Optical microfibers decorated with PdAu nanoparticles for fast hydrogen sensing

Optical microfibers decorated with PdAu nanoparticles are proposed for fast hydrogen sensing. The optical microfibers were fabricated by simply tapering conventional telecommunications fiber down to dimensions comparable to the wavelength of the guided light. The optical microfibers were then coated over a few millimeters with a PdAu layer in island form by depositing the layer at low deposition rate (0.1 Å/s). Then the islands were grown with a thermal annealing process until composite nanoparticles were formed. The PdAu nanoparticles deposited on the optical microfibers experience optical and physical changes when they are exposed to hydrogen. This gives rise to reversible transmission changes with an unusual pulsed like behavior which is attributed to scattering of the guided light. The devices are promising for detecting low concentrations of hydrogen (up to 8%) at room temperature with response and recovery times on the order of seconds, i.e., faster than many other hydrogen sensors that exploit phenomena at the nanoscale. The sensing of other gases is also feasible if the optical microfibers are decorated with suitable gas-permeable nanoparticles.