Magnetic properties of epsilon iron(III) oxide nanorod arrays functionalized with gold and copper(II) oxide

A sequential chemical vapor deposition (CVD) - radio frequency (RF)-sputtering approach was adopted to fabricate supported nanocomposites based on the scarcely investigated \u3b5-iron(III) oxide polymorph. In particular, \u3b5-Fe2O3 nanorod arrays were obtained by CVD, and their subsequent functionalization with Au and CuO nanoparticles (NPs) was carried out by RF-sputtering under mild operational conditions. Apart from a multi-technique characterization of material structure, morphology and chemical composition, particular efforts were dedicated to the investigation of their magnetic properties. The pertaining experimental data, discussed in relation to the system chemico-physical characteristics, are directly dependent on the actual chemical composition, as well as on the spatial distribution of Au and CuO nanoparticles. The approach adopted herein can be further implemented to control and tailor different morphologies and phase compositions of iron oxide-based nanomaterials, meeting thus the open requests of a variety of technological utilizations

Agri-food building performance evaluation by an integration of different measurement techniques: Case study of a bakery in south Italy

Abstract The performance of a building plays a key role in its sustainability, since a building cannot be sustainable if the needs of its users are not satisfied. In fact, the priority of a sustainable building is to meet the user requirements in an adequate manner, while limiting its environmental impact. The aim of this study is to supply a suitable Building Performance Evaluation method (BPE) to technicians, facility managers and designers, in order to improve the quality of management, design and construction by providing more sustainable agri-food buildings. In this study, in order to measure building performance with respect to user requirements, the simultaneous application of three different measurement techniques was proposed: a User survey by means of a questionnaire; an analysis of building documents and a walkthrough analysis by experts; and instrumental measurements and a direct survey of building characteristics. The proposed BPE method was based on a fuzzy weighted average at three levels. The fuzzy method proved to be particularly suitable for describing the vagueness of users when answering the questionnaire, for translating the document analysis, or considering the instrumental measurements for performance measures. The proposed method was applied to a typical agri-food building in southern Italy. This application demonstrated the correctness of the setting, its ease of application, and its ability to manage real cases. The method allowed for the evaluation of building performance by taking advantage of the positive characteristics of each measurement technique: the users' and occupants' perception, the knowledge and critical sense of expert technicians, and the accuracy and objectivity of instrumental measures. The results of the model were represented by mean fuzzy membership functions, which preserved the "vagueness" of the initial performance attributes. To obtain more synthetic values, a normalization procedure was applied to obtain a value performance judgment, expressed by a number in the range of 0 and 1 (where 0 is the worst and 1 is the best). The general performance of functional areas and the differences in performance in the same functional area were compared using this operation. The results of the case study demonstrated the reliability of the proposed method; in particular, it can determine the state of the building's functionality, drawing attention to weak points that should be monitored to prevent potential faults. The method proposed is a key element intended to help develop agri-food buildings that are effective and efficient and perform as expected and it contributes to improve the general quality of agri-food buildings

XPS analysis of Fe2O3-TiO2-Au nanocomposites prepared by a plasma-assisted route

Fe2O3 nanodeposits have been grown on fluorine-doped tin oxide (FTO) substrates by plasma enhanced-chemical vapor deposition (PE-CVD). Subsequently, the obtained systems have been functionalized through the sequential introduction of TiO2 and Au nanoparticles (NPs) by means of radio frequency (RF)-sputtering. The target nanocomposites have been specifically optimized in view of their ultimate functional application in solar-driven H2 generation. In the present study, our attention is focused on a detailed X-ray photoelectron spectroscopy (XPS) characterization of the surface composition for a representative Fe2O3-TiO2-Au specimen. In particular, this report provides a detailed discussion of the analyzed C 1s, O 1s, Fe 2p, Ti 2p, and Au 4f regions. The obtained results point to the formation of pure Fe2O3-TiO2-Au composites, with gold present only in its metallic state and each of the constituents maintaining its chemical identity

A study of Pt-/alpha-Fe2O3 nanocomposites by XPS

alpha-Fe2O3 matrices were deposited on Fluorine-doped Tin Oxide (FTO) substrates by Plasma Enhanced- Chemical Vapor Deposition (PE-CVD) from Fe(hfa)_2TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N’,N’-tetramethylethylenediamine). The obtained nanosystems were subsequently functionalized by platinum nanoparticles (NPs) via Radio Frequency (RF)-sputtering, exposing samples either to a pre- or post-sputtering thermal treatment at 650°C for one hour in air. Interestingly, Pt oxidation state in the final composite systems strongly depended on the adopted processing conditions. In this work, a detailed X-ray Photoelectron Spectroscopy (XPS) analysis was carried out in order to investigate the material chemical composition, with particular regard to the relative Pt(0)/Pt(II)/Pt(IV) content. The obtained results evidenced that, when annealing is performed prior to sputtering, only PtO and PtO2 are revealed in the final Pt/alpha-Fe2O3 nanocomposite. In a different way, annealing after sputtering results in the co-presence of Pt(0), Pt(II) and Pt(IV) species, the former arising from the thermal decomposition of PtO2 to metallic platinum

The Early Steps of Molecule-to-Material Conversion in Chemical Vapor Deposition (CVD): A Case Study

