Langmuir Films of n-Alkanethiol-Capped Gold Nanoparticles and n-Alkanes: Interfacial Mixing Scenarios Assessed by X-ray Reflectivity and Grazing Incidence Diffraction

Journal Article · Wed Jan 17 00:00:00 EST 2018 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.7b09874· OSTI ID:1426243

Raveendran, A. ^[1]; DeWolf, C. ^[2]; Bu, W. ^[3]; McWhirter, S. ^[1]; Meron, M. ^[3]; Lin, B.  ^[3]; Meli, M. -V.  ^[1]

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1. Mount Allison Univ., Sackville, NB (Canada)
2. Concordia Univ., Montreal, QC (Canada)
3. Univ. of Chicago, IL (United States)

A series of n-alkanes cospread with alkanethiol-stabilized gold nanoparticles (AuNP) were studied as Langmuir monolayers by synchrotron X-ray reflectivity and diffraction. Tetradecanethiol capped gold nanoparticles with core diameters close to 2 nm were used to make films at 20 °C, below the ligand order–disorder temperature. A variety of n-alkane chain lengths (Cn = C_nH_2n+2, where n = 12, 15 and 16) were tested to assess the interfacial assembly of nanoparticle films as a result of different mixing scenarios indicated in their surface pressure versus area isotherms. Synchrotron grazing incidence X-ray diffraction (GIXD) and reflectivity (XR) confirm that mixtures of n-alkane and AuNP exhibiting improved fluidity in their compression isotherm are indeed incorporating n-alkane into the AuNP ligand shell and stabilizing it at the air–water interface. The resulting films show a doubling of their correlation lengths and thus a significant improvement on their ordering, as well as increased lattice spacing that is dependent upon the n-alkane chain length. Mixtures that do not exhibit changes in their surface pressure vs area isotherm similarly show little change in the interfacial assembly of the nanoparticle films except to promote monolayer collapse and multilayer formation. Improvements to the film order are assigned to the initial formation of larger nanoparticle domains. Here, the nature of the chain length dependence and persistence of the n-alkane through compression suggest a favorable interaction with the nanoparticle ligand shell that results in the extension of methylene units of the longer alkanes beyond the thiol layer, which has implications for influencing nanoparticle interactions.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC); National Science Foundation (NSF); Natural Sciences and Engineering Research Council
• Grant/Contract Number: AC02-06CH11357; NSF/CHE-1346572; 03977; 341933
• OSTI ID: 1426243
• Journal Information: Journal of Physical Chemistry. C, Vol. 122, Issue 5; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
thin films
metal nanoparticles
layers
nanoparticles
compression