Plasmonic Light Illumination Creates a Channel To Achieve Fast

Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

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Plasmonic Light Illumination Creates a Channel To Achieve Fast Degradation of Ti3C2Tx Nanosheets Jiebo Li,†,‡,∇ Ruzhan Qin,§,∇ Li Yan,∥ Zhen Chi,⊥ Zhihao Yu,☆ Naitao Li,† Mingjun Hu,*,∥ Hailong Chen,*,⊥ and Guangcun Shan*,§ †

Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, 100191, China School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, China § School of Instrumentation Science and Optoelectronics Engineering, Beihang University, Beijing, 100191, China ∥ School of Materials Science and Engineering, Beihang University, Beijing, 100191, China ⊥ Beijing National Laboratory for Condensed Matter Physics, CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China ☆ College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences, Peking University, Beijing, 100871, China

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‡

S Supporting Information *

ABSTRACT: Two-dimensional (2D) material-controllable degradation under light radiation is crucial for their photonics and medical-related applications, which are yet to be investigated. In this paper, we first report the laser illumination method to regulate the degradation rate of Ti3C2Tx nanosheets in aqueous solution. Comprehensive characterization of intermediates and final products confirmed that plasmonic laser promoting the oxidation was strikingly different from heating the aqueous solution homogeneously. Laser illumination would nearly 10 times accelerate the degradation of Ti3C2Tx nanosheets in initial stage and create many smallersized oxidized products in a short time. Laser-induced fast degradation was principally ascribed to surface plasmonic resonance effect of Ti3C2Tx nanosheets. The degradation ability of such illumination could be controlled either by tuning the excitation wavelength or changing the excitation power. Furthermore, the laser- or thermal-induced degradation could be retarded by surface protection of Ti3C2Tx nanosheets. Our results suggest that plasmonic electron excitation of Ti3C2Tx nanosheets could build a new reaction channel and lead to the fast oxidation of nanosheets in aqueous solution, potentially enabling a series of water-based applications.

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INTRODUCTION

To better utilize MXene, versatile physical properties have been employed, such as photothermal conversion. MXene has showed plasmonic properties with free electrons.16−18 With outstanding energy conversion efficiency, laser excitation of MXene could find itself in energy and medical applications.19−26 A recent research work reported that MXene showed promising photothermal properties in converting light energy to water steam for practical solar energy utilization.9 In addition, MXene presented outstanding photothermal ablation performance on tumor cells under near-infrared light illumination.24,25 This efficient light-to-heat conversion could also be applied as photoacoustic imaging agent for guiding therapy.15 Therefore, laser illuminating MXene may be engineered to enhance and provide valuable control over the birth and applications of electron−hole pairs, offering the

Since this decade, MXene has been a new promising series of two-dimensional (2D) materials with excellent conductivity, hydrophilicity and mechanical properties.1−3 From the viewpoint of structure,4 MXenes, which have a general formula of Mn+1XnTx, are composed of stacked 2D sheets where M stands for an early transition-metal carbide (Ti, Ta, Mo, Nb, V, and Zr), X is either C or N, and Tx represents surface functional groups such as O, OH, and/or F. The precise and controllable preparation of MXene elements and structural units provides abundant physical and chemical foundation for the multifunctional exploration of MXene. Depending on the structure and composition design, MXene could have many exciting applications in energy storage and conversion,5,6 water splitting,7 water desalination8 and steaming,9 electronics,10 electrostatic shielding,11,12 cancer therapy,13 and thermal imaging.14,15 © XXXX American Chemical Society

Received: February 3, 2019

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DOI: 10.1021/acs.inorgchem.9b00329 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

Figure 1. (a) Schematic diagram of laser irradiation through aqueous Ti3C2Tx dispersion solution; (b) SEM image of multilayer Ti3C2Tx structure etched by LiF/HCl; (c) SEM image of delaminated few-layer Ti3C2Tx nanosheet; (d, e) respective TEM and HRTEM images of fresh delaminated Ti3C2Tx nanosheets; (f, g) respective TEM and HRTEM images of Ti3C2Tx nanosheets after 5 h of laser irradiation; (h, i) respective TEM and HRTEM images of the Ti3C2Tx oxidative products after laser irradiation for 5 h and then aging for 2 weeks.

of MXenes can be well-retained, and the composites showed several times higher photocatalytic activation for CO2 conversion to CH4 than single TiO2.37 In addition, the formation of MXene-nano-TiO2 composites could potentially be used as a new dehydrogenation catalyst.38 MXene-nanoTiO2 could also be applied to photoresistive sensing under UV irradiation.39 In view of a series of emerging and promising applications of MXene in photocatalysis, optoelectronics and photothermal conversion in recent years, the study of colloidal stability of MXene under light irradiation is of high importance.40−42 Thus, exploiting and modulating the controllable degradation of MXenes under light illumination would not only be meaningful for understanding the physicochemical mechanism of light excited MXene degradation, but also potentially useful in many practical applications. In this work, for the first time, we report the investigation of controlling the degradation of MXene (Ti3C2Tx nanosheets) with plasmonic laser illumination. With qualitative and quantitative studies, our results showed that laser illumination could significantly promote the oxidation of Ti3C2Tx nanosheets in aqueous solution, producing rutile TiO2 nanoparticles and amorphous carbon. The illumination power and wavelength are critical for the oxidation rates. Results suggested the plasmonic light induced electrons participate into the reaction. To decelerate the oxidation of Ti3C2Tx nanosheets under laseror heat-driven modes, surface coatings and protection are effective. Our results provide evidence that plasmonic laser illumination could facilitate chemical reactions on the

outstanding opportunities to stimulate useful applications of MXene in photonics and medical-related fields. In these applications, the stability of MXene colloidal solution has been a prominent problem, which is garnering enormous attention. As always, the reactivity and stability are a built-in paradox, especially for nanomaterials,27 and high reactivity usually results in poor stability. As the structural formula of Ti3C2Tx shows, MXenes are not supposed to be very stable due to the existence of a large proportion of lowvalence surface Ti atoms in planar nanosheets, which are easy to be oxidized into high valence ones, resulting in the defunctionalization of MXenes. The recent researches have shown that MXenes could be oxidized slowly in colloidal solution or oxidized rapidly at an elevated temperature.28−34 However, the oxidation is not always a bad thing if we can take the advantages well. In the case of MXenes, attributed to the controllability of the compositions, structures and functionalities of oxidative products, the controlled degradation of MXenes has raised notable interest in energy storage,35 microwave absorption,36 catalysis,37,38 and optoelectronic applications.39 For instance, Ahmed et al. employed H2O2 to control the oxidation of MXenes for producing the composites of TiO2 and MXenes that result in significantly promoted battery performance.35 Yin et al. used CO2 to oxidize MXenes at high temperature and fabricated well-defined carbon nanosheets/TiO2 nanoparticles/carbon nanosheets multilayered structures, which showed obviously improved microwave absorption ability.36 Low et al. fabricated TiO2/MXene Ti3C2 composites by calcination and found that the layered structure B


