NO和O2在Pt(110)面上吸附的TDS和PEEM研究

采用热脱附和光电子发射普微镜研究了Ｏ２和ＮＯ在Ｐｔ（１１０）面上的吸附和共吸附。结果表明，室温条件下，ＮＯ在Ｐｔ（１１０）面上有端式和桥式两种不同的吸附方式。Ｐｔ（１１０）表面预吸附的原子态氧占据了ＮＯ进入了桥式吸附的活性粒，从而阻遏了ＮＯ在Ｐｔ表面发生解离反应必须经过的桥式吸附中间态的形式，进而降低了ＮＯ在Ｐｔ表面直接分散的能力。     

The structure and catalytic activity of anatase and rutile titania supported manganese oxide catalysts for selective catalytic reduction of NO by NH3

The structure and catalytic properties of anatase and rutile supported manganese oxide catalysts prepared by impregnation method have been studied by using X-ray diffraction (XRD), laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), H(2) temperature-programmed reduction (H(2)-TPR) and BET surface area measurements combined with activity testing of selective catalytic reduction (SCR) of NO by NH(3). It has been shown that the manganese oxide loadings on the two TiO(2) supports exert great influences on the SCR activity. For the rutile supported manganese oxide catalysts, increasing manganese oxide loading leads to the increase of reducibility of dispersed manganese oxide species and the rate constant k, which reaches a maximum around 9.6 × 10(-6) mol g(Mn)(-1) s(-1) at 0.5 mmol Mn per 100 m(2) TiO(2). When the manganese oxide loading is beyond this value, the existence of amorphous MnO(x) multiple layers will certainly reduce the ratio of manganese oxide species exposed on the surface and the reducibility of dispersed manganese oxide species, resulting in the rapid decrease of rate constant k. The LRS and XPS results have revealed that for the anatase supported manganese oxide catalysts manganese oxide species exist in Mn(+4) as a major species with Mn(+3) species and partially undecomposed Mn-nitrate as the minor species. Under the SCR reaction conditions, Mn(+3) species on anatase are oxidized to Mn(+4) species, inserting in the surface of anatase and promoting the anatase-to-rutile transformation in the surface layers of the anatase support. Since these Mn(4+) cations are actually dispersed on the support with a rutile shell-anatase core structure and its concentration is very near to that of MnO(x)/TiO(2) (R) catalyst, the relation between the rate constant k and the MnO(x) loading on the anatase support is similar to that on the rutile support, and that the rate constant k values for anatase and rutile supported manganese oxide catalysts are very close at the same MnO(x) loading.     

氧化镧表面反应性对甲烷和氧分子活化的影响

以氧化镧催化剂在甲烷氧化偶联(OCM)反应中的结构敏感性实验研究为基础, 采用周期性密度泛函理论(DFT)计算研究氧化镧(001), (110)和(100)3个晶面及OCM反应物分子甲烷和氧在其上的吸附、 活化和解离. 结果表明, 氧化镧(001), (110)和(100)3个晶面的表面能大小顺序为(110)>(100)>(001), 3个晶面的价带和导带间隙大小顺序为(110)<(100)<(001), 即(001)是3个晶面中最稳定的晶面, 而(110)则是最活泼的晶面. 甲烷分子在氧化镧(001), (110)和(100)晶面上的吸附很弱(0.03 eV), H—CH₃解离吸附能分别为2.16, 0.68和0.90 eV, 解离反应的难易性与晶面的活性顺序一致; 而氧分子在氧化镧(001), (110)和(100)晶面上的分子吸附能分别为-0.04, -0.31和-0.12 eV, 解离吸附能分别为1.22, 0.53和1.52 eV, 即氧化镧晶面结构对氧分子吸附具有明显的影响, 其中, (001)晶面上吸附最弱, (110)晶面上吸附最强, 以致O—O在(110)晶面上可以较低能垒(0.53 eV)解离, 形成亲电的过氧物种. 由于氧分子在氧化镧表面的吸附较甲烷分子强, 因此, 氧化镧在OCM反应中结构敏感性应与氧分子的吸附和活化密切相关. 甲烷和氧分子在氧化镧表面上活化的本质源自于电子自表面流向甲烷和氧分子的反键轨道, 且表面结构的改变会导致不同强度的电子流动驱动.     

