Full Visible Spectrum Research Articles

Control of Protonated Schiff Base Excited State Decay within Visual Protein Mimics: A Unified Model for Retinal Chromophores.

Artificial biomimetic chromophore-protein complexes inspired by natural visual pigments can feature color tunability across the full visible spectrum. However, control of excited state dynamics of the retinal chromophore, which is of paramount importance for technological applications, is lacking due to its complex and subtle photophysics/photochemistry. Here, ultrafast transient absorption spectroscopy and quantum mechanics/molecular mechanics simulations are combined for the study of highly tunable rhodopsin mimics, as compared to retinal chromophores in solution. Conical intersections and transient fluorescent intermediates are identified with atomistic resolution, providing unambiguous assignment of their ultrafast excited state absorption features. The results point out that the electrostatic environment of the chromophore, modified by protein point mutations, affects its excited state properties allowing control of its photophysics with same power of chemical modifications of the chromophore. The complex nature of such fine control is a fundamental knowledge for the design of bio-mimetic opto-electronic and photonic devices.

High Gain Solution‐Processed Carbon‐Free BiSI Chalcohalide Thin Film Photodetectors

AbstractChalcohalide semiconductors are an emergent class of materials for optoelectronics. Here, the first work on BiSI chalcohalide thin film photodetectors (PDs) is presented. An entirely new method for the fabrication of bismuth chalcohalide thin films (BiOI and BiSI) is developed. This method circumvents the use of any ligands or counter ions during fabrication and provides highly pure thin films free of carbon residues and other contaminants. When integrated into lithographically patterned lateral PDs these BiSI thin films show outstanding performances and high stability. The direct ≈1.55 eV bandgap of BiSI perfectly accommodates optical sensing over the full visible spectrum. The responsivity (R) of the BiSI PDs reaches 62.1 A W−1, which is the best value reported to date across chalcohalide materials of any type. The BiSI PDs display remarkable sensitivity to low light levels, supporting a broad operational detectivity ≈1012 Jones over four decades in light intensity, with a peak specific detectivity (D*) of 2.01 × 1013 Jones. The dynamics of photocurrent generation are demonstrated to be dominated by photoconductive gain. These results cement BiSI as an exciting candidate for high performance photodetector applications and encourage ongoing work in BiSX (X = Cl, Br, I) materials for optoelectronics.

Inverse designed extended depth of focus meta-optics for broadband imaging in the visible

Abstract We report an inverse-designed, high numerical aperture (∼0.44), extended depth of focus (EDOF) meta-optic, which exhibits a lens-like point spread function (PSF). The EDOF meta-optic maintains a focusing efficiency comparable to that of a hyperboloid metalens throughout its depth of focus. Exploiting the extended depth of focus and computational post processing, we demonstrate broadband imaging across the full visible spectrum using a 1 mm, f/1 meta-optic. Unlike other canonical EDOF meta-optics, characterized by phase masks such as a log-asphere or cubic function, our design exhibits a highly invariant PSF across ∼290 nm optical bandwidth, which leads to significantly improved image quality, as quantified by structural similarity metrics.

Lanthanide Upconverted Microlasing: Microlasing Spanning Full Visible Spectrum to Near-Infrared under Low Power, CW Pumping.

The miniaturization of lasers holds promise in ultradense data storage and biosensing, but greater pump power is required to reach the lasing thresholds to overcome increased optical losses with reduced resonant cavity sizes. Here, the whispering galley mode (WGM) of Yb3+ /Tm3+ doped upconversion nanoparticles (UCNPs) coupled with microcavities (≈5µm) is used to achieve ultralow threshold upconverted lasing at 800nm with excitation fluences as low as 4Wcm-2 . The continuous-wave (CW) upconverted lasing, with a Q factor on the order of 103 , can remain stable for more than 6 h. In addition, ultralow threshold upconverted microlasers spanning the full visible spectrum from Yb3+ /Er3+ , Yb3+ /Ho3+ , and Yb3+ /Tm3+ doped UCNPs are obtained with the same WGM cavity design. These upconverted microlasers working under low power CW 980nm laser will enable promising applications in biosensing and imaging.

