Sol-gel derived silica possess many promising features, including low-temperature preparation procedure, porosity, chemical and physical stability. Applications exploiting porous materials to encapsulate sensor molecules, enzymes and many other compounds, are developing rapidly. In this paper some potential applications, with emphasis on biomedical and environmental ones, are reviewed. The material preparation procedure is described and practical remarks on silica-based sol-gels are included. It is reported that sol-gels with entrapped various molecules may be used in construction of implants and coatings with bioactive properties. It is shown how to exploit the sol-gel production route for construction of sol-gel coated fiberoptic applicators for lasertherapy. The applications of bioactive materials are discussed, as well. It is demonstrated that it is possible to immobilize photosensitive compounds in sol-gel matrix without loosing their photoactivity. Some examples of sol-gel based biosensors are demonstrated, as well, showing their potential for detecting various gases, toxic substances, acidity, humidity, enzymes and biologically active agents.

Metal nanoshells are a type of nanoparticle composed by a dielectric core and a metallic coating. These nanoparticles have stimulated interest due to their remarkable optical properties. In common with metal colloids, they show distinctive absorption peaks at specific wavelengths due to surface plasmon resonance. However, unlike bare metal colloids, the wavelengths at which resonance occurs can be tuned by changing the core radius and coating thickness. One basic application of such property is in medicine, where it is hoped that nanoshells with absorption peaks in the near−infrared can be attached to cancerous cells. In this paper, we study the changes of optical response in visible and near infrared wavelengths from single to randomly distributed clusters of nanoshells. The results were obtained using a novel formulation of Mie theory in evanescent wave conditions, with a finite−difference time−domain (FDTD) simulation and experimentally on BaTiO₃−gold nanoshells using a scanning near−optical microscope. The results show that the optical signal of a randomly distributed cluster of nanoshells can be supplementary tuned with respect to the case of single nanoshell depending by the geometric configuration of the clusters.