A new chromo-fluorogenic sensing protocol for anionic surfactants in aqueous environments using silica functionalised nanoparticles containing imidazolium and thiol groups has been developed. 相似文献
Excited-state interactions between (S)- or (R)-flurbiprofen ((S)- or (R)-FBP) and thymidine (dThd) covalently linked in dyads 1 or 2 have been investigated. In both dyads, the only emitting species is (1)FBP*, but with a lower fluorescence quantum yield (?(F)) and a shorter fluorescence lifetime (τ(F)) than when free in solution. These results indicate that dynamic quenching occurs either by electron transfer or via exciplex formation, with FBP as the charge-donating species. In acetonitrile, both mechanisms are favored, while in dioxane exciplex formation is predominating. Isomer 1 displays lower values of ?(F) and τ(F) than its analogue 2, indicating that the relative spatial arrangement of the chromophores plays a significant role. The triplet quantum yields (?(T)) of 1 and 2 are significantly higher than the expectations based solely on (1)FBP*-dThd intersystem crossing quantum yields (?(ISC)), with ?(T) (1) > ?(T) (2). This can be explained in terms of intramolecular charge recombination at the radical ion pairs and/or the exciplexes, which would be again dependent on geometrical factors. The triplet lifetimes (τ(T)) of (3)FBP*-dThd and free (3)FBP* are similar, indicating the lack of excited-state interactions at this stage. The FBP-dThd dyads could, in principle, constitute appropriate model systems for the elucidation of the excited-state interactions in noncovalent DNA-ligand complexes. 相似文献
Substituted 1,5‐benzodiazepines are selectively synthesized in one pot from substituted nitroaromatics and ketones. The reaction is performed in the presence of hydrogen and in the absence of solvent by using a bifunctional solid catalyst with a chemoselective hydrogenation functional group capable of reducing the nitro group to a diamino group and an acid functional group, which catalyzes the cyclocondensation of the amino group with the ketone. 相似文献
The Pr2BaCuO5 oxide has been prepared by using a precursor method. X‐ray and neutron diffraction data reveal that this mixed oxide crystallizes with the so‐called Nd2BaPtO5‐type structure, showing tetragonal symmetry and space group P4/mbm. Magnetic susceptibility, magnetization and specific heat measurements reveal that Pr2BaCuO5 oxide behaves as antiferromagnet, where the Pr3+ and Cu2+ sublattices become simultaneously ordered at 15 K. Preliminary neutron diffraction studies confirm this proposed antiferromagnetic ordering and it can be described by the wave vector k = [0,0,0]. 相似文献
The Ritter reaction of enantiopure 2-(1-aminoalkyl)aziridines 1 with different nitriles afford enantiopure tetrasubstituted imidazolines 2. The opening of the aziridine ring takes place with total regio- and stereoselectivity. A mechanism to explain the described addition reaction is proposed. [reaction: see text] 相似文献
An intelligent and versatile flow system is proposed for the in-line speciation and/or concentration of metal ions at a wide range of concentrations without requiring manifold reconfiguration. On one hand, sample enrichment strategies are accomplished using packed-bed reactors, on the other hand speciation procedures are readily performed exploiting the selective complexation of the different oxidation states with the appropriate chromogenic reagents.
The potentials of the automated methodology were evaluated using the spectrophotometric monitoring of iron as a model of chemistry. Under the optimised physical and chemical variables, linear analytical curves over the ranges 0.025–0.5 or 2.0–40 mg l−1 Fe were attained. The 3σ detection limit, the repeatability at the 0.5 mg l−1 level, the enrichment factor for a sampling volume of 10 ml, and the maximum injection throughput were 8.4 ng ml−1 Fe, 2.5%, 58.6 and 22 h−1, respectively. The flowing system was applied to the speciation analysis of iron in waters, pharmaceutical formulations and agricultural products, using ICP-OES detection as an external reference method for total iron determination.
A remarkable feature of the expert system hereby presented is the ability to decide by itself if the pre-concentration and/or oxidation of the sample zone is required. 相似文献