Process for the synthesis of nanosize metal-containing nanoparticles and nanoparticle dispersions
View Patent ↗The invention relates to a process for producing morphologically uniform and virtually monodisperse metal-containing nanoparticles, characterized in that the separation both in time and space of the nucleation and growth processes is achieved by regulation of the temperature and volume flows, with the reaction and particle formation preferably being initiated and carried out in a suitable microstructured modular reactor system. Modularization of the microreaction plant (micro heat exchanger, residence reactor, micromixer, etc.) allows optimal setting of the respective chemical and process-engineering process parameters and thus the preparation of virtually monodisperse and morphologically uniform nanoparticles.
1. A liquid phase process for preparing metal-containing nanoparticles and/or nanoparticle dispersions in a reactor, wherein nucleation and growth processes are separated in time and space by controlling the temperature and the volume flows.
2. The process according to claim 1 , wherein the process is carried out in a microreaction technology system.
3. The process according to claim 2 , wherein the process is carried out in a modular microreaction technology system.
4. A liquid phase process for preparing metal-containing nanoparticles and/or nanoparticle dispersions in a microreactor comprising the following steps:
a) injecting into or passing through a microreaction technology system of a pre-mixed first precursor solution containing at least one reactant (1 and/or 2) and at least one surfactant (1 and/or 2) with volume flow throughputs of preferably from 0.05 ml/min to 500 ml/min,
b) optionally injecting or passing of a second precursor solution containing at least one further reactant and at least one surfactant, and mixing of the first and second precursor solutions via a suitable mixing element to give a reaction solution,
c) initiating a chemical reaction by heating rapidly the reaction solution comprising the first and second precursor solutions to a temperature at which reaction and nucleation take place to a significant extent,
d) controlling growth of the nanoparticles by thermostatting/heating the reaction solution in a residence time reactor to a temperature of more than 150° C., with the temperature having to be lower than the temperature required for nucleation.
5. The process according to claim 4 , wherein, in a step e), particle growth is stopped abruptly by cooling the reaction solution, with the cooling temperature being lower than the nucleation temperature and the growth temperature.
6. The process according to claim 4 , wherein the process is carried out continuously.
7. The process according to claim 4 , wherein the temperature increase for step c) is achieved in a microheat exchanger with the aid of a heat transfer area-to-reaction volume ratio (A/V ratio) of at least 20 000 m 2 /m 3 .
8. The process according to claim 4 , wherein the temperature for step d) in the microstructured reactor is maintained with the aid of an A/V ratio of at least 1000 m 2 /m 3 and the residence time distribution thereof is distinctly narrower than in a tube or in a capillary, due to the use of static mixing internals.
9. The process according to claim 4 , wherein, in step e), particle growth in a microheat exchanger is stopped by abruptly lowering the temperature, with an A/V ratio of at least 20 000 m 2 /m 3 .
10. The process according to claim 4 for the synthesis of core-shell nanoparticles, doped nanoparticles, nanorods, nanoplates, nanotetrapods or polybranched nanostructures, wherein fresh precursor solution is metered in and step d) is repeated in a step f) which can be repeated any number of times.
11. The process according to claim 4 , wherein the nanoparticles prepared have a characteristic average particle dimension of up to 40 nm and a 0D, 1D, 2D or 3D structure.
12. The process according to claim 4 , wherein the particle size distribution has a standard deviation of ±10 nm.
13. The process according to claim 4 wherein the temperature at which reaction and nucleation take place is more than 200° C.
14. The process according to claim 4 wherein the nanoparticles property distribution does not exceed a standard deviation of ±20%.