Impacts of Climate Change on the Distribution of Suitable Habitats and Ecological Niche for Trollius Wildflowers in Ili River Valley, Tacheng, Altay Prefecture.

Xinjiang in China is distinguished by its distinctive regional landscape and high ecological sensitivity. Trollius wildflowers represent a unique and iconic element of the mountain flower landscape in Xinjiang. However, their populations are predominantly distributed in mountainous areas, making them susceptible to climate change. Despite this, the impacts of climate change on the distribution of suitable habitats and ecological niche differentiation for Trollius wildflowers have rarely been quantified. Consequently, simulations were conducted using the R-optimized MaxEnt model to predict the suitable habitat distribution of Trollius wildflowers. This was based on the occurrence data and environmental variables for the four species of Trollius (T. altaicus, T. asiaticus, T. dschungaricus, and T. lilacinus) that exist in the study area. The simulation was conducted over a period of time, beginning with the past glacial period and extending to the present, and then to the future (2050s, 2070s, and 2090s) under multiple scenarios (SSP1-2.6, SSP3-7.0, SSP5-8.5). The simulation of suitable habitats enabled the measurement of the ecological niche breadth and differentiation. The results demonstrate that the model predictions are precisely accurate, with AUC values exceeding 0.9. Annual mean temperature (Bio1), isothermality (Bio3), and precipitation in the warmest quarter (Bio18) are the dominant climate variables, in addition to vegetation, elevation, and soil factors. The proportion of suitable habitats for Trollius wildflowers varies considerably over time, from 0.14% to 70.97%. The majority of habitat loss or gain occurs at the edges of mountains, while stable habitats are concentrated in the core of the mountains. The gravity center of suitable habitats also shifts with spatial transfer, with the shifts mainly occurring in a northeasterly-southwesterly direction. The SSP1-2.6 scenario results in the sustained maintenance of habitats, whereas the SSP3-7.0 and SSP5-8.5 scenarios present challenges to the conservation of habitats. The threshold of ecological niche breadth for Trollius wildflowers is subject to fluctuations, while the ecological niche differentiation also varies. The study aims to examine the evolution of the habitat and ecological niche of Trollius wildflowers in Xinjiang under climate change. The findings will provide theoretical support for delineating the conservation area, clarify the scope of mountain flower tourism development and protection of mountain flower resources, and promote the sustainable development of ecotourism and effective utilization of territorial space in Xinjiang.

Controlled growth of 3R phase niobium diselenide and its properties.

Inversion symmetry broken 3R phase transition metal dichalcogenides (TMDs) show fascinating prospects in spintronics, valleytronics, and nonlinear optics. However, the controlled synthesis of 3R phase TMDs is still a great challenge. In this work, two-dimensional 3R-NbSe2 single crystals up to 0.2 mm were synthesized for the first time through chemical vapor deposition method by designing a space-confined system. The crystal size and morphology can be controlled by the location of the stacked substrates and the amount of the Nb2O5 precursor. Scanning transmission electron microscopy and Raman measurements reveal the NbSe2 exhibits a pure 3R stacking mode with relatively weak interlayer van der Waals interactions. Importantly, 3R-NbSe2 shows obvious second harmonic generation signal which intensity intensified as thickness increases. Density functional theory calculations and optical absorption demonstrate the coexistence of metallic and semiconducting optical properties of 3R-NbSe2. We designed a NbSe2/WS2/NbSe2 photodetector utilizing the metallicity of 3R-NbSe2, which shows good performance especially an ultrafast response (6-7 µs, 0.5 ms - 7.9 s for Au electrodes in literature). The proposed strategy and findings are of great significance for the growth of many other 3R-TMDs and applications of nonlinear optical and ultrafast devices.

Metavalently bonded tellurides: the essence of improved thermoelectric performance in elemental Te.

