Integration of ternary I-III-VI quantum dots in light-emitting diodes.

Ternary I-III-VI quantum dots (TQDs) are semiconductor nanomaterials that have been gradually incorporated in the fabrication of light-emitting diodes (LEDs) over the last 10 years due to their physicochemical and photoluminescence properties, such as adequate quantum yield values, tunable wavelength emission, and easy synthesis strategies, but mainly because of their low toxicity that allows them to be excellent candidates to compete with conventional Cd-Pb-based QDs. This review addresses the different strategies to obtain TQDs and how synthesis conditions influence their physicochemical properties, followed by the LEDs parameters achieved using TQDs. The second part of the review summarizes how TQDs are integrated into LEDs and white light-emitting diodes (WLEDs). Furthermore, an insight into the state-of-the-art LEDs development using TQDs, including its advantages and disadvantages and the challenges to overcome, is presented at the end of the review.

Enhancing the stability and efficiency of MAPbI3 perovskite solar cells by theophylline-BF4 - alkaloid derivatives, a theoretical-experimental approach.

Perovskite solar cells (PSCs) are an evolving photovoltaic field with the potential to disrupt the established silicon solar cell market. However, the presence of many transport barriers and defect trap states at the interfaces and grain boundaries has negative effects on PSCs; it decreases their efficiency and stability. The purpose of this work was to investigate the effects on efficiency and stability achieved by quaternary theophylline additives in MAPbI3 PSCs with the structure FTO/TiO2/perovskite/spiro-OMeTAD/Ag. The X-ray photoelectron spectroscopy (XPS) and theoretical calculation strategies were applied to study the additive's interaction in the layer. The tetrafluoroborinated additive results in an increase in device current density (J SC) (23.99 mA cm-1), fill factor (FF) (65.7%), and open-circuit voltage (V OC) (0.95 V), leading to significant improvement of the power conversion efficiency (PCE) to 15.04% compared to control devices (13.6%). Notably, films exposed to controlled humidity of 30% using the tetrafluoroborinated additive maintained their stability for more than 600 hours (h), while the control films were stable for less than 240 hours (h).

3-(4-Formylphenyl)-triazole functionalized coumarins as violet-blue luminophores and n-type semiconductors: synthesis, photophysical, electrochemical and thermal properties.

3-(4-Formylphenyl)-triazole-coumarin hybrid chromophores (FPhTCs) were synthesized in good yields, using a click chemistry protocol, and were also structurally characterized. Their photophysical, electrochemical and thermal properties were measured demonstrating that FPhTCs are luminescent in the blue-violet region of the electromagnetic spectrum, both in solution and the solid state. They showed an electrochemical band-gap values of 2.79 ± 0.08 eV, resistivity values between 104 and 105 Ω cm and are thermally stable up to 225 °C, properties that promise FPhTCs as good candidates for optoelectronic or imaging applications. Their solution and solid state photoluminescent properties are discussed and supported by theoretical calculations.

Fluorescence assay for acrylamide determination in fried products based on AgInS2/ZnS quantum dots.

AgInS2/ZnS quantum dots were synthesized via solvothermal aqueous phase method using 3-mercaptopropionic acid as the stabilizer. AgInS2/ZnS quantum dots were employed for acrylamide sensing under two strategies: (1) quenching of the fluorescence signal by the synthesis of polyacrylamide under UV light and (2) use of 2-naphthalenethiol for quenching of the fluorescence signal of quantum dots followed by a recovery of the signal after the addition of acrylamide. Both methodologies display adequate limits of detection, 15.6 and 4.8 µg L-1, respectively. However, the 2-napthalenethiol based method exhibited better precision and selectivity compared to the other methodology. Both methodologies were applied for acrylamide detection in fried snack products and acceptable accuracy was obtained using 2-napthalenethiol method.

Synthesis of photochromic oligophenylenimines: optical and computational studies.

Phenyleneimine oligomers 4,4'-(((1E,1'E)-(((1E,1'E)-(1,4-phenylenebis-(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy)-4,1-phenylene))bis(methanylyl-idene))-bis(azanylylidene))dianiline (OIC1MS) and 7,7'-(((1E,1'E)-(((1E,1'E)-((9H-fluorene-2,7-diyl)bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy)-4,1phenylene))bis- (methanylylidene))bis(azanylylidene))bis(9H-fluoren-2-amine) (OIC2MS) were prepared by means of conventional and mechanochemical synthesis and characterized by FT-IR, 1H- and 13C-NMR techniques. The optical properties of the compounds were studied in solution by using UV-visible spectroscopy, and the optical effects were analyzed as a function of solvent. The results show that OIC2MS exhibits interesting photochromic properties. Furthermore, the structural and electronic properties of the compounds were analyzed by TD-DFT. It was found that the mechanosynthesis is an efficient method for the synthesis of both tetraimines.

Perforated peptic ulcer treated by simple closure and Helicobacter pylori eradication.

Simple closure followed by Helicobacter pylori (Hp) eradication has become the most used procedure in perforated ulcer treatment. However, its efficacy and safety are still to be determined. To assess recurrence and re-perforation rates, and as a secondary objective, to analyze Hp infection rates in perforated ulcer patients and controls, we conducted a prospective study. Ninety-two consecutive patients (ages: 19-96 years) were operated on between 1996 and 2002, and treated by simple closure followed by Hp eradication and NSAID avoidance. The data were prospectively collected in a database. Hp infection was diagnosed in 68 patients (73.9%). Thirty-four patients (37%) consumed nonsteroidal anti-inflammatory drugs (NSAIDs), and 23 (25%) had both Hp infection and NSAID antecedents. The perforation was gastric in 4 cases and pre-pyloric, pyloric or duodenal in 88. There were postoperative complications in 24 patients (26%) and 4 patients died (4.3%). Hp eradication was shown in 46 patients. There was clinical ulcer recurrence in 4 (4.3%); in 3 of them recurrence manifested as re-perforation, all in gastric locations. Overall relapse and re-perforation 1-year crude rates were 6.1% and 4.1%, respectively. Crude rates for non-gastric ulcer recurrence were 0 at 1 year and 2.6% at 2 years and for non-gastric ulcer re-perforation rates were 0 at 1 and 2 years. This therapeutic strategy is associated with a low rate of recurrence and no re-perforations in case of duodenal, pyloric, or pre-pyloric perforated ulcers, but it is not acceptable for perforated gastric ulcers.

2-Methyl-1,4,5-triphenyl-1H-imidazole.

In 2-methyl-1,4,5-triphenyl-1H-imidazole, C(22)H(18)N(2), the three substituent phenyl groups are not delocalized with the imidazole moiety; the dihedral angles these phenyl groups form with the imidazole ring are in the range 25.90 (5)-63.49 (6) degrees.