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1.
Nanoscale ; 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32432271

RESUMO

Cadmium-free quantum dots (QDs) are attracting considerable research attention because of their low toxicity. However, the bandgap of most cadmium-free QDs avoids the pure-blue region, which leads to difficulty in realizing pure-blue quantum-dot light-emitting diodes (QLEDs). In this work, we successfully tuned the emission wavelength of ZnSe/ZnS quantum dots from the violet region (∼420 nm) to the pure-blue region (450-460 nm) by doping Te into the ZnSe core. The ZnSe:0.03Te/ZnSeS/ZnS QD sample with emission at 450 nm and a quantum yield of 30% was the most balanced formula. To overcome the energy gap between the hole-transfer layer and QD layers, a specific hole-transfer layer was developed for normal-structure QLEDs. A QLED with such a structure with ZnSe:0.03Te/ZnSeS/ZnS QDs achieved the pure-blue light emission at 455 nm, a low turn-on voltage of 4.4 V, and an external quantum efficiency of 0.33%. Overall, our cadmium-free QLED achieved pure-blue emission, revealing the potential of ZnSe-based pure-blue QLEDs for future displays.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32338495

RESUMO

The systematic substitution of Ba in the Sr site of Sr[Mg2Al2N4]:Eu2+ generates a deep-red-emitting phosphor with enhanced thermal luminescence properties. Gas pressure sintering (GPS) of all-nitride starting materials in Molybdenum (Mo) crucibles yields pure-phase red-orange-colored phosphors. Peaks in the synchrotron X-ray diffraction (SXRD) data show a systematic shift toward smaller angles due to the introduction of the larger Ba cation in the same crystal structure. The photoluminescence property reveals that Ba substitution shifts the original emission wavelength of Sr[Mg2Al2N4]:Eu2+ (625 nm) toward ∼690 nm for Ba[Mg2Al2N4]:Eu2+. Thermal stability measurement of Sr1-xBax[Mg2Al2N4] indicates a systematic increase in stability from x = 0 to x = 1. X-ray absorption near-edge spectroscopy (XANES) results demonstrate the coexistence of Eu2+ and Eu3+. The red-shift and the enhanced thermal stability reveals that the distance of the emitting 5d level to the conduction band of Ba[Mg2Al2N4]:Eu2+ is large. The ionic size mismatch of Eu occupying a Ba site reduces the symmetry, thereby further splitting the degenerate emitting 5d level and lowering the energy of the emitting center. The development of deep-red phosphors emitting at 670-690 nm (x = 0.8-1.0) offers possible candidates for plant lighting applications.

3.
Nanoscale ; 2020 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-32239028

RESUMO

Herein, ruthenium (Ru) nanoparticles were anchored on carbon nanotubes (Ru/CNTs) functionalized as catalyst cathodes for non-aqueous Li-CO2 cells. For cycling tests through a low cut-off capacity (100 mA h g-1), the origin of battery deterioration resulted from the accumulation of Li2CO3 discharging products on catalytic surfaces, identical to the observations in previous studies. However, the Li-CO2 cells in this work showed a sudden death within several cycles of high cut-off capacity (500 mA h g-1), and no Li2CO3 residues were investigated on the cathode. In contrast, Li dendrites and passivation materials (LiOH and Li2CO3) were generated on Li anodes upon cycling at a limited capacity of 500 mA h g-1, which dominantly contributed to the battery degradation. A Li foil-replacement method was adopted to make the Ru/CNT cathode perform continuous 100 cycles under a cut-off capacity of 500 mA h g-1. These results indicate that not only Li2CO3 residues blocked on the active sites of the cathode but also Li dendrites and passivation materials produced on the anode caused Li-CO2 battery deterioration. Moreover, in the present work, a carbon thin film was deposited on Li metal (C/Li) by a sputtering system for suppressing the dendrite formation upon cycling and promoting the defense of the H2O attack from the electrolyte disintegration. The Li-CO2 cell with a Ru/CNT catalyst and a C/Li anode revealed an improved electrochemical stability of 115 cycles at a limited capacity of 500 mA h g-1. This proto strategy provided a significant research direction focusing on Li anodes for elevating the Li-CO2 battery durability.

