Nitrogen-Doped Single-Walled Carbon Nanohorns as a Cost-Effective Carbon Host toward High-Performance Lithium-Sulfur Batteries

Fluorescent Nanocarbons: From Synthesis and Structure to Cancer Imaging and Therapy

Nanocarbons are emerging at the forefront of nanoscience, with diverse carbon nanoforms emerging over the past two decades. Early cancer diagnosis and therapy, driven by advanced chemistry techniques, play a pivotal role in mitigating mortality rates associated with cancer. Nanocarbons, with an attractive combination of well-defined architectures, biocompatibility, and nanoscale dimension, offer an incredibly versatile platform for cancer imaging and therapy. This paper aims to review the underlying principles regarding the controllable synthesis, fluorescence origins, cellular toxicity, and surface functionalization routes of several classes of nanocarbons: carbon nanodots, nanodiamonds, carbon nanoonions, and carbon nanohorns. This review also highlights recent breakthroughs regarding the green synthesis of different nanocarbons from renewable sources. It also presents a comprehensive and unified overview of the latest cancer-related applications of nanocarbons and how they can be designed to interface with biological systems and work as cancer diagnostics and therapeutic tools. The commercial status for large-scale manufacturing of nanocarbons is also presented. Finally, it proposes future research opportunities aimed at engendering modifiable and high-performance nanocarbons for emerging applications across medical industries. This work is envisioned as a cornerstone to guide interdisciplinary teams in crafting fluorescent nanocarbons with tailored attributes that can revolutionize cancer diagnostics and therapy.

Anchoring polysulfides via a CoS2/NC@1T MoS2 modified separator for high-performance lithium–sulfur batteries

CoS2/NC@1T MoS2 synthesized by a one-step hydrothermal method forms a unique hierarchical configuration with simultaneous internal and external modifications. A lithium–sulfur battery with a CoS2/NC@1T MoS2-PP separator shows superior cycling performance.

Highly sensitive electrochemical detection of carbendazim residues in water by synergistic enhancement of nitrogen-doped carbon nanohorns and polyethyleneimine modified carbon nanotubes

Carbendazim (CBZ) can protect crops from pathogens, but it is also easy to cause pesticide residues, threatening human health. In our work, an electrochemical sensor based on nitrogen-doped carbon nanohorns (N-CNHs) and polyethyleneimine-modified carbon nanotubes (PEI-CNTs) was developed for the detection of CBZ content in water. The results showed that N-doping provided the CN bonds for CNHs and improved the electrochemical reaction performance of N-CNHs surface. With the participation of PEI, the surface of CNTs was positively charged and contained a large number of NH bonds, which not only promoted the electrostatic assembly of N-CNHs and PEI-CNTs but also was beneficial to further enriching CBZ. After further ultrasound-assisted assembly of N-CNHs and PEI-CNTs, the electron transfer capacity, electrochemical active surface area, and catalytic activity of N-CNHs/PEI-CNTs were significantly improved. The sensor performed a wider linear range (15 nmol/L ~ 70 μmol/L), low detection limit (4 nmol/L) and satisfactory recovery (87.33 % ~ 117.67 %) under the optimal conditions. In addition, the sensor had good anti-interference, reproducibility, and stability. Our work provided a new strategy for quantification of CBZ in environment.

Sustainable Synthesis of Sulfur-Single Walled Carbon Nanohorns Composite for Long Cycle Life Lithium-Sulfur Battery

Lithium-sulfur batteries are considered one of the most appealing technologies for next-generation energy-storage devices. However, the main issues impeding market breakthrough are the insulating property of sulfur and the lithium-polysulfide shuttle effect, which cause premature cell failure. To face this challenge, we employed an easy and sustainable evaporation method enabling the encapsulation of elemental sulfur within carbon nanohorns as hosting material. This synthesis process resulted in a morphology capable of ameliorating the shuttle effect and improving the electrode conductivity. The electrochemical characterization of the sulfur-carbon nanohorns active material revealed a remarkable cycle life of 800 cycles with a stable capacity of 520 mA h/g for the first 400 cycles at C/4, while reaching a value around 300 mAh/g at the 750th cycle. These results suggest sulfur-carbon nanohorn active material as a potential candidate for next-generation battery technology.

