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Buerkle M, Lozac'h M, Mariotti D, Švrček V. Quasi-band structure of quantum-confined nanocrystals. Sci Rep 2023; 13:4684. [PMID: 36949161 PMCID: PMC10033514 DOI: 10.1038/s41598-023-31989-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Accepted: 03/21/2023] [Indexed: 03/24/2023] Open
Abstract
We discuss the electronic properties of quantum-confined nanocrystals. In particular, we show how, starting from the discrete molecular states of small nanocrystals, an approximate band structure (quasi-band structure) emerges with increasing particle size. Finite temperature is found to broaden the discrete states in energy space forming even for nanocrystals in the quantum-confinement regime quasi-continuous bands in k-space. This bands can be, to a certain extend, interpreted along the lines of standard band structure theory, while taking also finite size and surface effects into account. We discuss this on various prototypical nanocrystal systems.
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Affiliation(s)
- Marius Buerkle
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
| | - Mickaël Lozac'h
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
| | - Davide Mariotti
- Integrated Bio-Engineering Centre (NIBEC), University of Ulster, Coleraine, UK
| | - Vladimir Švrček
- National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
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2
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Cendejas AJ, Sun H, Hayes SE, Kortshagen U, Thimsen E. Predicting plasma conditions necessary for synthesis of γ-Al 2O 3 nanocrystals. NANOSCALE 2021; 13:11387-11395. [PMID: 34160531 DOI: 10.1039/d1nr02488d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Nonthermal plasma (NTP) offers a unique synthesis environment capable of producing nanocrystals of high melting point materials at relatively low gas temperatures. Despite the rapidly growing material library accessible through NTP synthesis, designing processes for new materials is predominantly empirically driven. Here, we report on the synthesis of both amorphous alumina and γ-Al2O3 nanocrystals and present a simple particle heating model that is suitable for predicting the plasma power necessary for crystallization. The heating model only requires the composition, temperature, and pressure of the background gas along with the reactor geometry to calculate the temperature of particles suspended in the plasma as a function of applied power. Complete crystallization of the nanoparticle population was observed when applied power was greater than the threshold where the calculated particle temperature is equal to the crystallization temperature of amorphous alumina.
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Affiliation(s)
- Austin J Cendejas
- Department of Energy, Environmental and Chemical Engineering, Washington University in Saint Louis, Saint Louis, Missouri, USA.
| | - He Sun
- Department of Chemistry, Washington University in Saint Louis, Saint Louis, Missouri, USA and Institute of Materials Science and Engineering, Washington University in Saint Louis, Saint Louis, Missouri, USA
| | - Sophia E Hayes
- Department of Chemistry, Washington University in Saint Louis, Saint Louis, Missouri, USA and Institute of Materials Science and Engineering, Washington University in Saint Louis, Saint Louis, Missouri, USA
| | - Uwe Kortshagen
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, USA
| | - Elijah Thimsen
- Department of Energy, Environmental and Chemical Engineering, Washington University in Saint Louis, Saint Louis, Missouri, USA. and Institute of Materials Science and Engineering, Washington University in Saint Louis, Saint Louis, Missouri, USA
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3
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Alessi B, Macias-Montero M, Maddi C, Maguire P, Svrcek V, Mariotti D. Bridging energy bands to the crystalline and amorphous states of Si QDs. Faraday Discuss 2020; 222:390-404. [PMID: 32133465 DOI: 10.1039/c9fd00103d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The relationship between the crystallization process and opto-electronic properties of silicon quantum dots (Si QDs) synthesized by atmospheric pressure plasmas (APPs) is studied in this work. The synthesis of Si QDs is carried out by flowing silane as a gas precursor in a plasma confined to a submillimeter space. Experimental conditions are adjusted to propitiate the crystallization of the Si QDs and produce QDs with both amorphous and crystalline character. In all cases, the Si QDs present a well-defined mean particle size in the range of 1.5-5.5 nm. Si QDs present optical bandgaps between 2.3 eV and 2.5 eV, which are affected by quantum confinement. Plasma parameters evaluated using optical emission spectroscopy are then used as inputs for a collisional plasma model, whose calculations yield the surface temperature of the Si QDs within the plasma, justifying the crystallization behavior under certain experimental conditions. We measure the ultraviolet-visible optical properties and electronic properties through various techniques, build an energy level diagram for the valence electrons region as a function of the crystallinity of the QDs, and finally discuss the integration of these as active layers of all-inorganic solar cells.
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Affiliation(s)
- Bruno Alessi
- Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), Ulster University, Newtownabbey, BT37 0QB, UK.
