Scalable bacterial production of moldable and recyclable biomineralized cellulose with tunable mechanical properties

Sustainable structural materials with excellent impact-resistance properties are urgently needed but challenging to produce, especially in a scalable fashion and with control over 3D shape. Here, we show that bacterial cellulose (BC) and bacterially precipitated calcium carbonate self-assemble into a layered structure reminiscent of tough biomineralized materials in nature (nacre, bone, dentin). The fabrication method consists of biomineralizing BC to form an organic/inorganic mixed slurry, in which calcium carbonate crystal size is controlled with bacterial poly(γ-glutamic acid) and magnesium ions. This slurry self-assembles into a layered material that combines high toughness and high impact and fire resistance. The rapid fabrication is readily scalable, without involving toxic chemicals. Notably, the biomineralized BC can be repeatedly recycled and molded into any desired 3D shape and size using a simple kitchen blender and sieve. This fully biodegradable composite is well suited for use as a component in daily life, including furniture, helmets, and protective garments.The authors thank Ward Groutars and Elvin Karana for useful discussions. K.Y. is supported financially by the China Scholarship Council (CSC no.201706630001). S.B. is funded by the Air Force Office of Scientific Research, Asian Office of Aerospace Research and Development (grant no. FA2386-18-1-4059)

Study of Structures and Crystallization Behavior of Amorphous Calcium Carbonate (ACC) and its Application in Bio-inspired Materials

Amorphous mineral phases, e.g. amorphous calcium carbonate (ACC) that occurs ubiquitously in nature, play a pivotal role in biomineralization processes and as such, are a focal point of vast interdisciplinary research. Studies into biogenic ACCs indicate the existence of different short-range orders, which can be understood within the notion of amorphous polymorphism (polyamorphism). It is speculated that distinct short-range orders in biogenic ACCs are triggered by various ions and biomolecules. However, it was shown that additive-free ACCs obtained from metastable solutions with equilibrated pre-nucleation clusters (PNCs) can also exhibit different proto-crystalline structures. The first part of this thesis concern with the importance of the existence of equilibrated PNCs for the development of proto-structures in ACCs. This was accomplished by directprecipitation of ACC in alcoholic media. Second, the role of pH and temperature in the development of short-range orders of ACCs is further explored. The aim is to complete and thereby corroborate the notion of ACC polyamorphism with the proto-aragonite (pa)-ACC form, which has not been reported for ambient pressures until now. Last, polymer-stabilized liquid precursors of CaCO3 were employed to selectively mineralize nanocellulose films via controlling the mineralization sites on nanocellulose fibres. The controlled mineralization enabled formation of mineralized and unmineralized layers of nanocellulose. This, in turn, yielded a bio-inspired, layered, nacre-like material outperforming the biological example in terms of plasticity.publishe

Synthesis and Characterization of ZnO Nanostructures by Polymeric Precursor Route

Zinc oxide nano- and submicrostructures have been synthesized controllably by polymeric precursor method (Pechini). In this approach, zinc acetate $Zn(CH_3COO^{-})_2 \cdot 2H_2O$, citric acid and ethylene glycol were used as the source of $Zn^{2+}$, the chelating agent and the connecting agent, respectively. The microstructure of the ZnO nano- and submicrostructures was characterized by X-ray diffractometry and scanning electron microscopy and the optical property was investigated by the room temperature photoluminescence spectra. The effect of ethylene glycol to citric acid mole ratio on the morphology and structure of the products was discussed

Disordered amorphous calcium carbonate from direct precipitation

© The Royal Society of Chemistry.Amorphous calcium carbonate (ACC) is known to play a prominent role in biomineralization. Different studies on the structure of biogenic ACCs have illustrated that they can have distinct short-range orders. However, the origin of so-called proto-structures in synthetic and additive-free ACCs is not well understood. In the current work, ACC has been synthesised in iso-propanolic media by direct precipitation from ionic precursors, and analysed utilising a range of different techniques. The data suggest that this additive-free type of ACC does not resemble clear proto-structural motifs relating to any crystalline polymorph. This can be explained by the undefined pH value in iso-propanolic media, and the virtually instantaneous precipitation. Altogether, this work suggests that aqueous systems and pathways involving pre-nucleation clusters are required for the generation of clear proto-structural features in ACC. Experiments on the ACC-to-crystalline transformation in solution with and without ethanol highlight that polymorph selection is under kinetic control, while the presence of ethanol can control dissolution re-crystallisation pathways

Distinct Short-Range Order Is Inherent to Small Amorphous Calcium Carbonate Clusters (<2 nm)

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimAmorphous intermediate phases are vital precursors in the crystallization of many biogenic minerals. While inherent short-range orders have been found in amorphous calcium carbonates (ACCs) relating to different crystalline forms, it has never been clarified experimentally whether such orders already exist in very small clusters less than 2 nm in size. Here, we studied the stability and structure of 10,12-pentacosadiynoic acid (PCDA) protected ACC clusters with a core size of ca. 1.4 nm consisting of only seven CaCO3 units. Ligand concentration and structure are shown to be key factors in stabilizing the ACC clusters. More importantly, even in such small CaCO3 entities, a proto-calcite short-range order can be identified but with a relatively high degree of disorder that arises from the very small size of the CaCO3 core. Our findings support the notion of a structural link between prenucleation clusters, amorphous intermediates, and final crystalline polymorphs, which appears central to the understanding of polymorph selection

Role of intercalated water in calcium hydroxide interlayers for carbonation reaction

Carbonation of calcium hydroxide (Ca(OH)2) is an indispensable process with applications in the stable storage of CO2, geological disposal of radioactive waste, and cement manufacture for the construction industry. In the carbonation reaction of Ca(OH)2, water plays an important role in the conversion of CO2 and increases the thermodynamic stability of calcium carbonate. Therefore, understanding the interaction between water and Ca (OH)2 is essential for controlling the kinetics and thermodynamics of the carbonation reaction of Ca(OH)2. In this study, changes in the physical and chemical properties of Ca(OH)2 that appear before the carbonation of hydrated Ca(OH)2 were observed through XRD and NMR analyses. Through XRD analysis, the interplanar distance of hydrated Ca(OH)2 increased by approximately 0.39% compared to that of the pristine Ca(OH)2. Furthermore, we quantified the intercalated water through NMR analysis based on water signal appearing around 0.9 ppm, which was approximately 3.0-7.0 wt% of Ca(OH)2. Through theoretical calculations, the hydrated Ca(OH)2 formed a stable structure with intercalated water molecules, resulting in lower reaction barrier and heat of reaction of the Ca(OH)2 carbonation. For the first time, the intercalation of water between the Ca(OH)2 interlayers is observed, and its importance in the carbonation reaction is established

Alignment of Amorphous Iron Oxide Clusters: A Non-Classical Mechanism for Magnetite Formation

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimDespite numerous studies on the nucleation and crystallization of iron (oxyhydr)oxides, the roles of species developing during the early stages, especially primary clusters and intermediate amorphous particles, are still poorly understood. Herein, both ligand-free and ligand-protected amorphous iron oxide (AIO) clusters (&lt;2 nm) were synthesized as precursors for magnetite formation. Thermal annealing can crystallize the clusters into magnetite particles, and AIO bulk phases with domains of pre-aligned clusters are found to be direct precursors to crystals, suggesting a non-classical aggregation-based pathway that differs from the reported oriented attachment or particle accretion mechanisms