Visible Luminescence Properties Research Articles

Visible and NIR steady-state luminescence properties of Dy3+ ions-doped calcium phosphate glasses for light-emitting diodes

In this paper, we systematically investigate photoluminescence attributes of dysprosium (Dy3+) ions-doped calcium phosphate, (99-x) P2O5 + x CaO + 1.0 Dy2O3 (x = 20, 30 and 40) (CaPDy) glass samples fabricated via the melt-quenching method. The luminescence emission spectra unveiled the visible emission at 484 nm and 573 nm and near-infrared emission at 1011 nm under the excitation wavelength of 349 nm. The emission decay kinetic studies reveal that the decay profiles exhibit non-exponential behaviour. Furthermore, the CIE chromaticity coordinates, and the ratio of Y/B using 573 nm 484 nm emission intensities were evaluated and further utilized to estimate the CCT values. The results show that the studied glass samples has potential for the yellowish cool light applications.

Effect of Eu3+ ions concentration on visible red luminescence and radiative shielding properties of SrO–Al2O3– BaCl2–B2O3– TeO2 glasses

Trivalent europium (Eu3+) ions doped 10SrO-(10-x)Al2O3–10BaCl2–60B2O3–10TeO2 glasses were fabricated by the melt-and-quenching technique and characterized for excitation, absorption, emission, decay methods to analyze the suitability of the glasses for photonic device applications. In addition, gamma attenuation data of the prepared glasses were Obtained for energies 15 keV ≤ E ≤ 10 MeV using FLUKA and XCOM methods to check their suitability for radiative shielding purposes. Direct allowed, indirect allowed band gaps and Urbach energies were estimated from absorption spectra. Emission spectra obtained for an excitation wavelength of 362 nm have been used to estimate J-O intensity parameters Ωλ (where λ = 2, 4). The intensity parameters Ω2 and Ω4 were again used to evaluate various radiative properties for the emission transition 5D0→7F2 of Eu3+ ions doped OCBT glasses. Decay curves were well fitted by single exponential and in turn used to estimate experimental lifetime (τexp) of metastable state (5D0) of Eu3+ions. The analysis on radiative properties showed that 2.5 mol % of Eu3+ ions activated OCBT glasses for the emission transition 5D0→7F2 is well suitable for visible red lasers and display applications. Analysis of evaluated interaction parameters for gamma radiation fast and thermal neutrons showed clear cut dependence on the Eu2O3 content of the glasses. In addition, the radiation absorption ability of the glasses was compared with different classes of concrete, commercial glass shields, and nonconventional shielding materials. The present glasses showed great potential for deployment in radiation absorption roles in nuclear technologies.

Revisiting the luminescence properties of Er3+, Tm3+ and Ho3+ doped Bi4Ge3O12 rod-type crystal fibers for the laser application

BGO single crystals doped with Er3+, Tm3+ and Ho3+ rare-earth ions were prepared in the form of rod-type crystal fibers via the micro-pulling down technique to perform an extensive investigation of their visible, near- and mid-infrared luminescence properties and to really decide on their interest as solid-state laser media in the various spectral domains. Revisiting and completing the absorption spectra already available in the literature led to the derivation of more reliable “effective” radiative lifetimes and branching ratios. Registration of the fluorescence decays of the most important emitting levels versus dopant concentrations led for the first time to an unambiguous determination of “intrinsic” emission lifetimes – corresponding to negligible contributions from inter-ionic energy-transfers - and non-radiative multiphonon relaxation rates. Such data also allowed for the determination of the dominant phonon energy which comes into play in the electron-phonon coupling responsible for these multiphonon relaxation processes and for its lattice vibration origin, i.e. a high phonon energy of the order of 820 cm−1 corresponding to the coupling between bending vibrations of (GeO4)4- tetrahedra and vibrations corresponding to motions of these (GeO4)4- tetrahedra against the Bi3+ ions for which the rare-earth dopant ions substitute. Using the above data and different methods for the calibration of the registered emission spectra in cross section unit and for the derivation of gain cross section curves finally show that mid-infrared emissions of Er:BGO, Tm:BGO and Ho:BGO around 1.55 μm, 1.9 μm and 2 μm, respectively, occur with comparable gain cross sections as in the most important reference mid-infrared laser materials, although over slightly shifted thus complementary spectral domains. It is shown that potentialities also exist with Tm:BGO in the blue, deep-red and near-infrared spectral domains around 470 nm, 800 nm and 1.45 μm, by pumping the crystals with conventional pump sources and using some suitable co-dopants to avoid detrimental self-terminating processes.

