Ultrathin Hybrid Films Research Articles

Preparation of polycyclosiloxane/ZnO nanoparticle hybrid ultrathin films by Layer-by-Layer assembly methods

Layer-by-layer (LbL) assembly methods through alternative dipping processes were used to prepare hybrid nanoassemblies of 5 nm ZnO nanoparticles (ZnONPs) with catechol-functionalized polycyclosiloxane (CFPS60, 51.9 mol% catechol content). ZnONPs were assembled on solid substrates regularly and firmly through interactions with 4 nm-thick CFPS60, proved using UV-vis absorption measurements, atomic force microscopy and peel-off test. ZnONPs exhibited yellow photoluminescence (PL) in CFPS60/ZnONPs films, and the PL intensity increased notably as the number of bilayers increased. The work demonstrates that CFPS60 has a good hybrid nanoassembly formation capability, which is promising for next-generation optoelectronic device applications.

High-speed laser writing of structural colors for full-color inkless printing

It is a formidable challenge to simultaneously achieve wide-gamut, high-resolution, high-speed while low-cost manufacturability, long-term stability, and viewing-angle independence in structural colors for practical applications. The conventional nanofabrication techniques fail to match the requirement in low-cost, large-scale and flexible manufacturing. Processing by pulsed lasers can achieve high throughput while suffering from a narrow gamut of ~15% sRGB or angle-dependent colors. Here, we demonstrate an all-in-one solution for ultrafast laser-produced structural colors on ultrathin hybrid films that comprise an absorbent dielectric TiAlN layer coating on a metallic TiN layer. Under laser irradiation, the absorption behaviours of the TiAlN-TiN hybrid films are tailored by photothermal-induced oxidation on the topmost TiAlN. The oxidized films exhibit double-resonance absorption, which is due to the non-trivial phase shifts both at the oxide-TiAlN interface, and at the TiAlN-TiN interface. By varying the accumulated laser fluence to modulate the oxidation depth, angle-robust structural colors with unprecedented large-gamut of ~90% sRGB are obtained. The highest printing speed reaches 10 cm2/s and the highest resolution exceeds 10000 dpi. The durability of the laser-printed colors is confirmed by fastness examination, including salt spray, double-85, light bleaching, and adhesion tests. These features render our technique to be competitive for industrial applications.

Laser-induced deep-subwavelength periodic nanostructures with large-scale uniformity

Femtosecond lasers are capable of fabricating uniform periodic nanostructures with a near-wavelength periodicity; however, it is challenging to produce subwavelength nanostructures with large-scale uniformity. Here, we investigate femtosecond laser-induced self-assembly of periodic nanostructures on Si-on-Pt hybrid ultrathin films via photothermal-induced oxidation. The coexistence of scattering light and surface plasmon polaritons on the hybrid films gives rise to a diversity of surface morphologies. Depending on the laser power and sample scanning velocity, beyond the traditional one-dimensional nanogratings that exhibit a near-wavelength periodicity, two types of nanostructures with subdiffraction-limit periodicity while large-scale uniformity are also observed. The first type, occurring at high laser energy and low scanning velocity, is generated by the spatial frequency doubling of the traditional laser-plasmon-interfering nanogratings. It exhibits a periodicity of <λ2. The second type, deep-subwavelength nanostructures, takes place at low pulse energy or low scanning velocity. It is in the form of two-dimensional nanoparticles and has a periodicity of <λ4. The far-field laser-plasmon interference associated with near-field scattering is attributed to the formation of such deep-subwavelength nanostructures, as confirmed by finite-difference time-domain numerical simulations. Our work provides a route toward high-throughput laser fabrication of large-scale deep-subwavelength periodic nanostructures.

Ultrathin and flexible hybrid films decorated by copper nanoparticles with a sandwich-like structure for electromagnetic interference shielding

The entering EM waves would be adsorbed by ultrathin Cu deposited layers and the CNT film with a filler of Cu nanoparticles. Thus, there is almost no chance for EM waves to pass through the hybrid membrane due to the multiple internal reflections.

