1
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Pitters J, Croshaw J, Achal R, Livadaru L, Ng S, Lupoiu R, Chutora T, Huff T, Walus K, Wolkow RA. Atomically Precise Manufacturing of Silicon Electronics. ACS NANO 2024; 18:6766-6816. [PMID: 38376086 PMCID: PMC10919096 DOI: 10.1021/acsnano.3c10412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 02/01/2024] [Accepted: 02/06/2024] [Indexed: 02/21/2024]
Abstract
Atomically precise manufacturing (APM) is a key technique that involves the direct control of atoms in order to manufacture products or components of products. It has been developed most successfully using scanning probe methods and has received particular attention for developing atom scale electronics with a focus on silicon-based systems. This review captures the development of silicon atom-based electronics and is divided into several sections that will cover characterization and atom manipulation of silicon surfaces with scanning tunneling microscopy and atomic force microscopy, development of silicon dangling bonds as atomic quantum dots, creation of atom scale devices, and the wiring and packaging of those circuits. The review will also cover the advance of silicon dangling bond logic design and the progress of silicon quantum atomic designer (SiQAD) simulators. Finally, an outlook of APM and silicon atom electronics will be provided.
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Affiliation(s)
- Jason Pitters
- Nanotechnology
Research Centre, National Research Council
of Canada, Edmonton, Alberta T6G 2M9, Canada
| | - Jeremiah Croshaw
- Department
of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Roshan Achal
- Department
of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
- Quantum
Silicon Inc., Edmonton, Alberta T6G 2M9, Canada
| | - Lucian Livadaru
- Department
of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
- Quantum
Silicon Inc., Edmonton, Alberta T6G 2M9, Canada
| | - Samuel Ng
- Department
of Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Robert Lupoiu
- School
of Engineering, Stanford University, Stanford, California 94305, United States
| | - Taras Chutora
- Department
of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Taleana Huff
- Canadian
Bank Note Company, Ottawa, Ontario K1Z 1A1, Canada
| | - Konrad Walus
- Department
of Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Robert A. Wolkow
- Department
of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
- Quantum
Silicon Inc., Edmonton, Alberta T6G 2M9, Canada
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2
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Chen K, Liu Z, Xie Y, Zhang C, Xu G, Song W, Xu K. Numerical analysis of vibration modes of a qPlus sensor with a long tip. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2021; 12:82-92. [PMID: 33564605 PMCID: PMC7849263 DOI: 10.3762/bjnano.12.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 12/20/2020] [Indexed: 05/14/2023]
Abstract
We study the oscillatory behavior of qPlus sensors with a long tilted tip by means of finite element simulations. The vibration modes of a qPlus sensor with a long tip are quite different from those of a cantilever with a short tip. Flexural vibration of the tungsten tip will occur. The tip can no longer be considered as a rigid body that moves with the prong of the tuning fork. Instead, it oscillates both horizontally and vertically. The vibration characteristics of qPlus sensors with different tip sizes were studied. An optimized tip size was derived from obtained values of tip amplitude, ratio between vertical and lateral amplitude components, output current, and quality factor. For high spatial resolution the optimal diameter was found to be 0.1 mm.
