@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 = {colloids, nanocrystal, quantum information science, surface modification},

pubstate = {published},

tppubtype = {article}

}

@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 = {colloids, nanocrystal, nanocrystal electronics, optical properties, quantum dots, semiconductors, spectroscopy, surface modification, synthesis, TEM, thin films, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Choi2023,

title = {Surface Engineering of Metal and Semiconductor Nanocrystal Assemblies and Their Optical and Electronic Devices},

author = {Yun Chang Choi and Jaeyoung Lee and Jonah J. Ng and Cherie R. Kagan},

url = {https://doi.org/10.1021/acs.accounts.3c00147},

doi = {10.1021/acs.accounts.3c00147},

year  = {2023},

date = {2023-06-21},

urldate = {2023-06-21},

journal = {Accounts of Chemical Research},

volume = {56},

number = {13},

pages = {1791–1802},

abstract = {Colloidal nanocrystals (NCs) are composed of inorganic cores and organic or inorganic ligand shells and serve as building blocks of NC assemblies. Metal and semiconductor NCs are well known for the size-dependent physical properties of their cores. The large NC surface-to-volume ratio and the space between NCs in assemblies places significant importance on the composition of the NC surface and ligand shell. Nonaqueous colloidal NC syntheses use relatively long organic ligands to control NC size and uniformity during growth and to prepare stable NC dispersions. However, these ligands create large interparticle distances that dilute the metal and semiconductor NC properties of their assemblies. In this Account, we describe postsynthesis chemical treatments to engineer the NC surface and design the optical and electronic properties of NC assemblies. In metal NC assemblies, compact ligand exchange reduces the interparticle distance and drives an insulator-to-metal transition tuning the dc resistivity over a 1010 range and the real part of the optical dielectric function from positive to negative across the visible-to-IR region. Juxtaposing NC and bulk metal thin films in bilayers allows the differential chemical and thermal addressability of the NC surface to be exploited in device fabrication. Ligand exchange and thermal annealing densifies the NC layer, creating interfacial misfit strain that triggers folding of the bilayers and is used to fabricate, with only one lithography step, large-area 3D chiral metamaterials. In semiconductor NC assemblies, chemical treatments such as ligand exchange, doping, and cation exchange control the interparticle distance and composition to add impurities, tailor stoichiometry, or make entirely new compounds. These treatments are employed in longer studied II–VI and IV–VI materials and are being developed as interest in III–V and I–III–VI2 NC materials grows. NC surface engineering is used to design NC assemblies with tailored carrier energy, type, concentration, mobility, and lifetime. Compact ligand exchange increases the coupling between NCs but can introduce intragap states that scatter and reduce the lifetime of carriers. Hybrid ligand exchange with two different chemistries can enhance the mobility-lifetime product. Doping increases carrier concentration, shifts the Fermi energy, and increases carrier mobility, creating n- and p-type building blocks for optoelectronic and electronic devices and circuits. Surface engineering of semiconductor NC assemblies is also important to modify device interfaces to allow the stacking and patterning of NC layers and to realize excellent device performance. It is used to construct NC-integrated circuits, exploiting the library of metal, semiconductor, and insulator NCs, to achieve all-NC, solution-fabricated transistors.},

keywords = {gold, ligand exchange, ligands, nanocrystal, nanoparticle assembly, Noble metal nanoparticles, optical metamaterials, optical properties, quantum dots, semiconductors, surface modification},

pubstate = {published},

tppubtype = {article}

}

@article{Ahn2021,

title = {Ink-Lithography for Property Engineering and Patterning of Nanocrystal Thin Films},

author = {Junhyuk Ahn and Sanghyun Jeon and Ho Kun Woo and Junsung Bang and Yong Min Lee and Steven J. Neuhaus and Woo Seok Lee and Taesung Park and Sang Yeop Lee and Byung Ku Jung and Hyungmok Joh and Mingi Seong and Ji-hyuk Choi and Ho Gyu Yoon and Cherie R. Kagan and Soong Ju Oh},

