Richiesta Di Un Nuovo Assegno Di Ricerca Budget Integrato, Maria Cristina Cassani, Dipartimento

Richiesta di un nuovo assegno di ricerca – budget integrato, Barbara Ballarin, Dipartimento di Chimica Industriale “Toso Montanari”

Title

Gold nanoparticles supported on functionalized surfaces: synthesis, characterization and applications

Research Context and Objectives

Context

Gold nanoparticles (AuNPs) have been the subject of several studies due to their size-dependent electronic and optical properties, good conductivity high biocompatibility, and remarkable catalytic activity1-3.These characteristics can be finely tuned depending on their size distribution and spatial dispersion, which, in turn, are related to the preparation and processing routes4-7, as well as to the adopted substrates. In this regard, structures composed by metal nanoparticles/functionalised surface have attracted an increasing attention thanks to their possible applications in different fields, encompassing molecular electronics, nanocatalysis and optical sensors8-10.

In particular, metal nanoparticles deposed on indium tin oxide (ITO), a transparent and conducting substrate,or on nanoparticles of silica, an attractive material due to its large abundance, stability, commercial availability, low cost, and ease of processing, are of great interest for use in a variety of electronic devices, including heat-reflective coatings, electroluminescent, LCD, plasma displays11-14 and catalytic purpouse15.

Functionalized surfaces can be obtained by a post-synthetic method (grafting)16 that involves further reaction of surface hydroxyl groups with organo-silane bearing various functional groups: this method typically results in inhomogeneous surface coverage where only part of those hydroxyl groups has been exploited. Alternatively, in the case of the silica nanoparticles, the co-condensation method17 yields instead stable hybrid organo-silica NPs with a homogenous distribution of the organic functionalities (such as amine, fluorescent dyes, carbazole, and alkyne moieties)18-21. Both techniques are however widely used to prepare -supported gold catalysts by anchoring to the silica surface functionalities that possess strong affinity for gold (e.g. thiols, amines, etc.) and are positively charged, hence avoiding mobility and aggregation of the AuNPs.22

Recently, we reported the synthesis of stable silica-supported gold nanoparticles (AuNPs/SiO2-PEI) suitable for catalysis, obtained by using, as the only reactants, chloroauric acid (HAuCl4) as gold precursor and commercially available polyethyleneimine-functionalized silica beads (SiO2-PEI), with the need for neither external reducing agents nor conventional stabilizing moieties.14The supported AuNPs presented sizes in the range of 70-100 nm, with kinetic constants for reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4 of the order of magnitude of 1 × 10-4 s-1.

Objectives

The aim of this project is the development of new silica- or ITO-supported gold nanoparticles (AuNPs) suitable for catalysis. The first task will be the synthesis of functionalized silica nanoparticles by co-condensation of tetraethoxysilane and an appropriate organo-silane containing one or more functional groups able to capture Au(III) salts and then reduce them to Au(0) in the form of gold nanoparticles (AuNPs-SiO2@Yne). At the same time ITO modified with self-assembled methods will be prepared testing different fluoroalkylsilane.The prepared AuNPs-SiO2@Yneas well as the AuNPs-ITO self-assembled will be thoroughly analyzed by X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS), FT-IR and UV-Vis spectroscopy.

The catalytic activity of such systems will investigated in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4and will be compared with data reported in the literature.

Research Plan and Technical Approach

The training of the Post doctoral researcher will represent a valuable experience for improving his/her research skills in the field of the synthesis and characterization of nanomaterials and their use in catalysis. In addition, the project is expected to improve the skills of the Post doctoral researcher in scientific communication, research work in a multidisciplinary environment and presentation of research results at international seminars or conferences. Such experience will be a valuable contribution to the development of the research abilities of the young researcher and a help for their future jobs in a scientific career.

References

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