Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 61
Filtrar
Más filtros

Banco de datos
País/Región como asunto
Tipo del documento
Intervalo de año de publicación
1.
Opt Express ; 32(8): 13851-13863, 2024 Apr 08.
Artículo en Inglés | MEDLINE | ID: mdl-38859344

RESUMEN

This paper introduces an innovative, compact, and high-gain metasurface antenna, covering both the 24 GHz millimeter wave (mmWave) radar band and the 5 G n257 and n258 bands. The proposed metasurface antenna consists of a wideband stacked patch antenna and a dual-layer metasurface to focus its radiation beams for multiple mmWave bands. The operating frequency can be slightly shifted by altering the distance between the feeder and the metasurface. The distribution of the metasurface unit cells is designed based on a simplified phase compensation formula. The dimension of the fabricated feeder is 6 mm × 6 mm, and the metasurface occupies a 65 mm × 65 mm radome area. Experimental results demonstrate a wide bandwidth from 23.5 GHz to 29.1 GHz for the feeder, and impressive maximum gains of 19.7 dBi and 19.5 dBi for the lower band and higher band of the metasurface antenna are achieved simultaneously. The frequency reconfiguration ability was characterized by a 750 MHz frequency shift with every 1 mm distance adjustment. The compact size and high gain performance of the proposed design underscore its potential for practical applications in millimeter wave joint communication and radar sensing systems.

2.
Angew Chem Int Ed Engl ; 62(52): e202314414, 2023 Dec 21.
Artículo en Inglés | MEDLINE | ID: mdl-37946623

RESUMEN

The integration of highly active single atoms (SAs) and atom clusters (ACs) into an electrocatalyst is critically important for high-efficiency two-electron oxygen reduction reaction (2e- ORR) to hydrogen peroxide (H2 O2 ). Here we report a tandem impregnation-pyrolysis-etching strategy to fabricate the oxygen-coordinated Fe SAs and ACs anchored on bacterial cellulose-derived carbon (BCC) (FeSAs/ACs-BCC). As the electrocatalyst, FeSAs/ACs-BCC exhibits superior electrocatalytic activity and selectivity toward 2e- ORR, affording an onset potential of 0.78 V (vs. RHE) and a high H2 O2 selectivity of 96.5 % in 0.1 M KOH. In a flow cell reactor, the FeSAs/ACs-BCC also achieves high-efficiency H2 O2 production with a yield rate of 12.51±0.18 mol gcat -1 h-1 and a faradaic efficiency of 89.4 %±1.3 % at 150 mA cm-2 . Additionally, the feasibility of coupling the produced H2 O2 and electro-Fenton process for the valorization of ethylene glycol was explored in detail. The theoretical calculations uncover that the oxygen-coordinated Fe SAs effectively regulate the electronic structure of Fe ACs which are the 2e- ORR active sites, resulting in the optimal binding strength of *OOH intermediate for high-efficiency H2 O2 production.

3.
Environ Sci Technol ; 56(19): 13786-13797, 2022 10 04.
Artículo en Inglés | MEDLINE | ID: mdl-36098667

RESUMEN

The biotransformation of heavy metals in the environment is usually affected by co-existing pollutants like selenium (Se), which may lower the ecotoxicity of heavy metals, but the underlying mechanisms remain unclear. Here, we shed light on the pathways of copper (Cu2+) and selenite (SeO32-) synergistic biodetoxification by Shewanella oneidensis MR-1 and illustrate how such processes are affected by anthraquinone-2,6-disulfonate (AQDS), an analogue of humic substances. We observed the formation of copper selenide nanoparticles (Cu2-xSe) from synergistic detoxification of Cu2+ and SeO32- in the periplasm. Interestingly, adding AQDS triggered a fundamental transition from periplasmic to extracellular reaction, enabling 14.7-fold faster Cu2+ biodetoxification (via mediated electron transfer) and 11.4-fold faster SeO32- detoxification (via direct electron transfer). This is mainly attributed to the slightly raised redox potential of the heme center of AQDS-coordinated outer-membrane proteins that accelerates electron efflux from the cells. Our work offers a fundamental understanding of the synergistic detoxification of heavy metals and Se in a complicated environmental matrix and unveils an unexpected role of AQDS beyond electron mediation, which may guide the development of more efficient environmental remediation and resource recovery biotechnologies.


