EP1200795A1 - Procede et appareil permettant de recueillir de l'information du spectre infrarouge en resolution temporelle simultanement a partir de plusieurs echantillons - Google Patents

Procede et appareil permettant de recueillir de l'information du spectre infrarouge en resolution temporelle simultanement a partir de plusieurs echantillons

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Publication number
EP1200795A1
EP1200795A1 EP00947403A EP00947403A EP1200795A1 EP 1200795 A1 EP1200795 A1 EP 1200795A1 EP 00947403 A EP00947403 A EP 00947403A EP 00947403 A EP00947403 A EP 00947403A EP 1200795 A1 EP1200795 A1 EP 1200795A1
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EP
European Patent Office
Prior art keywords
data
spectrometer
sample
spectral
scan
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00947403A
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German (de)
English (en)
Other versions
EP1200795A4 (fr
Inventor
Jochen A. Lauterbach
Christopher M. Snively
Jan P. Dicke
Gudbjorg Oskarsdottir
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Purdue Research Foundation
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Purdue Research Foundation
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Publication of EP1200795A1 publication Critical patent/EP1200795A1/fr
Publication of EP1200795A4 publication Critical patent/EP1200795A4/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/45—Interferometric spectrometry
    • G01J3/453—Interferometric spectrometry by correlation of the amplitudes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/2889—Rapid scan spectrometers; Time resolved spectrometry
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00274—Sequential or parallel reactions; Apparatus and devices for combinatorial chemistry or for making arrays; Chemical library technology
    • B01J2219/00583—Features relative to the processes being carried out
    • B01J2219/00585—Parallel processes
    • B01J2219/00587—High throughput processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00274—Sequential or parallel reactions; Apparatus and devices for combinatorial chemistry or for making arrays; Chemical library technology
    • B01J2219/0068—Means for controlling the apparatus of the process
    • B01J2219/00702—Processes involving means for analysing and characterising the products
    • B01J2219/00707—Processes involving means for analysing and characterising the products separated from the reactor apparatus

Definitions

  • the present invention generally relates to infrared spectral imaging systems and, more particularly, to a method and apparatus for simultaneous collection of time resolved infrared spectral information from multiple samples.
  • Infrared (IR) imaging has proved useful in the past for sensing many different phenomena.
  • the construction of an instrument for chemically sensitive imaging in the mid-IR requires an IR imaging element as the key component.
  • IR imaging systems focus on the measurement of temperature, night vision surveillance, and environmental and astronomic imaging in the near-IR range. While these are widely available, the near-IR region does not possess the highly chemically specific spectral bands that are present in the mid-IR spectral region.
  • Recent advances in technology however, have led to the development of powerful mid-IR focal plane array (FPA) detectors.
  • FPA focal plane array
  • FTIR Fourier Transform infrared imaging
  • FTIR Fourier Transform infrared imaging
  • Infrared-based techniques are extremely popular for the analysis of combinatorial libraries because of the benefits of low cost, ease of use, and rapid data collection.
  • One of these techniques is single bead FTIR microspectroscopy, which uses an FTIR microscope to acquire IR spectral information from a single bead. While this technique can provide highly detailed chemical information, it has the limitation of being able to examine only one bead at a time.
  • An extension of this technique, FTIR spectroscopic mapping has also been reported in the prior art. In this study, a map of approximately 300 different resin beads was collected, and the resulting spectra were used to determine the identity of the beads. While providing chemically specific information, this technique requires a collection time of 5 hours for each map.
  • infrared thermography has been used to select active supported catalysts. While being able to analyze a large number of samples at once, this technique provides no chemically specific information, and is therefore of limited utility for the characterization of supported ligands. Recently, it has been shown that a new technique that uses a near-IR imaging spectrometer can be used to simultaneously monitor the progress of reactions on several different supported resins. However, due to the low absorptivity inherent to near-IR spectral bands, this technique requires that the sample contain hundreds of supported resin beads in order to generate a measurable signal. Additionally, the near-IR spectral region has an inherently low chemical sensitivity, which complicates spectral interpretation and limits the applicability of this technique.
