Effect of Preparation Methods of Bi2O3 Nanoparticles on their Photocatalytic Activity

Bi2O3 nanoparticles were prepared by means of ammonia precipitation, polyol mediated methods and microemulsion chemical method. The structure and properties of the as-prepared nanoparticles, having been submitted to a heat-treatment test at 750℃, were characterized by means of XRD. BET, XPS and UV-Vis absorption techniques. The photocatalytic oxidation reactions of benzene, toluene and xylene were used as the model reaction to measure the photocatalytic activity of Bi2O3 nanoparticles, respectively. The results show that the crystallite size of Bi2O3 prepared with different methods and calcined at 750℃ were 50. 6, 38.5 and 31.5 nm, respectively. The photocatalytic activity of Bi2O3 nanoparticles prepared with the microemulsion chemical method was higher than that of the particles prepared with the polyol mediated method; and that of the particles prepared with the micromulsion chemical method was the highest among the three. The degradation rates of the three pollutants xylene, toluene and benzene decreased in sequence.     

Chemically binding Eu^3＋ onto CdS semiconductor nanoparticle surface

Europium ions were chemically bound to CdS nanoparticles surface by diethylenetri-aminepentaacetate (DTPA, 1) in a two-step synthetic route. First 1 was applied to chelate with cadmium on the surface of cadmium-rich CdS nanoparticles and act as a capping agent. Further, the purified 1-capped particles were used to bind with Eu~3 . The purified and redispersed particles were characterized by photoluminescence spectroscopy, TEM and SEM. It was observed that Eu~3 on the nanoparticle surface significantly increased the band gap emission and decreased the surface emission intensity of the CdS nanoparticles.     

Hydrogen Bonds in Coal -The Influence of Coal Rank and the Recognition of a New Hydrogen Bond in Coal

By means of in-situ diffuse reflectance FTIR.The IR spectra of 6 coals with different ranks were obtained from room temperature to 230℃.A new curve fitting method was used to recognize the different hydrogen bonds in the coals.and the influence of coal ranks on the distribution of hydrogen bonds(HBs) in the coals and their thermal stability were discussed.The results show that there is another new HB(around 2514cm^-1) between the-SH in mercaptans or thiophenols and the nitrogen in the pyridine-like compounds in the coals.and the evidence for that was provided.The controversial band of the HB between hydroxyl and the nitrogen of the pyridine-like compounds was determined in the range of 3028-2984cm^-1,and the result is comsistent with but more specific than that of Painter et al.It was ound that the stability of different HBs in the coals is influenced by both coal rank and temperature,For some HBs.the higher the coal rank,the higher the stability of them.Within the temperature range of our research,the stability of the HB between the hydroxyl and the π bond increases to some extent for some coals at temperatures higher than 110 or 140℃.     

In Situ Monitoring of the Generation of Monodisperse Silica Particles during the Hydrolysis of Tetraethyl Orthosilicate with Piezoelectric Quartz Crystal Impedance Analyzer

The piezoelectric quartz crystal(PQC)impedance analyzer was used to monitor in situ the generation of monodisperse silica particles during the hydrolysis of tetraethyl orthosilicate (TEOS) and their adsorption onto and Au electrode in alcohol solutions containing water(6-15mol/L)and ammonia(0.2-2.0 mol/L).The equivalent circuit parameters,the resonance frequencies and the half-peak width values of the conductance spectra of the PQC resonance were obtained.The resonant frequency decreased notably while the motional resistance changed very slightly(within 1Ω during the hydrolysis reaction,suggesting that the mass effect dominated the adsorption of generated monodisperse silica particles on the gold electrode in this system.Changes in f0 indicated that the ammonia concentration affected the hydrolytic reaction obviously,and the influence of water concentration on the reaction was small while the water was significantly excessive.Kinetics of monodisperse silica particle adsorption occurring at the electrode i solution interface was analyzed using a first-order reaction scheme.In addition,the electrolyte-induced precipitation of the monodisperse silica of adsorbed particles per area and the converge of monodisperse silica particles were obtained from scanning electron nicroscope(SEM)observations.     