Rapid large-scale synthesis of highly emissive solid-state metal halide perovskite quantum dots across the full visible spectrum

The practical applications of solid-state inorganic CsPbX3 perovskite quantum dots (PQDs) have been restricted by their poor stability. Herein, we report an efficient large-scale synthesis of solid-state CsPbX3 PQDs across the full visible spectra using 3-Aminopropyltrimethoxysilane as ligands at room temperature in open air. The obtained green CsPbBr3 solids display outstanding optical performance with high color purity of 90% and photoluminescence quantum yield of 69.2%. Thanks to the protection of silica coating, the solid-state product shows much higher thermal stability, photo stability and long-term stability than that of naked CsPbBr3 QDs. The blue CsPb(Br/Cl)3 and yellow or red CsPb(Br/I)3 PQDs solids can be simply obtained via using alkali metal halide aqueous solution as additives. The white LED fabricated by combining the obtained green CsPbBr3 QDs solid powders and commercial red K2SiF6: Mn4+ phosphor with a blue LED chip displays high luminous efficiency of 70.47 lm/W and the color gamut can cover over 129.4% of the National Television System Committee standard.

A panther chameleon skin-inspired core@shell supramolecular hydrogel with spatially organized multi-luminogens enables programmable color change

Organization of different iridophores into a [email protected] structure constitutes an evolutionary novelty for panther chameleons that allows their skins to display diverse color change. Inspired by this natural color-changing design, we present a responsive [email protected] multi-luminogen supramolecular hydrogel system that generates a programmable multi-color fluorescent change. Specifically, red Eu3+-amidopicolinate (R) luminogen is incorporated into the core hydrogel, while blue naphthalimide (B) and green perylene-tetracarboxylic acid (G) luminogens are grown into two supramolecular shell hydrogels. The intensities of G/B luminogens could then be controlled independently, which enables its emission color to be programmed easily from red to blue or green, nearly covering the full visible spectrum. Because of the differential excitation energies between these luminogens, a desirable excitation wavelength-dependent fluorescence is also achieved. Colorful materials with a patterned [email protected] structure are also demonstrated for anti-counterfeiting, opening up the possibility of utilizing a bioinspired [email protected] structure to develop an efficient multi-color fluorescent system with versatile uses.

Color of Copper/Copper Oxide.

Stochastic inhomogeneous oxidation is an inherent characteristic of copper (Cu), often hindering color tuning and bandgap engineering of oxides. Coherent control of the interface between metal and metal oxide remains unresolved. Coherent propagation of an oxidation front in single-crystal Cu thin film is demonstrated to achieve a full-color spectrum for Cu by precisely controlling its oxide-layer thickness. Grain-boundary-free and atomically flat films prepared by atomic-sputtering epitaxy allow tailoring of the oxide layer with an abrupt interface via heat treatment with a suppressed temperature gradient. Color tuning of nearly full-color red/green/blue indices is realized by precise control of the oxide-layer thickness; the samples cover ≈50.4% of the standard red/green/blue color space. The color of copper/copper oxide is realized by the reconstruction of the quantitative yield color from the oxide "pigment" (complex dielectric functions of Cu2 O) and light-layer interference (reflectance spectra obtained from the Fresnel equations) to produce structural color. Furthermore, laser-oxide lithography is demonstrated with micrometer-scale linewidth and depth through local phase transformation to oxides embedded in the metal, providing spacing necessary for semiconducting transport and optoelectronics functionality.

Construction of a novel supramolecular self‐assembly photocatalyst for full visible light spectrum photooxidation of phenol

AbstractThe sluggish full visible light response of organic supramolecular catalysts is a challenge that greatly restricts their development in the photocatalytic field. Herein, we successfully fabricated a K, Cl‐codoped Bi2WO6/perylene‐diimide(PDI) catalyst with a novel, general, and facile ultrasound assisted water bath heating method. The UV adsorption onset of K, Cl‐codoped Bi2WO6/PDI is redshifted from 750 to 760 nm compared with that of the heterojunction of Bi2WO6/PDI. Under visible light, the phenol is thoroughly mineralized into CO2 and H2O, and the phenol degradation rate was three times higher than that of pure Bi2WO6/PDI. The electrons transfer from PDI to K‐ and Cl‐codoped Bi2WO6/PDI according to the charge density difference calculation. The built‐in potential of K‐ and Cl‐codoped Bi2WO6/PDI could increase from 2.09 to 5.54 eV. The excellent full visible light spectrum photooxidation of phenol is attributed to the suitably strong built‐in potential at the heterojunction between PDI and K, Cl‐codoped Bi2WO6.

