溶剂效应制备核壳纳米银及荧光素金属增强荧光

直链或支链高分子可用来制备和稳定纳米材料,具有丰富羟基的高分子通过分子间和分子内氢键作用形成分子级别的"胶囊",用作生长纳米颗粒的模板[1].可溶性淀粉主要是直链淀粉,是由多个葡萄糖单元构成的含有丰富羟基的高分子,同时具有疏水性和亲水性[2].     

糖响应性生物基聚电解质胶囊的制备与性能研究

选用功能单体3-氨基苯硼酸(APBA)和乳糖酸(LA)分别对聚谷氨酸(γ-PGA)和壳寡糖(CS)接枝改性后制备聚谷氨酸-g-氨基苯硼酸(γ-PGA-g-APBA)及糖基化壳寡糖(GC); 以二氧化硅微球为模板, 通过γ-PGA-g-APBA和GC间的静电相互作用进行层层自组装, 再经脱除模板则可获得形貌规整可控的生物基胶囊. 通过红外光谱(FTIR)和核磁共振(¹H NMR)对聚合物化学结构、接枝率进行表征; 利用Zeta电位监测聚合物电解质层层自组装的进程, 并通过透射电镜(TEM)和扫描电镜(SEM)观测胶囊的形貌. 同时考察了胶囊在不同温度、盐浓度、pH值及糖浓度下的刺激响应, 研究结果表明胶囊在一定的温度、盐浓度、pH值下能稳定存在; 低浓度葡萄糖刺激时胶囊形貌完整, 而高浓度葡萄糖刺激时, 胶囊溶胀直至结构与形貌破坏, 说明功能单体LA和APBA的引入可赋予胶囊具有葡萄糖响应性. 这种具有良好稳定性和葡萄糖响应性的生物基胶囊有望应用于糖尿病的诊断和治疗.     

氧化石墨烯/聚电解质层层自组装制备单价离子选择性膜

采用层层自组装法在改性聚丙烯腈(PAN)膜表面交替沉积聚乙烯亚胺(PEI)和聚丙烯酸-氧化石墨烯(PAA-GO)混合液,制得了单价离子选择性复合膜。X射线衍射(XRD)测试结果表明成功合成了氧化石墨烯(GO)并在复合膜中均匀分散。扫描电镜(SEM)观察结果证实了多层聚电解质PEI/PAA-GO成功地组装在基膜上,并用紫外-可见(UV-Vis)光谱进一步证实了组装过程的均匀性和连续性。接触角和性能测试表明加入GO后,复合膜的亲水性和单价阳离子的选择性明显增大。这种高通量、高选择性的防污复合膜在分离和水的软化方面有很好的应用前景。     

层层组装构筑聚电解质/碳纳米管导电黏附膜

首先将聚烯丙基胺盐酸盐与碳纳米管制成复合物(PAH-CNT), 再通过层层组装技术构筑了聚丙烯酸和碳纳米管混合物(PAA-CNT)与PAH-CNT多层复合膜(PAH-CNT/PAA-CNT). PAH-CNT/PAA-CNT多层复合膜同时具有导电和黏附性能. 在玻璃和ITO基片上沉积的PAH-CNT/PAA-CNT多层复合膜的最大拉伸剪切强度接近7 MPa, 即1 cm²的黏附膜可以承受约70 kg的重物. 碳纳米管的引入使PAH-CNT/PAA-CNT多层复合膜具有更好的导电性.     

层层自组装结合后处理制备耐磨超亲水增透纳米粒子涂层

通过层层自组装方法制备的二氧化硅纳米粒子涂层由于具有增透、超亲水的良好性质, 引起了广泛关注. 然而, 这种涂层的耐磨性往往达不到实际应用的要求. 本工作尝试通过后处理来增强涂层耐磨性. 首先采用自制二氧化硅纳米颗粒, 聚二烯丙基二甲基氯化铵(PDDA)和聚苯乙烯磺酸钠(PSS), 通过层层自组装制备了PDDA/SiO₂纳米粒子涂层, 其中(PDDA/SiO₂)₆涂层透过率最高. 随后将(PDDA/SiO₂)₆涂层依次经过124 ℃水热处理1 h和700 ℃快速淬火200 s处理, 得到同时具有超亲水性和增透性的涂层, 其中(PDDA/SiO₂)₆涂层在可见光范围内最大透过率高达99.0%. 实验表明, 这种后处理也极大地提高了涂层的耐磨性.     

