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1.
J Phys Chem Lett ; : 4990-4997, 2020 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-32498513

RESUMO

Polar surfaces of ionic crystals are of growing technological importance, with implications for the efficiency of photocatalysts, gas sensors, and electronic devices. The creation of ionic nanocrystals with high percentages of polar surfaces is an option for improving their efficiency in the aforementioned applications but is hard to accomplish because they are less thermodynamically stable and prone to vanish during the growth process. Herein, we develop a strategy that is capable of producing polar surface-dominated II-VI semiconductor nanocrystals, including ZnS and CdS, from copper sulfide hexagonal nanoplates through cation exchange reactions. The obtained wurtzite ZnS hexagonal nanoplates have dominant {002} polar surfaces, occupying up to 97.8% of all surfaces. Density functional theory calculations reveal the polar surfaces can be stabilized by a charge transfer of 0.25 eV/formula from the anion-terminated surface to the cation-terminated surface, which also explains the presence of polar surfaces in the initial Cu1.75S hexagonal nanoplates with cation deficiency prior to cation exchange reactions. Experimental results showed that the HER activity could be boosted by the surface polarization of polar surface-dominated ZnS hexagonal nanoplates. We anticipate this strategy is general and could be used with other systems to prepare nanocrystals with dominant polar surfaces. Furthermore, the availability of colloidal semiconductor nanocrystals with dominant polar surfaces produced through this strategy opens a new avenue for improving their efficiency in catalysis, photocatalysis, gas sensing, and other applications.

2.
Adv Mater ; : e1905739, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31957161

RESUMO

The structure-property engineering of phase-based materials for redox-reactive energy conversion and environmental decontamination nanosystems, which are crucial for achieving feasible and sustainable energy and environment treatment technology, is discussed. An exhaustive overview of redox reaction processes, including electrocatalysis, photocatalysis, and photoelectrocatalysis, is given. Through examples of applications of these redox reactions, how structural phase engineering (SPE) strategies can influence the catalytic activity, selectivity, and stability is constructively reviewed and discussed. As observed, to date, much progress has been made in SPE to improve catalytic redox reactions. However, a number of highly intriguing, unresolved issues remain to be discussed, including solar photon-to-exciton conversion efficiency, exciton dissociation into active reductive/oxidative electrons/holes, dual- and multiphase junctions, selective adsorption/desorption, performance stability, sustainability, etc. To conclude, key challenges and prospects with SPE-assisted redox reaction systems are highlighted, where further development for the advanced engineering of phase-based materials will accelerate the sustainable (active, reliable, and scalable) production of valuable chemicals and energy, as well as facilitate environmental treatment.

3.
Small ; 16(12): e1902231, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31769587

RESUMO

For the first time, colloidal gold (Au)-ZnSe hybrid nanorods (NRs) with controlled size and location of Au domains are synthesized and used for hydrogen production by photocatalytic water splitting. Au tips are found to grow on the apices of ZnSe NRs nonepitaxially to form an interface with no preference of orientation between Au(111) and ZnSe(001). Density functional theory calculations reveal that the Au tips on ZnSe hybrid NRs gain enhanced adsorption of H compared to pristine Au, which favors the hydrogen evolution reaction. Photocatalytic tests reveal that the Au tips on ZnSe NRs effectively enhance the photocatalytic performance in hydrogen generation, in which the single Au-tipped ZnSe hybrid NRs show the highest photocatalytic hydrogen production rate of 437.8 µmol h-1 g-1 in comparison with a rate of 51.5 µmol h-1 g-1 for pristine ZnSe NRs. An apparent quantum efficiency of 1.3% for hydrogen evolution reaction for single Au-tipped ZnSe hybrid NRs is obtained, showing the potential application of this type of cadmium (Cd)-free metal-semiconductor hybrid nanoparticles (NPs) in solar hydrogen production. This work opens an avenue toward Cd-free hybrid NP-based photocatalysis for clean fuel production.

