Colorimetric and electrochemical sensing of As(III) using calix[4]pyrrole capped gold nanoparticles and evaluation of its cytotoxic activity

In the present study, for the first time, calixarene stabilized nanoparticles has been exploited for the selective detection of As(III) in aqueous media. Calix[4]pyrrole tetrahydrazide stabilized gold nanoparticles has been synthesized without the use of any external reducing agent. The non-covalent interactions of calix[4]pyrrole tetrahydrazide molecules on the surface of gold nanoparticles are demonstrated by molecular dynamics studies. The nanoparticles have been characterized using Transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Dynamic light scattering and zeta potential techniques. The capping of calix[4]pyrrole tetrahydrazide molecules around gold nanoparticles and its interaction with As(III) with colour change from pink to blue, red shift with broadening of SPR band and decrease in zeta potential are discussed. The nanoparticles have also been used for the electrochemical sensing of As(III), where amperometric response upto detection limit of 1 ppb has been achieved. Energy dispersive spectra data confirms the presence of As(III) associated with the nanoaprticles. It is fascinated to note that calix[4]pyrrole tetrahydrazide capped gold nanoparticles act as a selective colorimetric sensor for As(III) in the presence of environmentally relevant anions, including NO3-, Cl-, PO(4)(3-)and SO(4)(2-)ions. The present study also shows that the nanoparticles inhibited the proliferation of cancer cell line, MCF-7 which suggests the potential application of gold nanoparticles as cytotoxic agent.