A novel low-noise measurement principle for LAPS and its application to faster measurement of pH

Abu Bakar Abu, Hirokazu Sugihara, Tatsuo Yoshinobu, Hiroshi Iwasaki

Research output: Contribution to journalConference articlepeer-review

8 Citations (Scopus)


A novel measurement principle for the light-addressable potentiometric sensor (LAPS) system is proposed in this paper. With several features like low-noise and low-background, this measurement scheme extends the application of LAPS in faster high-sensitive direct monitoring of ionic concentration and small change in the surface potential without the need of costly instruments like potentiostat, lock-in amplifier. Using two out-of-phase modulated light sources applied at two different points of the Si surface of the heterostructure, a kind of differential LAPS response is obtained. Due to the addition of the two out-of-phase photocurrents, low-frequency components associated with the photocurrents are canceled out and a low-noise and hence highly sensitive response is expected. As an application of the new principle, the pH measurement of an electrolyte solution is investigated and a new instrumentation for the direct, high-sensitive, and faster measurement of pH is proposed.

Original languageEnglish
Pages (from-to)112-116
Number of pages5
JournalSensors and Actuators, B: Chemical
Issue number1-3
Publication statusPublished - 2001 Apr 15
Externally publishedYes
Event5th European Conference on Optical Chemical Sensors and Biosensors - Lyon, France
Duration: 2000 Apr 162000 Apr 19


  • Chemical sensor
  • Differential measurement
  • Light-addressable potentiometric sensor (LAPS)
  • pH sensor

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering
  • Materials Chemistry


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