Platinum nanoparticles incorporated in silsesquioxane for use in LbL films for the simultaneous detection of dopamine and ascorbic acid

摘要

We describe the preparation of platinum nanoparticles (PtNPs) using the 3-n-propylpyridinium silsesquioxane chloride (SiPy ~+Cl ~-) as a nanoreactor and stabilizer. The formation of PtNPs was monitored by UV-Vis spectroscopy by measuring the decrease in the intensity of the band at 375 nm, which is attributed to the electronic absorption of PtCl6 2- ions. TEM images of Pt-SiPy ~+Cl ~- nanohybrid indicated an average size of 3-40 nm for PtNPs. The Pt-SiPy ~+Cl ~- was used as a polycation in the preparation of layerby- layer films (LbL) on a glass substrate coated with fluorine-doped tin oxide (FTO) alternating with the polyanion poly(vinyl sulfonic acid) (PVS). The films were electrochemically tested in sulfuric acid to confirm the deposition of Pt-SiPy ~+Cl ~- onto the LbL films, observing the adsorption and desorption of hydrogen (E _(pa) = 0.1 V) and by the redox process of formation for PtO with E _(pa) = 1.3 V and E _(pc) = 0.65 V. FTIR and Raman spectra confirmed the presence of the PVS and Pt-SiPy ~+Cl ~- in the LbL films. A linear increase in the absorbance in the UV- Vis spectra of the Pt-SiPy ~+Cl ~- at 258 nm (φ → φ transition of the pyridine groups) with a number of Pt- SiPy ~+Cl ~-/PVS or PVS/SiPy ~+Cl ~- bilayers (R = 0.992) was observed. These LbL films were tested for the determination of dopamine (DA) in the presence of ascorbic acid (AA) with a detection limit (DL) on the order of 2.6 x 10 ~(-6) mol L ~(-1) and a quantification limit (QL) of 8.6 x 10 ~(-6) mol L ~(-1). The films exhibited a good repeatability and reproducibility, providing a potential difference of 550 mV for the oxidation of DA with AA interferent.