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Metal–insulator–metal (MIM) diodes are very interesting in many different applications exploiting environment-friendly renewable energy solutions.

We have studied the structural, electronic, magnetic, and optical properties of the VO2(B) polymorph using first-principles calculations based on density functional theory (DFT).

Reliable point-of-care (POC) rapid tests are crucial to detect infection and contain the spread of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The emergence of several variants of concern (VOC) can reduce binding affinity to diagnostic antibodies, limiting the efficacy of the currently adopted tests, while showing unaltered or increased affinity for the host receptor, angiotensin converting enzyme 2 (ACE2). We present a graphene field-effect transistor (gFET) biosensor design, which exploits the Spike-ACE2 interaction, the crucial step for SARS-CoV-2 infection. Extensive computational analyses show that a chimeric ACE2-Fragment crystallizable (ACE2-Fc) construct mimics the native receptor dimeric conformation. ACE2-Fc functionalized gFET allows in vitro detection of the trimeric Spike protein, outperforming functionalization with a diagnostic antibody or with the soluble ACE2 portion, resulting in a sensitivity of 20 pg/mL. Our miniaturized POC biosensor successfully detects B.1.610 (pre-VOC), Alpha, Beta, Gamma, Delta, Omicron (i.e., BA.1, BA.2, BA.4, BA.5, BA.2.75 and BQ.1) variants in isolated viruses and patient's clinical nasopharyngeal swabs. The biosensor reached a Limit Of Detection (LOD) of 65 cps/mL in swab specimens of Omicron BA.5. Our approach paves the way for a new and reusable class of highly sensitive, rapid and variant-robust SARS-CoV-2 detection systems.

Near-field scanning microwave microscopy is a technique with increasing popularity for the study of nanometer-scale electrical properties of samples. Here, we present an approach to quantify sample properties in images obtained with an inverted scanning microwave microscope (iSMM), recently introduced by our group. In particular, this study reports the analysis of the local electrical conductivity of a platinum diselenide sample and proves its semimetal behavior. The approach is validated by a full-wave numerical model, reproducing the complete iSMM operation as well as all steps of the calibration algorithms. To extract local sample properties, this article provides two calibration procedures, respectively, for transmission and reflection mode measurements, based on a two-port equivalent circuit of the iSMM. This enables the high-frequency quantitative characterization of a wide variety of samples and surfaces.

We have studied the structural, electronic, magnetic, and optical properties of the VO2(B) polymorph using first-principles calculations based on density functional theory (DFT). This polymorph was found to display four optimized structures namely VO2(B)PP, VO2(B)LP, VO2(B)PPD, and VO2(B)LPD using the generalized gradient approximation (GGA) PBE exchange-correlation functional by including/excluding van der Waals interaction. Our derivation provides a theoretical justification for adding an on-site Coulomb U value in the conventional DFT calculations to allow a direct comparison of the two methods. We predicted a zero bandgap of the VO2(B) structure based on GGA/PBE. However, by GGA/PBE + U, we found accurate bandgap values of 0.76, 0.66, and 0.70 eV for VO2(B)PP, VO2(B)LP, and VO2(B)PPD, respectively. The results obtained from DFT + U were accompanied by a structural transition from the metallic to semiconductor property. Here, we verified the non-magnetic characteristic of the monoclinic VO2(B) phase with some available experimental and theoretical data. However, the debate on the magnetic property of this polymorph remains unresolved. Imaginary and real parts of the dielectric function, as computed with the GGA/PBE functional and the GGA/PBE + U functional, were also reported. The first absorption peaks of all considered geometries in the imaginary part of the dielectric constants indicated that the VO2(B) structure could perfectly absorb infrared light. The computed static dielectric constants with positive values, as derived from the optical properties, confirmed the conductivity of this material. Among the four proposed geometries of VO2(B) in this study, the outcomes obtained by VO2(B)PPD reveal good results owing to the excellent consistency of its bandgap, magnetic and optical properties with other experimental and theoretical observations. The theoretical framework in our study will provide useful insight for future practical applications of the VO2(B) polymorph in electronics and optoelectronics.

HfO2 shows different polymorphs, including monoclinic and orthorhombic ones, that exhibit singular properties. Moreover, the character of HfO2 is also influenced by the Zr atoms as a doping agent. Here, an extensive study of the monoclinic P21/c and the orthorhombic Pca21 polymorphs of HfO2, Hf0.75Zr0.25O2, and Hf0.5Zr0.5O2 is reported. For all six systems, density functional theory (DFT) methods based on generalized gradient approximations (GGAs) were first used; then the GGA + U method was settled and calibrated to describe the electrical and optical properties of polymorphs and the responses to the oxygen vacancies. Zr had different effects in relation to the polymorph; moreover, the amount of Zr led to important differences in the optical properties of the Pca21 polymorph. Finally, oxygen vacancies were investigated, showing an important modulation of the properties of HfxZryO2 nanostructures. The combined GGA and GGA + U methods adopted in this work generate a reasonable prediction of the physicochemical properties of o- and m-HfxZryO2, identifying the effects of doping phenomena.

