Studying the origin of fluorescence emissions of neodymium porphyrin based on the analysis of energy level structure

This paper studies the origin of fluorescence emissions of metalloporphyrins. The absorption spectrum of neodymium-coordinated hematoporphyrin monomethyl ether (Nd-HMME) was found to have four Q bands, which is different from the accepted knowledge (two Q bands). The absorbance of Nd-HMME was comparable to the corresponding absorbance of HMME at wavelengths of 538 nm and 572 nm, but the absorbance of Nd-HMME at wavelengths of 502 nm and 622 nm was approximately 1/30 of that at 572 nm. The doping of Nd3+ enhanced the symmetry of HMME, and led to changes in energy level properties. Moreover, Nd-HMME still exhibited two fluorescence peaks at 624 nm and 686 nm, similar to HMME, which can be explained by the observation of a weak absorption peak of Nd-HMME at 622 nm.