生物源纳米二氧化硅对脲醛树脂降醛作用的研究

利用稻秸提取的生物源纳米二氧化硅,探讨了生物源纳米二氧化硅的添加量(0、0.5%、1.0%、1.5%和2.0%)和改性温度(50℃和70℃)对脲醛树脂胶黏剂同化特性、甲醛释放量和胶合强度的影响。结果表明,随着添加量从0增加到2.0%,甲醛释放量降低,胶合强度总体增加。改性温度为50℃时,生物源纳米二氧化硅在脲醛树脂中能够均匀分散,起到偶联剂的作用,胶的同化时间逐渐延长,甲醛释放量降低,胶合强度增加。

升温速率对活体硅藻壳提纯的影响

选用一种舟形藻作为实验材料,研究了不同升温速率下硅藻壳的形态和成分变化。首先,对从该种硅藻得到的细胞壳进行酸洗处理,以去除金属离子和其它无机盐;之后,分别以1,3,5和7℃/min的速率将硅藻壳升温至600℃,并保温2h。然后,使用扫描电子显微镜、能量色散X射线分析和傅里叶变换红外分析3种手段对不同阶段和不同处理条件下的硅藻壳进行分析表征。实验显示:生物SiO2的含量随着升温速率的降低而升高,以1℃/min升温到600℃并保温2h的硅藻壳的SiO2含量最高,其质量分数可达到90%,并且该硅藻壳能保持完整的原始形态。结果表明:由于硅藻的生物SiO2结构具有较好的隔热性,热传导速度慢,故较快的升温速率很难使生物有机质充分分解,而过高的温度或保温时间又会对硅藻壳形态造成新的威胁。所以,较为缓慢的升温速率有益于有机质的充分去除和保证硅藻壳外观的完整性。

硅藻细胞壁硅化过程中有机质-矿物的相互作用

生物成因二氧化硅,更为确切地说是无定形水合二氧化硅,是第二大类生物成因矿物,在丰度和分布上仅次于生物成因碳酸盐矿物。硅藻是海洋生物成因二氧化硅的主要贡献者,其复杂和多级结构的硅质细胞壁已经引起多学科研究的兴趣。生物化学研究表明,硅藻生物成因的二氧化硅是一种复合材料,除了无机的非晶质二氧化硅以外,还含有生物矿化过程中普遍存在的有机组分,例如多糖、蛋白质和长链聚胺等。对这些组分的功能研究显示,它们在诱导二氧化硅沉淀以及形成物种特异性纳米图案方面起着至关重要的作用。本文简要介绍硅藻和硅藻细胞壁组成和结构,同时着重介绍了硅化过程中的有机和生物分子的生物功能、提取于生物二氧化硅中矿化相关的有机分子参与的体外(invitro)实验以及模型有机添加剂存在下的仿生矿化等研究的最新进展。对硅藻调控的生物成因二氧化硅形成机制的深入了解,将可能从机理上把全球硅循环和碳循环联系起来;而对硅藻体内成分的鉴定和分类将有助于我们深入理解石油的物质来源和硅藻的进化历程。

偶联剂处理对阻燃稻秸/HDPE复合材料性能的影响

以稻秸为反应相,采用原位聚合反应在稻秸表面构筑聚磷酸铵(APP),再与高密度聚乙烯(HDPE)复合制成APP/稻秸/HDPE复合材料。通过添加偶联剂(异氰酸酯、钛酸酯偶联剂、γ-氨丙基三乙氧基硅烷)探讨偶联剂对APP/稻秸/HDPE复合材料性能的影响。极限氧指数测试表明,偶联剂有利于提高稻秸/HDPE复合材料的阻燃性能,当钛酸酯偶联剂的质量分数为3.0%时,复合材料的极限氧指数最大,为23.68%。力学性能测试表明,偶联剂改性对APP/稻秸/HDPE复合材料的拉伸强度和弯曲强度影响不大,但能显著增加复合材料的断裂伸长率,特别是钛酸酯偶联剂使APP/稻秸/HDPE复合材料的断裂伸长率和冲击强度得到改善。SEM分析显示,偶联剂的加入改善了APP、稻秸、HDPE之间的相容性,当偶联剂为钛酸酯偶联剂时,APP/稻秸/HDPE复合材料界面相容性最佳。

Fabrication of a solid superacid with temperature-regulated silica-isolated biochar nanosheets

This paper reports a new strategy for the structural reconstruction of biomass carbon sulfonic acid(BCSA)to its solid superacid counterpart.In this approach,a cheap layered biomass carbon(BC)source is chemically exfoliated by cetyltrimethyl ammonium bromide and then converted to silica-isolated carbon nanosheets(CNSs)by a series of conversion steps.The state of the silica-isolated CNSs and the stacking density of their nanoparticles are regulated by the dehydration temperature.Only the highly isolated and non-crosslinked CNSs with loose particle stacking structures obtained upon dehydration at 250℃ can be turned into superacid sites(with stronger acidity than that of 100%H2 SO4)after sulfonation.This is accompanied by the creation of abundant hierarchical slit pores with high external surface area,mainly driven by the strong hydrogen bonding interactions between the introduced sulfonic acid groups.In typical acid-catalyzed esterification,etherification,and hydrolysis reactions,the newly formed superacid exhibits superior catalytic activity and stability compared to those of common BCSA and commercial Amberlyst-15 catalysts,owing to its good structural stability,highly exposed stable superacidic sites,and abundance of mesoporous/macroporous channels with excellent mass transfer rate.This groundbreaking work not only provides a novel strategy for fabricating bio-based solid superacids,but also overcomes the drawbacks of BCSA,i.e.,unsatisfactory structural stability,acidity,and porosity.

