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In this study, a novel SERS sensor has been developed for repeatable detection of organic molecules and biological assays. Vertically oriented titania nanotube (TiO2 NT) arrays were grown by ultra-fast anodic oxidation of flexible titanium foils and then decorated with Ag nanoparticles (NPs) through d.c. sputtering deposition at room temperature. A parametric study was carried out taking into account the effect of sputtering parameters on the Ag NP arrangements on the NT surface. The structure morphology was investigated by means of scanning and transmission electron microscopy, evidencing the formation of hexagonal close-packed TiO2 NTs coated with Ag nanoparticles showing tunable diameter and distribution. The substrates were employed in a SERS optofluidic device, consisting of a polydimethylsiloxane cover irreversibly sealed to the silver-coated TiO2 NTs, able to detect Rhodamine molecules in ethanol over a wide range of concentrations down to 10−14 M, taking advantage of both electromagnetic and chemical enhancements. In order to evaluate the performances of the SERS substrates in terms of biosensing, an optimized protocol for the immobilization of oligonucleotide probes on the metal-dielectric surfaces was developed for verifying the hybridization events. [ABSTRACT FROM AUTHOR]

The coupling of optical Bloch surface waves at the truncated end of one dimensional porous silicon photonic crystals is exploited for fast vapour sensing. Self-standing multilayered membranes bound to transparent substrates were fabricated by electrochemical etching and used in an attenuated total reflection configuration to resonantly excite the surface waves and perform real-time sensing. [ABSTRACT FROM AUTHOR]

The effects on 4H-silicon carbide epilayers of irradiation with protons and electrons having particle energies, respectively, of 6.5 and 8.2 MeV were carefully studied and critically compared. In detail, the electronic levels associated with the irradiation-induced defects were analyzed by current-voltage characteristics and deep-level transient spectroscopy (DLTS) measurements up to 550 K. In the same temperature range the apparent free-carrier concentration was measured by capacitance-voltage characteristics in order to monitor compensation effects due to the deep levels associated with the induced defects. Introduction rate, enthalpy, and capture cross section of such deep levels were compared. We found that a set of deep levels (at ET=0.39 eV, ET=0.65 eV, and ET=0.75 eV) is the same in both cases of proton and electron irradiations, whereas two other pairs of levels (S1, ET=0.20 eV and S1*, ET=0.23 eV; S5, ET=1.09 eV and S5*, ET=0.89 eV) appearing in the same temperature range within the DLTS spectra should be associated with different defect complexes according to the irradiation type. Some conclusions regarding the microscopic nature of the defects related to the deep levels have been drawn. [ABSTRACT FROM AUTHOR]

Amorphous (a-Si1-xCx:H) and microcrystalline (μc-Si1-xCx:H) thin films have been deposited by plasma-enhanced chemical-vapor deposition using SiF4-CH4-H2 rf plasmas. Gas flow rates have been varied to deposit films with different carbon content and microstructure. The microstructure and optical properties have been investigated by IR/Raman spectroscopy and by spectroscopic ellipsometry in the energy range of 1.5-5.0 eV. Ellipsometric spectra have been analyzed in terms of the tetrahedron model combined with the Bruggeman effective-medium approximation to determine the film microstructure and silicon-carbon-bond configurations. Correlation between Si-C bond configurations and optical properties of films has been studied as a function of carbon content and microstructure. It is found that the optical properties and the band gap value depend not only on the carbon content, but also on the Si-C bond configuration and microcrystallinity. The films consist of Si-centered Si-Si4-υCυ (υ=0-3) Si-centered tetrahedra with segregation of μc-Si. The amorphous matrix changes from Si-Si3C to Si-SiC3 with the increase of the μc-Si phase. The optical gap is found to increase with both carbon content and microcrystallinity. [ABSTRACT FROM AUTHOR]

