Micellular fluorescence resonance energy transfer based fluorescent ratiometric response to hydrocarbon analytes.

Fluorescence resonance energy transfer (FRET) has been utilised to develop numerous selective and sensitive fluorescent ratiometric sensors. Typically, FRET-based fluorescent ratiometric sensors rely on chemical interactions between the sensor and analyte to illicit a response, thus unreactive hydrocarbons are a neglected analyte and a source for new sensors. By containing an unbound donor-acceptor system within micelles, energy transfer is enabled by spatial confinement. This offers the potential of a ratiometric response as a hydrocarbon analyte is added. Introducing a hydrocarbon analyte to this system causes micelles to swell, increasing the donor-acceptor distance and thus reducing the amount of observed energy transfer. We present InP/ZnS quantum dot donors interacting with a Nile Red acceptor, confined by cetyltrimethylammonium bromide (CTAB)-based micelles. We alleviated spatial confinement of the pair within micelles using common laboratory solvents to represent hydrocarbons, (toluene, hexane and octadecene). We constructed calibration curves for each solvent and found effective sensing ranges of 0.009-0.21, 0.008-0.27 and 0.003-0.06 M for toluene, hexane and octadecene, respectively. This study contributes towards the development of new hydrocarbon sensors utilising this new mechanism.

Tuneable emission in single molecule dyads mediated by a charge transfer state.

The demand for fluorescent organic dyes across a broad range of applications has led to investigation into tuneable emission dyes. The tuneable nature of these dyes makes them desirable for applications in a variety of fields, including organic light-emitting diodes (OLEDs), optical sensing devices, and fluorescence imaging. In recent investigations, there have only been a handful of mechanisms used to tune emission. Herein, we present four novel perylene-acene dyads that undergo solvent tuneable emission, and propose a novel mechanism for this tuneability based on the presence of a charge transfer state. These dyes were shown to reach photoluminescence quantum efficiencies (PLQEs) as high as 45%, depending on the solvent, showing the ability for this mechanism to be used to access higher PLQE tuneable emission.

Heterostructured Nanotetrapod Luminophores for Reabsorption Elimination within Luminescent Solar Concentrators.

Luminescent solar concentrators (LSCs) concentrate light via luminescence within a planar-waveguide and have potential use for building-integrated photovoltaics. However, their commercialization and potential applications are currently hindered greatly by photon reabsorption, where emitted waveguided light is parasitically reabsorbed by a luminophore. Nanotetrapod semiconductor materials have been theorized to be excellent luminophores for LSCs owing to their inherently large Stokes shifts. Here we present the first nanotetrapod-based LSCs (5 × 5 × 0.3 cm3) reported in the literature. External quantum efficiencies as high as 4.9 ± 0.5% were achieved under AM1.5G conditions. We also perform an in-depth investigation by optical characterization of the different operational metrics of our nanotetrapod-based LSCs and show reabsorption to be eliminated (mean number of average reabsorption events per photon equal to 0.00) in our most extended nanotetrapod devices.

Luminescent light diffuser for diffuse lighting applications.

The lighting industry currently accounts for a significant proportion of all energy demand. Luminescent white lighting is often impure, inefficient, expensive, and detrimentally emits as a point source, meaning the light is emitted from a focused point. A luminescent light diffuser offers the potential to create a spatially broad lighting fixture. We developed a luminescent light diffuser consisting of three commercially available luminescent dye species (rhodamine 6G, fluorescein, 7-diethylamino-4-methylcoumarin) dispersed within a polymer matrix (polyvinyl alcohol), or commercial paint, and coated on a planar waveguide. A Light-emitting diode (LED) (385 nm) is directed into the waveguide which excites the luminescent species, coating the panel, creating a device that emits spatially broad pure white light. As the emission depends on escape cone emission from the waveguide, the device's emission was found to depend highly on the coating film quality and components. We present two systems: a small 40 mm × 40 mm prototype, made using standard water-soluble polymer (polyvinyl alcohol), to study the underlying operational principles, and a 100 mm × 100 mm device with optimized efficiency fabricated with a clear commercial paint. By doping the polymer matrix with scattering silica microparticles we achieved a maximum photon outcoupling efficiency of 78%, whilst maintaining colour purity with an increased device size of more than 300 times (compared with the input LED). This work shows that it is possible to construct an inexpensive and spatially broad lighting source, whilst maintaining colour purity at a low cost.

The Rise and Future of Discrete Organic-Inorganic Hybrid Nanomaterials.

Hybrid nanomaterials (HNs), the combination of organic semiconductor ligands attached to nanocrystal semiconductor quantum dots, have applications that span a range of practical fields, including biology, chemistry, medical imaging, and optoelectronics. Specifically, HNs operate as discrete, tunable systems that can perform prompt fluorescence, energy transfer, singlet fission, upconversion, and/or thermally activated delayed fluorescence. Interest in HNs has naturally grown over the years due to their tunability and broad spectrum of applications. This Review presents a brief introduction to the components of HNs, before expanding on the characterization and applications of HNs. Finally, the future of HN applications is discussed.

