20
$\begingroup$

Gold is a very popular metal in nanotechnology. It is often used as a substrate in electronic applications, as a core of functionalized nanoparticles, and more.

Why is gold so attractive? Why are other metals not as popular? What makes gold the go-to material for new applications?

$\endgroup$
  • $\begingroup$ Not only gold. Other noble metals are useful: platinum, palladium, for example. $\endgroup$ – Gimelist Oct 16 '15 at 9:42
  • 1
    $\begingroup$ I can say something form catalysis perspective. It's because of Sabatier principle. To make a good catalysts you must have an optimum trade off between adsorption and desorption facility. Also in most of the cases gold's antibonding orbital is slightly higher than it's fermi level. That's why it offers very low interaction between metal and adsorbate which is interesting for the reaction to occur and also low binding energy facilitates the desorption and hence increases the yield. $\endgroup$ – mamun Dec 14 '15 at 19:56
  • $\begingroup$ You should be more specific in regard to which field of nano-technology. I thought this question related to electronics and would have answered as such, but you seem interested in colloidal solutions. $\endgroup$ – A.K. Dec 15 '15 at 11:48
  • $\begingroup$ @A.K. I'm not sure how you got this idea. I'm very much interested in electronics actually $\endgroup$ – Sparkler Dec 15 '15 at 13:35
  • $\begingroup$ Gold is easy to purify to very high degrees, and hence comparably cheap. Even if this sounds counterintuitive. $\endgroup$ – Gerhard Dec 21 '15 at 5:01
11
$\begingroup$

First, let's look at gold's properties.

  • Gold is the most malleable of all metals. This malleability alone is very useful in aiding scientists to create such small gold nanoparticles.
  • Gold also reflects infrared radiation very well and is an excellent conductor of heat and electricity.
  • Generally, gold is not easily affected by oxygen and is generally nonreactive with most acids and bases. This property serves well especially in the human body where there are an abundant of acidic and basic fluids and the circulatory system is enveloped with oxygen. Because gold is generally unaffected by most acids, bases, and oxygen, there is more assurance for scientists that their golden nanoparticles for medicinal uses would not react with other things before reaching their specific target.
  • Going back to gold's ability to reflect infrared radiation, an essential reason why physicians, scientists, and researchers utilize nanotechnology is to track down certain cells (cancer, etc), molecules, or processes. Thus, it is important to use such a metal that can reflect radiation to tell them where their targeted molecules are or where their targets are going. In essence, gold nanoparticles are suitable for "staining," or showing contrasts in cells more visible, such as in tissue samples. This can provide higher spatial resolutions for labeling applications.
  • Gold, as a nice heat conductor, can also absorb heat very well, as I mentioned earlier, and in these biotechnologies, strong absorption of light energy is also another crucial aspect for allowing gold to then dissipate this absorbed light energy in its surroundings so that these heated areas can also be tracked and help with drug delivery purposes.

Here are some references:

$\endgroup$
  • 3
    $\begingroup$ point one is not important, imo. gold nanoparticles are made by precipitation, not dispersing bulk material. $\endgroup$ – Karl Oct 13 '15 at 21:16
8
$\begingroup$

I don't know why everyone missed this point. At nanoscale materials tends to have some novel physical and chemical properties comparing to its macro scale. One such phenomenon which is seen especially in metal nanoparticles is Surface plasmon resonance (SPR)

Wikipedia:

"Surface plasmon resonance (SPR) is the resonant oscillation of conduction electrons at the interface between a negative and positive permitivity material stimulated by incident light. The resonance condition is established when the frequency of incident photons matches the natural frequency of surface electrons oscillating against the restoring force of positive nuclei. SPR in subwavelength scale nanostructures can be polaritonic or plasmonic in nature."

It is because of this phenomenon gold nanoparticles have different colours according to its shape and size. enter image description here

This phenomenon thus enables gold nanoparticles to be used in wide applications such as sensors, fluorescent agents, etc...

$\endgroup$
5
$\begingroup$

Gold is special:

  1. Electrodes: gold electrodes are advantageous because bulk gold is inert, so electrodes are air/water stable (do not oxidise), such that devices are more reliable in the long term.
  2. Catalyst: gold nanoparticles can be used as a catalyst (high surface to volume ratio, unlike bulk gold), for filtering purposes for example.
  3. Quantum dots: gold nanoparticles change color as a function of nanoparticle diameter (30-90 nm), making it useful in quantum dot applications.
  4. Low melting temperature: melting temperature of gold nanoparticles is relatively low (~300C), making it susceptible to thermal pre/post treatment.
  5. Easy functionalization: gold can be easily functionalized using thiol (sulfur) groups, making it possible to design adsorption behaviour and self-assembly.
  6. Conversion of light to heat: the absorption spectrum of gold nanoparticles can be tweaked by modifying the size of the nanoparticles, which influences on gold's conversion of light to heat. This can be used to thermally kill tumours.
$\endgroup$
  • $\begingroup$ In my knowledge we dont use gold nanoparticles as quantum dots. Quantum dots are semi-conductor nanoparticles where as gold nanoparticle is a metal $\endgroup$ – Eka Jan 10 '16 at 18:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.