Sharif Digital Repository

In this article, the novel concept of using magnetic nanofluidic electrolyte for redox flow batteries is demonstrated for the first time. In this regard, the stable magnetic nanofluidic electrolytes are prepared by dispersing magnetic modified multiwalled carbon nanotubes (MMWCNTs) in the positive electrolyte of a polysulfide-iodide redox flow battery at mass concentrations of less than 0.3 g L−1. The electrochemical behavior of magnetic nanofluidic electrolyte was examined using cyclic voltammetry at different mass concentrations of MMWCNTs with a carbon felt electrode. Higher and stable peak current densities were observed at larger mass concentrations of MMWCNTs. A polysulfide-iodide... 

An optical apta-nanosensor was designed and developed based on reduced graphene quantum dots (rGQDs) and multi-walled carbon nanotubes (MWCNTs) and applied for the selective detection of diazinon as one of the most widely used organophosphorus pesticides. Considering the GQDs and rGQDs high fluorescence emission and optical stability, efficient optical transducers could be designed and precise detection methods could be developed based on such transducers. Herein, by using rGQDs, diazinon specific aptamer, and MWCNTs, a simple economical fluorescence method has been introduced to detect and measure diazinon with the detection limit of 0.4 nM (0.1 μg/L) in the range of 4-31 nM, meeting the... 

Because of the low outflow temperature of the conventional photovoltaic thermal systems and lack of electrical production of the solar thermal collectors, a novel combined system is proposed to solve the two mentioned drawbacks. This novel system is achieved by connecting a photovoltaic thermal unit to a solar thermal collector in series. To increase the overall performance of this novel combined system, different hybrid nanofluids include (1) multiwall carbon nanotube-aluminum oxide (2) multiwall carbon nanotube-silicon carbide (3) graphene-aluminum oxide, and (4) graphene-silicon carbide are compared. The investigation is performed based on the three-dimensional simulation, and the... 

This study deals with an experimental investigation on the thermal performance of a mechanical wet cooling tower with counter flow arrangement by using multi-walled carbon nanotubes (MWNTs) and nanoporous graphene nanofluids. Stable nanofluids were prepared through two-step procedure by using water with properties taken from a working cooling tower in the South of Iran. Zeta potential revealed suitable stability of MWNTs and nanoporous graphene nanofluids. Thermal and rheological properties of the nanofluids were investigated. It was found that thermal conductivity increases by 20% and 16% at 45°C for MWNTs and nanoporous graphene nanofluids, respectively. The increase in density and... 

A dispersive micro-solid-phase extraction (D-μ-SPE) procedure coupled with surfactant-enhanced spectrofluorimetric detection was developed for determination of ofloxacin and lomefloxacin from biological and environmental samples. The D-μ-SPE procedure was performed using magnetic Fe3O4 nanoparticle grafted multi-walled carbon nanotube as an efficient adsorbent. The main factors affecting the signal enhancement (including surfactant concentration and pH) and extraction efficiency (including pH, extraction time, sample volume, amount of magnetic adsorbent, and desorption conditions) were investigated in detail. Under the optimized conditions, the calibration curves were linear (R2 0.9995) over... 

Convective heat transfer plays a significant role in numerous industrial cooling and heating applications. This method of heat transfer can be passively improved by reconfiguring flow passage, fluid thermophysical properties, or boundary conditions. The broader scope of nanotechnology introduced several studies of thermal engineering and heat transfer. Nano-fluids are one of such technology which can be thought of engineered colloidal fluids with nano-sized particles. In the present study, turbulent forced convection heat transfer to nanofluids in an axisymmetric abrupt expansion heat exchanger was investigated experimentally. During heat transfer investigation, the functionalized... 

In this research, polyaniline@Ba0.5Sr0.5Fe12O19@MWCNTs nanocomposite was prepared via co-precipitation and in-situ polymerization methods, respectively. Microstructural, magnetic and electromagnetic wave absorption analysis of the prepared nanocomposite were studied via XRD, FESEM, VSM and VNA. Compared with Ba0.5Sr0.5Fe12O19@MWCNTs, the microwave absorption bandwidth of the coated nanocompoite with polyaniline was significantly enhanced, which increased to approxiamately 4 GHz from 3 GHz. The effective microwave absorption performance of the Ba0.5Sr0.5Fe12O19@MWCNTs nanocomposite was attributed to increase in the interfacial polarization, improvement in impedance matching as well as porous... 

