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

Katjana Ehrlich (Lead / Corresponding author), Andras Kufcsák, Sarah McAughtrie, Holly Fleming, Nikola Krstajic, Colin J Campbell, Robert K Henderson, Kevin Dhaliwal, Robert R Thomson, Michael G Tanner

    Research output: Contribution to journalArticlepeer-review

    27 Citations (Scopus)
    160 Downloads (Pure)


    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
    Publication statusPublished - 11 Dec 2017


    • Journal Article


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