The design and synthesis of highly active non-noble metal oxide catalysts, such as transition-and rare-earth-metal oxides, have attracted significant attention because of their high efficiency and low cost and the resultant potential applications for the degradation of volatile organic compounds (VOCs). The structure-activity relationships have been well-studied and used to facilitate design of the structure and composition of highly active catalysts. Recently, non-noble metal oxides with porous structures have been used as catalysts for deep oxidation of VOCs, such as aromatic hydrocarbons, aliphatic compounds, aldehydes, and alcohols, with comparable activities to their noble metal counterparts. This review summarizes the growing literature regarding the use of porous metal oxides for the catalytic removal of VOCs, with emphasis on design of the composition and structure and typical synthetic technologies.

Control policies such as “odd-and-even license plate rule” were implemented by the Chinese government to restrict traffic and suspend factory production in Beijing and neighboring cities during the Asia-Pacific Economic Cooperation summit. We use ozone monitoring instrument (OMI), mobile differential optical absorption spectroscopy (DOAS), and multi-axis differential optical absorption spectroscopy (MAX-DOAS) to measure the variation of the spatial and temporal patterns of NO₂ column densities from October 24, 2014 to November 22, 2014. It is found that the NO₂ column densities during the episode of control policies are significantly lower than those during other periods, and the emission flux of NO₂ calculated by mobile DOAS is also lower than the results from other periods. Some daily low NO₂ column densities occur with the northwest wind direction. We then compare the relationship between OMI and mobile DOAS NO₂ column density observations, and the results of mobile DOAS are approximately 2.7 times larger than the OMI values. The largest discrepancy occurs in the northern part of Beijing city. In other parts, the two instruments have a better correlation coefficient (R²) of 0.61. The low NO₂ column densities that occur during the episode of control policies are affected by the control policies as well as meteorological conditions.

Ammonia (NH₃) plays vital roles in new particle formation and atmospheric chemistry. Although previous studies have revealed that it also influences the formation of secondary organic aerosols (SOA) from ozonolysis of biogenic and anthropogenic volatile organic compounds (VOCs), the influence of NH₃ on particle formation from complex mixtures such as vehicle exhausts is still poorly understood. Here we directly introduced gasoline vehicles exhausts (GVE) into a smog chamber with NH₃ absorbed by denuders to examine the role of NH₃ in particle formation from GVE. We found that removing NH₃ from GVE would greatly suppress the formation and growth of particles. Adding NH₃ into the reactor after 3 h photo-oxidation of GVE, the particle number concentration and mass concentrations jumped explosively to much higher levels, indicating that the numbers and mass of particles might be enhanced when aged vehicle exhausts are transported to rural areas and mixed with NH₃-rich plumes. We also found that the presence of NH₃ had no significant influence on SOA formation from GVE. Very similar oxygen to carbon (O:C) and hydrogen to carbon (H:C) ratios resolved by aerosol mass spectrometer with and without NH₃ indicated that the presence of NH₃ also had no impact on the average carbon oxidation state of SOA from GVE.

We present combined Mie lidar, ozone lidar and wide-range particle spectrometer observations which were carried out in Beijing, north China during two periods—one haze period before the Asia-Pacific Economic Cooperation (APEC) meeting and one moderate pollution period during the meeting in 2014. High extinction coefficient, moderate ozone concentration and variable particle number concentration were obtained throughout the first haze observation period. The mean extinction coefficients in the two pollution periods were 0.52 and 0.23 km^-1, respectively, at 532 nm. The ozone concentration during the first haze phase was more various with a higher average value of 49 ppb compared with that in the second pollution observations (32 ppb). Compared with the same metrological condition occurring at the end of October, the sharply decreased aerosol extinction coefficient and ozone concentration show the effectiveness of the emission-cutting measures implemented during APEC in November. The comparison of aerosols and ozone in different heights indicate different pollution sources and the complicated ozone process of generation and disappearance. The correlation between the scattering coefficient and particle number concentrations of various diameter depended on the ambient humidity. Especially the particle number concentration (500 nm-1 mm) contributed most to PM_2.5 concentration. The four-day back trajectories from a Hybrid Single-particle Lagrangian Integrated Trajectory (HYSPLIT) model indicate that the air masses in the lower boundary layer before and during APEC were advected from the densely populated south regions of China and the long pollution transportation passing through northern China.

