Graphitic Nanocapsules Research Articles

Controlling carbon nanostructure synthesis in thermal plasma jet: Correlation of process parameters, plasma characteristics, and product morphology

Thermal plasma has emerged as an effective approach for producing carbon nanostructures without the need for specific catalysts nor substrates. While efforts have focused on the effect of process parameters such as reaction pressure, input power or carbon source, the intricate role and relationship with plasma characteristics like density and temperature are often overlooked due to the complexity of the environment. This study addresses this gap by establishing a correlation between process parameters, plasma characteristics, and product morphology, essential for controlling the growth of carbon nanostructures. We explored the impact of carbon precursor type (CH4 and C2H2), hydrogen, pressure, and flow rate on nanostructure formation. Using in situ optical emission spectroscopy (OES), we mapped the distribution of both temperature and dicarbon molecule (C2) density within the plasma jet. We demonstrate that the growth of low-density nanostructures, such as carbon nanohorns (CNHs), is favoured at dilute C2 local densities and high temperatures, while denser nanostructures, such as onion-like polyhedral graphitic nanocapsules (GNCs), are favoured at higher C2 densities and lower temperatures. The carbon density can be controlled by the flow rate and the pressure, which in turn significantly influence the nanostructure morphology, evolving from graphene nanoflakes (GNFs) to GNCs as either parameter increases. Increasing the H/C ratio from 1 to 8 resulted in a morphological transition from CNHs to GNFs. During the synthesis, the plasma jet temperature surpassed 3000 K, with crystalline growth occurring 50–100 mm below the nozzle.

Magnetic Graphitic Nanocapsules: Fabrication, Classification, and Theranostic Applications.

Combining therapeutic and diagnostic capabilities in one dose using nanoparticles promises to push the biomedical field toward the next generation of personalized medicine. Magnetic graphitic nanocapsules (MGNs) represent a cutting-edge tool in the biomedical field because of their incomparable magnetic properties and versatile functionalization. This paper reviews a series of MGNs and provides instructive guidelines for the design of MGNs with enhanced properties. Then, we highlight recent progress in MGNs for biomedical application studies such as multimode imaging, magnetic navigation, imaging-guided therapy, and synergistic therapy. Finally, we discuss some future directions of MGNs that can produce pronounced effects in the biomedical field.

Synthesis and Growth of Onion-Like Polyhedral Graphitic Nanocapsules by Thermal Plasma

Synthesis and Growth of Onion-Like Polyhedral Graphitic Nanocapsules by Thermal Plasma

Impact of the growth environment in inductively coupled plasma on the synthesis and morphologies of carbon nanohorns

The fabrication of carbon nanohorns (CNHs) from a methane precursor with argon in an inductively coupled plasma was recently demonstrated with a high production rate of ∼20 g/h by Casteignau et al. [Plasma Chem. Plasma Process. 42, 465 (2022)]. The presence of a promotor gas such as hydrogen was found to be important for the growth of CNHs, but the mechanisms at play remain unclear. Here, we study the impact of different promotor gases by replacing hydrogen with nitrogen and helium at different promotor:precursor (Pm:Pr) ratios, X:CH4 = 0.3–0.7 (X = H2 or N2, Ar, and He), and global flow rates FX+FCH4=1.7 and 3.4 slpm. The nature of the promotor gas is shown to directly influence the morphology and the relative occurrence of CNHs, graphitic nanocapsules (GNCs), and graphene nanoflakes. Using quantitative transmission electron microscopy, we show that CNHs are favored by an X:CH4 = 0.5, preferably with X = He or N2. With a lower total flow rate (1.7 slpm) of N2, even larger production rates and higher selectivity toward CNHs are achieved. Optical emission spectroscopy was used to probe the plasma and to demonstrate that the nature promotor gas strongly modulates the C2 density and temperature profile of the plasma torch. It is shown that CNHs nucleation is favored by high C2 density at temperatures exceeding 3500 K localized at the exit-end of the nozzle, creating a reaction zone with extended isotherms. H2 favors CH4 dissociation and creates a high C2 density but cools the nucleation zone, which leads to structures with a strong graphitic character such as GNCs.

