Electrochemical synthesis of nanosized hydroxyapatite/graphene composite powder

Vesna Mišković-Stanković,Sanja Eraković,Ana Janković,Maja Vukašinović-Sekulić,Miodrag Mitrić,Young Chan Jung,Soo Jin Park,Kyong Yop Rhee 한국탄소학회 2015 Carbon Letters Vol.16 No.4

Electrochemical synthesis was employed to prepare a novel hydroxyapatite/graphene (HAP/ Gr) composite powder suitable for medical applications as a hard tissue implant (scaffold). The synthesis was performed in a homogeneous dispersion containing Na2H2EDTA·2H2O, NaH2PO4 and CaCl2 with a Ca/EDTA/PO4 3− concentration ratio of 0.25/0.25/0.15M, along with 0.01 wt% added graphene nanosheets, at a current density of 137 mA cm−2 and pH value of 9.0. The field emission scanning electron microscopy and transmission electron microscopy observations of the composite HAP/Gr powder indicated that nanosized hydroxyapatite particles were uniformly placed in the graphene overlay. Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction confirmed graphene incorporation in the HAP/Gr powder. The electrochemically prepared HAP/Gr composite powder exhibited slight antibacterial effect against the growth of the bacterial strain Staphylococcus aureus.

The complex viscosity of polymer carbon nanotubes nanocomposites as a function of networks properties

Zare Yasser,Mišković-Stanković Vesna,이경엽 한국탄소학회 2019 Carbon Letters Vol.29 No.5

Cross model correlates the dynamic complex viscosity of polymer systems to zero complex viscosity, relaxation time and power-law index. However, this model disregards the growth of complex viscosity in nanocomposites containing filler networks, especially at low frequencies. The current paper develops the Cross model for complex viscosity of nanocomposites by yield stress as a function of the strength and density of networks. The predictions of the developed model are compared to the experimental results of fabricated samples containing poly(lactic acid), poly(ethylene oxide) and carbon nanotubes. The model’s parameters are calculated for the prepared samples, and their variations are explained. Additionally, the significances of all parameters on the complex viscosity are justified to approve the developed model. The developed model successfully estimates the complex viscosity, and the model’s parameters reasonably change for the samples. The stress at transition region between Newtonian and power-law behavior and the power-law index directly affects the complex viscosity. Moreover, the strength and density of networks positively control the yield stress and the complex viscosity of nanocomposites. The developed model can help to optimize the parameters controlling the complex viscosity in polymer nanocomposites.

Effects of interphase regions and tunneling distance on the electrical conductivity of polymer carbon nanotubes nanocomposites

Zare Yasser,Mišković-Stanković Vesna,이경엽 한국탄소학회 2019 Carbon Letters Vol.29 No.6

In this paper, an analytical model is developed for electrical conductivity of nanocomposites, particularly polymer/carbon nanotubes nanocomposites. This model considers the effects of aspect ratio, concentration, waviness, conductivity and percolation threshold of nanoparticles, interphase thickness, wettability between polymer and filler, tunneling distance between nanoparticles and network fraction on the conductivity. The developed model is confirmed by experimental results and parametric studies. The calculations show good agreement with the experimental data of different samples. The concentration and aspect ratio of nanoparticles directly control the conductivity. Moreover, a smaller distance between nanoparticles increases the conductivity based on the tunneling mechanism. A thick interphase also causes an increased conductivity, because the interphase regions participate in the networks and enhance the effectiveness of nanoparticles.

The complex viscosity of polymer carbon nanotubes nanocomposites as a function of networks properties

Yasser Zare,Vesna Mišković‑Stanković,Kyong Yop Rhee 한국탄소학회 2019 Carbon Letters Vol.29 No.5

Cross model correlates the dynamic complex viscosity of polymer systems to zero complex viscosity, relaxation time and power-law index. However, this model disregards the growth of complex viscosity in nanocomposites containing filler networks, especially at low frequencies. The current paper develops the Cross model for complex viscosity of nanocomposites by yield stress as a function of the strength and density of networks. The predictions of the developed model are compared to the experimental results of fabricated samples containing poly(lactic acid), poly(ethylene oxide) and carbon nanotubes. The model’s parameters are calculated for the prepared samples, and their variations are explained. Additionally, the significances of all parameters on the complex viscosity are justified to approve the developed model. The developed model successfully estimates the complex viscosity, and the model’s parameters reasonably change for the samples. The stress at transition region between Newtonian and power-law behavior and the power-law index directly affects the complex viscosity. Moreover, the strength and density of networks positively control the yield stress and the complex viscosity of nanocomposites. The developed model can help to optimize the parameters controlling the complex viscosity in polymer nanocomposites.

