Synthesis of Ag nanoparticles for the electrochemical detection of anticancer drug flutamide

Ag nanoparticles were synthesized on the surface of a glassy carbon electrode modified with p‐tert‐butylcalix[4]arene and p‐tert‐butylcalix[6]arene by the deposition of Ag+at an open circuit potential ...     

Sensing behavior of BN nanosheet toward nitrous oxide: A DFT study

In order to develop a sensor for the detection of toxic N₂O molecules, the interaction of pristine and Aldoped BN nanosheets with an N₂O molecule was investigated using density functional theory calculations. It was found that unlike the pristine sheet, the Al-doped sheet can effectively interact with the N₂O molecule so that its electronic properties and conductivity are dramatically changed. Webelieve that replacing a B atom of the BN sheet with an Al atom may be a good strategy for improving the sensitivity of these nanosheets toward N₂O, which cannot be trapped and detected by the pristine sheet.     

Effect of different blend compositions on properties of low-density polyethylene/ethylene vinyl alcohol/clay toward high oxygen barrier nanocomposite films

In this study, high oxygen barrier nanocomposite films were prepared by melt blending of low-density polyethylene/ethylene vinyl alcohol/nanoclay/polyethylene-grafted-maleic anhydride (LDPE/EVOH/nanoclay/LDPE-g-MA). Effect of each component presence was determined by using Box-Behnken experiment design methodology. For all the responses obtained, R ² was between 0.956 and 0.981 indicating a very good fitting of the experimental data with the response surface method (RSM) in the models. Oxygen transfer rate (OTR) results shown that the addition of EVOH, compatibilizer, and nanoclay in formulations significantly decreases oxygen permeability. The experimental results showed that addition of 30 wt % EVOH, 4 wt % nanoclay, and 5 wt % LDPE-g-MA to the LDPE matrix gave the best oxygen barrier properties. The crystallization behaviors of the samples and thermal analysis have been characterized by using differential scanning calorimetry (DSC). The addition of nanoclay to the blends has resulted in increased crystallinity of LDPE phase. The state of nanoclay dispersion in the samples was examined by the X-ray diffraction (XRD) tests. The reduction of EVOH and nanoclay content, as well as the increase of LDPE-g-MA, has resulted in the better dispersion of nanoclay in the polymer matrix. The morphology of specimens was observed by using energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM).     

Reactively compatibilized and dynamically vulcanized thermoplastic elastomers based on high-density polyethylene and reclaimed rubber

Melt blending was employed to prepare thermoplastic elastomer (TPE) of reclaimed rubber (RR) and high density polyethylene (HDPE). Mechanical properties of TPE samples were improved in different methods including dynamic vulcanization and reactive blending (reactive compatibilization) during melt mixing in an internal Haake mixer. The physical and mechanical properties of the TPE blends were investigated by the dynamic mechanical analysis (DMA) and tensile tests. The thermal behavior was characterized by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The phase morphology of the blends was studied by scanning electron microscopy (SEM). Experimental results showed that, both static and dynamic mechanical properties of reactively-compatibilized and dynamically-vulcanized samples improved significantly compared with the virgin samples. The effect of dynamic-vulcanization and reactivecompatibilization on the mechanical properties revealed that the Young’s modulus and storage modulus increased with both improvement methods. SEM results showed that, dynamic-vulcanization and reactivecompatibilization methods improved the distribution of RR particles in HDPE matrix. Although both methods improved the thermal and mechanical properties of the HDPE/RR blends, dynamic-vulcanization was more effective and promising approach due to the higher properties of HDPE/RR blends prepared by this method.     

A functional series expansion method for response analysis of non-linear systems subjected to random excitations

A Wiener-Hermite functional series expansion method for response analysis of nonlinear systems under random excitations is presented. The formal procedure for the derivation of the deterministic equations governing the Wiener-Hermite kernel functions is described. A singleterm expansion is used to analyze the non-stationary responses of a damped Duffing oscillator subjected to several modulated white noises. An iterative procedure for evaluating the kernel functions and the mean-square responses of the Duffing oscillator is developed. For several values of non-linearity strength and different damping coefficients the non-stationary variances and autocorrelations of the response are obtained. The results are compared with those found by the digital simulations and the existing methods.     

Studies and X‐ray Determinations with 2‐(Acetonylthio)benzothiazole: Synthesis of 2‐(Benzothiazol‐2‐ylthio)‐1‐phenylethanone and 2‐(Acetonylthio)Benzothiazole by C―S Bond Cleavage of 2‐(Acetonylthio)benzothiazole in KOH

New route for the synthesis of 2‐(benzothiazol‐2‐ylthio)‐1‐phenylethanone ( 6 ) and 2‐(acetonylthio)benzothiazole ( 1 ) by using phenacyl bromide and α‐chloroacetone, respectively, through carbon–sulfur bond cleavage reactions in a basic medium has been generated. Treatment of 1 with malononitrile and elemental sulfur afforded the corresponding derivative of 2‐amino‐3‐cyanothiophene ( 12 ), whereas treatment of 1 with cyanoacetohydrazide afforded the corresponding derivative of cyanoacetylhydrazone derivative ( 13 ). The structure of the synthesis compounds has been established on the basis of elemental analyses, ¹H‐NMR, ¹³C‐NMR, correlation spectroscopy, heteronuclear single quantum coherence, MS spectra, and X‐ray crystallographic investigations.     

