1
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Bhar M, Rudra S, Bhunia N, Mukherjee S, Banerjee A, Mukherjee P. Remarkable Difference in Pre-Cation Exchange Reactions of Inorganic Nanoparticles in Cases with Eventual Complete Exchange. NEW J CHEM 2022. [DOI: 10.1039/d2nj03442e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Postsynthetic modification of inorganic nanoparticles (NPs) involving appropriate cation pairs at or near ambient conditions can exchange their spatial positions. The characterization of final products from these reactions although attracted...
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2
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Ming SK, Taylor RA, McNaughter PD, Lewis DJ, O’Brien P. Tunable structural and optical properties of Ag xCu yInS 2 colloidal quantum dots. NEW J CHEM 2022. [DOI: 10.1039/d2nj03169h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Herein is discussed tunable absorption and emission properties of AgxCuyInS2 quantum dots involving wurtzite to chalcopyrite phase transformation dependent on Ag+ dopant content.
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Affiliation(s)
- Shanna-Kay Ming
- Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago
| | - Richard A. Taylor
- Department of Chemistry, The University of the West Indies, St. Augustine, Trinidad and Tobago
| | - Paul D. McNaughter
- Department of Chemistry, University of Manchester, Manchester M13 9PL, UK
| | - David J. Lewis
- Department of Materials, University of Manchester, Manchester M13 9PL, UK
| | - Paul O’Brien
- Department of Chemistry, University of Manchester, Manchester M13 9PL, UK
- Department of Materials, University of Manchester, Manchester M13 9PL, UK
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3
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Kamath A, Melnychuk C, Guyot-Sionnest P. Toward Bright Mid-Infrared Emitters: Thick-Shell n-Type HgSe/CdS Nanocrystals. J Am Chem Soc 2021; 143:19567-19575. [PMID: 34752062 PMCID: PMC8630792 DOI: 10.1021/jacs.1c09858] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A procedure is developed for the growth of thick, conformal CdS shells that preserve the optical properties of 5 nm HgSe cores. The n-doping of the HgSe/CdS core/shell particles is quantitatively tuned through a simple postsynthetic Cd treatment, while the doping is monitored via the intraband optical absorption at 5 μm wavelength. Photoluminescence lifetime and quantum yield measurements show that the CdS shell greatly increases the intraband emission intensity. This indicates that decoupling the excitation from the environment reduces the nonradiative recombination. We find that weakly n-type HgSe/CdS are the brightest solution-phase mid-infrared chromophores reported to date at room temperature, achieving intraband photoluminescence quantum yields of 2%. Such photoluminescence corresponds to intraband lifetimes in excess of 10 ns, raising important questions about the fundamental limits to achievable slow intraband relaxation in quantum dots.
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Affiliation(s)
- Ananth Kamath
- Department of Chemistry and the James Franck Institute, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
| | - Christopher Melnychuk
- Department of Chemistry and the James Franck Institute, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
| | - Philippe Guyot-Sionnest
- Department of Chemistry and the James Franck Institute, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, United States
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4
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Carulli F, Pinchetti V, Zaffalon ML, Camellini A, Rotta Loria S, Moro F, Fanciulli M, Zavelani-Rossi M, Meinardi F, Crooker SA, Brovelli S. Optical and Magneto-Optical Properties of Donor-Bound Excitons in Vacancy-Engineered Colloidal Nanocrystals. NANO LETTERS 2021; 21:6211-6219. [PMID: 34260252 PMCID: PMC8397387 DOI: 10.1021/acs.nanolett.1c01818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/30/2021] [Indexed: 06/13/2023]
Abstract
Controlled insertion of electronic states within the band gap of semiconductor nanocrystals (NCs) is a powerful tool for tuning their physical properties. One compelling example is II-VI NCs incorporating heterovalent coinage metals in which hole capture produces acceptor-bound excitons. To date, the opposite donor-bound exciton scheme has not been realized because of the unavailability of suitable donor dopants. Here, we produce a model system for donor-bound excitons in CdSeS NCs engineered with sulfur vacancies (VS) that introduce a donor state below the conduction band (CB), resulting in long-lived intragap luminescence. VS-localized electrons are almost unaffected by trapping, and suppression of thermal quenching boosts the emission efficiency to 85%. Magneto-optical measurements indicate that the VS are not magnetically coupled to the NC bands and that the polarization properties are determined by the spin of the valence-band photohole, whose spin flip is massively slowed down due to suppressed exchange interaction with the donor-localized electron.
