Chapters authored
SiO2-Based Materials for Immobilization of Enzymes
It is well known that SiO2-based nanomaterials were widely used as support material for many chemically active species but also for compounds with biological activity such as antibodies and enzymes, due to their lack of toxicity and high surface area. The hybrid materials resulted from associating enzymes with various morphologies of SiO2 inorganic matrix, especially obtained by sol-gel method, are meant to develop a higher enzymatic activity and increased lifetime but also the recovery and reutilization advantage. The present contribution emphasized the synthesis of SiO2 nanomaterials with different morphologies and their physicochemical characteristics including biocatalytic activity of immobilized enzymes on simple SiO2. The morphology-dependent behavior of SiO2 inorganic carriers obtained by sol-gel method was also emphasized. Accordingly, SEM investigations, nitrogen sorption, electrokinetic potential, and spectroscopic measurements are presented. p-Nitrophenyl acetate (p-NPA) was used for testing the enzymatic activity of as-prepared lipase-SiO2 hybrid materials.
Part of the book: Nanomaterials
Influence of the Microwaves on the Sol-Gel Syntheses and on the Properties of the Resulting Oxide Nanostructures
Among the chemical methods in the liquid phase, the sol–gel technique is a versatile and efficient method for pure or doped metal oxide films or powders preparation, showing some advantages over other preparation techniques (high homogeneity, the possibility to introducing dopants in large amount, low processing temperature and control over the stoichiometry). Combining the sol–gel (SG)method with the effect of ultrasounds(US) or microwaves (MW) leads to improving the sol–gel procedure. The microwave-assisted sol–gel method is most frequently used for obtaining nanocrystalline, monodispersed oxide nanoparticles, or to transform amorphous gels into well-crystallized nanopowders. Less studied is the influence of the microwaves on the sol–gel reactions in solutions. The benefit of using microwave-assisted sol–gel preparation highly depends on the reagents used and on the composition of the studied systems. In the present chapter, results on the influence of the microwaves on the chemical reactions that take place during the sol–gel synthesis and on the properties of the resulted samples are discussed.
Part of the book: Microwave Heating