DNAzyme-Amplified Electrochemical Biosensor Coupled with pH Meter for Ca2+ Determination at Variable pH Environments

For more than 50% of multiparous cows, it is difficult to adapt to the sudden increase in calcium demand for milk production, which is highly likely to cause hypocalcemia. An electrochemical biosensor is a portable and efficient method to sense Ca2+ concentrations, but biomaterial is easily affected by the pH of the analyte solution. Here, an electrochemical biosensor was fabricated using a glassy carbon electrode (GCE) and single-walled carbon nanotube (SWNT), which amplified the impedance signal by changing the structure and length of the DNAzyme. Aiming at the interference of the pH, the electrochemical biosensor (GCE/SWNT/DNAzyme) was coupled with a pH meter to form an electrochemical device. It was used to collect data at different Ca2+ concentrations and pH values, and then was processed using different mathematical models, of which GPR showed higher detecting accuracy. After optimizing the detecting parameters, the electrochemical device could determine the Ca2+ concentration ranging from 5 μM to 25 mM, with a detection limit of 4.2 μM at pH values ranging from 4.0 to 7.5. Finally, the electrochemical device was used to determine the Ca2+ concentrations in different blood and milk samples, which can overcome the influence of the pH.

Perovskite-Type Oxide-Based Dual Composite Cathode for Solid Oxide Fuel Cells: A Short Review

A fuel cell is an electrochemical device that provides efficient power generation. Solid fuel oxide cell (SOFC) is an electrochemical device that generates electrical energy and heat from the gaseous state of fuel using an oxidant. SOFC is a highly efficient and environmentally friendly power generation technology that generates electrical energy from hydrogen gas, natural gas and other renewable fuel. The implementation of SOFCs is still facing challenges because their performance needs to be improved. Constructing cells with solid material alone is difficult because good electrical contacts between the components must be maintained. The concept of a dual composite cathode is important for the development of SOFC single cells. Introducing dual composite cathode can create an ideal cathode microstructure that can improve phase contiguity and interfacial coherence. This paper reviews the behaviour of a perovskite-type oxide-based dual composite cathode of SOFC for the selection of suitable materials and the preparation of a dual composite cathode.