4.
Adv Mater ; 31(49): e1905540, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31631407

RESUMO

Molecular surfactants are widely used to control low-dimensional morphologies, including 2D nanomaterials in colloidal chemical synthesis, but it is still highly challenging to accurately control single-layer growth for 2D materials. A scalable stacking-hinderable strategy to not only enable exclusive single-layer growth mode for transition metal dichalcogenides (TMDs) selectively sandwiched by surfactant molecules but also retain sandwiched single-layer TMDs' photoredox activities is developed. The single-layer growth mechanism is well explained by theoretical calculation. Three types of single-layer TMDs, including MoS2 , WS2 , and ReS2 , are successfully synthesized and demonstrated in solar H2 fuel production from hydrogen-stored liquid carrier-methanol. Such H2 fuel production from single-layer MoS2 nanosheets is COx -free and reliably workable under room temperature and normal pressure with the generation rate reaching ≈617 µmole g-1 h-1 and excellent photoredox endurability. This strategy opens up the feasible avenue to develop methanol-storable solar H2 fuel with facile chemical rebonding actualized by 2D single-layer photocatalysts.

5.
Nano Lett ; 19(9): 6315-6322, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31441658

RESUMO

One-dimensional (1D) semiconductor nanorods are important for numerous applications ranging from optics and electronics to biology, yet the direct synthesis of high-quality metal halide perovskite nanorods remains a challenge. Here, we develop an intermediate monomer reservoir synthetic strategy to realize the controllable growth of uniform and low-defect CsPbBr3 perovskite nanorods. Intermediates composed of CsPb2Br5 and Cs3In2Br9 are obtained through the substitution of Pb2+ with In3+ cations in the template of CsPbBr3 nanocubes and act as a precursor reservoir to gradually release monomers, ensuring both the slow growth rate and low defects of nanorods. We have used branched tris(diethylamino)phosphine as a ligand, which not only has unequal binding energies with different crystal faces to promote the orientation growth but also provides strong steric hindrance to shield the nanorods in solution. Because of minor amount of defects and an effective ligand passivation, in addition to significantly enhanced stability, the perovskite nanorods show a high photoluminescence quantum yield of up to 90% and exhibit a net mode gain of 980 cm-1, the latter being a record value among all the perovskite materials. An extremely low amplified spontaneous emission threshold of 7.5 µJ cm-2 is obtained under excitation by a nanosecond laser, which is comparable to that obtained using femtosecond lasers in other recent studies.

6.
J Phys Chem Lett ; 10(12): 3465-3471, 2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31184156

RESUMO

Herein we employed a first-principles method based on density functional theory to investigate the surface energy and growth kinetics of wurtzite nanoplatelets to elucidate why nanoplatelets exhibit a uniform thickness of eight monolayers. We synthesized a series of wurtzite nanoplatelets (ZnSe, ZnS, ZnTe, and CdSe) with an atomically uniform thickness of eight monolayers. As a representative example, the growth mechanism of 1.39 nm thick (eight monolayers) wurtzite ZnSe nanoplatelets was studied to substantiate the proposed growth kinetics. The results show that the growth of the seventh and eighth layers along the [112̅0] direction of 0.99 nm (six monolayers) ZnSe magic-size nanoclusters is accessible, whereas the growth of the ninth layer is unlikely to occur because the formation energy is large. This work not only gives insights into the synthesis of atomically uniform thick wurtzite semiconductor nanoplatelets but also opens up new avenues to their applications in light-emitting diodes, catalysis, detectors, and lasers.

7.
Nanoscale ; 11(25): 12169-12176, 2019 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-31197294

RESUMO

Novel materials from self-assembled nanocrystals hold great promise for applications ranging from inorganic catalysis to bio-imaging. However, because of the inherent anisotropic properties, it is challenging to assemble one-dimensional (1D) nanorods into higher-order structures (e.g. 2D sheets or 3D networks) without any support. Here, we have developed a facile strategy for the direct self-assembly of 1D nanorods into free-standing 2D nanorafts with lateral dimensions up to several micrometers. As a general approach, 2D nanorafts with diverse compositions, e.g. MgF2, WO2, CdS, ZnS, and ZnSe nanorafts, have been fabricated from the assembly of their 1D building blocks. More importantly, these nanorafts show high stability even when dispersed in different solvents, making them suitable for various applications. Because of their high porosity and strong adsorption capability, MgF2 nanorafts were investigated to illustrate the collective advantages generated from the assembly platform. Moreover, flexibility in the composition and structure of the building blocks demonstrated in this work will lead to next generation materials with rich functionalities.


