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41.
Hongwei Du Paul D. Hamilton Matthew A. Reilly Andr dAvignon Pramit Biswas Nathan Ravi 《Journal of colloid and interface science》2009,340(2):202-208
A series of highly water-soluble organo-silica nanoparticles, ranging from 2 to 10 nm in diameter, were synthesized by the cohydrolysis and copolycondensation reactions. ω-methoxy(polyethyleneoxy)propyltrimethoxysilane (PEG6-9) and hydroxymethyltriethoxysilane (HMTEOS) mixtures were catalyzed by sodium hydroxide in the presence of surfactant benzethonium chloride (BTC) with various ratios of PEG6-9/HMTEOS at room temperature. The synthesized organo-silica nanoparticles possess a core–shell structure with a core of organo-silica resulting from HMTEOS and a monolayer shell of PEG6-9. The chemo-physical characteristics of the particles were studied by gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, 29Si nuclear magnetic resonance (NMR), dynamic light scattering (DLS), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The molecular weight and particle size of the particles increased with increasing HMTEOS molar ratios. The richest HMTEOS composition for the water-soluble particles was found to be HMTEOS:PEG6-9 = 80:20, where the particles had a 6 nm diameter core and a 0.8 nm thick shell. We propose that these water-soluble organo-silica nanoparticles will be suitable for biomedical applications. 相似文献
42.
Jamieson AG Russell D Hamilton AD 《Chemical communications (Cambridge, England)》2012,48(31):3709-3711
A synthetic scaffold that mimics a peptide β-strand has been designed and synthesised based on a 1,3-phenyl-linked hydantoin oligomer. The conformational preferences of this oligomer were investigated using molecular modelling and solution NMR experiments and suggest a planar conformation that accurately mimics the i, i + 2 and i + 4 residues of a peptide β-strand. 相似文献
43.
On the basis of Altona's empirical generalization of the Karplus equation, an expression of 3JH,H as function of pseudorotation parameters for five-membered rings, was deduced. The resulting equation was parametrized by means of molecular mechanics calculations for tetrahydrofuran and tetrahydrothiophene. Estimation of 3JH,H for the full pseudorotational itinerary was made. From the best fit between calculated and measured 3JH,H values the preferred conformation of those rings may be established. The procedure was applied for the conformational analysis of 4-thiohexofuranose derivatives, having and β,
-galacto and D- manno, and -
-talo configurations. 相似文献
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46.
E.C. Paris M.F.C. Gurgel G.P. Casali T.M. Boschi J.A. Varela 《Journal of Physics and Chemistry of Solids》2010,71(1):12-17
Pb1−xSmxTiO3 (PST) powders with x varying from 0 to 0.1 were obtained by the polymeric precursor method, a soft chemical route. The vibrational properties relating tetragonal to pseudo-cubic phase transition were studied by Raman spectroscopy. The results obtained showed that the phase transition is extremely dependent upon the samarium content and presents a diffuse behavior. Monitoring of the oxygen 2p and titanium 3d orbitals was performed by the periodic mechanical quantum method, revealing the changes that occur with the distribution and contribution of the hybrid orbitals due to the samarium influence. 相似文献
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Strain concentrations associated with the presence of a microvascular network in a polymer matrix are measured using fluorescent digital image correlation (FDIC). The accuracy of the measurement technique is established for a specimen containing only a single microchannel. The influence of localized particle reinforcement around the channel is also investigated using this simplified geometry. Three-dimensional network specimens with different structural designs were fabricated and loaded in uniaxial tension. The resulting strain concentrations are compared as a function of channel spacing and location. As expected, decreasing channel spacing leads to increased strain local to the channels. In addition, the three-dimensional nature of the channel architecture influences the resulting strain. The results provide insight into the mechanical behavior of microvascular networks and demonstrate the utility of FDIC as a characterization tool at these length scales. 相似文献
50.
Celeste de Jesus Pereira Franco Oberdan Oliveira Ferreira ngelo Antnio Barbosa de Moraes Everton Luiz Pompeu Varela Lidiane Diniz do Nascimento Sandro Percrio Mozaniel Santana de Oliveira Eloisa Helena de Aguiar Andrade 《Molecules (Basel, Switzerland)》2021,26(11)
Essential oils (EOs) were extracted from Eugenia patrisii, E. punicifolia, and Myrcia tomentosa, specimens A and B, using hydrodistillation. Gas chromatography coupled with mass spectrometry (GC/MS) was used to identify the volatile constituents present, and the antioxidant capacity of EOs was determined using diphenylpicryl-hydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays. For E. patrisii, germacrene D (20.03%), bicyclogermacrene (11.82%), and (E)-caryophyllene (11.04%) were identified as the major constituents of the EOs extracted from specimen A, whereas specimen B primarily comprised γ-elemene (25.89%), germacrene B (8.11%), and (E)-caryophyllene (10.76%). The EOs of E. punicifolia specimen A contained β-Elemene (25.12%), (E)-caryophyllene (13.11%), and bicyclogermacrene (9.88%), while specimen B was composed of (E)-caryophyllene (11.47%), bicyclogermacrene (5.86%), β-pinene (5.86%), and γ-muurolene (5.55%). The specimen A of M. tomentosa was characterized by γ-elemene (12.52%), germacrene D (11.45%), and (E)-caryophyllene (10.22%), while specimen B contained spathulenol (40.70%), α-zingiberene (9.58%), and γ-elemene (6.89%). Additionally, the chemical composition of the EOs was qualitatively and quantitatively affected by the collection period. Furthermore, the EOs of the studied specimens, especially specimen A of E. punicifolia, showed a greater antioxidant activity in DPPH rather than TEAC, as represented by a significantly high inhibition percentage (408.0%). 相似文献