Morphologic and electrochemical characterization of carbon nitride / Highly Oriented Pyrolytic Graphite Sensor

MARIANA I. ROJAS; OMAR E. LINAREZ PÉREZ; CÉSAR G. GOMEZ; LUCÍA BERNARDITA AVALLE

Congreso; II Brazil-Argentine Microfluidics Congress/ V Congreso de Microfluídica Argentina; 2019

FaMAF-UNC

A new sensor was recently developed, consisting of a highly oriented pyrolytic graphite (HOPG) surface modified by deposition of a graphite carbon nitride film $(g-C_3N_4)$ [1]. The $g-C_3N_4$ was synthesized by heat treatment from melamine and chemically exfoliated. The texture of the nano-particles was characterized by electron transmission microscopy (TEM), scanning electron microscopy (SEM) and X-ray scattering spectroscopy (EDS). The particles were suspended in ethanol and the particle size distribution was characterized by dynamic light scattering (DLS). Two size distributions were found, one of greater intensity with an average particle size of (2.8 $\pm$ 0.6) $\mu$m and another of low intensity with an average particle size of (140 $\pm$ 6) $\mu$m. Fine particles are suspended by the Browinian movement that opposes the action of gravity, but due to collisions between particles, the distribution evolves over time. Larger particles precipitate producing a change in the concentration of the suspension over time. These concentration changes were studied by UV-Visible spectroscopy, recording the absorbance spectrum as a function of time. The film was deposited drop wise on the HOPG surface. Then, the surface was characterized by SEM. The film had a discontinuous texture formed by particle agglomerates (islands) with an average distribution of (30.8 $\pm$ 0.6) $\mu$m, which covering the surface in $\theta$ = 0.15. The average thickness of the film, which is 49.54 $\pm$ 0.01, which corresponds to a nano-film, was determined by atomic force microscopy (AFM). Once the sensor surface was prepared, the electrochemical response for the hydrogen peroxide reduction reaction (HPRR) was evaluated, showing excellent electro-catalytic activity and analytical response, which allowed the quantification of hydrogen peroxide in a sensitive and reliable way until a detection limit of 0.12$\mu$M. Current transients were measured at different concentrations and potentials applied.\\\noindent{[1] CG Gomez, A.M. Silva, M.C. Strumia, LB Avalle, MI Rojas, Nanoscale 9 (2017) 11170-11179}