jp511014q_si_001.pdf (337.35 kB)
Download fileReal-Time Monitoring Distance Changes in Surfactant-Coated Au Nanoparticle Films upon Volatile Organic Compounds (VOCs)
journal contribution
posted on 2015-03-05, 00:00 authored by M. C. Dalfovo, L. J. Giovanetti, J. M. Ramallo-López, R. C. Salvarezza, F. G. Requejo, F. J. IbañezWe explore into the role of the organic
ligands composition surrounding
Au nanoparticles (NPs) toward internanoparticles distance changes
and film structure during vapor sensing by the use of in situ grazing-incidence small-angle X-ray scattering (GISAXS) and other
relevant techniques. We observed distinct changes in core-to-core distance and film structure upon measured concentrations of polar
ethanol (EtOH) and nonpolar toluene (Tol) vapors. As-formed tetraoctylammonium
bromide (TOABr)-coated Au NPs (SNPs) film exhibited ∼0.4 nm
core-to-core increase in distance and improved SNPs correlation upon
80% Tol. In the presence of EtOH, SNPs distance seems not to change
and correlation critically diminishes, leading to an amorphous film.
As-formed films were exchanged with nonanedithiol (NDT) and exposed
to 100% Tol vapor. Interestingly, the incorporation of NDT increased
distance between NPs and rendered film flexibility. It is determine
that just a small number of S, from NDT ligands, binds to Au NPs,
and those exchanged alkanedithiol chains adopted a loop conformation
around the Au NPs as evidenced by X-ray absorption near-edge structure
(XANES) and kink defects by Fourier transformed infrared (FT-IR) experiments,
respectively. These findings may solve some fundamental questions
about internanoparticle distance-dependent phenomena such as electron
transport in chemiresistors and coupling effects in localized surface
plasmon resonance (LSPR) solid-state sensors.