  • FTIR imaging often referred to in the prior art as fast or hyperspectral FTIR imaging
  • FTIR imaging is a recent development that combines the chemically rich information available from mid-infrared spectroscopy with the ability to acquire this information in a spatially resolved manner.
  • a single data set consists of both spatial and spectral information.
  • the typical dimensions of this data set range from 64 x 64 to 320 x 256 pixels, with each pixel containing a full IR spectrum.
  • the end result is the ability to visualize the distribution of chemical species within complex systems.
  • FTIR imaging has so far been successfully applied to the study of biological and chemical systems, and is becoming increasing popular for the study of spatially heterogeneous systems.
  • FTER imaging instrumentation has consisted of a step- scan FTIR spectrometer, a microscope with Cassegrainian optics, and a focal plane array (FPA) detector.
  • FPA focal plane array
  • To collect a data set the moving mirror of the interferometer is translated, which modulates the light coming from an infrared source. At specified intervals, i.e. mirror retardations, the light intensity values at each pixel position (one frame) are measured.
  • the end result of the data collection process is that a complete interferogram is collected from each pixel in the focal plane array detector. All interferograms are then Fourier transformed to produce a set of spatially resolved infrared spectra.
  • the present invention provides simultaneous collection of time resolved infrared spectral information from multiple samples in a combinatorial library.
  • a FTIR spectrometer is used to illuminate the sample library in either step scan or rapid scan mode, and IR light absorbed by the combinatorial library (either by reflection or transmission) is recorded by a focal plane array detector. The Fourier transform of the measured data is then taken, resulting in a set of spatially-resolved IR spectroscopic images. Each spectrum in this data set is representative of the chemical makeup of that particular region of the sample. Additionally, if the absorbance value of a specific spectral band is plotted for all pixel positions, an image that is characteristic of the spatial distribution of the corresponding chemical species can be obtained.
  • FIG. 1 is a schematic block diagram of a first embodiment spectral imaging system of the present invention.
  • FIG. 2 is a graph of signals available from the spectrometer of FIG. 1.
  • FIG. 3 is a parametric interferogram produced by the system of FIG. 1.
  • FIG. 4 is a schematic diagram of a reflection-absorption measurement configuration for use with the system of FIG. 1.
  • FIG. 5 is a schematic diagram of a transmission measurement configuration for use with the system of FIG. 1.
  • FIG. 5A is a schematic diagram of an attenuated total reflection configuration for use with the system of FIG. 1.
  • FIG. 6 is an interferogram acquired using the system of FIGS. 1 and 5.
  • FIG. 7 is a spectrum corresponding to the interferogram of FIG. 6.
  • FIG. 8 is an infrared image of a 7-element library holder, demonstrating the spatial imaging capabilities of the system of FIG. 1.
  • FIG. 9 is a schematic block diagram of a second embodiment spectral imaging system of the present invention.
  • FIG. 10a is an absorbance spectrum of CO adsorbed on Pt/SiO 2 using a conventional, non-imaging FTIR spectrometer.
  • FIG. 10b is an absorbance spectrum of CO adsorbed on Pt/SiO 2 using the system of FIG. 1.
  • FIG. 10c is an absorbance spectrum of CO adsorbed on Pt/SiO 2 using the system of FIG. 9.
  • FIG. 11 is a graph of absorption bands of CO adsorbed on Cu-ZSM5 zeolite at three different temperatures.
  • FIG. 12 is an image generated using a specific absorbance value for each pixel in an array of data produced by the system of FIG. 9.
  • FIG. 13 is a set of images plotting absorbance values at different frequencies, using a data set created by the system of FIG. 9.
  • FIG. 14 is a set of absorbance spectra for each type of bead measured to create the data of FIG. 13.
  • FIG. 15 is an image of several beads separated from a reaction at different times, using the system of FIG. 9.
