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8 pages, 1729 KiB

Open AccessCommunication

H₂ Adsorption on Small Pd-Ni Clusters Deposited on N-Doped Graphene: A Theoretical Study

by Brenda García-Hilerio, Lidia Santiago-Silva, Adriana Vásquez-García, Alejandro Gomez-Sanchez, Víctor A. Franco-Luján and Heriberto Cruz-Martínez

C 2024, 10(3), 73; https://doi.org/10.3390/c10030073 - 13 Aug 2024

Viewed by 377

Abstract

The study of novel materials for H₂ storage is essential to consolidate the hydrogen as a clean energy source. In this sense, the H₂ adsorption on Pd_4-nNi_n (n = 0–3) clusters embedded on pyridinic-type N-doped graphene (PNG) was [...] Read more.

The study of novel materials for H₂ storage is essential to consolidate the hydrogen as a clean energy source. In this sense, the H₂ adsorption on Pd_4-nNi_n (n = 0–3) clusters embedded on pyridinic-type N-doped graphene (PNG) was investigated using density functional theory calculations. First, the properties of Pd_4-nNi_n (n = 0–3) clusters embedded on PNG were analyzed in detail. Then, the H₂ adsorption on these composites was computed. The E_int between the Pd_4-nNi_n (n = 0–3) clusters and the PNG was greater than that computed in the literature for Pd-based systems embedded on pristine graphene. Consequently, it was deduced that PNG can more significantly stabilize the Pd_4-nNi_n (n = 0–3) clusters. The analyzed composites exhibited a HOMO–LUMO gap less than 1 eV, indicating good reactivity. Based on the E_ads of H₂ on Pd_4-nNi_n (n = 0–3) clusters embedded on PNG, it was observed that the analyzed systems meet the standards set by the DOE. Therefore, these composites can be viable alternatives for hydrogen storage. Full article

(This article belongs to the Special Issue Adsorption on Carbon-Based Materials)

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14 pages, 7922 KiB

Open AccessArticle

Synthesis of Ni@SiC/CNFs Composite and Its Microwave-Induced Catalytic Activity

by Haibo Ouyang, Jiaqi Liu, Cuiyan Li, Leer Bao, Tianzhan Shen and Yanlei Li

C 2024, 10(3), 72; https://doi.org/10.3390/c10030072 - 9 Aug 2024

Viewed by 539

Abstract

Carbon nanomaterials are promising microwave catalytic materials due to their abundant inhomogeneous interfaces capable of producing ideal interfacial polarization and multiple relaxation, which are favorable for microwave attenuation and dissipation. However, the microwave absorption performance of carbon materials is not ideal in practical [...] Read more.

Carbon nanomaterials are promising microwave catalytic materials due to their abundant inhomogeneous interfaces capable of producing ideal interfacial polarization and multiple relaxation, which are favorable for microwave attenuation and dissipation. However, the microwave absorption performance of carbon materials is not ideal in practical applications due to poor impedance matching and single dielectric loss. To solve this problem, a ternary system of “carbon-magnetic” Ni@SiC/CNFs (C/Ni, C/SiC) composites was synthesized by electrostatic spinning, and they efficiently degraded methylene blue under microwave radiation. The results imply that the catalyst Ni@SiC/CNFs with a double-shell structure gave a 99.99% removal rate in 90 s for the degradation of methylene blue under microwave irradiation, outperforming the C/Ni and C/SiC and most other reported catalysts in similar studies. On the one hand, the possible mechanism of the methylene blue degradation should be ascribed to the fact that the double-shell structure increases the polarization source of the material, resulting in excellent microwave absorption properties; and on the other, the in situ generation of ·OH and O₂⁻ active species under microwave radiation and the synergistic coupling effect of metal plasma greatly improved the degradation efficiency of methylene blue. The findings of this study could provide a valuable reference for the green degradation of industrial dye wastewater and its sustainable development process. Full article

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

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22 pages, 5495 KiB

Open AccessArticle

Insight into Carbon Black and Silica Fume as Cement Additives for Geoenergy Wells: Linking Mineralogy to Mechanical and Physical Properties

by Thomas Sammer, Arash Nasiri, Nikolaos Kostoglou, Krishna Ravi and Johann G. Raith

C 2024, 10(3), 71; https://doi.org/10.3390/c10030071 - 8 Aug 2024

Viewed by 382

Abstract

The geoenergy industry has challenging demands on cements used as downhole materials. Once placed in the annular space, the cement sheath must be very low permeability and mechanically durable. Its characteristics are strongly influenced by its microstructure. A holistic approach, including combined mineralogical, [...] Read more.

