The Pros and Cons of the Use of Laser Ablation Synthesis for the Production of Silver Nano-Antimicrobials

Abstract

Silver nanoparticles (AgNPs) are well-known for their antimicrobial effects and several groups are proposing them as active agents to fight antimicrobial resistance. A wide variety of methods is available for nanoparticle synthesis, affording a broad spectrum of chemical and physical properties. In this work, we report on AgNPs produced by laser ablation synthesis in solution (LASiS), discussing the major features of this approach. Laser ablation synthesis is one of the best candidates, as compared to wet-chemical syntheses, for preparing Ag nano-antimicrobials. In fact, this method allows the preparation of stable Ag colloids in pure solvents without using either capping and stabilizing agents or reductants. LASiS produces AgNPs, which can be more suitable for medical and food-related applications where it is important to use non-toxic chemicals and materials for humans. In addition, laser ablation allows for achieving nanoparticles with different properties according to experimental laser parameters, thus influencing antibacterial mechanisms. However, the concentration obtained by laser-generated AgNP colloids is often low, and it is hard to implement them on an industrial scale. To obtain interesting concentrations for final applications, it is necessary to exploit high-energy lasers, which are quite expensive. In this review, we discuss the pros and cons of the use of laser ablation synthesis for the production of Ag antimicrobial colloids, taking into account applications in the food packaging field.

Keywords: food packaging; laser ablation synthesis in solution; nano-antimicrobials; silver nanoparticles.

Figure 1

Schematic representation of some of the main methods available for the synthesis of silver nanoparticles (AgNPs). Reprinted from [61], with permission from Elsevier.

Figure 2

Schematic representation of the known mechanisms of antibacterial action of silver nanoparticles and silver ions. Reprinted from [108], with permission from Elsevier.

Figure 3

Schematic diagram of bactericidal activity of AgNPs on Gram-positive and Gram-negative bacteria. Reprinted from [105], an open access article distributed under the Creative Commons Attribution License. ROS: reactive oxygen species.

Figure 4

Size-dependent effects of AgNPs in vitro. In general, adverse cellular effects are associated with exposure to smaller AgNPs. One exception is DNA damage; the magnitude of response appears to not depend on AgNP size. Reprinted from [100], with permission from Elsevier.

Figure 5

Summary of the NMs obtained by laser ablation of Au, Ag, and Fe bulk targets in different solvents with 9-ns pulses at 1064 nm and 10 J cm⁻². Reprinted from [166], an open access article distributed under the Creative Commons Attribution License.

Figure 6

UV-visible absorption spectra of AgNPs prepared for 30 min ablation times in ethylene glycol, chitosan, and deionized water. Reprinted from [168], an open access article distributed under the Creative Commons Attribution License.

Figure 7

TEM images and size distribution of silver colloids prepared by (a) 120-fs and (b) 8-ns laser pulses. Reprinted from [173], with permission from Elsevier.

Figure 8

Absorption spectra of Ag nanoparticles in acetone prepared at (a) 532 nm wavelength; (b) 1064 nm wavelength at several fluences (samples 1 and 4: 14 J/cm², samples 2 and 5: 18 14 J/cm², samples 3 and 6: 22 J/cm²). Reprinted from [175], with permission from Springer Nature.

Figure 9

Absorption spectra of Ag colloidal solution prepared with various wavelength laser lights. (a) The laser beam was not focused and laser fluence was 900 mJ/cm²; (b) The laser beam was focused and laser fluence was >12 J/cm². Reprinted from [176], with permission from Elsevier.

Figure 10

Ablated mass versus laser pulse fluency. Reprinted from [179], an open access article distributed under the Creative Commons Attribution License.

Figure 11

STEM images and corresponding histograms of silver colloidal nanoparticles prepared by laser ablation at different laser fluences (a) 2122.2 J/cm²; (b) 3183.3 J/cm² and (c) 4244.0 J/cm². Reprinted from [165], with permission from Elsevier.

Figure 11

STEM images and corresponding histograms of silver colloidal nanoparticles prepared by laser ablation at different laser fluences (a) 2122.2 J/cm²; (b) 3183.3 J/cm² and (c) 4244.0 J/cm². Reprinted from [165], with permission from Elsevier.