碳源对鱼骨式纳米碳纤维及其负载的钯催化剂性能的影响

分别以甲烷、一氧化碳和乙烯为碳源合成了3种鱼骨式结构的纳米碳纤维(FCNF-C1,FCNF-CO和FCNF-C2),并作为载体制备了3种钯催化剂(Pd0.5%),考察了在对苯二甲酸加氢精制中的催化活性,通过N2吸附-脱附、X射线衍射、程序升温脱附、电子透射显微镜及CO化学吸附等方法对载体以及催化剂的结构进行了表征.结果表明,从不同碳源合成的纳米碳纤维(CNF)具有相似的直径和鱼骨式石墨层排列方式,但其物理化学性能差异较大,其中CO作为碳源得到的CNF具有最大的比表面积,最高的石墨化程度和最多的表面含氧基团;不同碳源的鱼骨式CNF负载的钯催化剂的活性为:Pd/FCNF-CO>Pd/FCNF-C1>Pd/FCNF-C2,与Pd分散度的顺序一致.CNF的织构、晶体结构和表面化学等协同载体效应,决定了Pd金属在CNF上的分散状态以及催化性能,而CNF的石墨层排列方式对其影响很小.     

探究不同银配合物对银镜反应的影响

为探究配体与银形成不同银配合物对银镜反应的影响,以氨水、乙二胺、硫氰化钾和甲胺为配体,通过利用不同银配合物的稳定常数研究不同温度条件下银镜反应的情况,对银镜形成时间和质量做比较。结果表明,在这4种配体中,以乙二胺为配体形成的银配合物稳定常数较高,且碱性较强,室温条件下能快速形成高质量的银镜,利于课堂上开展银镜反应实验演示教学。     

Studies on Silver Accumulation and Nanoparticle Synthesis By <Emphasis Type="Italic">Cochliobolus lunatus</Emphasis>

Development of reliable and eco-friendly processes for synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. Biological systems provide a useful option to achieve this objective. In this study, potent fungal strain was selectively isolated from soil samples on silver supplemented medium, followed by silver tolerance (100–1,000 ppm) test. The isolated fungus was subjected to morphological, 18S rRNA gene sequencing and phylogenic studies and confirmed as Cochliobolus lunatus. The silver accumulation and nanoparticle formation potential of wet cell mass of C. lunatus was investigated. The accumulation and nanoparticle formation by wet fungal cell mass with respect to pH change was also studied. The desorbing assay was used to recover accumulated silver from cell mass. C. lunatus was found to produce optimum biomass (0.94 g%) at 635 ppm of silver. Atomic absorption spectroscopy study showed that at optimum pH (6.5 ± 0.2), cell mass accumulates 55.6% of 100 ppm silver. SEM and FTIR studies revealed that the cell wall of C. lunatus is the site of silver sorption, and certain organic groups such as carbonyl, carboxyl, and secondary amines in the fungal cell wall have an important role in biosorption of silver in nanoform. XRD determined the FCC crystalline nature of silver nanoparticles. TEM analysis established the shape of the silver nanoparticles to be spherical with the presence of very small-sized nanoparticles. Average size of silver nanoparticles (14 nm) was confirmed by particle sizing system. This study reports the synthesis and accumulation of silver nanoparticles through reduction of Ag⁺ ions by the wet cell mass of fungus C. lunatus.     

不同碳源制备的介孔碳分子筛的性能研究

以介孔分子筛SBA-15为模板剂,分别采用蔗糖、糠醇和酚醛树脂作为碳源制备介孔碳分子筛.用TGA、XRD、N2吸附-脱附和TEM对制备的样品进行了表征和比较.结果表明,三种碳源制备的介孔碳分子筛的结构有序性明显不同.用蔗糖为碳源能够得到结构高度有序的介孔碳分子筛,其比表面积和孔容最大,分别为1 422 m2·g和1.15 cm3·g;用糠醇为碳源制备的样品次之;用普通酚醛树脂为碳源制备的样品其结构有序性最差.     

单壁碳纳米管在不同材质基片银膜上的表面增强拉曼光谱

在玻璃、白宝石和石英基片上,利用化学沉积法和溶胶法制备了纳米结构活性银膜,系统地研究了两种不同方法制备的单壁碳纳米管(SWNT)的表面增强拉曼光谱(SERS)的G带和D带.同一样品的G带,在不同基片上的峰移量不同,在白宝石基片上移动更大,峰强更高,可以更敏感地反映SERS效应.D带的峰形随基片不同而改变.金属性管的含量较高的样品,其D带光谱的峰移较半导体性管含量较高的样品更显著,表明金属性碳纳米管与SERS活性银膜的界面相互作用更强.     

