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1.
(100-x) mole% SiO2-x mole% P2O5-glasses withx=1–9 have been prepared by the sol-gel process using tetraethylorthosilicate and triethylphosphate as precursors. The gels
were fired at various temperatures up to 950°C and then exposed to γ-ray irradiation to induce paramagnetic centers. CW-EPR
and FT-EPR Spectroscopies were employed at temperatures between 4 and 300 K in order to determine the resulting structures.
The dried gels exhibited four types of O
2
−
-ions trapped in pores of different sizes. The gels fired atT=670°C exhibited theE’
1-center and non-bridging oxygen as a results of the fracture of the Si-O-Si bonds. At higher temperatures, the spectra of
the POHC, POHC
b
,E’, and CH
3
−
-centers have been detected that are a function ofx andT. 相似文献
2.
Mathematical assessment of homogenisation progress of the granular material mixing process is presented. The mixing process
was realised using a vessel in the form of two partly penetrating horizontal cylinders equipped with two multi-ribbon agitators.
The experimental system consisted of three sets of particles of different colour. Random states of the mixed granular material
were characterised by the sampling procedure at different moments of the mixing process. Informational entropy as well as
the flow of quantum of information were applied to describe the progress of the homogenisation process. Analysis of this process
was based on experimental investigations in the form of informational entropy patterns and described by means of the average
informational entropy or the quantum of information.
Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May
2007. 相似文献
3.
Päivi Mäki-Arvela Elena V. Murzina Betiana Campo Teemu Heikkilä Anne-Riikka Leino Krisztian Kordas Dorit Wolf Anton V. Tokarev Dmitry Yu. Murzin 《Research on Chemical Intermediates》2010,36(4):423-442
Lactose oxidation was investigated at 70 °C and at pH 8 using oxygen as an oxidant over a comprehensive set of commercially
available mono- and multi-metallic as well as promoted Pd catalysts with active carbon, alumina and calcium carbonate as catalyst
supports. An optimum cluster size of 6–10 nm resulted in the highest initial turnover frequencies. High conversion levels
above 90% were achieved on Pd/C catalyst, as well as over Pd/Al2O3 and (Pd–Pb)/CaCO3, whereas (Pd–V)/C catalyst gave only 30% conversion after 200 min. The latter catalyst was relatively inactive due to its
high support acidity and profound deactivation during oxidation. Besides the main oxidation product, lactobionic acid, also,
lactulose was generated as a result of lactose isomerisation under alkaline conditions. The electrochemical potentials of
the catalysts were measured during lactose oxidation. The main result of these measurements was that, when the electrochemical
potential of the catalyst increased very quickly, its oxidation activity was low due to metal over-oxidation. The selectivities
to the desired product, lactobionic acid, were relatively high, above 80% for most of the catalysts, except for (Pd–V)/C.
Furthermore, the selectivity to the lactobionic acid decreased with increasing metal dispersion, thus, indicating that the
optimum metal particle sizes for producing high amounts of lactobionic acid is above 3 nm. 相似文献
4.
E. K. Efthimiadou C. Tapeinos P. Bilalis G. Kordas 《Journal of nanoparticle research》2011,13(12):6725-6736
Amphiphilic block copolymers are well established as building blocks for the preparation of micellar drug carriers. The functional
polymer micelles possess several advantages, such as high drug efficiency, targeted delivery, and minimized cytotoxicity.
The synthesis of block copolymers using nano-structured templates has emerged as a useful and versatile approach for preparing
drug carriers. Here, we report the synthesis of a smart polymeric compound of a diblock PLA-Lys-b-PEG copolymer containing doxorubicin. We have synthesized functionalized diblock copolymers, with lysinol, poly(lactide)
and monomethoxy poly(ethylene glycol) via thermal ring-opening polymerization and a subsequent six-step substitution reaction.
A variety of spectroscopic methods were employed here to verify the product of our synthesis. 1H-Nuclear magnetic resonance and Fourier transform infrared studies validated the expected synthesis of copolymers. Doxorubicin
is chemically loaded into micelles, and the ex vitro release can be evaluated either in weak acidic or in SBF solution by
UV–vis spectroscopy. Dynamic light scattering, thermo gravimetric analysis, and size exclusion chromatography have also been
used. 相似文献
5.
Ioannis Kartsonakis Ioannis Daniilidis George Kordas 《Journal of Sol-Gel Science and Technology》2008,48(1-2):24-31
Ceria nanocontainers were synthesized through a two-step process and then loaded with 8-hydroxyquinoline (8-HQ). The size of the containers was 110 nm as determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray diffraction analysis (XRD) showed that the ceria nanocontainers were of the cerianite crystalline phase. The presence of 8-HQ in the nanocontainers was confirmed with Fourier-transform infrared spectroscopy (FT-IR). The loading of the inhibitor in the nanocontainers was estimated with differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The loading amount of 8-HQ was 4.28% w/w. Based on the size of the nanocontainers and the assumption that they are not broken, we deduced that there were approximately 6.0 × 105 molecules of 8-HQ per container. Furthermore, release of 8-HQ in a corrosive environment was studied by potentiodynamic measurements, showing that the inhibitor is released from the nanocontainers, suppressing the corrosion activities by a strong barrier effect. SEM and dynamic light scattering (DLS) measurements confirmed that the nanocontainers are not significantly agglomerated and maintain their shape after suspension in 0.5 M NaCl solution for more than 72 h. 相似文献
6.
