Flow technologies for the synthesis of chemical intermediates have great potential at the industrial level and the synthesis of nanoparticles (NPs) can speed up the development of new products. In this context, we could find the technology for the synthesis of NPs. The NPs (Au, Ag, or Pt) are synthesized in a single step and are functionalized with polymeric stabilizers (such as PVP, PVA, PEG, or others) or with thio-glycosidic fragments. Synthesis proceeds through the injection of the precursor and ligand into a tubular reactor wrapped around a UV lighting system. During exposure to the light source (20 min to 2 hours), the precursor is photo-reduced and the stabilized NPs are formed. To purify and concentrate nanoparticles, simple centrifugation is used to remove and recover the unreacted linker. The colloidal solution that was obtained is a stable and homogeneous mixture of nanoparticles with a diameter of 2-4 nm, which can be used either as it is or freeze-dried without losing its morphological and chemical properties.
The innovative features that this type of synthesis offers are many. Some characteristics are proper of the flow technology, such as high reproducibility, the ability to work continuously, the possibility of scale-up working in parallel, or the potential addition of any automated modules. Our synthetic pathway offers an alternative to batch processes and allows precise dimensional control in the ultra-small NPs size range. In addition, the synthesis proceeds without the use of co-solvents, toxic stabilizers, or chemical-reducing agents, obtaining a final product that requires a simple step of purification by centrifugation. The use of the UV photo-reduction system allows it to operate at room temperature and introduces an additional element of sustainability. The whole synthetic process can be easily performed in a sterile environment to obtain a final product with low biological contamination. The methodology (albeit behind further development) allows the synthesis of systems based on other noble metals such as silver and platinum.