Oxygen and carbon dioxide sensors are involved in many chemical and biochemical reactions. Consequently, considerable efforts over years have been devoted to discover and improve suitable techniques for measuring gas concentrations by optical fiber sensors. Optical gas sensors consist of a gas-sensitive dye entrapped in a matrix with a high permeability to gas. With such sensors, gas concentration is evaluated based upon the reduction in luminescence intensity caused by gas quenching of the emitting state. However, the luminescence quenching effect of oxygen is highly sensitive to temperature. Thus, a simple, low-cost plastic optical fiber sensor for dual sensing of temperature and oxygen is presented. Also, a modified Stern-Volmer model is introduced to compensate for the temperature drift while the temperature is obtained by above dual sensor. Recently, we presented highly-sensitive oxygen and dissolved oxygen sensors comprising an optical fiber coated at one end with platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and PtTFPP entrapped core-shell silica nanoparticles embedded in an n-octyltriethoxysilane(Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. Also, two-dimensional gas measurement for the distribution of chemical parameters in non-homogeneous samples is developed and is of interest in medical and biological researches.

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This paper presents a high-sensitivity oxygen sensor that comprises an optical fibre coated at one end with tris (4, 7-diphenyl-1, 10-phenanthroline) ruthenium (II) ([Ru (dpp)3]2+) and porous silica nanoparticles embedded in an n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. The sensitivity of the optical oxygen sensor is quantified in terms of the ratio IN2/IO2, where IN2 and IO2 represent the detected fluorescence intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results show that the oxygen sensor has a sensitivity of 26. The experimental results show that compared to oxygen sensor based on Ru (II) complex immobilized in the sol-gel matrix, the proposed optical fibre oxygen sensor has higher sensitivity. In addition to the increased surface area per unit mass of the sensing surface, the porous silica nanoparticles increase the sensitivity because a substantial number of aerial oxygen molecules penetrate the porous silica shell. The proposed optical sensor has the advantages of easy fabrication, low cost, fast response and high sensitivity for oxygen monitoring using a cheap LED as a light source.