In recent decades, significant advances in drug‐delivery systems have enabled more effective drug administration. To deliver drugs to specific organs, a range of organic systems (e.g., micelles, liposomes, and polymeric nanoparticles) have been designed. They suffer from limitations, including poor thermal and chemical stability, and rapid elimination by the immune system. In contrast, silica particles offer a biocompatible, stable, and “stealthy” alternative. Bioactive molecules can be easily encapsulated within silica particles by combining sol–gel polymerization with either spray‐drying or emulsion chemistry. Spray‐drying faces challenges, including low yield, surface segregation, and size limitations. In contrast, sol–gel emulsions enable the production of nanoparticles with homogeneous drug distribution, and permit ambient temperature processing, necessary for handling biologicals. Independent control of the size and release rate can be readily achieved. Preliminary in‐vivo experiments reveal enhanced blood stability of the nanoparticles, which, coupled with sustained release of anti‐tumor agents, show good potential for cancer treatment.

The coordination of photosensitizing Ru(II) dyes to a nanocrystalline titania film, as employed in the Grätzel solar cell, has been examined by vibrational spectroscopy. The major infrared bands of the adsorbed dyes have been assigned by comparison with spectra (IR and Raman) of the parent dye molecules, and suggest a bidentate chelate or bridging coordination to the TiO2 surface via two carboxylate groups per dye molecule.

The speciation of water and hydroxyl groups bound to the surface of a nanocrystalline titania film has been investigated by in-situ infrared spectroscopy as a function of temperature. Calibration of the absorbance of the δ(H2O) mode at 1625 cm -1 by thermogravimetry has enabled an estimation of the concentration of surface H2O present during thermal dehydration of the films, which varied from 5 to 0.65 molecules per nm 2 over the temperature range 27-150 °C. Two types of coordinated H2O and both terminally bound and bridging hydroxyls have been identified by the temperature-dependent behavior of their corresponding O-H stretching modes. Hydrogen bonding was observed between coordinated H2O and terminally bound hydroxyls (ν(OH) ) 3730 cm -1 ), whereas bridging hydroxyls (ν(OH) ) 3670 cm -1 ) do not appear to be affected by similar H-bonding.

Silica nanoparticles for controlled release applications have been produced by the reaction of tetramethylorthosilicate (TMOS) inside the water droplets of a water-in-oil microemulsion, under both acidic (pH 1.05) and basic (pH 10.85) conditions. In-situ FTIR measurements show that the addition of TMOS to the microemulsion results in the formation of silica as TMOS, preferentially located in the oil phase, diffuses into the water droplets. Once in the hydrophilic domain, hydrolysis occurs rapidly as a result of the high local concentration of water. Varying the pH of the water droplets from 1.05 to 10.85, however, considerably slows the hydrolysis reaction of TMOS. The formation of a dense silica network occurs rapidly under basic conditions, with IR indicating the slower formation of more disordered silica in acid. SAXS analysis of the evolving particles shows that approximately 11 nm spheres are formed under basic conditions; these are stabilized by a water/surfactant layer on the particle surface during formation. Under acidic conditions, highly uniform approximately 5 nm spheres are formed, which appear to be retained within the water droplets (approximately 6 nm diameter) and form an ordered micelle nanoparticle structure that exhibits sufficient longer-range order to generate a peak in the scattering at q approximately equal to 0.05 A-1. Nitrogen adsorption analysis reveals that high surface area (510 m2/g) particles with an average pore size of 1 nm are formed at pH 1.05. In contrast, base synthesis results in low surface area particles with negligible internal porosity.

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