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Nano silver: applications, advantages and disadvantages

September 24, 2019

Index

 
 

Nanotechnology and its advantages

 
People use nanotechnology and nanomaterials in everyday life because of their unique or rather different chemical and physical properties. It is common to find various products with nanomaterials on the market. Very often we find hydrophobic coatings for cars, self-cleaning surfaces preventing dirt accumulation or T-shirts that remain fresh and odour free for an extended period of time. Unique nanomaterial properties steam from their size i.e. particles between 1 and 100 nanometers. On this size scale insulating materials can become conductive, water-insoluble materials can become soluble and etc. Also nanotechnology often means that You need only small amounts of raw nanomaterials to add a desired feature to your product. This is an attractive feature both from environmental and business perspective. People should use nanomaterials as any other advanced technology, i.e. responsibly so that offered benefits would not become risks.
 

Properties of silver

 
Silver was used as an antiseptic from ancient times. In principle pure silver, silver salts, silver and silica mixtures, nano silver, silver colloids or other silver compounds have a similar mode of operation. All of these substances release silver ions to liquid phase. Some of these materials release silver ions abruptly but for a short period of time whilst others release silver ions slower but over a longer time scale. Released silver ions interact strongly with nitrogen, phosphorus and sulfur containing compounds in bacteria, algae and fungi. This is how silver efficiently inhibits growth of these microorganisms. Silver as any other material can be useful and it may possess risks – all of which depends on how it is used and how it is managed. Therefore proper and professional quantity and quality control is essential for best results. Manufacturers use silver often for an electrical contact, because as a material it is highly conductive. Applications range from electronics, automotives to energy industry as well as many others. For instance one can manufacture electrical contacts using magnetron sputtering, silver pastes, electrolysis, ink-jet printing and other technologies. In particular there is a growing demand for transparent, flexible and conductive electrical contacts. LG uses such electrodes in roll-up TV screen, which they released recently.
 

Nano silver and silver compounds: applications, advantages and disadvantages

 

Silver vs nano silver

Nano silver inherits many of the properties from silver and its one of the useful materials that can be applied in multiple industries. It has a high electrical and heat conductivity. Likewise it can effectively control growth of over 650 species of bacterial, fungi and algae by releasing silver ions [1]. Nano silver is not an allergen. When a size of a silver nanoparticle is below a few nanometers it becomes fluorescent. Furthermore, nano silver is an efficient light scatterer. All of these properties enable us to use nano silver in medical, household, hygiene products as well as in textiles, electronics, solar cells, water filters, industrial fluids, farms and many other areas.
 
Silver bars

Silver bars

Identical quantity of silver and nano silver would have different surface area. For example, silver spheres with four times smaller diameter have four times higher surface area [2]. Silver ions are released in a different manner from nano silver compared to silver salts and bulk silver [3]:
  • Silver ions emerge faster from nano silver than from regular silver.
  • Highly soluble silver salts will have high pace yet short duration for silver ion emission.
  • Ion release from nano silver is slower and more consistent over longer periods of time.

Silver toxicity and applications

When using nano silver or any other silver compound for formulating new or existing products it is crucial to assess possible environmental impact and possible interactions with living beings. Scientists has undertaken an extensive study to measure how nano silver and silver salts affect water invertebrates, fish, water plants, algae, microorganisms, rabbits and rats. They have observed most pronounced effect for invertebrates, algae and microorganisms. Rabbits and rats were injected intravenously, ingested orally and dermally exposed to nano silver. Scientists has found only minor fraction of nano silver in kidneys, because tested animals excreted most of the orally consumed nano silver. No dermal or eye sensitization was observed even at an excessive dosage [4]. Manufacturers use silver nanoparticles in electrical applications due to their good electrical conductivity. Nano silver has a different melting point compared to macroscopic silver so it a good material for inks and pastes. Nano silver based ink can be applied to plastic surfaces or other materials prone to deformation at higher temperatures. For instance, manufacturer of radio frequency identification devices (RFID) uses nano silver based conductive inks for printing  on plastic stickers for clothes and flexible electronics.
 
Radio frequency identifying device

Radio frequency identifying device (RFID)

 

References

 
  1. Dakal, T.C., Kumar, A., Majumdar, R.S. and Yadav, V., 2016. Mechanistic basis of antimicrobial actions of silver nanoparticles. Frontiers in microbiology, 7, p.1831.
  2. Oberdörster G., Oberdörster E., Oberdörster J.., 2005. Nanotoxicology: an emerging discipline evolving from studies of ultrafine particles. Environ Health Perspect, 113(7):823-39.
  3. Mitrano, D.M., Rimmele, E., Wichser, A., Erni, R., Height, M. and Nowack, B., 2014. Presence of nanoparticles in wash water from conventional silver and nano-silver textiles. ACS nano, 8(7), pp.7208-7219.
  4. http://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=env/jm/mono(2017)31&doclanguage=en