Elemental Te is important for semiconductor applications including thermoelectric energy conversion. Introducing dopants such as As, Sb, and Bi has been proven critical for improving its thermoelectric performance. However, the remarkably low solubility of these elements in Te raises questions about the mechanism with which these dopants can improve the thermoelectric properties. Indeed, these dopants overwhelmingly form precipitates rather than dissolve in the Te lattice. To distinguish the role of doping and precipitation on the properties, we have developed a correlative method to locally determine the structure-property relationship for an individual matrix or precipitate. We reveal that the conspicuous enhancement of electrical conductivity and power factor of bulk Te stems from the dopant-induced metavalently bonded telluride precipitates. These precipitates form electrically beneficial interfaces with the Te matrix. A quantum-mechanical-derived map uncovers more candidates for advancing Te thermoelectrics. This unconventional doping scenario adds another recipe to the design options for thermoelectrics and opens interesting pathways for microstructure design.

Facile fabrication and biological investigations of metal oxides intercalated in kaolinite clay-based dressing material to improve wound healing ability in nursing care after post-operative period.

The present investigation aims to design and development of hybrid zinc oxide (ZnO) and manganese dioxide (MnO2) nanoparticles (NPs) doped-biopolymer matrix-based cost-effective technique for the synthesis of biocompatible Kaolinite/Chitosan (Ka/CS) nanocomposites (NCs) could be used as agents for wound healing due to their efficiency and low toxicity. The crystallite size, phase purity and surface morphology of the synthesised NCs were investigated systemic analytical methods. The results revealed that the metal oxide nanocomposites presented that in rod-crystalline in shape and additionally exhibits that 20-30 nm in size. In vitro antibacterial analyses demonstrates that NCs have significantly improved bactericidal inhibition efficiency when compared to the bare hybrid NPs and polymeric components. The in vitro biocompatibility observation demonstrates that prepared hybrid-NPs encapsulated NCs have enhanced cell survival rate (>90 %), which was established by MTT assay and Live/Dead fluorescence assay methods at different incubation time. The DPPH assay was used to investigate the synergistic effects of prepared dressing materials increased antioxidant activity. Preliminary research indicates that these nanocomposites, ZnO/MnO2 incorporated and decorated with Ka/CS NCs, could be a significant promoter and potential candidate for use as a robust wound healing agent in post-operative nursing care.

Sulfuric acid-assisted ball milling for the preparation of Si-O-enriched straw biochar: removal efficiency of rhodamine B and adsorption mechanism.

Traditional pyrolysis biochar has been widely employed to treat dye wastewater. However, there are some problems in the pyrolysis process, such as the generation of harmful gases and the low content of silico-oxygen functional groups to promote adsorption. Straw biochar (Ac-BCbm) was prepared by sulfuric acid co-ball milling method. The adsorption performance and adsorption mechanism of rhodamine B (RhB) under different preparation conditions and factors were investigated. The results showed that the adsorption rate of Ac-BCbm on RhB was up to 94.9%, which was 60.5% and 55.8% higher than that of ball-milling straw (STbm) and biochar prepared by pyrolysis (STBC600), respectively. The Ac-BCbm had better adaptability under different pH and common interfering ions for remove RhB. Characterization and DFT simulation analysis revealed that the sulfuric acid co-ball milling process promoted the formation of Si-OH and Si-O-CH3 oxygen-containing functional groups of Si component in straw, which enhanced the hydrogen bonding interactions and effectively improved the adsorption efficiency. This study investigated a new strategy for biochar preparation by sulfuric acid co-ball milling, which provides an additional development direction for the efficient resource utilization of straw.

Air-stable self-powered photodetector based on TaSe2/WS2/TaSe2 asymmetric heterojunction with surface self-passivation.