A set of Cu-Mn oxides was prepared through the simple and effective solution combustion synthesis method by varying the relative amount of copper and manganese. The physico-chemical properties of the samples were investigated through complementary techniques such as N 2 physisorption at − 196 °C, XRD, HR-TEM, Raman spectroscopy, temperature programmed analyses (H 2 -TPR, O 2 -TPD, and NH 3 -TPD), and XPS. The prepared catalysts were tested for the total oxidation of volatile organic compounds (ethylene, propylene, and toluene). The best performances, in terms of total VOC oxidation, were achieved with a copper content ranging from 15 at% to 45 at%. The catalytic test outcomes demonstrate the beneficial effect of acidic sites, oxygen mobility, and redox ability. In particular, ethylene oxidation is mainly favored by oxygen vacancies and redox properties, while propylene and toluene oxidation is mostly enhanced by acidic sites. All the catalysts prepared can totally oxidize the examined pollutants examined below 310 °C. Moreover, the binary oxides exhibit good catalytic stability over a time-on-stream of 7 h and low water vapor inhibition (5 vol% H 2 O in the gas stream). [Display omitted] • Cu-Mn oxides are effective catalysts for ethylene, propylene and toluene oxidations. • Solution Combustion Synthesis is the technique used to prepare Cu-Mn oxides. • The Cu-Mn oxide catalysts exhibit good stability. • Different oxidation mechanisms take place with ethylene, propylene and toluene. • Low catalytic deactivation occurs in the presence of water vapor 5 vol%. [ABSTRACT FROM AUTHOR]

In recent decades, climate change has become a major issue that needs to be addressed. Many efforts have been made on the reduction of CO 2 emissions and its conversion in energy carriers and high value-added products such as methane, methanol, dimethyl-ether, and hydrocarbons. The present study focuses on the development of catalysts for hydrogenating CO 2 to methanol, which is a useful chemical and an alternative liquid fuel. According to the literature, In 2 O 3 -based catalysts are particularly selective in the hydrogenation of CO 2 to methanol, reducing the production of CO even at high space velocities compared to the more common ternary catalysts such as Cu/ZnO/Al 2 O 3 or Cu/ZnO/ZrO 2. Therefore, the effects of CeO 2 and ZrO 2 on In 2 O 3 -based catalysts were investigated in the present study. The In x Ce 100−x and the In x Zr 100−x mixed oxides catalysts were synthesized via gel-oxalate coprecipitation by varying the atomic ratios between the elements. Subsequently, they were analysed with several characterisation techniques to rationalise the catalytic performances that were obtained by testing the samples in a fixed bed reactor under different reaction conditions. The addition of different amounts Ce or Zr modified the structure and morphology of the samples and promoted the adsorption of CO 2 from 1.8 mmol CO2 ⋅g cat −1 up to 10.6 mmol CO2 ⋅g cat −1. ZrO 2 stabilises the structure and the results suggests that the greater specific activity (168 mg CH3OH ⋅g In2O3 −1⋅h−1 at 300 °C and 2.5 MPa of In 40 Zr 60) could be ascribed to the electronic promotion of Zr. On the contrary, the addition of CeO 2 did not reveal a beneficial effect on the activity. Concerning the stability, In 2 O 3 -ZrO 2 binary oxides seemed to be affected mainly by sintering; whereas In 2 O 3 -CeO 2 were affected by at least three deactivating phenomena: sintering, reduction of In 2 O 3 to metallic indium and coking. Consequently, the deactivation rate of these binary oxides increased from 1.04 ⋅ 10−2 h−1 of the In 100 to 4.13 ⋅ 10−2 h−1 of the In 40 Ce 60. [Display omitted] • CeO 2 and ZrO 2 modify the morphology and boost the CO 2 adsorption rate. • The electronic promotion effect of Zr enhances the methanol synthesis from CO 2. • ZrO 2 stabilises the structure and mitigates the deactivation phenomena. • CeO 2 increases the reducibility of the samples without stabilising the structure. • In 2 O 3 -CeO 2 samples are affected by sintering, formation of metallic In and coking. [ABSTRACT FROM AUTHOR]

