Raman spectroscopy is an optical scattering technique that utilizes the intrinsic vibrational energies of the compound and detects the difference in the frequency between the incident and scattered light. Raman spectroscopy is widely used for material characterization, because it has beneficial features including intrinsically high molecular specificity, the requirement for minimal or no sample pre-treatment, the ability to measure complex solutions, immunity to high water content, the flexibility of sampling configurations, and suitability for automation. Furthermore, Raman technology has useful properties such as nondestructive, noncontact, label-free, fast and robust way of measurement, which make the use of this technique very convenient and easy.
A monochromatic excitation light source (laser) is commonly used for Raman spectroscopy. Sufficient Raman signal intensities can be obtained by increasing laser power to a moderate level and optimizing the detector integration time to ensure that laser and collection spots are properly focused on the target without damaging the sample. Several factors may impact the quality of the detected Raman signal, such as detector shot noise, black-body radiation, ambient light, and fluorescence.
The broad spectral disturbance of fluorescence in Raman measurements represents a major challenge and limits its wider application. An effective solution to this problem is time-gating, which is a general technique used in signal processing. Raman scattering and fluorescence emission phenomena differ in time scale. Raman scattering occurs fast, within sub picoseconds time scale, whereas fluorescence emission has much longer decay times. Thus, rejecting the fluorescence can be realized through temporal resolution of the spectral signal.
Time-gating Raman can be performed by various detection systems such as time-resolved photomultiplier tubes, intensified charge‐coupled devices (ICCDs), high-speed optical shutters based on a Kerr cell, quantum dot resonant tunneling diodes, and complementary metal-oxide semiconductor single-photon avalanche diodes (CMOS SPADs). SPADs can be used to detect even a single photon, and thus they are suitable for Raman photon collection. SPADs are integrated in standard CMOS technology and contain a basic p-n junction which is reverse‐biased above its breakdown, meaning that entry of even a single photon can trigger avalanche breakdown that can then be recorded.
PicoRaman spectrometer is the first commercial time-resolved Raman spectrometer. This novel Raman spectrometer uses time-gating to differentiate the fluorescence and Raman signals, and additionally gives temporal information on both. PicoRaman spectrometer is equipped with 100 picosecond pulsed excitation and time-resolved single-photon counting detector array to achieve effective, real fluorescence rejection from Raman signal, enabling more accurate quantitative and qualitative Raman spectroscopy analysis. Since fluorescence is no longer an interference, Raman analysis becomes more specific and reliable.
In addition to effective fluorescence rejection, PicoRaman based on Timegated®Raman measurement method provides a whole new data dimension - time. Not only can we see the spectral wavelength axis, but we can also see how photons occur in time dimension. This brings new features and benefits to Raman spectroscopy analysis. Using PicoRaman, both Raman scattering data and time-resolved information on fluorescence emission decay can be obtained.
The patented breakthrough innovation provides an affordable electrical gating solution using pulsed picosecond range lasers and new CMOS-SPAD array detectors. The picosecond range laser excitation source and the time-gated single photon counting array detector constitute a new type of spectrometer capable of acquiring Raman spectra with real fluorescence suppression. The spectrometer rejects the fluorescence interference (which has a longer average delay) while capturing the instantaneous Raman scattering signal. The spectrometer also enables the acquisition of time-resolved fluorescence spectra by sequentially sampling the emission pulses at different temporal positions. This approach simultaneously opens two windows for material characterization and provides valuable new information in several different application fields.
PicoRaman spectrometers open new opportunities for material research in the various fields of science and process industries, where fluorescence emission has previously been problematic for successful Raman analyses. Timegated® Raman technology allows effective fluorescence reduction over the conventional CW (continuous wave) Raman technologies. The reduction of fluorescence from the Raman signal improves signal-to-noise ratio (SNR).
In turn, the improved SNR simplifies and adds robustness to the chemometric models. In addition to fluorescence rejection, Timegated technology also works in ambient light and the measurements of materials and reactions, e.g., in high temperature processes with high thermal emissions succeed easily. Raman signal together with time-resolved fluorescence data provides fresh basis for advanced data analysis.
|Spectral resolution||5 cm-1|
|Spectral range||0-2500 cm-1|
|Detector type||Proprietary CMOS SPAD matrix, single photon counting|
|Time resolution||50 ps|
|532 NM PICOSECOND PULSED LASER|
|Spectral line width||< 0.1 nm|
|Pulse width||< 150 ps|
|Pulse energy||SW control to 1 µJ|
|Repetition rate||100-250 kHz|
|Laser power||SW controlled up to 100-200 mW at laser port|
|Spectrometer dimensions||425 mm(W) x 335 mm(D) x 160 mm(H)|
|Operating Conditions||Normal laboratory environment|
With an easy to install microprobe adapter, PicoRaman spectrometers can be conveniently used with any Olympus BX, CX and MX series upright microscope. Accurate identification and time resolved analysis of almost any microscopic sample area is now possible with this accessory. Users can observe the sample either through the oculars or the integrated USB camera which also enables capturing images or live video of the sample. The novel Raman Microprobe offers researchers new opportunities with PicoRaman spectrometers in wide range of application areas including geosciences, biopharmaceuticals, catalysis and forensics to name a few. The possibility to combine the PicoRaman spectrometer with microscopic mapping systems enables multi-point surface mapping.
Surface Enhanced Raman Spectroscopy (SERS) is an advanced surface-sensitive technique. This technique enables rapid analysis and imaging of single molecules at nanoscale. Amerigo Scientific offers ease-to-use SERS substrates for Raman-based quantitative and qualitative analysis, saving the time and effort of complex preparation.
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