Inkjet-Printed Flexible Ultrasensitive Chemiresistive Sensors for Aggregation Pheromone of Flour Beetles

This work reports the first demonstration that a chemoresistive sensor can be used to detect the aggregation pheromone of flour beetles. To prepare the sensing element of such a sensor, a novel functionalization method was developed to amplify amine groups on the surface of carbon nanotubes (CNTs). Unlike traditional amine-amplification approaches in which amplification efficiency is significantly reduced by self-crosslinking, the current amine amplification process was self-crosslinking-free due to the use of a home-made compound in which amine groups were protected by Boc (tert-butyloxycarbonyl) protecting groups and could be deprotected as needed. The inkjet ink formulated from the functionalized CNTs, together with an amine-rich compound and a commercial silver nanoparticle-based inkjet ink, was used to fabricate (via inkjet-printing and drop-casting) lightweight, flexible, and miniature-sized chemiresistive sensors for 4,8-dimethyldecanal (DMD), a compound known to be the aggregation pheromone of several species of flour beetles. A home-built gas sensing system, including a commercial gas generator, a DMD permeation tube with its emission rate certified, a data-acquisition system, and some home-developed LabVIEW-based programs, was utilized to perform the DMD sensing trials. The sensors showed ultra-high sensitivity to synthetic aggregation pheromone DMD, as indicated by their prompt and significant responses to 100 ppb DMD vapor. A mechanism for the sensitive sensing of DMD is proposed.

Graphical Abstract