Enhanced vibrational spectroscopy, intracellular refractive indexing for label-free biosensing and bioimaging by multiband plasmonic-antenna array

•A plasmonic-antenna array was presented for label-free, intracellular sensing and imaging.•This device senses the change of local refractive indices and enhances the signal of IR absorption.•This plasmonic-antenna array also supports multiband interrogations.

In this study, we report a multiband plasmonic-antenna array that bridges optical biosensing and intracellular bioimaging without requiring a labeling process or coupler. First, a compact plasmonic-antenna array is designed exhibiting a bandwidth of several octaves for use in both multi-band plasmonic resonance-enhanced vibrational spectroscopy and refractive index probing. Second, a single-element plasmonic antenna can be used as a multifunctional sensing pixel that enables mapping the distribution of targets in thin films and biological specimens by enhancing the signals of vibrational signatures and sensing the refractive index contrast. Finally, using the fabricated plasmonic-antenna array yielded reliable intracellular observation was demonstrated from the vibrational signatures and intracellular refractive index contrast requiring neither labeling nor a coupler. These unique features enable the plasmonic-antenna array to function in a label-free manner, facilitating bio-sensing and imaging development.