Voltammetric Studies on Gold Electrodes Coated with Chitosan-Containing Layer-by-Layer Films

A Comparative Study of PMETAC-Modified Mesoporous Silica and Titania Thin Films for Molecular Transport Manipulation

The manipulation and understanding of molecular transport across functionalized nanopores will take us closer to mimicking biological membranes and thus to design high-performance permselective separation systems. In this work, Surface-initiated atom transfer radical polymerization (SI-ATRP) of (2-methacryloyloxy)-ethyltrimethylammonium chloride (METAC) was performed on both mesoporous silica and mesoporous titania thin films. Pores were proven to be filled using ellipsometry and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Furthermore, the employed method leads to a polymer overlayer, whose thickness could be discriminated using a double-layer ellipsometry model. Cyclic voltammetry experiments reveal that the transport of electrochemically active probes is affected by the PMETAC presence, both due to the polymer overlayer and the confined charge of the pore-tethered PMETAC. A more detailed study demonstrates that ion permeability depends on the combined role of the inorganic scaffolds' (titania and silica) surface chemistry and the steric and charge exclusion properties of the polyelectrolyte. Interestingly, highly charged negative walls with positively charged polymers may resemble zwitterionic polymer behavior in confined environments.

Electrochemical Deposition of Polyelectrolytes Is Maximum at the Potential of Zero Charge

Electrochemical deposition of cationic and anionic polyelectrolyte on a Au electrode is studied as a function of applied potential between the electrode and the solution of monovalent electrolyte. The deposition is measured by open circuit potential relative to a pristine electrode in a reference solution (100 mM NaCl). The rate of deposition is measured by a home-built electrochemical-optical method in real time. It was discovered that the polarity of the potential and magnitude of the potential are not the primary reasons to enhance deposition. For example, both the amount and rate of deposition of negatively charged poly(styrenesulfonate) in NaCl are higher when the electrode is at -200 mV than at +200 mV with respect to the solution. The results are explained in terms of the charge state of the electrical double layer that is primarily controlled by supporting (small) ions.

Hybridized Tungsten Oxide Nanostructures for Food Quality Assessment: Fabrication and Performance Evaluation

Tungsten oxide based micro and nanosized structures possess good capacitance as well as enhanced rate capability. Such properties are useful in various applications including electrochemical supercapacitors. Apart from supercapacitance, WO3 and their 2D integrated structures have been modified using different methods to widen their range of the utility. Modification using layer coating, functionalization with other nanomaterial or molecules are methods that can be used to improve the core structure of WO3. But such modifications often alter electrochemical performance. The effects and outcomes of such modifications incorporated in WO3 structures were studied using electrochemical methods, sensing behavior, and morphological examination. One goal for such modifications was to improve robustness of the WO3 structures apart from any change in supercapacitance performance. After detailed electrochemical analyses of WO3 structures, a preliminary study was performed regarding the feasibility of the WO3 based sensors for food safety applications based on electrochemical detection of hazardous dyes in food. Preliminary results obtained after various electrochemical tests including pulsed voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy suggest the viability of WO3 structures for food safety applications.