Sandu Peretz

Improving the Properties of CdS Nanoparticles by Adding Polymers

The properties of cadmium sulfide (CdS) nanoparticles generated in the aqueous phase by adding a specially obtained maleic anhydride/styrene copolymer and polymers with different electrical charges—like alginate, chitosan, carrageenan, and polyvinyl pyrrolidone—were improved in order to reduce their toxicity. The cytotoxic effect of CdS semiconductor nanoparticles coated with polymers on cultures of Vero cells was investigated. CdS semiconductor nanoparticles were synthesized and stabilized in aqueous-polymeric system by mixing cadmium nitrate with sodium sulfide into aqueous polymeric solution, with nitrogen gas bubbled throughout the system. The fluorescence properties of nanoparticles depend on the nature of capping polymer. Transmission electronic microscopy gives the information about the size and size distribution of the nanoparticles. The computed size diagrams of CdS nanoparticles have different frequency depending of the used polymer. The nanoparticles coated with polymers presented low toxicity against cultures of Vero cells for a determined period of time. The toxicity diminished up to 10 times by covering the semiconductor nanoparticles with polymers.

ANALYTICAL ASPECTS REGARDING THE FLAVOR COMPOUNDS IN BEER

Contemporary population shows a great tendency to consume food capable of generating an intense feeling. Each food contains substances that generate sensations of taste and aroma. Beer is a food with specific flavor, which is mostly appreciated if, is fresh. It is considered that the beer flavor is dependent on the nature and the concentration of carbonyl compounds that are formed during the fermentation of the malt; the most important is the diacetyl (butandione). Carbonyl compounds in beer can be analyzed after a selective preconcentration. The methods of partial isolation as head space method and membrane process are designed to provide only qualitative information. For quantitative determination of carbonyl compounds present in beer, full extraction methods are used. The gas chromatographic separation method is used in order to study the mixtures obtained after the isolation of carbonyl compounds in beer. When the electron capture detector is used, only vicinal diketones can be identified and dosed in beer. The mixtures of 2,4-dinitrophenylhidrazone precipitates can be analyzed by spectrophotometric study or by liquid chromatographic separation. The analytical focus is the identification and dosing of the butandione and pentandione that have a key role in generating the sensation of flavor of beer. Brewers need rapidly and accurate information on the concentration of diacetyl in beer. In order to help the process, a neural sensor was proposed. It is used to determine the intensity of flavor sensation and it should provide the possibility of differentiating the products that come from different beer suppliers.

Chitosan/anionic surfactant microparticles synthesized by high pressure spraying method for removal of phenolic pollutants

AbstractBiopolymeric microparticles were prepared by rapid expansion of high pressure CO2-chitosan (Chi) solution in sodium bis-(2-ethyl hexyl) sulfosuccinate (AOT) solution. At pressures higher than 2 MPa, ultrafine particles were formed while under this value, wires were obtained. The formation of Chi/AOT complex was confirmed by Fourier Transform Infrared (FTIR) Spectroscopy, whereas scanning electron microscopy was used to characterize the morphology, size and shape of the particles. The FTIR spectrum proved the interaction between the sulfonate groups of AOT and the amino groups of Chi. Microparticles are quasi-spherical in wet conditions and irregular after freeze drying, presenting a rough surface with many pores. Lyophilized hydrophobic microparticles were used to remove phenol and o-cresol from aqueous solution, and the adsorption process showed a maximum efficiency in the 7–8 pH range. The uptake of phenol and o-cresol increased with the amount of particles and decreased with increasing the pollutant concentration. The adsorption occurred rapidly in the first 60–120 minutes, and leveled off thereafter.