Defect minimized Ag-ZnO microneedles for photocatalysis

Abstract

A facile solution processing strategy has been developed for the formation of Ag-modified ZnO microneedles at various calcination temperatures such as 300, 500, and 700 °C (AZ3, AZ5, and AZ7 respectively). Due to the heavy doping of AgNO 3 , Ag + ions have been incorporated in to the crystal lattice of ZnO in all the Ag-ZnO samples, which facilitated the formation of Ag-ZnO microneedle morphology with minimized defect states, and obviously, the plasmon peaks were observed due to Ag modification. These Ag-ZnO microneedle structures have been evaluated for their photocatalytic performance using methylene blue as model target contaminant and their activity was compared with the commercially available titania P25 photocatalyst. The photoactivity of all the Ag-ZnO microneedle structures was significantly higher than that of the commercially available P25 photocatalyst with the most active Ag-ZnO material having a photocatalytic activity ~ 1.4 times greater than that of P25 titania. Electronic supplementary material The online version of this article (10.1007/s11356-020-09433-5) contains supplementary material, which is available to authorized users.

Deep-Level Transient Spectroscopy Studies on Four Different Zinc Oxide Morphologies

“…By contrasting and comparing our DLTS results with the reported defect levels [43,47,55,62,65,67,74], the authors conclude that the origins of all the synthesized ZnO nanostructure's P 1 , P 2 , P 3 , P 4 , and P 5 defects are Zinc antisites (Zn o ), Zinc vacancies (V zn ), Zinc interstitials (Zn i ), Oxygen vacancies (V o ), and Oxygen interstitials (O i ), respectively. However, we did not identify any defect energy levels related to Oxygen antisites (O zn ).…”

“…However, researchers also have claimed that defect energies between 0.5 eV and 0.9 eV below the conduction energy band occur due to Oxygen vacancies (V o ) in ZnO crystalline samples [65][66][67][68][69]. Chai et al found a deep donor at 0.83 eV, which occurs due to Oxygen vacancies (V o ) [68].…”

“…The origin of the P 4 trap in ZnO is still controversial. According to the literature [65,67], we assume that the defect energy level around 0.75 eV to 0.94 eV is most likely due to Oxygen vacancies (V o ). Therefore, a proper interpretation of the origin of the P 5 trap is Oxygen interstitials (O i ) [74].…”