City Research Online

Wavelength dependent pH optical sensor using the layer-by-layer technique

Raoufi, N., Surre, F., Sun, T. , Rajarajan, M. & Grattan, K. T. V. (2012). Wavelength dependent pH optical sensor using the layer-by-layer technique. Sensors and Actuators B Chemical, 169, pp. 374-381. doi: 10.1016/j.snb.2012.05.024


In this work, the design and characteristics of a wavelength-dependent pH optical sensor have been studied. To create the sensor itself, brilliant yellow (BY) as a pH indicator and poly (allylamine hydrochloride) [PAH] as a cross-linker have been deposited on the end of a bare silica core of an optical fibre by use of a ‘layer-by-layer’ technique. In the experiments carried out to characterize the sensor, it was observed that the value of pKa (the dissociation constant) of the thin film is dependent both on the outer layer and the number of bilayers. A heat treatment process was applied to the sensor to reduce the effect on the deposited layers during the testing of the probe. As a result of these series of experiments, it could be concluded that the probe design on which were deposited structured layers comprising six double layers of (PAH/BY) showed the best sensitivity for a pH range from 6.80 to 9.00 (with an accuracy of ±0.20) and showing an average wavelength shift of 4.65 nm per 0.2 pH units, while the concentration of the BY and the PAH solutions was maintained as 0.25mM and 2.5mM respectively.

Publication Type: Article
Additional Information: NOTICE: this is the author’s version of a work that was accepted for publication in Sensors and Actuators B Chemical. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Sensors and Actuators B: Chemical, Volume 169, 5 July 2012, Pages 374–381.
Publisher Keywords: Brilliant yellow, pH sensor, optical sensor, Layer-by-Layer (LbL)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Departments: School of Science & Technology > Engineering
SWORD Depositor:
[thumbnail of Wavelength Dependent pH Optical Sensor Using the Layer-by-Layer Technique.pdf]
Download (467kB) | Preview


Add to AnyAdd to TwitterAdd to FacebookAdd to LinkedinAdd to PinterestAdd to Email


Downloads per month over past year

View more statistics

Actions (login required)

Admin Login Admin Login