First Principles Study of Reactions in Hybrid Film Growth: The Role of the Organic Precursor

Hybrid materials are a special class of materials with tunable features. This is related to their diphasic structures that leads to multifunctional materials with a wide range of applications. Molecular layer deposition (MLD) enables the fabrication of ultrathin and conformal hybrid films using sequential, selflimiting reactions, similar to ALD. Despite growing interest in these materials, there is little understanding of the atomistic mechanism of MLD film growth.In this contribution, we explore the molecular mechanisms of the growth of different hybrid organic−inorganic thin films by using density functional theory (DFT). The prototype for MLD organic−inorganic hybrids are composed of thin films of aluminium alkoxides, known as ”alucones”. We investigate the MLD reaction products between the post-TMA Monomethyl-Al2O3 (Al-CH3-Al2O3) and Dimethyl-Al2O3 (Al(CH3)2-Al2O3) surface and the organic precursors ethylene glycol (EG) and glycerol (GL). The DFT calculations show that while the organic precursors can bind to the TMA fragments via formation of Al-O bonds and loss of CH4, it is most favorable for the organic precursors to lie flat and create so-called double reactions through two terminal hydroxyl groups with the surface fragments, where the terminal groups bind to Al. For EG this potentially removes all the active sites and growth will be less favorable. For GL the third hydroxyl group is available and growth can proceed. We also showed that the TMA in the next pulse reacts favourably with this OH from GL.We also explored the growth mechanism of magnesium containing hybrid films known as “magnesicone” from the reaction of EG and GL at MgCp-terminated MgO(100) as a model system. Interaction energies presented some clear differences in reaction mechanism of films grown with EG and GL. While the ligand elimination process is favorable for both precursors, EG prefers to orient in a flat configuration and interacts at the MgO(100) surface and GL species prefers to lie in an upright position. As a consequence the change in thickness for GL-based process is larger than for EG-based process, resulting in a thicker GL-based magnesicone compared to the EG-based magnesicone.Finally we use DFT to explore the growth mechanism of titanium-containing hybrid organic−inorganic films known as “titanicones”. We investigate the reaction mechanism of titanicones grown using titanium tetrachloride (TiCl4) as metal source and either ethylene glycol (EG) or glycerol (GL) as organic reactants. This investigation contributes to the understanding of growth process of EG and GL based hybrid films at the molecular level and is valuable in supporting experimental data on hybrid film growth.

Molecular Layer Deposition of “Magnesicone”, a Magnesium-based Hybrid Material

Molecular layer deposition (MLD) offers the deposition of ultrathin and conformal organic or hybrid films which have a wide range of applications. However, some critical potential applications require a very specific set of properties. For application as desiccant layers in water barrier films, for example, the films need to exhibit water uptake and swelling and be overcoatable. For application as a backbone for a solid composite electrolyte for lithium ions on the other hand, the films need to be stable against lithium and need to be transformable from a hybrid MLD film to a porous metal oxide film. Magnesium-based MLD films, called magnesicone, are promising on both these aspects, and thus, an MLD process is developed using Mg(MeCp)(2) as a metal source and ethylene glycol (EG) or glycerol (GL) as organic reactants. Saturated growth could be achieved at 2 to 3 angstrom/cycle in a wide temperature window from 100 to 250 degrees C. The resulting magnesicone films react with ambient air and exhibit water uptake, which is in the case of the GL-based films associated with swelling (up to 10%) and in the case of EG-based magnesicone with Mg(CO)(3) formation, and are overcoatable with an ALD of Al2O3. Furthermore, by carefully tuning the annealing rate, the EG-grown films can be made porous at 350 degrees C. Hence, these functional tests demonstrate the potential of magnesicone films as reactive barrier layers and as the porous backbone of lithium ion composite solid electrolytes, making it a promising material for future applications.

