Engineered Metal Oxide Nanoparticles as Fungicides for Plant Disease Control

Metal oxide nanoparticles are considered to be good alternatives as fungicides for plant disease control. To date, numerous metal oxide nanoparticles have been produced and evaluated as promising antifungal agents. Consequently, a detailed and critical review on the use of mono-, bi-, and tri-metal oxide nanoparticles for controlling phytopathogenic fungi is presented. Among the studied metal oxide nanoparticles, mono-metal oxide nanoparticles-particularly ZnO nanoparticles, followed by CuO nanoparticles -are the most investigated for controlling phytopathogenic fungi. Limited studies have investigated the use of bi- and tri-metal oxide nanoparticles for controlling phytopathogenic fungi. Therefore, more studies on these nanoparticles are required. Most of the evaluations have been carried out under in vitro conditions. Thus, it is necessary to develop more detailed studies under in vivo conditions. Interestingly, biological synthesis of nanoparticles has been established as a good alternative to produce metal oxide nanoparticles for controlling phytopathogenic fungi. Although there have been great advances in the use of metal oxide nanoparticles as novel antifungal agents for sustainable agriculture, there are still areas that require further improvement.

A Comparative DFT Study on Process Control Agents in the Mechanochemical Synthesis of PbTe

A process control agent is an organic additive used to regulate the balance between fracturing and mechanical kneading, which control the size of the as-milled particles. Tributyl phosphate (TBP) is evaluated to act as surface modifier of PbTe, and it is compared with the results obtained using formaldehyde (CH₂O). In order to elucidate the nature of the interaction between TBP and the PbTe surface, global and local descriptors were calculated via the density functional theory. First, TBP and CH₂O molecules are structurally optimized. Then, vertical ionization energies as well as vertical electron affinities are calculated to elucidate how both molecules behave energetically against removal and electron gain, respectively. The results were compared with those obtained from the electrostatic potential mapped on the van der Waals isosurface. It is inferred that the theoretical insights are useful to propose adsorption modes of TBP and CH₂O on the PbTe surface, which are usable to rationalize the facets exposed by PbTe after the surface treatment. The optimized structures of the compound systems showed a close correlation between the surface energy shift (Δγ) and the PbTe facets exhibited. Finally, a Wulff construction was built to compare the usage of TBP and CH₂O molecules in PbTe morphology.

Role of Defect Engineering and Surface Functionalization in the Design of Carbon Nanotube-Based Nitrogen Oxide Sensors

Nitrogen oxides (NOx) are among the main atmospheric pollutants; therefore, it is important to monitor and detect their presence in the atmosphere. To this end, low-dimensional carbon structures have been widely used as NOx sensors for their outstanding properties. In particular, carbon nanotubes (CNTs) have been widely used as toxic-gas sensors owing to their high specific surface area and excellent mechanical properties. Although pristine CNTs have shown promising performance for NOx detection, several strategies have been developed such as surface functionalization and defect engineering to improve the NOx sensing of pristine CNT-based sensors. Through these strategies, the sensing properties of modified CNTs toward NOx gases have been substantially improved. Therefore, in this review, we have analyzed the defect engineering and surface functionalization strategies used in the last decade to modify the sensitivity and the selectivity of CNTs to NOx. First, the different types of surface functionalization and defect engineering were reviewed. Thereafter, we analyzed experimental, theoretical, and coupled experimental-theoretical studies on CNTs modified through surface functionalization and defect engineering to improve the sensitivity and selectivity to NOx. Finally, we presented the conclusions and the future directions of modified CNTs as NOx sensors.

Oriented-Attachment- and Defect-Dependent PbTe Quantum Dots Growth: Shape Transformations Supported by Experimental Insights and DFT Calculations

High-resolution transmission electron microscopy results reveal that oriented-attachment- and defect-dependent mechanisms rule the size and shape evolution of the monodispersed PbTe quantum dots (QDs). The former is characterized by the growth of quasi-cubic PbTe QDs, which depends on both the geometric constraints imposed by the {200} facets and the defect-free lattice, while the latter one is a defect-dependent mechanism which gives way to the formation of decahedral PbTe QDs (∼6 nm). Experimentally, formaldehyde is an important parameter for the mechanochemical synthesis of monodispersed PbTe QDs, which has not been studied until now. In a theoretical context, Fukui functions reveal that Pb surface atoms are the most reactive sites toward nucleophilic attacks, and the Lowdin charge analysis shows that formaldehyde molecules tend to donate their electron pairs to Pb atoms. Besides, formaldehyde-molecule-on-PbTe adsorption energies (-4.46 to -21.16 kcal mol^-1) agree with ligand-surface polar electrostatic interactions. Based on dispersion-corrected density functional theory calculations, PbTe QDs exhibited decahedral and faceted shapes. According to modified Wulff constructions, the decahedral shape is a result of (111) facets (Δγ = -2.79 meV Å^-2), whereas the faceted and rounded shapes are due to the interaction of (100), (110), and (111) facets.

Effect of Silk Fibroin on Cell Viability in Electrospun Scaffolds of Polyethylene Oxide

In this study, a coating from electrospun silk fibroin was performed with the aim to modify the surface of breast implants. We evaluated the effect of fibroin on polymeric matrices of poly (ethylene oxide) (PEO) to enhance cell viability, adhesion, and proliferation of HaCaT human keratinocytes to enhance the healing process on breast prosthesis implantation. We electrospun six blends of fibroin and PEO at different concentrations. These scaffolds were characterized by scanning electron microscopy, contact angle measurements, ATR-FTIR spectroscopy, and X-ray diffraction. We obtained diverse network conformations at different combinations to examine the regulation of cell adhesion and proliferation by modifying the microstructure of the matrix to be applied as a potential scaffold for coating breast implants. The key contribution of this work is the solution it provides to enhance the healing process on prosthesis implantation considering that the use of these PEO⁻fibroin scaffolds reduced (p < 0.05) the amount of pyknotic nuclei. Therefore, viability of HaCaT human keratinocytes on PEO⁻fibroin matrices was significantly improved (p < 0.001). These findings provide a rational strategy to coat breast implants improving biocompatibility.