Photoluminescence of 2,4,6-tris[4-(phenylethynyl)phenyl]-1,3,5-triazines dispersed in polymer films

Photoluminescence of three types of 1,3,5-triazine derivatives with three kinds of diphenylacetylene side chains was investigated. They showed quantum yields higher than 46% in chloroform, and the Stokes shift (66–114 nm) in chloroform depended on the kind of the diphenylacetylene side chain. In cast films, the three compounds gave a larger Stokes shift of 132–211 nm, suggesting formation of an excimer in the solid. The 1,3,5-triazine derivatives were dispersed in films of polymers such as polystyrene and poly(vinyl acetate), and photoluminescence of the films containing the 1,3,5-triazine derivatives was investigated. Dispersion of the compound in a poly(vinyl acetate) film still gave a rather larger Stokes shift of 128–203 nm. In contrast, dispersion in polystyrene reduced the Stokes shift to about 60 nm, revealing an excellent dispersing effect of polystyrene for the compounds.     

2,5-二[4-(4-溴苯氧基亚甲基)苯基]-1,3,4-噁二唑的合成与表征

以对甲基苯甲酸、水合肼为原料,通过关环、溴化、醚化合成了一种新型含噁二唑功能基有机聚合物电致发光材料单体2,5-二[4-(4-溴苯氧基亚甲基)苯基]-1,3,4-噁二唑,其化学结构由红外光谱仪及核磁共振氢谱仪进行了表征,产品总收率22.64%.     

Structural and magnetodielectric properties of poly(vinylidene-fluoride)-[0.8(Bi0.5Na0.5)TiO3-0.2CoFe2O4] polymer composite films

Composite thick films of xPoly(vinylidene-fluoride)-(1−x)[0.8(Bi_0.5Na_0.5)TiO₃-0.2CoFe₂O₄] with x = 0.1, 0.2, 0.3 and 0.4 were synthesized by hot press method. X-ray diffraction pattern of the composite films indicate the existence of distinct peaks of poly(vinylidene-fluoride), (Bi_0.5Na_0.5)TiO₃ and CoFe₂O₄ phases. The value of dielectric loss and saturation magnetization of polymer composite films decrease with increase in poly(vinylidene-fluoride) content. The magnetodielectric effect of the polymer composite films was found to improve with increasing poly(vinylidene-fluoride) content. The linear fitting of Δε ∼ γM² gives the value of magnetoelectric interaction coefficient (γ) of polymer composite films.     

Synthesis and characterization of N-[4-(chlorocarbonyl)phenyl]maleimide functionalized graphene oxide and reduced graphene oxide

Functionalization of graphene oxide leads improvement in thermal stability and flame retardancy. Acid chloride terminated N-[4-(chlorocarbonyl)phenyl]maleimide (Cl-CPMI) was synthesized to decorate hydroxyl group in graphene oxide (GEO) and glycine-reduced GEO (RGEO). Structural characterization of the materials was performed using FTIR, ¹³C NMR and Raman spectroscopic methods. Interlayer distance and surface morphology were also studied using X-ray diffraction and scanning electron microscopic methods, respectively. The absence of the band for C-Cl and shortening of the O-H band in the FTIR and peak in ¹³C NMR spectra confirm the functionalization of alcoholic group on the graphitic plane with Cl-CPMI. The ratio, I_D/I_G computed from Raman study, the nature of XRD pattern and interlayer distance between the adjacent graphitic layers were not affected by the functionalization of GEO and RGEO using Cl-CPMI. The tagging of maleimide unit with the graphitic plane was also confirmed by the cloudy appearance in the SEM images.     

Influence of ionic interactions on the photoinduced birefringence of poly[1-[4-(3-carboxy-4 hydroxyphenylazo) benzene sulfonamido]-1,2-ethanediyl, sodium salt] films

Electrostatic interactions govern most properties of polyelectrolyte films, as in the photoinduced birefringence of azo-containing polymers. In this paper we report a systematic investigation of optical storage characteristics of cast and layer-by-layer (LbL) films of poly[1 -[4-(3-carboxy-4 hydroxyphenylazo) benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO). Birefringence was photoinduced faster in PAZO cast films prepared at high pHs, with the characteristic writing times decreasing almost linearly with the pH in the range between 4 and 9. This was attributed to an increased free volume for the azochromophores with the enhanced electrostatic repulsion in PAZO charged to a greater extent. In contrast, in LbL films of PAZO alternated with poly(allylamine hydrochloride) (PAH), the electrostatic interactions between the oppositely charged polymers hampered photoisomerization and molecular rearrangement, thus leading to a slower writing kinetics for highly charged     

Charge injection into poly[methyl(phenyl)silylene]

Space-charge-limited currents have been measured in thin films of poly[methyl(phenyl)silylene] provided with Al and hole-injecting ITO electrodes. Electroluminescence observed at high voltages was interpreted as being due to a double injection. The thermo-modulated space-charge-limited current technique has been employed to determine the structure of traps in the low-voltage (single-injection) regime.     

