Refractive index sensing and surface-enhanced Raman spectroscopy using silver-gold layered bimetallic plasmonic crystals.

Herein we describe the fabrication and characterization of Ag and Au bimetallic plasmonic crystals as a system that exhibits improved capabilities for quantitative, bulk refractive index (RI) sensing and surface-enhanced Raman spectroscopy (SERS) as compared to monometallic plasmonic crystals of similar form. The sensing optics, which are bimetallic plasmonic crystals consisting of sequential nanoscale layers of Ag coated by Au, are chemically stable and useful for quantitative, multispectral, refractive index and spectroscopic chemical sensing. Compared to previously reported homometallic devices, the results presented herein illustrate improvements in performance that stem from the distinctive plasmonic features and strong localized electric fields produced by the Ag and Au layers, which are optimized in terms of metal thickness and geometric features.

Quantitative reflection imaging of fixed Aplysia californica pedal ganglion neurons on nanostructured plasmonic crystals.

Studies of the interactions between cells and surrounding environment including cell culture surfaces and their responses to distinct chemical and physical cues are essential to understanding the regulation of cell growth, migration, and differentiation. In this work, we demonstrate the capability of a label-free optical imaging technique-surface plasmon resonance (SPR)-to quantitatively investigate the relative thickness of complex biomolecular structures using a nanoimprinted plasmonic crystal and laboratory microscope. Polyelectrolyte films of different thicknesses deposited by layer-by-layer assembly served as the model system to calibrate the reflection contrast response originating from SPRs.

Functional protein microarrays by electrohydrodynamic jet printing.

This paper reports the use of advanced forms of electrohydrodynamic jet (e-jet) printing for creating micro- and nanoscale patterns of proteins on various surfaces ranging from flat silica substrates to structured plasmonic crystals, suitable for micro/nanoarray analysis and other applications in both fluorescent and plasmonic detection modes. The approaches function well with diverse classes of proteins, including streptavidin, IgG, fibrinogen, and γ-globulin. Detailed study reveals that the printing process does not adversely alter the protein structure or function, as demonstrated in the specific case of streptavidin through measurements of its binding specificity to biotin-modified DNA.

Soft embossing of nanoscale optical and plasmonic structures in glass.

We describe here soft nanofabrication methods using spin-on glass (SOG) materials for the fabrication of both bulk materials and replica masters. The precision of soft nanofabrication using SOG is tested using features on size scales ranging from 0.6 nm to 1.

Waterproof AlInGaP optoelectronics on stretchable substrates with applications in biomedicine and robotics.

Inorganic light-emitting diodes and photodetectors represent important, established technologies for solid-state lighting, digital imaging and many other applications. Eliminating mechanical and geometrical design constraints imposed by the supporting semiconductor wafers can enable alternative uses in areas such as biomedicine and robotics. Here we describe systems that consist of arrays of interconnected, ultrathin inorganic light-emitting diodes and photodetectors configured in mechanically optimized layouts on unusual substrates.

Functional nanostructured plasmonic materials.

Plasmonic crystals fabricated with precisely controlled arrays of subwavelength metal nanostructures provide a promising platform for sensing and imaging of surface binding events with micrometer spatial resolution over large areas. Soft nanoimprint lithography provides a robust, cost-effective method for producing highly uniform plasmonic crystals of this type with predictable optical properties. The tunable multimode plasmonic resonances of these crystals and their ability for integration into lab-on-a-chip microfluidic systems can both be harnessed to achieve exceptionally high analytical sensitivities down to submonolayer levels using even a common optical microscope, circumventing numerous technical limitations of more conventional surface plasmon resonance techniques.