Using highly water-stable wool keratin/CsPbBr3 nanocrystals as a portable amine-responsive fluorescent test strip for onsite visual detection of food freshness.

Perovskite nanocrystals (PNCs) have emerged as promising candidates for fluorescent probes owing to their outstanding photoelectric properties. However, the conventional CsPbBr3 (CPB) NCs are extremely unstable in water, which has seriously limited their sensing applications in water environment. Herein, we present a powerful ligand engineering strategy for fabricating highly water-stable CPB NCs by using a biopolymer of wool keratin (WK) as the passivator and the polyaryl polymethylene isocyanate (PAPI) as the cross-linking agent. In particular, WK with multi-functional groups can serve as a polydentate ligand to firmly passivate CPB NCs by the ligand exchange process in hot toluene; and then the addition of PAPI can further encapsulate CPB NCs by the crosslinking reaction between PAPI and WK. Consequently, the as-prepared CPB/WK-PAPI NCs can maintain âˆ¼ 80 % of their relative photoluminescence (PL) intensity after 60 days in water, and they still maintain âˆ¼ 40 % of their relative PL intensity even after 512 days in the same environment, which is one of the best water stabilities compared previously reported polymer passivation methods. As a proof-of their application, the portable CPB/WK-PAPI NCs-based test strips are further developed as a fluorescent nanoprobe for real-time and visual monitoring amines and food freshness. Among various amine analytes, the as-prepared test strips exhibit higher sensitivity towards conjugated amines, achieving a remarkable detection limit of 18.3 nM for pyrrole. Our research not only introduces an innovative strategy involving natural biopolymers to enhance the water stability of PNCs, but also highlights the promising potential of PNCs for visually and portably detecting amines and assessing food freshness.

Regioselective Reaction of 2-Indolylmethanols with Enamides.

A highly regioselective reaction of 2-indolylmethanols with enamides has been developed at room temperature by using AlCl3 as a catalyst. A wide range of hybrids (40 examples) of indoles and enamides were obtained in moderate to good yields (up to 98% yield). This transformation represents the efficient way to introduce biologically important indoles and enamides skeleton into structurally complex hybrids.

Photocorrosion-Based BiOCl Photothermal Materials for Synergistic Solar-Driven Desalination and Photoelectrochemistry Energy Storage and Release.

Solar-driven interfacial evaporation is one of the most promising desalination technologies. However, few studies have effectively combined energy storage with evaporation processes. Here, a novel multifunctional interfacial evaporator, calcium alginate hydrogel/bismuth oxychloride/carbon black (HBiC), is designed, which integrates the characteristics of interfacial evaporation and direct photoelectric conversion. Under illumination, the Bi nanoparticles which were produced by photoetching of BiOCl and its reaction heat are simultaneously used for the heating of water molecules. Meanwhile, part of the solar energy is converted into chemical energy through the photocorrosion reaction and stored in HBiC. At night, Bi NPs undergo autooxidation reaction and an electric current is generated during this process (like a metal-air battery), in which the maximum current density is more than 15 µA cm-2. This scientific design cleverly combines desalination with power generation and provides a new development direction for energy collection and storage.

Assembly of bimetallic (Au-Ag)FON composite films at liquid/solid interfaces and their tunable optical properties.

The regular structure provided by two-dimensional (2D) structural colloidal crystals is widely accepted to provide an ideal template that ensures that plasmonic bimetallic composite nanostructures are uniform. Herein, we report an effective method for fabricating bimetallic Au-Ag composite films loaded on the surfaces of 2D polystyrene@polyacrylic acid (PS@PAA) colloidal crystals. PS@PAA particles coated with uniform Ag particle layers (AgFON) were produced by a simple and effective sputtering-deposition technique, after which the galvanic replacement (GR) reaction was used to produce a bimetallic (Au-Ag)FON composite film at the liquid/solid interface in aqueous HAuCl4. The morphology and relative contents of the bimetallic (Au-Ag)FON composite film can be regulated by changing the kinetic factors that control the GR reaction, including the concentration and pH of the HAuCl4 solution, and the reaction time. We demonstrated that the fabricated bimetallic (Au-Ag)FON composite has localized surface plasmon resonance (LSPR) properties that can be regulated by varying the composite structure and Ag/Au composition. On the one hand, the regular 2D colloidal crystal structure provides an ideal template for preparing Au-Ag composite films, which ensures that the optical signals of plasmonic Au-Ag composite films are reproducible. On the other hand, the synergy between Ag and Au in the bimetallic alloy composite film ensures stable and tunable LSPR performance. Furthermore, the prepared 2D ordered (Au-Ag)FON Au-Ag bimetallic material is expected to be used in sensing and catalysis applications.

A sensitive cholesterol electrochemical biosensor based on biomimetic cerasome and graphene quantum dots.