Luminescence properties and excitation behavior of ICG-conjugated nanoparticles for optical theranostics

Combining photothermal/photodynamic effect of a nanocomposite with photosensitizer can work out a key component of the theranostic nanoplatform of physical therapy for tumors. Herein, we report a type of rare earth-doped core-dual-shell nanoparticles (CDSNPs) conjugated with indocyanine green (ICG), CDSNPs-ICG, which possess an enhancement of optical properties under 980 nm excitation. A relevant energy transfer mechanism underlying rare earth nanoparticles with ICG was proposed to interpret the enhancement of visible light, NIR-I and NIR-II luminescent properties. The excitation behavior of CDSNPs-ICG was theoretically addressed through the hole-electron analysis based on time-dependent density functional theory, and the approach reveal the charge transfer of ICG after compositing rare earth. Photothermal/photodynamic therapy capabilities of CDSNPs-ICG were appraised in vitro and in vivo, indicating that CDSNPs-ICG have a high potential to be applied to optical theranostics of tumor.

Visible and near-infrared luminescence properties of Nd3+/Yb3+ co-doped Gd2O3 phosphors for highly sensitive optical thermometry.

Phosphors with rare earth (RE) ions are widely applied to optical temperature measurements. Moreover, the near-infrared (NIR) emission of phosphors has potential applications in the biological field. Herein, Gd2O3:x%Nd3+/Yb3+(0.2 ≤ x ≤ 0.8) samples are successfully synthesized by the sol-gel method, and their phase and morphology are characterized. The XRD data are refined by Rietveld. Under 980 nm continuous wave (CW) laser excitation, the upconversion (UC) and downshift (DS) emissions are studied. The temperature sensing performances of thermally coupled levels (TCLs) and non-thermally coupled levels (non-TCLs) of Gd2O3: Nd3+/Yb3+ phosphors are investigated through the fluorescence intensity ratio (FIR) technology. In the temperature range of 303-523 K, the maximum relative sensitivity of I761 nm/I550 nm reaches 6.54% K-1, which is based on non-TCLs. At the same time, the maximum relative sensitivity of I761 nm/I1000 nm-1500 nm reaches 3.13%. In addition, the influence of the laser induced heating (LIH) effect is studied. Compared with square wave (SW) pumping, the relative sensitivity would decrease at CW excitation. Finally, the durability and temperature uncertainty are also discussed. The results prove that the Gd2O3:Nd3+/Yb3+ samples present higher relative sensitivity and durability and lower temperature uncertainty in the biological window. Therefore, the phosphors can be used as optical thermometers in the biological field.

Morphology modulation and near infrared to visible upconversion luminescence properties of Er3+/Yb3+-doped α-NiMoO4 nanoparticles

In this work, for the first time, the near infrared (NIR) to visible upconversion luminescence (UCL) properties of α-NiMoO4 were explored by doping with Er3+/Yb3+ ions. A microwave hydrothermal method was used to fabricate Er3+ (2 mol%)/Yb3+ (12–20 mol%)-doped α-NiMoO4 phosphors. X-ray diffraction patterns suggest the formation of the Yb2(MoO4)3 phase, which is beneficial for UCL enhancement. Nanorods (α-NiMoO4), bundles of rods (α-NiMoO4: Er3+), and cactus (α-NiMoO4: Er3+/Yb3+)-like morphologies were obtained, and a morphology modulation mechanism has been proposed. TEM elemental mapping, XPS, and UV–Vis DRS measurements confirm the existence of Ni, Mo, O, Er, and Yb elements in the samples. The synthesized samples demonstrate intense green (522 nm: 2H11/2 → 4I15/2 and 546: 4S3/2 → 4I15/2), weak red (660 nm: 4F9/2 → 4I15/2), and NIR (803 nm: 4S3/2 → 4I13/2) emissions under 980 nm excitation. Downshifting emission was also obtained at 1538 nm (Er3+: 4I13/2 → 4I15/2). The highest emission intensity was achieved in the Er3+ (2 mol%)/Yb3+ (15 mol%)-doped α-NiMoO4 sample. An intense green color and strong UCL were observed in the MN/Er2/Yb15 sample based on CIE chromaticity and fluorescence decay curves. A graph of pump power versus intensity for the phosphor samples indicates that the upconversion process occurs by two photonic processes. The proposed energy transfer process is explained based on ground state absorption and excited state absorption. The particles were found to be safe at doses up to 0.125 mg/mL, as assessed by cytotoxicity investigation in bovine skeletal muscle cells. The obtained results open the possibilities of potential applications of Er3+/Yb3+-doped α-NiMoO4 as an efficient luminescent material for bioimaging applications.

