Search Results (102)

Electroanalysis of monoamine neurotransmitters is a useful tool for monitoring relevant neurodegenerative disorders and diseases. Electroanalysis of neurotransmitters using analytical devices consisting of electrodes modified with tailored and nanostructured composite materials is an active research topic nowadays. Nano- and microstructured composite materials composed of various organic conductive polymers, metal/metal oxide nanoparticles, and carbonaceous materials enable an increase in the performance of electroanalytical sensing devices. Synergistic properties resulting from the combination of various pristine nanomaterials have enabled faster kinetics and increased overall performance. Herein, recent results related to the design and elaboration of electroanalytical sensing devices based on cost-effective and reliable nano- and microstructured composite materials for the quantification of monoamine neurotransmitters are presented. The discussion focuses on the fabrication procedures and detection strategies, highlighting the capabilities of the analytical platforms used in the determination of relevant analytes. The review aims to present the main benefits of using composite nanostructured materials in the electroanalysis of monoamine neurotransmitters. Full article

Semicrystalline polystyrene spheroidal nanoparticles (50–100 nm) were obtained via microemulsion polymerization. They were evaluated as coal collectors in a low-rank carbonaceous mineral containing 2% organic carbon. The recovery of coal using nanoparticles as collectors was 88.2%, in contrast to 53.2%, 46.4%, and 44.8% achieved using an amine-type compound, kerosene, and diesel, respectively. X-ray photoelectron spectroscopy (XPS) and zeta potential measurements confirmed the polystyrene–mineral surface chemical interaction. A Box–Behnken experimental design for flotation optimization was applied, and the results showed that the coal recovery increased up to 99.5% when the dosage of the collector was increased. A contact angle study and density functional theory calculations, together with XPS results, allowed us to postulate an interaction mechanism in which polystyrene nanoparticles adsorb onto the coal surface through hydrophobic interactions, rendering the oxidized surface hydrophobic and the coal buoyant by adhering to the gas bubbles. Full article

Biochar, a carbonaceous material derived from biomass, has garnered significant attention for its biomedical applications due to its unique physicochemical properties. Recent advances in functionalized and composite biochar materials have enabled their use in antibacterial and anticancer treatments, as well as biosensing technologies. This review highlights recent advances in the use of biochar for antimicrobial, anticancer, and biosensing applications. Derived from plant-, marine-, or animal-based biomass through pyrolysis, biochar can be functionalized with silver nanoparticles, metal oxides, or polymers to enhance its antimicrobial activity. In anticancer research, biochar demonstrates the ability to inhibit cancer cell proliferation, modulate the cell cycle, and deliver targeted therapeutics, showing selective cytotoxicity against specific cancer cell types. Furthermore, biochar-based biosensors, when integrated with biomolecules such as enzymes, DNA, or antibodies, exhibit high sensitivity and specificity, making them suitable for precise disease diagnostics. These findings suggest that biochar holds significant potential as a sustainable biomedical material, offering alternatives to conventional antibiotics, supporting cancer therapy, and enabling sensitive biosensing platforms. Future functionalization strategies may further facilitate its clinical translation and practical applications. Full article

Understanding and optimizing thermal conductivity in epoxy-based composites is crucial for efficient thermal management applications. This study investigates the anisotropic thermal conductivity of a tetra-functional epoxy resin filled with low concentrations (0.25–2.00 wt%) of carbonaceous nanofillers: 1D multiwall carbon nanotubes (MWCNTs) and 2D exfoliated graphite (EG) nanoparticles. Experimental measurements conducted using the Transient Plane Source (TPS) method reveal distinct behaviors depending on the nanofiller’s geometry. Epoxy formulations incorporating MWCNTs exhibit a ~60% increase in in-plane thermal conductivity (λ_{I-p dir.}) compared to the unfilled resin, with negligible changes in the through-plane direction (λ_{T-p dir.}). Conversely, EG nanoparticles enhance thermal conductivity in both directions, with a preference for the in-plane direction, achieving a ~250% increase at 2 wt%. In light of this, graphene-based fillers establish a predominant thermal transport direction in the resulting nanocomposites due to their layered structure, whereas MWCNTs create unidirectional thermal pathways. The TPS results were complemented by multiphysics simulations in COMSOL and theoretical studies based on the theory of thermal circuits to explain the observed phenomena and justify the experimental findings. This integrated approach, combining experiments, theoretical analyses, and simulations, demonstrates the potential for tailoring the thermal properties of epoxy nanocomposites. These insights provide a foundation for developing advanced materials optimized for efficient thermal management in high-performance systems. Full article

