Effect of molecular and electronic structure on the light harvesting properties of dye sensitizers

The systematic trends in structural and electronic properties of perylene diimide (PDI) derived dye molecules have been investigated by DFT calculations based on projector augmented wave (PAW) method including gradient corrected exchange-correlation effects. TDDFT calculations have been performed to study the visible absorbance activity of these complexes. The effect of different ligands and halogen atoms attached to PDI were studied to characterize the light harvesting properties. The atomic size and electronegativity of the halogen were observed to alter the relaxed molecular geometries which in turn influenced the electronic behavior of the dye molecules. Ground state molecular structure of isolated dye molecules studied in this work depends on both the halogen atom and the carboxylic acid groups. DFT calculations revealed that the carboxylic acid ligands did not play an important role in changing the HOMO-LUMO gap of the sensitizer. However, they serve as anchor between the PDI and substrate titania surface of the solar cell or photocatalyst. A commercially available dye-sensitizer, ruthenium bipyridine (RuBpy), was also studied for electronic and structural properties in order to make a comparison with PDI derivatives for light harvesting properties. Results of this work suggest that fluorinated, chlorinated, brominated, and iyodinated PDI compounds can be useful as sensitizers in solar cells and in artificial photosynthesis.Comment: Single pdf file, 14 pages with 7 figures and 4 table

Tracking the Mode of Carbon Deposition During Dry Reforming of Methane over Ni/γ‐Al2O3

Dry reforming of methane was studied over Ni/Al2O3 catalyst at 600 °C with varying CO2/CH4 ratios (0.2, 0.5, 1, 2, 5). 13CO2 as well as 12CO2 were used along with 12CH4 and resulting carbon was characterized with 13C solid state NMR spectroscopy in order to elucidate the role of CO2 in carbon build up. 13C NMR results revealed that carbon in the deposited coke not only came from CH4, but also from CO2. CO2 saturation coverage is determined by adsorption calorimetry as 0.02 mole/site at 323 K, populated on Al2O3. The critical CO2/CH4 ratio for the onset of carbon growth at atmospheric pressure was determined as 1.8 in good agreement with the literature. The effect of CO2/CH4 ratio on the type of carbon formation was investigated by HCTEM. Long-term reaction tests resulted in octopus carbon structure with several fibers growing from one nickel crystal. Above the critical CO2/CH4 ratio, carbon growth was inhibited, only a small amount of amorphous carbon could form. At CO2/CH4 ratios below the critical value, whisker formation was clearly observed. When the steady state operation of reforming reaction was changed to a transient operation by injecting pure CO2 flow to the reactor, coke deposition could be inhibited at the expense of hydrogen stoichiometry

Double Perovskite Structure Induced by Co Addition to PbTiO3_3 : Insights from DFT and Experimental Solid State NMR Spectroscopy

The effects of Co addition on the chemical and electronic structure of PbTiO$_3$ were explored both by theory and through experiment. Cobalt was incorporated to PbTiO$_3$ during sol gel process. The XRD data of the compounds confirmed the perovskite structure for the pure samples. The XRD lines broadened and showed emerging cubic-like features as the Co incorporation increased. The changes in the XRD pattern were interpreted as double perovskite structure formation. $^{207}$Pb NMR measurements revealed a growing isotropic component in the presence of Co. In line with the experiments, DFT calculated chemical-shift values corroborate isotropic coordination of Pb suggesting the formation of cubic Pb$_2$CoTiO$_6$ domains in the prepared samples. The state-of-the-art hybrid functional first-principles calculations indicate formation of Pb$_2$CoTiO$_6$ with cubic structure and confirms that Co addition can decrease oxygen binding energy significantly. Experimental UV-Vis spectroscopy results indicate that upon addition of Co, the band gap is shifted towards visible wavelengths which was confirmed by the energy bands and absorption spectra calculations. The oxygen binding energies were determined by temperature programmed reduction (TPR) measurements. Upon addition of Co, TPR lines shifted to lower temperatures and new features appeared in the TPR patterns. This shift was interpreted as weakening of oxygen cobalt bond strength. The change in the electronic structure by the alterations of oxygen vacancy formation energy and bond lengths upon Co insertion are determined by DFT calculations.Comment: 22 pages, 8 figures, 4 table

Externalizing, internalizing and fostering commitment: the case of born-global firms in emerging economies

This paper examines the HR practices of mature born-global firms from twenty-nine emerging economies. Through an examination of large scale survey data the paper questions the extent to which firm size impacts the employment of temporary workers, the employment of skilled workers and the extent of employee training. Findings suggest that as firm size increases the use of temporary workers decreases, the number of skilled workers increases and the number of employees receiving training also increases. The paper highlights how born-global firms are able to shift away from externalized, market-based approaches towards more internalized, commitment-based approaches in order to survive, adapt and grow