Enhancing the hydrogen evolution activity of MoS2 basal planes and edges using tunable carbon-based supports.

The hydrogen adsorption free energy (ΔGHads) on the basal plane and edges of MoS2 is studied using periodic density functional theory, with the catalyst supported by a range of two-dimensional carbon-based materials. Understanding how ΔGHads can be tuned with support gives insight into MoS2 as a catalyst for the hydrogen evolution reaction. The supports studied here include graphene oxide materials, heteroatom doped (S, B, and N) graphene, and some insulator materials (hexagonal boron nitride and graphitic carbon nitride). For the basal plane of MoS2, a wide range of values for ΔGHads are observed (between 1.4 and 2.2 eV) depending on the support material used. It is found that ΔGHads relates directly to the energy of occupied p-orbital states in the MoS2 catalyst, which is modified by the support material. On the Mo-edge of MoS2, different supports induce smaller variations in ΔGHads, with values ranging between -0.27 and 0.09 eV. However, a graphene support doped with graphitic N atoms produces a ΔGHads value of exactly 0 eV, which is thermodynamically ideal for hydrogen evolution. Furthermore, ΔGHads is found to relate closely and linearly to the amount of charge transfer between MoS2 and support when they adhere together. The support-induced tuning of ΔGHads on MoS2 observed here provides a useful tool for improving current MoS2 catalysts, and the discovery of variables which mediate changes in ΔGHads contributes to the rational design of new hydrogen evolution catalysts.

Looking on the Bright Side Reduces Worry in Pregnancy: Training Interpretations in Pregnant Women.

Background: Recent evidence suggests that anxiety is more common than depression in the perinatal period, however there are few interventions available to treat perinatal anxiety. Targeting specific processes that maintain anxiety, such as worry, may be one potentially promising way to reduce anxiety in this period. Given evidence that negative interpretation bias maintains worry, we tested whether interpretation bias could be modified, and whether this in turn would lead to less negative thought (i.e., worry) intrusions, in pregnant women with high levels of worry. Method: Participants (N = 49, at least 16 weeks gestation) were randomly assigned to either an interpretation modification condition (CBM-I) which involved training in accessing positive meanings of emotionally ambiguous scenarios, or an active control condition in which the scenarios remained ambiguous and unresolved. Results: Relative to the control condition, participants in the CBM-I condition generated significantly more positive interpretations and experienced significantly less negative thought intrusions. Conclusions: Our findings indicate that worry is a modifiable risk factor during pregnancy, and that it is possible to induce a positive interpretation bias in pregnant women experiencing high levels of worry. Although preliminary, our findings speak to exciting clinical possibilities for the treatment of worry and the prevention of perinatal anxiety.

Repetitive Negative Thinking and Interpretation Bias in Pregnancy.

Background: Repetitive negative thinking (RNT; e.g., worry about the future, rumination about the past) and the tendency to interpret ambiguous information in negative ways (interpretation bias) are cognitive processes that play a maintaining role in anxiety and depression, and recent evidence has demonstrated that interpretation bias maintains RNT. In the context of perinatal mental health, RNT has received minimal research attention (despite the fact that it predicts later anxiety and depression), and interpretation bias remains unstudied (despite evidence that it maintains depression and anxiety which are common in this period). Method: We investigated the relationship between RNT, interpretation bias and psychopathology (depression, anxiety) in a pregnant sample (n = 133). We also recruited an age-matched sample of non-pregnant women (n = 104), to examine whether interpretation bias associated with RNT emerges for ambiguous stimuli regardless of its current personal relevance (i.e., pregnancy or non-pregnancy-related). Results: As predicted, for pregnant women, negative interpretation bias, RNT, depression and anxiety were all positively associated. Interpretation bias was evident to the same degree for material that was salient (pregnancy-related) and non-salient (general), and pregnant and non-pregnant women did not differ. RNT was associated with interpretation bias for all stimuli and across the full sample. Conclusion: Our findings highlight the need to further investigate the impact of interpretation bias in pregnant women, and test the effectiveness of interventions which promote positive interpretations in reducing RNT in the perinatal period.

Visuo-tactile stimulation, but not type of movement, modulates pain during the vision of a moving virtual limb.

Aim: Evidence has revealed a relationship between pain and the observation of limb movement, but it is unknown whether different types of movements have diverse modulating effects. In this immersive virtual reality study, we explored the effect of the vision of different virtual arm movements (arm vs wrist) on heat pain threshold of healthy participants. Patients & methods: 40 healthy participants underwent four conditions in virtual reality, while heat pain thresholds were measured. Visuo-tactile stimulation was used to attempt to modulate the feeling of virtual limb ownership while the participants kept their arms still. Results: Effects on pain threshold were present for type of stimulation but not type of movement. Conclusion: The type of observed movement does not appear to influence pain modulation, at least not during acute pain states.