Molecular "Wiring" glucose oxidase in supramolecular architecture

Supramolecular organized multilayers were constructed by multiwalled carbon nanotubes modified with ferrocene-derivatized poly(allylamine) redox polymer and glucose oxidase by electrostatic self-assembly. From the analysis of voltammetric signals and fluorescence results, a linear increment of the coverage of enzyme per bilayer was estimated, which demonstrated that the multilayer is constructed in a spatially ordered manner. The cyclic voltammograms obtained from the indium tin oxide (ITO) electrodes coated by the (Fc-PAH@CNT/GOx)(n) multilayers revealed that bioelectrocatalytic response is directly correlated to the number of deposited bilayers; that is, the sensitivity is tunable by controlling the number of bilayers associated with ITO electrodes. The incorporation of redox-polymer-functionalized carbon nanotubes (CNT) into enzyme films resulted in a 6-10-fold increase in the glucose electrocatalytic current; the bimolecular rate constant of FADH(2) oxidation (wiring efficiency) was increased up to 12-fold. Impedance spectroscopy data have yielded the electron diffusion coefficient (D-e) of this nanostructure to be over 10(-8) cm(2) s(-1), which is typically higher than those systems without CNT by at least a factor of 10, indicating that electron transport in the new supramolecular architecture was enhanced by communication of the redox active site of enzyme, redox polymer, and CNT.

Alternate assemblies of polyelectrolyte functionalized carbon nanotubes and platinum nanoparticles as tunable electrocatalysts for dioxygen reduction

A novel method based on electrostatic layer-by-layer self-assembly (LBL) technique for alternate assemblies of polyelectrolyte functionalized multi-walled carbon nanotubes (MWNTs) and platinum nanoparticles (PtNPs) is proposed. The shortened MWNTs can be functionalized with positively charged poly(diallyldimethylammonium chloride) (PDDA) based on electrostatic interaction. Through electrostatic layer-by-layer assembly, the positively charged PDDA functionalized MWNTs (PDWNTs) and negatively charged citrate-stabilized PtNPs were alternately assembled on a 3-mercaptopropanesulfonic sodium (NIPS) modified gold electrode and also on other negatively charged surface, e.g. quartz slide and indium-tin-oxide (ITO) plate, directly forming the three-dimensional (3D) nanostructured materials. This is a very general and powerful technique for the assembling three-dimensional nanostructured materials containing carbon nanotubes (CNTs) and nanoparticles. Thus prepared multilayer films were characterized by ultraviolet-visiblenear-infrared spectroscopy (UV-vis-NIR), scanning electron microscopy (SEM) and cyclic voltammetry (CV). Regular growth of the mutilayer films is monitored by UV-vis-NIR.

Photochemical formation of silver and gold nanostructures at the air-water interface and their electrocatalytic properties

In this paper, we report a simple method of fabricating silver and gold nanostructures at the air - water interface, which can be spontaneously assembled through the reduction of AgNO3 and HAuCl4 with ultraviolet (UV) irradiation in the presence of polyacrylic acid (PAA), respectively. It was found that the building blocks in the silver nanostructure are mainly interwoven silver nanofilaments, while those of the gold nanostructure are mainly different sizes of gold nanoparticles and some truncated gold nanoplates, and even coalescence into networks. At the air - water interface, these silver and gold nanostructures can be easily transferred onto the surface of indium tin oxide (ITO) slides and used for electrochemical measurements. After a replacement reaction with H2PdCl4, the silver nanostructure is transformed into a Ag - Pd bimetallic nanostructure, with good electrocatalytic activity for O-2 reduction. The gold nanostructure can also show high electrocatalytic activity to the oxidation of nitric oxide (NO) with a detection limit of about 10 mu M NaNO2 at S/N = 3.

