114 research outputs found
Photodoping of doped metal oxide nanocrystals for energy storage electrodes
No full textIn an era where global warming presents significant challenges, advancing materials science is crucial to meet the collective goals of emissions reduction and the transitioning to clean energy. This PhD thesis delves into the exploration of novel heterostructures comprising Indium Tin Oxide nanocrystals (ITO NCs) and diverse NCs or chemicals, for cutting-edge light-driven optoelectronic nanodevices and energy storage systems. This research integrates the processes of energy harvesting, conversion, and storage into a singular hybrid nanomaterial. The use of Doped Metal Oxide (MO) NCs is gaining increasing attention in the realm of nano-supercapacitors, thanks to their capacity to hold additional charges within their electronic structure, achieving high values of specific capacitance. These materials are able to store charges upon illumination with light (photocharging or photodoping), via the absorption of photons and generation of photocharges. During my research, I first studied the charge accumulation process in a solution-based process, moving then to realizing MO NCs films, to work with an electrochemically functional device.
The scalability of colloidal synthesis for ITO NCs was demonstrated, highlighting the consistency of material properties such as size control, optical features, and crystalline phase across different batch sizes. The transition from small-scale to larger batches was achieved with increased efficiency and minimized mechanical losses, maintaining the quality of the nanoparticles. The material obtained was then employed to test ITO NCs charge accumulation ability both in solutions and in solid state (i.e. thin films). At first, solution-dispersed ITO NCs were tested to explore the potential combination with various redox couples (e.g., TEMPO, crystal violet, and ferrocene) to act as reversible hole scavengers and enhance photodoping in ITO NCs. The findings demonstrated that ferrocene effectively increases charge density in doped metal oxide nanoparticles. ITO NCs were then employed to fabricate thin films, underscoring the critical role of fabrication protocols in achieving optimal film properties such as uniformity and thickness. Photodoping was investigated in thin films, revealing the ability of ITO NCs to undergo photo-charging even when in solid-state dispersion, preparing their use for the final application of the work. Finally, the prepared thin films were employed as photo-electrodes in a photo-electrochemical system. The research highlighted the promising role of ITO NCs/visible light-sensitizer thin films as photo-electrodes in supercapacitor applications, with capacitances reaching up to the order of 1 mF/cm2. The use of a visible light sensitizer illustrated its compatibility with ITO NCs, enhancing the system's capacitance under UV and green light. Overall, the thesis presented a work on the scalable synthesis, photodoping capabilities, thin film fabrication, and photo-electrochemical applications of ITO NCs. The potential applications in energy conversion, storage, and photo-electrocatalysis position these findings at the forefront of sustainable energy research, opening doors to new innovations in solar energy technologies
Light-driven reversible charge transfers from ITO nanocrystals
No full textThe combination of semiconductors and redox active molecules for light-driven energy storage systems has emerged as a powerful solution for the exploitation of solar batteries. On account of this, transparent conductive oxide (TCO) nanocrystals (NCs) demonstrated to be interesting materials, thanks to the photo-induced charge accumulation enabling light harvesting and storage. The charge transfer process after light absorption, at the base of the proper use of these semiconductors, is a key step, often resulting in non-reversible transformations of the chemicals involved. However, if considering the photocharging through TCO NCs not only as a charge provider for the system but potentially as part of the storage role, the reversible transformation of the redox compound represents a crucial aspect. In this paper, we explore the possible interaction of indium tin oxide (ITO) NCs and typical redox mediators commonly employed in catalytic applications with a twofold scope of enhancing or supporting the light-induced charge accumulation on the metal oxide NC side and controlling the reversibility of the whole process. The work presented focuses on the effect of the redox properties on the doped metal oxide response, both from the stability point of view and the photodoping performance, by monitoring the changes in the optical behavior of ITO/redox hybrid systems upon ultraviolet illumination
