C | An Open Access Journal from MDPI

11 pages, 4468 KiB

Open AccessArticle

Kinetics of Thermal Decomposition of Carbon Nanotubes Decorated with Magnetite Nanoparticles

by Rubén H. Olcay, Elia G. Palacios, Iván A. Reyes, Laura García-Hernández, Pedro A. Ramírez-Ortega, Sayra Ordoñez, Julio C. Juárez, Martín Reyes, Juan-Carlos González-Islas and Mizraim U. Flores

C 2024, 10(4), 96; https://doi.org/10.3390/c10040096 - 15 Nov 2024

Abstract

Magnetite nanoparticles were synthesized using the green chemistry technique; ferric chloride was used as a precursor agent and Moringa oleifera extract was used as a stabilizer agent. A black powder, characteristic of magnetite, was obtained. X-ray diffraction was performed on the synthesis product [...] Read more.

Magnetite nanoparticles were synthesized using the green chemistry technique; ferric chloride was used as a precursor agent and Moringa oleifera extract was used as a stabilizer agent. A black powder, characteristic of magnetite, was obtained. X-ray diffraction was performed on the synthesis product and identified as magnetite (Fe₃O₄). Scanning electron microscopy characterization shows that nanoparticles have a spherical morphology, with sizes ranging from 15 nm to 35 nm. The synthesis of carbon nanotubes was carried out by the pyrolytic chemical deposition technique, from which multiwalled carbon nanotubes were obtained with diameters of 15–35 nm and of varied length. The decoration was carried out using the wet and sonification technique, where a non-homogeneous coating was obtained around the nanotubes. The thermal decomposition for both decorated and undecorated nanotubes presents two mass losses but with different slopes, where the activation energy for the decorated carbon nanotubes was 79.54 kJ/mol, which shows that the decoration gives more stability to the nanotubes since the activation energy of the undecorated nanotubes is 25.74 kJ/mol. Full article

(This article belongs to the Collection Novel Applications of Carbon Nanotube-Based Materials)

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20 pages, 5602 KiB

Open AccessArticle

Preferential Stripping Analysis of Post-Transition Metals (In and Ga) at Bi/Hg Films Electroplated on Graphene-Functionalized Graphite Rods

by Nastaran Ghaffari, Nazeem Jahed, Zareenah Abader, Priscilla G. L. Baker and Keagan Pokpas

C 2024, 10(4), 95; https://doi.org/10.3390/c10040095 - 12 Nov 2024

Abstract

In this study, we introduce a novel electrochemical sensor combining reduced graphene oxide (rGO) sheets with a bismuth–mercury (Bi/Hg) film, electroplated onto pencil graphite electrodes (PGEs) for the high-sensitivity detection of trace amounts of gallium (Ga³⁺) and indium (In³⁺) [...] Read more.

In this study, we introduce a novel electrochemical sensor combining reduced graphene oxide (rGO) sheets with a bismuth–mercury (Bi/Hg) film, electroplated onto pencil graphite electrodes (PGEs) for the high-sensitivity detection of trace amounts of gallium (Ga³⁺) and indium (In³⁺) in water samples using square wave anodic stripping voltammetry (SWASV). The electrochemical modification of PGEs with rGO and bimetallic Bi/Hg films (ERGO-Bi/HgF-PGE) exhibited synergistic effects, enhancing the oxidation signals of Ga and In. Graphene oxide (GO) was accumulated onto PGEs and reduced through cyclic reduction. Key parameters influencing the electroanalytical performance, such as deposition potential, deposition time, and pH, were systematically optimized. The improved adsorption of Ga³⁺ and In³⁺ ions at the Bi/Hg films on the graphene-functionalized electrodes during the preconcentration step significantly enhanced sensitivity, achieving detection limits of 2.53 nmol L⁻¹ for Ga³⁺ and 7.27 nmol L⁻¹ for In³⁺. The preferential accumulation of each post-transition metal, used in transparent displays, to form fused alloys at Bi and Hg films, respectively, is highlighted. The sensor demonstrated effective quantification of Ga³⁺ and In³⁺ in tap water, with detection capabilities well below the USEPA guidelines. This study pioneers the use of bimetallic films to selectively and simultaneously detect the post-transition metals In³⁺ and Ga³⁺, highlighting the role of graphene functionalization in augmenting metal film accumulation on cost-effective graphite rods. Additionally, the combined synergistic effects of Bi/Hg and graphene functionalization have been explored for the first time, offering promising implications for environmental analysis and water quality monitoring. Full article

(This article belongs to the Special Issue Carbon and Related Composites for Sensors and Energy Storage: Synthesis, Properties, and Application)

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17 pages, 2264 KiB

Open AccessArticle

Towards Photothermal Acid Catalysts Using Eco-Sustainable Sulfonated Carbon Nanoparticles—Part II: Thermal and Photothermal Catalysis of Biodiesel Synthesis

by María Paula Militello, Luciano Tamborini, Diego F. Acevedo and Cesar A. Barbero

C 2024, 10(4), 94; https://doi.org/10.3390/c10040094 - 4 Nov 2024

Abstract

The main goal of this work is to evaluate the ability of sulfonated carbon nanoparticles (SCNs) to induce photothermal catalysis of the biodiesel synthesis reaction (transesterification of natural triglycerides (TGs) with alcohols). Carbon nanoparticles (CNs) are produced by the carbonization of cross-linked resin [...] Read more.

