Characterization and optical properties of TeO2/ZnO nanocomposites synthesized in a narrow temperature range

Two different TeO2- and ZnO-based nanocomposites were synthesized by a continuous two-step gas phase transport process with a pre-deposited Au catalyst at different synthetic temperatures. The morphology and composition of the TeO2 nanowires showed successive changes with ZnO precursor powder with increasing temperature, going from TeO2 nanowires to TeO2/ZnO nanocomposites. The photoluminescence (PL) spectra of these samples indicated that (1) the as-synthesized TeO2 nanowires have a broad blue emission band at 420 nm as well as green (540 nm), orange (607 nm), and red (723 nm) emissions, and (2) the TeO2/ZnO nanocomposites display not only a narrow violet emission band at 380 nm but also green (510 and 540 nm), orange (607 and 645 nm), and red (723 nm) bands. The optical quality of two different samples, based on the emission intensity ratio (I excitonic/I defect) related to band to band transitions and deep level defects, has a tendency to decrease rapidly with increasing synthesis temperature. Simple control of the synthetic temperature zone between two different oxide composites may cause functional, compositional, and optical changes in the product.