Presentazione sul tema: "NANOMATERIALI. Per materiali nanostrutturati sintendono materiali costituiti da particelle con dimensioni < 100 nm. To call them nanomaterials at least."— Transcript della presentazione:
Per materiali nanostrutturati sintendono materiali costituiti da particelle con dimensioni < 100 nm. To call them nanomaterials at least one of their dimensions must be in the range between nm (nanometres). This means, clusters of atoms or grains less than 100 nm in size, fibres less than 100nm in diameters and films with thickness less than 100 nm I materiali nanostrutturati sono importanti perché le loro proprietà sono molto diverse sia da quelle dei materiali bulk sia da quelle degli atomi isolati
[1) size effects: al diminuire della dimensione delle particelle, le bande elettroniche diventano OM con valori discreti di energia proprietà ottiche e proprietà elettriche.] 2) effetti di superficie: unelevata percentuale degli atomi si trova sulla superficie i materiali nanostrutturati consentono di avere un intimo contatto e una connessione ottimale tra le particelle; hanno elevato area superficiale, che favorisce un adeguato scambio con lambiente (es. la lignina come tale) ad es. posso funzionalizzare la lignina; the use of a nanostructured component favors dispersion si può usare come nanofiller, allowing a significant improvement of the dispersion with respect to microsized or bulk materials, particularly important for loadings above 1 wt %.
Nanoporous materials Nanoporous materials are natural or synthetic, organic or inorganic, hybrid materials, with holes less than 100 nm in diameter (are called mesopores those with a diameter of 2 to 50 nm and macropores those with a 50 to 100 nm diameter) · Increased specific surface area (together with control over pores size and distribution this feature enhances adsorption properties and the possibilities for surface chemistry); · Improved sieving (including selectivity); · Reduced weight; · Thermal insulation; · Photonic properties (nanoporous materials can be tailored to exhibit photonic crystals properties). Vantaggi dei materiali nanoporosi
SINTESI DEI MATERIALI NANOPOROSI · Solution precipitation routes (incl. sol-gel); · Self-assembling; · Liquid crystal routes The solution precipitation routes could be used to produce a wide range of material structures such as nanoporous membranes and aerogels. The fact that the process works at room temperature enables its use in bio-encapsulation related applications. Self-assembling is a bottom up approach and its main advantage is that it doesnt require scaling down the manufacturing tools (as in all top down productions), uses less raw material and produces less wastes. Finally, liquid crystal phases (at high enough concentrations) can replicate their liquid crystalline structures
Nanoparticles/Nanocomposites Nanoparticles are usually referred to as particles with a size up to 100 nm. Below this size the physical properties of the material do not just scale down or up, but change to completely new or greatly improved properties. Even though nanoparticles can be made of a wide range of materials, the most common are metal oxide ceramics, metals, silicates and non-oxide ceramics. VANTAGGI DELLE NANOPARTICELLE High specific surface area (very high surface to volume ratio); · Magnetic and Electric properties (improved/specific magnetic and electric properties); · Optical properties: (absorption or emission wavelengths can be controlled by size selection, interaction with ligands and external perturbation.); · Chemical properties (enhanced chemical reactivity).
DENDRIMERI A dendrimer is generally described as a macromolecule which is characterized by its highly branched 3D structure that provides a high degree of surface functionality and versatility. Its structure is always built around a central multi-functional core molecule, with branches and end-groups. Dendrimers can be made out of virtually anything that can branch (metal atoms, organometallic groups, or purely organic materials) and can have a variety of functionalities depending on what they are built of and how. polyvalency (easy surface functionalisation with different ligands); defined architecture, size and shape control; · monodispersity (consistency of shape and form between molecules); · loading capacity, · biocompatibility / low toxicity (some); · transfection properties (transporting genetic material into cell interiors). VANTAGGI DEI DENDRIMERI
SINTESI DEI DENDRIMERI There are different methods to synthesise dendrimers. However two, the so called divergent and convergent synthesis, are the most common and extended ones. In general, it could be said that the convergent approach is appropriate for obtaining small dendrimers while the divergent approach is good for obtaining the large ones. For both the main technical challenges are found in establishing process control methods, high purity and well defined products, specifications and final product analytical methods.
SINTESI DEI FILM SOTTILI Chemical Vapour Deposition (CVD); · Physical Vapour Deposition (PVD); · Sol gel · Electrodeposition/electroplating · Spin coating · Spray coating ;
Thin film & coatings Thin films and coatings are material structures resulting from the deposition of one or more layers of material onto a surface. In the case of this report, the thickness of the thin film considered is below 100 nm. The main advantage of thin films (or any other coating for that matter) is that the properties of the materials deposited can be acquired by the surface. The substrate and the thin film become a material system where each of them provides the required functionality. In general, nanotechnology provide the tools for better controlling three key parameters of the surface deposit: chemical composition (and crystalline nano structure), thickness and topography.
