- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Cr3+ Doped Al2O3 Obtained by Non-Hydrolytic Sol-Gel Methodology
摘要： This paper reports the synthesis and characterization of Cr3+-doped alumina by the sol-gel non-hydrolytic methodology. The resulting sample was treated at different temperatures. X-ray diffraction revealed that the ruby phase emerged in the sample treated at 1100 oC, which was later confirmed by absorption bands correspondent to Cr3+ ions allowed transitions at 4A2 → 4T1, 4T2, and forbidden at 4A2 → 2T1, 2E, observed by diffuse reflectance UV-Vis. The luminescence spectroscopy showed the intensity band at 694 nm in red region, characterized of the Cr3+ ion. The peaks at 702 and 705 nm correspond to N1 and N2 lines, respectively, which arose from the second and fourth nearest-neighbor exchange-coupled pairs of chromium(III) ion, respectively, ascribed to high chromium(III) concentration. The Cr3+ cluster formation was observed in electron paramagnetic resonance signal as discussed in this work. Nuclear magnetic resonance evidenced that the 27Al symmetry changed in the samples treated between 900 and 1100 oC.
关键词： EPR,NMR,sol-gel,luminescence,ruby
更新于2025-09-09 09:28:46
-
X-Ray, IR, NMR, UV-visible spectra and DFT analysis of 5-aryloxy-(1H)-tetrazoles, structure, conformation and tautomerism
摘要： The predominant tautomeric forms of N1–H, N2–H of 5-(2,6-dimethyl- and 5-(2,6-diisopropylphenoxy)-(1H)-tetrazoles were analyzed at B3LYP method using 6-311G(d,p) basis set in the gas phase. The N1–H form of tetrazoles was found to be more stable than N2–H form in both solid and gas phases. Crystal structures of both tetrazoles show an intermolecular H-bond between N1-H and N4 atom of other tetrazole space. The hydrogen bonds between each tautomer of tetrazoles were evaluated at B3LYP/6-311G(d,p) level. The geometrical parameters and spectral data of tetrazoles and their variation were studied in both solid and gas phases.
关键词： 5-(2,6-Diisopropylphenoxy)-(1H)-tetrazole,DFT,NMR,X-ray,H-bond,Rotation barrier
更新于2025-09-09 09:28:46
-
Structure and Permeability of Porous Silicon Investigated by Self-Diffusion NMR Measurements of Ethanol and Heptane
摘要： The adsorption and phase transitions of con?ned ?uids in nanoporous materials have been studied intensely because of both their fundamental interest and their crucial role in many technologies. Questions relating to the in?uence of the con?nement of ?uids, and the disorder or elastic deformation of porous solids on the liquid-gas phase transition are still under debate. Model systems are needed to understand the adsorption phenomenon. In this context, Porous Silicon (PoSi), which is a single crystal obtained by etching a (100) silicon wafer is an excellent candidate. Indeed, it consists of non-connected tubular pores running parallel to the [100] axis perpendicular to the wafer surface, with transverse sections with a polygonal shape of nanometric size whose areas are widely distributed. Once detached from the wafer, free PoSi membranes can be considered a nanoscale disordered honeycomb. Adsorption/desorption experiments have been performed to characterize the structure: they have shown that evaporation occurs collectively, an intriguing observation generally associated with a disordered pore structure with many interconnections through narrow necks. The characterization of ?uid mobility inside the pores should give complementary information about the pore structure and topology. This paper focuses on the dynamics of a ?uid con?ned inside the structure of porous silicon, and in particular the self-diffusion measurements (pulsed ?eld gradient spin echo Nuclear Magnetic Resonance (NMR)). The results show a strong anisotropy of the self-diffusion tensor, as expected in this highly anisotropic structure. However, a non-zero self-diffusion in the directions perpendicular to the pore axis is observed. In order to interpret these puzzling results, molecular and Brownian dynamics calculations are underway.
关键词： Ethanol,Porous Silicon,Permeability,Heptane,Self-Diffusion NMR
更新于2025-09-09 09:28:46
-
Structure-directing lone pairs: Synthesis and Structural Characterization of SnTiO3
摘要： SnTiO3 was successfully synthesized for the first time in bulk form by soft chemistry. STEM and Rietveld refinement show that SnTiO3 adopts a structure similar to the archetypical ilmenite-type structure, forming a honeycomb lattice of edge-sharing TiO6-octahedra, which are decorated with Sn2+. Due to formation of a van der Waals gap between the individual layers and hence close energetic minima of different stacking types, SnTiO3 forms multiple stacking orders and twinning domains that we describe by systematic DIFFaX-simulations. The structure is governed by the tin lone pairs, which influence the stacking of the layers as well as local distortions observed by EELS and NMR potentially leading to a wide range of applications.
