Effect of sintering and infiltration conditions on nanoscale dual network SiO2/polymethyl metacrylate composites mimicking human enamel.

OBJECTIVE: The aim of this study was to achieve facile sintering conditions and rapid penetration of organic substances into the structure of sintered silica network on the nano-scale in order to prepare polymer infiltrated ceramic network mimicking human enamel. METHODS: Stepwise temperature programming (stepwise isothermal firing) was used to create a cohesive ceramic network containing interconnected pores, which is essential to provide polymer/ceramic dual networks. Liquid phase self-penetration, ultrasonic irradiation assisted liquid phase penetration and vapor phase penetration routes were used to infiltrate methyl methacrylate monomers and benzoyl peroxide reagent into the porous silica blocks. RESULTS: The use of stepwise isothermal firing route, in comparison with high temperature sintering methods, significantly reduces the time and temperature required for the preliminary preparation of the SiO2 samples and reaching the appropriate interconnected porous structure. The most appropriate method for monomer and oxidant reagents infiltration is to use liquid phase infiltration assisted by ultrasound irradiation of pre-sintered nano-silica blocks. It was found that the amount of infiltrated monomer and oxidizing agent, degree of conversion of the monomer to the polymer and surface hardness of the samples strongly depend on the infiltration route. CLINICAL SIGNIFICANCE: The use of inexpensive silica nanoparticles and low temperature sintering and the use of ultrasound waves to quickly and effectively penetrate methyl methacrylate monomers and increase the polymerization efficiency lead to the preparation of composites with a transparent appearance and mechanical properties similar to human tooth enamel.

H2S adsorption on pristine and metal-decorated (8, 0) SWCNT: a first principle study.

Adsorption of hydrogen sulfide (H2S) on the surface of catalytic systems containing (8, 0) single-walled carbon nanotube decorated with Ni and Pd transition metals was investigated using plane-wave density functional theory. SWCNT was modified by adding Ni and Pd atoms to both inside and outside the nanotube and replacing carbon atoms with these metals. All structures were relaxed, and their structural and electronic properties were investigated before and after H2S adsorption and compared with pristine (8, 0) SWCNT properties. Obtained results showed that decorating CNTs with metals increases CNT efficiency for H2S adsorption. The most negative adsorption energies were observed when H2S was adsorbed on the surfaces of metal-decorated nanotube. Electronic properties like band structures and density of states indicated that systems containing Ni on SWCNT are more effective at adsorbing and sensing H2S molecules. Hydrogen sulfide adsorption also changed the magnetization of Ni-decorated structures. Moreover, adsorption of H2S from H side to Ni-decorated SWCNT leads to dissociation of H2S to HS and S atom. Obtained results showed that metal-decorated nanotubes are potentially good candidates for separating H2S from industrial waste gas streams and for its use in H2S sensors.

Synthesis of benzo[a]furo[2, 3-c]phenazine derivatives through an efficient, rapid and via microwave irradiation under solvent-free conditions catalyzed by H3PW12O40@Fe3O4-ZnO for high-performance removal of methylene blue.

A rapid, one-pot synthesis of eight benzo[a]furo[2,3-c]phenazine derivatives has been achieved in moderate to good yields in good yields via a multi-component of 2-hydroxynaphthalene-1,4-dione, arylglyoxal, indole (H, CH3) in the presence of H3PW12O40@Fe3O4-ZnO magnetic core-shell nanoparticles (MCNPs) under solvent-free conditions using microwave irradiation. The catalyst was synthesised and characterised by X-ray diffraction, EDX, TEM, FESEM, TGA, VSM and atomic force microscope. As an application for the synthesised nanocatalyst, degradation of methylene blue as heavy-mass organic pollution was measured. These results showed advantages for synthesis, such as mild reaction conditions, low energy consumption and economically affordable.

An Efficient, Green, Microwave-assisted Synthesis of Benzo[a]furo[2, 3-c]phenazine Derivatives with TiO2-SO3H as Cost-effective and Recyclable Catalyst under Solventfree Conditions.

BACKGROUND: A rapid, efficient, and environmentally benign procedure for the synthesis of novel furo [2,3-c]phenazine derivatives has been developed via reactions of 2-hydroxynaphthalene-1,4-dione, arylglyoxals, and indole in the presence of TiO2-SO3H-catalyst (TSAC) as a recyclable heterogeneous catalyst under solventfree conditions using microwave irradiation. INTRODUCTION: This study describes a successful approach for the synthesis of 2-(4-bromophenyl)-1-(1H-indol-3- yl) benzo[a]furo[2,3-c] phenazine in the presence of TiO2-SO3H-catalyst using microwave irradiation. OBJECTIVES: In this paper, we report an efficient and convenient method for the synthesis of phenazine derivatives from benzo[a]phenazin-5-ol, arylglyoxal derivatives, and indoles in the presence of TiO2-SO3H-catalyst under microwave irradiation. MATERIALS AND METHODS: All reagents and solvents were purchased from Merck and Aldrich and used without further purification. 1H NMR spectra (DMSO) were recorded on the Gemini-500 MHz spectrophotometer with TMS as an internal standard. RESULTS AND DISCUSSION: To investigate the reaction conditions for the synthesis of 2-(4-bromophenyl)-1-(1Hindol- 3-yl) benzo[a]furo [2, 3-c] phenazine derivatives, we performed a reaction between 2-hydroxynaphthalene- 1,4-dione (1 mmol) and aromatic 1,2-diamines (1 mmol) as a model. CONCLUSION: We demonstrated a green and straightforward procedure for the efficient synthesis of novel benzo[ a]furo[2, 3-c] phenazine derivatives in high yields via a one-pot, four-component domino protocol by using TiO2-SO3H as a mild, effective, non-toxic, and inexpensive solid acid catalyst without the addition of an organic co-solvent.

