Synthesis of Carbonate-Based Micro/Nanoscale Particles With Controlled Morphology and Mineralogy

images[8]Biological structural materials such as bone, nacre and fish scales utilize unique material structures and chemistry, especially nanoscale structures to provide high strength as well as high ductility. To incorporate these design principles into the material design, novel synthesis methods need to be developed to fabricate composites with controlled morphology, orientation, organization and chemistry at nanoscale. In this study, the mineralogy and morphology of carbonate-based micro/nanoscale particles precipitated by reacting (NH4)2CO3 with mixed Ca, Sr, Mg, and Mn-acetates was investigated. As the proportion of the non-Ca component increased, the products shifted toward double carbonates and mixtures of double carbonates with single carbonates. Characterization by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) to determine crystal sizes, morphology, and structure of precipitated phases indicated a potential for re-crystallizing the products to form new composite materials. Ongoing research efforts are focused on using information obtained in the present study to develop composites by hydrothermal recrystallization of metastable phases.
Personal Author J. C. Weiss K. Torres-Cancel M. Q. Chandler P. G. Allison R. D. Moser
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Lipid Bilayer-Integrated Optoelectronic Tweezers for Nanoparticle Manipulations.

images[1]Remotely manipulating a large number of microscopic objects is important to soft-condensed matter physics, biophysics, and nanotechnology. Optical tweezers and optoelectronic tweezers have been widely used for this purpose but face critical challenges when applied to nanoscale objects, including severe photoinduced damages, undesired ionic convections, or irreversible particle immobilization on surfaces. We report here the first demonstration of a lipid bilayer-integrated optoelectronic tweezers system for simultaneous manipulation of hundreds of 60 nm gold nanoparticles in an arbitrary pattern. We use a fluid lipid bilayer membrane with a 5 nm thickness supported by a photoconductive electrode to confine the diffusion of chemically tethered nanoparticles in a two-dimensional space. Application of an external a.c. voltage together with patterned light selectively activates the photoconducting electrode that creates strong electric field localized near the surface. The field strength changes most significantly at the activated electrode surface where the particles tethered to the membrane thus experience the strongest dielectrophoretic forces. This design allows us to efficiently achieve dynamic, reversible, and parallel manipulation of many nanoparticles. Our approach to integrate biomolecular structures with optoelectronic devices offers a new platform enabling the study of thermodynamics in many particle systems and the selective transport of nanoscale objects for broad applications in biosensing and cellular mechanotransductions.

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Personal Author S. Ota S. Wang X. Yin X. Zhang Y. Wang