Cataloged from PDF version of article.We demonstrate that graphene oxide can be reversibly reduced and oxidized using\ud electrical stimulus. Controlled reduction and oxidation in two-terminal devices containing multilayer\ud graphene oxide films are shown to result in switching between partially reduced graphene oxide and\ud graphene, a process which modifies the electronic and optical properties. High-resolution tunneling\ud current and electrostatic force imaging reveal that graphene oxide islands are formed on multilayer\ud graphene, turning graphene into a self-assembled heterostructure random nanomesh. Charge\ud storage and resistive switching behavior is observed in two-terminal devices made of multilayer\ud graphene oxide films, correlated with electrochromic effects. Tip-induced reduction and oxidation\ud are also demonstrated. Results are discussed in terms of thermodynamics of oxidation and reduction\ud reactions

Cataloged from PDF version of article.A polymer-embedded dendritic, bodipy-based panchromatic absorber with a built-in energy gradient concentrates incident solar radiation at a terminal chromophore, resulting in a monochromatized emission directed to the sides of the polymer waveguide (see picture). This particular design minimizes self-absorption losses from the peripheral antenna units with an impressive S factor of 10 000

Timely detection of infectious agents is critical in early diagnosis and treatment of infectious diseases. Conventional pathogen detection methods, such as enzyme linked immunosorbent assay (ELISA), culturing or polymerase chain reaction (PCR) require long assay times, and complex and expensive instruments, which are not adaptable to point-of-care (POC) needs at resource-constrained as well as primary care settings. Therefore, there is an unmet need to develop simple, rapid, and accurate methods for detection of pathogens at the POC. Here, we present a portable, multiplex, inexpensive microfluidic-integrated surface plasmon resonance (SPR) platform that detects and quantifies bacteria, i.e., Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) rapidly. The platform presented reliable capture and detection of E. coli at concentrations ranging from ~105 to 3.2 × 107 CFUs/mL in phosphate buffered saline (PBS) and peritoneal dialysis (PD) fluid. The multiplexing and specificity capability of the platform was also tested with S. aureus samples. The presented platform technology could potentially be applicable to capture and detect other pathogens at the POC and primary care settings.

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