Ligand-Directed Self-Assembly of Organic-Semiconductor/Quantum-Dot Blend Films Enables Efficient Triplet Exciton-Photon Conversion.

Blends comprising organic semiconductors and inorganic quantum dots (QDs) are relevant for many optoelectronic applications and devices. However, the individual components in organic-QD blends have a strong tendency to aggregate and phase-separate during film processing, compromising both their structural and electronic properties. Here, we demonstrate a QD surface engineering approach using electronically active, highly soluble semiconductor ligands that are matched to the organic semiconductor host material to achieve well-dispersed inorganic-organic blend films, as characterized by X-ray and neutron scattering, and electron microscopies.

Triplet transfer from PbS quantum dots to tetracene ligands: is faster always better?

Quantum dot-organic semiconductor hybrid materials are gaining increasing attention as spin mixers for applications ranging from solar harvesting to spin memories. Triplet energy transfer between the inorganic quantum dot (QD) and organic semiconductor is a key step to understand in order to develop these applications. Here we report on the triplet energy transfer from PbS QDs to four energetically and structurally similar tetracene ligands.

Singlet exciton fission in a modified acene with improved stability and high photoluminescence yield.

We report a fully efficient singlet exciton fission material with high ambient chemical stability. 10,21-Bis(triisopropylsilylethynyl)tetrabenzo[a,c,l,n]pentacene (TTBP) combines an acene core with triphenylene wings that protect the formal pentacene from chemical degradation. The electronic energy levels position singlet exciton fission to be endothermic, similar to tetracene despite the triphenylenes.

Directed Energy Transfer from Monolayer WS to Near-Infrared Emitting PbS-CdS Quantum Dots.

Heterostructures of two-dimensional (2D) transition metal dichalcogenides (TMDs) and inorganic semiconducting zero-dimensional (0D) quantum dots (QDs) offer useful charge and energy transfer pathways, which could form the basis of future optoelectronic devices. To date, most have focused on charge transfer and energy transfer from QDs to TMDs, that is, from 0D to 2D. Here, we present a study of the energy transfer process from a 2D to 0D material, specifically exploring energy transfer from monolayer tungsten disulfide (WS) to near-infrared emitting lead sulfide-cadmium sulfide (PbS-CdS) QDs.

Thiol-Anchored TIPS-Tetracene Ligands with Quantitative Triplet Energy Transfer to PbS Quantum Dots and Improved Thermal Stability.

Triplet energy transfer between inorganic quantum dots (QDs) and organic materials plays a fundamental role in many optoelectronic applications based on these nanocomposites. Attaching organic molecules to the QD as transmitter ligands has been shown to facilitate transfer both to and from QDs. Here we show that the often disregarded thiol anchoring group can achieve quantitative triplet energy transfer yields in a PbS QD system with 6,11-bis[(triisopropylsilyl)ethynyl]tetracene-2-methylthiol (TET-SH) ligands.

Direct vs Delayed Triplet Energy Transfer from Organic Semiconductors to Quantum Dots and Implications for Luminescent Harvesting of Triplet Excitons.

Hybrid inorganic-organic materials such as quantum dots (QDs) coupled with organic semiconductors have a wide range of optoelectronic applications, taking advantage of the respective materials' strengths. A key area of investigation in such systems is the transfer of triplet exciton states to and from QDs, which has potential applications in the luminescent harvesting of triplet excitons generated by singlet fission, in photocatalysis and photochemical upconversion. While the transfer of energy from QDs to the triplet state of organic semiconductors has been intensely studied in recent years, the mechanism and materials parameters controlling the reverse process, triplet transfer to QDs, have not been well investigated.

Enhancing Photoluminescence and Mobilities in WS Monolayers with Oleic Acid Ligands.

Many potential applications of monolayer transition metal dichalcogenides (TMDs) require both high photoluminescence (PL) yield and high electrical mobilities. However, the PL yield of as prepared TMD monolayers is low and believed to be limited by defect sites and uncontrolled doping. This has led to a large effort to develop chemical passivation methods to improve PL and mobilities.