To study the HONO formation mechanisms during a pollution period, a continuous measurement was performed in both urban and suburban aeras of Beijing. During this period, the PM_2.5 concentrations increased to 201 and 137 mg/m³ in urban and suburban areas, respectively. The concentrations of HONO, CO, SO₂, O₃, NO, NO₂, NO_x were 1.45 ppbv, 0.61 ppmv, 8.7 ppbv, 4.3 ppbv, 44.4 ppbv, 37.4 ppbv, 79.4 ppbv and 0.72 ppbv, 1.00 ppmv, 1.2 ppbv, 7.9 ppbv, 3.7 ppbv, 8.2 ppbv, 11.9 ppbv, in urban and suburban areas, respectively. To compare possible pathways of HONO formation in both sites, the contributions of direct emissions, heterogeneous formations, and homogeneous productions were studied. HONO/NO₂ ratios in the two sites indicated that heterogeneous reactions of NO₂ were more efficient in suburban areas. And in both urban and suburban areas, the increase of PM_2.5 concentrations and RH would promote the conversion efficiency in RH that ranged from 0% to 85%. However, when RH was above 85%, the HONO formation slowed down. Moreover, the study of direct emissions and homogeneous reactions showed that they contributed to a majority of HONO increase in urban areas than the 20% contributions in suburban areas. It implied that the high NO_x concentrations and NO concentrations in urban areas or in pollution periods would make direct emissions and homogeneous reactions become dominant in HONO formations.

In February 2014, the Beijing-Tianjin-Hebei (BTH) area experienced a weeklong episode of heavy haze pollution. Cities such as Beijing (BJ) and Shijiazhuang (SJZ) issued heavy pollution alerts for the first time and took emergency control measures. This study employed the Nested Air Quality Prediction Modeling System (NAQPMS) to simulate and analyze the three-dimensional structure of the source contributions of PM_2.5 in the BTH area during this pollution episode and quantitatively assessed the effects of the emergency control measures. The results showed that during the polluted period (February 19-26), surface PM_2.5 mainly originated from local sources (48%-72%). In the entire BTH area, southern Hebei (SHB) represented the largest internal contribution (33%), while the main external contributions came from Shandong (SD) (10%) and Henan (HN) (4%). Vertically, the local contribution was constrained below the near-ground layer, and rapidly decreased with altitude. The regional transport path from SHB and Shanxi (SX) to BJ appeared at 0.5-1.5 and 1.5-2.5 km, with contributions of 32%-42% and 13%-27%, respectively. The non-local source regions for the BTH area were SD below 1 km and mainly SX and HN above 1 km. Compared to the non-polluted period (February 27-28), the contribution from regional transport increased during the polluted period, indicating the key role of regional transport in the pollution formation. The emergency control measures had a relatively large effect on NO_x and SO₂ concentrations, but a limited effect on PM_2.5. The stronger regional transport during the polluted period may have weakened the effects of the local emergency control measures. These results indicated that a coordinated emission control should be implemented not only over the BTH area but also over its surrounding provinces (e.g. SD, HN).

When gasoline is burned to power an automotive engine, a portion of the fuel remains unburned or is partially burned and leaves the engine as hydrocarbon and oxygenated compounds. In addition, a small portion of the fuel can escape the vehicle through evaporation. Changes in alkanes, olefins and aromatics each affect emissions differently, which could complicate control strategies for air pollution. In this study, we collected 31 gasoline samples over five provinces and cities (Beijing, Tianjin, Hebei, Shandong, and Shaanxi) in North China between 2012 and 2013. The organic composition of the gasoline samples was analyzed using the gas chromatography-mass spectrometry (GC-MS) method, and the aniline compounds were analyzed by solvent extraction and the GC-MS method. The ratios of alkanes, aromatics, olefins and other organic compounds in gasoline were 40.6%, 38.1%, 12.9% and 8.4%, respectively. The aromatic and benzene exceedances were 15 and 8 based on the China's gasoline standards (III), and they accounted for 48.4% and 25.8% of all the gasoline samples, respectively. Strong carcinogen aniline compounds were detected in all 31 samples, and the content of aniline compounds in 3 samples exceeded 1%. The high proportion of aromatics and olefins in the gasoline increased the emissions of carbon monoxide (CO) and toxics, as well as the atmospheric photochemical reactivity of exhaust emissions, which could hasten the formation of secondary pollutants. Our results are helpful for redefining government strategies to control air pollution in North China and relevant for developing new refining technology throughout China.

