Tunable optical and magneto-optical properties of nickel-polymer nanoparticles

Abstract

The optical and magneto-optical (MO) properties of composites containing magnetic nanoparticles were experimentally as well as theoretically found to be dependent on the interparticle spacing, surrounding medium and particle size of the constituent nanoparticles. In this work, the optical and MO properties of composites consisting of two nickel (Ni) nanoparticles (NP) and embedded in polymethyl methacrylate were theoretically investigated in the wavelength range of 400–900?nm using the discrete dipole approximation method, which accounts for optical coupling between Ni NPs. The theoretical calculations suggest that the shifts in spectral peak position depend on both interparticle distance and particle size corresponding to the experimental results. In addition, the observed optical spectra of Ni NPs showed the plasmon resonance in the visible light range in the electromagnetic wave. The basic results of this study might be used for fabricating optical and MO devices.     

Photosensors based on Ni-doped ZnO/p-Si junction prepared by sol-gel method

A high quality and adherent transparent layer of ZnO thin films were grown on p-type Si substrates to fabricate undoped and Ni-doped ZnO/p-Si heterojunction. The C _Adj ?V and G _Adj ?V plots of the diodes are significantly affected with the frequency and Ni-dopant contents. The interface state density (D _it ) is changed with the frequency and Ni contents. The high value of ideality factor (n) is due to the interface states at the interface of the diode and the effect of barrier inhomogeneities or to the high value of R _s . The transient photocurrent measurements were used to analyze the photoresponse of the diodes. The obtained results indicate that the diodes could be used as an optical sensor especially for the Ni-doped at 0.5 % ZnO/p-Si diode.     

Dielectric and electrostrictive properties of 0.9PMN-0.1PT multilayer ceramics with ZnO additive

Abstract

Multilayer cermaics based on the 0.9PMN-0.1PT were fabricated by tape casting and their dielectric and electrostrictive properties were investigated as a function of the number of active layers. The 0.9PMN-0.1PT ceramics modified with various amounts of ZnO were prepared by molten salt synthesis. An increase in the number of active layers led to linear increases in levels of capacitance and displacement. These properties increased with up to the 2mol% ZnO addition and then decreased with further addition regardless of number of active layers. In the case of 2 mol% ZnO addition, the specimens consisting of four active layers showed a maximum dielectric constant of 25,200 and electrostrictive strain of 5.8 × 10^?4 at 10kV/cm. These results can be explained by microstructure analysis.     

Electrically stable low voltage operating ZnO thin film transistors with low leakage current Ni-doped Ba0.6Sr0.4TiO3 gate insulator

We report on the fabrication of low-voltage ZnO thin-film transistors using 1% Ni-doped Ba_0.6Sr_0.4TiO₃ as the gate insulator. The Ni-doped BST, deposited by RF magnetron sputtering at room temperature, significantly reduced leakage current density to less than 6 × 10⁻⁹ A/cm, as compared to a current density of 5 × 10⁻⁴ A/cm for undoped BST films at 0.5 MV/cm. The ZnO thin-film transistor with the Ni-doped BST gate insulator exhibited a very low operating voltage of 4 V. The field-effect mobility, the current on/off ratio and subthreshold swing were 2.2 cm² V/s, 1.2 × 10⁶, and 0.21 V/dec respectively.     

Frequency and Voltage Dependent Dielectric Properties of Ni-doped Ba0.6Sr0.4TiO3 Thin Films

Highly (100) preferred undoped and 1–5% Ni-doped Ba_1–xSr_xTiO₃ (BST) thin films were deposited onto MgO (100) single crystal substrate at 750°C using pulsed laser deposition. BST thin film-based interdigital capacitors (IDC) were prepared by standard photolithography process. The microwave properties of BST films were measured at 10 GHz. Ni-doped BST films showed better dielectric properties by exhibiting improved dielectric Q while retaining an appropriate capacitance tuning compared to undoped BST films. 1% Ni-doped BST film showed the maximum figure of merit of 2896.1. It is suggested that 1 mol% Ni doped BST film is an effective candidate for high performance tunable device applications.     

Effects of different morphologies of ZnO films on hydrogen sensing properties

This paper describes the characteristics of chemiresistor hydrogen (H₂) sensors with different ZnO film structures in which ZnO dense films, nanoparticles (NPs), and nanorods (NRs) were prepared by RF magnetron sputtering, the sol–gel method, and the hydrothermal method, respectively. These were decorated with a Pt NP catalyst to investigate the performance of devices comprised of these structures. The effects of the ZnO morphology and operating temperature on the gas sensing behavior of the sensor are reported in detail. The various ZnO film morphologies, which contributed significantly to differences between sensors, play a very important role in enhancement of the supported Pt catalyst area and initial oxygen absorption on the ZnO surface. ZnO dense films prepared by sputtering showed the fastest response with a 13.5 % resistance variation at 1,000 ppm H₂ because gas adsorption occurred only on the film surface. The sensor with ZnO NRs showed a slower response, but the highest change in resistance of 65.5 % occurred at 1,000 ppm H₂ at room temperature. H₂ sensing performance of the chemiresistor sensors was improved due to the Pt catalyst, which was more efficient in dissociating H₂ gas molecules even at low temperature. The best chemiresistor sensor was fabricated using ZnO NRs and had a response time of approximately 10 s, a 27 s recovery time, and an 81.5 % change in resistance at 200 °C.     

Tailoring the structural and optical properties of RF magnetron sputtered ZnO/graphene thin films by annealing temperature

Abstract

ZnO and ZnO/Graphene thin films were deposited on Cu substrate using a low pressure chemical vapor deposition (LPCVD) and the magnetron sputtering method. The impacts of graphene layer growth and annealing temperature on the optical properties ZnO and ZnO/Graphene thin films were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), X-ray photoelectron spectroscopic (XPS), and photoluminescence (PL) measurements respectively. XRD and SEM results reveal that all the thin films preferred the crystalline [001] orientation along the c-axis direction, which were vertical grown on substrate surface. By comparing the results and analysis of their structure, morphology, chemical bonding and optical property, it is proved that using Graphene as a buffer layer can improve the crystal quality of ZnO thin films. For the annealed ZnO/graphene nanostructures, the area ratio of UV and visible emission region of ZnO/graphene thin films increase with increasing the annealing temperature, reaches a maximum at 500?°C and then starts decreasing with further increase in annealing temperature, which indicating that the controllable ZnO/Graphene thin films have the higher crystallization quality at the annealing temperature of 500?°C. Our results demonstrate that for high quality ZnO/graphene thin films deposition, decreasing the defect concentration should be preferable to simply applying the proper annealing temperature, which might have promising applications for various UV photodetectors devices.     

Microwave Tunable Properties of Ni-Doped (Ba0.5Sr0.5)TiO3 Thin Films Grown by Pulsed Laser Deposition

(Ba_0.5Sr_0.5)TiO₃ (BST) thin films were deposited by pulsed laser deposition (PLD) and investigated as a function of Ni dopant concentration in low and high frequency regions. In low frequency region (<10 MHz), the Ni-dopant concentration in BST films has a strong influence on the material properties including dielectric and tunable properties. Ni-doped (≤3 mol%) BST films showed denser, smoother morphologies and smaller grain sizes than those with 6 and 12 mol% Ni. Dielectric constant and loss of 3 mol% Ni-doped BST films were about 980 and 0.3%, respectively. In addition, tunability and figure of merit of 3 mol% doped BST films showed maximum values of approximately 39% and 108, respectively. In high frequency region (>1 GHz), the frequency tunability range at center frequency of undoped BST and 3 mol% Ni-doped BST coplanar waveguide (CPW) resonators showed 102 and 152 MHz, respectively at 30 V dc bias. The Ni-doped BST thin films are possible in applications of microwave tunable capacitors.     

