Redox Reactions in Nanoscale Confinement

Materialsconfinedattheatomicscaleexhibit� unusualpropertiesduetonanoconfinementeffect.� Chemistryinaconfinednanospacemaythus� bedifferentfromthatofbulksystem. � W ehave� demonstratedforthefirsttimetheintrinsicrole� ofnanoconfinementinfacilitatingthechemical� reductionofmetalionprecursorswithasuitable� reductantforthesynthesisofmetalnanoparticles,� whentheidenticalreactiondoesnotoccurinbulk� solution.� T akingthecaseofcitratereductionof� silverionsundertheunusualconditionof �(citrate)/ (Ag+)� » � 1, � ithasbeenobservedthatthesilver� citratecomplex, �stableinbulksolution, �decomposes� readilyinconfinednanodomainsofchargedand� neutralmatrices � (ion-exchangefilmandporous� polystyrenebeads), �leadingtotheformationofsilver� nanoparticles.1�Ithasbeenexperimentallyobserved� thatthenanoconfinedredoxdecompositionofsilver� citratecomplexisresponsiblefortheformationofAg� seeds,�whichthereaftercatalyzeoxidationofcitrate� andactaselectronsinkforsubsequentreduction� ofsilverions. �Atpresent, �thereisnoschemeforin� situformationofAgnanoparticlesusingAg+ �ions� inanion-exchangeandneutralmatrices. � TheAg� nanoparticlesthusformedareuncapped, � stable� andeasilyaccessiblethroughinterconnectedpores� orchannelsinthematrices. � Theeasyretrieval� ofthematrixsupportednanoparticlesfromthe� systemsmakesthemreusablenanocatalystswithout� contaminatingtheproductsandsystem.