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International audience; Technetium is an artificial element produced after fission of uranium in nuclear reactors. $^{99}$Tc is one of the most important fission product found in dissolution solutions of used nuclear fuel. In nitric acid medium, technetium is found at +VII oxidation state as pertechnetate anion TcO$_4$$^-$. Due to the large amounts of $^{99}$Tc produced by nuclear fission and to the long half-life of this radionuclide (2.1 x 10$^5$ years), technetium is an element of particular importance in nuclear waste management[3]. In this work, technetium cryptands in nitric acid medium are studied. The large size and low charge density of the oxoanion make selective recognition in aqueous solution a great challenge.For this purpose, a “polyammonium cage” ligand was studied for the pertechnetate anion recognition in nitric acid solution. Coordination studies were performed with its inactive surrogate, the perrhenate anion (ReO$_4$$^-$), by Infrared and RAMAN spectroscopies, single crystal XRD (Figure 1) and DFT calculations. As shown in Figure 1, the ligand conformation adapts itself to let one perrhenate anion enter the cavity (cage size expansion, hydrogens of the protonated amines directed towards the inside of the cavity). The complex stabilization is achieved by direct hydrogen bonds formation between the azacryptand and the perrhenate anion.

One of the main problems related to the low performance of the organic photovoltaic (OPV) devices, concerns the low mobility of the materials forming the heterojunction. For this reason, there is competition between the sweep-out and recombination of the photogenerated carriers within the thin film bulk heterojunction (BHJ). To overcome this problem, it is usual to operate by reducing the thickness of the active layer, so that the recombination of charge carriers is inhibited. This choice, however, also translates into a lower absorption of light by the active film itself. Plasmonic structures allow to reduce the "physical" thickness of heterojunction, maintaining constant the "optical" thickness. The addition of metal nanoparticles in the BHJ films could ensure a greater absorption and an enhanced photogeneration of mobile carriers[1]. In this work, we present a study of the effect of thiol-capped Au nanoparticles (AuNPs), within an organic device, by controlling on the nanoscale the position of the nanoparticles in the different interfaces of the device. Au-NPs have been obtained by laser ablation in liquid solution (LASiS) [2], have been functionalized both with 2-naphthalenethiol and alkanethiol having different length. Such systems in combination with poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) have been used to fabricate planar and bulk heterojunction thin films by Langmuir-Blodgett (LB) apparatus, which offers a simple method of producing ultra-thin films with fine control over thickness. We prepared at first planar heterojunction (PHJ) structures consisting of layers of P3HT, PCBM and Au-NPs by the horizontal lifting (Langmuir-Schaefer LS) technique. Then we induced a transition from PHJ to BHJ by thermal annealing to mix the layers. To study the effect of the position of the nanoparticles, different structures have been realized, which differ in the position of the Au-NPs layer, i.e. at substrate/P3HT or P3HT/PCBM interfaces as well as at the top of the PCBM layer. These films and their components have been studied by a number of microscopy and spectroscopy surface tools and by electrochemistry to investigate the energy levels. I/V curves and importantly fluorescence quenching analysis showed that 2-naphthalenethiol-capped Au-NPs film incorporated at the donor/acceptor interface ensures a more efficient charge transfer if compared to the same heterojunction without AuNPs. The beneficial effect of nanoparticles seems to be lost after the transition from PHJ to BHJ, where there is any control over the particles location. Other important advantages on the efficiency of these three components devices are discussed.

