- Collection:
- Atlanta University and Clark Atlanta University Theses and Dissertations
- Title:
- Syntheses and investigations of photo and radioluminescent stilbene- and anthracene- based lanthanide metal-organic frameworks, 2016
- Creator:
- Mathis, Stephan Roy
- Date of Original:
- 2010/2019
- Subject:
- Degrees, Academic
Dissertations, Academic - Location:
- United States, Georgia, Fulton County, Atlanta, 33.749, -84.38798
- Medium:
- theses
dissertations - Type:
- Text
- Format:
- application/pdf
- Description:
- This research explores the synthesis of anthracene and stilbene-based metal-organic framework (MOF) structures as potential scintillating (radioluminescent) materials for use in the detection of gamma radiation. The organic molecules 9,10-anthracenedicarboxylic acid (ADCH2) and trans-4,4-stilbenedicarboxylic acid (SDCH2), were each used as a linker, in combination with a range of lanthanide metal ions, to synthesize novel three dimensional MOF structures under hydrothermal conditions. With ADCH2, the early period lanthanides yield isostructures with the metal ion in higher coordination (nine) than for those with late period metals (seven). The ADC-MOFs show linker-based photoluminescence properties with well defined vibronic peaks in their emission profile and their emission (?max~435 nm) blue shifting from that of the ADCH2 powder (~500 nm) and closer to the organic molecule in monomer arrangement (?max ~ 420 nm). The structures also show photoluminescence lifetimes between 1 and 2 ns, which is similar to the reported value for monomeric anthracene units. The blue-shift and reduction in lifetime, compared to ADCH2, are indicative of minimal ?-? interactions amongst the aromatic moieties, thereby limiting the non-radiative relaxation pathways. On exposure to ionizing radiation (protons and g- rays), the ADC-MOFs demonstrated scintillation properties, with a radioluminescence lifetime of ~ 6 ns which is similar to that of the ADCH2 powder. A combination of SDCH2 and lanthanide metal ions produced two isostructured MOFs containing Tm3+ and Er3+, under the hydrothermal synthesis conditions explored. The 3-D structure contained ultra large diamond-shaped pores with dimensions of 16 x 30 . A blue-shift of fluorescence spectra was observed for the SDC-MOF structures (?max ~ 425 nm) compared to that of bulk SDCH2 powder (?max ~475 nm), and closely resembling that of monomeric isolated SDC units (?max~475 nm). Their photoluminescence lifetime is ~0.76 ns, about half of that observed for SDCH2 powder. The blue shift and reduction in lifetime (compared to SDCH2) is attributed to minimal ?-? interactions between SDC units in the MOF structure, thus minimizing associated non-radiative relaxation pathways. The isolation of anthracene and stilbene in MOF structures therefore has the potential to improve their performance as scintillators. KEY TERMS: Metal- Organic Frameworks, Scintillation, Radioluminescence, Lanthanides, Inorganic Chemistry, Materials Chemistry
Date of award: 5/16/2016
Degree type: dissertation
Degree name: Doctor of Philosophy (PhD)
Granting institution: Clark Atlanta University
Department: Chemistry
Advisor: Ingram, Conrad
Advisor: Reed, James
Advisor: Harruna, Issifu - Metadata URL:
- http://hdl.handle.net/20.500.12322/cau.td:2016_mathis_stephan
- Holding Institution:
- Atlanta University Center Robert W. Woodruff Library
- Rights:
-