Engineering Molecular Ligand Shells on Quantum Dots for Quantitative Harvesting of Triplet Excitons Generated by Singlet Fission.

Singlet fission is an exciton multiplication process in organic molecules in which a photogenerated spin-singlet exciton is rapidly and efficiently converted to two spin-triplet excitons. This process offers a mechanism to break the Shockley-Queisser limit by overcoming the thermalization losses inherent to all single-junction photovoltaics. One of the most promising methods to harness the singlet fission process is via the efficient extraction of the dark triplet excitons into quantum dots (QDs) where they can recombine radiatively, thereby converting high-energy photons to pairs of low-energy photons, which can then be captured in traditional inorganic PVs such as Si.

Photon upconversion utilizing energy beyond the band gap of crystalline silicon with a hybrid TES-ADT/PbS quantum dots system.

The recent introduction of inorganic semiconductor quantum dots (QDs) as triplet sensitizers for molecular semiconductors has led to significant interest in harvesting low energy photons, which can then be used for photon upconversion (PUC), triplet-triplet annihilation (TTA). A key goal is the harvesting of photons from below the bandgap of crystalline silicon 1.12 eV (≈1100 nm) and their upconversion into the visible region.

Excimer Formation in Carboxylic Acid-Functionalized Perylene Diimides Attached to Silicon Dioxide Nanoparticles.

The creation of artificial light-harvesting complexes involves the ordered arrangement of chromophores in space. To guarantee efficient energy-transfer processes, organic dyes must be brought into close proximity, often leading to aggregation and the formation of excimer states. In recent years, the attachment of ligand-based chromophores to nanoparticles has also generated interest in relation to improved solar harvesting and spin-dependent electronic interactions such as singlet fission and upconversion.

Singlet Fission and Triplet Transfer to PbS Quantum Dots in TIPS-Tetracene Carboxylic Acid Ligands.

Singlet exciton fission allows for the generation of two triplet excitons for each photon absorbed within an organic semiconductor. Efficient harvesting of these triplets could allow for the Shockley-Queisser limit on the power conversion efficiency of single-junction photovoltaics to be broken. Here, we show that singlet fission molecules bound directly to PbS quantum dots as ligands can undergo singlet fission with near unity efficiency and can transfer triplets sequentially into the PbS with near unity efficiency.

Convergence of Mie theory series: criteria for far-field and near-field properties.

We investigate the convergence of the series arising in Mie theory for the solution of electromagnetic scattering by a sphere. In contrast with previous studies that focused only on the scattering cross section, we here consider a wide spectrum of relevant properties, including scattering, extinction, and absorption cross sections, complex scattering amplitudes (i.e.

Troponin testing in the emergency department: a longitudinal study to assess the impact and sustainability of decision support strategies.

Aim: To evaluate the impact of decision support on the proportion of troponin I (cTnI) tests and associated costs over the period 2000-7 for patients presenting with chest pain in an emergency department (ED) setting.

Methods: A longitudinal study using linked data for patients presenting with chest pain from the ED and laboratory information systems of a metropolitan teaching hospital in Melbourne, Australia. The study period was divided into a pre-intervention period (2000-2), which contained no decision support; an initial post period (2003-4) after the introduction of a quality improvement initiative (utilising a paper-based guideline, education, audit and feedback) about cTnI test ordering and the incorporation of the guideline as a decision support feature of the computerised provider order entry system; followed by a post-modification period (2005-7) after the electronic decision support feature was modified to allow clinicians to bypass viewing the complete guideline.

Screening mammogram microcalcification due to basal cell carcinoma of the skin.

Basal cell carcinoma is the most common skin malignancy worldwide, typically presenting as a pearly or translucent papule. Histologically, approximately 21% contain areas of microcalcification. We report a case of a woman presenting with microcalcification on screening mammography that was suspicious.

