A new, photoelectrochemical immunosensor was proposed on the basis of the La-CdS/3D ZnIn 2 S 4 /Au@ZnO sensitization structure for detection of aminoterminal pro-brain natriuretic peptides (NT-proBNP). The Au@ZnO-modified electrode was first assembled with 3D ZnIn 2 S 4 , and then further deposited with lanthanum doped cadmium sulfide (La-CdS) via successive ionic layer adsorption and reaction strategy. The Au@ZnO has excellent photoelectric activity and electrical conductivity . The ZnIn 2 S 4 with 3D architectures not only exhibit high photocurrent intensity under visible-light irradiation but also have large surface for the La-CdS deposition. Meanwhile, the La-CdS doped structure could depress the charge recombination, which effectively promotes separation of the generated electron-hole (e - /h + ) pairs and consequently enhances the photocurrent conversion efficiency. The polydopamine (PDA) was used not only as a cross-linker reagent for the immobilization of the anti-NT-proBNP but also as an electron donor for promoting the photo-generated e - /h + separation of the semiconductors. Under optimal conditions, the well-designed photoelectrochemical immunoassay exhibited a low detection limit of 0.32 pg mL −1 and a wide linear range from 0.8 pg mL −1 to 45 ng mL −1 for target NT-proBNP detection. Meanwhile, it also presented good reproducibility, specificity, and stability and might open a new promising strategy for the detection of other important tumor markers.
The novel ternary reduced graphene oxide/1D TiO 2 nanotubes/3D ZnIn 2 S 4 microspheres (rGO/TiO 2 /ZIS) heterostructured photocatalyst with high-efficiency H 2 production capacity under visible light illumination is designed and prepared in this work. In rGO/TiO 2 /ZIS system, the 1D TiO 2 nanotubes are tightly inserted in the interspace of flower-like ZnIn 2 S 4 microspheres, which are further covered by rGO, leading to an intimate contact among ZnIn 2 S 4 , TiO 2 and rGO. The exquisite design of rGO/TiO 2 /ZIS makes it possess remarkable superiority in photocatalysis . Firstly, the unique 3D microsphere structure of ZIS increases the surface area and visible light absorption ability caused by their unique hollow structure. More importantly, the matched CB and VB positions between ZIS and TiO 2 contribute to separate photogenerated holes and electrons of ZIS efficiently under visible light; then, the separated electrons on TiO 2 are further transferred to rGO due to the superior-strong electron-attracting ability of rGO. At last, the thoroughly suppressing recombination of photogenerated holes and electrons is achieved by the mutually-reinforcing synergy among ZIS, TiO 2 and rGO, and thus the hydrogen generation capacity of ZIS is significantly enhanced. The H 2 production amount and rate of rGO/TiO 2 /ZIS (2.0 wt% rGO and 50 wt% ZIS) after 10 h are 4623 μmol/g and 462.3 μmol/g/h, respectively, which is 71.1 times of pristine TiO 2 and 1.6 times of ZIS under the same condition. The apparent quantum yield of rGO/TiO 2 /ZIS (2.0 wt% rGO and 50 wt% ZIS) in 10 h is about 0.6888%. This excellent photocatalytic performance is ascribed to the mutually-reinforcing synergy among ZIS, TiO 2 and rGO, which can be confirmed by X-ray photoelectron spectroscopy, photoelectrochemical measurements and photoluminescence spectrum. Based on the photocatalytic and characterization results, the corresponding mechanism is proposed.
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