Metal Graphitic Nanocapsules for Theranostics in Harsh Conditions.

Metal nanoparticles (NPs) with superior physicochemical properties and biocompatibility have shown great potential in theranostics. However, metal NPs show poor stability in some harsh conditions such as strong acid, oxidation, corrosion and high-temperature conditions, which limits their extensive bioapplications. To address such issue, a variety of superstable metal graphitic nanocapsules with the metal cores confined in the nanospace of few-layer graphitic shell have been developed for biodetection and therapy in harsh conditions. In this mini-review, we summarize the recent advances in metal graphitic nanocapsules for bioapplications in harsh conditions. Firstly, their theranostic performance in non-intrinsic physiological harsh environment, including oxidation, corrosion and high-temperature conditions, is systematically discussed. Then, we highlight their theranostic performance in the harsh stomach condition that is strong acidic and pepsin-rich. It is expected that this review will offer inspiration to facilitate the exploitation of novel theranostic agents that are stable in harsh conditions.

Advances in metal graphitic nanocapsules for biomedicine.

Metal graphitic nanocapsules have the advantages of both graphitic and metal nanomaterials, showing great promise in biomedicine. On one hand, the chemically inert graphitic shells are able to protect the metal core from external environments, quench the fluorescence signal from the biological system, offer robust platform for targeted molecules or drugs loading, and act as stable Raman labels or internal standard molecule. On the other hand, the metal cores with different compositions, sizes, and morphologies show unique physicochemical properties, and further broaden their biomedical functions. In this review, we firstly introduce the preparation, classification, and properties of metal graphitic nanocapsules, then summarize the recent progress of their applications in biodetection, bioimaging, and therapy. Challenges and their development prospects in biomedicine are eventually discussed in detail. We expect the versatile metal graphitic nanocapsules will advance the development of future clinical biomedicine.

Stabilizing Enzymes in Plasmonic Silk Film for Synergistic Therapy of In Situ SERS Identified Bacteria.

Increasing antibiotic resistance becomes a serious threat to public health. Photothermal therapy (PTT) and antibacterial enzyme‐based therapy are promising nonresistant strategies for efficiently killing drug‐resistant bacteria. However, the poor thermostability of enzymes in PTT hinders their synergistic therapy. Herein, antibacterial glucose oxidase (GOx) is embedded in a Ag graphitic nanocapsule (Ag@G) arrayed silk film to fabricate a GOx‐synergistic PTT system (named silk‐GOx‐Ag@G, SGA). The SGA system can stabilize GOx by a vitrification process through the restriction of hydrogen bond and rigid β‐sheet, and keep the antibacterial activity in the hyperthermal PTT environment. Moreover, the arrayed Ag@G possesses excellent chemical stability due to the protection of graphitic shell, providing stable plasmonic effect for integrating PTT and surface enhanced Raman scattering (SERS) analysis even in the GOx‐produced H2O2 environment. With in situ SERS identification of bacterial intrinsic signals in the mouse wound model, such SGA realizes superior synergistic antibacterial effect on the infected Escherichia coli, Staphylococcus aureus, and methicillin‐resistant Staphylococcus aureus in vivo, while without causing significant biotoxicity. This system provides a therapeutic method with low resistance and in situ diagnosis capability for efficiently eliminating bacteria.

Recent Advances in Multifunctional Graphitic Nanocapsules for Raman Detection, Imaging, and Therapy

