环境化学与生态毒理学国家重点实验室知识库

      因其独特的光、电学性能和良好的催化活性，纳米材料在环境污染物分析检测和催化降解方面具有广泛的应用前景。纳米材料的性能依赖于其尺寸 、 形貌 和空间排布 纳米材料的模板法可控组装可以实现对这些纳米材料形貌、尺寸和空间排列的精细调控。本文致力于开发 简单、高效和 低成本的模板，实现对不同贵金属纳米材料的有序组装， 并 以其为 表面增强拉曼 基底 SERS 和催化剂，实现对 某些 化合物的分析检测和芳硝基化合物的催化还原。
      首先，研制 了一种新型吡唑基超分子 纳米 微米 管。该管状结构是由一个极其简单的小分子 3,5 二甲基 4 碘吡唑（ DMIP ）自组装而成。通过不良溶剂方法DMIP 可以在乙醇 水中形成不透明的超分子凝胶状结构。该凝胶具有热可逆性（临界温度为 50 ℃）和较强的机械性能。通过基团的剔除 取代、拉曼光谱、核磁共振波谱（ NMR ）和 X 射线光电子能谱（ XPS ）等手段，证实了氢键和卤键驱动 DMIP 自组装形成超分子管状结构。结合实验所得数据和理论计算，我们推测了 DMIP 小分子的自组装过程，即三个 DMIP 分子通过氢键和卤键的作用进行组装，然后以其为最小单元进行延伸生长形成线状结构；该线状结构再进一步通过 I I 作用组装成条带状；根据能量最低原 则，其进一步卷曲形成管状结构。XPS 数据显示该组装体系中只有一小部分碘参与了非共价卤键作用，因此我们推测该自组装体系可以作为超分子软模板诱导与碘具有相互作用的纳米材料的组装。
      其次，以DMIP 超分子 纳米 微米管 为软模板， 通过模板上的碘基团与纳米材料的分子识别机制， 制备 了 高度有序 且 紧密排列的一维等离子体纳米 阵列 Au/ Ag ）），并 通过 改变 纳米 材料 的浓度 或粒径 来 实现对 纳米阵列的密度 或尺寸的调控。 更为重要的是， 等离子体 纳米阵列中的有机模板可以通过简单的加热（ 100来实现对模板的去除，且该过程对纳米组装阵列的 形貌不会产生任何影响。基于等离子纳米阵列中纳米颗粒之间的强的 LSPR 效应，将其用 作 S ERS 基底，用于检测结晶紫（ CV ）。其中以多列方式排布的 Au 纳米阵列会产生更多的“热点”，因此 CV 的 SERS 信号会强于以单排 链 或者双排 链 排列 的 Au 纳米阵列的 SERS信号，但是均匀性则稍弱。该纳米阵列对结晶紫的检测浓度可以低至10 10 M表明该组装的 SERS 平台具有极高的灵敏度。
      进一步，基于超分子作用和配位反应等，通过简单的还原策略，由 CuCl 2 和3,5 二甲基 4 碘吡唑（ DMIP ）协同组装形成 了 具有一定形貌的金属 有机微纳米复合物。利用场发射扫描电镜 FESEM 、 X 射线衍射（ XRD 、拉曼光谱、 X射线光电子能谱（ XPS 、热重、瞬态 稳态荧光光谱等 手段 对 Cu DMIP 复合物的形貌 和 性能进行了研究。 通过改变溶剂的极性实现 了 对 金属 有机复合物形貌的精确调控 如在高极性甲醇中形成棒状结构，而相对弱极性乙醇中形成纤维状结构。在 Cu DMIP 中， Cu 是以一价形态参与其组装的 。该铜基金属有机复合物具有较强的热稳定性， 300 ℃左右仍可以保持稳定。且研究表明 该复合物表现出了红色荧光发光性能。发光机制是热活性延迟荧光（ TADF ），来源是金属 Cu(Ι到配体 DMIP 的电荷转移（ MLCT ）。
      最后，以具有 氧化 还原活性的铜基金属 有机复合材料（ Cu DMIP ）为模板实现了 HAuCl 4 的原位还原组装和 Au 纳米颗粒与 Pd 纳米线的非原位组装。其中原位组装是通过固 液界面自发的氧化还原（置换反应）和歧化反应 来 实现 模板表面 AuCu 合金的生成 而纳米材料与 Cu DMIP 上碘官能团之间的相互作用则驱动着 Au 纳米颗粒 /Pd 纳米线在模板表面的非 原位 组装。可以通过改变 HAuCl 4或纳米颗粒的浓度来实现对 Cu DMIP 表面组装纳米材料的粒径或者密度的调控 。
      同时，考察了它们催化还原芳硝基化合物的性能 ，发现 Cu DMIP/Pd 表现出较高的催化活性。另外，由于贵金属与 Cu DMIP 之间的协同作用，组装的金属 有机复合材料的催化效率和选择性明显高于单独存在的组装单元。 本研究开创了一个利用 氧化 还原活性的金属 有机材料为还原剂、“锚定”剂和催化剂的平台。

      Nanomaterials have been widely applied in the trace detection and catalytic degradation of environmental pollut ants due to its unique optical, electronic and catalytic properties. However, th e properties of these nanomaterials are dependent on their morphologies, sizes and spatial layout, which could be precisely regulated through the controllable assembly of nanomaterials based on the template strategies.This study aimed to develop a simple, efficient and low cost template for the ordered assembly of noble metal nanomaterials. These assembled nanomaterials were used as surface enhanced Raman scattering substrates and catalysts for analytes detection and nitroarenes reduction.
