Graphene oxide–gellan gum–sodium alginate nanocomposites: synthesis,characterization, and mechanical behavior

This paper reports the preparation and characterization of graphene oxide–gellan gum–sodium alginate nanocomposites (GO–GG–Alg). The nanocomposites were prepared by a simple solution mixing-evaporation method. Fourier transform infrared spectroscopy, X-ray diffractions, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, and mechanical testing were conducted to study the structure and properties of the nanocomposites. The obtained findings reveal that gellan gum, sodium alginate, and graphene oxide are able to form a homogeneous mixture. Small amount of GO loading on GO–GG–Alg drastically improves its tensile strength and Young’s modulus. Detailed material characteristics of the nanocomposites are addressed.     

Sonochemical fabrication of gold nanoparticles–boron nitride sheets nanocomposites for enzymeless hydrogen peroxide detection

A simple sonochemical route was developed for the preparation of gold nanoparticles/boron nitride sheets (AuNPs/BNS) nanocomposites without using reducing or stabilizing agents. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and UV–vis absorption spectra were used to characterize the structure and morphology of the nanocomposites. The experimental results showed that AuNPs with approximately 20 nm were uniformly attached onto the BNS surface. It was found that the AuNPs/BNS nanocomposites exhibited good catalytic activity for the reduction of H₂O₂. The modified electrochemical sensor showed a linear range from 0.04 to 50 mM with a detection limit of 8.3 μM at a signal-to-noise ratio of 3. The findings provide a low-cost approach to the production of stable aqueous dispersions of nanoparticles/BNS nanocomposites.     

Ultrasonic-assisted synthesis of Pd–Pt/carbon nanotubes nanocomposites for enhanced electro-oxidation of ethanol and methanol in alkaline medium

Herein, a facile ultrasonic-assisted strategy was proposed to fabricate the Pd–Pt alloy/multi-walled carbon nanotubes (Pd–Pt/CNTs) nanocomposites. A good number of Pd–Pt alloy nanoparticles with an average of 3.4 ± 0.5 nm were supported on sidewalls of CNTs with uniform distribution. The composition of the Pd–Pt/CNTs nanocomposites could also be easily controlled, which provided a possible approach for the preparation of other architectures with anticipated properties. The Pd–Pt/CNTs nanocomposites were extensively studied by electron microscopy, induced coupled plasma atomic emission spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and applied for the ethanol and methanol electro-oxidation reaction in alkaline medium. The electrochemical results indicated that the nanocomposites had better electrocatalytic activities and stabilities, showing promising applications for fuel cells.     

ZnO nanoparticles favours heterogeneous nucleation in PET–ZnO nanocomposites

The structural and chemical properties with non-isothermal crystallization kinetics of PET–ZnO nanocomposites have been reported in this article. ZnO nanoparticles have been synthesized via chemical route with average diameter 19 nm which made confirm by transmission electron microscopy and X-ray diffractometer (XRD) techniques. PET–ZnO nanocomposites have been prepared by solution casting method. The structural and chemical changes occurred in poly (ethylene terephthalate) after inclusion of ZnO nanoparticles have been studied with the help of XRD and Fourier transform infrared spectroscopy, respectively. It was observed from differential scanning calorimeter that ZnO nanoparticles work as nucleating agent for heterogeneous nucleation in PET matrix under non-isothermal crystallization process. The combined Avrami and Ozawa models have been proved adequate to explain non-isothermal crystallization kinetics of PET–ZnO nanocomposites, and also, ZnO nanoparticles have been caused to reduce crystallization activation energy in pristine PET as per the applied Kissinger model.     

Synthesis,characterization and visible-light driven photocatalysis by differently structured CdS/ZnS sandwich and core–shell nanocomposites

CdS/ZnS sandwich and core–shell nanocomposites were synthesized by a simple and modified Chemical Precipitation method under ambient conditions. The synthesized composites were characterized by XRD, SEM, TEM, EDAX and FTIR. Optical properties were analyzed by UV–vis. Spectroscopy and the photoluminescence study was done to monitor the recombination of photo-generated charge-carriers. Thermal stability of the synthesized composites was analyzed by Thermal Gravimetric Analysis (TGA). XRD revealed the formation of nanocomposites as mixed diffraction peaks were observed in the XRD pattern. SEM and TEM showed the morphology of the nanocomposites particles and their fine particle size. EDAX revealed the appropriate molar ratios exhibited by the constituent elements in the composites and FTIR gave some characteristic peaks which indicated the formation of CdS/ZnS nanocomposites. Electrochemical Impedance Spectroscopy was done to study charge transfer properties along the nanocomposites. Photocatalytic properties of the synthesized composites were monitored by the photocatalytic kinetic study of Acid Blue dye and p-chlorophenol under visible light irradiation. Results revealed the formation of stable core–shell nanocomposites and their efficient photocatalytic properties.     

