Properties Of Nanofilms Research Articles

The peeling behavior of compliant nano-films in adhesive contact with a planar rigid substrate: Insights from molecular dynamics and continuum mechanics

Peeling compliant nano-films from supporting substrates is crucial in the mechanical exfoliation and transfer processes. However, the peeling behavior, especially concerning the peeling stiffness and peak peeling force, exhibits intricate interplay with the geometric and material properties of nano-films, as well as interfacial interactions, which have yet to be fully elucidated. In this work, both classical molecular dynamics (MD) simulations and continuum analysis are adopted to investigate the entire peeling process of compliant nano-films from a planar rigid substrate. Considering the atomic structure and van der Waals (vdW) interactions at the interface, we establish a continuum mechanics model to describe the entire peeling process, encompassing the initial, transitional, steady-state, and unstable peel-off stages. The theoretical predictions are reasonably consistent with the results obtained by MD simulations. The effects of film length and interface toughness on the peeling process, the peeling stiffness and peak peeling force, are thoroughly investigated, and a phase diagram for the peeling deformation modes is quantitatively constructed. Finally, dimensional analysis yields scaling relations for the peak peeling force in terms of the length and bending stiffness of compliant nano-films, as well as the governing parameters for interfacial vdW interactions. These results contribute to a better understanding of the peeling mechanics of various two-dimensional nano-films (e.g., graphene, hexagonal boron nitride, and molybdenum disulfide) adhered to substrates.

Surface effects and symmetry lowering effect on the anisotropic bending and equilibrium of freestanding nanofilms

A self-consistent theory for describing self bending, self equilibrium and symmetry lowering of nanofilms was proposed in this paper. The lowered symmetry and corresponding additional elastic parameter were considered to describe the mechanical properties of nanofilms. A freestanding nanofilm may spontaneously roll into a nanotube due to intrinsic surface stress imbalance. It is not necessarily isotropic for surface stress. The anisotropic surface stress is possible, Si nanofilm with (001) surface may behave (2 × 1) reconstruction, for example. The anisotropic surface stress induces anisotropic bending. And then, the isotropic Stoney formular should be modified to suit the anisotropic surface stress effect. A theory for anisotropic bending should be established. On the other hand, intrinsic surface stress balance induces uniform in-plane deformation of nanofilms. The theory in this paper was used to predict equilibrium strains of Cu, Ni, Ag, Au, Pd and Pt nanofilms, and was used to research Si nanofilm rolling behavior.

Study of the Influence of the Cobalt Structure on the Magnetic Properties of Nanofilms

Study of the Influence of the Cobalt Structure on the Magnetic Properties of Nanofilms

A novel method to predict nanofilm morphology on arbitrary-topographical substrate

As physical properties of nanofilms are strongly influenced by their adhered substrates and presented morphologies, it is of vital importance to determine their attaching morphologies on substrates. However, the complex topography of substrate in the practical applications hinders the prediction of attached nanofilm morphology. Previous theoretical methods fail to analyze the complex topography, and molecular dynamics (MD) simulations are limited to small time and size scales. In order to predict the morphology of a nanofilm with an arbitrary size on a substrate with an arbitrary topography, a novel universal method is proposed by combining the mechanical analysis, discrete cosine transform, and multi-resolution analysis together, named multi-resolution discrete cosine transform (MRDCT) method. In this method, the attaching analysis for a complex-topographical substrate is transformed level by level into a sequence of simple mechanical analyses for a 2D-cosine-topographical substrate, of which a semi-analytical model is derived in advance based on the principle of minimum potential energy. Taking the advantages of the pre-derived mechanical model and the multi-level analysis, the MRDCT method has an extremely high efficiency, only about 10−4 of time cost of MD simulations, and moreover, it is not limited by the size scale of nanofilms. The results from both MD simulations and experiments highlight the competency of this method for various complex-topographical substrates. Furthermore, a general conformation criterion in terms of the substrate roughness is derived analytically based on the MRDCT method to assess whether the substrate can be fully conformed by the nanofilm. The proposed MRDCT method can not only be used in the mechanical analysis of film/substrate systems but also provide a new paradigm to solve other complex mechanical problems.

