Identification of Volatile Organic Compounds in Extremophilic Bacteria and Their Effective Use in Biocontrol of Postharvest Fungal Phytopathogens

Phytopathogenic fungal growth in postharvest fruits and vegetables is responsible for 20–25% of production losses. Volatile organic compounds (VOCs) have been gaining importance in the food industry as a safe and ecofriendly alternative to pesticides for combating these phytopathogenic fungi. In this study, we analysed the ability of some VOCs produced by strains of the genera Bacillus, Peribacillus, Pseudomonas, Psychrobacillus and Staphylococcus to inhibit the growth of Alternaria alternata, Botrytis cinerea, Fusarium oxysporum, Fusarium solani, Monilinia fructicola, Monilinia laxa and Sclerotinia sclerotiorum, in vitro and in vivo. We analysed bacterial VOCs by using GC/MS and 87 volatile compounds were identified, in particular acetoin, acetic acid, 2,3-butanediol, isopentanol, dimethyl disulphide and isopentyl isobutanoate. In vitro growth inhibition assays and in vivo experiments using cherry fruits showed that the best producers of VOCs, Bacillus atrophaeus L193, Bacillus velezensis XT1 and Psychrobacillus vulpis Z8, exhibited the highest antifungal activity against B. cinerea, M. fructicola and M. laxa, which highlights the potential of these strains to control postharvest diseases. Transmission electron microscopy micrographs of bacterial VOC-treated fungi clearly showed antifungal activity which led to an intense degeneration of cellular components of mycelium and cell death.

Conductive, Superhydrophobic, and Microwave-Absorbing Cotton Fabric by Dip-Coating of Aqueous Silk Nanofibers Stabilized MWCNTs and Octadecanoyl Chain Bonding

A facile dip-coating method to endow cotton fabric (CF) with satisfactory conductivity, superhydrophobicity and microwave absorption performance was proposed based on the combination of multi-walled carbon nanotubes (MWCNTs) incorporation and hydrophobic octadecanoyl chain bonding. The entanglement and bundling of MWCNTs induced by the particularly high aspect ratio and high interaction energy renders homogeneous dispersion of MWCNTs a challenging. The durable coating adhesion of MWCNTs on hydrophilic CF remains the other challenge due to the absence of strong interactions with intrinsic hydrophobic MWCNTs. In this work, silk nanofibers (SNFs) were synthesized by degrading silk at high temperature, which was adopted as dispersant to prepare individually dispersed MWCNTs via ultrasonication and homogenization processes. The coating adhesion of MWCNTs to CF (MWCNTs-CF) was enhanced via dipping coating and thermal treatment induced chemical immobilization cycles. Octadecanoyl chain-tethered MWCNTs-CF (C18-MWCNTs-CF) was manufactured by further treatment with stearoyl chloride to achieve superhydrophobicity. The scanning and transmission electron microscopy micrographs demonstrated that the aggregates of MWCNTs were successfully de-bundled into individually dispersed nanotubes by taking advantages of the high π-π interaction and electrostatic repulsive interactions between MWCNTs and SNFs. SNFs has the superiority of chemical bonding with CF at high temperature and providing active sites for subsequent hydrophobic treatment. The electrical conductivity, surface properties, thermal stability, mechanical properties, and microwave absorption performance of the CF samples were evaluated systematically. Compared with pristine CF (1.04🞩1010 Ω), the C18-MWCNTs-CF exhibited excellent conductive property with surface resistance reaching 55 Ω when the loaded MWCNTs on CF were 247.5 mg/g in the case of 3 dipping-drying cycles and possessed a relatively greater microwave absorption performance of -36.08 dB at 9.28 GHz with merely 2.7 mm thickness. Compared with pristine CF, C18-MWCNTs-CF exhibited superhydrophobicity with the WCA increasing from 26° to 150° even after 20 scratching cycles due to the combination of facile octadecanoyl group tethering and the increased surface roughness. The biodegradable and recyclable C18-MWCNTs-CF exhibited reasonable electrical conductivity, superhydrophobicity and microwave absorption that promises an ideal application prospect in the field of smart textile and wearable electronic devices.

Tuning of Structural, Dielectric, and Electronic Properties of Cu Doped Co–Zn Ferrite Nanoparticles for Multilayer Inductor Chip Applications

