Sensitive Electrochemical Capsaicin Sensor Based on a Screen Printed Electrode Modified with Poly(sodium 4-styrenesulfonate) Functionalized Graphite.

A sensitive capsaicin sensor was constructed based on a poly(sodium 4-styrenesulfonate) functionalized graphite modified screen printed electrode (PSS-Grp/SPE) in this study. The PSS-Grp and poly(diallyldimethylammonium chloride) functionalized graphite (PDDA-Grp) were easily synthesized by interacting Grp with PSS and PDDA through sonication, and resulted in negative and with positive charges on the surface, respectively. The prepared PSS-Grp and PDDA-Grp were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet and visible spectroscopy (UV-vis). The electrochemical performance of PSS-Grp in a 50 µM capsaicin solution presented a current density of 33 µA cm-2, which was much higher than the PDDA-Grp of 1.5 µA cm-2. Our study showed that capsaicin could interact better with strong negative charges on the PSS-Grp/SPE surface to give a higher electrochemical response. The direct electrochemical sensing of capsaicin was achieved at PSS-Grp/SPE using differential pulse stripping voltammetry (DPSV) under the optimized conditions.

Selective and sensitive electrochemical detection of glucose in neutral solution using platinum-lead alloy nanoparticle/carbon nanotube nanocomposites.

Electrodeposition of Pt-Pb nanoparticles (PtPbNPs) to multi-walled carbon nanotubes (MWCNTs) resulted in a stable PtPbNP/MWCNT nanocomposite with high electrocatalytic activity to glucose oxidation in either neutral or alkaline medium. More importantly, the nanocomposite electrode with a slight modification exhibited high sensitivity, high selectivity, and low detection limit in amperometric glucose sensing at physiological neutral pH (poised at a negative potential). At +0.30 V in neutral solution, the nanocomposite electrode exhibited linearity up to 11 mM of glucose with a sensitivity of 17.8 microA cm(-2) mM(-1) and a detection limit of 1.8 microM (S/N=3). Electroactive ascorbic acid (0.1 mM), uric acid (0.1 mM) and fructose (0.3 mM) invoked only 23%, 14% and 9%, respectively, of the current response obtained for 3 mM glucose. At -0.15 V in neutral solution, the electrode responded linearly to glucose up to 5 mM with a detection limit of 0.16 mM (S/N=3) and detection sensitivity of approximately 18 microA cm(-2) mM(-1). At this negative potential, ascorbic acid, uric acid, and fructose were not electroactive, therefore, not interfering with glucose sensing. Modification of the nanocomposite electrode with Nafion coating followed by electrodeposition of a second layer of PtPbNPs on the Nafion coated PtPbNP/MWCNT nanocomposite produced a glucose sensor (poised at -0.15 V) with a lower detection limit (7.0 microM at S/N=3) and comparable sensitivity, selectivity and linearity compared to the PtPbNP/MWCNT nanocomposite. The Nafion coating lowered the detection limit by reducing the background noise, while the second layer of PtPbNPs restored the sensitivity to the level before Nafion coating.