The geoenergy industry has challenging demands on cements used as downhole materials. Once placed in the annular space, the cement sheath must be very low permeability and mechanically durable. Its characteristics are strongly influenced by its microstructure. A holistic approach, including combined mineralogical, physical, and mechanical investigations, provides a better understanding of how these characteristics interplay. Class G cement was investigated and compared to cement formulations containing carbon black or silica fu me, trying to tailor its performance. The addition of carbon black and silica fume has some effect on the modal and chemical phase composition and results in a much denser microstructure. Furthermore, porosity is reduced while the pore size distribution remains similar. Samples containing carbon black have a reduced Young’s modulus, indicating a more plastic behavior. The addition of silica fume increased both mechanical strength and permeability. However, comparable results can also be achieved by carefully tuning the water/cement ratio of the initial slurry. Full article

(This article belongs to the Collection Nanoporous Carbon Materials for Advanced Technological Applications)

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21 pages, 6472 KiB

Open AccessArticle

Two Birds with One Stone: High-Quality Utilization of COVID-19 Waste Masks into Bio-Oil, Pyrolytic Gas, and Eco-Friendly Biochar with Adsorption Applications

by Tongtong Wang, Di Zhang, Hui Shi, Sen Wang, Bo Wu, Junchao Jia, Zhizhen Feng, Wenjuan Zhao, Zhangyue Chang and Dalal Z. Husein

C 2024, 10(3), 70; https://doi.org/10.3390/c10030070 - 7 Aug 2024

Viewed by 635

Abstract

As a common necessity, masks have been used a lot in recent years, and the comprehensive utilization of waste masks has become a research priority in the post-COVID-19 pandemic era. However, traditional disposal methods suffer from a range of problems, including poor utilization [...] Read more.

As a common necessity, masks have been used a lot in recent years, and the comprehensive utilization of waste masks has become a research priority in the post-COVID-19 pandemic era. However, traditional disposal methods suffer from a range of problems, including poor utilization and insecurity. To explore new solution ideas and efficiently utilize waste resources, waste masks and biomass wastes were used as raw materials to prepare mask-based biochar (WMB), bio-oil, and pyrolytic gas via oxygen-limited co-pyrolysis in this study. The obtained solid–liquid–gas product was systematically characterized to analyze the physicochemical properties, and the adsorption properties and mechanisms of WMB on the environmental endocrine bisphenol A (BPA) were investigated. The co-pyrolysis mechanisms were also studied in depth. Furthermore, the strengths and weaknesses of products prepared by co-pyrolysis and co-hydrothermal synthesis were discussed in comparison. The results indicated that the waste masks could shape the microsphere structure, leading to richer surface functional groups and stable mesoporous of WMB. Here, the risk of leaching of secondary pollutants was not detected. The theoretical maximum adsorption of BPA by WMB was 28.73 mg·g⁻¹. The Langmuir and Pseudo-second-order models optimally simulated the isothermal and kinetic adsorption processes, which are a composite of physicochemical adsorption. Simultaneous pyrolysis of mask polymers with biomass polymers produces bio-oil and pyrolytic gas, which is rich in high-quality aliphatic and aromatic compounds. This could have potential as an energy source or chemical feedstock. The co-pyrolysis mechanisms may involve the depolymerization of waste masks to produce hydrocarbons and H radicals, which in turn undergo multi-step cleavage and oligomerization reactions with biomass derivatives. It is recommended to use the co-pyrolysis method to dispose of waste masks, as the products obtained are significantly better than those obtained by the co-hydrothermal method. This work provides a new contribution to the resourcing of waste masks into high-quality products. Full article

(This article belongs to the Special Issue Adsorption on Carbon-Based Materials)

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19 pages, 2186 KiB

Open AccessReview

Recent Advances in Carbon Nanotube Technology: Bridging the Gap from Fundamental Science to Wide Applications

by Zhizhi Tao, Yuqiong Zhao, Ying Wang and Guojie Zhang

C 2024, 10(3), 69; https://doi.org/10.3390/c10030069 - 6 Aug 2024

Viewed by 695

Abstract

Carbon nanotubes, as carbon allotropes distinguished by their intricate structures and exceptional physicochemical properties, have demonstrated substantial progress in recent years across diverse domains, including energy production, chemical synthesis, and environmental preservation. They exhibit notable attributes such as high thermal stability, superior adsorption [...] Read more.

