ZnO nanoparticles were produced through green synthesis using essential oils (lavender or thyme oils) mediated by Pluronic-assisted co-precipitation, followed by calcination at 500 °C. One part of the particles was doped with Pr₂O₃ (0.3-1 at.% ).

PXRD analysis, FTIR spectroscopy, SEM, EDS, and XPS were performed to determine the phase and chemical composition, structure, morphology [1], specific surface area, and textural characteristics of the samples.

The antimicrobial activity of the nanoparticles was tested on six Gram (-) (Aeromonas caviae, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enterica) and four Gram (+) bacterial species: Erysipelothrix rhusiopathiae, Bacillus subtilis, Bacillus cereus, Oerskovia paurometabola. The minimum inhibitory concentrations (MICs) of the materials against the test microorganisms were determined by the microdilution broth method.

The average MIC value is lowest for non-doped lavender-produced ZnO. The non-doped particles have a better effect than the doped ones. Among them, the Pr-doped sample, obtained with thyme essential oil, has the weakest effect. This may be due to the significantly larger atomic mass of praseodymium, which reduces the relative share of zinc oxide, the source of the antimicrobial effect. It is observed that MICs are higher in bacteria that have pathogenic potential. We assume that this effect is due to their better antioxidant protection, as it is a factor in the successful infection of the host, and the antimicrobial effect of metal oxide nanoparticles is due precisely to their ability to generate oxidative radicals.

Acknowledgments: Thanks the Bulgarian National Science Fund, KP-06-N69/8 (КП-06-Н69/8), “Novel polymer-hybrid materials containing (bio)synthesized metal oxide particles with improved photocatalytic and antimicrobial potential”, for the financial support and technical support from the project PERIMED BG05M2OP001-1.002-0005.

References

1. Ş. Ţălu, Micro and nanoscale characterization of three-dimensional surfaces. Basics and applications. Napoca Star Publishing House, Cluj-Napoca, Romania, 2015.

Nanostructured semiconductors have emerged as transformative materials for enhancing the efficiency of waste heat-to-electricity conversion through thermoelectric (TE) processes. By altering structural features at the nanoscale, these materials can simultaneously reduce lattice thermal conductivity and optimize electronic transport properties, thereby significantly improving the thermoelectric figure of merit (ZT). Recent studies have demonstrated that introducing periodic twin planes in III-V semiconductor nanowires can achieve a tenfold reduction in thermal conductivity while maintaining excellent electrical performance. Similarly, Pb₁₋ₓGeₓTe alloys, through controlled spinodal decomposition, form stable nanostructures that maintain low thermal conductivity even after undergoing thermal cycling, which is crucial for high-temperature applications. Enhancing electrical properties is another key advantage of nanostructuring. PbTe-based materials, when heavily doped and engineered with nanoscale inclusions, have achieved a ZT of approximately 1.9 and a thermoelectric efficiency of around 12% over a 590 K temperature difference. Single-walled carbon nanotubes (SWCNTs) exhibit strong correlations between their electronic structure and thermoelectric conductivity, highlighting their potential for next-generation devices. Two-dimensional silicon–germanium (SiₓGeᵧ) compounds offer ultra-low lattice thermal conductivity and high Seebeck coefficients, providing a promising pathway for future TE applications. Despite these advancements, challenges remain, particularly regarding scalability and integration into existing energy recovery systems. Techniques such as focused ion beam milling and solution-based synthesis of porous nanostructures are being developed to fabricate high-performance materials on a commercial scale. Moreover, integrating nanostructured semiconductors into real-world systems, such as automotive exhaust heat recovery units, requires improvements in material durability, fabrication efficiency, and device compatibility. In conclusion, nanostructured semiconductors offer a powerful route for enhancing waste heat-to-electricity conversion. Their ability to decouple electrical and thermal transport at the nanoscale opens new opportunities for high-efficiency, sustainable energy harvesting technologies. Continued research into scalable manufacturing techniques, material stability, and system integration is essential to fully unlock their potential for commercial thermoelectric applications

