Single-molecule identification

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A. Van Orden, N. P. Machara, P. M. Goodwin, and R. A. Keller, Single-molecule identification in flowing... 

Muller R et al 1996 Time-resolved identification of single molecules in solution with a pulsed semiconductor diode laser Chem. Phys. Lett. 262 716-22... 

Fries J R, Brand L, Eggeling C, Kdllner M and Seidel CAM 1998 Quantitative identification of different single molecules by selective time-resolved confocal fluorescence spectroscopy J. Phys. Chem. A 102 6602-13... 

Widengren, J., Kudryavtsev, V., Antonik, M., Berger, S., Gerken, M. and Seidel, C. A. (2006). Single-molecule detection and identification of multiple species by multiparameter fluorescence detection. Anal. Chem. 78,2039-50. 

The extremely small cross sections for conventional Raman scattering, typically 10 111 to 10-25 cm2/molecule has in the past precluded the use of this technique for single-molecule detection and identification. Until recently, optical trace detection with single molecule sensitivity has been achieved mainly using laser-induced fluorescence [14], The fluorescence method provides ultrahigh sensitivity, but the amount of molecular information, particularly at room temperature, is very limited. Therefore, about 50 years after the discovery of the Raman effect, the novel phenomenon of dramatic Raman signal enhancement from molecules assembled on metallic nanostructures, known as surface-enhanced Raman spectroscopy or SERS, has led to ultrasensitive single-molecule detection. 

The identification of size, shape, and axial ratio can also be done by direct observation in the electron microscope (EM). This is accomplished by depositing single molecules (if they can be obtained) directly on polymer-coated copper grids and then shadowing them with heavy metals or making a replica of the molecular surface on mica. The sample can then be viewed in the transmission EM and photographs can then be taken after calibration of the magnification factor. 

Photoconductivity induced by single-photon excitation of aromatic molecules in liquid hydrocarbons is thought to involve Rydberg states.A number of photophysical studies on glasses or crystals have appeared these include 2,4,5-trimethylbenzaldehyde in durene single crystals, identification of phenylcyclohexadienyl radicals in benzene crystals, hydronaphthyl radicals in dehydronaphthalene crystals,1-hydronaphthyl radicals in naphthalene crystals, phenylcyclohexadienyl radicals in biphenyl crystals, ... 

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