Site-specific Deposition of Colloidal Pd Nanoparticles on Self-assembled Microtubules from Biolipid

Lipid microtubules with wound ribbon features were fabricated by self-assembling method, and the deposition patterns of colloidal Pd particles on tubular template were investigated. The result indicates that colloidal Pd nanoparticles are preferentially decorated on the helical markings in the interior and on the exterior of preformed tubule and to the edge of loosely helical ribbons to obtain helical deposition features. The multi-bilayer microstructure of tubules can be marked by fine Pd nanoparticles deposited at the edge of helical ribbon. There are the site-specific interactions between lipid tubular template and colloidal Pd particles at the helical edge. A new route was illustrated that colloidal Pd particles firstly attach at the edge of thin flat membranes, and then thin membranes roll up and reassemble into tubule together with particles to form helical deposition patterns. The site-specific deposition of Pd is unbeneficial to obtain the homogeneous metal film on tubules, but it can be utilized to reveal the different chemical nature of lipid molecular assembly.     

分子自组装脂类微管的螺旋带特征分析

利用联乙炔基甘油磷脂酰胆碱分子的自组装特性,制备得到脂类微管结构,并在大量观察基础上,对脂类微管的螺旋带特征进行分析归纳．观察表明脂类微管是由螺旋带紧密缠绕形成的稳定结构,具有明显的螺旋缠绕特征;同时体系中存在少量不同形态的松驰螺旋带．体系中存在有单层脂膜包埋的螺旋带,这是一种新的结构形态．螺旋带边缘有明显的错位和分层现象,端部具有不同于其它区域的松驰现象．脂类微管的这些特征对其表面纳米颗粒的沉积产生很大的影响,金属钯和镍纳米颗粒在螺旋带边缘的分层沉积可清楚地显示脂类微管螺旋带的错位和分层特征．金属钯的分层沉积特征可尝试用于标志自组装膜的脂类双层数;同时,自组装脂类螺旋带的研究可用于揭示脂类分子自组装的本质,并在生物矿化和生物膜力学研究方面有重要意义．     

Fabrication of Ni-decorated helical ribbon composite microstructure from self-assembled lipid tubule by electroless metallization

Molecular self-assembly is a powerful approach for preparing new supermolecular architectures such as nanofibers and nanotubes[1]. Lipid molecules, due to their amphiphilic nature, can self-assemble to form a variety of microstructures, such as spherical liposome, tubules and helical ribbons[2]. Many lipid molecules can self-organize into the helical ribbon structures[3,4], for example, helical ribbons were self-assembled in a variety of multicomponent enantiomerically pure sys- tems that cont…     

Two-dimensional ordered arrays of aligned lipid tubules on substrates with microfluidic networks

Microfluidic networks is a powerful tool for aligning one-dimensional materials over a large area on solid substrates. Here we show that lipid nano- and microtubules can be assembled into two-dimensional (2-D) parallel arrays with controlled separations by combining fluidic alignment with dewetting, which occurs within microchannels. We also demonstrate that lipid tubules can be bent into a well-defined shape at the entrance of the channels by the capillary force. Atomic force microscopy is used to study the structure and stability of the aligned lipid tubules on substrates. The deposition experiments with silica colloidal particles show that the 2-D parallel-aligned tubules can be used as a template to synthesize silica films with controlled morphologies and patterns on substrates in a single-step process.     

Simultaneous deposition of Ni nanoparticles and wires on a tubular halloysite template: A novel metallized ceramic microstructure

Tubular halloysite can be used as a template to fabricate a novel metallized ceramic microstructure through electroless plating. Reduction of Pd ions by methanol is conducted to initiate Ni plating. There is a simultaneous deposition of Ni nanoparticles on the outer surface and discontinuous wires in the lumen site of the halloysite template obtained. The different deposition could be caused by the different composition distribution of ferric oxide impurity in the wall due to the isomorphic substitution during the formation of halloysite template. Its magnetic property is mainly attributed to the Ni nanoparticles, not the wires. The metallized ceramic microstructure has the potential to be utilized as a novel magnetic material.     

