Fabrication of TiO_2 Thin Film by Electrostatic Self-Assembly Method on Optical Fiber

Anionic surfactant sodium lauryl sulfate(SDS), cationic surfactant palmityl trimethyl ammonium chloride(CTAC) and TiO_2 were used to prepare multilayer films on quartz optic fibers by the electrostatic self-assembly (ESA) method. The whole self-assemble process, the function of surfactant and the effect of TiO_2 slurry′s concentration to the self-assemble were discussed. The isoelectric point of TiO_2 slurry measured by experiment is 6.8. The results show that whatever the concentration of the TiO_2 dispersion, a flat and compact adsorbed monolayer on the optic fiber can be built in a stable dispersion at lower pH. There is a adsorbed equilibrium on the substrate (fiber)/solution interface when enough time of incubation is given. A rough and loosen adsorbed layer is formed on the fiber surface by immersed the substrate in a high pH dispersion (pH>10) because the presence of hydroxyl on particle surface. Film thickness can be controlled by controlling the number of layers in the film.

Self-assembly of reverse micelle nanoreactors by zwitterionic polyoxometalate-based surfactants for high selective production ofβ-hydroxyl peroxides

Surfactants with polyoxometalates(POMs)as polar head groups have shown fascinating self-assembly behaviors and various functional applications.However,self-assembly them into reverse micelles is still challenging owing to the large molecular size and intermolecular strong electrostatic repulsions of POM heads.In this work,a zwitterionic POM-based surfactant was synthesized by covalently grafting two cationic long alkyl tails onto the lacunary site of[PW_(11)O_(39)]^(7-).With decreased electrostatic repulsions and increased hydrophobic effect,the POM-based reverse micelles with an average diameter of 5 nm were obtained.Interestingly,when these reverse micelles were applied for catalyzing the oxidation of styrene,an unprecedentedβ-hydroxyl peroxide compound of 2-hydroxyl-2-phenylethan-1-tert-butylperoxide was produced in high selectivity of 95.2%.In comparison,the cetyltrimethylammonium electrostatically encapsulated POMs mainly generated the epoxides or 1,2-diols.A free radical mechanism was proposed for the oxidation reaction catalyzed by the zwitterionic POM surfactants.

pH调控的两性多肽表面活性剂自组装

综合运用圆二色光谱、透射电镜、原子力显微镜以及zeta电位测定等多种技术手段,研究了两性多肽表面活性剂分子I3CGK—OH的pH响应性自组装行为。I3CGK—OH分子含有多个pH敏感基团,分别是伯氨基、羧基和巯基,随pH变化可以带有不同数量的正电荷或负电荷。所研究的3个pH值2.5、7.0和12.0下I3CGK—OH分子所带净电荷分别为+0.5、0和-1.9。净电荷的不同会影响分子组装过程和分子构象变化。pH值7.0时,分子基本不带电荷,静电斥力非常弱,可以在较低浓度达到组装平衡;分子在组装体中紧密折叠堆积,形成直径较小的初级纤维;同时低静电斥力也导致纤维间强的侧向堆积作用,形成条带状的高级组装结构。而在pH值2.5和12.0,分子净电荷较多,静电斥力增大,分子的平衡组装浓度不同程度地增加;分子在组装体中采取较为伸展的构象,形成直径较大的初级纤维;初级纤维可以单独存在,两根或多根初级纤维也可以通过互相扭结形成高级结构。

Supramolecular vesicles of cationic gemini surfactants modulated by p-sulfonatocalix[4]arene

Supramolecular binary vesicles were constructed by host-guest complex formation between p-sulfonatocalix[4]arene and three cationic gemini surfactants, which were identified by UV-vis, dynamic laser scattering, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and surface tension experiments. The critical aggregation concentration of gemini surfactants decreased pronouncedly by a factor of ca. 1000 owing to the complexation of p-sulfonato-calix[4]arene.

Phase Behaviors of Multi-tailed B_(2)AB_(2)-Type Regio-isomeric Giant Surfactants at the Columnar-Spherical Boundary

We report herein the precision synthesis and phase behaviors of multi-tailed B_(2)AB_(2)-type regio-isomeric giant surfactants consisting of a hydrophilic polyhedral oligomeric silsesquioxane(POSS)head tethered with four hydrophobic polystyrene(PS)tails.The synthesis was accomplished through two sequential"click"reactions to give a series of regio-isomeric giant surfactants S2DS2(where S is short for PS tails and D for hydroxyl-functionalized POSS)in para-,meta-,and ortho-configurations.Their phase structures and phase be-haviors at the columnar-spherical boundary were investigated with a single PS tail molecular weight of 1.4 kDa.Specifically,the para-and meta-isomers show hexagonally packed cylinders phases with slightly different order-disorder transition temperatures(~120℃ and~130℃)and the ortho-isomer exhibits an order-order transition from a kinetically favored,metastable dodecagonal quasi-crystal phase to a thermodynamically stable sigma phase at~120℃,as well as a further transition into the disordered state at~140℃.The phase diagram was constructed and their differences were rationalized based on the calculated interfacial area per molecule.This work demonstrates that tiny structural disparity could not only lead to unconventional phase formation in single-component macro-molecules,but also render dynamic and rich phase behaviors in these macromolecular assemblies.

