Chain order and mobility of high-density c(18) phases by solid-state NMR spectroscopy and liquid chromatography

C(18) phases prepared by different synthetic pathways are examined by solid-state NMR spectroscopy. Silane functionality is clearly indicated by (29)Si CP/MAS NMR spectroscopy. Order and mobility of the alkyl chains are investigated with high-speed (1)H MAS and (13)C CP/MAS NMR spectroscopy. Differences in coverage are monitored by (1)H line widths,( 13)C chemical shifts, (13)C cross-polarization constants, and (1)H relaxation times in the rotating frame. It is shown that C(18) phases prepared by the surface polymerization technique exhibit a more regular surface coverage than sorbents prepared by conventional polymeric synthesis. The findings from solid-state NMR investigations are discussed in the context of liquid chromatography (LC) separations of linear and bulky polycyclic aromatic hydrocarbon (PAH) solutes.     

Enrichment of H(2)(17)O from tap water, characterization of the enriched water, and properties of several (17)O-labeled compounds

A low-abundance form of water, H(2)(17)O, was enriched from 0.04% to ～90% by slow evaporation and fractional distillation of tap water. The density and refractive index for H(2)(17)O are reported. Gas chromatography-mass spectrometry (GC-MS) of (16)O- and (17)O-1-hexanols and their trimethyl silyl ethers and of (16)O- and (17)O-hexamethyl disiloxanes was used to determine the percentage of (17)O enrichment in the H(2)(17)O. Furthermore, the chemical shifts of labeled and nonlabeled water dissolved in CDCl(3) differed sufficiently that we could verify the enrichment of H(2)(17)O. (17)O hexanol was synthesized by the reaction of iodohexane with Na(17)OH. (17)O-Labeled trimethylsilanol and (17)O-labeled hexamethyldisiloxane were prepared by the reaction of H(2)(17)O with bis(trimethylsilyl)trifluoroacetamide (BSTFA). To generate standards for (17)O NMR, H(2)(17)O(2), and (17)O camphor were prepared. H(2)(17)O was electrolyzed to form (17)O-labeled hydrogen peroxide which was quantified using two colorimetric assays. (17)O-Labeled camphor was prepared by exchanging the ketone oxygen of camphor using H(2)(17)O. The (17)O-labeled compounds were characterized using (17)O, (1)H, and (13)C NMR and GC-MS. While we were characterizing the labeled camphor, we also detected an unexpected oxygen exchange reaction of primary alcohols, catalyzed by electrophilic ketones such as camphor. The reaction is a displacement of the alcohol OH group by water. This is an example of the usefulness of (17)O NMR in the study of a reaction mechanism that has not been noticed previously.     

Mesoporous silica-magnetite nanocomposite synthesized by using a neutral surfactant

Magnetite nanoparticles coated by mesoporous silica were synthesized by an alternative chemical route using a neutral surfactant and without the application of any functionalization method. The magnetite (Fe(3)O(4)) nanoparticles were prepared by precipitation from aqueous media, and then coated with mesoporous silica by using nonionic block copolymer surfactants as the structure-directing agents. The mesoporous SiO(2)-coated Fe(3)O(4) samples were characterized by x-ray diffraction, Fourier-transform infrared spectroscopy, N(2) adsorption-desorption isotherms, transmission electron microscopy, (57)Fe M?ssbauer spectroscopy, and vibrating sample magnetometry. Our results revealed that the magnetite nanoparticles are completely coated by well-ordered mesoporous silica with free pores and stable (～8?nm thick) pore walls, and that the structural and magnetic properties of the Fe(3)O(4) nanoparticles are preserved in the applied synthesis route.     

Trace detection of krypton using laser-induced fluorescence

Highly sensitive detection of neutral Kr atoms was accomplished by the use of laser-induced fluorescence. In one experiment, Kr at 40 parts per 10(12) in He was detected at a signal-to-noise ratio of 500 by time-resolved fluorescence measurements. The Kr metastable 1s(5) level was populated by cascade after two-photon excitation to the 2p(6) level by the frequency-tripled output of a pulsed single-longitudinalmode dye laser. After a delay, when scattered laser light and cascade resonance fluorescence became negligible, trace quantities of Kr were detected by the use of a pulsed-laser pumping scheme. In a related experiment, (78)Kr/(86)Kr isotope ratios ranging from 1 to 0.1 were measured with a resonant isotopic depletion technique first proposed by Makarov [Sov. J. Quantum Electron. 13, 722 (1983)]. The (86)Kr metastable population was selectively depleted by optical pumping to a higher-lying state that relaxed to the ground state by means of radiative cascade. After the (78)Kr/(86)Kr ratio of metastables had been enriched by a factor of 10, the (78)Kr population was probed by pulsed excitation. Premixed (78)Kr/(86)Kr ratios were measured to within an accuracy of 10%, even for unresolved, Doppler-broadened transitions.     

