31 results on '"Gonidec M"'
Search Results
2. Multiscale characterization of spin crossover complexes
- Author
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Penicaud, M., primary, Rosa, P., additional, Gonidec, M., additional, Poggini, L., additional, Squillantini, L., additional, and Carlà, F., additional
- Published
- 2022
- Full Text
- View/download PDF
3. Electric-field control of spin transitions in molecular compounds
- Author
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Utesov, O. I., primary, Burdin, S., additional, Rosa, P., additional, Gonidec, M., additional, Poggini, L., additional, and Andreev, S. V., additional
- Published
- 2019
- Full Text
- View/download PDF
4. A surface confined yttrium(iii) bis-phthalocyaninato complex: a colourful switch controlled by electrons† †Electronic supplementary information (ESI) available: Synthetic details and additional characterisation data. See DOI: 10.1039/c6sc00443a
- Author
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Alcón, I., Gonidec, M., Ajayakumar, M. R., Mas-Torrent, M., and Veciana, J.
- Subjects
Chemistry - Abstract
SAMs of a Y(iii) double-decker complex on ITO have been prepared and their electrical and optical properties explored, exhibiting three accessible stable redox states with characteristic absorption bands in the visible spectra, corresponding to three complementary colors (i.e., green, blue and red)., SAMs of a Y(iii) double-decker complex on ITO have been prepared and their electrical and optical properties explored, exhibiting three accessible stable redox states with characteristic absorption bands in the visible spectra, corresponding to three complementary colors (i.e., green, blue and red). These absorption bands are exploited as output signals of this robust ternary electrochemical switch, behaving hence as an electrochromic molecular-based device.
- Published
- 2016
5. X-ray absorption and magnetic circular dichroism investigation of bis(phthalocyaninato)terbium single-molecule magnets deposited on graphite
- Author
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Biagi, R, Fernandez-Rodriguez, J, Gonidec, M, Mirone, A, Corradini, V, Moro, F, De Renzi, V, Del Pennino, U, Cezar, J, Amabilino, D, Veciana, J, Biagi, R., Fernandez-Rodriguez, J., Gonidec, M., Mirone, A., Corradini, V., Moro, F., De Renzi, V., Del Pennino, U., Cezar, J. C., Amabilino, D. B., Veciana, J., Biagi, R, Fernandez-Rodriguez, J, Gonidec, M, Mirone, A, Corradini, V, Moro, F, De Renzi, V, Del Pennino, U, Cezar, J, Amabilino, D, Veciana, J, Biagi, R., Fernandez-Rodriguez, J., Gonidec, M., Mirone, A., Corradini, V., Moro, F., De Renzi, V., Del Pennino, U., Cezar, J. C., Amabilino, D. B., and Veciana, J.
- Abstract
Bisphthalocyaninato terbium complexes show a long magnetization relaxation time at relatively high temperatures-which makes them very interesting as magnets at single-molecule level. Their technological exploitation, however, requires the addressing of the individual molecules, therefore the deposition of single-molecule magnets on surfaces is a topic of great interest as the interaction with the substrate can play a crucial role in the definition of the molecule properties. In this work we investigate the electronic and magnetic properties of anionic and neutral forms of a bis(phthalocyaninato)terbium derivative deposited on graphite by means of x-ray absorption spectroscopy and x-ray magnetic circular dichroism, performed at low temperature and high magnetic field at the M4,5edge of Tb. We were able to reproduce the experimental spectra by means of multiplet calculations and to validate the applicability of sum rules to the present case. Sum rules were then used for determining the orbital and spin moments of thick (several monolayers) and of thin films (submonolayer range). Calculations of spectra as a function of the molecule orientation with respect to the impinging x-ray beam, allowed us to ascertain the adsorption geometry of molecules. For both compounds, molecules stay essentially flat when adsorbing as thin film on graphite. This result is also confirmed by scanning probe microscopy, which also finds a very interesting ordered arrangement for the molecules of the neutral form. In the thick film of the neutral compound the molecules keep the same orientational order, arranging almost flat as well. On the contrary, in the thick film of the anionic compound their orientation appears to be random. The origin of this different behavior can be related to the hindrance of the counterion moiety and/or to the different solvent used for each compound. Finally, the comparison of the magnetization values and their dependence on the external magnetic field and temperat
- Published
- 2010
6. Surface supramolecular organization of a terbium(III) double-decker complex on graphite and its single molecule magnet behavior
- Author
-
Gonidec, M, Biagi, R, Corradini, V, Moro, F, De Renzi, V, Del Pennino, U, Summa, D, Muccioli, L, Zannoni, C, Amabilino, D, Veciana, J, Gonidec, Mathieu, Biagi, Roberto, Corradini, Valdis, Moro, Fabrizio, De Renzi, Valentina, Del Pennino, Umberto, Summa, Domenico, Muccioli, Luca, Zannoni, Claudio, Amabilino, David B., Veciana, Jaume, Gonidec, M, Biagi, R, Corradini, V, Moro, F, De Renzi, V, Del Pennino, U, Summa, D, Muccioli, L, Zannoni, C, Amabilino, D, Veciana, J, Gonidec, Mathieu, Biagi, Roberto, Corradini, Valdis, Moro, Fabrizio, De Renzi, Valentina, Del Pennino, Umberto, Summa, Domenico, Muccioli, Luca, Zannoni, Claudio, Amabilino, David B., and Veciana, Jaume
- Abstract
