Analytical solution for temperature field in thin film initially heated by a short-pulse laser source

Analytical solution for electron and lattice temperature distribution in the solid initially heated by a laser short-pulse is presented. Strained parameters method is introduced when formulating electron and lattice temperature distributions. Laser short pulse heating of gold film is simulated numerically and temperature data at the end of the heating pulse are adopted as initial condition to the governing equations of energy transport for analytical solutions. This enables to solve the governing equations of energy analytically in the cooling period. It is found that electron temperature decays sharply while lattice site temperature increases gradually in the surface regions during the cooling cycle. As the depth from the surface increases change in both temperatures become gradual.     

Ordered Nanoporous Carbon-Based SPME and Determination by GC

CMK-1 (carbon mesoporous from Korea) type ordered nanoporous carbon was investigated as a novel solid-phase microextraction fiber for the first time. The microextraction process was coupled with GC-FID and used to extract benzene, toluene, ethylbenzene and xylenes (BTEX) from the head space of the solution samples. Prepared fibers featured advantages like easy and fast preparation, high thermal and mechanical stability in which a fiber could be used for more than 60 tests. Employing Taguchi method and orthogonal array design; OA₁₆ (4⁵), the HS-SPME of BTEX was optimized. Under the optimized conditions for all BTEX components, the linearity was from 3 to 800 μg L^?1, the relative standard deviation (RSD%) of the method was between 4.2 and 9.4% and limit of detections was between 0.27 and 1.1 μg L^?1. The recovery values were from 87.1 to 106.2% in water samples. Finally, the applicability of the proposed method was evaluated by the extraction and determination of BTEX in the water and petrochemical samples.     

Interaction of double-stranded DNA inside single-walled carbon nanotubes

Deoxyribonucleic acid (DNA) is the genetic material for all living organisms, and as a nanostructure offers the means to create novel nanoscale devices. In this paper, we investigate the interaction of deoxyribonucleic acid inside single-walled carbon nanotubes. Using classical applied mathematical modeling, we derive explicit analytical expressions for the encapsulation of DNA inside single-walled carbon nanotubes. We adopt the 6–12 Lennard–Jones potential function together with the continuous approach to determine the preferred minimum energy position of the dsDNA molecule inside a single-walled carbon nanotube, so as to predict its location with reference to the cross-section of the carbon nanotube. An analytical expression is obtained in terms of hypergeometric functions which provides a computationally rapid procedure to determine critical numerical values. We observe that the double-strand DNA can be encapsulated inside a single-walled carbon nanotube with a radius larger than 12.30 ?, and we show that the optimal single-walled carbon nanotube to enclose a double-stranded DNA has radius 12.8 ?.     

Synthesis and characterization of ordered mesoporous carbon as electrocatalyst for simultaneous determination of epinephrine and acetaminophen

In this research, we report an easy method for synthesis of ordered mesoporous carbon (OMC) with hexagonal arrays of tubes (CMK-5). The synthesized OMC was characterized using X-ray diffraction (XRD), scanning electronic microscopy (SEM) and nitrogen sorption isotherms techniques. Due to the large surface area and high conductivity of OMC, OMC-modified glassy carbon (OMCs/GC) electrode was prepared. The unique electrochemical activity of OMCs/GC electrode was illustrated using cyclic voltammetry (CV) and electron impedance spectroscopy (EIS) in which OMC showed a faster electron transfer rate, as compared with glassy carbon electrode. The electrochemical behavior of epinephrine (EN) and acetaminophen (AP) at OMC/GC electrode was also investigated using cyclic voltammetry. The OMC/GC electrode exhibited high electrocatalytic activities toward oxidation of EN and AP and displayed good voltammetric peak separation between them. In differential pulse voltammetry technique, both EN and AP give sensitive oxidation peaks at 120?mV and 320?mV, respectively. Therefore, investigated method was applied for simultaneous determination of EN and AP. AP and EN give linear response over the range of 0.2–15?μM and 4–100?μM, respectively. The lower detection limits were found to be 0.07?μM for AP and 0.94?μM for EN.     

Nanoporous Lanthanum Tungstate: A Viable Adsorbent for Heavy Metals and Organic Pollutants

Removal of heavy metal cations from synthetic and industrial electroplating effluents by means of mesoporous lanthanum tungstate sorbents was thoroughly investigated. Three types of such sorbents, namely I‐LT, II‐LT and III‐LT, uncalcined and calcined, were produced and characterized by means of X‐ray diffraction, nitrogen sorption isotherms and thermogravimetry analysis (TGA). Results of the experiments for chromium, copper, mercury, iron and lead removal from both synthetic and real industrial wastewater solutions, using these novel sorbents, exhibit promising. Details of this new approach towards wastewater treatment have been discussed and the potentials of technological advancement using mesoporous lanthanum tungstate for environmental purposes addressed. Comparison with the literature shows superiority of the produced adsorbents over reported products.     

Hg(II) Selective Complexation by Chromoionophoric Calix[4]arene Derivative

The present article describes an exploration regarding Hg(II) selective complexation behavior of 5,11,17,23-tetrakis[(N,N-dimethylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (4). The binding affinity of 4 toward selected transition metal ions such as Cd(II), Co(II), Cu(II), Hg(II), Ni(II), Pb(II) and Zn(II) have been investigated by UV-visible and fluorescence spectroscopies. From the results it has been noticed that 4 confers a pronounced preference for Hg(II) in complexation phenomenon even in the presence of other metal ions. The results of Job's plot analysis reveal 1:1 host-guest complex formation between Hg(II) and 4. The FT-IR spectroscopy also supports the complexation affinity of 4 for Hg(II).     

Hydrated titanium dioxide as an adsorbent for99Mo−99mTc generator

The adsorption behaviour of⁹⁹Mo in the form of molybdate and of^99mTc in the form of pertechnetate on hydrated titanium dioxide was investigated at different molarities of hydrochloric acid. The adsorption capacity of molybdate on hydrated TiO₂ is higher than on Al₂O₃. A^99mTc-generator is suggested. This generator is based on the adsorption of (⁹⁹Mo) molybdate on hydrated TiO₂, at acidities of 0.05–0.1M. HCl.^99mTc is eluted with 0.9% NaCl. Radionuclidic, radiochemical and chemical purities of the eluates were checked. This generator seems to have a great potential as compared to the traditional alumina generators.