4.
ChemSusChem ; 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32128983

RESUMO

Li-air batteries are limited to lab-scale research owing to the uninterrupted formation of discharge products. In the case of Li-CO2 batteries, the increase in overpotential caused by Li2 CO3 formation results in cell death. In this study, Cu2 O crystals having three different types of shapes (i.e., cubic, octahedral, and rhombic) were synthesized to compare their catalytic activity toward CO2 reactions. The full-cycle and long-term stability test revealed that rhombohedral Cu2 O facilitates Li2 CO3 decomposition more efficiently than that of cubic and octahedral Cu2 O. The cycle was extended to investigate the photocatalytic activity of the rhombic Cu2 O by illuminating the cell. The repeated cycles to 1 h showed a maximum overpotential of 1.5 V, which is 0.5 V lower than that of the cell without illumination. A postmortem analysis of the cell after dividing the cycles into segments demonstrated interesting results concerning the role of light and Cu2 O during the cell cycle.

5.
Artigo em Inglês | MEDLINE | ID: mdl-32202752

RESUMO

Li-CO2 batteries are of great interest among researchers due to their high energy density and utilization of the greenhouse gas CO2 to produce energy. However, several shortcomings have been encountered in the practical applications of Li-CO2 batteries, among which their poor cyclability and high charge overpotential necessary to decompose the highly insulating discharge product (Li2CO3) are the most important. Herein, the spinel zinc cobalt oxide porous nanorods with carbon nanotubes (ZnCo2O4@CNTs) composite is employed as a cathode material in Li-CO2 batteries to improve the latter's cycling performance. The ZnCo2O4@CNT cathode-based Li-CO2 battery exhibited a full discharge capacity of 4275 mAh g-1 and excellent cycling performance over 200 cycles with a charge overpotential below 4.3 V when operated at a current density of 100 mA g-1 and fixed capacity of 500 mAh g-1. The superior performance of the ZnCo2O4@CNT cathode composite was attributed to the synergistic effects of ZnCo2O4 and CNT. The highly porous ZnCo2O4 nanorod structures in the ZnCo2O4@CNT catalyst showed enhanced catalytic activity/stability, which effectively promoted CO2 diffusion during the discharging process and accelerated Li2CO3 decomposition at a low charge overpotential.

6.
Nanoscale ; 2020 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-31995086

RESUMO

Surface defects and synthesis methods play important roles in the photoluminescence quantum yield (PLQY), stability, and the device performance of lead halide perovskite quantum dots (PQDs). In this study, we report a quadruple-ligand (tri-n-octylphosphine, didodecyldimethylammonium bromide, tetraoctylammonium bromide, and oleic acid) assisted room-temperature method for synthesizing CsPbBr3 QDs (RT-CsPbBr3) with an absolute PLQY of 83%. X-ray photoelectron spectroscopy confirms the high completeness of the Pb-Br octahedron through the absence of lead ions and presence of more bromide ions on the surface of RT-CsPbBr3 QDs. The exciton dynamics of RT-CsPbBr3 QDs is studied by using femtosecond transient absorption, time-resolved PL, and single-dot spectroscopy, which provide strong evidence of the suppression of trion formation compared with the hot injection-synthesized CsPbBr3 (HI-CsPbBr3) QDs. The white light-emitting diode (LED) fabricated with RT-CsPbBr3 PQDs and a K2SiF6:Mn4+ phosphor for backlight applications achieved a wide color gamut of 124% of the National Television System Committee (NTSC) standard.