Assessment of the Microstructure and Mechanical Properties of Polycarbonate (PC)/Acrylonitrile Butadiene Rubber (NBR) Blends Reinforced with Multi-wall Carbon Nanotubes

Abstract

A series of polycarbonate (PC)/acrilonitrile butadiene rubber (NBR)/multi-wall carbon nanotube (MWCNT) nanocomposites were prepared via melt compounding in an internal mixer. The effect of the MWCNT content on the morphology and the thermal and mechanical properties of the prepared nanocomposites were studied. The morphologies of the samples were investigated by field-emission scanning electron microscopy (FESEM) and the thermal properties by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The tensile mechanical results of the nanocomposites showed a decrease in elongation at break with an increase of only 2?wt% of MWCNT content in the PC/NBR blends, and an increasing value in elastic modulus and tensile strength of the nanocomposites. The FESEM images showed that the MWCNTs had good affinity with the polymers and no compatibilizer was needed for making the nanocomposites. The DSC and TGA results showed an increase in thermal stability with addition of MWCNTs because of the more thermally stable carbon nanotubes particles which was uniformly dispersed within the nanocomposites.     

壳聚糖包裹AgInS_2的物理表征及生物毒性研究

选用天然多糖中唯一的碱性多糖——壳聚糖作为稳定剂和包裹剂,成功合成了水溶性的Ag In S2量子点/低分子量壳聚糖纳米复合材料(Ag In S2/LCSMS)。利用透射电子显微镜(TEM)、FT-IR傅里叶红外光谱仪、紫外吸收光谱、荧光分光光度计等表征手段对纳米复合材料的形貌、化学组成及光学性质进行了研究。结果表明,Ag In S2/LCSMS纳米复合材料的粒径约为5~6 nm,在水相中仍具有较稳定的发光。之后,对Ag In S2/LCSMS纳米复合材料的生物相容性进行了研究,对比Ag In S2/LCSMS纳米复合材料与Ag In S2量子点的细胞活性测试结果发现,Ag In S2/LCSMS纳米复合材料的细胞活性比Ag In S2量子点有了明显的提高,说明通过低分子量壳聚糖的包裹可以明显提高纳米材料的生物相容性。因此,这类具有较好水溶性和生物相容性的荧光Ag In S2/LCSMS纳米复合材料可作为优良的生物荧光标记材料在生物医学检验、细胞以及活体成像研究中有广泛的应用前景。     

Optical and photocatalytic properties of novel heterogeneous PtSe2–graphene/TiO2 nanocomposites synthesized via ultrasonic assisted techniques

Novel material PtSe₂–graphene/TiO₂ nanocomposites were successfully synthesized through a facile ultrasonic assisted method. The prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX),transmission electron microscopy (TEM), Raman spectroscopic analysis, UV–vis absorbance spectra and UV–vis diffuse reflectance spectra (DRS) analysis were obtained. The catalytic behavior was investigated through the decomposition of rhodamine B (Rh.B) as a standard dye. Enhanced photocatalytic activities were observed by increasing the weight% of graphene in the PtSe₂–graphene/TiO₂ nanocomposites. We observed that the coupling of TiO₂ with PtSe₂–graphene alter the optical properties by observing a precise band gap in the visible range.     

Time-dependent growth of crystalline Au0-nanoparticles in cyanobacteria as self-reproducing bioreactors: 1. Anabaena sp.

In the experiments, multifunctional nanocomposites with fluorescence, superparamagnetism, and bioactivity were synthesized to isolate and detect bacteria. Fluorescent-magnetic nanocomposites (FMNPs) (Fe₃O₄@SiO₂@FITC–SiO₂, core/shell) were first synthesized. Then, FMNPs were conjugated with N-hydroxysuccinimide-activated 4-oxo-4-(prop-2-ynyloxy) butanoic acid (NHS-activated ester) by the linker of 3-aminopropyltriethoxysilane, and alkyne-functionalized fluorescent-magnetic nanocomposites (FMNPs-alkyne) were produced. After 3′-azidopropyl-O-α-d-manno-pyranoside was grafted on the surface of FMNPs-alkyne by click chemistry, the final product—mannose derivatives-grafted fluorescent-magnetic nanocomposites (FMNPs-mannose) were obtained. Common techniques (Nuclear magnetic resonance, ESI mass spectra, etc.) indicated the successful synthesis of the target products. The results of scanning electron microscopy, transmission electron microscopy, and dynamic light scattering showed that FMNPs with one or more magnetic cores have regular structure with a diameter around 100 nm. Fluorescence spectra and fluorescence microscopy indicated that those nanocomposites exhibited strong and stable fluorescence property. FMNPs-mannose have a saturation magnization of 6.88 emu/g at room temperature. FMNPs-mannose were applied to adhere to Escherichia coli ATCC25722 and Staphylococcus aureus ATCC6538. The results showed that FMNPs-mannose were able to specifically adhere to E. coli ATCC25722. However, it had no effect with S. aureus ATCC6538. The obtained FMNPs-mannose will find its application in bacteria detection and separation.     

