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Changes in the Raman spectrum of Ti 3 C 2 T x are due to laser radiation. The laser power density varied from 10 kW/cm 2 to 1 MW/ cm 2 . Three spectral regions are marked as TiO 2 (spectral region of titanium oxide formation), phonon region (lower frequency vibrations), and disordered carbon region (vibrations of C−C bonds). The applied excitation wavelength was 633 nm.
Source publication
Extending applications of Ti3C2Tx MXene in nanocomposites and across fields of electronics, energy storage, energy conversion, and sensor technologies necessitates simple and efficient analytical methods. Raman spectroscopy is a critical tool for assessing MXene composites; however, high laser powers and temperatures can lead to the materials’ dete...
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... the latter band also shows sensitivity for the −O or −F content on the surface 51 and further underscores its dependence on the synthesis route. 42 When comparing the Raman spectra of single-layered MXene collected using different excitation wavelengths, notable changes are observed primarily under preresonance conditions ( Figure S4). From vis−NIR extinction spectra, the resonance Raman condition for MXene samples in our study was excitation with a wavelength of 750 nm ( Figure 2). ...
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... defects, which can be traced by Raman spectroscopy. The evolution of phonon bands was first examined using a 633 nm laser in the power density range of 10 kW/cm 2 −1 MW/cm 2 ( Figure 4). Additionally, samples were analyzed at a higher laser power density, which enables a rapid deterioration of the lattice, using a 532 nm laser (with the power density range of 20 kW/cm 2 −26 MW/cm 2 ) and a 457 nm laser (with the power density range of 240 kW/cm 2 −4.9 MW/cm 2 ) (Figures S7−S10). ...
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... for MXene deterioration were previously identified and include (i) inner titanium (Ti) atom diffusion to outer layers in the presence of lattice defect; (ii) the formation of C− C bonds between different MXene planes; and (iii) the formation of TiO 2 . 68 The first apparent sign of lattice disruption in MXene can be seen in the disordered carbon spectral region of 1000−1800 cm −1 (Figure 4). Amorphous carbon and hydrocarbons begin to form at excitation powers of 160 kW/cm 2 . ...
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... Under 633 nm excitation, the intensity of the G band of disordered carbon continuously increased with increasing power density, reaching its maximum at 875 kW/cm 2 . As the laser power density is further increased, the disordered carbon bands gradually weaken due to the widespread deterioration of C−C bonds, as shown in Figure 4. ...
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... the results for such samples are not included in the analysis. No significant differences were found when using various wavelengths for the excitation of Raman scattering ( Figure S4). Consequently, we focus on the results obtained with 633 nm excitation ( Figure 5). ...
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... this process, lattice deterioration becomes evident from 150 kW/cm 2 by the onset of C−C formation, as indicated by the appearance of spectral bands related to disordered carbon (Figure 4). This deterioration is characterized by a decrease in the I ω2/ I ω5(OH) and I ω5(O) /I ω5(OH) ratios. ...
Citations
... Using the 633 nm laser to measure the composite, the MXenes naturally present a different characteristic spectra [ Figure 1c], which can be useful to reveal their level of oxidation. The spectra shows the delaminated MXene [38] peak at 603 nm −1 , and no formation of TiO 2 , since this would be revealed by the appearance of a peak near 154 cm −1 , associated to the E g mode of the TiO 2 anatase phase. Only a slight red shift in the 620 nm −1 peak associated with oxidation [38] is observed. ...
... The spectra shows the delaminated MXene [38] peak at 603 nm −1 , and no formation of TiO 2 , since this would be revealed by the appearance of a peak near 154 cm −1 , associated to the E g mode of the TiO 2 anatase phase. Only a slight red shift in the 620 nm −1 peak associated with oxidation [38] is observed. Furthermore, if considerable oxidation had occurred, the spectral region between 1000 and 1600 cm −1 should also become sizable compared to the other regions, which is not the case. ...
As new materials are required to overcome the challenges presented by non-volatile resistive switching (RS) devices, organic based composites are gaining attention due to their easy preparation, tunability, scalability and good mechanical properties. Here, we study how the interaction between MXene and Polyvinylidene fluoride (PVDF) contribute to the RS phenomenon, and how different electrode materials [Ag (top) and W, ITO (bottom)] affect the conduction in these devices. Our detailed structural and electrical analyses of the composite layer reveals that the RS mechanism is related with the formation and rupture of conductive filaments pinned by the MXene sites. The W-based structure exhibits lower switching voltage (<1 V) and a higher ON/OFF resistance ratio of 15. In contrast, the ITO-based structure requires a higher bias voltage and displays a more gradual switching (ON/OFF ratio of 3), likely due to the competition between the migration of Ag⁺ ions and oxygen vacancies from ITO. This work paves the way in understanding how to exploit the integration of novel two-dimensional (2D) materials with polymers for neuromorphic computing.
