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1.
Nat Commun ; 10(1): 4597, 2019 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-31601812

RESUMO

While high sulfur loading has been pursued as a key parameter to build realistic high-energy lithium-sulfur batteries, less attention has been paid to the cathode porosity, which is much higher in sulfur/carbon composite cathodes than in traditional lithium-ion battery electrodes. For high-energy lithium-sulfur batteries, a dense electrode with low porosity is desired to minimize electrolyte intake, parasitic weight, and cost. Here we report the profound impact on the discharge polarization, reversible capacity, and cell cycling life of lithium-sulfur batteries by decreasing cathode porosities from 70 to 40%. According to the developed mechanism-based analytical model, we demonstrate that sulfur utilization is limited by the solubility of lithium-polysulfides and further conversion from lithium-polysulfides to Li2S is limited by the electronically accessible surface area of the carbon matrix. Finally, we predict an optimized cathode porosity to maximize the cell level volumetric energy density without sacrificing the sulfur utilization.


Assuntos
Fontes de Energia Elétrica , Lítio , Enxofre , Eletroquímica/métodos , Eletrodos , Lítio/química , Porosidade , Sulfetos/química
2.
Mater Sci Eng C Mater Biol Appl ; 104: 109896, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31499977

RESUMO

Zinc alloys have been explored as potential materials for biodegradable vascular stents due to their tolerable corrosion rates and tunable mechanical properties. However, the performances of Zn alloys were not supported with enough toxicity or biological compatibility evaluation, particularly hemocompatibility for vascular scaffolding application. In this work, the hemocompatibility of three zinc alloys (Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li) was evaluated with 316 L stainless steel and pure zinc as controls. The hemolysis ratios of 316 L stainless steel, pure Zn, Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li were 0.38 ±â€¯0.08%, 1.04 ±â€¯0.21%, 0.47 ±â€¯0.21%, 0.57 ±â€¯0.14% and 0.52 ±â€¯0.22%, respectively, for direct contact method. Platelets aggregation on the 316 L stainless steel was observed, while the adhered platelets on the Zn alloys exhibited round shape with few pseudopodia spreading. The number of adhered platelets on the three zinc alloys (Zn-0.8Cu, Zn-0.8Mn and Zn-0.8Li) had no statistically difference compared with 316 L stainless steel, while significant fewer than the pure Zn group. None remarkable platelet activation, hematocyte aggregation, coagulation or complement activation was observed in any Zn alloy group. Furthermore, the Zn alloys prolonged prothrombin time and partial thromboplastin time, demonstrating a potential function of anticoagulation. The results demonstrated that Zn alloys presented in this work are indeed meeting the hemocompatible requirements of implant and showing the promise for perspective application as biodegradable stent.


Assuntos
Ligas/química , Materiais Biocompatíveis/química , Lítio/química , Magnésio/química , Zinco/química , Implantes Absorvíveis , Ligas/administração & dosagem , Materiais Biocompatíveis/administração & dosagem , Coagulação Sanguínea/efeitos dos fármacos , Ativação do Complemento/efeitos dos fármacos , Corrosão , Hemólise/efeitos dos fármacos , Humanos , Lítio/administração & dosagem , Teste de Materiais/métodos , Ativação Plaquetária/efeitos dos fármacos , Aço Inoxidável/química , Stents , Zinco/administração & dosagem
3.
Molecules ; 24(17)2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31470618

RESUMO

The aggregation morphology of anode materials plays a vital role in achieving high performance lithium-ion batteries. Herein, Co3O4 anode materials with different aggregation morphologies were successfully prepared by modulating the morphology of precursors with different cobalt sources by the mild coprecipitation method. The fabricated Co3O4 can be flower-like, spherical, irregular, and urchin-like. Detailed investigation on the electrochemical performance demonstrated that flower-like Co3O4 consisting of nanorods exhibited superior performance. The reversible capacity maintained 910.7 mAh·g-1 at 500 mA·g-1 and 717 mAh·g-1 at 1000 mA·g-1 after 500 cycles. The cyclic stability was greatly enhanced, with a capacity retention rate of 92.7% at 500 mA·g-1 and 78.27% at 1000 mA·g-1 after 500 cycles. Electrochemical performance in long-term storage and high temperature conditions was still excellent. The unique aggregation morphology of flower-like Co3O4 yielded a reduction of charge-transfer resistance and stabilization of electrode structure compared with other aggregation morphologies.


