Xiaohong Zhao

As well known, the electrochemiluminescence (ECL) of tris(2,2′-bipyridine)ruthenium(ii) (Ru(bpy)₃²⁺) heavily relies on highly positive or negative triggered voltage, prejudicing the detection toward the bio-molecules. In this work, Ru(bpy)₃²⁺ could generate enhanced and stable ECL at a low potential of 0.05 V (vs. Ag/AgCl) on graphene-PtPd hybrid, attributing to its excellent electrocatalysis from the synergistic effect between Pt and Pd. The obtained low-potential-driven ECL could be quenched by MoS₂ nanoflowers. Based on the quenching effect, a sandwich “signal-off” ECL immunosensor was fabricated to sensitively detect carcinoembryonic antigen (CEA). A linear calibration curve from 1 fg mL⁻¹ to 1 ng mL⁻¹ was obtained along with a low detection limit of 0.54 fg mL⁻¹ (S/N = 3) under optimal conditions. The sensor showed satisfactory specificity, stability, and reproducibility and was successfully applied to determine CEA in actual samples. The recoveries ranged from 98.80 to 100.23%, and the relative standard deviation (RSD) was lower than 5%. Above all, this work explored new materials in low-potential-driven ECL system and provided a reliable sensing strategy for clinical applications. Graphical abstract

Acylated lignins with substituents consisting of different lengths of carbon chains were prepared by a mechanical activation-assisted solid phase synthesis (MASPS) technology with a customized stirring ball mill as a reactor. The structures and properties were analyzed by UV/Vis, FTIR, NMR, SEM, DSC, and TG. The results showed that the acylated lignins were successfully prepared with either non-cyclic or cyclic anhydrides as the acylating agents. Both aliphatic hydroxyl and phenolic hydroxyl groups of lignin reacted with non-cyclic anhydrides, and different reactivity of acylating agents resulted in different relative contents of phenolic and aliphatic substituents in the products. The reactivity of the cyclic anhydrides was weaker than that of the non-cyclic anhydrides, and the reactivity of the acylating agents decreased with increasing carbon chain length and unsaturated bonds of acyl groups. All of the acylated lignins except maleylated lignin had a lower glass transition temperature (T_g) than the original lignin. The acylated lignins prepared with non-cyclic anhydrides had better thermal stability than original lignin, and the thermal stability increased, but T_g decreased with an increasing chain length of the acyl groups. The acylated lignins prepared with cyclic anhydrides had higher a T_g than those with non-cyclic anhydrides with the same carbon number, and the thermal stability was not obviously improved.

Excited state charge transfer coupled excited state double proton transfer (ESCT/ESDPT) reaction in methanol (MeOH) for 3-cyano-7-azaindole(3-CNAI), 5-cyano-7-azaindole(5-CNAI), and 3,5-dicyano-7-azaindole(3,5-CNAI) were investigated using time-dependent density functional theory (TDDFT) method for the first time. The intermolecular hydrogen bonds of 3-CNAI-MeOH, 5-CNAI-MeOH, and 3,5-CNAI-MeOH complexes are demonstrated to be strengthened in the excited state and weakened in tautomer excited state, which indicates that reverse proton transfer reaction is not easy to take place. Due to the formation of intermolecular hydrogen bond, the absorption and excited state fluorescence spectra of the above three complexes are red-shifted in comparison with those of isolated molecules. The tautomer excited state fluorescence spectra that are induced by ESDPT reaction are also red-shifted relative to the excited state fluorescence for the above complexes. In addition, the sites where cyano group absorbed on 7-azaindole induces a large discrepancy of electron density distribution in excited state. Frontier molecular orbitals reflect that HOMO and LUMO orbitals of proton transfer PT-3-CNAI-MeOH, PT-5-CNAI-MeOH, and PT-3,5-CNAI-MeOH complexes are different with HOMO and LUMO orbitals of 3-CNAI-MeOH, 5-CNAI-MeOH, and 3,5-CNAI-MeOH complexes, respectively.

Hindered alkyl aldehydes react with benzotriazole and ammonia in dry ethanol or methanol to yield the corresponding bis[1-(benzotriazol-1-yl)alkyl]amines 2. The reaction of aryl aldehydes, however, yields 1-(benzotriazol-1-yl)-N-alkylidenealkylamines 3. The reactions of adducts 2 and 3 with lithium aluminum hydride furnishes dialkyl- and dibenzylamine derivatives 4. Although the reactions of 2 and 3 with organometallic reagents are not as general, in several cases the reactions of amines 2 with Grignard reagents yield 1-alkyl or aryl substituted N-alkylidenealkylamines 5. Similar reactions of amines 2 with phenyl lithium afford 1,1′-diphenyldialkylamines 7.