In situ fabrication of waveguide-compatible glass-embedded silver nanoparticle patterns by masked ion-exchange process

We report a study on the properties of silver nanoparticles formed in glass using a masked silver–sodium ion-exchange technique, a process that has been used to fabricate patterned optical waveguides. Characterizations reveal that spherical nanoparticles with a diameter of 5–10 nm are concentrated below the mask edge at a depth of 50–100 nm from the surface. The amount of nanoparticles and the wavelength of the associated localized surface plasmon resonance can be controlled by the spacing between adjacent mask openings. After gentle etching, the surface morphology of the sample shows well-defined nanoparticle patterns. These closely packed nanoparticles embedded in the glass surface have a potential to be used for high-sensitivity surface enhanced spectroscopy, in a glass waveguide device.     

On the selectivity in the bromination of selenophene-2-carbonyl derivatives in the presence of aluminum trichloride

Bromination reactions of 2-selenophenecarbaldehyde and 2-acetylselenophene in the presence of aluminum trichloride have been investigated and the reactivity and positional selectivity compared with those of the analogous thiophene derivatives.     

Application of principal component analysis to 13C NMR shifts of chalcones and their thiophene and furan analogues: A useful tool for the shift assignment and for the study of substituent effects

¹³C NMR shifts of 54 chalcones and their thiophene and furan analogues are analyzed by principal component analysis. Thus, a mathematical model is derived for the variation of the carbon shifts in each of seven classes. Two component models are found to be adequate by cross-validation. The first component corresponds to ordinary σ_para values, while the second one differentiates benzenes, thiophenes and furans. This type of data analysis is a useful tool for checking the consistencies of spectral parameters. The model parameters, which describe systematic variations within each class, are also used for the study of substituent effects and discussed in relation to substituent constants in linear free energy relationships.     

Synthesis of various 5-substituted 2′-deoxy-3′-5′-di-O-acetyluridines

The Pd(0)-catalyzed coupling reaction of β-5-iodo-2′-deoxy-3′,5′-di-O-acetyluridine with various heteroaryltrimethylstannyl compounds gave the corresponding β-5-heteroaryl-2′-deoxy-3′,5′-di-O-acetyluridines in moderate yields. This direct coupling approach for nucleosides represented an interesting alternative to the 5-heteroaryl functionalization of pyrimidines followed by the Hilbert-Johnson glycosylation reaction which often yields mixtures of the α and β anomers.     

On the synthesis of thieno[3,2-c]quinoline N-oxide and thieno-[3,2-C]isoquinoline N-oxide. The nmr spectra of the six isomeric thieno-fused quinoline and isoquinoline N-oxides

The synthesis of the two remaining isomeric monothieno-analogues of phenanthridine N-oxide, thieno-[3,2-c]quinoline N-oxide and thieno[3,2-c]isoquinoline N-oxide, is described. The ¹H and ¹³C nmr spectra of all six isomeric thieno-fused quinoline and isoquinoline N-oxides are discussed.     

On the orientation in lithiation and bromination of dithieno[3,4-b:3′,2′-d]pyridine

The 3-position of dithieno[3,4-b:3′,2′-d]pyridine was found to be most reactive with regard to lithiation, bromination and halogen-metal exchange. The lithium compounds were trapped as the formyl derivatives by reaction with N,N-dimethylformamide.     

Direct bromination of dithieno[3,4-b:3′,4′-d]pyridine and dithieno[2,3-b:3′,2′-d]pyridine

Bromination of dithieno[3,4-b:3′,4′-d]pyridine ( 1 ) and dithieno[2,3-b:3′,2′-d]pyridine ( 2 ) has been studied. Disubstitution occurred at both positions of the C ring. The substitution pattern is found to be similar to that of the nitration reaction. The structures of bromo derivatives were established by ¹H and ¹³C nmr spectroscopy.     

Synthesis of various 5-(3-substituted phenyl)-2′-deoxyuridines

A series pf 5-aryl-2′-deoxyuridines has been prepared and evaluated as antiviral agents. The following substituents have been used in position 3 of the phenyl ring: chloro, iodo, amino, azido, methylthio, and vinyl. None of the new compounds showed any significant activity when tested against human immunodeficiency virus 1 (HI V-I), herpes simplex virus 1 (HSV-I), or human cytomegalovirus (HCMV).     

Grafting of montmorillonite nano‐clay with butyl acrylate and methyl methacrylate by atom transfer radical polymerization: Blends with poly(BuA‐co‐MMA)

11‐(2‐Bromo‐2‐methyl)propionyl‐oxy‐undecyl trichlorosilane atom transfer radical polymerization (ATRP) initiator was covalently attached on montmorillonite clay platelets via silylation reactions. The initiator clay was used to polymerize butyl acrylate (BuA) and methyl methacrylate (MMA) on the clay surface. Polymerization was performed in bulk monomer solution or in DMSO. Polymer modified clay was mixed with a poly(BuA‐co‐MMA) matrix. Small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) showed that clay modified in DMSO gave exfoliated composites when mixed with the matrix copolymer. Mechanical properties of the composites were studied by dynamic mechanical thermal analysis (DMTA). The results showed that the mechanical properties were improved as a function of clay content, as well with an increasing homogeneity of the nanocomposite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3086–3097, 2009     

Cellulose nanofibrils—adsorption with poly(amideamine) epichlorohydrin studied by QCM-D and application as a paper strength additive

In this paper cellulose nanofibrils were used together with a cationic polylelectrolyte, poly(amideamine) epichlorohydrin (PAE), to enhance the wet and the dry strength of paper. The adsorption of nanofibrils and PAE on cellulose model surfaces was studied using quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM). The differences in fibril and polyelectrolyte adding strategies onto cellulose fibres were studied by comparing layer-structures and nano-aggregates formed by the nanofibrils and PAE. The results showed that when PAE was first adsorbed on the model fibre surface a uniform and viscous layer of nanofibrils could be adsorbed. When PAE and nanofibrils were adsorbed as cationic aggregates a non-uniform and more rigid layer was adsorbed. Paper sheets were prepared using both the bi-layer and nano-aggregate adding strategy of the nanofibrils and PAE. When PAE and nanofibrils were adsorbed on pulp fibres as a bi-layer system significant increase in both wet and dry tensile strength of paper could be achieved even at low added amounts of PAE. When the substances were added as nano-aggregates the improvements in paper strength properties were not as significant. Bulk and surface nitrogen content analyses of the paper samples showed that the adding strategy does not affect the total adsorbed amount of PAE but it has a strong effect on distribution of substances in the paper matrix which has a crucial effect on paper wet and dry strength development.