The electronic and optical properties of a triexciton in CdSe/ZnS core/shell quantum dot nanocrystals

In the study, we aim to investigate the electronic and optical properties of single excitons, biexcions and triexcitons in a CdSe/ZnS core/shell quantum dot nanocrystal. The electronic structure has been determined by solving of the Poisson–Schrödinger equations self-consistently. In calculations, the exchange-correlation effects between identical particles have been taken into account in the frame of the local density approximation. We have demonstrated that the optical properties of triexciton systems are remarkably different from the single and biexciton systems. Absorption peaks or transition energies of the triexciton system are well separated from those of single- and bi-exciton systems. We have observed that the core-radius dependent transition energy variations of triexcitons are higher when compared with single- and bi-excitonic systems. The transition energy shifts of double and triple excitons with respect to the single exciton have been calculated as a function of the core radius and we have shown that the energy shifts are inversely proportional with the radius. We have also investigated the radius-dependent changes in binding energies and lifetimes of the structures and the comparative results have been discussed in a detail manner.     

Understanding selectivity in the oxidative addition of the carbon-sulfur bonds of 2-cyanothiophene to Pt(0)

The reaction of 2-cyanothiophene with a zerovalent platinum bisalkylphosphine fragment yields two thiaplatinacycles derived from the cleavage of the substituted and unsubstituted C-S bonds. While cleavage away from the cyano group is preferred kinetically, cleavage adjacent to the cyano group is preferred thermodynamically. Density functional theory using B3LYP level of theory on a model of this system is consistent with experimental results in that the transition state energy leading to the formation of the kinetically favored C-S bond cleavage product is lower by 5.3 kcal mol(-1) than the barrier leading to the thermodynamically favored product. There is a 6.7 kcal mol(-1) difference between these two products. The cyano substituent at the 2- position of thiophene did not substantially change the mechanism involved in the C-S bond cleavage of thiophene previously reported.     

Synthesis,structural characterization,biological activity,and theoretical studies of some novel thioether-bridged 2,6-disubstituted imidazothiadiazole analogues

In this study, thioether-bridged imidazo[2,1-b][1,3,4]thiadiazole derivatives that contained both imidazole and 1,3,4-thiadiazole (compounds 7a-7i and 8a-8i ) were synthesized from the reactions of 2-amino-1,3,4-thiadiazole with phenacyl bromide ( 6a - 6i ) (at yields of 59% to 74%). The structure of the synthesized compounds was characterized using ¹H NMR, ¹³C NMR, Fourier-transform infrared spectroscopy, elemental analysis, mass spectroscopy, and X-ray diffraction analysis. Mycelial growth, mycelial growth inhibition, minimum inhibitory concentration, minimum fungicidal concentration, and lethal dose values against various plant pathogenic fungi were determined for all of the target compounds synthesized in the study. The test results showed that most of the compounds had moderate to good antifungal activity. In addition, the absorption, distribution, metabolism, excretion (ADME) parameters of the compounds were calculated, and it was observed that all of the compounds met the drug-likeness rules in general. Finally, using docking simulations, it was found that compounds 7h , 7i , 8h , and 8i showed high affinity to PDB ID:5TZ1, which is an CYP51 antifungal target structure.     

Facile Access to AgOCF3 and Its New Applications as a Reservoir for OCF2 for the Direct Synthesis of N−CF3, Aryl or Alkyl Carbamoyl Fluorides

The development of innovative fluorination strategies is greatly dependent also on the availability, safety and practicability of available fluorinating reagents. We herein show a straightforward and quantitative strategy for the preparation of valuable AgOCF₃ at room temperature and showcase its performance in trifluoromethoxylations or as reservoir for O=CF₂. This enabled the direct, practical and safe synthesis of valuable N-alkyl/aryl and N−CF₃ carbamoyl fluorides from secondary amines and isothiocyanides, respectively. Our mechanistic data indicate that AgOCF₃ does not liberate O=CF₂ until it is activated by a nucleophilic co-reagent, reinforcing the stability of the salt under our new preparation strategy.     

Fatty acid composition of six Centaurea species growing in Konya, Turkey

In this study, fatty acid compositions of six Centaurea species growing in the Konya region were determined. The fatty acid composition of Centaurea balsamita, Centaurea calolepis, Centaurea carduiformis subsp. carduiformis, Centaurea cariensis subsp. maculiceps, C. cariensis subsp. microlepis and Centaurea iberica were analysed. Four species of these six Centaurea are endemic to Turkey. The endemic Centaurea species are C. calolepis, C. carduiformis subsp. carduiformis, C. cariensis subsp. maculiceps and C. cariensis subsp. microlepis. Generally, C 18:2 ω6 linoleic acid, C 16:0 palmitic acid, C 18:3 ω3 linolenic acid and C 18:1 oleic acid were found to be the major fatty acids in all species. Polyunsaturated fatty acids (PUFAs) were found in higher amounts than saturated fatty acids and monounsaturated fatty acids in all species. PUFAs were determined at 55.10%, 50.25%, 51.41%, 41.02%, 46.18% and 58.80% in C. balsamita, C. calolepis, C. carduiformis subsp. carduiformis, C. cariensis subsp. maculiceps, C. cariensis subsp. microlepis and C. iberica, respectively.     

