Multifunctional, energy-autonomous textile sensors enabled by spray-coated two-dimensional heterostructures

The novel, ring-shaped, contraceptive vaginal system (CVS; Annovera™), contains 103 mg of SA and 17.4 mg of EE, and delivers a mean dose of SA 0.15/EE 0.013 mg/day. The CVS was designed to last thirteen cycles in a 21 day-in/7 day-out regimen. Objectives of these analyses were to determine the amount of SA/EE remaining in the CVS after 13 cycles of use and to estimate the SA level in serum after 1 year of continuous use.Residual SA/EE levels from CVS used by women (n=18) for 13 cycles of 21/7 regimen in a phase 3 clinical trial were further analyzed in vitro. Hypothetical SA level in serum after 1 year of continuous use was estimated using data from 39 women who participated in a 13-cycle pharmacokinetic study of the 21/7 CVS regimen. The serum data were used to construct a statistical model for the change in serum SA concentrations from cycle 1 to cycle 13. The data from each individual subject was modeled to estimate the serum SA level based on days of use. Each subject’s model was then used to estimate the serum SA level after 364 days of continuous CVS use. The average of all 364-day values from valid models was then calculated.After 13 cycles of a 21/7 regimen, the amount of SA/EE remaining in the CVS was 61.7 mg/14.0 mg (60%/80% of the original SA/EE load), which established the release of 0.15 mg SA and 0.013 mg EE per day for a total of 273 days. The model predicted that the mean serum SA level after 364 days of continuous use was 71 pmol/L with a lower limit of the 90% CI of 52 pmol/L.A high percentage of SA/EE remained in the CVS after 13 cycles of use. Serum SA levels predicted by the model following 1 year of continuous use were similar to those previously observed (mean 73 pmol/L) at 1 year in a SA silicone implant trial in which there were no reported pregnancies at 1 year (Sivin et al, Contraception. 2004;69:137-144). No pregnancy or PK data with continuous use of the CVS is available at this time. Further study on the continuous use of the CVS is warranted.

Making contact of transition metal dichalcogenides (TMDCs) with a metal surface is essential for fabricating and designing electronic devices and catalytic systems. It also generates strain in the TMDCs that plays significant role in both electronic and phonon structures. Therefore, detailed understanding of mechanism of the strain generation is important to fully comprehend the modulation effect for the electronic and phonon properties. Here, MoS2 and MoSe2 monolayers are grown on Au surface by chemical vapor deposition and it is demonstrated that the contact with a crystalline Au(111) surface gives rise to only out-of-plane strain in both MoS2 and MoSe2 layers, whereas no strain generation is observed on polycrystalline Au or SiO2 /Si surfaces. Scanning tunneling microscopy analysis provides information regarding consequent specific adsorption sites between lower S (Se) atoms in the SMoS (SeMoSe) structure and Au atoms via unique moiré superstructure formation for MoS2 and MoSe2 layers on Au(111). This observation indicates that the specific adsorption sites give rise to out-of-plane strain in the TMDC layers. Furthermore, it also leads to effective modulation of the electronic structure of the MoS2 or MoSe2 layer.

Transition metal dichalcogenides have gained considerable interest for vapour sensing applications due to their large surface-to-volume ratio and high sensitivity. Herein, we demonstrate a new self-powered volatile organic compounds (VOC) sensor based on asymmetric geometry multi-layer molybdenum disulfide (MoS2) diode. The asymmetric contact geometry of the MoS2 diode induces an internal built-in electric field resulting in self-powering via a photovoltaic response. While illuminated by UV-light, the sensor exhibited a high responsivity of ∼60% with a relatively fast response time of ∼10 sec to 200 ppm of acetone, without an external bias voltage. The MoS2 VOC diode sensor is a promising candidate for self-powered, fast, portable, and highly sensitive VOC sensor applications.

Bioactive compounds were produced from natural glucosinolates, secondary plant metabolites, using myrosinase (thioglucoside glucohydrolase EC 3.2.3.1) isolated from ripe seeds of Sinapis alba. The enzyme was immobilized on granular nylon 6.6 with the crosslinking technique. Immobilized myrosinase displayed extraordinary operational and storage stability. Using a small thermostatted continuous packed-bed bioreactor, the enzyme activity was unchanged after 15 days of continuous use at 37 degrees C and after >1 year of storage at room temperature. The bioreactor was particularly efficient in producing pure isothiocyanates, but it was less efficient for pure nitrile production.