A simple and sensitive electrochemical cholesterol biosensor was fabricated based on ceramic-coated liposome (cerasome) and graphene quantum dots (GQDs) with good conductivity. The cerasome consists of a lipid-bilayer membrane and a ceramic surface as a soft biomimetic interface, and the mild layer-by-layer self-assembled method as the immobilization strategy on the surface of the modified electrode was used, which can provide good biocompatibility to maintain the biological activity of cholesterol oxidase (ChOx). The GQDs promoted electron transport between the enzyme and the electrode more effectively. The structure of the cerasome-forming lipid was characterized by Fourier transform infrared (FT-IR). The morphology and characteristics of the cerasome and GQDs were characterized by transmission electron microscopy (TEM), zeta potential, photoluminescence spectra (PL), etc. The proposed biosensors revealed excellent catalytic performance to cholesterol with a linear concentration range of 16.0 × 10-6-6.186 × 10-3 mol/L, with a low detection limit (LOD) of 5.0 × 10-6 mol/L. The Michaelis-Menten constant (Km) of ChOx was 5.46 mmol/L, indicating that the immobilized ChOx on the PEI/GQDs/PEI/cerasome-modified electrode has a good affinity to cholesterol. Moreover, the as-fabricated electrochemical biosensor exhibited good stability, anti-interference ability, and practical application for cholesterol detection.

Pickering emulsion-embedded hierarchical solid-liquid hydrogel spheres for static and flow photocatalysis.

Pickering emulsion-based photocatalysis is considered to be a promising system due to its large active surface area and water/oil spatial separation capability for enrichment of substrates and products. In this work, a novel hierarchical structure composed of calcium alginate gel sphere wrapped ionic liquid-in-water Pickering emulsion with TiO2 in the water phase, which are stabilized by graphene oxide, is prepared via a facile one-step emulsion gelation method. Such subtle combination of Pickering emulsion, hydrogel and TiO2 with a multi-stage solid-liquid assemblage structure shows enhanced degradation activity of 2-naphthol into small molecular alkanes under simulated solar irradiation. The photodegradation activity is attributed to the ionic liquid as adsorption medium for 2-naphthol, and the high-efficient charge separation at graphene oxide/TiO2 interface superior to that of pure TiO2. More importantly, the as-prepared millimeter-sized assembled gel spheres can be directly used as the column filler to construct continuous flow photocatalytic system, maintaining the promising performance in removing pollutants from water with ~100% remove ability of 2-naphthol on stream. A charge transfer mechanism of the photocatalyst is proposed, i.e. photogenerated charges are separated in TiO2/graphene oxide p-n heterostructure at the interface of Pickering emulsion droplets.

Photo-Induced Charge Transfer on Pt/Bi2WO6 Composite Photocatalysts.

Pt/Bi2WO6 composite photocatalysts were prepared by a facile photoreduction method. Pt nanoparticles with an average size of 5-8 nm were successfully deposited on the surface of Bi2WO6 microspheres and the photocatalytic activity of Bi2WO6 was greatly improved by Pt nanoparticles. The photo-induced charge transfer properties of samples were studied by means of surface photovoltage (SPV) and transient photovoltage (TPV) techniques, giving an insight into the intrinsic reasons of the improvement in photocatalytic activity. The SPV and TPV results revealed that the deposited Pt nanoparticles could trap photo-induced electrons and then largely enhance the separation efficiency of photo-induced charge carriers.

Enhanced Efficiency of Planar Heterojunction Perovskite Solar Cells by a Light Soaking Treatment on Tris(pentafluorophenyl)borane-Doped Poly(triarylamine) Solution.

This research used Lewis acid tris(pentafluorophenyl)borane (BCF) as a p-type dopant and a light soaking (LS) treatment to improve the conductivity of poly(triarylamine) (PTAA). Specifically, the conductivity of PTAA films was improved by two orders of magnitude using BCF as a p-type dopant, and the conductivity of BCF-doped PTAA films could be further improved by using the LS treatment on its solution. The working mechanism of the formation of frustrated Lewis pairs between BCF and PTAA was proposed to explain the BCF doping and LS treatment effects on the hole transport property of PTAA. When 5 min LS-PTAA films with 8 wt % BCF were used as the hole transport layer in p-i-n planar heterojunction perovskite solar cells, a maximum power conversion efficiency of 17.12% was achieved. This work provides a deep understanding of the enhancement of the conductivity of PTAA by the BCF doping and LS treatment. In addition, a convenient and quick LS method was explored to improve the conductivity of the PTAA hole transport material. Our findings may help in improving the hole transport properties of other organic photoelectric materials and devices.

Improved Performance and Reproducibility of Perovskite Solar Cells by Well-Soluble Tris(pentafluorophenyl)borane as a p-Type Dopant.