AbstractBenefiting from their unique physicochemical properties, graphitic nanocapsules with a core–shell structure have attracted tremendous interest in bioanalysis and biomedicine recently. Using rational design, various types of graphitic nanocapsules with controllable properties are prepared to meet the demands of different biomedical applications. Graphitic nanocapsules exhibit excellent stability and superior capacity for loading nucleic acids, proteins, small molecules, and drugs due to the large specific surface area of their graphitic shells. Moreover, using the unique Raman bands of graphitic shells with large scattering cross‐sections, graphitic nanocapsules are applied in Raman‐based detection and imaging. Various types of nanocapsules with superior optical and magnetic properties are available for multimodal imaging applications. By making full use of the intrinsic near‐infrared optical absorbance of the graphitic shell and specific metal core, graphitic nanocapsule‐based light‐mediated therapies are realized, showing superior performance in the killing of cancer cells and pathogenic bacteria, as well as anti‐tumor therapeutic efficacy in animal experiments. This review summarizes the synthesis, properties, and functionalization of graphitic nanocapsules and discusses the recent advances in Raman detection and imaging, multimodal imaging, and light‐mediated therapy, including concerns related to toxicity. Future prospects of graphitic nanocapsules in biomedical applications are also highlighted.

Versatile metal graphitic nanocapsules for SERS bioanalysis

The novel graphitic nanomaterial of metal graphitic nanocapsules (MGNs) with superior stability, unique optical properties and biocompatibility possess great potential in biomedical and bioanalytical applications. The graphitic shell can quench the background fluorescence interference from external environments via a fluorescence resonance energy transfer (FRET) process and even avoid unnecessary reactions catalyzed by inner metal core. The graphitic shell with several characteristic Raman bands itself can act as Raman signal probe or internal standard (IS), especially the 2D-band within the cellular Raman-silent region helps to reduce the interference signals from external conditions. The present context attempts to give a comprehensive overview about the preparation and unique properties of MGNs as well as their applications in SERS biodetection and bioimaging.

Stable gold graphitic nanocapsule doped hydrogels for efficient photothermal antibacterial applications.

Herein, we have fabricated gold nanorod graphitic nanocapsule (AuNR@G) doped poly(vinyl alcohol) (PVA)/chitosan (CS) hydrogels, which possessed highly efficient and stable photothermal antibacterial properties for both Gram-negative E. coli and Gram-positive S. aureus under the irradiation of a near-infrared laser.

Simultaneous Application of Photothermal Therapy and an Anti‐inflammatory Prodrug using Pyrene–Aspirin‐Loaded Gold Nanorod Graphitic Nanocapsules

AbstractPhotothermal therapy (PTT) has been extensively developed as an effective approach against cancer. However, PTT can trigger inflammatory responses, in turn simulating tumor regeneration and hindering subsequent therapy. A therapeutic strategy was developed to deliver enhanced PTT and simultaneously inhibit PTT‐induced inflammatory response. 1‐Pyrene methanol was utilize to synthesize the anti‐inflammatory prodrug pyrene–aspirin (P‐aspirin) with a cleavable ester bond and also facilitate loading the prodrug on gold nanorod (AuNR)‐encapsulated graphitic nanocapsule (AuNR@G), a photothermal agent, through π–π interactions. Such AuNR@G‐P‐aspirin complexes were used for near‐infrared laser‐triggered photothermal ablation of solid tumor and simultaneous inhibition of PTT‐induced inflammation through the release of aspirin in tumor milieu. This strategy showed excellent effects in vitro and in vivo.

Simultaneous Application of Photothermal Therapy and an Anti-inflammatory Prodrug using Pyrene-Aspirin-Loaded Gold Nanorod Graphitic Nanocapsules.

Photothermal therapy (PTT) has been extensively developed as an effective approach against cancer. However, PTT can trigger inflammatory responses, in turn simulating tumor regeneration and hindering subsequent therapy. A therapeutic strategy was developed to deliver enhanced PTT and simultaneously inhibit PTT-induced inflammatory response. 1-Pyrene methanol was utilize to synthesize the anti-inflammatory prodrug pyrene-aspirin (P-aspirin) with a cleavable ester bond and also facilitate loading the prodrug on gold nanorod (AuNR)-encapsulated graphitic nanocapsule (AuNR@G), a photothermal agent, through π-π interactions. Such AuNR@G-P-aspirin complexes were used for near-infrared laser-triggered photothermal ablation of solid tumor and simultaneous inhibition of PTT-induced inflammation through the release of aspirin in tumor milieu. This strategy showed excellent effects in vitro and in vivo.

