Optoelectronics

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• Optoelectronics Nanobiophotonics
• Ultrasensitive surface plasmon resonance sensors
• Surface plasmon coupled emission
• What do different yeast strains look like
• Fluorescence enhancing substrate-
• Homogeneous Silver-Coated Nanoparticles
• Ewa M. Goldys,goldys_at_physics.mq.edu.au, room E7A
  204Department of Physics and Engineering

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Sensor design
Surface plasmon resonance sensors are important
for ultrasensitive immunoassays with applications
in health diagnostics
Principle of immunoassays Reactions between two
protein molecules can be extremely specific. One
type of molecule (antibody) can be immobilised
on gold sensor surface The second (antigen) will
bind changing the refractive index This change
will be detected by changed angle of surface
plasmon resonance

• Challenges
• LED must be stable, preferably at a level
  10-7
• Detector response must be linear, with similar
  accuracy
• Readout must be very fast

• Opportunities
• Surface plasmons probe ultrathin regions
  (monolayer is enough)
• System can use inexpensive components, can run
  on Palm
• Sample can be extremely small (microfluidics)

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• ? Fluorescence emission is strongly directional
• ? Applications for fluorescence bioassays

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• Aims and Significance
• ? Characterisation of microorganisms by using
  intrinsic fluorescence.
• ? Faster, simpler, reliable no reagents
  required.
• ? Possible application in industrial processes
• Process monitoring (ethanol, beer etc.)
• Identification of contaminants

Problem Variations between cells in pure
strain Diverse size, fluorescence intensity,
texture Solution Characterize populations
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Au Core Ag-shell NP Surface 47 nm Fluorescence
enhancement of about 10
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Bacteriuria urinary tract infection

• Lower fluorescence intensity in normal urine
  than in bacteriuria (factor of 20)

Proposed mechanism - Tryptophan depletion through
increased
IDO activity accompanying the infection