Two-dimensional (2D) transition metal dichalcogenides are highly suitable for constructing junction photodetectors because of their suspended bond-free surface and adjustable bandgap. Additional stable layers are often used to ensure the stability of photodetectors. Unfortunately, they often increase the complexity of preparation and cause performance degradation of devices. Considering the self-passivation behavior of TaSe2, we designed and fabricated a novel self-powered TaSe2/WS2/TaSe2 asymmetric heterojunction photodetector. The heterojunction photodetector shows excellent photoelectric performance and photovoltaic characteristics, achieving a high responsivity of 292 mA/W, an excellent specific detectivity of 2.43 × 1011 Jones, a considerable external quantum efficiency of 57 %, a large optical switching ratio of 2.6 × 105, a fast rise/decay time of 43/54 µs, a high open-circuit voltage of 0.23 V, and a short-circuit current of 2.28 nA under 633 nm laser irradiation at zero bias. Moreover, the device also shows a favorable optical response to 488 and 532 nm lasers. Notably, it exhibits excellent environmental long-term stability with the performance only decreasing âˆ¼ 5.6 % after exposed to air for 3 months. This study provides a strategy for the development of air-stable self-powered photodetectors based on 2D materials.

Self-Driven Gr/WSe2/Gr Photodetector with High Performance Based on Asymmetric Schottky van der Waals Contacts.

Two-dimensional (2D) self-driven photodetectors have a wide range of applications in wearable, imaging, and flexible electronics. However, the preparation of most self-powered photodetectors is still complex and time-consuming. Simultaneously, the constant work function of a metal, numerous defects, and a large Schottky barrier at the 2D/metal interface hinder the transmission and collection of optical carriers, which will suppress the optical responsivity of the device. This paper proposed a self-driven graphene/WSe2/graphene (Gr/WSe2/Gr) photodetector with asymmetric Schottky van der Waals (vdWs) contacts. The vdWs contacts are formed by transferring Gr as electrodes using the dry-transfer method, obviating the limitations of defects and Fermi-level pinning at the interface of electrodes made by conventional metal deposition methods to a great extent and resulting in superior dynamic response, which leads to a more efficient and faster collection of photogenerated carriers. This work also demonstrates that the significant surface potential difference of Gr electrodes is a crucial factor to ensure their superior performance. The self-driven Gr/WSe2/Gr photodetector exhibits an ultrahigh Ilight/Idark ratio of 106 with a responsivity value of 20.31 mA/W and an open-circuit voltage of 0.37 V at zero bias. The photodetector also has ultrafast response speeds of 42.9 and 56.0 µs. This paper provides a feasible way to develop self-driven optoelectronic devices with a simple structure and excellent performance.

Enhancing propellant performance through intermolecular interactions: cyclodextrin-based MOF loading in nitrocellulose.

Metal-organic frameworks (MOFs) offer promising opportunities for modifying energetic materials due to their micro-porous structure and high performance. In this study, we present a novel green MOF named cyclodextrin-MOF (CD-MOF), which incorporates potassium ions, synthesized using a simple methanol vapor diffusion approach. The CD-MOF incorporates potassium ions and enhances propellant performance through intermolecular force optimization with nitrocellulose (NC). Molecular dynamics simulations reveal stronger interactions between the CD-MOF and NC. The loading of the CD-MOF within NC forms a stable structure with resistance to migration and defense against crystalline precipitation and water absorption. Notably, in static combustion and pyrolysis tests, the CD-MOF exhibits efficient flame and flash inhibition. The thermal degradation and cauterization of the CD-MOF resulted in the formation of a complex microporous material capable of absorbing flammable and harmful gases such as CO, NO, NO2, and N2O. These findings shed light on the superior performance of the CD-MOF compared to conventional inorganic salts, and the comprehensive characterization and molecular simulations provide insights into the unique properties and applications of the CD-MOF, emphasizing its significant contribution to the field of green propellants.

Application of Deep Convolutional Neural Network for Automatic Detection of Digital Optical Fiber Repeater.

