Self-assembled copolymeric nanoparticles as chemically interactive materials for humidity sensors

Area of Science:

• Materials Science
• Nanotechnology
• Sensor Technology

Background:

• Chemical interactive materials (CIMs) are crucial for developing advanced sensor technologies.
• Polymeric nanoparticles offer tunable properties for specific applications.
• Bis(benzocyclobutene) (BCB) copolymers provide unique crosslinking capabilities.

Purpose of the Study:

• To synthesize and characterize poly(methylmethacrylate-co-bis(benzocyclobutene)) (P(MMA-co-BCB)) and poly(styrene-co-bis(benzocyclobutene)) (P(S-co-BCB)) nanoparticles.
• To fabricate and evaluate resistive relative humidity (RH) sensors based on these copolymeric nanoparticles.
• To assess the electrical response, stability, and sensitivity of the developed CIM-based sensors.

Main Methods:

• Modified emulsion technique for nanoparticle synthesis.
• Casting nanoparticle films onto interdigitated electrodes (Al, Au, Cr).
• Electrical characterization of sensors under varying RH (10-90%).
• Quartz microbalance (QMB) analysis for nanoparticle assembly and RH response.

Main Results:

• Nanoparticle dimensions and monodispersity were optimized by tuning co-monomer ratio and reaction time.
• Sensors exhibited a four-order-of-magnitude change in current (10^-12 to 10^-8 A) at 1 V across 10-90% RH.
• A response time of 130 s was recorded, with excellent reproducibility and stability over extended periods (two days and six months).
• QMB analysis showed high sensitivity, increasing from 30 Hz/% RH to 2000 Hz/% RH at 90% RH.

Conclusions:

• P(MMA-co-BCB) and P(S-co-BCB) nanoparticles are effective for fabricating stable and sensitive RH sensors.
• The developed CIMs demonstrate robust performance and versatile applicability in sensing technologies.
• The tunable nature of these copolymeric nanoparticles opens avenues for tailored sensor design.