This project includes two main parts. In the first part, Use of Sol-Gel method for modifying heterogeneous catalysts was applied. A new approach for increasing the lifetime of a solid catalyst is demonstrated about the esterification of fatty acids for the production of biodiesel by using GO-OSO 3 H@SiO 2 as a catalyst and in continuation of our strategy for improving the performance of heterogeneous catalysts, the GO-OSO 3 H@SiO 2 catalyst was applied as a very efficient solid acid catalyst for the Beckmann rearrangement. The influence of experimental factors such as the amount of catalyst, solvent, temperature and time of reaction on the yield of the reaction was evaluated. The optimum values for maximum esterification can be obtained using a central composite design (CCD)-united. The catalyst could be easily separated and reused. In the second part, a new methodology was applied for controlling the release of different drugs by encapsulating them in organic-inorganic hybrids via sol-gel technique. The synthesized organic-inorganic hybrids were based on zirconium(IV) propoxide, and tetraethyl orthosilicate as a precursor of inorganic network, and chitosan or N-triethylchitosan as organic or biopolymer components. In these hybrid composites, drug and biopolymer were coated with a mesoporous inorganic material. Then for investigating the role of sol-gel process, the release of metformin and sodium naproxen in the prepared hybrid composites was investigated as model drugs. Compare to drug/biopolymer composite, incorporation of ZrO 2 or SiO 2 coating enhanced the drug entrapment appreciably, and naturally reduced the rate of drug release. In last part, we have tried to combine the applicability and advantages of a biopolymer (N-triethylchitosan, TEC) with montmorillonite in conjunction with ciprofloxacin. We have been able to intercalate ciprofloxacin into the montmorillonite layers, preparing a series of composites, and then decorate the composites with a modified chitosan (TEC) as a biopolymer. The results showed that the decoration of ciprofloxacin/montmorillonite with N-Triethylchitosan enhanced the drug encapsulation efficiency of the composite, and controlled the release of drug from the composite. In the presence of N-triethylchitosan, the antibacterial activity of the antibiotic against staphylococcus aureus increased considerably.
