Simona Ungureanu

Novel monolith-type boron nitride hierarchical foams obtained through integrative chemistry

A novel class of monolith-type boron nitride hierarchical foams has been prepared through an integrative chemistry-based synthetic path. These materials contain interconnected pores in the nanometre to the micrometre range with high porosity (∼75 vol%), a specific surface area up to 300 m2 g−1 and a resistance toward mechanical stress making them suitable for innovative applications.

Tough silicon carbide macro/mesocellular crack-free monolithic foams

Taking the benefit of Si(HIPE) as a hard monolithic template to shape macro-mesoporous foams by using polycarbosilane as pre-ceramic precursor β-SiC, macro/mesocellular foams have been synthesized. Both macroscopic Plateau border morphology and final mechanical properties can be tuned through varying the starting amount of polycarbosilane precursor. Resulting silicon carbide foams, labeled SiC(HIPE), are composed of β-SiC at the microscopic length scale, while bearing 110 m2 g−1 as specific area at the mesoscopic length scale, and up to 92% of macroporosity. The as-synthesized crack-free SiC(HIPE) monolithic foams are associated with outstanding mechanical properties as, for instance, 50–58 MPa of compression Young modulus. The thermal behaviors of these foams are assessed with bulk heat capacities comprising between 0.15 J g−1 K−1 to 0.55 J g−1 K−1 that decrease when the foam porosity increases, while their heat conductivities are following the same rules ranging from 2.6 to 4.6 W m−1 K−1.

Far-field disentanglement of modes in hybrid plasmonic-photonic crystals by fluorescence nano-reporters

Abstract In this paper, the resonance modes exhibited by a hybrid nanostructure have been disentangled in the far-field owing to narrow-band fluorescence nano-reporters. Hybrid plasmonic-photonic crystals were fabricated using large (457 nm) monodisperse polystyrene spheres self-assembled into 2D photonic crystals and subsequently coated by a 30 nm thick silver layer. Such structures exhibit a complex resonance pattern, which has been elucidated owing to numerical simulations and electric near-field patterns obtained with a scattering type scanning near-field optical microscope (s-SNOM). For the sake of disentangling the resonance modes of the hybrid structure in the far-field, different types of semiconductor quantum dots (QDs), acting as nano-reporters of the local interactions, were dispersed on top of distinct structures. Depending on the relative overlap of the emission spectrum of a particular type of QDs with the resonance features of the hybrid structure, we affect their emission rate in a unique way, as a consequence of the complex interaction occurring between the plasmo-photonic modes and the excitons. Such plasmonic structures appear to be particularly relevant for fluorescence-based sensing devices.

Emitters as probes of a complex plasmo-photonic mode

We report on the experimental observation of an asymmetric wavelength-dependence of the emission rate enhancement in a two-dimensional plasmo-photonic crystal. This feature strongly contrasts with the traditional Lorentzian line shape exhibited at a resonance by the Purcell factor. The unusual dispersive behavior is shown to be reproducible for different combinations of emitters and structures measured in different geometries. It is further retrieved from finite-difference time-domain simulations and is dominantly attributed to the fact that a hybridized mode, resulting from the coupling of a Bragg mode and a surface plasmon polariton mode, is coupled to the emitters. Further studies of the emission detuning by hybrid plasmonic–photonic structures are expected to benefit many related fields and notably sensing and bio-sensing technologies.

Hybrid Foams, Colloids and Beyond: Advanced Ceramics through Integrative Chemistry

Today chemistry of materials and as such the ceramic field of research are addressed through more and more complex synthetic methodologies in order to optimize final material performances. The notion of complexity in chemical science is illustrated inhere through the concept of integrative chemistry. Particularly the integration between bi-liquid foams, sol-gel process, organo-silane functionnalization, lanthanides complexation and Pd heterogeneous nucleation is proposed as a non-exhaustive synthetic tool box to reach specific advanced ceramics. The first section is dealing with the synthesis of the first series of Si(HIPE) macrocellular foams where the oil volume fraction of the starting emulsion allows a nice tuning of the foams macroporosity. The second section is dealing with Europium complexation of diketone and malonamide hybrid Organo-Si(HIPE) leading to the Eu3+@Organo-Si(HIPE) luminescent foams, while the third part is dedicated to Pd heterogeneous nucleation within host hybrid foams. This last series of macrocellular ceramics are labeled Pd@Organo-Si(HIPE) which demonstrates good turn over number (TON) and turn over frequencies (TOF) when acting as supported catalysts for the Mizoroki-Heck coupling reactions. In the above mentioned foams the HIPE acronym is for High Internal Phase Emulsion.

Propagation and survival of frequency-bin entangled photons in metallic nanostructures

Abstract We report on the design of two plasmonic nanostructures and the propagation of frequency-bin entangled photons through them. The experimental findings clearly show the robustness of frequency-bin entanglement, which survives after interactions with both a hybrid plasmo-photonic structure, and a nano-pillar array. These results confirm that quantum states can be encoded into the collective motion of a many-body electronic system without demolishing their quantum nature, and pave the way towards applications of plasmonic structures in quantum information.