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Grizzle A, D'Angelo C, Martínez-Lillo J, Tyagi P. Spin state of a single-molecule magnet (SMM) creating long-range ordering on ferromagnetic layers of a magnetic tunnel junction - a Monte Carlo study. RSC Adv 2021; 11:32275-32285. [PMID: 35495500 PMCID: PMC9042143 DOI: 10.1039/d1ra05473b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 09/23/2021] [Indexed: 11/21/2022] Open
Abstract
Paramagnetic single-molecule magnets (SMMs) interacting with the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) produce a new system. The properties and future scope of new systems differ dramatically from the properties of isolated molecules and ferromagnets. However, it is unknown how far deep in the ferromagnetic electrode the impact of the paramagnetic molecule and ferromagnet interactions can travel for various levels of molecular spin states. Our prior experimental studies showed two types of paramagnetic SMMs, the hexanuclear Mn6 and octanuclear Fe–Ni molecular complexes, covalently bonded to ferromagnets produced unprecedented strong antiferromagnetic coupling between two ferromagnets at room temperature leading to a number of intriguing observations (P. Tyagi, et al., Org. Electron., 2019, 64, 188–194. P. Tyagi, et al., RSC Adv., 2020, 10, (22), 13006–13015). This paper reports a Monte Carlo Simulations (MCS) study focusing on the impact of the molecular spin state on a cross junction shaped MTJ based molecular spintronics device (MTJMSD). Our MCS study focused on the Heisenberg model of MTJMSD and investigated the impact of various molecular coupling strengths, thermal energy, and molecular spin states. To gauge the impact of the molecular spin state on the region of ferromagnetic electrodes, we examined the spatial distribution of molecule-ferromagnet correlated phases. Our MCS study shows that under a strong coupling regime, the molecular spin state should be ∼30% of the ferromagnetic electrode's atomic spins to create long-range correlated phases. Paramagnetic single-molecule magnets (SMMs) interacting with the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) produce new molecular spintronics testbed and highly ordered magnetic metamaterial promising for room temperature.![]()
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Affiliation(s)
- Andrew Grizzle
- Center for Nanotechnology Research and Education, Mechanical Engineering, University of the District of Columbia Washington DC-20008 USA
| | - Christopher D'Angelo
- Center for Nanotechnology Research and Education, Mechanical Engineering, University of the District of Columbia Washington DC-20008 USA
| | - José Martínez-Lillo
- Instituto de Ciencia Molecular (ICMol), Universitat de València c/ Catedrático José Beltrán 2 Paterna València 46980 Spain
| | - Pawan Tyagi
- Center for Nanotechnology Research and Education, Mechanical Engineering, University of the District of Columbia Washington DC-20008 USA
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2
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Machado M, Silva GA, Bitoque DB, Ferreira J, Pinto LA, Morgado J, Ferreira Q. Self-Assembled Multilayer Films for Time-Controlled Ocular Drug Delivery. ACS APPLIED BIO MATERIALS 2019; 2:4173-4180. [PMID: 35021432 DOI: 10.1021/acsabm.9b00417] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The patient's compliance on the therapeutics to treat glaucoma is significantly low contributing for a fast evolution of the disease. This article presents an autonomous system with controlled release using an alpha2-adrenergic receptor agonist, brimonidine, usually used to treat glaucoma. More specifically, biocompatible and layer-by-layer drug delivery films containing monolayers with brimonidine encapsulated in polymer-β-cyclodextrin were prepared with the objective to obtain a system able to release precise amounts of drug at specific times. To delay the erosion-controlled drug release, we included nanosheets of graphene oxide and layers of a biodegradable polymer (poly-β-aminoester) between the drug-containing monolayers to obtain a time-controlled drug delivery system. An increase in the number of graphene oxide layers is proportional to the brimonidine release delay and its kinetic release can be tuned as a function of the number of layers. Two types of films with brimonidine encapsulated in β-cyclodextrin were analyzed. One of them composed of barrier layers with PBAE and another with two types of barrier layers, PBAE and graphene oxide. The results indicate that one graphene oxide bilayer can delay the brimonidine release for more than 24 h. In vitro assays confirmed that the films have a cell viability of 100%.
