117,386 research outputs found
Solid State NMR Spectroscopy: A multiscale "lens" for understanding complex materials
No full textComplexity is an intrinsic feature typical of the most attractive innovative materials in many different research and application fields, as chemistry, optoelectronics, energy, recycling, medicine. Complexity arises from the coexistence of different chemical components, interfaces and phases, as well as from structural disorder and/ or heterogeneity. Complexity often hinders a detailed characterization of advanced materials, which, on the other hand, is crucial for understanding the functional performances and orienting the design and optimization of innovative materials. Solid State NMR spectroscopy (SSNMR) is an extremely powerful technique, which can effectively bridge this gap. Indeed, it can be applied to substantially every kind of soft and hard material and, by exploiting many nuclear probes and properties, it allows structural and dynamic properties to be characterized on very wide spatial (0.1-100 nm) and frequency (Hz-GHz) scales [1]. In this contribution I will show case studies of advanced materials characterized in the ICCOM-CNR/UNIPI joint lab [2], which, with the acquisition within the year of a last generation SSNMR spectrometer, will be the largest Italian laboratory for the study of materials by SSNMR. Hopefully this contribution will further increase the opportunity for the DSCTM community of taking advantage of this technique.
References:
[1] a. M. Geppi, S. Borsacchi, G. Mollica, C. A. Veracini, Appl. Spectr. Rev. 2009, 44, 1; b. M. Geppi, S. Borsacchi, G. Mollica, Encyclopedia of Magnetic Resonance, Wiley 2008.
[2] (a) F. Martini, M. Tonelli, M. Geppi, F. Ridi, S. Borsacchi, L. Calucci, Cem. Concr. Res. 2017, 102, 60; (b) F. Martini, S. Borsacchi, G. Barcaro, M. Caporali, M. Vanni, M. Serrano-Ruiz, M. Geppi, M. Peruzzini, L. Calucci J. Phys. Chem. Lett. 2019, 10, 5122; (c) E. Carignani, S. Borsacchi, P. Blasi, A. Schoubben, M. Geppi Mol. Pharmaceutics 2019, 16, 2569-2578
CAGE: Software for a critical analysis of H-2 spin-lattice relaxation in liquid crystals
No full textA software package of Mathematica, aimed at the analysis of 2H NMR Zeeman (T1Z) and quadrupolar (T1Q) spin-lattice relaxation times in liquid crystals in terms of diffusional models, is presented. The models most commonly used to describe internal, overall, and collective motions in liquid-crystalline phases are considered, and dynamic parameters are obtained by means of either single point or global target approaches using simulation or fitting procedures. The use of the software as a tool for highlighting the problems encountered in this kind of analysis as well as for dealing with such problems following suitable strategies is illustrated by means of applications to experimental 2H relaxation times of three different calamitic liquid crystals
Chemical Implantation of Group 4 Cations on Silica via Cyclopentadienyl- and N,N-Dialkylcarbamato Derivatives
No full textChemical implantation of Group 4 cations [Ti(III), Ti(IV), Zr(IV), Hf(IV)] has been carried out under mild
conditions by the reaction of polycyclopentadienyl- (MCpn; M = Ti, n = 3, 4; M = Zr, Hf, n = 4), mixed
cyclopentadienyl/N,N-dialkylcarbamato (MLx(O2CNEt2)y; M = Ti, L = Cp, C5Me5 (Cp*), x = 2, y = 1; M = Hf,
L = Cp, x = 1, y = 3), and N,N-dialkylcarbamato (M(O2CNR2)n, M = Ti, n = 3, R = iPr; M = Ti, Hf, n = 4,
R = Et; M = Zr, n = 4, R = iPr) derivatives, with the silanol groups of amorphous silica. Cyclopentadiene/
pentamethylcyclopentadiene and/or carbon dioxide and the secondary amine are released in the process.
The amount of implanted cations depends on the metal and on the ligands, the pentamethylcyclopentadienyl
complex being less reactive than the unsubstituted congener. The starting complexes and the final
products have been characterized by EPR or by 13C CP-MAS NMR spectroscopy
Orientational order of liquid crystals by B-11 NMR spectroscopy
No full textThe use of 11B NMR spectroscopy to obtain information on the orientational order of a borinated calamitic liquid crystal (4DBF2) was here shown for the first time. The combination of spectra recorded on a liquid crystalline sample uniformly aligned in the magnetic field, giving access to quadrupolar splittings, with solid state stationary and MAS spectra recorded on a powdered sample, providing the quadrupolar parameters useful for the interpretation of the quadrupolar splittings, can be seen as a self-consisting method of general applicability to liquid crystals containing boron atoms on the molecular core
Water/polymer interactions in poly(amidoamine) hydrogels by 1H nuclear magnetic resonance relaxation and magnetization transfer.
No full textHydrated crosslinked polymers belonging to the family of poly(amidoamine)s were investigated by high and low resoln. 1H NMR techniques in order to obtain information on water/polymer interactions in the swollen state. 1H spin-spin and spin-lattice relaxation time anal., as well as magnetization transfer expts., indicated that water and polymer proton pools are essentially uncoupled, with water mols. diffusing fast within the hydrogel structure and exchanging between "bound" and free sites. For the polymer characterized by the highest crosslinking degree, there is strong evidence of a bead-like structure resulting in higher network rigidity and hydrogel micrometric heterogeneity
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