Nano materials are prepared by top down and bottum up approach methods. In this bottum up more convenient. Very specifically sol-gel methods are most convenient one. By varying synthesis conditions, especially catalyst molecular size one can control the particle size of nano materials. Like this Is there any other methods are available in literature.
The answer totally depends on the preparation technique used. In each of them, parameters capable of influencing nanoparticle size may be different (and usually are).
In wet-chemistry approaches, as an example, concentrations in liquid phase, temperature, presence/absence of surface modifiers, and time are perhaps the most common and known parameters...
Another method is if we use Silanes, like octadecyltrimethoxy silane is used in the synthesis we can controle the resulting nanomaterials size. An another method is by heterogeneous sol-gel method also we control the particle size to some extent.
The process temperature is a critical parameter - higher temperatures lead to larger agglomerates and/or particles and better crystallization, while lower temperatures often result in amorphous materials. Also a post preparation heat treatment may be required, again, the higher the temperature and the longer the annealing time, the larger the crystallites (particles) usually are. The beat parameters depend on the actual synthesis route and the materials you are synthesizing!
Best regards, Dirk
Another influence is given by capping agents that prevent agglomeration and/or particle growth, and you always should be aware of phase transitions at more elevated temperatures, this is important e.g. in the TiO2 system!
If I may, allow me to ask for a clarification: are you interested in ways to control size in the sol-gel process or are you interested in other synthesis methods for nanoparticles and ways to control size in those processes?
Fundamentally, particle size and shape can be controlled either by exerting kinetic control or by thermodynamic control.
The answer totally depends on the preparation technique used. In each of them, parameters capable of influencing nanoparticle size may be different (and usually are).
In wet-chemistry approaches, as an example, concentrations in liquid phase, temperature, presence/absence of surface modifiers, and time are perhaps the most common and known parameters...
The nanomaterials size affected by the synthesis technique, like electrodeposition; current density, potential, pH, concentrations and additives can change the grain size.
Talking about silica sol-gel, not only the concentration of the silane is important, but also the concentration of water and ammonia in the ethanolic starting solution (using the Stober method).
it looks like you are using the sol-gel method to prepare your nanoparticles if I am not mistaken?. Reaction time (especially the time for the condensation process), temperature and the use of a capping agent/surfactant (CTAB is recommended) are critical as well as the concentration of your silanes. Last the catalyst acid Vs. base. and catalyst conc. Good luck.
One of the decisive factors a consequence of the size-dependence nanoparticles is the Ostwald-Ripening process. If consider a supersaturated solution μl - μs > 0, i.e., a solution in which the chemical potential of the solute in the solution is higher than the equilibrium solution. The solute will precipitate out of solution. Let us assume we have already solid particles of equal size in the solution. As long as the chemical potential of solution exceeds the chemical potential of the solids, solutes will deposit on the particles. Consequently, the chemical potential of the solution will decrease due to loss of solute to the solid phase. At some point, the solution will be in equilibrium with the solid particles.
ٰThis opinion Justifies the dimensional stability of nanometer particle.
Nano-particle size reduction depends on many factors like reaction method, controlling the temperature, reaction time, type of precursors we use , capping agents, power of reducing agents used etc.,
in microemulsions synthesis, the type and size of the surfactants have great effect on the particle size.
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