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Affiliation(s)
- Mónica Machado
- Instituto de Telecomunicações, Avenida Rovisco Pais, Lisbon 1049-001, Portugal
| | - Gabriela A Silva
- CEDOC Chronic Diseases Research Centre, NOVA Medical School, Universidade Nova de Lisboa, Campo Mártires da Pátria 130, Lisboa 1169-056, Portugal.,NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon 1169-056, Portugal
| | - Diogo B Bitoque
- CEDOC Chronic Diseases Research Centre, NOVA Medical School, Universidade Nova de Lisboa, Campo Mártires da Pátria 130, Lisboa 1169-056, Portugal
| | - Joana Ferreira
- Ophthalmology Department, Centro Hospitalar Universitário de Lisboa Central, Lisbon 1169-050, Portugal.,NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisbon 1169-056, Portugal
| | - Luís A Pinto
- Ophthalmology Department, Centro Hospitalar Universitário de Lisboa Norte, Lisbon 1649-035, Portugal.,Visual Sciences Study Centre, Faculty of Medicine, Universidade de Lisboa, Lisbon 1649-028, Portugal
| | - Jorge Morgado
- Instituto de Telecomunicações, Avenida Rovisco Pais, Lisbon 1049-001, Portugal.,Bioengineering Department, Instituto Superior Técnico, Universidade de Lisboa, Avenida Rovisco Pais, Lisbon 1049-001, Portugal
| | - Quirina Ferreira
- Instituto de Telecomunicações, Avenida Rovisco Pais, Lisbon 1049-001, Portugal
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Bu D, Xiong Y, Tan YN, Meng M, Liu CY. Control of the rectifying effect and direction by redox asymmetry in Rh 2-based molecular diodes. Chem Commun (Camb) 2018; 54:3632-3635. [PMID: 29577160 DOI: 10.1039/c8cc02062k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Four asymmetrical self-assembled monolayers (SAMs) consisting of two subunits with different Rh2 building blocks present a pronounced rectifying behavior. The rectification ratio (RR) increases on increasing the redox potential difference between the two Rh2 subunits, and the rectifying direction can be reversed by reordering the subunits in the assembly.
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Affiliation(s)
- Donglei Bu
- Department of Chemistry, Jinan University, 601 Huang-Pu Avenue West, Guangzhou 510632, China.
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Hemoglobin-mimetic oxygen adsorbent prepared via self-assembly of cysteinyl bolaamphiphiles. Colloids Surf B Biointerfaces 2016; 142:360-366. [DOI: 10.1016/j.colsurfb.2016.03.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 01/30/2016] [Accepted: 03/03/2016] [Indexed: 01/28/2023]
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Berritta M, Manrique DZ, Lambert CJ. Interplay between quantum interference and conformational fluctuations in single-molecule break junctions. NANOSCALE 2015; 7:1096-1101. [PMID: 25479372 DOI: 10.1039/c4nr05316h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We theoretically explored the combined role of conformational fluctuations and quantum interference in determining the electrical conductance of single-molecule break junctions. In particular we computed the conductance of a family of methylsulfide-functionalized trans-α,ω-diphenyloligoene molecules, with terminal phenyl rings containing meta or para linkages, for which (at least in the absence of fluctuations) destructive interference in the former is expected to decrease their electrical conductance compared with the latter. We compared the predictions of density functional theory (DFT), in which fluctuational effects are absent, with results for the conformationally-averaged conductance obtained from an ensemble of conformations obtained from classical molecular dynamics. We found that junctions formed from these molecules exhibit distinct transport regimes during junction evolution and the signatures of quantum interference in these molecules survive the effect of conformational fluctuations. Furthermore, the agreement between theory and experiment is significantly improved by including conformational averaging.
