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A simple and contactless intensity modulated displacement sensor is proposed and demonstrated for sensing uric acid concentration. For a concentration change of uric acid from 0 ppm to 500 ppm, two peak voltages are obtained from the displacement curve correspond to the highest reflectivity of each concentration. Those peak light intensities increase linearly with the concentration due to the increase of the refractive index of the uric acid solution. This implies that the higher concentration of uric acid tends to detect a stronger signal. The measured sensitivities are obtained at 0.0015 V/ppm and 0.0016 V/ppm for the first peak voltage and second peak voltage respectively. The result showed the percentage of similarity for the first peak to the second peak is almost 94% and the linearity more than 97% for both peak voltages is obtained suggested the consistency of the sensor system. The stability and simplicity of the contactless sensor offer a good and valuable opportunity for many applications especially in the hazardous chemical, pharmaceutical, process control and diagnostic sectors.

Abstract. Gold nanoparticles (GNPs) have been known as an excellent characteristic for Local Surface Plasmon Resonance (LSPR) sensors due to their sensitive spectral response to the local environment of the nanoparticle surface and ease of monitoring the light signal due to their strong scattering or absorption. Prior the technologies, GNPs based LSPR has been commercialized and have become a central tool for characterizing and quantifying in various field. In this review, we presented a brief introduction on the history of surface plasmon, the theory behind the surface plasmon resonance (SPR) and the principles of LSPR. We also reported on the synthetization as well of the properties of the GNPs and the applications in current LSPR sensors.

ZnO thin films have been prepared by the dip coating sol gel method. Zinc acetate dihydrate, 2-methoxyethanol and monoethanolamine (MEA) were used as precursor, solvent and stabilizer respectively. The synthesized sample was coated on glass substrate as the molarity of the solution was kept constant at 0.1 M. The structural properties and surface morphologies of ZnO thin film were characterized by XRD and FESEM. The optical properties such as transmittance, absorbance, reflectance and refractive index were studied by using UV-Vis. The functional group of the synthesized sample were verified by using FTIR. Average crystallite sizes of the samples were calculated by using Debye-Scherrer's formula. Next, ZnO is coated on POF in order to examine the reaction towards UV light.

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