title: Photometric flow injection determination of phosphate on a PDMS microchip using an optical detection system assembled with an organic light emitting diode and an organic photodiode.
abstract: A compact photometric detector was constructed from an organic light emitting diode (OLED) based on a europium complex, europium(diben-zoylmethanato)3(bathophenanthroline) (Eu(DBM)3bath), as the light source and an organic photodiode (OPD) fabricated from a hetero-junction of two layers of copper phthalocyanine (CuPc)/fullerene (C60) as the photo-detector on a microchip prepared from poly(dimethylsiloxan) (PDMS) and was applied to the determination of phosphate. The OLED and the OPD were fabricated by a vapor deposition method on an indium tin oxide (ITO) coated glass substrate with the following layered structure; Glass (0.7 mm)/ITO (110 nm)/4,4'-bis[N-(1-naphthyl)-N-phenyl amino]-biphenyl (α-NPD) (30 nm)/4,4'-di(N-carbazolyl)biphenyl (CBP): Eu(3+) (8 wt%, 30 nm)/bathocuproine (BCP) (30 nm)/aluminum tris(8-hydroxyquinoline) (Alq3) (25 nm)/magnesium and silver (MgAg) (100 nm)/Ag (10nm) and Glass (0.7 mm)/ITO (110 nm)/CuPc (35 nm)/C60 (50 nm)/BCP (10 nm)/Ag (50 nm), respectively. The OLED based on the europium complex emitted a sharp light at the wavelength of 612 nm with a full width at half maximum (FWHM) of 8 nm. The performance of the photometric detector assembled was evaluated based on measurements of the absorbance of different concentrations of malachite green (MG) solutions for a batch system with 1cm long path length. The molar absorptive coefficient of the MG solution, calculated from the photocurrent of the OPD, was in good agreement with the value reported in the literature. A microchip with two inlets and one outlet U-shaped channel was prepared by a conventional photolithograph method. The OLED and the OPD were configured so as to face each other through the PDMS microchip in parallel in order to align the light axis of the OLED and the OPD with the flow cell (optical path length of 5mm), which was located at the end of outlet. For the determination of phosphate, an ion-association reaction between MG and a molybdenum-phosphate complex was utilized and a good linear relationship between the concentration and absorbance was observed in the concentration range 0-0.2 ppm, with a detection limit (S/N=3) of 0.02 ppm. The assembled photometric detector was also applied to the determination of phosphate by the flow injection of river water samples using the reagent solution containing MG and molybdenum ammonium in sulfuric acid. A good recovery (97-99%) for the river water samples, which had been spiked with the standard 0.08 ppm, with an RSD of ca 5% (n=5) was obtained using the constructed system.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Rong
authors.initials: R
authors.lastname: Liu
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Ishimatsu
authors.affiliation: Institute of System, Information Technology and Nanotechnology, 2-1-22 Momochihama, Swawara-ku, Fukuoka 819-0395, Japan; Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yahiro
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan; Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Chihaya
authors.initials: C
authors.lastname: Adachi
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Nakano
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan. Electronic address: imato@cstf.kyushu-u.ac.jp.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Imato
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D055664:Electrochemical Techniques / Q000295:instrumentation; D005063:Europium / Q000737:chemistry; D017022:Flow Injection Analysis; D005618:Fresh Water / Q000737:chemistry*; D037741:Fullerenes / Q000737:chemistry; D007211:Indoles / Q000737:chemistry; D057230:Limit of Detection; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D009942:Organometallic Compounds / Q000737:chemistry; D010618:Phenanthrolines / Q000737:chemistry; D010710:Phosphates / Q000032:analysis*; D010783:Photometry / Q000295:instrumentation* / Q000379:methods; D012394:Rosaniline Dyes / Q000737:chemistry; D017971:Tin Compounds / Q000737:chemistry
chemical_list: D004129:Dimethylpolysiloxanes; D037741:Fullerenes; D007211:Indoles; D009942:Organometallic Compounds; D010618:Phenanthrolines; D010710:Phosphates; D012394:Rosaniline Dyes; D017971:Tin Compounds; C005095:malachite green; C015445:copper phthalocyanine; D005063:Europium; C109984:indium tin oxide; C069837:fullerene C60
keywords: Microfluidic; Organic light emitting diode; Organic photodiode; Photometry of phosphate