Determination of mineral phosphate species in sedimentary phosphate rock in Mardin, SE Anatolia, Turkey by sequential extraction

The importance of the effect of phosphate rock depends on the chemical form of phosphorus in which this element is combined. The paper presents the results of inorganic and organic forms of phosphorus in the phosphate rock from Mazidag-Derik, Semikan deposit located at Mardin city at SE Anatolia of Turkey. Total phosphorus concentration in the rock is an average 18.5%. The inorganic phosphorus mean % contents were 99.98% for studied sedimentary phosphate rock. Speciation of inorganic phosphorus was carried out using a method based on sequential extractions of the sedimentary phosphate rock each releasing four forms of inorganic phosphorus: loosely sorbed phosphorus, phosphorus bound to aluminium (P-Al), phosphorus bound to calcium (P-Ca) and phosphorus bound to iron (P-Fe). Calcium bound phosphorus is the dominant form of inorganic phosphorus in the studied sedimentary phosphate rock. Aluminium bound phosphorus is the second, iron bound phosphorus is the third most prevailing form. Loosely bound phosphorus is present in the lowest amounts. Analyses of phosphorus forms in sedimentary phosphate rock using a UV spectrophotometric method and ICP-AES are reported here. For the phosphorus the two methods give the same results and the concentrations are in good agreement with the reference values.     

A Novel Fluorescent Probe Based on Perylene Derivative for Hg2+ Ions and Biological Thiols and its Application in Live Cell Imaging and Theoretical Calculations

The selective and sensitive detection of biothiols; cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) in aqueous solutions is of considerable importance because of their pivotal roles in maintaining the reducing environment in the cells. This study describes a strategy for the determination of biothiols based on the PDI/Met‐Hg²⁺complex platform. We designed and fabricated methionine modified perylene diimide molecule as a selective sensing probe for Hg²⁺ ions in aqueous solutions ( PDI/Met‐Hg ²⁺). The complex between perylene bisimide derivative ( PDI/Met) and Hg²⁺ was investigated and it demonstrated turn‐on fluorescence response for the detection of the biological thiols. Besides, PDI/Met displayed fluorescence quenching response in the presence of mercury ions and the emission intensity of PDI/Met‐Hg²⁺ was recovered after transferring biothiols (Cys, Hcy, and GSH). Thus, PDI/Met could be utilized as a fluorescent chemosensor for the sequential recognition of mercury ions and biological thiols.     

Effects of Orange Leaves Extraction Conditions on Antioxidant and Phenolic Content: Optimization Using Response Surface Methodology

In the last few years, bioactive components or their extraction techniques are gaining special interest in scientific areas. In this framework, orange leaves were used for preparation of extracts with high content of biologically active compounds. To optimize the extraction process, three levels and three variables of Box–Behnken design with response surface methodology were applied. Investigated responses were the total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, cupric ion reducing antioxidant capacity (CUPRAC), and ferric reducing antioxidant power (FRAP). Independent variables were methanol concentration (10–90%), temperature (20–60°C), and extraction time (60–180?min). Experimentally obtained results were fit into a second-order polynomial model with multiple regression. Analysis of variance was used to estimate model fitness and determine optimal conditions for processing. Estimated optimal conditions were 90% methanolic solution, 60°C and 180?min using these parameters; the predicted values of investigated responses were 43.19?mg GAE/g (GAE: gallic acid equivalents), 43.04?mg TE/g (TE: trolox equivalents), 139.34 and 93.76?mg TE/g for TPC, DPPH, CUPRAC, and FRAP, respectively. The obtained optimal conditions could be considered as an alternative strategy for developing novel functional products.     

A Bifunctional Photosensitizer for Enhanced Fractional Photodynamic Therapy: Singlet Oxygen Generation in the Presence and Absence of Light

The photosensitized generation of singlet oxygen within tumor tissues during photodynamic therapy (PDT) is self‐limiting, as the already low oxygen concentrations within tumors is further diminished during the process. In certain applications, to minimize photoinduced hypoxia the light is introduced intermittently (fractional PDT) to allow time for the replenishment of cellular oxygen. This condition extends the time required for effective therapy. Herein, we demonstrated that a photosensitizer with an additional 2‐pyridone module for trapping singlet oxygen would be useful in fractional PDT. Thus, in the light cycle, the endoperoxide of 2‐pyridone is generated along with singlet oxygen. In the dark cycle, the endoperoxide undergoes thermal cycloreversion to produce singlet oxygen, regenerating the 2‐pyridone module. As a result, the photodynamic process can continue in the dark as well as in the light cycles. Cell‐culture studies validated this working principle in vitro.