  • FIG. 1 illustrates the first embodiment mid-IR step scan spectral imaging system of the present invention, indicated generally at 10, which consists of the following basic components: a step-scan FT-IR spectrometer 12, condensing optics 14, a combinatorial library 16, imaging optics 18, a focal plane array detector 20, spectrometer control computer 22, and FPA control computer 24.
  • the FTIR spectrometer 12 comprises a Nicolet Magna 860 FTIR spectrometer (available from Nicolet Instrument Corp., Madison, Wisconsin, USA), the condensing optics 14 and imaging optics 18 comprise infrared transparent CaF 2 elements, and the FPA 20 comprises a 64 X 64 pixel mercury cadmium telluride (MCT) focal plane array detector (available from Santa Barbara Research Center (Goleta, California, USA).
  • MCT 64 X 64 pixel mercury cadmium telluride
  • the condensing optics 14 are used to focus (condense) the beam from the interferometer 12 onto the library 16, while the focusing optics 18 are used to focus (image) the resulting beam onto the liquid nitrogen cooled FPA 20.
  • the cryogenic dewar (not shown) and FPA 20 support electronics are available from SE-IR Corporation (Goleta, California, USA).
  • the entire optical setup is housed in a purge enclosure (not shown), which minimizes spectral interference from CO 2 and H 2 O vapor.
  • the Nicolet FTIR spectrometer 12 is capable of both rapid and step scan operation, under control of the computer 22.
  • the FPA 20 and associated electronics are connected via high-speed interface to the computer 24, where Fourier transformation and other data handling 28 procedures are performed.
  • the final information is stored as a set of IR spectroscopic images 28, enabling the user to display intensity images at selected wavelengths or IR spectra at selected points in the image.
  • an accurate trigger signal 30 is provided by the spectrometer 12 after each scan step to the FPA 20 electronics so that for each mirror position (i.e., starting at zero retardation and then increasing the retardation) an IR image of the sample can be taken and stored.
  • FIG. 2 shows the sequence of signals available during data collection. After the mirror movement stops (interferometer retardation 32) and a user adjustable settle time 34 for mechanical stabilization of the moving mirror has passed, the spectrometer 12 supplies a trigger signal 30 to the FPA 20 to start data collection during the sampling interval. As discussed hereinabove, the step-scan FT-IR spectrometer 12 is used as the infrared "light source".
  • the step-scan system 12 contains an IR source (globar) and a step-scan Michelson interferometer, which is capable of providing a maximum spectral resolution below 0.1 cm "1 .
  • a typical rapid scan FTIR spectrometer the moving mirror of the interferometer is continuously scanned, and data are collected "on the fly.” This type of collection is possible because the detector response is extremely fast.
  • step scan mode the mirror is actually stopped at each data collection point, data are collected for a finite time period, and then the mirror is advanced to the next point. This process is repeated until the spectral data set is collected.
  • Step scan data collection is well-suited for this technique because the FPA detectors 20 employed are typically much slower than single element detectors used in standard rapid scan FTIR spectroscopy. Therefore, at each mirror step, the interferometer 12 sends a trigger signal 30 to the FPA 20, which tells the FPA 20 to collect data.
  • the step-scan interferometer 12 will collect double-sided interferograms.
  • the system 10 will first collect and store a background image, which serves as the reference for all spectra. After the background has been taken, the reactions, for example, will be initiated and the user will start the data collection process.
  • the step-scan data collection process will start at zero mirror retardation time t ⁇ . As can be seen from FIG. 3, at each mirror retardation and for a given time t x , one data point of the interferogram will be recorded.
  • the trigger signal will trigger the FPA 20 electronics to collect the data from the FPA 20. At this point, if necessary more than one data reading (i.e., IR image) can be taken and averaged to improve the signal-to-noise ratio.
  • the user will have to find the optimum balance between signal-to-noise ratio and the data integration time.
  • the mirror is stepped forward (t ⁇ -> t 2 ) and the FPA 20 electronics will be triggered (via trigger signal 30) to take another IR image or average over a set of images. This process will continue until one set of 128 x 128 (for example) interferograms is recorded. Then the mirror will return to zero retardation and the next interferogram can be recorded. This provides temporal resolution (time slice) and interferogram collection will stop when the desired time for the experiment has passed. The final data set will contain sets of 128 x 128 interferograms as a function of the location and time slice.