Assuntos
Cobalto/química , Fontes de Energia Elétrica , Lítio/química , Óxidos/química , Precipitação Química , Eletrodos , Humanos
4.
Molecules ; 24(16)2019 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-31405189

RESUMO

The influence of Li+, Na+ and Cs+ cations on the surface excess and structure of dodecyl sulfate (DS-) anions at the air-water interface was investigated with the vibrational sum-frequency generation (SFG) and surface tensiometry. Particularly, we have addressed the change in amplitude and frequency of the symmetric S-O stretching vibrations as a function of electrolyte and DS- concentration in the presence of Li+, Na+ and Cs+ cations. For the Li+ and Na+ ions, we show that the resonance frequency is shifted noticeably from 1055 cm-1 to 1063 cm-1 as a function of the surfactants' surfaces excess, which we attribute to the vibrational Stark effect within the static electric field at the air-water interface. For Cs+ ions the resonance frequency is independent of the surfactant concentration with the S-O stretching band centered at 1063 cm-1. This frequency is identical to the frequency at the maximum surface excess when Li+ and Na+ ions are present and points to the ion pair formation between the sulfate headgroup and Cs+ counterions, which reduces the local electric field. In addition, SFG experiments of the O-H stretching bands of interfacial H2O molecules are used in order to calculate the apparent double layer potential and the degree of dissociation between the surfactant head group and the investigated cations. The latter was found to be 12.0%, 10.4% and 7.7% for lithium dodecyl sulfate (LiDS), sodium dodecyl sulfate (SDS) and cesium dodecyl sulfate (CsDS) surfactants, which is in agreement with Collins 'rule of matching water affinities'.


Assuntos
Lítio/química , Dodecilsulfato de Sódio/química , Sódio/química , Tensoativos/química , Álcalis/química , Cátions Monovalentes/química
5.
Molecules ; 24(16)2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31416287

RESUMO

Electrochemical anodized titanium dioxide (TiO2) nanotubes are of immense significance as electrochemical energy storage devices owing to their fast electron transfer by reducing the diffusion path and paving way to fabricating binder-free and carbon-free electrodes. Besides these advantages, when nitrogen is doped into its lattice, doubles its electrochemical activity due to enhanced charge transfer induced by oxygen vacancy. Herein, we synthesized nitrogen-doped TiO2 (N-TiO2) and studied its electrochemical performances in supercapacitor and as anode for a lithium-ion battery (LIB). Nitrogen doping into TiO2 was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical performance of N-TiO2 nanotubes was outstanding with a specific capacitance of 835 µF cm-2 at 100 mV s-1 scan rate as a supercapacitor electrode, and it delivered an areal discharge capacity of 975 µA h cm-2 as an anode material for LIB which is far superior to bare TiO2 nanotubes (505 µF cm-2 and 86 µA h cm-2, respectively). This tailor-made nitrogen-doped nanostructured electrode offers great promise as next-generation energy storage electrode material.


Assuntos
Capacitância Elétrica , Fontes de Energia Elétrica , Eletrodos , Íons/química , Lítio/química , Nanotubos , Nitrogênio/química , Titânio/química , Técnicas Eletroquímicas , Eletroquímica , Nanotubos/ultraestrutura , Análise Espectral
6.
Molecules ; 24(16)2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31416186

RESUMO

Carba analogues of biologically relevant natural carbohydrates are promising structures for the development of future drugs endowed with enhanced hydrolytic stability. An open synthetic challenge in this field is the optimization of new methodologies for the stereo- and regioselective opening of α-gluco carbasugar 1,2-epoxides that allow for the preparation of pseudo mono- and disaccharides of great interest. Therefore, we investigated the effect of Lewis acids and solvate ionic liquids (SILs) on the epoxide ring opening of a model substrate. Of particular interest was the complete stereo- and regioselectivity, albeit limited to simple nucleophiles, toward the desired C(1) isomer that was observed using LiClO4. The results obtained with SILs were also remarkable. In particular, Li[NTf2]/tetraglyme ([Li(G4)]TFSI) was able to function as a Lewis acid and to direct the attack of the nucleophile preferentially at the pseudo anomeric position, even with a more complex and synthetically interesting nucleophile. The regioselectivity observed for LiClO4 and [Li(G4)]TFSI was tentatively ascribed to the formation of a bidentate chelating system, which changed the conformational equilibrium and ultimately permitted a trans-diaxial attack on C(1). To the best of our knowledge, we report here the first case in which SILs were successfully employed in a ring-opening process of epoxides.


