Artykuły w czasopismach: „Molecular adsorption”

1

Zhong, Shuying, Fanghua Ning, Fengya Rao, Xueling Lei, Musheng Wu i Lang Zhou. "First-principles study of nitrogen and carbon monoxide adsorptions on silicene". International Journal of Modern Physics B 30, nr 25 (28.09.2016): 1650176. http://dx.doi.org/10.1142/s0217979216501769.

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Atomic adsorptions of N, C and O on silicene and molecular adsorptions of N2 and CO on silicene have been investigated using the density functional theory (DFT) calculations. For the atomic adsorptions, we find that the N atom has the most stable adsorption with a higher adsorption energy of 8.207 eV. For the molecular adsorptions, we find that the N2 molecule undergoes physisorption while the CO molecule undergoes chemisorption, the corresponding adsorption energies for N2 and CO are 0.085 and 0.255 eV, respectively. Therefore, silicene exhibits more reactivity towards the CO adsorption than the N2 adsorption. The differences of charge density and the integrated charge calculations suggest that the charge transfer for CO adsorption ([Formula: see text]0.015[Formula: see text]) is larger than that for N2 adsorption ([Formula: see text]0.005[Formula: see text]). This again supports that CO molecule is more active than N2 molecule when they are adsorbed onto silicene.

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Wanaguru, Prabath, Asok K. Ray i Qiming Zhang. "Influence of H, H2, O and O2 on Armchair SiGe Nanotubes: A Theoretical Study". Journal of Nanoscience and Nanotechnology 16, nr 4 (1.04.2016): 3447–56. http://dx.doi.org/10.1166/jnn.2016.12342.

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A systematic, hybrid density functional theory study of interaction between SiGe nanotubes (SiGeNTs) and X (X = H, O, H2 and O2) have been performed using the hybrid functional B3LYP and an all electron 3-21G* basis set implemented in GAUSSIAN 09 suite of software. All possible internal and external adsorption sites were considered, and it was found that H prefers to move onto top of an atom site while O prefers to incorporate into NT wall by breaking the bonds. Adsorption energies for H is ∼2.0 eV and for O it is ∼5.0 eV. Controlled adsorption of atomic H and several molecular O give rises to defect density states in the frontier orbital region. H rich adsorptions predict the difference between highest occupied molecular orbital (HOMO) energy and the lowest unoccupied molecular orbital (LUMO) energy increase while O rich adsorptions predict the decrease in HOMO-LUMO energy gap. O and O2 adsorptions predict definite ionic bonding character while H atomic adsorptions predict covalent bonding. H2 is very neutral towards the adsorption into SiGeNTs and clearly shows the physisorption adsorption. Considering the all adsorptions, the adsorptions happened within the Si vicinity of the SiGeNT shows the most stable and preferred adsorption region.

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Zhao, Fei, XiShang Sun, Ruifeng Lu i Lihua Kang. "Adsorption of methanol, methanal, toluene, ethylbenzene, and styrene in zeolites: a grand canonical Monte Carlo simulation study". Canadian Journal of Chemistry 95, nr 12 (grudzień 2017): 1241–47. http://dx.doi.org/10.1139/cjc-2017-0218.

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In this study, the adsorption behaviors of methanol, methanal, toluene, ethylbenzene, and styrene molecules in FAU, FER, CON, and MWW zeolites were investigated. The adsorption isotherms of the five adsorbates in the four zeolites at 298 and 350 K were simulated using grand canonical Monte Carlo simulations. Moreover, binary component adsorptions were considered. The results revealed that the saturated adsorption capacity of single components in different zeolites decreased in the order of FAU > MWW > CON > FER, and the adsorption capacity of the five adsorbates in the same zeolite decreased in the order of methanal > methanol > toluene > styrene > ethylbenzene. The equilibrium adsorption capacity slightly decreased with increasing temperature. In terms of binary component adsorption, intense competition existed between the smaller adsorbed molecules. As the differences among the molecular structures increased, the competition in adsorption became more intense.

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Godo, Masazumi, Takeshi Takatsuka, Mutsuya Tomonari, Kunio Miura, Seiichi Takami, Momoji Kubo i Akira Miyamoto. "Adsorption Behavior of Chemical Contaminants by Molecular Simulation". Journal of the IEST 46, nr 1 (14.09.2003): 98–102. http://dx.doi.org/10.17764/jiet.46.1.7450w638377v5872.

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The adsorption process of chemical contaminants on silicon wafers was investigated by using molecular mechanics, molecular dynamics, Monte Carlo method, and computer graphics. The adsorption energy of organic gaseous contaminants, such as DBP, DOP, and D5, on the hydrogen terminated silicon surface and its oxide surface, were estimated and compared. The adsorption energy of chemical contaminants was larger than that of low molecular weight species, such as benzene, H2O and NH3. The adsorption energy on the hydrogen terminated silicon surface was smaller than that on its oxide surface. The equilibrium adsorption amount on the silicon wafer was also calculated. It was indicated that the configuration of the adsorbed DBP molecules over its gas concentration of 1.9x103 ng/m3 showed multi-layer adsorption. It was indicated that adsorption energy and the equilibrium adsorption amount is a good index to estimate the adsorption properties of organic molecules.

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Liu, Minqin, Yang Ding, Shimeng Peng, Yang Lu, Zhi Dang i Zhenqing Shi. "Molecular fractionation of dissolved organic matter on ferrihydrite: effects of dissolved cations". Environmental Chemistry 16, nr 2 (2019): 137. http://dx.doi.org/10.1071/en18235.

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Environmental contextCarbon sequestration and dynamics are influenced by adsorptive fractionation of dissolved organic matter (DOM) on minerals. We found that the molecular fractionation of DOM on ferrihydrite was highly dependent on the presence of Na, Ca and Cu ions in water. These results advance our mechanistic understanding of the dynamic behaviour of DOM, and contribute to predicting carbon cycling and contaminant behaviour in the natural environment. AbstractThe adsorptive fractionation of dissolved organic matter (DOM) at the ferrihydrite and water interface is a key geochemical process controlling DOM compositions and reactivity, thus affecting carbon cycling and contaminant behaviour in the environment. However, the effects of cations on DOM fractionation and the underlying mechanisms are poorly understood. In this study, Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with spectroscopic methods were employed to investigate molecular fractionation of DOM on ferrihydrite under different cations in the background electrolytes, including Na, Ca, and Cu ions. The results indicated that DOM fractionation was influenced by the combined effects of cation type, intrinsic molecular property, and extent of DOM adsorption. DOM adsorption on ferrihydrite exhibited the strongest and the weakest fractionation under Na and Ca background electrolytes, respectively. Both Ca and Cu background electrolytes reduced the adsorption of highly unsaturated and phenolic/polyphenolic molecules with high molecular weight and number of O atoms. In addition to the molecular acidity, the complexation of Ca and Cu ions to DOM binding sites and the coagulation effect of divalent cations may affect molecular fractionation. Additionally, DOM fractionation was enhanced with increasing DOM adsorption. Our results contribute to predicting carbon cycling and contaminant behaviour in the natural environment.

