Synthesis and small angle X-ray scattering (SAXS) characterization of silica spheres covered with gel-like particles formed by means of solvent evaporation

• Synthesis of spherical silica particles covered by nanosized gel-like structures
• Structural SAXS study
• Tailoring the specific surface area by easily accessible parameter
• Defined surface structuring
• Possible application for stabilization of nanodots against migration/sintering

A simple modification of the classic Stöber reaction is introduced, providing spherical silica particles covered by nanosized gel-like surface structures. The synthesis procedure is based on the sampling and heat-treating of reacting particle suspensions at 100 °C, leading to secondary structures preferentially formed on the surface of Stöber particles. Using small-angle X-ray scattering (SAXS), structural information on both the classic Stöber particles and the formed nanosized surface structures is achieved. The growth of Stöber particles is in agreement with the concept of a fractal growth mechanism, leading to narrow-distributed spheres, but having internal micropores. Moreover, the nanosized surface structures formed due to the evaporation of solvent are described by individual units with a gyration radius between 2 and 4 nm. While the size of the surface structures does not depend on the reaction time at which the particle suspensions are sampled and heat-treated afterwards, the amount of these can easily be influenced. In this way, the resulting surface area can be simply controlled via the reaction time of the foregoing Stöber process: Therefore this process allows the tailoring of the needed surface, a point of high interest for many applications, e.g. in the field of catalysis.

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