Coarsening of Au nanoparticles embedded in solid-supported lipid membrane at 80 °C under different humidity

Au nanoparticles (AuNPs) embedded in a lipid membrane were produced by direct deposition of Au on 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membranes in liquid crystalline state. The AuNPs embedded in DOTAP and DOPC membranes coarsened quickly at 80 °C in a humid environment (50% relative humidity) after 10 h (5.6 ± 1.5 → 8.7 ± 1.7 for DOTAP and 5.9 ± 1.8 → 10.4 ± 3.3 for DOPC). On the other hand, in a dry environment in which the lipid mobility was retarded the coarsening of the AuNPs was nearly completely suppressed at 80 °C. Meanwhile, the shape of the AuNPs annealed in a dry environment tended to be spherical whereas the final shape was dictated by the lipid head chemistry in the humid environment. Although polydispersity of the prepared AuNPs does not match the AuNPs fabricated using some of state-of-art techniques currently available, the annealing the AuNPs at a moderate temperature can be used as a means of tailoring the size and shape of the AuNPs distributed in a monolayer over a large area (2 cm × 2 cm).

Graphical abstract.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Au nanoparticles (AuNPs) were deposited in DOTAP and DOPC membranes. ► At 80 °C with no humidity, the AuNPs did not coarsen but became spherical in shape. ► With humidity, the AuNPs coarsened fast and became polyhedral. ► Coarsening behavior of the AuNPs also depended on the lipid head chemistry.