url = {https://pubs.acs.org/doi/abs/10.1021/acsnano.1c04772},

doi = {10.1021/acsnano.1c04772},

year  = {2021},

date = {2021-09-08},

urldate = {2021-09-08},

journal = {ACS Nano},

volume = {15},

issue = {10},

pages = {15667–15675},

abstract = {Next-generation devices and systems require the development and integration of advanced materials, the realization of which inevitably requires two separate processes: property engineering and patterning. Here, we report a one-step, ink-lithography technique to pattern and engineer the properties of thin films of colloidal nanocrystals that exploits their chemically addressable surface. Colloidal nanocrystals are deposited by solution-based methods to form thin films and a local chemical treatment is applied using an ink-printing technique to simultaneously modify (i) the chemical nature of the nanocrystal surface to allow thin-film patterning and (ii) the physical electronic, optical, thermal, and mechanical properties of the nanocrystal thin films. The ink-lithography technique is applied to the library of colloidal nanocrystals to engineer thin films of metals, semiconductors, and insulators on both rigid and flexible substrates and demonstrate their application in high-resolution image replications, anticounterfeit devices, multicolor filters, thin-film transistors and circuits, photoconductors, and wearable multisensors.},

keywords = {ink-lithography, ligand exchange, nanocrystal, nanocrystal ink-lithography ligand exchange surface modification patterning property engineering, patterning, property engineering, surface modification},

pubstate = {published},

tppubtype = {article}

}

@article{Goodwin2016,

title = {The effects of inorganic surface treatments on photogenerated carrier mobility and lifetime in PbSe quantum dot thin films},

author = {E.D. Goodwin and Daniel B. Straus and E. Ashley Gaulding and Christopher B. Murray and Cherie R. Kagan},

url = {https://www.sciencedirect.com/science/article/abs/pii/S0301010415002220},

doi = {10.1016/j.chemphys.2015.07.031},

year  = {2016},

date = {2016-06-01},

journal = {Chemical Physics },

volume = {471},

pages = {81-88},

abstract = {We used flash-photolysis, time-resolved microwave conductivity (TRMC) to probe the carrier mobility and lifetime in PbSe quantum dot (QD) thin films treated with solutions of the metal salts of Na2Se and PbCl2. The metal salt treatments tuned the Pb:Se stoichiometry and swept the Fermi energy throughout the QD thin film bandgap. A stoichiometric imbalance favoring excess Se heavily p-doped the QD thin film, shifted the Fermi energy toward the valence band, and yielded the highest TRMC mobility and lifetime. Introducing Pb first compensated the p-doping and shifted the Fermi level through mid-gap, decreasing the TRMC mobility. Further Pb addition created an excess of Pb, n-doped the QD thin film, moved the Fermi level to near the conduction band, and again increased the TRMC mobility. The increase in TRMC mobility as the Fermi energy was shifted toward the band edges by non-stoichiometry is consistent with the QD thin film density of states.},

keywords = {mobility, PbSe, quantum dots, surface modification, thin films, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Goodwin2014,

title = {Effects of Post-Synthesis Processing on CdSe Nanocrystals and Their Solids: Correlation between Surface Chemistry and Optoelectronic Properties},

author = {E. D. Goodwin and Benjamin T. Diroll and Soong Ju Oh and Taejong Paik and Christopher B. Murray and Cherie R. Kagan},

