diacylglycerol, sulfoquinovosyl diacylglycerol, and phosphatidylglycerol, in cyanobacteria Synechococcus sp. PCC 7002 by two-dimensional (normal- and reversed-phase) liquid chromatography online coupled to quadrupole time-of-flight mass spectrometry. Over twice as many lipid species were detected by our method compared to the previously reported methods. Ten new odd-chain fatty acid glycerolipids were discovered for the first time. Moreover, complete separation of isomers of monogalactosyl diacylglycerol and monoglucosyl diacylglycerol was achieved. According to the tandem mass spectrometry results, we found that the head group of monoglucosyl diacylglycerols was not as stable as that of monogalactosyl diacylglycerols, which might explain why the organism chose monogalactosyl diacylglycerols and digalactosyl diacylglycerols instead of monoglucosyl diacylglycerols as the main content of the photosynthetic membranes in the history of evolution. This work will benefit further research on the physiological function of glycerolipids.

The last deglaciation is of great interest because Northern Hemisphere climate has gone through several abrupt changes. We present an n-alkane and compound-specific carbon isotope record of the last deglaciation from the annually laminated sedimentary sequence of Lake Xiaolongwan, northeastern China. The n-alkane distribution suggests that the sparsely distributed vegetation prior to 14.7 ka BP, changed to wood plants and aquatic macrophytes in the early Bolling-Allerod, and was followed by a broadleaved deciduous forest after 11.4 ka BP. In this forest region, where the vegetation is dominated by C3 plants, the compound-specific δ13C value of the long-chain n-alkanes (nC27, nC29 and nC31) is interpreted as a proxy of effective precipitation, while temperature might play a minor secondary role. The positive δ13C27–31 values during the Bolling-Allerod suggest a dry-warm climatic condition, while the negative δ13C27–31 at 13.0–11.4 ka BP indicates a cold-wet climate during the Younger Dryas in this region. Two periods with lower δ13C27–31 occurred at 16.1–16.5 and 17.3–17.7 ka BP and could be associated with the Heinrich event-1a and the Heinrich event-1b, respectively. The synchroneity between the biomarker time series in Lake Xiaolongwan and the δ18O record from the Greenland ice core suggest the dominance of high latitude processes on regional monsoon evolution from the last glacial, the Bolling-Allerod, the Younger Dryas to early Holocene. Regionally, the Okhotsk High might have played an important role for abrupt changes during the glacial/interglacial transition.

Van der Waals heterostructures (vdWHs) based on two-dimensional (2D) materials are being studied extensively for their prospective applications in photodetectors. As the pristine WSe2/MoTe2 heterostructure is a type I (straddling gap) structure, it cannot be used as a photovoltaic device theoretically, although both WSe2 and MoTe2 have excellent photoelectric properties. The Fermi level of p-doped WSe2 is close to its valence band. The p-doped WSe2/MoTe2 heterostructure can perform as a photovoltaic device because a built-in electric field appears at the interface between MoTe2 and p-doped WSe2. Here, a 633 nm laser was used for scanning the surface of WSe2 in order to obtain the p-doped WSe2. x-ray photoelectron spectroscopy (XPS) and electrical measurements verified that p-type doping in WSe2 is produced through laser treatment. The p-type doping in WSe2 includes substoichiometric WOx and nonstoichiometric WSex. A photovoltaic device using p-doped WSe2 and MoTe2 was successfully fabricated. The band structure, light-matter reactions, and carrier-transport in the p-doped WSe2/MoTe2 heterojunction were analyzed. The results showed that this photodetector has an on/off ratio of ≈104, dark current of ≈1 pA, and response time of 72 μs under the illumination of 633 nm laser at zero bias (V ds = 0 V). The proposed p-doping method may provide a new approach to improve the performance of nanoscale optoelectronic devices.

Lipidomics is an important branch of metabolomics, which aims at the detailed analysis of lipid species and their multiple roles in the living system. In recent years, the development of various analytical methods for effective identification and characterization of lipids has greatly promoted the process of lipidomics. Meanwhile, as many diseases demonstrate a remarkable alteration in lipid profiles compared with that of healthy people, lipidomics has been extensively introduced to disease research. The comprehensive lipid profiling provides a chance to discover novel biomarkers for specific disease. In addition, it plays a crucial role in the study of lipid metabolism, which could illuminate the pathogenesis of diseases. In this review, after brief discussion of analytical methods for lipidomics in clinical research, we focus on the recent advances of lipidomics related to four types of diseases, including cancer, atherosclerosis, diabetes mellitus, and Alzheimer's disease.

