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Alkaline phosphatase (ALP) is an important enzyme that is associated with many human diseases, so the quantitative detection of ALP is vital from a clinical perspective. Nevertheless, most fluorescent assays for monitoring ALP depend on aggregation-induced quenching (ACQ), single-signal modulation, or a "signal off" mode, which suffer from poor sensitivity, a "false positive" problem, and low signal output. In this work, we utilized the electrostatically driven self-assembly of glutathione-capped gold nanoclusters (GSH-AuNCs, which show aggregation-induced emission, AIE) and amino-modified silicon nanoparticles (SiNPs) to create a hybrid probe (SiNPs@GSH-AuNCs). This nanohybrid probe showed emission from the SiNPs at around 470 nm as well as aggregation-induced emission enhancement (AIEE) of the GSH-AuNCs at 580 nm. The AIEE of the GSH-AuNCs was quenched in the presence of KMnO4, but the AIEE was recovered by adding ascorbic acid as an oxidation–reduction reaction occurred between KMnO4 and the ascorbic acid. The fluorescence of the SiNPs remained constant whether the AIEE was quenched or not, meaning that the fluorescence of the SiNPs could be used as an internal reference. In a typical enzymatic reaction, ascorbic acid 2-phosphate is hydrolyzed by ALP to produce ascorbic acid. Therefore, the hybrid probe was shown to allow the ratiometric detection of ALP, with a linear range of 0.5–10 U L−1 and a limit of detection (LOD) of 0.23 U L−1. Finally, the proposed analytical strategy was successfully applied to detect ALP in human serum samples and to determine the concentration of an ALP inhibitor. [ABSTRACT FROM AUTHOR]

Perfluorocarboxylic acids (PFCAs) in cod liver oil was analyzed for the first time using newly designed and synthesized quaternary ammonium–functionalized magnetic nanoparticles (Fe3O4@SiO2@QTA). Fe3O4@SiO2@QTA was characterized by TEM, IR, and magnetic hysteresis curve. It can interact with perfluorocarboxylic acids through electrostatic interactions, hydrogen bonding, and hydrophobic effect. Stable isotope labeling (SIL)–assisted liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to evaluate the adsorption efficiency. The obtained recoveries for all compounds were in the range of 85.0–98.5%, with relative standard deviations of less than 8.1%. The sorbent amount was 20 mg. Desorption conditions were as follows: sample pH 5–7.0; desorption time, 5 min; and elution volume, 1.0 mL. The limits of detection were in the range of 1.5–20 ng/L, while the limits of quantitation were in the range of 5.0–70 ng/L. The proposed method was successfully applied to the selective adsorption of PFCAs from cod liver oil with no matrix effect observed because of the double assurance of selective adsorption and high accurate SIL strategy. [ABSTRACT FROM AUTHOR]

Using electrocatalytic N2 reduction to make NH3 is considered to be an attractive environmentally-friendly alternative to the Haber–Bosch process, which is rather energy-intensive and has heavy CO2 emissions. However, only limited success has been achieved in identifying metal oxides as effective electrocatalysts for the N2 reduction reaction (NRR) under alkaline conditions. In this communication, we report that a K2Ti4O9 nanobelt is able to effectively electrocatalyze the ambient NRR for N2-to-NH3 fixation at alkaline pH. When tested in 0.1 M KOH, a high NH3 yield of 22.88 μg h−1 mg−1cat. and a faradaic efficiency of 5.87% were attained. Moreover, K2Ti4O9 also demonstrates good selectivity and high electrochemical stability for NH3 formation. [ABSTRACT FROM AUTHOR]

Herein, a universal and multifunctional fluorescence sensor platform is designed by the interaction of aggregation/dispersion gold nanoparticles (AuNPs) with Tb-metal–organic frameworks (Tb-MOFs). It is found that the dispersed AuNPs rather than the aggregated ones can quench effectively the fluorescence of Tb-MOFs, and the quenching process presumably involves the mechanism of inner filter effect (IFE), dynamic quenching effect (DQE), and fluorescence resonance energy transfer (FRET). The different affinities of aptamer and aptamer–target complex toward AuNPs are employed to modulate the fluorescence signal change of Tb-MOFs. As the proof of concept, prostate-specific antigen (PSA), an efficient tumor indicator for prostate cancer, is selected as the target. At first, the PSA aptamer can protect AuNPs against salt-induced aggregation, leading to the fluorescence of Tb-MOFs quenching. Subsequently, upon PSA introduction, the rigid aptamer–PSA complex is formed and cannot stabilize AuNPs in high salt conditions, so the AuNPs aggregate significantly and the fluorescence of Tb-MOFs is restored. The linear range of PSA is achieved from 1 to 100 ng/mL with a detection limit of 0.36 ng/mL. Finally, this method has been validated to be sensitive and specific for PSA in human urine samples. [ABSTRACT FROM AUTHOR]