Assuntos
Técnicas Biossensoriais , Nanocompostos/química , Nanotubos/química
8.
Adv Mater ; 31(25): e1900781, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31063615

RESUMO

Quasi-1D colloidal semiconductor nanorods (NRs) are at the forefront of nanoparticle (NP) research owing to their intriguing size-dependent and shape-dependent optical and electronic properties. The past decade has witnessed significant advances in both fundamental understanding of the growth mechanisms and applications of these stimulating materials. Herein, the state-of-the-art of colloidal semiconductor NRs is reviewed, with special emphasis on heavy-metal-free materials. The main growth mechanisms of heavy-metal-free colloidal semiconductor NRs are first elaborated, including anisotropic-controlled growth, oriented attachment, solution-liquid-solid method, and cation exchange. Then, structural engineering and properties of semiconductor NRs are discussed, with a comprehensive overview of core/shell structures, alloying, and doping, as well as semiconductor-metal hybrid nanostructures, followed by highlighted practical applications in terms of photocatalysis, photodetectors, solar cells, and biomedicine. Finally, challenges and future opportunities in this fascinating research area are proposed.

9.
Nanoscale ; 11(21): 10190-10197, 2019 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31112179

RESUMO

Herein we report a nanorod couple heterostructure made of dual semiconductors, in which two parallelly aligned ZnSe nanorods are connected by the growth of ZnS on both end and side facets, producing hetero-ZnS (short arms)-ZnSe (long arms)/ZnS shell nanorod couples. As evidenced by electronic structure studies, both experimental and theoretical, such core/shell nanorod couple heterostructures can act as a platform to precisely tailor the quantum confinement of charge carriers between the constituting components within a single nano-object, generating blue fluorescence after the overgrowth of an alloyed ZnCdS layer on the heterostructures. We foresee the mechanistic insights gained and electronic structures revealed in this work would shed light on the rational design of more complex heterostructures with novel functionalities.

10.
Chin Med J (Engl) ; 132(11): 1272-1282, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-30973448

RESUMO

BACKGROUND: Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) syndrome are highly prevalent respiratory conditions. Their coexistence is referred to as the overlap syndrome. They are both related to pulmonary hypertension (PH) development. This study investigated the effects of OSA on PH in patients with COPD and the associated factors. METHODS: Consecutive patients with stable COPD were recruited for an observational cross-sectional study from September 2016 to May 2018 at Peking University Third Hospital. In total, 106 patients with COPD were enrolled and performed home portable monitoring and echocardiography. OSA was defined by an apnea hypopnea index (AHI) ≥10 events/h. Based on OSA absence or presence, patients were divided into the COPD with OSA and COPD without OSA groups. Factors affecting pulmonary artery pressure (PAP) and PH were identified using univariate analysis and logistic regression models. RESULTS: In the 106 patients with COPD, the mean age was 69.52 years, 91.5% were men, and the mean forced expiratory volume in 1 s (FEV1) percentage of predicted was 56.15%. Fifty-six (52.8%) patients with COPD were diagnosed with OSA, and 24 (22.6%) patients with COPD were diagnosed as PH. Compared with COPD without OSA group, the median PAP in COPD with severe OSA group increased by 5 mmHg (36.00 [26.00-50.00] mmHg vs. 31.00 [24.00-34.00] mmHg, P = 0.036). COPD with percent of night-time spent with oxygen saturation below 90% (T90) > 10% group had higher PAP than COPD with T90 ≤ 1% group (36.00 [29.00-50.00)] mmHg vs. 29.00 [25.50-34.00] mmHg, F = 7.889, P = 0.007). Univariate analysis revealed age, FEV1% predicted, T90, and Charlson index had statistically significant effects on PH. Multiple regression analysis showed a significant and independent effect of both FEV1% predicted (odds ratio [OR] = 3.46; 95% confidence interval [CI]: 1.15-10.46; P = 0.028) and AHI (OR = 3.20; 95% CI: 1.09-19.35; P = 0.034) on PH. CONCLUSIONS: Patients with COPD with OSA are more susceptible to PH, which is associated with declining lung function and increased severity of OSA. Thus, nocturnal hypoxemia and OSA in elderly patients with COPD should be identified and treated.


