A double stranded DNA fragment shows a significant decrease in double-helix stability after binding of monofunctional platinum amine compounds

Metals in Catalysis, Biomimetics & Inorganic Material

X-ray imaging of aggregation in silica and zeolitic precursors

The resolution available in the King's College London scanning transmission x-ray microscope (STXM) can be exploited to study aggregate structures over a length scale from 100 nm to 10 micrometers that overlaps with and complements that available from small-angle x-ray scattering (SAXS) data. It is then possible to use these combined sets of data to test between different growth models for the aggregates, using the fractal dimension of the structures as a way of distinguishing the different models. In this paper we show some of the first transmission x-ray images taken of silica gels and zeolite precursors, materials that are of great practical and economic importance for certain selective catalytic processes in the chemical industry, and yet for which there is still only limited understanding of the complicated processes involved in their preparation. These images reveal clearly the fractal aggregates that are formed by the specimens

Growth and aging phenomena in silica gels

Growth and aging of silica aggregates are influenced both by temp. and by catalyzing fluorine ions as shown by SAXS and BET surface studies. It was found that both fluorine and increased temp. slightly increased the fractal dimension (Df) during aging, but the fluorine-catalyzed system showed a lower BET surface area. To understand the effect of fluorine and increased temp. on the aggregates, 2D aggregations and SAXS simulations were carried out using two new programs, GRASP and DALAI. In agreement with expts. it was found that binary RLCCA aggregates have a slightly higher Df value compared to DLCCA aggregates and that branch-flexibility during aging increases Df even furthe