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Inorganic Chemistry

Figure 2. SEM images of Ti3C2Tx samples: (a) initial sample, (b) after heating for 5 h, (c) after laser illumination for 5 h, and (d) after aging for 2 weeks. (e) XPS survey spectra of Ti3C2Tx samples under different oxidized states. XPS spectra of Ti 2p core level in Ti3C2Tx samples with different oxidized states: (f) original Ti3C2Tx nanosheets, (g) after laser illumination for 5 h, (h) after heating at 40 °C for 5 h, (i) after laser illumination for 1 week, and (j) after heating for 1 week at 40 °C.

Ti3C2Tx nanosheets were distributed on silicon substrates, and these nanosheets had an average size of 2.5 ± 1 μm in the lateral direction. For fresh delaminated Ti3C2Tx nanosheets (see Figures 1d and 1e), an interplanar spacing of ∼5.35 Å could be identified in the HRTEM image, which was much larger than the interspace of the (004) face in the corresponding MAX phase with lattice distance of 4.62 Å (JCPDS No. 00-052-0875). The results revealed that Al atom layers have been well-removed and the bond of MXene nanosheets has been dominated by van der Waals force.43,44 After 5 h of laser irradiation (808 nm, 0.7 W), the structure of Ti3C2Tx nanosheets changed significantly, with many TiO2 nanoparticles appearing on the surface of nanosheets (Figure 1f). The crystalline nanostructures were exhibited in Figure 1g, and these nanoparticles showed the interplanar spacing of 2.05 Å, which corresponded to the (210) crystal face in rutile TiO2, but not matching any crystal face in anatase phase, indicating that the main product derived from laser-induced oxidation was rutile TiO2, which was also supported by our XRD and Raman results (see Figures S1a and S1b in the Supporting Information). In the Raman spectra of the laser-illuminated sample, the characteristic peaks located at 435.9 and 623.7 cm−1 could be assigned to rutile TiO2.33,45 Further oxidation led to nearly complete conversion of low-valence titanium into TiO2, and the solution finally turned cloudy white. Figures 1h and 1i showed TEM and HRTEM images of the degradation products of Ti3C2Tx nanosheets after laser illumination, followed by long-time aging, where TiO2 nanoparticles became bigger and the number further increased, and most of them

plasmonic material surfaces, and open a venue for lightinduced chemical reactions based on MXene materials.

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RESULTS AND DISCUSSION Characterization of Ti3C2Tx Nanosheets and Degradation Products under Laser Illumination. In this work, the lasers with different wavelengths and powers were employed as light sources for the investigation of light stability of typical Ti3C2Tx aqueous dispersion solution. As a contrast, the degradation of Ti3C2Tx solution under heating was also studied by employing a separate heat source, such as an oven. Figure 1a shows a schematic diagram of laser irradiation through Ti3C2Tx solution, where the laser power remained constant in the entire illumination process and the solution temperature was measured by an infrared thermometer. The structures and compositions of Ti3C2Tx nanosheets before and after laser irradiation and heating were investigated. XRD patterns in Figure S1a in the Supporting Information clearly showed the changes of crystalline structure of the powders in different stages. Distinguished from raw materials of MAX phase, the strong diffraction peak at ∼6° was presented in the exfoliated sample; this is much less than 9.5°, which corresponds to the diffraction angle of (002) face of MAX ceramics, indicating effective exfoliation of Ti3AlC2 powders. Figures 1b and 1c showed SEM images of the exfoliated products, and well-defined multilayer structure and a typical few-layer 2D structure were presented, denoting that highquality Ti3C2Tx nanosheets were formed. Figure S2 in the Supporting Information displayed that many delaminated C


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Inorganic Chemistry

Figure 3. UV-vis-NIR spectra of Ti3C2Tx in solution under different conditions: (a) full spectrum after laser illumination; (b) stability results under heating at 40, 50, and 60 °C; (c) stability results after femtosecond laser illumination; (d) stability results under 808 nm CW laser illumination and heating at 40 °C; (e) stability results under 532, 980, and 808 nm CW laser illumination; and (f) dependence on laser intensity.

located at ∼455.2, 456.3, 457.5, and 459.7 eV respectively, with the area percentages of 39%, 33%, 20%, and 8%, respectively. According to some previous reports,29,35,46,47 these peaks can be assigned to Ti−C, Ti(II) suboxides and/or hydroxides, Ti(III) suboxides and/or hydroxides, and Ti(IV) oxides, respectively, indicative of dominant Ti−C component in original Ti3C2Tx nanosheets and little oxidation. After 5 h of laser illumination, we can see that the subpeaks of Ti−C and Ti(II) components decreased, and Ti(III) and Ti(IV) peaks were enhanced significantly (Figure 2g), indicating that rapid conversion of titanium from low valence to high valence states under laser irradiation. In contrast to a heat-treated sample (Figure 2h), the Ti(II) component in the laser-illuminated sample experienced a visibly quicker oxidation process into Ti(III) and Ti(IV) oxides while the degradation rate of Ti−C components did not display prominent difference, which is consistent with the XPS fitting result from carbon 1s core-level spectrum (Figure S3 in the Supporting Information). Accordingly, Ti(IV) oxides and Ti(III) suboxide components in the Ti 2p XPS spectrum of the 5-h laser-illuminated sample comprised a relatively larger percentage than that of the heated sample, indicating that laser is a more efficient mode to induce the conversion from Ti(II) suboxides to high-valence titanium. However, when the duration was extended to 1 week, laserilluminated Ti3C2Tx nanosheets did not degrade more rapidly than that by heat irradiation, and even in reaction residues, the laser-illuminated sample has more low-valence titanium residues (see Figures 2i and 2j). It may be due to slight aggregation of the Ti3C2Tx nanosheets after illumination oxidation, which results in poorer irradiation efficiency and the loss of plasmonic features of oxidized products that led to the weakening of the reactivity. In addition, we also fitted carbon 1s core-level XPS spectra of different Ti3C2Tx oxidative products with six subpeaks according to some previous reports,46 corresponding to C−Ti (281.9 eV), C−Ti−Tx (282.8 eV), CC (284.0 eV), C−C (285.1 eV), C−O

