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1.
The fabrication and catalytic application of a size‐tunable monodisperse nanoparticle array enabled by block copolymer lithography is demonstrated. Highly uniform vertical cylinder nanodomains are achieved in poly(styrene‐block‐4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer thin‐films by solvent annealing. The prominent diffusion of the anionic metal complexes into the protonated P4VP cylinder nanodomains occurs through specific electrostatic interactions in a weakly acidic aqueous solution. This well‐defined diffusion with nanoscale confinement enables preparation of the laterally ordered monodisperse nanoparticle array with sub‐nanometer level precise size tuning. The controlled growth of monodisperse nanoparticle arrays is proven by their catalytic use for vertical carbon nanotube (CNT) growth via plasma enhanced chemical vapor deposition (PECVD). Since the size of the catalyst particles is the decisive parameter for the diameters and wall‐numbers of CNTs, the highly selective growth of double‐walled or triple‐walled CNTs could be accomplished using monodisperse nanoparticle arrays.  相似文献   

2.
The fabrication and catalytic application of a size‐tunable monodisperse nanoparticle array enabled by block copolymer lithography is demonstrated. Highly uniform vertical cylinder nanodomains are achieved in poly(styrene‐block‐4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer thin‐films by solvent annealing. The prominent diffusion of the anionic metal complexes into the protonated P4VP cylinder nanodomains occurs through specific electrostatic interactions in a weakly acidic aqueous solution. This well‐defined diffusion with nanoscale confinement enables preparation of the laterally ordered monodisperse nanoparticle array with sub‐nanometer level precise size tuning. The controlled growth of monodisperse nanoparticle arrays is proven by their catalytic use for vertical carbon nanotube (CNT) growth via plasma enhanced chemical vapor deposition (PECVD). Since the size of the catalyst particles is the decisive parameter for the diameters and wall‐numbers of CNTs, the highly selective growth of double‐walled or triple‐walled CNTs could be accomplished using monodisperse nanoparticle arrays.  相似文献   

3.
Double stimuli‐responsive membranes are prepared by modification of pH‐sensitive integral asymmetric polystyrene‐b‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer membranes with temperature‐responsive poly(N‐isopropylacrylamide) (pNIPAM) by a surface linking reaction. PS‐b‐P4VP membranes are first functionalized with a mild mussel‐inspired polydopamine coating and then reacted via Michael addition with an amine‐terminated pNIPAM‐NH2 under slightly basic conditions. The membranes are thoroughly characterized by nuclear magnetic resonance (1H‐NMR), Fourier transform infrared spectroscopy and X‐ray‐induced photoelectron spectroscopy. Additionally dynamic contact angle measurements are performed comparing the sinking rate of water droplets at different temperatures. The pH‐ and thermo‐double sensitivities of the modified membranes are proven by determining the water flux under different temperature and pH conditions.  相似文献   

4.
A novel step‐wise approach for fabrication of periodic arrays of two different types of nanoparticles (NPs), selectively localized at different block copolymer phases is demonstrated. In the first step, pre‐synthesized ≈12 nm silver nanoparticles (AgNPs), stabilized with thiol‐terminated polystyrene, are mixed with poly(styrene‐block‐vinylpyridine) (PS‐b‐PVP) block copolymer in a common solvent. After film casting and consequent solvent vapor annealing the AgNPs are selectively localized within the PS phase of the block copolymer matrix due to the interaction with PS shell of the nanoparticles. In the second step, ≈2–5 nm gold, platinum, or palladium nanoparticles are directly deposited from their aqueous dispersion on the PVP domains of the self‐assembled block copolymer thin films. In such a way, thin films of nanostructured block copolymer with two types of nanoparticles, separated by the two distinct block copolymer phases, are prepared in a step‐wise manner. The presented method is very simple and can be applied for various combinations of pre‐synthesized nanoparticles where the characteristics of either type of nanoparticles are tuned accordingly in advance, which is more difficult to achieve for in situ synthesized nanoparticles.  相似文献   

