C | An Open Access Journal from MDPI

43 pages, 3704 KB

Open AccessReview

by Elena F. Sheka

C 2026, 12(1), 20; https://doi.org/10.3390/c12010020 - 28 Feb 2026

This review presents the covalent chemistry of carbon from the point of the spin-radical concept of electron interaction in the framework of the unrestricted molecular orbitals (UHF MO) theory. Using the language of valence bond trimodality, the regions of classical spinless spin-symmetric covalence [...] Read more.

This review presents the covalent chemistry of carbon from the point of the spin-radical concept of electron interaction in the framework of the unrestricted molecular orbitals (UHF MO) theory. Using the language of valence bond trimodality, the regions of classical spinless spin-symmetric covalence and its spin-dependent asymmetric counterpart are defined. Carbon is the only element exhibiting spin covalent chemistry. Classical covalent chemistry of carbon of molecular substances whose valence bond structure includes segregate or chained single sp³C − C bonds meet its spin counterpart only at these bonds breaking. Substances with double sp²C = C and triple sp¹C ≡ C bonds are the subject of spin covalent chemistry of carbon. The mathematical apparatus of the UHF MO allows forming algorithms controlling the chemical modification of carbon substances, polymerization processes, and catalysis involving them, making it possible to supplement the empirical spin covalent chemistry of carbon with its virtual analog. Full article

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

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17 pages, 7048 KB

Open AccessArticle

C/CuNi Composites for High-Speed Train Pantograph Sliders: Regulation of Mechanical and Friction Properties by Carbon Fiber Content

by Qi Qiang, Kezhi Li, Tianzhan Shen and Haibo Ouyang

C 2026, 12(1), 19; https://doi.org/10.3390/c12010019 - 26 Feb 2026

Abstract

The pantograph slider is a key friction component in high-speed train systems, and its performance directly affects the safety and efficiency of operation. In this study, Cf/C/CuNi composites with carbon fiber contents of 1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.% were [...] Read more.

The pantograph slider is a key friction component in high-speed train systems, and its performance directly affects the safety and efficiency of operation. In this study, Cf/C/CuNi composites with carbon fiber contents of 1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.% were prepared by a solvothermal method combined with spark plasma sintering (SPS). The influence of carbon fiber content on the mechanical and friction properties of the composites was systematically studied. The results show that the flexural strength of the composites increases from 20.20 MPa to 38.45 MPa with an increase in the carbon fiber content. However, excessive carbon fiber content can lead to fiber agglomeration and interface defects, thereby reducing the friction stability and increasing the wear rate from 0.64 g/m³ to 1.60 g/m³. A carbon fiber content of 1 wt.% helps to form a continuous lubricating film, resulting in a low and stable friction coefficient. This study provides valuable insights for the design and optimization of high-performance pantograph slider materials for high-speed railway applications. Full article

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10 pages, 1352 KB

Open AccessArticle

Rectifying and Photoconductive Responses in Graphene–Double-Insulator–Graphene (GI²G) Structures

by Takashi Uchino, Yanjun Heng, Chao Tang, Akira Satou, Hirokazu Fukidome and Taiichi Otsuji

C 2026, 12(1), 18; https://doi.org/10.3390/c12010018 - 20 Feb 2026

Abstract

Advanced solar energy-harvesting devices, such as optical rectennas, typically use metal–insulator–metal diodes because of the ultrafast response of these diodes at high frequencies. However, the diode performance is limited by weak current–voltage (I–V) asymmetry and optical losses in metallic [...] Read more.

Advanced solar energy-harvesting devices, such as optical rectennas, typically use metal–insulator–metal diodes because of the ultrafast response of these diodes at high frequencies. However, the diode performance is limited by weak current–voltage (I–V) asymmetry and optical losses in metallic electrodes. Graphene offers a promising alternative electrode material owing to its high carrier mobility, broadband optical transparency, and compatibility with nanoscale device architectures. Nevertheless, graphene-based optical rectennas face challenges associated with insufficient diode nonlinearity. In this study, we developed a vertically stacked graphene–double-insulator–graphene (GI²G) tunnel diode. Devices with various junction sizes were fabricated to investigate size-dependent rectifying behavior. A reduced graphene overlap area was defined by electron-beam lithography to introduce asymmetry and increase nonlinear conduction. An Al₂O₃/SiO₂ tunnel barrier composed of dielectrics with different band gaps and electron affinities improved the asymmetric I–V characteristics. Photoresponse measurements under AM1.5G illumination revealed a clear photocurrent, indicating rectification-related photoresponse. The photoresponse increased with decreasing junction area, which is consistent with enhanced rectification performance in smaller junctions. These results demonstrate that the GI²G tunnel diode provides a promising platform for next-generation energy harvesting and optical sensing applications. Full article

