Composite Silica-Based Films as Platforms for Electrochemical Sensors

Sol-gel-derived silica thin films generated onto electrode surfaces in the form of organic-inorganic hybrid coatings or other composite layers have found tremendous interest for being used as platforms for the development of electrochemical sensors and biosensors. After a brief description of the strategies applied to prepare such materials, and their interest as electrode modifier, this review will summarize the major advances made so far with composite silica-based films in electroanalysis. It will primarily focus on electrochemical sensors involving both non-ordered composite films and vertically oriented mesoporous membranes, the biosensors exploiting the concept of sol-gel bioencapsulation on electrode, the spectroelectrochemical sensors, and some others.

Hydrogenase-based electrode for hydrogen sensing in a fermentation bioreactor

The hydrogen-based economy will require not only sustainable hydrogen production but also sensitive and cheap hydrogen sensors. Commercially available H₂ sensors are limited by either use of noble metals or elevated temperatures. In nature, hydrogenase enzymes present high affinity and selectivity for hydrogen, while being able to operate in mild conditions. This study aims at evaluating the performance of an electrochemical sensor based on carbon nanomaterials with immobilised hydrogenase from the hyperthermophilic bacterium Aquifex aeolicus for H₂ detection. The effect of various parameters, including the surface chemistry, dispersion degree and amount of deposited carbon nanotubes, enzyme concentration, temperature and pH on the H₂ oxidation are investigated. Although the highest catalytic response is obtained at a temperature around 60 °C, a noticeable current can be obtained at room temperature with a low amount of protein less than 1 μM. An original pulse-strategy to ensure H₂ diffusion to the bioelectrode allows to reach H₂ sensitivity of 4 μA cm^-2 per % H₂ and a linear range between 1 and 20%. Sustainable hydrogen was then produced through dark fermentation performed by a synthetic bacterial consortium in an up-flow anaerobic packed-bed bioreactor. Thanks to the outstanding properties of the A. aeolicus hydrogenase, the biosensor was demonstrated to be quite insensitive to CO₂ and H₂S produced as the main co-products of the bioreactor. Finally, the bioelectrode was used for the in situ measurement of H₂ produced in the bioreactor in steady-state.

Development of chromatography at the Department of Analytical Chemistry of National Taras Shevchenko University of Kyiv

An information about teaching and scientific activities in the field of chromatographic methods of analysis at the Department of Analytical Chemistry of the National Taras Shevchenko University of Kiev for the period from the 70s of the twentieth century till present days given. The perspective directions of the development of academic disciplines and scientific research of the department in this area are outlined.

Controlled electrochemically-assisted deposition of sol-gel biocomposite on electrospun platinum nanofibers

The modification of platinum nanofibers by silica using the electrochemically-assisted deposition is reported here. Pt nanofibers are obtained by electrospinning and deposited on a glass substrate. The electrochemically-assisted deposition of the sol-gel material then gives the unique possibility to finely tune the silica film thickness around these nanofibers. It also allows the successful encapsulation of a biomolecule (glucose oxidase was chosen here as a model) while retaining its biological activity, as pointed out via the electrochemical monitoring of H(2)O(2) produced upon addition of glucose in the medium. This silica-glucose oxidase composite offers the possibility of comparing systematically the influence of the deposition time on the bioelectrode response and to compare it with the particular features of the deposits. It was found that the film first grew uniformly around the nanofibers and then started to deposit between them, covering the whole sample (fibers and glass substrate), and tended to fully embed the nanofibers for prolonged deposition. The thickness of the silica film is critical for the electroactivity of the biocomposite, the best response being obtained for a silica layer thickness in the range of the fiber diameter (∼50 nm).