Silver nanoparticles
Silver nanoparticles are particles of silver in the size range of 1-100 nanometers, they are widely used for their antimicrobial properties. They are yellow color in solution form and not the regular silver color. This is due to the nano size property of these particles.
Shabnam N, Sharmila P, Kim H, Pardha-Saradhi P (2016) Light Mediated Generation of Silver Nanoparticles by Spinach Thylakoids/Chloroplasts. PLoS ONE 11(12): e0167937. https://doi.org/10.1371/journal.pone.0167937
In the above image you can see the size of the particles are very small and they are mostly spherical in size. Such small particles cannot be easily visualized with regular optical microscopes they have to be seen through electron microscopes. Microscopes like TEM, SEM, are used to image such ultrasmall particles.
They have a high surface to volume ratios hence they show some unique properties compared to bulk.Silver nanoparticles (AgNPs) are widely used in many products in the market and there are toxicity concerns about them.
Silver nanoparticles can be synthesized by biological, chemical and physical methods. Biological include plant extracts, microbes, fruit extracts etc. Chemical methods includes use of synthetic reducing agents to reduce silver salts and capping with synthetic polymers.
They are widely used as antimicrobial agents. They are known to even destroy gram negative bacteria like Ecoli. They can be used against both gram positive and gram negative bacteria. They can be available in powder form or in colloidal form. There used in as wound healing agents in many dressings.
Image credits: www.dewwool.com
Do not consume silver nanoparticles, as it can be harmful. Research is still going on the toxicity of silver nanoparticles for humans. Nanoparticles of larger sizes are less toxic, and sometimes they are capped with some capping agents to make them less toxic. Toxicity is studied based on animal models first.