► An introduction to the function & classes of organic light-emitting diodes (OLEDs). ► A detailed description of the main physical processes occurring in OLEDs. ► Focus on OLEDs prepared using ...platinum(II) complexes as dopant phosphors. ► The combination of mono- and bi-molecular excited states to generate white light. ► Examples of OLEDs using cyclometallated complexes of dipyridylbenzene ligands.
This article provides an overview of molecular optoelectronic systems – particularly organic light emitting devices (OLEDs) – that make use of platinum(II) complexes as their emissive components. A comprehensive introduction to the function and classes of OLEDs in general is first provided. The diverse range of parameters that are used to quantify OLED performance can be bewildering, particularly to the chemist, and we set out the relationship between the key parameters, and provide a detailed description of the main physical processes that determine them. We then focus on OLEDs prepared using platinum(II) complexes as dopants. Pertinent recent developments in the chemistry of luminescent Pt(II) complexes containing cyclometallating bidentate and terdentate ligands are presented. Some of these complexes possess outstanding features from the point of view of their electronic structure, photophysical behaviour, processability, and environmental stability. An appreciation of the nature of their molecular excited states has facilitated understanding of the fundamental electronic processes at work within devices, and has led to the fabrication of high-performance OLEDs. In addition to single-colour and white light systems, some of them offer unusual characteristics and applications, such as plant growth OLED (PGOLED) or electro-photoluminescent (EL-PL) switches. Such devices fulfil the requirements to become an important part of ‘Green Photonics’.
Electronic circular dichroism and circularly polarized luminescence acid/base switching activity has been demonstrated in helicene‐bipyridine proligand 1 a and in its “rollover” cycloplatinated ...derivative 2 a. Whereas proligand 1 a displays a strong bathochromic shift (>160 nm) of the nonpolarized and circularly polarized luminescence upon protonation, complex 2 a displays slightly stronger emission. This strikingly different behavior between singlet emission in the organic helicene and triplet emission in the organometallic derivative has been rationalized by using quantum‐chemical calculations. The very large bathochromic shift of the emission observed upon protonation of azahelicene‐bipyridine 1 a has been attributed to the decrease in aromaticity (promoting a charge‐transfer‐type transition rather than a π–π* transition) as well as an increase in the HOMO–LUMO character of the transition and stabilization of the LUMO level upon protonation.
Rollover platination: A 6helicene‐bipyridine derivative has been used as a proligand for “rollover” cycloplatination and for the conception of acid/base chiroptical switches. Protonation triggers a change in the nature of the HOMO–LUMO transition, from a π–π* to a charge‐transfer transition, and significantly modifies the circularly polarized luminescence and electronic circular dichroism spectra of the organic and organometallic helicenes (see figure).
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•A triaxial electrospinning characterized by a new detachable tri-layer spinneret.•A blank cellulose acetate layer was precisely coated on medicated nanocomposites.•A tunable ...sustained release profile of a poorly water-soluble drug.•A clear process-structure-performance relationship was disclosed.
In this study, novel core-shell nanostructures were fabricated through a modified triaxial electrospinning process. These comprised a drug-protein nanocomposite coated with a thin cellulose acetate (CA) shell. They were generated through the simultaneous treatment of an outer solvent, an unelectrospinnable middle fluid, and an electrospinnable core solution in triaxial electrospinning. SEM and TEM results revealed that the core-shell nanofibers had linear and cylindrical morphologies with a diameter from 0.66 to 0.87 μm, and distinct core-shell structures with a shell thickness from 1.8 to 11.6 nm. The presence of a CA coating eliminated the initial burst release of ibuprofen seen from a monolithic drug-protein composite, and allowed us to precisely manipulate the drug release (for a 90% percentage) over a time period from 23.5 to 43.9 h in a tunable manner. Mathematical relationships between the processing conditions, the nanostructures produced, and their functional performance were elucidated.
Critical theorists have speculated for years about the emergence of
a new form of capitalist accumulation, while lacking terms for it.
This book gives language and scope to our new politico-economic
...conjuncture.Working from lived conditions in Latin America, this
monograph powerfully demonstrates the need not for a new politics,
but for a different relation to existence.Shows such social
phenomena as drug smuggling, mass migration to be not merely
"policy problems" but as deep, philosophical conundra that demand
another way of thinking and acting.
This book makes a case for infrapolitics as an
enactment of intellectual responsibility in the face of a
tumultuous world of war and of technological value extraction on a
planetary scale. Infrapolitical Passages proposes
to clear a way through some of the dominant political
determinations and violent symptoms of contemporary globalization.
In doing so, Gareth Williams makes a case for
infrapolitics as an enactment of intellectual
responsibility in the face of a tumultuous world of war and of
technological value extraction on a planetary scale. The book
offers a theory of globalization as a gigantic, directionless
crisis in humanity's symbolic organization, as well as a theory of
global economic warfare as the very positing of directionlessness
and, at the same time, facticity. Williams's infrapolitics stands
at a distance from the biopolitical, which it understands as
domination presenting itself as the production of specific forms of
subjectivity in the face of the commodity. The subsequent obscuring
of being signals the need to circumvent the instrumentalization of
life as subordination to the metaphysics of subjectivity,
representation, and politics. Infrapolitical Passages
works to confront that which is unavailable in subjectivity and
representation, opening a way for facticity in the age of
globalization in order to make room for the infrapolitical question
for existence.
