In this paper, a highly transparent, conductive, and bendable Ag nanowire (AgNW)-based electrode with excellent mechanical stability was prepared through the introduction of an adhesive polyelectrolyte multilayer between AgNW networks and a polyethylene terephthalate (PET) substrate. The introduction of the adhesive layer was performed based on a peel–assembly–transfer procedure, and the adhesive polyelectrolyte greatly improved the mechanical stability of the AgNW transparent conductive films (TCFs) without obviously attenuating the morphology and optoelectrical properties of the AgNW networks. The as-prepared AgNW TCFs simultaneously possess high optical transparency, good conductivity, excellent flexibility, and remarkable mechanical stability. It is believed that the proposed strategy would pave a new way for preparing flexible transparent electrodes with a long-term stability, which is significant in the development and practical applications of flexible transparent electronic devices operated in severe environments.

We have developed a rapid and convenient method for fabricating metal–organic framework (MOF) and infinite coordination polymer (ICP) nanosheets by spraying the atomized solution of metal ions onto the organic ligand solution. Nanosheet formation could be attributed to the anisotropic diffusion of metal ions in the ligand solution, which may give rise to a lateral interface of metal ions and organic ligands, where the crystals tend to grow laterally in the form of nanosheets. Three kinds of Zn- and Cu-based MOF nanosheets and two kinds of Co-based ICP nanosheets have been successfully obtained by spraying under mild conditions. The two-dimensional structures of nanosheets with a nanometer thickness and a homogeneous size can be evidenced by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Brunauer–Emmett–Teller, and Fourier transform infrared spectroscopy measurements. Furthermore, the fabricated ICP nanosheets have exhibited efficient catalytic performance for the conversion of CO2 to high-value-added chemicals. This spray technique simplifies the nanosheet production process by industrialized means and enhances its controllability by the fast liquid–liquid interfacial fabrication, thus allowing access to the industrialized fabrication of MOF and ICP nanosheets.

For decades, plasmonic nanostructures have been used as important optical sensing platforms, however, the necessity of sensitive optical instruments for detection greatly limits their practical application. Herein, a multi-responsive naked eye plasmonic indicator has been prepared through introduction of a responsive polymer brush (PNIPAm) into the cavity of a Ag nanovolcano array (Ag NVA). According to the phase change of the PNIPAm brush under different external conditions, the as-prepared Ag NVA shows responsive monochromatic colors, which allow the Ag NVA to serve as a plasmonic indicator detected by the naked eye. Importantly, the as-prepared Ag NVA also possesses a rapid response rate as well as excellent repeatability, and is compatible with conventional micro-fabrication methods. All of these excellent features make the as-prepared Ag NVA an attractive candidate for future optical indicating and intelligent color display applications.

Tellurium-containing photoresponsive polyelectrolyte multilayer films were fabricated by layer-by-layer assembly of a tellurium-containing polymer, photosensitizer, and poly(styrenesulfonate). The resulting films were investigated by UV/vis spectroscopy, XPS, EPR, and fluorescence spectroscopy. Under visible light, the photosensitizer in the film is excited and transforms triplet oxygen into singlet oxygen in aqueous solution. Singlet oxygen oxidizes −Te– to high valence state (Te═O) on the polymer backbone. The generated (Te═O) group makes the micelles more hydrophilic and looser, thereby facilitating the controlled release of the loaded cargo of micelles. These results show that the film has the potential to be used for cargo loading and controlled release, thus may provide a new way to combine photodynamic therapy and chemotherapy.

This work has developed a method to transfer a nanoparticle array from the parent substrate to the target surface. A close-packed and ordered Au nanoparticle (Au NP) array has been successfully transferred using poly(lactic acid) (PLA) as the mediator. For the transfer, the last step, i.e. removing the PLA mediator, plays a crucial role. The commonly-used dissolution of PLA in organic solvents cannot maintain array integrity. In this study, we have introduced wedging to peel off the PLA mediator. Relative to dissolution, wedging is a mild procedure and able to meet the requirement of transferring the vulnerable nanoparticle array. The Au NP arrays before and after transfer were thoroughly characterized by optical microscopy, TEM and SAXS. All the experimental results proved that the structure of the array was well preserved after transfer, at both the macroscopic and microscopic scales. Further, the transfer method was combined with layer-by-layer (LbL) self-assembly to fabricate a freestanding nanoparticle-array-sandwiched membrane. In the polymer/nanoparticle nanocomposite membrane, the nanoparticles were arranged in a close, ordered and single-layer way, which is hardly achieved by in situ LbL self-assembly. The distinct architecture endows the membrane with excellent mechanical properties. Buckling instability testing exhibited that the modulus of the transfer membrane is four times higher than that of the LbL analogues. This exploration indicates an efficient way to manipulate two-dimensional nanoparticle structures, enabling them to fulfill their true potential.

