Radial p-n nanowire heterojunction devices represent a favorable geometry to maximize the interfacial area and charge carrier separation due to the built-in field established across the junction. This report presents the functional characterization of a heterojunction device based on a single coaxial p-Si/n-ZnO nanowire that was integrated in a circuit by FIB nanolithography to study the electrical properties. Specifically, their photovoltaic and gas sensing performances were preliminary assessed. The gas sensing response of the p-n heterojunction could be usefully modulated by controlling the bias currents through the device, showing a complementary functionality of these nanoarchitectured devices. (C) 2012 Elsevier B.V. All rights reserved.