Counting molecules with a mobile phone camera using plasmonic enhancement

Cataloged from PDF version of article.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 10(6) to 10(7) 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

Improving students' understanding and explaining real life problems on concepts of reaction rate by using a four step constructivist approach

The aim of this study was to investigate the effects of activities developed based on a four-step constructivist approach on students' understanding and explaining real-life problems about reaction rate concepts in chemistry. The study was carried out with 41 eleventh grade students, from two different classes attending a secondary school in Turkey. Two classes were randomly designated as experimental and control groups. While teaching the subject, a four-step constructivist approach was used for the experimental group whereas in control group, students were taught by the traditional method. Teaching activities in both groups were observed by one of the researchers. In both groups, Real-life Relating Test (RRT), including the phenomena that students observe in their daily life about reaction rate concepts was implemented before and after the intervention. Also semi-structured interviews were conducted with 13 students chosen from the both groups. At the end of the study, it was determined that the intervention which was carried out based on a four-step constructivist approach helped more the students in explaining real-life problems in a scientific way and provide more lasting learning than traditional approach. It is suggested that such activities should be used in other abstract or problematic concepts in chemistry. © Sila Science. All rights reserved

International clinical rotations during U.S. residency training: Creating an accreditation council for graduate medical education-approved rotation

Healthcare professionals increasingly report interest in global health and participation in international healthcare delivery. Growth opportunities exist for trainees to improve knowledge, skills and attitudes through international experiences. Professional development via international medicine may have lasting effects on patient care and practice patterns following training. In 2010, the first resident took part in an international, exchange elective between The George Washington University’s Department of Anesthesiology in Washington, DC and La Universidad de San Francisco’s Department of Anesthesiology in Quito, Ecuador. This resident elective rotation resulted from a strategic partnership, initiated in 2008, between two training institutions with an established track record of medical student educational exchange programs. The goal of any resident elective rotation should be to enhance an educational experience, to improve upon a perceived training deficiency, or to create a unique offering that takes advantage of local assets and connections. International electives, if properly conceived, can accomplish all three goals. This guide for program leadership addresses the rationale and challenges, from concept to Accreditation Council for Graduate Medical Education approval, of creating an international clinical rotation for residents

Microwave sintering of SiAlON ceramics with TiN addition

α-β SiAlON/TiN composites with nominal composition of α:= β25:75 were fabricated by microwave sintering. The effect of titanium nitride addition on the phases, microstructure, microwave absorption ability and mechanical properties (Vickers hardness and fracture toughness) of the SiAlON-based composites were studied. Finite Difference Time Domain (FDTD) software was used for the numerical simulation in order to assess the most suitable experimental setup. Sintering trials were performed in a single mode microwave furnace operating at 2.45 GHz and a power output of 660W, for a reaction time of 30 min. SiC blocks were used as a susceptor to accelerate the microwave processing by hybrid heating, with reduced heat losses from the surface of the material of the α- βSiAlON/TiN composites. The optimum comprehensive mechanical properties, corresponding to a relative density of 96%, Vickers hardness of 12.98 ± 1.81 GPa and Vickers indentation fracture toughness of 5.52 ± 0.71 MPa.m1/2 were obtained at 850°C when the content of TiN was 5 wt.%

Rounding corners of nano-square patches for multispectral plasmonic metamaterial absorbers

Multispectral metamaterial absorbers based on metal-insulatormetal nano-square patch resonators are studied here. For a geometry consisting of perfectly nano-square patches and vertical sidewalls, double resonances in the visible regime are observed due to simultaneous excitation of electric and magnetic plasmon modes. Although slightly modifying the sizes of the square patches makes the resonance wavelengths simply shift, rounding corners of the square patches results in emergence of a third resonance due to excitation of the circular cavity modes. Sidewall angle of the patches are also observed to affect the absorption spectra significantly. Peak absorption values for the triple resonance structures are strongly affected as the sidewall angle varies from 90 to 50 degrees. Rounded corners and slanted sidewalls are typical imperfections for lithographically fabricated metamaterial structures. The presented results suggest that imperfections caused during fabrication of the top nanostructures must be taken into account when designing metamaterial absorbers. Furthermore, it is shown that these fabrication imperfections can be exploited for improving resonance properties and bandwidths of metamaterials for various potential applications such as solar energy harvesting, thermal emitters, surface enhanced spectroscopies and photodetection. © 2015 Optical Society of America

Probing hot-electron effects in wide area plasmonic surfaces using X-ray photoelectron spectroscopy

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. © 2014 AIP Publishing LLC

All-aluminum hierarchical plasmonic surfaces in the infrared

All-Aluminum metal-insulator-metal resonator structures withmultiple metal-insulator stacks showing resonances in the mid-infrared(MIR) are fabricated. Ultrathin native Al2O3 is used as the insulator layersenabling simple fabrication of the resonator structures. The structures withtwo oxide layers exhibit two distinct resonances in the MIR. Simulation ofthese structures shows confinement of magnetic field to the thicker bottomoxide at the shorter wavelength resonance and to the thinner top oxide at theother resonance. Simulations of higher order hierarchical structures with 3 and 4 oxide layers show multispectral response with precise control of theoxide thicknesses. The studied structures show great potential for IRapplications that require durability and multispectral characteristics. © 2016 Optical Society of America

Multispectral plasmonic structures using native aluminum oxide and aluminum

We report the use of native aluminum oxide to fabricate periodic metal-insulator-metal resonators with simultaneous resonances in the visible and IR wavelengths. The cavity size is in the order of λ3/25000 in the NIR. © 2017 OSA

Raman Enhancement on a Broadband Meta-Surface

Cataloged from PDF version of article.Plasmonic metamaterials allow confinement of light to deep subwavelength dimensions, while allowing for the tailoring of dispersion and electromagnetic mode density to enhance specific photonic properties. Optical resonances of plasmonic molecules have been extensively investigated; 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. Surface-enhanced 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 is demonstrated. On the basis of calculations of the field enhancement distribution within a unit cell, spatial uniformity of the enhancement at the nanoscale is discussed. Raman scattering constitutes an example of nonlinear optical processes, where the wavelength conversion during scattering may be viewed as a photonic transition between the bands of the meta-material

Grating coupler integrated photodiodes for plasmon resonance based sensing

Cataloged from PDF version of article.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 x 10(-6) RIU/root Hz is obtained by using an 8 mW He-Ne laser, compared to a shot-noise limited theoretical sensitivity of 5.61 x 10(-9) RIU/root 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