Photothermal Synergistic Catalysis over Defective Zn3In2S6 for CO2 Fixation.

Carbon dioxide (CO2) cycloaddition not only produces highly valued cyclic carbonate but also utilizes CO2 as C1 resources with 100% atomic efficiency. However, traditional catalytic routes still suffer from inferior catalytic efficiency and harsh reaction conditions. Developing multienergy-field catalytic technology with expected efficiency offers great opportunity for satisfied yield under mild conditions. Herein, Zn3In2S6 with sulfur vacancies (Sv) was fabricated with the assistance of cetyltrimethylammonium bromide (CTAB), which is further employed for photothermally driven CO2 cycloaddition first. Photoluminescence spectroscopy and photoelectrochemical characterization demonstrated its superior separation kinetics of photoinduced carriers induced by defect engineering. The temperature-programmed desorption (TPD) technique indicated its excellent Lewis acidity-basicity characters. Due to the combination of above merits from photocatalysis and thermal catalysis, defective Zn3In2S6-Sv achieved a yield as high as 73.2% for cyclic carbonate at 80 °C under blue LED illumination within 2 h (apparent quantum yield of 0.468% under illumination of 380 nm monochromatic light at 36 mW·cm-2), which is 2.9, 2.0, and 6.9 times higher than that in dark conditions and those of pristine Zn3In2S6 and industrial representative tetrabutylammonium bromide (TBAB) thermal-catalysis process under the same conditions, respectively. The synergistic reaction path of photocatalysis and thermal catalysis was discriminated by theoretical calculation. This work provides new insights into the photothermal synergistic catalysis CO2 cycloaddition with defective ternary metal sulfides.

Comparative Study of the Optical and Electronic Properties of Y6 Derivatives: A Theoretical Study.

A series of Y-series nonfullerene acceptors (Y-NFAs) including symmetric acceptors (Y6 and TTY6) as well as asymmetric acceptors (KY6, TY6, and KTY6) have been constructed, and the electronic structure, electronic properties, and excited-state properties have been comparatively studied. The optoelectronic properties, interfacial charge-transfer (CT) mechanism, and interfacial CT rate for the solar cells composed of PM6 as the donor and Y6 derivatives as the acceptors are investigated further. We show that asymmetric Y6 derivatives have high molecular planarity, strong and wide absorption spectra, and large intramolecular charge transfer (ICT). For the solar cells, the complexes of Y6 derivatives show increased open-circuit voltage, larger fill factor, and smaller energy loss compared to Y6. In addition, the complexes of Y6 derivatives have more charge-transfer states than Y6 in the low-energy region, such that there are multiple ways for CT generations, such as hot excitation, intermolecular electric field (IEF), and direct excitation. The detailed CT mechanism as well as interfacial CT rate depends on the type of complexes, and all Y6 derivatives have a similar magnitude of charge-transfer rate to the one of Y6. This work not only reveals the differences in performance between symmetric and asymmetric NFA but also reveals that proper terminal tuning is an effective way to improve photovoltaic properties.

A theoretical study on the excited-state deactivation paths for the A-5FU dimer.

The photostability of DNA plays a key role in the normal function of organisms. A-5FU is a base pair derivative of the A-T dimer where the methyl group is replaced by a F atom. Here, accurate static TDDFT calculations and non-adiabatic dynamic simulations are used to systematically investigate the excited-state decay paths of the A-5FU dimer related to the proton transfer and the out-of-plane twisting deformation motion of A and 5FU in the 1ππ* and 1nπ* states. CC2 is used to check the accuracy of the current TDDFT calculations. Our results show that the deformation of the C[double bond, length as m-dash]C or C[double bond, length as m-dash]N double bond in A and 5FU provides an efficient pathway for the depopulation of the lowest excited states, which can compete with the excited-state proton transfer paths in the dimer. This finding indicates that monomer-like decay paths could be important for the photostability of weakly hydrogen-bonded DNA base pairs and provide a new insight into the excited-state decay paths in base pairs and their analogues.

Solvent effects on the excited-state double proton transfer mechanism in the 7-azaindole dimer: a TDDFT study with the polarizable continuum model.

Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in the 7-azaindole (7AI) dimer were investigated using the time-dependent density functional theory (TDDFT) method. Excited-state potential energy profiles along the reaction paths in a locally excited (LE) state and a charge transfer (CT) state were calculated using the polarizable continuum model (PCM) to include the solvent effect. A series of non-polar and polar solvents with different dielectric constants were used to examine the polarity effect on the ESDPT mechanism. The present results suggest that in a non-polar solvent and a polar solvent with a small dielectric constant, ESDPT follows a concerted mechanism, similar to the case in the gas phase. In a polar solvent with a relatively large dielectric constant, however, ESDPT is likely to follow a stepwise mechanism via a stable zwitterionic intermediate in the LE state on the adiabatic potential energy surface, although inclusion of zero-point vibrational energy (ZPE) corrections again suggests the concerted mechanism. In the meantime, the stepwise reaction path involving the CT state with neutral intermediates is also examined, and is found to be less competitive than the concerted or stepwise path in the LE state in both non-polar and polar solvents. The present study provides a new insight into the experimental controversy of the ESDPT mechanism of the 7AI dimer in a solution.

Protic vs Aprotic Solvent Effect on Proton Transfer in 3-Hydroxyisoquinoline: A Theoretical Study.

In this work, the structures, energetics, and tautomerizations in 3-hydroxyisoquinoline (3HIQ) in both the ground state and the excited state have been theoretically investigated by the MP2, TDDFT, and CASPT2 methods, respectively. The solvent effect including the implicit solvent and explicit solvent on the structures, energetics, and tautomeizations are revealed. We found that the explicit solvent plays a more important role in the structures, energetics, and tautomerizations in 3HIQ than implicit solvent in both the ground state and the excited state. The proton transfer is more facilitated in explicit solvent (water or methanol) compared to that in the gas phase and in the implicit solvent in the excited state, and the reactive role of the molecular solvent is found to be related with the two linear hydrogen bonds.

Theoretical study of the excited-state double proton transfer in the (3-methyl-7-azaindole)-(7-azaindole) heterodimer.

Excited-state double proton transfer (ESDPT) in the (3-methyl-7-azaindole)-(7-azaindole) heterodimer is theoretically investigated by the long-range corrected time-dependent density functional theory method and the complete-active-space second-order perturbation theory method. The calculated potential energy profiles exhibit a lower barrier for the concerted mechanism in the locally excited state than for the stepwise mechanism through the charge-transfer state. This result suggests that the ESDPT in the isolated heterodimer is likely to follow the former mechanism, as has been exhibited for the ESDPT in the homodimer of 7-azaindole.

Theoretical study on water-mediated excited-state multiple proton transfer in 7-azaindole: significance of hydrogen bond rearrangement.

Excited-state multiple proton transfer (ESMPT) in the cluster of 7-azaindole with three water molecules [7-azaindole(H(2)O)(3)] is theoretically investigated by the TDDFT, CASPT2, and CC2 methods. Examination of the potential energy surface in the first excited state indicates that ESMPT in 7-azaindole(H(2)O)(3) proceeds initially with the rearrangement of hydrogen bond structure of water molecules from a bridged-planar isomer to a cyclic-nonplanar isomer, followed by triple proton transfer in the latter. This reaction is found to be energetically more favorable than quadruple proton transfer in the bridged-planar isomer without hydrogen bond reorganization. It is also shown that all proton-transfer processes follow a concerted mechanism rather than a stepwise mechanism. The computational results show good consistency with the unexpected experimental observations as to the electronic spectra and excited-state lifetime. In particular, the barrier of the hydrogen bond rearrangement is found to be less than 1 kcal/mol, consistent with the missing vibronic bands for 7-azaindole(H(2)O)(3) with an excess energy of more than 200 cm(-1) in the S(1) state.

The role of nitro group on the excited-state relaxation mechanism of P-Z base pair.

DNAs' photostability is significant to the normal function of organisms. P-Z is a hydrogen bonded artificial DNA base pair, where P and Z represent 2-amino-imidazo[1,2-a]-1,3,5-triazin-4(8H)one and 6-amino-5nitro-2(1H)-pyridone, respectively. The excited-state relaxation mechanism of P-Z pair is investigated using static TDDFT calculations combined with the non-adiabatic dynamic simulations at TDDFT level. The roles of nitro rotation, nitro out-of-plane deformation, and single proton transfer (SPT) along hydrogen bond are revealed. The results of potential energy profile calculations demonstrate that the SPT processes along the hydrogen bonds are unfavorable to occur statically, which is in great contrast to the natural base pair. The non-adiabatic dynamic simulations show that the excited-state nitro rotation and nitro out-of-plane deformation are the two important relaxation channels which lead to the fast internal conversion to S0 state. The SPT from Z to P is also observed, followed by distortion on P, inducing the fast internal conversion to S0 state. However, this channel (decay via SPT process) plays minor roles on the excited-state relaxation mechanism statistically. This work shows the great differences of the excited-state relaxation mechanism between the natural base pairs and artificial base pair, also sheds new light into the role of hydrogen bond and nitro group in P-Z base pair.