Structural Study of Sulfur-Added Carbon Nanohorns

In the past few decades, nanostructured carbons (NCs) have been investigated for their interesting properties, which are attractive for a wide range of applications in electronic devices, energy systems, sensors, and support materials. One approach to improving the properties of NCs is to dope them with various heteroatoms. This work describes the synthesis and study of sulfur-added carbon nanohorns (S-CNH). Synthesis of S-CNH was carried out by modified chemical vapor deposition (m-CVD) using toluene and thiophene as carbon and sulfur sources, respectively. Some parameters such as the temperature of synthesis and carrier gas flow rates were modified to determine their effect on the properties of S-CNH. High-resolution scanning and transmission electron microscopy analysis showed the presence of hollow horn-type carbon nanostructures with lengths between 1 to 3 µm and, diameters that are in the range of 50 to 200 nm. Two types of carbon layers were observed, with rough outer layers and smooth inner layers. The surface textural properties are attributed to the defects induced by the sulfur intercalated into the lattice or bonded with the carbon. The XRD patterns and X-ray microanalysis studies show that iron serves as the seed for carbon nanohorn growth and iron sulfide is formed during synthesis.

Electrochemical Performance of Carbon-Rich Silicon Carbonitride Ceramic as Support for Sulfur Cathode in Lithium Sulfur Battery

As a promising matrix material for anchoring sulfur in the cathode for lithium-sulfur (Li-S) batteries, porous conducting supports have gained much attention. In this work, sulfur-containing C-rich SiCN composites are processed from silicon carbonitride (SiCN) ceramics, synthesized at temperatures from 800 to 1100 °C. To embed sulfur in the porous SiCN matrix, an easy and scalable procedure, denoted as melting-diffusion method, is applied. Accordingly, sulfur is infiltrated under solvothermal conditions at 155 °C into pores of carbon-rich silicon carbonitride (C-rich SiCN). The impact of the initial porosity and microstructure of the SiCN ceramics on the electrochemical performance of the synthesized SiCN-sulfur (SiCN-S) composites is analysed and discussed. A combination of the mesoporous character of SiCN and presence of a disordered free carbon phase makes the electrochemical performance of the SiCN matrix obtained at 900 °C superior to that of SiCN synthesized at lower and higher temperatures. A capacity value of more than 195 mAh/g over 50 cycles at a high sulfur content of 66 wt.% is achieved.

Ultrafine Rh nanocrystals grown onto a boron and nitrogen codoped carbon support with a horn-shaped structure for highly efficient methanol oxidation

A facile and robust strategy is developed for the preparation of ultrafine Rh grown onto a B and N codoped horn-shaped carbon support, exhibiting exceptional electrocatalytic properties for methanol oxidation.

A review of size engineering-enabled electrocatalysts for Li-S chemistry

Li-S batteries (LSBs) have received extensive attention owing to their remarkable theoretical capacity (1672 mA h g^-1) and high energy density (2600 W h kg^-1), which are far beyond those of the state-of-the-art Li-ion batteries (LIBs). However, the retarded sulfur reaction kinetics and fatal shuttle effect have hindered the practical implementations of LSBs. In response, constructing electrocatalysts for Li-S systems has been considered an effective strategy to date. Particularly, size engineering-enabled electrocatalysts show high activity in the sulfur redox reaction, considerably contributing to the latest advances in Li-S system research. In this tutorial review, we provide a systematic summary of nano- to atomic-scale electrocatalysts employed in Li-S chemistry, aiming at figuring out the working mechanism of size engineering-enabled electrocatalysts in the sulfur redox reaction and guiding the rational construction of advanced LSBs toward practically viable applications.

Vapor-phase production of nanomaterials

The synthesis of nanomaterials, with characteristic dimensions of 1 to 100 nm, is a key component of nanotechnology. Vapor-phase synthesis of nanomaterials has numerous advantages such as high product purity, high-throughput continuous operation, and scalability that have made it the dominant approach for the commercial synthesis of nanomaterials. At the same time, this class of methods has great potential for expanded use in research and development. Here, we present a broad review of progress in vapor-phase nanomaterial synthesis. We describe physically-based vapor-phase synthesis methods including inert gas condensation, spark discharge generation, and pulsed laser ablation; plasma processing methods including thermal- and non-thermal plasma processing; and chemically-based vapor-phase synthesis methods including chemical vapor condensation, flame-based aerosol synthesis, spray pyrolysis, and laser pyrolysis. In addition, we summarize the nanomaterials produced by each method, along with representative applications, and describe the synthesis of the most important materials produced by each method in greater detail.

