Light-emitting Property Research Articles

Synthesis and Characterization of β-Ga2O3 Nanorod Array Clumps by Chemical Vapor Deposition

beta-Ga2O3 nanorod array clumps were successfully synthesized on Si (111) substrates by chemical vapor deposition. The composition, microstructure, morphology, and light-emitting property of these clumps were characterized by X-ray diffraction, Fourier transform infrared spectrophotometry, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence. The results demonstrate that the sample synthesized at 1050 degrees C for 15 min was composed of monoclinic beta-Ga2O3 nanorod array clumps, where each single nanorod was about 300 nm in diameter with some nano-droplets on its tip. These results reveal that the growth mechanism agrees with the vapor-liquid-solid (VLS) process. The photoluminescence spectrum shows that the Ga2O3 nanorods have a blue emission at 438 nm, which may be attributed to defects, such as oxygen vacancies and gallium-oxygen vacancy pairs. Defect-energy aggregation confinement growth theory was proposed to explain the growth mechanism of Ga2O3 nanorod array clumps collaborated with the VLS mechanism.

Effects of Synthesis Process on Luminescence Properties and Structure of Mesoporous Carbon–Silica Nanocomposite

The effects of hydrolysis and polycondensation reactions for synthesizing light-emitting mesoporous carbon–silica (MPCS) nanocomposite on the structure, chemical bonding state, and luminescence properties of MPCS were investigated by controlling the concentration (0.02 to 5 M) of HCl, which was used as a catalyst for hydrolysis and polycondensation. The progress of hydrolysis and polycondensation reactions provides a nanometer-order pore/wall structure and results in a strong light-emitting property. The pore/wall structure was obtained using HCl at concentrations of 0.2 M and higher, but it became disordered with increasing HCl concentration (2 and 5 M). The luminescence color of the MPCS nanocomposite can be changed from yellowish-white to bluish-white by changing the concentration of HCl.

Development of zeolite-derived novel aluminosilicate phosphors

In this research, zeolite-derived aluminosilicate phosphors were synthesized through the ion exchange route. Red light-emitting property of Eu3+-doped aluminosilicate phosphors were discussed from a view point of the Eu content, heat-treatment condition and the oxidation state of Eu ions. The crystalline phase of the host aluminosilicates could be successfully controlled as designed based on the published NaAlO2–SiO2 binary phase diagram. Orange-red emission peaks derived from the 5D0→7Fj (j=0, 1, 2, 3, 4) transition of Eu3+ were observed around 590–700nm, and 4f65d→4f7 transition of Eu2+ was observed at around 400–500nm. The relative intensity I(5D0→7F2) of the dominant emission peak at 612nm increased consistently with the Eu content. The results of the XANES spectroscopy analysis revealed that Eu2+ ion in the 1400°C as heat-treated host aluminosilicate were successfully converted to Eu3+ by the additional annealing at 1100°C. The Eu contents and heat-treatment conditions were determined to exhibit the best performance as a red phosphor, which were 10wt% and 1500°C, respectively

Reversible Tuning Luminescent Color and Emission Intensity: A Dipeptide‐Based Light‐Emitting Material

A smart luminescent material whose emission color and emission intensity can be separately modulated by external force is demonstrated. The rational manipulation of rich noncovalent interactions and fluorophore packing style promotes an in-depth understanding between supramolecular structure and photophysical property and offers an effective strategy to modulate the light-emitting property in a predicative way.

Light-emitting property of simple AIE compounds in gel, suspension and precipitates, and application to quantitative determination of enantiomer composition

It was found that simple AIE compounds could emit different intensity of fluorescence in gel, suspension and precipitates for the first time, which could be applied to fluorescence switches and quantitative determination of enantiomer composition.

P‐i‐n Homojunction in Organic Light‐Emitting Transistors

A new method for investigating light-emitting property in organic devices is demonstrated. We apply the ambipolar light-emitting transistors (LETs) to directly observe the recombination zone, and find a strong link between the transistor performance and the zone size. This finding unambiguously indicates that the light emission comes from the electric-field-induced p-i-n homojunction in ambipolar LETs.