Near-field scanning microwave microscopy (SMM) employs microwave radiation to image and characterize samples down to the atomic scale, including soft biological structures or inorganic materials, such as ferroelectric films. However, SMM generally also senses sample topography; hypersensitivity to topography becomes problematic with additional parasitic contributions and may partially or completely mask nontopographic sample features in the data, such as contrast in electrical conductivity or permittivity. This work proposes a simple and effective procedure to remove unwanted parasitic effects from SMM images. Differently from existing procedures, the method is applicable either in postprocessing or in real time, i.e., during the scanning operation. This allows the immediate visualization of nontopographic sample features in the instrument screen. As a proof of concept, hafnium zirconium oxide (HfZrO) ferroelectric film with high surface roughness is studied; unwanted contributions were removed from SMM data, providing a clear map of the sample ferroelectric structure that was originally hidden.

In this work, we present the design, atomistic/circuit/electromagnetic simulations, and the experimental results for graphene monolayer/zirconium-doped hafnium oxide (HfZrO) ultra-thin ferroelectric-based field effect transistors fabricated at the wafer scale, regarding the pyroelectricity generation directly from microwave signals, at room temperature and below it, namely at 218 K and at 100 K. The transistors work like energy harvesters, i.e. they collect low-power microwave energy and transform it into DC voltages with a maximum amplitude between 20 and 30 mV. The same devices function as microwave detectors in the band 1–10.4 GHz and at very low input power levels not exceeding 80 μW when they are biased by using a drain voltage, with average responsivity values in the range 200–400 mV mW−1.

Fast, reliable and point-of-care systems to detect the SARS-CoV-2 infection are crucial to contain viral spreading and to adopt timely clinical treatments. Many of the rapid detection tests currently in use are based on antibodies that bind viral proteins1. However, newly appearing virus variants accumulate mutations in their RNA sequence and produce proteins, such as Spike, that may show reduced binding affinity to these diagnostic antibodies, resulting in less reliable tests and in the need for continuous update of the sensing systems2. Here we propose a graphene field-effect transistor (gFET) biosensor which exploits the key interaction between the Spike protein and the human ACE2 receptor. This interaction is one of the determinants of host infections and indeed recently evolved Spike variants were shown to increase affinity for ACE2 receptor3. Through extensive computational analyses we show that a chimeric ACE2-Fc construct mimics the ACE2 dimer, normally present on host cells membranes, better than its soluble truncated form. We demonstrate that ACE2-Fc functionalized gFET is effective for in vitro detection of Spike and outperforms the same chip functionalized with either a diagnostic antibody or the soluble ACE2. Our sensor is implemented in a portable, wireless, point-of-care device and successfully detected both alpha and gamma virus variants in patient’s clinical samples. As incomplete immunization, due to vaccine roll-out, may offer new selective grounds for antibody-escaping virus variants4, our biosensor opens to a class of highly sensitive, rapid and variant-robust SARS-CoV-2 detection systems.

Electrochemical microscopy techniques have extended the understanding of surface chemistry to the micrometer and even sub-micrometer level. However, fundamental questions related to charge transport at the solidelectrolyte interface, such as catalytic reactions or operation of individual ion channels, require improved spatial resolutions down to the nanoscale. A prerequisite for single-molecule electrochemical sensitivity is the reliable detection of a few electrons per second, that is, currents in the atto-Ampere (10−18 A) range, 1000 times below today’s electrochemical microscopes. This work reports local cyclic voltammetry (CV) measurements at the solid-liquid interface on ferrocene self-assembled monolayer (SAM) with sub-atto-Ampere sensitivity and simultaneous spatial resolution < 80 nm. Such sensitivity is obtained through measurements of the charging of the local faradaic interface capacitance at GHz frequencies. Nanometer-scale details of different molecular organizations with a 19% packing density difference are resolved, with an extremely small dispersion of the molecular electrical properties. This is predicted previously based on weak electrostatic interactions between neighboring redox molecules in a SAM configuration. These results open new perspectives for nano-electrochemistry like the study of quantum mechanical resonance in complex molecules and a wide range of applications from electrochemical catalysis to biophysics.

