The role of CNT in surface defect passivation and UV emission intensification of ZnO nanoparticles

Abstract

We report on the controlled enhancement of the UV emission from ZnO nanoparticles synthesized via hydrothermal sol-gel routes. Various characterization techniques were used in this study to determine the crystal structure, defect formation, morphology and size of the ZnO nanoparticles. Firstly, the crystallinity of the ZnO nanoparticles was assessed by X-ray diffraction. The role of the precursor quantities on their morphology and bandgap states was investigated via transmission electron microscopy and photoluminescence spectroscopy, respectively. Subsequently, the impurity content and related bonds were evaluated by Fourier-transform infrared spectroscopy. In this work, the ZnO nanoparticles manifest a sharp UV emission along with a subdued green emission in the visible region. Conjoining ZnO with carbon nanotubes (CNT) suppressed the visible emission, as well as blueshifted and intensified the UV emission by ∼5-fold. These results suggest that CNT are effective in passivating the surface states of ZnO nanoparticles.

Relevance of alcoholic solvents in the growth of ZnO nanoparticles and ZnO hierarchical nanorod structures on their optical and opto-electrical properties

“…Sample ZnO-Et aq (figure 3(d)) shows needle-like and hexagonally shaped nanoparticles. In a previous study, the effect of varying the NaOH molar ratio on the morphology of ZnO nanoparticles with an aqueous ethanol solvent was investigated [8]. The authors demonstrated that reaction kinetics leading to the growth of ZnO nanoparticles are accelerated by increasing quantities of OH − ions in the solution.…”

“…The origin of the DLE is attributed to the combination of several point defects, such as V O , V Zn , O i, Zn i , and their complexes [45,46]. Whereas, the NBE emission originates from the recombination of excitons due to band-to-band transitions [8]. Moreover, the ratio of NBE-to-DLE is indicative of the crystalline quality of the sample.…”

“…In sol-gel synthesis of ZnO, the polar property and the nature of the organic solvent govern the reaction kinetics that subsequently affect the nucleation and growth of ZnO nanostructures [7]. Also, the presence of water in alcoholic solvents accelerates the growth process, leading to a non-uniform morphology of the nanostructures [8,9]. In contrast, using absolute alcohol produces spherically shaped nanoparticles (<10 nm) with a uniform size distribution, thus allowing a better control of the reaction kinetics [10].…”

Revealing the Dependency of Dye Adsorption and Photocatalytic Activity of ZnO Nanoparticles on Their Morphology and Defect States

“…Previous reports have demonstrated that the ZnO-nanoparticle synthesis route has an enormous impact on its photocatalytic activity [ 7 , 8 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. Synthesis routes tailor the morphology, size and specific surface of the nanoparticle.…”

Zinc Oxide Nanoparticles—Solution-Based Synthesis and Characterizations

“…These various structures achieved by the nanostructures of ZnO make these materials unique, with a diverse set of characteristics and prospective uses in a variety of nanotechnology disciplines. Several methods for the synthesis of ZnO nanostructures have been reported, such as microemulsion synthesis [48,49], sol-gel techniques [50][51][52], mechanochemical processing [53,54], spray pyrolysis and drying [55,56], thermal decomposition of organic precursor [57,58], RF plasma synthesis [59,60], supercritical water processing [61,62], self-assembling [63], hydrothermal processing [64][65][66], vapor transport process [67,68], microwave assisted synthesis [69,70], direct precipitation, and homogeneous precipitation [71,72].…”