5.
The effects of using a blocking dielectric layer and metal nanoparticles (NPs) as charge‐trapping sites on the characteristics of organic nano‐floating‐gate memory (NFGM) devices are investigated. High‐performance NFGM devices are fabricated using the n‐type polymer semiconductor, poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2)), and various metal NPs. These NPs are embedded within bilayers of various polymer dielectrics (polystyrene (PS)/poly(4‐vinyl phenol) (PVP) and PS/poly(methyl methacrylate) (PMMA)). The P(NDI2OD‐T2) organic field‐effect transistor (OFET)‐based NFGM devices exhibit high electron mobilities (0.4–0.5 cm2 V?1 s?1) and reliable non‐volatile memory characteristics, which include a wide memory window (≈52 V), a high on/off‐current ratio (Ion/Ioff ≈ 105), and a long extrapolated retention time (>107 s), depending on the choice of the blocking dielectric (PVP or PMMA) and the metal (Au, Ag, Cu, or Al) NPs. The best memory characteristics are achieved in the ones fabricated using PMMA and Au or Ag NPs. The NFGM devices with PMMA and spatially well‐distributed Cu NPs show quasi‐permanent retention characteristics. An inkjet‐printed flexible P(NDI2OD‐T2) 256‐bit transistor memory array (16 × 16 transistors) with Au‐NPs on a polyethylene naphthalate substrate is also fabricated. These memory devices in array exhibit a high Ion/Ioff (≈104 ± 0.85), wide memory window (≈43.5 V ± 8.3 V), and a high degree of reliability.  相似文献   

6.
Block copolymers of poly(pentafluorostyrene) (PFS) and poly(methyl methacrylate) (PMMA) (PFS‐b‐PMMA) have been synthesized using atom transfer radical polymerization (ATRP). Then, nanoporous fluoropolymer films have been prepared via selective UV decomposition of the PMMA blocks in the PFS‐b‐PMMA copolymer films. The chemical composition and structure of the PFS homopolymers and copolymers have been characterized using nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS), and molecular‐weight measurements. The cross‐sectional and surface morphologies of the PFS‐b‐PMMA copolymer films before and after selective UV decomposition of the PMMA blocks have been studied using field‐emission scanning electron microscopy (FESEM). The nanoporous fluoropolymer films with pore sizes in the range 30–50 nm and porosity in the range 15–40 % have been obtained from the PFS‐b‐PMMA copolymers of different PMMA content. Dielectric constants approaching 1.8 have been achieved in the nanoporous fluoropolymer films which contain almost completely decomposed PMMA blocks.  相似文献   

7.
Due to their unique morphology‐related properties, yolk@shell materials are promising materials for catalysis, drug delivery, energy conversion, and storage. Despite their proven potential, large‐scale applications are however limited due to demanding synthesis protocols. Overcoming these limitations, a simple soft‐templated approach for the one‐pot synthesis of yolk@shell nanocomposites and in particular of multicore metal nanoparticle@metal oxide nanostructures (MNP@MOx) is introduced. The approach here, as demonstrated for AuNP@ITOTR (ITOTR standing for tin‐rich ITO), relies on polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) inverse micelles as two compartment nanoreactor templates. While the hydrophilic P4VP core incorporates the hydrophilic metal precursor, the hydrophobic PS corona takes up the hydrophobic metal oxide precursor. As a result, interfacial reactions between the precursors can take place, leading to the formation of yolk@shell structures in solution. Once calcined these micelles yield AuNP@ITOTR nanostructures, composed of multiple 6 nm sized Au NPs strongly anchored onto the inner surface of porous 35 nm sized ITOTR hollow spheres. Although of multicore nature, only limited sintering of the metal nanoparticles is observed at high temperatures (700 °C). In addition, the as‐synthesized yolk@shell structures exhibit high and stable activity toward CO electrooxidation, thus demonstrating the applicability of our approach for the design of functional yolk@shell nanocatalysts.  相似文献   

8.
Vertical orientation of lamellar and cylindrical nanodomains of block copolymers on substrates is one of the most promising means for developing nanopatterns of next‐generation microelectronics and storage media. However, parallel orientation of lamellar and cylindrical nanodomains is generally preferred due to different affinity between two block segments in a block copolymer toward the substrate and/or air. Thus, vertical orientation of the nanodomains is only obtained under various pre‐ or post‐treatments such as surface neutralization by random copolymers, solvent annealing, and electric or magnetic field. Here, a novel self‐neutralization concept is introduced by designing molecular architecture of a block copolymer. Star‐shaped 18 arm poly(methyl methacrylate)‐block‐polystyrene copolymers ((PMMA‐b‐PS)18) exhibiting lamellar and PMMA cylindrical nanodomains are synthesized. When a thin film of (PMMA‐b‐PS)18 is spin‐coated on a substrate, vertically aligned lamellar and cylindrical nanodomains are obtained without any pre‐ or post‐treatment, although thermal annealing for a short time (less than 30 min) is required to improve the spatial array of vertically aligned nanodomains. This result is attributed to the star‐shaped molecular architecture that overcomes the difference in the surface affinity between PS and PMMA chains. Moreover, vertical orientations are observed on versatile substrates, for instance, semiconductor (Si, SiOx), metal (Au), PS or PMMA‐brushed substrate, and a flexible polymer sheet of polyethylene naphthalate.  相似文献   

