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The aqueous micro batteries (AMBs) are expected to be one of the most promising micro energy storage devices for its safe operation and cost‐effectiveness. However, the performance of the AMBs is not satisfactory, which is attributed to strong interaction between metal ions and the electrode materials. Here, the first AMBs are developed with NH4+ as charge carrier. More importantly, to solve the low conductivity and the dissolution during the NH4+ intercalation/extraction problem of perylene material represented by perylene‐3,4,9,10‐tetracarboxylic dianhydride (PTCDA), the Ti3C2Tx MXene with high conductivity and polar surface terminals is introduced as a conductive skeleton (PTCDA/Ti3C2Tx MXene). Benefitting from this, the PTCDA/Ti3C2Tx MXene electrodes exhibit ultra‐high cycle life and rate capability (74.31% after 10 000 galvanostatic chargedischarge (GCD) cycles, and 91.67 mAh g−1 at 15.0 A g−1, i.e., capacity retention of 45.2% for a 30‐fold increase in current density). More significantly, the AMBs with NH4+ as charge carrier and PTCDA/Ti3C2Tx MXene anode provide excellent energy density and power density, cycle life, and flexibility. This work will provide strategy for the development of NH4+ storage materials and the design of AMBs. [ABSTRACT FROM AUTHOR]

Ruddlesden–Popper (RP) faults are well known in oxide perovskites, and are also observed in promising metal halide perovskites. However, the effect of RP faults on optical properties of perovskite has not been systematically investigated. In this study, it is found that RP faults are common planar faults in all‐vacuum deposited CsPbBr3‐based perovskite polycrystal thin films, and the density of RP planar faults can be greatly increased by non‐stoichiometric composition (Cs‐rich) as well as reduced dimensionality (quasi‐2D) strategies. The photoluminescence (PL) measurement reveals monotonically increasing peak intensities with higher densities of RP planar faults from Cs‐rich, quasi‐2D to Cs‐rich & quasi‐2D samples. The corresponding atomic‐scale differential phase contrast maps indicate strongly confined charges within the RP planar fault network, which explains well the relationship between PL enhancement and the density of RP planar faults, and offers an alternative pathway for tailoring the optoelectronic properties of perovskite. [ABSTRACT FROM AUTHOR]

Two-dimensional layered materials have attracted increasing attention due to their unique structures and outstanding mechanical and physical properties. Transition metal dichalcogenides (TMDs) possess unique physical properties and optical properties that meet the basic requirements of photodetectors. As representative TMDs, MoS2 has excellent mechanical properties due to its strong covalent bonds and great elasticity. The monolayer MoS2 has a direct bandgap of around 1.8 eV. In addition, MoS2-based optoelectronic devices have high switching ratio and carrier mobility. However, due to the characteristic of atomic-scale thickness, the light-harvesting ability of layered TMDs is very weak, which largely limits the responsivity and detection rate of photodetectors, thus inhibiting the practical application of such devices. The slow photo response rate is also a problem that often occurs in TMDs devices. Researchers have reported several strategies to improve the performance of TMDs-based photodetectors. At present, there are two main optimization schemes, namely surface modification, and heterostructure construction. The utilization of metal plasmon effect and the construction of heterojunctions are both effective means to improve the performance of MoS2 photodetectors. These schemes can improve the light absorption capability of MoS2 and broaden the range of light detection. However, there are also disadvantages of the complex processes and limited enhancement effects in large-area fabrication. Therefore, it is of vital significance to further explore the response range and performance of MoS2 photodetectors. [ABSTRACT FROM AUTHOR]

