Challenges in Nano and Micro Scale Science and Technology
Volume:13 Issue: 1, Winter-Spring 2025

The direct conversion of wasted mechanical energy into electrical energy is of significant interest, both from an environmental perspective and for applications such as self-powered sensors and electrical circuits in wireless networks. A power generator based on the reverse electrowetting concept has recently been introduced and extensively studied by researchers. A detailed understanding of the influence of design parameters on device performance is essential for further advancement. Accordingly, a reverse electrowetting-on-dielectric (REWOD) has been designed and mathematically modeled. The variable capacitance model is employed, and a numerical code has been developed to simulate the nanogenerator under diverse configurations and operating conditions. A comparison between the numerical results and those reported in the literature has been conducted to validate the simulations. The effects of parameters including dielectric thickness, bias voltage, frequency of mechanical motion, and external load resistance on the performance of the reverse electrowetting nanogenerator are systematically investigated and discussed. We acknowledge that reducing the dielectric layer thickness from 10−4 to 10−6 significantly enhances device performance, as the output power increases by approximately a factor of 40. Results indicate that increasing the bias voltage amplifies the induced electric field, thereby enhancing water droplet polarization. Furthermore, the nanogenerator’s power output is shown to increase with both bias voltage and the frequency of mechanical motion.

Hybrid nanomaterials combining metals with fullerene provide unique synergistic properties, enabling the development of a new generation of advanced materials. This study reports the green synthesis and comprehensive characterization of a novel core-shell hybrid nanomaterial composed of silver nanoparticles (Ag NPs) encapsulated within a fullerene-citric acid (FCA) nanocomposite matrix. The FCA nanocomposite was first synthesized via two distinct pathways: a conventional thermal method and a greener enzymatic approach utilizing Novozym 435. This FCA product served a dual function as both a reducing agent and a stabilizer in the subsequent synthesis of silver nanoparticles from silver nitrate. Successful formation of the ester bond in FCA was confirmed by FT-IR spectroscopy, showing a characteristic peak around 1730 cm⁻¹. UV-Vis spectroscopy of the final hybrid revealed two key absorption peaks, one at ~268 nm corresponding to the π-π* transitions of the fullerene moiety and a distinct surface plasmon resonance (SPR) band at ~423 nm, confirming the formation of Ag NPs. Electron microscopy (FESEM and TEM) analysis demonstrated spherical nanoparticles with an average size of approximately 25 nm and provided clear evidence of the core-shell structure, where Ag NPs form the core surrounded by the FCA shell. The presented methodology offers an efficient route to stable fullerene-metal hybrid nanostructures with potential for advanced applications in catalysis, sensing, and biomedicine.

The increasing demand for sustainable and functional food packaging materials has stimulated research into biodegradable polymers reinforced with active compounds. This study addresses this need by developing a novel polylactic acid (1)-based film combined with green-method synthesized iron nanoparticles (using Artemisia absinthium extract) and nanochitosan to create an active packaging material with enhanced antibacterial and antioxidant properties. A biodegradable food packaging film was developed using polylactic acid, nanochitosan, and iron nanoparticles synthesized via a green-method using Artemisia absinthium (wormwood) extract. The main objective was to create a material with antibacterial and antioxidant properties to extend the shelf life of food products. Iron nanoparticles were synthesized using the extract and FeCl₃·6H₂O and then coated with chitosan. The films were produced by solvent casting and their properties were investigated. The results showed that the antibacterial and antioxidant capabilities were significantly improved by adding the extract and nanoparticles. The film containing 5% extract showed optimal flexibility and antibacterial performance. The DPPH radical scavenging activity increased with increasing extract concentration and the films showed strong inhibition against S. aureus and E. coli. The films had lower water vapor permeability, average thickness of 0.089 ± 0.01 cm, moisture content of 65.61 ± 3.84% and solubility of 18.09 ± 2.51% indicating good stability. SEM, FTIR and XRD confirmed the successful synthesis and incorporation of nanoparticles. The greenness of the method was evaluated using AGREEprep software and scored 0.8, indicating high environmental compatibility.

In this study, a walnut shell-derived Graphene based TiO₂ nanocomposite was successfully synthesized and applied for the photocatalytic degradation of Reactive Red 198 dye in aqueous solutions. The nanocomposite was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR), confirming its crystalline structure, high surface area, and effective functionalization. The effects of catalyst dose, H₂O₂ concentration, reaction time, and initial pH on dye removal efficiency were systematically investigated using Response Surface Methodology (RSM). The results indicated that the optimal conditions acidic pH, higher catalyst dosage, sufficient H₂O₂ concentration, and prolonged reaction time achieved the maximum dye removal efficiency of 83%. Numerical optimization and RSM modeling provided reliable predictions of process performance, demonstrating the potential of this green, biomass-derived nanocomposite as an efficient and sustainable photocatalyst for wastewater treatment.Numerical optimization and RSM modeling provided reliable predictions of process performance, demonstrating the potential of this green, biomass-derived nanocomposite as an efficient and sustainable photocatalyst for wastewater treatment.

The interesting subject of gas nanobubbles has attracted great attention of many scientists due to their extraordinary and “mysterious” properties. Nanobubbles are a scientific challenge due to their special properties such as very small size, very large surface-to-volume ratio, high internal pressure, rapid adhesion to hydrophobic surfaces, and long-term stability on a time scale. Due to these unique properties, diverse applications of nanobubbles have been developed in many fields of science and technology such as chemical, biological, materials, and medical industries. Despite theoretical considerations that predict that spherical gas bubbles cannot reach stable equilibrium, various experiments demonstrate the existence of stable nanobubbles which can be survived during several hours or even days. Can it be proven that nanobubbles exist and, if so, how can they survive? Given the importance and variety of applications of nanobubbles, it is essential to review recent advances in nanobubbles and their stability mechanisms. This article summarizes the latest scientific studies on the properties of nanobubbles. We believe that the results of this study will help researchers to understand nanobubbles better and more deeply and pave the way for future studies by researchers.

Metal oxides based on cerium structures have become the focus on new functional materials due to their good electrical, optical and other properties. In the present study, a simple method based on green chemistry has used for the synthesis of cerium nanostructures. For achieving the purpose, barberry extract has applied for the synthesis of the nanostructures. Then, various techniques were used to characterize the synthesized nanostructures. Therefore, at first Fourier transform infrared (FT-IR) spectroscopy was used for initial characterization. Then, the structural characterization was accomplished by X-ray diffraction spectroscopy (XRD) technique. Also, morphologic studies was investigated by field emission scanning electron microscopy (FE-SEM). In following the effect of barberry extract on the nanostructures properties was accomplished using electrochemical experiments. The data showed the presence of extracts in the synthesis route can be create an enhanced properties in the synthesized nanostructures. The data showed the presence of extracts in the synthesis route can be create an enhanced properties in the synthesized nanostructures.