were located on a layer of 2D membrane, which was suggested to be amorphous carbon.29 Scanning electron microscopy (SEM) was adopted to analyze the morphology evolution of Ti3C2Tx nanosheets before and after heating and laser illumination. Figure 2a presented the morphology of fresh Ti3C2Tx nanosheets. After 5 h heating at 40 °C, small amount of oxide nanoparticles appeared at the edges and cracks of nanosheets (Figure 2b), meaning that oxidation happened first at defect sites. In contrast to the heated sample, significantly more oxide nanoparticles could be observed in laser-illuminated samples, which is indicative of a rapider oxidation rate under laser illumination. In addition, we can also see that the nanosheets after laser illumination seem to present a smaller size (Figure 2c) than that observed after 5 h of heating and may be attributed to laser-induced generation of microcracks on nanosheets. After the following room-temperature standing of a few days, the products would turn cloudy white, which indicates the generation of many TiO2 nanoparticles, which was also verified by SEM imaging (Figure 2d). X-ray photoelectron spectroscopy were used to characterize the chemical composition of original Ti3C2Tx nanosheets and oxidative products. XPS survey spectra of Ti3C2Tx samples with different oxidation states were presented in Figure 2e, and the presence of several main elements, including Ti, C, O, N, and F, was confirmed. After different oxidation durations, the intensity of O 1s peak was enhanced gradually and F 1s peak was weakened, indicating that Ti−F bonds were broken and new Ti−O bonds were formed with the increase of titanium valence states. High-resolution XPS spectra of Ti3C2Tx in Ti 2p region and C 1s region were performed to study the change of the valence and circumstance of titanium and carbon elements during oxidation. Ti 2p core-level XPS spectrum of original Ti3C2Tx nanosheets was displayed in Figure 2f, and the spectrum was fitted into four pairs of peaks (Ti 2p3/2 and Ti 2p1/2) with a fixed area ratio of 2:1. Four Ti 2p3/2 peaks were D


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Inorganic Chemistry (286.2 eV), and O−CO (289.1 eV), respectively. By comparing the C 1s XPS spectra between a laser-irradiated sample and a heat-irradiated sample (see Figures S3b and S3c in the Supporting Information), we suggested that, with the oxidation of low-valence titanium, oxygen molecules (O2) captured electrons from surface titanium atom and weakened the C−Ti bonds. With the continuous attack of oxygen, C−Ti bonds would break completely, generating TiO2, and a new π bond would form to produce CC bonds, which was the reason why the amount of CC (sp2) bonds increased markedly and C−C bonds decreased. Figures S3b and S3c also show that the 5-h laser-irradiated sample possessed a bigger share of C−C component than the heat-irradiated sample, probably because of the formation of the C−H bond derived from the reaction of CC bonds with hydrogen or hydrogen free radicals under high-power laser irradiation. With the continuous oxidation of Ti3C2Tx nanosheets, the laser effect dropped off, and the oxidation rate decreased obviously, leaving a small amount of unoxidized residues in the laserilluminated sample. As control studies, XPS spectra of the products of the resulting Ti3C2Tx solution treated by 5 h of laser illumination, followed by 2 weeks of room temperature aging, as well as 5 h of heating at 40 °C plus room temperature aging for 2 weeks were also investigated (Figure S4 in the Supporting Information). It was found that the degradation of Ti3C2Tx nanosheets in these cases was more complete, in contrast to the sample illuminated for 1 week by laser, and the peak that was assigned to the Ti−C component almost disappeared in both samples, but in relative terms, the amounts of Ti−C residues in the laser-illuminated sample were still greater than those observed for the heated one. The residues were mainly composed of amorphous carbon, TiO2, and a small amount of titanium carbides and Ti(II) suboxides. The survival of lowvalence titanium might be due to the protection of amorphous carbon membrane due to strain-induced conformal package, which, however, would not happen under heat irradiation, because of a slow reaction rate and timely stress release. In addition, according to high-resolution C 1s core-level spectra in these two samples, obviously more CC components could be found in the laser-illuminated sample than in the heated one, in accord with the results observed for the sample that was laser-illuminated for 1 week, which was indicative of moreobvious oxidation of C−C bonds under laser illumination, which was also consistent with Raman results in Figures S1d and S1e. Degradation Dynamics of Ti3C2Tx Nanosheets under Laser Illumination and Heating. To quantitatively understand the laser-induced degradation phenomenon, UV-vis-NIR spectra measurements of the solution were performed. As shown in Figure 3a, Ti3C2Tx nanosheets in water present three distinctive peaks. With increasing laser illumination time, the intensity of the 260 nm peak would increase, and the intensities of the 325 and 770 nm peaks would decrease during degradation. According to the Lambert−Beer law, the CMXene is proportional to the peak intensity. To capture the degradation rates comparable with references,29 the intensity at the plasmonic peak center was chosen to identify the concentration of Ti3C2Tx nanosheets. Thus, it was suitable for choosing the peak intensity at 770 nm, as a function of time, to track the degradation of the colloidal solution. In this paper, we employed the single exponential decay function to fit peak intensities points to an empirical function, CMXene = C0

exp(−t/τ), where CMXene represents the unreactive Ti3C2Tx nanosheets, C0 means the initial concentration of Ti3C2Tx nanosheets, and τ is the time constant (hours). As shown in Table 1, we first obtained the Ti3C2Tx degradation time Table 1. Lifetime Decay Time Constants of Ti3C2Tx Nanosheets in Solutions under Different Temperatures conditions storing at room temperature storing at 40 °C storing at 50 °C storing at 60 °C in ethanol

time constant 395 280 114 65 2907

h h h h h

constant in aqueous solution at room temperature. This time constant395 h in our work (see Figure S5)is slower than the pioneer’s reported data (9 days).29 This might be due to the size difference. The average size of our sample is 2.5 μm (Figure S2), which is much larger than the reported flake size (0.8 μm),29 which leads to the much slower dissociation rate. To evaluate whether this degradation is temperature-dependent, we tuned the storage temperature of the samples from room temperature to 60 °C, and obtained the spectra in real time. It is found that the spectra red shift and the center of absorption spectra of 770 nm is slightly broadened (see Figure S6). The plotted dynamic data are shown in Figure 3b. The fitting results were listed in Table 1, pointing out that the degradation time was shortened from 280 h to 65 h if the storage temperature was increased from 40 °C to 60 °C. The results indicated that the Ti3C2Tx degradation should be a thermally driven chemical reaction. Thus, based on the fitting time constants listed in Table 1, we could calculate a reaction activation energy of 63 ± 13 kJ/mol, using the Arrhenius equation,

