Selective and Sensitive Electrochemical-Sensor for Determination of Dichromate Anion Based on Modified Mesoporous Silica Nanomaterial

Nanotechnology has great potential for application in the field of chemical and electrochemical sensors. Particularly, hybrid nanomaterials due to their unique characteristics have recently been recognized as promising systems in this branch of modern chemistry. In this paper, the channels of mesoporous silica (SBA-15) has been modified by the aluminum complex of 8-hydroxyquinoline according to the method described in the literature [1]. The synthesized nanomaterial (SBA-AlQ) shows a remarkable fluorescence emission at 486 nm, which is quenched in the presence of dichromate anion. In addition, the UV-vis absorption spectrum of SBA-AlQ upon the addition of dichromate onion indicates a specific isosbestic point at 210 nm, confirming the presence of a stable complex with a certain stoichiometric ratio between SBA-AlQ and dichromate anion. These results indicate that this fluorescence nanomaterial can be used as a chemosensor for detecting anion dichromate in aqueous solutions. In addition, due to the selective interaction with dichromate anions, it can be used as a sensing material in a new electrochemical sensor. Accordingly, the carbon paste electrode was made by combining 5% multi-walled carbon nanotubes (MWNTs), 55% graphite powder, 20% ionic liquid and 20% SBA-AlQ. This sensor worked well with the Nernstian response of -28.6±0.3 mV decade-1 of dichromate anion in a wide dynamic concentration range of 1.0×10-6-1.0×10-1 M. The electrode also has a relatively short response time (about 23 s) and produces stable responses for more than 8 weeks.