High efficiency tandem organic light-emitting devices with Al/WO3/Au interconnecting layer

An interconnecting layer of Al (2 nm)/WO3 (3 nm)/Au (16 nm) was studied for application in tandem organic light-emitting devices. It can be seen that the Al/WO3/Au structure plays the role of an excellent interconnecting layer. The introduction of WO3 in the connection unit significantly improves the device efficiency as compared to the case of Al/Au. Thus, the current efficiency of the two-unit tandem devices is enhanced by two factors with respect to the one-unit devices. The green two-unit tandem device of indium tin oxide/MoO3/4,4(')-N,N-'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl(NPB)/tris(8-hydroxylquinoline) aluminum (Alq(3)):10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one (C545T)/Alq(3)/LiF/Al/WO3/Au/MoO3/NPB/Alq(3):C545T/Alq(3)/LiF/Al showed a maximum current efficiency of 33.9 cd/A and a power efficiency of 12.0 lm/W.

Near infrared light-emitting diodes based on composites of near infrared dye, CdSe/CdS quantum dots and polymer

Near infrared (NIR) light emitting diodes employing composites of an IR fluorescent dye, CdSe/CdScore/shell semiconductor quantum dots and poly( N-vinylcarbazole) (PVK) have been demonstrated. The device, with a configuration of indium-tin-oxide (ITO)//PEDOT:PSS//PVK:NIR Dye:CdSe/CdS//Al, had a turn-on voltage of 7 V, emitted the NIR light with a maximum at 890 nm and the irradiance intensity of 96 mu W. The electroluminescence efficiency of 0.02% was achieved at a current density of 13 mA cm(-2).

White electroluminescence from a single-polymer system with simultaneous two-color emission: Polyfluorene as blue host and 2,1,3-benzothiadiazole derivatives as orange dopants on the side chain

Four single polymers with two kinds of attachment of orange chromophore to blue polymer host for white electroluminescence (EL) were designed. The effect of the side-chain attachment and main-chain attachment on the EL efficiencies of the resulting polymers was compared. The side-chain-type single polymers are found to exhibit more efficient white EL than that of the main-chain-type single polymers. Based on the side-chain-type white single polymer with 4-(4-alkyloxy-phenyl)-7-(4-diphenylamino-phenyl)-2,1,3-benzothiadiazoles as the orange-dopant unit and polyfluorene as the blue polymer host, white EL with simultaneous orange (lambda(max) = 545 nm) and blue emission (lambda(max) = 432 nm/460 nm) is realised. A single-layer device (indium tin oxide/poly(3,4-ethylenedioxythiophene)/polymer/Ca/Al) made of these polymers emits white light with the Commission Internationale de l'Eclairage coordinates of (0.30,0.40), possesses a turn-on voltage of 3.5 V, luminous efficiency of 10.66 cd A(-1), power efficiency of 6.68 lm W-1, and a maximum brightness of 21240 cd m(-2).

Synthesis and characterization of white-light-emitting polyfluorenes containing orange phosphorescent moieties in the side chain

Two orange phosphorescent iridium complex monomers, 9-hexyl-9-(iridium (III)bis(2-(4'-fluorophenyl)-4-phenylquinoline-N, C-2')(tetradecanedionate-11,13))-2,7-dibromofluorene (Br-PIr) and 9-hexyl-9-(iridium(III)bis(2-(4'-fluorophenyl)-4-methylquinoline-N, C-2')(tetradecanedionate-11,13))-2,7-dibromofluorene (Br-MIr), were successfully synthesized. The Suzuki polycondensation of 2,7-bis(trimethylene boronate)-9,9-dioctylfluorene with 2,7-dibromo-9,9-dioetylfluorene and Br-Plr or Br-MIr afforded two series of copolymers, PIrPFs and MIrPFs, in good yields, in which the concentrations of the phosphorescent moieties were kept small (0.5-3 mol % feed ratio) to realize incomplete energy transfer. The photoluminescence (PL) of the copolymers showed blue- and orange-emission peaks. A white-light-emitting diode with a configuration of indium tin oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/PIr05PF (0.5 mol % feed ratio of Br-PIr)/Ca/Al exhibited a luminous efficiency of 4.49 cd/A and a power efficiency of 2.35 lm/W at 6.0 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.46, 0.33). The CIE coordinates were improved to (0.34, 0.33) when copolymer MIr10PF (1.0 mol % feed ratio of Br-MIr) was employed as the white-emissive layer. The strong orange emission in the electroluminescence spectra in comparison with PL for these kinds of polymers was attributed to the additional contribution of charge trapping in the phosphorescent dopants.

