Qiuhua Liang

First-Principles Study of Sulfur Dioxide Sensor Based on Phosphorenes

The adsorption behaviors of sulfur dioxide (SO2) gas molecule over pristine, boron-, silicon-, sulfur-, and nitrogen-doped phosphorenes are theoretically studied using first-principles approach based on density-functional theory. The adsorption energy (Ea), adsorption distance (d), and Mulliken charge (Q) of SO2 molecules adsorbed on the different phosphorenes are calculated. The simulation results demonstrate that pristine phosphorene is sensitive to SO2 gas molecule with a moderate adsorption energy and an excellent charge transfer, while evidence of negative effect is observed during doping with S and N. We also observe that B- or Si-doped phosphorene exhibits extremely high reactivity toward SO2 with a stronger adsorption energy, indicating that they are not suitable for use as SO2 sensors, but have potential applications in the development of metal-free catalysts for SO2. Therefore, we suggest that pristine phosphorene could be an excellent candidate as sensor for the polluting gas SO2.

First Principles Investigation of Small Molecules Adsorption on Antimonene

The gas-adsorption behaviors of the pristine antimonene are investigated by first principles calculations to exploit its potential for high-performance gas sensing. The results show that the atmospheric gas molecules (N2, CO2, O2, and H2O) presented ubiquitously in the sensing environments weakly bind to antimonene, while the polluted gas adsorbates (NH3, SO2, NO, and NO2) show stronger affinity toward antimonene with considerable adsorption energies and elevated charge transfers. Considering the susceptibility of the electronic properties of antimonene induced by the adsorbed molecules, we suggest that single-layered antimonene could be an eligible sensing material for polluted gases detection.

First-principles study of the effect of functional groups on polyaniline backbone

We present a first-principles density functional theory study focused on how the chemical and electronic properties of polyaniline are adjusted by introducing suitable substituents on a polymer backbone. Analyses of the obtained energy barriers, reaction energies and minimum energy paths indicate that the chemical reactivity of the polyaniline derivatives is significantly enhanced by protonic acid doping of the substituted materials. Further study of the density of states at the Fermi level, band gap, HOMO and LUMO shows that both the unprotonated and protonated states of these polyanilines are altered to different degrees depending on the functional group. We also note that changes in both the chemical and electronic properties are very sensitive to the polarity and size of the functional group. It is worth noting that these changes do not substantially alter the inherent chemical and electronic properties of polyaniline. Our results demonstrate that introducing different functional groups on a polymer backbone is an effective approach to obtain tailored conductive polymers with desirable properties while retaining their intrinsic properties, such as conductivity.

Functionalization-induced changes in the structural and physical properties of amorphous polyaniline: a first-principles and molecular dynamics study

In this paper, we present a first-principles and molecular dynamics study to delineate the functionalization-induced changes in the local structure and the physical properties of amorphous polyaniline. The results of radial distribution function (RDF) demonstrate that introducing -SO3−Na+ groups at phenyl rings leads to the structural changes in both the intrachain and interchain ordering of polyaniline at shorter distances (≤5 Å). An unique RDF feature in 1.8–2.1 Å regions is usually observed in both the interchain and intrachain RDF profiles of the -SO3−Na+ substituted polymer (i.e. Na-SPANI). Comparative studies of the atom-atom pairs, bond structures, torsion angles and three-dimensional structures show that EB-PANI has much better intrachain ordering than that of Na-SPANI. In addition, investigation of the band gap, density of states (DOS), and absorption spectra indicates that the derivatization at ring do not substantially alter the inherent electronic properties but greatly change the optical properties of polyaniline. Furthermore, the computed diffusion coefficient of water in Na-SPANI is smaller than that of EB-PANI. On the other hand, the Na-SPANI shows a larger density than that of EB-PANI. The computed RDF profiles, band gaps, absorption spectra, and diffusion coefficients are in quantitative agreement with the experimental data.

Ab Initio Study of Temperature, Humidity, and Covalent Functionalization-Induced Bandgap Change of Single-Walled Carbon Nanotubes

The effects of temperature, humidity, and covalent functionalization on the bandgap of single-walled carbon nanotubes (SWCNTs) are systematically investigated by ab initio calculations. The bandgap of SWCNTs has been found to decrease with the increase of temperature. Analysis of humidity effect indicates that water adsorption on the outer wall of SWCNTs widens the bandgap, but when the water molecules are adsorbed on the inner wall, SWCNTs with different radii and chiralities show different bandgap changes. We also show that covalent functionalization of SWCNTs leads to drastic deformation of the tube. Upon increasing the functional groups, the deformation is more obvious. It is worth noting that the tube deformation also greatly contributes to the change of the bandgap.