Transition metal complexes with \u3b2-diketonate and diamine ligands are valuable precursors for chemical vapor deposition (CVD) of metal oxide nanomaterials, but the metal-ligand bond dissociation mechanism on the growth surface is not yet clarified in detail. We address this question by density functional theory (DFT) and ab initio molecular dynamics (AIMD) in combination with the Blue Moon (BM) statistical sampling approach. AIMD simulations of the Zn \u3b2-diketonate-diamine complex Zn(hfa)2TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N\u2032,N\u2032-tetramethylethylenediamine), an amenable precursor for the CVD of ZnO nanosystems, show that rolling diffusion of this precursor at 500 K on a hydroxylated silica slab leads to an octahedral-to-square pyramidal rearrangement of its molecular geometry. The free energy profile of the octahedral-to-square pyramidal conversion indicates that the process barrier (5.8 kcal/mol) is of the order of magnitude of the thermal energy at the operating temperature. The formation of hydrogen bonds with surface hydroxyl groups plays a key role in aiding the dissociation of a Zn-O bond. In the square-pyramidal complex, the Zn center has a free coordination position, which might promote the interaction with incoming reagents on the deposition surface. These results provide a valuable atomistic insight on the molecule-to-material conversion process which, in perspective, might help to tailor by design the first nucleation stages of the target ZnO-based nanostructures

Supported Gold Nanoparticles for Alcohols Oxidation in Continuous-Flow Heterogeneous Systems

Gold nanoparticles (AuNPs) were anchored on alkynyl carbamate-functionalized support materials having the suitable features for application as catalysts in continuous-flow packed bed reactors. The functionalization step was carried out by grafting with the di-functional organosilane [3-(2-propynylcarbamate)propyl]triethoxysilane (PPTEOS) three commercial micrometer-sized oxide supports, i.e. silica, alumina, and titania. The alkynyl-carbamate moieties were capable to straightforwardly reduce the gold precursor HAuCl4 yielding the supported AuNPs systems Au/SiO2@Yne, Au/Al2O3@Yne, and Au/TiO2@Yne. A comparison among the three materials revealed that silica allowed the highest organic functionalization (12 wt%) as well as the highest gold loading (3.7 wt%). Moreover, TEM investigation showed only for Au/SiO2@Yne the presence of homogeneously distributed, spherically shaped AuNPs (av. diameter 15 nm). Au/SiO2@Yne is an efficient catalyst, both in batch and flow conditions, in the oxidation of a large variety of alcohols, using H2O2 as oxidizing agent, at a temperature of 90 \ub0C. Furthermore, under flow conditions, the catalyst worked for over 50 h without any significant decrease in the catalytic activity. The catalytic activity of the three catalysts was evaluated and compared in the oxidation of 1-phenylethanol as a model substrate. We found that the flow approach plays a strategic role in preserving the physical and chemical integrity of the solid catalysts during its use, with remarkable consequences for the reaction conversion (from 2% in batch to 80 % in flow) in the case of Au/TiO2@Yne

WO3-decorated ZnO nanostructures for light-activated applications

In the present work, a two-step vapor-phase route was implemented for the tailored design of ZnO\u2013WO3 nanoheterostructures supported on fluorine-doped tin oxide (FTO) substrates. Under optimized conditions, the sequential use of chemical vapor deposition (CVD) and radio frequency (RF)-sputtering for the deposition of zinc and tungsten oxides respectively, resulted in the growth of calyx-like ZnO nanostructures uniformly decorated by a conformal dispersion of low-sized WO3 nanoparticles. The target materials were characterized by means of a multi-technique approach, with particular regard to their structural, compositional, morphological and optical properties. Finally, their photocatalytic performances were preliminarily tested in the abatement of NOX gases (NO and NO2). Due to the unique porous morphology of the ZnO nanodeposit and the high density of ZnO\u2013WO3 heterojunctions, WO3-decorated ZnO revealed appealing De-NOX characteristics in terms of both degradation efficiency and selectivity. Such features, along with the photoinduced superhydrophilicity and self-cleaning properties of the present nanomaterials, candidate them as promising functional platforms for applications in smart windows and building materials for environmental remediation

Controllable Anchoring of Graphitic Carbon Nitride on MnO₂ Nanoarchitectures for Oxygen Evolution Electrocatalysis

International audienc

Surface Functionalization of Grown-on-Tip ZnO Nanopyramids: From Fabrication to Light-Triggered Applications

We report on a combined chemical vapor deposition (CVD)/radio frequency (RF) sputtering synthetic strategy for the controlled surface modification of ZnO nanostructures by Ti-containing species. Specifically, the proposed approach consists in the CVD of grown-on-tip ZnO nanopyramids, followed by titanium RF sputtering under mild conditions. The results obtained by a thorough characterization demonstrate the successful ZnO surface functionalization with dispersed Ti-containing species in low amounts. This phenomenon, in turn, yields a remarkable enhancement of photoactivated superhydrophilic behavior, self-cleaning ability, and photocatalytic performances in comparison to bare ZnO. The reasons accounting for such an improvement are unravelled by a multitechnique analysis, elucidating the interplay between material chemico-physical properties and the corresponding functional behavior. Overall, the proposed strategy stands as an amenable tool for the mastering of semiconductor-based functional nanoarchitectures through <i>ad hoc</i> engineering of the system surface