Preparation And Properties Of The Triplets Annihilation Photon Upconversion Materials Inside Nanocapsules

Upconversion (UC), which is the observation of emission (or population of excited states) at higher energy after excitation at lower energy. The triplet-triplet-annihilation (TTA)-based upconversion has a broad application prospect, such as solar cells, photocatalytic hydrogen and biological fileds etc, because of its high upconversion efficiency and low-intensity excitation light. The system of TTA-based upconversion consists of triplet sensitizer and acceptor. At present, the TTA-based upconversion mainly occurred in organic solvent not as a single unit, which will significantly limit its applications. It is one of the key problems for the application of TTA based upconversion that how to encapsulate the triplet sensitizer and acceptor and obtain the solid upconversion materials. In this thesis, two works were taken to solve the problems existing in TTA-UC, which is designed sensitizer and encapsulation of the triplet-triplet-annihilation upconversion system. The upconversion quantum efficiency was successfully improved by modified the molecule structure of triplet sensitizers. Moreover, encapsulation of the triplet sensitizer and acceptor with nanocapsules was studied. The main contents of this thesis are summarized as follows:(1) The triplet photosensitizer BDP-2 was successfully synthesized based on parent BODIPY with -OCH2CH2N3 moieties as pendant groups. The effects of side chains (-OCH2CH2N3) modified sensitizer BDP-2 on the upconversion efficiency were studied. The results showed that it can effectively improve the triplet energy transfer between sensitizer and receptors. For the BDP-2, a higher upconversion quantum yield (9.47%) were observed which is about 1.7 times higher than that of BDP-1 (?UC=5.40%).(2) The triplet-triplet-annihilation upconversion based on polystyrene nanocapsu-les were successfully synthesized by the method of microemulsion, the quantum efficiency of polystyrene nanocapsules were studied with soybean oil and n-hexadecane (HD) as inner solvent, respectively. The results showed that the higher quantum efficiency of polystyrene nanocapsules was obtained with soybean oil as inner solvent, the quantum efficiency was 2.05%. In order to further improve the quantum efficiency, the effects of the dosage of PIB on the quantum efficiency of polystyrene nanocapsules were studied. The results showed that when the dosage of PIB was 5%, the upconversion efficiency of polystyrene nanocapsules reached to 2.53%.(3) The triplet-triplet-annihilation upconversion based on TiO2 nanocapsules were successfully synthesized by soft template method. The effects of different catalyst, dosage, reaction time on the quantum efficiency were studied. The results show that when ammonia as catalyst and the dosage of butyl titanate was 0.5 mL, the thickness of the coated layer of TiO2 nanocapsules was about 15nm, and the quantum efficiency of reached to 6.60%.