Synthesis and characterization of water-soluble carbon nanotubes from mustard soot

Carbon nanotubes (CNT) has been synthesized by pyrolysing mustard oil using an oil lamp. It was made water-soluble (wsCNT) through oxidative treatment by dilute nitric acid and was characterized by SEM, AFM, XRD, Raman and FTIR spectroscopy. The synthesized wsCNT showed the presence of several junctions and defects in it. The presence of curved graphene structure (sp²) with frequent sp³ hybridized carbon is found to be responsible for the observed defects. These defects along with the presence of di- and tri-podal junctions showed interesting magnetic properties of carbon radicals formed by spin frustration. This trapped carbon radical showed ESR signal in aqueous solution and was very stable even under drastic treatment by strong oxidizing or reducing agents. Oxidative acid treatment of CNT introduced several carboxylic acid group functionalities in wsCNT along with the nicking of the CNT at different lengths with varied molecular weight. To evaluate molecular weights of these wsCNTs, an innovative method like gel electrophoresis using high molecular weight DNA as marker was introduced.     

Synthesis of deuterium-enriched and fluorine-substituted plinabulin derivatives and evaluation of their antitumor activities

Deuterium-enriched and fluorine-substituted compounds have been widely applied in drug discovery due to their advantages in the studies of clinical pharmacokinetics and metabolic profiles. Herein we synthesized a library of deuterated and fluorine-substituted plinabulin derivatives, and all 15 D- or F-compounds were characterized by MS, \(^{1}\hbox {H}\) NMR and \(^{ 13}\hbox {C}\,\hbox {NMR}\). Their antitumor activities were evaluated against human Jurkat T lymphocyte cells.     

Synthesis, thermal and optical properties of metal(II) complexes with a novel ligand derived from pyrazolone-5

Three novel metal(II) complexes, CoL₂, NiL₂ and CuL₂ (L = (Z)-4-(2-(1,3-dimethyl-5-oxo-1H-pyrazol-4(5H)-ylidene)hydrazinyl)-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one were synthesized. Their structures were postulated based on elemental analyses, ¹H NMR, ESI-MS, FT-IR spectra and UV-vis spectra. The effect of different central metal(II) ions on absorption bands of the metal(II) complexes in CHCl₃ solutions was researched. The result indicates that the bathochromic shift is CuL₂ > NiL₂ > CoL₂. The absorption properties of thin films and thermal stability of these complexes are also discussed. In addition, the optical constants (complex refractive index N=n+ik) and thickness of the complex thin films on polished single-crystal silicon substrates were measured by spectroscopic ellipsometry. Results indicate that the metal(II) complexes would be a promising recording medium candidate for blu-ray recordable optical storage system due to good absorption at 405 nm, high thermal stability and sharp thermal decomposition, and a high n values of 1.35–1.45 and a low k values of 0.33–0.39.     

Identification of novel antitumor agents from mixture-based synthetic combinatorial libraries using cell-based assays

A new strategy is presented here which integrates combinatorial library technology with the antitumor in vitro screening system at the National Cancer Institute in the search for novel antitumor agents. Mixture-based synthetic combinatorial libraries (SCLs) representing hundreds of thousands to millions of individual compounds were screened against the cell-based assay, which evaluates compounds for their ability to inhibit the growth of 60 different human tumor cell lines. Five different SCLs, composed of peptides, peptidomimetics, polyamines or small molecules were first tested against three cell lines to identify the most active SCLs. Two SCLs, namely the N-perbenzylated pentamine and the N-acylated permethylated triamine, were deconvoluted to yield individual compounds having significant activities against the 60 tumor cell lines. Active compounds were tested in mice to determine the maximum tolerated dose, followed by in vivo testing in a hollow fiber assay. Using this strategy, three different compounds identified directly from SCLs are currently being evaluated in human tumor xenografts. This study demonstrates for the first time the use of in vitro cell-based assays to identify antitumor lead compounds from mixture-based combinatorial libraries.     

