Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels
The diffusion behavior of fluid water in nanochannels with hydroxylation of silica gel and silanization of different modified chain lengths was simulated by the equilibrium molecular dynamics method. The diffusion coefficient of fluid water was calculated by the Einstein method and the Green–Kubo me...
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MDPI AG
2021-07-01
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| Series: | Molecules |
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| Online Access: | https://www.mdpi.com/1420-3049/26/13/4030 |
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| author | Gengbiao Chen Zhiwen Liu |
| author_facet | Gengbiao Chen Zhiwen Liu |
| author_sort | Gengbiao Chen |
| collection | DOAJ |
| description | The diffusion behavior of fluid water in nanochannels with hydroxylation of silica gel and silanization of different modified chain lengths was simulated by the equilibrium molecular dynamics method. The diffusion coefficient of fluid water was calculated by the Einstein method and the Green–Kubo method, so as to analyze the change rule between the modification degree of nanochannels and the diffusion coefficient of fluid water. The results showed that the diffusion coefficient of fluid water increased with the length of the modified chain. The average diffusion coefficient of fluid water in the hydroxylated nanochannels was 8.01% of the bulk water diffusion coefficient, and the diffusion coefficients of fluid water in the –(CH<sub>2</sub>)<sub>3</sub>CH<sub>3</sub>, –(CH<sub>2</sub>)<sub>7</sub>CH<sub>3</sub>, and –(CH<sub>2</sub>)<sub>11</sub>CH<sub>3</sub> nanochannels were 44.10%, 49.72%, and 53.80% of the diffusion coefficients of bulk water, respectively. In the above four wall characteristic models, the diffusion coefficients in the <i>z</i> direction were smaller than those in the other directions. However, with an increase in the silylation degree, the increased self-diffusion coefficient due to the surface effect could basically offset the decreased self-diffusion coefficient owing to the scale effect. In the four nanochannels, when the local diffusion coefficient of fluid water was in the range of 8 Å close to the wall, Dz was greater than Dxy, and beyond the range of 8 Å of the wall, the Dz was smaller than Dxy. |
| first_indexed | 2024-03-10T09:50:49Z |
| format | Article |
| id | doaj.art-74e4d516dd8a4739b1e42cac043c129f |
| institution | Directory Open Access Journal |
| issn | 1420-3049 |
| language | English |
| last_indexed | 2024-03-10T09:50:49Z |
| publishDate | 2021-07-01 |
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| series | Molecules |
| spelling | doaj.art-74e4d516dd8a4739b1e42cac043c129f2023-11-22T02:46:53ZengMDPI AGMolecules1420-30492021-07-012613403010.3390/molecules26134030Effect of Modification on the Fluid Diffusion Coefficient in Silica NanochannelsGengbiao Chen0Zhiwen Liu1College of Automotive and Mechanical Engineering, Changsha University of Science and Technology, Changsha 410114, ChinaCollege of Automotive and Mechanical Engineering, Changsha University of Science and Technology, Changsha 410114, ChinaThe diffusion behavior of fluid water in nanochannels with hydroxylation of silica gel and silanization of different modified chain lengths was simulated by the equilibrium molecular dynamics method. The diffusion coefficient of fluid water was calculated by the Einstein method and the Green–Kubo method, so as to analyze the change rule between the modification degree of nanochannels and the diffusion coefficient of fluid water. The results showed that the diffusion coefficient of fluid water increased with the length of the modified chain. The average diffusion coefficient of fluid water in the hydroxylated nanochannels was 8.01% of the bulk water diffusion coefficient, and the diffusion coefficients of fluid water in the –(CH<sub>2</sub>)<sub>3</sub>CH<sub>3</sub>, –(CH<sub>2</sub>)<sub>7</sub>CH<sub>3</sub>, and –(CH<sub>2</sub>)<sub>11</sub>CH<sub>3</sub> nanochannels were 44.10%, 49.72%, and 53.80% of the diffusion coefficients of bulk water, respectively. In the above four wall characteristic models, the diffusion coefficients in the <i>z</i> direction were smaller than those in the other directions. However, with an increase in the silylation degree, the increased self-diffusion coefficient due to the surface effect could basically offset the decreased self-diffusion coefficient owing to the scale effect. In the four nanochannels, when the local diffusion coefficient of fluid water was in the range of 8 Å close to the wall, Dz was greater than Dxy, and beyond the range of 8 Å of the wall, the Dz was smaller than Dxy.https://www.mdpi.com/1420-3049/26/13/4030porous silica gelhydroxylationsilylationwall characteristicsdiffusion coefficient |
| spellingShingle | Gengbiao Chen Zhiwen Liu Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels Molecules porous silica gel hydroxylation silylation wall characteristics diffusion coefficient |
| title | Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels |
| title_full | Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels |
| title_fullStr | Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels |
| title_full_unstemmed | Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels |
| title_short | Effect of Modification on the Fluid Diffusion Coefficient in Silica Nanochannels |
| title_sort | effect of modification on the fluid diffusion coefficient in silica nanochannels |
| topic | porous silica gel hydroxylation silylation wall characteristics diffusion coefficient |
| url | https://www.mdpi.com/1420-3049/26/13/4030 |
| work_keys_str_mv | AT gengbiaochen effectofmodificationonthefluiddiffusioncoefficientinsilicananochannels AT zhiwenliu effectofmodificationonthefluiddiffusioncoefficientinsilicananochannels |