Investigating parameters on the preparation of mesoporous activated carbons by the combination of chemical and physical activations using the Taguchi method

Mesoporous activated carbons were prepared from coconut shell by the combination of chemical and physical activation methods. Zinc chloride and CO₂ were used as chemical and physical agents, respectively. Optimum parameters were obtained from investigating the effect of various factors at different levels on the methane storage of wet activated carbons using the Taguchi experimental design method. Soaking time, carbonization temperature, and carbonization time were found as effective parameters in the methane storage. Finally, after achieving optimum levels for each factors based on the enhancement of methane storage, a confirmation experiment was conducted. Methane uptakes of the activated carbons were measured at temperature of 2?^°C up to the pressure of 80 bar and it turned out that the maximum amount of methane storage (241?V/V) had a good agreement with the predicted result from the Taguchi method.     

Sol–gel-based molecularly imprinted xerogel for capillary microextraction

A novel molecularly imprinted xerogel (MIX) based on organically modified silica (ORMOSIL) was successfully prepared for on-line capillary microextraction (CME) coupled with high-performance liquid chromatography (HPLC). The sol-gel-based xerogel was prepared using only one precursor and exhibited extensive selectivity towards triazines along with significant thermal and chemical stability. Atrazine was selected as a model template molecule and 3-(trimethoxysilyl)propylmethacrylate (TMSPMA) as a precursor in which the propylmethacrylate moiety was responsible for van der Waals, dipole-dipole, and hydrogen-bond interactions with the template. This moiety plays a key role in creation of selective sites while methoxysilyl groups in TMSPMA acted as crosslinkers between the template and the propylmethacrylate moiety. Moreover, a non-imprinted xerogel (NIX) was also prepared in the absence of the template for evaluating the extraction efficiency of the prepared MIX. Then, the prepared imprinted and non-imprinted xerogels were used for extraction of three selected analytes of triazines class including atrazine, ametryn, and terbutryn, which have rather similar structures. The extraction efficiency of the prepared xerogel for atrazine, the template molecule, was found to be ten times greater than the efficiency achieved by the non-imprinted one. In the meantime, the extraction efficiency ratio of MIX to NIX for ametryn and terbutryn was also rather significant (eight times). Moreover, other compounds from different classes including dicamba, mecoprop, and estriol were also analyzed to evaluate the selectivity of the prepared MIX towards triazines. The ratio of enrichment factors (EF) of MIX to NIX for atrazine, ametryn, terbutryn, dicamba, mecoprop, and estriol were about 10, 8, 8, 2, 2, and 3, respectively. The linearity for the analytes was in the range of 5-700 μg L(-1). Limit of detection was in the range of 1-5 μg L(-1) and the RSD% values (n = 5) were all below 6.6% at the 20 μg L(-1) level. The developed method was also applied to real water samples and the relative recovery percentages obtained for the spiked water samples were from 92 to 104%. The CME loop, containing the prepared MIX, exhibited a rather long life time due to its remarkable solvent and mechanical stability. Even after 100 runs, no decrease in the peak areas was observed. The developed method could easily provide the possibility of preparing a selective sorbent in a unique way with the lowest possible cost and time.     

Copper Supported on the SiO2 Nanoparticle in Click Chemistry: An Alternative Catalytic System for Regioselective and One‐Pot Synthesis of 1,2,3‐Triazoles and β‐Hydroxytriazoles

In this work, readily prepared copper supported on the SiO₂ nanoparticles has been found to effectively catalyze the 1,3‐dipolar cycloaddition of a variety of azides, alkynes, epoxides and sodium azide, furnishing the corresponding 1,2,3‐triazoles and β‐hydroxytriazoles. Click reaction proceeds in short reaction times and under mild reaction conditions, and the resulting products are obtained in good yields at ambient temperature.     

Performance evaluation of ion‐exchange chromatography in capillary format

The performance of a recently introduced capillary ion‐exchange chromatography system was explored. Experiments were conducted in isocratic mode with a commercial capillary anion‐exchange column (id = 0.4 mm, L = 15 cm) using a five‐anion standard mixture. The achieved results were compared to the performance of a standard bore ion‐exchange system (id = 4 mm, L = 15 cm), which was considered as a reference. The first‐generation capillary columns exhibited a minimal reduced plate‐height value below two witnessing a good packing quality and system performance. However, compared to the standard bore system the capillary system displayed an increased apparent C‐term which could be due to a difference in packing morphology and/or possible external band‐broadening contributions. For fast separations, the standard bore system outperformed the capillary system, while for complex separations both systems performed nearly equally well. In addition, the retention characteristics of the capillary system were investigated. To illustrate the suitability of the capillary system, the analysis of real‐world water samples originating from two local Belgian rivers was demonstrated.     

On the biological properties of alkynyl phosphine gold(i) complexes

Golden times for metal-based drugs? Alkynyl triphenylphosphine gold(I) complexes display interesting biological properties and show high potential for future drug development. They are strong inhibitors of the enzyme thioredoxin reductase, trigger antiproliferative effects in tumor cells, and influence tumor cell metabolism, mitochondrial respiration, and angiogenesis in zebrafish embryos.     