多孔二氧化硅对聚环氧乙烷结晶行为的影响

高分子化合物由于具有很长的分子链,不易进行规整排列,结晶速度通常很慢,为提高结晶速度,有时需要加入成核剂．多孔二氧化硅（ＳｉＯ２）具有较大的比表面积,故吸附作用较强,有可能作为成核剂影响部分结晶高聚物的结晶过程．聚环氧乙烷（ＰＥＯ）为部分结晶高聚物,其结晶行为对杂质较为敏感．本文目的在于通过结晶动力学及结晶与熔融行为的研究,探索多孔二氧化硅对ＰＥＯ结晶行为的影响．１　实验部分　　聚环氧乙烷（ＰＥＯ,Ｍｗ＝１×１０５）．两种多孔二氧化硅（ＳｉＯ２）按文献［１］方法制备,平均粒度为０．３μｍ,平均孔…     

以两亲性共聚物为模板溶胶-凝胶法制备WO3多孔薄膜及其 氢致变色特性的研究

报道了以六氯化钨为原料, 以两亲性的无规共聚物聚苯乙烯-co-聚烯丙醇(PS-co-PAAL)和三嵌段共聚物聚氧乙烯-b-聚氧丙烯-b-聚氧乙烯(PEO-b-PPO-b-PEO)为模板, 采用溶胶-凝胶法制备了WO3多孔薄膜. 利用热重分析仪(TGA)、粉末X射线衍射仪(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)等表征手段, 研究了模板和热处理温度对薄膜孔结构的影响; 并通过H2敏测试以及利用紫外可见分光光度计(UV), 研究了薄膜的氢敏性能和着色前后的透射光谱. 结果表明, 以无规共聚物PS-co-PAAL为模板制得的WO3薄膜, 经400 ℃热处理后, 可得到呈交联网状的多孔结构, 并表现出最佳的氢致变色性能.     

Cuprous oxide nanoparticles dispersed on reduced graphene oxide as an efficient electrocatalyst for oxygen reduction reaction

Cuprous oxide (Cu(2)O) nanoparticles dispersed on reduced graphene oxide (RGO) were prepared by reducing copper acetate supported on graphite oxide using diethylene glycol as both solvent and reducing agent. The Cu(2)O/RGO composite exhibits excellent catalytic activity and remarkable tolerance to methanol and CO in the oxygen reduction reaction.     

Enantioselectivity of adsorption sites created by chiral 2-butanol adsorbed on Pt(111) single-crystal surfaces

The adsorption and thermal chemistry of 2-butanol and propylene oxide, each individually and when coadsorbed together, were characterized on Pt(111) single-crystal surfaces by using temperature programmed desorption and reflection-adsorption infrared spectroscopies. The formation of chiral superstructures on the surface upon the deposition of submonolayer coverages of enantiopure 2-butoxide species, produced by thermal dehydrogenation of 2-butanol, was highlighted by their difference in behavior toward the adsorption of the two enantiomers of propylene oxide. It was found that a significant enhancement in adsorption is possible on surfaces with the same chirality of the probe molecule, that is, for (R)-propylene oxide adsorption on (R)-2-butoxide layers and for (S)-propylene oxide adsorption on (S)-2-butoxide layers. The propylene oxide probe was found to also adsorb with the ring closer to the surface in those cases. Finally, less butoxide decomposition is seen at higher temperatures from the homochiral pairing, presumably because the coadsorbed propylene oxide forces the alkoxides into a more compact and better packed structure on the surface.     

Vibrational Spectroscopy Study of Selenate and Sulfate Adsorption Mechanisms on Fe and Al (Hydr)oxide Surfaces

The coordination and speciation of selenate (SeO(4)) and sulfate (SO(4)) on goethite and Al oxide were studied using Raman and ATR-FTIR spectroscopy. Raman spectra were collected from pastes of suspensions containing 4 mM SeO(4) or SO(4). For SO(4), complementary data were collected by ATR-FTIR spectroscopy in goethite systems with 1 mM SO(4) and in Al oxide systems with 4 mM SO(4). The combined data set of Raman and ATR-FTIR spectra indicate that both inner- and outer-sphere surface complexes of SeO(4) and SO(4) occur on these metal (hydr)oxide surfaces. These spectral data show that SeO(4) and SO(4) have a similar complexation behavior on the same adsorbent. On goethite, these form predominantly monodentate inner-sphere surface complexes at pH <6, while at pH >6 these anions exist predominantly as outer-sphere surface complexes. On Al oxide, in contrast, these anions exist predominantly as outer-sphere surface complexes, but a small fraction is also present as an inner-sphere complex at pH <6. A comparison of the spectral intensities of these anions on goethite and Al oxide shows that complexation of these anions with Al oxide is weaker than with Fe oxide. Copyright 2000 Academic Press.     

