Voltammetric Tracing of Al(III) Using Supramolecular Metal-Polyphenolic Nanofilms Obtained via Electrochemically Assisted Self-Assembly

Supramolecular metal-polyphenolic thin sensor films represent a unique class of composite materials. Their properties and sensitivity can be easily modified via controlled self-assembly of their molecular components. Among the different assembly methods, electrochemically triggered processes are extremely powerful because they allow spatial confinement of the film buildup via an electrical stimuli-controlled process. In this article, an approach to employ the electrochemically assisted self-assembly of a multicomponent supramolecular film based on a naturally occurring polyphenol, tannic acid (TA), is featured. Here, the capacity of polyphenolic compounds to form complexes with metal ions, as well as to act both as reducing agents and stabilizers in colloidal synthesis of metal nanoparticles (NPs) is utilized. The electrochemically triggered self-assembly can be coupled with the ion – printing method, in which the targeted metal ion, in this case Al(III), is incorporated into the film during the synthesis and chemically removed afterwards. This procedure results in a template-like structure of the film with openings ready to bind the same metal ion from the probed solution, thus significantly improving the selectivity of the sensor formed and enhancing its applicability for sensing of toxic metal ions in complex aqueous solutions, such as physiological fluids

Electrodeposition and Characterization of SiOx Films Photoactive in Organic Solution

The photoactive silicon based films were potentiostatically deposited on Au electrodes from 0.5MSiHCl(3) dissolved in 0.1 M solution of tetrabutylammonium bromide (TBAB) in propylene carbonate (PC). The cyclic voltammetry measurements showed that the range of SiHCl3 reduction was between -2.4 and -2.9 V vs. Ag quasi reference electrode (Ag). Dependence of different ratio of silicon oxides (SiOx) and hydrogen terminated silicon (Si:H) on the electrodeposition potential was characterized by Raman and X-ray Photoelectron Spectroscopies (XPS). The spectroscopic studies revealed that the concentration of SiHCl3 and the electrodeposition potential were the most significant parameters of the deposition process. The highest concentration of lowly oxidized SiOx was observed for the films obtained at -2.7 V. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) observations revealed dependence of the layers' morphology on the deposition potential value i.e. the most uniform films were obtained at -2.7 V, whereas at -2.5 and -2.85 V the deposits were of a granular and sponge-like morphology. Deposits obtained at -2.5 and -2.7 V have shown n-type photoactivity in 0.1 M solution of TBAB in PC and the registered photocurrent density was up to 24 mu A x cm(-2)