Publications by authors named "Ahmed Najari"

New aromatic compounds with a pyridazine core have been synthesized. Four electron-withdrawing monomers have been easily prepared from simple condensation reactions and ring closure procedures. Optimized HOMO, LUMO, and bandgap energy levels have been obtained.

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A new low-band-gap thieno[3,4-c]pyrrole-4,6-dione-based copolymer, PBDTTPD, has been designed and synthesized. PBDTTPD is soluble in chloroform or o-dichlorobenzene upon heating and shows a broad absorption in the visible region. The HOMO and LUMO energy levels were estimated to be at -5.

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Two new low-bandgap block copolymers derived from dithienylbenzothiadiazole (DTBT) and different electron-rich functional groups (dioctoxyl benzene and N-octyl-diphenylamine), poly(1,4-dioctoxyl-2,5-divinylbenzene-co-4,7-dithiophene-2'-yl-2,1,3-benzothiadiazole) (PPV-DTBT), poly(3,8-divinyl-N-octyl-diphenylamine-co-4,7-dithiophene-2'-yl-2,1,3-benzothiadiazole) (PDPAV-DTBT), were synthesized by Heck cross-coupling polymerization. PPV-DTBT and PDPAV-DTBT are easily soluble in common organic solvents such as o-dichlorobenzene and chloroform. DSC and TGA results indicate that these copolymers possess good thermal stabilities.

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In recent years, intense research has been carried out worldwide with the goal of developing simple, sensitive, and specific detection tools for biomedical applications. Along these lines, we reported in 2002 on cationic polythiophene derivatives able to provide ultrasensitive detection levels and the capability to distinguish perfect matches from oligonucleotides having as little as a single base mismatch. It was shown that the intrinsic fluorescence of the random-coil polymers quenches as a result of the planar, highly conjugated conformation adopted by the polymers when complexed with a single-strand DNA (ssDNA) capture probe but increases again after hybridization with the perfectly matched complementary strand.

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Self-assembled molecular structures immobilized on solid substrates and composed of fluorophore-tagged oligonucleotide probes and an optical polymeric transducer were investigated for the trace level detection of DNA target molecules. Rapid and efficient energy transfer between the polymeric transducer and fluorophores within the molecular aggregates leads to a massive intrinsic amplification of the fluorescence signal and to the label-free detection of as little as 300 DNA molecules, with the specificity required for the detection of single-nucleotide mismatches. This capacity for attomolar detection levels while the sensing structures are attached onto solid supports could lead to the development of biochip platforms for fast and simple PCR-free multitarget DNA detection.

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