气单胞菌SH10吸附银离子机制的研究

以气单胞菌SH10为生物吸附材料,从静电吸附作用、离子交换作用、络合作用、沉淀作用几方面研究了SH10吸附Ag 过程可能存在的作用机制.结果表明,气单胞菌SH10吸附银离子依赖于静电吸附作用;吸附Ag 前后溶液中Na 、K 、Mg2 浓度的变化较小,说明吸附过程中离子交换不明显;SH10表面的羧基、氨基和脂类基团经化学屏蔽后,对Ag 的吸附量明显下降,结合红外光谱分析结果,确定酰胺基CO-NH为SH10与银离子发生络合作用的主要官能团;电镜扫描结果表明,SH10在吸附过程中可以和Ag 形成沉淀沉积在细胞表面.     

Cu/ZnO-RGO的抗菌性能及应用

采用溶胶-凝胶法制备铜锌复合氧化物（Cu/ZnO）,并将Cu/ZnO纳米粒子负载到还原氧化石墨烯（RGO）表面制备Cu/ZnO-RGO复合材料.对Cu/ZnO-RGO复合材料进行表征分析及抗菌性能考察,结果表明,Cu/ZnO纳米粒子成功负载在RGO表面,负载前后Cu/ZnO纳米粒子形态不发生改变,复合材料纯度较高.Cu/ZnO-RGO复合材料对大肠杆菌与金黄色葡萄球菌均有着优异的抗菌性能,可以破坏细菌细胞膜,导致细菌内容物流出,延长细菌进入对数生长期所需的时间.当RGO质量分数为15%?Cu/ZnO-RGO复合材料使用量为120μg/mL时,在循环冷却水系统中作用2h即可拥有96.76%的抗菌率.     

金属离子诱导Trichoderma sp.WL-Go合成纳米金特性研究

生物法合成纳米金是一种环境友好且经济高效的合成途径,受到广泛关注.普遍认为微生物合成纳米金是通过胞外分泌生物大分子而实现的一种自发脱毒过程.同时,相关研究表明低浓度的重金属离子对菌株胞外酶的活性会产生一定的影响,进而会对菌株合成纳米金的能力产生影响.基于此,本研究选择一株前期筛选得到的真菌Trichoderma sp. WL-Go,探究不同金属离子诱导菌株对其合成的纳米金特性的影响.结果表明,经Co~(2+)、Al~(3+)、Zn~(2+)、Sn~(2+)、Ni~(2+)等金属离子诱导后,菌株WL-Go合成纳米金的能力均有所提升,而Pb~(2+)、Cu~(2+)、Fe~(3+)与对照组相比,其合成的纳米金浓度及转化率都无明显变化.此外,Co~(2+)诱导菌株合成的纳米金呈现肉眼可见的团簇状,发生明显的团聚现象.本实验还考察了生物合成纳米金对4-硝基苯酚还原的催化特性,结果表明,Sn~(2+)和Pb~(2+)的诱导使菌株WL-Go合成的纳米金催化速率得到明显提升,而其他金属离子均有所抑制.最后选取革兰氏阳性菌Arthrobacter sp. W1和革兰氏阴性菌Escherichia coli BL21 (DE3)验证了不同金属离子诱导后合成的纳米金均具有良好的生物相容性.综上,本研究为对于拓宽纳米金的工业化应用前景有着重要意义.     