9.
Metallic and dielectric nanoparticles (NPs) have synergistic electromagnetic properties but their positioning into morphologically defined hybrid arrays with novel optical properties still poses significant challenges. A template‐guided self‐assembly strategy is introduced for the positioning of metallic and dielectric NPs at pre‐defined lattice sites. The chemical assembly approach facilitates the fabrication of clusters of metallic NPs with interparticle separations of only a few nanometers in a landscape of dielectric NPs positioned hundreds of nanometers apart. This approach is used to generate two‐dimensional interdigitated arrays of 250 nm diameter TiO2 NPs and clusters of electromagnetically strongly coupled 60 nm Au NPs. The morphology‐dependent near‐ and far‐field responses of the resulting multiscale optoplasmonic arrays are analyzed in detail. Elastic and inelastic scattering spectroscopy in combination with electromagnetic simulations reveal that optoplasmonic arrays sustain delocalized photonic–plasmonic modes that achieve a cascaded E‐field enhancement in the gap junctions of the Au NP clusters and simultaneously increase the E‐field intensity throughout the entire array.  相似文献   

10.
Here, reactive imprint lithography (RIL) is introduced as a new, one‐step lithographic tool for the fabrication of large‐area topographically patterned, chemically activated polymer platforms. Films of polystyrene‐block‐poly(tert‐butyl acrylate) (PS‐b‐PtBA) are imprinted with PDMS master stamps at temperatures above the corresponding glass transition and chemical deprotection temperatures to yield structured films with exposed carboxylic acid and anhydride groups. Faithful pattern transfer is confirmed by AFM analyses. Transmission‐mode FTIR spectra shows a conversion of over 95% of the tert‐butyl ester groups after RIL at 230 °C for 5 minutes and a significantly reduced conversion to anhydride compared to thermolysis of neat films with free surfaces in air or nitrogen. An enrichment of the surface layer in PS is detected by angle‐resolved X‐ray photoelectron spectroscopy (XPS). In order to demonstrate application potentials of the activated platforms, a 7 nm ± 1 nm thick NH2‐terminated PEG layer (grafting density of 0.9 chains nm?2) is covalently grafted to RIL‐activated substrates. This layer reduces the non‐specific adsorption (NSA) of bovine serum albumin by 95% to a residual mass coverage of 9.1 ± 2.9 ng cm?2. As shown by these examples, RIL comprises an attractive complementary approach to produce bio‐reactive polymer surfaces with topographic patterns in a one‐step process.  相似文献   

11.
Ordered nanostructured crystals of thin organic–inorganic metal halide perovskites (OIHPs) are of great interest to researchers because of the dimensional‐dependence of their photoelectronic properties for developing OIHPs with novel properties. Top‐down routes such as nanoimprinting and electron beam lithography are extensively used for nanopatterning OIHPs, while bottom‐up approaches are seldom used. Herein, developed is a simple and robust route, involving the controlled crystallization of the OIHPs templated with a self‐assembled block copolymer (BCP), for fabricating nanopatterned OIHP films with various shapes and nanodomain sizes. When the precursor solution consisting of methylammonium lead halide (MAPbX3, X = Br?, I?) perovskite and poly(styrene)‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) is spin‐coated on the substrate, a nanostructured BCP is developed by microphase separation. Spontaneous crystallization of the precursor ions preferentially coordinated with the P2VP domains yields ordered nanocrystals with various nanostructures (cylinders, lamellae, and cylindrical mesh) with controlled domain size (≈40–72 nm). The nanopatterned OIHPs show significantly enhanced photoluminescence (PL) with high resistance to both humidity and heat due to geometrically confining OIHPs in and passivation with the P2VP chains. The self‐assembled OIHP films with high PL performance provide a facile control of color coordinates by color conversion layers in blue‐emitting devices for cool‐white emission.  相似文献   

