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Bi 2 S 3 nanorods anchored over reduced graphene oxide (rGO/Bi 2 S 3 ) were successfully synthesized via a one-pot hydrothermal process, where in-situ generation of Bi 2 S 3 nanorods and reduction of GO occurred simultaneously. Moreover, the controlled synthesis of rGO/Bi 2 S 3 nanocomposite with tunable size was achieved by adjusting the dosage of GO. The nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy, respectively. Because of the particular construction of as-prepared nanocomposite and the synergistic effect between rGO sheets and Bi 2 S 3 nanorods, the rGO/Bi 2 S 3 film can effectively accelerate electron transport and extend catalytic active sites, leading to the remarkable electrochemical performance for dopamine sensing. The rGO/Bi 2 S 3 -1/GCE sensor exhibited excellent electrocatalytic activity toward the dopamine oxidation with a wide linear range of 0.01–40 μM and a low detection limit of 12.3 nM. Furthermore, the as-prepared sensor could be feasibly applied to detect dopamine in urine samples. Hence, the prepared rGO/Bi 2 S 3 composite is one of the low cost, extremely promising and nontoxicity materials for electrocatalysis and relevant fields. [ABSTRACT FROM AUTHOR]

A polymerized film of copper-2-amino-5-mercapto-1,3,4-thiadiazole (Cu(II)-AMT) complex (poly(Cu-AMT)) was successfully achieved via a simple and low-cost electrochemical methodology. Subsequently, a noncovalent nanohybrid of poly(Cu-AMT) with reduced graphene oxide (rGO) (rGO-poly(Cu-AMT)) was prepared through π–π stacking interaction as an efficient mimetic enzyme for the ultrasensitive and selective detection of dopamine (DA). The rGO-poly(Cu-AMT) nanocomposites showed considerable mimetic enzyme catalytic activity, which may be attributed to the significant promotion of the electron transfer between the substrate and graphene-based carbon materials, and also the synergistic electrocatalytic effect in mimetic enzyme between rGO sheet and poly(Cu-AMT). The electrocatalytic and sensing performances of the biomimetic sensor based on the rGO-poly(Cu-AMT) nanocomposites were evaluated in detail. The biomimetic sensor enables a reliable and sensitive determination of DA with a linear range of 0.01–40 μM and a detection limit of 3.48 nM at a signal-to-noise ratio of 3. In addition, we applied the proposed method to detect DA in real sample with satisfactory results. Accordingly, the rGO-poly(Cu-AMT) is one of the promising mimetic enzyme for electrocatalysis and biosensing. [ABSTRACT FROM AUTHOR]

In this paper, linking with the butoxycarbonyl (BOC) protection of proline, a new tailed metalloporphyrin with many useful active functions, nickel (II) 5-[4-N-(tert-Butoxycarbonyl)- l -prolinecoxylpropyloxy]phenyl-10,15,20-triphenylporphyrin (NiTBLPyP), was designed and synthesized. And the NiTBLPyP polymer (poly(NiTBLPyP)) was successfully obtained via a low-cost electrochemical method and exploited as an efficient mimic enzyme. Subsequently, a noncovalent nanohybrid of poly(NiTBLPyP) with graphene (rGO) sheet (rGO-poly(NiTBLPyP)) was prepared through π–π stacking interaction for the ultrasensitive and selective detection of DA. The nanohybrid was characterized by UV–vis spectroscopy, Fourier transform infrared spectra, Raman spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopy. Due to the excellent electrocatalytic ability of poly(NiTBLPyP) film and aromatic π–π stacking interaction between poly(NiTBLPyP and rGO sheet, the obtained rGO-poly(NiTBLPyP) film exhibited a great synergistic amplification effect toward dopamine oxidation. Under optimum experimental conditions, the logarithm of catalytic currents showed a good linear relationship with that of the dopamine concentration in the range of 0.01–200 μM with a low detection limit of 1.40 nM. With good sensitivity and selectivity, the present method was applied to the determination of DA in real sample and the results was satisfactory. Thus, the rGO-poly(NiTBLPyP) film is one of the promising mimetic enzyme for electrocatalysis and relevant fields. [ABSTRACT FROM AUTHOR]

