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1.
J Chem Phys ; 151(22): 224501, 2019 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-31837660

RESUMO

Coupled colloidal quantum dot molecules composed of two fused CdSe/CdS core/shell sphere monomers were recently presented. Upon fusion, the potential energy landscape changes into two quantum dots separated by a pretuned potential barrier with energetics dictated by the conduction and valence band offsets of the core/shell semiconductors and the width controlled by the shell thickness and the fusion reaction conditions. In close proximity of the two nanocrystals, orbital hybridization occurs, forming bonding and antibonding states in analogy to the hydrogen molecule. In this study, we examine theoretically the electronic and optical signatures of such a quantum dot dimer compared to its monomer core/shell building-blocks. We examine the effects of different core sizes, barrier widths, different band offsets, and neck sizes at the interface of the fused facets on the system wave-functions and energetics. Due to the higher effective mass of the hole and the large valence band offset, the hole still essentially resides in either of the cores, breaking the symmetry of the potential for the electron as well. We found that the dimer signature is well expressed in a red shift of the band gap both in absorption and emission, in slower radiative lifetimes and in an absorption cross section which is significantly enhanced relative to the monomers at energies above the shell absorption onset, while remains essentially at the same level near the band-edge. This study provides essential guidance to predesign of coupled quantum dot molecules with specific attributes which can be utilized for various new opto-electronic applications.

2.
Nat Commun ; 10(1): 5401, 2019 12 16.
Artigo em Inglês | MEDLINE | ID: mdl-31844043

RESUMO

Coupling of atoms is the basis of chemistry, yielding the beauty and richness of molecules. We utilize semiconductor nanocrystals as artificial atoms to form nanocrystal molecules that are structurally and electronically coupled. CdSe/CdS core/shell nanocrystals are linked to form dimers which are then fused via constrained oriented attachment. The possible nanocrystal facets in which such fusion takes place are analyzed with atomic resolution revealing the distribution of possible crystal fusion scenarios. Coherent coupling and wave-function hybridization are manifested by a redshift of the band gap, in agreement with quantum mechanical simulations. Single nanoparticle spectroscopy unravels the attributes of coupled nanocrystal dimers related to the unique combination of quantum mechanical tunneling and energy transfer mechanisms. This sets the stage for nanocrystal chemistry to yield a diverse selection of coupled nanocrystal molecules constructed from controlled core/shell nanocrystal building blocks. These are of direct relevance for numerous applications in displays, sensing, biological tagging and emerging quantum technologies.

3.
J Nanosci Nanotechnol ; 19(8): 4549-4555, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30913747

RESUMO

Highly luminescent semiconductor with ultrasmall size is always desirable for biomedical applications. Here, we developed a novel solvent-directing strategy to prepare ultrasmall monodispersed Ag2S quantum dots (QDs) with strong luminescence in the second near infrared (NIR-II) range (1000∼1400 nm). The particle size and luminescence of these Ag2S QDs could be desirably tuned by adjusting the solvents of the system. With further surface modification, the hydrophilic Ag2S QDs could be successfully utilised for cancerous cells imaging, indicating great potentials in biomedical fields.

4.
Opt Express ; 26(16): 20603-20613, 2018 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-30119369

RESUMO

To meet the ever-increasing bandwidth demands in the future broadband wireless networks, the millimeter-wave (mm-wave) frequency region is being actively perused, owing to its broad bandwidth and high frequencies. In this paper, a photonic mm-wave system is proposed and experimentally demonstrated based on the injection locking of a direct multilevel modulated laser to a spacing-tunable two-tone light. Since the mm-wave frequency of the generated signal is locked to the frequency spacing of the injected two-tone light, it shows better frequency stabilization than the schemes based on two free-running lasers. Moreover, by simply tuning the tone spacing, the mm-wave frequency could be easily re-configured, offering flexibility in the mm-wave signal generation. Instead of using complex and expensive optical modulators, the multilevel modulation on the mm-wave data carrier is implemented through the direct multilevel modulation of a laser and the injection locking. A 28 Gbps four-level pulse amplitude modulation (PAM4) is realized by biasing a 10 G-class laser at a current far from the threshold, providing a cost-effective and simple mm-wave generation scheme. In the experiment, a photonic approach to generating 28 Gbps PAM4 60 GHz/80 GHz mm-wave signals is experimentally demonstrated. A power penalty of less than 0.2 dB is observed for the filtered-out PAM4 signals with respect to the original PAM4. Besides, an ultra-low phase noise of up to -98 dBc/Hz is obtained for the mm-wave carriers after the injection locking. The proposed scheme possesses the flexibility and frequency stability of the mm-wave frequency, and also has low cost and implementation complexity.

