Strong Light Emission Research Articles

Monodisperse and core-shell structured SiO2@Lu2O3:Ln3+ (Ln=Eu, Tb, Dy, Sm, Er, Ho, and Tm) spherical particles: A facile synthesis and luminescent properties

The core-shell structured SiO2@Lu2O3:Ln3+ particles were realized by coating the Lu2O3:Ln3+ phosphors onto the surface of non-aggregated, monodisperse and spherical SiO2 particles by the Pechini sol–gel method. The as-synthesized products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray (EDX) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photolumiminescence (PL), and low-voltage cathodoluminescence (CL). The results indicate that the 800°C annealed sample consists of crystalline Lu2O3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. The as-obtained particles show strong light emission with different colors corresponding to different Ln3+ ions under ultraviolet–visible light excitation and low-voltage electron beams excitation, which have potential applications in fluorescent lamps and field emission displays.

1.55 µm InAs/GaAs Quantum Dots and High Repetition Rate Quantum Dot SESAM Mode-locked Laser

High pulse repetition rate (≥10 GHz) diode-pumped solid-state lasers, modelocked using semiconductor saturable absorber mirrors (SESAMs) are emerging as an enabling technology for high data rate coherent communication systems owing to their low noise and pulse-to-pulse optical phase-coherence. Quantum dot (QD) based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the development of an epitaxial process for the realization of high optical quality 1.55 µm In(Ga)As QDs on GaAs substrates, their incorporation into a SESAM, and the realization of the first 10 GHz repetition rate QD-SESAM modelocked laser at 1.55 µm, exhibiting ∼2 ps pulse width from an Er-doped glass oscillator (ERGO). With a high areal dot density and strong light emission, this QD structure is a very promising candidate for many other applications, such as laser diodes, optical amplifiers, non-linear and photonic crystal based devices.

(Invited) Blue Phosphorescence in Oxidized Nano-Porous Silicon

Heavily oxidized porous silicon treated by high-pressure water vapor annealing exhibits a strong blue light emission band which includes a long-lived phosphorescence (Ph) component. This Ph is particularly strong below 200 K. Above 200 K, it experiences a progressive thermally activated quenching. The intensity of the Ph and the peak of its spectrum depend on the excitation energy, and a large Stokes shift was observed. The Ph spectrum included six components exhibiting similar optical properties and likely due to vibronic features of molecular-like species. The Ph was modeled as the result of recombinations from triplet states to ground levels. Its origin is related to silicon nanostructures in an oxide matrix.

Low temperature preparation and optical properties of K2Ti6O13

A simple and cost-effective route was developed for the low temperature (700°C) synthesis of K2Ti6O13 powder, using low-melting-point KNO3 and high-reactive-activity P25 TiO2 nanocrystals as the reactants. The characterization results from X-ray diffraction and field emission scanning electron microscopy revealed the successful preparation of monoclinic phase K2Ti6O13 crystallites with a rodlike morphology. UV–vis diffuse reflectance spectrum disclosed that the as-synthesized K2Ti6O13 had a direct optical band gap of about 3.47eV. Besides, the as-synthesized K2Ti6O13 displayed strong and wide visible light emission in the wavelength range of about 400–700nm upon laser excitation at 325nm at room temperature, enabling its use as a promising blue light-emitting material.

Morphology Evolution and Luminescence Properties of YF<sub>3</sub>: Sm Nano-/Microcrystals

Abstract. Recently, there has been increasting interest in the doping of nano-/microcrystal hosts with Sm3+. However, very few examples of Sm3+ doped YF3 -based nanophosphors have been reported. In this paper, a variety of uniform YF3:Sm nano-/microcrystals have been successfully prepared by a facile, effective, and environmentally friendly hydrothermal method. The morphology evolution process has been investigated by quenching the reaction at different time. Based on the results, a possible growth mechanism is presented in detail. The as-obtained YF3:Sm nano-/microcrystals show strong yellow and red light emissions under room temperature, which is quite different from those reported previously and might find potential applications in fields such as light phosphor powers and advanced flat panel display devices.

