Synthesis and Photochemistry of Novel 3,5-Diacetyl-1,4-dihydropyridines. II [1]

Summary. In continuation of previous work some novel 3,5-diacetyl-1,4-dihydropyridine derivatives were synthesized and their photochemical behavior was studied under oxygen and argon atmosphere. Oxidation of the dihydropyridine ring and formation of pyridine derivatives was the result of the reaction. The presence of oxygen affects not only on the rate of oxidation, but also the formation of some unidentified by-products was observed on irradiation under this atmosphere.     

In Situ Synthesis of Manganese Oxide as an Oxygen-Evolving Catalyst: A New Strategy

All studies on oxygen-evolution reaction by Mn oxides in the presence of cerium(IV) ammonium nitrate (CAN) have been so far carried out by synthesizing Mn oxides in the first step. And then, followed by the investigation of the Mn oxides in the presence of oxidants for oxygen-evolution reaction (OER). This paper presents a case study of a new and promising strategy for in situ catalyst synthesis by the adding Mn^II to either CAN or KMnO₄/CAN solution, resulting in the formation of Mn-based catalysts for OER. The catalysts were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Both compounds contained nano-sized particles that catalyzed OER in the presence of CAN. The turnover frequencies for both catalysts were 0.02 (mmol /mol_Mn⋅s).     

Interaction of small molecules (NO,H2, N2, and CH4) with BN nanocluster surface

Structural Chemistry - The interactions between BN nanocluster of B12N12 and small molecules (H2, NO, N2, and CH4) were investigated by using density functional computations, exploiting the...     

A theoretical study of CO adsorption on aluminum nitride nanotubes

Adsorption of toxic CO molecule on single-walled aluminum nitride nanotubes (AlNNTs) was investigated using density functional theory calculations. A detailed analysis of the energetic, geometry, and electronic structure of various CO adsorptions on the tube exterior surface was performed. In contrast to carbon and BN nanotubes, our results indicated that AlNNTs can strongly interact with CO molecules. The adsorption energy of the most stable configuration was calculated to be about −0.25 eV. The Morokuma–Kitaura decomposition for molecular interaction energies was used to investigate the nature of C–Al bond in the most stable CO–AlNNT complex, demonstrating that electrostatic forces and polarization term are basic factors of attractive interaction between CO and AlNNT. They provide 37.9 and 40.4% of attractive interaction and charge transfer energies make a little contribution to the adsorption energy of CO.     

Nanosized rhodium oxide for water oxidation: An organometallic precursor for the preparation of rhodium oxide

Electrochemical production of hydrogen from water splitting is a promising process to allow storage of intermittent energies. However, anodic water oxidation, which is a complicated four‐proton, four‐electron transfer process, affects the efficiency of hydrogen generation due to the need to apply large overpotentials. Herein, we synthesized nanosized rhodium(III) oxide by the thermal decomposition of a known rhodium organometallic precursor and characterized it using scanning and transmission electron microscopies, powder X‐ray diffraction, energy‐dispersive X‐ray, diffuse reflectance infrared and Fourier transform infrared spectroscopies, and electrochemical methods. The results showed that the nanosized rhodium oxide is a promising catalyst for water oxidation.     

A Potentiometric Sensor for Cd2+ Based on Carbon Nanotube Paste Electrode Constructed from Room Temperature Ionic Liquid,Ionophore and Silica Nanoparticles

A novel and effective potentiometric sensor for the rapid determination of Cd²⁺ based on carbon paste electrode consisting of the room temperature ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate, multiwalled carbon nanotubes, silica nanoparticles and ionophore was constructed. The prepared composite has a low potential drift, high selectivity and fast response time, which leads to a more stable potential signal. A linear dynamic range of 4.50×10^?9–1.00×10^?1 mol L^?1 with a detection limit of 2.00×10^?9 mol L^?1 was obtained. The modified electrode was successfully applied to the accurate determination of trace amounts of Cd²⁺ in environmental and biological samples.     

A novel needle trap sorbent based on carbon nanotube-sol-gel for microextraction of polycyclic aromatic hydrocarbons from aquatic media

A new type of composite material based on carbon nanotubes (CNTs) and sol–gel chemistry was prepared and used as sorbent for needle trap device (NTD). The synthesized composite was prepared in a way to disperse CNTs molecules in a sol–gel polymeric network. CNT/silica composites with different CNT doping levels were successfully prepared, and the extraction capability of each composite was evaluated. Effects of surfactant and the oxidation duration of CNTs on the extraction efficiency of synthesized composites were also investigated. The applicability of the synthesized sorbent was examined by developing a method based on needle trap extraction (NTE) and gas chromatography mass spectrometry detection (GC–MS) for the determination of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Important parameters influencing the extraction process were optimized and an extraction time of 30 min at 50 °C and sampling flow rate of 2.5 mL min⁻¹ gave maximum peak area, when NaCl (15%, w/v) was added to the aqueous sample. The linearity for acenaphthene, acenaphthylene and fluorene was in the concentration range of 0.01–20 ng mL⁻¹ and for naphthalene and anthracene was in the range of 0.1–50 ng mL⁻¹. Limits of detection was 0.001 ng mL⁻¹, for acenaphthene, acenaphthylene and fluorene, and 0.01 ng mL⁻¹, for naphthalene and anthracene using time-scheduled selected ion monitoring (SIM) mode, and the RSD% values (n = 3) were all below 11.2% at the 1 ng mL⁻¹ level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 73.8 to 113.8%.     

New Grafted Nanosilica-Based Sorbent for Needle Trap Extraction of Polycyclic Aromatic Hydrocarbons from Water Samples Followed by GC/MS

In this work, the preparation of a new grafted nanosilica-based sorbent was extensively investigated. An inexpensive modifier, cis-9-octadecenoic acid (oleic acid) was selected to be grafted on the surface of the nanosilica particles as the support. The grafting process was accurately confirmed by Fourier transform infra-red spectrometry (FT-IR). Applicability of the prepared sorbent was thoroughly examined by needle trap extraction (NTE) method. The grafted sorbent was dispersed in the appropriate solvent and carefully packed inside a steel needle. Feasibility of the method was completely examined using polycyclic aromatic hydrocarbons (PAHs), as model compounds. For extraction of analytes from aqueous samples, the prepared needle trap device (NTD) was placed in the headspace of the sample and another needle was also inserted into the sample solution to purge the circulating headspace into the sample. For increasing the extraction efficiency, influencing parameters including extraction time and temperature, flow rate of analyte through the needle trap, the ionic strength, desorption temperature, and time were optimized. The limit of detection (LOD) and relative standard deviation (RSD) values of the method under optimized conditions were 2?C5 ng L^?1 and 1.1?C4.8%, respectively. The RSD% for fluorene was somewhat higher and a value of 16.8% at 40 ng L^?1 was achieved. Finally the developed method was applied to the analysis of tap water and Zayandeh-roud river samples and the relative recovery (RR %) values were found to be in the range of 77?C109%, under the optimized conditions.