Fully Inkjet-Printed, 2D Materials-Based Field-Effect Transistor for Water Sensing

Despite significant progress in solution-processing of 2D materials, it remains challenging to reliably print high-performance semiconducting channels that can be efficiently modulated in a field-effect transistor (FET). Herein, electrochemically exfoliated MoS2 nanosheets are inkjet-printed into ultrathin semiconducting channels, resulting in high on/off current ratios up to 103. The reported printing strategy is reliable and general for thin film channel fabrication even in the presence of the ubiquitous coffee-ring effect. Statistical modeling analysis on the printed pattern profiles suggests that a spaced parallel printing approach can overcome the coffee-ring effect during inkjet printing, resulting in uniform 2D flake percolation networks. The uniformity of the printed features allows the MoS2 channel to be hundreds of micrometers long, which easily accommodates the typical inkjet printing resolution of tens of micrometers, thereby enabling fully printed FETs. As a proof of concept, FET water sensors are demonstrated using printed MoS2 as the FET channel, and printed graphene as the electrodes and the sensing area. After functionalization of the sensing area, the printed water sensor shows a selective response to Pb2+ in water down to 2 ppb. This work paves the way for additive nanomanufacturing of FET-based sensors and related devices using 2D nanomaterials

Concurrently Approaching Volumetric and Specific Capacity Limits of Lithium Battery Cathodes via Conformal Pickering Emulsion Graphene Coatings

To achieve the high energy densities demanded by emerging technologies, lithium battery electrodes need to approach the volumetric and specific capacity limits of their electrochemically active constituents, which requires minimization of the inactive components of the electrode. However, a reduction in the percentage of inactive conductive additives limits charge transport within the battery electrode, which results in compromised electrochemical performance. Here, an electrode design that achieves efficient electron and lithium-ion transport kinetics at exceptionally low conductive additive levels and industrially relevant active material areal loadings is introduced. Using a scalable Pickering emulsion approach, Ni-rich LiNi0.8Co0.15Al0.05O2 (NCA) cathode powders are conformally coated using only 0.5 wt% of solution-processed graphene, resulting in an electrical conductivity that is comparable to 5 wt% carbon black. Moreover, the conformal graphene coating mitigates degradation at the cathode surface, thus providing improved electrochemical cycle life. The morphology of the electrodes also facilitates rapid lithium-ion transport kinetics, which provides superlative rate capability. Overall, this electrode design concurrently approaches theoretical volumetric and specific capacity limits without tradeoffs in cycle life, rate capability, or active material areal loading.11Nsciescopu

Effects of forms and rates of potassium fertilizers on cadmium uptake by two cultivars of spring wheat (Trictium aestivum, L)

A greenhouse pot experiment was conducted to study the influence of potassium fertilizers in different forms and rates on cadmium (Cd) uptake by two cultivars of spring wheat (Triticum aestivum, L.): Brookton and Krichauff. Potassium fertilizers were added to soil at four levels: 0, 55, 110 and 166 mg K kg⁻¹ soil as KNO₃ (N), KCl (C) or K₂SO₄ (S). CdCl₂ was added to all the treatments at a uniform rate equivalent to 15 mg Cd kg⁻¹ soil. Plant shoot and root dry weights (DW) of both cultivars were reduced significantly by the addition of K-fertilizer in C and S treatments but there were only marginal changes in the N treatments. The Cd concentrations in shoots and whole plants increased significantly (P<.001) with increasing K addition, from 37.5 to 81.4 mg kg⁻¹ and from 42.9 to 86.8 mg kg⁻¹ for Brookton and Krichauff, respectively. However, no obvious effect was observed in the N treatments, except for the highest K level (K3) where there was a sharp increase in Cd concentration compared to the lower additions. Forms of K-fertilizers significantly influenced the Cd concentrations in plant shoots and roots (P<.001), but there was no significant difference between C and S treatments. This experiment showed that anions Cl⁻ and SO₄²⁻ increase Cd uptake by plants, which can be interpreted as Cl⁻ and SO₄²⁻ complexing readily with Cd²⁺ and thereby increasing the bioavailability of Cd²⁺ in soils. The effect of potassium itself on plant uptake of Cd was also observed. We suggest that when applying potassium fertilizer to Cd-contaminated soils, the forms and rates should be considered.Zhong-Qiu Zhao, Yong-Guan Zhu, Hui-Ying Li, Sally E. Smith and F. Andrew Smit