5.
J Am Chem Soc ; 140(18): 5890-5894, 2018 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-29676908

RESUMO

We report the multifunctional nanocomposites (NCs) consisting of 19F-moieties grafted Cu7S4-Au nanoparticles (NPs) for negligible background 19F-magnetic resonance imaging (19F-MRI) and computed tomography (CT) imaging guided photothermal therapy. The localized surface plasmon resonance (LSPR) absorption can be reasonably tuned to the in vivo transparent window (800-900 nm) by coupling Au (<10 nm, LSPR ∼530 nm) with Cu7S4 (<15 nm, LSPR ∼1500 nm) into Cu7S4-Au heterodimers. The in vivo photothermal tests show that Cu7S4-Au show deeper light penetration with 808 nm irradiation, better photothermal efficacy, and less damage to normal tissues than Cu7S4 with 1500 nm irradiation. Moreover, compared to traditional 1H-MRI, the 19F-MRI based on these NCs demonstrates much better sensitivity due to the negligible background. This work offers a promising strategy for multimodal imaging guided photothermal therapy of deep tissue with good efficacy.


Assuntos
Cobre/química , Flúor/química , Ouro/química , Fototerapia , Enxofre/química , Animais , Dimerização , Imagem por Ressonância Magnética de Flúor-19 , Humanos , Camundongos , Nanopartículas/química , Neoplasias Experimentais/diagnóstico por imagem , Neoplasias Experimentais/terapia , Tamanho da Partícula , Propriedades de Superfície , Tomografia Computadorizada por Raios X
6.
Appl Opt ; 56(18): 5307-5312, 2017 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-29047585

RESUMO

In this paper, a scheme for optical modulation format conversion from one 20 Gbps quadrature phase-shift keying (QPSK) signal to one 20 Gbps binary phase-shift keying (BPSK) signal with information integrity is proposed and verified by simulation. The theory of degenerate phase-sensitive amplifier (PSA) employed as a phase de-multiplexer is derived in detail and used to decompose the in- (I) and quadrature- (Q) phase components of QPSK. Then the I and Q components are parallel-to-series converted into one BPSK. The constellations show that the phase noise of the original signal is effectively restrained by the conversion system through use of the PSA. The error vector magnitude and bit-error rate (BER) of the QPSK, converted BPSK, and a back-to-back BPSK are measured and compared with each other. We find that the BER performance of the converted BPSK is better than QPSK and maintains the original information integrity with different input signal quality. Some potential issues are also discussed as to practical implementation of the scheme. This modulation-format-conversion scheme has potential applications in improving the signal BER performance and flexible transmitters and receivers in software-defined networks.

7.
Small ; 13(8)2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27943543

RESUMO

Hydrogen production from water splitting through an efficient photoelectrochemical route requires photoinduced electron transfer from light harvesters to efficient electrocatalysts. Here, the plasmon-enhanced photoelectrical nanocatalysts (NCs) have been successfully developed by coating a monolayer MoS2 on the Cu1.75 S-Au hetero-nanoparticle for hydrogen evolution reaction (HER). The plasmonic NCs dramatically improve the HER, leading to 29.5-fold increase of current under 650 nm excitation (1.0 W cm-2 ). These NCs generate an exceptionally high current density of 200 mA cm-2 at overpotential of 182.8 mV with a Tafel slope of 39 mV per decade and excellent stability, which is better than or comparable to the Pt-free catalysts with carbon rod as counter electrode. The enhanced HER performance can be attributed to the significantly improved broad light absorption (400-3000 nm), more efficient charge separation and abundant active edge sites of monolayer MoS2 . The studies may provide a facile strategy for the fabrication of efficient plasmon-enhanced photoelectrical NCs for HER.


