Researchers: Dr. Damiano Genovese, Nadia Licciardello, Chien-Wei Hsu

Contents:

• Mesoporous Films as Responsive Membranes

• Light Amplification with Soft Materials

• Silicon Nanoparticles

• Luminescent Mesoporous Nanomaterials

• Damiano Genovese's short CV

Mesoporous films as responsive membranes
Researchers involved: Dr. Damiano Genovese

We design, prepare and investigate mesoporous films to gate or release chemical species upon external triggers.

Fig. 6: Schematic mesoporous films behavior as membranes

In particular, mesoporous organic–inorganic hybrid materials are our materials of choice to produce such functional membranes, since combining the hardness of the inorganic components with the softness of the organic counterpart allows the implementation of several functionalities in a single material.

We then study, by means of dynamic techniques, the diffusion of molecular species through the composite film in situ and in real time.

Such materials can find application as artificial membranes, or for targeted and time-controlled drug delivery, or as thin layers with switchable optoelectronic properties.

Light Amplification with Soft Materials

Researchers involved: Dr. Damiano Genovese, Dr. Valentin Barna (Bucharest University)

Light Amplification with new Flexible, Diffusive, Soft Matter Based Systems

Confinement of light in nanometer and micron size cavities or in highly diffusive media (in various solid or liquid states) represents a modern scientific challenge and many interesting phenomena -such as weak/strong (Anderson) localization of light, high scattering and backscattering events, spontaneous emission and amplification, stimulated emission and lasing- are still to be fully explored and understood.

Our multidisciplinary research aims to develop and characterize novel periodic and aperiodic systems built from soft materials and fluorescent dyes.

The controlled design, fabrication and characterization of self-assembled soft material structures over several length scales are currently some of the most important challenges in material science arena. Soft fluorescent anisotropic materials having various shapes and properties can be also manipulated by external fields (mechanical, electrical, optical) and will open new research frontiers aimed at creating innovative reconfigurable and flexible photonic devices with unparalleled characteristics.

We aim to explore fundamental physics of responsive periodic, partially ordered and quasi-periodic soft composite materials that allow for moulding the flow of light.

Figure Caption. LASER action from a flexible-shape dye doped soft matter micro system. (b) Associated spectra demonstrates that LASER emission is obtained at ca. 576nm wavelength (yellow).

Silicon nanoparticles

Researchers involved: Chien-Wei Hsu and Nadia Licciardello

Silicon nanoparticles (Si Nps) are a very interesting field of research because of their applications in biological fluorescence imaging and in optoelectronic devices. Due to quantum confinement effects, silicon nanoparticles have special optical and electronic properties and, in particular, they show a bright luminescence that is strongly dependent on their size.  Recently Si NPs get more and more attention because of their several advantages like non-toxicity, highly stability against photobleaching and easiness to be further functionalized with biomolecules (like antibodies) to be used as luminescent labels.

Obtaining Si Nps with a size smaller than 5 nm is still challenging because they are very prone to oxidation that can be avoided only with a complete capping of the surface.We are one of the partners of the project of Helmholtz Virtual Institute 'NanoTracking' (http://www.hzdr.de/db/Cms?pNid=2452), a project between several groups whose major aim is to develop nanomaterials for cancer imaging.In our group, we are mainly focused on the preparation (by wet chemistry) and characterization of amine and alkene capped silicon nanoparticles with different sizes and, in particular, with a size between 1.5-3 nm. The methods that we used are both reduction and oxidation methods. 

