Alizarin-modified sulfonate carbon nanoparticles in vanadium sensing

The adsorption processes of alizarin onto hydrophilic carbon nanoparticles (Emperor 2000 (TM)) are investigated. The significant increase in voltammetric responses for pre-adsorbed alizarin compared with those for solution confirms high affinity of alizarin to carbon nanoparticles (possibly due to pi-pi stacking interaction between aromatic rings of alizarin and surface-sulfonated carbon nanoparticles). To obtain the optimum of adsorption conditions, the effects of pH, agitation rate, and adsorption time are investigated. Under square wave voltammetry conditions, the peak current for the reduction of alizarin shows a linear relationship with concentration in the range from 2.0 to 10.0 nM. The limit of detection is estimated 5.8 x 10(-9) mol L-1. Next, alizarin is applied as a receptor for sensing of trace vanadium in acetate buffer pH 5. Linear calibration curves are obtained for vanadium in the range of 1.0 x 10(-6) to 1.0 x 10(-4) mol L-1 and the limit of detection is estimated 9.6 x 10(-8) mol L-1. Determination of vanadium in real samples such as sea and tap water is demonstrated.