[Epidemiological characteristics of subclinical target organ damage in urban adult residents with hypertension in Tianjin and its relationships with renin-angiotensin-aldosterone system].

OBJECTIVE: To investigate the epidemiological characteristics of subclinical target organ damage (TOD) among urban adult residents with hypertension in Tianjin and evaluate its relationships with circulating renin-angiotensin-aldosterone system (RAAS). METHODS: An epidemiological survey was conducted on urban adult residents in Tianjin. The participants with uncomplicated hypertension were followed up to examine for target organ involvement, including left ventricular hypertrophy (LVH), carotid plaque or intima-media thickening (IMT), microalbuminuria (MAU) and estimated glomerular filtration rate (eGFR). Multivariate logistic regression was used to evaluate the relations between subclinical TOD and RAAS. RESULTS: A total of 1547 subjects with uncomplicated hypertension underwent further examinations for target organ involvement. The prevalence rates of LVH, carotid plaque, carotid IMT, MAU and eGFR < 60 ml×min(-1)×(1.73 m(2))(-1) were 37.7%, 38.2%, 35.4%, 33.7% and 4.4%, respectively. The prevalence rates were categorized according to the absence or presence of one marker, two or three markers of TOD at 20.5%, 34.7%, 33.7% and 11.1% respectively. According to the logistic regression analysis adjusting for age, gender, current smoking, current drinking, previous antihypertensive treatment, body mass index, mean systolic blood pressure, mean diastolic blood pressure, duration of hypertension and other risk factors, plasma renin activity (OR 0.870, 95%CI 0.791 - 0.958, P = 0.005) and plasma angiotensin II (OR 1.005, 95%CI 1.001 - 1.009, P = 0.021) levels were independently associated with LVH, serum aldosterone level was independently associated with carotid IMT or plaque (OR 1.025, 95%CI 1.000 - 1.050, P = 0.048) and MAU (OR 1.049, 95%CI 1.024 - 1.074, P < 0.001). CONCLUSION: Subclinical TOD is fairly common among urban adult residents with hypertension in Tianjin. And RAAS plays an important role in the pathogenesis of subclinical TOD.

Visible-near-infrared-responsive g-C3N4Hx+ reduced decatungstate with excellent performance for photocatalytic removal of petroleum hydrocarbon.

The development of photocatalysts making full use of natural light sources is highly desired for the remediation of marine oil spill pollution, which is full of challenges. Herein, we demonstrate a well-defined visible-near-infrared-responsive g-C3N4Hx+ reduced decatungstate charge-transfer salt (RCD-CTS), which possess efficient light-absorption ability ranging from visible light to the near infrared region. The RCD-CTS photocatalyst exhibits excellent performance for photocatalytic removal of petroleum hydrocarbon. The structural characterization and theoretical calculation confirmed strong chemical interaction between components and partly reduction of decatungstate results in the plasmonic properties and the absorption of near infrared light. As a results, it is proposed that"hot electrons"transfer process generated by plasmon effect promotes the efficient separation of charge-carriers. Ultimately, this work sheds light on the discovery and application of visible-near-infrared-responsive optical materials that may be exploited further in artificial photosynthesis, solar energy conversion, and phototherapy.

Theoretical study on the reactions of the cyclic trinitrogen radical toward oxygen and water.

Recently, the detection of the neutral simplest all-nitrogen ring, cyclic-N(3) radical, has been realized via various techniques, which has led to numerous studies on its structures, energetics, and spectroscopy. In particular, it has been postulated as a possible building block of high energy density materials. Yet, its intermolecular reactivity is poorly understood. In this paper, we for the first time studied the reactions of cyclic-N(3) with the widespread oxygen and water at the CCSD(T)/aug-cc-pVTZ //B3LYP/6-311++G(d,p)+ZPVE and G3B3//B3LYP/6-311++G(d,p) (italics) levels. An addition-elimination mechanism was revealed for the cyclic-N(3) + O(2) reaction that results in the elementary product N(2) + NO + (3)O with an overall barrier as high as 11.8 (11.0) kcal/mol. The calculated low rate constants (even at high temperatures) show that the cyclic-N(3) radical is stable against oxygen. The cyclic-N(3) + H(2)O reaction is associated with a quasi H-abstraction mechanism forming the product cyclic-N(3)H + OH with the rather high barrier of 35.7 (36.2) kcal/mol. This indicates that cyclic-N(3) is chemically inert toward H(2)O. Chemical implications of the present work are discussed.

