Nano Thin Films Research Articles

Polyethylenimine-functionalized magnetic amorphous carbon fabricated from oil palm leaves as a novel adsorbent for Hg(II) from aqueous solutions

PEI (polyethylenimine) functionalized magnetic amorphous carbon thin film nano composite (Fe3O4-PEI-ACTF NC), was successfully synthesized and characterized by High Resolution Transmission Electron Microscope (HR-TEM), X-ray diffraction (XRD), Fourier-transform infrared spectrometer (FTIR), and Thermo gravimetric analysis (TGA). The synthesized nano composite Fe3O4-PEI-ACTF was developed as a highly efficient adsorbent for Hg(II) from aqueous samples. Effect of pH, contact time, adsorbent dose, initial concentration and temperature were investigated and optimized through batch adsorption technique. Besides, good magnetic performance of Fe3O4-PEI-ACTF NC makes it easily recovered from water with magnetic separation at low magnetic field. The adsorption kinetic data described well with the pseudo-second-order model and the equilibrium data fitted well to Langmuir isotherm model. The maximum adsorption capacity was 714 µg/g of Hg(II). Thermodynamic studies (ΔG° < 0, ΔH° > 0, ΔS° > 0) implied an endothermic and spontaneous adsorption process in nature. Furthermore, the excellent reproducibility indicated that Fe3O4-PEI-ACTF NC has a promising application for removing heavy metals from aqueous environments due to high adsorption capacity and easily and quick separation.

Structure, Properties, and Degradation of Nanothin Ionomer Films in Fuel Cell Catalytic Layers

The structure of electrodes for proton-exchange membrane fuel cells and electrolysis has a major impact on performance and degradation. Ionomer films covering Pt/C agglomerates in fuel cell electrodes have a thickness in the range of 4 to 15 nm. Such nanothin ionomer films differ significantly in structure and conductivity from bulk ionomer To access their thickness-structure-conductivity correlations, self-assembled model layers deposited on platinum-covered Si were investigated by material-sensitive and conductive AFM at conditions close to operation. The dependence of transient current on ionomer film height measured directly at samples with a varying thickness has two distinct changes of slope which indicates three distinct length scales (< 4-5 nm, ~ 4-8 nm, > 8 nm) over which structure and subsequently the conductivity of nanothin films varies.

Ionic liquid-assisted synthesis of Pt nano thin films at toluene–water interface: Enhanced CO tolerance in methanol fuel cells and adsorptive removal of p-nitrophenol from water

In this investigation, we report a one-pot method for the synthesis of Pt/ionic liquid nano thin films at organic-aqueous media at room temperature without using any harsh conditions. Synthesized Pt/ionic liquid thin films were characterized with common analytical techniques. Transmission electron microscope images confirmed the formation of spherical particles having a size distribution in the range of 4–12 nm. Ionic liquids have a key role in the control of better size distribution and prevent from agglomeration of nanostructures by preparing a shell around particles. These catalysts were applied for the reduction of toxic p-nitrophenol into non-toxic p-aminophenol and exhibited good catalytic activity. Also, they exhibit excellent CO tolerance in methanol oxidation process of fuel cells. This method provides a novel, rapid, low cost and economical alternative for the reduction of toxic organic pollutants in water and also to prepare high quality catalysts with low metal loading for methanol fuel cells. Pt/1-aminoethyl-3-methylimidazolium bromide exhibits better CO tolerance than Pt/1-methyl-3-octylimidazolium chloride and Pt/1-methyl-3-octylimidazolium tetrafluoroborate thin films.

Preparation and optical characterization of β-MnO2 nano thin films for application in heterojunction photodiodes

The present work shows that manganese dioxide (β-MnO2) nano films can be applied as a potential candidate for solar energy conversion. β-MnO2 nano thin films were successfully grown on glass and quartz substrates using thermal evaporation technique. The structural properties of as-deposited and annealed thin films were analyzed using both X-ray diffraction and field emission scanning electron microscopy techniques. The spectroscopic characterizations of β-MnO2 nano thin films with different film thickness were studied using spectrophotometric technique in the wavelength of 200–2400 nm. The optical constants of these films were calculated and showed variation with film thickness and annealing temperature. Wemple -DiDomenico oscillator model was applied in the non-absorbing region of refractive index spectrum in order to evaluate the dispersion parameters. The nonlinear optical parameters were calculated using the linear optical parameters. The annealing temperature considered to be a good tool for enhancement of the nonlinear optical parameters of β-MnO2 nano films. Unraveling the correlated optical properties with the photoresponse characterizations of β-MnO2 nano films opens the avenue to design and fabricate heterojunction photodiodes based on β-MnO2 nano-films. The photoresponsivity, photoconductivity and specific detectivity of fabricated Au/β-MnO2/p-Si/Al photodiodes were studied.