The main goal of this work is to evaluate the ability of sulfonated carbon nanoparticles (SCNs) to induce photothermal catalysis of the biodiesel synthesis reaction (transesterification of natural triglycerides (TGs) with alcohols). Carbon nanoparticles (CNs) are produced by the carbonization of cross-linked resin nanoparticles (RNs). The RNs are produced by condensation of a phenol (resorcinol or natural tannin) with formaldehyde under ammonia catalysis (Stober method). The method produces nanoparticles, which are carbonized into carbon nanoparticles (CNs). The illumination of CNs increases the temperature proportionally (linear) to the nanoparticle concentration and exposure time (with saturation). Solid acid catalysts are made by heating in concentrated sulfuric acid (SEAr sulfonation). The application of either light or a catalyst (SCNs) (at 25 °C) induced low conversions (<10%) for the esterification reaction of acetic acid with bioethanol. In contrast, the illumination of the reaction medium containing SCNs induced high conversions (>75%). In the case of biodiesel synthesis (transesterification of sunflower oil with bioethanol), conversions greater than 40% were observed only when light and the catalyst (SCNs) were applied simultaneously. Therefore, it is possible to use sulfonated carbon nanoparticles as photothermally activated catalysts for Fischer esterification and triglyceride transesterification (biodiesel synthesis). Full article

(This article belongs to the Special Issue Carbons for Health and Environmental Protection (2nd Edition))

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15 pages, 4495 KiB

Open AccessArticle

Fabrication of Cu-Doped Diamond-like Carbon Film for Improving Sealing Performance of Hydraulic Cylinder of Shearers

by Yanrong Yang, Xiang Yu, Zhiyan Zhao and Lei Zhang

C 2024, 10(4), 93; https://doi.org/10.3390/c10040093 - 30 Oct 2024

Abstract

During shearer operation, the piston rod is susceptible to wear from the invasion of pollutants, thus ruining the sealing ring in the hydraulic cylinder. This work attempts to conduct a systematic investigation of Cu-doped diamond-like carbon (Cu-DLC) film to improve the seal performance. [...] Read more.

During shearer operation, the piston rod is susceptible to wear from the invasion of pollutants, thus ruining the sealing ring in the hydraulic cylinder. This work attempts to conduct a systematic investigation of Cu-doped diamond-like carbon (Cu-DLC) film to improve the seal performance. The failure process of the cylinder was analyzed, and relevant parameters were determined. Several Cu-DLC films were deposited on the substrate of the piston rod in a multi-ion beam-assisted system, and their structures and combined tribological performances were investigated. The hardness of the film ranges from 27.6 GPa to 14.8 GPa, and the internal stress ranges from 3500 MPa to 1750 MPa. The steady-state frictional coefficient of the film ranges from 0.04 to 0.15; the wear rate decreases first and then increases, and it reaches its lowest (5.0 × 10⁻⁹ mm³/N·m) at 9.2 at.% content. a:C-Cu_9.2% film presents optimal combined tribological performances in this experiment. The modification mechanism of Cu-DLC film for the seal performance may come from the synergistic effects of (i) the contact force and friction-heat-induced film graphitization, (ii) Cu doping improves the toughness of the film and acts as a solid lubricant, and (iii) the transfer layer plays a role in self-lubrication. Full article

(This article belongs to the Special Issue Micro/Nanofabrication of Carbon-Based Devices and Their Applications)

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25 pages, 2092 KiB

Open AccessReview

Advanced Graphene-Based Technologies for Antibiotic Removal from Wastewater: A Review (2016–2024)

by Joydip Sengupta and Chaudhery Mustansar Hussain

C 2024, 10(4), 92; https://doi.org/10.3390/c10040092 - 15 Oct 2024

Abstract

The increasing presence of antibiotics in wastewater poses significant environmental risks, including the promotion of antibiotic resistance and harm to aquatic ecosystems. This study reviews advancements in graphene-based technologies for removing antibiotics from wastewater between 2016 and 2024. Graphene-based platforms, such as graphene [...] Read more.

