Raman Spectroscopy and Its Applications

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Raman Spectroscopy and Its Applications

  1. 1. Raman Spectroscopy & Applications Dr. Tong Zhang Sales Manager – UK & Ireland Renishaw PLC
  2. 2. Dr. Sir C. V. Raman (1888-1970) Process Monitoring & Reaction Control Hospital Universities & research units Justice & Custom Archaeology & gemmology
  3. 3. Outline <ul><li>Principle </li></ul><ul><li>Instrument </li></ul><ul><li>Application </li></ul><ul><li>Challenge </li></ul><ul><li>Summary </li></ul>
  4. 4. Raman Principles <ul><li>Inelastic scattering – an energy gain/loss or say – colour change </li></ul><ul><li>Probability: 1 per 10 7 or 10 8 </li></ul><ul><li>Assessing molecular motion & fingerprinting </li></ul><ul><li>Normal energy range: 200 – 4000 cm –1 ( i.e. 0.4 – 8  10 -20 J, or 0.025 – 0.5 eV) </li></ul>Excitation Energy Electronic Ground State 1st Electronic Excited State Vib. states 2nd Electronic Excited State Raman Stokes Anti-Stokes fluorescence Impurity IR fluorescence Resonance Raman Raleigh 3.2 3.44 ZnO 1.43 1.52 GaAs 0.17 0.23 InSb 1.11 1.17 Si RT 0 K Energy gap (eV) Material
  5. 5. Raman Instrument
  6. 6. Renishaw Incoming light Scattered light
  7. 7. Raman Strength & Limitations <ul><li>Easily identify chemical structure – fingerprint technique) </li></ul><ul><li>Widely applicable for various materials </li></ul><ul><li>Samples can be solid or aqueous (water is a weak Raman scatterer) </li></ul><ul><li>Little or no sample preparation required </li></ul><ul><li>Non-invasive, non-destructive method </li></ul><ul><li>Remote control with fiber optics </li></ul><ul><li>Fluorescence especially when the incident light goes to blue </li></ul><ul><li>Technique and cost of laser sources </li></ul><ul><li>Low excitation Probability: 1 per 10 7 or 10 8 </li></ul><ul><li>Spatially refrained by optical limit </li></ul><ul><li>Distanced Raman </li></ul>
  8. 8. Raman Applications - Moving from Discovery to Practice <ul><li>Pharmaceutical / Biomedical </li></ul><ul><li>Material science / nanotechnology </li></ul><ul><li>Forensic /anti-crime / anti-terrorism </li></ul><ul><li>Gemmology / geology / mineralogy </li></ul><ul><li>Archaeology / art / heritage </li></ul><ul><li>… </li></ul><ul><li>Anywhere need identifications with close proximity between inspecting tools (including fibre laser sources) and samples. </li></ul><ul><li>Easily identify chemical structure – fingerprint technique) </li></ul><ul><li>Widely applicable for various materials </li></ul><ul><li>Samples can be solid or aqueous (water is a weak Raman scatterer) </li></ul><ul><li>Little or no sample preparation required </li></ul><ul><li>Non-invasive, non-destructive method </li></ul><ul><li>Remote control with fiber optics </li></ul>
  9. 9. In vivo Source: National Institutes of Health, US <ul><li>Features </li></ul><ul><ul><li>Simple Non-invasive </li></ul></ul><ul><ul><li>High sensitivity High specificity </li></ul></ul><ul><li>… </li></ul>Diode Laser CCD 830 nm Raman probe 1 cm 2.5 mm Probe inside breast biopsy needle FC ( Collagen) 20 40 60 80 100 10 20 30 40 50 60 70 Fibrocystic change Cancer Normal FC (Fat) 0 <ul><li>Cholesterol-like </li></ul><ul><li>Fat </li></ul><ul><li>Collagen </li></ul><ul><li>Cell Nucleus </li></ul><ul><li>Cell Cytoplasm </li></ul><ul><li>N/C Parameter </li></ul>
  10. 10. Material Science Source: Imperial College, Hong Kong Poly Univ. & Jasco Conducting polymers Textile & fabrics Citrine Topaz Gemmology
  11. 11. Raman Challenge <ul><li>Surface enhancement – Surface-Enhanced Raman Spectroscopy ( SERS) </li></ul><ul><ul><li>for better signals </li></ul></ul><ul><li>Combining with SPM – Tip-enhanced Raman spectroscopy ( TERS) </li></ul><ul><ul><li>for better spatial resolution </li></ul></ul><ul><li>Offset Raman signals – SORS </li></ul><ul><ul><li>for seeing deeper (without physical damage) </li></ul></ul><ul><li>Fluorescence especially when the incident light goes to blue </li></ul><ul><li>Technique and cost of laser sources </li></ul><ul><li>Low excitation Probability: 1 per 10 7 or 10 8 </li></ul><ul><li>Spatially refrained by optical limit </li></ul><ul><li>Distanced Raman </li></ul>
  12. 12. Raman Challenge - SERS Source: Imperial College 731 725 1327 652 DNA sequence identification Pillar Multiple Torus DS-DNA SS-DNA
  13. 13. Raman Challenge - TERS Source: Rochester Univ. Raman on SWNT: Spatial Resolution (~15 nm) Raman TERS Diffraction limit to beat
  14. 14. Summary <ul><li>Raman is a vibrational spectroscopy which is capable of providing chemical and component information with high spatial resolution </li></ul><ul><li>Raman spectroscopy is of great potential in a broad range of applications, from pharmaceutical, material science to gem identifications and forensic. </li></ul><ul><li>Traditionally Raman applications were limited by low cross sections and diffraction limit. But developments in these areas have brought a bright future and enormous opportunities. </li></ul>Thank you!

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