Sonochemical synthesis and application of rhodium–graphene nanocomposite

Abstract  

Highly water dispersible rhodium–graphene nanocomposite have been successfully synthesized by the simple reduction of Rh³⁺ salt on poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO/PPO/PEO) triblock copolymer or pluronic-stabilized graphene oxide (GO) nanosheets with borohydride. Rhodium nanoparticles, having average size of 1–3 nm, are homogeneously distributed through out the graphene sheets. Some porous structures of graphene sheets have also been observed after the reduction of pluronic-stabilized GO in the presence of metal ions. The material is very effective for hydrogenation of arenes, especially for benzene as the substrate material at the room temperature and 5 atm pressure of hydrogen.     

Facile synthesis and photocatalytic activity of ZnO–CuO nanocomposite

Nanostructured ZnO–CuO composite with an open and porous surface was successfully prepared through a simple one-step homogeneous coprecipitation method under low temperature (80 °C), without using any organic solvent or surfactant. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and UV–vis spectroscopy. The results demonstrated that the ZnO–CuO nanocomposite presented a hierarchical 3D morphology composed of flower-like ZnO microstructures adorned with leaf-like CuO nanopatches. The photocatalytic activity of ZnO–CuO nanocomposite was evaluated by the photodegradation of rhodamine B under the simulated sunlight irradiation, and compared with those of the monocomponent oxides synthesized by the identical synthetic route and their physical mixture in the approximate molar ratio as that of the nanocomposite. The results indicated that the ZnO–CuO nanocomposite exhibited an appreciable photocatalytic activity, which was mainly attributed to the extended photo-responding range and the increased charge separation rate in the nanocomposite.     

Laser ablative approach for the synthesis of cadmium hydroxide–oxide nanocomposite

Cadmium hydroxide/oxide nanocomposite material is synthesized by pulsed laser ablation of cadmium metal in double distilled water. As-synthesized cadmium hydroxide/oxide particles transforms into pure oxide after annealing at 350 °C for 9 h. As-obtained particles are spherical in shape with 15 nm average diameter, while spherical as well as rod shaped nanostructures are formed after annealing. PL spectrum of annealed powder has peaks corresponding to the defect levels rather than the band gap transitions.     

Ultrasound assisted synthesis of polyacrylic acid–nanoclay nanocomposite and its application in sonosorption studies of malachite green dye

Synthesis of nanoclay nanocomposite has been undertaken by using polyacryalic acid (PAA) in aqueous medium and ultrasound environment and its application in dye removal has been investigated. The synthesized product was characterized by using FTIR and XRD techniques. The sonosorption capacity of the product namely PAA–nanoclay composite was determined by choosing malachite green (MG) dye as a model pollutant. The effects of various parameters such as nanocomposite loading, pH, various process conditions etc. have been studied. On comparing the results obtained with that of nanoclay as an adsorbent, it was found for an initial concentration of 500 mg/l, the PAA–nanoclay nanocomposite exhibited higher percentage of pollutant removal (68%) and for nanoclay it was 54%. The adsorption data has been correlated using Langmuir and Freundlich models. The fit of the Freundlich isotherm model was found to be good in the entire range of concentration for the experimental sorption data obtained on the nanoclay nanocomposite. A plausible reaction mechanism for use of PAA–nanoclay nanocomposite as an adsorbent is also proposed.     

Apple – biomorphic synthesis of porous ZnO nanostructures for glucose direct electrochemical biosensor

