Search Results (45)

The manufacturing techniques, structural features, and optical attributes of titanium dioxide (TiO₂) nanoparticles are highlighted in this study. These nanoparticles are notable for their remarkable photocatalytic activity, cheap cost, chemical stability, and biocompatibility. TiO₂ consists of three polymorph structures: anatase, rutile, and brookite. Because of its electrical characteristics and large surface area, anatase is the most efficient for photocatalysis when exposed to UV light. The crystallinity, size, and shape of titania nanoparticles (NPs) are influenced by diverse production techniques. Sol-gel, hydrothermal, solvothermal, microwave-assisted, and green synthesis with plant extracts are examples of common methods. Different degrees of control over morphology and surface properties are possible with each approach, and these factors ultimately affect functioning. For example, microwave synthesis provides quick reaction rates, whereas sol-gel enables the creation of homogeneous nanoparticles. XRD and SEM structural investigations validate nanostructures with crystallite sizes between 15 and 70 nm. Particle size, synthesis technique, and annealing temperature all affect optical characteristics such as bandgap (3.0–3.3 eV), fluorescence emission, and UV-visible absorbance. Generally speaking, anatase has a smaller crystallite size and a greater bandgap than rutile. TiO₂ nanoparticles are used in gas sensing, food packaging, biomedical coatings, dye-sensitized solar cells (DSSCs), photocatalysis for wastewater treatment, and agriculture. Researchers are actively exploring methods like adding metals or non-metals, making new composite materials, and changing the surface to improve how well they absorb visible light. Full article

This study investigates the structural and magnetic properties of CoFe₂O₄ nanoparticles prepared by five different synthesis methods: coprecipitation, ultrasound-assisted coprecipitation, coprecipitation coupled with mechanochemical treatment, microemulsion and microwave-assisted hydrothermal synthesis. The produced powders were additionally functionalized with starch to improve biocompatibility and colloidal stability. The starch-coating procedure itself by sonication in starch solution, as well as its result, affects the structural and magnetic properties of functionalized nanoparticles. The resulting changes of properties in the process of ligand addition depend significantly on the starting nanoparticles, or rather, on the method of their synthesis. The structural, magnetic and spectroscopic properties of the resulting materials were systematically investigated using X-ray diffraction (XRD), Raman spectroscopy, Mössbauer spectroscopy and magnetic measurements. Taken together, XRD, Raman and Mössbauer spectroscopy show that starch deposition reduces structural disorder and internal stress, resulting in nanoparticles with a more uniform size distribution. These changes, in turn, affect all magnetic properties—magnetization, coercivity and magnetic anisotropy. Magnetic responses are preserved what is desirable for future biomedical applications. This work emphasizes the importance of surface modification for tailoring the properties of magnetic nanoparticles while maintaining their desired functionality. Full article

Carbon microspheres were prepared by microwave-assisted hydrothermal treatment, at 180 °C, of commercial carbohydrates (saccharose, glucose, and xylose) and xylose extract obtained from almond shells with varying synthesis parameters. When 1.6 M aqueous solutions of commercial carbohydrates were used, 2–10 μm carbon microspheres were obtained from saccharose after 15 min, while a longer amount of time (60 min) and the addition of acid medium (1% v/v H₂SO₄, 1% v/v H₃PO₄) were needed to obtain carbon microspheres from commercial xylose and glucose (≤ 1 μm). The higher reactivity of saccharose could be related to the formation, during heating, of fructose, which is more reactive than glucose and xylose. An increase in the acid concentration and in the carbohydrate concentration increased the formation and size of the microspheres. Comparative experiments with conventional heating did not produce a solid. Interestingly, when xylose extract obtained from almond shells was used, small carbon microspheres (1–3 μm) were obtained at a much lower concentration (0.2 M) and time (15 min) than with commercial xylose. This could be related to the acid medium used during extraction of xylose from the biomass. Activation of microspheres with CO₂ resulted in high-surface area materials (243–326 m²/g) with great potential as catalytic supports. Full article