  • sample single beam images as a function of time are available.
  • the spectral bandwidth will be decreased with an optical filter, allowing for a larger sample spacing resulting in smaller data files without sacrificing spectral resolution.
  • the resolution of the spectra will typically be 8 or 16 cm '1 due to the large amount of data.
  • Typical file sizes for images (12-bit numbers, 1200 data points per spectrum at a sample spacing of 8, 128 x 128 image size) are calculated to ⁇ 20 MB.
  • the spectrometer 12 hardware is capable of achieving a much higher spectral resolution and, if desired, the best resolution of 0.1 cm "1 can be selected.
  • Fast Fourier Transform and other spectral operations 26 are performed in the FPA control computer 24.
  • the JJ . beam exiting the FT-IR spectrometer 12 is an approximately parallel, slightly diverging beam with a diameter of ⁇ 2 cm.
  • optical elements suitable for the mid-IR spectral range to widen the IR beam to the size of the library 16 and then to focus it back onto the FPA 20.
  • lens materials are readily available for the use in mid-IR, such as Calcium Fluoride (CaF ), Zinc Selenide (ZnSe), and Germanium (Ge).
  • CaF is an isotropic crystalline material that is very slightly hygroscopic. Typically, it lasts for years under normal laboratory conditions, which is an important cost factor for the long-term use of the instrument 10.
  • CaF transmits over a broad spectral range (from 60,000 cm “ ' to 1,000 cm “1 ) and has low dispersion resulting in little chromatic aberration.
  • a 3 mm thick CaF 2 lens has an external transmittance greater than 93% in the range between 1,300 cm '1 and 30,000 cm “1 , ensuring that the loss in intensity caused by the lenses is minimized (vide infra).
  • CaF 2 lenses are widely available as plano-convex lenses with focal lengths between 50 mm and 500 mm and as plano-concave lenses with focal lengths between -50 mm and -250 mm. Other focal lengths can be specially ordered.
  • the instrument 10 is designed so that it can be used in several distinctly different modes, thereby increasing its flexibility.
  • the transmission mode allows the analysis of combinatorial libraries 16, transparent to infrared radiation. For example, this will open new avenues to follow photo-induced polymerization reactions or reactions in liquid phase. With slight modifications, this set-up will also allow for the chemically sensitive imaging of any IR transparent sample and the instrument can function similar to an IR microscope, however, with a much larger field of view and a much better temporal resolution.
  • the reflection- abso ⁇ tion mode of instrument 10 operation allows IR spectra to be acquired from chemical species adsorbed on a reflecting substrate.
  • the attenuated total reflection mode allows the collection of infrared spectra from combinatorial libraries, which are opaque or optically thick.
  • the design of the instrument 10 is rather flexible, so that the use of this system is by no means restricted to combinatorial sciences, but also presents a breakthrough in chemically sensitive IR imaging on millimeter and larger length scales of a wide variety of biological
  • optical set-up for the transmission mode the reflection- abso ⁇ tion mode, and the attenuated total reflection mode are described. Position and specifications of the optical elements are determined by the specifics of the sample libraries under study.
  • FT-IRAS Reflection - absorption mode
  • sample 16 surfaces are typically irradiated with IR light at an angle of incidence of - 80 degrees, depending on the substrate material. This leads to an enhancement of the parallel reflected beam (parallel to plane of incidence, i.e., pe ⁇ endicular to the surface) up to a factor of 2, depending upon angle and sample material.
  • the FT-IRAS set-up is frequently used to follow abso ⁇ tion, deso ⁇ tion, and reaction in situ.
  • the standard FT-IRAS set-up uses a FT-IR spectrometer on one side of the sample, focusing optics, and a single element MCT detector on the other side. Typically, the optical path is either purged with dry air or pumped to rough vacuum to prevent IR abso ⁇ tion bands from the ambient air.
  • the present invention uses a similar geometry with imaging elements rather than focusing mirrors, as shown in FIG. 4.
