a b s t r a c tWe demonstrate a surface plasmon resonance imaging platform integrated with a smartphone to be used in the field with high-throughput biodetection. Inexpensive and disposable SPR substrates are produced by metal coating of commercial Blu-ray discs. A compact imaging apparatus is fabricated using a 3D printer which allows taking SPR measurements from more than 20.000 individual pixels. Real-time bulk refractive index change measurements yield noise equivalent refractive index changes as low as 4.12 × 10 −5 RIU which is comparable with the detection performance of commercial instruments. As a demonstration of a biological assay, we have shown capture of mouse IgG antibodies by immobilized layer of rabbit anti-mouse (RAM) IgG antibody with nanomolar level limit of detection. Our approach in miniaturization of SPR biosensing in a cost-effective manner could enable realization of portable SPR measurement systems and kits for point-of-care applications.

Label free imaging of the chemical environment of biological specimens would readily bridge the supramolecular and the cellular scales, if a chemical fingerprint technique such as Raman scattering can be coupled with super resolution imaging. We demonstrate the possibility of label-free super-resolution Raman imaging, by applying stochastic reconstruction to temporal fluctuations of the surface enhanced Raman scattering (SERS) signal which originate from biomolecular layers on large-area plasmonic surfaces with a high and uniform hot-spot density (>1011/cm2, 20 to 35 nm spacing). A resolution of 20 nm is demonstrated in reconstructed images of self-assembled peptide network and fibrilated lamellipodia of cardiomyocytes. Blink rate density is observed to be proportional to the excitation intensity and at high excitation densities (>10 kW/cm2) blinking is accompanied by molecular breakdown. However, at low powers, simultaneous Raman measurements show that SERS can provide sufficient blink rates required for image reconstruction without completely damaging the chemical structure.

P lasmonic excitations of metallic nanostructures have attracted a great deal of attention in past decades, due to the rich variety of geometric configurations, the associated optical properties and phenomena, and the wide range of present and potential future applications. 1,2 Propagating and localized plasmons have been utilized in the design of photonic structures to efficiently couple free-space propagating light onto highly confined surface modes, resulting in the enhancement of electromagnetic field intensities. Nonlinear optical effects benefit from plasmonic field enhancement, 3,4 and plasmonics has the potential to be an enabling technology for quantum optics and all-optical information processing. 5,6 It has been shown that plasmonic field enhancement allows the observation of Raman scattering from single molecules with low excitation powers down to microwatts. 7,8 The lack of reliability resulting from the spatially non-uniform nature of plasmonic field enhancement can be a problem for applications requiring repeatability. In the case of surfaceenhanced Raman scattering (SERS), regions with high enhancement (so-called hot spots) are typically major contributors to the observed signal. Raman intensity enhancement is estimated through I SERS = I 0 |E(ω exc )E(ω det )/E 0 (ω exc )E 0 (ω det )| 2 , where ω exc and ω det are the excitation and detection frequencies, and E and E 0 are the electric field intensities with and without the presence of plasmonic structures. Defining an enhancement factor, EF(ω) = |E(ω)/E 0 (ω)| 2 , overall Raman enhancement factor can be written as the product of excitation and detection factors, EF SERS = EF(ω exc )EF(ω det ). Spatial nonuniformity of the electric field directly translates into a spatial non-uniformity of EF SERS and can be an important disadvantage for repeatability. Hot spots are typically formed when two metal regions come close (within a few nanometers) to each other, and even periodic structures may display a wide distribution of enhancement factors. 9 In order to achieve high and spatially uniform field enhancement, engineered surfaces that exhibit plasmon modes at both the excitation and scattering wavelengths are needed. 10À13 Previously, metal nanoparticle clusters (bottom-up approach) and sparse structures or biharmonic gratings with however, benefits of strong coupling of dimers have been overlooked. Here, we construct a plasmonic meta-surface through coupling of diatomic plasmonic molecules which contain a heavy and light meta-atom. Presence and coupling of two distinct types of localized modes in the plasmonic molecule allow formation and engineering of a rich band structure in a seemingly simple and common geometry, resulting in a broadband and quasi-omni-directional meta-surface. Surfaceenhanced Raman scattering benefits from the simultaneous presence of plasmonic resonances at the excitation and scattering frequencies, and by proper design of the band structure to satisfy this condition, highly repeatable and spatially uniform Raman enhancement ...