Reduction method:

Fig. 1: General reaction scheme

Fig. 2: TEM image, corresponding particle size distribution histogram and dominant emission of 3-aminopropyl terminated Si Nps in water (particle size distribution of 1.57 ± 0.24 nm) Picture of a UV irradiated solution of amine capped Si Nps (size 1-4 nm) obtained in our laboratories   

Oxidation method:

Fig. 3: General reaction scheme and picture of a UV irradiated solution of Si-C4H7 nanoparticles prepared in our laboratory

Mesoporous Materials and Luminescent Mesoporous Silica Nanoparticles

Researchers involved: Dr. Céline Rosticher (now at ESPCI, Paris, FR)

Mesoporous silica and zeolites are nanoporous materials presenting a pore size ranging from 2 to 15 nm with a large surface area up to 1300 m2. In many of the potential applications for mesoporous materials, especially as molecular host, ordered morphology and pore structure could be accounted as a key factor for enhancing the applicability. In addition, mesoporous materials present advantages such as: 1) Easily tailored structure; 2) Tunable size; 3) Controllable surface properties of both external and internal surface. Indeed, the external surface of the nanoparticles and the inner surface of the pores can be tuned to be either hydrophobic, hydrophilic or even have ionic charge; 4) Adjustable length of the channels.   

Fig. 4: SEM and TEM images of mesoporous silica having large surface area.  

To satisfy our need for photonics and bio applications we are developing mesoporous silica/zeolites nanoparticles and films.

We develop mesoporous silica nanoparticles with optical properties for various applications such as OLED, bio imaging or drug delivery. For bio imaging and drug delivery applications, size is a matter. Using a modified procedure to synthesize mesoporous silica, we are able to incorporate a wide range of luminescent materials including metal complexes, metallic clusters and organic dye in specific location in silica nanoparticles with controllable size.

Luminescent materials based on copper species in nanoporous materials

Rare-earth based phosphors are commonly used for application as phosphors in lighting applications, since these are the only commercially viable materials that are sufficiently photostable upon UV or blue excitation. However, they present major drawbacks: they are quite expensive, scarce and environment-unfriendly. Our aim is to develop new materials with promising optical properties, low cost, non-toxicity to replace them, in particular Cu(I) complexes and Cu(0) nanoclusters.

Indeed, luminescent complexes based on Cu(I) have recently attracted a lot of interest due their promising photophysical properties. The biggest advantage of such Cu(I)-complexes is that their d-orbitals are completely filled and therefore non-radiative d-d-deactivation pathways are avoided. Their emission can also be tuned from the blue to the red part of the electromagnetic spectrum.

As its luminescence comes mainly from metal-to-ligand charge-transfer (MLCT) states, the metal center changes formally its oxidation state from Cu(I) to Cu(II) during the excitation process. This triggers undesired non-radiative pathways by distortions of the tetrahedral conformation, caused by flattening, wagging and rocking of the ligand around the metal center.

  Fig. 5: Structural rearrangement of a Cu(I) complex during excitation  

Our strategy used to prevent these drawbacks is to develop copper complexes in constrained space, i.e. built in the pores of zeolites and mesoporous materials in order to stabilize their structures with respect to their coordination geometry and even produce species which would not be stable in any other condition. The wall of the zeolite or of other silica based frameworks will help to protect and to have the desired geometry even in the excited state.

The development of sub-nanometer sized copper clusters with promising luminescence properties have been recently reported by Wei et al. These clusters with a size of around 8 Cu-atoms show a bright orange emission under UV-illumination. We expect a similar luminescence behavior from copper clusters stabilized inside the pores of mesoporous materials, such as mesoporous silica nanoparticles or zeolites, where sizes between 2 and 10 atoms can be realized without capping agents.

Damiano Genovese short CV

Damiano Genovese was born in Messina in 1983, and he obtained his PhD in Chemistry at University of Bologna in 2011 under the supervision of prof Luca Prodi. As a student, he received two grants to fund his research stays in Ecole Normale Superieure (France) and Harvard University (USA). He was awarded the ENI prize 2013 for his Debut in Research. He is now a Humboldt Fellow at Karlsruhe Institute of Technology in the research group of prof. De Cola. His research has been focused on colloidal systems, on self-assembling architectures, and on nanostructured functional materials for optoeletronics, sensing, and biomedicine. He works now on mesoporous silica films to be applied as functional and responsive materials

Work and education

Key Publications