Poly-2-[4-(diethylaminophenyl) imino]-5-nitrophenol (PEAPINP) and 2-[4-(diethylaminophenyl) imino]5- nitro-phenol (EAPINP) were prepared as new pH sensors. Spectrophotometric and spectrofluorometric response of the novel sensors in various p(H) values were investigated. EAPINP has the ability to respond linearly at alkaline p(H) values, 8 to 9, and can be utilized in absorption and wavelength radiometric methods. PEAPINP has the ability to respond linearly at lower pH values, 6 to 7, and can be used as an alternative pH sensor in this range. The new sensors are yellow-colored in acidic and neutral media and red-colored in alkaline P(H)s. With their colorimetric responses at different pH ranges EAPINP and PEAPINP can be used to develop color-tunable P-H sensors.