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In this work, 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT) was pre-doped into agarose hydrogels; consequently, sustained hydrogel systems with modulated release performance were constructed for simple operation and recyclability in point-of-care detection of formaldehyde (FA). With the increase in FA concentrations, the absorbance response of the supernatant solutions showed linear relationships and the color of the reaction mixtures gradually increased. The detection limit was calculated to be 0.013 μg mL -1 . To verify its practical application, a simple, rapid and low-cost FA detection platform was built on the basis of the optimized conditions, and the method shows the merits of simplicity, high sensitivity and selectivity. More importantly, the developed hydrogels are recyclable and can be used at least five times without any loss in sensing performance. Significantly, the sensory hydrogels can be employed by non-skilled people for monitoring food safety and applied for the practical detection of FA in foods.

Semiconducting MoS 2 layers offer the electrons, reducing conjugated Au(I) to Au atoms, and sebsequently serve as desirable substrates for supporting the interfacial growths of gold nanostructures. Au-covering MoS 2 heterostructures perform morphology-varied optical characteristics, and the surface engineering of MoS 2 involved by Hg 2+ ions results in the differential growths of nanostructures and morphological diversities. Naked-eye colorimetric responses to mercury ions, with a low limit of detection of 1.27 nM, are achieved based on the in situ grown heterostructures.

Electrochemical water splitting is widely studied in the hope of solving environmental deterioration and energy shortage. The design of inexpensive metal catalysts exhibiting desired catalytic performance and durable stability for efficient oxygen evolution is the pursuit of sustainable and clean energy fields. Herein, a three-dimensional (3D) flower-like NiSe 2 primary structure, modified with highly dispersed CuSe 2 nanoclusters as the secondary structure, is obtained by regulating the growth trend of the nanosheets. Benefiting from the metallicity of selenides and the formation of a heterogeneous interface, NiSe 2 @CuSe 2 /NF shows comparable performance toward the oxygen evolution reaction (OER) in an alkaline environment. Upon regulating the synthesis conditions, the catalyst exhibits its optimal performance with ultralow overpotential for the OER when the Ni/Cu molar ratio is 1 : 0.2 and the hydrothermal temperature and hydrothermal time are 200 °C and 6 h, respectively. It provides a current density of 10 mA cm -2 when a potential of 201 mV is applied without iR compensation. In this work, the hierarchical heterostructures of NiSe 2 and CuSe 2 are synthesized, which exhibit high electrocatalytic activity towards the oxygen evolution reaction and provides a new possibility for the extensive application of copper-based compounds in advanced energy fields.

The design of Earth-abundant and cost-effective electrocatalysts for highly active and stable electrochemical water splitting in practical production is the primary demand. Herein, bimetallic oxides anchored to three-dimensional (3D) porous conductive nickel foam (NF) are constructed using a simple in situ hydrothermal method for efficient overall water splitting. The vertically aligned Mn3O4/Fe2O3 heterojunction nanosheets have synergy between hierarchical metal oxides and heterogeneous interface, and show excellent performance toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in an alkaline environment. By adjusting the molar ratio of Fe : Mn, the morphology, composition and electronic structure of MnFeO-NF-x composites (x represents the ratio of Fe : Mn) can be adjusted to exhibit diverse catalytic activities. In particular, MnFeO-NF-0.4 (0.4 indicates the Fe : Mn ratio of 0.4 : 1) and MnFeO-NF-0.8 display outstanding performance with ultralow overpotentials of 157 mV for the OER and 64 mV for the HER to achieve a current density of 10 mA cm-2, respectively. Furthermore, MnFeO-NF-0.4 and MnFeO-NF-0.8 are assembled into a water splitting electrolyzer, which can reach a current density of 10 mA cm-2 with a low voltage of 1.59 V. Interestingly, Mn-M (M = Co, Ni, and Mo) products can be obtained easily by using different metal salts, indicating the universality of the current one-pot hydrothermal method.