The two-dimensional self-assembly of a terbium(III) double-decker phthalocyanine on highly oriented pyrolitic graphite (HOPG) was studied by atomic force microscopy (AFM), and it was shown that it forms highly regular rectangular two-dimensional nanocrystals on the surface, that are aligned with the graphite symmetry axes, in which the molecules are organized in a rectangular lattice as shown by scanning tunneling microscopy. Molecular dynamics simulations were run in order to model the behavior of a collection of the double-decker complexes on HOPG. The results were in excellent agreement with the experiment, showing that-after diffusion on the graphite surface-the molecules self-assemble into nanoscopic islands which align preferentially along the three main graphite axes. These low dimension assemblies of independent magnetic centers are only one molecule thick (as shown by AFM) and are therefore very interesting nanoscopic magnetic objects, in which all of the molecules are in interaction with the graphite substrate and might therefore be affected by it. The magnetic properties of these self-assembled bar-shaped islands on HOPG were studied by X-ray magnetic circular dichroism, confirming that the compounds maintain their properties as single-molecule magnets when they are in close interaction with the graphite surface. © 2011 American Chemical Society
- Published
- 2011
7. X-ray absorption and magnetic circular dichroism investigation of bis(phthalocyaninato)terbium single-molecule magnets deposited on graphite
- Author
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Biagi, R., primary, Fernandez-Rodriguez, J., additional, Gonidec, M., additional, Mirone, A., additional, Corradini, V., additional, Moro, F., additional, De Renzi, V., additional, del Pennino, U., additional, Cezar, J. C., additional, Amabilino, D. B., additional, and Veciana, J., additional
- Published
- 2010
- Full Text
- View/download PDF
8. Surface supramolecular organization of a terbium (III) double-decker complex on graphite and its single molecule magnet behavior
- Author
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Luca Muccioli, Umberto del Pennino, Claudio Zannoni, Jaume Veciana, Valentina De Renzi, Fabrizio Moro, Valdis Corradini, David B. Amabilino, Domenico Summa, Roberto Biagi, Mathieu Gonidec, M. Gonidec, R. Biagi, V. Corradini, F. Moro, V. De Renzi, U. del Pennino, D. Summa, L. Muccioli, C. Zannoni, D. B. Amabilino, J. Veciana, Gonidec, M, Biagi, R, Corradini, V, Moro, F, De Renzi, V, Del Pennino, U, Summa, D, Muccioli, L, Zannoni, C, Amabilino, D, and Veciana, J
- Subjects
PHTHALOCYANINES ,Indoles ,Surface Properties ,single molecule magnet ,terbium ,graphite ,HOPG ,surface ,monolayer ,XMCD ,chemistry.chemical_element ,Terbium ,02 engineering and technology ,GRAPHITE SURFACE ,Isoindoles ,Molecular Dynamics Simulation ,Microscopy, Atomic Force ,010402 general chemistry ,ATOMISTIC SIMULATIONS ,01 natural sciences ,Biochemistry ,Catalysis ,Catalysi ,law.invention ,Magnetics ,Molecular dynamics ,chemistry.chemical_compound ,Condensed Matter::Materials Science ,Colloid and Surface Chemistry ,law ,Monolayer ,Single-molecule magnet ,Graphite ,Nanoscopic scale ,Chemistry (all) ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Crystallography ,chemistry ,Phthalocyanine ,SINGLE MOLECULE MAGNETS ,Scanning tunneling microscope ,0210 nano-technology - Abstract
The two-dimensional self-assembly of a terbium(III) double-decker phthalocyanine on highly oriented pyrolitic graphite (HOPG) was studied by atomic force microscopy (AFM), and it was shown that it forms highly regular rectangular two-dimensional nanocrystals on the surface, that are aligned with the graphite symmetry axes, in which the molecules are organized in a rectangular lattice as shown by scanning tunneling microscopy. Molecular dynamics simulations were run in order to model the behavior of a collection of the double-decker complexes on HOPG. The results were in excellent agreement with the experiment, showing that-after diffusion on the graphite surface-the molecules self-assemble into nanoscopic islands which align preferentially along the three main graphite axes. These low dimension assemblies of independent magnetic centers are only one molecule thick (as shown by AFM) and are therefore very interesting nanoscopic magnetic objects, in which all of the molecules are in interaction with the graphite substrate and might therefore be affected by it. The magnetic properties of these self-assembled bar-shaped islands on HOPG were studied by X-ray magnetic circular dichroism, confirming that the compounds maintain their properties as single-molecule magnets when they are in close interaction with the graphite surface. © 2011 American Chemical Society
- Published
- 2011
- Full Text
- View/download PDF
9. X-ray absorption and magnetic circular dichroism investigation of bis(phthalocyaninato)terbium single-molecule magnets deposited on graphite
- Author
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Alessandro Mirone, J. Fernandez-Rodriguez, Valdis Corradini, Mathieu Gonidec, David B. Amabilino, U. del Pennino, V. De Renzi, Roberto Biagi, Julio C. Cezar, Fabrizio Moro, Jaume Veciana, Biagi, R, Fernandez-Rodriguez, J, Gonidec, M, Mirone, A, Corradini, V, Moro, F, De Renzi, V, Del Pennino, U, Cezar, J, Amabilino, D, and Veciana, J
- Subjects
Materials science ,Absorption spectroscopy ,Magnetic circular dichroism ,terbium ,Electronic, Optical and Magnetic Material ,chemistry.chemical_element ,Terbium ,Condensed Matter Physics ,Molecular physics ,Spectral line ,Electronic, Optical and Magnetic Materials ,Magnetic field ,molecular nanomagnets ,Magnetization ,Nuclear magnetic resonance ,Tb ,chemistry ,single-molecule magnets ,monolayer ,Absorption (chemistry) ,Thin film ,Physics::Chemical Physics - Abstract