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Affiliation(s)
- Kebei Chen
- School of Nano Technology and Nano Bionics, University of Science and Technology of China, Suzhou 215123, China
- Platform for Characterization and Test, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123, China
- CAS Key Laboratory of Nanophotonic Materials and Devices, Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China
| | - Zhenghui Liu
- Platform for Characterization and Test, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123, China
- CAS Key Laboratory of Nanophotonic Materials and Devices, Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China
| | - Yuchen Xie
- Platform for Characterization and Test, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123, China
| | - Chunyu Zhang
- Platform for Characterization and Test, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123, China
- CAS Key Laboratory of Nanophotonic Materials and Devices, Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China
| | - Gengzhao Xu
- Platform for Characterization and Test, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123, China
- CAS Key Laboratory of Nanophotonic Materials and Devices, Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China
| | - Wentao Song
- Platform for Characterization and Test, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123, China
- CAS Key Laboratory of Nanophotonic Materials and Devices, Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China
| | - Ke Xu
- Platform for Characterization and Test, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123, China
- CAS Key Laboratory of Nanophotonic Materials and Devices, Suzhou Institute of Nano-Tech and Nano-Bionics, Suzhou 215123, China
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3
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Will M, Bampoulis P, Hartl T, Valerius P, Michely T. Conformal Embedding of Cluster Superlattices with Carbon. ACS APPLIED MATERIALS & INTERFACES 2019; 11:40524-40532. [PMID: 31588723 DOI: 10.1021/acsami.9b14616] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Iridium cluster superlattices on the graphene moiré with Ir(111) are embedded with elemental carbon through vapor-phase deposition. Using scanning tunneling microscopy and spectroscopy, we find that carbon embedding is conformal and does not deteriorate the excellent order of the iridium clusters. The thermal and mechanical stability of the embedded clusters is greatly enhanced. Smoluchowski ripening as well as cluster pick-up by the scanning tunneling microscopy tip are both suppressed. The only cluster decay path left takes place at an elevated temperature of around 1050 K. The cluster material penetrates through the graphene sheet, whereby it becomes bound to the underlying metal. It is argued that conformal carbon embedding is an important step towards the formation of a new type of sintering-resistant cluster lattice material for nanocatalysis and nanomagnetism.
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Affiliation(s)
- Moritz Will
- II. Physikalisches Institut , Universität zu Köln , Cologne D-50937 , Germany
| | - Pantelis Bampoulis
- II. Physikalisches Institut , Universität zu Köln , Cologne D-50937 , Germany
| | - Tobias Hartl
- II. Physikalisches Institut , Universität zu Köln , Cologne D-50937 , Germany
| | - Philipp Valerius
- II. Physikalisches Institut , Universität zu Köln , Cologne D-50937 , Germany
| | - Thomas Michely
- II. Physikalisches Institut , Universität zu Köln , Cologne D-50937 , Germany
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4
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Stehlik S, Ondic L, Varga M, Fait J, Artemenko A, Glatzel T, Kromka A, Rezek B. Silicon-Vacancy Centers in Ultra-Thin Nanocrystalline Diamond Films. MICROMACHINES 2018; 9:E281. [PMID: 30424214 PMCID: PMC6187497 DOI: 10.3390/mi9060281] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 05/25/2018] [Accepted: 05/30/2018] [Indexed: 11/18/2022]
Abstract
Color centers in diamond have shown excellent potential for applications in quantum information processing, photonics, and biology. Here we report the optoelectronic investigation of shallow silicon vacancy (SiV) color centers in ultra-thin (7⁻40 nm) nanocrystalline diamond (NCD) films with variable surface chemistry. We show that hydrogenated ultra-thin NCD films exhibit no or lowered SiV photoluminescence (PL) and relatively high negative surface photovoltage (SPV) which is ascribed to non-radiative electron transitions from SiV to surface-related traps. Higher SiV PL and low positive SPV of oxidized ultra-thin NCD films indicate an efficient excitation-emission PL process without significant electron escape, yet with some hole trapping in diamond surface states. Decreasing SPV magnitude and increasing SiV PL intensity with thickness, in both cases, is attributed to resonant energy transfer between shallow and bulk SiV. We also demonstrate that thermal treatments (annealing in air or in hydrogen gas), commonly applied to modify the surface chemistry of nanodiamonds, are also applicable to ultra-thin NCD films in terms of tuning their SiV PL and surface chemistry.
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Affiliation(s)
- Stepan Stehlik
- Institute of Physics ASCR, Cukrovarnická 10, Prague 16200, Czech Republic.
| | - Lukas Ondic
- Institute of Physics ASCR, Cukrovarnická 10, Prague 16200, Czech Republic.
| | - Marian Varga
- Institute of Physics ASCR, Cukrovarnická 10, Prague 16200, Czech Republic.
| | - Jan Fait
- Institute of Physics ASCR, Cukrovarnická 10, Prague 16200, Czech Republic.
