Recently, many metal oxide nanostructures have attracted much attention due to their potential to develop different unique electrochemical sensors or nano sensor devices. Metal oxide-based nanostructures are widely used to develop electrochemical sensors due to their unique properties. The combination of different nanomaterials to form a composite configuration can produce a material with new synergetic properties. However, chemical properties, sensitivity, and stability of nanomaterial limit the number of possible nanocomposites. 

This thesis focuses on the synthesis of different morphologies and characterization of some metal oxides (ZnO, α-Fe₂O₃ and Au nanoparticles (NPs)), well suitable for electrochemical sensors applications. This thesis is divided into two parts: 

In the first part of this research work, the fabrication of α-Fe₂O₃ nanorods (NRs) and nanoparticles (NPs) using different techniques to further develop nanocomposites is presented. The α-Fe₂O₃ NRs were synthesized using different concentrations of urea using the hydrothermal method. Then, ZnO NRs were composited onto the α-Fe₂O₃ NRs surface forming a nano-heterojunction. This composite optical properties and electrical conductivity is investigated and presented in paper I. 

The α-Fe₂O₃ NPs were synthesized in different precursor concentrations by the dip coating techniques. The deposition of the α-Fe₂O₃ NPs onto the ZnO NRs surface samples, were then characterized by cyclic voltammetry for arsenic detection in various solutions and is presented in paper II. 

The development of screen-printed electrode for electrochemical sensors by drop casting of ZnO NPs and α-Fe₂O₃ NPs samples was demonstrated. The samples were characterized by linear sweep voltammetry method for arsenic (V) detection and are presented in paper III. 

In the second part of the thesis, Au NPs were deposited onto the ZnO/α-Fe₂O₃ nanocomposite surface and were utilized to develop an electrochemical sensor. The ZnO/α-Fe₂O₃/Au NPs samples were characterized by linear sweep voltammetry techniques and were presented in paper IV. 

As a summary, the development of nano sensors devices that possess high sensitivity, low limit of detection and have relatively fast response time were demonstrated. The developed sensors were tested for detecting Arsenic in drinking water. The results indicated that the developed sensor properties are acceptable when comparing the performance to the world health organization (WHO) regarding the lower allowed limit of Arsenic in drinking water.