Amino acid-modified carbon interfaces have huge applications in developing electrochemical sensing applications. Earlier reports suggested that the amine group of amino acids acted as an oxidation center at the amino acid-modified electrode interface. It was interesting to locate the oxidation centers of amino acids in the presence of guanidine. In the present work, we modeled the arginine-modified carbon interface and utilized frontier molecular orbitals and analytical Fukui functions based on the first principle study computations to analyze arginine-modified CPE (AMCPE) at a molecular level. The frontier molecular orbital and analytical Fukui results suggest that the guanidine (oxidation) and carboxylic acid (reduction) groups of arginine act as additional electron transfer sites on the AMCPE surface. To support the theoretical observations, we prepared the arginine-modified CPE (AMCPE) for the cyclic voltammetric sensing of dopamine (DA). The AMCPE showed excellent performance in detecting DA in blood serum samples.

Synthesis of zirconium oxide (zirconia) (ZrO2) nanoparticles (ZNPs) through gel combustion technique as well as their structural and morphological characterization using XRD, SEM and TEM forms the central theme of this work. Along with structural and morphological characterization, an electrochemical detection of Serotonin (5-HT) is described using ZNPs Modified Carbon Paste Electrode (ZMCPE). The XRD results confirms that particles are well crystallized in tetragonal phase with average particle size of 35 nm. From SEM it can be observed that, the materials formed is porous in nature and the particles are seems to be uniform in size. HRTEM reveals that, the particles size in the order of 30–40 nm and the crystallinity was supported by SAED pattern of the ZNPs and these results are in close agreement with the results obtained through XRD. The Electrochemical detection of Serotonin (5-HT) was performed through cyclic voltammetric and differential pulse voltammetric method at different circumstances like concentration of the analyte, applied potentials and pH of the medium. The DPV experiments shows that ZMCPE displays high sensitivity for the quantification of serotonin (5-HT) in the range 10–50 μM and the limit of detection is 0.585 μM. The ZMCPE gives good reproducibility, high catalytic activity and sensitivity for the electrochemical quantification of Serotonin.