This study reports the synthesis and evaluation of iron molybdate (Fe₂(MoO₄)₃) and iron tungstate (FeWO₄) as photocatalysts for the degradation of a real industrial effluent from aluminum anodizing processes under visible light irradiation. The oxides were synthesized via a co-precipitation method in an aqueous medium, followed by microwave-assisted hydrothermal treatment. Structural and morphological characterizations were performed using X-ray diffraction, field-emission scanning electron microscopy, Raman spectroscopy, ultraviolet–visible (UV–vis), and photoluminescence (PL) spectroscopies. The effluent was characterized by means of ionic chromatography, total organic carbon (TOC) analysis, physicochemical parameters (pH and conductivity), and UV–vis spectroscopy. Both materials exhibited well-crystallized structures with distinct morphologies: Fe₂(MoO₄)₃ presented well-defined exposed (001) and (110) surfaces, while FeWO₄ showed a highly porous, fluffy texture with irregularly shaped particles. In addition to morphology, both materials exhibited narrow bandgaps—2.11 eV for Fe₂(MoO₄)₃ and 2.03 eV for FeWO₄. PL analysis revealed deep defects in Fe₂(MoO₄)₃ and shallow defects in FeWO₄, which can influence the generation and lifetime of reactive oxygen species. These combined structural, electronic, and morphological features significantly affected their photocatalytic performance. TOC measurements revealed degradation efficiencies of 32.2% for Fe₂(MoO₄)₃ and 45.3% for FeWO₄ after 120 min of irradiation. The results highlight the critical role of morphology, optical properties, and defect structures in governing photocatalytic activity and reinforce the potential of these simple iron-based oxides for real wastewater treatment applications. Full article

Aquatic biomass—ranging from fish scales and crustacean shells to various algae species—offers an abundant, renewable source for carbon dot (CD) synthesis, aligning with circular economy principles. This review highlights recent studies for valorizing aquatic biomass into high-performance carbon-based nanomaterials—specifically aquatic biomass-based carbon dots (AB-CDs)—briefly summarizing green synthesis approaches (e.g., hydrothermal carbonization, pyrolysis, and microwave-assisted treatments) that minimize environmental impact. Subsequent sections highlight the varied applications of AB-CDs, particularly in biosensing (including the detection of marine biotoxins), environmental monitoring of water pollutants, and drug delivery systems. Physically AB-CDs show unique optical and physicochemical properties—tunable fluorescence, high quantum yields, enhanced sensitivity, selectivity, and surface bio-functionalization—that make them ideal for a wide array of applications. Overall, the discussion underlines the significance of this approach; indeed, transforming aquatic biomass into carbon dots can contribute to sustainable nanotechnology, offering eco-friendly solutions in sensing, environmental monitoring, and therapeutics. Finally, current challenges and future research directions are discussed to give a perspective of the potential of AB-CDs; the final aim is their integration into multifunctional, real-time monitoring and therapeutic systems—for sustainable nanotechnology innovations. Full article

This review discusses the potential of emerging technologies, as well as their integration with conventional methods, to optimize the extraction of lignocellulosic compounds from cocoa pod hull (CPH), an agro-industrial residue that represents approximately 76% of the total weight of the fruit. CPH is primarily composed of cellulose, hemicellulose, lignin, and pectin. Emerging technologies such as microwave-assisted extraction, hydrothermal treatment, subcritical water, ionic liquids, deep eutectic solvents, and ultrasound treatment have proven effective in recovering value-added compounds, especially when combined with conventional techniques to improve process efficiency. Furthermore, the use of technologies such as high-voltage electric discharge (HVED) is proposed to reduce inorganic contaminants, such as cadmium, ensuring the safety of by-products. The CPH compounds’ applications include use in the food, pharmaceutical, cosmetics, agricultural, biopolymer, and environmental industries. The conversion of CPH to biochar and biofuels via pyrolysis and supercritical extraction is also discussed. The integration of technologies presents an opportunity to valorize CPH and optimize by-product development; however, as research continues, process scalability and economic viability must be assessed. Full article