Abstract: The edge‐functionalization of graphene nanoplatelets (GnP) is carried out exploiting diazonium chemistry, aiming at the synthesis of edge decorated nanoparticles to be used as building blocks in the preparation of engineered nanostructured materials for enhanced heat transfer. Indeed, both phenol functionalized and dianiline‐bridged GnP (GnP‐OH and E‐GnP, respectively) are assembled in nanopapers exploiting the formation of non‐covalent and covalent molecular junctions, respectively. Molecular dynamics allow to estimate the thermal conductance for the two different types of molecular junctions, suggesting a factor 6 between conductance of covalent vs noncovalent junctions. Furthermore, the chemical functionalization is observed to drive the self‐organization of the nanoflakes into the nanopapers, leading to a 20% enhancement of the thermal conductivity for GnP‐OH and E‐GnP while the cross‐plane thermal conductivity is boosted by 190% in the case of E‐GnP. The application of chemical functionalization to the engineering of contact resistance in nanoparticles networks is therefore validated as a fascinating route for the enhancement of heat exchange efficiency on nanoparticle networks, with great potential impact in low‐temperature heat exchange and recovery applications. [ABSTRACT FROM AUTHOR]

Ceria-based catalysts doped with manganese and copper were obtained via the hydrothermal synthesis. Four systems were synthesized: CeO (pure ceria), CeMn (Mn/Ce at. ratio = 1/19), CeCu (Cu/Ce at. ratio = 1/19) and CeMnCu (Mn/Cu/Ce at. ratio = 1/1/38). The catalytic activity of the prepared materials was tested for the CO and soot oxidations. Complementary techniques (XRD, N physisorption at − 196 °C, FESEM, XPS, Raman spectroscopy, CO-TPR and Soot-TPR) were performed to investigate their physico-chemical properties. The samples were characterized by nanocubes, in the case of CeO, and by nanopolyhedra for binary (CeMn and CeCu) and ternary oxides (CeMnCu). The CO-TPR analysis has confirmed that the reducibility follows the order: CeO < CeMn < CeMnCu < CeCu. A similar trend appears for the surface defective sites (Raman spectroscopy). These findings suggest the beneficial role of dopants in improving the structural defects and the surface reducibility of ceria. Both properties promote the CO oxidation activity. In fact, the CeCu was the most effective catalyst for the CO oxidation. The CeMn sample exhibited the best performance in soot oxidation. The following order was achieved: CeMnCu < CeCu < CeO ≈ CeMn, in agreement with the reduction profiles obtained by the Soot-TPR above 400 °C. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Copper-ceria mixed oxides are widely considered promising catalysts for oxidation reactions, especially when the participation of lattice oxygen is required. However, the mechanistic understanding of these catalytic systems is still incomplete, due to their considerable complexity. In fact, copper doping of ceria results in the formation of a significant number of different interacting sites in continuous evolution during the catalytic processes. In the present study, pure and Cu-doped ceria samples were deeply investigated through combined spectroscopic techniques, i.e. XPS, EPR, and in situ FTIR and Raman spectroscopy. Through this systematic approach, the copper sites and lattice defects responsible for the enhanced CO oxidation activity of doped ceria were elucidated. Superficial Cu+ species and small Cu0 clusters promote the adsorption of CO at low temperature, while isolated Cu2+ monomers and dimers well-dispersed in the ceria matrix foster lattice oxygen mobility, involving the sub-surface in the redox phenomena. Consequently, the structure of Cu-doped ceria undergoes substantial modifications throughout CO oxidation in the absence of O 2 , with the formation of oxygen vacancy clusters. Anyway, these changes are reversible, and structural reorganization in the presence of O 2 can occur even at room temperature. The excellent performance of Cu-doped ceria eventually stems from the effective cooperation among the different catalytic sites in the mixed oxide. [Display omitted] • The different defects and Cu sites in doped ceria are complementarily investigated. • Cu+ sites and small Cu0 clusters at the catalyst surface enhance CO adsorption. • Isolated Cu2+ monomers and dimers in the CeO 2 matrix foster lattice oxygen mobility. • Clusters of oxygen vacancies may form when the oxygen demand at the surface is high. • The effective cooperation of the different sites promotes ceria catalytic activity. [ABSTRACT FROM AUTHOR]

In this work, several nanostructured ceria catalysts were prepared by means of a hydrothermal procedure, in which the synthesis conditions (i.e., temperature and pH values) were varied. CeO2 samples of different shapes and structural properties were obtained, namely cubes, rods, cube and nanorod mixtures, and other polyhedra. The prepared materials were tested using four probe catalytic reactions: CO oxidation, NO oxidation, NOx-free soot oxidation, and NOx-assisted soot oxidation. The physicochemical properties of the prepared catalysts were studied by means of complementary techniques (i.e., XRD, N2-physisorption at --196 °C, CO-TPR (temperature-programmed reduction), field emission scanning electron microscopy (FESEM), micro-Raman spectroscopy). The abundance of defects of the catalysts, measured through in-situ Raman spectroscopy at the typical temperatures of each catalytic process, was correlated to the CO and NO oxidation activity of the prepared catalysts, while the soot oxidation reaction (performed in loose conditions), which was hindered by a poor soot-catalyst contact, was found to be less sensitive to the observed structural defects. [ABSTRACT FROM AUTHOR]

