Among the many techniques for the sensing of H2S, fluorescence has the advantage of sensitivity, selectivity, simplicity and fast response. Huan-Tsung Chang and his students from the National Taiwan University (NTU) in Taiwan had previously developed DNA-stabilized Ag/Au nanoclusters and thiol-capped Au nanodots for the sensing of H2S; but the use of expensive DNA and salt-dependent photoluminescence (PL) properties were a concern.

Advantages of aggregation

The team in NTU then prepared luminescent penicillamine (PA)-capped copper nanocluster (PA-Cu NC) aggregates from copper ions using PA as both a capping and reducing agent. The PA-Cu NCs emit light at 580 nm when excited at 326 nm through an aggregation-induced emission effect. The PL properties of PA-Cu NC aggregates show interesting polarity dependence; the emission colour can be tuned from red to yellow by varying organic solvent.

Photoluminescence quenching

Reporting here, the as-prepared PA-Cu NCs aggregates are applied to the detection of H2S, based on analyte-induced PL quenching. Upon addition of 200 µM H2S to the aqueous solution of PA-Cu NCs aggregates, the yellow emission of PA-Cu NCs aggregates is completely quenched within 20 seconds through the formation of larger non-photoluminescent CuS nanoparticles. The PL quenching is dependent on the H2S concentration over a linear range of 1–100 µM. The PA-Cu NCs aggregates are sensitive (limit of detection is 500 nM) and selective towards H2S. This allows the detection of H2S in hot spring samples with results in agreement with that from the more conventional methylene blue method.

Although the PA-Cu NC aggregates hold great potential for environmental analysis of H2S, their use in bioanalysis is still a challenge. A method of preparing highly water soluble and highly fluorescent PA-Cu NCs aggregates is still under investigation.

Full details can be found in the journal Nanotechnology 25 195502.

Further reading

Nanoclusters tailor the response of nanowire-based gas sensors (Apr 2012)
ZnO nanowire nanogenerators inspire self-powered active gas sensor (July 2013)
Controlling emission from one dimensional photonic crystals for improved detection (Feb 2014)
Biological scaffolds boost performance of toxic gas sensors (Feb 2014)