Hi! I’m trying to obtain silver nanoparticles using AgNO3 (1mM) and different plants extracts (spruce bark polyphenolic extracts obtained via different methods: boiling in water, UAE using water as solvent, UAE using EtOH 70% as solvent and SFE with CO2 and EtOH 70% as cosolvent). I’ve succeed to obtain good results (the reduction process occurs with visible colour changes, the presence of AgNP could be recorded in UV-VIS at the specific λ, etc.) when as reductant agent was used the plant extract obtained using water as solvent (both through boiling and UAE) but when I’m trying the ethanolic extracts (obtained by UAE and/or SFE) - with higher concentration of polyphenols (responsible with Ag ions reduction), the reduction doesn’t occur. Even if I’ve eliminate the ethanol from the extracts under vacuum, I didn’t get any success. Have anyone try other solvents for obtaining plants extracts used as reductants for these kind of processes and observed similar behaviour? Or could someone help me with an explication of how or why the extraction process/ solvents used, have influence on the later reductants proprieties of the extracts, even if their concentration in phenolics is higher and it’s supposed to enhance the reduction process?
It is well known that solvents significantly affect on chemical and physical processes (reaction rates, selectivity, chemical equilibria, position and intensity of spectral absorption bands). In addition to the nonspecific Coulombic, inductive and dispersion interactions, other interactions, such as specific hydrogen bonding, electron pair donor–acceptor and solvophobic interactions, may play a part in the solvent effects. In extraction processes, materials move from one phase to another phase based on estent of interactions of a molecule in these phases. It is evident that by any changes in the extraction solvent, there will be considerable changes in composition of extract and you have to empirically design the best solvent for your reduction reaction (Ag+ to metallic silver), because you do not have exact information about composition of your mixture and types of solvent-solute interactions in the extraction system. For more information, please refer to Dr. Christian Reichardt, Prof. Dr. Thomas Welton, Solvents and Solvent Effects in Organic Chemistry, Fourth Edition (2010), Print ISBN: 9783527324736, Online ISBN: 9783527632220, DOI: 10.1002/9783527632220
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It is well known that solvents significantly affect on chemical and physical processes (reaction rates, selectivity, chemical equilibria, position and intensity of spectral absorption bands). In addition to the nonspecific Coulombic, inductive and dispersion interactions, other interactions, such as specific hydrogen bonding, electron pair donor–acceptor and solvophobic interactions, may play a part in the solvent effects. In extraction processes, materials move from one phase to another phase based on estent of interactions of a molecule in these phases. It is evident that by any changes in the extraction solvent, there will be considerable changes in composition of extract and you have to empirically design the best solvent for your reduction reaction (Ag+ to metallic silver), because you do not have exact information about composition of your mixture and types of solvent-solute interactions in the extraction system. For more information, please refer to Dr. Christian Reichardt, Prof. Dr. Thomas Welton, Solvents and Solvent Effects in Organic Chemistry, Fourth Edition (2010), Print ISBN: 9783527324736, Online ISBN: 9783527632220, DOI: 10.1002/9783527632220
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