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Affiliation(s)
- Francesco Carulli
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via Cozzi 55, IT-20125 Milano, Italy
| | - Valerio Pinchetti
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via Cozzi 55, IT-20125 Milano, Italy
| | - Matteo L. Zaffalon
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via Cozzi 55, IT-20125 Milano, Italy
| | - Andrea Camellini
- Dipartimento
di Energia, Politecnico di Milano, IT-20133 Milano, Italy
| | | | - Fabrizio Moro
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via Cozzi 55, IT-20125 Milano, Italy
| | - Marco Fanciulli
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via Cozzi 55, IT-20125 Milano, Italy
| | | | - Francesco Meinardi
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via Cozzi 55, IT-20125 Milano, Italy
| | - Scott A. Crooker
- National
High Magnetic Field Laboratory, Los Alamos
National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Sergio Brovelli
- Dipartimento
di Scienza dei Materiali, Università
degli Studi di Milano-Bicocca, via Cozzi 55, IT-20125 Milano, Italy
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5
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Zhao Q, Gouget G, Guo J, Yang S, Zhao T, Straus DB, Qian C, Oh N, Wang H, Murray CB, Kagan CR. Enhanced Carrier Transport in Strongly Coupled, Epitaxially Fused CdSe Nanocrystal Solids. NANO LETTERS 2021; 21:3318-3324. [PMID: 33792310 DOI: 10.1021/acs.nanolett.1c00860] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Strongly coupled, epitaxially fused colloidal nanocrystal (NC) solids are promising solution-processable semiconductors to realize optoelectronic devices with high carrier mobilities. Here, we demonstrate sequential, solid-state cation exchange reactions to transform epitaxially connected PbSe NC thin films into Cu2Se nanostructured thin-film intermediates and then successfully to achieve zinc-blende, CdSe NC solids with wide epitaxial necking along {100} facets. Transient photoconductivity measurements probe carrier transport at nanometer length scales and show a photoconductance of 0.28(1) cm2 V-1 s-1, the highest among CdSe NC solids reported. Atomic-layer deposition of a thin Al2O3 layer infiltrates and protects the structure from fusing into a polycrystalline thin film during annealing and further improves the photoconductance to 1.71(5) cm2 V-1 s-1 and the diffusion length to 760 nm. We fabricate field-effect transistors to study carrier transport at micron length scales and realize high electron mobilities of 35(3) cm2 V-1 s-1 with on-off ratios of 106 after doping.
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6
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Zhao FA, Xiao HY, Bai XM, Zu XT. Effects of Ag doping on the electronic and optical properties of CdSe quantum dots. Phys Chem Chem Phys 2019; 21:16108-16119. [PMID: 31290876 DOI: 10.1039/c9cp02433f] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Cadmium selenide (CdSe) nanocrystals are important photoelectric materials. Doping heterovalent impurities such as silver (Ag) in CdSe nanocrystal quantum dots (QDs) can provide additional charge carriers, which can significantly enhance the performance of CdSe QDs for their potential applications in high-efficiency photovoltaic devices. Using density functional theory (DFT) based calculations with the Heyd-Scuseria-Ernzerhof (HSE06) screened hybrid functional, we demonstrate that Ag doping can affect the structural, electronic and optical properties of CdSe QDs significantly. The location and number of Ag dopant atoms are critical factors for modifying the electronic structure, in particular the change of energy position and shape of the valence and conduction band edges. It is found that doping of Ag atoms into the core region of a CdSe nanoparticle induces metallic-like electronic characteristics with a dense number of electrons emerging at the Fermi level. However, incorporation of Ag dopant into the surface of a CdSe quantum dot introduces some mid-gap states that mainly consist of Se 4p states, and results in a new sub-bandgap electronic transition from mid-gap states to the conduction band. The calculated absorption spectra indicate that doping of just one or two Ag atoms greatly strengthens the absorption in the ultraviolet-visible regime and extends the absorption edges of CdSe QDs into the infrared regime. In particular, the spectra show a high-intensity absorption band between 424 and 600 nm with just 1 Ag atom incorporated into the CdSe QDs. Based on the improved absorption spectra, the present results provide a science-based strategy for designing Ag-doped CdSe QDs with enhanced visible light absorption for their application in high-efficiency photovoltaic devices.