To investigate the sensitivity of secondary aerosol formation and oxidation capacity to NO_x in homogeneous and heterogeneous reactions, a series of irradiated toluene/NO_x/air and α-pinene/NO_x/air experiments were conducted in smog chambers in the absence or presence of Al₂O₃ seed particles. Various concentrations of NO_x and volatile organic compounds (VOCs) were designed to simulate secondary aerosol formation under different scenarios for NO_x. Under “VOC-limited” conditions, the increasing NO_x concentration suppressed secondary aerosol formation, while the increasing toluene concentration not only contributed to the increase in secondary aerosol formation, but also led to the elevated oxidation degree for the organic aerosol. Sulfate formation was suppressed with the increasing NO_x due to a decreased oxidation capacity of the photooxidation system. Secondary organic aerosol (SOA) formation also decreased with the presence of high concentration of NO_x, because organo-peroxy radicals (RO₂) react with NO_x instead of with peroxy radicals (RO₂ or HO₂), resulting in the formation of volatile organic products. The increasing concentration of NO_x enhanced the formation of sulfate, nitrate and SOA under “NO_x-limited” conditions, in which the heterogeneous reactions played an important role. In the presence of Al₂O₃ seed particles, a synergetic promoting effect of mineral dust and NO_x on secondary aerosol formation in heterogeneous reactions was observed in the photooxidation. This synergetic effect strengthened the positive relationship between NO_x and secondary aerosol formation under “NO_x-limited” conditions but weakened or even overturned the negative relationship between NO_x and secondary aerosol formation under “VOC-limited” conditions. Sensitivity of secondary aerosol formation to NO_x seemed different in homogeneous and heterogeneous reactions, and should be both taken into account in the sensitivity study. The sensitivity of secondary aerosol formation to NO_x was further investigated under “winter-like” and NH₃-rich conditions. No obvious difference for the sensitivity of secondary aerosol formation except nitrate to NO_x was observed.

In order to provide scientific support to policy makers in the regulation of PM_2.5 pollution in China, it is important to accurately assess the current status, spatiotemporal characteristics and regionalization data for this air pollutant. An analysis of the pollution status of PM_2.5 was conducted using daily averaged mass concentration data recorded in 74 cities in 2013 and 161 cities in 2014. The rotated empirical orthogonal function (REOF) method was applied to analyze this data. Results showed that the average annual PM_2.5 concentration in urban areas of China is 62.2±21.5 mg/m³, and that the distribution is spatially heterogeneous. The North China Plain, middle and lower Yangtze River Plain, Sichuan Basin and Guanzhong Plain had relatively high annual PM_2.5 concentrations compared with the southeast coastal region, the Tibetan Plateau and the Yungui Plateau. PM_2.5 mass concentrations tended to be higher in winter than in summer, however, the data for many cities showed a small peak in concentrations from May to July. An analysis of the spatial correlation of PM_2.5 indicated a significant influence of topographic conditions. A lower correlation was observed where terrain features varied greatly. Based on the results of the REOF analysis and topographic characteristics, ten regions were identified in mid-eastern China, which could be considered as basic pollution prevention divisions for PM_2.5; these include the North China Plain region, Pearl River Delta region, Jianghuai Plain region, middle Yangtze River Plain region, Northeast Plain region, Jiangnan coastal region, Sichuan Basin region, Qiantao Plain region, Guanzhong-Central Plain region and Yungui Plateau region. Seasonal variations in the regionalization data were observed, especially for the North China Plain and Pearl River Delta regions. Among the ten regions identified in this study, the North China Plain, Guanzhong-Central Plain, middle Yangtze River Plain and Jianghuai Plain had relatively high PM_2.5 mass concentrations in comparison with the others. Therefore, these regions should be considered as the key regions to target in developing PM_2.5 pollution prevention strategies. This study improves the present understanding of the spatial distribution, seasonal changes and regional status of PM_2.5 pollution in China and helps establish possible control strategies for the reduction of this air pollutant.