关键词： DFT,van der Waals gap,Rietveld refinement,soft chemistry,STEM,ilmenite-type structure,EELS,SnTiO3,NMR
更新于2025-09-09 09:28:46
-
Using NMR Relaxometry to Probe Yb <sup>3+</sup> – Er <sup>3+</sup> Interactions in Highly Doped Nanocrystalline NaYF <sub/>4</sub> Nanostructures
摘要： Solid–state nuclear magnetic resonance (NMR) spectroscopy is used to study heavily Yb3+ and Er3+ doped, fluorescent NaY1–x–yYbxEryF4 nanoparticles. An understanding of the 19F wide line NMR response suggests that the 0 ppm portion of the 19F NMR spectrum can be used as a probe of trivalent lanthanide content via spin lattice relaxation time changes. A Yb3+ and Er3+ magnetic interaction is manifest as a cooperative contribution to the 19F spin lattice relaxation rate in heavily co–doped nanoparticle samples. The results from this study will help understand the mechanism of enhanced optical up–conversion among these well–known nanostructures.
关键词： Solid–State NMR,Yb3+ – Er3+ Interactions,Nanocrystalline NaYF4,Optical Up–Conversion,NMR Relaxometry
更新于2025-09-04 15:30:14
-
NMR, ESR, NQR and IR Studies of Paramagnetic Macro Cyclic Complexes of 1st Transition Series Metal Ions Exhibiting MLCT Phenomenon: A DFT Application.Part: 1. [Bis (2, 2/-bi-pyridine)] Complexes
摘要： DFT implemented in ADF. 2012.01 was applied to study the structures of 8 macrocyclic paramagnetic four coordinate complexes: [Bipy2M]2+ {M= Mn (II), Fe(II), Co(II), Ni(II), Cu (II)}, [Bipy2M]3+{M=Ti(III),V(III)} and [Bipy2V]4+( Bipy=2,2/-bipyridine) by using 4 spectral techniques. After optimization of complexes, the software was run by using Single Point, LDA or GGA, Default, Relativity, Spin Orbit, ZORA, Unrestricted, None, Collinear , Nosym using TZP or TP2Z Basis sets in ESR/EPR/EFG/ZFS Program to obtain ESR parameters:g11, g22, g33, giso; a11, a22, a33, A ten. ESR parameters (gn. A ten, ZFS) and NQR parameters {h, q11, q22, q33, NQCC} were obtained by replacing Spin Orbit by scalar command in a new ADF Input. On running the “NMR Program” with Single Point, Default, None, Collinear, Nosym and using the same Basis sets leaving Unrestricted command blank gave the Shielding Constants (σ M, σ 13C, σ 17O), Chemical Shifts (δ M, δ13C, δ17O), 2 diamagnetic, 4 paramagnetic and 4 spin orbit contributing terms in σ values of constituents. The software was run with Frequencies to obtain IR frequencies of the normal modes of the (3n-6) fundamental vibration bands of complexes. This study was important because: (i) the 5 parameter: σ, δ, h, gn . A ten, NQCC of 14N; 4 parameters: σ, δ, g n. A ten, h of 13C and 3 parameters: σ, δ, g. A ten of 1H corroborated to infer that in these complexes, the 20 C were of 5 types; the16 H of 4 types while the 4 N were spatially of the same type (ii) it confirmed MLCT phenomenon in the complexes by NMR(iii) we calculated another parameter of each of NMR (H^)and ESR {DEh f )and two of NQR {Asymmetric coefficient (h), Laplace equation} (iv)it classified 117 fundamental bands of each complex into vibration symmetries and IR activities(v) it gave thermal parameters of the complexes.
关键词： Effective Spin Hamiltonian,Total NMR Shielding Tensor,Chemical Shift,Nuclear Quadrupole Coupling Constant,Asymmetric Coefficient
更新于2025-09-04 15:30:14
-
Aurophilicity and Photoluminescence of (6-Diphenylpnictogenoacenaphth-5-yl)gold Compounds
摘要： The organotin precursors 6-Br-Ace-5-SnBu3 (6, Ace = acenaphthyl) and 6-Ph2E-Ace-5-SnBu3 (7a: E = P; 7b: E = As; 7c: E = Sb) were prepared and used for the synthesis of organogold complexes, namely, the homodinuclear arylgold(I) species (6-Ph2E-Ace-5-Au)2 (8a: E = P; 8b: E = As; 8c: E = Sb), arylgold(III) dichloride 6-Ph2P-Ace-5-AuCl2 (9), diarylgold(III) chloride [trans-(6-Ph2P-Ace-5-)2Au]Cl ([10]Cl) as well as the heterodinuclear gold complexes 6-Ph2P(AuX)-Ace-5-Au(AsPh3) (11a: X = Cl; 11b: X = Br). Compounds 8a - 8c, 11a, and 11b show significant aurophilic interactions, which are related to their photoluminescence upon exposure to UV light. In the solid state, 11a and 11b show green-yellow emission, whereas 8a - 8c are non-emissive. In solution under an argon atmosphere, all five compounds 8a - 8c as well as 11a and 11b show green-yellow emission. The organogold complexes were characterized by multinuclear NMR spectroscopy, photoluminescence spectroscopy, single-crystal X-ray crystallography as well as (TD-)DFT calculations including real-space bond indicators derived from atoms-in-molecules (AIM), the electron localization indicator (ELI-D), and the non-covalent interaction (NCI) index.
