Synthesis of Copper Graphene Materials Functionalized by Amino Acids and Their Catalytic Applications

Graphene oxide and its derivative have attracted extensive interests in many fields, including catalytic chemistry, organic synthesis, and electrochemistry, recently. We explored whether the use of graphene after chemical modification with amino acids to immobilize copper nanoparticles could achieve a more excellent catalytic activity for N-arylation reactions. A facile and novel method to prepare copper supported on amino-acid-grafted graphene hybrid materials (A–G–Cu) was first reported. The as-prepared hybrid materials were characterized by a variety of techniques, including Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and inductively coupled plasma–atomic emission spectrometry. The results showed that the morphology, distribution, and loading of copper nanoparticles could be well-adjusted by controlling the type of amino acids grafted on graphene. Moreover, most A–G–Cu hybrid materials could catalyze N-arylation of imidazole with iodobenzene with yields more than 90%, while the copper supported on graphene (G–Cu) displayed a yield of just 65.8%. The high activity of A–G–Cu can be ascribed to the good synergistic effects of copper nanoparticles (Cu NPs) and amino-acid-grafted graphene

Molecular efficacy of radio- and chemotherapy sequences from direct DNA damage measurements

<p><b>Purpose:</b> To investigate the molecular aspects of the synergy between ionizing radiation and platinum (Pt) chemotherapeutic agents in cancer treatment with chemoradiation therapy (CRT) by measuring damages induced by low-energy electrons (LEE) to DNA bound to cisplatin. LEE are produced abundantly by any type of ionizing radiation and cisplatin represents a typical Pt-chemotherapeutic agents.</p> <p><b>Materials and methods:</b> Our strategy involves two parallel administrations of cisplatin and irradiation with a 4.6 and 9.6 eV electron fluence of 1.1 × 10¹²: (1) LEE bombardment of supercoiled DNA and its subsequent reaction with cisplatin; (2) the reaction of DNA with cisplatin followed by LEE irradiation. The damage yields for the loss of supercoiled (LS), single-strand breaks (SSB) and double-strand breaks (DSB) were obtained from gel electrophoresis analysis. Base modifications were revealed by treating the samples with <i>Escherichia coli</i> base excision repair endonuclease (Nth and Fpg).</p> <p><b>Results:</b> The yields were deduced from the respective time–response for the reaction of DNA with cisplatin. The results show that binding cisplatin to DNA followed by LEE irradiation, consistently yields more DNA damages than the reverse order. In comparison to non-treated DNA, administration (2) results in an increase of LS and SSB of 1.4–3.3 folds and of DSB by more than an order of magnitude. Furthermore, after enzyme treatment, the yields of DSB rise by factors of 5.3–15.4, indicating a large increase of clustered damages, which should at least partially translate into an increase of lethal damages in cancer cells during the CRT.</p> <p><b>Conclusions:</b> Our results demonstrate that a strong synergy between radiation and cisplatin can only be achieved at the molecular level, if the drug is present at the time of irradiation. Furthermore, this work confirms the LEE mechanism previously proposed to explain the synergy between radiation and Pt drugs in CRT. It involves chemical sensitization of DNA prior to irradiation, to facilitate strand breaks and clustered damages induced by the highly reactive LEE.</p

Comparison of Fe/surfactant improved montmorillonite: adsorbing and in situ decomposing methylene blue and recycling use