Bisphthalocyaninato terbium complexes show a long magnetization relaxation time at relatively high temperatures-which makes them very interesting as magnets at single-molecule level. Their technological exploitation, however, requires the addressing of the individual molecules, therefore the deposition of single-molecule magnets on surfaces is a topic of great interest as the interaction with the substrate can play a crucial role in the definition of the molecule properties. In this work we investigate the electronic and magnetic properties of anionic and neutral forms of a bis(phthalocyaninato)terbium derivative deposited on graphite by means of x-ray absorption spectroscopy and x-ray magnetic circular dichroism, performed at low temperature and high magnetic field at the M4,5edge of Tb. We were able to reproduce the experimental spectra by means of multiplet calculations and to validate the applicability of sum rules to the present case. Sum rules were then used for determining the orbital and spin moments of thick (several monolayers) and of thin films (submonolayer range). Calculations of spectra as a function of the molecule orientation with respect to the impinging x-ray beam, allowed us to ascertain the adsorption geometry of molecules. For both compounds, molecules stay essentially flat when adsorbing as thin film on graphite. This result is also confirmed by scanning probe microscopy, which also finds a very interesting ordered arrangement for the molecules of the neutral form. In the thick film of the neutral compound the molecules keep the same orientational order, arranging almost flat as well. On the contrary, in the thick film of the anionic compound their orientation appears to be random. The origin of this different behavior can be related to the hindrance of the counterion moiety and/or to the different solvent used for each compound. Finally, the comparison of the magnetization values and their dependence on the external magnetic field and temperature suggest that the magnetic properties of molecules are preserved when adsorbed onto the graphite surface. © 2010 The American Physical Society
- Published
- 2010
10. Effect of the heteroatom on the magnetic and luminescence properties of hybrid lanthanide-substituted Keggin-type polyoxometalates.
- Author
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Bustamante-Fernández J, Ruiz-Bilbao E, Rodríguez-Esteban C, Gonidec M, García JA, Lezama L, Gutiérrez-Zorrilla JM, Oyarzabal I, and Artetxe B
- Abstract
Replacement of the heteroatom from Si to Ge has a strong influence on the luminescence properties of a series of hybrid, sandwich-type K
5 [Ln(α-GeW11 O39 )(C20 H22 Br2 N2 O4 )]·14H2 O (1Ge-Ln, Ln = Sm to Lu) anions. Interestingly, the Gd and Yb derivatives retain their ability to display slow relaxation of magnetisation.- Published
- 2024
- Full Text
- View/download PDF
11. On the Electrochemical Growth of a Crystalline p-n Junction From Aqueous Solutions.
- Author
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Felici R, Baroni T, Carlà F, Cioffi N, Di Benedetto F, Fontanesi C, Giaccherini A, Giurlani W, Gonidec M, Lavacchi A, Berretti E, Marcantelli P, Montegrossi G, Bonechi M, Picca RA, Poggini L, Russo F, Sportelli MC, Torsi L, and Innocenti M
- Abstract
Our society largely relies on inorganic semiconductor devices which are, so far, fabricated using expensive and complex processes requiring ultra-high vacuum equipment. Here we report on the possibility of growing a p-n junction taking advantage of electrochemical processes based on the use of aqueous solutions. The growth of the junction has been carried out using the Electrochemical Atomic Layer Deposition (E-ALD) technique, which allowed to sequentially deposit two different semiconductors, CdS and Cu
2 S, on an Ag(111) substrate, in a single procedure. The growth process was monitored in situ by Surface X-Ray Diffraction (SXRD) and resulted in the fabrication of a thin double-layer structure with a high degree of crystallographic order and a well-defined interface. The high-performance electrical characteristics of the device were analysed ex-situ and show the characteristic feature of a diode., (© 2024 Wiley-VCH GmbH.)- Published
- 2024
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12. Size-tunable silicon nanoparticles synthesized in solution via a redox reaction.
- Author
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Parker MA, De Marco ML, Castro-Grijalba A, Ghoridi A, Portehault D, Pechev S, Hillard EA, Lacomme S, Bessière A, Cunin F, Rosa P, Gonidec M, and Drisko GL
- Abstract
A current challenge in silicon chemistry is to perform liquid-phase synthesis of silicon nanoparticles, which would permit the use of colloidal synthesis techniques to control size and shape. Herein we show how silicon nanoparticles were synthesized at ambient temperature and pressure in organic solvents through a redox reaction. Specifically, a hexacoordinated silicon complex, bis( N , N '-diisopropylbutylamidinato)dichlorosilane, was reduced by a silicon Zintl phase, sodium silicide (Na
4 Si4 ). The resulting silicon nanoparticles were crystalline with sizes tuned from a median particle diameter of 15 nm to 45 nm depending on the solvent. Photoluminescence measurements performed on colloidal suspensions of the 45 nm diameter silicon nanoparticles indicated a blue emission signal, attributed to the partial oxidation of the Si nanocrystals or to the presence of nitrogen impurities.- Published
- 2024
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13. High temperature spin crossover behaviour of mononuclear bis-(thiocyanato)iron(II) complexes with judiciously designed bidentate N-donor Schiff bases with varying substituents.
