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

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 layer-by-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 (π → π* 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 × 10−6 mol L−1 and a quantification limit (QL) of 8.6 × 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.