C | March 2025 - Browse Articles

17 pages, 1485 KiB

Open AccessArticle

TiO₂/SWCNts: Linear and Nonlinear Optical Studies for Environmental Applications

by Saloua Helali

C 2025, 11(1), 11; https://doi.org/10.3390/c11010011 - 26 Jan 2025

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A series of single-walled carbon nanotube/titanium dioxide (SWCNTs/TiO₂) composites were prepared by the incorporation of various concentrations (0, 5, 10, 20 V.%) of SWCNTs in TiO₂. The prepared solutions were successfully formed on silicon and quartz substrates using the [...] Read more.

A series of single-walled carbon nanotube/titanium dioxide (SWCNTs/TiO₂) composites were prepared by the incorporation of various concentrations (0, 5, 10, 20 V.%) of SWCNTs in TiO₂. The prepared solutions were successfully formed on silicon and quartz substrates using the sol–gel spin-coating approach at 600 °C in ambient air. The X-ray diffraction method was used to investigate the structure of the samples. The absorbance and transmittance data of the samples were measured using a UV–vis spectrophotometer. Through the analysis of these data, both the linear and nonlinear optical properties of the samples were examined. Wemple–DiDomenico’s single-oscillator model was used to calculate the single-oscillator energy and dispersion energy. Finally, all samples’ photocatalytic performance was studied by the photodegradation of methylene blue (MB) in an aqueous solution under UV irradiation. It is found that the photocatalytic efficiency increases when increasing the SWCNT content. This research offers a new perspective for the creation of new photocatalysts for environmental applications. Full article

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

14 pages, 7961 KiB

Open AccessArticle

Markedly Enhanced Photoluminescence of Carbon Dots Dispersed in Deuterium Oxide

by Corneliu S. Stan, Adina Coroaba, Conchi O. Ania, Cristina Albu and Marcel Popa

C 2025, 11(1), 10; https://doi.org/10.3390/c11010010 - 22 Jan 2025

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Abstract

In this work, we report some surprisingly interesting results in our pursuit to improve the photoluminescent emission of Carbon Dots (CDs) prepared from various precursors. By simply replacing the regular water with deuterium oxide (D₂O) as a dispersion medium, the emission [...] Read more.

In this work, we report some surprisingly interesting results in our pursuit to improve the photoluminescent emission of Carbon Dots (CDs) prepared from various precursors. By simply replacing the regular water with deuterium oxide (D₂O) as a dispersion medium, the emission intensity and the subsequent quantum efficiency of the radiative processes could be markedly enhanced. The present study was performed on our previous reported works related to CDs; in each case, the preparation path was maintained accordingly. For each type of CD, the emission intensity and the absolute photoluminescence quantum yield (PLQY) were highly improved, with, in certain cases, more-than-doubled values being recorded and the gain in performance being easily noticeable with the naked eye even in plain daylight. For each type of CD dispersed in regular water and heavy water, respectively, the photoluminescent properties were thoroughly investigated through Steady State, lifetime, and absolute PLQY. To further elucidate the mechanism involved in the photoluminescence intensity enhancement, samples of D₂O and H₂O dispersed CDs were embedded in a crosslinked Poly(acrylic acid) polymer matrix. The investigations revealed the major influence of the deuterium oxide dispersion medium over the PL emission properties of the investigated CDs. Full article

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

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16 pages, 2648 KiB

Open AccessArticle

Raman Spectroscopy of Graphene/CNT Layers Deposited on Interdigit Sensors for Application in Gas Detection

by Stefan-Marian Iordache, Ana-Maria Iordache, Ana-Maria Florea (Raduta), Stefan Caramizoiu, Catalin Parvulescu, Flaviu Baiasu, Irina Negut and Bogdan Bita

C 2025, 11(1), 9; https://doi.org/10.3390/c11010009 - 20 Jan 2025

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Abstract

Graphene/CNT layers were deposited onto platinum electrodes of an interdigitated sensor using radio-frequency magnetron sputtering. The graphene/CNTs were synthesized in an Argon atmosphere at a pressure of (2 × 10⁻²–5 × 10⁻³) mbar, with the substrate maintained at 300 [...] Read more.

