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Your search keyword '"Andolina, Christopher M."' showing total 138 results
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138 results on '"Andolina, Christopher M."'

1. Exploring the formation of gold/silver nanoalloys with gas-phase synthesis and machine-learning assisted simulations

Author

Gromoff, Quentin, Benzo, Patrizio, Saidi, Wissam A., Andolina, Christopher M., Casanove, Marie-José, Hungria, Teresa, Barre, Sophie, Benoit, Magali, and Lam, Julien

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

While nanoalloys are of paramount scientific and practical interests, the main processes leading to their formation are still poorly understood. Key structural features in the alloy systems, including crystal phase, chemical ordering, and morphology, are challenging to control at the nanoscale, making it difficult to transfer their usage to industrial applications. In this contribution, we focus on the gold/silver system that has two of the most prevalent noble metals, and combine experiments with simulations to uncover the formation mechanisms at the atomic-level. Nanoparticles are produced using state-of-the-art inert-gas aggregation source and analyzed using transmission electron microscopy and energy-dispersive x-ray spectroscopy. Machine-learning-assisted molecular dynamics simulations are employed to model the crystallization process from liquid droplets to nanocrystals. Our study finds a preponderance of nanoparticles with five-fold symmetric morphology, including icosahedron and decahedron which is consistent with previous results on mono-metallic nanoparticles. However, we observe that gold atoms, rather than silver atoms, segregate at the surface of the obtained nanoparticles for all the considered alloy compositions. These segregation tendencies are in contrast to previous studies and have consequences on the crystallization dynamics and the subsequent crystal ordering. We finally show that the underpinnings of this surprising segregation dynamics is due to charge transfer and electrostatic interactions rather than surface energy considerations.

Published
2024
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2. Convergence Acceleration in Machine Learning Potentials for Atomistic Simulations

Author

Bayerl, Dylan, Andolina, Christopher M., Dwaraknath, Shyam, and Saidi, Wissam A.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Disordered Systems and Neural Networks
Abstract

Machine learning potentials (MLPs) for atomistic simulations have an enormous prospective impact on materials modeling, offering orders of magnitude speedup over density functional theory (DFT) calculations without appreciably sacrificing accuracy in the prediction of material properties. However, the generation of large datasets needed for training MLPs is daunting. Herein, we show that MLP-based material property predictions converge faster with respect to precision for Brillouin zone integrations than DFT-based property predictions. We demonstrate that this phenomenon is robust across material properties for different metallic systems. Further, we provide statistical error metrics to accurately determine a priori the precision level required of DFT training datasets for MLPs to ensure accelerated convergence of material property predictions, thus significantly reducing the computational expense of MLP development., Comment: Digital discovery, accepted

Published
2022

3. Optimization and Validation of a Deep Learning CuZr Atomistic Potential: Robust Applications for Crystalline and Amorphous Phases with near-DFT Accuracy

Author

Andolina, Christopher M., Williamson, Philip, and Saidi, Wissam A.

Subjects
Condensed Matter - Materials Science
Abstract

We show that a deep-learning neural network potential (DP) based on density functional theory (DFT) calculations can well describe Cu-Zr materials, an example of a binary alloy system that can coexist in several ordered intermetallics and as an amorphous phase. The complex phase diagram for Cu-Zr makes it a challenging system for traditional atomistic force-fields that fail to describe well the different properties and phases. Instead, we show that a DP approach using a large database with ~300k configurations can render results generally on par with DFT. The training set includes configurations of pristine and bulk elementary metals and intermetallics in the liquid and solid phases in addition to slab and amorphous configurations. The DP model was validated by comparing bulk properties such as lattice constants, elastic constants, bulk moduli, phonon spectra, surface energies to DFT values for identical structures. Further, we contrast the DP results with values obtained using well-established two embedded atom method potentials. Overall, our DP potential provides near DFT accuracy for the different Cu-Zr phases but with a fraction of its computational cost, thus enabling accurate computations of realistic atomistic models especially for the amorphous phase.

Published
2020
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5. Polymeric Gd-DOTA amphiphiles form spherical and fibril-shaped nanoparticle MRI contrast agents

Author

Randolph, Lyndsay M, LeGuyader, Clare LM, Hahn, Michael E, Andolina, Christopher M, Patterson, Joseph P, Mattrey, Robert F, Millstone, Jill E, Botta, Mauro, Scadeng, Miriam, and Gianneschi, Nathan C

Subjects
Rare Diseases, Bioengineering, Nanotechnology, Chemical Sciences
Abstract

A Gd3+-coordinated polymerizable analogue of the MRI contrast agent Gd-DOTA was used to prepare amphiphilic block copolymers, with hydrophilic blocks composed entirely of the polymerized contrast agent. The resulting amphiphilic block copolymers assemble into nanoparticles (NPs) of spherical- or fibril-shape, each demonstrating enhanced relaxivity over Gd-DOTA. As an initial examination of their behavior in vivo, intraperitoneal (IP) injection of NPs into live mice was performed, showing long IP residence times, observed by MRI. Extended residence times for particles of well-defined morphology may represent a valuable design paradigm for treatment or diagnosis of peritoneal malignances.