Theoretical Design of Near-Infrared Fluorescent Sensor for F Anion Detection Based on 10-Hydroxybenzo[h]quinoline Backbone.

Proper design and development of near-infrared (NIR) fluorescent sensors is very important for applications in vivo. In this work, we theoretically designed a ratiometric and NIR fluorescent sensor based on the 10-hydroxybenzo[h]quinoline (HBQ) backbone via systematically investigating the substituent effects of electron-donating groups (-NH2, -CH3, -C(CH3)3) and electron-withdrawing groups (-NO2, -CN, -F, -Cl, -CF3) at the proton donor site on the proton transfer process in HBQ in both the S0 and the S1 states. According to the calculated potential energy profiles along the proton transfer as well as the photophysical properties among all the derivatives, we successfully screened out that 7NH2-HBQ is a promising fluorescent sensor exhibiting the near IR emission spectra accompanied by the large Stokes shift. The potential use of 7NH2-HBQ for F- detection among anions (F-, Cl-, and Br-) was further studied, and the results showed that 7NH2-HBQ is very sensitive and selective toward F- based on the intermolecular hydrogen bonding interaction between F- and OH bond, forming a new complex FACS0 . The ratiometric change in the fluorescence intensity could be induced by the H-F bond transfer from the O atom to the N atom in the S1 state.

[Effects of Xinfeng Capsule on behaviors and myocardial ultrastructure in adjuvant arthritis rats].

OBJECTIVE: To observe the effects of Xinfeng Capsule (XFC), a compound Chinese herbal medicine, on behaviors and myocardial ultrastructure in adjuvant arthritis (AA) rats. METHODS: Fifty-five rats were randomly divided into normal control group, untreated group, methotrexate (MTX) group, Tripterygium wilfordii glycosides tablet (TGT) group and XFC group. There were 11 rats in each group. Except for those in the normal control group, the rats in the other groups were all intracutaneously given 0.1 ml Freund's complete adjuvant in the right hind limb. Changes of behaviors and myocardial ultrastructure of the rats in different groups were observed. RESULTS: Voix pedis' swelling and arthritis index in XFC, MTX and TPT groups were all obviously improved as compared with the untreated group. After XFC treatment, the autonomic activities were obviously increased, number of errors in exercise period and test period were obviously decreased, step-down latency (SDL) was lengthened and escape latency (EL) was shortened. Overall structure of myocardial myofibril and the majority of cristae was intact in XFC group. The effects of XFC in improving the behaviors and myocardial ultrastructure were better than those of MTX and TPT. CONCLUSION: Changes of behaviour and myocardial ultrastructure of AA rats can be observed. XFC can improve the myocardial ultrastructure of AA rats as well as their behaviors.

Carbon Excess C3N: A Potential Candidate as Li-Ion Battery Material.

Xu et al.'s recent experimental work ( Adv. Mater. 2017, 29, 1702007) suggested that C3N is a potential candidate as Li-ion battery with unusual electrochemical characteristics. However, the obvious capacity loss (from 787.3 to 383.3 mA h·g-1) occurs after several cycles, which restricts its high performance. To understand and further solve this issue, in the present study, we have studied the intercalation processes of Li ions into C3N via first-principle simulations. The results reveal that the Li-ion theoretical capacity in pure C3N is only 133.94 mA h·g-1, the value is obviously lower than experimental one. After examining the experimental results in detail, it is found that the chemical component of the as-generated C xN structure is actually C2.67N with N excess. In this case, the calculated theoretical capacity is 837.06 mA h·g-1, while part of Li ions are irreversibly trapped in C2.67N, resulting in the capacity loss. This phenomenon is consistent with the experimental results. Accordingly, we suggest that N excess C3N, but not pure C3N, is the proposed Li-ion battery material in Xu et al.'s experiment. To solve the capacity loss issue and maintain the excellent performance of C3N-based anode material, the C3N with slightly excess C (C3.33N), which has been successfully fabricated in the experiment, is considered in view of its relatively low chemical activity as compared with N excess C3N. Our results reveal that the C excess C3N is a potential Li-ion battery material, which exhibits the low open circle voltage (0.12 V), high reversible capacity (840.35 mA h·g-1), fast charging/discharging rate, and good electronic conductivity.

