Cherie R Kagan Research Group
The Kagan group’s research is focused on studying the chemical and physical properties of nanostructured materials and in integrating materials with optical, electrical, magnetic, mechanical, and thermal properties for (multi-)functional devices. We combine the flexibility of chemistry and bottom-up assembly with top-down fabrication techniques to design materials and devices. We explore the properties of materials and measure the characteristics of devices using spatially- and temporally-resolved optical spectroscopies, AC and DC electrical techniques, electrochemistry, scanning probe and electron microscopies, and analytical measurements.
Announcements
- Congratulations, Jaeyoung!
Congratulations to Jaeyoung on defending his PhD thesis!
- Congratulations to Cherie on being named an MRS Fellow!
MRS Fellows are honored for their distinguished research accomplishments and outstanding contributions to the advancement of materials research (more).
- Congratulations, Sarah!
Congratulations to Sarah on defending her PhD thesis!
- Welcome, Ilia!
Ilia Geints has joined our group as a first-year PhD student in the Electrical and Systems Engineering (ESE) department.
- Welcome, Gary!
Gary Chen has joined our group as a first-year PhD student in the chemistry department.
- Welcome, Anamika!
Anamika Singh has joined our group as a postdoctoral researcher.
Research Highlights
Shulevitz, Henry J.; Amirshaghaghi, Ahmad; Ouellet, Mathieu; Brustoloni, Caroline; Yang, Shengsong; Ng, Jonah J.; Huang, Tzu-Yung; Jishkariani, Davit; Murray, Christopher B.; Tsourkas, Andrew; Kagan, Cherie R.; Bassett, Lee C.
Nanodiamond emulsions for enhanced quantum sensing and click-chemistry conjugation Journal Article
In: ACS Applied Nano Materials, 2024.
@article{Shulevitz2024,
title = {Nanodiamond emulsions for enhanced quantum sensing and click-chemistry conjugation},
author = {Henry J. Shulevitz and Ahmad Amirshaghaghi and Mathieu Ouellet and Caroline Brustoloni and Shengsong Yang and Jonah J. Ng and Tzu-Yung Huang and Davit Jishkariani and Christopher B. Murray and Andrew Tsourkas and Cherie R. Kagan and Lee C. Bassett},
url = {https://pubs.acs.org/doi/10.1021/acsanm.4c01699},
doi = {10.1021/acsanm.4c01699},
year = {2024},
date = {2024-06-29},
urldate = {2023-12-04},
journal = {ACS Applied Nano Materials},
abstract = {Nanodiamonds containing nitrogen-vacancy (NV) centers can serve as colloidal quantum sensors of local fields in biological and chemical environments. However, nanodiamond surfaces are challenging to modify without degrading their colloidal stability or the NV center's optical and spin properties. Here, we report a simple and general method to coat nanodiamonds with a thin emulsion layer that preserves their quantum features, enhances their colloidal stability, and provides functional groups for subsequent crosslinking and click-chemistry conjugation reactions. To demonstrate this technique, we decorate the nanodiamonds with combinations of carboxyl- and azide-terminated amphiphiles that enable conjugation using two different strategies. We study the effect of the emulsion layer on the NV center's spin lifetime, and we quantify the nanodiamonds' chemical sensitivity to paramagnetic ions using T1 relaxometry. This general approach to nanodiamond surface functionalization will enable advances in quantum nanomedicine and biological sensing.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Nanodiamonds containing nitrogen-vacancy (NV) centers can serve as colloidal quantum sensors of local fields in biological and chemical environments. However, nanodiamond surfaces are challenging to modify without degrading their colloidal stability or the NV center's optical and spin properties. Here, we report a simple and general method to coat nanodiamonds with a thin emulsion layer that preserves their quantum features, enhances their colloidal stability, and provides functional groups for subsequent crosslinking and click-chemistry conjugation reactions. To demonstrate this technique, we decorate the nanodiamonds with combinations of carboxyl- and azide-terminated amphiphiles that enable conjugation using two different strategies. We study the effect of the emulsion layer on the NV center's spin lifetime, and we quantify the nanodiamonds' chemical sensitivity to paramagnetic ions using T1 relaxometry. This general approach to nanodiamond surface functionalization will enable advances in quantum nanomedicine and biological sensing.
Xu, Jun; Zhao, Tianshuo; Zaccarin, Anne-Marie; Du, Xingyu; Yang, Shengsong; Ning, Yifan; Xiao, Qiwen; Kramadhati, Shobhita; Choi, Yun Chang; Murray, Christopher B.; III, Roy H. Olsson; Kagan, Cherie R.