A Study on the Improvement of Using Raw Lacquer and Electrospinning on Properties of PVP Nanofilms.

Raw lacquer (RL), ethanol being used as the solvent, was added to polyvinyl pyrrolidone (PVP) and then electrospun into RL/PVP nanofilms. Manufacturing parameters such as RL/PVP ratio, voltage, flow velocity, needle type, and the distance between syringe and the collection board were systematically investigated. A scanning electronic microscope (SEM) was used to observe the surface morphology of nanofilms; the block drop method was used to measure the water contact angle; the mechanical properties of RL/PVP nanofilms of different proportions were tested by universal material testing machine; and Fourier-transform infrared spectroscopy (FT-IR) was used to characterize the structure. Based on the water resistance and acid resistance measurements, the proposed nanofilms demonstrated to be water and acid resistant were successfully produced. The results show that PVP that melts in water becomes incompatible with water after adding raw lacquer, and the acid resistance is greatly improved. Furthermore, the smaller the fiber diameter, the better the mechanical properties of the nanofilms are under low ratio of RL/PVP. With a high proportion of RL/PVP, the inner structure of the nanofilm is denser, and the water resistance and acid resistance are better. The dense structure can protect the inner material of the nanofilms.

Воздействие некоторых сложных хемостимуляторов и модификаторов на термооксидирование InP

Воздействие некоторых сложных хемостимуляторов и модификаторов на термооксидирование InP

Investigation and preparation of biodegradable starch-based nanofilms for potential use of curcumin and garlic in food packaging applications

In this study, biodegradable starch-based nano films were developed by turmeric extract curcuma longa (CC), octaphenyl-polyhedral oligomeric silsesquioxane (POSS), garlic extract with antibacterial properties (GC) and clay nanoparticles. Ag+-Mt-POSS-CC-CS, Mt-CC-CS and Mt-GC-CS nanofilms were synthesized as the final products. The antibacterial and surface-active corn starch-based nanofilms that were synthesized were analyzed by using the methods of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM). After this, the antibacterial resistances of the corn starch nanofilms against the bacteria Salmonella and Staphylococcus aureus (S. aureus) and their surface-active properties against the bacteria S. aureus, E. coli, Listeria monocytogenes and Salmonella were examined. The synthesized nano films were subjected to migration analyses, which are an important criterion for food packaging films, and their results were compared.According to the results of the analysis, while the starch nanofilms containing garlic showed antibacterial resistance against salmonella and S. aureus bacteria, the starch nano films containing curcumin and octaphenyl-POSS did not form an inhibition zone. Comparing surface activity properties, curcumin and octaphenyl-POSS-containing nano films showed surface activity, while the garlic-containing nanofilms did not show surface activity. This result shows that the mechanical properties of nanofilm containing garlic have given stronger results. Migration analysis results show that the synthesized nanofilm has found to suitable for use in the packaging of all food products such as milk products, fatty foods, liquid, acidic and dry foods according to the results of all migration analyses.

Growth and Properties of Nanofilms Produced by the Thermal Oxidation of MnO2/InP under the Effect of Mn3(PO4)2

MnO2 surface layers and the addition of Mn3(PO4)2 through the gas phase have an advantageous combined effect on the thermal oxidation of InP, increasing the growth rate of the oxide film, ensuring rapid chemical binding of the indium, blocking its diffusion into the film, and activating phosphate formation processes, which leads to the formation of dielectric nanofilms with resistivity as high as 1010 Ω cm.