Asunto(s)
Contaminantes Ambientales , Selenio , Antraquinonas , Cobre , Hemo , Sustancias Húmicas , Proteínas de la Membrana , Oxidación-Reducción , Ácido Selenioso
4.
Angew Chem Int Ed Engl ; 61(42): e202208040, 2022 Oct 17.
Artículo en Inglés | MEDLINE | ID: mdl-35831687

RESUMEN

Platinum on carbon (Pt/C) catalyst is commercially adopted in fuel cells but it undergoes formidable active-site poisoning by carbon monoxide (CO). In particular, given the sluggish kinetics of hydrogen oxidation reaction (HOR) in anion-exchange membrane fuel cell (AEMFC), the issues of Pt poisoning and slow rate would combine mutually, notably worsening the device performances. Here we overcome these challenges through incorporating cobalt (Co) into molybdenum-nickel alloy (MoNi4 ), termed Co-MoNi4 , which not only shows superior HOR activity over the Pt/C catalyst in alkali, but more intriguingly exhibits excellent CO tolerance with only small activity decay after 10 000 cycles in the presence of 500 parts per million (ppm) CO. When feeding with CO (250 ppm)/H2 , the AEMFC assembled by this catalyst yields a peak power density of 394 mW cm-2 , far exceeding the Pt/C catalyst. Experimental and computational studies reveal that weakened CO chemisorption originates from the electron-deficient Ni sites after Co incorporation that suppresses d→CO 2π* back-donation.

5.
Environ Sci Technol ; 55(10): 7063-7071, 2021 05 18.
Artículo en Inglés | MEDLINE | ID: mdl-33961405

RESUMEN

As one of the extensively used feed additives in livestock and poultry breeding, p-arsanilic acid (p-ASA) has become an organoarsenic pollutant with great concern. For the efficient removal of p-ASA from water, the combination of chemical oxidation and adsorption is recognized as a promising process. Herein, hollow/porous Mn-Fe-mixed oxide (MnFeO) nanocubes were synthesized and used in coupling with peroxymonosulfate (PMS) to oxidize p-ASA and remove the total arsenic (As). Under acidic conditions, both p-ASA and total As could be completely removed in the PMS/MnFeO process and the overall performance was substantially better than that of the Mn/Fe monometallic system. More importantly, an interface-promoted direct oxidation mechanism was found in the p-ASA-involved PMS/MnFeO system. Rather than activate PMS to generate reactive oxygen species (i.e., SO4·-, ·OH, and 1O2), the MnFeO nanocubes first adsorbed p-ASA to form a ligand-oxide interface, which improved the oxidation of the adsorbed p-ASA by PMS and ultimately enhanced the removal of the total As. Such a direct oxidation process achieved selective oxidation of p-ASA and avoidance of severe interference from the commonly present constituents in real water samples. After facile elution with dilute alkali solution, the used MnFeO nanocubes exhibited superior recyclability in the repeated p-ASA removal experiments. Therefore, this work provides a promising approach for efficient abatement of phenylarsenical-caused water pollution based on the PMS/MnFeO oxidation process.


Asunto(s)
Arsénico , Contaminantes Químicos del Agua , Ácido Arsanílico , Oxidación-Reducción , Óxidos , Peróxidos
6.
Angew Chem Int Ed Engl ; 59(32): 13423-13429, 2020 Aug 03.
Artículo en Inglés | MEDLINE | ID: mdl-32367577

