C | An Open Access Journal from MDPI

12 pages, 5425 KB

Open AccessArticle

Effect of Carbon Fixation Time on the Properties of Gangue–Fly Ash Composite Filling Materials: Carbon Fixation Amount and Rheological Properties

by Haiquan Liu, Qiang Guo, Yong Chen, Yifan Zhang, Binbin Huo and Meng Li

C 2025, 11(3), 71; https://doi.org/10.3390/c11030071 - 8 Sep 2025

Abstract

Coal-based solid wastes are used for carbon fixation, which can achieve the dual purpose of resource utilization of coal-based solid wastes and CO₂ storage, but carbon fixation has a negative impact on the rheological properties of filling slurry. This paper explores the [...] Read more.

Coal-based solid wastes are used for carbon fixation, which can achieve the dual purpose of resource utilization of coal-based solid wastes and CO₂ storage, but carbon fixation has a negative impact on the rheological properties of filling slurry. This paper explores the effect of carbon fixation time on the carbon fixation performance and rheological properties of coal gangue (CG)–fly ash (FA) composite filling materials (CFS) through rheometer, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and other testing methods. The results show that, with an increase in the carbon fixation time, the carbon fixation amount of the CFS shows a trend of increasing first and then stabilizing. Considering the carbon fixation amount and rheological properties of the CFS together, the optimal carbon fixation time is 2 h. At this time, the carbon fixation amount of the CFS is 1.18%, and the yield stress and plastic viscosity are 155.93 Pa and 0.17 Pa·s, respectively. However, with a further increase in the carbon fixation time, the carbon fixation amount basically tends to be stable, mainly because the calcium ions in the CFS are gradually consumed by the reaction as the carbon fixation time increases. The research results are of great significance for improving the utilization of coal-based solid waste and CO₂ storage. Full article

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15 pages, 3020 KB

Open AccessArticle

Enhanced Electrocatalytic Activity for ORR Based on Synergistic Effect of Hierarchical Porosity and Co-N_x Sites in ZIF-Derived Heteroatom-Doped Carbon Materials

by Yan Yang, A-Min Tan, Qiu-Xuan Ren and Gai Zhang

C 2025, 11(3), 70; https://doi.org/10.3390/c11030070 - 8 Sep 2025

Abstract

The hierarchical porosity and active sites of porous carbon materials have significant impacts on the oxygen reduction reaction (ORR) process. The heteroatom-doped porous carbon materials (Z67-900, Z8-900, Z11-900, Z12-900) were synthesized by pyrolysis of ZIFs to reveal the synergistic effect of hierarchical porosity [...] Read more.

The hierarchical porosity and active sites of porous carbon materials have significant impacts on the oxygen reduction reaction (ORR) process. The heteroatom-doped porous carbon materials (Z67-900, Z8-900, Z11-900, Z12-900) were synthesized by pyrolysis of ZIFs to reveal the synergistic effect of hierarchical porosity and Co-N_x sites. The structures of prepared materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectra, and nitrogen adsorption. The results of electrocatalytic performance show that Z67-900 has the best performance among the four materials prepared. The onset potential (E₀) of Z67-900 is close to commercial Pt/C (20%), and the half-wave potential (E_1/2) of Z67-900 is 80 mV positive than that of Pt/C in an O₂-saturated 0.1 M KOH solution (1600 rpm) with sweep rate of 5 mV·s⁻¹. Moreover, Z67-900 has better methanol resistance. The hierarchical pore structure of Z67-900 facilitates mass transfer, while the Co-N_x sites provide active catalytic centers. This study provides a solid foundation for the rational design of highly efficient ZIF-derived heteroatom-doped catalysts. Full article

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

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18 pages, 1709 KB

Open AccessArticle

Formation of Improved Metallurgical Properties and Carbon Structure of Coke by Optimizing the Composition of Petrographically Heterogeneous Interbasin Coal Batches

by Denis Miroshnichenko, Kateryna Shmeltser, Maryna Kormer, Leonid Bannikov, Serhii Nedbailo, Mykhailo Miroshnychenko, Natalya Mukina and Mariia Shved

C 2025, 11(3), 69; https://doi.org/10.3390/c11030069 - 4 Sep 2025

Abstract

Given the multi-basin raw material base for coking that has been formed at most industry enterprises, there is an urgent need to optimize the component composition and improve the basic technological methods of coal raw material preparation, taking into account the petrographic characteristics [...] Read more.