Preconcentration of U(VI) ions on few-layered graphene oxide nanosheets from aqueous solutions

Graphene oxide nanosheets have attracted multidisciplinary attention due to their unique physicochemical properties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using a modified Hummers method and were characterized by TEM, AFM, Raman spectroscopy, XPS, FTIR spectroscopy, TG-DTA and acid-base titrations. The prepared few-layered graphene oxide nanosheets were used as adsorbents for the preconcentration of U(VI) ions from large volumes of aqueous solutions as a function of pH, ionic strength and temperature. The sorption of U(VI) ions on the graphene oxide nanosheets was strongly dependent on pH and independent of the ionic strength, indicating that the sorption was mainly dominated by inner-sphere surface complexation rather than by outer-sphere surface complexation or ion exchange. The abundant oxygen-containing functional groups on the surfaces of the graphene oxide nanosheets played an important role in U(VI) sorption. The sorption of U(VI) on graphene oxide nanosheets increased with an increase in temperature and the thermodynamic parameters calculated from the temperature-dependent sorption isotherms suggested that the sorption of U(vi) on graphene oxide nanosheets was an endothermic and spontaneous process. The maximum sorption capacities (Q(max)) of U(VI) at pH 5.0 ± 0.1 and T = 20 °C was 97.5 mg g(-1), which was much higher than any of the currently reported nanomaterials. The graphene oxide nanosheets may be suitable materials for the removal and preconcentration of U(VI) ions from large volumes of aqueous solutions, for example, U(VI) polluted wastewater, if they can be synthesized in a cost-effective manner on a large scale in the future.     

Elucidation of the molecular structure of hydrated vanadium oxide species by X-ray absorption spectroscopy: correlation between the V...V coordination number and distance and the point of zero charge of the support oxide

The effect of the point of zero charge (PZC) of the support oxide (Al(2)O(3), Nb(2)O(5), SiO(2) and ZrO(2)) on the molecular structure of hydrated vanadium oxide species has been investigated with EXAFS spectroscopy for low-loaded vanadium oxide catalysts. It was found that the degree of clustering (i.e., the V[dot dot dot]V coordination number) and the V...V distance increase with decreasing PZC of the support oxide; i.e., Al(2)O(3) (8.7) < ZrO(2) (7) < Nb(2)O(5) (3.3) < SiO(2) (2). Upon hydration the silica-supported vanadium oxide exhibited a clear alteration in the position of the oxygen atoms surrounding the central vanadium atom and the number of oxygen atoms around vanadium increased to five. In contrast, only minor changes in the molecular structure were detected for the alumina-, niobia- and zirconia-supported vanadium oxide catalysts. Based on a detailed analysis of the EXAFS data a semi-quantitative distribution of vanadium oxide species present on the surface of the different support oxides can be obtained, which is in good agreement with earlier characterization studies primarily making use of Raman spectroscopy.     

Evaluation of acylphosphine oxide polymerization initiators using differential scanning calorimetry

This study examines the polymerization of dental monomers catalyzed by synthesized acylphosphine oxides in a differential scanning calorimetry (DSC) cell. This research focuses on establishing a relationship between radicals generated by the acylphosphine oxide photoinitiators and the kinetic reaction rates of methyl methacrylate (MMA) and acrylamide (ACM), a model monomer. The thermal stability of mono- and di-acylphosphine oxides was examined by DSC. Endothermic melting and exothermic polymerization reactions initiated with the two initiators were recorded. The acrylamide model system laid the ground work for the critical evaluation of the synthesized new initiators of mono (2,4,6-trimethylbenzoyl) diphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide. The bis(acyl) phosphine oxide photoinitiator was more reactive than the mono-(acyl) phosphine oxide with methyl methacrylates under laboratory conditions. In exothermic reactions, temperatures rose higher and more rapidly for bis(acyl) phosphine oxide initiated reactions than mono-(acyl) phosphine oxide initiated reactions.     