Effects of graphene oxide on tomato growth in different stages

The nano-carbon graphene has unique structural and physicochemical properties, which are conducive to various biomedical applications. We assessed the effect of graphene oxide (GO) on tomato plants at the seedling and mature stages in terms of morphological and biochemical indices. GO treatment significantly improved the shoot/stem growth of tomato in a dose-dependent manner by increasing the cortical cells number, cross-sectional area, diameter and vascular-column area. In addition, GO also promoted the morphological development of the root system and increased biomass accumulation. The surface area of root tips and hairs of tomato plants treated with 50 mg/L and 100 mg/L GO were significantly greater compared to the untreated control. At the molecular level, GO induced the expression of root development-related genes (SlExt1 and LeCTR1) and inhibited the auxin-responsive gene (SlIAA3). However, 50 mg/L and 100 mg/L GO significantly increased the root auxin content, which in turn increased the number of fruits and hastened fruit ripening compared to the control plants. Taken together, GO can improve the tomato growth when used at the appropriate concentration, and is a promising nano-carbon material for agricultural use.

Efficient Removal of Uranium(VI) from Aqueous Solutions by Triethylenetetramine-Functionalized Single-Walled Carbon Nanohorns

In the present study, SWCNH-COOH and SWCNH-TETA were fabricated using single-walled carbon nanohorns (SWCNHs) via carboxylation and grafting with triethylenetetramine (TETA) for uranium (VI) ion [U(VI)] removal. The morpho-structural characterization of as-prepared adsorbing materials was performed by transmission electron microscopy, X-ray diffractometry, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Several parameters including the pH value of the aqueous solutions, contact time, temperature, and U(VI) concentration were used to evaluate the sorption efficiency of SWCNH-COOH and SWCNH-TETA. The Langmuir isotherm model could well represent the as-obtained adsorption isotherms, and the kinetics was successfully modeled by pseudo-second-order kinetics in the adsorption process. The maximum adsorption capacity of SWCNH-TETA was calculated as 333.13 mg/g considering the Langmuir isotherm model. Thermodynamic studies showed that adsorption proved to be a spontaneous endothermic process. Moreover, SWCNH-TETA exhibited excellent recycling performance and selective adsorption of uranium. Furthermore, the possible mechanism was investigated by XPS and density functional theory calculations, indicating that the excellent adsorption was attributed to the cooperation capability between uranium ions and nitrogen atoms in SWCNH-TETA. This efficient approach can provide a strategy for developing high-performance adsorbents for U(VI) removal from wastewater.

Polyacrylic acid assisted synthesis of free-standing MnO2/CNTs cathode for Zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted significant attention due to the distinguishing characteristics of zinc metal, including its low price, abundance in earth, safety and high theoretical specific capacity of 820 mAh g^-1. Manganese dioxide (MnO₂) is a promising cathode for ZIBs due to high theoretical specific capacity, high discharge voltage plateau, cost-effectiveness and nontoxicity. However, the low electronic conductivity and volumetric changes during electrochemical cycling hinder its practical utilization. Herein, we demonstrate a polyacrylic acid (PAA)-assisted assembling strategy to fabricate freestanding and flexible MnO₂/carbon nanotube/PAA (MnO₂/CNT/PAA) cathodes for ZIBs. PAA plays an important role in providing excellent mechanical properties to the free-standing electrode. Moreover, the presence of CNT forms an electron conductive network, and the porous structure of MnO₂/CNT/PAA electrode accommodates the volumetric variations of MnO₂ during charge/discharge cycling. The as-fabricated quasi-solid-state Zn-MnO₂/CNT/PAA battery delivers a high charge storage capacity of 302 mAh g^-1 at 0.3 A g^-1 and retains 82% of the initial capacity after 1000 charge/discharge cycles at 1.5 A g^-1. The calculated volumetric energy density of Zn-MnO₂/CNT/PAA battery is 8.5 mW h cm^-3 (with a thickness of 0.08 cm), which is significantly higher than the reported alkali-ion batteries (1.3 mW h cm^-3) and comparable to supercapacitors (6.8 mW h cm^-3) and Ni-Zn batteries (7.76 mW h cm^-3). The current work demonstrates that free-standing MnO₂/CNT/PAA composite is a promising cathode for ZIBs.