Ultra-high molecular-weight polyethylene has been used in total joint replacement for the last three decades. Many attempts have been made to improve the wear behaviour of this material. Highly cross-linked polyethylene (XLPE) has been developed to decrease the wear rate, while the addition of stabilizers such as vitamin E has been proposed to slow the oxidation processes. In this study, we compared the wear behaviour of conventional ultra-high molecular-weight polyethylene, XLPE and vitamin E-added XLPE acetabular cups for total hip arthroplasty. The samples were run for five million cycles on a hip joint simulator (first test), then underwent an accelerated ageing treatment, were tested again for two million cycles (second test) and finally were run for another two million cycles in presence of third-body particles (third test). Our study showed that vitamin E-added XLPE cups had a better wear behaviour only in the long-term and more severe testing conditions: in the third test, they underwent the lowest increase in wear rate. Micro-Raman spectroscopy allowed us to analyse the wear degradation of the cups on a molecular scale, and differences in the wear mechanisms were revealed. The presence of vitamin E did not prevent structural changes upon the first test, while it did in ageing and in the second test. In the third test, more significant structural changes were observed; the XLPE cups, which lost the lowest mass, had the most modified articular surface. These morphological aspects should be taken into account, together with gravimetric wear rates, in the characterization of wear degradation. Copyright © 2017 John Wiley & Sons, Ltd.

Scanning microwave microscopy (SMM) is based on the interaction between a sample and an electromagnetic evanescent field, in the microwave frequency range. SMM is usually coupled with a scanning probe microscopy (SPM) technique such as in our case, a scanning tunneling microscope (STM). In this way, the STM tip is used to control the distance between the probe and the sample while acting as an antenna for the microwave field. Thanks to the peculiarity of our home-made setup, the SMM is a suitable method to study blisters formed on HOPG surface as consequence of an electrochemical treatment. Our system has a “broad-band” approach that opens the way to perform local microwave spectroscopy over a broad frequency range. Moreover, microwaves have the ability to penetrate into the sample allowing the sub-surface characterization of materials. The application of the SMM to characterize blisters formed on the HOPG surface provides information on the sub-layer structures.

Near-field scanning microwave microscopy (SMM) is a technique gaining popularity for the study of the electrical properties of both soft and hard matter on the nanometer scale. Despite the current focus on semiconductors, the applications of SMM on new two-dimensional materials such as platinum diselenide (PtSe2) are still in an initial stage. In this work, the imaging capabilities of an innovative SMM and the analysis of the electrical properties of PtSe2 are demonstrated.

A series of molecules in which 9H-carbazole (electron donor, D) and 2,2':6',2''-terpyridine (electron acceptor, A) are connected through rigid π-conjugated bridges (D-π-A systems) have been synthesized and their photophysical properties examined in detail, with the support of DFT calculations. The bridges are made of different sequences of ethynylene, phenylene, and anthracene groups. The synthetic strategies involve condensation of 2-acetylpyridine with the aromatic aldehyde moiety on different functionalized π-conjugated bridges and couplings with carbazole derivatives. The system incorporating anthracene in the bridge shows the typical absorption and emission fingerprints of this polycyclic hydrocarbon. The other systems have HOMOs and LUMOs centred, respectively, over the carbazole and the bridge and exhibit solvatochromic charge-transfer (CT) luminescence with high photoluminescence yield up to 70 %, except when an ethynylene unit is directly attached to the carbazole ring, due to a trans-bent non-emissive π-σ* excited state.

Silk fabrics from Bombyx mori silkworm were grafted with 2-hydroxyethyl methacrylate (HEMA) as well as a binary system of HEMA and 4-hydroxybutyl acrylate (HBA) and then analysed by Raman and infrared (IR) spectroscopy to elucidate the interactions between the components and their possible conformational changes. The samples were then dissolved in trifluoroacetic acid and electrospun; the influence of the grafted polymers on the silk fibroin rearrangements upon these treatments was investigated by vibrational spectroscopy. Upon grafting, the fabrics underwent conformational rearrangements towards a more unordered state, although they kept their prevailing β-sheet conformation; also the polymeric component underwent hydrogen bonding and backbone rearrangements upon interaction with silk fibroin and the occurrence of strong covalent bonds cannot be excluded. By immersing the as-electrospun grafted and pure fibroin nanofibres (prevalently unordered) in aqueous methanol, they partially recovered the β-sheet content observed in the corresponding starting fabrics; the percentage of recovery decreased along the series: pure silk > HEMA-grafted silk > HEMA and HBA-grafted silk. This trend suggests that the presence of the polyHEMA grafted component hinders the silk fibroin recrystallization into β-sheet upon aqueous methanol treatment; moreover, the addition of the more sterically hindered HBA monomer in the grafting system further prevented this process. Copyright © 2016 John Wiley & Sons, Ltd.

