Poly(3-octylthiophene) nanoparticles for turn-on fluorescent sensor

A novel concept of optical fluorescent sensing using conducting polymer nanostructures poly(3-octylthiophene) as an optical receptor is proposed. A conducting polymer was encapsulated within polymeric nanospheres obtained from poly(maleic anhydride-alt-1-octadecene) in a simple procedure, resulting in formation of core-shell nanostructures. In the presence of carboxyl groups at the outer shell of nanospheres the conducting polymer undergoes spontaneous oxidation (e.g. by oxygen dissolved in the solution), leading to decrease of native fluorescence of poly(3-octylthiophene). Thus obtained core-shell nanospheres are sensitive to changes of the solution redox potential, due to dependence of poly(3-octylthiophene) emission spectra on its oxidation state. The decrease in redox potential is accompanied with increase of emission intensity of the conducting polymer core, which allows application of nanospheres as turn-on probe for reducing agents. The sensitivity and selectivity of obtained nanoprobes can be fine-tuned taking the advantage of the presence of charged groups in the shell layer of the nanostructures obtained. As a model analyte, ascorbic acid was chosen. A linear response was recorded, with increase of emission intensity for increasing ascorbic acid concentration, within the range from 10−6 to 0.1 M.