Nano Ball-Milling Using Titania Nanoparticles to Anchor Cesium Lead Bromine Nanocrystals and Energy Transfer Characteristics in TiO2 @CsPbBr3 Architecture.

Recently, all-inorganic halide perovskite (CsPbX3 , (X = Cl, Br, and I)) nanocrystals (NCs) based hybrid architectures have attracted extensive attention owing to their distinct luminescence characteristics. However, due to stress and lattice mismatch, it is still a challenge to construct heterojunctions between perovskite NCs and the nanostructures with different lattice parameters and non-cubic contour. In this work, a room temperature mechanochemical method is presented to construct TiO2 @CsPbBr3 hybrid architectures, in which TiO2 nanoparticles (NPs) with a hard lattice as nano "balls" mill off the angles and anchor to the CsPbBr3 NCs with a soft lattice. On the contrary, to ball-mill without TiO2 or with conventional ceramics balls replacing TiO2 , CsPbBr3 NCs still maintain cubic contour deriving from their cubic crystal structures. Moreover, the TiO2 @CsPbBr3 architectures display distinct improvement of photoluminescence quantum yields and more excellent thermal stability in contrast with pristine CsPbBr3 owing to the passivation of surface defect, small surface area, and energy transfer from CsPbBr3 to TiO2 . Meanwhile, there is distinct luminous decay characteristic under the radiation of UV and visible light due to the "on" and "off" TiO2 response. The method provides an alternative strategy to acquire other anchoring heterojunctions based on perovskite NCs for further regulating their luminescent characteristics.

Synthesis of wheatear-like ZnO nanoarrays decorated with Ag nanoparticles and its improved SERS performance through hydrogenation.

Semiconductor/noble metal composite SERS substrates have been extensively studied due to their unique bifunctionality. In this work, wheatear-like ZnO nanoarrarys have been fabricated via a modified low-temperature solution method. The hierarchical nanostructures that are constructed by stacked nanoflakes and long whiskers of ZnO possess a substantial number of characteristic nano corners and edges, which are proved to be beneficial to deposit more Ag nanoparticles (NPs). Furthermore, hydrogenated wheatear-like ZnO/AgNP composite substrates are achieved via a safe and facile solid hydrogen source (NaBH4). The hydrogenated ZnO/AgNPs (H-ZnO/Ag) substrates exhibit greatly improved SERS activity in detecting R6G molecules with an enhancement factor (EF) up to ∼0.49 × 10(8), over two orders of magnitude higher than that of the substrates before hydrogenation. The outstanding SERS performance of wheatear-like H-ZnO/Ag substrates benefits from the emerging porous structure of ZnO and abundant surface defects introduced by hydrogenation. In addition, the as-prepared substrates also show high detection sensitivity, good repeatability and recyclability, indicating great potential for practical applications.

Heterojunctions of Mercury Selenide Quantum Dots and Halide Perovskites with High Lattice Matching and Their Photodetection Properties.

Heterojunction semiconductors have been extensively applied in various optoelectronic devices due to their unique carrier transport characteristics. However, it is still a challenge to construct heterojunctions based on colloidal quantum dots (CQDs) due to stress and lattice mismatch. Herein, HgSe/CsPbBrxI3-x heterojunctions with type I band alignment are acquired that are derived from minor lattice mismatch (~1.5%) via tuning the ratio of Br and I in halide perovskite. Meanwhile, HgSe CQDs with oleylamine ligands can been exchanged with a halide perovskite precursor, acquiring a smooth and compact quantum dot film. The photoconductive detector based on HgSe/CsPbBrxI3-x heterojunction presents a distinct photoelectric response under an incident light of 630 nm. The work provides a promising strategy to construct CQD-based heterojunctions, simultaneously achieving inorganic ligand exchange, which paves the way to obtain high-performance photodetectors based on CQD heterojunction films.

Ultrafast and Highly Sensitive Dual-Channel FET Photodetector Based on a Two-Dimensional MoS2 Homojunction.

Two-dimensional transition metal dichalcogenide-based phototransistors have been intensively studied in recent years due to their high detection rate and flexibility. However, the photogating effect, usually appearing in the devices, leads to a poor transient photoresponse, which slows down the imaging rate of the camera based on the devices. Here, we demonstrate a dual-channel two-dimensional field-effect phototransistor composed of a vertical molybdenum disulfide (MoS2) p-n homojunction as the sensitizing channel layer. Owing to the effective separation by the vertical built-in electric field and rapid migration of photoexcited electrons and holes in the separated channels, the fabricated dual-channel FET device simultaneously exhibits prominent responsivity and greatly improved time response in comparison to the pristine MoS2 FET detectors. Excellent device performance has been achieved, with a responsivity of 3.4 × 104 A/W at a source-drain voltage (VDS) of 1 V, corresponding to a detectivity (D*) of 1.9 × 1013 Jones@532 nm and a gain of more than 105 electrons per photon, an external quantum efficiency of 9.6%, and a response time of tens of milliseconds. Especially, the response time of the dual-channel FET device is 3 orders of magnitude faster than that of the pristine device. Our results provide a new way to overcome the inherent photogating drawback of two-dimensional FET optoelectronic devices and to develop a related high frame rate imaging system.

Bio-Separated and Gate-Free 2D MoS2 Biosensor Array for Ultrasensitive Detection of BRCA1.

