Electric-field assisted spatioselective deposition of MIL-101(Cr)PEDOT to enhance electrical conductivity and humidity sensing performance

• Published in: Journal of colloid and interface science 2025-01, Vol.678 (Pt A), p.979-986
• Main Authors: Benseghir, Youven, Tsang, Min Ying, Schöfbeck, Flora, Hetey, Daniel, Kitao, Takashi, Uemura, Takashi, Shiozawa, Hidetsugu, Reithofer, Michael R., Chin, Jia Min
• Format: Article
• Language: English
• Subjects: Conductive MOFs; Electric-field alignment; Electrical conductivity; Metal-organic frameworks; Sensors
• ISSN: 0021-9797; 1095-7103; 1095-7103
• DOI: 10.1016/j.jcis.2024.08.221

Conductive MIL-101(Cr)PEDOT has been drop cast on interdigitated electrodes. When regularly deposited, the nanoparticles are randomly dispersed on the surface leading to a poor conductivity. When an electric field is applied during the drop casting, the particles are spatioselectively deposited between the finger electrodes, enhancing both the resulting conductivity and sensitivity to water vapor. [Display omitted] Precise deposition of metal–organic framework (MOF) materials is important for fabricating high-performing MOF-based devices. Electric-field assisted drop-casting of poly(3,4-ethylenedioxythiophene)-functionalized (PEDOT) MIL-101(Cr) nanoparticles onto interdigitated electrodes allowed their precise spatioselective deposition as percolating nanoparticle chains in the interelectrode gaps. The resulting aligned materials were investigated for resistive and capacitive humidity sensing and compared with unaligned samples prepared via regular drop-casting. The spatioselective deposition of MOFs resulted in up to over 500 times improved conductivity and approximately 6 times increased responsivity during resistive humidity sensing. The aligned samples also showed good capacitive humidity sensing performance, with up to 310 times capacitance gain at 10 versus 90 % relative humidity. In contrast, the resistive behavior of the unaligned samples rendered them unsuitable for capacitive sensing. This work demonstrates that applying an alternating potential during drop-casting is a simple yet effective method to control MOF deposition for greater efficiency, conductivity, and enhanced humidity sensing performance.