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...

Plasmon enhanced hot carrier formation in metallic nanostructures increasingly attracts attention due to potential applications in photodetection, photocatalysis, and solar energy conversion. Here, hot-electron effects in nanoscale metal-insulator-metal (MIM) structures are investigated using a non-contact X-ray photoelectron spectroscopy based technique using continuous wave X-ray and laser excitations. The effects are observed through shifts of the binding energy of the top metal layer upon excitation with lasers of 445, 532, and 650 nm wavelength. The shifts are polarization dependent for plasmonic MIM grating structures fabricated by electron beam lithography. Wide area plasmonic MIM surfaces fabricated using a lithography free route by the dewetting of evaporated Ag on HfO2 exhibit polarization independent optical absorption and surface photovoltage. Using a simple model and making several assumptions about the magnitude of the photoemission current, the responsivity and external quantum efficiency of wide area plasmonic MIM surfaces are estimated as 500 nA/W and 11 × 10−6 for 445 nm illumination.

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