Ge quantum dots light-emitting devices

Si photonics becomes one of the research focuses in the field of photonics. Si-based light-emitting devices are one of the most important devices in this field. In this paper, we review the Si-based light-emitting devices fabricated by embedding Ge self-assembled quantum dots into optical microcavities. Ge self-assembled quantum dots emit light in the telecommunication wavelength range from 1.3 to 1.6 μm, for which Si is transparent. Ge self-assembled quantum dots were grown on silicon-oninsulator (SOI) by molecular beam epitaxy (MBE) in Stranski-Krastanov (S-K) mode. Then, electron beam lithography (EBL) was used to define the pattern of optical microcavities on the wafer. Finally, the pattern was transferred onto the Si/Ge slab by inductive coupled plasma (ICP) dry etching. Room-temperature photoluminescence (PL) was used to characterize the light-emitting properties of fabricated devices. The results showed that strong resonant light emission was observed in different optical microcavities. Significant enhancement of the intensity was obtained by the optical resonance. Based on the results of PL, we designed and fabricated current-injected light-emitting devices based on Ge self-assembled quantum dots in optical microcavities. Room-temperature resonant light emission was observed from Ge dots in a 3.8 μm microdisk resonator.

Carbazole-Functionalised Poly(1-phenyl-1-alkyne)s: Synthesis, Light Emission, and Fluorescent Photopatterning

Carbazole-containing 1-phenyl-1-alkynes with different spacer lengths [C6H5C≡C(CH2)mCar 1(m) (m = 3, 4, 9), Car =9-carbazolyl] were synthesised in high yields by consecutive substitution and coupling reactions of n-chloro-1-alkynes. Polymerisation of the monomers was effected by NbCl5– and WCl6–Ph4Sn catalysts, furnishing soluble polymers P1(m) with high molecular weights in high yields. All the polymers were thermally stable, commencing to lose their weights at high temperatures (≥ 400°C). Photoexcitation of their THF solutions induced strong blue light emissions with high quantum efficiencies up to 92 %. Multilayer electroluminescence devices with configurations of ITO/P1(m)(:PVK)/BCP/Alq3/LiF/Al were constructed, which gave blue light with maximum luminance and external quantum efficiency of 438 cd m–2 and 0.63 %. UV irradiation of a thin film of P1(4) through a mask oxidized and quenched the light emission of the exposed parts, generating a two-dimensional luminescent photopattern.

Blue Phosphorescence in Oxidized Nano-Porous Silicon

Heavily oxidized porous silicon treated by high-pressure water vapor annealing exhibits a strong blue light emission band which includes a long-lived phosphorescence (Ph) component. This Ph is particularly strong below 200 K. Above 200 K, it experiences a progressive thermally activated quenching. The intensity of the Ph and the peak of its spectrum depend on the excitation energy, and a large Stokes shift was observed. The Ph spectrum included six components exhibiting similar optical properties and likely due to vibronic features of molecular-like species. The Ph was modeled as the result of recombinations from triplet states to ground levels. Its origin is related to silicon nanostructures in an oxide matrix.

Synthesis and enhanced luminescence of uniform and well-dispersed quasispherical YVO4:Ln3+(Ln = Eu, Dy) nanoparticles by a solvothermal method

Uniform and well-dispersed quasi-spherical YVO4:Ln3+ (Ln = Eu, Dy) nanoparticles have been successfully synthesized through a solvothermal approach using EG and PVP as solvent and surfactant, respectively. SEM and TEM images indicate that the as-obtained quasispheres are composed of tiny packed nanocrystallites. The YVO4:Eu3+ and YVO4:Dy3+ samples show strong red and yellow light emissions under ultraviolet excitation. The luminescence intensities of the phosphors are greatly enhanced by co-doping Ba2+ ions into the YVO4 host lattice. Nitrogen adsorption–desorption measurements reveals that the as-synthesized luminescent quasi-spherical nanoparticles have a porous structure, which might find potential applications in the fields of luminescence, drug delivery, and disease therapy.