A successful attempt to fabricate nanoparticle arrays with sub-nanometre spacing by thermal annealing of the prepared nanoparticle self-assembly was made. The molecular dynamics simulation indicated that the spacing decrease could be attributed to the temperature-enhanced mobility of the ligand, which promoted the relaxation of the nanoparticles to a more compact arrangement.

A fully branched hyperbranched polymer with a focal point has been prepared by superelectrophilic polycondensation of AB2 monomers with a core with six functional arms (B6′) in a slow addition manner. To reduce the chance of the homopolymerization of the monomers, the acenaphthenequinone group with higher reactivity was chosen as B′ for the core and the isatin group with lower reactivity as B in the monomer. The obtained polymers were characterized by 1H NMR, 13C NMR, TGA and GPC. The thermo-decomposition temperature of the polymer could reach 400 °C. The NMR spectra indicated the 100% branching degree of the hyperbranched polymers and the successful introduction of the core. The proportions of the terminal/dendritic groups in the hyperbranched polymers with low monomer/core feeding ratio were evaluated through NMR and GPC data respectively. Through comparison and analysis it was revealed that most of the hyperbranched polymers possessed quasi-spherical structures. The molecular weights of the hyperbranched polymers increased almost linearly with the feeding ratio of the monomer to the core and the polydispersities of the polymers were greatly influenced by the monomer concentration. At the optimal monomer concentration, the main parts of the GPC curves were symmetric and narrow. Although there were traces of faint shoulder, the molecular weight distributions of the polymers were still acceptable. The branching degree of 100%, controllable molecular weights, narrow distribution, plus the quasi-spherical and hierarchical architectures of cores, dendritic and terminal units made the fully branched polymer with a focal point analogous to dendrimers in all respects, offering a highly efficient option to fabricate dendrimer substitutes.

We have developed a new method to fabricate multilayer films, which uses prepared thin films as modular blocks and transfer as operation mode to build up multilayer structures. In order to distinguish it from the in situ fabrication manner, this method is called modular assembly in this study. On the basis of such concept, we have fabricated a multilayer film using the silver mirror film as the modular block and poly(lactic acid) as the transfer tool. Due to the special double-layer structure of the silver mirror film, the resulting multilayer film had a well-defined stratified architecture with alternate porous/compact layers. As a consequence of the distinct structure, the interaction between the adjacent layers was so weak that the multilayer film could be layer-by-layer stripped. In addition, the top layer in the film could provide an effective protection on the morphology and surface property of the underlying layers. This suggests that if the surface of the film was deteriorated, the top layer could be peeled off and the freshly exposed surface would still maintain the original function. The successful preparation of the layer-by-layer strippable silver multilayer demonstrates that modular assembly is a feasible and effective method to build up multilayer films capable of creating novel and attractive micro/nanostructures, having great potential in the fabrication of nanodevices and coatings.

This work demonstrates a facile post-treatment strategy, vacuum thermal annealing, to fabricate a dodecanethiol-passivated gold nanoparticle (Au NP) array with organic solvent sensitivity. Through investigating the structure change of the Au NP array, it was found that the interparticle distance decreased during vacuum heat treatment, which meant a closer arrangement of the particles and a more dense packing of the dodecanethiol ligands in the interparticle region. The condensation would increase the interaction of the alkyl chain and enhance their interdigitation. Furthermore, on the basis of the stretching of the alkyl chains in organic solvents, the thermally treated Au NP array showed a good response to organic solvent or vapor by using the interdigitated dodecanethiol network as its responsive unit. The alkyl chains stretch to different extents in different organic solvents, leading to differences in interparticle distance, which provided a distinct blue shift of maximum wavelength upon exposure to various organic solvents or vapors. All of these results indicated that thermal annealing was an efficient way to confer responsivity to inert Au NP arrays. Together with the cost-effectiveness of such NP arrays, this study has potential in the development of economical sensors for medical diagnostics, food safety screening, and environmental pollution monitoring.

The patterning of layer-by-layer (LbL) polyelectrolyte multilayers with metal ions is important for the facile fabrication of circuits or selective catalysis. The strategy includes two issues: the incorporation of metal ions and their controlled assembly–disassembly, which require a good understanding of the assembly mechanism. Therefore, we explored the LbL assembly between a polycation, poly-(diallyldimethylammonium chloride) (PDDA) and an inorganic single charged molecule, [AuCl4]−, which could assemble at pH = 3.7 and disassemble at lower pH values. Moreover, we have demonstrated that the driving force in the assembly is a ligand-to-metal charge transfer interaction. Combining the controlled assembly–disassembly of PDDA–[AuCl4]− multilayers and photolithography, we obtained a surface pattern of PDDA–[AuCl4]− multilayers.