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Botelho do Rego, A. M., Anna Maria Ferrari, M. Rei Vilar, J. El Beghdadi i R. Naaman. "Molecular Adsorption on GaAs Studied by HREELS". Solid State Phenomena 99-100 (lipiec 2004): 247–50. http://dx.doi.org/10.4028/www.scientific.net/ssp.99-100.247.

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Gallium arsenide coating by molecular layers is a of increasing interest both for its surface passivation and for its use as a chemical or biochemical sensor. The surface state of GaAs and the nature of the molecular functionality to be bound to the surface are very important to assure good and durable adhesion. This work, using both the vibrational and the electronic energy loss range of high resolution electron energy loss spectra, showed that the water content in the solvent – acetonitrile – has a dramatic effect on the amount of phenylphosphonic acid molecules adsorbed on the GaAs substrate. There is a poor molecular adsorption for water contents ranging from 0 to 4% volume: HREELS spectrum is always a combination of the substrate and the adsorbed molecule spectra. For a water content of 5% there is an abrupt jump in the HREELS spectra shape: they become typical of phenyl groups in the electronic region. In the vibrational region, the typical C-H stretching peaks of aliphatic chains disappear showing that the extreme surface is exclusively covered by phenyl functions. Also for the samples, where a large adsorption occurs, surfaces become negatively charged under electron irradiation showing the existence of a large number of traps for incident electrons. Sonication of such well covered substrates destroys intermolecular bonds but keeps molecules that are chemically bound to the substrate.

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Liu, Pingan, Junpeng Liu i Mengjun Wang. "Adsorption of ethanol molecules on the Al (1 1 1) surface: a molecular dynamic study". Royal Society Open Science 6, nr 1 (styczeń 2019): 181189. http://dx.doi.org/10.1098/rsos.181189.

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The adsorption process of ethanol molecules on Al slabs was investigated by molecular dynamic simulations with a ReaxFF force field. The force field used in this paper has been validated by comparing adsorption energy results with quantum mechanical (QM) calculations. All simulations were performed under the canonical (NVT) ensemble. The single-molecule adsorption simulation shows that the hydroxyl group plays a more important role in the whole progress than the ethyl group. Besides, decomposition of hydroxyl groups was also observed during multimolecule adsorption processes. Simulations of adsorption processes of Al slab by ethanol molecules at different temperatures and pressures (controlled by the number of ethanol molecules) was also performed. System energy and radial distribution function (RDF) plots were invoked to describe adsorption processes and centro-symmetry parameter (CSP) analysis was adopted to study the surface properties with coating layers. Our results indicate that the whole adsorption process can be divided into two periods and the greater the pressure, the more ethanol molecules diffuse into the Al slab. How raising the temperature helps the adsorption processes is related to the initial number of molecules. The crystal structure of the Al surface will become amorphous under the constant impact of ethanol molecules.

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Avilova, Marta M., Ekaterina A. Mar'yeva, Olga V. Popova i Tat'yana G. Ivanova. "MOLECULAR MODELING OF ADSORPTION OF POLLUTANT GASES ON CADMIUM-CONTAINING POLYACRYLONITRILE". IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 63, nr 4 (16.04.2020): 49–54. http://dx.doi.org/10.6060/ivkkt.20206304.6008.

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The paper presents theoretical studies of the adsorption of pollutant gases on the surface of cadmium-containing polyacrylonitrile (Cd-polyacrylonitrile) in the absence and presence of water molecules and oxygen molecules in the environment. The list of gases to which the Cd-polyacrylonitrile surface may have the highest sensitivity is determined. Nitrogen dioxide, methane, ammonia, sulfur oxide (II), hydrogen sulfide, ozone, carbon monoxide, carbon oxide (II), chlorine were chosen as pollutant gases. The following software packages are used for modeling: HyperChem, Gaussian 09, Сhemoffice 2010. Polyacrylonitrile macromolecule models were obtained from HyperChem, Gaussian 09, from which a pentamer macromolecule was chosen to produce a Cd-polyacrylonitrile cluster. Then, implementing the molecular mechanics method in Сhemoffice 2010, namely in the Chem3D subroutine, the Cd-polyacrylonitrile cluster model is constructed. Further, using the molecular modeling method, the following thermodynamic parameters were determined: «Cd-polyacrylonitrile cluster – gas molecule», «Cd-polyacrylonitrile cluster – oxygen molecule», «Cd-polyacrylonitrile cluster – water molecule», «Cd-polyacrylonitrile cluster – oxygen molecule gas molecule», «Cd-polyacrylonitrile cluster – water molecule – gas molecule». As a result of molecular modeling, it was established that Cd-polyacrylonitrile in the atmospheric air exhibits selective sensitivity to gaseous chlorine and carbon monoxide; in an oxygen-free environment – also to hydrogen sulfide. The results of molecular modeling confirm the previously obtained experimental data on the evaluation of the gas sensitivity of Cd-polyacrylonitrile and indicate the presence of van der Waals forces between the Cd-polyacrylonitrile and the adsorbed gas molecule. The presence or absence of water molecules in atmospheric air should not affect the change in the sensitivity of Cd-polyacrylonitrile to pollutant gases.

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DU, HONGBO, ABIR DE SARKAR, YU JIA i RUI-QIN ZHANG. "CHARACTERISTIC VIBRATIONAL MODES OF H2O ADSORBED MOLECULARLY AND DISSOCIATIVELY ON TITANIUM OXIDE CLUSTERS". Journal of Theoretical and Computational Chemistry 11, nr 06 (grudzień 2012): 1289–95. http://dx.doi.org/10.1142/s0219633612500861.

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To provide useful information on dissociation of water molecule on ( TiO2 )n clusters for experimental verification, we have calculated the infrared (IR) and Raman spectra of three possible states involved, namely molecularly adsorbed state, metastable state and dissociatively adsorbed state, using density functional theory at the B3LYP/6-311G(d) level. We find that the characteristic bands of H2O molecules below 2000 cm-1 in both IR and Raman spectra vanish upon both molecular and dissociative adsorption of H2O . In the high frequency range of 3600–4200 cm-1, the adsorption caused the single IR peak of water to split into two bands, while the dissociation removed the one at lower frequency and blue shifted slightly the higher frequency band. The two Raman peaks of the water molecule in the same high frequency range were slightly blue shifted upon adsorption but the one at lower frequency was removed upon dissociation, while the one at high frequency blue shifted slightly. The intensities of vibrational modes of water in 3600–4200 cm-1 are generally significantly enhanced upon both molecular and dissociative adsorption. Our results show clearly signatures of dissociation of water molecule into hydroxyl radical at the terminal site.

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Mohamed Ameen, Hiba, Sándor Kunsági-Máté, Péter Noveczky, Lajos Szente i Beáta Lemli. "Adsorption of Sulfamethazine Drug onto the Modified Derivatives of Carbon Nanotubes at Different pH". Molecules 25, nr 11 (27.05.2020): 2489. http://dx.doi.org/10.3390/molecules25112489.