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Affiliation(s)
- F A Zhao
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China. and Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
| | - H Y Xiao
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China.
| | - X M Bai
- Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
| | - X T Zu
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, China.
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7
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Capitani C, Pinchetti V, Gariano G, Santiago-González B, Santambrogio C, Campione M, Prato M, Brescia R, Camellini A, Bellato F, Carulli F, Anand A, Zavelani-Rossi M, Meinardi F, Crooker SA, Brovelli S. Quantized Electronic Doping towards Atomically Controlled "Charge-Engineered" Semiconductor Nanocrystals. NANO LETTERS 2019; 19:1307-1317. [PMID: 30663314 DOI: 10.1021/acs.nanolett.8b04904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
"Charge engineering" of semiconductor nanocrystals (NCs) through so-called electronic impurity doping is a long-standing challenge in colloidal chemistry and holds promise for ground-breaking advancements in many optoelectronic, photonic, and spin-based nanotechnologies. To date, our knowledge is limited to a few paradigmatic studies on a small number of model compounds and doping conditions, with important electronic dopants still unexplored in nanoscale systems. Equally importantly, fine-tuning of charge engineered NCs is hampered by the statistical limitations of traditional approaches. The resulting intrinsic doping inhomogeneity restricts fundamental studies to statistically averaged behaviors and complicates the realization of advanced device concepts based on their advantageous functionalities. Here we aim to address these issues by realizing the first example of II-VI NCs electronically doped with an exact number of heterovalent gold atoms, a known p-type acceptor impurity in bulk chalcogenides. Single-dopant accuracy across entire NC ensembles is obtained through a novel non-injection synthesis employing ligand-exchanged gold clusters as "quantized" dopant sources to seed the nucleation of CdSe NCs in organic media. Structural, spectroscopic, and magneto-optical investigations trace a comprehensive picture of the physical processes resulting from the exact doping level of the NCs. Gold atoms, doped here for the first time into II-VI NCs, are found to incorporate as nonmagnetic Au+ species activating intense size-tunable intragap photoluminescence and artificially offsetting the hole occupancy of valence band states. Fundamentally, the transient conversion of Au+ to paramagnetic Au2+ (5d9 configuration) under optical excitation results in strong photoinduced magnetism and diluted magnetic semiconductor behavior revealing the contribution of individual paramagnetic impurities to the macroscopic magnetism of the NCs. Altogether, our results demonstrate a new chemical approach toward NCs with physical functionalities tailored to the single impurity level and offer a versatile platform for future investigations and device exploitation of individual and collective impurity processes in quantum confined structures.