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

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17 pages, 2950 KB

Open AccessArticle

Biocompatible Carbon Nanotube-Based Drug Delivery System for Neurodegenerative and Regenerative Biomedical Applications

by Stefano Bellucci

C 2026, 12(1), 17; https://doi.org/10.3390/c12010017 - 18 Feb 2026

Abstract

Carbon nanotubes (CNTs) represent promising nanoplatforms for drug delivery due to their high surface area, tunable surface chemistry, and unique physicochemical properties. This study investigated the effect of chemical functionalization on the dispersion, drug loading, release behavior, aerosolization, and preliminary in vitro cytotoxicity [...] Read more.

Carbon nanotubes (CNTs) represent promising nanoplatforms for drug delivery due to their high surface area, tunable surface chemistry, and unique physicochemical properties. This study investigated the effect of chemical functionalization on the dispersion, drug loading, release behavior, aerosolization, and preliminary in vitro cytotoxicity of CNT-based drug delivery systems, with a view toward potential intranasal applications. Pristine CNTs and CNTs functionalized with hydroxyl (–OH) and carboxyl (–COOH) groups were loaded with methylene blue as a model therapeutic compound. The nanosystems were characterized using Raman spectroscopy, UV–Vis analysis, aerosol deposition measurements, electrical mapping by conductive atomic force microscopy (C-AFM), and MTT cytotoxicity assays. Functionalization significantly enhanced CNT dispersion stability and drug release control, with COOH–CNTs exhibiting the most sustained release profile and improved cytocompatibility, maintaining cell viability above XX% at concentrations up to YY µg/mL. Aerosolization tests demonstrated stable droplet formation compatible with nasal delivery devices. Overall, this work provides a proof-of-concept physicochemical and technological assessment of functionalized CNTs as potential carriers for intranasal drug delivery, laying the groundwork for future in vivo validation. Full article

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

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29 pages, 8435 KB

Open AccessReview

In Situ and Operando Monitoring Techniques for Carbon- and Silicon-Based Anodes in Lithium-Ion Batteries: A Review

by Mingjie Wang, Siqing Chen, Yue Guo, Hengshan Mao, Gaoce Han, Yu Ding, Yuxin Fan and Yifei Yu

C 2026, 12(1), 16; https://doi.org/10.3390/c12010016 - 9 Feb 2026

Abstract

Lithium-ion batteries (LIBs) power devices from portable electronics to electric vehicles and grid storage, yet their reliable operation requires real-time monitoring of battery state, particularly at the anode where complex reactions and structural changes occur. Sensor technologies capable of capturing dynamic physical and [...] Read more.

Lithium-ion batteries (LIBs) power devices from portable electronics to electric vehicles and grid storage, yet their reliable operation requires real-time monitoring of battery state, particularly at the anode where complex reactions and structural changes occur. Sensor technologies capable of capturing dynamic physical and chemical signals have therefore gained increasing attention for probing internal battery processes. This review summarizes recent operando and in situ monitoring strategies for carbon-based and silicon-based anodes, highlighting advances in electrical, optical, and acoustic sensing. These methods reveal degradation mechanisms and morphological evolution in real time. Multimodal sensing strategies that integrate multiple signals for improved battery state estimation are also discussed. Finally, future directions are outlined, focusing on real-time anode monitoring and the integration of sensing technologies with next-generation battery designs. This review aims to guide the development of smart battery sensing for artificial-intelligence-assisted and multimodal sensing, providing solutions for battery management system that enable accurate synchronous detection of mechanical, thermal, and electrical signals. Full article

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

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19 pages, 8787 KB

Open AccessArticle

Mechanisms of Halomethane Adsorption on Functionalized Carbons: How Surface Chemistry Governs Selectivity in Realistic Gas Mixtures

by María E. Farías Hermosilla and Alberto G. Albesa

C 2026, 12(1), 15; https://doi.org/10.3390/c12010015 - 6 Feb 2026

Abstract

Halomethanes (CH₃X, where X = F, Cl, Br) are potent atmospheric pollutants, and their removal via adsorption on activated carbons (ACs) is a critical remediation strategy. However, the molecular-level influence of AC surface chemistry on adsorption, especially under realistic environmental conditions, [...] Read more.

