Entire Visible Light Research Articles

Prevention of melasma relapses with sunscreen combining protection against UV and short wavelengths of visible light: A prospective randomized comparative trial

Prevention of melasma relapses with sunscreen combining protection against UV and short wavelengths of visible light: A prospective randomized comparative trial

High‐Performance Flexible Broadband Photodetector Based on Organolead Halide Perovskite

Organolead halide perovskites have attracted extensive attentions as light harvesting materials for solar cells recently, because of its high charge‐carrier mobilities, high photoconversion efficiencies, low energy cost, ease of deposition, and so on. Herein, with CH3NH3PbI3 film deposited on flexible ITO coated substrate, the first organolead halide perovskite based broadband photodetector is demonstrated. The organolead halide perovskite photodetector is sensitive to a broadband wavelength from the ultraviolet light to entire visible light, showing a photo‐responsivity of 3.49 A W−1, 0.0367 A W−1, an external quantum efficiency of 1.19×103%, 5.84% at 365 nm and 780 nm with a voltage bias of 3 V, respectively. Additionally, the as‐fabricated photodetector exhibit excellent flexibility and robustness with no obvious variation of photocurrent after bending for several times. The organolead halide perovskite photodetector with high sensitivity, high speed and broad spectrum photoresponse is promising for further practical applications. And this platform creates new opportunities for the development of low‐cost, solution‐processed and high‐efficiency photodetectors.

CdS sensitized 3D hierarchical TiO2/ZnO heterostructure for efficient solar energy conversion.

For conventional dye or quantum dot sensitized solar cells, which are fabricated using mesoporous films, the inefficient electron transport due to defects such as grain boundaries and surface traps is a major drawback. To simultaneously increase the carrier transport efficiency as well as the surface area, optimal-assembling of hierarchical nanostructures is an attractive approach. Here, a three dimensional (3D) hierarchical heterostructure, consisting of CdS sensitized one dimensional (1D) ZnO nanorods deposited on two dimensional (2D) TiO2 (001) nanosheet, is prepared via a solution-process method. Such heterstructure exhibits significantly enhanced photoelectric and photocatalytic H2 evolution performance compared with CdS sensitized 1D ZnO nanorods/1D TiO2 nanorods photoanode, as a result of the more efficient light harvesting over the entire visible light spectrum and the effective electron transport through a highly connected 3D network.

Realizing full visible spectrum metamaterial half-wave plates with patterned metal nanoarray/insulator/metal film structure

Abrupt phase shift introduced by plasmonic resonances has been frequently used to design subwavelength wave plates for optical integration. Here, with the sandwich structure consisting of a top periodic patterned silver nanopatch, an in-between insulator layer and a bottom thick Au film, we realize a broadband half-wave plate which is capable to cover entire visible light spectrum ranging from 400 to 780 nm. Moreover, when the top layer is replaced with a periodic array of composite super unit cell comprised of two nanopatches with different sizes, the operation bandwidth can be further improved to exceed an octave (400-830 nm). In particular, we demonstrate that the designed half-wave plate can be used efficiently to rotate the polarization state of an ultra-fast light pulse with reserved pulse width. Our result offers a new strategy to design and construct broadband high efficiency phase-response based optical components using patterned metal nanoarray/insulator/metal structure.

Structure and morphology evolution in mechanochemical processed CuInS2 powder

CuInS2 powders were synthesized by mechanochemical process from copper, indium and sulfur powders. A self-propagating combustion occurred during the milling process. Phase structure, morphology evolution and component uniformity of Cu–In–S system have been studied by X-ray diffraction, scanning electron microscope and energy dispersive analysis, respectively. Optical property of ball milled CuInS2 has been detected by UV–Vis spectroscopy. The results show that there is no intermetallic phase was observed before the self-propagating combustion though morphology changed obviously during this stage. The detected composition of mixed powder converges toward the original proportion with increased milling as the particle sizes decreased. Homogeneous CuInS2 particles less than 5μm are obtained after milling 120min. The reason of mechanically induced self-propagating reaction occurs during milling in this system is also discussed. The UV–Vis absorption spectrum shows the milled CuInS2 has a broad absorption over the entire visible light and extending into the near-infrared region and its band gap is 1.52eV.

