Cross-Linked Gold Nanoparticles on Polyethylene: Resistive Responses to Tensile Strain and Vapors

Abstract

In this study, coatings of cross-linked gold nanoparticles (AuNPs) on flexible polyethylene (PE) substrates were prepared via layer-by-layer deposition and their application as strain gauges and chemiresistors was investigated. Special emphasis was placed on characterizing the influence of strain on the chemiresistive responses. The coatings were deposited using amine stabilized AuNPs (4 and 9 nm diameter) and 1,9-nonanedithiol (NDT) or pentaerythritol tetrakis(3-mercaptopropionate) (PTM) as cross-linkers. To prepare films with homogeneous optical appearance, it was necessary to treat the substrates with oxygen plasma directly before film assembly. SEM images revealed film thicknesses between ∼60 and ∼90 nm and a porous nanoscale morphology. All films showed ohmic I-V characteristics with conductivities ranging from 1 × 10⁻⁴ to 1 × 10⁻² Ω⁻¹ cm⁻¹, depending on the structure of the linker and the nanoparticle size. When up to 3% strain was induced their resistance increased linearly and reversibly (gauge factors: ∼20). A comparative SEM investigation indicated that the stress induced formation and extension of nanocracks are important components of the signal transduction mechanism. Further, all films responded with a reversible increase in resistance when dosed with toluene, 4-methyl-2-pentanone, 1-propanol or water vapor (concentrations: 50-10 000 ppm). Films deposited onto high density PE substrates showed much faster response-recovery dynamics than films deposited onto low density PE. The chemical selectivity of the coatings was controlled by the chemical nature of the cross-linkers, with the highest sensitivities (∼1 × 10⁻⁵ ppm⁻¹) measured with analytes of matching solubility. The response isotherms of all film/vapor pairs could be fitted using a Langmuir-Henry model suggesting selective and bulk sorption. Under tensile stress (1% strain) all chemiresistors showed a reversible increase in their response amplitudes (∼30%), regardless of the analytes' permittivity. Taking into consideration the thermally activated tunneling model for charge transport, this behavior was assigned to stress induced formation of nanocracks, which enhance the films' ability to swell in lateral direction during analyte sorption.

Alkylthiol self-assembled monolayers on Au(111) with tailored tail groups for attaching gold nanoparticles

“…Before deposition, atomically-flat terraces were prepared by annealing in a propane-butane flame ( ~50º С − 150º С for 90 sec, then at ~ 350º С, 2 − 3 sec). STM images of the resulting substrate reveal the well-known herringbone reconstruction pattern of Au(111) (figure 1-a) as an evidence of the chemical purity of the surface before molecules deposition [32]. As it is well known the herringbone structure is made of alternative hcp and fcc domains [17].…”

“…Applications are considered in nanoelectronics [1,2], sensing [23,35], catalysis by gold nanoparticles [26,27] nanoparticle immobilisation [7,11], adhesion control [14,46] and in fabrication of nanohybrid architectures [27,32,48]. Within this well-organized organic monolayer, the alkanethiol molecules are all parallel, with the −SH group that forms a covalent bond with the gold surface (~ 50 kcal·mol −1 ) [45].…”

“…For example, -CH3 and -CF3 as tail groups make the SAM surface hydrophobic, metallophobic and highly anti-adherent, [36], while -COOH, -NH2 or -OH tail groups yield hydrophilic surfaces with good metal ion and protein binding properties [3,25,45]. Among tail groups a very popular one is the -SH (thiol) end-group since it allows attaching various nanoobjects (noble metal 3 nanoparticles, nanorods, etc) to a gold substrate or cross-link them between each other [5,6,18,27,32,34,48]. To that end, dithiol molecules are of particular interest because they can be used for attaching gold nanoparticles (AuNPs).…”

Gold nanoparticle superlattices: structure and cavities studied by GISAXS and PALS

“…7,36 Indeed, several studies indicated their inuence on the sensing properties. [37][38][39][40] For example, assemblies of thiol-stabilized cubic platinum nanoparticles, revealing a more compact structure than their spherical counterparts, showed considerably higher response amplitudes. 38 Further, the perforation of assemblies of thiol-stabilized GNPs has been shown to markedly alter the chemiresistive response.…”

Optical Properties of Gold Nanoparticle Assemblies on a Glass Surface

“…Two- and three-dimensional arrays of metallic nanoparticles allowed to create downscaled contact electrodes [1–5]; touch sensors [6, 7]; and optically [8–10], chemically [11], and mechanically controlled [12] resistors. The architecture of nanoparticle assemblies can be controlled by employing of AuNP with various size, shape [1, 13], and by modification of the interparticle spacing.…”