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Cu nanoparticles (NPs) encapsulated within a hollow carbon spheres (Cu@HCS) is an effective catalyst with optimal structural design for the oxidative carbonylation of methanol to dimethyl carbonate (DMC). Control of the structural properties of both the shell and the core plays a vital role in determining the catalytic properties. In this study, mesoporous HCS with an average diameter of 190 nm and a shell thickness of 15 nm were obtained using silica micropheres as a hard template and by tuning the amount of resorcinol and formaldehyde. Cu@HCS catalysts were fabricated by hydrothermal impregnation followed by hydrogen reduction, and the size of Cu NPs was delicately controlled by varying heating rate of reduction process. The results show that a thin mesoporous carbon shell of Cu@HCS is beneficial to the diffusion of reactants and products, and that Cu NPs with very small size can provide a large active specific surface area. In comparison with the commercial CuCl catalyst, the Cu@HCS-5 catalyst displays superior catalytic activity; its turnover frequency and apparent activation energy reaches 23.1 h−1 and 20.5 kJ·mol−1, respectively. In addition, it exhibits higher stability than that of CuCl because the carbon shell prevents the aggregation and leaching of copper NPs during the reaction. With the advantages in catalytic activity, corrosion effect, and recovery performance, the Cu@HCS catalyst has a promising potential for realizing the cleaner production of DMC.

The first principle calculations with on-site Coulomb repulsion U terms were carried out to investigate the 5-hydroxymethylfurfural (HMF) adsorption on the CuO(1 1 1) and Co3O4(1 1 0) surfaces, two widely used oxidation catalysts. The adsorption of HMF molecule is energetically favoured in both cases, and HMF is more inclined to bridge adsorption via hydroxyl and formyl groups binding with surface O and metal sites. Moreover, the adsorption energy relies on both the coordination type of surface lattice oxygen to which the H atom binds and the formation of H-bond involving hydroxyl and formyl groups on the adsorbed HMF. Also, the hydroxyl O H bond breaking is very easy and is likely to be the first step in HMF oxidation, and then the OH insertion reaction to produce 2,5-furandicarboxylic acid (FDCA). The corresponding experimental results also show that the CuO and Co3O4 surfaces are promising candidate catalysts.

A critical aspect in the improvement of the catalytic performance of Cu-based catalysts for the synthesis of dimethyl carbonate (DMC) is the development of an appropriate support. In this work, nitrogen-doped hollow carbon spheres (NHCSs), with 240 nm average diameter, 17 nm shell thickness, uniform mesoporous structure and a specific surface area of 611 m2 g−1, were prepared via a two-step Stӧber method. By varying the quantity of nitrogen-containing phenols used in the preparation it has been possible to control the nitrogen content and, consequently, the sphericity of the NHCSs. It was found that perfect spheres were obtained for nitrogen contents below 5.4 wt.%. The catalysts (Cu@NHCSs) were prepared by the hydrothermal impregnation method. The catalytic activity towards DMC synthesis was notably enhanced due to the immobilization effect on Cu particles and the enhanced electron transfer effect exercised by the effective nitrogen species, including pyridinic-N and graphitic-N. When the average size of the copper nanoparticles was 7.4 nm and the nitrogen content was 4.0 wt.%, the values of space-time yield of DMC and of turnover frequency (TOF) reached 1528 mg/(g h) and 11.0 h–1, respectively. The TOF value of Cu@NHCSs was 6 times higher than non-doped Cu@Carbon (2.1 h−1). The present work introduces the potential application of nitrogen-doped carbon materials and presents a novel procedure for the preparation of catalysts for DMC synthesis.

The mechanism for dimethyl carbonate (DMC) synthesis by oxidation carbonylation of methanol on a single-atom Cu1/graphene catalyst was investigated by density-functional theory calculations. Carbon vacancies in graphene can significantly enhance the interaction between Cu atoms and graphene supports, and provide an increased transfer of electrons from Cu atoms to the graphene sheet. Compared with Cu-doped divacancy graphene (Cu/DG), Cu-doped monovacancy graphene (Cu/MG) provides a stronger interaction between adsorbents and the catalyst surface. Among the reaction processes over Cu1/graphene catalysts, CO insertion into methoxide was more favorable than dimethoxide. The rate-limiting step on the Cu/DG surface is the carbomethoxide reaction with methoxide, which is exothermic by 164.6 kJ mol−1 and has an activation barrier of 190.9 kJ mol−1 energy. Compared with that on the Cu crystal surface, Cu4 and Cu3Rh clusters, and the Cu2O(111) surface, the rate-determining step for DMC formation on Cu/MG, which is CO insertion into methoxide, needs to overcome the lowest barrier of 73.5 kJ mol−1 and is exothermic by 44.6 kJ mol−1. Therefore, Cu/MG was beneficial to the formation of DMC as a single-atom catalyst.