Halomethanes (CH₃X, where X = F, Cl, Br) are potent atmospheric pollutants, and their removal via adsorption on activated carbons (ACs) is a critical remediation strategy. However, the molecular-level influence of AC surface chemistry on adsorption, especially under realistic environmental conditions, is not fully understood. This work utilizes Grand Canonical Monte Carlo (GCMC) simulations to investigate the adsorption of CH₃F, CH₃Cl, and CH₃Br on realistic carbon models, comparing unfunctionalized graphitic surfaces (AC0) with surfaces functionalized with alcohol (AC1), carbonyl (AC2), and carboxyl (AC3) groups. We analyze the process for both pure components and in realistic mixtures (Quarantine and Pre-Shipment concentrations). Our findings reveal a critical inversion in adsorption preference. For pure components, CH₃Br adsorption is highest on the unfunctionalized (AC0) surface, driven by strong adsorbate–adsorbate interactions leading to condensation, characterized by a rising isosteric heat of adsorption (

Q_{s t} \approx 35 - 45

kJ/mol) that matches the enthalpy of sublimation. Conversely, in realistic humid mixtures, the pristine surface suffers a capacity collapse (>90% loss). The functionalized surfaces (especially AC3) demonstrate superior performance, exhibiting a thermodynamic selectivity of

S_{C H_{3} B r / A i r} > 100

(compared to

S \approx 15

for AC0) and retaining approximately 60% of their dry-condition affinity. This study elucidates the distinct roles of surface chemistry and intermolecular forces, providing a molecular basis for designing carbon materials optimized for high selectivity in complex environmental gas streams. Full article

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17 pages, 2736 KB

Open AccessArticle

Bimetallic Catalysts on Activated Carbon for Enhanced NO Reduction

by Patrícia S. F. Ramalho, Olívia S. G. P. Soares, José L. Figueiredo and Manuel F. R. Pereira

C 2026, 12(1), 14; https://doi.org/10.3390/c12010014 - 4 Feb 2026

Abstract

Reducing emissions of nitrogen compounds represents a significant challenge in environmental protection, and catalytic treatment is an effective approach. Carbon-based catalysts offer a promising alternative by exploiting the redox properties of carbon materials and eliminating the need for external reducing agents. In this [...] Read more.

Reducing emissions of nitrogen compounds represents a significant challenge in environmental protection, and catalytic treatment is an effective approach. Carbon-based catalysts offer a promising alternative by exploiting the redox properties of carbon materials and eliminating the need for external reducing agents. In this study, nitrogen-free and nitrogen-doped activated carbons were used for NO reduction. The catalysts were developed by incorporating transition metals (Cu and Fe), alkali metals (K), and bimetallic Cu-K formulations. The addition of K to Cu and the presence of nitrogen functionalities improved the catalytic performance and an optimum Cu/K ratio was identified. The best-performing catalyst, AC_M_BM@5Cu5K, achieved 100% NO conversion at 410 °C, producing mainly N₂ and CO₂, while N₂O was detected as an intermediate and CO was not observed. The catalyst’s stability was evaluated in a 100 h continuous test at 376 °C, during which the catalyst maintained approximately 90% NO conversion for 40 h before deactivation. The deactivation mechanism is discussed in detail. Full article

(This article belongs to the Section Combustion Emissions)

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28 pages, 6547 KB

Open AccessArticle

Contamination of Amorphous Carbon Thin Films: Modelling the Transport of Atoms in Gases During Deposition

by Pedro M. A. Guerreiro, Ana Rita G. E. Pires, Susana M. C. S. Fidalgo, Orlando M. N. D. Teodoro, Pedro Costa Pinto and Nenad Bundaleski

C 2026, 12(1), 13; https://doi.org/10.3390/c12010013 - 4 Feb 2026

Abstract

Monte Carlo simulations of the transport of atoms in gases related to the deposition process and the contamination of amorphous carbon thin films during deposition in magnetron discharges have been performed. These films are of interest in accelerator technology due to their low [...] Read more.

