Interacting nanoparticle systems materials

Other materials derived from clay-organic systems include small semiconductor nanoparticles (CdS, for instance), which are extremely interesting in terms of new nanoelectronic and optoelectronic devices. The functionalization of sepio-lite using 3-MPTMS (see Sec. VI.A) allows complexation of Cd ions by thiol-cation interactions (200). These materials are potentially very attractive for their quantum dot properties, because it can be expected that treatment with H2S gas or Na2S solutions could produce semiconducting CdS particles of nanosized dimensions. In addition, such systems would be of interest in terms of photocata-lytic activity, such as for the generation of H2 from isopropanol, as was observed for MCM mesoporous silica that was functionalized in a similar way (230). 

In biological applications we need to consider the nanoparticle system (composition, size and structure, surface substitution), the given in vitro or in vivo biologic system (media, serum, cells, tissues, animal model, etc), and the mechanisms, through which they interact. We have to determine the properties that are biologically relevant. Some of the physical properties of nanoparticles are easy to measure, but irrelevant from a biological point of view, and vice versa. As an example, low ethylenediamine contamination of technical PAMAM materials is not easy to measure, but this data is very significant in toxicity experiments. 

Simulations of physical properties of realistic Pt/support nanoparticle systems can provide interaction parameters that are used by molecular-level simulations of self-organization in CL inks. Coarse-grained MD studies presented in the section Mesoscale Model of Self-Organization in Catalyst Layer Inks provide vital insights on structure formation. Information on agglomerate formation, pore space morphology, ionomer structure and distribution, and wettability of pores serves as input for parameterizations of structure-dependent physical properties, discussed in the section Effective Catalyst Layer Properties From Percolation Theory. CGMD studies can be applied to study the impact of modifications in chemical properties of materials and ink composition on physical properties and stability of CLs. 

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