Highly exposed facets TiO2 attracts enormous attention due to its excellent separation effect of photogenerated electron-hole pairs and induced high performance of photocatalytic activity. Herein, a novel hydrothermal etching reaction was used to synthesize graphene-wrapped TiO2 hollow core-shell structures. Different with the reported co-exposed facets TiO2 single crystal nanoparticles, the present TiO2 core layer is composed by the mutually independent exposed {001} and {101} facets nanocrystals. Combined with the reduced graphene oxide shell layer, this graphene-wrapped TiO2 hollow core-shell structures formed a Z-scheme photocatalytic system, which possess simultaneously the high charge-separation efficiency and strong redox ability. Additionally, the as-prepared samples show a higher absorption property for organic molecules and visible light due to the presence of graphene. All of these unique properties ensure the excellent photocatalytic activity for the graphene-wrapped TiO2 hollow structures in the synergistic photo-oxidation of organic molecules and photo-reduced of Cr(VI) process. The TiO2 core composed with mutually independent exposed {001} and {101} facets nanocrystals is propose to play an important role in the fabrication of this Z-scheme photocatalytic system. Fabrication of Z-scheme photocatalytic system based on this unique exposed facets TiO2 nanocrystals will provides a new insight into the design and fabrication of advanced photocatalytic materials.
Hollow TiO modified reduced graphene oxide microspheres (hollow TiO-rGO microspheres or H-TiO-rGO MS) have been synthesized and then be used to immobilize hemoglobin (Hb) to fabricate a mediator-free biosensor. The morphology and structure of hollow TiO-rGO microspheres were characterized by scanning electron microscopy, transmission electronic microscopy and X-ray diffraction. Results of spectroscopy and electrochemistry tests revealed that hollow TiO-rGO microsphere is an excellent immobilization matrix with biocompatibility for redox protein, affording good protein bioactivity and stability. The hollow TiO-rGO microspheres with special structure and component enhance the immobilization efficiency of proteins and facilitate the direct electron transfer, which result in the better HO detection performance-the wide linear range of 0.1-360μM for HO (sensitivity of 417.6 μA mM cm) and the extremely low detection limit of 10nM for HO. Moreover, the hollow microsphere can provide a protective microenvironment for Hb to make the as-prepared biosensor improve long-term stability. The as-prepared biosensor retains 95.4% of the initial response to HO after 60-d storage. Hence, this work suggests that if can be fabricated a mediator-free biosensor, hollow TiO-rGO microspheres will find wide potential applications in environmental analysis and biomedical detection.
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