Enhancing Raman spectrographic sensitivity by using solvent extraction of vapor or particulate trace materials, improved surface scatter from nano-structures on nano-particles, and volumetric integration of the Raman scatter from the nano-particles' surfaces
First Claim
1. A method to increase the sensitivity of the Raman effect by multiple orders of magnitude, allowing detection of one or more trace molecules that are exuded from a chemical compound of interest and present in a medium, thus enabling a real-time, stand-off sensor, comprising:
- selecting as an impingement base a colloid, said colloid comprising;
a liquid solvent forming a medium of suspension;
into which particles of a material strongly attractive to the one or more trace molecules, are suspended;
taking a sample from the sensor'"'"'s environment by pumping the colloid through a sampling unit, thereby exposing the colloid to the medium where the one or more trace molecules may be present;
maximizing, throughout the volume of the sample, the surface-to-surface interaction between the medium and colloid, thereby maximizing the interaction between the surfaces of the suspended particles with the one or more trace molecules;
binding one or more of the particles within the colloid with one or more of the trace molecules, as a result of such interaction;
focusing a monochromatic laser light on said sample;
generating thereby Raman spectra from said sample;
producing a re-constructed Raman spectra of the one or more trace molecules by eliminating from the generated Raman spectra both Rayleigh scatter and Raman scattering from the colloid before it was mixed with the medium;
comparing said re-constructed Raman spectra to Raman spectra contained in a database of Raman spectra for known chemical compounds, to determine the presence of one or more trace molecules exuded from the chemical compound of interest; and
,reporting the result of the preceding steps.
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Abstract
This invention is a method to enhance by orders of magnitude accurate, real-time, stand-off detection by a sensor using Raman spectra of one or more trace compounds of interest (particularly explosives, bioterror organisms, or Volatile Organic Compounds). A colloid, whose medium of suspension is a liquid solvent with a weak Raman spectrum and in which are suspended particles of a noble metal that are preferentially nano-sized to maximize the surface-to-mass ratio for each particle, forms an impingement base. A sample of this colloid is air-pumped through a sampling module, exposed to air potentially carrying trace molecules from the compound of interest, then sent to a detection module that subjects the sample to Raman spectroscopy. The result is first corrected to obtain a unique Raman spectra from the trace molecules, then matched against Raman spectra in a database. Extensions include modifying, flushing, further processing, or recirculating the colloid sample.
41 Citations
40 Claims
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1. A method to increase the sensitivity of the Raman effect by multiple orders of magnitude, allowing detection of one or more trace molecules that are exuded from a chemical compound of interest and present in a medium, thus enabling a real-time, stand-off sensor, comprising:
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selecting as an impingement base a colloid, said colloid comprising; a liquid solvent forming a medium of suspension; into which particles of a material strongly attractive to the one or more trace molecules, are suspended; taking a sample from the sensor'"'"'s environment by pumping the colloid through a sampling unit, thereby exposing the colloid to the medium where the one or more trace molecules may be present; maximizing, throughout the volume of the sample, the surface-to-surface interaction between the medium and colloid, thereby maximizing the interaction between the surfaces of the suspended particles with the one or more trace molecules; binding one or more of the particles within the colloid with one or more of the trace molecules, as a result of such interaction; focusing a monochromatic laser light on said sample; generating thereby Raman spectra from said sample; producing a re-constructed Raman spectra of the one or more trace molecules by eliminating from the generated Raman spectra both Rayleigh scatter and Raman scattering from the colloid before it was mixed with the medium; comparing said re-constructed Raman spectra to Raman spectra contained in a database of Raman spectra for known chemical compounds, to determine the presence of one or more trace molecules exuded from the chemical compound of interest; and
,reporting the result of the preceding steps. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 36, 37, 40)
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38. A method to increase the Raman effect by multiple orders of magnitude by impingement and solvent enhancement of particulate or vapor materials in air or from materials found on surfaces or in liquids so that trace materials can be detectable comprising:
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selecting an impingement material constructed from a material characterized with the requisite surface chemical and sufficient surface area characteristics for concentrating the materials of interest, contacting trace material with said impingement material, extracting trace material from the impingement material with a solvent and further process said solvent so that the trace material of interest is contained in liquid to form a target at sufficient concentration of the trace material present to exhibit a detectable Raman effect, focusing a light incident on said target and receiving Raman spectra from said target to accomplish analysis by one mono-chromatic laser light source followed by another mono-chromatic light laser light source with an appropriately selected different wavelength and subtract one of the Raman spectra resulting from said first laser source from the Raman spectra resulting from the second laser source and produce a re-constructed Raman spectra using the body of knowledge available from literature on Raman spectra; comparing said re-constructed Raman spectra to a database containing Raman spectra of known materials of interest to determine the presence and concentration of one or more of the trace materials of interest; and
,reporting the result of the preceding steps. - View Dependent Claims (39)
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Specification