Assuntos
Hipertensão Pulmonar/fisiopatologia , Apneia Obstrutiva do Sono/complicações , Apneia Obstrutiva do Sono/fisiopatologia , Idoso , Ecocardiografia , Feminino , Volume Expiratório Forçado/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Razão de Chances , Polissonografia , Prevalência , Doença Pulmonar Obstrutiva Crônica/fisiopatologia , Índice de Gravidade de Doença , Inquéritos e Questionários
11.
J Am Chem Soc ; 141(14): 5863-5870, 2019 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-30884944

RESUMO

Electrically insulating objects gain a net electrical charge when brought in and out of contact. This phenomenon-triboelectricity-involves the flow of charged species, but conclusively establishing their nature has proven extremely difficult. Here, we demonstrate an almost linear relationship between a plastic sample's net negative charge and the amount of solution metal ions discharged to metallic particles with a coefficient of proportionality linked to its electron affinity (stability of anionic fragments). The maximum magnitude of reductive redox work is also material dependent: metallic particles grow to a larger extent over charged dielectrics that yield stable cationic fragments (smaller ionization energy). Importantly, the extent to which the sample can act as electron source greatly exceeds the net charging measured in a Faraday pail/electrometer set up, which brings direct evidence of triboeletricity being a mosaic of positive and negative charges rather than a homogeneous ensemble and defines for the first time their quantitative scope in electrochemistry.

12.
Nanoscale ; 10(45): 20963-20989, 2018 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-30418466

RESUMO

Metal-halide perovskites have emerged as efficient, low-cost energy materials owing to their remarkable optoelectronic properties. In particular, the dimensionality and morphology of crystallites may have a striking influence on their chemical and physical properties and therefore affect their optoelectronic applications. One-dimensional halide perovskites have superior carrier transportation in one dimension, high crystalline quality, and consequently, high quantum efficiencies and long carrier diffusion lengths, which are important for the performance of perovskite-based nanoscale optoelectronic and photonic devices. In this review, we highlight recent advances in the synthesis of one-dimensional halide perovskites and their unique properties as well as their novel optoelectronic applications. This review aims to provide an overview of the achievements in synthesis techniques and nanoscale optoelectronic applications based on one-dimensional perovskite nanocrystals.

13.
Small ; 14(48): e1803233, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30334350

RESUMO

Durability is still one of the key obstacles for the further development of photocatalytic energy-conversion systems, especially low-dimensional ones. Encouragingly, recent studies show that nanoinsulators such as SiO2 and MgO exhibit substantially enhanced photocatalytic durability than the typical semiconductor p25 TiO2 . Extending this knowledge, MgO-Au plasmonic defect nanosystems are developed that combine the stable photoactivity from MgO surface defects with energy-focusing plasmonics from Au nanoparticles (NPs), where Au NPs are anchored onto monodispersed MgO nanotemplates. Theoretical calculations reveal that the midgap defect (MGD) states in MgO are generated by oxygen vacancies, which provide the main avenues for upward electron transitions under photoexcitation. These electrons drive stable proton photoreduction to H2 gas via water splitting. A synergistic interaction between Au's localized plasmons and MgO's oxygen vacancies is observed here, which enhances MgO's photoactivity and stability simultaneously. Such co-enhancement is attributed to the stable longitudinal-plasmon-free Au NPs, which provide robust hot electrons capable of overcoming the interband transition barrier (≈1.8 eV) to reach proton reduction potential for H2 generation. The demonstrated plasmonic defect nanosystems are expected to open a new avenue for developing highly endurable photoredox systems for the integration of multifunctionalities in energy conversion, environmental decontamination, and climate change mitigation.

14.
Int J Chron Obstruct Pulmon Dis ; 13: 3269-3280, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30349232

RESUMO

Purpose: To investigate the gender difference in knowledge, attitude, and practice of COPD diagnosis and treatment in China. Patients and methods: A nationwide, multicenter, cross-sectional questionnaire study was carried out to investigate patients' understanding and experience of COPD between September 2007 and December 2008. Results: Two thousand and seventy-two patients were recruited from eleven centers. The final effective questionnaires were those of 1,698 cases, of which 32% were female. Women were younger, had higher body mass index, were more never smokers, and had lesser pack-years (all P<0.01). More women had under elementary education level and monthly income <1,000 RMB (about 160 USD) (all P<0.01). Women had higher ratio of FEV1/FVC (54.1±10.9 vs 50.2±11.5), FEV1% (50.0±19.1 vs 45.4±29.0), and lower short form-36 mental component summary (57.5±26.8 vs 61.3±25.0) (all P<0.01). Fewer women reported severe exacerbation (defined as an acute worsening of respiratory symptoms that results in patient's hospitalization) in the previous year (44.5% vs 51.6%, P<0.05). More women reported that they never heard of COPD before (67.0% vs 59.0%, P<0.01). Less women reported that physician had to tell them they had emphysema (50.5% vs 60.4%) or COPD (31.9% vs 37.9%). Less women had pulmonary function test (PFT) done before (65.2% vs 70.4%, P<0.05). More women reported that they would not repeat PFT annually (91.7% vs 87.6%, P<0.05) and did not know the PFT results (78.6% vs 73.1%, P<0.05). More women reported not having had pulmonary rehabilitation before (87.8% vs 83.6%, P<0.05). Fewer women reported knowing that COPD should be given combined therapy (38.3% vs 44.5%) and long-term treatment (46.1% vs 51.9%) (all P<0.05). Conclusion: Male and female patients had different experiences on COPD diagnosis and treatment. Physicians should pay more attention to patients' education on COPD, especially of women.


