Introduction
Gold nanoparticles are one of the earlier nanomaterials studied and are generally referred to as colloidal gold in biological research. Its particle size is generally between 1 and 100 nm, and it shows different colors with the change of particle size[1].
Spherical AuNPs possess useful attributes such as size and shape-related optoelectronic properties,large surface-to-volume ratio, excellent biocompatibility, and low toxicity. These properties make AuNPs an important tool in bionanotechnology . AuNPs exhibit several significant physical features Important physical properties of AuNPs include surface plasmon resonance (SPR) and the ability to quench fluorescence[2].Spherical AuNPs exhibit a range of colors (e.g., brown, orange, red and purple) in aqueous solution as the core size increases from 1 to 100 nm, and generally show a size-relative absorption peak from 500 to 550 nm[3].Furthermore, particles with high charges can cause double layers to form in aqueous environments, and they can be discrete, dispersed, or suspended in the solution.
Among the physical properties of AuNPs, localized surface plasmon resonance (LSPR), radioactivity and high X-ray absorption coefficient are widely used in the diagnosis and treatment of tumors. The LSPR of AuNPs can further lead to surface-enhanced Raman spectroscopy (SERS), surface enhanced fluorescence (SEF), photothermal conversion, photochemical conversion and colorimetric responses. These excellent qualities have been widely applied for non-invasive detection in vivo and in situ, imaging, PTT, PDT and in vitro diagnostics (IVD). The radioactivity of AuNPs can be used for radiotherapy and radionuclide imaging (RNI)[4].
As opposed to the bulk shape, the energy levels of electrons in a substance in nano-form are not as continuous. The containment of the electronic wave function in up to three physical dimensions separates them. This causes a change in surface area and electron containment; the change in material properties is controlled in the same way that melting point, fluorescence, electrical conductivity, and magnetic permeability are .Ion coaters are an easy and direct method for generating uniform gold nanoparticles with a narrow size distribution by combining an ion coater on glycerin with a viscous liquid capture medium[5].The surface plasmon resonance peak appeared at 530 nm in the absorption spectrum during the formation of gold nanoparticles; the red-shift with increasing particle size indicated that gold nanoparticles were successfully developed using the ion coater[6].
Application
Genomics
Immunoassay
Detection of Microorganisms
Targeted delivery
Clinical chemistry
Advantages
High stability
Good biocompatibility
Surface is easy to be modified
Precise control of size and shape
References
[1]Kourkoutis L F, Plitzko J M, Baumeister W. Electron microscopy of biological materials at the nanometer scale[J]. Annual review of materials research, 2012, 42(1): 33-58.
[2]Yeh Y C, Creran B, Rotello V M. Gold nanoparticles: preparation, properties, and applications in bionanotechnology[J]. Nanoscale, 2012, 4(6): 1871-1880.
[3]Jain P K, Lee K S, El-Sayed I H, et al. Calculated absorption and scattering properties of gold nanoparticles of different size, shape, and composition: applications in biological imaging and biomedicine[J]. The journal of physical chemistry B, 2006, 110(14): 7238-7248.
[4]Bai X, Wang Y, Song Z, et al. The basic properties of gold nanoparticles and their applications in tumor diagnosis and treatment[J]. International journal of molecular sciences, 2020, 21(7): 2480.
[5]Hammami I, Alabdallah N M. Gold nanoparticles: Synthesis properties and applications[J]. Journal of king Saud university-science, 2021, 33(7): 101560.
[6]Teimouri M, Khosravi-Nejad F, Attar F, et al. Gold nanoparticles fabrication by plant extracts: synthesis, characterization, degradation of 4-nitrophenol from industrial wastewater, and insecticidal activity–a review[J]. Journal of Cleaner Production, 2018, 184: 740-753.
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