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C, Volume 11, Issue 3 (September 2025) – 19 articles

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22 pages, 1937 KiB  
Review
Carbon Dot Nanozymes in Orthopedic Disease Treatment: Comprehensive Overview, Perspectives and Challenges
by Huihui Wang
C 2025, 11(3), 58; https://doi.org/10.3390/c11030058 - 1 Aug 2025
Viewed by 191
Abstract
Nanozymes, as a new generation of artificial enzymes, have attracted increasing attention in the field of biomedicine due to their multiple enzymatic characteristics, multi-functionality, low cost, and high stability. Among them, carbon dot nanozymes (CDzymes) possess excellent enzymatic-like catalytic activity and biocompatibility and [...] Read more.
Nanozymes, as a new generation of artificial enzymes, have attracted increasing attention in the field of biomedicine due to their multiple enzymatic characteristics, multi-functionality, low cost, and high stability. Among them, carbon dot nanozymes (CDzymes) possess excellent enzymatic-like catalytic activity and biocompatibility and have been developed for various diagnostic and therapeutic studies of diseases. Here, we briefly review the representative research on CDzymes in recent years, including their synthesis, modification, and applications, especially in orthopedic diseases, including osteoarthritis, osteoporosis, osteomyelitis, intervertebral disc degenerative diseases, bone tumors, and bone injury repair and periodontitis. Additionally, we briefly discuss the potential future applications and opportunities and challenges of CDzymes. We hope this review can provide some reference opinions for CDzymes and offer insights for promoting their application strategies in the treatment of orthopedic disease. Full article
(This article belongs to the Special Issue Carbon Nanohybrids for Biomedical Applications (2nd Edition))
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11 pages, 1936 KiB  
Communication
Diffusion of C-O-H Fluids in a Sub-Nanometer Pore Network: Role of Pore Surface Area and Its Ratio with Pore Volume
by Siddharth Gautam and David Cole
C 2025, 11(3), 57; https://doi.org/10.3390/c11030057 - 1 Aug 2025
Viewed by 175
Abstract
Porous materials are characterized by the pore surface area (S) and volume (V) accessible to a confined fluid. For mesoporous materials NMR measurements of diffusion are used to assess the S/V ratio, because at short times, only [...] Read more.
Porous materials are characterized by the pore surface area (S) and volume (V) accessible to a confined fluid. For mesoporous materials NMR measurements of diffusion are used to assess the S/V ratio, because at short times, only the diffusivity of molecules in the adsorbed layer is affected by confinement and the fractional population of these molecules is proportional to the S/V ratio. For materials with sub-nanometer pores, this might not be true, as the adsorbed layer can encompass the entire pore volume. Here, using molecular simulations, we explore the role played by S and S/V in determining the dynamical behavior of two carbon-bearing fluids—CO2 and ethane—confined in sub-nanometer pores of silica. S and V in a silicalite model representing a sub-nanometer porous material are varied by selectively blocking a part of the pore network by immobile methane molecules. Three classes of adsorbents were thus obtained with either all of the straight (labeled ‘S-major’) or zigzag channels (‘Z-major’) remaining open or a mix of a fraction of both types of channel blocked, resulting in half of the total pore volume being blocked (‘Half’). While the adsorption layers from opposite surfaces overlap, encompassing the entire pore volume for all pores except the intersections, the diffusion coefficient is still found to be reduced at high S/V, especially for CO2, albeit not so strongly as would be expected in the case of wider pores. This is because of the presence of channel intersections that provide a wider pore space with non-overlapping adsorption layers. Full article
(This article belongs to the Section Carbon Cycle, Capture and Storage)
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16 pages, 3508 KiB  
Article
Stability of Carbon Quantum Dots for Potential Photothermal and Diagnostic Applications
by María Fernanda Amezaga Gonzalez, Abdiel Ramirez-Reyes, Monica Elvira Mendoza-Duarte, Alejandro Vega-Rios, Daniel Martinez-Ozuna, Claudia A. Rodriguez-Gonzalez, Santos-Adriana Martel-Estrada and Imelda Olivas-Armendariz
C 2025, 11(3), 56; https://doi.org/10.3390/c11030056 - 29 Jul 2025
Viewed by 306
Abstract
Theranostic agents enable the simultaneous diagnosis and treatment of diseases, and they are particularly useful in fluorescent imaging and cancer therapies. In this study, carbon quantum dots were synthesized via a microwave-assisted method using citric acid and bovine serum albumin (BSA) as precursors. [...] Read more.
Theranostic agents enable the simultaneous diagnosis and treatment of diseases, and they are particularly useful in fluorescent imaging and cancer therapies. In this study, carbon quantum dots were synthesized via a microwave-assisted method using citric acid and bovine serum albumin (BSA) as precursors. The resulting CQDs exhibited spherical morphology, an average size of 4 nm, and an amorphous graphitic structure. FT-IR characterization revealed the presence of amide bonds and oxygenated functional groups. At the same time, optical analysis showed excitation at 320 nm and emission between 360 and 400 nm, with fluorescent stability maintained for one month. Furthermore, the CQDs demonstrated good thermal stability and photothermal efficiency, reaching temperatures above 41 °C within 15 min under NIR irradiation, with a mass loss of less than 1%. Their stability was evaluated in media with different pH levels, simulating physiological and tumor environments. While their behavior was affected under acidic conditions, their excellent photothermal conversion capacity and overall stability in triple-distilled water positioned them as promising candidates for theranostic applications in cancer, effectively combining diagnostic imaging and thermal therapy. Full article
(This article belongs to the Special Issue Carbon Nanohybrids for Biomedical Applications (2nd Edition))
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15 pages, 2645 KiB  
Article
Carbon Footprint and Uncertainties of Geopolymer Concrete Production: A Comprehensive Life Cycle Assessment (LCA)
by Quddus Tushar, Muhammed A. Bhuiyan, Ziyad Abunada, Charles Lemckert and Filippo Giustozzi
C 2025, 11(3), 55; https://doi.org/10.3390/c11030055 - 28 Jul 2025
Viewed by 729
Abstract
This study aims to estimate the carbon footprint and relative uncertainties for design components of conventional and geopolymer concrete. All the design components of alkaline-activated geopolymer concrete, such as fly ash, ground granulated blast furnace slag, sodium hydroxide (NaOH), sodium silicate (Na2 [...] Read more.
This study aims to estimate the carbon footprint and relative uncertainties for design components of conventional and geopolymer concrete. All the design components of alkaline-activated geopolymer concrete, such as fly ash, ground granulated blast furnace slag, sodium hydroxide (NaOH), sodium silicate (Na2SiO3), superplasticizer, and others, are assessed to reflect the actual scenarios of the carbon footprint. The conjugate application of the life cycle assessment (LCA) tool SimPro 9.4 and @RISK Monte Carlo simulation justifies the variations in carbon emissions rather than a specific determined value for concrete binders, precursors, and filler materials. A reduction of 43% in carbon emissions has been observed by replacing cement with alkali-activated binders. However, the associative uncertainties of chemical admixtures reveal that even a slight increase may cause significant environmental damage rather than its benefit. Pearson correlations of carbon footprint with three admixtures, namely sodium silicate (r = 0.80), sodium hydroxide (r = 0.52), and superplasticizer (r = 0.19), indicate that the shift from cement to alkaline activation needs additional precaution for excessive use. Therefore, a suitable method of manufacturing chemical activators utilizing renewable energy sources may ensure long-term sustainability. Full article
(This article belongs to the Section Carbon Cycle, Capture and Storage)
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24 pages, 3016 KiB  
Article
Industrial Off-Gas Fermentation for Acetic Acid Production: A Carbon Footprint Assessment in the Context of Energy Transition
by Marta Pacheco, Adrien Brac de la Perrière, Patrícia Moura and Carla Silva
C 2025, 11(3), 54; https://doi.org/10.3390/c11030054 - 23 Jul 2025
Viewed by 469
Abstract
Most industrial processes depend on heat, electricity, demineralized water, and chemical inputs, which themselves are produced through energy- and resource-intensive industrial activities. In this work, acetic acid (AA) production from syngas (CO, CO2, and H2) fermentation is explored and [...] Read more.
Most industrial processes depend on heat, electricity, demineralized water, and chemical inputs, which themselves are produced through energy- and resource-intensive industrial activities. In this work, acetic acid (AA) production from syngas (CO, CO2, and H2) fermentation is explored and compared against a thermochemical fossil benchmark and other thermochemical/biological processes across four main Key Performance Indicators (KPI)—electricity use, heat use, water consumption, and carbon footprint (CF)—for the years 2023 and 2050 in Portugal and France. CF was evaluated through transparent and public inventories for all the processes involved in chemical production and utilities. Spreadsheet-traceable matrices for hotspot identification were also developed. The fossil benchmark, with all the necessary cascade processes, was 0.64 kg CO2-eq/kg AA, 1.53 kWh/kg AA, 22.02 MJ/kg AA, and 1.62 L water/kg AA for the Portuguese 2023 energy mix, with a reduction of 162% of the CO2-eq in the 2050 energy transition context. The results demonstrated that industrial practices would benefit greatly from the transition from fossil to renewable energy and from more sustainable chemical sources. For carbon-intensive sectors like steel or cement, the acetogenic syngas fermentation appears as a scalable bridge technology, converting the flue gas waste stream into marketable products and accelerating the transition towards a circular economy. Full article
(This article belongs to the Section Carbon Cycle, Capture and Storage)
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12 pages, 11599 KiB  
Article
Dual pH- and Temperature-Responsive Fluorescent Hybrid Materials Based on Carbon Dot-Grafted Triamino-Tetraphenylethylene/N-Isopropylacrylamide Copolymers
by Huan Liu, Yuxin Ding, Longping Zhou, Shirui Xu and Bo Liao
C 2025, 11(3), 53; https://doi.org/10.3390/c11030053 - 22 Jul 2025
Viewed by 243
Abstract
Carbon dots (CDs), a class of carbon-based fluorescent nanomaterials, have garnered significant attention due to their tunable optical properties and functional versatility. In this study, we developed a hybrid material by grafting pH- and temperature-responsive copolymers onto CDs via reversible addition-fragmentation chain-transfer (RAFT) [...] Read more.
Carbon dots (CDs), a class of carbon-based fluorescent nanomaterials, have garnered significant attention due to their tunable optical properties and functional versatility. In this study, we developed a hybrid material by grafting pH- and temperature-responsive copolymers onto CDs via reversible addition-fragmentation chain-transfer (RAFT) polymerization. Triamino-tetraphenylethylene (ATPE) and N-isopropylacrylamide (NIPAM) were copolymerized at varying ratios and covalently linked to CDs, forming a dual-responsive system. Structural characterization using FTIR, 1H NMR, and TEM confirmed the successful grafting of the copolymers onto CDs. The hybrid material exhibited pH-dependent fluorescence changes in acidic aqueous solutions, with emission shifting from 450 nm (attributed to CDs) to 500 nm (aggregation-induced emission, AIE, from ATPE) above a critical pH threshold. Solid films of the hybrid material demonstrated reversible fluorescence quenching under HCl vapor and recovery/enhancement under NH3 vapor, showing excellent fatigue resistance over multiple cycles. Temperature responsiveness was attributed to the thermosensitive poly(NIPAM) segments, with fluorescence intensity increasing above 35 °C due to polymer chain collapse and ATPE aggregation. This work provides a strategy for designing multifunctional hybrid materials with potential applications in recyclable optical pH/temperature sensors. Full article
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11 pages, 3598 KiB  
Article
NMR Spectroelectrochemistry in Studies of Procarbazine Oxidation by Laser-Induced Graphene Thin Films
by Zhe Wang, Xiaoping Zhang, Shihui Xu, Lin Yang, Lina Wang, Yijing Wang, Ahmad Mansoor and Wei Sun
C 2025, 11(3), 52; https://doi.org/10.3390/c11030052 - 21 Jul 2025
Viewed by 313
Abstract
In this paper, nanoscale graphene film electrodes were prepared using laser-induced technology, and an in situ electrochemical cell was constructed. The normalized peak areas at 2.82 ppm for the samples without the in situ electrochemical cell and with an in situ electrochemical cell [...] Read more.
In this paper, nanoscale graphene film electrodes were prepared using laser-induced technology, and an in situ electrochemical cell was constructed. The normalized peak areas at 2.82 ppm for the samples without the in situ electrochemical cell and with an in situ electrochemical cell are 4.02 and 4.41, respectively. Tests showed that this in situ electrochemical cell has minimal interference from the nuclear magnetic resonance (NMR) magnetic field, allowing for high-resolution in situ spectra. Using this in situ electrochemical cell and employing in situ electrochemistry combined with NMR techniques, we investigated the oxidation reaction of 0.01 M procarbazine (PCZ) in real-time. We elucidated the following oxidation mechanism for procarbazine: the oxidation of PCZ first generates azo-procarbazine, which then undergoes a double bond shift to hydrazo-procarbazine. hydrazo-procarbazine undergoes hydrolysis to yield benzaldehyde-procarbazine, and then finally oxidizes to produce N-isopropylterephthalic acid. This confirms that the combination of in situ electrochemistry and nuclear magnetic resonance technology provides chemists with an effective tool for in situ studying the reaction mechanisms of drug molecules. Full article
(This article belongs to the Section Carbon Materials and Carbon Allotropes)
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18 pages, 6572 KiB  
Article
Tuning Optical Excitations of Graphene Quantum Dots Through Selective Oxidation: Effect of Epoxy Groups
by Igor V. Ershov, Anatoly A. Lavrentyev, Dmitry L. Romanov and Olga M. Holodova
C 2025, 11(3), 51; https://doi.org/10.3390/c11030051 - 14 Jul 2025
Viewed by 371
Abstract
Graphene quantum dots (GQDs) have strong potential in optoelectronics, particularly in LEDs, photodetectors, solar cells, and nanophotonics. While challenges remain in efficiency and scalability, advances in functionalization and hybrid material integration could soon make them commercially viable for next-generation optoelectronic devices. In this [...] Read more.
Graphene quantum dots (GQDs) have strong potential in optoelectronics, particularly in LEDs, photodetectors, solar cells, and nanophotonics. While challenges remain in efficiency and scalability, advances in functionalization and hybrid material integration could soon make them commercially viable for next-generation optoelectronic devices. In this work, we assess the stability of various epoxy positions and their impact on the electronic and optical properties of GQDs. The oxygen binding energies and the potential barrier heights at different positions of epoxy groups at the edges and in the core of the GQD were estimated. The effect of possible transformations of epoxy groups into other edge configurations on the structural and optical properties of GQDs was evaluated. The results demonstrate that the functionalization of the GQD surface and edges with an epoxy groups at varying binding sites can result in substantial modification of the electronic structure and absorption properties of the GQDs. The prospects of low temperature annealing for controlling optical properties of epoxidized GQDs were discussed. The present computational work offers atomistic insights that can facilitate the rational design of optoelectronic systems based on GQD materials. Full article
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18 pages, 1777 KiB  
Review
Biochar in Agriculture: A Review on Sources, Production, and Composites Related to Soil Fertility, Crop Productivity, and Environmental Sustainability
by Md. Muzammal Hoque, Biplob Kumar Saha, Antonio Scopa and Marios Drosos
C 2025, 11(3), 50; https://doi.org/10.3390/c11030050 - 11 Jul 2025
Viewed by 847
Abstract
Due to soil nutrient depletion and rising food demand from an increasing global population, it is essential to find sustainable ways to boost crop yields, improve soil health, and address the environmental issues induced by agriculture. The most appropriate approach is to consider [...] Read more.
Due to soil nutrient depletion and rising food demand from an increasing global population, it is essential to find sustainable ways to boost crop yields, improve soil health, and address the environmental issues induced by agriculture. The most appropriate approach is to consider sustainable amendments, such as biochar and its derivatives, which are vital constituents of soil health due to their affordability, low reactivity, large surface area, and reduced carbon footprint. In this context, biochar and its derivatives in farming systems focus on improving soil structure, nutrient holding capacity, microbial activities, and the perpetuation of soil fertility. Despite its benefits, biochar, if it is used in high concentration, can sometimes become highly toxic, causing soil erosion due to reducing surface area, increasing pH levels, and altering soil properties. This review highlights the production methods and sources of feedstocks, emphasizing their important contribution to the soil’s physicochemical and biological properties. Furthermore, it critically evaluates the environmental applications and their impacts, providing data built upon the literature on contaminant removal from soil, economic factors, heavy metal immobilization, carbon sequestration, and climate resilience. This review emphasizes the main challenges and future prospects for biochar use in comparison to modified biochar (MB) to propose the best practices for sustainable farming systems. Full article
(This article belongs to the Special Issue Carbons for Health and Environmental Protection (2nd Edition))
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11 pages, 2969 KiB  
Article
First-Principles Study of CO, C2H2, and C2H4 Adsorption on Penta-Graphene for Transformer Oil Gas Sensing Applications
by Min-Qi Zhu and Xue-Feng Wang
C 2025, 11(3), 49; https://doi.org/10.3390/c11030049 - 9 Jul 2025
Viewed by 375
Abstract
Penta-graphene, a novel two-dimensional carbon allotrope entirely composed of pentagonal carbon rings, has attracted increasing attention due to its unique geometric structure, mechanical robustness, and intrinsic semiconducting nature. In this study, we systematically investigate the adsorption behavior of three typical dissolved gases in [...] Read more.
Penta-graphene, a novel two-dimensional carbon allotrope entirely composed of pentagonal carbon rings, has attracted increasing attention due to its unique geometric structure, mechanical robustness, and intrinsic semiconducting nature. In this study, we systematically investigate the adsorption behavior of three typical dissolved gases in transformer oil (CO, C2H2, and C2H4) on penta-graphene using first-principles calculations based on density functional theory. The optimized adsorption configuration, adsorption energy, charge transfer, adsorption distance, band structure, density of states, charge density difference, and desorption time are analyzed to evaluate the sensing capability of penta-graphene. Results reveal that penta-graphene exhibits moderate chemical interactions with CO and C2H2, accompanied by noticeable charge transfer and band structure changes, whereas C2H4 shows weaker physisorption characteristics. The projected density of states analysis further confirms the orbital hybridization between gas molecules and the substrate. Additionally, the desorption time calculations suggest that penta-graphene possesses good sensing and recovery potential, especially under elevated temperatures. These findings indicate that penta-graphene is a promising candidate for use in gas sensing applications related to the monitoring of dissolved gases in transformer oils. Full article
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19 pages, 2749 KiB  
Article
Mechanism of Fluorescence Characteristics and Application of Zinc-Doped Carbon Dots Synthesized by Using Zinc Citrate Complexes as Precursors
by Yun Zhang, Yiwen Guo, Kaibo Sun, Xiaojing Li, Xiuhua Liu, Jinhua Zhu and Md. Zaved Hossain Khan
C 2025, 11(3), 48; https://doi.org/10.3390/c11030048 - 7 Jul 2025
Viewed by 494
Abstract
Zn-doped carbon dots (Zn@C-210 calcination temperature at 210 °C and Zn@C-260 calcination temperature at 260 °C) were synthesized via an in situ calcination method using zinc citrate complexes as precursors, aiming to investigate the mechanisms of their distinctive fluorescence properties. A range of [...] Read more.
Zn-doped carbon dots (Zn@C-210 calcination temperature at 210 °C and Zn@C-260 calcination temperature at 260 °C) were synthesized via an in situ calcination method using zinc citrate complexes as precursors, aiming to investigate the mechanisms of their distinctive fluorescence properties. A range of analytical methods were employed to characterize these nanomaterials. The mechanism study revealed that the coordination structure of Zn-O, formed through zinc doping, can induce a metal–ligand charge-transfer effect, which significantly increases the probability of radiative transitions between the excited and ground states, thereby enhancing the fluorescence intensity. The Zn@C-210 in a solid state and Zn@C-260 in water exhibited approximately 71.50% and 21.1% quantum yields, respectively. Both Zn@C-210 and Zn@C-260 exhibited excitation-independent luminescence, featuring a long fluorescence lifetime of 6.5 μs for Zn@C-210 and 6.2 μs for Zn@C-260. Impressively, zinc-doped CDs displayed exceptional biosafety, showing no acute toxicity even at 1000 mg/kg doses. Zn@C-210 has excellent fluorescence in a solid state, showing promise in anti-photobleaching applications; meanwhile, the dual functionality of Zn@C-260 makes it useful as a folate sensor and cellular imaging probe. These findings not only advance the fundamental understanding of metal-doped carbon dot photophysics but also provide practical guidelines for developing targeted biomedical nanomaterials through rational surface engineering and doping strategies. Full article
(This article belongs to the Special Issue Carbon Nanohybrids for Biomedical Applications (2nd Edition))
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14 pages, 4383 KiB  
Article
Optimized Adsorptive Desulfurization Using Waste Tire-Derived Carbon
by Ming-Liao Tsai, An-Ya Lo, Jun-Hao Liu and Yong-Ming Dai
C 2025, 11(3), 47; https://doi.org/10.3390/c11030047 - 7 Jul 2025
Viewed by 474
Abstract
The inclusion of adsorption thermodynamic analysis and performance benchmarking with existing adsorbents reinforces both the theoretical significance and practical applicability of this study. The modified rubber-derived carbon demonstrated a remarkably high DBT adsorption capacity of 254.45 mg/g. These results establish it as a [...] Read more.
The inclusion of adsorption thermodynamic analysis and performance benchmarking with existing adsorbents reinforces both the theoretical significance and practical applicability of this study. The modified rubber-derived carbon demonstrated a remarkably high DBT adsorption capacity of 254.45 mg/g. These results establish it as a promising alternative to conventional materials such as commercial activated carbon, zeolites, and even metal–organic framework materials. In addition to confirming the superior performance of the adsorbent, the findings provide a deeper understanding of the DBT adsorption mechanism and offer a solid scientific basis for large-scale fuel desulfurization applications. This research highlights the potential of transforming end-of-life tire waste into value-added functional materials and contributes to the advancement of sustainable and efficient desulfurization technologies. Future work should focus on optimizing surface functionalization and regeneration strategies to further improve long-term adsorption stability and practical deployment. Full article
(This article belongs to the Special Issue Carbon Functionalization: From Synthesis to Applications)
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13 pages, 1309 KiB  
Article
Thermal Conductivity of Graphene Moiré Superlattices at Small Twist Angles: An Approach-to-Equilibrium Molecular Dynamics and Boltzmann Transport Study
by Lorenzo Manunza, Riccardo Dettori, Antonio Cappai and Claudio Melis
C 2025, 11(3), 46; https://doi.org/10.3390/c11030046 - 30 Jun 2025
Viewed by 919
Abstract
We investigate the thermal conductivity of graphene Moiré superlattices formed by twisting bilayer graphene (TBG) at small angles, employing approach-to-equilibrium molecular dynamics and lattice dynamics calculations based on the Boltzmann Transport Equation. Our simulations reveal a non-monotonic dependence of the thermal conductivity on [...] Read more.
We investigate the thermal conductivity of graphene Moiré superlattices formed by twisting bilayer graphene (TBG) at small angles, employing approach-to-equilibrium molecular dynamics and lattice dynamics calculations based on the Boltzmann Transport Equation. Our simulations reveal a non-monotonic dependence of the thermal conductivity on the twisting angle, with a local minimum near the first magic angle (θ1.1°). This behavior is attributed to the evolution of local stacking configurations—AA, AB, and saddle-point (SP)—across the Moiré superlattice, which strongly affect phonon transport. A detailed analysis of phonon mean free paths (MFP) and mode-resolved thermal conductivity shows that AA stacking suppresses thermal transport, while AB and SP stackings exhibit enhanced conductivity owing to more efficient low-frequency phonon transport. Furthermore, we establish a direct correlation between the thermal conductivity of twisted structures and the relative abundance of stacking domains within the Moiré supercell. Our results demonstrate that even very small changes in twisting angle (<2°) can lead to thermal conductivity variations of over 30%, emphasizing the high tunability of thermal transport in TBG. Full article
(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)
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14 pages, 18495 KiB  
Article
Analysis of Biochar–Cement Composites by SEM/EDS: Interfacial Interactions and Effects on Mechanical Strength
by Rafaela Paula, Jaqueline Carvalho, Antônio Júnior, Filipe Fagundes, Robson de Lima, Evaneide Lima, Carlos Oliveira, Magno de Oliveira, Augusto Bezerra, Osania Ferreira and Alan Machado
C 2025, 11(3), 45; https://doi.org/10.3390/c11030045 - 29 Jun 2025
Cited by 1 | Viewed by 699
Abstract
Portland cement production is one of the main global sources of CO2 emissions, driving the search for sustainable solutions to reduce its environmental footprint. This study evaluated the use of biochar derived from sugarcane bagasse as a partial cement replacement in cementitious [...] Read more.
Portland cement production is one of the main global sources of CO2 emissions, driving the search for sustainable solutions to reduce its environmental footprint. This study evaluated the use of biochar derived from sugarcane bagasse as a partial cement replacement in cementitious composites, aiming to investigate its effects on mechanical and microstructural properties. Composites were prepared with 0, 2, and 5 (% w w−1) biochar at two water-to-cement (w/c) ratios: 0.28 and 0.35. It was hypothesized that the porous structure and carbon-rich composition of biochar could enhance the microstructure of the cementitious matrix and contribute to strength development. Characterization of the biochar indicated compliance with the European Biochar Certificate (EBC) standard, high thermal stability, and notable water retention capacity. Mechanical testing revealed that incorporating 5% w w−1 biochar increased compressive strength by up to 48% in the 0.35 w/c formulation compared to the control. Microstructural analyses (SEM/EDS) showed good interaction between the biochar and the cementitious matrix, with the formation of hydration products at the interfaces. The results confirm the potential of sugarcane bagasse biochar as a supplementary cementitious material, promoting more sustainable composites with improved mechanical performance and reduced environmental impact. Full article
(This article belongs to the Section Carbon Materials and Carbon Allotropes)
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18 pages, 1917 KiB  
Article
Bimetallic Copper–Indium Co-Doped Titanium Dioxide Towards Electrosynthesis of Urea from Carbon Dioxide and Nitrate
by Youcai Meng, Tianran Wei, Zhiwei Wang, Caiyun Wang, Junyang Ding, Yang Luo and Xijun Liu
C 2025, 11(3), 44; https://doi.org/10.3390/c11030044 - 27 Jun 2025
Viewed by 435
Abstract
Electrocatalytic urea synthesis offers great potential for sustainable strategies through CO2 and NO3 reduction reactions. However, the development of high-performance catalysts is often hampered by the complexity of synthetic methodologies and the unresolved nature of C-N coupling pathways. In this [...] Read more.
Electrocatalytic urea synthesis offers great potential for sustainable strategies through CO2 and NO3 reduction reactions. However, the development of high-performance catalysts is often hampered by the complexity of synthetic methodologies and the unresolved nature of C-N coupling pathways. In this study, we present a copper–indium co-doped titanium dioxide (CuIn-TiO2) catalyst that exhibits remarkable efficacy in enhancing the synergistic reduction of CO2 and NO3 to produce urea. The bimetallic CuIn site functions as the primary active site for the C-N coupling reaction, achieving a urea yield rate of 411.8 μg h−1 mgcat−1 with a Faradaic efficiency of 6.7% at −0.8 V versus reversible hydrogen electrode (vs. RHE). A body of experimental and theoretical research has demonstrated that the nanoscale particles enhance the density of active sites and improve the feasibility of reactions on the surface of TiO2. The co-doping of Cu and In has been shown to significantly enhance electronic conductivity, increase the adsorption affinity for *CO2 and *NO3, and promote the C-N coupling process. The CuIn-TiO2 catalyst has been demonstrated to effectively promote the reduction of NO3 and CO2, as well as accelerate the C-N coupling reaction. This effect is a result of a synergistic interaction among the catalyst’s components. Full article
(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)
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10 pages, 1436 KiB  
Article
Theoretical Investigation of O2 and CO2 Adsorption on Small PdNi Clusters Supported on N-Doped Graphene Quantum Dots
by Brenda García-Hilerio, Lidia Santiago-Silva, Pastor T. Matadamas-Ortiz, Alejandro Gomez-Sanchez, Víctor A. Franco-Luján and Heriberto Cruz-Martínez
C 2025, 11(3), 43; https://doi.org/10.3390/c11030043 - 27 Jun 2025
Viewed by 478
Abstract
A density functional theory (DFT) investigation was conducted to study the O2 and CO2 adsorption on very small Pd3−nNin (n = 0–2) clusters supported on N-doped graphene quantum dots (N-GQDs). The study was carried out in two stages. [...] Read more.
A density functional theory (DFT) investigation was conducted to study the O2 and CO2 adsorption on very small Pd3−nNin (n = 0–2) clusters supported on N-doped graphene quantum dots (N-GQDs). The study was carried out in two stages. First, the interaction between Pd3−nNin (n = 0–2) clusters and N-GQDs was analyzed. Subsequently, the adsorption behavior of O2 and CO2 molecules on the supported clusters was examined. The calculated interaction energies (Eint) of Pd3−nNin (n = 0–2) clusters on N-GQDs were found to be higher than those on pristine graphene, indicating enhanced cluster stability on N-GQDs. Furthermore, the adsorption energies (Eads) of the O2 molecule on the Pd3 and Pd2Ni clusters deposited on N-GQDs were similar. Meanwhile, the PdNi2 cluster deposited on N-GQDs exhibited the highest Eads (−1.740). The Eads of CO2 on Pd3−nNin (n = 0–2) clusters embedded in N-GQDs were observed to be close to or exceed 1 eV. Upon adsorption of O2 and CO2 on the Pd3−nNin (n = 0–2) clusters supported on N-GQDs, an elongation of the O–O and C–O bond lengths was observed, respectively. This structural change may facilitate the dissociation of these molecules on the supported clusters. Full article
(This article belongs to the Section Carbon Materials and Carbon Allotropes)
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14 pages, 61510 KiB  
Article
Enhancing High-Temperature Oxidation Stability of Recycled Carbon Fibers Through Ceramic Coating
by Carmela Borriello, Sabrina Portofino, Loredana Tammaro, Pierpaolo Iovane, Gabriella Rametta and Sergio Galvagno
C 2025, 11(3), 42; https://doi.org/10.3390/c11030042 - 26 Jun 2025
Viewed by 586
Abstract
Carbon fiber-reinforced composites (CFRCs) have attracted considerable attention in recent years due to their excellent properties, enabling their use across various sectors. However, their application at high temperatures is limited by the fibers’ lack of oxidation resistance. This study demonstrates a significant advancement [...] Read more.
