Professor Il-Doo Kim in the Department of Materials Science and Engineering at Korea Advanced Institute of Science and Technology (KAIST) is developing ultrasensitive and highly selective gas sensors to diagnose diseases by exhaled breath analysis. Professor Kim has led the development of semiconductor metal oxide-based nanofiber sensor arrays, which are optimized for pattern recognition of breath prints.
Human breath contains a number of volatile organic compounds(VOCs). Accurate detection of specific VOCs in exhaled breath can provide essential information for the early diagnosis of diseases. For example, acetone, H2S, ammonia, and toluene can be used to evaluate diabetes, halitosis, kidney malfunction, and lung cancer, respectively, where the diagnosis of these diseases can be achieved by analyzing the concentration of VOCs in exhaled breath, originating from the molecular exchange between lung tissue and blood.
Ref: WO3 Nanofiber-Based Biomarker Detectors Enabled by Protein-Encapsulated Catalyst Self-Assembled on Polystyrene Colloid Templates. Small (5 January 2016) | DOI: 10.1002/smll.201502905
A novel catalyst functionalization method, based on protein-encapsulated metallic nanoparticles (NPs) and their self-assembly on polystyrene (PS) colloid templates, is used to form catalyst-loaded porous WO3 nanofibers (NFs). The metallic NPs, composed of Au, Pd, or Pt, are encapsulated within a protein cage, i.e., apoferritin, to form unagglomerated monodispersed particles with diameters of less than 5 nm. The catalytic NPs maintain their nanoscale size, even following high-temperature heat-treatment during synthesis, which is attributed to the discrete self-assembly of NPs on PS colloid templates. In addition, the PS templates generate open pores on the electrospun WO3 NFs, facilitating gas molecule transport into the sensing layers and promoting active surface reactions. As a result, the Au and Pd NP-loaded porous WO3 NFs show superior sensitivity toward hydrogen sulfide, as evidenced by responses (Rair/Rgas) of 11.1 and 43.5 at 350 °C, respectively. These responses represent 1.8- and 7.1-fold improvements compared to that of dense WO3 NFs (Rair/Rgas = 6.1). Moreover, Pt NP-loaded porous WO3 NFs exhibit high acetone sensitivity with response of 28.9. These results demonstrate a novel catalyst loading method, in which small NPs are well-dispersed within the pores of WO3 NFs, that is applicable to high sensitivity breath sensors.