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.