Mechanochromic luminescence of 4-[bis(4-methylphenyl)amino]benzaldehyde

The title compound was found to exhibit mechanochromic luminescence; the fluorescent color of the crystalline powder was changed from light blue to greenish yellow by grinding and then returned to the original by keeping at room temperature. The phenomenon was suggested to be due to formation of the supercooled liquid state of the material by grinding and following recrystallization.     

Birefringence dynamics of poly{1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt} cast films

Photoinduced birefringence creation/decay dynamics in poly{1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt}cast films, has been characterized in the 5 to 100 mW writing laser power range at the wavelength of 514 nm. The maximum birefringence magnitude increased with laser beam power, being the largest value of 0.03, measured at 632.8 nm. Birefringence creation kinetics followed a biexponential behavior, where a slow process and a fast process could be clearly distinguished. The fast process accounted for more than 60% of birefringence. The time constants for both fast and slow processes decreased with increasing power of writing beam. Birefringence relaxation after removal of writing laser beam revealed to be independent of beam power and, was found to be ruled by two processes, described by a biexponential curve plus a constant term accounting for residual birefringence. A high residual birefringence signal of 85 ± 3% was attained, with the fast process contributing to 67% of decay from maximum value. The large values obtained for time constants for both birefringence creation and relaxation processes are believed to arise from stabilization of azo-group either by the formation of an ionic network, or by local short range interactions that are coming through as a result polyelectrolyte coiling due to its high degree of ionization.     

双酚A型二醚二酐的合成及对环氧树脂固化的影响

以4-氯代邻苯二甲酸酐(4-CPA)和双酚A为主要原料,经缩合、水解、酸化、脱水,合成了双酚A型二醚二酐(BPADA),并用核磁共振氢谱和红外光谱对产物的结构进行了表征。利用差示扫描量热分析和动态力学分析方法研究了BPADA作为E-51环氧树脂的固化剂并与邻苯二甲酸酐(PA)进行了比较,考察了2种固化体系所得产物的力学性能。结果表明,采用四步法成功合成出了BPADA,2种体系的固化反应活化能和反应级数相近,但BPADA体系活化能稍高于PA体系,且PA体系具有更高的反应速率。BPADA体系固化物的Tg比PA体系提高了40℃。相比PA体系,BPADA体系的冲击强度提高了35%,而弯曲性能略有下降,E-51/BPADA固化体系的冲击断面呈典型的韧性断裂,而E-51/PA固化体系呈典型的脆性断裂。     

Large resonant third-order optical nonlinearity of thin film containing J-like aggregates of a bis[4-(N-dibutylamino)phenyl]squarylium dye

The third-order optical nonlinearity and response of thin film containing J-like aggregates of a bis[4-(N-dibutylamino)phenyl]squarylium dye were measured by degenerate four-wave mixing (DFWM) technique under resonant conditions. The temporal profile of DFWM signal was obtained with a time resolution of 0·3 ps (FWHM), and was found to consist of at least two components, i.e. the coherent instantaneous nonlinear response (electronic response) and the slow response due to the excited state population grating. The effective χ ⁽³⁾ value of thin squarylium dye film was evaluated to be as high as 1·1 × 10^???7 esu, and the figure of merit of third-order nonlinearity F (F =?χ ⁽³⁾/α), was calculated to be about 2·1 × 10^???13 esu cm.     

Dielectric properties of polymer films based on [NiSalen] complexes

The temperature dependence of the dielectric characteristics of metal-containing polymer films obtained using electrochemical polymerization of a Ni(II) complex monomer [NiSalen] have been studied in a temperature interval from 290 to 370 K. The low-frequency polarization characteristics of poly[NiSalen] film samples exhibit a temperature hysteresis. It is suggested that the observed features of a relaxation type are related to reversible transformations of the redox form of the polymer.     

Synthesis and characterization of 1-phenyl-3-(4-phenyl-[1,2,3]triazol-1-yl)-4-styryl-azetidin-2-one films for light-emitting applications

Triazole derivatives have attracted considerable interest in OLEDs because of their electron transporting as well as hole blocking and/or exciton confining properties. To improve the quantum efficiency and lower the operating voltage of OLEDs, a novel derivative of triazole namely 1-phenyl-3-(4-phenyl-[1,2,3]triazol-1-yl)-4-styryl-azetidin-2-one (TAZ) has been designed as an electron transporting material. Thin films of TAZ have been prepared by the vacuum evaporation technique onto a glass substrate kept at different temperatures under different experimental conditions. These films have been systematically studied for their structural, optical and electrical properties. X-ray diffraction and FESEM studies of the films show an increase in crystallinity with an increase in the substrate temperature. The electrical resistance of these films is found to be 10⁷ ohm at room temperature. Analysis of optical absorption measurements on the films indicate that the interband transition energies lie within 3.4-3.6 eV. These wide band gaps show that TAZ layers can work as a hole blocking (HB) material in OLED.     