The Development of Catalyst Materials for the Advanced Lithium–Sulfur Battery

The lithium–sulfur battery is considered as one of the most promising next-generation energy storage systems owing to its high theoretical capacity and energy density. However, the shuttle effect in lithium–sulfur battery leads to the problems of low sulfur utilization, poor cyclability, and rate capability, which has attracted the attention of a large number of researchers in the recent years. Among them, the catalysts with efficient catalytic function for lithium polysulfides (LPSs) can effectively inhibit the shuttle effect. This review outlines the progress of catalyst materials for lithium–sulfur battery in recent years. Based on the structure and properties of the reported catalysts, the development of the reported catalyst materials for LPSs was divided into three generations. We can find that the design of highly efficient catalytic materials needs to consider not only strong chemical adsorption on polysulfides, but also good conductivity, catalysis, and mass transfer. Finally, the perspectives and outlook of reasonable design of catalyst materials for high performance lithium–sulfur battery are put forward. Catalytic materials with high conductivity and both lipophilic and thiophile sites will become the next-generation catalytic materials, such as heterosingle atom catalysis and heterometal carbide. The development of these catalytic materials will help catalyze LPSs more efficiently and improve the reaction kinetics, thus providing guarantee for lithium sulfur batteries with high load or rapid charge and discharge, which will promote the practical application of lithium–sulfur battery.

Polymer Electrolyte Membrane with High Ionic Conductivity and Enhanced Interfacial Stability for Lithium Metal Battery

Solid polymer electrolyte is one of the best choices to improve the safety of lithium metal batteries (LMBs). However, its widespread application is hindered because of the low ionic conductivity at room temperature and large interfacial resistance. Here, a cross-linked polymer is synthesized with an unsaturated polyester and used as a polymer electrolyte membrane (PEM). The PEM has a high ionic conductivity (1.99 × 10^-3 S cm^-1 at 30 °C) and a low glass transition temperature (-54.2 °C), contributing to decreasing interfacial resistance, promoting more uniform Li deposition, and suppressing Li dendrite penetration. The PEM also has a wide electrochemical stable window (∼4.6 V) and superior thermal stability (>150 °C), showing high potential in LMBs. The LiFePO₄-Li coin cells and pouch pack batteries with PEM present very stable cycle performance and high safety, indicating that the PEM can be a promising candidate for future solid-state LMBs.

Three-Dimensional Porous Nitrogen-Doped Carbon Nanosheet with Embedded NixCo3-xS4 Nanocrystals for Advanced Lithium-Sulfur Batteries

The shuttle effect of lithium polysulfides (Li₂S_n) in electrolyte and the low conductivity of sulfur are the two key hindrances of lithium sulfur (Li-S) batteries. In order to address the two issues, we propose a three-dimensional porous nitrogen-doped carbon nanosheet with embedded Ni_xCo_3-xS₄ nanocrystals derived from metal-organic frameworks for the durable-cathode host material in Li-S batteries. Experiments and density functional theory simulations show that the large porosity, robust N-doped carbon framework, and evenly embedded Ni_xCo_3-xS₄ nanocrystals with high polarity act as strong "traps" for the immobilization of Li₂S_n, which leads to an effective suppressing of the shuttle effect and promotes efficient utilization of sulfur. The Ni_xCo_3-xS₄/N-doped carbon hybrid material exhibits a high reversible capacity of 1122 mAh g^-1 at a current density of 0.5 C after 100 cycles. Even at high areal sulfur loadings of 10 and 12 mg cm^-2, the hybrid cathode materials can maintain good areal capacities of 7.2 and 7.6 mAh cm^-2 after 100 cycles. The present study sheds light on the principles of the anchoring behaviors of Li₂S_n species on bimetallic sulfide hybrid materials and reveals an attractive route to design the highly desirable cathode materials for Li-S batteries.

Manipulating the Structural Transformation of Fullerene Microtubes to Fullerene Microhorns Having Microscopic Recognition Properties

We report the production of fullerene microtubes (FMTs), having solid cores bisecting their tubular cavities, from solutions of mixtures of fullerene C₆₀ and C₇₀ and have demonstrated the structural transformation of FMTs to fullerene microhorns (FMHs) upon their exposure to alcohol/mesitylene mixtures at 25 °C. The conically shaped microhorns have hollow interiors and exhibit preferential recognition of silica particles over fullerene C₇₀, polystyrene (PS) latex, PS hydroxylate, or PS carboxylate particles of similar dimensions due to strong electrostatic interactions between negatively charged FMHs and positively charged silica particles.

