The design and engineering of antibacterial materials are key for preventing bacterial adherence and proliferation in biomedical and household instruments. Silver nanoparticles (AgNPs) and chitosan (CHI) are broad-spectrum antibacterial materials with different properties whose combined application is currently under optimization. This study proposes the formation of antibacterial films with AgNPs embedded in carboxymethylcellulose/chitosan multilayers by the layer-by-layer (LbL) method. The films were deposited onto nanoporous silicon (nPSi), an ideal platform for bioengineering applications due to its biocompatibility, biodegradability, and bioresorbability. We focused on two alternative multilayer deposition processes: cyclic dip coating (CDC) and cyclic spin coating (CSC). The physicochemical properties of the films were the subject of microscopic, microstructural, and surface–interface analyses. The antibacterial activity of each film was investigated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria strains as model microorganisms. According to the findings, the CDC technique produced multilayer films with higher antibacterial activity for both bacteria compared to the CSC method. Bacteria adhesion inhibition was observed from only three cycles. The developed AgNPs–multilayer composite film offers advantageous antibacterial properties for biomedical applications.
N. Naveas, R. Pulido, V. Torres-Costa, F. Agulló-Rueda, M. Santibanez, F. Malano, G. Recio-Sánchez, K. Garrido-Miranda, M. Manso-Silván, J. Hernandez-Montelongo, «Antibacterial Films of Silver Nanoparticles Embedded into Carboxymethylcellulose/Chitosan Multilayers on Nanoporous Silicon: a Layer-by-Layer Assembly Approach Comparing Dip and Spin Coating,» Int. J. Mol. Sci. 24, 10595 (2023)
The present study aims at the integration of the “oxalic conversion” route into “green chemistry” for the synthesis of copper oxide nanoparticles (CuO-NPs) with controllable structural, morphological, and magnetic properties. Two oxalate-containing precursors (H2C2O4.2H2O and (NH4)2C2O4.H2O) and different volume ratios of a mixed water/glycerol solvent were tested. First, the copper oxalates were synthesized and then subjected to thermal decomposition in air at 400 °C to produce the CuO powders. The purity of the samples was confirmed by X-ray powder diffraction (XRPD), and the crystallite sizes were calculated using the Scherrer method. The transmission electron microscopy (TEM) images revealed oval-shaped CuO-NPs, and the scanning electron microscopy (SEM) showed that morphological features of copper oxalate precursors and their corresponding oxides were affected by the glycerol (V/V) ratio as well as the type of C2O42- starting material. The magnetic properties of CuO-NPs were determined by measuring the temperature-dependent magnetization and the hysteresis curves at 5 and 300 K. The obtained results indicate the simultaneous coexistence of dominant antiferromagnetic and weak ferromagnetic behavior.
F. Mbarek, I. Chérif, A. Chérif, J. M. Alonso, I. Morales, P. de la Presa, S. Ammar, «Insights into the Synthesis Parameters Effects on the Structural, Morphological, and Magnetic Properties of Copper Oxide Nanoparticles,» Materials 16, 3426 (2023)
The disordered structure of the columnar misfit ∼ PbCr2S4 phase (∼ character indicates that it is close to the stoichiometric composition but slightly away) has been revealed by means of transmission electron microscopy (TEM) varied techniques such as selected area electron diffraction (SAED), high-resolution TEM (HRTEM), dark-field TEM and high-angle annular dark field (HAADF) in scanning-transmision (STEM) mode. The structure consists of a hexagonal framework (Cr21S36), with unit cell parameters a0 = b0 = 21.407 (1) Å and c0 3.476 (1), and with hexagonal (Pb6Cr2S6) and trigonal columns (Pb3S) with the same a and b parameters and different c: c3 = 3.98 Å; c6 = 5.62 Å, measured by electron diffraction. While the framework exhibit no crystalline disorder, the arrangement of the two types of columns is disordered. This disorder is shown by electron diffraction as diffuse scattering planes which are perpendicular to the framework c axis and parallel to the a∗b∗ plane. While the disorder between hexagonal columns is due to the lack of correlation between different columns, we observe in the trigonal columns also the presence of intra-columnar atomic disorder. X-ray wavelength dispersive spectroscopy (XWDS) analyses produce Pb0.81(1)Cr2S3.97(6) composition. TEM imaging techniques suggest lack of correlation between trigonal columns as the cause for the observed disorder as well as inside-the-column structural disorder in Pb3S trigonal columns.