A titration microcalorimeter and the vesicle of mixed surfactants

A titration microcalorimeter with the sample cells of 1 mL and 3 mL volume was constructed by combining LKB-2107 ampule microcalorimeter with an improved Thermometric titration microcalorimeter. Its sensitivity and precision were tested with the baseline noise and stability, the measurement of energy equivalent, and the linear relation of electric energy and integral area as the function of voltage(V)-time (t). Its accuracy was demonstrated by measuring the dilution enthalpy of a concentrated sucrose solution and the micelle-forming enthalpy of sodium dodecyl sulfate (SDS) in aqueous solution respectively. At the same time, the enthalpy of interaction between SDS and didodecyldimethylammonium bromide (DDAB) was measured by using the titration microcalorimeter, and the phase behavior of SDS-DDAB aqueous mixture was discussed. The microcalorimetric results show that the enthalpy of interaction between SDS and DDAB micelles is -29.53 kJ/mol, the enthalpy of formation of 1:1 SDS-DDAB salt is -125.8 kJ/mol, the vesicle-forming enthalpy of SDS-DDAB is 41.23 kJ/mol, and the enthalpy of phase transition from vesicles to SDS rich micelle is 32.10 kJ/mol.

The construction of pseudo-Janus silica/surfactant assembly and their application to stabilize Pickering emulsions and enhance oil recovery

Nanoparticles with high surface energy and chemical activity have drawn substantial attention in petroleum industry. Recently, Janus nanoparticles exhibited tremendous potential in enhanced oil recovery (EOR) due to their asymmetric structures and properties. In this study, a series of amphiphilic pseudo-Janus@OTAB (PJ@C18) nanoparticles with different concentrations of stearyltrimethylammoium bromide (OTAB) were successfully fabricated. The structures and properties of PJ@C18 were characterized by Fourier transform infrared spectroscopy and ζ-potential measurements. Based on the emulsification experimental results, the interaction models and the self-assembly behavior between hydrophilic nanoparticles (SiO_(2)@NH_(2)) and OTAB molecules at the oil/water interface were proposed, which was further confirmed via the measurements of the contact angle and dynamic interfacial tension. Interestingly, it was found that the change of pH value from 7.5 to 4.0 caused the type reversal of the PJ@C18-1000 stabilized Pickering emulsions. Furthermore, the PJ@C18-1000 stabilized Pickering emulsion system with excellent salt and temperature tolerances (10000 mg∙L^(–1), 90℃) significantly improved the oil recovery in the single-tube (more than 17%) and double-tube (more than 25%) sand pack model flooding tests. The findings of this study could help to better understand the construction mechanism of pseudo-Janus silica/surfactant assembly and the potential application of PJ@C18-1000 stabilized Pickering emulsions for EOR.

Synthesis and catalytic performance of bimetallic NiMo-and NiW-ZSM-5/MCM-41 composites for production of liquid biofuels

This work presents a synthesis of bimetallic NiMo and NiW modified ZSM-5/MCM-41 composites and their heterogeneous catalytic conversion of crude palm oil( CPO) to biofuels. The ZSM-5/MCM-41 composites were synthesized through a self-assembly of cetyltrimethylammonium bromide( CTAB) surfactant with silica-alumina from ZSM-5 zeolite,prepared from natural kaolin by the hydrothermal technique. Subsequently,the synthesized composites were deposited with bimetallic NiMo and NiW by impregnation method. The obtained catalysts presented a micro-mesoporous structure,confirmed by XRD,SEM,TEM,EDX,NH_3-TPD,XRF and N_2 adsorption-desorption measurements. The results of CPO conversion demonstrate that the catalytic activity of the synthesized catalysts decreases in the series of NiMo-ZSM-5/MCM-41 > NiW-ZSM-5/MCM-41 > Ni-ZSM-5/MCM-41 > Mo-ZSM-5/MCM-41 > W-ZSM-5/MCM-41 > NiMo-ZSM-5 > NiW-ZSM-5 > ZSM-5/MCM-41 > ZSM-5 > MCM-41. It was found that the bimetallic NiMo-and NiW-ZSM-5/MCM-41 catalysts give higher yields of liquid hydrocarbons than other catalysts at a given conversion. Types of hydrocarbon in liquid products,identified by simulated distillation gas chromatography-flame ionization detector( SimDis GC-FID),are gasoline( 150-200 ℃; C5-12),kerosene( 250-300 ℃; C5-20) and diesel( 350 ℃; C7-20).Moreover,the conversion of CPO to biofuel products using the NiMo-and NiW-ZSM-5/MCM-41 catalysts offers no statistically significant difference( P> 0.05) at 95% confidence level,evaluated by SPSS analysis.

