| Discovering and revealing the mechanism of the light and heat-driven energy transfer processes is a widely studied subject in the field of science, since these processes are significant steps in chemical reactions and life activities. Over the years, studying of the mechanism of energy transfer in oxide-zeolite based host-guest composite systems has attracted particular attention, which is research emphasis and hotpot in the field of host-guest chemistry. However, the optical inactivity and the insulating nature of oxide-based zeolites severely limit host-involving energy transfer and transport as well as other processes. The thesis is to utilize metal-chalcogenide-based zeolites or zeolitic analogs with semiconducting property and optical activity as host materials, and further implant the organic dye molecules with optical properties into the host materials. It aims to construct a new-type of host-guest composites, explore the mechanism and efficiency of energy transfer between open-framework semiconducting host materials and restricted guest units, and turn the efficiency of multi-step energy transfer. The main works are summarized as follows: 1. Multi-step host-guest energy transfers between inorganic chalcogenide-based semiconductor zeolite material and organic dye moleculesInorganic chalcogenide-based semiconductor zeolite material(coded as RWY) serving as UV-vis light-harvesting host constructs host-guest antenna system. To construct the system with efficient the multistep vectorial energy transfer necessities the criteria: the emission spectra of host framework overlap with the absorption spectra of restricted guest units. Considering that,we choose acridine orange(AO) and rhodamine B as the guests. It is noted that, diluted AO aqueous solution absorbed at around 490 nm, which overlap with the emission spectra of RWY and the emission spectrum showed a peak at 525 nm, which is close to 550 nm where RhB chromophore showed its absorption maximum. In summary, a multistep vectorial energy transfer assay could be fabricated by further covering RWY?AO capsules with RhB to study multi-step energy transfer between inorganic chalcogenide-based semiconductor zeolite material and AO as well as RhB. 2. Tuning the efficiency of multi-step energy transfer in a host–guest antenna system based on a chalcogenide semiconductor zeolite through acidification and solvation of guests This optically active chalcogenide-based zeolite, capable of integrating porosity with semi-conductivity and photoluminescence, provides a whole new opportunity for framework-involved energy transfer between an inorganic host and organic guest. Nevertheless, in this case, the energy transfer efficiency(12%) between the RWY host and the guest dye molecule did not reach our expectations. Thus, we are still confronted with a big challenge on how to boost the multi-step energy transfer efficiency in such host–guest antenna systems. Herein, we turn the efficiency of multi-step energy transfer in a host–guest antenna system through acidification and solvation of guest. Firstly, the environmental acidity directly controls the protonation of the amino groups on PF molecules. The different existence forms(PF, PFH+ and PFH2+) possess distinctive absorption and emission spectra in either aqueous solution or the solid state, which effectively increase the energy transfer efficiency due to the increasing of overlap between the emission spectra of RWY and the absorption spectra of PFH+. Secondly, the organic solvent molecules surrounding the guest ions not only change the relative orientation of the donor–acceptor transition dipoles, but also affect the distance between the donor and acceptor. In addition, the electronic dipole moment of guest molecules can be also accordingly influenced by the polar environment created by polar solvent molecules surrounding the gues t. Thus, solvation of guest ions by solvent molecules with different polarity will in principle strongly influence energy transfer efficiency. The project will provide new-type composites and basic theoretical guidance for sensor monitoring, semiconductor photocatalysis, contaminant removal and photochemical field as well as environmental protection. |
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