Life Cycle Assessment of a system for the extraction and transformation of Waste Water Treatment Sludge (WWTS)-derived lipids into biodiesel

In recent years, the demand for biofuels has been growing exponentially, as has the interest in biodiesel produced from organic matrices. Particularly interesting, due to its economic and environmental advantages, is the use of the lipids present in sewage sludge as a raw material for the synthesis of biodiesel. The possible processes of this biodiesel synthesis, starting from lipid matter, are represented by the conventional process with sulfuric acid, by the process with aluminium chloride hexahydrate and by processes that use solid catalysts such as those consisting of mixed metal oxides, functionalized halloysites, mesoporous perovskite and functionalized silicas. In literature there are numerous Life Cycle Assessment (LCA) studies concerning biodiesel production systems, but not many studies consider processes that start from sewage sludge and that use solid catalysts. In addition, no LCA studies were reported on solid acid catalysts nor on those based on mixed metal oxides which present some precious advantages, over the homogeneous analogous ones, such as higher recyclability, prevention of foams and corrosion phenomena, and an easier separation and purification of biodiesel product. This research work reports the results of a comparative LCA study applied to a system that uses a solvent free pilot plant for the extraction and transformation of lipids from sewage sludge via seven different scenarios that differ in the type of catalyst used. The biodiesel synthesis scenario using aluminium chloride hexahydrate as catalyst has the best environmental profile. Biodiesel synthesis scenarios using solid catalysts are worse due to higher methanol consumption which requires higher electricity consumption. The worst scenario is the one using functionalized halloysites. Further future developments of the research require the passage from the pilot scale to the industrial scale in order to obtain environmental results to be used for a more reliable comparison with the literature data.

An Old but Lively Nanomaterial: Exploiting Carbon Black for the Synthesis of Advanced Materials

Carbon black (CB) is an old-concept but versatile carbonaceous material prone to be structurally and chemically modified under quite mild wet conditions. Recently, we exploited the potentiality of CB for the production of a highly varied array of advanced materials with applications in energetics, water remediation and sensoristic. The proposed approaches are devised to meet specific needs: low production costs, scalable synthetic approaches, flexibility i.e. easy tuning of chemico-physical properties of the carbon-based advanced materials. Two main approaches have been exploited: modification of CB at the surface and highly CB de-structuration. The former approach allows obtaining highly homogenous CB-modified nanoparticles (around 160 nm) with tunable surface properties (hydrophilicity, typology of functional groups and surface charge density, pore size distribution), supports for ionic liquid (SILP) and composites (carbon-iron oxide). The latter approach exploiting a top-down demolition of CB produces a highly versatile graphene related material (GRM), made up by stacked short graphene-like layers (GL) particularly suitable for advanced composites synthesis and ultrathin carbon-based films production.

The Characteristics of Graphene Obtained from Rice Husk and Graphite

In this paper methods for obtaining graphene oxide from rice husk were developed, which using a downward approach based on a four-stage strategy: preliminary carbonization, desilication, activation with KOH, and exfoliation and its comparison with the method of graphite oxidation. The samples were analyzed by elemental analysis, SEM, Raman, TGA and FTIR. The elemental analysis show that the proposed approach allows to produce graphene materials with a carbon content around 70% and rich in inorganic matter (0–20 wt.%) (K, Fe, Si). To remove inorganic contents, purification and functionalization step were applied. The Raman spectra of the samples indicate the presence of a mixture of graphene layers and amorphous carbon. The thermogravimetric profile of samples is characterized by a slowly weight decrease up to a final residue of ~10 wt.%. FTIR spectra are characterized by the typical broad shape of large condensed aromatic carbon bonds; only the peak due to C=C stretching modes and the overlapped peaks between 900 and 1500 cm-1 due to skeleton vibrations are detected.

Study of the correlation between sensing performance and surface morphology of inkjet-printed aqueous graphene-based chemiresistors for NO2 detection

The extremely high sensitivity to the external environment and the high specific surface area, as well as the absence of bulk phenomena that could interfere with the response signal, make graphene highly attractive for the applications in the field of sensing. Among the various methods for producing graphene over large areas, liquid phase exfoliation (LPE) appears to be very promising, especially if combined with inkjet printing (IJP), which offers several advantages, including the selective and controlled deposition of small ink volumes and the versatility of the exploitable inks and substrates. Herein we present a feasibility study of chemiresistive gas sensors inkjet-printed onto paper substrates, in which a LPE graphene suspension dispersed in a water/isopropanol (H₂O/IPA) mixture is used as sensing ink. The device performances, in terms of relative conductance variations, upon exposure to NO₂ at standard ambient temperature and pressure, are analysed. In addition, we examine the effect of the substrate morphology and, more specifically, of the ink/substrate interaction on the device performances, by comparing the response of different chemiresistors fabricated by dispensing the same suspension also onto Al₂O₃ and Si/SiO₂ substrates and carrying out a supportive atomic force microscopy analysis. The results prove the possibility to produce sensor devices by means of a wholly environmentally friendly, low-cost process that meets the requests coming from the increasing field of paper-based electronics and paving the way towards a flexible, green-by-design mass production.