Facile in situ hydrothermal synthesis of BiVO4/MWCNT nanocomposites as high performance visible-light driven photocatalysts

Visible-light responsive monoclinic BiVO₄/MWCNT nanocomposites were facilely prepared via an in situ hydrothermal method by using sodium dodecyl sulfonate (SDS) as a guiding surfactant. The as-prepared BiVO₄/MWCNT nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), the Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectroscopy. The results showed that the hydrothermal temperature and adding SDS had significant influence on the morphology and size of BiVO₄. The photocatalytic activities of BiVO₄/MWCNT nanocomposites were investigated by degrading methylene blue (MB) under visible-light irradiation. Remarkable enhancement in photodecomposition of MB was observed with BiVO₄/MWCNT composite compared with bare BiVO₄ particles. This improvement of photocatalytic was attributed to the effective charge transfer from BiVO₄ nanocrystals to MWCNT, which promoted the migration efficiency of photogenerated electron–hole. Furthermore, a possible mechanism for the photocatalytic oxidative degradation was also discussed.     

Glass transition temperature and thermal stability of ZnS/PMMA nanocomposites

In this article, ZnS nanoparticles were prepared by wet chemical precipitation method using zinc sulphate (ZnSO₄), sodium sulphide (Na₂S) and thio-glycerol. These nanoparticles were characterized through X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The solution-based processing was used to prepare Poly methyl methacrylate (PMMA) nanocomposites with different weight percents (0, 2, 4, 6 and 8) of ZnS nanoparticles. The obtained ZnS/PMMA nanocomposites were characterized through XRD, scanning electron microscope and TEM measurements. The dynamic mechanical analyzer was used to obtain the storage modulus and glass transition temperature (T _g) of the nanocomposites. The apparent activation energy of the glass transition region was also determined using the Vogel–Fulcher–Tammann equation. The results indicated that the thermal stability of ZnS/PMMA nanocomposites was higher than PMMA and 6 wt. % of ZnS nanoparticles in PMMA matrix showed the maximum activation energy, which indicated that this nanocomposite had higher thermal stability than other composites.     

Magnetic ionic liquid-assisted synthesis of polyaniline/AgCl nanocomposites by interface polymerization

A simple strategy for the one-step synthesis of polyaniline/AgCl nanocomposites at the water/magnetic ionic liquid interface was reported. By controlling the reactive conditions, highly dispersed polyaniline/AgCl nanocomposites with their size ranging around 50–80 nm were obtained with magnetic ionic liquid as the oxidant. Transmission electron microscopy was used to show the morphology of the nanocomposites. The nanocomposites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Moreover, polyaniline/AgCl nanocomposites on a glassy carbon electrode showed strong electrocatalytic activity for H₂O₂ and could be used to construct a H₂O₂ biosensor.     

Structure and Mechanical Properties of Melt Intercalated Po1lypropylene–Organomontmorillonite Nanocomposites

The preparation and properties of polymer nanocomposites, obtained by melt-compounding of polypropylene (PP) and organomontmorillonite (OMMT) modified by different alkyl ammonium salts, are described. A copolymer of maleic anhydride and PP was used as a compatibilizing additive. Nanocomposites with OMMT content of 1, 5 and 10 wt% were prepared and tested. The influence of OMMT content on the tensile stress–strain curves, elastic modulus, yield and tensile strength, and ultimate elongation of the nanocomposites is determined. The results of measuring the microhardness and impact strength of polymer nanocomposites are presented. Long-term creep tests were performed to predict the long-term deformation behavior of nanocomposites. The crystallinity of nanocomposites was analyzed by means of differential scanning calorimetry and optical microscopy, while the structural features were studied by X-ray diffraction and scanning electron microscopy methods.     

siRNA-loaded PEGylated porous silicon nanoparticles for lung cancer therapy

The BiPO₄/reduced graphene oxide (RGO) nanocomposites were prepared by a facile solvothermal approach. The prepared samples were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, electrochemical impedance spectra, and Mott–Schottky and the photoluminescence spectra. A large quantity of BiPO₄ nanoparticles with sizes of ca. 150 nm were well dispersed on the RGO nanosheets. The absorbance of the BiPO₄/RGO nanocomposites is largely enhanced in the range of 400–800 nm compared with that of BiPO₄, and the BiPO₄/RGO showed better photocatalytic activities under simulated sunlight irradiation than the BiPO₄ nanocrystals.     