  • the parallel beam 36 from the spectrometer 12 is focused onto the sample 16 using a plano-convex lens A and a plane mirror B.
  • Another plane mirror C, on the reflected side 38 of the beam, directs the light through a biconvex lens D to image the sample onto the focal plane array 20.
  • the sample is IR transparent such that the measurements are made through the sample.
  • the set-up may be configured to perform spatially resolved IR transmission spectroscopy.
  • FIG. 5 For the scanning of liquid phase libraries 16, it will be easier to have the library 16 in a horizontal position. This can be achieved by placing a flat mirror (not shown) close to the spectrometer 12 output (left side of FIG. 5) and deflecting the beam 36 from the spectrometer 12 by 90 degrees. By adding another flat mirror after the sample, the beam is then directed towards the FPA 20.
  • One piano convex lens E focuses the parallel beam 36 exiting the spectrometer 12 onto the sample 16.
  • a biconvex lens F on the opposite side of the library 16 is then used to image the sample onto the focal plane array 20.
  • the theoretical diffraction limited resolution for this setup is calculated to be about 150 microns for a library 16 size of 10 mm.
  • the practical resolution is primarily limited by spherical aberration to a value of approximately 300 microns, which was calculated by properly applying a third order treatment of refraction at a spherical interface.
  • the sample is not required to be IR transparent. Measurements are made by placing the sample in contact with an infrared transparent prism that has a refractive index higher than the sample.
  • the setup for this mode of operation is shown in FIG. 5 A.
  • a flat mirror G is placed close to the spectrometer 12 output (left side of FIG. 5 A) and deflects the beam 36 from the spectrometer 12 to a piano convex lens H, which focuses the beam 36 onto the sample 16 through the prism I.
  • the beam is then directed towards the FPA 20.
  • a biconvex lens K on the opposite side of the library 16 is then used to image the sample onto the focal plane array 20.
  • IR spectroscopy can be the contribution of the atmospheric background (predominantly from H 2 O, CO 2 , and CO) to the IR spectrum. As long as the background remains relatively stable (which can be expected during the proposed experiments), this is not a major problem since the contributions cancel out by division of sample spectra and reference spectrum. If it should become necessary to remove the atmospheric background contribution, the simplest solution is to continuously purge the beam path with dry air. This requires a sealed housing for the optical elements, which can be easily built from plastic sheet material.
  • the preferred embodiment of detector is a 64 X 64 MCT focal plane array detector 20 (from SE-IR, Santa Barbara, California, USA).
  • the FPA's high spatial resolution is combined with an excellent sensitivity in the mid-IR and a variable frame rate up to 180 Hz. Integration times can be chosen electronically depending upon the frame rate.
  • the individual pixel size of the detector 20 is 61 X 61 ⁇ m.
  • the operating temperature is 80 K, which is readily achieved with liquid nitrogen cooling.
  • the signal response of the FPA 20 is better than 5 X 10 "4 mV/(ph/cm 2 sec) and the flux range is 1 x 10 14 to 1 x 10 16 ph/cm 2 sec.
  • the FPA 20 is mounted in a commercial camera head, which consists of a cryogenic liquid nitrogen dewar for cooling the FPA 20, clock driver electronics, low noise bias supplies, signal conditioning electronics, and analog-to-digital converters (A/D).
  • the signal conditioning electronics consist of analog electronics for controlling offset and gain before A/D conversion, which allows the user to digitize the FPA 20 output signals with a maximized dynamic range.
  • the A/D outputs are multiplexed into a single 16-bit video data stream. These data, along with sync signals, are sent over a high speed RS-422 interface to the computer 24. This configuration allows the interface cable to be over 150 feet away from the rest of the electronics setup, while still maintaining the full data transfer rate. This allows the camera head and digital electronics to be separated, as may be required in some applications.
  • the interferometer 12 is set running.
  • the moving mirror of the interferometer 12 steps through a specific distance (determined by the desired spectral resolution) in a specific number of steps (determined by the desired spectral range and resolution).