... Nevertheless, the 2 , 3 , and 4 peaks were observable at x = 0 to 0.25 in 32-MXene films, which suggests the retention of high electrical conductivity within this composition range. [42] In particular, the 2 peak shifted toward lower wavenumbers with increasing nitrogen content, from 213 cm −1 in Ti 3 C 2 T z to ≈210 cm −1 in Ti 3 C 1.25 N 0.75 T z , suggesting that nitrogen substitution induces local structural softening ( Figure S34, Supporting Information). Figure 4a demonstrates the EMI SE of Ti 3 C 1.9 N 0.1 T z films across the X-, K a -, and W-bands at varying thicknesses. ...
Broadband and ultrathin electromagnetic interference (EMI)‐shielding materials are crucial for efficient high‐frequency data transmission in emerging technologies. MXenes are renowned for their outstanding electrical conductivity and EMI‐shielding capability. While substituting nitrogen (N) for carbon (C) atoms in the conventional MXene structure is theoretically expected to enhance these properties, synthesis challenges have hindered progress. Here, it is demonstrated that TixCyNx‐y‐1Tz MXene films with optimized N content achieve a record‐high electrical conductivity of 35 000 S cm⁻¹ and exceptional broadband EMI shielding across the X (8–12.4 GHz), Ka (26.5–40 GHz), and W (75–110 GHz) bands—outperforming all previously reported materials even at reduced thicknesses. By synthesizing a full series of high‐stoichiometric TixAlCyNx‐y‐1 MAX phases without intermediate phases, the impact of N substitution on the physical and electrical properties of TixCyNx‐y‐1Tz MXene flakes is systematically explored, achieving complete composition tunability in both dispersion and film forms. These findings position TixCyNx‐y‐1Tz MXenes as promising candidates for applications spanning from conventional lower‐frequency domains to next‐generation sub‐THz electronics.
... [53,54] Moreover, as shown in Figure 3c, the Raman spectra of Ti 3 C 2 MXene, A18-Ti 3 C 2 , and E18-Ti 3 C 2 exhibit characteristic vibration bands in the 100-1000 cm −1 range, with peaks at 212 and 712 cm −1 corresponding to A 1g symmetric out-of-plane vibrations of Ti and C atoms, respectively, indicating that the MXene framework's structural integrity is preserved. Additionally, the peaks at 390 and 632 cm −1 correspond to E g group vibrations associated with the in-plane shear modes of Ti and C. [55][56][57][58] We observed slight shifts in these peaks for A18-Ti 3 C 2 and E18-Ti 3 C 2 compared to pristine-Ti 3 C 2 , due to interactions between the MXene surface and the organic quaternary ammonium ions, which influence the Ti─C bond vibrations. These changes suggest that surface functionalization via the EEF slightly alters the local bonding and vibrational properties of Ti 3 C 2 MXene. ...
External electric field (EEF), as a stimulating factor, is an effective method for optimizing the surface composition and structure of materials. Ti3C2 MXene surface enriched with negatively charged functional groups (─OH, ─O, etc.) will exhibit high sensitivity to EEF. However, the impact of EEF on the interaction mechanisms between the guest ions and MXene surface remains unclear and requires further investigation. Herein, the density functional theory (DFT) is employed to simulate the adsorption energies between butyl trimethylammonium ion (BTA⁺) and MXene surfaces under different intensities of EEFs (±0.9, ±0.7, ±0.5, ±0.3, ±0.1, and 0 V Å⁻¹), indicating EEF can effectively regulate adsorption. It will increase the encapsulation degree of BTA⁺ on the MXene surface, thereby enhancing surface passivation. Based on theoretical predictions, quaternary‐ammonium ions with different chain‐lengths (BTA⁺, DTA⁺, STA⁺) are selected as guest ions to unveil the mechanism of EEF on MXene surface passivation. The applied‐EEF promotes the formation of Ti─O─N bonds between ─OH and ammonium groups to construct more‐denser protective layer, leading to enhancement of surface passivation and obviously increasing the capacitance retention after 100,000 cycles (50.8% to 97.5%). This work provides a new pathway and theoretical support for the surface passivation of MXene.
