2D Nb2C Research Articles

2D Catalytic Niobium Carbide MXenzyme for Ameliorating Noise‐Induced Hearing Loss

AbstractNoise‐induced hearing loss (NIHL), a prevalent sensory disability affecting a majority of the global population, is dominantly induced by mitochondrial dysfunction and oxidative stress, but no effective therapeutic strategy is available. Herein, the potential of a 2D catalytic niobium carbide (Nb2C) MXenzyme is investigated as a nanomedicine for treating NIHL by scavenging reactive oxygen species (ROS). The findings reveal that 2D Nb2C MXenzyme effectively eliminates free radicals, resulting in a substantial reduction of ROS in House Ear Institute‐Organ of Corti 1 (HEI‐OC1) cells treated with hydrogen peroxide (H2O2). Additionally, the 2D Nb2C MXenzyme demonstrates significant protection on hair cells by preventing cytotoxicity and apoptosis induced by H2O2. In vivo experiments further support the efficacy of the 2D Nb2C MXenzyme in restoring hearing impairment caused by extensive noise exposure. Specifically, it restores the raised amplitude of Wave I in auditory brainstem response (ABR) records and promotes the recovery of damaged ribbon synapses in inner hair cells. Notably, the therapeutic effect of the 2D Nb2C MXenzyme is attributed to its ability to suppress cochlear oxidative stress evidenced by immunohistochemical analysis. This research provides a new approach for treating hearing loss‐related ear diseases by utilizing catalytic biomaterials and nanomedicine with enzyme‐mimicking properties.

Intralayered ostwald ripening impelled nanoarchitectonics of MXene nanorods on MXene nanosheets with boron carbon nitride for robust supercapacitor application

Utilizing 2D layered materials as one of the composite's members in the synthesis of active material for supercapacitors is acquiring imperative attention on account of the extraordinary outcomes due to their wholesome hale structural and electrochemical affinity. Here, by rousing from intralayer ostwald ripening impelled growth of in situ spawned 1D Nb2C rods on 2D Nb2C sheets, in short form (h)Nb2C are generated via hydrothermal low temperature treatment without, which overwhelms the electrochemical performance of pure 2D MXene sheets. Later the residue less direct pyrolysis method was adopted for the in-situ development of 2D BCN nanosheets over MXene, 1D-2D/2D MXene/BCN hybrid nanoarchitectonics. The process method enabled the interrelated structural growth of BCN particles on MXene and helps in empowering the pseudocapacitive activity of the enlarged portion of Nb sites by the removal of the terminal groups. Thus, the fabricated 1D-2D/2D Nb2C/BCN (NBCN) electrode showed a specific capacitance of 765 F g− 1 at 2 A g− 1 current density with a high specific energy of 35 Wh kg−1. Eventually, the solid-state supercapacitor device further withstands 100,000 cycles displaying high efficiency and ∼100% retention. Henceforth, the 1D-2D/2D heterostructures with magnificent electrochemical properties can act as a feasible energy storage system.

Redox chemistry-enabled stepwise surface dual nanoparticle engineering of 2D MXenes for tumor-sensitive T1 and T2 MRI-guided photonic breast-cancer hyperthermia in the NIR-II biowindow.

With the fast advent of two-dimensional (2D) MXenes, several therapeutic paradigms based on 2D MXenes flourish, but a generic strategy for MXene functionalization to achieve theranostic functionalities and desirable performance is still lacking. In this work, we report a facile and efficient stepwise surface-functionalization strategy to achieve distinct tumor microenvironment (TME)-responsive T1 and T2 magnetic resonance (MR) imaging-guided photothermal breast-cancer hyperthermia in the second near-infrared (NIR-II) biowindow. This approach is based on the stepwise growth of superparamagnetic Fe3O4 and paramagnetic MnOx nanocomponents onto the large surface of ultrathin 2D niobium carbide (Nb2C) MXene nanosheets (Fe3O4/MnOx-Nb2C) by making full use of the redox status/chemistry of the 2D MXene surface. Such a surface-nanoparticle engineering strategy endows Fe3O4/MnOx-Nb2C composite nanosheets with a series of properties that include high photothermal-conversion efficiency in the NIR-II biowindow (1064 nm, η 30.9%) for effective photothermal tumor eradication without further reoccurrence. It also allows TME-responsive T1- and T2-weighted MR imaging and high biocompatibility for guaranteeing further potential clinical transformation. This work not only makes the efficient diagnostic T1- and T2-weighted MR imaging-guided photonic hyperthermia of breast cancer possible, but also broadens the biomedical applications of MXene-based nanoplatforms by developing novel surface-engineering strategies to construct 2D Nb2C MXene-based composite multifunctional nanoplatforms.