The transfer of inorganic films from the as-grown substrates to arbitrary surfaces has been demonstrated and investigated as a facile and versatile approach to alter surface properties. The transfer method employed soluble poly(lactic acid) delivery for ease of operation and flexibility in surface adhesion. Superhydrophobic Au and Ag thin films fabricated by electrochemical and chemical solution deposition, respectively, were chosen as the to-transfer inorganic films. A variety of materials, including silica, metal, ceramic, copper mesh, and lens tissue, were successfully coated with the two kinds of inorganic thin films by this transfer method. As a result of the transfer, the superhydrophobicity of Au and Ag films was imparted to these surfaces; SEM and comparison of contact angle before and after transfer indicated that the morphology and properties of the parent film were substantially preserved after transfer. This transfer method could eliminate the restriction of as-grown substrates on thin films, broadening thin film applications.

A facile and efficient approach has been developed to speed up the fabrication of LBL films through sequential dipping in vigorously agitated solutions. By this agitated-dipping (AD) LBL technique, the multilayer films of PAH and PSS were fabricated. The resulting films were explored by UV−vis spectroscopy, X-ray reflectivity, and AFM. Meanwhile, the comparison of the AD and conventional LBL films was made, which demonstrated that AD LBL can decrease dipping time by more than 15 times without reducing film quality remarkably. In addition, to verify the generality of AD LBL, we studied the AD LBL films of PDDA/PSS and PAH/PAA preliminarily as well. AD LBL promotes the efficiency of conventional LBL greatly while preserving its most advantages, such as simplicity, cheapness, precise control, universality in substrates, recycling use of sample solutions, and so on. It would be a promising alternative to build up LBL films rapidly.

Layer-by-layer (LBL) films of poly(lactic acid) nanoparticles (PLA NPs) and poly(ethyleneimine) (PEI) were fabricated as a novel drug-delivery system. The PLA NPs, which encapsulated pyrene as a model drug, were prepared by nanoprecipitation methods. The assembly process of PLA NPs/PEI LBL films was monitored by UV−vis spectroscopy, and the load of pyrene in the multilayer films was verified by fluorescence spectroscopy. The morphology of the PLA NPs/PEI LBL films was observed by SEM. The release profile of pyrene from the LBL films in PBS solutions was further studied, and the result indicated that the PLA NPs/PEI films were capable of sustainably releasing pyrene as expected. The fabrication of PLA NPs/PEI LBL films provides a new facile method for drug delivery and paves the way for loading multiple types of drugs into a single LBL film.

A successful attempt to fabricate nanoparticle arrays with sub-nanometre spacing by thermal annealing of the prepared nanoparticle self-assembly was made. The molecular dynamics simulation indicated that the spacing decrease could be attributed to the temperature-enhanced mobility of the ligand, which promoted the relaxation of the nanoparticles to a more compact arrangement.

The patterning of layer-by-layer (LbL) polyelectrolyte multilayers with metal ions is important for the facile fabrication of circuits or selective catalysis. The strategy includes two issues: the incorporation of metal ions and their controlled assembly–disassembly, which require a good understanding of the assembly mechanism. Therefore, we explored the LbL assembly between a polycation, poly-(diallyldimethylammonium chloride) (PDDA) and an inorganic single charged molecule, [AuCl4]−, which could assemble at pH = 3.7 and disassemble at lower pH values. Moreover, we have demonstrated that the driving force in the assembly is a ligand-to-metal charge transfer interaction. Combining the controlled assembly–disassembly of PDDA–[AuCl4]− multilayers and photolithography, we obtained a surface pattern of PDDA–[AuCl4]− multilayers.

This work has developed a method to transfer a nanoparticle array from the parent substrate to the target surface. A close-packed and ordered Au nanoparticle (Au NP) array has been successfully transferred using poly(lactic acid) (PLA) as the mediator. For the transfer, the last step, i.e. removing the PLA mediator, plays a crucial role. The commonly-used dissolution of PLA in organic solvents cannot maintain array integrity. In this study, we have introduced wedging to peel off the PLA mediator. Relative to dissolution, wedging is a mild procedure and able to meet the requirement of transferring the vulnerable nanoparticle array. The Au NP arrays before and after transfer were thoroughly characterized by optical microscopy, TEM and SAXS. All the experimental results proved that the structure of the array was well preserved after transfer, at both the macroscopic and microscopic scales. Further, the transfer method was combined with layer-by-layer (LbL) self-assembly to fabricate a freestanding nanoparticle-array-sandwiched membrane. In the polymer/nanoparticle nanocomposite membrane, the nanoparticles were arranged in a close, ordered and single-layer way, which is hardly achieved by in situ LbL self-assembly. The distinct architecture endows the membrane with excellent mechanical properties. Buckling instability testing exhibited that the modulus of the transfer membrane is four times higher than that of the LbL analogues. This exploration indicates an efficient way to manipulate two-dimensional nanoparticle structures, enabling them to fulfill their true potential.