Pd Nanoparticles Loaded on Cu Nanoplate Sensor for Ultrasensitive Detection of Dopamine.

The detection of dopamine is of great significance for human health. Herein, Pd nanoparticles were loaded on Cu nanoplates (Pd/Cu NPTs) by a novel liquid phase reduction method. A novel dopamine (DA) electrochemical sensor based on the Pd NPs/Cu/glass carbon electrode (Pd/Cu NPTs/GCE) was constructed. This sensor showed a wide linear range of 0.047 mM to 1.122 mM and a low limit of detection (LOD) of 0.1045 µM (S/N = 3) for DA. The improved performance of this sensor is attributed to the obtained tiny Pd nanoparticles which increase the catalytic active sites and electrochemical active surface areas (ECSAs). Moreover, the larger surface area of two-dimensional Cu nanoplates can load more Pd nanoparticles, which is another reason to improve performance. The Pd/Cu NPTs/GCE sensor also showed a good reproducibility, stability, and excellent anti-interference ability.

Tough, self-healing, adhesive double network conductive hydrogel based on gelatin-polyacrylamide covalently bridged by oxidized sodium alginate for durable wearable sensors.

Pursuing high-performance conductive hydrogels is still hot topic in development of advanced flexible wearable devices. Herein, a tough, self-healing, adhesive double network (DN) conductive hydrogel (named as OSA-(Gelatin/PAM)-Ca, O-(G/P)-Ca) was prepared by bridging gelatin and polyacrylamide network with functionalized polysaccharide (oxidized sodium alginate, OSA) through Schiff base reaction. Thanks to the presence of multiple interactions (Schiff base bond, hydrogen bond, and metal coordination) within the network, the prepared hydrogel showed outstanding mechanical properties (tensile strain of 2800 % and stress of 630 kPa), high conductivity (0.72 S/m), repeatable adhesion performance and excellent self-healing ability (83.6 %/79.0 % of the original tensile strain/stress after self-healing). Moreover, the hydrogel-based sensor exhibited high strain sensitivity (GF = 3.66) and fast response time (<0.5 s), which can be used to monitor a wide range of human physiological signals. Based on this, excellent compression sensitivity (GF = 0.41 kPa-1 in the range of 90-120 kPa), a three-dimensional (3D) array of flexible sensor was designed to monitor the intensity of pressure and spatial force distribution. In addition, a gel-based wearable sensor was accurately classified and recognized ten types of gestures, achieving an accuracy rate of >96.33 % both before and after self-healing under three machine learning models (the decision tree, SVM, and KNN). This paper provides a simple method to prepare tough and self-healing conductive hydrogel as flexible multifunctional sensor devices for versatile applications in fields such as healthcare monitoring, human-computer interaction, and artificial intelligence.

Synthesis of Co3O4 Nanoplates by Thermal Decomposition for the Colorimetric Detection of Dopamine.

Inorganic nanomaterials with enzyme-like activity have been attracting much attention due to their low cost, favorable stability, convenient storage, and simple preparation. Herein, Co3O4 nanoplates with a uniform nanostructure were prepared by the thermolysis of cobalt hydroxide at different temperatures, and the influence of the annealing temperature on the performance of the mimetic enzyme also was reported for the first time. The results demonstrated that Co3O4 nanoplates obtained at an annealing temperature of 200 °C possessed strong oxidase activity and efficiently catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) without the addition of hydrogen peroxide to generate the blue color product ox-TMB. Once the annealing temperature was increased to 500 °C and 800 °C, the oxidase activity of Co3O4 decreased rapidly, and was even inactivated. This might be attributed to the relatively large specific surface area of Co3O4 annealed at 200 °C. Besides this, based on the TMB-Co3O4 nanoplate system, a colorimetric analysis method was developed to detect dopamine with a limit of 0.82 µmol/L in a linear range from 1.6 µmol/L to 20 µmol/L.

Preparation of Copper Nanoplates in Aqueous Phase and Electrochemical Detection of Dopamine.

Compared with gold and silver, cheap copper has attracted more attention and can potentially be applied in non-enzymatic electrochemical sensors due to its excellent conductivity and catalytic activity. In this paper, copper nanoplates were rapidly synthesized using copper bromide as the copper precursor, polyethyleneimine as the stabilizer, and ascorbic acid as a reducing agent in the presence of silver nanoparticles at a reaction temperature of 90 °C. The Cu nanoplates with an average side length of 10.97 ± 3.45 µm were obtained after a short reaction time of 2 h, demonstrating the promoting effect of an appropriate amount of silver nanoparticle on the synthesis of Cu nanoplates. Then, the electrochemical dopamine sensor was constructed by modifying a glass carbon electrode (GCE) with the Cu nanoplates. The results obtained from the test of cyclic voltammetry and chronoamperometry indicated that the Cu-GCE showed a significant electrochemical response for the measurement of dopamine. The oxidation peak current increased linearly with the concentration of dopamine in the range of 200 µmol/L to 2.21 mmol/L, and the corresponding detection limit was calculated to be 62.4 µmol/L (S/N = 3). Furthermore, the anti-interference test showed that the dopamine sensor was not affected by a high concentration of ascorbic acid, glucose, uric acid, etc. Therefore, the constructed Cu-GCE with good selectivity, sensitivity, and stability possesses a high application value in the detection of dopamine.

