Nanotechnology-General Aspects: A Chemical Reduction Approach to the Synthesis of Nanoparticles

Abstract

The role of nanotechnology is increasingly important in our society. Through it, scientists are acquiring the ability to understand the structure and properties of materials and manipulate them at the scale of atoms and molecules. Nanomaterials are at the forefront of the rapidly growing field of nanotechnology. The synthesis of nanostructured materials, especially metallic nanoparticles, has attracted tremendous interest over the past decade due to their unique properties, making these materials excellent and indispensable in many areas of human activity. These special properties can be attributed to the small size and large specific surface area of nanoparticles, which are very different from those of bulk materials. Nanoparticles of different sizes and shapes are needed for many applications, so a variety of protocols are required to produce monodisperse nanoparticles with controlled morphology. The purpose of this review is firstly to introduce the reader to the basic aspects related to the field of nanotechnology and, secondly, to discuss metallic nanoparticles in greater detail. This article explains the basic concepts of nanotechnology, introduces methods for synthesizing nanoparticles, and describes their types, properties, and possible applications. Of many methods proposed for the synthesis of metal nanoparticles, a chemical reduction is usually preferred because it is easy to perform, cost-effective, efficient, and also allows control of the structural parameters through optimization of the synthesis conditions. Therefore, a chemical reduction method is discussed in more detail-each factor needed for the synthesis of nanoparticles by chemical reduction is described in detail, i.e., metal precursors, solvents, reducing agents, and stabilizers. The methods that are used to characterize nanomaterials are described. Finally, based on the available literature collection, it is shown how changing the synthesis parameters/methods affects the final characteristics of nanoparticles.

Keywords: chemical reduction; metal nanoparticles; nanotechnology.

Figure 1

Number of publications in the field of nanotechnology according to the Web of Science (literature items that include the prefix “nano” in the topic); data as of 20 May 2023.

Figure 2

Potential applications of nanotechnology products.

Figure 3

Schematic representation of nanostructure fabrication methods, based on [50].

Figure 4

Selected important examples of chemical, physical, biological, and other methods for the preparation of metallic nanoparticles based on [54].

Figure 5

Scheme of nanoparticle formation (using silver as an example) by chemical reduction; based on [60].

Figure 6

Schematic representation of the ways to stabilize metal nanoparticles (using silver as an example) by using stabilizers: (a) surfactants, (b) polymers, (c) ligands; based on [137].

Figure 7

Schematic representation of parameters needed to be determined to characterize nanoparticles, based on [147].

Figure 8

Effect of Na₂CO₃/AgNO₃ ratio on the silver average size and its standard deviation. Reproduced with permission from [94].

Figure 9

TEM morphologies of nano-silver particles with different CTAB amounts, CTAB/AgNO₃: (a) 0.5, (b) 0.8, (c) 1.2. Reproduced with permission from [95].

Figure 10

TEM morphologies of nano-silver particles at different reaction temperatures: (a) 20 °C, (b) 40 °C, (c) 60 °C. Reproduced with permission from [95].

Figure 11

TEM images of nano-silver particles under different pH conditions: (a) pH = 3, (b) pH = 6, (c) pH = 9. Reproduced with permission from [95].

Figure 12

TEM image and particle size distribution of silver nanoparticles obtained at 1.0 mM (A) and 2.0 mM (B) of citrate of sodium solution. Reproduced with permission from [91].

Figure 12

TEM image and particle size distribution of silver nanoparticles obtained at 1.0 mM (A) and 2.0 mM (B) of citrate of sodium solution. Reproduced with permission from [91].

Figure 13

UV-Vis absorption spectra of the silver nanoparticles prepared via reduction in AgNO₃ at different initial concentrations. Reproduced with permission from [89].

Figure 14

UV-Vis absorption spectra of the silver nanoparticles prepared at different NaBH₄/AgNO₃ molar ratios. Reproduced with permission from [89].

Figure 15

UV-Vis absorption spectra of the silver nanoparticles prepared with different SDS/AgNO₃ weight ratios. Reproduced with permission from [89].

Figure 16

Absorption spectra of AgNPs at different pH values. Reproduced with permission from [96].

Figure 17

TEM image of nanoparticles formed at different pH values. Reproduced with permission from [96].

Figure 18

SEM micrographs at different temperatures and pH values. Reproduced with permission from [83].

Figure 19

The effects of (a) SDS/RuCl₃ MR and (b) NaBH₄/RuCl₃ MR on the particle size using a particle size analyzer. Reproduced with permission from [105].

Figure 20

Study the effect of different types of stabilizing agents on particle size using a particle size analyzer. Reproduced with permission from [105].