Akash Bachhuka1*, Sabrina Heng1, Heike Ebendorff- Heidepriem1


ARC Centre of Excellence for Nanoscale BioPhotonics, Institute for Photonics and Advanced Sensing, School of Physical Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia
*Email: akashbachhuka01@adelaide.edu.au


Ions such as Aluminum, Lithium, Calcium and Iron are known to have great impact on human health and environment. Several staining based techniques have been developed for the detection of these ions. The problem with these existing techniques is there adaptability for real time analysis. Current strategies to overcome this problem utilizes microstructured optical fibers (MOF’s). The exposed core inside the MOF’s act as tiny chamber for surface functionalization or chemical reactions, making it a more sensitive and versatile technique for sensing ions. The current issue with using MOF’s for sensing is the availability of techniques that can be employed to modify the core of these fibers. Moreover, the present techniques for surface modification of MOF’s have low reproducibility and stability in different buffer solutions.

To address this gap, we report a one step, dry process for surface functionalization of exposed core fibers (ECF’s) employing plasma polymerization. Plasma polymerisation was used to generate thin amine functional films on ECF’s without any pre-treatment. Fluorophores specific to Aluminium and Lithium Ions were synthesized in house with a carboxylic acid moiety at its end, to bind with the amine coated ECF’s. These ppECF’s showed sensitivity to Lithium and Aluminium ions at a concentration of 1mM and 1µM respectively as shown in Figure 1. Moreover, minimal variability was observed in the fluorescence intensity across different sections of the same fiber, demonstrating homogeneity of the polymer coatings across the length of a fiber. Furthermore, ppECF’s showed stability in different buffer solutions. Overall, data demonstrates that this method of surface functionalizing ECF’s can generate coatings that are homogeneous, reproducible and stable. The method reported here can open new opportunities in the field of optical ion sensing.