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The sulfamethazine drug interaction with carbon nanotubes was investigated with the aim of improving the adsorption capacity of the adsorptive materials. Experiments were performed to clarify how the molecular environment affects the adsorption process. Single-walled carbon nanotubes have a higher removal efficiency of sulfamethazine than pristine or functionalized multi-walled carbon nanotubes. Although the presence of cyclodextrin molecules improves the solubility of sulfamethazine, it reduces the adsorption capacity of the carbon nanotube towards the sulfamethazine drug and, therefore, inhibits the removal of these antibiotic pollutants from waters by carbon nanotubes.

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Afshari, Tooba, i Mohsen Mohsennia. "Transition metals doped ZnO nanocluster for ethylene oxide detection: A DFT study". Main Group Metal Chemistry 42, nr 1 (16.07.2019): 113–20. http://dx.doi.org/10.1515/mgmc-2019-0012.

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Abstract Density functional theory (DFT) studies at B3LYP/6-31G (d) (Becke, 3-parameter, Lee-Yang-Parr) level were performed to evaluate adsorption interactions between ethylene oxide (EO) molecule, and pristine and transition metals (TM) (i.e., Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) doped ZnO nanocluster (TM-doped Zn12O12). The adsorption energy (Ead), band gap energy (Eg), Mulliken charge transfer (QT) and molecular electrostatic potential (MEP) were calculated to examine the sensitivity of the Zn12O12 and its TM-doped forms toward EO detection. It was found that in contrast to the pristine Zn12O12, the electronic properties of TM-doped Zn12O12 were sharply sensitive to the presence of EO gas molecules. The results revealed that among the studied TM-doped Zn12O12, Cr- and V-doped Zn12O12 have great potential applicability as EO sensor, due to their highest Eg change (ΔEg) values, after the EO adsorption. Moreover, the density of state (DOS) calculations confirmed that strong electronic interaction between Cr- and V-doped Zn12O12 and EO molecules can makes them interesting empirical candidate for detection and adsorptive removal of EO gas molecules.

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Yang, Siyuan, Linjiang Chen, Daniel Holden, Ruiyao Wang, Yuanyuan Cheng, Mona Wells, Andrew I. Cooper i Lifeng Ding. "Understanding the effect of host flexibility on the adsorption of CH4, CO2 and SF6 in porous organic cages". Zeitschrift für Kristallographie - Crystalline Materials 234, nr 7-8 (26.07.2019): 547–55. http://dx.doi.org/10.1515/zkri-2018-2150.

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Abstract Molecular simulations for gas adsorption in microporous materials with flexible host structures is challenging and, hence, relatively rare. To date, most gas adsorption simulations have been carried out using the grand-canonical Monte Carlo (GCMC) method, which fundamentally does not allow the structural flexibility of the host to be accounted for. As a result, GCMC simulations preclude investigation into the effect of host flexibility on gas adsorption. On the other hand, approaches such as molecular dynamics (MD) that simulate the dynamic evolution of a system almost always require a fixed number of particles in the simulation box. Here we use a hybrid GCMC/MD scheme to include host flexibility in gas adsorption simulations. We study the adsorption of three gases – CH4, CO2 and SF6 – in the crystal of a porous organic cage (POC) molecule, CC3-R, whose structural flexibility is known by experiment to play an important role in adsorption of large guest molecules [L. Chen, P. S. Reiss, S. Y. Chong, D. Holden, K. E. Jelfs, T. Hasell, M. A. Little, A. Kewley, M. E. Briggs, A. Stephenson, K. Mark Thomas, J. A. Armstrong, J. Bell, J. Busto, R. Noel, J. Liu, D. M. Strachan, P. K. Thallapally, A. I. Cooper, Separation of rare gases and chiral molecules by selective binding in porous organic cages. Nat. Mater. 2014, 13, 954, D. Holden, S. Y. Chong, L. Chen, K. E. Jelfs, T. Hasell, A. I. Cooper, Understanding static, dynamic and cooperative porosity in molecular materials. Chem. Sci. 2016, 7, 4875]. The results suggest that hybrid GCMC/MD simulations can reproduce experimental adsorption results, without the need to adjust the host–guest interactions in an ad hoc way. Negligible errors in adsorption capacity and isosteric heat are observed with the rigid-host assumption for small gas molecules such as CH4 and CO2 in CC3-R, but the adsorption capacity of the larger SF6 molecule in CC3-R is hugely underestimated if flexibility is ignored. By contrast, hybrid GCMC/MD adsorption simulations of SF6 in CC3-R can accurately reproduce experiment. This work also provides a molecular level understanding of the cooperative adsorption mechanism of SF6 in the CC3-R molecular crystal.

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Wen, Zhihui, Yunpeng Yang, Qi Wang i Banghua Yao. "Mechanism and Characteristics of CH4/CO2/H2O Adsorption in Lignite Molecules". Geofluids 2021 (20.03.2021): 1–11. http://dx.doi.org/10.1155/2021/5535321.

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Adsorption characteristics of coalbed methane (CBM) are significant to investigate the absorption of coal, shale, and porous media. In particular, adsorption characteristics of CH4, CO2, and H2O play an important role in predicting CBM output and geologic sequestration potentials of CO2 in research fields of CO2-enhanced CBM recovery (CO2-ECBM) and sequestration of CO2. In this work, adsorption characteristics of CH4, CO2, and H2O in lignite molecules were simulated through the grand canonical Monte Carlo (GCMC) method and molecular dynamics (MD) method. Research results demonstrated that given the same temperature and pressure, the ultimate adsorption capacity of lignite per unit to H2O is the highest, followed by those of CO2 and CH4 successively. All isothermal adsorption curves conform to the “I-type” characteristics. In the saturated molecular configuration, gas molecules show different distribution patterns at two sides of the lignite molecule chain. Lignite has typical physical adsorption to CH4 and CO2, with adsorption energy provided by nonbonding energy. However, lignite has both physical adsorption and chemical adsorption to H2O, with adsorption energy provided by both nonbonding energy and hydrogen bond energy. High temperature is against adsorption of CH4, CO2, and H2O. Temperature might inhibit adsorption of gas molecules. Research conclusions lay foundations for the exploitation and development of CBM and relevant studies on sequestration of CO2.

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Kopešťanský, Josef. "Reversible adsorption of hydrogen in adsorption-saturated acetylene layers on palladium surfaces". Collection of Czechoslovak Chemical Communications 50, nr 8 (1985): 1801–7. http://dx.doi.org/10.1135/cccc19851801.

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Palladium films with preadsorbed acetylene layers were interacted with molecular hydrogen. Reversibly adsorbed hydrogen in the molecular form was found on the surface. The molecule probably occurs in a more reactive state than the molecule of hydrogen gas; this state precedes the dissociative adsorption of hydrogen and it may be involved in catalytic reactions of hydrocarbons on metals.

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Walter, Wendy K., i Robert G. Jones. "1,2-dichloroethane adsorption on Cu(111): molecular adsorption". Surface Science 264, nr 3 (marzec 1992): 391–405. http://dx.doi.org/10.1016/0039-6028(92)90194-b.

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Kong, Lingmei, Axel Enders, Talat S. Rahman i Peter A. Dowben. "Molecular adsorption on graphene". Journal of Physics: Condensed Matter 26, nr 44 (7.10.2014): 443001. http://dx.doi.org/10.1088/0953-8984/26/44/443001.