二氧化钛纳米颗粒对湖滨沼泽土壤氮矿化的影响

二氧化钛纳米颗粒（TiO₂NPs）的广泛应用使其环境释放量不断增加,从而影响到土壤氮的转化过程.然而,目前关于TiO₂NPs对湖滨沼泽土壤氮矿化的影响机制尚不明确.因此,本研究以典型沼泽土壤为研究对象,通过室内培养实验研究不同剂量TiO₂NPs处理（0 mg·kg^-1（CK）、10 mg·kg^-1（A10）、100 mg·kg^-1（A100）、250 mg·kg^-1（A250）、1000 mg·kg^-1（A1000））对土壤理化性质、酶活性和氮矿化过程的影响,探讨TiO₂NPs输入对土壤氮矿化过程影响的内在机制.结果表明：①不同剂量TiO₂NPs处理显著降低了土壤pH和总有机碳（TOC）含量（p<0.05）,A100、A250和A1000处理显著降低了硝态氮（NO₃^--N）含量（p<0.05）.②A250和A1000处理显著抑制了过氧化氢酶活性（p<0.05）;培养7 d,不同剂量TiO₂NPs处理均显著促进了脲酶活性（p<0.05）,抑制了脱氢酶活性（p<0.05）;随着培养时间延长,TiO₂NPs处理对脲酶和脱氢酶活性的抑制作用逐渐减弱,表明TiO₂NPs的负面作用会随时间减弱.③不同剂量TiO₂NPs处理对氨化速率没有显著影响（p>0.05）,A250、A1000处理对硝化和矿化速率有显著抑制作用（p<0.01）.④土壤氮矿化速率与土壤pH、总磷（TP）、NO₃^--N含量呈显著正相关,与脲酶、过氧化氢酶活性呈显著负相关.TiO₂NPs主要通过改变沼泽土壤NO₃^--N含量影响氮矿化过程.本研究可为湖滨湿地保护和TiO₂NPs环境风险评估提供理论依据.     

Application of nanoparticle tracking analysis for characterising the fate of engineered nanoparticles in sediment-water systems

Novel applications of nanotechnology may lead to the release of engineered nanoparticles (ENPs), which result in concerns over their potential environmental hazardous impact. It is essential for the research workers to be able to quantitatively characterise ENPs in the environment and subsequently to assist the risk assessment of the ENPs. This study hence explored the application of nanoparticle tracking system (NTA) to quantitatively describe the behaviour of the ENPs in natural sediment-water systems. The NTA allows the measurement of both particle number concentration (PNC) and particle size distribution (PSD) of the ENPs. The developed NTA method was applied to a range of gold and magnetite ENPs with a selection of surface properties. The results showed that the positively-charged ENPs interacted more strongly with the sediment than neutral and negatively-charged ENPs. It was also found that the citrate coated Au ENPs had a higher distribution percentage (53%) than 11-mercaptoundecanoic acid coated Au ENPs (20%) and citrate coated magnetite ENPs (21%). The principles of the electrostatic interactions between hard (and soft) acids and bases (HSAB) are used to explain such behaviours; the hard base coating (i.e. citrate ions) will interact more strongly with hard acid (i.e. magnetite) than soft acid (i.e. gold). The results indicate that NTA is a complementary method to existing approaches to characterise the fate and behaviour of ENPs in natural sediment.     

Effects of TiO2 nanoparticles on the aquatic plant Spirodela polyrrhiza: Evaluation of growth parameters, pigment contents and antioxidant enzyme activities

Plants are essential components of all ecosystems and play a critical role in environmental fate of nanoparticles. However, the toxicological impacts of nanoparticles on plants are not well documented. Titanium dioxide nanoparticles (TiO₂-NPs) are produced worldwide in large quantities for a wide range of purposes. In the present study, the uptake of TiO₂-NPs by the aquatic plant Spirodela polyrrhiza and the consequent effects on the plant were evaluated. Initially, structural and morphological characteristics of the used TiO₂-NPs were determined using XRD, SEM, TEM and BET techniques. As a result, an anatase structure with the average crystalline size of 8nm was confirmed for the synthesized TiO₂-NPs. Subsequently, entrance of TiO₂-NP_S to plant roots was verified by fluorescence microscopic images. Activity of a number of antioxidant enzymes, as well as, changes in growth parameters and photosynthetic pigment contents as physiological indices were assessed to investigate the effects of TiO₂-NPs on S. polyrrhiza. The increasing concentration of TiO₂-NPs led to the significant decrease in all of the growth parameters and changes in antioxidant enzyme activities. The activity of superoxide dismutase enhanced significantly by the increasing concentration of TiO₂-NPs. Enhancement of superoxide dismutase activity could be explained as promoting antioxidant system to scavenging the reactive oxygen species. In contrast, the activity of peroxidase was notably decreased in the treated plants. Reduced peroxidase activity could be attributed to either direct effect of these particles on the molecular structure of the enzyme or plant defense system damage due to reactive oxygen species.     