The effects of exhaustive swimming and probiotic administration in trained rats: Oxidative balance of selected organs, colon morphology, and contractility

The duration and intensity of exercise are significant factors in oxidative, morphological, and functional changes of the gastrointestinal tract. This study aimed to investigate the effects of both exhaustive swimming and probiotic VSL#3 on rats that had been previously trained with moderate swimming. The rats were divided into four groups labeled: control (C), probiotic (P), exercise (E), and probiotic-exercise (PE). Groups P and PE were fed with probiotic mixture VSL#3. Groups E and PE had a 5-week moderate swimming program (1 h/day for 5 days/week), followed by a 1-week exhaustive swimming program (trained like in moderate program but 3 times with 150 min resting sessions, for 5 days/week). At the end of the program, the rats were euthanized. Malondialdehyde, superoxide dismutase, catalase, and reduced glutathione levels were measured in tissue samples from the gastrocnemius muscle, heart, liver, kidney, and colon. In vitro contractile activity and histomorphology of the colon were also determined. Exercise and/or probiotic decreased the oxidative stress and also increased the level of one or more of the antioxidant enzymes in some of the organs. Probiotics had more pronounced effects on colon morphology than exercise but unexpectedly this effect was non-trophic. In the colon, the thickness of the tunica muscularis and the number of goblet cells were not affected; however, probiotic administration decreased the crypt depth and tunica mucosa thickness. Exercise increased the Emax value of acetylcholine (ACh), while decreased its sensitivity. These findings suggest that exhaustive swimming does not cause oxidative stress and that probiotic consumption improves oxidative balance in trained rats. The probiotic intake does not alter the effect of exercise on the contractile activity of the colon. Colon mucosal changes induced by probiotics are independent of exercise.Adnan Menderes University Research Fund [VTF14017]This study was funded by the Adnan Menderes University Research Fund (project number: VTF14017). Another part of this study was published in Kafkas Univ Vet Fak 2017; 23: 101 and published as meeting abstract (PC049) in Acta Physiologica (2016; 218: 44-44). The authors would like to thank Amanda Chilaka for her kind help in careful proofreading of this manuscript

Apolipoprotein J is a hepatokine regulating muscle glucose metabolism and insulin sensitivity

Crosstalk between liver and skeletal muscle is vital for glucose homeostasis. Hepatokines, liver-derived proteins that play an important role in regulating muscle metabolism, are important to this communication. Here we identify apolipoprotein J (ApoJ) as a novel hepatokine targeting muscle glucose metabolism and insulin sensitivity through a low-density lipoprotein receptor-related protein-2 (LRP2)-dependent mechanism, coupled with the insulin receptor (IR) signaling cascade. In muscle, LRP2 is necessary for insulin-dependent IR internalization, an initial trigger for insulin signaling, that is crucial in regulating downstream signaling and glucose uptake. Of physiologic significance, deletion of hepatic ApoJ or muscle LRP2 causes insulin resistance and glucose intolerance. In patients with polycystic ovary syndrome and insulin resistance, pioglitazone-induced improvement of insulin action is associated with an increase in muscle ApoJ and LRP2 expression. Thus, the ApoJ-LRP2 axis is a novel endocrine circuit that is central to the maintenance of normal glucose homeostasis and insulin sensitivity

Forging a New Frontier: Antimicrobial Peptides andNanotechnology Converging to Conquer GastrointestinalPathogens

Gastrointestinal infections, which are caused primarily by pathogenicbacteria, remain a significant global health challenge. Their resilience isreinforced by various physical, biological, and biopharmaceutical barriers thatcomplicate conventional therapeutic strategies. This review delves into theintricate landscape of managing these infections, addressing microbiotaimbalances, the emergence of multidrug-resistant strains, and the impact ofdysbiosis and antibiotic overuse. Faced with these challenges, traditionaltherapies often fail, which is hindered by low bioavailability, prolongedregimens, and a growing risk of resistance. In this context, nanotechnologyapplied to antimicrobial peptides (AMPs) has emerged as a promisingsolution to enhance their stability and targeted delivery. Through a criticalapproach, diverse nanocarriers and their efficacy against intestinal pathogensare evaluated both in vitro and in vivo. This review advocates for intensifiedresearch on the encapsulation and functionalization of AMPs, envisioningtheir potential to redefine the control of intestinal infections on a global scale

Phenoxazine Based Units- Synthesis, Photophysics and Electrochemistry

A few new phenoxazine-based conjugated monomers were synthesized, characterized, and successfully used as semiconducting materials. The phenoxazine-based oligomers have low ionization potentials or high-lying HOMO levels (~4.7 eV), which were estimated from cyclic voltammetry. Conjugated oligomers offer good film—forming, mechanical and optical properties connected with their wide application. These results demonstrate that phenoxazine-based conjugated mers are a promising type of semiconducting and luminescent structures able to be used as thin films in organic electronics