NANOSCIENZE E NANOTECNOLOGIE

Negli ultimi anni una piccola parola con un grande potenziale si \ue8 insinuata nella nostra vita. Questa parola \ue8 \u201cnano\u201d. Il prefisso nano- indica una grandezza matematica pari a 10-9, circa 1/80.000 del diametro di un capello umano. La dimensione nano viene considerata una dimensione \u201cmagica\u201d poich\ue9 \ue8 il punto di incontro tra le dimensioni degli atomi isolati e dei materiali bulk. Accade quindi spesso che nei materiali nanometrici vengano sconvolte le leggi normalmente valide nella materia macrometrica. A questa scala le propriet\ue0 fisico-chimiche esibite dai materiali possono quindi risultare sorprendentemente diverse da quelle possedute a scala pi\uf9 grande. Le propriet\ue0 elettroniche, magnetiche, ottiche, chimiche e termiche dei materiali cambiano nel momento in cui si passa dalla scala macroscopica alla scala atomica o molecolare. Un esempio \ue8 fornito dall\u2019oro che, in forma massiva, appare di colore giallo mentre nel momento in cui si sintetizza sotto forma di aggregati di nanoparticelle e viene posto in soluzione, cambia colore a seconda della loro dimensione e forma. Ma cosa determina il cambiamento di colore nell\u2019oro? Con il termine nanotecnologia si fa riferimento ad un insieme di tecnologie, tecniche e processi che richiedono un approccio multidisciplinare, piuttosto che ad una specifica area scientifica o dell\u2019ingegneria. I campi di applicazione sono potenzialmente illimitati e tutti i settori produttivi pi\uf9 importanti ne saranno influenzati in maniera significativa. Le nanotecnologie oggi rappresentano un campo in fortissima espansione sul quale stanno lavorando i migliori gruppi di ricercatori di tutto il pianeta. Finanziamenti pubblici e privati per ricerche nell\u2019ambito delle nanotecnologie sono infatti in continua crescita e si prospetta che la loro ricaduta sul mercato mondiale possa portare i prodotti nanostrutturati a raggiungere un giro d\u2019affari stimato intorno ai 600 miliardi di Euro entro il 2015 e alla creazione di oltre due milioni di nuovi posti di lavoro. Le nanotecnologie rappresentano un salto innovativo radicale che, a detta di molti analisti, produrr\ue0 una nuova rivoluzione industriale paragonabile, se non di portata superiore, a quella generata dall\u2019introduzione nel mercato dei semiconduttori nei primi anni \u201880. Ad oggi sono gi\ue0 stati commercializzati vari prodotti basati sulle nanotecnologie, di cui poi vedremo qualche esempio e si stima che questi prodotti rappresentino attualmente un mercato di circa 2.5 miliardi di euro

Organic transformations catalyzed by gold nanoparticles supported on functionalized silica

Recently, we presented the preparation, without any need of additional reducing and/or stabilizing agents, of a variety of stable silica-supported gold nanoparticles (AuNPs) by using as the only reactants an aqueous solution of HAuCl4 and different functionalized-silica supports. We started using commercial polyethyleneimine-functionalized silica beads (SiO2-PEI)1 and we went on preparing silica nanoparticles with alkynyl carbamate moieties (SiO2-Yne, Fig. 1)2 later post-functionalized by thiol-yne radical chemistry to give the amino-sulfide-branched silica (SiO2@AeThio).3 Fig. 1 Alkyne- and amino-sulfide-modified silica nanoparticles SiO2@Yne and SiO2@AeThio. All the AuNPs-modified systems are catalytically active and possess a remarkable activity in the reduction of 4-nitrophenol to 4-aminophenol. We now present the latest results obtained with these catalysts in the field of selective catalytic oxidation of alcohols in aqueous medium via continuous-flow chemistry. References 1. “Straightforward Synthesis of Gold Nanoparticles Supported on Commercial Silica-Polyethyleneimine Beads”, S. Fazzini , D. Nanni , B. Ballarin , M. C. Cassani , M. Giorgetti , C. Maccato, A. Trapananti , G. Aquilanti, S. I. Ahmed, J. Phys. Chem. C, 2012, 116, 25434−25443. 2. "Novel Synthesis of Gold Nanoparticles Supported on Alkyne-Functionalized Nanosilica", S. Fazzini, M.C. Cassani, B. Ballarin, E. Boanini, J.-S. Girardon, A.-S. Mamede, A. Mignani, D. Nanni, J. Phys. Chem. C, 2014, 118, 24538-24547. 3. “Functionalizaton of Silica through Thiol-Yne Radical Chemistry: a Catalytic System based on Gold Nanoparticles Supported on Amino-Sulfide-Branched Silica” M. C. Cassani, B. Ballarin, D. Barreca, E. Boanini, E. Bonansegna, G. Carraro, S. Fazzini, A. Mignani, D. Nanni, D. Pinelli, RSC Adv., 2016, 6, 25780-25788

Supported nanoparticles for catalysis and biomedical applications

Introduction In recent years we have prepared a large variety of stable supported metal nanoparticles by using supports such as silica, alumina, titania, magnetite (hereafter generally termed as Oxide Supports, OS) and hydroxyapatite (HA) to be employed as catalytic systems and biomaterials. Material and Methods In this framework, our research group has developed a convenient method for the anchoring, without the addition of any external reducing and/or stabilizing agent, of AuNPs on different OS previously modified with a propynylcarbamate organic functionality. In the HA case, we have instead reported an easy, green and low-cost method to support AgNPs onto multifunctionalized HA-R crystals (R = zoledronate, (9R)-9-hydroxystearate). Results and Discussion It was found that among the investigated systems AuNPs/SiO2 catalyst demonstrated to be the most active in the oxidation of a large variety of primary and secondary alcohols both in batch and in continuous-flow packed bed reactors, yielding very stable performances as a function of time without any detrimental activity degradation and for this reason it has been successively employed as heterogeneous catalysts in hydroamination reactions. With regard to the hydroxyapatite support, loading of AgNPs onto modified HA-R gave rise to multifunctional materials that combine the biological properties of R with a significant long-standing antibacterial activity of silver that hindered the development of bone-associated infections thanks to their significant inhibition of the growth of multi-drug resistant Gram positive and Gram negative bacteria