Preparation and Characterization of Silica Modified with Calix[4]arene Derivatives

Three new silica gel modified with calix[4]arene derivatives （p-tert-butyl-calix[4]arene （PC4）, calix[4]arene （C4） and calix[4]arene sulfonate （C4S）） have been prepared via modification of activated silica gel with toluene 2,4-di-iso-cyanate （TDI） as linker in tow step. The modified silica were characterized by fourier transform infrared spectroscopy （FT1R）, thermal analysis （TGA） and elemental analysis. The FTIR spectra and TGA analysis verified that the calix[4]arene derivates are covalent attached to the silica. Scanning electron microscope SEM and Brunauer-Emmett-Teller BET analysis have been done to get information about the sample＇s surface shape and area. SEM and BET analysis reveal that the modified silica are in the range of microporous adsorbent.

Preparation and characteristics of biosilica derived from marine diatom biomass of Nitzschia closterium and Thalassiosira

In this study, biosilica of high purity was successfully prepared from marine diatom （Nitzschia closterium and Thalassiosira） biomass using an optimized novel method with acid washing treatment followed by thermal treatment of the biomass. The optimal condition of the method was 2% diluted HCl washing and baking at 600℃. The SiO2 contents of N. closterium biosilica and Thalassiosira biosilica were 92.23% and 91.52%, respectively, which were both higher than that of diatomite biosilica. The SiO2 morphologies of both biosilica are typical amorphous silica. Besides, IV. closterium biosilica possessed micropores and fibers with a surface area of 59.81 m^2/g. And Thalassiosira biosilica possessed a mesoporous hierarchical skeleton with a surface area of 9.91 m^2/g. The results suggest that the biosilica samples obtained in this study present highly porous structures. The prepared porous biosilica material possesses great potential to be used as drug delivery carrier, biosensor, biocatalyst as well as adsorbent in the future.

Biogenic characteristics of Mesozoic cherts in southern Tibet and its significance

The Xialu chert, which contains abundant biological information, were investigated by major element analysis, micro-Raman, SEM and EPMA. The results show that SiO2 content of chert is 84.12%-93.08%, averaging 89.84%. The close packed structures of low degree crystallinity of quartz indicate the hydrothermal origin. SiO2 of modern hot springs exhibit loose silica pellets and nodular, beaded structures. Under polarization microscope, the presence of biological skeleton structures indicate that biological activities are involved in the hydrothermal deposition, which correspond to the geochemical characteristics: w(SiO2)/ w(K2O+Na2O), w(SiO2)/w(Al2O3) and w(SiO2)/w(MgO), with average values of 295.29, 68.88 and 284.45, respectively. SiO2 is enriched in the organism(radiolarian) centers, the degree order of SiO2 within the biologic structures is much higher than that of outside. The impurity minerals albites are formed earlier than the original deposition. Kaolinites, feldspars and mixture of organic materials display lower degree of crystallinities and accumulate as vermicular aggregates.

基于硅藻微纳结构的生物制造

硅藻壳体(细胞壁)具有独特的微纳米结构,是一种新兴的生物功能材料.现有研究多直接利用硅藻壳体原有结构,使硅藻器件功能范围窄、结构规模单一.本文从制造角度介绍硅藻壳体的形体、材质特性与结构,结合最新研究报道论述对壳体进行结构提取与微加工、改质处理、与器件的装配连接、排列定位与组装的方法与技术可行性,目的是拓展壳体的功能,满足更多微器件的设计要求.最后以基于硅藻的生物检测器件和光敏染料太阳能电池为例,展示硅藻微器件应用的潜力,展望基于硅藻的生物制造技术发展.

Laccase biosensor using magnetic multiwalled carbon nanotubes and chitosan/silica hybrid membrane modified magnetic carbon paste electrode

A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10-7 to 0.165×10-3 mol/L. The corresponding detection limit is 3.34×10-8 mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.

High-yield preparation of robust gold nanoshells on silica nanorattles with good biocompatiblity

Although gold nanoshells are widely considered as one of the promising photothermal nanomaterials used for biomedicine, the high cost, low yield and poor stability severely limit their potential application in clinical trials.Herein, robust gold nanoshells on silica nanorattles(GSNs)were easily prepared in a high yield by an improved seedmediated method employing polyvinylpyrrolidone(PVP) as a stabilizing and capping agent. The present method is very simple, effective and reproducible and can well control the growth process of gold nanoshells. The as-prepared GSNs have a narrow size distribution(<10 % in standard deviation). Furthermore, the utilization rate of Au in the solution used for the growth of gold nanoshells increases by 70 %than that in previous method. The resultant GSNs have a good structural stability after placing over 6 months due to the protection of PVP. More importantly, in vivo and in vitro toxic studies indicate that the GSNs have good biocompatibility. We believe that our preparation method will remarkably promote the use of gold nanoshells for biomedicine.

