Gold Nanoparticle/Tetrapyridylporphyrin Hybrid Material: Spectroscopic and Electrocatalytic Properties and Sensor Application

An electrocatalytic active hybrid material prepared by successive stepwise coordinative deposition of 20 nm diameter gold nanoparticles (AuNP) with 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (TPyP) on fluorine-doped tin oxide (FTO) substrates previously modified with 3-mercaptopropylsilane is described. Their interaction and assembly were studied by UV-Vis spectroscopy and surface enhanced Raman spectroscopy to understand the kinetics as well as the conformation on the porphyrin macrocycle on the electrode surface as a function of its concentration. The hybrid nanomaterial was a build-up in reproducible successive deposition steps as confirmed by the linear rise of the absorption bands assigned to AuNP and TPyP as a function of the number of AuNP/porphyrin hybrid deposition steps, as supported by scanning electron microscopy (SEM) images. Electrodes modified with the hybrid nanomaterials were prepared and characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), as well as their electrocatalytic properties for the oxidation of nitrite and sulfite investigated. FTO electrodes modified with the AuNP/TPyP hybrid showed remarkable electrocatalytic activity as confirmed by reproducible and sensitive amperometric responses for sensing nitrite and sulfite in comparison to the bare electrode while reducing overpotentials respectively to 0.8 and 0.4 V and improving the dynamic range (linear response allowing quantification in the 50 to 500 µmol L-1 range) for detection of analytes.