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1.
Nano Lett ; 24(22): 6585-6591, 2024 Jun 05.
Artículo en Inglés | MEDLINE | ID: mdl-38785400

RESUMEN

The gallium-doped hafnium oxide (Ga-HfO2) films with different Ga doping concentrations were prepared by adjusting the HfO2/Ga2O3 atomic layer deposition cycle ratio for high-speed and low-voltage operation in HfO2-based ferroelectric memory. The Ga-HfO2 ferroelectric films reveal a finely modulated coercive field (Ec) from 1.1 (HfO2/Ga2O3 = 32:1) to an exceptionally low 0.6 MV/cm (HfO2/Ga2O3 = 11:1). This modulation arises from the competition between domain nucleation and propagation speed during polarization switching, influenced by the intrinsic domain density and phase dispersion in the film with specific Ga doping concentrations. Higher Ec samples exhibit a nucleation-dominant switching mechanism, while lower Ec samples undergo a transition from a nucleation-dominant to a propagation-dominant reversal mechanism as the electric field increases. This work introduces Ga as a viable dopant for low Ec and offers insights into material design strategies for HfO2-based ferroelectric memory applications.

2.
Nanotechnology ; 35(12)2024 Jan 04.
Artículo en Inglés | MEDLINE | ID: mdl-38081066

RESUMEN

The resistive switching property in HfO2have attracted increasing interest in recent years. In this work, amorphous HfO2nanocrystals are synthesized by a facile hydrothermal method. Then, the as-synthesized nanocrystals are rapid thermal annealed in different atmospheres for improving the crystal quality, and monoclinic phase is determined as the main crystal structure of the annealed HfO2. Subsequently, metal-insulator-metal structure devices based on HfO2samples are fabricated. Electrical measurement indicates that 700 °C annealing processes in Air and Ar environments can slightly improve the bipolar resistive switching and retention behaviors. Higher annealed temperature (900 °C) will further improve the crystal quality of HfO2, while the resistive switching and retention behaviors of the devices continuously attenuate, which can be ascribed to the reduction of the conductive filaments induced by defects.

3.
Nanotechnology ; 2024 Jul 29.
Artículo en Inglés | MEDLINE | ID: mdl-39074487

RESUMEN

Recently discovered ferroelectricity in fluorite-structure ZrO2 thin film has attracted increasing and intense interest due to its lower crystallization temperature and higher content in nature in comparison to hafnium oxide. Here, the effect of HfO2 interfacial layer on the ferroelectric properties of ZrO2 thin films is investigated systematically by designing four types of interfacial structures. It is revealed that the ferroelectric orthorhombic phase, remanent polarization, and endurance can be improved in ZrO2 thin film by inserting both a top- and bottom-HfO2 interfacial layer. A maximal ferroelectric remanent polarization (2Pr) of 53.4 µC/cm2 and an optimal endurance performance of 3×107 field cycles under frequency of 100 kHz are achieved in Pt/HfO2/ZrO2/HfO2/Pt capacitors, with ferroelectric stacks being crystallized at 450 ℃ via post-deposition annealing method. X-ray photoelectron spectroscopy analysis confirms that the HfO2 bottom-layer plays a very important role in the formation of a higher ratio o-phase, thus enhancing the ferroelectricity. These results suggest that designing appropriate interfaces would help achieve excellent ferroelectric properties in ZrO2 films.