PACKAGING TECHNOLOGY AND SCIENCE Packag. Technol. Sci. 2007; 20: 325–335 Published online 27 October 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: /pts.761 Innovative Packaging for Minimally Processed Fruits By M. Avella,1,* G. Bruno,2 M. E. Errico,1 G. Gentile,1 N. Piciocchi,2 A. Sorrentino2 and M. G.Volpe2 Novel nanocomposite films for use in the packaging of foods ready for consumption and based on isotactic polypropylene (iPP) filled with innovative calcium carbonate nanoparticles, as well as having spherical and elongated shape and covered with appropriate coating agent able to better interact with the iPP matrix, were prepared and characterized. Morphological, thermal, mechanical and transport characterizations on nanocomposite films were performed. The results evidenced a good dispersion of the nanofiller into the polymeric matrix as well as an increase in mechanical parameters such as modulus. Moreover, a drastic reduction of iPP permeability to both oxygen and carbon dioxide was also recorded.
Morphological and Optical Characterization of Polyelectrolyte Multilayers Incorporating Nanocrystalline Cellulose Emily D. Cranston and Derek G. Gray* Received March 24, 2006; Revised Manuscript Received July 3, 2006 Aqueous layer-by-layer (LbL) processing was used to create polyelectrolyte multilayer (PEM) nanocomposites containing cellulose nanocrystals and poly(allylamine hydrochloride). Solution-dipping and spin-coating assembly methods gave smooth, stable, thin films. Morphology was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and film growth was characterized by X-ray photoelectron spectroscopy (XPS), ellipsometry, and optical reflectometry. Relatively few deposition cycles were needed to give full surface coverage, with film thicknesses ranging from 10 to 500 nm. Films prepared by spin-coating were substantially thicker than solution-dipped films and displayed radial orientation of the rod-shaped cellulose nanocrystals. The relationship between film color and thickness is discussed according to the principles of thin film interference and indicates that the iridescent properties of the films can be easily tailored in this system
Dendritic cyclotriphosphazene derivative with hexakis(alkylazobenzene) substitution as photosensitive trigger. Takafuji, Makoto; Shirosaki, Tomohiro; Yamada, Taisuke; Sakurai, Toshihiko; Alekperov, Dzhamil; Popova, Galina; Sagawa, Takashi; Ihara, Hirotaka. A dendritic cyclotriphosphazene deriv. [i.e., 2,2,4,4,6,6-hexakis[4-[[4- (dodecyloxy)phenyl]azo]phenoxy]-2,2,4,4,6,6-hexahydro-1,3,5,2,4,6- triazatriphosphorine] (I) was prepd. by substitution with six alkylazobenzenes onto cyclotriphosphazene. Photoinduced trans-to-cis isomerization of the azobenzene moieties in I was discussed on each substituent. It was also investigated whether the dendrimer acted as a photosensitive trigger for microenvironmental modification of chirally self-assembled organogels through the isomerization. Organogels of I with a lipophilic L-glutamide deriv. were prepd. and investigated. Photosensitive azobenzene derivs. have potential applications for control of drug release, orientation of liq. crystal mols., elec. cond. of films, and to induce self-organization of dye mols. The properties of 2-[4-[[4-(dodecyloxy)phenyl]azo]phenoxy]-2,2,4,4,6,6- hexahydro-1,3,5,2,4,6-triazatriphosphorine (II) in an organogel with a lipophilic L- glutamide deriv. and effects of UV irradn. in CD spectra were also studied.
Nanocrystalline Cellulose and Poly(allyl)amine Hydrochloride Multilayers for Ordered Thin Films. Cranston, Emily D.; Gray, Derek G.; Barrett, Christopher J. Department of Chemistry, McGill University, Montreal, QC, Can. Anisotropic nanocryst. cellulose was prepd. by acid hydrolysis of cellulose fibers resulting in a stable colloidal suspension of rod-shaped crystals ( nm long by 5-10 nm wide). Electrostatic layer-by-layer self-assembled films of the nanocryst. cellulose and poly(allyl)amine hydrochloride (PAH) were prepd. by spin-coating and conventional dip-coating. Surface characterization was performed with at. force microscopy, indicating that the nanocrystals were evenly dispersed and that complete coverage was achieved after 5-10 layers. Surface orientation of the nanocrystals, film roughness and stability to solvent were compared for the two multilayer prepn. methods. Similar results were obtained for surface orientation and root-mean-square roughness in spin-coated and dipped films. Ionically crosslinked dip-coated films were stable in water whereas physisorbed spin-coated films re-dispersed in solvent. Attempts were made to induce alignment of the cellulose nanocrystals by varying the substrate, substrate pre-treatment, cellulose concn. and by applying a magnetic field. Two-dimensional order parameters were calcd. to quantify orientation in multilayered thin films of nanocryst. cellulose and PAH.