Lateral flow immunochromatographic assay for sensitive pesticide detection by using Fe3O4 nanoparticle aggregates as color reagents

Magnetic Fe(3)O(4) particle aggregates were prepared by cross-linking Fe(3)O(4) nanoparticles bearing surface carbonyl groups with poly-L-lysine. Upon further coupling with antiparaoxon methyl polyclonal antibody, the resultant particle aggregate-based probes were used in a lateral flow immunochromatographic assay (LFIA) of pesticide residue of paraoxon methyl. The results were compared with that achieved by using the mother Fe(3)O(4) nanoparticles. More quantitative results on the signal amplification effect endowed by the controlled aggregation of Fe(3)O(4) nanoparticles were extracted by relative optical density analysis. Under optimized conditions, a detection limit of 1.7 ng/mL for paraoxon methyl was achieved by using the particle aggregates, which is almost 40-fold lower than that based on the mother Fe(3)O(4) nanoparticles.     

Application of Vis–NIR hyperspectral imaging in classification between fresh and frozen-thawed pork Longissimus Dorsi muscles

Fresh and frozen-thawed (F-T) pork meats were classified by Vis–NIR hyperspectral imaging. Eight optimal wavelengths (624, 673, 460, 588, 583, 448, 552 and 609 nm) were selected by successive projections algorithm (SPA). The first three principal components (PCs) obtained by principal component analysis (PCA) accounted for over 99.98% of variance. Gray-level-gradient co-occurrence matrix (GLGCM) was applied to extract 45 textural features from the PC images. The correct classification rate (CCR) was employed to evaluate the performance of the partial least squares-discriminate analysis (PLS-DA) models, by using (A) the reflected spectra at full wavelengths and (B) those at the optimal wavelengths, (C) the extracted textures based on the PC images, and (D) the fused variables combining spectra at the optimal wavelengths and textures. The results showed that the best CCR of 97.73% was achieved by applying (D), confirming the high potential of textures for fresh and F-T meat discrimination.     

聚(ε-己内酯)-b-聚丙烯酸嵌段聚合物的合成

结合配位-插入开环聚合(CROP)及原子转移自由基聚合(ATRP)成功制备出一种两亲性新型四臂星型聚合物聚(ε-己内酯)-b-聚丙烯酸(PCL4-b-PAA4)。首先以季戊四醇为四官能团引发剂,辛酸亚锡Sn(Oct)2为催化剂,由ε-己内酯制备出分子量为8000、分子量分布为1.13的四臂星型聚(ε-己内酯)(PCL4),其末端羟基与小分子2-溴异丁酰溴进行酯化反应,得到用于ATRP聚合的星型大分子引发剂(PCL-Br)4,然后引发丙烯酸叔丁酯(tBA)聚合,把得到的PCL4-b-Pt-BA4水解,得到目标产物PCL4-b-PAA4。水解3 h和6 h的样品通过凝胶渗透色谱(GPC)测试可知,分子量分布很窄,分别为1.31和1.40。用核磁共振(1H-NMR)和红外光谱(FT-IR)等手段,对中间及最终产物进行了详细表征。     

Binding characteristics of copper and cadmium by cyanobacterium Spirulina platensis

Cyanobacteria are promising biosorbent for heavy metals in bioremediation. Although sequestration of metals by cyanobacteria is known, the actual mechanisms and ligands involved are not very well understood. The binding characteristics of Cu(II) and Cd(II) by the cyanobacterium Spirulina platensis were investigated using a combination of chemical modifications, batch adsorption experiments, Fourier transform infrared (FTIR) spectroscopy and X-ray absorption fine structure (XAFS) spectroscopy. A significant increase in Cu(II) and Cd(II) binding was observed in the range of pH 3.5-5.0. Dramatical decrease in adsorption of Cu(II) and Cd(II) was observed after methanol esterification of the nonliving cells demonstrating that carboxyl functional groups play an important role in the binding of metals by S. platensis. The desorption rate of Cu(II) and Cd(II) from S. platensis surface was 72.7-80.7% and 53.7-58.0% by EDTA and NH(4)NO(3), respectively, indicating that ion exchange and complexation are the dominating mechanisms for Cu(II) and Cd(II) adsorption. XAFS analysis provided further evidence on the inner-sphere complexation of Cu by carboxyl ligands and showed that Cu is complexed by two 5-membered chelate rings on S. platensis surface.     