Tunable Lyotropic Photonic Liquid Crystal Based on Graphene Oxide

A direct colloidal self-assembly approach was utilized to prepare photonic crystals based on exfoliated graphene oxide (GO) in aqueous solution. The GO sheets form ordered photonic structure spontaneously without the need for multiple processing steps. The wavelength of light reflected by the GO photonic crystal dispersion can be controlled over the entire visible light spectrum simply by varying the GO concentration. The aspect ratio of the GO sheets and mediation of the intersheet forces are found to be the key factors influencing the stability of photonic crystal formation. The usefulness and limitations of the GO photonic crystals prepared in this study are discussed.

Fabrication of hollow-sphere films of wurtzite CuInS2 on copper substrate

As important semiconductors, I–III–VI2 compounds have attracted wide attention, among which the wurtzite structured CuInS2 has been the research focus due to its metastable phase. In this paper, the wurtzite CuInS2 hollow-sphere films have been successfully prepared on copper substrate in a self-designed solvothermal detached system. The films of Cu(OH)2 one-dimensional nanostructure arrays and thioacetamide were used as the precursors and triethylene glycol was used as the solvent. Experiments showed that the amount of indium trichloride played a determinative role in the final morphology of the products. Meanwhile, the one-dimensional nanostructure arrays and the detached solvothermal system have great influences on the crystal shape as well. Based on the experimental results, a possible formation mechanism for the CuInS2 hollow spheres was also proposed. The UV–Vis absorption spectrum showed a broad absorption over the entire visible light and extending into the near-infrared region and presented the band gap of 1.53 eV for the as-prepared wurtzite CuInS2, which indicates the potential applications in solar cells.

Dendritic Light-harvesting Antennas with Excitation Energy Gradients

Abstract Dendritic architectures provide attractive scaffolds for the precise arrangement of considerable numbers of antenna chromophores. Multichromophoric antennas are advantageous for obtaining intense absorption over the entire visible light spectrum. The strategic arrangement of various antenna chromophores produces the lowest excitation energy gradient for efficient energy transfer. Large light-harvesting systems can be constructed by the proper arrangement of the antennas.

Spinel Indium Sulfide Precursor for the Phase-Selective Synthesis of Cu–In–S Nanocrystals with Zinc-Blende, Wurtzite, and Spinel Structures

Group I–III–VI ternary chalcogenides have attracted extensive attention as important functional semiconductors. Among them, Cu–In–S compounds have seen strong research interest due to their potential applications in high-efficiency solar cells. However, the controllable synthesis of Cu–In–S nanostructures with different phases is always difficult. In this research, zinc-blende CuInS2, wurtzite CuInS2, and spinel CuIn5S8 could be selectively synthesized using spinel In3–xS4 as the precursor by a simple solvothermal method. X-ray powder diffraction was used to determine the phase and crystal structure, and transmission electron microscopy was employed to characterize the morphologies of the as-prepared samples. Experiments showed that the acidity–basicity of the reaction system and the coordination and reducibility of the capping ligands were crucial to the final phases of the products. The UV–vis–NIR spectra of the three phases all exhibited a broad-band absorption over the entire visible light and extendi...

One-pot, rapid synthesis of chalcopyrite CuInSe2 nanoparticles for low-cost thin film solar cell

In this work, highly dispersed and near stoichiometric chalcopyrite CuInSe2 nanoparticles were successfully synthesized via a facile and rapid one-pot method. The effects of reaction temperature and reaction time on the crystal phase, morphology, element composition and the absorption spectrum of the as-synthesized CuInSe2 nanoparticles were investigated by x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and UV-Vis-IR spectrophotometer, respectively. The XRD patterns showed that the as-synthesized nanoparticles had pure chalcopyrite phase with the particle size in the range of 50–300nm confirmed by FE-SEM images. The Vis-IR absorption spectra showed strong absorption in the entire visible light to near-infrared region, the estimated band gap of the as-synthesized nanoparticles matched very well with that of the bulk CuInSe2 material. All results suggested that the as-synthesized CuInSe2 nanoparticles were good light absorber layer material for thin film solar cell.

