Colorimetric sensor of schiff's reagent for formaldehyde gas detection

Two gas sensing elements were developed for naked-eye detection of formaldehyde gas. Polyvinyl alcohol film and silica gel were doped with Schiff’s reagent as sensing reagent of different concentrations (0.8, 1.0 and 1.3 mM). The sensors were characterized by ATR-FTIR spectrophotometer, UV-Visible spectrophotometer and DR-UV-Vis spectrophotometer. The film sensor (size 0.7x0.8 cm, thickness 0.162 ±0.001 mm) was enclosed into a glass tube (4.5 mm i.d.) while the solid-phase sensor (0.01 g) was packed into a glass tube for easy usage. The formaldehyde generation system was developed in-house and their performance was tested. Formaldehyde gas with concentration of ca. 6 ppb and 62 ppb were used to test the performance of film and solid phase sensors. The gas mixture flow rate of 100 mL min-1 was used in this study. The both sensors showed color change from yellow to magenta or purple after exposure to formaldehyde gas and the intensity of the color depended on both Schiff’s reagent concentration and formaldehyde concentration. The solid sensor doped with 0.8 and 1.0 mM Schiff’s reagent could detect formaldehyde gas and gave different color tint with response time of 2 and 3 min, respectively. The film sensor doped with 1.3 mM could detect only ca. 62 ppb formaldehyde with response time of 11 min. The performance of the prepared sensors was evaluated by applying the sensors to detect a synthetic gas sample.本研究开发了两种可实现甲醛气体目视检测的气敏传感单元。分别以聚乙烯醇薄膜与硅胶为载体，掺杂不同浓度（0.8、1.0和1.3 mM）的希夫试剂（Schiff’s reagent）作为传感试剂。采用衰减全反射傅里叶变换红外（ATR-FTIR）光谱仪、紫外-可见（UV-Visible）分光光度计以及漫反射紫外-可见（DR-UV-Vis）分光光度计对所制备的传感器进行了表征。将尺寸为0.7×0.8 cm、厚度为0.162±0.001 mm的薄膜传感器封装于内径为4.5 mm的玻璃管中；同时将0.01 g的固相传感器装填至玻璃管内，以方便使用。本研究自主搭建了甲醛气体发生系统，并对两款传感器的性能进行了测试。分别采用浓度约为6 ppb与62 ppb的甲醛气体，测试薄膜型与固相传感器的传感性能。本实验中气体混合物流速设置为100 mL·min⁻¹。两款传感器在暴露于甲醛气体后均会出现从黄色至品红色或紫色的颜色变化，且颜色深浅同时取决于希夫试剂的掺杂浓度与甲醛气体浓度。掺杂0.8 mM与1.0 mM希夫试剂的固相传感器可有效检测甲醛气体，且分别在2 min与3 min的响应时间内呈现出不同的色泽。而掺杂1.3 mM希夫试剂的薄膜传感器仅可检测浓度约为62 ppb的甲醛气体，响应时间为11 min。通过将传感器应用于合成气体样品的检测，对所制备传感器的整体性能进行了评估。