Assuntos
Carbaçúcares/química , Compostos de Epóxi/química , Etilenoglicóis/química , Líquidos Iônicos/química , Lítio/química , Estrutura Molecular , Estereoisomerismo
7.
Chem Pharm Bull (Tokyo) ; 67(10): 1046-1049, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31341115

RESUMO

A new catalytic system comprising chiral Ag complex and Li aryloxide/bisphosphine oxide is developed for the synthesis of ß2,2-amino acids via direct asymmetric Mannich-type reaction of 4-subsituted isoxazolidin-5-ones. The Mannich adduct is a direct precursor of ß-peptidic compounds otherwise difficult to obtain.


Assuntos
Aminoácidos/síntese química , Carbonatos/química , Complexos de Coordenação/química , Bases de Lewis/química , Lítio/química , Aminoácidos/química , Catálise , Complexos de Coordenação/síntese química , Isoxazóis/química , Estrutura Molecular , Prata/química
8.
J Chromatogr A ; 1603: 438-441, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31301799

RESUMO

The expansion of lithium ion battery (LIB) application is accompanied by the growth of battery pack sizes. This progression emphasizes the consideration of electrolyte safety as well as environmental aspects in case of abuse, accident, or recycling. Hexafluorophosphate is one of the most commonly used conducting salt anions in electrolytes. It has great potential to degrade to various acidic and non-acidic organo(fluoro)phosphates with presence of water and during battery cell operation. Consequently, toxicological investigation on these organo(fluoro)phosphates has emerged because they either have structural similarities as chemical warfare agents or play a widespread physiological role as phosphates in the human body. This circumstance underlines the need of isolated examination of these compounds for safety assessment. In this work, we used hydrophilic interaction liquid chromatography for the extraction of acidic organofluorophosphates from thermally aged LIB electrolytes. The developed two-step fractionation method provided high separation selectivity towards acidic head groups, which allowed the separation of undesired matrix and target compounds. These findings facilitate isolated toxicological investigations on organofluorophosphates that are beneficial for environmental and safety research, the battery cell industry, and human safety surveillance in regard to aged LIB electrolytes.


Assuntos
Cromatografia Líquida/métodos , Fontes de Energia Elétrica , Eletrólitos/química , Interações Hidrofóbicas e Hidrofílicas , Lítio/química , Organofluorfosfonatos/química , Humanos , Íons , Água
9.
Molecules ; 24(13)2019 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-31269689

RESUMO

Lithium-collaborating organic batteries (Li-[28]hexs) were investigated with [28]hexaphyrin(1.1.1.1.1.1) as an active electrode material. Each hexaphyrin of [28]Hex cathode ideally involved four electrons per unit cycle and performed a typical charge/discharge processes of Li-organic battery. Li-[28]Hex batteries set with fast charging rates showed reasonably stable charge and discharge performances over 200 cycles even though it caused incomplete (2~3 electrons) charge/discharge cycles due to failing the complete charging process. UV absorption changes of [28]hexaphyrin in CH2Cl2 were supplementary for the electrochemical oxidation, which performed a conversion from [28]hexaphyrin to [26]hexaphyrin.


Assuntos
Fontes de Energia Elétrica , Lítio/química , Porfirinas/química , Cor , Eletroquímica , Eletrodos , Conformação Molecular , Oxirredução
10.
Chem Pharm Bull (Tokyo) ; 67(5): 452-460, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31061370

RESUMO

The Michael reaction of malonates with maleates afforded the corresponding adducts in high yields with high enantioselectivities (up to 98% enantiomeric excess (ee)) by using dilithium 3,3'-dichlorobinaphtholate as a catalyst. The obtained Michael adducts could be converted to optically active tricarboxylic acid (TCA) derivatives via the Krapcho reaction.


