Gold nanoparticles, also called AuNPs, are nanoparticles of gold that appear red in solution. AuNPs are very stable and have unique optical and electronic properties that make them useful for a wide range of applications. Historically, medieval artists first created AuNPs unintentionally when mixing gold into glass to produce stained glass windows with various colors. Today, AuNPs are commonly synthesized using the Turkevich method and characterized using techniques like TEM, SEM, and UV-Vis spectroscopy. Current applications of AuNPs include uses in electronics, medicine for cancer detection and therapy, and as catalysts.

1. Gold Nanoparticles

2. 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.

3. 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.

4. 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.

5. History
The 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

6. Synthesis
Turkevich 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

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

8. SEM image of colloidal gold

9. TEM image of colloidal gold

10. 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.

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

12. 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.

13. 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.