EE235 Nanofabrication Technology Multifunctional Nanowire Evanescent Optical Sensors

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EE235 Nanofabrication TechnologyMultifunctional
Nanowire Evanescent Optical Sensors

• By By Donald J. Sirbuly, Andrea Tao, Matt Law,
  Rong Fan, and Peidong Yang

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Multifunctional Nanowire Evanescent Optical
Sensors

• Optical sensor
• Use nanowire to define the solution type and
  detect the solution concentration.

• Goal
• Reusable
• Small
• Multifunctional

Nanowire works as a sensor
Setup of the microchannel and the optical sensor
Setup of the microchannel and the optical sensor
Setup of the microscope
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Agenda

• Agenda
• Work function
• Experimental results
• Determine concentration
• Influence of Ag nanocube
• Influence of cladding refraction index
• Clean and reuse (remove metallic containment)
• Conclusion

Sketch of the microchannel
Optical sensor in the microchannel
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Work Function

• Nanowire
• Made by single crystal SnO2
• High refractive indices (ngt2)
• High aspect ratios (gt103) to allow longer device
• Chemical and mechanical properties to withstand
  harsh cleaning conditions
• Molecule of the solution influence the evanescent
  field
• Emit photons from one side of the nanowire and
  collect the output from the other side
• calculate the absorbance to gain the
  concentration and type of the solution

Clean PL
Sense PL
PL Intensity
Absorbance
Absorbance
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Concentration (I)

• EITC is the dye of the absorption measure.
• Absorbance varies with the concentration of the
  solution and the wavelength
• Peak absorbance is a linear function of
  concentration of EITC

Absorbance increases with concentration of EITC
Absorbance for different concentration
Linear!!
3 mM solution of EITC pass through a single
sensing channel
Peak absorbance v.s concentration
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Concentration (II)

• Different nanowire size
• Thinner nanowire (dlt150nm) has a decreased
  absorbance in longer wavelength
• Photons emitted near the ribbon surface are
  recaptured
• Thicker nanowire (dgt200nm) has a larger linewidth
• Penetration depth of evanescent field is a
  function of wavelength

A decreased absorbance
Larger linewidth
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Nanocube and Cladding Type

• Work function
• Nanocube is absorbed to the waveguide surface
• Nanocube scatter 5-10 waveguide light
• Complete attenuation occurred when 10-15
  nanoparticle
• Scattering is stronger if the evanescent has a
  larger refraction index

The inverse dependence of intensity of the index
of refraction is cased by the increase in
waveguide loss as the cladding index increase
Attach NPs
The PL intensity for different evanescent
refraction index
SnO2 waveguid bridge a single sensing channel
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Metallic Containment (Resue)

• Reuse can be achieved
• Remove metal nanostructures and regain the
  original waveguiding properties
• Use solution of aqua(11 HNO3/HClH2O)

Scattering images of a metal-decorated waveguide
upon introduction of a 11 HCl/HNO3H2O solution.
The time elapsed is 30 sec.
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Conclusion

• Nanowire is used to make a optical sensor
• Concentration and type of the solution can be
  easily determined with this new setup
• Reuse of this optical sensor can be achieved by
  removing the metallic containment with aqua.