| 1. |
- Li, Xuechao, et al.
(författare)
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Direct transformation of n-alkane into all-trans conjugated polyene via cascade dehydrogenation
- 2021
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Ingår i: National Science Review. - : Oxford University Press. - 2095-5138 .- 2053-714X. ; 8:10
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Tidskriftsartikel (refereegranskat)abstract
- Selective C(sp(3))-H activation is of fundamental importance in processing alkane feedstocks to produce high-value-added chemical products. By virtue of an on-surface synthesis strategy, we report selective cascade dehydrogenation of n-alkane molecules under surface constraints, which yields monodispersed all-trans conjugated polyenes with unprecedented length controllability. We are also able to demonstrate the generality of this concept for alkyl-substituted molecules with programmable lengths and diverse functionalities, and more importantly its promising potential in molecular wiring.
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| 2. |
- Chen, Hao, et al.
(författare)
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A DFT study of the electronic structures and optical properties of (Cr, C) co-doped rutile TiO2
- 2018
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Ingår i: Chemical Physics. - : Elsevier. - 0301-0104 .- 1873-4421. ; 501, s. 60-67
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Tidskriftsartikel (refereegranskat)abstract
- To get an effective doping model of rutile TiO2, we systematically study geometrical parameters, density of states, electron densities, dielectric functions, optical absorption spectra for the pure, C mono-doping, Cr mono-doping and (Cr,C) co-doping rutile TiO2, using density functional calculations. We find that a C doped system presents higher stability under Ti-rich condition, while Cr doped and (Cr,C) co-doped systems are more stable under O-rich condition. For (Cr,C) co-doping situation, the imaginary part of the dielectric function reflects the higher energy absorption efficiency for incident photons. Moreover, co-doping system exhibits much bigger red-shift of optical absorption edge compared with Cr/C single doping systems, because of the great reduction of the direct band gap. The calculated optical absorption spectra show that the (Cr,C) co-doping rutile TiO2 has higher photocatalytic activity in the visible light region.
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| 3. |
- Chen, Hao, et al.
(författare)
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A DFT study on modification mechanism of (N,S) interstitial co-doped rutile TiO2
- 2018
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Ingår i: Chemical Physics Letters. - : Elsevier B.V.. - 0009-2614 .- 1873-4448. ; 695, s. 8-18
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Tidskriftsartikel (refereegranskat)abstract
- To obtain a more efficient (N,S) co-doping scheme, we systematically analyze the geometrical parameters, density of states, charge densities, relative dielectric functions and UV–Vis absorption spectra for pure, N/S substitution/interstitial doped and (N,S) substitution/interstitial co-doped TiO2 by using density functional calculations. Compared with (N,S) substitution co-doping, (N,S) interstitial co-doping TiO2 exhibits a more obvious red-shift of absorption edge, because of the band gap is further reduced. Furthermore, there are shallow impurity levels coupling with the top of valence band. The calculated UV–Vis absorption spectra illustrate that (N,S) interstitial co-doping TiO2 has much higher photocatalytic activity in the visible light region. © 2018
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| 4. |
- Hao, Zhengming, et al.
(författare)
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Converting n-Alkanol to Conjugated Polyenal on Cu(110) Surface at Mild Temperature
- 2022
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Ingår i: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 13:14, s. 3276-3282
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Tidskriftsartikel (refereegranskat)abstract
- Achieving C(sp(3))-H activation at a mild temperature is of great importance from both scientific and technologic points of view. Herein, on the basis of the on-surface synthesis strategy, we report the significant reduction of the C(sp(3))-H activation barrier, which results in the full C(sp(3))-H to C(sp(2))-H transformation of n-alkanol (octacosan-1-ol) at a mild temperature as low as 350 K on the Cu(110) surface, yielding the conjugated polyenal (octacosa-tridecaenal) as the final product. The reaction mechanism is revealed by the combined scanning tunneling microscope, density functional theory, and synchrotron radiation photoemission spectroscopy.
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| 5. |
- Hao, Zhengming, et al.
(författare)
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From n-alkane to polyacetylene on Cu (110): Linkage modulation in chain growth
- 2022
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Ingår i: Science in China Series B. - : SCIENCE PRESS. - 1674-7291 .- 1869-1870. ; 65:4, s. 733-739
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Tidskriftsartikel (refereegranskat)abstract
- Direct coupling or transformation of inert alkanes based on the selective C-H activation is of great importance for both chemistry and chemical engineering. Here, we report the coupling of polyenes that are transformed from n-dotriacontane (n-C32H66) through on-surface cascade dehydrogenation on Cu (110) surface, leading to the formation of polyacetylene (PA). Three distinct linkages have been resolved by scanning tunneling microscope (STM) and noncontact atomic force microscope (nc-AFM). Apart from the alpha-type linkage which is the stemless coupling of the terminal C-C double bond in trans-configuration, beta- and gamma-type linkages appear as knots or defects which are, in fact, the C-C couplings in cis-configurations. Interestingly, the "defects" can be effectively suppressed by adjusting the surface coverage, thus making it of general interest for uniform structure modulation.
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| 6. |
- Li, Xuechao, et al.
(författare)
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Pyridinic Nitrogen Modification for Selective Acetylenic Homocoupling on Au(111)
- 2023
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 145:8, s. 4545-4552
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Tidskriftsartikel (refereegranskat)abstract
- On-surface acetylenic homocoupling has been proposed to construct carbon nanostructures featuring sp hybrid-ization. However, the efficiency of linear acetylenic coupling is far from satisfactory, often resulting in undesired enyne products or cyclotrimerization products due to the lack of strategies to enhance chemical selectivity. Herein, we inspect the acetylenic homocou-pling reaction of polarized terminal alkynes (TAs) on Au(111) with bond-resolved scanning probe microscopy. The replacement of benzene with pyridine moieties significantly prohibits the cyclotrimerization pathway and facilitates the linear coupling to produce well-aligned N-doped graphdiyne nanowires. Combined with density functional theory calculations, we reveal that the pyridinic nitrogen modification substantially differentiates the coupling motifs at the initial C-C coupling stage (head-to-head vs head-to-tail), which is decisive for the preference of linear coupling over cyclotrimerization.
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| 7. |
- Wang, Xuechao, et al.
(författare)
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A study on kinematics of electric-bicycle-rider in car collisions based on traffic accident data
- 2013
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Ingår i: Proceedings - 2013 5th Conference on Measuring Technology and Mechatronics Automation, ICMTMA 2013. - 9780769549323 ; , s. 106-109
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Konferensbidrag (refereegranskat)abstract
- The impact scenarios, impact velocity were investigated based on 224 car-electric bicycle collision cases in IVAC (In-depth Investigation of Car Accident in Changsha) database. Cars were classified into three types: sedan, SUV and one box. According to analysis of traffic accident data, car-electric bicycle collision models were built up by using MADYMO. In order to analyze the kinematics of electric-bicycle-riders, this paper conducted a series of numerical experiments by changing the types of cars. Results show that the most prominent impact modes were frontal impact (54%) and side impact (33%), rider's head tend to strike sedan at upper part of the windscreen', 'SUV at the front end of bonnet, and one box at lower part of the windscreen, The peak values of head's and pelvis' acceleration were higher and occurred earlier when a SUV or one box impacted with electric bicycle.
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