RESUMEN
Screen-printed sensors with chemically deposited boron-doped diamond electrodes (BDDE) were modified with different types of gold nanoparticles (AuNPs) according to a new original procedure. Physically and electrochemically deposited AuNPs had various sizes and also nanoporous character. They also differ in shape and density of surface coverage. The developed sensors were characterized using scanning electron microscopy and Raman spectroscopy. Their electrochemical properties were studied using cyclic voltammetry and electrochemical impedance spectrometry of selected outer sphere ([Ru(NH3)6]Cl3) and inner sphere (K3[Fe(CN)6], dopamine) redox markers. The application possibilities of such novel screen-printed sensors with BDDE modified by AuNPs were verified in the analysis of the neurotransmitter dopamine. The best analytical performance was achieved using printed sensors modified with the smallest AuNPs. The achieved limit of detection values in nanomolar concentrations (2.5 nmol L-1) are much lower than those of unmodified electrodes, which confirms the significant catalytic effects of gold nanoparticles on the surface of the working electrode. Sensors with the best electrochemical properties were successfully applied in the analysis of a model solution and spiked urine samples.
RESUMEN
New screen-printed sensor with a boron-doped diamond working electrode (SP/BDDE) was fabricated using a large-area linear antenna microwave chemical deposition vapor system (LA-MWCVD) with a novel precursor composition. It combines the advantages of disposable printed sensors, such as tailored design, low cost, and easy mass production, with excellent electrochemical properties of BDDE, including a wide available potential window, low background currents, chemical resistance, and resistance to passivation. The newly prepared SP/BDDEs were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. Their electrochemical properties were investigated by cyclic voltammetry and electrochemical impedance spectroscopy using inner sphere ([Fe(CN)6]4-/3-) and outer sphere ([Ru(NH3)6]2+/3+) redox probes. Moreover, the applicability of these new sensors was verified by analysis of the anti-inflammatory drug lornoxicam in model and pharmaceutical samples. Using optimized differential pulse voltammetry in Britton-Robinson buffer of pH 3, detection limits for lornoxicam were 9 × 10-8 mol L-1. The oxidation mechanism of lornoxicam was investigated using bulk electrolysis and online electrochemical cell with mass spectrometry; nine distinct reaction steps and corresponding products and intermediates were identified.
