Sandwich-type electrochemical immunosensor based on Au NPs/3D hierarchical porous carbon network and Au NPs/Cu9S8 nanocages for the detection of alpha-fetoprotein

Alpha-fetoprotein (AFP), serves as a reliable and vital biomarker for precise diagnosis and effective monitoring of hepatocellular carcinoma, requires precise detection. Herein, a sandwich-structured electrochemical immunosensor was crafted, employing three-dimensional layered porous carbon modified with gold nanoparticles (Au NPs) as the substrate and Au NPs/Cu9S8 as the labeling compound for accurate and sensitive detection of AFP. Due to the effective coordination between the 3D carbon network, Au NPs, and hollow Cu9S8 nanocubes, the sandwich-structured electrochemical immunosensor was able to produce three distinct response signals via various detection techniques, demonstrating a broad linear range (0.0001-400 ng/mL), exceptional sensitivity, and a remarkably low detection limit of 2.63 fg/mL. Moreover, the constructed immunosensor could be used to detect AFP in human serum. This research may offer a novel material framework for developing highly sensitive immunosensors.

Photoreduction of CO2 to CH4 over Efficient Z-Scheme γ-Fe2O3/g-C3N4 Composites

A series of composite γ-Fe₂O₃/g-C₃N₄ (denoted as xFeCN with x equal 5, 10, 15, and 20 of γ-Fe₂O₃ percentage in weight) was prepared by calcination and precipitation-impregnation methods. X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectrometry (XPS) characterizations indicated the successful synthesis of Z-scheme FeCN composites. A red shift of the light absorption region was revealed by UV-vis diffuse reflectance spectroscopy (UV-DRS). In addition, photoluminescence spectroscopy (PL) spectra showed an interface interaction of two phases Fe₂O₃ and g-C₃N₄ in the synthesized composites that improved the charge transfer capacity. The photocatalytic activity of these materials was studied in the photoreduction of CO₂ with H₂O as the reductant in the gaseous phase. The composites exhibited excellent photoactivity compared to undoped g-C₃N₄. The CH₄ production rate over 10FeCN and 15FeCN composites (2.8 × 10^-2 and 2.9 × 10^-2 μmol h^-1 g^-1, respectively) was ca. 7 times higher than that over pristine g-C₃N₄ (0.4 × 10^-2 μmol h^-1 g^-1). This outstanding photocatalytic property of these composites was explained by the light absorption expansion and the prevention of photogenerated electron-hole pairs recombination due to its Z-scheme structure.

ZnIn2S4 nanosheet growth on amine-functionalized SiO2 for the photocatalytic reduction of CO2

The growth of ZnIn2S4 nanosheets on NH–SiO2 promotes charge carrier separation and provides active sites for CO2 activation, therefore significantly boosting CO2 photoreduction efficiency.

Fabrication of size-controlled hierarchical ZnS@ZnIn2S4 heterostructured cages for enhanced gas-phase CO2 photoreduction

Designing and constructing advanced heterojunction architectures are desirable for boosting CO₂ photoreduction performance of semiconductor photocatalysts. Herein, we have prepared hierarchical ZnS@ZnIn₂S₄ core-shell cages with controlled particle sizes using sequential synthesis of Zeolitic imidazolate (ZIF-8) polyhedrons, ZnS cages, and ZnIn₂S₄ nanosheets on the ZnS polyhedron cages. ZIF-8 polyhedrons are firstly synthesized by a liquid-phase approach. The subsequent sulfidation of the ZIF-8 polyhedrons results in the formation of ZnS polyhedron cages, which act as substrates for fabricating ZnS@ZnIn₂S₄ core-shell cages by growing ZnIn₂S₄ nanosheets. The size of ZnS cages can be tuned to optimize CO₂ photoreduction performance of hierarchical ZnS@ZnIn₂S₄ core-shell cages. The synergy of the unique hierarchical core-shell cage-like structure and heterojunction composition endows the hybrid catalyst high incident light utilization, abundant active sites, and effective separation of photoexcited charge carriers. Benefiting from these advantages, the optimized hierarchical ZnS@ZnIn₂S₄ core-shell cages exhibit enhanced performance for CO₂ photoreduction with the CO yield of 87.43 μmol h^-1g^-1 and 84.3% selectivity, which are much superior to those of single ZnIn₂S₄ or ZnS. Upon Au decoration, the CO₂ photoreduction performance of ZnS@ZnIn₂S₄ core-shell cages is further enhanced because of the Schottky junctions and surface plasmon resonance effect.

Particulate photocatalytic reactors with spectrum-splitting function for artificial photosynthesis

We have applied spectrum splitting, which is the most reliable way for highly efficient solar energy utilization, to particulate photocatalytic reactors. We have elucidated that the spectrum splitting is feasible using plural cells/compartments, in which photocatalyst particles of different bandgaps are suspended respectively, arranged optically in series. When the particles are sufficiently small (≤20 nm in diameter), high-energy photons are absorbed in the wide-gap cell/compartment on the solar illumination side while low-energy photons reach the backside narrow-gap cell/compartment with being scarcely diffuse-reflected. We have proposed two concrete configurations of the reactors: wide-gap cell/narrow-gap Z-scheme cell (WG/Z), and wide-gap cell/two-compartment cell of middle-gap and narrow-gap (WG/MG-NG), based on the previous configuration of a two-compartment cell of wide-gap and narrow-gap (WG-NG). We have constructed a new model of the carrier supply process from the semiconductor photocatalysts to the active sites, and calculated the practical upper limits of the carrier supply rates and solar-to-chemical conversion efficiencies. The spectrum-splitting reactors can yield higher efficiencies of artificial photosynthetic H2 and CO production by up to 1.5-1.6 times than the conventional Z-scheme reactors. The newly proposed WG/Z reactor widens the room of the material developments and improves the robustness against solar spectrum variation, and hence would be a promising practical solution, although the efficiency is slightly lower than that for the ideal WG-NG reactor. The WG/MG-NG reactor yields the highest efficiency among the three configurations, with high spectral robustness.

In situ construction of a direct Z-scheme CdIn2S4/TiO2 heterojunction for improving photocatalytic properties

Direct Z-scheme photocatalytic systems driven by visible light to eliminate organic pollutants in wastewater have become important scientific tools in the field of photocatalysis.