L. Escobar-Alarcón’s research while affiliated with Instituto Nacional de Investigaciones Nucleares and other places

This study investigates the synthesis and photoluminescent properties of carbon quantum dots (CQDs) derived from Actinidia deliciosa using the hydrothermal method. The effect of concentration and pH on the composition, structure, and optical properties of CQDs was analyzed using characterization techniques such as TEM, EDS, FTIR, UV-Vis, and photoluminescence (PL) spectroscopy. The CQDs exhibited particle sizes ranging from 1 to 10 nm, with a graphitic structure and oxygen-containing functional groups, as identified by FTIR bands corresponding to OH, C=O, and C=C. The stability analysis revealed particle agglomeration over 30 days, increasing the size up to <40 nm. Regarding the optical properties, the CQDs displayed absorption peaks at 225 and 280 nm and a bandgap of ~3.78–3.82 eV. The PL characterization demonstrated tunable emission from violet to green, depending on the excitation wavelength. CQDs synthesized at an acidic pH of 2 exhibited enhanced luminescence due to protonation effects, whereas an alkaline pH led to a reduction in emission intensity. The hydrothermal method enabled a simple and eco-friendly synthesis, using water as the sole solvent, yielding stable CQDs with a luminescence lifespan exceeding 30 days. Their optical and electronic properties make them promising candidates for photocatalysis, heavy metal detection, and bioimaging applications.

In this work, it is reported the physicochemical characterization and photocatalytic activity evaluation of TiO2 thin films modified with Eu, Pd, Fe and Bi. Several characterization techniques were used to investigate thin film properties. The chemical composition as well as the chemical environment of the elements present were determined by X-ray photoelectron spectroscopy (XPS). The crystalline structure was characterized by X-ray diffraction (XRD) and micro-Raman spectroscopy (RS) whereas the optical band gap was determined using UV-Vis spectroscopy. The photocatalytic activity was evaluated in the degradation of the Malachite Green (MG) dye using simulated sunlight. It was found that films modified with Fe and Pd reached MG degradations close to 64.7 and 58.1% after 180 min of reaction. Additionally, thin films were photocatalytically evaluated under UV light (λ=254 nm) using wastewater containing diclofenac (DCF). The best catalytic performance (44% was reached by the film modified with Fe followed by the films modified with Pd (39%) and Bi (38%). To identify the role of reactive species for degradation of MG and DCF, triethanolamine (TEOA), isopropyl alcohol (IPA), ascorbic acid (AA) and benzoquinone (BZQ) were employed as scavenger’s molecules. The results obtained revealed that the O2• radical is the reactive specie that mainly contributes to the MG and DCF degradation. Graphical abstract

Este trabajo reporta la extracción y purificación de fibras de celulosa (FC) a partir de desechos de sargazo y nopal, empleadas en la síntesis de nanofibras de celulosa (NFC) impregnadas con nanopartículas de plata (NPs-Ag), formando nanocompuestos NPs-Ag/NFC. Las FC se obtuvieron utilizando hidróxido de sodio, hipoclorito de sodio y ácido acético, evitando la generación de residuos tóxicos. Las NFC se sintetizaron mediante el método TEMPO y las NPs-Ag por ablación láser en agua. Los resultados confirmaron la viabilidad de obtener FC y NFC de residuos orgánicos de nopal y sargazo, con algunas variaciones en tamaño y grupos funcionales. Los nanocompositos NPs-Ag/NFC con 5.0% en peso de plata redujeron la energía de banda prohibida de 5.6 eV a 2.8 eV y 2.9 eV para los nanocompuestos de nopal y sargazo, respectivamente, sugiriendo su potencial fotocatalítico. Sin embargo, solo los nanocompositos NPs-Ag/NFC de sargazo mostraron estabilidad en medios acuosos.

Se evaluó la actividad fotocatalítica de películas delgadas de TiO2:Co en la reacción de fotodegradación de verde de malaquita (10 µM/L), con una fuente de luz solar simulada, se estudiaron las especies reactivas responsables de la degradación mediante el uso de moléculas inhibidoras. Las películas delgadas se depositaron sobre sustratos de vidrio y silicio, ablacionando blancos metálicos de titanio y cobalto utilizando un láser pulsado Nd-YAG con emisión en 1064 nm y una presión de trabajo de 1x10-3 Torr, posteriormente se trataron térmicamente a 450 °C por 2 horas en una mufla de convección de aire. Los depósitos sobre silicio se caracterizaron por espectroscopía fotoelectrónica de rayos X (XPS) y los depositados sobre vidrio comercial por ultravioleta-visible (UV-Vis), y de energía dispersiva (EDS) así como difracción de rayos X (XRD). Los resultados de la evaluación fotocatalítica muestran que estos materiales presentan fotoactividad, siendo el radical superóxido O2- la especie responsable de la degradación del colorante verde de malaquita.

This work shows the synthesis of graphene oxide (GO) by a fast and efficient method, based on the use of acetone as solvent to accelerate the washing and drying process. Also, the structural and morphological evolution of graphene oxide (gO) to GO from sonication at different times (2–8 h) is shown. SEM and AFM analysis revealed the formation of GO thin sheets. XRD analysis showed a shift of the (001) plane from 11.3° to 10.6° (2θ). This change confirmed the evolution from gO to GO. FTIR showed the presence of characteristic functional groups. Raman analysis showed an increase in the ID/IG ratio and a decrease in the crystallite size in the plane from 19 to 13 nm with increasing sonication time.

Nanomaterials such as titanium dioxide and magnetite are increasingly used in several fields, such as water remediation and agriculture. However, this has raised environmental concerns due to potential exposure to organisms like humans. Nanomaterials can cause adverse interactions depending on physicochemical characteristics, like size, morphology, and composition, when interacting with living beings. To ensure safe use and prevent the risk of exposure to nanomaterials, their biocompatibility must be assessed. In vitro cell cultures are beneficial for assessing nanomaterial–cell interactions due to their easy handling. The present study evaluated the biocompatibility of TiO2, Fe3O4, and TiO2/Fe3O4 nanomaterials thermally treated at 350 °C and 450 °C in erythrocytes and HepG2 cells. According to the hemolysis experiments, non-thermally treated NMs are toxic (>5% hemolysis), but their thermally treated counterparts do not present toxicity (<2%). This behavior indicates that the toxicity derives from some precursor (solvent or surfactant) used in the synthesis of the nanomaterials. All the thermally treated nanomaterials did not show hemolytic activity under different conditions, such as low-light exposure or the absence of blood plasma proteins. In contrast, non-thermally treated nanomaterials showed a high hemolytic behavior, which was reduced after the purification (washing and thermal treatment) of nanomaterials, indicating the presence of surfactant residue used during synthesis. An MTS cell viability assay shows that calcined nanomaterials do not reduce cell viability (>11%) during 24 h of exposure. On the other hand, a lactate dehydrogenase leakage assay resulted in a higher variability, indicating that several nanomaterials did not cause an increase in cell death as compared to the control. However, a holotomographic microscopy analysis reveals a high accumulation of nanomaterials in the cell structure at a low concentration (10 µg mL−1), altering cell morphology, which could lead to cell membrane damage and cell viability reduction.