Two-dimensional nanomaterials have become one of the most extensively studied subfields in nanoscience, with particular interest in transition metal dichalcogenides (TMDs). Transition metal dichalcogenides (TMDCs) are a class of layered materials that exhibit highly interesting electronic and photonic properties. Exfoliation methods that combine chemical and physical processes have emerged as efficient techniques to produce two-dimensional materials, such as molybdenum disulfide (MoS₂). These methods exploit the interaction between electromagnetic radiation and polar molecules within the material, generating localized and rapid heating that facilitates the separation of layers. In this study, we employed microwave-assisted chemical exfoliation to delaminate MoS₂ using various solvent combinations with acetone, water, and 1,4-butanediol. The selection of solvents was guided by Hansen Solubility Parameters, allowing us to predict the most suitable systems for effective exfoliation. Mixtures of acetone, water, and butanodiol were identified as optimal based on their thermodynamic compatibility with MoS₂. The exfoliation process was evaluated via X-ray diffraction (XRD) and Raman spectroscopy, which confirmed the preservation of the crystalline structure along with increased interlayer spacing, indicative of successful delamination. Furthermore, morphological analysis using scanning electron microscopy (SEM) supported the presence of thin, exfoliated layers. These findings suggest that microwave-assisted exfoliation using tailored solvent systems is a promising approach for producing MoS₂ nanomaterials.

MXene has been widely evaluated as a 2D reinforcement in polymer-based composites due to its large specific surface area, abundant surface chemical bonding sites, and robust layer bonding. However, when considering the polymer-based solid lubricant, MXene not only displays crucial roles in the aspects of mechanical properties but also contributes to the frictional processes. Particularly, unlike traditional van der Waals crystals (graphite, MoS₂, etc.), MXene nanoflakes have much stronger interlayer interactions. Therefore, the detailed mechanism of MXene on self-lubricating and anti-wear performances must be clarified. Herein, by introducing Ti₃C₂T_x MXene in a poly(ether-ether-ketone) (PEEK) and poly(tetrafluoroethylene) (PTFE) composites, a series of composites with different component ratios are prepared, and their self-lubricating performance is evaluated under dry-sliding conditions. The positive role of Ti₃C₂T_x nanoflakes on tribofilm formation is probed, which includes improving the interfacial bonding between the polymer grains, enhancing the adhesion of PTFE chains on the counterpart ZrO₂ balls, and dispersing the stress on counter surfaces during friction. Eventually, MXene-reinforced PEEK-based composites display both a lower coefficient of friction and a lower wear rate than the previously reported PEEK-PTFE composites, which exhibit comparable self-lubricating performance to pure PTFE and a tensile strength of over 100 MPa. The current studies illuminate the crucial roles of MXene in PEEK-based solid lubricants and pave the way for theconstruction of novel solid lubricants as well.

Introduction: In the food industry, the growing demand for sustainable food packaging has drawn attention towards active biodegradable forms of food packaging. In the presented work, alginate-based films incorporating zinc oxide nanoparticles (ZnO NPs) were prepared and evaluated for extending the shelf life of packed black grapes.

Methodology: ZnO NPs were biosynthesized using a green microalgae strain, Dictyosphaerium HSM, isolated and identified via ITS sequencing. Synthesis was confirmed through UV-Vis, FTIR, XRD, and TGA, revealing hexagonal nanoparticles (<100 nm) via SEM and AFM. Alginate–ZnO films with different ZnO ratios were prepared via solvent casting. XRD and SEM analysis confirmed uniform NP distribution and surface morphology.

Results: The ZnO NPs exhibited strong antibacterial, antifungal, and antibiofilm effects and minimal cytotoxic effects. Mechanical testing showed enhanced tensile strength, reduced moisture content, and increased hydrophobicity. Antimicrobial and antibiofilm activities were evaluated using disc diffusion and SEM, using E. coli as a model organism. The films significantly lessened the microbial load on inoculated grapes, extending their shelf life from 7 to 9 days at room temperature.

