Selective placement of carbon nanotubes on metal-oxide surfaces

We describe a method to selectively position carbon nanotubes on Al2O3 and HfO2 surfaces. The method exploits the selective binding of alkylphosphonic acids to oxide surfaces with large isoelectric points (i.e. basic rather than acidic surfaces). We have patterned oxide surfaces with acids using both microcontact printing and conventional lithography. With proper choice of the functional end group (e.g., -CH3 or -NH2), nanotube adhesion to the surface can be either prevented or enhanced.     

A constructive approach to the finite wavelet frames over prime fields

In this article, we present a constructive method for computing the frame coefficients of finite wavelet frames over prime fields using tools from computational harmonic analysis and group theory.     

Application of organo-nanoclay as a solid sorbent for rhodium complex separation and preconcentration

An organo-nanoclay is used as a new, easily accessible, and stable solid sorbent for the preconcentration of trace amounts of rhodium ions from aqueous solution, this followed by its determination by flame atomic absorption spectrometry (FAAS). Rh(III) ion was first complexed with 2,3,5,6-tetra(2-pyridyl) pyrazine (TPPZ) at pH values between 3.0 and 4.7, and then the complex was then adsorbed onto the nanoclay. The rhodium ions were eluted from the sorbent with HCl. The rhodium in the effluent was determined by FAAS. The linear analytical range is between 0.14 ng mL^?1 and 20.0 μg mL^?1 in the initial solution, the relative standard deviation at 2.0 μg mL^?1 of rhodium is 2.6% (n?=?8), the detection limit is 0.03 ng mL^?1, and the preconcentration factor is 140. Experimental parameters including the pH, eluent type, interference by other ions and breakthrough volume were optimized. The method was applied to the determination of rhodium in water, road dust and synthetic samples.     

Complexation of Dioxovanadium (V) with CDTA in the Water + Methanol Solvent System

The solvent effect has been studied in this research for the interaction of the $ {\text{VO}}_{2}^{ + } $ VO 2 + cation with trans-1,2-diaminocyclohexane-N, N, N′, N′- tetraacetic acid monohydrate at T = 298 K, I = 0.10 mol·dm^?3 sodium perchlorate, and in the range of 0–45 % water + methanol mixtures. UV absorbance data as a function of pH and dissociation constants, obtained from potentiometric titrations, were used for the determination of stability constants. The Kamlet–Abboud–Taft (KAT) model has been investigated for a plausible interpretation and calculation of the linear solvation energy relationship coefficient contribution to the formation of three species VO₂H₂L, VO₂HL^? and VO₂L^2?, which were identified in this work.     

Sonochemical synthesis and crystal structure of indium(III) complex as a modifier for electrochemical simultaneous determination of dopamine and acetylcholine

A novel mixed-ligand complex of [In(Me-phen)Cl₃(DMSO)] (1) was acquired and specified via spectral approaches (IR, UV–Vis, ¹H-NMR, and luminescence), thermal evaluation such as thermogravimetric, differential thermal analyses, and single-crystal X-ray diffraction. In this study, we have also reported the nanosize of [In(Me-phen)Cl₃(DMSO)] (1) that has been synthesized via the sonochemical process. Characterization of nanoparticle (1) was carried out via X-ray powder diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The sample size assembled via the sonochemical approach was approximately 20 nm. Also, a novel screen-printed electrode modified with indium nanocomplex (In NC/SPE) was developed. An electrochemical examination of the adjusted electrode in addition to its efficiency in dopamine electro-oxidation is explained. It was proven that dopamine oxidation at adjusted electrode surface takes place at 150 mV potential less positive compared to an unadjusted screen-printed electrode. The relevant detection limit for dopamine was 2.0 × 10⁻⁷ M via differential pulse voltammetry. Moreover, the adjusted electrode was utilized to simultaneously determine dopamine and acetylcholine. Lastly, the adjusted electrode was utilized to determine dopamine and acetylcholine within real specimens.     

