Effect of radiation dose on the properties of natural rubber nanocomposite

Effect of radiation dose and carbon nanotubes (CNT) on the mechanical properties of standard Malaysian rubber (SMR) was investigated in this study. SMR nanocomposites containing 1–7 phr CNT were prepared using the solvent casting method and the nanocomposites were radiated at doses of 50–200 kGy. The change in mechanical properties, especially, tensile strength (Ts), elongation at break (Eb), hardness and tensile modulus at 100% elongation (M₁₀₀) were studied as a function of radiation dose. The structure and morphology of reinforced natural rubber was investigated by FESEM, TEM and AFM in order to gain further evidence on the radiation-induced crosslinking. It was found that the Ts, M₁₀₀ and the hardness of the SMR/CNT nanocomposites significantly increased with radiation dose; the elongation at break exhibited an increase up to 100 kGy, and a downward trend thereafter. Results on gel fraction further confirmed the crosslinking of SMR/CNT nanocomposites upon radiation.     

Substituted pyridopyrimidinones. Part 5. Behavior of 2-hydroxy-4-oxo-4<Emphasis Type="Italic">H</Emphasis>-pyrido[1,2-<Emphasis Type="Italic">α</Emphasis>]pyrimidine-3-carbaldehyde in nucleophilic condensation reactions

Reactivity of 2-hydroxy-4-oxo-4H-pyrido[1,2-a]pyrimidine-3-carbaldehyde (I) towards N- and C-nucleophiles was described. A series of new enaminones II–III, Schiff’s base IV, and hydrazinomethylenediketones V–VIII and X were prepared in good yields. Cyclization of compounds X was achieved by an action of acetic acid to give pyrazolo[3,4-d]pyrido[1,2-a]pyrimidines XI. Base catalyzed Knoevenagel condensation of aldehyde I with some active methyl and methylene compounds led to a series of chalcone-like derivatives XII, XV, XVII, XX, XXIII, XXV, XXVII, XXIX, XXXI, XXXII, and XXXV, in fair yields. Cyclization of enones XII, XV, and XX with hydrazine gave novel heterocyclyl substituted pyrazoles XIII, XVII, and XXI, respectively. Pyrano[2,3-d]pyrido[1,2-a]pyrimidine-2,5-diones XXXIII, XXXIV, and XXXVI derivatives were obtained via cyclization of their respective enone derivatives.     

Ruthenium(II) complexes of azoimine and α-diimine ligands: synthesis,spectroscopic and electrochemical properties,crystal structures and DFT calculations

Five octahedral ruthenium(II) complexes with azoimine–quinoline (Azo) and α-diimine (L) ligands having the general formula [Ru^II(L)(Azo)Cl](PF₆) (1–5) {Azo: PhN=NC(COMe)=NC₉H₆N, L = 4,4′-dimethoxy-2,2′-bipyridine (dmeb) (1), 4,4′-di-tertbutyl-2,2′-bipyridine (dtb) (2), 1,10-phenanthroline (phen) (3), 5-chlorophenanthroline (Clphen) (4), or 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen) (5)} were prepared by stepwise addition of the tridentate azoimine (H₂Azo) and α-diimine (L) pro-ligands to RuCl₃ in refluxing EtOH. The tridentate azoimine–quinoline ligands coordinate to ruthenium via the Azo-N′, N′-imine and N″-quinolone nitrogen atoms. The spectroscopic properties (IR, UV/Vis, ¹H, ¹³C and ¹⁹F NMR) and electrochemical behavior of complexes 1–5 and the X-ray crystal structures of complexes 2 and 3 are presented. The coordination of Ru(II) to these strong π-acceptor ligands (Azo and L) results in a large anodic shift for the Ru(III/II) couples of 1.63–1.72 V versus NHE. The electronic spectra in MeCN and IR spectra in CH₂Cl₂ for complex 3 in its oxidized 3 ⁺ and reduced 3 ^? forms were investigated. The calculated absorption spectrum of 3 in MeCN was used to assign the UV–Vis absorption bands.     

Enantiopure Ferrocene‐Based Planar‐Chiral Iridacycles: Stereospecific Control of Iridium‐Centred Chirality

Reaction of [IrCp*Cl₂]₂ with ferrocenylimines (Fc=NAr, Ar=Ph, p‐MeOC₆H₄) results in ferrocene C?H activation and the diastereoselective synthesis of half‐sandwich iridacycles of relative configuration S_p*,R_Ir*. Extension to (S)‐2‐ferrocenyl‐4‐(1‐methylethyl)oxazoline gave highly diastereoselective control over the new elements of planar chirality and metal‐based pseudo‐tetrahedral chirality, to give both neutral and cationic half‐sandwich iridacycles of absolute configuration S_c,S_p,R_Ir. Substitution reactions proceed with retention of configuration, with the planar chirality controlling the metal‐centred chirality through an iron–iridium interaction in the coordinatively unsaturated cationic intermediate.     

Catalytic enantioselective domino oxa-michael/aldol condensations: asymmetric synthesis of benzopyran derivatives

The first direct organocatalytic asymmetric domino oxa-Michael/aldol condensation reaction is presented. The unprecedentedly simple, chiral, pyrrolidine-catalyzed asymmetric domino reactions between salicylic aldehyde derivatives and alpha,beta-unsaturated aldehydes proceed with high chemo- and enantioselectivities to give the corresponding chromene-3-carbaldehyde derivatives in high yields and with ee values of 83-98%.     

Development of multiplex loop mediated isothermal amplification (m-LAMP) label-based gold nanoparticles lateral flow dipstick biosensor for detection of pathogenic Leptospira

In recent years extensive numbers of molecular diagnostic methods have been developed to meet the need of point-of-care devices. Efforts have been made towards producing rapid, simple and inexpensive DNA tests, especially in the diagnostics field. We report on the development of a label-based lateral flow dipstick for the rapid and simple detection of multiplex loop-mediated isothermal amplification (m-LAMP) amplicons. A label-based m-LAMP lateral flow dipstick assay was developed for the simultaneous detection of target DNA template and a LAMP internal control. This biosensor operates through a label based system, in which probe-hybridization and the additional incubation step are eliminated. We demonstrated this m-LAMP assay by detecting pathogenic Leptospira, which causes the re-emerging disease Leptospirosis. The lateral flow dipstick was developed to detect of three targets, the LAMP target amplicon, the LAMP internal control amplicon and a chromatography control. Three lines appeared on the dipstick, indicating positive results for all representative pathogenic Leptospira species, whereas two lines appeared, indicating negative results, for other bacterial species. The specificity of this biosensor assay was 100% when it was tested with 13 representative pathogenic Leptospira species, 2 intermediate Leptospira species, 1 non-pathogenic Leptospira species and 28 other bacteria species. This study found that this DNA biosensor was able to detect DNA at concentrations as low as 3.95 × 10⁻¹ genomic equivalent ml⁻¹. An integrated m-LAMP and label-based lateral flow dipstick was successfully developed, promising simple and rapid visual detection in clinical diagnostics and serving as a point-of-care device.