... Studies have reported that MXenes can degrade through oxidative pathways, leading to structural changes that might affect their mechanical and electrical properties. [54] While PVA and MXene exhibit properties that make them attractive for green and biomedical applications, it is crucial to assess energy requirements, waste generation, and the overall environmental footprint when integrating these materials, considering their entire lifecycle from synthesis to disposal. [55] ...
MXene‐based materials have gained attention in the biomedical field due to their promising biocompatibility, improved mechanical strength, and conductivity. In this study, the focus is on optimizing MXene‐incorporated electrospun fibers and subsequent characterizations to assess their potential for biomedical applications. Polyvinyl alcohol (PVA) is used as the appropriate matrix material and process parameters are finetuned to ensure effective incorporation of MXene. XRD and spectroscopic analysis confirm the successful synthesis and integration of MXenes into the nanofibers. Morphological analysis shows that MXene led to the formation of sub‐micrometer fibers with smooth surfaces and reduced the fiber diameter (587 ± 191 nm) compared to pure PVA (696 ±160 nm). Investigations on the electrical characteristics demonstrate a fourfold increase in conductivity of nanofibers (σ = 1.90 ± 0.45 × 10⁻⁸ S cm⁻¹) after MXene addition (compared to σ = 0.46 ± 0.05 × 10⁻⁸ S cm⁻¹ of PVA‐only fibers). Furthermore, the MXene‐PVA system demonstrates a nearly twofold increase in mechanical stiffness, with E = 136.87 ± 19.63 MPa than 71.42 ± 16.56 MPa for PVA. Moreover, the initial in vitro experiments indicate improved L929 cell viability. These findings position MXene‐PVA composites as a highly versatile platform for advanced biomedical devices, such as electroactive tissue scaffolds and wearable sensors.
... Both CNT array and the graphene sample exhibit distinct peaks at approximately 1350 cm −1 and 1580 cm −1 , which correspond to the characteristic D peak and G peak of carbon, respectively. In addition, Ti 3 C 2 T x displays characteristic peaks at 200 cm −1 , 400 cm −1 , and 600 cm −1 , which is consistent with literature reports [43,44]. ...
... Both CNT array and the graphene sample exhibit distinct peaks at approximately 1350 cm −1 and 1580 cm −1 , which correspond to the characteristic D peak and G peak of carbon, respectively. In addition, Ti3C2Tx displays characteristic peaks at 200 cm −1 , 400 cm −1 , and 600 cm −1 , which is consistent with literature reports [43,44]. Judging from the spectra of the composite films, there are characteristic peaks of both carbon and Ti3C2Tx. ...
Stretchability and flexibility are essential characteristics for high-performance electromagnetic interference (EMI) shielding materials in wearable and smart devices. However, achieving these mechanical properties while also maintaining high EMI shielding effectiveness (SE) for shielding materials remains a significant challenge. Here, a stretchable patterned carbon nanotube (CNT) array composite film, reinforced with two-dimensional (2D) nanomaterials (Ti3C2Tx and graphene), is fabricated using a straightforward scraping method. The resulting CNT array/Ti3C2Tx/graphene composite films possess a periodic grid structure. Specifically, the composite film with a regular hexagonal pattern demonstrates an EMI SE of 36.5 dB in the X-band at a thickness of 350 μm. Additionally, the composite film exhibits excellent stretchability, flexibility, and stability. After undergoing 10,000 stretching cycles, the EMI SE remains stable. Simulation results further indicate that surface reflection is the primary EMI shielding mechanism. This simple scraping method offers a promising approach for developing stretchable and high-performance EMI shielding films, making them well suited for application in flexible devices.
... Fig. 1c illustrates Raman spectra of Ti 3 C 2 T x MXene. The vibrational modes with characteristic peaks of MXene are obvious and match the previously reported results [45]. Moreover, the complete exfoliation of Ti 3 C 2 T x MXene flakes, with a high aspect ratio, is confirmed by TEM imaging, as shown in Fig. 1d. ...