The increasing presence of antibiotics in wastewater poses significant environmental risks, including the promotion of antibiotic resistance and harm to aquatic ecosystems. This study reviews advancements in graphene-based technologies for removing antibiotics from wastewater between 2016 and 2024. Graphene-based platforms, such as graphene oxide (GO), reduced graphene oxide (rGO), and graphene composites, have shown great promise in this field because of their exceptional adsorption capacities and rapid photocatalytic degradation capabilities. Functionalized graphene materials and graphene integrated with other substances, such as metal oxides and polymers, have enhanced performance in terms of antibiotic removal through mechanisms such as adsorption and photocatalysis. These technologies have been evaluated under various conditions, such as pH and temperature, demonstrating their practical applicability. Despite challenges related to scalability, cost-effectiveness, and environmental impact, the advancements in graphene-based technologies during this period highlight their significant potential for effective antibiotic removal, paving the way for safer and more sustainable environmental management practices. Full article

(This article belongs to the Special Issue Carbon-Based Materials Applied in Water and Wastewater Treatment)

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17 pages, 5669 KiB

Open AccessArticle

Stacking Fault Nucleation in Films of Vertically Oriented Multiwall Carbon Nanotubes by Pyrolysis of Ferrocene and Dimethyl Ferrocene at a Low Vapor Flow Rate

by Ayoub Taallah, Shanling Wang, Omololu Odunmbaku, Lin Zhang, Xilong Guo, Yixin Dai, Wenkang Li, Huanqing Ye, Hansong Wu, Jiaxin Song, Jian Guo, Jiqiu Wen, Yi He and Filippo S. Boi

C 2024, 10(4), 91; https://doi.org/10.3390/c10040091 - 12 Oct 2024

Abstract

Recent observations of superconductivity in low-dimensional systems composed of twisted, untwisted, or rhombohedral graphene have attracted significant attention. One-dimensional moiré superlattices and flat bands have interestingly been identified in collapsed chiral carbon nanotubes (CNTs), opening up new avenues for the tunability of the [...] Read more.

Recent observations of superconductivity in low-dimensional systems composed of twisted, untwisted, or rhombohedral graphene have attracted significant attention. One-dimensional moiré superlattices and flat bands have interestingly been identified in collapsed chiral carbon nanotubes (CNTs), opening up new avenues for the tunability of the electronic properties in these systems. The nucleation of hexagonal moiré superlattices and other types of stacking faults has also been demonstrated in partially collapsed and uncollapsed carbon nano-onions (CNOs). Here, we report a novel investigation on the dynamics of stacking fault nucleation within the multilayered lattices of micrometer-scale vertically oriented films of multiwall CNTs (MWCNTs), resulting from the pyrolysis of molecular precursors consisting of ferrocene or dimethyl ferrocene, at low vapor flow rates of ~5–20 mL/min. Interestingly, local nucleation of moiré-like superlattices (as stacking faults) was found when employing dimethyl ferrocene as the pyrolysis precursor. The morphological and structural properties of these systems were investigated with the aid of scanning and transmission electron microscopies, namely SEM, TEM, and HRTEM, as well as X-ray diffraction (XRD) and Raman point/mapping spectroscopy. Deconvolution analyses of the Raman spectra also demonstrated a local surface oxidation, possibly occurring on defect-rich interfaces, frequently identified within or in proximity of bamboo-like graphitic caps. By employing high-temperature Raman spectroscopy, we demonstrate a post-growth re-graphitization, which may also be visualized as an alternative way of depleting the oxygen content within the MWCNTs’ interfaces through recrystallization. Full article

(This article belongs to the Special Issue Characterization of Disorder in Carbons (2nd Edition))

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10 pages, 1212 KiB

Open AccessArticle

Optimizing Graphene Oxide Film Quality: The Role of Solvent and Deposition Technique

by Grazia Giuseppina Politano

C 2024, 10(4), 90; https://doi.org/10.3390/c10040090 - 10 Oct 2024

Abstract

Graphene oxide (GO) is a promising material due to its high mechanical strength, electrical conductivity, and optical transparency, making it suitable for applications like optoelectronics and energy storage. This study focuses on a simplified method of depositing and characterizing GO films via drop [...] Read more.

Graphene oxide (GO) is a promising material due to its high mechanical strength, electrical conductivity, and optical transparency, making it suitable for applications like optoelectronics and energy storage. This study focuses on a simplified method of depositing and characterizing GO films via drop casting, particularly using isopropanol and water as solvents, and compares the results with reference samples of graphene produced by chemical vapor deposition (CVD) and GO films deposited by electrophoretic deposition (EPD). The optical properties of these films were analyzed using Variable Angle Spectroscopic Ellipsometry (VASE). The study revealed that GO films prepared with isopropanol exhibited a lower refractive index compared to those using water. Therefore, the research highlighted the significance of solvent choice and deposition method on the overall film quality. This work provides insights into optimizing GO film properties through careful solvent selection, contributing to the broader understanding and application of GO in advanced technologies. Full article

(This article belongs to the Topic Application of Graphene-Based Materials, 2nd Edition)

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24 pages, 5981 KiB

Open AccessArticle

Impact of Dispersive Solvent and Temperature on Supercapacitor Performance of N-Doped Reduced Graphene Oxide

by Ankit Yadav, Rajeev Kumar, Deepu Joseph, Nygil Thomas, Fei Yan and Balaram Sahoo

C 2024, 10(4), 89; https://doi.org/10.3390/c10040089 - 10 Oct 2024

Abstract

This study evaluates the critical roles of the dispersion medium and temperature during the solvothermal synthesis of nitrogen-doped reduced graphene oxide (NG) for enhancing its performance as an active material in supercapacitor electrodes. Using a fixed volume of a solvent (THF, ethanol, acetonitrile, [...] Read more.

