Dopamine-Sensing Characteristics and Mechanism by Using N2/O2 Annealing in Pt/Ti/n-Si Structure

Dopamine detection by using N2/O2 annealing in a Pt/Ti/n-Si structure is investigated for the first time. To achieve repeatable and stable dopamine detection, a Pt membrane is annealed at elevated temperatures of 500 to 700 °C. N2/O2 gas ambient is used to optimize the membrane. The Pt membrane with thicknesses from 5 to 2 nm is optimized. Novel Pt/Ti/n-Si Schottky contact in a metal–electrolyte–membrane–silicon (MEMS) structure detects dopamine with a low concentration of 1 pM. The Pt membrane with N2 ambient annealing shows the lowest concentration of dopamine sensing with a small volume of 10 µL, acceptable stability, and repeatability. Scan rate-dependent dopamine concentration sensing is also investigated in the two-terminal measurement method. This study is useful for the early diagnosis of Parkinson’s disease in the near future.

ZIF-8 Coupling with Reduced Graphene Oxide to Enhance the Electrochemical Sensing of Dopamine

A reduced graphene oxide@zeolitic imidazolate framework-8 (rGO@ZIF-8) based electrochemical sensor was developed and used for dopamine detection. ZIF-8 was rapidly prepared by zinc hydroxide nitrate (Zn-HDS, Zn5(OH)8(NO3)2·2H2O) as precursor. Subsequently, rGO was introduced to enhance the performance of ZIF-8 (e. g., high carrier mobility, favorable stability), and a label-free electrochemical dopamine sensor based on the composite material was obtained with high specific surface area and better conductivity verified by Brunauer-Emmett-Teller surface analysis and electrochemical impedance spectroscopy, respectively. Consequently, rGO@ZIF-8 complex exhibited an admirable electrochemical catalytic performance. For determination of dopamine, the sensor behaves wide linear range from 2.0 x 10-6 to 1.4 x 10-4 mol/L and lower detection limit of 2.0 x 10-8 mol//L (S/N = 3). It also showed sufficient repeatability and durability due to the coordinated amplification effect of rGO and ZIF-8.

Electrosynthesized Poly(o-aminophenol) Films as Biomimetic Coatings for Dopamine Detection on Pt Substrates

Dopamine (DA) is a neurotransmitter, and its levels in the human body are associated with serious diseases. The need for a suitable detection method in medical practice has encouraged the development of electrochemical sensors that take advantage of DA electroactivity. Molecularly imprinted polymers (MIPs) are biomimetic materials able to selectively recognize target analytes. A novel MIP sensor for DA is proposed here based on a thin film of poly(o-aminophenol) electrosynthesized on bare Pt. A fast and easy method for executing the procedure for MIP deposition has been developed based on mild experimental conditions that are able to prevent electrode fouling from DA oxidation products. The MIP exhibited a limit of detection of 0.65 μM, and appreciable reproducibility and stability. The high recognition capability of poly(o-aminophenol) towards DA allowed for the achievement of notable selectivity: ascorbic acid, uric acid, serotonin, and tyramine did not interfere with DA detection, even at higher concentrations. The proposed sensor was successfully applied for DA detection in urine samples, showing good recovery.