Synthesis of nitrogen-doped graphitic carbon nanocapsules from a poly(ionic liquid) for CO2 capture

Synthesis of nitrogen-doped graphitic carbon nanocapsules from a poly(ionic liquid) for CO2 capture

In situ targeted MRI detection of Helicobacter pylori with stable magnetic graphitic nanocapsules

Helicobacter pylori infection is implicated in the aetiology of many diseases. Despite numerous studies, a painless, fast and direct method for the in situ detection of H. pylori remains a challenge, mainly due to the strong acidic/enzymatic environment of the gastric mucosa. Herein, we report the use of stable magnetic graphitic nanocapsules (MGNs), for in situ targeted magnetic resonance imaging (MRI) detection of H. pylori. Several layers of graphene as the shell effectively protect the magnetic core from corrosion while retaining the superior contrast effect for MRI in the gastric environment. Boronic-polyethylene glycol molecules were synthesized and modified on the MGN surface for targeted MRI detection. In a mouse model of H. pylori-induced infection, H. pylori was specifically detected through both T2-weighted MR imaging and Raman gastric mucosa imaging using functionalized MGNs. These results indicated that enhancement of MRI using MGNs may be a promising diagnostic and bioimaging platform for very harsh conditions.

Graphitic nanocapsules: design, synthesis and bioanalytical applications.

Graphitic nanocapsules are emerging nanomaterials which are gaining popularity along with the development of carbon nanomaterials. Their unique physical and chemical properties, as well as good biocompatibility, make them desirable agents for biomedical and bioanalytical applications. Through rational design, integrating graphitic nanocapsules with other materials provides them with additional properties which make them versatile nanoplatforms for bioanalysis. In this feature article, we present the use and performance of graphitic nanocapsules in a variety of bioanalytical applications. Based on their chemical properties, the specific merits and limitations of magnetic, hollow, and noble metal encapsulated graphitic nanocapsules are discussed. Detection, multi-modal imaging, and therapeutic applications are included. Future directions and potential solutions for further biomedical applications are also suggested.

Modulating the Morphology of Gold Graphitic Nanocapsules for Plasmon Resonance-Enhanced Multimodal Imaging.

With their unique optical properties and distinct Raman signatures, graphitic nanomaterials can serve as substrates for surface-enhanced Raman spectroscopy (SERS) or provide signal amplification for bioanalysis and detection. However, a relatively weak Raman signal has limited further biomedical applications. This has been addressed by encapsulating gold nanorods (AuNRs) in a thin graphitic shell to form gold graphitic nanocapsules. This step improves plasmon resonance, which enhances Raman intensity, and has the potential for integrating two-photon luminescence (TPL) imaging capability. However, changing the morphology of gold graphitic nanocapsules such that high quality and stability are achieved remains a challenge. To address this task, we herein report a confinement chemical vapor deposition (CVD) method to prepare the construction of AuNR-encapsulated graphitic nanocapsules with these properties. Specifically, through morphological modulation, we (1) achieved higher plasmon resonance with near-IR incident light, thus achieving greater Raman intensity, and (2) successfully integrated two-photon luminescence dual-modal (Raman/TPL) bioimaging capabilities. Cancer-cell-specific aptamers were further modified on the AuNR@G graphitic surface through simple, but strong, π-π interactions to achieve imaging selectivity through differential cancer cell recognition.

Fabrication of GO/magnetic graphitic nanocapsule/TiO2 assemblies as efficient and recyclable photocatalysts

In this work, we fabricate an efficient and stable photocatalyst system which has superior recyclability even under concentrated acidic conditions. The photocatalyst is prepared by assembling magnetic graphitic nanocapsules, titania (TiO2) and graphene oxide (GO) into a complex system through π-π stacking and electrostatic interactions. Such catalytic complex demonstrates very high stability. Even after dispersal into a concentrated acidic solution for one month, this photocatalyst could still be recycled and maintain its catalytic activity. With methyl orange as the model molecule, the photocatalyst was demonstrated to rapidly decompose the molecules with very high photocatalytic activity under both concentrated acidic and neutral condition. Moreover, this photocatalyst retains approximately 100 wt% of its original photocatalytic activity even after multiple experimental runs, of magnetic recycling. Finally, using different samples from natural water sources and different dyes, this GO/magnetic graphitic nanocapsule/TiO2 system also demonstrates its high efficiency and recyclability for practical application.

