Insights on the structural and electrical transport of sodium titanate nanotubes decorated with CuInS2 quantum dots heterostructures

Abstract

In this work we present the synthesis of nanoscale heterostructures comprising sodium titanate nanotubes Na2Ti2O5·H2O (NaNT) decorated with CuInS2 (CIS) quantum dots with different sizes and weight fractions. Our study focused on the structural, microstructural, electrical and optical characterization of the nanoscale heterostructure by means of high-resolution transmission electron microscopy, atomic force microscopy, grazing incidence small angle X-ray scattering, confocal Raman microscopy, UV–Vis and impedance spectroscopy analyses. In most cases, these nanoscale heterostructures exhibited considerable enhancement on the electrical conductivity explained in terms of efficient interconnections between the titanate nanotubes and CIS quantum dots. UV–Vis spectroscopy characterization showed a decrease in the optical band gap in comparison to the pure NaNT from 3.68 to 3.45 eV. Impedance spectroscopy analysis confirmed the efficient electrical interconnections between titanate nanotubes, yielding not only to a decrease in the titanate junction resistance but also to an apparent decrease in the junction barrier voltage. All these features could postulate these nanoscale heterostructures as good candidates as photoelectrodes in solar cell applications.