Constrained by the strong Coulombic interaction of electron–hole pairs in semiconductor photocatalysts, the charge carrier separation and the resultant photocatalytic capability are greatly compromised. In this work, we rationally construct a built-in electric field (BEF) from the (111) facet of CdTe quantum dots (CdTeQDs) to the (200) facet of two-dimensional Bi2WO6 (2DBWO) nanosheets by the formation of a Te–O x bond. We validate experimentally and theoretically that the BEF can profoundly promote the dissociation of a photoexcited exciton and separation of a charge carrier, resulting in the formation of a Z-scheme electronic structure of the CdTeQDs/2DBWO photocatalyst. Benefiting from the role of the BEF, the photoinduced generation of the superoxide anion radical and hydroxyl radical is significantly promoted, based on which photodegradation performances of the CdTeQDs/2DBWO photocatalyst are 6.64, 1.95, and 5.4 times those of pure 2DBWO for tetracycline, phenol, and rhodamine B, respectively. This work provides a mechanistic insight into the design and optimization of semiconductor heterojunction photocatalysts for efficient charge carrier separation and environmental remediation.

Nanoparticles of Prussian blue (PB) and its cyanometallate structural analogues are validated as multienzyme mimetics, while there remains a need for improved activities of PB-based nanozymes through rational atomic engineering on the species and amount of doping metal. Herein, we find that the doping of a second divalent 3d metal ion (Co 2+ , Ni 2+ , and Cu 2+ ) into the PB framework results in discriminated peroxidase-like activity, by catalyzing the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) with H 2 O 2 . The order of the catalyzed reaction generally follows Cu 2+ -doped PB (CuPB) > PB > Co 2+ -doped PB (CoPB) > Ni 2+ -doped PB (NiPB). Besides the atomic preference over Cu doping, the amount of doped Cu 2+ is rationally engineered for the optimization of peroxidase-like activity. By coupling the optimized CuPB nanoparticles with natural uricase, we develop a cascade reaction system for measuring the uric acid level in human urine specimens, the results of which are well correlated with the standard values determined on instrumentation (R 2 = 0.975). Due to the simplicity of the platform and capability of preparing CuPB nanozyme in a large scale, we envisage the method to be translated into urinalysis of uric acid, especially packaged as a type of assay kits for point-of-care testing.

Herein, a novel magnetic iron-based carbon microsphere was prepared by cohydrothermal treatment of tobacco waste liquid (TWL) and waste iron residue (WIR) to form WIR@TWL. After that, WIR@TWL was coated with sodium polyacrylate (S.P.) to fabricate WIR@TWL@SP, whose removal efficiency for bivalent cadmium (Cd(II)) was studied in water and soil. As a result, WIR@ TWL@SP possessed a high Cd(II) removal efficiency, which could reach 98.5% within 2 h. The adsorption process was consistent with the pseudo-second-order kinetic model because of the higher value of adjusted R 2 (0.99). The thermodynamic data showed that the adsorption process was spontaneous (ΔG°< 0) and exothermic (ΔH°= 32.42 KJ•mol −1 > 0). Cd(II) removal mechanisms also include cation exchange, electrostatic attraction, hydrogen-bond interaction, and cation−π interaction. Notably, pot experiments demonstrated that WIR@TWL@SP could effectively reduce Cd absorption by plants in water and soil. Thus, this study offers an effective method for remediating Cd(II)-contaminated water and soil and may have a practical application value.