url = {https://pubs.acs.org/doi/full/10.1021/jp5076912},

doi = {10.1021/jp5076912},

year  = {2014},

date = {2014-10-21},

urldate = {2014-10-21},

journal = {The Journal of Physical Chemistry C},

volume = {118},

number = {46},

pages = {27097–27105},

abstract = {In this work, we report the effects on CdSe nanocrystal (NC) surface chemistry of acetone and methanol when used as the antisolvents for NC washing and as the solvents for ligand exchange of NC solids with ammonium thiocyanate (NH4SCN). We find that NCs washed with methanol have significantly fewer remaining organic ligands and lower photoluminescence quantum yield than those washed with acetone. When used as the ligand exchange solvent, methanol leaves more organic ligands and introduces fewer bound thiocyanates on the NC surface than when acetone is used. We demonstrate the effect of these different surface chemistries on NC solid optoelectronic properties through photoconductivity measurements, showing a greater photocurrent in NC solids with greater organic ligand coverage. We also show that NC washing with methanol or ligand exchange with NH4SCN in methanol removes a significant number of surface Cd atoms from the NCs, creating Cd vacancies that act as traps for recombination. Independent of the wash and exchange process, the NC surface may be repaired by introducing CdCl2 to the NC surface, enhancing the measured photocurrent.},

keywords = {CdSe, nanocrystal, nanocrystal electronics, optical properties, optical stability, semiconductors, surface modification, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Oh2014,

title = {Engineering Charge Injection and Charge Transport for High Performance PbSe Nanocrystal Thin Film Devices and Circuits},

author = {Soong Ju Oh and Zhuqing Wang and Nathaniel E. Berry and Ji-Hyuk Choi and Tianshuo Zhao and E. Ashley Gaulding and Taejong Paik and Yuming Lai and Christopher B. Murray and Cherie R. Kagan},

url = {https://pubs.acs.org/doi/full/10.1021/nl502491d},

doi = {10.1021/nl502491d},

year  = {2014},

date = {2014-10-09},

journal = {Nano Letters},

volume = {14},

number = {11},

pages = {6210–6216},

abstract = {We study charge injection and transport in PbSe nanocrystal thin films. By engineering the contact metallurgy and nanocrystal ligand exchange chemistry and surface passivation, we demonstrate partial Fermi-level pinning at the metal–nanocrystal interface and an insulator-to-metal transition with increased coupling and doping, allowing us to design high conductivity and mobility PbSe nanocrystal films. We construct complementary nanocrystal circuits from n-type and p-type transistors realized from a single nanocrystal material by selecting the contact metallurgy.},

keywords = {doping, interfaces, ligand exchange, mobility, nanocrystal, nanocrystal electronics, PbSe, surface interactions, surface modification, thin films, transistors, transport},

pubstate = {published},

tppubtype = {article}

}

@article{Lai2014,

title = {Low-Frequency (1/f) Noise in Nanocrystal Field-Effect Transistors},

author = {Yuming Lai and Haipeng Li and David K. Kim and Benjamin T. Diroll and Christopher B. Murray and Cherie R. Kagan},

url = {https://pubs.acs.org/doi/full/10.1021/nn504303b},

doi = {10.1021/nn504303b},

year  = {2014},

date = {2014-09-07},

journal = {ACS NAno},

volume = {8},

number = {9},

pages = {9664–9672},

abstract = {We investigate the origins and magnitude of low-frequency noise in high-mobility nanocrystal field-effect transistors and show the noise is of 1/f-type. Sub-band gap states, in particular, those introduced by nanocrystal surfaces, have a significant influence on the 1/f noise. By engineering the device geometry and passivating nanocrystal surfaces, we show that in the linear and saturation regimes the 1/f noise obeys Hooge’s model of mobility fluctuations, consistent with transport of a high density of accumulated carriers in extended electronic states of the NC thin films. In the subthreshold regime, the Fermi energy moves deeper into the mobility gap and sub-band gap trap states give rise to a transition to noise dominated by carrier number fluctuations as described in McWhorter’s model. CdSe nanocrystal field-effect transistors have a Hooge parameter of 3 × 10–2, comparable to other solution-deposited, thin-film devices, promising high-performance, low-cost, low-noise integrated circuitry.},

keywords = {CdSe, defects, mobility, nanocrystal, nanocrystal electronics, surface interactions, surface modification, transistors},

pubstate = {published},

tppubtype = {article}

}