pH-dependent loading of Pt nanoparticles protected by dendrimer in calcium phosphate matrices

• Calcium phosphate was hybridized with dendrimer-protected Pt nanoparticle.
• The hybrids were mesoporous nanocomposites incorporating Pt nanoparticles.
• Crystalline structures were hydroxyapatite (alkaline pH) and monetite (acid pH).
• Amount of Pt nanoparticles in composites increased with decreasing pH.

Composites (CaP-DENPtNPs) of calcium phosphate particles (CaPs) with Pt nanoparticles protected by dendrimers (DENPtNPs) were synthesized at different pH following a hydrothermal synthesis method. The CaP matrix in CaP-DENPtNPs composites possessed hydroxyapatite crystalline structures at pH 12 and 8, but monetite crystals were obtained at pH 4. The particle sizes of the composites increased with decreasing pH, and at the same time the amount of PtNPs in the composites also increased. Furthermore, it was confirmed that CaP-DENPtNPs were mesoporous nanocomposites, and DENPtNPs nanoparticles were incorporated mainly on the surface of CaP particles at high pH, but most of DENPtNPs were encapsulated inside CaPs at low pH. The uptake of well-dispersed Pt nanoparticles up to 60 wt% in CaPs suggests the possibility of these materials as effective catalysts.

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