12.
Directly patterned mesoporous silicate films are prepared using positive‐ and negative‐tone strategies by performing phase selective silica condensation within lithographically exposed poly(styrene‐btert‐butyl acrylate) (PS‐b‐PtbA) templates containing photoacid generators. The use of supercritical fluid as a process medium enables rapid diffusion of the silicate precursor within the prepatterned block copolymer template film without disrupting its morphology. Template exposure through the mask triggers area selective generation of acid, which in turn both deprotects the poly(tert‐butyl acrylate) block to yield a poly(acrylic acid) block and provides a catalyst for silica precursor condensation yielding pattern formation at the device level. Because the acid generated in the UV exposed field preferentially segregates into hydrophilic poly(acrylic acid) domains of the phase segregated, deprotected block copolymer, precursor condensation is simultaneously controlled at nanoscopic length scales via templating by the underlying block copolymer morphology. The ability of PS‐b‐PtbA to undergo chemical transformation in two stages, deprotection followed by crosslinking, enables precise replications of the photomask in positive and negative tones. Detemplating via calcination yields patterned mesoporous silicate films without etching. Template formulations are optimized using infrared spectroscopic studies and the silicate films are characterized using electron microscopy and scanning force microscopy.  相似文献   

13.
We investigate the effect of surface topology of a block copolymer/neutral surface/SiO2 trilayered gate insulator on the properties of pentacene organic thin film transistor (OTFT) by the controlled etching of self assembled poly(styrene‐b‐methyl methacrylate) (PS‐b‐PMMA) block copolymer. The rms roughness of the uppermost block copolymer film directly in contact with pentacenes was systematically controlled from 0.27 nm to approximately 12.5 nm by the selective etching of cylindrical PMMA microdomains hexagonally packed and aligned perpendicular to SiO2 layer with 20 and 38 nm of diameter and periodicity, respectively. Both mobility and On/Off ratio were significantly reduced by more than 3 orders of magnitudes with the film roughness in OTFTs having 60 nm thick pentacene active layer. The poor device performance observed with the etched thin film of block copolymer dielectric is attributed to a defective pentacene active layer and the mixed crystalline structure consisting of thin film and bulk phase arising from the massive nucleation of pentacene preferentially at the edge of each cylindrical etched hole.  相似文献   

14.
Here, a novel and simple route to fabricate highly dense arrays of palladium nanodots and nanowires with sub‐30 nm periodicity using nanoporous templates fabricated from supramolecular assemblies of a block copolymer, polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) and a low molecular weight additive, 2‐(4′‐hydroxybenzeneazo) benzoic acid (HABA) is demonstrated. The palladium nanoparticles, which are directly deposited in the nanoporous templates from an aqueous solution, selectively migrate in the pores mainly due to their preferential attraction to the P4VP block covering the pore wall. The polymer template is then removed by oxygen plasma etching or pyrolysis in air resulting in palladium nanostructures whose large scale morphology mirrors that of the original template. The method adopted in this work is general and versatile so that it could easily be extended for patterning a variety of metallic materials into dot and wire arrays.  相似文献   

15.
The precisely controllable self‐assembly phenomenon of block copolymers (BCPs) has garnered much attention because it yields well‐defined periodic nanostructures with a periodicity of 5–50 nm. However, from both thermodynamic and kinetic viewpoints, it still remains a challenge to develop a BCP material that can provide sub‐10 nm resolution, high pattern quality, fast pattern formation, and sufficient etch selectivity. To address these challenges, this study reports a BCP system containing a random‐copolymerized block (poly(2‐vinylpyridine‐co‐4‐vinylpyridne)‐b‐poly(dimethylsiloxane) (P(2VP‐co‐4VP)‐b‐PDMS)) that can provide sub‐6 nm resolution, 3σ line edge roughness of 0.89 nm, sub‐1‐min assembly time, and a high etch selectivity over 10. Calculation of the Flory–Huggins interaction parameter (χ) based on Leibler's mean‐field theory and small‐angle X‐ray scattering measurement data confirms the gradual tunability of χ with the controlled addition of 4VP fraction in the P(2VP‐co‐4VP) block. While guaranteeing kinetically fast self‐assembly within one minute using microwave annealing, the best pattern quality resulting from the thermodynamic suppression of line edge fluctuation is achieved with a 4VP weight fraction of 33% in the random‐copolymerized block. This approach enables systematical control of sub‐6 nm scale BCP self‐assembly and will provide a practical patterning solution for diverse nanostructures and devices.  相似文献   