Electrochemical detection of dopamine (DA) plays an important role in medical diagnosis. In this paper, tremella-like graphene–Au (t-GN–Au) composites were synthesized by a one-step hydrothermal method for selective detection of DA. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy were used to characterize as-prepared t-GN–Au composites. The t-GN–Au composites were directly used for the determination of DA via cyclic voltammetry (CV) and the chronoamperometry (CA) technique. CA measurement gave a wide linear range from 0.8 to 2000 μM, and the detection limit of 57 nM (S/N = 3) for DA. The mechanism and the heterogeneous electron transfer kinetics of the DA oxidation were discussed in the light of rotating disk electrode (RDE) experiments. Moreover, the modified electrode was applied to the determination of DA in human urine and serum samples. [ABSTRACT FROM AUTHOR]

β-Cyclodextrin functionalized graphene/Ag nanocomposite (β-CD/GN/Ag) was prepared via a one-step microwave treatment of a mixture of graphene oxide and AgNO3. β-CD/GN/Ag was employed as an enhanced element for the sensitive determination of 4-nitrophenol. A wide linear response to 4-nitrophenol in the concentration ranges of 1.0×10−8-1.0×10−7 mol/L, and 1.0×10−7-1.5×10−3 mol/L was achieved, with a low detection limit of 8.9×10−10 mol/L ( S/N=3). The mechanism and the heterogeneous electron transfer kinetics of the 4-nitrophenol reduction were discussed according to the rotating disk electrode experiments. Furthermore, the sensing platform has been applied to the determination of 4-nitrophenol in real samples. [ABSTRACT FROM AUTHOR]

• A kind of NS@GO core-shell nanoparticles was synthesized and firstly applied to reinforce cementitious materials. • The incorporation of NS@GO could more effectively enhance the mechanical property of cement composites. • A hypothesis named sandwich effect was proposed to explain the reinforcing results of NS@GO. Graphene oxide (GO) has enormous potential to improve properties of cementitious materials. Well dispersed GO in hardened cement matrix could be more effective in strengthening concrete compared to aggregated GO. While GO agglomeration is somewhat inevitable due to its fine nature, the degree of agglomeration could be tuned through particle separation. In this study, nanoSiO 2 @graphene-oxide (NS@GO) nanoparticles were synthesized using GO and colloid nanoSiO 2 (NS) by a electrostatic self-assembly method. NS, GO and the prepared NS@GO were characterized by x-ray diffraction, scanning electron microscopy, atomic force microscopy, and Fourier transmission infrared, and, the influence of NS@GO addition on the mechanical properties of cementitious composites was investigated. The results show that NS@GO can increase the flexural strength of cement composites by 49.2% at later age. A "sandwich effect" was proposed as an important reinforcing mechanism of NS@GO based on the microstructure and hydration products of NS@GO added composites. Compared with the simple NS-GO blend, NS@GO can better maintain the spatial structure of GO when mixed with cement. In addition, there would be more interactions between calcium silicate hydrates and GO during the cement hydration process, which contributes to the strength gain in NS@GO added mix. The research sheds new light on using GO and NS to optimize cementitious material design, as well as spatial coordination of different types of nanoparticles. [ABSTRACT FROM AUTHOR]

An antifouling electrochemical aptasensor for ATP is described that has a zwitterionic self-assembled sensing interface on a glassy carbon electrode modified with a reduced graphene oxide carbon nanofiber (GO-CNF). The GO-CNF was first modified by self-polymerization of dopamine which provided a platform for simultaneously self-assembly of the ATP aptamer and cysteine. By using hexacyanoferrate as the electrochemical probe, in the presence of ATP, the aptamer strands fold around ATP molecules, thus leading to the variation of the electrochemical signal. The aptasensor has a linear response in the 0.1 pM to 5 nM ATP concentration range, and a 13 fM lower detection limit. The electrode is strongly resistant to nonspecific adsorption and biofouling. This enabled the detection of ATP even in spiked human plasma. Graphical abstract An antifouling electrochemical aptasensor employing reduced graphene oxide carbon nanofiber as conductive substrate and zwitterionic cysteine as antifouling material for adenosine triphosphate detection. [ABSTRACT FROM AUTHOR]

One-pot green approach to the synthesis of Prussian blue nanocubes/reduced graphene oxide (PBNCs/RGO) nanocomposite had been attempted. It was based on the extract of mushroom with K 3 [Fe(CN) 6 ] and graphene oxide (GO) as precursors, where the reduction of GO and the deposition of PBNCs occurred simultaneously. The obtained nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and electrochemical techniques. With the introduction of β-cyclodextrin (β-CD), the β-CD/PBNCs/RGO system showed linear behavior in the range from 0.01 to 700 μM for 4-nitrophenol with a low detection limit of 2.34 nM (S/N = 3). [ABSTRACT FROM AUTHOR]