Design And Performance Investigations In Conjugated Coordination Polymers Of Scintillation

With the continuous development of physics,diagnosis and treatment,and security detection,nuclear medicine and nuclear physics detection technology continue to develop,so the research of scintillation materials has become one of the research hotspots in the world today.Traditional scintillation materials mainly involve inorganic and organic substances.The two aspects of scintillation materials have been developed in the past ten years with rich structure-type coordination compounds.At the same time,the research on materials has intersected nature and diversity.The scintillation properties of metal organic coordination polymer compounds have also attracted the attention of scientists..A metal organic coordination polymer formed by the bonding of a large conjugate organic group with a ray response and a metal ion,which has the advantages of rapid response of organic groups to rays and the mechanism of inorganic sensitization,and an approximate breakthrough in combination with the configuration.This strategy provides a promising research direction for exploring new scintillation materials.Firstly,the luminescence mechanism of inorganic scintillation materials,organic scintillation materials and metal-organic framework compounds is described.A clear understanding of the light emission mechanism is of guiding significance for the design and synthesis of scintillation materials with excellent properties.Existing methods for synthesizing metal-organic framework compounds are described,and the hydrothermal method using metal-organic framework compounds is a simple and rapid synthesis method.In terms of ligand design,macro-conjugated organic carboxylic compounds are mainly used,such as macro-conjugated carboxylic acid imidazole ligand 2-(2-carboxylic acid phenyl)imidazole(4,5-f)(1,10)phenanthrene(HNCP)and 3-(benzimidazol-1-yl)benzoic acid(Hbmb),etc.These two ligands,including the O atom coordination of carboxylic acid and the N atom coordination of imidazole,which has the potential to build a variety of materials.On the other hand,transition or rare earth ions are used as metal ions,such as Zn²⁺ions with d¹⁰ structure,or Lu³⁺ions of lanthanide materials with 4f orbitals.In this thesis,a series of metal-organic framework compounds were constructed using in situ hydrothermal methods.The X-ray single crystal diffractometer was used to analyze the crystal structure,elemental analysis,infrared radiation spectra(IR),thermogravimetric analysis(TGA),powder X-ray diffraction(PXRD),fluorescence test,and first-principles calculation.Means to analyze the properties of compounds and deduced the mechanism of scintillation and luminescence.2-(2-formylphenyl)imidazole(4,5-f)(1,10)phenanthroline(HNCP)was used as the organic ligand,and the transition metal Zn(II)was used as the metal ion.Synthesized a new coordination polymer[Zn₂(NO₃)(NCP)₃(H₂O)₃]_n·2n H₂O(1).It was found through single crystal diffraction analysis and crystal structure analysis that it belongs to the P2₁/n space group,and the frame contains a 1D continuous structure.Three NCP^–ligands(labeled as L_I,L_II,L_III),the L_I and L_IIligands display similar coordination mode:?₂-?²?¹,while the L_II ligand adopts a?₂-?²?² mode.The L_I and L_IIligands connect adjacent Zn(1)and Zn(2)ions into a tetranuclear zinc(II)cluster.Then,the paratactic L_IIIligands,acting as double linkers,bridge neighboring zinc(II)clusters to generate a 1D chain along the c-direction.The two metal ions are two coordination modes,Zn(1)ions are four coordination modes,and Zn(2)center is six coordination.Through the fluorescence test of coordination polymer1 and ligand and the first-principles calculation of coordination polymer 1,the light-emitting mechanism of complex 1 is explained.Furthermore,photoluminescent spectra demonstrate that coordination polymer 1 might be a good candidate for an efficient green emission material.The next we select 3-(benzimidazol-1-yl)benzoic acid(Hbmb)as the organic ligand and rare earth ion Lu(III)as the metal ion.Synthesized a new coordination polymer Lu(bmb)₃1/2H₂O(2).These Lu-MOFs belong to the monoclinic space group P2₁/C space group and features a 2D chain structure,Three bmb^?ligands(labeled as L_I,L_II,L_III).The three ligands adopt two coordination modes,L_I,L_II The ligand adopts the?1-?2coordination mode,while the L_IIIligand adopts the?2-?2?1 coordination mode.Lu(III)metal ions are linked to form a two-core structure through L_I and L_II ligands.The two-core form a one-dimensional chain in the direction of b under the connection of the ligand L_III.Lu element forms seven coordination with 6 oxygen and one nitrogen atom.Under X-ray excitation,coordination polymer 2 has fluorescent properties and shows a short fluorescence lifetime.The calculation of the first-principle principle explains that the principle of luminescence is formed by ligand-ligand and a small amount of metal-ligand electron transfer.Under the excitation of X-ray,this combination has flickering light emission,and coincides with the spectral peak excited by Xe lamp.Study on rare earth substitution modification based on coordination polymer 2.The scintillation properties of coordination polymer 2 were changed by using different classifications such as rare earth chloride,nitrate and acetate.The substitution of Eu Cl₃ and Tb Cl₃ has the largest enhancement of the scintillation performance,and the luminescence is characteristic of Eu³⁺and Tb³⁺emission.In the study of substitution with different proportions of Tm(NO₃)₃,it was found that when the substitution concentration was 4%,the radiation emission was the strongest;if the substitution concentration continued to increase,an ion quenching effect would occur.Similarly,in the studies on the substitution of Eu Cl₃ and Tb Cl₃ with different concentrations,the optimal substitution concentrations were found to be 3%and 10%respectively.It is concluded that the doping of rare earth ions of will increase the way of energy transfer,thereby increasing the intensity of scintillation light emission...