7.
Theranostics ; 10(2): 782-796, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31903150

RESUMO

Nanobubble (NB), which simultaneously enhances ultrasound (US) images and access therapeutic platforms, is required for future cancer treatment. Methods: We designed a theranostic agent for novel cancer treatment by using an NB-encapsulated hybrid nanosystem that can be monitored by US and fluorescent imaging and activated by near-infrared (NIR) light. The nanosystem was transported to the tumor through the enhanced permeability and retention effect. The hybrid nanosystem comprised upconversion nanoparticle (UCNP) and mesoporous silica-coated gold nanorod (AuNR@mS) with the photosensitizer merocyanine 540 to realize dual phototherapy. Results: With the NIR light-triggered, the luminous intensity of the UCNP was enhanced by doping holmium ion and emitted visible green and red lights at 540 and 660 nm. The high optical density state between the UCNP and AuNR@mS can induce plasmonic enhancement to improve the photothermal and photodynamic effects, resulting in cell death by apoptosis. The nanosystem showed excellent stability to avoid the aggregation of nanoparticles during the treatment. JC-1 dye was used as an indicator of mitochondrial membrane potential to identify the mechanism of cell death. The results of in vitro and in vivo analyses confirmed the curative effect of improved dual phototherapy. Conclusion: We developed and showed the therapeutic functions of a novel nanosystem with the combination of multiple theranostic nanoplatforms that can be triggered and activated by 808 nm NIR laser and US.

8.
Chem Asian J ; 15(2): 242-252, 2020 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-31794155

RESUMO

Lead-free perovskite structures have been recently attracting considerable attention because of their eco-friendly nature and properties, such as their lead-based structure. In this work, we reviewed the lead-free double perovskite (LFDP) structure because of its unique electronic dimensions, chemical stability, and substitutional chemistry compared with other lead-free structures. We highlighted the recent progress on crystal structure prediction, synthesis methods, metal dopants, and ligand passivation on LFDPs. LFDPs are useful for several applications, such as solar cells, light-emitting diodes, degradation of photocatalytic dyes, sensors, and X-ray detectors. This report provides a summary of recent progress as a reference for further research on lead-free perovskite structures.

9.
Nanotechnology ; 31(13): 134004, 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-31751976

RESUMO

Pathogenic bacterial infection, especially in the wound, may threaten human health. Developing new antibacterial materials for wound healing is still urgent. Metal nanoclusters have been explored as a novel antibacterial agent. Herein, biomolecule gelatin was chosen as a substrate and functionalized with gold/silver clusters for bacterial killing. Through a simple amidation reaction, gold/silver clusters were successfully conjugated in a gelatin substrate to obtain a Au/Ag@gelatin sponge. The presence of gold/silver clusters modified the porous structure of the gelatin. Thus, the water absorption and water retention of the Au/Ag@gelatin sponge were enhanced. More importantly, the gold/silver clusters show aggregation-enhanced emission and strong reactive oxygen generation, that endow the Au/Ag@gelatin sponge with a good antibacterial property. The good physical performance and favorable bactericidal activity of the Au/Ag@gelatin sponge suggest its potential for application as a wound dressing.

10.
Inorg Chem ; 59(1): 376-385, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31823613

RESUMO

Two types of infrared fluoride phosphors, Cr3+-doped K3AlF6 and K3GaF6, were developed in this research. The K3Al1-xF6:xCr3+ and K3Ga1-yF6:yCr3+ fluoride phosphors were proven to be pure phase via X-ray diffraction refinement, which demonstrated that the procedure can be applied to large-scale production. Electron paramagnetic resonance measurements indicated that Cr3+ ions in cubic with respect to noncubic are coupled better with K3GaF6 than with K3AlF6. The main differences between these two phosphors, the site symmetry and pressure behavior of the spectra, were obtained in temperature- and pressure-dependent spectra. According to the calculation results, Cr3+ in fluorine coordination at ambient pressure indicates an intermediate crystal field. For the phosphor-converted light-emitting diodes (LEDs) fabricated from these two phosphors, the spectral range is from 650 to 1000 nm, which resulted in a radiant flux of 7-8 mW with an input power of 1.05 W. The research reveals detailed luminous properties, which will lead to a new way of studying Cr3+-doped fluoride phosphors and their application in LEDs.

