In this study, CsPbBr₃@SiO₂ perovskite nanocrystal composites (CsPbBr₃@SiO₂ PNCCs) were synthesized by a benzyl bromide nucleophilic substitution strategy. Homogeneous halide exchange between CsPbBr₃@SiO₂ PNCCs and Cl⁻ solution (aqueous phase) was applied to the determination of Cl⁻ in sea sand samples. Fast halide exchange with Cl⁻ in the aqueous phase without any magnetic stirring or pH regulation resulted in the blue shift of the photoluminescence (PL) wavelength and vivid PL color changes from green to blue. The results show that the PL sensing of Cl⁻ in aqueous samples could be implemented by using the halide exchange of CsPbBr₃@SiO₂ PNCCs. A linear relationship between the PL wavelength shift and the Cl⁻ concentration in the range of 0 to 3.0% was found, which was applied to the determination of Cl⁻ concentration in sea sand samples. This method greatly simplifies the detection process and provides a new idea for further broadening PL sensing using the CsPbBr₃ PNC halide.

To investigate the mechanical properties of graphene (G) and calcium silicate hydrate (C-S-H) composites in different directions, molecular dynamics (MD) simulations and experiments were used, and the effects of temperature, loading rate, and graphene defects were also investigated. The experimental results show that the addition of graphene can improve the flexural, compressive, and tensile strength of the composite. The results of molecular dynamics simulation show that the addition of graphene in x and z directions can enhance the tensile strength of G/C-S-H in three directions, while the addition of graphene in y direction can reduce the tensile strength of G/C-S-H. At the same time, the tensile strength of G/C-S-H decreases with the increase in temperature and increases with the increase in loading rate. Meanwhile, the mechanical properties of G/C-S-H can be improved using a certain concentration of monatomic vacancy defects, diatomic vacancy defects, and S-W defects.

Iron tailings-based ultra-high-performance concrete (UHPC) was developed using iron tailings as aggregates, with steel fiber incorporation ranging from 0% to 2.5%. This study investigates the effects of steel fiber dosage and curing age on the electrical, electrothermal, and thermal conductivity properties of iron tailings-based UHPC. A comprehensive evaluation protocol was implemented to quantify resistivity, electrothermal conversion efficiency, and heat transfer characteristics, providing a systematic understanding of the material’s multifunctional properties. Results demonstrate that steel fiber incorporation significantly reduces electrical resistivity, achieving optimal conductivity at 1.5% fiber content. Electrothermal analysis under a 60 V applied voltage revealed maximum heating efficiency (ΔT = 32.5 °C/30 min for UHPC cured for 7 days and ΔT = 8.0 °C/30 min for UHPC cured for 28 days) at 1.5% fiber content. Thermal conductivity measurements identified a non-monotonic relationship with steel fiber content, initially increasing and then decreasing, with maximum thermal conductivity observed at 1.5% fiber content. This trend aligns with the observed resistivity behavior, suggesting a strong correlation between electrical and thermal properties. Fiber distribution within the iron tailings-based UHPC matrix revealed that steel fiber dispersion significantly affects material properties, with 1.5% fiber content achieving optimal percolation network formation for electrical current flow and heat transfer.

In order to study the microstructure changes of C-S-H under the freeze-thaw cycling, the freeze-thaw cycle simulation of C-S-H is carried out based on molecular dynamics in this paper. It was found that the density of C-S-H gradually increased with time during the freezing process and gradually decreased with time during the thawing process. The larger the temperature difference, the greater the change of the density of C-S-H, and the more obvious the movement of molecules during the freeze-thaw cycle. The increase of temperature rise and fall rate will increase the density change rate and the stress of the system. As the number of freeze-thaw cycle increases, the atomic motion in C-S-H becomes more intense, and the degree of atomic motion during freeze-thaw cycle also increases with the increase of the ratio of calcium and silicon atoms (C/S) and the ratio of water molecule and silicon atoms (W/S) in C-S-H. These research results provide theoretical guidance for further exploring the freeze-thaw failure mechanism of cement-based materials.