Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán 04510, México DF, México.
Langmuir. 2010 May 18;26(10):6954-9. doi: 10.1021/la904197k.
BaSO(4) nanostructures with controlled morphologies were successfully produced via one-step process through precipitation of BaSO(4) in aqueous and organic media. The synthesis is carried out by mixing solutions of BaCl(2) and Na(2)SO(4) in presence of EDTA (disodium ethylenediaminetetraacetic acid) at room temperature. The influence of the reaction conditions such as initial reactants concentration, pH, EDTA/[Ba(2+)] ratio and aging on the BaSO(4) nanoparticles organization is studied. Using EDTA in aqueous media, spherical secondary particles of 500 nm diameter are obtained, which are formed by 4 nm size primary particles. With dimethyl sulfoxide and small amounts of water (5%) and EDTA, the aging process allows the production of long homogeneous fibers, related to hierarchical organization of BaSO(4) nanoparticles. Direct observation of self-assembling of primary particles by HRTEM allows proposing a mechanism for fiber formation, which is based on multipolar attractions that lead to a brick-by-brick organization along a preferential orientation. Results evidence the role of EDTA as controlling agent of the morphology and primary and secondary mean particle size.
通过一步沉淀法在水相和有机相介质中成功制备了具有可控形貌的 BaSO4 纳米结构。该合成方法是在室温下混合 BaCl2 和 Na2SO4 溶液，并加入 EDTA（乙二胺四乙酸二钠）。研究了反应条件（如初始反应物浓度、pH 值、EDTA/[Ba2+] 比和老化时间）对 BaSO4 纳米粒子结构的影响。在水相介质中使用 EDTA，可得到 500nm 直径的球形二次粒子，其由 4nm 大小的一次粒子组成。在二甲基亚砜和少量水（5%）和 EDTA 的存在下，老化过程可生成长而均匀的纤维，这与 BaSO4 纳米粒子的分级组织有关。通过高分辨 TEM 对初级粒子的自组装进行直接观察，提出了一种纤维形成的机制，该机制基于多极吸引力，导致沿着优先取向的积木式组织。结果表明 EDTA 作为形貌和初级及次级平均粒径的控制剂的作用。
