Efficient electrochemical detection of guanine, uric acid and their mixture by composite of nano-particles of lanthanides ortho-ferrite XFeO3 (X = La, Gd, Pr, Dy, Sm, Ce and Tb)

Nanoparticles of lanthanides orthoferrites were found to be efficient electrodes for detection of guanine (GU) and uric acid (UA). These perovskite type lanthanide orthoferrite nano particles of XFeO3 (where X = La, Ce, Pr, Sm, Gd, Tb and Dy) were synthesized by combustion techniques using lanthanides nitrate and ferric nitrate as precursor materials in the presence of ethanolamine and sugar as fuel. The powders were characterized by FESEM, TEM and XRD. The synthesized nano particles have orthorhombic crystal structure and have average crystallite sizes ranging from 40 to 45 nm as calculated by Debye-Scherrer equation. The electrochemical activities of these oxides with graphite powder as sensor electrodes were studied for the detection of guanine and uric acid individually as well as in mixture by cyclic voltammetery (CV) and also by differential pulse voltammetry (DPV) techniques and found to be better than reported literatures. The efficient detection of biomolecules may be due to the unique band gap of these ortho-ferrite semiconductors having the bad-gap value around 2.0 eV. The detection limit varies from 100 to 400 nM for guanine and 200 to 500 nM for uric acid at the surface of XFeO3 electrodes. The best electrode was obtained from LaFeO3 with lowest detection limit 100 nM for GU & 200 nM for UA maintaining the linear range from 0.5 mu M to 120 mu M. All electrochemical experiments have been carried out in the presence of Phosphate buffer solution of pH 5.0 as a supporting electrolyte with scan rate 100 mV s(-1) and 50 mV s(-1) for CV and DPV respectively.