Self-Assembly of Glass-Ceramic / CdSe / Protein Aggregations in the Optical Trap
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Self-Assembly of Glass-Ceramic / CdSe / Protein Aggregations in the Optical Trap Andrey Zavalin, W. Eugene Collins, Steven Morgan Physics Department, Fisk University, Nashville, TN37208, U.S.A. ABSTRACT Aggregations, created in 2-component suspension inside the optical trap zone were studied. Particles of porous glass-ceramic of CaO-TiO2-P2O5 composition and 1-50 um size were mixed with BSA molecules in water or with CdSe-TOPO 20 nm particles in toluene. Dynamic aggregations up to 300 um size were created inside the optical trap. These aggregations in comparison with one-component aggregations have a 30% higher growth rate. This effect could be explained by the stronger bonding of the protein molecules and CdSe-TOPO particles inside the glass-ceramic particle aggregations. Micro-Raman spectra, taken from dynamic and stable permanent aggregations show several new peaks, possibly associated with creation of chemical bonds. INTRODUCTION In experiments we used a prospective diagnostic and material developing technique - an optical trapping in the laser beam, having a special high-gradient intensity profile, first invented by Ashkin [1]. In the major part of research and applications of this method a single object, trapped inside the single optical trap was considered. The technique has been successfully used in micro- and molecular biology, and as an advanced microscopy method. The main advantage of the one-beam optical trap configuration is simplicity and a wide spectrum of applications. Sub-micron size of the optical trap zone and the possibility to control position and motion precisely can satisfy the requirements of assembly in the integrated optics and optical sensors, photonic crystals and bio-chip production. New exciting effects, arise if to place several objects inside the optical trap and to study behavior of system of the objects. First time this method has been applied by researchers from Rowland Institute at Harvard [2]. We propose a similar method, utilizing the one-beam optical trap, integrated with micro-Raman spectrometer for trapping the nano- and micro- scale objects and spectroscopic studies of the created aggregations. This method has many promising features for the applications in material science, such as on-chip assembling tool, photon crystal growing environment and a wide spectrum of others. In the previous experiments [3] for behavior of many particles, trapped in the gradient onebeam optical trap it has been shown that trapped particles create quasi-molecular dynamic structures, assembled together by evanescent fields. These structures exist only in the presence of a trapping laser radiation. Under the certain conditions photon bonding is converted to the chemical bonding and the aggregation, formed in the trap, is stable without optical field. By slow translation the optical trap zone along the surface of substrate it is possible to create on-chip structures. In other words, in the optical trapping a synthesis of material and deposition on the surface are available at the same time
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