Nano Thin Film Research Articles

Effect of etching time on characterizations of porous silicon passivated by a nano-silver layer

Porous silicon (PS) is a candidate for silicon-based optoelectronic applications. This paper presents the effect of etching time on the properties of PS deposited by a nano-thin film of a silver layer (10 nm Ag/PS) using radio frequency (RF)-sputtering technique at room temperature (RT). The PS was prepared by electrochemical etching (ECE) method for n-type (111) Si in an electrolyte solution containing hydrofluoric acid (HF) and ethanol (C2H6O) at a volume ratio of 1:4 with a direct current of 10 mA for different etching duration (30, 45, and 60 min). Structural, surface, and optical characterizations of the samples were carried out by using field emission scanning electron microscopy (FESEM), energy dispersive X-rays (EDX), X-ray diffraction (XRD), UV–Vis spectrophotometer, and photoluminescence (PL) spectroscopy. The results show that the sample prepared for 30 min demonstrated enhancement in the PL and reflectivity spectra compared to other samples which indicate a higher etching rate and a thinner wall between the pores on the surface over a larger exposed area was obtained.

Low-cost electrochemical detection of l-tyrosine using an rGO-Cu modified pencil graphite electrode and its surface orientation on a Ag electrode using an ex situ spectroelectrochemical method.

A low cost reduced graphene oxide–copper hybrid nano thin-film modified Pencil Graphite Electrode has been employed to detect the l-tyrosine enantiomer. The free-standing rGO–Cu hybrid nano-thin film was prepared by a simple one-step liquid–liquid interface method. Electrochemical Cyclic Voltammetry, Differential Pulse Voltammetry, pH-dependent and scan rate dependent studies on bare PGE, Cu, rGO, and rGO–Cu for l-tyrosine have been explained in detail. The rGO–Cu modified PGE based biosensor exhibits good detection of l-tyrosine. The linear range detection limit was estimated to be 1 × 10−7 M. The calculated sensitivity is 0.4 μA ppm−1 mm2. This electroactive biosensor is easily fabricated and controlled and is cost-effective. The surface orientation of l-tyrosine on the Ag electrode at a particular potential and its comparison with vibrational DFT calculations have been studied for the first time.

Atomic Layer Deposition Coating of TiO2 Nano-Thin Films on Magnesium-Zinc Alloys to Enhance Cytocompatibility for Bioresorbable Vascular Stents.

Background and purposeA coronary stent is a well-known cardiovascular medical device implanted to resolve disorders of the circulatory system due to bloodstream narrowing. Since the implanted device interacts with surrounding biological environments, the surface properties of a typical implantable stent play a critical role in its success or failure. Endothelial cell adhesion and proliferation are fundamental criteria needed for the success of a medical device. Metallic coronary stents are commonly used as biomaterial platforms in cardiovascular implants. As a new generation of coronary stents, bioresorbable vascular scaffolds have attracted a great deal of attention among researchers and studies on bioresorbable materials (such as magnesium and zinc) remain a target for further optimization. However, additional surface modification is needed to control the biodegradation of the implant material while promoting biological reactions without the use of drug elution.MethodsHerein, precise temperature and thickness controlled atomic layer deposition (ALD) was utilized to provide a unique and conformal nanoscale TiO2 coating on a customized magnesium-zinc stent alloy.ResultsImpressively, results indicated that this TiO2 nano-thin film coating stimulated coronary arterial endothelial cell adhesion and proliferation with additional features acting as a protective barrier. Data revealed that both surface morphology and surface hydrophilicity contributed to the success of the ALD nanoscale coating, which further acted as a protection layer inhibiting the release of harmful degradation products from the magnesium-zinc stent.ConclusionOverall, the outcome of this in vitro study provided a promising ALD stent coating with unique nano-structural surface properties for increased endothelialization, and as a result, ALD should be further studied for numerous biomedical applications.

Preparation Nano Thin Film of Polyaniline/MWCNT and Study of Their Response to Some Organic Matter Fumes

Preparation Nano Thin Film of Polyaniline/MWCNT and Study of Their Response to Some Organic Matter Fumes

Self-bonding of semi-crystalline PEEK by nano thin film polymer coatings facilitated by multiple plasma depositions

Self-bonding of PEEK is an enabling process for the use of PEEK for devices that require hermetic seals such as active medical implants. Self-bonding of semi-crystalline polyether ether ketone (PEEK) has been successfully demonstrated through plasma immersion ion implantation and deposition (PIIID) treatment. The surface properties, such as wetting property, free energy, and roughness, of PEEK that influence the adhesive strength are manipulated according to the ionization power and excitation reactivity of the plasma gas implemented in the treatment. Temperature, one of the self-bonding process condition parameters, is a factor influencing the functionalities of the plasma gas. In general, the combinations of plasma gases, C2H2, CH4, and O2, were capable of achieving at least fivefold adhesive strengths of PEEKs with only CH4 plasma gas showing a negative response. Single O2/CH4- and C2H2-PIIID plasma treatments performed effectively in enhancing the adhesive strength of PEEK with almost eightfold compared to untreated control while double C2H2/O2+O2/CH4-PIIID/PIIID plasma treatment obtained an equivalent achievement.

Ab initio calculations of optoelectronic properties of antimony sulfide nano-thin film for solar cell applications

Antimony sulfide (Sb2S3) micro thin-film have been received great interest as an absorbing layer for solar cell technology. In this study, to explore its further potential, electronic and optical properties of Sb2S3 simulated nano-thin film are investigated by the first-principles approach. To do so, the highly accurate full-potential linearized augmented plane wave (FP-LAPW) method framed within density functional theory (DFT) as implemented in the WIEN2k package is employed. The films are simulated in the [0 0 1] direction using the supercell method with a vacuum along z-direction so that slab and periodic images can be treated independently. From our calculations, indirect band gap energy values of Sb2S3 for various slabs are found to be 0.568, 0.596 and 0.609 eV for 1, 2 and 4 slabs respectively. Moreover, optical properties comprising of real and imaginary parts of the complex dielectric function, absorption coefficient, refractive index are also investigated to understand the optical behavior of the obtained simulated Sb2S3 thin films. From the analysis of their optical properties, it is clearly seen that Sb2S3 thin films have good values for optical absorption parameters in the visible and ultraviolet wavelength range, showing the aptness of antimony sulphide thins films for versatile optoelectronic applications as a base material.

Influence of surface roughness on the adhesion hysteresis of nano thin film

The influence of surface roughness on adhesion hysteresis of Cu thin films with different thickness was studied. The Cu thin films were fabricated using dc magnetron sputtering technology and their surface adhesion forces were measured using force-displacement curves of atomic force microscopy. The experiment results show that the unload curve exhibits obvious adhesion hysteresis and that the roughness and adhesion force have opposite change tendency. The theoretical analysis on the influence of thin film roughness to the adhesion hysteresis was carried out using the Johnson-Kendall-Roberts model. The results show that the load curve and unload curve constitute a closed curve and that the smoother the surface, the more obvious adhesion hysteresis, i.e. the rougher the surface, the less obvious adhesion hysteresis. The theoretical analysis results are in good agreement with the experimental results.

Study of the effect of nanocomposite thin film coating on cutting tool tip for tribological applications

The present paper focuses on the effect of nano thin film coating on cutting tool tip for tribological applications. Chemical Vapor Deposition (CVD) technique was employed to coat nano thin film composed of graphene and molybdenum disulphide nanoparticles on to the cement carbide cutting tool tip surface. An optimum design in microstructure of the coating was made to inhibit dislocation because of the difference in the elastic modulus of the two materials used as reinforcements could lead to enhancement in the mechanical properties such as compressive stress, resistance against crack propagation and high thermal stability of the modified composite. An increase in 63% Hardness, 58% Young’s modulus, 56% Elastic recovery and 72% increase in plastic deformation was observed in case of modified tool tips as compared to the cutting tips without coating.

Computer simulation of nano-thin film condensation process in a vacuum

In this paper, the role of nano-thin film condensation process in thin film technology is shown. It was demonstrated by using the computer simulation method that the abovementioned process determines the quality of the thin film. Proprietary models were used in order to analytically calculate the condensation process of a particle on the potential field of ideal crystal substrate and to simulate the processes of condensation and growth for atoms with isotropic or anisotropic bonds with other atoms. The numerical method is based on the algorithm of a random chosen active atom, the direction of motion of this atom is calculated by the quasi-Newton method and the step of atom movement is considerably shorter than the optimal distance of two atoms.

Surface active flexible palladium nano-thin-film electrode development for biosensing

Metal atoms on surface edges or with specific coordinates possess high surface potentials, and serve as core atoms for organic molecule bonding. However, these active metal atoms may lose their activity by self-diffusion on the surface. A polyethylene terephthalate (PET) substrate provided a stable rough surface in nanoscale for metal atoms absorption and formation of a stable and active nano-thin-film (NTF) surface. However, the NTF surface roughness decreased with increasing thickness of palladium (Pd) granules, indicating that the surface growth of the Pd film followed a Stranski-Krastanov-like growth model. Therefore, the proper thickness of Pd-NTF on PET substrate (Pd NTF-PET) was developed for electrochemical impedance spectroscopy (EIS). Protein was immobilized on the Pd NTF-PET electrodes within 15 min and its biosensing sensitivity was as low as 0.1 ng per-test in 1 μl. We expect that the developed Pd NTF-PET electrode can be used for other biosensing applications as well.

Sensing properties of long-period fiber grating with coating InSnO by pulsed laser deposition

The influence of different film thickness on grating coupling coefficient and transmittance has been analyzed based on a four-layer structure model of grating and matrix transformation, in which the optimum thickness of coating [(In2O3)9(SnO2)1][indium tin oxide (ITO)] is found, and the influence of environmental refractive index and wavelength for the effective refractive index of cladding mode is simulated in theory, respectively. A structure of long-period fiber grating (LPFG) coated with ITO of high-index nanothin film by the pulsed laser deposition technology is reported. The difference of refractive index sensitivity of LPFG with ITO coating or not is analyzed in experiment. The refractive index sensitivity of LPFG with ITO coating or not is −298 and −150 nm / RIU, respectively.

Core-shell structured metal-organic framework-derived carbon with redox-active polydopamine nanothin film

In this study, three-dimensional (3D) ZIF-8-derived carbon (ZIF-8C) polyhedrons have been successfully coated with polydopamine (PDA) nanothin layer via a facile synthetic method that exploits oxidative self-polymerization of dopamine in alkaline solutions. It is observed that ca. 20 nm of PDA nanothin film is coated on ZIF-8C surface with a good homogeneity. Our results show clear morphological changes in core-shell structured PDA-coated ZIF-8C (ZIF-8C@PDA) as compared to bare ZIF-8C. In addition, the cyclic voltammetry shows conspicuous redox peaks in ZIF-8C@PDA. The observed redox activity is attributed to a series of redox reactions of oxygen species of catechol and quinone groups of PDA. With superior adhesive property and redox activity as additional surface functionality, ZIF-8C@PDA can be used in various applications, especially in energy storage applications in the future.

Performance of resistance in the variation on a nano thin film flow influenced by thermal deposition: The Buongiorno model

In the current study, the flow of Casson liquid thin film, together with heat transfer towards a stretching surface extracting out from a narrow slit in the presence of a magnetic field, viscous dissipation and thermal radiation effects, is examined. The contribution of nanoparticles is investigated by employing the Buongiorno model. Mathematical modelling is carried out in the Cartesian coordinate system and similarity analysis is opted for simplification. The numerical analysis is performed in the reduced system using the shooting method. The effects of the prominent parameters are discussed using line and bar graphs. The key finding is that the temperature drop is prominent in the case of Casson nanofluid compared to the nanofluid.

Significant enhancement in thermoelectric performance of Mg3Sb2 from bulk to two-dimensional mono layer

Thermoelectric materials can effectively convert waste heat into electrical energy and receive more and more attention. Zintl phase Mg3Sb2 is a typical layered thermoelectric material and the anisotropy in crystalline structure induces strong anisotropy in its thermoelectric properties. As a result, polycrystalline Mg3Sb2 usually can not achieve the maximum thermoelectric performance. Our research proves that the dimensionality reduction in material structure can not only avoid certain crystalline direction's poor thermoelectric properties but also effectively reduce the lattice thermal conductivity. Within the framework of the density functional theory, the thermoelectric performance of two-dimensional Mg3Sb2 mono layer is accurately investigated. The ZT value of the Mg3Sb2 nano-thin film can reach 2.5 at 900 K, which is larger than that of the bulk. The theoretical results indicate that the process of nano-engineered structure can significantly enhance the energy conversion efficiency of thermoelectrics.

Highly-transparent perovskite thin films obtained by a wet chemical processesing method

Barium titanate thin films are key materials for use in the solid-state devices, including capacitors, memories, thermistors, sensors, actuators and so on. High transmittance barium titanate thin films are suitable candidate for various electro-optic applications such as dielectric mirrors. In this research high transmittance barium titanate nanothin films were prepared by sol - gel dip - coating method, then the optical properties of the prepared nanofilms was characterized. Experimental results indicate that the surface morphology of prepared nanothin films were improved and as a result of that, a better optical properties, less optical losses were obtained in contrast with other reported data. It was found that optical propagation loss of barium titanate nanothin film was much lower than normal polycrystalline barium titanate thin film. Results also indicate that Increment of the calcination temperature reduces the thin films transparency and thickness. Other results show that increment of withdrawal rate of the substrate from the prepared sol lead to increment of thin films thickness and decrease in thin films transparency. The prepared high transparent nanothin film was amourphous and was as thin as 30 nm. It seems to us that, prepared barium titanate nanothin films would be suitable for several optical and electro-optical applications.

Multi-field coupling thermo-acoustic radiation using free-standing nano-thin films in a static magnetic field

Thermo-acoustic radiation from nano-thin film has been widely reported these years. In this paper, a static magnetic field is introduced to enhance the acoustic power in the multi-field thermo-acoustic generation. The coupled thermo-acoustic system in a static magnetic field shares the same acoustical unit with very few additional components. In the presence of a static magnetic field, thin-film vibration is excited instead of being still in the classical thermo-acoustic system. Not surprisingly, a steady magnetic field has very little impact on the thermo-acoustic generation system when a constant amplitude sinusoidal current is introduced. The oscillation perpendicular to the nano-thin film is driven by the electromagnetic force. The system response of thermo-acoustics and magneto-acoustics can be generally matched when suitable parameters are introduced. The acoustical pressure output can be significantly improved in the presence of a static magnetic field although more electrical input power should be provided in the multi-field thermo-acoustic system. Evidently, the coupled multi-field acoustical system is able to handle more electrical power input and the power input can be more easily dissipated relatively. The results show that the acoustic response of this new multi-filed coupled system can be significantly improved as compared to the classical system without magnetic effects.

Phthalocyanine-doped polystyrene fluorescent nanocomposite as a highly selective biosensor for quantitative determination of cancer antigen 125

A novel, simple, sensitive, and precise spectrofluorometric assay of cancer antigen [CA 125] is described. This modality is based on monitoring the quenching of the luminescence intensity at 790 nm of the phthalocyanine fluorophore, in a nanocomposite comprising the fluorophore and cationic polystyrene, which results from interaction with CA 125. The remarkable quenching of the luminescence intensity of the Ni-phthalocyanine complex doped in PS matrix by various concentrations of CA 125 was successfully utilized as an optical sensor for the determination of CA 125 in different serum samples of ovarian disease. The performance of the designed biosensor is determined through monitoring the quenching of the luminescence intensity at 790 nm by cancer antigen 125 after excitation at 685 nm, pH 7.3 in water. The calibration plot was achieved over the concentration range 1.0 × 10−2 – 127 U mL−1 CA-125 with a correlation coefficient of 0.99 and detection limit of 1.0 × 10−4 U mL−1. The mechanism of the interaction between the nano thin film nickel(II)phthalocyanine and CA-125 was discussed. A significant correlation between the proposed method for the assessment of CA 125 and the standard method was applied to patients and controls.