Surface elasticity and surface slice thickness effects on the elastic properties of nanofilms

A formula for size-dependent Young’s modulus was obtained by considering surface elasticity effect and surface slice thickness effect. Due to the influence of surface slice thickness, the second and third surface modifications, i.e., nonlinear surface modifications were introduced. The first surface modification, i.e., the linear surface modification of Young’s modulus is induced by surface elastic coefficient and nonlinear surface modifications are induced by surface slice thickness. For given surface Young’s modulus Ys, surface slice thickness strongly enhanced surface effect; while for given surface elastic coefficient S, surface slice thickness weakened surface effect. The influence of surface slice thickness effect on nanofilm effective Young’s modulus is more obviously in the condition that the surface slice thickness is comparable with film thickness, the film with only several nanometers or with oxidated surface for example. The present theoretical scheme is envisaged to provide helpfulness for further research of mechanical properties of nanofilms and useful insights for designing and application of nanofilm-based devices.

Continuous assembly of supramolecular polyamine-phosphate networks on surfaces: preparation and permeability properties of nanofilms.

Supramolecular self-assembly of molecular building blocks represents a powerful "nanoarchitectonic" tool to create new functional materials with molecular-level feature control. Here, we propose a simple method to create tunable phosphate/polyamine-based films on surfaces by successive assembly of poly(allylamine hydrochloride) (PAH)/phosphate anions (Pi) supramolecular networks. The growth of the films showed a great linearity and regularity with the number of steps. The coating thickness can be easily modulated by the bulk concentration of PAH and the deposition cycles. The PAH/Pi networks showed chemical stability between pH 4 and 10. The transport properties of the surface assemblies formed from different deposition cycles were evaluated electrochemically by using different redox probes in aqueous solution. The results revealed that either highly permeable films or efficient anion transport selectivity can be created by simply varying the concentration of PAH. This experimental evidence indicates that this new strategy of supramolecular self-assembly can be useful for the rational construction of single polyelectrolyte nanoarchitectures with multiple functionalities.

Controlling structure and properties of polyamide nanofilms by varying amines diffusivity in organic phase

Optimizing thickness and structure of polyamide (PA) selective layer of thin film composite (TFC) membranes is critical to improve the performance of the membranes. Here, we employed controlled interfacial polymerization to fabricate free-standing PA nanofilms on a thermal-reversible agarose hydrogel. Manipulation of the nanofilms structure was approached by tailoring the amine diffusivity in organic phase composed of benzene and n-hexane mixtures. An UV–vis method was firstly developed to in-situ monitor the diffusion process of amines from aqueous phase to organic phase. The structure and properties of the nanofilms were systematically analyzed by SEM, AFM and ATR-IR. Experimental results revealed that the diffusion kinetics of amines in organic phase is strongly depends on the content of benzene in the mixture solvent and therefore give rise to different thickness and structure of the nanofilms. The amines diffusion rate was accelerated at higher benzene content, causing a rougher surface, thicker thickness and smaller Young's modulus of the resultant nanofilms. Remarkably, with good fitting coefficient of R2 = 0.9936, the thickness of the nanofilms exhibits a linear relationship with their surface roughness.

Symmetry lowering and surface elasticity effects on Young’s modulus and Poisson’s ratio of nanofilms

Physical and mechanical properties of nanosized materials and structures are strongly affected by surface effects. In this paper, a self-consistent theoretical scheme for describing the elastic properties of nanofilms was proposed. The Young’s modulus, biaxial modulus and Poisson’s ratio of nanofilms were obtained analytically with considerations of symmetry lowering, surface elasticity, elastic parameter splitting and additional elastic coefficient. Applications of present theory to elastic systems such as Si nanofilm Young’s modulus, Cu nanofilm biaxial modulus and Poisson’s ratio yield good agreement with previous calculated results. We found that Young’s modulus and Poisson’s ratio were split due to symmetry lowering, and this splitting confirms the symmetry lowering. For a nanofilm with a given thickness, Young’s modulus and biaxial modulus increase with surface elastic coefficients increase except $$c_{{12}}^{{\alpha ,s}}$$ . The larger positive $$c_{{12}}^{{\alpha ,s}}$$ drives Young’s modulus towards smaller abnormally. The present study in this paper is envisaged to provide useful insights for the design and application of nanofilm-based 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.

The structural and optical properties of Y (Y = Al, B, Si and Ti)-doped ZnO nano thin films from the first principles calculations

Based on the density functional theory, the structural stability and optical properties of undoped and Y (Y = Al, B, Si and Ti)-doped ZnO nano thin films are investigated. The good stability of the films based on the ZnO (0 0 0 1) can be obtained when the layer is larger than 12. Moreover, the dielectric function, refractive index, absorption, and reflectivity of doped ZnO nano thin films have been analyzed in detail. In the visible light range, the values of ZnO films from 12 to 24 layers are all smaller than those of the bulk. And with the augment of the layers, the values keep increasing. All the results signify that the nano film of 12 layers possesses the lowest reflectivity and weakest absorption. In addition, there is an evident impact of some doped element on the properties of nano films. The absorption and reflectivity of Ti, Si-doped ZnO nano thin films are higher than those of the clean films, while Al, B-doped are lower, especially B-doped. Moreover, the conductivity of the doped structure is better than that of the bulk. Thus, the B-doped ZnO nano thin films could be potential candidate materials of transparent conductive films.

Kalay dioksit nano ince filmlerin üretimi ve morfolojik karakterizasyonu

Tin dioxide (SnO 2 ) nanofilms were obtained by coating the sols produced by the sol-gel method on stainless steel substrates with a spin coating device. Tartaric acid which acts as a gelation agent were used as a stabilizer in the production of sols. In addition to the nanofilms produced with and without stabilizer addition, SnO 2 film coatings were also performed with an aging process involving tartaric acid to demonstrate the effect of aging on grain size. The morphology, structure, crystal and grain size of SnO 2 nanofilms were investigated and the effect of tartaric acid stabilizer on grain size and morphology was investigated. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) for the characterization of surface properties of nanofilms, and also X-ray diffraction (XRD) analysis for the examination of the crystal structure and the calculation of the crystal size were performed.

Structural and optical properties of single and bilayer silver and gold films

An experimental study of structural and optical properties of silver and gold thin films, as well as bilayer films based on these metals, has been carried out. To study properties of nanofilms, reflection spectra upon excitation of surface plasmons in the Kretschmann geometry and spectra of ellipsometric parameters have been investigated. The reflection spectra were analyzed using a theoretical model for determining (effective) dielectric constants of the films. The calculated dielectric constants of the films differ from data obtained by ellipsometry. The features in determining dielectric constants by different methods and characteristics of manufactured films in relation to the influence of the substrate are discussed.

Temperature-dependent specific heat of suspended platinum nanofilms at 80–380 K**Project supported by the National Natural Science Foundation of China (Grant Nos. 51327001 and 51636002), and partially supported by CREST, JST, and JSPS KAKENHI (Grant Nos. 16H04280, 26289047, 16K14174, and 16K06126).

Metallic nanofilms are important components of nanoscale electronic circuits and nanoscale sensors. The accurate characterization of the thermophysical properties of nanofilms is very important for nanoscience and nanotechnology. Currently, there is very little specific heat data for metallic nanofilms, and the existing measurements indicate distinct differences according to the nanofilm size. The present work reports the specific heats of 40-nm-thick suspended platinum nanofilms at 80–380 K and ∼5×10−4 Pa using the 3ω method. Over 80–380 K, the specific heats of the Pt nanofilms range from 166–304 J/(kg·K), which are 1.65–2.60 times the bulk values, indicating significant size effects. These results are useful for both scientific research in nanoscale thermophysics and evaluating the transient thermal response of nanoscale devices.

