Method and apparatus for distributed sensing of volatiles using a long period fiber grating sensor with modulated plastic coating for environmental monitoring

Optical time domain reflectometry caused by absorption of a volatile or analyte into the fiber optic cladding is used as an optical nose. The fiber optics (14) are covered with a gas permeable film (44) which is patterned to leave millimeter wide gas permeable notches (48a-48d). The notches contain a sensing polymer that responds to different gases by expanding or contracting

Method and apparatus for chemical and topographical microanalysis

A scanning probe microscope is combined with a laser induced breakdown spectrometer to provide spatially resolved chemical analysis of the surface correlated with the surface topography. Topographical analysis is achieved by scanning a sharp probe across the sample at constant distance from the surface. Chemical analysis is achieved by the means of laser induced breakdown spectroscopy by delivering pulsed laser radiation to the sample surface through the same sharp probe, and consequent collection and analysis of emission spectra from plasma generated on the sample by the laser radiation. The method comprises performing microtopographical analysis of the sample with a scanning probe, selecting a scanned topological site on the sample, generating a plasma plume at the selected scanned topological site, and measuring a spectrum of optical emission from the plasma at the selected scanned topological site. The apparatus comprises a scanning probe, a pulsed laser optically coupled to the probe, an optical spectrometer, and a controller coupled to the scanner, laser and spectrometer for controlling the operation of the scanner, laser and spectrometer. The probe and scanner are used for topographical profiling the sample. The probe is also used for laser radiation delivery to the sample for generating a plasma plume from the sample. Optical emission from the plasma plume is collected and delivered to the optical spectrometer so that analysis of emission spectrum by the optical spectrometer allows for identification of chemical composition of the sample at user selected sites

Scanning probe chemical and topographical microanalysis

The last decade has seen a rapid rise of Scanning Probe Microscopy, SPM, as a prominent and versatile approach for surface studies. SPM instruments are differentiated from the beam-based ones by the fact that they use solid proximal probes for localized analysis. The most commonly used SPM methodology is Atomic Force Microscopy, AFM. In its basic implementation, AFM provides topographical information with nanometer resolution. The most common modifications allow the magnetic, electrostatic, and specific chemical environment to be examined. However, there is no direct way today to perform general chemical analysis with AFM probes. Near-field Scanning Optical Microscopy, NSOM, is another variation of SPM where sharp tapered optical fibers serve dual purposes, being proximal probes of sample topography, and providing the means for localized light delivery for optical studies with sub-wavelength spatial resolution. Again, NSOM itself does not have a general chemical contrast capability. However, the capability to deliver light to localized area opens the way to a multitude of experiments that can be devised using different aspects of light interaction with the sample. This thesis demonstrates several approaches for combined topographical and chemical investigations. Infrared spectroscopy is a sensitive molecular analysis tool. Without scanning proximal probe, IR microscopy has very poor spatial resolution. Enabling methodology for probe fabrication for Near-field Scanning Infrared Microscopy, NSIM, is presented. The efforts in combining NSOM with mass spectrometry, which is probably the most general chemical analysis tool, are outlined. We have demonstrated the possibility of simultaneous topographical and molecular imaging. Another variation of chemical imaging is the combination of SPM and Laser Induced Breakdown Spectroscopy, LIBS. In this method the elemental composition of samples is obtained by analyzing optical emissions from transient plasma plumes formed by intense laser pulses delivered through fiber probes. We have demonstrated the feasibility of this approach. The instrument that we have developed is an attractive complementary tool for established methods of spatial elemental analysis, such as X-ray Fluorescence. Among its attractive features are operation in ambient conditions, minimal requirements for sample preparation, and ease of use