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Affiliation(s)
- Chiara Capitani
- Glass to Power SpA, Via Fortunato Zeni 8 , I-38068 Rovereto, , Italy
| | | | - Graziella Gariano
- Glass to Power SpA, Via Fortunato Zeni 8 , I-38068 Rovereto, , Italy
| | - Beatriz Santiago-González
- International Iberian Nanotechnology Laboratory, Nanophotonics Department , Ultrafast Bio- and Nanophotonics Group , Avenida Mestre José Veiga s/n , 4715-330 Braga , Portugal
| | - Carlo Santambrogio
- Dipartimento di Biotecnologie e Bioscienze , Università degli Studi di Milano-Bicocca , Piazza della Scienza 2 , I-20126 Milano , Italy
| | | | - Mirko Prato
- Istituto Italiano di Tecnologia , Via Morego 30 , 16163 Genova , Italy
| | - Rosaria Brescia
- Istituto Italiano di Tecnologia , Via Morego 30 , 16163 Genova , Italy
| | - Andrea Camellini
- Dipartimento di Energia , Politecnico di Milano and IFN-CNR , Milano , Italy
| | | | | | | | | | | | - Scott A Crooker
- National High Magnetic Field Laboratory , Los Alamos National Laboratory , Los Alamos , New Mexico 87545 , United States
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8
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Lu H, Carroll GM, Chen X, Amarasinghe DK, Neale NR, Miller EM, Sercel PC, Rabuffetti FA, Efros AL, Beard MC. n-Type PbSe Quantum Dots via Post-Synthetic Indium Doping. J Am Chem Soc 2018; 140:13753-13763. [DOI: 10.1021/jacs.8b07910] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Haipeng Lu
- Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Gerard M. Carroll
- Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Xihan Chen
- Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Dinesh K. Amarasinghe
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Nathan R. Neale
- Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Elisa M. Miller
- Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Peter C. Sercel
- T. J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, United States
| | | | - Alexander L. Efros
- Center for Computational Materials Science, Naval Research Laboratory, Washington, District of Columbia 20375, United States
| | - Matthew C. Beard
- Chemistry & Nanoscience Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
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9
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Rudra S, Debnath GH, Mukherjee P. Role of reactant concentration and identity of added cation in controlling emission from post-synthetically modified terbium incorporated zinc sulfide nanoparticles: an avenue for the detection of lead(ii) cations. RSC Adv 2018; 8:18093-18108. [PMID: 35542071 PMCID: PMC9080542 DOI: 10.1039/c8ra02403k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 04/28/2018] [Indexed: 01/20/2023] Open
Abstract
This work reports the photophysical properties of 1-thioglycerol capped hydrophilic terbium cation incorporated (doped) zinc sulfide [Zn(Tb)S] nanoparticles, which have been post-synthetically modified using Pb2+ [Zn(Tb)S/Pb] under ambient conditions with [Zn(Tb)S] : [Pb2+] = 1 : 10−5–1 : 10, essentially providing a scenario with low to heavy co-doping and ultimately the possibility of forming a material of different chemical identity. The effects of selected concentrations of [Zn(Tb)S] : [Mn+] = 1 : 1 and 1 : 10−2 have also been evaluated for the post-synthetic addition of Hg2+, Cd2+, Ca2+, Mg2+, Na+ and K+. The broad zinc sulfide nanoparticle and sharp Tb3+ emission have different dependence on the relative reactant concentration, with cation identity playing a significant role. The underlying photophysical processes have been rationalized based on the interplay among the (i) cation exchange, (ii) modification of the structural properties of the nanoparticles without necessarily exchanging the cations and (iii) emission enhancement of terbium dopants. In cases where Tb3+ emission is apparent, all the nanoparticles studied demonstrate an optical antenna effect, thus accessing a lower Tb3+ concentration regime compared to in bulk environments. The results presented provide an avenue for the detection of heavy metal ions in general and Pb2+ in particular, with a limit of detection that is at least in the range of sub-ppm, using either the broad ZnS or sharp Tb3+ emission, respectively. This strategy provides an avenue to combine (i) the extremely sensitive and easily accessible analytical technique of photoluminescence spectroscopy, (ii) post-synthetic modification reactions in semiconductor nanoparticles that can be performed with less experimental demand, (iii) time-gated measurement related to the longer luminescence lifetime of terbium cations and (iv) the simultaneous use of broad ZnS nanoparticle and sharp Tb3+ emission from the same assembly, helping eliminate false positive results. Reactant concentration and the identity of the added cation control the emission in post-synthetically modified terbium incorporated zinc sulfide nanoparticles.![]()
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Affiliation(s)
- Saoni Rudra