4.
Curr Neurol Neurosci Rep ; 24(2): 35-46, 2024 02.
Artículo en Inglés | MEDLINE | ID: mdl-38148387

RESUMEN

PURPOSE OF THE REVIEW: Magnetoencephalography (MEG) is a functional neuroimaging technique that records neurophysiology data with millisecond temporal resolution and localizes it with subcentimeter accuracy. Its capability to provide high resolution in both of these domains makes it a powerful tool both in basic neuroscience as well as clinical applications. In neurology, it has proven useful in its ability to record and localize epileptiform activity. Epilepsy workup typically begins with scalp electroencephalography (EEG), but in many situations, EEG-based localization of the epileptogenic zone is inadequate. The complementary sensitivity of MEG can be crucial in such cases, and MEG has been adopted at many centers as an important resource in building a surgical hypothesis. In this paper, we review recent work evaluating the extent of MEG influence of presurgical evaluations, novel analyses of MEG data employed in surgical workup, and new MEG instrumentation that will likely affect the field of clinical MEG. RECENT FINDINGS: MEG consistently contributes to presurgical evaluation and these contributions often change the plan for epilepsy surgery. Extensive work has been done to develop new analytic methods for localizing the source of epileptiform activity with MEG. Systems using optically pumped magnetometry (OPM) have been successfully deployed to record and localize epileptiform activity. MEG remains an important noninvasive tool for epilepsy presurgical evaluation. Continued improvements in analytic methodology will likely increase the diagnostic yield of the test. Novel instrumentation with OPM may contribute to this as well, and may increase accessibility of MEG by decreasing cost.


Asunto(s)
Epilepsia , Magnetoencefalografía , Humanos , Magnetoencefalografía/métodos , Epilepsia/diagnóstico , Epilepsia/cirugía , Electroencefalografía/métodos , Neuroimagen , Neuroimagen Funcional
5.
Mar Drugs ; 22(7)2024 Jul 19.
Artículo en Inglés | MEDLINE | ID: mdl-39057431

RESUMEN

High Fischer ratio oligopeptides (HFOs) have a variety of biological activities, but their mechanisms of action for anti-fatigue are less systematically studied at present. This study aimed to systematically evaluate the anti-fatigue efficacy of HFOs from Antarctic krill (HFOs-AK) and explore its mechanism of action through establishing the fatigue model of endurance swimming in mice. Therefore, according to the comparison with the endurance swimming model group, HFOs-AK were able to dose-dependently prolong the endurance swimming time, reduce the levels of the metabolites (lactic acid, blood urea nitrogen, and blood ammonia), increase the content of blood glucose, muscle glycogen, and liver glycogen, reduce lactate dehydrogenase and creatine kinase extravasation, and protect muscle tissue from damage in the endurance swimming mice. HFOs-AK were shown to enhance Na+-K+-ATPase and Ca2+-Mg2+-ATPase activities and increase ATP content in muscle tissue. Meanwhile, HFOs-AK also showed significantly antioxidant ability by increasing the activities of superoxide dismutase and glutathione peroxidase in the liver and decreasing the level of malondialdehyde. Further studies showed that HFOs-AK could regulate the body's energy metabolism and thus exert its anti-fatigue effects by activating the AMPK signaling pathway and up-regulating the expression of p-AMPK and PGC-α proteins. Therefore, HFOs-AK can be used as an auxiliary functional dietary molecules to exert its good anti-fatigue activity and be applied to anti-fatigue functional foods.


Asunto(s)
Euphausiacea , Fatiga , Oligopéptidos , Animales , Ratones , Fatiga/tratamiento farmacológico , Euphausiacea/química , Oligopéptidos/farmacología , Masculino , Natación , Metabolismo Energético/efectos de los fármacos , Condicionamiento Físico Animal , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Antioxidantes/farmacología
6.
Int J Toxicol ; 43(1): 4-18, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-37860941

RESUMEN

HFO-1234ze (E) is proposed as a near zero global warming propellant for use in metered dose inhaled (MDI) products. This paper describes the non-clinical safety assessment in mice, rats, and dogs and supplements previously reported data (genetic toxicology, short-term toxicology, and reproductive toxicology). In all species, HFO-1234ze (E) was only detectable in blood for a short period after dosing with no evidence of accumulation. HFO-1234ze (E) was without any toxicological effects at very high doses in subchronic (13-week mouse) and chronic (39-week dog) studies. Chronic (26-week) administration to rats at very high doses was associated with an exacerbation of rodent progressive cardiomyopathy, a well-documented background finding in rodents. In a 2-generation study, extremely high doses were associated with the early euthanasia of some lactating female rats. This finding was considered to be significantly influenced by a state of negative energy balance, reflecting the specific vulnerability of rats during lactation. These findings are considered to not pose a risk to humans with typical MDI use given they occurred at doses which far exceed those expected in patients. Overall, the nonclinical safety data for HFO-1234ze (E) support its further development as an MDI propellant.