Films fabricated from two-dimensional (2D) materials introduce a distinct assembly structure that imparts the inherent properties of pristine 2D materials into a macroscopic scale. Freestanding Ti3C2Tx MXene films have a highly compacted structure of hierarchically assembled nanoflakes and are candidates for various applications. We experimentally investigated various factors impacting the mechanical properties of Ti3C2Tx MXene films for acquiring improved strength and toughness. To scrutinize the effect of the fabrication technique and the thickness of the Ti3C2Tx MXene films, vacuum-assisted filtration (VAF) and casting processes were utilized to fabricate Ti3C2Tx MXene films with varying thicknesses. Additionally, the influence of annealing temperature on the acquired Ti3C2Tx MXene films' mechanical properties, under various straining rates, was elucidated. The annealing temperature, ranging between room temperature (RT) and 300 °C, has a major impact on the obtained mechanical properties of Ti3C2Tx MXene films. For all strain rates, ranging between 10−1 min−1 and 10−5 min−1, the tensile strength of the film increases with an increase of temperature, to 200 °C. Annealing treatment at 200 °C improved the average tensile strength and Young's modulus by about 44.6 % and 35.1 %, respectively, for films made via VAF. Similarly, they increased by 32.8 % and 20 %, respectively, for films made via casting process. This behavior is independent of the fabrication technique and the thickness. However, thin Ti3C2Tx MXene films showed superior mechanical properties compared to thick films. Additionally, the mechanical properties of casted films were inferior to those fabricated via VAF process. The obtained deformation mechanism seems to be highly dependent on the structural features of the film and the characteristics of interlayer spacing between adjacent Ti3C2Tx MXene flakes.
... The CdS-MXe heterostructures showed typical peaks at 205 cm −1 , corresponding to the out-plane vibrations of Ti and C atoms. The intense peak at 157 cm −1 related to the oxidized Ti 3 C 2 could be due to the increased laser power on the layered surface [42]. The D and G bands were observed at 1352 and 1567 cm −1 , respectively, representing the graphic carbon functionality of MXene tagged on the CdS surface. ...
Energy scarcity and environmental pollution have prompted research in hydrogen generation from solar to develop clean energy through highly efficient, effective, and long-lasting photocatalytic systems. Designing a catalyst with robust stability and an effective carrier separation rate was achieved through heterostructure assembly, but certain functionalities must be explored. In this paper we designed a ternary heterostructure assembly of CdS nanospheres wrapped with hierarchical shell walls of layered MXene-tagged MoS 2 nanoflakes, forming intimate interfaces through an in-situ growth process. An in-layered shell wall of MXene with surface-wrapped MoS 2 nanoflakes as a core–shell assembly improved the photo-corrosion resistance and accelerated the production of photocatalytic H 2 (38.5 mmol g ⁻¹ h ⁻¹ ), which is 10.7, 3.1, and 1.9 times faster than that of CdS, CdS–MXe, and CdS–MoS 2 nanostructures, respectively. The apparent quantum efficiency of the CdS–MXe 2.4 /MoS 2 heterostructure was calculated to be 34.6% at λ = 420 nm. X-ray and ultraviolet photoelectron spectroscopies validated the electronic states, energy band alignment, and work function of the heterostructures, whilst time-resolved photoluminescence measured the carrier lifespan to evaluate the effective charge migration in the CdS-MXe/MoS 2 heterostructure. The dual surface wrapping of MXe/MoS 2 over CdS nanospheres confirmed the structural durability that remained intact throughout the photocatalytic reaction, promoting approximately 93.1% of its catalytic property even after five repeatable cycles. This study examined how the MXene heterostructure template improves the catalytic efficiency and opens a new way to design MXene-based durable heterostructure catalysts for solar-energy conversion.
Graphical Abstract
... The D band denotes out-of-plane vibrations associated with disordered carbon structures, confirming the presence of defects. Conversely, the G band is attributed to in-plane vibrations of carbon, indicating the crystallinity and symmetry of the carbonaceous material under investigation [42][43][44][45]. In this context, the calculated I D :I G ratio of 0.96 indicates a degree of graphitization and carbon architecture within the examined material. ...
To address the challenge of low electronic and ionic conductivities in lithium-ion batteries (LIBs), we synthesized oxidized mixed-phase Ti3C2Tx MXene nanosheets using a wet chemical etching route. This prepared negative electrode demonstrated a reversible specific discharge capacity of 538.49 mAh/g at 0.1C (67 mA/g), which is significantly higher than the pristine MXene and retained 75.46% of its initial capacity during the rate performance test. During its testing for cycling stability, it demonstrated a stable discharge capacity of 383.33 mAh/g after 264 cycles at 0.1C (67 mA/g) and showed an increasing profile with a rosed capacity of 551.98 mAh/g after 404 cycles at 0.4C (268 mA/g). The exceptional electrochemical performance is attributed to the Ti3C2Tx MXene architecture, with oxidation of its nanosheets resulting in an increase in exposed Li⁺ sites leading to structural stability. The galvanostatic intermittent titration technique (GITT) was performed for the numerical analysis of Li⁺ mobility. To analyze the effective charge storage mechanism, electrochemical impedance spectroscopy (EIS) was also performed. This MXene electrode is found to be a promising negative electrode with a simple synthesis route demonstrating enhanced electrochemical performance and stability.
