A SIMPLE METHOD FOR THE INCORPORATION OF LOW MOLECULAR WEIGHT DYES IN ULTRATHIN FILMS

A simple method for the fabrication of ultrathin films containing low molecular weight dye material is introduced(post-adsorption technique). The chromophore used is 4-nitro-4'-decyloxy azobenzene quaternary ammonium salt (azo-10Q).In classical layer-by-layer (LBL) procedures, where the substrate is dipped alternately into the chromophore solution and thecomplementary polyelectrolyte, the chromophore tends to desorb from the film during subsequent immersion in thepolyanion solution, and there is little or no indication of multilayer growth. The extent of desorption depends somewhat onthe selection of polyelectrolyte, the ionic strength and the pH of solution. An alternative approach is to first prepareconventional LBL films from a pair of oppositely charged polyelectrolytes, and then to soak this film into the chromophoresolution, where adsorption by penetration into the LBL film may take place. In preliminary results, a linear dependence ofUV absorbance on layer number of LBL film thus prepared was found, demonstrating the apparent effectiveness of the post-adsorption technique for the preparation of azo-10Q-containing ultrathin films.     

In situ Coordination and Surface Morphology of Langmuir Films of Non－amphiphilic Dithizone with Metal Ions on Air／Water Interface

A spread Langmuir film on the air/water in-terface can serve as a basic model for the under-standing of organized molecular systems[1] .Gener-ally,it is considered that only those compoundsthat possess simultaneously a hydrophilic headgroup and a long- alkyl chain can be spread on theair/water interface[2— 4] .Therefore,researches onthe organized molecular films are mainly concernedwith typical amphiphiles.In order to expand thechoice in molecular film to form materials and omitthe tedious sy…     

Nanofriction properties of molecular deposition films

The nanofriction properties of Au substrate and monolayer molecular deposition film and multilayer molecular deposition films on Au substrate and the molecular deposition films modified with alkyl-terminal molecule have been investigated by using an atomic force microscope. It is concluded that ( i ) the deposition of molecular deposition films on Au substrate and the modification of alkyl-terminal molecule to the molecular deposition films can reduce the frictional force; (ii) the molecular deposition films with the same terminal exhibit similar nanofriction properties, which has nothing to do with the molecular chain-length and the layer number; (iii) the unstable nanofriction properties of molecular deposition films are contributed to the active terminal of the molecular deposition film, which can be eliminated by decorating the active molecular deposition film with alkyl-terminal molecule, moreover, the decoration of alkyl-terminal molecule can lower the frictional force conspicuously; (iv) the relat     

Enhancement of morphological and emission stability of deep-blue small molecular emitter via a universal side-chain coupling strategy for optoelectronic device

Film morphology of emissive layers is crucial to the performance and stability of solution-processable organic light-emitting diodes(OLEDs). Compared to the interpenetration of conjugated polymer chain,small molecular emitter with a flexible side chain always presents easily aggregation upon external treatment, and caused π-electronic coupling, which is undesirable for the efficiency and stability of deep-blue OLEDs. Herein, we proposed a side-chain coupling strategy to enhance the film morpholo...     

Enhancement of morphological and emission stability of deep-blue small molecular emitter via a universal side-chain coupling strategy for optoelectronic device

Film morphology of emissive layers is crucial to the performance and stability of solution-processable organic light-emitting diodes(OLEDs). Compared to the interpenetration of conjugated polymer chain,small molecular emitter with a flexible side chain always presents easily aggregation upon external treatment, and caused π-electronic coupling, which is undesirable for the efficiency and stability of deep-blue OLEDs. Herein, we proposed a side-chain coupling strategy to enhance the film morpholo...     

Ultrathin Multilayer Films Incorporating Keggin-type Heteropolyanion Clusters

In recent years, there has been considerable interest in the fabrication of self-assembled ultrathin multilayer films, because of their availability to form nanostructured materials with tailored architecture and properties1. The layer-by-layer (LBL) self-assembly, initially developed for pairs of oppositely charged polyelectrolytes2, is an unusually simple and versatile technique to built up of ultrathin multilayer films. A special feature of the multilayer films is that the composition, t…     

High-performance nonfused ring electron acceptor with a steric hindrance induced planar molecular backbone

Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs.     

拉伸热历史对取向聚对苯二甲酸乙二酯膜在热处理过程中收缩和伸长的影响

The effects of drawing temperature and draw ratio on the contraction and extension of oriented amorphous PET film during thermal treatment has been studied. It has been shown that considerable thermal contraction of the oriented PET film before crystallization is due to relaxation of molecular chains in global sense while the spontaneous extension is related to crystallization of the oriented PET film. The maximum amount of contraction of the oriented PET film during thermal treatment increased with increasing λfor λ>2.3,owing to faster crystallization rate of PET film in highly oriented state. The maximum extension exibits similar behavior as that of maximum contraction with increasing λ and showed a peak at λ≌ 3.3,which isalmost the same draw ratio above which the densityof PET film began to increase during drawing.     