Chemically Driven Sintering of Colloidal Cu Nanocrystals for Multiscale Electronic and Optical Devices Journal Article
In: ACS Nano, 2024.
@article{Xu2024,
title = {Chemically Driven Sintering of Colloidal Cu Nanocrystals for Multiscale Electronic and Optical Devices},
author = {Jun Xu and Tianshuo Zhao and Anne-Marie Zaccarin and Xingyu Du and Shengsong Yang and Yifan Ning and Qiwen Xiao and Shobhita Kramadhati and Yun Chang Choi and Christopher B. Murray and Roy H. Olsson III and Cherie R. Kagan},
url = {https://pubs-acs-org.proxy.library.upenn.edu/doi/10.1021/acsnano.4c02007},
year = {2024},
date = {2024-06-25},
urldate = {2024-06-25},
journal = {ACS Nano},
abstract = {Emerging applications of Internet of Things (IoT) technologies in smart health, home, and city, in agriculture and environmental monitoring, and in transportation and manufacturing require materials and devices with engineered physical properties that can be manufactured by low-cost and scalable methods, support flexible forms, and are biocompatible and biodegradable. Here, we report the fabrication and device integration of low-cost and biocompatible/biodegradable colloidal Cu nanocrystal (NC) films through room temperature, solution-based deposition, and sintering, achieved via chemical exchange of NC surface ligands. Treatment of organic-ligand capped Cu NC films with solutions of shorter, environmentally benign, and noncorrosive inorganic reagents, namely, SCN– and Cl–, effectively removes the organic ligands, drives NC grain growth, and limits film oxidation. We investigate the mechanism of this chemically driven sintering by systemically varying the Cu NC size, ligand reagent, and ligand treatment time and follow the evolution of their structure and electrical and optical properties. Cl–-treated, 4.5 nm diameter Cu NC films yield the lowest DC resistivity, only 3.2 times that of bulk Cu, and metal-like dielectric functions at optical frequencies. We exploit the high conductivity of these chemically sintered Cu NC films and, in combination with photo- and nanoimprint-lithography, pattern multiscale structures to achieve high-Q radio frequency (RF) capacitive sensors and near-infrared (NIR) resonant optical metasurfaces.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Emerging applications of Internet of Things (IoT) technologies in smart health, home, and city, in agriculture and environmental monitoring, and in transportation and manufacturing require materials and devices with engineered physical properties that can be manufactured by low-cost and scalable methods, support flexible forms, and are biocompatible and biodegradable. Here, we report the fabrication and device integration of low-cost and biocompatible/biodegradable colloidal Cu nanocrystal (NC) films through room temperature, solution-based deposition, and sintering, achieved via chemical exchange of NC surface ligands. Treatment of organic-ligand capped Cu NC films with solutions of shorter, environmentally benign, and noncorrosive inorganic reagents, namely, SCN– and Cl–, effectively removes the organic ligands, drives NC grain growth, and limits film oxidation. We investigate the mechanism of this chemically driven sintering by systemically varying the Cu NC size, ligand reagent, and ligand treatment time and follow the evolution of their structure and electrical and optical properties. Cl–-treated, 4.5 nm diameter Cu NC films yield the lowest DC resistivity, only 3.2 times that of bulk Cu, and metal-like dielectric functions at optical frequencies. We exploit the high conductivity of these chemically sintered Cu NC films and, in combination with photo- and nanoimprint-lithography, pattern multiscale structures to achieve high-Q radio frequency (RF) capacitive sensors and near-infrared (NIR) resonant optical metasurfaces.
Marino, Emanuele; Vo, Thi; Gonzalez, Cristian; Rosen, Daniel J.; Neuhaus, Steven J.; Sciortino, Alice; Bharti, Harshit; Keller, Austin W.; Kagan, Cherie R.; Cannas, Marco; Messina, Fabrizio; Glotzer, Sharon C.; Murray, Christopher B.
Porous Magneto-Fluorescent Superparticles by Rapid Emulsion Densification Journal Article
In: Chemistry of Materials, 2024.