- Faculty of Electrical Engineering, Czech Technical University in Prague, Technická 2, Prague 16627, Czech Republic.
| | - Anna Artemenko
- Institute of Physics ASCR, Cukrovarnická 10, Prague 16200, Czech Republic.
| | - Thilo Glatzel
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland.
| | - Alexander Kromka
- Institute of Physics ASCR, Cukrovarnická 10, Prague 16200, Czech Republic.
| | - Bohuslav Rezek
- Institute of Physics ASCR, Cukrovarnická 10, Prague 16200, Czech Republic.
- Faculty of Electrical Engineering, Czech Technical University in Prague, Technická 2, Prague 16627, Czech Republic.
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5
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Structure-performance relationship of nanodiamonds @ nitrogen-doped mesoporous carbon in the direct dehydrogenation of ethylbenzene. Catal Today 2018. [DOI: 10.1016/j.cattod.2017.05.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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6
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Herbig C, Knispel T, Simon S, Schröder UA, Martínez-Galera AJ, Arman MA, Teichert C, Knudsen J, Krasheninnikov AV, Michely T. From Permeation to Cluster Arrays: Graphene on Ir(111) Exposed to Carbon Vapor. NANO LETTERS 2017; 17:3105-3112. [PMID: 28426934 DOI: 10.1021/acs.nanolett.7b00550] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Our scanning tunneling microscopy and X-ray photoelectron spectroscopy experiments along with first-principles calculations uncover the rich phenomenology and enable a coherent understanding of carbon vapor interaction with graphene on Ir(111). At high temperatures, carbon vapor not only permeates to the metal surface but also densifies the graphene cover. Thereby, in addition to underlayer graphene growth, upon cool down also severe wrinkling of the densified graphene cover is observed. In contrast, at low temperatures the adsorbed carbon largely remains on top and self-organizes into a regular array of fullerene-like, thermally highly stable clusters that are covalently bonded to the underlying graphene sheet. Thus, a new type of predominantly sp2-hybridized nanostructured and ultrathin carbon material emerges, which may be useful to encage or stably bind metal in finely dispersed form.
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Affiliation(s)
- Charlotte Herbig
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | - Timo Knispel
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | - Sabina Simon
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | - Ulrike A Schröder
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | | | | | - Christian Teichert
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
| | | | - Arkady V Krasheninnikov
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf , 01328 Dresden, Germany
- Department of Applied Physics, Aalto University School of Science , P.O. Box 11100, 00076 Aalto, Finland
| | - Thomas Michely
- II. Physikalisches Institut, Universität zu Köln , Zülpicher Straße 77, 50937 Köln, Germany
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7
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Wu X, Ou G, Yang C, Ge J, Wu H. Enhanced enzymatic reactions by solar-to-thermal conversion nanoparticles. Chem Commun (Camb) 2017; 53:5048-5051. [DOI: 10.1039/c7cc01522d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this study, we demonstrate that enzymatic reactions can be easily enhanced by visible light irradiation.
