Infrared-spectroscopic mapping ofasingle virus bynear-field microscopy

2005 
Nanoscale-resolving near-field microscopy iscombined withinfrared fingerprint spectroscopy touniquely assess local chemical andstructural properties. Herewefocus onamide vibrational contrast onvarious locations onasingle tobacco mosaic virus. Mid-Infrared fingerprint spectroscopy islongknownforits unique features that makeitapowerful tool forchemical andstructural analysis notonlyinbiology. Therelative long wavelength has, however, prevented achieving aresolution better than afewpmandthus hasstrongly limited theapplications ofthis technique. Scattering scanning near-field optical microscopy (s-SNOM) hasovercome this limit byexploiting thenear-field coupling between asharp tipandthesample, allowing resolutions of20nmevenatmid-infrared wavelengths [1]. In oursetup ametallized tipofanatomic force microscope isilluminated withinfrared light ofaCO-laser. Thebackscattered light isthendetected inaninterferometric setup whichallows ustomeasure bothamplitude andphase ofthe scattered light. Spectroscopy isimplemented bystep-tuning thelaser between 5and6pmwavelength. Application of spectroscopic near-field microscopy tonanoscale polymer composites hasrecently beendemonstrated [2]. Hereweshowinfrared-spectroscopic mapping ofasingle virus within thespectral range oftheprotein amide-I band (z1600-1700 cm-') demonstrating aresolution of;100times better compared toclassical infrared microscopy. Incontrast toother microscopic methods ourtechnique doesnotrequire anymodification ofthesample suchasstaining orlabeling, astheinherent andcharacteristic feature ofvibrational absorption isusedtodistinguish between different components.
    • Correction
    • Cite
    • Save
    • Machine Reading By IdeaReader
    0
    References
    0
    Citations
    NaN
    KQI
    []