Studies at Colorado State University will be described which have lead to the first two, apparently more general, 4-step mechanisms for nanocluster / nanoparticle formation and subsequent growth and agglomeration.  The pseudo-elementary steps for the first of the two, previously unknown mechanisms consist of (i) slow continuous nucleation, (ii) autocatalytic growth, and then (iii) bimolecular agglomeration and (iv) autocatalytic agglomeration.  In the second, closely related mechanism, the first three of the four steps are the same: (i) slow continuous nucleation, (ii) autocatalytic growth, (iii) bimolecular agglomeration, but then a different fourth step consisting of (iv') secondary autocatalytic growth.  Examples from both solution nanoparticle formation, and also from supported-nanoparticle heterogeneous catalyst formation, will be described. A recent lead reference is (see also the references cited therein): �A Four-Step Mechanism for the Formation of Supported-Nanoparticle Heterogeneous Catalysts in Contact with Solution: The Conversion of Ir(1,5-COD)Cl/?-Al2O3 to Ir(0)~170/?-Al2O3�, Kent, P. D.; Mondloch, J. E.; Finke, R. G. J. Am. Chem. Soc. 2014 , 136, 1930-1941. Time permitting, very recent evidence for bimolecular nucleation will also be presented�an exceedingly important finding in its own right because of its implications regarding the inapplicability of Classical Nucleation Theory (CNT) for strongly bonding, transition-metal nanoparticle systems.

Two 4-step mechanisms for nanocluster nucleation, growth, bimolecular agglomeration and then autocatalytic agglomeration or secondary autocatalytic growth

248th National Meeting (2014)

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