Microdialysis-based continuous glucose measuring systems are desirable candidates for accurate and biologically safe monitoring of glucose level in diabetic patients. However, it is necessary to improve these systems by utilizing highly reliable non-enzymatic sensors instead of enzymatic ones, while lowering the size and lessening the dialysis fluid consumption. Our purpose is to design an implantable integrated microfluidic device for regular nonenzymatic microdialysis-based glucose measurement. We report a novel nonenzymatic microfluidic glucose sensor based on Pt-Ni nanoparticles - multiwalled carbon nanotubes/screen-printed carbon electrode (Pt-Ni NPs-MWCNTs/SPE). Devised microfluidic... 

An efficient and commercially available method is introduced for preparation of a binder-free electrode for capacitive deionization (CDI) application. An interconnected porous composite consisting of polyphosphate (PPO), graphene (Gr) and multi-walled carbon nanotube (CNT) is fabricated and assembled on a Ni foam substrate to prepare a binder-free electrode (Ni/PPOGrCNT). The resulting electrodes were characterized using various instrumental techniques such as TEM, SEM, EDS, XRD, FT-IR, Raman, XPS and XRF. Characterization results indicated that a mesoporous PPO structure is formed on a 3D assembly of carbon backbone. Accordingly, the 3-D porous structure facilitates the ion diffusion into... 

Although Multi-Walled Carbon NanoTubes (MWCNTs) are found to influence the rheological behavior of drilling fluids, there are yet some controversies regarding their performance towards reducing formation damage induced by the invasion of water-based drilling fluids (WBFs). To address this important question, we synthesized novel nanocomposite materials via modifying the MWCNT via varying the proportion of carboxylated MWCNTs to PolyVinyl Alcohol (PVA). These nanocomposites were then used to make nano-based drilling-fluids (NDFs). The performance of the NDFs was evaluated by a set of rheological behavior tests, filtration experiments, and core-scale mud flow tests. To distinguish between the... 

There are high attractions in the development of conducting polymer (CP) coatings to improve the electrochemical properties and biocompatibility of electrodes in the area of biosensors. A new type of the modified electrodes is prepared in a layer-by-layer process by using multi-walled carbon nanotube (MWCNT) and poly-pyrrole. In this procedure, the glassy carbon electrode is casted by a drop suspension of MWCNT, which leads to form a thin film of nanotube on its surface. In the second step, electrochemical polymerization of pyrrole in the presence of tiron (used as doping anion) is performed on the surface of the MWCNT pre-coated electrode. The modification procedure led to fabrication of a... 

The effects of HCl, HNO3, H2SO4 and HF acids on the purification and the electrochemical hydrogen storage of multi-walled carbon nanotubes (MWCNTs) were studied. The MWCNTs were synthesized on Fe-Ni catalyst by thermal chemical vapor deposition method. The X-ray diffraction and thermal gravimetric analysis results indicated that the MWCNTs purified by HF acid had the highest impurities as compared with the other acids. The N2 adsorption results at 77 K indicated that all the samples were mainly mesoporous and the purified MWCNTs by HF acid had the highest surface area as compared with the other acids. The hydrogen storage capacities of the purified MWCNTs by the following acids were in... 

In this research, the effect of Ni, Pd and Ni-Pd catalysts have studied on morphology and structure of synthesized multi-wall carbon nanotubes (MWCNTs). Initially, thin films of Ni (with two thicknesses of 10 and 20 nm), Pd/Ni (5/10 nm) and Pd (10 nm) were deposited as catalysts on SiO 2 (60 nm)/Si(1 0 0) substrates, using dc magnetron sputtering technique. The deposited films were annealed at 900 °C in ammonia environment for 45 min, in order to obtain nano-structured catalyst on the surface. Using scanning electron microscopy (SEM), the average size of Ni nano-islands (synthesized by the 10 and 20 nm Ni films), Pd and Ni-Pd nano-islands were measured about 55, 110, 45 and 50 nm,... 