E y i k = A expjjj − a zzz k RT { In the experiment, 800 nm femtosecond laser illumination on the aqueous solution could raise the temperature close to 40 °C (see Figure S7 in the Supporting Information). Thus, the control experiment was to store the vial at 40 °C. The extinctive spectra peak intensities in both cases were decreased (see Figure S8 in the Supporting Information). The stability results are shown in Figure 3c. Obviously, laser illumination created significant differences. Fitting the stability curve (Figure S7) of the peak intensity with single exponential decay function CMXene = C0 exp(−t/τ) provided a time constant of 34 h, which is extremely faster than the thermally driven oxidation (280 h). The data obtained in Figure 3c were based on the high-power femtosecond laser to demonstrate the fast illumination degradation effect. However, in practical applications, high-power femtosecond lasers are difficult to deliver into the inside of human body through optical fibers for therapeutic applications, such as laser thermal therapy. Thus, in order to enable controllable Ti3C2Tx degradation under laser illumination for more ubiquitous utilizations, we switched to a continuous-wave (CW) laser in the subsequent experiments to confirm that the laser illumination is a general method to control the Ti3C2Tx degradation. We then employed the 808 nm CW laser to illuminate the larger-sized vial (the setup is shown in Figure S9a in the Supporting Information) to track the spectrum dynamics of the solution from dark to white. The

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Figure 4. Methods and results for retarding the degradation of MXene: (a) schematics of CTAB protection on Ti3C2Tx surface; (b) schematics of NH2 coating protection on the Ti3C2Tx surface; (c) stability results under 808 laser illumination with CTAB; (d) stability results under 808 nm laser illumination with/without an amino-phenyl coating; and (e) stability results under heating of 60 °C with/without an amino-phenyl coating.

Figure 5. Schematics of MXene (Ti3C2Tx) degradation.

decay curve was showed in Figure 3d. The fitting curve suggested that the decay lifetime under this condition (largesized vial) was ∼81 h (see Figure S9b in the Supporting Information), which was still much faster than the thermally driven oxidation. We further tuned the laser wavelength and power to control the oxidation rates. Various CW lasers (808, 532, and 980 nm) were used in this study, with the same power and beam sizes, to irradiate Ti3C2Tx solution. As shown in Figure 3e, the illuminations of all three of these lasers could decrease the intensities of the peaks. The time constants of 980 and 532 nm illumination were 220 and 168 h, respectively. The SEM image also confirmed that, after absorbing 980 nm laser illumination, some nanoparticles started to appear at the edges of the plane (see Figure S10 in the Supporting Information). Clearly, the

808 nm laser was closer to the center of the extinctive spectra of Ti3C2Tx nanosheets than the 980 and 532 nm lasers. The dynamic studies suggested that the 808 nm CW laser led to more manifest irradiation effect than the two other wavelength lasers. Then, as shown in Figure 3f, we set the excitation power at 0.3−0.9 W, leading to the degradation time constant being shortened from 120 h to 45 h. The power-dependent curve in Figure 3f showed that stronger irradiation power could result in faster decay rate, indicating the oxidation could be controlled by power. All of the fitting parameters are listed in the Supporting Information. Surface Protection Retards the Degradation of Ti3C2Tx Nanosheets. Moreover, to slow down or avoid the degradation, we also tried two methods to enhance the stability of Ti3C2Tx solution under light irradiation and heating in an F


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Inorganic Chemistry

constant of ∼80 h. The femtosecond laser illumination was even more notable. The initial 5 h femtosecond laser illumination could decrease the total absorption from 0.90 to 0.67 (see Figure S7). Thus, substituting these values into the single exponential decay function CMXene = C0 exp(−t/τ), the apparent reaction rate constant during this laser illumination was calculated to be 16 h. After the femtosecond laser illumination, the Ti3C2Tx degradation time constant was 34 h. In contrast, the sample cell in the 40 °C oven had a slower degradation constant (∼280 h). The one order time constant differences indicated that laser illumination on the sample was more effective in promoting the Ti3C2Tx degradation than merely raising the temperature of the solution. For the moreeffective laser-illumination-driven degradation, the mechanisms may be beyond the description of the Arrhenius equation. The characterizations confirmed that, compared with homogeneous heating (thermally driven), laser illumination would create oxidation reaction more at the edges and defects. The ∼800 nm laser illumination was more likely to create the plasmonic excitation on Ti3C2Tx, generating electrons and holes with transient higher-energy states. These carriers then migrate into edges and defects.49 Thus, based on the pioneers’ research of plasmonic excitation-induced chemical reactions on metal nanoparticles,50−52 we proposed two possible mechanisms for the Ti3C2Tx oxidation reaction. First, because plasmonic excitation intrinsically occurs in an ultrafast time scale, inside the Ti3C2Tx structure, like other plasmonic materials, the decay and recombination of electrons with holes at defect sites can lead to significantly heating of the local sites and the environment surrounding the edges and defects immediately in a very short time. The electron−hole pair recombination might release heat in ultrafast time scale to dramatically raise the temperature at reaction sites. Thus, the local high temperature can prompt the oxidation reaction, described by the Arrhenius equation. Based on this physical picture, we roughly calculated the initial interface temperature in the Supporting Information. As shown in our roughly estimation, the femtosecond laser could efficiently elevate the interface water temperature from 20 °C to over 100 °C. In contrast, the CW laser illumination could not significantly promote the binding layer water temperature at the initial time. For CW laser illumination, the faster reaction rates in a relatively lower temperature indicated some other reaction mechanisms different from 40 °C homogeneous heating. Equally, the laser resonance illuminations generate high-energy (higher than Femi level) carriers, providing the chances to promote hot electron of Ti3C2Tx injecting into the antibonding orbitals of surrounding oxygen on surface or offering hot hole transfer between the highest occupied molecular orbital level of surface molecules and Ti3C2Tx, especially on the edges, defects and cracks, imposing the oxides stress there, and inducing oxidation of Ti−C to TiO2. Both mechanisms occurred in an ultrafast time scale. That is the reason why the femtosecond laser illumination created a notable oxidation effect, providing more initial energy for electron hole pairs to react with surface molecules or heating up the local sites. For CW laser plasmonic illumination, the average surface thermal effect might be not notable at an ultrafast time scale. Thus, the dominating mechanism might be the direct interaction between the generated electrons and interfacial molecules, creating a new channel to achieve fast Ti3C2Tx degradation. Therefore, the large absorption cross section of plasmonresonant light illumination50 was particularly critical for

