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Optical Characterization and Nanophotonics Laboratory

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Interferometric Reflectance Imaging Sensor

Direct monitoring of primary molecular-binding interactions without the need for secondary reactants would markedly simplify and expand applications of high-throughput label-free detection methods. A simple interferometric technique is presented that monitors the optical phase difference resulting from accumulated biomolecular mass. As an example, 50 spots for each of four proteins consisting of BSA, human serum albumin, rabbit IgG, and protein G were dynamically monitored as they captured corresponding antibodies. Dynamic measurements were made at 26 pg/mm2 SD per spot and with a detectable concentration of 19 ng/ml. The presented method is particularly relevant for protein microarray analysis because it is label-free, simple, sensitive, and easily scales to high-throughput.

Carlos A. Lopez

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Apertureless Near-Field Scanning Optical Microscopy

Near-field scanning optical microscopy (NSOM) provides optical and topographic sample characterization with a spatial resolution on the order of tens of nanometers – providing the benefits of optical microscopy while circumventing the spatial resolution limits of far-field optical microscopy. We are building an NSOM system that will characterize the local electromagnetic field intensity and local Raman signal enhancement on substrates with gold nanostructures positioned in an array according to aperiodic mathematical sequences. A near-field characterization of these deterministic aperiodic nanostructures is likely to reveal “hot spots” with Raman enhancement factors that are greater than the spatially averaged values that have been reported. The nanoscale study of the light-matter interactions on these samples may lead to the design of substrates that are tuned to yield an even greater Raman signal enhancement.

Marc Mcguigan

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GK12: Boston Urban Fellows

Boston Urban Fellows (formerly Project STAMP – Science, Technology and Math Partnerships) partners graduate fellows in biology, chemistry, engineering, mathematics, and physics with teachers in K-12 classrooms in Boston public schools. Its purpose is to enhance the curricula in science, mathematics, and technology classrooms by partnering graduate and undergraduate student fellows with K12 teachers. The expected outcome is that these teacher-fellow teams will form close working relationships, share their experiences and expertise with one another, and provide additional resources and enhanced content within the classroom. Boston University has forged partnerships with four area school districts, Boston, Chelsea, Quincy, and Newton. Boston Urban Fellows typically spend 10 hours per week in the class, teaching lessons, assisting in laboratories, and working directly with students.

Bennett B. Goldberg

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Graphene Spectroscopy

Graphene is a thin, monoatomic layer of graphite. Despite the fact that it is produced virtually every time a pencil is used, it was first fabricated on silicon oxide substrates in 2004. Graphene shows remarkable electronic properties. Its valence and conduction bands touch, which makes graphene a zero gap metal or semiconductor, depending on its doping level. Around the Dirac point, the point in momentum space where the bands touch, the electronic dispersion relation is linear in momentum, mimicking the behavior of mass-less relativistic particles such as photons. Therefore graphene is an exciting condensed matter model system for relativistic physics. During the last four years, a quickly growing number of physicists has been conducting research on the electronic and optical properties of graphene. In our lab, spatially resolved Raman spectroscopy on mono- and bilayer graphene samples in low temperatures is carried out. Electrical transport measurements on gated samples are also under investigation.

Sebastian Christoph Remi

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Nanotube spectroscopy

A carbon nano-tube can be thought of as a graphite sheet rolled up into a cylinder. The diameter is of the order of 1 nm while the tube can be several micrometers long. Due to the small circumference, the electronic structure is effectively one-dimensional and it depends solely on the direction the graphite sheet is rolled up (the chirality) and the diameter of the tube. Specifically, the tubes can be either semi-conducting with varying energy gap, or metallic, depending on the rollup parameters. Hence these tubes provide the means to explore fundamental 1D physics, as well as potential applications such nm scale semiconductor devices. We use resonant Raman scattering to characterize the tubes, where we utilize the strong dependence of the resonance conditions on the lattice vibrations and the electronic structure.

Anna K. Swan

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Numerical Aperture Increasing Lens Microscopy

The numerical aperture increasing lens (NAIL) is a plano-convex lens placed on the planar surface of an object to enhance the amount of light coupled from subsurface structures within the object. In particular, a NAIL allows for the collection of otherwise inaccessible light at angles beyond the critical angle of the planar surface of the object. Therefore, the limit on numerical aperture increases from unity for conventional subsurface microscopy to the refractive index of the object for NAIL microscopy. Spherical aberration associated with conventional subsurface microscopy is also eliminated by the NAIL. Consequently, both the amount of light collected and diffraction-limited spatial resolution are improved beyond the limits of conventional subsurface microscopy.

Fatih Hakan Koklu

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Opto-Electrical Wireless Neural Stimulators

Electrically powered implanted actuators are commonly used for neural tissue micro-stimulation to research treatment of a variety of neurological disorders. Currently, these actuators are being activated by electrical power delivered through electrodes tethered to the skull, resulting in tissue damage for long-term implants. Optically powered silicon photodiodes can electrically stimulate neural tissue without causing tissue damage. At the near-infrared range of 850nm, an optical power source can safely penetrate human tissue. We have designed and fabricated silicon photodiodes for implantation and opto-electrical stimulation of neural tissue to meet both electrical performance and tissue biocompatibility demands. These devices are expected to facilitate advancements in the study of neurological disease treatment.

David S. Freedman

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Platform for Quantified High-throughput Measurement of Protein Induced Conformation Changes in DNA

A new strategy exploits a platform developed at TUM that can accommodate multiple spots of microarrayed dsDNA on individually controlled, lithographically-designed electrodes. This platform allows biomedical researchers to measure DNA conformation changes in real-time. While biomedical researchers have long traced the onset of many diseases to genetic code irregularities, they’re paying increased attention to another potential source: a class of molecules that bind to specific sequences of the double stranded DNA (dsDNA) molecules. Transcription factor proteins, nucleosomes and other DNA-binding molecules may bend DNA and bring distant segments of DNA into close proximity, thereby causing genes to turn on or off. By better understanding the impact of DNA-binding molecules upon different DNA sequences, scientists hope to accelerate efforts to discover the causes of and potential treatments for a wide range of genetic diseases.

Philipp Stefan Spuhler

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Quantum Dot Spectroscopy

Time resolved micro-photoluminescence(PL) and nano-PL of InGaAs quantum dots spectroscopy. With the techneque of solid immersion microscopy, we are working on high resolution spectroscopy of individual quantum dots. We also do time resolved spectroscopy to investigate the dynamcis of quantum dots system.

Abdulkadir Yurt

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Research Experiences for Teachers Site in Biophotonics

RET places teams of two K-12 teachers, usually middle or high school science teachers, in biophotonics laboratories for a six week program in summers 2010, 2011, and 2012. RET teachers are here to see how research engineering happens, and to understand the skills and habits of thought that make a good engineer/researcher.  They will then share these observations with their students and colleagues, and some will present at a special NSTA (National Science Teachers Association) session on RET.

Michael F. Ruane

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