Electrical Conductivity and Vapor-Sensing Properties of ω-(3-Thienyl)alkanethiol-Protected Gold Nanoparticle Films

Abstract

Gold nanoparticles protected with thiophene-terminated alkanethiols having different alkane chain lengths have been synthesized, and vapor-sensing properties of their spin-coated films have been investigated. Transmission electron microscopy and measurement of the sulfur and gold peak areas of the films by X-ray photoelectron spectroscopy indicate gold core diameters in the 3−5-nm range. Exposure of the films to chloroform, toluene, hexane, and ethanol vapors results in significant and selective increases in electrical resistance, with the response to the vapors having the following order: toluene > chloroform > hexane ≫ ethanol. The magnitude of the maximum resistance change correlates well with solubility properties of the protected gold nanoparticles, as determined by optical absorbance spectroscopy and the energy of the gold plasmon. The detection sensitivity of the films increases with increasing alkanethiol chain length. These data are consistent with a sensing mechanism in which organic vapors cause swelling of the nanoparticle film, resulting in increased distance between the gold cores. In the case of ethanol, a decrease in resistance occurs at high vapor concentration, presumably due to an increase in the dielectric constant of the medium between the cores.

Inkjet-printed gold nanoparticle chemiresistors: Influence of film morphology and ionic strength on the detection of organics dissolved in aqueous solution

“…Thin films of such gold nanoparticle-organic hybrids can be used as chemiresistor sensors, whereby changes in the conductivity of the thin film can be observed in the presence of an analyte as a result of an increase in the nanoparticle separation due to swelling of the nanoparticle film [16][17][18][19][20][21]. Although the concept of using gold nanoparticles for chemical sensing is well established for vapor-phase sensing, we have recently demonstrated that hexanethiol-Au NP can be used as chemiresistors to determine the presence of organic molecules even in a highly concentrated salt solution (1 M KCl) [7] through appropriate design of the electrode geometry (electrode length and separation) and by the application of a low frequency (1 Hz) AC voltage.…”

Hierarchical Self‐Assembly of Tetrakis(1‐pyrenyl)porphyrins into Microscopic Petals and Flowers with Ultrasensitive Room‐Temperature NO2 Sensing in a Broad Humidity Range

“…The current‐voltage ( I–V ) characteristics for the self‐assembled aggregates of 1 and 2 deposited on insulating glass substrates with ITO interdigitated electrodes (IDEs) are shown in Figure and summarized in Table . The devices made from two different kinds of aggregates exhibited similar conductive behavior, with the conductivity(σ) of about 1.1×10 −5 S cm −1 and 3.7×10 −5 S cm −1 in dry nitrogen (RH=0%) for the aggregates of 1 and 2 , respectively, Figure (solid lines). The higher conductivity of 2 with respect to that of 1 might be attributed to the higher ordered molecular arrangement due to the stronger π‐π interactions among the adjacent molecules in the aggregate of 2 as revealed by the UV‐vis, IR spectra and SEM experiments.…”

Highly sensitive alkane odour sensors based on functionalised gold nanoparticles

“…They have proposed a physical, rather than chemical, approach to the sensing of combustible odours. Inspired by Wohltjen and Snow, Ahn and co-workers [11] exposed films of -(3-thienyl)alkanethiol-gold core/shell nanoparticles to several combustible odours, and found an increase in resistance due to swelling of the films in the odour.…”

“…Such ligands are expected to be most compatible with similarly apolar alkane odours, but to reject more polar or hydrogen-bonding odours. Also, rather than spincasting [11], we processed core/shell nanoparticles by the Langmuir-Schäfer (LS) printing method [13]. The LS printing allows the formation of dense, highly ordered monolayer films on a water surface prior to transferring films to the solid substrate, while still avoiding the coalescence and fusing of neighbouring gold particles.…”