Superoleophilic and Superhydrophobic Inverse Opals for Oil Sensors

An inverse opal with both superoleophilic (oil contact angle (CA), 5.1 degrees +/- 1.2 degrees) and superhydrophobic (water CA, 153.8 degrees +/- 1.2 degrees) properties is fabricated using a phenolic resin (PR) as precursor and poly(styrene-methyl methacrylate-acrylic acid) (poly(St-MMA-AA)) colloidal crystals as templates. The stopband of the inverse opal can shift reversibly upon sorption of oils, whereby the peak position is a linear function of the refractive index of the adsorbed oil, e.g., a variation in refractive index of 0.02 will result in a stopband shift of 26 rim. Therefore, the inverse opals show a high sensitivity and selectivity for different petroleum oils. Moreover, as-prepared PR inverse opals show excellent oil-sensing stability in cyclic sorption experiments, which suggests a promising and economical alternative to traditional oil-sensing materials, and will provide a new approach to in situ petroleum monitoring and detection.