Monte Carlo simulations of the transport of atoms in gases related to the deposition process and the contamination of amorphous carbon thin films during deposition in magnetron discharges have been performed. These films are of interest in accelerator technology due to their low secondary electron yield when their structures are dominated by sp² carbon. Two codes, which practically share the same algorithm, are introduced: TAGs 1 simulates the transport of sputtered atoms from the target to the substrate, and TAGs 2 simulates the transport of atoms from the plasma towards the target and the substrate. The similar results of TAGs 1 and the well-established SIMTRA for the same input parameters imply the algorithm’s accuracy. The codes were used to model the transport of different atoms (C, H, O, D) in a magnetron Ar discharge. The simulations reveal that the operating pressure should be higher than 1 Pa for a sample-target distance of 90 mm to secure sp² carbon formation. The contamination mechanisms of amorphous carbon coatings were then studied by merging the results obtained with both programs. Preliminary comparisons with experiments suggest that the combined results of TAGs 1 and 2 agree very well with the experiments. Full article

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14 pages, 3213 KB

Open AccessReview

Flexible Sensors Based on Carbon-Based Materials and Their Applications

by Jihong Liu and Hongming Liu

C 2026, 12(1), 12; https://doi.org/10.3390/c12010012 - 3 Feb 2026

Abstract

In recent years, the rapid commercialization and widespread adoption of portable and wearable electronic devices have imposed increasingly stringent performance requirements on flexible sensors, including enhanced sensitivity, stability, response speed, comfort, and integration. This trend has driven extensive research and technological advancement in [...] Read more.

In recent years, the rapid commercialization and widespread adoption of portable and wearable electronic devices have imposed increasingly stringent performance requirements on flexible sensors, including enhanced sensitivity, stability, response speed, comfort, and integration. This trend has driven extensive research and technological advancement in sensor material systems, among which carbon-based materials have emerged as core candidates for high-performance flexible sensors due to their exceptional electrical conductivity, mechanical flexibility, chemical stability, and highly tunable structural features. Meanwhile, new sensing mechanisms and innovative device architectures continue to emerge, demonstrating significant value in real-time health monitoring, early disease detection, and motion-state analysis, thereby expanding the functional boundaries of flexible sensors in the health-care sector. This review focuses on the application progress and future opportunities of carbon-based materials in flexible sensors, systematically summarizing the critical roles and performance-optimization strategies of carbon nanotubes, graphene, carbon fibers, carbon black, and their derivative composites in various sensing systems, including strain and pressure sensing, physiological electrical signal detection, temperature monitoring, and chemical or environmental sensing. In response to the growing demands of modern health-monitoring technologies, this review also examines the practical applications and challenges of flexible sensors—particularly those based on emerging mechanisms and novel structural designs—in areas such as heart-rate tracking, blood-pressure estimation, respiratory monitoring, sweat-component analysis, and epidermal electrophysiological signal acquisition. By synthesizing the current research landscape, technological pathways, and emerging opportunities of carbon-based materials in flexible sensors, and by evaluating the design principles and practical performance of diverse health-monitoring devices, this review aims to provide meaningful reference insights for researchers and support the continued innovation and practical deployment of next-generation flexible sensing technologies. Full article

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

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24 pages, 1432 KB

Open AccessReview

A Review of Graphene Oxide and Reduced Graphene Oxide Applications: Multifunctional Nanomaterials for Sustainable Environmental and Energy Devices

by Ikbal Adrian Milka, Bijak Riyandi Ahadito, Desnelli, Nurlisa Hidayati and Muhammad Said

C 2026, 12(1), 11; https://doi.org/10.3390/c12010011 - 23 Jan 2026

Cited by 1

Abstract

Graphene oxide (GO) and reduced graphene oxide (rGO) have solidified their role as cornerstone nanomaterials in the pursuit of sustainable technology. This review synthesizes recent advances in harnessing the unique properties of GO and rGO such as their tunable surface chemistry and exceptional [...] Read more.

