We synthesize lipophilic, highly efficient, and pH-insensitive oleic acid-modified quantum dots (QDs) with maximum emission at a wavelength of 628 nm. The pH sensing film is fabricated by encapsulating 5-hexadecanoylamino-fluorescein and QDs as the reference in D4–hydromed and plasticized polystyrene. Using a light-emitting diode with a central wavelength of 410 nm as an excitation source, it is shown that the emission wavelengths of the pH sensitive indicator and reference dye have no spectral overlap and match respectively the channels of a 3CCD (RGB) camera with low cross-talk. A series of validation experiments shows that this ratiometric pH optode has good properties of high sensitivity, long-term stability, and photostability. It had a fast response time of $<20\mathrm{s}$ when going from pH 6.3 to pH 8.0. The pH images suggest that the proposed ratiometric pH-sensing approach has great advantage and promise for field applications.

By using the hydrolysis of Al 3+ salt under near-neutral conditions, Al(OH) 3 colloidal solution has been prepared. The polypropylene based ultrafiltration (UF) membrane materials were uniformly coated with Al(OH) 3 colloid via hydraulic spin coating technique. It was indicated that the degree of hydrophobicity of membrane increases with the extension of coating time. The surface of polypropylene membrane with colloidal structure was analyzed by scanning electron microscopy, infrared spectroscopy and field emission scanning electron microscope. Samples characterization with the aid of Fourier transform infrared spectroscopy (FTIR) found that the interaction between colloidal coating and PP membrane is due to the physical force. It was shown that nano-particles are formed on the surface, which increases the surface area and thereby increases the hydrophobicity behavior of the samples.