Amorphous Nanofilm Research Articles

Interfacial oligomer splicing toward 3D silicon-centered polyimine nanofilm for rapid molecule/ion differentiation

3D porous organic polymers —renowned for rich interpenetrated, hierarchical pores and exceptional structural durability— showcase the potential for precise membrane-based separations. However, the challenge lies in processing these chemically stable polymers into a selective thin film under mild conditions. Herein, an interfacial oligomer splicing (IOS) approach via Schiff-base reactions is presented to create 3D silicon-centered porous polyimine (PPIn) nanofilms. The pre-synthesized oligomers from 4,4′,4″,4‴-silanetetrayltetrabenzaldehyde (TFS) and m-phenylenediamine (MPD) with high steric hindrance and hydrophobic character are precisely confined at the oil boundary, initiating IOS to yield an amorphous nanofilm on a Kevlar hydrogel surface. These silicon-centered 3D nanofilms exhibited an exceptional thermal and mechanical stability, while offering abundant low-resistance transport nanochannels. The nanofilm backbone, composed of rigid nonplanar aromatic skeleton and robust imine linkage, contributed to open and interpenetrated selective nanochannels, corroborated by both experimental and simulation and results. It was shown that 83-nm-thick PPIn nanofilms grown on the hydrogel achieved high-efficient molecule/ion differentiation, evident in excellent dye retention (>99.0 %), high NaCl permeation (92.8 %), and remarkable water permeability (74.3 L m−2 h−1 bar−1). This study establishes an innovative IOS approach for fabricating silicon-centered 3D-POP membranes and underscores their potential for efficient molecule/ion differentiation.

Amorphous Nickel Nanofilms for Efficient Hydrogen Generation from ammonia borane

AbstractClean and sustainable hydrogen production through liquid hydrogen storage material requires highly active and stable earth‐abundant non‐noble metal to replace expensive and rare noble metals. Herein, nickel nanofilms (Ni/NiO‐NFs) were prepared by the ionic liquid/water interface route. The cationic carbon chain length of the ionic liquid affects the phase composition of the nickel nanofilm, and the ionic liquid with [OMIm][PF6] as the anion has good thermal stability during the synthesis process. The efficiency of Ni/NiO‐NFs catalysts was tested by comparative kinetic analysis of the AB hydrolysis for hydrogen production. The as‐prepared Ni/NiO‐NFs catalyst exhibits excellent hydrogen generation performances, including a hydrogen production rate (2917 ml min−1 gNi−1), and a low activation energy (48.1 kJ/mol). The transition of nickel oxide to metallic nickel and the destruction of the catalyst structure is responsible for the decreased durability. This work highlights the significance of amorphous nanofilms catalysts via the ionic interface method on the regulation of activity for AB hydrolysis.

Magnetron Sputtered Non‐Toxic and Precious Element‐Free TiZrGe Metallic Glass Nanofilms with Enhanced Biocorrosion Resistance

AbstractThe chemical composition and structural state of advanced alloys are the decisive factors in optimum biomedical performance. This contribution presents unique TiZrGe metallic glass thin‐film compositions fabricated by magnetron sputter deposition targeted for nanocoatings for biofouling prevention. The amorphous nanofilms with nanoscale roughness exhibit a large relaxation and supercooled liquid regions as revealed by flash differential scanning calorimetry. Ti68Zr8Ge24 shows the lowest corrosion (0.17 µA cm−2) and passivation (1.22 µA cm−2) current densities, with the lowest corrosion potential of −0.648 V and long‐range stability against pitting, corroborating its excellent performance in phosphate buffer solution at 37 °C. The oxide layer is comprised of TiO2, TiOx and ZrOx, as determined using X‐ray photoelectron spectroscopy by short‐term ion‐etching of the surface layer. The two orders of magnitude increase in the oxide and interface resistance (from 14 to 1257 Ω cm2) along with an order of magnitude decrease in the capacitance parameter of the oxide interface (from 1.402 × 10−5 to 1.677 × 10−6 S sn cm−2) of the same composition is linked to the formation of carbonyl groups and reduction of the native oxide layer during linear sweep voltammetry.