11.
J Am Chem Soc ; 141(51): 20118-20126, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31804069

RESUMO

Designing atomically dispersed metal catalysts for oxygen reduction reaction (ORR) is a promising approach to achieve efficient energy conversion. Herein, we develop a template-assisted method to synthesize a series of single metal atoms anchored on porous N,S-codoped carbon (NSC) matrix as highly efficient ORR catalysts to investigate the correlation between the structure and their catalytic performance. The structure analysis indicates that an identical synthesis method results in distinguished structural differences between Fe-centered single-atom catalyst (Fe-SAs/NSC) and Co-centered/Ni-centered single-atom catalysts (Co-SAs/NSC and Ni-SAs/NSC) because of the different trends of each metal ion in forming a complex with the N,S-containing precursor during the initial synthesis process. The Fe-SAs/NSC mainly consists of a well-dispersed FeN4S2 center site where S atoms form bonds with the N atoms. The S atoms in Co-SAs/NSC and Ni-SAs/NSC, on the other hand, form metal-S bonds, resulting in CoN3S1 and NiN3S1 center sites. Density functional theory (DFT) reveals that the FeN4S2 center site is more active than the CoN3S1 and NiN3S1 sites, due to the higher charge density, lower energy barriers of the intermediates, and products involved. The experimental results indicate that all three single-atom catalysts could contribute high ORR electrochemical performances, while Fe-SAs/NSC exhibits the highest of all, which is even better than commercial Pt/C. Furthermore, Fe-SAs/NSC also displays high methanol tolerance as compared to commercial Pt/C and high stability up to 5000 cycles. This work provides insights into the rational design of the definitive structure of single-atom catalysts with tunable electrocatalytic activities for efficient energy conversion.

12.
Nanoscale ; 11(32): 14993-15003, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31380525

RESUMO

Quantum dots (QDs) have extensive application prospects in the fields of optics, magnetism, catalysis, and biomedicine. New carbon-doped QDs are currently being used in these research fields. Graphitic carbon nitride QDs (g-CNs) composed of only carbon and nitrogen have attracted attention because of their unique optical and catalytic properties. g-CNs have numerous electronic properties and can be used as photocatalytic modifiers in a wide range of applications in electrochemistry. Additionally, g-CNs also have biological potential and due to their chemical composition have extremely low toxicity; their blue light emission can be applied to biological imaging, and their appropriate energy level (2.7 eV) allows electrons to be deposited on their surface, which allows g-CNs to be used as photosensitizers in optical therapy. Finally, g-CNs can be combined with other nanomaterials to form composite materials, which can result in new advantages not seen in either of the materials alone. In this manuscript, we thoroughly report the most recent findings regarding the synthesis of g-CNs and their respective properties. We report the advantages of g-CNs conferred by their unique properties and their advantages for application in current biology and medicines.


Assuntos
Grafite/química , Nanocompostos/química , Compostos de Nitrogênio/química , Animais , Técnicas Biossensoriais/métodos , Humanos , Nanocompostos/uso terapêutico , Neoplasias/tratamento farmacológico , Fármacos Fotossensibilizantes/química , Fármacos Fotossensibilizantes/farmacologia , Fármacos Fotossensibilizantes/uso terapêutico , Pontos Quânticos/química , Cicatrização/efeitos dos fármacos
13.
Nanomedicine (Lond) ; 14(14): 1791-1804, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31305218

RESUMO

Aim: Matrix metalloproteinase-2 (MMP2) plays an important role in extracellular matrix remodeling, that is, it increases significantly during cancer progression. In this regard, MMP2 monitoring is important. Experiment: A well-designed MMP2-sensitive polypeptide chain was used to link indium phosphide quantum dots (InP QDs) with upconversion nanoparticles (UCNPs) to form a nanocomposite that was utilized as biosensor. Results: We produced a biosensor that can be recognized by MMP2 and determined the presence or absence of MMP2 in cells by identifying difference in fluorescence wavelength. The InP QDs modified the arginylglycylaspartic acid molecules as targeting ligand based on chitosan. Conclusion: The MMP2-based biosensor, named UCNP-p@InP-cRGD, is sensitive and can be applied for biosensing probes.