Assuntos
Cobre/química , Dissulfetos/química , Eletricidade , Ouro/química , Hidrogênio/análise , Luz , Molibdênio/química , Nanopartículas/química , Catálise , Eletroquímica , Nanopartículas/ultraestrutura , Semicondutores , Água/química
8.
Angew Chem Int Ed Engl ; 55(22): 6502-5, 2016 05 23.
Artigo em Inglês | MEDLINE | ID: mdl-27094459

RESUMO

Increasing the active edge sites of molybdenum disulfide (MoS2 ) is an efficient strategy to improve the overall activity of MoS2 for the hydrogen-evolution reaction (HER). Herein, we report a strategy to synthesize the ultrasmall donut-shaped Cu7 S4 @MoS2 hetero-nanoframes with abundant active MoS2 edge sites as alternatives to platinum (Pt) as efficient HER electrocatalysts. These nanoframes demonstrate an ultrahigh activity with 200 mA cm(-2) current density at only 206 mV overpotential using a carbon-rod counter electrode. The finding may provide guidelines for the design and synthesis of efficient and non-precious chalcogenide nanoframe catalysts.

9.
ACS Nano ; 10(1): 1355-62, 2016 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-26741791

RESUMO

(19)F magnetic resonance imaging (MRI) is a powerful noninvasive, sensitive, and accurate molecular imaging technique for early diagnosis of diseases. The major challenge of (19)F MRI is signal attenuation caused by the reduced solubility of probes with increased number of fluorine atoms and the restriction of molecular mobility. Herein, we present a versatile one-pot strategy for the fabrication of a multifunctional nanoprobe with high (19)F loading (∼2.0 × 10(8 19)F atoms per Cu1.75S nanoparticle). Due to the high (19)F loading and good molecular mobility that results from the small particle size (20.8 ± 2.0 nm) and ultrathin polymer coating, this nanoprobe demonstrates ultrahigh (19)F MRI signal. In vivo tests show that this multifunctional nanoprobe is suitable for (19)F MRI and photothermal therapy. This versatile fabrication strategy has also been readily extended to other single-particle nanoprobes for ablation and sensitive multimodal imaging.


Assuntos
Cobre/química , Imagem por Ressonância Magnética de Flúor-19/métodos , Neoplasias Mamárias Experimentais/terapia , Nanopartículas/química , Fototerapia/métodos , Animais , Sobrevivência Celular/efeitos dos fármacos , Meios de Contraste/administração & dosagem , Feminino , Radioisótopos de Flúor/administração & dosagem , Células HeLa , Humanos , Injeções Subcutâneas , Glândulas Mamárias Animais , Neoplasias Mamárias Experimentais/patologia , Camundongos , Camundongos Endogâmicos BALB C , Nanopartículas/administração & dosagem , Nanopartículas/ultraestrutura , Tamanho da Partícula
10.
Anal Chem ; 87(22): 11592-8, 2015 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-26494177

RESUMO

Optical imaging of latent fingerprints (LFPs) has been widely used in forensic science and for antiterrorist applications, but it suffers from interference from autofluorescence and the substrates background color. Cu7S4 nanoparticles (NPs), with excellent photothermal properties, were synthesized using a new strategy and then fabricated into amphiphilic nanocomposites (NCs) via polymerization of allyl mercaptan coated on Cu7S4 NPs to offer good affinities toward LFPs. Here, we develop a facile and versatile photothermal LFP imaging method based on the high photothermal conversion efficiency (52.92%, 808 nm) of Cu7S4 NCs, indicating its effectiveness for imaging LFPs left on different substrates (with various background colors), which will be extremely useful for crime scene investigations. Furthermore, by fabricating Cu7S4-CdSe@ZnS NCs, a fluorescent-photothermal dual-mode imaging strategy was used to detect trinitrotoluene (TNT) in LFPs while still maintaining a complete photothermal image of LFP.


Assuntos
Dermatoglifia , Diagnóstico por Imagem , Nanocompostos/química , Processos Fotoquímicos , Semicondutores , Temperatura , Humanos , Trinitrotolueno/análise
11.
Nano Lett ; 15(10): 6295-301, 2015 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-26373787