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Abbasi, Amirali, i Jaber Jahanbin Sardroodi. "Theoretical investigation of the adsorption behaviors of CO and CO2 molecules on the nitrogen-doped TiO2 anatase nanoparticles: Insights from DFT computations". Journal of Theoretical and Computational Chemistry 16, nr 01 (luty 2017): 1750005. http://dx.doi.org/10.1142/s0219633617500055.

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Over the past years, an interest has arisen in resolving the problems of the increased carbon monoxide and carbon dioxide emissions, leading to the serious air pollution and many detrimental effects. A convenient solution would be a process that could utilize metal oxide nanoparticles such as TiO2 to control the concentration of atmospheric pollutants. The chemisorption of CO and CO2 molecules over the semiconductor titanium dioxide (TiO[Formula: see text] is such a process. In this way, density functional theory (DFT) calculations were performed to investigate CO and CO2 adsorptions on undoped and N-doped TiO2 anatase nanoparticles. The supercell approach is conducted to construct the considered nanoparticles and the adsorption of COx molecule was simulated by use of these chosen nanoparticles. By including van der Waals (vdW) interactions between COx molecule and TiO2 nanoparticle, we found that both CO and CO2 molecules can bind strongly to the N-doped nanoparticles. The adsorption on the five-fold coordinated titanium site of TiO2 nanoparticles including the bond lengths, bond angles, adsorption energies, density of states (DOSs), Mulliken population analysis and molecular orbitals has been broadly studied in this work. Based on the obtained results, it can be concluded that the adsorption on the N-doped nanoparticle is more energetically favorable than the adsorption on the pristine one, representing the higher tendency of N-doped nanoparticles for COx detention, compared to the undoped ones. Therefore, the results indicate that the N-doped TiO2 would be an ideal COx gas sensor in the environment.

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ZHENG, HAO, YONG XU, GUO-CAI DONG, JÖRG KRÖGER i RICHARD BERNDT. "STRUCTURE OF A PHTHALOCYANINE DYE ON ZnO". Surface Review and Letters 26, nr 06 (lipiec 2019): 1850204. http://dx.doi.org/10.1142/s0218625x18502049.

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Room temperature scanning tunneling microscopy was used to investigate the adsorption of a dye molecule, iron-phthalocyanine (FePc), on ZnO(0001). Submolecular resolution reveals the orientation of molecules with respect to crystallographic directions of the surface. Upon adsorption, the molecular symmetry is reduced. First-principles calculations trace these observations to a strong molecule-substrate bond, which induces deformations of the molecule.

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Li, Danhui, Fengting Wang, Zhiyuan Zhang, Wanrun Jiang, Yu Zhu, Zhigang Wang i Rui-Qin Zhang. "The nature of small molecules adsorbed on defective carbon nanotubes". Royal Society Open Science 6, nr 8 (sierpień 2019): 190727. http://dx.doi.org/10.1098/rsos.190727.

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In this work, we perform a comprehensive theoretical study on adsorption of representative 10-electron molecules H 2 O, CH 4 and NH 3 onto defective single-walled carbon nanotubes. Results of adsorption energy and charge transfer reveal the existence of both chemical adsorption (CA) and physical adsorption (PA). While PA processes are common for all molecules, CA could be further achieved by the polar molecule NH 3 , whose lone-pair electrons makes it easier to be bonded with the defective nanotube. Our systematic work could contribute to the understanding on intermolecular interactions and the design of future molecular detectors.

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Ding, Xue, Fu Yu Liu i Chao He Yang. "Grand Canonical Monte Carlo Simulations of Olefins Adsorption in Zeolite ZSM-5". Advanced Materials Research 550-553 (lipiec 2012): 321–24. http://dx.doi.org/10.4028/www.scientific.net/amr.550-553.321.

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The adsorption behavior of ethylene and propylene in zeolite ZSM-5 was studied by Grand Canonical Monte Carlo (GCMC) simulations. It is found that ethylene and propylene molecules show different adsorption behaviors in the zeolite cavum. The adsorption isotherms of ethylene and propylene in ZSM-5 at 298K and 823K were simulated. The results exhibit that the molecular adsorption is influenced at various temperatures and pressures, leading to different rules for the adsorption of ethylene and propylene molecules in zeolite. At low temperature, when the pressure is enhanced from 100kpa to 1000 kpa, the adsorption amounts of olefin molecule increase obviously and the loading of ethylene are significantly larger than those of propylene. The adsorption of propylene has a preferential adsorption site in cross position, and nearly reaches saturation at pressure higher than 300kPa. While at 823K the adsorption of ethylene is inhibited with lower loading than those of propylene.

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Pizzone, Mattia, Maria Grazia Grimaldi, Antonino La Magna, Neda Rahmani, Silvia Scalese, Jost Adam i Rosaria A. Puglisi. "Study of the Molecule Adsorption Process during the Molecular Doping". Nanomaterials 11, nr 8 (24.07.2021): 1899. http://dx.doi.org/10.3390/nano11081899.

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Molecular Doping (MD) involves the deposition of molecules, containing the dopant atoms and dissolved in liquid solutions, over the surface of a semiconductor before the drive-in step. The control on the characteristics of the final doped samples resides on the in-depth study of the molecule behaviour once deposited. It is already known that the molecules form a self-assembled monolayer over the surface of the sample, but little is known about the role and behaviour of possible multiple layers that could be deposited on it after extended deposition times. In this work, we investigate the molecular surface coverage over time of diethyl-propyl phosphonate on silicon, by employing high-resolution morphological and electrical characterization, and examine the effects of the post-deposition surface treatments on it. We present these data together with density functional theory simulations of the molecules–substrate system and electrical measurements of the doped samples. The results allow us to recognise a difference in the bonding types involved in the formation of the molecular layers and how these influence the final doping profile of the samples. This will improve the control on the electrical properties of MD-based devices, allowing for a finer tuning of their performance.

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Fujimoto, Yoshitaka. "Quantum transport, electronic properties and molecular adsorptions in graphene". Modern Physics Letters B 35, nr 08 (9.02.2021): 2130001. http://dx.doi.org/10.1142/s0217984921300015.

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Molecular sensor applications are used in different fields including environmental monitoring and medical diagnosis. Graphene, a single atomic layer consisting of the hexagonally arranged carbon material, is one of the most promising materials for ideal channels in field-effect transistors to be used as electronic sensing applications owing to its lightweight, mechanical robustness, high electronic conductivity and large surface-to-volume ratio. This paper provides a review of molecular adsorptions, electronic properties and quantum transport of graphene based on the first-principles density-functional study. The adsorption properties of environmentally polluting or toxic molecules and electronic transport of graphene are revealed. The possibility of detecting these molecules selectively is also discussed for designing the graphene-based sensor applications.

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Xu, Chenhong, Suqin Zhou, Jing Chen, Yuxiang Wang i Lei He. "Adsorption mechanism of CO molecule on Al(111) surface: periodic DFT investigation". Canadian Journal of Chemistry 96, nr 12 (grudzień 2018): 993–99. http://dx.doi.org/10.1139/cjc-2018-0169.