In this work, well-soluble tris(pentafluorophenyl)borane (BCF) is introduced for the first time into 2,2',7,7'-tetrakis(N,N'-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) as a p-dopant. The conductivity of spiro-OMeTAD films is dramatically enhanced. When the BCF-doped spiro-OMeTAD film is used as a hole-transport layer (HTL) in perovskite solar cells (PSCs), nearly double increase in power conversion efficiency (PCE) is obtained compared to that of the PSCs based on a pristine spiro-OMeTAD HTL. By the introduction of lithium bis(trifluoromethanesulfonyl)imide and 4-tert-butylpyridine into the BCF-doped spiro-OMeTAD film, the conductivity of spiro-OMeTAD film can be further enhanced, and an optimum PCE of 14.65% is obtained. In addition, the average efficiency of the device and the reproducibility of BCF-based PSCs are better than those of FK209-based PSCs. The working mechanism of the BCF doping effect on spiro-OMeTAD is studied in detail. The strong electron-accepting ability, excellent solubility in common organic solvents, and the low cost make BCF a very attractive p-type dopant for spiro-OMeTAD.

[101Ì 0] oriented multichannel ZnO nanowire arrays with enhanced optoelectronic device performance.

Crystallographic orientation and microstructure of metal oxide nanomaterials have great impact on their properties and applications. Here, we report [101̅0] oriented ZnO nanowire (NW) arrays with a multichannel mesostructure. The NW has a preferential growth of low energy (101̅0) crystal plane and exhibits 2-3 orders of magnitude faster electron transport rate than that in nanoparticle (NP) films. Furthermore, the surface area of the as-prepared NW arrays is about 5 times larger than that of conventional NW arrays with similar thickness. These lead to the highest power conversion efficiency of ZnO NW array-based sensitized solar cells. We anticipate that the unique crystallographic orientation and mesostructure will endow ZnO NW arrays new properties and expand their application fields.

Oriented assembled TiO2 hierarchical nanowire arrays with fast electron transport properties.

Developing high surface area nanostructured electrodes with rapid charge transport is essential for artificial photosynthesis, solar cells, photocatalysis, and energy storage devices. Substantial research efforts have been recently focused on building one-dimensional (1D) nanoblocks with fast charge transport into three-dimensional (3D) hierarchical architectures. However, except for the enlargement in surface area, there is little experimental evidence of fast electron transport in these 3D nanostructure-based solar cells. In this communication, we report single-crystal-like 3D TiO2 branched nanowire arrays consisting of 1D branch epitaxially grown from the primary trunk. These 3D branched nanoarrays not only demonstrate 71% enlargement in large surface area (compared with 1D nanowire arrays) but also exhibit fast charge transport property (comparable to that in 1D single crystal nanoarrays), leading to 52% improvement in solar conversion efficiency. The orientated 3D assembly strategy reported here can be extended to assemble other metal oxides with one or multiple components and thus represents a critical avenue toward high-performance optoelectronics.

Investigation of photocatalytic activities over Bi2WO6/ZnWO4 composite under UV light and its photoinduced charge transfer properties.

Bi(2)WO(6)/ZnWO(4) composite photocatalysts have been successfully synthesized by a facile hydrothermal process. The catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microcopy (TEM), and UV-vis diffuse reflectance spectrum (DRS). The results show that Bi(2)WO(6) nanoparticles grow on the primary ZnWO(4) nanorods. The Bi(2)WO(6)/ZnWO(4) composites have better UV light photocatalytic activities compared to single ZnWO(4) nanorods. Furthermore, the photoinduced charge transfer properties of Bi(2)WO(6)/ZnWO(4) composites were investigated by means of transient photovoltage (TPV) technique in detail. The interconnected interface of Bi(2)WO(6)/ZnWO(4) composites led to the low recombination ratios of photoinduced electron-hole pairs and enhanced photocatalytic activities.

Analysis of sulfonamides in environmental water samples based on magnetic mixed hemimicelles solid-phase extraction coupled with HPLC-UV detection.

The magnetic mixed hemimicelles solid-phase extraction (MMHSPE), based on the adsorption of cation surfactant octadecyltrimethylammonium bromide (OTMABr) onto magnetite nanoparticles (Fe(3)O(4) NPs) to form mixed hemimicelles, was proposed for the preconcentration of several sulfonamides (SAs) compounds including sulfamethoxazole (SMX), sulfamethoxydiazine (SMD), sulfadimethoxine (SDM) and sulfaquinoxaline (SQX) from environmental water samples. This method avoided the time-consuming column-passing process of loading large volume samples in traditional SPE through the rapid isolation of OTMABr-coated Fe(3)O(4) NPs with an adscititious magnet. Mixed hemimicelles formed on the surface of Fe(3)O(4) NPs by OTMABr showed great adsorptive tendency towards analytes. The OTMABr-coated Fe(3)O(4) NPs adsorbents were easy to be prepared, low cost and environmentally friendly. A comprehensive study on the adsorption conditions such as the amount of the surfactant, the solution pH, the desorption condition and the maximum extraction sample volume were optimized. A concentration factor of 1000 was achieved by the extraction of 500 mL of environmental water samples using MMHSPE. Detection limits obtained for SMX, SMD, SDM and SQX were 0.026, 0.024, 0.033 and 0.030 microg L(-1), respectively. Good recoveries (70-102%) with low relative standard deviations (1-6%) were achieved in analyzing spiked water samples. Low concentration of SQX was found in hospital primary and final sewage effluent sample.