Effect of Different Carbon Sources on Cellulase Production by Marine Strain Microbulbifer hydrolyticus IRE-31-192

Cellulase is an important enzyme that can be used to breakdown lignocellulose into glucose. Microbulbifer hydrolyticus IRE-31(ATCC 700072) is a kind of marine bacterium, which could grow in high salinity medium and has fast-strong growth ability. In this study, a novel strain was screened from Microbulbifer hydrolyticus IRE-31 through mutations to produce cellulase. The effect of different carbon sources on the growth as well as on the production of cellulase of the new strain was studied. Carboxymethyl-cellulase (CMCase) activity selected to represent cellulase was proven to be effectively promoted while xylose, galactose, and melibiose as well as glucose were used as carbon sources. When xylose and glucose were chosen to be further investigated, 472.57 U/L and 266.01 U/L CMCase activity were obtained from 30 g/L glucose and 10 g/L xylose, respectively. These results clarified the effect of different carbon sources on the production of cellulase, which laid a good foundation for the further research in the production of cellulase by marine bacteria.

     

Catalytic Effect on Silver Electrodeposition of Gold Deposited on Carbon Electrodes

A new methodology, based on silver electrocatalytic deposition and designed to quantify gold deposited onto carbon paste electrode (CPE) and glassy carbon electrode (GCE), has been developed in this work. Silver (prepared in 1.0 M NH₃) electrodeposition at ?0.13 V occurs only when gold is previously deposited at an adequate potential on the electrode surface for a fixed period of time. When a CPE is used as working electrode, an adequate oxidation of gold is necessary. This oxidation is carried out in both 0.1 M NaOH and 0.1 M H₂SO₄ at oxidation potentials. When a GCE is used as working electrode, the oxidation steps are not necessary. Moreover, a cleaning step in KCN, which removes gold from electrode surface, is included. To obtain reproducibility in the analytical signal, the surface of the electrodes must be suitably pretreated; this electrodic pretreatment depends on the kind of electrode used as working electrode. Low detection limits (5.0×10^?10 M) for short gold deposition times (10 min for CPE and 5 min for GCE) were achieved with this novel methodology. Finally, sodium aurothiomalate can be quantified using silver electrocatalytic deposition and GCE as working electrode. Good linear relationship between silver anodic stripping peak and aurothiomalate concentration was found from 5.0×10^?10 M to 1.0×10^?8 M.     

不同碳源对产甲烷生物阴极性能的影响

以"H"型电池为主体装置,考察和比较了有机和无机碳源对产甲烷生物阴极启动期和稳定运行期性能的影响.结果表明,有机碳源可以加速产甲烷生物阴极的形成,并使其在稳定运行期维持较高的运行性能;有机碳源条件下所形成的产甲烷生物阴极具有较好的电化学活性,当阴极电势为-0.75 V(vs.SHE)时,其电流密度可达(2.34±0.15)A/m2;通过投加有机碳源,可以实现CO2(或HCO-3)的原位供给,与无机碳源直接供给方式相比,可在一定程度上缓解气液传质限制,提高微生物的生长速率,最终使产甲烷生物阴极表面生物量是无机碳源培养下的4倍多.从微生物分析角度解释了有机碳源提高产甲烷生物阴极性能的原因.     

不同银膜粒径对单壁碳纳米管SERS谱的影响

利用化学沉积法和溶胶法制备了粒径在20～100nm范围内不同的表面增强纳米结构活性银膜,系统地研究了单壁碳纳米管（SWCNT）的表面增强拉曼光谱（SERS）的G—band和D—band、比较玻璃和石英两种不同基片上的结果发现,单壁碳管的SERS谱随银膜粒径的变化有相同的变化趋势,G-band峰移对20～100nm范围内活性银膜粒径的差异不敏感,表明该波段所对应的碳管六元环本征振动比较稳定,与界面的化学相互作用较弱．D—band的峰形随基片和活性银膜粒径不同均有改变,且随着粒径变小,高频振动贡献有增大的趋势,表明无序碳与活性银膜间存在很强的相互作用。     

Effects of Different Carbon and Nitrogen Sources on Naphthoquinone Production of Cordyceps unilateralis BCC 1869

The production of six naphthoquinone derivatives, erythrostominone, deoxyerythrostominone, 4-O-methyl erythrostominone, epierythrostominol, deoxyerythrostominol, and 3,5,8-trihydroxy-6-methoxy-2-(5-oxohexa- 1,3-dienyl)-1,4-naphthoquinone, was examined during the growth of Cordyceps unilateralis BCC 1869 on different carbon and nitrogen sources. Erythrostominone production by the fungus accounted for more than 50% of total naphthoquinones, but production of each of the other five derivatives accounted for less than 20% of total naphthoquinones. The highest volumetric production rate of erythrostominone and overall naphthoquinone production rate were obtained on mannose as a sole carbon source and ammonium sulfate as a sole nitrogen source (4922.4 +/- 118.8 mg/[L.d] and 5.03 g/[L.d], respectively). The highest growth rate was obtained on arabinose (0.043 h-1), whereas the maximum overall naphthoquinone concentration was obtained on lactose (2 g/L) at 237 h. These naphthoquinones were produced with no pH control and were first detected at a pH of about 3.0 to 4.0. These results suggest that carbon and nitrogen influenced directly the production of naphthoquinones.     

