Studies On The Applications Of Light Emitting Diode On Spectral Analysis

Semiconductor opoelectronic device, light emitting diode (LED for short) has been widely used in many fields because of its low cost, low energy-consuming, small size and long life, such as communication, irradiation, instrumentation, etc.. In this thesis, applications of LED on spectral analysis are studied comprehensively. Different emitting colour of LED as light source to determine the content of formaldehyde, ammonia, mixture of rhadomine B and malachite green and calcium ion are reported in the thesis. The research plays an important role in pushing the development of LED on spectrum analysis. This thesis is consisted of five parts as follows:Chapter 1:ReviewA brief introduction about LED, including the principle, development, the characteristics and applications, especially in spectral analysis including the absorption spectrometry, florescence spectrometry and on-line detection is summarized. Based on the basic understanding of LED, the topic of this thesis is proposed.Chapter 2:Studies on the device for the detection of formaldehyde based on LEDAn LED absorption detection device is designed and fabricated for the determination of formaldehyde. The results show that the linear range and detection limit of the device are 0.1～3.0μg and 0.008μg respectively. The recovery rate is between 95%～105%.The determination results of the LED device are compared with that of the traditional UV-visible spectrophotometry, a good agreement is obtained. The results prove the new device is feasible and has the advantages of low cost, low energy-consuming and small size.Chapter 3:Studies on the Nile Blue sensitive film sensor for the detection of ammonia based on LEDAn ammonia sensor made of Nile Blue sensitive film and LED is described. The preparation process of Nile Blue sensitive film and parameter optimization of the sensor were investigated. It shows that this sensor has high sensitivity, short response time, low cost and good reversibility. It has been used to determine the samples with satisfying results.Chapter 4:Studies on the detection of individual component in mixture of dyes using multiple LEDsThe content of individual component in a mixed solution of rhadomine B and malachite green is determined simultaneously using three different colours of LEDs as light sources, namely green, blue and red. The linear range and calibration curves are 4～15 μg/mL, AA=0.0789mR-0.2449 for rhadomine B and 4～25 μg/mL, △A=0.0547mR-0.1128 for malachite green. The relative standard deviation is below 5 percent.Chapter 5:Studies on a plugging-in detection device for the determination of calcium ion based on LEDA small LED detection device is fabricated for the determination calcium ion in water and milk samples. The results show that the linear range of the new method is 0.03～0.5μg, the limit of detection is 0.010μg, The recovery rate of samples is between 95%-105%. The new device has small size which allows the usage of on-line detection and process analysis.