Color Of Emitted Light Research Articles

A Color-Tunable Fluorescent Supramolecular Hyperbranched Polymer Constructed by Pillar[5]arene-Based Host-Guest Recognition and Metal Ion Coordination Interaction.

Fluorescent supramolecular polymers are an important kind of smart material. In this work, a new fluorescent supramolecular hyperbranched polymer (FSHP) is constructed by orthogonal self-assembly: pillararene-based host-guest interaction and metal ion complexation interaction. The FSHP exhibits concentration-controllable fluorescence emissions. The photoluminescence spectra and light-emitting colors of FSHP can be effectively tuned by changing metal ion types or using mixed metal ions. The fluorescence quenching of FSHP solutions or FSHP-based films would occur when removing the metal ions from the backbone of FSHP. This study supplies a convenient approach toward the construction of structure-tunable fluorescent supramolecular materials with different colors.

Photoluminescence property adjustment of ZnO quantum dots synthesized via sol–gel method

Quantum dots (QDs) are zero dimensional nanomaterials and promising materials in the fluorescent label, LED display, metal ions sensor, catalysis and so on. ZnO QDs are one kind of ideal QDs, due to their non-poisonous, easy prepared, plentiful, economical properties. The visible light emission colour and quantum yields of ZnO QDs is determined by their band structures and defect structures. Main method to adjust the optical performance is controlling the particle sizes, band structures and defect structures by adjusting synthesis method and doping. Therefore, it is important to investigate the mechanisms of particle growth and defects variation. In this paper, a sol–gel method were employed to synthesize stable ZnO QDs used in fluorescence labeling and solar cells. Effects of reactants concentration, material ratio and reaction time on particle sizes and defects structures of ZnO QDs synthesized by sol–gel method were studied. Changing the synthesis process of ZnO QDs can adjust their photoluminescence defects structures and particle sizes. The ZnO QDs synthesized with c(Zn2+) = 0.1 mol L− 1, n(OH−):n(Zn2+) = 2:1, for 1.5 h reaction showed the highest photoluminescence quantum yields (40%) with green emission under 359 nm UV-light excitation. The visible light emission of the ZnO QDs synthesized with c(Zn2+) = 0.025 mol L− 1, n(OH−):n(Zn2+) = 3:1, for 1.5 h min is blue-green colour excited under 337 nm.

Brazilian Bioluminescent Beetles: Reflections on Catching Glimpses of Light in the Atlantic Forest and Cerrado.

Bioluminescence - visible and cold light emission by living organisms - is a worldwide phenomenon, reported in terrestrial and marine environments since ancient times. Light emission from microorganisms, fungi, plants and animals may have arisen as an evolutionary response against oxygen toxicity and was appropriated for sexual attraction, predation, aposematism, and camouflage. Light emission results from the oxidation of a substrate, luciferin, by molecular oxygen, catalyzed by a luciferase, producing oxyluciferin in the excited singlet state, which decays to the ground state by fluorescence emission. Brazilian Atlantic forests and Cerrados are rich in luminescent beetles, which produce the same luciferin but slightly mutated luciferases, which result in distinct color emissions from green to red depending on the species. This review focuses on chemical and biological aspects of Brazilian luminescent beetles (Coleoptera) belonging to the Lampyridae (fireflies), Elateridae (click-beetles), and Phengodidae (railroad-worms) families. The ATP-dependent mechanism of bioluminescence, the role of luciferase tuning the color of light emission, the "luminous termite mounds" in Central Brazil, the cooperative roles of luciferase and superoxide dismutase against oxygen toxicity, and the hypothesis on the evolutionary origin of luciferases are highlighted. Finally, we point out analytical uses of beetle bioluminescence for biological, clinical, environmental, and industrial samples.

Color tuning and white light emission by codoping in isostructural homochiral lanthanide metal-organic frameworks.