@article{Marino2024,
title = {Porous Magneto-Fluorescent Superparticles by Rapid Emulsion Densification},
author = {Emanuele Marino and Thi Vo and Cristian Gonzalez and Daniel J. Rosen and Steven J. Neuhaus and Alice Sciortino and Harshit Bharti and Austin W. Keller and Cherie R. Kagan and Marco Cannas and Fabrizio Messina and Sharon C. Glotzer and Christopher B. Murray},
url = {https://pubs.acs.org/doi/full/10.1021/acs.chemmater.3c03209},
doi = {10.1021/acs.chemmater.3c03209},
year = {2024},
date = {2024-04-01},
urldate = {2024-04-01},
journal = {Chemistry of Materials},
abstract = {Porous superstructures are characterized by a large surface area and efficient molecular transport. Although methods aimed at generating porous superstructures from nanocrystals exist, current state-of-the-art strategies are limited to single-component nanocrystal dispersions. More importantly, such processes afford little control over the size and shape of the pores. Here, we present a new strategy for the nanofabrication of porous magneto-fluorescent nanocrystal superparticles that are well controlled in size and shape. We synthesize these composite superparticles by confining semiconductor and superparamagnetic nanocrystals within oil-in-water droplets generated using microfluidics. The rapid densification of these droplets yields spherical, monodisperse, and porous nanocrystal superparticles. Molecular simulations reveal that the formation of pores throughout the superparticles is linked to repulsion between nanocrystals of different compositions, leading to phase separation during self-assembly. We confirm the presence of nanocrystal phase separation at the single superparticle level by analyzing the changes in the optical and photonic properties of the superstructures as a function of nanocrystal composition. This excellent agreement between experiments and simulations allows us to develop a theory that predicts superparticle porosity from experimentally tunable physical parameters, such as nanocrystal size ratio, stoichiometry, and droplet densification rate. Our combined theoretical, computational, and experimental findings provide a blueprint for designing porous, multifunctional superparticles with immediate applications in catalytic, electrochemical, sensing, and cargo delivery applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Porous superstructures are characterized by a large surface area and efficient molecular transport. Although methods aimed at generating porous superstructures from nanocrystals exist, current state-of-the-art strategies are limited to single-component nanocrystal dispersions. More importantly, such processes afford little control over the size and shape of the pores. Here, we present a new strategy for the nanofabrication of porous magneto-fluorescent nanocrystal superparticles that are well controlled in size and shape. We synthesize these composite superparticles by confining semiconductor and superparamagnetic nanocrystals within oil-in-water droplets generated using microfluidics. The rapid densification of these droplets yields spherical, monodisperse, and porous nanocrystal superparticles. Molecular simulations reveal that the formation of pores throughout the superparticles is linked to repulsion between nanocrystals of different compositions, leading to phase separation during self-assembly. We confirm the presence of nanocrystal phase separation at the single superparticle level by analyzing the changes in the optical and photonic properties of the superstructures as a function of nanocrystal composition. This excellent agreement between experiments and simulations allows us to develop a theory that predicts superparticle porosity from experimentally tunable physical parameters, such as nanocrystal size ratio, stoichiometry, and droplet densification rate. Our combined theoretical, computational, and experimental findings provide a blueprint for designing porous, multifunctional superparticles with immediate applications in catalytic, electrochemical, sensing, and cargo delivery applications.
Lee, J; Zhao, T; Yang, S; Muduli, M; Murray, CB; Kagan, CR
One-pot heat-up synthesis of short-wavelength infrared, colloidal InAs quantum dots Journal Article
In: The Journal of Chemical Physics, vol. 160, pp. 071103, 2024.
@article{nokey,
title = {One-pot heat-up synthesis of short-wavelength infrared, colloidal InAs quantum dots},
author = {J Lee and T Zhao and S Yang and M Muduli and CB Murray and CR Kagan},
url = {https://pubs.aip.org/aip/jcp/article/160/7/071103/3266823},
doi = {10.1063/5.0187162},
year = {2024},
date = {2024-02-21},
urldate = {2024-02-21},
journal = {The Journal of Chemical Physics},
volume = {160},
pages = {071103},
abstract = {III–V colloidal quantum dots (QDs) promise Pb and Hg-free QD compositions with which to build short-wavelength infrared (SWIR) optoelectronic devices. However, their synthesis is limited by the availability of group-V precursors with controllable reactivities to prepare monodisperse, SWIR-absorbing III–V QDs. Here, we report a one-pot heat-up method to synthesize ∼8 nm edge length (∼6.5 nm in height) tetrahedral, SWIR-absorbing InAs QDs by increasing the [In3+]:[As3+] ratio introduced using commercially available InCl3 and AsCl3 precursors and by decreasing the concentration and optimizing the volume of the reducing reagent superhydride to control the concentration of In(0) and As(0) intermediates through QD nucleation and growth. InAs QDs are treated with NOBF4, and their deposited films are exchanged with Na2S to yield n-type InAs QD films. We realize the only colloidal InAs QD photoconductors with responsivity at the technologically important wavelength of 1.55 μm.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
III–V colloidal quantum dots (QDs) promise Pb and Hg-free QD compositions with which to build short-wavelength infrared (SWIR) optoelectronic devices. However, their synthesis is limited by the availability of group-V precursors with controllable reactivities to prepare monodisperse, SWIR-absorbing III–V QDs. Here, we report a one-pot heat-up method to synthesize ∼8 nm edge length (∼6.5 nm in height) tetrahedral, SWIR-absorbing InAs QDs by increasing the [In3+]:[As3+] ratio introduced using commercially available InCl3 and AsCl3 precursors and by decreasing the concentration and optimizing the volume of the reducing reagent superhydride to control the concentration of In(0) and As(0) intermediates through QD nucleation and growth. InAs QDs are treated with NOBF4, and their deposited films are exchanged with Na2S to yield n-type InAs QD films. We realize the only colloidal InAs QD photoconductors with responsivity at the technologically important wavelength of 1.55 μm.