Preparation, characterization and adhesive properties of di- and tri-hydroxy benzoyl chitosan nanoparticles

Modified chitosans with 3,4-di-hydroxy benzoyl groups (CS-DHBA) and 3,4,5-tri-hydroxy benzoyl groups (CS-THBA) were synthesized and their nanoparticles were prepared via ionic crosslinking by tripolyphosphate (TPP). The chemical structure and degree of substitution (DS) of di-and tri-hydroxy benzoyl chitosans are determined by FTIR and 1H-NMR spectroscopy. The morphology of particles, size distribution and zeta potential of nanoparticles were studied using transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The mean diameters of particles of CS-DHBA and CS-THBA nanoparticles were 144 nm and 112 nm, respectively. It was found that the particles size decreased slightly with decreasing the degree of substitution and increasing degree of deacetylation (DD), due to increasing of ionic crosslinking of ammonium ions and polyanions of tripolyphosphate. The TEM photographs of CS-DHBA show that these particles are spherical in shape, but the particles of CS-THBA show some aggregation. In addition, the solubility and the mechanical properties of the prepared modified chitosans and their nanoparticles were evaluated for bio-adhesive and biomedical application. The results of solubility tests indicated that, the CS-DHBA and CS-THBA have higher solubility at pH > 7 comparing to CS. Also the CS-DHBA, CS-THBA and their nanoparticles showed a significant adhesive capacity and enhanced tensile strength and tensile modulus.     

Facile Fabrication of Platinum Nanoparticles Supported on Nitrogen-doped Carbon Nanotubes and Their Catalytic Activity

A facile impregnation method under mild condition is designed for synthesis of highly dispersed Pt nanoparticles with a narrow size of 4-7 nm on nitrogen-doped carbon nanotubes （CNx）. CNx do not need any pre-surface modification due to the inherent chemical activity. The structure and nature of Pt/CNx were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy spectrum. All the experimental results revealed that the large amount of doped nitrogen atoms in CNx was virtually effective for capturing the Pt（IV） ions. The improved surface nitrogen functionalities and hydrophilicity contributed to the good dispersion and immobi- lization of Pt nanoparticles on the CNx surface. The Pt/CNx served as active and reusable catalysts in the hydrogenation of allyl alcohol. This could be attributed to high dispersion of Pt nanoparticles and stronger interaction between Pt and the supports, which prevented the Pt nanoparticles from aggregating into less active Pt black and from leaching as well.     

Studies on droplet size distributions during coalescence in immiscible polymer blends filled with silica nanoparticles

The effect of silica nanoparticles on the morphology of （10/90 wt%） PDMS/PBD blends during the shear induced coalescence of droplets of the minor phase at low shear rate was investigated systematically in situ by using an optical shear technique. Two blending procedures were used： silica nanoparticles were introduced to the blends by pre-blending silica particles first in PDMS dispersed phase （procedure 1） or in PBD matrix phase （procedure 2）. Bimodal or unimodal droplet size distributions were observed for the filled blends during coalescence, which depend not so much on the surface characteristics of silica but mainly on blending procedure. For pure （10/90 wt%） PDMS/PBD blend, the droplet size distribution exhibits bimodality during the early coalescence. When silica nanoparticles （hydrophobic and hydrophilic） were added to the blends with procedure l, bimodal droplet size distributions disappear and unimodal droplet size distributions can be maintained during coalescence; the shape of the different peaks is invariably Gaussian. Simultaneously, coalescence of the PDMS droplets was suppressed efficiently by the silica nanoparticles. It was proposed that with this blending procedure the nanoparticles should be mainly kinetically trapped at the interface or in the PDMS dispersed phase, which provides an efficient steric barrier against coalescence of the PDMS dispersed phase. However, bimodal droplet size distributions in the early stage of coalescence still occur when incorporating silica nanoparticles into the blends with procedure 2, and then coalescence of the PDMS droplets cannot be suppressed efficiently by the silica nanoparticles. It was proposed that with this blending protocol the nanoparticles should be mainly located in the PBD matrix phase, which leads to an inefficient steric barrier against coalescence of the PDMS dispersed phase; thus the morphology evolution in these filled blends is similar to that in pure blend and bimodal droplet size distributions can be observed during the early coalescence. These results imply that exploiting non-equilibrium processes by varying preparation protocol may provide an elegant route to regulate the temporal morphology of the filled blends during coalescence.     

Design and Synthesis of Glycosylated Aromatic Nitrogen Mustard Derivatives

Antibody-directed enzyme prodrug therapy(ADEPT) is a new strategy for the treatment of cancer that has arisen in recent twenty years, the main merits of which are that it can improve the selectivity of anticancer drugs and reduce the side effects in remote tissue. In the present study, two prodrugs-glycosylated aromatic nitrogen mustard derivatives were synthesized. Glucose and lactose were converted into glycosyl donors-trichloroacetimidate; the obtained glycosyl donors were glycosylated with p-nitrophenol(glycosyl donors) to form β-glucosyl p-nitrobenzene and β-lactosyl p-nitrobenzene that were protected by acetyl in a stereoselective manner; the two products were reduced by zinc dust and then treated with ethylene oxide, afforded two glycosylated nitrogen mustard derivatives that were protected by acetyl; the last step was to deacetylate and then afforded the two target compounds that could be used as prodrugs of ADEPT for further Anti-tumor research.     

