Graphene modified indium tin oxide electrodes for organic solar cells

In this thesis, we explore the use of graphene incorporated onto indium tin oxide (G/ITO) as a structural template to modify the orientation of copper phthalocyanine (CuPc) molecules for organic photovoltaic (OPV) device applications. We also investigate the effectiveness of 2,3,5,65 tetrafluoro57,7,8,85tetracyanoquinodimethane (F45TCNQ) as a work function modifier for G/ITO without compromising the templating properties of graphene. Photoemission spectroscopy (PES) is employed to assess the electronic properties at the anode5CuPc interface, while X5ray diffraction (XRD) and near5edge X5ray absorption fine structure (NEXAFS) are used to determine the molecular orientation of CuPc. OPV devices are fabricated to attempt to correlate the observations at the microscopic level with the macroscopic device performance. First, we investigate the electronic properties of CuPc deposited on G/ITO and ITO using PES. While the interaction between CuPc molecules and ITO and G/ITO is similar, the hole injection barrier (HIB) is ~0.9 eV for CuPc/G/ITO as compared to 0.5 eV for CuPc/ITO. Therefore, further modification of G/ITO to reduce the HIB is required. The XRD spectrum of CuPc molecules deposited onto graphene grown on copper foil (G/Cu) verifies that graphene is an effective structural template, causing CuPc molecules to ‘lie’ on the substrate. NEXAFS data shows that the orientation of CuPc molecules changes from ‘standing’ on ITO to ‘tilted’ on G/ITO. Next, the effectiveness of F45TCNQ deposited on ITO and G/ITO as a work function modifier is assessed. A thin layer of F45TCNQ is able to increase the substrate work function to ~5 eV, which is close to the ionization potential of CuPc molecules. This suggests that barrierless extraction of holes from CuPc into F45TCNQ modified ITO or G/ITO may be possible. F45TCNQ molecules are found to be predominantly tilted on G/ITO, suggesting that the templating property of graphene may be propagated through F45TCNQ molecules. CuPc molecules deposited onto F45 TCNQ/G/ITO attain a ‘lying’ configuration, confirming that the templating property of graphene is preserved despite the inclusion of a layer of F45TCNQ. The HIB is dramatically reduced to ~0.2 eV for CuPc/F45TCNQ/G/ITO, and ~0.1 eV for CuPc/F45TCNQ/ITO. Optical absorption of templated CuPc molecules over the visible range is enhanced by over 40% as compared to the non5templated molecules. Therefore, the structure of F45TCNQ/G/ITO appears to be a potential anode design to improve OPV device performance. Our test cells however do not show an improvement in OPV parameters due to the poor quality of transferred graphene, and the high series resistance in our unoptimized OPV device. Finally, the diffusion of F45TCNQ through a CuPc film is studied using time5of5flight secondary ion mass spectrometry (TOF5SIMS). The F5 depth profiles establish that a higher quantity of F45 TCNQ molecules diffuse into CuPc on the G/ITO sample. This is attributed to the weaker interfacial adhesion between F45TCNQ and graphene, and the crystallinity of the templated CuPc film. The quantity of diffused F45TCNQ in the G/ITO sample is only about 0.2 mol%. At this dopant concentration, the conductivity of the film should increase; thus doping of the whole organic film may be favourable for OPV devices.Open Acces

Roles of mechanistic target of rapamycin and transforming growth factor-B signaling in the molting gland (Y-organ) of the blackback land crab, Gecarcinus lateralis

Molting in decapod crustaceans is controlled by molt-inhibiting hormone (MIH), an eyestalk neuropeptide that suppresses production of ecdysteroids by a pair of molting glands (Y-organs or YOs). Eyestalk ablation (ESA) activates the YOs, which hypertrophy and increase ecdysteroid secretion. At mid premolt, which occurs 7–14 days post-ESA, the YO transitions to the committed state; hemolymph ecdysteroid titers increase further and the animal reaches ecdysis ~ 3 weeks post-ESA. Two conserved signaling pathways, mechanistic target of rapamycin (mTOR) and transforming growth factor-β (TGF-β), are expressed in the Gecarcinus lateralis YO. Rapamycin, an mTOR antagonist, inhibits YO ecdysteroidogenesis in vitro. In this study, rapamycin lowered hemolymph ecdysteroid titer in ESA G. lateralis in vivo; levels were significantly lower than in control animals at all intervals (1–14 days post-ESA). Injection of SB431542, an activin TGF-β receptor antagonist, lowered hemolymph ecdysteroid titers 7 and 14 days post-ESA, but had no effect on ecdysteroid titers at 1 and 3 days post-ESA. mRNA levels of mTOR signaling genes Gl-mTOR, Gl-Akt, and Gl-S6k were increased by 3 days post-ESA; the increases in Gl-mTOR and Gl-Akt mRNA levels were blocked by SB431542. Gl-elongation factor 2 and Gl-Rheb mRNA levels were not affected by ESA, but SB431542 lowered mRNA levels at Days 3 and 7 post-ESA. The mRNA level of an activin TGF-β peptide, Gl-myostatin-like factor (Mstn), increased 5.5-fold from 0 to 3 days post-ESA, followed by a 50-fold decrease from 3 to 7 days post-ESA. These data suggest that (1) YO activation involves an up regulation of the mTOR signaling pathway; (2) mTOR is required for YO commitment; and (3) a Mstn-like factor mediates the transition of the YO from the activated to the committed state

