Optimized reduction conditions for the microfluidic synthesis of 1.3 ± 0.3 nm Pt clusters

Abstract

Recently, small (\2 nm) and monodispersed Pt clusters has gained much attention due to their high catalytic activity in the aerobic oxidations. However, the chemical synthesis of small Pt clusters is not trivial; high temperature is often required to completely reduce the Pt 4?/2? ions to Pt 0 , which accelerates the growth of the Pt clusters. Here, we discussed a very simple microfluidic reduction of Pt 4? to Pt 0 by NaBH 4 in the presence of PVP that produces \2 nm Pt clusters in any variable reduction conditions. The microfluidic reduction conditions were optimized for the synthesis of possible smallest Pt clusters in terms of five reaction parameters: (1) temperature, (2) concentration of H 2 PtCl 6 , (3) molar ratio of NaBH 4 to Pt 4? ions, (4) molar ratio of PVP-monomer to Pt 4? ions, and (5) molecular weight/chain length of PVP. We found that possible smallest particles with average diameter 1.3 ± 0.3 nm were produced when aqueous solutions of H 2 PtCl 6 (4 mM) and NaBH 4 (40 mM) containing PVP (160 mM) were injected into the micromixer placed in an icebath at a flow rate of 200 mL/h. The produced particles were characterized by UV-visible absorption spectrophotometry, powder X-ray diffractometry and transmission electron microscopy.

Preference for low-coordination sites by adsorbed CO on small platinum nanoparticles

“…Pt:PVP particles with diameters of 1.4 nm were produced according to our previous protocol. 32,33 In brief, an icecooled Pt precursor (4 mM, 35 mL) and NaBH 4 solution (20 mM, 35 mL) both containing 80 mM PVP (with respect to monomer) were passed through a micromixer (interdigital triangular) at room temperature with the help of syringe pumps. Aer discarding the initial few milliliters, the eluent was collected to a conical ask with continuous stirring for an hour.…”

“…All of the optical spectra exhibited proles with a tendency to exponentially increase in the short wavelength with no obvious absorption peak due to intra-and inter-band optical transitions, as have been reported for Pt NPs. 32,33,[36][37][38]…”

Neuroprotective Effect of Platinum Nanoparticles Is Not Associated with Their Accumulation in the Brain of Rats

“…We synthesized nPts by reducing an aqueous solution of Pt salts with NaBH 4 , which can quickly and completely restore Pt ions [45]. It is important to note that the obtained nPts were characterized by small sizes (3 ± 1 nm), which could play a positive role in their ability to penetrate the BBB.…”

Advances in Microfluidic Synthesis of Solid Catalysts

“…Microfluidic reactor technology thus offers great development opportunities in the field of synthetic chemistry in both academia and industry, including the controllable synthesis of solid catalysts as well [28,29]. Up to now, various solid catalyst particles have been successfully synthesized in microflow, such as noble metal nanoparticles (Au, Ag, Pd, Pt) [30][31][32][33], bimetallic nanoparticles [34,35], supported-metal nanoparticles [36], metal oxide nanoparticles (ZnO, CeO 2 , TiO 2 ) [37][38][39], zeolites [40], metal-organic frameworks (MOFs) [41,42] and so on.…”