Polymer-fullerene or polymer-polymer based bulk heterojunction (BHJ) solar cells can be fabricated by using low-cost manufacturing methods. However, because of the low mobility of organic materials, there is a competition between separation and recombination of the photogenerated carriers within the thin BHJ film. Thus, there is a need to develop strategies to increase light harvesting in the films without increasing the film thickness. Nanoparticles (NPs) have been receiving a lot of interest for exhibiting interesting optical, electrical, and magnetic properties. These novel properties can be exploited in nanotechnology by forming compact and ordered architectures of nanoparticles within of BHJ film. The addition of metal NPs in the BHJ films could ensure a greater absorption and an enhanced photogeneration of mobile carriers [1]. In this work, we present a study of the effect of thiol-capped Au nanoparticles (AuNPs), within an organic device, by controlling on the nanoscale the position of the nanoparticles in the different interfaces of the device. Au-NPs have been obtained by laser ablation in liquid solution (LASiS) [2] and have been functionalized both with 2-naphthalenethiol and alkanethiol having different length. Such particles in combination with poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C61 butyric acid methyl ester (PCBM) and Poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) have been used to fabricate two different BHJ (P3HT:PCBM and P3HT:F8BT) with three components thin films. In particular we have realized planar and bulk heterojunction thin films by the Langmuir-Blodgett (LB) apparatus, which offers a simple method of producing ultra-thin films with fine control over thickness. We prepared at first planar heterojunction (PHJ) structures consisting of layers of P3HT, Au-NPs and PCBM or F8BT by the horizontal lifting (Langmuir-Schaefer LS) technique. Then we induced a transition from PHJ to BHJ by thermal annealing to mix the layers. To study the effect of the position of the nanoparticles, different structures have been realized, which differ in the position of the Au-NPs layer, i.e. at substrate/donor or donor/acceptor interfaces as well as at the top of the acceptor layer. These structures and their components have been studied by microscopy and spectroscopy surface tools and by electrochemistry to investigate the energy levels. I/V curves and importantly fluorescence quenching analysis showed that 2-naphthalenethiol-capped Au-NPs film incorporated at the P3HT/PCBM interface ensures a more efficient charge transfer if compared to the same heterojunction without AuNPs. The beneficial effect of nanoparticles seems to be lost after the transition from PHJ to BHJ, where there is any control over the particles location. Other important advantages on the efficiency of these three components devices are discussed.

We present an all-optical tuning at IR wavelength in a novel photonic crystal consisting of a polystyrene opal with gold nanoparticles. The band-gap can be finely tuned with permanent shifts as large as 30 nm irradiating the sample with ps pulses at a low rep-rate in the visible.

We report on light-driven tuning of the optical properties of colloidal photonic crystals (polystyrene opals) doped with gold nanoparticles (Au-np). Using picosecond pulses at 532 nm we obtained permanent changes in the stop band around 1700 nm, with resonance blue shifts as large as 30 nm.

In this work, we employed for the first time a dinuclear bis[tris(2-aminoethyl)amine] cryptate to obtain the self-assembly of pseudorotaxane structures in an aqueous solution. The goal was achieved by exploiting the well-known affinity of the dicopper azacryptate with diphenyl spacers for the terephthalate anion. In particular, a series of molecular threads were synthesized by appending either alkyl or polyoxyethylene chains on both sides of the terephthalate benzene ring. The obtained dicarboxylic acids were precipitated as sodium salts, and their affinity toward the dicopper azacryptate was determined in a methanol/water mixture (pH 7). Experimental investigations showed that the chains' length and nature have a small impact on the 1:1 binding constants, whose values range between 4.98 and 5.18 log units. Computational studies indicated that the molecular axle is threaded through the azacryptate cavity, with the terephthalate group wedged between the two copper ions, coordinating both of them in the apical position (the one that, in the free azacryptate, is occupied by a water molecule). Compared to the inclusion complex with the plain terephthalate anion, a slight strain was found in the pseudorotaxane structure, induced by the inner chain of the thread inside the cavity. These results may be of great interest in all of the fields of science and technology in which host-guest recognition and molecular cages are applied.

Precisely positioning functionalized gold nanoparticles assemblies at planar donor-acceptor interfaces results in 14-fold enhancement of power conversion efficiency in P3HT/PCBM organic solar cells on plastic (ITO/PET) substrates. This result has been achieved by employing naphthalenethiol-capped gold nanoparticles (NT-Au-NPs) produced by laser ablation in liquid and size varied in the 10-30 nm range. Upon surface functionalization with the aromatic thiol, these particles self-assemble in submicrometer aggregates, which give increased light scattering. When these aggregates are deposited in the planar heterojunction between the donor and the acceptor systems, the localized scattering leads to a larger exciton formation just in the region of interest for charge transfer. (Graph Presented).

