Novel hollow-core fiber-based system with surface plasmon-enhanced autofluorescence spectroscopy for the sensitive detection of molecules

Abstract Autofluorescence (AF) detection uses the distinct fluorescence signatures of molecules to identify and characterize them without the need for labels. The current study focuses on the development of a field-portable, user-friendly opto-fluidic system utilizing hollow-core silver-coated fiber. It facilitates the collection of a samples enhanced AF spectra, owing to its increased interaction and strong coupling efficiency of light with the analyte along the fiber. The AF enhancement of the developed system was systematically investigated using fluorescein dye (Fd) as a probe molecule across various concentrations ranging from (10 −3 M to10 −9 M). Furthermore, the study investigated the surface plasmon-enhanced AF spectroscopy (SPEAS) of Fd molecules using silver (Ag) and gold (Au) nanoparticles (NPs). The Ag and Au NPs used in the study were synthesized using a microwave synthesizer technique. A comparative analysis of the SPEAS enhancement study demonstrated that Au NPs performed better than Ag NPs showing 31-fold and 12-fold signal enhancement, respectively. Additionally, the developed methodology was utilized to characterize the SPEAS spectra of E. coli bacteria for various concentrations using Ag and Au NPs, showing 20-fold and 35-fold signal enhancement, respectively allowing detection up to concentrations as low as 10 2 cfu ml −1 . This study highlights the usefulness of the developed system in detecting AF and SPEAS spectra of molecules using a field-portable and compact device.