Investigation on charge transfer bands of Ce4+ in Sr2CeO4 blue phosphor

Bulk and nano-materials Sr2CeO4 were prepared by solid-state reaction and sol-gel technique, respectively. Photoluminescence shows that luminescence has the characteristic of a ligand-to-metal charge transfer (CT) emission. Compared with bulk Sr2CeO4, the nano-material exhibits stronger emission intensity, longer decay time, and higher CT excitation energy. Three CT excitation peaks were observed in both bulk and nano samples.

Electrical instability in vanadyl-phthalocyanine thin-film transistors

We investigated the electrical instability of vanadyl-phthalocyanine (VOPc) thin-film transistors (TFTs) at various temperatures. The results demonstrate a slow threshold voltage shift in the bias stress process and a rapid recovery after the removal of bias stress, which indicates that a slower degradation process occurs in the on state while a faster removal in the off state of VOPc TFTs. The shift of threshold voltage comes from traps generated at the organic/dielectrics interface. Additionally, a relaxation time of 10(7) s was obtained at room temperature according to the stretched exponential model, which is comparable to a-Si: H TFTs. Therefore, VOPc TFTs are suitable to be applied in flat panel displays.

Energy transfer and tunable luminescence properties of Eu3+ in TbBO3 microspheres via a facile hydrothermal process

Tb(1-x)BO3:xEu(3+) (x = 0-1) microsphere phosphors have been successfully prepared by a simple hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as lifetimes were used to characterize the samples.

Synthesis and characterization of color-stable electroluminescent polymers: Poly(dinaphtho [1,2-a : 1 ',2 '-g]-s-indacene)s

Two new stepladder conjugated polymers, that is, poly(7,7,15,15-tetraoctyldinaphtho[1,2-a:1',2'-g]-s-indacene) (PONSI) and poly(7,7,15,15-tetra(4-octylphenyl)dinaphtho[1,2-a:1',2'-g]-s-indacene) (PANSI) with alkyl and aryl substituents, respectively, have been synthesized and characterized. In comparison with poly(indenofluorene)s, both polymers have extended conjugation at the direction perpendicular to the polymer backbone because of the introduction of naphthalene moieties. The emission color of the polymers in film state is strongly dependent on the substituents. While PONSI emits at a maximum of 463 nm, PANSI with the same backbone but aryl substituents displays dramatically redshifted emission with a maximum at 494 nm.

Synthesis and luminescent properties of Lu3Ga5O12 : RE3+ (RE = Eu, Tb, and Pr) nanocrystalline phosphors via sol-gel process

Lu3Ga5O12:Eu3+, Lu3Ga5O12:Tb3+, and Lu3Ga5O12:Pr3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence, and cathodoluminescence spectra were utilized to characterize the synthesized phosphors. The XRD results reveal that the sample begins to crystallize at 800 degrees C and fully crystallined pure Lu3Ga5O12 phase can be obtained at 1000 degrees C. The FESEM image indicates that the phosphor sample is composed of aggregated rice grainlike particles with sizes around 80-120 nm.

Fabrication of an integrated pixel with an organic light-emitting diode driven by copper phthalocyanine organic thin film transistors

An organic integrated pixel with organic light-emitting diodes (OLEDs) driven by organic thin film transistors (OTFTs) is fabricated by a greatly simplified processing. The OTFTs are based on copper phthalocyanine as the active medium and fabricated on indium-tin-oxide (ITO) glass with top-gate structure, thus an organic integrated pixel is easily made by integrating OLED with OTFT. The OTFTs show field-effect mobility of 0.4 cm(2) /Vs and on/off ratio of 10(3) order. The OLED is driven well and emits the brightness as large as 2100cd/m(2) at a current density of 14.6 mu A/cm(2) at -19.7 V gate voltage. This simple device structure is promising in the future large-area flexible OLED displays.

Hydrogen peroxide biosensor based on direct electrochemistry of soybean Peroxidase immobilized on single-walled carbon nanohorn modified electrode

Single-walled carbon nanohorns (SWCNHs) were used as a novel and biocompatible matrix for fabricating biosensing devices. The direct immobilization of acid-stable and thermostable soybean peroxidase (SBP) on SWCNH modified electrode surface can realize the direct electrochemistry of enzyme. Cyclic voltammogram of the adsorbed SBP displays a pair of redox peaks with a formal potential of -0.24V in pH 5 phosphate buffer solution.

Very low hysteresis organic thin-film transistors

Very low hysteresis vanadyl-phthalocyanine/para-sexiphenyl thin-film transistors (TFTs) have been fabricated using benzocyclobutenone (BCBO) derivatives/tantalum pentoxide (Ta2O5)/BCBO triple gate dielectrics. The field effect mobility, on/off current ratio and threshold voltage of organic TFTs are 0.45 cm(2) V-1 s(-1), 3.5 x 10(4) and -6.8 V, respectively. To clarify the mechanism of hysteresis, devices with different dielectrics have been studied. It is found that the bottom BCBO derivatives (contact with a gate electrode) block the electron injection from a gate electrode to dielectrics.

Synthesis and properties of novel sulfonated poly(phenylquinoxaline)s as proton exchange membranes

Two series of sulfonated poly(phenylquinoxaline)s (SPPQ-x and SPPQ(O)-x, x refers to molar percentage of sulfonated tetraamine monomer) were first synthesized from a sulfonated tetraamine (4,4'-bis(3,4-diaminophenoxy)biphenyl-3.3'-disulfonic acid) and two aromatic bisbenzils (4-phenylglyoxalylbenzil and p,p'-oxydibenzil) in a mild condition. The structures of SPPQ-x and SPPQ(0)-x were characterized by IR and H-1 NMR spectra. The properties of these polymer films, such as water uptake, water swelling ratio, proton conductivity, thermal properties, methanol permeability, hydrolytic and oxidative stability were also investigated. The resulting polymers generally showed good solubility in DMAc and DMSO. Flexible and tough membranes with high mechanical strength were prepared. They show very high thermal, thermooxidative, hydrolytic stabilities and low methanol permeability. SPPQ-100 with the IEC value (2.41 mmol/g) displays the conductivity of 0.1 S/cm and a swelling ratio of 7.3% at 100 degrees C.