This study evaluates the critical roles of the dispersion medium and temperature during the solvothermal synthesis of nitrogen-doped reduced graphene oxide (NG) for enhancing its performance as an active material in supercapacitor electrodes. Using a fixed volume of a solvent (THF, ethanol, acetonitrile, water, N,N-Dimethylformamide, ethylene glycol, or N-Methyl-2-pyrrolidone) as the dispersive medium, a series of samples at different temperatures (60, 75, 95, 120, 150, 180, and 195 °C) are synthesized and investigated. A proper removal of the oxygen moieties from their surface and an optimum number of N-based defects are essential for a better reduction of graphene oxide and better stacking of the NG sheets. The origin of the supercapacitance of NG sheets can be correlated to the inherent properties such as the boiling point, viscosity, dipole moment, and dielectric constant of all the studied solvents, along with the synthesis temperature. Due to the achievement of a suitable synthesis environment, NG synthesized using N,N-Dimethylformamide at 150 °C displays an excellent supercapacitance value of 514 F/g at 0.5 A/g, which is the highest among all our samples and also competitive among several state-of-the-art lightweight carbon materials. Our work not only helps in understanding the origin of the supercapacitance exhibited by graphene-based materials but also tuning them through a suitable choice of synthesis conditions. Full article

(This article belongs to the Special Issue Carbon and Related Composites for Sensors and Energy Storage: Synthesis, Properties, and Application)

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17 pages, 3329 KiB

Open AccessArticle

Role of Graphene Oxide in Disentangling Amyloid Beta Fibrils

by Brianna Duswalt, Isabella Wolson and Isaac Macwan

C 2024, 10(4), 88; https://doi.org/10.3390/c10040088 - 3 Oct 2024

Abstract

Recently, the accumulation of Amyloid Beta (Aβ) in the brain has been linked to the development of Alzheimer’s disease (AD) through the formation of aggregated plaques and neurofibrillary tangles (NFTs). Although carbon nanoparticles were previously shown as having a potential to address AD, [...] Read more.

Recently, the accumulation of Amyloid Beta (Aβ) in the brain has been linked to the development of Alzheimer’s disease (AD) through the formation of aggregated plaques and neurofibrillary tangles (NFTs). Although carbon nanoparticles were previously shown as having a potential to address AD, the interactions of Aβ with such nanoparticles have not been studied extensively. In this work, molecular dynamic simulations are utilized to simulate the interactions between a single atomic layer of graphene oxide (GO) and a 12-monomer Aβ fibril. These interactions are further compared to those between GO and five individual monomers of Aβ to further understand the conformational changes in Aβ as an individual monomer and as a component of the Aβ fibril. It was found that out of the 42 residues of the Aβ monomers, residues 27–42 are the most affected by the presence of GO. Furthermore, stability analysis through RMSD, conformational energies and salt bridges, along with nonbonding energy, illustrate that Aβ–Aβ interactions were successfully interrupted and dismantled by GO. Overall, the differences in the interactions between monomeric Aβ consisting of five monomers with GO, an Aβ fibril with GO, and control Aβ monomers among themselves, helped elucidate the potential that GO has to disentangle the Aβ tangles, both in case of individual monomers forming a cluster and as part of the Aβ fibril. Full article

(This article belongs to the Special Issue Carbon Nanohybrids for Biomedical Applications)

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13 pages, 5615 KiB

Open AccessArticle

Self-Assembled Synthesis of Graphene Tubes from Melamine Catalyzed by Calcium Carbonate

by Wenping Zeng, Jingxiang Meng, Xinbo Zheng, Tingting Mao, Jintao Huang and Yonggang Min

C 2024, 10(4), 87; https://doi.org/10.3390/c10040087 - 26 Sep 2024

Abstract

This study investigates the carbon products generated by melamine under various heat-treatment temperatures with the catalysis of calcium carbonate. We discovered that the cost-effective precursor melamine readily self-assembles and curls into graphene tubes when catalyzed by the alkaline earth salt CaCO₃ at [...] Read more.

