Alberto Zeffiro

Graphene-derivatized silica as an efficient solid-phase extraction sorbent for pre-concentration of fluoroquinolones from water followed by liquid-chromatography fluorescence detection.

This work presents a novel analytical method based on graphene for the determination of five widely used fluoroquinolones (FQs) in aqueous matrices. The procedure entails solid-phase extraction (SPE) on graphene-derivatized silica (200mg), followed by liquid chromatography with fluorescence detection. Monolayer graphene oxide (GO) flakes were covalently bonded onto aminopropyl silica microparticles, and then treated with aqueous hydrazine to obtain the reduced GO (RGO). The final material (RGO-silica) was characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and BET analysis, and for the first time evaluated as mixed-mode sorbent for the SPE of FQs from natural waters. Accuracy was studied on tap/raw river water in the concentration range 5-10,000ngL(-1), obtaining mean absolute recoveries from 72 to 118%. The inter-day precision was good, showing relative standard deviations (RSDs) in the range 5-15%. Sample volumes up to 1L provided enrichment factors up to 1000, achieving accurate quantification of concentrations as low as 5ngL(-1). The analytes were simultaneously and quantitatively eluted from the RGO-silica cartridge in a single fraction by using acetonitrile combined with aqueous tetrabutyl ammonium hydroxide. The batch-to-batch reproducibility was verified on three independently prepared RGO-silica samples. RGO-silica was advantageous in terms of adsorption capacity and reusability with respect to commercial sorbents; the cartridge proved to be reusable for at least 10 consecutive extractions, with no significant loss of efficiency (recovery >70%). The analytical procedure was applied to the determination of FQs in actual environmental waters.

Testing and linearity calibration of films of phenol compounds exposed to thermal neutron field for EPR dosimetry.

This paper reports the preliminary results obtained by Electron Paramagnetic Resonance (EPR) measurements on films of IRGANOX® 1076 phenols with and without low content (5% by weight) of gadolinium oxide (Gd2O3) exposed in the thermal column of the Triga Mark II reactor of LENA (Laboratorio Energia Nucleare Applicata) of Pavia (Italy). Thanks to their size, the phenolic films here presented are good devices for the dosimetry of beams with high dose gradient and which require accurate knowledge of the precise dose delivered. The dependence of EPR signal as function of neutron dose was investigated in the fluence range between 10(11) cm(-2) and 10(14) cm(-2). Linearity of EPR response was found and the signal was compared with that of commercial alanine films. Our analysis showed that gadolinium oxide (5% by weight) can enhance the thermal neutron sensitivity more than 18 times. Irradiated dosimetric films of phenolic compound exhibited EPR signal fading of about 4% after 10 days from irradiation.

EPR/alanine pellets with low Gd content for neutron dosimetry.

This paper reports on results obtained by electron paramagnetic resonance (EPR) measurements and Monte Carlo (MC) simulation on a blend of alanine added with low content of gadolinium oxide (5 % by weight) to improve the sensitivity to thermal neutron without excessively affecting tissue equivalence. The sensitivity is enhanced by this doping procedure of more an order of magnitude. The results are compared with those obtained with the addition of boric acid (50 % by weight) where boron is in its natural isotopic composition in order to produce low-cost EPR dosemeters. The gadolinium addition influences neutron sensitivity more than the boron addition. The presence of additives does not substantially change the fading of the EPR signal induced by neutrons. The MC simulations agree the experimental results in case of gadolinium addition.

Pretreatment of alfalfa stems by wood decay fungus Perenniporia meridionalis improves cellulose degradation and minimizes the use of chemicals

Enzymes of wood decay fungi can be exploited to degrade lignocellulosic wastes for sustainable production of bioethanol. Perenniporia meridionalis was tested for growing at different temperatures on stems of alfalfa. The process aims to produce fermentable sugars and can be divided into the following steps: (1) fungal treatment to degrade lignin, (2) microwave pretreatment in water or in phosphoric acid, and (3) enzymatic hydrolysis of cell wall carbohydrates. Thermogravimetric analysis assessed the biomass content of cellulose and lignin after the fungal treatment. Throughout all steps HPLC analysis of sugars, oligomers and by-products (furfural, hydroxymethylfurfural and acids) was performed. Scanning electron microscopy was used for visual inspection and characterization of the experimental material during the treatments. The P. meridionalis pretreatment enhanced the yield of fermentable sugars obtainable by enzymatic hydrolysis in samples subjected to microwave-assisted pretreatment in water, but not in those in acid medium. This is probably related to the very selective removal of lignin by P. meridionalis, exposing cellulose fibers without depleting them. Furthermore, microwave treatment in water produced less byproducts than in acid medium. By exploiting the P. meridionalis lignin degradation is therefore possible to avoid H3PO4 use during the alfalfa stem pre-treatment, reducing economic and environmental impacts.

Structural modification of alfalfa stems during hot water and enzymatic hydrolysis for sugar production

Bioethanol production from non-food lignocellulosic material is one of the most important topics in the field of biofuel production. We report on experiments with a treatment for the production of fermentable sugars from the fibrous parts of alfalfa (Medicago sativa L.), a widely used forage plant. The process is divided into several consecutive steps: ball milling, microwave assisted pretreatment in aqueous medium and enzymatic hydrolysis with a mixture of cellulase and β-glucosidase leading to the final production of fermentable sugars. This process was followed by a detailed HPLC analysis for the detection of sugars, oligomers and by-products, such as furfural, hydroxymethylfurfural and acids. Scanning electron microscopy was used for a visual characterization of the material throughout all these steps. Several plant structures were identified and their successive changes during the different treatment steps were monitored and followed.

Properties of Glauconite/Polyaniline Composite Prepared in Aqueous Solution of Citric Acid

Hybrid composite made of glauconite and polyaniline was prepared in aqueous solution of citric acid. Scanning electron microscopy combined with energy dispersive X-ray analysis shows uniform aggregates made of glauconite microparticles and polyaniline matrix. The results of X-ray powder diffraction suggest that: (1) citric acid used for the polymerisation of aniline causes formation of emeraldine salt where macromolecular ordering in the amorphous polymer takes place; (2) no chemical interaction between glauconite and emeraldine takes place in the prepared composite. FT-IR spectra of the prepared polymer and composite show features indicating all the functional groups that are present in the diiminoquinone–diaminobenzene state of polyaniline. Thermal stability of the composite was higher than the prepared polymer suggesting the occurrence of an interphase interaction between glauconite and emeraldine. After pyrolysis in purified nitrogen the composite still remained glauconite, and ε-Fe3N together with amorphous and graphitic carbon were found as reaction products. The values of electrical conductivity and magnetization of the composite suggest that optimization of these values might be achieved based upon the relationship between glauconite and polyaniline.

Formation of Hexamethylenetetramine (HMT) from HCHO and NH3--Relevance to Prebiotic Chemistry and B3LYP Consideration.

Despite its importance in the prebiotic and biochemical fields, a complete theoretical study of the formation of hexamethylenetetramine (HMT) starting from its precursors ammonia and formaldehyde has not received due considerations in the literature with regard to the thermodynamic feasibility of many of the mechanistically proposed intermediates in its formation. Most of the studies in this area have been mostly concerned with the initial steps of the reaction between formaldehyde and ammonia, while poor attention is dedicated to successive steps. In this article, different results from published literature were critically considered and the most probable hypothesis regarding the mechanism of HMT formation is discussed on the basis of B3LYP calculations of free energies.