Visible light photoelectrochemical sensor for ultrasensitive determination of dopamine based on synergistic effect of graphene quantum dots and TiO2 nanoparticles

We have demonstrated a facile approach for fabricating graphene quantum dots–TiO₂ (GQDs–TiO₂) nanocomposites by a simple physical adsorption method. Compared with pure GQDs and TiO₂ nanoparticles (NPs), the as-prepared GQDs–TiO₂ nanocomposites showed enhanced photoelectrochemical (PEC) signal under visible-light irradiation. The photocurrent of GQDs–TiO₂/GCE was nearly 30-fold and 12-fold enhancement than that of GQDs/GCE and TiO₂/GCE, respectively, which was attributed to the synergistic amplification between TiO₂ NPs and GQDs. More interestingly, the photocurrent of GQDs–TiO₂ nanocomposites was selectively sensitized by dopamine (DA), and enhanced with the increasing of DA concentration. Further, a new PEC methodology for ultrasensitive determination of DA was developed, which showed linearly enhanced photocurrent by increasing the DA concentration from 0.02 to 105 μM with a detection limit of 6.7 nM (S/N = 3) under optimized conditions. This strategy opens up a new avenue for the application of GQDs-based nanocomposites in the field of PEC sensing and monitoring.     

Immobilization of glucose oxidase based on the sodium alginate-modified products of a functionalized metal organic framework and the application for one-pot analysis of glucose

A self-assembled functionalized metal-organic framework, Zn₄O(NH₂BDC)₃ microcrystalline (IRMOF3) could be prepared by washing complex with DMF and CH₂Cl₂. Via modification with sodium alginate (AA), IRMOF3-AA samples could be obtained. IR and TEM were used for structural confirmation of IRMOF3-AA samples. PEG-GOD could be obtained via PEGylation of glucose oxidase (GOD), which could be confirmed by X-ray photoelectron spectroscopy (XPS) and used for further application. IRMOF3-AA@PEG-GOD samples could be obtained by the immobilization of PEG-GOD to IRMOF3-AA, and the best immobilization condition was achieved by adjusting the amount of GOD. From the view point of enzyme mimics, combined with peroxidase-like properties of the IRMOFS-AA samples, the determination of glucose was demonstrated with a linear range from 5?×?10^?5 mol/L to 1.6?×?10^?3 mol L^?1 using tetramethylbenzidine (TMB) as chromogenic substrate. The prepared IRMOF3-AA@PEG-GOD samples exhibited dual functional enzyme-like (peroxidase and GOD-like) activities, with simple experimental steps.

     

Syntheses and characterization of carbazole based new low‐band gap copolymers containing highly soluble benzimidazole derivatives for solar cell application

Newly designed 2H‐benzimidazole derivatives which have solubility groups at 2‐position have been synthesized and incorporated into two highly soluble carbazole based alternating copolymers, poly[2,7‐(9‐(1′‐octylnonyl)‐9H‐carbazole)‐alt‐5,5‐(4′,7′‐di(thien‐2‐yl)‐2H‐benzimidazole‐2′‐spirocyclohexane)] (PCDTCHBI) and poly[2,7‐(9‐(1′‐octylnonyl)‐9H‐carbazole)‐alt‐5,5‐(4′,7′‐di(thien‐2‐yl)‐2H‐benzimidazole‐2′‐spiro‐4′′‐((2′′′‐ethylhexyl)oxy)‐cyclohexane)] (PCDTEHOCHBI) for photovoltaic application. These alternating copolymers show low‐band gap properties caused by internal charge transfer from an electron‐rich unit to an electron‐deficient moiety. HOMO and LUMO levels are –5.53 and –3.86 eV for PCDTCHBI, and –5.49 and –3.84 eV for PCDTEHOCHBI, respectively. Optical band gaps of PCDTCHBI and PCDTEHOCHBI are 1.67 and 1.65 eV, respectively. The new carbazole based the 2H‐benzimidazole polymers show 0.11–0.13 eV lower values of band gaps as compared to that of carbazole based benzothiadiazole polymer, poly[N‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT), while keeping nearly the same deep HOMO levels. The power conversion efficiencies of PCDTCHBI and PCDTEHOCHBI blended with [6,6]phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) are 1.03 and 1.15%, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Catalytic application of sulfonic acid‐functionalized titana‐coated magnetic nanoparticles for the preparation of 1,8‐dioxodecahydroacridines and 2,4,6‐triarylpyridines via anomeric‐based oxidation

We have developed green, efficient and powerful protocols for the preparation of 2,4,6‐triarylpyridines and 1,8‐dioxodecahydroacridines in the presence of Fe₃O₄@TiO₂@O₂PO₂(CH₂)₂NHSO₃H as a sulfonic acid‐functionalized titana‐coated magnetic nanoparticle catalyst under mild and solvent‐free reaction conditions. These protocols furnished the desired products in short reaction times with good to high yields (20–40 min and 80–86% in the case of 2,4,6‐triarylpyridines; 15–90 min and 80–93% in the case of 1,8‐dioxodecahydroacridines). The final step of the mechanistic route in the synthesis of 2,4,6‐triarylpyridines proceeds via an anomeric‐based oxidation. Also, the nanomagnetic core–shell catalyst can be recycled and reused in both cases of the scrutinized one‐pot multicomponent reactions with high turnover number and turnover frequency.