Different Hearth, Different Worth: Sustaining an Emerging Festival in the New Cultural City of Singapore

This study examines some challenges and draws lessons for a new cultural city promoting an emerging festival. This was done by considering the valuation of the festival and its determinants by foreign tourists, domestic tourists, and potential attenders (a group often ignored in the literature). For a young festival, it was encouraging to find that the festival's social value to tourists, local attenders, and potential attenders exceeded the entry fee. Overall, the Biennale was more popular with younger people, and local attenders appreciated the educational dimension of the event. This augurs well for the future of this festival. However, for the festival's sustainability, it is important to strike a balance between catering to preferences of international and local attenders as well as avoid trying to achieve multiple objectives that may lead to a dilution in the focus and identity of the new festival

Selinexor, a novel selective inhibitor of nuclear export, reduces SARS-CoV-2 infection and protects the respiratory system in vivo

The novel coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the recent global pandemic. The nuclear export protein (XPO1) has a direct role in the export of SARS-CoV proteins including ORF3b, ORF9b, and nucleocapsid. Inhibition of XPO1 induces anti-inflammatory, anti-viral, and antioxidant pathways. Selinexor is an FDA-approved XPO1 inhibitor. Through bioinformatics analysis, we predicted nuclear export sequences in the ACE-2 protein and confirmed by in vitro testing that inhibition of XPO1 with selinexor induces nuclear localization of ACE-2. Administration of selinexor inhibited viral infection prophylactically as well as therapeutically in vitro. In a ferret model of COVID-19, selinexor treatment reduced viral load in the lungs and protected against tissue damage in the nasal turbinates and lungs in vivo. Our studies demonstrated that selinexor downregulated the pro-inflammatory cytokines IL-1β, IL-6, IL-10, IFN-γ, TNF-α, and GMCSF, commonly associated with the cytokine storm observed in COVID-19 patients. Our findings indicate that nuclear export is critical for SARS-CoV-2 infection and for COVID-19 pathology and suggest that inhibition of XPO1 by selinexor could be a viable anti-viral treatment option

Precision Farming Protocols. Part 2. Comparison of Sampling Approaches for Precision Phosphorus Management

Research is needed to compare the different techniques for developing site‐specific phosphorus (P) recommendations on a field‐wide basis. The objective of this study was to determine the impact different techniques for developing site‐specific P recommendation maps on yield and profitability. Enterprise analysis combined with a crop simulation model and detailed field characterization was used to estimate the value of spatial P information in a system where N was not limiting. The systems evaluated were continuous corn (Zea mays) and corn and soybean (Gfycine max) rotations where sampling and fertilizer applications were applied annually and semi‐annually, respectively. The sampling techniques tested were: (i) an unfertilized P control; (ii) whole field; (iii) whole field plus historic information (feedlot); (iv) landscape positions; (v) soil type; (vi) soil type plus historic information (feedlot); and (vii) 90‐m grid sampling. The finding of this study were based on soil samples collected from a 30 by 30‐m grid. The value of the spatial information was dependent on the crops response to P, the accuracy of the different sampling techniques, crop rotation, and the length of time between sampling dates. All of the sampling techniques produced different application maps. The recommendation map based on a single composite sample under fertilized 56.5% of the field. Increasing the sampling density reduced the percentage of under‐fertilized land. If corn had a low P response, then simulation/enterprise analysis indicated that applying P did not increased profits. For all scenarios tested: (i) the soil type + historic sampling approach had higher potential profits than the 90 m grid sampling approach; and (ii) there was no economic benefit associated with the 90‐m grid sampling. However, if research shows that amortization of sampling and analysis costs over 3 or 4 years is appropriate, then it may be possible to derive economic benefit from a 90‐m grid sampling. For a corn/soybean rotation, where fertilizer was applied when corn was planted and N and P was not applied to soybeans, enterprise/ simulation analysis (2.8 Mg ha‐1 soybean yield goal and a moderate P model) showed that soil + historic sampling approach increased profitability $3.74 ha‐1 when compared to the uniform P treatment