辉光放电电解等离子体引发合成高吸水性树脂

以淀粉、丙烯酸和腐殖酸钠为原料,以N,N-亚甲基双丙烯酰胺为交联剂,采用辉光放电电解等离子体在水溶液中引发聚合制备淀粉-聚丙烯酸/腐殖酸钠复合高吸水树脂。考察了放电电压、放电时间,单体与淀粉质量比、腐殖酸钠含量、交联剂、温度及中和度对树脂吸水率的影响。用红外光谱和热重分析分别对树脂进行了结构表征和稳定性测试,结果表明,在优化合成条件下,所得的复合树脂具有较高的吸水性和耐盐性,常温下对蒸馏水吸收量为862g/g,对0.9%NaCl溶液的吸收量为69g/g。     

Synthesis and inclusion properties of pillar[n]arenes

A detailed study of the reaction conditions revealed that a quantitative cyclocondensation of 1,4-dialkoxy-2,5-bis(alkoxymethyl)-benzenes to pillar[n]arenes can be achieved by catalysis of p-toluenesulfonic acid in CH₂Cl₂. Major product of this new reaction is in each case a cyclopentamer (n = 5), but small amounts of the pillar[n]arenes with n = 6, 7 and 10 can be obtained as well. Different alkoxy groups in 1- and 4-position lead to regioisomers. All cyclooligomers exist in pillar structures as pair of enantiomers, which show a racemisation at room temperature, which is fast in terms of the NMR time scale. The racemisation process occurs by rotation of the 1,4-phenylene segments in the macrocyclic rings. Pillar[n]arenes exhibit novel host–guest behavior.     

Preparation and photocatalytic antibacterial property of nitrogen doped TiO2 nanoparticles

Nitrogen doped TiO₂ (N-TiO₂) nanoparticles with about 30 nm in size were produced by a sol–gel method and characterized respectively by UV–vis, X-ray diffraction (XRD), Transmission electron microscopy, X-ray photoelectron spectroscopy (XPS). Their photocatalytic antibacterial properties were evaluated by the antibacterial ratio against Escherichia coli in dark and under simulated sunlight respectively. The XRD pattern showed that the doped nano-TiO₂ was mainly composed of anatase phase. The XPS spectra of the N-TiO₂ sample indicated that TiO₂ was doped by nitrogen atom. The nitrogen doping created a new N 2p state slightly above the valence band top consists of O 2p state, and this pushes up the valence band top and decreased the band gap. Which leaded to the absorption edge was red-shifted to the visible light region of UV–vis spectra of nitrogen doped nano-TiO₂ comparing with pure nano-TiO₂. The antibacterial percentage of N-TiO₂ against E. coli reached to 90 % under simulated sunlight for 2 h, which was much better than that in dark, also than that of pure nano-TiO₂. The photo-catalytic antibacterial activity was activated under visible light. The structure and integrity of cell wall and cell membrane were destructed, and even caused the bacteria death.     

Preparation and characterization of ZrCO/C composite aerogels

Zr-containing organic aerogels were synthesized by ligand substitution reaction of polyzirconoxone and 2, 4-dihydroxybenzoic acid, followed by polymerization with formaldehyde, and then supercritical drying using CO₂. After carbonization and carbothermal reduction under an argon atmosphere, ZrCO/C composite aerogels with controllable zirconium content (47.8–78.6 wt%) were obtained. The carbothermal reduction was substantially completed at 1,500 °C, and the obtained ZrCO/C composite aerogels exhibit low oxygen contents (9.4–6.7 wt%) and high surface areas (589–147 m²/g). Pore morphologies of the ZrCO/C composite aerogels were investigated in detail by nitrogen sorption measurements, scanning electron microscopy and its associated energy-dispersive X-ray microanalysis measurements. The results show that the aerogels are composed of carbon framework and Zr-conglomerations, and the surface area of aerogel is severely affected by its zirconium content. The presence of reductive ZrC crystals can greatly enhance the oxidation resistance ability of amorphous carbon framework and prevent collapse.     

Chemoselectivity Control: Gold(I)‐Catalyzed Synthesis of 6,7‐Dihydrobenzofuran‐4(5H)‐ones and Benzofurans from 1‐(Alkynyl)‐7‐oxabicyclo[4.1.0]heptan‐2‐ones

New and chemoselective gold(I)‐catalyzed transformations of 1‐(arylethynyl)‐7‐oxabicyclo[4.1.0]‐ heptan‐2‐ones were developed. Two completely different products—6,7‐dihydrobenzofuran‐4(5H)‐ones and benzofurans—could be obtained from the same starting material. The selectivity is determined by the ligand of the gold catalyst: triphenylphosphine delivers 6,7‐dihydrobenzofuran‐4(5H)‐ones, and 1,3‐bis(diisopropylphenyl)imidazol‐2‐ylidene leads to benzofurans. Eleven examples of each case are provided. The mechanistic suggestions for the pathways to both product types are supported by isotope labeling experiments.     