Carbon nanotubes, as carbon allotropes distinguished by their intricate structures and exceptional physicochemical properties, have demonstrated substantial progress in recent years across diverse domains, including energy production, chemical synthesis, and environmental preservation. They exhibit notable attributes such as high thermal stability, superior adsorption capacity, and a substantial specific surface area, rendering them superb catalyst supports. Particularly in electrochemical energy storage, CNTs are extensively employed in supercapacitor electrodes owing to their elevated electrical conductivity, mechanical robustness, and electrocatalytic prowess, which facilitate significant energy storage capabilities. Their intricate pore architecture and reactive sites make functionalized carbon nanotubes well suited for synthesizing composite materials with diverse components, which are ideal for sequestering carbon dioxide from both atmospheric and indoor environments. This review presents a comprehensive examination of carbon nanotube synthesis methodologies, encompassing chemical vapor deposition, arc discharge, and laser ablation, and evaluates their impacts on the structural and functional properties of carbon nanotubes. Furthermore, this article underscores the applications of carbon nanotubes in fields such as fuel cells, photocatalysis, ammonia synthesis, dry methane reforming, Fischer–Tropsch synthesis, and supercapacitors. Despite the considerable potential of carbon nanotubes, their manufacturing processes remain intricate and costly, impeding large-scale industrial production. This review concludes by addressing the challenges in fabricating carbon nanotube composites and outlining future development prospects. Full article

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

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17 pages, 6455 KiB

Open AccessArticle

Indirect Voltammetry Detection of Non-Electroactive Neurotransmitters Using Glassy Carbon Microelectrodes: The Case of Glutamate

by Sandra Lara Galindo, Surabhi Nimbalkar, Alexis Oyawale, James Bunnell, Omar Nunez Cuacuas, Rhea Montgomery-Walsh, Amish Rohatgi, Brinda Kodira Cariappa, Abhivyakti Gautam, Kevin Peguero-Garcia, Juyeon Lee, Stephanie Ingemann Bisgaard, Carter Faucher, Stephan Sylvest Keller and Sam Kassegne

C 2024, 10(3), 68; https://doi.org/10.3390/c10030068 - 31 Jul 2024

Viewed by 580

Abstract

Glassy carbon (GC) microelectrodes have been successfully used for the detection of electroactive neurotransmitters such as dopamine and serotonin through voltammetry. However, non-electroactive neurotransmitters such as glutamate, lactate, and gamma-aminobutyric acid (GABA) are inherently unsuitable for detection through voltammetry [...] Read more.

Glassy carbon (GC) microelectrodes have been successfully used for the detection of electroactive neurotransmitters such as dopamine and serotonin through voltammetry. However, non-electroactive neurotransmitters such as glutamate, lactate, and gamma-aminobutyric acid (GABA) are inherently unsuitable for detection through voltammetry techniques without functionalizing the surface of the microelectrodes. To this end, we present here the immobilization of the L-glutamate oxidase (GluOx) enzyme on the surface of GC microelectrodes to enable the catalysis of a chemical reaction between L-glutamate, oxygen, and water to produce H₂O₂, an electroactive byproduct that is readily detectable through voltammetry. This immobilization of GluOx on the surface of bare GC microelectrodes and the subsequent catalytic reduction in H₂O₂ through fast-scan cyclic voltammetry (FSCV) helped demonstrate the indirect in vitro detection of glutamate, a non-electroactive molecule, at concentrations as low as 10 nM. The functionalized microelectrodes formed part of a four-channel array of microelectrodes (30 μm × 60 μm) on a 1.6 cm long neural probe that was supported on a flexible polymer, with potential for in vivo applications. The types and strengths of the bond between the GC microelectrode surface and its functional groups, on one hand, and glutamate and the immobilized functionalization matrix, on the other hand, were investigated through molecular dynamic (MD) modeling and Fourier transform infrared spectroscopy (FTIR). Both MD modeling and FTIR demonstrated the presence of several covalent bonds in the form of C-O (carbon–oxygen polar covalent bond), C=O (carbonyl), C-H (alkenyl), N-H (hydrogen bond), C-N (carbon–nitrogen single bond), and C≡N (triple carbon–nitrogen bond). Further, penetration tests on an agarose hydrogel model confirmed that the probes are mechanically robust, with their penetrating forces being much lower than the fracture force of the probe material. Full article