RESUMO

We report a highly efficient photocatalyst comprised of Cu7S4@Pd heteronanostructures with plasmonic absorption in the near-infrared (NIR)-range. Our results indicated that the strong NIR plasmonic absorption of Cu7S4@Pd facilitated hot carrier transfer from Cu7S4 to Pd, which subsequently promoted the catalytic reactions on Pd metallic surface. We confirmed such enhancement mechanism could effectively boost the sunlight utilization in a wide range of photocatalytic reactions, including the Suzuki coupling reaction, hydrogenation of nitrobenzene, and oxidation of benzyl alcohol. Even under irradiation at 1500 nm with low power density (0.45 W/cm(2)), these heteronanostructures demonstrated excellent catalytic activities. Under solar illumination with power density as low as 40 mW/cm(2), nearly 80-100% of conversion was achieved within 2 h for all three types of organic reactions. Furthermore, recycling experiments showed the Cu7S4@Pd were stable and could retain their structures and high activity after five cycles. The reported synthetic protocol can be easily extended to other Cu7S4@M (M = Pt, Ag, Au) catalysts, offering a new solution to design and fabricate highly effective photocatalysts with broad material choices for efficient conversion of solar energy to chemical energy in an environmentally friendly manner.

12.
Small ; 11(33): 4183-90, 2015 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-25981697

RESUMO

According to the simulation, the self-assembly of Cu7 S4 nanocrystals would enhance the photothermal conversion efficiency (PCE) because of the localized surface plasmon resonance effects, which is highly desirable for photothermal therapy (PTT). A new strategy to synthesize Cu7 S4 nanosuperlattices with greatly enhanced PCE up to 65.7% under irradiation of 808 nm near infrared light is reported here. By tuning the surface properties of Cu7 S4 nanocrystals during the synthesis via thermolysis of a new single precursor, dispersed nanoparticles (NPs), rod-like alignments, and nanosuperlattices are obtained, respectively. To explore their PTT applications, these hydrophobic nanostructures are transferred into water by coating with home-made amphiphilic polymer while maintaining their original structures. Under identical conditions, the PCE are 48.62% and 56.32% for dispersed NPs and rod-like alignments, respectively. As expected, when the nanoparticles are self-assembled into nanosuperlattices, the PCE is greatly enhanced up to 65.7%. This strong PCE, along with their excellent photothermal stability and good biocompatibility, renders these nanosuperlattices good candidates as PTT agents. In vitro photothermal ablation performances have undoubtedly proved the excellent PCE of our Cu7 S4 nanosuperlattices. This research offers a versatile and effective solution to get PTT agents with high photothermal efficiency.


Assuntos
Cobre/química , Fototerapia/instrumentação , Pontos Quânticos/química , Compostos de Enxofre/síntese química , Antineoplásicos/química , Antineoplásicos/farmacologia , Doxiciclina/química , Doxiciclina/farmacologia , Células HeLa , Humanos , Interações Hidrofóbicas e Hidrofílicas , Raios Infravermelhos , Nanoestruturas/química , Fototerapia/métodos , Compostos de Enxofre/química , Compostos de Enxofre/farmacologia , Propriedades de Superfície
13.
Talanta ; 115: 512-7, 2013 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-24054626

RESUMO

Composite nanospheres containing dithizone, luminescent LaVO4:Eu(3+) nanoparticles (NPs), and amphiphilic polymer have been composed for the rapid, selective, and visual luminescence turn-on detection of mercury ions (Hg(2+)) in water. Due to the absorption of dithizone, the strong red luminescence of LaVO4:Eu(3+) NPs encapsulated in nanospheres was quenched noticeably. As a result, these as-prepared nanocomposites (NCs) demonstrate very weak red luminescence. However, in the presence of Hg(2+), the red luminescence of nanocomposites was turned on dramatically, which can be attributed to the strong binding of mercury (II) ions by dithizone and forming a complex without absorption in the red emission range. Meanwhile, other cations have no influence on the detection of Hg(2+), suggesting a good selectivity for Hg(2+) sensing. Due to the high photostability and chemical stability of the nanocomposites, operation simplicity, low cost, and good selectivity, this newly developed method is highly desirable for field assay of Hg(2+) in aqueous media ranging from 40.0 nM to 4.0 µM with a limit of detection of 32.0 nM and a good linearity (r=0.9980). Therefore, a facile, rapid, selective, and visual luminescence turn-on technology has been successfully developed for Hg(2+) detection.


Assuntos
Ditizona/química , Medições Luminescentes , Mercúrio/química , Nanopartículas Metálicas/química , Nanocompostos/química , Poluentes Químicos da Água/análise , Cátions Bivalentes , Elementos da Série dos Lantanídeos/química , Limite de Detecção , Soluções , Água
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