Four lanthanide-based homochiral metal–organic frameworks (Ln-HMOFs), {[Ln2(HL)2(H2O)4]·2Cl·5H2O}n [Ln = Gd (1), Eu (2), Tb (3) and Dy (4)], have been synthesized through solvothermal reactions of chiral ligand (S)-5-(((1-carboxyethyl)amino)methyl)isophthalic acid (H3L) with corresponding LnCl3·6H2O. They are binodal (3,6)-connected frameworks with kgd nets based on binuclear cluster units and zwitterionic (HL)2− linkers. Considering the isostructuralism of these Ln-HMOFs as well as the blue emission of compound 1 and the strong typical Eu3+ and Tb3+ emissions of compounds 2 and 3, single-phase mixed-lanthanide HMOFs have been prepared by doping of Ln3+ into the Ln-HMOFs to modulate light-emitting color. Interestingly, the bimetallic doped Eu/Tb-HMOFs [(EuxTb1−x)2(HL)2(H2O)4]·2Cl·5H2O display a fluent change of light-emitting color among green, yellow, orange, orange-red, and red by adjusting the doping concentration of Eu3+ ions into the Tb-HMOF. Very importantly, the trimetallic doped Eu/Gd/Tb-HMOF [(Eu0.1388Gd0.6108Tb0.2504)2(HL)2(H2O)4]·2Cl·5H2O emits white light upon excitation at 355 nm, whose emission can also be switched between different colors when excited with different ultraviolet light. Furthermore, the fluorescence response of Tb-HMOF to various usual metal ions, and especially fluorescent sensing behaviours to Fe3+, Cr3+ and Al3+ have been preliminarily investigated.

Luminescence and energy transfer in warm white-light-emitting K3Y(PO4)2:Tb,Eu phosphor for LEDs applications

To obtain warm white-emission in a new single-phase phosphor, a series of Tb–Eu doped K3Y(PO4)2 (KYP) samples were prepared by solid-state reaction method, and their photoluminescence properties were investigated. For Tb-single-doped KYP, the green emission mainly owing to the 5D4–7FJ (J = 3–6) transitions was obtained. For Eu-single-doped KYP, two kinds of emissions were observed, i.e., the line-peak and broad-band emissions, belonging to the Eu3+ 5D0–7FJ (J = 0–4) and Eu2+ d–f transitions, respectively. When Tb–Eu ions were co-doped into the KYP host, the Eu2+, Tb3+ and Eu3+ emissions were all found, which contribute to the blue, green and red components in the visible spectrum, respectively. By adjusting the relative concentrations of Tb and Eu, the emitting light color can be tuned and the warm white-emission was gained in the KYP:0.03 Tb,0.03Eu phosphor. The thermal luminescence stability of the KYP:0.03 Tb,0.03Eu sample was studied. The above investigations reveal that the present phosphors could have potential application in white LEDs.

Fluorescent Supramolecular Polymers Based on Pillar[5]arene for OLED Device Fabrication.

A series of AA/BB-type supramolecular polymers (SP1-3) based on pillar[5]arene host-guest interactions was developed and their photoelectric properties were further evaluated. The formation of SP1 was confirmed by multiple measurements via nuclear magnetic resonance and specific viscosity studies. The electroluminescence properties of SP1-3 were also investigated. As a result of the efficient energy transfer caused by the exciton trapping on narrow band gap guest G2, by applying a doping strategy, the light-emitting color of the resulting polymers could be easily turned from blue to green. Meanwhile, photoluminescent efficiencies up to 81.6% were obtained. All the supramolecular polymers prepared in this work were utilized as the emissive layers (EMLs) in light-emitting devices and a maximum luminance efficiency (LE) of nearly 5 cd A-1 was achieved.

Tunable upconversion luminescence of monodisperse Y2O3: Er3+/Yb3+/Tm3+ nanoparticles

Abstract Monodisperse Y 2 O 3 : Er 3+ /Yb 3+ /Tm 3+ nanoparticles with various dopant concentrations have been synthesized successfully by a homogeneous precipitation method. Their phase structures and surface morphologies have been characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The diversities of upconversion luminescence spectra and CIE coordinates of prepared samples are investigated in detail at room temperature under 980 nm excitation. Through adjusting the concentrations of Yb 3+ , Tm 3+ and Er 3+ ions, three upconversion emission bands in red, green and blue region could be tunable to achieve the color of interest and near white light emission can be obtained in the tri-doped Y 2 O 3 nanoparticles for a variety of application.

Creation of the tunable color light emission of cellulose hydrogels consisting of primary rare-earth compounds

In this study cellulose hydrogels with lanthanide ions nanoparticles embedded in were prepared via in situ doping using a low-temperature alkali hydroxide/urea aqueous solution as a cellulose solvent. Depending on the type and relative concentrations of the constituent lanthanide ions, the color of light emission were modulated to generate the three primary colors and other adjusted colors by blending red, green and blue at certain ratios. This work has opened new and convenient pathway to create regulated fluorescent cellulose hydrogels for potential applications in the fields of bioimaging and fluoroimmunoassay.

