Studies On The Growth Of PbS And CdS Crystals Induced By Monolayer Film

Biomineralization, as the intersection of the life science, inorganic chemistry, biophysics and materialsscience, has become a hot research topic. Biomimetic synthesis is a synthesis method simulating thebiomineralization process in which the inorganic materials are induced and controlled by organic matrix.Biomimetic mineralization of inorganic crystals using Langmuir monolayer as template has drawn moreand more attention. A great amount of inorganic crystals with special morphology and structure have beenprepared by this method.In the general research of biomimetic mineralization, the regulation of organic Langmuir monolayeron the nucleation and growth of inorganic materials was considered and researched as the importantfoundation of biomimetic synthesis. However, as an important factor, the influence of biomimeticmineralization interface, especially, the movement freedom of nuclei and small crystal at the interface onthe regulation of crystal structure and aggregation status has not got enough attention. In order to solve thisproblem，in the present study, unlike the conventional method using Langmuir monolayers in high surfacepressure region as templates, we reduced the surface pressure of Langmuir monolayer in order to increasethe interface degrees of freedom and change the subphase concentration to introduce the biomimeticinterfacial control. PbS and CdS crystals with special morphology and structure were prepared by thismethod. The influence of various factors on the regulation of PbS and CdS crystals growth was discussedthe. This study shows that the special interface changes the way of crystals aggregation, providing aneffective strategy for biomimetic synthesis of the inorganic functional materials with special morphology.The specific work includes the three sections as following:1. The three-foot PbS crystals growth under arachidic acid Langmuir monolayerUsing an AA Langmuir monolayer as organic template, the regular three-foot PbS crystals were preparedat the air-solution interface by controlling the surface pressure, subphase concentration and reaction time.XRD result shows the crystals oriented growth along (111) planes. This was possibly because of theelectrostatic interaction between the template and ions in solution as the premise of the nucleation andcrystallization of PbS crystals. At low surface pressure, local regulation and reorganization of the AA Langmuir monolayer affected the nucleation and oriented growth of PbS. The generation of triangle PbScrystals have a large movement freedom and aggregate through oriented attachment to form three-footnanomaterials in the air-solution interface. The present study provides a new attempt to synthesize crystalswith special morphology under mild condition and a new method to simulate biomineralization process.2. The study on the formation process of three-foot PbS crystals growth under arachidic acidLangmuir monolayerIn order to reveal the evolution of the three-foot PbS crystals, we study the morphology of PbScrystals at different crystallization stages. The results show the triangular particles were formed under AALangmuir monolayer at first, then the triangular particles aggregate through oriented attachment because oflarge degrees of freedom to move at low surface pressure. The revelation of the mechanism provides abetter way to biomimetic synthesize inorganic functional materials with special structure.3. Preparation and regulation of aggregation status of CdS crystals by biomimetic mineralizationmethodOn the base of the second chapter in which the structure of PbS crystals can be effectively regulatedby changing the ratio of positive ions and negative ions, we study the growth and aggregation of CdScrystals under a PBA Langmuir monolayer in the presence of controlled ammonia solution diffusion. Theconcentration of ammonia solution could effectively change the hydrolysis velocity of thiacetamide, andcontrol the growth and aggregation of the CdS crystals at the vapor-liquid interface, which provides amethod which can effectively regulate aggregation status of biomimetic crystals at the interface.