jp4091969_si_001.pdf (13.2 MB)
Elastic and Viscoelastic Properties of Cross-Linked Gold Nanoparticles Probed by AFM Bulge Tests
journal contribution
posted on 2014-02-27, 00:00 authored by Hendrik Schlicke, Elisabeth
W. Leib, Alexey Petrov, Jan H. Schröder, Tobias VossmeyerTo enable applications of nanoparticle
films in flexible electronics,
actuators, and sensors, their mechanical properties are of critical
concern. Here, we demonstrate that the elastic and viscoelastic properties
of covalently cross-linked gold nanoparticles (GNPs) can be probed
using AFM bulge tests. For this purpose 30–60 nm thick films
consisting of 1,9-nonanedithiol (NDT) cross-linked GNPs (3.8 nm core
diameter) were transferred onto substrates with ∼100 μm
circular apertures. The resulting freestanding membranes were bulged
by applying pressure differences of up to 10 kPa, and the deflection
was measured by intermittent contact atomic force microscopy (AFM).
Analyzing the pressure-deflection data using the spherical cap model,
either by taking into account the peak deflection values or the measured
arc profiles of the bulge, yielded 2.3 ± 0.3 and 2.7 ± 0.4
GPa for Young’s modulus, respectively. When cycling the stress–strain
measurements at overpressures up to 2.4 kPa, hysteresis was observed
and assigned to viscoelastic effects. Creep tests performed at a pressure
of 2 kPa revealed both viscoelastic retardation (time constant: 3.3
× 10–3 s–1) and nonrecoverable
relaxation (creep rate: 9.0 × 10–8 s–1). Several membranes resisted pressures up to 10 kPa without fracturing,
indicating that the ultimate biaxial tensile strength of the films
was above ∼30 MPa.