Colorimetric and Resistive Polymer Electrolyte Thin Films for Real-time Humidity Sensors

We have developed fast responsive, colorimetric and resistive-type polymeric humidity sensors from a series of self-assembled poly(styrenesulfonate-methylbutylene) (PSS-b-PMB) block copolymers with tailored hygroscopic properties. In dry state, the PSS-b-PMB films exhibit hexagonal cylindrical morphology where hydrophobic PMB cylinders are dispersed within a PSS matrix. Under levels of humidity, the PSS-b-PMB thin films self-displayed discernible reflective color changes, covering almost entire visible light regions from violet (RH = 20%) to red (RH = 95%). The sensors also revealed a few orders of magnitude changes in impedance with exposure to humid air by taking advantages of strong polymer electrolytes characteristics. Remarkably, the time to complete the changes in the signals was only a few seconds, as rationalized by good connectivity of the PSS domains and short water diffusion pathways in nanometer scales. Repeated hydration/dehydration tests demonstrated reliable sensor properties, which is in sharp contrast to the poor stability of PSS homopolymer sensors lacking organization.

Comparison of Three Receiver Designs for Optical Wireless Communications using White LEDs

Three visible light optical wireless communication systems using asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and white light emitting diodes (LEDs) are compared. The LEDs considered have a larger modulation bandwidth for the blue optical frequencies than for the rest of the transmitted optical spectrum. It is shown that for typical parameter values, a novel diversity combining receiver has slightly greater capacity than a system optimized for reception of blue light only, and that both have greater capacity than a system designed to receive the entire visible light spectrum.

Full-field imaging-based instantaneous hyperspectral absolute refractive index measurement

Multispectral refractometers typically measure refractive index (RI) at discrete monochromatic wavelengths via a serial process. We report on the demonstration of a white light full-field imaging-based refractometer capable of instantaneous multispectral measurement of absolute RI of clear liquid-gel samples across the entire visible light spectrum. The broad optical bandwidth refractometer is capable of hyperspectral measurement of RI in the range 1.30-1.70 between 400 and 700 nm with a maximum error of 0.0036 units (0.24% of actual) at 414 nm for an η=1.50 sample. We present system design and calibration method details as well as results from a system validation sample.

Efficient hybrid white polymer light-emitting devices with electroluminescence covered the entire visible range and reduced efficiency roll-off

We report efficient hybrid white polymer light emitting devices (WPLEDs) fabricated via simple solution-proceeded process from a newly synthesized wide band-gap fluorene-co-dibenzothiophene-S,S-dioxide copolymer, which dually function as fluorescent blue emitter and host material for electrophosphorescent sky-blue, yellow, and saturated-red dyes. The Commission Internationale d’Énclairage coordinates of the best devices are (0.356, 0.334), with electroluminescence covered the entire visible light spectrum from 400 to 780 nm, resulting in a high color rendering index of 90. Incorporation of a bilayer electrode consisting of water/alcohol-soluble conjugated polymer and Al as electron-injection cathode boosts an enhancement of 50% in device efficiency, leading to external quantum efficiency of 12.6%, and peak power efficiency of 21.4 l m W−1 as measured in an integrating sphere. Both the efficiency and the color quality of the obtained device are ranking among one of the highest values for WPLEDs reported to date. Furthermore, as compared with those all-phosphorescent WPLEDs, the hybrid WPLEDs studied here exhibit a significantly reduced efficiency roll-off due to the very low doping concentration.

A tunable warm-white-light Sr3Gd(PO4)3:Eu2+,Mn2+phosphor system for LED-based solid-state lighting

A novel tunable full-color-emitting Sr3Gd(PO4)3:Eu2+,Mn2+ phosphor system was successfully developed. Its excitation wavelength ranging from 230 to 450 nm fits well with the characteristic emission of UV light-emitting diode (LED) chips. The color emission of these phosphors can be tuned across almost the entire visible light spectrum resulting in white light emission with varied hue and correlated color temperature (CCT) by varying the molar ratios of Eu2+ and Mn2+. Moreover, the efficient energy transfer from Eu2+ to Mn2+ was demonstrated via a dipole–quadrupole mechanism by the luminescence spectra and the fluorescence decay dynamics based on the Inokuti–Hirayama theoretical model. These results indicate that the developed phosphor may be promising as a single-component white-light-emitting phosphor for white LEDs.

