Abstract：
OBJECTIVE: Graphene Oxide (GO)-templated deposition of inorganic materials through synthesis on dispersed single sheets of GO is often complicated by the loss of the desired 2D morphology owing to the coagulation of GO sheets at high salt concentrations and non-templated homogenous nucleation. Modifying GO with anionic polymer is expected to solve both problems by i) enhancing electrostatic(steric) stabilization upon exposure to high concentrations of the ionic precursors, and ii) offering additional nucleation sites at the grafted anionic moieties to avoid homogeneous secondary nucleation.
METHODS: GO was grafted with branched copolymers of poly(ethylene glycol) methacrylate (PEGMA 500) and diethylene glycol dimethacrylate (DEGDMA) and ω-vinyl terminated methacrylic acid macromonomer (P(MAA)), the latter serving as an addition-fragmentation chain transfer agent. The colloidal stability of GO dispersions in water toward salt was evaluated before and after modification. Precipitation of calcium phosphate (CaP) was performed by incubating modified GO in the precursor solutions. The conditions were optimized to maximize the nucleation selectively onto GO without homogeneous CaP nucleation and coagulation of the GO-sheets.
RESULTS: The copolymer grafted GO-sheets shows superior colloidal stability when dispersed in water. No aggregation occurs in the incubating ionic CaP precursor solutions. The optimum templated deposition of CaP onto the GO sheets by precipitation is to add a second shot of precursors after the nucleation stage to obtain GO sheets fully decorated with calcium phosphate nanorods without self-nucleation. Via the careful design on the GO modification and incubation process, the growth of calcium phosphate nanorods were confined in the desired 2D order exclusively, hereby achieving the goal of an efficient GO-templated synthesis.
METHODS: GO was grafted with branched copolymers of poly(ethylene glycol) methacrylate (PEGMA 500) and diethylene glycol dimethacrylate (DEGDMA) and ω-vinyl terminated methacrylic acid macromonomer (P(MAA)), the latter serving as an addition-fragmentation chain transfer agent. The colloidal stability of GO dispersions in water toward salt was evaluated before and after modification. Precipitation of calcium phosphate (CaP) was performed by incubating modified GO in the precursor solutions. The conditions were optimized to maximize the nucleation selectively onto GO without homogeneous CaP nucleation and coagulation of the GO-sheets.
RESULTS: The copolymer grafted GO-sheets shows superior colloidal stability when dispersed in water. No aggregation occurs in the incubating ionic CaP precursor solutions. The optimum templated deposition of CaP onto the GO sheets by precipitation is to add a second shot of precursors after the nucleation stage to obtain GO sheets fully decorated with calcium phosphate nanorods without self-nucleation. Via the careful design on the GO modification and incubation process, the growth of calcium phosphate nanorods were confined in the desired 2D order exclusively, hereby achieving the goal of an efficient GO-templated synthesis.
摘要：
目的:通过在分散的单层GO上合成的无机材料的氧化石墨烯(GO)模板化沉积通常由于在高盐浓度和非模板化均匀成核下GO片材的凝固而导致所需的2D形态的损失而变得复杂。用阴离子聚合物改性GO有望通过以下方式解决这两个问题:i)在暴露于高浓度的离子前体时增强静电(空间)稳定,和ii)在接枝阴离子部分处提供额外的成核位点以避免均匀的二次成核。
方法：用聚（乙二醇）甲基丙烯酸酯（PEGMA500）和二甘醇二甲基丙烯酸酯（DEGDMA）和ω-乙烯基封端的甲基丙烯酸大分子单体（P（MAA））的支化共聚物接枝GO，后者用作加成-断裂链转移剂。在改性之前和之后评价GO分散体在水中对盐的胶体稳定性。通过在前体溶液中孵育改性的GO来进行磷酸钙(CaP)的沉淀。优化条件以使选择性地在GO上的成核最大化,而没有GO片的均匀CaP成核和凝结。
结果:共聚物接枝的GO-片材在分散于水中时显示出优异的胶体稳定性。在孵育的离子CaP前体溶液中没有发生聚集。通过沉淀将CaP模板化沉积到GO片上的最佳方法是在成核阶段之后添加第二次前体,以获得用磷酸钙纳米棒完全装饰而没有自成核的GO片。通过对GO修饰和孵化过程的精心设计，磷酸钙纳米棒的生长仅限于所需的2D顺序，由此实现了有效的GO模板化合成的目标。
方法：用聚（乙二醇）甲基丙烯酸酯（PEGMA500）和二甘醇二甲基丙烯酸酯（DEGDMA）和ω-乙烯基封端的甲基丙烯酸大分子单体（P（MAA））的支化共聚物接枝GO，后者用作加成-断裂链转移剂。在改性之前和之后评价GO分散体在水中对盐的胶体稳定性。通过在前体溶液中孵育改性的GO来进行磷酸钙(CaP)的沉淀。优化条件以使选择性地在GO上的成核最大化,而没有GO片的均匀CaP成核和凝结。
结果:共聚物接枝的GO-片材在分散于水中时显示出优异的胶体稳定性。在孵育的离子CaP前体溶液中没有发生聚集。通过沉淀将CaP模板化沉积到GO片上的最佳方法是在成核阶段之后添加第二次前体,以获得用磷酸钙纳米棒完全装饰而没有自成核的GO片。通过对GO修饰和孵化过程的精心设计，磷酸钙纳米棒的生长仅限于所需的2D顺序，由此实现了有效的GO模板化合成的目标。