Analysis of neonatal T cell and antigen presenting cell functions.

Neonates are more susceptible to infection than adults and exhibit more intense or prolonged clinical symptoms. The extent to which deficiencies in T cell or antigen presenting cell (APC) function underlie hyporesponsiveness is incompletely understood. Here, immune function of cord blood mononuclear cells (CBMC), from healthy, full-term neonates was compared with adult PBMC.

Adjuvant intraoperative photodynamic therapy in experimental colorectal cancer using a new photosensitizer.

Background: Photodynamic therapy is a promising anticancer modality. The effect of adjuvant intraoperative photodynamic therapy (AIOPDT) using photosensitizers Photofrin or mesotetra (hydroxyphenyl) chlorin (m-THPC) was evaluated in a mouse model of local recurrence of colorectal cancer.

Methods: Animals were injected with either photosensitizer 24 h before surgery.

Maternal prolactin secretion is phasic during induced term and post-term labor.

Objective: We hypothesized that regimens of labor induction do not alter the biphasic secretion of maternal prolactin (PRL) seen during spontaneous labor.

Methods: Serial blood samples drawn from 12 women before, during, and after induced labor were assayed for PRL and hCG and compared with cervical dilatation and uterine contraction frequency (UCF). Induction methods were cervical ripening with dinoprostone gel (Prepidil) followed by oxytocin infusion (n = 1), amniotomy followed by oxytocin (n = 4), oxytocin followed by amniotomy (n = 3), amniotomy only (n = 2), and oxytocin only (n = 2).

Phasic maternal prolactin secretion during spontaneous labor is associated with cervical dilatation and second-stage uterine activity.

Objective: In this study, we attempted to determine the physiologic roles of prolactin (PRL) and hCG during labor.

Methods: Serial blood samples were collected from 19 women (15 multiparous and four nulliparous) before, during, and after labor; assayed for PRL and hCG; and compared with cervical dilatation and uterine contraction frequency.

Results: Prolactin levels decreased in association with progressive cervical dilatation during the first stage of labor and reached a nadir at full dilatation.

Photodynamic therapy for malignant tumours of the ampulla of Vater.

Ten patients with ampullary carcinoma, not suitable for surgery, were treated with endoscopic photodynamic therapy (PDT) to evaluate the feasibility and safety of treatment. Patients received 4 mg kg-1 of haematoporphyrin derivative intravenously. Two days later, a duodenoscopy was performed and red (630 nm) light delivered to the tumour at fixed energy densities of 50 J or 200 J cm-1 per application, depending on the type of optical fibre used.

Adjuvant intraoperative photodynamic therapy in experimental colorectal cancer.

A reliable animal model for quantitative assessment of local recurrence of colorectal cancer was developed using colo26 tumour in BALB/c mice. The effect of adjuvant intraoperative photodynamic therapy to potentially curative surgery on local recurrence was examined in four study and four control groups. Study groups received 15 mg kg-1 Photofrin (a photosensitizing drug) 24 h before surgery.

Adjuvant intraoperative photodynamic therapy for colorectal carcinoma: a clinical study.

The local recurrence rate of colorectal carcinoma after surgery is unacceptable in most series, and adjuvant therapies have made only a small impact on this. There is experimental evidence that adjuvant intraoperative photodynamic therapy (AIOPDT) may be effective. AIOPDT involves systematically photosensitizing the patient preoperatively with a drug (HpD) which relatively localizes to tumour and is activated using visible light.

Hyperviscosity syndrome in disseminated breast adenocarcinoma.

Circulation within the bloodstream of mucin derived from mucin-producing adenocarcinomas has been documented infrequently but has been associated with vascular occlusion, organ infarction, and hyperviscosity. The nature of the mucin and the therapeutic role of plasmapheresis in this condition has not been reported. A 64-yr-old female, who had undergone a mastectomy 3 yrs previously for an infiltrating mucinous breast adenocarcinoma, presented with dementia.