LaMer process

V. K. LaMer, ed.. Retardation of Evaporation by Monolayers Transport Processes, Academic Press, New York, 1962. 

Under certain conditions both the diffusional growth and the aggregative growth pathways may lead to monodispersed" systems. As mentioned earlier, the mechanism by which the former process could yield uniform particles was proposed by Victor K. LaMer (6), whose original scheme, reproduced numerous times, is shown in Figure 1.1.4. This kind of process is most likely operational in the formation of nanosized particles or larger amorphous spheres. 

LaMer, Monomer Addition Growth Model. Most of the recent publications (13,18,37,43-45) concerning the Stober silica precipitation describe a first-order hydrolysis of TEOS as the rate-limiting process in the silica particle precipitation. The second reaction step, the condensation reaction, was found to be faster by at least a... 

Egon Matijevic, Ph.D. Victor K. LaMer Professor, Department of Chemistry and Center for Advanced Materials Processing, Clarkson University, Potsdam, New York... 

Lamer T, Spinnler HE, Souchon I, Voilley A (1996) Process Biochem 31 533... 

For several decades, Ostwald s work was the foundation of crystallization theory. In 1950, an American chemist, Victor Kuhn LaMer (1895-1966), advanced our understanding of crystallization of colloidal sols. LaMer assumed that crystallization was a diffusion-driven process (LaMer, 1952 Boistelle and Astier, 1988), as described in previous chapters. LaMer s model is described in three steps, presented in Figure 4.1. In the initial steps of the reaction, the concentration of the molecular materials builds until a critical concentration is reached. This critical concentration, called supersaturation, can be written as... 

In the application of equation (69) an arbitrary value of a is chosen so as to give calculated activity coeflScients which agree with those derived by direct experiment the proper choice of a is made by a process of trial and error until a value is found that is satisfactory over a range of concentrations. There is no doubt that the Gronwall-LaMer-Sandved extension represents an important advance over the simple Debye-Hilckel treatment, for it frequently leads to more reasonable values of the mean ionic diameter. The validity of equation (69) has been tested by a variety of activity measurements and the results have been found satisfactory were it not for the tedious nature of the calculations it would probably be more widely used. 

Colloidal particles with a narrow size distribntion have been pursued by colloid chemists for a long time. The work of LaMer and Dinegar gave us some basic principles for the formation of monodispersed particles. According to the theory, to produce colloidal particles having a narrow size distribution, the nucle-ation and growth process must be carefully controlled. It should also be noted that many experimental results contradict this theory. For example, many monodispersed particles are formed by the association of subunits of small particles. Privman et al. proposed a theory for the growth of monodispersed particles in solutions in order to explain the experimental results. 

Lamer T and Voilley A. Influence of different parameters on the pervaporation of aroma compounds. In Bakish. R., ed.. Proceedings of the 5th International Conference. Pervaporation Process in the Chemical Industry. Englewood, NJ Bakish Material Corporation, 1991 110. 

As one would expect, the understanding of the mechanism of the formation of monodispersed colloids by precipitation has been of major concern to workers in the field. For a long time the concept developed by LaMer was generally accepted that is, such dispersions should be generated, if a short lived burst of nuclei in a supersaturated solution is followed by controlled diffusion of constiment solutes onto these nuclei, resulting in the final uniform particles. This mechanism is indeed operational in some, albeit limited, cases, and more often only at the initial stage of the precipitation process. 

Voilley A, Lamer T, Nguyen T, Simatos D. 1989. Extraction of aroma compounds by pervaporation. In Bakish R (ed.). Proceedings of the Fourth International Conference on Pervaporation Processes in the Chemical Industry, p. 332. Bakish Materials Corporation, Englewood, NJ. 

Oda S, Inada Y,Kato A,Matsudomi N,Ohta H (1996)J Ferment Bioeng 80 559 Lamer T, Spinnler HE, Souchon I,Voilley A (1996) Process Biochem 31 533 Moiinari F, Aragozzini F, Cabral JMS, Prazeres DMF (1997) Enzyme Microb Technol... 

Although the LaMer mechanism describes the different stages of nanocrystal nucleation and growth, it does not account for the kinetics of these processes. The kinetics of nanocrystal nucleation can be easily derived on the assumption that nuclei are spherical and grow isotropically. Then, the magnitude of surface free energy required to create a nanoparticle of radius r is ... 

Lamer T,SpinnlerHE,Souchon I andVoilley A (1996), Extraction of benzaldehyde from fermentation broth by pervaporation . Process Biochem, 31,533-542... 

Even the concept of molecular switch is an important topic from a variety of perspectives ranging from the modelling of biological processes to the design of devices for molecular electronics. The idea of switching directly the NLO properties has recently been envisioned [151]. Lamere et al. have reported on the synthesis and characterization of a boronate chromophore built up from two push-pull NLO sub-units in a quasi-free rotation around a chemical axis. They discussed on the possibility to use such a system as a molecular NLO switch induced by an electric field [152]. 

Martinez, J.A., Zhang, Z., Svetlov, S.I., Hayes, R.L., Wang, K.K., and Lamer, S.F. 2010. Calpain and caspase processing of caspase-12 contribute to the ER stress-induced cell death pathway in differentiated PC 12 cells. Apoptosis An International Journal on Programmed Cell Death, 15(12), 1480-1493. doi 10.1007/sl0495-010-0526-4. 

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