Synthesis and application of a novel solid-phase microextraction adsorbent: hollow fiber supported carbon nanotube reinforced sol-gel for determination of phenobarbital

The present study reports the development, validation and application of a new green liquid chromatographic method for the determination of glutathione (GSH) in vegetable samples. In this work we introduce—for the first time—ethyl propiolate (EP) as an advantageous post-column derivatization reagent for thiolic compounds. GSH (t_R = 6.60 min) and N-acetylcysteine (NAC, internal standard) (t_R = 11.80 min) were separated efficiently from matrix endogenous compounds by using a 100% aqueous mobile phase (0.1%, v/v CH₃COOH in 1 mmol L⁻¹ EDTA, Q_V = 0.5 mL min⁻¹) and a Prevail^® reversed phase column that offers the advantage of stable packing material in aqueous mobile phases. The parameters of the post-column reaction (pH, amount concentration of the reagent, flow rates, length of the reaction coil and temperature) were studied. The linear determination range for GSH was 1–200 μmol L⁻¹ and the LOD was 0.1 μmol L⁻¹ (S/N = 3). Total endogenous GSH was determined in broccoli, potato, asparagus and Brussels sprouts using the standards addition approach. The accuracy was evaluated by both recovery experiments (R = 91–110%) and comparison to an o-phthalaldehyde/glycine corroborative post-column derivatization fluorimetric method.     

Chemisorption of NH3 at the open ends of boron nitride nanotubes: a DFT study

Considering the thermodynamic aspects and reaction pathways of chemical adsorption of NH₃ molecule at the open ends of boron nitride nanotubes (BNNTs), theoretically, it was found that the open-ended BNNTs are able to cleave the N–H bond of NH₃ via a one- or two-stepwise mechanism. The N-enriched and B-enriched open-ended BNNTs show a nucleophilic and electrophilic behavior toward the NH₃, respectively. Besides, some effects of this chemical adsorption on the electronic properties of BNNTs were explored.     

Synthesis and application of a novel solid-phase microextraction adsorbent: Hollow fiber supported carbon nanotube reinforced sol–gel for determination of phenobarbital

A novel solid-phase microextraction technique using a hollow fiber-supported sol–gel combined with multi-walled carbon nanotubes was employed in the determination of phenobarbital in wastewater. In this new technique, a silica-based, organic–inorganic polymer containing functionalized multi-walled carbon nanotubes (MWCNTs) was prepared with sol–gel technology via the reaction of tetraethylorthosilicate (TEOS) with an acidic catalyst (HCl). This sol was injected into a polypropylene hollow fiber segment for in situ gelation. This device operated in direct immersion sampling mode. The experimental setup is simple and affordable, and the device is disposable, so there is no risk of cross-contamination or carry-over. Parameters affecting extraction such as pH of the aqueous solution, ageing and extraction times, aqueous sample volume, agitation speed and carbon nanotube amount were optimized. Linearity was observed over a range of 0.50–5000 ng mL⁻¹, with an estimation coefficient (r²) higher than 0.982. The limit of detection (LOD) was 0.32 ng mL⁻¹ (n = 5), and repeatability (RSD% = 2.9) was from the average of three levels of analyte concentrations (1, 1000 and 4500 ng mL⁻¹) with three replicates for each within a single day. Finally, a pre-concentration factor of 2100 was obtained for phenobarbital.     

Study binding of Al-curcumin complex to ds-DNA, monitoring by multispectroscopic and voltammetric techniques

In this work a complex of Al3+ with curcumin ([Al(curcumin) (EtOH)2](NO3)2) was synthesized and characterized by UV-vis, FT-IR, elemental analysis and spectrophotometric titration techniques. The mole ratio plot revealed a 1:1 complex between Al3+ and curcumin in solution. For binding studies of this complex to calf thymus-DNA various methods such as: UV-vis, fluorescence, circular dichroism (CD), FT-IR spectroscopy and cyclic voltammetry were used. The intrinsic binding constant of ACC with DNA at 25°C was calculated by UV-vis and cyclic voltammetry as 2.1×10(4) and 2.6×10(4), respectively. The thermodynamic studies showed that the reaction is enthalpy and entropy favored. The CD results showed that only the Δ-ACC interacts with DNA and the Δ-ACC form has not any tendency to interact with DNA, also the pure curcumin has not any stereoselective interaction with CT-DNA. Fluorimetric studies showed that fluorescence enhancement was initiated by a static process in the ground state. The cyclic voltammetry showed that ACC interact with DNA with a binding site size of 2. From the FT-IR we concluded that the Δ-ACC interacts with DNA via partial electrostatic and minor groove binding. In comparison with previous works it was concluded that curcumin significantly reduced the affinity of Al3+ to the DNA.