STUDY ON THE GASEOUS PRODUCTS OF HIGH TEMPERATURE PYROLYSIS OF ACRYLONITRILE POLYMERS BY ON-LINE FTIR METHOD

The gaseous products of high temperature pyrolysis (300℃ to 960℃) of aerylonitrile polymers were measured continuously under nitrogen atmosphere by on-line Fourier Transform Infrared Spectroscopic method (FTIR). From the variations of characteristic peaks it was found that the nitrogen of macromolecules evolved were mainly in the form of hydrogen cyanide and ammonia. During the pyrolysis amorphous carbonaceous element was formed, and crosslinked to form network structure. Three kinds of samples were used for comparison. The experimental results show that the gaseous products of volatile small molecules were HCN, NH_3, CH_4, C_2H_6 and cyanide. CO and CO_2 were also formed when copolymers of PAN were thermally pyrolyzed.     

Fabrication of virus-like particles with strip-pattern surface: A two-step self-assembly approach

Spherical nanostructures with striped patterns on the surfaces resembling the essential structures of natural virus particles were constructed through a two-step self-assembly approach of polystyrene-boligo(acrylic acid)(PS-b-oligo-AA) and poly(γ-benzyI L-glutamate)-b-poly(ethylene glycol)(PBLG-bPEG) copolymer mixtures in solution.On the basis of difference in hydrophilicity and self-assembly properties of the two copolymers,the two-step self-assembly process is realized.It was found that PS-boligo-AA copolymers formed spherical aggregates by adding a certain amount of water into polymer solutions in the first step.In the second step,two polymer solutions were mixed and water was further added,inducing the self-assembly of PBLG-b-PEG on the surfaces of PS-b-oligo-AA spheres to form striped patterns.In-depth study was conducted for the indispensable defects of striped patterns which are dislocations and +1/2 disclinations.The influencing factors such as the mixing ratio of two copolymers and the added water content in the first step on the morphology and defects of the striped patterns were investigated.This work not only presents an idea to interpret mechanism of the cooperative self-assembly behavior,but also provides an effective approach to construct virus-like particles and other complex structures with controllable morphology.     

Hydrogenated Bismuth Molybdate Nanoframe for Efficient Sunlight‐Driven Nitrogen Fixation from Air

Sunlight‐driven dinitrogen fixation can lead to a novel concept for the production of ammonia under mild conditions. However, the efficient artificial photosynthesis of ammonia from ordinary air (instead of high pure N₂) has never been implemented. Here, we report for the first time the intrinsic catalytic activity of Bi₂MoO₆ catalyst for direct ammonia synthesis under light irradiation. The edge‐exposed coordinatively unsaturated Mo atoms in an Mo?O coordination polyhedron can act as activation centers to achieve the chemisorption, activation, and photoreduction of dinitrogen efficiently. Using that insight as a starting point, through rational structure and defect engineering, the optimized Bi₂MoO₆ sunlight‐driven nitrogen fixation system, which simultaneously possesses robust nitrogen activation ability, excellent light‐harvesting performance, and efficient charge transmission was successfully constructed. As a surprising achievement, this photocatalytic system demonstrated for the first time ultra‐efficient (1.3 mmol g^?1 h^?1) and stable sunlight‐driven nitrogen fixation from air in the absence of any organic scavengers.     

Promoted Electrocatalytic Nitrogen Fixation in Fe‐Ni Layered Double Hydroxide Arrays Coupled to Carbon Nanofibers: The Role of Phosphorus Doping

The key to bringing the electrocatalytic nitrogen fixation from conception to application lies in the development of high‐efficiency, cost‐effective electrocatalysts. Layered double hydroxides (LDHs), also known as hydrotalcites, are promising electrocatalysts for water splitting due to multiple metal centers and large surface areas. However, their activities in the electrocatalytic nitrogen fixation are unsatisfactory. Now, a simple and effective way of phosphorus doping is presented to regulate the charge distribution in LDHs, thus promoting the nitrogen adsorption and activation. The P‐doped LDHs are further coupled to a self‐supported, conductive matrix, that is, a carbon nanofibrous membrane, which prevents their aggregation as well as ensuring rapid charge transfer at the interface. By this strategy, decent ammonia yield (1.72×10^?10 mol s^?1 cm^?2) and Faradaic efficiency (23 %) are delivered at ?0.5 V vs. RHE in 0.1 m Na₂SO₄.     

