Multimodal near-infrared spectroscopy for biosensing applications

Abstract: The near infrared (NIR) region of the electromagnetic spectrum contains valuable information about vibrational overtone and combination modes. Additionally, fluorophores that emit in the NIR are desired because this spectral range falls into the tissue transparency window. However, NIR techniques are not as widespread as their counterparts in the visible range because detectors, microscopes and fluorophores are less available. Here, we present a NIR multimodal and low footprint spectroscopy (NIR-MMS) setup. The setup excites NIR fluorescence using a LED or uses broadband NIR light to capture absorption spectra in the range from 900 nm to 1650 nm with a fiber-coupled InGaAs spectrograph. We demonstrate the measurement of NIR fluorescent materials and biosensors for the neurotransmitter dopamine. Additionally, the setup allows to simultaneously measure absorption and emission spectra to assess chemical changes in NIR fluorescent carbon nanotubes. Overall, this small footprint setup provides simultaneous access to NIR fluorescence and absorption spectra with broad applications in biosensing.