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

Sensors

King Tong Lau¹  R. Shepherd²  Danny Diamond² 

[1] id="af1-sensors-06-00848">National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin, Irela

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: mdpi

【 摘 要 】

A low-power, high sensitivity, very low-cost light emitting diode (LED)-based device developed for low-cost sensor networks was modified with bromocresol green membrane to work as a solid-state pH sensor. In this approach, a reverse-biased LED functioning as a photodiode is coupled with a second LED configured in conventional emission mode. A simple timer circuit measures how long (in microsecond) it takes for the photocurrent 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 light intensity measurements for a few cents. A light dependent resistor (LDR) modified with similar sensor membrane was also used as a comparison method. Both the LED sensor and the LDR sensor responded to various pH buffer solutions in a similar way to obtain sigmoidal curves expected of the dye. The pKa value obtained for the sensors was found to agree with the literature value.

【 授权许可】

Unknown   
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