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排序方式: 共有332条查询结果,搜索用时 15 毫秒
1.
Benjamin Klemmed Dr. Lucas V. Besteiro Dr. Albrecht Benad Maximilian Georgi Prof. Zhiming Wang Prof. Alexander Govorov Prof. Alexander Eychmüller 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1713-1719
Solar radiation is a versatile source of energy, convertible to different forms of power. A direct path to exploit it is the generation of heat, for applications including passive building heating, but it can also drive secondary energy-conversion steps. We present a novel concept for a hybrid material which is both strongly photo-absorbing and with superior characteristics for the insulation of heat. The combination of that two properties is rather unique, and make this material an optical superheater. To realize such a material, we are combining plasmonic nanoheaters with alumina aerogel. The aerogel has the double function of providing structural support for plasmonic nanocrystals, which serve as nanoheaters, and reducing the diffusion rate of the heat generated by them, resulting in large local temperature increases under a relatively low radiation intensity. This work includes theoretical discussion on the physical mechanisms impacting the system's balanced thermal equilibrium. 相似文献
2.
Dong Gun Oh Prof. Hristiyan A. Aleksandrov Haneul Kim Dr. Iskra Z. Koleva Dr. Konstantin Khivantsev Prof. Georgi N. Vayssilov Prof. Ja Hun Kwak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(49):e202200684
Pd-based catalysts are the most widely used for CO oxidation because of their outstanding catalytic activity and thermal stability. However, fundamental understanding of the detailed catalytic processes occurring on Pd-based catalysts under realistic conditions is still lacking. In this study, we investigated CO oxidation on metallic Pd clusters supported on Al2O3 and SiO2. High-angle annular dark-field scanning transmission electron microscopy revealed the formation of similar-sized Pd clusters on Al2O3 and SiO2. In contrast, CO chemisorption analysis indicated a gradual change in the dispersion of Pd (from 0.79 to 0.2) on Pd/Al2O3 and a marginal change in the dispersion (from 0.4 to 0.24) on Pd/SiO2 as the Pd loading increased from 0.27 to 5.5 wt %; these changes were attributed to differences in the metal-support interactions. Diffuse reflectance infrared Fourier-transform spectroscopy revealed that fewer a-top CO species were present in Pd supported on Al2O3 than those in Pd supported on SiO2, which is related to the morphological differences in the metallic Pd clusters on these two supports. Despite the different dispersion profiles and surface characteristics of Pd, O2 titration demonstrated that linearly bound CO (with an infrared signal at 2090 cm−1) reacted first with oxygen in the case of CO-saturated Pd on Al2O3 and SiO2, which suggests that a-top CO on the terrace site plays an important role in CO oxidation. The experimental observations were corroborated by periodic density functional calculations, which confirmed that CO oxidation on the (111) terrace sites is most plausible, both kinetically and thermodynamically, compared to that on the edge or corner sites. This study will deepen the fundamental understanding of the effect of Pd clusters on CO oxidation under reaction conditions. 相似文献
3.
Shchelkanova Mariya S. Shekhtman Georgi Sh. Kalashnova Anastasia V. Reznitskikh Olga G. 《Journal of Solid State Electrochemistry》2018,22(9):2959-2964
Journal of Solid State Electrochemistry - Lithium ion conductivity of lithium hexaoxozirconate Li8ZrO6 doped by Mg2+, Sr2+, Nb5+, V5+, and Ce4+ cations was studied using impedance spectroscopy. The... 相似文献
4.
5.
Ingolf Kahle Stefan Krause Cornelius Krasselt Alexander Jakob Alexander Oehlke Colin Georgi Steffen Schulze Heinrich Lang Michael Hietschold Stefan Spange Christian von Borczyskowski 《Applied Physics A: Materials Science & Processing》2014,115(2):617-625
Optical properties of nanomaterials such as semiconductor and metal quantum dots are important for sensors and photovoltaic applications. We report on optical, microscopic, and AFM investigations on bulk and single nanoobjects such as metal and semiconducting nanoparticles. Firstly, of special interest is the investigation of Ag metal nanoaggregates formed in zeolites. Here, the defined structure of the zeolite serves both as size directing and a stabilizing agent. The size selected Ag aggregates fluoresce in the zeolite cages even after storage under ambient conditions for almost one year. In addition, single Ag particles escape the cages and can be investigated by fluorescence microscopy also with respect to sensor applications. Secondly, with respect to photovoltaic applications, energy transfer among organic dye molecules and semiconductor quantum dots is of great importance. We report on the extension of the optical absorption of ZnSe quantum dots into the UV regime and investigate excitation energy transfer within self-assembled nanoaggregates of surface functionalized QDs and fluorescent styrylpyridine dyes. 相似文献
6.
A practical synthesis of new chiral aminophosphine ligands based on the camphane scaffold bearing alkoxy groups was accomplished. The application of these ligands in the Pd-catalyzed allylic alkylation of (E)-1,3-diphenyl-2-propenyl acetate proceeded with excellent conversions and ee’s of up to 91%. Variation of the alkoxy substituents did not substantially influence the catalytic performance. 相似文献
7.
