Fine Color Tuning Research Articles

Protein Charge Neutralization Is the Proximate Driver Dynamically Tuning Reflectin Assembly.

Reflectin is a cationic, block copolymeric protein that mediates the dynamic fine-tuning of color and brightness of light reflected from nanostructured Bragg reflectors in iridocyte skin cells of squids. In vivo, the neuronally activated phosphorylation of reflectin triggers its assembly, driving osmotic dehydration of the membrane-bounded Bragg lamellae containing the protein to simultaneously shrink the lamellar thickness and spacing while increasing their refractive index contrast, thus tuning the wavelength and increasing the brightness of reflectance. In vitro, we show that the reduction in repulsive net charge of the purified, recombinant reflectin-either (for the first time) by generalized anionic screening with salt or by pH titration-drives a finely tuned, precisely calibrated increase in the size of the resulting multimeric assemblies. The calculated effects of phosphorylation in vivo are consistent with these effects observed in vitro. The precise proportionality between the assembly size and charge neutralization is enabled by the demonstrated rapid dynamic arrest of multimer growth by a continual, equilibrium tuning of the balance between the protein's Coulombic repulsion and short-range interactive forces. The resulting stability of reflectin assemblies with time ensures a reciprocally precise control of the particle number concentration, encoding a precise calibration between the extent of neuronal signaling, osmotic pressure, and the resulting optical changes. The charge regulation of reflectin assembly precisely fine-tunes a colligative property-based nanostructured biological machine. A physical mechanism is proposed.

Highly efficient color mixing system for the fine-tuning of white light–PLEDs using blue and red poly-chromophores

The fine tuning of color and white light emission was achieved from the simple blending of two different types of polychromophores. The π-conjugated polymeric chromophores (blue and red) were synthesized and characterized for white light polymer emitting diode (WPLED) applications. The binary luminescent materials, Blue polymeric chromophore (BPy) and (Red polymeric chromophore (RPy), were obtained from the respective monomers via a standard Suzuki coupling reaction. The tuning of colors and white light emission were attained directly mixing of two polymeric chromophores (blue, red) in different ratio. The prepared polymer materials were confirmed using standard tehniques such as, Fourier transform infrared (FT-IR) and 13C and 1H-nuclear magnetic resonance (NMR) spectroscopy, while the gel-permeation chromatography result revealed the polymeric properties of the materials. The polymeric materials surfaces morphologies were analysed throught the FE-SEM and AFM analysis. The TGA (Thermogravymetric analysis) used to study the thermal property of the two prepared polymeric materials. The UV–visible and fluorescence spectrophotometry was applied to examine the optical features of the materials. The BPy and RPy polymers shows absorption peaks at 375 nm and 426 nm, respectively. The obatined emission peaks of BPy and RPy are at 426 nm and 603 nm, respectively. These results show that BPy and RPy belong to the blue and red emissive categories, and the white light emission was obtained with the mixing ratio of BPy(80%)-RPy(20%). The bandgap of these materials was calculated by cyclic voltammetry, and the theoretical bandgap of the materials was calculated by density functional theory analysis. Finely structured devices were fabricated, and the efficiencies of the BPy, RPy, and BPy-RPy were analyzed to assess the luminance productivity of the materials. In summary, this paper proposes a simple method to achieve white color emission by mixing polymeric chromophores at different ratios.

New Carboxylate Anionic Sm-MOF: Synthesis, Structure and Effect of the Isomorphic Substitution of Sm3+ with Gd3+ and Tb3+ Ions on the Luminescent Properties

Two new compounds, namely {(NMe2H2)}[Ln(TDA)(HCOO)] 0.5H2O, Ln = Sm3+ (Sm-TDA) and Gd3+ (Gd-TDA), where TDA3− is the anion of 1H-1,2,3-triazole-4,5-dicarboxylic acid (H3TDA), were synthesized by the solvothermal method in a DMF:H2O mixture. According to single-crystal X-ray diffraction data, the compounds are 3d-MOFs with an anionic lattice and dimethylammonium cations occupying part of the cavities. Based on these compounds, two series of mixed-metal complexes, [NMe2H2][SmxLn1-x(TDA)(HCOO)], (x = 0.9 (Sm0.9Ln0.1-TDA), x = 0.8 (Sm0.8-Ln0.2-TDA)…Sm0.02Ln0.98-TDA, Ln = Tb, Gd), were also obtained and characterized by powder XRD. The luminescent properties of the compounds were studied and it was shown that the resulting compounds are two- or three-component emitters with the possibility of fine color tuning by changing the intensities of fluorescence and phosphorescence of the ligand, as well as the luminescence of Sm3+ and Tb3+ f-ions.

