A sensing mechanism based on single metal nanoparticle is an ideal answer to the quest of sensor miniaturization. A single metal nanoparticle may exhibit environment-dependent localized surface plasmon resonance (LSPR), which provide us an excellent model system to study micro-environment influence on LSPR and vice versa, i.e.,to derive changes in the physical and chemical environment surrounding the particle. Gold nanoparticle (GNP) is the most studied nanomaterial for sensor development. Previous studies on using the LSPR of individual GNP for sensing relies on how to accurately derive the peak position change. However, poor signal to noise ratio in the extinction spectra of single nanoparticles usually results in poor precision and sensitivity. In this study, a home-built photothermal imaging instrument is able to sense temperature change around single GNP by using 532nm laser for heating and 633nm laser for probing. We found that the GNP’s photothermal signal is a function of the thermal transport properties of the ambient gas, and hence its composition. The photothermal signal appears to be a quadratic function of gas pressure when it is between 10 kPa and 90 kPa, probably due to increase of particle collision rate. At a fixed pressure (e.g. 50kPa), helium mixtures with argon, air, and nitrogen exhibit increasing photothermal signal with increasing helium concentration between 0% and about 15%, and have the following order argon&gt;air&gt;nitrogen. When helium concentration is above 15%, the photothermal signal shows non-monotonous correlation, decreasing first and then increasing. In conclusion, the detection of gas composition with single GNP using photothermal method has a few advantages such as high sensitivity and detection in real-time.

Single gold nanoparticle gas sensing based on photothermal effect

253rd National Meeting (2017)

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