Graphene oxide (GO) and reduced graphene oxide (rGO) have solidified their role as cornerstone nanomaterials in the pursuit of sustainable technology. This review synthesizes recent advances in harnessing the unique properties of GO and rGO such as their tunable surface chemistry and exceptional electrical conductivity for applications spanning environmental remediation and energy storage. In the environmental domain, they function as superior adsorbents and catalysts for the removal of hazardous pollutants. Concurrently, in the energy sector, their integration into supercapacitors and battery electrodes significantly enhances energy and power density. The adaptability of these materials also facilitates the creation of highly sensitive sensors and biosensors. However, the transition from laboratory research to widespread industrial application is hindered by challenges in scalable production, environmental health and safety concerns, and long-term stability. This review enhances the understanding of GO and rGO’s diverse applications and paves the way for future sustainable technologies in energy and environmental sectors. Full article

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

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11 pages, 3164 KB

Open AccessArticle

Influence of MgO Binder Regulation on the Interfacial Structure of Lithium Thermal Batteries

by Zhi-Yang Fan, Xiao-Min Wang, Wei-Yi Zhang, Li-Ke Cheng, Wen-Xiu Gao and Cheng-Yong Shu

C 2026, 12(1), 10; https://doi.org/10.3390/c12010010 - 22 Jan 2026

Abstract

Lithium thermal batteries are primary reserve batteries utilizing solid molten salt electrolytes. They are regarded as ideal power sources for high-reliability applications due to their high power density, rapid activation, long shelf life, wide operating temperature range, and excellent environmental adaptability. However, existing [...] Read more.

Lithium thermal batteries are primary reserve batteries utilizing solid molten salt electrolytes. They are regarded as ideal power sources for high-reliability applications due to their high power density, rapid activation, long shelf life, wide operating temperature range, and excellent environmental adaptability. However, existing electrode systems are limited by insufficient conductivity and the use of high-impedance MgO binders. This results in sluggish electrode reaction kinetics and incomplete material conversion during high-temperature discharge, causing actual discharge capacities to fall far below theoretical values. To address this, FeS₂-CoS₂ multi-component composite cathode materials were synthesized via a high-temperature solid-phase method. Furthermore, two distinct MgO binders were systematically investigated: flake-like MgO (MgO-F) with a sheet-stacking structure and spherical MgO (MgO-S) with a low-tortuosity granular structure. Results indicate that while MgO-F offers superior electrolyte retention via physical confinement, its high tortuosity limits ionic conduction. In contrast, MgO-S facilitates the construction of a wettability-enhanced continuous ionic network, which effectively reduces interfacial impedance and enhances system conductivity. This regulation promoted Li⁺ migration and accelerated interfacial reaction kinetics. This study provides a feasible pathway for improving the electrochemical performance of lithium thermal batteries through morphology-oriented MgO binder regulation. Full article

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

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18 pages, 667 KB

Open AccessReview

Reassessed Ability of Carbon-Based Physisorbing Materials to Keep Pace with Evolving Practical Targets for Hydrogen Storage

by Patrick L. Langlois, Chavdar P. Chilev and Farida D. Lamari

C 2026, 12(1), 9; https://doi.org/10.3390/c12010009 - 21 Jan 2026

Abstract

This study provides a comprehensive overview of research and advancements on carbon materials with regard to practical targets for hydrogen storage in terms of gravimetric and volumetric capacities. For the sake of clarity, only the most relevant references on hydrogen storage by adsorption [...] Read more.

This study provides a comprehensive overview of research and advancements on carbon materials with regard to practical targets for hydrogen storage in terms of gravimetric and volumetric capacities. For the sake of clarity, only the most relevant references on hydrogen storage by adsorption are presented, although the study was conducted in the same exhaustive manner as the one initially carried out by Anne C. Dillon and Michael J. Heben in 2001 with a particular emphasis on emerging technologies and potential applications in various sectors. This study also focuses on the importance of carbon-based materials with high specific surface areas and porous structures optimised to maximise adsorption—including at high pressure—while primarily limiting references herein to experimentally validated results. It therefore offers insights into the porous materials, as well as the methodologies—including a fully comprehensive and so-far proven highly transferable intermolecular hydrogen model combining van der Waals’s and Coulomb’s forces—used to improve hydrogen solid storage efficiency. Full article

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

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19 pages, 3780 KB

Open AccessArticle

Carbon Nanotube-Based Filters for the Adsorption of Toxic Compounds in Cigarette Smoke

by Luigi Madeo, Pietro Figliuzzi, Assunta Perri, Anastasia Macario, Carlo Siciliano and Pierantonio De Luca

C 2026, 12(1), 8; https://doi.org/10.3390/c12010008 - 20 Jan 2026

Abstract

This study investigates the use of carbon nanotubes (CNTs) in the development of a filter capable of capturing toxic and carcinogenic compounds found in cigarette smoke dispersed in the environment. The aim is to contribute to the reduction in passive exposure to these [...] Read more.