Comparison of two turbulent models in simulating evaporating liquid film in a wiped molecular distillator

Wiped molecular distillation is one kind of molecu-lar distillations, and its difference from others comes from the force by which the evaporating liquid film is formed. With quick rotation of the wiper, the liquid becomes thin-film well distributed on th…     

Novel Covalently Linked Self-Assembled Films from a Functional Hyperbranched Conjugated Poly(Phenylene Vinylene)

The hotSPOt in the fields of molecular films focuses on highly ordered, ultrathin filmswith molecularly controllable surface properties. It is attractive tO stUdy supramolecularfunctional POlymeric materials with suitable physical properties and abilities to formorganized superstrUctures at the interfacesl'2'3A. Dendritic macromolecules are a kind ofmaterials which is capable of self-organizing into superstrUctUres'. So a new dendrimerlike POly(Phenylene vinylene)- --hyperbranched conj "…     

Synthesis of Chitosan Quaternary Ammonium Salts

Chitosan has a wide scale of applications1-3. Interestingly, some antibacterial and antifungal activities have been described with chitosan and modified chitosan derivatives4-6. In polycationic biocides, generally, it is reasonably assumed7 that the charge density of the polyelectrolyte increases with increase in the molecular weight of its single coil, which leads to the enhanced adsorption of polycations onto the negatively charged cell surface. This is also favorable for the binding of t…     

Molecular Arrangement of a Bolaamphiphilic Anthrancene Derivative in Langmuir-Blodgett Film

Langmuir monolayer at the air/water interface is the basis to understand the molecular arrangement and to fabricate the organized molecular films1. Bolaamphiphiles describes the molecules in which two head functional groups are linked by one or two hydrophobic chains2,3. In comparison with the one-headed amphiphile, abundant configurations of Langmuir monolayer are expected in bolaamphiphiles. Generally, three kinds of configurations of the Langmuir monolayers of bolaamphiphile at the air/w…     

Uniaxial alignment of poly(3-hexylthiophene) nanofibers by zone-casting approach

The preparation of large area coverage of films with uniaxially aligned poly(3-hexylthiophene)(P3HT) nanofibers by using zone-casting approach is reported.The length and the orientation of the nanofibers are defined by the solubility of the solvent,the P3HT molecular weight and the substrate temperature.The length of the oriented nanofibers could be increased from 1 μm to more than 10 μm by adding poor solvent into the P3HT solution.It is found that for P3HT of relatively low molecular weight,a solvent with relatively low solubility has to be chosen to get the oriented film.While for the high molecular weight P3HT,the solvent with a relatively high solubility has to be used.The well-aligned film could be obtained because of the solute concentration gradient in the region where the critical concentration is reached during the zone-casting process.Particularly,the solvent evaporation rate and crystallization rate must be chosen properly to satisfy the stationary conditions above,which were controlled by an appropriate choice of solvent and substrate temperature.The film prepared by zone-casting approach had microcrystalline P3HT domains with more inter-chain order than spin-coating film.Meanwhile,the P3HT π-π stacking direction was parallel to the alignment direction of the nanofibers.     

Homogeneous DNA Detection Based on Fluorescence Quenching by Nanoparticles in Single-step Format :Target-Induced Configuration Transform

A new strategy for homogeneous detection of DNA hybridization in single-step format was developed based on fluorescence quenching by gold nanoparticles. The gold nanoparticle is functionalized with 5’-thiolated 48-base oligonucleotide (probe sequence), whose 3’-terminus is labeled with fluorescein (FAM), a negatively charged fluorescence dye. The oligonucleotide adopts an extended configuration due to the electrostatic repulsion between negatively charged gold nanoparticle and the FAM-attached probe sequence. After addition of the complementary target sequence, specific DNA hybridization induces a conformation change of the probe from an extended structure to an arch-like configuration, which brings the fluorophore and the gold nanoparticle in close proximity. The fluorescence is efficiently quenched by gold nanoparticles. The fluorescence quenching efficiency is related to the target concentration, which allows the quantitative detection for target sequence in a sample. A linear detection range from 1.6 to 209.4 nmol/L was obtained under the optimized experimental conditions with a detection limit of 0.1 nmol/L. In the assay system, the gold nanoparticles act as both nanoscaffolds and nanoquenchers. Furthermore, the proposed strategy, in which only two DNA sequences are involved, is not only different from the traditional molecular beacons or reverse molecular beacons but also different from the commonly used sandwich hybridization methods. In addition, the DNA hybridization detection was achieved in homogenous solution in a single-step format, which allows real-time detection and quantification with other advantages such as easy operation and elimination of washing steps.     

