The ability to detect even the slightest physiological change in the human body with high sensitivity and accurately monitor processes that impact human nature and their surroundings has led to an immense improvement in the quality of life. Biosensors continue to play a critical role across a myriad of fields including biomedical diagnosis, monitoring of treatment and disease progression, drug discovery, food control and environmental monitoring. These novel analytical tools are small devices that use a biological recognition system to investigate or detect molecules. This chapter covers the design and development of biosensors, beginning with a brief historical overview. The working principle and important characteristics or attributes of biosensors will also be addressed. Furthermore, the basic types of biosensors and the general applications of these biosensors in various fields will be discussed.

Noble transition metal chalcogenide gold selenide is a relatively unexplored layered material.

A series of MgO nanoparticles were prepared by first precipitating and isolating Mg(OH) 2 nanoparticles from Mg(NO 3) 2 at three different temperatures using NaOH followed by their thermal decomposition also at three temperature settings. The effects of temperature at which precipitation and thermal decomposition of the hydroxide occurred were studied to assess their influence on nanoparticle size and surface area. The synthesised nanoparticles were characterized using a suite of techniques including Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Scanning Electron Microscope (SEM) analysis. The average diameter range of MgO nanoparticles ranged between 15 and 35 nm, while for the precursor Mg(OH) 2 it varied between 28 and 45 nm. The nanoparticle surface area obtained from BET studies was found in all cases to increase from 77 to 106.4 m 2 /g with increasing temperature of precipitation. Antibacterial activities of the prepared Mg(OH) 2 and MgO nanoparticles were evaluated against the Gram-negative bacteria, Escherichia coli, and the Gram-positive bacteria, Staphylococcus aureus, using agar diffusion method. A correlation between surface area and antibacterial activity supported the mechanism of bacterial inactivation as the generation of reactive species. The Mg(OH) 2 and MgO nanoparticles both exhibited pronounced bactericidal activity towards the Gram positive bacteria than Gram negative bacteria as indicated by the extend of the zone of inhibition around the nanoparticle.

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