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MMTNS were introduced into carboxymethyl cellulose-chitosan system to synthesize porous hydrogel adsorbent with stable structure and high dye handling capacity. Al-OH on edge of MMTNS formed hydrogen-bond (-OH···+NH3-) with -NH2 on CS, CS then cooperated with CMC via amidation and chains interleaving, forming three-dimensional hydrogel. Morphology characterization revealed that hydrogel possessed microporous open-framework structure, facilitating free entrance of macromolecular MB dye to react with internal reaction sites in hydrogel. Factor tests indicated that high removal (97%) of MB was achieved via 0.2 g/L hydrogel within 360 min even after 5 adsorption-regeneration cycles. Adsorption process followed Pseudo-first-order, Pseudo-second-order kinetic model and Sips isotherm model, owing to both monolayer physical and chemical adsorption behavior of MB molecules onto homogeneous surface of hydrogel. Adsorption mechanism was attributed to ion-exchange, groups combination of carboxyl and hydroxyl, and Si active sites reaction. Such hydrogel realized promotion of polysaccharide polymers in materials design and wastewater treatment.

The grain refinement resulting from the addition of yttrium (Y) (1, 3 pct, and 9 wt pct) and zirconium (Zr) (0.1, 0.2, and 0.5 wt pct) to magnesium (Mg) under a wide range of cooling rates (0.8 to 160 K/s) has been investigated. This study quantifies the effect of Y and Zr on the grain size (dgs) of Mg-Y base alloys followed by examination of the effect of cooling rate on these alloys. The Interdependence Model was able to describe the reduction in grain size caused by the growth restriction provided by Y and soluble Zr, and the introduction of potent Zr particles. It is shown that by incorporating a term for cooling rate into the Interdependence model the effect of cooling rate on grain size can be assessed for the range of growth restriction values and cooling rates investigated.

Different atmospheric gas molecules (e.g., N2, O2, CO2, H2O, CO, NO, NO2, NH3, and SO2) are absorbed on the pristine hexagonal boron arsenide (BAs) through density functional theory calculations. For each gas molecules, various adsorption positions were considered. The most stable adsorption depended on position, adsorption energy, charge transfer, and work function. SO2 gas molecules had the best adsorption energy, the shortest distance for BAs surface in the atmospheric gas molecule, and a certain amount of charge transfer. The calculation of work function was important for exploring the possibilities of adjusting the electronic and optical properties. Our results presented BAs materials can be the potential gas sensor of SO2 with high sensitivity and selectivity.

The adsorption of Hg2+ on thermally modified molybdenum disulfide was explored in this work. The X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) results revealed that thermal treatment led to partial oxidation of MoS2 to MoO3 and a creation of edge defects on the surface of molybdenum disulfide. The density functional theory (DFT) calculation indicated that the oxidative etchings were terminated with oxygen atoms, and both the vacancy and perfect surface could be oxidized during thermal treatment. The batch tests indicated that thermal treatment enabled the surface of molybdenum disulfide to be highly reactive as Hg2+ adsorbent. The adsorption rate and capacity of 500 °C heated molybdenum disulfide were 17.6 times faster and 11-fold higher compared to that of molybdenum disulfide without thermal modification. The tremendous enhancement of Hg2+ adsorption was significantly related to the oxidation of molybdenum disulfide and the increase of atom activity ...

In this work, graphene for use as methane (CH4) sensors has been designed and evaluated via first-principles theory. Firstly, the effect of the number of layers of graphene on methane adsorption is investigated. The results show that the methane adsorption will be increased with the number of layers, the maximum energy is 0.267 eV. Furthermore, the adsorption of CH4 leads to a small opening of the band structure of graphene. As for the doping (Al-doped) in graphene, we mainly focus on the concentration of Al atoms. The Al atom was found to cause a huge increment in methane adsorption energy that can be up to 3.212 eV when the concentration of Al atoms is 5.555%. Meanwhile, the doping of Al atoms also enhances the conductive properties of graphene. Lastly, the effect of defects was also investigated. While slightly smaller than that of pristine graphene, the methane adsorption energy of defected graphene is also increased with the number of layers. It was found that the model with the methane on the top of the empty atom and the H atoms on the top of the center of the carbon ring results in the best methane adsorption. Keywords: Adsorption, Band structure, Density-functional theory, Methane sensor

Hg0 has gradually become a serious environmental problem that need to be solved, due to its strong volatility and insolubility in water. In this study, the adsorption behavior of X(O, Se, Te)-doped monolayer MoS2 for was studied via DFT calculation to evaluate its potential for Hg0 removal. Oxygen group atoms X(O, Se, Te) doped MoS2 systems all have extremely high bonding energies, in which the strong interaction between the dopant atoms and the S vacancy of monolayer MoS2, resulting that dopant systems were greatly stable. Compared with pristine monolayer MoS2, X(O, Se, Te)-doped MoS2 has stronger adsorption performance and electrical conductivity in adsorbing Hg0, which is mainly attributed to the facilitation of electrons transfer between Hg0 and MoS2. The oxygen doping system exhibits best adsorption performance to Hg0, primarily due to the relatively stronger interaction between the dopant oxygen and Hg0. The results reveal that the O-doped monolayer MoS2 can effectively improve the adsorption efficiency of Hg0 increasing the application potential for mercury emissions control in coal-fired power plants.