Near-Infrared Spatial Self-Phase Modulation in Ultrathin Niobium Carbide Nanosheets

Spatial self-phase modulation (SSPM) as a purely coherent non-linear optical effect (also known as Kerr effect) can support strong broadband phase modulation, which is essential for all-optical applications. Besides this, the increasing use of two-dimensional (2D) materials opens up new prospects in this field of research. In this work, we report a broadband SSPM response from 2D transition metal carbonitrides (MXenes) and Nb2C, arising in the near-infrared (1,550 nm) range. Based on the SSPM measurements of few-layer Nb2C nanosheets, the third-order non-linear optical parameters of Nb2C, including the non-linear refractive index n2 and susceptibility χ(3), were determined at 400, 800, 1,300, and 1,550 nm. Moreover, the physics mechanism of the dynamic formation process of SSPM diffraction rings was exploited. The formation time of SSPM diffraction rings can be divided into two typical parts which correspond to the polarization and reorientation of 2D Nb2C nanosheets. As a proof of concept, we demonstrate the nonreciprocal light propagation at wavelengths of 1,300 and 1,550 nm by constructing an Nb2C/water hybrid structure. Our results reveal strong optical phase modulation of Nb2C in the infrared region, thus showing the great potential of MXene materials for use in passive photonic devices.

Un-doped and Er-adsorbed layered Nb2C MXene for efficient hydrazine sensing application

In this work, 2D Nb2C MXene, synthesized from the wet-chemical etching route, is used as direct electrode material for electrochemical hydrazine sensing. Also, the Erbium (Er)adsorbed Nb2C MXene was prepared using the hydrothermal process in a weight-percentage ratio of 2.5%, 5%, 7.5% and 10%. The X-ray diffraction of Nb2C and Er-doped Nb2C samples confirmed the existence of 2D MXene structure with c-lattice parameter increase from 13.83 Å to 22.7 Å and successful adsorption of Er into MXene, respectively. The scanning electron microscopy (SEM) shows the layered structure morphology of all the samples with clear sheet separation. The sample with the highest surface area, determined by Brunauer–Emmett–Teller (BET) technique, was used for hydrazine sensing using cyclic voltammetry and linear sweep voltammetry techniques. The sensitivity for MXene and Er-doped sample was observed to be 169µA m−1 M−1 cm−2 and 276µA m−1 M−1 cm−2, respectively which shows that the Er-doped MXene is much more sensitive than the unmodified one. Our results provide hydrazine sensing ability for 2D Nb2C MXene as well as Er-doped Nb2C which will help explore their potential for future sensor applications.

Third‐Order Nonlinear Optical Response of Few‐Layer MXene Nb2C and Applications for Square‐Wave Laser Pulse Generation

AbstractNiobium carbide (Nb2C), a newly developed 2D MXene material, has attracted much attention due to its outstanding electronic and optical properties. In this work, few‐layer 2D Nb2C nanosheets are synthesized by magnetron sputtering deposition method. Z‐scan measurements with pump source operating at 1.0 µm are performed to study the third‐order nonlinear optical response, revealing excellent light modulation capabilities of 2D Nb2C. The effective nonlinear absorption coefficient (βeff ≈ –105 cm GW–1) caused by saturable absorption effect is determined to be two orders of magnitude larger than that induced by reverse saturable absorption processes (two‐photon absorption, etc.). The positive nonlinear refractive index n2 is determined to be ≈10–13 m2 W–1 for the first time. Moreover, by decorating 2D Nb2C onto microfiber, microfiber‐based 2D Nb2C saturable absorber is fabricated and applied for compact square‐wave pulse mode‐locking ytterbium‐fiber laser. The pulse duration of SWP increases from 0.652 to 1.616 ns with the pulse energy increasing linearly up to 0.89 nJ while the peak power remains a constant. The results not only verify the capability of 2D Nb2C as an optical modulator, but also pave a new way for exploring SWP laser sources.

Functionalized 2D Nb2C nanosheets for primary and recurrent cancer photothermal/immune-therapy in the NIR-II biowindow.