Real-Time Monitoring of Low Pressure Oxygen Molecules over Wide Temperature Range: Feasibility of Ultrathin Hybrid Films of Iridium(III) Complexes and Clay Nanosheets

Abstract An ultrathin film was prepared by hybridizing a cationic Ir(III) complex with exfoliated nanosheets of clay minerals such as natural montmorillonite (denoted by MON) or synthetic saponite (denoted by SAP). The utilized Ir(III) complex with two long alkyl chains was [Ir(dfppy)2(dc9bpy)]+ (fppyH = 2-(2′,4′-difluorophenyl)pyridine; dc9bpy = 4,4′-dinonyl-2,2′-bipyridine) (denoted by DFPPY). Hybridization was performed at an air-water interface between a floating monolayer of the Ir(III) complex and the nanosheets exfoliated in an aqueous subphase. The hybrid floating film thus formed was transferred onto a hydrophilic quartz plate by a vertical dipping method. The emission from the deposited films exhibited rapid reversible change of intensity in response to the introduction or evacuation of oxygen gas in the pressure range of 0.1–101.3 kPa and the temperature range from 253 K to 313 K. The lifetime of the emission decay was measured as a function of oxygen pressure, confirming the occurrence of dynamic quenching of excited Ir(III) complexes by oxygen molecules.

Polyethylene separators modified by ultrathin hybrid films enhancing lithium ion transport performance and Li-metal anode stability

Poor stability of lithium metal anodes in liquid electrolytes hinders its practical application in rechargeable batteries with very high energy density. Herein, we present an approach to tackle the intrinsic problems of Li metal anodes from the standpoint of separators. By a facile and versatile method based on mussel-inspired surface chemistry, a hybrid polydopamine/octaammonium POSS (PDA/POSS) coating was spontaneously formed on the surface of PE separators through the self-polymerization and strong adhesion feature of dopamine. This ultrathin PDA/POSS coating endows PE separators with different surface characteristics while keeping its microporous structure almost unchanged. The altered surface characteristics influence the separator/electrolyte interaction, and lead to remarkable enhanced ionic conductivity (from 0.36 mS cm−1 to 0.45 mS cm−1) and Li+ ion transference number (from 0.37 to 0.47) of PE separators as well as the improved stability of lithium/electrolyte interface, which effectively decreases the electrode polarization and suppresses the lithium dendrites formation, contributing to superior C-rates capability and cycling performance of cells.

Oxygen Sensing by the Hybrid Langmuir-Blodgett Films of Iridium(III) Complexes and Synthetic Saponite on the Basis of Energy Transfer

An ultra-thin hybrid film of amphiphilic iridium(III) complexes and synthetic saponite was manipulated by means of the modified Langmuir-Blodgett method. In the film deposited onto a quartz substrate, the external mixed molecular layer of amphiphilic iridium(III) complexes was reinforced by the inner layer of exfoliated synthetic saponite. As components of the molecular layer, two iridium(III) complexes were used: [Ir(dfppy)2(dc9bpy)]+ (dfppyH = 2-(4′,6′-difluorophenyl) pyridine; dc9bpy = 4,4′-dinonyl-2,2′-bipyridine) (denoted as DFPPY) and [Ir(piq)2(dc9bpy)]+ (piqH = 1-phenyisoquinoline)) denoted as PIQ). The emission spectra from the films changed from blue to red maxima with the decrease of a ratio of DFPPY/PIQ due to the energy transfer from excited DFPPY to PIQ. The intensity of red decreased with the increase of oxygen pressure through the quenching of excited iridium(III) complexes, promising a possibility as an oxygen-sensing film.

Active modulation of visible light with graphene-loaded ultrathin metal plasmonic antennas.

Electro-optical modulation of visible and near-infrared light is important for a wide variety of applications, ranging from communications to sensing and smart windows. However, currently available approaches result in rather bulky devices, suffer from low integrability, and can hardly operate at the low power consumption levels and fast switching rates required by microelectronic drivers. Here we show that planar nanostructures patterned in ultrathin metal-graphene hybrid films sustain highly tunable plasmons in the visible and near-infrared spectral regions. Strong variations in the reflection and absorption of incident light take place when the plasmons are tuned on- and off-resonance with respect to externally incident light. As a result, a remarkable modulation depth (i.e., the maximum relative variation with/without graphene doping) exceeding 90% in transmission and even more dramatic in reflection (>600%) is predicted for graphene-loaded silver films of 1–5 nm thickness and currently attainable lateral dimensions. These new structures hold great potential for fast low-power electro-optical modulation.

