Self-assembled MnO2 nanowires were hydrothermally synthesized and electrically characterized under different conditions. The nanowires were approximately 3–10 µm long and about 20–100 nm in diameter. Single nanowires were aligned perpendicularly across two parallel gold electrode transducers by means of the dielectrophoresis (DEP) technique. Resistivity changes in synthetic air, nitrogen, and NO2 were tested in a range from 100 °C up to 300 °C. The resistivity changes were observed to account for the oxygen reduction on the NWs’ surface as the electrons were moving from the NWs to the oxygen. The resistivity was explored through a constant current arrangement test. Based on the resistivity changes, electrical properties, such as activation energy and type of semiconductor, were estimated.
Food safety is one of the most contemporary subjects under the scope of the scientific community since it is a fundamental issue for the general population. The desire to use a simple, inexpensive, easy-to-read package freshness-indicator led to a multitude of proposals for package real-time sensors for food freshness indicators. The sensors’ design strategy is to target a physical or chemical modification that occurs by the spoiling process, such as changes in temperature, moisture, or the detection of foodborne pathogens. One of the most common approaches is evaluating changes in pH, since a significant amount of food spoilage occurs with significant alterations (e.g., acidity increases on dairy products). However, some safety concerns emerge from the use of complex artificial chemical molecules such as pH indicators in active labels/packages for food. Naturally occurring anthocyanins are a safe alternative to classic pH indicators and have been applied as sensitive molecules for pH changes aimed at the development of active labels and active packing for food. This proposal briefly reviews the latest scientific contributions on the application of anthocyanins in food spoilage sensors.
The voltammetric behavior of hydroxocobalamin (OH-CBL) was firstly studied by employing a bare boron-doped diamond electrode as a working electrode. It was found that OH-CBL provided four anodic signals on BDDE in acidic supporting electrolytes and one cathodic signal. The anodic peak situated at +412 mV (vs. Ag|AgCl|KCl (sat.) recorded in 0.1 mol/L H2SO4) was found to be suitable for analytical purposes due to its position and shape. A novel voltammetric approach based on differential pulse voltammetry was developed and it was found as a sensitive analytical tool, with low limit of detection (LD = 13.2 nmol/L), applicable in analysis of vitamin preparations.
The aim of this work was the synthesis of functional hydrogel materials obtained via photopolymerization. The resulting systems were characterized in terms of chemical structure using Fourier transform infrared spectroscopy. Subsequently, their sorption capacity and surface morphology were determined along with roughness analysis. The resulting materials have been modified with fluorescein dye and can be used in many branches of industry and medicine, for example, in innovative diagnostic systems.
