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1. Corrosion Protective Coatings from Poly(heterocyclic diphenylamine): Polyaniline Analogues

   https://doi.org/10.1021/acsapm.3c02347  

   Awoyemi, R. F.; Almtiri, M.; Giri, H.; Scott, C. N.; Wipf, D. O. (March 2024, ACS applied polymer materials)

   This study explores conducting polymers with side chains containing long, branched alkyl groups as candidates for corrosion suppression coatings. These polymers, containing carbazole, phenothiazine, and phenoxazine cores, may be considered as analogues to polyaniline, which is often employed in corrosion control applications. The polymers are prepared from the corresponding dibrominated carbazole, phenothiazine, and phenoxazine monomers with 2,5-dimethyl-1,4-phenylenediamine by the Buchwald−Hartwig coupling reaction. The effectiveness of these coatings for corrosion suppression was tested by potentiodynamic polarization studies and electrochemical impedance spectroscopy. The morphology of the coatings was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Corrosion testing of coated AISI 4130 steels in 3.5 wt % NaCl showed that the phenothiazine- and carbazole-containing polymers display excellent corrosion resistance. The protection efficiency (PE) of 95.9% for phenothiazine outperformed the other polymers, including polyaniline coating. SEM images indicate that the polymers are still uniformly coated with stable morphology after 24 h of exposure to corrosive media. These results suggest that phenothiazine and carbazole-based PANI analogues may be candidates for protective organic coatings in transportation, aviation, marine, and oil and gas industrial applications. 

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2. Oligoaniline-assisted self-assembly of polyaniline crystals

   https://doi.org/10.1039/D2MH01344D  

   Hill, Ian M.; Wu, Di; Xu, Bohao; Wang, Yue (April 2023, Materials Horizons)

   The conductivity and charge transport mobility of conjugated polymers (CPs) are largely correlated with their degree of crystallinity, rendering the crystallization of CPs an important endeavour. However, such tasks can be challenging, especially in the absence of sidechain functionalization. In this study, we demonstrate that the incorporation of a small amount of oligomers, specifically tetraaniline, can induce crystallization of the parent polymer, polyaniline, through a single-step self-assembly process. The resulting crystals are compositionally homogeneous because the oligomers and their parent polymer share the same repeating unit and are both electroactive. Mechanistic studies reveal that the tetraaniline forms a crystalline seed that subsequently guides the assembly of polyaniline due to their structural similarities. Applying this oligomer-assisted crystallization approach to polyaniline with defined molecular weights resulted in single crystalline nanowires for 5000 Da polyaniline, and nanowires with strong preferential chain orientation for those with molecular weights between 10 000 and 100 000 Da. Absorption studies reveal that the polymer chains are in an expanded conformation, which likely contributed to the high degree of packing order. Two-probe, single nanowire measurements show that the crystals have conductivity as high as 19.5 S cm −1 . This method is simple, general, and can potentially be applied to other CPs. 

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3. Climate Change Sensing through Terahertz Communication Infrastructure: A Disruptive Application of 6G Networks

   https://doi.org/10.1109/MNET.2023.3321523  

   Wedage, Lasantha Thakshila; Butler, Bernard; Balasubramaniam, Sasitharan; Koucheryavy, Yevgeni; Jornet, Josep M.; Vuran, Mehmet C. (October 2023, IEEE Network)

   Climate change resulting from releasing greenhouse gases into the atmosphere continues to affect the Earth’s ecosystem. This pressing issue is driving the development of novel technologies to sense and measure harmful gas emissions. In parallel, the evolution of wireless communication networks requires the wider deployment of mobile telecommunication infrastructure. The terahertz (THz) spectrum is currently under-utilized but is expected to feature in 6G. The use of this spectrum is explored simultaneously for ultra-broadband communication and atmospheric sensing. For atmospheric sensing, the absorption of THz signals by gas molecules is used to estimate atmospheric gas composition. Molecular absorption loss profiles for each gas isotopologue are taken from the HITRAN database and compared with data from transceivers in sensing mode. Preliminary results are presented, showing the effects of signal path loss and power spectral density. A 6G network architecture is proposed to indicate how 6G infrastructure can perform climate change sensing, in addition to its primary purpose of wireless communication. 

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4. Novel gas sensing platform based on a stretchable laser-induced graphene pattern with self-heating capabilities

   https://doi.org/10.1039/c9ta07855j  

   Yang, Li; Yi, Ning; Zhu, Jia; Cheng, Zheng; Yin, Xinyang; Zhang, Xueyi; Zhu, Hongli; Cheng, Huanyu (April 2020, Journal of Materials Chemistry A)

   Measurements of the gas sensing performance of nanomaterials typically involve the use of interdigitated electrodes (IDEs). A separate heater is often integrated to provide elevated temperature for improved sensing performance. However, the use of IDEs and separate heaters increases fabrication complexity. Here, a novel gas sensing platform based on a highly porous laser-induced graphene (LIG) pattern is reported. The LIG gas sensing platform consists of a sensing region and a serpentine interconnect region. A thin film of metal ( e.g. , Ag) coated in the serpentine interconnect region significantly reduces its resistance, thereby providing a localized Joule healing in the sensing region ( i.e. , self-heating) during typical measurements of chemoresistive gas sensors. Dispersing nanomaterials with different selectivity in the sensing region results in an array to potentially deconvolute various gaseous components in the mixture. The self-heating of the LIG gas sensing platform is first studied as a function of the applied voltage during resistance measurement and LIG geometric parameters ( e.g. , linewidth from 120 to 240 μm) to achieve an operating temperature from 20 to 80 °C. Systematic investigations of various nanomaterials demonstrate the feasibility of the LIG gas sensing performance. Taken together with the stretchable design layout in the serpentine interconnect region to provide mechanical robustness over a tensile strain of 20%, the gas sensor with a significant response (6.6‰ ppm −1 ), fast response/recovery processes, excellent selectivity, and an ultralow limit of detection (1.5 parts per billion) at a modest temperature from self-heating opens new opportunities in epidermal electronic devices. 

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5. Reflected path enhanced absorbance in an integrated photonic sensor

   https://doi.org/10.1117/12.2664033  

   Shen, Jianhao; Donnelly, Daniel; Chakravarty, Swapnajit (June 2023, Proceedings of the SPIE)

   Sanders, Glen A.; Lieberman, Robert A.; Udd Scheel, Ingrid (Ed.)

   Evanescent wave sensors in photonic integrated circuits have been demonstrated for gas sensing applications. While some methods rely on the distinctive response of certain polymers for sensing specific gases, absorption spectroscopy identifies any gas uniquely from their unique vibration signatures. Based on the Beer-Lambert principle, the sensitivity of absorption by a gas on chip relies on the length of the sensing region, the optical overlap integral with the analyte gas and the absorption cross-section at the wavelength with the fundamental vibration signature. The overlap of the optical mode with the analyte has been enhanced in photonic devices by combining slot waveguide confinements with photonic crystal slow light effects. While the absorption cross-section is a property of the gas, the length of the sensing region is limited by the available area on a chip and waveguide propagation losses that limit the minimum signal to noise ratio. In this paper, we show that by incorporating reflecting loop mirrors, the absorption path length can be doubled for the same geometric length of the absorption sensing waveguide. Light from a waveguide is split into two paths, each with a slow light photonic crystal waveguide, by a 2×2 multimode interference (MMI) power splitter. Each path is terminated by a loop mirror that causes the light to retrace its path back down the sensing arms thereby doubling the optical path length over which light interacts with the analyte. Results on the enhancement of phase sensitivity and absorbance sensitivity in the interferometric configuration are presented 

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