Francesca Parenti

Electrostatic layer-by-layer construction and characterization of photoelectrochemical solar cells based on water soluble polythiophenes and carbon nanotubes

Positively and negatively charged functionalized polythiophenes and single walled carbon nanotubes were sequentially adsorbed on indium tin oxide electrodes by electrostatic and van der Waals interactions using the layer-by-layer deposition method. The resulting donor/acceptor photoelectrodes were tested as photoelectrochemical cells. Upon illumination, monochromatic incident photoconversion efficiencies of 8.2 and 4.3% were determined for eight stacks of single walled carbon nanotubes with ammonium and sulfonate polythiophene derivatives, respectively.

Citron and lemon under the lens of HR-MAS NMR spectroscopy.

High Resolution Magic Angle Spinning (HR-MAS) is an NMR technique that can be applied to semi-solid samples. Flavedo, albedo, pulp, seeds, and oil gland content of lemon and citron were studied through HR-MAS NMR spectroscopy, which was used directly on intact tissue specimens without any physicochemical manipulation. HR-MAS NMR proved to be a very suitable technique for detecting terpenes, sugars, organic acids, aminoacids and osmolites. It is valuable in observing changes in sugars, principal organic acids (mainly citric and malic) and ethanol contents of pulp specimens and this strongly point to its use to follow fruit ripening, or commercial assessment of fruit maturity. HR-MAS NMR was also used to derive the molar percentage of fatty acid components of lipids in seeds, which can change depending on the Citrus species and varieties. Finally, this technique was employed to elucidate the metabolic profile of mold flavedo.

A nanogap–array platform for testing the optically modulated conduction of gold– octithiophene –gold junctions for molecular optoelectronics

We studied the light dependent conduction of gold–oligothiophene–gold molecular junctions as a fully–customized platform. The flexibility and novelty of the platform relies on its plug-and-play connection to an external electronic board to perform eight parallel nanogap fabrications by Electromigration Induced Break Junction (EIBJ) and molecular electrical characterization. In addition, the octithiophene molecules are synthesized ad-hoc to efficiently self-assembly and selectively bridge the nanogap electrodes upon deposition, which can be carried out directly and in parallel on the 8 nanogap array platforms. The high portability of the platform is well suited for in–situ microscopic and spectroscopic analyses. In particular, we tested the electrical functionality of the octithiophene molecular junctions by coupling electrical current–voltage (I–V) characterization with fluorescence and Raman spectroscopies. In addition, surface-enhanced Raman spectroscopy (SERS) was used for the first time to precisely correlate the position of the molecule with the conductance of the junction. Modulation of the electrical conductance can also be achieved by varying the light excitation wavelength. Such electrical transduction of the junction revealed a peak in molecule conduction around the light excitation wavelength of 450 nm, with a photoresponsive modulation of the current at low bias voltage up to 120% with respect to the initial value at 300 nm. The proposed ad-hoc platform design makes molecular junctions real working blocks, which can be interfaced with external circuitries to serve the function of electronic components or sensors and overcome the limitations of usability, cost and portability of traditional molecular contacting methods, such as Mechanically Controlled Break Junction (MCBJ) or scanning probe microscopy. We thus demonstrate that the optoelectronic properties of oligothiophenes can be exploited in the form of molecular junctions to fabricate optoelectronic devices for molecular electronics.

On the Recovery of 3JH,H and the Reduction of Molecular Symmetry by Simple NMR Inverse Detection Experiments

Simple 1H,13C correlation spectra obtained by inverse detection techniques provide useful evidence of molecular symmetry. The emblematic case of cis- and trans-stilbenes together with that of a symmetric terthiophene are reported as examples. The effects of a reduction of symmetry on both direct and long-range correlations are reported.

The effect of Pd(II) coordination on the properties of an alkylsulfanyl substituted polythiophene. Comparison with the corresponding monomer

The synthesis of a conducting polymer partially coordinated with Pd(II) ions is reported. The aim is to study the influence of the metal on the properties of the material as a whole, which is very appealing for possible applications in the field of amperometric sensors. An alkylsulfanyl substituted polythiophene is used in this first approach, due to the well known affinity of the sulfur atom for soft metals. The interaction between the organic and inorganic moieties results in the easy formation of partially coordinated polymer. The presence of the metal ions is found to affect the chemical, physical, and electrochemical properties of the organic macromolecules, owing to interactions between the polymer π-conjugation system and the metal d orbitals. Synthesis and characterisation of the relevant monomer complex helps to better understand the behaviour of the complex polymer-metal system.

Π-Stacking Signature in NMR Solution Spectra of Thiophene-Based Conjugated Polymers

Studies on conjugated polymers seldom report on their NMR characterization in solution. This paper shows how NMR experiments, both 1H NMR and routine 2D NMR spectra, can help in gaining a further insight into the aggregation behavior of conjugated polymers and could be used to flank the more employed solid-state NMR and other spectroscopy and microscopy techniques in the understanding of the aggregation processes. NMR spectroscopy allows distinguishing, within the class of poorly solvatochromic conjugated polymers, those highly prone to form π-stacked aggregates from the ones that have a low tendency toward π-stacking.

An Ab‐Initio Theoretical Study of the Electrochemical Grafting Process of Alkynil(aryl)iodonium Salts on Glassy Carbon Surfaces

The behaviour of alkynil(aryl)iodonium salts upon electrochemical reduction, on glassy carbon electrodes, is here studied by comparing both theoretical and experimental results. In particular, experimental results are obtained by means of cyclic voltammetry and chronocoulometric measurements as well as by collecting XPS spectra, while the standard electrode potential and different dissociation paths (I‐C, arylic, compared to the I‐C, alkynil, bond cleavage) have been characterized theoretically at the B3LYP/3‐21g** level of the theory (the solvation free Gibbs energy of the cation and of the neutral radical species have been calculated by using the CPCM method).

Chapter 15 – Chiral Polythiophenes

This review reports the synthesis and the properties of chiral polythiophenes (PTs) and in particular it is focused on PTs bearing a sulfur atom directly bonded to the thiophene ring. These polymers show remarkable properties, related to their chirality and electrical conductivity and to the ability to interact with chiral molecules opening the possibility for using them in new potential applications, like chiral sensors, chiral resolution and electrodes.