Research

The research activity of our group is focused on two main general topics:

- Materials for advanced diagnostics (e.g. Surface Enhanced Raman Scattering)

- Materials for environment: energy conversion and pollutant removal

Part of our research activity is focused on developing new routes for the synthesis of nanostructured materials. In particular, we are active in the synthesis of plasmonic nanoparticles and nanostructures, hierarchically organized multi‐scale architectures and hybrid metal/polymer or metal/oxide systems.

Our materials are obtained by combining: Colloidal Synthesis Routes, Sol-Gel Methods and Atomic Layer Deposition.

Great attention is focused on the sustainability of synthesis protocols, reducing the environmental impact of the involved reactants and employing wastes (in particular, organic waste) as starting materials.

What follows is a brief description of our recent research:


  • Advanced Materials for Enhanced Vibrational Spectroscopy

Ultrasensitive vibrational spectroscopy techniques allow decisive breakthroughs in many disciplines, including chemistry, physics, materials, and life sciences, because they can provide insightful information about intra- and inter-atomic bonds and physico-chemical processes dynamics. Surface-enhanced Raman scattering (SERS) is a leading non-destructive technique that can extend the sensitivity of Raman spectroscopy to the level of single molecule. However, for several important applications, such as in situ Raman monitoring of chemical reactions, plasmon-based SERS substrates can introduce strong perturbations into the systems under investigation. This prevents extraction of unbiased data and represents a still unsolved major drawback.

Parallely, to more convential plasminic SERS substrates, we are currently investigating alternative approaches to develop new materials based on core/shell multifunctional beads and nanostructures. The goal of this activity is to advance in understanding the mechanisms and dynamics of technology-relevant processes under real working conditions, with a special focus on energy conversion and environmental remediation.

This part of the research activity led to the discovery and development of all-dielectric beads (T-rex) and related core/shell architectures which enabled to develop plasmon-free SERS, with exciting applications for environmental science and bio-diagnostics.

We are also trying to develop new strategies that enable to perform multimodal detection, by combining complementary techniques, such as Raman Spectroscopy+Mass Spectrometry or Raman Spectroscopy+Optical Sensing.

References:

T-rex and related all-dielectric systems:

Plasmonic SERS-active substrates

  • Active Multipurpose Hydrogels and Low-Impact Materials for Environmental Remediation

Finding new strategies for environmental monitoring and remediation, portable and locally applicable in places of interest, is essential to respond to the pressing demand for clean water and soil. At the same time, it is necessary that the new solutions are based on simple materials and techniques, they have low cost and they are characterized by low environmental impact.

In this regard, we have started developing hydrogels based on natural polymers (i.e. alginate, chitosan, pectin..) which can be easily functionalized with molecular receptors (able to control interaction with particular classes of pollutants) and optical antennas (able to concentrate light in their surrounding and facilitate pollutant detection with spectroscopic techniques and pollutant photo-degradation). In this way, it is possible to combine absorption capabilities and easy manipulation, typical of hydrogels, with functional activities typical of the other building blocks and obtain multifunctional systems, which can perform both pollutant detection and removal.

As anticipated, great attention is dedicated to the environmental sustainability of the production process, and different studies are conducted for the research of new procedures for green extraction of natural polymers.

Over the years, various systems have been developed for active removal of different types of pollutants. Examples are food-waste based membranes for Cr(VI) reduction and adsorption and oxide macro-beads for dye and pharmaceutical compounds adsorption and photo-degradation.

References:

Hydrogels and natural polymers extraction:

Other systems for pollutant removals:

  • Stimuli-Responsive Materials and Interfaces

Smart materials, i.e. materials that can change their structural and/or functional properties in response to external stimuli, (light, pH, electrical and magnetic fields, mechanical stress, corrosion, etc.) are attracting ever growing interests in several key sectors of materials science. Adaptive interfaces, bioinspired actuators, self-healing polymer coatings nanoparticles and tissues are only a few of the most intensively investigated systems.

