Intrinsic ferromagnetism created by vacancy injection in a semiconductor oxide Ti<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2 − δ</Subscript>

The possibility of creating room-temperature intrinsic ferromagnetism in a highly doped oxide semiconductor has been investigated. The results indicate that such state of a ferromagnetic semiconductor can be achieved by magnetron sputtering deposition of a semiconductor oxide doped with a transition metal followed by low-temperature vacuum annealing.     

Understanding the process of microwave-assisted digestion combining diluted nitric acid and oxygen as auxiliary reagent

Sample preparation has a long history when thinking about the conversion of solid samples to representative solutions using concentrated acid solutions and high temperature. However, chemical sciences are evolving to cleaner procedures and surely, sample preparation must follow these steps. The advent of microwave-assisted digestion led to new devices that have allowed the development of new procedures based on diluted solutions of nitric acid and more recently the use of oxygen as a reagent. No doubts oxygen has played a major role in most dry and wet digestion procedures for digestion of organic samples, but its role was improved by using it to regenerate nitric acid and consequently decreasing the volumes of acids needed to promote efficient digestions. These aspects were clearly demonstrated by comparing the efficiency of whole milk powder digestions under different pressures of oxygen, atmospheric air or inert argon atmosphere. The pressure profiles in these conditions were also evaluated and indicate the regeneration process. The efficiency of the digestion process using oxygen was demonstrated by measuring residual carbon contents and residual acidity in digests and it was shown that both parameters were fully compatible with requirements of modern instrumental analysis without any further extensive dilution of the digestates.     

Improvement of microwave-assisted digestion of milk powder with diluted nitric acid using oxygen as auxiliary reagent

The feasibility of using diluted HNO₃ solutions under oxygen pressure for decomposition of whole and non-fat milk powders and whey powder samples has been evaluated. Digestion efficiency was evaluated by determining the carbon content in solution (digests) and the determination of Ca, Cd, Cu, Fe, K, Mg, Mn, Mo, Na, Pb and Zn was performed by inductively coupled plasma optical emission spectrometry and Hg by chemical vapor generation coupled to inductively coupled plasma mass spectrometry. Samples (up to 500 mg) were digested using HNO₃ solutions (1 to 14 mol L^− 1) and the effect of oxygen pressure was evaluated between 2.5 and 20 bar. It was possible to perform the digestion of 500 mg of milk powder using 2 mol L^− 1 HNO₃ with oxygen pressure ranging from 7.5 to 20 bar with resultant carbon content in digests lower than 1700 mg L^− 1. Using optimized conditions, less than 0.86 mL of concentrated nitric acid (14 mol L^− 1) was enough to digest 500 mg of sample. The accuracy was evaluated by determination of metal concentrations in certified reference materials, which presented an agreement better than 95% (Student's t test, P < 0.05) for all the analytes.     

Spectroelectrochemistry of the redox activation of anti-cancer drug mitoxantrone

The redox behaviour of the anti-cancer drug mitoxantrone was investigated in aprotic media (dimethylsulfoxide-DMSO) by coupled electrochemical and spectral EPR and UV/VIS absorption techniques. The cyclic voltammetry study with stationary and rotating disc electrode (RDE) of the reductive pathway of mitoxantrone points to two-electron transfers and evidences as intermediate species the anion radical, the dianion and the corresponding protonated species. EPR and optical spectra registered during the electrochemical reduction allow the identification of these species and suggest the possibility of back oxidation of the drug by electron transfer to molecular oxygen. The possibility of reductive activation of molecular oxygen by the intermediate species in the redox processes of mitoxantrone is discussed in connection with the cardiotoxicity of the drug. Gas phase and solvent-dependent AM1 and PM3 semiempirical MO calculations allow a rationalization of the experimental results regarding the reactivity in redox processes.