Dear Hyeonjeong Jang ,

Although in old scientific literature you can find a wide variety of names, nowadays the most general use of the term nanocluster indicates a cluster with less than a few hundreds of atoms. In the case of gold, you need about 300 atoms to form a spherical nanoparticle with 2 nm diameter, so that could be the limit.

Those gold nanoclusters (from a few atoms to 300) can exhibit different morphologies: flat islands with irregular edges, chain like-shape, quasi-spherical… In any case, they have higher surface/volume ratio than nanoparticles, so they are of particular interest for catalysis.

Regarding nanoparticles, they exhibit localized surface plasmon resonances (LSPRs). If the nanoparticles are spheres, the LSPR peak shifts to lower energy (i.e. longer wavelength) with increasing diameter. If they have other shapes, they can exhibit several LSPRs. For instance, gold nanorods have two LSPRs: one with low energy for light polarization along the rod axis, and another with high energy for light polarization perpendicular to it.

Dear Researcher,

The nanoclusters can be composed either of a single or of multiple elements and typically are less than 2 nm in diameter while nanoparticles size is typically between 10 nm to 100 nm. Moreover, metal nanoparticles display intense colors due to surface plasmon resonance whereas a nanocluster behaves like a molecule and does not exhibit plasmonic behavior. Nanoparticles have also a stable structure and compartment than nanoclusters in various applications, especially biomedical fields. However, nanoclusters exhibit attractive electronic, optical, and chemical properties compared to nanoparticles and are suitable for designing Nanobiosensors.

Please check the following manuscripts

Spontaneous growth of gold nanoclusters to form gold nanoparticles in the presence of high molecular weight poly(ethylene glycol)

Article Spontaneous growth of gold nanoclusters to form gold nanopar...

Gold nanoclusters are favoured by most researchers due to their strong stability in fluorescence and adjustability in fluorescence wavelength when compared to traditional organic fluorescent dyes. For gold nanoparticles with diameters between 3–100 nm, the strong surface plasmon resonance (SPR) dominates in the absorption spectrum, which is caused by collective excitation of free electrons. In contrast, ultra-small gold nanoparticles consisting of tens to hundreds of gold atoms, often called gold nanoclusters, show multiple absorption bands spanning the UV-visible NIR range because of discrete energy levels.

Interesting discussion dear Hyeonjeong Jang

I agree completely with points raised by Jose-Miguel Garcia-Martin and Soad Mohialdin

Thanks