Plasmonic field enhancement enables the acquisition of Raman spectra at a single molecule level. Here we investigate the detection of surface enhanced Raman signal using the unmodified image sensor of a smart phone, integrated onto a confocal Raman system. The sensitivity of a contemporary smart phone camera is compared to a photomultiplier and a cooled charge-coupled device. The camera displays a remarkably high sensitivity, enabling the observation of the weak unenhanced Raman scattering signal from a silicon surface, as well as from liquids, such as ethanol. Using high performance wide area plasmonic substrates that enhance the Raman signal 106 to 107 times, blink events typically associated with single molecule motion, are observed on the smart phone camera. Raman spectra can also be collected on the smart phone by converting the camera into a low resolution spectrometer with the inclusion of a collimator and a dispersive optical element in front of the camera. In this way, spectral content of the blink events can be observed on the plasmonic substrate, in real time, at 30 frames per second. (Figure Presented) © 2013 American Chemical Society

Aluminum, despite its abundance and low cost, is usually avoided for plasmonic applications due to losses in visible/infrared regimes and its interband absorption at 800 nm. Yet, it is compatible with silicon CMOS processes, making it a promising alternative for integrated plasmonic applications. It is also well known that a thin layer of native Al 2 O 3 is formed on aluminum when exposed to air, which must be taken into account properly while designing plasmonic structures. Here, for the first time we report exploitation of the native Al 2 O 3 layer for fabrication of periodic metal−insulator−metal (MIM) plasmonic structures that exhibit resonances spanning a wide spectral range, from the nearultraviolet to mid-infrared region of the spectrum. Through fabrication of silver nanoislands on aluminum surfaces and MIM plasmonic surfaces with a thin native Al 2 O 3 layer, hierarchical plasmonic structures are formed and used in surface-enhanced infrared spectroscopy (SEIRA) and surface-enhanced Raman spectrocopy (SERS) for detection of self-assembled monolayers of dodecanethiol. KEYWORDS: aluminum plasmonics, metal−insulator−metal cavities, surface-enhanced Raman spectroscopy, surface-enhanced infrared spectroscopy, nanoparticles, hierarchical structures R ecent advancement in plasmonics enabled the development of better performing plasmonic materials for the ultraviolet (UV) 1−5 and infrared (IR) 6−13 portion of the light spectrum. Typically gold (Au) and silver (Ag) are the most common materials used to fabricate nanostructures to study novel plasmon-enhanced materials and enable optical phenomena such as negative refraction, 14,15 transformation optics, 16 surface plasmon sensors, 17,18 surface-enhanced Raman spectroscopy (SERS), 19,20 surface-enhanced infrared absorption spectroscopy (SEIRA), 21,22 and plasmon-enhanced solar cells and detectors. 23,24 Au has an internal band transition around 500 nm, which limits utilization of gold toward the UV portion of the visible spectrum. 25 Due to its chemically inert properties, stability, and tailorable binding to biomolecules, Au is widely used for surface plasmon resonance sensor applications working at visible wavelengths closer to the NIR regime. Ag is considered the optimal material for plasmonic applications in the visible spectrum due to its low loss compared to other metals. 25 However, Ag suffers from atmospheric sulfur contamination and oxidation. 26 Aluminum arises as a promising material for UV 27,28 and deep UV plasmonic applications 3,4,29−31 owing to its high plasma frequency. Al has high losses from the visible to IR range as well as an interband absorption around 800 nm, which makes it less favorable as a NIR plasmonic material. 1,25,32 Still, localized plasmon resonances in Al have been demonstrated in several geometries, including nanoparticles, 27,30,33 triangles, 3,28,34 discs, 4,35,36 rods, and nanoantennas. 31,37,38 The relative abundance of Al can be advantageous for the design of plasmonic absorbers in solar energy conversion or for i...