INFLUENCE OF DEPOSITION TEMPERATURE AND N2 FLOW RATE ON HIGH QUALITY ZNO THIN FILM DEPOSITED ON SiO2/SI SUBSTRATE BY ULTRASONIC SPRAY PYROLYSIS

ABSTRACT

ZnO thin films were prepared on SiO₂/Si substrate by ultrasonic spray pyrolysis (USP) method using the aqueous solution of zinc acetate dehydrate. X-ray diffraction (XRD) and atomic force microscopy (AFM) were employed to analyze the crystalline and microscopic structure of the films. The properties of ZnO films were investigated with respect to deposition temperature (T_s) and N₂ flow rate (f). The results show that ZnO thin films exhibit hexagonal wurtzite structure and the highly preferential orientation along c-axis under T_s = 320°C and f = 5 L/min deposition condition.     

Materials Characterization of Cobalt Antimonide Nanostructures as Thermoelectric Material

Abstract

Cobalt antimonide (CoSb₃) nanoparticles, a binary skutterudite structure, are synthesized by following solvothermal method using water as solvent. The solvothermally processed powders are annealed to remove the excess Sb to achieve single phase CoSb₃ nanoparticles, and are examined by X-ray diffraction (XRD) indicating the formation of cubic phase of CoSb₃. The structural analysis by selected area electron diffraction (SAED) and the elemental composition of 1:3 for Co and Sb using energy dispersive X-ray spectrophotometer (EDX) predicts formation of high purity crystalline CoSb₃ nanoparticles. Morphology of the annealed CoSb₃ powders observed using field emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) indicates particle size of 50-100?nm. The ultraviolet–visible (UV-Vis) absorption spectroscopy estimates an energy gap of 3?eV. The nanosized CoSb₃ skutterudites are potential intermediate-temperature thermoelectric materials with further application in developing efficient thermoelectric modules.     

A Comparative Study on the Photocatalytic Activity of Eucalyptus Leaf Assisted Green Synthesized ZnO and Chemically Synthesized ZnO towards the Degradation of Malachite Green Dye

Abstract

The photocatalytic activities of ZnO nanoparticles, synthesized by two methods, towards the degradation of Malachite green (MG) dye were studied and compared. Green synthesized ZnO nanoparticle was observed to be more effective in photodegradation and the effect of operating parameters such as catalyst loading, initial dye concentration and pH was investigated. Optimum condition was observed at catalyst load 0.24?g/L, initial dye concentration 20?ppm and pH nine which degrades 90% of the dye under 1?h of irradiation. X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX), UV-Vis spectroscopy and Fourier Transform Infrared spectroscopy(FTIR) were employed as characterization techniques for the samples.     

Combination of Mn-Ni Oxide Nanoparticles on Carbon Nanotubes through Nitrogen-Doping to Catalyze Oxygen Reduction

Abstract

With the depletion of petrochemical energy and the greenhouse effect issues caused by petrochemical energy. It is imperative to develop a kind of fuel cell has the advantages of environmental-friendly, energy saving, and low waste emission, which has great potential in future. Therefore, it’s necessary to develop a composite material with low-cost, environmental-friendly, and good stability to replace the Pt-based electrocatalyst. In this research, we prepared the Mn,Ni-doped carbon nanotubes (Mn,Ni/NCNTs) by one-step in-situ method. The transition metal (Mn, Ni) nanoparticles were coated on the acidified-carbon nanotubes to prepare the precursor. After calcined at a certain temperature, the Mn,Ni/NCNTs composite was obtained successfully. The catalytic performance of the catalysts prepared by different transition metals and different calcination temperatures were systematically studied. The results showed the produced composites had layered tubular structure, large surface area, and possessed excellent stability and methanol resistance. This kind of composite is a promising catalyst in the future practical application.     