First direct synthesis of highly ordered bifunctionalized mesoporous silica thin films

Optically transparent and highly ordered mesoporous organosilica thin films functionalized with two different organic groups in various proportions were synthesized by templated-directed cocondensation of tetraethylorthosilicate (TEOS) and a mixture of two distinct and functional organotriethoxysilanes [NC(CH2)3Si(OEt)3 and O=P(OEt)2(CH2)3Si(OEt)3]. The mesostructured films obtained by evaporation induced self-assembly (EISA) approach were deposited on glass or silicon substrates by dip-coating. They were characterized by Grazing Incidence Small Angle X-ray Scattering (GISAXS) and X-ray reflectivity. We showed that whatever the proportion in organic groups, only 2D hexagonal phase having p6m symmetry was observed for all the materials indicating a good compatibility between the organic groups. The bi-functionalization of the internal pores surface by the organotriethoxysilanes groups was clearly evidenced by using micro-Raman spectroscopy.     

The comprehensive investigation on removal mechanism of Cr(VI) by humic acid-Fe(II) system structured on V,Ti-bearing magnetite surface

The Cr(VI) could be adsorbed and reduced by the humic acid (HA)-Fe(II) system structured on the V, Ti-magnetite (VTM) surface. The Cr(VI) removal process included adsorption and reduction stages. First, the Cr(VI) was adsorbed on the VTM-HA surface via the ionic bonds between the Ti atoms of VTM core and the O atoms of the HCrO₄^?. The adsorption of Cr(VI) is uniform, monolayer, and controlled by Cr(VI) diffusion. Subsequently, the adsorbed Cr(VI) was reduced by the HA-Fe(II) system on the VTM-HA surface. During the Cr(VI) reduction process, the HA and Fe(II) have a synergistic effect. The Cr(VI) was reduced to the Cr(III) by the HA and Fe(II). Meanwhile, the HA could also reduce Fe(III) to Fe(II), making Fe(II) continue to participate in the Cr(VI) reduction. The olefin, hydroxyl, and aldehyde groups of HA were the primary electron donors during the Cr(VI) reduction. The Fe(II) acted as an electron bridge, transferring the electron from HA to Cr(VI). The reduced Cr(III) was deposited on the VTM-HA surface via the complexation with the carboxyl and hydroxyl groups of HA. The results demonstrated that the Cr(VI) could be adsorbed, reduced and complexed by the HA-Fe(II) system on the VTM-HA surface synchronously.     

Higher visible photocatalytic activities of nitrogen doped In2TiO5 sensitized by carbon nitride

N-doped In(2)TiO(5) modified by carbon nitride (CN) composite (NICN) has been prepared by the pyrogenation of the mixture of urea and In(2)TiO(5) through a polymerizable complex (PC) method. The powder samples were characterized by XRD, FESEM, TEM, UV-vis, and XPS. It is shown by XRD that the precursor sintered at 1000°C is pure and nitrogen dopant does not change the crystal structure of In(2)TiO(5). FESEM and TEM reveal a hole-like morphology of the prepared NICN. With the increase of nitrogen content, the light absorption onset of In(2)TiO(5) shifts from 410 nm to 450 nm, revealing significant narrowing of the band gap. XPS results suggest that only 2.2% of the nitrogen atoms were doped into In(2)TiO(5) through the urea pyrogenation method. Furthermore, the decomposition of Rhodamine B (Rh-B) under visible light reveals that Rh-B can be degraded completely within 20 min and recycling experiments indicate NICN has stable structure and durable photocatalytic activity, suggesting a promising utilization of such photocatalyst under visible light. Finally, an innovative mechanism of N-doped In(2)TiO(5) sensitized by carbon nitride polymer is proposed.     

