Electrochemical synthesis of phosphorus and sulfur co-doped graphene quantum dots as efficient electrochemiluminescent immunomarkers for monitoring okadaic acid

Abstract(#br)In this study, water-dispersed, uniform-sized phosphorus and sulfur co-doped graphene quantum dots (P, S-GQDs) were prepared by the one-step electrolysis of a graphite rod in an alkaline solution containing sodium phytate and sodium sulfide. Compared with GQDs and mono-doped GQDs (P-GQDs and S-GQDs), the P, S-GQDs dramatically improved the electrochemiluminescence (ECL) performance. Therefore, they were used as bright ECL signaling markers through conjugation with a monoclonal antibody against okadaic acid (anti-OA-MAb). Moreover, as an effective matrix for OA immobilization, the carboxylated multiwall carbon nanotubes-poly(diallyldimethylammonium) chloride-Au nanocluster (CMCNT-PDDA-AuNCs) composite promoted electron transfer and enlarged the surface area. Owing to the multiple amplifications, a competitive indirect ECL immunosensor for highly sensitive quantitation of OA has been developed. Under the optimized conditions, the 50% inhibitory concentration (IC 50 ) of the immunosensor was 0.25 ng mL −1 , and its linear range was 0.01–20 ng mL −1 with a low detection limit of 0.005 ng mL −1 . Finally, the proposed ECL sensor was successfully utilized to detect OA contents in mussel samples. Therefore, this study provides new insights into the designation of ECL luminophores and expands application of co-doped GQDs in fabrication of ECL immunosensors for shellfish toxin determination

Au nanoparticles on citrate-functionalized graphene nanosheets with a high peroxidase-like performance

Japan Society for Promotion of Science (JSPS); National Natural Science Foundation of China [21305050]; Special Foundation for Young researchers of Health Department of Fujian [2013-2-106]; Scientific Research Foundation of Shangda Li, Jimei University [ZC2013005]; JSPS KAKENHI [2402335, 24550100]In this paper, Au nanoparticles (AuNPs) have been homogeneously deposited on citrate-functionalized graphene nanosheets (Cit-GNs) by a simple one-pot reducing method. The morphology and composition of the thus-prepared AuNPs/Cit-GNs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results showed that the AuNPs with a uniform size are well dispersed on the surface of the Cit-GNs. Significantly, the as-prepared AuNPs/Cit-GNs possess intrinsic peroxidase-like activity, which can catalyze the oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) to develop a blue color in aqueous solution. The catalysis was in accordance with Michaelis-Menten kinetics and the AuNPs/Cit-GNs showed a strong affinity for both H2O2 and TMB. Moreover, by comparing with Cit-AuNPs, AuNPs/GNs and AuNPs/PVP-GNs, the AuNPs/Cit-GNs composite exhibits a higher catalytic ability with a lower Michaelis constant (Km) value, suggesting that the GNs with a large surface area and the citrate ions with more carboxyl groups around the AuNPs can greatly enhance the peroxidase-like activity of AuNPs/Cit-GNs. Taking the advantages of the high catalytic activity, the good stability and the low cost, the novel AuNPs/Cit-GNs represent a promising candidate as an enzyme mimic and may find a wide range of new applications in biochemistry and biotechnology

PtPd nanodendrites supported on graphene nanosheets: A peroxidase-like catalyst for colorimetric detection of H2O2

Japan Society for the Promotion of Science (JSPS) for the fellowship; National Natural Science Foundation of China [21305050]; Special Foundation for Young Researchers of the Health Department of Fujian [2013-2-106]; Scientific Research Foundation of the Education Department of Fujian [FB2013006]; JSPS KAKENHI [24.02335, 24550100]Well-dispersed PtPd nanodendrites on graphene nanosheets (PtPdNDs/GNs) were synthesized by a simple and green method with the reduction of ethanol. The morphology, structure and composition of the thus-prepared PtPdNDs/GNs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Furthermore, the peroxidase-like catalytic ability of PtPdNDs/GNs was studied and it is interesting that the PtPdNDs/GNs can efficiently catalyze the classical peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). By comparing with mono Pt nanoflowers (NFs)/GNs, Pd nanoparticles (NPs)/GNs, bimetallic PtPd nanoalloys (NAs)/GNs and core-shell Pd@PtNFs/GNs, the PtPdNDs/GNs showed a stronger affinity for TMB with a lower Michaelis-Menten constant (Km) value at an optimum pH of 4.4. Take the advantage of the high catalytic activity, the as-prepared PtPdNDs/GNs was used to develop a novel colorimetric sensor for H2O2 with fast response, wide linear range (0.5-150 mu M) and low detection limit (0.1 mu M). The rapid, simple and sensitive TMB-H2O2-PtPdND5/GN5 sensing platform shows great promising applications in the pharmaceutical, clinical and industrial detection of H2O2. (C) 2014 Elsevier B.V. All rights reserved