The persistent threat of heavy metal ions (e.g., Pb²⁺, Hg²⁺, Cd²⁺) in aqueous environments to human health underscores an urgent need for advanced sensing platforms capable of rapid and precise pollutant monitoring. Graphitic carbon nitride (g-C₃N₄), a metal-free polymeric semiconductor, has emerged as a revolutionary material for constructing next-generation environmental sensors due to its exceptional physicochemical properties, including tunable electronic structure, high chemical/thermal stability, large surface area, and unique optical characteristics. This review systematically explores the integration of g-C₃N₄ with functional nanomaterials (e.g., metal nanoparticles, metal oxide nanomaterials, carbonaceous materials, and conduction polymer) to engineer high-performance sensing interfaces for heavy metal detection. The structure-property relationship is critically analyzed, emphasizing how morphology engineering (nanofibers, nanosheets, and mesoporous) and surface functionalization strategies enhance sensitivity and selectivity. Advanced detection mechanisms are elucidated, including electrochemical signal amplification, and photoinduced electron transfer processes enabled by g-C₃N₄’s tailored bandgap and surface active sites. Furthermore, this review addresses challenges in real-world deployment, such as scalable nanomaterial synthesis, matrix interference mitigation, and long-term reliable detection. This work provides valuable insights for advancing g-C₃N₄-based electrochemical sensing technologies toward sustainable environmental monitoring and intelligent pollution control systems. Full article

This study investigates the formation of by-product species during flame spray synthesis (SFS) of superparamagnetic maghemite (γ-Fe₂O₃) nanoparticles. Four samples are synthesized by utilizing two standardized burner types (SpraySyn1 and SpraySyn2) and varying the iron (III) nonahydrate (INN) concentration (0.1 M and 0.2 M) in the precursor feed while using ethanol and 2-ethylhexanoic acid as solvent. Conducting complementary powder analysis revealed a predominant presence of carboxylates and carbonates as by-product species (~14–18 wt.%), while no strong indications for elemental carbon and precursor/solvent residues can be found. Carbonates/carboxylates are located on particle surfaces, and the particles’ surface loadings by these species are independent of the precursor concentration but depend on burner type, with SpraySyn2 exhibiting lower values, indicating a more complete combustion for this burner. Through time-resolved thermophoretic sampling, we further demonstrate that carbon forms temporally in the visible flame center when using SpraySyn1. Since carbon solely forms momentarily within large flame pulses and decomposes further downstream, its temporal formation is of minor relevance for the final particle purity. However, its local co-existence aside from γ-Fe₂O₃ in the flame has potential to bias in situ diagnostics. Full article

The development of nanofluids (NFs) has significantly advanced the thermal performance of heat transfer fluids (HTFs) in heating and cooling applications. This review examines the synergistic effects of different nanoparticles (NPs)—including metallic, metallic oxide, and carbonaceous types—on the thermal conductivity (TC) and specific heat capacity (SHC) of base fluids like molecular, molten salts and ionic liquids. While adding NPs typically enhances TC and heat transfer, it can reduce SHC, posing challenges for energy storage and sustainable thermal management. Key factors such as NP composition, shape, size, concentration, and base fluid selection are analyzed to understand the mechanisms driving these improvements. The review also emphasizes the importance of interfacial interactions and proper NP dispersion for fluid stability. Strategies like optimizing NP formulations and utilizing solid–solid phase transitions are proposed to enhance both TC and SHC without significantly increasing viscosity, a common drawback in NFs. By balancing these properties, NFs hold great potential for renewable energy systems, particularly in improving energy storage efficiency. The review also outlines future research directions to overcome current challenges and expand the application of NFs in sustainable energy solutions, contributing to reduced carbon emissions. Full article