RESUMEN

Single-atom catalysts have demonstrated their superiority over other types of catalysts for various reactions. However, the reported nitrogen reduction reaction single-atom electrocatalysts for the nitrogen reduction reaction exclusively utilize metal-nitrogen or metal-carbon coordination configurations as catalytic active sites. Here, we report a Fe single-atom electrocatalyst supported on low-cost, nitrogen-free lignocellulose-derived carbon. The extended X-ray absorption fine structure spectra confirm that Fe atoms are anchored to the support via the Fe-(O-C2 )4 coordination configuration. Density functional theory calculations identify Fe-(O-C2 )4 as the active site for the nitrogen reduction reaction. An electrode consisting of the electrocatalyst loaded on carbon cloth can afford a NH3 yield rate and faradaic efficiency of 32.1 µg h-1 mgcat. -1 (5350 µg h-1 mgFe -1 ) and 29.3 %, respectively. An exceptional NH3 yield rate of 307.7 µg h-1 mgcat. -1 (51 283 µg h-1 mgFe -1 ) with a near record faradaic efficiency of 51.0 % can be achieved with the electrocatalyst immobilized on a glassy carbon electrode.

7.
Environ Sci Technol ; 53(18): 10917-10925, 2019 Sep 17.
Artículo en Inglés | MEDLINE | ID: mdl-31432660

RESUMEN

The pertechnetate anion (99TcO4-) is a long-lived radioactive species that is soluble in aqueous solution, in contrast to sparingly soluble 99TcO2. Results are reported for photocatalytic reduction and removal of perrhenate (ReO4-), a nonradioactive surrogate for 99TcO4-, using a TiO2 (P25) nanoparticle suspension in formic acid under UV-visible irradiation. Re(VII) removal up to 98% was achieved at pH = 3 under air or N2. The proposed mechanism is Re(VII)/Re(IV) reduction mediated by reducing radicals (·CO2-) from oxidation of formic acid, not direct reduction by photogenerated electrons of TiO2. Recycling results indicate that photocatalytic reduction of ReO4- exhibits excellent regeneration and high activity with >95% removal even after five cycles. 99Tc(VII) is more easily reduced than Re(VII) in the presence of NO3- with very slow redissolution of reduced 99Tc. This study presents a novel method for the removal of ReO4-/99TcO4- from aqueous solution, with potential application for deep geological disposal.


Asunto(s)
Renio , Pertecnetato de Sodio Tc 99m , Aniones , Agua
8.
J Am Chem Soc ; 140(31): 9942-9951, 2018 08 08.
Artículo en Inglés | MEDLINE | ID: mdl-30008218

RESUMEN

All-inorganic perovskite nanocrystals (NCs) have emerged as a new generation of low-cost semiconducting luminescent system for optoelectronic applications. The room-temperature photoluminescence quantum yields (PLQYs) of these NCs in the green and red spectral range approach unity. However, their PLQYs in the violet are much lower, and an insightful understanding of such poor performance remains missing. We report a general strategy for the synthesis of all-inorganic violet-emitting perovskite NCs with near-unity PLQYs through engineering local order of the lattice by nickel ion doping. A broad range of experimental characterizations, including steady-state and time-resolved luminescence spectroscopy, X-ray absorption spectra, and magic angle spinning nuclear magnetic resonance spectra, reveal that the low PLQY in undoped NCs is associated with short-range disorder of the lattice induced by intrinsic defects such as halide vacancies and that Ni doping can substantially eliminate these defects and result in increased short-range order of the lattice. Density functional theory calculations reveal that Ni doping of perovskites causes an increase of defect formation energy and does not introduce deep trap states in the band gap, which is suggested to be the main reason for the improved local structural order and near-unity PLQY. Our ability to obtain violet-emitting perovskite NCs with near-perfect properties opens the door for a range of applications in violet-emitting perovskite-based devices such as light-emitting diodes, single-photon sources, lasers, and beyond.

9.
Chemistry ; 24(35): 8875-8882, 2018 Jun 21.
Artículo en Inglés | MEDLINE | ID: mdl-29655241

RESUMEN

Engineering oxygen coordination environments of cations in oxides has received intense interest thanks to the opportunities for the discovery of novel oxides with unusual properties. Herein, the synthesis of stoichiometric layered BaBiO2.5 by a nontopotactic phase transformation of perovskite BaBiO3 is presented. By analyzing the synchrotron X-ray diffraction data by the maximum-entropy method/Rietveld technique, it was found that Bi is involved in an unusual chemical bonding situation with four oxygen atoms featuring one ionic bond and three covalent bonds, which results in an asymmetric coordination geometry. Photophysical characterization revealed that this peculiar structure shows near-infrared luminescence differing from that of conventional Bi-containing compounds. Experimental and theoretical results led to the proposal of an excitonic nature of the luminescence. This work highlights that synthesizing materials with uncommon Bi-O bonding and Bi coordination geometry provides a pathway to the discovery of systems with new functionalities. This could inspire interest in the exploration of a range of materials containing heavier p-block elements with prospects for finding systems with unusual properties.