Conclusion: These findings strongly indicate the potential of alginate–ZnO nanocomposite films as active, eco-friendly food packaging materials able to reduce the spoilage caused by microbial contamination. Their antimicrobial potential and their enhanced mechanical characteristics make them an effective solution for the long-term preservation of food.

Hexagonal boron nitride (h-BN) is a material of outstanding interest because of its exceptional properties and diverse applications across various fields, including electronics, optoelectronics, and quantum technologies.

Theoretical investigations of h-BN have involved advanced numerical methodologies, including the density functional theory (DFT), which allow us to computationally address material's properties, such as its thermal and electrical conductivity, stability, and electronic structure.

In particular, h-BN in its 2D monolayer form has emerged as a promising emitter of quantum light due to its optical, chemical, thermal, and fabrication properties. Its emission spectrum spans from ultraviolet to infrared wavelengths, making it a compelling subject for investigating photon emission properties toward applications in quantum computing, quantum crystallography, and quantum metrology.

An important aspect of material characterization involves understanding the role of defects in a crystalline structure. From a theoretical point of view, this is typically studied using the supercell method, which has a high computational cost, especially as the system complexity increases. To address these challenges, we explore an alternative approach which can achieve small substitutions using Virtual Crystal Approximation (VCA). By incorporating virtual atoms into DFT calculations, VCA provides results comparable to those obtained with the supercell method, but at a significantly reduced computational cost.

By combining VCA with the simple approach used to identify hydrogenoid defects, we obtain the band structure of slightly carbon-doped h-BN and determine how the monolayer emission can be significantly changed. This underscores the versatility of h-BN as a photon emitter for multiple applications, highlighting its importance in the current landscape of emerging quantum technologies.

Perovskite solar cells (PSCs) have garnered significant attention in recent years due to their remarkable optoelectronic properties and promising potential in next-generation photovoltaic technologies. Despite rapid advancements in device design and fabrication, challenges related to long-term stability, charge transport, and overall power conversion efficiency persist. Addressing these limitations requires the development of efficient and stable charge transport layers. In this study, we present a comprehensive experimental and numerical investigation of a novel twin carbazole-based hole transport material (HTM) integrated into a perovskite solar cell structure. The SCAPS-1D simulation tool was employed to model the device architecture and systematically optimize the thickness and configuration of each layer. Experimental characterization revealed that the twin HTM exhibits strong optical absorption in the ultraviolet region, which is particularly advantageous for broad-spectrum solar harvesting. Additionally, the optical band gap was determined using the Tauc plot method, confirming its suitability for photovoltaic applications. Numerical results further confirmed the excellent charge transport capability and energetic alignment of the material with the perovskite absorber layer. The integration of this HTM also demonstrated the potential to enhance photovoltaic performance while maintaining material and processing cost-efficiency. Overall, the findings of this work emphasize the relevance of carbazole-based twin HTMs as promising candidates for high-performance, stable, and low-cost perovskite solar cell technologies.

Metal mirrors fabricated from aluminium, beryllium, and similar alloys offer significant advantages, including ease of forming, high lightweighting potential, and integrated optical–mechanical properties, making them highly promising for optical systems in airborne detection, space astronomy, earth observation, and deep-space navigation. However, as these applications increasingly demand operation at visible, ultraviolet, and even X-ray wavelengths, the required surface figure accuracy and surface quality become exceptionally stringent. This presents a critical challenge because aluminium and beryllium substrates are inherently sensitive to machining damage, and directly machined surfaces typically fail to meet the demanding specifications of short-wavelength optical systems. To overcome this limitation, a common approach employs aluminum or beryllium substrates coated with a thick (tens to hundreds of microns) Nickel-Phosphorus (NiP) layer applied via electroless nickel plating. The NiP layer provides a dense, corrosion-resistant, ductile, and highly machinable surface modification. While ultra-precision turning is the standard method for machining NiP-coated mirrors, its achievable accuracy is fundamentally limited by the machine tool's "error replication principle," limiting its suitability for the most demanding short-wavelength applications. This study addresses this gap by introducing a novel sequential machining process: ultra-precision turning followed by magnetorheological polishing (MRF) and concluding with smoothing polishing. This combined approach leverages MRF to significantly enhance the surface figure accuracy initially achieved by turning. The subsequent smoothing and polishing step then refines the surface quality, effectively reducing roughness and micro-defects. Consequently, this integrated turning and polishing strategy demonstrably improves both the form accuracy and surface finish quality of NiP-coated metal mirrors, enabling their successful application in high-performance optical systems operating at short wavelengths.