Urea-bridged diferrocene derivatives N,N'-diferrocenylurea (1) and N,N'-dimethyl-N,N'-diferrocenylurea (2) were prepared and characterized. Single-crystal X-ray analysis shows that Compound 1 has a trans-trans linear conformation whereas Compound 2 has a trans-cis conformation. Both compounds display two consecutive redox couples with, respectively, E_1/2 of +0.29 and +0.42 V vs. Ag/AgCl for 1 and +0.31 and +0.50 V for 2. Spectroelectrochemical studies show the presence of distinct intervalence charge transfer (IVCT) transitions for the one-electron-oxidized mixed-valent Compound 1⁺, with an estimated electronic coupling parameter of 190 cm^-1. By contrast, the one-electron-oxidized Compound 2⁺ shows much weaker IVCT transitions.

A series of bimetallic lanthanide bis(amido) complexes stabilized by bridged bis(guanidinate) ligands {[(Me₃Si)₂N]₂Ln[(RN)₂-CN(CH₂)₂]}₂ [R=ⁱPr, Ln=Sm (1), Yb (2), Y (3); R=cyclohexyl (Cy), Ln=Sm (4), and Yb (5)] were synthesized through the metathesis reactions of {Ln(μ-Cl)[N(SiMe₃)₂]₂(THF)}₂ (Ln=Sm, Yb, Y) with lithium guanidinate {Li[(RN)₂CN(CH₂)₂]}₂ (R=ⁱPr, Cy), the latter of which was generated in situ by the reaction of carbodiimides with lithium amides. Complexes 1-5 were well characterized by elemental analyses, IR spectra, and (for Complex 3) NMR spectroscopy. The solid-state molecular structures of all of the complexes were determined by single-crystal X-ray analyses with the exception of Complex 3, which showed similar unsolvated centrosymmetric dinuclear structures. Each of the lanthanide centers is four-coordinated with two nitrogen atoms from a guanidinate ligand and two nitrogen atoms from two amido groups. The piperazidine rings adopt chair conformations in all cases. These organolanthanide complexes were found to be efficient catalysts for the hydrophosphonylation reaction of various aldehydes and unactivated ketones and to afford a-hydroxyphosphonates in high yields under low catalyst loading (0.1 mol%) in a short reaction time.

Successful gene vectors should be with high transfection efficiency and minimal cytotoxicity. Natural polysaccharides, due to their good biocompatibility and biodegradability, have been widely studied and applied. Amylopectin is one of polysaccharides with dendritic structure and numerous hydroxyl groups that could be used for subsequent modification. In this work, a series of dendritic cationic gene vectors comprising amylopectin backbones and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) side chains with different lengths (termed as AMY-PDs) were readily prepared by atom transfer radical polymerization (ATRP). The gene condensation ability, cytotoxicity and gene transfection of AMY-PDs carriers were investigated. In comparison with “gold-standard” poly(ethyleneimine) (PEI, 25 kDa), the AMY-PDs exhibited higher transfection efficiency with lower cytotoxicity. AMY-PDs could be further modified with Au nanoparticles (termed as AMY-PD@Au). The potential of the AMY-PD@Au vectors to be utilized as a CT contrast agent for imaging of cancer cells was investigated. Such AMY-PD@Au vectors may realize gene therapy with the ability of real-time imaging.

In this paper, we present the coil-to-globule (CG) transitions of homopolymers and multiblock copolymers with different topology and stiffness by using molecular dynamics with integrated tempering sampling method. The sampling method was a novel enhanced method that efficiently sampled the energy space with low computational costs. The method proved to be efficient and precise to study the structural transitions of polymer chains with complex topological constraint, which may not be easily done by using conventional Monte Carlo method. The topological constraint affects the globule shape of the polymer chain, thus further influencing the CG transition. We found that increasing the topological constraint generally decreased CG transition temperature for homopolymers. For semiflexible chains, an additional first-order like symmetry-broken transition emerged. For block copolymers, the topological constraint did not obviously change the transition temperature, but greatly reduced the energy signal of the CG transition.

