Luca Malfatti

Applications of magnetic metal–organic framework composites

The high and regular porosity of metal–organic frameworks (MOFs) provides exceptional properties suitable for technological applications. The increasing interest of the scientific community is based on the exploration of these advantageous properties for industrial applications. Pure MOFs are specifically designed to offer a huge surface area; such a high specific surface area has been explored and exploited for gas storage, separation, or catalysis in a variety of chemical processes. A different and promising scientific trend aims to combine MOFs with extrinsic functionalities such as functional nanoparticles; this strategy enables the preparation of new nanocomposite materials with unprecedented properties. An interesting case is offered by the synergic combination of magnetic particles with MOF crystals. In the resulting nanocomposite material, the adaptive functional responses can be triggered by an external magnetic field. In this context, different protocols have been developed for the efficient preparation of magnetic framework composites (MFCs), a class of materials that combines magnetic nano- or micro-particles with MOFs crystals. This application paper highlights the progress on MFCs for drug delivery, environmental control, catalysis, sensing and miniaturized device fabrication.

Fabrication of Advanced Functional Devices Combining Soft Chemistry with X‐ray Lithography in One Step

Deep X-ray lithography combined with sol-gel techniques offers facile fabrication of controlled patterned films. Using sol-gel, different functional properties can be induced; deep X-ray lithography alters the functionality in the exposed regions. Miniaturized devices based on local property changes are easily fabricated: this technique requires no resist, enabling direct patterning of films in a one-step lithographic process.

Sophorolipids: a yeast-derived glycolipid as greener structure directing agents for self-assembled nanomaterials

Sophorolipids, fully natural glycolipids, can form in water nanometre-size micelles of various geometries depending on their concentration as shown by small angle neutron scattering experiments. This property allows use of them, for the first time, as structure directing agents in the synthesis of nanostructured silica thin films via the evaporation induced self-assembly (EISA) process.

Evaporation of Ethanol and Ethanol-Water Mixtures Studied by Time-Resolved Infrared Spectroscopy

The knowledge of the physics and the chemistry behind the evaporation of solvents is very important for the development of several technologies, especially in the fabrication of thin films from liquid phase and the organization of nanostructures by evaporation-induced self-assembly. Ethanol, in particular, is one of the most common solvents in sol-gel and evaporation-induced self-assembly processing of thin films, and a detailed understanding of its role during these processes is of fundamental importance. Rapid scan time-resolved infrared spectroscopy has been applied to study in situ the evaporation of ethanol and ethanol-water droplets on a ZnSe substrate. Whereas the evaporation rate of ethanol remains constant during the process, water is adsorbed by the ethanol droplet from the external environment and evaporates in three stages that are characterized by different evaporation rates. The adsorption and evaporation process of water in an ethanol droplet has been observed to follow a complex behavior: due to this reason, it has been analyzed by two-dimensional infrared correlation. Three different components in the water bending band have been resolved.

Nanocomposite mesoporous ordered films for lab-on-chip intrinsic surface enhanced Raman scattering detection.

Mesoporous nanocomposite materials have been fabricated through integration of evaporation-induced self-assembly and deep X-ray lithography. Micropatterned films made using a mesoporous ordered silica matrix which contains silver nanoparticles have been obtained. The exposure of the mesoporous films to high energy X-rays, which are generated by a synchrotron source, produces several effects: the removal of the surfactant, the densification of the silica backbone and the formation of silver nanoparticles. This integrated process produces a nanocomposite material which has a 2D-hexagonal organized porosity and silver nanoparticles with a sharp size distribution around 5 nm. The patterned nanostructured films have been tested as a lab-on-chip device for intrinsic surface enhanced Raman scattering detection using a solution containing rhodamine 6G in ethanol and measuring Raman response as a function of laser power.

Evaporation-induced crystallization of pluronic F127 studied in situ by time-resolved infrared spectroscopy.

Rapid scan time-resolved infrared spectroscopy has been used to study in situ the crystallization induced by evaporation in an aqueous solution of a triblock copolymer, Pluronic F127. A droplet of the solution was cast on a silicon substrate and the evaporation followed by an infrared microscope in transmission mode. The evaporation rate of water, in the last stage of the process, has been shown to be correlated to the changes in the block copolymer; four different stages can be distinguished. The block copolymer passes from an amorphous micellar state in water to a partially crystallized phase in well-defined stages of the evaporation; the complete change from amorphous to crystalline state of Pluronic F127 is observed only after all water is evaporated.

Thermal-induced phase transitions in self-assembled mesostructured films studied by small-angle X-ray scattering

Two examples of phase transition in self-assembled mesostructured hybrid thin films are reported. The materials have been synthesized using tetraethoxysilane as the silica source hydrolyzed with or without the addition of methyltriethoxysilane. The combined use of transmission electron microscopy, small-angle X-ray scattering and computer simulation has been introduced to achieve a clear identification of the organized phases. A structural study of the self-assembled mesophases as a function of thermal treatment has allowed the overall phase transition to be followed. The initial symmetries of mesophases in as-deposited films have been linked to those observed in samples after thermal treatment. The monodimensional shrinkage of silica films during calcination has induced a phase transition from face-centered orthorhombic to body-centered cubic. In hybrid films, instead, the phase transition has not involved a change in the unit cell but a contraction of the cell parameter normal to the substrate.

Hard X-rays meet soft matter: when bottom-up and top-down get along well

The combined approach of bottom-up and top-down routes allows direct soft matter patterning and fabrication of devices using faster and more versatile protocols. In this research news, we briefly describe some of the fundamentals, development, recent progress and perspectives in the fabrication and patterning of functional nanostructured materials by interaction with high energy X-rays.

Chemical tailoring of hybrid sol-gel thick coatings as hosting matrix for functional patterned microstructures.

A phenyl-based hybrid organic - inorganic coating has been synthesized and processed by hard X-ray lithography. The overall lithography process is performed in a two-step process only (X-rays exposure and chemical etching). The patterns present high aspect ratio, sharp edges, and high homogeneity. The coating has been doped with a variety of polycyclic aromatic hydrocarbon functional molecules, such as anthracene, pentacene, and fullerene. For the first time, hard X-rays have been combined with thick hybrid functional coatings, using the sol-gel thick film directly as resist. A new technique based on a new material combined with hard X-rays is now available to fabricate optical devices. The effect due to the high-energy photon exposure has been investigated using FT-IR and Raman spectroscopy, laser scanner, optical profilometer, and confocal and electron microscope. High-quality thick hybrid fullerene-doped microstructures have been fabricated.

Shaping Mesoporous Films Using Dewetting on X-ray Pre-patterned Hydrophilic/Hydrophobic Layers and Pinning Effects at the Pattern Edge

Ordered mesoporous silica micrometer-sized structures have been fabricated via selective dewetting of the coating sol on a hydrophilic/hydrophobic fluorinated silica substrate, which had been pre-patterned using deep X-ray lithography with a synchrotron radiation source. We have observed that deposition of mesoporous films on the pre-patterned areas can be used as a design tool for obtaining regions of specific geometry and dimensions. The evaporation of the solution in constrained conditions because of pinning at the pattern edges gives layers with thicker edges. This edge effect appears dependent upon the dimension of the pre-patterned hydrophilic/hydrophobic layer; in smaller patterns, the evaporation is too fast and thickening of the edges is not observed. We have used infrared imaging, optical profilometry, and atomic force microscopy to characterize the patterned layers and the edge effect, produced by pinning at the border of the microstructures.