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Fernandez A, Ferrando-Soria J, Pineda EM, Tuna F, Vitorica-Yrezabal IJ, Knappke C, Ujma J, Muryn CA, Timco GA, Barran PE, Ardavan A, Winpenny RE. Making hybrid [n]-rotaxanes as supramolecular arrays of molecular electron spin qubits. Nat Commun 2016; 7:10240. [PMID: 26742716 PMCID: PMC4729860 DOI: 10.1038/ncomms10240] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 11/17/2015] [Indexed: 02/04/2023] Open
Abstract
Quantum information processing (QIP) would require that the individual units involved--qubits--communicate to other qubits while retaining their identity. In many ways this resembles the way supramolecular chemistry brings together individual molecules into interlocked structures, where the assembly has one identity but where the individual components are still recognizable. Here a fully modular supramolecular strategy has been to link hybrid organic-inorganic [2]- and [3]-rotaxanes into still larger [4]-, [5]- and [7]-rotaxanes. The ring components are heterometallic octanuclear [Cr7NiF8(O2C(t)Bu)16](-) coordination cages and the thread components template the formation of the ring about the organic axle, and are further functionalized to act as a ligand, which leads to large supramolecular arrays of these heterometallic rings. As the rings have been proposed as qubits for QIP, the strategy provides a possible route towards scalable molecular electron spin devices for QIP. Double electron-electron resonance experiments demonstrate inter-qubit interactions suitable for mediating two-qubit quantum logic gates.
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Spielberg ET, Gilb A, Plaul D, Geibig D, Hornig D, Schuch D, Buchholz A, Ardavan A, Plass W. A Spin-Frustrated Trinuclear Copper Complex Based on Triaminoguanidine with an Energetically Well-Separated Degenerate Ground State. Inorg Chem 2015; 54:3432-8. [DOI: 10.1021/ic503095t] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Moro F, Kaminski D, Tuna F, Whitehead GFS, Timco GA, Collison D, Winpenny REP, Ardavan A, McInnes EJL. Coherent electron spin manipulation in a dilute oriented ensemble of molecular nanomagnets: pulsed EPR on doped single crystals. Chem Commun (Camb) 2014; 50:91-3. [DOI: 10.1039/c3cc46326e] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Nam MS, Mézière C, Batail P, Zorina L, Simonov S, Ardavan A. Superconducting fluctuations in organic molecular metals enhanced by Mott criticality. Sci Rep 2013; 3:3390. [PMID: 24292063 PMCID: PMC3844941 DOI: 10.1038/srep03390] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 11/11/2013] [Indexed: 11/09/2022] Open
Abstract
Unconventional superconductivity typically occurs in materials in which a small change of a parameter such as bandwidth or doping leads to antiferromagnetic or Mott insulating phases. As such competing phases are approached, the properties of the superconductor often become increasingly exotic. For example, in organic superconductors and underdoped high-Tc cuprate superconductors a fluctuating superconducting state persists to temperatures significantly above Tc. By studying alloys of quasi-two-dimensional organic molecular metals in the κ-(BEDT-TTF)2X family, we reveal how the Nernst effect, a sensitive probe of superconducting phase fluctuations, evolves in the regime of extreme Mott criticality. We find strong evidence that, as the phase diagram is traversed through superconductivity towards the Mott state, the temperature scale for superconducting fluctuations increases dramatically, eventually approaching the temperature at which quasiparticles become identifiable at all.
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George RE, Edwards JP, Ardavan A. Coherent spin control by electrical manipulation of the magnetic anisotropy. PHYSICAL REVIEW LETTERS 2013; 110:027601. [PMID: 23383938 DOI: 10.1103/physrevlett.110.027601] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2012] [Indexed: 06/01/2023]
Abstract
High-spin paramagnetic manganese defects in polar piezoelectric zinc oxide exhibit a simple, almost axial anisotropy and phase coherence times of the order of a millisecond at low temperatures. The anisotropy energy is tunable using an externally applied electric field. This can be used to control electrically the phase of spin superpositions and to drive spin transitions with resonant microwave electric fields.
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Plant SR, Jevric M, Morton JJL, Ardavan A, Khlobystov AN, Briggs GAD, Porfyrakis K. A two-step approach to the synthesis of N@C60 fullerene dimers for molecular qubits. Chem Sci 2013. [DOI: 10.1039/c3sc50395j] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Wedge CJ, Timco GA, Spielberg ET, George RE, Tuna F, Rigby S, McInnes EJL, Winpenny REP, Blundell SJ, Ardavan A. Chemical engineering of molecular qubits. PHYSICAL REVIEW LETTERS 2012; 108:107204. [PMID: 22463450 DOI: 10.1103/physrevlett.108.107204] [Citation(s) in RCA: 153] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Indexed: 05/05/2023]
Abstract
We show that the electron spin phase memory time, the most important property of a molecular nanomagnet from the perspective of quantum information processing, can be improved dramatically by chemically engineering the molecular structure to optimize the environment of the spin. We vary systematically each structural component of the class of antiferromagnetic Cr(7)Ni rings to identify the sources of decoherence. The optimal structure exhibits a phase memory time exceeding 15 μs.