催化剂对纳米聚团床法制备的纳米碳材料形貌的影响

 在纳米聚团床中用催化化学气相沉积法批量制备了碳纳米管，研\r\n究了过渡金属催化剂对碳纳米管形貌和产量的影响．实验结果表明，含\r\n铁催化剂的活性较低，产率较低，但产品质量较好；含镍催化剂的活性\r\n较高，产率较高，但产品质量较差；在钴催化剂作用下发现了一种新型\r\n的针状纳米碳材料．用含载体较少的铁催化剂可以得到纯度较高且微观\r\n结构较好的碳纳米管，但产率较低；不含任何载体的纯镍催化剂则不能\r\n得到碳纳米管．适宜的催化剂组成、催化剂活性点的均匀分布和裂解速\r\n度的控制等构成了纳米聚团床大批量制备碳纳米管技术的关键．     

温度对碳球形貌及超级电容性能的影响

以三氯乙烷和二氯乙烷为原料, 金属钠为还原剂, 在溶剂热条件(100~150 ℃)下使氯代乙烷中的碳氯键和碳氢键发生断裂制备了碳纳米球, 并对制备的碳纳米球进行了表征. X射线衍射结果表明, 样品为类石墨结构, 衍射信号宽且弱, 表明样品的结晶性较差; 拉曼光谱分析结果也表明样品具有较高的无序度. 样品的SEM与TEM分析结果表明, 在较高的反应温度下, 碳球具有更好的单分散性, 碳球的粒径随温度的升高而增大; 选区电子衍射结果表明碳球内部为无定形的类石墨结构. 以碳纳米球为负极材料的锂离子电池测试结果表明, 50周循环后比容量为941 mA·h/g, 库仑效率接近100%, 放电容量保持率为103.7%, 具有良好的循环稳定性. 测试了不同温度下制备样品的超级电容器性能, 发现120 ℃下制备的碳纳米球具有较高的比电容和较低的内阻值, 比电容高达130 F/g, 经过1000周循环充放电后比电容衰减比例低于14%, 具有较高的稳定性.     

Fe-N共掺杂纳米碳材料的形貌对电化学还原反应的影响

众所周知,石墨烯片（GS）和碳纳米管是能源转化和储存应用中有效的催化剂. 然而,过渡金属基氮（N）掺杂的体系中经常形成GS和碳纳米管的复合物,使得该体系内的构效关系研究变得十分困难. 为了可控制备出含有理想物种的催化剂,作者尝试通过利用氮对碳纳米管生长的效应调节生成产物的形貌. 本文中,作者采用一步法制备了一系列Fe-N共掺杂的GS、GS/竹节碳纳米管(BCNTs)复合物及BCNTs催化剂. 为了评估碳形貌对催化剂性能的影响,作者采用氧气还原反应（ORR）及二氧化碳还原反应（CO₂RR）作为模型反应. 电化学测试结果表明,所有的样品当中仅含BCNTs的催化剂表现出最好的ORR活性（起始电位E_onset = 1.02 V_RHE）及CO₂RR活性（CO生成法拉第效率FE_CO = 91.1%,-0.6 V_RHE）. 进一步的研究表明,优异的活性与独特的BCNTs中存在的缺陷、较大的比表面积、高含量的吡啶N及FeN_x相关. 该工作加深了作者对形貌相关的ORR及CO₂RR过程的认识和理解.     

Effect of Different Energy Sources on Ochrobactrum anthropi Bacteria Chromium Reduction

Ochrobactrum anthropi CTS-325 isolated from a chromium-contaminated site had better resistance to Cr(Ⅵ) in LB medium under aerobic condition.Meanwhile,it was found that the reduction of Cr(Ⅵ) is not complete during the experimental process.Therefore,a series of small molecule energy sources including nitrogen and carbon sources were added into the LB medium in the bacterial stationary phase to promote the chromium reducibility.The result showed that the bacterial growth was positively correlated with the chromium reduction.SDS-PAGE analysis indicated that the protein groups were changed when the bacteria were stimulated by the chromium.Additionally,it was revealed that O.anthropi CTS-325 could utilize the cheaper alternative of sugar(sucrose residue leaching solution) well for further growth and restart the chromium reduction,which offered a new method for practical appli-cations.     