Trap assisted visible light luminescent properties of hydrothermally grown Gd doped ZnO nanostructures

Pristine ZnO and Gd-doped ZnO nanostructures were synthesized via the hydrothermal route to study the influence of Gd doping on the growth and properties of the nanostructures. Synthesized nanostructures were characterized by powder x-ray diffraction technique (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS) and UV–visible spectroscopy. Optical study demonstrated that the nanostructures exhibit good visible light transmittance and absorbs ultraviolet light energy. Photoluminescence (PL) study of the nanostructures showed that Gd-doping enhanced the PL activity of the nanostructures by possible introduction of the defect levels. The corresponding augmentation in PL intensity (visible light luminescent intensity) is attributed to comparative increase in crystallinity, complex defects (traps) and electron hole pair recombination rate. This enhanced luminescent property of Gd-doped ZnO nanostructures can be exploited for the luminescence based applications like sensors, UV-Lasers, phosphors, LEDs, luminescent biolabels, etc.

Visible and near-infrared luminescent properties of Pr3+/Yb3+ co-doped lanthanum ortho-niobate phosphors

Pr3+ – Yb3+ co-doped LaNbO4 phosphors were obtained by solid-state reaction and their upconversion properties were investigated. XRD analysis demonstrated the absence of secondary phase in the as-prepared materials. UC measurements revealed RGB and IR bands whose intensities have been improved by the increment of Yb3+ concentration. In addition, the phosphors showed a deep red emission at 652 nm (3P0 → 3F2) which is strongly related to the local asymmetry of Pr3+ sites according to the Judd–Ofelt's theory. The CIE color coordinates shift from the green region to the blue region suggesting the phosphors can be tuned by adjusting the concentration of Yb3+. Furthermore, the chromatic coordinates of the LNO: Pr0.1% - Yb2% phosphor did not show significant variation at different pump powers indicating this material could be employed in non-tunable display devices and security applications.

Er3+-doped niobium alkali germanate glasses and glass-ceramics: NIR and visible luminescence properties

Niobium alkali germanate glasses doped with Er3+ up to 4.0 mol% were synthesized by the melt-quenching technique. Glass-ceramics were obtained by controlled heat treatment of the pristine glass. Thermal and optical properties were investigated and are shown to depend on the erbium content. The main radiative parameters were obtained based on the Judd-Ofelt theory. The change of radiation energy processes and modification of the environment of the earth-rare ion occurs in samples with high erbium concentrations. In general, strong enhancement of upconversion emission occurs due to the efficient process of excited-state absorption for the high erbium content samples. Visible tunable phosphors emitting either red-to-green light depends on the erbium content and heat treatment. In addition, these glasses and glass-ceramics samples have high thermal stability and wide transmission window. For these reasons, Er3+-doped niobium germanate glasses and glass-ceramics may be suitable for photonic device applications, especially as visible laser.

Visible and near-infrared luminescent properties of Pr3+ doped strontium molybdate thin films by a facile polymer-assisted deposition process

Quartz substrate supported Praseodymium (Pr) doped strontium molybdate (SrMoO4) thin films with good uniformity and outstanding fluorescent properties are successfully fabricated via a facile polymer-assisted deposition (PAD) method. In combination with the strong chelating effect of water-soluble polymer on metal cations, the free cations without chelating are effectively ruled out but the remaining chelating metal cations are employed for the highly uniform and accurate stoichiometry luminescent SrMoO4: Pr thin films, layer-by-layer mounting on the common quartz substrates. More importantly, the excellent release of stress from polymer during the growth process of epitaxial thin film can effectively overcome the mismatch between thin film and common quartz substrate and then guarantee the quality of thin film. Under the ultraviolet (UV) light excitation, the samples show high luminescence intensity both in visible and near-infrared (NIR) regions peaked at 646 nm and 1037 nm, mainly ascribing to the transitions of 3P0 → 3F2 and 1G4 → 3H4 of Pr3+ ions. The luminescent properties can be tailored by optimizing the number of spin-coated layers and doping concentrations. The maximum emission occurs at 4 mol% of Pr3+ dopant, and it exhibits an impressive high photoluminescence quantum yield (QY) of up to 86.12%. These results evidently demonstrate the present PAD method is a useful prototype for preparing high performance luminescent thin films even on the cheap quartz substrate.