Graphene/CNT layers were deposited onto platinum electrodes of an interdigitated sensor using radio-frequency magnetron sputtering. The graphene/CNTs were synthesized in an Argon atmosphere at a pressure of (2 × 10⁻²–5 × 10⁻³) mbar, with the substrate maintained at 300 °C either through continuous heating with an electronically controlled heater or by applying a −200 V bias using a direct current power supply throughout the deposition process. The study compares the surface morphology, carbon atom arrangement within the layer volumes, and electrical properties of the films as influenced by the different methods of substrate heating. X-ray diffraction and Raman spectroscopy confirmed the formation of CNTs within the graphene matrix. Additionally, scanning electron microscopy revealed that the carbon nanotubes are aligned and organized into cluster-like structure. The graphene/CNT layers produced at higher pressures present exponential I–V characteristics that ascertain the semiconducting character of the layers and their suitability for applications in gas sensing. Full article

(This article belongs to the Special Issue New Advances in Graphene Synthesis and Applications)

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27 pages, 17276 KiB

Open AccessReview

PPE Waste-Derived Carbon Materials for Energy Storage Applications via Carbonization Techniques

by Nur Amaliyana Raship, Siti Nooraya Mohd Tawil and Murniati Syaripuddin

C 2025, 11(1), 8; https://doi.org/10.3390/c11010008 - 16 Jan 2025

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Abstract

Starting from the COVID-19 pandemic in early 2020, billions of personal protective equipment (PPE), mainly face masks (FMs), are reported to be worn and thrown away every month worldwide. Most of the waste winds up in landfills and undergoes an incineration process after [...] Read more.

Starting from the COVID-19 pandemic in early 2020, billions of personal protective equipment (PPE), mainly face masks (FMs), are reported to be worn and thrown away every month worldwide. Most of the waste winds up in landfills and undergoes an incineration process after being released into the environment. This could pose a significant risk and long-term effects to both human health and ecology due to the tremendous amount of non-biodegradable substances in the PPE waste. Consequently, alternative approaches for recycling PPE waste are imperatively needed to lessen the harmful effects of PPE waste. The current recycling methods facilitate the conventional treatment of waste, and most of it results in materials with decreased values for their characteristics. Thus, it is crucial to create efficient and environmentally friendly methods for recycling FMs and other PPE waste into products with added value, such as high-quality carbon materials. This paper reviews and focuses on the techniques for recycling PPE waste that are both economically viable and beneficial to the environment through carbonization technology, which transforms PPE waste into highly valuable carbon materials, as well as exploring the possible utilization of these materials for energy storage applications. In conclusion, this paper provides copious knowledge and information regarding PPE waste-derived carbon-based materials that would benefit potential green energy research. Full article

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

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15 pages, 766 KiB

Open AccessArticle

Monte Carlo Simulation of Aromatic Molecule Adsorption on Multi-Walled Carbon Nanotube Surfaces Using Coefficient of Conformism of a Correlative Prediction (CCCP)

by Alla P. Toropova, Andrey A. Toropov, Alessandra Roncaglioni and Emilio Benfenati

C 2025, 11(1), 7; https://doi.org/10.3390/c11010007 - 14 Jan 2025

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Abstract

Using the Monte Carlo technique via CORAL-2024 software, models of aromatic substance adsorption on multi-walled nanotubes were constructed. Possible mechanistic interpretations of such models and the corresponding applicability domains were investigated. In constructing the models, criteria of the predictive potential such as the [...] Read more.