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Farrington BJ, Jevric M, Rance GA, Ardavan A, Khlobystov AN, Briggs GAD, Porfyrakis K. Chemistry at the Nanoscale: Synthesis of an N@C60-N@C60 Endohedral Fullerene Dimer. Angew Chem Int Ed Engl 2012; 51:3587-90. [PMID: 22383390 DOI: 10.1002/anie.201107490] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Indexed: 11/09/2022]
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Farrington BJ, Jevric M, Rance GA, Ardavan A, Khlobystov AN, Briggs GAD, Porfyrakis K. Chemistry at the Nanoscale: Synthesis of an N@C60-N@C60 Endohedral Fullerene Dimer. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201107490] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Dalili D, Fouladdel S, Rastkari N, Samadi N, Ahmadkhaniha R, Ardavan A, Azizi E. Prodigiosin, the red pigment of Serratia marcescens, shows cytotoxic effects and apoptosis induction in HT-29 and T47D cancer cell lines. Nat Prod Res 2011; 26:2078-83. [PMID: 21985476 DOI: 10.1080/14786419.2011.622276] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
In this study, a red pigment of Serratia marcescens PTCC 1111 was purified and identified for antiproliferative activities in HT-29 and T47D cancer cell lines. (1)H-NMR spectroscopy and LC/MS analysis confirmed prodigiosin structure. The antiproliferative effects of prodigiosin were determined by employing the MTT assay. The changes in cell cycle pattern were studied with 4',6-diamidino-2-phenylindole (DAPI) reagent using flow cytometry assay, and Annexin V-PI method was used for apoptotic analysis. Results of MTT assay showed that HT-29 cells were more sensitive to prodigiosin than T47D cells. Prodigiosin-treated HT-29 cells showed increase in S phase and decrease in G2/M, but treated T47D cells showed cell cycle pattern relatively similar to Roswell Park Memorial Institute medium (RPMI). Apoptotic effect of prodigiosin was higher than doxorubicin in HT-29 cells. The data reported here indicate that prodigiosin is a promising antineoplastic agent that triggers apoptosis in different cancer cell lines.
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Ardavan A, Briggs GAD. Quantum control in spintronics. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:3229-3248. [PMID: 21727123 DOI: 10.1098/rsta.2011.0009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Superposition and entanglement are uniquely quantum phenomena. Superposition incorporates a phase that contains information surpassing any classical mixture. Entanglement offers correlations between measurements in quantum systems that are stronger than any that would be possible classically. These give quantum computing its spectacular potential, but the implications extend far beyond quantum information processing. Early applications may be found in entanglement-enhanced sensing and metrology. Quantum spins in condensed matter offer promising candidates for investigating and exploiting superposition and entanglement, and enormous progress is being made in quantum control of such systems. In gallium arsenide (GaAs), individual electron spins can be manipulated and measured, and singlet-triplet states can be controlled in double-dot structures. In silicon, individual electron spins can be detected by ionization of phosphorus donors, and information can be transferred from electron spins to nuclear spins to provide long memory times. Electron and nuclear spins can be manipulated in nitrogen atoms incarcerated in fullerene molecules, which in turn can be assembled in ordered arrays. Spin states of charged nitrogen vacancy centres in diamond can be manipulated and read optically. Collective spin states in a range of materials systems offer scope for holographic storage of information. Conditions are now excellent for implementing superposition and entanglement in spintronic devices, thereby opening up a new era of quantum technologies.
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Liu G, Khlobystov AN, Ardavan A, Briggs GAD, Porfyrakis K. Photochemical stability of N@C60 and its pyrrolidine derivatives. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.04.039] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Brown RM, Tyryshkin AM, Porfyrakis K, Gauger EM, Lovett BW, Ardavan A, Lyon SA, Briggs GAD, Morton JJL. Coherent state transfer between an electron and nuclear spin in (15)N@C(60). PHYSICAL REVIEW LETTERS 2011; 106:110504. [PMID: 21469852 DOI: 10.1103/physrevlett.106.110504] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Indexed: 05/30/2023]
Abstract
Electron spin qubits in molecular systems offer high reproducibility and the ability to self-assemble into larger architectures. However, interactions between neighboring qubits are "always on," and although the electron spin coherence times can be several hundred microseconds, these are still much shorter than typical times for nuclear spins. Here we implement an electron-nuclear hybrid scheme which uses coherent transfer between electron and nuclear spin degrees of freedom in order to both effectively turn on or off interqubit coupling mediated by dipolar interactions and benefit from the long nuclear spin decoherence times (T(2n)). We transfer qubit states between the electron and (15)N nuclear spin in (15)N@C(60) with a two-way process fidelity of 88%, using a series of tuned microwave and radio frequency pulses and measure a nuclear spin coherence lifetime of over 100 ms.