- Author
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Bhar K, Guo W, Gonidec M, Nikhil Raj M V, Bhatt S, Perdih F, Guionneau P, Chastanet G, and Sharma AK
- Abstract
We present herein a family of molecular cis -[Fe
II (X-PPMA)2 (NCS)2 ]·H2 O [4-X- N -(phenyl(pyridin-2-yl)methylene)aniline; X-PPMA; X = -Cl (1), -Br (2), and -CH3 (3)] complexes that exhibit spin crossover behaviour above room temperature. Judiciously designed bidentate N-donor Schiff bases of 2-benzoylpyridine and para -substituted anilines in combination with Fe(NCS)2 were used for the synthesis of complexes 1-3. The relatively strong ligand field of the Schiff bases stabilises the low spin state of iron(II) up to 300 K which is evident from magnetic measurements, room temperature Mössbauer spectra and crystallographic bond/angle distortion parameters. Interestingly, complexes 1-3 crystallize in a tetragonal system with either a P 43 21 2 or P 41 21 2 chiral space group from achiral building units due to the supramolecular helical arrangements of molecules through intermolecular (pyridine)C-H⋯C(NCS) interactions in the crystalline state. Complexes 1 and 2 exhibit complete, gradual and slightly irreversible spin crossover behaviour in the temperature range of 300-500 K with equilibrium temperatures ( T1/2 ) 375 K (1) and 380 K (2). The spin state evolution of iron(II) in complexes 1 and 2 is monitored between 150 K and 450 K through variable temperature crystallographic studies in the warming mode. The structural data are in good agreement with the 94% (1) and 87% (2) high spin conversion of iron(II) at 450 K. At a high temperature (450 K), some minor irreversible ligand motion is noticed in complexes 1 and 2, in addition to a complete solvent loss that may induce the slight irreversibility of the spin crossover. On the other hand, complex 3 shows a complete and gradual spin crossover in the temperature range of 10-475 K with strong irreversible features. The equilibrium temperatures obtained upon first warming ( T1/2 ↑) and second cooling ( T1/2 ↓) are 375 K and 200 K, respectively. In complex 3, the loss of a water molecule triggers strong deviations in the spin crossover behaviour. Moreover, dehydrated complex 3 exhibits photoswitching LIESST effect with a relaxation temperature T(LIESST) = 60 K.- Published
- 2022
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14. Magnetic Ordering in Ultrasmall Potassium Ferrite Nanoparticles Grown on Graphene Nanoflakes.
- Author
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Hof F, Poggini L, Otero E, Gobaut B, Gonidec M, Duttine M, Rosa P, Sandre O, and Pénicaud A
- Abstract
Magnetic nanoparticles are central to the development of efficient hyperthermia treatments, magnetic drug carriers, and multimodal contrast agents. While the magnetic properties of small crystalline iron oxide nanoparticles are well understood, the superparamagnetic size limit constitutes a significant barrier for further size reduction. Iron (oxy)hydroxide phases, albeit very common in the natural world, are far less studied, generally due to their poor crystallinity. Templating ultrasmall nanoparticles on substrates such as graphene is a promising method to prevent aggregation, typically an issue for both material characterization and applications. We generate ultrasmall nanoparticles, directly on the carbon framework by the reaction of a graphenide potassium solution, charged graphene flakes, with iron(II) salts. After mild water oxidation, the obtained composite material consists of ultrasmall potassium ferrite nanoparticles bound to the graphene nanoflakes. Magnetic properties as evidenced by magnetometry and X-ray magnetic circular dichroism, with open magnetic hysteresis loops near room temperature, are widely different from classical ultrasmall superparamagnetic iron oxide nanoparticles. The large value obtained for the effective magnetic anisotropy energy density K
eff accounts for the presence of magnetic ordering at rather high temperatures. The synthesis of ultrasmall potassium ferrite nanoparticles under such mild conditions is remarkable given the harsh conditions used for the classical syntheses of bulk potassium ferrites. Moreover, the potassium incorporation in the crystal lattice occurs in the presence of potassium cations under mild conditions. A transfer of this method to related reactions would be of great interest, which underlines the synthetic value of this study. These findings also give another view on the previously reported electrocatalytic properties of these nanocomposite materials, especially for the sought-after oxygen reduction/evolution reaction. Finally, their longitudinal and transverse proton NMR relaxivities when dispersed in water were assessed at 37 °C under a magnetic field of 1.41 T, allowing potential applications in biological imaging.- Published
- 2022
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15. Space Charge-Limited Current Transport Mechanism in Crossbar Junction Embedding Molecular Spin Crossovers.