... This property is less pronounced in graphene or graphene derivatives, where intercalation can be more challenging due to their planar structure [12,17]. In addition, MXenes can also be easily exfoliated into single or a few layered structures, enabling tunable properties based on the number of layers [18,19]. ...
In the present mini-review article, we have compiled the previously reported literature on the fabrication of MXenes and their hybrid composite materials based electrochemical sensors for the determination of phenolic compounds and counter electrodes for platinum (Pt)-free dye-sensitized solar cells (DSSCs). MXenes are two-dimensional (2D) materials with excellent optoelectronic and physicochemical properties. MXenes and their composite materials have been extensively used in the construction of electrochemical sensors and solar cell applications. In this paper, we have reviewed and compiled the progress in the construction of phenolic sensors based on MXenes and their composite materials. In addition, co1.unter electrodes based on MXenes and their composites have been reviewed for the development of Pt-free DSSCs. We believe that the present review article will be beneficial for the researchers working towards the development of phenolic sensors and DSSCs using MXenes and their composites as electrode materials.
... These peaks are consistent with the reported literature and are attributed to the shear and longitudinal vibrations of Ti and Al atoms, with ω 1 specifically linked to the vibrations of Al [42,43]. The absence of the ω 1 peak in the B-MX spectrum confirms the removal of Al during the etching process, leading to the formation of MXene [42,43]. ...
... These peaks are consistent with the reported literature and are attributed to the shear and longitudinal vibrations of Ti and Al atoms, with ω 1 specifically linked to the vibrations of Al [42,43]. The absence of the ω 1 peak in the B-MX spectrum confirms the removal of Al during the etching process, leading to the formation of MXene [42,43]. The characteristics of Raman peaks in the B-MX spectrum are notably upshifted and broadened compared to those in the MAX phase, which can be attributed to the intercalation of surface groups introduced during etching. ...
... The broadening of these peaks aligns with a reduction in structural order, consistent with the exfoliation process, as also evidenced by XRD analysis. A broad peak around 630 cm − 1 indicates nonstoichiometric TiC x [42][43][44]. Notably, in the B-MX spectrum, weaker bands observed around 1345 cm − 1 and 1570 cm − 1 , designated as ω 5 and ω 6 , correspond to the D-and G-bands of carbon [43]. These bands are associated with free carbon and indicate disorder within the sample. ...
Selecting distinct materials to design a tribopositive and tribonegative electrode pair for a triboelectric nanogenerator (TENG) device is a challenging task, as the interfacial electric field causes surface charges to diffuse into the air or within the material itself, leads to charge deterioration. To address these challenges, there is a strong demand for engineered materials and electrode designs that enable effective charge accumulation and trapping to regulate their performance optimally. Herein, we introduce a unique electrode design for a contact-separation (CS) mode triboelectric nanogenerator TENG featuring multilayered Ti3C2Tx MXene/Kapton as tribonegative electrodes. For the tribopositive electrode, we developed an innovative synthesis strategy to create MXene-seeded layered TiO2 superstructures/PVA-based tribopositive electrodes. After optimization of both triboelectric layers, the optimized TENG showed an open-circuit voltage (Voc) ∼ 120 V, short-circuit current (Isc) ∼ 25 μA, and power density of 5.66 W·m−2. The surface terminations groups in highly conductive black MXene nanosheets and the oxygen vacancies in TiO2-layered superstructures provide abundant charge accumulation and trapping sites due to organized multilayered structures at both ends. Moreover, the induced polarization in the tribopositive layer due to the hybrid film could further hinder the free electrons’ drift to the bottom electrode, preventing charge recombination. The optimized TENG was tested as a pressure sensor to monitor different sensitive physiological movements of the human body. Further application of the designed TENG has been revealed by humidity sensing characteristics, powering LEDs, stopwatches, pedometers, and swiftly charging micro-capacitors by utilizing direct output power. By employing a controlled synthesis strategy, our approach leverages the unique properties of MXenes to function as both tribo-positive and tribonegative electrodes within the same device. This dual-function capability simplifies material selection and enhances overall device performance, presenting a transformative solution for next-generation TENG applications.
