Metal clusters quantum size effect

There are families of metal cluster compounds (Fig. 6.40) containing metal clusters surrounded by ligands (Lewis Green, 1982). In small cluster compounds, the electrons are paired, but in large clusters there will be closely spaced electronic levels, as in metal particles. In such clusters, quantum size effects would be expected. Benfield et al (1982) have found intrinsic paramagnetism in H20sio(CO)24 below 70K as expected of an osmium particle of approximate diameter of 10 A the excess paramagnetism increases with cluster size in osmium compounds (Johnson et al, 1985). 

Model calculations for the Cs suboxides in comparison with elemental Cs have shown that the decrease in the work function that corresponds to an increase in the Fermi level with respect to the vacuum level can be explained semi-quantitatively with the assumption of a void metal [65], The Coulomb repulsion of the conduction electrons by the cluster centers results in an electronic confinement and a raising of the Fermi energy due to a quantum size effect. 

Metal cluster Assembly of metal atoms exhibiting distinct quantum size effects. 

The average g-value of metallic Na, reported values [11], Ag = -0.0024 is to be compared with -0.0008 for bulk Na. Whether this difference is due to a quantum size effect cannot be decided, as surface effects and interaction of the metallic cluster with the zeolitic host may also come into play. 

Size Dependence of E (Ag, -Ag ). The quantum-size effect on metal clusters redox properties in solution is the most important feature for cluster chemistry in solution. Most of data have been obtained on silver clusters suitable as an experimental model (J-4, 22). 

Phase-separated metal-containing block co-polymers formed by ROMP offer interesting possibilities for the controlled formation of semiconductor and metal nanoclusters, which are of intense interest as a result of their size-dependent electronic and optical properties, as well as their catalytic behavior. Zinc-containing block co-polymers generated by ROMP have been shown to form ZnS nanoclusters within the phase-separated organozinc domains upon treatment with gaseous The cluster sizes generated were up to 30 A and their small size led to quantum size effects. For example,... 

Apart from their interesting structures, molecular clusters are intensively studied because of their physical properties. It has been shown for transition-metal clusters that small uniform particles of a certain size show interesting electronic, size-dependent effects (quantum size effects). In Au55(PR3)i2Cl6 a few electrons are trapped in a metallic state and single electrons tunnel between the cluster units. (SET, single electron tunneling).Such effects have yet to be observed in main-... 

---