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22 results on '"Hassan, Asra"'

9. 20 µs-resolved high-throughput X-ray photon correlation spectroscopy on a 500k pixel detector enabled by data-management workflow

Author

Zhang, Qingteng, primary, Dufresne, Eric M., additional, Nakaye, Yasukazu, additional, Jemian, Pete R., additional, Sakumura, Takuto, additional, Sakuma, Yasutaka, additional, Ferrara, Joseph D., additional, Maj, Piotr, additional, Hassan, Asra, additional, Bahadur, Divya, additional, Ramakrishnan, Subramanian, additional, Khan, Faisal, additional, Veseli, Sinisa, additional, Sandy, Alec R., additional, Schwarz, Nicholas, additional, and Narayanan, Suresh, additional

Published
2021
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13. Halogen Etch of Ti3AlC2MAX Phase for MXene Fabrication

Author

Jawaid, Ali, Hassan, Asra, Neher, Gregory, Nepal, Dhriti, Pachter, Ruth, Kennedy, W. Joshua, Ramakrishnan, Subramanian, and Vaia, Richard A.

Abstract

The versatile property suite of two-dimensional MXenes is driving interest in various applications, including energy storage, electromagnetic shielding, and conductive coatings. Conventionally, MXenes are synthesized by a wet-chemical etching of the parent MAX-phase in HF-containing media. The acute toxicity of HF hinders scale-up, and competing surface hydrolysis challenges control of surface composition and grafting methods. Herein, we present an efficient, room-temperature etching method that utilizes halogens (Br2, I2, ICl, IBr) in anhydrous media to synthesize MXenes from Ti3AlC2. A radical-mediated process depends strongly on the molar ratio of the halogen to MAX phase, absolute concentration of the halogen, the solvent, and temperature. This etching method provides opportunities for controlled surface chemistries to modulate MXene properties.

Published
2021
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14. Charge Carriers Modulate the Bonding of Semiconductor Nanoparticle Dopants As Revealed by Time-Resolved X-ray Spectroscopy

Author

Hassan, Asra, primary, Zhang, Xiaoyi, additional, Liu, Xiaohan, additional, Rowland, Clare E., additional, Jawaid, Ali M., additional, Chattopadhyay, Soma, additional, Gulec, Ahmet, additional, Shamirian, Armen, additional, Zuo, Xiaobing, additional, Klie, Robert F., additional, Schaller, Richard D., additional, and Snee, Preston T., additional

Published
2017
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16. Governing Uranium in Pakistan

Author

Sultan, Maria, Jaspal, Mohammad Riaz, Hashmi, Jawad, Hassan, Asra, and Ellahi, Malik A.

Subjects
ddc:300
Abstract

Pakistan has three operating nuclear power plants and two under construction with another two planned. Although not a global player in the uranium market with small production figures (around 40 tonnes of uranium per year), Pakistan is revitalising its uranium exploration efforts and plans to significantly increase the share of nuclear energy in its domestic power generation. [...] This report contextualises Pakistan's dual search for energy as well as military security as it mastered the front-end of the nuclear fuel cycle. While information specific to uranium governance is limited in Pakistan given the highly classified nature of the programme, the report provides a substantial sense of the organisational and management of Pakistan's nuclear programme, its legislation and work of the regulator in overseeing the front and back end of Pakistan's nuclear infrastructure. The Pakistan country report is part of the larger global 'Governing Uranium' project on uranium governance, led by DIIS, which seeks to identify governance gaps in uranium accountability and control and provide policy recommendations for improving front-end transparency, security, and regulation.

Published
2015

19. Monolayer Silane‐Coated, Water‐Soluble Quantum Dots

Author

Zhang, Xi, primary, Shamirian, Armen, additional, Jawaid, Ali M., additional, Tyrakowski, Christina M., additional, Page, Leah E., additional, Das, Adita, additional, Chen, Ou, additional, Isovic, Adela, additional, Hassan, Asra, additional, and Snee, Preston T., additional

Published
2015
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20. Anomalous Perturbation of the O2Sensitivity of Poly(aromatic) Hydrocarbons by Magnetic Quantum Dots

Author

Hassan, Asra, Shamirian, Armen, Zhang, Xi, and Snee, Preston T.

Abstract

Molecular oxygen is known to be an efficient quencher of the excited states of organic molecules. This fact has been exploited to develop fluorescent O2sensors, which is topical for cancer screening and many other applications. In this regard, our group and others have reported the development of robust, ratiometrically reporting chemosensors by conjugating O2-sensitive organic chromophores to inorganic quantum dots. Recently, an attempt was made to prepare a multifunctional sensor system by attaching the emissive poly(aromatic) hydrocarbons pyrene and perylene to magnetic nanomaterials, specifically CdSe/CdMnZnS and ZnSe/ZnMnS/ZnS quantum dots. However, the fluorescence of both dyes became invariant to oxygen levels even if the solutions were fully saturated. We ruled out any material dependency beyond the presence of Mn2+ions by studying control samples, while molecular dynamics simulations negated any possibility of spatial sequestration of O2by the magnetic fields. In the case of pyrene, the proximity of the magnetic dots induces significant singlet–triplet mixing; however, this does not explain this curious observation. As such, we believe that the exchange interaction between O2and the dyes is perturbed by both the microenvironment of the system and the inhomogeneous magnetic fields such that quenching is not observed.

Published
2017
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22. Halogen Etch of Ti 3 AlC 2 MAX Phase for MXene Fabrication.

Author

Jawaid A, Hassan A, Neher G, Nepal D, Pachter R, Kennedy WJ, Ramakrishnan S, and Vaia RA

Abstract

The versatile property suite of two-dimensional MXenes is driving interest in various applications, including energy storage, electromagnetic shielding, and conductive coatings. Conventionally, MXenes are synthesized by a wet-chemical etching of the parent MAX-phase in HF-containing media. The acute toxicity of HF hinders scale-up, and competing surface hydrolysis challenges control of surface composition and grafting methods. Herein, we present an efficient, room-temperature etching method that utilizes halogens (Br 2 , I 2 , ICl, IBr) in anhydrous media to synthesize MXenes from Ti 3 AlC 2 . A radical-mediated process depends strongly on the molar ratio of the halogen to MAX phase, absolute concentration of the halogen, the solvent, and temperature. This etching method provides opportunities for controlled surface chemistries to modulate MXene properties.

Published
2021
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