oven. The first method was to introduce surfactant into Ti3C2Tx solution, and the concentration of surfactant molecule CTAB (cetyltrimethylammonium bromide) was set at 0.1 g/L. As shown in Figure 4a, a surfactant protection layer could be formed on the surface of Ti3C2Tx, and it can prevent the oxygen or H2O from direct contact with Ti3C2Tx, thereby improving the colloidal stability. The second approach was to coat a thin layer of organic molecules on Ti3C2Tx nanosheets covalently, via a diazotization reaction (Figure 4b). Thus, we increased the intensity at each peak as the metric for monitoring the concentration of the Ti3C2Tx nanosheets with coating and without coating. As shown in Figure 4c, when the Ti3C2Tx nanosheets were protected by surfactants, the degradation time constant was retarded from 80 h to 380 h, which is nearly 5 times slower. Once Ti3C2Tx nanosheets were protected by the “−NH2 groups”, the degradation time could be extended significantly, under either laser illumination (Figure 4d) or via a thermally driven mode (Figure 4e). The results suggested that surface status is critical for the degradation of Ti3C2Tx nanosheets in aqueous solution. Alternately, we also changed the storage conditions from a water solution to an ethanol solution. The stability data showed that Ti3C2Tx nanosheets in an ethanol solution did not change its vis-NIR absorption intensity, even after 24 h (time constant = 2900 h; see Figure S5). These results were consistent with pioneers’ studies that ethanol provides weaker interaction with the Ti3C2Tx surface than with water.48 In addition, if Ti3C2Tx nanosheets was stored as solid film, it was also very stable by monitoring the absorption intensity (see Figure S11 in the Supporting Information). Therefore, the combination of these results indicated that oxygen and water molecules in aqueous solutions play key roles in facilitating the degradation of Ti3C2Tx nanosheets. Proposed Mechanisms for Laser-Induced Ti3C2Tx Degradation. In summary, we have noted that either changing the physical conditions (light, heat) or chemical conditions (surface protection/modification) could control the decomposition rate of Ti3C2Tx. The laser- and heat-induced degradation processes are schematically illustrated in Figure 5. The degradation behavior of Ti3C2Tx colloidal solutions can be summarized as follows: the dissolved oxygen and water could interact with Ti3C2Tx if there is no surface protection. The degradation could accompany acidic solution formation (pH ∼4.5), indicating that the final products contain acidic components. The edge sites were more vulnerable than the basal planes under laser/thermal driven, leading to faster degradation. The oxidative sites would behave as nucleation center to initiate the growth of cracks and finally make large nanosheets fall apart into smaller sheets (Figure S12 in the Supporting Information), which would further accelerate the degradation of Ti3C2Tx nanosheets. The characterization results confirmed that, during aging at high temperature, the “branches” grow from the edge sites to the Ti3C2Tx basal plate and eventually shredded the flakes into TiO2 particles and amorphous carbon. For heating Ti3C2Tx solution in an oven, this was a temperature-driven thermodynamic reaction. The kinetics could be described by the Arrhenius equation and higher temperature could accelerate the reaction. The thermally driven approach provided homogeneous heat for the entire solution sample without specific targeting on the reaction sites. Our results pointed out that CW laser illumination only on a small portion of the sample vial created a degradation reaction G


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obtained by the setup described in Figure S9. For the 980 nm laser experiment (LSR980H), we applied a 980 nm laser with 0.7 W output energy and the beam size was ∼0.3 cm. For the 808 nm laser experiment, we applied an 808 nm CW laser with an output energy of 0.7 W, and the beam size was ∼0.3 cm. For the 532 nm laser experiment, we applied a 532 nm CW laser with an output energy of 0.7 W, and the beam size was ∼0.3 cm. Characterization. X-ray diffraction (XRD) analyses were recorded with a Model D/MAX-2500 diffractometer (Rigaku). UVvis absorption of the Ti3C2Tx solution was conducted on a UV-vis spectrometer with integrated sphere (Model UV 2600, Shimadzu, Japan). Fourier transform infrared (FT-IR) spectra were collected by a Nicolet 6700 FT-IR spectrometer. XPS measurements was performed on an X-ray photoelectron spectrometer (ESCALAB 250Xi, Thermo Scientific) using the Al Kα monochromatic beam (1486.6 eV) with an input power of 150 W, and every spectrum was corrected according to C 1s at 284.5 eV (graphite-like carbon). Morphology and microstructures of Ti3C2Tx were observed via scanning electron microscopy (SEM) (ZEISS, Model Supra55/ 3195#). High-resolution transmission electron microscopy (HRTEM) images were obtained using a field-emission transmission electron microscopy (FESEM) system (Tecnai, Model G2 F20 STWIN) at an accelerating voltage of 200 kV.

Ti3C2Tx degradation. Based on these two possible mechanisms, plasmonic light was trapped in the material and could be the effective driving force for the Ti3C2Tx degradation.

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CONCLUSIONS Manipulating the lifetime of Ti3C2Tx colloidal solutions is of importance with regard to 2D MXenes, which are providing exciting opportunities in various applications. Particularly, the plasmonic laser illumination in aqueous solution could accelerate the decay of Ti 3C2Tx nanosheets, and the degradation rate can be well-controlled by laser wavelength and power. The degradation products are smaller-sized TiO2 nanoparticles, amorphous carbon, and possibly a small amount of acid, which can create opportunities for exploring new layered multifunctional materials as well as providing more approaches for the release of MXene-capsulated drug and excretion of MXene-based implant devices. In addition, surface modification of MXene could not only extend the lifetime of MXenes but also add new functions into the material. Such results would be potentially useful for the application of MXenes in a wider field.