In this paper, the effects of the multi-walled carbon nanotubes (MWCNTs) and nanographene (GP) on the mechanical performance of the cementitious mortars were investigated in different environments. Six mix designs were fabricated by considering the previous studies and exposed to potable water, acidic, and alkaline environments. The GP and MWCNTs partially replaced the cement with 0.25 %, 0.5 %, and 1 % of its weight. The standard mechanical tests, X-ray diffraction (XRD), and scanning electron microscope (SEM) analysis were performed on the specimens. The results indicated that including the MWCNTs and GP increases the compressive strength by 10 % and 20 % and similarly improves the tensile... 

Correlations between electrical and thermal conduction in polymer composites are blurred due to the complex contribution of charge and heat carriers at the nanoscale junctions of filler particles. Conflicting reports on the lack or existence of thermal percolation in polymer composites have made it the subject of great controversy for decades. Here, we develop a generalized percolation framework that describes both electrical and thermal conductivity within a remarkably wide range of filler-to-matrix conductivity ratios (Y f / Y m), covering 20 orders of magnitude. Our unified theory provides a genuine classification of electrical conductivity with typical Y f / Y m ≥ 10 10 as... 

Palladium nanocatalysts supported on reduced graphene oxide (rGO), multi walled carbon nanotubes (MWCNT), and rGO/CNT composite were synthesized by a wet impregnation method using PdCl2 as a precursor. Palladium loading was 0.3 wt %, and the catalysts were reduced at 300°C. The catalysts were characterized by inductively coupled plasma, Brunauer-Emmett-Teller (BET) analysis, Fourier transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, temperatue-programmed reduction, temperatue-programmed desorption, and Raman spectroscopy. The performance of the catalysts was investigated for hydro-purification of crude terephthalic acid (CTA) containing... 

Imidazolium-based ionic liquids (ILs) have been perceived as a promising candidate for bridging polyaniline (PANI) on well-dispersed carbon nanotubes (CNTs) via formation of IL-stabilized multiwalled carbon nanotubes (MWCNTs) dispersion in which outer walls of CNTs, as well as benzene rings of the aniline monomer and the growing polymer, have been potently effective in such procurement. The sulfonated water-soluble PANI-[C16C1im]Cl-MWCNT nanocomposites (SPANI-IL-MWCNTs) are directly deposited on a graphite-based current collector using a simple and cost-effective electrophoretic deposition (EPD) method. The SPANI-IL-MWCNT electrodes exhibit remarkable electrochemical performance compared to... 

Carbon-based nanocarriers such as multiwall carbon nanotubes (MWCNTs) and reduced graphene oxide (rGO) have shown promising delivery capabilities due to their low immunogenicity, superior internalization, and suitable cell penetration efficiency. Herein, a molecular engineering strategy is advanced for the one-pot synthesized rGO/MWCNT/Fe3O4/ZnO to enhance the stability of the nanocarrier in the biological matrix; green synthesized ZnO was responsible for water uptake and reduced cytotoxicity, while Fe3O4controlled the cellular internalization for gene delivery. Surface morphology of the ensuing nanocomposite was correlated with photocatalytic and gene delivery (CRISPR/Cas9) features. For... 

Hybrid bioactive inorganic-organic carbon-based nanocomposites of reduced graphene oxide (rGO) nanosheets enlarged with multi-walled carbon nanotubes (MWCNTs) were decorated to provide a suitable space forin situgrowth of CoNi2S4and green-synthesized ZnO nanoparticles. The ensuing nanocarrier supplied π-π interactions between the DOX drug and a stabilizing agent derived from leaf extracts on the surface of ZnO nanoparticles and hydrogen bonds; gene delivery of (p)CRISPR was also facilitated by chitosan and alginate renewable macromolecules. Also, these polymers can inhibit the potential interactions between the inorganic parts and cellular membranes to reduce the potential cytotoxicity.... 

Demand for high-capacity, long cycle life, and aqueous batteries based on abundant metals such as nickel, zinc, aluminum, and so on is rising in the energy storage field. In this study, we design a hierarchical morphology as a nanosheet-built microsphere of nickel vanadium layered double hydroxide (NiV LDH) with conductive agents graphene oxide (GO) and multiwalled carbon nanotubes (CNTs) through a low-cost hydrothermal synthesis method. The experimental results demonstrate that the graphitic structures and functional groups of the GO and CNT play an important role in controlling nucleation, growth speed, size, and finally morphology of hierarchical nanosheets. The electrochemical results...