Er-doped phosphate glasses were fabricated by melt-quenching technique. The changes in their thermal, structural and luminescence properties with the addition of Al 2 O 3 , TiO 2 or ZnO were studied. Physical and thermal properties were investigated through density measurement and differential thermal analysis. Structural characterization was performed using the Raman and Infrared spectroscopy. In order to study the influence of the composition on the luminescence properties of the glasses, the refractive index, the luminescence spectra and the lifetime values were measured. The results show that with the addition of Al 2 O 3 and TiO 2 the phosphate network becomes more connected increasing the glass transition temperature, whereas the addition of ZnO does not show significant changes in the optical, thermal and structural properties but it leads to a larger emission cross-section at 1540 nm as compared to the other glasses. As the site of the Er 3+ is not strongly affected by the change in the glass composition, we think that the emission properties of the glasses depend on the glass structure connectivity, which has an impact on the Er 3+ ions solubility. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous silicon nitrides (a-SiN x :H) and oxycarbides (a-SiO x C y :H) have been grown by means of plasma enhanced chemical vapor deposition (PECVD) at a low power density (40–60 mW/cm 2 ) using silane, ammonia, methane and carbon dioxide as silicon, nitrogen, carbon and oxygen precursors, respectively. Their refractive index dispersion curves have been analyzed by means of specular reflectance spectroscopy and their structural properties by FTIR spectroscopy. Taking advantage of their optical properties, the alloys have been fruitfully applied in dielectric stratified structures, optimized for the propagation of surface electromagnetic waves. [ABSTRACT FROM AUTHOR]

• In this study, l -cysteine is proposed as reducing/capping agents for the production of Ag nanonets. • Ag nanonets showed different morphologies by varying the synthesis conditions. • Ag nanonets were deposited onto PDMS membranes and their SERS performance tested against 4-MBA as non-resonant probe. • A correlation between morphology and SERS response has been proposed. Highly-branched plasmonic nanostructures are interesting substrates to be exploited in Surface-Enhanced Raman Scattering (SERS) detection, as sources of efficient Raman "hot-spots". In this study, l -cysteine is proposed as reducing/capping agents for the production of Ag nanonets showing different morphologies by varying the synthesis conditions. Substrates are coupled to PDMS membranes and characterized by Raman spectroscopy using 4-MBA to define their SERS performance. Experimental evidences confirm that only the thinnest structures are able to guarantee significant SERS responses. [ABSTRACT FROM AUTHOR]

The present study reports an improved design for Pd/Ce-Pr catalysts. Pd-impregnated nanostructured ceria-praseodymia catalysts with different compositions were comprehensively characterized and tested for dry and wet methane oxidation. The strong PdO-PrO x interaction, detected via XRD, TPR/TPO, Raman and HRTEM analyses, retains Pd mainly in its oxidized form in the materials with high praseodymium content, thus resulting in a lower activity. Conversely, the introduction of a limited amount of Pr in ceria allows to obtain a more active catalyst (2% of Pd supported on a mixed oxide with 10% of Pr) than the typical Pd/CeO 2 systems. Hence, the simultaneous presence of Pd in its reduced and oxidized forms results to be a key factor for high activity. Additionally, the higher hydrophobicity of this sample, investigated through NMR and in situ FTIR, markedly reduces the H 2 O inhibition effect typical of Pd-based materials, paving the way for using this system in real applications. [Display omitted] • Pd on nanostructured Ce-Pr oxides were studied for the complete methane oxidation. • The effect of the support composition on the Pd oxidation state was investigated. • A small amount of Pr (Pd/Ce90Pr10) was promising for dry and wet methane oxidation. • Pd/Ce90Pr10 higher activity was related to optimized hydrophobicity/hydrophilicity. [ABSTRACT FROM AUTHOR]