Nanocomposites based on Fe₃O₄ and carbonaceous nanoparticles (CNPs), including carbon nanotubes (CNTs) and graphene derivatives (graphene oxide (GO) and reduced graphene oxide (RGO)), such as Fe₃O₄@GO, Fe₃O₄@RGO, and Fe₃O₄@CNT, have demonstrated considerable potential in a number of health applications, including tissue regeneration and innovative cancer treatments such as hyperthermia (HT). This is due to their ability to transport drugs and generate localized heat under the influence of an alternating magnetic field on Fe₃O₄. Despite the promising potential of CNTs and graphene derivatives as drug delivery systems, their use in biological applications is hindered by challenges related to dispersion in physiological media and particle agglomeration. Hence, a solid foundation has been established for the integration of various synthesis techniques for these nanocomposites, with the wet co-precipitation method being the most prevalent. Moreover, the dimensions and morphology of the composite nanoparticles are directly correlated with the value of magnetic saturation, thus influencing the efficiency of the composite in drug delivery and other significant biomedical applications. The current demand for this type of material is related to the loading of a larger quantity of drugs within the hybrid structure of the carrier, with the objective of releasing this amount into the tumor cells. A second demand refers to the biocompatibility of the drug carrier and its capacity to permeate cell membranes, as well as the processes occurring within the drug carriers. The main objective of this paper is to review the synthesis methods used to prepare hybrids based on Fe₃O₄ and CNPs, such as GO, RGO, and CNTs, and to examinate their role in the formation of hybrid nanoparticles and the correlation between their morphology, the dimensions, and optical/magnetic properties. Full article

Electrochemical biosensors have emerged as predominant devices for sensitive, rapid, and specific sensing of biomolecules, with significant applications in clinical diagnostics, environmental observation, and food processing. The improvement of inventive materials, especially carbon-based materials, and metal/metal oxide nanoparticles (M/MONPs), has changed the impact of biosensing, improving the performance and flexibility of electrochemical biosensors. Carbon-based materials, such as graphene, carbon nanotubes, and carbon nanofibers, have excellent electrical conductivity, a high surface area, large pore size, and good biocompatibility, making them ideal electrocatalysts for biosensor applications. Furthermore, M and MONPs have highly effective synergistic, electronic, and optical properties that influence signal transduction, selectivity, and sensitivity. This study completely explored continuous progressions and upgrades in carbonaceous materials (CBN materials) and M/MONPs for electrochemical biosensor applications. It analyzed the synergistic effects of hybrid nanocomposites that combine carbon materials with metal nanoparticles (MNPs) and their part in upgrading sensor performance. The paper likewise incorporated the surface alteration procedures and integration of these materials into biosensor models. The study examined difficulties, requirements, and possibilities for executing these innovative materials in practical contexts. This overview aimed to provide specialists with insights into the most recent patterns in the materials study of electrochemical biosensors and advance further progressions in this dynamic sector. Full article

Carbonaceous materials have gained significant attention in recent years for their various applications in the field of medicine and biotechnology. This comprehensive review explores the synthesis and characterization of carbon-based materials and their potentials in various medical applications. The paper delves into the methods of fabrication of carbon-based nanoparticles, such as carbon nanotubes, biochar, and graphene, while highlighting their unique properties. Characterization techniques, such as microscopy, spectroscopy, and surface analysis, are discussed to provide insights into the chemical and structural properties of these materials. Furthermore, the review examined their wide-ranging medical applications, encompassing tissue engineering, drug delivery, biosensing, and imaging, showcasing the versatility and promising contributions of carbonaceous materials in the healthcare industry. The review outlines the current challenges and prospects in the field, emphasizing the growing significance of carbon-based materials as valuable tools in advancing medical science and technology, as well as public health. Full article

After the synthesis of carbon in the core of asymptotic giant branch (AGB) stars, carbon is dredged up to the surface by convection. Many carbon-based molecules are formed in the subsequently developed stellar wind. These include acetylene, which can link together to form benzene in post-AGB evolution. The emergence of the spectral signatures of aromatic and aliphatic compounds in the transition phase between AGB stars and planetary nebulae suggests that complex organic compounds can be formed in the circumstellar environment over very short (10³ yr) timescales. We suggest that the carrier of the family of unidentified infrared emission bands is an amorphous carbonaceous compound—mixed aromatic/aliphatic nanoparticles (MAONs). The implications of the synthesis of complex organics in evolved stars are discussed. Full article

