Journal
ACS NANO
Volume 10, Issue 8, Pages 7443-7450Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.6b01721
Keywords
nanoparticle; self-assembly; in situ TEM; nanoparticle chains
Categories
Funding
- National University of Singapore [NUSYIA-FY14-P17]
- Singapore National Research Foundation's Competitive Research Program [NRF-CRP9-2011-04]
- NSF DMR grant [1309765]
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Using in situ liquid cell transmission electron microscopy (TEM), we visualized a stepwise self-assembly of surfactant-coated and hydrated gold nanoparticles (NPs) into linear chains or branched networks. The NP binding is facilitated by linker molecules, ethylenediammonium, which form hydrogen bonds with surfactant molecules of neighboring NPs. The observed spacing between bound neighboring NPs, similar to 15 angstrom, matches the combined length of two surfactants and one linker molecule. Molecular dynamics simulations reveal that for lower concentrations of linkers, NPs with charged surfactants cannot be fully neutralized by strongly binding divalent linkers, so that NPs carry higher effective charges and tend to form chains, due to poor screening. The highly polar NP surfaces polarize and partly immobilize nearby water molecules, which promotes NPs binding. The presented experimental and theoretical approach allows for detail observation and explanation of self-assembly processes in colloidal nanosystems.
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