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The adsorption mechanism of the CO molecule on Al(111) surface has been investigated systematically at the atom-molecule level by the method of periodic density functional theory. The adsorption energies, adsorption structures, charge transfer, and density of states have been calculated in a wide range of coverage. It is found that the hcp-hollow site is the energetically favorable site. A significant positive correlation has been found between the adsorption energy (Eads) and coverage. The adsorbed CO molecules are almost perpendicular on the surface with the C atom facing the surface. There is an obvious charge transfer from Al atoms to the C atom; the Al atoms that have interaction with the C atom offer the most charge. The 4σ, 1π, and 5σ molecular orbitals of CO are found to contribute to bonding with the Al. The charges filling in the 2π molecular orbital contribute to C–O bond activation. In conclusion, the passivation of aluminum surface and the activation of CO molecule occur simultaneously in the adsorption of CO on Al surface.

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Nejad, Marjan A., i Herbert M. Urbassek. "Adsorption and Diffusion of Cisplatin Molecules in Nanoporous Materials: A Molecular Dynamics Study". Biomolecules 9, nr 5 (27.05.2019): 204. http://dx.doi.org/10.3390/biom9050204.

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Using molecular dynamics simulations, the adsorption and diffusion of cisplatin drug molecules in nanopores is investigated for several inorganic materials. Three different materials are studied with widely-varying properties: metallic gold, covalent silicon, and silica. We found a strong influence of both the van der Waals and the electrostatic interaction on the adsorption behavior on the pore walls, which in turn influence the diffusion coefficients. While van der Waals forces generally lead to a reduction of the diffusion coefficient, the fluctuations in the electrostatic energy induced by orientation changes of the cisplatin molecule were found to help desorb the molecule from the wall.

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Lu, Q., i G. Sorial. "Impact of pore size on competitive adsorption of phenolic compounds". Water Supply 4, nr 5-6 (1.12.2004): 1–7. http://dx.doi.org/10.2166/ws.2004.0086.

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Single and binary solute adsorption of phenol and o-cresol at 23°C on three activated carbons with different pore size were conducted in this study. One granular activated carbon (GAC) F400 and two activated carbon fibers (ACFs) were considered. Anoxic (absence of molecular oxygen) and oxic (presence of molecular oxygen) conditions were evaluated. For the single solute system, the three adsorbents studied have shown higher adsorptive capacities under oxic conditions as compared to anoxic conditions. The degree of adsorption enhancement was related to the pore size of the adsorbent. For binary adsorption on ACC-10, which has the least average pore size (1.76 nm), the oxic and anoxic adsorption isotherms overlapped, indicating no impact of the presence of molecular oxygen on the adsorptive capacity. Significant differences on adsorptive capacities were noticed for the binary solute adsorption on ACC-15 (2.10 nm) and F400 (2.48 nm). The Ideal Adsorbed Solution Theory (IAST) predicted well all binary systems for ACC-10 and anoxic isotherms on ACC-15 and F400. Poor model predictions for GAC and ACC-15 under oxic conditions were attributed to the oligomerization of the adsorbates on the surface of activated carbon. The unique pore size of ACFs has been shown to be a limiting factor in hampering the oligomerization under oxic conditions.

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26

Filinchuk, Yaroslav, Nikolay Tumanov, Voraksmy Ban, Hyunchul Oh, Michael Hirscher, Bo Richter, Torben Jensen i in. "Unprecedented adsorption of molecular hydrogen in the porous hydride framework". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C1473. http://dx.doi.org/10.1107/s205327331408526x.

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"Recently the first porous hydride, gamma-Mg(BH4)2, featuring so-called ""borohydride framework"" and capable to store reversibly guest species was discovered [1]. This example clearly shows that the covalently bound hydride anions, such as borohydride, can act as directional ligands, capable to form molecular and polynuclear complexes, as well as framework structures typically occurring in classical coordination chemistry. Various small molecules are reversibly absorbed in gamma-Mg(BH4)2. In this work we show that molecular hydrogen and nitrogen have different adsorption sites in gamma-Mg(BH4)2, leading to different capacities on saturation and to different H2 and N2 BET areas. Only up to 0.66 N2 molecules are adsorbed per Mg atom, but the saturation capacity is double for the smaller hydrogen molecule. Moreover, at higher pressures, the second hydride phase forms with unprecedented hydrogen content of ~22 weight % (!). The density of hydrogen adsorbed into the pores is much higher than in liquid hydrogen, having no analogues among other porous systems. On the technical side, we will illustrate how in-situ diffraction at neutron and synchrotron sources allows to follow adsorption isobars, aiming for extraction of isosteric heats of adsorption directly from diffraction data, as well as for clarifying the microscopic mechanisms in terms of guest-host and guest-guest interactions."

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27

Yang, Lilong, Xiang Zhou, Kewei Zhang, Fanhua Zeng i Zhouhua Wang. "Investigation of dynamical properties of methane in slit-like quartz pores using molecular simulation". RSC Advances 8, nr 59 (2018): 33798–816. http://dx.doi.org/10.1039/c8ra06678g.

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Varghese, Seba Sara, Sundaram Swaminathan, Krishna Kumar Singh i Vikas Mittal. "Molecular Oxygen Adsorbed on Gallium Doped Graphene: A First-Principles Study". Materials Science Forum 890 (marzec 2017): 117–20. http://dx.doi.org/10.4028/www.scientific.net/msf.890.117.

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The adsorption of molecular oxygen on gallium doped graphene sheet is investigated using first-principles density functional theory calculations. The adsorption energy of O2 on gallium doped graphene is calculated after determining the energetically favourable adsorption configuration. The change in the electronic properties of gallium doped graphene after O2 adsorption is also determined to understand the nature their interactions. The results show that gallium doped graphene has large adsorption energy and small binding distance, which correspond to chemical adsorption. The calculated band structure and density of states plots of gallium doped graphene before and after adsorption show dramatic changes in the electronic properties due to the strong interactions of gallium doped graphene with adsorbed O2 molecule. These results indicate that gallium doped graphene is highly reactive to molecular oxygen and hence not a suitable choice for harmful gas detection in the presence of O2.

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29

Roldan, A., i N. H. de Leeuw. "Catalytic water dissociation by greigite Fe 3 S 4 surfaces: density functional theory study". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, nr 2188 (kwiecień 2016): 20160080. http://dx.doi.org/10.1098/rspa.2016.0080.

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The iron sulfide mineral greigite, Fe 3 S 4 , has shown promising capability as a hydrogenating catalyst, in particular in the reduction of carbon dioxide to produce small organic molecules under mild conditions. We employed density functional theory calculations to investigate the {001},{011} and {111} surfaces of this iron thiospinel material, as well as the production of hydrogen ad-atoms from the dissociation of water molecules on the surfaces. We systematically analysed the adsorption geometries and the electronic structure of both bare and hydroxylated surfaces. The sulfide surfaces presented a higher flexibility than the isomorphic oxide magnetite, Fe 3 O 4 , allowing perpendicular movement of the cations above or below the top atomic sulfur layer. We considered both molecular and dissociative water adsorption processes, and have shown that molecular adsorption is the predominant state on these surfaces from both a thermodynamic and kinetic point of view. We considered a second molecule of water which stabilizes the system mainly by H-bonds, although the dissociation process remains thermodynamically unfavourable. We noted, however, synergistic adsorption effects on the Fe 3 S 4 {001} owing to the presence of hydroxyl groups. We concluded that, in contrast to Fe 3 O 4 , molecular adsorption of water is clearly preferred on greigite surfaces.