Nonlinear thickness and oxidation-dependent transparency and conductance of sputtered titanium suboxide nanofilms

Optically transparent and electrically conductive semiconducting titanium suboxide nanometer thick films, which are technologically important in a wide variety of applications, show a nonlinear dependency of optical and electrical properties on film thickness and oxidation time. The optical, electrical, chemical, and structural properties of the sputter-deposited titanium suboxide nanofilms on fused quartz glass at room temperature are investigated by varying the film thickness, and the additional oxidation is controlled by the duration of air exposure. The optical properties of the nanofilms are simulated by considering them as both a homogeneous film as well as an inhomogeneous film with the combination of the Lorentz Drude model and the Maxwell Garnett effective medium theory (MG-EMT). Their electrical properties are simulated with the MG-EMT. The optical transmittance, electrical conductivity, secondary ion mass spectroscopy, x-ray photoemission spectroscopy analysis, and simulation of titanium suboxide nanofilms indicate that inhomogeneous film growth and oxidation are responsible for the nonlinear dependency. The oxygen atomic ratios to titanium for the as-deposited films depend on the deposition time and vary in 1.60–1.73, while those exposed to air for seven days increase to 1.79–1.99.

Self-healing gold mirrors and filters at liquid-liquid interfaces.

The optical and morphological properties of lustrous metal self-healing liquid-like nanofilms were systematically studied for different applications (e.g., optical mirrors or filters). These nanofilms were formed by a one-step self-assembly methodology of gold nanoparticles (AuNPs) at immiscible water-oil interfaces, previously reported by our group. We investigated a host of experimental variables and herein report their influence on the optical properties of nanofilms: AuNP mean diameter, interfacial AuNP surface coverage, nature of the organic solvent, and nature of the lipophilic organic molecule that caps the AuNPs in the interfacial nanofilm. To probe the interfacial gold nanofilms we used in situ (UV-vis-NIR spectroscopy and optical microscopy) as well as ex situ (SEM and TEM of interfacial gold nanofilms transferred to silicon substrates) techniques. The interfacial AuNP surface coverage strongly influenced the morphology of the interfacial nanofilms, and in turn their maximum reflectance and absorbance. We observed three distinct morphological regimes; (i) smooth 2D monolayers of "floating islands" of AuNPs at low surface coverages, (ii) a mixed 2D/3D regime with the beginnings of 3D nanostructures consisting of small piles of adsorbed AuNPs even under sub-full-monolayer conditions and, finally, (iii) a 3D regime characterised by the 2D full-monolayer being covered in significant piles of adsorbed AuNPs. A maximal value of reflectance reached 58% in comparison with a solid gold mirror, when 38 nm mean diameter AuNPs were used at a water-nitrobenzene interface. Meanwhile, interfacial gold nanofilms prepared with 12 nm mean diameter AuNPs exhibited the highest extinction intensities at ca. 690 nm and absorbance around 90% of the incident light, making them an attractive candidate for filtering applications. Furthermore, the interparticle spacing, and resulting interparticle plasmon coupling derived optical properties, varied significantly on replacing tetrathiafulvalene with neocuproine as the AuNP capping ligand in the nanofilm. These interfacial nanofilms formed with neocuproine and 38 nm mean diameter AuNPs, at monolayer surface coverages and above, were black due to aggregation and broadband absorbance.

Molecular statics simulations of the size-dependent mechanical properties of copper nanofilms under shear loading

Molecular statics simulations are conducted on single-crystal copper nanofilms subjected to shear loading to examine the effect of thickness on the mechanical properties of nanofilms. Simulation results show that not only the yield strength but also the shear modulus increases with decreasing film thickness. In order to better relate the yield strength of a copper nanofilm to its thickness, a Hall–Petch-like fitting function is proposed to predict the variation of yield strength with film thickness. The initial yield is found to be associated with the nucleation of dislocations. The energy required for the first nucleation of dislocations is calculated and plotted as a function of film thickness to elucidate the origin of the thickness effect on yield strength. In addition, the production of vacancy clusters is also found to depend on film thickness and three new patterns of vacancy clusters are observed in our simulations.