Calcium phosphates are the main minerals in human bone, enamel, atherosclerosis, and dental calculus. Amorphous precursors may play a key role in biomineralization. We studied the formation and transformation of calcium phosphate particles of amorphous phase by stopped-flow spectrophotometry, simultaneous measurements of particle size and solution pH, and high-resolution transmission electron microscopy. Ion pairs and clusters formed in the first few seconds. They then constituted initial amorphous phase containing protonated phosphates and hydrated calcium ions, which was different from that containing Ca 9 (PO 4 ) 6 . Crystalline domains developed at multiple sites inside the primary particles of the amorphous phase. With the consuming of interdomain constituents, these particles partially collapsed, liberating crystallites and inducing rapid precipitation. This study sheds new light on the understanding of crystallization in amorphous phase, as well as the induction period in precipitation kinetics.
Highlights d Crystal structure of glucose-bound PfHT1 was determined at 2.6-A ˚resolution d Crystal structure of PfHT1 bound to a selective inhibitor, C3361, was elucidated d C3361 binding induces a pocket that can be employed for inhibitor optimization d Rational design yielded more potent selective inhibitors with low cytotoxicity
A facile electrospinning method with subsequent heat treatments is employed to prepare carbon nanofibers (CNFs) containing uniformly dispersed Co3O4 nanoparticles as electrodes for supercapacitors. The Co3O4/CNF electrodes with ∼68 wt % active particles deliver a remarkable capacitance of 586 F g(-1) at a current density of 1 A g(-1). When the current density is increased to 50 A g(-1), ∼66% of the original capacitance is retained. The electrodes also present excellent cyclic stability of 74% capacity retention after 2000 cycles at 2 A g(-1). These superior electrochemical properties are attributed to the uniform dispersion of active particles in the CNF matrix, which functions as a conductive support. The onionlike graphitic layers formed around the Co3O4 nanoparticles not only improve the electrical conductivity of the electrode but also prevent the separation of the nanoparticles from the carbon matrix.
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