<p>Montmorillonite (MMt) was intercalated by polymeric Fe, or by N-ethyl dodecyl nicotinate bromide (EDNB), or by both. The improved MMt designated as Fe/MMt, EDNB/MMt, and EDNB/MMt/Fe, respectively. A comparison was performed on the improved MMt in the uptake and in the degradation of methylene blue (MB) as well as in the recycling use. The results showed that EDNB/MMt adsorbed more MB than the other two; however, Fe/MMt and EDNB/MMt/Fe acted faster than the former. The adsorption of MB on the three adsorbents followed Langmuir isotherm and pseudo-second-order kinetics. In addition, MB adsorbing on EDNB/MMt was also well described by intraparticle diffusion model. MB removal by EDNB/MMt experienced an endothermic and entropy driving process, but an exothermic and entropy declining process by the other two. pH of the solution affected MB removal. When pH of the solution is high than 10, MB uptake diminished on Fe/MMt and EDNB/MMt/Fe; however, it slightly increased on EDNB/MMt. MB could be decomposed by Fenton reagent on the improved MMt, and the adsorbents could be reused. By coupling the adsorption and degradation <i>in situ</i> by H₂O₂/Fe²⁺ or Fe³⁺, MB removal by Fe/MMt and EDNB/MMt/Fe was almost maintained in the ten cycles. So, present work deepens the understanding of modified MMt in the application of dye wastewater treatment.</p

A Comparison of New Gemini Surfactant Modified Clay with its Monomer Modified One: Characterization and Application in Methyl Orange Removal

New gemini surfactant, glycol bis-<i>N</i>-tetradecyl nicotinate dibromide (designated E_G), and the corresponding monomer, methyl <i>N</i>-tetradecyl nicotinate bromide (E_S), were synthesized and utilized to modify sodium bentonite (Na-Bt). E_G-Bt and E_S-Bt, the surfactant modified bentonites, were then used for methyl orange (MO) removal from the dye solution. E_G was more effective than E_S at expanding the interlayer space of Na-Bt. The adsorption of E_G, E_S and MO obeyed well the pseudo-second-order kinetic model and Langmuir isotherms on Na-Bt or on the modified bentonite. However, the adsorption of E_G was more spontaneous than that of E_S, and E_G replaced more small particles, such as Na⁺ and water, than E_S did during the adsorption on Na-Bt. The elevated temperature impairs the adsorption of the surfactants, but enhances that of MO. MO absorbed more easily on E_G-Bt than on E_S-Bt. When the dosage of the surfactants used goes beyond a certain amount, the uptake of MO by E_G-Bt/E_S-Bt decreases slowly owing to desorption of the surfactants. E_G and E_S formed a complex with MO on the modified bentonite as evidenced by UV–vis spectra, and E_G exhibited the stronger interaction with MO

Self-Assembly and Anticorrosive Property of <i>N</i>‑Alkyl-4-[2-(methoxycarbonyl)vinyl]pyridinium Bromides on X70 Steel in an Acid Medium: an Experimental and Theoretical Probe

A new type of self-assembly inhibitors, <i>N</i>-alkyl-4-[2-(methoxycarbonyl)­vinyl]­pyridinium bromide surfactants (designated as PPA-<i>n</i>, <i>n</i> = 8, 10, 12, and 14), has been synthesized and characterized by various spectrum methodologies. The anticorrosive performance of PPA-<i>n</i> on X70 steel in 5 M HCl was evaluated via weight loss and electrochemical methods as well as theoretical calculation. Scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy evidenced that PPA-<i>n</i> molecules self-assembled and formed a compact monolayer on the X70 surface, which blocked the active sites and elevated the energy barrier of the corrosion reaction of X70 steel. The inhibitory efficiency of PPA-<i>n</i> was up to 98% at 75 μM PPA-14. The inhibition capacity as well as resistance to corrosion at higher temperature increased with prolonged alkyl chain in PPA-<i>n</i>. Density functional theory calculation suggested that the ester group and pyridinium ring might be the most active sites for PPA-<i>n</i> adsorbing on the X70 steel surface via the π* orbital of the pyridinium accepting the 4s electrons of iron and empty 3d orbital of iron taking up the nonpair electrons of the O atom in PPA-<i>n</i>. The energy gap of the frontier orbitals of PPA-<i>n</i> are in the order of PPA-8 > PPA-10 > PPA-12 > PPA-14, inferring a contrary order in the inhibition efficiency