Self assembly of shape-controlled ZnS nanostructures with novel yellow light photoluminescence and excellent hydrophobic properties

Large scale ZnS nanowire bundles and nanorod arrays have been successfully obtained by a facile solvothermal method at a mild temperature. The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and water contact angle (CA) measurements. These nanostructures grow along the [0001] direction and possess a single crystalline wurtzite structure. Possible formation mechanisms for the growth of the ZnS nanostructures were proposed based on the experimental results. PL spectra of the as-synthesized products presented strong yellow light emission peaks. Water contact angle data demonstrated that the ZnS nanowire bundles possessed an excellent superhydrophobic ability.

A novel conjugated polyfluorene: synthesis, characterization and application in label-free ECL immunoassays for biomarker detection

Download options Please wait... Article information DOI https://doi.org/10.1039/C2JM15481A Article type Paper Submitted 27 Oct 2011 Accepted 09 Jan 2012 First published 09 Feb 2012 Download Citation J. Mater. Chem., 2012,22, 5568-5573 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions A novel conjugated polyfluorene: synthesis, characterization and application in label-free ECL immunoassays for biomarker detection M. Yan, W. Gao, S. Ge, L. Ge, C. Chu, J. Yu, X. Song and S. Hou, J. Mater. Chem., 2012, 22, 5568 DOI: 10.1039/C2JM15481A To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Mei Yan Weiqiang Gao Shenguang Ge Lei Ge Chengchao Chu Jinghua Yu Xianrang Song Shengnan Hou

A New Family of Light Emitting Si Nanoparticles

ABSTRACTColor-tuning of UV luminescent silicon nanocrystals (Si NCs) was successfully achieved by precise size control of non-oxidized NCs. The alkoxy-capped Si NCs was synthesized via sodium biphenylide reduction of SiCl4 encapsulated with inverse micelles, and subsequent alkoxylation of surface Si-Cl bonds. Due to the high molecular packing density of alkoxy monolayers, outermost surface of the NCs was completely protected from oxidation even under ambient conditions. Interestingly, the optical absorption and emission spectra were blueshifted with reduction of non-oxidized NC size, and we found strong light emission in the UV range when the NCs were smaller than 2.5 nm. More than 20% of PL quantum efficiencies (QYs) were estimated from those UV luminescent NCs. Monodispersed NCs without oxide can provided narrow PL spectra with 35-40 nm of line-widths, while the presence of oxidized surface region of NCs led to the broad PL spectra. In addition, the redshift of PL spectra were observed from the partially-oxidized NCs which were formed due to the lower surface molecular coverage, suggesting the significant difference in optical transition of photogenerated carriers between the non-oxidized and the partially-oxidized NCs. This can be well-illustrated by comparing decay profiles of the carriers for each sample through the time-resolved PL spectroscopic observation.

Uniform and well-dispersed GdVO4 hierarchical architectures: hydrothermal synthesis, morphology evolution, and luminescence properties

GdVO4 nano/microcrystals with different morphologies were successfully synthesized via an efficient and facile hydrothermal process using trisodium citrate (Na3Cit) as the chelating ligand. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectra (XPS), fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) and cathodoluminescence (CL) spectra were employed to characterize the samples. By tuning the reaction time, vanadium sources, and Na3Cit content, GdVO4 samples with different morphologies and sizes have been successfully synthesised. The possible formation mechanism for these diverse architectures is proposed on the basis of time-dependent experiments. Under ultraviolet (UV) and low-voltage electron beam excitation, GdVO4 : Ln3+ (Ln3+ = Eu, Dy, and Sm) phosphors show strong light emissions with different colors coming from various Ln3+ ions due to an efficient energy transfer from vanadate groups to the dopants. The ability to generate GdVO4 nano/microstructures with diverse shapes, and multicolor emission provides a great opportunity for systematically evaluating their luminescence properties, as well as fully exploring their applications in light emitting phosphors, advanced flat panel display, field emission display devices or biological labeling.