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30

Lipkowski, Jacek. "1998 Alcan Award Lecture Surface electrochemistry - surface science with a joy stick". Canadian Journal of Chemistry 77, nr 7 (1.07.1999): 1163–76. http://dx.doi.org/10.1139/v99-124.

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This lecture gives a review of thermodynamic, spectroscopic, STM and AFM imaging, and X-ray diffraction studies of molecular and ionic adsorption at Au(111) electrodes. In the first part, thermodynamics of adsorption of simple ions such as sulfate, chloride, bromide, and iodide will be discussed. At high coverages, anions adsorbed at a single crystal surface form ordered 2D adlayers. We show that the structure of these adlayers can be studied by STM and surface X-ray diffraction techniques. Next, the information concerning adsorption of simple ions is used to describe mixed adlayers formed by coadsorption of anions and metal adatoms. We demonstrate how to combine electrochemical experiments with in situ polarization-dependent Cu K-edge X-ray absorption spectroscopy to determine the composition and the structure of mixed films formed by deposition of Cu on Au(111) in the presence of SO42-. In the last part we review our efforts to describe coordination of organic molecules to gold electrodes. First, we will discuss adsorption of benzonitrile at the Au(111) electrode surface. We combine electrochemical methods with in situ infrared spectroscopy to describe (i) the energetics of molecular adsorption at the gold electrode surface, (ii) the character of the interaction of the adsorbed molecule with the metal substrate, and (iii) the influence of the electric field on the orientation of the adsorbed molecule. In the last section we describe surface aggregation phenomena. We apply AFM and STM to determine the structure of hemimicelles formed at the Au(111) electrode surface by adsorbed molecules of sodium dodecyl sulfate and we discuss the potential-controlled transformation of these hemimicelles into a condensed monolayer.Key words: surface electrochemistry, electrosorption, surface aggregation, gold electrodes, molecular adsorption, ionic adsorption.

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31

Qi, Chongchong, Lang Liu, Jianyong He, Qiusong Chen, Li-Juan Yu i Pengfei Liu. "Understanding Cement Hydration of Cemented Paste Backfill: DFT Study of Water Adsorption on Tricalcium Silicate (111) Surface". Minerals 9, nr 4 (27.03.2019): 202. http://dx.doi.org/10.3390/min9040202.

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Understanding cement hydration is of crucial importance for the application of cementitious materials, including cemented paste backfill. In this work, the adsorption of a single water molecule on an M3-C3S (111) surface is investigated using density functional theory (DFT) calculations. The adsorption energies for 14 starting geometries are calculated and the electronic properties of the reaction are analysed. Two adsorption mechanisms, molecular adsorption and dissociative adsorption, are observed and six adsorption configurations are found. The results indicate that spontaneous dissociative adsorption is energetically favored over molecular adsorption. Electrons are transferred from the surface to the water molecule during adsorption. The density of states (DOS) reveals the bonding mechanisms between water and the surface. This study provides an insight into the adsorption mechanism at an atomic level, and can significantly promote the understanding of cement hydration within such systems.

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32

Tenner, M. G., E. W. Kuipers, A. W. Kleyn i S. Stolte. "Steric effects in molecular adsorption". Journal of Chemical Physics 89, nr 10 (15.11.1988): 6552–53. http://dx.doi.org/10.1063/1.455376.

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Steele, William. "Molecular interactions for physical adsorption". Chemical Reviews 93, nr 7 (listopad 1993): 2355–78. http://dx.doi.org/10.1021/cr00023a002.

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34

Cai, H., A. C. Hillier, K. R. Franklin, C. C. Nunn i M. D. Ward. "Nanoscale Imaging of Molecular Adsorption". Science 266, nr 5190 (2.12.1994): 1551–55. http://dx.doi.org/10.1126/science.266.5190.1551.

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35

Risović, Dubravko. "Interfacial adsorption with molecular reorientation". Journal of Electroanalytical Chemistry 588, nr 1 (marzec 2006): 122–28. http://dx.doi.org/10.1016/j.jelechem.2005.12.018.

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36

Kaneko, Katsumi, Tomonori Ohba, Takahiro Ohkubo, Shigenori Utsumi, Hironobu Kanoh, Masako Yudasaka i Sumio Iijima. "Nanospace Molecular Science and Adsorption". Adsorption 11, S1 (lipiec 2005): 21–28. http://dx.doi.org/10.1007/s10450-005-5893-8.

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37

Lipkowski, J., L. Stolberg, D. F. Yang, B. Pettinger, S. Mirwald, F. Henglein i D. M. Kolb. "Molecular adsorption at metal electrodes". Electrochimica Acta 39, nr 8-9 (czerwiec 1994): 1045–56. http://dx.doi.org/10.1016/0013-4686(94)e0019-v.

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38

Al-Zaid, Khairya, Saed Akashah, Fathi Owaysi, G. V. Jeffreys, Yu A. Eltekov i C. Mumford. "Adsorption of Aromatic Compounds from Solutions on Molecular Sieve 13X". Adsorption Science & Technology 4, nr 3 (wrzesień 1987): 196–210. http://dx.doi.org/10.1177/026361748700400305.

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Measurements of the equilibrium extent of adsorption of individual aromatic hydrocarbons: mono, di, trinuclear aromatic and heterocyclo compounds from iso-octane solutions by molecular sieves 13X were carried out at 303 and 343 K and at concentrations up to 5 wt.% The limiting values of adsorption were essentially determined by using modified Brunauer-Emmett-Teller equation (BET). The coverages and numbers of adsorbate molecules occupied in the unit cell of the molecular sieves were calculated at different temperatures. The isosteric heats of adsorption of aromatic hydrocarbons were also determined using Clausius-Clapeyron equation. It was found that the heats of adsorption of aromatic compounds varied from 4 to 60 kJ mol-1

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Zhao, Yi, Han Wang i Tianhao Wang. "Preparation of molecularly imprinted adsorbents and NO adsorption property". Functional Materials Letters 10, nr 02 (kwiecień 2017): 1650070. http://dx.doi.org/10.1142/s1793604716500703.

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Two groups of molecularly imprinted NO adsorbents were prepared by molecularly self-assembly procedures, in which methanoic acid, acetic acid, ethanedioic acid were used as templates; acrylic acid (AA) and acryl amide (AAM) were used as functional monomers, respectively. The pore size distribution and the special surface area of the adsorbents varied with different functional monomers and templates regularly. NO adsorption capacities all decreased with the increasingly molecular diameter of templates, and when the template was the same, the adsorbents in group 1 had better NO adsorption capacities than those in group 2 due to the stronger hydrogen bond interaction between the functional monomer and NO molecule. The adsorption stability was also tested and both of MIPa1 in group 1 and MIPb1 in group 2 could maintain steady adsorption capacity during 50 times of adsorption–desorption cycle.