Near-infrared-II (NIR-II) cancer photothermal therapy (PTT) has become more and more attractive as the NIR-II light shows a higher tissue penetrating depth, which leads to better anti-cancer effects. Recently, the members of the MXene family have been reported as NIR-II photothermal agents, possessing a high specific surface area and a fascinating light-to-heat conversion rate at the same time. Herein, we reported a combination of NIR-II photothermal therapy and immune therapy based on the MXene family member niobium carbide (Nb2C). First, Nb2C nanosheets (NSs) under 50 nm were prepared. They showed a high photothermal conversion efficiency under a 1064-nm laser, and the NIR-II light showed a deeper tissue penetration depth. Then, a nanoplatform with high R837 stability and a high loading rate was obtained after modification with a polydopamine (PDA) layer on the surface of Nb2C. With the R837 modification, the percentage of mature dendritic cells (DCs) increased and the immune response enhanced, compared with the immune response caused by PTT only. Finally, a red blood cell (RBC) membrane was applied as a coat over the nanoplatform in order to avoid excessive blood clearance. During in vivo experiments, blood circulation of Nb2C@PDA-R837@RBC nanoparticles (NPs) was prolonged, and all primary tumors were eliminated. Secondary tumors were also inhibited effectively due to the strengthened immune response, proving that Nb2C@PDA-R837@RBC NPs could inhibit tumor recurrence. All the results above indicated Nb2C@PDA-R837@RBC NPs as a potential RBC camouflaged nanoplatform for the combination of effective PTT and immune therapy towards tumor treatment.

Niobium Carbide MXenes with Broad-Band Nonlinear Optical Response and Ultrafast Carrier Dynamics.

Exploring the nonlinear photonics of emerging promising two-dimensional (2D) materials like MXenes will boost the development of broad-band optoelectronic and photonic applications. In this paper, the broad-band nonlinear optical response and the excited-carrier dynamics of an emerging MXene, Nb2C, are systematically investigated for the wavelength range of visible to the near-infrared band. The obtained nonlinear optical response shows a wavelength and excitation intensity dependence. The imaginary part of the third-order nonlinear optical susceptibility Imχ(3) and figure of merit were found to be -1.4 × 10-10 esu and 7.5 × 10-12 esu cm, respectively. The interesting nonlinear absorption response inversion properties (e.g., a shift from saturable absorption to two-photon absorption) of Nb2C nanosheets in the near-infrared promise possible important applications in nonlinear photonics, such as an optical switch. We also demonstrate that the wavelength-dependent relaxation times consist of two different relaxation components, that is, time constants in which one is hundreds of femtoseconds and the other is several picoseconds. Our results indicate promising potential in near-infrared nanophotonic applications of 2D Nb2C and offer a promising candidate for 2D-material-based nanophotonic devices and beyond.

Peculiar magnetic behaviour and Meissner effect in two-dimensional layered Nb2C MXene

Currently, superconductivity in two-dimensional (2D) materials is a hot topic of research owing to their enormous potential applications. We have observed peculiar magnetic Meissner effect in 2D Nb2C MXene leading to signatures of superconductivity in the material with an onset transition temperature of 12.5 K. Systematically optimized chemical etching process of bulk Nb2AlC MAX phase led to the formation of 2D Nb2C MXene as confirmed using scanning electron microscope (SEM) and x-ray diffraction (XRD) indicating a significant increase in the c-lattice parameter from 13.83 Å to 22.72 Å. The Meissner effect and its unusual magnetic nature is observed using superconducting quantum interference device (SQUID: Quantum Design). Fittings of experimentally obtained lower and upper critical fields as a function of temperature to the Ginzburg-Landau (GL) theory confirms possibility of presence of type-II superconductivity in our Nb2C samples. This peculiar magnetic behaviour, observed in as-synthesized Nb2C MXene in powder form is intrinsic property of our sample. It is to be noted that we have tried to measure the transport properties of our sample but due to its powdered nature, this was not possible. We insist that this work is a significant advancement in the field of magnetism and superconductivity in 2D MXene which may be explored further to determine superconductivity by measuring the transport properties in future.

Highly Catalytic Niobium Carbide (MXene) Promotes Hematopoietic Recovery after Radiation by Free Radical Scavenging.

Ionizing radiation (IR) has been extensively used in industry and radiotherapy, but IR exposure from nuclear or radiological accidents often causes serious health effects in an exposed individual, and its application in radiotherapy inevitably brings undesirable damage to normal tissues. In this work, we have developed ultrathin two-dimensional (2D) niobium carbide (Nb2C) MXene as a radioprotectant and explored its application in scavenging free radicals against IR. The 2D Nb2C MXene features intriguing antioxidant properties in effectively eliminating hydrogen peroxide (H2O2), hydroxyl radicals (•OH), and superoxide radicals (O2•-). Pretreatment with biocompatible polyvinylpyrrolidone (PVP)-functionalized Nb2C nanosheets (Nb2C-PVP NSs) significantly reduces IR-induced production of reactive oxygen species (ROS), resulting in enhanced cell viability in vitro. A single intravenous injection of Nb2C-PVP significantly enhances the survival rate of 5 and 6.5 Gy irradiated mice to 100% and 81.25%, respectively, and significantly increases bone marrow mononuclear cells after IR. Critically, Nb2C-PVP reverses the damage of the hematopoietic system in irradiated mice. Single administration of Nb2C-PVP significantly increases superoxide dismutase (SOD) activities, decreases malondialdehyde levels, and thereby reduces IR-induced pathological damage in the testis, small intestine, lung, and liver of 5 Gy irradiated mice. Importantly, Nb2C-PVP is almost completely eliminated from the mouse body on day 14 post treatment, and no obvious toxicities are observed during the 30-day post treatment period. Our study pioneers the application of 2D MXenes with intrinsic radioprotective nature in vivo.