Breathing Effect in a Cobalt Phosphonate upon Dehydration/Rehydration: A Single‐Crystal‐to‐Single‐Crystal Study

Two cobalt phosphonates, [Co₂(2,2′‐bpy)₂(H₂O)(pbtcH)] ( 1 ) and [Co₂(H₂O)(pbtcH)(phen)₂] ( 2 ; pbtcH₅=5‐phosphonatophenyl‐1,2,4‐tricarboxylic acid, 2,2′‐bpy=2,2′‐bipyridine, phen=1,10‐phenanthroline), with layer structures are reported. Compound 1 contains O‐C‐O and O‐P‐O bridged tetramers of Co₄, which are further connected by pbtcH^4? units to form a layer. In compound 2 , the cobalt tetramers made up of water‐bridged Co₂ dimers and O‐P‐O linkages are connected into a layer by pbtcH^4? units. Upon dehydration, compounds 1 and 2 experience single‐crystal‐to‐single‐crystal (SC–SC) structural transformations to form [Co₂(2,2′‐bpy)₂(pbtcH)] ( 1 a ) and [Co₂(pbtcH)(phen)₂] ( 2 a ), respectively. The process is reversible in each case. Notably, a breathing effect is observed for 1 , accompanied by pore opening and closing due to the reorientation of the coordinated 2,2′‐bpy molecules. The transformation was also monitored by in situ IR measurements. Magnetic studies reveal that antiferromagnetic interactions are mediated between the magnetic centers in compounds 1 and 1 a , whereas ferromagnetic interactions are dominant in compound 2 .     

Quantum Chemical Insight of the Dimetallic Sulfide Endohedral Fullerene Sc2S@C70: Does It Possess the Conventional D5h Cage?

Like C₆₀, C₇₀ is one of the most representative fullerenes in fullerene science. Even though there are 8149 C₇₀ isomers, only two of them have been found before: the conventional D_5h and an isolated pentagon rule (IPR)‐violating C_2v(7854). Through the use of quantum chemical methods, we report a new unconventional C₇₀ isomer, C₂(7892), which survives in the form of dimetallic sulfide endohedral fullerene Sc₂S@C₇₀. Compared with the IPR‐obeying C₇₀ and the C_2v(7854) fullerene with three pairs of pentagon adjacencies, the C₂(7892) cage violates the isolated pentagon rule and has two pairs of pentagon adjacencies. In Sc₂S@C₂(7892)‐C₇₀, two scandium atoms coordinate with two pentalene motifs, respectively, presenting two equivalent Sc? S bonds. The strong coordination interaction, along with the electron transfer from the Sc₂S cluster to the fullerene cage, results in the stabilization of the non‐IPR endohedral fullerene. The electronic structure of Sc₂S@C₇₀ can be formally described as [Sc₂S]⁴⁺@[C₇₀]^4?; however, a substantial overlap between the metallic orbitals and cage orbitals has also been found. Electrochemical properties and electronic absorption, infrared, and ¹³C NMR spectra of Sc₂S@C₇₀ have been calculated theoretically.     

Determination of the total purity of a high-purity silver material to be used as a primary standard for element determination

A candidate material for the use as primary standard for silver determination was characterized with respect to total purity. Except the radioactive elements and He, all possible impurities were considered. Based on glow discharge mass spectrometry, inductively coupled plasma-mass spectrometry and carrier gas hot extraction measurements, the demonstrated total purity and its standard uncertainty is w(Ag) = (99.999 52 ± 0.000 11) %. The purity value and its uncertainty is dominated by the contributions from the measurements of the nonmetallic impurities, namely S, N, C and O.     

Effect of hydrolysis degree of hydrolyzed polyacrylamide grafted carboxymethyl cellulose on dye removal efficiency

In this present work, a series of hydrolyzed polyacrylamide grafted carboxymethyl cellulose (CMC-g-HPAM) was prepared. The structure and solution properties of CMC-g-HPAM were characterized by FTIR, ¹H-NMR, elemental analysis and zeta potential measurements. The graft copolymers were applied as flocculants to remove methylene blue (MB), a cationic dye, from aqueous solutions. In comparison with its precursors, carboxymethyl cellulose (CMC) and polyacrylamide CMC-g-PAM, CMC-g-HPAM exhibited higher removal efficiencies. Furthermore, the flocculation performance of the copolymers was significantly improved with the increase of the hydrolysis degree, and the MB removal efficiency was more than 90 % when the hydrolysis degree of CMC-g-HPAM was higher than 80 %. More importantly, image analysis in combination with fractal theory demonstrated that the graft copolymers could produce notably denser and larger flocs, which was of great significance in practical water treatment. The improved flocculation performance was ascribed to both charge neutralization and bridging effects.