Synthesis of Micro-Spikes and Herringbones Structures by Femtosecond Laser Pulses on a Titanium Plate-A New Material for Water Organic Pollutants Degradation

(1) Background: The shrinkage of water resources, as well as the deterioration of its quality as a result of industrial human activities, requires a comprehensive approach relative to its protection. Advanced oxidation processes show high potential for the degradation of organic pollutants in water and wastewater. TiO₂ is the most popular photocatalyst because of its oxidizing ability, chemical stability and low cost. The major drawback of using it in powdered form is the difficulty of separation from the reaction mixture. The solution to this problem may be immobilization on a support (glass beads, molecular sieves, etc.). In order to avoid these difficulties, the authors propose to prepare a catalyst as a titanium plate covered with an oxide layer obtained with laser treatment. (2) Methods: In the present work, we generated titanium oxide structures using a cheap and fast method based on femtosecond laser pulses. The structurized plates were tested in the reaction of methylene blue (MB) degradation under UVA irradiation (365 nm). The photocatalytic activity and kinetic properties for the degradation of MB are provided. (3) Results: Studies of X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirm a titanium oxide layer with laser-induced generated structures that are called “spikes” and “herringbones”. The structurized plates were effective photocatalysts, and their activity depends on the structure of the oxide layer (spike and herringbone). (4) Conclusions: The immobilization of the catalyst on a solid support can be performed in a fast and reproducible manner by using the technique of laser ablation. The layers obtained with this method have been shown to have catalytic properties.

Noncytotoxic silver nanoparticles as a new antimicrobial strategy

Drug-resistance of bacteria is an ongoing problem in hospital treatment. The main mechanism of bacterial virulency in human infections is based on their adhesion ability and biofilm formation. Many approaches have been invented to overcome this problem, i.e. treatment with antibacterial biomolecules, which have some limitations e.g. enzymatic degradation and short shelf stability. Silver nanoparticles (AgNPs) may be alternative to these strategies due to their unique and high antibacterial properties. Herein, we report on yeast Saccharomyces cerevisiae extracellular-based synthesis of AgNPs. Transmission electron microscopy (TEM) revealed the morphology and structure of the metallic nanoparticles, which showed a uniform distribution and good colloid stability, measured by hydrodynamic light scattering (DLS). The energy dispersive X-ray spectroscopy (EDS) of NPs confirms the presence of silver and showed that sulfur-rich compounds act as a capping agent being adsorbed on the surface of AgNPs. Antimicrobial tests showed that AgNPs inhibit the bacteria growth, while have no impact on fungi growth. Moreover, tested NPs was characterized by high inhibitory potential of bacteria biofilm formation but also eradication of established biofilms. The cytotoxic effect of the NPs on four mammalian normal and cancer cell lines was tested through the metabolic activity, cell viability and wound-healing assays. Last, but not least, ability to deep penetration of the silver colloid to the root canal was imaged by scanning electron microscopy (SEM) to show its potential as the material for root-end filling.

Functionalization of Polycaprolactone Electrospun Osteoplastic Scaffolds with Fluorapatite and Hydroxyapatite Nanoparticles: Biocompatibility Comparison of Human Versus Mouse Mesenchymal Stem Cells

A capability for effective tissue reparation is a living requirement for all multicellular organisms. Bone exits as a precisely orchestrated balance of bioactivities of bone forming osteoblasts and bone resorbing osteoclasts. The main feature of osteoblasts is their capability to produce massive extracellular matrix enriched with calcium phosphate minerals. Hydroxyapatite and its composites represent the most common form of bone mineral providing mechanical strength and significant osteoinductive properties. Herein, hydroxyapatite and fluorapatite functionalized composite scaffolds based on electrospun polycaprolactone have been successfully fabricated. Physicochemical properties, biocompatibility and osteoinductivity of generated matrices have been validated. Both the hydroxyapatite and fluorapatite containing polycaprolactone composite scaffolds demonstrated good biocompatibility towards mesenchymal stem cells. Moreover, the presence of both hydroxyapatite and fluorapatite nanoparticles increased scaffolds' wettability. Furthermore, incorporation of fluorapatite nanoparticles enhanced the ability of the composite scaffolds to interact and support the mesenchymal stem cells attachment to their surfaces as compared to hydroxyapatite enriched composite scaffolds. The study of osteoinductive properties showed the capacity of fluorapatite and hydroxyapatite containing composite scaffolds to potentiate the stimulation of early stages of mesenchymal stem cells' osteoblast differentiation. Therefore, polycaprolactone based composite scaffolds functionalized with fluorapatite nanoparticles generates a promising platform for future bone tissue engineering applications.