The digital optical fiber repeater (DOFR) is an important infrastructure in the LTE networks, which solve the problem of poor regional signal quality. Various types of conventional measurement data from the LTE network cannot indicate whether a working DOFR is present in the cell. Currently, the detection of DOFRs relies solely on maintenance engineers for field detection. Manual detection methods are not timely or efficient, because of the large number and wide geographical distribution of DOFRs. Implementing automatic detection of DOFR can reduce the maintenance cost for mobile network operators. We treat the DOFR detection problem as a classification problem and employ a deep convolutional neural network (DCNN) to tackle it. The measurement report (MR) we used in this paper are tabular data, which is not an ideal input for DCNN. We propose a novel MR representation method that takes the overall MR data of a cell as a sample rather than a single record in the table, and represents the MR data as a pseudo-image matrix (PIM). The PIM will be used as the input for training DCNN, and the trained DCNN will be used to perform DOFR detection tasks. We conducted a series of experiments on real MR data, and the classification accuracy can achieve 93%. The proposed AI-based method can effectively detect the DOFR in a cell.

SIRT1-mediated p53 deacetylation inhibits ferroptosis and alleviates heat stress-induced lung epithelial cells injury.

OBJECTIVE: Acute lung injury (ALI) is a common complication of heat stroke (HS) and a direct cause of death. However, the mechanism underlying ALI following HS remains unclear. METHOD: To investigate whether ferroptosis is involved in HS-ALI. We established a HS model of mice and mouse lung epithelial-2 cells (MLE-2). The severity of lung injury was measured by H&E staining, the wet-to-dry lung weight ratio, and Transmission electron microscopy. Potential markers of ferroptosis Fe2+, malondialdehyde (MDA), hydroxynonenal (4-HNE) and lipid peroxidation were detected. The percentages of cell death and viability induced by HS were assessed by LDH and CCK8 assays. SLC7A11, ACSL4, GPX4, SIRT1, p53, and p53 K382 acetylation levels were measured by Western blot. RESULTS: The administration of ferroptosis inhibitor ferrostatin-1(Fer-1) could significantly ameliorate lung injury, inhibiting levels of MDA and 4-HNE, and ameliorating HS-induced increased ACSL4, decreased SLC7A11 and GPX4, suggesting ferroptosis was involved in HS-induced ALI in vivo and in vitro. Moreover, SIRT1 expression decreased, and p53 K382 acetylation levels increased in MLE-2 cells. Activation of SIRT1 could improve lung epithelial ferroptosis caused by HS in vivo ang in vitro. Besides, the activation of SIRT1 could significantly reduce the p53 K382 acetylation levels, suggesting that activation of SIRT1 could prevent ferroptosis via inhibiting p53 acetylation. CONCLUSION: These findings substantiate the vital role of the SIRT1/p53 axis in mediating ferroptosis in HS-ALI, suggesting that targeting SIRT1 may represent a novel therapeutic strategy to ameliorate ALI during HS.

Suppression of Interfacial Diffusion in Mg3Sb2 Thermoelectric Materials through an Mg4.3Sb3Ni/Mg3.2Sb2Y0.05/Mg4.3Sb3Ni-Graded Structure.

The Zintl compound, n-type Mg3Sb2, has been extensively investigated as a promising thermoelectric material. However, performance degradation caused by the loss of Mg element during device preparation and service is a main disadvantage in its utilization in thermoelectric devices. To suppress volatilization, diffusion, or reaction of Mg, we designed a graded concentration junction to control the interfacial elemental diffusion and improve the stability of the thermoelectric joint. We utilized the reaction product at the Ni/Mg3.2Sb2Y0.05 interface, the phase Mg4.3Sb3Ni, as a barrier layer material, and prepared Mg4.3Sb3Ni/Mg3.2Sb2Y0.05/Mg4.3Sb3Ni junctions. The results show that the interface behavior of the thermoelectric junction is optimized by the gradation of elemental concentration, thermal expansion coefficient, and work function. The Mg4.3Sb3Ni/Mg3.2Sb2Y0.05/Mg4.3Sb3Ni single-leg device showed high thermal stability at 673 K for 20 days, the contact resistance was stable at around 10 µΩ cm2, and the shear strength was maintained at about 20 MPa. The conversion efficiency of its single-leg device maintains nearly 90% of the best performance after aging at 673 K for 20 days.

