A tip-based fiber-optic localized surface plasmon resonance (LSPR) sensor is reported for sensing of acetone. It is designed by coating the tip of multi-mode optical fiber with gold nanoparticles (size: ~ 40 nm) via a chemisorption process and further functionalization with a metal-organic framework (MOF) HKUST-1 via a layer-by-layer process. Two sensors with a different number of layers (80 and 120) corresponding to different thicknesses are reported. Both sensors show a redshift of resonance wavelength to acetone as a result of an increase in local refractive index induced by acetone adsorption into the HKUST-1 thin film. Sensors gradually saturate as acetone concentration increases and are fully reversible when the concentration decreases. The sensor with a thicker film exhibits slightly higher sensitivity to acetone than the thinner film with a wavelength shift of 5.27 nm for the concentration of 3.4 %.
An optical fibre temperature sensor modified with coating a thermochromic liquid crystal (TLC) film on the tip of fibre is reported. The interrogation is conducted in the wavelength domain using a CCD spectrometer and halogen light source. The TLC sensor shows a reversible wavelength shift of the reflective light peak in the detected temperature range (28 – 46°C). The response of the sensor to temperature was linear with a sensitivity of -4.52 nm/°C for temperature increasing and -4.60 nm/°C for decreasing. There is no measurable hysteresis in the temperature calibration experiment for TLC sensor.