Interfacial microstructure function in organic light-emitting diodes: Assembled tetraaryldiamine and copper phthalocyanine interlayers

A study on interfacial microstructure function in organic light emitting diodes (OLED) was performed. A spincoated, hole injecting tetraaryldiamine TPD-Si2 layer was shown to increase maximum OLED luminance and quantum efficiency. Devices with a TPD-Si2 anode adhesion layer provided a maximum luminance level of 15,000 cd m-2 in the absence of dopants or low work function cathodes. It was shown that copper phthalocyanine interlayers nucleated TPD crystallization on heating above the glass transition temperature of TPD

Realization of high-efficiency/high-luminance small-molecule organic light-emitting diodes: Synergistic effects of siloxane anode functionalization/hole-injection layers, and hole/exciton-blocking/electron-transport layers

Realization of high-efficiency/high-luminance small-molecule organic ligh-emitting diodes (OLED) was discussed. OLEDs were fabricated by combining thin, covalently-bound triarylamine hole injection/adhesion interlayers. Results showed that enhancing hole injection via covalently linked TPDSi2 injection/adhesion interlayers can be synergistically combined with BCP hole/excition-blocking interlayers to yield highly efficient small molecule OLEDs

Fabrication and Properties of Organic Light-Emitting "Nanodiode" Arrays

Fabrication of discrete, structurally regular, highly ordered, nanoscale organic light-emitting diode (OLED) arrays using a variant of nanosphere lithography is communicated. We report patterning, imaging, and the device current-voltage-luminescence characteristics of arrays of OLED nanostructures (ITO/self-assembled N(p-C6H4CH2CH2CH 2SiCl3)3-derived injection layer/1,4-bis(1-naphthylphenylamino)biphenyl/aluminum tris-(8-hydroxyquinolate) (Alq): 1% N/N′-di-isoamyl quinacridone/Al) of a length scale previously unrealized (40-90 nm/side). Minimal alteration/ degradation of device response characteristics is demonstrated for OLED size compression to nanoscale, thereby offering new possibilities for nanoscale optoelectronic devices

High-brightness blue light-emitting polymer diodes via anode modification using a self-assembled monolayer

Modification of polymer light-emitting diodes indium tin oxide (PLED ITO) anode with a silyl-functionalized triarylamine hole-transporting AM leads to two orders of magnitude enhancement in the maximum luminance and quantum efficiency for a single-layer PFO-based blue PLED device. Even compared to a device with PEDOT-PSS as the HTL, the SAM-based device exhibits ∼3 times higher maximum luminance, as well as comparable quantum and power efficiencies. While good hole-injection capacity was shown to be an important factor in the improved performance, other SAM characteristics, such as ultra-low visible absorption, lower active layer thickness, and high interfacial stability were additional attractions

Regulatory ecotoxicity testing of engineered nanoparticles: Are the results relevant to the natural environment?

Engineered nanoparticles (ENPs) will be released to the environment during use or following the disposal of ENP-containing products and concerns have been raised over the risks of ENPs to the environment. Many studies have explored the toxicity of ENPs to aquatic organisms but these studies have usually been performed with little understanding of the ENPs' behaviour in the test media and the relationship between behaviour in the media to behaviour in natural waters. This study evaluated and compared the aggregation behaviour of four model gold nanoparticle (NP) types (coated with neutral, negative, positive and amphoteric cappings) in standard ecotoxicity test media and natural waters. The effects of humic acid (HA) and test organisms on aggregation were also investigated. In standard media, positive and neutral NPs were stable, whereas amphoteric and negative NPs generally showed substantial aggregation. In natural waters, amphoteric NPs were generally found to be stable, neutral and positive NPs showed substantial aggregation while negative NPs were stable in some waters and unstable in others. HA addition stabilised the amphoteric NPs, destabilised the positive NPs and had no effect on stability of negative NPs. The presence of invertebrates generally lowered the degree of particle aggregation while macrophytes had no effect. Given the dramatically different behaviours of ENPs in various standard media and natural waters, current regulatory testing may either under- or overestimate the toxicity of nanomaterials to aquatic organisms. Therefore, there is a pressing need to employ ecotoxicity media which better represent the behaviour of ENPs in natural system. \ua9 2014 Informa UK, Ltd.Peer reviewed: YesNRC publication: Ye