Assembly of neutral conjugated polymers with layered double hydroxide nanosheets by the layer-by-layer method

This article reports that the neutral conjugated polymers (NCPs) can also be assembled with exfoliated MgAl-layered double hydroxide (LDH) nanosheets to form the ordered inorganic/organic hybrid ultrathin films via the LbL assembly technique.

Controllable Fabrication of Flexible Multi-Walled Carbon Nanotubes/Reduced Graphene Oxide Hybrid Ultrathin Films

Multi-walled carbon nanotubes/reduced graphene oxide (MWCNT/rGO) hybrid films have attracted increasing massive attention due to their unique advantages such as high conductivity, superior mechanical property and thermal properties. In this work, a novel, facile and low cost method was developed to fabricate the MWCNT/rGO flexible ultrathin hybrid films with the thickness of about 55 nm. These hybrid films can be fabricated repeatedly through layer-by-layer exfoliation on the surface of liquids, and transferred to various substrates. The devices based on MWCNT/rGO hybrid films offer a unique platform for integrating carbon nanomaterials for advanced electronics, energy, and sensor applications.

Layer-by-layer assembled multilayer films of exfoliated layered double hydroxide and carboxymethyl-β-cyclodextrin for selective capacitive sensing of acephatemet

Novel organic–inorganic hybrid ultrathin films were fabricated by alternate assembly of cationic exfoliated Mg–Al-layered double hydroxide (LDH) nanosheets and carboxymethyl-β-cyclodextrin (CMCD) as a polyanion onto a glassy carbon electrode (GCE) via a layer-by-layer (LBL) approach. The multilayer films were then characterized by means of X-ray powder diffraction (XRD), infrared spectroscopy (IR), and scanning electron microscopy (SEM). These films were found to possess a long range stacking order in the normal direction of the substrate with a continuous and uniform morphology. Its electrochemical performance was systematically investigated. Our results demonstrate that such a newly designed (LDH/CMCD)n multilayer film, combining the individual properties of CMCD (a high supramolecule recognition and enrichment capability) together with LDH nanosheets (a rigid inorganic matrix), can be applied to a sensitive, simple, and label-free capacitive detection of acephatemet (AM). Molecular docking calculations further disclose that the selective sensing behavior toward AM may be attributed to the specific binding ability of CMCD to AM. Under the optimized conditions, the capacitive change of AM was proportional to its concentration ranging from 0.001 to 0.10μgmL−1 and 0.1 to 0.8μgmL−1 with a detection limit 0.6ngmL−1 (S/N=3). Toward the goal for practical applications, this simple probe was further evaluated by monitoring AM in real samples.

Ultrathin hybrid films of polyoxohydroxy clusters and proteins: layer-by-layer assembly and their optical and mechanical properties.

The hierarchical assembly of inorganic and organic building blocks is an efficient strategy to produce high-performance materials which has been demonstrated in various biomaterials. Here, we report a layer-by-layer (LBL) assembly method to fabricate ultrathin hybrid films from nanometer-scale ionic clusters and proteins. Two types of cationic clusters (hydrolyzed aluminum clusters and zirconium-glycine clusters) were assembled with negatively charged bovine serum albumin (BSA) protein to form high-quality hybrid films, due to their strong electrostatic interactions and hydrogen bonding. The obtained hybrid films were characterized by scanning electron microscope (SEM), UV-vis, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and X-ray diffraction (XRD). The results demonstrated that the cluster-protein hybrid films exhibited structural homogeneity, relative transparency, and bright blue fluorescence. More importantly, these hybrid films displayed up to a 70% increase in hardness and up to a 100% increase in reduced Young's modulus compared to the pure BSA film. These hybrid cluster-protein films could be potentially used as biomedical coatings in the future because of their good transparency and excellent mechanical properties.

A general strategy for hybrid thin film fabrication and transfer onto arbitrary substrates.

