Transmission Electron Microscopy Operating Yam ntxwv
Taw qhia
Lub hauv paus ntsiab lus ntawm kev kos duab ntawm electron microscope thiab optical microscope yog qhov zoo ib yam, qhov sib txawv yog qhov qub siv hluav taws xob hluav taws xob ua lub teeb ci thiab electromagnetic teb li lub lens. Tsis tas li ntawd, vim hais tias lub zog nkag ntawm lub tshuab hluav taws xob hluav taws xob yog qhov tsis muaj zog, cov qauv siv rau lub tshuab ntsuas hluav taws xob yuav tsum tau ua rau hauv ib qho ultra-thin seem nrog lub thickness ntawm txog 50nm. Cov kab no yuav tsum tau ua nrog ib qho ultramicrotome. Lub magnification ntawm electron microscope tuaj yeem ncav cuag ze li ib lab zaug. Nws muaj tsib ntu: illumination system, imaging system, lub tshuab nqus tsev, kaw lus kaw lus, thiab cov khoom siv hluav taws xob. Yog tias nws yog subdivided: qhov tseem ceeb yog lub lens hluav taws xob thiab cov duab kaw lus. Cov phom hluav taws xob, cov iav condenser, cov qauv chav, lub hom phiaj lo ntsiab muag, daim iav diffraction, iav nruab nrab, cov iav tsom iav, cov ntxaij vab tshaus fluorescent thiab cov koob yees duab hauv lub tshuab nqus tsev.
Lub tshuab ntsuas hluav taws xob yog lub tshuab ntsuas hluav taws xob uas siv cov khoom siv hluav taws xob los nthuav tawm sab hauv lossis qhov chaw ntawm ib qho khoom. Lub wavelength ntawm high-speed electrons luv dua li qhov pom lub teeb (wave-particle duality), thiab qhov kev daws teeb meem ntawm lub tshuab tsom iav yog txwv los ntawm lub wavelength nws siv. Yog li ntawd, qhov kev daws teeb meem theoretical ntawm electron microscope (txog 0.1 nanometers) yog ntau dua li ntawm optical microscope. tus nqi (li 200 nm).
Transmission electron microscope (TEM luv luv), hu ua kis tau tus mob electron microscope [1], yog los tsim cov kab hluav taws xob nrawm nrawm thiab muaj zog rau cov qauv nyias nyias, thiab cov hluav taws xob sib tsoo nrog cov atoms hauv cov qauv hloov cov kev taw qhia, yog li ua lub kaum ntse ntse tawg. . Qhov luaj li cas ntawm lub kaum sab xis yog cuam tshuam nrog qhov ntom thiab tuab ntawm cov qauv, yog li cov duab sib txawv ntawm qhov ci thiab qhov tsaus ntuj tuaj yeem tsim tau, thiab cov duab yuav raug tso tawm ntawm cov khoom siv duab (xws li cov ntxaij vab tshaus fluorescent, zaj duab xis, thiab cov khoom sib txuas photosensitive) tom qab zooming thiab tsom.
Vim yog luv luv de Broglie wavelength ntawm electron, qhov kev daws teeb meem ntawm kis tau tus mob electron microscope yog ntau dua li ntawm lub optical microscope, uas muaj peev xwm ncav cuag 0.1-0.2nm, thiab lub magnification yog kaum txhiab mus rau lab lub sij hawm. Yog li ntawd, kev siv cov tshuab hluav taws xob xa hluav taws xob tuaj yeem siv los soj ntsuam cov qauv zoo ntawm cov qauv, txawm tias cov qauv ntawm tsuas yog ib kem ntawm atoms, uas yog kaum tawm txhiab zaus me dua li cov qauv me tshaj plaws uas tuaj yeem pom los ntawm optical microscopy. TEM yog ib qho tseem ceeb analytical txoj kev nyob rau hauv ntau yam scientific teb hais txog physics thiab biology, xws li kev tshawb fawb mob cancer, virology, ntaub ntawv science, raws li zoo raws li nanotechnology, semiconductor kev tshawb fawb, thiab lwm yam.
Ntawm qhov tsis tshua muaj magnifications, qhov sib piv hauv TEM imaging feem ntau yog vim qhov sib txawv ntawm cov khoom siv hluav taws xob vim qhov txawv thickness thiab muaj pes tsawg leeg ntawm cov khoom. Thaum lub magnification ntau yog siab, complex fluctuations yuav ua rau qhov sib txawv ntawm brightness ntawm daim duab, yog li kev txawj ntse yuav tsum tau soj ntsuam cov duab tau. Los ntawm kev siv cov qauv sib txawv ntawm TEM, nws muaj peev xwm ua kom pom cov qauv los ntawm nws cov khoom siv tshuaj, crystallographic orientation, hluav taws xob qauv, hluav taws xob theem hloov los ntawm cov qauv, thiab feem ntau los ntawm kev nqus ntawm electrons.
Thawj TEM yog tsim los ntawm Max Knorr thiab Ernst Ruska hauv 1931, pawg tshawb fawb no tau tsim thawj TEM nrog kev daws teeb meem dhau qhov pom kev pom hauv xyoo 1933, thiab thawj TEM kev lag luam hauv xyoo 1939 ua tiav.
Loj TEM
Loj-scale kis tau tus mob electron microscopes (paub TEM) feem ntau siv 80-300kV electron beam acceleration voltage. Cov qauv sib txawv sib txawv rau qhov sib txawv electron beam acceleration voltages. Qhov kev daws teeb meem muaj feem xyuam rau cov hluav taws xob hluav taws xob acceleration voltage, uas tuaj yeem ncav cuag 0.2-0.1nm. Cov qauv high-end tuaj yeem ua tiav qhov sib txawv ntawm atomic.
Tsawg-voltage TEM
Lub tshuab hluav taws xob hluav taws xob acceleration voltage (5kV) siv nyob rau hauv qhov tsawg-voltage me me TEM (Low-Voltage electron microscope, LVEM) yog qis dua qhov loj TEM. Ib qho hluav taws xob qis dua yuav txhim kho lub zog ntawm kev sib cuam tshuam ntawm cov kab hluav taws xob thiab cov qauv, yog li txhim kho cov duab sib piv thiab qhov sib txawv, tshwj xeeb tshaj yog tsim rau cov qauv xws li polymers thiab biology; Nyob rau tib lub sijhawm, qhov hluav taws xob tsawg-voltage kis tau tus mob electron microscope yuav ua rau muaj kev puas tsuaj tsawg rau cov qauv.
Qhov kev daws teeb meem yog qis dua qhov loj electron microscope, 1-2nm. Vim qhov tsis tshua muaj hluav taws xob, TEM, SEM thiab STEM tuaj yeem ua ke hauv ib lub cuab yeej
Cryo-EM
Cryo-microscopy feem ntau yog nruab nrog cov khoom siv khov nab kuab ntawm cov khoom siv hluav taws xob sib kis zoo tib yam kom txias cov qauv mus rau qhov kub ntawm cov kua nitrogen (77K), uas yog siv los soj ntsuam cov ntsuas kub-rhiab heev xws li cov protein thiab cov kab mob lom. Los ntawm khov cov qauv, qhov kev puas tsuaj ntawm cov kab hluav taws xob rau cov qauv tuaj yeem raug txo, qhov deformation ntawm cov qauv tuaj yeem raug txo, thiab cov qauv zoo dua tuaj yeem tau txais.