This study investigates the carbon products generated by melamine under various heat-treatment temperatures with the catalysis of calcium carbonate. We discovered that the cost-effective precursor melamine readily self-assembles and curls into graphene tubes when catalyzed by the alkaline earth salt CaCO₃ at elevated temperatures. Under heat-treatment conditions of 1100 °C and 1200 °C, the growth morphology of graphene tubes with open structures and exceptionally large diameters was observed, and the diameters reached the micron level. These products exhibit a high degree of carbonization and an extremely low nitrogen content, as low as 1.7%. Further, the intensity ratio (ID/IG) of the D band and the G band is as low as 0.79 in Raman characterization. The results show that the products have a certain graphite structure, which proves the catalytic activity of CaCO₃. This is attributed to the incorporation of CaCO₃ into the raw material system, which impedes the complete thermal decomposition of melamine. On the other hand, the resulting CaO particles are evenly distributed along the tubular products, providing certain support for their self-assembly and growth, thereby achieving the efficient growth of graphene tubes. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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27 pages, 8205 KiB

Open AccessReview

Recent Advances in Carbon-Based Interfacial Photothermal Converters for Seawater Desalination: A Review

by Xiaoyu Jia, Yuke Niu, Shufang Zhu, Hongwei He and Xu Yan

C 2024, 10(3), 86; https://doi.org/10.3390/c10030086 - 22 Sep 2024

Abstract

Along with the rapid development of society, freshwater shortages have become a global concern. Although existing desalination technologies have alleviated this pressure to some extent, their long-term environmental impact and energy consumption are still questionable. Therefore, it is necessary to find a new [...] Read more.

Along with the rapid development of society, freshwater shortages have become a global concern. Although existing desalination technologies have alleviated this pressure to some extent, their long-term environmental impact and energy consumption are still questionable. Therefore, it is necessary to find a new effective way for seawater desalination with cleaner energy. Solar-driven interfacial water evaporation technology has the advantages of environmental protection, energy saving, high evaporation efficiency, low cost, and strong sustainability, and is considered one of the most effective technologies to relieve water resource stress. This review summarized the recent advances in carbon-based interfacial photothermal converters focused on the preparation methods of 2D and 3D photothermal absorbers, the potential ways to enhance the efficiency of photothermal conversion. Finally, this paper proposed the challenges and future trends of interfacial photothermal converters. Full article

(This article belongs to the Section Carbon Materials and Carbon Allotropes)

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18 pages, 10499 KiB

Open AccessArticle

Numerical Assessment of Effective Elastic Properties of Needled Carbon/Carbon Composites Based on a Multiscale Method

by Jian Ge, Xujiang Chao, Haoteng Hu, Wenlong Tian, Weiqi Li and Lehua Qi

C 2024, 10(3), 85; https://doi.org/10.3390/c10030085 - 16 Sep 2024

Abstract

Needled carbon/carbon composites contain complex microstructures such as irregular pores, anisotropic pyrolytic carbon, and interphases between fibers and pyrolytic carbon matrices. Additionally, these composites have hierarchical structures including weftless plies, short-cut fiber plies, and needled regions. To predict the effective elastic properties of [...] Read more.

Needled carbon/carbon composites contain complex microstructures such as irregular pores, anisotropic pyrolytic carbon, and interphases between fibers and pyrolytic carbon matrices. Additionally, these composites have hierarchical structures including weftless plies, short-cut fiber plies, and needled regions. To predict the effective elastic properties of needled carbon/carbon composites, this paper proposes a novel sequential multiscale method. At the microscale, representative volume element (RVE) models are established based on the microstructures of the weftless ply, short-cut fiber ply, and needled region, respectively. In the microscale RVE model, a modified Voronoi tessellation method is developed to characterize anisotropic pyrolytic carbon matrices. At the macroscale, an RVE model containing hierarchical structures is developed to predict the effective elastic properties of needled carbon/carbon composites. For the data interaction between scales, the homogenization results of microscale models are used as inputs for the macroscale model. By comparing these against the experimental results, the proposed multiscale model is validated. Furthermore, the effect of porosity on the effective elastic properties of needled carbon/carbon composites is investigated based on the multiscale model. The results show that the effective elastic properties of needled carbon/carbon composites decrease with the increase in porosity, but the extent of decrease is different in different directions. Full article

(This article belongs to the Special Issue Micro/Nanofabrication of Carbon-Based Devices and Their Applications)

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16 pages, 5753 KiB

Open AccessArticle

Enhanced Antibacterial Activity of Carbon Dots: A Hybrid Approach with Levofloxacin, Curcumin, and Tea Polyphenols

by Khurram Abbas, Haimei Zhu, Weixia Qin, Meiyan Wang, Zijian Li and Hong Bi

C 2024, 10(3), 84; https://doi.org/10.3390/c10030084 - 15 Sep 2024

Abstract

Bacterial infections and their increasing resistance to antibiotics pose a significant challenge in medical treatment. This study presents the synthesis and characterization of novel carbon dots (CDs) using levofloxacin (Lf), curcumin (Cur), and tea polyphenols (TP) through a facile hydrothermal method. The synthesized [...] Read more.