This study investigates the use of carbon nanotubes (CNTs) in the development of a filter capable of capturing toxic and carcinogenic compounds found in cigarette smoke dispersed in the environment. The aim is to contribute to the reduction in passive exposure to these substances, with potential benefits for public health and air quality. Carbon nanotubes were selected for their exceptional adsorption properties, attributed to their high specific surface area and porous structure. The material’s adsorptive performance was evaluated based on the quantity used, to determine the optimal mass that ensures the best filtering capacity. To test the system, an experimental setup was assembled to simulate real-world smoke emission conditions. Filters containing CNTs were subjected to gravimetric analysis to measure the amount of retained substances, and to gas chromatography to identify the adsorbed chemical compounds. The results confirm the potential of carbon nanotubes as an advanced filtering material, paving the way for robust solutions to mitigate the environmental impact of secondhand smoke. The results indicate that CNT-based filters, particularly those containing 0.06 g of material, are highly effective in retaining several toxic components of cigarette smoke, including nicotine. This configuration achieves a strong reduction in harmful organic species while using a moderate amount of adsorbent, suggesting a promising selectivity of CNTs toward the most hazardous molecules. Full article

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48 pages, 681 KB

Open AccessReview

Organic Amendments for Sustainable Agriculture: Effects on Soil Function, Crop Productivity and Carbon Sequestration Under Variable Contexts

by Oluwatoyosi O. Oyebiyi, Antonio Laezza, Md Muzammal Hoque, Sounilan Thammavongsa, Meng Li, Sophia Tsipas, Anastasios J. Tasiopoulos, Antonio Scopa and Marios Drosos

C 2026, 12(1), 7; https://doi.org/10.3390/c12010007 - 19 Jan 2026

Abstract

Soil amendments play a critical role in improving soil health and supporting sustainable crop production, especially under declining soil fertility and climate-related stress. However, their impact varies because each amendment influences the soil through different biogeochemical processes rather than a single universal mechanism. [...] Read more.

Soil amendments play a critical role in improving soil health and supporting sustainable crop production, especially under declining soil fertility and climate-related stress. However, their impact varies because each amendment influences the soil through different biogeochemical processes rather than a single universal mechanism. This review synthesizes current knowledge on a wide range of soil amendments, including compost, biosolids, green and animal manure, biochar, hydrochar, bagasse, humic substances, algae extracts, chitosan, and newer engineered options such as metal–organic framework (MOF) composites, highlighting their underlying principles, modes of action, and contributions to soil function, crop productivity, and soil carbon dynamics. Across the literature, three main themes emerge: improvement of soil physicochemical properties, enhancement of nutrient cycling and nutrient-use efficiency, and reinforcement of plant resilience to biotic and abiotic stresses. Organic nutrient-based amendments mainly enrich the soil and build organic matter, influencing soil carbon inputs and short- to medium-term increases in soil organic carbon stocks. Biochar, hydrochar, and related materials act mainly as soil conditioners that improve structure, water retention, and soil function. Biostimulant-type amendments, such as algae extracts and chitosan, influence plant physiological responses and stress tolerance. Humic substances exhibit multifunctional effects at the soil–root interface, contributing to improved nutrient efficiency and, in some systems, enhanced carbon retention. The review highlights that no single amendment is universally superior, with outcomes governed by soil–crop context. Its novelty lies in its mechanism-based, cross-amendment synthesis that frames both yield and carbon outcomes as context-dependent rather than universally transferable. Within this framework, humic substances and carbon-rich materials show potential for climate-smart soil management, but long-term carbon sequestration effects remain uncertain and context-dependent. Full article

(This article belongs to the Section Carbon Cycle, Capture and Storage)

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10 pages, 3658 KB

Open AccessArticle

A Constructed 2D-Cu₂O/Carbon Nitride Heterojunction for Efficient CO₂ Photoreduction to CH₄

by Jialiang Liu, Xiaoxuan Zhang, Jiaxuan Gao and Xuanhe Liu

C 2026, 12(1), 6; https://doi.org/10.3390/c12010006 - 18 Jan 2026

Abstract

With the dual challenges of global energy scarcity and worsening environmental issues, the efficient and selective conversion of CO₂ into CH₄-an environmentally friendly fuel with high energy density—offers considerable application potential. In this study, a 2D-Cu₂O/carbon nitride (2D-Cu [...] Read more.