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METHODS

ASSOCIATED CONTENT

S Supporting Information *

Synthesis of Ti3C2Tx Nanosheets. Ti3C2Tx nanosheets were prepared by selectively etching Al atom layer of MAX phase of Ti3AlC2 (Micronano Tech. China), using the etchant solution containing LiF (Alfa, 98+%) and hydrochloric acid (Greagent, 36%−38%). In a typical synthesis process, 1 g LiF was dissolved into 20 mL of 9 mol/L hydrochloric acid, and then 1 g of Ti3AlC2 powders (200 mesh) of MAX phase was added into the etchant solution and reacted at 35 °C for 24 h under gentle stirring. Subsequently, the products were washed copiously with deionized (DI) water by centrifugation at 3500 rpm for 5 min each cycle until pH value was >6. To obtain highly dispersible nanosheets, after centrifugation, the supernatant was decanted, and the sediment was redispersed in DI water by manual shaking for 5 min. Thereafter, the dispersion solution was centrifuged at 3500 rpm for 20 min, and the resulting supernatant was collected for further test and characterization, and the concentration of nanosheets was measured by weighing the solids in dispersion solution after drying, and the nanosheets solution with specified concentration was prepared by diluting the initial concentrated solution. The Preparation of Ti3C2Tx Nanosheets-φ-NH2. Amino-groupmodified Ti3C2Tx nanosheets was prepared by diazotization reaction of p-phenylenediamine in acidic aqueous solution. In a typical synthetic process, 0.3 g of nanosheets were well-dispersed in 70 mL of DI water and then stored in a refrigerator at 4 °C for use. At the same time, 10 mL of aqueous solution containing NaNO2 of 0.69 g, 10 mL of dimethylformamide (DMF) solution containing 1.08 g of pphenylenediamine, and 10 mL of 37% hydrochloric acid were also prepared and stored in a refrigerator at 4 °C for use. Thereafter, asstored p-phenylenediamine solution, NaNO2 solution and hydrochloric acid were successively added into the Ti3C2Tx dispersion solution sitting in a water bath of 4 °C under a gentle stirring. The reaction proceeded for 4 h and then the products was washed repeatedly with DI water, absolute methanol, DMF, and acetone by centrifugation until the solution became clear. Subsequently, the products were washed by DI water several times again and freezedried for further use and characterization. Laser Illuminations. As shown in Figure 1a, we just employed the laser (Phidia-c, UPTEK Solutions) to illuminate the sample in a sealed vial. The beam size was ∼0.7 cm, and the power energy was 0.9 W. The light center frequency is 800 nm with a spectra width of ∼25 nm. The pulse duration is ∼120 fs, and the repeated frequency is 1 kHz. Figure 3c data also came from femtosecond laser irradiation. The setups are shown in Figure S7 in the Supporting Information. For Figures 3d−f, we employed CW lasers. Figure 3d and XPS data were

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b00329.

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Experimental details, calculation, fitting parameters, XRD, Raman, SEM, XPS, UV-vis, and schematic diagram (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (M. Hu). *E-mail: [email protected] (H. Chen). *E-mail: [email protected] (G. Shan). ORCID

Mingjun Hu: 0000-0002-5474-6022 Hailong Chen: 0000-0002-3456-7836 Author Contributions ∇

These authors contributed equally to this work;

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work is supported by National Natural Science Foundation of China (NSFC-21773302, NSFC-21771017, NSFC-51702009, NSFC-21603270), Fundamental Research Funds for the Central Universities, and the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB30000000). J.L. also thanks for NSFC- 21803006. Z.Y. thanks for NSFC-21804004.

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REFERENCES

(1) Anasori, B.; Lukatskaya, M. R.; Gogotsi, Y. 2D Metal Carbides and Nitrides (MXenes) for Energy Storage. Nat. Rev. Mater. 2017, 2, 16098. (2) Naguib, M.; Mashtalir, O.; Carle, J.; Presser, V.; Lu, J.; Hultman, L.; Gogotsi, Y.; Barsoum, M. W. Two-dimensional Transition Metal Carbides. ACS Nano 2012, 6, 1322−1331.

