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18,841
result(s) for
"Colors (materials)"
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El monstruo de colores
El monstruo de colores no sabe qué le pasa. Se ha hecho un lío con las emociones y ahora toca deshacer el embrollo. ¿Será capaz de poner en orden la alegría, la tristeza, la rabia, el miedo y la calma? -- Back cover.
Temporal full-colour tuning through non-steady-state upconversion
The emission wavelength of upconversion nanocrystals can be tuned by varying the shape and intensity of the excitation pulses.
Developing light-harvesting materials with tunable emission colours has always been at the forefront of colour display technologies
1
,
2
,
3
. The variation in materials composition, phase and structure can provide a useful tool for producing a wide range of emission colours, but controlling the colour gamut in a material with a fixed composition remains a daunting challenge
4
,
5
. Here, we demonstrate a convenient, versatile approach to dynamically fine-tuning emission in the full colour range from a new class of core–shell upconversion nanocrystals by adjusting the pulse width of infrared laser beams. Our mechanistic investigations suggest that the unprecedented colour tunability from these nanocrystals is governed by a non-steady-state upconversion process. These findings provide keen insights into controlling energy transfer in out-of-equilibrium optical processes, while offering the possibility for the construction of true three-dimensional, full-colour display systems with high spatial resolution and locally addressable colour gamut.
Journal Article
Chinese New Year colors
\"This bilingual color concept book celebrates a rainbow of traditional objects seen during the Chinese New Year.\"-- Publisher's description.
Book
A highly efficient directional molecular white-light emitter driven by a continuous-wave laser diode
Tailored light sources have greatly advanced technological and scientific progress by optimizing the emission spectrum or color and the emission characteristics. We demonstrate an efficient spectrally broadband and highly directional warm-white-light emitter based on a nonlinear process driven by a cheap, low-power continuous-wave infrared laser diode. The nonlinear medium is a specially designed amorphous material composed of symmetry-free, diamondoid-like cluster molecules that are readily obtained from ubiquitous resources. The visible part of the spectrum resembles the color of a tungsten-halogen lamp at 2900 kelvin while retaining the superior beam divergence of the driving laser. This approach of functionalizing energy-efficient state-of-the-art semiconductor lasers enables a technology complementary to light-emitting diodes for replacing incandescent white-light emitters in high-brilliance applications.
Journal Article
Silk inverse opals
Periodic nanostructures provide the facility to control and manipulate the flow of light through their lattices. Three-dimensional photonic crystals enable the controlled design of structural colour, which can be varied by infiltrating the structure with different (typically liquid) fillers. Here, we report three-dimensional photonic crystals composed entirely of a purified natural protein (silk fibroin). The biocompatibility of this protein, as well as its favourable material properties and ease of biological functionalization, present opportunities for otherwise unattainable device applications such as bioresorbable integration of structural colour within living tissue or lattice functionalization by means of organic and inorganic material doping. We present a silk inverse opal that demonstrates a pseudo-photonic bandgap in the visible spectrum and show its associated structural colour beneath biological tissue. We also leverage silk's facile dopability to manufacture a gold nanoparticle silk inverse opal and demonstrate patterned heating mediated by enhancement of nanoparticle absorption at the band-edge frequency of the photonic crystal.
Researchers bring together silk and photonic crystals and report the manufacturing of robust, freestanding, three-dimensional photonic crystals with different lattice constants in the structural form of an inverse opal entirely composed of silk fibroin. These silk-based inverse opals add a new dimension at the interface of nanophotonics and biological applications.
Journal Article
Colour Change in Heated Concrete
This paper presents an analysis of colour change in concrete under the influence of heat. The colour change observed in concrete is primarily a result of the gradual dehydration of the cement paste, but also of transformations occurring within the aggregate. The colour change may be used to reveal the exposure temperature of concrete from which the corresponding fire damage of concrete can be estimated. The paper presents the results of tests carried out on ordinary and high performance concretes (OC and HPC) prepared with natural river-bed aggregates. In addition, mortars and cement pastes prepared with the same components were observed to change colour upon heating. The colour change was investigated using Scion Image v. 4.0.3, an image analysis software package (Scion Corporation ©, USA). In the proposed method the digital image is split into three RGB colour components: red, green and blue, which are then presented as a histogram using counts of pixel intensity. The histogram results show colour distributions in unheated cementitious material and in material heated to temperatures ranging from 100°C to 1000°C. The concrete colour changes as a result of heating are linked to the physical and chemical transformations taking place in the heated material.