液晶微胶囊制备宽波反射凝胶

Chiral nematic(N*) liquid crystal can reflect incident light selectively,and the reflective bandwidth is less than 150 nm commonly.Five N* liquid crystals were prepared from a nematic liquid crystal with negative dielectric anisotropy SLC10V513-200 and chiral compounds R1011,CB15.Their reflective spectra could cover with the entire visible spectrum.Polyurea microcapsules containing above N* liquid crystals were prepared by interfacial polymerization of isophorone diisocyanate(IPDI).By mixing same weight of five kinds of microcapsules together in surfactant OP-10 and IPDI,a gel was obtained.Applying an alternating electric field to an 80.0 μm gel film,the liquid crystal molecules in microcapsules would align parallel with the substrates.Curing monomer in the microcapsules with UV light and planar texture can be fixed,so the gel film which could reflect entire visible light wavelength range was prepared.

Single pixel transmissive and reflective liquid crystal display using broadband cholesteric liquid crystal film

We propose a single mode transflective liquid crystal display (LCD) which is operated as the transmissive and reflective modes in a single pixel without dividing into sub-pixels. The single pixel transflective LCD was composed of the cross-polarized nematic LCD as a light modulator and the broadband cholesteric liquid crystal film (BCLCF) as a half mirror. The BCLCF, simply prepared by the exposure of ultraviolet light to the mixture of the nematic LC and the reactive mesogen with chirality, selectively reflects a certain circular polarization but transmits the orthogonal circular polarization in entire visible light. The electro-optical properties in both transmissive and reflective modes coincide with each other.

Novel rare-earth-free tunable-color-emitting BCNO phosphors

We present a facile synthesis of novel, rare-earth (RE)-ion-free boron carbon oxynitride (BCNO) phosphors. The preparation method, chemical composition, luminescent properties and emission mechanisms, as well as current trends in BCNO phosphors are reviewed. The novel BCNO phosphors were synthesized from inexpensive and environmentally friendly raw materials by a straightforward route using liquid precursors at low temperatures under atmospheric pressure. The newly developed BCNO phosphors demonstrated tunable color emission, high quantum efficiency, and long-duration afterglow. The color emission of these phosphors can be tuned across almost the entire visible light spectrum by varying the molar ratios of the raw materials.

Optical and electrical properties of TiO 2/Au/TiO 2 multilayer coatings in large area deposition at room temperature

TiO 2/Au/TiO 2 multilayer thin films were deposited at polymer substrate at room temperature using dc (direct current) magnetron sputtering method. By varying the thickness of each layer, the optical and electrical properties of the TiO 2/Au/TiO 2 multilayer films can be tailored to suit different applications. The thickness and optical properties of the Au layer and the quality of the Au-dielectric interfaces are critical for the electrical and optical performance of the Au-dielectric multilayer thin films. At the thickness of 8 nm, the Au layer forms a continuous structure having the lowest resistivity and it must be thin for high transmittance. The multilayer stack can be optimized to have a sheet resistance of 6 Ω/sq. at a transmittance over 80% at 680 nm in wavelength. The peak transmittance shifts towards the long wavelength region when the thickness of the two TiO 2 (upper and lower) layers increases. When the film thickness of the two TiO 2 film is 45 nm, a high transmittance value is obtained for the entire visible light wavelength region.

Generation and Characterization of a Rat Monoclonal Antibody Specific for Multiple Red Fluorescent Proteins

Abstract Fluorescent proteins (FP) are widely used as in vivo reporter molecules and are available in multiple colors spanning almost the entire visible light spectrum. Genetically fused to any protein target, FPs offer a powerful tool to study protein localization and dynamics. After the isolation of the prototypical green fluorescent protein (GFP) from the jellyfish Aequorea victoria, a red fluorescent protein (DsRed) was discovered in the coral Discosoma sp. that provided a better spectral separation from cellular autofluorescence and allowed multicolor tracking of fusion proteins. However, the obligate tetramerization of DsRed caused serious problems for its use in live-cell imaging. Subsequent mutageneses of the red progenitor have resulted in several monomeric red FPs (mRFP1, mCherry, mOrange, mPlum, etc). These improved red FPs are characterized by higher brightness and photostability, complete chromophore maturation, and promise a wide variety of features for biological imaging and multicolor labeling. Here we report the generation and characterization of the first rat monoclonal antibody (MAb) against multiple red FPs, designated as multi-red 5F8. We demonstrate that multi-red 5F8 is a MAb with high affinity and specificity against the DsRed derivatives and corresponding fusion proteins, and that it is suitable for ELISA, immunoblotting, immunoprecipitation, and immunofluorescence assays. Applying our versatile antibody, one and the same red fluorescent protein tag can be used to perform not only microscopic studies, but also multiple biochemical assays.