  • These parameters are set by the software executed by the spectrometer control computer 22 and are identical to those used in typical wide beam FTIR experiments.
  • a triggering pulse 30 is sent from the interferometer 12 to the FPA 20.
  • one data point is collected from each of the 4096 pixels of the array. This process is repeated until the entire interferogram is collected.
  • the data set is comprised of 4096 spatially resolved interferograms, one from each pixel.
  • the data is a 64 x 64 x 2080 point array.
  • the interferogram data are then processed using MATLAB 26, a commercial mathematical processing package (available from The Math Works, Natick, Massachusetts, USA) or a custom analysis software.
  • the processing 26 includes fast Fourier transformation and ratioing to background to produce absorbance spectra. These steps are identical to those used in conventional FTIR data processing, but the process is more time consuming because 4096 spectra must be processed for each imaging data set collected.
  • the final data set is a collection 28 of spatially-resolved infrared abso ⁇ tion spectra. Each spectrum in this set is representative of the chemical makeup of that particular region of the sample. Additionally, if the absorbance value of a specific spectral band is plotted for all pixel positions, an image that is characteristic of the spatial distribution of the corresponding chemical species can be obtained.
  • FIG. 6 shows an interferogram
  • FIG. 7 shows a corresponding spectrum of a thin polymer film acquired in the transmission mode, using the experimental setup of FIGS. 1 and 5. These data were collected in situ while the polymer was curing. These data are from a single pixel representing a 300 x 300 micron sample area. As described hereinabove, the preferred embodiment setup 10 can collect 4096 such data sets during the course of a single experiment.
  • FIG. 8 shows an IR image of a 7-element library 16 holder, demonstrating the spatial imaging capabilities of the present invention.
  • the individual library 16 elements (circles) are 6mm in diameter.
  • the present invention allows spectral data to be collected from a wide area, we can examine all of the elements in the library 16 at once. Spectral data are then isolated from pixels corresponding to each library 16 element. These data can be used to track the reaction at each library 16 element as a function of the control parameters (for example, catalyst temperature and feed composition), therefore allowing the performance of all elements in the library 16 to be evaluated simultaneously. For example, a spectral band corresponding to a reactant or product can be monitored for each library 16 element to determine the reaction rate at that element.
  • control parameters for example, catalyst temperature and feed composition
  • the data at each point would not be collected at a well-defined retardation, but would be spread out over a range of retardations.
  • Two instrumental modifications utilized in the second embodiment of the present invention allow the circumvention of this problem to successfully employ a rapid scanning spectrometer as the light source for mid-IR imaging.
  • the specific electronics employed are sensitive enough to allow the collection of data with a reasonable signal-to-noise ratio (SNR) by acquiring only one frame per interferogram data point. Additionally, since only a single frame is acquired at each data point, any artifacts that would result from collecting data over a range of retardations are minimized.
  • SNR signal-to-noise ratio
  • FIG. 9 A diagram of the second embodiment system is shown in schematic form in FIG. 9 and indicated generally at 100. It consists of a FTIR spectrometer 112 (Nicolet Magna 860, for example), calcium fluoride (CaF 2 ) condensing 114 and refocusing 118 optics, a wide bandpass filter 115, a KBr diffuser 117, a reference library 116, and a 64 x 64 pixel mercury cadmium telluride (MCT) focal plane array detector 120 (Santa Barbara Research Center, Goleta, California, USA).
  • the cryogenic dewar (not shown) and FPA support electronics were manufactured by SE-IR Co ⁇ oration (Goleta, California, USA).
  • the entire optical setup is housed in a purge enclosure (not shown), which minimizes spectral interference from CO 2 and H O vapor.
  • the Nicolet spectrometer 112 is capable of both rapid and step scan operation and was used for the collection of all data.
  • the spectrometer 112 includes an IR source S and a Michelson interferometer comprising moveable mirror Ml, stationary mirror M2 and beam splitter B/S.
  • the FPA 120 and associated electronics are connected via high-speed interface to the computer 124, where Fourier transformation and other data handling 128 procedures are performed.