With the dual challenges of global energy scarcity and worsening environmental issues, the efficient and selective conversion of CO₂ into CH₄-an environmentally friendly fuel with high energy density—offers considerable application potential. In this study, a 2D-Cu₂O/carbon nitride (2D-Cu₂O/CN) heterojunction catalyst was successfully prepared. Notably, 2D-Cu₂O/CN shows enhanced light absorption capacity, reduced charge-transfer resistance, and efficient separation of photogenerated electron–hole pairs. It exhibits a CH₄ yield of 14.1 μmol·g⁻¹·h⁻¹, 4-fold higher than that of CN. This study provides a feasible approach for the design of high-efficiency photocatalysts for CO₂ reduction to CH₄. Full article

(This article belongs to the Section Carbon Cycle, Capture and Storage)

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19 pages, 6114 KB

Open AccessArticle

Hydrogen Storage on Activated Carbons from Avocado Biomass Residues: Synthesis Route Assessment, Surface Properties and Multilayer Adsorption Modeling

by Zayda V. Herrera-Cuadrado, Lizeth J. Bastidas-Solarte, Erwin García-Hernández, Adrián Bonilla-Petriciolet, Carlos J. Duran-Valle, Didilia I. Mendoza-Castillo, Hilda E. Reynel-Ávila, Ma. del Rosario Moreno-Virgen, Gloria Sandoval-Flores and Sofía Alvarado-Reyna

C 2026, 12(1), 5; https://doi.org/10.3390/c12010005 - 12 Jan 2026

Abstract

This manuscript reports the preparation, surface characterization, and modeling of chars and activated carbons obtained from avocado biomass for hydrogen storage. Activated carbons were prepared from avocado biomass via the following stages: (a) pyrolysis of avocado biomass, (b) impregnation of the avocado-based char [...] Read more.

This manuscript reports the preparation, surface characterization, and modeling of chars and activated carbons obtained from avocado biomass for hydrogen storage. Activated carbons were prepared from avocado biomass via the following stages: (a) pyrolysis of avocado biomass, (b) impregnation of the avocado-based char using an aqueous lithium solution, and (c) thermal activation of lithium-loaded avocado char. The synthesis conditions of char and activated carbon samples were tailored to maximize their hydrogen adsorption properties at 77 K, where the impact of both pyrolysis and activation conditions was assessed. The hydrogen storage mechanism was discussed based on computational chemistry calculations and multilayer adsorption simulation. The modelling focuses on the analysis of the saturation of activated carbon active sites via the adsorption of multiple hydrogen molecules. The results showed that the activated carbon samples displayed adsorption capacities higher than their char counterparts by 71–91% because of the proposed activation protocol. The best activated carbon obtained from avocado residues showed a maximum hydrogen adsorption capacity of 142 cm³/g, and its storage performance can compete with other carbonaceous adsorbents reported in the literature. The hydrogen adsorption mechanism implied the formation of 2–4 layers on activated carbon surface, where physical interactions via oxygenated functionalities played a relevant role in the binding of hydrogen dimers and trimers. The results of this study contribute to the application of low-cost activated carbons from residual biomass as a storage medium in the green hydrogen supply chain. Full article

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23 pages, 2371 KB

Open AccessArticle

Turning Waste into Solutions: Activated Carbons from Shrimp Shell for Nicotine Adsorption in Aqueous Phase

by Miguel Garcia-Rollan, Miguel Miranda, Silvia Ponce, Carolina Belver and Jorge Bedia

C 2026, 12(1), 4; https://doi.org/10.3390/c12010004 - 6 Jan 2026

Abstract

In this study, removal of nicotine, highly toxic and persistent environmental contaminant, was successfully conducted using activated carbons prepared via chemical activation with KOH from shrimp shell, a byproduct of the food industry. The activation process yielded activated carbons with an exceptionally developed [...] Read more.

