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1.
Noble PF Cayre OJ Alargova RG Velev OD Paunov VN 《Journal of the American Chemical Society》2004,126(26):8092-8093
Novel colloidosome microcapsules with aqueous gel cores and integral shells of rodlike polymeric particles have been prepared and characterized. The synthesis is based on templating water-in-oil emulsions stabilized by rodlike particles followed by gelling of the aqueous phase, dissolution of the oil phase in ethanol, and redispersion of the obtained colloidosome capsules in water. Such capsules may find applications as vehicles for delivery and controlled release of drugs, cosmetics, and food supplements. 相似文献
2.
A constructive approach is developed for studying local chiral algebras generated by a pair of oppositely charged fields Ψ (z, ±g) such that the operator product expansion (OPE) of Ψ(z1, g) Ψ(z2, −g) involves a U(1) current. The main tool in the study is the factorization property of the charged fields (exhibited in [PT 2, 3]) for Virasoro central charge c < 1 into U(1)-vertex operators tensored with ZAMOLODCHIKOV-FATEEV [ZF1] (generalized) Zk-parafermions. The case Δ2 = 4 (Δ1 − 1), where Δv = Δk−v(Δ0 = 0) are the conformaldimensions of the parafermionic currents, is studied in detail. For Δv = 2v(1 − v/k) the theory is related to GEPNER'S [Ge] Z2 [so (k)] parafermions and the corresponding quantum field theoretic (QFT) representations of the chiral algebra are displayed. The Coulomb gas method of [CR] is further developed to include an explicit construction of the basic parafermionic current Ψ of weight Δ = Δ1. The characters of the positive energy representations of the local chiral algebra are written as sums of products of Kac's string functions and classical θ-functions. 相似文献
3.
The Epitaxy of single silver crystals on tungsten single crystal surfaces in UHV is studied. The substrate was a W-ribbon recrystalized at high temperature. After the high temperatur treatment many differently oriented single crystal regions appeared on substrate surface. The orientation of the single crystal regions crystal regions was determined by means of etch pits. The experimentally found change of the silver crystal orientation with changing the substrate orientation gives the following epitaxial relationship It is shown that the observed epitaxial growth of silver on tungsten is due to the structural similarity of the parallel growing Ag/W-planes. 相似文献
4.
Thermal desorption spectra (TDS) of Ag condensates deposited at two substrate temperatures Ts = 300 K and Ts = 779 K have been obtained. A shift of the temperature Tm of the maximum of the desorption flux Re was observed. It was established that the shift of the maximum depends on the value of the initial coverage σ0. A significant difference was found to exist between TDS of silver condensates deposited on oxidized and clean W substrates due to differences in the mechanism of condensation. Silver condensates were deposited on oxidized W at different initial conditions (Ts, impingement rates Ri, etc.) but equal σ0. The corresponding TDS were compared and a conclusion has been drawn that the shift of Tm is due to the different structure of Ag condensates. TDS of Ag condensates deposited at room temperature (Ts = 300 K) were interpreted using the method of Bauer et al. [J. Appl. Phys. 45 (1974) 5164: Surface Sci. 53 (1975) 87]. The dependence of the desorption flux Re on the substrate temperature Ts and coverage σ was treated on the basis of the Polanyi-Wigner equation and some parameters of the condensation process were evaluated. 相似文献
5.
M. Paunov 《Crystal Research and Technology》1998,33(2):165-176
Simple lattice model is used to consider the influence of adsorption on the thin film growth mode. It is found that the presence of an adsorbate in a heterogeneous system does not change the general form of the Wulff-Kaischew theorem provided the surface sensitive quantities are correctly defined. An extended criterion for the layer-by-layer growth mechanism is obtained. Contrary to the Bauer's 3-σ rule in the generalized criterion enter interfacial free energies only whereby all surface free energies are absent. As a consequence the change of the growth mode (3D → 2D) upon adsorption could be explained by purely thermodynamic reasons. It is shown also that the adsorbate changes drastically the chemical potential of the underlying layer rendering it close to the chemical potential of the infinitely large three-dimensional crystal. Therefore, the growth on a preadsorbed foreign substrate takes place practically as on an own substrate. An exchange process between incoming atoms and adsorbate particles keeps the adsorbate predominantly on the top of the growing surface rather than in the bulk of the film. The driving force of this process is the free energy difference between “in bulk” and “on surface” configurations of the system. The phenomenon reveals the thermodynamic principle that the spontaneous processes lower the free energy and render the system to its ground state. 相似文献
6.
