Cherie R Kagan Research Group

@article{Zhao2022,

title = {Engineering the Surface Chemistry of Colloidal InP Quantum Dots for Charge Transport},

author = {Tianshuo Zhao and Qinghua Zhao and Jaeyoung Lee and Shengsong Yang and Han Wang and Ming-Yuan Chuang and Yulian He and Sarah M. Thompson and Guannan Liu and Nuri Oh and Christopher B. Murray and Cherie R. Kagan},

url = {https://pubs.acs.org/doi/full/10.1021/acs.chemmater.2c01840},

doi = {10.1021/acs.chemmater.2c01840},

year  = {2022},

date = {2022-09-07},

urldate = {2022-09-07},

journal = {Chemistry of Materials},

abstract = {Colloidal InP quantum dots (QDs) have emerged as potential candidates for constructing nontoxic QD-based optoelectronic devices. However, charge transport in InP QD thin-film assemblies has been limitedly explored. Herein, we report the synthesis of ∼8 nm edge length (∼6.5 nm in height), tetrahedral InP QDs and study charge transport in thin films using the platform of the field-effect transistor (FET). We design a hybrid ligand-exchange strategy that combines solution-based exchange with S2– and solid-state exchange with N3– to enhance interdot coupling and control the n-doping of InP QD films. Further modifying the QD surface with thin, thermally evaporated Se overlayers yields FETs with an average electron mobility of 0.45 cm2 V–1 s–1, ∼10 times that of previously reported devices, and a higher on–off current ratio of 103–104. Analytical measurements suggest lower trap-state densities and longer carrier lifetimes in the Se-modified InP QD films, giving rise to a four-time longer carrier diffusion length.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gabinet2022,

title = {Magnetic Field Alignment and Optical Anisotropy of MoS2 Nanosheets Dispersed in a Liquid Crystal Polymer},

author = {Uri R. Gabinet and Changyeon Lee and Na Kyung Kim and Martin Hulman and Sarah M. Thompson and Cherie R. Kagan and Chinedum O. Osuji},

url = {https://pubs.acs.org/doi/full/10.1021/acs.jpclett.2c01819},

doi = {10.1021/acs.jpclett.2c01819},

year  = {2022},

date = {2022-08-19},

urldate = {2022-08-19},

journal = {The Journal of Physical Chemistry Letters},

volume = {13},

issue = {34},

pages = {7994–8001},

abstract = {Molybdenum disulfide (MoS2) nanosheets exhibit anisotropic optical and electronic properties, stemming from their shape and electronic structure. Unveiling this anisotropy for study and usage in materials and devices requires the ability to control the orientation of dispersed nanosheets, but to date this has proved a challenging proposition. Here, we demonstrate magnetic field driven alignment of MoS2 nanosheets in a liquid crystal (LC) polymer and unveil the optical properties of the resulting anisotropic assembly. Nanosheet optical anisotropy is observed spectroscopically by Raman and direction-dependent photoluminescence (PL) measurements. Resulting data indicate significantly lower PL emission due to optical excitation with electric field oscillation out of plane, parallel to the MoS2c-axis, than that associated with perpendicular excitation, with the dichroic ratio Iperp/Ipar = 3. The approach developed here provides a useful route to elucidate anisotropic optical properties of MoS2 nanosheets and to utilize such properties in new materials and devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Marino2022,

title = {Nanocrystal Superparticles with Whispering-Gallery Modes Tunable through Chemical and Optical Triggers},

author = {Emanuele Marino and Harshit Bharti and Jun Xu and Cherie R. Kagan and Christopher B. Murray},