Gold nanoparticles produced by laser ablation in water and in graphene oxide suspension

The comparison between two different approaches based on the use of the laser ablation in medium to synthetise gold nanoparticles is presented and discussed. Deionised water as well as a graphene oxide (GO) suspension in deionised water have been employed as solution to produce gold nanoparticles by laser ablation. In the former case, the nanoparticles assembly has been stabilised by using surfactants, but in the latter case to avoid undesired effects the use of chemicals was not necessary and Au reduced graphene oxide (Au-rGO) nanocomposites have been obtained. The structure, size and composition of the gold nanoparticles and of the Au–rGO nanocomposites have been monitored by UV–Vis–NIR absorption spectroscopy and Raman spectroscopy, the transmission and scanning electron microscopies and the X-ray energy-dispersive spectroscopy. The presented methodology of Au rGO nanocomposites preparation could represent a green alternative on the production of metallic nanoparticles in biocompatible environment.     

Different strategies for the synthesis of graphene/ZnO composite and its photocatalytic properties

Owing to its unique physical and chemical properties, graphene has attracted tremendous attention in the preparation of graphene-based composites for various applications. In this study, two different strategies have been developed to load zinc oxide (ZnO) nanorods onto reduced graphene oxide (RGO) sheets, i.e., in situ growth and a self-assembly approach. The microstructure and morphology of the synthesized RGO/ZnO nanocomposites was investigated by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and Brunauer–Emmett–Teller (BET) measurements. Fluorescence emission spectra (PL) of RGO/ZnO composites were performed to attribute quality of combination between RGO and ZnO. Significantly enhanced photocatalytic activity of RGO/ZnO nanocomposites in comparison to bare ZnO nanoparticles was revealed by the degradation of methylene blue under irradiation, which can be attributed to the inhibition of electron–hole pair recombination and enhanced adsorption due to the presence of RGO sheets.     

Preparation of SnO2–graphene from SnS–graphene oxide for enhanced reversible lithium ion storage

SnO₂–graphene nanocomposites (SnO₂–GNS) have been prepared through a simple hydrothermal reaction with SnS–graphene oxide composites as the precursor. The composite material as prepared was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller analysis, and thermogravimetric analysis. The results indicate that SnO₂ nanoparticles possess a good dispersion on the surface of graphene. Electrochemical tests demonstrate the high reversible lithium ion storage properties of SnO₂–GNS. The nanocomposites retained a reversible capacity of 503 mAh?g^?1 after 40 cycles. Moreover, the composite material exhibited higher capacity and better cyclic performance compared to free SnO₂ nanoparticles physically mixed with graphene in the relative weight ratio. The results suggest that the combination of SnO₂ and graphene leads to synergistic performance, which enhances lithium ion storage properties of the overall system.     

Fabrication of Prussian blue nanocubes through reducing a single-source precursor with graphene oxide and their electrocatalytic activity for H2O2

Nanostructured ZnO has been synthesized by wet chemical route. Poly(vinylpyrrolidone) is used for stabilization and surface passivation of synthesized nanoparticles, thus tailoring the growth of ZnO at nanoscale. Structural characterization using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron micoroscopy and Fourier transformed infrared spectroscopy of the synthesized nanoparticles confirm the evolution of nanocrystalline ZnO prevailing in hexagonal wurtzite phase. UV–Vis and photoluminescence spectroscopy studies show blue shift phenomenon in the synthesized nanoparticle in contrast to the bulk ZnO furnishing evidence in support of quantum size effect. The nanocomposites of ZnO and poly [9,9-dioctylfluorenyl-2,7-diyl] are prepared and characterized to investigate its luminescent and spectral emission effects. The nanocomposites are then incorporated in light-emitting diodes, and influence of ZnO on the device performance has been explored via electroluminescence, current density evaluation, and corresponding CIE coordinates calculation.     

Thermal,Mechanical, and Rheological Characterization of Polylactic Acid/Halloysite Nanotube Nanocomposites

Halloysite nanotube (HNT) clay and biodegradable polylactic acid (PLA) nanocomposites were fabricated by a melt-blending method with five different clay levels (1, 3, 5, 7, and 9 wt%). The effect of HNT loading on the thermal and mechanical properties of the PLA/HNT nanocomposites was examined by thermogravimetric analysis and universal tensile testing, respectively. Morphological characteristics were investigated by transmission electron microscopy. The composites' melt rheological characteristic analyses were conducted using a rotational rheometer in both steady-shear and oscillatory dynamic testing modes. The data were found to be well-analyzed using the Carreau model, Cox–Merz rule, modified Cole–Cole plot, and van Gurp–Palmen plot.