J.-H. Yoon, L. Langolf, W. Xie,R. Grzeschik, E. Stepula,

X. Wang, Y. Zhang, Sebastian Schlücker

University Duisburg-Essen

Department of Chemistry

www.uni-due.de/schluecker-lab

Surface-enhanced Raman Spectroscopy and Imaging with Molecularly Functionalized Noble Metal Nanoparticles

Raman Workshop@ETHZ13th June 2018

ω0 ωvib

Modulated electricfield with angular frequency ω0 ωvib+-

ω0 ωvib-ω0 ωvib+ ω0

Classical Description of Raman Scattering

Induced dipole moment:

Nano-Antenna: Receiver and Transmitter

Localized Surface Plasmon Resonance (LSPR) Excitation on AuNP

Normal versus Surface-Enhanced Raman Scattering (SERS)

Normal Raman:IR ∝ E2

The Electromagnetic Enhancement (EM) Contribution

SERS:ISERS ∝ │EL(ω0)│2

E∝ 1/d3

∝ 1/d12 Sensitivity

· │EL(ωR)│2 ≈ E4

Surface selectivity

Normal versus Surface-Enhanced Raman Scattering (SERS)

A Short History of Surface-enhanced Raman Scattering (SERS)

1973 - First observation (Fleischmann) 1977 - First explanation & quantitative measurement (Van Duyne)1978 - Electromagnetic model for SERS (Moskovits)1997 - First observation of single-molecule SERS (Nie, Kneipp)

SERS Enhancement Factor (EF):SERS Signal/Number of Molecules on Surface

Normal Raman Signal/Number of Molecules in Solution

EM = plasmonic (up to ~1011) × CM (non-plasmonic up to ~102-3)

SERS labels (nanotags)

NP

= Raman label= Raman reporter

SERSlabel

vs. Label-free

NP

= analyte moleculein solution

SERS Applications with Noble Metal Colloids

• Detection of Analytesbiomolecules, drugs, explosives, food components, pharmaceuticals, pigments (e.g., in paintings)

• Chemical Reaction Monitoring

• Immunoassays• iSERS Microscopy

SERS Literature: From Fundamentals to Applications

Surface-Enhanced Raman Spectroscopy: Concepts and Chemical Applications

Angew. Chem. Int. Ed. 2014, 53, 4756-4795.

Maximum Signal Enhancement: Dimers for Ultrasensitive SERS

DimerMonomer

Hot SpotDependent on Gap Distance

Dimers: Generating a HOT SPOT

Inter-gap

Intra-gap

Crevice

Physical Chemistry I @ UDE

Precision Plasmonics

SERS nanotags/labelsimmuno-SERS (iSERS)

Chemical Energy Conversion

Small 2018

Angew. Chem. 2009

Chem. Comm. 2014

Small 2010

Nanoscale 2013

Small 2011

PCCP 2015Analyst 2016

Anal. Chem. 2018

Chem. Comm. 2012 JACS 2011

JACS 2013

Angew. Chem. 2016

Nature Comm. 2017

Nature Comm. 2015

Anal. Chem. 2017

Theory: Ideal Dimers of Gold Nanospheres

Plasmon Hybridization(cf. LCAO theory)

Nordlander et al.

kE

Two spheres separated by a very small defined gap

Towards Ideal Dimers: Experimental Challenges

Colloidal AuNPs

Gold nanoparticles are not perfectly spherical

but are nanocrystals

NPs by EBL

kE

Two spheres separated by a very small defined gap

Halas et al. Nano Lett. 2013, 13, 3281.

Non-Spherical Particles with Controlled Gap Distance

Single particle dark fieldscattering spectra

Controlled short gap distance:C8 dithiol (ca. 1.3 nm)

Non-idealdimers

Precision Plasmonics: Ideal Dimers of Gold Nanospheres

Non-idealdimers

idealdimers

Precision Plasmonics: Ideal Dimers of Gold Nanospheres

idealdimers

Small 2018

Correlative Single-Particle Rayleigh/SERS Imaging in Suspension

Rayleigh

Raman

Anal. Chem. 2018

Single-Particle SERS of Dimers in Suspension

100 ms / frame

Rayleigh

Raman Raman

Rayleigh

10 ms / frame

Anal. Chem. 2018

Summary 1: Precision Plasmonics with AuNP Dimers

Correlative Rayleigh/SERS video rate imaging of single NPs in suspension

uniform structure (gap morphology) uniform scattering spectra

2: Rayleigh/Mie

1: Raman orFluorescence

100 % (Ref.)

x % (?!)