Poly(Butylene Terephthalate) Filled with Sb2O3 Nanoparticles: Effects of Particle Surface Treatment,Particle Size,Particle Morphology and Particle Loading on Mechanical Properties of Composites

Abstract

Poor dispersion of nanoparticles in polymer matrix would limit the development and application of particulate-filled polymer composites. Therefore, the Sb₂O₃ nanoparticles were functionalized by a combination of cetyltrimethyl ammonium bromide (CTAB) and silane coupling agent KH-560 via water bath modification method so as to improve the dispersion of Sb₂O₃ nanoparticles in poly(butylene terephthalate) (PBT) matrix and enhance the interfacial adhesion between nanoparticles and polymer matrix. Besides, the coating efficiency of compound modifiers on the surface of Sb₂O₃ nanoparticles was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA). The Sb₂O₃ nanoparticles with different morphologies were systemically measured using transmission electron microscopy and dynamic light scattering measurement. The effects of particle surface treatment, particle size, particle morphology and particle loading on mechanical properties of composites were studied by the X-ray diffraction (XRD), tensile test machine and impact strength machine. The tensile strength of nanocomposites gradually increases with decreasing the particle size at the same amount of Sb₂O₃ nanoparticle fillers, which is attributed to improvement of interfacial contact area and stronger interfacial adhesion between Sb₂O₃ nanoparticles and PBT matrix. And the compound modified Sb₂O₃ nanoparticles are homogeneously dispersed in PBT matrix and play an important role in the properties enhancement. Moreover, taking consideration of the tensile and impact strengths, the optimal loading is 3?wt%.     

One step synthesis of Fe3O4/GO nanocomposites at 100°C and its magnetic properties

ABSTRACT

In the research work, we had planned a one-step procedure to prepare magnetite/graphene oxide (Fe₃O₄/GO) nanocomposites by using chemical co-precepitation method. The polycrystalline phase formation of the magnetite nanoparticles was confirmed by using X-ray diffraction setup. Structural and surface morphology properties of Fe₃O₄/GO nanocomposites are analysed by scanning electron microscopy and transmission electron microscopy. The Raman spectrum of Fe₃O₄/GO nanocomposites shows the enhancement of D and G band, which are associated with GO sheets due to the presence of Fe₃O₄ nanoparticles. Magnetic property measurement was carried out by physical property measurement system (PPMS), which shows its superparamagnetic behaviour.     

Electrical and dielectric properties of barium titanate – polydimethylsiloxane nanocomposite with 0-3 connectivity modified with carbon nanotube (CNT)

Abstract

This study explored the preparation and electrical properties of 0–3 barium titanate/polydimethylsiloxane nanocomposites by dispersing barium titanate nanoparticles (BaTiO₃; BT) into the polydimethylsiloxane (PDMS) matrix phase. The effect of barium titanate nanoparticles on electrical properties has been investigated systematically, and the relative permittivity of nanocomposites was found to increase significantly with increasing barium titanate content. Different theoretical models were used to predict the dielectric constant of these composites and compare their experimental value with the theoretical value in order to find an appropriate equation. The result indicated that the dielectric properties of composites are influenced not only by relative permittivity of the components but also dependence on interactions between ceramics and polymers. Furthermore, the preparation and dielectric properties of BT/PDMS nanocomposites modified with carbon nanotube (CNT) were also studied. The dielectric results demonstrate that adding CNT can enhance the relative permittivity of the BT/PDMS composite via improvement of dispersion and distribution of the BT nanoparticles in the PDMS matrix phase. Moreover, the electrical outputs from the BT/PDMS/CNT nanocomposites generator were measured under periodic knocking. The nanocomposites innovatively expand the feasibility of self-powered energy systems for smart sensor and energy harvesting applications.     