Assuntos
Conhecimentos, Atitudes e Prática em Saúde , Educação de Pacientes como Assunto/normas , Doença Pulmonar Obstrutiva Crônica , Testes de Função Respiratória , Fatores Sexuais , Fumar , Adulto , Idoso , China/epidemiologia , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Determinação de Necessidades de Cuidados de Saúde , Prevalência , Doença Pulmonar Obstrutiva Crônica/diagnóstico , Doença Pulmonar Obstrutiva Crônica/epidemiologia , Doença Pulmonar Obstrutiva Crônica/psicologia , Doença Pulmonar Obstrutiva Crônica/terapia , Testes de Função Respiratória/métodos , Testes de Função Respiratória/psicologia , Fatores de Risco , Fumar/epidemiologia , Fumar/psicologia , Inquéritos e Questionários
15.
Adv Mater ; 30(39): e1803351, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30059172

RESUMO

Quasi-1D cadmium chalcogenide quantum rods (QRs) are benchmark semiconductor materials that are combined with noble metals to constitute QR heterostructures for efficient photocatalysis. However, the high toxicity of cadmium and cost of noble metals are the main obstacles to their widespread use. Herein, a facile colloidal synthetic approach is reported that leads to the spontaneous formation of cadmium-free alloyed ZnSx Se1-x QRs from polydisperse ZnSe nanowires by alkylthiol etching. The obtained non-noble-metal ZnSx Se1-x QRs can not only be directly adopted as efficient photocatalysts for water oxidation, showing a striking oxygen evolution capability of 3000 µmol g-1 h-1 , but also be utilized to prepare QR-sensitized TiO2 photoanodes which present enhanced photo-electrochemical (PEC) activity. Density functional theory (DFT) simulations reveal that alloyed ZnSx Se1-x QRs have highly active Zn sites on the (100) surface and reduced energy barrier for oxygen evolution, which in turn, are beneficial to their outstanding photocatalytic and PEC activities.

16.
Anal Chem ; 88(7): 3449-54, 2016 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-26916365

RESUMO

Optical imaging through the near-infrared (NIR) window provides deep penetration of light up to several centimeters into biological tissues. Capable of emitting 800 nm luminescence under 980 nm illumination, the recently developed upconversion nanoparticles (UCNPs) suggest a promising optical contrast agent for in vivo bioimaging. However, presently they require high-power lasers to excite when applied to small animals, leading to significant scattering background that limits the detection sensitivity as well as a detrimental thermal effect. In this work, we show that the time-gating approach implementing pulsed illumination from a NIR diode laser and time-delayed imaging synchronized via an optical chopper offers detection sensitivity more than 1 order of magnitude higher than the conventional approach using optical band-pass filters (S/N, 47321/6353 vs 5339/58), when imaging UCNPs injected into Kunming mice. The pulsed laser illumination (70 µs ON in 200 µs period) also reduces the overall thermal accumulation to 35% of that under the continuous-wave mode. Technical details are given on setting up the time-gating unit comprising an optical chopper, a pinhole, and a microscopy eyepiece. Being generally compatible with any camera, this provides a convenient and low cost solution to NIR animal imaging using UCNPs as well as other luminescent probes.