Over high or low dietary protein levels depressed the growth, TOR signaling, apoptosis, immune and anti-stress of abalone Haliotis discus hannai.

A 120-day feeding trial was conducted to investigate the effects of relative higher and lower dietary protein levels on the growth, immunity and anti-stress of abalone Haliotis discus hannai fed diets with 17.64% (low), 30.49% (normal) and 43.27% (high) of proteins, respectively. The results showed that compared with 30.49% of dietary protein, 17.64% and 43.27% of dietary protein levels significantly decreased the weight gain rate and the activities of α-amylase, trypsin, alanine aminotransferase and aspartate aminotransferase in the hepatopancreas and serum of abalone (P < 0.05). Abalone fed 30.49% of dietary protein had the highest activity of superoxidase, acid phosphatase, alkaline phosphatase, lysozyme and the total anti-oxidative capacity, and the lowest content of malondialdehyde in the serum and hepatopancreas (P < 0.05). The gene expressions of TOR, S6k, Bcl-2, IκB, NfκB, TNF-α and Nrf2 were significantly up-regulated in the group with 30.49% of dietary protein (P < 0.05). Pathological abnormalities in hepatocyte cells of abalone were found in the groups with 17.64% and 43.27% of dietary protein. Meanwhile, accumulative mortalities of abalone after the Vibrio parahaemolyticus challenge test and heat stress test were significantly increased within these two groups (P < 0.05). In conclusion, the excessive (43.27) or deficient (17.64) dietary protein levels depressed the growth and immunity of abalone. Combined with the stress tests results, 17.63% or 43.27% of dietary protein contents are not recommended to the abalone facing the stress of vibriosis or high-water temperature (≥28 °C).

Charge compensation weakening ionized impurity scattering and assessing the minority carrier contribution to the Seebeck coefficient in Pb-doped Mg3Sb2 compounds.

This work reports the electrical and thermal transport processes in p-type Pb-doped Mg3(1+x)Sb2-yPby (0.02 ≤ x ≤ 0.08; 0 ≤ y ≤ 0.02) compounds. Low-energy electron acceptor defects Mg vacancies are easy to form, which can provide holes and make p-type transport in the Mg3Sb2 matrix. However, with an increase in excess Mg, the transport behavior changes from p type to n type as manifested synergistically by both the Hall coefficient and Seebeck coefficient. This indicates the effective role of Mg in tuning carrier type and concentration for a pristine Mg3Sb2 compound. Upon substitution of Sb by Pb, the hole concentration slightly increases, and mobility is greatly improved by 133% at room temperature. The significant increase in mobility is attributed to the weakening ionized impurity scattering, stemming from the decreasing concentration induced by Pb doping. Thus, the power factor is enhanced with a 146% improvement at room temperature. Consequently, the figure of merit ZT of the Pb-doped sample is 1.8 times larger than the pristine one at around 300 K. Moreover, the non-degenerate transport behavior revealed by electrical properties is simply analyzed regarding the effects of minority carriers on the overall Seebeck coefficient. This study proposes a new strategy of charge compensation for improving mobility and a simple way to guide the prediction about the onset of bipolar conduction for Mg3Sb2-based compounds and other potential thermoelectric materials.

Immune response to acute heat stress in the intestine of the red swamp crayfish, Procambarus clarkii.