Using the Monte Carlo technique via CORAL-2024 software, models of aromatic substance adsorption on multi-walled nanotubes were constructed. Possible mechanistic interpretations of such models and the corresponding applicability domains were investigated. In constructing the models, criteria of the predictive potential such as the iIndex of Ideality of Correlation (IIC), the Correlation Intensity Index (CII), and the Coefficient of Conformism of a Correlative Prediction (CCCP) were used. It was assumed that the CCCP could serve as a tool for increasing the predictive potential of adsorption models of organic substances on the surface of nanotubes. The developed models provided good predictive potential. The perspectives on the improvement of the nano-QSPR/QSAR were discussed. Full article

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

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17 pages, 3233 KiB

Open AccessReview

Fluorination to Enhance the Tribological Properties of Carbonaceous Materials

by Guillaume Haddad, Nadiège Nomède-Martyr, Philippe Bilas, Katia Guérin, Philippe Thomas, Karl Delbé and Marc Dubois

C 2025, 11(1), 6; https://doi.org/10.3390/c11010006 - 7 Jan 2025

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Abstract

This review compiles data from 77 articles on the tribological properties of fluorinated carbons CFx. Covalent grafting of fluorine atoms improves the tribological properties. The C-F bonding plays a key role in reducing friction. The tribological stability of CFx, along with their ability [...] Read more.

This review compiles data from 77 articles on the tribological properties of fluorinated carbons CFx. Covalent grafting of fluorine atoms improves the tribological properties. The C-F bonding plays a key role in reducing friction. The tribological stability of CFx, along with their ability to form protective films from the very first cycles, provides a significant advantage in reducing wear and extending the lifespan of mechanical components. The role of the presence of fluorine atoms, their content, their distribution in the carbon lattice, and the C-F bonding, as well as the dimensionality and the size of the materials, are discussed. Some ways of improving lubrication performance and investigating friction-reducing properties and mechanisms are proposed. Full article

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

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20 pages, 3964 KiB

Open AccessArticle

Degradation Kinetics, Mechanisms, and Antioxidant Activity of PCL-Based Scaffolds with In Situ Grown Nanohydroxyapatite on Graphene Oxide Nanoscrolls

by Lillian Tsitsi Mambiri and Dilip Depan

C 2025, 11(1), 5; https://doi.org/10.3390/c11010005 - 3 Jan 2025

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Abstract

Polycaprolactone (PCL) degradation is critical in bone tissue engineering, where scaffold degradation must align with tissue regeneration to ensure stability and integration. This study explores the effects of nanofillers, hydroxyapatite (nHA), and graphene oxide nanoscrolls (GONS) on PCL-based scaffold degradation kinetics. Both PHAP [...] Read more.

Polycaprolactone (PCL) degradation is critical in bone tissue engineering, where scaffold degradation must align with tissue regeneration to ensure stability and integration. This study explores the effects of nanofillers, hydroxyapatite (nHA), and graphene oxide nanoscrolls (GONS) on PCL-based scaffold degradation kinetics. Both PHAP (nHA-PCL) and PGAP (nHA-GONS-PCL) scaffolds exhibited changes to relaxation-driven degradation, as indicated by adherence to the Korsmeyer–Peppas model (R² = 1.00). PHAP scaffolds showed lower activation energies (5.02–5.54 kJ/mol), promoting faster chain relaxation and degradation in amorphous regions. PGAP scaffolds, with higher activation energies (12.88–12.90 kJ/mol), displayed greater resistance to chain relaxation and slower degradation. Differential scanning calorimetry (DSC) revealed that both nanofillers disrupted the crystalline regions, shifting degradation behavior from diffusion-based to relaxation-driven mechanisms in the amorphous zones, which was also reflected by changes in crystallization temperature (Tc) and melting temperature (T_m). Additionally, PGAP scaffolds demonstrated antioxidant potential, which decreased over time as degradation progressed. These results provide a mechanistic understanding of how nanofiller-modulated degradation dynamics can be strategically leveraged to optimize scaffold performance, facilitating precise control over degradation rates and bioactivity. Full article

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

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14 pages, 3865 KiB

Open AccessArticle

Adsorption of Asymmetric and Linear Hazardous Gases on Graphene Oxides: Density Functional Study

by Yongju Kwon, Taeyang Kim, Jaemyeong Choi, Sangeon Lee, Sungmin Cha and Soonchul Kwon

C 2025, 11(1), 4; https://doi.org/10.3390/c11010004 - 2 Jan 2025

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Abstract

The introduction of functional groups, such as graphene oxide, can improve the reactivity between molecules, increasing the potential for their use in many fields such as gas sensing and adsorption. It was reported that that graphene materials are actively utilized in toxic gas [...] Read more.