Tunable spin polarization and superconductivity in engineered oxide interfaces

Advances in growth technology of oxide materials allow single atomic layer control of heterostructures. In particular delta doping, a key materials' engineering tool in today's semiconductor technology, is now also available for oxides. Here we show that a fully electric-field-tunable spin-polarized and superconducting quasi-2D electron system (q2DES) can be artificially created by inserting a few unit cells of delta doping EuTiO3 at the interface between LaAlO3 and SrTiO3 oxides. Spin polarization emerges below the ferromagnetic transition temperature of the EuTiO3 layer (TFM = 6-8 K) and is due to the exchange interaction between the magnetic moments of Eu-4f and of Ti-3d electrons. Moreover, in a large region of the phase diagram, superconductivity sets in from a ferromagnetic normal state. The occurrence of magnetic interactions, superconductivity and spin-orbit coupling in the same q2DES makes the LaAlO3/EuTiO3/SrTiO3 system an intriguing platform for the emergence of novel quantum phases in low-dimensional materials.

Emergence of coherence in the charge-density wave state of 2H-NbSe2

A charge-density wave (CDW) state has a broken symmetry described by a complex order parameter with an amplitude and a phase. The conventional view, based on clean, weak-coupling systems, is that a finite amplitude and long-range phase coherence set in simultaneously at the CDW transition temperature T_cdw. Here we investigate, using photoemission, X-ray scattering and scanning tunnelling microscopy, the canonical CDW compound 2H-NbSe₂ intercalated with Mn and Co, and show that the conventional view is untenable. We find that, either at high temperature or at large intercalation, CDW order becomes short-ranged with a well-defined amplitude, which has impacts on the electronic dispersion, giving rise to an energy gap. The phase transition at T_cdw marks the onset of long-range order with global phase coherence, leading to sharp electronic excitations. Our observations emphasize the importance of phase fluctuations in strongly coupled CDW systems and provide insights into the significance of phase incoherence in ‘pseudogap’ states.

Charge density waves are described by a complex order parameter whose amplitude is expected to vanish at the transition temperature. This study shows that the transition in 2H-NbSe₂ is driven by fluctuations of the phase of the order parameter, with a finite amplitude surviving in the disordered state.

Towards the realization of label-free biosensors through impedance spectroscopy integrated with IDES technology

Impedance spectroscopy (IS) is a powerful technique for analysis of the complex electrical impedance of a large variety of biological systems, because it is sensitive both to surface phenomena and to changes of bulk properties. A simple and convenient method of analysis of cell properties by IS is described. An interdigitated electrodes configuration was used for the measurements; human epithelial cells were grown on the device to investigate the complex dielectric response as a function of frequency, in order to test the suitability of the device for use as a label-free biosensor. To test the ability of the device to detect channels in the cell membrane, the effect of drugs known to affect membrane integrity was also investigated. The frequency response of the admittance (i.e. the reciprocal of the impedance) can be well fitted by a model based on very simple assumptions about the cells coating the device surface and the current flow; from the calculations, membrane-specific capacitance and information about cell adhesion can be inferred. These preliminary efforts have shown that our configuration could lead to a label-free non-invasive technique for biosensing and cellular behavior monitoring which might prove useful in investigation of the basic properties of cells and the effect of drugs by estimation of some fundamental properties and modification of the electrical characteristics of the device.

Scanning tunnelling spectroscopy study of paramagnetic superconducting β''-ET(4)[(H(3)O)Fe(C(2)O(4))(3)]·C(6)H(5)Br crystals

Scanning tunnelling spectroscopy (STS) and microscopy (STM) were performed on the paramagnetic molecular superconductor β''-ET(4)[(H(3)O)Fe(C(2)O(4))(3)]·C(6)H(5)Br. Under ambient pressure, this compound is located near the boundary separating superconducting and insulating phases of the phase diagram. In spite of a strongly reduced critical temperature T(c) (T(c) = 4.0 K at the onset, zero resistance at T(c) = 0.5 K), the low temperature STS spectra taken in the superconducting regions show strong similarities with the higher T(c) ET κ-derivatives series. We exploited different models for the density of states (DOS), with conventional and unconventional order parameters to take into account the role played by possible magnetic and non-magnetic disorder in the superconducting order parameter. The values of the superconducting order parameter obtained by the fitting procedure are close to the ones obtained on more metallic and higher T(c) organic crystals and far above the BCS values, suggesting an intrinsic role of disorder in the superconductivity of organic superconductors and a further confirmation of the non-conventional superconductivity in such compounds.