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

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11 pages, 2769 KiB

Open AccessArticle

A Nitrogen/Oxygen Dual-Doped Porous Carbon with High Catalytic Conversion Ability toward Polysulfides for Advanced Lithium–Sulfur Batteries

by Xiaoyan Shu, Yuanjiang Yang, Zhongtang Yang, Honghui Wang and Nengfei Yu

C 2024, 10(3), 67; https://doi.org/10.3390/c10030067 - 30 Jul 2024

Viewed by 488

Abstract

Lithium–sulfur batteries (LSBs) have attracted widespread attention due to their high theoretical energy density and low cost. However, their development has been constrained by the shuttle effect of lithium polysulfides and their slow reaction kinetics. In this work, a nitrogen/oxygen dual-doped porous carbon [...] Read more.

Lithium–sulfur batteries (LSBs) have attracted widespread attention due to their high theoretical energy density and low cost. However, their development has been constrained by the shuttle effect of lithium polysulfides and their slow reaction kinetics. In this work, a nitrogen/oxygen dual-doped porous carbon (N/O-PC) was synthesized by annealing the precursor of zeolitic imidazolate framework-8 grown in situ on MWCNTs (ZIF-8/MWCNTs). Then, the N/O-PC composite served as an efficient host for LSBs through chemical adsorption and providing catalytic conversion sites of polysulfides. Moreover, the interconnected porous carbon-based structure facilitates electron and ion transfer. Thus, the S/N/O-PC cathode exhibits high cycling stability (a stable capacity of 685.9 mA h g⁻¹ at 0.2 C after 100 cycles). It also demonstrates excellent rate performance with discharge capacities of 1018.2, 890.2, 775.1, 722.7, 640.4, and 579.6 mAh g⁻¹ at 0.2, 0.5, 1.0, 2.0, 3.0, and 5.0 C, respectively. This work provides an effective strategy for designing and developing high energy density, long cycle life LSBs. Full article

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

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12 pages, 9147 KiB

Open AccessArticle

Impact of Dispersion Methods on Mechanical Properties of Carbon Nanotube (CNT)/Iron Oxide (Fe₃O₄)/Epoxy Composites

by Zulfiqar Ali, Saba Yaqoob and Alberto D’Amore

C 2024, 10(3), 66; https://doi.org/10.3390/c10030066 - 27 Jul 2024

Viewed by 367

Abstract

Integrating nanomaterials like carbon nanotubes (CNTs) and iron oxide (Fe₃O₄) into epoxy composites has attracted significant interest due to their potential to enhance mechanical properties. This study evaluates the impact of dispersion quality on the mechanical performance of CNT/Fe [...] Read more.

Integrating nanomaterials like carbon nanotubes (CNTs) and iron oxide (Fe₃O₄) into epoxy composites has attracted significant interest due to their potential to enhance mechanical properties. This study evaluates the impact of dispersion quality on the mechanical performance of CNT/Fe₃O₄/epoxy composites, comparing stirring and sonication methods at three different loadings: 0.1, 0.3, and 0.5 wt.%. Tensile testing revealed that sonicated composites consistently outperformed stirred composites, with a significant increase in the elastic modulus and ultimate tensile strength (UTS). However, fracture strain decreased in both composite types compared to pure epoxy, with sonicated composites experiencing a more significant reduction than stirred composites. These results underscore the importance of high-quality dispersion for optimizing mechanical properties. Full article

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

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24 pages, 7633 KiB

Open AccessReview

Unlocking the Carbon Sequestration Potential of Horticultural Crops

by Tamilselvan Ilakiya, Ettiyagounder Parameswari, Ramakrishnan Swarnapriya, Gunasekaran Yazhini, Periasamy Kalaiselvi, Veeraswamy Davamani, Sudha Singh, Nedunchezhiyan Vinothini, Chelladurai Dharani, Sneha Leela Garnepudi and Ramasamy Ajaykumar

C 2024, 10(3), 65; https://doi.org/10.3390/c10030065 - 26 Jul 2024

Viewed by 554

Abstract

As the world grapples with the escalating threat of global warming, exploring sustainable agricultural practices has become imperative. Carbon sequestration is one such efficient method to mitigate carbon emissions and reduce global warming. Among the numerous sequestration options, terrestrial methods, notably via horticultural [...] Read more.