url = {https://pubs.acs.org/doi/full/10.1021/acs.nanolett.2c01011},

doi = {10.1021/acs.nanolett.2c01011},

year  = {2022},

date = {2022-06-01},

journal = {Nano Letters},

volume = {22},

issue = {12},

pages = {4765–4773},

abstract = {Whispering-gallery microresonators have the potential to become the building blocks for optical circuits. However, encoding information in an optical signal requires on-demand tuning of optical resonances. Tuning is achieved by modifying the cavity length or the refractive index of the microresonator. Due to their solid, nondeformable structure, conventional microresonators based on bulk materials are inherently difficult to tune. In this work, we fabricate irreversibly tunable optical microresonators by using semiconductor nanocrystals. These nanocrystals are first assembled into colloidal spherical superparticles featuring whispering-gallery modes. Exposing the superparticles to shorter ligands changes the nanocrystal surface chemistry, decreasing the cavity length of the microresonator by 20% and increasing the refractive index by 8.2%. Illuminating the superparticles with ultraviolet light initiates nanocrystal photo-oxidation, providing an orthogonal channel to decrease the refractive index of the microresonator in a continuous fashion. Through these approaches, we demonstrate optical microresonators tunable by several times their free spectral range.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Electrochemically deposited molybdenum disulfide surfaces enable polymer adsorption studies using quartz crystal microbalance with dissipation monitoring (QCM-D)},

author = {Christopher S. O'Bryan and Joseph Rosenfeld and Aria Zhang and Austin W. Keller and Denis Bendejacq and Cherie R. Kagan and Christopher B. Murray and Daeyeon Lee and Russell J. Composto},

url = {https://www.sciencedirect.com/science/article/pii/S0021979722001114},

doi = {10.1016/j.jcis.2022.01.098},

year  = {2022},

date = {2022-05-15},

urldate = {2022-05-15},

journal = {Journal of Colloid and Interface Science},

volume = {614},

pages = {522-531},

abstract = {Polymer and small molecules are often used to modify the wettability of mineral surfaces which facilitates the separation of valuable minerals such as molybdenum disulfide (MoS2) from gangue material through the process of froth flotation. By design, traditional methods used in the field for evaluating the separation efficacy of these additives fail to give proper access to adsorption kinetics and molecule conformation, crucial aspects of flotation where contact times may not allow for full thermodynamic equilibrium. Thus, there is a need for alternative methods for evaluating additives that accurately capture these features during the adsorption of additives at the solid/liquid interface. Here, we present a novel method for preparing MoS2 films on quartz crystals used for Quartz Crystal Microbalance with Dissipation (QCM-D) measurements through an electrochemical deposition process. The resulting films exhibit well-controlled structure, composition, and thickness and therefore are ideal for quantifying polymer adsorption. After deposition, the sensors can be annealed without damaging the quartz crystal, resulting in a phase transition of the MoS2 from the as-deposited, amorphous phase to the 2H semiconducting phase. Furthermore, we demonstrate the application of these sensors to study the interactions of additives at the solid/liquid interface by investigating the adsorption of a model polymer, dextran, onto both the amorphous and crystalline MoS2 surfaces. We find that the adsorption rate of dextran onto the amorphous surface is approximately twice as fast as the adsorption onto the annealed surface. These studies demonstrate the ability to gain insight into the short-term kinetics of interaction between molecules and mineral surface, behavior that is key to designing additives with superior separation efficiency.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kim2022,

title = {Dynamic magnetic field alignment and polarized emission of semiconductor nanoplatelets in a liquid crystal polymer},

author = {Dahin Kim and Dennis Ndaya and Reuben Bosire and Francis K. Masese and Weixingyue Li and Sarah M. Thompson and Cherie R. Kagan and Christopher B. Murray and Rajeswari M. Kasi and Chinedum O. Osuji},

url = {https://www.nature.com/articles/s41467-022-30200-2},

doi = {10.1038/s41467-022-30200-2},

year  = {2022},

date = {2022-05-06},

urldate = {2022-05-06},

journal = {Nature Communications},

volume = {13},

number = {2507 },

abstract = {Reconfigurable arrays of 2D nanomaterials are essential for the realization of switchable and intelligent material systems. Using liquid crystals (LCs) as a medium represents a promising approach, in principle, to enable such control. In practice, however, this approach is hampered by the difficulty of achieving stable dispersions of nanomaterials. Here, we report on good dispersions of pristine CdSe nanoplatelets (NPLs) in LCs, and reversible, rapid control of their alignment and associated anisotropic photoluminescence, using a magnetic field. We reveal that dispersion stability is greatly enhanced using polymeric, rather than small molecule, LCs and is considerably greater in the smectic phases of the resulting systems relative to the nematic phases. Aligned composites exhibit highly polarized emission that is readily manipulated by field-realignment. Such dynamic alignment of optically-active 2D nanomaterials may enable the development of programmable materials for photonic applications and the methodology can guide designs for anisotropic nanomaterial composites for a broad set of related nanomaterials.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}