This article provides an overview of various microwave-assisted techniques, such as microwave-assisted extraction (MAE), microwave-assisted organic synthesis (MAOS), microwave-assisted pyrolysis (MAP), microwave-assisted hydrothermal treatment (MAHT), microwave-assisted acid hydrolysis (MAAH), microwave-assisted organosolv (MAO), microwave-assisted alkaline hydrolysis (MAA), microwave-assisted enzymatic hydrolysis (MAEH), and microwave-assisted fermentation (MAF). Microwave-assisted biomass pretreatment has emerged as a promising method to improve the efficiency of biomass conversion processes, in particular microwave-assisted pyrolysis (MAP). The focus is on microwave-assisted pyrolysis, detailing its key components, including microwave sources, applicators, feedstock characteristics, absorbers, collection systems, and reactor designs. Based on different studies reported in the literature and a mathematical model, a mechanical design of a microwave oven adapted for pyrolysis is proposed together with a computer-aided design and a finite element analysis. The semi-continuous system is designed for a 40 L capacity and a power of 800 W. The material with which the vessel was designed is suitable for the proposed process. The challenges, opportunities, and future directions of microwave-assisted technologies for the sustainable use of biomass resources are presented. Full article

Hydrothermal carbonization (HTC) is a novel thermochemical process that turns biomass into hydrochar, a substance rich in carbon that has potential uses in advanced material synthesis, energy production, and environmental remediation. With an emphasis on important chemical pathways, such as dehydration, decarboxylation, and polymerization, that control the conversion of lignocellulosic biomass into useful hydrochar, this review critically investigates the fundamental chemistry of HTC. A detailed analysis is conducted on the effects of process variables on the physicochemical characteristics of hydrochar, including temperature, pressure, biomass composition, water ratio, and residence time. Particular focus is placed on new developments in HTC technology that improve sustainability and efficiency, like recirculating process water and microwave-assisted co-hydrothermal carbonization. Furthermore, the improvement of adsorption capacity for organic contaminants and heavy metals is explored in relation to the functionalization and chemical activation of hydrochar, namely through surface modification and KOH treatment. The performance of hydrochar and biochar in adsorption, catalysis, and energy storage is compared, emphasizing the unique benefits and difficulties of each substance. Although hydrochar has a comparatively high higher heating value (HHV) and can be a good substitute for coal, issues with reactor design, process scalability, and secondary waste management continue to limit its widespread use. In order to maximize HTC as a sustainable and profitable avenue for biomass valorization, this study addresses critical research gaps and future initiatives. Full article

This study investigated the influence of chemical reagent selection on the properties of ZnO nanoparticles synthesized using the microwave-assisted hydrothermal method to control the intensities of near-band-edge (NBE) and defect-related deep-level (DLE) emissions. Two zinc precursors—zinc nitrate and zinc chloride—along with three different precipitating agents (NaOH, KOH, and NH₄OH) were used. ZnO nanoparticles from the ZnCl₂ precursor exhibited two orders of magnitude higher NBE/DLE intensity ratio compared to those obtained from zinc nitrate characterized by a higher contribution from defect-related emissions. Chlorine ions in ZnO nanoparticles play a key role in passivating defects by forming V₀-Cl₂ complexes, quenching luminescence associated with oxygen vacancies (V₀). Thermal treatment in a nitrogen atmosphere enhanced defect-related luminescence, possibly due to chlorine atom diffusion. This study highlights a successful synthesis of ZnO nanoparticles with low defect-related luminescence (DLE) achieved via the microwave-assisted hydrothermal method, a result rarely reported in the literature. The results emphasize the importance of reagent selection in controlling the morphology and optical properties, especially the defect density of ZnO nanoparticles. Optimizing these properties is crucial for biomedical applications such as bioimaging, antibacterial treatments, and photocatalysis. Full article

