Anisotropic Gold Nanoparticles: Synthesis, Properties, Applications, and Toxicity

Abstract

Anisotropic gold nanoparticles (AuNPs) have attracted the interest of scientists for over a century, but research in this field has considerably accelerated since 2000 with the synthesis of numerous 1D, 2D, and 3D shapes as well as hollow AuNP structures. The anisotropy of these nonspherical, hollow, and nanoshell AuNP structures is the source of the plasmon absorption in the visible region as well as in the near-infrared (NIR) region. This NIR absorption is especially sensitive to the AuNP shape and medium and can be shifted towards the part of the NIR region in which living tissue shows minimum absorption. This has led to crucial applications in medical diagnostics and therapy ("theranostics"), especially with Au nanoshells, nanorods, hollow nanospheres, and nanocubes. In addition, Au nanowires (AuNWs) can be synthesized with longitudinal dimensions of several tens of micrometers and can serve as plasmon waveguides for sophisticated optical devices. The application of anisotropic AuNPs has rapidly spread to optical, biomedical, and catalytic areas. In this Review, a brief historical survey is given, followed by a summary of the synthetic modes, variety of shapes, applications, and toxicity issues of this fast-growing class of nanomaterials.

Formation of Variously Shaped Gold Nanoparticles by Anabaena laxa

“…Currently, the non-typical (non-spherical) shaped nanoparticles have attracted interest because their structural, optical, electronic, magnetic, and catalytic properties are different from spherical particles and allow wider applications [14]. Additionally, the smallest particles (size approximately 5 nm), which were obtained in the cultures of A. laxa supplemented with the lowest tested concentration of gold ions (0.1 mM), seemed to be a stable form of seed particles up to the fourth day after the reduction.…”

“…The AuNPs have found numerous applications in different disciplines of science and industry, such as: catalysis [9], detection of toxic ions [10], biosensors and bioprobes [11], molecular recognition [12], and nanoelectrodes [13]. Non-spherical particles also demonstrate catalytic activity on textured surfaces and the enhancement of the surface enhanced Raman spectroscopy SERS effect [14]. Some NPs have been examined as antibacterial agents [15,16].…”

Predictor Packing in Developing Unprecedented Shaped Colloidal Particles

“…and size of metallic structures have remained under the extensive debate and generated significant interest in several newly emerging areas of nanoscience and nanotechnology [20][21][22]. It has been shown that shape entropy drives the phase behavior of systems of anisotropic shapes through directional entropic forces [23].…”

Spatial Analysis of Metal–PLGA Hybrid Microstructures Using 3D SERS Imaging

“…[26] However, anisotropic nanoparticles are often grown in water or other solvents with high dielectric constants, which may hinder their encapsulation in polymers. [27][28][29] We present here a universal method to embed metal nanoparticles of various composition, shape and size, in PLGA nanomaterials by means of the so-called electrohydrodynamic (EHD) co-jetting process. This process has been well established for PLGA over the last decade and offers a high throughput method to synthesize PLGA microgels of different sizes and morphologies.…”