Claudia Barolo

Determination of banned Sudan dyes in food samples by molecularly imprinted solid phase extraction-high performance liquid chromatography.

A method for molecularly imprinted SPE of banned Sudan azo-dyes from food samples was investigated. The molecularly imprinted polymer was obtained by suspension polymerization using 1-(4-chlorophenyl)azonaphthalen-2-ol as the mimic template. The molecular recognition properties of imprinted beads were evaluated for use as a SPE sorbent, in order to develop a selective extraction protocol for the Sudan class of dyes. The optimized extraction protocol resulted in a reliable molecularly imprinted SPE (MISPE) method suitable for HPLC analysis. It was selective for the main analyte, Sudan I, and the related azo-dyes Sudan II, III, IV, Sudan Red B, and Sudan Red 7B, while the permitted azo-dyes Allura Red AC, Neococcin, and Sunset Yellow FCF were not extracted. The method was tested for Sudan I, II, III, and IV in five different food samples (hot chilli pepper, hot chilli tomato sauce, sausage, tomato sauce, and hard boiled egg yolk) at three concentration levels (15, 100, and 300 microg/g). It demonstrated itself to be insensitive to the presence of different complex matrices, precise, accurate, and with good recovery rates (85-101%). The LOD and LOQ were satisfactory for most analytical determinations.

Sublimation Not an Innocent Technique : A Case of Bis-Cyclometalated Iridium Emitter for OLED

Isomerization of a neutral bis-cyclometalated iridium(III) complex has been observed for the first time during the preparation of vacuum-processed organic light-emitting devices (OLEDs) and reproduced in solution. Isolation of the isomer revealed a cis organization of the two pyridine rings of the cyclometalating ligands. Photophysical studies show very similar emission properties of the two isomers. However, due to in situ isomerization, it is only possible to prepare vacuum-processed OLED devices having a mixture of isomers.

Approaching truly sustainable solar cells by the use of water and cellulose derivatives

Aqueous dye-sensitized solar cells (DSSCs) are emerging as the first truly safe, cheap and eco-friendly photovoltaic technology, at the same time overcoming the well-known instability upon moisture/water contamination typical of many solar cells. While many aqueous DSSCs recently proposed still contain little amounts of organic solvents or petroleum-derived polymeric matrices, here we propose the first 100% hydrogel electrolyte, consisting of carboxymethylcellulose as a green jellifying agent, water and iodide/triiodide redox mediator. Electrochemical and photoelectrochemical properties of the resulting electrolytes and solar cells are thoroughly investigated, with a special focus on the long-term stability of the aqueous devices under different operating and aging conditions. The obtained promising efficiencies and stabilities, combined with a metal-free sensitizer, lead here to sustainable, stable, transparent and building-integrable solar cells, without suffering from any safety and/or toxicity issues.

Enhancing the efficiency of a dye sensitized solar cell due to the energy transfer between CdSe quantum dots and a designed squaraine dye

The power conversion efficiency of a dye-sensitized solar cell with tailored squaraine dye enhanced by 47%, due to Forster resonance energy transfer from CdSe quantum dots to the squaraine dye. The incident photons to collection efficiency of electrons indicate panchromatic response from the visible to the near-infrared spectrum.

Panchromatic ruthenium sensitizer based on electron-rich heteroarylvinylene π-conjugated quaterpyridine for dye-sensitized solar cells

The first example of a heteroarylvinylene π-conjugated quaterpyridine Ru(II) sensitizer (N1044) was synthesized and used in dye-sensitized solar cells; the dye has an effective panchromatic absorption band, covering the entire visible spectrum up to the NIR region, and superior electrochemical characteristics (HOMO/LUMO and bandgap energies) with respect to previous representative Ru(II) bi- and quaterpyridine sensitizers. A record IPCE curve ranging from 360 to 920 nm has been measured with a maximum of 65% at 646 nm and still 33% efficiency at 800 nm; this leads to substantially increased photocurrent (19.2 mA cm(-2)) when compared to the prototype N719 Ru(II) sensitizer.

Synthesis and properties of cationic surfactants with tuned hydrophylicity

A series of pyridinium-based cationic surfactants has been synthesised and their amphiphilic properties have been studied by conductivity and surface tension measurements. The modification of the substitution pattern on the pyridinium ring by hydrophobic moieties (methyl vs. hydrogen and presence or not of condensed benzene ring) gave the opportunity to investigate structure-activity relationships. Characterization by conductivity and surface tension measurements shed light on the behaviour at the air/water interface and in the micellar environment. In particular, the tendency to form ion pairs at very low concentration was evidenced for all the surfactants substituted on the ring, but not for the simple pyridinium ones. The formation of ion pairs affects both the conductivity and the surface tension plots, showing that a series of steps is involved during the adsorption to the air/water surface. An attempt was made to qualify the single steps in the adsorption at the surface layer. Those steps were attributed to different chemical species (free surfactant ions or ion pairs) and to different arrangements of the surfactant. This work also represents a contribution of investigation at very low surfactant concentrations and high surface tension values.

Microwave-Assisted Synthesis of Near-Infrared Fluorescent Indole-Based Squaraines

A microwave-assisted method for the preparation of a wide color range of 2,3,3-trimethylindolenine-based squaraines and their intermediates is described. This practical approach allows the rapid preparation of both symmetrical and nonsymmetrical squaraine dyes, reducing reaction time from days to minutes with more than 2-fold improvement in product yields when compared to conventional methods.

Design of high surface area poly(ionic liquid)s to convert carbon dioxide into ethylene carbonate

A series of porous poly(ionic liquid)s (PILs) were synthesized using an innovative method which involves the synthesis of non-ionic co-polymers such as divinylbenzene and vinylimidazole, followed by an alkylation step to introduce the ionic liquid functionality in the polymeric matrix. This synthetic strategy allowed us to obtain tunable imidazolium type PILs having simultaneously high surface area and exposed ionic moieties. A set of PILs was obtained by changing systematically the alkyl chains, the anions and the cross-linking degree. This approach allowed us to elucidate the effect of each synthetic variable on the catalytic performances of PILs towards the carbon dioxide cycloaddition reaction under very mild conditions (room temperature and low pressure). Finally, in situ FTIR spectroscopy allowed us to establish a relationship between the structure of PILs and their catalytic properties.

Combining label-free and fluorescence operation of Bloch surface wave optical sensors

We report on the design, fabrication, and characterization of optical sensors based on Bloch surface waves propagating at the truncation edge of one-dimensional photonic crystals. The sensors can be simultaneously operated in both a label-free mode, where small refractive index changes at the surface are detected, and a fluorescence mode, where the fluorescence from a novel heptamethyne dye label in the proximity of the surface is collected. The two modes operate in the near-infrared spectral range with the same configuration of the optical reading apparatus. The limit of detection is shown to be smaller than that of equivalent surface plasmon sensors and the fluorescence collection efficiency is such that it can be efficiently analyzed by the same camera sensor used for label-free operation.

Near-infrared sensitization in dye-sensitized solar cells

Dye-sensitized solar cells (DSCs) are a low cost and colorful promising alternative to standard silicon photovoltaic cells. Though many of the highest efficiencies have been associated with sensitizers absorbing only in the visible portion of the solar radiation, there is a growing interest for NIR sensitization. This paper reviews the efforts made so far to find sensitizers able to absorb efficiently in the far-red NIR region of solar light. Panchromatic sensitizers as well as dyes absorbing mainly in the 650-920 nm region have been considered.