Syntheses, structures and luminescence properties of five coordination polymers based on designed 2,7-bis(4-benzoic acid)-N-(4-benzoic acid) carbazole

Herein we report five porous luminescent coordination polymers (CPs), namely, [Zn3(L27)2(DMA)6(H2O)4]n (TCZ-001), [Zn3(L27)2(DMA)6(CH3CH2OH)2]n (TCZ-002), [Zn3(L27)2(DMA)6(CH3OH)]n (TCZ-003), [Cd3(L27)2(DMA)6(H2O)2]n (TCZ-004), and [Cd9(L27)6DMA13(4,4′-BPY)2(OH)2(H2O)13.5]n (TCZ-005) [H3L27 = 2,7-bis(4-benzoic acid)-N-(4-benzoic acid) carbazole, DMA = N,N-dimethylacetamide, 4,4′-BPY = 4,4′-bipyridine, TCZ = “T”-shape carbazole-based polymers, L27 = fully deprotonated H3L273− ligand]. All of the five CPs were assembled from a novel luminescent carbazole-based ligand. X-ray crystallography showed that TCZ-001 is a 3-connected one-dimensional (1D) chain structure with a {42·6} topology. TCZ-002 possesses a 3,6-connected three-dimensional (3D) framework with a point symbol of {42·6}2{44·62·87·102}. TCZ-003 displays a 3,6-connected two-dimensional 2D network with a Schlafli symbol of {411·64}·{43}2, which is a new topology. TCZ-004 features a 3,6-connected 2D net with a {43}2·{46·66·83} topology. In TCZ-005, the structure can be classified into two groups: one of the two groups is a 3-connected 1D chain structure with a {42·6} topology, similar to TCZ-001; the other one possesses a 3,3,3,4-connected network with a Schlafli symbol of {42·63·8}{42·6}3. The structure of TCZ-005 could be described as an SP 1-periodic net (4,4)(0,2) in the 1D_2D.ttd database. TCZ-001, TCZ-003 and TCZ-004 show a remarkable response to the Ni2+ concentration in DMA, H2O or EtOH. Some of Zn2+ ions were replaced by Ni2+ ions and the rate of the transmetalation depended on the concentration of Ni2+ ions. Also, changing part of the metal node would transform the colour of emitted light. Additionally, the colour of the luminescence displays a linear correlation with the Ni2+ concentration range from 0.005 to 0.35 M (mol L−1). Besides selective sensing of Ni2+, TCZ-004 can also be utilized to detect Eu3+ in DMA solution. Thus, several potential sensory probe materials for Ni2+ and Eu3+ detection in DMA solution have been obtained.

Color-tunable luminescence in Ce-, Dy-, and Eu-doped oxyfluoride aluminoborosilicate glasses

A series of Ce-, Dy-, and Eu doped oxyfluoride aluminoborosilicate glasses prepared by melt-quenching method are studied for light emitting diodes applications. These glasses are investigated via optical absorption, photoluminescence, X-ray diffraction, Fourier transform infrared spectra, Commission International de I’Eclairage (CIE) color coordinates, and correlated color temperatures (CCTs). We find that the emission bands of Ce3+ ions move to the longer wavelengths with increasing excitation wavelengths and the molar ratio of B2O3/SiO2, Al2O3/SiO2, and B2O3/Al2O3 in the glass compositions. The precipitation of CaF2 crystals in glass can also lead to the red shift of the emission of Ce3+. The energy transfer processes among Ce3+, Dy3+, Eu3+, and Eu2+ ions are also investigated. The influence of the variation of glass network structure on the luminescence of Ce/Dy/Eu codoped glasses is studied. The CIE color coordinates and CCTs could be effectively tuned by adjusting the glass matrix compositions and excitation wavelengths. Furthermore, the near-ideal white light emission (color coordinate x=0.32, y=0.31) from the Ce/Dy/Eu codoped glass under near ultraviolet (UV) light excitation is realized.