14.
ACS Appl Mater Interfaces ; 11(22): 20143-20149, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31070881

RESUMO

The use of red phosphors with low light-scattering loss could improve the luminous efficacy and color rendering of white-light-emitting diodes (LEDs). Thus, the discovery of such phosphors is highly desired. In this work, high-efficiency two-dimensional red-emitting K2TiF6:Mn4+ (KTFM) were synthesized via an alcohol-assisted coprecipitation route. The synergistic effects of 1-propanol and hydrofluoric acid on the growth of KTFM microsheets (MSs) were studied through the first-principles calculations, which revealed that 1-propanol promoted the growth of KTFM MSs by preferentially adsorbing on the H-terminated K2TiF6 (001) surface. The photoluminescence quantum efficiency (QE) of Mn4+-activated K2TiF6 MSs was highly related to their size and thickness. The morphology-optimal KTFM MSs presented high internal QE (>90%), external QE (>71%), and thermal quenching temperature (102% at 150 °C relative to that at 25 °C). A prototype phosphor-converted LED with KTFM as the red-emitting component showed excellent color rendition ( Ra = 91, R9 = 79) and high luminous efficacy (LE = 156 lm/w).

15.
Angew Chem Int Ed Engl ; 58(23): 7767-7772, 2019 Jun 03.
Artigo em Inglês | MEDLINE | ID: mdl-30957924

RESUMO

In this study, a series of Sr(LiAl3 )1-x (SiMg3 )x N4 :Eu2+ (SLA-SSM) phosphors were synthesized by a solid-solution process. The emission peak maxima of SLA-SSM range from 615 nm to 680 nm, which indicates structural differences in these materials. 7 Li solid-state NMR spectroscopy was utilized to distinguish between the Li(1)N4 and Li(2)N4 tetrahedra in SLA-SSM. Differences in the coordination environments of the two Sr sites were found which explain the unexpected luminescent properties. Three discernible morphologies were detected by scanning electron microscopy. Temperature-dependent photoluminescence and decay times were used to understand the diverse environments of europium ions in the two strontium sites Sr1 and Sr2, which also support the NMR analysis. Moreover, X-ray absorption near-edge structure studies reveal that the Eu2+ concentration in SLA-SSM is much higher than that in in SrLiAl3 N4 :Eu2+ and SrSiMg3 N4 :Eu2+ phosphors. Finally, an overall mechanism was proposed to explain the how the change in photoluminescence is controlled by the size of the coordinated cation.

16.
Nanotechnology ; 30(18): 182001, 2019 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-30645984

RESUMO

Applying nanobubbles (NBs) for contrast-enhanced ultrasound imaging has received increased attention. NBs are biocompatible, multifunctional, theranostic agents. Their properties of high echogenicity and stability create an agent suitable for ultrasonography diagnosis. Their favorable properties of size, in vivo stability, and ease of modification are being exploited to implement a theranostic platform for cancer treatment. The considerable development offers the potential to overcome drug resistance and adverse side effects that are associated with traditional chemotherapy. This review outlines the principles of ultrasonography and angiogenesis. Microbubbles and micelles are also discussed to underline the superior capabilities of NBs for the application. NBs could passively accumulate to tumor tissue by enhanced permeability and retention effect. In addition, it can also achieve the active transportation by surface modification. Active targeting modalities and stimuli-responsive drug delivery modifications generate a therapeutic vehicle. The cytotoxicity of NBs formulations, multimodal imaging capability, active targeting mechanisms, and drug delivery methods are highlighted to confirm the NB as a vehicle for targeted treatment and enhanced ultrasound imaging.