Asunto(s)
Fluorocarburos , Calentamiento Global , Animales , Perros , Femenino , Ratones , Ratas , Administración por Inhalación , Lactancia
7.
Nano Lett ; 23(21): 9711-9718, 2023 Nov 08.
Artículo en Inglés | MEDLINE | ID: mdl-37875263

RESUMEN

Filamentary-type resistive switching devices, such as conductive bridge random-access memory and valence change memory, have diverse applications in memory and neuromorphic computing. However, the randomness in filament formation poses challenges to device reliability and uniformity. To overcome this issue, various defect engineering methods have been explored, including doping, metal nanoparticle embedding, and extended defect utilization. In this study, we present a simple and effective approach using self-assembled uniform Au nanoelectrodes to controll filament formation in HfO2 resistive switching devices. By concentrating the electric field near the Au nanoelectrodes within the BaTiO3 matrix, we significantly enhanced the device stability and reduced the threshold voltage by up to 45% in HfO2-based artificial neurons compared to the control devices. The threshold voltage reduction is attributed to the uniformly distributed Au nanoelectrodes in the insulating matrix, as confirmed by COMSOL simulation. Our findings highlight the potential of nanostructure design for precise control of filamentary-type resistive switching devices.

8.
Nano Lett ; 23(4): 1395-1400, 2023 Feb 22.
Artículo en Inglés | MEDLINE | ID: mdl-36763845

RESUMEN

The discovery of ferroelectric doped HfO2 enabled the emergence of scalable and CMOS-compatible ferroelectric field-effect transistor (FeFET) technology which has the potential to meet the growing need for fast, low-power, low-cost, and high-density nonvolatile memory, and neuromorphic devices. Although HfO2 FeFETs have been widely studied in the past few years, their fundamental switching speed is yet to be explored. Importantly, the shortest polarization time demonstrated to date in HfO2-based FeFET was ∼10 ns. Here, we report that a single subnanosecond pulse can fully switch HfO2-based FeFET. We also study the polarization switching kinetics across 11 orders of magnitude in time (300 ps to 8 s) and find a remarkably steep time-voltage relation, which is captured by the classical nucleation theory across this wide range of pulse widths. These results demonstrate the high-speed capabilities of FeFETs and help better understand their fundamental polarization switching speed limits and switching kinetics.

9.
Small ; 19(32): e2300341, 2023 08.
Artículo en Inglés | MEDLINE | ID: mdl-37029564

RESUMEN

With the rapid development of nanotechnology and nanomedicine, there are great interests in employing nanomaterials to improve the efficiency of disease diagnosis and treatment. The clinical translation of hafnium oxide (HfO2 ), commercially namedas NBTXR3, as a new kind of nanoradiosensitizer for radiotherapy (RT) of cancers has aroused extensive interest in researches on Hf-based nanomaterials for biomedical application. In the past 20 years, Hf-based nanomaterials have emerged as potential and important nanomedicine for computed tomography (CT)-involved bioimaging and RT-associated cancer treatment due to their excellent electronic structures and intrinsic physiochemical properties. In this review, a bibliometric analysis method is employed to summarize the progress on the synthesis technology of various Hf-based nanomaterials, including HfO2 , HfO2 -based compounds, and Hf-organic ligand coordination hybrids, such as metal-organic frameworks or nanoscaled coordination polymers. Moreover, current states in the application of Hf-based CT-involved contrasts for tissue imaging or cancer diagnosis are reviewed in detail. Importantly, the recent advances in Hf-based nanomaterials-mediated radiosensitization and synergistic RT with other current mainstream treatments are also generalized. Finally, current challenges and future perspectives of Hf-based nanomaterials with a view to maximize their great potential in the research of translational medicine are also discussed.


