1,310 research outputs found
Photoinduced Doughnut-Shaped Nanostructures
We show that an incoherent unpolarized single-beam illumination is able to
photoinduce nano-doughnuts on the surface of azopolymer thin films. We
demonstrate that individual doughnut-shaped nano-objects as well as clusters of
several adjacent nano-doughnuts can be formed and tailored with wide range of
typical sizes, thus providing a rich field for applications in nanophotonics
and photochemistry.Comment: 13 pages, 3 figures, first version to chem. phys. lett. 201
A macroscopic quantum state analysed particle by particle
Explaining how microscopic entities collectively produce macroscopic
phenomena is a fundamental goal of many-body physics. Theory predicts that
large-scale entanglement is responsible for exotic macroscopic phenomena, but
observation of entangled particles in naturally occurring systems is extremely
challenging. Synthetic quantum systems made of atoms in optical lattices have
been con- structed with the goal of observing macroscopic quantum phenomena
with single-atom resolution. Serious challenges remain in producing and
detecting long-range quantum correlations in these systems, however. Here we
exploit the strengths of photonic technology, including high coherence and
efficient single-particle detection, to study the predicted large-scale
entanglement underlying the macroscopic quantum phenomenon of polarization
squeezing. We generate a polarization-squeezed beam, extract photon pairs at
random, and make a tomographic reconstruction of their joint quantum state. We
present experimental evidence showing that all photons arriving within the
squeezing coherence time are entangled, that entanglement monogamy dilutes
entanglement with increasing photon density and that, counterintuitively,
increased squeezing can reduce bipartite entanglement. The results provide
direct evidence for entanglement of macroscopic numbers of particles and
introduce micro-analysis to the study of macroscopic quantum phenomena
Dependence of nonlinear refractive index of ZnSe on Be and Mg content
The values of the nonlinear refractive index n(2) and the two-photon absorption coefficient beta of ternary and quaternary ZnSe-based mixed crystals were extracted from the standard backward degenerate four wave mixing (DFWM) and nonlinear transmission measurements at 532 nm, respectively. Studied crystals were grown by the modified high-pressure Bridgman method. We found that the value of the nonlinear refractive index n(2) for Zn(0.79)Be(0.21)Se is higher than that for Zn(0.80)Mg(0.20)Se. However, the opposite behaviour was found in the case of two-photon absorption coefficient beta for these compounds. We also found that the values of the nonlinear refractive index n(2) and the two-photon absorption coefficient beta for Zn(0.83)Be(0.04)Mg(0.13)Se are about five times lower and three times higher than that for Zn(0.80)Mg(0.13)Se, respectively. In the case of ternary ZnSe-based crystals we noticed that the value of the nonlinear refractive index n2 decreases with increasing Mg or Be content. However, the value of the two-photon absorption coefficient beta increases with increasing Mg or Be content
Biomaterials with potential use in bone tissue regeneration-collagen/chitosan/silk fibroin scaffolds cross-linked by EDC/NHS
Blending of different biopolymers, e.g., collagen, chitosan, silk fibroin and cross-linking modifications of these mixtures can lead to new materials with improved physico-chemical properties, compared to single-component scaffolds. Three-dimensional scaffolds based on threecomponent mixtures of silk fibroin, collagen and chitosan, chemically cross-linked, were prepared and their physico-chemical and biological properties were evaluated. A mixture of EDC (N-(3- dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride) and NHS (N-hydroxysuccinimide) was used as a cross-linking agent. FTIR was used to observe the position of the peaks characteristic for collagen, chitosan and silk fibroin. The following properties depending on the scaffold structure were studied: swelling behavior, liquid uptake, moisture content, porosity, density, and mechanical parameters. Scanning Electron Microscopy imaging was performed. Additionally, the biological properties of these materials were assessed, by metabolic activity assay. The results showed that the three-component mixtures, cross-linked by EDC/NHS and prepared by lyophilization method, presented porous structures. They were characterized by a high swelling degree. The composition of scaffolds has an influence on mechanical properties. All of the studied materials were cytocompatible with MG-63 osteoblast-like cells.This research was founded by National Science Centre, grant 2018/31/N/ST8/01391 and by Polish National Agency for Academic Exchange, Iwanowska project PPN/IWA/2018/1/00064/U/00001
Near-Field Optical control of Doughnut-Shaped Nanostructures
The application of a local near-field optical excitation can be used to
control step-by-step the reshape of individual doughnut-shaped azopolymer
nano-objects by varying the time of illumination demonstrating its promising
performance as a functional nano-object. The possibility to provide both
photoinduced reshaping opens a way to the fundamental study of size-dependent
scaling laws of optical properties, photoinduced reshaping efficiency and
nanoreactor or nanoresonator behavior at nanometer scale. As an example the
nano-object is used to self-assembly polystyrene nanospheres in a supraball.Comment: 15 pages, 6 figure
Smart nanogels at the air/water interface: structural studies by neutron reflectivity
STFC
for provision of consumables and subsistence and access to
the ILL facility through the STFC managed UK contribution to
the facility (EXP: 9-13-530, 9-11-1721 and 9-11-17446). The
European Commission (FP7 Marie Curie Actions, NANOLEM,
PIEF-GA-2013-627146 to KZ) and the Chinese Scholarship
Council (studentship to HS) are gratefully acknowledged for
financial support
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