| In the past two decades,the research on triplet-triplet annihilation?TTA?fluorescence upconversion has attracted much attention,however,there is lack systematic research about the solvent effect,the intramolecule energy transfer of photosensitizer,the energy level matching relationship between the photosensitizer and the acceptor molecule,et al.In this dissertation,the dynamic processes of the whole TTA upconversion is studied by means of steady-state spectroscopy,femtosecond and nanosecond transient spectroscopy,electrochemistry,and DFT theory calculation.It mainly includes:design and synthesis of Bodipy-fullerene photosensitizer that applied to TTA upconversion;The effect of solvent viscosity and polarity on TTA upconversion dynamic process is studied;Three S-T excited photosensitizers are synthesized and applied to TTA upconversion;Two heavy-atom-free photosensitizers were synthesized and applied to photocatalytic oxidation.Application of the Bodipy-fullrene dyad in TTA upconversion as triplet photosensitizersDesigned and synthesized three Bodpy-C60 derivatives with different ?-conjugation as triplet photosensitizers by analysising of the molecular structure of Bodipy-C60 has been reported.Steady-state and transient spectroscopy experiments indicate the energy transfer from Bodipy to C60,and the energy level matching of donor and acceptor is beneficial to intramolecular energy transfer,and the highest upconversion quantum yield is about 8%.Based on the resonance energy transfer mechanism,the molecular design concept of Bodipy-C60 was spread to Bodipy-C70.The energy transfer efficiency is close to 100%and the triplet state lifetime is up to 80 ?s.The upconversion quantum yield is as high as 10.3%,the total upconversion capability is as high as 4417 M-1·cm-1,and it has better optical stability than the C70 monomer.Solvents effect on TTA upconversion dynamicIn this chapter,viscosity and polarity of solvents effect on the upconversion dyanmic of Bodipy-C60/Perylene were studied.Five solvents were selected:toluene,chlorobenzene,o-dichlorobenzene,dioxane,THF.According to the viscosity and polarity of the solvent,combined with theoretical calculations,the effects of solvent on intramolecular energy transfer,TTET and TTA processes were studied.The upconversion quantum yield was up to 14.1%in dichlorobenzene,which is the highest upconversion quantum yield obtained by the fullerene derivative as a photosensitizer.According to the law of spin statistics and previous studies,the spin statistic factor f=0.4 for perylene,and the f>0.4 for DPA.The former explanation for f>0.4 is the existence of reverse intersystem crossing?RISC?from T2?SI,but this conclusion has not been proved.In this section,toluene,chlorobenzene,dichlorobenzene,bromobenzene,tetrahydrofuran and N,N-dimethylformamide?DMF?were selected as solvents to study the effect of solvent on the each step efficiency of PtOEP/DPA system upconversion.The upconversion quantum yield was measured.Based on the above conclusions,the spin statistic factor f in different solvents was calculated.The mechanism of the solvent effect on the spin statistic factor f was studied by theoretical calculation and non-radiative transition theory.The existence of RISC was proved in experiment.Near infrared-to-near ultraviolet triplet-triplet annihilation upconversion by strong spin-forbidden transitionThree new Os???complexes were synthesized with ligands of 2,2'-dipyridyl,1,10-phenanthroline monohydrate and 4,7-diphenyl-1,10-phenanthroline,and were applied as triplet photosensitizers for TTA upconversion.The lifetimes of lowest triplet state of these complexes were determined to be 107 ns,373 ns and 386 ns for Os-dipy,Os-phen and Os-diphen respectively.The energies of triplet states were derived,e.g.1.75 eV for Os-dipy,1.80 eV for Os-phen and 1.74 eV for Os-diphen.Using these photosensitizers,strong upconverted fluorescence of triplet acceptors,9,10-diphenylanthracene?DPA?,perylene and 9,10-Bis?phenethynyl?anthracene?BPEA?,were observed in a range of visible to near-ultraviolet.Especially,a fluorescence emission with the largest anti-stokes shift of 1.14 e V was observed for the Os-phen/DPA system,and the upconverted fluorescence quantum yield was determined as 5.9%in deoxygenated dichloroethane.This is the largest anti-Stokes shift that has been reported so far.Research on heavy-atom-free photosensitizer of Bodipy-carbazole Derivatives and Application in Photocatalytic OxidationTwo heavy-atom-free photosensitizers of Bodpy-carbazole derivatives were designed and synthesized?BC and CBC?.Nanosecond transient absorption spectroscopy have been confirmed that BC and CBC produced triplet states,and triplet quantum yield and lifetime were highly dependent on solvent polarity.The triplet quantum yield of BC and CBC is 4.1%and 9.1%in the non-polar solvent cyclohexane,and 0.5%and 1.8%in the polar solvent acetonitrile.The triplet lifetime is 9.6 ?s and 109.7 ?s in the non-polar solvent,and increased to 204.7 ?s and 347.1 ?s in the polar solvent dichloroethane.BC and CBC were applied to photocatalytic oxidation of DHN,and the photoreaction rate constants reached 1.11×10-3 min-1 and 2.54×10-3 min-1. |
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