Assuntos
Lítio/química , Maleatos/química , Malonatos/química , Ácidos Tricarboxílicos/síntese química , Catálise , Técnicas de Química Sintética , Maleatos/síntese química , Malonatos/síntese química , Estereoisomerismo , Ácidos Tricarboxílicos/química
11.
Molecules ; 24(9)2019 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-31052152

RESUMO

Layered lithium-rich manganese oxide (LLO) cathode materials have attracted much attention for the development of high-performance lithium-ion batteries. However, they have suffered seriously from disadvantages, such as large irreversible capacity loss during the first cycle, discharge capacity decaying, and poor rate performance. Here, a novel method was developed to coat the surface of 0.4Li2MnO3∙0.6LiNi1/3Co1/3Mn1/3O2 cathode material with reduced graphene-oxide (rGO) in order to address these drawbacks, where a surfactant was used to facilitate the well-wrapping of rGO. As a result, the modified LLO (LLO@rGO) cathode exhibits superior electrochemical performance including cycling stability and rate capability compared to the pristine LLO cathode. In particular, the LLO@rGO with a 0.5% rGO content can deliver a high discharge capacity of 166.3 mAh g-1 at a 5C rate. The novel strategy developed here can provide a vital approach to inhibit the undesired side reactions and structural deterioration of Li-rich cathode materials, and should be greatly useful for other cathode materials to improve their electrochemical performance.


Assuntos
Fontes de Energia Elétrica , Eletrodos , Grafite/química , Lítio/química , Óxidos/química , Íons , Manganês , Microscopia Eletrônica , Pós/química , Análise Espectral
12.
Nano Lett ; 19(6): 3811-3820, 2019 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-31082246

RESUMO

Optimizing the chemical and morphological parameters of lithium-ion (Li-ion) electrodes is extremely challenging, due in part to the absence of techniques to construct spatial and temporal descriptions of chemical and morphological heterogeneities. We present the first demonstration of combined high-speed X-ray diffraction (XRD) and XRD computed tomography (XRD-CT) to probe, in 3D, crystallographic heterogeneities within Li-ion electrodes with a spatial resolution of 1 µm. The local charge-transfer mechanism within and between individual particles was investigated in a silicon(Si)-graphite composite electrode. High-speed XRD revealed charge balancing kinetics between the graphite and Si during the minutes following the transition from operation to open circuit. Subparticle lithiation heterogeneities in both Si and graphite were observed using XRD-CT, where the core and shell structures were segmented, and their respective diffraction patterns were characterized.


Assuntos
Grafite/química , Lítio/química , Silício/química , Eletrodos , Tomografia Computadorizada por Raios X , Difração de Raios X
13.
Nano Lett ; 19(6): 3634-3640, 2019 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-31095394

RESUMO

X-ray diffraction is measured on individual bilayer and multilayer graphene single-crystals and combined with electrochemically induced lithium intercalation. In-plane Bragg peaks are observed by grazing incidence diffraction. Focusing the incident beam down to an area of about 10 µm × 10 µm, individual flakes are probed by specular X-ray reflectivity. By deploying a recursive Parratt algorithm to model the experimental data, we gain access to characteristic crystallographic parameters of the samples. Notably, it is possible to directly extract the bi/multilayer graphene c-axis lattice parameter. The latter is found to increase upon lithiation, which we control using an on-chip peripheral electrochemical cell layout. These experiments demonstrate the feasibility of in situ X-ray diffraction on individual, micron-sized single crystallites of few- and bilayer two-dimensional materials.