Shedding light on helical microtubules: real-time observations of microtubule self-assembly by light microscopy

Helical tubules are a fascinating and an intriguing class of self-assemblies. They occur frequently in biology and are believed to be intermediates in formation of gallstones. The pathway by which amphiphiles transform from an initial state of vesicles or micelles into such tubules has puzzled soft matter physicists, and it has raised important questions about the interplay between molecular chirality and self-assembly. Here, for the first time, we demonstrate direct, real-time observations by light microscopy of the pathway to helical microtubules from an initial solution of nanoscale vesicles. The tubules are formed in aqueous mixtures of the single-tailed diacetylenic surfactant, 10,12-pentacosadiynoic acid (PCDA), and a short-chain alcohol. The stepwise process involves nucleation of thin helical microribbons from the vesicle solution. These ribbons then thicken, rearrange, and fold into closed tubules. Subsequently, most tubules further rearrange into plate-like structures, and once again, we are able to visualize this process in real time. A notable aspect of the above system is that the precursors are achiral; yet, the tubules are formed from helical ribbons. Our study provides new insights into tubule formation that will be valuable in clarifying and refining theoretical models for these fascinating structures.     

Spatial organization and patterning of palladium nanoparticles on a self-assembled helical ribbon lipid

A cholesterol derivative forms self-assembled helical ribbons in organic solvent, and treatment of this helical ribbon lipid as a template with Pd(Ac)2 provides helically-patterned arrays of palladium nanoparticles followed by reduction.     

Phospholipid tubelets

A novel electron microscopy specimen protocol shows that the presumed phospholipid bilayer membrane ribbons that wind helically to form the cylinders known as "tubules" are actually flattened tubes. These flattened tubes are alternatively found with a helical twist about the tube's long axis or occasionally flat with no winding or twist. Flat, cylindrically wound and axially twisted segments are routinely found along a single tube's length, and at the helically wound and axially twisted segment junctions, the chiral sense of the structure often, but not always, changes chiral sense.     

Amphiphilic Nanoparticles Control the Growth and Stability of Lipid Bilayers with Open Edges

Molecular amphiphiles self‐assemble in polar media to form ordered structures such as micelles and vesicles essential to a broad range of industrial and biological processes. Some of these architectures such as bilayer sheets, helical ribbons, and hollow tubules are potentially useful but inherently unstable owing to the presence of open edges that expose the hydrophobic bilayer core. Here, we describe a strategy to stabilize open bilayer structures using amphiphilic nanoparticle surfactants that present mixtures of hydrophilic and hydrophobic ligands on their surface. We observe that these particles bind selectively to the open edge of bilayer membranes to stabilize otherwise transient amphiphile assemblies. We show how such particles can precisely control the size of lipid tubules, how they can inhibit the formation of undesirable assemblies such as gallstone precursors, and how they can stabilize free‐floating lipid microdiscs.     

甘氨酸为络合剂是钯和葡萄糖氧化酶的电化学共沉积研究

甘氨酸和Ｐｄ（ＮＨ３）２Ｃｌ３组成镀液,用于钯和葡萄糖氧化酶（ＧＯＤ）的电化学共沉积以制备金属化酶电极、ＵＶ／Ｖ光谱实验表明甘氨酸能与Ｐｄ＾２＋离子发生络合作用,并使镀液在一定ｐＨ范围内具有较稳定的化学组成。伏安法实验证实甘氨酸的存在降低了Ｐｄ的沉积电位,有利于防止钯氢化合物的形成,讨论了钯和ＧＯＤ电化学共沉积的合适条件。     

Controlled morphology and photoreduction characteristics of polyoxometalate(POM)/lipid complexes and the effect of hydrogen bonding at molecular interfaces

Supramolecular complexes consisting of anionic polyoxometalate (POM) and chiral, cationic lipids are newly developed. They give nanofibers, helical ribbons, and nanotapes in organic media depending on the chemical structure of lipid molecules. Lipid ammonium groups exert significant influence on their photoreduction characteristics.     

甘氨酸为络合剂时钯和葡萄糖氧化酶的电化学共沉积研究

甘氨酸和Pd(NH3 ) 2 Cl2 组成镀液 ,用于钯和葡萄糖氧化酶 (GOD)的电化学共沉积以制备金属化酶电极、UV/V光谱实验表明甘氨酸能与Pd2 + 离子发生络合作用 ,并使镀液在一定 pH范围内具有较稳定的化学组成 .伏安法实验证实甘氨酸的存在降低了Pd的沉积电位 ,有利于防止钯氢化合物的形成 .讨论了钯和GOD电化学共沉积的合适条件 .     

