ECE280: Nano-Plasmonics and Its Applications

Week2Week2

Surface Plasmon Resonance SensingSurface Plasmon Resonance Sensing

Surface Plasmon ResonanceSurface Plasmon Resonance

Surface Plasmons:

• Coherent fluctuations of free electrons• Nonradiative, evanescent confinement

21 ε

ω

+p

pω

ck=ω

xk

1.00

0.75

0.50

0.25

0

500

750

1000

1250

1500

Wav

elen

gth

(nm

)Incident Angle (degree)

62 7064 6866

SP Based SensorsSP Based SensorsConcept: the refractive index change will shift the resonance angle

2/1

22

22

⎟⎟⎠

⎞⎜⎜⎝

⎛

+=

m

mx n

nc

kεεω

)sin(1 θnk x =

n1

Operation Modes of SPR SensorOperation Modes of SPR Sensor

62 63 64 65 66 67 680.0

0.2

0.4

0.6

0.8

1.0

Δθ

refle

ctiv

ity

angle62 63 64 65 66 67 68

ΔR

angle

angular shift measurement intensity change measurement

SPR SensorsSPR Sensors

• Real-time• Label-free• Kinetic study• Sub-monolayer

sensitivity• High time

resolution• Regeneration of

fluid cells

• High specificity and sensitivity depending on the surface treatment• High level of integration, e.g. on-chip mass spectrum or

electrochemical analysis Nature Reviews Drug Discovery 1, 515-528 (July 2002)

A typical binding cycle observed with an SPR biosensor

ApplicationsApplications

Life ScienceLife Science• Immunosensing (ligand-receptor, antibody-antigen, etc.)• DNA/protein, protein/protein and protein/drug interactions• Protein unfolding and conformational changes• Drug discovery and development

Electrochemical SPR MeasurementsElectrochemical SPR Measurements• Anodic stripping analysis • Electropolymerization, electrodeposition, and corrosion• Conformational changes of immobilized redox molecules• Charge transfer processes• Potential-controlled molecular adsorption processes

Chemical Vapor Sensing Chemical Vapor Sensing • Fundamental solid-gas interface studies • Detection of toxic molecules in the environment• Chemical analysis of human breathes for medical research

One Example: One Example: ellipsometricellipsometric techniquetechnique

Sensitivity Sensitivity

Refractive index sensitivity ~ 2*10-7

Optical Fiber SPP SensorsOptical Fiber SPP Sensors

DualDual--Channel SPR SensorChannel SPR Sensor

Electronics Letters 35, 1105, 1999

Commercial SPR SensorsCommercial SPR Sensors

Resolution ~ 10Resolution ~ 10--66 RIURIU

GoosGoos--HHäänchen Effectnchen Effect

• Total internal reflection• Requirement of energy penetration

L. Dutriaux, et al., Phys. Rev. Lett. 68 931 (1992)

krx ∂Φ−∂=Δ /

Phase Singularity & SensitivityPhase Singularity & Sensitivity

(a) Reflectivity (b) Phase (c) GH shifts of an ATR device under different

excitation conditions.

For a fixed system configuration:PrismMetal (thickness)

GoosGoos--HHäänchen Shift SPR Sensornchen Shift SPR Sensor

42 44 66 68 70 72-10

0

10

20

30

400.00.20.40.60.81.0 BK7/Au/Liquid

45nm 48nm 50nm

@ 750nm

refle

ctiv

ityΔ

TE-T

M (λ

) BK7/Au/Liquid 45nm 48nm 50nm

@ 632.8nm

BK7/Ag/Air 35nm 50nm 60nm

@ 632.8nm

angle

Design Parameters of GH SPR SensorDesign Parameters of GH SPR Sensor

• Incident wavelength (λ)• Material parameters

– ATR device: Prism / Gold / Liquid (~1.35)– Critical angle, and SPR angle are determined

• Sensor Geometry – Incident angle– Metal film thickness– Fluidic cell volume

• Quantities probed– Reflectivity

• Quantum efficiency, wavelength– Goos-Hänchen effect

• Sensitivity & Tolerance

One ExampleOne ExampleWavelength 980 nm (diode)Wavelength 980 nm (diode)Materials BK7/Gold/WaterMaterials BK7/Gold/Water

thickness 420 Athickness 420 ASPR Angle < 65 degreeSPR Angle < 65 degreeVolume ~ 200Volume ~ 200μμll

ImplementationImplementation

64.0 64.5 65.0 65.50.0

0.2

0.4

0.6

0.8

1.0

Incident Angle (degree)

Ref

lect

ivity

0

20

40

60

80

GH

Shifts (μm)

Sensitivity of the Sensitivity of the ghSPRghSPR SensorSensor

0 2 4 6 839.0

40.0

41.0

42.0

43.0

44.01.000 1.002 1.004 1.006 1.008 1.010

0 10 20 30 40 50 6039

40

41

42

Shift

s (μm

)

Index Change (10-5 RIU)

Concentration (M)

Time (min)

NaClNaCl Aqueous Solution Aqueous Solution

Reflective index Reflective index 8.7x108.7x10--33 RIU/MRIU/M

SensitivitySensitivity0.56x100.56x1055 μμm/RIUm/RIU7.7x107.7x10--77 RIURIU

Appl. Phys. Let. 89, 21108, 2006

Application of the Application of the ghSPRghSPR SensorSensor

low affinity proteinlow affinity protein--antibody bindingantibody bindingoptical amplificationoptical amplification

fobj

flen

100len

obj

fDd f

δδ

= >

NA = 1.45 or 1.65

PSD

0.600

0.800

1.000

PBS injection (twice)

Shi

ftsstrepatavidin0.1 mg/ml ~ 0.5 ml

peptide-MHC

PBS injection (twice)

α-H2Kb (negative)

0.05 mg/ml

PBS injection (twice)

PBS injection (twice)

IEk (positive)0.02 mg/ml

0 30 60 90 120 150 1805

Time (min)