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

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

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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 click here 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 iphone 13 atlanta toagree with the literature value.