Flame atomic absorption spectrometry for the determination of trace amount of rhodium after separation and preconcentration onto modified multiwalled carbon nanotubes as a new solid sorbent

The present article reports on the application of modified multiwalled carbon nanotubes (MMWCNTs) as a new, easily prepared and stable solid sorbent for the preconcentration of trace rhodium ion in aqueous solution. Rhodium ions were complexed with 1-(2-pyridylazo)-2-naphthol (PAN) in the pH range of 3.2-4.7 and then the formed Rh-PAN complex was adsorbed on the oxidized MWCNTs. The adsorbed complex was eluted from MWCNTs sorbent with 5.0 mL of N,N-dimethylformamide (DMF). The rhodium in eluted solution was determined by flame atomic absorption spectrometry (FAAS). Linear range for the determination of rhodium was maintained between 0.16 ng mL⁻¹ and 25.0 μg mL⁻¹ in initial solution. Relative standard deviation for the 10 replicated determination of 4.0 μg mL⁻¹ of rhodium was ±0.97%. Detection limit was 0.010 ng mL⁻¹ in initial solution (3S_bl, n = 10) and preconcentration factor was 120. Sensitivity for 1% absorbance of rhodium (III) was 0.112 μg mL⁻¹. The sorption capacity of oxidized MWCNTs for Rh (III) was 6.6 mg g⁻¹. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type, breakthrough volume and interference ions were studied for the preconcentration of Rh³⁺. The proposed method was successfully applied to the extraction and determination of rhodium in different samples.     

Comparison of photonic crystal narrow filters with metamaterials and dielectric defects

The photonic band-gap of the two kinds of 1D photonic crystal structure which is composed of the form of (AB) ^N1 C ^m (BA) ^N2 , one with a metamaterial defect layer (MDL) and the other one with a dielectric defect layer (DDL) are studied. Our results show that in both cases, where there is only one defect layer, m=1, no defect mode exists, but for two defect layers (m=2) there is a single defect mode which is centered in the middle of the band-gap. The width of the defect mode in DDL is narrower than that in MDL. For a number of defects of more than two (m>2) and even, in both of the MDL and DDL structures, there is only one defect mode. For m>2 and odd, the defect mode in the MDL vanishes, but for DDL there is two defect-mode symmetrically centered in the middle of the band-gap. The effects of the defect layers refractive index value, the periodicity number of the structures and the incident angle on the properties of the defect modes and the transmittance spectrum are discussed.     

Exact electrostatic solitons in a magnetoplasma with degenerate electrons

Fully nonlinear planar ion-acoustic solitary waves (IASWs) moving obliquely to an external magnetic field are studied in a collisionless magnetoplasma with degenerate electrons. The features of the nonlinear IASWs are investigated through the derivation of an energy balance-like equation involving the Sagdeev-type potential as well as the nonlinear dispersion relation.     

Electrospun Nylon-66/5-(4-dimethylaminobenzyliden) rhodanine composite nanofibres for solid phase extraction of palladium ions from wastewater samples

In the present work, a simple procedure is presented for the extraction and determination of pre-concentrated trace amounts of palladium ions through solid phase extraction (SPE) and flame atomic absorption spectrophotometry. This process was performed using Nylon-66/5-(4-dimethylaminobenzylidene) rhodanine composite nanofibres. These nanofibres were produced under optimised conditions via two-axial electrospinning technique and characterised by scanning electron microscopy and Fourier-transform infrared spectroscopy. The effect of experimental parameters including solution pH, the type and volume of eluent and contact time was investigated in extraction and desorption process. Under the optimised conditions, good linearity in the range of 0.07–8 μg L^?1 and low detection limit of 0.015 μg L^?1 were obtained. High enrichment factor of 187.5 and good relative standard deviation of ±2.2% at 5 μg L^?1 of palladium had been achieved. The sorbent capacity for palladium adsorption was obtained 27 mg palladium per gram of nanofibres. So, the SPE was successfully applied to pre-concentrate and determine Pd(II) ions with flame atomic absorption spectrophotometer in real samples.     

Poly (3-aminobenzoic acid) @ MWCNTs hybrid conducting nanocomposite: preparation,characterization, and application as a coating for copper corrosion protection

Nowadays, corrosion is a widely observed phenomenon in metal and one of the most important reasons of degradation in industrial parts. As a result, developing and applying the methods to reduce corrosion costs in industry is essential. In this research, emulsion polymerization route was used to prepare poly (3-aminobenzoic acid) @ multi-walled carbon nanotubes (P3ABA@MWCNTs) hybrid conducting nanocomposite film. Different techniques like Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to evaluate structure and morphology of resultant materials. P3ABA@MWCNTs hybrid conducting nanocomposite demonstrated an improvement in the crystallinity as well as thermal stability. In this literature for the first time, P3ABA and P3ABA@MWCNTs hybrid conducting nanocomposite films were used as a coating for corrosion protection of copper metal. The corrosion inhibition applicability of the P3ABA and P3ABA@MWCNTs hybrid conducting nanocomposite films on copper immersed in salt solution (3.5 wt.%) was investigated by potentiodynamic polarization, electrochemical impedance spectroscopic (EIS), and open circuit potential (OCP) measurements. The results showed that the presence of MWCNTs in P3ABA matrix considerably improved the corrosion inhibition efficiency of copper metal where corrosion potential (E_corr) and corrosion current density (I_corr) were ?103 mV and 0.562 μA cm^?2, respectively. The good anti-corrosion activity of P3ABA@MWCNTs hybrid nanocomposite was most likely due to physical barrier effect, and anodic protection performance of P3ABA together enhances the overall compactness of the MWCNTs.     