A systematic review on 2D materials for volatile organic compound sensing

Chemiresistive gas sensors are essential for detecting harmful gases such as NO2, CO, H2S, and volatile organic compounds, as exposure to these gases poses severe risks to human health, including fatal outcomes. Prior to recent advancements and research in two-dimensional (2D) transitional metal dichalcogenides (TMDs), metal-oxide-based gas sensors were predominantly used.[1] However, their high operating temperatures and reliance on ionized oxygen present challenges for the development of low-power and miniaturized devices.As a promising alternative material, TMDs have garnered significant attention in the field of sensors for their high surface-to-volume ratio, enabling the sensitive detection of aforementioned gas species even at room temperature.[2] Despite its immense potential, intrinsic defects or vacancies on the TMD basal plane—where strong chemisorption of gas molecules occurs—hinder the recovery rate of TMD based gas sensors, compromising their reliability and long-term performance.[3] In this work, we use Atomic Layer Deposition (ALD) to selectively deposit and passivate defects and grain boundaries of WS2 and MoS2, resulting in a significant enhancement of the device’s recovery rate and longevity. We evaluate the gas-sensing properties of pristine and Al2O3-passivated MoS2 and WS2 when exposed to NH3 and NO2 gases at ppb levels. SEM analysis confirms selective nucleation and growth of Al2O3 on the defects and grain boundaries.As a result, the recovery rate of passivated sensors increased significantly from 74% (pristine sensors) to 96%. Additionally, Al₂O₃-passivated sensors demonstrated superior responsiveness to NO₂ gas compared to their pristine counterparts. The effects of ALD-deposited Al₂O₃ on the 2D TMD surface were characterized using Raman and photoelectron spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and field-emission scanning electron microscopy (FE-SEM).Our findings establish that passivation is a pivotal strategy for significantly enhancing the recovery performance and long-term reliability of 2D TMD-based gas sensors.[1] M. Swan et al., J. Sens. Actuator Networks 1 (2012) 217–253.[2] Lee, K et al., Adv. Mater. 25, 6699-6702 (2013).[3] H. Li et al., Small 8, 63–67 (2012). Figure 1

Enhanced cataluminescence sensing of volatile organic compounds using CeO2/MxOy nanocomposites.

Transition metal dichalcogenides (TMDs) have been studied for their wide range of unique optical, electronic and mechanical properties.[1] Due to weak interlayer attraction, single layers of TMDs can be isolated by mechanical exfoliation. Some properties depend on the number of TMD layers. For example, as MoS2 is thinned from bulk to a monolayer, it changes from a 1.2 eV indirect band gap semiconductor to a 1.9 eV direct band gap semiconductor.[2]DFT calculations have shown that Li+ will form an ionic bond with the Mo in MoS2.[3] By applying an electrolyte containing Li+ to the MoS2 surface, ions can be driven by an applied field to the MoS2, yielding both electrostatic and electrochemical doping.Here, we fabricate a MoS2 FET device and drop-cast a solid polymer electrolyte (SPE) of polyethylene oxide (PEO) and LiClO4 onto the MoS2 surface. The device is top-gated by making contact to the surface of the electrolyte with a probe tip (Fig. 1 inset). Prior to the deposition of PEO:LiClO4, all devices show n-channel behavior when modulated by a backgate, regardless of MoS2 thickness. Devices with 2-3 layers of MoS2 (thickness measured with Raman spectroscopy) continue to show n-channel behavior with the electrolyte present, with an on/off ratio of 105. (Fig. 1) However, for devices with >10 layers of MoS2, p-channel behavior is observed, with an on/off ratio of ~100. (Fig. 2)The p-channel devices also show features at Vg = -8 V and Vg = 22 V, suggestive of electrochemical reactions between the MoS2 and the polymer electrolyte. Is it possible that these features are associated with the electrochemical reduction and oxidation of Li+. Because the features only appear in the data for devices with >10 layers, we propose that Li+ may be intercalating between layers of MoS2 and undergoing reversible redox reactions.Though both p- and n- channel devices show hysteresis, p-channel devices show two distinct states. After what appears to a forming step where the current increases to ~1 mA (Fig 2, Run 1), the threshold voltage shifts depending on the direction of the sweep. We define the threshold near 40 V as the “0” state and the threshold near 0 V as the “1” state. The state is set by the previous gate bias (i.e., it increases on the forward sweep to state “0” and decreases to state “1” on the reverse). Retention characteristics were tested by applying a bias (±25 V) to the topgate for 100 seconds, then removing the bias and measuring Id over time. The device retains state “0” for ~30 s and “1” for >1000 s (Fig. 3).We demonstrate for the first time the hysteretic response of an MoS2 FET with an SPE gate dielectric. Devices with >10 layers of MoS2 have a variable threshold that shifts depending on the previous gate bias. These devices may have application in novel ionic memory and steep subthreshold devices. Acknowledgements: This work was supported in part by the Center for Low Energy Systems Technology (LEAST), one of the six SRC STARnet Centers, sponsored by MARCO and DARPA.[1] Q. Wang, et al., Nature Nanotech, 7, p. 699-712, (2012)[2] B. Radisavljevic, et al., Nature Nanotech., 6, p. 147-150, (2011)[3] J. Chang, et al., arXiv, 1305.7162 (2013)