High temperature is an important environmental factor that affects the survival and immunity of aquatic animals. The intestine of crustaceans is their first line of defense, and the physiological homeostasis of this organ can be influenced by high temperature stress. The red swamp crayfish Procambarus clarkii is an important commercial aquaculture species in China, but little is known about its intestinal immune response to acute heat stress. In this study, we investigated the intestinal immune response of P. clarkii individuals that were assigned to the control (25 °C) and heat stress (35 °C) groups. Biochemical assays were conducted for the oxidative stress parameters ·O2- generation capacity, lipid peroxide content, and malondialdehyde content; the activities of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase; and the activities of the immunity-related enzymes alkaline phosphatase, acid phosphatase, and lysozyme. The relative expression level of the antioxidant genes heat shock protein 70 (hsp70), ferritin (fer), and metallothione (met) was examined by RT-PCR. Based on the data obtained, all the parameters tended to increase, peak and then decrease with time, and were significantly different between the two groups (P < 0.05). These findings reveal that acute heat stress adversely affects the antioxidant status and immune function in the P. clarkii intestine. They lay the groundwork for future studies on the effect of rising water temperatures on immune function and survival of this species.

Irreversible tautomerization as a powerful tool to access unprecedented functional porous organic polymers with a tris(ß-keto-hydrazo)cyclohexane subunit (TKH-POPs).

Porous organic polymers (POPs) have received much attention, due to their multiple potential applications and flexibility in chemical structure design. Creation of a novel chemical structure has been the central task in the research of POPs, which are usually constructed by direct coupling polymerizations. The fascinating rearrangement/tautomerization could lead to some novel structures, which are hard to access by conventional direct coupling polymerizations. Herein, the tautomerization from tris(ß-hydroxyl-azo)benzene to the tris(ß-keto-hydrozo)cyclohexane structure has been proved unambiguously based on an advanced 2D NMR technique such as 15N-1H-HSQC and 1H-1H-NOESY. The crucial tautomerization was used to synthesize TKH-POPs for the first time. The as-synthesized TKH-POP-1 was found to have an adsorption capacity as high as 66.3 mmol g-1 (at 273 K and P/P0 = 0.98) towards acetonitrile vapor, which was the highest among all the reported materials. The general and flexible strategy to make functional POPs with tunable pores such as ultramicropores, micropores and mesopores will help develop interesting functional POPs in the near future.

The effect of nitrite and sulfide on the antioxidant capacity and microbial composition of the intestines of red swamp crayfish, Procambarus clarkii.

Nitrite and sulfide are harmful pollutants in water ecosystems that negatively influence the survival and growth of crayfish. It is currently known that the intestine of crustaceans acts as a significant immune organ, serving as the front line of defense against diseases. In this study, we investigated how the oxidative damage parameters, antioxidant status and microbial composition of the intestine of Procambarus clarkii were influenced under acute nitrite (60 mg/L) and sulfide (18 mg/L) stress for 72 h. Compared with the control, after exposure to nitrite and sulfide stress, the production of reactive oxygen species, and the lipid peroxide and malondialdehyde contents increased in the intestines and were significantly higher after 72 h of exposure. The superoxide dismutase, catalase and glutathione peroxidase activities increased to maximum levels at 6, 24 and 12 h, respectively. These activities then decreased gradually and were significantly lower than those of the control after 48 or 72 h of exposure. In the crayfish exposed to stress, the expression of antioxidant genes including heat shock protein 70, ferritin and metallothionein increased to their maximum values at 12, 48 and 12 h, respectively. The expression levels then decreased gradually, and after 72 h, were lower than, or lacked significant differences with, the expression levels in the control. Additionally, nitrite and sulfide exposure restructured the intestinal microbial community of P. clarkii. This led to decreases in the abundance of some genera such as Citrobacter. However, the abundance of other genera, such as Shewanella and Acinetobacter, increased. Therefore, the health of P. clarkii was seriously impaired when exposed to nitrite and sulfide stress.

Quasi-Metal for Highly Sensitive and Stable Surface-Enhanced Raman Scattering.

Compared with the noble-metal surface-enhanced Raman scattering (SERS) substrates activated by the surface plasmon resonance (SPR)-induced electromagnetic mechanism (EM), the relative low sensitivity and stability of the chemical mechanism (CM)-based substrates are the biggest obstacles to their applications. Herein, we report that quasi-metallic VO2 nanosheet arrays can be used as a sensitive and stable SERS substrate. The lowest detectable limit of analyte adsorbed on the VO2 nanosheets achieves 10-10 M and the maximum Raman enhancement factor (EF) reaches 6.7 × 107, which is comparable with that of the noble metals. The experimental and theoretical results demonstrate that the SERS performance of the VO2 nanosheets comes from the strong interfacial interactions based on charge transfer and the vigorous SPR effects. Our research results demonstrate that quasi-metals are very promising SERS detection platforms and reveal that CM, like EM, contributes significantly to the SERS activity of quasi-metals.