  • the final information is stored as a set of IR spectroscopic images 28, enabling the user to display intensity images at selected wavelengths or IR spectra at selected points in the image.
  • a control computer 122 controls operation of the spectrometer 112.
  • the spectrometer 112 scanning speed and resolution are first set, and the mirror Ml is continuously scanned.
  • the FPA 120 control software is set up to collect the maximum number of data points that can be collected based on the scan speed, spectral resolution, and FPA 120 frame rate. Data collection is triggered by the forward movement of the interferometer mirror Ml. In this configuration, the spectral resolution is precisely controlled by the total interferometer retardation. The maximum spectral range is then determined by the total number of data points collected. Employment of a broad bandpass filter is desired to only allow light from a specific spectral region to be collected, and to minimize Fourier fold-over noise. In a typical experiment, a 64 x 64 x 1360 point data set is collected, occupying 1 1 MB of disk space. All data processing, including fast Fourier transformation, background subtraction, and baseline correction was performed on computer 124.
  • the first example relates to the adso ⁇ tion of carbon monoxide (CO) on both Cu-ZSM5 zeolite and silica supported platinum (Pt/SiO 2 ) catalysts.
  • Adso ⁇ tion of CO was used as a model system to demonstrate the capability of the system 100 to monitor adsorbate monolayers.
  • the reactor holding the catalyst elements was custom-built and allows up to seven supported catalyst pellets to be examined in situ in transmission mode under realistic reaction conditions.
  • the reactor was loaded with three Pt/SiO and three Cu-ZSM5 IR transparent catalyst pellets, each 6 mm in diameter and pressed from 10 mg of catalyst powder.
  • the catalysts were pretreated using standard procedures under flowing hydrogen and oxygen at 200 C and 300 C, respectively, and by heating in vacuum (10 mTorr) up to 350C.
  • FIG. 10A-C shows three representative spectra of CO adsorbed on Pt/SiO 2 at room temperature.
  • FIG. 12 shows an image generated by plotting the absorbance values at 2157cm "1 for each pixel in the array.
  • the three zeolite catalyst pellets can be unambiguously identified in the image (high absorbance intensity), while the other pellets (position shown by white circles) do not shown any intensity.
  • Similar images (not shown) can also be created for other oxidation states of the zeolite and for CO adsorbed on the Pt/SiO 2 pellets by plotting the abso ⁇ tion bands at the appropriate frequencies.
  • FTIR imaging has therefore only been able in the prior art to follow dynamic processes that change over the time span of a half hour or more due to the long data collection times associated with step scan data collection.
  • FTIR imaging has therefore only been able in the prior art to follow dynamic processes that change over the time span of a half hour or more due to the long data collection times associated with step scan data collection.
  • much faster screening of adsorbates on catalysts as a function of the process conditions is necessary. This information can then provide insight into fundamental reaction mechanisms as a function of catalyst composition.
  • CO was preadsorbed onto the Cu-ZSM5 zeolite catalysts of Example 1 at room temperature, and the catalyst temperature was increased at a rate of 8K min.
  • the peaks shown in FIG. 11 can be assigned to CO adsorbed on the Cu +1 oxidation state (2157cm 1 ) and CO adsorbed on the Cu +1 oxidation state with a water molecule in the coordination sphere of the Cu ion (2139cm 1 ).
  • This technique is applicable to the identification of resin-bound compounds from a split-and-pool synthesis, where beads carrying different ligands are mixed together.
  • Resin-bound ligands were identified in a mixture of -25 beads comprised of 4 natural amino acids. A mixture of these beads was placed onto a polished CaF 2 window and swollen with methylene chloride. The solvent was allowed to evaporate, and another CaF 2 window was placed on top. Slight pressure was maintained in order to flatten the beads, which was necessary to obtain spectra free from saturation effects. This sample was placed in the field of view of the spectrometer 112, and images were collected. After this analysis, the beads could be recovered without damage and submitted for further analysis by simply reswelling them in solvent, causing them to resume their spherical shape.
  • FIG. 13 The images from this experiment are shown in FIG. 13.
