Chapter 14 - Multifunctional gold nanoparticles for biosensing: effects of surface plasmon resonance, localized surface plasmon resonance, fluorescence, and aggregation

Abstract

The chapter explores various synthesis pathways, characterization, and biosensing applications where gold nanoparticles (Au NPs) have been employed abundantly. The chapter is organized with piecewise discussions on several processes of Au NPs synthesis, characterization, the factors that guide the size of Au NPs during synthesis, and the details on various types of Au NPs-based biosensors developed so far. The discussion initiates with the stepwise detailed discussions on all the available techniques for synthesizing Au NPs such as sodium borohydride reduction, sodium citrate reduction, mixed reducing agent reduction, and green synthesis, among other relevant methods. Thereafter, the chapter elucidates various factors such as the experimental procedure of synthesis, pH of the medium, mix rate, and other salts in the synthesis medium, which considerably determine the size, color, and stability of Au NPs. Following this, the attention has been given to jot down diverse characterization techniques for Au NPs, including UV-Visible spectroscopy, transmission electron microscopy analysis, and dynamic light scattering methods. These methodologies are the conventional ones accepted worldwide for the identification of morphology, materials, size, and size distribution of the Au NPs. Finally, the focus has been shifted toward the biosensing applications based on Au NPs, and their subsequent utility in fields like agriculture, forensic science, analytical calculations, food industry, and biomedical engineering. In particular, special attention has been paid to a few biosensing principles, like surface plasmon resonance, localized surface plasmon resonance, fluorescence, and salt aggregation methods in the detection processes. The chapter concludes with a tight summary on the pros and cons of different sensing mechanisms employing Au NPs.