工程纳米颗粒在环境中的聚合及其与天然颗粒的二元组装

Recent development in nanotechnology and production and usage of diverse nanomaterials paved the way for their environmental release and subsequent interactions with plants and organisms. Among these emerging contaminants, recent studies have proven that several of these anthropogenic nanomaterials are toxic to plants and organisms including human cell lines. Therefore, environmental fate and transport and subsequent bioavailability of these anthropogenic nanomaterials have profound environmental relevance. Previous studies including ours have demonstrated NOM induced fate and transport behavior of these nanomaterials. However, very few studies have underscored the importance of colloidal interactions of these emerging contaminants with naturally occurring mineral particulates, especially iron oxide and oxy hydroxide and silica nano and micro particles. In aquatic environment, homo and hetero aggregation of anthropogenic NPs as well as their entropic depletion within the aggregates or clusters of naturally abundant particulates may strongly attenuate or facilitate bioavailability of the former upon environmental release. The role of structurally different NOM and naturally abundant electrolytes on the above mentioned interactions is still relatively unaddressed regarding fate and transport of these emerging contaminants. .The proposed research is to understand the formation mechanism of self-assembled structures (SAS) binary assembly (BA) of metal and metal oxide NPs (MNP) and fullerene with iron oxide and oxy hydroxide and silica particles. The SAS of anthropogenic and naturally occurring surface modified MNPs and fullerene on air-water interfaces will be examined. Hetero-association between fullerene with natural particles will be investigated. These natural particles include surface modified or unmodified naturally abundant iron oxide and oxy hydroxide, and silica nano and microparticles. Binary association and assembly formation of pure and surface modified anthropogenic MNPs and fullerene will be studied. NOM will also be included as an additional colloid in the binary association. The overarching hypothesis of our proposed study is that the exposure of variety of anthropogenic nanomaterials in the environment will lead to their mutual interaction, and conjugation with naturally occurring iron oxide and oxy hydroxide and silica particles and NOM; hence, resulting in self and binary assembly formation along with amorphous aggregates on environmental interfaces. The shape anisotropy of anthropogenic MNPs and naturally abundant iron oxy hydroxide may influence capillary assisted assembly formation and subsequent retention on air-water interface prevalent in unsaturated soil columns. This study will provide fundamental information for anticipating MNP behavior, which is fundamental for the risk assessment and administration of MNP manufacturing and application.

随着纳米技术的快速发展，大量工程纳米颗粒（MNPs）可能通过各种途径进入环境。近期的研究指出，一些MNPs对植物、动物、人体细胞有显著的毒性，因此，需要对这些新型人为源污染物的行为和归趋进行准确的理解。然而，这些MNPs进入环境以后的聚合特征，及其与天然颗粒之间的相互作用，还不为人知。因此，本研究考察MNPs在环境体系中的聚合行为，重点是其自组装和与环境颗粒的二元组装。MNPs包括金属氧化物纳米材料、不同形态的金属纳米颗粒以及富勒烯，天然颗粒中重点考察铁氧化物、氢氧化物，二氧化硅颗粒以及天然有机质。本研究的总体假设是：MNPs环境介质中发生自组装，或者与天然颗粒发生二元组装，具有各向异性的MNPs和天然纳米颗粒（比如铁氢氧化物）可能通过毛细管力进行组装，从而在非饱和土柱中的气-水界面滞留，淋溶缓慢。本研究的结果将为MNPs行为的预测提供基础理论依据，是对其进行风险评估和管理控制的必经之路。

随着纳米技术的蓬勃发展和包括金属氧化物纳米颗粒（NPS）和富勒烯等在内的各种纳米材料的生产，以及存量丰富的天然矿物胶体，它们在环境介质中产生了不同的自组装或二元或多元的组装结构，形成了具有高热力学稳定性，机械稳定性的聚集体。这些高热力学稳定的组装结构也阻碍了人工纳米材料的生物利用度。此外，这些在环境界面上产生的组装结构可能有不同的潜在应用，比如括膜的能量收集等。在天然单宁酸存在下，富勒烯-水悬浮液（FWS）与钠饱和高岭石（Na-kaolite）之间的胶体杂化结合，以及由原位原子力显微镜（AFM）测定的空气-水界面上Ca2+离子浓度产生的扩散限制区而形成的的鱼骨状结构。云母衬底的对称性，云母的二面体性质以及180°旋转生长导致高岭石和单宁酸修饰的官能化富勒烯的二元组装有序化外延生长。富勒烯的两亲性排列和钠饱和高岭石在功能化富勒烯双链螺旋主链处的包封作用产生了一维生长。根据开尔文探针力显微镜（KPFM）的测定，在新解理的云母上普遍存在着可交换K+，该离子引导着具有手性纳米孔的纳米管和二维片状石墨结构的生长。然而，由于较高的Ehrlich-Schwoebel势垒（ESB）和螺旋位错辅助粒子的运动，增强成核的富勒烯产生顶部螺旋形的丘体的三维生长。在单宁酸存在下，由于异质结合而引起的静电势垒增加，富勒烯与钠饱和高岭土颗粒在水相中异质结合表现出较低的异质成核速率。然而在酸性pH条件下，富勒烯与钠饱和高岭石的胶体结合产生紧密堆积的聚集体，可能产生板条状或者具有潜在过渡的纳米管状埃洛石结构。我们进一步研究了在二价阳离子存在下酚酸产生的聚集体的生长形貌变化。利用原位原子力显微镜（AFM）和高分辨（HR）透射电镜（TEM）研究了这种螺旋位错产生的具有纳米管结构和二维二元超晶格的生长。我们还观察到了类神经元生长结构，如在原位液下原子力显微镜下测定的苏万尼河富里酸与赤铁矿核聚集体在空气-水界面上的生长。此外，使用胶体探针研究了在无机和有机阳离子存在的条件下，天然有机质与赤铁矿复合物形成的非共价结合起到了稳定土壤团聚体的作用。