- Centre for Research in Nanoscience and Nanotechnology
- University of Calcutta
- Kolkata-700106
- India
| | - Gouranga H. Debnath
- Centre for Research in Nanoscience and Nanotechnology
- University of Calcutta
- Kolkata-700106
- India
| | - Prasun Mukherjee
- Centre for Research in Nanoscience and Nanotechnology
- University of Calcutta
- Kolkata-700106
- India
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10
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Kortshagen UR, Sankaran RM, Pereira RN, Girshick SL, Wu JJ, Aydil ES. Nonthermal Plasma Synthesis of Nanocrystals: Fundamental Principles, Materials, and Applications. Chem Rev 2016; 116:11061-127. [DOI: 10.1021/acs.chemrev.6b00039] [Citation(s) in RCA: 248] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Uwe R. Kortshagen
- Department
of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - R. Mohan Sankaran
- Department
of Chemical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Rui N. Pereira
- Department
of Physics and I3N, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
- Walter
Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany
| | - Steven L. Girshick
- Department
of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jeslin J. Wu
- Department
of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Eray S. Aydil
- Department
of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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11
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Stavrinadis A, Konstantatos G. Strategies for the Controlled Electronic Doping of Colloidal Quantum Dot Solids. Chemphyschem 2016; 17:632-44. [DOI: 10.1002/cphc.201500834] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Alexandros Stavrinadis
- ICFO-Institut de Ciencies Fotoniques; The Barcelona Institute of Science and Technology; 08860 Castelldefels Barcelona Spain
| | - Gerasimos Konstantatos
- ICFO-Institut de Ciencies Fotoniques; The Barcelona Institute of Science and Technology; 08860 Castelldefels Barcelona Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010; Barcelona Spain
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12
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Synthesis and optical properties of oleic-capped CdSe quantum dots doped with silver and indium. MENDELEEV COMMUNICATIONS 2015. [DOI: 10.1016/j.mencom.2015.09.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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13
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Gresback R, Kramer NJ, Ding Y, Chen T, Kortshagen UR, Nozaki T. Controlled doping of silicon nanocrystals investigated by solution-processed field effect transistors. ACS NANO 2014; 8:5650-5656. [PMID: 24832958 DOI: 10.1021/nn500182b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The doping of semiconductor nanocrystals (NCs), which is vital for the optimization of NC-based devices, remains a significant challenge. While gas-phase plasma approaches have been successful in incorporating dopant atoms into NCs, little is known about their electronic activation. Here, we investigate the electronic properties of doped silicon NC thin films cast from solution by field effect transistor analysis. We find that, analogous to bulk silicon, boron and phosphorus electronically dope Si NC thin films; however, the dopant activation efficiency is only ∼10(-2)-10(-4). We also show that surface doping of Si NCs is an effective way to alter the carrier concentrations in Si NC films.
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Affiliation(s)
- Ryan Gresback
- Department of Mechanical Science and Engineering, Graduate School of Science and Engineering, Tokyo Institute of Technology , 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
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14
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Wolf O, Dasog M, Yang Z, Balberg I, Veinot JGC, Millo O. Doping and quantum confinement effects in single Si nanocrystals observed by scanning tunneling spectroscopy. NANO LETTERS 2013; 13:2516-2521. [PMID: 23662693 DOI: 10.1021/nl400570p] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We have applied scanning tunneling spectroscopy in studies of the electronic level structure of surface-functionalized colloidal Si nanocrystals (Si-NCs) as a function of their size for various capping ligands. The energy gaps extracted from the tunneling spectra increase with decreasing NC size, manifesting the effect of quantum confinement. This is consistent with the blueshift revealed by photoluminescence (PL) from dodecene functionalized Si-NCs. The tunneling spectra measured on NCs functionalized with NH4Br or allylamine show band-edge shifts toward higher energies, akin to p-type doping. This behavior can be accounted for by the combined contributions of the ligands' dipole moments and charge transfer between a Si-NC and its surface groups. Concomitantly, size-independent PL spectra, which cannot be associated with NC band gap variations, were observed for the latter Si-NCs.