Assuntos
Grafite/química , Lítio/química , Nanoestruturas/química , Algoritmos , Nanoestruturas/ultraestrutura , Difração de Raios X , Raios X
14.
Molecules ; 24(10)2019 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-31100980

RESUMO

Solid-solution Li-ion cathode materials transform through a single-phase reaction thus leading to a long-term structural stability and improved cyclability. In this work, a two- to single-phase Li+-extraction/insertion mechanism is studied through tuning the stoichiometry of transition-metal Fe/V cations to trigger a transition in the chemical reactivity path. Tavorite triclinic-structured LiFe1-xVxPO4F (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) solid-solution powders were prepared by a facile one-step solid-state method from hydrothermal-synthesized and commercial raw materials. The broad shape of cyclic voltammetry (CV) peaks, sloping charge/discharge profiles and sloping open-circuit voltage (OCV) profiles were observed in LiFe1-xVxPO4F solid-solution cathodes while 0 < x < 1. These confirm strongly a single-phase behavior which is different from the two-phase behavior in the end-members (x = 0 or 1). The electronegativity of M (M = Fe1-xVx) for the redox potential of Fe2+/3+ couple or the M-O4F2 bond length for the V3+/4+ couple plays respectively a dominant role in LiFe1-xVxPO4F solid-solution cathodes.


Assuntos
Íons/química , Lítio/química , Oxirredução , Algoritmos , Difusão , Modelos Teóricos , Estrutura Molecular , Soluções , Análise Espectral
15.
J Chromatogr A ; 1602: 206-216, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31133423

RESUMO

Adsorptive membrane-based chromatography can provide the high separation efficiency common to column chromatography but at a lower working pressure. Herein, a novel membrane chromatography system for lithium isotope adsorptive separation is reported. It uses polysulfone-graft-4'-aminobenzo-15-crown-5-ether (PSf-g-AB15C5) porous membranes (0.52 mmol/g of immobilization crown ether, average pore size of 62.7 nm, porosity of 80.4%) as a stationary phase packed in a chromatography column (Ø 25 × 100 mm). Furthermore, a four-stage tandem membrane chromatography system was designed to enhance lithium isotope separation performance. The partial eluate from the former column was used as the feed solution for the next stage. Results show that the flow rate of the eluent could reach 18 mL/h owing to the lower internal diffusion resistance of membranes. Meanwhile, adsorption isotherms and adsorption kinetics show that Li+ adsorption was an exothermic and spontaneous process. The surface diffusion, multilayer adsorption and ion-pore electrostatic interaction between Li+ and the crown ether groups on the membranes played a key role in the separation of 7Li+ and 6Li+ by membrane chromatography. The separation factor obtained from the single-stage membrane chromatography was up to 1.0232. The abundances of 7Li+ and 6Li+ gradually increased with an increase in the elution stages. The relative abundances of 7Li+ and 6Li+ obtained from the four-stage tandem membrane chromatography increased by 0.26% (from 92.40 to 92.66%) and 0.2% (from 7.60 to 7.80%), respectively. In conclusion, our current research opens a new avenue for the simultaneous enrichment of 7Li+ and 6Li+ during lithium isotope adsorptive separation.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia , Éteres/química , Isótopos/isolamento & purificação , Lítio/isolamento & purificação , Adsorção , Difusão , Isótopos/química , Cinética , Lítio/química , Membranas Artificiais , Porosidade
16.
J Colloid Interface Sci ; 551: 219-226, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31078977

RESUMO

Improving the insulating nature of sulfur and retaining the soluble polysulfides in sulfur cathodes are crucial for realizing the practical application of lithium-sulfur batteries (LSBs). Biomass-based carbon is becoming increasingly popular for fabricating economical and efficient cathodes for LSBs owing to its unique structure. Herein, we report a facile strategy to transform bovine bone with an organic-inorganic structure into cellular hierarchical porous carbon via carbonization and KOH activation, followed by CoS2 modification through hydrothermal treatment. The synthesized composite can load abundant sulfur and produce a dual effect of "physical confinement and chemical entrapment" on polysulfides. The conductive carbon frame with the developed porous structure provides adequate space to accommodate sulfur and physically suppress the shuttle effect of polysulfides. The embedded half-metallic CoS2 sites can chemically anchor the polysulfides and enhance the electrochemical reaction activity as well. Owing to the multifunctional structure and dual restraint effect, the designed electrode exhibits enhanced electrochemical properties including high initial capacity (1230.9 mAh g-1 at 0.2 C), improved cycling stability and enhanced rate capability.


