Gold Nanoparticles

Introduction• AuNPs also called as Gold Colloids.• Colloidal gold is a sol or colloidal

suspension of submicrometre-size nanoparticles of gold in a fluid, usually water.• The liquid appear deep red to black

in solution. In fact, a whole range of colours can be observed depending on the size of the AuNPs.

Introduction• AuNPs are the most stable metal nanoparticles• Due to the unique optical, electronic, and molecular-recognition

properties of gold nanoparticles, they are the subject of substantial research, with applications in a wide variety of areas, including electron microscopy, electronics, nanotechnology and materials science.

History• Medieval artistians were the first nanotechnologists.

They made stained glass by mixing gold chloride into molten glass.• They created tiny gold spheres which absorbed and

reflected sunlight in a way that produced a variety of colours.• They knew that by putting varying, tiny amounts of

gold and silver in the glass, they could produce the effects found in stained-glass windows.

HistoryThe Lycurgus cup• 4th-century Roman glass cage cup made

of a dichroic glass• Shows a different colour depending on

whether or not light is passing through it• Shows red color when lit from behind and

green when lit from in front.• Dichroic effect achieved by making the

glass with tiny proportions of gold and silver nps dispersed in colloidal form

SynthesisTurkevich method:

10 ml of 0.002 M aq. chloroauric acid H[AuCl4]

Stir for 15 minutes at 800 C

Add 10 ml of 0.01 M aq. Sodium Citrate

Stir for 30 minutes at 800 C

Clear Solution turns to red indicating formation of Gold nanoparticles

Characterization• TEM (Transmission Electron Microscopy)• SEM (Scanning Electron Microscopy)• Gel Electrophoresis• UV-Visible spectroscopy• Dynamic Light Scattering (DLS)

SEM image of colloidal gold

TEM image of colloidal gold

Applications• As conductors from printable inks to electronic chips.• To detect various cancers like breast cancer and oral cancer, and

other diseases like neoplasia and rheumatoid arthritis.• For cancer therapy to eradicate targeted tumors.• Lasers that react with AuNPs could be used to destroy cancer cells.• To optimize the bio-distribution of drugs to diseased organs, tissues

or cells, in order to improve and target drug delivery.• As catalyst in number of chemical reactions.

Applications• As an effective tools in cellular nanosurgery.• The red color in stained glass windows is due to colloidal gold.

Advantages• AuNP is simple for diagnosis.• It is less invasive.• It is non-toxic to human beings.• As compared to other metallic nanostructures, AuNP provide

advantages of their simple and fast preparation and bioconjugation.

Disadvantages• Optical signals of AuNPs may not be as strong as quantum dot.• It exhibits difficulties like biocompatibility, in vivo kinetics, and tumour

target efficiency.• It leads to acute or chronic toxicity.