Efficient Color Tunable ZnWO4:Er3+-Yb3+Phosphor for High Temperature Sensing

The single monoclinic phase with nano-structured crystallites in the $\rm{ZnWO}_{\rm{4}}\rm{:Er}^{3+ }\rm{-Yb}^{3+ }$ phosphor have been detected from structural investigations by using the X-ray diffraction (XRD) analysis. The spectral studies performed in the codoped phosphor upon 980 nm excitation emit radiations within the UV—NIR wavelength region. Diffuse reflectance and Fourier transform infrared (FTIR) analysis have been done to identify the presence of active ions and impurities in the prepared phosphor. The pump power dependence study results in green to red intensity ratio variation and thus a tuning in color of emitted light is observed. The observed emissions have been explained on the basis of excited state absorption (ESA), energy transfer (ET), and temporal evolution analysis. The temperature sensing performance of synthesized material studied upto $\sim \text{798}\; \text{K}$ results the highest sensor sensitivity of about $\text{14.63}\times \text{10}^{-\text{3}}\;\text{K}^{-\text{1}}$ which confirms the suitability of present material for high temperature sensing with very good sensitivity.

The evolution of adult light emission color in North American fireflies.

Firefly species (Lampyridae) vary in the color of their adult bioluminescence. It has been hypothesized that color is selected to enhance detection by conspecifics. One mechanism to improve visibility of the signal is to increase contrast against ambient light. High contrast implies that fireflies active early in the evening will emit yellower luminescence to contrast against ambient light reflected from green vegetation, especially in habitats with high vegetation cover. Another mechanism to improve visibility is to use reflection off the background to enhance the light signal. Reflectance predicts that sedentary females will produce greener light to maximize reflection off the green vegetation on which they signal. To test these predictions, we recorded over 7500 light emission spectra and determined peak emission wavelength for 675 males, representing 24 species, at 57 field sites across the Eastern United States. We found support for both hypotheses: males active early in more vegetated habitats produced yellower flashes in comparison to later-active males with greener flashes. Further, in two of the eight species with female data, female light emissions were significantly greener as compared to males.

Tunable white light and energy transfer of Dy3+ and Eu3+ doped Y2Mo4O15 phosphors

A series of Dy3+ or/and Eu3+ doped Y2Mo4O15 phosphors were successfully synthesized at a low temperature of 600°C via solid state reaction. The as-prepared phosphors were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM), photoluminescence (PL) excitation, emission spectra and PL decay curves. XRD results demonstrate that Y2Mo4O15: Dy3+, Eu3+ has the monoclinic structure with the space group of p21/C(14). Under the excitation of ultraviolet (UV) or near-UV light, the Dy3+ and Eu3+ ions activated Y2Mo4O15 phosphors exhibit their characteristic emissions in the blue, yellow and red regions. The emitting light color of the Y2Mo4O15: 0.08Dy3+, yEu3+ phosphors can be adjusted by varying the concentration ratio of Dy3+ to Eu3+ ions and a white light is achieved when the doping concentration of Eu3+ is 5%. In addition, the energy transfer from Dy3+ to Eu3+ is also confirmed based on the luminescence spectra and decay curves.

Color control of electrochemiluminescence based on duty ratio of applied waveform voltage

In this research, we succeeded in controlling the light-emitting color obtained from the light-emitting surface of an organic electrochemiluminescence (ECL) device with a duty ratio of the applied voltage. The color change was based on the absorption of light by the light-emitting layer. Because we were able to control the light-emitting relative quantities in each electrode by changing the duty ratio. Long light-emitting lifetime will be expected in the future, because the light-emitting material used was poly(3-hexylthiophene-2,5-diyl) (P3HT), a conductive polymer. We fabricated the ECL device with a light-emitting layer thickness of 25.0 µm. In this device, the ECL color was changed from orange to red by changing the duty ratio from 50 to 10%. More ECL colors are expected to be realized by selecting the light-emitting material with appropriate absorption and ECL spectra.

Ce3+‐ and Dy3+‐Doped Oxyfluoride Borosilicate Glasses with Near White Luminescence

A series of Ce3+/Dy3+‐doped oxyfluoride borosilicate glasses prepared by melt‐quenching method are investigated for light‐emitting diodes applications. These glasses are studied via X‐ray diffraction (XRD), optical absorption, photoluminescence (PL), color coordinate, and Fourier transform infrared (FT‐IR) spectra. We find that the absorption and emission bands of Ce3+ ions move to the longer wavelengths with increasing Ce3+ concentrations and decreasing B2O3 and Al2O3 contents in the glass compositions. We also discover the emission behavior of Ce3+ ions is dependent on the excitation wavelengths. The glass structure variations with changing glass compositions are examined using the FT‐IR spectra. The influence of glass network structure on the luminescence of Ce3+/Dy3+ codoped glasses is studied. Furthermore, the near‐ideal white light emission (color coordinate x = 0.32, y = 0.32) from the Ce3+/Dy3+ codoped glasses excited at 350 nm UV light is realized.