Assuntos
Osso e Ossos/química , Carbono/química , Cobalto/química , Fontes de Energia Elétrica , Lítio , Animais , Produtos Biológicos/química , Bovinos , Condutividade Elétrica , Técnicas Eletroquímicas/métodos , Eletrodos , Lítio/química , Minerais/química , Estrutura Molecular , Porosidade , Sulfetos/química
17.
Molecules ; 24(7)2019 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-30959780

RESUMO

Hydrogenation of a lithium-potassium (double-cation) amide (LiK(NH2)2), which is generated as a product by ammonolysis of litium hydride and potassium hydride (LiH-KH) composite, is investigated in details. As a result, lithium amide (LiNH2) and KH are generated after hydrogenation at 160 °C as an intermediate. It is noteworthy that the mixture of LiH and KNH2 has a much lower melting point than that of the individual melting points of LiNH2 and KH, which is recognized as a eutectic phenomenon. The hydrogenation temperature of LiNH2 in the mixture is found to be significantly lower than that of LiNH2 itself. This improvement of reactivity must be due to kinetic modification, induced by the enhanced atomic mobility due to the eutectic interaction.


Assuntos
Amidas/química , Hidrogênio/química , Lítio/química , Potássio/química , Amônia/química , Hidrogenação , Cinética
18.
Macromol Rapid Commun ; 40(9): e1800832, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30892757

RESUMO

Recently, many researchers have developed advanced energy storage and energy conversion systems to address the increased demand for energy resources. The performance of these electrochemical energy storage and conversion devices depends considerably on the properties of their unique electrode materials. Among electrode materials, graphene (GR) has attracted much attention due to its unique properties of high flexibility, a large specific surface area, and superior electric conductivity rates that are well-suited to energy storage systems. Specifically, aerosol-made 3D GR composites are known to be more resistant to compressive forces such as paper balls owing to their stronger and harder compressive tolerance levels and higher and more stable surface areas compared to 2D GR sheets. These unique properties of 3D GR composites result in enhanced electrochemical performances for energy storage systems. This review focuses on recent studies of aerosol-made 3D GR-based composites for energy storage systems such as supercapacitors, lithium-ion batteries, and sodium-ion batteries.


Assuntos
Aerossóis/química , Fontes de Energia Elétrica , Grafite/química , Nanocompostos/química , Técnicas Eletroquímicas/métodos , Eletroquímica/métodos , Lítio/química
19.
Chem Asian J ; 14(9): 1506-1514, 2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-30825361

RESUMO

Near-infrared (NIR) long-persistent phosphors (LPPs) have emerged as a potential solution for bio-imaging applications over the past few years. However, there are enormous challenges regarding their in situ application based on their dependence on short-wavelength excitation. In this paper, we report a multi-spectral excited NIR LPP, Li5 Zn8 Ga5 Ge9 O36 : 1.5 % Cr3+ , 0.5 % Ti4+ , which overcomes the limitations of functional processes in biological tissues and other complex systems. This LPP exhibits a high luminescent intensity and a long emission duration in the NIR region (700-800 nm). The applicability of this phosphor to tissue imaging is demonstrated experimentally. Its persistent luminescence (PersL) can easily penetrate approximately 2 mm of pork flesh. More importantly, this phosphor can be re-charged in situ using a red LED or laser diode array to provide renewed NIR PersL for biological tissues, which is beneficial for long-term biological tissue imaging applications with high signal-to-noise ratios. Systematic investigations of the nature of energy traps and PersL mechanisms are also reported in this paper.


Assuntos
Corantes Fluorescentes/química , Medições Luminescentes/métodos , Carne/análise , Animais , Transferência Ressonante de Energia de Fluorescência , Gálio/química , Germânio/química , Luz , Lítio/química , Suínos , Titânio/química , Raios Ultravioleta , Zinco/química
20.
Org Lett ; 21(6): 1930-1934, 2019 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-30835486

RESUMO

Efficient asymmetric alkylation of ß,γ-unsaturated carboxylic acids without prior functionalization is enabled by chiral lithium amides. Enantioselectivity is imparted by a putative mixed lithium amide-enediolate aggregate that acts a traceless auxiliary formed in situ, allowing for a direct asymmetric alkylation and a simple recovery of the chiral reagent.


Assuntos
Amidas/química , Ácidos Carboxílicos/química , Lítio/química , Alquilação , Indicadores e Reagentes , Estrutura Molecular , Estereoisomerismo
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