Rosaria Anna Picca

MIP sensors – the electrochemical approach

This review highlights the importance of coupling molecular imprinting technology with methodology based on electrochemical techniques for the development of advanced sensing devices. In recent years, growing interest in molecularly imprinted polymers (MIPs) in the preparation of recognition elements has led researchers to design novel formats for improvement of MIP sensors. Among possible approaches proposed in the literature on this topic, we will focus on the electrosynthesis of MIPs and on less common hybrid technology (e.g. based on electrochemistry and classical MIPs, or nanotechnology). Starting from the early work reported in this field, an overview of the most innovative and successful examples will be reviewed.

Fluorine–thiophene-substituted organic dyes for dye sensitized solar cells

Novel triphenylamine (TPA)-based organic dyes were synthesized and assessed for their performance in dye-sensitized solar cells (DSSCs). In the dyes considered the TPA group and the cyanoacetic acid have the role of electron-donor and -acceptor, respectively, whereas a thienyl–fluoro-phenyl-substituted was introduced as π-linker to improve the dye performance in DSSCs. Experimental characterizations empasize that the presence of electron withdrawing substituents in the linker close to the electron-acceptor moiety leads to a more efficient intramolecular photoinduced charge transfer. In fact, photovoltaic experiments reveal that the DSSCs based on the thienyl–o-fluoro-phenyl substituted dyes yield a better solar-energy-to-electricity conversion efficiency.

QCM sensors for aqueous phenols based on active layers constituted by tetrapyrrolic macrocycle Langmuir films

Three different metalated tetrapyrrolic macrocycles have been transferred by Langmuir-Blodgett technique directly onto piezoelectric quartz crystal covered with gold electrodes of a commercial quartz crystal microbalance instrument in order to perform a flow injection analysis. All floating films at the air-water interface have been analyzed by registration of Langmuir curves and by UV-vis reflection spectroscopy and brewster angle microscopy. The sensing performances of the modified gold electrodes were investigated by monitoring the frequency variation induced by the presence of several toxic phenols. The explored concentrations ranged around 10-3 M and the corresponding frequency variations ranged between 10 and 200 Hz. All responses observed were fast, reproducible and reversible; moreover, the active layers are stable over long periods of utilization. The observation that interferences from fulvic acid are absolutely negligible is also noteworthy. The responses are not selective for each singular phenol derivative; notwithstanding this, to the best of our knowledge, this contribution represents one of the first examples of sensing layers for the monitoring of the total content of phenols.

Synthesis of a new substituted zinc phthalocyanine as functional monomer in the preparation of MIPs

A new zinc phthalocyanine peripherally substituted with methacrylic groups was synthesized to be employed as a functional monomer in the formation of molecularly imprinted polymers as nucleoside receptors. The binding affinity and selectivity of the synthesized phthalocyanine towards nucleosides were evaluated by UV-vis titration experiments in CH2Cl2 at 298 K. The binding constant (Ka) and Gibbs free energy changes (-ΔG0) were calculated according to the modified Benesi-Hildebrand equation. Binding experiments showed that Ka of phthalocyanine with tri-O-acetyladenosine (TOAA) is 1.35 × 104, 500 times that of phthalocyanine with tri-O-acetyluridine (TOAU), indicating a high selectivity of the synthesized phthalocyanine derivative.

The effect of XPS background removing method on the appraisal of Ti and Fe: The case of phlogopites and brookite

Abstract The determination of the oxidation state and structural role of transition metals in minerals is a crucial challenge. XPS has proven to have a great potential in probing the site distribution and chemical states of Fe and Ti transition elements, provided that the right method to process the spectra is used. XPS spectra of these elements have the 2p core level region usually rich of features but the choice of the method for background removing can seriously affect the results of the quantitative analysis. Single crystals of brookite (TiO2) and natural micas (phlogopites) are investigated to examine the effect of background subtraction on Ti2p and Fe2p signals. The backgrounds used are: the “Linear” background; the traditional “Shirley” background; three different Tougaard-like backgrounds; and the more recent “shape parameter, κ” method. In the case of the studied natural micas, the Fe chemical state proportion (Fe2+/Fetot) obtained with the corrected spectra varies by 10%. It is shown that TiO2 oxides are not suitable as standard for octahedral Ti4+ signal in the studied micas. The “shape parameter, κ” method proves to provide supplementary information useful for a full interpretation of XPS signals.