Novel temperature-activated humidity-sensitive optical sensor

SENSORS AND ACTUATORS B-CHEMICAL

卷:240

Article

Mills, A.¹  Hawthorne, D.¹  Burns, L.¹  Hazafy, D.¹ 

[1] Queens Univ Belfast, Sch Chem & Chem Engn, David Keir Bldg,Stranmillis Rd, Belfast BT7 1NN, Antrim, North Ireland

关键词: Indicator;    Humidity;    Methylene blue;    Hydroxypropyl cellulose;   

DOI  :  10.1016/j.snb.2016.08.182

来源: Elsevier

【 摘 要 】

A novel, colorimetric, temperature-activated humidity indicator is presented, with a colour change based on the semi-reversible aggregation of thiazine dyes (esp. methylene blue, MB) encapsulated within the polymer, hydroxypropyl cellulose (HPC). The initially purple MB/HPC film is activated by heat treatment at 370 degrees C for 4 s, at which point the film (with a colour associated with that of a highly aggregated form of MB; lambda(max) = 530 nm) becomes blue (indicating the presence of monomeric and dimeric MB; i.e. with lambda(max) = 665; 605 nm respectively). The blue, heat-treated MB/HPC films respond to an ambient environment with a relative humidity (RH) exceeding 70% at 21 degrees C within seconds, returning to their initial purple colour. This colour change is irreversible until the film is heat-treated once more. When exposed to a lower RH of up to ca. 47%, the film is stable in its blue form. In contrast, a MB/HPC film treated only at 220 degrees C for 15 s also turns a blue colour and responds in the same way to a RH value of ca. 70%, but it is unstable at moderate RH 37-50% values, so that it gradually returns to its purple form over a period of approximately 6 h. The possible use of the high heat-treated MB/HPC humidity indicator in the packaging of goods that cannot tolerate high RH, such as dry foods and electronics, is discussed. (C) 2016 Elsevier B.V. All rights reserved.

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