Structural Properties of Ga-Doped ZnO Nanoparticles Synthesized by Co-Precipitation Process

Ga-doped ZnO (GZO) nanoparticles were synthesized by co-precipitation process from starting precursors zinc dichloride (ZnCl₂) and Gallium (III) nitrate hydrate (GaN₃O₉). The deionized (DI) water was selected as the solvent. The as-precipitated powders were calcined at different temperature of 700 and 1000 °C for 2 h. For all samples, their crystal structures were investigated by X-ray diffraction (XRD) and surface morphologies were observed by a field emission scanning electron microscope (FE-SEM). The XRD results revealed that, the crystallinity of powders increases when the calcination temperature increases. Moreover, it is noticed that the intermixture phases of ZnO and Ga₂O₃ occur when the Ga doping content is exceeded the solubility limit of about 10%. In addition, SEM micrographs show the decrease of particle size with increasing Ga doping content due to lattice distortion that can hinder the crystal growth of ZnO.     

Sol-Gel Synthesis of Zn Doped MgO Nanoparticles and Their Applications

Abstract

The physicochemical properties of metal oxide nanoparticles can be significantly improved by doping. MgO and Zn²⁺ doped MgO (Zn:MgO) offers potential applications in photonic devices falling in the UV and visible region. In the present paper, sol gel method was employed to synthesize pure and Zn²⁺ doped MgO nanoparticles. XRD pattern inferred the crystalline nature of material and also the slight change in peak due to the dopant. FESEM showed the formation of nanoparticles with almost same shapes and dimensions with little agglomeration. Optical properties were studied by using UV-Vis and PL techniques. Doping of Zn²⁺ in MgO nanoparticles was verified by EDS.     

An Ecr-sputtered zno epitaxial film and its characteristics

Abstract

The properties of ZnO film deposited by an RF-magentron-mode Electron Cyclotron Resonance (ECR) sputtering system, which has added magnets to the outside of a cylindrical Zn metal target of the RF-mode ECR sputtering system reported previously^[1], are investigated. The ZnO film on the glass substrate deposited by this system was capable of driving a 1.3 GHz fundamental Rayleigh SAW for the first time. These films exhibit almost the same effective electromechanical coupling factors Keff as the theoretical Keff values calculated by finite element method (FEM).     

Optical and electrical properties of ZnO thin film containing nano-sized Ag particles

Low-temperature crystallized ZnO thin film was achieved by sol–gel process using zinc acetate dihydrate and 2-methoxyethanol as starting precursor and solvent, respectively. Ag nanoparticles were prepared with uniform size at 4.4 nm by spontaneous reduction method of Ag 2-ethylhexanoate in dimethyl sulfoxide (DMSO). The optical and electrical properties of ZnO thin films containing various contents of Ag-nanoparticles were monitored. Light scattering and charge emission and scattering behaviors of Ag nanoparticles in ZnO film were found. The incorporation of Ag nanoparticles into Al-doped ZnO film was also investigated. The optical transmittance was not degraded but the increase of electrical sheet resistance was found. The effect of Al-dopant on the transmittance and electrical sheet resistance of ZnO film was found too great to distinguish the positive effect of the incorporation of Ag nanoparticles into Al-doped ZnO thin films.     

Effects of doping Y2O3 on the microstructure and electrical properties of ZnO-Bi2O3−based varistor ceramics

ZnO-based varistor ceramics doped with different amount of Y₂O₃ have been made by two-step solid-state reaction route including the pre-calcination and subsequent sintering procedures, using nanosized ZnO powder and corresponding additives as the raw material. The phase composition, microstructure and electrical properties were studied by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM) and direct current electrical measurement. It was found that the electrical properties of the varistor ceramics sintered at 950 °C from the powder pre-calcined at 800 °C were enhanced by doped appropriate amount of Y₂O_3. Particularly, ZnO varistors doped with 1.2 mol% Y₂O₃ possessed the best comprehensive electrical properties with the breakdown field of 2113 V/mm, the nonlinear coefficient of 184.6 and the leakage current of 0.4 μA. Y₂O₃ phase, Y-rich phase and the other secondary phase particles were confirmed to distribute along the grain boundaries of predominant ZnO grains from XRD and SEM analyses. The results illustrated that doping Y₂O₃ should be a promising route to obtain varistor ceramics with excellent electrical properties.