Biomorphic porous ZnO nanostructures were successfully synthesized via an aqueous sol–gel soaking process using pieces of apple flesh and skin as templates and employed for glucose direct electrochemical biosensor. The structure and morphology of ZnO nanostructures were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). By modifying glassy carbon electrode with the biomorphic ZnO nanostructures and Nafion, two glucose biosensors were constructed and their direct electrochemistry of glucose oxidase (GOD) was successfully investigated by cyclic voltammetry (CV). The biomorphic porous ZnO nanostructures using apple skin template (S-ZnO) were more effective in facilitating the electron transfer of immobilized GOD than that of using flesh apple template (F-ZnO). This may be a result of the unique morphology and smaller average crystallite size of the S-ZnO nanostructure. GOD immobilized on Nafion-porous S-ZnO nanostructure composite display direct, reversible, and surface-controlled redox reaction with a detection limit of 10 μM, a response time of 7 s, high sensitivity of 23.4 μA/mM cm² and a fast heterogeneous electron transfer rate with a rate constant (k_s) of 3.9 s^?1. It was found that S-ZnO significantly has improved the direct electron transfer between GOD and glassy carbon electrode with good stability and reproducibility.     

Ultrasonic-assisted synthesis of Pd–Pt/carbon nanotubes nanocomposites for enhanced electro-oxidation of ethanol and methanol in alkaline medium

Herein, a facile ultrasonic-assisted strategy was proposed to fabricate the Pd–Pt alloy/multi-walled carbon nanotubes (Pd–Pt/CNTs) nanocomposites. A good number of Pd–Pt alloy nanoparticles with an average of 3.4 ± 0.5 nm were supported on sidewalls of CNTs with uniform distribution. The composition of the Pd–Pt/CNTs nanocomposites could also be easily controlled, which provided a possible approach for the preparation of other architectures with anticipated properties. The Pd–Pt/CNTs nanocomposites were extensively studied by electron microscopy, induced coupled plasma atomic emission spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and applied for the ethanol and methanol electro-oxidation reaction in alkaline medium. The electrochemical results indicated that the nanocomposites had better electrocatalytic activities and stabilities, showing promising applications for fuel cells.     

Facile synthesis of a sulfur/multiwalled carbon nanotube nanocomposite cathode with core–shell structure for lithium rechargeable batteries

A novel sulfur/multiwalled carbon nanotube nanocomposite (S/MWCNT) was prepared by a facile quasi-emulsion template method in an O/W system. Transmission and scanning electronic microscopy show the formation of a highly developed core–shell tubular structure consisting of S/MWCNT composite with uniform sulfur coating on its surface. The homogenous dispersion and integration of MWCNT in the S/MWCNT composite create a highly conductive and mechanically flexible framework, enhancing the electronic conductivity and consequently the rate capability of the material. The S/MWCNT composite cathode could deliver a stable discharge (the fifth cycle) capacity of about 903 mAh g^?1 at 0.1 C, 751 mAh g^?1 at 0.5 C, and 631 mAh g^?1 at 1 C.     

Surface adsorption studies of benzyl bromide and bromobenzyl cyanide vapours on black phosphorene nanosheets – a first-principles perception

In this research, two-dimensional material, black-phosphorene nanosheets (Black-PNS) have been deployed as a sensing substrate for detecting two tear gas molecules, namely, benzyl bromide and bromobenzyl cyanide. The stability of black phosphorene sheet structure can be ensured by observing its formation energy, which is found to have ?3.895?eV/atom. Besides, the semiconducting nature of Black-PNS reinforces that it can be a potential base material to get deployed as a chemical sensor. The deviations in the density of states are noticed upon adsorption of benzyl bromide and bromobenzyl cyanide molecules on black phosphorene nanosheets. The energy of adsorption, energy gap variation and Bader charge transfer analysis are intended to investigate the assimilation properties of benzyl bromide and bromobenzyl cyanide on Black-PNS. The final results exhibit the possibility of using Black-PNS as a nanosensor substrate for lachrymator agents such as benzyl bromide and bromobenzyl cyanide.     