2D molybdenum disulfide (MoS2)-based thin film transistors are widely used in biosensing, and many efforts have been made to improve the detection limit and linear range. However, in addition to the complexity of device technology and biological modification, the compatibility of the physical device with biological solutions and device reusability have rarely been considered. Herein, we designed and synthesized an array of MoS2 by employing a simple-patterned chemical vapor deposition growth method and meanwhile exploited a one-step biomodification in a sensing pad based on DNA tetrahedron probes to form a bio-separated sensing part. This solves the signal interference, solution erosion, and instability of semiconductor-based biosensors after contacting biological solutions, and also allows physical devices to be reused. Furthermore, the gate-free detection structure that we first proposed for DNA (BRCA1) detection demonstrates ultrasensitive detection over a broad range of 1 fM to 1 µM with a good linear response of R2 = 0.98. Our findings provide a practical solution for high-performance, low-cost, biocompatible, reusable, and bio-separated biosensor platforms.

Berberine reduces the occurrence of neonatal necrotizing enterocolitis by reducing the inflammatory response.

Necrotizing enterocolitis (NEC) is a life-threatening disease that occurs in premature infants. The aim of the present study was to investigate the effects of berberine, an isoquinoline alkaloid mainly used to treat digestive diseases, in a rat model of NEC. NEC models were established in newborn rats via inhalation of N2 for 90 sec every 4 h and oral administration of 4 mg/kg/day lipopolysaccharides on days 0 and 1. Berberine was administered via oral gavage. In the NEC model group, Toll-like receptor (TLR)4, nuclear factor NF-κB (NF-κB), inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10 were upregulated. Symptoms of NEC in the berberine intervention group were significantly relieved, with a clear reduction in the incidence of NEC compared with the NEC group. TLR4, NF-κB, iNOS, TNF-α, IL-6 and IL-10 expression was decreased following berberine intervention. Furthermore, the expression of mucin-2 (MUC2) and RNA polymerase σ factor SigA (SIgA) were decreased in the NEC model group and increased following berberine intervention, when compared with the untreated group. It was also demonstrated that the incidence of NEC was reduced following berberine administration, possibly owing to changes in the inflammatory responses. The results of the current study support a potential therapeutic role of berberine for the treatment of NEC.

One-Pot and Facile Fabrication of Hierarchical Branched Pt-Cu Nanoparticles as Excellent Electrocatalysts for Direct Methanol Fuel Cells.

Hierarchical branched nanoparticles are one promising nanostructure with three-dimensional open porous structure composed of integrated branches for superior catalysis. We have successfully synthesized Pt-Cu hierarchical branched nanoparticles (HBNDs) with small size of about 30 nm and composed of integrated ultrathin branches by using a modified polyol process with introduction of poly(vinylpyrrolidone) and HCl. This strategy is expected to be a general strategy to prepare various metallic nanostructures for catalysis. Because of the special open porous structure, the as-prepared Pt-Cu HBNDs exhibit greatly enhanced specific activity toward the methanol oxidation reaction as much as 2.5 and 1.7 times compared with that of the commercial Pt-Ru and Pt-Ru/C catalysts, respectively. Therefore, they are potentially applicable as electrocatalysts for direct methanol fuel cells.

Hydrogenated blue titania with high solar absorption and greatly improved photocatalysis.

Hydrogenated black titania, with a crystalline core/amorphous shell structure, has attracted global interest due to its excellent photocatalytic properties. However, the understanding of its structure-property relationships remains a great challenge and a more effective method to produce hydrogenated titania is desirable. Herein, we report a TiH2 assisted reduction method to synthesize bluish hydrogenated titania (TiO2-x:H) that is highly crystallized. The characteristic amorphous shells, which are essential for the enhancement of solar absorption and photocatalysis in many reported hydrogenated titania, are completely removed by hydrogen peroxide. The blue TiO2-x:H sample without amorphous shells delivers not only significantly improved visible- and infrared-light absorption but also greatly enhanced photocatalytic activity compared to pristine TiO2. Its water decontamination is 2.5 times faster and the hydrogen production was 1.9-fold higher over pristine TiO2. Photoelectrochemical measurement reveals greatly improved carrier density and photocurrent (a 4.3-fold increase) in the reduced TiO2-x:H samples. This work develops a facile and versatile method to prepare hydrogenated titania and proposes a new understanding of the hydrogenated titania that doped hydrogen atoms, instead of the amorphous shells, are essential for its high photocatalytic performance.

Large-scale template-free synthesis of ordered mesoporous platinum nanocubes and their electrocatalytic properties.

Here we report a facile, one-pot and template-free approach to synthesize mesoporous monocrystalline Pt nanocubes with uniform shapes and sizes, in which small Pt particles with a size of ∼5 nm are three-dimensionally and periodically built up into cubes with a size of ∼50 nm. The forming process is illustrated through a novel meso-crystal self-assembly mechanism. Very interestingly, the mesoporous structures are ordered, which are thought to be beneficial to increase their catalytic activity. Compared with nonporous Pt nanoparticles and porous Pt nanoparticles without order, the ordered mesoporous Pt nanocubes exhibit a highly improved electrocatalytic ability for methanol and formic acid oxidation, and are potentially applicable as electrocatalysts for direct methanol and formic acid fuel cells. Furthermore, this approach can be used to synthesize other Pt-series metallic mesoporous nanoparticles, such as Pd.