PtOEP–PDMS-based optical oxygen sensor

• Published in: Sensors (Basel, Switzerland) Vol. 21; no. 16; pp. 1 - 15
• Main Authors: Penso, Camila Maria Ramos Aires Moreira, Rocha, João Luís Lopes, Martins, Marcos Silva, Sousa, Paulo Jorge Teixeira, Pinto, Vânia Cristina Gonçalves, Minas, Graça, Silva, Maria Manuela, Gonçalves, L. M.
• Format: Journal Article
• Language: English
• Published: Basel Multidisciplinary Digital Publishing Institute (MDPI) 21.08.2021; MDPI AG; MDPI
• Subjects: Ação climática; Biofouling; Cellulose acetate; Chemical sensors; Dissolved oxygen; Film thickness; Luminescence; Matrix materials; Medical equipment; Membranes; Microfluidic devices; Oceanography; Optical measuring instruments; Optical sensor; Oxygen probes; PDMS; Permeability; Phosphorescence; Photodiodes; Polydimethylsiloxane; Polymers; PtOEP; Room temperature; Science & Technology; Sensors; Solvents; Ultrasonic imaging; Germany
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s21165645

The advanced and widespread use of microfluidic devices, which are usually fabricated in polydimethylsiloxane (PDMS), requires the integration of many sensors, always compatible with microfluidic fabrication processes. Moreover, current limitations of the existing optical and electrochemical oxygen sensors regarding long-term stability due to sensor degradation, biofouling, fabrication processes and cost have led to the development of new approaches. Thus, this manuscript reports the development, fabrication and characterization of a low-cost and highly sensitive dissolved oxygen optical sensor based on a membrane of PDMS doped with platinum octaethylporphyrin (PtOEP) film, fabricated using standard microfluidic materials and processes. The excellent mechanical and chemical properties (high permeability to oxygen, anti-biofouling characteristics) of PDMS result in membranes with superior sensitivity compared with other matrix materials. The wide use of PtOEP in sensing applications, due to its advantage of being easily synthesized using microtechnologies, its strong phosphorescence at room temperature with a quantum yield close to 50%, its excellent Strokes Shift as well as its relatively long lifetime (75 µs), provide the suitable conditions for the development of a miniaturized luminescence optical oxygen sensor allowing long-term applications. The influence of the PDMS film thickness (0.1–2.5 mm) and the PtOEP concentration (363, 545, 727 ppm) in luminescent properties are presented. This enables to achieve low detection levels in a gas media range from 0.5% up to 20%, and in liquid media from 0.5 mg/L up to 3.3 mg/L at 1 atm, 25 °C. As a result, we propose a simple and cost-effective system based on a LED membrane photodiode system to detect low oxygen concentrations for in situ applications. This work was co-financed by national funds through FCT—Fundação para a Ciência e Tecnologia, I.P. under project SONDA (PTDC/EME-SIS/1960/2020), by Programa Operacional Regional do Norte (NORTE2020), through Fundo Europeu de Desenvolvimento Regional (FEDER), Project NORTE-01-0145-FEDER-000032—NextSea, by the European Regional Development Fund (ERDF) through INTERREG V-A Spain-Portugal Programme (POCTEP) 2014–2020, Project N. 0591_FOODSENS_1_E and by FCT national funds, under the national support to R&D units grants, through the reference projects UIDB/04436/2020 and UIDP/04436/2020.