Luminescence studies of CaLa4Si3O13 doped with Er3+ ions

A series of Er3+-doped CaLa4Si3O13 phosphors with varying doping concentration (x = 0.005 ≤ x ≤ 0.09) was synthesized via sol-gel technique. The formation of CaLa4Si3O13 was confirmed by XRD analysis. The prepared phosphor was further characterized by FT-IR spectroscopy, UV–visible diffuse reflectance, and photoluminescence (PL) investigations. The PL study revealed that the prepared phosphors exhibit efficient green emission at 549 nm, when excited at 379 nm excitation wavelength. The CIE chromaticity study demonstrated the capability for fine color tuning in the green region by varying the Er3+ doping concentration. The PL study indicated that the prepared phosphors are suitable for use in near UV excited LEDs, display appliances and correlated applications.

Electrochemical Triggering of Reflectin Protein Assembly

In this work, we demonstrate electrochemical triggering and assembly of reflectin, the protein that mediates neuronal fine-tuning of color reflected from skin cells used for camouflage and communication in squids. Electrochemical reduction of histidine residues in the protein acts as an in vitro surrogate for phosphorylation in vivo, driving the assembly previously shown to regulate its function. Using micro-drop voltammetry and in situ dynamic light scattering, we demonstrate selective reduction of the imidazolium sidechains of histidine in monomers, oligopeptides and reflectin in acidic solution. The formal reduction potential of imidazolium proves readily distinguishable from those of hydronium and primary amines, allowing unequivocal confirmation of the direct and energetically-selective deprotonation of histidine in reflectin. The resulting “electro-assembly” methodology provides a new approach to probe, understand, and control the mechanisms that dynamically tune protein structure and function. Figure 1

Color-tunable arylaminoanthraquinone dyes through hydrogen-bond-assisted charge transfer interaction.

We prepared a series of arylaminoanthraquinone derivatives, including those with electron-accepting sulfone units and/or with electron-donating dialkylamino units. A color-tunable anthraquinone library that reached into the NIR region could be prepared through the precise control of frontier orbitals. Fine color-tuning was achieved through proper selection and positioning of the substituents. Effective intramolecular hydrogen-bond-assisted charge transfer interaction between electron-donating aniline/p-phenylenediamine and electron-accepting anthraquinone substructures induced a significant bathochromic shift of anthraquinone. The number and position of the substituents and the molecular conformation also significantly contributed to determining photophysical properties.

Electrospun Composite TiO2 Fibers for Color Tuning in Electrochromic Devices

Engineering one-dimensional (1D) nanostructures with multiple components can unlock properties that are not attainable by single elements alone. Herein, we use coaxial electrospinning for the synthesis of non-woven webs nanofibers with different metal(oxide) nanoparticles (NPs), i.e. silver (Ag), gold (Au), and copper oxide (CuO). The approach includes the structuring of nanofibers with an average diameter of 198.7±21.5 nm comprised of mesoporous TiO2 nanopowders mixed with metal(oxide) NPs to enable color tuning upon the application of an electrical potential. The nanofiber composites are supported on a fluorine-doped tin oxide (FTO) glass substrate and assembled in an electrochromic device in a half-cell configuration. It is observed that the color attained can be altered by changing the NP composition; such that Ag shows a black-brown color, Au yields dark blue, and CuO leads to a dark green color under negative bias. Fast color switching (<10 seconds) is possible per each TiO2 nanofiber/NP configuration. This is attributed to the faster kinetics of electrospun nanofibers in redox reactions gained by the high surface area to volume ratio. Band-gap deployment of the nanofiber composites is also observed, depending on the synthesized TiO2 nanofibers the band gap can be modulated between 2.76 to 3.01 eV allowing fine-color tuning upon EC cycles between ±2V. The rational design of the composite nanofibers is confirmed chemically, structurally and optically. The experiments show that material functionalities like color tuning are achievable with the use of metal(oxide) NPs. These findings can pave a new path for the rational design of nanofiber materials with applications in smart colored windows.