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Affiliation(s)
- O Wolf
- Racah Institute of Physics and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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15
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Kang MS, Sahu A, Frisbie CD, Norris DJ. Influence of silver doping on electron transport in thin films of PbSe nanocrystals. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2013; 25:725-731. [PMID: 23161581 DOI: 10.1002/adma.201203114] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 10/19/2012] [Indexed: 06/01/2023]
Abstract
Field-effect transistors are fabricated from thin films of Ag-doped PbSe nanocrystals to analyze the influence of electronically active impurities on electrical transport in this important material for nanocrystal applications. Data is collected as a function of nanocrystal size, dopant concentration, and temperature. Changes in the Fermi level and transport parameters indicate that Ag is acting as a p-type dopant (acceptor).
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Affiliation(s)
- Moon Sung Kang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, 55455, USA
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16
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Rivest JB, Jain PK. Cation exchange on the nanoscale: an emerging technique for new material synthesis, device fabrication, and chemical sensing. Chem Soc Rev 2012; 42:89-96. [PMID: 22968228 DOI: 10.1039/c2cs35241a] [Citation(s) in RCA: 270] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cation exchange is an age-old technique for the chemical conversion of liquids or extended solids by place-exchanging the cations in an ionic material with a different set of cations. The technique is undergoing a major revival with the advent of high-quality nanocrystals: researchers are now able to overcome the limitations in bulk systems and fully exploit cation exchange for materials synthesis and discovery via rapid, low-temperature transformations in the solid state. In this tutorial review, we discuss cation exchange as a promising materials synthesis and discovery tool. Exchange on the nanoscale exhibits some unique attributes: rapid kinetics at room temperature (orders of magnitude faster than in the bulk) and the tuning of reactivity via control of nanocrystal size, shape, and surface faceting. These features make cation exchange a convenient tool for accessing nanocrystal compositions and morphologies for which conventional synthesis may not be established. A simple exchange reaction allows extension of nanochemistry to a larger part of the periodic table, beyond the typical gamut of II-VI, IV-VI, and III-V materials. Cation exchange transformations in nanocrystals can be topotactic and size- and shape-conserving, allowing nanocrystals synthesized by conventional methods to be used as templates for production of compositionally novel, multicomponent, or doped nanocrystals. Since phases and compositions resulting from an exchange reaction can be kinetically controlled, rather than governed by the phase diagram, nanocrystals of metastable and hitherto inaccessible compositions are attainable. Outside of materials synthesis, applications for cation exchange exist in water purification, chemical staining, and sensing. Since nanoscale cation exchange occurs rapidly at room temperature, it can be integrated with sensitive environments such as those in biological systems. Cation exchange is already allowing access to a variety of new materials and processes. With better mechanistic understanding and control, researchers may be able to advance the field to a stage where a custom nanostructure of arbitrary complexity would be achievable by simple cation exchange chemistry and a basic understanding of the periodic table.
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Affiliation(s)
- Jessy B Rivest
- The Molecular Foundry, Materials Science Division, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA
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17
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Sahu A, Kang MS, Kompch A, Notthoff C, Wills AW, Deng D, Winterer M, Frisbie CD, Norris DJ. Electronic impurity doping in CdSe nanocrystals. NANO LETTERS 2012; 12:2587-94. [PMID: 22533700 DOI: 10.1021/nl300880g] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We dope CdSe nanocrystals with Ag impurities and investigate their optical and electrical properties. Doping leads not only to dramatic changes but surprising complexity. The addition of just a few Ag atoms per nanocrystal causes a large enhancement in the fluorescence, reaching efficiencies comparable to core-shell nanocrystals. While Ag was expected to be a substitutional acceptor, nonmonotonic trends in the fluorescence and Fermi level suggest that Ag changes from an interstitial (n-type) to a substitutional (p-type) impurity with increased doping.
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Affiliation(s)
- Ayaskanta Sahu
- Optical Materials Engineering Laboratory, ETH Zurich, 8092 Zurich, Switzerland
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