Efficient NIR energy conversion of plasmonic silver nanostructures fabricated with the laser-assisted synthetic approach for endodontic applications

Silver nanoparticles were synthesized with the laser-assisted wet chemical approach at room temperature. The effect of light exposure on the silver nanoparticles' spatial parameters shaping the localized surface plasmon resonance has been evaluated. The optical, structural and morphological characterizations of the Ag nanostructures were conducted with UV-VIS-NIR spectrophotometry, DLS and TEM techniques. The ability of the light-modified Ag nanostructures for energy conversion under the influence of 445 and 880 nm laser radiation is estimated. We have found that the most efficient heat generation can be achieved using triangular Ag nanostructures under the NIR irradiation (880 nm). The temperature effect on the Ag nanostructures' antibacterial properties has been evaluated against the Staphylococcus aureus population. The prospects of triangular Ag nanostructures' application on modern endodontics for the rapid nano-laser disinfection of the root canal system of the human tooth have been demonstrated.

Energy conversion by plasmonic silver nanostructures fabricated with the laser assisted synthetic approach at room temperature.

Correction: Efficient NIR energy conversion of plasmonic silver nanostructures fabricated with the laser-assisted synthetic approach for endodontic applications

Correction for ‘Efficient NIR energy conversion of plasmonic silver nanostructures fabricated with the laser-assisted synthetic approach for endodontic applications’ by Tetiana Bulavinets et al., RSC Adv., 2020, 10, 38861–38872, DOI: 10.1039/D0RA06614A.

Alternative Approach for Fighting Bacteria and Fungi: Use of Modified Fluorapatite

The recent studies on fluorapatite and hydroxyapatite, in the context of their medical applications, have shown that the former has relatively higher thermal stability and better mechanical properties than the latter. Moreover, the presence of fluoride ions is relevant for protection of teeth from dental caries since they stimulate processes of mineralization and crystallization. In this report, a silver modified fluorapatite (FAP/Ag), considered as a novel biomedical compound, was tested for its bactericidal, fungicidal and cytotoxicity activity. All these features were compared to the impact of pure FAP and were evaluated against the bacteria and fungi strains, which constitute main pathogenic species among orthopedic clinical isolates of implant-associated infections. Generally, considerable increase in the antimicrobial activity was observed when silver modified fluorapatite was compared to the pure material. This was manifested among others by disturbance of cell growth pattern and various deformations in the final cell shape as revealed using atomic force microscopy (AFM). Regarding toxicity nowadays as a major issue in implantation, we additionally examined whether the Ag⁺ ions have an impact on human keratinocytes and mouse fibroblasts using a cytotoxicity assay. To conclude, owing to a great bactericidal potential without collateral cytotoxicity effect the fluorapatite doped with silver ions may be considered a promising biocomponent useful in medical and healthcare applications.

Experimental Investigation of Electrical Conductivity and Permittivity of SC-TiO 2 -EG Nanofluids

The paper presents experimental studies of dielectric properties of nanofluids based on ethylene glycol and SC-TiO2 nanoparticles with average size of 15-40 nm with various mass concentrations. The dielectric permittivity both real part and imaginary part as a function of temperature and frequency were measured. Also, dependence ac conductivity on frequency, temperature, and mass concentration were investigated. Based on the curves of ac conductivity, dc conductivity was calculated, and 400 % enhancement in dc conductivity was exposed.

Synthesis, Characterization, and Photocatalytic Properties of Sulfur- and Carbon-Codoped TiO2 Nanoparticles

One-step TiO2 nanoparticle synthesis based on the interaction between thiourea and metatitanic acid is applied for sulfur and carbon anatase codoping. The synthesis of the doped TiO2 has been monitored by means of differential thermal analysis and thermogravimetric analysis (DTA-TG), which allows determining the optimal thermal conditions for the process. Electron microscopy showed micrometer-sized (5-15 μm) randomly distributed crystal aggregates, consisting of many 15-40-nm TiO2 nanoparticles. The obtained phase composition and chemical states of the doping elements are analyzed by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared (IR) and Raman spectroscopies, and electron paramagnetic resonance (EPR). XRD displays in both samples (doped and pristine) the existence of only one crystalline phase-the tetragonal modification of TiO2-anatase. Further data assessment by means of Rietveld refinement allowed detection of a slight c lattice parameter and volume increase related to incorporation of the doping elements. XPS demonstrated the presence of carbon and sulfur as doping elements in the material. It was confirmed that carbon is in elemental form and also present in oxygen-containing compounds, which are adsorbed on the particle surface. The binding energy for sulfur electron core shell corresponds to the established data for sulfate compounds, where sulfur is in 6+ oxidation state. The synthesized S- and C-codoped TiO2 showed excellent photocatalytic performance during the degradation of organic dyes (rhodamine B, methylene blue), gas-phase oxidation of ethanol under visible light, and photocatalytic hydrogen generation from ethanol under ultraviolet light.