Variability in the composition and export of silica in the Huanghe River Basin

Concentrations of suspended particle material(SPM), dissolved silicate(DSi), biogenic silica(BSi), phytoliths(plant produced siliceous microscopic structures), and other parameters were analyzed to examine the influence of both natural processes and human activities on silica delivery to the estuary of the Huanghe River(Yellow River). Our results indicate that the concentrations of DSi in the river decreased significantly since 1986. Approximately 34% of dissolved silica was trapped in the basin between 1986 and 2010 due to a reduction of soil erosion. Phytoliths comprised 67.2%–96.3% of BSi, with the smoothing bar type being the dominant form. Concentrations of BSi are significantly higher in the Huanghe River compared to other major rivers throughout the world due to its high sediment yield. We also found that the ratios of BSi/(BSi+DSi) and BSi/SPM were approximately 0.5 and 0.003 at Lijin near the river mouth, indicating that BSi carried in suspension by the Huanghe River was an important component of the rivers silica load. Significant amounts of BSi were also composed of phytoliths in Bohai Sea sediments near the Huanghe River estuary with the smoothing bar form again being the most abundant. The relatively high specific fluxes of BSi in the Huanghe River reflect its high turbidity and high erosion rates in the basin. The high sediment load originating on the Loess Plateau is likely responsible for the higher BSi flux, in agreement with a general trend of increasing BSi flux with increasing sediment flux in global river systems. This study demonstrates that BSi transported by rivers can be composed largely of phytoliths originating from the erosion of topsoils. The flux of phytoliths in river's suspended sediment load may therefore represent a significant contribution to the biogeochemical cycle of silica in coastal waters.

Hollow mesoporous Ia3d silica nanospheres with single- unit-cell-thick shell： Spontaneous formation and drug delivery application

Mesoporous silica nanoparticles （MSNs） are promising for drug delivery and other biomedical applications owing to their excellent chemical stability and biocompatibility. For these applications, a hollow morphology with thin shell and open mesopores is preferred for MSNs in order to maximize the loading capacity of drugs. Herein we report a novel and direct synthesis of such an ideal drug delivery system in a dilute and alkaline solution of benzylcetyl- dimethylammonium chloride and diethylene glycol hexadecyl ether. The mixed surfactants can guide the formation of MSNs with cubic Ia3d mesostructure, and at a concentration of sodium hydroxide between 9.8 and 13.5 mM, hollow MSNs with uniform sizes of 90-120 nm and a single-unit-cell-thick shell are formed. A mechanism for the formation of the hollow Ia3d MSNs, designated as MMT-2, is proposed based on in situ small-angle X-ray scattering measurements and other analyses. MMT-2 exhibits much higher loading capacity of ibuprofen and degrades faster in simulated body fluid and phosphate buffered saline than non-hollow MSNs. The degradation of MMT-2 can be significantly retarded by modification with polyethylene glycol. More interestingly, the degradation of MMT-2 involves fragmentation instead of void formation, a phenomenon beneficial for their elimination. The results demonstrate the uniqueness of the hollow Ia3d MSNs and the great potential of the material for drug delivery and biomedical applications.

Bimetal-organic framework-derived carbon nanocubes with 3D hierarchical pores as highly efficient oxygen reduction reaction electrocatalysts for microbial fuel cells

Noble metal-free and highly efficient electrocatalytic materials with hierarchically porous structures continue to be studied for the oxygen reduction reaction(ORR) in microbial fuel cells(MFCs). We report bimetal-organic framework(bi-MOF)-derived nanocubic Swiss cheese-like carbons with a novel three-dimensional hierarchically porous structure(3D Co-N-C) prepared by utilizing cetyltrimethylammonium bromide(CTAB) as a structure-directing agent to control the formation of a nanocubic skeleton, and silica spheres as a template to form a mesoporous structure. The elemental composition and chemical morphology of this material can be tuned through the Zn/Co ratio to optimize its ORR catalytic activity. The optimized 3D Co-N-C displays excellent ORR catalytic performance(half-wave potential as high as 0.754 V vs. reversible hydrogen electrode and diffusion-limiting current density of 5.576 mA cm^(-2)) in 0.01 mol L^(-1) phosphate-buffered saline(PBS electrolyte),showing it can compete with the commercial 20 wt% Pt/C catalysts. The catalytic capability and long-term durability of 3D Co-N-C as an air-filled cathode electrocatalyst in an MFC device are tested, showing that the 3D CoNC-MFC can reach a high power density of 1257 mW m^(-2) and provide a competitive voltage during a periodic feeding operation for 192 h;these values are much higher than those of the Pt/C-MFC.