The introduction of functional groups, such as graphene oxide, can improve the reactivity between molecules, increasing the potential for their use in many fields such as gas sensing and adsorption. It was reported that that graphene materials are actively utilized in toxic gas sensor materials by modifying the surface with their chemical and structural stability. In order to understand the mechanisms of graphene and graphene oxides for adsorbing the hazardous gases, we classified the four gases (H₂S, NH₃, HF and COS) with their phases (two asymmetric and two linear), and conducted density functional theory calculations to determine the adsorption affinity, which represents the binding energy, bond distance, energy charge (Mulliken and Hirshfeld methods) and band gap between the HOMO (Highest Occupied Molecular Orbital) and the LUMO (Lowest Unoccupied Molecular Orbital). The results showed that introducing a functional group enhanced the binding energy with a narrowed band gap in asymmetric gas adsorption (H₂S and NH₃), while the results of the linear gases (HF and COS) showed lowered binding energy with a narrowed band gap. It is judged that the oxygen functional groups can narrow the band gap by introducing localized states between the valence and conduction bands or by forming new hybrid states through interactions with all the gases. However, from the differences in the phases, the linear gases stably interacted with a defect-free, porous and flat structure like with π–π interactions. In short, the theoretical findings confirm that the oxidation functional groups narrowed the band gap with a local interaction; however, linear gases showed enhanced binding energies with pristine graphene, which highlights the importance of surface material selection dependent on the target gases. Full article

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

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24 pages, 7558 KiB

Open AccessReview

Graphene-Enhanced Piezoelectric Nanogenerators for Efficient Energy Harvesting

by Joydip Sengupta and Chaudhery Mustansar Hussain

C 2025, 11(1), 3; https://doi.org/10.3390/c11010003 - 1 Jan 2025

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Abstract

Graphene-based piezoelectric nanogenerators (PENGs) have emerged as a promising technology for sustainable energy harvesting, offering significant potential in powering next-generation electronic devices. This review explores the integration of graphene, a highly conductive and mechanically robust two-dimensional (2D) material, with PENG to enhance their [...] Read more.

Graphene-based piezoelectric nanogenerators (PENGs) have emerged as a promising technology for sustainable energy harvesting, offering significant potential in powering next-generation electronic devices. This review explores the integration of graphene, a highly conductive and mechanically robust two-dimensional (2D) material, with PENG to enhance their energy conversion efficiency. Graphene’s unique properties, including its exceptional electron mobility, high mechanical strength, and flexibility, allow for the development of nanogenerators with superior performance compared to conventional PENGs. When combined with piezoelectric materials, polymers, graphene serves as both an active layer and a charge transport medium, boosting the piezoelectric response and output power. The graphene-based PENGs can harvest mechanical energy from various sources, including vibrations, human motion, and ambient environmental forces, making them ideal for applications in wearable electronics, and low-power devices. This paper provides an overview of the fabrication techniques, material properties, and energy conversion mechanisms of graphene-based PENGs, and integration into real-world applications. The findings demonstrate that the incorporation of graphene enhances the performance of PENG, paving the way for future innovations in energy-harvesting technologies. Full article

(This article belongs to the Special Issue New Advances in Graphene Synthesis and Applications)

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25 pages, 8926 KiB

Open AccessArticle

Development and Characterization of Biomass-Derived Carbons for the Removal of Cu²⁺ and Pb²⁺ from Aqueous Solutions

by Vahid Rahimi, Catarina Helena Pimentel, Diego Gómez-Díaz, María Sonia Freire, Massimo Lazzari and Julia González-Álvarez

C 2025, 11(1), 2; https://doi.org/10.3390/c11010002 - 29 Dec 2024

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Abstract

This research explores the synthesis and application of carbon-based adsorbents derived from olive stones and almond shells as low-cost biomass precursors through carbonization at 600 °C combined with chemical activation using KOH, H₃PO₄, and ZnCl₂ with carbon/activating agent [...] Read more.

