Bioplastics and Carbon-Based Sustainable Materials, Components, and Devices: Toward Green Electronics

The continuously growing number of short-life electronics equipment inherently results in a massive amount of problematic waste, which poses risks of environmental pollution, endangers human health, and causes socioeconomic problems. Hence, to mitigate these negative impacts, it is our common interest to substitute conventional materials (polymers and metals) used in electronics devices with their environmentally benign renewable counterparts, wherever possible, while considering the aspects of functionality, manufacturability, and cost. To support such an effort, in this study, we explore the use of biodegradable bioplastics, such as polylactic acid (PLA), its blends with polyhydroxybutyrate (PHB) and composites with pyrolyzed lignin (PL), and multiwalled carbon nanotubes (MWCNTs), in conjunction with processes typical in the fabrication of electronics components, including plasma treatment, dip coating, inkjet and screen printing, as well as hot mixing, extrusion, and molding. We show that after a short argon plasma treatment of the surface of hot-blown PLA-PHB blend films, percolating networks of single-walled carbon nanotubes (SWCNTs) having sheet resistance well below 1 kω/□ can be deposited by dip coating to make electrode plates of capacitive touch sensors. We also demonstrate that the bioplastic films, as flexible dielectric substrates, are suitable for depositing conductive micropatterns of SWCNTs and Ag (1 kω/□ and 1 ω/□, respectively) by means of inkjet and screen printing, with potential in printed circuit board applications. In addition, we exemplify compounded and molded composites of PLA with PL and MWCNTs as excellent candidates for electromagnetic interference shielding materials in the K-band radio frequencies (18.0-26.5 GHz) with shielding effectiveness of up to 40 and 46 dB, respectively.Business Finland (project 1212/31/2020, All green structural electronics), EU Horizon 2020 BBI JU (project 792261, NewPack), and EU Interreg Nord Lapin liitto (project 20201468, Flexible transparent conductive f ilms as electrodes) and Academy of Finland (project 316825, Nigella)

An ultra-sensitive NH3 gas sensor enabled by an ion-in-conjugated polycroconaine/Ti3C2Tx core-shell composite

Funding Information: This work was financially supported in part by Walter Ahlströmin säätiö and China Scholarship Council. We acknowledge funding from the Academy of Finland (Center of Excellence Program in Life-inspired Hybrid Materials (LIBER, No. 346108) and Project No. 330214). The authors thank Dr Rhodri Mansell and Sreeveni Das for the assistance in materials synthesis and measurements, and the personnel of the Centre for Material Analysis at the University of Oulu for technical assistance. Prof. Hannu-Pekka Komsa (University of Oulu) is also greatly acknowledged for his comments on the manuscript. Publisher Copyright: © 2023 The Royal Society of Chemistry.MXenes are emerging sensing materials due to their metallic conductivity and rich surface chemistry for analytes; they, however, suffer from poor stability. Incorporation with functional polymers can largely prevent the performance decay and enhance the sensing performance. Herein, we demonstrate a core-shell composite, Ti3C2Tx@croconaine (poly(1,5-diaminonaphthalene-croconaine), PDAC) prepared by a facile in situ polymerization reaction, suitable for NH3 detection. Compared to pristine Ti3C2Tx, the sensor made of a Ti3C2Tx-polycroconaine composite exhibits a significantly enhanced sensitivity of 2.8% ppm−1 and an estimated achievable limit of detection of 50 ppb. The improved sensing performance could be attributed to the presence of PDAC facilitating the adsorption of NH3 and changing the tunneling conductivity between Ti3C2Tx domains. Density functional theory (DFT) calculations reveal that the adsorption energy of NH3 on PDAC is the highest among the tested gases, which supports the selectivity of the sensor to this analyte. Benefiting from the protection conferred by the PDAC shell, the composite has a reliable operation period of at least 40 days. In addition, we demonstrated a flexible paper-based sensor of the Ti3C2Tx@PDAC composite, without attenuated performance upon mechanical deformation. This work proposed a novel mechanism and a feasible methodology to synthesize MXene-polymer composites with improved sensitivity and stability for chemical sensing.Peer reviewe

Ultrafast photoresponse of vertically oriented TMD films probed in a vertical electrode configuration on Si chips