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4
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Haq AU, Buerkle M, Askari S, Rocks C, Ni C, Švrček V, Maguire P, Irvine JTS, Mariotti D. Controlling the Energy-Level Alignment of Silicon Carbide Nanocrystals by Combining Surface Chemistry with Quantum Confinement. J Phys Chem Lett 2020; 11:1721-1728. [PMID: 32040322 PMCID: PMC7145349 DOI: 10.1021/acs.jpclett.9b03828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 02/10/2020] [Indexed: 06/10/2023]
Abstract
The knowledge of band edges in nanocrystals (NCs) and quantum-confined systems is important for band alignment in technologically significant applications such as water purification, decomposition of organic compounds, water splitting, and solar cells. While the band energy diagram of bulk silicon carbides (SiCs) has been studied extensively for decades, very little is known about its evolution in SiC NCs. Moreover, the interplay between quantum confinement and surface chemistry gives rise to unusual electronic properties and remains barely understood. Here, we report for the first time the complete band energy diagram of SiC NCs synthesized such that they span the regime from strong to intermediate to weak quantum confinement. The absolute positions of the highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbitals show clear size dependence. While the HOMO level follows the expected behavior for quantum-confined electronic states, the LUMO energy shifts below the bulk conduction band minimum, which cannot be explained by a simple quantum confinement caused by the size effect. We show that this effect is a result of the interplay between quantum confinement and the formation of surface states due to partial and site-selective oxygen passivation.
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Affiliation(s)
- Atta Ul Haq
- Nanotechnology
& Integrated Bioengineering Centre (NIBEC), Ulster University, Shore Road, Newtownabbey BT37 0QB, United Kingdom
| | - Marius Buerkle
- National
Institute of Advanced Industrial Science and Technology (AIST), Central 2, Tsukuba 305-8568, Japan
| | - Sadegh Askari
- Institute
for Experimental and Applied Physics, Christian-Albrechts-Universität
zu Kiel, Leibnizstraße
17, 24118 Kiel, Germany
| | - Conor Rocks
- Nanotechnology
& Integrated Bioengineering Centre (NIBEC), Ulster University, Shore Road, Newtownabbey BT37 0QB, United Kingdom
| | - Chengsheng Ni
- School
of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, United Kingdom
- College
of Resources and Environment, Southwest
University, 400715, Chongqing, China
| | - Vladimir Švrček
- National
Institute of Advanced Industrial Science and Technology (AIST), Central 2, Tsukuba 305-8568, Japan
| | - Paul Maguire
- Nanotechnology
& Integrated Bioengineering Centre (NIBEC), Ulster University, Shore Road, Newtownabbey BT37 0QB, United Kingdom
| | - John T. S. Irvine
- School
of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, United Kingdom
| | - Davide Mariotti
- Nanotechnology
& Integrated Bioengineering Centre (NIBEC), Ulster University, Shore Road, Newtownabbey BT37 0QB, United Kingdom
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5
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Chakrabarti S, Carolan D, Alessi B, Maguire P, Svrcek V, Mariotti D. Microplasma-synthesized ultra-small NiO nanocrystals, a ubiquitous hole transport material. NANOSCALE ADVANCES 2019; 1:4915-4925. [PMID: 36133136 PMCID: PMC9417055 DOI: 10.1039/c9na00299e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 10/21/2019] [Indexed: 05/27/2023]
Abstract
We report on a one-step hybrid atmospheric pressure plasma-liquid synthesis of ultra-small NiO nanocrystals (2 nm mean diameter), which exhibit strong quantum confinement. We show the versatility of the synthesis process and present the superior material characteristics of the nanocrystals (NCs). The band diagram of the NiO NCs, obtained experimentally, highlights ideal features for their implementation as a hole transport layer in a wide range of photovoltaic (PV) device architectures. As a proof of concept, we demonstrate the NiO NCs as a hole transport layer for three different PV device test architectures, which incorporate silicon quantum dots (Si-QDs), nitrogen-doped carbon quantum dots (N-CQDs) and perovskite as absorber layers. Our results clearly show ideal band alignment which could lead to improved carrier extraction into the metal contacts for all three solar cells. In addition, in the case of perovskite solar cells, the NiO NC hole transport layer acted as a protective layer preventing the degradation of halide perovskites from ambient moisture with a stable performance for >70 days. Our results also show unique characteristics that are highly suitable for future developments in all-inorganic 3rd generation solar cells (e.g. based on quantum dots) where quantum confinement can be used effectively to tune the band diagram to fit the energy level alignment requirements of different solar cell architectures.