Impact of density of coating agent on antibacterial activity of silver nanoparticle impregnated plasma treated activated carbon

To use stabilized nanoparticles(NPs) in water as disinfectants over a very long period, the amount of coating agent(for NP stabilization) needs to be optimized. To this end, silver nanoparticles(Ag-NPs) with two different coating densities of tri-sodium citrate(12.05 and46.17 molecules/nm~2, respectively), yet of very similar particle size(29 and 27 nm, respectively)were synthesized. Both sets of citrate capped NPs were then separately impregnated on plasma treated activated carbon(AC), with similar Ag loading of 0.8 and 0.82 wt.%, respectively. On passing contaminated water(containing 10~4 CFU Escherichia coli/m L of water) through a continuous flow-column packed with Ag/AC, zero cell concentration was achieved in 22 and 39 min, with Ag-NPs(impregnated on AC, named as Ag/AC) having lower and higher coating density, respectively. Therefore, even on ensuring similar Ag-NP size and loading, there is a significant difference in antibacterial performance based on citrate coating density in Ag/AC.This is observed in lower coating density case, due to both:(i) higher Ag~+ ion release from Ag-NP and(ii) stronger binding of individual Ag-NPs on AC. The latter ensures that, Ag-NP does not detach from the AC surface for a long duration. TGA-DSC shows that Ag-NPs with a low coating density bind to AC with 4.55 times higher adsorption energy, compared to Ag/AC with a high coating density, implying stronger binding. Therefore, coating density is an important parameter for achieving higher antibacterial efficacy, translating into a faster decontamination rate in experiments, over a long period of flow-column operation.     

纳米银对胶州湾西北部海区及河口区沉积物反硝化能力和功能基因丰度的影响

在胶州湾西北部海区和大沽河河口区选择S站和E站2个研究站位,现场采样带回实验室进行模拟培养,研究纳米银对沉积物反硝化能力、反硝化酶活性及功能基因丰度的影响.将不同剂量(0、135、1 350 mg·L~(-1))的纳米银添加至由表层沉积物和原位底层海水组成的培养体系中培养6 d,测定其在不同时间内NO_3~-和NO_2~-含量、NO_3~-还原酶和NO_2~-还原酶活性、反硝化功能基因narG和nirS相对丰度的变化,探讨纳米银对不同区域沉积物反硝化过程的影响和可能的作用途径.结果表明,纳米银胁迫对2个站位沉积物NO_3~-和NO_2~-的还原能力、NO_3~-和NO_2~-还原酶活性及narG和nirS的基因丰度均具有明显的抑制效应,纳米银浓度越高,抑制程度越强,并会导致NO_2~-累积量的增加;纳米银对NO_2~-还原酶的抑制程度明显大于NO_3~-还原酶,对功能基因nirS的抑制程度明显大于narG;纳米银胁迫对NO_3~-还原过程的影响主要通过对功能基因的抑制作用,而对NO_2~-还原过程的影响主要是通过对还原酶活性的抑制作用;纳米银对胶州湾西北部海域反硝化能力、NO_3~-还原酶和基因丰度的抑制程度大于大沽河河口区.     

超声辅助纳米铁降解酸性红G的实验研究

通过硼氢化纳还原法制备了铁纳米颗粒,并用十二烷基硫酸钠对其进行保护。所得铁纳米颗粒大小在13nm左右,体心立方相。对比了在机械搅拌和超声辅助条件下纳米铁对酸性红G的降解率,超声条件下纳米铁和微米铁对酸性红G的降解率,以及纳米铁投加量、pH值对酸性红G降解率的影响。结果表明,超声辅助下,pH=6～7时,4min内纳米铁对酸性红G有较高的降解率。机理分析表明超声辅助条件下纳米铁对酸性红G的降解主要是超声分散下纳米铁的还原作用得到提高以及纳米铁氧化产物的絮凝作用。     

Effects of silica nanoparticles on growth and photosynthetic pigment contents of Scenedesmus obliquus

To assess the aquatic ecosystem safety for silica (SiO2) nanoparticles (NPs), the growth inhibition and photosynthetic pigment contents of Scenedesmus obliquus in logarithm growth phase exposed to SiO2 NPs and SiO2 bulk particles (BPs) suspensions were measured. SiO2 NPs with 10-20 nm diameters were found to be toxic. The 20% effective concentration (EC20) values for 72 and 96 hr were 388.1 and 216.5 mg/L, respectively. The contents of chlorophyll decreased significantly under moderate and high concentratio...