Asunto(s)
Antineoplásicos , Nanoestructuras , Neoplasias , Humanos , Hafnio/química , Nanoestructuras/química , Neoplasias/diagnóstico por imagen , Neoplasias/terapia , Nanotecnología/métodos
10.
Small ; : e2304650, 2023 Oct 20.
Artículo en Inglés | MEDLINE | ID: mdl-37863809

RESUMEN

Implementation of proton-exchange membrane water electrolyzers for large-scale sustainable hydrogen production requires the replacement of scarce noble-metal anode electrocatalysts with low-cost alternatives. However, such earth-abundant materials often exhibit inadequate stability and/or catalytic activity at low pH, especially at high rates of the anodic oxygen evolution reaction (OER). Here, the authors explore the influence of a dielectric nanoscale-thin oxide layer, namely Al2 O3 , SiO2 , TiO2 , SnO2 , and HfO2 , prepared by atomic layer deposition, on the stability and catalytic activity of low-cost and active but insufficiently stable Co3 O4 anodes. It is demonstrated that the ALD layers improve both the stability and activity of Co3 O4 following the order of HfO2 > SnO2 > TiO2 > Al2 O3 , SiO2 . An optimal HfO2 layer thickness of 12 nm enhances the Co3 O4 anode durability by more than threefold, achieving over 42 h of continuous electrolysis at 10 mA cm-2 in 1 m H2 SO4 electrolyte. Density functional theory is used to investigate the superior performance of HfO2 , revealing a major role of the HfO2 |Co3 O4 interlayer forces in the stabilization mechanism. These insights offer a potential strategy to engineer earth-abundant materials for low-pH OER catalysts with improved performance from earth-abundant materials for efficient hydrogen production.

11.
Nanotechnology ; 34(23)2023 Mar 20.
Artículo en Inglés | MEDLINE | ID: mdl-36863007

RESUMEN

Y-doping can effectively improve the performance of HfOx-based resistive random-access memory (RRAM) devices, but the underlying physical mechanism of Y-doping affecting the performance of HfOx-based memristors is still missing and unclear. Although impedance spectroscopy (IS) has been widely used to investigate impedance characteristics and switching mechanisms of RRAM devices, there is less IS analysis on Y-doped HfOx-based RRAM devices as well as devices at different temperatures. Here, the effect of Y-doping on the switching mechanism of HfOx-based RRAM devices with a Ti/HfOx/Pt structure were reported using current-voltage characteristics and IS. The results indicated that doping Y into HfOxfilms could decrease the forming/operate voltage and improve the RS uniform. Both doped and undoped HfOx-based RRAM devices obeyed the oxygen vacancies (VO) conductive filament model along the grain boundary (GB). Additionally, the GB resistive activation energy of the Y-doped device was inferior to that of the undoped device. It exhibited a shift of theVOtrap level towards the conduction band bottom after Y-doping in the HfOxfilm, which was the main reason for the improved RS performance.

12.
Nanotechnology ; 34(32)2023 May 22.
Artículo en Inglés | MEDLINE | ID: mdl-37137295

RESUMEN

Molybdenum disulfide (MoS2) is an emerging class of new materials with a wide range of potential practical applications. However, the uncontrollability of monolayer MoS2synthesized by traditional chemical vapor deposition method and the low responsivity of MoS2photodetectors limit its further development in the field of photoelectric detection. To achieve controlled growth of monolayer MoS2and construct MoS2photodetectors with a high responsivity, we propose a novel single crystal growth strategy of high-quality MoS2by controlling the Mo to S vapor ratio near the substrate, and deposit a layer of hafnium oxide (HfO2) on the surface of MoS2to enhance the performance of the pristine metal-semiconductor-metal structure photodetector. At a reverse bias of 8 V, the HfO2passivated MoS2photodetector features an extremely high responsivity of1201AW-1,a response time of around 0.5 s, and a detectivity of7.7×1011Jones.Meanwhile, we deeply investigate the effect of the HfO2layer on the performance of the fabricated MoS2photodetector and propose a physical mechanism to interpret the obtained experiment results. These results might facilitate a better understanding on the performance modulation of the MoS2photodetectors and accelerate the development of MoS2-based optoelectronic devices.