10.
Chemistry ; 24(39): 9976-9982, 2018 Jul 11.
Artículo en Inglés | MEDLINE | ID: mdl-29683534

RESUMEN

The synthesis of luminescent polyoxometalates (POMs) typically relies on the assembly of POM ligands with rare earth or transition metals, placing significant constraints on the composition, structure, and hence the luminescence properties of the resultant systems. Herein, we show that the ion-exchange strategy can be used for the synthesis of novel POM-based luminescent materials. We demonstrate that introducing bismuth ions into an ion-exchangeable, microporous POM compound yields an unconventional system luminescing in the near-infrared region. Experimental characterization, coupled with quantum chemical calculations, confirms that bismuth ions site-specifically occupy an off-center site in the lattice, and have an asymmetric coordination geometry unattainable by other means, thus giving rise to peculiar emission. Our findings offer an effective strategy for the synthesis of POM-based luminescent materials, and the design concept may potentially be adapted to the creation of POM-based systems with other functionalities.

11.
Environ Sci Technol ; 51(10): 5666-5674, 2017 May 16.
Artículo en Inglés | MEDLINE | ID: mdl-28409920

RESUMEN

The separation and recovery of uranium from radioactive wastewater is important from the standpoints of environmental protection and uranium reuse. In the present work, magnetically collectable TiO2/Fe3O4 and its graphene composites were fabricated and utilized for the photocatalytical removal of U(VI) from aqueous solutions. It was found that, under ultraviolet (UV) irradiation, the photoreactivity of TiO2/Fe3O4 for the reduction of U(VI) was 19.3 times higher than that of pure TiO2, which is strongly correlated with the Fe0 and additional Fe(II) generated from the reduction of Fe3O4 by TiO2 photoelectrons. The effects of initial uranium concentration, solution pH, ionic strength, the composition of wastewater, and organic pollutants on the U(VI) removal by TiO2/Fe3O4 were systematically investigated. The results demonstrated its excellent performance in the cleanup of uranium contamination. As graphene can efficiently attract the TiO2 photoelectrons and thus decrease their transfer to Fe3O4, the photodissolution of Fe3O4 in the TiO2/graphene/Fe3O4 composite can be largely alleviated compared to that of the TiO2/Fe3O4, rendering this ternary composite a much higher stability. In addition, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES), and X-ray photoelectron spectroscopy (XPS) were used to explore the reaction mechanisms.


Asunto(s)
Titanio , Uranio , Grafito , Magnetismo , Purificación del Agua
12.
Sichuan Da Xue Xue Bao Yi Xue Ban ; 48(1): 120-123, 2017 Jan.
Artículo en Zh | MEDLINE | ID: mdl-28612572

RESUMEN

OBJECTIVES: To compare the neuroprotection effect of two methods of Lidocaine administration in rabbit model of subarachnoid hemorrhage. METHODS: Forty New Zealand white rabbits were randomly divided into sham group, subarachnoid hemorrhage group (SAH), Lidocaine intravenous injection group (L1), and Lidocaine intracisternal administration group (L2). The rabbits were given general anaesthesia, then 1.5 mL autologous nonheparinized arterial blood was injected into cisterna magna to establish SAH model, while 1.5 mL saline was used in sham group. Thirty minutes later, the rabbits in L1 and L2 group respectively received 0.3 mL 2% Lidocaine administration of intravenously and intracisternally injection. All animals were sacrificed at 72 h after SAH. The samples of basilar artery and hippocampus tissue were processed for morphometric analysis. At pre-operation and 72 h after SAH, the level of interleukin-6 (IL-6) in serum was measured. HE staining and C fos immunohistochemical staining were performed in L1 and L2 groups. Artery area and artery diameter of basal arteries, normal neuron density and C-fos positive cell in hippocampus were measured at 72 h after SAH. RESULTS: The baseline level of IL-6 was not significant different in four groups (P>0.05). The level of IL-6 at 72 h after SAH was significantly higher than that at pre-operation in SAH, L1 and L2 groups (P<0.05), while the level of IL-6 in SAH and L1 group was higher than that in L2 group (P<0.05). Compared to sham and L2 group, the cross-section area and diameter of basal artery were smaller in SAH and L1 group, while the normal neuron density of hippocampus was less (P<0.05). CONCLUSIONS: Intracisternal administration of Lidocaine could provide neuroprotection in rabbit model of subarachnoid hemorrhage.