AlN/BP Heterostructure Photocatalyst for Water Splitting

In this letter, the structural, electronic, and optical properties of blue phosphorene (BP) and graphene-like aluminum nitride (AlN) nanocomposite are investigated by the first-principles method. Despite the indirect bandgap nature of the BP and AlN monolayers, AlN/BP heterostructure exhibits a direct bandgap characteristic in the most stable pattern. Moreover, we also find that the optically active states of the maximum valence and the minimum conduction bands are localized on opposite monolayers, leading to the electrons and holes spontaneously separated (type-II band alignment), which enhances the photocatalytic efficiency. Most interestingly, the AlN/BP heterobilayer exhibits enhanced optical properties in the visible and UV light zone, which is comparable or even superior to pristine BP - overall, the suitable direct gap and band edges positions, type-II band alignment, and fascinating visible and UV light adsorption, which enable AlN/BP heterostructure to have great potential applications in the field of solar energy conversion and photocatalytic water splitting.

SiGe/h-BN heterostructure with inspired electronic and optical properties: a first-principles study

The structure along with the electronic and optical properties of a SiGe/BN monolayer heterostructure were theoretically researched using density functional theory calculations. There are small interactions between a SiGe monolayer and a BN monolayer in the stacking model of a SiGe/BN heterostructure via van der Waals forces. The binding energies of the different stacking models, the DOS, and the charge density difference are calculated and analyzed. According to our investigation, the heterostructure maintains the most unique electronic properties of the SiGe monolayer, especially linear dispersion at the K point, and enlarges the band gap to ∼57 meV, benefiting its application in the microelectronic field. Moreover, the band gap can be modified through external electric fields and strains to a large extent. The optical property is also investigated to find an enhancement effect at the ultraviolet region. In general, the calculated results indicate that the SiGe monolayer layered on the BN substrate possesses great potential in microelectronic and optoelectronic applications.

Sorption and Diffusion of Water Vapor and Carbon Dioxide in Sulfonated Polyaniline as Chemical Sensing Materials.

A hybrid quantum mechanics (QM)/molecular dynamics (MD) simulation is performed to investigate the effect of an ionizable group (–SO3−Na+) on polyaniline as gas sensing materials. Polymers considered for this work include emeraldine base of polyaniline (EB-PANI) and its derivatives (Na-SPANI (I), (II) and (III)) whose rings are partly monosubstituted by –SO3−Na+. The hybrid simulation results show that the adsorption energy, Mulliken charge and band gap of analytes (CO2 and H2O) in polyaniline are relatively sensitive to the position and the amounts of –SO3−Na+, and these parameters would affect the sensitivity of Na-SPANI/EB-PANI towards CO2. The sensitivity of Na-SPANI (III)/EB-PANI towards CO2 can be greatly improved by two orders of magnitude, which is in agreement with the experimental study. In addition, we also demonstrate that introducing –SO3−Na+ groups at the rings can notably affect the gas transport properties of polyaniline. Comparative studies indicate that the effect of ionizable group on polyaniline as gas sensing materials for the polar gas molecule (H2O) is more significant than that for the nonpolar gas molecule (CO2). These findings contribute in the functionalization-induced variations of the material properties of polyaniline for CO2 sensing and the design of new polyaniline with desired sensing properties.

First-principles study of gas adsorptin on indium nitride monolayer as gas sensor applications

Using first-principles calculation within density functional theory, we study the gas (H₂O, H₂, H₂S, and CO₂) adsorption properties of single-layer indium nitride (InN). The four different adsorption sites (Bridge, In, N, Hollow) are chosen to investigate and the most sensitive adsorption site is found (N site for H₂ and H₂O gases; In site for H₂S; center site for CO₂) based on the adsorption energy, band gap and charge transfer. Through our research, the results indicate that InN is sensitive to NH₃ and H₂O. It is shown that H₂ gas molecules act as charge acceptors for the monolayer, except H₂S, H₂O adsorption which are found to be a charge donor. We perform a perpendicular electric field to the system and find its enhancement effect for adsorption energy of gas adsorption. Our theoretical results indicates that monolayer InN is a promising candidate for gas sensing applications.

Graphane/fully hydrogenated h-BN bilayer: Marvellous dihydrogen bonding and effective band structure engineering

In this work, density functional theory (DFT) computations with van der Waals (vdW) corrections were performed to investigate the dihydrogen bondings and their effects on the electronic band structures of graphane/fully hydrogenated h-BN (G/fHBN) bilayers. The type of dihydrogen bonding (C-H···H-B or C-H···H-N) defined the conformation and stability of G/fHBN bilayer, leads to significant band structure modifications of the nanosystems. Interestingly, the bilayer combined by C-H···H-B bilayers has an energy gap (~1.2 eV) much lower than those of individual building blocks graphane and fHBN. Especially, changing the direction and strength of external electric field can effectively tune the band gap of G/fHBN bilayer, and correspondingly cause a semiconductor-metal transition. These findings offer new opportunities for developing electronic and opto-electronic devices based on G/fHBN bilayer, and inspire more endeavor in the usage of weak interactions for band structure engineering.