Effective interface thermal resistance and thermal conductivity of dielectric nanolayers

Analytical expressions for the effective interface thermal resistance (ITR) and thermal conductivity k of dielectric nanolayers are derived and analyzed, based on the analytical solution of the phonon Boltzmann transport equation under the gray relaxation time approximation. This is achieved by using accurate expressions for the temperature and one-dimensional heat flux propagating across nanolayers supporting a diffusive phonon scattering at their interfaces. It is shown that the effective ITR between two layers can be symmetric on their thermal properties, such that its asymptotic value in the ballistic regime is higher than that in the diffusive one. In the ballistic-diffusive regime, the effective ITR depends strongly on the ratio λ=L/l, between the layer thickness L and mean free path l of phonons. Our predictions for the effective ITR in the ballistic regime are in good agreement with those of the diffuse mismatch model, while they differ by about 16% in the diffusive regime. On the other hand, k increases with λ until reaching saturation for bulk layers and agrees rather well with previous predictions reported in the literature. The obtained results could be useful for analytically describing the heat transport in dielectric nanothin films and superlattices, in which the gray approximation is valid.

Quantum resonances of Landau damping in the electromagnetic response of metallic nanoslabs.

The resonant quantization of Landau damping in far-infrared absorption spectra of metal nano-thin films is predicted within the Kubo formalism. Specifically, it is found that the discretization of the electromagnetic and electron wave numbers inside a metal nanoslab produces quantum nonlocal resonances well-resolved at slab thicknesses smaller than the electromagnetic skin depth. Landau damping manifests itself precisely as such resonances, tracing the spectral curve obtained within the semiclassical Boltzmann approach. For slab thicknesses much greater than the skin depth, the classical regime emerges. Here the results of the quantum model and the Boltzmann approach coincide. Our analytical study is in perfect agreement with corresponding numerical simulations.

Temperature-and thickness -dependent dynamic magnetic properties of sputtered CoFeB/Ta bilayer films

A series of CoFeB/Ta bilayer nano-thin films was fabricated on Si substrate using magnetron sputtering at room temperature. The temperature-and thickness-dependent dynamic magnetic properties of these films were investigated in detail using commercialized coplanar waveguide ferromagnetic resonance technique. The results showed that the Gilbert damping constant of bilayer films was monotonically decreases with the increase of temperature and thickness within certain range. We considered that the reasons for enhanced damping for the thinner magnetic films were derived from spin-pumping effect, two-magnon scatter, and magnetic dead layer. From thickness-dependent data, the surface/interface anisotropy constant, bulk damping contribution, and surface/interface damping contribution were obtained. Our results indicated that the bilayer films had perpendicular anisotropy when the CoFeB thickness was less than 1.38 nm. The results suggested that the influence of Ta on the dynamic properties of magnetic films cannot be ignored. The simplest stack structure of films was beneficial to understand the physical mechanism clearly.

(Invited) Atomic Layer Deposition for Interface Engineering of (Thin-Film) Lithium-Ion Battery

Atomic layer deposition (ALD) is a gas-phase deposition technique based on sequential self-limiting surface reactions [1]. The self-limiting nature of these gas-surface interactions give ALD several advantages over other deposition techniques if exploited properly: excellent conformality on and in 3D-structured substrates (powders, pores, trenches [2]), smooth and pinhole-free films and ultimate thickness control (~0.1nm precision). These near-unique advantages can be exploited to advance energy storage devices, lithium-ion batteries foremost amongst them [3,4]. On the one hand the excellent step coverage inherent to atomic layer deposition can be exploited to construct complex engineered micro- and nano-structured batteries. These 3D thin-film nano- and microbatteries are interesting storage modes for electronics thanks to their relatively high capacity and very high power densities [5-6]. However, ALD is not without disadvantages. The slow deposition rate (0.1nm/s-0.1nm/min) and high cost compared to for example wet chemical deposition methods typically prevent a full battery stack grown with ALD from being commercially viable. The real strength of ALD lies not in the micron-thick films needed for the electrodes in a thin-film battery, but rather in thin films in the range of 0.1nm to 100nm. An electrochemical storage system consists of many interfaces, and most of the important phenomena occur at those interfaces. Tuning or engineering of these interfaces can be of paramount importance to enhance battery characteristics or unlock novel battery chemistries. In that respect, ALD can be used to deposit conductive coatings as current collector on non-conductive scaffolds, seed layers to enable adhesion or prevent current collector oxidation, protective coatings at the electrode/liquid electrolyte interface and solid electrolytes to prevent the liquid electrolyte all together [3,4]. In this talk, two examples will be highlighted. Firstly, ALD has been heavily investigated for electrode/electrolyte interface engineering since 2010, with the main focus on ALD of Al2O3, given the ease of deposition and proven scalability of this process. However, using model-system thin film electrodes, we can show that ALD Al2O3 films beyond 3nm are completely blocking towards Li+ ions, while thinner coatings impose a significant impedance of >1012 Ω cm. ALD TiO2 on the other hand is shown to be not blocking towards Li+ ions, and can alleviate solvent decomposition or metal dissolution, two important capacity fading mechanisms found at this interface [5,7]. Secondly, electrolytic manganese oxide (EMD) and its converted form to LiMn2O4 (LMO) are considered interesting cathode materials. However, the electrodeposition of thick films of EMD is challenged by film adhesion and current collector oxidation of non-noble current collectors (eg TiN or Ni), limiting the deposition of and electrochemically active film in acidic electrolytes to approx. 50nm. It is shown that using an ALD MnO2 seed layer of only a 2-4 nm, the adhesion was improved and substrate oxidation was alleviated, allowing electrochemically active EMD films up to 1µm. This could also be demonstrated on 3D-structured substrates, thanks to the conformal nature of both electrodeposition and ALD [8]. In conclusion, despite the slow deposition rates typical for ALD, it can be used as a powerful tool in engineering of interfaces in lithium-ion battery development. [1] George, S. M., Ott, A. W. & Klaus, J. W. Surface Chemistry for Atomic Layer Growth. J. Phys. Chem. 100, 13121–13131 (1996). [2] Detavernier, C., Dendooven, J., Sree, S. P., Ludwig, K. F. & Martens, J. A. Tailoring nanoporous materials by atomic layer deposition. Chem. Soc. Rev. 40, 5242–5253 (2011). [3] Meng, X., Yang, X.-Q. & Sun, X. Emerging Applications of Atomic Layer Deposition for Lithium-Ion Battery Studies. Adv. Mater. 24, 3589–3615 (2012). [4] Liu, J. & Sun, X. Elegant design of electrode and electrode/electrolyte interface in lithium-ion batteries by atomic layer deposition. Nanotechnology 26, 024001 (2015). [5] Kurttepeli, M. et al. Heterogeneous TiO2/V2O5/Carbon Nanotube Electrodes for Lithium-Ion Batteries. ACS Appl. Mater. Interfaces 9, 8055–8064 (2017). [6] Mattelaer, F., Geryl, K., Rampelberg, G., Dendooven, J. & Detavernier, C. Amorphous and Crystalline Vanadium Oxides as High-Energy and High-Power Cathodes for Three-Dimensional Thin-Film Lithium Ion Batteries. ACS Applied Materials & Interfaces 9, 13121–13131 (2017). [7] Mattelaer, F., Vereecken, P. M., Dendooven, J. & Detavernier, C. The Influence of Ultrathin Amorphous ALD Alumina and Titania on the Rate Capability of Anatase TiO2 and LiMn2O4 Lithium Ion Battery Electrodes. Advanced Materials Interfaces 1601237 (2017). [8] Timmermans, M. Y. et al. Electrodeposition of Adherent Submicron to Micron Thick Manganese Dioxide Films with Optimized Current Collector Interface for 3D Li-Ion Electrodes. J. Electrochem. Soc. 164, D954–D963 (2017).

Model-Based Analyses of Confined Polymer Electrolyte Nanothin Films Experimentally Probed by Polarized ATR–FTIR Spectroscopy

Orientational ordering within nanoscale (70–8 nm) thickness fluorinated ionomer films on Si substrates was investigated through the use of attenuated total reflection Fourier transform infrared (ATR–FTIR) spectroscopy in conjunction with electromagnetic field calculations. A spectral model was developed for Nafion thin films across the 1400–950 cm–1 region from frequency-dependent, isotropic optical constants derived from Kramers–Kronig analysis of ionomer transmission infrared spectra. The model considered infrared light propagation within the parallel boundary regions between the Ge ATR crystal, the ionomer film, and the Si substrate supporting the film. The calculations reproduced overall polymer thickness-dependent changes in peak frequencies and band shapes observed in experimental spectra recorded with p- and s-polarized light. General trends were traceable to effects of anomalous dispersion and electric field enhancement within the nanoscale gap separating the Ge and Si phases. However, optical eff...

Preparation, growth and characterization of nonvacuum Cu-doped ZnO thin films

We investigated the effects of increasing Cu dopant concentration on the microstructure and optical properties of Zn1−xCuxO thin films. The transparent Zn1−xCuxO solution concentrations were varied from x = 0.0 to x = 0.05 with an increment of 0.01. All nano films were prepared by dip coating system using the sol-gel method. X-ray diffraction (XRD) measurements, scanning electron microscopy (SEM) observations, energy-dispersive X-ray spectroscopy (EDS) analyses, and atomic force microscopys (AFM) analyses revealed a fine-grained structure resulting from doping of Cu into the ZnO structure. In addition, UV–Vis spectrophotometer was used to determine the optic properties of ZnO based nano thin films. XRD analysis also showed that the undoped ZnO and Cu-doped ZnO films oriented along the (002) as the dominant plane. In the 400–700 nm wavelength range, a decrease in transparency was observed in the Zn1−xCuxO thin films with increasing Cu concentration. Although the optical band gap of the Cu-doped ZnO thin films was lower than that of the undoped ZnO thin film, the Urbach energy of the all of the doped thin films was higher than the undoped ZnO thin film.

Solution Coating of Pharmaceutical Nanothin Films and Multilayer Nanocomposites with Controlled Morphology and Polymorphism.

Nanosizing is rapidly emerging as an alternative approach to enhance solubility and thus the bioavailability of poorly aqueous soluble active pharmaceutical ingredients (APIs). Although numerous techniques have been developed to perform nanosizing of API crystals, precise control and modulation of their size in an energy and material efficient manner remains challenging. In this study, we present meniscus-guided solution coating as a new technique to produce pharmaceutical thin films of nanoscale thickness with controlled morphology. We demonstrate control of aspirin film thickness over more than 2 orders of magnitude, from 30 nm to 1.5 μm. By varying simple process parameters such as the coating speed and the solution concentration, the aspirin film morphology can also be modulated by accessing different coating regimes, namely the evaporation regime and the Landau-Levich regime. Using ellipticine-a poorly water-soluble anticancer drug-as another model compound, we discovered a new polymorph kinetically trapped during solution coating. Furthermore, the polymorphic outcome can be controlled by varying coating conditions. We further performed layer-by-layer coating of multilayer nanocomposites, with alternating thin films of ellipticine and a biocompatible polymer, which demonstrate the potential of additive manufacturing of multidrug-personalized dosage forms using this approach.

Preparation and characterization of nano sized pure ZnTe and antimony doped ZnTe nano thin films by spray pyrolysis technique

&#x0D; &#x0D; &#x0D; Antimony doped ZnTe thin films developed by spray pyrolysis technique. The deposited thin films are characterized by X-ra diffraction (XRD), scanning electron microscope (SEM), energy dispersive electron microscopy (EDS) and ulra-violet visible spectroscopy (UV-Vis). XRD studies indicate that antimony doping in host result a crystallinity change. The average particle size calculated from XRD values is in good agreement with the SEM results. EDS spectrum is a good evidence of confirm the formation of antimony doped ZnTe. An optical band gap calculated value varying from 2.3 eV to1.9 eV. The extinction coefficient increases depending on the temperature 300 ̊ C, 350 ̊ C and 400 ̊ C.&#x0D; &#x0D; &#x0D;

Recent advance in multiple exciton generation in semiconductor nanocrystals

The multiple exciton generation (MEG), a process in which two or even more electron-hole pairs are created in nanostructured semiconductors by absorbing a single high-energy photon, is fundamentally important in many fields of physics, e.g., nanotechnology and optoelectronic devices. Many high-performance optoelectronic devices can be achieved with MEG where quite an amount of the energy of an absorbed photon in excess of the band gap is used to generate morei additional electron-hole pairs instead of rapidly lost heat. In this review, we present a survey on both the research context and the recent progress in the understanding of MEG. This phenomenon has been experimentally observed in the 0D nanocrystals, such as PbX (X=Se, S, and Te), InX (X=As and P), CdX (X=Se and Te), Si, Ge, and semi-metal quantum dots, which produce the differential quantum efficiency as high as 90%10%. Even more remarkably, experiment advances have made it possible to realize MEG in the one-dimensional (1D) semiconductor nanorods and the two-dimensional (2D) nano-thin films. Theoretically, three different approaches, i.e., the virtual exciton generation approach, the coherent multiexciton mode, and the impact ionization mechanism, have been proposed to explain the MEG effect in semiconductor nanostructures. Experimentally, the MEG has been measured by the ultrafast transient spectroscopy, such as the ultrafast transient absorption, the terahertz ultrafast transient absorption, the transient photoluminescence, and the transient grating technique. It is shown that the properties of nanostructured semiconductors, e.g., the composition, structure and surface of the material, have dramatic effects on the occurrence of MEG. As a matter of fact, it is somewhat hard to experimentally confirm the signature of MEG in nanostructured semiconductors due to two aspects:i) the time scale of the MEG process is very short; ii) the excitation fluence should be extremely low to prevent the multi-excitons from being generated by multiphoton absorption. There are still some controversies with respect to the MEG effect due to the challenge in both the experimental measurement and the explanation of signal data. The successful applications of MEG in practical devices, of which each is composed of the material with lower MEG threshold and higher efficiency, require the extraction of multiple charge carriers before their ultrafast annihilation. Such an extraction can be realized by the ultrafast electron transfer from nanostructured semiconductors to molecular and semiconductor electron acceptors. More recently, an experiment with PbSe quantum dot photoconductor has demonstrated that the multiple charge extraction is even as high as 210%. It is proved that MEG is of applicable significance in optoelectronic devices and in ultra-efficient photovoltaic devices. Although there are still some challenges, the dramatic enhancement of the efficiency of novel optoelectronic devices by the application of MEG can be hopefully realized with the rapid improvement of nanotechnology.

Effect of Oxygen Sputter Pressure on the Structural, Morphological and Optical Properties of ZnO Thin Films for Gas Sensing Application

ZnO thin films were prepared on glass substrates at low (5 × 10−4 mbar) and high (3 × 10−3 mbar) sputter pressure using dc reactive magnetron sputtering. The structural, morphological, compositional and optical properties of the thin films were investigated. XRD patterns of both films confirmed the polycrystalline nature of the films with hexagonal Wurtzite structure. SEM study indicates that the surface of the film formed at high sputter pressure was more uniform, compact and porous in nature. From the EDAX analysis, no other characteristic peaks of other impurities were observed and the formation of single phase of ZnO was confirmed. From the study of photoluminescence, three peaks were observed, one strong near band-edge emission at 390 nm followed by weak and broad visible emissions around 420–480 nm. Room temperature ammonia sensing characteristics of ZnO nanothin films formed at higher sputter pressure were studied for different ammonia vapour concentration levels. The response of the Ammonia sensor at room temperature (30 °C) operation was observed to be of high sensitivity with quick response and recovery times.

Ti Capping Layer Effects in Microstructure and Magnetic Properties of Sputter-Deposited FePt Thin Film

Ti/FePt/Fe nano-thin films were fabricated by a DC facing-target magnetron sputtering method onto glass substrates at room temperature and were subsequently annealed in situ in vacuum. The impacts of the Ti capping layer on microstructural and magnetic properties of the FePt films were investigated in detail. X-ray diffraction (XRD) patterns demonstrate that the film is deposited onto glass substrates and the addition of a Ti layer forms ternary TiFePt, and binary PtTi and FeTi alloys. The results reveal refined granularity, decreased roughness, and enhanced coercivity and degree of squareness after the introduction of a Ti capping layer.

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.

Preparation and properties of amine functionalized graphene filled epoxy thin film nano composites for electrically conductive adhesive

The study was carried out to investigate the effect of amine coupling agent of graphene nanopowder (GNP) on the properties of epoxy-based electrically conductive adhesives. Amine-based coupling agent for GNP (m-GNP)/epoxy thin film nanocomposites and GNP/epoxy thin film nanocomposites were fabricated using an ultrasonication and spin-coating techniques. Subsequently, the effect of GNP with different filler loading (0.05–1 vol%) on the tensile properties and electrical properties of the epoxy composites was studied. The GNPs functionalized with amine coupling agent was confirmed with FTIR, AFM and Raman spectroscopy. Generally, it was found that the addition of GNPs decreased the tensile properties of epoxy composites. However, m-GNP/epoxy composites showed higher tensile properties than GNP/epoxy composites at the same filler loading. While, it was found that the percolation threshold of the m-GNP/epoxy composites (0.6 vol%) was much higher than that of the GNP/epoxy (0.1 vol%). Morphological analysis of the GNP fillers by TEM images showed that the average dimensions of m-GNPs layers were far smaller than the average dimensions of GNPs before functionalization. SEM images of the tensile samples cross section confirmed the existence of strong interfacial bonding between m-GNP and the epoxy matrix.