Self-assembled N-doped carbon with a tube-in-tube nanostructure for lithium-sulfur batteries

Lithium-sulfur batteries hold broad prospects as the low-cost and high-energy storage system. However, the practical application is limited by the intrinsic insulating nature of sulfur and severe shuttle effect of soluble polysulfide intermediates. Herein, we demonstrate a convenient self-assembly strategy for encapsulating carbon nanotubes in nitrogen-doped hollow carbon shells, to construct a nitrogen-doped tube-in-tube carbon nanostructure (NTTC) as a host material of sulfur. In this peculiar structure, the highly conductive carbon nanotube cores facilitate the electron transfer while the hollow porous structure is capable of accommodating high sulfur content of 70 wt% in the composites. Moreover, the nitrogen doping helps to alleviate the shuttle effect owing to enhanced chemisorption towards polysulfides. Benefiting from these merits, the NTTC/S composite with the high areal mass loading of ~2.5 mg cm^-2 presents a high reversible capacity (1346.9 mAh g^-1 at 0.05 C) and excellent rate capability (533.5 mAh g^-1 at 3C). More impressively, NTTC/S electrode exhibits good cycling stability at a high rate of 2 C corresponding to slight capacity decay of 0.055% per cycle over 500 discharge/charge cycles.

Carbon Nitride Phosphorus as an Effective Lithium Polysulfide Adsorbent for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are attracting substantial attention because of their high-energy densities and potential applications in portable electronics. However, an intrinsic property of Li-S systems, that is, the solubility of lithium polysulfides (LiPSs), hinders the commercialization of Li-S batteries. Herein, a new material, that is, carbon nitride phosphorus (CNP), is designed and synthesized as a superior LiPS adsorbent to overcome the issues of Li-S batteries. Both the experimental results and the density functional theory (DFT) calculations confirm that CNP possesses the highest binding energy with LiPS at a P concentration of ∼22% (CNP22). The DFT calculations explain the simultaneous existence of Li-N bonding and P-S coordination in the sulfur cathode when CNP22 interacts with LiPS. By introducing CNP22 into the Li-S systems, a sufficient charging capacity at a low cutoff voltage, that is, 2.45 V, is effectively implemented, to minimize the side reactions, and therefore, to prolong the cycling life of Li-S systems. After 700 cycles, a Li-S cell with CNP22 gives a high discharge capacity of 850 mA h g^-1 and a cycling stability with a decay rate of 0.041% cycle^-1. The incorporation of CNP22 can achieve high performance in Li-S batteries without concerns regarding the LiPS shuttling phenomenon.

Self-supporting Ti3C2Tx foam/S cathodes with high sulfur loading for high-energy-density lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries, with high theoretical energy density, cost-effective preparation and environmental benignancy, have been deemed as new encouraging energy storage solutions. However, their development and applications are limited by their low practical energy density and rapid capacity fading. Herein, self-supporting Ti₃C₂T_x foam, as a novel sulfur host, was synthesized via direct stacking of Ti₃C₂T_x flakes into film followed by hydrazine-induced foaming. This Ti₃C₂T_x foam exhibits a well-defined porous structure, increased surface area, enlarged pore volume, and enhanced exposure of Lewis acidic sites, thus effectively strengthening the capability of physical and chemical co-adsorption for polysulfides under a high sulfur loading of 5.1 mg cm^-2. Combined with a favorable electrolyte wettability and extraordinary structural stability, the resultant self-supporting Ti₃C₂T_x foam/S cathodes demonstrated excellent performances: a high initial discharge capacity (1226.4 mA h g^-1 at 0.2C), exceptional rate performance (711.0 mA h g^-1 at 5C), and extraordinary long-term cycling stability (689.7 mA h g^-1 at 1C after 1000 cycles with ultralow capacity decay of ≈0.025% per cycle). Remarkably, the self-supporting structure confers a significantly elevated gravimetric energy density (1297.8 W h kg^-1). Therefore, this elaborately designed Ti₃C₂T_x foam/S cathode opens new delightful opportunities for constructing practical high-energy-density Li-S batteries.