16.
Tailoring the size and surface chemistry of nanoparticles allows one to control their position in a block copolymer, but this is usually limited to one‐dimensional distribution across domains. Here, the hierarchical assembly of poly(ethylene oxide)‐stabilized gold nanoparticles (Au‐PEO) into hexagonally packed clusters inside mesostructured ultrathin films of polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) is described. A close examination of the structural evolution at different nanoparticle filling fractions and PEO ligand molecular weights suggests that the mechanism leading to this structure‐within‐structure is the existence of two phase separation processes operating on different time scales. The length of the PEO ligand is shown to influence not only the interparticle distances but also the phase separation processes. These conclusions are supported by novel mesoscopic simulations, which provide additional insight into the kinetic and thermodynamic factors that are responsible for this behavior.  相似文献   

17.
Achieving sub‐10 nm high‐aspect‐ratio patterns from diblock copolymer self‐assembly requires both a high interaction parameter (χ, which is determined by the incompatibility between the two blocks) and a perpendicular orientation of microdomains. However, these two conditions are extremely difficult to achieve simultaneously because the blocks in a high‐χ copolymer typically have very different surface energies, favoring in‐plane microdomain orientations. A fully perpendicular orientation of a high‐χ block copolymer, poly(styrene‐block‐dimethylsiloxane) (PS‐b‐PDMS) is realized here using partially hydrolyzed polyvinyl alcohol (PVA) top coats with a solvent annealing process, despite the large surface energy differences between PS and PDMS. The PVA top coat on the block copolymer films under a solvent vapor atmosphere significantly reduces the interfacial energy difference between two blocks at the top surface and provides sufficient solvent concentration gradient in the through‐thickness direction and appropriate solvent evaporation rates within the film to promote a perpendicular microdomain orientation. The effects of interfacial energy differences and the swellability of PVA top coats controlled by the degree of hydrolysis on the orientation of micro­domains are examined. The thickness of the BCP film and top coats also affects the orientation of the BCP film.  相似文献   

18.
Surface‐initiated photoiniferter‐mediated photopolymerization (SI‐PMP) in presence of tetraethylthiuram disulfide is used to directly synthesize surface‐grafted poly(methacrylic acid)‐block‐poly(N‐isopropylacrylamide) (PMAA‐b‐PNIPAM) layers. The response of these PMAA‐b‐PNIPAM bi‐level brushes to changes in pH, temperature and ionic strength is investigated by using in‐situ multi‐angle ellipsometry to measure changes in solvated layer thickness. As expected for a block copolymer architecture, PMAA blocks swell as pH is increased, with the maximum change in the thickness occurring near pH = 5, and PNIPAM blocks exhibit lower critical solution temperature (LCST) behavior, marked by a broad transition between swollen and collapsed states. The response of the bi‐level brushes to changes in added salt at constant pH is complex, as the swelling behaviors of both the weak polyelectrolyte, PMAA, and thermoresponsive PNIPAM are affected by changes in ionic strength. This work demonstrates not only the robustness of SI‐PMP for making novel, bi‐level stimuli‐responsive brushes, but also the complex links between synthesis, structure, and response of these materials.  相似文献   

19.
Here, we report the preparation of hierarchically structured polymer brushes with well‐defined geometries via multiple step microcontact printing (MS‐µCP) of inks containing different ratios of initiator‐terminated thiols and non‐reactive alkylthiols. Thick (and dense), polymer brushes grew from self‐assembled monolayers (SAMs) with high concentration of initiator‐terminated thiols, and these brushes exhibited high chemical etch‐resistance, compared to thin (and less dense), brushes grown from more dilute initiator‐terminated SAMs. Upon etching, patterned crosslinking polymer brush films decorated with thin layers of Au, could be lifted off the surface to form geometrically well‐defined free‐standing hierarchical films. These polymer brush films showed interesting buckling instabilities when compressed. Areas with different brush thicknesses and Au backing showed markedly different buckling behavior, leading to unusual patterns of wrinkles with different wavelengths and orientations toward the force field.  相似文献   

20.
Through in situ reduction of a gold precursor, we have tethered gold nanoparticles (Au NPs) to the side chains of poly{2,7‐(9,9′‐dioctylfluorene)‐co‐4‐diphenylamino‐4′‐bipenylmethylsulfide} (PF‐DBMS) through its ArSCH3 anchor groups. The presence of 1 wt % of the tethered Au NPs led to a reduction in the degree of aggregation of the polymer chains, resulting in a 50 % increase in its quantum yield. The electroluminescence of a 1 wt % Au/PF‐DBMS device was almost four times higher in terms of its maximum brightness and its full‐width‐at‐half‐maximum emission peak was much narrower than that of a pure PF‐DBMS device; the presence of a small amount of Au NPs significantly enhances the electron injection and transport and suppresses the photo‐oxidation of PF‐DBMS.  相似文献   

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