Journal Article
Efficient colour splitters for high-pixel-density image sensors
When the pixel size of image sensors shrinks to the wavelength of light, this results in low signal levels for a given photon flux per pixel as a result of scaling laws. Because many image sensors require colour filters, it becomes crucial for small-pixel sensors to have an efficient filtering method that can capture all incident photons without absorbing them. Here, we propose a new method to split colours by using a microscale plate-like structure with a transparent medium that has a higher refractive index than the surrounding material. We experimentally demonstrate that this principle of colour splitting based on near-field deflection can generate colour images with minimal signal loss. From comparisons of the sum of the total integrated values for the colour channels, we confirm the amount of light received is 1.85 times that of the conventional colour filter method of the Bayer array, while maintaining the same level of resolution.
Colour filters that split light by employing near-field interference effects instead of absorption provide enhanced signal levels for dense, small-pixel image sensors.
Journal Article
Hot Subluminous Stars
Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Most hot subdwarf stars are chemically highly peculiar and provide a laboratory to study diffusion processes that cause these anomalies. The most obvious anomaly lies with helium, which may be a trace element in the atmosphere of some stars (sdB, sdO) while it may be the dominant species in others (He-sdB, He-sdO). The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope (CE) phase of evolution. Asteroseismology has advanced enormously thanks to the high-precision Kepler photometry and allowed stellar rotation rates to be determined, the interior structure of gravity-mode pulsators to be probed and stellar ages to be estimated.
Journal Article
The GROWTH Marshal: A Dynamic Science Portal for Time-domain Astronomy
We describe a dynamic science portal called the GROWTH Marshal that allows time-domain astronomers to define science programs; program filters to save sources from different discovery streams; coordinate follow-up with various robotic or classical telescopes; analyze the panchromatic follow-up data; and generate summary tables for publication. The GROWTH marshal currently serves 137 scientists, 38 science programs, and 67 telescopes. Every night, in real time, several science programs apply various customized filters to the 105 nightly alerts from the Zwicky Transient Facility. Here, we describe the schematic and explain the functionality of the various components of this international collaborative platform.
Journal Article
Scalable, ultra-resistant structural colors based on network metamaterials
Structural colors have drawn wide attention for their potential as a future printing technology for various applications, ranging from biomimetic tissues to adaptive camouflage materials. However, an efficient approach to realize robust colors with a scalable fabrication technique is still lacking, hampering the realization of practical applications with this platform. Here, we develop a new approach based on large-scale network metamaterials that combine dealloyed subwavelength structures at the nanoscale with lossless, ultra-thin dielectric coatings. By using theory and experiments, we show how subwavelength dielectric coatings control a mechanism of resonant light coupling with epsilon-near-zero regions generated in the metallic network, generating the formation of saturated structural colors that cover a wide portion of the spectrum. Ellipsometry measurements support the efficient observation of these colors, even at angles of 70°. The network-like architecture of these nanomaterials allows for high mechanical resistance, which is quantified in a series of nano-scratch tests. With such remarkable properties, these metastructures represent a robust design technology for real-world, large-scale commercial applications.
Metamaterials: bird feathers inspire robust colour
The feathers of the South American bird Cotinga maynana have inspired the design of a nanoscale material that exhibits brilliant colour. The colour originates from the material’s intricate structure rather than a pigment or dye. Andrea Fratalocchi of King Abdullah University of Science and Technology in Saudi Arabia and co-workers report that the material provides saturated colours in the visible region. Importantly, the colour can be observed over a very wide range of observation angles (up to 70 degrees) and persists even when the material’s surface is scratched. The nanomaterial consists of 300-nanometre-thick layers of dealloyed PtYAl metallic nanowires, which are sputtered onto SiN
x
/Si substrates and then coated with 60-nanometre layers of a dielectric coating of Al
2
O
3
. The resulting nanomaterial is robust, lightweight and suitable for large-area fabrication.
Journal Article