       Firstly, novel pyrazolyl based supramolecular nanotubes/microtubes have been developed through self assembly of an extremely simple molecule,3,5 dimethyl 4 iodopyrazole (DMIP). DMIP molecules could interconnect into a stiff and thermo reversible opaque gel with a gel sol transition temperature of 50 °C in ethanol/water solution. By jointly considering functional group modification/elimination, Raman spectral modification, temperature dependent 13 CNMR analysis and XPS results, it can be verified that intermolecular hydrog en bond and halogen bond act ed as the driving forces to promote the formation of supramolecular tubular architectures. On the basis of obtained data and theory calculation s , a plausible molecular model for formation process of supramolecular tubes was prov ided. Three molecules, as the basic self assembly unit, were held together by a combination of intermolecular hydrogen bonding and halogen bonding on adjacent molecules. The propagation further grow along the basic self assembly unit to form a linear struc tures, which associated with each other via I···I interaction to create sheets. Finally, due to the high surface areas of the sheets, they have a high tendency to scroll up to yield supramolecular tubules, thus minimizing the surface energy of the system. The supramolecular tube like architectures with partial functionally free iodine groups were expected to be a promising scaffold for nanomaterials assembly.
       Secondly, taking advantage of specific metal DMIP recognition, the self assembled DMIP supramolecular nanotubes/microtubes could serve as template to stabilize Au NPs and Ag NPs, thus enabling the generation of highl y ordered, linear nanoparticles arrays on macroscopic areas. More importantly, the DMIP template can be easily removed by heati ng to approximately 100 °C without collapsing the NP sarrays. Furthermore, these NPs assemblies exhibit fascinating integrated properties resulting from the plasmon coupling between the adjacent NPs, delivering excellent surface enhanced Raman scattering (SERS) activities for crystal violet detection. Compared with multiple lines assemblies, the SERS spectra along single line or double lines Au NPs exhibited noticeably weaker but more consistent signals. A plausible explanation for these results may be the generation of more “hot spots” by the multiple strand s of close packed NPs implying the significant role of the microstructural morphology in determining the SERS activities of the hierarchically assembled SERS active substrate. Discriminable signals for CV could still be observed with a concentration as lo w as 10 10 M, manifesting the excellent sensitivity in the assembled SERS platform.
      Based on intermolecular interactions between supramolecules and coordination reaction, an organic inorganic complex was further constructed through the synergistic assembly of CuCl 2 and 3,5 dimethyl 4 iodopyrazole (DMIP). The morphologies and properties of these Cu DMIP complexes were studied with field emission scanning electron microscopy (FESEM), X ray diffraction (XRD), Raman spectroscopy, XPS, thermogravimetric and tran sient/steady state fluorescence
spectroscopy. The morphology of metal organic complexes could be precisely regulated by changing the polarity of the solvent. For example, a rod like structure was formed in highly polar methanol, while a fibrous structure w as produced in relatively weaker polar ethanol. T he copper based metal organic composites complex possessed high thermal stability and remain stable at around 300 Cu participated in its assembly in a monovalent form. Moreover, the composites exhibited r edfluorescent luminescence properties. The luminescence mechanism is thermal activity
delayed fluorescence (TADF), which is derived from the charge transfer (MLCT) from metal Cu (Ι) to ligand DMIP.
       Finally,in situ reduction assembly of HAuCl 4 and ex situ assembly of Au nanoparticles and Pd nanowires were conducted by using a copper based redox active metal organic complex (Cu DMIP) as template. In situ assembly was achieved via spontaneous oxidation reduction reaction (galvanic replacement) and disproport ionation reaction at the solid liquid interface to form AuCu alloy on the surface of templates, while the interaction between the nanomaterials and the iodine functional groups on Cu DMIP drove the ex situ assembly of Au nanoparticles/Pd
nanowires. The nan oparticle sizes or densities of assembled nanomaterials on the Cu DMIP could be well regulated by changing the concentration of HAuCl 4 or nanoparticles. Meanwhile, their catalytic activities for the reduction of aryl nitro compounds were examined. Compared with other assembled arrays, Cu DMIP/Pd exhibited higher catalytic activity. In addition, due to the synergy effects between the noble metal s and Cu DMIP, the catalytic efficiency and selectivity of the assembled inorganic organic/nanomaterials composites were significantly higher than those of the unassembled building blocks. The study pioneered a platform for the use of redox active metal organic materials as reducing agents, "anchoring" agents and catalysts.