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Ternary metal oxide SnO2/Co3O4 has attracted much attention for its excellent sensitivity and structural stability. We prepared hollow, rough, and porous SnO2/Co3O4 nanofibers using the electrostatic spinning technique in this study. These nanofibers were subsequently compounded with Ta2O5 via the solvothermal method, resulting in the successful synthesis of nanofiber-structured Ta2O5@SnO2/Co3O4 heterojunction materials with outstanding room-temperature ethanol sensing performance. The nanofiber structure of SnO2/Co3O4 significantly enhanced the interface for active oxygen adsorption on the Ta2O5 surface, thereby increasing the number of reactive sites for ethanol gas sensitivity. The Ta2O5@SnO2/Co3O4 heterojunction can detect ethanol concentrations as low as 1 ppm at room temperature, with a response value of 6.53 for 100 ppm ethanol. The theoretical detection limit of ethanol for this material can be as low as 522 ppb, as determined by curve fitting. Nanofiber-structured Ta2O5@SnO2/Co3O4 heterojunction materials exhibited comprehensive and excellent room-temperature gas-sensitive properties, suggesting that combining the morphology regulation and heterostructure can provide innovative strategies for room-temperature sensing. [ABSTRACT FROM AUTHOR]

The continuous, random three-dimensional nanostructure of aerogels is the key determinant of their exceptional thermal insulating performance. However, at elevated temperatures, sintering can lead to disruption of this nanostructure. SiOC and SiZrOC aerogels were prepared by pyrolyzing organic–inorganic precursor aerogels at 1000 °C under an Ar atmosphere. The pyrolysis treatment resulted in the formation of a Si–O–C structure with excellent thermal stability. Following calcination at 1000 °C for 0.5 h, SiZrOC demonstrated a specific surface area retention rate of 76.8% and a pore volume retention rate of 75.8%, surpassing the most advanced ZrO2–SiO2 aerogel. Additionally, SiZrOC consistently exhibited outstanding thermal insulation performance, with thermal conductivities of 0.0273 and 0.0332 W m–1 K–1 before and after calcination at 1000 °C, respectively. Notably, it was observed for the first time that the rearrangement of Si–C and Si–O bonds caused by pyrolysis induced a loosening effect on the SiO4 structure within the aerogel. Consequently, during subsequent aerobic calcination, SiOC and SiZrOC underwent another phase separation stage, resulting in a further increase in the number of Si–O–C structures, which offers an approach to improve thermal insulation properties in extreme environments. The superior thermal stability and thermal insulation performance make SiZrOC a promising candidate for applications in high-temperature nanoscale thermal insulation materials. [ABSTRACT FROM AUTHOR]

Salicylate hydmxylase (SHL) catalyzes the production of catechol (plus C[O.sub.2] and [H.sub.2]O) from salicylate, NADH, and [O.sub.2]. Coimmobilization of SHL with a NAD(P)-dependent dehydrogenase in front of a Clark-type oxygen electrode has been investigated in the development of a general type of dehydrogenase-based biosensors that can detect various biological analytes; however, currently, no fluorophores are available for these applications. We synthesized the first new long-wavelength latent fluorogenic substrate SHLF (3) for SHL In the presence of NADH and under aerobic conditions, SHL catalyzes the decarboxylative hydroxylation of SHLF followed by a quinone methide-type rearrangement reaction concomitant with the ejection of a fluorescence coumarin 2, which is spontaneous and irreversible at physiological temperatures in aqueous media. The fuorescence signal generated by this process is specific and, in the near red spectral region with an emission maximum at 595 nm, is suppressed by salicylic acid. The fluorescence response of SHLF is insensitive to various biological reactive oxygen species (ROS) and reductants. Furthermore, SHLF is a sensitive fluorimetric indicator for analyte determination in the SHL-coupled dehydrogenase assay in which NAD+ is converted to NADH. This novel fluorescence assay detected 3-hydroxybutyrate and cholesterol in the nanomolar range and is more sensitive than the current SHL--dehydrogenase amperometric sensors, making it applicable to the construction of a fiber-optic fluorescence biosensor for clinical diagnostic uses. 10.1021/ac101281p

Hydrogen sulfide (H2S) gas is one of the highly toxic, lethal, and corrosive gases in the environment that can cause a series of inimical effects after human exposure. Therefore, developing gas-sensitive nanomaterials that could effectively detect the ultralow concentration of H2S is of utmost significance. In this study, a perovskite quantum dot (QD) structure is synthesized through a simple solution method in which CsPbBr3 QDs are surface capped with tributyltin oxide (TBTO). It was employed as a chemiresistor to H2S, exhibiting exceptional repeatability, superior selectivity, and an ultralow limit of detection of 250 ppb with a response sensitivity of 0.58 at room temperature, which is the highest value for H2S sensors based on metal-halide perovskite structure. The response/recovery time is 278/730 s at a 100 ppm concentration of H2S. Furthermore, we proposed the sensing mechanism of dispersion-sensing effect of the metallo-organic ligand by theory calculation to explain the excellent response performance. The chemical adsorption sensitivity of the related chemical groups is amended when the metallo-organic molecular is engrossed on the surface of CsPbBr3 QDs and becomes an isolated ligand. Thus, the H2S molecule is first absorbed by the isolated TBTO molecule, which prevents H2S from penetrating the perovskite CsPbBr3, forming a Pb–S bond, and damaging the sensing performance. Meanwhile, the H2S adsorption also affects the charge distribution of the internal CsPbBr3 QDs through a metallo-organic TBTO molecule, enhancing the sensitivity and response to H2S. Overall, the nanomaterial's structure and gas response mechanism could be extended to detecting other gases. [ABSTRACT FROM AUTHOR]

An efficient and simple way has been described to prepare gold and silver bimetallic alloy nanoparticles (Au-AgNPs) in an organic framework with a metal-free core. The growth of alloy Au-AgNPs was monitored by UV–visible spectroscopy (UV–vis) and confirmed using various spectral, microscopy, and electrochemical techniques. The field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results revealed that the covalent organic framework (COF) had a uniform flake-like morphology, and the alloy-based Au-AgNPs had a flower-like structure. The results of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) indicated that Au-AgNPs are metallic in nature and highly crystalline. The surface of a glassy carbon electrode (GCE) was then modified with Au-AgNPs-COF, which was subsequently employed for enzyme-free electrochemical reduction of H2O2. The electrocatalytic cyclic voltammetry performance of the different modified electrodes was in the following order: COF (−14.82 μA) < AgNPs-COF (−26.95 μA) < AuNPs-COF (−31.78 μA) < Au-AgNPs-COF (−46.15 μA). The Au-AgNPs-COF/GCE displayed an excellent electrocatalytic activity toward reduction of H2O2, over a dynamic range of 2.0 nM–1.0 mM with a limit of detection (LOD) of 0.44 nM (S/N = 3). Furthermore, the present sensor showed appreciable selectivity, stability, and reproducibility against the reduction of H2O2. Practicality was demonstrated in fetal bovine serum (FBS), cat blood serum (CBS), and living cells (RAW 264.7). [ABSTRACT FROM AUTHOR]