Semiconductor Laser Diode

A semiconductor laser diode having high indium composition ratio and light-emitting property is provided to reduce the deterioration of crystal according to low temperature by minimizing heat damage of high indium composition ratio. A semiconductor laser diode(100) comprises a substrate(101), an n-type clad layer(102), an active layer(104) and a p-type cladding layer(106). A transparent electrode layer(107) is formed on the ridge structure of the p-type cladding layer. N-type and P-contacts are formed in the lower-part of substrate and upper side of the transparent electrode layer. An insulating layer(108) covering the ridge structure and transparent electrode layer is formed on the p-type cladding layer. N-type and p-type cladding layer corresponds to the respective top clad layer.

Synthesis and Curing of Hyperbranched Poly(triazole)s with Click Polymerization for Improved Adhesion Strength

We successfully synthesized hyperbranched poly(triazole)s by in situ click polymerization of diazides 1 and triyne 2 monomers on different metal surfaces (copper, iron, and aluminum) and characterized their adhesive properties. Optimizations were performed to obtain high adhesive strength at different temperatures by analyzing the effects of curing kinetics, annealing temperature and time, catalyst, monomer ratio, surface conditions, alkyl chain length of diazides 1, etc. The adhesive bonding strength with metal substrate is 2 orders of magnitude higher than similar hyperbranched poly(triazole)s made by click polymerization and clearly higher than some commercial adhesives at elevated temperatures. With the same conditions, adhesives prepared on aluminum and iron substrates have higher adhesive strength than those prepared on copper substrate, and an excess of triyne 2 monomer in synthesis has greater adhesive strength than an excess of diazide 1 monomer. Tof-SIMS experiment was employed to understand these phenomena, and the existence of an interphase between the polymer and metal surface was found to be critical for adhesive bonding with thicker interphase (excess of triyne 2 monomer) and the higher binding energy between polymer atoms and substrate atoms (e.g., aluminum substrate) generating the higher bonding strength. In addition, the light-emitting property of synthesized polymers under UV irradiation can be used to check the failure mode of adhesive bonding.

Fluorescent Carbon Nanoparticles: Synthesis, Characterization, and Bioimaging Application

Fluorescent carbon nanoparticles (CNPs) 2−6 nm in size with a quantum yield of about ∼3% were synthesized via nitric acid oxidation of carbon soot, and this approach can be used for milligram-scale synthesis of these water-soluble particles. These CNPs are nanocrystalline with a predominantly graphitic structure and show green fluorescence under UV exposure. Nitric acid oxidation induces nitrogen and oxygen incorporation into soot particles, which afforded water solubility and a light-emitting property; the isolation of small particles from a mixture of different sized particles improved the fluorescence quantum yield. These CNPs show encouraging cell-imaging applications. They enter into cells without any further functionalization, and the fluorescence property of these particles can be used for fluorescence-based cell imaging applications.

Photoluminescence from Nd Doped Anodic Aluminium Oxide

We prepare Nd doped anodic aluminium oxide (Nd: AAO) template by using Nd doped aluminium foils through two-step anodization processes. Photoluminescence (PL) from the Nd: AAO template with the annealing temperature higher than 400°G is observed, and the PL intensity enhanced with the increasing annealing temperature is found. We investigate the crystallization of Nd: AAO template and the excitation wavelength dependence of PL intensity, showing that the PL results from the Nd doped in the template. The approach presented may probably facilitate the fabricating of AAO with good light-emitting property, which can be used in fabrication of multifunctional nanosized films and may find applications in photonic devices.

Direct Encapsulation of Organic Light-Emitting Devices (OLEDs) Using Photo-Curable co-Polyacrylate/Silica Nanocomposite Resin

