Two-photon vibrational spectroscopy for biosciences based on surface-enhanced hyper-Raman scattering.

Area of Science:

• Spectroscopy and Microscopy
• Plasmonics
• Chemical Probing

Background:

• Two-photon excitation is increasingly significant in spectroscopy and microscopy.
• There is a need for versatile optical labels and ultrasensitive chemical probing methods.

Purpose of the Study:

• Introduce a new approach for versatile optical labels.
• Enable ultrasensitive, nondestructive chemical probing using two-photon excitation.
• Investigate surface-enhanced hyper-Raman scattering (SEHRS).

Main Methods:

• Utilized hyper-Raman scattering (HRS), an incoherent inelastic scattering of two photons.
• Enhanced HRS using local optical fields of gold and silver nanostructures (SEHRS).
• Demonstrated HRS on biological structures like single cells with gold nanoparticles.

Main Results:

• SEHRS provides structurally sensitive vibrational information, complementary to SERS.
• Achieved effective two-photon cross-sections for SEHRS on the order of 10^-46 to 10^-45 cm^4 s.
• Successfully demonstrated HRS on biological samples.

Conclusions:

• SEHRS combines advantages of two-photon spectroscopy, vibrational spectroscopy, and plasmonics.
• SEHRS offers high sensitivity and nanometer-scale confinement for chemical probing.
• The developed method is suitable for biological imaging and chemical analysis.