Ecosystem-scale compensation points of formic and acetic acid in the central Amazon

Abstract. Organic acids, central to terrestrial carbon metabolism and atmospheric photochemistry, are ubiquitous in the troposphere in the gas, particle, and aqueous phases. As the dominant organic acids in the atmosphere, formic acid (FA, HCOOH) and acetic acid (AA, CH3COOH) control precipitation acidity in remote regions and may represent a critical link between the terrestrial carbon and water cycles by acting as key intermediates in plant carbon and energy metabolism and aerosol-cloud-precipitation interactions. However, our understanding of the exchange of these acids between terrestrial ecosystems and the atmosphere is limited by a lack of field observations, the existence of biogenic and anthropogenic primary and secondary sources whose relative importance is unclear, and the fact that vegetation can act as both a source and a sink. Here, we first present data obtained from the tropical rainforest mesocosm at Biosphere 2 which isolates primary vegetation sources. Strong light and temperature dependent emissions enriched in FA relative to AA were simultaneously observed from individual branches (FA/AA = 3.0 ± 0.7) and mesocosm ambient air (FA/AA = 1.4 ± 0.3). We also present long-term observations of vertical concentration gradients of FA and AA within and above a primary rainforest canopy in the central Amazon during the 2010 dry and 2011 wet seasons. We observed a seasonal switch from net ecosystem-scale deposition during the dry season to net emissions during the wet season. This switch was associated with reduced ambient concentrations in the wet season (FA < 1.3 nmol mol−1, AA < 2.0 nmol mol−1) relative to the dry season (FA up to 3.3 nmol mol−1, AA up to 6.0 nmol mol−1), and a simultaneous increase in the FA/AA ambient concentration ratios from 0.3–0.8 in the dry season to 1.0–2.1 in the wet season. These observations are consistent with a switch between a biomass burning dominated source in the dry season (FA/AA < 1.0) to a vegetation dominated source in the wet season (FA/AA > 1.0). Our observations provide the first ecosystem-scale evidence of bidirectional FA and AA exchange between a forest canopy and the atmosphere controlled by ambient concentrations and ecosystem scale compensation points (estimated to be 1.3 ± 0.3 nmol mol−1: FA, and 2.1 ± 0.4 nmol mol−1: AA). These results suggest the need for a fundamental change in how future biosphere-atmosphere exchange models should treat FA and AA with a focus on factors that influence net exchange rates (ambient concentrations and ecosystem compensation points) rather than treating emissions and deposition separately.

Gallium and indium co‐doped ZnO thin films for white light emitting diodes

AbstractGa and In co‐doped ZnO (GIZO) thin films together with ZnO, In‐doped ZnO (IZO), Ga‐doped ZnO (GZO), and IZO/GZO multilayer for comparison, were grown on corning glass and boron doped Si substrates by PLD. The photoluminescence spectra of GIZO showed a strong white light emission and the current–voltage characteristics showed relatively lower turn‐on voltage and larger forward current. The CIE coordinates for GIZO were observed to be (0.31, 0.33) with a correlated colour temperature of 6650 K, indicating a cool white light, and establishing a possibility of white light emitting diodes. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Low temperature synthesis of CuGeO3 nanoflowers from n-heptane solvent

Abstract CuGeO3 nanoflowers have been synthesized by solvothermal treatment of GeO2 and Cu(CH3COO)2 · H2O in n-heptane solvent without using any surfactants. The influence of temperature and reaction time on the formation of the CuGeO3 nanoflowers has been analyzed. The room temperature photoluminescence spectrum of the CuGeO3 nanoflowers has also been investigated. The synthesized nanoflowers are composed of orthorhombic phase, based on X-ray diffraction and scanning electron microscopy characterizations. The temperature and reaction time have important roles in the formation and size of the CuGeO3 nanoflowers. The room temperature photoluminescence spectrum of the CuGeO3 nanoflowers demonstrates strong blue light emission centered at 421 nm and 488 nm and a poor green light emission centered at 530 nm and 543 nm, suggesting that the CuGeO3 nanoflowers have good optical properties.

