Applications of Surface-Enhanced Raman Scattering (SERS)

Hui-Hsin LuPostdoctoral fellow to Prof. Chii-Wann Lin

Outline

• History • Principle of Raman spectroscopy• Principle of SERS• Various of SERS-active substrates• Applications

– Nanostructures– Immunoassay– Living cell– Tumor tag– Microfludics

History of Raman scattering

• 1923– Predicted by Adolf Smekal

• 1928 – Observe on particle– By means of sunlight

• 1930– Nobel Prize for Physics

• 1960– Laser

• 1974 – SERS

• Recently, nano-tech….. C. V. Raman, 1888-1970 /rɑːmən/

Vibration spectra of molecules

Molecular spectra

Molecular structure

Molecule

Energy

Internuclear separation

Excited electric state

Ground state

Electronic transition (in

VIS or UV)

Vibration transition (in

infrared)

Rotation transition (in microwave)

Virtual state

(Raman)

Vibration spectra[Cu(pic)2].2H2O

Principle of Raman scattering

MLS hhh MLS hhh 2

The Vs is the Raman spectra.

Setup of Raman scattering system

Based on this simple scheme…• Embedded to microscopy• Embedded to SNOM• Embedded to optical tweezers• Embedded with time-resolved

module• Embedded with FCS or TPM• Develop a portable device• ……..

LaserUV-NIR

Specimen

BSpolarizer Notch filter or

long pass filter

spectrograph

Energy monitor

CCD camera

Interference filter

What is SERS?• Surface-Enhanced Raman Scattering• The first time in 1974,

– pyridine molecules – Electrochemically roughened silver

surface • Electromagnetic contribution

– the increase of the optical field intensity in the proximity of sharp points

– Local surface plasmon resonance (LSPR)

• Chemical effect– the mixing of the orbital of the

adsorbed molecule and the metal atoms.

•Example of electric field localization in colloids and sharp point samples. •The field intensity depends on the inter-particle distance and particle shape

www.d3technologies.co.uk/en/10256.aspx

Principle of SERS

)( LI

)( LI

sSERSI

Rfree

sNRSI

N molecules with

Metal particle (10~100nm)

Rads

N’ molecules with

LRfreeNRS INI

•Raman signal is too weak•Surface enhanced Raman scattering (SERS) technique can enhance Raman signal to 108 times•Electromagnetic effect and chemical effect between nanoparticles and molecules.

22' sLLRadssSERS AAINI

So far, the theoretical understanding is not clear…..Katrin Kneipp, Harald Kneipp, J. Phys.: Condens. Matter 14 (2002)

How does SERS work?

• (1) laser light incident on the metal substrate (2) plasmons excitation (3) light scattered by the molecule (4) Raman scattered light transferred back to plasmons and scattered in air (5)

• The plasmon properties – such a wavelength and width of its resonance – depend on the nature of the metal surface and on its geometry.

www.d3technologies.co.uk/en/10256.aspx

Lowest detection limitation

• In 1977, Van Duyne and Jeanmaire and, independently, Albrecht and Creighton confirmed SERS experiment in 1974

• Surface effect + nanostructure effect• Prove the EM effect• SERS enhancement factors

– Modest 103 to 105

– Dye 1010 to 1011

• 1995, effective cross section=(anti-Stocks)/(Stocks), to identify no resonance SERS cross section to 10-16 cm2 per molecule, and 1014 order of magnitude.

ACCOUNTS OF CHEMICAL RESEARCH / VOL. 39, NO. 7, 2006

SERS-active substrates

• Rough metal surface at nanometer• Gold/ silver colloid• Gold/ silver periodic nano-structures• Other nanostructures…..

www.tedpella.com/gold_html/goldsols.htm

Applications of SERS

• Light source: NIR/ VS/ UV• Subtracts: various metal nanostructures• Analytes:

– Single molecule detection (R6G….)– Identification of a single DNA base molecule – Glucose sensor (J. AM. CHEM. SOC. 9 VOL. 125, NO. 2, 2003)

– Protein– Cell

Assembly of Gold Nanostructured Films Templated by Colloidal Crystals and Use in SERS

J. Am. Chem. Soc. 2000, 122, 9554-9555

trans-1,2-bis(4-pyridyl)ethylene (BPE)

1gold NPs (25 nm)2 no latex3 only bulk BPE

4EC rough gold5 after heating 500 C6 glass wo metal

Single Molecule Detection Using SERS

• Measured spectra of a single crystal violet molecule in aqueous colloidal silver solution using one second collection time and nonresonant near-infrared excitation show a clear “fingerprint” of its Raman features between 700 and 1700 cm-1. Spectra observed in a time sequence for an average of 0.6 dye molecule in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1, 2, or 3 molecules.

