6 research outputs found
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 Wā1 and an ultrafast response time in the sub-Ī¼s 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
An ultra-sensitive NHā gas sensor enabled by an ion-in-conjugated polycroconaine/TiāCāTā coreāshell 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 coreāshell composite, TiāCāTā@croconaine (poly(1,5-diaminonaphthalene-croconaine), PDAC) prepared by a facile in situ polymerization reaction, suitable for NHā detection. Compared to pristine TiāCāTā, the sensor made of a TiāCāTāāpolycroconaine composite exhibits a significantly enhanced sensitivity of 2.8% ppmā»Ā¹ 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 NHā and changing the tunneling conductivity between TiāCāTā domains. Density functional theory (DFT) calculations reveal that the adsorption energy of NHā 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 TiāCāTā@PDAC composite, without attenuated performance upon mechanical deformation. This work proposed a novel mechanism and a feasible methodology to synthesize MXeneāpolymer 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 (TiāCāTā MXene) intercalated with organic molecules have been widely used in batteries and supercapacitors, but are quite rarely reported for gas sensing. Since TiāCāTā is sensitive to oxygen, most methods for preparing the intercalated TiāCāTā involve stirring the reactants with TiāCāTā for several hours under nitrogen protection. Herein, a method to prepare a hybrid of TiāCāTā 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 TiāCāTā 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 NHā with a 2.2% ppmā»Ā¹ 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 HāS gas sensor based on TiāCāTā MXeneāorganic composites
Abstract
Cost-effective and high-performance HāS 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 NHā and VOCs, with generally positive responses that are not highly selective to the target gases. Here, we report on a negative response of pristine TiāCāTā thin films for HāS gas sensing (in contrast to the other tested gases) and further optimization of the sensor performance using a composite of TiāCāTā 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 TiāCāTā, exhibits an HāS 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 HāS sensors and deepens the understanding of their gas sensing mechanisms
Bioplastics and carbon-based sustainable materials, components, and devices:toward green electronics
Abstract
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 kĪ©/ā” 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 kĪ©/ā” and 1 Ī©/ā”, 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 (18.0ā26.5 GHz) with shielding effectiveness of up to 40 and 46 dB, respectively