We report on maar lakes and lacustrine carbonate varves in Myanmar. Carbonate varves are well developed in maar lake Twin Taung, the deepest of five maar lakes in Myanmar. Lamination consists of light and brown-colored laminate couplets in thin sections. A light- colored layer is composed mainly of calcite crystals with thickness 50-400 mm, and a dark-colored layer consists of other organic and siliceous matter. Climatic conditions in the study region are determined by the Indian monsoon and have a pronounced rainfall seasonality. The dry and hot season is between December and April, and warm and humid conditions prevail in summer and autumn. These characteristics are key to varve formation. In the dry and hot season, calcite crystals form with less precipitation and strong evaporation, whereas clastic and organic matter are deposited during the warm and humid season. An independent chronology derived from 137Cs and 210Pb shows good agreement with counted laminations. To compare with instrumental data, synchrotron radiation X-ray fluorescence measurement was used for extracting minor element datasets with high resolution. Based on principal component analysis and comparison between elemental variation and regional rainfall data, we interpret the elemental data in terms of climate variables such as precipitation and temperature. The first component includes lithogenic elements such as K, Ti, Fe, Cu, Zn, Rb and Zr, and might be controlled by various factors such as physical and chemical weathering processes, rainfall, and dust input. The second component, calcium and strontium, might be principally regulated by the balance between evaporation and precipitation. During drought periods, the calcium ion might supersaturate, causing carbonate calcite precipitation from the water column. Our preliminary result suggests that elements Ca and Sr in the annually laminated sediment might be useful indicators for studying paleoclimatic change at high resolution.

We present an n-alkane and compound-specific carbon isotope record of the past 9 ka from the annually laminated sedimentary sequence of Lake Xiaolongwan, northeastern China. The n-alkane distribution suggests that Lake Xiaolongwan has undergone a shift from an oligotrophic state with low algal production and little emergent/submerged macrophytes in the early Holocene, to a eutrophic state with high algal production and abundant emergent/submerged macrophytes since the middle Holocene. The pattern of variation observed in the biomarker proxies ACL (the n-alkane average chain length), Paq (aquatic macrophyte versus aquatic macrophyte and terrestrial plant ratio), and LPTP (lake productivity/ terrigenous organic production) is throughout the record similar to that of the total organic carbon. The variation of compound-specific carbon isotopic values in the middle- and short-chain alkanes was mainly regulated by lake productivity and the accumulating organic pool through time. In this forested region, where the vegetation is dominated by C 3 plants, the long-chain n-alkanes (C27eC31) are predominantly derived from leaf wax lipids. The compound-specific d 13 C27e31 value is sensitive to effective precipitation, and therefore represents a useful indicator of regional monsoonal precipitation. Spectral analysis on the d 13 C27e31 time series reveals significant periodicities of 87e89, 205e212, 1020e1050 and 1750e2041 years. On the centennial timescale, the quasi-periodicities around 88 and 210 years suggest a strong link between solar activity and monsoon rainfall. The millennial monsoon cycle in northeastern China is associated with sea surface temperature (SST) variations in two active centers of the summer monsoon, the western Pacific Subtropical High (WPSH) and the Okhotsk High. Increasing SST in the subtropical sea may cause a northwards shift of the WPSH, which extends the monsoon rain band (Meiyu) to northeastern China, and thus increasing rainfall in that region. Meanwhile, decreasing SST in the Okhotsk Sea may strengthen the Okhotsk high, bringing more moisture into northeastern China. We suggest that the Pacific Ocean is a main regulator for summer monsoon rainfall in northeastern China at present and at different time scales during the Holocene.

Soil water is one of the most important components in hydrological cycle. The stable isotopes (e.g., deuterium, 2 H, oxygen-18, 18 O) in soil water have been increasingly used as natural tracers in the ecological, environmental and hydrological research. In view of different techniques for extracting soil water, there are significant differences in the δD and δ 18 O compositions. This paper presents a method for the accelerated solvent extraction (ASE) of soil water for stable isotope analyses by mass spectrometry. The optimum parameters of extracting soil water were as follows: dichloromethane as the extraction solvent, temperature of 100 °C, pressure of 10.3 MPa, static time of 10 min. The samples were extracted three times, and with cycle values four, four and three, respectively. The extracted water was enriched in deuterium and oxygen-18 by 2.12%–4.58% and −0.17%–0.93%, respectively, compared with the added water. The reproducibility of replicate extractions of soil water was around ±0.89% for δD and ±0.37% for δ 18 O.

Glycerolipid is a main component of membranes in oxygenic photosynthetic organisms. Up to now, the majority of publication in this area has focused on the physiological functions of glycerolipids and lipoprotein complexes in photosynthesis, but the study on the separation and identification of glycerolipids in thylakoid membrane in cyanobacteria is relatively rare. Here we report a new method to separate and identify five photosynthetic glycerolipid classes, including monoglucosyl diacylglycerol, monogalactosyl diacylglycerol, digalactosyl diacylglycerol, sulfoquinovosyl diacylglycerol, and phosphatidylglycerol, in cyanobacteria Synechococcus sp. PCC 7002 by two-dimensional (normal- and reversed-phase) liquid chromatography online coupled to quadrupole time-of-flight mass spectrometry. Over twice as many lipid species were detected by our method compared to the previously reported methods. Ten new odd-chain fatty acid glycerolipids were discovered for the first time. Moreover, complete separation of isomers of monogalactosyl diacylglycerol and monoglucosyl diacylglycerol was achieved. According to the tandem mass spectrometry results, we found that the head group of monoglucosyl diacylglycerols was not as stable as that of monogalactosyl diacylglycerols, which might explain why the organism chose monogalactosyl diacylglycerols and digalactosyl diacylglycerols instead of monoglucosyl diacylglycerols as the main content of the photosynthetic membranes in the history of evolution. This work will benefit further research on the physiological function of glycerolipids.