- Author
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Cucinotta G, Poggini L, Giaconi N, Cini A, Gonidec M, Atzori M, Berretti E, Lavacchi A, Fittipaldi M, Chumakov AI, Rüffer R, Rosa P, and Mannini M
- Abstract
Spin crossover complexes are among the most studied classes of molecular switches and have attracted considerable attention for their potential technological use as active units in multifunctional devices. A fundamental step toward their practical implementation is the integration in macroscopic devices adopting hybrid vertical architectures. First, the physical properties of technological interest shown by these materials in the bulk phase have to be retained once they are deposited on a solid surface. Herein, we describe the study of a hybrid molecular inorganic junction embedding the spin crossover complex [Fe(qnal)
2 ] (qnal = quinoline-naphthaldehyde) as an active switchable thin film sandwiched within energy-optimized metallic electrodes. In these junctions, developed and characterized with the support of state of the art techniques including synchrotron Mössbauer source (SMS) spectroscopy and focused-ion beam scanning transmission electron microscopy, we observed that the spin state conversion of the Fe(II)-based spin crossover film is associated with a transition from a space charge-limited current (SCLC) transport mechanism with shallow traps to a SCLC mechanism characterized by the presence of an exponential distribution of traps concomitant with the spin transition temperature.- Published
- 2020
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16. Synchrotron-based Mössbauer spectroscopy characterization of sublimated spin crossover molecules.
- Author
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Cini A, Poggini L, Chumakov AI, Rüffer R, Spina G, Wattiaux A, Duttine M, Gonidec M, Fittipaldi M, Rosa P, and Mannini M
- Abstract
The spin crossover (SCO) efficiency of [
57 Fe(bpz)2 (phen)] (where bpz = bis(pyrazol-1-yl)borohydride and phen = 9,10-phenantroline) molecules deposited on gold substrates was investigated by means of synchrotron Mössbauer spectroscopy. The spin transition was driven thermally, or light induced via the LIESST (light induced excited spin-state trapping) effect. Both sets of measurements show that, once deposited on a gold substrate, the efficiency of the SCO mechanism is modified with respect to molecules in the bulk phase. A correlation in the distribution of hyperfine parameters in the sublimated films, not evidenced so far in the bulk phase, is reported. This translates into geometrical distortions of the first coordination sphere of the iron atom that seem to correlate with the decreased spin conversion. The work reported clearly shows the potentiality of synchrotron Mössbauer spectroscopy for the characterization of nanostructured Fe-based SCO systems, thus resulting as a key tool in view of their applications in innovative nanoscale devices.- Published
- 2020
- Full Text
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17. Effect of solvent on silicon nanoparticle formation and size: a mechanistic study.
- Author
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Semlali S, Cormary B, De Marco ML, Majimel J, Saquet A, Coppel Y, Gonidec M, Rosa P, and Drisko GL
- Abstract
Silicon has emerged as the most desirable material for optical dielectric metamaterials, however chemists struggle to obtain the required silicon nanoparticle dimensions. Here the average diameter of silicon nanoparticles is varied between 3 and 15 nm by changing the reaction solvent. Electrochemistry and NMR elucidate the role of solvent on the synthetic mechanism. Surprisingly the solvent does not stabilize the nanoparticles and there is no trend associated with chain length or open-chain versus cyclical solvent molecules. The solvent's main role is to stabilize the by-products, which prolongs the reaction lifetime.
- Published
- 2019
- Full Text
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18. Extreme downsizing in the surfactant-free synthesis of spin-crossover nanoparticles in a microfluidic flow-focusing junction.
- Author
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González-Estefan JH, Gonidec M, Daro N, Marchivie M, and Chastanet G
- Abstract
A new surfactant-free, flow-focusing droplet microfluidic approach was developed as an important alternative to existing synthesis techniques for the preparation of spin crossover nanoparticles. It enables great control of the mixing of the reactants, and produces crystals of [Fe(pyrazine)(Pt(CN)4)] with an unexpected 20-fold downsizing compared to classical bulk synthesis.
- Published
- 2018
- Full Text
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19. Locking and Unlocking the Molecular Spin Crossover Transition.
- Author
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Zhang X, Costa PS, Hooper J, Miller DP, N'Diaye AT, Beniwal S, Jiang X, Yin Y, Rosa P, Routaboul L, Gonidec M, Poggini L, Braunstein P, Doudin B, Xu X, Enders A, Zurek E, and Dowben PA
- Abstract
The Fe(II) spin crossover complex [Fe{H
2 B(pz)2 }2 (bipy)] (pz = pyrazol-1-yl, bipy = 2,2'-bipyridine) can be locked in a largely low-spin-state configuration over a temperature range that includes temperatures well above the thermal spin crossover temperature of 160 K. This locking of the spin state is achieved for nanometer thin films of this complex in two distinct ways: through substrate interactions with dielectric substrates such as SiO2 and Al2 O3 , or in powder samples by mixing with the strongly dipolar zwitterionic p-benzoquinonemonoimine C6 H2 (-⋯ NH2 )2 (-⋯ O)2 . Remarkably, it is found in both cases that incident X-ray fluences then restore the [Fe{H2 B(pz)2 }2 (bipy)] moiety to an electronic state characteristic of the high spin state at temperatures of 200 K to above room temperature; that is, well above the spin crossover transition temperature for the pristine powder, and well above the temperatures characteristic of light- or X-ray-induced excited-spin-state trapping. Heating slightly above room temperature allows the initial locked state to be restored. These findings, supported by theory, show how the spin crossover transition can be manipulated reversibly around room temperature by appropriate design of the electrostatic and chemical environment., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2017
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20. Anomalously Rapid Tunneling: Charge Transport across Self-Assembled Monolayers of Oligo(ethylene glycol).