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Lang V, Lo CC, George RE, Lyon SA, Bokor J, Schenkel T, Ardavan A, Morton JJL. Electrically detected magnetic resonance in a W-band microwave cavity. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2011; 82:034704. [PMID: 21456773 DOI: 10.1063/1.3557395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We describe a low-temperature sample probe for the electrical detection of magnetic resonance in a resonant W-band (94 GHz) microwave cavity. The advantages of this approach are demonstrated by experiments on silicon field-effect transistors. A comparison with conventional low-frequency measurements at X-band (9.7 GHz) on the same devices reveals an up to 100-fold enhancement of the signal intensity. In addition, resonance lines that are unresolved at X-band are clearly separated in the W-band measurements. Electrically detected magnetic resonance at high magnetic fields and high microwave frequencies is therefore a very sensitive technique for studying electron spins with an enhanced spectral resolution and sensitivity.
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Zaka M, Ito Y, Wang H, Yan W, Robertson A, Wu YA, Rümmeli MH, Staunton D, Hashimoto T, Morton JJL, Ardavan A, Briggs GAD, Warner JH. Electron paramagnetic resonance investigation of purified catalyst-free single-walled carbon nanotubes. ACS NANO 2010; 4:7708-7716. [PMID: 21082779 DOI: 10.1021/nn102602a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Electron paramagnetic resonance of single-walled carbon nanotubes (SWCNTs) has been bedevilled by the presence of paramagnetic impurities. To address this, SWCNTs produced by laser ablation with a nonmagnetic PtRhRe catalyst were purified through a multiple step centrifugation process in order to remove amorphous carbon and catalyst impurities. Centrifugation of a SWCNT solution resulted in sedimentation of carbon nanotube bundles containing clusters of catalyst particles, while isolated nanotubes with reduced catalyst particle content remained in the supernatant. Further ultracentrifugation resulted in highly purified SWCNT samples with a narrow diameter distribution and almost no detectable catalyst particles. Electron paramagnetic resonance (EPR) signals were detected only for samples which contained catalyst particles, with the ultracentrifuged SWCNTs showing no EPR signal at X-band (9.4 GHz) and fields < 0.4 T.
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Wu H, George RE, Wesenberg JH, Mølmer K, Schuster DI, Schoelkopf RJ, Itoh KM, Ardavan A, Morton JJL, Briggs GAD. Storage of multiple coherent microwave excitations in an electron spin ensemble. PHYSICAL REVIEW LETTERS 2010; 105:140503. [PMID: 21230819 DOI: 10.1103/physrevlett.105.140503] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Indexed: 05/30/2023]
Abstract
Strong coupling between a microwave photon and electron spins, which could enable a long-lived quantum memory element for superconducting qubits, is possible using a large ensemble of spins. This represents an inefficient use of resources unless multiple photons, or qubits, can be orthogonally stored and retrieved. Here we employ holographic techniques to realize a coherent memory using a pulsed magnetic field gradient and demonstrate the storage and retrieval of up to 100 weak 10 GHz coherent excitations in collective states of an electron spin ensemble. We further show that such collective excitations in the electron spin can then be stored in nuclear spin states, which offer coherence times in excess of seconds.
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Schaffry M, Filidou V, Karlen SD, Gauger EM, Benjamin SC, Anderson HL, Ardavan A, Briggs GAD, Maeda K, Henbest KB, Giustino F, Morton JJL, Lovett BW. Entangling remote nuclear spins linked by a chromophore. PHYSICAL REVIEW LETTERS 2010; 104:200501. [PMID: 20867015 DOI: 10.1103/physrevlett.104.200501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 04/01/2010] [Indexed: 05/29/2023]
Abstract
Molecular nanostructures may constitute the fabric of future quantum technologies, if their degrees of freedom can be fully harnessed. Ideally one might use nuclear spins as low-decoherence qubits and optical excitations for fast controllable interactions. Here, we present a method for entangling two nuclear spins through their mutual coupling to a transient optically excited electron spin, and investigate its feasibility through density-functional theory and experiments on a test molecule. From our calculations we identify the specific molecular properties that permit high entangling power gates under simple optical and microwave pulses; synthesis of such molecules is possible with established techniques.