Phys. Rev. Lett. 78, 1667 - 1670 (1997)

Cite # 1138

Science ,1997, Vol. 275. no. 5303, pp. 1102 - 1106

Quantitative Simultaneous Multianalyte Detection of DNA by Dual-Wavelength SERS• Quantitative identification of specific DNA sequences in a mixture• Silver nanoparticles

Angew. Chem. 2007, 119, 1861 –1863

Femtomolar Detection of Prostate-Specific Antigen: An Immunoassay Based on SERS and Immuno gold Labels

Anal. Chem. 2003, 75, 5936-5943

Infrared reflection spectra of a DSNB-derived monolayer on gold before (spectrum A) and after (spectrum B) exposure to the anti-PSA tracer antibody.

Demonstration of a SERS-based free PSA immunoassay. (A) SERS spectra, offset for clarity, acquired at various PSA concentrations. (B) Dose-response curve for free PSA in human serum. The dose-response curve was constructed by calculating the average reading of the response for 6-8 different locations on the surface of each sample, which typically varied by 10% (see text for further details).

Anal. Chem. 2003, 75, 5936-5943

SERS in Local Optical Fields of Silver and Gold Nanoaggregatess From Single-Molecule Raman Spectroscopy to Ultrasensitive Probing in Live Cells

Acc. Chem. Res. 2006, 39, 443-450

Kneipp et al.

Stokes and anti-Stokes SERS spectra of crystal violet attached to isolated and aggregated gold nanospheres.

Schematic of hyper-Raman and Raman scattering and surface-enhanced Raman and hyper-Raman spectra of crystal violet on silver nanoclusters, excitation 850 nm, 107 W/cm2.

(a) Cells of a fibroblast cell line, NIH/3T3 (nonphagocytic) (left), and a macrophage cell line, J774 (phagocytic) (right), after uptake of gold nanoparticles; particle accumulations are visible as black dots inside the cells. Scale bars ) 20 ím. (b) Examples of SERS spectra acquired from NIH/3T3 cells after 3 h incubation withgold nanostructures, excitation wavelength 830 nm, 1 s collection time.

Acc. Chem. Res. 2006, 39, 443-450

Ex: proteins (1245 cm-1, 1267 cm-1 amide III, side chains Phe 1002 cm-1, Tyr 825 cm-1) and various nucleic acid constituents (e.g. 1580, 1575, 1098 cm-1)

In vivo tumor targeting and spectroscopic detection with surface-enhanced Raman nanoparticle tags

NATURE BIOTECHNOLOGY VOLUME 26 NUMBER 1 JANUARY 2008

In vivo SERS spectra obtained from pegylated gold nanoparticles injected into subcutaneous and deep muscular sites in live animals.

5hr, N=4

Optical aggregation of metal nanoparticles in a microfluidic channel for surface-enhanced Raman scattering analysis

Lab Chip, 2009, 9, 193–195

For tweezers, 830nm

514.5 nm

Dark field (DF) images and time series SERS spectra during an optical trapping process in the microfluidic channel.

SERS measurements using a Y-shaped channel.

Lab Chip, 2009, 9, 193–195

1s integration, 10s interval

Flow rate of 0.001ml/min

Advantages of SERS

• Include all advantages of Raman spectroscopy– Fingerprint of molecules– Identify target in mixture– Living cell and the specimen contained water

• Low concentration of biomolecue• Modification technique for those metal nanoparticles or

other nanostructure with biomolecule• Integrated into bio-MEMS• Powerful probe for these applications with extreme low

concentration.

Thanks for your attention!