ATRFTIR衰减全反射光谱的原理.ppt

Attenuated Total Reflection Flourier transformed Infrared Spectroscopy,ATR-FTIR,catalogue,Brief introduction of ATR,Attenuated Total Reflectance (ATR) is an IR sampling technique. It measures the changes in an infrared beam with totally internal reflection when it comes into contact with a sample. ATR is used for surface analysis of solids and liquids. ATR generally allows qualitative or quantitative analysis of samples with little or no sample preparation which greatly speeds sample analysis.,How ATR Works,With ATR sampling we direct the IR beam into a crystal of relatively higher refractive index at a certain angle. The IR beam reflects from the internal surface of the crystal and creates an evanescent wave. It extends beyond the surface of the crystal into the sample held in contact with the crystal.,where n2 is the refractive index of the sample, n1 is the refractive index of the crystal and c is the critical angle.,1 when exceeding the critical angle, we will get a totally reflection of the IR beam. 2 n1n2 ,the crystal has a relatively high refractive index.,Light path in the ATR setup,The sample is put on top of the blue crystal.,The IR beam picks up a signal as it passes a few micron into the sample and creates an evanescent wave.,While the evanescent wave extends only 0.5-5 m beyond the crystal surface and into the sample.,schematic illustration,Equipment to push the sample onto the crystal,This can be achieved by pressing the sample down on the crystal.,If the substance under study is a liquid, it is simply dropped onto the crystal, thereby obtaining optimal contact.,Therefore it is important to obtain good contact between the crystal and the sample.,Tinfoil,Traditional IR spectroscopy need preparation of the sample.,schematic illustration,First a couple of milligram of sample is mixed with about 200 mg of KBr powder. Then the mixture is pressed into a tablet which is then used in the analysis.,Traditional IR does not work quite effectively , and for analyzing surface layer structure. ATR-FTIR has become a kind of beneficial tool and means for analyzing samples and surface properties. ATR-FTIR has been applied to every realm such as spinning and weaving, quality testing , public security and so on.,applications,Characterization of Surface Treatments of Cork Stoppers by FTIR-ATR,J. Agric. Food Chem. 2006, 54, 4932-4936,The paper proposed an analytical method for identification of the presence of surface treatments in cork stoppers.,Bands 1258, 1079, 1010and 787 cm-1 are specific of silicone.,Bands 2963, 2916, and2850 cm-1, which are less specific, corresponding to C-H bonds, had intensities that differed greatly in both types of compounds,The 2963 cm-1 band is due to CH3 and occurs in silicones exclusively as the only alkane.,These spectra exhibit bands corresponding to the cork matrix. The most intense occurring at 1735 cm-1, due to carbonyl bonds, mainly from suberin, and bands at 1010-1300 cm-1,due mainly to carbohydrate and lignin C-O. The latter can overlap with those of silicone.,By determination of the absorbance at the selected bands, it was possible to differentiate the type of treatment applied to a given stopper. It concludes that the characteristics of the proposed method (ATR-FTIR) make it certainly applicable in industry settings.,Anal. Chem. 2010, 82, 31393145,in situ studies on electrochemically induced processes at IR waveguide surfaces via evanescent field absorption spectroscopy,scheme of the SECM-ATR-FTIR setup,the ATR crystal has been built into an electrochemical cell as the central part of the base plate,The -H peak areas were integrated from 670 to 710 cm -1.,the polymerization levels for different reaction times were calculated by determining the percentage of peak area change It is between the integrated -H peak area of polymerized SNS at the different polymerization times and the integrated -H area of the SNS monomer.,Present the first instrumental combination of scanning electrochemical microscopy (SECM) with in situ attenuated total reflection infrared spectroscopy (IR-ATR) using a single bounce ATR crystal as SECM substrate. The level of polymerization could be evaluated by the recorded IR spectra.,While using ATR technique ,we only need little or no p