High-temperature stable, iron-based core-shell catalysts for ammonia decomposition

High‐temperature, stable core–shell catalysts for ammonia decomposition have been synthesized. The highly active catalysts, which were found to be also excellent model systems for fundamental studies, are based on α‐Fe₂O₃ nanoparticles coated by porous silica shells. In a bottom‐up approach, hematite nanoparticles were firstly obtained from the hydrothermal reaction of ferric chlorides, L ‐lysine, and water with adjustable average sizes of 35, 47, and 75 nm. Secondly, particles of each size could be coated by a porous silica shell by means of the base‐catalyzed hydrolysis of tetraethylorthosilicate (TEOS) with cetyltetramethylammonium bromide (CTABr) as porogen. After calcination, TEM, high‐resolution scanning electron microscopy (HR‐SEM), energy‐dispersive X‐ray (EDX), XRD, and nitrogen sorption studies confirmed the successful encapsulation of hematite nanoparticles inside porous silica shells with a thickness of 20 nm, thereby leading to composites with surface areas of approximately 380 m² g^?1 and iron contents between 10.5 and 12.2 wt %. The obtained catalysts were tested in ammonia decomposition. The influence of temperature, iron oxide core size, possible diffusion limitations, and dilution effects of the reagent gas stream with noble gases were studied. The catalysts are highly stable at 750 °C with a space velocity of 120 000 cm³ g_cat^?1 h^?1 and maintained conversions of around 80 % for the testing period time of 33 h. On the basis of the excellent stability under reaction conditions up to 800 °C, the system was investigated by in situ XRD, in which body‐centered iron was determined, in addition to FeN_x, as the crystalline phase under reaction conditions above 650 °C.     

Fabrication and optical properties of gallium phosphide nanoparticulate thin film

The gallium phosphide (GaP) nanoparticulate thin films were fabricated by colloidal suspensions deposition with GaP nanoparticles dispersed in N,N-dimethylformamide (DMF). The microstructure and optical properties of the film have been studied by scanning electron microscopy, high resolution transmission electron microscope, and optical absorption and fluorescence spectra. The morphology of the film was found to be composed of nanoparticle aggregates, and with an irregularly rough surface. From the result of fluorescence, it can be established that the film not only retains the violet and blue light emissions which ascribed to transition from conduction band to valence band of gallium phosphide particles, but has an excellent luminescence property. The correlation between the optical properties and the microstructure of the thin film is discussed.     

Ammonia Synthesis Under Ambient Conditions: Selective Electroreduction of Dinitrogen to Ammonia on Black Phosphorus Nanosheets

Constructing efficient catalysts for the N₂ reduction reaction (NRR) is a major challenge for artificial nitrogen fixation under ambient conditions. Herein, inspired by the principle of “like dissolves like”, it is demonstrated that a member of the nitrogen family, well‐exfoliated few‐layer black phosphorus nanosheets (FL‐BP NSs), can be used as an efficient nonmetallic catalyst for electrochemical nitrogen reduction. The catalyst can achieve a high ammonia yield of 31.37 μg h^?1 mg^?1_cat. under ambient conditions. Density functional theory calculations reveal that the active orbital and electrons of zigzag and diff‐zigzag type edges of FL‐BP NSs enable selective electrocatalysis of N₂ to NH₃ via an alternating hydrogenation pathway. This work proves the feasibility of using a nonmetallic simple substance as a nitrogen‐fixing catalyst and thus opening a new avenue towards the development of more efficient metal‐free catalysts.     

Electrocatalysis of N2 to NH3 by HKUST‐1 with High NH3 Yield

Electrolytic ammonia synthesis from nitrogen at ambient conditions is appearing as a promising alternative to the Haber‐Bosch process which is consuming high energy and emitting CO₂. Here, a typical MOF material, HKUST‐1 (Cu?BTC, BTC=benzene‐1,3,5‐tricarboxylate), was selected as an electrocatalyst for the reaction of converting N₂ to NH₃ under ambient conditions. At ?0.75 V vs. reversible hydrogen electrode, it achieves excellent catalytic performance in the electrochemical synthesis of ammonia with high NH₃ yield (46.63 μg h^?1 mg^?1 _cat. or 4.66 μg h^?1 cm^?2) and good Faraday efficiency (2.45%). It is indicated that the good performance of the HKUST‐1 catalyst may originate from the formation of Cu(I). In addition, the catalyst also has good selectivity for N₂ to NH₃.     