Esters of 4-nitrocinnamic acids and 4-halogene-4’-hydroxyazobenzenes – synthesis,mesogenic and optical studies

Six new compounds were synthesized that have no alkyl chains in their structure: 4-nitrocinnonates of 4-hydroxyazobenzene, 4-nitro-4’-hydroxyazobenzene, 4-fluoro-4’-hydroxyazobenzene, 4-chloro-4’-hydroxyazobenzene, 4-bromo-4’-hydroxyazobenzene and 4-iodo-4’-hydroxyazobenzene. Using the polarizing microscopy and differential scanning calorimetry, enthalpies and temperatures of phase transitions were determined. All investigated compounds have an enantiotropic nematic phase. These compounds proved to be extremely thermally stable. Thermal decomposition was observed in temperatures above 300°C. Investigated compounds contain two different chromophore groups (i.e. azo and ethene moieties), which influenced the complex trans–cis isomerization processes of both groups (three time-separated processes were observed). It was shown that the presence of the ethene group significantly shifts the π-π* band towards higher energies. The substituent polarity in the azo group also affected the energy of this absorption band. A weak luminescence effect was observed in the 4-nitrocinnonates of 4-hydroxyazobenzene compound.     

Features of superconducting transition in nanocomposite consisting of “insulating matrix (porous alkali-borosilicate glass)” – “granular metallic filler (indium)”

Patterns in temperature and magnetic field behavior of the electrical resistance of nanocomposite consisting of “insulating matrix (7 nm-pore alkali-borosilicate glass)” – “granular metallic filler (indium)” (PG7+In) has been found and analyzed in the vicinity of superconducting transition. Insulating behavior in the electrical resistivity has been observed in a normal state. External magnetic field shifts the transition to lower temperatures and the same time gradually strengths the insulating behavior above the superconducting transition. Hopping conductivity mechanism developed for the granular conductor systems can be responsible for the insulating behavior in normal-state electrical resistance. Electron hopping in the granular conductor system is realized as tunneling of electrons through intergranular contacts between the metallic granules. The superconducting transition has been found to be rather broad. Broadening in the superconducting transition can be attributed to fluctuation conductivity. Above the superconducting transition, the Aslamazov-Larkin contribution to the conductivity characteristic for three-dimensional systems has been found to be main correction to the conductivity.     

A facile one-pot ultrasound assisted for an efficient synthesis of 1H-spiro[furo[3,4-b]pyridine-4,3′-indoline]-3-carbonitriles

A convenient one-pot protocol was developed for the synthesis of 1H-spiro[furo[3,4-b]pyridine-4,3′-indoline]-3-carbonitrile derivatives. This reaction was carried out through a three component condensation reaction of isatins, malononitrile, and anilinolactones in the presence of a catalytic amount of Et₃N as an inexpensive and available basic catalyst in THF under ultrasound irradiation. The products were obtained in high yields and short reaction times. The main advantage of this synthetic method is that the obtained products in ultrasonic irradiations are different from classical heating.     

Carbon and nitrogen isotope analyses coupled with palynological data of PM10 in Wrocław city (SW Poland) – assessment of anthropogenic impact

We have applied both palynological and carbon and nitrogen isotopic analyses of PM10 (particulate matter with a diameter of 10 μm or less) to trace its origin and to assess the anthropogenic impact for the area under study. The PM10 samples were collected in Wroc?aw (SW Poland) by the Regional Inspectorate for Environment Protection during the year 2007. The usefulness of the palynological observations in the case of PM10 is much lower than that for total suspended particles due to the resolution of absorbed particles, but is still helpful for distinguishing C₃/C₄ plants that indicate long-distance transport of pollutants. The δ¹³C(PM10) values varied seasonally from?26.9 to?25.1‰. The δ¹⁵N(PM10) values showed chaotic fluctuations and varied from 5.0 to 13.7‰. Our results indicated that during the heating period, the PM10 particles in Wroc?aw are derived mainly from local home heaters, whereas in the growing period, PM10 particles are derived from local transport and are partially generated by the industrial application of coal combustion outside the city of Wroc?aw.     

Domino Michael–<Emphasis Type="Italic">O</Emphasis>-alkylation: one-pot synthesis of dialkyl 4-oxo-2,3-dihydro-2,3-furandicarboxylates

Abstract  

The KSCN-catalyzed reaction of dialkyl acetylenedicarboxylates with pentane-2,4-dione in acetone, led to dialkyl 2-(1-acetyl-2-oxopropyl)-2-butenedioates in excellent yields. When these reactions were carried out in MEK (butane-2-one), dialkyl 4-oxo-2,3-dihydro-2,3-furandicarboxylates were obtained exclusively. This difference in reactivity is discussed in terms of the possibility of cationic exchange in butane-2-one.     