7.
A. Kirilin S. Sahin A. Tokarev P. Mäki-Arvela K. Kordas A. -R. Leino A. Shchukarev J. -P. Mikkola L. M. Kustov T. Salmi D. Yu. Murzin 《Kinetics and Catalysis》2010,51(6):809-815
The kinetics and reaction network of the one-pot synthesis of R-1-phenylethyl acetate was investigated at 70°C in toluene over a combination of three different catalysts: PdZn/Al2O3 as a catalyst for acetophenone hydrogenation, lipase as an enzymatic catalyst for R-1-phenylethanol acylation with ethyl acetate and Ru/Al2O3 as a racemization catalyst for S-1-phenylethanol. In addition to the desired reactions, other reactions, namely hydrogenolysis and dehydration of (R, S)-1-phenylethanol and debenzylation of (R, S)-1-phenylethyl acetate also occurred. The kinetic results revealed that ethylbenzene formation was enhanced with higher amounts of PdZn/Al2O3, whereas lipase did not catalyze ethylbenzene formation. Furthermore, ethylbenzene was formed in the hydrogenolysis of (R, S)-phenylethanol and in the debenzylation of (R, S)-1-phenyl-ethylacetate over Pd/Al2O3 catalyst. The presence of Ru/Al2O3 catalyst, in which Ru was in the oxidation state of 3+, enhanced the formation of R-1-phenylethyl acetate, although no clear racemization of S-1-phenylethanol during the one-pot synthesis of R-1-phenylethyl acetate was observed. Dynamic kinetic resolution of (R, S)-1-phenylethanol in toluene, was, however, demonstrated over Ru/Al2O3 and lipase. 相似文献
8.
Noncollinear difference frequency mixing of dye laser and Nd:YAG second harmonic (fundamental) radiation from a commercial
laser system is employed for the generation of 2.7–5.3 μm (1.6–1.7 μm) radiations in a flux-grown KTiOAsO1 crystal. The generated radiation is used to scan the methane absorption in the fundamental (v
3) and its first overtone (2v
3) band at pressure 90 torr in a laboratory made single pass gas cell of length 33 cm. 相似文献
9.
CW and Pulsed EPR Study of Silver Nanoparticles in a SiO2 Matrix 总被引:1,自引:0,他引:1
G. Mitrikas Y. Deligiannakis C.C. Trapalis N. Boukos G. Kordas 《Journal of Sol-Gel Science and Technology》1998,13(1-3):503-508
Metallic silver nanoparticles were prepared by the sol-gel method in an SiO2 matrix. The process includes complexation of silicon alkoxides with metal salts, hydrolysis, polycondensation, formation of powder, and subsequent thermal treatment first in oxidizing and second in reducing atmospheres. The sizes of metallic particles were determined both by X-ray diffraction and transmission electron microscopy. These measurements revealed sizes of metallic particles between 1 and 20 nm, depending upon processing conditions. The magnetic properties were investigated using electron paramagnetic resonance spectroscopy in the temperature range between 4 and 300 K. The spin-lattice relaxation time T1 was measured by pulsed EPR. The temperature dependence of T1 is described by the relation 1/T1 Tn, where 0.4 < n < 1. This behavior is unusual and different from any well-known relaxation processes such as Raman, Direct or the Orbach-Aminov. 相似文献
10.
Calcium hydroxyapatite powder was prepared by sol-gel method using calcium acetate and PO(OC2H5)3 as initial compounds, and alcohol (methyl, ethyl, and propyl-alcohol) as solvent. Homogeneous solution and gels were prepared
using a molar ratio of Ca/P=1.67. The evolution of the structure was detected by X-ray diffraction, IR, and FT-n(=1,2,3)D-EPR spectroscopy. The dried gels exhibit a signal characterized by a central line and two satellites. The 2D spectrum
(ESEEM vs. field sweep) showed the same modulation for the central line. The FT-EPR spectrum vs. field sweep 2D-spectrum indicated
that the satellites are due to an hfs splitting with water. The central region of this 2D spectrum is influenced by P and
H in a concentration ratio of [H]/[P]=2.5. The ESEEM spectrum was simulated assuming the equation Vmod=Vmod(P)mVmod(H)n for two spin systems S=1/2 and I=1/2. This simulation gave form andn the values of 2 and 5, respectively. This finding suggests the structure:
for the unpaired state. It appears that one ethyl group does not hydrolyse in the gelation process. The ESEEM spectra of
hydroxyapatite exhibit a modulation generated by P, H and Ca atoms. 相似文献