The first C(O)NHP(O)-based phosphoric triamide structure with an N‒H···π hydrogen bonding: A combination of X-ray crystallography and theoretical study to evaluate the strength of hydrogen bonds

The hydrogen bond pattern of N-(4-methoxybenzoyl)-N′,N″-bis(4-methylbenzyl)-phosphoric triamide, C₂₄H₂₈N₃O₃P, (I), was investigated. In the crystal structure, the molecules are aggregated through N_CP―H···O═P and N_P―H···O═C hydrogen bonds in a one-dimensional arrangement parallel to the c axis (N_CP is the nitrogen atom in the C(O)NHP(O) segment and N_P stands for the two other nitrogen atoms bonded to the P atom). There is also a novel N_P?H···π hydrogen bond in the crystal which extends the aggregation of the molecules to a two-dimensional array parallel to the bc plane. A Cambridge Structural Database (CSD, version 5.37, Feb 2016) analysis shows that the N―H···π hydrogen bond was not observed in any of 156 [RC(O)NH]P(O)[NR¹R² Allen, F. H.; Taylor, R. Chem. Soc. Rev. 2004, 33, 463-475.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]]₂ (R¹ ≠ H, R² = H or ≠ H) phosphoric triamide structures reported so far. The theoretical calculations at the B3LYP/6-311G^** level of theory (DFT, AIM, and NBO) were performed to evaluate the strengths of N_CP―H···O═P, N_P―H···O═C and N_P―H···π hydrogen bonds, considering two-aggregate molecular assemblies containing these hydrogen bonds. The calculations on the title compound suggest that the intermolecular N_CP―H···O═P hydrogen bond is stronger than N_P―H···O═C and N_P―H···π interactions. The hydrogen bond strength was investigated by NBO, topological analysis, geometry calculation, Hirshfeld surface analysis and experimental spectroscopic results, which are in agreement with each other.     

Chemically assisted directed assembly of carbon nanotubes for the fabrication of large-scale device arrays

We report the directed assembly of single-walled carbon nanotubes (SWCNTs) at lithographically defined positions on gate oxide surfaces, allowing for the high yield ( approximately 90%) and parallel fabrication of SWCNT device arrays. SWCNTs were first chemically functionalized through diazonium chemistry with a hydroxamic acid end group that both renders the SWCNTs water-soluble and discriminately binds the SWCNTs to basic metal oxide surfaces (i.e., hafnium oxide (HfO2)). The functionalized SWCNTs are then assembled from an aqueous solution into narrow trenches etched into SiO2 films with HfO2 at the bottom. The side walls of the patterned trenches induce alignment of the SWCNTs along the length of the trenches. Heating the structures to 600 degrees C removes the organic moieties, leaving pristine SWCNTs as evidenced by Raman spectroscopy and electrical measurements. Palladium source-drain electrodes deposited perpendicular to the trench length readily contact the ends of the aligned SWCNTs. The resultant devices exhibit the electrical performance expected for SWCNT devices, with no performance deterioration as a result of the placement process. This technique allows for the directed assembly and alignment of SWCNTs over a large area and results in a high yield of working devices, presenting a promising path toward large-scale SWCNT device integration.     

Synthesis of new phosphonato esters by reaction between triphenyl or trialkyl phosphite and acetylenic diesters in the presence of NH‐containing compounds

The reaction between triphenyl or trialkyl phosphite and acetylenic esters in the presence of some heterocyclic or aromatic NH compounds such as thiazolidine‐2,4‐dione, 2‐methyl indole, 5‐bromoisatine, 3‐nitroacetanilide, saccharin, 5,5‐dimethylhydantoin, 2‐nitroaniline, 4‐nitroaniline, benzophenon hydrazine, and anthranilic acid led to the formation of phosphonato esters in high yield. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:630–639, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20725     

Synthesis and conformational analysis of 2'-fluoro-5-methyl-4'-thioarabinouridine (4'S-FMAU)

An improved synthesis of 2'-deoxy-2'-fluoro-5-methyl-4'-thioarabinouridine (4'S-FMAU) is described. Participation of the 3'-O-benzoyl protecting group in the thiosugar precursor influenced the stereochemistry of the N-glycosylation reaction in nonpolar solvents, permitting a higher beta/alpha ratio than previously observed for similar Lewis acid catalyzed glycosylations. Conformational analysis of the nucleoside using 3JHH and 3JHF NMR coupling constants together with the PSEUROT program showed that it adopted a predominantly northern conformation in contrast to 2'-deoxy-2'-fluoro-5-methylarabinouridine (FMAU), whose PSEUROT conformational analysis is presented here for the first time, which showed a dominantly southeast conformation. The sharp conformational switch attained by replacing the ring heteroatom is attributed to a decrease in relevant steric and stereoelectronic effects.