Synthesis, characterization and thermal degradation of functional benzoxazine monomers and polymers containing phenylphosphine oxide

Three phosphorus-containing bisphenol compounds, bis(4-hydroxyphenyl)phenylphosphine oxide (BHPPO), bis(4-hydroxyphenoxyphenyl)phenylphosphine oxide (BPPPO), and bis(4-hydroxyphenoxy)phenylphosphine oxide (BPHPPO) have been synthesized as starting materials for the synthesis of benzoxazine monomers. Benzoxazine monomers containing phenylphosphine oxide have been prepared and subsequently characterized by FT-IR and ¹H NMR. The monomers are thermally initiated and polymerized via ring-opening polymerization. Thermogravimetric analysis indicates that phosphorylation can have a profound effect on increasing char yield and on thermal degradation temperatures.     

石墨烯纳米载药体系的制备及对人口腔鳞癌细胞杀伤效果

利用化学氧化还原法制备了氧化石墨烯,进一步超声破碎剥离,得到纳米氧化石墨烯,并对其进行聚乙二醇(PEG)的功能化修饰后载药顺铂。 采用扫描电子显微镜(SEM)、紫外-可见吸收光谱(UV-Vis)、傅立叶变换红外光谱(FTIR)对石墨烯纳米载药体系进行表征,细胞存活率实验(MTT)法检验石墨烯纳米载药体系对人口腔鳞癌(KB)细胞的杀伤作用。 结果表明,石墨烯纳米载药体系对顺铂的负载率为42.4%,聚乙二醇修饰后可以降低纳米氧化石墨烯的细胞毒性并提高生物相容性,对KB细胞具有双重的杀伤作用,为纳米氧化石墨烯在肿瘤治疗的临床应用提供了理论依据。     

Compatibility studies of styrene and hydroxyl containing styrene copolymers with poly(ethylene oxide)

Copolymers of styrene with vinylphenyl trifluoromethyl carbinol, p-vinylphenyl trifluoromethyl carbinol, vinylphenyl hexafluorodimethyl carbinol, and p-vinylphenol are conditionally compatible with poly(ethylene oxide), depending on their composition and blending ratios, whereas copolymers of styrene and vinylphenyl methyl carbinol are much less compatible with poly(ethylene oxide), as determined by T_g criteria and differential scanning calorimetry. The crystallinity of poly(ethylene oxide) is changed in the copolymer/poly(ethylene oxide) blends, as indicated by depressions of the poly(ethylene oxide) melting point. Hydrogen-bond formation has been studied in two selected blends by infrared (IR) spectroscopy. Hydrogen bonding dissociation and reassociation as a function of temperature are reported. The conformation changes of poly(ethylene oxide) in the blends, the interaction between copolymer and poly(ethylene oxide) as well as in the reference blend, polystyrene/poly(ethylene oxide), are also investigated.     

Enhanced activity of gold-supported cobalt oxide for the electrochemical evolution of oxygen

Scanning electron microscopy, linear sweep voltammetry, chronoamperometry, and in situ surface-enhanced Raman spectroscopy were used to investigate the electrochemical oxygen evolution reaction (OER) occurring on cobalt oxide films deposited on Au and other metal substrates. All experiments were carried out in 0.1 M KOH. A remarkable finding is that the turnover frequency for the OER exhibited by ～0.4 ML of cobalt oxide deposited on Au is 40 times higher than that of bulk cobalt oxide. The activity of small amounts of cobalt oxide deposited on Pt, Pd, Cu, and Co decreased monotonically in the order Au > Pt > Pd > Cu > Co, paralleling the decreasing electronegativity of the substrate metal. Another notable finding is that the OER turnover frequency for ～0.4 ML of cobalt oxide deposited on Au is nearly three times higher than that for bulk Ir. Raman spectroscopy revealed that the as-deposited cobalt oxide is present as Co(3)O(4) but undergoes progressive oxidation to CoO(OH) with increasing anodic potential. The higher OER activity of cobalt oxide deposited on Au is attributed to an increase in fraction of the Co sites present as Co(IV) cations, a state of cobalt believed to be essential for OER to occur. A hypothesis for how Co(IV) cations contribute to OER is proposed and discussed.     