Effects of interphase regions and tunneling distance on the electrical conductivity of polymer carbon nanotubes nanocomposites

Yasser Zare,Vesna Mišković‑Stanković,Kyong Yop Rhee 한국탄소학회 2019 Carbon Letters Vol.29 No.6

In this paper, an analytical model is developed for electrical conductivity of nanocomposites, particularly polymer/carbon nanotubes nanocomposites. This model considers the effects of aspect ratio, concentration, waviness, conductivity and percolation threshold of nanoparticles, interphase thickness, wettability between polymer and filler, tunneling distance between nanoparticles and network fraction on the conductivity. The developed model is confirmed by experimental results and parametric studies. The calculations show good agreement with the experimental data of different samples. The concentration and aspect ratio of nanoparticles directly control the conductivity. Moreover, a smaller distance between nanoparticles increases the conductivity based on the tunneling mechanism. A thick interphase also causes an increased conductivity, because the interphase regions participate in the networks and enhance the effectiveness of nanoparticles.

Kinetic models of swelling and thermal stability of silver/poly(vinyl alcohol)/chitosan/graphene hydrogels

Katarina Nešovi c,Ana Jankovic,Aleksandra Peri c-Gruji c,Maja Vukašinovic-Sekulic,Tamara Radeti c,Ljiljana Živkovi c,박수진,이경엽,Vesna Miškovi c-Stankovi c 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.77 No.-

Silver nanoparticles (AgNPs) were synthesized by in situ electrochemical reduction of Ag+ ions in poly(vinyl alcohol)/chitosan/graphene (PVA/CHI/Gr) hydrogel matrices with different concentrations ofchitosan. The physicochemical properties of nanocomposite hydrogels were investigated by UV–visspectroscopy (UV–vis), dynamic light scattering (DLS), transmission electron microscopy (TEM), X-rayphotoelectron spectroscopy (XPS),field-emission scanning electron microscopy (FE-SEM) and Fourier-transform infrared spectroscopy (FT-IR), thermal characteristics were determined by differentialscanning calorimetry (DSC) and mechanical properties were measured by tensile test. The swellingstudies were carried out in phosphate buffer to simulate natural physiological environment and datawerefitted by several kinetic models to determine the diffusion mechanism and diffusion coefficients ofthe swelling medium through the hydrogel matrices. It was shown that the presence of silvernanoparticles increased the uptake capability and equilibrium swelling degree of the compositehydrogels. The antibacterial activity was confirmed against Escherichia coli and Staphylococcus aureus,while the hydrogels without AgNPs exhibited antibacterial properties due to the presence of chitosan. With the addition of AgNPs, the samples showed stronger activity and fast reduction in the number ofcolonies, confirming the synergistic effect of chitosan and AgNPs on the antibacterial activity.

Comprehensive electrochemical study on corrosion performance of graphene coatings deposited by chemical vapour deposition at atmospheric pressure on platinum-coated molybdenum foil

Naghdi, Samira,Neš,ović,, Katarina,Miš,ković,-Stanković,, Vesna,Rhee, Kyong Yop Pergamon Press 2018 Corrosion science Vol.130 No.-

<P><B>Abstract</B></P> <P>In this work, we present the results of electrochemical, Raman, FE-SEM/EDS, and XPS studies of graphene coatings deposited by chemical vapour deposition at atmospheric pressure on Mo foil and Pt-coated Mo foil as catalysts. The results showed that the graphene coating synthesized on Pt-coated molybdenum foil was bi-layer and had fewer defects, while the graphene coating on Mo foil was few-layer with more defects. The corrosion studies indicated that both graphene coatings on bare Mo and Pt-coated Mo exhibited good protective properties and can act as a barrier against corrosion in 0.1M NaCl.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Graphene chemical vapour deposition (CVD) at atmospheric pressure on molybdenum. </LI> <LI> Platinum thin film on molybdenum provided catalytic effect for CVD of graphene. </LI> <LI> Graphene coating on Pt-coated Mo samples had larger grain size and fewer defects. </LI> <LI> Both graphene coatings on Mo and Pt-coated Mo exhibited corrosion protection. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Reinforcements in multi-scale polymer composites: Processing, properties, and applications