A new self-condensing vinyl polymerization system consisting of AB_f^*-type inimers is studied by the principle of statistical mechanics. To obtain the relevant average properties of the system, a differential equation satisfied by the polymeric moment of interest is given, and as a result the zeroth, first, second, and third polymeric moments together with the size distribution function of hyperbranched polymers (HBPs) are explicitly presented. As an application of the method of statistical mechanics, several thermodynamic quantities such as the equilibrium free energy, law of mass action, isothermal compressibility, internal energy, and the specific heat associated with the polymerization are all derived. Furthermore, the scaling behavior of asymptotic size distribution function is discussed, by which a reasonable interpretation of the polydispersity index near the end of polymerization can be made. Also, the expressions of some structural parameters such as the numbers of inimers, terminal units, chain units, branched units, and the degree of branching (DB) are calculated. It is found that a high functionality is helpful to improve the DB of the resultant HBPs. These results show that the functionality f has a significant effect on the thermodynamic quantities and structural properties of HBPs.

Semiconductor sensitized solar cells (SSSCs) are promising candidates for the third generation of cost-effective photovoltaic solar cells and it is important to develop a group of robust, environment-friendly and visible-light-responsive semiconductor sensitizers. In this paper, we first synthesized bismuth vanadate (BiVO₄) quantum dots by employing facile successive ionic layer adsorption and reaction (SILAR) deposition technique, which we then used as a sensitizer for solar energy conversion. The preliminary optimised oxide SSSC showed an efficiency of 0.36%, nearly 2 orders of magnitude enhancement compared with bare TiO₂, due to the narrow bandgap absorption of BiVO₄ quantum dots and intimate contact with the oxide substrate. This result not only demonstrates a simple method to prepare BiVO₄ quantum dots based solar cells, but also provides important insights into the low bandgap oxide SSSCs.

Tip-enhanced Raman spectrum (TERS) is a scanning probe technique for acquiring chemical information at high spatial resolution and with high chemical sensitivity. The sensitivity of TERS with atomic force microscopy (AFM) system is mainly determined by the metalized tips. Here, we report a fabrication protocol for AFM-TERS tips that incorporate a copper (Cu) primer film between a gold (Au) layer and a Si AFM tip. They were fabricated by coating the Si tip with a 2 nm Cu layer prior to adding a 20 nm Au layer. For top illumination TERS experiments, these tips exhibited superior TERS performance relative to that observed for tips coated with Au only. Samples included graphene, thiophenol and brilliant cresyl blue. The results may derive from the surface roughness of the tip apex and a Cu/Au synergism of local surface plasmon resonances.

TiO₂ nanowire (NW) is one of the potential scattering layer materials in dye-sensitized solar cells (DSSCs) owing to its fast electron conductivity and excellent light scattering property resulting from its one-dimensional (1D) morphology. However, TiO₂ NWs used as scattering layers in previous work were either aggregated or shortened into shuttles that cannot use their unique 1D properties. In this paper, we present the preparation of a well-dispersed long NW paste (exceeding 1 mm) by a mild method and used as a scattering layer in DSSC. The paste achieved a photoconversion efficiency of 5.73% and an efficiency enhancement of 12% compared with commercial scattering layer (P200 paste). Compared with the DSSC without a scattering layer, an efficiency enhancement of 54.9% was achieved. Also, the largest efficiency of 6.89% was obtained after optimization of photoanode thickness. The photoanodes were investigated through dye desorbed experiments and transmission spectra, which suggested that P25 nanoparticles with the as-prepared NW scattering layer loaded more dye than those with P200 paste. These results indicate that well-dispersed long NW paste has a potential application in scattering layers.

Protein protected gold nanoclusters have outstanding physical and chemical properties that make them excellent scaffolds for the construction of novel chemical and biological probes. In this study, a simple one-pot synthesis method was proposed for the preparation of fluorescent probes based on ovalbumin-stabilized gold nanoclusters. This strategy allowed the generation of water-soluble gold nanoclusters within 5 min. The as-prepared fluorescent probe exhibited a red fluorescence emission at 625 nm, and good thermostability. The fluorescent probe was applied to measure glucose concentrations based on the hydrogen peroxide-induced fluorescence quenching principle, and showed favorable biocompatibility, high sensitivity and good selectivity. As a result of the advantageous properties and performance of this fluorescent probe, the present assay allowed for the selective determination of glucose in the range of 5.0×10^-6 to 10.0×10^-3 mol/L with a detection limit of 1.0×10^-6 mol/L. Moreover, the glucose content in urinary samples was analyzed using the constructed fluorescent probe: this indicated the potential of the fluorescent gold nanoclusters for applications in biological and clinical diagnosis and therapy.