Tuning Fe doping Co/CoOx amorphous nanofilms to enhance the hydrolytic activity towards ammonia borane

Hydrolytic dehydrogenation of ammonia borane (AB) has attracted much attention due to its high hydrogen content and stability. Therefore, the design and construction of low-cost and high-performance catalysts for AB hydrolysis are of great significance. In this work, Co/CoFeOx-X (X is the additional content of Fe precursor) bimetallic oxide nanofilms having an amorphous structure were prepared on an (IL)/water interface for the hydrolysis of AB. Strategies including the rapid addition of metal precursors and variation of Co/Fe atom ratios were employed to induce an amorphous structure for inhibiting the rearrangement of the formed metal nuclei and optimizing the alloying effect on the IL/water interface. This ultrathin amorphous nanofilm structure can expose more metal active sites. Moreover, the electronic interaction between Fe and Co after doping Fe into the Co/CoOx nanofilms facilitates the adsorption and activation for AB and H2O molecules. As a result, the optimized Co/CoFeOx-25 catalyst exhibits excellent catalytic activity with a turnover frequency (TOF) value of 12.25 molH2·molCo–1·min–1, which is considerably higher than that of the monometallic Co/CoOx catalyst. This enhanced activity can be ascribed to the morphology advantages and the electronic effect of Fe and Co on the Co/CoFeOx-25 catalyst. This work provides a promising method to design the highly efficient non-noble metal catalysts for the hydrolysis of chemical hydrides.

Tuning Fe Doping Co/Coox Amorphous Nanofilms to Enhance the Hydrolytic Activity Towards Ammonia Borane

Tuning Fe Doping Co/Coox Amorphous Nanofilms to Enhance the Hydrolytic Activity Towards Ammonia Borane

Direct Distinguishing of Methanol over Ethanol with a Nanofilm‐Based Fluorescent Sensor

AbstractMethanol is extremely toxic to humans if ingested or if vapors are inhaled. Facile and reliable detection of methanol is an efficient way to reduce the risk of methanol poisoning. A great challenge in methanol detection lies in distinguishing methanol under high ethanol background. In this work, a nanofilm‐based fluorescent sensor for direct distinguishing methanol from pure ethanol or liquor is presented, where no sample pretreatment or sensor array is needed. The flexible, uniform, and amorphous nanofilm is synthesized via dynamic covalent binding‐driven self‐assembly of BTN and CB‐CHO at air/DMSO interface. The nanofilm shows a large Stokes shift (≈175 nm) and excellent photostability. Different from sensing films based on drip‐permeance or drop cast of organic fluorophores, sensing performance of the nanofilm shows little dependence on substrate. With the film, an optical sensor for methanol vapor detection is built and it can distinguish methanol not only from the mixture of methanol and ethanol (with ethanol content up to 90%), but also from the liquor (45% vol). The sensor shows excellent reusability and high selectivity over many commonly used organic solvent vapors. Moreover, the sensor can be used to discriminate industrial alcohol from medical alcohol and detect methanol gas leak.

Surface-governed electrochemical hydrogenation in FeNi-based metallic glass

The hydrogenation and oxide formation behavior of Fe–Ni-based metallic glasses (MGs), where measurements by the conventional gas-solid reaction method are difficult, is analyzed by a two-step approach: chronoamperometry followed by cyclic voltammetry (CA + CV). We introduce a concept of effective volume by measuring the thickness of the region where the hydrogen and hydroxyl ion interactions with Fe-based MG take place, which is characterized by high-angle annular dark-field scanning transmission electron microscopy. A very constant film thickness influenced by the OH− and H+ is confirmed by TEM, where the chemical homogeneity is maintained within this region. The weight percent of hydrogen and the corresponding hydrogen-to-metal ratio are determined as 1.16% and 0.56, respectively. When compared to previous studies conducted by the electrochemical-permeation method, the H/M ratio is found to be an order of magnitude larger. Electrochemical impedance spectroscopy (EIS) and subsequent equivalent circuit modeling (ECM) of the tested ribbons resolve the surface-diffusion processes for hydride formation and oxidation kinetics. This contribution provides a different perspective for the design and study of low-cost and high-performance amorphous nanofilms for hydrogen-energy applications, particularly when the common gas-adsorption methods are problematic.

Electrical transport in amorphous nanofilms embedded with crystalline grains at low temperatures

Amorphous and ferromagnetic Al–Ni nanofilms have been grown by the magnetron-sputtering method with some nanosized crystalline grains embedded therein. Resistivity is demonstrated to transit from a positive temperature coefficient to a negative temperature coefficient (NTC) with increasing the fraction of Ni atoms in the Al–Ni nanofilms. The lattice disorder is deduced to induce the Anderson localization of electrons and the formation of polarons so that the NTC of the resistivity is driven in the Al–Ni nanofilms, different from that in the elemental Al and Ni nanofilms. The electron transport in the Al–Ni nanofilms is dominated by polaron hopping while it is also determined by electron–magnon and electron–phonon scatterings. The electron–magnon scatterings are further revealed to have a more important contribution to the electron transport at low temperatures than electron–phonon scatterings in the amorphous Al–Ni nanofilms. A so-called polaron–metal physical model has thus been proposed to well explain the electron transport in disorder lattices with crystalline grains embedded therein. This study may help to optimize the design of nano-engineered devices.

Scaling theory of the mechanical properties of amorphous nano-films

Numerical Simulations are employed to create amorphous nano-films of a chosen thickness on a crystalline substrate which induces strain on the film. The films are grown by a vapor deposition technique. Using the exact relations between the Hessian matrix and the shear and bulk moduli we explore the mechanical properties of the nano-films as a function of the density of the substrate and the film thickness. The existence of the substrate dominates the mechanical properties of the combined substrate-film system. Scaling concepts are then employed to achieve data collapse in a wide range of densities and film thicknesses.

A Universal Strategy to Design Superior Water‐Splitting Electrocatalysts Based on Fast In Situ Reconstruction of Amorphous Nanofilm Precursors

The development of efficient bifunctional electrodes with extraordinary mass activity and robust stability is an eternal yet challenging goal for the water-splitting process. Surface reconstruction during electrocatalysis can form fresh-composition electrocatalysts with unusual amorphous phases in situ, which are more active but difficult to prepare by conventional methods. Here, a facile strategy based on fast reconstruction of amorphous nanofilm precursors is proposed for exploring precious-metal-free catalysts with good electronic conductivity, ultrahigh activity, and robust stability. As a proof of concept, an amorphous SrCo0.85 Fe0.1 P0.05 O3- δ (SCFP) nanofilm precursor with weak chemical bonds deposited onto a conductive nickel foam (NF) substrate (SCFP-NF) is synthesized by utilizing a high-energy argon plasma to break the strong chemical bonds in a crystalline SCFP target. The quickly reconstructed SCFP-NF bifunctional catalysts show ultrahigh mass activity of up to 1000 mA mg-1 at an overpotential of 550 mV and extremely long operational stability of up to 650 h at 10 mA cm-2 , significantly overperforming state-of-the-art precious-metal catalysts. Such a strategy is further demonstrated to be a universal method, which can be applied to accelerate the reconstruction of other material systems to obtain various efficient electrocatalysts.

Thermal Stability and Deformation Mechanisms in Graphene- or Silicene-Reinforced Layered and Matrix Metallic Composites

The methods of increasing the structural and thermodynamic stability of the interface states in metal/2D crystal interfaces are considered. These states determine the main characteristics of layered and matrix metal/graphene and metal/silicene nanocomposites (M/2D–G and M/2D–Si, were M = Al, Mg, Ir, Pd, Ru, Ni, Ti, Ag), which can be fabricated by the dispersion of graphene or silicene nanoparticles in melts and by an additive 3D typing technology (PVD, CVD) with layer-by-layer growth of metallic crystalline or amorphous nanofilms on preliminarily deposited graphene or silicene layers (from one to several layers). The experimental data and the results of combined calculations of the structure, the unique electronic properties, and the mechanisms of ultrahigh strength of the nanocomposites, which were performed in terms of the density functional theory, are systematically analyzed.

Nanocrystallization of Anatase or Rutile TiO2 by Laser Treatment

We present an original way to produce anatase titanium dioxide (TiO2) nanoparticles from amorphous nanofilm. TiO2 nanofilm has been deposited by reactive magnetron sputtering on glass and subsequently irradiated by ultraviolet (UV) radiation using a krypton-fluor (KrF) excimer laser. X-ray diffraction and transmission electron microscopy reveal that the film has been nanostructured. Experimental results are compared with theoretical predictions concerning the structural phase stability with the size of nanostructures. The size distribution of spherical nanoparticles confirms that the most stable phase is anatase for particle sizes smaller than ∼40 nm and rutile for sizes bigger than ∼40 nm.

Defects and separation of amorphous nanofilms from crystalline substrates

The conditions of separation of an amorphous nanofilm from a crystalline substrate are theoretically studied in terms of a disclination-dislocation model for a crystal-glass interface. In this model, such an interface is characterized by a high density of disclinations and dislocations. A criterion for the separation of an amorphous nanofilm from a crystalline substrate is obtained. The critical nanofilm thickness above which a film begins to separate is calculated as a function of the characteristics of the disclination-dislocation system and the dilatation misfit.