13.
Nanotechnology ; 35(1)2023 Oct 13.
Artículo en Inglés | MEDLINE | ID: mdl-37751722

RESUMEN

The potential of neuromorphic computing in synaptic simulation has led to a renewed interest in memristor. However, the demand for multilevel resistive switching with high reliability and low power consumption is still a great resistance in this application. In this work, the electronic synaptic plasticity and simulated bipolar switching behavior of Pt/Al2O3(2 nm)/HfO2(10 nm)/Al2O3(2 nm)/Ti tri-layer memristor is investigated. The effect of Al2O3layer embedded at the top electrode and the bottom electrode on the resistive performance of the memristor was studied. It is found that both of them can effectively improve the reliability of the device (104cycles), the resistive window (>103), the tunable synaptic linearity and reduce of the operating voltage. RRAM with Al2O3embedded at the top electrode have higher uniformity and LTP linearity, while those with Al2O3embedded at the bottom electrode significantly reduce the operating current (∼10µA) and improve LTD linearity. Electron transport mechanisms were compared between single-layer HfO2and tri-layer Al2O3/HfO2/Al2O3samples under DC scanning. The results showed that the thin Al2O3layer at the top electrode led to Fowler Northeim tunneling in the low-resistance state, while the thin Al2O3layer at the bottom electrode led to Schottky emission in the high-resistance state. The Al2O3/HfO2/Al2O3memristors were successfully used to achieve synaptic properties, including enhancement, inhibition, and spike time-dependent plasticity, demonstrating an important role in high-performance neuromorphic computing applications.

14.
Nanotechnology ; 34(36)2023 Jun 23.
Artículo en Inglés | MEDLINE | ID: mdl-37285830

RESUMEN

We have fabricated Sb70Se30/HfO2superlattice-like structure thin films for phase change memory by magnetron sputtering method, and investigated the effect of the HfO2layer on the crystalline characteristics and phase change behavior of Sb70Se30/HfO2thin films. The experimental results show that as the HfO2thickness increases, the crystallization temperature rises, the data retention capacity increases as well as the band gap widens, which is beneficial for improving the thermal stability and reliability of Sb70Se30/HfO2thin films. It was also found that the HfO2composite layer inhibited the grain growth of the Sb70Se30thin film, reducing the grain size and resulting in a smoother surface. In addition, the volume fluctuation of the Sb70Se30/HfO2thin films changes by only 5.58% between amorphous and crystalline. The threshold and reset voltages of the cell based on Sb70Se30/HfO2thin films are 1.52 V and 2.4 V respectively. We found that the HfO2composite layer plays a significant role in improving thermal stability, refining grain size of Sb70Se30phase change films and reducing device power consumption.


Asunto(s)
Reproducibilidad de los Resultados , Cristalización , Temperatura
15.
Nanotechnology ; 34(26)2023 Apr 12.
Artículo en Inglés | MEDLINE | ID: mdl-36962937

RESUMEN

To strengthen the downscaling potential of top-gate amorphous oxide semiconductor (AOS) thin-film transistors (TFTs), the ultra-thin gate insulator (GI) was comparatively implemented using the atomic-layer-deposited (ALD) AlOxand HfOx. Both kinds of high-kGIs exhibit good insulating properties even with the physical thickness thinning to 4 nm. Compared to the amorphous indium-gallium-zinc oxide (a-IGZO) TFTs with 4 nm AlOxGI, the 4 nm HfOxenables a larger GI capacitance, while the HfOx-gated TFT suffers higher gate leakage current and poorer subthreshold slope, respectively originating from the inherently small band offset and the highly defective interface between a-IGZO and HfOx. Such imperfect a-IGZO/HfOxinterface further causes noticeable positive bias stress instability. Both ALD AlOxand HfOxwere found to react with the underneath a-IGZO channel to generate the interface defects, such as metal interstitials and oxygen vacancies, while the ALD process of HfOxgives rise to a more severe reduction of a-IGZO. Moreover, when such a defective interface is covered by the top gate, it cannot be readily restored using the conventional oxidizing post-treatments and thus desires the reduction-resistant pre-treatments of AOSs.