Synthesis, microstructure and visible luminescence properties of vertically aligned lightly doped porous silicon nanowalls

Abstract Silicon nanowall templates in nonporous and porous forms have been prepared by 4.8 M HF and 0.2 M H2O2 etching of lightly boron doped silicon (100) wafers at room temperature and their morphology, microstructure and visible photoluminescence properties were studied. Metal assisted chemical and metal assisted anodic polarization etching methods were used respectively to produce these morphologically distinct silicon nanowalls. It is shown from the analysis of photoluminescence results that porous silicon nanowalls emit red and orange radiation signals. This observation is in contrast with nonporous silicon nanowalls that did not show any visible luminescence features. The microscopy results revealed that pores and inter-pore Si regions in porous silicon nanowalls are interconnected in the form of skeletal morphology with quantum dimensions. Based on the temperature dependent luminescence results and the structure dimensions evaluated from the microscopy results, it is concluded that the red and orange emission in porous silicon nanowalls originates from silicon quantum structures and Si-O-Si bonded amorphous structures respectively. The effect of Si nanostructures and its dimensional dependence on photoluminescence properties in porous silicon nanowalls are also discussed. The synthesis and photoluminescence mechanism discussed in this work is very much useful for the development of silicon based functional porous materials for nanoscale devices application.

Up-conversion luminescence in low phonon heavy metal oxide glass co-doped with Er3+/Ho3+

In this paper, heavy metal oxide glasses co-doped with erbium and holmium ions have been synthesized. Glass composition, based on the bismuth and germanium oxides, has been selected in terms of high thermal stability (delta T = 125 °C), high refractive index (n = 2.19) and low maximum phonon energy (hvmax = 724 cm-1). Up-conversion luminescence spectra under the 980 nm laser diode excitation have been observed as a result of radiative transitions within the quantum energy level structures of Er3+ and Ho3+ ions. Optimization of rare earth ions content has been conducted, the highest emission intensity in the visible wavelength range has been observed in glass co-doped with molar concentration 0.5 Er2O3 / 0.5 Ho2O3. Full Text: PDF ReferencesF. Zhang, Z. Bi, A. Huang, Z. Xiao, "Visible luminescence properties of Er3+?Pr3+ codoped fluorotellurite glasses", Opt. Materials 41, 112 (2014). CrossRef S. Li, S. Ye, T. Liu, H. Wang, D. Wang, "Enhanced up-conversion emissions in ZnO-LiYbO2:RE3+ (RE = Er or Ho) hybrid phosphors through surface modification", J. All. Comp. 658, 85 (2016). CrossRef J. Fu, X. Zhang, Z. Chao, Z. Li, J. Liao, D. Hou, H. Wen, X. Lu, X. Xie, "Enhanced upconversion luminescence of NaYF4:Yb, Er microprisms via La3+ doping", Opt. Laser Tech. 88, 280 (2017). CrossRef Y. Tian, R. Xu, L. Hu, J. Zhang, "2.7 ?m fluorescence radiative dynamics and energy transfer between Er3+ and Tm3+ ions in fluoride glass under 800 nm and 980 nm excitation", J. Quant. Spec. Rad. Tra. 113, 87 (2012). CrossRef M. Zhang, A. Yang, Y. Peng, B. Zhang, H. Ren, W. Guo, Y. Yang, C. Zhai, Y. Wang, Z. Yang, D. Tang, "Dy3+-doped Ga?Sb?S chalcogenide glasses for mid-infrared lasers", Mat. Res. Bul. 70, 55 (2015). CrossRef G. Yang, T. Li, "Broadband 1.53 ?m emission in Er3+-doped Ga-Bi-Pb-Ge heavy metal oxide glasses", J. Rare Earths 26, 924 (2008). CrossRef Y. Guo, Y. Tian, L. Zhang, L. Hu, J. Zhang, "Erbium doped heavy metal oxide glasses for mid-infrared laser materials", J. Non-Cryst. Solids 377, 119 (2013). CrossRef Z. Hou, Z. Xue, F. Li, M. Wang, X. Hu, S. Wang, "Luminescence and up-conversion mechanism of Er3+/Ho3+ co-doped oxyfluoride tellurite glasses and glass?ceramics", J. All. Comp. 577, 523 (2013). CrossRef X. Li, Q. Nie, S. Dai, T. Xu, L. Lu, X. Zhang, "Energy transfer and frequency upconversion in Ho3+/Yb3+ co-doped bismuth-germanate glasses", J. All. Comp. 454, 510 (2008). CrossRef S.S. Rojas, J.E. De Souza, M.R.B. Andreeta, A.C. Hernandes, "Influence of ceria addition on thermal properties and local structure of bismuth germanate glasses", J. Non-Cryst. Solids 356, 2942 (2010). CrossRef M.S. Ebrahim, Irina, Mid-infrared coherent sources and applications, Springer (2008). CrossRef T. Ragin, J. Zmojda, M. Kochanowicz, P. Miluski, P. Jelen, M. Sitarz, D. Dorosz, "Enhanced mid-infrared 2.7 ?m luminescence in low hydroxide bismuth-germanate glass and optical fiber co-doped with Er3 +/Yb3 + ions", J. Non-Cryst. Solids 457, 169 (2017). CrossRef K. Biswas, A.D. Sontakke, R. Sen, K. Annapurna, "Enhanced 2 ?m broad-band emission and NIR to visible frequency up-conversion from Ho3+/Yb3+ co-doped Bi2O3?GeO2?ZnO glasses", Spectr. Acta. Part A, Mol. Biomol. Spectr. 112, 301-308 (2013). CrossRef R.S. Romaniuk, D. Dorosz, J. Żmojda, M. Kochanowicz, W. Mazerski, "Upconversion luminescence in tellurite glass codoped with Yb3+/Ho3+ ions", Proc. of SPIE 8903, 890307 (2013). CrossRef