This book is centered on the Venetian humanist Pietro Bembo (1470–1547), on his stay in Sicily in 1492–4 to study the ancient Greek language under the Byzantine émigré Constantine Lascaris, and above ...all on his ascent of Mount Etna in 1493. The more particular focus of this study is on the imaginative capacities that crucially shape Bembo’s elegantly crafted account, in Latin, of his Etna adventure in his so-called De Aetna, published at the Aldine Press in Venice in 1496. This work is cast in the form of a dialogue that takes place between the young Bembo and his father, Bernardo (himself a prominent Venetian statesman with strong humanist involvements), after Pietro’s return to Venice from Sicily in 1494. But De Aetna offers much more than a one-dimensional account of the facts, sights, and findings of Pietro’s climb. Three mutually informing features that are critical to the artistic originality of De Aetna receive detailed treatment in this study: (i) the stimulus that Pietro drew from the complex history of Mount Etna as treated in the Greco-Roman literary tradition from Pindar onward; (ii) the striking novelty of De Aetna’s status as the first Latin text produced at the nascent Aldine Press in the prototype of what modern typography knows as Bembo typeface; and (iii) Pietro’s ingenious deployment of Etna as a powerful, multivalent symbol that simultaneously reflects the diverse characterizations of, and the generational differences between, father and son in the course of their dialogical exchanges within De Aetna.
Microbial infections present a major global healthcare challenge, in large part because of the development of microbial resistance to the currently approved antimicrobial drugs. This demands the ...development of new antimicrobial agents. Metal oxide nanoparticles (MONPs) are a class of materials that have been widely explored for diagnostic and therapeutic purposes. They are reported to have wide‐ranging antimicrobial activities and to be potent against bacteria, viruses, and protozoans. The use of MONPs reduces the possibility of resistance developing because they have multiple mechanisms of action (including via reactive oxygen species generation), simultaneously attacking many sites in the microorganism. However, despite this there are to date no MONPs clinically approved for antimicrobial therapy. This review explores the recent literature in this area, discusses the mechanisms of MONP action against microorganisms, and considers the barriers faced to the use of MONPs in humans. These include biological challenges, of which the potential for an immune response and off‐target toxicity are key. We explore in detail the possible benefits/disbenefits of an immune response being initiated, and consider the effect of production method (chemical vs. green synthesis) on cytotoxicity. There are also a number of technical and manufacturing challenges hindering MONP translation to the clinic which are additionally discussed in depth. In the short term, there are potentially some “quick wins” from the repurposing of already‐approved nanoparticle‐based medicines for anti‐infective applications, but a number of hurdles, both technical and biological, lie in the path to long‐term clinical translation of new MONP‐based formulations.
This article is categorized under:
Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease
Therapeutic Approaches and Drug Discovery > Emerging Technologies
Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials
Metal oxide nanoparticles have efficient antimicrobial activity but there are many biological challenges restricting their application in man, as well as hurdles to scaled‐up manufacture for the clinic.
The incorporation of a rhenium atom within an extended helical π-conjugated bi-pyridine system impacts the chiroptical and photophysical properties of the resulting neutral or cationic complexes, ...leading to the first examples of rhenium-based phosphors that exhibit circularly polarized luminescence.
Coral bleaching is the detrimental expulsion of algal symbionts from their cnidarian hosts, and predominantly occurs when corals are exposed to thermal stress. The incidence and severity of bleaching ...is often spatially heterogeneous within reef-scales (<1 km), and is therefore not predictable using conventional remote sensing products. Here, we systematically assess the relationship between in situ measurements of 20 environmental variables, along with seven remotely sensed SST thermal stress metrics, and 81 observed bleaching events at coral reef locations spanning five major reef regions globally. We find that high-frequency temperature variability (i.e., daily temperature range) was the most influential factor in predicting bleaching prevalence and had a mitigating effect, such that a 1 °C increase in daily temperature range would reduce the odds of more severe bleaching by a factor of 33. Our findings suggest that reefs with greater high-frequency temperature variability may represent particularly important opportunities to conserve coral ecosystems against the major threat posed by warming ocean temperatures.
Poly(methyl methacrylate) (PMMA) bone cement has been widely used in orthopedic surgeries including total hip/knee replacement, vertebral compression fracture treatment, and bone defect filling. ...However, aseptic loosening of the interface between PMMA bone cement and bone often leads to failure. Hence, the development of modified PMMA that facilitates the growth of bone into the modified PMMA bone cement is key to reducing the incidence of aseptic loosening. In this study, MgAl-layered double hydroxide (LDH) microsheets modified PMMA (PMMA&LDH) bone cement with superior osseointegration performance has been synthesized. The maximum polymerization reaction temperature of PMMA&LDH decreased by 7.0 and 11.8 °C, respectively, compared with that of PMMA and PMMA&COL-I (mineralized collagen I modified PMMA). The mechanical performance of PMMA&LDH decreased slightly in comparison with PMMA, which is beneficial to alleviate stress-shielding osteolysis, and indirectly promote osseointegration. The superior osteogenic ability of PMMA&LDH has been demonstrated in vivo, which boosts bone growth by 2.17- and 18.34-fold increments compared to the PMMA&COL-I and PMMA groups at 2 months, postoperatively. Moreover, transcriptome sequencing revealed four key osteogenic pathways: p38 MAPK, ERK/MAPK, FGF, and TGF-β, which were further confirmed by IPA, qPCR, and Western blot assays. Hence, LDH-modified PMMA bone cement is a promising biomaterial to enhance bone growth with potential applications in relevant orthopedic surgeries.
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