- Author
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Baghbanzadeh M, Bowers CM, Rappoport D, Żaba T, Yuan L, Kang K, Liao KC, Gonidec M, Rothemund P, Cyganik P, Aspuru-Guzik A, and Whitesides GM
- Abstract
This paper describes charge transport by tunneling across self-assembled monolayers (SAMs) of thiol-terminated derivatives of oligo(ethylene glycol) (HS(CH
2 CH2 O)n CH3 ; HS(EG)n CH3 ); these SAMs are positioned between gold bottom electrodes and Ga2 O3 /EGaIn top electrodes. Comparison of the attenuation factor (β of the simplified Simmons equation) across these SAMs with the corresponding value obtained with length-matched SAMs of oligophenyls (HS(Ph)n H) and n-alkanethiols (HS(CH2 )n H) demonstrates that SAMs of oligo(ethylene glycol) have values of β (β(EG)n = 0.29 ± 0.02 natom -1 and β = 0.24 ± 0.01 Å-1 ) indistinguishable from values for SAMs of oligophenyls (β(Ph)n = 0.28 ± 0.03 Å-1 ), and significantly lower than those of SAMs of n-alkanethiolates (β(CH = 0.94 ± 0.02 n2 )natom -1 and 0.77 ± 0.03 Å-1 ). There are two possible origins for this low value of β. The more probable involves hole tunneling by superexchange, which rationalizes the weak dependence of the rate of charge transport on the length of the molecules of HS(EG)n CH3 using interactions among the high-energy, occupied orbitals associated with the lone-pair electrons on oxygen. Based on this mechanism, SAMs of oligo(ethylene glycol)s are good conductors (by hole tunneling) but good insulators (by electron and/or hole drift conduction). This observation suggests SAMs derived from these or electronically similar molecules are a new class of electronic materials. A second but less probable mechanism for this unexpectedly low value of β for SAMs of S(EG)n CH3 rests on the possibility of disorder in the SAM and a systematic discrepancy between different estimates of the thickness of these SAMs.- Published
- 2017
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21. Fabrication of Nonperiodic Metasurfaces by Microlens Projection Lithography.
- Author
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Gonidec M, Hamedi MM, Nemiroski A, Rubio LM, Torres C, and Whitesides GM
- Abstract
This paper describes a strategy that uses template-directed self-assembly of micrometer-scale microspheres to fabricate arrays of microlenses for projection photolithography of periodic, quasiperiodic, and aperiodic infrared metasurfaces. This method of "template-encoded microlens projection lithography" (TEMPL) enables rapid prototyping of planar, multiscale patterns of similarly shaped structures with critical dimensions down to ∼400 nm. Each of these structures is defined by local projection lithography with a single microsphere acting as a lens. This paper explores the use of TEMPL for the fabrication of a broad range of two-dimensional lattices with varying types of nonperiodic spatial distribution. The matching optical spectra of the fabricated and simulated metasurfaces confirm that TEMPL can produce structures that conform to expected optical behavior.
- Published
- 2016
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22. Charge Tunneling along Short Oligoglycine Chains.
- Author
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Baghbanzadeh M, Bowers CM, Rappoport D, Żaba T, Gonidec M, Al-Sayah MH, Cyganik P, Aspuru-Guzik A, and Whitesides GM
- Abstract
This work examines charge transport (CT) through self-assembled monolayers (SAMs) of oligoglycines having an N-terminal cysteine group that anchors the molecule to a gold substrate, and demonstrate that CT is rapid (relative to SAMs of n-alkanethiolates). Comparisons of rates of charge transport-using junctions with the structure Au(TS)/SAM//Ga2O3/EGaIn (across these SAMs of oligoglycines, and across SAMs of a number of structurally and electronically related molecules) established that rates of charge tunneling along SAMs of oligoglycines are comparable to that along SAMs of oligophenyl groups (of comparable length). The mechanism of tunneling in oligoglycines is compatible with superexchange, and involves interactions among high-energy occupied orbitals in multiple, consecutive amide bonds, which may by separated by one to three methylene groups. This mechanistic conclusion is supported by density functional theory (DFT)., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2015
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23. Combining Step Gradients and Linear Gradients in Density.
- Author
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Kumar AA, Walz JA, Gonidec M, Mace CR, and Whitesides GM
- Subjects
- Chlorides chemistry, Manganese Compounds chemistry, Polyethylene Glycols chemistry, Salts chemistry, Solutions, Sulfates chemistry, Surface-Active Agents chemistry, Thermodynamics, Water chemistry, Magnetic Fields
- Abstract
Combining aqueous multiphase systems (AMPS) and magnetic levitation (MagLev) provides a method to produce hybrid gradients in apparent density. AMPS—solutions of different polymers, salts, or surfactants that spontaneously separate into immiscible but predominantly aqueous phases—offer thermodynamically stable steps in density that can be tuned by the concentration of solutes. MagLev—the levitation of diamagnetic objects in a paramagnetic fluid within a magnetic field gradient—can be arranged to provide a near-linear gradient in effective density where the height of a levitating object above the surface of the magnet corresponds to its density; the strength of the gradient in effective density can be tuned by the choice of paramagnetic salt and its concentrations and by the strength and gradient in the magnetic field. Including paramagnetic salts (e.g., MnSO4 or MnCl2) in AMPS, and placing them in a magnetic field gradient, enables their use as media for MagLev. The potential to create large steps in density with AMPS allows separations of objects across a range of densities. The gradients produced by MagLev provide resolution over a continuous range of densities. By combining these approaches, mixtures of objects with large differences in density can be separated and analyzed simultaneously. Using MagLev to add an effective gradient in density also enables tuning the range of densities captured at an interface of an AMPS by simply changing the position of the container in the magnetic field. Further, by creating AMPS in which phases have different concentrations of paramagnetic ions, the phases can provide different resolutions in density. These results suggest that combining steps in density with gradients in density can enable new classes of separations based on density.