An interesting example is represented by pressure-sensitive adhesives (PSAs), a class of materials including acrylics, polyurethanes, polyesters, and silicones. Upon modification with electrically conductive fillers, such as carbon or metals, they can be applied as antistatic self-adhesive tapes for electromagnetic-shielding purposes. Is it possible to make conductive PSAs ‘‘smarter’’ and further extend their application range? And if so, how?

We have demonstrated that carbon-filled PSAs can be easily adapted to work as laser-writable and rewritable adhesive substrates. This system is based on cooperative interplay between the viscoelastic properties of PSAs and enhanced thermal conductivity provided by a thin overlayer of gold. The information stored can be either preserved or erased depending on surface modifications (e.g., by adding protecting coatings). In particular, the generation of self-expiring graphical tracks can have an impact on security, anti-forgery, labeling, quality control, and so on. From a fundamental standpoint, the interest for these studies encompasses self-catalytic systems and stimuli-responsive membranes.

More recently, we have successfully exploited oscillating chemical reactions to store temporary graphical information in cellulose-based supports, with precise temporal and spatial control. In this way, it has been possible to develop a sort of smart paper.

We have also developed “the phactalyst”, a bimorph photo-actuator (obtained by combining polycarbonate membranes with Carbone Nanotubes and TiO2 NPs) which can be activated by means of common table lamps and can be used for chemical applications, such as the remote and safe triggering of chemical reaction, or as optical shutter for the control of the occurrence of photo-chemical reactions, according to the wavelength of the illuminating light.

Now, we are investigating the possibility to introduce “smartness” and “stimuli-responsivity” to systems generally characterized by a lower degree of dynamicity, such as photonics, energy production and catalysis.

  • Energy Conversion

Finding efficient strategies to produce energy vectors, such as H2 or CH4, is fundamental to respond to the need of alternative fuels. In this regard, we are working on the development of new types of electrocatalysts for water splitting, catalysts for CH4 oxidation and systems for CO2 adsorption and reduction.

We have demonstrated that AuFe nanoalloys, with a non-thermodynamic stable composition, are able to significantly enhance oxygen evolution, thanks to the presence of a high number of Fe active sites distributed over a conductive matrix.

Now, we are working in the framework of the Biomass Hub project, for the development of efficient catalysts for CH4 oxidation.

References:

  • Plasmon Assisted Chemical Reactions and Exploitation of Plasmonic Heating

Plasmonic nanostructures offer unique opportunities to assist chemical reactions through either photocatalytic or thermal pathways. Our research is focused on coupling plasmonic nanoparticles and nanostructures to functional oxides, which are typically used as catalysts to promote different kind of reactions, like the photodegradation of environmental pollutants and the production of energy vectors (e.g. H2) from renewable sources.

For example, we have fabricated different model-systems based on TiO2 and ZnO photocatalytic beads coupled to Au nanoantenna arrays.

These systems allow for either broadband or selective, efficient light harvesting in the Vis-NIR range. Light is concentrated within nanogap regions, generating intense locale electromagnetic fields, that can assist surface reactions in several ways. We demonstrated that the photo-degradation of different organic pollutants can be controlled with unprecedented spatial and time resolution and the reaction rate can be remarkably enhanced.

The ongoing research is addressed to the production of similar catalysts over a large scale through low-cost strategies.

Metal NPs can be exploited as very efficient photon-thermal converters to generate localized heat at the micro- and nano-scale (optothermal conversion). This key property is currently being investigated for a number of important applications in various research fields, including drug delivery, cancer diagnostics and therapy. Further important sectors that can benefit from plasmonic heating are micro- and nano-fabrication and plasmon-assisted chemical vapor deposition.

We used Au NPs as light harvesting centers to bring extremely localized heating into colloidal particles and colloidal assemblies, obtaining a selective modification of their morphology.

Moreover, we demonstrated how plasmonic heating can be harnessed to yield ‘‘hot’’ sites for surface enhanced Raman spectroscopy (SERS), which were based on in situ generated metal oxides.

References: