Strongest Emission Intensity Research Articles

Fluorescence Intensity and Lifetime Cell Imaging with Luminescent Gold Nanoclusters

In this article, luminescent properties of gold nanoclusters (AuNCs) were studied at the single nanoparticle level and also used as novel imaging agents in cell media. Two types of water-soluble AuNCs which were stabilized with a monolayer composed of either mercaptosuccinic acid (MSA) or tiopronin thiolate ligands were synthesized by a chemical reduction reaction. These AuNCs were determined to have an average core diameter of less than 2 nm. On a time-resolved confocal microscope, the emission signals from the single AuNCs were distinctly recordable. The quantum yields of these AuNCs were measured to be ca. 5%. The lifetime of these AuNCs is also much longer than the lifetime of cellular autofluorescence in lifetime cell imaging as well as the lifetime of organic dye Alexa Fluor 488. After being derivatized with polyethylene glycol (PEG) moieties, the AuNCs were uploaded efficiently in the HeLa cells. Fluorescence intensity and lifetime cell images were recorded on the time-resolved confocal microscope in which the emission from the AuNCs was readily differentiated from the cellular autofluorescence background because of their relatively stronger emission intensities and longer lifetimes. These loaded nanoclusters in the cells were observed to widely distribute throughout the cells and especially densely loaded near the cell nucleuses. The AuNCs in the cells were also tested to have a better photostability relative to the organic fluorophores under the same conditions. We thus conclude that the AuNCs have a great potential as novel nanoparticle imaging agents, especially as lifetime imaging agents, in fluorescence imaging applications. We also prospect much broader applications of these AuNCs after further improvements of their luminescence quantum yields.

Sandwich-structured upconversion nanoparticles with tunable color for multiplexed cell labeling

The need for a more efficient biological label to meet their burgeoning utility in rapidly developing multiplexing applications may be realized through the recent advent of upconversion nanoparticles (UCNs). UCNs fabricated to-date, however, are either not displaying strong fluorescence or have limited available colors. Here, we report on fabricating sandwich-structured UCNs with a NaYbF4 matrix sandwiched between two NaYF4 layers. Such sandwich design allows for efficient absorption of the excitation energy by the absorber ion-rich NaYbF4 layer that then transfers it to the adjacent NaYF4 layers on either side for an improved fluorescence efficiency. By doping different emitters into each of the shells and adjusting their thickness, different color output tunable based on the RGB color model were obtained. In this study, multicolor UCNs with strong emission intensity have been facilely synthesized and used for multiplex detection of three subcellular targets with a single near-infrared excitation wavelength.

Synthesis and Photoluminescence Properties of Eu3+‐Doped Silica@Coordination Polymer Core–Shell Structures and Their Calcinated Silica@Gd2O3:Eu and Hollow Gd2O3:Eu Microsphere Products

The conjugation of Eu(3+)-doped coordination polymers constructed from Gd(3+) and isophthalic acid (H(2)IPA) with silica particles is investigated for the production of luminescent microspheres. A series of doping ratio-controlled silica@coordination polymer core-shell spheres is easily synthesized by altering the amounts of metal nodes used in the reactions, where the ratios of Gd(3+) and Eu(3+) are 10:0 (1a), 9:1 (1b), 8:2 (1c), 7:3 (1d), 5:5 (1e), and 0:10 (1f). The formation of monodisperse uniform core-shell structures is achieved throughout the entirety of a series. Investigations of the photoluminescence property of the resulting series of silica@coordination polymer core-shell spheres reveal that 20% Eu(3+)-doped product (1c) has the strongest emission intensity. The subsequent calcination process on the silica@coordination polymer core-shell structures (1a-f) results in the formation of a series of doping ratio-controlled silica@Gd(2)O(3):Eu core-shell microspheres (2a-f) with uniform shell thickness. During the calcination step, the coordination polymers within silica@coordination polymer core-shells are transformed into metal oxides, resulting in silica@Gd(2)O(3):Eu core-shell structures. The final etching process on the silica@Gd(2)O(3):Eu core-shell microspheres (2a-f) produces a series of hollow Gd(2)O(3):Eu microspheres (3a-f) as a result of the elimination of silica cores. The luminescence intensities of silica@Gd(2)O(3):Eu core-shell (2a-f) and hollow Gd(2) O(3):Eu microspheres (3a-f) also vary depending upon the doping ratio of Eu(3+) ions.

Effects of growth temperature on high-quality In0.2Ga0.8N layers by plasma-assisted molecular beam epitaxy

High-quality In0.2Ga0.8N epilayers were grown on a GaN template at temperatures of 520 and 580 °C via plasma-assisted molecular beam epitaxy. The X-ray rocking curve full widths at half maximum (FWHM) of (10.2) reflections is 936 arcsec for the 50-nm-thick InGaN layers at the lower temperature. When the growth temperature increases to 580 °C, the FWHM of (00.2) reflections for these samples is very narrow and keeps similar, while significant improvement of (10.2) reflections with an FWHM value of 612 arcsec has been observed. This improved quality in InGaN layers grown at 580 °C is also reflected by the much larger size of the crystalline column from the AFM results, stronger emission intensity as well as a decreased FWHM of room temperature PL from 136 to 93.9 meV.

Observation of exceptional strong emission transitions 5Dj (j=1−3) to 7Fj (j=1−3): Multicolor from single Eu3+ ion doped La2O3 nanoparticles

Eu3+ ion doped La2O2CO3 and La2O3 nanoparticles have been synthesized through hydrothermal route with subsequent heat-treatment. It is found that La2O2CO3 phase is highly stable at ambient atmosphere and decomposes to La2O3 at or above 700°C. Exceptional stronger emissions from 5Dj (j=1−3) to 7Fj (j=1−3) transitions are observed compared to most probable 5D0 to 7Fj (j=1−3) transitions in 1 and 3at% Eu3+ doped samples heated at 900°C under 278nm excitation. This may be ascribed due to minimum cross-relaxation among 5Dj (j=1−3) levels. Significant decrease of emission intensity from 5D1 or 5D2 level and subsequent increase of emission intensity from 5D0 level on increasing Eu3+concentration up to 10at% indicate relaxation of excited electrons from 5Dj=1, 2 to 5D0 level. Excitation at 394nm shows strong background emission intensity in 425–600nm due to different defect states/intermediate bands present within host electronic band. Colors including blue, green, yellow, pink and red to white could be produced by changing concentration of Eu3+, excitation wavelength and annealing temperature. Samples are dispersible and could be incorporated in polyvinyl alcohol (PVA) films. Materials will also be potential candidates for light emitting diodes (LEDs) and bio-labeling.

Spatial variation behaviors of argon inductively coupled plasma during discharge mode transition

A Langmuir probe and an ICCD are employed to study the discharge mode transition in Ar inductively coupled plasma. Electron density and plasma emission intensity are measured during the E (capacitive discharge) to H (inductive discharge) mode transitions at different pressures. It is found that plasma exists with a low electron density and a weak emission intensity in the E mode, while it has a high electron density and a strong emission intensity in the H mode. Meanwhile, the plasma emission intensity spatial (2D image) profile is symmetrical in the H mode, but the 2D image is an asymmetric profile in the E mode. Moreover, the electron density and emission intensity jump up discontinuously at high pressure, but increase almost continuously at the E to H mode transition under low pressure.

Effects of substrate temperature upon optical properties of ZnTe epilayers grown on (100) GaAs substrates by MOVPE

AbstractThe photoluminescence (PL) properties of the ZnTe epilayers grown on (100) GaAs substrates with various substrate temperatures have been investigated. It has been demonstrated that the PL spectra depend strongly on the substrate temperature. A too low (390 °C) or too high (440 °C) substrate temperature deteriorates the epilayer quality due to the formation of defects or/and to the inclusion of impurities. A moderate substrate temperature (around 420 °C) is suitable to obtain a high‐quality epilayer with the narrow spectral width and strong emission intensity. This is attributed to the moderate substrate temperature improving the crystallinity of the ZnTe epilayer by enhancing recrystallization of the adsorbed precursors.

New Luminescent Mesoporous Material Covalent Bonded with Europium (III) Organic/Inorganic/Polymeric Hybrid

Luminescent ternary organic-inorganic-polymeric mesoporous hybrid material Eu-(PA-SBA-15)-PMAA was prepared in situ through hydrothermal and solvothermal method based on hydrolysis and co-polycondensation. The organic ligand PA (O-phthalic anhydride) was modified by silane coupling reagent APS ((3-aminopropyl) triethoxysilane) to generate the precursor PA-Si which was used to form the ordered inorganic Si-O networks through direct co-hydrolysis and co-polycondensation process with SBA-15 in the presence of Pluronic P123 surfactant as a template. TEOS (tetraethoxysilane) was used to promote the hydrolysis and condensation process. Eu3+ complex Eu(PA-Si)3 was covalently linked to the ordered mesoporous SBA-15 and organic polymer PMMA which was synthesized by addition polymerization reaction of the monomer MMA (methyl methacrylate) in the presence of the initiator BPO (benzoyl peroxide). Moreover, the binary organic-inorganic mesoporous hybrid material Eu (PA-SBA-15)3 without polymer was also synthesized simultaneously for comparison. The luminescence properties of the hybrids were characterized in detail. The results show the ternary hybrid exhibits stronger emission intensity, longer lifetime and higher quantum efficiency than binary one which proves that the introduction of the organic polymer PMMA brings improvement to the hybrid system.

Ru(II)–M(I) (M = Rh and Ir) bimetallic complexes based on a bridging ligand composed of 1,10-phenanthroline and N-heterocyclic carbene: Coordination chemistry and detection property of carbon monoxide

A series of mono-RuII and di-nuclear complexes, [RuII–MI(COD)Cl and RuII–MI(CO)2Cl] (M=Ir, Rh), have been prepared by using a bridging ligand, 1,3-dibutyl-2,3-dihydro-1H-imidazo[4,5-f][1,10]phenanthroline-2-yl (IL). This bridging ligand consists of 1,10-phenanthroline and N-heterocyclic carbene (NHC) and has two coordinating sites which can bind two different metals. The complexes synthesized have been fully characterized by 1H NMR, 13C NMR, high resolution mass spectrometry (HRMS), elemental analysis, and X-ray crystallography in one case. These complexes exhibited typical π–π∗ and metal-to-ligand charge transfer (MLCT) bands in the UV and visible regions, respectively. Compounds RuII–IrI(CO)2Cl and RuII–RhI(CO)2Cl have the stronger emission intensities and the longer luminescence lifetimes (τ) than those of RuII–IrI(COD)Cl and RuII–RhI(COD)Cl, respectively. Complex RuII–IrI(COD)Cl was applied to detect carbon monoxide.

Synthesis and optical properties of water soluble CdSe/CdS quantum dots for biological applications

Water soluble CdSe/CdS quantum dots (QDs) have been synthesized directly in aqueous solution with sodium citrate as surfactant agent. The QDs are mono-dispersed in water and have strong luminescent emission intensity under excitation of ultraviolet light. The emission maxima of the QDs can be tuned in a wider range from 555 to 615 nm in water by changing synthesis conditions. The result of the synthesis of water-soluble CdSe and CdSe/CdS QDs shows the high quality of the QDs with the quite narrow luminescence emission band and photostability. The results show the strongest intensity of photoluminescence emission in media with pH value at about from 8–8.5, which are pH physiological environments. The luminescence intensity increases when the QDs are coated with a polyethylene glycol (PEG) or bovine serum albumin (BSA) protein layer, the lifetime also increases.

Characteristics of microwave plasma induced by lasers and sparks

Characteristics of the plasma light source of microwave (MW) plus laser-induced breakdown spectroscopy (LIBS) or spark-induced breakdown spectroscopy (SIBS) were studied. The plasma was initially generated by laser- or spark-induced breakdown as a plasma seed. A plasma volume was then grown and sustained by MWs in air. This MW plasma had a long lifetime, large volume, strong emission intensity, and high stability with time. These characteristics are suitable for applications in the molecular analysis of gases such as OH or N(2). Because the plasma properties did not depend on laser or spark plasma seeds, the resulting plasma was easily controllable by the input power and duration of the MWs. Therefore, a significant improvement was achieved in the spectral intensity and signal-to-noise ratio. For example, the peak intensity of the Pb spectra of LIBS increased 15 times, and that of SIBS increased 880 times without increases in their background noise. A MW-enhanced plasma light source could be used to make the total system smaller and cheaper than a conventional LIBS system, which would be useful for real-time and in situ analysis of gas molecules in, for example, food processing, medical applications, chemical exposure, and gas turbine or automobile air-to-fuel ratio and exhaust gas measurement.

Photoluminescence characterization of a novel red-emitting phosphor In2(MoO4)3:Eu3+ for white light emitting diodes

The red-emitting phosphor In2(MoO4)3:Eu3+ with cubic crystal structure was synthesized by a conventional solid-state reaction technique and its photoluminescence properties were investigated. The prepared phosphor can be efficiently excited by ultraviolet (395nm) and blue (466nm) light. The emission spectra of the phosphor manifest intensive red-emitting lines at 612nm due to the electric dipole 5D0→7F2 transitions of Eu3+. The chromaticity coordinates of x=0.63, y=0.35 (λex=395nm) and x=0.60, y=0.38 (λex=466nm) are close to the standard of National Television Standard Committee values (NTSC) values. The concentration quenching of In2(MoO4)3:Eu3+ is 40mol% and the concentration self-quenching mechanism under 466nm excitation was the dd intereaction. As a result of the strong emission intensity and good excitation, the phosphor In2(MoO4)3:Eu3+ is regarded as a promising red-emitting conversion material for white LEDs.

Influence of Ammoniating Temperatures on Microstructures, Morphologies and Optical Properties of GaN/Nb Nanostructures by RF Magnetron Sputtering Technique

AbstractGaN nanowires and nanorods have been successfully synthesized on Si (111) substrates by magnetron sputtering through ammoniating Ga2O3/Nb thin films and the effects of ammoniation temperatures on growth of GaN nanowires and nanorods were analyzed in detail. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra were carried out to characterize microstructures, morphologies, and optical properties of GaN samples. The results demonstrate that sample after ammoniation at 950 °C is single crystal GaN with hexagonal wurtzite structure and high crystalline quality, having the size of 30 - 80 nm in diameter. After ammoniation at 1000 °C, GaN nanorods appear with smooth and clean surface and more than 100 nm in diameter. The optical properties of GaN nanowires grown at 950 °C and nanorods grown at 1000 °C are best with strong emission intensities.

The influences of Sr or Ba substitution on the structure and luminescence properties for Ca2.955Si2O7: 0.045Eu2+ phosphor

A series of Ca2.955-xMxSi2O7: 0.045Eu2+ (M= Sr, Ba, x= 0.10.5) phosphors is prepared by solid-state reaction method. The influences of Sr or Ba with larger radius substitution on the structure and luminescence properties for Ca2.955Si2O7: 0.045Eu2 + phosphor are investigated. The XRD results show that a small quantity of Sr or Ba substitution of Ca does not change the structure of Ca3Si2O7 host which has a monoclinic crystal structure. Before the substitution, the emission peak is at about 574 nm. If the Ca2+ ions are substituted by Sr2+ or Ba2+ ions, the emission peak is blue shifted when the Sr or Ba concentration is 0.5. In addition, for the same doping contents of Sr and Ba, the Ba doped phosphors have stronger emission intensity.

Electrospinning Fabrication of Tb(BA)3phen/PANI/PVP Luminescence-Electricity Bifunctional Composite Nanofibers

A new kind of luminescence-electricity bifunctional Tb(BA)3phen/PANI/PVP composite nanofibers was fabri- cated through doping of polyaniline (PANI) and terbium complex (Tb(BA)3phen) in polyvinyl pyrrolidone (PVP) via elec- trospinning. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), fluorescence spectrometer and broadband dielectric spectrometer were used to characterize the samples. The results indicated that the average diameter of the Tb(BA)3phen/PANI/PVP composite nanofibers was ca. (331±43) nm. Under the excitation of 276 nm ultraviolet, Tb(BA)3phen/PANI/PVP composite nanofibers emitted the predominant emission peaks at 491, 547 and 585 nm, corre- sponding to 5 D4→ 7 F6, 5 D4→ 7 F5 and 5 D4→ 7 F4 transitions of Tb 3 + , respectively. The strongest emission intensity was acquired when the mass ratios of Tb(BA)3phen, PANI and PVP was 15∶10∶100. The electric conductivity of the composite nanofi- bers was increased with the increase of PANI content, and reached 1.531×10 -6 S/cm in high frequency electric field (10 6 Hz) when the mass ratio of PANI to PVP was 50%. The luminescent intensity and electric conductivity of Tb(BA)3phen/ PANI/PVP composite nanofibers can be tuned via adding of various amounts of Tb(BA)3phen and PANI into the composite nanofibers. This preparative technique is of universal significance and can be used to fabricate other similar bifunctional lu- minescence-electricity composite nanofibers. This new type bifunctional luminescence-electricity composite nanofibers will have wide applications in many fields due to their excellent fluorescence and conductivity. Keywords electrospinning; Tb(BA)3phen/PANI/PVP; nanofiber; polyaniline

2.1 μm emission of Tm3+/Ho3+ - doped antimony-silicate glasses for active optical fibre

2.1 μm emission of Tm3+/Ho3+ - doped antimony-silicate glasses for active optical fibre Tm3+/Ho3+ - doped antimony-silicate optical fibre with 2.1 μm emission has been presented. Luminescence corresponding to 5I7 → 5I8 transition in holmium was obtained by energy transfer between Tm3+ and Ho3+ ions. The analysis of the luminescence mechanism showed a significant influence of the glass composition (low phonon content) on the emission intensity. Optimization of the active elements content, presented in the paper, allowed to indicate that a strong emission intensity at 2 μm in the fabricated glasses was obtained for the molar composition of 1% Tm2O3 : 0.75% Ho2O3. According to the Förster-Dexter theory, the efficiency of energy transfer of the 3F4 (Tm3+) → 5I7 (Ho3+) transition was calculated. Moreover, it was found that the full width at half maximum (FWHM) of luminescence in the range of 1.6 - 2.2 μm strongly depends on the Tm3+/Ho3+ ratio. The optimization of Tm3+/Ho3+ transfer in antimony-silicate glasses allowed to fabricate optical fibre with narrowing and red-shifting of emission at 2.1 μm.

Characterization and Luminescence of Eu3+ Ions Doped 12CaO·7Al2O3 Nanopowders

Eu3+ ions doped 12CaO 7Al2O3 (C12A7) powders with different Eu3+ concentrations were prepared by sol-gel combined with solid state reaction method. The results of XRD and Raman spectra showed that single cubic phase polycrystalline C12A7:Eu3+ powders were prepared. The absorption peaks attributed to f-f transition of Eu3+ ion can be observed, indicating that Eu3+ had been incorporated into C12A7 lattice site. Visible PL peaks around 578, 588, 614 nm were ascribed to 5D0 --> 7FJ (J = 0, 1, 2) transitions of Eu3+ under the excitation of 488 nm line. The PL of C12A7:Eu3+ showed the strongest emission intensity at Eu3+ concentration of 0.5 at%. Two different types of Eu3+ centers were identified by the two lines from 5D0 --> 7F0 transition emission. The doping mechanism of C12A7:Eu3+ might be attributed to Eu3+ ions substitution for two types of Ca2+ lattice sites in C12A7. The temperature dependent PL spectra of Eu-doped C12A7 were measured in the range from 100 to 300 K under the excitation of 488 nm laser line. The PL intensities as a function of temperature were well fitted by using a unified theoretical model, considering thermal activation and nonradiative energy transfer processes.

VUV photoluminescence of La1−xGdxPO4:Tb3+ green phosphors synthesized by ultrasonic spray pyrolysis

(La1−xGdx)0.94PO4:Tb0.06 (0 ≤ x ≤ 1.0) green phosphors were synthesized by an ultrasonic spray pyrolysis process. The annealed (La1−xGdx)0.94PO4:Tb0.06 phosphors exhibited the formation of a single-phase oxide with the monoclinic monazite structure. Higher Gd3+ content yielded a smaller lattice parameter. The phosphors emitted green light due to the 5D4→7FJ (J = 3, 4, 5, and 6) transition of Tb3+ at 489 nm, 543 nm, 585 nm, and 621 nm, respectively. The predominant peak at 543 nm was nearly a single peak, which was responsible for the green color emission. Among the (La1−xGdx)0.94PO4:Tb0.06 phosphors, the strongest emission intensity was obtained for (La0.25Gd0.75)0.94PO4:Tb0.06.

Fluorescent metal nanoshell and CK19 detection on single cell image

In this article, we report the synthesis strategy and optical properties of a novel type of fluorescence metal nanoshell when it was used as imaging agent for fluorescence cell imaging. The metal nanoshells were made with 40 nm silica cores and 10 nm silver shells. Unlike typical fluorescence metal nanoshells which contain the organic dyes in the cores, novel metal nanoshells were composed of Cy5-labelled monoclonal anti-CK19 antibodies (mAbs) on the external surfaces of shells. Optical measurements to the single nanoparticles showed that in comparison with the metal free labelled mAbs, the mAb-Ag complexes displayed significantly enhanced emission intensity and dramatically shortened lifetime due to near-field interactions of fluorophores with metal. These metal nanoshells were found to be able to immunoreact with target cytokeratin 19 (CK19) molecules on the surfaces of LNCAP and HeLa cells. Fluorescence cell images were recorded on a time-resolved confocal microscope. The emissions from the metal nanoprobes could be clearly isolated from the cellular autofluorescence backgrounds on the cell images as either individuals or small clusters due to their stronger emission intensities and shorter lifetimes. These emission signals could also be precisely counted on single cell images. The count number may provide an approach for quantifying the target molecules in the cells.

Spectroscopic studies on the lanthanide sensitized luminescence and chemiluminescence properties of fluoroquinolone with different structure

Lanthanide sensitized luminescence and chemiluminescence (CL) are of great importance because of the unique spectral properties, such as long lifetime, large Stokes shifts, and narrow emission bands characteristic to lanthanide ions (Ln 3+). With the fluoroquinolone (FQ) compounds including enoxacin (ENX), norfloxacin (NFLX), lomefloxacin (LMFX), fleroxacin (FLRX), ofloxacin (OFLX), rufloxacin (RFX), gatifloxacin (GFLX) and sparfloxacin (SPFX), the luminescence and CL properties of Tb 3+–FQ and Eu 3+–FQ complexes have been investigated in this contribution. Ce 4+–SO 3 2− in acidic conditions was taken as the CL system and sensitized CL intensities of Tb 3+–FQ and Eu 3+–FQ complexes were determined by flow-injection analysis. The luminescence and CL spectra of Tb 3+–FQ complexes show characteristic peaks of Tb 3+ at 490 nm, 545 nm, 585 nm and 620 nm. Complexes of Tb 3+–ENX, Tb 3+–NFLX, Tb 3+–LMFX and Tb 3+–FLRX display relatively strong emission intensity compared with Tb 3+–OFLX, Tb 3+–RFX, Tb 3+–GFLX and Tb 3+–SPFX. Quite weak peaks with unique characters of Eu 3+ at 590 nm and 617 nm appear in the luminescence and CL spectra of Eu 3+–ENX, but no notable sensitized luminescence and CL of Eu 3+ could be observed when Eu 3+ is added into other FQ. The distinct differences on emission intensity of Tb 3+–FQ and Eu 3+–FQ might originate from the different energy gap between the triplet levels of FQ and the excited levels of the Ln 3+. The different sensitized luminescence and CL signals among Tb 3+–FQ complexes could be attributed to different optical properties and substituents of these FQ compounds. The detailed mechanism involved in the luminescence and CL properties of Tb 3+–FQ and Eu 3+–FQ complexes has been investigated by analyzing the luminescence and CL spectra, quantum yields, and theoretical calculation results.