Flexible Room-Temperature NH3 Sensor for Ultrasensitive, Selective, and Humidity-Independent Gas Detection

Hua Yao Li, Chul Soon Lee, Do Hong Kim, Jong Heun Lee

Research output: Contribution to journalArticlepeer-review

135 Citations (Scopus)


Ammonia (NH3) is an irritant gas with a unique pungent odor; sub-parts per million-level breath ammonia is a medical biomarker for kidney disorders and Helicobacter pylori bacteria-induced stomach infections. The humidity varies in both ambient environment and exhaled breath, and thus humidity dependence of gas-sensing characteristics is a great obstacle for real-time applications. Herein, flexible, humidity-independent, and room-temperature ammonia sensors are fabricated by the thermal evaporation of CuBr on a polyimide substrate and subsequent coating of a nanoscale moisture-blocking CeO2 overlayer by electron-beam evaporation. CuBr sensors coated with a 100 nm-thick CeO2 overlayer exhibits an ultrahigh response (resistance ratio) of 68 toward 5 ppm ammonia with excellent gas selectivity, rapid response, reversibility, and humidity-independent sensing characteristics at room temperature. In addition, the sensing performance remains stable after repetitive bending and long-term operation. Moreover, the sensors exhibit significant response to the simulated exhaled breath of patients with H. pylori infection; the simulated breath contains 50 ppb NH3. The sensors thus show promising potential in detecting sub-parts per million-level NH3, regardless of humidity fluctuations, which can open up new applications in wearable devices for in situ medical diagnosis and indoor/outdoor environment monitoring.

Original languageEnglish
Pages (from-to)27858-27867
Number of pages10
JournalACS Applied Materials and Interfaces
Issue number33
Publication statusPublished - 2018 Aug 22


  • CeO-coated CuBr
  • ammonia
  • exhaled breath analysis
  • gas sensor
  • humidity dependence
  • medical diagnosis
  • selectivity

ASJC Scopus subject areas

  • Materials Science(all)


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