Bombyx mori silk fibroin fibers were grafted with methacrylamide (MAA) and characterized by Raman and infrared (IR) vibrational spectroscopy before and after hydrolysis in NaOH 5% to elucidate the possible interactions between the two components and the stability of the fibers toward alkaline hydrolysis. Upon grafting, the fibers underwent conformational rearrangements toward a more unordered state and lost orientation at weight gains higher than 60%. Vibrational spectroscopy disclosed the occurrence of intermolecular interactions (mainly hydrogen bonds) between B. mori silk fibroin and polyMAA in the grafted fibers, and the formation of covalent bonds has been explored. These strong interactions made the grafted fibers as a whole more stable toward alkaline hydrolysis because they prevented the solubilization of the polymer upon hydrolysis and made slower the transformation of its CONH2 groups into COOH and COO− groups. Upon hydrolysis, silk fibroin underwent an enrichment in the β-sheet crystalline domains, because of the preferential removal of the unordered domains, which were more prone to the OH− attack. IR and Raman spectroscopy proved valid techniques to investigate the degradation mechanism and kinetics of grafted silk fibroin fibers and so for designing high-performing silk-based materials. The A731/A1004 Raman intensity ratio was proposed to spectroscopically evaluate the composition of the grafted samples; its value was found to linearly increase with weight gain (R2 = 0.998), envisaging the possibility of using Raman spectroscopy as a routine analytical technique for qualitative and quantitative characterization of grafted industrial samples. Copyright © 2016 John Wiley & Sons, Ltd.

Recently, near-field scanning microwave microscope has become popular in the characterization of materials, in particular, semiconductors on the nanometer scale. However, its application to biological structures is still at the embryo stage due to challenges in probing wet and soft samples with little dielectric contrast. In this work, we used our homemade scanning microwave microscope to overcome some of the challenges to demonstrate the imaging and characterization of isolated mitochondria in the frequency range 28–33 GHz.

The extracellular guanosine 5′-triphosphate, GTP, has been demonstrated to be an enhancer of myogenic cell differentiation in a murine cell line, not yet in human muscle cells. Our hypothesis was that GTP could influence also human skeletal muscle regeneration, specifically in the first phases. We tested GTP stimulus on human muscle precursor cells established in culture by human satellite cells derived from Vastus Lateralis of three young male. Our data show that extracellular GTP (a) up-regulated miRNA (specifically miR133a and miR133b) and myogenic regulator factor and (b) induces human myogenic precursor cells to release exosomes stuffed with guanosine based molecules (mainly guanosine) in the extracellular milieu. We think that probably these exosomes could be addressed to influence by means of their content (mainly guanosine) in paracrine or autocrine manner the surrounding cells and/or at distance other muscles or tissues.

Exosomes are nanovesicles known to mediate intercellular communication. Although it is established that zinc ions can act as intracellular signaling factors, the measurement of zinc in circulating nanovesicles has not yet been attempted. Providing evidence of the existence of this zinc fraction and methods for its measurement might be important to advance our knowledge of zinc status and its relevance in diseases. Exosomes from 0.5 ml of either fresh or frozen human plasma were isolated by differential centrifugation. A morphological and dimensional evaluation at the nanoscale level was performed by atomic force microscopy (AFM) and Transmission Electron Microscopy (TEM). Energy Dispersive X-Ray Microanalysis (EDX) revealed the elemental composition of exosomes and their respective total Zinc content on a quantitative basis. The zinc mole fraction (in at%) was correlated to the phosphorous mole fraction, which is indicative for exosomal membrane material. Both fresh (Zn/P 0.09 ± 0.01) and frozen exosomes (Zn/P 0.08 ± 0.02) had a significant zinc content, which increased up to 1.09 ± 0.12 for frozen exosomes when treated with increasing amounts of zinc (100-500 μM; each p 0.05). Interestingly, after zinc addition, the Calcium mole fractions decreased accordingly suggesting a possible exchange by zinc. In order to estimate the intra-exosomal labile zinc content, an Imaging Flow Cytometry approach was developed by using the specific membrane permeable zinc-probe Fluozin-3AM. A labile zinc content of 0.59 ± 0.27 nM was calculated but it is likely that the measurement may be affected by purification and isolation conditions. This study suggests that circulating nano-vesicular-zinc can represent a newly discovered zinc fraction in the blood plasma whose functional and biological properties will have to be further investigated in future studies.

