Thin Film Matrices Research Articles

Dislocation-Assisted Quasi-Two-Dimensional Semiconducting Nanochannels Embedded in Perovskite Thin Films.

Defect engineering in perovskite thin films has attracted extensive attention recently due to the films' atomic-scale modification, allowing for remarkable flexibility to design novel nanostructures for next generation nanodevices. However, the defect-assisted three-dimensional nanostructures in thin film matrices usually has large misfit strain and thus causes unstable thin film structures. In contrast, defect-assisted one- or two-dimensional nanostructures embedded in thin films can sustain large misfit strains without relaxation, which make them suitable for defect engineering in perovskite thin films. Here, we reported the fabrication and characterization of edge-type misfit dislocation-assisted two-dimensional BiMnOx nanochannels embedded in SrTiO3/La0.7Sr0.3MnO3/TbScO3 perovskite thin films. The nanochannels are epitaxially grown from the surrounding films without noticeable misfit strain. Diode-like current rectification was spatially observed at nanochannels due to the formation of Schottky junctions between BiMnOx nanochannels and conducting La0.7Sr0.3MnO3 thin films. Such atomically scaled heterostructures constitute more flexible ultimate functional units for nanoscale electronic devices.

Optimizing the Surface Structural and Morphological Properties of Silk Thin Films via Ultra-Short Laser Texturing for Creation of Muscle Cell Matrix Model.

Temporary scaffolds that mimic the extracellular matrix’s structure and provide a stable substratum for the natural growth of cells are an innovative trend in the field of tissue engineering. The aim of this study is to obtain and design porous 2D fibroin-based cell matrices by femtosecond laser-induced microstructuring for future applications in muscle tissue engineering. Ultra-fast laser treatment is a non-contact method, which generates controlled porosity—the creation of micro/nanostructures on the surface of the biopolymer that can strongly affect cell behavior, while the control over its surface characteristics has the potential of directing the growth of future muscle tissue in the desired direction. The laser structured 2D thin film matrices from silk were characterized by means of SEM, EDX, AFM, FTIR, Micro-Raman, XRD, and 3D-roughness analyses. A WCA evaluation and initial experiments with murine C2C12 myoblasts cells were also performed. The results show that by varying the laser parameters, a different structuring degree can be achieved through the initial lifting and ejection of the material around the area of laser interaction to generate porous channels with varying widths and depths. The proper optimization of the applied laser parameters can significantly improve the bioactive properties of the investigated 2D model of a muscle cell matrix.

Construction of a thermoresponsive magnetic porous polymer membrane enzyme reactor for glutaminase kinetics study.

Fabrication of polymer membranes with nanopores and a confinement effect toward enzyme immobilization has been an enabling endeavor. In the work reported here, an enzyme reactor based on a thermoresponsive magnetic porous block copolymer membrane was designed and constructed. Reversible addition-fragmentation chain transfer polymerization was used to synthesize the block copolymer, poly(maleic anhydride-styrene-N-isopropylacrylamide), with poly(N-isopropylacrylamide) as the thermoresponsive moiety. The self-assembly property of the block copolymer was used for preparation of magnetic porous thin film matrices with iron oxide nanoparticles. By covalent bonding of glutaminase onto the surface of the membrane matrices and changing the temperature to tune the nanopore size, we observed enhanced enzymolysis efficiency due to the confinement effect. The apparent Michaelis-Menten constant and the maximum rate of the enzyme reactor were determined (Km = 32.3 mM, Vmax = 33.3 mM min-1) by a chiral ligand exchange capillary electrochromatography protocol with L-glutamine as the substrate. Compared with free glutaminase in solution, the proposed enzyme reactor exhibits higher enzymolysis efficiency, greater stability, and greater reusability. Furthermore, the enzyme reactor was applied for a glutaminase kinetics study. The tailored pore sizes and the thermoresponsive property of the block copolymer result in the designed porous membrane based enzyme reactor having great potential for high enzymolysis performance. Graphical abstract ᅟ.

A comprehensive review on thin film-based nano-biosensor for uric acid determination: arthritis diagnosis

This article aims to provide a survey on the development of thin film-based nano-biosensor over the decade, which includes sensing principles, electrode types and various thin film matrices. The theoretical and experimental results suggest that the thin film-based sensor are suitable for highly sensitive detection of low concentration bio molecules and can be used for early diagnosis and screening of arthritis, kidney diseases and other cardiovascular diseases. This review concludes that enzyme immobilisation and surface functionalisation methods were used to increase sensitivity of the biosensor and new combination of polymer nano-composites with metal oxide thin films results in increased efficiency due to its high biocompatibility.

Engineered optical properties of silver-aluminum alloy nanoparticles embedded in SiON matrix for maximizing light confinement in plasmonic silicon solar cells

Self-assembled silver-aluminum (Ag-Al) alloy nanoparticles (NPs) embedded in SiO2, Si3N4, and SiON dielectric thin film matrices explored as a hybrid plasmonic structure for silicon solar cells to maximize light confinement. The Ag2Al NPs prepared by ex-vacuo solid-state dewetting, and alloy formation confirmed by X-ray diffraction and photoelectron spectroscopy analysis. Nanoindentation by atomic force microscopy revealed better surface adhesion of alloy NPs on silicon surface than Ag NPs due to the Al presence. The SiON spacer layer/Ag2Al NPs reduced silicon average reflectance from 22.7% to 9.2% due to surface plasmonic and antireflection effects. The SiON capping layer on NPs reduced silicon reflectance from 9.2% to 3.6% in wavelength region 300–1150 nm with preferential forward light scattering due to uniform Coulombic restoring force on NPs’ surface. Minimum reflectance and parasitic absorptance from 35 nm SiON/Ag2Al NPs/25 nm SiON structure reflected in plasmonic cell’s photocurrent enhancement from 26.27 mA/cm2 (of bare cell) to 34.61 mA/cm2 due to the better photon management. Quantum efficiency analysis also showed photocurrent enhancement of cell in surface plasmon resonance and off-resonance regions of NPs. We also quantified dielectric thin film antireflection and alloy NPs plasmonic effects separately in cell photocurrent enhancement apart from hybrid plasmonic structure role.

Thermogravimetric analysis for rapid assessment of moisture diffusivity in polydisperse powder and thin film matrices

Accurate description of moisture diffusivity is key to precisely understand and predict moisture transfer behaviour in a matrix. Unfortunately, measuring moisture diffusivity is not trivial, especially at low moisture values and/or elevated temperatures. This paper presents a novel experimental procedure to accurately measure moisture diffusivity based on thermogravimetric approach. The procedure is capable to measure diffusivity even at elevated temperatures (>70°C) and low moisture values (>1%). Diffusivity was extracted from experimental data based on “regular regime approach”. The approach was tailored to determine diffusivity from thin film and from poly-dispersed powdered samples. Subsequently, measured diffusivity was validated by comparing to available literature data, showing good agreement. Ability of this approach to accurately measure diffusivity at a wider range of temperatures provides better insight on temperature dependency of diffusivity. Thus, this approach can be crucial to ensure good accuracy of moisture transfer description/prediction especially when involving elevated temperatures.

Multiferroic Consequence of Porous (BiFeO3) x –(BiCrO3)1−x Composite Thin Films by Novel Sol–Gel Method

In this work, we have presented a spin-coating method to produce thin films started with pure BiCrO3 (BCO) and ended up with BiFeO3 (BFO) by increasing x values in the (BiFeO3) x –(BiCrO3)1−x composites. All the produced thin films have been crystallized at the annealing temperatures of 400 °C for 0.5 h. The XRD and EDAX spectrums give insight that the two crystal phases related to BCO and BFO stayed together within the thin film matrices. SEM analysis showed that the prepared composite had macroporous morphology with interconnected pores and its width (size) decreased with increasing x values. The strong correlations are observed among the microstructure, dielectric, ferroelectric, ferromagnetic properties and Fe concentration. Among all composites, the composition of 0.75 shows an attractive magnetization, polarization, switching and improved dielectric behaviors at room temperature. Significant increase in the multiferroic characteristics of 0.75 composition is due to arise of lower leakage current by causing reduction in oxygen vacancy density, and enhancement of super-exchange magnetic interaction between Fe3+ and Cr3+ at BFO/BCO interface layers. Our result shows that the thin layer on Pt (111)/Ti/SiO2/Si substrate possesses simultaneously improved ferroelectric and ferromagnetic properties which make an inaccessible potential application for nonvolatile ferroelectric memories.

Anodization of sputtered substoichiometric aluminum oxide thin-films for improved nanorod array fabrication

Optical sensing based on plasmonic nanorod arrays witnesses an increased interest for device applications due to a manifold of benefits of these structures, such as broadband optical tunability and low-cost bottom-up fabrication. Key to this success is the assembly of nanorod antenna arrays mediated through high-quality anodized aluminum oxide (AAO) matrices. The present work reports the greatly improved fabrication of thin-film AAO matrices based on aluminum thin-films deposited by magnetron sputtering under controlled argon/oxygen atmosphere, and investigates the influence of oxygen on the aluminum morphology and hence AAO pore formation upon anodization. Such optimized templates then subsequently allow the fast and reproducible fabrication of nanorod arrays with a nearly 100% pore-filling degree, which is favorable in plasmonic applications, with the plasmonic properties greatly benefiting from homogeneous distances between neighboring nanorods. For an optimal oxygen content of 10–22 at.%, we find the long-axis plasmon resonance peak to show the least optical losses, confirming the optimized nanostructure fabrication and performance.

Carbon nanotube thin film strain sensors: comparison between experimental tests and numerical simulations

Carbon nanotubes can be randomly deposited in polymer thin film matrices to form nanocomposite strain sensors. However, a computational framework that enables the direct design of these nanocomposite thin films is still lacking. The objective of this study is to derive an experimentally validated and two-dimensional numerical model of carbon nanotube-based thin film strain sensors. This study consisted of two parts. First, multi-walled carbon nanotube (MWCNT)-Pluronic strain sensors were fabricated using vacuum filtration, and their physical, electrical, and electromechanical properties were evaluated. Second, scanning electron microscope images of the films were used for identifying topological features of the percolated MWCNT network, where the information obtained was then utilized for developing the numerical model. Validation of the numerical model was achieved by ensuring that the area ratios (of MWCNTs relative to the polymer matrix) were equivalent for both the experimental and modeled cases. Strain sensing behavior of the percolation-based model was simulated and then compared to experimental test results.

Development of high dielectric dual phase [Bi4Ti3O12]X–[CaCu3Ti4O12]1 − X nanocomposite thin films for modern microelectronic device applications

A dual phase system with different compositions (X=0, 0.2, 0.4, 0.6, 0.8, 1.0) of (Bi4Ti3O12)X–(CaCu3Ti4O12)1−X, [(BTO)X–(CCTO)1−X] thin films have been grown on a platinized silicon substrate using the spin-coating technique. The X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Raman results show that the two different crystal phases, orthorhombic BTO and cubic CCTO exist together within the thin film matrices. The effect of BTO phase concentration on the dielectric and the P-E hysteresis behavior of the composites was investigated. In an unexpected observation, the incorporation of CCTO into BTO is found to enhance the dielectric constant of the nanocomposite, in accordance with the percolation theory. The ferroelectric hysteresis (P-E) loops were altered with relating to stoichiometry compositions. Near the percolation threshold for 20mol% BTO with 80mol% CCTO in composite, high dielectric constant (~6378), and high coercivity (~162kV/cm) is obtained compared to the single phase BTO and CCTO. These results show that the (Bi4Ti3O12)0.2–(CaCu3Ti4O12)0.8 is a good candidate for the miniaturization of modern microelectronic devices.

Self-assembly of very-low height/width aspect-ratio Li3Ni2NbO6 disks embedded in Li3NbO4 epitaxial films

We here report the self-assembly of Li3Ni2NbO6 (LNNO) epitaxial disks with very low height/width aspect ratios. An epitaxial LNNO thin film is obtained at a substrate temperature (Ts) of 400°C, using a pulsed laser deposition technique, and by increasing the Ts to 600°C, Li3NbO4 epitaxial domains are formed inside the LNNO epitaxial film. Further increasing the Ts to 700°C leads to the formation of LNNO disks (with diameters of a few micrometers and a typical height of ~100nm) embedded in a Li3NbO4 film. Interestingly, transmission electron microscopy observations reveal that the LNNO disks are separated from the Li3NbO4 films by amorphous compounds, indicating the formation of a planar core-shell structure. Understanding of the growth processes of these unique nanostructures pave the way to fabrication of higher hierarchical structures embedded in thin film matrices.

