Precursor Customized Assembly of Wafer‐Scale Polymerized Aniline Thin Films for Ultrasensitive NH₃ Detection

Abstract

2D conducting polymer thin film recently has garnered numerous interests as a means of combining the molecular aggregate ordering and promoting in-plane charge transport for large-scale/flexible organic electronics. However, it remains far from satisfactory for conducting polymer chains to achieve desirable surface topography and crystallinity due to lack of control over the precursor-involved interfacial assembly. Herein, wafer-size polyaniline (PANI) and tetra-aniline thin films are developed via a controlled interfacial synthesis with customized surface morphology and crystallinity through two typical aniline precursors selective polymerization. Two crucial competing assembly mechanisms, a) direct interfacial polymerization, b) solution polymerization and subsequent interfacial assembly, are investigated to play a vital role in determining elemental chain length and aggregate architecture. The optimal PANI thin film manifests ultraflat surface topography and unambiguous crystalline domains, which also enabling fascinating ammonia sensing capability with 31.4% ppm −1 sensitivity, fast response time (88 s) with astonishing selectivity, repeatability, and recovery capability. The thus-demonstrated strategy with wafer-scale processing potential and flexible microdevice offers a promising route for large-scale manufacturing thin-film organic electronics.

Polyaniline-Based Biological and Chemical Sensors: Sensing Mechanism, Configuration Design, and Perspective

“…It requires quantitative analysis in specific sensing scenarios and customizable synthetic method development, e.g., precursor-customized assembly. 31 In addition, the conductivity and charge-transfer properties of PANI are usually reduced due to microscopic deformations caused by dopant intercalation. A highly robust, stable, and reversible PANI material design has not been clarified yet.…”

“…As shown in Figure 2a, a chemi-resistive sensor consists of a sensing region (usually a thin film on a macroscopic scale) bridging a pair of conductive electrodes (e.g., Au/Ag). 31 As a result, the chemi-resistive sensor is mainly utilized to detect target gases and volatile substances like NH 3 , NO 2 , water vapor, and volatile organic compounds (VOCs), with applications in a series of scenarios, including human health, environmental conservation, food industry, and public security. 29,32,33 In spite of their advantages�easy-to-fabricate, simple data processing, and strong response to specific targets�the PANI-based chemi-resistive sensors still suffer from a series of challenges, such as unsatisfactory sensitivity, selectivity, and long-term stability.…”

“…While the PANI-based sensing active layer is in contact with the external environment, the acidic/​alkaline and oxidizing/​reducing atmosphere in the environment could lead to the transformation of the PANI’s chemical structure, such as doping/​de‑doping reactions. , This generates a conspicuous variation in the conductivity of PANI, thereby converting chemical signals into resistance signals. As shown in Figure a, a chemi-resistive sensor consists of a sensing region (usually a thin film on a macroscopic scale) bridging a pair of conductive electrodes (e.g., Au/Ag) . As a result, the chemi-resistive sensor is mainly utilized to detect target gases and volatile substances like NH 3 , NO 2 , water vapor, and volatile organic compounds (VOCs), with applications in a series of scenarios, including human health, environmental conservation, food industry, and public security. ,, In spite of their advantageseasy-to-fabricate, simple data processing, and strong response to specific targetsthe PANI-based chemi-resistive sensors still suffer from a series of challenges, such as unsatisfactory sensitivity, selectivity, and long-term stability …”

“…(e) Precursor customized assembly of PANI/TANI films with tunable morphologies and crystallinities for highly sensitive gas sensors. Reproduced with permission from ref . Copyright 2022 Wiley-VCH.…”

“…The distinguishing sensing performance can be attributed to the ultra-thinness of the film with fully available active sites as well as the long-range-ordered chain structure, which facilitates adsorption of the NH 3 molecule and charge carrier diffusion. To further shed light on the effects of PANI film morphology, thickness, and crystallinity on sensing performance, Shao et al conducted a systematic study focusing on PANI/TANI thin-film interfacial assemblies with customized morphology, thickness, crystallinity, and their corresponding gas-sensing performance (Figure e) . The precursor-induced interface synthesis processes, including (i) direct interfacial polymerization and (ii) solution polymerization and subsequent interfacial assembly, resulted in a crystalline PANI film with an ultra-flat surface and an amorphous TANI film with a rough brush-like morphology, respectively.…”