Bismuth telluride iodide monolayer flakes with nonlinear optical response obtained via gold-assisted mechanical exfoliation
No full textBismuth telluride iodide (BiTeI) is a layered material known as Rashba semiconductor, which is promising for several applications such as spintronics, nonlinear optics, and energy-related devices. Due to its layered structure and low cleavage energy, BiTeI is particularly suitable for producing two-dimensional (2D) BiTeI crystals, allowing for the development of devices at the nanoscale. However, traditional methods of mechanically exfoliating BiTeI have encountered significant challenges. To address this, we used the so-called gold-assisted mechanical exfoliation to successfully obtain 2D BiTeI flakes. Through extensive characterization employing a range of techniques including Raman spectroscopy and second-harmonic generation (SHG) measurements, we examine the morphological, structural, and chemical properties of the gold-assisted mechanically exfoliated BiTeI flakes. We confirm their crystalline nature while also providing information about strain and defects present within the flakes. Moreover, SHG measurements revealed a significant nonlinear optical response, and the non-centrosymmetric structure observed in these flakes can be attributed to quantum confinement effects and the absence of phase-matching requirements typically found in bulk nonlinear crystals
Development of prebiotics for livestock use.
No full textWeaning imposes tremendous stress on piglets and the period following is characterized by a high incidence of intestinal disturbances with diarrhea and depression of growth performance in piglets. For the last several decades, antimicrobial compounds have been used to promote piglet growth at weaning through the prevention of subclinical and clinical disease.
At the same time in recent years, there is an ongoing interest to minimize the use of antibiotics and to find alternatives for antimicrobial growth promoters and new strategies that have been used to enhance gastrointestinal function.
Aim of this study was to develop a prebiotic food for piglets characterized by bifidogenic activity, capable of improving the health gut of the animals.
Thirty strains of Propionibacterium freudenreichii subsp. shermanii (Cousin et al. 2011) were isolated from dairy products and were tested for their ability to produce bifidogenic growth stimulator (BGS), a prebiotic preparation that selectively stimulates the growth of Bifidobacteria through the action of its component 1,4-dihydroxy-2- naphthoic acid.
The BGS activity was determined by an agar diffusion plate assay as reported by Mori et al. , 1997. Bifidogenic activity has been tested on several species of Bifidobacteria previously isolated from piglets stool samples: Bifidobacterium tsurumiense, B. pseudolongum subsp. pseudolongum, B. choerinum, B. thermophilum B. thermacidophilum, B. indicum, B. boum. The two strains of Propionibacterium freudenreichii subsp. shermanii, which showed greatest BGS activity, were reproduced in a pilot plant. The surnatant was submitted to a spray treatment in order to obtain a powder product mixable with the feed. The results showed that BGS activity was unaffected by spray treatment and remained stable in the 12 months after production.
The oral BGS administration with the feed could be a possible way to improve the well-being of the weaned animals by modulating intestinal microflora and reduce the incidence of diarrhea.
These encouraging preliminary results lead us to propose a randomized, controlled trial of BGS in piglets to demonstrate its efficacy in vivo
Transparent conducting metal oxides nanoparticles for solution-processed thin films optoelectronics
No full textSemiconductor nanomaterials, and in particular, metal oxides offer great functionality and versatility for many applications at the forefront of material science research. One of the most significant advantage of these compounds at the nanoscale, both for the technological and commercial implications, is the solution synthesis and the consequent exploitation of solution processing. In this work, we present a detailed analysis of ITO nanoparticles solution deposition via the spin coating technique, considering its most common use in optoelectronics as thin films. The results and discussion can provide a list of guidelines for the optimization in the use of these class of materials
Genealogie estensi e falsificazione epigrafica. In appendice: Girolamo Falletti e lo studio delle iscrizioni nel XVI sec.
No full text
Persistent photocurrent studies to unveil charge storage and transport mechanisms in ITO nanocrystals
No full text- …
