The electrochemical or optical sensors for environmental pollutants are developed over the past several years. Nowadays, the development of colorimetric sensing is particularly challenging since it requires no equipment at all as color changes can be detected by the naked eye. Visual detection can give immediate qualitative information and is becoming increasingly appreciated in terms of quantitative analysis. In addition, simple colorimetric-sensor have shown useful in the detection,

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... tion, and quantification of volatile organic compounds(VOC) in gas phase or heavy metal ion in aqueous phase. In this review, we investigated the wide applications and some drawbacks of colorimetricsensors. And thus, we try to suggest the methodologies of development approach of multi-functional and reversible colorimetric-sensor.