STED stimulated emission depletion

Fig. 19.4. Stimulated emission depletion (STED) microscopy reveals densely packed charged nitrogen vacancy (NV) color centers in a diamond crystal, (a) State diagram of NV centers in diamond (see inserted sketch) showing the triplet ground ( A) and fluorescent state ( E) along with a dark singlet state ( E) and the transitions of excitation (Exc), emission (Em), and stimulated emission (STED). (b) The steep decline in fluorescence with increasing intensity /sted shows that the STED-beam is able to switch off the centers almost in a digital-like fashion. This nearly rectangular ...

B. Hein, K. WiUig, S.W. HeU, Stimulated emission depletion (STED) nanoscopy of a fluorescent protein - labeled organelle inside a living cell. Proc. Natl. Acad. Sci. USA 105(38), 14271-14276 (2008)... 

Several far-field light microscopy methods have recently been developed to break the diffraction limit. These methods can be largely divided into two categories (1) techniques that employ spatially patterned illumination to sharpen the point-spread function of the microscope, such as stimulated emission depletion (STED) microscopy and related methods using other reversibly saturable optically linear fluorescent transitions (RESOLFT) [1,2], and saturated structured-illumination microscopy (SSIM) [3], and (2) a technique that is based on the localization of individual fluorescent molecules, termed Stochastic Optical Reconstruction Microscopy (STORM [4], Photo-Activated Localization Microscopy (PALM) [5], or Fluorescence Photo-Activation Localization Microscopy (FPALM) [6]. In this paper, we describe the concept of STORM microscopy and recent advances in the imaging capabilities of STORM. 

Figure 11.21 StimuLated emission depletion (STED) microscopy. The sample is excited using single-photon excitation (PUMP pulse) in a confocal microscope arrangement. A time-delayed DUMP pulse selectively depletes close to 100% of the exdted state population in a region around the focus of the PUMP pulse. Using this approach. Hell and co-workers were able to obtain a 5-fold reduction in the fluorescent spot size in the vertical (Z-direction) and a greater than a 2-fold reduction in the horizontal Y/X) direction, leading to a final image size of 97 by 104 nm...

Stimulated emission depletion (STED) microscopy is another microscopy approach to overcome the diffraction limitation of light microscopy by inhibiting fluorescence outside of the focal spot [9]. In this context, fluorescence is viewed as spontaneous light emission while stimulating emission via synchronized laser... 

To realize the observation/detection on nanofluidics, the LIF with high resolution is a vital factor. With the release of stimulated emission depletion (STED) fluorescence microscope, the super-resolution LIF microscope on confocal manner, the high resolution at the order of nanometer was obtained [7, 8]. It was utilized to measure the velocity of fluorescent probes in nanofluidics and to observe the ion... 

Light microscopy is the oldest and the simplest imaging method. However, the lower resolution limit for conventional light microscopy lies above 200 nm. Its application to colloidal particles is, therefore, restricted to rather large colloids and aggregates of them. Even though recent developments, like stimulated emission depletion (STED) microscopy, have shifted the optical resolution limit below 100 nm (Hell 2007), light microscopy is not really relevant for the characterisation of colloidal suspensions. 

Apart from SNOM (or NSOM), two new, highly resolving techniques are emerging that deserve brief mention here. These are stimulated emission depletion (STED) using focal and doughnut-focal beam shapes, and the microscopy with super lenses out of negative index of refraction materials (NIMs). 

One way to deplete the fluorescence, stimulated emission depletion (STED) microscopy, is to return the excited fluorophores to the ground state by stimulated emission as we discussed above in connection with temporal resolution of Stokes shifts (Sect. 5.2). Another approach is to use a variant of GFP that can be switched between fluorescent and non-flourescent states by light of different wavelengths (Sect. 5.7). This switching can be achieved with lower light intensities than are needed to induce stimulated emission [149, 229]. The essential requirements in either case are for the depletion pulse intensity to be zero at or near the focus of the excitation, and for the depletion process to approach saturation rapidly as the pulse intensity increases. 

Whereas, near-field microscopy achieves a high resolution by illuminating a nanometric area with localized light around a small probe tip, the super-resolution techniques extract nanometer-scale information from optical images captured using conventional lens-based optics. Among several super-resolution techniques that have been reported, stimulated emission depletion (STED) microscopy [43-45] and... 

WiMig KI, Nagerl UV (2012) Stimulated emission depletion (STED) imaging of dendritic spines in living hippocampal slices. Cold Spring Harb Protoc 2012 db... 

For many fluorescence-based imaging techniques, such as confocal laser scanning microscopy, spinning disk confocal microscopy, 4pi microscopy, stimulated emission depletion (STED) microscopy, and other superresolution microscopy techniques, we refer to the indicated literature. 

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