The development of thin film-based structures/devices often requires thin films to be transferred onto arbitrary substrates/surfaces. Controllable and non-destructive transfer method, although highly desired, remains quite challenging. Here we report a general method for fabrication and transfer of hybrid (ultra)thin films. The proposed solution-based in-situ transfer method shows not only its robust ability for thin film transfer onto arbitrary substrates but also its highly controlled and non-destructive characteristic. With a hole structure as the support, fully-stretched free-standing thin film is prepared. The successful transfer to a curved surface demonstrates the possibility for production of thin film-coated complex optical components. Ultrathin (35 nm) hybrid film transferred onto PET (50 μm thick) shows high transparency (>90% in visible range), conductivity (1.54 × 104 S/m), and flexibility (radius of curvature down to mm scale). The reported transfer method would provide a powerful route towards complex thin film-based structures/devices.

Development of an ultra-thin film comprised of a graphene membrane and carbon nanotube vein support

Graphene, exhibiting superior mechanical, thermal, optical and electronic properties, has attracted great interest. Considering it being one-atom-thick, and the reduced mechanical strength at grain boundaries, the fabrication of large-area suspended chemical vapour deposition graphene remains a challenge. Here we report the fabrication of an ultra-thin free-standing carbon nanotube/graphene hybrid film, inspired by the vein-membrane structure found in nature. Such a square-centimetre-sized hybrid film can realize the overlaying of large-area single-layer chemical vapour deposition graphene on to a porous vein-like carbon nanotube network. The vein-membrane-like hybrid film, with graphene suspended on the carbon nanotube meshes, possesses excellent mechanical performance, optical transparency and good electrical conductivity. The ultra-thin hybrid film features an electron transparency close to 90%, which makes it an ideal gate electrode in vacuum electronics and a high-performance sample support in transmission electron microscopy.

Star Polymer Unimicelles on Graphene Oxide Flakes

We report the interfacial assembly of amphiphilic heteroarm star copolymers (PSnP2VPn and PSn(P2VP-b-PtBA)n (n = 28 arms)) on graphene oxide flakes at the air-water interface. Adsorption, spreading, and ordering of star polymer micelles on the surface of the basal plane and edge of monolayer graphene oxide sheets were investigated on a Langmuir trough. This interface-mediated assembly resulted in micelle-decorated graphene oxide sheets with uniform spacing and organized morphology. We found that the surface activity of solvated graphene oxide sheets enables star polymer surfactants to subsequently adsorb on the presuspended graphene oxide sheets, thereby producing a bilayer complex. The positively charged heterocyclic pyridine-containing star polymers exhibited strong affinity onto the basal plane and edge of graphene oxide, leading to a well-organized and long-range ordered discrete micelle assembly. The preferred binding can be related to the increased conformational entropy due to the reduction of interarm repulsion. The extent of coverage was tuned by controlling assembly parameters such as concentration and solvent polarity. The polymer micelles on the basal plane remained incompressible under lateral compression in contrast to ones on the water surface due to strongly repulsive confined arms on the polar surface of graphene oxide and a preventive barrier in the form of the sheet edges. The densely packed biphasic tile-like morphology was evident, suggesting the high interfacial stability and mechanically stiff nature of graphene oxide sheets decorated with star polymer micelles. This noncovalent assembly represents a facile route for the control and fabrication of graphene oxide-inclusive ultrathin hybrid films applicable for layered nanocomposites.

Bifunctional sensor of pentachlorophenol and copper ions based on nanostructured hybrid films of humic acid and exfoliated layered double hydroxide via a facile layer-by-layer assembly

A new, highly sensitive bifunctional electrochemical sensor for the simultaneous determination of pentachlorophenol (PCP) and copper ions (Cu2+) has been developed, where organic–inorganic hybrid ultrathin films were fabricated by alternate assembly of humic acid (HA) and exfoliated Mg–Al-layered double hydroxide (LDH) nanosheets onto ITO substrates via a layer-by-layer (LBL) approach. The multilayer films were then characterized by means of UV–vis spectrometry, scanning electron microscopy (SEM), and atomic force microscope (AFM). These films were found to have a relatively smooth surface with almost equal amounts of HA incorporated in each cycle. Its electrochemical performance was systematically investigated. Our results demonstrate that such a newly designed (LDH/HA)n multilayer films, combining the individual properties of HA (dual recognition ability for organic herbicides and metal ions) together with LDH nanosheets (a rigid inorganic matrix), can be applied to the simultaneous analysis of PCP and Cu(II) without interference from each other. The LBL assembled nanoarchitectures were further investigated by X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR), which provides insight for bifunctional sensing behavior. Under the optimized conditions, the detection limit was found to be as low as 0.4nM PCP, well below the guideline value of PCP in drinking water (3.7nM) set by the United States Environmental Protection Agency (U.S. EPA), and 2.0nM Cu2+, much below the guideline value (2.0mgL−1, ~31.2nM) from the World Health Organization (WHO), respectively. Toward the goal for practical applications, this simple and cost-effective probe was further evaluated by monitoring PCP and Cu(II) in water samples.