Yuri P. Rybakov Georgi N. Shikin Yuri A. Popov Bijan Saha 《Central European Journal of Physics》2011,9(5):1165-1172
We consider an interacting system of massless scalar and electromagnetic fields, with the Lagrangian explicitly depending
on the electromagnetic potentials, i.e., interaction with broken gauge invariance. The Lagrangian for interaction is chosen
in such a way that the electromagnetic field equation acquires an additional term, which in some cases is proportional to
the vector potential of the electromagnetic field. This equation can be interpreted as the equation of motion of photon with
induced nonzero rest-mass. This system of interacting fields is considered within the scope of Bianchi type-I (BI) cosmological
model. It is shown that, as a result of interaction the isotropization process of the expansion takes place. 相似文献
8.
Georgi Chernev Nadezhda Rangelova Petar Djambazki Sanchi Nenkova Isabel Salvado Maria Fernandes Aiying Wu Lyudmila Kabaivanova 《Journal of Sol-Gel Science and Technology》2011,58(3):619-624
The purpose of the present work is the sol–gel synthesis, structure characterization and potential application of hybrid biomaterials
based on silica precursor (MTES) and natural polymers such as gelatin or pectin. The structure formation in the biomaterials
was investigated by XRD, FTIR, BET and AFM. The results showed that all studied hybrid biomaterials have an amorphous structure.
The FT-IR spectra of the obtained materials with MTES showed chemical bonds at 2,975, 1,255, 880 and 690 cm−1 due to the presence of Si–O–R (CH3 and C2H5) and Si–C bonds. In the samples synthesized with TEOS the inorganic and organic components interact by hydrogen bonding,
Van der Waals or electrostatic forces. Surface area of investigated samples decreases with increasing of the natural polymers
content. The structure evolution was studied by AFM and roughness analysis. Depending on the chemical composition a different
design and size of particles and their aggregates on the surface structure were established. The hybrid biomaterials were
used for immobilization of bacterial cells and applied in the biodegradation of the toxic compound 4-chlorobutyronitrile,
possible constituent of waste water effluents in a laboratory glass bioreactor. Optimization of the process at different temperatures
was carried out. 相似文献
9.
Maria N. Mancheva Reni S. Iordanova Yanko B. Dimitriev Georgi G. Tyuliev Tzvetoslav Ch. Iliev 《Central European Journal of Chemistry》2011,9(3):460-465
ZrMo2O7(OH)2·2H2O was obtained from ZrOCl2·2H2O and Na2MoO4·2H2O by a coprecipitation method. The phase and structural changes occurred during the heat-treatment of ZrMo2O7(OH)2·2H2O were investigated by XRD, IR and XPS analysis. The sequence of phase transformation can be divided into three stages: (1)
transformation of ZrMo2O7(OH)2·2H2O to orthorhombic LT-ZrMo2O8 up to 300°C; (2) obtaining of mixture of both polymorphs of ZrMo2O8: cubic and trigonal at 400°C; (3) conversion to single trigonal (α) ZrMo2O8 above 450°C. The microstructure of the obtained trigonal (α) ZrMo2O8 was observed by scanning electron microscopy (SEM). The particle sizes were below 0.5 μm. The specific surface area was measured
by modified BET method. The photocatalytic activity of the obtained trigonal (α) ZrMo2O8 powders was investigated by degradation of a model aqueous solution of Malachite Green (MG) upon UV-light irradiation. 相似文献
10.
Andrea Preuß Marcus Korb Tobias Rüffer Jörn Bankwitz Colin Georgi Alexander Jakob Stefan E. Schulz Heinrich Lang 《无机化学与普通化学杂志》2020,646(13):670-680
The template synthesis of ethylenediamine ( 1 ) with 2-acetylcyclopentanone ( 2 ) and [Cu(OAc)2 · H2O] ( 5 ) produced [Cu(1-(2-cC5H6(O))C(Me)NCH2)2)] ( 6 ) in 82 % yield. Reaction of 5 with bis(benzoylacetone)diethylenetriamine ( 7 , = L H)[1] gave [Cu(μ-OAc)( L )(H2O)]2 ( 8 ). The solid-state structures of 6 and 8 were determined confirming that 8 possesses intra- and intermolecular hydrogen bonds resulting in a dimer formation. The thermal behavior of 6 – 8 was studied by TG and TG-MS. Under oxygen CuO was formed, whereas under Ar Cu/Cu2O ( 6 ) or Cu ( 8 ) was obtained. Complex 6 was used as CVD precursor for Cu and Cu-oxide deposition (substrate temp., 400–500 °C, N2, 60 mL · min–1; O2, 60 mL · min–1; pressure, 0.87–1.5 mbar). The as-obtained deposits show separated particles of different appearance at the substrate surface as evidenced by SEM. Non-volatile 8 was applied as spin-coating precursor for Cu and CuO formation [conc. 0.25 mol · L–1; volume 0.2 mL; 3000 rpm; depos. time 2 min; heating rate 50 K · min–1; holding time 60 min (Ar), 120 min (air) at 800 °C]. The samples on silicon consist of granulated particles (Ar) or are non-dense with a grainy topography (air). EDX and XPS measurements confirmed the formation of Cu (Ar) or CuO (O2) with up to 13 mol-% C impurity. 相似文献