Current defect theories significantly guide broad research progress, whereas the recognition of defect status remains challenging. Herein, MoS2 defect type, density and exposed state are visually identified with a reagent indicator of HAuCl4. Mo-terminated defects spontaneously reduce [AuCl4]- anions and oxidized Mo species are dissociated. Consequently, MoS2 edges guide the epitaxial branch of Au nanocrystals (NCs), followed by sequential growths at their planar defects. The size-evolution processes of LaMer growth and planar packages of the aggregative growth of Au/MoS2 nanoseeds result in the occupation of Au atomic layers on heterostructures. Consequently, shell-core hybrids are presented with localized surface plasmon resonance characteristics. The mechanism is systematically explored via the discriminated performance of plasmonic characteristics of Au nanostructures on semiconducting MoS2 substrates. With plasmonic identification, defect-associated size and interfacial diversities of MoS2 are visually information-rich. Tunable morphologies and synergistic optical characteristics of plasmonic semiconductor heterostructures inspire many more applications through the edge and planar defects intrinsic in layered MoS2.

Designing low-cost and high-active bifunctional catalysts for overall water splitting has attracted increasing research interest. Herein, the brilliant overall water splitting performance of cobalt-vanadium bimetal-based nanocomposites is explored. Co-V based nanocomposites are synthesized through a one-step hydrothermal method, in which the cobalt species is introduced into the lepidocrocite VOOH and further cobalt vanadium oxide is formed. The additive level of cobalt is optimized and the corresponding effect on electrocatalytic activity is also investigated in this work, systematically. The targeted catalyst (denoted as Co0.2-VOOH) exhibits a unique sheet-like morphology, resulting in the high exposure of catalytically active sites. When used as the bifunctional catalyst, Co0.2-VOOH can achieve a current density of 10 mA cm-2 at the overpotentials of 210 mV for water oxidation and 130 mV for hydrogen generation, respectively. Notably, it only requires low cell voltages of 1.57 and 1.74 V to drive the catalytic current densities of 10 and 100 mA cm-2 during the water splitting process. This work significantly indicates that cobalt-vanadium based materials are promising alternatives for overall water splitting.

Herein, we focus on preparing a highly efficient photocatalytic material to construct a signal-on photoelectrochemical (PEC) sensing platform in view of the rigorous demand of accurate miRNA quantification. The well-dispersed Pt nanoclusters-coated copper phosphate ultrathin nanosheets (PtNCs/Cu 3 (PO 4 ) 2 NSs) were first successfully synthesized as a photoelectrode material. Because of the ultrathin two-dimensional lamellar structure of Cu 3 (PO 4 ) 2 NSs with a 1.3 nm thickness, as well as the homogeneous size and abundant PtNCs loaded on Cu 3 (PO 4 ) 2 NSs, the resultant PtNCs/Cu 3 (PO 4 ) 2 NSs were employed as a photoelectrode material for the first time and revealed outstanding photocatalytic activity in PEC sensing as a substrate. As a well-designed protocol, we realized accurate miRNA quantification via a novel signal amplification strategy based on G-wire superstructure exponentially ligating a signal probe, which possesses efficient and simple operation compared to the traditional amplification method. Moreover, the electron donor is generated in situ by lactate oxidase (Lox) labels catalyzing lactate for H 2 O 2 production, boosting the efficient separation of electron-hole pairs for further signal amplification. Impressively, this PEC sensing platform is commendably utilized to determine miRNA-141 from prostate carcinoma cell line 22Rv1. This study, considering the excellent PtNCs/Cu 3 (PO 4 ) 2 NSs combined with G-wire superstructure for exponential signal amplification strategy, paves a new path in biosensing and clinical diagnosis.

Electrochemically induced Fenton (electro-Fenton) reaction was used for efficient and controllable preparation of hydroxyl radicals, leading to the generation of luminescent quantum dots through etching of as-exfoliated MoS2 nanosheets. Morphologic changes of MoS2 nanosheets during the electro-Fenton reaction were monitored using transmission electron microscopy, showing that etching of MoS2 nanosheets induced by hydroxyl radicals resulted in rapid homogeneous fracturing of the sheets into small dots via a transition of nanoporous morphology. The as-generated dots with vertical dimensional thickness of ca. 0.7 nm and plane size of ca. 5 nm were demonstrated to be MoS2 quantum dots (MoS2-QDs), and their photoluminescence properties were explored based on quantum confinement, edge effect, and intrinsic characteristics. Moreover, the degree of etching and the concomitant porosity of MoS2 nanosheets could be conveniently tuned via the electro-Fenton reaction time, resulting in a new morphology of nanoporous MoS2 nanosheets, with potential new applications in various significant areas.