Direct electrochemistry and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified by Nafion and ordered mesoporous silica-SBA-15

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified by ordered mesoporous silica-SBA-15 and Nafion. The sorption behavior of GOD immobilized on SBA-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that SBA-15 can facilitate the electron exchange between the electroactive center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and SBA-15 matrices displays direct, nearly reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 3.89 s(-1) in 0.1 M phosphate buffer solution (PBS) (pH 7.12).

Electrochemistry of Microperoxidase-11 (MP-11) on Glassy Carbon Electrode Modified with Chitosan

In this paper, microperoxidase-11 (MP-11) was immobilized on glassy carbon electrode surface modified with chitosan by physical adsorption. The direct electrochemistry and the electrocatalytic behaviours to O-2 and the H2O2 of MP-11 on glassy carbon electrode modified with chitosan were characterized by cyclic voltammetry. The results indicate that MP-11 on modified electrode displays a quasi-reversible electrochemical process coupled with proton transfer in the phosphate buffer solutions(pH = 7.12). Direct electrochemical reaction of MP-11 on modified electrode has been realized. MP-11 on modified electrode can catalyze reduction for O-2 and H2O2. Both of the catalytic reductions are surface-controlled electrochemical process.

Synthesis and Luminescent Properties of LaAlO3:RE3+ (RE = Tm, Tb) Nanocrystalline Phosphors via a Sol-Gel Process

LaAlO3:Tm3+ and LaAlO3:Tb3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. The XRD results reveal that the fully crystalline pure LaAlO3 Phase can be obtained at 800 degrees C. The FE-SEM image indicates that the phosphor samples are composed of aggregated spherical particles with sizes ranging from 40 to 80 nm. Under the excitation of ultraviolet light (230 nm) and low-voltage electron beams (1-3 kV), the LaAlO3:Tm3+ and LaAlO3:Tb3+ phosphors show the characteristic emissions of Tb3+ (D-1(2)-> H-3(6,4),F-3(4) transitions) and Tm3+ (D-5(3,4)-> F-7(6,5,4,3) transitions) respectively. The CL of the LaAlO3:Tm3+ phosphors have high color purity and comparable intensity to the Y2SiO5:Ce3+ commercial product, and the CL colors of Tb3+-doped LaAlO3 phosphors can be tuned from blue to green by changing the doping concentration of Tb3+ to some extent.

Preparation and Luminescence Properties of Gd2MoO6:Eu3+ Nanofibers and Nanobelts by Electrospinning

Gd2MoO6:Eu3+ nanofibers and nanobelts have been prepared by a combination method of the sol-gel process and electrospinning. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy, photoluminescence, and low voltage cathodoluminescence as well as kinetic decays were used to characterize the resulting samples. The results of XRD and FTIR indicate that the Gd2MoO6:Eu3+ samples have crystallized at 600 degrees C with the monoclinic (alpha) structure. The SEM and TEM results indicate that the as-formed precursor fibers and belts are uniform and that the as-prepared nanofibers and nanobelts consist of nanoparticles. Gd2MoO6:Eu3+ phosphors show their strong characteristic emission under UV excitation (353 nm) and low voltage electron-beam excitation (3 kV), making the materials have potential applications in fluorescent lamps and field-emission displays.

Tunable Photoluminescence and Cathodoluminescence Properties of Eu3+-Doped LaInO3 Nanocrystalline Phosphors

LaInO3:Eu3+ phosphors were prepared by a Pechini sol-gel process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), diffuse reflectance, photoluminescence, cathodoluminescence spectra, as well as lifetimes were utilized to characterize the synthesized phosphors. XRD results reveal that the sample begins to crystallize at 600 degrees C and pure LaInO3 phase can be obtained at 800 degrees C. The crystallinity increases upon raising the annealing temperature. The FE-SEM images indicate that LaInO3:Eu3+ phosphors are composed of fine and spherical grains around 40-80 nm in size. Under the excitation of UV light and low-voltage electron-beams, LaInO3:Eu3+ phosphors show the characteristic emissions of the Eu3+ (D-5(J)-F-7(J) J,J(')=0,1,2,3 transitions). The luminescence colors can be tuned from yellowish warm white to red by changing the doping concentration of Eu3+ to some extent. The corresponding luminescence mechanisms have been proposed.

Formation of low surface energy separators with undercut structures via a full-solution process and its application in inkjet printed matrix of polymer light-emitting diodes

In this paper, low surface energy separators With undercut structures were fabricated through a full solution process, These low Surface energy separators are more suitable for application in inkjet printed passive-matrix displays of polymer light-emitting diodes. A patterned PS film was formed on the P4VP/photoresist film by microtransfer printing firstly. Patterned Au-coated Ni film was formed on the uncovered P4VP/photoresist film by electroless deposition. This metal film was used as mask to pattern the photoresist layer and form undercut structures with the patterned photoresist layer. The surface energy of the metal film also decreased dramatically from 84.6 mj/m(2) to 21.1 mJ/m(2) by modification of fluorinated mercaptan self-assemble monolayer on Au surface. The low surface energy separators were used to confine the flow of inkjet printed PFO solution and improve the patterning resolution of inkjet printing successfully. Separated PFO stripes, complement with the pattern of the separators, formed through inkjet printing.