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Affiliation(s)
- Marco Berritta
- Department of Physics and Astronomy, Uppsala University, Box 516, S-75120 Uppsala, Sweden
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Ferreira Q, Alcácer L, Morgado J. Stepwise preparation and characterization of molecular wires made of zinc octaethylporphyrin complexes bridged by 4,4'-bipyridine on HOPG. NANOTECHNOLOGY 2011; 22:435604. [PMID: 21971409 DOI: 10.1088/0957-4484/22/43/435604] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Molecular-scale devices can be made using a step-by-step procedure, in a controllable and highly versatile way. In this report, we describe the growth of molecular wires (MW) from zinc (II) octaethylporphyrin (ZnOEP) assembled on highly oriented pyrolytic graphite (HOPG) by a step-by-step approach using 4,4'-bipyridine (BP) to bridge the porphyrin units, via coordination of the nitrogen atom to zinc. In order to gain an insight into the molecular self-organization of these wires, we carried out a detailed scanning tunnelling microscopy (STM) analysis of each monolayer, using a solid/liquid interface technique, up to a complete ZnOEP/BP/ZnOEP/BP/ZnOEP-assembled structure. The electrical properties of the MWs were assessed by scanning tunnelling spectroscopy (STS) and by current-sensing atomic force microscopy (CS-AFM), showing an increase of electrical resistance with the length of the MW.
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Affiliation(s)
- Quirina Ferreira
- Instituto de Telecomunicações, Instituto Superior Técnico, Avenida Rovisco Pais, P-1049-001 Lisboa, Portugal.
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Ashwell GJ, Phillips LJ, Robinson BJ, Barnes SA, Williams AT, Urasinska-Wojcik B, Lambert CJ, Grace IM, Cox TI, Sage IC. Synthesis of Covalently Linked Molecular Bridges between Silicon Electrodes in CMOS-Based Arrays of Vertical Si/SiO2/Si Nanogaps. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201102791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Ashwell GJ, Phillips LJ, Robinson BJ, Barnes SA, Williams AT, Urasinska-Wojcik B, Lambert CJ, Grace IM, Cox TI, Sage IC. Synthesis of Covalently Linked Molecular Bridges between Silicon Electrodes in CMOS-Based Arrays of Vertical Si/SiO2/Si Nanogaps. Angew Chem Int Ed Engl 2011; 50:8722-6. [DOI: 10.1002/anie.201102791] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 05/24/2011] [Indexed: 11/06/2022]
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Ballesteros LM, Martín S, Pera G, Schauer PA, Kay NJ, López MC, Low PJ, Nichols RJ, Cea P. Directionally oriented LB films of an OPE derivative: assembly, characterization, and electrical properties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:3600-3610. [PMID: 21370920 DOI: 10.1021/la104734j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Langmuir films have been fabricated from 4-[4'-(4''-thioacetyl-phenyleneethynylene)-phenyleneethynylene]-aniline (NOPES) after cleavage of the thioacetyl protecting group. Characterization by surface pressure vs area per molecule isotherms and Brewster angle microscopy reveal the formation of a high quality monolayer at the air-water interface. One layer Langmuir-Blodgett (LB) films were readily fabricated by the transfer of the NOPES Langmuir film onto solid substrates. X-ray photoelectron spectroscopy (XPS), surface polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and quartz crystal microbalance (QCM) experiments conclusively demonstrate the formation of one layer LB films in which the functional group associated with binding to the substrate can be tailored by the film transfer conditions. Using LB methods this molecule could be transferred to gold samples with either the amine or thiol group attached to the gold surface. The amine group is directly attached to the gold substrate (Au-NH(2)-OPE-SH) when the substrate is initially immersed in the subphase and withdrawn during the transfer process; in contrast, monomolecular films in which the thiolate group is attached to the gold substrate (Au-S-OPE-NH(2)) are obtained when the substrate is initially out of the subphase and immersed during the transfer process. The morphology of these films was analyzed by atomic force microscopy (AFM), showing the formation of homogeneous layers. Film homogeneity was confirmed by cyclic voltammetry, which revealed a large passivation of gold electrodes covered by NOPES monolayers. Electrical properties for both polar orientated junctions have been investigated by scanning tunnelling microscopy (STM), with both orientations featuring a nonrectifying behavior.
