Self-assembly of Ag nanoparticles using hydroxypropyl cyclodextrin: synthesis, characterisation and application for the catalytic reduction of p-nitrophenol

A green synthetic approach for the preparation of silver nanoparticles (AgNPs) in aqueous alkaline medium using cyclodextrin (CD) derivatives as reducer and stabliser is reported. The CD-AgNPs are characterised using UV-visible (UV), FT-IR, mass spectroscopic and cyclic voltammetric (CV) techniques. The difference in morphology is observed with respect to the CD derivatives by transmission electron microscopy and the formation mechanism of AgNPs is discussed. CD-AgNPs display remarkably strong blue emission at 478 and 540 nm upon excitation at 400 nm. The monodispersed and self-assembled AgNPs capped by beta-hydroxypropyl cyclodextrin (beta-HPCD) show photoluminescence enhancement in the presence of Hg(II), but it is strongly quenched by Al(III). beta-HPCD-AgNPs possess good selectivity and sensitivity for the determination of Hg(II) and Al(III) in the concentration range of 20-200 mu M. Furthermore, the as-prepared AgNPs serve as an effective catalyst to activate the reduction of p-nitrophenol in the presence of sodium borohydride, which shows comparable catalytic activity. The homogeneous and heterogeneous catalytic activities of CD-AgNPs are assessed using UV and CV techniques, respectively.