A. Gómez-Herrero, A. R. Landa-Cánovas, and L. C. Otero-Díaz, “TEM study of ∼PbCr2S4 columnar misfit phases,” J. Solid State Chem. 319, 123826 (2023)
A. Gómez‐Herrero, A. R. Landa‐Cánovas and L. C. Otero‐Díaz, “New Order in (BiS)1.19(Bi1/3Cr2S4) Misfit Layer Compound,” Z. Anorg. Allg. Chem. 647, 1–7 (2021).
In a sample with nominal composition BiCr2S5 a new misfit layer compound has been synthesized and studied via transmission electron microscopy (TEM). It presents a composite modulated structure with a composition that can be formulated as (BiS)1.19[(CrS2)-Bi1/3-(CrS2)]. It consists of the periodic stacking of a Q layer (BiS) with two H layers (CrS2), …QHHQHH…, with additional bismuth atoms inserted between the H layers. Selected area electron diffraction (SAED) patterns show an almost commensurate fit between the pseudo-tetragonal Q (BiS) and the pseudo-orthohexagonal H (Bi1/3Cr2S4) subcells along the misfit direction a, being b the same for both sublattices and c the layers stacking direction. In addition to the characteristic misfit modulation between the two sub-structures, a second modulation is observed in the H sub-structure produced by the ordering of bismuth atoms within the Van der Waals gap that occurs between consecutive H layers. High resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) images show ordered stacking sequences between the (BiS) and (Bi1/3Cr2S4) layers. Besides, disordered intergrowths have been occasionally found as well as different kinds of twinning defects.
En una muestra con composición nominal BiCr2S5 un nuevo compuesto de «misfit layer» ha sido sintetizado y estudiado a través de microscopía electrónica de transmisión (TEM). Presenta una estructura modulada compuesta con una composición que puede formularse como (BiS)1.19[(CrS2)-Bi1/3-(CrS2)]. Consiste en el apilamiento periódico de una capa Q (BiS) con dos capas H (CrS2), … QHHQHH…, con átomos de bismuto adicionales insertados entre las capas H. Los patrones de difracción de electrones de área seleccionada (SAED) muestran un ajuste casi conmensurable entre las subceldas pseudo-tetragonal Q (BiS) y la pseudo-ortohexagonal H (Bi1/3Cr2S4) a lo largo de la dirección de «misfit» a, siendo b el mismo para ambos sublátices y c la dirección de apilamiento de las capas. Además de la modulación de «misfit» característica entre los dos subestructuras, se observa una segunda modulación en la subestructura H producido por el orden de los átomos de bismuto dentro de la brecha de Van der Waals que se produce entre capas H consecutivas. La microscopía electrónica de transmisión de alta resolución (HRTEM) y las imágenes de microscopía electrónica de transmisión de barrido (STEM) muestran secuencias de apilamiento ordenadas entre capas (BiS) y (Bi1/3Cr2S4). Además, los intercrecimientos desordenados han sido ocasionalmente defectos de macla.
Published in Zeitschrift für anorganische und allgemeine Chemie (Journal of Inorganic and General Chemistry)
A. Fernández García, V. Torres-Costa, O. de Melo, F. Agulló-Rueda, G. R. Castro and M. Manso Silvan, “Growth of out-of-plane standing MoTe2(1−x)Se2x/MoSe2 composite flake films by sol-gel nucleation of MoOy and isothermal closed space telluro-selenization,” Appl. Surf. Sci. 546, 149076 (2021)
N. Naveas, M. Manso-Silván, R. Pulido, F. Agulló-Rueda, V. Torres-Costa, T. Plaza, H. Pesenti, G. Recio, and J. Hernandez-Montelongo, “Fabrication and characterization of nanostructured porous silicon-silver composite layers by cyclic deposition: dip-coating vs spin-coating,“ Nanotechnol. 31, 365704 (2020)