As the world grapples with the escalating threat of global warming, exploring sustainable agricultural practices has become imperative. Carbon sequestration is one such efficient method to mitigate carbon emissions and reduce global warming. Among the numerous sequestration options, terrestrial methods, notably via horticultural crops, have enormous potential. Horticultural crops, which encompass a diverse array of fruits, vegetables, plantations, and ornamental plants, offer a unique chance to sequester a considerable amount of atmospheric carbon dioxide. In particular, perennial horticultural systems provide numerous benefits over annual crops, such as increased productivity, reduced water and input requirements, and higher economic returns via carbon credits. However, the transition from annual to perennial crops presents logistical and financial challenges. The carbon sequestration capacity of plantations and horticulture crops is larger, at 16.4 Gt C, compared to the agroforestry system, which is at 6.3 Gt C. In order to fully use this capacity, it is essential to employ effective carbon management systems. These methods include growing higher biomass, recycling agricultural waste, employing animal manure, switching to perennial crops, adopting crop rotation, and encouraging agroforestry systems. Although there are advantages, substantial initial investments and continuous management are required to ensure effectiveness, and these demands might hinder widespread acceptance. This review emphasizes the critical role of horticulture systems in improving soil carbon levels, soil organic matter dynamics, different forms of carbon, and their overall potential for carbon sequestration. By unlocking the potential of horticultural crops to sequester carbon, we can help minimize atmospheric carbon dioxide levels, lessen the impact of climate change, and ensure nutritional security and economic benefits. Full article

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

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12 pages, 6521 KiB

Open AccessArticle

Novel Superhard Tetragonal Hybrid sp³/sp² Carbon Allotropes C_x (x = 5, 6, 7): Crystal Chemistry and Ab Initio Studies

by Samir F. Matar and Vladimir L. Solozhenko

C 2024, 10(3), 64; https://doi.org/10.3390/c10030064 - 16 Jul 2024

Viewed by 554

Abstract

Novel superhard tetragonal carbon allotropes C₅, C₆, and C₇, characterized by the presence of sp³- and sp²-like carbon sites, have been predicted from crystal chemistry and extensively studied by quantum density functional theory [...] Read more.

Novel superhard tetragonal carbon allotropes C₅, C₆, and C₇, characterized by the presence of sp³- and sp²-like carbon sites, have been predicted from crystal chemistry and extensively studied by quantum density functional theory (DFT) calculations. All new allotropes were found to be cohesive, with crystal densities and cohesive energies decreasing along the C₅-C₆-C₇ series due to the greater openness of the structures resulting from the presence of C=C ethene and C=C=C propadiene subunits, and they were mechanically stable, with positive sets of elastic constants. The Vickers hardness evaluated by different models qualifies all allotropes as superhard, with H_v values ranging from 90 GPa for C₅ to 79 GPa for C₇. Phonon band structures confirm that the new allotropes are also dynamically stable. The electronic band structures reveal their metallic-like behavior due to the presence of sp²-hybridized carbon. Full article

(This article belongs to the Collection Nanocarbon-Based Composites and Their Thermal, Electrical, and Mechanical Properties)

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17 pages, 3208 KiB

Open AccessArticle

Unveiling the Structure of Metal–Nanodiamonds Bonds: Experiment and Theory

by Danil W. Boukhvalov, Vladimir Yu. Osipov, Abay Serikkanov and Kazuyuki Takai

C 2024, 10(3), 63; https://doi.org/10.3390/c10030063 - 14 Jul 2024

Viewed by 376

Abstract

In this study, we conducted a theoretical simulation to compare the effects of various factors on the atomic and electronic structures and the magnetic properties of copper and gadolinium ions bonded to carboxylated species of (111) diamond surfaces. It was experimentally found that [...] Read more.

