Nanotechnology is a large research area where many fields such as chemical, physics and engineering, and life sciences meet, enrich one another and provide a fertile ground for the development of science, engineering and technology. It deals with science, engineering, and technology conducted at the nanoscale, with dimensions in the range of 0.1 to 100 nm. K.E.Drexler is an American engineer who explained nanotechnology in depth and popularized the subject. He is known for increasing the value of molecular nanotechnology and being the father of nanotechnology. The potential of nanotechnology recognized by many industries and commercial products are being manufactured. The main areas of nanotechnology application are in electronics, photonics, pharmaceuticals and cosmetics, food and finishes for surfaces and textiles. It’s also the application of science to control matter at the molecular level.
Great growth in nanotechnology has opened up novel fundamental and applied frontiers in materials science and engineering, such as nanobiotechnology, bionanotechnology, quantum dots, surface-enhanced Raman scattering (SERS) and applied microbiology (Chan and Nie, 1998; Tian and Ren, 2004). The new packaging technologies will depend on the development of nanomaterials and nanoparticles; these may include nanoparticles, nanotubes, fullerenes, nanofibers, nanocylinder, and nanosheets (Cushen et al., 2012). The unique optical and electronic properties of this nanomaterial enable the development of a new generation of electronic devices, for example, nanotransistors to build future nanoprocessors, nanomemory and nanosensors (Sorkin et al., 2011 and Abadal et al., 2013).
Today, nanotechnology is a powerful interdisciplinary tool for the development of innovative products, and it is considered to be one of the key technologies of the future (Mihindukulasuriya et al., 2014). Nanotechnology involves the study, design, creation, synthesis, manipulation, and application of materials, devices, and functional systems through the control and exploitation of phenomena and properties of matter on a very small scale.
Noble Metal Nanoparticles
Noble metal nanoparticles (NPs) play an important role in the development of new biosensors and/or in the enhancement of existing biosensing techniques to fulfill the demand for more specific and highly sensitive biomolecular diagnostics. The unique physicochemical properties of such metals at the nanoscale have led to the development of a wide variety of biosensors like nanobiosensors for the point of care disease diagnosis, nanoprobes for in vivo sensing/imaging, cell tracking and monitoring disease pathogenesis or therapy monitoring and other nanotechnology-based tools that benefit scientific research on basic biology (Baptista et al., 2011).
Nanoparticle is one of the most common nanotechnology-based approaches for developing biosensors, due to their simplicity, physiochemical malleability and high surface areas (Azzazy and Mansour, 2009). They can measure between 1 to 100 nm in diameter, have different shapes and can be composed of one or more inorganic compounds, such as noble metals, heavy metals, iron, etc. The majority of them exhibit size-related properties that differ significantly from those observed in microparticles or bulk materials. Depending on their size and composition, we can observe peculiar properties, such as quantum confinement in semiconductor nanocrystals, surface plasmon resonance in some metal NPs and superparamagnetism in magnetic materials. Noble metal nanoparticles, in particular gold and silver have drawn remarkable interest in the recent few years as they exhibit strong absorption of electromagnetic waves in the visible region due to surface plasmon resonance (SPR), highly stable dispersions, chemical inertness, and biocompatibility (Burda et al., 2005 and Shukla et al., 2005). A small change in the NPs size, shape, surface nature, and distance between particles leads to tunable changes in their optical properties, which find application in the fabrication of optical devices, catalysis, surface-enhanced Raman scattering (SERS) (Flores et al., 2011) bioimaging (Erathodiyil et al., 2011) colorimetric sensors (Zhou et al., 2012) and so on.
As a result of their uses in the biological and chemical applications, researchers were inspired to integrate “green chemistry” approaches to functionalize the AgNPs and AuNPs using biomolecules like carbohydrate, proteins, amino acids, biopolymers, etc. (Mandal et al., 2007). Few groups have focused on green synthetic pathways for nanomaterials synthesis. Among them, some authors focus on green synthesis of noble metal nanoparticles using plant extracts, vitamins, biosurfactants, etc. in aqueous medium (Nadagouda et al., 2007).