Ahmad Shukri Muhammad Noor

Application of polypyrrole-chitosan layer for detection of Zn (II) and Ni (II) in aqueous solutions using surface plasmon resonance

In this study, a polypyrrole-chitosan layer was applied to detect zinc and nickel ions in aqueous solution using surface plasmon resonance. The resonance angle shift was found to monitor the binding interaction between ions and the polymer film. The polypyrrole-chitosan film was coated on the gold layer with an electrochemical deposition method. The Langmuir model was compared with the Freundlich model to explain the binding. Consequently, the Langmuir model was fitted with experimental data better than the Freundlich equation, and the detection limit was 0.01 ppm.

Application of polypyrrole multi-walled carbon nanotube composite layer for detection of mercury, lead and iron ions using surface plasmon resonance technique.

Polypyrrole multi-walled carbon nanotube composite layers were used to modify the gold layer to measure heavy metal ions using the surface plasmon resonance technique. The new sensor was fabricated to detect trace amounts of mercury (Hg), lead (Pb), and iron (Fe) ions. In the present research, the sensitivity of a polypyrrole multi-walled carbon nanotube composite layer and a polypyrrole layer were compared. The application of polypyrrole multi-walled carbon nanotubes enhanced the sensitivity and accuracy of the sensor for detecting ions in an aqueous solution due to the binding of mercury, lead, and iron ions to the sensing layer. The Hg ion bonded to the sensing layer more strongly than did the Pb and Fe ions. The limitation of the sensor was calculated to be about 0.1 ppm, which produced an angle shift in the region of 0.3° to 0.6°.

Multi-wavelength generation by self-seeded four-wave mixing.

A cost effective method of generating multi-wavelength based on the cascaded four wave mixing effect is experimentally demonstrated. The proposed scheme is free from external tunable laser sources and pump modulators, resulting from the use of a broadened linewidth tunable dual wavelength erbium-doped fiber laser as intracavity pump. In this configuration, the number of four wave mixing cascades becomes larger in tandem with the increment of erbium-doped fiber amplifier output power. When its output power is set at 20.57 dBm, six waves having optical signal to noise ratio larger than 10 dB are generated. The six waves are stable with peak power fluctuations less than 1 dB within 30 minutes period and tunable with wavelength spacing ranging from 1.03 nm to 11.31 nm.

Relative Intensity Noise Reduction by Optimizing Fiber Grating Fabry–Perot Laser Parameters

A set of nonlinear rate equations that can describe an external cavity laser with any arbitrary external optical feedback (OFB) level are derived. A comprehensive study on the relative intensity noise (RIN) characteristics of a fiber grating Fabry-Perot is performed numerically. In this paper, fiber Bragg grating (FBG) is used as a wavelength lasing selective element to control the external OFB level, thereby control the RIN. In addition to the external OFB level, the effect of other external cavity parameters such as temperature, injection current, cavity volume, gain compression factor, and FBG parameters on RIN characteristics is investigated. The temperature dependence (TD) of RIN is calculated according to TD of laser parameters instead of well-known Parkove relationship. Results show that by optimization, the peak value of the RIN can be reduced down to around -150 dB/Hz. The optimum and the shortest external cavity length that provides the minimum RIN is found to be around 3.1 cm. In addition, by optimization, the relaxation oscillation frequency of RIN spectra is shifted toward around 5.6 GHz.

Optical nonlinear refractive index of laser-ablated gold nanoparticles graphene oxide composite

Gold nanoparticles were prepared in graphene oxide using laser ablation technique. The ablation times were varied from 10 to 40 minutes, and the particle size was decreased from 16.55 nm to 5.18 nm in spherical shape. The nanoparticles were capped with carboxyl and the hydroxyl groups were obtained from Fourier transform infrared spectroscopy. Furthermore, the UV-visible peak shifted with decreasing of nanoparticles size, appearing from 528 nm to 510 nm. The Z-scan technique was used to measure the nonlinear refractive indices of graphene oxide with different concentrations and a gold nanoparticle graphene oxide nanocomposite. Consequently, the optical nonlinear refractive indices of graphene oxide and gold nanoparticle graphene oxide nanocomposite were shifted from 1.63 × 10-9 cm2/W to 4.1 × 10-9 cm2/W and from 1.85 × 10-9 cm2/W to 5.8 × 10-9 cm2/W, respectively.

