Barbara Lasio

Exfoliated Graphene into Highly Ordered Mesoporous Titania Films: Highly Performing Nanocomposites from Integrated Processing

To fully exploit the potential of self-assembly in a single step, we have designed an integrated process to obtain mesoporous graphene nanocomposite films. The synthesis allows incorporating graphene sheets with a small number of defects into highly ordered and transparent mesoporous titania films. The careful design of the porous matrix at the mesoscale ensures the highest diffusivity in the films. These exhibit an enhanced photocatalytic efficiency, while the high order of the mesoporosity is not affected by the insertion of the graphene sheets and is well-preserved after a controlled thermal treatment. In addition, we have proven that the nanocomposite films can be easily processed by deep X-ray lithography to produce functional arrays.

Combining Top-Down and Bottom-Up Routes for Fabrication of Mesoporous Titania Films Containing Ceria Nanoparticles for Free Radical Scavenging

Nanocomposite thin films formed by mesoporous titania layers loaded with ceria nanoparticles have been obtained by combining bottom-up self-assembly synthesis of a titania matrix with top-down hard X-ray lithography of nanocrystalline cerium oxide. At first the titania mesopores have been impregnated with the ceria precursor solution and then exposed to hard X-rays, which triggered the formation of crystalline cerium oxides within the pores inducing the in situ growth of nanoparticles with average size of 4 nm. It has been observed that the type of coordinating agent in the solution plays a primary role in the formation of nanoparticles. Different patterns have been also produced through deep X-ray lithography by spatially controlling the nanoparticle growth on the micrometer scale. The radical scavenging role of the nanocomposite films has been tested using as a benchmark the UV photodegradation of rhodamine 6G. After impregnation with a rhodamine 6G solution, samples with and without ceria have shown a remarkably different response upon exposure to UV light. The dye photodegradation on the surface of nanocomposite films appears strongly slowed down because of the antioxidation effect of ceria nanoparticles.

Multifunctionalization of wool fabrics through nanoparticles: A chemical route towards smart textiles

A new approach towards the design of smart nanotextiles with innovative properties is presented. Silica (SiO2), titania (TiO2), and silver (Ag) nanoparticles (NPs), were synthesized without the use of any toxic organic compound and then were used, alone and in combination, to functionalize wool fabrics. Electrostatic forces, influenced by a low pH of the solutions, allowed the interactions between wool fabrics and NPs, enabling a robust functionalization. This was verified by X-ray microfluorescence and visualized by scanning electron microscopy measurements. The antibacterial Ag NPs were embedded in a polymer, alginic acid, to reduce the possible side effect due to their direct contact with the skin. SiO2 NPs, instead, were used to change the hydrophilicity of wool while the functionalization with TiO2 NPs was chosen to provide self-cleaning properties. The antibacterial activity of the fabrics was studied against the bacteria Escherichia coli, while the hydrophilicity of wool was studied by contact angle measurements and the self-cleaning properties were tested by estimating the visible discoloring of a dye stain under sunlight irradiation. Interestingly the combination of three different types of NPs provided the best results. SiO2 and Ag made the wool superhydrophilic providing at the same time the best antibacterial properties, while fabrics with titania (alone or in combination) were hydrophobic and showed the best self-cleaning properties.

Molecularly imprinted La-doped mesoporous titania films with hydrolytic properties toward organophosphate pesticides

The present work is aimed at developing a titania-based mesoporous film with catalytic properties toward organophosphate pesticides by combining two different approaches: the molecular imprinting and the self-assembly with a supramolecular template. The mesoporosity of the material has been obtained by using a tri-block copolymer (Pluronic F127) as a micellar template while the molecular imprinted cavities have been templated by a complex between La3+ and bis-4-nitro-phenyl-phosphate. The template removal allowed opening, in one step, both the mesopores and the imprinted cavities with a simultaneous estimation of the active sites. The catalytic activity of the molecularly imprinted and not imprinted films toward the pesticide Paraoxon® has been evaluated by means of UV-Vis spectroscopy titration of the 4-nitro-phenolate released by the Paraoxon® hydrolysis. The analysis of the initial rates of molecularly imprinted and not imprinted films has shown that the presence of a very low number of molecular cavities improves the catalytic properties of the imprinted film when compared to the not imprinted films and the background hydrolysis.

Release of ceria nanoparticles grafted on hybrid organic-inorganic films for biomedical application.

The controlled release of nanoparticles from a hybrid organic-inorganic surface allows for developing several applications based on a slow delivery of oxygen scavengers into specific environments. We have successfully grafted ceria nanoparticles on a hybrid film surface and tested their release in a buffer solution; the tests have shown that the particles are continuously delivered within a time scale of hours. The hybrid film has been synthesized using 3-glycidoxypropyltrimethoxysilane as precursor alkoxide; the synthesis has been performed in highly basic conditions to control the polycondensation reactions of both organic and inorganic networks via controlled aging of the solution. Only films prepared from aged solutions are able to graft ceria nanoparticles on their surface. The ceria nanoparticles have been characterized by X-ray diffraction, transmission electron microscopy and UV-vis spectroscopy, the hybrid films have been analyzed by Fourier transform infrared spectroscopy, atomic force microscopy and Raman spectroscopy. Raman imaging has been used for the release test. The hybrid film-ceria nanoparticles system fulfils the requirements of optical transparency and stability in buffer solutions which are necessary for biomedical applications.