Sensitive gas sensors are becoming increasingly important in toxic gas detection and environmental monitoring. The applications of conventional gas sensors are limited due to their low sensitivity or high operating temperature. MXenes with high conductivity are conducive to the rapid transmission of electrons and are suitable as highly sensitive NH3 gas sensors. Considering the limited research on the experimental details and sensing mechanism of MXene-based NH3 gas sensors, our research focuses on precisely controlling the atomic structure of MXenes to improve the performance of NH3 gas sensors. The atomic structures of a typical monolayer Ti3C2O2 MXene and its Ti-deficient counterpart as the NH3 gas sensor are systematically studied through first-principles calculations and the nonequilibrium Green's function method. The Ti-deficient Ti3C2O2 MXene has a relatively stronger physical interaction with NH3 and is comparatively more suitable as a highly sensitive NH3 gas sensor. Atomic-level device simulations show that the current has a greater change when NH3 is adsorbed on the surface of Ti-deficient Ti3C2O2. These detailed calculations provide substantial theoretical support and a useful design scheme to improve the sensitivity of MXene-based gas sensors by deliberately introducing Ti vacancies in the MXene. [ABSTRACT FROM AUTHOR]

Pharmaceutically active compounds (PhACs) are excreted by humans and animals and released into the aquatic environment through wastewater, which can have potential negative impacts on ecological systems. To conduct a nationwide investigation of the occurrence of PhACs in water resources in China, an analytical procedure based on solid-phase extraction (SPE) and LC-MS/MS was used to measure 45 PhACs in surface water samples from a network of 29 rivers across 31 provinces in China in 2014 and 2015. PhACs were prevalent in all sampled streams. The concentrations of commonly detected PhACs were comparable to those detected in other countries. High total concentrations (mean > 1 μg L −1 ) of all tested PhACs were primarily detected in areas under extreme water stress, specifically northern and eastern coastal areas. Source apportionment based on the profiles of the target compounds found that 54% of the PhACs in China originated from freshly discharged untreated sewage. Metformin (MET) and its biodegradation product, guanylurea (GUL), were used as a pair of indicators to predict PhAC contamination levels and differentiate between biotreated and unbiotreated wastewater. High MET/GUL can be used to indicate untreated wastewater, whereas low MET/GUL values are a strong indicator of treated wastewater. Furthermore, wastewater biotreatment ratios were calculated. We estimated that the biotreatment ratios of most of the provinces in China were less than 50%. We conclude that more attention should be paid to untreated sewage water, especially water in rural areas rather than the existing concentration on urban sewage treatment-oriented management. [ABSTRACT FROM AUTHOR]

The photochemical transformation of pharmaceutical and personal care products (PPCPs) in wastewater effluents is an emerging concern for environmental scientists. In the current study, the photodegradation of 29 PPCPs was examined in effluents under simulated solar irradiation. Direct photodegradation, triplet state effluent organic matter (3EfOM*)-mediated and hydroxyl radical (HO•)-mediated degradation are three major pathways in the removal process. With the photodegradation of trace levels of PPCPs, the excitation-emission matrix (EEM) fluorescence intensities of the effluents were also gradually reduced. Therefore, fluorescence peaks have been identified, for the first time, as appropriate surrogates to assess the photodegradation of PPCPs. The humic-like fluorescence peak is linked to direct photolysis-labile PPCPs, such as naproxen, ronidazole, diclofenac, ornidazole, tinidazole, chloramphenicol, flumequine, ciprofloxacin, methadone, and dimetridazole. The tyrosine-like EEM peak is associated with HO•/CO3•--labile PPCPs, such as trimethoprim, ibuprofen, gemfibrozil, atenolol, carbamazepine, and cephalexin. The tryptophan-like peak is associated with 3EfOM*-labile PPCPs, such as clenbuterol, metoprolol, venlafaxine, bisphenol A, propranolol, ractopamine, salbutamol, roxithromycin, clarithromycin, azithromycin, famotidine, terbutaline, and erythromycin. The reduction in EEM fluorescence correlates well with the removal of PPCPs, allowing a model to be constructed. The solar-driven removal of EEM fluorescence was applied to predict the attenuation of 11 PPCPs in five field samples. A close correlation between the predicted results and the experimental results suggests that fluorescence may be a suitable surrogate for monitoring the solar-driven photodegradation of PPCPs in effluents. [ABSTRACT FROM AUTHOR]