Nanocluster

Metal nanoclusters consist of a small number of atoms, at most in the tens.^{[1] [2]}These nanoclusters can be composed either of a single or of multiple elements, and typically measure less than 2 nm.^[3][4] Such nanoclusters exhibit attractive electronic, optical, and chemical properties compared to their larger counterparts.^[3][4][5][6] Materials can be categorized into three different regimes, namely bulk, nanoparticles or nanostructures and atomic clusters. Bulk metals are electrical conductors and good optical reflectors, while metal nanoparticles display intense colors due to surface plasmon resonance.^[5][6] When the size of metal nanoclusters is further reduced, to 1 nm or less, in other words to just a few atoms, the band structure becomes discontinuous and breaks down into discrete energy levels, somewhat similar to the energy levels of molecules.^{[5][6][7][8][9]}

Therefore, a nanocluster behaves like a molecule^[10] and does not exhibit plasmonic behavior; nanoclusters are known as the bridging link between atoms and nanoparticles.^{[11][5][6][7][8][9][12][13][14][15][16]} The nanoclusters are also synonymously called as molecular nanoparticles.^[17]

To identify top publications, to identify top authors, to identify top journals, to identify top institutions on nanoclusters, visit the bibliometrics analysis page of Microsoft Academic.^[18]

History of nanoclusters[]

The concept of atomic nanoclusters dates to prehistoric times. The formation of stable nanoclusters such as Buckminsterfullerene (C₆₀) has been suggested to have occurred during the creation of the universe. The first set of experiments to form nanoclusters can be traced back to 1950s and 1960s.^[19][12] During this period, nanoclusters were produced from intense molecular beams at low temperature by supersonic expansion. The development of laser vaporization technique made it possible to create nanoclusters of a clear majority of the elements in the periodic table. Since 1980s, there has been tremendous work on nanoclusters of semiconductor elements, compound clusters and transition metal nanoclusters.^[12]

Size and number of atoms in metal nanoclusters[]

According to the Japanese mathematical physicist Ryogo Kubo, the spacing of energy levels can be predicted by

${\displaystyle \delta ={\frac {E_{\rm {F}}}{N}}}$

where E_F is Fermi energy and N is the number of atoms. For quantum confinement