The colorimetric biosensors have attracted intensive interest; however, their relatively low sensitivity limits their applications in clinic detection. Herein, we develop an effective colorimetric biosensor based on highly catalytic active Au nanoparticle-decorated Bi2Se3 (Au/Bi2Se3) nanosheets. Au/Bi2Se3 nanosheets are facilely synthesized by simply sonicating Au precursor with the as-synthesized Bi2Se3 nanosheets in aqueous solution. Because of the low redox potential and typical topological insulating properties, Bi2Se3 nanosheets is capable of providing and accumulating electrons on its surface. Such unique properties of Bi2Se3 nanosheets contribute to strong synergistic catalytic effects with Au nanoparticles, particularly when Au/Bi2Se3 nanosheets are utilized for catalyzing the reduction of 4-nitrophenol (4-NP) by NaBH4 (K = 386.67 s–1g–1). The excellent catalytic activity of Au/Bi2Se3 nanosheets can be “switched off” upon treatment of antibody of cancer biomarker such as anticarcinoembryonic antibody (anti-CEA). Addition of the corresponding antigen such as cancer biomarker carcinoembryonic antibody (CEA) can successively help “switch on” the catalytic activity of Au/Bi2Se3 nanosheets, where the resuming degree however depends on the antigen concentration. This cancer biomarker depended catalytic behavior therefore allows Au/Bi2Se3 nanosheets to be employed as a colorimetric sensor for detection of a particular cancer biomarker, for the reduction of 4-nitrophenol (4-NP) by NaBH4 itself involves apparent color change. The sensor shows high sensitivity and selectivity for the cancer biomarker, even for a concentration as low as 160 pg/mL for CEA, which fully satisfies the requirement for real clinical applications. The developed colorimetric sensor shows good generality for detection of different types of cancer biomarkers, such as α-fetoprotein (AFP) and prostate-specific antigen (PSA). Furthermore, real clinic sample analyzing result shows that the prepared biosensor is efficient for detection of CEA, providing an alternative method in cancer diagnosis.Keywords: 2D nanomaterials; cancer diagnosis; catalysis-based colorimetric biosensor; hybrid nanomaterials; topological insulator;

•Hollow NiPd catalysts with nanochannels were synthesized successfully.•Pd loading of HNiPd catalyst can easily controlled by varying the PdCl2 content.•The HNiPd catalyst showed high catalytic activity for ethanol oxidation.In this work, bimetallic NiPd hollow nanoporous (HNiPd) catalysts are prepared by in-situ deposition of Pd nanoparticles (Pd NPs) on hollow Ni (HNi) microspheres. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) reveal the hollow nanoporous essence of HNiPd catalysts. Meanwhile, using high-angle annular dark-field scanning TEM (HAADF-STEM) and elemental mapping, it is found that tiny dendritic-like NiPd nanocomposites attach on the exterior of microspheres. The content of Pd is easily tailored to constitute HNiPd catalysts with different Ni/Pd atomic ratios. Further electrochemical evaluation vindicates that the as-prepared HNiPd catalysts have a good catalytic activity and stability toward ethanol oxidation reaction (EOR) in alkaline medium. Notably, the peak current density of HNi3.1Pd catalyst and the chronoamperometric current density of HNi4.6Pd catalyst are 4 and 2 times of Pd/C (JM) catalyst, respectively, which show that HNiPd catalysts hold great potential in application of alkaline direct ethanol fuel cells (DEFCs).Download high-res image (303KB)Download full-size image

•The NixSy@CoS double-shelled polyhedral nanocages are prepared by a facile method.•The NixSy@CoS nanocages are amorphous and have a typical 3D hollow structure.•The nanocages have a homogenous microstructure and size distribution about 700 nm.•The nanocages display remarkable specific capacitance of 2091 F g−1 at 2 A g−1.•The nanocages have excellent long-term cycle-life as an electrode material.The design and development of durable and high efficient supercapacitors is highly desired in electronic and energy storage devices. Traditional carbon based capacitors suffer from low specific capacitance and energy density. Recently transition metal sulfides are attractive alternatives for crystal electrode materials. Herein we demonstrate a facial design and synthetic method to grow novel metal sulfide double-shelled polyhedral nanocages consisting of mesoporous amorphous NixSy@CoS via a metal-organic-framework engaged strategy for use in supercapacitors. The NixSy@CoS polyhedrons with the inner and outer-shells respectively consisting of CoS and NixSy are obtained at mild room temperature without further thermal-treatment. The outer-shell is easily adjustable to suit various combinations according to the requirement. The morphological and structural evolution of the NixSy@CoS nanocages was studied systematically. Further electrochemical performance shows that the NixSy@CoS exhibits remarkably high capacitance of 2291 F g−1 at 1.0 A g−1 in 6 M KOH aqueous solution.Download high-res image (114KB)Download full-size image

