| Ray
Dessy's
RESEARCH AREAS |
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 Surface
Plasmon Resonance Sensors
Dialkyl
DithioPhosphate Monolayers
Ionic
Self-Assemblying Poly-layers
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| Surface
Plasmons are oscillations of electrons in thin films that may be excited
by photons. At resonance conditions there is a maximum transfer of
energy from the photon flux to the plasmon. This is surface plasmon
resonance (SPR).
The technique is well suited to examination of the nature of thin films on surfaces, and for the creation of bioanalytical and polymer property sensing. Typical configurations for such devices are : |
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| The exciting photon radiation and the plasmon are associated with an energy called a wave-vector. For the photons, this wave-vector is controlled by the angle that the light beam strikes the metal film supporting the sample, the wave-length of the light source, and the refractive index of the wave-guides. The plasmon's wave-vector is determined by the composition and thickness of all the laminate layers above the wave-guide. We have little control over the later, but can easily alter the angle and wave-length of the photon beam. The angle or wave-length of light that causes maximum energy transfer is the measured analytical response. As the effective refractive index and/or thickness of the laminate layers is changed, the analytical response also changes. The plasmon energy field extends only about 100 nm into the layers above the metal film, so SPR is ideal for measuring changes in thin films on the surface. In biosensors this change usually involves one member of a bioconjugate pair bound to the surface, and introduction of the other conjugate into the environment. Our lab is also interested in the development of arrays of SPR sensors which rely on a third tuning mechanism to attain resonance. This involves changing the refractive index of the wave-guide, using electro-optic materials and applied electric fields. In this way one can construct an array with hundreds of sensors, each having a diameter of ~ 100 u, that can be randomly addressed in an X-Y coordinate manner. | ||||||||||||
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| The devil in SPR is tethering the analyte system to the metal surface. Traditionally, alkyl thiols are the first step in the process. Our lab is interested in the dialky dithiophosphates as an alternate. These materials have two bonding groups which help orient the molecules in the self-assemblying monolayer. The two alkyl groups can be different, creating a herring-bone pattern at the surface. On top of this growing parfait, it is possible to create alternating monolayers of charged polymer films. The electrostatic forces between films of opposite charge create a strong construction that also provides a matrix for bioconjugate materials. | ||||||||||||
| On top of this growing parfait, it is possible to create alternating monolayers of charged polymer films. The electrostatic forces between films of opposite charge create a strong construction that also provides a matrix for bioconjugate materials. | ||||||||||||
| The
acoustics of historical woodwinds is a deceivingly simple area. You blow
into a tube, and a sound is created. But what are the physical principles
involved? Even today, these principles are often elusive and controversial.
Engineers such as John Coltman, or physicists such as Arthur Benade have
pursued the area with vigor. Our lab also pursues these elusive notes,
and some of its efforts appear on the well-reputed website: http://www.iinet.net.au/~nickl/wood.html
The music that some of these instruments play has an equally elusive history. The African-American Blues, born at the turn of the last Century, is an example. A short history of the subject for the Baroque recorder can be found at: http://iinet.net.au/~nickl/blues.html A longer analysis of the "Blues Gene" from a technological and political vantage point is found in Garland's "Essays in American Music, Vol. III": http://www.chem.vt.edu/chem-dept/dessy/blues/blues.htm Finally, it is fun playing these instruments for street audiences, an activity called "busking", a term presumably derived from boots that traditional stage actors wore. Some comments on this activity can be found in "Down and Out in Bonn and Brussels" that describes some playing environments we have experienced: http://www.iinet.net.au/~nickl/busking.html We are also interested in the acosutics of the fretted dulcimer and the harmonica, just several hundred years old. Keep listening for details. |
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