微芯片毛细管电泳电化学/电化学发光同时检测药物分子

提出了基于毛细管电泳芯片的电化学和电化学发光同时检测技术.在此芯片系统中,三联吡啶钌Ru(bpy)2+3[Tris(2,2'-bypiridyl) ruthenium(Ⅱ)]既作为电化学发光(ECL)检测所需的发光试剂与被分析物反应,生成激发态的Ru(bpy)2+3*,从而产生电化学发光信号;又具有催化作用参与电极表面的电化学反应,从而得到增强的电流响应.电化学信号与电化学发光信号同时产生并被分别纪录,从而实现了电化学和电化学发光的同时检测.这种芯片由两部分构成,分别是带有分离和进样通道的聚二甲基硅氧烷(PDMS)层和ITO(Indium tin oxide)工作电极底片.PDMS层与ITO电极底片采用可逆键合的方式组成芯片,该芯片大大简化了操作过程,提高了发光信号的采集效率.在整个实验过程中,ITO电极表现出良好的稳定性,可长时间多次使用.选用山莨菪碱和氧氟沙星两种药物分子作为被分析物,对芯片系统性能进行了表征.

White electroluminescence from polyfluorene chemically doped with 1,8-napthalimide moieties

An efficient white light-emitting polymer was developed with blue polyfluorene (PFO) chemically doped with orange fluorescent 1, 8-naphthalimide moieties. The emission spectrum can be easily tuned by varying the content of 1, 8-naphthalimide moieties. A white polymeric light-emitting diode (WPLED) with a structure of indium tin oxide (ITO)/the complex of (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid (PEDOT)/polymer/Ca/Al showed a current efficiency of 5.3 cd/A and a power efficiency of 2.8 Lm/W at 6 V with the Commission Internationale de L'Eclairage (CIE) coordinates at (0.25,0.35). Moreover, the WPLED from the copolymer showed a very stable white light emission at different driving voltage and brightness. The CIE coordinates of the WPLED were (0.25, 0.35), (0.26, O.36), and (0.26, 0.36) under driving voltages of 6, 8, and 10 V, corresponding to the brightness of 82, 3555, and 7530 cd/m(2), respectively. This approach for realization of white light emission is promising over the polymer blending system in terms of both efficiency and color stability.

White electrolumineseence from a single-polymer system with simultaneous two-color emission: Polyfluorene as the blue host and a 2,1,3-benzothiadiazole derivative as the orange dopant on the main chain

New single-polymer electroluminescent systems containing two individual emission species - polyfluorenes as a blue host and 2,1,3-benzothiadiazole derivative units as an orange dopant on the main chain - have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue(lambda(max) = 421 nm/445 nm) and orange emission (lambda(max) = 564 nm)from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light-emitting diodes (PLEDs) based on the single-polymer systems has been investigated. The introduction of the highly efficient 4,7-bis(4-(N-phenyl-N-(4-methylphenyl)amino)phenyl)-2,1,3-benzothiadiazole unit to the main chain of polyfluorene provides significant improvement in EL efficiency. For a single-layer device fabricated in air (indium tin oxide/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure-white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m(-2), luminance efficiency of 7.30 cd A(-1), and power efficiency of 3.34 lm W-1 can be obtained.

Highly efficient pure-white-light-emitting diodes from a single polymer: Polyfluorene with naphthalimide moieties

Light-emitting diodes exhibiting efficient pure-white-light electroluminescence have been successfully developed by using a single polymer: polyfluorene derivatives with 1,8-naphthalimide chromophores chemically doped onto the polyfluorene backbones. By adjusting the emission wavelength of the 1,8-naphthalimide components and optimizing the relative content of 1,8-naphthalimide derivatives in the resulting polymers, white-light electroluminescence from a single polymer, as opposed to a polymer blend, has been obtained in a device with a configuration of indium tin oxide/poly(3,4-ethyleiledioxythiophene)(50 nm)/polymer(80 nm)/Ca(10 nm)/Al(100 nm). The device exhibits Commission Internationale de I'Eclairage coordinates of (0.32,0.36), a maximum brightness of 11900 cd m(-2), a current efficiency of 3.8 cd A(-1), a power efficiency of 2.0 lm W-1. an external quantum efficiency of 1.50 %, and quite stable color coordinates at different driving voltages, even at high luminances of over 5000 cd m(-2).