Some novel three-dimensional Euclidean crystalline networks derived from two-dimensional hyperbolic tilings

We demonstrate the usefulness of two-dimensional hyperbolic geometry as a tool to generate three-dimensional Euclidean (E³) networks. The technique involves projection of edges of tilings of the hyperbolic plane (H²) onto three-periodic minimal surfaces, embedded in E³. Given the extraordinary wealth of symmetries commensurate with H², we can generate networks in E³ that are difficult to construct otherwise. In particular, we form four-, five- and seven-connected (E³) nets containing three- and five-rings, viz. (3, 7), (5, 4) and (5, 5) tilings in H². Received 14 January 2002 / Received in final form 12 August 2002 Published online 4 February 2003 RID="a" ID="a"e-mail: stephen.hyde@anu.edu.au     

Synthesis of boron,nitrogen co-doped porous carbon from asphaltene for high-performance supercapacitors

Oxidized asphaltene(OA), a thermosetting material with plenty of functional groups, is synthesized from asphaltene(A) using HNO3/H2SO4as the oxidizing agent. Boron, nitrogen co-doped porous carbon(BNC–OA) is prepared by carbonization of the mixture of boric acid and OA at 1173 K in an argon atmosphere. X-ray photoelectron spectroscopy(XPS) characterization reveals that the BNC–OA has a nitrogen content of 3.26 at.% and a boron content of 1.31 at.%, while its oxidation-free counterpart(BNC–SA) has a nitrogen content of 1.61 at.% and a boron content of 3.02 at.%. The specific surface area and total pore volume of BNC–OA are 1103 m2·g-1and 0.921 cm3·g-1, respectively. At a current density of0.1 A·g-1, the specific capacitance of BNC–OA is 335 F·g-1and the capacitance retention can still reach 83% at 1 A·g-1.The analysis shows that the superior electrochemical performance of the BNC–OA is attributed to the pseudocapacitance behavior of surface heteroatom functional groups and an abundant pore-structure. Boron, nitrogen co-doped porous carbon is a promising electrode material for supercapacitors.     

Synthesis and biological evaluation of novel SIPI-7623 derivatives as farnesoid X receptor (FXR) antagonists

Most of reported steroidal FXR antagonists are restricted due to low potency. We described the design and synthesis of novel nonsteroidal scaffold SIPI-7623 derivatives as FXR antagonists. The most potent compound A-11 (IC₅₀?=?7.8?±?1.1 μM) showed better activity compared to SIPI-7623 (IC₅₀?=?40.8?±?1.7 μM) and guggulsterone (IC₅₀?=?45.9?±?1.1 μM). Docking of A-11 in FXR’s ligand-binding domain was also studied.

     

Synthesis and biological evaluation of benzomorpholine derivatives as novel EZH2 inhibitors for anti-non-small cell lung cancer activity

The histone lysine methyltransferase EZH2 has been reported to play important roles in cancer aggressiveness, metastasis and poor prognosis. In this study, a series of benzomorpholine derivatives were synthesized and biologically evaluated as EZH2 inhibitors. The target compounds were obtained in good yields from 3-amino-5-bromo-2-hydroxybenzoic acid via cyclization, Suzuki coupling and amidation as the key steps. A preliminary optimization study led to the discovery of several potent novel EZH2 inhibitors (6b, 6c, 6x and 6y). Moreover, 6y inhibited the A549 and NCI-H1975 cell lines (IC₅₀?=?1.1 µM and 1.1 µM, respectively). Further studies indicated that 6y can reduce EZH2 expression in intact cells and cause cell arrest in the G2/M phase.