Light-Driven Molecular Dynamics in Perylenes with Medium-Controlled Emission.

Highly fluorescent light emitters with medium-tunable clear colors were obtained from the skeleton of perylenedicarboximide by the attachment of donor-substituted aryl groups at the peri-position. The 4-methoxynaphthyl derivative 3a is preferred because of its strong solvatochromism in fluorescence where a mechanism of incomplete PLICT is made responsible both for the large Stokes' shift and the strong medium influence on fluorescence, allowing the fine tuning of color.

Fine-Tuning the Colors of Natural Pigment Emodin with Superior Stability through Cocrystal Engineering

Due to the increasing concern of toxicity when using synthetic pigments, naturally occurring materials have regained attention. However, the limited hues and instability restrict their applications. Emodin (EM) is considered as a naturally sourced pigment and has been added in chemic necessities for many years. In this work, continuous color changes can be achieved by careful selection of coformers via a cocrystal engineering approach. This fine color tuning could be attributed to the different π–π and charge-transfer interactions after cocrystal formation. Furthermore, EM cocrystals were found to have superior stability in formulations. Fine color modifications and better stability behaviors in cocrystals may provide a new pathway to develop naturally sourced pigments without chemical synthesis.

Orange–Yellow Phosphorescent Iridium(III) Complex for Solution‐processed Organic Light‐Emitting Diodes: Structural, Optical and Electroluminescent Properties of Bis(2‐phenylbenzothiazole)[2‐(2‐hydroxyphenyl)benzothiazole]iridium(III)

New orange–yellow phosphorescent cyclometalated iridium(III) complex, (bt)2Ir(btz), where btH = 2‐phenylbenzothiazole and btzH = 2‐(2‐hydroxyphenyl)benzothiazole, was synthesized, and its structural, photophysical and electroluminescence properties were investigated to apply for organic light‐emitting diodes (OLEDs) applications. The coordination geometry around iridium metal ion was distorted octahedral, exhibiting cis‐C, C′ and trans‐N, N′ chelate dispositions with narrow ligand bite angles ranging from 79.7° (2) to 84.5° (1). The optical properties revealed that the π‐conjugated nature of bt ligand caused a bathochromic shift in emission and btz ligand played a role in fine color tuning. The synthesized (bt)2Ir(btz) was soluble in common organic solvents and the emitting layer was readily spin‐coated in chlorobenzene solution onto substrate. The OLED fabricated with the configuration of ITO/PEDOT:PSS/PVK:TCTA:OXD‐7: (bt)2Ir(btz) (32:32:28:8)/Bphen/LiF/Al exhibited a maximum external quantum efficiency (EQE) of 4.67% and a maximum luminance efficient (LE) of 8.61 cd/A with CIE (x, y) coordinates of (0.54,0.45).

Correction: Controlled size and morphology, and phase transition of YF3:Yb3+,Er3+ and YOF:Yb3+,Er3+ nanocrystals for fine color tuning

Correction for ‘Controlled size and morphology, and phase transition of YF3:Yb3+,Er3+ and YOF:Yb3+,Er3+ nanocrystals for fine color tuning’ by Yongsheng Zhu et al., J. Mater. Chem. C, 2016, DOI: 10.1039/c5tc03473f.

Realization of color tuning via solid-solution and energy transfer in Ca3−xSrx(PO4)2:Eu2+,Mn2+phosphors

Based on Grassman's law of color mixing, the fine color tuning of Ca3−xSrx(PO4)2:Eu2+,Mn2+is realizedviasolid-solution and energy transfer.