Natural Passivity of Amorphous Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 Alloys

The natural passive films forrned on Fe_(40)Ni_(40)P_(14)B_6 and Fe_(54.6)Ni_(38)Si_(4.1)B_(2.3)V_1 amorphous alloys long-term exposed in air have been studied by X-ray photoelectron spectroscopy (XPS) and Auger electron (including Ar+ ion depth profiling) spectroscopy (AES). The following aspects have been investigated: (1) chemical states of the elements in the films. binding energies and the chemical shifts measured by XPSf (2) structure and composition of the films fand (3) thickness of the passive films determined by AES depth profiling and XPS analysis.     

军民两用硝铵炸药的配方和某些爆炸性能的相互关系

研究了AN-AN-TNT-DNT、AN-TNT-DNT-Al两种军民两用硝铵炸药的配方和某些爆炸性能之间的相互关系.结果发现:对于AN-TNT-DNT炸药,随着DNT含量由0%增加到5%,炸药的爆热Qv减少1.6%,比容V0增加1.0%,Qv V0的乘积下降0.6%;随着氧平衡由0%降低-2.50%,炸药的爆热Qv减少2.2%,比容V0增加0.7%,Qv V0的乘积下降1.5%.对于AN-TNT-DNT-Al炸药,随着铝粉含量由0%增至14%,炸药的爆热Qv增加58.34%,比容V0下降15.7%,Qv V0的乘积增加33.5%.     

Metastable Ge1-xCx alloy nanowires

Carbon-containing alloy materials such as Ge(1-x)C(x) are attractive candidates for replacing silicon (Si) in the semiconductor industry. The addition of carbon to diamond lattice not only allows control over the lattice dimensions, but also enhances the electrical properties by enabling variations in strain and compositions. However, extremely low carbon solubility in bulk germanium (Ge) and thermodynamically unfavorable Ge-C bond have hampered the production of crystalline Ge(1-x)C(x) alloy materials in an equilibrium growth system. Here we successfully synthesized high-quality Ge(1-x)C(x) alloy nanowires (NWs) by a nonequilibrium vapor-liquid-solid (VLS) method. The carbon incorporation was controlled by NW growth conditions and the position of carbon atoms in the Ge matrix (at substitutional or interstitial sites) was determined by the carbon concentration. Furthermore, the shrinking of lattice spacing caused by substitutional carbon offered the promising possibility of band gap engineering for photovoltaic and optoelectronic applications.     

Quantification of nitryl chloride at part per trillion mixing ratios by thermal dissociation cavity ring-down spectroscopy

Nitryl chloride (ClNO(2)) is an important nocturnal nitrogen oxide reservoir species in the troposphere. Here, we report a novel method, thermal dissociation cavity ring-down spectroscopy (TD-CRDS), to quantify ClNO(2) mixing ratios with tens of parts-per-trillion by volume (pptv) sensitivity. The mixing ratios of ClNO(2) are determined by blue diode laser CRDS of NO(2), produced from quantitative thermal dissociation of ClNO(2) in an inlet heated to 450 °C, relative to NO(2) observed in an unheated reference channel. ClNO(2) was generated by passing Cl(2) gas over a slurry containing a 1:10 mixture of NaNO(2) and NaCl. The TD-CRDS response was evaluated using parallel measurements of ClNO(2) by chemical ionization mass spectrometry (CIMS) using I(-) as the reagent ion and NO(y) (= NO + NO(2) + HNO(3) + ΣRO(2)NO(2) + ΣRONO(2) + HONO + 2N(2)O(5) + ClNO(2) + ...) chemiluminescence (CL). The linear dynamic range extends from the detection limit of 20 pptv (1 σ, 1 min) to 30 parts-per-billion by volume (ppbv), the highest mixing ratio tested. The ClNO(2) TD profile overlaps with those of alkyl nitrates, which has implications for nocturnal measurements of total alkyl nitrate (ΣAN = ΣRONO(2)) abundances by thermal dissociation (with detection as NO(2)) in ambient air.     

