A luminescent supramolecular assembly composed of a single-walled carbon nanotube and a molecular magnet precursor (original) (raw)
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Magnetic Properties of 1D Iron–Sulfur Compounds Formed Inside Single‐Walled Carbon Nanotubes
physica status solidi (RRL) – Rapid Research Letters, 2020
In this work, we perform the filling of single-walled carbon nanotubes (SWCNTs) with sulfur and study the magnetic properties of the formed nanomaterials. Encapsulation of sulfur species results in the appearance of a specific magnetic ordering in the system due to the formation of nanoscopic grains composed of sulfur and residual catalytic Fe nanoparticles contained in the SWCNTs. We study the magnetic character of the obtained 1D nanostructures using SQUID magnetometer and reveal a sequential ferromagnetic-antiferromagnetic ordering in the material. Magnetic and optical properties are strongly dependent on the synthesis protocols. We obtain a significant Raman intensity increase related to the encapsulated nanostructures when filling is performed at high-pressure high-temperature conditions. Simultaneously, the magnetic susceptibility gets strongly reduced for high-pressure filling which is related to the escape of iron particles from the nanotube interior, and the magnetic properties of the material are governed by a weak ferromagnetic ordering of Fe-S structures remained inside SWCNTs. Sulfur encapsulation provides the new route for controlling the magnetic properties in 1D nanomaterials that pave the way for advanced magnetooptical applications. Text Carbon-encapsulated magnetic nanoparticles are very prospective in the context of biomedical applications [ 1 ], memory devices [ 2 ], and magnetic sensors [ 3 ]. Single-walled carbon nanotubes (SWCNTs) stand out among other different protective materials. They not only serve as a template for nano-dimensional growth [ 4 ] and promote interactions between the encapsulated species, but also can influence the properties of the formed host-guest structures [ 5,6,7 ]. Indeed, the SWCNT ensures a fine dispersion of magnetic species along the longitudinal axis thus restricting the magnetic coupling between them and thereby enhancing the inherent properties of nanoparticles [ 8-11 ]. A reduction of intermolecular dipole-dipole interactions between the neighboring encapsulated molecules leading to enhanced magnetic properties was recently demonstrated for single-molecule magnets [ 12 ]. 1D arrangement of single-molecule magnets provides the suppression
Anchoring of Rare-Earth-Based Single-Molecule Magnets on Single-Walled Carbon Nanotubes
Journal of the American Chemical Society, 2009
A new heteroleptic bis(phthalocyaninato) terbium(III) complex 1, bearing a pyrenyl group, exhibits temperature and frequency dependence of ac magnetic susceptibility, typical of single-molecule magnets. The complex was successfully attached to single-walled carbon nanotubes (SWNTs) using π-π interactions, yielding a 1-SWNT conjugate. The supramolecular grafting of 1 to SWNTs was proven qualitatively and quantitatively by high-resolution transmission electron microscopy, emission spectroscopy, and atomic force spectroscopy. Giving a clear magnetic fingerprint, the anisotropy energy barrier and the magnetic relaxation time of the 1-SWNT conjugate are both increased in comparison with the pure crystalline compound 1, likely due to the suppression of intermolecular interactions. The obtained results propose the 1-SWNT conjugate as a promising constituent unit in magnetic single-molecule measurements using molecular spintronics devices.
International Journal of Molecular Sciences, 2011
We built new hybrid devices consisting of chemical vapor deposition (CVD) grown carbon nanotube (CNT) transistors, decorated with TbPc 2 (Pc = phthalocyanine) rare-earth based single-molecule magnets (SMMs). The drafting was achieved by tailoring supramolecular π-π interactions between CNTs and SMMs. The magnetoresistance hysteresis loop measurements revealed steep steps, which we can relate to the magnetization reversal of individual SMMs. Indeed, we established that the electronic transport properties of these devices depend strongly on the relative magnetization orientations of the grafted SMMs. The SMMs are playing the role of localized spin polarizer and analyzer on the CNT electronic conducting channel. As a result, we measured magneto-resistance ratios up to several hundred percent. We used this spin valve effect to confirm the strong uniaxial anisotropy and the superparamagnetic blocking temperature (T B ~ 1 K) of isolated TbPc 2 SMMs. For the first time, the strength of exchange interaction between the different SMMs of the molecular spin valve geometry could be determined.
2004
The discovery that individual molecules can function as magnets provided a new, “bottom-up” approach to nanoscale magnetic materials, and such molecules have since been called single-molecule magnets (SMMs). Each molecule is a single-domain magnetic particle that, below its blocking temperature, exhibits the classical macroscale property of a magnet, namely magnetization hysteresis. In addition, SMMs straddle the classical/quantum interface in also displaying quantum tunneling of magnetization (QTM) and quantum phase interference, which are the properties of the microscale. SMMs have various potential applications, including very high-density information storage with each bit stored as the magnetization orientation of an individual molecule, and as quantum bits for quantum computing by taking advantage of the quantum superposition of states provided by the QTM. For a number of reasons, including facilitating development of techniques for addressing individual SMMs, we have sought to...
Magnetism of Covalently Functionalized Carbon Nanotubes
2011
We investigate the electronic structure of carbon nanotubes functionalized by adsorbates anchored with single C-C covalent bonds. We find that, despite the particular adsorbate, a spin moment with a universal value of 1.0 muB\mu_BmuB per molecule is induced at low coverage. Therefore, we propose a mechanism of bonding-induced magnetism at the carbon surface. The adsorption of a single molecule creates a dispersionless defect state at the Fermi energy, which is mainly localized in the carbon wall and presents a small contribution from the adsorbate. This universal spin moment is fairly independent of the coverage as long as all the molecules occupy the same graphenic sublattice. The magnetic coupling between adsorbates is also studied and reveals a key dependence on the graphenic sublattice adsorption site.
Magneto-optical studies of single-wall carbon nanotubes
Physical Review B, 2007
We report a detailed study of the magnetophotoluminescence of single-wall carbon nanotubes at various temperatures in fields up to 58 T. We give direct experimental evidence of the diameter dependence of the Aharanov-Bohm phase-induced band gap shifts. Large increases in intensity are produced by the magnetic field at low temperatures which are also significantly chiral index ͓͑n , m͔͒ dependent. These increases are attributed to the magnetic field induced mixing of the wave functions of the exciton states. A study of the emission from nanotubes aligned perpendicular to the applied magnetic field shows even larger field-induced photoluminescence intensity enhancements and unexpectedly large redshifts in band gap energies, not predicted theoretically.
physica status solidi (b), 2012
Spin resonance, magnetic measurements, and structural analysis are reported for metal-semiconductor separated SWCNTs after filling with ferrocene. Raman scattering performed after a heat treatment confirms partial transformation to double-walled CNTs but results from spin resonance (FMR), X-ray diffraction, and TEM evidence in addition the growth of ferromagnetic nanoparticles. For the metallic tubes the particles are identified as magnetite (Fe 3 O 4 ) with full chemical stoichiometry. From the temperature dependence of the FMR response and from measurements of the magnetization by dc and ac SQUID the magnetite crystals are shown to undergo a Verwey transition. The transition temperature from the SQUID experiment is around 125 K as expected but considerably higher than observed from the FMR analysis. Results for semiconducting tubes are similar but magnetic particles are an order of magnitude smaller and exhibit different structures in addition to magnetite.