Carbon fiber-reinforced composites (CFRCs) have attracted considerable attention in recent years due to their excellent properties, enabling their use across various sectors. However, their application at high temperatures is limited by the fibers’ lack of oxidation resistance. This study demonstrates a significant advancement in enhancing the oxidation stability performance of carbon fiber-reinforced composites (CFRCs) by developing a silicon carbide (SiC) coating through the ceramization of carbon fibers using silicon (Si) powder. For the first time, this method was applied to recycled carbon fibers from CF thermoplastic composites. The key findings include the successful formation of a uniform SiC coating, with coating thickness increasing with process duration and decreasing at higher temperatures. The treated fibers exhibited substantially improved oxidation resistance, maintaining structural stability above 700 °C—markedly better than that of their uncoated counterparts. Thermogravimetric analysis confirmed that oxidation resistance varied depending on the CF/Si ratio, highlighting this parameter’s critical role. Overall, this study offers a viable pathway to enhance the thermal durability of recycled carbon fibers for high-temperature applications. Full article
(This article belongs to the Special Issue High-Performance Carbon Materials and Their Composites (2nd Edition))
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13 pages, 6606 KiB  
Article
Preparation and Properties of C/C-(TiZrHfNbTa)C Composites via Inorganic Salt Precursor Method
by Haibo Ouyang, Jiyong Liu, Cuiyan Li, Tianzhan Shen, Jiaqi Liu, Mengyao He, Yanlei Li and Leer Bao
C 2025, 11(3), 41; https://doi.org/10.3390/c11030041 - 25 Jun 2025
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Abstract
Using low-cost transition-metal chlorides and furfuryl alcohol as raw materials, the (TiZrHfNbTa)C precursor was prepared, and a three-dimensional braided carbon fiber preform (C/C) coated with pyrolytic carbon (PyC) was used as the reinforcing material. A C/C-(TiZrHfNbTa)C composite was successfully fabricated through the precursor [...] Read more.
Using low-cost transition-metal chlorides and furfuryl alcohol as raw materials, the (TiZrHfNbTa)C precursor was prepared, and a three-dimensional braided carbon fiber preform (C/C) coated with pyrolytic carbon (PyC) was used as the reinforcing material. A C/C-(TiZrHfNbTa)C composite was successfully fabricated through the precursor impregnation pyrolysis (PIP) process. Under extreme oxyacetylene ablation conditions (2311 °C/60 s), this composite material demonstrated outstanding ablation resistance, with a mass ablation rate as low as 0.67 mg/s and a linear ablation rate of only 20 μm/s. This excellent performance can be attributed to the dense (HfZr)6(TaNb)2O17 oxide layer formed during ablation. This oxide layer not only has an excellent anti-erosion capability but also effectively acts as an oxygen diffusion barrier, thereby significantly suppressing further ablation and oxidation within the matrix. This study provides an innovative strategy for the development of low-cost ultra-high-temperature ceramic precursors and opens up a feasible path for the efficient preparation of C/C-(TiZrHfNbTa)C composites. Full article
(This article belongs to the Special Issue High-Performance Carbon Materials and Their Composites (2nd Edition))
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17 pages, 5479 KiB  
Article
Fracture Mechanics of Tetragraphene: Effects of Structural Variations and Loading Conditions
by Elnaz Haddadi and Alireza Tabarraei
C 2025, 11(3), 40; https://doi.org/10.3390/c11030040 - 24 Jun 2025
Viewed by 530
Abstract
Despite the promising electronic properties of graphene, its lack of an intrinsic bandgap limits its applicability in semiconductor technologies. This has catalyzed the investigation of newly developed two-dimensional carbon materials, including tetragraphene (TG), a quasi-2D semiconducting material featuring a combination of hexagonal and [...] Read more.
Despite the promising electronic properties of graphene, its lack of an intrinsic bandgap limits its applicability in semiconductor technologies. This has catalyzed the investigation of newly developed two-dimensional carbon materials, including tetragraphene (TG), a quasi-2D semiconducting material featuring a combination of hexagonal and tetragonal rings. This study aims to investigate the mechanical and fracture behaviors of TG using density functional theory (DFT) and molecular dynamics (MD) simulations, studying two distinct atomic configurations of tetragraphene. DFT simulations assess the mechanical properties, while MD simulations explore the fracture dynamics subjected to mixed mode I (opening mode) and mode II (in-plane shear mode) loading. Our analysis focuses on the influence of loading phase angle, crack edge chirality, crack tip configuration, and temperature on crack propagation paths and critical stress intensity factors (SIFs) in TG structures. Our results show that the critical SIF varies by 12.5–21% depending on the crack chirality. Across all loading conditions, increasing the temperature ranging from 300 K to 2000 K reduces the critical SIF by 10–45%, with the largest reductions observed under pure mode I loading. These outcomes offer important insights into the structural integrity of TG and inform its potential integration into flexible nanoelectronic devices, where mechanical reliability is essential. Full article
(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)
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