This study focuses a new ratiometric optical fiber carbon dioxide (CO2) sensor based on CdSe/ZnS QDs and pH sensitive dye Polym-H7, those were immobilized within the Ethyl cellulose (EC). These CO2 sensing materials were coated on the surface of the optical fiber end and a 375 nm LED light was employed as an excitation source, it is shown that the emission wavelength of fluorescence dyes have no spectral overlap, so the fluorescence intensity ratio of two dyes can be used to design a ratiometric optical fiber CO2 sensor. The experimental result reveals the sensitivity of ratiometric optical fiber carbon dioxide sensor as R0/R=1.84 and exhibits a uniquely linear response for CO2 concentrations in the range of 0-100%. The suggested new ratiometric sensing approach suppresses the effects of imitation fluctuations in the intensity of excitation source.
This paper presents a ratiometric optical broad range pH sensor that comprises an optical fiber coated at one end with CdSe/ZnS quantum dots (QDs) and Oxazine 170 perchlorate (O170) embedded in ethyl cellulose (EC) matrix. The feasibility of coating an optical fiber with the sensing film to fabricate a ratiometric fiber optic broad range pH sensor is investigated. Using an LED with a central wavelength 405 nm as an excitation light source, the CdSe/ZnS QDs shows that the emission wavelength at 575 nm highly sensitive to pH and O170 shows the emission wavelength at 655 nm insensitive to pH. The ratio of fluorescence intensities at 575 nm and 655 nm has a linear relationship with pH in the 0.9–12.2 range. The ratiometric sensing approach presented in this study has the advantage of suppressing spurious fluctuations in the intensity of the excitation source and optical transmission properties of the optical fiber sensor.
A new optical carbon dioxide sensor based on the colormetric change of pH indicator α-naphtholphthalein with the internal reference fluorescent CIS/ZnS quantum dots (QDs) was developed. The luminescence intensity of CIS/ZnS QDs increased with increasing carbon dioxide concentration. The sensing films consisting of α-naphtholphthalein in polyIBM and CIS/ZnS QDs in polystyrene layer. The sensitivity of optical carbon dioxide sensor is quantified in terms of the ration I100/I0, where I100 and I0 represent the detected luminescence intensities in pure carbon dioxide and pure nitrogen environments, respectively. The experimental result reveals that the new optical carbon dioxide sensor has sensitivity of I100/I0=13.4.
A simple, low cost technique to fabricate a ratiometric optical fiber ammonia (NH3) sensor has been presented. The ratiometric optical fiber ammonia sensor was based on the ammonia induced absorbance change of sensing material Oxazine 170 perchlorate (O170) in ethyl cellulose (EC) with the luminescence intensity of 7-amino-4-trifluoromethyl coumarin (AFC). The observed luminescence intensity from AFC at 487 nm decreased with increasing the ammonia concentration. The sensitivity of optical ammonia sensor is quantified in terms of the ratio I0/I100, where I0 and I100 represent the detected luminescence intensities in nitrogen and 1000 ppm ammonia concentration, respectively. The experimental result shows that the sensitivity of the ratiometric optical fiber ammonia sensor is estimated to be 1.44. The sensitive optical ammonia sensor based on fluorescence intensity changes of AFC due to the absorption change of Oxazine 170 perchlorate in EC layer with ammonia is achieved. The ratiometric sensing approach presented in this study has the advantage of suppressing spurious fluctuations in the intensity of the excitation source and optical transmission properties of the optical sensor.
A new, simple signal processing, low-cost technique for the fabrication of a portable oxygen sensor based on time-resolved fluorescence is described. The sensing film uses the oxygen sensing dye platinum meso-tetra (pentfluorophenyl) porphyrin (PtTFPP) embedded in a polymer matrix. The experimental results reveal that the PtTFPP-doped oxygen sensor has a sensitivity of 2.2 in the 0-100% range. A preparation procedure for coating the photodiodes with the oxygen sensor film that produces repetitive and reliable sensing devices is proposed. The developed time-resolved optical oxygen sensor is portable, low-cost, has simple signal processing, and lacks optical filter elements. It is a cost-effective alternative to traditional electrochemical-based oxygen sensors and provides a platform for other optical based sensors.