Hierarchical structured Ni nanoring and hollow sphere arrays by morphology inheritance based on ordered through-pore template and electrodeposition

Fabrication of micro/nano-hierarchical Ni ordered nanostructured arrays is demonstrated by electrochemical deposition on the ordered alumina through-pore template induced by solution-dipping the colloidal monolayer. The morphology of the Ni nanostructured arrays exhibits a ringlike or hollow spherical structure depending on the template geometry and appropriate deposition parameters. The skeletons of the arrays are of floc- or flakelet-like fine structure on the nanoscale. The formation of such morphologies is attributed to the preferential growth along the inner wall of the alumina pores, while the nanoflakelet fine structure originates from a morphology inheritance process or the transitional product Ni(OH)2 which leads to the final nanostructured Ni crystals. This morphology inherence could be useful in the field of nanofabrication. Such micro/nano-hierarchically structured arrays show good magnetic properties and will find applications in the fields of catalysis, magnetics, optoelectrics, surface-enhanced Raman scattering (SERS), and new nanodevices.     

Open-framework Borophosphate:(NH4)_(0.5)Fe~II_(0.5)Fe~III_(0.5)(H_2O)_2BP_2O_8·0.5H_2O

We are investigating the synthesis and properties of a new class of open framework borophosphate solids with the goal of being able to use in optical devices and magnetic materials. Only a few open-framework ferric borophosphate compounds with a chiral tetraheda-tetraheda helices, KFe(H2O)2BP2O8)H2O(1), Fe(H2O)2BP2O8H2O(2), (NH4)0.4-FeII0.55FeIII0.5(H2O)[BP2O8]0.6H2O(3) have been reported by Boy et al.1, Ylmaze et al.2 and Huang and Schfer et al.3. However, Huang and Schfer et…     

Counterion, temperature, and time modulation of nanometric chiral ribbons from gemini-tartrate amphiphiles

Amphiphile supramolecular assemblies result from the cooperative effects of multiple weak interactions between a large number of subcomponents. As a result, prediction of and control over the morphologies of such assemblies remains difficult to achieve. Here, we described the fine-tuning of the shape, size, and morphology transitions of twisted and helical membranes formed by non-chiral dicationic n-2-n gemini amphiphiles complexed with chiral tartrate anions. We have reported that such systems express the chirality of the tartrate components at a supramolecular level and that the mechanism of the chiral induction by counterions involves specific anion cation recognition and the induction of conformationally labile chirality in the cations. Here, we demonstrate that the morphologies and dimensions of twisted and helical ribbons, as well as tubules, can be controlled and that interconversion between these structures can be induced upon modifying temperature, upon introducing small amounts of additives, or slightly modifying molecular structure. Specifically, electron microscopy, IR spectroscopy, and small-angle X-ray scattering show that (i) varying the hydrophobic chain length or adding gemini having bromide counterions (1%) or the opposite enantiomer (10%) leads to an increase of the diameter of membrane tubules from 33 to 48.5 nm; (ii) further addition (1.5%) of gemini bromide or a slight increase in temperature induces a transition from tubules to twisted ribbons; (iii) the twist pitch of the ribbons can be continuously tuned by varying enantiomeric excess; and (iv) it was also observed that the morphologies of these ribbons much evolve with time. Such unprecedented observations over easy tuning of the chiral supramolecular structures are clearly related to the original feature that the induction of chirality is solely due the counterions, which are much more mobile than the amphiphiles.     

Self-assembling structures of long-chain phenyl glucoside influenced by the introduction of double bonds

Four long-chain phenyl glucoside amphiphiles possessing a saturated or unsaturated long alkyl chain group as the self-assembling unit of a highly organized molecular architecture were synthesized. Their self-assembling properties were investigated by EF-TEM, SEM, CD, FT-IR, and XRD. Compound 2 possessing one double bond in the lipophilic portion showed twisted helical fibers, which formed a bilayered structure with a 3.59 nm period, while compound 3 showed the helical ribbons and left-handed nanotubular structures with 150-200 nm inner diameters and ca. 20 nm of wall. Very interestingly, compound 4 possessing three double bonds showed a nanotubular structure with ca. 70 nm of inner diameter through a helical ribbon, which formed a loose bilayered structure with 4.62 nm. These results indicate that self-assembling properties strongly depend on the number of cis double bonds.     