聚电解质层层自组装纳滤膜

层层自组装技术能够方便地对膜的微观结构和组成进行调控,已在制备复合型纳滤膜方面取得了迅速的发展。本文综述了近年来用于聚电解质层层自组装纳滤膜的制备方法,种类以及影响因素。介绍了静态层层交替沉积、压力驱动自组装和电场强化自组装等三种制备方法;归纳了均聚型、共聚型和有机/无机杂化型等三类用于层层自组装纳滤膜的聚电解质的特点;讨论了聚电解质的荷电性、电荷密度和电离程度等因素对其自组装膜分离性能的影响。总结了聚电解质自组装纳滤膜在水处理和有机溶剂中物质的分离等方面的应用。同时,对提高聚电解质自组装纳滤膜的组装效率,分离性能和发展方向提出了设想和建议。     

以聚电解质多层膜为纳米反应器制备Au@Pt核壳纳米粒子

以聚二烯丙基二甲基氯化铵和聚苯乙烯磺酸钠为构筑单元,通过静电层层自组装制备了多层膜,利用薄膜中存在的抗衡阴离子,选择AuCl-4和PtCl2-6作为Au和Pt的前驱体,通过连续的阴离子交换/还原,原位制备了Au-Pt双金属纳米粒子。 紫外-可见分光光度法、透射电子显微镜和能量色散X射线能谱数据表明,在聚电解质多层薄膜中成功地制备了具有核壳结构的Au@Pt双金属纳米粒子。 这种纳米粒子在电化学催化、燃料电池方面具有潜在的应用价值。     

Metal-Enhanced Fluorescence of Phycobiliproteins from Heterogeneous Plasmonic Nanostructures

We report here the use of plasmonic metal nanostructures in the form of silver island films (SiFs) to enhance the fluorescence emission of five different phycobiliproteins. Our findings clearly show that the phycobiliproteins display up to a 9-fold increase in fluorescence emission intensity, with a maximum 7-fold decrease in lifetime when they are assembled as a monolayer above SiFs, as compared to a monolayer assembled on the surface of amine-terminated glass slides of the control sample. The study was also repeated with a thin liquid layer of the phycobiliproteins sandwiched between two glass substrates (and a SiFs and a glass substrate) clamped together. Similarly, the results show a maximum 10-fold increase in fluorescence emission intensity coupled with a 2-fold decrease in lifetime of the phycobiliproteins in the SiF-glass setup as compared to the glass control sample, implying that near-field enhancement of phycobiliprotein emission can be attained both with and without chemical linkage of the proteins to the SiFs. Hence, our results clearly show that metal-enhanced fluorescence (MEF) can potentially be employed to increase the sensitivity and detection limit of the plethora of bioassays that employ phycobiliproteins as fluorescence labels, such as in fluoro-immunoassays where the assay can be tethered on the surface of SiFs, and also in flow cytometry where analytes in the liquid phase could potentially flow through channels coated with SiFs without actually being attached to the silver.     

Preparation and Research of Butylene Fipronil Microencapsulation by Layer-by-Layer Polyelectrolyte Self-Assembly

This paper introduced the preparation of butylene fipronil-loaded microcapsules with oppositely charged chitosan and sodium lignosulfonate as shell materials. It summed up the performance, preparation methods of microcapsules and sketched the application status of layer-by-layer self-assembly. The whole progress of the preparation was controlled by measuring the change of the Zeta potential and the morphology of microcapsules was characterized by microscope and SEM. Entrapment efficiency and slow release performance of the microcapsule were determined as measurement index. The results of experiment showed that the surface of the microcapsules was rougher than the butylene fipronil particles. With the increasing layer number of assembly, the entrapment efficiency reduced while the slow release performance increased. After encapsulation, the photodegradation rate of butylene fipronil under the UV decreased obviously. Results showed that the condition of preparation was the best when NaCl with the concentration of 0.5 mol/L and PH of 5.0.     

DAR Assisted Layer-by-Layer Assembly of Aromatic Compounds

A facile DAR (diphenylamine-4-diazonium-formaldehyde resin)assisted layer-by-layer (LbL) assembly of uitrathin organic film of aromatic compounds has been investigated. The muitilayer of pyrene or anthracene was fabricated through simple dipping of the glass slide into the mixed solution of DAR with the target compounds. In this method, DAR acted as an assistant compound to help the assembling of the aromatic compounds. Such a convenient deposition method not only reserves the advantages of the traditional LbL technique but also simplifies the technique and extends the effectiveness of LbL technique to small molecules without any charge.     