Direct encapsulation of organic light-emitting devices (OLEDs) was realized by using highly transparent, photo-curable co-polyacrylate/silica nanocomposite resin. Feasibility of such a resin for OLED encapsulation was evaluated by physical/electrical property analysis of resins and driving voltage/luminance/lifetime measurement of OLEDs. Electrical property analysis revealed a higher electrical insulation of photocured nanocomposite resin film at 3.20times1012 Omega in comparison with that of oligomer film at 1.18times1012 Omega at 6.15 V to drive the bare OLED. This resulted a lower leakage current and the device driving voltage was efficiently reduced so that the nanocomposite-encapsulated OLED could be driven at a lower driving voltage of 6.09 V rather than 6.77 V for the oligomer-encapsulated OLED at the current density of 20 mA/cm2. Luminance measurement revealed a less than 1.0% luminance difference of OLEDs encapsulated by various types of resins, which indicates that the photo-polymerization takes very little effect on the light-emitting property of OLEDs. Lifetime measurement of OLEDs found that , the time span for the normalized luminance of device drops to 80%, for nanocomposite-encapsulated OLED is 350.17 h in contrast to 16.83 h for bare OLED and 178.17 h for the oligomer-encapsulated OLED. This demonstrates that nanocomposite resin with optimum properties is feasible to OLED packaging and a compact device structure could be achieved via the method of direct encapsulation.

Photo-cross-linkable light-emitting polymers for holographic patterning

Blue light-emitting poly(1-phenyl-1-alkyne)s containing photo-cross-linkable vinyl pendants were synthesized and photophysically characterized. Photoluminescence quantum yields are virtually unchanged for pristine and photo-cross-linked films, showing excellent stability and light-emitting property of the insoluble polymer film after photo-cross-linking process. By using laser interference lithography technique, active submicron two-dimensional photonic crystal structures have been fabricated by exposure to UV light. The obtained high quality nanostructures demonstrate that these polymers are applicable in active photonic devices such as distributed feedback laser. Furthermore, the achievable resolution of these polymers is ∼50nm, implying that these polymers may find potential applications in active nanodevices.

Nanoparticle-induced negative differential resistance and memory effect in polymer bistable light-emitting device

Recently, electrical bistability was demonstrated in polymer thin films incorporated with metal nanoparticles [J. Ouyang, C. W. Chu, C. R. Szmanda, L. P. Ma, and Y. Yang, Nat. Mater. 3, 918 (2004)]. In this letter, we show the evidence that electrons are the dominant charge carriers in these bistable devices. Direct integration of bistable polymer layer with a light-emitting polymer layer shows a unique light-emitting property modulated by the electrical bistability. A unique negative differential resistance induced by the charged gold nanoparticles is observed due to the charge trapping effect from the nanoparticles when interfaced with the light-emitting layer.

On the origin of light emission from porous anodic alumina formed in sulfuric acid

We have investigated the photoluminescence (PL) property of porous anodic alumina membranes (PAAMs) formed on bulk Al foils in 0.3 M sulfuric acid. Different from that from the PAAMs formed in oxalic acid, the obtained PL spectra show two emission bands which have different origins. One centered at ∼465 nm (α-band) weakens its intensity in the PAAM annealed in O 2 and is thus attributed to optical transition in oxygen vacancies. The other in the blue (β-band) redshifts with increasing excitation wavelength. On the basis of spectral examinations and analyses, we ascribe the β-band to radiative recombination of carriers in the isolated hydroxyl groups at the surface of the pore wall, whereas the photogeneration of carriers takes place in oxygen vacancies in the pore wall. This work improves the understanding of the light-emitting property of the PAAMs formed in sulfuric and oxalic acid.

Self-catalytic synthesis and light-emitting property of highly aligned Mn-doped Zn2SiO4 nanorods

Highly aligned Mn-doped Zn2SiO4 nanorods were fabricated by using a modified vapor-phase evaporation method. Their microstructure and chemical bond configurations were investigated with the help of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared absorption spectroscopy, and X-ray photoelectron spectroscopy. The formation process of the Mn-doped Zn2SiO4 nanorods can be elucidated on the basis of a self-catalytic vapor–liquid–solid growth mechanism in which Mn chloride hydrate acts as the catalyst and impurity source. Photoluminescence measurements revealed that an intensive green luminescence peak appears at 523 nm, which corresponds to the electronic transition 4T1(4G)→6A1(6S) of Mn2+ ions. Our experimental results provide a useful approach to directly fabricate Si-based nanoscale light-emitting materials using ZnO–Zn2SiO4 composite.