Asunto(s)
Lidocaína/administración & dosificación , Neuroprotección , Hemorragia Subaracnoidea/tratamiento farmacológico , Administración Intravenosa , Animales , Arteria Basilar , Cisterna Magna , Modelos Animales de Enfermedad , Inyecciones , Interleucina-6/sangre , Conejos
13.
Sichuan Da Xue Xue Bao Yi Xue Ban ; 48(2): 230-233, 2017 Mar.
Artículo en Zh | MEDLINE | ID: mdl-28612532

RESUMEN

OBJECTIVES: To determine the neuroprotection mechanism of lidocaine on early brain injury resulted from subarachnoid hemorrhage. METHODS: Eighteen New Zealand white rabbits were randomly divided into three groups: Sham group, subarachnoid hemorrhage (SAH) group and lidocaine treatment (LD) group. Operations were performed on all animals under anesthesia. Autologous nonheparinized arterial blood (1 mL/kg, body mass) was injected into cisterna magna of rabbits in the SAH and LD groups, while saline (1 mL/kg, body mass) was given to rabbits in the sham group. Thirty minutes later, intravenous injection of 0.6 mL 20 mg/mL lidocaine was given to those in the LD group, and intravenous injection of 0.6 mL saline was given to those in the Sham and SAH groups. Food intake and neurological impairments of the rabbits were assessed 72 h after the induction of SAH. The protein and mRNA experssions of Caspase-3 and cytochrome-c (Cyt-c) in hippocampus tissues were detected using real-time PCR (RT-PCR) and Western blot. RESULTS: Rabbits in the SAH and LD groups had lower food intake and higher mRNA and protein expressions of Caspase-3 and Cyt-c than those in the sham groups, which was accompanied with varying degrees of neurological impairments. No significant differences in food intake and neurological impairments were found between the SAH and LD groups (P >0.05). However, rabbits in the LD group had lower levels of mRNA and protein expressions of Caspase-3 and Cyt-c than those in the SAH group (P <0.05). CONCLUSION: The neuroprotection mechanism of lidocaine on early brain injury in rabbits with subarachnoid hemorrhage may be associated with inhibition of mitochondrial pathway and downregulated mRNA and protein expressions of Caspase-3 and Cyt-c in brain tissues.


Asunto(s)
Lidocaína/farmacología , Fármacos Neuroprotectores/farmacología , Hemorragia Subaracnoidea/tratamiento farmacológico , Animales , Caspasa 3/metabolismo , Modelos Animales de Enfermedad , Complejo IV de Transporte de Electrones/metabolismo , Conejos , Distribución Aleatoria
14.
Angew Chem Int Ed Engl ; 56(26): 7430-7434, 2017 06 19.
Artículo en Inglés | MEDLINE | ID: mdl-28544453

RESUMEN

Semiconductor photocatalysts are hardly employed for overall water splitting beyond 700 nm, which is due to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts are known to overcome this limitation through interband transitions for creating electron-hole pairs; however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Black tungsten nitride is now employed as a metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red-light irradiation for tungsten nitride. This work represents the first red-light responsive photocatalyst for overall water splitting, and may open a promising venue in searching of metallic materials as efficient photocatalysts for solar energy utilization.