Biolox® delta has been widely used in joint replacements thanks to its high strength and wear resistance. In this study, eleven Biolox® delta femoral head retrievals affected by metal transfer (MT) were analysed by Raman spectroscopy to estimate the tetragonal to monoclinic zirconia phase transformation, whose occurrence may compromise ceramic chemical stability and mechanical strength. The residual stress state was evaluated by both Raman and photoemission spectroscopy. Vm monoclinic zirconia contents were higher near the centre of the articulating surface and in the MT area than in the border control area of the retrievals. In only one retrieval, stress related to MT appeared a more severe condition, able to induce zirconia phase transformation; for all the others, stresses related to loading in the central region and related to MT, were conducive to a zirconia phase transformation of nearly the same extent. Vm depth profiling analyses showed that the transformation involved different thicknesses in different samples. Raman data allowed for the investigation of the mechanism of zirconia phase transformation and confirmed that the growth stage was absent and the nucleation stage was not occurring as freely as it would in unconstrained zirconia.

This study was aimed at investigating the effects of the transfer of metallic debris during an in vitro wear test on ceramic femoral heads articulating against metallic acetabular cups. In particular, Biolox® Delta ceramic femoral heads of two different diameters (32 and 36 mm, three samples of each set) were run for five million cycles onto a hip wear simulator using bovine calf serum as lubricant. Wear and degradation of Biolox® Delta Composite femoral heads were evaluated by a gravimetric method and by micro-Raman spectroscopy, which was used to investigate possible phase changes upon the particles deposit, by assessing the monoclinic zirconia content and quantifying the tetragonal → monoclinic zirconia transformation. Our results showed that after five million cycles, the 32 mm-acetabular cups lost a mass higher than the 36 mm-ones. Metal transfer was observed on all the Biolox® Delta ceramic femoral heads and determined a worsening of all roughness parameters. The micro-Raman analyses of the in vitro tested femoral heads confirmed the results previously obtained on retrievals, i.e. the stress related to metal transfer appeared to be a particularly severe condition able to induce the tetragonal→monoclinic zirconia phase transformation. The extent of the transformation appeared higher than that observed in vivo for Biolox® Delta-on-Biolox® Delta couplings. On average, the 36 mm-femoral heads seemed more detrimentally affected by metal transfer than the 32 mm-ones; one femoral head belonging to the first set of samples underwent the highest extent of phase transformation and the highest depth involved, which in the worn centre area appeared on average higher for the 36 mm-components than for the 32 mm-ones.

International audience; Four RuII complexes of general formula [Ru(PT)3]2+, [Ru(NT)3]2+, [Ru(PT)(bpy)2]2+, and [Ru(NT)(bpy)2]2+, where PT = 10,13-bis((triisopropylsilyl)ethynyl)dipyrido[3,2-a:2′,3′-c]phenazine, NT = 10,15-bis((triisopropylsilyl)ethynyl)benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine and bpy = 2,2′-bipyridine have been synthesized. Their electrochemical and photophysical properties have been studied, with the aid of DFT and TD-DFT theoretical methods. The extended phenanthroline ligand PT exhibits two reduction processes at −0.98 and −1.55 (versus SCE) and no clearly detectable oxidation processes; the more extended analogue NT is substantially easier to reduce by about 300 mV. In the four complexes, the two first reduction processes are centered on the extended phenanthroline ligands, and, according to DFT calculations, also oxidations are likely to be located on such moieties. PT and NT exhibit green-yellow fluorescence at 298 and 77 K with photoluminescence quantum yields of 3.4% and 62.1%, respectively, at room temperature. At 77 K, a strong and long-lived phosphorescence is detected only for PT (λmax = 658 nm, τ = 29 ms). In oxygen-free solution at 298 K [Ru(PT)3]2+ and [Ru(PT)(bpy)2]2+ exhibit a very weak emission band with λmax at about 700 nm, which extends towards the near infrared region and is unambiguously attributed to emission from the lowest triplet level centered on the PT ligand; its emission intensity is strongly enhanced at 77 K where lifetimes of 724 and 767 ns are measured for [Ru(PT)3]2+ and [Ru(PT)(bpy)2]2+, respectively. The two complexes with the NT ligand show no triplet emission as observed for the PT analogues, but only a faint fluorescence signal attributable to negligible amounts of free ligand in solution. Photophysical data are fully rationalized with DFT methods, which always predict that the lowest triplet excited state is centered on the extended phenanthroline ligand in all of the investigated RuII complexes. The estimated energy of the lowest triplet level of the PT-based compounds is in good agreement with the experimental value determined from the phosphorescence spectra. Moreover, the theoretical model rationalizes the lack of phosphorescence for the NT series, because the lowest triplet is estimated to be at 0.97 eV above the ground state (≈1280 nm), where non-radiative deactivations prevail.

