Photoinducedly electrochemical preparation of Prussian blue film and electrochemical modification of the film with cetyltrimethylammonium cation

Abstract

This work presents a photoinducedly electrochemical preparation of Prussian blue from a single sodium nitroprusside and insertion of cetyltrimethylammonium cations into Prussian blue as counter ions. The product of photoinducedly electrochemical reactions has a couple of voltammetric peaks at E° = 0.266 V in 0.2 mol l −1 KCl solution, the measurements of X-ray powder diffraction and FT-IR spectroscopy show that it is Prussian blue (PB). The formation mechanism of a pre-photochemical reaction and subsequent electrochemical reaction is suggested. The cyclic voltammetric treatment of the freshly as-prepared PB film in 1.0 mmol l −1 cetyltrimethylammonium (CTA) bromide solution leads to the insertion of cetyltrimethylammonium cations into the channels of Prussian blue, which substitutes for potassium ions as counter ions in Prussian blue. The Prussian blue containing CTA counter ions shows two couples of voltammetric peaks at E° = −0.106 V and E° = 0.249 V in 0.2 mol l −1 KCl solution containing 1.0 mmol l −1 cetyltrimethylammonium bromide. Compared with the electrochemical behaviors of KFeFe(CN) 6 in 0.1 mol l −1 KOH alkali solution, CTAFeFe(CN) 6 shows relatively durable voltammetric currents due to the hydrophobic effects of cetyltrimethylammonium. The diffusion coefficients for CTA and potassium cations were estimated to be D CTA 1.25 × 10 −12 cm 2 s −1, D K 2.59 × 10 −12 cm 2 s −1, respectively. The peak current of electro-catalytic oxidization on hydrogen peroxide showed a linear dependence from 6.59 × 10 −6 to 2.20 × 10 −4 mol l −1 with R = 0.99947 ( n = 8). The linear regression equation was I p (mA) = 0.82949 + 0.00594C (μmol l −1) with errors of ±7.92833 × 10 −5 for the slope and ±0.01085 for the intercept with the detection limit of 1.46 × 10 −6 mol l −1. Thus, it is expected to find its application in neutral or weak alkali medium for biosensors.