Structural and photoluminescence investigation of ZnSe nanocrystals dispersed in organic and inorganic matrices

In this work, we report on the investigation of the effect of dispersion of zinc selenide (ZnSe) nanocrystallites into polystyrene (PS) and silica (SiO2) thin films on their structural, morphological and photoluminescence properties. The ZnSe/PS nanocomposites thin films were synthesized by a direct dispersion of ZnSe crystallites into polymers solution, whereas the ZnSe–SiO2 films were prepared on glass substrates by the sol–gel dip-coating technique. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-rays (EDX), UV–visible spectrophotometry and photoluminescence spectroscopy (PL) techniques have been used to study the structural, morphological and optical properties of the prepared nanocomposite thin films. XRD patterns have demonstrated the incorporation of cubic ZnSe in both organic and inorganic matrices. SEM micrographs have indicated that ZnSe dispersion in the films is homogeneous. UV–visible absorption spectra of the nanocomposite thin films have put into evidence that the dispersion of ZnSe nanocrystals in the thin film matrices improved their optical absorption. Room temperature PL spectra have shown that the addition of ZnSe enhanced the UV emission of PS and all the emission of SiO2 thin films.

Effect of tin on the processes of silicon-nanocrystal formation in amorphous SiO x thin-film matrices

The effect of tin on the processes of silicon-nanocrystal formation in amorphous silicon oxide (a-SiO x , x ≈ 1.15) thin-film matrices is studied. It is established that the tin impurity accelerates the processes of crystallization of amorphous silicon. After heat treatment in an argon atmosphere, silicon crystallites embedded in the tin-containing silicon oxide (a-SiO x Sn) matrix are smaller in size (6–9 nm) compared to crystallites in a-SiO x (≥10 nm). It is shown that, upon annealing of a-SiO x Sn at temperatures increased from 800 to 1100°C, the volume fraction of the crystalline phase increases from 20 to 80%. At the same time, in the samples free from tin, the silicon crystalline phase appears only upon annealing at 1000°C and 1100°C, and the volume fraction of the crystalline phase is 45 and 65%, respectively.

Producing CuO and ZnO composite thin films using the spin coating method on microscope glasses

In this work, we have presented a new route to produce pure ZnO and composite ZnO-CuO thin films. In the process we have started with pure ZnO thin films and ended up with CuO by doping Cu in various percentages, ranging from 0% to 100%. We have managed to attain crystal phases in all doping concentrations. All the produced thin films have been crystallized at the annealing temperatures of 600 and 700 °C for 6 h. The X-ray diffraction (XRD) spectra have been performed to see the formation of crystal phases of all pure ZnO and composite ZnO-CuO thin films. These give insight that the two crystal phases related to ZnO and CuO stayed together within the thin film matrices, which were produced in different doping concentrations, i.e. nZnO + mCuO (0 ≤ n, m ≤ 100%). The scanning electron microscopy (SEM) micrographs and UV–vis absorption spectra have also been taken to elucidate the structure and composition of the all films.

C60 and C70 Electronic Absorption Spectra in Different Solvents and Matrices

The electronic absorption spectra of C60 and C70 molecules have been reported in various solvents viz., polar, aliphatic and aromatic. In addition the electronic absorption spectra of C60 and C70 also recorded in different matrices viz., sol-gel, polymer and thin film. The solvent effect has been observed in polar, aliphatic and aromatic solvents. The aromatic solvent shows larger red shift as compared to other solvents. The solution form electronic absorption spectra C60 and C70 show the conjugation effect and compared with the absorption spectra reported in different matrices like sol-gel, polymer and thin film. In the case of sol-gel, polymer and thin film matrices of C60 and C70, it is found that the broader absorption bands with less intensity suffer from intermolecular interaction.

SIMS depth profiling of polymer blends with protein based drugs

We report the results of the surface and in-depth characterization of two component blend films of poly( l-lactic acid) (PLLA) and Pluronic surfactant [poly(ethylene oxide) (A) poly(propylene oxide) (B) ABA block copolymer]. These blend systems are of particular importance for protein drug delivery, where it is expected that the Pluronic surfactant will retain the activity of the protein drug and enhance the biocompatibility of the device. Angle dependant X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) employing an SF 5 + polyatomic primary ion source were both used for monitoring the surfactant's concentration as a function of depth. The results show an increased concentration of surfactant at the surface, where the surface segregation initially increases with increasing bulk concentration and then remains constant above 5% (w/w) Pluronic. This surface segregated region is immediately followed by a depletion region with a homogeneous mixture in the bulk of the film. These results suggest the selection of the surfactant bulk concentration of the thin film matrices for drugs/proteins delivery should achieve a relatively homogeneous distribution of stabilizer/protein in the PLLA matrix. Analysis of three component blends of PLLA, Pluronic and insulin are also investigated. In the three component blends, ToF-SIMS imaging shows the spatial distribution of surfactant/protein mixtures. These data are reported also as depth profiles.

Anisotropic observation of absorption and fluorescence transition dipoles in exciton–polariton properties of PIC J-aggregates

Fibril-shaped J-aggregates of pseudoisocyanine dyes are prepared in thin-film matrices of polyvinyl sulfate and their microscopic fluorescence and reflectance imaging are investigated at room temperatures. Improved experiment, both in sample preparations and in microscope optics, allows us to resolve the higher-energy bands in the spectrum and to determine the directions of local absorption and fluorescence transition dipoles more precisely. Based on the anisotropies of the local transition dipoles, we have assigned the 540 nm middle band to be the upper exciton, Davidov split, transition and the higher 495 nm to its vibronic sub-band, while the J-band at 572 nm to be the lower Frenkel exciton transition. Assuming linear chain directions of individual J's to be parallel in average to the long axis of the fibril, the result also implies that a zigzag-type molecular conformation is most suitable for the model of PIC-J aggregates.

Thin films of Type 1 collagen for cell by cell analysis of morphology and tenascin-C promoter activity.

BackgroundThe use of highly reproducible and spatiallyhomogeneous thin film matrices permits automated microscopy and quantitative determination of the response of hundreds of cells in a population. Using thin films of extracellular matrix proteins, we have quantified, on a cell-by-cell basis, phenotypic parameters of cells on different extracellular matrices. We have quantitatively examined the relationship between fibroblast morphology and activation of the promoter for the extracellular matrix protein tenascin-C using a tenascin-C promoter-based GFP reporter construct.ResultsWe find that when considering the average response from the population of cells, cell area correlates with tenascin-C promoter activity as has been previously suggested; however cell-by-cell analysis suggests that cell area and promoter activity are not tightly correlated within individual cells.ConclusionThis study demonstrates how quantitative cell-by-cell analysis, facilitated by the use of thin films of extracellular matrix proteins, can provide insight into the relationship between phenotypic parameters.

Self-organization of Patterned CaCO3/Polymer Composite Films: Tuning of Their Morphologies by the Change of Molecular Weights of Acidic Polymers

Abstract Calcium carbonate (CaCO3) thin films with periodic surface patterns are formed on thin film matrices of a polysaccharide derivative from a solution containing poly(acrylic acid) (PAA). The morphologies of the patterned films have been tuned by the change of molecular weights of the PAA.

Au–Pt alloy nanocrystals incorporated in silica films

Au, Pt and Au–Pt alloy nanocrystals have been prepared in thin SiO2 film matrices by sol–gel spin-coating, followed by heating at 450 °C in 10% H2–90% Ar. X-Ray diffraction patterns reveal that the Au and Au–Pt nanocrystals have a preferential (111) orientation. Upon increasing the Pt concentration, part of the Pt does not alloy with Au, but instead forms a shell around the Au–Pt alloy core. The alloy composition itself goes up to Au(50) : Pt(50), and the Pt shells are formed around the alloy above an alloy composition of Au(75) : Pt(25). The surface plasmon resonance (SPR) band at 544 nm of Au gradually disappears due to the formation of Au–Pt alloys and core–shell structures.