One of the most recognized and widely used treatment modality in cancer is radiation therapy which depends on the radiosensitivity of tumour tissue. Over the past few years there has been lot of interest in the use of formulations to enhance radiotherapeutic effects, especially using metallic (mainly gold) based nanoparticles. Our goal here is to fabricate nanoparticles (NPs) that can be delivered to tumor tissue to increase its radiosensitivity. This would increase efficiency of radiation absorption by the tumor tissue and reduce radiation doses delivered during radiotherapy. This could potentially decrease radiation exposure related side effects to patients. We have achieved this by synthesizing nanoparticles of high Z elements such as gold, silver and a more efficient bimetallic silver-gold size ranging from 3nm to 72nm using chemical reduction and hydrothermal method. The synthesized metallic nanoparticles were characterised using Ultraviolet (UV)-Visible Spectroscopy, Fluorescence spectroscopy and Dynamic Light Scattering. The metallic nanoparticles showed radiosensitizing activity in colloidal form by absorbing radiations when irradiated by 60 Co source which emits two gamma rays of energy 1173keV and 1332keV. Based on our results, we are of the opinion that such radio-sensitizing agent if injected into the tumour tissue would increase radiation absorption and enhance treatment effect with lower therapeutic radiation dosage.