pH sensing through a single optical fibre using SERS and CMOS SPAD line arrays

Katjana Ehrlich, A. Kufcsák, Sarah McAughtrie, H. Fleming, N. Krstajic, C. J. Campbell, R. K. Henderson, K. Dhaliwal, Robert R. Thomson, Michael George Tanner

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)
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Full exploitation of fibre Raman probes has been limited by the obstruction of weak Raman signals by background fluorescence of the sample and the intrinsic Raman signal of the delivery fibre. Here we utilised functionalised gold nanoshells (NS) to take advantage of the surface-enhanced Raman spectroscopy (SERS) effect to enhance the pH responsive spectrum of 4-mercaptobenzoic acid (MBA). However, the fibre background is still dominant. Using the photon arrival time-resolving capability of a CMOS single-photon avalanche diode (SPAD) based line sensor, we recover the SERS spectrum without a fibre background in a 10 s measurement. In this manner, pH sensing through a multimode fibre at a low excitation power that is safe for future in vivo applications, with short acquisition times (10 or 60 s), is demonstrated. A measurement precision of ± 0.07 pH units is thus achieved.
Original languageEnglish
Pages (from-to)30976-30986
Number of pages11
JournalOptics Express
Issue number25
Early online date27 Nov 2017
Publication statusPublished - 11 Dec 2017


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