Hydrothermal Synthesis and Luminescence Properties of Multiform Lanthanide Ions doped YVO4 Architectures

YVO4 flowerlike architectures with well-aligned microneedles and urchin-like architectures with nanorods have been synthesized using a facile hydrothermal method in the presence of disodium ethylenediamine tetraacetate (Na2H2L). The morphology of the YVO4 flowerlike architectures can be easily controlled by adjusting the pH value of the reaction system. Proper reaction temperature and the basic source ammonia are key requirements for the fabrication of the flowerlike architectures. The additive Na2H2L can coordinate with metal ions to form strong complexes and be absorbed on specific crystal surfaces of the initial colloidal precipitates, which serve as seeds for the anisotropic growth. The formation mechanism for the YVO4 assemblies has been discussed on the basis of time-dependent experiments. YVO4:Ln3+ (Ln = Eu, Dy and Sm) phosphors preserved the architecture morphologies show strong light emissions with different colors coming from different activated ions under ultraviolet excitation.

Optical amplification in Er/Yb silicate strip loaded waveguide

An Er/Yb silicate strip loaded waveguide was fabricated for optical amplification purpose. A 2.4-μm-wide SiO2 strip was deposited on top of the Er/Yb silicate active layer. Experiment data showed a 5.5 dB signal enhancement in a 7.8-mm-long waveguide pumped by a laser of 372 mW at 1480 nm. The signal is not saturated and can be further enhanced by increasing pumping power and decreasing waveguide loss. The strong red light emission at 660 nm was also observed due to excited state absorption and Yb3+ participated energy transfer upconversion processes.

Origin of Blue Emission from Silicon Nanoparticles: Direct Transition and Interface Recombination

Blue light luminescent Si nanoparticles (NPs) have many potential applications in optoelectronics. However, blue light emission from Si is not stable in many cases, which severely hinders their real applications. Here, it is found that Si NPs prepared by laser ablation have strong and aging-enhancement blue light emissions. Subsequent annealing treatment of the aged Si NPs will weaken the blue emission dramatically. Through monitoring the photoluminescence (PL) evolutions (including the peak position and intensity) during different treatments of the Si NPs, we studied the origin of the blue light emission. In this case, such blue light emission cannot be simply ascribed to the quantum confinement effect of Si nanocrystals or surface states. The most plausible luminescent mechanism is that excitons first formed within Si nanocrystals by direct transitions at Γ or X point, then some of the formed excitons are trapped by nonradiative Pb centers, and the others transfer to and recombine at near-interface traps located at the interface areas between Si and the surrounding SiOx (0 < x < 2) layer, giving rise to the strong blue light emission. According to this scenario, aging enhancement and annealing reduction of the blue emission could be satisfactorily explained. On the basis of the understanding of the blue light emission mechanism, a time-saving hydrothermal approach is supplied to generate Si NPs with strong blue light emission instead of a time-consuming aging process. This investigation deepens the insight into the mechanism of the blue light emission from Si NPs prepared by laser ablation.

Magnetic, luminescent and core–shell structured Fe 3O 4@YF 3:Ce 3+,Tb 3+ bifunctional nanocomposites

Bifunctional magnetic–luminescent nanocomposites with Fe 3O 4 nanoparticles as the cores and YF 3:Ce 3+,Tb 3+ as the shells were synthesized by a facile direct precipitation method. Transmission electron microscopy (TEM) images revealed that the obtained bifunctional nanocomposites had a core–shell structure, in a spherical shape with a size ranging from 160 to 220 nm, and the shell thickness of about 25 nm. The X-ray diffraction (XRD) patterns showed that a cubic spinel structure of Fe 3O 4 core and an orthogonal phase of YF 3 shell were obtained. Photoluminescence (PL) spectra confirmed that the nanocomposites displayed a strong green light emission. Magnetic measurements indicated that the obtained bifunctional nanocomposites exhibited a stronger magnetic behavior at room temperature. Therefore, the bifunctional nanocomposites are expected to develop many potential applications in biomedical fields.