This paper presents for the first time an innovative instrument called an inverted scanning microwave microscope (iSMM), which is capable of noninvasive and label-free imaging and characterization of intracellular structures of a live cell on the nanometer scale. In particular, the iSMM is sensitive to not only surface structures, but also ectromagnetic properties up to one micrometer below the surface. Conveniently, the iSMM can be constructed through straightforward conversion of any scanning probe microscope, such as the atomic force microscope or the scanning tunneling microscope, with a simple metal probe to outperform traditional SMM in terms of ruggedness, and width, sensitivity and dynamic range. By contrast, the application of the traditional SMM to date has been limited to mainly surface physics and semiconductor technology, because the traditional SMM requires a fragile and expensive probe and is incompatible with saline solution or live biological cells., 5 pages, 4 figures, published in Applied Physics Letters

The Reversible Addition-Fragmentation chain-Transfer (RAFT) synthesis of poly(glycidyl methacrylate) (PGMA) copolymers followed by the post-polymerisation treatment with morpholine allows the rational design of amphiphilic block copolymers that are capable of efficiently dispersing single walled carbon nanotubes (SWCNTs) in aqueous media, as shown by comparative photophysical characterisation and AFM analysis.

Tussah silk fibroin fibres were modified by grafting with methacrylamide (MAA), with weight gains ranging between 2.6% and 71.4%. Raman and IR spectroscopic analyses showed that upon grafting the fibres underwent slight conformational changes towards a more unordered state, due to the covalent and hydrogen bonds interactions occurring between the polymer (polyMAA) and the amorphous domains of silk fibres. To test the stability towards alkaline hydrolysis, the untreated and MAA-grafted silk fibres (weight gain of 71.4%) were immersed in NaOH 5% at 50°C for different times; the IR and Raman spectroscopic techniques were utilized to elucidate the degradation mechanism as well as the rearrangements of the fibres induced by the treatment. Upon hydrolysis, both the untreated and grafted fibres underwent an enrichment in β-sheet conformation, due to the preferential removal of the unordered domains. As a result of the covalent interactions with silk fibroin, the polymer increased its stability towards alkaline hydrolysis, since its complete solubilization was avoided and the transformation of its CONH2 groups into COO(-) and COOH was delayed. Vibrational spectroscopy proved to be a valid technique to investigate the mechanism and the effects of the hydrolytic attack, which are both fundamental to design new-generation silk-based materials.

The covalent functionalization of (7, 6)-enriched single-walled carbon nanotubes (SWCNTs) with oligophenylenevinylene (OPV) moieties terminating with a dimethylamino group is proposed as an efficient way to enhance the affinity of CNTs with Spiro-MeOTAD in perovskite-based solar cells. The evidence of SWCNTs functionalization and the degree of OPV substitution on SWCNTs are established from TGA, XPS, TEM and Raman techniques. Our tailored doping materials display photovoltaic performances in line with conventional Li-doped spiro-MeOTAD system, showing at the same time a significantly improved chemical stability of the perovskite component over time. Furthermore, the comparison of the photovoltaic performances with those obtained with non-functionalized SWCNTs clearly suggest that the presence of the organic appends ensures highly reproducible PV performances. Our results demonstrate the suitability of this material as a valid doping agent for spiro-MeOTAD, representing a viable alternative to the conventional Li-salt.

The objective of this study is to evaluate the effects of third-body particles on the in vitro wear behaviour of three different sets of polyethylene acetabular cups after prolonged testing in a hip simulator and accelerated ageing. Vitamin E-blended, cross-linked polyethylene (XLPE_VE), cross-linked polyethylene (XLPE) and conventional polyethylene (STD_PE) acetabular cups were simulator tested for two million cycles under severe conditions (i.e. by adding third-body particles to the bovine calf serum lubricant). Micro-Fourier Transform Infrared and micro-Raman spectroscopic analyses, differential scanning calorimetry, and crosslink density measurements were used to characterize the samples at a molecular level. The STD_PE cups had twice mass loss than the XLPE_VE components and four times than the XLPE samples; statistically significant differences were found between the mass losses of the three sets of cups. The observed wear trend was justified on the basis of the differences in cross-link density among the samples (XLPE>XLPE_VE>STD_PE). FTIR crystallinity profiles, bulk DSC crystallinity and surface micro-Raman crystallinity seemed to have a similar behaviour upon testing: all of them (as well as the all-trans and ortho-trans contents) revealed the most significant changes in XLPE and XLPE_VE samples. The more severe third-body wear testing conditions determined more noticeable changes in all spectroscopic markers with respect to previous tests. Unexpectedly, traces of bulk oxidation were found in both STD_PE (unirradiated) and XLPE (remelting-stabilized), which were expected to be stable to oxidation; on the contrary, XLPE_VE demonstrated a high oxidative stability in the present, highly demanding conditions.