In this study, we conducted a theoretical simulation to compare the effects of various factors on the atomic and electronic structures and the magnetic properties of copper and gadolinium ions bonded to carboxylated species of (111) diamond surfaces. It was experimentally found that in the temperature range above 120 K, the magnetic moments of chelated Gd³⁺ and Cu²⁺ equal 6.73 and 0.981 Bohr magnetons, respectively. In the temperature range from 12 to 2 K, these magnetic moments sharply decrease to 6.38 and 0.88 Bohr magnetons. Specifically, we examined the effects of the number of covalent adatom–diamond substrate bridges, coordination of water molecules, and shallow carbon-inherited spins in the substrate on the physical properties of the metal center. Our simulation predicted that increasing the number of bonds between the chelated metal ion and substrate while decreasing the number of coordinating water molecules corresponded to a decrease in the magnetic moment of metal ions in a metal–diamond system. This is due to the redistribution of the electron charge density in an asymmetric metal–diamond system. By comparing our theoretical results with experimental data, we proposed configurations involving one and, in a minor number of cases, two surface –COO⁻ groups and maximum coordination of water molecules as the most realistic options for Cu- and Gd-complexes. Full article

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

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12 pages, 12253 KiB

Open AccessArticle

Photocatalytic N-Formylation of CO₂ with Amines Catalyzed by Diethyltriamine Pentaacetic Acid

by Xuexin Yuan, Qiqi Zhou, Yu Chen, Hai-Jian Yang, Qingqing Jiang, Juncheng Hu and Cun-Yue Guo

C 2024, 10(3), 62; https://doi.org/10.3390/c10030062 - 11 Jul 2024

Viewed by 620

Abstract

In the present work, inexpensive and commercially available diethyltriamine pentaacetic acid (DTPA) was used as an initiator to catalyze the N-formylation reaction of CO₂ with amines via the construction of C-N bonds in the presence of xanthone as the photosensitizer and PhSiH [...] Read more.

In the present work, inexpensive and commercially available diethyltriamine pentaacetic acid (DTPA) was used as an initiator to catalyze the N-formylation reaction of CO₂ with amines via the construction of C-N bonds in the presence of xanthone as the photosensitizer and PhSiH₃ as the reducing agent. After a systematic study of various factors, the optimal conditions for the photocatalytic reaction were obtained: 2.5 mmol of amine, 2.5 mmol of PhSiH₃, 10 mol% of DTPA, 20 mol% of xanthone, 1 mL of dimethylsulfoxide (DMSO), atmospheric pressure, and 35 W UV lamp irradiation for 48 h. Under the optimal conditions, the catalyst system afforded high performance for the N-formylation of amines (primary and secondary amines) and CO₂, and the yields of the N-formylated products of dialkylamines were above 70%. Further studies exhibit that the catalytic system has a wide scope of substrate applications. For various alicyclic secondary amines, heterocyclic secondary amines, aliphatic primary amines, and aromatic primary amines, the corresponding N-formylation products can be obtained efficiently. In addition, the catalyst can be recycled by simple precipitation and filtration. After five cycles of recycling, there was no significant change in the catalytic and structural properties of DTPA. Finally, a possible reaction mechanism is proposed. Full article

(This article belongs to the Section CO₂ Utilization and Conversion)

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15 pages, 2536 KiB

Open AccessArticle

Enhanced Adsorption of Arsenate from Contaminated Waters by Magnesium-, Zinc- or Calcium-Modified Biochar—Modeling and Mechanisms

by Despina Vamvuka, Elena Sdoukou, Antonios Stratakis and Despina Pentari

C 2024, 10(3), 61; https://doi.org/10.3390/c10030061 - 10 Jul 2024

Viewed by 899

Abstract

The adsorption of arsenate from wastewaters was investigated by applying Mg-, Zn- or Ca-modified nut residue biochar activated by nitrogen/steam. The parameters studied were the contact time, adsorbent dose, initial arsenate concentration and solution pH. The adsorption mechanism was investigated. Various analyses of [...] Read more.

The adsorption of arsenate from wastewaters was investigated by applying Mg-, Zn- or Ca-modified nut residue biochar activated by nitrogen/steam. The parameters studied were the contact time, adsorbent dose, initial arsenate concentration and solution pH. The adsorption mechanism was investigated. Various analyses of the material before and after arsenate adsorption were carried out, and experimental data were simulated by applying two isotherm models. The results indicated that the maximum removal efficiency of arsenate was 29.4% at an initial concentration of 10 mg/L. The modification of biochar by Mg, Zn or Ca oxides increased the removal rate significantly, from 49.4% at 100 mg/L As⁵⁺ up to 8%, 97% and 97%, respectively. Zn-modified biochar presented an excellent performance for both low and high As⁵⁺ concentrations. All experimental data were accurately fitted by the Freundlich isotherm model (R² = 0.94–0.97), confirming a multilayer adsorption mechanism. For a biochar dose of 2 g/L, the maximum capacity of adsorption was enhanced after Mg-, Zn- or Ca-modification from 12.4 mg/g to 35 mg/g, 50 mg/g and 49 mg/g, respectively. The potential mechanisms of adsorption were ligand exchange, chemical complexation, surface precipitation and electron coordination. Full article