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Affiliation(s)
- Xiaoling Wu
- Key Lab for Industrial Biocatalysis
- Ministry of Education
- Department of Chemical Engineering
- Tsinghua University
- Beijing 100084
| | - Gang Ou
- State Key Laboratory of New Ceramics and Fine Processing
- School of Materials Science and Engineering
- Tsinghua University
- Beijing 100084
- China
| | - Cheng Yang
- Key Lab for Industrial Biocatalysis
- Ministry of Education
- Department of Chemical Engineering
- Tsinghua University
- Beijing 100084
| | - Jun Ge
- Key Lab for Industrial Biocatalysis
- Ministry of Education
- Department of Chemical Engineering
- Tsinghua University
- Beijing 100084
| | - Hui Wu
- State Key Laboratory of New Ceramics and Fine Processing
- School of Materials Science and Engineering
- Tsinghua University
- Beijing 100084
- China
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8
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Stehlik S, Varga M, Ledinsky M, Jirasek V, Artemenko A, Kozak H, Ondic L, Skakalova V, Argentero G, Pennycook T, Meyer J, Fejfar A, Kromka A, Rezek B. Size and Purity Control of HPHT Nanodiamonds down to 1 nm. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2015; 119:27708-27720. [PMID: 26691647 PMCID: PMC4677353 DOI: 10.1021/acs.jpcc.5b05259] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Revised: 07/27/2015] [Indexed: 05/19/2023]
Abstract
High-pressure high-temperature (HPHT) nanodiamonds originate from grinding of diamond microcrystals obtained by HPHT synthesis. Here we report on a simple two-step approach to obtain as small as 1.1 nm HPHT nanodiamonds of excellent purity and crystallinity, which are among the smallest artificially prepared nanodiamonds ever shown and characterized. Moreover we provide experimental evidence of diamond stability down to 1 nm. Controlled annealing at 450 °C in air leads to efficient purification from the nondiamond carbon (shells and dots), as evidenced by X-ray photoelectron spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, and scanning transmission electron microscopy. Annealing at 500 °C promotes, besides of purification, also size reduction of nanodiamonds down to ∼1 nm. Comparably short (1 h) centrifugation of the nanodiamonds aqueous colloidal solution ensures separation of the sub-10 nm fraction. Calculations show that an asymmetry of Raman diamond peak of sub-10 nm HPHT nanodiamonds can be well explained by modified phonon confinement model when the actual particle size distribution is taken into account. In contrast, larger Raman peak asymmetry commonly observed in Raman spectra of detonation nanodiamonds is mainly attributed to defects rather than to the phonon confinement. Thus, the obtained characteristics reflect high material quality including nanoscale effects in sub-10 nm HPHT nanodiamonds prepared by the presented method.
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Affiliation(s)
- Stepan Stehlik
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
- E-mail:
| | - Marian Varga
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
| | - Martin Ledinsky
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
| | - Vit Jirasek
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
| | - Anna Artemenko
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
| | - Halyna Kozak
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
| | - Lukas Ondic
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
| | - Viera Skakalova
- Physics of Nanostructured
Materials, Faculty of Physics, University
of Vienna, Boltzmanngasse
5, 1090 Vienna, Austria
- SUT Center for Nanodiagnostics, Vazovova 5, 812 43 Bratislava, Slovakia
| | - Giacomo Argentero
- Physics of Nanostructured
Materials, Faculty of Physics, University
of Vienna, Boltzmanngasse
5, 1090 Vienna, Austria
| | - Timothy Pennycook
- Physics of Nanostructured
Materials, Faculty of Physics, University
of Vienna, Boltzmanngasse
5, 1090 Vienna, Austria
| | - Jannik
C. Meyer
- Physics of Nanostructured
Materials, Faculty of Physics, University
of Vienna, Boltzmanngasse
5, 1090 Vienna, Austria
| | - Antonin Fejfar
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
| | - Alexander Kromka
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
| | - Bohuslav Rezek
- Institute
of Physics ASCR, Cukrovarnická
10, 162 00 Prague
6, Czech Republic
- Faculty of Electrical Engineering, Czech
Technical University in Prague, Technická 2, 16627 Prague 6, Czech Republic
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9
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Pawlak R, Marot L, Sadeghi A, Kawai S, Glatzel T, Reimann P, Goedecker S, Güntherodt HJ, Meyer E. Chain-like structure elements in Ni40Ta60 metallic glasses observed by scanning tunneling microscopy. Sci Rep 2015; 5:13143. [PMID: 26268430 PMCID: PMC4542518 DOI: 10.1038/srep13143] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 07/21/2015] [Indexed: 11/09/2022] Open
Abstract
The structure of metallic glasses is a long-standing question because the lack of long-range order makes diffraction based techniques difficult to be applied. Here, we used scanning tunneling microscopy with large tunneling resistance of 6 GΩ at low temperature in order to minimize forces between probe and sample and reduce thermal fluctuations of metastable structures. Under these extremely gentle conditions, atomic structures of Ni40Ta60 metallic glasses are revealed with unprecedented lateral resolution. In agreement with previous models and experiments, icosahedral-like clusters are observed. The clusters show a high degree of mobility, which explains the need of low temperatures for stable imaging. In addition to icosahedrons, chain-like structures are resolved and comparative density functional theory (DFT) calculations confirm that these structures are meta-stable. The co-existence of icosahedral and chain-like structures might be an key ingredient for the understanding of the mechanical properties of metallic glasses.
