Organic Materials and Organic/Inorganic Heterostructures in Atom Probe Tomography

Joester, Derk; Hillier, Andrew C.; Zhang, Yi; Prosa, Ty J.

doi:10.1017/s1551929512000260

Cited by 21 publications

(18 citation statements)

References 22 publications

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“…The absence of any molecular signatures with higher than 5 C atoms in the observed mass-to-charge spectra most conclusively implies a fragmentation mechanism operating during APT. At present, a number of investigations are ongoing to identify the mechanism of the ionization of organic molecules during laser-assisted APT, which is focused on distinguishing the direct ionization or molecular fragmentation process48. However, it can be conclusively stated that the elemental peaks of C and molecular species of C and H observed in APT mass-to-charge spectra originated from the carbonaceous molecules trapped in zeolite pores, thereby providing the clear demonstration of a spatially resolved mapping of carbonaceous molecules in a spent HZSM-5 catalyst material after being exposed to realistic catalytic conditions.…”

Section: Resultsmentioning

confidence: 99%

Discerning the Location and Nature of Coke Deposition from Surface to Bulk of Spent Zeolite Catalysts

Devaraj

Vijayakumar

Bao

et al. 2016

Sci Rep

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The formation of carbonaceous deposits (coke) in zeolite pores during catalysis leads to temporary deactivation of catalyst, necessitating regeneration steps, affecting throughput, and resulting in partial permanent loss of catalytic efficiency. Yet, even to date, the coke molecule distribution is quite challenging to study with high spatial resolution from surface to bulk of the catalyst particles at a single particle level. To address this challenge we investigated the coke molecules in HZSM-5 catalyst after ethanol conversion treatment by a combination of C K-edge X-ray absorption spectroscopy (XAS), 13C Cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopy, and atom probe tomography (APT). XAS and NMR highlighted the aromatic character of coke molecules. APT permitted the imaging of the spatial distribution of hydrocarbon molecules located within the pores of spent HZSM-5 catalyst from surface to bulk at a single particle level. 27Al NMR results and APT results indicated association of coke molecules with Al enriched regions within the spent HZSM-5 catalyst particles. The experimental results were additionally validated by a level-set–based APT field evaporation model. These results provide a new approach to investigate catalytic deactivation due to hydrocarbon coking or poisoning of zeolites at an unprecedented spatial resolution.

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Section: Resultsmentioning

confidence: 99%

Discerning the Location and Nature of Coke Deposition from Surface to Bulk of Spent Zeolite Catalysts

Devaraj

Vijayakumar

Bao

et al. 2016

Sci Rep

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“…Surface atoms are ionized and removed from the apex of the needle by an electric field or a combination of pulsed-laser heating and electric field. 152,153 An electric field accelerates the ions to the detector in a mass spectrometer. The x-y and z positions of the elements in the original sample are determined.…”

Section: Atom Probe Tomography (Apt)mentioning

confidence: 99%

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

et al. 2017

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ABSTRACT:Recently, there has been an explosive growth in research based on hybrid lead-halide perovskites for photovoltaics owing to rapid improvements in efficiency. The advent of these materials for solar applications has led to widespread interest in understanding the key enabling properties of these materials. This has resulted in renewed interest in related compounds and a search for materials that may replicate the defect-tolerant properties and long lifetimes of the hybrid lead-halide perovskites. Given the rapid pace of development of the field, the rises in efficiencies of these systems have outpaced the more basic understanding of these materials. Measuring or calculating the basic properties, such as crystal/electronic structure and composition, can be challenging because some of these materials have anisotropic structures, and/or are composed of both heavy metal cations and volatile, mobile, light elements. Some consequences are beam damage during characterization, composition change under vacuum, or compound effects, such as the alteration of the electronic structure through the influence of the substrate. These effects make it challenging to understand the basic properties integral to optoelectronic operation. Compounding these difficulties is the rapid pace with which the field progresses. This has created an ongoing need to continually evaluate best practices with respect to characterization and calculations, as well as to identify inconsistencies in reported values to determine if those inconsistencies are rooted in characterization methodology or materials synthesis. This article describes the difficulties in characterizing hybrid lead-halide perovskites and new materials, and how these challenges may be overcome. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 challenges discussed. The focus in this article is on crystallography, composition measurements, photoemission spectroscopy and calculations on perovskites and new, related absorbers. We suggest how some of the important artifacts could be avoided and how the reporting for each technique could be streamlined between groups to ensure reproducibility as the field progresses.

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“…38,39,42 Despite APT's excellent spatial and chemical resolution and the relative maturity of the technique, the body of APT analyses of organic systems is small. [43][44][45][46][47][48][49][50][51] Most of these studies looked at polymers, which, because of their chain structure, fragment during field evaporation. [47][48][49][50][51] In 2012, Joester et al examined a blend of poly(3hexylthiophene-2,5-diyl) (P3HT) and C 60 ; 51 as before, the P3HT polymer proved difficult to study due to uneven fragmentation, but the mass-spectrum had a clear C 60 signal, suggesting that small-molecule organic systems should be amenable to study with APT.…”

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confidence: 99%

Atom Probe Tomography of Molecular Organic Materials: Sub-Dalton Nanometer-Scale Quantification

et al. 2019

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In this paper, we demonstrate how to apply atom probe tomography (APT) to molecular organic electronic materials. We demonstrate that APT can provide an unprecedented combination of mass resolution of < 1 Da, spatial resolution of ∼ 0.3 nm in z and ∼ 1 nm in x-y, and an analytic sensitivity of ∼ 50 ppm. We detail two systems that demonstrate the power of APT to uncover structure-property relationships in organic systems that have proven extremely difficult to probe using existing techniques: (1) a model organic photovoltaic system in which we show a chemical reaction occurs at the heterointerface; and (2) a model organic lightemitting diode system in which we show molecular segregation occurs. These examples illustrate the power of APT to enable new insights into organic molecular materials.

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Organic Materials and Organic/Inorganic Heterostructures in Atom Probe Tomography

Cited by 21 publications

References 22 publications

Discerning the Location and Nature of Coke Deposition from Surface to Bulk of Spent Zeolite Catalysts

Discerning the Location and Nature of Coke Deposition from Surface to Bulk of Spent Zeolite Catalysts

Perovskite-Inspired Photovoltaic Materials: Toward Best Practices in Materials Characterization and Calculations

Atom Probe Tomography of Molecular Organic Materials: Sub-Dalton Nanometer-Scale Quantification

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