15.
Angew Chem Int Ed Engl ; 55(16): 4967-71, 2016 Apr 11.
Artículo en Inglés | MEDLINE | ID: mdl-26971863

RESUMEN

A low-temperature topochemical reduction strategy is used herein to prepare unconventional phosphors with luminescence covering the biological and/or telecommunications optical windows. This approach is demonstrated by using Bi(III)-doped Y2O3 (Y(2-x)Bi(x)O3) as a model system. Experimental results suggest that topochemical treatment of Y(2-x)Bi(x)O3 using CaH2 creates randomly distributed oxygen vacancies in the matrix, resulting in the change of the oxidation states of Bi to lower oxidation states. The change of the Bi coordination environments from the [BiO6] octahedra in Y(2-x)Bi(x)O3 to the oxygen-deficient [BiO(6-z)] polyhedra in reduced phases leads to a shift of the emission maximum from the visible to the near-infrared region. The generality of this approach was further demonstrated with other phosphors. Our findings suggest that this strategy can be used to explore Bi-doped or other classes of luminescent systems, thus opening up new avenues to develop novel optical materials.

16.
Inorg Chem ; 54(4): 1992-9, 2015 Feb 16.
Artículo en Inglés | MEDLINE | ID: mdl-25629464

RESUMEN

Room temperature ionic liquids (RTILs) represent a recent new class of solvents applied in liquid/liquid extraction based nuclear fuel reprocessing, whereas the related coordination chemistry and detailed extraction processes are still not well understood and remain of deep fundamental interest. The work herein provides a new insight of coordination and extraction of uranium(VI) with N-donating ligands, e.g., N,N'-diethyl-N,N'-ditolyldipicolinamide (EtpTDPA), in commonly used RTILs. Exploration of the extraction mechanism, speciation analyses of the extracted U(VI), and crystallographic studies of the interactions of EtpTDPA with U(VI) were performed, including the first structurally characterized UO2(EtpTDPA)2(NTf2) and UO2(EtpTDPA)2(PF6)2 compounds and a first case of crystallographic differentiation between the extracted U(VI) complexes in RTILs and in molecular solvents. It was found that in RTILs two EtpTDPA molecules coordinate with one U(VI) ion through the carbonyl and pyridine nitrogen moieties, while NTf2(-) and PF6(-) act as counterions. The absence of NO3(-) in the complexes is coincident with a cation-exchange extraction. In contrast, both the extracted species and extraction mechanisms are greatly different in dichloromethane, in which UO2(2+) coordinates in a neutral complex form with one EtpTDPA molecule and two NO3(-) cations. In addition, the complex formation in RTILs is independent of the cation exchange since incorporating UO2(NO3)2, EtpTDPA, and LiNTf2 or KPF6 in a solution also produces the same complex as that in RTILs, revealing the important roles of weakly coordinating anions on the coordination chemistry between U(VI) and EtpTDPA. These findings suggest that cation-exchange extraction mode for ILs-based extraction system probably originates from the supply of weakly coordinating anions from RTILs. Thus the coordination of uranium(VI) with extractants as well as the cation-exchange extraction mode may be potentially changed by varying the counterions of uranyl or introducing extra anions.


Asunto(s)
Complejos de Coordinación/química , Complejos de Coordinación/aislamiento & purificación , Líquidos Iónicos/química , Ácidos Picolínicos/química , Temperatura , Uranio/química , Complejos de Coordinación/síntesis química , Cristalografía por Rayos X , Líquidos Iónicos/aislamiento & purificación , Ligandos , Modelos Moleculares , Conformación Molecular , Ácidos Picolínicos/aislamiento & purificación
17.
Angew Chem Int Ed Engl ; 54(39): 11467-71, 2015 Sep 21.
Artículo en Inglés | MEDLINE | ID: mdl-26291331

RESUMEN

The efficiency of solar-energy-conversion devices depends on the absorption region and intensity of the photon collectors. Organic chromophores, which have been widely stabilized on inorganic semiconductors for light trapping, are limited by the interface between the chromophore and semiconductor. Herein we report a novel orange zinc germanate (Zn-Ge-O) with a chromophore-like structure, by which the absorption region can be dramatically expanded. Structural characterizations and theoretical calculations together reveal that the origin of visible-light response can be attributed to the unusual metallic Ge-Ge bonds which act in a similar way to organic chromophores. Benefiting from the enhanced light harvest, the orange Zn-Ge-O demonstrates superior capacity for solar-driven hydrogen production.

