Potential of hybrid gold nanoparticles/graphene oxide (AuNPs/GO) coated single mode fiber (SMF) sensor by exploiting localized surface plasmon resonance (LSPR) effect for Musta’mal water identification was studied. Three structure shapes of fiber optics such as straightshape, loop-shape and u-shape had been prepared. Three layers of AuNPs with 50 nm in diameter were drop-casted onto the partially unclad polished single mode fiber (SMF) to observe the maximum sensitivity of LSPR. To enhance the LSPR effect, one layer of GO was deposited on top of the AuNPs layer. Two optical light sources with least attenuation (1310 nm and 1550 nm) were employed to study the optical power output as the sensor immersed in different type of water samples. The u-shape SMF portrayed the maximum output power about 24.2 dBm at 1550 nm wavelength. According to the analysis, the deployment of 1550 nm laser wavelength resulted in better sensitivity with 23.2% improvement compared to 1310 nm wavelength. Apparently, the LSPR phenomenon created by AuNPs/GO able to enhance the plasmonic signal up to 51.9% than the uncoated SMF. The thinnest diameter of SMF’s cladding, d=0.1195 mm with U-shape structure exhibited the highest power different of 1.10 dBm, in which suggested the best sensing performance. In conclusion, the optimization of AuNPs/GO u-shape polished SMF resulted in the maximum sensitivity with value of S=72.7 dBm/RIU for Musta'mal water identification.

The consumption of low-power electronic devices has increased rapidly, where almost all applications use power electronic devices. Due to the increase in portable electronic devices’ energy consumption, the piezoelectric material is proposed as one of the alternatives of the significant alternative energy harvesters. This study aims to create a prototype of “Smart Shoes” that can generate electricity using three different designs embedded by piezoelectric materials: ceramic, polymer, and a combination of both piezoelectric materials. The basic principle for smart shoes’ prototype is based on the pressure produced from piezoelectric material converted from mechanical energy into electrical energy. The piezoelectric material was placed into the shoes’ sole, and the energy produced due to the pressure from walking, jogging, and jumping was measured. The energy generated was stored in a capacitor as piezoelectric material produced a small scale of energy harvesting. The highest energy generated was produced by ceramic piezoelectric material under jumping activity, which was 1.804 mJ. Polymer piezoelectric material produced very minimal energy, which was 55.618 mJ. The combination of both piezoelectric materials produced energy, which was 1.805 mJ from jumping activity.

This work is carried out to study the effect of noble metal thicknesses, namely gold and silver on the SPR characteristics for smart food packaging technology applications. A Kretschmann prism coupling was introduced to excite surface plasmon polaritons (SPP). The optical refractive indices values of gold and silver were set as Rgold=0.1759+3.4104i and Rsilver=0.0585+4.2665i respectively. The thicknesses of noble metal thin films were varied between t=25nm and 95nm with the increment of 10nm for each reading. SPR signal analyses were performed by studying the characteristics of SPR peaks such as Q-factor and FWHM. Both analyses demonstrated an outstanding optical properties of silver at t=55nm in comparison with gold due to its low FWHM and high Q-factor values which proves its ability to generate excellent amount of SPP. The employment of silver witnessed the enhancement of Q-factor value up to 7.09% and the decrement of FWHM about 76.58%, relatively with gold. The introduction of silver able to convert 87.20% SPP, whilst the usage of gold only capable to excite 81.4% SPP. In conclusion, application of silver noble metal at t=55nm able to generate maximum SPR. This excellent criterion placed silver as a spectacular candidate in the development of low cost and high sensitive SPR sensor for food quality assessment applications.

