RESUMEN

Biopolymers such as carboxymethyl cellulose and hyaluronic acid are alternative substrates for conformable organic light-emitting diodes (OLEDs). However, drawbacks such as mechanical stress susceptibility can hinder the device's performance under stretched conditions. To overcome these limitations, herein, we developed a nanocomposite based on CMC/HA (carboxymethyl cellulose/hyaluronic acid) and synthetic Laponite, intending to improve the mechanical strength without compromising the film flexibility and transparency (transmittance >80%; 380-700 nm) as substrates for conformable OLEDs. From XRD, FTIR, CP-MAS NMR, and TGA/DTG characterization techniques, it was possible to conclude the presence of Laponite randomly dispersed between the polymer chains. CMC/HA with 5% (w/w) Laponite, CMC/HA 5, presented a higher tensile strength (370.6 MPa) and comparable Young's modulus (51.0 ± 1.2 MPa) in comparison to the nanocomposites and pristine films, indicating a better candidate for the device's substrates. To produce the OLED, the multilayer structure ITO/MoO3/NPB/TCTA:Ir(ppy)3/TPBi:Ir(ppy)3/BPhen/LiF was deposited onto the CMC/HA 5 substrate. The OLEDs fabricated using CMC/HA 5 substrates showed higher luminance (12 kcd/m2) and irradiance (0.9 mW/cm2) values when compared with those based on commercial bacterial cellulose. However, the same device presented a lower efficiency (3.2 cd/A) due to a higher current density. Moreover, the OLED fabricated onto the Laponite-modified biopolymer presented reproducible behavior when submitted to continuous bending stress. Thus, CMC/HA 5 demonstrates potential as a transparent conductor substrate for biopolymer-based OLEDs with comparable performance to commercial bacterial cellulose features.

RESUMEN

A new adsorbent matrix (Cel-SiN) for the adsorption of the dye eosin yellow (EY) and the drug amitriptyline (AMI) from aqueous media has been synthesized. The Cel-SiN matrix was obtained via chemical modification of cellulose with (3-aminopropyl)trimethoxysilane. Successful modification was confirmed using Fourier transform infrared (FTIR) and 13C and 29Si solid state nuclear magnetic resonance (SSNMR) spectroscopies, thermal analysis (TG/DTG), X-ray diffraction (XRD), and elemental analysis. The effects of pH, contact time, concentration, and temperature were evaluated in batch adsorption tests. Cel-SiN efficiently adsorbed AMI and EY in aqueous media, with maximum adsorption capacities of 92.28 ±â€¯1.34 mg g-1 for AMI (pH = 7, time =240 min, and temperature = 318 K) and 61.0 ±â€¯0.36 mg g-1 for EY (pH = 5, time =80 min, and temperature = 298 K). The adsorption process occurs mainly via hydrogen bonding interactions for AMI and electrostatic interactions for EY.

RESUMEN

Ultrafast transient absorption spectroscopy, NOESY-NMR, and EPR spectroscopy shed light on how π-π stacking interactions combined with electrostatic interactions can be used to form stable ion-pair complexes between pyrylium and tetraarylborate ions in which the interaction of the π-delocalized clouds promotes the observation of new radiative processes and also electron transfer processes excitation using visible light. The results exhibit a striking combination of properties, chemical stability and photophysical and photochemical events, that make these ion-pair complexes as a step toward the realization of chromophore/luminescent materials and also their use as a new monophotoinitiator system in radical polymerization reactions.

RESUMEN

CdFe2O4 nanoparticles of around 3.9 nm were synthesized using the coprecipitation method and protected by a silica layer. The nanoparticles were mixed with a coacervate and transformed into phosphate glasses with 1, 4 and 8% in mass of nanoparticles by the melt-quenching method. TEM images confirm that the nanoparticles were successfully incorporated into the matrix without inducing crystallization. 31P NMR and Raman spectral analyses show that new P-O-Si bonds are formed in the glasses containing nanoparticles. The glass transition increases as a function of the nanoparticle content due to an increase in the connectivity of the phosphate glass chains. The UV-Vis spectra show bands at 415 and 520 nm assigned to Fe3+ ions and at 1025 nm, characteristic of Fe2+ ions, indicating that some of the nanoparticles dissolve during the melting process. The sample with 8% CdFe2O4 presents a paramagnetic behavior. The glasses obtained are transparent, non-hygroscopic and possess enormous thermal stability which is important for the production of optical devices.

RESUMEN

In this work we explored the fabrication of flexible and transparent hybrids of silk fibroin (SF) and epoxy-modified siloxane for photonic applications. It is well-known that regenerated SF solutions can form free-standing films with high transparency. Although SF has a restricted number of chemically reactive side groups, the main issues of as-cast pristine SF films regard the high solubility into aqueous media, brittleness, and low thermal stability. The design of SF films with enhanced functionality but high transparency triggers new opportunities on a broader range of applications in biophotonics. Here we present a simple, functional, yet remarkably versatile hybrid material derived from silica sol-gel process based on SF protein and (3-glycidyloxypropyl)trimethoxysilane (GPTMS), an organically modified silicon-alkoxide owning a reactive terminal epoxy group. Specifically, we investigated the effect of the addition of GPTMS into SF solutions on the processability, morphology, crystallinity, and mechanical and optical properties of the resulting hybrid films. Highly transparent (ca. 90%) and flexible free-standing hybrid films were achieved. Cell viability assays revealed that the hybrid films are noncytotoxic to rat osteoblast cells even at high GPTMS content (up to 70 wt %). The hybrid films showed enhanced thermal stability and were rich in organic (epoxy) and inorganic (silanol) functional groups according to the content of GPTMS. We also evaluated the successful preparation of high-quality optical red emissive SF hybrid films by loading YVO4:Eu3+ nanoparticles at low concentration (<5 wt %). A meaningful description of the hybrid film structure is reported from the combination of scanning electron and atomic force microscopies, vibrational spectroscopy, solid-state NMR, and X-ray diffraction analyses.

Asunto(s)

Silanos/química , Animales , Resinas Epoxi , Fibroínas , Ratas , Seda , Solubilidad

RESUMEN

Glasses having the composition (100 - x)As2P2S8-xGa2S3 with x ranging from 0 to 50% were investigated to determine the compositional effect on properties and local structure. The glass transition temperature (Tg) and the stability parameter against crystallization (Tx - Tg) increased with the addition of Ga2S3. The structure of these glasses was probed by Raman scattering, Fourier transform infrared (FT-IR) and 31P nuclear magnetic resonance. On the basis of the observed vibrations and the strength of the 31P-31P homonuclear magnetic dipolar coupling, two scenarios can be proposed for the structural evolution induced by the addition of Ga2S3. For x or= 30% we have depolymerization of the As2P2S8 units and the formation of a network of GaPS4 units with each PS 4/2 unit (Q4) species carrying a single positive formal charge.