Abstract Integrated photodetectors based on transition metal dichalcogenides (TMDs) face the challenge of growing their high-quality crystals directly on chips or transferring them to the desired locations of components by applying multi-step processes. Herein, we show that vertically oriented polycrystalline thin films of MoS2 and WS2 grown by sulfurization of Mo and W sputtered on highly doped Si are robust solutions to achieve on-chip photodetectors with a sensitivity of up to 1 mA W−1 and an ultrafast response time in the sub-μs regime by simply probing the device in a vertical arrangement, i.e., parallel to the basal planes of TMDs. These results are two orders of magnitude better than those measured earlier in lateral probing setups having both electrodes on top of vertically aligned polycrystalline TMD films. Accordingly, our study suggests that easy-to-grow vertically oriented polycrystalline thin film structures may be viable components in fast photodetectors as well as in imaging, sensing and telecommunication devices

MXene-Polymer Hybrid for High-Performance Gas Sensor Prepared by Microwave-Assisted In-Situ Intercalation

Funding Information: This manuscript has been co‐authored by UT‐Battelle, LLC, under contract DE‐AC05‐00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid‐up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe‐public‐access‐plan ). Funding Information: This material is based upon work supported in part by: the U.S. Department of Energy, Office of Science, Office of Advanced Scientific Computing Research, Applied Mathematics program under contracts and awards ERKJ314, ERKJ331, ERKJ345; the AEOLUS (Advances in Experimental Design, Optimization and Learning for Uncertain Complex Systems) Department of EnergyMathematical Multifaceted Capabilities Center; the Scientific Discovery through Advanced Computing (SciDAC) program through the FASTMath Institute under Contract No. DE‐AC02‐05CH11231; and by the Laboratory Directed Research and Development program at the Oak Ridge National Laboratory, which is operated by UT‐Battelle, LLC., for the U.S. Department of Energy under contract DE‐AC05‐00OR22725. Publisher Copyright: © 2022 The Authors. Advanced Materials Technologies published by Wiley-VCH GmbH2D transition-metal carbides (Ti3C2Tx MXene) intercalated with organic molecules have been widely used in batteries and supercapacitors, but are quite rarely reported for gas sensing. Since Ti3C2Tx is sensitive to oxygen, most methods for preparing the intercalated Ti3C2Tx involve stirring the reactants with Ti3C2Tx for several hours under nitrogen protection. Herein, a method to prepare a hybrid of Ti3C2Tx and intercalated polysquaraine through microwave-assisted in situ polymerization that takes only a few minutes without the need of using a protective atmosphere is demonstrated. Owing to the increased interlayer space of the Ti3C2Tx after the polymerization, the gas sensors based on the hybrid exhibit a good sensing performance for NH3 detection, being able to detect at least 500 ppb NH3 with a 2.2% ppm−1 of sensitivity. This study provides a facile preparation method for developing intercalated MXenes, which are expected to be useful for a wide range of applications.Peer reviewe

Highly Selective H2S Gas Sensor Based on Ti3C2TxMXene-Organic Composites

Funding Information: This work was financially supported in part by the University of Oulu (projects: Entity, ROAR, and Memristors and neuromorphic sensors from vertically aligned layered materials). We acknowledge funding from the EU Erasmus + programme (project: TACMEE), and the Academy of Finland (Center of Excellence Program in Life-inspired Hybrid Materials (LIBER), and projects: 311058, 325185, and 330214). We thank the personnel of the Centre for Material Analysis at the University of Oulu for providing us with technical assistance. We also thank CSC Finland for the generous grants of computer time. Publisher Copyright: © 2023 The Authors. Published by American Chemical Society.Cost-effective and high-performance H2S sensors are required for human health and environmental monitoring. 2D transition-metal carbides and nitrides (MXenes) are appealing candidates for gas sensing due to good conductivity and abundant surface functional groups but have been studied primarily for detecting NH3 and VOCs, with generally positive responses that are not highly selective to the target gases. Here, we report on a negative response of pristine Ti3C2Tx thin films for H2S gas sensing (in contrast to the other tested gases) and further optimization of the sensor performance using a composite of Ti3C2Tx flakes and conjugated polymers (poly[3,6-diamino-10-methylacridinium chloride-co-3,6-diaminoacridine-squaraine], PDS-Cl) with polar charged nitrogen. The composite, preserving the high selectivity of pristine Ti3C2Tx, exhibits an H2S sensing response of 2% at 5 ppm (a thirtyfold sensing enhancement) and a low limit of detection of 500 ppb. In addition, our density functional theory calculations indicate that the mixture of MXene surface functional groups needs to be taken into account to describe the sensing mechanism and the selectivity of the sensor in agreement with the experimental results. Thus, this report extends the application range of MXene-based composites to H2S sensors and deepens the understanding of their gas sensing mechanisms.Peer reviewe