Assuntos
Meios de Contraste/uso terapêutico , Sistemas de Liberação de Medicamentos/métodos , Microbolhas/uso terapêutico , Nanopartículas/uso terapêutico , Neoplasias , Nanomedicina Teranóstica/métodos , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Humanos , Neoplasias/diagnóstico por imagem , Neoplasias/tratamento farmacológico , Ultrassonografia
17.
Angew Chem Int Ed Engl ; 58(7): 2069-2072, 2019 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-30556265

RESUMO

Light-emitting diodes break barriers of size and performance for displays. With devices becoming smaller, the materials also need to get smaller. Chromium(III)-doped oxide phosphors, which emit near-infrared (NIR) light, have recently been used in small electronic devices. In this work, mesoporous silica nanoparticles were used as nanocarriers. The nanophosphor ZnGa2 O4 :Cr3+ ,Sn4+ formed in the mesopore after sintering. Good dispersity and morphology were performed with average diameters of 71±7 nm. It emitted light at 600-850 nm; the intensity was optimized by tuning the doping ratio of Cr3+ and Sn4+ . Meanwhile, the light conversion efficiency increased from 7.8 % to 37 % and the molar concentration increased from 0.125 m to 0.5 m. The higher radiant flux of 3.3 mW was obtained by operating an input current of 45 mA. However, the NIR nanophosphor showed good performance on mini light-emitting diode chips.

18.
Inorg Chem ; 57(21): 13071-13074, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-30351076

RESUMO

In this paper, we report a simple, rapid, and stable method for the continuous synthesis of highly stable Cs4PbBr6 perovskite microcrystals (MCs) using a microfluidic system. To demonstrate the potential application of Cs4PbBr6 MCs, the sample was fabricated with K2SiF6:Mn4+ phosphor onto InGaN blue chips as white-light-emitting diodes (LEDs). Our white-LED device achieved a high National Television Standards Committee value of 119% for backlight display, which indicated that the Cs4PbBr6 MC is a promising material for future applications.

19.
ACS Appl Mater Interfaces ; 10(43): 37142-37149, 2018 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-30296046

RESUMO

Cobalt sulfide (CoS x) functioned as a co-catalyst to accelerate the kinetics of photogenerated electrons on Si photocathode, leading to the enhancement of solar hydrogen evolution efficiency. By doping phosphorus heteroatoms, CoS x materials showed an improved catalytic activity because of superior surface area and quantity of active sites. Furthermore, increased vacancies in unoccupied electronic states were observed, as more phosphorus atoms doped into CoS x co-catalysts. Although these vacant sites improved the capability to accept photoinduced electrons from Si photoabsorber, chemisorption energy of atomic hydrogen on catalysts was the dominant factor affecting in photoelectrochemical performance. We suggested that P-doped CoS x with appropriate doping quantities showed thermoneutral hydrogen adsorption. Excess phosphorus dopants in CoS x contributed to excessively strong adsorption with H atoms, causing the poor consecutive desorption ability of photocatalytic reaction. The optimal P-doped CoS x-decorated Si photocathode showed a photocurrent of -20.6 mA cm-2 at 0 V. Moreover, a TiO2 thin film was deposited on the Si photocathode as a passivation layer for improving the durability. The current density of 10 nm TiO2-modified photocathode remained at approximately -13.3 mA cm-2 after 1 h of chronoamperometry.

20.
Nanotechnology ; 29(50): 505401, 2018 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-30240363

RESUMO

In the present report, vertically-aligned graphene nanowalls are grown on Ni foam (VA-G/NF) using plasma-enhanced chemical vapor deposition method at room temperature. Optimization of the growth conditions provides graphene sheets with controlled defect sites. The unique architecture of the vertically-aligned graphene sheets allows sufficient space for the ionic movement within the sheets and hence enhancing the catalytic activity. Further modification with ruthenium nanoparticles (Ru NPs) drop-casted on VA-G/NF improves the charge overpotential for lithium-oxygen (Li-O2) battery cycles. Such reduction we believe is due to the easier passage of ions between the perpendicularly standing graphene sheets thereby providing ionic channels.

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