Polymers are used in many industrial areas due to their longevity and inexpensive production, as well as their many advantageous physical and chemical properties. The low recycling rate of polymers, however, makes them harmful to the environment. Biopolymers from renewable raw materials are a sustainable alternative to polymers from finite raw materials, such as crude oil. Such biopolymers are CO₂-neutral and can be bio-degradable. On the other hand, their mechanical properties are often inferior in comparison with those of crude oil-based polymers.

In our work, we prepared biopolymer films from potato starch, corn starch, chitosan, and casein. The wet thickness of the films was optimized to enable them to be detached from the glass substrate without damage. Both starch films were found to be more elastic and stretchable than the chitosan and casein films. The casein film was more stable than the chitosan film, which showed small air cavities during drying.

Afterwards, all biopolymer films were coated by electrospinning. To achieve this, the wire-based electrospinning machine “Nanospider Lab” (Elmarco) was used. Spinning solutions were prepared from 16% poly(acrylonitrile) in dimethyl sulfoxide (DMSO). Electrospinning of the films was performed for 30 min under optimized conditions. The nanofibrous mats adhered well to the biopolymer films during electrospinning, but could be mechanically separated afterwards.

A universal testing machine was used for the mechanical tests. Although nanofiber mats usually do not have very good mechanical properties, the composites made with biopolymer and nanofibrous coatings showed significantly improved tensile strength, as compared to the pure biopolymer, for all materials under investigation. The results of this project can be used to prepare biopolymer films with significantly improved mechanical properties, e.g., for packaging applications or wound dressings.

Metal oxide nanomaterials have emerged as transformative materials in the quest to enhance the energy density and overall performance of lithium-ion batteries (LIBs) and solid-state batteries (SSBs). Their unique properties—high surface areas and short ion diffusion pathways—make them ideal for next-generation energy storage technologies. In LIBs, the high surface-to-volume ratio of metal oxide nanomaterials significantly enlarges the active interfacial area and shortens the lithium-ion diffusion paths, leading to an improved high-rate performance and enhanced energy density. Transition metal oxides (TMOs) such as nickel oxide (NiO), copper oxide (CuO), and zinc oxide (ZnO) have demonstrated high theoretical capacities, while binary systems like NiCuO offer further improvements in the cycling stability and energy output. Additionally, layered lithium-based TMOs, particularly those incorporating nickel, cobalt, and manganese, have shown remarkable promise in achieving high specific capacities and long-term stability. The synergistic integration of metal oxides with carbon-based nanostructures, such as carbon nanotubes (CNTs), enhances the electrical conductivity and structural durability further, leading to a superior electrochemical performance in LIBs. In SSBs, the use of oxide-based solid electrolytes like garnet-type Li₇La₃Zr₂O₁₂ (LLZO) and sulfide-based electrolytes has facilitated the development of high-energy-density systems with excellent ionic conductivity and chemical stability. However, challenges such as high interfacial resistance at the electrode–electrolyte interface persist. Strategies like the application of lithium niobate (LiNbO₃) coatings have been employed to enhance the interfacial stability and maintain electrochemical integrity. Furthermore, two-dimensional (2D) metal oxide nanomaterials, owing to their high active surface areas and rapid ion transport, have demonstrated considerable potential to boost the performance of SSBs. Despite these advancements, several challenges remain. Morphological optimization of nanomaterials, improved interface engineering to reduce the interfacial resistance, and solutions to address dendrite formation and mechanical degradation are critical to achieving the full potential of these materials.