Comparative chemical analysis of volatile compounds of Echinops ilicifolius using hydrodistillation and headspace solid-phase microextraction and the antibacterial activities of its essential oil.

The volatile compounds from various parts of Echinops ilicifolius (Compositae) such as flowers, leaves and roots obtained by hydrodistillation (HD) and headspace solid-phase microextraction (HS-SPME) methods were subsequently analysed by GC and GC/MS and compared. Thirty-seven and 20 components of the flower of E. ilicifolius were characterized, representing 99.7% and 100.0% of the total compositions using the HD and HS-SPME methods, respectively. The major constituents of the hydrodistilled oil were identified as linalool (58.6%), geraniol (17.4%), n-dodecane (10.9%) and nerol (5.4%), whereas HS-SPME extract was rich in n-octane (34.0%), n-decane (25.1%), p-cymene (11.1%), γ-terpinene (5.3%) and 1,8-cineole (5.1%). n-Hexadecanoic acid (32.3%), linalool (16.4%) and geraniol (8.3%) were the main components among 43 constituents identified in hydrodistilled extract of the leaf, representing 99.5% of the total components detected, whereas 16 compounds representing 99.9% of the HS-SPME method were identified, among which n-decane (32.6%), p-cymene (14.0%), n-octane (10.3%), limonene (9.2%), γ-terpinene (9.1%), 1,8-cineole (7.9%) and α-pinene (5.9%) were the major ones. Among 23 components comprising 91.2% of the total hydrodistilled oil detected, n-decane (23.1%), n-dodecane (14.5%), silphiperfol-4,7(14)-diene (11.1%), selin-11-en-4-a-ol (9.5%), n-hexadecanoic acid (7.8%) and n-tetradecane (5.3%) were the main constituents in the root of E. ilicifolius, whereas 1,8-cineole (29.0%), n-decane (12.6%), n-octane (12.6%), camphor (12.0%), p-cymene (9.6%) and γ-terpinene (5.9%) were the main components among the 20 constituents characterized in HS-SPME extract, representing 99.9% of the total components detected. The antibacterial activity of the flower, leaf and root oils of E. ilicifolius against six Gram-positive and Gram-negative bacteria was determined using the MIC method. The growth inhibitory zone (mm) was also measured.

Benzofuran-derived benzylpyridinium bromides as potent acetylcholinesterase inhibitors.

A series of benzofuran-based N-benzylpyridinium derivatives 5a-o were designed and synthesized as novel AChE inhibitors. The synthetic pathway of the compounds involved the preparation of 4-(benzofuran-2-yl)pyridine intermediates via the reaction of different salicylaldehyde derivatives and 4-(bromomethyl)pyridine, followed by intramolecular cyclization. Subsequently, the 4-(benzofuran-2-yl)pyridines were N-benzylated by using appropriate benzyl bromide to afford the final product 5a-o. The results of in vitro AChE activity evaluation of synthesized compounds revealed that all compound had potent anti-AChE activity comparable or more potent than standard drug donepezil. The N-(3,5-dimethylbenzyl) derivative 5e with IC50 value of 4.1 nM was the most active compound, being 7-fold more potent than donepezil.

Composition of the essential oils and antibacterial activities of Hymenocrater yazdianus, Stachys obtusicrena and Nepeta asterotricha three Labiatae herbs growing wild in Iran.

Water-distilled essential oils from leaves of Hymenocrater yazdianus Rech.f., flowers of Stachys obtusicrena Boiss., and stems and flowers of Nepeta asterotricha Rech.f., which are endemic to Iran, were analyzed by GC and GC/MS. Fifty-five components of the leaf oil of H. yazdianus were characterized, representing 95.1% of the total components detected. The major constituents were identified as 1,8-cineole (17.6%), beta-caryophyllene (13.9%), alpha-pinene (10.6%) and caryophyllene oxide (10.4%). Germacrene-D (37.5%) and alpha-bisabolol (23.5%) were the main components among the twenty constituents characterized in the flower oil of S. obtusicrena, representing 90.8% of the total components detected. Thirty-five compounds representing 93.0% of the stem oil of N. asterotrica were identified among which terpinen-4-ol (22.8%) and gamma-terpinene (14.1%) were the major ones. The flower oil of the species was characterized by higher amounts of terpinen-4-ol (24.8%), 4a alpha, 7a beta-nepetalactone (18.2%) and 1,8-cineole (11.6%) among the thirty-three components comprising 98.5% of the total oil detected. The antibacterial activity of the stem, leaf and flower oils of Hymenocrater yazdianus, Stachys obtusicrena and Nepeta asterotricha against seven Gram-positive and Gram-negative bacteria were determined using the MIC method. The growth inhibitory zone (mm) was also measured.