electrochemical approaches to myriad medical and environmental challenges are highly attractive due to their strong potential for extensive and green applications. point of care diagnostics through the electrochemical monitoring of clinically and environmentally relevant molecules are gaining attraction due to their low cost and simple fabrication procedures. the development of highly stable and sensitive electrochemical sensors/biosensors, for a wide variety of biomolecules in actual samples, makes these methods alternative analytical tools in different pharmaceutical and hospital laboratories. electrochemical biocatalysis is an additional promising area to address the removal of bacteria for the generation of safe potable water. as the world’s population is dealing with lack of access to safe drinking water, photoelectrocatalysis has been investigated as a very efficient technique for the destruction of pathogenic bacteria in water. nanomaterials with dimensions of less than 100 nm have great potential to enhance the performance of electrochemical methods, due to their excellent electronic, mechanical, and thermal properties. these materials have the capacity to greatly enhance biocatalytic activity, and thus greatly improve the performance of electrochemical sensors/biosensors. this remarkable improvement in bacterial catalysis has been studied using a novel synergistic approach, which incorporates both photocatalysts and electrocatalysts. for my phd thesis, we designed a high-performance electrochemical sensor based on graphene for the sensitive detection of acetaminophen, valacyclovir, and mixtures thereof. this sensor was fabricated through the concurrent electrochemical reduction and deposition of graphene oxide (go) onto a glassy carbon electrode (gce) using cyclic voltammetry (cv). the electrocatalytic properties of the electrochemically reduced graphene (erg) for the oxidation of acetaminophen were analyzed via cyclic voltammetry (cv), differential pulse voltammetry, (dpv) and chronoamperometry. for comparison, various erg/gces were prepared under different electrodeposition cycles to optimize the required quantity of erg. our experimental results indicated that the optimized erg/gce possessed robust activity toward the electrochemical oxidation of acetaminophen, valacyclovir, and their mixture, leading to the development of a highly sensitive electrochemical sensor for its detection. an extremely low detection limit of 2.13 nm for acetaminophen, and 1.34 nm for the exclusive detection of valacyclovir was achieved. a wide linear detection range of from 5.0 nm to 800 μm was achieved via the combination of an amperometric technique and dpv. the developed electrochemical sensor was further employed for the determination of acetaminophen, valacyclovir, and their mixture in human serum, with excellent recovery, ranging from 96.08% to103.2%. the fabricated electrochemical sensor also demonstrated high selectivity, stability and reproducibility.