Enhanced photostability of chlorophyll by introducing Mg 2 Si as an O 2 -depleting agent

The application of chlorophyll (Chl) is limited due to its low photostability. The regulation of oxygen status including both oxygen (O 2 ) and singlet oxygen ( 1 O 2 ) around Chl molecules is important to improve their stability. Here, we designed a macroscopic Chl solution system to evaluate the role of magnesium silicide (Mg 2 Si) as O 2 -depleting agent in the elimination of dissolved oxygen and singlet oxygen for improving Chl photostability. The results showed that the photostability of Chl solution followed the order of oxygen free (OF) > oxygen blocking (OB) > normoxic (ON) solution conditions upon ultraviolet light irradiation. Based on the oxygen blocking condition, the addition of Mg 2 Si in Chl solution further created OBC condition that kept Chl in similar oxygen free condition through oxygen blockage and dissolved oxygen consumption. The existence of Mg 2 Si effectively reduced the content of dissolved oxygen and the generation of singlet oxygen, determined from dissolved oxygen content monitoring, electron spin-resonance spectroscopy and spectroscopic spectroscopy. After 60 min of irradiation, the absorbance retention rate of the Chl solution in the OBC condition reached 68.1%, while the absorbance retention rate of pristine Chl was as low as around 5%. When Mg 2 Si and β-carotene were added to the Chl solution together, the absorbance retention rate reached 81.6%. This work demonstrated the availability of MgSi 2 as O 2 -depleting agent and provides a new thought to create both O 2 -depleting and 1 O 2 -depleting environment for improving Chl photostability. Graphical abstract