H


Article

Inorganic Chemistry (3) Naguib, M.; Mochalin, V. N.; Barsoum, M. W.; Gogotsi, Y. 25th Anniversary Article: MXenes: A New Family of Two-dimensional Materials. Adv. Mater. 2014, 26, 992−1005. (4) Alhabeb, M.; Maleski, K.; Anasori, B.; Lelyukh, P.; Clark, L.; Sin, S.; Gogotsi, Y. Guidelines for Synthesis and Processing of TwoDimensional Titanium Carbide (Ti3C2Tx MXene). Chem. Mater. 2017, 29, 7633−7644. (5) Pomerantseva, E.; Gogotsi, Y. Two-dimensional Heterostructures for Energy Storage. Nat. Energy 2017, 2, 17089. (6) Xia, Y.; Mathis, T. S.; Zhao, M.-Q.; Anasori, B.; Dang, A.; Zhou, Z.; Cho, H.; Gogotsi, Y.; Yang, S. Thickness-independent Capacitance of Vertically Aligned Liquid-crystalline MXenes. Nature 2018, 557, 409−412. (7) Guo, Z.; Zhou, J.; Zhu, L.; Sun, Z. MXene: A Promising Photocatalyst for Water Splitting. J. Mater. Chem. A 2016, 4, 11446− 11452. (8) Srimuk, P.; Halim, J.; Lee, J.; Tao, Q.; Rosen, J.; Presser, V. TwoDimensional Molybdenum Carbide (MXene) with Divacancy Ordering for Brackish and Seawater Desalination via Cation and Anion Intercalation. ACS Sustainable Chem. Eng. 2018, 6, 3739−3747. (9) Li, R.; Zhang, L.; Shi, L.; Wang, P. MXene Ti3C2: An effective 2D light-to-heat Conversion Material. ACS Nano 2017, 11, 3752− 3759. (10) Tuo, M.; Xu, C.; Mu, H.; Bao, X.; Wang, Y.; Xiao, S.; Ma, W.; Li, L.; Tang, D.; Zhang, H.; et al. Ultrathin 2D Transition Metal Carbides for Ultrafast Pulsed Fiber Lasers. ACS Photonics 2018, 5, 1808−1816. (11) Shahzad, F.; Alhabeb, M.; Hatter, C. B.; Anasori, B.; Man Hong, S.; Koo, C. M.; Gogotsi, Y. Electromagnetic Interference Shielding with 2D Transition Metal Carbides (MXenes). Science 2016, 353, 1137−1140. (12) Hu, M.; Zhang, N.; Shan, G.; Gao, J.; Liu, J.; Li, R. K. Twodimensional Materials: Emerging Toolkit for Construction of Ultrathin High-efficiency Microwave Shield and Absorber. Front. Phys. 2018, 13, 138113. (13) Huang, K.; Li, Z.; Lin, J.; Han, G.; Huang, P. Two-dimensional Transition Metal Carbides and Nitrides (MXenes) for Biomedical Applications. Chem. Soc. Rev. 2018, 47, 5109−5124. (14) Xue, Q.; Zhang, H.; Zhu, M.; Pei, Z.; Li, H.; Wang, Z.; Huang, Y.; Huang, Y.; Deng, Q.; Zhou, J.; Du, S.; Huang, Q.; Zhi, C. Photoluminescent Ti3C2 MXene Quantum Dots for Multicolor Cellular Imaging. Adv. Mater. 2017, 29, 1604847. (15) Dai, C.; Chen, Y.; Jing, X.; Xiang, L.; Yang, D.; Lin, H.; Liu, Z.; Han, X.; Wu, R. Two-Dimensional Tantalum Carbide (MXenes) Composite Nanosheets for Multiple Imaging-Guided Photothermal Tumor Ablation. ACS Nano 2017, 11, 12696−12712. (16) Mauchamp, V.; Bugnet, M.; Bellido, E. P.; Botton, G. A.; Moreau, P.; Magne, D.; Naguib, M.; Cabioc’h, T.; Barsoum, M. W. Enhanced and Tunable Surface Plasmons in Two-dimensional Ti3C2 Stacks: Electronic Structure versus Boundary effects. Phys. Rev. B: Condens. Matter Mater. Phys. 2014, 89, 235428. (17) Jiang, X.; Liu, S.; Liang, W.; Luo, S.; He, Z.; Ge, Y.; Wang, H.; Cao, R.; Zhang, F.; Wen, Q.; Li, J.; Bao, Q.; Fan, D.; Zhang, H. Broadband Nonlinear Photonics in Few-Layer MXene Ti3C2Tx (T= F, O, or OH). Laser Photonics Rev. 2018, 12, 1700229. (18) Chaudhuri, K.; Alhabeb, M.; Wang, Z.; Shalaev, V. M.; Gogotsi, Y.; Boltasseva, A. Highly Broadband Absorber Using Plasmonic Titanium Carbide (MXene). ACS Photonics 2018, 5, 1115−1122. (19) Han, X.; Huang, J.; Lin, H.; Wang, Z.; Li, P.; Chen, Y. 2D Ultrathin MXene-Based Drug-Delivery Nanoplatform for Synergistic Photothermal Ablation and Chemotherapy of Cancer. Adv. Healthcare Mater. 2018, 7, 1701394. (20) Yang, C.; Xu, D.; Peng, W.; Li, Y.; Zhang, G.; Zhang, F.; Fan, X. Ti2C3Tx Nanosheets as Photothermal Agents for Near-Infrared Responsive Hydrogels. Nanoscale 2018, 10, 15387−15392. (21) Liu, Z.; Zhao, M.; Lin, H.; Dai, C.; Ren, C.; Zhang, S.; Peng, W.; Chen, Y. 2D magnetic Titanium Carbide MXene for Cancer Theranostics. J. Mater. Chem. B 2018, 6, 3541−3548.

(22) Lin, H.; Chen, Y.; Shi, J. Insights into 2D MXenes for Versatile Biomedical Applications: Current Advances and Challenges Ahead. Adv. Sci. 2018, 5, 1800518. (23) Liu, Z.; Lin, H.; Zhao, M.; Dai, C.; Zhang, S.; Peng, W.; Chen, Y. 2D Superparamagnetic Tantalum Carbide Composite MXenes for Efficient Breast-Cancer Theranostics. Theranostics 2018, 8, 1648− 1664. (24) Lin, H.; Gao, S.; Dai, C.; Chen, Y.; Shi, J. A Two-dimensional Biodegradable Niobium Carbide (MXene) for Photothermal Tumor Eradication in NIR-I and NIR-II Biowindows. J. Am. Chem. Soc. 2017, 139, 16235−16247. (25) Liu, G.; Zou, J.; Tang, Q.; Yang, X.; Zhang, Y.; Zhang, Q.; Huang, W.; Chen, P.; Shao, J.; Dong, X. Surface Modified Ti3C2MXene Nanosheets for Tumor Targeting Photothermal/ Photodynamic/Chemo Synergistic Therapy. ACS Appl. Mater. Interfaces 2017, 9, 40077−40086. (26) Yu, X.; Cai, X.; Cui, H.; Lee, S.-W.; Yu, X.-F.; Liu, B. Fluorinefree Preparation of Titanium Carbide MXene Quantum Dots with High Near-infrared Photothermal Performances for Cancer Therapy. Nanoscale 2017, 9, 17859−17864. (27) Xu, L.; Liang, H.-W.; Yang, Y.; Yu, S.-H. Stability and Reactivity: Positive and Negative Aspects for Nanoparticle Processing. Chem. Rev. 2018, 118, 3209−3250. (28) Naguib, M.; Mashtalir, O.; Lukatskaya, M. R.; Dyatkin, B.; Zhang, C.; Presser, V.; Gogotsi, Y.; Barsoum, M. W. One-step synthesis of nanocrystalline transition metal oxides on thin sheets of disordered graphitic carbon by oxidation of MXenes. Chem. Commun. 2014, 50, 7420−7423. (29) Zhang, C. J.; Pinilla, S.; McEvoy, N.; Cullen, C. P.; Anasori, B.; Long, E.; Park, S.-H.; Seral-Ascaso, A. s.; Shmeliov, A.; Krishnan, D.; Morant, C.; Liu, X.; Duesberg, G. S.; Gogotsi, Y.; Nicolosi, V.; et al. Oxidation stability of colloidal two-dimensional titanium carbides (MXenes). Chem. Mater. 2017, 29, 4848−4856. (30) Lotfi, R.; Naguib, M.; Yilmaz, D. E.; Nanda, J.; van Duin, A. C. A Comparative Study on the Oxidation of Two-dimensional Ti3C2 MXene Structures in Different Environments. J. Mater. Chem. A 2018, 6, 12733−12743. (31) Wang, K.; Zhou, Y.; Xu, W.; Huang, D.; Wang, Z.; Hong, M. Fabrication and Thermal Stability of Two-dimensional Carbide Ti3C2 Nanosheets. Ceram. Int. 2016, 42, 8419−8424. (32) Rakhi, R. B.; Ahmed, B.; Hedhili, M. N.; Anjum, D. H.; Alshareef, H. N. Effect of Postetch Annealing Gas Composition on the Structural and Electrochemical Properties of Ti2CTx MXene Electrodes for Supercapacitor Applications. Chem. Mater. 2015, 27, 5314−5323. (33) Ghassemi, H.; Harlow, W.; Mashtalir, O.; Beidaghi, M.; Lukatskaya, M.; Gogotsi, Y.; Taheri, M. L. In situ Environmental Transmission Electron Microscopy Study of Oxidation of Twodimensional Ti3C2 and Formation of Carbon-supported TiO2. J. Mater. Chem. A 2014, 2, 14339−14343. (34) Habib, T.; Zhao, X.; Shah, S. A.; Chen, Y.; Sun, W.; An, H.; Lutkenhaus, J. L.; Radovic, M.; Green, M. J. Oxidation Stability of Ti3C2Tx MXene Nanosheets in Solvents and Composite Films. NPJ. 2D Mater. Appl. 2019, 3, 8. (35) Ahmed, B.; Anjum, H. D.; Hedhili, N. M.; Gogotsi, Y.; Alshareef, N. H. H2O2 assisted room temperature oxidation of Ti2C MXene for Li-ion battery anodes. Nanoscale 2016, 8, 7580−7587. (36) Han, M.; Yin, X.; Li, X.; Anasori, B.; Zhang, L.; Cheng, L.; Gogotsi, Y. Laminated and Two-dimensional Carbon-supported Microwave Absorbers Derived from MXenes. ACS Appl. Mater. Interfaces 2017, 9, 20038−20045. (37) Low, J.; Zhang, L.; Tong, T.; Shen, B.; Yu, J. TiO2/MXene Ti3C2 Composite with Excellent Photocatalytic CO2 Reduction Activity. J. Catal. 2018, 361, 255−266. (38) Fan, Y.; Yuan, Z.; Zou, G.; Zhang, Q.; Liu, B.; Peng, Q. Twodimensional MXene/A-TiO2 Composite with Unprecedented Catalytic Activation for Sodium Alanate. Catal. Today 2018, 318, 167− 174. I