Low Thermal Conductivity and Optimized Thermoelectric Properties of p-Type Te-Sb2Se3: Synergistic Effect of Doping and Defect Engineering.

Elemental tellurium exhibits a promising thermoelectric performance, largely due to the optimization of the carrier concentration stemming from effective chemical doping. In this study, we demonstrate a novel approach to realize the collaborative manipulation of the electrical and thermal transport properties in the Te system via introduction of Sb2Se3. A series of p-type Te1-x(Sb2Se3)x (0 ≤ x ≤ 0.2) samples were fabricated through the melting method followed by spark plasma sintering. Electrically, antimony as a successful dopant enables a remarkable improvement of the carrier concentration, from ∼1018 to ∼1019 cm-3, thus resulting in a desired power factor across the entire temperature range. Thermally, utilization of defects engineering containing point defects, grain boundaries, dislocations, and secondary phase precipitates effectively reduces the lattice thermal conductivity. The coexistence of multi-frequency phonon scattering centers derived from the addition of Sb2Se3 leads to a minimum lattice thermal conductivity of 0.5 W m-1 K-1, approaching the amorphous limit. As a result, Te0.95(Sb2Se3)0.05 shows the highest figure of merit ZT ∼1 at 600 K, comparable to that of the toxic Te(As) thermoelectrics. This work not only points out that synergistic effects of both doping and defect engineering play a vital role in decoupling the thermoelectric parameters in the Te1-x(Sb2Se3)x system but also gives a referential strategy for a higher thermoelectric performance in other Te-based materials.

Metallic and plasmonic MoO2 monocrystalline ultrathin mesoporous nanosheets for highly sensitive and stable surface-enhanced Raman spectroscopy.

Structure and size control are always considered as effective routes to enhance sensitive performance. Different from common polycrystalline porous nanosheets, herein, the general synthesis of monocrystalline ultrathin porous nanosheets (MUPNSs) by a facile decompressing decomposition (DPD) route is reported. Accompanied with the properties inherited from MUPNSs, i.e., high adsorption and strong plasma resonance, these MoO2 MUPNSs presented high sensitive activity as a surface enhanced Raman spectrum (SERS) substrate. The SERS sensitivity of MoO2 MUPNSs was about 1000 times higher than MoO2 polycrystalline ultrathin porous nanosheets (PUPNSs).

Measurement of hydrogen peroxide and organic hydroperoxide concentrations during autumn in Beijing, China.

Gaseous peroxides play important roles in atmospheric chemistry. To understand the pathways of the formation and removal of peroxides, atmospheric peroxide concentrations and their controlling factors were measured from 7:00 to 20:00 in September, October, and November 2013 at a heavily trafficked residential site in Beijing, China, with average concentrations of hydrogen peroxide (H2O2) and methyl hydroperoxide (MHP) at 0.55ppb and 0.063ppb, respectively. H2O2 concentrations were higher in the afternoon and lower in the morning and evening, while MHP concentrations did not exhibit a regular diurnal pattern. Both H2O2 and MHP concentrations increased at dusk in most cases. Both peroxides displayed monthly variations with higher concentrations in September. These results suggested that photochemical activity was the main controlling factor on variations of H2O2 concentrations during the measurement period. Increasing concentrations of volatile organic compounds emitted by motor vehicles were important contributors to H2O2 and MHP enrichment. High levels of H2O2 and MHP concentrations which occurred during the measurement period probably resulted from the transport of a polluted air mass with high water vapor content passing over the Bohai Bay, China.