•The PtRu NPs with narrow size distribution are prepared by polyol method.•Catalyst supported carbon with core–shell structure is successfully prepared.•The PtRu/C shows high activity and stability compared with PtRu/C (JM).•The electrooxidation performance of PtRu/C for EOR is better than for MOR.Carbon supported PtRu core–shell catalyst is prepared by a facile and efficient method, in which the Ru nanoparticles are prepared with microwave-assisted method followed by in-situ reduction of Pt on Ru nanoparticles forming the PtRu core–shell structure. The catalyst is characterized by energy-dispersive X-ray spectroscope (EDX) analyzer attached to scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The TEM results show that the synthesized PtRu/C catalysts have small particle size and narrow size distribution. The PtRu/C catalyst shows higher electrochemical performance toward ethanol oxidation reaction (EOR) compared with methanol oxidation reaction (MOR). Notably, the PtRu/C catalysts exhibit higher mass activity and stability than that of the commercial PtRu/C (JM) catalyst for ethanol electrooxidation.

•Hollow Pt/Ru core–shell catalysts with nanochannels were synthesized.•Integrity of the Pt shell could be easily controlled by varying the H2PtCl6 content.•The H–PtRu catalysts showed high catalytic activity for MOR.•The H–PtRu catalyst with high Ru content showed the highest stability.This work reports the preparation of hollow PtRu core–shell catalysts with TiO2 as template, in which the Pt nanoparticles (NPs) grow on the exterior surface of Ru layer. The quantity of Pt NPs is easily tailored to control the integrity of Pt shell through varying the concentration of H2PtCl6 solution. Scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and selected-area electron diffraction (SAED) are used to characterize the structure and morphology of H–PtRu. The core–shell structure is confirmed by the high-angle annular dark-field scanning TEM (HAADF-STEM) with energy-disperse X-ray spectroscopy (EDX). The electrochemical performance of H–PtRu is investigated by cyclic voltammetry and chronoamperometry. Results show that the catalytic activity of H–PtRu toward methanol oxidation reaction (MOR) is ∼2.5 times higher than that of Pt/C (JM), and the electrocatalytic stability improves with the increase of Ru content. Furthermore, H–PtRu exhibits better stability for methanol oxidation compared to Pt/C (JM) and PtRu/C (JM).

•Smart shape-controlled PNIPAM/CS/Fe3O4 microgels were flexibly synthesized.•The as-prepared microgels possessed of spindle-shaped, cuboid and spherical shapes.•The microgels exhibited good magnetic, thermo- and pH-sensitivities.•The microgels show a great promise in bioseparation and many other fields.A novel approach was developed to synthesize smart shape-controlled PNIPAM/CS/Fe3O4 microgels with uniform size. Interestingly, the microgels in spindle-shaped, cuboid and spherical morphologies were successfully prepared using the micro-emulsion polymerization at a low temperature from 28 to 40 °C based on the theory of “coil-to-globule”. The morphology and properties of the as-prepared products were investigated using scanning electron microscope (SEM), dynamic light scattering (DLS) and superconducting quantum interference device (SQUID). Results revealed that the PNIPAM/CS/Fe3O4 microgels exhibited good thermo- and pH-sensitivities, and the size of the microgels decreased sharply upon increasing the temperature around 32 °C. The microgels with various shapes show a great promise in bioseparation and many other fields in the future.

•A facile strategy using TiO2 was successful adopted to form H-PtAu by one step.•The utilization of Pt atoms was improved due to hollow and nanoporous structure.•Nanoporous H-PtAu catalysts enhance electro-catalytic activities towards DAFCs.•The catalytic performance of H-PtAu increases with Au particles size decreasing.In the work, hollow nanoporous Au/Pt core–shell (H-PtAu) catalysts with nanochannels were prepared with different sizes of gold nanoparticles of a narrow size distribution in the range of 1.8 ± 0.3, 3.2 ± 0.3 and 4.6 ± 0.5 nm. The hollow spheres were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and an energy-dispersive X-ray (EDX) analyzer. The electrochemical methods by cyclic voltammetric and chronoamperometry demonstrate that the catalytic performance of hollow nanoporous Au/Pt sphere electrocatalysts increases with the decrease of Au particles size in the samples. The nanoporous hollow structure of the electrocatalysts improves the efficiency for electro-oxidation of methanol and ethanol. More importantly, the nanoporous H-PtAu electrocatalysts have a higher catalytic activity and better steady-state performance for ethanol oxidation than methanol.

Bimetallic hollow PtAu sphere (H-PtAu) was prepared with TiO2 (titanium glycolate spheres) as a template in the presence of citric acid, and the template was removed during the formation of H-PtAu. The morphology and surface structure of H-PtAu were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The results show that the structure of hollow sphere is strongly dependent on the concentration of citric acid. The H-PtAu with uniform size is well dispersed; the Pt shell thickness can be controlled by the amount of Pt precursor. Electrocatalytic activities of H-PtAu with different Pt/Au atomic ratios were investigated by cyclic voltammetry (CV) in 0.5 M NaOH + 0.5 M methanol aqueous solution. Results show that H-PtAu catalyst has higher methanol oxidation activity than the commercial Pt/C (JM) catalyst, and the optimal Pt/Au molar ratio is 1.0.