Interfacial assembly and characterization of hybrid ultrathin films of manganese 5,10,15,20-tetra (4-pyridyl) porphine chloride tetrakis (methochloride) and its polymeric derivative with poly (4-vinylpyridine)

Monolayers of a water-soluble metalloporphyrin, manganese tetra-(4-pyridyl) porphine chloride tetrakis (methochloride) (MnTMPyP), and its polymeric derivative with poly (4-vinylpyridine) (MnTMPyP-PVP) have been investigated at the air–water interface. These monolayers were transferred on the substrate surfaces to form hybrid ultrathin films by the Langmuir-Blodgett (LB) method. It was revealed that, although the water-soluble MnTMPyP could not form insoluble monomolecular layer on the pure water surface, it could be stabilized on the NaB(C6H5)4 subphase surface due to an electrostatic interaction between MnTMPyP and B(C6H5)4−, resulting in the formation of MnTMPyP-B(C6H5)4 hybrids. On the other hand, its polymeric derivative of MnTMPyP-PVP could form stable insoluble monolayers on the pure water, NaB(C6H5)4 and Na2PdCl4 subphase surfaces. Composition, structure and microscopic morphology of the as-prepared LB films were characterized by using UV–vis absorption, infrared and X-ray photoelectron spectroscope, as well as scanning electron microscope. The results suggested formation of the hybrid MnTMPyP-B(C6H5)4 and MnTMPyP-(PVP-)B(C6H5)4 and Pd-MnTMPyP-PVP coordination polymer ultrathin films at the interfaces. Cyclic voltammograms of the LB films revealed two couples of reversible redox waves centered at 0.2–0.3 and −0.1 to −0.2V (vs Ag/AgCl), corresponding to the Mn(II)/Mn(III)TMPyP-(PVP-)B(C6H5)4 and Mn(III)/Mn(IV)TMPyP-(PVP-)B(C6H5)4 electron transfer processes of the manganese porphyrins in the LB films.

Hybrid films of reduced graphene oxide with noble metal nanoparticles generated at a liquid/liquid interface for applications in catalysis

Free-standing ultra-thin hybrid films of reduced graphene oxide (rGO) with Au, Ag and Pd nanoparticles are generated at an aqueous/organic interface by in situ chemical reduction and spontaneous assembly. The reduction is initiated at a ‘bare’ interface or a ‘modified’ interface in a single step or two-step synthetic strategy. The hybrid materials are characterized by UV-visible, infra-red and Raman spectroscopies, X-ray diffraction, scanning electron (SEM), transmission electron (TEM) and atomic force microscopies (AFM). UV-visible spectra confirm the presence of isolated metal nanoparticles grafted on to rGO layers and Raman spectra signal a charge transfer across the constituent metal nanoparticles and rGO in the hybrid material. SEM and AFM studies show that the morphology of the hybrid films constitutes a homogeneous dispersion of metal nanoparticles and rGO for reduction at the ‘bare’ interface, and a random grafting of metal nanoparticles on rGO for reduction at the ‘modified’ interface. A mechanism for the formation of the films is proposed that involves a simultaneous transport and reduction of GO sheets and metal precursor at the interface or a directed reduction of metal precursor on rGO surface, facilitated by external aids. The utility of these hybrid films as catalysts is exemplified in p-nitrophenol reduction. Our method provides a fast, simple and inexpensive route to obtain free-standing hybrid films of rGO with metal nanoparticles for various applications.