Fe(ClO4)3· 6H2O: a mild and efficient catalyst for one-pot three component synthesis of β-acetamido carbonyl compounds under solvent-free conditions

A one-pot multi-component reaction for the synthesis of β-acetamido carbonyl compounds is reported. The reaction uses a variety of aldehydes, acetophenone derivatives or methyl acetoacetate, acetonitrile, and acetyl chloride in the presence of ferric perchlorate, a mild, efficient and inexpensive catalyst effective under solvent free conditions.     

Ultrasonic-assisted synthesis of graphene oxide – fungal hyphae: An efficient and reclaimable adsorbent for chromium(VI) removal from aqueous solution

In this study, a hybrid film bio-nanocomposite material was developed based on the graphene oxide/fungal hyphae (GO-FH) interaction. The developed GO-FH bio-nanocomposite material was used for the removal of hexavalent chromium from aqueous solution. The GO-FH bio-nanocomposite material was prepared by ultrasonic irradiation technique. The synthesized GO-FH bio-nanocomposite material was characterized by XRD, FT-IR, SEM, TEM and TGA. The adsorption experiments were carried out in batch mode to optimize parameters such as pH, adsorbent dosage, initial Cr(VI) ion concentration, contact time and shaking speed. The results indicated that the adsorption of Cr(VI) onto GO-FH bio-nanocomposite material was pH dependant, with the maximum adsorption capacity of 212.76 mg/g occurred at pH 2.0. The adsorption studies followed, Langmuir isotherm and pseudo second order kinetic model. Findings demonstrates that GO-FH bio-nanocomposite material exhibited excellent regeneration performance.     

New one-pot synthesis of spiro[furo[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidine-6,5′-pyrimidine]pentaones and their sulfur analogues

Reaction of barbituric acid (BA), 1,3-dimethyl barbituric acid (DMBA) and 2-thiobarbituric acid (TBA) with cyanogen bromide and various aldehydes in presence of triethylamine afforded a new class of heterocyclic stable 5-alkyl and/or 5-aryl-1H, 1′H-spiro[furo[2,3-d]pyrimidine-6,5′-pyrimidine]2,2′,4,4′,6′(3H,3′H,5H)-pentaones which are dimeric forms of barbiturate (uracil and thiouracil derivatives) at 0 °C to ambient temperatures. Structure elucidation is proved by X-ray crystallography, ¹H NMR, ¹³C NMR, FT-IR, CHN and mass analyses techniques. Mechanisms of the formations are discussed.     

A three component one-pot procedure for the synthesis of [1,2,4]triazolo/benzimidazolo-quinazolinone derivatives in the presence of H6P2W18O62 · 18H2O as a green and reusable catalyst

A rapid and efficient one-pot method for the synthesis of quinazolinone derivatives and related heterocycles by condensation of 2-amino benzimidazole and 3-amino-1,2,4-triazole, as amine sources, with dimedone and different aldehydes in the presence of H6P2W18O(62).18H2O as a green and reusable catalyst in refluxing acetonitrile has been developed.     

The application of poly(N, N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) and N, N, N′, N′-tetrabromobenzene-1,3-disulfonamide as catalysts for one-pot synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles and 1,5-benzodiazepines, and new reagents for synthesis of benzimidazoles

A new, facile, and efficient procedure for conjugate addition of indole and pyrrole with Michael acceptors have been developed for pulverization–activation reaction catalyzed by wet cyanuric chloride (2,4,6-trichloro-[1,3,5]-triazine or TCT) through grinding under solvent-free conditions at room temperature. Also, double-conjugate 1,4-addition of indoles to dibenzylidenacetones and conjugate addition of thiols with Michael acceptors using wet-TCT as catalyst is reported.