Simple and compact optode for real-time in-situ temperature detection in very small samples

Real-time in-situ temperature detection is essential in many applications. In this paper, a simple and robust optode, which uses Ruthenium (II) complex as a temperature indicator, has been developed for rapid and sensitive temperature detection in small volume samples (<5 μL). Transmission of excitation light and collection and transmission of fluorescence are performed by a homemade single-multi mode fiber coupler, which provides the entire system with a simple and robust structure. The photoluminescence intensity of Ruthenium (II) complex diminishes monotonically from 0°C to 80°C, and the response to temperature is rapid and completely reversible. When temperature is less than (or higher than) 50°C, a linear correlation exists between the fluorescence intensity and the temperature. Excellent agreement was also observed between the continuous and in situ measurements obtained by the presented optode and the discrete temperature values measured by a conventional thermometer. The proposed optode has high sensitivity, high photostability and chemical stability, a wide detection range, and thermal reversibility, and can be applied to real-time in-situ temperature detection of a very small volume biological, environmental, and chemical sample.