Bacterial infections and their increasing resistance to antibiotics pose a significant challenge in medical treatment. This study presents the synthesis and characterization of novel carbon dots (CDs) using levofloxacin (Lf), curcumin (Cur), and tea polyphenols (TP) through a facile hydrothermal method. The synthesized curcumin-tea polyphenol@carbon dots (Cur-TP@CDs) and levofloxacin-tea polyphenol@carbon dots (Lf-TP@CDs) were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy, confirming their unique structural and chemical properties. Cur-TP@CDs exhibited an average particle size of 1.32 nanometers (nm), while Lf-TP@CDs averaged 1.58 nm. Both types demonstrated significant antibacterial activity, with Lf-TP@CDs showing superior effectiveness against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in broth dilution and disc diffusion assays. Biofilm inhibition assays revealed a significant reduction in biofilm formation at higher concentrations. The ultraviolet-visible (UV-vis) and photoluminescence (PL) spectral analyses indicated efficient photon emission, and electron paramagnetic resonance (EPR) analysis showed increased singlet oxygen generation, enhancing bactericidal effects. Live and dead bacterial staining followed by scanning electron microscopy (SEM) analysis confirmed dose-dependent bacterial cell damage and morphological deformities. These findings suggest that Cur-TP@CDs and Lf-TP@CDs are promising antibacterial agents, potentially offering a novel approach to combat antibiotic-resistant bacterial infections. Full article

(This article belongs to the Special Issue Carbon Nanohybrids for Biomedical Applications)

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18 pages, 4255 KiB

Open AccessArticle

Emission Ellipsometry Study in Polymeric Interfaces Based on Poly(3-Hexylthiophene), [6,6]-Phenyl-C₆₁-Butyric Acid Methyl Ester, and Reduced Graphene Oxide

by Ana Clarissa Henrique Kolbow, Everton Crestani Rambo, Maria Ruth Neponucena dos Santos, Paulo Ernesto Marchezi, Ana Flávia Nogueira, Alexandre Marletta, Romildo Jerônimo Ramos and Eralci Moreira Therézio

C 2024, 10(3), 83; https://doi.org/10.3390/c10030083 - 11 Sep 2024

Abstract

We analyzed the interaction of three materials, reduced graphene oxide (RGO), [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), and poly(3-hexylthiphene) (P3HT), as well as the dependence of its photophysical properties within the temperature range of 90 to 300 K. The nanocomposite of the [...] Read more.

We analyzed the interaction of three materials, reduced graphene oxide (RGO), [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM), and poly(3-hexylthiphene) (P3HT), as well as the dependence of its photophysical properties within the temperature range of 90 to 300 K. The nanocomposite of the films was analyzed by optical absorption ultraviolet–visible (UV-Vis) and photoluminescence (PL) and emission ellipsometry (EE) as a function of sample temperature. The surface morphology was studied by atomic force microscopy (AFM). We noted that onset levels (E_onset) of the nanocomposite of P3HT and RGO are smaller than the others. The PL spectra showed the presence of anomalies in the emission intensities in the nanocomposite of P3HT and PCBM. It was also possible to determine the electron–phonon coupling by calculating the Huang–Rhys parameters and the temperature dependence of samples. Through EE, it was possible to analyze the degree of polarization and the anisotropy. We observed a high degree of polarized emission of the P3HT films, which varies subtly according to the temperature. For nanocomposites with RGO, the polarization degree in the emission decreases, and the roughness on the surface increases. As a result, the RGO improves the energy transfer between adjacent polymer chains at the cost of greater surface roughness. Then, the greater energy transfer may favor applications of this type of nanocomposite in organic photovoltaic cells (OPVCs) with enhancement in energy conversion efficiency. Full article

(This article belongs to the Special Issue Carbon-Based Polymer Composites: Synthesis, Processing, Characterization and Applications)

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14 pages, 5675 KiB

Open AccessArticle

A Novel Non-Enzymatic Efficient H₂O₂ Sensor Utilizing δ-FeOOH and Prussian Blue Anchoring on Carbon Felt Electrode

by Karoline S. Nantes, Ana L. H. K. Ferreira, Marcio C. Pereira, Francisco G. E. Nogueira and André S. Afonso

C 2024, 10(3), 82; https://doi.org/10.3390/c10030082 - 9 Sep 2024

Abstract

In this study, an efficient H₂O₂ sensor was developed based on electrochemical Prussian blue (PB) synthesized from the acid suspension of δ-FeOOH and K₃[Fe(CN)₆] using cyclic voltammetry (CV) and anchored on carbon felt (CF), yielding an [...] Read more.