16.
Environ Sci Technol ; 57(23): 8650-8659, 2023 06 13.
Artículo en Inglés | MEDLINE | ID: mdl-37235871

RESUMEN

Hydrofluoroolefins (HFOs) are being used as substitutes for potent greenhouse gas hydrofluorocarbons (HFCs). However, the use and environmental impacts of HFOs are of great concern due to the rapid degradation of HFOs to produce persistent and phytotoxic trifluoroacetic acid (TFA). Here, we provide a comprehensive projection of HFO emissions in China during 2024-2060 for the first time. Under the Kigali Amendment to the Montreal Protocol, China's HFO emissions are estimated to increase from 1.7 (1.3-2.3) to 148.8 (111.4-185.4) kt in 2024-2060 with cumulative emissions of 2.8 (2.0-3.5) Gt, and cumulative reduced HFCs emissions are evaluated to be 5.4 Gt CO2-equivalent. High HFO emissions would be distributed mainly in the North China Plain and the eastern and coastal areas. HFO-1234yf (2,3,3,3-tetrafluoropropene) contributes most of HFO emissions with a cumulative emission of 1.7 Gt in 2024-2060, while the cumulative increment of TFA deposition from HFO-1234yf emissions would reach 0.4-1.0 Gt. The long-term national-gridded HFO emission inventories can provide scientific support for evaluating the environmental risks of HFOs and developing HFC phase-out pathways for addressing climate change.


Asunto(s)
Fluorocarburos , Hidrocarburos Fluorados , Rwanda , Fluorocarburos/análisis , Cambio Climático
17.
Arch Toxicol ; 97(12): 3095-3111, 2023 12.
Artículo en Inglés | MEDLINE | ID: mdl-37792044

RESUMEN

1,1,2-Trifluoroethene (HFO-1123) is anticipated for use as a refrigerant with low global warming potential. Inhalation studies on HFO-1123 in rats indicated a low potential for toxicity (NOAELs ≥ 20,000 ppm). In contrast, single inhalation exposure of Goettingen® minipigs (≥ 500 ppm) and New Zealand white rabbits (≥ 1250 ppm) resulted in severe toxicity. It has been suggested that these pronounced species-differences in toxicity may be attributable to species-differences in biotransformation of HFO-1123 via the mercapturic acid pathway. Therefore, the overall objective of this study was to evaluate species-differences in glutathione (GSH) dependent in vitro metabolism of HFO-1123 in susceptible versus less susceptible species and humans as a basis for human risk assessment. Biotransformation of HFO-1123 to S-(1,1,2-trifluoroethyl)-L-glutathione (1123-GSH) and subsequent cysteine S-conjugate ß-lyase-mediated cleavage of the corresponding cysteine conjugate (1123-CYS) was monitored in hepatic and renal subcellular fractions of mice, rats, minipigs, rabbits, and humans. While 1123-GSH formation occurred at higher rates in rat and rabbit liver S9 compared to minipig and human S9, increased ß-lyase cleavage of 1123-CYS was observed in minipig kidney cytosol as compared to cytosolic fractions of other species. Increased ß-lyase activity in minipig cytosol was accompanied by time-dependent formation of monofluoroacetic acid (MFA), a highly toxic compound that interferes with cellular energy production via inhibition of aconitase. Consistent with the significantly lower ß-lyase activity in human cytosols, the intensity of the MFA signal in human cytosols was only a fraction of the signal obtained in minipig subcellular fractions. Even though the inconsistencies between GSH and ß-lyase-dependent metabolism do not allow to draw a firm conclusion on the overall contribution of the mercapturic acid pathway to HFO-1123 biotransformation and toxicity in vivo, the ß-lyase data suggest that humans may be less susceptible to HFO-1123 toxicity compared to minipigs.


