Search NASA⌕ Search

Engineering topics

Zhang, Yilin

Publications and source records attributed to Zhang, Yilin.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Superionic fluoride gate dielectrics with low diffusion barrier for two-dimensional electronics

Exploration of new dielectrics with a large capacitive coupling is an essential topic in modern electronics when conventional dielectrics suffer from the leakage issue near the breakdown limit. Here, to address this looming challenge, we demonstrate that rare-earth metal fluorides with extremely low ion migration barriers can generally exhibit an excellent capacitive coupling over 20 μF cm -2 (with an equivalent oxide thickness of ~0.15 nm and a large effective dielectric constant near 30) and great compatibility with scalable device manufacturing processes. Such a static dielectric capability of superionic fluorides is exemplified by MoS 2 transistors exhibiting high on/off current ratios over 10 8 , ultralow subthreshold swing of 65 mV dec -1 and ultralow leakage current density of ~10 -6 A cm -2 . Therefore, the fluoride-gated logic inverters can achieve notably higher static voltage gain values (surpassing ~167) compared with a conventional dielectric. Furthermore, the application of fluoride gating enables the demonstration of NAND, NOR, AND and OR logic circuits with low static energy consumption. In particular, the superconductor–insulator transition at the clean-limit Bi 2 Sr 2 CaCu 2 O 8+δ can also be realized through fluoride gating. In conclusion, our findings highlight fluoride dielectrics as a pioneering platform for advanced electronic applications and for tailoring emergent electronic states in condensed matter.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Flash NanoPrecipitation as an Agrochemical Nanocarrier Formulation Platform: Phloem Uptake and Translocation after Foliar Administration

The increasing severity of pathogenic and environmental stressors that negatively affect plant health has led to interest in developing next-generation agrochemical delivery systems capable of precisely transporting active agents to specific sites within plants. In this work, we adapt Flash NanoPrecipitation (FNP), a scalable nanocarrier (NC) formulation technology used in the pharmaceutical industry, to prepare organic core–shell NCs and study their efficacy as foliar or root delivery vehicles. NCs ranging in diameter from 55 to 200 nm, with surface zeta potentials from -40 to +40 mV, and with seven different shell material properties were prepared and studied. Shell materials included synthetic polymers poly(acrylic acid), poly(ethylene glycol), and poly(2-(dimethylamino)ethyl methacrylate), naturally occurring compounds fish gelatin and soybean lecithin, and semisynthetic hydroxypropyl methylcellulose acetate succinate (HPMCAS). NC cores contained a gadolinium tracer for tracking by mass spectrometry, a fluorescent dye for tracking by confocal microscopy, and model hydrophobic compounds (alpha tocopherol acetate and polystyrene) that could be replaced by agrochemical payloads in subsequent applications. After foliar application onto tomato plants with Silwet L-77 surfactant, internalization efficiencies of up to 85% and NC translocation efficiencies of up to 32% were observed. Significant NC trafficking to the stem and roots suggests a high degree of phloem loading for some of these formulations. Results were corroborated by confocal microscopy and synchrotron X-ray fluorescence mapping. NCs stabilized by cellulosic HPMCAS exhibited the highest degree of translocation, followed by formulations with a significant surface charge. The results from this work indicate that biocompatible materials like HPMCAS are promising agrochemical delivery vehicles in an industrially viable pharmaceutical nanoformulation process (FNP) and shed light on the optimal properties of organic NCs for efficient foliar uptake, translocation, and delivery.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Role of Ho Doping in Magnetization Mechanism of BiFeO{sub 3} Thin Films

BiFeO{sub 3} (BFO) as one of the considerable interesting multiferroic materials has been widely investigated for its fantastic science and potential application. Herein, effects of Ho doping on the structure, morphology, and magnetic properties of BFO thin films were systematically studied. X-ray diffraction (XRD) indicates a successful substitution of Ho at Bi site and a transition in crystal structure of Bi{sub 0.9}Ho{sub 0.1}FeO{sub 3} (BHFO) thin film. Raman scattering spectrum is further evidence of XRD analysis results. The Ho-doped BFO thin films possess uniform morphology. X-ray photoelectron spectroscopy (XPS) confirms that the substitution of Bi{sup 3+} ions with Ho{sup 3+} ions is beneficial. The remanent magnetization of BHFO thin films is about three times than that of the BFO thin films under a maximum magnetic field of 15,000 Oe. And we systematically discussed several possible reasons for the enhancement of magnetization.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Nanoparticle Size and Coating Chemistry Control Foliar Uptake Pathways, Translocation, and Leaf-to-Rhizosphere Transport in Wheat

Nano enabled foliar-applied agrochemicals can potentially be safer and more efficient than conventional products. However,limited understanding about how nanoparticle properties influence their interactions with plant leaves, uptake, translocation through the mesophyll to the vasculature, and transport to the rest of the plant prevents rational design. This study used a combination of Auquantification and spatial analysis to investigate how size (3, 10, or50 nm) and coating chemistry (PVP versus citrate) of gold nano-particles (AuNPs) influence these processes. Following wheat foliar exposure to AuNPs suspensions (~280 ng per plant), adhesion on the leaf surface was increased for smaller sizes, and PVP-AuNPs compared to citrate-AuNPs. After 2 weeks, there was incomplete uptake of citrate-AuNPs with some AuNPs remaining on the outside of the cuticle layer. However, the fraction of citrate-AuNPs that had entered the leaf was translocated efficiently tothe plant vasculature. In contrast, for similar sizes, virtually all of the PVP-AuNPs crossed the cuticle layer after 2 weeks,but its transport through the mesophyll cells was lower. As a consequence of PVP-AuNP accumulation in the leaf mesophyll, wheat photosynthesis was impaired. Regardless of their coating and sizes, the majority of the transported AuNPs accumulated in younger shoots (10-30%) and in roots (10-25%), and 5-15% of the NPs <50 nm were exuded into the rhizosphere soil. A greater fraction of larger sizes AuNPs (presenting lowerζpotentials) was transported to the roots. The key hypotheses about the NPs physical-chemical and plant physiology parameters that may matter to predict leaf-to-rhizosphere transport are also discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