Hierarchical porous carbon derived from discarded biomass for energy storage materials has attracted increasing research attention due to its cost-effectiveness, ease of fabrication, environmental protection, and sustainability. Brewed tea leaves are rich in heteroatoms that are beneficial to capacitive energy storage behavior. Therefore, we synthesized high electrochemical performance carbon-based composites from Tie guan yin tea leaf waste using a facile procedure comprising hydrothermal, chemical activation, and calcination processes. In particular, potassium permanganate (KMnO₄) was incorporated into the potassium hydroxide (KOH) activation agent; therefore, during the activation process, KOH continued to erode the biomass precursor, producing abundant pores, and KMnO₄ synchronously underwent a redox reaction to form MnO nanoparticles and anchor on the porous carbon through chemical bonding. MnO nanoparticles provided additional pseudocapacitive charge storage capabilities through redox reactions. The results show that the amount of MnO produced is proportional to the amount of KMnO₄ incorporated. However, the specific surface area of the composite material decreases with the incorporated amount of KMnO₄ due to the accumulation and aggregation of MnO nanoparticles, thereby even blocking some micropores. Optimization of MnO nanocrystal loading can promote the crystallinity and graphitization degree of carbonaceous materials. The specimen prepared with a weight ratio of KMnO₄ to hydrochar of 0.02 exhibited a high capacitance of 337 F/g, an increase of 70%, owing to the synergistic effect between the Tie guan yin tea leaf-derived activated carbon and MnO nanoparticles. With this facile preparation method and the resulting high electrochemical performance, the development of manganese oxide/carbon composites derived from tea leaf biomass is expected to become a promising candidate as an energy storage material for supercapacitors. Full article

The emergence of bio-based carbonaceous materials for various applications has attracted significant attention during the last few years. Here, we report a rapid, efficient, and reproducible microwave-assisted synthesis of graphene quantum dots (GQDs) with identical features irrespective of the nature of biomass waste investigated. The synthesized GQDs were fully characterized by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, and dynamic light scattering. The nanoparticles displayed narrow sizes of 1–2 nm and high solubility in polar solvents such as water and ethanol. The protocol described herein is advantageous in comparison to dealing with the synthesis of GQDs from biomass waste previously reported since our protocol is faster owing to the use of microwave heating and the avoidance of dialysis for the purification step. Furthermore, in solution, the water-soluble particles showed excitation-dependent photoluminescence ranging from blue to orange emission wavelengths. Interestingly, thin films displayed white-light emission under 325 nm UV-light excitation, while aggregation-induced quenching was usually observed, opening the way for their potential use as a phosphor in white-light-emitting diodes. Full article

Given the pressing climate and sustainability challenges, shifting industrial processes towards environmentally friendly practices is imperative. Among various strategies, the generation of green, flexible materials combined with efficient reutilization of biomass stands out. This review provides a comprehensive analysis of the hydrothermal carbonization (HTC) process as a sustainable approach for developing carbonaceous materials from biomass. Key parameters influencing hydrochar preparation are examined, along with the mechanisms governing hydrochar formation and pore development. Then, this review explores the application of hydrochars in supercapacitors, offering a novel comparative analysis of the electrochemical performance of various biomass-based electrodes, considering parameters such as capacitance, stability, and textural properties. Biomass-based hydrochars emerge as a promising alternative to traditional carbonaceous materials, with potential for further enhancement through the incorporation of extrinsic nanoparticles like graphene, carbon nanotubes, nanodiamonds and metal oxides. Of particular interest is the relatively unexplored use of transition metal dichalcogenides (TMDCs), with preliminary findings demonstrating highly competitive capacitances of up to 360 F/g when combined with hydrochars. This exceptional electrochemical performance, coupled with unique material properties, positions these biomass-based hydrochars interesting candidates to advance the energy industry towards a greener and more sustainable future. Full article

The increase in the world population and the intensification of agricultural practices have resulted in the release of several contaminants into the environment, especially pesticides and heavy metals. This article reviews recent advances in using adsorbent and catalytic materials for environmental decontamination. Different materials, including clays, carbonaceous, metallic, polymeric, and hybrid materials, are evaluated for their effectiveness in pollutant removal. Adsorption is an effective technique due to its low cost, operational simplicity, and possibility of adsorbent regeneration. Catalytic processes, especially those using metallic nanoparticles, offer high efficiency in degrading complex pesticides. Combining these technologies can enhance the efficiency of remediation processes, promoting a more sustainable and practical approach to mitigate the impacts of pesticides and other agricultural pollutants on the environment. Therefore, this review article aims to present several types of materials used as adsorbents and catalysts for decontaminating ecosystems affected by agricultural pollutants. It discusses recent works in literature and future perspectives on using these materials in environmental remediation. Additionally, it explores the possibilities of using green chemistry principles in producing sustainable materials and using agro-industrial waste as precursors of new materials to remove contaminants from the environment. Full article