Investigation Nano coating for Corrosion Protection of Petroleum Pipeline Steel Type A106 Grade B; Theoretical and Practical Study in Iraqi Petroleum Sector

In the present investigation, titania (TiO2) nano-thin films were deposited on steel type A106-B, by using the Pulse Laser Deposition (PLD) technique to obtain passive layers of nano-coating. Electrochemical methods (Tafel completion) are used for study corrosion behavior of steel coating. The A106-B specimens were evaluated in 3.5 wt. % NaCl aqueous solution by using polarization technique with pH adjustment to 4.0 in order to determine the corrosion rate. The samples of TiO2 thin films were characterized by SEM, AFM, XRD, and FTIR. The input parameters were substrate temperature (100, 200 and 300) ’0C’, number of pulse (300, 400 and 500) and fluencies energy (800, 900 and 1000) mJ/cm2, have been investigated to detect their impact on corrosion reduction rate using Taguchi methodology orthogonal array and Analysis of Variance (ANOVA).The ANOVA results indicates that number of shoots pulse significantly affecting the corrosion rate in PLD technique, which is highest among the contributions of the other parameters which is (58.03%) about three times of the fluencies energy (19.12%).The results show that the TiO2 deposition on steels offers an excellent corrosion resistance about 99 times as compared with uncoated steel. The optimum conditions to minimum values corrosion rate are: temperature of 300ºC, number of laser pulses at 300, and fluencies energy equal to 1000 mJ/cm2. Finally the optimal parameters that was used to predict the conclusions were (98.6) to the response of corrosion rate.

Development of flexible Ni80Fe20 magnetic nano-thin films

Flexible magnetic Ni80Fe20 thin films with excellent adhesion, mechanical and magnetic properties have been fabricated using magnetron plasma deposition. We demonstrate that flexible Ni80Fe20 thin films maintain their non-flexible magnetic properties when the films are over 60nm thick. However, when their thickness is reduced, the flexible thin films display significant increase in their magnetic coercive field compared to identical films coated on a solid Silicon substrate. For a 15nm flexible Ni80Fe20 film coated onto 110µm Polyvinylidene fluoride polymer substrate, we achieved a remarkable 355% increase in the magnetic coercive field relative to the same film deposited onto a Si substrate. Experimental evidence, backed by micro-magnetic modelling, indicates that the increase in the coercive fields is related to the larger roughness texture of the flexible substrates. This effect essentially transforms soft Ni80Fe20 permalloy thin films into medium/hard magnetic films allowing not only mechanical flexibility of the structure, but also fine tuning of their magnetic properties.

Improved surface-enhanced Raman and catalytic activities of reduced graphene oxide-osmium hybrid nano thin films.

Reduced graphene oxide–osmium (rGO-Os) hybrid nano dendtrites have been prepared by simple liquid/liquid interface method for the first time. The method involves the introduction of phase-transfered metal organic precursor in toluene phase and GO dispersion in the aqueous phase along with hydrazine hydrate as the reducing agent. Dendritic networks of Os nanoparticles and their aggregates decorating rGO layers are obtained. The substrate shows improved catalytic and surface-enhanced activities comparable with previous reports. The catalytic activity was tested for the reduction of p-nitroaniline into p-phenyldiamine with an excess amount of NaBH4. The catalytic activity factors of these hybrid films are 2.3 s−1 g−1 (Os film) and 4.4 s−1 g−1 (rGO-Os hybrid film), which are comparable with other noble metal nanoparticles such as Au, Ag, but lower than Pd-based catalysts. Surface-enhanced Raman spectroscopy (SERS) measurements have been done on rhodamine 6G (R6G) and methylene blue dyes. The enhancement factor for the R6G adsorbed on rGO-Os thin film is 1.0 × 105 and for Os thin film is 7 × 103. There is a 14-fold enhancement observed for Os hybrids with rGO. The enhanced catalytic and SERS activities of rGO-Os hybrid thin film prepared by simple liquid/liquid interface method open up new challenges in electrocatalytic application and SERS-based detection of biomolecules.