Rosanna Pagano

Enhancement of Open Circuit Voltage of a ZnO-Based Dye-Sensitized Solar Cell by Means of Piezotronic Effect

Two of the most known properties of ZnO were used to improve the performance of a dye-sensitized solar cell (DSSC) using a nanoadduct formed by zinc oxide and the well-known ruthenium dye N719. The wurtzite form of zinc oxide suffers from piezoelectricity and its energetic levels are very similar to those of the most used inorganic semiconductor employed in DSSCs, that is, TiO2 . We demonstrate that the synthesis of a ZnO@N719 nanoadduct does not affect the electronic communication between the inorganic semiconductor and the organic dye. The I-V characteristics in the dark and under illumination highlight a photoactivity of the ZnO@N719 active layer with values of Jsc , Voc and fill factor comparable to the data reported in the literature. When a mechanical strain is applied to the ZnO@N719 film, a piezopotential is recorded and it depends on the intensity of the applied pressure. According to the piezotronic effect, mechanical strain contributes to increase the open circuit voltage by about 14 %.

Conformational switching of ethano-bridged Cu,H2-bis-porphyrin induced by aromatic amines.

Summary Cu,H2-bis-porphyrin (Cu,H2-Por2), in which copper porphyrin and free-base porphyrin are linked together by an ethano-bridge, was dissolved in chloroform and spread at the air/liquid subphase interface of a Langmuir trough. The bis-porphyrin derivative, floating film was characterized by reflection spectroscopy and the surface pressure of the floating film was studied as a function of the mean area per molecule. When aromatic amines are dissolved in the subphase, an evident interaction between the bis-porphyrin host and the aromatic amine guest is observed. A clear-cut variation of the profile of surface pressure vs area per molecule curve is observed. Reflection spectroscopy highlights that the aromatic amines dissolved in the subphase are able to induce the syn-to-anti conformational switching in the bis-porphyrin derivative. The Langmuir–Schaefer technique has been used to transfer the floating bis-porphyrin film (when using pure water as a subphase) to a surface plasmon resonance (SPR) substrate and the resulting device was able to detect the presence of aniline at concentrations as low as 1 nM in aqueous solution. The high selectivity of the SPR sensing device has been verified by checking the spectral response of the active layer towards other analytes dissolved in the aqueous solutions.

An SPR based immunoassay for the sensitive detection of the soluble epithelial marker E-cadherin

Protein biomarkers are important diagnostic tools for cancer and several other diseases. To be validated in a clinical context, a biomarker should satisfy some requirements including the ability to provide reliable information on a pathological state by measuring its expression levels. In parallel, the development of an approach capable of detecting biomarkers with high sensitivity and specificity would be ideally suited for clinical applications. Here, we performed an immune-based label free assay using Surface Plasmon Resonance (SPR)-based detection of the soluble form of E-cadherin, a cell-cell contact protein that is involved in the maintaining of tissue integrity. With this approach, we obtained a specific and quantitative detection of E-cadherin from a few hundred microliters of serum of breast cancer patients by obtaining a 10-fold enhancement in the detection limit over a traditional colorimetric ELISA.

Stimulatory Effects of Methyl-β-cyclodextrin on Spiramycin Production and Physical–Chemical Characterization of Nonhost@Guest Complexes

Spiramycin is a macrolide antibiotic and antiparasitic that is used to treat toxoplasmosis and various other infections of soft tissues. In the current study, we evaluated the effects of α-cyclodextrin, β-cyclodextrin, or methyl-β-cyclodextrin supplementation to a synthetic culture medium on biomass and spiramycin production by Streptomyces ambofaciens ATCC 23877. We found a high stimulatory effect on spiramycin production when the culture medium was supplemented with 0.5% (w/v) methyl-β-cyclodextrin, whereas α-cyclodextrin or β-cyclodextrin weakly enhanced antibiotic yields. As the stimulation of antibiotic production could be because of spiramycin complexation with cyclodextrins with effects on antibiotic stability and/or efflux, we analyzed the possible formation of complexes by physical–chemical methods. The results of Job plot experiment highlighted the formation of a nonhost@guest complex methyl-β-cyclodextrin@spiramycin I in the stoichiometric ratio of 3:1 while they excluded the formation of complex between spiramycin I and α- or β-cyclodextrin. Fourier-transform infrared spectroscopy measurements were then carried out to characterize the methyl-β-cyclodextrin@spiramycin I complex and individuate the chemical groups involved in the binding mechanism. These findings may help to improve the spiramycin fermentation process, providing at the same time a new device for better delivery of the antibiotic at the site of infection by methyl-β-cyclodextrin complexation, as it has been well-documented for other bioactive molecules.

The role of the central metal ion of ethane-bridged bis-porphyrins in histidine sensing

Ethane-bridged bis-porphyrin derivatives are reported for the selective detection of various analytes in sensing applications. The central metal ion is able to rule specific molecular arrangements upon analyte binding. Three bis-porphyrin compounds: a free base (metal free), Ni complex, and Cu complex, have been tested for histidine detection in aqueous media. Histidine is involved in various biological processes, including such deadly disease as lung cancer. The conformational changes of bis-porphyrins, induced by histidine binding, can be detected by monitoring the Soret band position. The spectroscopic characterization, at the air-water subphase interface, indicates that, in the presence of histidine, the Ni and Cu metallated derivatives undergo conformational changes. This behaviour was confirmed when these two derivatives were deposited onto the solid support by Langmuir-Schaefer (LS) technique. A prototypal Surface Plasmon Resonance (SPR) detection system for histidine based on these two porphyrin LS films was developed. The Cu substituted compound based SPR system allows the histidine sensing down to nanomolar concentration. Furthermore, a SPR response of the Ni bis-porphyrin shows a semilogarithmic dependence on the histidine concentration up to 10-6 M proposing the use of these two porphyrins in a sensor array for the monitoring of histidine levels in plasma.

Discrimination of mercuric ions in piezoelectric sensors with a conjugated polymeric active layer.

The synthetic conjugated poly(1,4-arylene-2,5-thienylene) containing benzo[c][2,1,3]thiadiazole monomeric units (Bz-PAT) is proposed as active layer for the selective detection of mercuric ions. The Bz-PAT polymer chemical structure induces the formation of a disordered film with numerous vacancies and the size of these defects could be exploited for a reversible trapping of mercuric ions. For these reasons the Langmuir-Schaefer (LS) deposition method has been employed for transferring Bz-PAT layers with the desired accurate bi-dimensional organization control of the layer and with a high control of the deposition parameters. In this contribution, the frequency variation of quartz crystal microbalances functionalized with 10, 20, 30 and 40 LS runs of Bz-PAT have been investigated in response to the injection of aqueous solutions of HgCl2, Pb(NO3)2, NiCl2, CdCl2 and ZnSO4 at different concentrations (0.5 mM, 1 mM, 5 mM). An almost linear dependence on the number of the LS layers and hence on the film thickness, measured by means of ellipsometric spectroscopy, has been found in terms of sensor response to concentration of Hg2+ ions fluxed. By means of UV-Vis spectroscopy, the variations in the π-π* absorption band of the polymer, attributed to the thiophene segment, induced by HgCl2 injection has been analyzed and explained as a consequence of the electron transfer from the mercuric ion to the polymer solid film. These results, together with the linear relation found between the number of deposited layers and LS film thickness, suggest that the sensing mechanism can be explained both by an electron interaction between active layer and analyte and a diffusion mechanism of Hg2+ into the solid film that reaches an asymptotic value at 30 runs (about 80 nm), then a higher number of layers does not influence the sensor sensibility.