Zinc oxide based nano-composites for multifunctional applications
Creators: name: Esmaiel Zadeh Kandjani, Ahmad
Publisher: name: RMIT University
Year: 2024

description: Most of the spectroscopic and other analytical sensing technologies get frequently interfered from the instrumental noise and background in the spectra. Especially scattering based technique such as Surface Enhanced Raman Spectroscopy (SERS), where the Raman scattering signal component often has significant contributions from the background and noise, and therefore needs a proper removal of these unfavourable components from the signals. As the sensing technique in this thesis was based on SERS method, in this research a new methodology has been introduced to answer the needs for more reliable background correction for ultrahigh sensitive nanosensing applications. Photocatalytic activities of zinc oxide nano-arrays and ability of integrating this property with the other useful applications like biological and chemical sensing can bring a variety of novel applications. The controllable synthesis of this material with desired physical parameters, different substrates and also their ability to form heterojunction with the highest controllability are some of the advantages of using these nanostructures for different applications. These arrays have shown a good reproducibility and morphological control during synthesis procedure which makes them interesting materials to be used as SERS based sensing substrates in order to obtain higher reproducibility and sensitivity. Also, as zinc oxide is a photocatalyst, using this material can give broader functionality to the sensing platform. Not only can it make the senso re-generable, but also, it can be used for removing the heavy metal ions from the water. The combination of ZnO/Ag nano-arrays can make dual sensing ability of biological sensing and selective Hg2+ sensing abilities. Organic semiconductors have attracted many researchers’ attention as they are easy to control based on the band-gap, thus opening new applications where the inorganic semiconductors fail to operate. In addition, the heterojunction formation between organic and inorganic semiconductors can bring more possibilities and opportunities for developing new optoelectronics devices. In this regard, decorating silver nanostructures on the surface of an inorganic semiconductor can bring other functionalities to n-type ZnO nanostructures as Ag can be easily changed to metal-organic semiconductor molecule of AgTCNQ. The method for fabricating reproducible and simple approach to syntheses of inorganic-organic hybrids of AgTCNQ-ZnO (p-n heterojunction) was another aim of this research. In this thesis, this heterojunction has been synthesized and studied for increasing the activities of ZnO photocatalyst, where proposed method can be extended for synthesis of other controlled heterojunctions. The work presented in this thesis focuses on fine-tuning the morphology of ZnO semiconductors and preparing functional materials such as ZnO-metal and ZnO-organic semiconductor hybrids. Applications of these materials in photocatalytic degradation of environmental pollutants and sensing of ecotoxic chemical species are the major focus of the thesis. Also, and innovative approach has been introduced in this thesis that addressed the problems regarding the signal processing of Rama spectroscopy techniques to obtain trustful data for SERS analyses.