Supramolecular Photocatalyts for Pollutant Degradation and Tumor Removal
A new class of organic supramolecular photocatalysts with full visible spectrum response has been successfully developed. The texture structure, crystal structure, photoelectric physicochemical properties, organic electron energy band structure, photocatalytic oxidation and anticancer properties can be adjusted via molecular structure and stacking structure. The degradation ability, water splitting ability and anticancer came from the HOMO and LUMO level. The photocatalytic activity came from molecular dipole, ordered stacking and nanostructure.
Self-assembled PDINH supramolecular is an effective visible-light photocatalyst for the photodegradation of pollutants and even split water for oxygen evolution. Compared with monomeric PDINH, self-assembled PDINH supramolecular have band-like electronic energy level structure similar to inorganic semiconductor due to orbital overlaps between PDINH-molecular units. Strong π-π stacking between PDINH molecules enables effective long-range electrons delocalization and accordingly promotes photo-generated charge migration and separation, leading to its remarkable photocatalytic activity.
Supramolecular organic nanofibers, self-assembled by a carboxy-substituent PDI molecule via H-type π-π stacking and hydrogen bonding, can act as an effective photocatalyst for both organic pollutants degradation and water oxidation under full visible light. The high activity came from the molecular dipole and the nanocrystallization. Higher π-π supramolecular packing leads to a smaller bandgap, a deeper valence band position, enhanced light absorption and photo-oxidation capability. The inter-electronic field raised from ordered dipole can effectively promote the migration and separation of photo-generated carriers. H/J-type aggregated PDI supramolecular nanostructures were constructed via length of linear carboxy-substituent side-chains. H-aggregates have higher π-electron conjugation and show more semiconductor characteristics, which results in higher carrier separation and migration efficiency. Whereas, J-aggregates exhibit more molecular properties due to low π-electron conjugation caused by head-to-tail stacking mode. H-aggregated PDI mainly forms superoxide radicals (·O2-) and holes (h+) through electron-transfer (ET). In contrast, J-aggregated PDI mainly generates singlet oxygen species (1O2) via energy-transfer (EnT). Benefit from the stronger oxidization ability of·O2- and h+, H-aggregated PDI shows higher photocatalytic activity for degradation and oxygen evolution under visible light. Whereas, J-aggregated PDI exhibits good photocatalytic anti-cancer activity owing to short length of nanofiber.
The full spectrum responsive supramolecular photocatalyst, SA-TCPP has been synthesized via an easy-conducted π-π stacking. The SA-TCPP can powerfully spilt water to hydrogen and oxygen at 40.8 and 36.1 μmol·g-1·h-1 without co-catalyst. The organic pollutants can be efficiently mineralized by the SA-TCPP under visible light irradiation. The degradation performances of SA-TCPP were over 10 times better than the inorganic photocatalysts. The single crystalline structure of π-π stacking promoted the transportation and separation of photogenerated carriers. Supramolecular photocatalyst SA-TCCP of bio-safe amount, targeted injection into the solid tumor inside, completely kill the tumor within 10 min under the deep penetration of red light (600-700 nm) irradiation. Photogenerated holes work as the most significant radical in the photocatalytic therapy process, which is abundant on the surface of photocatalyst in cytoplasm. The solid tumors was completely removed via photocatalysts injection and red-light irradiation.
Prof. Yongfa Zhu received his BA degree in 1985 from Nanjing University and obtained his master degree in 1988 from Peking University. He had studied and worked at Tsinghua University since 1992 to now and received a PhD degree at 1995. He is currently a full professor of Tsinghua University and associate editor for Applied Catalysis B.
His current research is focused on photocatalysis, environmental and energy catalysis and nanomaterials. He is the author and co-author of 306 original research papers published in SCI journals. The total cited numbers reached about 20300 and the H-index arrived at 77. About 31 papers was selected as High-Cited Papers by Essential Science Indicators. Besides, he has written about 5 books and applied about 24 patents.