Electrochemiluminescent detection based on solid-phase extraction at tris(2,2 '-bipyridyl)ruthenium(II)-modified ceramic carbon electrode

A sensitive electrochemiluminescent detection scheme by solid-phase extraction at Ru(bpy)(3)(2+)-modified ceramic carbon electrodes (CCEs) was developed. The as-prepared Ru(bpy)(3)(2+)-modified CCEs show much better long-term stability than other Nafion-based Ru(bpy)(3)(2+)-modified electrodes and enjoy the inherent advantages of CCEs. The log-log calibration plot for dioxopromethazine is linear from 1.0 x 10(-9) to 1.0 x 10(-4) mol L-1 using the new detection scheme. The detection limit is 6.6 x 10(-10) mol L-1 at a signal-to-noise ratio of 3. The new scheme improves the sensitivity by similar to 3 orders of magnitude, which is the most sensitive Ru(bpy)(3)(2+) ECL method. The scheme allows the detection of dioxopromethazine in a urine sample within 3 min. Since Ru(bpy)(3)(2+) ECL is a powerful technique for determination of numerous amine-containing substances, the new detection scheme holds great promise in measurement of free concentrations, investigation of protein-drug interactions and DNA-drug interactions, pharmaceutical analysis, and so on.

Negative differential resistance effect in organic devices based on an anthracene derivative

The authors observed a negative differential resistance (NDR) in organic devices consisting of 9,10-bis-(9,9-diphenyl-9H-fluoren-2-yl)-anthracene (DPFA) sandwiched between Ag and indium tin oxide electrodes. The large NDR shown in current-voltage characteristics is reproducible, resulting in that the organic devices can be electrically switched between a high conductance state (on state) and a low conductance state (off state). It can be found that the currents at both on to off states are space-charge limited and attributed to the electron traps at the Ag/DPFA interface. The large and reproducible NDR makes the devices of tremendous potential in low power memory and logic circuits.

Blue light-emitting polymer with polyfluorene as the host and highly fluorescent 4-dimethylamino-1,8-naphthalimide as the dopant in the sidechain

The dopant/host concept, which is an efficient approach to enhance the electroluminescence (EL) efficiency and stability for organic light-emitting diodes (OLEDs) devices, has been applied to design efficient and stable blue light-emitting polymers. By covalently attaching 0.2 mol % highly fluorescent 4-dimethylamino-1,8-naphthalimide (DMAN) unit (photoluminescence quantum efficiency: Phi(PL)=0.84) to the pendant chain of polyfluorene, an efficient and colorfast blue light-emitting polymer with a dopant/host system and a molecular dispersion feature was developed. The single-layer device (indium tin oxide/PEDOT/polymer/Ca/Al) exhibited the maximum luminance efficiency of 6.85 cd/A and maximum power efficiency of 5.38 lm/W with the CIE coordinates of (0.15, 0.19). Moreover, no undesired long-wavelength green emission was observed in the EL spectra when the device was thermal annealed in air at 180 degrees C for 1 h before cathode deposition. These significant improvements in both efficiency and color stability are due to the charge trapping and energy transfer from polyfluorene host to highly fluorescent DMAN dopant in the molecular level.

Memory devices based on lanthanide (SM3+, EU3+, Gd3+) complexes

Memory effects in single-layer organic light-emitting devices based on Sm3+, Gd3+, and Eu3+ rare earth complexes were realized. The device structure was indium-tin-oxide (ITO)/3,4-poly(ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT)/Poly(N-vinyl carbazole) (PVK): rare earth complex/LiF/Ca/Ag. It was found experimentally that all the devices exhibited two distinctive bistable conductivity states in current-voltage characteristics by applying negative starting voltage, and more than 10(6) write-read-erase-reread cycles were achieved without degradation. Our results indicate that the rare earth organic complexes are promising materials for high-density, low-cost memory application besides the potential application as organic light-emitting materials in display devices.