Fiber-shaped H-aggregates with lengths of up to 300 microm are synthesized by self-assembly of thiacyanine (TC) dye molecules in solution. Photoluminescence (PL) images and spatially resolved PL spectra of the fibers that are transferred onto a glass substrate reveal that the fibers act as single-mode optical waveguides that propagate PL in the range of 520 to 560 nm over 250 microm without any loss.

The advent of image-activated cell sorting and imaging-based cell picking has advanced our knowledge and exploitation of biological systems in the last decade. Unfortunately, they generally rely on fluorescent labeling for cellular phenotyping, an indirect measure of the molecular landscape in the cell, which has critical limitations. Here we demonstrate Raman image-activated cell sorting by directly probing chemically specific intracellular molecular vibrations via ultrafast multicolor stimulated Raman scattering (SRS) microscopy for cellular phenotyping. Specifically, the technology enables real-time SRS-image-based sorting of single live cells with a throughput of up to~100 events per second without the need for fluorescent labeling. To show the broad utility of the technology, we show its applicability to diverse cell types and sizes. The technology is highly versatile and holds promise for numerous applications that are previously difficult or undesirable with fluorescence-based technologies.

For surface-enhanced Raman scattering (SERS)-based protein identification, immunoassay, and drug screening, metal sandwich substrates bridged by proteins have been created in the present study. The sandwich architectures are fabricated based on a layer-by-layer (LbL) technique. The first gold monolayer is prepared by the self-assembling of gold nanoparticles on a poly(diallyldimethylammonium chloride) (PDDA)-coated glass slide. The second gold or silver layer is produced by the interactions between proteins in the middle layer of the sandwich architecture and the metal nanoparticles. Highly reproducible surface-enhanced resonance Raman scattering (SERRS) and SERS spectra can be obtained by the present gold-protein-gold (Au/Au) and gold-protein-silver (Au/Ag) sandwiches, and we find that the latter yields about 7 times stronger SERRS than the former. Because of contributions from the two metal layers to the SERS, this sandwich strategy holds great potential in highly sensitive and reproducible protein detections.