Polyelectrolyte multilayers: a versatile bottom-up nanofabrication technique

We have recently described the synthesis and characterization of amino-functionalized N-heterocyclic carbene complexes of silver(I), Ag(I)-NHCs, using the Boc-protected and deprotected 1-(2-aminoethyl)-3-methyl imidazolium salts [NH2(CH2)2ImMe]X, [1]X (X = I, PF6) as carbene precursors [1]. We are now presenting the preparation of a new gold(III)-alkylamino imidazolium aurate salt [Cl3AuNH2(CH2)2ImMe)][AuCl4] (2) (Figure 1). Demonstrating the great versatility of the amino-functionalized imidazolium salts, such compound is an useful precursor for the preparation of gold nanoparticle (AuNPs) films via the layer-by-layer (LBL) assembly method [2]. Assembling appropriate polyelectrolytes such as poly(ethyleneimine) (PEI) on Indium Tin Oxide Glasses (ITO) a monolayer film of 2 can be easily grafted on the surface and after subsequent reduction, well controlled, in size and distribution, immobilized AuNPs can be generated. The morphology of the AuNPs layers was investigated by using AFM and SEM microscopy and X-ray diffraction (XRD). References [1] L. Busetto, M.C. Cassani, C. Femoni, A. Macchioni, R. Mazzoni, D. Zuccaccia, J. Organomet. Chem. 693, 2579 (2008). [2] J.F. Quinn, A.P.R. Johnston, G.K. Such, A.N. Zelikin, F. Caruso, Chem. Soc. Rev. 36, 707 (2007)

Immobilization of [Rh(NBD)(C5H4CO2(CH2)2OH)] on polystyrene resins

We have recently reported that the reaction between the novel [Rh[C5H4CO2(CH2)2O2C-Im](NBD)] (1), obtained from [Rh[C5H4CO2(CH2)2OH](NBD)] (2) and carbonyldiimidazole, and polypropylenimine dendrimers DAB-dendr-(NH2)n (n = 4, 8, 16, 32, 64) leads to the quantitative formation of the new, completely functionalised, organometallic macromolecules of the type DAB-dendr-[NH(O)COCH2CH2OC(O)C5H4Rh(NBD)]n containing up to 64 peripheral alkoxycarbonylcyclopentadienyl complexes of rhodium(I). Here we report on the extension of this procedure to the direct and quantitative immobilization of [Rh[C5H4CO2(CH2)2O2C-Im](NBD)] (1) on the -NH2 functionalized (aminomethyl)polystyrene resin. The development of an alternative synthetic method toward the grafting of [Rh[C5H4CO2(CH)2OH](NBD)] (2) on an imidazolide carbamates functionalized Wang resin will be also presented and discussed. The new materials have been characterized by means of spectroscopic (IR Microscopy) and analytical Inductively Coupled Plasma \u2013 Atomic Emission Spectrometry (ICP-AES) measurements.Studies on the catalytic activity of these supported systems (dendrimers and resins) in the hydroformylation and hydrogenation of 1-hexene and styrene are currently under investigation

Clean and Efficient Synthesis of Air Stable Polymer-Supported Alkoxycarbonylcyclopentadienyl Rhodium(I) Complexes

Polymer-supported alkoxycarbonylcyclopentadienyl rhodium(I) complexes have been obtained through immobilization of [RhC5H4CO2(CH2)2O2C-Im(NBD)] (2) (Im = imidazole) on an (aminomethyl)polystyrene resin. An alternative approach toward the supportation of [RhC5H4CO2(CH2)2OH(NBD)] (1) on a Wang resin has been also developed. Spectroscopic characterization of all the new functionalised resins with particular accent on ICP-OES measurements is presented and discussed

Amino-functionalized imidazolium salts as modular precursors for the synthesis of N-heterocyclic carbene complexes

Increasing attention has been addressed on using N-heterocyclic carbenes (NHCs) as ancillary ligands for a number of metal catalytic reactions. Our attention has been focused on NHC-amino metal complexes whose chelating and anchoring abilities have been scarcely employed in catalysis so far. We herein describe a new , selective synthesis of the 1-(2\u2019-NHBoc-ethyl-)-3-methylimidazolium iodide (1) and its use as precursor for the synthesis of NHC metal complexes. Reaction of imidazolium salt (1) with Ag2O allows the straightforward formation of silver complexes employed as transmetallating agents for the formation of Rhodium- and Palladium-NHC complexes

Amino-functionalized imidazolium salts as modular precursors for the synthesis of N-heterocyclic carbene complexes

Increasing attention has been addressed on using N-heterocyclic carbenes (NHCs) as ancillary ligands for a number of metal catalytic reactions. Our attention has been focused on NHC-amino metal complexes whose chelating and anchoring abilities have been scarcely employed in catalysis so far. We herein describe a new , selective synthesis of the 1-(2’-NHBoc-ethyl-)-3-methylimidazolium iodide (1) and its use as precursor for the synthesis of NHC metal complexes. Reaction of imidazolium salt (1) with Ag2O allows the straightforward formation of silver complexes employed as transmetallating agents for the formation of Rhodium- and Palladium-NHC complexes