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

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30 pages, 11216 KiB

Open AccessReview

Carbon Dots for Future Prospects: Synthesis, Characterizations and Recent Applications: A Review (2019–2023)

by Habtamu Fekadu Etefa, Aster Aberra Tessema and Francis Birhanu Dejene

C 2024, 10(3), 60; https://doi.org/10.3390/c10030060 - 5 Jul 2024

Viewed by 1298

Abstract

Carbon dots (CDs) have emerged as a promising class of carbon-based nanomaterials due to their unique properties and versatile applications. Carbon dots (CDs), also known as carbon quantum dots (CQDs) or graphene quantum dots (GQDs), are nanoscale carbon-based materials with dimensions typically less [...] Read more.

Carbon dots (CDs) have emerged as a promising class of carbon-based nanomaterials due to their unique properties and versatile applications. Carbon dots (CDs), also known as carbon quantum dots (CQDs) or graphene quantum dots (GQDs), are nanoscale carbon-based materials with dimensions typically less than 10 nanometers. They exhibit intriguing optical, electronic, and chemical properties, making them attractive for a wide range of applications, including sensing, imaging, catalysis, and energy conversion, among many others. Both bottom-up and top-down synthesis approaches are utilized for the synthesis of carbon dots, with each method impacting their physicochemical characteristics. Carbon dots can exhibit diverse structures, including amorphous, crystalline, or hybrid structures, depending on the synthesis method and precursor materials used. CDs have diverse chemical structures with modified oxygen, polymer-based, or amino groups on their surface. These structures influence their optical and electronic properties, such as their photoluminescence, bandgap, and charge carrier mobility, making them tunable for specific applications. Various characterization methods such as HRTEM, XPS, and optical analysis (PL, UV) are used to determine the structure of CDs. CDs are cutting-edge fluorescent nanomaterials with remarkable qualities such as biocompatibility, low toxicity, environmental friendliness, high water solubility, and photostability. They are easily adjustable in terms of their optical properties, making them highly versatile in various fields. CDs find applications in bio-imaging, nanomedicine, drug delivery, solar cells, photocatalysis, electrocatalysis, and other related areas. Carbon dots hold great promise in the field of solar cell technology due to their unique properties, including high photoluminescence, high carbon quantum yield (CQY), and excellent charge separation. Full article

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19 pages, 4311 KiB

Open AccessArticle

Theoretical Studies on the Dynamical Behavior of Atom/Ion Migration on the Surface of Pristine and BN-Doped Graphene

by Tong-Kun Zhang, Li-Jun Zhou and Jian-Gang Guo

C 2024, 10(3), 59; https://doi.org/10.3390/c10030059 - 3 Jul 2024

Viewed by 574

Abstract

Using the potential function method, a theoretical model of the interaction was presented, and the interaction force between atoms/ions and (doped) graphene was obtained. Based on the interaction force, the dynamical control equation of atom/ion migration was derived. The dynamical behavior of atom/ion [...] Read more.

Using the potential function method, a theoretical model of the interaction was presented, and the interaction force between atoms/ions and (doped) graphene was obtained. Based on the interaction force, the dynamical control equation of atom/ion migration was derived. The dynamical behavior of atom/ion migrating on finite-size graphene surfaces along a specific direction and the regulation of boron nitride (BN) doping on the migration behavior were studied. The results show that the atoms/ions exhibit different migration mechanical behaviors due to different lateral forces inside and at the edges of the graphene surface. In addition, near the normal equilibrium height, atoms/ions are mainly affected by the lateral force, and their migration behavior is also influenced by the initial position, initial height, initial lateral velocity, etc. Furthermore, BN doping can affect the energy barrier of atom/ion migration on the graphene surface and effectively regulate the migration behavior of atoms/ions at the edge of the graphene surface. The research results can provide a theoretical reference for graphene surface localization modification and graphene-based atom/ion screening and detection. Full article

(This article belongs to the Special Issue Adsorption on Carbon-Based Materials)

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16 pages, 5137 KiB

Open AccessArticle

Highly Porous Cellulose-Based Carbon Fibers as Effective Adsorbents for Chlorpyrifos Removal: Insights and Applications

by Tamara Tasić, Vedran Milanković, Christoph Unterweger, Christian Fürst, Stefan Breitenbach, Igor A. Pašti and Tamara Lazarević-Pašti

C 2024, 10(3), 58; https://doi.org/10.3390/c10030058 - 27 Jun 2024

Viewed by 1003

Abstract

The extensive utilization of the organophosphate pesticide chlorpyrifos, combined with its acute neurotoxicity, necessitates the development of effective strategies for its environmental removal. While numerous methods have been explored for chlorpyrifos removal from water, adsorption is the most promising. We investigated the potential [...] Read more.

