Functional noble metal nanoparticle superlattices grown at interfaces

Nanoparticle crystals or superlattices (SLs) are three dimensional arrangements of nanoparticles in the micrometre regime. In SLs, the particles are periodically arranged in a coherent long range order and hence they show collective properties. Various spectroscopic, scattering and imaging techniques have been used to understand the structure of self-assembled SLs. Extensive interest in particle SLs is due to the collective properties of the building blocks, which help us to understand the evolution in properties of organized structures. Controlling the assembly of such organized solids may open up new opportunities for fundamental studies as well as for engineering advanced materials with useful attributes. This review presents our efforts in creating SLs of noble metal nanoparticles and studies performed with those materials

Dynamic morphology of mesoscopic pseudoisocyanine J aggregates on mica induced by humidity treatments

Abstract The effect of humidity treatments on the surface morphology of spin-coated pseudoisocyanine (PIC) dye films on mica was investigated by absorption spectroscopy, fluorescence microscopy, and atomic force microscopy (AFM). We demonstrated that the humidity treatment caused dynamic changes of mesoscopic J aggregate morphology due to the mobile nature of PIC molecules on mica surface. Under dry condition, lots of microcrystalline PIC J aggregates were isolatedly distributed on mica. In a low-humidity treatment (32% relative humidity (RH)), characteristic branch-like and patchy leaf-like J aggregate islands could be observed together with non-emissive disordered aggregates. The J aggregate islands grew to possess large patchy leaf-like morphology in a high-humidity treatment of 65% RH. The mobile properties of PIC on a mica surface under humid environments can be explained by capillary condensation of water around hydrophilic microcrystals on the surface and consequent disjoining pressure