PtOEP–PDMS-Based Optical Oxygen Sensor

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.

Solvent Resistant O2 Sensor Integrated in Pressured Flow Reactors

In this contribution we present an optical oxygen sensor that can easily be integrated into continuous flow reactors. The sensors are pressure resistant to up to 8 bars and are able to continuously measure oxygen for several hours in organic solvents. The dynamic range was evaluated up to 42 mmol/L O2 and several calibrations showed the sensors to perform linearly according to Stern-Volmer, which allows convenient two-point calibrations. By using state-of-the-art HPLC connectors and materials the sensor can be implemented at virtually every point of a standard flow reactor. Readout is conducted via a 4-channel USB phase fluorimeter.

Platinum porphyrin/3-(trimethoxysily)propylmethacrylate functionalized flexible PDMS micropillar arrays as optical oxygen sensors

A PtTPP/TPMA functionalized PDMS-based micropillar array film was presented as a flexible optical oxygen sensor with efficiently improved sensing capabilities.