Promoted Electrocatalytic Nitrogen Fixation in Fe-Ni Layered Double Hydroxide Arrays Coupled to Carbon Nanofibers: The Role of Phosphorus Doping

The key to bringing the electrocatalytic nitrogen fixation from conception to application lies in the development of high-efficiency, cost-effective electrocatalysts. Layered double hydroxides (LDHs), also known as hydrotalcites, are promising electrocatalysts for water splitting due to multiple metal centers and large surface areas. However, their activities in the electrocatalytic nitrogen fixation are unsatisfactory. Now, a simple and effective way of phosphorus doping is presented to regulate the charge distribution in LDHs, thus promoting the nitrogen adsorption and activation. The P-doped LDHs are further coupled to a self-supported, conductive matrix, that is, a carbon nanofibrous membrane, which prevents their aggregation as well as ensuring rapid charge transfer at the interface. By this strategy, decent ammonia yield (1.72×10⁻¹⁰ mol s⁻¹ cm⁻²) and Faradaic efficiency (23 %) are delivered at −0.5 V vs. RHE in 0.1 m Na₂SO₄.     

Boosting the photocatalytic nitrogen reduction to ammonia through adsorption-plasmonic synergistic effects

Ammonia is one of the most essential chemicals in the modern society but its production still heavily relies on energy-consuming Haber-Bosch processes. The photocatalytic reduction of nitrogen with water for ammonia production has attracted much attention recently due to its synthesis under mild conditions at room temperature and atmospheric pressure using sunlight. Herein, we report a high-performance Au/MIL-100(Cr) photocatalyst, comprising MIL-100(Cr) and Au nanoparticles in photocatalytic nitrogen reduction to ammonia at ambient conditions under visible light irradiation. The optimized photocatalyst (i.e., 0.10Au/MIL-100(Cr)) achieved the excellent ammonia production rate with 39.9 µg g_cat^?1 h^?1 compared with pure MIL-100(Cr) (2.73 µg g_cat^?1 h^?1), which was nearly 15 times that on pure MIL-100(Cr). The remarkable activity could be attributed to the adsorption-plasmonic synergistic effects in which the MIL-100(Cr) and Au are responsible to the strong trapping and adsorption of N₂ molecules and photo-induced plasmonic hot electrons activating and decomposing the N₂ molecules, respectively. This study might provide a new strategy for designing an efficient plasmonic photocatalyst to improve the photocatalytic performance of N₂ fixation under visible light irradiation.     

Synthesis and Characterization of Spinel‐Type Gallia‐Alumina Solid Solutions

By precipitation with ammonia of ethanolic solutions containing the appropriate proportions of gallium and aluminium nitrate, following by calcination of the resulting gels at 773 K, mixed Ga₂O₃/Al₂O₃ oxides having Ga:Al ratios of 9:1, 4:1, 1:1, 1:4 and 1:9 were obtained. Powder X‐ray diffraction showed that these mixed metal oxides form a series of solid solutions having the spinel‐type structure; also shown by γ‐Al₂O₃ and γ‐Ga₂O₃. The specific surface area (determined by nitrogen adsorption at 77 K) was found to range from 160 m² g^?1 for the mixed oxide having Ga:Al = 9:1 up to 370 m² g^?1 for that having Ga:Al = 1:9. High resolution MAS NMR showed that Ga³⁺ and Al³⁺ ions occur at both tetrahedral and octahedral sites in the spinel‐type structure of the mixed metal oxides, although there is a preferential occupation of tetrahedral sites by Ga³⁺ ions. A proportion of penta‐coordinated Al³⁺ ions was also found. IR spectra of carbon monoxide adsorbed at 77 K showed that the mixed metal oxides have a considerable Lewis acidity, related mainly to tetrahedrally coordinated metal ions exposed at crystal surfaces. The characteristic infrared absorption band of coordinated (adsorbed) CO appears in the range 2205–2190 cm^?1, and its peak wavenumber is nearly independent of Ga:Al ratio in the mixed gallia‐alumina oxides.     

Synthesis of high-purity GaP nanowires using a vapor deposition method

High-purity gallium phosphide (GaP) nanowires were successfully synthesized on the nickel monoxide (NiO) or the cobalt monoxide (CoO) catalyzed alumina substrate by a simple vapor deposition method. To synthesize the high-purity GaP nanowires, the mixture source of gallium (Ga) and GaP powder was directly vaporized in the range of 850–1000 °C for 60 min under argon ambient. The diameter of GaP nanowires was about 38–105 nm and the length was up to several hundreds of micrometers. The GaP nanowires have a single-crystalline zinc blend structure and reveal the core-shell structure, which consists of the GaP core and the GaPO₄/Ga₂O₃ outer layers. We demonstrate that the mixture of Ga/GaP is an ideal source for the high-yield GaP nanowires.