In this work, we have investigated the properties of novel fluorescent semi(thio)carbazone systems with anions by UV-vis, spectrofluorimetric and NMR studies, in acetonitrile and DMSO solutions. Conformational preferences were determined by theoretical calculations within the DFT approach. For the free receptors, these studies pointed out a marked prevalence of anti conformations, which are stabilized by intramolecular H-bonds between the (thio)urea NH group and the imino nitrogen atom. For the julolidine-based thiosemicarbazone system, intermolecular interactions involving the thiourea NH groups and the S atoms of two receptor molecules were also found in the crystals, leading to the formation of supramolecular dimers. Theoretical studies showed that anion binding involved a change of the conformation of the receptors from anti to syn. In the syn isomers, two NH groups actually point in the same direction, thus favouring the binding of anions, e.g. the Y-shaped acetate ion. This thorough study on the novel semi(thio)carbazones provides useful information for the application of this type of molecule in all the fields of chemistry, in which urea-based systems are employed (e.g. anion recognition and transport, catalysis, soft materials, etc.).

A new class of copolymers containing oligothiophene moieties with different length and fullerene units have been designed and prepared by an easy and inexpensive one-step synthetic approach. The incorporation of small quantities of these copolymers into bulk heterojunction (BHJ) solar cells with donor regioregular polythiophene (P3HT) and acceptor fullerene derivate (PCBM) results in a good control of the phase separation process without further affecting the BHJ optoelectronic properties. Indeed, these copolymers allow modulating under thermal annealing the growth of domains whose size depends on the length of the copolymer repetitive units. Domain size on the same length scale of the P3HT exciton diffusion length with a good continuity between the electrodes gives an efficient exciton dissociation and charge mobility. Thus by employing copolymers containing oligothiophenic chains with size of about 8 nm, the power conversion efficiency (PCE) (4.46 %) and short current density (JSC) (16.15 mA cm-2) values results in the highest reported so far for P3HT:PCBM solar cells on plastic substrates.

For the first time, the tetrafluorobenzyl unit has been considered as a C-H center dot center dot center dot anion binding motif. In synergy with imidazolium groups within a bowl-shaped receptor, it has allowed for the effective binding of chloride in solution. Remarkable affinity was observed in organic-water mixtures.

In this work, we present a study on the effect of thiol-capped AuNPs of various sizesin an organic solar cell.AuNPs have been obtained by laser ablation in liquid solution[2], have been functionalized both with 2-naphthalenethiol and alkanethiol having different length. In addition to bulk heterojunction structures with optimized interpenetrating network of donors and acceptor domains, we have chosen to study planar heterojunctions (PHJs), consisting of three component thin films realized by sequential deposition of P3HT, AuNPs and PCBM from orthogonal solvents.

In this chapter, we discuss the relevant physical and chemical properties of gold nanoparticles that are exploited for analytical applications in a variety of different fields. This chapter was conceived to collect in a single place an overview of the properties of gold nanoparticles that are important for technological applications, with prevalent reference to the scientific literature that has appeared in the last six years. Given the extremely broad expertise needed for an in-depth discussion, the chapter is co-authored with experts in the specific field dealing with optical properties, ab initio calculations of electronic properties, magnetic, electrochemical and chemical properties.

The amplification of Raman signals of the heteroaromatic cation 1-(N-methylpyrid-4-yl)-2-(N-methylpyrrol-2-yl)ethylene (PEP+)) bound to Au nanorods (NRs) was investigated at different excitation wavelengths to study the effect of the laser resonance with the absorption band of the PEP+ moiety and with the two plasmon oscillation modes of the NR. Two different PEP+ derivatives, differing in the length of the alkyl chain bearing the anchoring group, were used as target molecules. Raman spectra obtained exciting at 514 or at 785 nm (i.e., exciting the transverse or the longitudinal plasmon band) present a higher intensity than that at 488 nm suggesting a higher Raman amplification when the laser excitation wavelength is resonant with one of the two plasmon modes. Moreover, considering results of Discrete Dipole Approximation (DDA) calculations of the local field generated at the NR surface when either the transverse or the longitudinal plasmon modes are excited, we deduced that the resonance condition of the 514-nm laser excitation with the absorption band of the dye strongly contributes to the amplification of the Raman signal. © 2014 The Author(s).

We report on light-induced optical tuning of colloidal photonic crystals doped with gold nanoparticles (Au-nps). By resonantly exciting the Au-np surface plasmon absorption with picosecond pulses at 0.53 micron in a standard pump-probe setup, we observed permanent changes in the stop band resonance around 1.7 micron, with blue wavelength shifts as large as 30 nm and associated to a nanoparticle reshaping. Fine tuning was achieved by controlling either the pulse energy or the irradiation time.