Detection of pH and Enzyme-Free H2O2 Sensing Mechanism by Using GdOx Membrane in Electrolyte-Insulator-Semiconductor Structure
Journal
Nanoscale Research Letters
Journal Volume
11
Journal Issue
1
Date Issued
2016
Author(s)
Kumar, P.
Maikap, S.
Qiu, J.-T.
Jana, S.
Roy, A.
Singh, K.
Cheng, H.-M.
Chang, M.-T.
Mahapatra, R.
Chiu, H.-C.
Yang, J.-R.
Abstract
A 15-nm-thick GdO x membrane in an electrolyte-insulator-semiconductor (EIS) structure shows a higher pH sensitivity of 54.2 mV/pH and enzyme-free hydrogen peroxide (H2O2) detection than those of the bare SiO2 and 3-nm-thick GdO x membranes for the first time. Polycrystalline grain and higher Gd content of the thicker GdO x films are confirmed by transmission electron microscopy (TEM) and X-ray photo-electron spectroscopy (XPS), respectively. In a thicker GdO x membrane, polycrystalline grain has lower energy gap and Gd(2+) oxidation states lead to change Gd(3+) states in the presence of H2O2, which are confirmed by electron energy loss spectroscopy (EELS). The oxidation/reduction (redox) properties of thicker GdO x membrane with higher Gd content are responsible for detecting H2O2 whereas both bare SiO2 and thinner GdO x membranes do not show sensing. A low detection limit of 1 μM is obtained due to strong catalytic activity of Gd. The reference voltage shift increases with increase of the H2O2 concentration from 1 to 200 μM owing to more generation of Gd(3+) ions, and the H2O2 sensing mechanism has been explained as well.
Type
journal article