Numerical investigation of the performance of an SPR-based optical fiber sensor in an aqueous environment using finite-difference time domain

We investigate a surface plasmon resonance (SPR)-based optical fiber sensor using 2-D finite-difference time domain (FDTD) simulations. The optical sensor is designed by polishing a single-mode optical fiber by symmetrically removing a portion of its cladding forming two sensing regions. We analyze the effects of two physical parameters of the sensor in an aqueous medium, i.e. the thickness of the metal layer and the amount of residual cladding using numerical simulations. The results show that a good transmission dip can be obtained by optimizing these parameters. Thus, the sensor structure can be deployed as an optical biosensor in aqueous environments.

Preparation of graphene oxide stabilized nickel nanoparticles with thermal effusivity properties by laser ablation method

Nickel nanoparticles were dispersed uniformly in a graphene oxide solution, using a laser ablation technique with different ablation times that ranged from 5 to 20 minutes. The results indicate that the nickel nanoparticle sizes inside the graphene oxide decreased, and the volume fraction for the nickel nanoparticles in the graphene oxide increasedwith an increasing ablation time. Further, using Fourier Transform Infrared Spectroscopy, the nickel nanoparticles in the graphene oxide demonstrate greater stability from possible agglomeration when the nanoparticle was capped with oxygen from the carboxyl group of the graphene oxide. The thermal effusivity of the graphene oxide and nickel nanoparticle graphene oxide composite was measured using a photoacoustic technique. The concentration of graphene oxide shifted from 0.05mg/L to 2mg/L, and the thermal effusivity increased from 0.153Wċs1/2ċcm-2ċK-1 to 0.326Wċs1/2ċcm-2ċK-1. In addition, the thermal effusivity of the nickel nanoparticles graphene oxide composite increased with an increase in the volume fraction of nickel nanoparticles from 0.1612Wċs1/2ċcm-2ċK-1 to 0.228Wċs1/2ċcm-2ċK-1.

Application of Surface Plasmon Resonance Based on a Metal Nanoparticle

Surface plasmon resonance (SPR) is a powerful technique to retrieve information on optical properties of biomaterial and nanomaterials. Biosensor based on SPR is a versatile technique for biological analysis applications. Essentially, SPR depends on the optical properties of metal layer [1] and enviromental changes so it is related to charge density oscillation at the interface between them [2]. Hence, biomolecular possess an extreme sensitivity to plasmon resonance and they remove the requirement for extrinsic biomolecular labeling [3]. One advantage of SPR is, the light beam never passes through the dielectric medium of interest and hence the effect of absorption of the light in the analyte can be ignored. Hence, the main potential of surface plasmon resonance is characterization of medium after the metal layer.

Polypyrrole thin film sensor base surface plasmon resonance for detection of Cu(II) and Fe(III) in aqueous solution

In this study, the performance of surface plasmon resonance method incorporated with polypyrrole sensing layer was examined for detection of Cu (II) and Fe (III) ions in aqueous solutions. The polypyrrole was prepared by electro-oxidation method on a gold layer for the detecting low concentration ions (0.1, 1 5 10 20 ppm). The experiments carried out at room temperature, and each sample was flowed through the flow cell. A photodiode registered the SPR signals as the function of rotation angle and thickness of layers. For observing the association and dissociation processes, the experiments repeated more than ten times, and the sensorgrams were obtained. Furthermore, Langmuir model was utilized to describe the binding interactions of ions with the polypyrrole layer. The lower concentration detection limit was about 0.1 ppm and the terminal resonance angles were occurred after the 300 s. The sensor was also found to be more sensitive to the presence of Cu than Fe ions.

Self-seeded four-wave mixing cascades with low power consumption

The efficient generation of self-seeded four-wave mixing (FWM) cascades utilizing a double pass technique is demonstrated. To prove the efficiency of this technique, FWM cascades with a double-pass scheme are compared to their counterpart with a single-pass scheme. Experimental results indicate that the double-pass scheme consumes less power than the single-pass scheme. For the generation of ten spectral lines, the double-pass scheme requires an erbium-doped fiber amplifier (EDFA) output power of 114.02 mW, representing a 69% improvement over the single-pass scheme, which demands an EDFA output power of 366.32 mW. This is attributed to the use of the first-pass FWM cascades as seeds in the double-pass scheme, in contrast to two intracavity pumps as seeds in the single-pass scheme. The proposed scheme is not only free from external laser sources and phase modulators but also needs low power for operation, leading to the double-pass scheme being more cost effective than the single-pass scheme.