Reed KM Borovicka J Horozov TS Paunov VN Thompson KL Walsh A Armes SP 《Langmuir : the ACS journal of surfaces and colloids》2012,28(18):7291-7298
A series of five near-monodisperse sterically stabilized polystyrene (PS) latexes were synthesized using three well-defined poly(glycerol monomethacrylate) (PGMA) macromonomers with mean degrees of polymerization (DP) of 30, 50, or 70. The surface coverage and grafting density of the PGMA chains on the particle surface were determined using XPS and (1)H NMR spectroscopy, respectively. The wettability of individual latex particles adsorbed at the air-water and n-dodecane-water interfaces was studied using both the gel trapping technique and the film calliper method. The particle equilibrium contact angle at both interfaces is relatively insensitive to the mean DP of the PGMA stabilizer chains. For a fixed stabilizer DP of 30, particle contact angles were only weakly dependent on the particle size. The results are consistent with a model of compact hydrated layers of PGMA stabilizer chains at the particle surface over a wide range of grafting densities. Our approach could be utilized for studying the adsorption behavior of a broader range of sterically stabilized inorganic and polymeric particles of practical importance. 相似文献
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8.
Taylor P Xu C Fletcher PD Paunov VN 《Chemical communications (Cambridge, England)》2003,(14):1732-1733
A novel technique for the preparation of monodisperse giant liposomes has been developed based on a combination of micro-patterning of ITO glass slides with lipid solution and electroformation. The average diameter of the produced liposomes is determined by size of the micro-pattern features. 相似文献
9.
Nia Petrova Momchil Paunov Petar Petrov Violeta Velikova Vasilij Goltsev Sashka Krumova 《Molecules (Basel, Switzerland)》2021,26(19)
Single-walled carbon nanotubes (SWCNT) have recently been attracting the attention of plant biologists as a prospective tool for modulation of photosynthesis in higher plants. However, the exact mode of action of SWCNT on the photosynthetic electron transport chain remains unknown. In this work, we examined the effect of foliar application of polymer-grafted SWCNT on the donor side of photosystem II, the intersystem electron transfer chain and the acceptor side of photosystem I. Analysis of the induction curves of chlorophyll fluorescence via JIP test and construction of differential curves revealed that SWCNT concentrations up to 100 mg/L did not affect the photosynthetic electron transport chain. SWCNT concentration of 300 mg/L had no effect on the photosystem II donor side but provoked inactivation of photosystem II reaction centres and slowed down the reduction of the plastoquinone pool and the photosystem I end acceptors. Changes in the modulated reflection at 820 nm, too, indicated slower re-reduction of photosystem I reaction centres in SWCNT-treated leaves. We conclude that SWCNT are likely to be able to divert electrons from the photosynthetic electron transport chain at the level of photosystem I end acceptors and plastoquinone pool in vivo. Further research is needed to unequivocally prove if the observed effects are due to specific interaction between SWCNT and the photosynthetic apparatus. 相似文献
10.
Cathryn G. Conner Anka N. Veleva Vesselin N. Paunov Simeon D. Stoyanov Orlin D. Velev 《Particle & Particle Systems Characterization》2020,37(7):2000122
A highly controllable and scalable process for fabrication of large amounts of concentrated lignin nanoparticles (LNPs) is reported. These lignin core nanoparticles are formed through flash nanoprecipitation, however, scaling up of the fabrication process requires fundamental understanding of their operational formation mechanism and surface properties. It is shown how a semicontinuous synthesis system with a recirculation loop makes it possible to produce flash precipitated lignin nanoparticles in large amounts for practical applications. The roles of the process parameters, including flow rates and lignin concentration, are investigated and analyzed. The results indicate that the LNPs are formed by a process of continuous burst nucleation at the point of mixing without diffusive growth, which yields nanoparticles of highly uniform size following a modified LaMer nucleation and growth mechanism. This mechanism makes possible facile process control and scale-up. Effective control of the resulting nanoparticle size is achieved through the initial concentration of lignin in the injected solution. The impressive capability to produce suspensions of any predesigned multimodal distribution is demonstrated. The resulting nanofabrication technique can produce large volumes of concentrated LNP suspensions of high stability and tightly controlled size distributions for biological or agricultural applications. 相似文献