Directed Assembly of Multi-Walled Nanotubes and Nanoribbons of Amino Acid Amphiphiles Using a Layer-by-Layer Approach

Monodisperse unilamellar nanotubes (NTs) and nanoribbons (NRs) were transformed to multilamellar NRs and NTs in a well-defined fashion. This was done by using a step-wise approach in which self-assembled cationic amino acid amphiphile (AAA) formed the initial NTs or NRs, and added polyanion produced an intermediate coating. Successive addition of cationic AAA formed a covering AAA layer, and by repeating this layer-by-layer (LBL) procedure, multi-walled nanotubes (mwNTs) and nanoribbons were formed. This process was structurally investigated by combining small-angle neutron scattering (SANS) and cryogenic-transmission electron microscopy (cryo-TEM), confirming the multilamellar structure and the precise layer spacing. In this way the controlled formation of multi-walled suprastructures was demonstrated in a simple and reproducible fashion, which allowed to control the charge on the surface of these 1D aggregates. This pathway to 1D colloidal materials is interesting for applications in life science and creating well-defined building blocks in nanotechnology.     

Self‐Assembly of Gold Nanoparticles/Electroactive Polyelectrolyte Multilayer Films for Tunable Electrocatalysis

This study described fabrication, characterization, and application of multilayer films based on layer‐by‐layer assembly of ferrocene poly(ethylenimine) and gold nanoparticles. Assembly process of the multilayer film was investigated by atomic force microscopy, UV‐visible absorption spectroscopy and electrochemical impedance spectroscopy. The multilayer films exhibited a pair of well‐defined redox peaks as revealed by cyclic voltammetry, as well as bifunctional and fine‐tunable electrocatalysis for oxidation of ascorbic acid and reduction of oxygen. Both the outer layer and layer number had effect on the electrocatalytic response. Electrocatalytic activity of the films could be controlled with assemblies at the nanoscale level by simply adjusting deposition cycles or amount of component in the films.     

Ag@SiO2纳米复合物金属增强荧光释放法检测葡萄糖

制备了Ag@SiO2纳米复合物,罗丹明B通过物理掺杂结合在SiO2壳层。由于金属增强荧光效应,罗 丹明B的荧光增强到4.7倍。Ag核易被H2O2氧化,Ag核氧化后产生荧光增强释放效应。基于金属增强荧光 释放建立了一种新型葡萄糖检测方法,采用交联法在罗丹明B掺杂的Ag@SO2纳米复合物的SiO2壳层固定 葡萄糖氧化酶。检测浓度范围为0.2～6.8 mmol/L,检测限可达0.06 mmol/L。由于H2O2氧化Ag核反应迅 速,检测体系对葡萄糖的响应快速。     

Layer‐by‐Layer Assembly of Polyelectrolyte and Nanoparticles,Monitored by Capillary Electrophoresis

Layer‐by‐layer (LBL) assembly is a versatile nanofabrication technique, and investigation of its kinetics is essential for understanding the assembly mechanism and optimizing the assembly procedure. In this work, the LBL assembly of polyelectrolyte and nanoparticles were monitored in situ by capillary electrophoresis (CE) for the first time. The assembly of poly(diallyldimethylammonium chloride) (PDDA), and gold nanoparticles (AuNPs) on capillary walls causes surface‐charge neutralization and resaturation, and thus yields synchronous changes in the electroosmotic flow (EOF). The EOF data show that formation of multilayers follows first‐order adsorption kinetics. On the basis of the fit results, influencing factors, including number of layers, concentration of materials, flow rate, and size of AuNPs, were investigated. The stability and robustness of the assembled coatings were also characterized by CE. It was found that degradation of PDDA layers follows first‐order chemical kinetics, while desorption of AuNPs takes place in a disorderly manner. The substrate strongly affects assembly of the underlying layer, while this effect is rapidly screened with increasing number of layers. Furthermore, we demonstrate that the EOF measuring step does not disturb LBL assembly, and the proposed method is reliable and rugged. This work not only studies in detail the LBL adsorption/desorption process of polyelectrolyte and nanoparticles, but also offers an alternative tool for monitoring multilayer buildup. It may also reveal the potential of CE in fields other than analytical separation.     

Using the Intrinsic Fluorescence of DNA to Characterize Aptamer Binding

The reliable, readily accessible and label-free measurement of aptamer binding remains a challenge in the field. Recent reports have shown large changes in the intrinsic fluorescence of DNA upon the formation of G-quadruplex and i-motif structures. In this work, we examined whether DNA intrinsic fluorescence can be used for studying aptamer binding. First, DNA hybridization resulted in a drop in the fluorescence, which was observed for A30/T30 and a 24-mer random DNA sequence. Next, a series of DNA aptamers were studied. Cortisol and Hg²⁺ induced fluorescence increases for their respective aptamers. For the cortisol aptamer, the length of the terminal stem needs to be short to produce a fluorescence change. However, caffeine and adenosine failed to produce a fluorescence change, regardless of the stem length. Overall, using the intrinsic fluorescence of DNA may be a reliable and accessible method to study a limited number of aptamers that can produce fluorescence changes.     

Ligand‐Induced Evolution of Intrinsic Fluorescence and Catalytic Activity from Cobalt Ferrite Nanoparticles

To develop CoFe₂O₄ as magneto‐fluorescent nanoparticles (NPs) for biomedical applications, it would be advantageous to identify any intrinsic fluorescence of this important magnetic material by simply adjusting the surface chemistry of the NPs themselves. Herein, we demonstrate that intrinsic multicolor fluorescence, covering the whole visible region, can be induced by facile functionalization of CoFe₂O₄ NPs with Na‐tartrate. Moreover, the functionalized CoFe₂O₄ NPs also show unprecedented catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, pioneering the potential application of these NPs in therapeutics and wastewater treatment. Detailed investigation through various spectroscopic tools unveils the story behind the emergence of this unique optical property of CoFe₂O₄ NPs upon functionalization with tartrate ligands. We believe our developed multifunctional CoFe₂O₄ NPs hold great promise for advanced biomedical and technological applications.     

Ion-selective Membranes Prepared Upon Layer-by-Layer Assembly of Azamacrocycles and Polyelectrolytes

Summary : Recent studies on ion transport across multilayered membranes of azamacrocycles and polyelectrolytes are reviewed. Membranes were built up on porous PAN/PET supports using electrostatic layer-by-layer assembly. Two types of separation membranes were prepared, type I consisting of protonated hexaazacyclooctadecane and polyvinylsulfate, and type II of hexaazacyclo-octadecane hexaacetic acid and protonated polyvinylamine. Ion transport was studied under dialysis, nanofiltration and reverse osmosis conditions. Type I membranes were suitable for efficient separation of mono- and divalent anions, whereas type II membranes were suited for separation of mono- from di- and trivalent cations.     

Preparation of Gold Nanoparticles Protected with Polyelectrolyte

Gold nanoparticles were synthesized through the reduction of tetrachlorauric acid (HAuCh) by NaBH4, with polyethyleneimine(PEI) as stabilizer. The nanoparticles were characterized by UV-vis spectroscopy and atomic force microscopy(AFM).     

Theranostic Layer-by-Layer Nanoparticles for Simultaneous Tumor Detection and Gene Silencing

Layer-by-layer nanoparticles (NPs) are modular drug delivery vehicles that incorporate multiple functional materials through sequential deposition of polyelectrolytes onto charged nanoparticle cores. Herein, we combined the multicomponent features and tumor targeting capabilities of layer-by-layer assembly with functional biosensing peptides to create a new class of nanotheranostics. These NPs encapsulate a high weight percentage of siRNA while also carrying a synthetic biosensing peptide on the surface that is cleaved into a urinary reporter upon exposure to specific proteases overexpressed in the tumor microenvironment. Importantly, this biosensor reports back on a molecular signature characteristic to metastatic tumors and associated with poor prognosis, MMP9 protease overexpression. This nanotheranostic mediates noninvasive urinary-based diagnostics in mouse models of three different cancers with simultaneous gene silencing in flank and metastatic mouse models of ovarian cancer.     

Silver-Gold Nanocomposite Substrates for Metal-Enhanced Fluorescence: Ensemble and Single-Molecule Spectroscopic Studies

In recent years, there has been a growing interest in the studies involving the interactions of fluorophores with plasmonic nanostructures or nanoparticles. These interactions lead to several favorable effects such as increase in the fluorescence intensities, increased photostabilities, and reduced excited-state lifetimes that can be exploited to improve the capabilities of present fluorescence methodologies. In this regard, we report the use of newly developed silver-gold nanocomposite (Ag-Au-NC) structures as substrates for metal-enhanced fluorescence (MEF). The Ag-Au-NC substrates have been prepared by a one-step galvanic replacement reaction from thin silver films coated on glass slides. This approach is simple and suitable for the fabrication of MEF substrates with large area. We have observed about 15-fold enhancement in the fluorescence intensity of ATTO655 from ensemble fluorescence measurements using these substrates. The fluorescence enhancement on the Ag-Au-NC substrates is also accompanied by a reduction in the fluorescence lifetime of ATTO655, which is consistent with the fluorophore-plasmon coupling mechanism. Single-molecule fluorescence measurements have been performed to gain more insight into the metal-fluorophore interactions and to unravel the heterogeneity in the interaction of individual fluorophores with the fabricated substrates. The single-molecule studies are in good agreement with the ensemble measurements and show maximum enhancements of ~50-fold for molecules located in proximity to the "hotspots" on the substrates. In essence, the Ag-Au-NC substrates have a very good potential for various MEF applications.