     

An ENDOR study of radical spin adducts derived from novel 2-substituted-5,5-dimethyl-pyrroline-N-oxide spin traps

ENDOR spectra of a series of carbon- and oxygen-centered radical adducts of 2-substituted DMPO-type nitrones are reported. They include the novel cyclic nitrones, 2-phenyl-5,5-dimethyl-pyrroline-N-oxide (2-Ph-5,5-M₂PO), 2,5,5-trimethyl-l-pyrroline-N-oxide (2,5,5-M₃PO), and 2-phenyl-3,3,5,5,-tetramethyl-l-pyrroline-N-oxide (2-Ph-3,3,5,5-M₄PO). Electron paramagnetic resonance (EPR) was used to ascertain the nitrogen hyperfine splittings (hfs’s) while¹H ENDOR was employed to determine the long-range (γ) hydrogen hfs’s. The magnitude of the nitrogen hfs combined with the numbers and sizes of the long-range γ-H hfs’s of spin adducts of these new spin traps are shown to help disclose the identities of various added radicals (or radical addends). It should be noted that the three new spin traps presented here are keto-nitrones not aldo-nitrones. Thus, there is alkyl (e.g. CH₃) or aryl (e.g. C₆H₅) substitution at the 2-position of the pyrroline-N-oxide ring. This feature is part of our search for modified spin traps that yield spin adducts with greater stability.     

Synthesis of nitrogen doped graphite oxide and its electrochemical properties

We herein report a synthesis nitrogen-doped graphite oxide (N-doped GO) by heat treatment with melamine. The N-doped GO contains 4 at % of nitrogen, incurring the oxygen reduction reaction by nitrogen functional groups. Two kinds of aqueous electrolytes are used for finding the electrocatalytic activities, resulting in symmetric oxygen reduction reaction peaks at −0.8 and 0 V in 6 M KOH and 1 M H₂SO₄ electrolytes, respectively. The N-doped GO is more activated in the acid electrolyte compared to thermally reduced graphite oxide (TrGO). Specific volumetric capacitance of N-doped GO in 1.8 M tetraethylmethylammonium tetrafluoroborate electrolyte is 57.4 F cc⁻¹ which is higher than 30.5 F cc⁻¹ of the TrGO, demonstrating positive effects of the nitrogen doping in the organic electrolytes for the energy storage devices.     

Synthesis, characterization and catalytic properties of sol-gel derived mixed oxides

Alumina and 1:1 mixed oxides of Al₂O₃-ZrO₂, Al₂O₃-TiO₂, SiO₂-TiO₂ and ZrO₂-TiO₂ were synthesized via a sol-gel process by the so-called neutral amine route, followed by calcination at 600 °C. The mixed oxides were characterized before calcination by X-ray diffraction, revealing ordered hexagonal (Al₂O₃, Al₂O₃-ZrO₂, ZrO₂-TiO₂) and lamellar (SiO₂-TiO₂, Al₂O₃-TiO₂) structures. After calcination, all samples exhibited amorphous structures. Surface areas and pore characteristics of all materials were determined by nitrogen adsorption isotherms. The calcined oxides are active catalysts in the epoxidation of cyclooctene with tert-butyl hydroperoxide as oxidant. Epoxide yields from 14 to 45% were found for reaction times of 24 h. The titanium oxide containing catalysts are the most active and selective ones. On the other hand, the poisoning of acidic centers yields a decreasing activity while increasing selectivity.     

Synthesis and stereochemical analysis of some norephedrine‐derived isoxazolidines

The diastereoselectivity in the cycloaddition reactions of several mono‐ and disubstituted alkenes with a (‐)norephedrine‐derived methylenenitrone has been investigated. The stereochemical analysis of the addition products (i.e., isoxazolidines) has been carried out by X‐ray, NMR, and chemical conversions. The NMR spectra of the isoxazolidines at low temperatures indicated the presence of either a single or a predominant invertomer. The stereochemistry of the invertomers and nitrogen inversion barriers are determined using complete line‐shape analysis and their dependence on solvent is discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis of silicon nanowires and novel nano-dendrite structures

We report a study on the effects of various parameters on the synthesis of silicon nanowires (5--50 nm in diameter) by pulsed laser ablation. A novel silicon nanodendrite structure is observed by changing some of the growth parameters abruptly. This growth mechanism is explained by a qualitative model. These nanodendrites show a promise of being used as a template in fabricating nanocircuits. Thermal quantum confinement effects were also observed on the silicon nanowires and have been reported.