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Affiliation(s)
- Luz M Ballesteros
- Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009 Spain
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Ashwell GJ, Phillips LJ, Robinson BJ, Urasinska-Wojcik B, Lambert CJ, Grace IM, Bryce MR, Jitchati R, Tavasli M, Cox TI, Sage IC, Tuffin RP, Ray S. Molecular bridging of silicon nanogaps. ACS NANO 2010; 4:7401-7406. [PMID: 21082817 DOI: 10.1021/nn102460z] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The highly doped electrodes of a vertical silicon nanogap device have been bridged by a 5.85 nm long molecular wire, which was synthesized in situ by grafting 4-ethynylbenzaldehyde via C-Si links to the top and bottom electrodes and thereafter by coupling an amino-terminated fluorene unit to the aldehyde groups of the activated electrode surfaces. The number of bridging molecules is constrained by relying on surface roughness to match the 5.85 nm length with an electrode gap that is nominally 1 nm wider and may be controlled by varying the reaction time: the device current increases from ≤1 pA at 1 V following the initial grafting step to 10-100 nA at 1 V when reacted for 5-15 min with the amino-terminated linker and 10 μA when reacted for 16-53 h. It is the first time that both ends of a molecular wire have been directly grafted to silicon electrodes, and these molecule-induced changes are reversible. The bridges detach when the device is rinsed with dilute acid solution, which breaks the imine links of the in situ formed wire and causes the current to revert to the subpicoampere leakage value of the 4-ethynylbenzaldehyde-grafted nanogap structure.
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In Situ Stepwise Synthesis of Functional Multijunction Molecular Wires on Gold Electrodes and Gold Nanoparticles. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200906607] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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13
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Ashwell G, Urasinska-Wojcik B, Phillips L. In Situ Stepwise Synthesis of Functional Multijunction Molecular Wires on Gold Electrodes and Gold Nanoparticles. Angew Chem Int Ed Engl 2010; 49:3508-12. [DOI: 10.1002/anie.200906607] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Loscutoff PW, Zhou H, Clendenning SB, Bent SF. Formation of organic nanoscale laminates and blends by molecular layer deposition. ACS NANO 2010; 4:331-41. [PMID: 20000603 DOI: 10.1021/nn901013r] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Nanoscale organic films are important for many applications. We report on a system of molecular layer deposition that allows for the deposition of conformal organic films with thickness and composition control at the subnanometer length scale. Nanoscale polyurea films are grown on silica substrates in a layer-by-layer fashion by dosing 1,4-phenylene diisocyanate (PDIC) and ethylenediamine (ED) in the gas phase. Ellipsometry measurements indicate that the film growth occurs at a constant growth rate, with film thicknesses consistent with molecular distances calculated using density functional theory. Characterization of the films by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy reveals formation of stable polyurea films with nearly stoichiometric composition, and transmission electron microscopy indicates that the films uniformly coat the substrate surface. Subnanometer control over the film composition was demonstrated using 2,2'-thiobis(ethylamine) (TBEA) as an alternate diamine to vary the composition of the films. By substituting TBEA for ED, blended films, with homogeneous composition through the film, and nanolaminates, with discrete layers of differing film chemistry, were created.
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Affiliation(s)
- Paul W Loscutoff
- Department of Chemical Engineering, Stanford University, Hillsboro, Oregon, USA
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