single plasmonic nanoparticles as biosensors · single plasmonic nanoparticles as biosensors...

Single Plasmonic Nanoparticles as Biosensors

Jan Becker, Carsten Sönnichsen

Plasmonic nanostructures for applications in the lif e sciences


�Sensing properties of plasmonic particles

�Darkfield-microscopy (fastSPS)

�Protein-membrane interaction

�Improvement of Sensors

550 600 650 7000

1

0.2

0.4

0.6

0.8

Wavelength [nm]scat

terin

g ef

ficen

cy [a

rb.u

]400 600500 700

0

1

0.2

0.6

0.4

0.80.8

Wavelength [nm]

scat

terin

g ef

ficen

cy [a

rb.u

.]

λλλλ

Qsca

400 nm 700 nm λλλλ

Qsca

400 nm 700 nm

Optical Properties Depend on:

Material Shape Surrounding refractive index

�Resonance Position

�Linewidth (FWHM)

n=1.33 n=1.5

silver goldsphere

Darkfield Microscopy

objective

direct light

sample

DF condenser

scatteredlight

CCDspectrometer

grating

Entrance slit/pinhole

100 nm

TEM

CCDspectrometer

grating


Real color image

10 µm

Concept of single particle plasmon sensors

Statistics very important

Shift in resonancewavelength

For stochastic process investigation

λλλλ

Iscat

Conventional Method to Measure Single-Particle Spectra

400 450 500 550 600 650 700 7500

200

400

600

800

1000

Wavelength [nm]C

ou

nts/

10

sec/

11B

insSelect one particle

Disperse lightCapture the spectrum

serial process �� very slow!

CCD

The Scanning Method

wavelength

�� still slow!

Entrance Slit

The fastSPS Method

wavelength

LCD

�� many particles auto-matically observable in parallel

CCDspectrometer

grating


CCDspectrometer

grating

Entrance slit/pinholeLCD

fastSPS: fast Single Particle Spectroscopy

Nano Lett. (2007), 7, 1664

Au rods as Biosensor for Protein Binding

0 50 100 150 200 250 300655

660

665

Time [min]

Res

onan

ce W

avel

engt

h [n

m] Lipids STV TritonBuffer

0 50 100 150 200 250 300655

660

665

Time [min]

Res

onan

ce W

avel

engt

h [n


Nano Lett. (2008), 8, 1724

n=1.5H2O (n=1.33)

glass

FastSPS gives statistics with only one experiment

0 50 100 150 200 250 300655

660

665

Time [min]

Res

onan

ce W

avel

engt

h [n


0 50 100 150 200 250 300655

660

665

Time [min]

Res

onan

ce W

avel

engt

h [n


Single particle spectra:

-5 0 5 100

0.2

0.4

0.6

0.8

1.0

Shift [nm]C

umul

ativ

e P

roba

bilit

y add STV

∆=2.9nm

lipid

∆=3.6nm

triton

∆=0.5nm

Statistics on 29 particles

Nano Lett. (2008), 8, 1724

Sensitive detection of small spacer length

No biotin∆=1.2 ± 0.1nm

Incl. biotin:∆=5.3 ± 0.7nm

Incl. spacer∆=2.4 ± 0.4nm

glass

H2O

glass

H2O

glass

H2O

� smaller shift with longer spacer

� Membrane suppresses nonspecific interactions

-2 0 2 4 6 8 100

0.2

0.4

0.6

0.8

1

Shift to membrane coated rod[nm]

Cum

ula

tive

Pro

ba

bilit

y

Shift due to streptavidin binding:

Nano Lett. (2008), 8, 1724





�Improvement of Sensors�Reduction of Single Particle Linewidth

�Increasing Plasmon Sensitivity

Sensor Improvement

λλλλ

Iscat

n=1.33 n=1.5

∆λ∆λ∆λ∆λ

� Reduction of single particle linewidth increases resolution


λλλλ

n=1.33 n=1.5

Iscat

Ag Coating Reduces Single Particle Linewidth

Nano Lett. (2008), 8, 1719

550 600 650 700

30

40

50

60

Resonance wavelength (nm)