Article

Inorganic Chemistry (39) Chertopalov, S.; Mochalin, V. N. Environment Sensitive Photoresponse of Spontaneously Partially Oxidized Ti3C2Tx MXene Thin Films. ACS Nano 2018, 12, 6109−6116. (40) Zhu, J.; Ha, E.; Zhao, G.; Zhou, Y.; Huang, D.; Yue, G.; Hu, L.; Sun, N.; Wang, Y.; Lee, L. Y. S.; Xu, C.; Wong, K.-Y.; Astruc, D.; Zhao, P. Recent Advance in MXenes: A Promising 2D Material for Catalysis, Sensor and Chemical Adsorption. Coord. Chem. Rev. 2017, 352, 306−327. (41) Lin, H.; Wang, X.; Yu, L.; Chen, Y.; Shi, J. Two-dimensional Ultrathin MXene Ceramic Nanosheets for Photothermal Conversion. Nano Lett. 2017, 17, 384−391. (42) Xuan, J.; Wang, Z.; Chen, Y.; Liang, D.; Cheng, L.; Yang, X.; Liu, Z.; Ma, R.; Sasaki, T.; Geng, F. Organic-Base-Driven Intercalation and Delamination for the Production of Functionalized Titanium Carbide Nanosheets with Superior Photothermal Therapeutic Performance. Angew. Chem. 2016, 128, 14789−14794. (43) Naguib, M.; Kurtoglu, M.; Presser, V.; Lu, J.; Niu, J.; Heon, M.; Hultman, L.; Gogotsi, Y.; Barsoum, M. W. Two-dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2. Adv. Mater. 2011, 23, 4248−4253. (44) Mashtalir, O.; Naguib, M.; Mochalin, V. N.; Dall’Agnese, Y.; Heon, M.; Barsoum, M. W.; Gogotsi, Y. Intercalation and Delamination of Layered Carbides and Carbonitrides. Nat. Commun. 2013, 4, 1716. (45) Mazza, T.; Barborini, E.; Piseri, P.; Milani, P.; Cattaneo, D.; Li Bassi, A.; Bottani, C. E.; Ducati, C. Raman Spectroscopy Characterization of TiO2 Rutile Nanocrystals. Phys. Rev. B: Condens. Matter Mater. Phys. 2007, 75, 045416. (46) Wang, Y.; Li, Y.; Qiu, Z.; Wu, X.; Zhou, P.; Zhou, T.; Zhao, J.; Miao, Z.; Zhou, J.; Zhuo, S. Fe3O4@Ti3C2 MXene Hybrids with Ultrahigh Volumetric Capacity as An Anode Material for Lithium-ion Batteries. J. Mater. Chem. A 2018, 6, 11189−11197. (47) Shah, S.; Habib, T.; Gao, H.; Gao, P.; Sun, W.; Green, M.; Radovic, M. Template-free 3D Titanium Carbide (Ti3C2Tx) MXene Particles Crumpled by Capillary Forces. Chem. Commun. 2017, 53, 400−403. (48) Maleski, K.; Mochalin, V. N.; Gogotsi, Y. Dispersions of Twodimensional Titanium Carbide MXene in Organic Solvents. Chem. Mater. 2017, 29, 1632−1640. (49) Chi, Z.; Chen, H.; Chen, Z.; Zhao, Q.; Chen, H.; Weng, Y. Ultrafast Energy Dissipation via Coupling with Internal and External Phonons in Two-Dimensional MoS2. ACS Nano 2018, 12, 8961− 8969. (50) Mukherjee, S.; Zhou, L.; Goodman, A. M.; Large, N.; AyalaOrozco, C.; Zhang, Y.; Nordlander, P.; Halas, N. J. Hot-electroninduced Dissociation of H2 on Gold Nanoparticles Supported on SiO2. J. Am. Chem. Soc. 2014, 136, 64−67. (51) Brongersma, M. L.; Halas, N. J.; Nordlander, P. Plasmoninduced Hot Carrier Science and Technology. Nat. Nanotechnol. 2015, 10, 25−34. (52) Zhou, L.; Swearer, D. F.; Zhang, C.; Robatjazi, H.; Zhao, H.; Henderson, L.; Dong, L.; Christopher, P.; Carter, E. A.; Nordlander, P.; Halas, N. J. Quantifying Hot Carrier and Thermal Contributions in Plasmonic Photocatalysis. Science 2018, 362, 69−72.

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