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40

Xu, Long, Ze-Xin Zhao, Yun-An Huang i Qiu-Jin Zhu. "Preparation of Chitosan Molecularly Imprinted Polymers and the Recognition Mechanism for Adsorption of Alpha-Lipoic Acid". Molecules 25, nr 2 (13.01.2020): 312. http://dx.doi.org/10.3390/molecules25020312.

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Two effective molecularly imprinted polymers for the adsorption of alpha-lipoic acid (ALA) were synthesized by the cross-linking of chitosan with epichlorohydrin (ECH) and glutaraldehyde (GLU), respectively, in the presence of ALA as template molecules. Investigations on the molar ratios of ALA and chitosan (–NH2) in the preparation of chitosan molecularly imprinted polymers (MIPs) were carried out with a factor of ALA rebinding capabilities. The surface morphology and chemical properties of the polymers were characterized. The optimized MIPs crosslinked by ECH (MIPs–ECH) and MIPs crosslinked by GLU (MIPs–GLU) had adsorption capabilities of 12.09 mg/g and 19.72 mg/g for ALA, respectively. The adsorption behaviors of two kinds of chitosan MIPs including adsorption kinetics and isotherms were investigated in detail. Adsorption and kinetic binding experiments showed that the prepared MIPs–ECH and MIPs–GLU had selective adsorption and excellent affinity for ALA. In addition, the possible binding models between ALA and chitosan oligosaccharide were predicted by molecular dynamics simulation.

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41

Galvez-Martinez, Santos, i Eva Mateo-Marti. "Ultraviolet Irradiation on a Pyrite Surface Improves Triglycine Adsorption". Life 8, nr 4 (25.10.2018): 50. http://dx.doi.org/10.3390/life8040050.

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We characterized the adsorption of triglycine molecules on a pyrite surface under several simulated environmental conditions by X-ray photoemission spectroscopy. The triglycine molecular adsorption on a pyrite surface under vacuum conditions (absence of oxygen) shows the presence of two different states for the amine functional group (NH2 and NH3+), therefore two chemical species (anionic and zwitterionic). On the other hand, molecular adsorption from a solution discriminates the NH2 as a unique molecular adsorption form, however, the amount adsorbed in this case is higher than under vacuum conditions. Furthermore, molecular adsorption on the mineral surface is even favored if the pyrite surface has been irradiated before the molecular adsorption occurs. Pyrite surface chemistry is highly sensitive to the chemical changes induced by UV irradiation, as XPS analysis shows the presence of Fe2O3 and Fe2SO4—like environments on the surface. Surface chemical changes induced by UV help to increase the probability of adsorption of molecular species and their subsequent concentration on the pyrite surface.

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42

Ulfa, Maria, i Farhah Nayla Fawzia. "Study of Adsorption Capacity of Dibenzotiofen Molecules on Mesoporous Carbon with Pore Geometry Model". JKPK (Jurnal Kimia dan Pendidikan Kimia) 2, nr 2 (7.09.2017): 110. http://dx.doi.org/10.20961/jkpk.v2i2.11908.

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<p>Adsorption models in a simple and accurate way to describe the geometry of the pores have been studied and validated experimentally to predict the adsorption capacity dibenzotiofen molecules on mesoporous carbon. The model is designed according to the size of the pore channels of mesoporous carbon and molecular arrangement dibenzotiofen that goes into the pores. To test the accuracy of the model is done by comparation with results of analysis of nitrogen adsorption-desorption to calculate the volume filled. The results showed that the results of the experimental adsorption data are within the range of values of the pore volume of mesoporous carbon. These results indicate that the pore geometry model molecule can accurately predict the adsorption capacity of a molecule in a mesoporous material.</p><p class="AbstracttitleDERJournal"> </p>

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43

Tsapatsis, Michael, i George R. Gavalas. "Synthesis of Porous Inorganic Membranes". MRS Bulletin 24, nr 3 (marzec 1999): 30–35. http://dx.doi.org/10.1557/s0883769400051885.

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Here we will attempt a brief overview of recent synthetic efforts for micropore and lower-end mesopore membranes. We will not address the very important classes of nonporous membranes, such as dense metals and solid electrolytes with applications in H2 and O2 separations, or meso- and macroporous membranes, which find applications in food processing and water treatment. Microporous materials provide high permselectivities for molecules encountered in the chemical-processing industry but suffer from low intrinsic permeabilities. Therefore, in order to bring microporous membrane materials to commercial applications, functional composites with small effective thicknesses (in the micron or submicron range) must be developed. For example, to achieve economical membrane-reactor sizes, fluxes as high as 0.1 mol/(m2 s) are desirable. Approaches to microporous membranes include modification of mesoporous membranes by sol-gel and chemical-vapor-deposition (CVD) techniques, carbonization of polymers to form molecular-sieve carbon, and polycrystalline-film growth of zeolites and other molecular sieves.Microporous carbon is widely used for liquid or gas purification because of its strong adsorptive properties and high surface area. It is also used for air separation by pressure swing adsorption (PSA), relying on its adsorptive and molecular-sieving properties. From the standpoint of applications, microporous carbons are classified into activated carbons with pore size 0.8–2 nm, and ultramicroporous carbons or carbon molecular sieves with pores 0.3–0.6 nm. Activated carbons are used because of their strong adsorption properties, while carbon molecular sieves are useful on account of their molecular-sieving as well as adsorption properties.

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44

Liu, Guangzeng, Shenhao Chen, Ma Hongfang i Xiuyu Liu. "Molecular simulation study of 1,5-diphenylcarbazide self-assembled monolayers on a copper surface". Journal of the Serbian Chemical Society 72, nr 5 (2007): 475–84. http://dx.doi.org/10.2298/jsc0705475l.

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In this study, the adsorption process of 1,5- diphenylcarbazide (DPC) self-assembled monolayers on a copper surface was investigated by using molecular mechanics. The results indicated that the interaction of the ?-electrons in the -NH-NH- group and the ?-electrons in the phenyl ring could lead to strong adsorption of the highly symmetric DPC molecules on a copper surface. The synergy effect of the phenyl ring and the -NH-NH- group made the whole DPC molecule lay in parallel orientation on a copper surface when the coverage was low. However, at high coverage, the phenyl ring was slightly tilted because of the repulsion of the DPC molecules, while the -NH-NH- groups remained parallel to the copper surface.

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45

Du, Xiaoming. "Molecular Simulation of Hydrogen Storage in Ion-Exchanged X Zeolites". Advances in Materials Science and Engineering 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/189745.

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Grand Canonical Monte Carlo (GCMC) method was employed to simulate the adsorption properties of molecular hydrogen on ion-exchanged X zeolites at 100–293 K and pressures up to 10 MPa in this paper. The effect of cation type, temperature, and pressure on hydrogen adsorption capacity, heat of adsorption, adsorption sites, and adsorption potential energy of ion-exchanged X zeolites was analyzed. The results indicate that the hydrogen adsorption capacity increases with the decrease in temperatures and the increase in pressures and decreases in the order ofKX<LiX<CaX. The isosteric heat of adsorption for all the three zeolites decreases appreciably with the increase in hydrogen adsorption capacity. The hydrogen adsorption sites in the three zeolites were determined by the simulated distribution of hydrogen adsorption energy and the factors that influence their variations were discussed. Adsorption temperature has an important effect on the distribution of hydrogen molecules in zeolite pores.

