Thin Films Composed of Multiwalled Carbon Nanotubes, Gold Nanoparticles and Myoglobin for Humidity Detection at Room Temperature

Abstract

Optically transparent and electrically conductive nanocomposite thin films consisting of multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs) and myoglobin molecules that glue GNPs and MWCNTs together are fabricated for the first time on glass substrates from aqueous solution. The nanocomposite thin film is capable of varying its resistance, impedance or optical transmittance at room temperature in response to changes in ambient humidity. The conductometric sensitivity to relative humidity (RH) of the nanocomposite thin film is compared with those of the pure and Mb-functionalized MWCNT layers. The pure MWCNT layer shows a small increase in its resistance with increasing RH due to the effect of p-type semiconducting nanotubes present in the film. In contrast, a four times higher sensitivity to RH is observed for both the nanocomposite and Mb-functionalized MWCNT thin films. The sensitivity enhancement is attributable to swelling of the thin films induced by water absorption in the presence of Mb molecules, which increases the inter-nanotube spacing and thereby causes a further increase of the film resistance. A humidity change as low as DeltaRH=0.3 % has been readily detected by conductometry using the nanocomposite thin film.

Carbon Nanotube Gas and Vapor Sensors

“…CNT devices show sensitivity to H 2 O vapor, but the exact influence on the CNT electronic structure is still under debate, and differing opinions include electronic donation into the CNT,101 hydrogen bonding with oxygen defect sites on the CNT,102 and the introduction of charge‐trapping sites on the CNT through direct H 2 O adsorption and/or interaction with the SiO 2 substrate 103. Regardless of this debate, several groups have developed humidity sensors containing CNTs,104 LiClO 4 ‐doped CNTs,105 polymer‐functionalized CNTs,106 CNT–biomolecule complexes,107 as well as CNT‐based capacitor,108 field‐ionization,109 and quartz‐crystal microbalance (QCM) sensors 110. The sensitivity to water is a challenge that researchers need to consider when designing sensor architectures using CNTs.…”

Gas‐ und Dampfsensoren auf der Basis von Kohlenstoff‐Nanoröhren

“…Postuliert wurden die Elektronenabgabe an die CNT,101 die Bildung von Wasserstoffbrücken zu Sauerstoffdefektplätzen auf der CNT102 und die Einführung von Ladungsfallen auf der CNT infolge einer direkten H 2 O‐Adsorption und/oder der Wechselwirkung mit dem benachbarten SiO 2 ‐Substrat 103. Mehrere Forschungsgruppen haben das Ansprechverhalten auf H 2 O genutzt, um Feuchtesensoren auf der Basis von reinen CNTs,104 LiClO 4 ‐dotierten CNTs,105 polymerfunktionalisierten CNTs,106 CNT‐Biomolekül‐Komplexen107 und CNT‐basierten Kondensator‐,108 Feldionisations‐109 und Quarzmikrowaage(QCM)‐Sensoren110 zu entwickeln. Beim Entwurf von Sensorarchitekturen mit CNT‐Elementen ist dieses Ansprechverhalten auf Wasser stets eine technische Herausforderung.…”

Electroreduction of oxygen on gold nanoparticle/PDDA-MWCNT nanocomposites in acid solution

“…Qi et al used myoglobin (Mb) as a glue to connect MWCNTs and AuNPs into a three-dimensional hybrid network. Mb was responsible for the functionalization and homogeneous dispersion of the MWCNTs in water [20].…”