Transient-state kinetic analysis of complex formation between photoprotein clytin and GFP from jellyfish Clytia gregaria.

Luminous organisms use different protein-mediated strategies to modulate light emission color. Here, we report the transient-state kinetic studies of the interaction between photoprotein clytin from Clytia gregaria and its antenna protein, cgreGFP. We propose that cgreGFP forms a transient complex with Ca(2+)-bound clytin before the excited singlet state of the coelenteramide product is formed. From the spectral distribution and donor-acceptor separation distance, we infer that clytin reaction intermediates may interact only with the middle side part of cgreGFP.

Synthesis and photoluminescence of multicolor tunable K3Gd(VO4)2:Eu3+ phosphors

Eu3+-activated novel potassium gadolinium double vanadates K3Gd(VO4)2 phosphors have been synthesized via solid-state reaction. The crystal phase, surface morphology and photoluminescence properties of the phosphor were investigated. X-ray diffraction results demonstrate that K3Gd1−xEux(VO4)2 has the monoclinic structure with the space group of p21/m(11). The emission spectra suggest that K3Gd1−xEux(VO4)2 phosphors present an intense charge transfer band at 314 nm and a strong red emission of Eu3+ (5D0 → 7F2 transition) at 617 nm. The optimum doping concentration of Eu3+ ions in K3Gd1−xEux(VO4)2 phosphors is around 50 mol% and the major mechanism for concentration quenching is the exchange interaction. The emitting light color of the phosphors can be tunable by varying excitation wavelength and a warm white light is achieved by the excitation at 337 nm. The luminescence properties suggest that the present phosphors may have potential applications as red and white emitting materials for w-LEDs in solid state lighting.

Organic–inorganic hybrid nanomaterials based on inorganic oxides and a mesomorphic polyazomethine

Organic–inorganic hybrid materials have been obtained by impregnating a mesomorphic polyazomethine into a porous inorganic matrix of zinc oxide (ZnO), tin dioxide (SnO2), or mixed ZnO/SnO2. The porous inorganic matrix has been obtained by magnetron sputtering technique and proved a very high crystallinity degree. The resulting hybrid materials were characterized from morphological and optical points of view by scanning electron microscopy, atomic force microscopy, and ultraviolet-visible and photoluminescence spectroscopy. The inorganic matrix itself exhibited a highly rough surface, which became smoother after polymer impregnation, indicating its complete coverage. The violet emission of the separate inorganic and organic components turned into a blue and green light emission, respectively, of the hybrid materials, suggesting the possibility to modulate the color of emitted light by the simple choice of the inorganic matrix. Considerations with regard of interface phenomena that prompted the photophysical changes of the hybrid materials were done.

Light Emission Color Conversion of Polyfluorene-Blend OLEDs Induced by Thermal Annealing

This paper investigated the applicability of thermal annealing to be used for the color conversion of organic light-emitting diodes (OLEDs) made of a blend of light-emitting polyfluorenes. Blue-light-emitting polyfluorene poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) was used as the host material and green-light-emitting polyfluorene poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) as the dopant material. Annealing treatment was conducted at the temperatures of 150 °C and 270 °C, before top contact deposition. Both nonannealed OLEDs and those annealed at 270 °C showed green color emission, implying that emission was taking place via the dopant material F8BT. Instead, the light emission color of the OLEDs annealed at 150 °C was shifted to white upon a rise of a blue spectral component. The origin of the blue light emission was attributed to PFO and indicated considerable phase separation between PFO and F8BT. This paper showed that thermal annealing can be applied to modify the light emission color of polyfluorene-blend OLEDs.

Three primary colors upconversion phosphors and combined white upconversion luminscence in Y2O2S matrix

Three primary colors upconversion phosphors in Y2O2S matrix of Y2O2S:Er, Y2O2S:Yb/Er, Y2O2S:Yb/Ho, Y2O2S:Yb/Eu and Y2O2S:Yb/Tm were prepared by flux method. SEM, XRD, UPL and CIE were used to characterize the particle morphology, phase composition, luminescent properties and the emitting light color. Through the optimization of active ion doping concentration, upconversion luminescent properties were promoted. The upconversion luminescent colors of the obtained phosphors were green/red for Y2O2S:Er and Y2O2S:Yb/Er, green for Y2O2S:Yb/Ho, red for Y2O2S:Yb/Eu and blue/red for Y2O2S:Yb/Tm. Different combinations of three primary colors upconversion phosphors were investigated to obtain white upconversion luminescence.