Currently, industrial-scale NH3 production mainly relies on the energy-intensive and CO2-emitting Haber–Bosch process from atmospheric N2 and fossil fuels. Electrochemical N2 fixation offers an eco-friendly and sustainable alternative to ambient NH3 synthesis with the aid of efficient electrocatalysts for the N2 reduction reaction (NRR). Here, a perylene-3,4,9,10-tetracarboxylic acid nanorod-reduced graphene oxide (PTCA–rGO) nanohybrid is proposed as a metal-free electrocatalyst to synergistically enhance N2 reduction under ambient reaction conditions. In 0.1 M HCl, the PTCA–rGO hybrid provides a large NH3 yield of 24.7 μg h−1 mgcat.−1 and a high faradaic efficiency of 6.9% at −0.50 V vs. the reversible hydrogen electrode, which are much superior to those of PTCA and rGO counterparts. This catalyst also shows a high electrochemical and structural stability. Density functional theory calculations suggest that the NRR over the hybrid catalyst takes place via both distal associative and partially alternative routes. [ABSTRACT FROM AUTHOR]

Abstract Chemical isotope labelling in combination with high-performance liquid chromatography-tandem mass spectrometry (CIL-HPLC-MS/MS) is a powerful method for quantitative profiling of targeted molecules. In the current work, we successfully developed a novel CIL-HPLC-MS/MS method for quantitative profiling of residual organophosphorus thioester pesticides (OPTPs) in agricultural products through the determination of the cleavage products of thiol (CP-thiol) compounds. In this method, we synthesized a novel pair of CIL reagents, i.e., N-(4-(carbazole-9-yl)-phenyl)-N-maleimide (NCPM-d 0) and its deuterated analogue NCPM-d 2 , both of which contain a maleimide moiety as the reactive group and an isotope tag to sensitively label CP-thiol compounds. NCPM-d 0 was used to label CP-thiol compounds cleaved from OPTPs in the investigated agricultural product samples, and NCPM-d 2 was used to label CP-thiol compounds cleaved from OPTPs in the standard substance-spiked organic agricultural product samples. The heavily labelled derivatives were used as the internal standards (ISs) to compensate for the matrix effects during MS analysis. The NCPM-d 0 - and NCPM-d 2 -labelled derivatives generated two characteristic product ions (PIs) at m / z 372.5 and 374.5 under collision induced dissociation, respectively, which are used to establish the multiple reaction monitoring (MRM) mode-based detection. The precursor ions of NCPM-d 0 and NCPM-d 2 labelled derivatives of CP-thiol compounds were deduced according to the structures of the OPTPs. The peak pairs with a fixed mass difference and similar retention times were assigned as potential CP-thiol candidates for the identification of the corresponding OPTPs. Using the proposed method, we successfully determined seven residual OPTPs in agricultural product samples. Taken together, the presented method was demonstrated to be a promising new technique in the quantitation of OPTPs in agricultural product samples with high reliability. Graphical abstract Image 1 Highlights • A CIL-HPLC-MS/MS method was developed for determination of organophosphorus thioester pesticides (OPTPs). • A novel methodology based on in-syringe dispersive solid phase cleanup and in situ cleavage was used for sample preparation. • LODs for OPTPs were in the micrograms per kilogram level. • The proposed method was successfully applied to the determination of OPTPs. [ABSTRACT FROM AUTHOR]

It is of great importance to search for efficient and stable metal-free catalysts toward electrochemical N2-to-NH3 conversion. In this communication, a chemically oxidized carbon nanotube material (O-CNT) is verified as an active electrocatalyst for the N2 reduction reaction under ambient conditions. In 0.1 M LiClO4, O-CNT achieves a large NH3 yield of 32.33 μg h−1 mgcat.−1 and a high faradaic efficiency of 12.50% at −0.4 V vs. the reversible hydrogen electrode. It also demonstrates superior stability. Density functional theory calculations suggest that C–O groups play a key role in the electrochemical N2 fixation. [ABSTRACT FROM AUTHOR]

To achieve superior performance of electrode materials, the design of rational and advantageous hierarchical structures has been confirmed as an effective and feasible approach. Herein, we report an effective strategy for the synthesis of hierarchical NiSe2 spheres composed of nanoparticles: Ni(OH)2 flowers were firstly prepared as the precursor via a solvothermal method followed by a solvothermal selenylation reaction to prepare hierarchical NiSe2 spheres. Investigated as electrode materials for asymmetric supercapacitors, the NiSe2 spheres//AC device exhibits enhanced electrochemical performance with a high specific capacitance of 99.7 F g−1 at a current density of 2 A g−1. In addition, high energy/power density and long-term cycling stability over 10 000 cycles have been shown, which derive from the nanosized building-blocks and secondary micro-architecture. [ABSTRACT FROM AUTHOR]

Photoinduced electron transfer (PET) has been used as reporter in the field of photoluminescence sensors and switches, and intermolecular PET is believed to be responsible for fluorescence quenching. Herein, the emissions of Tb-MOF can be quenched effectively by protamine based on PET. Compared with conventional electrostatic attraction mechanism, this approach suffers less interference from other charged substances and has a broader linear range of protamine from 3 to 5000 ng/mL with limit of detection (LOD) 1.21 ng/mL. Subsequently, the strong binding effect of protamine toward Hep ascribed to electrostatic attraction hinders the interaction between Tb-MOF and protamine, resulting in the high emissions of framework. The detection of Hep also shows a good linear range from 0.5 to 5 μM with LOD 0.27 μM. Finally, this novel probe is also successfully applied to the determination of protamine and Hep in human serum with satisfactory results. [ABSTRACT FROM AUTHOR]