Ag Aerogel-Supported Single-Atom Hg Nanozyme Enables Efficient SERS Monitoring of Enhanced Oxidase-Like Catalysis.

In this work, three-dimensional (3D) Ag aerogel-supported Hg single-atom catalysts (SACs) were explored as an efficient surface-enhanced Raman scattering (SERS) substrate to monitor the enhanced oxidase-like reaction. The influence of the concentrations of Hg2+ to prepare 3D Hg/Ag aerogel networks on their SERS properties to monitor the oxidase-like reaction has been investigated, and a specific enhancement with an optimized addition of Hg2+ has been achieved. The formation of Ag-supported Hg SACs with the optimized Hg2+ addition was identified from a high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image and X-ray photoelectron spectroscopy (XPS) measurement at an atomic level. This is the first discovery of Hg SACs for enzyme-like reaction applications inferred by SERS techniques. And density functional theory (DFT) was used to further reveal the oxidase-like catalytic mechanism of Hg/Ag SACs. This study provides a mild synthetic strategy to fabricate Ag aerogel-supported Hg single atoms to display promising prospects in various catalytic fields.

SERS Resolving of the Significance of Acetate on the Enhanced Catalytic Activity of Nanozymes.

Understanding the structure-activity correlation and reaction mechanism of the catalytic process in an acetic acid-sodium acetate (HAc-NaAc) buffer environment is crucial for the design of efficient nanozymes. Here, we first reported a lattice restructuration of Au-LaNiO3-δ nanofibers (NFs) after acidification with the HAc-NaAc buffer to show a significantly enhanced oxidase-like property. Surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculation confirm the direct evidence for the formation of specific enhanced intermediate O-O species after acidification, indicating that the insertion of the carboxyl group in the A-Au/LaNiO3-δ NFs plays crucial roles in both producing vacancies in HAc-NaAc solution from its dissociation during the catalytic process and the protection of the vacancies, which can be directly interacted with oxygen in the environment to produce O-O species, realizing the enhanced oxidation of substrate molecules. The insertion of the carboxyl group increased the oxidase-like catalytic activity by 2.38 times and the SERS activity by 5.27 times. This strategy offers a way to construct an efficient nanozyme-linked immunosorbent assay system for the diagnosis of cancer through the highly sensitive SERS identification of exosomes.

Pore Structure Characteristics and Adsorption and Desorption Capacity of Coal Rock after Exposure to Clean Fracturing Fluid.

In the hydraulic fracturing process, fracturing fluid contacts coal rock and physical and chemical reactions occur, which inevitably damage the pore structure of the coal rock and affect the adsorption and desorption capacity of the coal rock. In this paper, a low-temperature N2 adsorption method and scanning electron microscopy (SEM) were used to characterize coal samples. Using gas adsorption/desorption tests, high-, medium-, and low-rank coal samples before and after the clean fracturing fluid treatment were systematically studied. According to the relationship between coal pore structure parameters and gas adsorption/desorption characteristics, a correlation between the microscopic pore structure and the macroscopic gas adsorption/desorption characteristics of coal was obtained. The results show that the number of closed pores in high-, medium-, and low-rank coal samples increased after the clean fracturing fluid treatment. The micropore volume increased by 0.0009, 0.00143, and 0.0035 mL/g, respectively, and the specific surface area increased by 4.87, 9.06, and 57.60%. The fractal dimension also increased compared with that of raw coal. SEM analysis indicated that the influence degree of clean fracturing fluid treatment on the pore structure of different-rank coal samples was Gengcun low-rank coal > Pingba middle-rank coal > Jiulishan high-rank coal. The experimental results of methane adsorption and desorption showed that the adsorption capacity of the coal samples after clean fracturing fluid treatment was enhanced, which is related to increases in the micropore proportion, micropore volume, and specific surface area of the coal. The desorption capacity of the coal samples was also enhanced. The desorption rate of medium- and high-rank coal samples increased after the clean fracturing fluid treatment but that of low-rank coal samples decreased. The main reason is the increase in the number of micropores in low-rank coal, which enhances the gas adsorption ability and makes gas desorption difficult. Therefore, clean fracturing fluid is suitable for medium- and high-grade metamorphic coalbed methane mines. These research results provide a theoretical basis for the application of clean fracturing fluid in different coalbed methane wells.