In this study, an efficient H₂O₂ sensor was developed based on electrochemical Prussian blue (PB) synthesized from the acid suspension of δ-FeOOH and K₃[Fe(CN)₆] using cyclic voltammetry (CV) and anchored on carbon felt (CF), yielding an enhanced CF/PB-FeOOH electrode for sensing of H₂O₂ in pH-neutral solution. CF/PB-FeOOH electrode construction was proved by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), and electrochemical properties were verified by impedance electrochemical and CV. The synergy of δ-FeOOH and PB coupled to CF increases electrocatalytic activity toward H₂O_2, with the sensor showing a linear range of 1.2 to 300 μM and a limit of detection of 0.36 μM. Notably, the CF/PB-FeOOH electrode exhibited excellent selectivity for H₂O₂ detection in the presence of dopamine (DA), uric acid (UA), and ascorbic acid (AA). The calculated H₂O₂ recovery rates varied between 93% and 101% in fetal bovine serum diluted in PBS. This work underscores the potential of CF/PB-FeOOH electrodes in progressing electrochemical sensing technologies for various biological and environmental applications. Full article

(This article belongs to the Special Issue Carbon and Related Composites for Sensors and Energy Storage: Synthesis, Properties, and Application)

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20 pages, 4937 KiB

Open AccessArticle

Miscanthus-Derived Biochar as a Platform for the Production of Fillers for the Improvement of Mechanical and Electromagnetic Properties of Epoxy Composites

by Salvatore Scavuzzo, Silvia Zecchi, Giovanni Cristoforo, Carlo Rosso, Daniele Torsello, Gianluca Ghigo, Luca Lavagna, Mauro Giorcelli, Alberto Tagliaferro, Marco Etzi and Mattia Bartoli

C 2024, 10(3), 81; https://doi.org/10.3390/c10030081 - 5 Sep 2024

Abstract

The production of multipurpose sustainable fillers is a matter of great interest, and biochar can play a pivotal role. Biochar is a biomass-derived carbon source that can act as a versatile platform for the engineering of fillers as neat or functionalized materials. In [...] Read more.

The production of multipurpose sustainable fillers is a matter of great interest, and biochar can play a pivotal role. Biochar is a biomass-derived carbon source that can act as a versatile platform for the engineering of fillers as neat or functionalized materials. In this work, we investigate the utilization of 800 °C annealed Miscanthus-derived biochar as a filler for the production of epoxy composites with promising mechanical and electrical properties. We also used it in the production of an iron-rich hybrid filler in order to fine-tune the surface and bulk properties. Our main findings reveal that hybrid composites containing 20 wt.% biochar exhibit a 27% increase in Young’s modulus (YM), reaching 1.4 ± 0.1 GPa, while the ultimate tensile strength (UTS) peaks at 30.3 ± 1.8 Mpa with 10 wt.% filler, a 27% improvement over pure epoxy. However, higher filler loadings (20 wt.%) result in decreased UTS and maximum elongation. The optimal toughness of 0.58 ± 0.14 MJ/m³ is observed at 5 wt.% filler content. For organic composites, YM sees a notable increase of 90%, reaching 2.1 ± 0.1 Gpa at 20 wt.%, and UTS improves by 32% with the same filler content. Flexural tests indicate an enhanced elastic modulus but reduced maximum elongation as filler content rises. Electromagnetic evaluations show that hybrid fillers maintain a primarily dielectric behavior with a negligible impact on permittivity, while biochar–epoxy composites exhibit increased conductivity at higher filler loadings, suitable for high-frequency applications. In light of these results, biochar-based fillers demonstrate significant potential for enhancing the mechanical and electrical properties of epoxy composites. Full article

(This article belongs to the Special Issue Carbon-Based Polymer Composites: Synthesis, Processing, Characterization and Applications)

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14 pages, 9087 KiB

Open AccessArticle

The Influence of Annealing Temperature on the Interfacial Heat Transfer in Pulsed Laser Deposition-Grown Ga₂O₃ on Diamond Composite Substrates

by Lin Gu, Yi Shen, Wenjie Chen, Yuanhui Zuo, Hongping Ma and Qingchun Zhang

C 2024, 10(3), 80; https://doi.org/10.3390/c10030080 - 4 Sep 2024

Abstract

As devices become more miniaturized and integrated, the heat flux density has increased, highlighting the issue of heat concentration, especially for low thermal conductivity gallium oxide (Ga₂O₃). This study utilizes diamond composite substrates with an AlN transition layer to [...] Read more.

As devices become more miniaturized and integrated, the heat flux density has increased, highlighting the issue of heat concentration, especially for low thermal conductivity gallium oxide (Ga₂O₃). This study utilizes diamond composite substrates with an AlN transition layer to assist Ga₂O₃ in rapid thermal dissipation. All samples were prepared using pulsed laser deposition (PLD) and annealed at 600–1000 °C. The microstructure, surface morphology, vacancy defects, and thermal characteristics of post-annealed Ga₂O₃ were then thoroughly investigated to determine the mechanism by which annealing temperature influences the heat transfer of heterostructures. The results demonstrate that increasing the annealing temperature can improve the crystallinity of Ga₂O₃ while also reducing oxygen vacancy defects from 20.6% to 9.9%. As the temperature rises to 1000 °C, the thermal conductivity of Ga₂O₃ reaches a maximum of 12.25 W/(m·K). However, the interface microstructure has no direct correlation with annealing temperature. At 700 °C, Ga₂O₃/diamond exhibits a maximum thermal boundary conductance of 127.06 MW/(m²·K). Higher temperatures (>800 °C) cause irregular mixtures to form near the heterointerface, intensifying phonon interface scattering and sharply deteriorating interfacial heat transfer. These findings contribute to a better understanding of the heterointerface thermal transfer influence mechanism and provide theoretical guidance for the thermal management design and physical analysis of Ga₂O₃-based power devices. Full article

