Advanced Materials Division@C4T

Research

The research activity is mainly focused on two main general topics:

-Materials for energy conversion

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

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

Atomic Layer Deposition

Some references:

I. Alessandri, M. Zucca, M. Ferroni, E. Bontempi, L. E. Depero, Tailoring the Pore Size and Architecture of CeO2/TiO2 Core/Shell Inverse Opals by Atomic Layer DepositionSmall (2009) 5, 336.

I. Alessandri, M. Zucca, M. Ferroni, E. Bontempi, L. E. Depero, Growing ZnO Nanocrystals on Polystyrene Nanospheres by Extra-Low-Temperature Atomic Layer DepositionCrystal Growth & Design (2009) 9, 1258.

I. Alessandri, E. Bontempi, P. Bergese, L. E. Depero, Materials from colloidal beads: synthesis and applications, in Encyclopedia of Nanoscience and Nanotechnology ed, S. H. Nalwa, American Scientific Publishers (2011).

L. Borgese, E. Bontempi, P. Colombi, L. E. Depero, I. Alessandri, Tailoring phase and composition at the nanoscale: atomic layer deposition of Zn-Ti-O thin filmsCrystal Engineering Communications (2011) 13, 6621.


What follows is a brief description of our recent research:

Plasmon Assisted Chemical Reactions 

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 recently fabricated different model-systems based on TiO2 and ZnO photocatalytic beads coupled to Au nanoantenna arrays. These systems allow for either broadband or selective, very efficient light harvesting in the Vis-NIR range. Light is concentrated within nanogap regions, generating intense local electromagnetic fields that can assist surface reactions in several ways. We demonstrated that the photodegradation 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.

References: 


Project: PLASMA (Plasmonic Smart Materials)-PID 2011

Exploiting plasmonic heating to drive physical and chemical transformations

Metal NPs can be exploited as very efficient photon-thermal converters to generate localized heat at the micro- and nanoscale (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 nanofabrication and plasmon-assisted chemical vapour 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 and conveniently employed to yield ‘‘hot’’ sites for surface enhanced Raman spectroscopy (SERS) which were based on in situ generated metal oxides.

References:

 I. Alessandri, M. Ferroni, L. E. Depero, Plasmon-assisted, spatially resolved laser generation of transition metal oxides from liquid precursorsJournal of Physical Chemistry C (2011) 115, 5174.

 I. AlessandriPlasmonic heating assisted deposition of bare Au nanoparticles on titania nanoshellsJournal of Colloid and Interface Science (2010) 351, 576.

I. Alessandri, L. E. Depero, Using plasmonic heating of gold nanoparticles to generate local SER(R)S-active TiO2 spotsChemical Communications (2009), 17, 2359.

I. Alessandri, M. Ferroni, L. E. Depero, In situ plasmon heating-induced generation of Au/TiO2 “hot spots” on colloidal crystalsChemPhysChem, (2009), 10, 1017.

 I. Alessandri, M. Ferroni, Exploiting optothermal conversion for nanofabrication: site-selective generation of Au/TiO2 inverse opalsJournal of Materials Chemistry (2009), 19, 7990.

I. Alessandri, L. E. Depero, Laser-induced modification of polymeric beads coated with gold nanoparticlesNanotechnology (2008) 19, 305301.


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, a class of materials including acrylics, polyurethanes, polyesters, and silicones, are widely used for a variety of applications in everyday life.  In particular, upon modification

with electrically conductive fillers, such as carbon or metals, they can be applied as antistatic self-adhesive tapes for electromagnetic-shielding purposes in various contexts. Is t 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.


References:
I. Alessandri, Writing, self-healing and self erasing on conductive pressure-sensitive adhesivesSmall (2010) 6, 1679-1685.
I. Alessandri, Self-healing hybrid nanocomposites: role and activation of inorganic moieties and hybrid nanophases in Self-Healing at the Nanoscale: Mechanisms and Key Concepts of Natural and Artificial Systems-Taylor &Francis-CRC, Boca Raton (FL): ISBN: 978-1-4398-5473-0 (2011).

More recently, we have successfully exploited oscillating chemical reactions to store temporary information in cellulose-based supports with precise control of self-erasing time and good spatial resolution.


References:

I. Vassalini, I. Alessandri, Spatial and temporal control of information storage in cellulose by chemically activated oscillations  ACS-Applied Materials and Interfaces  (2015)


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 interatomic bonds and physico-chemical processes dynamics. Surface-enhanced Raman scattering (SERS) is a leading nondestructive technique that can extend the sensitivity of Raman spectroscopy to the level of single molecule. However, for a number of 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.

We are currently investigating alternative approaches to develop new materials based on core/shell multifunctional beads and nanostructures. The ultimate 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 recently 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 biodiagnostics.

References:

T-rex and related all-dielectric systems:

I. AlessandriEnhancing Raman scattering without plasmons: unprecedented sensitivity achieved by TiO2 shell-based resonators, Journal of the American Chemical Society (2013) 135(15), 5541-5544.

N. Bontempi, M. Salmistraro, M. Ferroni, L. E. Depero, I. AlessandriProbing the spatial extension of light trapping-induced enhanced Raman scattering in high-density Si nanowire arraysNanotechnology (2014) 25, 465705.

I. Alessandri, N. Bontempi, L. E. DeperoColloidal lenses as universal Raman scattering enhancers, RSC Advances (2014) 4, 38152-38158.

I. Alessandri, L. E. DeperoAll-Oxide Raman-Active Traps for Light and Matter: Probing Redox Homeostasis Model Reactions in Aqueous Environment, Small (2014) 10, 1294-1298.

 I. Alessandri, E. Biavardi, A. Gianoncelli, P. Bergese, E. Dalcanale, Cavitands Endow All-Dielectric Beads With Selectivity for Plasmon-Free Enhanced Raman Detection of Nε-Methylated Lysine, ACS-Applied Materials & Interfaces (2015), in press, DOI: 10.1021/acsami.5b08190


Recyclable plasmonic SERS-active substrates

G.Sinha, L.E. Depero, I. Alessandri, Recyclable SERS substrates based on Au- coated nanorods, ACS-Applied Materials and Interfaces (2011) 3(7), 2557-2563.

 S. Pal, L. E. Depero, I. Alessandri, Using aggregates of gold nanorods in SER(R)S experiments: an empirical evaluation of some critical aspectsNanotechnology (2010), 21, 42570.

I. Vassalini, E. Rotunno, L. Lazzarini, I. Alessandri, “Stainless” gold nanorods: preserving shape, optical properties and SERS activity in oxidative environment, ACS-Applied Materials & Interfaces (2015), 7, 18794-18802.