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Facet-controlled Growth of SrTiO₃Polyhedral Nanocrystals and Their Biological Behaviors

Author: DongLingQing
Tutor: WengWenJian;HanWeiQiang;ChengZuo
School: Zhejiang University
Course: Materials Science
Keywords: SrTiO3polyhedral nanocrystals shape controlled growth alcoholmolecules surfactant facet-selective protein adsorption cell interaction behavior
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Type: PhD thesis
Year: 2014
Downloads: 3
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Abstract

The biological effects of nanomaterials have gradually attracted widespread attention and they are often dependent on protein adsorption behavior. Furthermore, the surface atomic structure of nanomaterial is considered to play a critical role on protein adsorption behavior. Therefore, selecting an ideal model material system and using its special surface atomic structure to control its interaction behaviors with protein and cell have been considered to be important to in-depth understand their mechanisms, evaluate the biological security of nanomaterials and broaden its biological application. We select simple cubic perovskite oxide SrTiO3nanocrystals as model, since its surface atomic structure of low Miller indexes are significantly different. SrTiO3polyhedral nanocrystals with the nonpolar facet{100} and polar facet{110} are controlled by using surfactant under hydrothermal method. Moreover, we study the influence of{110}/{100} ratio on its interaction behavior with proteins and cell subsequently. The main results are:LiOH is used as the mineralization agent instead of KOH. Because Li+ions can adsorb on the surface of the crystal surface and promote the dehydration reaction of OH" on the surface, thereby reducing the resistance of crystal growth and the probability of OH-ions into the lattice, resulting in a perfect cube morphology (100%of{100} facet) of SrTiO3nanocrystals products. And the average particle sizes are from about50nm to250nm with narrow size distribution.We sucessfully synthesize of size and shape controlled SrTiO3nanocrystals by using a series of alcohols with different PKa values as the surfactant molecules. The morphology of obtained nanocrystals are cubic bounded by six{100} facets and truncated rhombic dodecahedra bounded by six{100} facets and12{110} facets, and the ratio of{110}/{100} are varied between0and0.95. And the average particle sizes are from about30nm to250nm with narrow size distribution.The growth mechanism is considered to be a dissolution-recrystallization growth mechanism.In this system, the stability of new-formed SrTiO3nucleus can be enhanced by the TiO2·nH2O gel surrounding them, which will produce smaller particle size, therefore the particle size decreases with the increasing of alcohol concentration. And we here assume that the relative interaction strength (adsorption energy) between {110} facet and alcohol molecules would be enhanced with the reduced pKa value of alcohol molecular added, thus expose more surface area of{110} facets of nanocrystal surface. By using1,2-propanediol as the surfactant, we have also synthesized BaTiO3nanocrystals with systematic morphology evolution from cubic to edge-truncated cubic and rhombic dodecahedral. These results indicate that alcohols could be a general surfactants in the shape-controlled synthesis of pervoskite titanates with systematic morphology evolution.We also study the adsorption behavior of proteins on model truncated rhombic dodecahedra SrTiO3nanocrystals, which are bounded by six{100} facets and12{110} facets, and the average particle sizes are200nm. SEM results show that all the proteins achieve high packing density on the{100} facets of truncated rhombic dodecahedra, while{110} facets adsorb nothing. We further carry out atomistic molecular dynamic (MD) simulations to explore the structures of the interfacial water molecules onto the{100} and{110} facets of SrTiO3, to gain insight into the facet-selective adsorption of proteins onto the facets of SrTiO3nanocrystals. The results indicate that the immobile surface hydration layer might play a role of barrier to effectively prevent protein adsorption on specific{110} facet. Moreover, we compare the results of the protein adsorption behavior on SrTiO3single crystal substrates to show the special effects of nanoscale.The effects of proportion of different facets exposed of SrTiO3nanocrystals on their interaction behavior with cell are also study. We study cell uptake behavior of Hela of SrTiO3nanocrystals after8h incubation. The results indicate that the amount of cell uptake of SrTiO3nanocrystals increase upon on the increasing ratio of{100} facets. And the amount of cell uptake of cubic nanocrystal is almost60s more than that nanocrystal with{110}/{100} of0.9. We further study cell interaction behavior on the same facet exposed substrate. The results suggest that the protein interaction behavior might be the main cause of the differences in cell uptake behavior. In this study, shape controlled SrTiO3polyhedral nanocrystals with different ratio of {110}/{100} are achieved by using alcohol molecules as surfactant under hydrothermal method. And we found that the differences in surface atomic structure of SrTiO3{110} and{100} facets determine the protein adsorption and cell interaction behavior subsequently.It is concluded that the design and combination of surface atomic structure of single nanocrystal is an effective means to control its biological effects.

Facet-controlled Growth of SrTiO3Polyhedral Nanocrystals and Their Biological Behaviors

Abstract

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Facet-controlled Growth of SrTiO₃Polyhedral Nanocrystals and Their Biological Behaviors