Characterization of a DC-driven microplasma between a capillary tube and water surface

A microplasma generated between a stainless-steel capillary and water surface in ambient air with flowing argon as working gas appears as a bright spot at the tube orifice and expands to form a larger footprint on the water surface, and the dimensions of the bell-shaped microplasma are all below 1 mm. The electron density of the microplasma is estimated to be ranging from 5.32 × 109 cm−3 to 2.02 × 1014 cm−3 for the different operating conditions, which is desirable for generating abundant amounts of reactive species. A computational technique is adopted to fit the experimental emission from the N2 second positive system with simulation results. It is concluded that the vibrational temperature (more than 2000 K) is more than twice the gas temperature (more than 800 K), which indicates the non-equilibrium state of the microplasma. Both temperatures showed dependence on the discharge parameters (i.e., gas flow and discharge current). Such a plasma device could be arranged in arrays for applications utilizing plasmainduced liquid chemistry.

Self-organized ZnO nanodot arrays : effective control using SiNx interlayers and low-temperature plasmas

An advanced inductively coupled plasma (ICP)-assisted rf magnetron sputtering deposition method is developed to synthesize regular arrays of pear-shaped ZnO nanodots on a thin SiNx buffer layer pre-deposited onto a silicon substrate. It is shown that the growth of ZnO nanodots obey the cubic root-law behavior. It is also shown that the synthesized ZnO nanodots are highly-uniform, controllable by the experimental parameters, and also feature good structural and photoluminescent properties. These results suggest that this custom-designed ICP-based technique is very effective and highly-promising for the synthesis of property- and size-controllable highly-uniform ZnO nanodots suitable for next-generation light emitting diodes, energy storage, UV nanolasers, and other applications.

Design research for the real world : a design-led innovation model for action research

The aim of this paper is to aid researchers in undertaking action research within industry with a particular focus on the study of design-led innovation. This paper presents the research design of a case study shaped to solve real world problems concerning a major Australian Airport Corporation by bridging the chasm between academia and industry. The researcher’s role is one of design-innovation catalyst, facilitating the integration of design as a new strategic capability and innovation approach within an organisation’s fabric. A discussion of the researcher experience within industry will provide evidence on the challenges facing such a research role, with strategies for overcoming these barriers presented. Based on the authors’ experience as a researcher within industry and reflection within practice, a project progression model for action research is presented to enable the improved management of industry based research.

Electron tomography reveals the steps in filovirus budding

The filoviruses, Marburg and Ebola, are non-segmented negative-strand RNA viruses causing severe hemorrhagic fever with high mortality rates in humans and nonhuman primates. The sequence of events that leads to release of filovirus particles from cells is poorly understood. Two contrasting mechanisms have been proposed, one proceeding via a "submarine-like" budding with the helical nucleocapsid emerging parallel to the plasma membrane, and the other via perpendicular "rocketlike" protrusion. Here we have infected cells with Marburg virus under BSL-4 containment conditions, and reconstructed the sequence of steps in the budding process in three dimensions using electron tomography of plastic-embedded cells. We find that highly infectious filamentous particles are released at early stages in infection. Budding proceeds via lateral association of intracellular nucleocapsid along its whole length with the plasma membrane, followed by rapid envelopment initiated at one end of the nucleocapsid, leading to a protruding intermediate. Scission results in local membrane instability at the rear of the virus. After prolonged infection, increased vesiculation of the plasma membrane correlates with changes in shape and infectivity of released viruses. Our observations demonstrate a cellular determinant of virus shape. They reconcile the contrasting models of filovirus budding and allow us to describe the sequence of events taking place during budding and release of Marburg virus. We propose that this represents a general sequence of events also followed by other filamentous and rod-shaped viruses.

High mobility top-gate and dual-gate polymer thin-film transistors based on diketopyrrolopyrrole-naphthalene copolymer

In this letter, the performance characteristics of top-gate and dual-gate thin-film transistors (TFTs) with active semiconductor layers consisting of diketopyrrolopyrrole-naphthalene copolymer are described. Optimized top-gate TFTs possess mobilities of up to 1 cm 2 /V s with low contact resistance and reduced hysteresis in air. Dual-gate devices possess higher drive currents as well as improved subthreshold and above threshold characteristics compared to single-gate devices. We also describe the reasons that dual-gate devices result in improved performance. The good stability of this polymer combined with their promising electrical properties make this material a very promising semiconductor for printable electronics.

