RESUMEN
Electrical stimulation has emerged as a cornerstone technique in the rapidly evolving field of biomedical engineering, particularly within the realms of tissue engineering and regenerative medicine. It facilitates cell growth, proliferation, and differentiation, thereby advancing the development of accurate tissue models and enhancing drug-testing methodologies. Conductive hydrogels, which enable the conduction of microcurrents in 3D in vitro cultures, are central to this advancement. The integration of high-electroconductive nanomaterials, such as graphene oxide (GO), into hydrogels has revolutionized their mechanical and conductivity properties. Here, we introduce a novel electrostimulation assay utilizing a hybrid hydrogel composed of methacryloyl-modified small intestine submucosa (SIS) dECM (SISMA), chitosan methacrylate (ChiMA), and GO-polyethylene glycol (GO-PEG) in a 3D in vitro culture within a hypoxic environment of umbilical cord blood cells (UCBCs). Results not only demonstrate significant cell proliferation within 3D constructs exposed to microcurrents and early growth factors but also highlight the hybrid hydrogel's physiochemical prowess through comprehensive rheological, morphological, and conductivity analyses. Further experiments will focus on identifying the regulatory pathways of cells subjected to electrical stimulation.
RESUMEN
The discharge of synthetic dyes from different industrial sources has become a global issue of concern. Enormous amounts are released into wastewater each year, causing concerns due to the high toxic consequences. Photocatalytic semiconductors appear as a green and sustainable form of remediation. Among them, graphitic carbon nitride (g-C3N4) has been widely studied due to its low cost and ease of fabrication. In this work, the synthesis, characterization, and photocatalytic study over methylene blue of undoped, B/S-doped, and exfoliated heterojunctions of g-C3N4 are presented. The evaluation of the photocatalytic performance showed that exfoliated undoped/S-doped heterojunctions with 25, 50, and 75 mass % of S-doped (g-C3N4) present enhanced activity with an apparent reaction rate constant (kapp) of 1.92 × 10-2 min-1 for the 75% sample. These results are supported by photoluminescence (PL) experiments showing that this heterojunction presents the less probable electron-hole recombination. UV-vis diffuse reflectance and valence band-X-ray photoelectron spectroscopy (VB-XPS) allowed the calculation of the band-gap and the valence band positions, suggesting a band structure diagram describing a type I heterojunction. The photocatalytic activities calculated demonstrate that this property is related to the surface area and porosity of the samples, the semiconductor nature of the g-C3N4 structure, and, in this case, the heterojunction that modifies the band structure. These results are of great importance considering that scarce reports are found concerning exfoliated B/S-doped heterojunctions.
RESUMEN
Polypyrrole (PPy) is a promising material for the fabrication of flexible energy storage devices and much research has been published. However, no statistical tools have been used to relate PPy synthesis conditions to its energy storage performance, considering not only the main synthesis factors but also their interactions. In this work, we use a factorial design of experiments to evaluate the influence of two electropolymerization methods and three synthesis parameters on the energy storage capacity of PPy coatings. The polymers were characterized by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), electrochemical impedance spectroscopy (EIS), Raman spectroscopy, and scanning electron microscopy (SEM). Statistical tests showed that ClO4 --doped PPy exhibits higher capacitances than p-toluenesulfonate (pTS)-doped PPy, with a maximum capacitance of 353.75 ± 1.6 F g-1 at 1 A g-1. However, the pTS-doped PPy had better cycling stability, losing only 10% of its original energy storage capability after 5000 charge-discharge cycles at 1 A g-1. The best energy densities and power densities were 49.1 ± 0.2 Wh kg-1 and 2297 ± 15 W kg-1 (ClO4 --doped PPy) and 47.8 ± 1.5 Wh kg-1 and 2191 ± 91 W kg-1 (pTS-doped PPy), respectively, which indicates that through statistical tools, the optimal synthesis conditions are refined to take advantage of the energy storage properties of this polymer.
RESUMEN
The atomic layer deposition (ALD) of Al2O3 between perovskite and the hole transporting material (HTM) PEDOT:PSS has previously been shown to improve the efficiency of perovskite solar cells. However, the costs associated with this technique make it unaffordable. In this work, the deposition of an organic-inorganic PEDOT:PSS-Cl-Al2O3 bilayer is performed by a simple electrochemical technique with a final annealing step, and the performance of this material as HTM in inverted perovskite solar cells is studied. It was found that this material (PEDOT:PSS-Al2O3) improves the solar cell performance by the same mechanisms as Al2O3 obtained by ALD: formation of an additional energy barrier, perovskite passivation, and increase in the open-circuit voltage (Voc) due to suppressed recombination. As a result, the incorporation of the electrochemical Al2O3 increased the cell efficiency from 12.1% to 14.3%. Remarkably, this material led to higher steady-state power conversion efficiency, improving a recurring problem in solar cells.