Published
2016

6. Polycatechol Nanoparticle MRI Contrast Agents

Author

Li, Yiwen, Huang, Yuran, Wang, Zhao, Carniato, Fabio, Xie, Yijun, Patterson, Joseph P, Thompson, Matthew P, Andolina, Christopher M, Ditri, Treffly B, Millstone, Jill E, Figueroa, Joshua S, Rinehart, Jeffrey D, Scadeng, Miriam, Botta, Mauro, and Gianneschi, Nathan C

Subjects
Bioengineering, Biomedical Imaging, Nanotechnology, Catechols, Contrast Media, HeLa Cells, Humans, Magnetic Phenomena, Magnetic Resonance Imaging, Micelles, Nanoparticles, Polymers, Proton Magnetic Resonance Spectroscopy, melanin, micelles, polycatechols, contrast agents, relaxivity, Hela Cells, contrast agents, relaxivity, Nanoscience & Nanotechnology
Abstract

Amphiphilic triblock copolymers containing Fe(III) -catecholate complexes formulated as spherical- or cylindrical-shaped micellar nanoparticles (SMN and CMN, respectively) are described as new T1-weighted agents with high relaxivity, low cytotoxicity, and long-term stability in biological fluids. Relaxivities of both SMN and CMN exceed those of established gadolinium chelates across a wide range of magnetic field strengths. Interestingly, shape-dependent behavior is observed in terms of the particles' interactions with HeLa cells, with CMN exhibiting enhanced uptake and contrast via magnetic resonance imaging (MRI) compared with SMN. These results suggest that control over soft nanoparticle shape will provide an avenue for optimization of particle-based contrast agents as biodiagnostics. The polycatechol nanoparticles are proposed as suitable for preclinical investigations into their viability as gadolinium-free, safe, and effective imaging agents for MRI contrast enhancement.

Published
2016

16. Tuning electrical and interfacial thermal properties of bilayer MoS2 via electrochemical intercalation

Author

Xiong, Feng, primary, Yalon, Eilam, additional, McClellan, Connor J, additional, Zhang, Jinsong, additional, Aslan, Ozgur Burak, additional, Sood, Aditya, additional, Sun, Jie, additional, Andolina, Christopher M, additional, Saidi, Wissam A, additional, Goodson, Kenneth E, additional, Heinz, Tony F, additional, Cui, Yi, additional, and Pop, Eric, additional

Published
2021
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20. Tuning electrical and interfacial thermal properties of bilayer MoS2 via electrochemical intercalation.

Author

Xiong, Feng, Yalon, Eilam, McClellan, Connor J, Zhang, Jinsong, Aslan, Ozgur Burak, Sood, Aditya, Sun, Jie, Andolina, Christopher M, Saidi, Wissam A, Goodson, Kenneth E, Heinz, Tony F, Cui, Yi, and Pop, Eric

Subjects
CARRIER density, MECHANICAL properties of condensed matter, RAMAN spectroscopy, MAGNITUDE (Mathematics), NANOSTRUCTURED materials, THERMAL properties
Abstract

Layered two-dimensional (2D) materials such as MoS2 have attracted much attention for nano- and opto-electronics. Recently, intercalation (e.g. of ions, atoms, or molecules) has emerged as an effective technique to modulate material properties of such layered 2D films reversibly. We probe both the electrical and thermal properties of Li-intercalated bilayer MoS2 nanosheets by combining electrical measurements and Raman spectroscopy. We demonstrate reversible modulation of carrier density over more than two orders of magnitude (from 0.8 × 1012 to 1.5 × 1014 cm−2), and we simultaneously obtain the thermal boundary conductance between the bilayer and its supporting SiO2 substrate for an intercalated system for the first time. This thermal coupling can be reversibly modulated by nearly a factor of eight, from 14 ± 4.0 MW m−2 K−1 before intercalation to 1.8 ± 0.9 MW m−2 K−1 when the MoS2 is fully lithiated. These results reveal electrochemical intercalation as a reversible tool to modulate and control both electrical and thermal properties of 2D layers. [ABSTRACT FROM AUTHOR]

Published
2021
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30. In situ environmental TEM observation of two-stage shrinking of Cu2O islands on Cu(100) during methanol reduction.

Author

Chi, Hao, Curnan, Matthew T., Li, Meng, Andolina, Christopher M., Saidi, Wissam A., Veser, Götz, and Yang, Judith C.