Lin

ew

idth

(n

m)

550 600 650 700

λres

FWHM

λres

FWHM

a 0 30 50 80 110 140 160 µM

b

Distance (nm)

Cou

nts

in 1

08

0 20 40

0

2

4

6

8

Ag

Au

Particle Characterization

Sensor Improvement

λλλλ

Iscat

n=1.33 n=1.5


� Reduction of single particle linewidth increases resolution

� Increased plasmon sensitivity results in larger wavelength shifts


λλλλ

n=1.33 n=1.5

∆λ∆λ∆λ∆λ’

λλλλ

n=1.33 n=1.5


λλλλ

n=1.33 n=1.5

Iscat

Iscat Iscat

Gold Nanorattles Show Improved Sensitivity

1.32 1.34 1.36 1.38

580

600

620

640

660

λλλλres ~185 n

Pla

smon

wav

elen

gth

λ res

[nm

]

Refractive index n [RIU]

λλλλres ~ 231 n

λλλλres ~ 227 n

Pla

smon

sen

stiv

ity Ю

[nm

/RIU

]

Starting plasmon wavelength 8res [nm]

550 600 6500

40

80

120

160

200

240

[1]

[2]

[2]

[3]

JACS, submitted

[1] Raschke et al. Nano Lett. (2003), 3, 935[2] Chen et al. Langmuir (2008), 24, 5233[3] Raschke et al. Nano Lett. (2004), 4, 1853

0 100 200 300 4000

0.2

0.4

0.6

0.8

1.0

Yu [nm/RIU]

Cum

ulat

ive

Pro

babi

lity

Ю

0 100 200 300 400Yu [nm]

∆Ю = 30nm/RIU

Plasmonic sensitivity Ю [nm/RIU]

Ю [nm/RIU]

50nm

Conclusions

� fastSPS allows continuous observation of many (up to 30) nano-particles in parallel

� Membrane and protein binding can be detected by shift in resonance wavelength of single nanorods

� Simple functionalizability of membranes (many different headgroups available) � ideal characterization tool for biomolecules

� Ag coating of Au rods reduces the single particle linewidth (at same resonance wavelength)

� Gold Nanorattles show improved sensitivity on changes in refractive index

wavelength

LCD

-5 0 5 100

0.2

0.4

0.6

0.8

1.0

Shift [nm]

Cum

ulat

ive

Pro

babi

lity add STV

∆=2.9nm

lipid

∆=3.6nm

triton0.5nm

-5 0 5 100

0.2

0.4

0.6

0.8

1.0

Shift [nm]

Cum

ulat

ive

Pro

babi

lity add STV

∆=2.9nm

lipid

∆=3.6nm

triton0.5nm

add STV

∆=2.9nm

add STV

∆=2.9nm

lipid

∆=3.6nm

lipid

∆=3.6nm

triton0.5nm

triton0.5nm

550 600 650 700

30

40

50

60

Resonance wavelength (nm)

Lin

ew

idth

(n

m)

550 600 650 700550 600 650 700

Pla

smon

sen

stiv

ity Ю

[nm

/RIU

]

Starting plasmon wavelength 8res [nm]

550 600 6500

40

80

120

160

200

240

[1]

[2]

[2]

[3]

Acknowledgement

Carsten Sönnichsen

CollaboratorsAndreas Janshoff, Cristina Baciu

Carl-Zeiss-Foundation

www.nano-bio-tech.de

Financial Support

More information:

I. Ament L. Carbone

I. ZinsC. RosmanS. Pierrat

Y. KhalavkaA. JakabA. Henkel

O. Schubert

A. Jakab

single plasmonic nanoparticles as biosensors · single plasmonic nanoparticles as biosensors...

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