Posted on Jul 09, 2013, 6 a.m.
Metal-oxide nanofiber based chemiresistive gas sensors offer greater usability for real-time breath tests on smart phones or tablet PCs in the near future.
Your smartphone or tablet PC may soon enable a breath test for real-time assessment to detect diabetes and lung cancer. Il-Doo Kim, from the Korea Advanced Institute of Science and Technology (Republic of Korea), and colleagues have developed a highly sensitive exhaled breath sensor by using hierarchical SnO2 fibers that are assembled from wrinkled thin SnO2 nanotubes. The team has innovated a morphological evolution of SnO2 fibers, called micro phase-separations, which takes place between polymers and other dissolved solutes when varying the flow rate of an electrospinning solution feed and applying a subsequent heat treatment afterward. The morphological change results in nanofibers that are shaped like an open cylinder inside which thin-film SnO2 nanotubes are layered and then rolled up. A number of elongated pores ranging from 10 nanometers (nm) to 500 nm in length along the fiber direction were formed on the surface of the SnO2 fibers, allowing exhaled gas molecules to easily permeate the fibers. The inner and outer wall of SnO2 tubes is evenly coated with catalytic platinum (Pt) nanoparticles. According to the researchers, highly porous SnO2 fibers, synthesized by eletrospinning at a high flow rate, showed five-fold higher acetone responses than that of the dense SnO2 nanofibers created under a low flow rate. The catalytic Pt coating shortened the fibers' gas response time dramatically as well. The study authors submit that: “These results demonstrate the novel and practical feasibility of thin-wall assembled metal oxide based breath sensors for the accurate diagnosis of diabetes and potential detection of lung cancer.”
Jungwoo Shin, Seon-Jin Choi, Inkun Lee, Doo-Young Youn, Chong Ook Park, Jong-Heun Lee, Harry L. Tuller, Il-Doo Kim. “Thin-Wall Assembled SnO2 Fibers Functionalized by Catalytic Pt Nanoparticles and their Superior Exhaled-Breath-Sensing Properties for the Diagnosis of Diabetes.” Advanced Functional Materials, Volume 23, Issue 19, May 20, 2013, Pages: 2357–2367.