- Published
- 2015
- Full Text
- View/download PDF
24. Looking Inside the Perchlorinated Trityl Radical/Metal Spinterface through Spectroscopy.
- Author
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Mugnaini V, Calzolari A, Ovsyannikov R, Vollmer A, Gonidec M, Alcon I, Veciana J, and Pedio M
- Subjects
- Electron Spin Resonance Spectroscopy, Metals chemistry, Perchlorates chemistry, Trityl Compounds chemistry
- Abstract
We report on a spectroscopic multitechnique approach to study the metal/radical spinterface formed by a perchlorinated trityl radical derivative and either gold or silver. The spectroscopic fingerprint of their paramagnetic properties could be determined by comparison with their diamagnetic precursor and by DFT calculations. Thanks to the presented approach, we could gain unprecedented insight into the radical-metal interaction and how this latter perturbs the spin polarization and consequently the magnetoelectronic properties of the radical adlayer. Knowledge of the factors influencing the spinterface is an essential tool toward the tailoring of the properties of spin-based electronic devices.
- Published
- 2015
- Full Text
- View/download PDF
25. Metal-amplified Density Assays, (MADAs), including a Density-Linked Immunosorbent Assay (DeLISA).
- Author
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Subramaniam AB, Gonidec M, Shapiro ND, Kresse KM, and Whitesides GM
- Subjects
- Animals, Antibodies immunology, Antigen-Antibody Reactions, Humans, Milk chemistry, NADPH Oxidases blood, NADPH Oxidases immunology, Neomycin analysis, Neomycin immunology, Treponema pallidum chemistry, Viral Nonstructural Proteins analysis, Viral Nonstructural Proteins immunology, Gold chemistry, Immunoassay, Immunosorbents chemistry, Metal Nanoparticles chemistry, Silver chemistry
- Abstract
This paper reports the development of Metal-amplified Density Assays, or MADAs - a method of conducting quantitative or multiplexed assays, including immunoassays, by using Magnetic Levitation (MagLev) to measure metal-amplified changes in the density of beads labeled with biomolecules. The binding of target analytes (i.e. proteins, antibodies, antigens) to complementary ligands immobilized on the surface of the beads, followed by a chemical amplification of the binding in a form that results in a change in the density of the beads (achieved by using gold nanoparticle-labeled biomolecules, and electroless deposition of gold or silver), translates analyte binding events into changes in density measureable using MagLev. A minimal model based on diffusion-limited growth of hemispherical nuclei on a surface reproduces the dynamics of the assay. A MADA - when performed with antigens and antibodies - is called a Density-Linked Immunosorbent Assay, or DeLISA. Two immunoassays provided a proof of principle: a competitive quantification of the concentration of neomycin in whole milk, and a multiplexed detection of antibodies against Hepatitis C virus NS3 protein and syphilis T. pallidum p47 protein in serum. MADAs, including DeLISAs, require, besides the requisite biomolecules and amplification reagents, minimal specialized equipment (two permanent magnets, a ruler or a capillary with calibrated length markings) and no electrical power to obtain a quantitative readout of analyte concentration. With further development, the method may be useful in resource-limited or point-of-care settings.
- Published
- 2015
- Full Text
- View/download PDF
26. Engineering shadows to fabricate optical metasurfaces.
- Author
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Nemiroski A, Gonidec M, Fox JM, Jean-Remy P, Turnage E, and Whitesides GM
- Subjects
- Colloids, Crystallization, Nanotechnology, Surface Properties, Optics and Photonics
- Abstract
Optical metasurfaces-patterned arrays of plasmonic nanoantennas that enable the precise manipulation of light-matter interactions-are emerging as critical components in many nanophotonic materials, including planar metamaterials, chemical and biological sensors, and photovoltaics. The development of these materials has been slowed by the difficulty of efficiently fabricating patterns with the required combinations of intricate nanoscale structure, high areal density, and/or heterogeneous composition. One convenient strategy that enables parallel fabrication of periodic nanopatterns uses self-assembled colloidal monolayers as shadow masks; this method has, however, not been extended beyond a small set of simple patterns and, thus, has remained incompatible with the broad design requirements of metasurfaces. This paper demonstrates a technique-shadow-sphere lithography (SSL)-that uses sequential deposition from multiple angles through plasma-etched microspheres to expand the variety and complexity of structures accessible by colloidal masks. SSL harnesses the entire, relatively unexplored, space of shadow-derived shapes and-with custom software to guide multiangled deposition-contains sufficient degrees of freedom to (i) design and fabricate a wide variety of metasurfaces that incorporate complex structures with small feature sizes and multiple materials and (ii) generate, in parallel, thousands of variations of structures for high-throughput screening of new patterns that may yield unexpected optical spectra. This generalized approach to engineering shadows of spheres provides a new strategy for efficient prototyping and discovery of periodic metasurfaces.