Herein, we report the synthesis of nanoparticles and doping of Cu-doped Co–Zn ferrites using the auto-combustion sol–gel synthesis technique. X-ray diffraction studies confirmed the single-phase structure of the samples with space group Fd3m and crystallite size in the range of 20.57–32.69 nm. Transmission electron microscopy micrographs and selected area electron diffraction patterns confirmed the polycrystalline nature of the ferrite nanoparticles. Energy-dispersive X-ray spectroscopy revealed the elemental composition in the absence of any impurity phases. Fourier-transform infrared studies showed the presence of two prominent peaks at approximately 420 cm−1 and 580 cm−1, showing metal–oxygen stretching and the formation of ferrite composite. X-ray photoelectron spectroscopy was employed to determine the oxidation states of Fe, Co, Zn, and Cu and O vacancies based on which cationic distributions at tetrahedral and octahedral sites are proposed. Dielectric spectroscopy showed that the samples exhibit Maxwell–Wagner interfacial polarization, which decreases as the frequency of the applied field increases. The dielectric loss of the samples was less than 1, confirming that the samples can be used for the fabrication of multilayer inductor chips. The ac conductivity of the samples increased with increasing doping and with frequency, and this has been explained by the hopping model. The hysteresis loops revealed that coercivity decreases slightly with doping, while the highest saturation magnetization of 55.61 emu/g was obtained when x = 0.1. The magnetic anisotropic constant was found to be less than 0.5, which suggests that the samples exhibit uniaxial anisotropy rather than cubic anisotropy. The squareness ratio indicates that the samples are useful in high-frequency applications.

Evaluation of saponin-rich/poor leaf extract-mediated silver nanoparticles and their antifungal capacity

One-pot green synthesis of silver nanoparticles (AgNPs) has attracted much attention due to its simplicity, high feasibility in scaling up production, abundantly renewable sources, and environmental friendliness. Herein, Ocimum tenuiflorum and Phyllanthus urinaria leaf extracts (OT-ext and P.uri.ext, respectively) were chosen as reacting agents with rich and poor saponins to fabricate two biogenic AgNPs and characterize them. OT-AgNPs were simply and successfully generated by OT-ext. Ultraviolet-visible spectra showed the peak centered at 434 nm, which confirmed the presence of AgNPs after an 8-h reaction. FT-IR showed the organic functional groups (OH, C═O, C═C, CH, and COC) capping the surface of OT-AgNPs, which agreed with energy-dispersive X-ray spectroscopy analysis exhibiting the composition containing C, O, and Ag. Transmission electron microscopy micrographs revealed that OT-AgNPs possess spherical morphology, with a size range of 5–61 nm, and the majority having a small size within that range. In comparison, P.uri.AgNPs formed by P.uri.ext had a size distribution in a similar range, but the P.uri.AgNP diameter shifted toward larger sizes. Further, OT-AgNPs and P.uri.AgNPs showed an effective antifungal ability against Fusarium oxysporum, Aspergillus niger, and Aspergillus flavus. Overall, it was found that the rich saponins in the extracts lead to the formation of smaller AgNPs, but all extract-mediated AgNPs with a size less than 100 nm can act as a fungicide for various applications.

Hexagonal Nanocrystals into AlGaN Powders Obtained via Pyrolysis from an Organometallic Compound

Hexagonal nanocrystals into Al0.2Ga0.8N and Al0.6Ga0.4N powders via pyrolysis from an organometallic compound, followed by a nitridation process in ammonia flow at 1000 °C for two hours were obtained. X-ray diffraction patterns demonstrated a shift towards greater angles to the right for the AlGaN powders with respect to GaN powders, this shift could indicate the formation of the AlGaN powders. Scanning electron microscopy micrographs showed the obtaining from semi-plates of porous appearance for the Al0.2Ga0.8N powders until well-defined plates for the Al0.6Ga0.4N powders. High resolution transmission electron microscopy micrographs demonstrated the presence of hexagonal nanocrystals into Al0.2Ga0.8N powders with an average crystal size of 10.3 nm, while that for the Al0.6Ga0.4N powders an average crystal size of 9.7 nm was observed. UV-visible spectra showed a transmittance cut-off for the Al0.2Ga0.8N powders of 3.71 eV (334.2 nm) and a transmittance cut-off of 4.53 eV (273.7 nm) for the Al0.6Ga0.4N powders.

AA2219 Aluminum Alloy Processed via Multi-Axial Forging in Cryogenic and Ambient Environments

This paper presents the microstructure and the mechanical behavior of nanocrystalline AA2219 processed by multi axial forging (MAF) at ambient and cryogenic temperatures. The X-ray diffraction pattern and transmission electron microscopy micrographs in the initial microstructure characterization indicate a more effective severe plastic deformation during the cryogenic MAF than the same process conducted at room temperature. MAF at cryogenic temperature results in crystallite size reduction to nanoscales as well as second phase particles breakage to finer particles which are the crucial factors to increasing the mechanical properties of the material. Fractography analysis and tensile tests results show that cryogenic forging does not only increase the mechanical strength and toughness of the alloys significantly, but also improves the ductility of the material in comparison with the conventional forging. In this comparative regard, cryogenic processing provides 44% increase in the tensile strength of the material only after 2 forging cycles when compared to the room temperature process. In addition, further forging process to the next cycles slightly enhances the tensile strength at the expense of ductility due to less ability of the dislocations to accumulate. However, the ductility of the ambient temperature forged samples decreases at a faster rate than that of cryoforged samples.