Application of the dissociative electron transfer theory and its extension to the case of in-cage interactions in the electrochemical reduction of arene sulfonyl chlorides

Important aspects of the electrochemical reduction of a series of substituted arene sulfonyl chlorides are investigated. An interesting autocatalytic mechanism is encountered where the starting material is reduced both at the electrode and through homogeneous electron transfer from the resulting sulfinate anion. This is due to the homogenous electron transfer from the two-electron reduction produced anion (arene sulfinate) to the parent arene sulfonyl chloride. As a result, the reduction process and hence the generated final products depend on both the concentration of the substrate and the scan rate. A change is also observed in the reductive cleavage mechanism as a function of the substituent on the phenyl ring of the arene sulfonyl chloride. With 4-cyano and 4-nitrophenyl sulfonyl chlorides a "sticky" dissociative ET mechanism takes place where a concerted ET mechanism leads to the formation of a radical/anion cluster before decomposition. With other substituents (MeO, Me, H, Cl, and F) a "classical" dissociative ET is followed, where the ET and bond cleavage are simultaneous. The dissociative electron transfer theory, as well as its extension to the case of strong in-cage interactions between the produced fragments, along with gas phase chemical quantum calculations results helped us to rationalize both the observed change in the ET mechanism and the occurrence of the "sticky" dissociative ET mechanism. The radical/anion pair interactions have been determined both in solution as well as in the gas phase. The study also shows that despite the low magnitude of in-cage interactions in acetonitrile compared to the gas phase their existence strongly affects the dynamics of the involved reactions. It also shows that, as expected, these interactions are reinforced by the existence of strong electron-withdrawing substituents. The occurrence of an autocatalytic process and the existence of the radical/anion interaction may explain the differences previously observed in the reduction of these compounds in different media.     

Cytotoxicity and cellular impact of dinuclear organoiridium DNA intercalators and nucleases with long rigid bridging ligands

The DNA binding modes and cleavage properties of novel dinuclear Ir(III) polypyridyl (pp) complexes [{(η(5)-C(5)Me(5))Ir(pp)}(2)(μ-B)](CF(3)SO(3))(4) depend on the lengths of their rigid bridging dipyridinyl ligands B. Mono-intercalation and strong DNA cleavage properties were observed for the dipyrido[2,3-a:2',3'-c]phenazine (dppz) complexes 1 (B = 4-[(E)-2-(4-pyridinyl)ethenyl]pyridine) and 3 (B = 4-(2-pyridin-4-ylethynyl)pyridine), whose intracationic Ir···Ir' distances are about 13.1 and 13.3 ?, respectively. In contrast, UV/Vis and CD spectra were in accordance with a stable intertwined bis-intercalation mode for pairs of cations of 5 (B = 1,4-di(2-pyridin-4-ylethynyl)benzene), whose much longer Ir···Ir' distance of 20.6 ? allows a stack of five aromatic chromophores to be sandwiched between its effectively parallel dppz ligands. Whereas both 1 and 3 cleaved DNA in the dark, complex 5 exhibited only photoinduced nuclease activity. A significantly higher antiproliferative activity towards MCF-7 breast carcinoma cells was observed for the nucleases 1 and 3, whose IC(50) values of 0.61 and 0.49 were much lower than that of 2.2 μM for bis-intercalator 5. Values of 3.8 μM, only slightly higher than that of 5, were recorded for the 5,6-dimethylphenanthroline complexes 4 and 6, whose bridging ligands are identical to those of 3 and 5, respectively. Marked antileukemic activity (IC(50) = 6-7 μM) associated with increased levels of reactive oxygen species and apoptosis induction was recorded for both 3 and 5 towards Jurkat cells at concentrations of 5 μM and above. Online studies with a sensor chip system indicated that 5 μM solutions of these complexes invoke a rapid and massive reduction in MCF-7 cell respiration.     

Efficacy of Ficus spp. on renal injury induced by hypercholesterolaemia

The ethanol and hexane extracts of Ficus microcarpa, Ficus religiosa and Ficus mysorensis leaves were evaluated against renal injury induced by hypercholesterolaemia. Phytochemical screening of the investigated plants was undertaken. For the in vivo study, all rats were orally given cholesterol (30?mg?kg?1 body weight, BW) and leaves extract (500?mg?kg?1 BW) five times per week for 9 weeks. Hypercholesterolaemic rats showed significant increases in urea nitrogen and creatinine while serum protein and albumin levels, nitric oxide (NO), Na?-K?-ATPase and phospholipids in kidney tissue were all decreased. Treatment with leaves extract improved kidney function indices (urea nitrogen, creatinine, serum protein and albumin), kidney disorder biochemical parameters (NO, Na?-K?-ATPase and phospholipids), haematological profile (haemoglobin, RBCs and WBCs) and kidney histopathology. In conclusion, Ficus spp. succeeded in improving renal injury induced by hypercholesterolaemia, with the most potent effects seen while using Ficus microcarpa hexane extract.     

Identification problems for degenerate parabolic equations

This paper deals with multivalued identification problems for parabolic equations. The problem consists of recovering a source term from the knowledge of an additional observation of the solution by exploiting some accessible measurements. Semigroup approach and perturbation theory for linear operators are used to treat the solvability in the strong sense of the problem. As an important application we derive the corresponding existence, uniqueness, and continuous dependence results for different degenerate identification problems. Applications to identification problems for the Stokes system, Poisson-heat equation, and Maxwell system are given to illustrate the theory.     

Specific heat and electrical conductivity of deuterated triglycine selenate single crystals

Measurements of the specific heat were carried out on deuterated trigylcine selenate (DTGSe) single crystals to clarify its critical nature near the ferroelectric transition point (T_c ). The results obtained have indicated that DTGSe crystals deuterated by 90% exhibit a first-order phase transition.

This paper presents also the electrical conductivity (δ) of DTGSe crystals. The deuterium substitution induces an increase in the Curie point T_c , and a decrease in the conductivity in the para- and ferroelectric phases accompanied by an increase in the activation energy (W) in both phases.