Characteristics of high-performance ambipolar organic field-effect transistors based on a diketopyrrolopyrrole-benzothiadiazole copolymer

In this paper, we report the device characteristics of ambipolar thin-film transistors (TFTs) based on a diketopyrrolopyrrole-benzothiadiazole copolymer. This polymer semiconductor exhibits the largest comparable electron and hole mobility values in a single organic semiconductor. The key to realizing such high mobility values, which are $0.5&cm}{2}/\hbox{V}̇\hbox{s, is molecular design, i.e., the use of suitable surface treatments of the source/drain contact electrodes and device architectures, particularly top-gate configurations. The subthreshold characteristics of the TFT devices are greatly improved by the use of dual-gate device geometry. We also report the first measurement of the velocity distribution of electron and hole velocities in an ambipolar organic semiconductor.

3,6-Di(furan-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione and bithiophene copolymer with rather disordered chain orientation showing high mobility in organic thin film transistors

Pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione or diketopyrrolopyrrole (DPP) is a useful electron-withdrawing fused aromatic moiety for the preparation of donor-acceptor polymers as active semiconductors for organic electronics. This study uses a DPP-furan-containing building block, 3,6-di(furan-2-yl)pyrrolo[3,4- c]pyrrole-1,4(2H,5H)-dione (DBF), to couple with a 2,2′-bithiophene unit, forming a new donor-acceptor copolymer, PDBFBT. Compared to its structural analogue, 3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DBT), DBF is found to cause blue shifts of the absorption spectra both in solution and in thin films and a slight reduction of the highest occupied molecular orbital (HOMO) energy level of the resulting PDBFBT. Despite the fact that its thin films are less crystalline and have a rather disordered chain orientation in the crystalline domains, PDBFBT shows very high hole mobility up to 1.54 cm 2 V-1 s-1 in bottom-gate, top-contact organic thin film transistors.

Excited-state dynamics in diketopyrrolopyrrole-based copolymer for organic photovoltaics investigated by transient optical spectroscopy

We investigate the photoexcited state dynamics in a donor-acceptor copolymer, poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]- pyrrole-1,4-dione-alt-naphthalene} (pDPP-TNT), by picosecond fluorescence and femtosecond transient absorption spectroscopies. Timeresolved fluorescence lifetime measurements of pDPP-TNT thin films reveal that the lifetime of the singlet excited state is 185 ± 5 ps and that singlet-singlet annihilation occurs at excitation photon densities above 6 × 1017 photons/cm3. From the results of singlet-singlet annihilation analysis, we estimate that the single-singlet annihilation rate constant is (6.0 ± 0.2) × 109cm3 s-1 and the singlet diffusion length is -7 nm. From the comparison of femtosecond transient absorption measurements and picosecond fluorescence measurements, it is found that the time profile of the photobleaching signal in the charge-transfer (CT) absorption band coincides with that of the fluorescence intensity and there is no indication of long-lived species, which clearly suggests that charged species, such as polaron pairs and triplet excitons, are not effectively photogenerated in the neat pDPP-TNT polymer.

A study of diphenylfumaronitrile and furan-substituted diketopyrrolopyrrole alternating copolymer and its thin-film transistors

A fused aromatic furan-substituted diketopyrrolopyrrole and novel diphenylfumaronitrile conjugated building blocks are used for the synthesis of an alternating copolymer (DPFN-DPPF) via Suzuki polycondensation. In this paper, the first attempt to use the diphenylfumaronitrile building block for the synthesis of conjugated polymer is described. The number-average and weight-average molecular weights calculated for DPFN-DPPF are 20?661 and 66?346 g mol-1, respectively. The optical bandgap calculated for DPFN-DPPF is 1.53 eV whereas the highest occupied molecular orbital (HOMO) value calculated by photoelectron spectroscopy in air (PESA) is 5.50 eV. The calculated HOMO value is lower, which is suitable for stable organic electronic devices. DPFN-DPPF polymer is used as an active layer in bottom-contact bottom-gate organic thin-film transistor devices and the thin film exhibits a hole mobility of 0.20 cm2 V-1 s-1 in air.

