Bekale Laurent Adonis - Beneficial role of gold nanoparticles as photoprotector of magnesium tetraphenylporphyrin

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      The photoprotection of porphyrins is of immense importance for   their utilisation in several photo-related applications. In the   present study, we have employed gold nanoparticles (AuNPs) to   photoprotect a porphyrin, magnesium tetraphenylporphyrin (MgTPP).   Absorption, fluorescence and X-ray photoemission spectroscopic   (XPS) studies of MgTPP under illumination in the absence and in   the presence of AuNPs have been carried out to assess their   effect on the photostability of MgTPP. The results show that with   an appropriate concentration of AuNPs, virtually 100%   photoprotection can be provided to MgTPP. The protecting ability   of AuNPs is the result of their binding with MgTPP at its   nitrogen sites, inhibiting, thus, the binding of reactive oxygen   species (ROS) at these sites, known to cause the photodegradation   of MgTPP and several other porphyrins under aerobic conditions.   Further, the decreased formation of excited singlet states of   MgTPP, as a result of its binding with AuNPs, also suppresses the   generation of ROS and improves the photostability of MgTPP. The   binding between MgTPP and AuNPs may also be responsible for the   photoprotection provided to MgTPP by AuNPs under anaerobic   conditions too. The use of gold nanoparticles thus offers us a   new strategy to photoprotect various porphyrins.

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