Novel redox-active ionic thermotropic liquid crystalline complexes of polyelectrolyte and ferrocenyl surfactants

Redox-active polyelectrolyte-surfactant complexes（PSC） were prepared via the ionic self-assembly of sodium poly（styrenesulfonate） （PSS） and ferrocenyl surfactant,（11-ferrocenylundecyl）trimethylammonium bromide（FTMA） in aqueous solution. The PSS-FTMA complex exhibited an ordered interdigitated monolayer mesomorphous structure with the long period of d = 3.13 nm,and was in the ionic thermotropic liquid crystal SmA state at room temperature.Interestingly,in the solid complex, the ferrocenyl moieties formed H-aggregation showing an increase in theπ-π~＊ energy transfer of cyclopentadienes in the ferrocene moieties as known from the blue-shift in the UV spectrum.The complexes showed higher thermal stability compared with their components due to the ionic interaction.The PSS-FTMA film had a good redox reversibility,which promised to be used in electrochemical sensors.

Interaction of Plasma Proteins with Tri-quaternary Ammonium Salt Cationic Surfactant Studied by QCM-D

A tri-quaternary ammonium salt cationic surfactant was synthesized.Its structure was confirmed by using Fourier-transform infrared spectroscopy,^(1)H nuclear magnetic resonance spectroscopy,and X-ray photoelectron spectroscopy analyses.Three model surfaces,including Au-CH_(3),Au-OH and Au-COOH,were fabricated.Adsorptions of surfactant on the three model surfaces and subsequent plasma proteins adsorption were investigated by quartz crystal microbalance with dissipation(QCM-D).The mass of surfactant on the Au-COOH surface was the largest,followed by that on the Au-CH_(3)surface,and that on the Au-OH surface.These results suggested that the main driving force of surfactant immobilization was electrostatic interaction followed by hydrophobic interaction.Based on the results obtained,we concluded that the protein mass adsorbed on Au-CH_(3)-S,Au-OH-S,and Au-COOH-S surfaces depended on the protein size and orientation.The mass and thickness of S on the Au-COOH surface is the largest and the protein adsorption capacity of Au-COOH-S surface is inferior to that of Au-CH_(3)-S.The Au-COOH-S surface could inhibit lysozyme adsorption,maintain the adsorption balance of bovine serum albumin,and induce fibrinogen-binding protein adsorption.

Cooperative organizations of small molecular surfactants and amphiphilic block copolymers:Roles of surfactants in the formation of binary co-assemblies

The construction of highly ordered organizations through self-assembly is one of the most popular phenomena both in natural and artificial environments.Amphiphilic molecules are the most commonly used building blocks for the self-assembly,which are conventionally known as amphiphilic low molecular weight surfactants with polar heads and nonpolar tails,or amphiphilic block copolymers(BCPs)consisting of covalently bonded hydrophilic and hydrophobic block chains.Compared with single surfactant self-assembly system,binary amphiphiles co-assembly systems composing of both small mass surfactants and amphiphilic BCPs feature high flexibilities and versatilities in materials designing and structure regulation,ascribing to the vast possibilities of intermolecular interactions within the systems and facile component modulations during the assembly processes.The amphiphilic features of the two kinds of molecules endow them with similar self-assembly behaviors,while the unique and distinct characters of each kind of amphiphiles lead to various complex but highly diversified co-assembly systems.According to the roles of the surfactant played in the co-assembly system,in this review,we summarize the binary coassembly systems from three distinct types:1)the co-micellization system in which the surfactants are added into the BCPs assemblies as a self-assembly assistant;2)the co-emulsification system in which the surfactants work as an emulsion stabilizer to assist and confine the assembly of BCPs in 3D geometries;3)the co-templating system where the individual micelles of both surfactant and BCPs are hierarchically arranged and distributed to guide the formation of hierarchical nanomaterials.Following this,the major potential applications of the nanomaterials synthesized from the binary amphiphiles in biological field are described.Finally,we shortly discuss the current challenges and future perspectives of the binary amphiphiles selfassembly systems.

Cellulose nanofibril matrix drives the dynamic formation of spheroids

Multicellular spheroids,which mimic the natural organ counterparts,allow the prospect of drug screening and regenerative medicine.However,their application is hampered by low processing efficiency or limited scale.This study introduces an efficient method to drive rapid multicellular spheroid formation by a cellulose nanofibril matrix.This matrix enables the facilitated growth of spheroids(within 48 h)through multiple cell assembly into size-controllable aggregates with well-organized physiological microstructure.The efficiency,dimension,and conformation of the as-formed spheroids depend on the concentration of extracellular nanofibrils,the number of assembled cells,and the heterogeneity of cell types.The above strategy allows the robust formation mechanism of compacted tumoroids and hepatocyte spheroids.