Facile Aqueous-Phase Synthesis of Bimetallic (AgPt, AgPd, and CuPt) and Trimetallic (AgCuPt) Nanoparticles.

Multi-metallic nanoparticles continue to attract attention, due to their great potential in various applications. In this paper, we report a facile aqueous-phase synthesis for multi-metallic nanoparticles, including AgPt, AgPd, CuPt, and AgCuPt, by a co-reduction method within a short reaction time of 10 min. The atomic ratio of bimetallic nanoparticles was easily controlled by varying the ratio of each precursor. In addition, we found that AgCuPt trimetallic nanoparticles had a core-shell structure with an Ag core and CuPt shell.

Facile aqueous-phase synthesis of Ag-Cu-Pt-Pd quadrometallic nanoparticles.

Ag-Cu-Pt-Pd quadrometallic nanoparticles which small Pt and Pd nanoparticles were attached on the surface of AgCu Janus nanoparticles were firstly synthesized by sequential reduction of Pt and Pd precursor in the presence of Janus AgCu bimetallic nanoparticles as seeds in an aqueous solution. Even though there was a small amount of Cu2O on the surface, the synthesized nanoparticles were mainly composed of four independent metallic part, not alloy parts. By theoretical calculation and growth mechanism study, we found that different reducing rate between Ag+ and Cu2+ and sequential reduction of Pt and Pd precursors would be key roles for the formation of the quadrometallic nanoparticles.

Fabrication of Superhydrophobic Surface with Controlled Wetting Property by Hierarchical Particles.

Hierarchical particles were prepared by synthetically joining appropriately functionalized polystyrene spheres of poly[styrene-co-(3-(4-vinylphenyl)pentane-2,4-dione)] (PS-co-PVPD) nanoparticles and poly(styrene-co-chloromethylstyrene) (PS-co-PCMS) microparticles. The coupling reaction of nucleophilic substitution of pendent ß-diketone groups with benzyl chloride was used to form the hierarchical particles. Since the polymeric nanoparticles and microparticles were synthesized by dispersion polymerization and emulsion polymerization, respectively, both the core microparticles and the surface nanoparticles can be different size and chemical composition. By means of changing the size of the PS-co-PVPD surface nanoparticles, a series of hierarchical particles with different scale ratio of the micro/nano surface structure were successfully prepared. Moreover, by employing the PS-co-PVPD microparticles and PS-co-PCMS nanoparticles as building blocks, hierarchical particles with surface nanoaprticles of different composition were made. These as-prepared hierarchical particles were subsequently assembled on glass substrates to form particulate films. Contact angle measurement shows that superhydrophobic surfaces can be obtained and the contact angle of water on the hierarchically structured surface can be adjusted by the scale ratio of the micro/nano surface structure and surface chemical component of hierarchical particles.

The Surface Modification and Antimicrobial Activity of Basic Magnesium Hypochlorite Nanoparticles.

The basic magnesium hypochlorite (BMH) nanoparticles were prepared by two micro-emulsion techniques and modified with sodium stearate. The influences of the main technical parameters such as the addition amount of sodium stearate, reaction temperature and reaction time on the Lipophilic degree (LD) of the modified BMH nanoparticles were investigated. The characteristics of the BMH nanoparticles were analysed by means of Malvern Instruments, transmission electron microscopy (TEM), water contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and thermogravimetry analysis (TGA). The antimicrobial activity of the modified BMH nanoparticles was investigated with the antibacterial circle test. The results showed that the average size of the BMH nanoparticles was 305 nm. The BMH nanoparticles had been successfully modified by sodium stearate and the LD of.the modified BMH nanoparticles was 8.4% when the addition amount of sodium stearate was 0.15 g, the reaction temperature was 10 °C and the reaction time was 5 h. The dispersibility and hydrophobicity of the modified BMH nanoparticles were improved and the contact angle was up to 103 °, the modified BMH nanoparticles still had excellent antimicrobial activity after modification.

Preparation and microstructure of nanocrystalline Ni-Mo films.

Ni-Mo films were prepared by electrodeposition technique with citric acid as a complexing agent. The influence of the main technical parameters such as the concentration of Na2MoO4 x 2H2O, the current density, the bath temperature and pH on the component content in the Ni-Mo films were investigated by energy dispersive spectrometer (EDS), the microstructure and surface morphology of Ni-Mo films were characterized by employing X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results showed that the excellent Ni-Mo films with 35.51 wt% Mo was obtained when the concentration of Na2MoO4 x 2H2O was 15 g/L, the current density was 8 A/dm2, the bath temperature was 30 degrees C and the pH was 5.0. The mircostructure of the Ni-Mo films were nanocrystalline and the average size of grain was about 20.12 nm by calculating using Scherrer Equation.