RESUMEN
Polypyrrole (PPy) is one of the most attractive conducting polymers for thin film applications due to its good electrical conductivity, stability, optical properties, and biocompatibility. Among the technologies in which PPy has gained prominence are optoelectronics and solar energy conversion, where transparent electrodes such as fluorine-doped tin oxide (FTO) or indium tin oxide (ITO) are frequently used. However, FTO substrates have the notable advantage that their components are widely available in nature, unlike those of ITO. Recognizing the importance that the FTO/polypyrrole system has gained in various applications, here, we studied for the first time the nucleation and growth mechanism of electro-synthesized PPy on FTO. Additionally, the effect of the synthesis potential (0.9, 1.0, 1.1, and 1.2 V vs. Ag/AgCl) on the homogeneity, adhesion, conductivity, and HOMO energy levels of PPy films was determined. From current-time transients and scanning electron microscopy, it was found that films synthesized at 0.9 and 1.0 V exhibit 3D growth with progressive nucleation (as well as lower homogeneity and higher adhesion to FTO). In contrast, films synthesized at 1.1 and 1.2 V follow 2D growth with instantaneous nucleation. It was also evident that increasing the polymerization potential leads to polymers with lower conductivity and more negative HOMO levels (versus vacuum). These findings are relevant to encourage the use of electro-synthesized PPy in thin film applications that require a high control of material properties.
RESUMEN
Cobalt porphyrins have emerged as promising catalysts for electrochemical and photoelectrochemical applications because of their good performance, low cost and the abundance of cobalt in the earth. Herein, a negatively charged porphyrin meso-tetra-(4-sulfonatophenyl)-porphin (TPPS) was immobilized in polypyrrole (PPy) during the electro-polymerization, and then it was metallized with cobalt to obtain meso-tetra-(4-sulfonatophenyl)-porphyrinato cobalt (II) (CoTPPS) as a dopant in PPy. The coatings were evaluated as photoelectrodes towards thiosulfate oxidation and oxygen reduction. For comparison purposes, the photoelectrochemical behavior of ClO4--doped polypyrrole films was also evaluated. Characterizations by chronoamperometry, UV-Vis spectroscopy and Raman spectroscopy showed that polypyrrole is stable under anodic and cathodic conditions, but CoTPPS and TPPS immobilized in PPy are degraded during the anodic process. Thus, decreases in photocurrent of up to 87% and 97% for CoTPPS-doped PPy and TPPS-doped PPy were observed after a 30-min chronoamperometry test. On the other hand, good stability of CoTPPS and TPPS immobilized in PPy was observed during photoelectrochemical oxygen reduction, which was reflected in almost constant photocurrents obtained by chronoamperometry. These findings are relevant to understanding the role of CoTPPS as a catalyst or pre-catalyst in photoelectrochemical applications such as water splitting. In addition, these results could pave the way for further research to include CoTPPS-doped PPy in the design of novel photocathodes.
RESUMEN
The understanding of oxidized species derived from the neurotransmitter dopamine (DA) is a relevant topic for both the medical field (Parkinson's disease) as well as for the field of materials science where the formation process of polydopamine (PDA) films is an active area of research. Polymers that interact strongly with almost all surfaces but have a low electrical conductivity have been obtained by the chemical oxidation of DA. Since electrical conductivity is a desired property for several applications, deposition alternatives such as electrochemical PDA synthesis have been proposed, but the results are still insufficient. In this context, we propose a new PDA chemical-electrochemical deposition process on glassy carbon electrodes. The chemical oxidation step that converts dopamine into dopamine-o-quinone previous to the electrochemical deposition was crucial to decrease the precursor concentration to the micromolar range. The PDA-like films synthesized by this method had high adhesion and low charge-transfer resistance, which was evidenced by impedance measurements and the successful electrodeposition of a polypyrrole coating on top of a PDA-like film. In addition, we observed that anodization of GC surfaces increases sensitivity toward six electroactive couples derived from DA oxidation in the pH regimes studied. These results show the complexity of the intermediates formed during the electrochemical polymerization of PDA.