The compatibilization effect of exfoliated graphene on rheology, morphology, and mechanical and thermal properties of immiscible polypropylene/polystyrene (PP/PS) polymer blends

In this article, the compatibilizing effect of exfoliated graphene nanoplatelets (xGnPs) on polypropylene/polystyrene (PP/PS) (80/20) blends was investigated, focusing on the rheology, morphology, and mechanical and thermal properties. Rheological analyses were shown, the addition of xGnP tends to increase the storage modulus and complex viscosity, due to the confinement of polymer chains and reducing their motion. Scanning electron microscope observation revealed that incorporation of xGnP results in obvious reduction in the domain diameter of dispersed PS phase, indicating that xGnP is an effective compatibilizer. Transmission electron microscopy micrographs showed the presence of graphene nanoparticles in the phase interface as expected. The addition of xGnP to PP/PS blend increased the tensile modulus and decreased elongation at break because of its rigidity and intrinsic mechanical characteristics. Reinforcement of flexible polymer chains with very high modulus graphene pellets leads to a more brittle and a stiffer blend. It was also shown that graphene nanoplatelets can increase crystalline part of the samples and affect the behavior of blends.

Size distribution and visible luminescence of silicon nanoparticles embedded in SiNx thin film: Role of RF power in PECVD

This paper presents, the studies of the influence of (radio frequency) RF power on the size distribution and visible photoluminescence (PL) of SiNx thin film deposited at 300[Formula: see text]C of substrate temperature by plasma enhanced chemical vapor deposition. RF power was varied (5–50[Formula: see text]W), and its aftereffect on the optical properties of thin films was investigated. By increasing the RF power between 5[Formula: see text]W and 25[Formula: see text]W, main PL peak showed a red shift with an increase in PL intensity, which is associated with an increase in the silicon nanocrystals size and density, respectively. Results obtained were confirmed with High-resolution transmission electron microscopy micrographs and from the statistical calculations. By attaining a precise RF power value, stable silicon nitride thin film with suitable optical properties can be achieved for the potential fabrication of optoelectronic devices.

Morphology control of silica/poly(methyl methacrylate-co-styrene) hybrid nanoparticles via multiple-miniemulsion approach

An appropriate approach has been used for the preparation of silica/P(MMA-co-St) hybrid nanoparticles through converting previously prepared inverse miniemulsions into a direct miniemulsion and consequently, using the droplet nucleation polymerization technique. In the early stage of the procedure, silica particles were synthesized from TEOS in the presence of NH4OH or HCl as a catalyst through a base or acid-catalyzed sol-gel process. TEOS, ethanol and tirmethoxyvinylsilan were mixed in MMA:St (50:50) to create the inverse miniemulsion I, similarly CTAB, NH4OH/HCl and distilled water were dispersed into MMA:St (50:50) and called inverse miniemulsion II. Then, the two mentioned inverse miniemulsions were emulsified in water to achieve direct miniemulsion. The nature of the catalyst and TEOS concentration varied, for the aims of investigation, their effect on the morphology and size of hybrid nanoparticles. This route provided a unique process for silica/polymer hybrid nanoparticles production, avoiding organic solvents. Transmission electron microscopy micrographs revealed that, the morphology of the hybrid nanoparticles can be controlled by the nature of the catalyst.

Quantifying Dispersion of Nanoparticles in Polymer Nanocomposites Through Transmission Electron Microscopy Micrographs

The property of nanocomposites is crucially affected by nanoparticle dispersion. Transmission electron microscopy (TEM) is the “golden standard” in nanoparticle dispersion characterization. A TEM Micrograph is a two-dimensional (2D) projection of a three-dimensional (3D) ultra-thin specimen (50–100 nm thick) along the optic axis. Existing dispersion quantification methods assume complete spatial randomness (CSR) or equivalently the homogeneous Poisson process as the distribution of the centroids of nanoparticles under which nanoparticles are randomly distributed. Under the CSR assumption, absolute magnitudes of dispersion quantification metrics are used to compare the dispersion quality across samples. However, as hard nanoparticles do not overlap in 3D, centroids of nanoparticles cannot be completely randomly distributed. In this paper, we propose to use the projection of the exact 3D hardcore process, instead of assuming CSR in 2D, to firstly account for the projection effect of a hardcore process in TEM micrographs. By employing the exact 3D hardcore process, the thickness of the ultra-thin specimen, overlooked in previous research, is identified as an important factor that quantifies how far the assumption of Poisson process in 2D deviates from the projection of a hardcore process. The paper shows that the Poisson process can only be seen as the limit of the hardcore process as the specimen thickness tends to infinity. As a result, blindly using the Poisson process with limited specimen thickness may generate misleading results. Moreover, because the specimen thickness is difficult to be accurately measured, the paper also provides robust analysis of various dispersion metrics to the error of the claimed specimen thickness. It is found that the quadrat skewness and the K-function are relatively more robust to the misspecification of the specimen thickness than other metrics. Furthermore, analysis of detection power against various clustering degrees is also conducted for these two selected robust dispersion metrics. We find that dispersion metrics based on the K-function is relatively more powerful than the quadrat skewness. Finally, an application to real TEM micrographs is used to illustrate the implementation procedures and the effectiveness of the method.