Mittal, Garima,Rhee, Kyong Y.,Miš,ković,-Stanković,, Vesna,Hui, David Elsevier 2018 Composites Part B, Engineering Vol.138 No.-

<P><B>Abstract</B></P> <P>Smart and novel materials require the replacement of conventional composites with superior ones, which requires an advanced class of composites with multi-functionality. Multi-scale composites are advanced composites that are reinforced with nanoscale materials along with macroscale fibers, and these materials have attracted the attention of researchers as well as various industries. Multi-scale composites have potential applications in almost every field due to their remarkable features like extraordinary mechanical, electrical, and optical properties; extremely high aspect ratios of the nanomaterial constituents; and the uniformity, flexibility, and stability of the fibers. To optimize the performance of these kinds of composites, it is crucial to understand the selection of appropriate reinforcements, processing, and utilization of these advanced materials. Most reviews in this area concentrate only on CNTs, while this review considers other nanomaterials too. Additionally, various methods to improve the dispersion of nanomaterials into the matrix are also discussed. Overall, this article focuses on the components of multi-scale composites, key challenges related to their processing, and the multi-functionality of designed multi-scale composites.</P>

Chemical vapour deposition at atmospheric pressure of graphene on molybdenum foil: Effect of annealing time on characteristics and corrosion stability of graphene coatings

Naghdi, Samira,Jevremović,, Ivana,Miš,ković,-Stanković,, Vesna,Rhee, Kyong Yop Elsevier 2016 Corrosion science Vol.113 No.-

<P><B>Abstract</B></P> <P>In this work, the effect of pre-annealing of Mo substrate on the quality of graphene layers grown by chemical vapour deposition was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. Moreover, different electrochemical techniques were employed to investigate the corrosion stability of the graphene coated Mo in 0.1M NaCl. Longer annealing time resulted in less defective graphene coatings with fewer layers. Graphene coating on the annealed Mo provided better protection against corrosion during the initial exposure times, while after prolonged exposure times, both graphene coatings on annealed and non-annealed Mo exhibited nearly the same corrosion inhibitive properties.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Atmospheric pressure chemical vapor deposition of graphene on molybdenum foils. </LI> <LI> Quality and domain size of graphene layers increased with longer annealing times. </LI> <LI> The number of graphene layers decreased with longer annealing times. </LI> <LI> Graphene coatings on molybdenum foils exhibited corrosion inhibitive properties. </LI> </UL> </P>

Silver/poly(vinyl alcohol)/chitosan/graphene hydrogels – Synthesis, biological and physicochemical properties and silver release kinetics

Neš,ović,, Katarina,Janković,, Ana,Kojić,, Vesna,Vukaš,inović,-Sekulić,, Maja,Perić,-Grujić,, Aleksandra,Rhee, Kyong Yop,Miš,ković,-Stankovi Elsevier 2018 Composites. Part B, Engineering Vol.154 No.-

<P><B>Abstract</B></P> <P>This study presents the synthesis of novel silver/poly(vinyl alcohol)/chitosan/graphene (Ag/PVA/CHI/Gr) nanocomposite hydrogels by <I>in situ</I> electrochemical reduction of silver ions in the hydrogel matrix and their thorough characterization by UV–visible and Raman spectroscopies, field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and silver release measurements. The influence of chitosan content on the incorporation and stabilization of silver nanoparticles (AgNPs) was investigated, and we found that hydrogels with higher chitosan content contain higher amounts of AgNPs. In addition, the cytotoxicity and antibacterial activity of Ag/PVA/CHI/Gr nanocomposite hydrogels were evaluated. Based on <I>in vitro</I> investigations, the obtained materials exhibit diffusion-controlled release profiles over 28 days, strong antibacterial activity against <I>Staphylococcus aureus</I> and <I>Escherichia coli</I> bacterial strains, and no cytotoxicity toward human and mice fibroblast cell lines.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>In situ</I> electrochemical synthesis of silver nanoparticles in PVA/CHI/Gr hydrogels. </LI> <LI> Effect of chitosan concentration on the amount of embedded silver nanoparticles. </LI> <LI> Effect of chitosan concentration on the silver release kinetics. </LI> <LI> Strong antibacterial activity against <I>S. aureus</I> and <I>E. coli</I>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>