This paper reports the effect of microbending losses in single mode optical fiber for pressure sensing system application. Several types of periodical corrugated plates were fabricated, namely cylindrical-structured surface (Plate A) and rectangular-structured surface (Plate B) with thicknesses of corrugated parts were varied at 0.1 cm, 0.2 cm and 0.3 cm. Laser sources with excitation wavelengths of 1= 1310 nm and 2= 1550 nm were launched at the first end of the fiber. The values of losses were recorded by using an optical power meter. It was clearly seen that the microbending losses were polynomially increased with the increment of applied pressure and the thicknesses of corrugated parts of Plate A and Plate B. The maximum microbending losses of 1.5185 dBm/kPa was resulted as SMF was coupled with corrugated plates B with thicknesses of 0.3cm by using excitation wavelength of 1550nm. These values reduced to 0.7628 dBm/kPa and 0.4014 dBm/kPa as the thicknesses were decreased to 0.2cm and 0.1cm respectively. In comparison with a plain plate which acted as a reference indicator, the maximum percentage of microbending losses was obtained as 74.29 % for Plate A and 95.02 % for Plate B. In conclusions, we successfully proved the ability of SMF as a pressure sensor by manipulating the microbending losses experienced by the fiber. The employment of 1550nm of laser wavelength results better sensitivity sensor where the system able to detect large losses as the pressure applied on the corrugated surfaces.

Humidity measurement in biomedicals, industry and electronic manufacturing applications needs an accurate and fast measurement of relative humidity by the sensor. In recent years, electronic sensors are utilized in the market, but optical humidity sensors provide several advantages over it. This paper reports the classification of optical fiber humidity sensors based on their working principles, such as fiber Bragg gratings, interferometers, and resonators. Along with the mentioned optical fiber structures, their fabrication process, equipment required for humidity sensing and the coating technique used are explained in this review. Recently, metal oxide semiconductors have been widely used as sensing material, specifically in humidity sensor applications. Thus, this paper explores optical fiber humidity sensors based on the three working principles mentioned, all of which incorporate metal oxide coatings. This review reveals that the most commonly used metal oxide for optical fiber humidity sensing is graphene oxide. This is because graphene oxide offers high sensitivity, fast response and recovery time over the other types of metal oxide. A large number of oxygen-containing groups on the surface and edge of graphene oxide also contribute to humidity sensing performance since it can permeate and absorb more water molecules. The use of hybrid nanomaterials is recently discovered and their potential as emerging coating material for optical applications are not fully exploited yet. Thus, there is still an opportunity for improvement in terms of sensitivity, response and recovery time in the context of optical fiber humidity sensor.

We report a fabrication and characterization of ZnO, TiO2 and ZnO:TiO2 composite thin films. The films were prepared on glass substrates by using the dip coating sol-gel method. ZnO was synthesized by using Zinc acetate dehydrated, glacial acetic acid and ethanol. Meanwhile, TiO2 was prepared by using titanium isopropoxide, acetic acid, isopropyl alcohol and methanol. The single sols were mixed with fixed molarity of 0.2 mol to obtain ZnO:TiO2 composite films. The optical properties of metal oxide, such as transmittance, absorbance and band gap were determined using UV-Vis spectrometer. FTIR was used to determine the chemical bonds of the materials. ZnO has the highest transmittance spectra (91%), followed by TiO2 (70%) and ZnO:TiO2 (35%) composite films. The absorbance edge shifted to the longer wavelength for ZnO:TiO2 composite film. The energy band gap of ZnO, TiO2 and ZnO: TiO2 composite were 3.8 eV, 3.6 eV and 3.5 eV, respectively.

A plastic optical fiber (POF) pH sensor is developed based on a sol-gel film. A sol-gel film was prepared by mixing tetramethyl orthosilicate (TMOS), trimethoxymethylsilane (MTMS), ethanol, distilled water and Neutral Red (NR) powder. Then, plastic optical fiber is coated by manually depositing the sol-gel film onto the tip of the POF. The sensing probe is dissolved into analytes with different pH levels, such as Coca-Cola (pH 3), tomato sauce (pH 4), black coffee (pH 5), tea (pH 6), distilled water (pH 7), soap (pH 8), baking soda (pH 9) and Clorox bleach(pH 10). The Refractive index will increase when the analytes are more acidic or more alkaline because they are concentrated with hydrogen and hydroxide ions at pH 3 and pH 10. The output power is varied based on the chemical reaction with the pH sol-gel film in the fiber-optic sensing probe. From the experimental results, it is concluded that the sensitivity of coated POF sensor, which is 0.0566 a.u/RIU, is higher than the sensitivity of the uncoated POF, which is 0.0429 a.u/RIU.