Thiophene-benzothiadiazole-thiophene (D-A-D) based polymers : Effect of donor/acceptor moieties adjacent to D-A-D segment on photophysical and photovoltaic properties

New push-pull copolymers based on thiophene (donor) and benzothiadiazole (acceptor) units, poly[4,7-bis(3-dodecylthiophene-2-yl) benzothiadiazole-co- thiophene] (PT3B1) and poly[4,7-bis(3-dodecylthiophene-2-yl) benzothiadiazole-co-benzothiadiazole] (PT2B2), are designed and synthesized via Stille and Suzuki coupling routes respectively. Gel permeation chromatography shows the number average molecular weights are 31100 and 8400 g mol-1 for the two polymers, respectively. Both polymers have shown absorption throughout a wide range of the UV-vis region, from 300 to 650 nm. A significant red shift of the absorption edge is observed in thin films compared to solution of the copolymers; the optical band gap is in the range of 1.7 to 1.8 eV. Cyclic voltammetry indicates reversible oxidation and reduction processes with HOMO energy levels calculated to be in the range of 5.2 to 5.4 eV. Upon testing both materials for organic field-effect transistors (OFETs), PT3B1 showed a hole mobility of 6.1 × 10-4 cm2 V-1 s -1, while PT2B2 did not show any field effect transport. Both copolymers displayed a photovoltaic response when combined with a methanofullerene as an electron acceptor. The best performance was achieved when the copolymer PT3B1 was blended with [70]PCBM in a 1:4 ratio, exhibiting a short-circuit current of 7.27 mA cm-2, an open circuit voltage of 0.85 V, and a fill factor of 41% yielding a power conversion efficiency of 2.54% under simulated air mass (AM) 1.5 global (1.5 G) illumination conditions (100 mW cm-2). Similar devices utilizing PT2B2 in place of PT3B1 demonstrated reduced performance with a short-circuit current of 4.8 mA cm -2, an open circuit voltage of 0.73 V, and a fill factor of 30% resulting in a power conversion efficiency of roughly 1.06%.

Furan substituted diketopyrrolopyrrole and thienylenevinylene based low band gap copolymer for high mobility organic thin film transistors

A novel solution processable donor-acceptor (D-A) based low band gap polymer semiconductor poly{3,6-difuran-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4- c]pyrrole-1,4-dione-alt-thienylenevinylene} (PDPPF-TVT), was designed and synthesized by a Pd-catalyzed Stille coupling route. An electron deficient furan based diketopyrrolopyrrole (DPP) block and electron rich thienylenevinylene (TVT) donor moiety were attached alternately in the polymer backbone. The polymer exhibited good solubility, film forming ability and thermal stability. The polymer exhibits wide absorption bands from 400 nm to 950 nm (UV-vis-NIR region) with absorption maximum centered at 782 nm in thin film. The optical band gap (Eoptg) calculated from the polymer film absorption onset is around 1.37 eV. The π-energy band level (ionization potential) calculated by photoelectron spectroscopy in air (PESA) for PDPPF-TVT is around 5.22 eV. AFM and TEM analyses of the polymer reveal nodular terrace morphology with optimized crystallinity after 200 °C thermal annealing. This polymer exhibits p-channel charge transport characteristics when used as the active semiconductor in organic thin-film transistor (OTFT) devices. The highest hole mobility of 0.13 cm 2 V -1 s -1 is achieved in bottom gate and top-contact OTFT devices with on/off ratios in the range of 10 6-10 7. This work reveals that the replacement of thiophene by furan in DPP copolymers exhibits such a high mobility, which makes DPP furan a promising block for making a wide range of promising polymer semiconductors for broad applications in organic electronics.