Progress in high work function TCO OLED anode alternatives and OLED nanopixelation

The progress in high work function transparent conducting oxide (TCO) organic light-emitting diodes (OLED) anode alternatives and OLED nanopixelation was presented. Two complementary areas of interest in OLED science and engineering, development and application of new transparent conducting oxide (TCO) materials and OLED anodes, and effective patterning strategies for nanofabrication were addressed. Results showed that the Alq-based OLED heterostructures exhibited no apparent influence of quantum confinement or accompanying degradation of either rectification of emissive efficiency

Mechanistic insights into the effect of nanoparticles on zebrafish hatch

Aquatic organisms are susceptible to waterborne nanoparticles (NP) and there is only limited understanding of the mechanisms by which these emerging contaminants may affect biological processes. This study used silicon (nSi), cadmium selenide (nCdSe), silver (nAg) and zinc NPs (nZnO) as well as single-walled carbon nanotubes (SWCNT) to assess NP effects on zebrafish (Danio rerio) hatch. Exposure of 10 mg/L nAg and nCdSe delayed zebrafish hatch and 100 mg/L of nCdSe as well as 10 and 100 mg/L of uncoated nZnO completely inhibited hatch and the embryos died within the chorion. Both the morphology and the movement of the embryos were not affected, and it was determined that the main mechanism of hatch inhibition by NPs is likely through the interaction of NPs with the zebrafish hatching enzyme. Furthermore, it was concluded that the observed effects arose from the NPs themselves and not their dissolved metal components. \ua9 2014 Informa UK, Ltd.Peer reviewed: YesNRC publication: Ye

Cytotoxicity of surface-functionalized silicon and germanium nanoparticles: the dominant role of surface charges

Although it is frequently hypothesized that surface (like surface charge) and physical characteristics (like particle size) play important roles in cellular interactions of nanoparticles (NPs), a systematic study probing this issue is missing. Hence, a comparative cytotoxicity study, quantifying nine different cellular endpoints, was performed with a broad series of monodisperse, well characterized silicon (Si) and germanium (Ge) NPs with various surface functionalizations. Human colonic adenocarcinoma Caco-2 and rat alveolar macrophage NR8383 cells were used to clarify the toxicity of this series of NPs. The surface coatings on the NPs appeared to dominate the cytotoxicity: the cationic NPs exhibited cytotoxicity, whereas the carboxylic acid-terminated and hydrophilic PEG- or dextran-terminated NPs did not. Within the cationic Si NPs, smaller Si NPs were more toxic than bigger ones. Manganese-doped (1% Mn) Si NPs did not show any added toxicity, which favors their further development for bioimaging. Iron-doped (1% Fe) Si NPs showed some added toxicity, which may be due to the leaching of Fe3+ ions from the core. A silica coating seemed to impart toxicity, in line with the reported toxicity of silica. Intracellular mitochondria seem to be the target for the toxic NPs since a dose-, surface charge- and size-dependent imbalance of the mitochondrial membrane potential was observed. Such an imbalance led to a series of other cellular events for cationic NPs, like decreased mitochondrial membrane potential (¿¿m) and ATP production, induction of ROS generation, increased cytoplasmic Ca2+ content, production of TNF-a and enhanced caspase-3 activity. Taken together, the results explain the toxicity of Si NPs/Ge NPs largely by their surface characteristics, provide insight into the mode of action underlying the observed cytotoxicity, and give directions on synthesizing biocompatible Si and Ge NPs, as this is crucial for bioimaging and other applications in for example the field of medicine