Assuntos
Luminescência , Animais , Raios Infravermelhos , Lasers , Substâncias Luminescentes/administração & dosagem , Substâncias Luminescentes/química , Camundongos , Camundongos Endogâmicos , Nanopartículas/administração & dosagem , Nanopartículas/química , Temperatura , Fatores de Tempo
17.
Inorg Chem ; 54(9): 4200-7, 2015 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-25880613

RESUMO

Three luminescent polymorphs based on a new copper(I) complex Cu(2-QBO)(PPh3)PF6 (1, PPh3 = triphenylphosphine, 2-QBO = 2-(2'-quinolyl)benzoxazole) have been synthesized and characterized by FT-IR, UV-vis, elemental analyses, and single-crystal X-ray diffraction analyses. Each polymorph can reversibly convert from one to another through appropriate procedures. Interestingly, such interconversion can be distinguished by their intrinsic crystal morphologies and colors (namely α, dark yellow plate, ß, orange block, γ, light yellow needle) as well as photoluminescent (PL) properties. X-ray crystal structure analyses of these three polymorphs show three different supramolecular structures from 1D to 3D, which are expected to be responsible for the formation of three different crystal morphologies such as needle, plate, and block. Combination of the experimental data with DFT calculations on these three polymorphs reveals that the polymorphic interconversion is triggered by the conformation isomerization of the 2-QBO ligand and can be successfully controlled by the polarity of the process solvents (affecting the molecular dipole moment) and thermodynamics (affecting the molecular total energy). It is also found that the different crystal colors of polymorphs and their PL properties are derived from different θ values (dihedral angle between benzoxazolyl and quinolyl group of the 2-QBO ligand) and P-Cu-P angles based on TD-DFT calculations. Moreover, an interesting phase interconversion between γ and ß has also been found under different temperature, and this result is consistent with the DFT calculations in which the total energy of ß is larger than that of γ. This polymorphism provides a good model to study the relationship between the structure and the physical properties in luminescent copper(I) complexes as well as some profound insights into their PL properties.

18.
J Am Chem Soc ; 136(31): 11121-7, 2014 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-25032504

RESUMO

Quasi-one-dimensional (1D) semiconductor nanocrystals manifest linearly polarized emission, reduced lasing threshold, and improved charge transport compared with their counterparts such as spherical quantum dots. Present investigations of colloidal semiconductor quantum rods are mainly based on cadmium chalcogenide systems because of their facile synthetic accessibility. However, it is still a big challenge to fabricate quasi-1D zinc chalcogenide nanocrystals with controlled aspect ratios. Here we report a general strategy for synthesizing zinc chalcogenide quantum rods via a colloidal chemical synthetic approach. Unlike the most common growth mechanisms of quasi-1D colloidal nanocrystals such as monomer attachment and particle coalescence, the synthesis of zinc chalcogenide quantum rods is performed by a ripening process starting from their respective ultrathin nanowires through thermodynamically driven material diffusion. We anticipate that this strategy is general and could be applied to other systems to construct quasi-1D nanostructures. Moreover, the presence of cadmium-free (or "green") zinc chalcogenide quantum rods synthesized through this strategy provides a desirable platform for eco-friendly photocatalysis, optoelectronic devices, biolabeling, and other applications.

19.
Nat Mater ; 13(3): 301-7, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24553656

RESUMO

Colloidal nanocrystal synthesis provides a powerful approach for creating unique nanostructures of relevance for applications. Here, we report that wurtzite ZnSe nanorod couples connected by twinning structures can be synthesized by means of a self-limited assembly process. Unlike for individual nanorods, the band-edge states calculated for the nanorod couples are predominantly confined to the short edges of the structure and this leads to low photoluminescence polarization anisotropy, as confirmed by single-particle fluorescence. Through a cation-exchange approach, the composition of nanorod couples can be readily expanded to additional materials, such as CdSe and PbSe. We anticipate that this family of nanorod-couple structures with distinct compositions and controlled properties will constitute an ideal system for the investigation of electronic coupling effects between individual nanorod components on the nanoscale, with relevance to applications in optics, photocatalysis and optoelectronic devices.

20.
Phys Chem Chem Phys ; 12(33): 9933-7, 2010 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-20532375

RESUMO

The emission spectra of the tripositive lanthanide ion Eu(3+) have often been employed to probe its environment in the solid state, and the intensity ratio of magnetic dipole ((5)D(0)-->(7)F(1)) and forced electric dipole ((5)D(0)-->(7)F(2)) transitions has been used to estimate the "degree of asymmetry" of a crystal site. From the site-selective, low temperature emission spectra of Eu(3+) doped into a glass, a new empirical relation has been found between the width of spectral features and the relative intensity of the (5)D(0)-->(7)F(0) zero phonon line. In order to explain the observations from experiments with excitation at different wavelengths, a generic quantitative relation has been developed from basic theory and validated from our experimental results. This work gives a deeper insight and understanding of the spectral characteristics of Eu(3+) electronic spectra in the visible region.


Assuntos
Európio/química , Vidro/química , Espectrofotometria , Temperatura
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