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46

Cárdenas, Harry, i Erich Müller. "Molecular Simulation of the Adsorption and Diffusion in Cylindrical Nanopores: Effect of Shape and Fluid–Solid Interactions". Molecules 24, nr 3 (9.02.2019): 608. http://dx.doi.org/10.3390/molecules24030608.

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We report on molecular simulations of model fluids composed of three tangentially bonded Lennard-Jones interaction sites with three distinct morphologies: a flexible “pearl-necklace” chain, a rigid “stiff” linear configuration, and an equilateral rigid triangular ring. The adsorption of these three models in cylindrical pores of diameters 1, 2, and 3 nm and with varying solid–fluid strength was determined by direct molecular dynamics simulations, where a sample pore was placed in contact with a bulk fluid. Adsorption isotherms of Type I, V, and H1 were obtained depending on the choice of pore size and solid–fluid strength. Additionally, the bulk-phase equilibria, the nematic order parameter of the adsorbed phase, and the self-diffusion coefficient in the direction of the pore axis were examined. It was found that both the molecular shape and the surface attractions play a decisive role in the shape of the adsorption isotherm. In general, the ring molecules showed a larger adsorption, while the fully flexible model showed the smallest adsorption. Morphology and surface strength were found to have a lesser effect on the diffusion of the molecules. An exceptional high adsorption and diffusion, suggesting an enhanced permeability, was observed for the linear stiff molecules in ultraconfinement, which was ascribed to a phase transition of the adsorbed fluid into a nematic liquid crystal.

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47

Jakšić, Olga, Marko Spasenović, Zoran Jakšić i Dana Vasiljević-Radović. "Monolayer Gas Adsorption on Graphene-Based Materials: Surface Density of Adsorption Sites and Adsorption Capacity". Surfaces 3, nr 3 (24.08.2020): 423–32. http://dx.doi.org/10.3390/surfaces3030031.

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Surface density of adsorption sites on an adsorbent (including affinity-based sensors) is one of the basic input parameters in modeling of process kinetics in adsorption based devices. Yet, there is no simple expression suitable for fast calculations in current multiscale models. The published experimental data are often application-specific and related to the equilibrium surface density of adsorbate molecules. Based on the known density of adsorbed gas molecules and the surface coverage, both of these in equilibrium, we obtained an equation for the surface density of adsorption sites. We applied our analysis to the case of pristine graphene and thus estimated molecular dynamics of adsorption on it. The monolayer coverage was determined for various pressures and temperatures. The results are verified by comparison with literature data. The results may be applicable to modeling of the surface density of adsorption sites for gas adsorption on other homogeneous crystallographic surfaces. In addition to it, the obtained analytical expressions are suitable for training artificial neural networks determining the surface density of adsorption sites on a graphene surface based on the known binding energy, temperature, mass of adsorbate molecules and their affinity towards graphene. The latter is of interest for multiscale modelling.

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48

Masas, Daria S., Maria S. Ivanova, Gocha Sh Gogelashvili, Alexander S. Maslennikov, Yury B. Grunin i Tatiana Yu Grunina. "Analysis of water state adsorbed by cellulose fibers". Butlerov Communications 58, nr 5 (31.05.2019): 24–31. http://dx.doi.org/10.37952/roi-jbc-01/19-58-5-24.

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Modernized model of microfibril cellulose layered structure is proposed. This model considers presence of slit-shaped micropores in space between elementary fibrils and cellulose microfibrils. It’s discussed the nature of donor-acceptor hydrogen bonds formation: intra-, intermolecular, and interlayer bonds inherent in each glucopyranous cellulose link. It’s described the mechanism of water molecules specific adsorption interactions in a monolayer with active centers located on the hydrophilic surfaces of elementary fibrils. Dipole-dipole energy transition into energy of hydrogen bond is discussed during adsorption process between active centers of cellulose and water adsorptive molecules. Analysis of water molecules dipole-dipole interactions with surface hydroxyl groups of cellulose showed that at distance of 2.5-3 Å energy of this interaction transforms into energy of hydrogen bond. It is discussed the formation mechanism of water molecules donor-acceptor bonds with cellulose surface hydroxyl groups. Thermodynamic parameters characterizing adsorbate state the in these layers are determined by proton magnetic relaxation and sorption measurements. It’s established the possibility of determining adsorption net heat in bilayer considering Arrhenius nature of adsorbate thermal molecular motions correlation times. Increase in entropy of adsorbed water during adsorption process is revealed basis on Vant Hoff equation and certain adsorption equilibrium constant. The calculation established that distance between nearest active centers of cellulose is 6.5 Å. This leads to disunity of adsorbed water molecules and allows application of Langmuir and BET adsorption theory. Analysis of spin-lattice relaxation times dependence on cellulose moisture content made it possible to establish the cause of its crystallite wedging from adsorbed water molecules at adsorption initial stages. Decline of the spin-lattice relaxation unambiguously indicates the process of cellulose dispersion into its structural elements. It was established that during adsorption a part of the internal regions of crystallites passes to their surface with participation of cellulose hydroxyl groups. During desorption reverse process is observed.

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Zhu, Sheng-Bai. "Theoretical Study of Molecular Contamination on Silicon Wafers: Kinetics". Journal of the IEST 41, nr 5 (14.09.1998): 36–43. http://dx.doi.org/10.17764/jiet.41.5.y28564q840587783.

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In an earlier paper ["Theoretical Study of Molecular Contaminants on Silicon wafers: Interactions Between Molecular Contaminants and the Silicon Surface," Journal of the IEST, July/August 1998] a simple formulation was developed to describe interactions between gas phase molecules and solid surfaces.1 Adsorption energies of various organic/inorganic molecules on silicon wafer surfaces were derived, In this paper, the relationship between the gas phase molecule concentration and the surface contamination density based on simple kinetic theories is established. The most important approximations in this derivation include the neglect of possible chemical reactions on the surface and the assumption that gas phase concentrations of pollutants are constants, both in time and in location. The mass transport mechanisms are ignored. With these approximations, the equilibrium in surface kinetics can be reached almost instantly for all the molecules investigated, even for those having activation energies as high as ∼ 72 kJ/mole. This agrees with the experimental data for moisture adsorption on stainless steel.2 A guide is provided for material selection.

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WEGNER, H., K. WEISS i CH WÖLL. "FORMATION OF ORDERED MOLECULAR OVERLAYERS BY A TEMPERATURE-INDUCED SURFACE REACTION: HEXABUTYLOXYTRIPHENYLENE ON Cu(111)". Surface Review and Letters 06, nr 02 (kwiecień 1999): 183–92. http://dx.doi.org/10.1142/s0218625x99000214.

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Molecular monolayers obtained by the adsorption of hexabutyloxytriphenylene (HBT) on Cu (111) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and thermal desorption spectroscopy (TDS). Adsorption at room temperature results in the formation of a disordered layer of physisorbed molecules. Annealing at temperatures of 600 K is found to induce a chemical reaction of the molecule with the substrate, leading to a desorption of the butyl fragments. This chemical reaction is accompanied by the formation of a highly ordered, well-defined oxytriphenylene layer which is stable for temperatures of up to 600 K.

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