Nano-gold corking and enzymatic uncorking of carbon nanotube cups.

Because of their unique stacked, cup-shaped, hollow compartments, nitrogen-doped carbon nanotube cups (NCNCs) have promising potential as nanoscale containers. Individual NCNCs are isolated from their stacked structure through acid oxidation and subsequent probe-tip sonication. The NCNCs are then effectively corked with gold nanoparticles (GNPs) by sodium citrate reduction with chloroauric acid, forming graphitic nanocapsules with significant surface-enhanced Raman signature. Mechanistically, the growth of the GNP corks starts from the nucleation and welding of gold seeds on the open rims of NCNCs enriched with nitrogen functionalities, as confirmed by density functional theory calculations. A potent oxidizing enzyme of neutrophils, myeloperoxidase (MPO), can effectively open the corked NCNCs through GNP detachment, with subsequent complete enzymatic degradation of the graphitic shells. This controlled opening and degradation was further carried out in vitro with human neutrophils. Furthermore, the GNP-corked NCNCs were demonstrated to function as novel drug delivery carriers, capable of effective (i) delivery of paclitaxel to tumor-associated myeloid-derived suppressor cells (MDSC), (ii) MPO-regulated release, and (iii) blockade of MDSC immunosuppressive potential.

Fluorescent nanosensor for probing histone acetyltransferase activity based on acetylation protection and magnetic graphitic nanocapsules.

Protein acetylation catalyzed by histone acetyltransferases (HATs) is significant in biochemistry and pharmacology because of its crucial role in epigenetic gene regulations. Herein, an antibody-free fluorescent nanosensor is developed for the facile detection of HAT activity based on acetylation protection against exopeptidase cleavage and super-quenching ability of nanomaterials. It is shown for the first time that HAT-catalyzed acetylation could protect the peptide against exopeptidase digestion. FITC-tagged acetylated peptide causes the formation of a nano-quenchers/peptide nano-complex resulting in fluorescence quenching, while the unacetylated peptide is fully degraded by exopeptidase to release the fluorophore and restore fluorescence. Four kinds of nano-quenchers, including core-shell magnetic graphitic nanocapsules (MGN), graphene oxide (GO), single-walled carbon nanotubes (SWCNTs), and gold nanoparticles (AuNPs), are comprehensively compared. MGN shows the best selectivity to recognize the acetylated peptide and the lowest detection limit because of its excellent quenching efficiency and magnetic enrichment property. With this MGN-based nanosensor, HAT p300 is detected down to 0.1 nM with wide linear range from 0.5 to 100 nM. This sensor is feasible to assess HAT inhibition and detect p300 activity in cell lysate. The proposed nanosensor is simple, sensitive, and cost-effective for HAT assay, presenting a promising toolkit for epigenetic research and HAT-targeted drug discovery.

Hollow graphitic nanocapsules as efficient electrode materials for sensitive Hydrogen peroxide detection

Carbon nanomaterials are typically used in electrochemical biosensing applications for their unique properties. We report a hollow graphitic nanocapsule (HGN) utilized as an efficient electrode material for sensitive hydrogen peroxide detection. Methylene blue (MB) molecules could be efficiently adsorbed on the HGN surfaces, and this adsorption capability remained very stable under different pH regimes. HGNs were used as three-dimensional matrices for coimmobilization of MB electron mediators and horseradish peroxidase (HRP) to build an HGN–HRP–MB reagentless amperometric sensing platform to detect hydrogen peroxide. This simple HGN–HRP–MB complex demonstrated very sensitive and selective hydrogen peroxide detection capability, as well as high reproducibility and stability. The HGNs could also be utilized as matrices for immobilization of other enzymes, proteins or small molecules and for different biomedical applications.