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Ito Y, Warner JH, Brown R, Zaka M, Pfeiffer R, Aono T, Izumi N, Okimoto H, Morton JJL, Ardavan A, Shinohara H, Kuzmany H, Peterlik H, Briggs GAD. Controlling intermolecular spin interactions of La@C(82) in empty fullerene matrices. Phys Chem Chem Phys 2010; 12:1618-23. [PMID: 20126778 DOI: 10.1039/b913593f] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ESR properties and crystal structures of solid-state La@C(82) in empty fullerene matrices were investigated by changing the concentration of La@C(82) and the species of an empty fullerene matrix: C(60), C(70), C(78)(C(2v)(3)), C(82)(C(2)) and C(84)(D(2d)(4)). The rotational correlation time of La@C(82) molecules tended to be shorter when La@C(82) is dispersed in larger fullerene matrices because large C(2n) molecules provide more space for La@C(82) molecules for rotating. La@C(82) dispersed in a hcp-C(82) matrix showed the narrowest hyperfine structure (hfs) due to the ordered nature of La@C(82) molecules in the C(82) crystal. On the other hand, in a C(60) matrix, La@C(82) molecules formed clusters because of the large different solubility, which leads to the ESR spectra being broad sloping features due to strong dipole-dipole and exchange interactions.
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Wesenberg JH, Ardavan A, Briggs GAD, Morton JJL, Schoelkopf RJ, Schuster DI, Mølmer K. Quantum computing with an electron spin ensemble. PHYSICAL REVIEW LETTERS 2009; 103:070502. [PMID: 19792625 DOI: 10.1103/physrevlett.103.070502] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Indexed: 05/28/2023]
Abstract
We propose to encode a register of quantum bits in different collective electron spin wave excitations in a solid medium. Coupling to spins is enabled by locating them in the vicinity of a superconducting transmission line cavity, and making use of their strong collective coupling to the quantized radiation field. The transformation between different spin waves is achieved by applying gradient magnetic fields across the sample, while a Cooper pair box, resonant with the cavity field, may be used to carry out one- and two-qubit gate operations.
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Plant SR, Dantelle G, Ito Y, Ng TC, Ardavan A, Shinohara H, Taylor RA, Briggs GAD, Porfyrakis K. Acuminated fluorescence of Er3+ centres in endohedral fullerenes through the incarceration of a carbide cluster. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.05.042] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Jones JA, Karlen SD, Fitzsimons J, Ardavan A, Benjamin SC, Briggs GAD, Morton JJL. Magnetic Field Sensing Beyond the Standard Quantum Limit Using 10-Spin NOON States. Science 2009; 324:1166-8. [DOI: 10.1126/science.1170730] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Plant SR, Ng TC, Warner JH, Dantelle G, Ardavan A, Briggs GAD, Porfyrakis K. A bimetallic endohedral fullerene: PrSc@C80. Chem Commun (Camb) 2009:4082-4. [DOI: 10.1039/b902520k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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48
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Ardavan A, Blundell SJ. Storing quantum information in chemically engineered nanoscale magnets. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b809525f] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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49
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Morton JJL, Tyryshkin AM, Brown RM, Shankar S, Lovett BW, Ardavan A, Schenkel T, Haller EE, Ager JW, Lyon SA. Solid-state quantum memory using the 31P nuclear spin. Nature 2008. [DOI: 10.1038/nature07295] [Citation(s) in RCA: 317] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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50
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Morton JJL, Tiwari A, Dantelle G, Porfyrakis K, Ardavan A, Briggs GAD. Switchable ErSc2N rotor within a C80 fullerene cage: an electron paramagnetic resonance and photoluminescence excitation study. PHYSICAL REVIEW LETTERS 2008; 101:013002. [PMID: 18764109 DOI: 10.1103/physrevlett.101.013002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Indexed: 05/26/2023]
Abstract
Motivated by the possibility of observing photoluminescence and electron paramagnetic resonance from the same species located within a fullerene molecule, we initiated an EPR study of Er3+ in ErSc2N@C80. Two orientations of the ErSc2N rotor within the C80 fullerene are observed in EPR, consistent with earlier studies using photoluminescence excitation (PLE) spectroscopy. For some crystal field orientations, electron spin relaxation is driven by an Orbach process via the first excited electronic state of the 4I(15/2) multiplet. We observe a change in the relative populations of the two ErSc2N configurations upon the application of 532 nm illumination, and are thus able to switch the majority cage symmetry. This photoisomerization, observable by both EPR and PLE, is metastable, lasting many hours at 20 K.
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