Development of L-stein sensor with multi-walled carbon nanotube supported metal catalysts

In this study, the determination activity of the amino acid L-cysteine in buffer solution (PBS, pH 7.2) was investigated by electrochemical methods. In electrochemical investigations, a glassy carbon electrode (GCE) was modified with metal-containing catalysts and an electrochemical sensor for L-cysteine was developed.In all phases of the research, Ru/MWCNT, Pd/MWCNT, Pt/MWCNT, Mo/MWCNT, Ga/MWCNT, and Co/MWCNT were synthesized as monometallic nanocatalyst systems as a result of chemical reduction by interacting carbon nanotube (CNT) surfaces with salt solutions containing Ru, Pd, Mo, Ga, Co and Pt. These synthesized catalysts were subjected to various characterizations such as X-ray diffraction spectroscopy (XRD), X-ray energy dispersive spectroscopy (EDX), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Induced plasma-mass spectroscopy (ICP-MS), Breaneur-Emmet-Teller (BET) spectroscopy and Ultraviolet visible region spectroscopy (UV-Vis). GCEs were modified with catalyst systems and their electrochemical activities for L-cysteine electrooxidation were investigated. Electrooxidation-reduction behavior of L-cysteine in PBS medium was investigated with these modified electrodes. Sensitivity, selectivity, detection type and interference effect studies were carried out to determine the electrochemical sensor quantities. Advanced electroanalytical methods such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance (EIS) were used. Accordingly, the sensitivities of GCEs modified with Ru/MWCNT, Ga/MWCNT, Mo/MWCNT, Co/MWCNTwere determined as 4307.05, 114, 200, 65 µA/mMcm2 respectively. The LOD/LOQ values of the respective electrodes were determined as 0.353/1.060, 0.05/0.15, 0.25/0.75, 0.02/0.06 µA/mMcm2 respectively. The analytical ranges of these catalysts were reported as 0-200, 0-200, 0-150, 10 – 500 μM. As a result of these electroanalytical studies, it was determined that the Co/MWCNT catalyst system performed better than other catalysts for the sensitive detection of L-cysteine. As a result of the studies, it was determined that all catalyst systems have the ability to sensitively detect L-cysteine and the best electrochemical sensor responses were obtained from Co/MWCNT modified GCE.