This research explores the synthesis and application of carbon-based adsorbents derived from olive stones and almond shells as low-cost biomass precursors through carbonization at 600 °C combined with chemical activation using KOH, H₃PO₄, and ZnCl₂ with carbon/activating agent (C/A) ratios of 1:2 and 1:4 (w/w) at 850 °C for the removal of Cu²⁺ and Pb²⁺ ions from aqueous solutions. The carbons produced were characterized using different techniques including SEM-EDX, FTIR, XRD, BET analysis, CHNS elemental analysis, and point of zero charge determination. Batch-mode adsorption experiments were carried out at adsorbent doses of 2 and 5 g L⁻¹, initial metal concentrations of 100 and 500 mg L⁻¹, and natural pH (around 5) with agitation at 350 rpm and 25 °C for 24 h. KOH-activated carbons, especially at a 1:4 (w/w) ratio, exhibited superior adsorption performance mainly due to their favorable surface characteristics and functionalities. Pb²⁺ was entirely removed (100%) at the highest initial concentration of 500 mg L⁻¹ and an adsorbent dosage of 5 g L⁻¹, while for Cu²⁺, the maximum adsorption efficiency was 86.29% at an initial concentration of 100 mg L⁻¹ and a dosage of 2 g L⁻¹. The results of this study will help advance knowledge in the design and optimization of adsorption processes for heavy metal removal, benefiting industries seeking green technologies to mitigate environmental pollution. Full article

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

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28 pages, 2500 KiB

Open AccessReview

The Advanced Role of Carbon Quantum Dots in Nano-Food Science: Applications, Bibliographic Analysis, Safety Concerns, and Perspectives

by Abdul Majid, Khurshid Ahmad, Liju Tan, Waqas Niaz, Wang Na, Li Huiru and Jiangtao Wang

C 2025, 11(1), 1; https://doi.org/10.3390/c11010001 - 24 Dec 2024

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Abstract

Carbon quantum dots (CQDs) are innovative carbon-based nanomaterials that can be synthesized from organic and inorganic sources using two approaches: “top-down” (laser ablation, arc discharge, electrochemical, and acidic oxidation) and “bottom-up” (hydrothermal, ultrasound-assisted, microwave, and thermal decomposition). Among these, hydrothermal synthesis stands out [...] Read more.

Carbon quantum dots (CQDs) are innovative carbon-based nanomaterials that can be synthesized from organic and inorganic sources using two approaches: “top-down” (laser ablation, arc discharge, electrochemical, and acidic oxidation) and “bottom-up” (hydrothermal, ultrasound-assisted, microwave, and thermal decomposition). Among these, hydrothermal synthesis stands out as the best option as it is affordable and eco-friendly and can produce a high quantum yield. Due to their exceptional physical and chemical properties, CQDs are highly promising materials for diverse applications, i.e., medicine, bioimaging, and especially in food safety, which is one of the thriving fields of recent research worldwide. As an innovative sensing tool, CQDs with different surface functional groups enable them to detect food contaminants, i.e., food additives in processed food, drug residues in honey, and mycotoxins in beer and flour, based on different sensing mechanisms (IFE, PET, and FRET). This article discussed the sources, fabrication methods, advantages, and limitations of CQDs as a sensing for the detection of food contaminants. In addition, the cost-effectiveness, eco-friendliness, high quantum yield, safety concerns, and future research perspectives to enhance food quality and security were briefly highlighted. This review also explored recent advancements in CQD applications in food safety, supported by a bibliometric analysis (2014–2024) using the PubMed database. Full article

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

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