Modified Single Mode Optical Fiber Ammonia Sensors Deploying PANI Thin Films

Modified optical fiber sensors received increasing attention because of their superior properties over electrical sensors. These properties include their immunity towards electromagnetic interference and the ability to be deployed in corrosive and volatile environment. Several optical fiber platforms have been developed for chemical sensing applications based on modifying optical fiber cladding layer such as etched, tapered, D-shaped and etched-tapered. The modifications purpose is to extend the evanescent wave propagating out of the core physical dimensions. Thus, evanescent wave interaction with analyte is enhanced. Modified optical transducing platforms are integrated in gas sensing applications, such as ammonia. Modified optical fiber sensors coated with nanostructured thin films have been developed and gained popularity as practical devices towards gases with low concentrations. The development and characterization of the modified SMF sensing platforms including etched, tapered and etched-tapered platforms against ammonia will be presented in this chapter. These platforms were coated with PANI nanostructured thin film. The 50 μm etched-tapered SMF coated with PANI produced response, recovery times, and sensitivity of 58 s, 475 s, and 231.5%, respectively, in the C-band range. The limit of detection of the modified fiber sensor was 25 ppm. The developed sensors exhibit good repeatability, reversibility, and selectivity

Improving the electrical conductivity of carbon fiber reinforced epoxy composite using reduced graphene oxide

In this research a reduced graphene oxide (rGO) is used to coat the carbon fiber reinforced epoxy composite (CFRE) to improve and enhance its electrical conductivity that can be used in the aviation applications, because CFRE has poor electrical conductivity, and cannot withstand high electrical current coming from lightning strike. The results show that the electrical conductivity of CFRE is enhanced and increased significantly when it is coated with rGO by about 8015%, where the electrical conductivity of CFRE is increased from 1.38 × 103 (S/m) to 1.12 × 105 (S/m). Also when the content of rGO increased, the electrical conductivity of CFRE neat will be increased to higher values. The self-heating of all tested specimens was analyzed by the Joule effect. It is found that the self-heating of CFRE is enhanced and improved after coating it with rGO, therefore the self- heating of CFRE become more homogeneous, effective, reaching higher temperatures, than CFRE neat

Metal Oxide Based Optical Fiber for Methane Gas Detection

Semiconductor metal oxide (SMO) as a sensing layer for gas detection has been widely used. Many researches have been performed to enhance the sensing performance including its sensitivity, reliability and selectivity. Electrical sensors that use resistivity as an indicator of its sensing are popular and well established. However, the optical based sensor is still much to explore in detecting gas. By integrating it with SMO, the sensor offers good alternative to overcome some drawbacks from electrical sensors

Polyaniline coated on tapered multimode fiber for ammonia sensing

This paper presents optical response of polyaniline coated on tapered multimode fiber towards ammonia gas. Polyaniline was deposited onto tapered multimode fiber by spray-coating method. Surface morphology of the coating was observed under scanning electron microscope. Absorbance measurement was done using spectrometer while the coated fiber was exposed to ammonia gas with concentration varies from 0.125% to 1% at room temperature. The absorbance is proportional to the ammonia concentration. The response and recovery time is 2.27 minutes and 10 minutes, respectively

Enhancement of chitosan-graphene oxide SPR sensor with a multi-metallic layers of Au–Ag–Au nanostructure for lead(II) ion detection

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

Optical fiber coated Zinc Oxide (ZnO) nanorods decorated with Palladium (Pd) for hydrogen sensing

A novel hydrogen (H-2) sensor was developed using acid-etched optical fiber coated with zinc oxide (ZnO) nanorods. The sensing performance was done by comparing the acid-etched fiber coated with ZnO nanorods with and without decorated Palladium (Pd). The conventional optical single-mode fiber (SMF) with a diameter of 125 mu m has been modified as a transducing platform by etching it to 11 mu m diameter using hydrofluoric acid (HF) to enhance the evanescent field of the light propagates in the fiber core. The etched fiber was coated with ZnO nanorods via hydrothermal process by using seeding and growth solution method. The sensing layer was characterized through Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and X-Ray Diffraction (XRD) to verify the properties of ZnO. Catalyst Palladium (Pd) was sputtered onto the ZnO nanorods to improve H-2 detection. The developed sensor operating temperature was found to be 150 degrees C that produces 6.36 dBm increase in response towards the 1% concentration of H-2 in synthetic air. It was then tested with different concentration of H-2. The sensor decorated with Pd has better performance in sensing compared to non-decorated Pd based on the output power versus time. The sensor best response and recovery times is 6 and 5 min respectively, for acid-etched optical fiber coated with ZnO nanorods decorated with Pd for 0.75% of H-2 concentrations at 150 degrees C. The results indicate the optical fiber sensor might improve the performance towards H-2 as oppose to the conventional electrical sensor

Hydrogen sensors based on 2D WO3 nanosheets prepared by anodization

Two dimensional tungsten trioxide (WO3) films made of nanosheets were prepared using high temperature anodization of tungsten (W) thin films. The W thin films were deposited by R.F. magnetron sputtering onto quartz substrates and then anodized at 50 °C in an aqueous solution containing 1.5 M HNO3. The structural and morphological properties of the prepared films were fully characterized prior to employing them for hydrogen gas sensing application. The hydrogen gas sensing performance of WO3 thin films was investigated at different temperatures through the measurement of conductance changes upon gas exposure. Hydrogen gas exposure resulted in the intercalation and subsequent reduction of WO3 sheets, changing the charge carrier concentration and hence the conductivity of the films. The fabricated sensors were found to exhibit excellent sensitivity and repeatability when they were exposed to hydrogen gas while using air as the carrier gas. The effects of different operating temperatures on the sensitivity of the devices were studied in the range of 20–250 °C. The dynamic response of the 2D WO3 nanosheets based sensors at different operating temperatures are presented and discussed

Optimization on the preparation of microfluidic channel using dry film resist

In this work, microfluidic channel was explored using dry film resist (DFR) method. Many of previous studies used SU-8 and PDMS as the medium to fabricate microfluidic channel for making a microfluidic chamber. Microscope slides were used as the substrate for the applications with bio components since it is inert and stable. The DFR serves to be the spacer to form the channel. Several processes which include cleaning, drying, prebaking, laminating, UV exposure and finally post-baking were involved in channel making. These processes need to be optimized in order to obtain a good chamber. Silicon rubber and UV glue were used to seal the chamber system to prevent any leakages

Review of energy conservation using duty cycling schemes for IEEE 802.15.4 wireless sensor network (WSN)

Energy conservation is one of the crucial issues in wireless sensor network (WSN). A significant solution to conserve energy is done by deploying duty cycle management mechanisms in the WSN applications. This paper reviews several duty cycle mechanisms in WSN such as Duty Cycle Learning Algorithm, adaptive media access control (MAC) protocol for efficient IEEE 802.15.4 (AMPE), distributed duty cycle management (DDCM), distributed duty cycle management low power broadcast (DDCM + LPB) and distributed beacon only period. These mechanisms change their parameters such as idle listening, packet accumulation and delay in the end device transmitting queue to improve the energy conservation in WSN. The performances of these different energy conservation mechanisms have been compared at the MAC layer of IEEE 802.15.4 standard. It is found that the DDCM + LPB has made approximately 100 % enhancement in terms of average energy efficiency as compared to the other mechanisms. DDCM + LPB has significant enhancements by adapting the duty cycle according to the network traffic load condition. Using this mechanism, the duty cycle is increased when the traffic load increases and vice versa. Its energy efficiency also outperforms the conventional DDCM by the average of 10 %