  • a spectral frequency that is unique for each ligand By selecting a spectral frequency that is unique for each ligand and plotting the absorbance value for each pixel at that frequency, an image is generated that clearly reveals the location of each type of supported ligand.
  • Representative spectra from each type of bead are shown in FIG. 14. Each one of these spectra were acquired from a single pixel of an image, without any coaddition or smoothing. It should be noted that this type of analysis is not limited to ligands that have well-separated spectral bands. More complex types of classification routines, such as principal component analysis, can also be interfaced with this technique to identify the ligands where the spectra are either highly convoluted, or where a minimum of human intervention is desired.
  • This technique is amenable to the in situ analysis of reactions performed on supported ligands, where different types of beads are placed in a parallel reactor, greatly reducing the time required to collect kinetics data. Additionally, beads isolated from a reaction mixture at different times during the course of a reaction can also be analyzed simultaneously.
  • the example demonstrated here is the oxidation of a primary alcohol to an aldehyde, which has been described previously in the prior art.
  • the reaction was carried out on beads placed in a flow cell equipped with CaF 2 windows. The reactants, which were dissolved in a solvent that swelled the beads, was introduced in to the flow cell and IR images were collected as a function of reaction time.
  • the data from this experiment are shown in FIG. 15 and 16.
  • the thickness-corrected intensities were normalized by dividing by the maximum integrated absorbance.
  • the resulting data are shown in FIG. 16. These data were fitted into a single exponential function.

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  • General Physics & Mathematics (AREA)
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  • Spectrometry And Color Measurement (AREA)

Abstract

La présente invention concerne l'utilisation d'un spectromètre FTIR (100), c'est-à-dire pour spectroscopie à l'infrarouge à base de transformées de Fourier, pour éclairer une échantillothèque, soit en mode d'exploration pas à pas, soit en mode d'exploration rapide. A cet effet, les rayonnements infrarouges émis par l'échantillothèque combinatoire sont enregistrés par un vidéo-détecteur matriciel. Il suffit dès lors d'enregistrer la transformée de Fourier des données mesurées.
EP00947403A 1999-07-16 2000-07-17 Procede et appareil permettant de recueillir de l'information du spectre infrarouge en resolution temporelle simultanement a partir de plusieurs echantillons Withdrawn EP1200795A4 (fr)

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PCT/US2000/019325 WO2001006209A1 (fr) 1999-07-16 2000-07-17 Procede et appareil permettant de recueillir de l'information du spectre infrarouge en resolution temporelle simultanement a partir de plusieurs echantillons

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DE10144214C1 (de) 2001-09-08 2003-04-03 Bruker Optik Gmbh Verfahren zur Aufnahme eines ortsaufgelösten Spektrums mittels eines Fourier-Transform (FT) - Spektrometers sowie Fourier-Transform(FT)-Spektrometer
WO2005017502A1 (fr) 2003-07-28 2005-02-24 Symyx Technologies, Inc. Procede et dispositif de spectroscopie infrarouge parallele
DE102008063225A1 (de) 2008-12-23 2010-07-01 Carl Zeiss Meditec Ag Vorrichtung zur Swept Source Optical Coherence Domain Reflectometry
US8203715B2 (en) * 2009-05-14 2012-06-19 Raytheon Company Knowledge based spectrometer

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US4542295A (en) * 1983-09-29 1985-09-17 Mattson David R Spectrometer with selectable area detector
US5440388A (en) * 1993-08-02 1995-08-08 Erickson; Jon W. Chemical analysis and imaging by discrete fourier transform spectroscopy

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DE3005520C2 (de) * 1980-02-14 1983-05-05 Kayser-Threde GmbH, 8000 München Zweistrahl-Interferometer zur Fourierspektroskopie

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US4542295A (en) * 1983-09-29 1985-09-17 Mattson David R Spectrometer with selectable area detector
US5440388A (en) * 1993-08-02 1995-08-08 Erickson; Jon W. Chemical analysis and imaging by discrete fourier transform spectroscopy

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