Modulating artificial membrane morphology: pH-induced chromatic transition and nanostructural transformation of a bolaamphiphilic conjugated polymer from blue helical ribbons to red nanofibers.

Design and characterization of helical ribbon assemblies of a bolaamphiphilic conjugated polymer and their color-coded transformation into nanofibers are described. An L-glutamic acid modified bolaamphiphilic diacetylene lipid was synthesized and self-assembled into right-handed helical ribbons with micron scale length and nano scale thickness under mild conditions. The ribbon structures were further stabilized by polymerizing well-aligned diacetylene units to form bisfunctional polydiacetylenes (PDAs). Transitions from flat sheets to helical ribbons and tubes were observed by transmission electron microscopy. The helical ribbons appear to originate from the rupture of flat sheets along domain edges and the peeling off between stacked lipid layers. These results point to the applicability of chiral packing theory in bolaamphiphilic supramolecular assemblies. Contact mode atomic force microscopy observations revealed that high order existed in the surface packing arrangement. Hexagonal and pseudorectangular packings were observed in flat and twisted regions of the ribbons, respectively, suggesting a correlation between microscopic morphologies and nanoscopic packing arrangements. The tricarboxylate functionalities of the bolaamphiphilic lipid provide a handle for the manipulation of the bisfunctional PDAs' morphology. Increasing solution pH caused the fraying of helical ribbons into nanofibers accompanied by a sharp blue-to-red chromatic transition. A dramatic change in circular dichroism spectra was observed during this process, suggesting the loss of chirality in packing. A model is proposed to account for the pH-induced morphological change and chromatic transition. The color-coded transition between two distinct microstructures would be useful in the design of sensors and other "smart" nanomaterials requiring defined molecular templates.     

Palladium Nanotubes Formed by Lipid Tubule Templating and Their Application in Ethanol Electrocatalysis

Palladium nanotubes were fabricated by using lipid tubules as templates for the first time in a controlled manner. The positively charged lipid 1,2‐dioleoyl‐3‐trimethylammoniumpropane (DOTAP) was doped into lipid tubules to adsorb PdCl₄^2? on the tubule surfaces for further reduction. The lipid tubule formation was optimized by studying the growing dynamics and ethanol/water ratio. The DOTAP‐doped tubules showed pH stability from 0 to 14, which makes them ideal templates for metal plating. The Pd nanotubes are open‐ended with a tunable wall thickness. They exhibited good electrocatalytic performance in ethanol. Their electrochemically active surface areas were 6.5, 10.6, and 83.2 m² g^?1 for Pd nanotubes with 77, 101, and 150 nm wall thickness, respectively. These Pd nanotubes have great potential in fuel cells. The method demonstrated also opens up a way to synthesize hollow metal nanotubes.     

Electroless metallization onto pulsed plasma deposited poly(4-vinylpyridine) surfaces

Pulsed plasma-chemical deposition of poly(4-vinylpyridine) is found to be a highly effective way of functionalizing solid surfaces with pyridine ring centers. These surfaces can be metallized via complexation to Pd2+ ions from solution, followed by autocatalytic electroless deposition of either copper or nickel films.     

Pd掺杂的Ni催化剂表面CH4解离吸附的理论研究

使用密度泛函理论研究了Pd掺杂的Ni(111),Ni(100)和Ni(211)表面最稳定的结构,同时考察了干净的和Pd掺杂的Ni表面催化CH₄解离反应的活性.结果表明,由Pd原子取代最外层Ni原子而形成的表面Pd掺杂的Ni表面在热力学上最为稳定,亚表面Pd掺杂的Ni表面在热力学上都不稳定; 而对于表面Pd吸附的Ni表面,只有Pd/Ni(211)表面是稳定的.表面掺杂的Pd/Ni表面上CH₄解离中间体(CH₄,CH₃,CH,C,H)吸附能的计算结果表明,Pd的掺杂在不同程度上减弱了除CH₄之外各解离中间体的吸附能.另外,CH₄和CH均优先在Ni(211)和Pd/Ni(211)台阶面上解离,其次是在比较开阔的Ni(100)和Pd/Ni(100)表面上.Pd的掺杂不同程度上提高了CH₄和CH解离的能垒,对于活性最高的Ni(211)面,Pd的掺杂使得CH脱氢的能垒较CH₄脱氢的高,改变了其速率控制步骤,从而抑制了积碳的生成.