Diosgenin inhibits angiotensin II-induced extracellular matrix remodeling in cardiac fibroblasts through regulating the TGF­ß1/Smad3 signaling pathway.

The proliferation of cardiac fibroblasts (CFs) and deposition of extracellular matrix (ECM) proteins are pivotal in the development of cardiac fibrosis. Recent studies have indicated that diosgenin may inhibit high glucose­induced renal tubular fibrosis; however, to the best of our knowledge, no studies have focused on the effects of diosgenin on cardiac fibrosis. Therefore, the present study aimed to explore the effects of diosgenin on angiotensin II (Ang II)­induced ECM remodeling, and its possible mechanism in rat CFs. CFs were pre­incubated with diosgenin (1, 5 and 10 µM) for 24 h and were then stimulated with Ang II (100 nM) for 24 h. Cell proliferation was estimated using the MTS assay. The expression levels of α­SMA, fibronectin, collagen I, TGF­ß1, in addition to phosphorylation of Smad3 were detected by western blotting. The results demonstrated that diosgenin inhibited Ang II­induced CF proliferation and the differentiation of CFs to myofibroblasts. In addition, diosgenin was able to inhibit Ang II­induced ECM expression in rat CFs. Furthermore, diosgenin inhibited Ang II­induced expression of transforming growth factor­ß1 (TGF­ß1) and Smad3 phosphorylation in CFs. Taken together, these results suggest that diosgenin may inhibit Ang II­induced ECM remodeling by suppressing the TGF­ß1/Smad3 signaling pathway in rat CFs. Therefore, diosgenin may possess therapeutic potential for the treatment of cardiac fibrosis.

Role of miRNA-1 in regulating connexin 43 in ischemia-reperfusion heart injury: a rat model.

MiRNA-1 may participate in regulating ischemia-reperfusion injury (IRI) by affecting the expression and distribution of connexin 43 (Cx43). The aim of this study is to investigate miR-1 expression and its potential role in regulating Cx43 during ischemic postconditioning (IPOST) in a rat model. Fifty-five Wistar male rats were randomly divided into five groups: N, IR, IPOST, agomir-1, and antagomir-1 group. The hearts were perfused with the Langendorff system. The reperfusion arrhythmia (RA) and myocardial infarct size were observed and recorded. The miRNA-1 expression and the Cx43 expression and distribution were assessed by RT-PCR, immunoblotting, and immunohistochemistry. First, the RA score in the IR group was higher than that in the control group, whereas there was no difference between the IPOST and antagomir-1 groups. Second, the myocardial infarct size was larger in the agomir-1 than in the IPOST group; there was no difference between the antagomir-1 and the IPOST group. Third, the miRNA-1 expression increased by 78% in the agomir-1 group but decreased by 32% in the antagomir-1 group compared with the IPOST group. Fourth, compared with the Control group, the Cx43 expression in the IR group decreased, the Cx43 expression decreased in the agomir-1 group compared with the IPOST group. Fifth, the distribution of Cx43 was irregular and disorganized in the IR and agomir-1 groups. In the IPOST and antagomir-1 groups, Cx43 was neatly distributed in the intercalated disk area. Our findings suggest that IPOST can inhibit the up-regulation of miRNA-1 induced by ischemia-reperfusion and that the down-regulation of miRNA-1 can prevent the decrease and redistribution of Cx43, which will protect the heart from IRI.

Atomic Insight into the Origin of Various Operation Voltages of Cation-Based Resistance Switches.

Low operation voltage (VSET), which means low power consumption and good stability, is one of the most important factors in designing the resistance switches with high performance. However, the atomic details for the various VSET values of such devices are still lacking, which hinders their further improvement. In the present study, by taking Ag/Ta2O5/Pt (VSET = 0.6 V) and Cu/Ta2O5/Pt (VSET = 2.0 V) as the examples, we have examined the switching mechanisms of these two cation-based devices by using first principle simulation. Several possible reasons have been addressed to explain the much lower VSET of Ag/Ta2O5/Pt than that of Cu/Ta2O5/Pt: (i) the faster diffusion of Ag ions in Ta2O5 compared to Cu ions; (ii) the more preferable nucleation process of Ag ions at Pt/Ta2O5 interface compared to Cu ions; (iii) the lower Schottky barrier height (SBH) of Ag/Ta2O5/Pt than that of Cu/Ta2O5/Pt. On the basis of these results, several key factors have been suggested to design the cation-based resistance switches (oxidizable-metal/Ta2O5/inert-metal) with low VSET values: (i) the weak interaction strength between oxidizable metal ions and Ta2O5 surface; (ii) the low formation energy of oxidizable metal ions on inert electrode; (iii) the low SBH, which could be controlled by tuning the ambient water pressure during the device fabrication process.

