Scintillating Metal Organic Frameworks

Novel Scintillators Based on Metal Organic Frameworks F. P. Doty Sandia National Laboratories Livermore, CA Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Sandia MOF Team ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Available PSD Scintillators Poor Match to Fission Spectrum ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Efficiency of liquid scintillator NE213 (EJ 301 equivalent) compared to the normalized Watt spectrum. The evaluated efficiency was obtained for a cylinder (diameter 53 mm, height 101 mm) using a 252 Cf source (86 kBq) incident perpendicular to the cylinder axis, threshold 0.15 MeV, and acquisition time 210 hours. Data from J. Cub, et al., Nuclear Instruments and Methods A274 (1989) 217-221 Brighter, more proportional scintillator materials are needed to increase efficiency

Volume dependence of PSD FOM ,[object Object],[object Object],[object Object],The figure of merit, M, at the gate of 0.3 MeV recoil electron energy versus the initial delay of 250 ns wide gate. The same dependences for the M factor normalized to the photoelectron number. Moszynski, M.; Costa, G. J.; Guillaume, G.et al."Study of n  discrimination with NE213 and BC501A liquid scintillators of different size," Nucl. Inst. Meth. Phys. Res. A 1994, 350, 226. Limited Practical Volume New scintillator materials are needed to increase volume and sensitivity

Stilbene MOFs: multiple structures result from the same starting materials under different synthetic conditions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Formula unit: ZnL 3 (DMF) 2 L = 4,4’-stilbenedicarboxylic acid Formula unit: Zn 4 OL 3 C. A. Bauer, T. V. Timofeeva, T. B. Settersten, B. D. Patterson, V. H. Liu, B. A. Simmons, M. D. Allendorf, J. Am. Chem. Soc. 2007, 129, 7136.

Fluorescence Spectra Correlate with Structure ,[object Object],[object Object],[object Object],[object Object],[object Object],Single crystal fluorescence and excitation spectra Decreasing linker interactions C. A. Bauer, et al., J. Am. Chem. Soc. 2007, 129, 7136.

Ion Beam Induced Luminescence (IBIL) Fluorescence/excitation curves for the 3D stilbene MOF, compared with the IBIL emission. Inset shows optical micrograph under UV illumination. Fluorescence/excitation curves for the 2D stilbene MOF, compared with the IBIL emission. Inset shows optical micrograph under UV illumination. F. P. Doty, C. A. Bauer, P. G. Grant, B. A. Simmons, A. J. Skulan, and M. D. Allendorf, Radioluminescence and radiation effects in metal organic framework materials, Proc. of SPIE Vol. 6707 67070F-2 (2007)

IBIL Spectra Less Structure Dependent ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],E(Stokes) ~ large E(Stokes): intermediate E(Stokes):~ small Linker MOF-S2 MOF-S1 F. P. Doty, C. A. Bauer, A. J. Skulan, P. G. Grant, and M. D. Allendorf , Adv. Mater. 2009 , 21, 95–101  E(Stokes)

Analysis of IBIL Vibronic Progressions Linker crystal SDCH2 MOF-S1 MOF-S2 F. P. Doty, C. A. Bauer, A. J. Skulan, P. G. Grant, and M. D. Allendorf , Adv. Mater. 2009 , 21, 95–101 ,[object Object],[object Object],[object Object],[object Object],[object Object]

Dose Dependence of IBIL ,[object Object],[object Object],Inset: Proton ion-beam-induced luminescence spectra for MOF-S2, obtained using a continuous 3 MeV proton beam depositing a 5 Mrad/s dose rate for thin samples. Spectra were taken at 2 s intervals. F. P. Doty, C. A. Bauer, A. J. Skulan, P. G. Grant, and M. D. Allendorf , Adv. Mater. 2009, 21, 95–101

 source PM tube  PIN diode  h  Ortec 142A Scintillating Powder Decay Time F. P. Doty, Ronald J. T. Houk, R. K. Bhakta, Ida M. B. Nielsen, Gyorgy Vizkelethy, Mark D. Allendorf, SPIE conference on CBRNE Sensing X, Orlando, FL United States 16 April 2009

MOF S2 Scintillation Response F. P. Doty, Ronald J. T. Houk, R. K. Bhakta, Ida M. B. Nielsen, Gyorgy Vizkelethy, Mark D. Allendorf, SPIE conference on CBRNE Sensing X, Orlando, FL United States 16 April 2009

[object Object],[object Object],Timing Characteristics of MOF S2 ,[object Object],[object Object]

Timing Spectral Dependence ,[object Object],[object Object],[object Object],All Components due to Emission from the Same Excited State 42% 58% Long and Short Wavelengths Show Exactly the Same Decay

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],MOF S2 Luminescence: Working Hypothesis Three Timing Components due to Three Paths to Neutral Dimer: Tunneling from traps should depend on particle LET Hot electrons Thermalized electrons Trapped electrons

LET dependence of MOF S2 scintillations ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],12% of counts delayed 35% of counts delayed 3-fold increase in delayed light for alphas

Summary and conclusions ,[object Object],[object Object],[object Object],[object Object],Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. ,[object Object],[object Object],[object Object],[object Object],[object Object]

3c. Excitons in Scintillator Radiation Detector Materials . Excitons are a fundamental means by which energy is transported in scintillators, including organic and inorganic compounds. For example, when organic materials are irradiated with neutrons, the triplet excitons formed are known to migrate, and upon encountering other excitons, they self-annihilate giving rise to singlet excitons with a characteristic delayed emission that is a signature for neutrons (known as pulse shape discrimination, PSD). We are soliciting both theoretical and experimental optical projects that elucidate the dynamics of excitons in terms of their migration and interactions, as they pertain to these crucial mechanisms of scintillators: pulse shape discrimination and nonproportionality. Aspects of excitons that are of interest include, but are not limited to, diffusion rate and distance, radiative and nonradiative lifetimes, exciton-exciton Auger upconversion, and trapping by activators and defects. Applicants in this area are strongly encouraged to team with a DOE laboratory that has experience developing practical radiation detectors. ,[object Object],[object Object]

Scintillating Metal Organic Frameworks

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