Thermo-acoustic radiation of free-standing nano-thin film in viscous fluids

In this paper, the theory of thermo-acoustic wave emission and propagation is further generalized to consider media viscosity effects. The fully coupled thermo-acoustic field theory and solution for a free-standing nano-thin film in viscous fluid are further developed where fluid viscosity was usually ignored in many early works on thermo-acoustic interaction. The effects of heat loss, heat capacity and heat exchange are also considered in this investigation. In addition to examining the double frequency effect when a sinusoidal alternating current acts on the nano thin film, we have successfully decoupled the thermal wave propagation from the acoustic effect by reformulating the governing differential equations. With appropriate simplification, an analytical prediction for near-field and far-field acoustic pressure response with viscosity effect is derived. We illustrate in some practical examples that the analytical predictions are in excellent agreement with experiments. Further referring to some past works, an analytical solution of higher-order accuracy with respect to the wavenumber omitted in the previous studies is obtained. Although the viscous effect may have limited influence in the vicinity of the thermo-acoustic source, it is vital for the subsequent propagation of acoustic waves. This work may have shown great potentials for the design of thermo-acoustic projectors for new underwater sonars as compared with the electro-acoustic traditional designs that are induced by membrane vibrations.

Improving Polymethyl Methacrylate Resin Using a Novel Titanium Dioxide Coating.

The objective of this study was to improve the surface characteristics of poly (methyl methacrylate) (PMMA) by developing a novel, thin film coating process and to characterize the resulting coated surface. An atomic layer deposition (ALD) technique was developed to deposit a titanium dioxide (TiO2 ) nano-thin film on PMMA. The surface wettability for both coated and uncoated PMMA was determined by measuring water contact angle. Wear resistance was assessed using a mechanical tooth-brushing device with a 50 g load for 6000 strokes after 5 months of water storage. A denture cleanser challenge test was performed by using sonication in 3.8% sodium perborate for 1 hour with aged specimens. X-ray photoelectron spectroscopy (XPS) was used before and after the brushing test and challenge test to analyze the PMMA surface chemical composition. The mechanical strength of coated and uncoated PMMA was measured using a three-point bending test. Surface microbial interactions were also evaluated by assessing Candida albicans biofilm attachment. Nano-TiO2 coating (30 nm thick) was successfully deposited on PMMA at 65°C. After coating, water contact angle decreased from 70° to less than 5°. After brushing test, the coating remained intact. XPS analysis revealed no loss of TiO2 from coated specimens following brushing and denture cleanser sonication for 1 hour. There was no statistically significant difference in mechanical strength (MPa) (mean ± SD) between PMMA (139.4 ± 11.3) and TiO2 -PMMA (160.7 ± 37.1) (p = 0.0995). C. albicans attachment decreased by 63% to 77% on the coated PMMA surface. ALD is a promising technique to modify surface properties of PMMA and resulted in a stable adherent thin film. By depositing a TiO2 coating, PMMA surface properties may lead to significantly reduced microorganism adhesion and easier pathogen removal from PMMA. For patients who wear dentures, reducing the oral microbial biofilm burden using a TiO2 -coated PMMA surface could positively impact their oral and systemic health.

Techniques to Investigate the Application of Cold Spray in Fabrication of Nanoplasmonic films: Parameter Identification

The decomposition of a complex system allows identification of its interacting variables. In this article the coupling between the Cold Spray (CS) thin film fabrication and functional properties in Surface Plasmon Polaritons (SPP) are investigated with a view to optimise the CS fabrication process in nano thin films. There are many reported advantages of the cold gas spray over other thermal spray technologies. However the fabrication of thin films by cold gas is limited on the capability of the transport system. This study is meant on finding ways to improve the cold gas spray for deposition of nano particles. In particular, the deposition of plasmonics nano particles for functional films in the nano scale regime. Since the requirements for each film application are different, this study is specifically targeted at films used in biosensor technology with a focus on the plasmonics sensor that use gold or silver nano particles. The paper gives the details of the parameter identification process that was used to determine missing links between the cold spray process and the optical functional thin film characteristics. In the preliminary study, intuitively, the systems engineering and pattern recognition techniques were used to explore the most probable driving variables for the cold gas coating process in functional films. This process determines the deposition parameters that characterize the surface roughness, interface roughness and film thickness as would be required for functional thin films. We have since designed a systematic numerical process for the iterations towards this direction. This study opens new avenues for further research and advancement of the cold gas spray method in nano thin film.