18.
Anal Chem ; 86(3): 1687-92, 2014 Feb 04.
Artículo en Inglés | MEDLINE | ID: mdl-24397707

RESUMEN

A highly phosphorescent molecular Au(I) cluster capable of rapid, sensitive, and selective detection of cyanide has been successfully fabricated. The origin of the outstanding sensing performance of the molecular Au(I) cluster toward cyanide is justified by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses. The response mechanism employed with the molecular Au(I) cluster and the cost-effectiveness in cyanide detection affords several key sensor features, making this molecular Au(I) cluster-based sensor unique compared to other cyanide sensing schemes. Importantly, by exploring the phosphorescent properties of the molecular Au(I) cluster in solid state, we demonstrate the first example of the molecular gold(I) cluster-based macroporous sensing film for colorimetric detection of cyanide in complex samples, including red wine, coffee, juice, and soil. Remarkably, the as-prepared sensing film inherits the sensing ability of the molecular Au(I) cluster, and offers a high mechanical flexibility and novel opportunities for real-time monitoring cyanide release in cassava manufacturing.

19.
Chemistry ; 20(8): 2138-44, 2014 Feb 17.
Artículo en Inglés | MEDLINE | ID: mdl-24403011

RESUMEN

The process of using solar energy to split water to produce hydrogen assisted by an inorganic semiconductor is crucial for solving our energy crisis and environmental problems in the future. However, most semiconductor photocatalysts would not exhibit excellent photocatalytic activity without loading suitable co-catalysts. Generally, the noble metals have been widely applied as co-catalysts, but always agglomerate during the loading process or photocatalytic reaction. Therefore, the utilization efficiency of the noble co-catalysts is still very low on a per metal atom basis if no obvious size effect exists, because heterogeneous catalytic reactions occur on the surface active atoms. Here, for the first time, we have synthesized isolated metal atoms (Pt, Pd, Rh, or Ru) stably by anchoring on TiO2 , a model photocatalystic system, by a facile one-step method. The isolated metal atom based photocatalysts show excellent stability for H2 evolution and can lead to a 6-13-fold increase in photocatalytic activity over the metal clusters loaded on TiO2 by the traditional method. Furthermore, the configurations of isolated atoms as well as the originality of their unusual stability were analyzed by a collaborative work from both experiments and theoretical calculations.

20.
Artículo en Inglés | MEDLINE | ID: mdl-38416632

RESUMEN

This paper presents a reconfigurable near-sensor anomaly detection processor to real-time monitor the potential anomalous behaviors of amputees with limb prostheses. The processor is low-power, low-latency, and suitable for equipment on the prostheses and comprises a reconfigurable Variational Autoencoder (VAE), a scalable Self-Organizing Map (SOM) Array, and a window-size-adjustable Markov Chain, which can implement an integrated miniaturized anomaly detection system. With the reconfigurable VAE, the proposed processor can support up to 64 sensor sampling channels programmable by global configuration, which can meet the anomaly detection requirements in different scenarios. A scalable SOM array allows for the selection of different sizes based on the complexity of the data. Unlike traditional time accumulation-based anomaly detection methods, the Markov Chain is utilized to detect time-series-based anomalous data. The processor is designed and fabricated in a UMC 40-nm LP technology with a core area of 1.49 mm2 and a power consumption of 1.81 mW. It achieves real-time detection performance with 0.933 average F1 Score for the FSP dataset within 24.22 µs, and 0.956 average F1 Score for the SFDLA-12 dataset within 30.48 µs, respectively. The energy dissipation of detection for each input feature is 43.84 nJ with the FSP dataset, and 55.17 nJ with the SFDLA-12 dataset. Compared with ARM Cortex-M4 and ARM Cortex-M33 microcontrollers, the processor achieves energy and area efficiency improvements ranging from 257×, 193× and 11×, 8×, respectively.

SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA