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Macrobends are optical fiber structures suitable for detecting motion changes. This structure has been developed using single-mode fibers and a combination of single-mode and multimode fibers called hetero-core. In this study, a new macrobending structure was designed and developed by adding a nano-ZnO element to the fiber optic core based on Revolution 4.0. The addition of nanomaterial elements involves an etching process that uses harmful chemicals or high-cost laser technology. Therefore, hetero-core was applied in this study to replace the etching process. The ZnO-coated fiber optics with 10 (ZnO1), 20 (ZnO2), and 30 (ZnO3) times of dip coating were developed using the dip-coating method and characterized using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Sensitivity measurement was conducted with glued optical fiber in the form of bending using a tape with a bending dimension of 2.5 cm × 1.5 cm and a wavelength of 1,550 nm. Morphological characterization using SEM proves that nanoparticles are attached to the optical fiber, and the EDX characterization confirms that the nanoparticles are ZnO elements. Optical fiber sensor sensitivity using core sizes 9, 50–9–50, 50–9–50 (ZnO1), 50–9–50 (ZnO2), and 50–9–50 (ZnO3) achieved sensitivity values of 0.91, 1.61, 2.98, 3.34, and 3.51, respectively. This study successfully produced ZnO-coated optical fiber sensors with a hetero-core structure without performing the etching process and successfully increased the sensitivity of the sensors.

Kretschmann-based Surface Plasmon Resonance (SPR) optical sensor was applied to detect the presence of kidney wastes such as urea in solutions. To enhance the sensitivity of the SPR sensor, nanolaminated gold film (thickness of 50 nm) was used. In this work, the SPR response to urea in various concentrations were measured and investigated using optical wavelengths of 670 nm and 785 nm. The signals were compared between pure urea solution versus mixed solution in the presence of the 0.227 μmol urease enzyme. The proposed mixed solution is to eliminate doping and gel entrapment process for enzyme immobilization in conventional method. Angular interrogation technique was used to measure the sensor performance in urea detection using pure and mixed solutions with urea concentration of 0 - 800 mM. Upon exposure to mixed solution using 785 nm optical wavelength, the nanolaminated gold film exhibited higher SPR sensitivity as much as 7.8 M-1 than a pure urea solution (1.4 M-1). The coupling activity between urea and urease molecules in the mixed solution near the nanolaminated gold film surface lead to sensitivity enhancement. Angle shifting of mixed solution on 50 nm-thick nanolaminated gold film using 670 nm optical wavelength was greater by ~50% compared to 785 nm. Sensorgram data shows a steady and linear increment in SPR incident angle shifting when urea concentration increased. To the best of our knowledge, this is the first time that Kretschmann-based SPR has been used for urea sensing at 670 nm and 785 nm optical wavelengths.

Silicon-based photonic integrated circuit (PIC) is a research focus in producing high-density photonics. One of the potential applications of silicon PIC is the sensing and measurement system. In this work, we use the one-dimensional photonic crystal (1D-PhC) cavity design which and utilize it at the PIC level design. The 1D PhC design used as the compact model has the same characteristics as experimentally demonstrated in previous works. The compact model is made from the S-parameter extraction of the 1D-PhC device which is done by using Lumerical FDTD software. The PIC design integrates the 1D-PhC device as a sensing component with a PN-phase shifter (PN-PS) to function as a refractive index (RI) sensor calibration or tuning circuit. A custom design of PN-PS device is used by simulating and extracting the bias voltage-effective index (bias-Neff) data by using Lumerical DEVICE and MODE into the circuit simulator. The circuit-level simulation is done by using Lumerical Interconnect software. Finally, we show the GDSII layout design of the 1D-PhC based photonic sensor calibration circuit with an analysis of generic silicon PIC design rules. The designed PIC is applicable for the bio-sensing applications and photonic SOC component. This work also shows the promise of PIC design approach for further PIC development.

Bending losses in optical fibers comprise one of the extrinsic attenuations that contribute to optical loss and they are essential for optical fiber bending sensor applications. This work investigated the optical loss in a standard single-mode step-index fiber optics due to fiber bending at 1550 nm wavelength. Variations in macro-bending loss with curvature radius and turn number have been measured. Curvature radius and turn number are examined for sinusoidal and elliptical shaped bending configurations. It has been found that the loss increases as the bending radius and number of turns increase. The result also showed that elliptical shaped bending configuration produced more loss in contrast to that of sinusoidal shaped at bending angles of 180° and 360°. The study on the macro-bending loss in terms of curvature radius and turn number for both elliptical and sinusoidal shaped bending configurations is beneficial for future fiber optic sensor applications.

This chapter was presented to promote the development of Wavelength Division Multiplexing, WDM networking system based on Polymer Optical Fiber (POF). 1 × 3 POF coupler has been fully utilized to couple the WDM optical signals. An optimum efficiency analysis and mathematical modeling has been conducted to produce an effective device to be integrated into WDM-POF system. But despite its high speed data transmission feature, optical fiber technology remains an expensive option in optical network, although the installation costs associated with fiber through the transmission network can be minimized through the fabrication of 1 × 3 POF coupler. The objective of this chapter is identifying the differences in factors affecting the output power of the POF 1 × 3 coupling. It is then able to develop an efficient WDM-POF network system with high output power at a minimal cost. Several measurements using a power meter record performance and analysis device losses and power outputs. The demultiplexer efficiency is approximately 70%. Demultiplexer fabrication is easy with color and epoxy filters, although for some parts it requires careful attention. The output shows that Ecofriendly WDM-POF Optical Coupler can be used as one of the low-cost media for home networking and automotive applications.

The purpose of this study was to design a model for microring resonators (MRRs) for biochemical detection. As a model, two types of MRRs were proposed. The Lumerical application software was used to optimize and analyze the design of MRRs device. Several parameters influencing the detection process were investigated, including the gap separation, the ring radius, the waveguide width and the etching depth dimension of MRRs. The results showed that these parameters highly influenced the condition of MRRs. The optimum parameters yielding optimum detection of biochemical are 4.5 um, 90 nm, 470 nm and 220 nm, corresponding to ring radius, separation gap, waveguide width and etching depth, respectively. The both models of MRRs proposed in this paper yield large values of FSR (free spectral range) and Q-factor therefore are suitable for biochemical detection.

The ray tracing of unclad U-shape multimode fiber optic is examined by using Zemax simulation have been proposed. The influence of the geometry of sensing region such as absorbing medium refractive index, n2, shape of fiber and the bending radius is analyzed. Number of analysis ray is determined and the value of n2 is varied at 1, 1.3314, 1.359, 1.36, 1.37 and 1.4. The intensity of light propagate inside the fiber is reducing at high n2 and this graph pattern is supported by experimental result. A U-shaped sensor is used for the analysis because of the sensitivity is higher than straight fiber design due to their higher penetration depth. Zemax simulation shows that the fiber with bending radius 1.5 mm has higher response compared to fiber with radius 2.5 mm.

There is increasing interest in tuning the physical properties of semiconductor nanostructures using metal nanoparticles. In this work, ZnO nanosphere covered with Ag nanoparticles were synthesized using gamma–radiation-assisted method. The amount of deposited Ag nanoparticles is controlled by changing irradiation dose in the range of 30–100 kGy in order to tune the semiconductor–metal interaction. The successful deposition of Ag on the ZnO nanoparticles is examined by analyzing the morphology, microstructure, optical, and magnetic properties of ZnO/Ag nanoparticles through field emission scanning electron (FESEM), microscopy X-ray diffraction spectra, UV-visible absorption, photoluminescence measurement, and vibrating sample magnetometer. FESEM and elemental mapping results confirmed that Ag nanoparticles have been concentrated at the surface of spherical ZnO particles. Moreover, formation of pure metallic Ag nanoparticles has been confirmed by XRD analysis. UV-visible absorption spectra of obtained ZnO/Ag showed two combined peaks, a weak peak at the shoulder around 360 nm corresponds to ZnO and a sharp absorption at 420 nm refers to spherical Ag nanoparticles. Obtained results from photoluminescence revealed that the near-band-edge emission and defect-related visible emission bands of ZnO could be enhanced dramatically at the same time by deposition of Ag nanoparticles, which was ascribed to localized surface plasmon–exciton coupling and surface plasmon scattering. Controlling the semiconductor and metal coupling effect is interesting because of its application in highly efficient optoelectronic devices and biosensor.

This paper describes the immobilization of glucose oxidase, GOx onto polymer matrix comprising of poly(pyrrole), PPy and poly(vinyl alcohol), PVA using gamma irradiation technique. Py/PVA-GOx film was prepared by spreading PVA:GOx, 1:1 solution onto dried pyrrole film and exposed to gamma irradiation from cobalt 60 source at doses ranging from 0 to 60 kGy. The films were subjected to structural and morphological analyses by using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM), Field emission scanning electron microscope (FESEM) and Atomic-force microscopy (AFM) techniques. Similar studies were also made on pristine pyrrole film which served as control. The SEM and FTIR spectra of Py/PVA-GOx film revealed that pyrrole has been successfully polymerized through irradiation-induced reactions. The results on the morphological properties of the samples characterize using FESEM, SEM and AFM further confirmed the occurrence of radiation-induced modification of Py/PVA-GOx film. The FTIR spectra showed the existence of intermolecular interaction between polymer matrix and GOx indicating that GOx had been successfully immobilized onto Ppy/PVA matrix by radiation-induced reactions. Results revealed that radiation induced reactions such as polymerization of pyrrole, crosslinking of PVA, grafting between the adjacent PVA and pyrrole molecules as well as immobilization of GOx onto Ppy/PVA matrix occurred simultaneously upon gamma irradiation. The optimum dose for GOx immobilization in the polymer matrix found to be 40 kGy. Therefore it is clear that this irradiation technique offered a simple single process to produce Py/PVA-GOx film without additional crosslinking and polymerization agents.

A platinum/reduced graphene oxide (Pt/rGO) nanocomposite acting as a counter electrode (CE) was fabricated using a chemical bath deposition method for In2O3-based dye-sensitized solar cell (DSSC) via sol-gel technique. The report analyzes the morphological and electrochemical impedance spectroscopy of the annealing Pt/rGO films at 350, 400, and 450 °C. Micrograph images obtained from field emission scanning electron microscopy demonstrated the annealed films are highly porous. The energy-dispersive X-ray results show that the carbon atoms were homogeneously distributed on the film annealed at 400 °C. A good photovoltaic performance was exhibited with high photocurrent density of 8.1 mA cm−2 and power conversion efficiency (η) of 1.68 % at the Pt/rGO CE annealed at 400 °C. The employed electrochemical impedance spectroscopy analysis quantifies that the Pt/rGO films annealed at 400 °C provide more efficient charge transfer with the lowest effective recombination rate and high electron life time, hence improving the performance of Pt/rGO CE.

Conducting polymers are excellent host materials for nanoparticles of metals and semiconductors. PANI-Ag-Co nanocomposite was prepared by chemical oxidative polymerization of aniline monomer in the presence of nitric acid. PANI-Ag-Co thin films were deposited on the glass substrate using spin-coating technique. The films were characterized by UV-Vis spectroscopy, XRD, AFM and TEM to analyze the internal structure and surface morphology. The performance of the sensor was conducted using I–V measurement to obtain the changes in the current before and after the incubation with E. coli bacteria in water. In UV-visible absorbance bands, a single peak appears at 421.6 nm in each band indicating the Ag-Co alloy nanoparticles were formed. The peaks in the XRD patterns show the crystals are oriented along (111) planes for Ag while (200) plane for Co. AFM images indicate the surface roughness of the PANI-Ag-Co films decreases when the concentration of Co increased. TEM image shows spherical shaped of Ag-Co alloy particles with diameter in the range of 6 – 10 nm. I–V measurements show that the current change of the films increased when incubated in E. coli. The sensitivity on E. coli increases as we increase the Co concentration. PANI-Ag-Co nanocomposite thin films can be explored further for microbial sensor application in future study.

This study highlights the structural, morphological, photovoltaic and electron transport properties of zinc oxide-multi-walled carbon nanotubes (ZnO-MWCNTs) based dye-sensitized solar cell (DSSC) prepared at different concentrations of 0.0, 0.1, 0.3 and 0.5 wt.%. The ZnO-MWCNTs thin films were prepared by a chemical bath deposition method. X-ray diffraction (XRD) analysis proved the formation of hexagonal wurtzite of the samples. The crystallite sizes, D of ZnO-MWCNTs was measured varies from 21 nm to 11 nm. The oat-like ZnO nanoflakes structure and the presence of MWCNTs were captured by field-emission scanning electron microscopy (FESEM) analysis. Transmission electron microscopy (TEM) analysis measured the inner (~6.81 nm) and outer (~28.31 nm) diameter of MWCNTs. The optimum concentration of 0.1 wt.% MWCNTs produced the highest photocurrent density, Jsc of 13.5 mA/cm2, open-circuit voltage, Voc of 0.149 V, fill factor, FF of 0.406 and power conversion efficiency, PCE of 0.817 %. Optimum doping of 0.1 wt.% MWCNTs generated short electron lifetime, τeff of 0.67 ms, low effective electron chemical diffusion coefficient, Deff of 9.5 x 10-8 cm2 s-1 and higher electron recombination rate, keff of 1497.48 s-1. The addition of MWCNTs has influenced the structural, morphological, photovoltaic and electron transport properties of ZnO-MWCNTs based DSSC.

SiO2 compound was introduced into zinc ferrite using formula (1-x)ZnFe2O4 – xSiO2 synthesized by sol-gel method where distilled water and citric acid was used as a solvent and binder agent. The produced samples were annealed at 450 °C for 1h. The AFM result analysis show that the average surface roughness and particle size decreased as the compositions of x was increased. XRD results analysis confirmed the formation of spinel structures with crystallite size within range 11.27 – 4.72 nm. UV-Vis analysis to determine the energy band gap of the (1-x)ZnFe2O4 – xSiO2 samples. It shows that the energy band gap increased as the composition of SiO2 was increased due to the dielectric properties of silicon dioxide. FTIR results analysis exhibit common band in the range of 400 – 4000 cm-1. The observed band near 2350 cm-1 shows the presence of oxygen-oxygen bond in the face centered cubic (fcc) crystal lattice of oxygen atoms. The addition of SiO2 into ZnFe2O4 will help to enhance the morphological structures and optical properties. This new proposed dielectric material can be used as dielectric substrate microstrip patch antenna.

Titanium dioxide (TiO2) based dye-sensitized solar cells (DSSCs) doped with reduced graphene oxide, rGO also known as graphene were fabricated at concentrations of 0.01 wt.% . The performance of TiO2/graphene based DSSC and TiO2 based DSSC were studied using electrolytes; PAN-based gel electrolyte. The thin films were characterized using several characterizations such as scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and current-voltage (I-V) measurement. The micrograph images obtained by SEM demonstrated that the thin films are highly porous. The XRD characterization showed that the crystalline particle of thin films is an anatase state and high percentage of carbon composition can be determined using EDX analysis. Through I-V characteristic, the current density Jsc, open circuit-voltage Voc, fill-factor FF, and efficiency η of the TiO2-based DSSC were 0.196 mA/cm2, 0.44 V, 0.496 and 0.043% respectively. I-V characteristic showed an increase in values for rGO/TiO2 based DSSC such as Jsc = 1.177 mA/cm2, Voc = 0.66 V, FF = 0.656 and η = 0.509%. The addition of rGO concentration has improved the efficiency of DSSC while the use of electrolyte gel can sustain the stability of the cell.

The Zn(1-x)TixAl2O4 (x = 0.00, 0.05, 0.15 & 0.25) nanocrystals thin films were prepared by sol-gel method. The properties of Zn(1-x)TixAl2O4 were investigated by X-ray diffraction (XRD), Atomic Force Microscope (AFM), Fourier transform infrared spectra (FTIR) and (UV-Vis). By indexing the XRD patterns, we identified three structural types which is ZnAl2O4, anatase and rutile. The addition of TiO2 increased the crystallite size from 14.65 to 25.25 nm. The direct band gap was found to be around 3.35 to 3.84 eV. The addition of TiO2 increased the crystallite size, surface roughness, and lattice parameters of the resultant films, evidently affecting their density and dielectric constant (). The thin films were characterized in the certain frequency to determine the using LCR spectrometer. The and density value of the Zn(1-x)TixAl2O4 films increase linearly from 8.56 to 13.48 and 4.60 to 4.70 g/cm3 with the increasing of x value, respectively. Based on the material analysis and microwave antenna theory, GPS patch antennas were fabricated using the Zn(1-x)TixAl2O4 material. The fabricated GPS antenna with the highest (13.48) material exhibits the smallest size of antenna which is 7.45 cm2. The performances and the operating frequencies were measured using a PNA series network analyzer. The result showed that all patch antennas operate at frequency of 1.570 GHz. The GPS patch antenna fabricated from Zn0.25Ti0.75Al2O4 showed an excellent combination of return loss (-29.6 dB), smallest size (7.85 cm2), and wide bandwidth (195 MHz). All fabricated antennas are meets the requirements of GPS applications.

We demonstrate the enhancement of surface plasmon resonance (SPR) technique by implementing a multi-metallic layers of Au–Ag–Au nanostructure in the chitosan-graphene oxide (CS-GO) SPR sensor for lead(II) ion detection. The performance of the sensor is analyzed via SPR measurements, from which the sensitivity, signal-to-noise ratio and repeatability are determined. The nanostructure layers are characterized using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). We showed that the proposed structure has increased the shift in the SPR angle up to 3.5° within the range of 0.1–1 ppm due to the enhanced evanescent field at the sensing layer-analyte interface. This sensor also exhibits great repeatability which benefits from the stable multi-metallic nanostructure. The SNR value of 0.92 for 5 ppm lead(II) ion solution and reasonable linearity range up to that concentration shows that the tri-metallic CS-GO SPR sensor gives a good response towards the lead(II) ion solution. The CS-GO SPR sensor is also sensitive to at least a 10−5 change in the refractive index. The results prove that our proposed tri-metallic CS-GO SPR sensor demonstrates a strong performance and reliability for lead(II) ion detection in accordance with the standardized lead safety level for wastewater.

In this research, the fabrication of silver nanoparticles and experimental nonlinear response (NLO). The fabrication of the silver nanoparticles has been done using E-Beam evaporation on a glass substrate (Ag-NPs) and investigation of their nonlinear optical response (NLO). The silver nanoparticles was evaluated by optical spectrum (UV-Vis) that shows localized surface Plasmon band at 375 nm. The experiment shows the nonlinear absorption and nonlinear refraction effect of silver nanoparticles, the silver nanoparticles is analysed by Z-Scan technique using a femtoseconds laser with 800 nm wavelength. The result shows the nonlinear absorption (NLA) is at 4.87×10−4cmW−1, while (NLR) is at 7.94×10−9cm2W−1.

This paper reports on the optimization of full-width-at-half-maximum (FWHM) of the surface plasmon resonance (SPR) curve from a graphene-based SPR biosensor. The biosensor was designed in the Kretschmann configuration which is commonly known as the most effective technique for plasmon excitation using Lumerical's finite-difference-time-domain (FDTD) analysis. The performance of the SPR biosensor can be monitored by analysing the FWHM of the SPR curves where a smaller value is desired due to a narrower resonance peak which generally corresponds to a higher transmission power resulting in a more sensitive bio-detection. To optimise the biosensor's FWHM, Taguchi's L9 orthogonal array method was utilized involving four control factors at three level values using the objective function of Smaller-the-Better (STB) signal-to-noise ratio (SNR) characteristic. The results show that the FWHM improved to 1.1261°with best settings of A3B2C3D1. The Taguchi-optimized biosensor achieved 36.98% increase in sensitivity for urea detection.

In this work, a study of two-dimensional (2D) photonic crystal (PhC) cavities on a triangular photonic crystal lattice on Gallium Nitride have been demonstrated by using the 2D Finite Different Time Domain (FDTD) method. The resonant wavelength and quality factor (Q-factor) of designed PhC structures were studied. The forbidden region or stopband observed are between 420 to 520 nm. Therefore, the resonant wavelength of GaN-based PhC cavity was observed at $\sim460$ nm for H1 and L3 cavity. Both results show a high Qfactor obtained and calculated with a value of 65 700 and 65 957 respectively.

The technique to enhance and control the sensitivity of a one dimensional photonic crystal biosensor has been investigated by using 3D FDTD and Eigen mode solver in Lumerical software. Our results show that by reducing the waveguide width, sensitivity of the ID-PhC biosensor device will increase. This can be explained by observing the evanescent field strength shown by the mode profile which differs at particular width. By using this technique, the sensitivity can be enhanced and control geometrically. The highest sensitivity obtained is 307 nm/RIU. However by shifting the light energy from inside to outside of the waveguide, light confinement is sacrificed and may result in lower quality factor device.

This work investigates the surface plasmon resonance (SPR) response of 50-nm thick nano-laminated gold film using Kretschmann-based biosensing for detection of urea and creatinine in solution of various concentrations (non-enzymatic samples). Comparison was made with the presence of urease and creatininase enzymes in the urea and creatinine solutions (enzymatic samples), respectively. Angular interrogation technique was applied using optical wavelengths of 670 nm and 785 nm. The biosensor detects the presence of urea and creatinine at concentrations ranging from 50-800 mM for urea samples and 10-200 mM for creatinine samples. The purpose of studying the enzymatic sample was mainly to enhance the sensitivity of the sensor towards urea and creatinine in the samples. Upon exposure to 670 nm optical wavelength, the sensitivity of 1.4°/M was detected in non-enzymatic urea samples and 4°/M in non-enzymatic creatinine samples. On the other hand, sensor sensitivity as high as 16.2°/M in urea-urease samples and 10°/M in creatinine-creatininase samples was detected. The enhanced sensitivity possibly attributed to the increase in refractive index of analyte sensing layer due to urea-urease and creatinine-creatininase coupling activity. This work has successfully proved the design and demonstrated a proof-of-concept experiment using a low-cost and easy fabrication of Kretschmann based nano-laminated gold film SPR biosensor for detection of urea and creatinine using urease and creatininase enzymes.

The link power improvement in a coarse wavelength division multiplexing (CWDM) system which is transmitted using a hybrid erbium-doped fiber amplifier (EDFA) and semiconductor optical amplifier (SOA) scheme as a pre-amplifier, is discussed. The network is designed for amplifying 8 CWDM channels ranging from 1471 nm to 1611 nm. The hybrid amplifiers’ gain measurement is obtained from experimental work with gain peak at 22 dB which is observed at 1531 nm. The amplifiers also caused power increment of 5.06 dB in the transmission link before the signal is split individually at the receiving end. Based on the higher gain peaks and power spectrum at 1531 nm and 1551 nm wavelengths, the proposed amplified link would be useful for the transmission of video applications.

The nanocomposite of polyaniline (PANI) and bimetallic nanoparticles of silver and iron were prepared by the oxidative polymerization of aniline and the reduction process of bimetallic compound with the presence of nitric acid and PVA. The nanocomposite thin films in various compositions were deposited using spin-coating technique. The films were characterized by UV-visible spectroscopy to study the optical and structural properties. The microphotograph from TEM image shows the nanospherical of Ag-Fe alloy particles in 5 – 25 nm diameter size. The sensitivity performance was tested using I-V measurement to obtain the changes of resistivity before and after the incubation with E. coli bacteria in water. UV-visible absorption bands show the single absorbance peak at 422 – 424 nm in each band indicating the Ag-Fe alloy nanoparticles form. I-V characteristic shows the sample which contains Fe-rich Ag-Fe alloy performed high sensitivity on E. coli.

Zinc aluminate (ZnAl2O4) and zinc ferrite (ZnFe2O4) nanocrystalline structures dispersed into SiO2 matrix were prepared by sol-gel method. Phase formation of ZnAl2O4 and ZnFe2O4 was confirmed by X-ray diffraction (XRD) analysis. The crystallite sizes was determine using Scherer’s equation from the broadening of dominant peak at (311) plane. It was found the crystallite size of both compound decreased due to the decrement compositions of Zn2+ ion and Al3+ / Fe3+ ions. The crystallite sizes for ZnAl2O4 and ZnFe2O4 was calculated to be around ~ 14.16 – 11.27 nm and ~ 11.27 – 4.72 nm, respectively. FTIR analysis was done to determine the formation of spinel structures. FTIR results analysis confirmed that the formation of spinel structure where it has been observed that the bands around 800 cm-1 was associated to the vibrations of aluminum-oxygen and metal-oxygen-aluminum bonds. This characteristic was identified to the formation of zinc aluminate spinel structure. The optical properties have been done to determine the energy bandgap of ZnAl2O4 and ZnFe2O4 samples. The Uv-Visible absorption spectra have been done within wavelength 300 – 800 nm and the graph was plotted into the Tauc plot. This new dielectric material was purposed to improve the value of dielectric permittivity with addition of SiO2 where it can be applied as microwave dielectric material without changing the original spinel structures.

Development of tin/multi-walled carbon nanotube (SnO2/MWCNTs) thin films were prepared by sol-gel method. The synthesis of tin oxide (SnO2) was carried out by dissolving tin (II) chloride (SnCl3) in a solvent of 2-methoxyethanol. Different annealing temperatures of 400 °C, 450 °C, 500 °C, 550 °C and 600 °C were proposed in this study. The changes in the structural properties were analyzed by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis. AFM results indicated very rough surface area of SnO2/MWCNTs thin films where roughness values increased linearly from 1.8 nm to 11 nm by increasing the annealing temperatures from 400 °C to 600 °C. The SnO2/MWCNTs-based DSSC exhibited good photovoltaic performance with power conversion efficiency (η), photocurrent density (Jsc), open circuit voltage (Voc) and fill factor (FF) of 0.62 %, 5.6 mA cm-2, 0.55 V and 0.65 respectively. The obtained structural and photovoltaic performance analysis was proposed as a suitable benchmark for Sn/MWCNTs based dye-sensitized solar cell (DSSC) application.

The effect of gamma radiation on fabricated ZnO doped PVA nanocomposite thin films for determination of Escherichia coli has been investigated. Thin films of ZnO doped PVA were exposed to 60Co γ-radiation source at difference dose rate, ranging from 0 to 30 kGy at room temperature. The structural, morphological and electrical properties of the sample were investigated using X-ray diffraction (XRD), Atomic force microscopy (AFM) and Current-voltage (I-V) measurement. The X-ray diffraction (XRD) spectra have been performed to see the formation of crystal phases of all pure ZnO thin films. The diffraction patterns reveal the good crystalline quality and indicate the crystallization of the ZnO-PVA films strongly depends on radiation dose. The roughness of the thin film surface which can be seen by conducting Atomic force microscopy (AFM) measurement became smoother as the gamma radiation increased. The presence of Escherichia coli as a bacterial contamination in water was identified by measuring the changes of conductivity of thin films using current–voltage (I-V) measurement. The sensitivity of the sensors has been observed to be higher at a higher radiation dose.

Polyvinyl alcohol (PVA) doped with Ag thin films were synthesized from aqueous solution via sol gel method. The nanoparticle of silver was synthesized by chemical reduction using hydrazine hydrate. PVA-Ag thin films were deposited on the glass substrate by spin coating technique. Samples were varied with different combinations of metals such as Ag-Co and Ag-Al. The solutions and the films were characterized by using XRD, UV-Visible spectroscopy, AFM and TEM. XRD analysis indicates the formation of the single crystal Ag, Co and Al nanoparticles laid on (111) lattice planes. The crystallite sizes decrease when Co and Al are added to the PVA-Ag. UV-Vis absorption spectra confirmed the formation of Ag nanoparticles in the PVA matrix and the resonance plasmon band located at 417, 421 and 429 nm. Surface roughness of PVA-Ag nanocomposite thin film increased with the addition of Co and Al. TEM images show the non-agglomerated spherical particles in all samples. The performance of the sensor has been fabricated using I-V measurement with and without incubated the sensor electrode into E. coli. The result shows PVA-Ag nanocomposite thin film performed the higher sensitivity.

In this work, luminescent triangular silver nanoparticles were synthesized by radiolytic reduction method. The results showed that by variation of irradiation dose, morphology of silver nanoparticles can be converted from spherical to triangular. These shape variations mainly arise from competition between adsorption rate of polymer chains on (111) facets and reduction rate of the Ag+ ions along (110) facets during increasing dose. Furthermore, the dramatically enhanced photoluminescence spectra were observed from triangular Ag nanoparticles. This unusual behavior can be explained by excitation of dipolar and quadrupolar resonance in triangular nanoparticles which increase the electric fields at the surface.

The structural changes of radiolytically prepared aluminium–copper (Al–Cu) bimetallic nanoparticles by adjusting the precursors’ mole ratio and gamma radiation dose were investigated by transmission electron microscopy, field emission scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and X-band continuous wave electron paramagnetic resonance (EPR). The EPR spectrum was also analysed through the simulation of the powder-like EPR spectra. The results note that in prepared samples with higher Al contents, formation of core–shell structure is dominant, whereas in Cu-rich samples, the final structures are primarily in alloy and oxide forms. According to the analysis of data obtained from X-ray diffraction, FTIR, and EPR, we found that the unpaired electron of the Cu2+ ion in various phases play the main role in structural phase transformation of Al–Cu nanoparticles. Additionally, based on the information extracted from simulated EPR peaks of Cu–Cu, the diameter of the Cu core in core–shell structures was obtained. We showed that by increasing the gamma radiation dose from 80 to 120 kGy, the overall size of nanoparticles decreases from 9.47 to 3.75 nm, but the contribution of copper core increases from 11 to 22 % of overall particle size.

Zn(1 − x)Ti x Al2O4-based microwave dielectric ceramics were prepared by sol–gel method. The obtained compounds were characterized and fabricated as GPS patch antennas. The XRD patterns show a three-phase system with a spinel ZnAl2O4, anatase and a rutile (TiO2). The addition of TiO2 increased the crystallite size and grain size, and surface morphology tended to increase the ceramics density (4.61–4.75 g/cm3) and dielectric constant, e r (8.56–13.51). Based on the material investigated and microwave antenna theory, GPS patch antennas were fabricated using Zn(1 − x)Ti x Al2O4 and then measured using a PNA series network analyzer. The surface of the GPS patch antennas and ground plane was coated with 200-nm-thick silver to enhance ohmic contact. The patch antenna sizes decreased as e r increased from 2.88 × 4.37 cm (12.58 cm2) to 3.53 × 2.21 cm (7.80 cm2). Among these antennas, the Zn0.70Ti0.30Al2O4 shows an excellent performance combination between return loss (−28.71 dB), small size (3.53 × 2.21 cm), and wide bandwidth (270 MHz).

Zinc oxide–reduced graphene oxide (ZnO–rGO) thin films were fabricated on a fluorine-doped tin oxide glass substrate by a chemical bath deposition method. The thin films were immersed in the Eosin Y dye for 24 and 48 h to be fabricated as a dye-sensitized solar cell. ZnO hexagonal wurtzite structures were analyzed by X-ray diffraction analysis. Field effect scanning electron microscope showed the images of ZnO nanoparticles and nanobranches. The atomic force microscopy analysis estimated the average roughness of ZnO–rGO films doped with 0.01, 0.05 and 0.1 wt% which varied from 178 to 267 nm. The electrical or photovoltaic performance of ZnO–rGO were measured and compared accordingly by considering their power conversion efficiency, η, photocurrent density, J sc , open-circuit voltage, V oc and fill factor, FF. The cell’s efficiency of ZnO with 0.01 wt% rGO, 0.05 wt% rGO and 0.1 wt% rGO reached η = 2.36, 0.78 and 0.38 %, respectively. EIS analysis estimated the effective electron lifetime, τ eff , effective electron chemical diffusion coefficient, D eff , effective electron diffusion length of the photoanode, L n , charge transport resistance, R ct and transport resistance, R t .

Hollow Fe x Ni(1−x)OOH nanospheres with average diameter and shell thickness of about 15 and 5 nm were successfully synthesized for the first time through the radiation induced self-template method. The fast outward diffusion of Fe(III) ions due to Kirkendall effect between the core (FeOOH) and the shell (Fe x Ni(1−x)OOH) is the main reason for appearing the hollow nanoparticles. The results showed that a passive layer of Fe(III) species was formed at core and shell interface and Ni(II) ions play an important role in hollowing process of nanoparticles.