Titanium Carbide MXene Nanosheets Research Articles

Tuning of fluorescence in titanium carbide MXene nanosheets with La3+ ion doping for the recognition of creatinine biomarker in biofluids

There is a strong correlation between the concentration of creatinine in human urine and the overall health of the kidneys. Therefore, there has been a persistent need for a rapid, and cost-effective quantitative method to assay creatinine levels in urine. Herein, green fluorescent La3+ doped titanium carbide nanosheets (La3+-doped Ti3C2 NSs) are fabricated via HF etching method by using Ti3AlC2 as MAX phase material and La(NO3)3 as a doping agent. As synthesized fluorescent La3+-doped Ti3C2 NSs are stable, showing green fluorescence under UV light. The as-synthesized La3+-doped Ti3C2 NSs act as a fluorescent sensor for the sensitive recognition of creatinine biomarker. The La3+-doped Ti3C2 NSs-based fluorescence method showed a fluorescence quenching at emission wavelength 518 nm towards creatinine with a linear range of 0.25–7.5 μM and detection limit of 63.44 nM. The paper strip based on La3+-doped Ti3C2 NSs was developed for the visual identification of creatinine. Furthermore, La3+-doped Ti3C2 NSs were used as probes for imaging of Saccharomyces cerevisiae cells. Also, the as-fabricated La3+-doped Ti3C2 NSs propose a quick response giving a cost-effective analytical strategy for the selective assay of creatinine in biofluids (plasma and urine).

MXene/Gold nanoparticles heterostructure as catalase mimic for colorimetric detection of penicillin G

Penicillin G (PenG) is a common antibiotic used to fight bacterial infections in livestock. Its excessive use leads to animal products tainted with antibiotic residues. Consumption of foods contaminated with antibiotics can cause their accumulation in our bodies and pose threats to our health. We developed a colorimetric assay to detect the presence of PenG in real matrices using a hierarchical nanostructure material composed of layered titanium carbide MXene nanosheets (Ti3C2Tx) decorated with gold nanoparticles (AuNPs). The AuNPs were directly grown on the MXene nanosheets via a facile method, which significantly enhanced the catalase-like enzyme activity of MXene. The Ti3C2Tx/AuNPs nanocomposite catalyzed the enzymatic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to its oxidized form in the presence of hydrogen peroxide, and the reaction products turned the sample solution greenish blue. However, this color-change reaction does not occur when PenG is present in the solution. Our assay performed well with a limit of detection (LOD) of 7.51 nM, which is below the established maximum residue limits for raw milk. We hypothesized and experimentally verified that superoxide anions (O2•-) generated play a critical role in the catalysis of PenG. Our results may help develop a simple and inexpensive colorimetric sensor for the routine detection of PenG in food samples.

Synthesis of Titanium Carbide MXene Nanosheets by Ecofriendly Technique for Strontium Ion Adsorption

2D titanium carbide (Ti3C2Tx, where Tx indicates the surface termination) MXene nanosheets are synthesized by etching the Ti3AlC2 MAX phase using two kinds of etchants: potassium hydroxide (KOH) base and hydrofluoric (HF) acid. This study aims to reduce the environmental side effects caused by the etchant in fabricating MXene nanosheets to extract strontium ions (Sr2+) from nuclear wastewater. Ti3C2Tx MXene synthesized using alkaline KOH etchant shows a 99% Sr2+ removal rate, which is much higher than that synthesized using the conventional HF etchant (82%). The enhanced Sr2+ removal rate associated with KOH etching is explained by unique surface termination, which offers more active adsorption sites for Sr2+ by the partial hydrolysis of TiC bonds on the surface of MXene nanosheets.

