A controllably fabricated polypyrrole nanorods network by doping a tetra-ß-carboxylate cobalt phthalocyanine tetrasodium salt for enhanced ammonia sensing at room temperature.

The morphology adjustment and functional doping optimization of polypyrrole (PPy) are of great significance in improving its gas sensing performance. Here, the PPy-0.5TcCoPc nanorods with a uniform dispersed 3-D network were prepared using one-step in situ polymerization using the electrostatic interaction between dopant counterion substituents in tetra-ß-carboxylate cobalt phthalocyanine tetrasodium salt (TcCoPcTs) with larger space structure and pyrrole (Py) molecules, in which TcCoPcTs is not only used as a dopant molecule crosslinking PPy chains to obtain a 3-D network, thus improving the conductivity, but also as a sensor accelerator to improve the gas-sensing performance. The resulting PPy-TcCoPc hybrid exhibits superior NH3-sensing properties than PPy and tetra-ß-carboxylate cobalt phthalocyanine (TcCoPc) under the same test conditions, especially the PPy-0.5TcCoPc sensor shows ultrafast response/recovery time to 50 ppm NH3 (8.1 s/370.8 s), low detection limit of 8.1 ppb and excellent gas selectivity at room temperature (20 °C). Besides, the PPy-0.5TcCoPc sensor also maintains superior response (49.3% to 50 ppm NH3), humidity resistance and conspicuous stability over 45 days. The excellent NH3-sensing performance of the PPy-0.5TcCoPc hybrid arises from the excellent gas selectivity of TcCoPc, the remarkable response mechanism between PPy and NH3, the high electrical conductivity, abundant active sites and good electron transport ability of the unique 3-D network with large specific surface area. The morphology regulation and functional doping optimization strategy of TcCoPcTs doped PPy broaden the research direction of ideal gas sensor materials.

A highly sensitive ppb-level H2S gas sensor based on fluorophenoxy-substituted phthalocyanine cobalt/rGO hybrids at room temperature.

The peripheral and non-peripheral substitution of 4-trifluoromethylphenoxy groups in the design of gas sensing phthalocyanine cobalt/reduced graphene oxide (rGO) hybrids with two different positions of the substituents was realized. Tetra-α(ß)-(4-trifluoromethylphenoxy)phthalocyanine cobalt/reduced graphene oxide (3(4)-cF3poPcCo/rGO) hybrids were prepared through noncovalent interaction, and were analyzed by FT-IR, UV-vis, TGA and SEM. The gas sensing performance of the cF3poPcCo/rGO hybrid gas sensors towards ppb hydrogen sulfide (H2S) was measured at room temperature. The results show that the 4-cF3poPcCo/rGO sensor has better sensitivity, selectivity and reproducibility than the 3-cF3poPcCo/rGO sensor, as well as a perfect linear response to the concentration of H2S. For the 4-cF3poPcCo/rGO sensor, the response sensitivity to 1 ppm H2S is as high as 46.58, the response and recovery times are 600 s and 50 s for 1 ppm H2S, and the detection limit is as low as 11.6 ppb. This is mainly due to the loose and porous structure of the cF3poPcCo/rGO hybrids, the fact that graphene is an excellent conductive agent, and the fact that the electron-withdrawing capability of the trifluoromethyl group can increase the holes of rGO and PcCo. In addition, through electrochemical impedance spectroscopy (EIS) and I-V curves, and density functional theory, the influence of different positions of the substituents of cF3poPcCo/rGO on the sensing performance and the sensing mechanism for improving sensitivity were discussed and confirmed in detail.

A high-sensitive room temperature gas sensor based on cobalt phthalocyanines and reduced graphene oxide nanohybrids for the ppb-levels of ammonia detection.

Highly sensitive gas sensing materials are of great importance for environmental pollution monitoring. In this study, four nanohybrid materials containing different phenoxyl substituents of cobalt phthalocyanines (tetra-ß-carboxylphenoxylphthalocyanine cobalt (cpoPcCo), tetra-ß-(4-carboxy-3-methoxyphenoxy)phthalocyanine cobalt (cmpoPcCo), tetra-ß-phenoxylphthalocyanine cobalt (poPcCo), and tetra-ß-(3-methoxyphenoxy)phthalocyanine cobalt (mpoPcCo)) and reduced graphene oxide (rGO) (RPcCo/rGO) were synthesized via non-covalent interactions as a high performance gas sensing materials for the ppb-level detection of ammonia (NH3). Various characterization techniques, including FT-IR, Raman, UV-vis, TGA, XPS and SEM, were used to confirm the structure, element information and morphology of the as-synthesized materials. The obtained materials were used in interdigital electrodes to fabricate the sensing device, and the gas sensing performance was investigated at room temperature. The obtained sensors exhibited excellent sensitivity, selectivity, good reproducibility and perfect response-concentration linearity towards NH3, which are mainly ascribed to the synergetic effects of RPcCo and rGO due to the specific surface area structure for NH3 diffusion, the abundant active sites to adsorb NH3, and excellent conductivity for efficient electron transport, particularly the effect of RPcCo. For example, the cpoPcCo/rGO-based sensor showed a higher and faster response for low concentration of NH3 (∼2.5 and 45 s for 100 ppb of NH3), a ppb level detection and superior stability over 60 days. Besides, the effect of different phenoxyl substituents of cobalt phthalocyanines on the sensing performance and the sensing mechanism for the sensitivity enhancement were discussed and confirmed by the first-principles density functional theory calculations and electrochemical impedance spectroscopy (EIS).