Asunto(s)
Acetilcisteína , Liasas , Ratas , Ratones , Animales , Humanos , Conejos , Porcinos , Porcinos Enanos/metabolismo , Liasas/metabolismo , Biotransformación , Glutatión/metabolismo , Riñón/metabolismo
18.
IEEE Trans Electron Devices ; 70(3): 1236-1242, 2023 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-36972181

RESUMEN

In this work, a novel sensing structure based on Au nanoparticles/HfO2/fully depleted silicon-on-insulator (AuNPs/HfO2/FDSOI) MOSFET is fabricated. Using such a planar double gate MOSFET, the electrostatic enrichment (ESE) process is proposed for the ultrasensitive and rapid detection of the coronavirus disease 2019 (COVID-19) ORF1ab gene. The back-gate (BG) bias can induce the required electric field that enables the ESE process in the testing liquid analyte with indirect contact with the top-Si layer. It is revealed that the ESE process can rapidly and effectively accumulate ORF1ab genes close to the HfO2 surface, which can significantly change the MOSFET threshold voltage ([Formula: see text]). The proposed MOSFET successfully demonstrates the detection of zeptomole (zM) COVID-19 ORF1ab gene with an ultralow detection limit down to 67 zM (~0.04 copy/[Formula: see text]) for a test time of less than 15 min even in a high ionic-strength solution. Besides, the quantitative dependence of [Formula: see text] variation on COVID-19 ORF1ab gene concentration from 200 zM to 100 femtomole is also revealed, which is further confirmed by TCAD simulation.

19.
Luminescence ; 38(4): 450-461, 2023 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-36808703

RESUMEN

Li2 O-HfO2 -SiO2 -Tm2 O3 :Au2 O3 glass samples (containing fixed content of Tm2 O3 and different concentration of Au2 O3 ) were prepared and characterized. Bearing of Au0 metallic particles (MPs) on improving blue emission of thulium ions (Tm3+ ) ions was explored. Optical absorption (OA) spectra exhibited multiple bands excited from 3 H6 of Tm3+ . Additionally, a broad peak in the wavelength range 500-600 nm due to surface plasmon resonance (SPR) of Au0 MPs was noticed in the spectra. Photoluminescence (PL) spectra (of thulium free glasses) indicated a peak in the visible range due to sp → d electronic transition of Au0 MPs. Luminescence spectra of Tm3+ and Au2 O3 co-doped glasses exhibited intense blue emission with substantial increase of intensity with increase of Au2 O3 content. Bearing of Au0 MPs on the reinforcement of blue emission of Tm3+ was discussed in detail with kinetic rate equations.


Asunto(s)
Vidrio , Dióxido de Silicio , Iones , Litio , Luminiscencia
20.
Angew Chem Int Ed Engl ; 62(37): e202308690, 2023 Sep 11.
Artículo en Inglés | MEDLINE | ID: mdl-37470697

RESUMEN

The selective transition-metal catalyzed C-F bond functionalization of inexpensive industrial fluorochemicals represents one of the most attractive approaches to valuable fluorinated compounds. However, the selective C(sp2 )-F bond carbofunctionalization of refrigerant hydrofluoroolefins (HFOs) remains challenging. Here, we report a nickel-catalyzed selective C(sp2 )-F bond alkylation of HFO-1234yf with alkylzinc reagents. The resulting 2-trifluoromethylalkenes can serve as a versatile synthon for diversified transformations, including the anti-Markovnikov type hydroalkylation and the synthesis of bioactive molecule analogues. Mechanistic studies reveal that lithium salt is essential to promote the oxidative addition of Ni0 (Ln ) to the C-F bond; the less electron-rich N-based ligands, such as bipyridine and pyridine-oxazoline, feature comparable or even higher oxidative addition rates than the electron-rich phosphine ligands; the strong σ-donating phosphine ligands, such as PMe3 , are detrimental to transmetallation, but the less electron-rich and bulky N-based ligands, such as pyridine-oxazoline, facilitate transmetallation and reductive elimination to form the final product.

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