Given the multi-basin raw material base for coking that has been formed at most industry enterprises, there is an urgent need to optimize the component composition and improve the basic technological methods of coal raw material preparation, taking into account the petrographic characteristics of coal batches. A comprehensive study of the components included in a coke chemical enterprise’s coking raw material base was carried out. The work used standardized methods for studying coal and coal batches’ technological and plastic–viscous properties. The qualitative characteristics of coke were determined using physical–mechanical and thermochemical methods of studying standardized indicators: crushability (M₂₅), abrasion (M₁₀), reactivity (CRI), post-reaction strength (CSR), and specific electrical resistance (ρ). The results were analyzed using the licensed Microsoft Excel computer program. Based on the results of proximate, plastometric, and petrographic analyses of the studied coal samples and data from experimental industrial coking, proposals were made to optimize the component composition, properties of the coal batch, and technology for its preparation for coking. The established inverse dependence of Gibbs free energy (ΔG_f,total) on the reaction capacity of coke CRI and its direct reliance on its post-reaction strength CSR confirmed the feasibility of using ΔG_f,total as a thermodynamic predictive parameter for optimizing and compiling coal batches that produce less reactive, stronger coke. This made it possible to improve the quality indicators of metallurgical coke. Thus, according to the M₂₅ crushability index, the mechanical strength increased by 0.6%, and the M₁₀ abrasion decreased by 0.4%. Significant improvements in thermochemical properties and an increase in the orderliness of the carbon structure were recorded: the CRI reactivity decreased by 3.1%, the CSR post-reaction strength increased by 8.3%, and the specific resistance decreased by 8.4%. Full article

(This article belongs to the Topic Advances in Carbon-Based Materials)

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13 pages, 3960 KB

Open AccessArticle

NaOH-Modified Activated Carbon Materials for Hydrogen Sulfide Removal

by Meriem Abid, Manuel Martínez-Escandell and Joaquín Silvestre-Albero

C 2025, 11(3), 68; https://doi.org/10.3390/c11030068 - 3 Sep 2025

Abstract

A high-surface-area activated carbon material (RG) is used as a platform to create highly concentrated NaOH composites. These materials are tested for the removal of H₂S under industrially relevant conditions (800 ppm H₂S in CO₂-, H₂ [...] Read more.

A high-surface-area activated carbon material (RG) is used as a platform to create highly concentrated NaOH composites. These materials are tested for the removal of H₂S under industrially relevant conditions (800 ppm H₂S in CO₂-, H₂O- and O₂-containing streams). The experimental results show that the breakthrough performance highly depends on the amount of NaOH incorporated and the experimental conditions used (e.g., relative humidity). The most promising material (RG-NaOH-30) reaches a saturation uptake of up to 800 mgH₂S/g at 25 °C and atmospheric pressure. This value is among the most promising results reported in the literature for H₂S removal, and it is well above traditional commercial samples. Breakthrough column tests confirm the promoting role of humidity in the reaction mechanism. Analysis of the adsorbents after H₂S confirms the formation of well-defined sulfur (S_n) microcrystals as the main reaction product. Full article

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

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15 pages, 4854 KB

Open AccessArticle

Atomic-Scale Mechanisms of Catalytic Recombination and Ablation in Knitted Graphene Under Hyperthermal Atomic Oxygen Exposure

by Yating Pan, Yunpeng Zhu, Donghui Zhang and Ning Wei

C 2025, 11(3), 67; https://doi.org/10.3390/c11030067 - 2 Sep 2025

Abstract

Effective ablative thermal protection systems are essential for ensuring the structural integrity of hypersonic vehicles subjected to extreme aerothermal loads. However, the microscopic reaction mechanisms at the gas–solid interface, particularly under non-equilibrium high-enthalpy conditions, remain poorly understood. This study employs reactive molecular dynamics [...] Read more.

Effective ablative thermal protection systems are essential for ensuring the structural integrity of hypersonic vehicles subjected to extreme aerothermal loads. However, the microscopic reaction mechanisms at the gas–solid interface, particularly under non-equilibrium high-enthalpy conditions, remain poorly understood. This study employs reactive molecular dynamics (RMD) simulations with the ReaxFF-C/H/O force field to investigate the atomic-scale ablation behavior of a graphene-based knitted graphene structure impacted by atomic oxygen (AO). By systematically varying the AO incident kinetic energy (from 0.1 to 8.0 eV) and incidence angle (from 15° to 90°), we reveal the competing interplay between catalytic recombination and ablation processes. The results show that the catalytic recombination coefficient of oxygen molecules reaches a maximum at 5.0 eV, where surface-mediated O₂ formation is most favorable. At higher energies, the reaction pathway shifts toward enhanced CO and CO₂ production due to increased carbon atom ejection and surface degradation. Furthermore, as the AO incidence angle increases, the recombination efficiency decreases linearly, while C-C bond breakage intensifies due to stronger vertical energy components. These findings offer new insights into the anisotropic surface response of knitted graphene structures under hyperthermal oxygen exposure and provide valuable guidance for the design and optimization of next-generation thermal protection materials for hypersonic flight. Full article

(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)

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3 pages, 200 KB

Open AccessEditorial

Editorial for Special Issue “Carbon-Based Materials Applied in Water and Wastewater Treatment”

by Athanasia K. Tolkou

C 2025, 11(3), 66; https://doi.org/10.3390/c11030066 - 2 Sep 2025

Abstract

In the past decade, carbon nanostructures have emerged as one of the most rapidly advancing areas of research [...] Full article

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

14 pages, 2007 KB

Open AccessArticle

Graphene Oxide Promoted Light Activation of Peroxymonosulfate for Highly Efficient Triphenyl Phosphate Degradation

by Yilong Li, Yi Xie, Xuqian Wang and Yabo Wang

C 2025, 11(3), 65; https://doi.org/10.3390/c11030065 - 21 Aug 2025

Abstract

The treatment of organic phosphate ester (OPE) pollutants in water is a challenging but highly necessary task. In this study, an advanced oxidation process through light activation of peroxymonosulfate (PMS) involving graphene oxide (GO) as a promoter was developed to degrade OPE in [...] Read more.

The treatment of organic phosphate ester (OPE) pollutants in water is a challenging but highly necessary task. In this study, an advanced oxidation process through light activation of peroxymonosulfate (PMS) involving graphene oxide (GO) as a promoter was developed to degrade OPE in water, taking triphenyl phosphate (TPhP) as an example. The developed “Light+PMS+GO” system demonstrated good convenience, high TPhP degradation efficiency, tolerance in a near-neutral pH, satisfactory re-usability, and a low toxicity risk of degradation products. Under the investigated reaction conditions, viz., the full spectrum of a 300 W Xe lamp, PMS of 200 mg L⁻¹, GO of 4 mg L⁻¹, and TPhP of 10 μmol L⁻¹, the “Light+PMS+GO” system achieved nearly 100% TPhP degradation efficiency during a 15 min reaction duration with a 5.81-fold enhancement in the reaction rate constant, compared with the control group without GO. Through quenching experiments and electron paramagnetic resonance studies, singlet oxygen was identified as the main reactive species for TPhP degradation. Further studies implied that GO could accumulate both oxidants and pollutants on the surface, providing additional reaction sites for PMS activation and accelerating electron transfer, which all contributed to the enhancement of TPhP degradation. Finally, the TPhP degradation pathway was proposed and a preliminary toxicity evaluation of degradation intermediates was conducted. The convenience, high removal efficiency, and good re-usability indicates that the developed “Light+PMS+GO” reaction system has great potential for future applications. Full article

(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)

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15 pages, 5132 KB

Open AccessArticle

Characterisation of a Biodegradable Electrode Substrate Based on Psyllium Husk–Carbon Nanoparticle Composites

by Cliodhna McCann, Victoria Gilpin, Regan McMath, Chris I. R. Gill, Karl McCreadie, James Uhomoibhi, Pagona Papakonstantinou and James Davis

C 2025, 11(3), 64; https://doi.org/10.3390/c11030064 - 17 Aug 2025

Abstract

Unrefined psyllium husk derived from Plantago ovata constitutes a complex mixture of water-soluble and insoluble polymeric chains that form an interpenetrating network capable of entrapping carbon nanoparticles. While the resulting composite was found to swell in aqueous electrolyte, it exhibited hydrogel-like properties where [...] Read more.

Unrefined psyllium husk derived from Plantago ovata constitutes a complex mixture of water-soluble and insoluble polymeric chains that form an interpenetrating network capable of entrapping carbon nanoparticles. While the resulting composite was found to swell in aqueous electrolyte, it exhibited hydrogel-like properties where the electrochemical activity was retained and found to be stable upon repetitive voltammetric cycling. Planar film systems were characterized by electron microscopy, Raman spectroscopy, tensile testing, gravimetric analysis, contact angle and cyclic voltammetry. A key advantage of the composite lies in its ability to be cast in 3D geometric forms such as pyramidal microneedle arrays (700 μm high × 200 μm base × 500 μm pitch) that could serve as viable electrode sensors. In contrast to conventional composite electrode materials that rely on non-aqueous solvents, the psyllium mixture is processed entirely from an aqueous solution. This, along with its plant-based origins and simple processing requirements, provides a versatile matrix for the design of biodegradable electrode structures that can be manufactured from more sustainable sources. Full article

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

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15 pages, 1152 KB

Open AccessArticle

Formation and Melting of Hydrate with Binary CO₂/C₂H₆ Mixtures in Silica Sand: Comparison Between Dissociation Data and Phase Equilibrium of Pure CO₂ and C₂H₆ Hydrates

by Alberto Maria Gambelli, Federico Rossi and Giovanni Gigliotti

C 2025, 11(3), 63; https://doi.org/10.3390/c11030063 - 17 Aug 2025

Abstract

The present study deals with hydrate formation with binary gaseous mixtures consisting of carbon dioxide mixed with ethane at varying concentrations. Since the production of hydrates is recognised as a stochastic process and also due to the marked influence that experimental apparatuses often [...] Read more.

The present study deals with hydrate formation with binary gaseous mixtures consisting of carbon dioxide mixed with ethane at varying concentrations. Since the production of hydrates is recognised as a stochastic process and also due to the marked influence that experimental apparatuses often have on the results, the continuous updating of the literature with new experimental data is needed. Hydrates were produced and dissociated in excess water and in unstirred conditions. The dissociation values were collected and tabulated. Each test was plotted and compared with the phase boundary equilibrium conditions of pure ethane and pure carbon dioxide hydrates. The results confirmed the lowering of pressures required for hydrate formation with the increase in ethane concentration in the gas mixture. In detail, the dissociation condition for CO₂/C₂H₆ hydrates was tested within the following thermodynamic ranges: 0.1–13 °C and 11.26–36.75 bar for the 25/75 vol% mixture, 0.1–13 °C and 9.74–35.07 bar for the 50/50 vol% mixture and 7.0–12.9 °C and 17.36–30.05 bar for the 75/25 vol% mixture. When 75 vol% ethane was used, the dissociation of hydrates occurred at conditions corresponding to the phase equilibrium of pure ethane hydrates, denoting that the system reached the most favourable thermodynamic conditions possible despite the presence of 25 vol% CO₂. Full article

(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)

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34 pages, 10992 KB

Open AccessArticle

Graphene-like Carbon Materials from King Grass Biomass via Catalytic Pyrolysis Using K₃[Fe(CN)₆] as a Dual Catalyst and Activator

by Alba N. Ardila Arias, Erasmo Arriola-Villaseñor, Madelyn Ortiz-Quiceno, Lucas Blandón-Naranjo and José Alfredo Hernández-Maldonado

C 2025, 11(3), 62; https://doi.org/10.3390/c11030062 - 14 Aug 2025

Abstract

The potential of king grass biomass as a precursor for carbon-based materials was evaluated through comprehensive physicochemical characterization. The biomass showed high fixed carbon content, reactive oxygenated groups, and favorable atomic ratios, supporting its suitability for conversion into porous carbon structures. This study [...] Read more.