Alkanolamine intercalation assisted liquid phase exfoliation of titanium carbide MXene nanosheets for highly efficient photocatalytic CO2 reduction

Two-dimensional titanium carbide (Ti3C2Tx) MXene nanosheets have been widely concerned due to its abundant surface functional groups, high conductivity, excellent photoelectrochemical properties and thermal conductivity. Nevertheless, it is still a challenge for the mass production of high-quality Ti3C2Tx MXene nanosheets. Herein, the bulk Ti3C2Tx MXene powders were stripped into monolayer or few layer nanosheets in propylene carbonate through liquid-phase exfoliation strategy assisted via alkanolamine as intercalators. It is shown that the stripping yield is up to 59.3 %, which is the recorded value for the delamination of Ti3C2Tx MXene nanosheets from bulk Ti3C2Tx MXene powder, and 62.2 % of nanosheets are monolayer. The ability of hydrogen bond donor and molecular size of alkanolamine have important effects on the yield. Moreover, Ti3C2Tx MXene nanosheets have been employed as catalysts in the photocatalytic CO2 reduction. The yield of CO is 149.7 μmol g-1h−1, which is about five times that of bulk Ti3C2Tx MXene powder. This work paves the way for the mass production of MXene nanosheets with high activity photocatalysis.

Atomistic Investigation of the Titanium Carbide MXenes under Impact Loading

2D Titanium carbide MXenes with a structural formula recognized as Tin+1Cn have attracted attention from both the academic and industry fields due to their intriguing mechanical properties and appealing potential in a variety of areas such as nano-electronic circuits/devices, bio sensors, energy storage and reinforcing material for composites. Based on mutli-body comb3 (third-generation Charge-Optimized Many-Body) potential, this work investigated the impact resistance of monolayer Tin+1Cn nanosheets (namely, Ti2C Ti3C2 and Ti4C3) under hypervelocity up to 7 km/s. The deformation behavior and the impact resist mechanisms of Tin+1Cn nanosheets were assessed. Penetration energy is found to positively correlate with the number of titanium atom layer (n). However, in tracking atomic Von Mises stress distribution, Ti2C exhibits the most significant elastic wave propagation velocity among the examined nanosheets, suggesting the highest energy delocalization rate and stronger energy dissipation via deformation prior to bond break. Consistently, Ti2C presents superior specific penetration energy due its Young’s-modulus-to-density ratio, followed by Ti3C2 and Ti4C3, suggesting an inverse correlation between the titanium atom layer number and specific penetration energy. This study provides a fundamental understanding of the deformation and penetration mechanisms of titanium carbide MXene nanosheets under impact, which could be beneficial to facilitating their emerging impact protection applications.

Orally administered titanium carbide nanosheets as anti-inflammatory therapy for colitis.

Rationale: Oxidative stress, resulting from excessive reactive oxygen species (ROS), plays an important role in the initiation and progression of inflammatory bowel disease (IBD). Therefore, developing novel strategies to target the disease location and treat inflammation is urgently needed.Methods: Herein, we designed and developed a novel and effective antioxidant orally-administered nanoplatform based on simulated gastric fluid (SGF)-stabilized titanium carbide MXene nanosheets (Ti3C2 NSs) with excellent biosafety and multiple ROS-scavenging abilities for IBD therapy.Results: This broad-spectrum and efficient ROS scavenging performance was mainly relied on the strong reducibility of Ti-C bound. Intracellular ROS levels confirmed that Ti3C2 NSs could efficiently eliminate excess ROS against oxidative stress-induced cell damage. Following oral administration, negatively-charged Ti3C2 NSs specifically adsorbed onto the positively-charged inflamed colon tissue via electrostatic interaction, leading to efficient therapy of dextran sulfate sodium salt (DSS)-induced colitis. The therapeutic mechanism mainly attributed to decreased ROS levels and pro-inflammatory cytokine secretion, and increased M2-phenotype macrophage infiltration and anti-inflammatory cytokine secretion, efficiently inhibiting inflammation and alleviating colitis symptoms. Due to their excellent ROS-scavenging performance, Ti3C2-based woundplast also promoted skin wound healing and functional vessel formation.Conclusions: Our study introduces redox-mediated antioxidant MXene nanoplatform as a novel type of orally administered nanoagents for treating IBD and other inflammatory diseases of the digestive tract.