破译pH值和金属离子编程的家蚕纺丝机制

Silk is one of the toughest fibrous materials known despite spun at ambient temperature and pressure with water as a solvent.It is a great challenge to reproduce high-performance artificial fibers comparable to natural silk by bionic for the incomplete understanding of silkworm spinning in vivo.Here,we found that amphipol and digitonin stabilized the structure of natural silk fibroin(NSF)by a large-scale screening in vitro,and then studied the close-to-native ultrastructure and hierarchical assembly of NSF in the silk gland lumen.Our study showed that NSF formed reversible flexible nanofibrils mainly composed of random coils with a sedimentation coefficient of 5.8 S and a diameter of about 4 nm,rather than a micellar or rod-like structure assembled by the aggregation of globular NSF molecules.Metal ions were required for NSF nanofibril formation.The successive p H decrease from posterior silk gland(PSG)to anterior silk gland(ASG)resulted in a gradual increase in NSF hydrophobicity,thus inducing the sol-gelation transition of NSF nanofibrils.NSF nanofibrils were randomly dispersed from PSG to ASG-1,and self-assembled into anisotropic herringbone patterns at ASG-2 near the spinneret ready for silkworm spinning.Our findings reveal the controlled self-assembly mechanism of the multi-scale hierarchical architecture of NSF from nanofibrils to herringbone patterns programmed by metal ions and p H gradient,which provides novel insights into the spinning mechanism of silk-secreting animals and bioinspired design of high-performance fibers.

Frank-Kasper and related quasicrystal spherical phases in macromolecules

Creation of diverse ordered nanostructures via self-assembly of macromolecules is a promising "bottom-up" approach towards next-generation nanofabrication technologies. It is therefore of critical importance to explore the possibilities to form new self-assembled phases in soft matter systems. In this review, we summarized recent advances on the identification of several unconventional spherical phases in the self-assembly of functional macromolecules, including Frank-Kasper(F-K) phases and quasicrystals originally observed in metal alloys. We believe that these results provide a new strategy towards the rational design of novel functional materials with hierarchically ordered structures.

Structural Control of Mesoporous 1,4-Phenylene-silica Using the Mixture of CTAB/SDS

The morphology, pore architecture and crystallinity of the mesoporous 1,4-phenylene-silicas were controlled using the mixtures of cetyltrimethylammonium bromide （CTAB） and sodium dodecylsulfate （SDS）. When the SDS/CTAB molar ratio increased from 0 to 1.0, the morphology of the mesoporous 1,4-phenylene-silicas changed in a sequence of sphere, hexagonal short rod, worm-like, bent flake and flower-like structure; the pore architecture of them changed from a hexagonal arranged tubular structure to a lamellar one; and the organization of the smallest repeat units within the wall changed from a random structure to a crystalline structure. At the SDS/CTAB molar ratios of 0.3 and 0.5, 1,4-phenylene-silica nanofibers with lamellar mesopores outside and tubular pore channels inside were obtained. The lamellar mesopores should be formed by merging the rod-like micelles during the reaction process.

Concentric Circular Approach in Mesoporous Silica Transition Process from Hexagonal to Vesicular Structure

We studied the synthesis of mesoporous silica from cetyltrimethyl ammonium bromide（CTAB） and so- dium dodecyl sulfate（SDS） at different molar ratios（R）. X-ray diffraction（XRD）, scanning electron spectroscopy （SEM）, transmission electron spectroscopy（TEM） and nitrogen sorption analysis were then used to further investigate the internal relationship among different morphologies and structures, as well as the mechanism of the transition from hexagonal to vesicular structure. The results reveal that as R increased, a consistent and gradual transition occurred via a concentric circular secondary structure formed. The antagonistic effect between the decreasing curvature of surfactant micelle and increasing curvature of secondary structures may be the reason for the complex morphologies synthesized, and the increasing bending energy AGb is the main driving force for the transition.

On Water Growth of Continuous Thin Films of Two-Dimensional Covalent Organic Frameworks with Large Single-Crystal Domains

A core feature of two-dimensional covalent organic frameworks is crystallinity, but it remains challenging to gain their thin films with high crystallinity. Here, we presented growth of thin films of two-dimensional covalent organic frameworks with an average domain size of ~2.83 μm^(2) and maximum domain size of up to ~26.19 μm^(2) using amphiphilic glycine derivatives on water surface. We envisage that this work will inspire the growth of a wide variety of organic two-dimensional materials with high crystallinity and boost their structure property investigations.