Solid State pH Sensor Based on Light Emitting Diodes (LED) As Detector Platform

Sensors

卷:6

关键词: pH sensing;    solid-state pH sensor;    optical sensing;    colorimetric sensor;    light emitting diode;    light dependent resistor.;   

DOI  :  10.3390/s6080648

来源: DOAJ

【 摘 要 】

A low-power, high sensitivity, very low-cost light emitting diode (LED)-baseddevice developed for low-cost sensor networks was modified with bromocresol greenmembrane to work as a solid-state pH sensor. In this approach, a reverse-biased LEDfunctioning as a photodiode is coupled with a second LED configured in conventionalemission mode. A simple timer circuit measures how long (in microsecond) it takes for thephotocurrent generated on the detector LED to discharge its capacitance from logic 1 ( 5 V)to logic 0 ( 1.7 V). The entire instrument provides an inherently digital output of lightintensity measurements for a few cents. A light dependent resistor (LDR) modified withsimilar sensor membrane was also used as a comparison method. Both the LED sensor andthe LDR sensor responded to various pH buffer solutions in a similar way to obtainsigmoidal curves expected of the dye. The pKa value obtained for the sensors was found toagree with the literature value.

【 授权许可】

Unknown