In this study, removal of nicotine, highly toxic and persistent environmental contaminant, was successfully conducted using activated carbons prepared via chemical activation with KOH from shrimp shell, a byproduct of the food industry. The activation process yielded activated carbons with an exceptionally developed porous texture, exhibiting, in the best case, a surface area of nearly 2000 m²/g and a surface enriched with diverse oxygenated functional groups, as confirmed by XPS and FTIR analyses. Nicotine adsorption studies demonstrated that the adsorption process was more favorable at near-neutral pH values (pH = 8) and higher temperatures. Kinetic and thermodynamic analyses, combined with material characterization, revealed that the adsorption process is governed by both physical and chemical interactions between the adsorbate and the adsorbent, being overall spontaneous and endothermic. The Sips isotherm model closely fits the adsorption data, highlighting the heterogeneity of the activated carbon surface. Under these conditions, adsorption was studied at three different temperatures, with the highest temperature (45 °C) exhibiting the most significant adsorption capacity, slightly below 500 mg/g. In addition, column adsorption tests demonstrated the high efficiency of activated carbons in nicotine removal, making shrimp head shells a promising carbon precursor for use as a raw material in preparing activated carbons for use as nicotine adsorbents for industry. Full article

(This article belongs to the Topic Environmental Pollutant Management and Control)

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15 pages, 1329 KB

Open AccessArticle

Differential Cytotoxic Effects of Graphene Oxide and Its Functionalized Derivatives on Colon 26 Carcinoma Cells: Implications for Cancer Therapeutic Applications

by Solange Amigues, Natalia Krasteva, Kamelia Hristova-Panusheva, Milena Keremidarska-Markova, Giorgio Speranza and Firas Awaja

C 2026, 12(1), 3; https://doi.org/10.3390/c12010003 - 6 Jan 2026

Abstract

Graphene oxide (GO)-based nanomaterials hold significant potential for targeted cancer therapy owing to their tunable physicochemical properties and surface versatility. In this study, we systematically evaluated the cytotoxicity of pristine GO (graphene oxide) and its surface-functionalized derivatives, GO-CH₄ (methyl), GO-NH₂ (amine), [...] Read more.

Graphene oxide (GO)-based nanomaterials hold significant potential for targeted cancer therapy owing to their tunable physicochemical properties and surface versatility. In this study, we systematically evaluated the cytotoxicity of pristine GO (graphene oxide) and its surface-functionalized derivatives, GO-CH₄ (methyl), GO-NH₂ (amine), and GO-O₂ (carboxyl), against murine Colon 26 carcinoma cells. Cell morphology, adhesion, and proliferation were assessed after three days of exposure using fluorescein diacetate (FDA) live/dead staining and the WST-1 mitochondrial activity assay. Distinct material-dependent biological responses were observed: GO-CH₄ (methyl) and GO-O₂ (carboxyl) exhibited pronounced cytotoxicity, reducing cell adhesion and proliferation by more than 50% relative to controls, whereas GO-NH₂ (amine) induced only moderate effects. Pristine GO (graphene oxide) showed minimal impact on cell viability and morphology, consistent with its limited cellular internalization. These results demonstrate that surface functionalization critically governs GO (graphene oxide) biocompatibility and cytotoxicity, underscoring its potential as a tunable platform for developing graphene-based cancer therapeutics, implant coatings, and biointerfaces with controlled cellular responses. Full article

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

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12 pages, 1228 KB

Open AccessArticle

Background Issues in X-Ray Diffraction and Raman Spectroscopy of Carbon Materials

by Pascal Puech, Sébastien Moyano, Petros Mubari, Elsa Weiss-Hortala and Marc Monthioux

C 2026, 12(1), 2; https://doi.org/10.3390/c12010002 - 27 Dec 2025

Abstract

Removing background signals is a common preprocessing step, but it is not without drawbacks. In X-ray diffraction data, background correction can artificially symmetrize diffraction peaks, which becomes a critical issue for lamellar materials such as graphenic carbon when the Laue indices lie in [...] Read more.

Removing background signals is a common preprocessing step, but it is not without drawbacks. In X-ray diffraction data, background correction can artificially symmetrize diffraction peaks, which becomes a critical issue for lamellar materials such as graphenic carbon when the Laue indices lie in the plane (e.g., the 10 and 11 peaks). We discuss several approaches to background correction and their implications for the resulting data. In Raman spectroscopy, defects activate the phonon density of states, leading to higher intensity below the D band than above the G band, with respect to the Raman shift. After discussing the linear and circular polarization on the Raman selection rules, we show how flattening the background—a widely used measure of disorder—alters the I_D/I_G ratio. Finally, principal component analysis (PCA) provides a useful preliminary exploration of data structure; however, because its components may include negative contributions, it cannot be directly applied to spectral decomposition. In contrast, non-negative component decomposition offers an optimal way to preserve the Raman background, even in the presence of luminescence. We confirm our analysis with ANOVA p-values. Full article

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

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C — Journal of Carbon Research

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