Near—infrared SERS Study of the Adsorption of a PMMA Dip—coated onto Silver Mirror Substrate

The interface between a-PMMA thin film and silver mirror substrate was investigated using surface-enhanced Raman scattering (SERS). It is found that the molecular chain axis of a-PMMA tends to parallel the substrate in the interface. When the sample is annealed at different temperatures, some interesting changes appear in the SERS spectra. The spectra differences and their transition are due to the surface geometry change of the ester group.     

Electrochemical Behavior and Redox Switch Properties of [Zn(dmit)_2]~(2-)

The redox behavior of [Zn(dmit)2]2- and its electrodeposited film were investigated by cyclic voltammetry, and the Ⅰ-Ⅴ properties of the electrodeposited film were measured. The results show that [Zn(dmit)2]2- possesses good redox switch properties which exhibit good repeatability. It could be considered as a new material for molecular switch and memory.     

Unraveling the stabilization mechanism of solid electrolyte interface on ZnSe by rGO in sodium ion battery

Transition metal selenides have been widely studied as anode materials of sodium ion batteries(SIBs),however,the investigation of solid-electrolyte-interface(SEI)on these materials,which is critical to the electrochemical performance of SIBs,remains at its infancy.Here in this paper,ZnSe@C nanoparticles were prepared from ZIF-8 and the SEI layers on these electrodes with and without reduced graphene oxide(rGO)layers were examined in details by X-ray photoelectron spectroscopies at varied charged/discharged states.It is observed that fast and complicated electrolyte decomposition reactions on ZnSe@C leads to quite thick SEI film and intercalation of solvated sodium ions through such thick SEI film results in slow ion diffusion kinetics and unstable electrode structure.However,the presence of rGO could efficiently suppress the decomposition of electrolyte,thus thin and stable SEI film was formed.ZnSe@C electrodes wrapped by rGO demonstrates enhanced interfacial charge transfer kinetics and high electrochemical performance,a capacity retention of 96.4%,after 1000 cycles at 5 A/g.This study might offer a simple avenue for the designing high performance anode materials through manipulation of SEI film.     

Morphologies and Structures of Perovskite Thin Film on Zn-face and O-face of ZnO Single Crystal

ZnO single crystal was used as the substrate to study the effect of ZnO crystal plane polarity on the morphology and structure of CH_3NH_3PbI_3(MAPbI_3) perovskite film and carrier transport properties,which is meaningful for improving ZnO-based perovskite solar cell. It is found that perovskite thin film has small grain size(about 190 nm) and high coverage rate on the O-face of ZnO single crystal,and the dominant exposed crystal plane of perovskite film is(110) plane. While the MAPbI_3 thin film has large grain size(about 1.03 μm) and low coverage rate on the Zn-face,and the(022) plane is dominantly exposed for the perovskite film. The injection of photogenerated electrons from MAPbI_3 film into the O-face of ZnO single crystal is faster and more effective than that to Zn-face. It is supposed that O-face is more suitable for ZnO single crystal based perovskite cell fabrication than Zn-face.     

Synthesis of Substituted 3H-Indole-modified b-Cyclodextrin

The hydrophobic cavities of cyclodextrins and the inclusion with various organic molecules in the aqueous solution make them useful in chemical and biological activities1, one of which is the modified cyclodextrins acting as indicators of molecular recognition. Cyclodextrins, which are spectroscopically inert, can be converted into spectroscopically active compounds by modifing one or two of the hydroxy groups with appropriate chromophores, and used as molecular sensor due to the capability of…     

Characterization of self-assembled monolayers of thiols on Au(111)

Self-assembled monolayers (SAMs) of n-butanethiol, n-dodecanethiol and their equimolar mixture on Au(111) were prepared and characterized by ellipsometry, contact angle measurement, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results revealed that these SAMs are oriented ultrathin films with the thickness of nanometer scale, and the SAMs were influenced by the molecular chain length, the lattice orientation and cleanliness of the substrates. The surface of the longer chain SAM is hydrophobic. The thicknesses of three SAMs of n-butanethiol, n-dodecanethiol and their mixture revealed by ellipsometry and XPS are about 0.59 - 0.67nm, 1.60- 1.69 nm and 1.23 - 1.32nm, respectively. AFM images further demonstrated that the SAM formed by the mixture has some microdomains with two different thicknesses.