An ultra-sensitive NH₃ gas sensor enabled by an ion-in-conjugated polycroconaine/Ti₃C₂Tₓ core–shell composite

Abstract MXenes are emerging sensing materials due to their metallic conductivity and rich surface chemistry for analytes; they, however, suffer from poor stability. Incorporation with functional polymers can largely prevent the performance decay and enhance the sensing performance. Herein, we demonstrate a core–shell composite, Ti₃C₂Tₓ@croconaine (poly(1,5-diaminonaphthalene-croconaine), PDAC) prepared by a facile in situ polymerization reaction, suitable for NH₃ detection. Compared to pristine Ti₃C₂Tₓ, the sensor made of a Ti₃C₂Tₓ–polycroconaine composite exhibits a significantly enhanced sensitivity of 2.8% ppm⁻¹ and an estimated achievable limit of detection of 50 ppb. The improved sensing performance could be attributed to the presence of PDAC facilitating the adsorption of NH₃ and changing the tunneling conductivity between Ti₃C₂Tₓ domains. Density functional theory (DFT) calculations reveal that the adsorption energy of NH₃ on PDAC is the highest among the tested gases, which supports the selectivity of the sensor to this analyte. Benefiting from the protection conferred by the PDAC shell, the composite has a reliable operation period of at least 40 days. In addition, we demonstrated a flexible paper-based sensor of the Ti₃C₂Tₓ@PDAC composite, without attenuated performance upon mechanical deformation. This work proposed a novel mechanism and a feasible methodology to synthesize MXene–polymer composites with improved sensitivity and stability for chemical sensing

MXene-polymer hybrid for high-performance gas sensor prepared by microwave-assisted in-situ intercalation

Abstract 2D transition-metal carbides (Ti₃C₂Tₓ MXene) intercalated with organic molecules have been widely used in batteries and supercapacitors, but are quite rarely reported for gas sensing. Since Ti₃C₂Tₓ is sensitive to oxygen, most methods for preparing the intercalated Ti₃C₂Tₓ involve stirring the reactants with Ti₃C₂Tₓ for several hours under nitrogen protection. Herein, a method to prepare a hybrid of Ti₃C₂Tₓ and intercalated polysquaraine through microwave-assisted in situ polymerization that takes only a few minutes without the need of using a protective atmosphere is demonstrated. Owing to the increased interlayer space of the Ti₃C₂Tₓ after the polymerization, the gas sensors based on the hybrid exhibit a good sensing performance for NH3 detection, being able to detect at least 500 ppb NH₃ with a 2.2% ppm⁻¹ of sensitivity. This study provides a facile preparation method for developing intercalated MXenes, which are expected to be useful for a wide range of applications

Highly selective H₂S gas sensor based on Ti₃C₂Tₓ MXene–organic composites

Abstract Cost-effective and high-performance H₂S sensors are required for human health and environmental monitoring. 2D transition-metal carbides and nitrides (MXenes) are appealing candidates for gas sensing due to good conductivity and abundant surface functional groups but have been studied primarily for detecting NH₃ and VOCs, with generally positive responses that are not highly selective to the target gases. Here, we report on a negative response of pristine Ti₃C₂Tₓ thin films for H₂S gas sensing (in contrast to the other tested gases) and further optimization of the sensor performance using a composite of Ti₃C₂Tₓ flakes and conjugated polymers (poly[3,6-diamino-10-methylacridinium chloride-co-3,6-diaminoacridine-squaraine], PDS-Cl) with polar charged nitrogen. The composite, preserving the high selectivity of pristine Ti₃C₂Tₓ, exhibits an H₂S sensing response of 2% at 5 ppm (a thirtyfold sensing enhancement) and a low limit of detection of 500 ppb. In addition, our density functional theory calculations indicate that the mixture of MXene surface functional groups needs to be taken into account to describe the sensing mechanism and the selectivity of the sensor in agreement with the experimental results. Thus, this report extends the application range of MXene-based composites to H₂S sensors and deepens the understanding of their gas sensing mechanisms