Comment on "Magnetic-field-enabled resolution enhancement in super-resolution imaging" by M. Zhang et al., Phys. Chem. Chem. Phys., 2015, 17, 6722-6727

Certain fluorophores, in particular those that can undergo photoinduced radical pair reactions are known to exhibit a magnetic field dependent fluorescence summarized in the term magnetic field effect (MFE). We tried to reproduce experiments that reported magnetic field enhanced fluorescence for commonly used organic dyes with a high quantum yield suitable for single molecule localization microscopy. We find that the enhanced fluorescence is due to fluorescence reflected by the magnet's surface rather than MFE. Spectral fluorimetry demonstrates that common organic fluorophores such as Alexa 647 exhibit no magnetic field enhanced fluorescence in the absence/presence of a strong magnet.