Investigating the Photothermal Disinfecting Properties of Light-Activated Silver Nanoparticles

Abstract

The medicinal applications of noble metal nanomaterials are of considerable interest due to the unique properties they possess. The following contribution will showcase one of these properties, the photothermal effect produced by silver nanoparticles (AgNPs), and show how AgNPs can serve as potential viricidal materials for PPE (i.e., personal protective equipment) disinfection. In the context of the COVID-19 global pandemic, PPE disinfection is critical for addressing the shortfalls in the supply chains that ensure rapid and reliable sources of PPE for both medical professionals and the public. Two AgNP composites were prepared using both photochemical and pulsed laser ablation in liquid techniques. Then, to improve the durability of the NPs’ coating, they were mixed in a commercially available tent protectant solution or with a chitosan suspension. Transmission electron microscopy and spectroscopic analyses of the AgNP/protectant composites present mostly monodisperse, spherical particles of ∼5–10 nm in diameter, dependent on the route of nanoparticle synthesis. Blue light-emitting diodes (LEDs) were utilized to activate the surface plasmon resonance effects of the AgNP-coated materials at ∼400 nm. The resultant photothermal activation produced elevated surface temperatures on the fabrics, up to 150 °C, approaching the ignition temperature of the fabric samples, and well above the threshold required to deactivate the SARS-CoV-2 virus responsible for the COVID-19 pandemic. Photothermal heating was found to be largely dependent on both proximity of the coated sample surface to the LED source and illumination intensity. Furthermore, the rate of temperature increase was determined to be considerably faster than traditional or photothermal heating studies conducted on aqueous nanoparticle colloids, illustrating the efficiency of this methodology. Finally, durability studies of the AgNP/protectant coatings were examined and were found to maintain photothermal activity over long durations of exposure and after a 3-month storage timeframe. A marginal decrease in heating can be noticed following laundering with traditional detergent cleaners, mainly during the first washing cycle. The coating resistance to washing could be improved by the cross linkage of a biodegradable polymer, chitosan.

Nanomaterials for Photothermal Antimicrobial Surfaces

“…The intrinsic bactericidal property of silver nanomaterials is well-known and largely reported in the literature. − Cell death occurs due to the release of Ag + ions and to the direct “nanomechanical” action of the high energy nanoparticles surface, which promotes the disruption of bacterial membranes. Spherical silver nanoparticles (AgNPs) synthesized with sodium borohydride and sodium citrate as capping and reducing agents typically show a LSPR band centered around 400 nm. ,, The LSPR band, however, can be easily tuned and red-shifted to the NIR region just by changing the shape and size of the AgNPs. ,, Using silver nanomaterials with a LSPR band centered in the NIR allows enhancement of the intrinsic antibacterial effect of silver with a switchable, on demand photothermal effect under NIR radiation , (Figure A). The use of NIR light is also crucial for in vivo applications, since these wavelengths are in the biotransparent window, allowing direct irradiation through living tissue.…”

Photothermal Hyperthermia Study of Ag/Ni and Ag/Fe Plasmonic Particles Synthesized Using Dual-Pulsed Laser

“…The photothermal conversion efficiency of iron oxide nanoparticles, where the thermal response is predominantly owing to electronic transitions between d-orbitals of nearby Fe ions inside the lattice, deviates from the normal photo-induced hyperthermia [66]. In order to deactivate the SARS-CoV-2 virus, surface temperatures on the textiles were raised to as high as 150 • C by photothermal activation of spherical silver nanoparticles that ranged in diameter from 5 to 10 nm [5]. For the purpose of focused photothermal cancer treatment, plasmonic Ag nanoparticles with rounded forms and a diameter of 35.4 ± 1.6 nm have been reported [67].…”

“…Nanoscale studies of silver and gold have been explored for several applications due to their plasmonic properties, including photocatalysis [1], photoluminescence imaging [2], sensor [3], photothermal hyperthermia [4], and potential viricidal material for personal protective equipment [5]. Furthermore, they might also be utilized in other areas, such as liquid crystals, as a dopant in order to change the optical (linear/non-linear), dielectric, and electro-optical properties of the liquid crystals [6].…”

Dipole–multipole plasmonic coupling between gold nanorods and titanium nitride nanoparticles for enhanced photothermal conversion

“…2 When the irradiated light is in resonance with a plasmonic nanoparticle, part of the light energy will be absorbed and converted into the form of heat through electron-electron and electron-phonon interactions. 3 Due to this unique optical property, plasmonic nanomaterials have been widely applied in photothermal therapy, [4][5][6] solar energy collection, [7][8][9] bioimaging, [10][11][12][13][14] photonic disinfection, 15,16 solar desalination, 17,18 solar steam generation, 19,20 and so on.…”