Image fluorescence SNOM

Figure4.2 Fluorescence SNOM image ofa single Rhodamine 6G molecule. Panel (b) indicates the cross-section profile for the dashed line in panel (a).

Figure 4.3 shows the fluorescence SNOM images of single PMMA-Pe chains embedded in the unlabeled PMMA matrix. In the SNOM image, each PMMA-Pe chain was observed as an isolated fluorescent spot. The molecular weight of each chain can be estimated from the integrated fluorescence intensity [19], and Figure 4.3... 

Figure 10 Simultaneous shear-force AFM (a, a ) and apertureless fluorescence SNOM (b, b ) of dye nanoparticles in polyvidone resin showing angular aggregation by the difference in shape of topographic and optical image both in the top views (a, b) and in the surface-views (a, b ). ...

Fig. 25 (a) Fluorescence SNOM image of a PMMA gel labeled with Pe and Eo dyes (b) Fluorescence decay curves of Pe observed for (curves A and B) PMMA gel at points A and B indicated in panel a, (curve C) PMMA bulk sample without crosslinker, (curve D) spin-cast PMMA film containing Pe dyes. Reprinted with permission of [26], copyright (2003) The Chemical Society of Japan... 

Figure 19.7 Fluorescence SNOM images of the phase-separation structure of a blend monolayer of pyrene-labeled PiBMA and pe -lene-labeled PODMA. The SNOM images were [53] 2002, Elsevier.

Figure 19.8 Fluorescence SNOM images of a phase-separated blend of polystyrene and poly (9,9-dioctylfluorene). (a-c) Surface topography, transmittance, and fluorescence images, respectively (d and e) Mapping of the amplitude and lifetime of the fluorescence decay...

Figure 2 Fluorescence image of PNA probe (arrow) hybridized on the lambda phage DNAnwlecule using SNOM/AFM.

Only a few combinations of SNOMs with fluorescence lifetime imaging have been published yet [241, 300, 353], Because of the small excited volume high efficiency of the FLIM technique is important. All published applications used TCSPC techniques in eombination with SPAD detectors. However, NSOM lifetime images presented so far are not very impressive. It is not clear whether the reason is lack of photons, detector background, or inefficient data analysis and image-reconstraction software. 

Generally, the SNOM principle can be combined with fluorescence lifetime imaging in the same way as in the slow scan setup described in Fig. 5.96. Especially TCSPC in the Sean Sync In mode can relatively easily be implemented in... 

It is commonly known that the proximity of the SNOM tip changes the fluorescence lifetime in the seanned point of the sample. Whether this effect makes lifetime imaging in a SNOM useless or particularly interesting is hard to say as tong as only a few results exist. However, multidimensional TCSPC may be one way to make use of the dependenee of the lifetime on the tip distance. At a t)q)ical vibration frequency of the tip of a few hundred kHz, the photons for different tip dis-tanee eould be routed into different memory blocks. The result would be several images for different tip distance. 

Near-field scanning optical microscopes (NSOM or SNOM) are mainly used in fluorescence and VIS measurements. They provide optical images with spatial resolution less than the Abbe s limit of Ajl. The high lateral resolution is commonly achieved by using the optical near-field, e. g. in close vicinity of a very narrow fiber tip. Figure 5.16 illustrates the design of a near-field microscope. 

Optical near-field microscopy (SNOM and NSOM [24,25]) is a novel technique with a spatial resolution power well beyond the diffraction limit. It was applied to image the fluorescence of single molecules at room temperature [26, 27] (see Chapter 2). Typical spectral linewidths reported were around 20 000 GHz [27], due to the room temperature operation. At liquid helium temperatures the linewidths are reduced to about 10-100 MHz, which allows study of the special effects on single molecular resonators. Moemer et al. [28, 29] combined the SNOM-technique with Single Mol-... 

The SNOM image depicts chemical (or material) contrast between different materials. It depends on various factors including Rayleigh, Raman, and fluorescence emissions, absorption, polarization, and also on specific shear-force influences. Even different polymorphs are differentiated by the material contrast. ... 

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