Abnormally Strong Electron–Phonon Scattering Induced Unprecedented Reduction in Lattice Thermal Conductivity of Two-Dimensional Nb2C

In most materials the electron-phonon (e-p) scattering is far weaker than phonon-phonon (p-p) scattering, and the e-p scattering is usually proportional to the e-p coupling strength. Here, we report strong e-p scattering but low e-p coupling strength in two-dimensional(2D) Nb2C by first-principles calculations. Moreover, the intensity of e-p scattering is close to that of p-p scattering at 300 K in sharp contrast to normal cases. This abnormal e-p scattering is understood by a specific feature that the energy difference between occupied and empty electron states near the Fermi level is in the order of the characteristic phonon energy. By calculating the phonon transport property of 2D Nb2C, we show that this strong e-p scattering can result in great reduction in the lattice thermal conductivity.Our work also highlights a new way for searching novel 2D materials with low lattice thermal conductivity.

Therapeutic mesopore construction on 2D Nb2C MXenes for targeted and enhanced chemo-photothermal cancer therapy in NIR-II biowindow.

Two-dimensional (2D) MXenes have emerged as a promising planar theranostic nanoplatform for versatile biomedical applications; but their in vivo behavior and performance has been severely influenced and hindered by a lack of necessary surface chemistry for adequate surface engineering. To solve this critical issue, this work employs versatile sol-gel chemistry for the construction of a unique “therapeutic mesopore” layer onto the surface of 2D niobium carbide (Nb2C) MXene.Methods: The in situ self-assembled mesopore-making agent (cetanecyltrimethylammonium chloride, in this case) was kept within the mesopores for efficient chemotherapy. The abundant surface saline chemistry of mesoporous silica-coated Nb2C MXene was further adopted for stepwise surface engineering including PEGylation and conjugation with cyclic arginine-glycine-aspartic pentapeptide c(RGDyC) for targeted tumor accumulation.Results: 2D Nb2C MXenes were chosen based on their photothermal conversion capability (28.6%) in the near infrared (NIR)-II biowindow (1064 nm) for enhanced photothermal hyperthermia. Systematic in vitro and in vivo assessments demonstrate targeted and enhanced chemotherapy and photothermal hyperthermia of cancer (U87 cancer cell line and corresponding tumor xenograft; inhibition efficiency: 92.37%) in the NIR-II biowindow by these mesopore-coated 2D Nb2C MXenes.Conclusion: This work not only significantly broadens the biomedical applications of 2D Nb2C MXene for enhanced cancer therapy, but also provides an efficient strategy for surface engineering of 2D MXenes to satisfy versatile application requirements.

A Two-Dimensional Biodegradable Niobium Carbide (MXene) for Photothermal Tumor Eradication in NIR-I and NIR-II Biowindows.

Conventionally, ceramics-based materials, fabricated by high-temperature solid-phase reaction and sintering, are preferred as bone scaffolds in hard-tissue engineering because of their tunable biocompatibility and mechanical properties. However, their possible biomedical applications have rarely been considered, especially the cancer phototherapeutic applications in both the first and second near-infrared light (NIR-I and NIR-II) biowindows. In this work, we explore, for the first time as far as we know, a novel kind of 2D niobium carbide (Nb2C), MXene, with highly efficient in vivo photothermal ablation of mouse tumor xenografts in both NIR-I and NIR-II windows. The 2D Nb2C nanosheets (NSs) were fabricated by a facile and scalable two-step liquid exfoliation method combining stepwise delamination and intercalation procedures. The ultrathin, lateral-nanosized Nb2C NSs exhibited extraordinarily high photothermal conversion efficiency (36.4% at NIR-I and 45.65% at NIR-II), as well as high photothermal stability. The Nb2C NSs intrinsically feature unique enzyme-responsive biodegradability to human myeloperoxidase, low phototoxicity, and high biocompatibility. Especially, these surface-engineered Nb2C NSs present highly efficient in vivo photothermal ablation and eradication of tumor in both NIR-I and NIR-II biowindows. This work significantly broadens the application prospects of 2D MXenes by rationally designing their compositions and exploring related physiochemical properties, especially on phototherapy of cancer.