Abstract

The structural dynamics of Cu catalyst regeneration from Cu2O under methanol is poorly understood. In situ Environmental TEM on Cu(100)-supported Cu2O islands reveals a transition from anisotropic to isotropic shrinking during reduction. Two-stage reduction is statistically supported and explained by preferential methanol reactivity on Cu2O nano-islands with DFT simulations. [ABSTRACT FROM AUTHOR]

Published
2020
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31. Structure and Function of Iron-Loaded Synthetic Melanin

Author

Li, Yiwen, primary, Xie, Yijun, additional, Wang, Zhao, additional, Zang, Nanzhi, additional, Carniato, Fabio, additional, Huang, Yuran, additional, Andolina, Christopher M., additional, Parent, Lucas R., additional, Ditri, Treffly B., additional, Walter, Eric D., additional, Botta, Mauro, additional, Rinehart, Jeffrey D., additional, and Gianneschi, Nathan C., additional

Published
2016
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33. Structure and Function of Iron-Loaded Synthetic Melanin

Author

Li, Yiwen, Xie, Yijun, Wang, Zhao, Zang, Nanzhi, Carniato, Fabio, Huang, Yuran, Andolina, Christopher M., Parent, Lucas R., Ditri, Treffly B., Walter, Eric D., Botta, Mauro, Rinehart, Jeffrey D., and Gianneschi, Nathan C.

Abstract

We describe a synthetic method for increasing and controlling the iron loading of synthetic melanin nanoparticles and use the resulting materials to perform a systematic quantitative investigation on their structure–property relationship. A comprehensive analysis by magnetometry, electron paramagnetic resonance, and nuclear magnetic relaxation dispersion reveals the complexities of their magnetic behavior and how these intraparticle magnetic interactions manifest in useful material properties such as their performance as MRI contrast agents. This analysis allows predictions of the optimal iron loading through a quantitative modeling of antiferromagnetic coupling that arises from proximal iron ions. This study provides a detailed understanding of this complex class of synthetic biomaterials and gives insight into interactions and structures prevalent in naturally occurring melanins.

Published
2024
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35. Polycatechol Nanoparticle MRI Contrast Agents

Author

Li, Yiwen, primary, Huang, Yuran, additional, Wang, Zhao, additional, Carniato, Fabio, additional, Xie, Yijun, additional, Patterson, Joseph P., additional, Thompson, Matthew P., additional, Andolina, Christopher M., additional, Ditri, Treffly B., additional, Millstone, Jill E., additional, Figueroa, Joshua S., additional, Rinehart, Jeffrey D., additional, Scadeng, Miriam, additional, Botta, Mauro, additional, and Gianneschi, Nathan C., additional

Published
2015
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41. Assembly of Near???Infrared Luminescent Lanthanide Host(Host???Guest) Complexes With a Metallacrown Sandwich Motif

Author

Department of Chemistry, University of Michigan, Ann Arbor, 930 N. University Ave, Ann Arbor, MI 48109???1055 (USA), Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720???1460 (USA), Chemical Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, CA 94720???1460 (USA), Jankolovits, Joseph, Andolina, Christopher M., Kampf, Jeff W., Raymond, Kenneth N., Pecoraro, Vincent L., Department of Chemistry, University of Michigan, Ann Arbor, 930 N. University Ave, Ann Arbor, MI 48109???1055 (USA), Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720???1460 (USA), Chemical Sciences Division, Lawrence Berkeley National Laboratories, Berkeley, CA 94720???1460 (USA), Jankolovits, Joseph, Andolina, Christopher M., Kampf, Jeff W., Raymond, Kenneth N., and Pecoraro, Vincent L.

Published
2011

44. Copper Deposition on Gold Nanoprism Substrates.

Author

Straney, Patrick J., Andolina, Christopher M., and Millstone, Jill E.

Subjects
*GOLD, *NANOSTRUCTURED materials, *COPPER, *NANOPARTICLES, *CRYSTALLOGRAPHY
Abstract

Copper-containing nanomaterials are attractive due to the natural abundance, low cost, and unique catalytic properties of copper metal. Copper may also be used as a representative system to study the formation of mixed metal nanoparticles containing 3d transition metals. These elements pose challenges to traditional metal nanoparticle synthesis strategies due to competing formation of both oxides and hydroxides, depending on metal identity. Here, we analyze copper deposition pathways on gold nanoprism substrates using a combination of electron microscopy and X-ray photoelectron spectroscopy techniques, demonstrating conditions for both core@shell and island growth modes. Elemental analysis by X-ray photoelectron spectroscopy and Auger electron spectroscopy indicate that the final nanoparticle products contain metallic copper. Together, these results elucidate important trends for incorporating 3d transition metals into traditional colloidal syntheses of multimetallic nanostructures. [ABSTRACT FROM AUTHOR]

Published
2016
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