Strain modulation is one of the most popular tuning methods for the electronic properties of low-dimensional systems. In the present work, by using first-principle calculations, strain engineering is used to module the band gap transition of two novel van der Waals (vdW) heterostructures based on 2D Blue Phosphorene (Blue P) supported on XC (X = Ge, Si), producing Blue P/XC bilayer systems. The results show that the biaxial strain is more effective than uniaxial strain for controlling the electronic properties of Blue P materials. The band gap of Blue P/GeC vdW heterostructures increases when increasing the strain value from −8% to 0%, whereas after 0% strain value not increases in the band gap is observed. The band gap of Blue P/SiC vdW heterostructures increased and reached the maximum of 1.09 eV at strain value of 0%, and it decreased with further increasing of strain value. The present work provides an effective avenue to tune the electronic structure and band gap of Blue P/XC vdW heterostructures.

Base on the strong activation activity and affinity of transition metal ions and MoS2 for peroxymonosulfate (PMS), respectively, Co(Ⅱ)-doped MoS2 nano-flowers (Co-MoS2 NFs) with a great photo-response property was facilely synthesized to achieve a more efficient PMS activation for ofloxacian (OFX) degradation. It was found that Co-MoS2 NFs exhibits superior catalytic activity for OFX degradation under visible-light irradiation, which was attributed to the synergetic effect of doped Co(Ⅱ) and photo-generated carriers to PMS activation. Besides, Co-MoS2 NFs was able to efficiently degrade OFX within 4 cycles in the presence of PMS while leaked minute amount of Mo and Co ions, implying the excellent cycle stability of Co-MoS2 NFs. Furthermore, SO4•− and 1O2 were detected as the primary reactive radicals for OFX degradation in the Co-MoS2 NFs-PMS system through EPR and quenching tests. This new strategy of coupling doped Co(Ⅱ) and photo-generated carriers for more efficient PMS activation, which will greatly benefit the development of SO4•−-based AOPs as well as cater to the demand for environmental remediation in the future.

Novel molybdenum disulfide-montmorillonite (MoS2@2DMMT) hydrogels for Cu(II) removal and inhibition on bacterial growth were successfully prepared. MoS2 was first in-situ growth onto 2DMMT platelet through hydrothermal method and then cross-linked with organic reagents to form hydrogels. The flower-like structure of synthesized MoS2 could be clearly observed in MoS2@2DMMT by SEM. The synthesized hydrogels possessed a three-dimensional macroporous structure, offering a free access for contaminants to get inside and combine with the active sites. Adsorption tests revealed that efficient Cu(II) removal (65.75 mg/g) could be achieved within a short time (30 min) at pH 5. The pseudo-second-order kinetics model and Langmuir isotherm model indicated the existence of chemisorption and monolayer absorption for Cu(II) onto MoS2@2DMMT hydrogels. Characterizations of EDS and XPS indicated that Cu(II) reacted with groups of carboxyl, hydroxyl and amidogen. Bacteriostatic tests revealed that almost a complete bacteriostatic was achieved with just small dosage (0.8 mg/mL) of MoS2@2DMMT hydrogels after the Cu(II) removal under the normal illumination. The mechanism was ascribed to the destructive effect of Cu(II) to the cytomembrane and the damage of reactive oxygen species (ROS) to the DNA. Such hydrogel not only provided insights for treating co-existing contaminates, but also guides for designing novel polymer materials from two-dimensional (2D) nano-materials.

The adsorption behaviors of methane adsorbed on different graphenes (pristine, and B-, N-, P-, and Al-doped monolayer and multilayer) are analyzed using density-functional theory. The results demonstrate that the sensing performance of graphene as a methane sensor strongly depends on the selection of dopants and the number of layers. The adsorption energy on monolayer P-doped or Al-doped graphene shows about one order of magnitude higher than that with other dopants. In addition, graphenes doped with different impurities show different responses to the charge transfer. A further analysis indicates that the multilayer structure has a positive effect on the adsorption energy on the pristine, B-doped, and N-doped graphene, while the P-doped or Al-doped graphene shows a significant decrease with the increase in the number of layers. Moreover, the multilayer structure has a minor effect on the charge transfer. Based on the combined effects on the adsorption energy and the charge transfer, Al-doped monolayer graphene is the optimal candidate for methane sensing.