Physical Chemistry I @ UDE

Precision Plasmonics

SERS nanotags/labelsimmuno-SERS (iSERS)

Chemical Energy Conversion

Small 2018

Angew. Chem. 2009

Chem. Comm. 2014

Small 2010

Nanoscale 2013

Small 2011

PCCP 2015Analyst 2016

Anal. Chem. 2018

Chem. Comm. 2012 JACS 2011

JACS 2013

Angew. Chem. 2016

Nature Comm. 2017

Nature Comm. 2015

Anal. Chem. 2017

Applications of SERS with Plasmonic Nanoparticles

Label-free SERS

NP

= analyte moleculein solution

SERS NP labels = Nanotags

NP

= Raman label= Raman reporter molecule

SERSlabel

vs.

vs.

Spectral Multiplexing: Small Width of Raman Peaks

Nanoscale 2014

Spectral Multiplexing with SERS Labels

Detection of multiple labelsin a single measurement!

# 1label

# 2 label

# 3 label

# 4 label

Wavenumber (cm-1)

Anal. Bioanal. Chem. 2009

SERS Multiplexing: Quantitative 6-plex

400 600 800 1000 1200 1400 1600 18000.0

0.2

0.4

0.6

0.8

1.0 Mixture (measured) Mixture (calculated) Difference

norm

. SER

S In

tens

ity

wavenumber [cm-1]

BMBATFMBATN MMTAA MNBAMMC+ + + + +111 1 11: : : : :

Quantitative 6-Color SERS Experiments (Cuvette)

1 2 3 4 50

0.5

1

1.5

2

2.5

3

3.5

1:1:1:1:1:1 1:1:1:3:3:3 1:3:1:3:1:3 3:1:3:1:3:1 3 :3:3:1:1:1

J. Raman Spectrosc. 2016

Example: Benign vs. Cancerous Prostate Biopsies

Benign: (+)-P63 (tumor suppressor; cancer-specific)

Cancerous: (-)-P63iSERSBF & iSERS iF iF & iSERS

Benign

PSA

P63

+

+

+

-

Cancerous

2-Color-iSERS: Benign vs. Cancerous Prostate Biopsies

Benign

PSA

P63

+

+

+

-

Cancerous

2-Color-iSERS: Benign vs. Cancerous Prostate Biopsies

Summary 2: SERS nanotags for iSERS microscopy & assays

SERS label= plasmonic NP & Raman reporter& shell (optional)

Multiplexing (colours) & Quantification

photostable& bright (single NPs!)

Long term goal: Personalized diagnostics(quantitative, multi-marker)

iSERS= immuno-SERS microscopy

Physical Chemistry I @ UDE

Precision Plasmonics

SERS nanotags/labelsimmuno-SERS (iSERS)

Chemical Energy Conversion

Small 2018

Angew. Chem. 2009

Chem. Comm. 2014

Small 2010

Nanoscale 2013

Small 2011

PCCP 2015Analyst 2016

Anal. Chem. 2018

Chem. Comm. 2012 JACS 2011

JACS 2013

Angew. Chem. 2016

Nature Comm. 2017

Nature Comm. 2015

Anal. Chem. 2017

Plasmonic NPs for Chemical Energy Conversion

J. Am. Chem. Soc. 2011

Au

Pt

BifunctionalAu/Pt/Au

nanoraspberries

Microfluidic SERS: Label-free Kinetic Reaction Monitoring

4-NTP 4-ATPNO2

S

NH2

S

NaBH4, Pt-Kat.

NP NP

4-ATP

Angew. Chem. Int. Ed. 2016, 55, 13729.

NO2

S

NH2

S

NaBH4, Pt-Kat.

NP NP

NO2

S

NaBH4, Pt-

NP

Model Reaction: Nitro to Amino Reduction (NaBH4, Pt-cat.)

4-NTP

4-ATP

AgS

NO2

AgS

NH2hν

HCL

Wavenumber / cm-1

H2SO4

HCl

NaCl

H2SO4 + NaCl

Ram

an In

tens

ity

νs(NO2)

νs(C−C)(4-ATP)

νs(C−C)(4-NTP)

H2O

Surprise: Hydride Reduction without Hydride Reagents!

no NaBH4 !

4-NTP

Ag core/Ag satellite NPs

4-ATP

Hot Electrons & Photorecycling (AgX)

Formally: Hydride reduction without hydridesH- equivalent in protic environment: H- = H+ + 2e-

-

Nature Comm. 2015

Hot Electrons Drive Nano-Localized Chemistry

Nature Comm. 2017

d)

Plasmon

Radiative channelScattering

Non-radiative channel

Electron-phonon coupling

Heat

Hot electrons

Absorption

Charge carrier generation

Label-freeSERSOR

iSERS labels

ReductionChemistry;

Photorecycling

Photothermaleffect

Decay

Summary 3: from label-free SERS to plasmonic chemistry

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