- Published
- 2014
- Full Text
- View/download PDF
27. Highly reduced double-decker single-molecule magnets exhibiting slow magnetic relaxation.
- Author
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Gonidec M, Krivokapic I, Vidal-Gancedo J, Davies ES, McMaster J, Gorun SM, and Veciana J
- Subjects
- Electrochemical Techniques, Isoindoles, Magnetic Phenomena, Models, Molecular, Oxidation-Reduction, Indoles chemistry, Lanthanoid Series Elements chemistry, Magnets chemistry
- Abstract
F64Pc2Ln (1Ln, Ln = Tb or Lu) represent the first halogenated phthalocyanine double-decker lanthanide complexes, and 1Tb exhibits single-molecule magnet properties as revealed by solid-state magnetometry. The fluorine substituents of the phthalocyanine rings have a dramatic effect on the redox properties of the F64Pc2Ln complexes, namely, a stabilization of their reduced states. Electrochemical and spectroelectrochemical measurements demonstrate that the 1Tb(-/2-) and 1Tb(2-/3-) couples exhibit redox reversibility and that the 1Tb(-), 1Tb(2-) and 1Tb(3-) species may be prepared by bulk electrolysis in acetone. Low-temperature MCD studies reveal for the first time magnetization hystereses for the super-reduced dianionic and trianionic states of Pc2Ln.
- Published
- 2013
- Full Text
- View/download PDF
28. Novel double-decker phthalocyaninato terbium(III) single molecule magnets with stabilised redox states.
- Author
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Gonidec M, Amabilino DB, and Veciana J
- Subjects
- Coordination Complexes chemical synthesis, Coordination Complexes chemistry, Electrochemical Techniques, Ions chemistry, Isoindoles, Oxidation-Reduction, Spectrophotometry, Ultraviolet, Indoles chemistry, Magnets, Terbium chemistry
- Abstract
Double-decker phthalocyanine lanthanide complexes are single molecule magnets (SMMs) presenting a thermally activated magnetic relaxation with relatively high effective barriers. For this reason they are potential candidates as components for data storage and spintronic devices. One of the disadvantages of these compounds is their redox instability: they are oxidized or reduced in the presence of mild oxidizing and reducing agents. To solve this issue, we designed, prepared and characterized new double-decker phthalocyanine based SMMs bearing electron withdrawing groups and therefore presenting an increased redox stability. In the present article, the synthesis and characterization of these novel compounds is presented and we demonstrate how the magnetic behavior of the complexes is virtually identical to that of the parent unsubstituted compounds.
- Published
- 2012
- Full Text
- View/download PDF
29. Surface supramolecular organization of a terbium(III) double-decker complex on graphite and its single molecule magnet behavior.
- Author
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Gonidec M, Biagi R, Corradini V, Moro F, De Renzi V, del Pennino U, Summa D, Muccioli L, Zannoni C, Amabilino DB, and Veciana J
- Subjects
- Isoindoles, Magnetics, Microscopy, Atomic Force, Molecular Dynamics Simulation, Surface Properties, Graphite chemistry, Indoles chemistry, Terbium chemistry
- Abstract
The two-dimensional self-assembly of a terbium(III) double-decker phthalocyanine on highly oriented pyrolitic graphite (HOPG) was studied by atomic force microscopy (AFM), and it was shown that it forms highly regular rectangular two-dimensional nanocrystals on the surface, that are aligned with the graphite symmetry axes, in which the molecules are organized in a rectangular lattice as shown by scanning tunneling microscopy. Molecular dynamics simulations were run in order to model the behavior of a collection of the double-decker complexes on HOPG. The results were in excellent agreement with the experiment, showing that-after diffusion on the graphite surface-the molecules self-assemble into nanoscopic islands which align preferentially along the three main graphite axes. These low dimension assemblies of independent magnetic centers are only one molecule thick (as shown by AFM) and are therefore very interesting nanoscopic magnetic objects, in which all of the molecules are in interaction with the graphite substrate and might therefore be affected by it. The magnetic properties of these self-assembled bar-shaped islands on HOPG were studied by X-ray magnetic circular dichroism, confirming that the compounds maintain their properties as single-molecule magnets when they are in close interaction with the graphite surface., (© 2011 American Chemical Society)
- Published
- 2011
- Full Text
- View/download PDF
30. A liquid-crystalline single-molecule magnet with variable magnetic properties.
- Author
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Gonidec M, Luis F, Vílchez A, Esquena J, Amabilino DB, and Veciana J
- Subjects
- Calorimetry, Differential Scanning, Indoles chemistry, Isoindoles, Ligands, Organometallic Compounds chemistry, Liquid Crystals chemistry, Magnetics, Organometallic Compounds chemical synthesis, Terbium chemistry
- Published
- 2010
- Full Text
- View/download PDF
31. Probing the magnetic properties of three interconvertible redox states of a single-molecule magnet with magnetic circular dichroism spectroscopy.
- Author
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Gonidec M, Davies ES, McMaster J, Amabilino DB, and Veciana J
- Subjects
- Circular Dichroism, Electrochemistry, Organometallic Compounds chemistry, Oxidation-Reduction, Spectrophotometry, Ultraviolet, Temperature, Magnetics
- Abstract
The hysteresis of magnetization of the anionic, neutral, and cationic forms of a bis(phthalocyaninato)terbium-based complex ([Pc(2)Tb](-/0/+)) have been determined using magnetic circular dichroism (MCD) spectroscopy in frozen dilute solutions at low temperatures (1.5 K) showing that the three oxidation states of the complex exhibit single-molecule magnetic behaviors.
- Published
- 2010
- Full Text
- View/download PDF
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