关键词： DFT calculations,aurophilicity,photoluminescence,X-ray crystallography,NMR spectroscopy,organogold complexes
更新于2025-09-04 15:30:14
-
[IEEE 2018 XXIIIrd International Seminar/Workshop on Direct and Inverse Problems of Electromagnetic and Acoustic Wave Theory (DIPED) - Tbilisi, Georgia (2018.9.24-2018.9.27)] 2018 XXIIIrd International Seminar/Workshop on Direct and Inverse Problems of Electromagnetic and Acoustic Wave Theory (DIPED) - Magnetometry and NMR Study of Carbon Nanopowders Doped with Cobalt Nanoclusters and Self-assembly of their Polymer Nanocomposites under Magnetic Field
摘要： The RF resonant magnetometry and NMR studies were carried out on carbon nanoparticles doped with magnetic cobalt clusters, which were synthesized by a technology combining of the hydrocarbon vapor pyrolysis and the chemical vapor deposition (CVD) process in a horizontal continuous reactor. The RF resonant magnetometry data show that the obtained carbon cobalt nanopowders are superparamagnetic at room temperatures and ferromagnetic at liquid nitrogen temperatures. The NMR study with the excitation by additional magnetic video-pulses of nanopowders obtained by using different hydrocarbons pyrolysis made it possible a fast assessment of their magnetic phase and hardness properties. The simple non-contact RF resonant magnetometry study of self-assembling processes in carbon cobalt polymer composite films synthesized using these nanopowders was made also.
关键词： magnetic nanoclusters,carbon nanopowder,core-shell structure,self-assembly,NMR,cobalt
更新于2025-09-04 15:30:14
-
Phosphorus and Silicon Containing Inorganic Polymers. Poly(dimethylsilane H-phosphonate): Synthesis and NMR Characterization
摘要： In this paper we have demonstrated a new synthetic approach to a phosphorus and silicon containing inorganic polymer with a chain structure [-O-P(O)(H)-O-Si(CH3)2-]. It has been obtained from dichlorodimethylsilane and dimethyl ester of H-phosphonic acid taken in excess via catalyst and solvent free process, performed in two stages. The first one involved dealkylation reaction which was favoured by the nucleophilic attack of the chlorine atoms from the silane derivative at the α–carbon atoms of the dialkyl H-phosphonate. At the second polycondensation stage the molecular mass of the product increased. In the present study dimethyl H-phosphonate and dichlorodimethylsilane were used at a molar ratio 1.3:1 and the process was carried out at temperature up to 65 °C. The structure of the new polymer was proved by multinuclear NMR spectroscopy in solution and solid state. The thermal properties of the polymer product were measured.
关键词： silanes,inorganic polymers,NMR spectroscopy,copolymerization,phosphonates
更新于2025-09-04 15:30:14
-
Terahertz rectangular corrugated transmission line with Gaussian mode filtering for DNP-NMR
摘要： Gyrotrons have been developed as terahertz wave sources in dynamic nuclear polarisation (DNP) system to increase the sensitivity of nuclear magnetic resonance (NMR) in the high-magnetic field regime. However, the transmission of the Gaussian beam from the gyrotron output window to the NMR system proves to be a critical challenge. In this study, a terahertz transmission system, composed of a rectangular corrugated waveguide and a back-to-back rectangular corrugated horn for Gaussian mode filtering, is proposed. The attenuation in the optimised 0.33?THz corrugated waveguide remains lower than 0.01 dB/m in a broad frequency range from 280?GHz to 450?GHz. Besides, the coupling coefficient from the electric field in the 0.33 THz mode-filtering horn to the fundamental HE11 mode in the rectangular corrugated waveguide is obtained nearly 99.5%. This terahertz transmission system is potential to be applied in DNP-NMR spectrometer based on continuous wave gyrotrons.
关键词： DNP-NMR,Gaussian mode filtering,terahertz,transmission line,gyrotron
更新于2025-09-04 15:30:14