The different mechanisms of CO2 methanation on Ni(111) surfaces have been investigated by density functional theory with and without the formation of CO as an intermediate. The most stable adsorption configurations of all reaction species (O, OH, CO, CH, CH2, CH3, CH4, HCOO, C(OH)2, CH2O, etc.) in three paths of CO2 methanation adsorbed on the Ni(111) surface are described. The energy barriers and reaction energies for the overall processes involved in the various paths are presented. The rate-determining steps for the three mechanisms are HCOO→CO + OH for path 1, CO → C + O for path 2 and CO2 + 2H → C(OH)2 for path 3 with maximum energy barriers of 306.8 kJ/mol, 237.4 kJ/mol and 292.3 kJ/mol, respectively. Path 2 is therefore the optimum of the three mechanisms. The path starts with CO2 dissociation into CO and O, CO decomposition into C and O species and C species hydrogenation to form CH4: CO2 → CO + O → C + O + 4H → CH2 + 2H → CH3 + H → CH4.

To enhancing enhanced sunlight harvesting, long persistence phosphor (LPP) materials were often incorporated into photoanodes of photoelectric devices. However, the role of LPP layer on the photoelectric enhancements is not yet clear. Here, the authors have systematically studied the effect of green LPP (SrAl2O4: Eu3+) and its thickness on photoelectric behaviours of dye-sensitized solar cells (DSSCs). Results showed that the P25/LPP DSSCs generates power conversion efficiency (PCE) of 7.16% at the optimal LPP thickness, which is 24.3% higher than that of the P25 ones. Series of analysis indicate that the enhancements in short-circuit current density and PCE could mainly be due to the LPP’s function of back scattering (containing down-conversion effect and enhancement in light absorption) of incident sunlight. Moreover, the enhanced carriers’ lifetime and open-circuit voltage are mainly due to the LPP layer’s afterglow effect. In addition, the P25/LPP DSSCs can still generate an output power density (82.15 μW cm−2) with a high PCE value of 46.94% in dark.

In this paper, we tested the hypothesis that there is an increased sensitivity for detecting and measuring disease biomarkers (such as human cardiac troponin I, cTnI) by a decrease of nonspecific adsorption in diluted self-assembled monolayers (SAMs) on planar sputtered gold films. Combining grazing angle Fourier-transform infrared spectroscopy (FT-IR) and antibody–antigen–antibody (sandwich) fluorescence-based immunoassay, we examined the relationship of sensitivity, specificity of detection of cTnI and the level of nonspecific protein adsorption in the following SAMs: pure MHA (16-mercaptohexadecanoic acid, 1 mM, with head COO − , x = 1.0), a mixed SAM comprising MHA (0.1 mM) and UDT (1-undecane thiol, 0.9 mM, with hydrophobic head CH 3 , x = 0.1 UDT ), and a mixed SAM comprising MHA (0.1 mM) and MUD (11-mercapto-1-undecanol, 0.9 mM, with hydrophilic head OH, x = 0.1 MUD ). Our data revealed that nonspecific binding to SAMs is favored in the following order: CH 3 > COO − > OH, consistent with previous studies. Compared with pure SAMs, diluting MHA SAMs with MUD increases the sensitivity of cTnI, whereas diluted MHA SAMs with UDT has the same sensitivity of detection of cTnI, suggesting it is the nature of the second diluting thiol that plays an important role on the amount of adsorbed protein on the surface. We obtained a 10-fold increase in the limit of detection of cTnI to 10 ng/ml using x = 0.1 MUD due to a decrease of nonspecific binding. Further, specific binding between the antigen cTnI and its antibody is unaltered on pure and diluted SAMs.

The adsorption and dissociation of O 2 on CuCl(1 1 1) surface have been systematically studied by the density functional theory (DFT) slab calculations. Different kinds of possible modes of atomic O and molecular O 2 adsorbed on CuCl(1 1 1) surface and possible dissociation pathways are identified, and the optimized geometry, adsorption energy, vibrational frequency and Mulliken charge are obtained. The calculated results show that the favorable adsorption occurs at hollow site for O atom, and molecular O 2 lying flatly on the surface with one O atom binding with top Cu atom is the most stable adsorption configuration. The O–O stretching vibrational frequencies are significantly red-shifted, and the charges transferred from CuCl to oxygen. Upon O 2 adsorption, the oxygen species adsorbed on CuCl(1 1 1) surface mainly shows the characteristic of the superoxo (O 2 − ), which primarily contributes to improving the catalytic activity of CuCl, meanwhile, a small quantity of O 2 dissociation into atomic O also occur, which need to overcome very large activation barrier. Our results can provide some microscopic information for the catalytic mechanism of DMC synthesis over CuCl catalyst from oxidative carbonylation of methanol.

The comparison of the performance and morphology was carried out between neat PVDF membrane and PVDF composite membranes with nanosized TiO2 particles of different size. The results of permeability and instrumental analysis illustrated that nanometer size obviously affected the performance and structure of the PVDF membranes. The smaller nanoparticles could improve the antifouling property of the PVDF membrane more remarkably. The surface and cross-section of the membranes were observed with an atomic force microscopy (AFM), a scanning electron microscope (SEM). The TiO2/PVDF membrane with smaller nanoparticles had smaller mean pore size on its surface and more apertures inside the membrane. X-ray diffraction (XRD) experiments also suggested that smaller TiO2 nanoparticles had stronger effect on the crystallization of PVDF molecules.