Negative dielectric constant of water confined in nanosheets

Electric double-layer capacitors are efficient energy storage devices that have the potential to account for uneven power demand in sustainable energy systems. Earlier attempts to improve an unsatisfactory capacitance of electric double-layer capacitors have focused on meso- or nanostructuring to increase the accessible surface area and minimize the distance between the adsorbed ions and the electrode. However, the dielectric constant of the electrolyte solvent embedded between adsorbed ions and the electrode surface, which also governs the capacitance, has not been previously exploited to manipulate the capacitance. Here we show that the capacitance of electric double-layer capacitor electrodes can be enlarged when the water molecules are strongly confined into the two-dimensional slits of titanium carbide MXene nanosheets. Using electrochemical methods and theoretical modeling, we find that dipolar polarization of strongly confined water resonantly overscreens an external electric field and enhances capacitance with a characteristically negative dielectric constant of a water molecule.

In Situ Formed Protective Barrier Enabled by Sulfur@Titanium Carbide (MXene) Ink for Achieving High-Capacity, Long Lifetime Li-S Batteries.

Sulfur (S) is an attractive cathode material with advantages including high theoretical capacity and low cost. However, issues such as the lithium polysulfide shuttle effect and its insulating properties greatly limit the future applications of lithium‐sulfur (Li‐S) batteries. Here, a viscous aqueous ink with nanoscale S uniformly decorated on the polar, metallically conductive titanium carbide MXene nanosheets (S@Ti3C2Tx) is reported to address these issues. Importantly, it is observed that the conductive Ti3C2Tx mediator efficiently chemisorbs the soluble polysulfides and converts them into thiosulfate/sulfate. The in situ formed sulfate complex layer acts as a thick protective barrier, which significantly retards the shuttling of polysulfides upon cycling and improves the sulfur utilization. Consequently, the binder‐free, robust, highly electrically conductive composite film exhibits outstanding electrochemical performance, including high capacities (1244–1350 mAh g‐1), excellent rate handling, and impressive cycling stability (0.035–0.048% capacity loss per cycle), surpassing the best MXene‐S batteries known. The fabrication of a pouch cell based on the freestanding S@Ti3C2Tx film is also reported. The prototype device showcases high capacities and excellent mechanical flexibility. Considering the broad family of MXenes and their unique roles in immobilizing the polysulfides, various S@MXene composites can be similarly fabricated with promising Li+ storage capability and long lifetime performance.

Flexible MXene/Graphene Films for Ultrafast Supercapacitors with Outstanding Volumetric Capacitance

A strategy to prepare flexible and conductive MXene/graphene (reduced graphene oxide, rGO) supercapacitor electrodes by using electrostatic self‐assembly between positively charged rGO modified with poly(diallyldimethylammonium chloride) and negatively charged titanium carbide MXene nanosheets is presented. After electrostatic assembly, rGO nanosheets are inserted in‐between MXene layers. As a result, the self‐restacking of MXene nanosheets is effectively prevented, leading to a considerably increased interlayer spacing. Accelerated diffusion of electrolyte ions enables more electroactive sites to become accessible. The freestanding MXene/rGO‐5 wt% electrode displays a volumetric capacitance of 1040 F cm−3 at a scan rate of 2 mV s−1 , an impressive rate capability with 61% capacitance retention at 1 V s−1 and long cycle life. Moreover, the fabricated binder‐free symmetric supercapacitor shows an ultrahigh volumetric energy density of 32.6 Wh L−1, which is among the highest values reported for carbon and MXene based materials in aqueous electrolytes. This work provides fundamental insight into the effect of interlayer spacing on the electrochemical performance of 2D hybrid materials and sheds light on the design of next‐generation flexible, portable and highly integrated supercapacitors with high volumetric and rate performances.