Penta-graphene: A Promising Anode Material as the Li/Na-Ion Battery with Both Extremely High Theoretical Capacity and Fast Charge/Discharge Rate.

Recently, a new two-dimensional (2D) carbon allotrope named penta-graphene was theoretically proposed ( Zhang , S. ; et al. Proc. Natl. Acad. Sci. U.S.A. 2015 , 112 , 2372 ) and has been predicted to be the promising candidate for broad applications due to its intriguing properties. In this work, by using first-principles simulation, we have further extended the potential application of penta-graphene as the anode material for a Li/Na-ion battery. Our results show that the theoretical capacity of Li/Na ions on penta-graphene reaches up to 1489 mAh·g-1, which is much higher than that of most of the previously reported 2D anode materials. Meanwhile, the calculated low open-circuit voltages (from 0.24 to 0.60 V), in combination with the low diffusion barriers (≤0.33 eV) and the high electronic conductivity during the whole Li/Na ions intercalation processes, further show the advantages of penta-graphene as the anode material. Particularly, molecular dynamics simulation (300 K) reveals that Li ion could freely diffuse on the surface of penta-graphene, and thus the ultrafast Li ion diffusivity is expected. Superior performance of penta-graphene is further confirmed by comparing with the other 2D anode materials. The light weight and unique atomic arrangement (with isotropic furrow paths on the surface) of penta-graphene are found to be mainly responsible for the high Li/Na ions storage capacity and fast diffusivity. In this regard, except penta-graphene, many other recently proposed 2D metal-free materials with pentagonal Cairo-tiled structures may be the potential candidates as the Li/Na-ion battery anodes.

Monolayer Ti2CO2: A Promising Candidate for NH3 Sensor or Capturer with High Sensitivity and Selectivity.

Ti2C is one of the thinnest layers in MXene family with high potential for applications. In the present study, the adsorption of NH3, H2, CH4, CO, CO2, N2, NO2, and O2 on monolayer Ti2CO2 was investigated by using first-principles simulations to exploit its potential applications as gas sensor or capturer. Among all the gas molecules, only NH3 could be chemisorbed on Ti2CO2 with apparent charge transfer of 0.174 e. We further calculated the current-voltage (I-V) relation using the nonequilibrium Green's function (NEGF) method. The transport feature exhibits distinct responses with a dramatic change of I-V relation before and after NH3 adsorption on Ti2CO2. Thus, we predict that Ti2CO2 could be a promising candidate for the NH3 sensor with high selectivity and sensitivity. On the other hand, the adsorption of NH3 on Ti2CO2 could be further strengthened with the increase of applied strain on Ti2CO2, while the adsorption of other gases on Ti2CO2 is still weak under the same strain, indicating that the capture of NH3 on Ti2CO2 under the strain is highly preferred over other gas molecules. Moreover, the adsorbed NH3 on Ti2CO2 could be escapable by releasing the applied strain, which indicates the capture process is reversible. Our study widens the application of monolayer Ti2CO2 not only as the battery material, but also as the potential gas sensor or capturer of NH3 with high sensitivity and selectivity.

Theoretical investigation on the healing mechanism of divacancy defect in CNT growth by C2H2 and C2H4.

Experimental studies have shown that chemical vapor decomposition method by using C2H2/C2H4 as carbon source could dramatically decrease the defects in prepared CNT. However, the inherent mechanism with regards to reduction of defects is quite unclear. In the present paper, density functional theory is used to study the healing process of CNT with divacancy defect by C2H2/C2H4 molecule. The healing processes undergo three evolution steps: (i) the chemisorption of the first C2H2/C2H4 molecule on defective CNT; (ii) the insertion of C atoms from C2H2/C2H4 molecule into defective CNT; (iii) the removal of the H atoms on CNT, forming perfect CNT. The estimated adsorption energy barrier of C2H2/C2H4 molecules on defective CNT is within the range from 1.10 to 1.63 eV, and the eventual formation of CNT is strongly exothermic (4.40/4.54 eV in (8, 0) CNT). In light of the unique conditions of CNT synthesis, i.e., high temperature in a closed container, such healing processes could most likely take place. Therefore, we propose that during CNT synthesis procedures, both C2H2 and C2H4 could act as a carbon source and the defect healer.