By means of different spectroscopic techniques, we investigate a novel series of porphyrin derivatives (H2TPP), connected to dibenzo-24-crown-8 (DB24C8) moieties, which undergo self-assembly with different methano[60]fullerene units bearing dibenzylammonium (DBA) cations. The formation of both [2] and [3]pseudorotaxanes was proved by means of NMR, UV-Vis-NIR absorption and emission spectroscopies. With the support of molecular modelling studies, spectroscopic investigations showed the presence of a secondary interaction between the porphyrin and the C60 chromophores leading to the formation of different types of ‘‘face-to-face’’ assemblies. Remarkably, investigations of the non-linear optical response of these supramolecular systems showed that individual porphyrin and fullerene derivatives exhibit significantly lower second hyperpolarizability values when compared to their pseudorotaxanes functionalised counterparts. This proves that this class of supramolecular materials possesses relevant NLO response, which strongly depends on the structural arrangement of the chromophores in solution. Introduction

First-generation (irradiated and remelted or annealed) and second-generation (irradiated and vitamin E blended or doped) highly crosslinked polyethylenes were introduced in the last decade to solve the problems of wear and osteolysis. In this study, the influence of the Vitamin-E addition on crosslinked polyethylene (XLPE_VE) was evaluated by comparing the in vitro wear behavior of crosslinked polyethylene (XLPE) versus Vitamin-E blended polyethylene XLPE and conventional ultra-high molecular weight polyethylene (STD_PE) acetabular cups, after accelerated ageing according to ASTM F2003-02 (70.0±0.1 °C, pure oxygen at 5 bar for 14 days). The test was performed using a hip joint simulator run for two millions cycles, under bovine calf serum as lubricant. Mass loss was found to decrease along the series XLPE_VE>STD_PE>XLPE, although no statistically significant differences were found between the mass losses of the three sets of cups. Micro-Raman spectroscopy was used to investigate at a molecular level the morphology changes induced by wear. The spectroscopic analyses showed that the accelerated ageing determined different wear mechanisms and molecular rearrangements during testing with regards to the changes in both the chain orientation and the distribution of the all-trans sequences within the orthorhombic, amorphous and third phases. The results of the present study showed that the addition of vitamin E was not effective to improve the gravimetric wear of PE after accelerated ageing. However, from a molecular point of view, the XLPE_VE acetabular cups tested after accelerated ageing appeared definitely less damaged than the STD_PE ones and comparable to XLPE samples.

We have fabricated and electrically characterized at the wafer scale tens of metal-ferroelectric (HfZrO)-semiconductor capacitors and metal-graphene monolayer-ferroelectric (HfZrO)-semiconductor capacitors with the same top electrode dimensions. We have found that the memory windows of the capacitors containing graphene are 3-4 times larger than the ferroelectric capacitors without graphene, and increase even more after annealing. This physical effect can be attributed to the additional electric field exerted by the graphene monolayer on the HfZrO ferroelectric semiconductor capacitor, and to the negative thermal extension coefficient of graphene, respectively.

Luminescence and photoinduced energy and electron transfer are fundamental processes that are acquiring an increasing importance for a number of applications in several fields. Our group is particularly concerned with those related to lighting and solar energy conversion, which entail the design, preparation and characterization of suitably designed molecules, metal complexes, supramolecular arrays and nanomaterials. Some of our recent results in this area will be briefly illustrated, particularly on (i) transition metal complexes, (ii) luminescent hybrid materials made of inorganic luminophores and carbon nanotubes, and (iii) photoinduced processes in multichromophoric systems containing fullerene as electron acceptor combined with suitable electron donors. In an effort to keep a tutorial approach and a broader view, we will introduce the data presented in light of their potential applications and, more generally, in the context of the energy transition to be accomplished in the present century.

Our research is focused on the design, synthesis and investigation of photo-active molecules, supramolecular systems and nanomaterials with specific light-driven functionalities, which are of interest for many technological applications. In particular: LUMINESCENT METAL COMPLEXES. Due to their chemical and optical versatility these compounds are of widespread interest for energy conversion, electroluminescent devices (LEC, OLED), probing of drug and cellular systems, and sensors. We work on both transition metal (Cu, Ir, Ru) and lanthanide (Eu, Tb) materials. CARBON NANOSTRUCTURES. We have a consolidated experience in the investigation of multicomponent architectures containing functionalized C60's and featuring photoinduced energy- and electron transfer for solar energy conversion devices. Our interest is also concerned with carbon nanotubes as scaffolds for luminescent compounds and polymers, to be developed for lighting technologies. SUPRAMOLECULAR PHOTOACTIVE NANOMATERIALS. We have prepared new organic materials to be used as scaffolds or active components of molecular devices capable of elaborating chemical information and afford useful functions, mainly via light stimulation. Our research has been carried out in the frame of past and present national and European projects. The development of these materials are of interest both in fundamental science and for real life applications, such as efficient lighting, imaging and telecommunications.

Four RuII complexes of general formula [Ru(PT)3]2+, [Ru(NT)3]2+, [Ru(PT)(bpy)2]2+, and [Ru(NT)(bpy)2]2+, where PT = 10,13-bis((triisopropylsilyl)ethynyl)dipyrido[3,2-a:2',3'-c]phenazine, NT = 10,15-bis((triisopropylsilyl)ethynyl)benzo[i]dipyrido[3,2-a:2',3'-c]phenazine and bpy = 2,2'-bipyridine have been synthesized. Our goal is to illustrate their electrochemical and photophysical properties with the aid of DFT and TD-DFT theoretical methods, in order to evaluate their potential for applications on solar energy conversion [1]. Additionally, we want to get exhaustive photophysical data for RuII homoleptic complexes with extended ligands, which have been scarcely investigated [2]. The electrochemical data for the phenanthroline ligands PT and NT show two successive one-electron reduction processes, while in the four complexes, also according to DFT calculations, the two first reduction processes are located on the extended phenanthrolines. Both ligands display green-yellow fluorescence at 298 and 77 K, whereas a strong and long-lived phosphorescence is detected only in the case of the PT ligand. In oxygen-free THF solution at 298 K, [Ru(PT)3]2+ and [Ru(PT)(bpy)2]2+ exhibit a very weak emission band, which is unequivocally attributed to emission from the lowest triplet level centered on the PT ligand since the emission band of the complexes is virtually identical to the phosphorescence of the free ligand. The two complexes of the more extended chelator, [Ru(NT)3]2+ and [Ru(NT)(bpy)2]2+, do not emit under any conditions; only a weak fluorescence signal attributable to a slight amount of free ligand in solution is observed. Photophysical data are fully rationalized with DFT methods, which always predict that the lowest triplet excited state is centered on the extended phenanthroline ligand in all of the complexes. These RuII compounds are long wavelength light absorbers, which are potentially useful for the harvesting of solar energy. [1] Monti F., Hahn U., Pavoni E., Delavaux-Nicot B., Nierengarten J.-F., Armaroli N., Polyehdron, 2014, doi:10.1016/j.poly.2014.05.030, Special Issue on Molecular Materials for Solar Energy Conversion. [2] Puntoriero F., Nastasi F., Galletta M., Campagna S., Photophysics and Photochemistry of Non-Carbonyl-Containing Coordination and Organometallic Compounds, in: Eds. J. Reedijk, K. Poeppelmeier Comprehensive Inorganic Chemistry II (2nd Edition), Elsevier, 2013, pp. 255-337.

Single-walled carbon nanotubes (SWCNTs) exhibit excellent mechanical, electrical, thermal, and optical properties. They are considered promising materials for a number of applications for which, however, individual SWCNTs are required instead of the complex mixture of metallic and semiconducting species obtained upon their preparation. The establishment of dispersion and separation protocols for SWCNTs is therefore of capital importance to enable their effective exploitation. There are many different approaches for the dispersion of SWCNTs, which typically entail non-covalent interactions between amphiphilic molecules and the wall of the tubes in aqueous solution. Common surfactants (e.g. SDS, SC, SDBS) are typically used for this purpose. We report an effective strategy for the preparation of single-walled carbon nanotube dispersions, based on the use of an amphiphilic polymer (PHMPMA-b-PSt) and compare it with a standard surfactant (SDBS) and another polymer lacking pendant phenyl groups (PHMPMA-b-PMMA). The polymers used in this work are new and obtained by post-polymerization treatments of RAFT synthesized poly(glycidyl methacrylate) (PGMA). We found that the polymer can form micelles around the SWCNTs through its hydrophobic chain, whilst the hydrophilic part prompts dispersion in water. The excellent dispersion capability of our polymer is demonstrated by electronic absorption spectra, photoluminescence mapping of the SWCNTs (Figure 1) and AFM studies. 1 H. Wang, Curr. Opin. Colloid Interface Sci., 2009, 14, 364-371. 2 M. Benaglia, A. Alberti, L. Giorgini, F. Magnoni and S. Tozzi, Polym. Chem., 2013, 4, 124-132.