Tetramethylammonium Neptunium(IV) Isothiocyanate [N(CH3)4]4[Np(NCS)8]

A new Np(IV) complex, [N(CH₃)₄]₄[Np(NCS)₈], was prepared. Its crystal structure was determined, and the absorption spectra in the IR and near IR ranges were measured. Crystal data: a = 27.280(6), b = 12.288(3), c = 13.493(3) Å, space group Pna2₁, Z = 4, V = 4523(2) A³, R = 0.044, wR(F ²) = 0.091. The crystal structure of the compound consists of [Np(NCS)₈]^{4 -} anions and N(CH₃)₄ ⁺ cations. The coordination polyhedron of the Np atom is a distorted tetragonal antiprism formed by the nitrogen atoms of eight NCS^- ions.     

In vivo microdialysis and thermospray tandem mass spectrometry of the dopamine uptake blocker 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)-piper azine (GBR-12909)

Microdialysis in conjunction with thermospray tandem mass spectrometry was employed in following the time course of the experimental drug GBR-12909 in vivo. GBR-12909 is 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-3(phenylpropyl)-piperazine. An important feature of microdialysis exploited in the method is the elimination of sample cleanup procedures. The detection limit was determined to be 100 pg and the relative standard deviation of estimates for standard solution in the range of 50 nmol/L to 1 mumol/L concentrations was found to be 17%. Important factors in obtaining high sensitivity and reproducibility were carrier phase composition and operation in the flow injection mode. The maximum concentration of GBR-12909 in the brain for a dose of 100 mg/kg i.p. was determined to be 250 nmol/L with the maximal concentration occurring approximately 2 h postinjection. This represents a 40-fold lower concentration of GBR-12909 in the brain as compared to cocaine concentration obtained at a dose of 30 mg/kg, which was estimated earlier under similar experimental conditions. This observation could explain the discrepancy between relative in vivo and in vitro potencies of the two drugs.     

Electrochemical and quantum chemical study of 4-[(E)-[(2,4-dihydroxy phenyl) methylidine] amino]-6-methyl-3-sulphanylidine-2,3,4,5-tetra hydro-1,2,4-triazin-5-one [DMSTT]

The inhibition of mild steel in aerated 1 M hydrochloric acid solution was studied using conventional weight loss method, potentiodynamic polarization studies (Tafel), linear polarization studies (LPR), electrochemical impedance spectroscopy (EIS) and quantum chemical calculation in the presence and absence of different concentrations of DMSTT. The inhibition efficiency increased markedly with increase in the additive concentrations, but slightly decreased with increasing temperature. The presence of DMSTT decreases the double layer capacitance and increases the charge-transfer resistance. The value of activation energy (E_a) for mild steel corrosion and thermodynamic parameters such as adsorption equilibrium constant (K_ads), free energy of adsorption (ΔG_ads) values were calculated and discussed. The inhibitor molecule first adsorbed on mild steel surface according to Langmuir adsorption isotherm.     

Electro-optical properties of poly(1-(difluorophenyl)-2-(4-alkylcyclohexyl phenyl)acetylene) organic light-emitting diodes

For organic light-emitting diodes (OLEDs) applications, we have investigated novel polymers, using substituted polyacetylenes (PA), poly(1-(fluorophenyl)-2-(alkylcyclohexylphenyl)acetylene) (PDPA-nF) (n = 1 or n = 2) which exhibit air stability, better solubility in common organic solvent and higher luminescence than polyacetylene. In this study, we have used poly[(1-(3,4-difluorophenyl)-2-(4-pentylcyclohexylphenyl)acetylene)] (PDPA-2F) as an emitter in OLEDs and their performance was determined by measuring the current-voltage-luminance characteristic. The devices have a maximum brightness of 827 candela (cd)/m² at 12 V and a maximum current efficiency of 0.78 cd/A at 9 V with a maximum luminescence at 536 nm. Influence of the metal electrode on the charge injection was studied using several cathode configurations (Ca, Al and Au) for the devices. Furthermore, the charge injection and transport processes were correlated to the presence of traps inside the polymer, determined by deep level transient spectroscopy (DLTS).     

2,4,6-Tris (2-pyridyl)-1,3,5-triazine nanobelts as an effective fluorescent sensing platform for DNA detection

In the present study, we report on the use of 2,4,6-tris (2-pyridyl)-1,3,5-triazine nanobelts (TPTNBs) as an effective fluorescent sensing platform for DNA detection for the first time. The general concept used in this approach is based on adsorption of fluorescently labeled single-stranded DNA (ssDNA) probe by TPTNB, due to the strong pi-pi stacking between unpaired DNA bases and TPTNB. As a result, the fluorophor is brought into close proximity of TPTNB, leading to fluorescence quenching. Upon presence of the target ssDNA, specific hybridization with the target takes place to form a double-stranded DNA (dsDNA). The resultant dsDNA cannot be adsorbed by TPTNB due to its rigid conformation and the absence of unpaired DNA bases. Thus, the fluorophor is seperated from TPTNB accompanied by fluorescence recovery. The present system shows a detection limit as low as 3 nM and has a high selectivity down to single-base mismatch.