Two-component spin-coated Ag/CNT composite films based on a silver heterogeneous nucleation mechanism adhesion-enhanced by mechanical interlocking and chemical grafting

In this paper, a new method for the synthesis of silver carbon nanotube (Ag/CNT) composite films as conductive connection units for flexible electronic devices is presented. This method is about a two-component solution process by spin coating with an after-treatment annealing process. In this method, multi-walled carbon nanotubes (MWCNTs) act as the core of silver heterogeneous nucleation, which can be observed and analyzed by a field-emission scanning electron microscope. With the effects of mechanical interlocking, chemical grafting, and annealing, the interfacial adhesive strength between films and PET sheets was enhanced to 12 N cm^-1. The tensile strength of the Ag/CNT composite films was observed to increase by 38% by adding 5 g l^-1 MWCNTs. In the four-probe method, the resistivity of Ag/CNT-5 declined by 78.2% compared with pristine Ag films. The anti-fatigue performance of the Ag/CNT composite films was monitored by cyclic bending deformation and the results revealed that the growth rate of electrical resistance during the deformation was obviously retarded. As for industrial application, this method provides an efficient low-cost way to prepare Ag/CNT composite films and can be further applied to other coating systems.

Novel Magnetic Cross-Linked Cellulase Aggregates with a Potential Application in Lignocellulosic Biomass Bioconversion

The utilization of renewable biomass resources to produce high-value chemicals by enzymatic processes is beneficial for alternative energy production, due to the accelerating depletion of fossil fuels. As immobilization techniques can improve enzyme stability and reusability, a novel magnetic cross-linked cellulase aggregate has been developed and applied for biomass bioconversion. The crosslinked aggregates could purify and immobilize enzymes in a single operation, and could then be combined with magnetic nanoparticles (MNPs), which provides easy separation of the materials. The immobilized cellulase showed a better activity at a wider temperature range and pH values than that of the free cellulase. After six cycles of consecutive reuse, the immobilized cellulase performed successful magnetic separation and retained 74% of its initial activity when carboxylmethyl cellulose (CMC) was used as the model substrate. Furthermore, the structure and morphology of the immobilized cellulase were studied by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Moreover, the immobilized cellulase was shown to hydrolyze bamboo biomass with a yield of 21%, and was re-used in biomass conversion up to four cycles with 38% activity retention, which indicated that the immobilized enzyme has good potential for biomass applications.

Mechanisms underlying the enhancement of toxicity caused by the coincubation of zinc oxide and copper nanoparticles in a fish hepatoma cell line

Ecosystems are exposed to a wide variety of individual substances, including at the nano-scale; and the potential adverse effects of their interactions are an increasing concern. The purpose of the present study was to determine whether zinc oxide nanoparticles (ZnONPs) at a no-observed-effect concentration modulate the cytotoxicity of copper nanoparticles (CuNPs) in the fish hepatoma cell line PLHC-1 after 48 h of exposure and the contribution of the released ions to these effects. Cells were exposed to 50-nm CuNPs (0.39-25.0 µg/mL), alone or in combination with ZnONPs (25 nm or 100 nm), at 6.25 µg/mL. Cells were exposed to suspensions of NPs or to their supernatants, as well as to their combinations. The effects on cell viability were assessed through cytotoxicity assays. Changes in cell morphology and metal internalization were also evaluated. The cytotoxicity exerted by CuNPs was enhanced in the presence of nontoxic concentrations of ZnONPs. On the contrary, Zn ions protected the cell line from the CuNP toxicity, this effect being related to an increase in the intracellular levels of Zn. This increase of metal was not observed in cells exposed to both ZnONPs and CuNPs, even when they were visualized inside the cell. The results indicated that the internalization of ZnONPs, but not the Zn ions, was responsible for the enhanced toxicity of the CuNPs. Environ Toxicol Chem 2016;35:2562-2570. © 2016 SETAC.

Response surface modeling of lead (׀׀) removal by graphene oxide-Fe3O4 nanocomposite using central composite design

BACKGROUND

Magnetic graphene oxide (Fe3O4@SiO2-GO) nanocomposite was fabricated through a facile process and its application as an excellent adsorbent for lead (II) removal was also demonstrated by applying response surface methodology (RSM).

METHODS

Fe3O4@SiO2-GO nanocomposite was synthesized and characterized properly. The effects of four independent variables, initial pH of solution (3.5-8.5), nanocomposite dosage (1-60 mg L(-1)), contact time (2-30 min), and initial lead (II) ion concentration (0.5-5 mg L(-1)) on the lead (II) removal efficiency were investigated and the process was optimized using RSM. Using central composite design (CCD), 44 experiments were carried out and the process response was modeled using a quadratic equation as function of the variables.

RESULTS

The optimum values of the variables were found to be 6.9, 30.5 mg L(-1), 16 min, and 2.49 mg L(-1) for pH, adsorbent dosage, contact time, and lead (II) initial concentration, respectively. The amount of adsorbed lead (II) after 16 min was recorded as high as 505.81 mg g(-1) for 90 mg L(-1) initial lead (II) ion concentration. The Sips isotherm was found to provide a good fit with the adsorption data (KS = 256 L mg(-1), nS = 0.57, qm = 598.4 mg g(-1), and R(2) = 0.984). The mean free energy Eads was 9.901 kJ/mol which confirmed the chemisorption mechanism. The kinetic study determined an appropriate compliance of experimental data with the double exponential kinetic model (R(2) = 0.982).

CONCLUSIONS

Quadratic and reduced models were examined to correlate the variables with the removal efficiency of Fe3O4@SiO2-GO. According to the analysis of variance, the most influential factors were identified as pH and contact time. At the optimum condition, the adsorption yield was achieved up to nearly 100 %.

Adsorption of naphthalene onto high-surface-area nanoparticle loaded activated carbon by high performance liquid chromatography: response surface methodology, isotherm and kinetic study

Naphthalene removal from aqueous solution was investigated using zinc sulfide nanoparticle loaded activated carbon (ZnS-NPs-AC).