Near-Infrared Light Induced Dynamic Structural Color Change of Amorphous Photonic Hydrogel

Light-induced photonic systems are rare in nature and usually lack a full color response in artificial systems. Herein, we first report a near-infrared (NIR) light controlled optical hydrogel; its structural color covers the full visible spectrum range. The hydrogel was fabricated by embedding dry thermoresponsive microgels film into a thermoresponsive hydrogel. Under the synergistic effect of the microgels and hydrogel, the hydrogel displayed a dynamic color with temperature changing, and it was reversible. Moreover, the structural colors were angle independent for the amorphous microgel arrays. When carbon nanotubes were integrated into the matrix hydrogel, dynamic structural colors can be displayed under NIR irradiation. Such NIR light-responsive photonic hydrogel film may provide potential applications in artificial skin, the military, and other fields.

Near-zero reflection of all-dielectric structural coloration enabling polarization-sensitive optical encryption with enhanced switchability

Abstract Structural coloration using metasurfaces has been steadily researched to overcome the limitations of conventional color printing using pigments by improving the resolution, lowering the toxicity, and increasing the durability. Many metasurfaces have been demonstrated for dynamic structural coloration to convert images at the visible spectrum. However, the previous works cannot reach near-zero scattering when colors are turned-off, preventing it from being cryptographic applications. Herein, we propose a completely on/off switchable structural coloration with polarization-sensitive metasurfaces, enabling full-colored images to be displayed and hidden through the control of the polarization of incident light. It is confirmed that the nanostructure exhibits the polarization-dependent magnetic field distributions, and near-zero scattering is realized when the polarization of incident light is perpendicular to the long axis of the nanofins. Also, the metasurfaces are made up of triple-nanofin structures whose lengths affect locations of resonance peaks, resulting in full-color spectrum coverages. With such advantages, a QR code image, a two-color object image, and an overlapped dual-portrait image are obtained with the metasurfaces. Such demonstrations will provide potential applications in the fields of high-security information encryption, security tag, multichannel imaging, and dynamic displays.

Full Visible Spectrum Panchromatic Triple Donor Dye for Dye-Sensitized Solar Cells

An organic dye with three electron donating groups is studied that has broad full visible spectrum panchromatic absorption in solution. The donor groups introduce six significant optical transition...

Angular-Independent Photonic Pigments via the Controlled Micellization of Amphiphilic Bottlebrush Block Copolymers.

Photonic materials with angular-independent structural color are highly desirable because they offer the broad viewing angles required for application as colorants in paints, cosmetics, textiles, or displays. However, they are challenging to fabricate as they require isotropic nanoscale architectures with only short-range correlation. Here, porous microparticles with such a structure are produced in a single, scalable step from an amphiphilic bottlebrush block copolymer. This is achieved by exploiting a novel "controlled micellization" self-assembly mechanism within an emulsified toluene-in-water droplet. By restricting water permeation through the droplet interface, the size of the pores can be precisely addressed, resulting in structurally colored pigments. Furthermore, the reflected color can be tuned to reflect across the full visible spectrum using only a single polymer (Mn = 290kDa) by altering the initial emulsification conditions. Such "photonic pigments" have several key advantages over their crystalline analogues, as they provide isotropic structural coloration that suppresses iridescence and improves color purity without the need for either refractive index matching or the inclusion of a broadband absorber.

Full-Color Spectrum Coverage by High-Color-Purity Perovskite Nanocrystal Light-Emitting Diodes

Summary Although many synthetic methods such as hot injection and anionic exchange can produce full-color perovskite nanocrystals (PNCs), their emission spectra are broadened by compositional non-uniformity. Here, we propose the synthetic method, hydrogen halide (HX; X = Cl, Br, and I)-mediated uniform halide anion exchange at mild temperatures, for high color-purity PNCs emitters across the full-color spectrum. The HX-mediated exchange reaction produces high-purity PNCs without metallic Pb impurities due to the use of volatile HX as the X source. The blue, green, and red PNCs show narrow emission spectra, with 16, 18, and 18.5 nm of full width at half-maximum, respectively. The red PNC emitter synthesized by the HX-mediated method has a single photoluminescent (PL) peak, with a narrow emission spectrum at low temperature due to compositional uniformity, whereas the PNCs produced by other methods have multiple PL peaks. Accordingly, the red/green/blue electroluminescent devices also have narrow emission spectra.

