Photocatalytic Activity of Ag Nanoparticles Deposited on Thermoexfoliated g-C3N4.

The limited access to fresh water and the increased presence of emergent pollutants (EPs) in wastewater has increased the interest in developing strategies for wastewater remediation, including photocatalysis. Graphitic carbon nitride (g-C3N4) is a 2D non-metal material with outstanding properties, such as a 2.7 eV bandgap and physicochemical stability, making it a promising photocatalyst. This work reports the process of obtaining high-surface-area (SA) g-C3N4 using the thermal-exfoliation process and the posterior effect of Ag-nanoparticle loading over the exfoliated g-C3N4 surface. The photocatalytic activity of samples was evaluated through methylene blue (MB) degradation under visible-light radiation and correlated to its physical properties obtained by XRD, TEM, BET, and UV-Vis analyses. Moreover, 74% MB degradation was achieved by exfoliated g-C3N4 compared to its bulk counterpart (55%) in 180 min. Moreover, better photocatalytic performances (94% MB remotion) were registered at low Ag loading, with 5 wt.% as the optimal value. Such an improvement is attributed to the synergetic effect produced by a higher SA and the role of Ag nanoparticles in preventing charge-recombination processes. Based on the results, this work provides a simple and efficient methodology to obtain Ag/g-C3N4 photocatalysts with enhanced photocatalytic performance that is adequate for water remediation under sunlight conditions.

Antimicrobial and Virus Adsorption Properties of Y-Zeolite Exchanged with Silver and Zinc Cations.

The antimicrobial activity of silver and zinc exchanged cations in Y-zeolite (Ag/CBV-600, Zn/CBV-600) is evaluated against Staphylococcus aureus (gram (+)) and Escherichia coli (gram (-)) bacteria along with their adsorption capacity for viruses: brome mosaic virus (BMV), cowpea chlorotic mottle virus (CCMV), and the bacteriophage MS2. The physicochemical properties of synthesized nanomaterials are characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), UV-Vis spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). According to the obtained results, the main species associated with the exchanged ions are Ag+ and Zn2+ cations with the concentration of around 1 atomic %. The incorporation of cations does not modify the Y-zeolite framework. The Ag/CBV-600 and Zn/CBV-600 materials show an inactivation of 90% for both gram (+) and gram (-) bacteria at 16 h at a relatively low concentration of nanomaterial (0.5 mg/mL). Moreover, the samples present good adsorption capacity for BMV, CCMV, and MS2 viruses showing adsorption higher than 40% after 2 h of interaction with the viruses. These prominent results allow the further usage of nanomaterials as an effective remedy to inhibit and reduce the spread of viruses such as SARS-CoV-2 or other gram (+) or gram (-) bacteria.

Green synthesis of TiO2 for furfural production by photohydrolysis of tortilla manufacturing waste.

Corn nixtamalization generates a waste byproduct that requires diverse environmental preservation measures depending on the country. Such measures could include catalytic and advanced oxidation processes. This study aims to exploit the hemicellulose within the nejayote (32.5%) to create added value chemicals such as furfural using photocatalytic hydrolysis. In the present work, titania (TiO2) nanoparticles (NPs) were greenly synthesized using Ricinus Communis (RC), Moringa Oleifera (MO) or Bougainvillea Spectabilis (BS) plant extracts. Obtained nanoparticles were characterized using XRD, SEM, EDS, BET, XPS and UV-vis techniques. Furthermore, the photocatalytic performance of the obtained samples was evaluated in the furfural production from nejayote. Furfural yield reached 44% in 30 min using the BS synthesized material, which is 1.6 × the yield obtained by the material synthesized with MO extract (26.4% at 45 min) and 6 × the yield obtained by the material obtained with RC (7.2% at 90 min). Such results have not been reported before in the literature and could be the groundwork for novel waste treatments in the tortilla-making industry.

Synthesis by spray pyrolysis of gold nano species confined in iron oxide nanospheres effective in the reduction of 4-nitrophenol to 4-aminophenol.

The highly effective Au/Fe2O3-@Au/Fe2O3nanoreactors for the 4-nitrophenol (4-NP) reduction are successfully obtained by one-pot synthesis using the spray pyrolysis (SP) technique. The Au/Fe2O3-@Au/Fe2O3nanoreactors manifest superior catalytic activity in the reduction of 4-NP in the presence of sodium borohydride (NaBH4) compared to gold-iron oxide nanoreactors prepared via a colloidal approach. The negative effect of the reaction product accumulation, the 4-aminophenol (4-AP), on the catalytic reduction of 4-NP over Au/Fe2O3-@Au/Fe2O3is examined by a direct pre-injection of 4-AP to the reaction media. To the best of our knowledge, it is the first experimental evidence of gold active sites blocking by 4-AP. All obtained samples are characterized by the yolk-shell spherical hollow structure mainly consisted of two embedded hollow nanospheres. The reduction of iron oxide precursor concentration diminishes the diameter of final iron oxide nanospheres. According to STEM-EDS analysis and STEM, Au nano species are uniformly dispersed on both iron oxide nanospheres. The SP technique presently used to synthesize Au/Fe2O3-@Au/Fe2O3nanoreactors manifests high potential for the one-pot fabrication of a large variety of nanoreactors with various active materials applied as heterogeneous catalysts in numerous catalytic processes.

Electrospun Fibers and Sorbents as a Possible Basis for Effective Composite Wound Dressings.

Skin burns and ulcers are considered hard-to-heal wounds due to their high infection risk. For this reason, designing new options for wound dressings is a growing need. The objective of this work is to investigate the properties of poly (ε-caprolactone)/poly (vinyl-pyrrolidone) (PCL/PVP) microfibers produced via electrospinning along with sorbents loaded with Argovit™ silver nanoparticles (Ag-Si/Al2O3) as constituent components for composite wound dressings. The physicochemical properties of the fibers and sorbents were characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and inductively coupled plasma optical emission spectroscopy (ICP-OES). The mechanical properties of the fibers were also evaluated. The results of this work showed that the tested fibrous scaffolds have melting temperatures suitable for wound dressings design (58-60 °C). In addition, they demonstrated to be stable even after seven days in physiological solution, showing no macroscopic damage due to PVP release at the microscopic scale. Pelletized sorbents with the higher particle size demonstrated to have the best water uptake capabilities. Both, fibers and sorbents showed antimicrobial activity against Gram-negative bacteria Pseudomona aeruginosa and Escherichia coli, Gram-positive Staphylococcus aureus and the fungus Candida albicans. The best physicochemical properties were obtained with a scaffold produced with a PCL/PVP ratio of 85:15, this polymeric scaffold demonstrated the most antimicrobial activity without affecting the cell viability of human fibroblast. Pelletized Ag/Si-Al2O3-3 sorbent possessed the best water uptake capability and the higher antimicrobial activity, over time between all the sorbents tested. The combination of PCL/PVP 85:15 microfibers with the chosen Ag/Si-Al2O3-3 sorbent will be used in the following work for creation of wound dressings possessing exudate retention, biocompatibility and antimicrobial activity.