Reparation Of Wood-Based Formaldehyde Colorimetric Sensor And Wettability Control Of Its Surface

Indoor formaldehyde(FA,HCHO)pollution seriously endangers people’s life and health,and it is especially important to detect indoor low concentration formaldehyde quickly and conveniently for people’s healthy home environment.The colorimetric sensing method can visualize formaldehyde pollution under visual observation,which is a simple and efficient technique for indoor formaldehyde detection.However,because the substrate of colorimetric sensor generally uses complex polymers to realize the dispersion and fixation of colorimetric sensor,and the actual application cost of these complex polymers is high.At the same time,the reaction process of formaldehyde colorimetric sensor is vulnerable to the interference of humidity.Therefore,the reasonable selection of formaldehyde colorimetric sensor substrate is of great significance for green and efficient detection of indoor formaldehyde pollution.As a natural porous material with a wide range of sources and large specific surface area,wood has hydroxyl functional groups on its surface to enhance the capture of formaldehyde gas and the sequestration of the sensing substance.Based on this,this thesis proposes the use of natural poplar wood to construct an environmentally friendly wood-based formaldehyde colorimetric sensor,which utilizes the porous structure of natural poplar wood for efficient dispersion and fixation of the colorimetric sensor,and its anisotropy to construct different substrate interfaces.Based on the pH value of the system,the effects of alkali addition and the layered structure of natural poplar wood on the colorimetric sensing properties of formaldehyde were investigated,the sensing performance and the resistance to external interference of the wood-based formaldehyde colorimetric sensor were evaluated,and the relationship between the wettability regulation of the surface of the colorimetric sensor and the colorimetric performance was studied.The main research contents and results are as follows.(1)Starting from the anisotropy of natural poplar wood,the effects of sodium hydroxide addition and different cuts on the formaldehyde properties were investigated by constructing transverse(W-c)and longitudinal(W-l)colorimetric sensors by impregnation with methyl yellow-hydroxylamine sulfate colorimetric sensing substances.Comparative analysis revealed that the structural anisotropy of different sections had significant differences on their formaldehyde colorimetric sensing effect and morphology.The best sensitivity was found at the base addition of 0.025 ml(W-l0.025)sensor and at the base addition of 0.85 ml(W-c0.85)sensor.both the W-l0.025 sensor and the W-c0.85 sensor were exclusively selective for formaldehyde molecules.In the time gradient test,the colorimetric performance of the W-c0.85 sensor increased with time,while the colorimetric performance of the W-l0.025 sensor was optimal at 20 min.Both had the optimal colorimetric sensing performance at 60%RH,but fluctuated greatly by humidity.(2)Surface hydrophobic modulation of W-l0.025 inductors by methyltriethoxysilane to investigate the effect of hydrophobic treatment on W-l0.025 inductors.Firstly,two woodbased formaldehyde colorimetric sensors,W-l0.025-MTES-l and W-l0.025-MTES-2,were produced by constructing a hydrophobic layer on the surface of W-l0.025 sensors through the coating method to investigate the effect of different treatment times on their surface wettability.The contact angle test revealed that W-l0.025-MTES-1 had a higher hydrophobic angle and both surface wettability changed from hydrophilic to hydrophobic.The W-l0.025MTES-1 inductor was found to exhibit a higher hydrophobic angle and colorimetric sensing performance and to be more resistant to humidity interference than the W-10.025 inductor when a single coating was applied,and its resistance to humidity interference was twice as high as that of the W-l0.025 sensor effectively reducing the effect of humidity on sensing performance.(3)The surface wettability of the W-l0.025-MTES-1 sensor was adjusted by perfluorooctyltriethylsilane(PFOTES),and its surface wettability increased from 127° to 151.5°.The formaldehyde colorimetric sensing results increased and then decreased with increasing surface wetting of the inductor.At a PFOTES addition of 0.30 g,the surface wetting humidity was 141.7°,and the W-l.025-MTES-1-PFOTES0.30g had the best colorimetric sensing performance,but the colorimetric sensing performance decreased compared with the W-l0.025-MTES-1 sensor.(4)To further investigate the mechanism of constructing formaldehyde colorimetric sensor on wood substrate,the wood W-1 is an excellent substrate for colorimetric sensor by using common fabrics for comparison,and the material formaldehyde adsorption performance test and its colorimetric sensing performance test,surface morphology and its actual available specific surface area.The abundance of hydroxyl groups on the surface of wood W-l and the actual available area larger than the macroscopic area enable the adsorption of a large amount of formaldehyde in a short time,providing reactants for subsequent color development reactions as well as more active sites.(5)Colorimetric sensors with different surface wettability and their colorimetric performance were investigated.The W-l0.025 sensor for hydrophilic surfaces,the 10.025MTES-1 sensor for hydrophobic surfaces,and the W-l0.025-MTES-1-PFOTES0.50g sensor for superhydrophobic surfaces were investigated.By comparing the humidity interference resistance and sensitivity,the W-l0.025-MTES-1 sensor was found to have the best sensing performance.In addition,tape peel tests on the stability of the three showed that only the hydrophilic W-l0.025 sensor could maintain about 60%of its original performance,while the other two sensors with hydrophobic interfaces had almost no colorimetric sensing performance.In this paper,an environmentally friendly colorimetric sensor was successfully constructed using natural poplar wood with green,renewable and porous structure as the substrate of the colorimetric sensor,and the relationship between different additions of sodium hydroxide on the colorimetric sensing characteristics of formaldehyde and the wood cut surface was obtained.The influence of the surface wettability of the wood-based formaldehyde colorimetric sensor against moisture interference was also investigated.This study provides research ideas for the utilization of wood in environmental monitoring,especially formaldehyde colorimetric sensors.