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Affiliation(s)
- Rémy Pawlak
- Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Laurent Marot
- Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Ali Sadeghi
- Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
- Department of Physics, Shahid Beheshti University, Evin, 19839 Theran, Iran
| | - Shigeki Kawai
- Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Thilo Glatzel
- Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Peter Reimann
- Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
| | - Stefan Goedecker
- Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
| | | | - Ernst Meyer
- Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
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10
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Continuous engineering of nano-cocrystals for medical and energetic applications. Sci Rep 2014; 4:6575. [PMID: 25300652 PMCID: PMC4192619 DOI: 10.1038/srep06575] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 09/12/2014] [Indexed: 11/10/2022] Open
Abstract
Cocrystals, solid mixtures of different molecules on molecular scale, are supposed to be tailor made materials with improved employability compared to their pristine individual components in domains such as medicine and explosives. In medicine, cocrystals are obtained by crystallization of active pharmaceutical ingredients with precisely chosen coformers to design medicaments that demonstrate enhanced stability, high solubility, and therefore high bioavailability and optimized drug up-take. Nanoscaling may further advance these characteristica compared to their micronsized counterparts – because of a larger surface to volume ratio of nanoparticles. In the field of energetic materials, cocrystals offer the opportunity to design smart explosives, combining high reactivity with significantly reduced sensitivity, nowadays essential for a safe manipulation and handling. Furthermore, cocrystals are used in ferroelectrics, non-linear material response and electronic organics. However, state of the art batch processes produce low volume of cocrystals of variable quality and only have produced micronsized cocrystals so far, no nano-cocrystals. Here we demonstrate the continuous preparation of pharmaceutical and energetic micro- and nano-cocrystals using the Spray Flash Evaporation process. Our laboratory scale pilot plant continuously prepared up to 8 grams per hour of Caffeine/Oxalic acid 2:1, Caffeine/Glutaric acid 1:1, TNT/CL-20 1:1 and HMX/Cl-20 1:2 nano- and submicronsized cocrystals.
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11
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Schuler B, Liu SX, Geng Y, Decurtins S, Meyer G, Gross L. Contrast formation in Kelvin probe force microscopy of single π-conjugated molecules. NANO LETTERS 2014; 14:3342-6. [PMID: 24849457 DOI: 10.1021/nl500805x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report the contrast formation in the local contact potential difference (LCPD) measured by Kelvin probe force microscopy (KPFM) on single charge-transfer complexes (CTCs) on a NaCl bilayer on Cu(111). At different tip heights, we found quantitatively different LCPD contrasts that characterize different properties of the molecule. In the small distance regime, the tip penetrates the electron density of the molecule, and the contrast is related to the size and topography of the electron shell of the molecule. For larger distances, the LCPD contrast corresponds to the electrostatic field above the molecule. However, in the medium-distance regime, that is, for tip heights similar to the size of the molecule, the nonspherical distribution of π- and σ-electrons often conceals the effect of the partial charges within the molecule. Only for large distances does the LCPD map converge toward the simple field of a dipole for a polar molecule.
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Affiliation(s)
- Bruno Schuler
- IBM Research-Zurich , Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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