Tipologie strutturali e caratteristiche funzionali delle aree verdi periurbane: il caso di studio della città di Bari

n/

Analisi della diversità funzionale di coleotteri carabidi (Coleoptera, Carabidae) del Parco Naturale Regionale Lama Balice (Puglia)

FUNCTIONAL DIVERSITY OF THE GROUND BEETLES (COLEOPTERA, CARABIDAE) ON LAMA BALICE NATURE RESERVE (PUGLIA, ITALY) Preliminary information about population of Ground Beetles (Coleoptera Carabidae) of Natural Regional Park of Lama Balice (South Italy, Bari) are reported here. Study of species composition and dominance structure pointed out presence of few dominant species. Analysis of sampled vegetation macro-units (or habitats) highlighted that functional diversity of sampled ground beetles community showed valuable differences in structural and functional features of communities between different habitats. In the “macchia- gariga” (shrub-garrigue) there was an increase of feeding-opportunistic species and we found sole seedeaters. In the “ vegetazione erbacea di fondo lama” (grass vegetation of deep lama) we found specialised predators. Key word: biodiversity, functional groups. Con il presente lavoro sono state fornite informazioni preliminari inerenti il popolamento di Coleotteri Carabidi presenti all’interno del Parco. La struttura di dominanza, descrive una comunità con poche specie dominanti (Laemostenus cimmerius cimmerius F.; Pterostichus melas italicus D.; Calathus fuscipes graecus D.; Pseudoophonus rufipes D.). La diversità funzionale della carabidofauna campionata, evidenzia cambiamenti delle caratteristiche strutturali e funzionali, nella serie di “macrounità o habitat vegetazionali” investigate nell’ecotopo del Lama. La variazione, evidenzia che nella macchia-gariga si ha un aumento degli opportunisti alimentari, e compaiono i spermofagi esclusivi. Nella vegetazione erbacea di fondo lama ritroviamo i predatori zoofagi specializzati. Parole chiave: biodiversità, parametri adattativi, guild

Performance Assessment in Fingerprinting and Multi Component Quantitative NMR Analyses

An interlaboratory comparison (ILC) was organized with the aim to set up quality control indicators suitable for multicomponent quantitative analysis by nuclear magnetic resonance (NMR) spectroscopy. A total of 36 NMR data sets (corresponding to 1260 NMR spectra) were produced by 30 participants using 34 NMR spectrometers. The calibration line method was chosen for the quantification of a five-component model mixture. Results show that quantitative NMR is a robust quantification tool and that 26 out of 36 data sets resulted in statistically equivalent calibration lines for all considered NMR signals. The performance of each laboratory was assessed by means of a new performance index (named Qp-score) which is related to the difference between the experimental and the consensus values of the slope of the calibration lines. Laboratories endowed with a Qp-score falling within the suitable acceptability range are qualified to produce NMR spectra that can be considered statistically equivalent in terms of relative intensities of the signals. In addition, the specific response of nuclei to the experimental excitation/relaxation conditions was addressed by means of the parameter named NR. NR is related to the difference between the theoretical and the consensus slopes of the calibration lines and is specific for each signal produced by a well-defined set of acquisition parameters

Promoting oxygen vacancy formation and p-type conductivity in SrTiO3 via alkali metal doping: a first principles study

Strontium titanate (SrTiO3, STO) is a prototypical perovskite oxide, widely exploited in many technological applications, from catalysis to energy conversion devices. In the context of solid-oxide fuel cells, STO has been recently applied as an epitaxial substrate for nano-sized layers of mixed ion-electron conductive catalysts with enhanced electrochemical performances. To extend the applications of such heterogeneous nano-cathodes in real devices, also the STO support should be active for both electron transport and oxide diffusion. To this end, we explored using first-principles calculations the strategy of doping of STO at the Sr site with sodium and potassium. These two ions fit in the perovskite structure and induce holes in the STO valence band, so as to obtain the desired p-type electronic conduction. At the same time, the doping with alkali ions also promotes the formation of oxygen vacancies in STO, a prerequisite for effective oxide diffusion. Analysis of electron density rearrangements upon defect formation allows relating the favorable vacancy formation energies to an improved electronic delocalization over the oxide sub-lattice, as observed in closely related materials (e.g. Sr2Fe1.5Mo0.5O6). Overall, our results suggest the alkali-doped STO as a new potential substrate material in nanoscale heterogeneous electrodes for solid oxide electrochemical cells

First-principles study of trimethylamine adsorption on anatase TiO2 nanorod surfaces

Titanium dioxide (TiO2) nanorods are widely employed in many energy-related applications thanks to their peculiar electronic and physicochemical properties. Here we report a periodic DFT and DFT-D study of the three most exposed surfaces of stoichiometric anatase TiO2 nanorods, i.e., (100), (001) and (101). On these surfaces, we investigated the adsorption of a tertiary amine (trimethylamine, TMA): Energetic, structural and electronic features have been characterized, paying particular attention on the effects of dispersion forces on the adsorption process. We found evidence of the formation of a coordinative bond between the molecules and the titanium site of adsorption. As expected, the inclusion of dispersion correction strongly enhances the adsorption process. Moreover, in some cases TMA adsorption introduces new electronic states at the edge of the valence band. Overall, our results provide new insights on the interactions between TiO2 nanorods and nitrogen compounds, which have many scientific and technological implications

Do thermal treatments influence the ultrafast opto-thermal processes of eumelanin?

After light absorption, melanin converts very rapidly the energy gained into heat. The time scale of this process ranges from tens of femtoseconds to a few nanoseconds. Femtosecond transient absorption allows for exploration of such photo-induced carrier dynamics to observe the de-excitation pathways of the biological complex. Here, we report on the ultrafast relaxation of suspensions of Sepia melanin in DMSO at room temperature using a femtosecond broadband pump and probe technique by photoexciting in the UV and probing in the entire visible range. In particular, we focus on the possible role that different heat treatments, performed in the temperature range 30-80 degrees C might have on the relaxation of charge carriers photogenerated by UV radiation in such suspensions. Experimental data indicate that in all the investigated suspensions, photoexcited carriers always follow a tri-exponential route to relaxation. Moreover, we find that the relaxation time constants are essentially the same in all cases, within the experimental error. We take this as evidence that all the investigated suspensions essentially exhibit the same relaxation dynamics, regardless of the temperature at which the heat treatment has been performed and of the heat-induced denaturation of the proteinaceous compounds bound to the photoactive pigment. Our experiments represent a significant step towards the understanding of the stability of melanin with respect to temperature changes

COLLOIDAL TiO2 NANORODS FOR PHOTOCATALYSIS: A FEMTOSECOND TRANSIENT ABSORPTION STUDY

Concept: The excitation-dependent relaxation dynamics of charge carriers in anatase TiO2 nanorods (NRs) was investigated by femtosecond transient absorption spectroscopy. This technique is a widely known effective tool with unique capabilities for elucidating the electron-hole (e--h+) recombination dynamics of nanocrystals. Colloidal dispersions of such anisotropic nanocrystals were excited in the UV−vis range using three different pump wavelengths, i.e. above, close to, and below the direct band gap of anatase. We show that the ultrafast dynamics strongly depends on the excitation wavelength, and influences most of the processes contributing to the relaxation dynamics. Motivations and objectives: TiO2 nanocrystals are successfully exploited in applications related to energy conversion, such as photocatalysis and photovoltaics, thanks to their ability to generate e--h+ pairs under proper lighting. In addition, the rod-like nanocrystal shape magnifies this effect, due to a larger surface/volume ratio and a higher number of active sites of interaction with the environment. The conversion efficiency is correlated to the lifetimes of e- and h+ before their recombination, which in turn are influenced by several factors. Excitation energy plays a major role, as it defines the initial potential of the carriers. An excitation-dependent investigation of the charge carrier dynamics is thus expected to provide major information crucial for understanding their reactivity and for further rationalizing their behavior in photocatalytic applications. Results and discussion: TiO2 NRs were synthesized by a colloidal chemistry route and dispersed in an organic solvent, thanks to oleate ions coordinating the nanocrystal surfaces. We performed pump-probe experiments in a weak-excitation regime by pumping at 300, 350, and 430 nm and probing in a broadband spectral range extending from 450 to 750 nm. The temporal evolution of photoinduced absorption changes was found to be strongly dependent on the excitation conditions, both at short and long time delays. Nonetheless, the initial charge carriers trapping in surface defect states occurs very rapidly after the photogeneration in all investigated cases. The two distinct TA bands at 500 and 700 nm, typically attributed to trapped h+ and e- in anatase, are accessible only when TiO2 nanorods are photoexcited well above the band gap, while there is no evidence of such bands when excitation occurs close to or below the band gap. In such cases the observed dynamics are attributed to excitonic states. This evidence is also supported by the persistence of a long-lasting TA contribution ascribable to such bound states

Spectroscopic Study on Imidazolium-Based Ionic Liquids: Effect of Alkyl Chain Length and Anion

Room temperature ionic liquids are currently used as functional materials in several application and their optical investigation can provide a better understanding of their physical and chemical behavior. Absorption and emission properties of imidazolium-based ILs have been attributed to the imidazolium moiety and related to the presence of energetically different aggregates. Here, time-integrated and time-resolved investigation has been carried out on 1-alkyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate ionic liquids with different chain lengths in order to probe the occurrence of energy transfer processes, and hence to disclose the presence of various states with different energy. Such a study contributes to provide relevant insight on the effect of alkyl chain and anion type on the emission characteristics, and, hence, on the presence of associated structures