Batch Fermentation Model of Propionic Acid Production by Propionibacterium acidipropionici in Different Carbon Sources

Propionic acid (PA) is widely used as additive in animal feed and also in the manufacturing of cellulose-based plastics, herbicides, and perfumes. Salts of propionic acid are used as preservative in food. PA is mainly produced by chemical synthesis. Nowadays, PA production by fermentation of low-cost industrial wastes or renewable sources has been an interesting alternative. In the present investigation, PA production by Propionibacterium acidipropionici ATCC 4965 was studied using a basal medium with sugarcane molasses (BMSM), glycerol or lactate (BML) in small batch fermentation at 30 and 36 degrees C. Bacterial growth was carried out under low dissolved oxygen concentration and without pH control. Results indicated that P. acidipropionici produced more biomass in BMSM than in other media at 30 degrees C (7.55 g l(-1)) as well as at 36 degrees C (3.71 g l(-1)). PA and biomass production were higher at 30 degrees C than at 36 degrees C in all cases studied. The best productivity was obtained by using BML (0.113 g l(-1) h(-1)), although the yielding of this metabolite was higher when using glycerol as carbon source (0.724 g g(-1)) because there was no detection of acetic acid. By the way, when using the other two carbon sources, acetic acid emerged as an undesirable by-product for further PA purification.     

Production of Cellulolytic Enzymes by Fungi Acrophialophora nainiana and Ceratocystis paradoxa Using Different Carbon Sources

Although a number of filamentous fungi, such as Trichoderma and Aspergillus, are well known as producers of cellulases, xylanases, and accessory cellulolytic enzymes, the search for new strains and new enzymes has become a priority with the increase in diversity of biomass sources. Moreover, according to the type of pretreatment applied, biomass of the same type may require different enzyme blends to be efficiently hydrolyzed. This study evaluated cellulases, xylanases, and β-glucosidases produced by two fungi, the thermotolerant Acrophialophora nainiana and Ceratocystis paradoxa. Cells were grown in submerged culture on three carbon sources: lactose, wheat bran, or steam-pretreated sugarcane bagasse, a commonly used cattle feed in Brazil. Xylanase and endo-1-4-β-glucanase (CMCase) highest production were found in A. nainiana growing on lactose and reached levels of 2,200 and 2,016 IU/L, respectively. C. paradoxa showed highest activity for xylanase when grown on wheat bran and for β-glucosidase when grown on steam-treated bagasse, at levels of 12,728 and 1,068 IU/mL, respectively.     

S2-控制剂对Ag纳米产物的形貌及光学性能的影响

采用改装的微波冷凝回流装置,以乙二醇作为还原剂和溶剂,在表面活性剂聚乙烯吡咯烷酮的保护下,添加Na2S与AgNO3反应生成Ag2S,对Ag2S进行热分解即可获得Ag纳米产物。保持其它参数(加热功率、加热时间、表面活性剂浓度和反应物溶液浓度等)不变的条件下,通过改变Na2S的浓度得到不同形貌的Ag纳米产物。利用扫描电子显微镜、X射线衍射仪和紫外-可见分析仪对所得Ag纳米产物的形貌、物相和光学性能进行分析表征,结果表明,在微波冷凝回流作用下,Na2S浓度的逐渐增大使银纳米产物经历了一个类球形-立方体-线形的形貌演变。此外,通过分析反应过程,对S2-如何影响Ag纳米产物的形貌及Ag纳米线的生长机理作了进一步研究探讨。     

Carbon Dispersion and Morphology in Carbon-Mineral Adsorbents

Carbon-mineral composite adsorbents prepared by deposition of carbon on various mineral supports have been studied extensively by a new textural approach. The evidence of significant influence of both organization of initial mineral support porous space and mobility of carbon precursors over the surface of mineral support on carbon localization has been obtained. Restricted mobility of carbon precursors leads to homogeneous distribution of carbon clusters over the support surface despite the presence of narrow mesopores in the structure of the support if the entire support surface is equiaccessible. Unrestricted mobility over the smooth surface of the mineral support without narrow mesopores leads to the similar resulting carbon distribution. However, unrestricted mobility of carbon precursors in densely packed porous materials seems to be the reason for carbon pulling and deposition in narrow mesopores. These peculiarities of carbon deposition influence the carbon/mineral (hydrophobic/hydrophilic) composition of the composite surface. Trapping of carbon in narrow mesopores leads to a decrease and, in contrast, homogeneous dispersion of carbon over the whole support surface leads to an increase in the part of the composite surface, which can be appropriated to carbon. Copyright 2000 Academic Press.