Fast and long term optical sensors for pH based on sol–gels

Phenol red immobilized PVA membrane for an optical pH sensor with two determination ranges and long-term stability

“…3. These similar observations were also reported by Wang et al These wider dynamic ranges may be due to the multiple different interactions between the immobilized PRF and the PVA substrate [14]. The neutral pH range is very helpful to construct a sensor for biological use, ammonium ions or seawater, and the low pH range for high acidity (up to 5 M [H + ]).…”

“…The pK a was changed from 7.9 to 8.5 and the optode could be repeatedly used for 12 months. However, the response properties of another range at low pH were not discussed in this paper [14].…”

“…Phenol red (phenolsulfonphthalein) and its derivatives are commonly used for pH determination. A great number of papers had been reported to deal with their immobilizations and pH response properties [11][12][13][14][15][16][17]. Among them, Peterson et al developed a copolymerization method to covalently immobilize phenol red into the microspheres of polyacrylamide [11].…”

Plastic Optical Fiber pH Sensor Using a Sol-Gel Sensing Matrix

“…7; the maximum of all the spectra is well visible at the wavelength of about 560 nm. According to literature (Wang, 2003), at this wavelength the phenol red (a) (b) Fig. 6.…”

A New Optical Sensor for Selective Monitoring of Nickel Ion Based on A Hydrazone Derivative Immobilized on the Triacetyl Cellulose Membrane

“…Optical chemical sensors (optodes), are usually based on acid-base indicators, which can be adsorbed on the surface of support materials [5][6][7]. Several different support materials including lipophilic polymers and plasticizers, hydrophilic polymers, ionic polymers, sol-gel glass and molecularly imprinted polymers have been used for preparation of optical sensors [5][6][7][8].…”