Fe3O4@SiO2@ADMPT/H6P2W18O62: a novel Wells–Dawson heteropolyacid-based magnetic inorganic–organic nanohybrid material as potent Lewis acid catalyst for the efficient synthesis of 1,4-dihydopyridines

A novel Wells–Dawson heteropolyacid-based magnetic Inorganic–organic nanohybrid, Fe₃O₄@SiO₂@ADMPT/H₆P₂W₁₈O₆₂, was fabricated and used as a green, efficient, eco-friendly, and highly recyclable catalyst for the one-pot and multi-component synthesis of 1,4-Dihydopyridine (1,4-DHP) derivatives from the reaction of various aromatic aldehydes with ethyl acetoacetate and ammonium acetate with good to excellent yields and in a short span of time. The nanohybrid catalyst was prepared by the chemical anchoring of Wells–Dawson heteropolyacid H₆P₂W₁₈O₆₂ onto the surface of functionalized Fe₃O₄ nanoparticles with 2,4-bis(3,5-dimethylpyrazol)-triazine (ADMPT) linker. These nanocatalysts were identified by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and vibrating sample magnetometer (VSM). This protocol is developed as a safe, cost-effective and convenient alternate method for the synthesis of 1,4-DHP derivatives utilizing an eco-friendly, and a highly reusable catalyst.     

Selective placement of carbon nanotubes on metal-oxide surfaces

We describe a method to selectively position carbon nanotubes on Al2O3 and HfO2 surfaces. The method exploits the selective binding of alkylphosphonic acids to oxide surfaces with large isoelectric points (i.e. basic rather than acidic surfaces). We have patterned oxide surfaces with acids using both microcontact printing and conventional lithography. With proper choice of the functional end group (e.g., -CH3 or -NH2), nanotube adhesion to the surface can be either prevented or enhanced.     

High-performance,solution-processed organic thin film transistors from a novel pentacene precursor

The Lewis acid-catalyzed Diels-Alder reaction of the organic semiconductor pentacene with N-sulfinylacetamide yields a soluble adduct. Spin-coated thin films of this adduct undergo solid-phase conversion to form thin films of pentacene at moderate temperatures. Organic thin film transistors fabricated by spin-coating this adduct, followed by thermal conversion to pentacene, exhibit the highest mobility reported to date for a solution-processed organic semiconductor.     

Flame atomic absorption spectrometry determination of trace amounts of copper after separation and preconcentration onto TDMBAC-treated analcime pyrocatechol-immobilized

A simple and reliable method has been developed for green separation and preconcentration of trace amounts of copper ions in aqueous solutions for subsequent measurement by flame atomic absorption spectrometry (FAAS). The Cu²⁺ ions are adsorbed selectively and quantitatively during the passage of an aqueous solution through TDMBAC-treated analcime pyrocatechol-immobilized. The retained copper ions were desorbed from the column with 5.0 mL of 4 mol L⁻¹ nitric acid solutions as eluent and were determined by FAAS. The linear range was 0.2-75 ng mL⁻¹ in the original solution with a correlation coefficient of 0.9987. In this case we can concentrate 0.1 μg of copper from 1000 mL of solution and the proposed method permits a large enrichment factor (about 200). The detection limit of the proposed method is 0.05 ng mL⁻¹ in the original solution (2σ_bl). Determination of copper in standard alloys showed that the proposed method has good accuracy (recovery was more than 97%). The method was successfully applied for recovery and determination of copper in several water samples.     

Determination of Buprenorphine (BUP) with Molecularly Imprinted Polymer Zn/La3+ Metal Organic Framework on Modified Glassy Carbon Electrode (GCE)

In this study we report the Zn/La³⁺ metal organic frameworks (MOFs) were synthesized with the co-precipitation assisted microwave method. Zn/La³⁺ MOFs were used as a new nanocomposite for the design and construction of a nanosensor based on glassy carbon electrode (GCE). MOFs due to their unique and excellent physicochemical properties can be used in sensors based on glassy carbon electrode (GCE). The synergistic effect of MOFs on glassy carbon electrode increases the power of the limits of detection (LOD). In this study, a new chemical sensor was fabricated by electro polymerization to measure buprenorphine with MOFs based on molecularly imprinted polymer. Zn/La³⁺ MOFs nanostructures were identified with scanning electron microscopy (SEM), Dynamic light scattering (DLS), Transmission electron microscopy (TEM) and the Fourier-transform infrared spectroscopy (FT-IR) spectra. Buprenorphine was used as a template, pyrrole was used as a monomer, potassium ferrocyanide as an electrochemical active tracer in electropolymerization processes and the parameters affecting the sensor response were optimized. At the Zn/La³⁺ MOF/MIP electrode, the calibration curve in the linear region was obtained in the concentration range between 4 to 50 ng/ml and the detection limit was 1.08 ng/ml. In a new strategy, Zn/La³⁺ MOFs nanostructures can be introduced as new materials with high efficiency which used at chemical sensors for detection of the opiates in all over the world.