Metal oxides are considered to be potential alternative materials for silicon in the electronics industry because the range of electronic and optical properties they support is remarkable. Also, quasi-1D nanostructures have emerged as an important class of materials which facilitate, through controlled growth, making of novel electronic and optoelectronic devices. Formation of heterojunction using such quasi-1D metal oxides widens the application domain even further due to the integration of properties of both the materials and novel interface effects. In my research work, I have focused on the synthesis of p-type cuprous oxide (Cu2O) nanoneedles and their heterojunctions with ZnO and TiO2 using simple synthesis protocols. These materials have been studied for a few applications covering important current areas such as photo-sensing, field electron emission, photocatalysis and water splitting for hydrogen generation. The synthesis of cuprous oxide (Cu2O) nanoneedles was done directly on copper substrate using anodization method followed by annealing in vacuum. I have studied these Cu2O nanoneedles for photodetector application by making p-Cu2O nanoneedles/n-ZnO nanorods flip-chip heterojunction device. I have also observed that the nanowire heterojunction photo-response is far stronger as compared to a thin film heterojunction made of the same materials [Nanoscale, 2011, 3, 4706]. To further improve the properties of the heterojunction, an interesting Cu2O/ZnO hetero-nanobrush assembly has been fabricated. The hetero-nanobrushes show excellent field electron emission performance and photocatalytic activity compared to bare Cu2O nanoneedles [J. Mater. Chem., 2012, 22, 17055]. In my recent work, I have studied photo-electrochemical water splitting using Cu2O nanoneedles on copper as photocathode. This shows fairly good performance which got improved by the TiO2 capping on Cu2O nanoneedles.