Sensing behavior of silica-coated Au nanoparticles towards nitrobenzene

In the present work, we report silica-stabilized gold nanoparticles (SiO2/Au NPs) as a wide-range sensitive sensing material towards nitrobenzene (NB). Surface hydroxyl groups of silica selectively form Meisenheimer complex with electron-deficient aromatic ring of NB and facilitate its immobilization and subsequent catalytic reduction by Au cores. Silica-coated Au NPs were synthesized and characterized for their chemical, morphological, structural, and optical properties. SiO2/Au NPs-modified electrodes were characterized with impedometric and cyclic voltammetric electrochemical techniques. SiO2/Au NPs are found to have a higher optical detection window of range, 0.1 M to 1 mu M and a lower electrochemical detection window of range, 10(-4) to 2.5 x 10(-2) mM with a detection limit of 12.3 ppb. A significant enhancement in cathodic peak current, C (1), and sensitivity (102 mu A/mM) was observed with modified electrode relative to bare and silica-modified electrodes. The I (P) was found to be linearly co-related to NB concentration (R (2) = 0.985). The interference of cationic and anionic species on sensor sensitivity was also studied. Selectivity in the present sensing system may be further improved by modifying silica with specific functional moieties.