(This article belongs to the Special Issue Micro/Nanofabrication of Carbon-Based Devices and Their Applications)

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18 pages, 8468 KiB

Open AccessArticle

One-Stage Synthesis of Microporous Carbon Adsorbents from Walnut Shells—Evolution of Porosity and Structure

by Ilya E. Men’shchikov, Andrey A. Shiryaev, Andrey V. Shkolin, Alexander E. Grinchenko, Elena V. Khozina, Alexey A. Averin and Anatolii A. Fomkin

C 2024, 10(3), 79; https://doi.org/10.3390/c10030079 - 2 Sep 2024

Abstract

One-stage synthesis technology for preparing carbon adsorbents with tailored porosity from agricultural waste is worthwhile due to their extensive application value. Thermal gravimetric analysis, low-temperature N₂ adsorption, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and Raman spectroscopy were used to record the [...] Read more.

One-stage synthesis technology for preparing carbon adsorbents with tailored porosity from agricultural waste is worthwhile due to their extensive application value. Thermal gravimetric analysis, low-temperature N₂ adsorption, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and Raman spectroscopy were used to record the structure transformations of carbon materials, namely pore development, proceeding in the course of the step-wise pyrolysis of renewable and low-cost raw materials such as walnut shells (WNSs), which was carried out within a temperature range of 240–950 °C in a CO₂ flow. The minimum threshold carbonization temperature for preparing nanoporous carbon materials from WNSs, determined by the examination of the N₂ adsorption data, was 500 °C. The maximum specific micropore volume and BET surface achieved in the process without holding a material at a specified temperature were only 0.19 cm³/g and 440 m²/g, respectively. The pyrolysis at 400–600 °C produced amorphous sp² carbon. At a temperature as high as 750 °C, an increase in the X-ray reflection intensity indicated the ordering of graphite-like crystallites. At high burn-off degrees, the size of coherently scattering domains becomes smaller, and an increased background in X-ray patterns indicates the destruction of cellulose nanofibrils, the disordering of graphene stacks, and an increase in the amount of disordered carbon. At this stage, pores develop in the crystallites. They are tentatively assigned to crystallites with sizes of 15–20 nm and to micropores. According to the Raman spectra combined with the XRD and SAXS data, the structure of all the pyrolysis products is influenced by the complex structure of the walnut shell precursor, which comprises cellulose nanofibrils embedded in lignin. This structure was preserved in the initial stage of pyrolysis, and the graphitization of cellulose fibrils and lignin proceeds at different rates. Most of the pores accessible for gas molecules in the resulting carbon materials are associated with former cellulose fibrils. Full article

(This article belongs to the Special Issue Characterization of Disorder in Carbons (2nd Edition))

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45 pages, 12156 KiB

Open AccessReview

Research Progress in Graphene-Based Adsorbents for Wastewater Treatment: Preparation, Adsorption Properties and Mechanisms for Inorganic and Organic Pollutants

by Guangqian Li, Ruiling Du, Zhanfang Cao, Changxin Li, Jianrong Xue, Xin Ma and Shuai Wang

C 2024, 10(3), 78; https://doi.org/10.3390/c10030078 - 29 Aug 2024

Abstract

Graphene-based adsorbents show great potential for application in the field of environmental pollution treatment due to their unique two-dimensional structure, high specific surface area, and tunable surface chemistry. This paper reviews the research on the application of graphene and its derivatives as novel [...] Read more.

Graphene-based adsorbents show great potential for application in the field of environmental pollution treatment due to their unique two-dimensional structure, high specific surface area, and tunable surface chemistry. This paper reviews the research on the application of graphene and its derivatives as novel adsorbents in the field of wastewater treatment in recent years, focusing on the preparation and functionalization of graphene-based adsorbents, as well as their adsorption performance and mechanism of action in the removal of inorganic and organic pollutants, and provides an outlook on the future directions of the research on graphene-based adsorbents. The analysis in this paper focuses on the functionalization of graphene-based adsorbents by introducing magnetic particles, hybridization with other materials, and grafting with polymers. The modified graphene-based adsorbents showed significant adsorption and removal of pollutants and were easy to recycle and regenerate. The adsorption of pollutants on graphene-based adsorbents is mainly carried out through π–π interaction, hydrogen bonding, and electrostatic interaction, which is related to the structure of the pollutants. Future research directions on graphene-based adsorbents should focus on in-depth adsorption mechanism studies and the development of cost-effective graphene-based adsorbents for wastewater treatment. Full article

(This article belongs to the Special Issue Carbon-Based Materials Applied in Water and Wastewater Treatment)

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