Green chemistry seeks to find alternative synthesis routes that are less harsh to living organisms and the environment. In this communication, a microwave-assisted hydrothermal technique and a thermal annealing method were used in the reduction of graphene oxide (GO) to make reduced GO (rGO). Graphite powder was oxidised using the Improved Hummers’ method, exfoliated, and freeze-dried. Thereafter, an aqueous suspension of GO was reduced under microwave (MW) irradiation for 10 min at 600 W with and without the help of a reducing agent (hydrazine hydrate). Thermal annealing reduction was also conducted under a nitrogen atmosphere at 300 °C for 1 h. Prepared samples were analysed using Raman laser spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), the Brunauer–Emmett–Teller (BET) method, and X-ray photoelectron spectroscopy (XPS). A successful reduction in the GO functional groups between the sheets was established using XRD. In the Raman analysis, the ratio of the intensity of the D and G band (I_D/I_G) in graphene sheets assisted in assessing the quality of the graphene films. An estimation of the number of structural defects was calculated using the I_D/I_G ratio. The Raman analysis showed an increase in the I_D/I_G ratio after both oxidation and reduction processes. The defect densities of both MW-treated samples were comparable while an increased defect density was evident in the thermally annealed sample. TEM micrographs confirmed the sheet-like morphology of the samples. The rGO sheets obtained from the MW-treated method appeared to be smaller when compared to the rGO ones obtained by thermal treatment. It was also evident from XRD analysis that thermal treatment promoted the coalition of graphitic layers, such that the estimated number of layers was larger than that of GO. The elemental analysis showed that the C/O ratio of GO increased from 2 to 7.8 after MW hydrazine reduction. Full article

Novel AB-Polybenzimidazole (AB-PBI)/TiO₂ nanocomposite membranes have been prepared using a synthetic green chemistry approach. Modified Eaton’s reagent (methansulfonic acid/P₂O₅) was used as both reaction media for microwave-assisted synthesis of AB-PBI and as an efficient dispersant of partially agglomerated titanium dioxide powders. Composite membranes of 80 µm thickness have been prepared by a film casting approach involving subsequent anti-solvent inversion in order to obtain porous composite membranes possessing high sorption capacity. The maximal TiO₂ filler content achieved was 20 wt.% TiO₂ nanoparticles (NPs). Titania particles were green synthesized (using a different content of Mentha Spicata (MS) aqueous extract) by hydrothermal activation (150 °C), followed by thermal treatment at 400 °C. The various methods such as powder X-ray diffraction and Thermogravimetric analyses, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Energy-dispersive X-ray spectroscopy, Electronic paramagnetic resonance, Scanning Electron Microscopy and Transmission Electron Microscopy have been used to study the phase and surface composition, structure, morphology, and thermal behavior of the synthesized nanocomposite membranes. The photocatalytic ability of the so-prepared AB-Polybenzimidazole/bio-TiO₂ membranes was studied for decolorization of Reactive Black 5 (RB5) as a model azo dye pollutant under UV light illumination. The polymer membrane in basic form, containing TiO₂ particles, was obtained with a 40 mL quantity of the MS extract, exhibiting the highest decolorization rate (96%) after 180 min of UV irradiation. The so-prepared AB-Polybenzimidazole/TiO₂ samples have a powerful antibacterial effect on E. coli when irradiated by UV light. Full article

This study investigates the potential of converting waste biosolids from industrial sources, focusing on economic viability and heavy metal removal efficiency. Traditional management methods like landfilling and incineration are increasingly impractical due to land constraints and environmental concerns, prompting a shift towards thermal and biological conversion technologies including anaerobic digestion, pyrolysis, gasification, and hydrothermal liquefaction. Incorporating a pretreatment for heavy metal removal is essential, as industrial wastes are highly subjected to metal contamination. The study screens a range of metal removal processes, including precipitation, adsorption, ion exchange, and microwave induction. Although a techno-economic analysis can help give a perspective on the economic viability and environmental impact of each technology, it does not account for technical limitations and variations in the treated waste stream. A mixed integer linear programming (MILP) optimization model is developed to fill in this gap and assist in waste stream allocation to the most appropriate technology, taking into account both technology capacities and feed characteristics. This study looked into the optimal treatment route at different feed moisture contents and varying flow rates. The results demonstrate that the model distributes the feed across the different technologies on the basis of maximizing the capacity of the optimal technology while ensuring the moisture and heavy metal content limits are satisfied. Thus, it maximizes profitability and ensures heavy metal removal efficiency. By optimizing industrial biosolids treatment pathways, this study promotes sustainable resource recovery aligning with circular economy principles in waste management. The developed model facilitates informed decision-making in biosolids management and industrial waste treatment practices. Full article

Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly dispersive Co/MPC material. Characterization results indicated that Co nanoparticles were wrapped by thin carbon layers and uniformly dispersed on a carbon-based skeleton via a microwave-assisted hydrothermal synthesis approach, providing high-activity space. Thus, the prepared material was limited to glassy carbon; on the electrode surface, a cobalt-based sensing platform (Co/MPC/GCE) was built. On the basis of this constructed sensing platform, a linear equation was fitted by the concentration change of current signal I and H₂O₂. The linear range was 0.55–100.05 mM; the detection limit was 1.38 μM (S/N = 3); and the sensitivity was 103.45 μA cm⁻² mM⁻¹. In addition, the effect this sensor had on H₂O₂ detection of actual water samples was conducted by using a standard addition recovery method; results disclosed that the recovery rate and RSD of H₂O₂ in tap water samples were 94.0–97.6% and 4.1–6.5%, respectively. Full article

In this work, a series of thermosensitive ionic liquid functionalized polymers, PN_x(IL)_y, with controllable morphology and particle size were prepared by free radical polymerization. Then, using the polymer PN₆₄(IL)₈ with uniform morphology as a templating agent, the ZnO composite photocatalytic materials doped with rare earth metal Ce were prepared in combination with a microwave-assisted and templated hydrothermal reaction method. Series different Ce-doping amount photocatalytic materials ZnO-Ce-x‰ were characterized by XRD, SEM, TEM, XPS, and other methods. The results demonstrated that the templated materials PN₆₄(IL)₈ can prepare ZnO-Ce-2‰ with uniform petaloid ambulacra shape, good distribution of elements, and excellent photocatalytic performance. Photocatalytic degradation experiments of methyl orange (MO) showed that when the Ce-doping amount is only 2‰, the degradation rate of organic dyes can reach 96.5% by reacting the photocatalytic materials in water for 1 h. In addition, this kind of photocatalyst can be used for the degradation of high-concentration MO, as well as being easily recovered and effectively reused by simple filtration. Therefore, the structure of this kind of photocatalyst is controllable in the preparation process with an extremely low Ce-doping amount compared with current reports, and it has a good application prospect in the field of wastewater treatment technology. Full article

This research examines the structural and magnetic properties of monodomain cobalt ferrite nanoparticles with the formula (Co_1−xFe_x)^A[Fe_2−xCo_x]^BO₄. The particles were synthesized using various methods, including coprecipitation (with and without ultrasonic assistance), coprecipitation followed by mechanochemical treatment, microemulsion, and microwave-assisted hydrothermal techniques. The resulting materials were extensively analyzed using X-ray diffraction (XRD) and magnetic measurements to investigate how different synthesis methods affect the structure and cation distribution in nanoscale CoFe₂O₄. For particles ranging from 15.8 to 19.0 nm in size, the coercivity showed a near-linear increase from 302 Oe to 1195 Oe as particle size increased. Saturation magnetization values fell between 62.6 emu g⁻¹ and 74.3 emu g⁻¹, primarily influenced by the inversion coefficient x (0.58–0.85). XRD analysis revealed that as the larger Co²⁺ cations migrate from B- to A-sites (decreasing x), the lattice constants and inter-cation hopping distances increase, while the average strength of super-exchange interactions decreases. This study establishes a connection between the magnetic properties of the synthesized samples and their structural features. Importantly, this research demonstrates that careful selection of the synthesis method can be used to control the magnetic properties of these nanoparticles. Full article