Exposure to harmful gases may cause health problems like bone marrow deficiency, which eventually drops the number of red blood cells, causing anemia and many other dangerous diseases. This work was carried out to study the potential development of a highly sensitive Kretschmann-based surface plasmon resonance (SPR) sensor for gas sensing applications using hybrid thin films of gold/titanium (Au/Ti). To optimize the excitation of surface plasmon polaritons (SPP), the light incident wavelength was varied from visible to infrared spectra. The thickness of Au thin film with a refractive index of n= 0.1758 + 3.4101k was fixed at 50 nm. Meanwhile, the thicknesses of Ti were controlled between 1 nm to 5 nm to optimize the SPR signal. Four different types of gas samples, such as benzene, methane, carbon monoxide, and carbon dioxide, were exposed to the sensor's surface. The proposed Au/Ti-based SPR sensor with thicknesses of Ti within 1 nm to 5 nm using visible and IR wavelengths able to detect various types of gaseous. Apparently, the deployment of infrared wavelength (λ=1550 nm) at Ti thickness of 3 nm resulted in the highest sensitivity up to 2412.06°/RIU and showed excellent selectivity to differentiate different types of gases. In conclusion, Au/Ti thin films are promising hybrid materials for gas sensing applications. Obviously, the sensor's sensitivity with total hybrid thin films of 53 nm was successfully enhanced as additional material, Ti, coated on the Au thin film's surface.

There are two categories in the graphene preparations which are top-down and bottom-up methods. Top-down methods consist of mechanical exfoliation, chemical exfoliation and chemical synthesis reduction. Meanwhile, chemical vapor deposition (CVD), pyrolysis and epitaxial growth synthesis under bottom-up methods. Graphene has its own limitation and unsuitable for certain applications. Thus, functionalizing the graphene with selected molecules and nanomaterials may result in graphene functionalized nanomaterials that improve the feature of the graphene. Many methods can be done to synthesise graphene based on nanocomposites and cab be divided into two types which are in-situ methods and ex-situ methods. Hydrothermal methods, electrochemical deposition methods and reduction methods are categorized in in-situ methods, while covalent interaction and non-covalent interaction are categorized in ex-situ methods. Application of graphene based nanocomposite on biosensor and supercapacitor is discussed in this review paper.

Uric acid is a waste product of the human body where high levels of it or hyperuricemia can lead to gout, kidney disease and other health issues. In this paper, Finite Difference Time Doman (FDTD) simulation method was used to develop a plasmonic optical sensor to detect uric acid with molarity ranging from 0 to 3.0 mM. A hybrid layer of gold-zinc oxide (Au–ZnO) was used in this Kretschmann-based Surface Plasmon Resonance (K-SPR) technique with angular interrogation at 670 nm and 785 nm visible optical wavelengths. The purpose of this study is to observe the ability of the hybrid material as a sensing performance enhancer for differentiating between healthy and unhealthy uric acid levels based on the refractive index values from previous study. Upon exposure to 670 nm wavelength, the average sensitivity of this sensor was found to be 0.028◦/mM with a linearity of 98.67 % and Q-factor value of 0.0053 mM− 1. While at 785 nm, the average sensitivity is equal to 0.0193◦/mM with slightly lower linearity at 94.46 % and Q-factor value of 0.0076 mM− 1. The results have proven the ability of hybrid material Au–ZnO as a sensing performance enhancer for detecting uric acid when compared with bare Au and can be further explored in experimental work.