The potential of king grass biomass as a precursor for carbon-based materials was evaluated through comprehensive physicochemical characterization. The biomass showed high fixed carbon content, reactive oxygenated groups, and favorable atomic ratios, supporting its suitability for conversion into porous carbon structures. This study focused on the synthesis of graphene-like materials via high-temperature pyrolysis (~1000 °C), employing FeCl₃ and potassium ferricyanide (K₃[Fe(CN)₆]) as catalytic agents. Although FeCl₃ is widely studied, it showed limited capacity to promote graphitic ordering. In contrast, K₃[Fe(CN)₆] exhibited a synergistic effect, combining iron-based catalytic species (Fe, Fe₃C) and potassium-derived activating compounds (K₂CO₃), which significantly enhanced graphitization and porosity. Characterization by Raman spectroscopy, XRD, and SEM confirmed that materials synthesized with K₃[Fe(CN)₆] presented improved crystallinity, lower defect densities (I_D/I_G = 0.37–1.11), and distinct 2D bands (I_2D/I_G = 0.32–0.80), indicating the formation of few-layer graphene domains. The most promising structure was obtained from cellulose treated with alkaline peroxide and deoxygenated prior to pyrolysis with K₃[Fe(CN)₆], showing properties comparable to commercial graphene. BET analysis revealed surface areas up to 714.50 m²/g. While non-catalyzed samples yielded higher mass, the catalytic approach with K₃[Fe(CN)₆] demonstrates a sustainable and efficient pathway for producing graphene-like carbon materials from lignocellulosic biomass. Full article

(This article belongs to the Special Issue Carbon Innovations in Renewable Energy Systems and Environmental Sustainability)

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24 pages, 10422 KB

Open AccessArticle

Optimizing Distribution of Light Irradiation in Column Reactor Array and Glass Chamber for Microalgae Carbon Sequestration Facilities

by Xiangjin Liang, Jun Lu, Yapeng Chen, Guangbiao Zhou, Zeyan Tao, Zhenyu Hu, Ying Liu, Wanlin Liu, Yang Xu and Jun Cheng

C 2025, 11(3), 61; https://doi.org/10.3390/c11030061 - 12 Aug 2025

Abstract

The column photobioreactor has become the predominant approach for carbon sequestration by microalgae in power plant settings, owing to its capacity for high-density cultivation and efficient light energy utilization. Due to the dense arrangement of the columnar photobioreactor and its height, insufficient light [...] Read more.

The column photobioreactor has become the predominant approach for carbon sequestration by microalgae in power plant settings, owing to its capacity for high-density cultivation and efficient light energy utilization. Due to the dense arrangement of the columnar photobioreactor and its height, insufficient light became one of the main factors limiting the carbon sequestration rate of microalgae growth. In this paper, a light resource optimization method of reflective baffle and top diffusing glass was proposed. When the angle of reflective baffle on the north and east walls was 35°, and the angle of reflective baffle on the west and south floors was 0°, the overall light radiation intensity of the reactor array became the largest, reaching up to 916.81 W/m², which was 14.39% higher than that before the optimization. The replacement of the top glass with diffusing material converted the direct radiation of solar radiation into scattered radiation. When the transmittance was 95% and the haze was 95%, the overall average light radiation intensity of the algal solution reached 830.93 W/m², which was an increase of 3.7%. Four new exhaust air distribution methods were proposed, in which the three-entrance staggered-arrangement type glasshouse had the lowest algal liquid temperature. Full article

(This article belongs to the Special Issue 10th Anniversary of C — Journal of Carbon Research)

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15 pages, 4099 KB

Open AccessArticle

Pulsed Laser Annealing of Deposited Amorphous Carbon Films

by Arianna D. Rivera, Eitan Hershkovitz, Panagiotis Panoutsopoulos, Manny X. de Jesus Lopez, Bradley Simpson, Honggyu Kim, Rajaram Narayanan, Jesse Johnson and Kevin S. Jones

C 2025, 11(3), 60; https://doi.org/10.3390/c11030060 - 8 Aug 2025

Abstract

Pulsed laser annealing (PLA) was performed on a 0.3 μm thick hydrogenated amorphous carbon (a-C:H) film deposited on silicon substrate by plasma-enhanced chemical vapor deposition (PECVD). The 532 nm, 32 ns PLA ranged in fluence from 0.2 to 0.94 J cm⁻². [...] Read more.

Pulsed laser annealing (PLA) was performed on a 0.3 μm thick hydrogenated amorphous carbon (a-C:H) film deposited on silicon substrate by plasma-enhanced chemical vapor deposition (PECVD). The 532 nm, 32 ns PLA ranged in fluence from 0.2 to 0.94 J cm⁻². There were no visible signs of film delamination over the entire fluence range for a single pulse. As the fluence increased, graphitization of the amorphous film bulk was observed. However, at the near surface of the film, there was a concomitant increase in sp³ content. The sp³ bonding observed is the result of the formation of a thin diamond-like layer on the surface of the carbon film. Along with increasing laser fluence, the film swelled by 75% up to 0.6 J cm⁻². In addition, carbon fiber formation was observed at 0.6 J cm⁻², increasing in size and depth up through 0.94 J cm⁻². The origin of this transformation may be associated with a rapid outgassing of hydrogen from the amorphous carbon during the PLA step. Additionally, there was a dramatic increase in the visible light absorption of these thin films with increasing laser fluence, despite the films being less than a micron thick. These results suggest that PLA of a-C:H film is a useful method for modifying the surface structure for optical or electrochemical applications without film ablation. Full article

(This article belongs to the Special Issue Carbon Functionalization: From Synthesis to Applications)

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11 pages, 4453 KB

Open AccessArticle

In Silico Exfoliation of ReaxFF Graphite—Temperature, Speed, Angle Dependence, and the Effect of Gold Overlayer

by Teruki Ando, Seiya Yokokura, Hiroki Waizumi, Hironori Suzuki, Kenji Kawashima and Toshihiro Shimada

C 2025, 11(3), 59; https://doi.org/10.3390/c11030059 - 7 Aug 2025

Abstract

Exfoliation of layered materials is an important technique for preparing atomic-layer materials. To provide fundamental mechanistic insights for optimizing this process, we investigated the exfoliation process of nano graphite using molecular dynamics simulations with the ReaxFF force field. The impact of temperature, speed, [...] Read more.

Exfoliation of layered materials is an important technique for preparing atomic-layer materials. To provide fundamental mechanistic insights for optimizing this process, we investigated the exfoliation process of nano graphite using molecular dynamics simulations with the ReaxFF force field. The impact of temperature, speed, and angle of removing the top layer has been examined to gain insight into obtaining thin, uniform layers. The bending rigidity of the ReaxFF graphite is temperature-dependent and affects the cleavage behavior. The impact of the Au overlayer, which has recently been utilized to obtain a large area, was also studied, and it was confirmed to be effective in improving repeatability. Full article

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

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22 pages, 1937 KB

Open AccessReview

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

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 KB

Open AccessCommunication

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

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 KB

Open AccessArticle

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

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 KB

Open AccessArticle

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

Cited by 1

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 KB

Open AccessArticle

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

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 CO_2-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 KB

Open AccessArticle

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

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

(This article belongs to the Special Issue Carbon-Based Polymer Composites: Synthesis, Processing, Characterization and Applications (2nd Edition))

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C — Journal of Carbon Research

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