Tuneable red, green, and blue single-mode lasing in heterogeneously coupled organic spherical microcavities

Tuneable microlasers that span the full visible spectrum, particularly red, green, and blue (RGB) colors, are of crucial importance for various optical devices. However, RGB microlasers usually operate in multimode because the mode selection strategy cannot be applied to the entire visible spectrum simultaneously, which has severely restricted their applications in on-chip optical processing and communication. Here, an approach for the generation of tuneable multicolor single-mode lasers in heterogeneously coupled microresonators composed of distinct spherical microcavities is proposed. With each microcavity serving as both a whispering-gallery-mode (WGM) resonator and a modulator for the other microcavities, a single-mode laser has been achieved. The colors of the single-mode lasers can be freely designed by changing the optical gain in coupled cavities owing to the flexibility of the organic materials. Benefiting from the excellent compatibility, distinct color-emissive microspheres can be integrated to form a heterogeneously coupled system, where tuneable RGB single-mode lasing is realized owing to the capability for optical coupling between multiple resonators. Our findings provide a comprehensive understanding of the lasing modulation that might lead to innovation in structure designs for photonic integration.

Learned rotationally symmetric diffractive achromat for full-spectrum computational imaging

Diffractive achromats (DAs) promise ultra-thin and light-weight form factors for full-color computational imaging systems. However, designing DAs with the optimal optical transfer function (OTF) distribution suitable for image reconstruction algorithms has been a difficult challenge. Emerging end-to-end optimization paradigms of diffractive optics and processing algorithms have achieved impressive results, but these approaches require immense computational resources and solve non-convex inverse problems with millions of parameters. Here, we propose a learned rotational symmetric DA design using a concentric ring decomposition that reduces the computational complexity and memory requirements by one order of magnitude compared with conventional end-to-end optimization procedures, which simplifies the optimization significantly. With this approach, we realize the joint learning of a DA with an aperture size of 8 mm and an image recovery neural network, i.e., Res-Unet, in an end-to-end manner across the full visible spectrum (429–699 nm). The peak signal-to-noise ratio of the recovered images of our learned DA is 1.3 dB higher than that of DAs designed by conventional sequential approaches. This is because the learned DA exhibits higher amplitudes of the OTF at high frequencies over the full spectrum. We fabricate the learned DA using imprinting lithography. Experiments show that it resolves both fine details and color fidelity of diverse real-world scenes under natural illumination. The proposed design paradigm paves the way for incorporating DAs for thinner, lighter, and more compact full-spectrum imaging systems.

High Color-Purity Perovskite Nanocrystal Light Emitting Diodes at Full Color Spectrum

HIGHLIGHTS ∙ HX(X=Cl, Br, and I) mediated anion exchange produces compositionally uniform perovskite nanocrystals (PNCs). ∙ The HX mediated exchange reaction does not remain Pb/PbX 2 impurities due to the use of volatile HX as X source. ∙ The PNCs have high color purity with narrow emission spectrum (< 20 nm) at full color spectrum.

Differential sunlight exposure affects settling behaviour of hemlock woolly adelgid crawlers

Abstract Previous research demonstrated that elevated sunlight improves carbon balance and growth of eastern hemlock (Tsuga canadensis (L.) Carrière) seedlings infested with the invasive hemlock woolly adelgid (Adelges tsugae Annand). This study examined the hypothesis that elevated visible and ultraviolet sunlight directly affects the settling behaviour of A. tsugae crawlers. Hemlock seedlings were manually infested with equal densities of A. tsugae and placed into artificial shade treatments (0%, 40% and 80% shade). The density of settled nymphs of the ensuing generation on shaded seedlings was three times higher than the density on unshaded seedlings. Adelges tsugae ovisacs were also attached to hydrated hemlock branches placed beneath acrylic filter treatments that selectively allowed transmission of various sunlight wavelengths. The proportion of adelgid crawlers that settled on the branch (vs. dropping from it) was higher beneath filters that blocked the widest spectrum of solar radiation (opaque and amber filters) than beneath full sun. In the March‐April trial, exposure to full sun and the full visible spectrum only (clear‐UV filter) significantly increased the proportion of crawlers that settled on the bottom (vs. top) side of the branch. Our results suggest that A. tsugae crawlers are negatively phototactic and/or thermotactic, with behaviour influenced more by visible light than ultraviolet light.