White organic light-emitting diodes with an ultra-thin premixed emitting layer

We described an approach to achieve fine color control of fluorescent White Organic Light-Emitting Diodes (OLED), based on an Ultra-thin Premixed emitting Layer (UPL). The UPL consists of a mixture of two dyes (red-emitting 4-di(4′-tert-butylbiphenyl-4-yl)amino-4′-dicyanovinylbenzene or fvin and green-emitting 4-di(4′-tert-butylbiphenyl-4-yl)aminobenzaldehyde or fcho) premixed in a single evaporation cell: since these two molecules have comparable structures and similar melting temperatures, a blend can be evaporated, giving rise to thin films of identical and reproducible composition compared to those of the pre-mixture. The principle of fine color tuning is demonstrated by evaporating a 1-nm-thick layer of this blend within the hole-transport layer (4,4′-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (α-NPB)) of a standard fluorescent OLED structure. Upon playing on the position of the UPL inside the hole-transport layer, as well as on the premix composition, two independent parameters are available to finely control the emitted color. Combined with blue emission from the heterojunction, white light with Commission Internationale de l'Eclairage 1931 color coordinates (0.34, 0.34) was obtained, with excellent color stability with the injected current. The spectrum reveals that the fcho material does not emit light due to efficient energy transfer to the red-emitting fvin compound but plays the role of a host matrix for fvin, allowing for a very precise adjustment of the red dopant amount in the device.

Size-Dependent Color Tuning of Efficiently Luminescent Germanium Nanoparticles

It is revealed that rigorous control of the size and surface of germanium nanoparticles allows fine color tuning of efficient fluorescence emission in the visible region. The spectral line widths of each emission were very narrow (<500 meV). Furthermore, the absolute fluorescence quantum yields of each emission were estimated to be 4-15%, which are high enough to be used as fluorescent labeling tags. In this study, a violet-light-emitting nanoparticle is demonstrated to be a new family of luminescent Ge. Such superior properties of fluorescence were observed from the fractions separated from one mother Ge nanoparticle sample by the fluorescent color using our developed combinatorial column technique. It is commonly believed that a broad spectral line width frequently observed from Ge nanoparticle appears because of an indirect band gap nature inherited even in nanostructures, but the present study argues that such a broad luminescence spectrum is expressed as an ensemble of different spectral lines and can be separated into the fractions emitting light in each wavelength region by the appropriate postsynthesis process.

The Pi‐Nature of Methyl Obtained by the Natural Bond Orbital Method: Orbital‐Based Rationalizations of Site‐Dependent Substitution Effects on Fine Color‐Tuning of Luminescence

AbstractBoth C‐H bonding and antibonding (σCH and σ*CH) of a methyl group would contribute to the highest occupied or lowest unoccupied molecular orbitals (HOMO or LUMO) in methylated derivatives of Ir(ppz)23iq (ppz = 1‐phenylpyrazole and 3iq = isoquinoline‐3‐carboxylate). This is found by analysis of HOMO (or LUMO) formed by linear combination of bond orbitals using the natural bond orbital (NBO) method. The elevated level of HOMO (or LUMO) uniformly found for each methylated derivative, indicating the σCH‐destabilization outweighs the σ*CH‐stabilization. To broaden the HOMO‐LUMO gap, methylation at a carbon having smaller contribution to HOMO and/or larger contribution to LUMO is suggested.

Fine tuning of color via copolymerization and its electrochromic device application

In this study electrochemical copolymerization of 1-(perfluorophenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole and 3,4-ethylenedioxythiophene was used to fulfill a strategy in achieving desired multichromic properties. The resultant polymer displayed distinct color changes between red–violet, amber, green and blue color with good switching times and optical contrast. A direct correlation between the color of the polymer in neutral state and the applied potential during synthesis was observed. Hence, it was possible to achieve colors from maroon, red–violet, and eggplant to indigo depending on the applied potential. A dual type electrochromic device of the copolymer and poly(3,4-ethylenedioxythiophene) was constructed to evaluate the possible use of such copolymer in device applications. The device displayed multichromism, with 1.1 s switching time and good electrochromic memory.

Color Tuning of Cyclometalated Iridium Complexes through Modification of Phenylpyrazole Derivatives and Ancillary Ligand Based on ab Initio Calculations

Various iridium complexes consisting of phenylpyrazole (ppz) ligands and isoquinolinecarboxylic acids (iq) as ancillary ligands were designed by energy band-gap calculations via ab initio calculations and synthesized to give rise to various emission wavelengths as expected. Fine color tuning was achieved through varying the position of the methyl substituent on the phenylpyrazole moiety with HOMO electron densities. Additional color tuning was made possible by altering the LUMO through the use of different ancillary ligands such as 1-isoquinolinecarboxylic acid (1iq) and 3-isoquinolinecarboxylic acid (3iq).