Why is silver used in nanotechnology

Nanosilver

Nanosilver is the abbreviation for silver nanoparticles. Nanosilver is therefore a particle of silver whose size is in the nanometer range (1 nm = 0.000001 mm), i.e. between 1 nm and 100 nm.

There are a number of applications and products for nanosilver or preparations with silver nanoparticles, for example in household appliances (coatings), functional clothing, cosmetic and hygienic articles, food supplements and in water treatment, among others.

 

effect

The motivation for the use of nanosilver in these products is often the antibacterial effect, which is based on the one hand on the biocidal properties of the silver and on the other hand on the increase in the surface area of ​​nanoparticles compared to their volume .

Under suitable conditions, nanosilver sets silver ions (Ag+) that have a toxic effect on microorganisms such as bacteria, (viruses?), fungi and algae. By reacting with sulfur-containing and phosphorus-containing proteins, these silver ions cause changes in the cell membrane, which disrupts cell metabolism and other cell functions, which can ultimately lead to cell death. At the same time, the silver nanoparticles act as a silver ion depot, which gradually add Ag+Release ions. Concentrations from 7 to 70 mg silver per liter have a toxic effect [1].

The health and environmental risks associated with the use of nanosilver are currently being discussed controversially and are the subject of current research.

 

synthesis

The production of nanosilver can take place in different ways with different sizes, shapes, charges and functionalizations; The most important material in the chemical process is the silver compound silver nitrate AgNO3.

 

A general distinction is made between two production routes:

* Top down - Methods are based on solids that are reduced in size by physical / mechanical processes until the individual particles are on the nanoscale. In these mostly complex and time-consuming processes, appropriate equipment is used (e.g. ball mills, colloid mills) or other processes are applied (plastic deformation).

* Bottom up - Methods deliver nanoparticles based on atomic or molecular basic units.

 

Bottom-up procedures include:

* precipitation

* Sol-gel process

* Microemulsion process

* Vapor deposition; Chemical vapor deposition, CVD

* Inert gas condensation (IGC)

* Electrodeposition

 

Delimitation of terms

Often - also in product names and product descriptions - the terms nanosilver, colloidal silver and silver dispersion are used synonymously. In general, the terms mentioned are defined by the respective particle sizes; Whether there is actually nanosilver actually depends on the particle size:

descriptionParticle sizeDescription, notes
Silver ions<>Silver ions dissolved in water Ag+
Nanosilver1 - 100 (300) nmHomogeneously distributed silver particles on surfaces or in liquid form as a dispersion of silver ions, metallic silver, etc.
Collodial silverup to 1000 nmHomogeneously distributed particles of slightly soluble silver compounds, silver ions and metallic silver. Cloudy liquid (opalescence).
Silver suspension> 1000 nmMixture of metallic silver particles and sparingly soluble silver compounds.

The terms silver sol or silver water are less common.

 

Sources and further information

* [1] - Nikolay Stefanov Plachkov:
Bactericidal treatment of plastics using silver and silver alloy nanoparticles.
Dissertation chemistry, Saarland University, (2006), urn: nbn: de: bsz: 291-scidok-6241.

* [2] - Siddhartha Shrivastava et al.:
Characterization of enhanced antibacterial effects of novel silver nanoparticles.
Nanotechnology, (2007), DOI 10.1088 / 0957-4484 / 18/22/225103.

* [3] - BUND (editor):
Nano silver - the gloss is deceptive.
BUND study, (2009).

* [4] - Nanosilver - tried and tested with a new label.
Internet chemistry news, Article, (2011).

* [5] - Safety of nanosilver unclear.
Internet chemistry news, (2011).

* [6] - Peter Heinzerling:
Colored silver colloids.
Chemkon, 'Das Experiment', (2011), DOI 10.1002 / ckon.201110166.

* [7] - Jörg Diendorf:
Silver nanoparticles. Synthesis, stability and biological effects.
Dissertation chemistry, University of Duisburg-Essen (2012), urn: nbn: de: hbz: 464-20120723-093245-9.

* [8] - Svitlana Chernousova, Matthias Epple:
Silver as an antibacterial agent: ion, nanoparticle, metal.
applied chemistry, (2012), DOI 10.1002 / anie.201205923.

* [9] - Silver particles in the washing machine.
Internet chemistry news, (2014).

 

Special:

Polyol process

* [S1] - Pierre-Yves Silvert et al.:
Preparation of colloidal silver dispersions by the polyol process. Part 1 - Synthesis and characterization.
Journal of Materials Chemistry, (1996), DOI 10.1039 / JM9960600573.

* [S2] - Pierre-Yves Silvert, Ronaldo Herrera-Urbina, Kamar Tekaia-Elhsissen:
Preparation of colloidal silver dispersions by the polyol process.
Journal of Materials Chemistry, (1997), DOI 10.1039 / A605347E.

 


Updated on 19th February 2019.

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