This paper presents a highly-sensitive oxygen sensor that comprises an optical fiber coated at one end with platinum
(II) meso-tetrakis (pentrafluorophenyl)porphine (PtTFPP) and PtTFPP entrapped core-shell silica nanaparticles
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 I0/I100, where I0 and I100 represent the detected fluorescence
intensities in pure nitrogen and pure oxygen environments, respectively. The experimental results reveal that the oxygen
sensor has a sensitivity of 166. The response time was 1.3 s when switching from pure nitrogen to pure oxygen, and 18.6
s when switching in the reverse direction.
A simple low-cost technique for the fabrication of portable optical oxygen sensors is described. The sensing film is based on the oxygen sensing dye tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) {[Ru(dpp)3]2+} and dye-entrapped core-shell silica nanoparticles embedded in a sol-gel matrix. The feasibility of coating a photodiode with the oxygen sensing film to fabricate a portable optical sensing device is investigated. The sensitivity of the 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 result reveals that the portable optical oxygen sensor has sensitivity of 41. The sensor exhibits a linear response for oxygen concentrations in the range 0 to 60%. A preparation procedure for coating photodiodes with the oxygen film that produces repetitive and reliable sensing devices is proposed. The developed optical oxygen sensor is portable, low-cost, highly sensitive, and lacks optical filter elements. The proposed sensor is a cost-effective alternative to traditional electrochemical-based oxygen sensors and provides a platform for other optically based sensors.
This paper presents a high-performance fiber-optic carbon dioxide (CO2) sensor based on sol-gel matrix composed
of n-octyltriethoxysilane (Octyl-triEOS)/tetraethylorthosilane (TEOS) doped with pH-sensitive fluorescent dye and silica
particles. The sensor film consists of 1-hydroxy-3,6,8-pyrenetrisulfonic acid trisodium salt (HPTS, PTS-), silica particles,
tetraoctylammonium cation (TOA+), and a tetraoctylammonium hydroxide (TOAOH) phase transfer agent (i.e. the base)
immobilized within the sol-gel matrix. The sensor has a sensitivity of approximately 26 and exhibits a uniquely linear
response for CO2 concentrations in the range 0~100 %. The response time of the sensor is 9.8 s when switching from a
pure N2 atmosphere to a pure CO2 atmosphere and 195.4 s when switching from CO2 to N2.
This paper presents a high-performance fiber-optic carbon dioxide (CO2) sensor based on hybrid xerogels composed
of alkyl and perfluoroalkyl ORMOSILs (organically modified silicates) doped with pH-sensitive fluorescent dye. The
sensor film consists of 1-hydroxy-3,6,8-pyrenetrisulfonic acid trisodium salt (HPTS, PTS-), tetraoctylammonium cation
(TOA+), and a tetraoctylammonium hydroxide (TOAOH) phase transfer agent (i.e. the base) immobilized within the
hybrid xerogels. The sensor has a sensitivity of approximately 18 and exhibits a linear response for CO2 concentrations
in the range 0 ~ 30 %. The response time of the sensor is 1.7 s when switching from a pure nitrogen atmosphere to a pure
CO2 atmosphere and 38.5 s when switching from CO2 to nitrogen.
This study presents a low-cost plastic optical fiber sensor for the dual sensing of temperature and oxygen. The
sensor features a commercially available epoxy glue coated on the side-polished fiber surface for temperature sensing
and a fluorinated xerogel doped with platinum tetrakis pentrafluoropheny porphine (PtTFPP) coated on the fiber end for
oxygen sensing. The temperature and oxygen indicators are both excited using a UV LED light source with a wavelength
of 380 nm. The luminescence emission spectra of the two indicators are well resolved and exhibit no cross-talk effects.
Overall, the results indicate that the dual sensor presented in this study provides an ideal solution for the non-contact,
simultaneous sensing of temperature and oxygen in general biological and medical applications.
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