Solvent effect on light-emitting property of Si nanocrystals

Using ultrasonic vibrations of as-made porous silicon in water, benzene, chloroform, and toluene solvent, four groups of suspensions of Si nanocrystals are prepared for exploring the influence of solvents on the light-emitting properties of Si nanocrystals. Photoluminescence (PL) spectral examinations show that the strongest PL spectrum appears in the toluene suspension with the smallest HOMO/LUMO gap. This result is explained on the basis of the frontier orbital theory and toluene chemisorption model. In addition, shift of the PL peak was also observed in different suspensions. This behavior is considered to be due to the influence of the solvent polarity.

Influence of polar solvent on light-emitting property of SiO$\mathsf{_{x}}$ ($\mathsf{x = 1.2-1.6}$) nanoparticles irradiated by ultraviolet ozone

SiO x (x = 1.2-1.6) powder with nanoparticle sizes of 5-15 nm was irradiated by ultraviolet ozone (UVO), followed by immersion into polar solvent to form a sol-like sample for investigating the influence of a polar solvent on light-emitting property of SiO x nanoparticles. Photoluminescence (PL) spectral examinations reveal that the intensity of a broad blue-emitting band peaked at around 420 nm strongly depends upon UVO irradiation and meanwhile relates with the solvent polarity. PL excitation spectral analysis and Fourier-transform infrared absorption measurements suggest that the blue PL band arise from optical transition in the -OH binding states (possibly H bonds to the interstitial oxygen) at the surfaces of SiO x nanoparticles, which are induced by the interaction of polar solvent with SiO x nanoparticles. This work clearly indicates that we cannot ignore the influence of solvent polarity on the light-emitting property of a composite of organic material and inorganic nanocrystals.

Design of combinatorial shadow masks for complete ternary-phase diagramming of solid state materials.

We report on a novel mask design for the combinatorial synthesis of a ternary composition spreads library, which allows such libraries to be deposited through a series of simple masks on a rotatable mount. This eliminates the use of complicated actuation of a heated substrate. In our configuration, this design leads to a standard linear phase diagram by varying the growth rate of each constituent nearly linearly from 0 to 100% at a triangular area on the substrate. Film growth occurs as a series of cycles in which one molecular layer of the material is deposited over the entire area of the spread by a synchronization of the mask movement, target exchange, and laser pulses. The technique has been applied to the synthesis of photoluminescent TbCa(4)O(BO(3))(3)-ScCa(4)O(BO(3))(3)-PrCa(4)O(BO(3))(3), demonstrating its value for the mapping of direct relationship between composition and the light-emitting property.

Synthesis and Functional Properties of Donor−Acceptor π-Conjugated Oligomers

Novel donor−acceptor oligophenylenevinylenes (OPVs) bearing an electron-donating 2-(2-butoxyethoxy)ethoxy group at one end and various electron-withdrawing groups including alkylsulfonyl, cyano, and nitro functionalities at the other end have been synthesized for investigation of structure−functional property relationships. Depending on the nature of the electron-withdrawing group, the newly synthesized donor−acceptor OPVs can exhibit an efficient light-emitting property or a large photovoltaic effect. The asymmetrically disubstituted OPV bearing 2-(2-butoxy-ethoxy)ethoxy-hexylsulfonyl functionalities possesses superior molecular properties for light-emitting applications than the symmetrically 2-(2-butoxyethoxy)ethoxy-disubstituted counterparts. In addition, our first observation and investigation on the photovoltaic response in polyalkyleneoxy-nitro disubstituted OPV series is reported. The spectral responsivity of the photovoltaic device corresponds to the absorption characteristics of the oligomer. Most importantly, the photocurrent responsivity increases with an extension of the conjugated length of the oligomer.

Shape-persistent cyclyne-type azamacrocycles: synthesis, unusual light-emitting characteristics, and specific recognition of the Sb(V) ion

Simple members of arene–azaarenecyclynes as a novel family of geometrically-controlled and shape-persistent azamacrocycles have been synthesized. Noteworthy is the specific recognition function for Sb(V). The synthesized azamacrocycles, in particular the Sb(V) complex, have unusually strong light-emitting property.