Phase transformation of amorphous silica to cristobalite at a relatively low temperature of 800 °C has been achieved on bacterial surfaces.

As environmental and energy problems have worsened worldwide, research for developing renewable energy has become urgent. Presently, the primary focus of such research is directed towards the photocatalytic decomposition of water to produce hydrogen as an energy source. Herein, ZnO nanosheet/CdS nanoparticle heterostructures were synthesized by a mild wet chemical reaction and displayed a high photocatalytic efficiency (1040 μmol g⁻¹ h⁻¹) without Pt loading under visible light radiation. The structure was prepared by first constructing two-dimensional nanocrystalline ZnO flowers and then loading CdS nanoparticles onto the nanocrystals. Results show that this structure can facilitate the separation of photogenerated electrons and holes and improve the photocatalytic efficiency and stability of the materials in the photocatalytic decomposition of water. By changing different experimental conditions to prepare a variety of samples and test their properties, we can analyze the optimal parameters for the preparation of this material.

Confinement is common in biological systems and plays a critical role in the structure-forming process of biominerals. However, the knowledge of confinement effects on biomineralization is limited due to the lack of specific chemical structures and elaborate spatial distribution. In this article, we explore the confined mineralization of amorphous calcium carbonate (ACC) within collagen fibrils. Three issues of the confined mineralization of ACC within collagen fibrils were investigated, including the morphology and characteristics of the confined mineralization of ACC within collagen fibrils; the initiation and development of the confined mineralization of ACC within collagen fibrils; and the driving mechanism of ACC infiltration into collagen fibrils. Results show that the negatively charged ACC droplets were attracted to positively charged gap regions of collagen fibrils through electrostatic interactions, infiltrated into collagen fibrils, and then transformed into the crystalline phase. The observation of juxtaposed crystalline and amorphous phases on the surface of fibrils indicates that a secondary nucleation mechanism may be responsible for the co-orientation of calcite nanocrystals. Through modifying the wettability of amorphous calcium carbonate with magnesium ions, it is verified that the infiltration of ACC into collagen fibrils was driven by capillary forces. The present study not only provides evidence of the confinement effects in biomineralization but also facilitates the understanding of the in vivo bone formation process. It may also open up a new avenue in the bioprocess-inspired synthesis of advanced materials.

Taking lessons from the structure-forming process of biominerals in animals and plants, one can find tremendous inspirations and ideas for developing advanced synthesis techniques, which is called bio-process inspired synthesis. Bone, as a typical representative of biominerals, is constituted of mineralized collagen fibrils, which are formed under the functions of non-collagenous proteins (NCPs). Intrafibrillar mineralization is the consequence of a synergy among several NCPs. In the present study, we have designed a multi-functional protein, named (MBP)–BSP–HAP, based on bone sialoprotein (BSP) and hydroxyapatite binding protein (HAP), to mimic the intrafibrillar mineralization process in vitro. The three functional domains of (MBP)–BSP–HAP provide the artificial protein with multiple designated functions for intrafibrillar mineralization including binding calcium ions, binding collagen, and binding hydroxyapatite. Platelet-like hydroxyapatite crystals periodically arranged inside the collagen fibrils have been achieved under the function of (MBP)–BSP–HAP. The mechanism of intrafibrillar mineralization directed by the multi-functional protein was proposed. This work may not only shed light on bio-process inspired approaches for more economic and efficient biomimetic synthesis, but also be helpful in understanding the natural process of bone formation for bone regeneration and tissue repair.

Biomineral formation processes in nature are temporally and spatially regulated under the functions of biomolecules in a confined space. It is potentially very productive to rationally design a mineralized system by taking into account confined space as well as biomolecules. The laboratory technique of “bacterial cell surface display” is an ideal platform to host catalytically active proteins in a three-dimensionally confined space. In the present study, aiming to regulate the synthesis of nanostructured TiO₂ anatase, repeating segments of silaffin were displayed on Escherichia coli surfaces through genetic manipulation. The displayed protein electrostatically interacted with a titanium source and catalyzed the hydrolysis of titanium dioxide precursors through hydrogen bonding interactions on the cell surface. In the subsequent calcination process, the genetically modified cells not only served as a framework for producing rod-shaped TiO₂ assembled by nanoparticles, but also provided a carbon source in situ. The size of nanoparticles was controlled by changing the number of tandem repeats of the protein segment. The as prepared TiO₂ anatase exhibited unique characteristics including nanosized anatase crystals, mesoporous structure and carbon coating. When tested as the anode electrode of a lithium-ion battery, it showed excellent lithium storage performance. The carbon coated anatase anode shows a higher specific capacity of 207 mA h g⁻¹ after 200 cycles at a current rate of 1C and an ultra-long cycling lifetime of 5000 cycles with an outstanding retention capacity of 149 mA h g⁻¹ at a higher rate of 10C. This bioprocess-inspired approach may help broaden the scope and impact of nanosized biominerals.