RESUMEN

A supramolecular approach based on self-assembled structures allows the formation of large structured co-assemblies based on chiral and achiral compounds with original physicochemical features. In this contribution, an achiral and hydrophobic porphyrin was co-assembled at the air-water interface with mesoscopic silica nano-helices dispersed in the water subphase of a Langmuir trough without covalent bond formation. This procedure allowed transferring the porphyrin/nano-helix co-assemblies on a solid support within a thin hybrid layer. The interaction between the two species was characterized using spectroscopic techniques and atomic force microscopy. As evidenced by the circular dichroism measurements performed directly on solid films, tunable chirality was induced to the porphyrin aggregates according to the chirality of the silica nano-helices. When the co-assemblies were transferred on surface plasmon resonance (SPR) slides and exposed to aqueous solutions of histidine enantiomers, selective chiral discrimination was observed which was determined by the matching/mismatching between the chirality of the analyte and the helicity of the nano-helical structure.

RESUMEN

Inorganic chiral nanoparticles are attracting more and more attention due to their peculiar optical properties and potential biological applications, such as bioimaging, therapeutics, and diagnostics. Among inorganic chiral nanoparticles, gold chiral nanostructures were demonstrated to be very interesting in this context, with good physical chemical stability and also the possibility to decorate the surface, improving biomedical application as the interaction with the bio-systems. Gold (Au) nanostructures were synthesized according to a seed-mediated procedure which envisages the use of cetyltrimethylammonium bromide (CTAB) as the capping agent and L- and D-cysteine to promote chirality. Au nanostructures have been demonstrated to have opposite circular dichroism signals depending on the amino acid enantiomer used during the synthesis. Then, a procedure to decorate the Au surface with penicillamine, a drug used for the treatment of Wilson's disease, was developed. The composite material of gold nanoparticles/penicillamine was characterized using electron microscopy, and the penicillamine functionalization was monitored by means of UV-Visible, Raman, and infrared spectroscopy, highlighting the formation of the Au-S bond. Furthermore, electron circular dichroism was used to monitor the chirality of the synthesized nanostructures and it was demonstrated that both penicillamine enantiomers can be successfully bonded with both the enantiomers of the gold nanostructures without affecting gold nanoparticles' chirality. The effective modification of nanostructures' surfaces via penicillamine introduction allowed us to address the important issue of controlling chirality and surface properties in the chiral nano-system.

RESUMEN

A Langmuir film of cubane-bridged bisporphyrin (H2por-cubane-H2por) at the air/water interface was developed and characterized. The floating film was successfully employed for the chiral discrimination between l- and d-histidine. The enantioselective behavior persisted after the deposition of the film on a solid support using the Langmuir-Schaefer method. Distinct absorption and reflection spectra were observed in the presence of l- or d-histidine, revealing that conformational switching was governed by the interaction between H2por-cubane-H2por and the histidine enantiomer. The mechanism of chiral selection was investigated using an ad hoc modified nulling ellipsometer, indicating the anti-conformation was dominant in the presence of l-histidine, whereas the presence of d-histidine promoted the formation of tweezer conformation.

Asunto(s)

RESUMEN

Carbon nanomaterials are a group of materials characterized by sp2/sp3 carbon backbone which, combined with surface atoms and/or chemical groups, ensures peculiar physical chemical features for a wide range of applications. Among these materials, carbon dots and carbon nanoparticles belong to carbon nanomaterials with a few nanometer dimensions. In this work, carbon nanoparticles were produced from spent coffee grounds as sustainable carbon source through a simple, cheap and eco-friendly procedure according to an oxidation process (at controlled temperature) driven by hydrogen peroxide. Atomic Force Microscope (AFM) and fluorescence, UV-Vis absorption, FT-IR and Raman spectroscopy were used to assess the formation of carbon nanomaterials of about 10 nm with the typical emission and absorption properties of carbon dots and peculiar surface features. In fact, the presence of heteroatoms, i.e., phosphorus, and the carbonyl/carboxyl surface groups on carbon nanoparticles, was proposed to confer peculiar properties allowing the fast Mn(VII) reduction to Mn(II) at neutral pH and the Cr(VI) reduction to Cr(III) in weak acid aqueous media.

RESUMEN

The interaction between homochiral substituted perylene bisimide (PBI) molecule and the D enantiomer of phenylalanine amino acid was monitored. Spectroscopic transitions of PBI derivative in aqueous solution in the visible range were used to evaluate the presence of D-phenylalanine. UV-visible, fluorescence, FT-IR, and AFM characterizations showed that D-phenylalanine induces significant variations in the chiral perylene derivative aggregation state and the mechanism is enantioselective as a consequence of the 3D analyte structure. The interaction mechanism was further investigated in presence of interfering amino acid (D-serine and D-histidine) confirming that both chemical structure and its 3D structure play a crucial role for the amino acid discrimination. A D-phenylalanine fluorescence sensor based on perylene was proposed. A limit of detection (LOD) of 64.2 ± 0.38 nM was calculated in the range 10-7-10-5 M and of 1.53 ± 0.89 µM was obtained in the range 10-5 and 10-3 M.

RESUMEN

Many strategies have been adopted to improve the photoinduced features of zinc oxide nanostructures for different application fields. In this work, zinc oxide has been synthesised and decorated by plasmonic metal nanoparticles to enhance its photocatalytic activity in the visible range. Furthermore, an insulating layer of SiO2 has been grown between the surface of zinc oxide nanoflakes and silver nanoparticles. A synthetic procedure that allows the accurate modulation of the insulating layer thickness in the range 5-40 nm has been developed. Evidences highlight the crucial role of the SiO2 layer in dramatically increasing photocatalytic water oxidation promoted by the nanostructure under both UV and visible illumination. An ideal thickness value of about 10 nm has been demonstrated to guarantee the plasmon-induced resonance energy-transfer process and to quench the Förster resonance energy-transfer mechanism; thus, optimising the local surface plasmon resonance effect and water oxidation properties.