Double-shell-structured β-NaYF4:Yb(3+),Tm(3+)/Er(3+)@SiO2@TiO2 upconversion photocatalysts have been successfully synthesized by a simple hydrothermal method. It is found that the double-shell-structured photocatalyst consists of uniform β-NaYF4:Yb(3+),Tm(3+)/Er(3+) nanocrystals, SiO2 as the media shell, and anatase TiO2 nanocrystals exposed with the high-reactive {001} facets as the outer shell. The TiO2 shell is modified to absorb both the UV and visible light in order to make sufficient use of the upconverted light from β-NaYF4:Yb(3+),Tm(3+)/Er(3+) for photocatalysis. Effective energy transfer from β-NaYF4:Yb(3+),Tm(3+)/Er(3+) to TiO2 and its importance are confirmed. The photocatalytic activity in the degradation of Rhodamine B (RhB) under the near-infrared (NIR) (980 nm laser) irradiation suggests that the NIR-driven photocatalytic activity of the double-shell-structured photocatalyst is significantly dependent on the properties of the upconversion materials and the irradiated NIR power density. Moreover, the NIR-driven photocatalyst shows stable photocatalytic degradation of RhB in the recycled tests. This study suggests a promising system and a new insight to understand the application of appropriate upconversion materials to effectively utilize the NIR for photocatalytic applications of TiO2-based photocatalysts, which may advance the application of solar energy in the future.

The aim of this study was to investigate the effects of PLLA nanofibrous microspheres (NF-MS) as a cell delivery carrier in combination with controlled release of BMP-2 from PLGA microspheres on the induction of odontogenic differentiation of human stem cells of apical papilla (SCAP). Injectable NF-MS, which mimic the physical architecture of collagen fibers on the nano scale, were fabricated by combining thermally-induced phase separation techniques with an emulsification process. SCAP cultured in a monolayer or cultured on NF-MS in spinner flasks were treated with 100 ng/ml BMP-2 in vitro. Odontogenic differentiation was characterized by measuring alkaline phosphatase activity, odontogenic gene expression levels, calcium content, and dentin sialophosphoprotein accumulation. The results demonstrated that BMP-2 enhanced human SCAP odontogenic differentiation both in monolayer culture and on 3D NF-MS in spinner flask culture in vitro. We also developed and tested a system combining NF-MS with controlled BMP-2 release for dentin regeneration in vivo. The results indicate that controlled release of BMP-2 promoted more mineralization and osteodentin formation compared to a BSA-releasing control in a dose-dependent and time-dependent manner. In summary, the NF-MS combined with controlled release of BMP-2 provides an excellent microenvironment for SCAP to regenerate dentin tissue.

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Boron (B) doped bismuth oxybromide (B-BiOBr) nanosheets were synthesized using a hydrothermal method and their photocatalytic activities were investigated through inactivating a typical bacterium, Escherichia coli K-12 using fluorescence tubes as visible light (VL) sources. B atoms are successfully doped into the crystal lattice of BiOBr. However, the morphology, crystal structure, and {001}-facet exposed feature of B-BiOBr nanosheets remain unchanged compared with pure BiOBr nanosheets. Significantly, the as-prepared B-BiOBr nanosheets show superior activity in the photocatalytic inactivation of E. coli K-12 over pure BiOBr nanosheets under VL irradiation. Photogenerated h + is evidenced to be the major reactive species accounting for the inactivation process of B-BiOBr. With its electron-deficient characteristics, the B dopant is favorable to accept extra e − from VB of BiOBr, leading to improved charge carrier separation efficiency. The greatly enhanced bacterial inactivation efficiency was attributed to the synergic advantages of enhanced VL adsorption capability and more amount of photogenerated h + with higher oxidative ability. In addition, the destruction process of bacterial cell was also observed from the destruction of cell membrane to the intracellular components.

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