The extensive utilization of the organophosphate pesticide chlorpyrifos, combined with its acute neurotoxicity, necessitates the development of effective strategies for its environmental removal. While numerous methods have been explored for chlorpyrifos removal from water, adsorption is the most promising. We investigated the potential of two cellulose-derived porous carbons as adsorbents for chlorpyrifos removal from water, prepared by either CO₂ or H₂O activation, resulting in similar morphologies and porosities but different amounts of heteroatom functionalities. The kinetics of batch adsorption removal from water fits well with the pseudo-first-order and pseudo-second-order kinetic models for both materials. The Freundlich, Langmuir, Dubinin–Radushkevich, and Sips isotherm models described the process of chlorpyrifos adsorption very well in all investigated cases. The maximum adsorption capacity determined from the Sips isotherm model gave values of 80.8 ± 0.1 mg g⁻¹ and 132 ± 3 mg g⁻¹ for the H₂O and CO₂ activated samples, respectively, reflecting the samples’ differences in heteroatom functionalities. Additionally, the application of either adsorbent led to reduced toxicity levels in all tested samples, implying that no harmful by-products were generated during adsorption. Comparative analysis with the existing literature further validates the study’s findings, suggesting the efficacy and applicability of cellulose-based porous carbons for sustainable chlorpyrifos remediation. Full article

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

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16 pages, 3219 KiB

Open AccessArticle

Multichannel Sensor for Detection of Molybdenum Ions Based on Nitrogen-Doped Carbon Quantum Dot Ensembles

by Antônio A. C. Cruz, Natália D. G. Souza, João P. B. de Souza, Samuel V. Carneiro, Claudenilson S. Clemente, Jeanlex S. Sousa, Lillian M. U. D. Fechine, Sebastián Michea, Pierre B. A. Fechine and Rafael M. Freire

C 2024, 10(3), 57; https://doi.org/10.3390/c10030057 - 22 Jun 2024

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Abstract

Trace elements such as cobalt (Co), molybdenum (Mo), and zinc (Zn) play necessary roles in different biological functions. Co is a microelement that influences the vascular system. Mo works as an enzymatic cofactor of three enzymes (aldehyde oxidase, sulfite oxidase, and xanthine oxidase [...] Read more.

Trace elements such as cobalt (Co), molybdenum (Mo), and zinc (Zn) play necessary roles in different biological functions. Co is a microelement that influences the vascular system. Mo works as an enzymatic cofactor of three enzymes (aldehyde oxidase, sulfite oxidase, and xanthine oxidase dehydrogenase). However, these elements are difficult to detect, since the analytical methods developed have a high cost, which restrict their applicability. In this sense, fluorescent sensors are an alternative for detecting trace elements, such as Mo⁴⁺ ions. Herein, a new multichannel trace elements sensor has been proposed to detect Mo entities. In this sense, two different N-CQDs were synthesized and fully characterized. The N-CQDs presented quantum yield values of 25.93% and 6.02% and excellent solubility in water. Also, a mixture of these two carbon-based nanoparticles was used to identify and to quantify Mo in water between seven different trace elements. The method was found to reach 1.28 and 3.88 ppm for limit of detection (LOD) and quantification (LOQ), respectively. To further verify the potential of the detection platform, the multichannel sensor was applied to identify the different concentrations of metal ions (Fe²⁺, Co²⁺, Mn²⁺, Cu²⁺, Zn²⁺, Mg²⁺, and Mo⁴⁺) in water. The data matrix was treated using different algorithms, such as K-Means and Discriminant Analysis (DA). The detection strategy has successfully identified the molybdenum ions at 5 ppm. This result shows the potential application of a multichannel sensor toward the detection of Mo entities, since it is comparable with the molybdenum test already available on the market. Full article

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C, Volume 10, Issue 3 (September 2024) – 17 articles

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