Vânia Freitas

University of Aveiro | UA · CICECO - Centre for Research in Ceramics and Composite Materials

The variety of H bond (HB) interactions is a source of inspiration for bottom-up molecular engineering through self-aggregation. Non-conventional intermolecular HB between N,N′-disubstituted urea and thiourea are studied in details by vibrational spectroscopies and ab-initio calculations. Raman and IR mode assignments are given. We show that it is...

To address the challenges of the next generation of smart windows for energy-efficient buildings, new electrochromic devices (ECDs) are introduced. These include indium molybdenum oxide (IMO), a conducting oxide transparent in the near-infrared (NIR) region, and a NIR-emitting electrolyte. The novel electrolytes are based on a sol-gel-derived di-ur...

We investigate the magnetic dilution effect on the relaxation mechanisms and the estimation of the energy barrier in a photo-luminescent Dy(III)/Y(III) based Single-Ion Magnet (SIM). The photo-luminescent spectroscopy permits the careful determination of the Orbach barrier, which is in a good agreement with the ab initio calculations. This barrier...

This manuscript reports the synthesis and characterization of the first organic-inorganic hybrid material exhibiting efficient multimodal spectral converting properties. The nanocomposite, made of Er(3+), Yb(3+) codoped zirconia nanoparticles (NPs) entrapped in a di-ureasil d-U(600) hybrid matrix, is prepared by an easy two-step sol-gel synthesis l...

The field of research on hybrid materials has been driven by the development of diverse organic–inorganic hybrids with potential for solid-state lighting (SSL) technologies, including dye-doped hybrids and dye-bridged hybrids. This chapter summarizes the work reported in the literature in the last decade on the generation of white light based on th...

Correction for ‘Di-amidosils with tunable structure, morphology and emission quantum yield: the role of hydrogen bonding’ by S. C. Nunes et al., J. Mater. Chem. C, 2015, 3, 6844–6861.

Tailoring of the structure (from amorphous to highly ordered lamellar), morphology (from a homogenous texture to fibers, microparticles, seaweeds- and desert rose-like shapes) and photoluminescence features of five di-amide crossed-linked decyl/siloxanes (di-amidosils, d-A(10)) was achieved via sol-gel chemistry and self-assembly from a single prec...

The sol−gel preparation of a bridged silsesquioxane containing europium(III) salts and 2-thenoyltrifluoroacetone has been achieved from a new ethane tetracarboxamide-based organosilane. Free-standing films with thicknesses up to 440 μm and maximum absolute quantum yield (q) of 0.34 ± 0.03 (excitation at 320 nm) were prepared by the drop cast method...

White light-emitting diodes (WLEDs) are candidates to revolutionize the lighting industry towards energy efficient and environmental friendly lighting and displays. The current challenges in WLEDs encompass high luminous efficiency, chromatic stability, high colour-rending index and price competitiveness. Recently, the development of efficient and...

Ordered mono-amide cross-linked alkyl/siloxane hybrids (mono-amidosils) incorporating a Rhodamine (B) methyl ester perchlorate dye (Rh(B)CH3ClO4) have been synthesized through the sol–gel process and self-directed assembly. The host hybrid matrix m-A(14) is a lamellar bilayer hierarchically structured hybrid composed of short methyl-capped alkyl ch...

Transparent monoliths and films of urea crosslinked tripodal siloxane-based hybrids (named tri-ureasils) were prepared by the sol–gel process, under controlled atmosphere (inside a glove box) and ambient conditions and their structure and optical features were compared. X-ray diffraction data point out that all the materials are essentially amorpho...

Novel electrolytes composed of a sol-gel derived di-urethane cross-linked poly(epsilon-caprolactone) (d-PCL (530))/siloxane (where 530 is the average molecular weighting mol(-1)) biohybrid network doped with a 50:50 molar mixture of lithium and erbium triflates were prepared in the light of the "mixed cation effect". These environmentally friendly...

Following a computational-experimental approach, a highly luminescent β-diketonate-europium(III) complex containing 2-thenoyltrifluoracetonate (tta−) and 5,6-epoxy-5,6-dihydro-[1,10] phenanthroline (ephen) ligands, Eu(tta)3ephen (II), was theoretically studied by DFT/TD-DFT calculations, synthesized from Eu(tta)3(H2O)2(I) and fully characterized by...

This work reports the synthesis of novel sol–gel derived urea cross-linked tripodal siloxane-based hybrids (classed as tri-ureasils) modified by the addition of phenyl-triethoxysilane (PTES) and diphenyldimethoxysilane (DPDMS). The materials were produced as transparent monoliths and thin films (thickness = 3.3–17.5 ± 0.1 lm) and characterized by X...

The design, production and characterization of tailored printable optical filters for visible optical communications are demonstrated. As result, the average color difference between the specified and the produced filters is 32.6, quantified in terms of CIELAB coordinates.

Transparent monoliths of urea cross-linked tripodal siloxane-based hybrids, named tri-ureasils, were prepared by the sol–gel process, using a wide concentration range of hydrochloric acid catalyst (1.0 × 10–3 ≤ [HCl] ≤ 2.0 M). The gelation time of the monoliths was controlled by varying the amount of water (2.2 and 22.2 mmol) and HCl (between 4.0 ×...

A simple one-pot approach based on the “benzyl alcohol route” is used for the preparation of benzoate- and biphenolate-capped zirconia and, benzoate-capped Eu-doped zirconia nanoparticles. Powder X-ray diffraction studies and high- resolution transmission electron microscopy (HR-TEM) showed that the nanoparticles present high crystallinity and unif...

Stable, cost-effective, brightly luminescent, and metal-free organosilica nanoparticles (NPs) were prepared using the Stöber method without any thermal treatment above 318 K. The white-light photoluminescence results from a convolution of the emission originated in the NH(2) groups of the organosilane and oxygen defects in the silica network. The t...

We demonstrate an improvement of the emission quantum yield and the luminance figures of merit of metal-free bridged silsesquioxanes-by a factor of 2, 0.43 +/- 0.04, and by two orders of magnitude, (1.4 +/- 0.1) x 10 4 cd m(-2), respectively-by changing the regioisomer of the silylated precursor. The organic-inorganic hybrids are easily excited by...