Ning, Yifan; Yang, Shengsong; Yang, Dai-Bei; Cai, Yi-Yu; Xu, Jun; Li, Ruipeng; Zhang, Yugang; Kagan, Cherie R.; Saven, Jeffery G.; Murray, Christopher B.
Dynamic Nanocrystal Superlattices with Thermally Triggerable Lubricating Ligands Journal Article
In: Journal of the American Chemical Society, vol. 146, no. 6, pp. 3785-3795, 2024.
@article{Ning2024,
title = {Dynamic Nanocrystal Superlattices with Thermally Triggerable Lubricating Ligands},
author = {Yifan Ning and Shengsong Yang and Dai-Bei Yang and Yi-Yu Cai and Jun Xu and Ruipeng Li and Yugang Zhang and Cherie R. Kagan and Jeffery G. Saven and Christopher B. Murray},
url = {https://pubs-acs-org.proxy.library.upenn.edu/doi/full/10.1021/jacs.3c10706},
doi = {10.1021/jacs.3c10706},
year = {2024},
date = {2024-01-31},
urldate = {2024-01-31},
journal = {Journal of the American Chemical Society},
volume = {146},
number = {6},
pages = {3785-3795},
abstract = {The size-dependent and collective physical properties of nanocrystals (NCs) and their self-assembled superlattices (SLs) enable the study of mesoscale phenomena and the design of metamaterials for a broad range of applications. However, the limited mobility of NC building blocks in dried NCSLs often hampers the potential for employing postdeposition methods to produce high-quality NCSLs. In this study, we present tailored promesogenic ligands that exhibit a lubricating property akin to thermotropic liquid crystals. The lubricating ability of ligands is thermally triggerable, allowing the dry solid NC aggregates deposited on the substrates with poor ordering to be transformed into NCSLs with high crystallinity and preferred orientations. The interplay between the dynamic behavior of NCSLs and the molecular structure of the ligands is elucidated through a comprehensive analysis of their lubricating efficacy using both experimental and simulation approaches. Coarse-grained molecular dynamic modeling suggests that a shielding layer from mesogens prevents the interdigitation of ligand tails, facilitating the sliding between outer shells and consequently enhancing the mobility of NC building blocks. The dynamic organization of NCSLs can also be triggered with high spatial resolution by laser illumination. The principles, kinetics, and utility of lubricating ligands could be generalized to unlock stimuli-responsive metamaterials from NCSLs and contribute to the fabrication of NCSLs.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The size-dependent and collective physical properties of nanocrystals (NCs) and their self-assembled superlattices (SLs) enable the study of mesoscale phenomena and the design of metamaterials for a broad range of applications. However, the limited mobility of NC building blocks in dried NCSLs often hampers the potential for employing postdeposition methods to produce high-quality NCSLs. In this study, we present tailored promesogenic ligands that exhibit a lubricating property akin to thermotropic liquid crystals. The lubricating ability of ligands is thermally triggerable, allowing the dry solid NC aggregates deposited on the substrates with poor ordering to be transformed into NCSLs with high crystallinity and preferred orientations. The interplay between the dynamic behavior of NCSLs and the molecular structure of the ligands is elucidated through a comprehensive analysis of their lubricating efficacy using both experimental and simulation approaches. Coarse-grained molecular dynamic modeling suggests that a shielding layer from mesogens prevents the interdigitation of ligand tails, facilitating the sliding between outer shells and consequently enhancing the mobility of NC building blocks. The dynamic organization of NCSLs can also be triggered with high spatial resolution by laser illumination. The principles, kinetics, and utility of lubricating ligands could be generalized to unlock stimuli-responsive metamaterials from NCSLs and contribute to the fabrication of NCSLs.