Sol–gel chemistry for graphene–silica nanocomposite films

Fabrication of graphene nanocomposite films via sol–gel chemistry is still a challenging task because of the low solubility of graphene in common solvents. In the present work we have successfully developed a suitable synthesis method employing a solution of exfoliated graphene in 1-vinyl-2-pyrrolidone that is added to an anhydrous sol of silicon tetrachloride in ethanol. Thin graphene–silica films with high optical transparency have been obtained; the graphene sheets are composed of two layers and do not aggregate at a large range of concentrations upon incorporation into the matrix. Thermal processing of the silica films allows complete removal of 1-vinyl-2-pyrrolidone without oxidation or degradation of the graphene sheets which are embedded in the oxide.

Elemental investigation on Spanish dinosaur bones by x-ray fluorescence

In this paper we examine the chemical composition results obtained on a collection of 18 dinosaur fossil bones from Spain studied using a portable x-ray fluorescence spectrometer together with a reverse Monte Carlo numerical technique of data analysis. This approach is applied to the hypothesis of arbitrarily rough surfaces in order to account for the influence of the surface state of specimens on the chemical content evaluation. It is confirmed that the chemical content of elements is essential for understanding the changes brought about by diagenetic and taphonomic processes. However, for precise knowledge of what changes fossil bones have undergone after animal life and burial, it is necessary to use a multi-technique approach making use of other instruments like x-ray diffraction in order to describe accurately the transformations undergone by the mineralogical and bioinorganic phases and the properties of specific molecular groups.

Engineering the surface of hybrid organic–inorganic films with orthogonal grafting of oxide nanoparticles

Superparamagnetic iron oxide nanoparticles of magnetite have been grafted on the surface of a hybrid organic–inorganic film prepared using an organically modified alkoxide, 3-glycidoxypropyltrimethoxysilane, as precursor. A solventless synthesis of the hybrid films at high pH has been employed and the surface chemistry of the deposited films has been processed by controlling the aging time of the sol. The films have been characterized by FTIR, Raman and UV spectroscopy and grazing incidence X-ray diffraction. Films prepared with fresh sols have shown a mixed presence of epoxides and hydroxyls on the surface, which enabled the successful grafting of the iron oxide nanoparticles. Films from aged sols, which contain only hydroxyls, have failed to bind the iron particles but have instead shown the capability of grafting ceria nanoparticles. This method has, therefore, allowed a direct grafting of nanoparticles on the hybrid surface without any post-synthetic functionalization step. Moreover, the phase transition induced in iron oxide nanoparticles by means of a laser beam has been exploited to pattern the film surface creating different domains of magnetite and hematite.

In situ growth of Ag nanoparticles in graphene–TiO2 mesoporous films induced by hard X-ray

The controlled growth of Ag nanoparticles into graphene–TiO2 mesoporous films has been triggered by hard X-ray exposure provided by a synchrotron storage ring. The kinetic process has been studied by UV–visible spectroscopy as a function of the X-ray dose and compared to the nanoparticle growth induced in a bare mesoporous titania matrix. The graphene layers act as a preferential nucleation sites, allowing a faster nucleation of the nanoparticles. Moreover, the growth of larger nanoparticles is also promoted as a function of the exposure dose. The combined bottom-up and top-down approach to fabricate nanocomposites porous films embedding both graphene and plasmonic nanoparticles is expected to be a fundamental tool for the design of new analytical platforms based on the enhancement of the Raman signals.Graphical Abstract

3D spatially controlled chemical functionalization on alumina membranes

Among the myriad microfabrication approaches, Deep X-ray Lithography (DXRL) takes advantage of the high penetration depth of hard X-rays. For the first time, this feature has been exploited for the precise control of surface chemical functionalities on a thick porous ceramic material. As a proof of concept, porous alumina membranes with controlled thickness (50 µ m) have been chosen to test the potential of DXRL. The Al 2 O 3 membranes were decorated with fluoro- and amino-silanes. These functionalized ceramic membranes were exposed to hard X-rays in a synchrotron facility, which allowed for the selective decomposition of the chemical functionalities in controlled areas. The water contact angle of hydrophobic-functionalized samples was measured to confirm the decomposition of the fluoro-silane in the exposed area, and water diffusion through the 200 nm pores of the alumina membranes was observed to occur only in the exposed area. The patterned amino-functionalized Al 2 O 3 samples were tested with an alcoholic solution containing Au cations, where it was found that gold nanoparticles only formed in the unexposed areas, whereas the amino functionality survived the radiation damage induced by the X-rays.