Super-resolution imaging of self-assembly of amphiphilic photoswitchable macrocycles

Self-assembly of an amphiphilic photoswitchable fluorescent macrocycle methoxy-tetraethylene glycol-substituted hexaarylbiimidazole-borondipyrromethene can be observed directly under a super-resolution fluorescence microscope, with the nanoscale resolution beyond the optical diffraction limitation.

Factors Affecting Practical Performance of the STEM at High Voltages

In addition to limited electron source brightness, lens aberrations and the diffraction limitation, which, taken together, represent a fundamental limit of the point-to-point resolving power of a STEM at voltages above 100 k V (at low voltages the use of the field emission gun simplifies the situation somewhat), there are a number of instrumental and/or operational defficiencies that contribute to the gap between the theoretical and practical performance. In fixed beam instruments, operating at up to 100 kV the practical resolution equals the theoretically expected resolving power for suitable specimens. At higher voltages this is not true anymore, mainly due to (i) mechanical instabilities, (ii) electrical instabilities, and (iii) larger aberration coefficients of objective lenses. Exposure times being almost two orders of magnitude longer in the STEM than in TEM at HV, the requirements concerning the electrical and mechanical stabilities become even more severe for STEM.