Towards microphase separation in epoxy systems containing PEO/PPO/PEO block copolymers by controlling cure conditions and molar ratios between blocks. Part 2. Structural characterization

The influence of addition of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO–PPO–PEO) copolymers on final morphologies of modified epoxy matrices has been investigated as a function of PEO:PPO molar ratio and cure conditions by comparison with the cured epoxy blends only containing poly(ethylene oxide) (PEO) or poly(propylene oxide) (PPO) homopolymers. Atomic force microscopy (AFM) has been used to characterize structural features of blends. Whilst diglycidyl ether of bisphenol-A (DGEBA)/4,4’-diaminodiphenylmethane (DDM)/PPO system macrophase separates, the interactions between PEO and cured epoxy are responsible for miscibility of DGEBA/DDM/PEO system. Depending on PEO:PPO molar ratio, micro- or macrophase separated morphologies have been obtained for block copolymer modified epoxy matrices. Moreover, the influence of both copolymer content and cure temperature on final morphologies has also been investigated by both experimental and theoretical analysis.     

外延定向生长氧化铌模型催化剂的制备

为用现代表面科学技术研究金属氧化物催化剂，在Pt（111）上于超高真空系统中原位蒸镀制备了NbO、NbO2、NbO2、单晶薄膜（＞2nm）．通过AES、ISS、LEED、ILS等手段研究了单晶薄膜的成长模式、化学计量和几何结构．表明通过选择合适的废物和控制制备条件，可制备出确定结构的金属氧化物单晶薄膜表面作为体相氧化物催化剂的模型表面．这种方法克服了电子能谱技术研究金属氧化物表面的困难，为研究金属氧化物催化剂的表面化学物理性质提供了方法     

Preparation of gold microparticles using halide ions in bulk block copolymer phases via photoreduction

Gold microparticles were prepared from the gold salt in the solid bulk phase of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer via a photoreduction process in the presence of halide ions. The shapes and sizes of the gold microparticles were found to be dependent on the types and amount of halide ions as well as the types of cations used due to the combined effects of the adsorption power and oxidative dissolution ability of the additives on gold surfaces. Gold nanorods were obtained when poly(ethylene oxide) was used instead of the block copolymer. This suggests that the poly(propylene oxide) (PPO) parts in the block copolymer are essential for the formation of gold microparticles, even though the degree of the direct interaction between the PPO blocks and gold salt is not significant.     

Graphene materials preparation methods have dramatic influence upon their capacitance

Graphene related materials are widely expected to play a major role as materials for the construction of supercapacitors. We demonstrate here that graphene oxides prepared by various well-established methods exhibit dramatically different capacitances. We exfoliated graphite oxide sonographically to graphene oxide (GO) and we reduced GO by chemical or electrochemical means to chemically reduced graphene oxide (CRGO) and electrochemically reduced graphene oxide (ERGO); in addition, graphite oxide was thermally exfoliated leading to thermally reduced graphene oxide (TRGO). We found clear dependence of weight specific capacitance upon amount of oxygen containing groups presented on the surface of these graphenes. GO exhibits the lowest and TRGO the highest values of weight specific capacitance.     

A new P‐heterocyclic family: A variety of six‐membered and bridged P‐heterocycles with 1‐benzyl substituent

The ring enlargement of 1‐benzyl‐2,5‐dihydro‐1H‐phosphole oxide ( 1 ) via the corresponding 2‐phosphabicyclo[3.1.0]hexane 2‐oxide ( 2 ) afforded, depending on the conditions, the double bond isomers ( A and B ) of 1,2‐dihydrophosphinine oxide 4 or that of 3‐substituted 1,2,3,6‐tetrahydrophosphinine oxides 5 and 6 . Dihydrophosphinine oxides ( 4 ) were suitable starting materials for 1,2,3,4,5,6‐hexahydrophosphinine oxide 7 and 1,2,3,6‐tetrahydrophosphinine oxide 8 obtained by reductive approaches and for the double bond isomers ( A and B ) of 2‐phosphabicyclo[2.2.2]octadiene 2‐oxide 9 and phosphabicyclooctene oxide 10 prepared in Diels–Alder cycloaddition. Precursor 9 was utilized in the fragmentation‐related phosphorylation of alcohols. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:28–34, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20363