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In drug delivery systems, graphene materials are promising drug carriers. Drug molecules are loaded on graphene through π-π interaction between graphene and benzene ring structure, which is widely found in organic drug molecules. Then the drug molecules are released under different conditions, such as different environmental pH, at lesion site. In the application, the adsorption and desorption between benzene ring structure in drug molecules and graphene play a key role. Herein, an experimental method for measuring the adhesion force between a single phenyl and graphene is proposed, and the adsorption and desorption mechanical properties of a benzene ring structure on graphene surface at different environmental pH are firstly measured. The experimental results show that the adhesion force decreases with the increase of environmental pH. Moreover, molecular dynamics simulations show that the influence of pH on adhesion force is mainly realized by changing the electrostatic potential distribution on graphene surface, and the interaction force between a single benzene and graphene changes from attractive to repulsive with the increase of environmental alkalinity. In addition, a molecular dynamics model for the dynamic adsorption and desorption capacities of benzene molecules on graphene surface at different quantity of ions is established. Benzene molecules can achieve full adsorption on the surface of graphene when there are 10 and 20 hydrogen ions. And benzene molecules can achieve full desorption on the surface of graphene when there are 10 and 20 hydroxide ions. [Display omitted] [ABSTRACT FROM AUTHOR]

In field of drug delivery, graphene is a potential material as drug carrier due to its large specific surface area and excellent chemical stability. Many kinds of drug molecules can be adsorbed on graphene surface through single or multiple benzene ring structures in drug molecules. Graphene loaded with drug molecules needs to be transported to the lesion site through blood. The content of water molecules in blood accounts for 92%. Therefore, the influence of water molecule on adsorption performance cannot be ignored. Here, the influence and mechanism of water molecule on the adsorption properties between benzene molecule and graphene is studied. The adsorption models of benzene molecule on graphene surface in vacuum and water environments are established, respectively. The adhesion energy, adhesion force and stable adsorption position of benzene molecule in two environments are analyzed by molecular dynamics simulation and potential function theory. Moreover, a model of preadsorption of a single water molecule on graphene surface is further presented, which explains the reason of the difference in adsorption performance in vacuum and water environment from the perspective of energy. The preadsorption of water molecule on graphene surface promotes the adsorption of benzene molecule. [Display omitted] [ABSTRACT FROM AUTHOR]

As a typical semiconductor, ZnO is considered as a favorable photocatalyst due to its excellent photoelectrochemical properties. However, low response of visible light and the recombination of photoinduced carriers limits its application in photocatalysis. Herein, a novel, robust and recyclable heterogeneous photocatalyst based on flower-like Co doped ZnO microspheres was presented without changing the hierarchical morphology. The crystal structure, light absorption, and electrochemical performance were systematically investigated, and the response of Co doped ZnO to visible light significantly enhanced with the gap band reduced from 3.20 eV to 2.54 eV. Due to the transformation of Co2+ to Co3+, more oxygen vacancies were produced, with more photoinduced electrons transferring to Co3+ which would greatly inhibit the recombination of photoinduced electrons and holes and improve photocatalytic activity. 2-Mercaptobenzothiazole (MBT) which is considered as a long half-life intermediate of antibiotic medicine is chosen as a target. As a result, the 7% Co-ZnO photocatalyst exhibited excellent photocatalytic activity for the degradation of MBT with the rate constant of 0.1498 min−1 and removing ratio of 97.3% in 50 min. The formation of excess oxygen vacancies and the conversion between Co2+ to Co3+ were further identified by XPS analysis. This work provides new sights for doping transition metal with different chemical valence in semiconductors for producing oxygen vacancy and improving the photocatalytic efficiency. [Display omitted] • A novel and recyclable heterogeneous flower-like Co doped ZnO microspheres is prepared via simple procedure. • Doping of Co species effectively reduces the band gap energy of ZnO with the formation of abundant oxygen vacancies. • Electrons are trapped due to the transformation of Co2+ and Co3+ which hinders the recombination of photo-induced carriers. • The formation of oxygen vacancies and the conversion between Co2+ to Co3+ are further identified by XPS analysis. • The prepared photocatalyst exhibits excellent photocatalytic activity for degradation of 2-mercaptobenzothiazole. [ABSTRACT FROM AUTHOR]