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Affiliation(s)
- Supriya Chakrabarti
- Nanotechnology & Integrated Bio-Engineering Centre (NIBEC), Ulster University Jordanstown, Newtownabbey Co. Antrim BT37 0QB UK
- Centre for Carbon Materials, International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) Balapur P.O. Hyderabad 500005 India
| | - Darragh Carolan
- Nanotechnology & Integrated Bio-Engineering Centre (NIBEC), Ulster University Jordanstown, Newtownabbey Co. Antrim BT37 0QB UK
| | - Bruno Alessi
- Nanotechnology & Integrated Bio-Engineering Centre (NIBEC), Ulster University Jordanstown, Newtownabbey Co. Antrim BT37 0QB UK
| | - Paul Maguire
- Nanotechnology & Integrated Bio-Engineering Centre (NIBEC), Ulster University Jordanstown, Newtownabbey Co. Antrim BT37 0QB UK
| | - Vladimir Svrcek
- National Institute of Advanced Industrial Science and Technology (AIST), Department of Energy and Environment, Research Center of Photovoltaics, Advanced Processing Team Central 2, Umezono 1-1-1 Tsukuba Ibaraki 305-8568 Japan
| | - Davide Mariotti
- Nanotechnology & Integrated Bio-Engineering Centre (NIBEC), Ulster University Jordanstown, Newtownabbey Co. Antrim BT37 0QB UK
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6
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Size-dependent stability of ultra-small α-/β-phase tin nanocrystals synthesized by microplasma. Nat Commun 2019; 10:817. [PMID: 30778052 PMCID: PMC6379433 DOI: 10.1038/s41467-019-08661-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 01/18/2019] [Indexed: 11/24/2022] Open
Abstract
Nanocrystals sometimes adopt unusual crystal structure configurations in order to maintain structural stability with increasingly large surface-to-volume ratios. The understanding of these transformations is of great scientific interest and represents an opportunity to achieve beneficial materials properties resulting from different crystal arrangements. Here, the phase transformation from α to β phases of tin (Sn) nanocrystals is investigated in nanocrystals with diameters ranging from 6.1 to 1.6 nm. Ultra-small Sn nanocrystals are achieved through our highly non-equilibrium plasma process operated at atmospheric pressures. Larger nanocrystals adopt the β-Sn tetragonal structure, while smaller nanocrystals show stability with the α-Sn diamond cubic structure. Synthesis at other conditions produce nanocrystals with mean diameters within the range 2–3 nm, which exhibit mixed phases. This work represents an important contribution to understand structural stability at the nanoscale and the possibility of achieving phases of relevance for many applications. Key features of tin, including electronic band structure and opto-electronic properties, are influenced by the crystal structure. Here the authors report a microplasma process for the synthesis of ultra-small tin nanocrystals in which the crystal structure is dependent on crystallite size.
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7
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Levchenko I, Xu S, Teel G, Mariotti D, Walker MLR, Keidar M. Recent progress and perspectives of space electric propulsion systems based on smart nanomaterials. Nat Commun 2018; 9:879. [PMID: 29491411 PMCID: PMC5830404 DOI: 10.1038/s41467-017-02269-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 11/16/2017] [Indexed: 11/23/2022] Open
Abstract
Drastic miniaturization of electronics and ingression of next-generation nanomaterials into space technology have provoked a renaissance in interplanetary flights and near-Earth space exploration using small unmanned satellites and systems. As the next stage, the NASA's 2015 Nanotechnology Roadmap initiative called for new design paradigms that integrate nanotechnology and conceptually new materials to build advanced, deep-space-capable, adaptive spacecraft. This review examines the cutting edge and discusses the opportunities for integration of nanomaterials into the most advanced types of electric propulsion devices that take advantage of their unique features and boost their efficiency and service life. Finally, we propose a concept of an adaptive thruster.
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Affiliation(s)
- I Levchenko
- Plasma Sources and Applications Centre, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore, 637616, Singapore.
- School of Chemistry, Physics, and Mechanical Engineering, Queensland University of Technology (QUT), Brisbane, QLD, 4000, Australia.
| | - S Xu
- Plasma Sources and Applications Centre, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore, 637616, Singapore
| | - G Teel
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, 20052, USA
| | - D Mariotti
- Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), Ulster University, Newtownabbey, BT37 0QB, UK
| | - M L R Walker
- School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA, 30332-0150, USA
| | - M Keidar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, 20052, USA
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Jayanthi S, Muthu DVS, Jayaraman N, Sampath S, Sood AK. Semiconducting Conjugated Microporous Polymer: An Electrode Material for Photoelectrochemical Water Splitting and Oxygen Reduction. ChemistrySelect 2017. [DOI: 10.1002/slct.201700505] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Swetha Jayanthi
- Centre for Nano Science and Engineering; Indian Institute of Science; Bangalore-560012 India
| | - D. V. S. Muthu
- Department of Physics; Indian Institute of Science; Bangalore-560012 India
| | - N. Jayaraman
- Department of Organic Chemistry; Indian Institute of Science; Bangalore-560012 India
| | - S. Sampath
- Department of Inorganic and Physical Chemistry; Indian Institute of Science; Bangalore-560012 India
| | - A. K. Sood
- Department of Physics; Indian Institute of Science; Bangalore-560012 India
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