Single Analyte Molecule Research Articles

Grouping of Independent Single Molecules on Silicon Surfaces

We evaluated the possibilities of preparing single analyte molecules on silicon surfaces for chemical analysis based on fluorescence measurement. A single-molecule imaging technique involving far-field optical microscopy was used to visualize rhodamine B (rhB) molecules in submonolayers prepared on Si wafers. This technique revealed that fluorescence of solvent-free, adsorbed rhB molecules in submonolayers appeared in two different forms: isolated fluorescent spots in which a countable number of independent single rhB molecules were grouped together and diffused fluorescence in the region with no fluorescent spots. On the basis of the fluorescence imaging and time-resolved fluorometry of individual fluorescent spots, together with examination of light-scattering sites on Si wafers, we discussed the possibility that the isolated fluorescent spots occurred on crystal-originated sites dotted on Si wafers. Our findings should provide guiding principles for developing vials for single analyte molecules on Si surfaces.

A NEW MODEL OF GAS LIQUID CHROMATOGRAPHY APPLYING THE KINETICS OF GASEOUS ADSORPTION AT SURFACES

The dependence of the adjusted retention volume, V1R, in gas liquid chromatograph on carrier gas flow rate, u, was studied for several solutes using 5% squalane stationary phase and 40-60 mesh fluoropak 8 as support. In all cases V1R increases in a stepwise fashion as u increases. In each step the rate o increase of V1R is lntitially high, but gradually decreases until V1R levels off. V1R is further shown to be directly proportional to n, the number of adsorbant sites in the stationary phase recognised by a single analyte molecule during its passage through the column and, based on this relationship between V1R and n, a new model of gas chromatography applying the kinetics of gaseous adsorption at surfaces, and whose predictions are consistent with the experimental data above, is presented.