Semiconducting two-dimensional (2D) transition-metal dichalcogenides (TMDCs) are considered promising sensing materials due to the high surface-to-volume ratio and active sensing sites. However, the reported strategies for 2D TMDCs toward sensing of volatile organic compounds (VOCs) present with some drawbacks. These include high operation temperatures, low gas response, and complex fabrication, limiting the development of room-temperature gas sensors. In this study, 2D MoS2 nanoflakes were prepared by liquid-phase exfoliation, and their surface was functionalized with Au nanoparticles (NPs) through a facile solution mixing method. MoS2 decorated with Au NPs with an average size of 10 nm was used as a material platform for an electrochemical sensor to detect a wide variety of VOCs at room temperature. Through dynamic sensing tests, the enhancement of gas-sensing performance in terms of response and selectivity, especially in detecting oxygen-based VOCs (acetone, ethanol, and 2-propanol), was demonstrated. After Au functionalization, the response of the gas sensor to acetone improved by 131% (changing from 13.7% for pristine MoS2 to 31.6% for MoS2-Au(0.5)). Sensing tests under various relative humidity values (10-80%), bending or long-term conditions, indicated the sound robustness and flexibility of the sensor. Density functional theory simulations suggested that the adsorption energy of VOC molecules on MoS2-Au is significantly higher than that on pristine MoS2, contributing to the gas-sensing enhancement; a VOC-sensing mechanism for Au-decorated MoS2 nanoflakes was proposed for the first time for the highly sensitive and selective detection of oxygen-based VOCs.

Controlled epitaxial growth of strain-induced large-area bilayer MoS2 by chemical vapor deposition based on two-stage strategy

The transfer of charge carriers across the optically excited hetero-interface of graphene and semiconducting transition metal dichalcogenides (TMDCs) is the key to convert light to electricity, although the intermediate steps from the creation of excitons in TMDC to the collection of free carriers in the graphene layer are not fully understood. Here, we investigate photo-induced charge transport across graphene–MoS2 and graphene–WSe2 hetero-interfaces using time-dependent photoresistance relaxation with varying temperature, wavelength, and gate voltage. In both types of heterostructures, we observe an unprecedented resonance in the inter-layer charge transfer rate as the Fermi energy (EF) of the graphene layer is tuned externally with a global back gate. We attribute this to a resonant quantum tunneling from the excitonic state of the TMDC to EF of the graphene layer and outline a new method to estimate the excitonic binding energies (Eb) in the TMDCs, which are found to be 400 meV and 460 meV in MoS2 and WSe2 layers, respectively. The gate tunability of the inter-layer charge transfer timescales may allow precise engineering and readout of the optically excited electronic states at graphene–TMDC interfaces.

Monolayer transition metal dichalcogenides (TMDs) are promising for optoelectronics because of their high optical quantum yield and strong light-matter interaction. In particular, the van der Waals (vdW) heterostructures consisting of monolayer TMDs sandwiched by large gap hexagonal boron nitride have shown great potential for novel optoelectronic devices. However, a complicated stacking process limits scalability and practical applications. Furthermore, even though lots of efforts, such as fabrication of vdW heterointerfaces, modification of the surface, and structural phase transition, have been devoted to preserve or modulate the properties of TMDs, high environmental sensitivity and damage-prone characteristics of TMDs make it difficult to achieve a controllable technique for surface/interface engineering. Here, we demonstrate a novel way to fabricate multiple two-dimensional (2D) vdW heterostructures consisting of alternately stacked MoS2 and MoOx with enhanced photoluminescence (PL). We directly oxidized multilayer MoS2 to a MoOx/1 L-MoS2 heterostructure with atomic layer precision through a customized oxygen plasma system. The monolayer MoS2 covered by MoOx showed an enhanced PL intensity 3.2 and 6.5 times higher in average than the as-exfoliated 1 L- and 2 L-MoS2 because of preserved crystallinity and compensated dedoping by MoOx. By using layer-by-layer oxidation and transfer processes, we fabricated the heterostructures of MoOx/MoS2/MoOx/MoS2, where the MoS2 monolayers are separated by MoOx. The heterostructures showed the multiplied PL intensity as the number of embedded MoS2 layers increases because of suppression of the nonradiative trion formation and interlayer decoupling between stacked MoS2 layers. Our work shows a novel way toward the fabrication of 2D material-based multiple vdW heterostructures and our layer-by-layer oxidation process is beneficial for the fabrication of high performance 2D optoelectronic devices.

International Differences in the Location and Use of Arteriovenous Accesses Created for Hemodialysis: Results From the Dialysis Outcomes and Practice Patterns Study (DOPPS)

Impact of the COVID-19 pandemic on the prevalence of opioid agonist therapy discontinuation in Ontario, Canada: A population-based time series analysis

Non-steroidal anti-inflammatory drugs and risk of serious coronary heart disease: an observational cohort study