一釜法合成明胶/水溶性PbS生物微纳米复合物及其形成机制

背景：生物纳米复合材料的合成和形成机制的研究,可为无机/有机复合材料的设计及其在生物医学领域的广泛应用提供必要的理论基础。 目的：在生理pH值7.40下,合成水溶性明胶/水溶性PbS微纳米复合物,研究PbS颗粒在明胶大分子基体上的结合机制。 方法：以明胶、Pb(NO₃)₂和Na₂S?9H₂O为原料,采用一釜化学反应法,即将Pb²⁺和S^2?依次加入明胶水溶液中,原位生成PbS/明胶微纳米复合物。利用扫描电子显微镜、动态光散射、紫外-可见和傅里叶变换红外光谱等技术测定其形貌、粒径及其光谱性质。 结果与结论：扫描电镜显示,所合成的PbS颗粒在低Pb²⁺浓度时为不规则多面体,较高Pb²⁺浓度时呈橄榄形。动态光散射结果显示,当Pb²⁺浓度为2.0×10^?5,8.0×10^?5,2.0×10^?4 mol/L时,明胶/水溶性PbS复合物的平均粒径分别为75,91,109 nm。PbS/明胶复合物的量子尺寸效应明显。形成机制为：Pb²⁺与明胶大分子肽链上的羰基氧相互作用并引起明胶大分子的构象由α-螺旋到β-折叠的变化以利于PbS成核;明胶大分子包覆于PbS颗粒表面使明胶/水溶性PbS复合物在水中具有较好的稳定性。

One-pot synthesis and formation mechanism of water-soluble PbS/gelatin micro-nano biocomposite

BACKGROUND:Studieds about the synthesis and formation mechanism of bionanocomposites can provide theoretical basis for the design and wide application of inorganic/organic composites in biomedical area. OBJECTIVE:To synthesize water-soluble PbS/gelatin micro-nano biocomposites at pH value of 7.40, and to study the intergration mechanism of PbS particles in the macromolecules of gelatin. METHODS:The water-soluble PbS/gelatin micro-nano biocomposites were synthesized via one-pot chemical route involving the reaction of Pb²⁺ with S^2? in gelatin aqueous solution at pH value of 7.40. The particle shape, size and spectral quality of samples were characterized by scanning electron microscopy, dynamic light scattering, UV-vis spectroscopy and Fourier transform infrared spectroscopy. RESULTS AND CONCLUSION:Scanning electron microscopy images showed that the morphologies of PbS particles were mainly irregular polyhedrons and olive-shape in the lower and higher concentration of Pb²⁺, respectively. Dynamic light scattering results indicated that the average particle sizes of PbS/gelatin micro-nano biocomposites were 75, 91 and 109 nm in the presence of 2.0×10^-5, 8.0×10^-5 and 2.0×10^-4 mol/L of Pb²⁺, respectively. And they showed an obvious quantum confinement effect. Based on the experimental results, the possible formation mechanism is proposed as follows: there is a main interaction between the Pb²⁺ ions and the ketonic oxygen on the peptide chain of gelatin macromolecules, which causes the gelatin macromolecules conformation changed from α-helix to β-sheet for the oriented nucleation of PbS; and then the S^2? is combined with Pb²⁺ to form PbS nanoparticles. The PbS/gelatin micro-nano biocomposites showed a better stability in aqueous solution, owing to gealtin polypeptide chain coating on the surface of PbS nanoparticles.