Synthesis of Fe(2)O(3)/TiO(2) nanorod-nanotube arrays by filling TiO(2) nanotubes with Fe

Synthesis of hematite (α-Fe(2)O(3)) nanostructures on a titania (TiO(2)) nanotubular template is carried out using a pulsed electrodeposition technique. The TiO(2) nanotubes are prepared by the sonoelectrochemical anodization method and are filled with iron (Fe) by pulsed electrodeposition. The Fe/TiO(2) composite is then annealed in an O(2) atmosphere to convert it to Fe(2)O(3)/TiO(2) nanorod-nanotube arrays. The length of the Fe(2)O(3) inside the TiO(2) nanotubes can be tuned from 50 to 550?nm by changing the deposition time. The composite material is characterized by scanning electron microscopy, transmission electron microscopy and diffuse reflectance ultraviolet-visible studies to confirm the formation of one-dimensional Fe(2)O(3)/TiO(2) nanorod-nanotube arrays. The present approach can be used for designing variable one-dimensional metal oxide heterostructures.     

Microcapsules for cell entrapment by template polymerization of a synthetic hydrogel coating around calcium alginate gel: preliminary development

Stable, water-soluble copolymers of glycidyl methacrylate with n-vinyl pyrrolidinone (I) were prepared by free-radical polymerization. Water-soluble copolymers of 2-hydroxyethyl methacrylate with methacrylic acid (II) were examined as co-reactants with (I) to form hydrogel matrices. Upon mixing of (I) and (II) in solution, a covalently crosslinked hydrogel was formed, presumably by etherification of epoxy functionality on (I) with hydroxyls on (II). Synthetic hydrogel-coated gel beads were prepared from an aqueous mixture of sodium alginate and (II) by treatment with solution containing (I) and calcium ion. An elastic, defect free and indefinitely stable covalently crosslinked hydrogel coating was formed around the calcium alginate by surface reaction of (I) and (II). Encapsulated guinea-pig red blood cells suffered minimal lysis over a 4 day period due to isolation and protection from the reacting species by the interior alginate gel matrix.     

Competitive immobilization of multiple component chlorinated solvents by cyclodextrin derivatives

Immobilization of chlorinated solvents with hydropropyl and methyl cyclodextrins (CDs) was observed by head-space analysis to obtain the stability constants in single and multiple component systems. In each single component system, the highest stability constant was 0.299 mM(-1) for perchloroethylene (PCE) by methyl-beta-cyclodextrin (M-beta-CD), 0.136 mM(-1) for trichloroethylene (TCE) by M-beta-CD, 0.106 mM(-1) for cis-dichloroethylene (cis-DCE) by hydropropyl-alpha-cyclodextrin, and 0.090 mM(-1) for trans-dichloroethylene (trans-DCE) by M-beta-CD. When HP-beta-CD and M-beta-CD were used, the stability constants of PCE and TCE increased and those of DCEs decreased in a multiple component system. Differences in stability constants of single and multiple component systems thus should be important parameters when cyclodextrins are applied to solubilization of multiple chlorinated solvents.     

官能团化聚丙烯改性Mg(OH)2/PP中PP结晶的异相成核作用

用DSC研究了外加官能团化聚烯烃(FPP)、接枝单体和原位形成FPP改性Mg(OH)2／聚丙烯中的异相成核作用。Mg(OH)2表面的异相成核作用使聚丙烯(PP)结晶温度提高;外加FPP使PP结晶温度进一步提高,接枝单体加入也使复合材料中PP结晶温度提高,但原位形成FPP使PP结晶温度、熔点和结晶度降低。认为在改性复合材料中存在Mg(OH)2表面异相成核作用和FPP活化Mg(OH)2表面异相成核的协同作用。     

两亲嵌段共聚物的合成及纳米自组装

首先用苄氧羰基赖氨酸和三光气反应合成苄氧羰基赖氨酸酸酐,然后将聚乙二醇中活性较弱的羟基转化为氨基,最后以双端氨基聚乙二醇作为引发剂,采用阴离子开环聚合合成了聚(Nε-苄氧羰基赖氨酸)-聚乙二醇-聚(Nε-苄氧羰基赖氨酸)(PLL(Z)-PEG-PLL(Z))。PLL(Z)-PEG-PLL(Z)经去保护后得到带正电荷的聚赖氨酸-聚乙二醇-聚赖氨酸(PLL-PEG-PLL)。PLL(Z)-PEG-PLL(Z)在水溶液中自组装形成的聚集体类似于纳米多孔聚集体结构,具有疏松的空洞,原子力显微镜观测其呈球形,其大小为220 nm左右。