Site-selective occupation of Eu2+ activators toward full-visible-spectrum emission in well-designed borophosphate phosphors

Efficient modulation of the site-selection of activators is of great significance for designing high-performance phosphors. Herein, we report that site-selective occupation of Eu2+ activators in mixed anion-group realizes full visible spectrum emission in borophosphate K2BaCa(PO4)2−x(BO3)x:0.03Eu2+ phosphors, which are designed by using K2BaCa(PO4)2:0.03Eu2+ cyan-emitting phosphor. In the pristine sample, there are four crystallographic sites (Ca, Ba, K1 and K2), yet, Eu2+ ions only occupy the K1 and K2 sites. By anion-group cosubstituting (PO4)3− with (BO3)3− units, the most strikingly discoveries here are that a Eu2+-substitution new pathway is opened up, rendering partial Eu2+ ions enter Ca crystallographic site that could never be occupied before, yielding an intense Eu2+ red emission band at 660 nm, and consequently realizing spectral tuning from original cyan-emitting to white-light emission. The structural analysis and DFT calculations support the concept that Eu2+ ion preferably occupy the Ca site, and revealing impressive insights of site-selective occupation of Eu2+ in the borophosphate white-light phosphors. Importantly, using only this full-visible-spectrum phosphor (x = 0.4), as-prepared WLED shows excellent color quality (Ra = 90.4 and R9 = 93.8). This work not only presents an in-depth investigation of site-selection of Eu2+, but also opens a new way to design full-visible-spectrum phosphors.

Osmosis manipulable morphology and photonic property of microcapsules with colloidal nano-in-micro structure

Full visible spectrum photonic droplets and consequent microcapsules with nano-in-micro structure were prepared through microfluidic technique. Photo-curable resin and suspension of monodispersed soft nanogels were used as shell and core of the microcapsules, respectively. Upon UV irradiation, the droplets can be subsequently transformed into photonic microcapsules with an ultrathin polymeric shell. The shell thickness of the photonic microcapsules was found to be approximately 700 nm. Due to the ultrathin shell and soft core, the photonic microcapsules with nano-in-micro structure display dramatic changes both in shapes and photonic property under the impact of osmosis effect or temperature stimulus. Typically, the shell and core parts of nano-in-micro structure could respectively undergo a size expansion/even rupture and a size decrease/buckling under hypotonic and hypertonic condition. Correspondingly, the peak value of the reflection spectra of the microcapsules showed a redshift and blue shift, respectively. The mechanism to the structure and optical properties variation involves the osmotic pressure induced the volume-fraction change of the nanogel-based photonic dispersion and the shell buckling of the core/shell microcapsules.

George Eliot and Van Gogh: Radiant Realism

Vincent Van Gogh had a deep and abiding interest in the fiction of George Eliot and her mode of depicting the ordinary matter of ‘provincial life’ in luminous detail. This article argues that Eliot’s influence on Van Gogh can be seen in the formal, and not just thematic, radicalism shared by both. How might we read Van Gogh’s works as an ekphrastic reworking of Eliot’s insistence on the full colour spectrum of aesthetic experience lurking within the apparently dull and everyday and the need for radical shifts in perspective in the journey of life; a shared quest for the sacred within a secularized world? This underacknowledged debt that crosses media, periods, and national boundaries brings into focus the radical experimentalism of Eliot’s works and the redemptive forms of provincial realism. Eliot’s use of settings in rural or provincial life in the recent ‘just’ past is often read as nostalgic and conceived of as part of a conservative aesthetics of her realism. We tend to think of Van Gogh’s work, conversely, as part of that broad shift towards a cosmopolitan and experimental modernism in the twentieth century, as writers and artists looked beyond Britain for new ways of seeing the world. The story of Van Gogh’s passion for Eliot’s art reminds us that the forms of nineteenth-century realist provincialism have within them a means of radically transforming the appreciation of the everyday and stimulating modernity at large.