A three dimensional (3D) rare cubane-like tetrameric Cu(II)-based MOF 1 having formula [Cu 4 (O)(OH) 3 (bb) 4 (NO 3) 3 0.3 H 2 O·3CH 3 CN] n (bb = 4,4'-bis (imidazolyl) biphenyl) has been synthesized and characterized. The MOF 1 possess 4-fold dia topology and effectively catalyzes the photodegradation of basic green (BG), rhodamine B (RhB), methyl blue (MB) and methyl orange (MO) dyes under UV light irradiation. The effects of initial solution pH, concentration of dyes, and photocatalyst dose have been monitored on the photocatalytic performance of 1. The photocatalytic results suggest that MOF 1 exhibits best photocatalytic activity for BG amongst all the four dyes investigated. Under the optimal reaction condition, ∼96.8 % photodegradation of BG has been observed at pH 5, at 40 ppm concentration of BG and 30 mg photocatalyst concentration in 120 min time span. The radical trapping experiments suggest that O 2 ·− and·OH are the main active species that catalyzes the photodecomposition of dyes. The possible mechanism for the BG degradation of 1 is proposed using density of states (DOS) calculations and Hirshfeld surface analysis. [Display omitted] • A new Cu(II) MOF with 4-fold dia topology synthesized using 4,4'-bis (imidazolyl) biphenyl ligand. • The MOF was characterized using different physico-chemical techniques. • The MOF used as photocatalyst for photodegradation of dyes especially basic green. [ABSTRACT FROM AUTHOR]

A three dimensional (3D) rare cubane-like tetrameric Cu(II)-based MOF 1 having formula [Cu 4 (O)(OH) 3 (bb) 4 (NO 3) 3 0.3 H 2 O·3CH 3 CN] n (bb = 4,4'-bis (imidazolyl) biphenyl) has been synthesized and characterized. The MOF 1 possess 4-fold dia topology and effectively catalyzes the photodegradation of basic green (BG), rhodamine B (RhB), methyl blue (MB) and methyl orange (MO) dyes under UV light irradiation. The effects of initial solution pH, concentration of dyes, and photocatalyst dose have been monitored on the photocatalytic performance of 1. The photocatalytic results suggest that MOF 1 exhibits best photocatalytic activity for BG amongst all the four dyes investigated. Under the optimal reaction condition, ∼96.8 % photodegradation of BG has been observed at pH 5, at 40 ppm concentration of BG and 30 mg photocatalyst concentration in 120 min time span. The radical trapping experiments suggest that O 2 ·− and·OH are the main active species that catalyzes the photodecomposition of dyes. The possible mechanism for the BG degradation of 1 is proposed using density of states (DOS) calculations and Hirshfeld surface analysis. [Display omitted] • A new Cu(II) MOF with 4-fold dia topology synthesized using 4,4'-bis (imidazolyl) biphenyl ligand. • The MOF was characterized using different physico-chemical techniques. • The MOF used as photocatalyst for photodegradation of dyes especially basic green. [ABSTRACT FROM AUTHOR]

Soil and ground water pollution by heavy metal is an identified global environment concern. Montmorillonite is widely adopted as an adsorbent used in retardation of heavy metals due to its excellent adsorption capacity, conveniency, and stability. However, the adsorption mechanism of heavy metal ions in the interlayer and nanopore of montmorillonite needs to be further studied. The classical grand canonical monte carlo (GCMC) and molecular dynamics (MD) simulations were performed to quantify the structural and dynamic properties of heavy metal ions in the interlayer and nanopore of montmorillonite (MMT). Two layer charge densities of MMT, two cation concentrations, and three typical heavy metal ions (Pb2+, Ba2+, and Cs+) were considered. With the increase of layer charge density, outer-sphere adsorption (OSA) was transformed into inner-sphere adsorption (ISA) for three heavy metal ions. The adsorption quantity increased with the increase of layer charge density and cation concentration. The calculated diffusion coefficients of three heavy metal caions in montmorillonite was bulk solution > nanopore > interlayer. The results and adsorption mechanism are helpful for understanding the natural processes of heavy metal ions in environment and developing more efficient remediation materials. [Display omitted] • Outer-sphere adsorption occurred for Pb2 + and Ba2 + on low-charge montmorillonite surface. • The adsorption capacity of high-charge montmorillonite was stronger than low-charge montmorillonite. • Higher cation concentration increases adsorption quantity but doesn't change adsorption pattern. • The mobility of cations in montmorillonite follow the order of interlayer < nanopore < solution. [ABSTRACT FROM AUTHOR]