Solid-state assemblies and optical properties of conjugated oligomers combining fluorene and thiophene units

Two conjugated oligomers, representing elementary segments of fluorene-thiophene copolymers, are compared in terms of the microscopic morphology and the optical properties of thin deposits. The atomic force microscopy morphological data and the solid-state absorption and emission spectra are interpreted in terms of the assembly of the conjugated molecules. The compound with a terthiophene central unit and fluorene end-groups shows well-defined monolayer-by-monolayer assembly into micrometer-long stripe-like structures, with a crystalline herringbone-type organization within the monolayers. Polarized confocal microscopy indicates a strong orientation of the crystalline domains within the stripes. In contrast, the compound with a terfluorene central unit and thiophene end groups forms no textured aggregates and the optical spectra in the solid-state are very similar to those recorded in solution, suggesting that the molecules interact only weakly in the solid. The difference in behaviour between the two compounds most probably originates from their different capability to form densely-packed assemblies of interacting π-systems.

Nanoscale phase domain structure and associated device performance of organic solar cells based on a diketopyrrolopyrrole polymer

We investigate the blend morphology and performance of bulk heterojunction organic photovoltaic devices comprising the donor polymer, pDPP-TNT (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1, 4-dione-alt-naphthalene}) and the fullerene acceptor, [70]PCBM ([6,6]-phenyl C71-butyric acid methyl ester). The blend morphology is heavily dependent upon the solvent system used in the fabrication of thin films. Thin films spin-coated from chloroform possess a cobblestone-like morphology, consisting of thick, round-shaped [70]PCBM-rich mounds separated by thin polymer-rich valleys. The size of the [70]PCBM domains is found to depend on the overall film thickness. Thin films spin-coated from a chloroform:dichlorobenzene mixed solvent system are smooth and consist of a network of pDPP-TNT nanofibers embedded in a [70]PCBM-rich matrix. Rinsing the films in hexane selectively removes [70]PCBM and allows for analysis of domain size and purity. It also provides a means for investigating exciton dissociation efficiency through relative photoluminescence yield measurements. Devices fabricated from chloroform solutions show much poorer performance than the devices fabricated from the mixed solvent system; this disparity in performance is seen to be more pronounced with increasing film thickness. The primary cause for the improved performance of devices fabricated from mixed solvents is attributed to the greater donor-acceptor interfacial area and resulting greater capacity for charge carrier generation.

Centrobin regulates the assembly of functional mitotic spindles

The proper function of the spindle is crucial to the high fidelity of chromosome segregation and is indispensable for tumor suppression in humans. Centrobin is a recently identified centrosomal protein that has a role in stabilizing the microtubule structure. Here we functionally characterize the defects in centrosome integrity and spindle assembly in Centrobin-depleted cells. Centrobin-depleted cells show a range of spindle abnormalities including unfocused poles that are not associated with centrosomes, S-shaped spindles and mini spindles. These cells undergo mitotic arrest and subsequently often die by apoptosis, as determined by live cell imaging. Co-depletion of Mad2 relieves the mitotic arrest, indicating that cells arrest due to a failure to silence the spindle checkpoint in metaphase. Consistent with this, Centrobin-depleted metaphase cells stained positive for BubR1 and BubR1 S676. Staining with a panel of centrosome markers showed a loss of centrosome anchoring to the mitotic spindle. Furthermore, these cells show less cold-stable microtubules and a shorter distance between kinetochore pairs. These results show a requirement of Centrobin in maintaining centrosome integrity, which in turn promotes anchoring of mitotic spindle to the centrosomes. Furthermore, this anchoring is required for the stability of microtubule–kinetochore attachments and biogenesis of tension-ridden and properly functioning mitotic spindle.

Facebook Versus Ghaddafi : social networking as a tool for democratic change in Libya

The emergence of the Internet is one of the most significant leaps in the history of humanity. Information, knowledge and culture are exchanged among masses of people through interconnected information platforms. These platforms enable our culture to be analysed and rewritten, and fundamentally opens our perceptions to a wide variety of concepts and beliefs. The connected networks of the Internet have shaped a virtual — but communicative — space where people can cross borders freely within a realm characterised by the ability to go anywhere, see anything, learn, compare and understand. This chapter focuses on the Libyan experience with social networking platforms in actualising democratic change in the uprising of 17 February 2011. After briefly outlining the political and economic situation under the regime of Colonel Mummar Ghaddafi, the chapter discusses the role that social networking platforms played during the struggle of the Libyan people for democratic change. Finally, it points out the positive changes that resulted from the uprising and the potential role that social media might play in the ongoing democratization and development of Libyan society.