Gold nanoparticle coated silicon nitride chips for intracellular surface-enhanced raman spectroscopy

Using surface-enhanced Raman spectroscopy on gold-nanoparticle-decorated silicon nitride chips, we monitor the release of dextran-rhodamin molecules from capsules inside living cells. This demonstrates the feasibility of using photonic chips for intracellular sensing at visible wavelengths

Gold nanodome-patterned microchips for intracellular surface-enhanced Raman spectroscopy

While top-down substrates for surface-enhanced Raman spectroscopy (SERS) offer outstanding control and reproducibility of the gold nanopatterns and their related localized surface plasmon resonance, intracellular SERS experiments heavily rely on gold nanoparticles. These nanoparticles often result in varying and uncontrollable enhancement factors. Here we demonstrate the use of top-down gold-nanostructured microchips for intracellular sensing. We develop a tunable and reproducible fabrication scheme for these microchips. Furthermore we observe the intracellular uptake of these structures, and find no immediate influence on cell viability. Finally, we perform a proof-of-concept intracellular SERS experiment by the label-free detection of extraneous molecules. By bringing top-down SERS substrates to the intracellular world, we set an important step towards time-dependent and quantitative intracellular SERS

On-chip enhanced raman spectroscopy using metal slot waveguide

info:eu-repo/semantics/publishe

Silicon-nitride waveguides for on-chip Raman spectroscopy

The evanescent tail of the guided modes can efficiently excite Raman active molecules located in the cladding of a waveguide. Similarly, a significant fraction of the total emitted Stokes power is evanescently coupled to the same mode. Further, the enhancement effects inherent to the waveguide, alongside with the long interaction length, lead to an increased light-matter interaction, resulting in a higher sensitivity as required by spectroscopic applications, especially in the context of Raman spectroscopy. We calculate the spontaneous Raman scattering efficiency as a function of siliconnitride strip waveguide dimensions and show that under typical conditions, the overall efficiency is approximately two orders of magnitude higher than in confocal configuration in the free space. We also report the experimental demonstration of the use of silicon-nitride based photonic waveguides in a lab-on-a-chip context for Raman spectroscopy. To the best of our knowledge, this is the first demonstration of Raman spectroscopy using photonic waveguides

Nanophotonic waveguide enhanced Raman spectroscopy of biological submonolayers

Characterizing a monolayer of biological molecules has been a major challenge. We demonstrate nanophotonic wave-guide enhanced Raman spectroscopy (NWERS) of monolayers in the near-infrared region, enabling real-time measurements of the hybridization of DNA strands and the density of sub-monolayers of biotin-streptavidin complex immobilized on top of a photonics chip. NWERS is based on enhanced evanescent excitation and collection of spontaneous Raman scattering near nanophotonic waveguides, which for a one centimeter silicon nitride waveguide delivers a signal that is more than four orders of magnitude higher in comparison to a confocal Raman microscope. The reduced acquisition time and specificity of the signal allows for a quantitative and real-time characterization of surface species, hitherto not possible using Raman spectroscopy. NWERS provides a direct analytic tool for monolayer research and also opens a route to compact microscope-less lab-on-a-chip devices with integrated sources, spectrometers and detectors fabricated using a mass-producible CMOS technology platform

Nanodome coins for intracellular surface-enhanced raman spectroscopy

Surface-enhanced Raman spectroscopy offers a tremendous potential for intracellular sensing, because it combines fingerprint specificity with sensitive signals. However, the colloidal gold nanoparticles used for this purpose lead to strong spatiotemporal variations in intracellular SERS experiments. This unpredictable behaviour, which complicates reproducible measurements, strongly contrasts to the advances made in the last decades on the fabrication of controllable and robust plasmonic substrates with high enhancement factors. Here, we propose an alternative approach to intracellular SERS by developing planar, nanostructured microcoins which enable to use top-down fabricated substrates for intracellular applications. We develop a nanosphere-lithography based technique for the fabrication of gold-nanotriangle and -nanodome structured silicon-nitride micron-sized chips (micro-coins). These microcoins can be lifted off form their substrate and are subsequently incorporated into fibroblast-and HeLa cells. In a model experiment, the SERS sensors are used for the label-free detection of extraneous molecules in live cells. The use of reproducible SERS substrates for intracellular sensing is expected to be an important step towards reproducible and quantitative live-cell, label-free measurements

Lab-on-a-chip Raman sensors outperforming Raman microscopes

We demonstrate that the signal-to-noise ratio and signal collection efficiency in evanescent waveguide-based Raman spectroscopy exceeds that in Raman microscopes. We investigate the effect of silicon-nitride waveguide geometry to further improve the performance