PtPd nanodendrites supported on graphene nanosheets: A peroxidase-like catalyst for colorimetric detection of H2O2

Japan Society for the Promotion of Science (JSPS) for the fellowship; National Natural Science Foundation of China [21305050]; Special Foundation for Young Researchers of the Health Department of Fujian [2013-2-106]; Scientific Research Foundation of the Education Department of Fujian [FB2013006]; JSPS KAKENHI [24.02335, 24550100]Well-dispersed PtPd nanodendrites on graphene nanosheets (PtPdNDs/GNs) were synthesized by a simple and green method with the reduction of ethanol. The morphology, structure and composition of the thus-prepared PtPdNDs/GNs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Furthermore, the peroxidase-like catalytic ability of PtPdNDs/GNs was studied and it is interesting that the PtPdNDs/GNs can efficiently catalyze the classical peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). By comparing with mono Pt nanoflowers (NFs)/GNs, Pd nanoparticles (NPs)/GNs, bimetallic PtPd nanoalloys (NAs)/GNs and core-shell Pd@PtNFs/GNs, the PtPdNDs/GNs showed a stronger affinity for TMB with a lower Michaelis-Menten constant (Km) value at an optimum pH of 4.4. Take the advantage of the high catalytic activity, the as-prepared PtPdNDs/GNs was used to develop a novel colorimetric sensor for H2O2 with fast response, wide linear range (0.5-150 mu M) and low detection limit (0.1 mu M). The rapid, simple and sensitive TMB-H2O2-PtPdND5/GN5 sensing platform shows great promising applications in the pharmaceutical, clinical and industrial detection of H2O2. (C) 2014 Elsevier B.V. All rights reserved

Platinum nanoflowers supported on graphene oxide nanosheets: their green synthesis, growth mechanism, and advanced electrocatalytic properties for methanol oxidation

National Basic Research Program of China [2010CB732402]; National Natural Science Foundation of China [21175112, 20975085]; NFFTBS [J1030415]This paper reports a nontoxic, rapid, one-pot and template-free synthesis of three-dimensional (3D) Pt nanoflowers (PtNFs) with high yield and good size monodispersity supported on graphene oxide (GO) nanosheets. The key synthesis strategy employed a low-cost, green solvent, ethanol as the reductant and an advanced, powerful 2D carbon material, GO nanosheets as the stabilizing material. The resulting PtNFs-GO nanosheets were characterized by transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. It was found that the monodispersed, porous PtNFs supported on GO nanosheets were a uniform size of 30 nm and each was composed of numerous "clean'' and small (4 nm) Pt nanoparticles, which revealed an unusually high activity for methanol oxidation reaction compared to commercial Pt black. Furthermore, based on a systematic study of the PtNFs growth conditions, a possible mechanism, and especially the importance of GO in the formation was proposed. Our study demonstrates that GO is a promising support material for developing next-generation advanced Pt based fuel cells and their relevant electrodes in the field of energy

Flexible Method for Generating Arbitrary Vector Beams Based on Modified Off-Axis Interference-Type Hologram Encoding

A novel experimental setup for the generation of arbitrary vector beams is proposed. The system major includes two reflective liquid crystal spatial light modulators (RLC-SLM) and a polarizing beam splitting prism. Moreover, this method is not limited by the wavelength of light wave and the pixel size of SLM. Theoretical analysis shows that when Gaussian beam or a plane beam is illuminated on a computer-generated hologram (CGH) specially designed in this work, the complex amplitudes of the vector field’s two orthogonal polarization components may be changed by modifying the encoding parameters, resulting in a vector beam with arbitrary complex amplitude and polarization in the output field. The experimental results also show that the two independent coding channels of the device have good polarization-selective imaging ability, which greatly improves the flexibility of generating arbitrary vector beams

Platinum nanoflowers supported on graphene oxide nanosheets: Their green synthesis, growth mechanism, and advanced electrocatalytic properties for methanol oxidation

This paper reports a nontoxic, rapid, one-pot and template-free synthesis of three-dimensional (3D) Pt nanoflowers (PtNFs) with high yield and good size monodispersity supported on graphene oxide (GO) nanosheets. The key synthesis strategy employed a low-cost, green solvent, ethanol as the reductant and an advanced, powerful 2D carbon material, GO nanosheets as the stabilizing material. The resulting PtNFs-GO nanosheets were characterized by transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. It was found that the monodispersed, porous PtNFs supported on GO nanosheets were a uniform size of 30 nm and each was composed of numerous 'clean' and small (4 nm) Pt nanoparticles, which revealed an unusually high activity for methanol oxidation reaction compared to commercial Pt black. Furthermore, based on a systematic study of the PtNFs growth conditions, a possible mechanism, and especially the importance of GO in the formation was proposed. Our study demonstrates that GO is a promising support material for developing next-generation advanced Pt based fuel cells and their relevant electrodes in the field of energy. 漏 2012 The Royal Society of Chemistry