Gas molecules (CH4, CO, H2O and H2S) adsorption on VC (001)surface: a first principles study

The first principle plane wave pseudo-potential method based on density functional theory system is used to calculate and simulate the geometric structure, density of states and optical properties of intrinsic VC materials. And we further studied the adsorption performance of small gas molecules (CH4, CO, H2O, H2S) on the surface of VC(001). The most stable adsorption geometry of CH4, CO, H2O and H2S on the intrinsic VC(001) was determined, and the electronic structure and differential charge were calculated by the first principle method. The results show that the adsorption stability of the same molecule on the surface is related to the interaction position between the molecule and the surface after adsorption. According to the analysis of the differential charge density and the charge layout number, the charge layout number of the central atom C, O, S of the gas molecule increases after adsorption, and the adsorption strength of the gas molecule on the surface is CO>H2S>H2O>CH4. The H2S adsorbed on VC surface has the strongest adsorption energy (-1.442 eV) and more transfer charge (-0.12 e). The calculated dielectric function results shows that the existence of gases molecules inhibited the photon adsorbed on VC(001) surface. Our research provide a theoretical basis for further research on the gas sensing properties of material.

A Computational Validation of Water Molecules Adsorption on an NaCl Surface

It was reported that a scanning tunneling microscopy (STM) study observed the adsorption geometry of a water monomer and a tetramer on NaCl(100) film. Based on first-principles density functional theory (DFT), the adsorption behavior of water on the NaCl surface was simulated with CASTEP code. The results showed that the water monomer almost lay on the NaCl(001) surface with one O–H bond tilted slightly downward. This was quite different from the STM observations. In fact, the experimental observation was influenced by the Au(111) substrate, which showed an upright form. A recent report on observations of two-dimensional ice structure on Au(111) substrate verified our simulations. However, the water tetramer formed a stable quadrate structure on the surface, which was consistent with observation. The intermolecular hydrogen bonds present more strength than surface adsorption. The simulations presented a clearer picture than experimental observations.

Adsorption Geometry of Alizarin on Silver Nanoparticles: A Computational and Spectroscopic Study

The knowledge of the adsorption geometry of an analyte on a metal substrate employed in surface enhanced Raman scattering (SERS) spectroscopy is important information for the correct interpretation of experimental data. The adsorption geometry of alizarin on silver nanoparticles was studied through ab initio calculations in the framework of density functional theory (DFT) by modeling alizarin taking into account all the different charged species present in solution as a function of pH. The calculations allowed a faithful reproduction of the measured SERS spectra and to elucidate the adsorption geometry of this dye on the silver substrate.

The Influence of Surface Proximity on Photoswitching Activity of Stilbene-Functionalized N-Heterocyclic Carbene Monolayers

Self-assembly of photo-responsive molecules is a robust technology for reversibly tuning the properties of functional materials. Herein, we probed the crucial role of surface-adsorbate interactions on the adsorption geometry of...

Using Photoactive N-Heterocyclic Carbenes Monolayers to Identify the Influence of Surface Proximity on Photoswitching Activity

<p>Self-assembly of photoresponsive molecules is a robust technology for reversibly tuning the chemical and electronic properties of functional materials. In most systems the photoactive group is separated from the surface by a spacer and thus the photo-responsiveness does not benefit from interactions with the metal. Herein, the impact of metal photoactive-group interactions on photoswitchability and surface potential were probed by self-assembly of N-heterocyclic carbene molecules (NHCs) that were functionalized with stilbene group directly on their imidazole ring. Stilbene-NHCs that were adsorbed on weakly interacting Au surface accumulated a vertical orientation, as identified by FTIR measurements. This positioning enabled structural flexibility and high photoisomerization efficiency that induced reversible changes in surface potential. Stilbene-NHCs that were anchored on Pt film accumulated flat-lying adsorption geometry due to strong metal-adsorbate interactions. These interactions limited the structural flexibility of the stilbene groups and induced deteriorated photoswitchability that led to lower photoinduced changes in surface potential. While stronger metal-adsorbate interactions hindered the photo-induced isomerization yield of stilbene, these interactions prompted the <i>cis</i>-to-<i>trans</i> thermal-induced isomerization rate, which was an order of magnitude higher on Pt than on Au. </p>

Using Photoactive N-Heterocyclic Carbenes Monolayers to Identify the Influence of Surface Proximity on Photoswitching Activity

<p>Self-assembly of photoresponsive molecules is a robust technology for reversibly tuning the chemical and electronic properties of functional materials. In most systems the photoactive group is separated from the surface by a spacer and thus the photo-responsiveness does not benefit from interactions with the metal. Herein, the impact of metal photoactive-group interactions on photoswitchability and surface potential were probed by self-assembly of N-heterocyclic carbene molecules (NHCs) that were functionalized with stilbene group directly on their imidazole ring. Stilbene-NHCs that were adsorbed on weakly interacting Au surface accumulated a vertical orientation, as identified by FTIR measurements. This positioning enabled structural flexibility and high photoisomerization efficiency that induced reversible changes in surface potential. Stilbene-NHCs that were anchored on Pt film accumulated flat-lying adsorption geometry due to strong metal-adsorbate interactions. These interactions limited the structural flexibility of the stilbene groups and induced deteriorated photoswitchability that led to lower photoinduced changes in surface potential. While stronger metal-adsorbate interactions hindered the photo-induced isomerization yield of stilbene, these interactions prompted the <i>cis</i>-to-<i>trans</i> thermal-induced isomerization rate, which was an order of magnitude higher on Pt than on Au. </p>