We report a convenient excess anion modification and post-reduction step to the impregnation method which permits the reproducible preparation of supported bimetallic AuPd nanoparticles having a tight particle size distribution comparable to that found for sol-immobilization materials but without the complication of ligands adsorbed on the particle surface. The advantageous features of the modified impregnation materials compared to those made by conventional impregnation include a smaller average particle size, an optimized random alloy composition, and improved compositional uniformity from particle-to-particle resulting in higher activity and stability compared to the catalysts prepared using both conventional impregnation and sol immobilization methods. Detailed STEM combined with EDX analyses of individual particles have revealed that an increase in anion concentration increases the gold content of individual particles in the resultant catalyst, thus providing a method to control/tune the composition of the nanoalloy particles. The improved activity and stability characteristics of these new catalysts are demonstrated using (i) the direct synthesis of hydrogen peroxide and (ii) the solvent-free aerobic oxidation of benzyl alcohol as case studies.

We report the selective oxidation of glucose to gluconic acid under mild conditions and show that if a basic support is used then the reaction can be carried out without the addition of sacrificial base or pH control. The use of sol-immobilisation prepared catalysts supported on magnesium oxide facilitates the use of ambient air as an oxidant source. These mild conditions resulted in an excellent selectivity towards gluconic acid. Different heat treatments result in an improvement in the activity of the catalyst, these improvements are discussed in terms of XRD, DRIFTD and TEM analysis of the catalysts, despite significant particle growth and phase segregation occurring during the thermal treatments.

No abstract

A Teflon AF-2400 tube-in-tube microreactor is investigated for the continuous, solvent-free, catalytic oxidation of benzyl alcohol with oxygen. The semipermeable Teflon AF-2400 tube acts as the interface between the gaseous oxidant and the liquid substrate. Because of the inherent safety of this contacting method, the use of pure oxygen is possible. The semipermeable tube was packed with 1 wt % Au−Pd/TiO 2 catalyst particles and placed inside a PTFE tube to provide an annular region which was pressurized with pure oxygen. This design allowed continuous penetration of oxygen through the inner tube during the reaction, resulting in higher oxygen concentration in the catalyst bed and significantly improved conversion compared to a reactor operating with an oxygen presaturated feed. The amount of oxygen available for reaction in the tube-in-tube microreactor was 2 orders of magnitude higher than that in a nonpermeable reactor with oxygen presaturated feed. The semipermeable tube reactor performance in terms of both conversion and selectivity was enhanced by increasing the gas pressure, the catalyst contact time and by dilution of the catalyst. The highest conversion of benzyl alcohol obtained for the range of conditions investigated was 44.1%, with 73.0% selectivity to benzaldehyde, at 120°C; catalyst contact time, 115 g cat ·s/g alcohol ; and catalyst dilution factor, 4.

No abstract

Anthraquinones are privileged chemical motifs with diverse therapeutic applications, especially in the treatment of cancer. The extensive literature highlights the significance of anthraquinones as potent anticancer agents.

The synthesis of stable, supported, bimetallic nanoalloys with controlled size, morphology and composition for selective alcohol oxidation.

Chelation therapy is one of the most effective and widely accepted methods of treatment to reduce metal toxicity caused by an excess amount of essential metals. Essential minerals play an important role in maintaining healthy human physiology. However, the presence of an excess amount of such essential metals can cause cell injury, which finally leads to severe life-threatening diseases. Chelating complexes can efficiently capture the targeted metal and can easily be excreted from the body. Commonly utilized metal chelators have major side effects including long-term damage to some organs, which has pointed out the need of less harmful biocompatible chelating agents. In this work, we have investigated the iron chelating property of curcumin through various spectroscopic tools by synthesizing and characterizing the iron−curcumin (Fe−Cur) complex. We have also investigated whether the synthesized materials are able to retain their antioxidant activity after the chelation of a substantial amount of metal ion. Our study unravels the improved antioxidant activity of the synthesized chelate complex. We further demonstrate that the proposed complex generates no significant reactive oxygen species (ROS) under dark conditions, which makes it a promising candidate for chelation therapy of iron toxicity. Femtosecond-resolved fluorescence studies further provide insight into the mechanism of activity of the new complex where electron transfer from ligand to metal has been observed prominently. Thus, the Fe−Cur complex has a potential to act as a dual activity medicine for excretion of toxic metal ions via chelation and as a therapeutic agent of oxidative stress caused by the metal ion as well.