In this work, we demonstrate an integrated sensor combining a grating-coupled plasmon resonance surface with a planar photodiode. Plasmon enhanced transmission is employed as a sensitive refractive index (RI) sensing mechanism. Enhanced transmission of light is monitored via the integrated photodiode by tuning the angle of incidence of a collimated beam near the sharp plasmon resonance condition. Slight changes of the effective refractive index (RI) shift the resonance angle, resulting in a change in the photocurrent. Owing to the planar sensing mechanism, the design permits a high areal density of sensing spots. In the design, absence of holes that facilitate resonant transmission of light, allows an easy-to-implement fabrication procedure and relative insensitivity to fabrication errors. Theoretical and experimental results agree well. An equivalent long-term RI noise of 6.3 × 10(-6) RIU/√Hz is obtained by using an 8 mW He-Ne laser, compared to a shot-noise limited theoretical sensitivity of 5.61 × 10(-9) RIU/√Hz. The device features full benefits of grating-coupled plasmon resonance, such as enhancement of sensitivity for non-zero azimuthal angle of incidence. Further sensitivity enhancement using balanced detection and optimal plasmon coupling conditions are discussed.

blueshifts as described by the Planck's law. The broad spectrum is useful for illumination purposes in the visible and as well as in the infrared. On the other hand, spectrally selective thermal emission is desired for applications like thermophotovoltaics, [1][2][3] radiative cooling, [4,5] sensing, [6][7][8] and near-infrared communication [9,10] by modifying the emissivity of the surfaces. The emissivity of a surface is equal to its absorbance in thermal equilibrium according to the Kirchhoff's law of thermal emission, ranging from 0 for a perfect mirror to 1 for a perfect absorber or a blackbody. A simple approach to modify the emissivity is finding a dielectric with phonon bands at the desired absorption wavelength range. A recent example is embedding glass microspheres in an infrared transparent polymer matrix for radiative cooling. [11] The dielectric dimensions can be as thin as micrometers when a back mirror, typically an optically thick metal layer is employed. This approach has been preferred for selective thermal emission since early 1980s, e.g., using ≈1 µm thick silicon monoxide on Al for radiative cooling. Owing to the simplicity of the structure, surfaces consisting of polar-dielectric-coated mirrors are still popular. [12] Stacking more than one type of polar dielectric layers broadens the absorption bands, that is especially useful for radiative cooling. [13] Using single [14] or multiple [1,15] lossless, that is infrared transparent, layers together with polar dielectrics introduce additional design parameters, hence offers better thermal-emission tunability.Despite the simplicity that the polar dielectrics offer, their emission spectra are limited with the absorption bands. An arbitrary emission spectrum can be achieved by optical resonators such as Salisbury screens that consist of a lossless dielectric layer between a bottom mirror and a thin lossy layer on the top. [16][17][18][19] The absorbance wavelengths (resonances) are mainly determined by the optical thickness of the lossless dielectric layer. Alternatively, the lossy dielectric can be coated directly on the mirror layer exhibiting strong interference effects. [20][21][22] The absorbance wavelengths in this case are primarily determined by the optical properties of the lossy layer and its thickness. The strong interference surfaces consist of a simple bilayer structure, but exhibit broad absorbance spectra. Nanostructured films of metal or lossy materials, e.g., micrometerscale gratings, [23] photonic crystals, [24] antennas, [15,25,26] provide a better control over the emission spectrum at the expense of the ease of fabrication. The emitter design can be as complex Spectrally selective thermal emission is in high demand for thermophotovoltaics, radiative cooling, and infrared sensing applications. Spectral control of the emissivity is historically achieved by choosing the material with suitable infrared properties. The recent advancements in nanofabrication techniques that lead to enhanced light-matter interactions enable optical pr...

Metal surfaces coated with ultrathin lossy dielectrics enable color generation through strong interferences in the visible spectrum. Using a phase-change thin film as the coating layer offers tuning the generated color by crystallization or re-amorphization. Here, we study the optical response of surfaces consisting of thin (5–40 nm) phase-changing Ge2Sb2Te5 (GST) films on metal, primarily Al, layers. A color scale ranging from yellow to red to blue that is obtained using different thicknesses of as-deposited amorphous GST layers turns dim gray upon annealing-induced crystallization of the GST. Moreover, when a relatively thick (>100 nm) and lossless dielectric film is introduced between the GST and Al layers, optical cavity modes are observed, offering a rich color gamut at the expense of the angle independent optical response. Finally, a color pixel structure is proposed for ultrahigh resolution (pixel size: 5 × 5 μm2), non-volatile displays, where the metal layer acting like a mirror is used as a heater element. The electrothermal simulations of such a pixel structure suggest that crystallization and re-amorphization of the GST layer using electrical pulses are possible for electrothermal color tuning.