Self-assembly of luminescent Zn–Ln (Ln = Sm and Nd) nanoclusters with a long-chain Schiff base ligand

Two Zn–Ln rectangular nanoclusters [Zn8Ln4L8(OAc)8](OH)4 (Ln = Sm (1) and Nd (2)) with sizes of 9 × 19 × 28 Å were constructed using a long-chain Schiff base ligand built around a flexible (CH2)3O(CH2)2O(CH2)3 backbone, and their visible and NIR luminescence properties were determined.

Construction of luminescent high-nuclearity Zn–Ln rectangular nanoclusters with flexible long-chain Schiff base ligands

Three Zn-Ln clusters [Ln8Zn6(L1)2(OAc)20(O)2(NO3)4(OH)4] (Ln = Sm (1) and Nd (2)) and [Nd4Zn4(L2)2(OAc)10(NO3)2(OH)4] (3) were prepared using two long-chain Schiff base ligands. The Zn-Ln clusters exhibit interesting nano-square-like structures. Their visible and NIR luminescence properties were investigated.

Employing one crystalline phase to gain different phosphor emissions for distinctive applications: Preparation, crystallization and luminescence of SrAl2B2O7 with different additions via glass ceramic technique

SrAl2B2O7 phosphor was crystallized via glass-ceramic technique. The effect of adding TiO2, Eu2O3, Dy2O3 and CeO2 on both crystallization process and luminescent properties were studied using differential thermal analysis (DTA), X-Ray diffraction analysis (XRD), scanning electron microscope (SEM), Fourier-Transform infrared absorption spectra (FT-IR), optical ultra violet (UV) -visible near infrared (NIR) absorption and fluorescence spectrophotometer. The batches were melted around 1450°C. New method to revealed reducing atmosphere was applied. DTA results show broad exothermic peak revealing surface crystallization. The XRD patterns depict crystallization of pure SrAl2B2O7 in hexagonal form. Presence of CeO2 enhances the crystallization of SrAl2B2O7 phase while TiO2 inhibit it. Increasing the time or temperature of heat treatment didn’t affect the nature of the crystalline phase. Optical UV–visible NIR absorption and luminescent properties clarified the presence of titanium and cerium ions as Ti4+ and Ce3+ form, while europium present in both Eu2+ and Eu3+. The resulting phosphor revealed different colors depending on the excited wavelength used and heat treatment applied.

Enhanced visible emissions of Pr3+-doped oxyfluoride transparent glass-ceramics containing SrF2 nanocrystals

The Pr3+-doped oxyfluoride transparent glass and glass-ceramic (GC) with the composition of 41SiO2 + 10Al2O3 + 25.5LiF + 23SrF2 + 0.5Pr2O3 were prepared and investigated their optical and luminescence properties. The formation of SrF2 nanocrystals in GC has been confirmed by X-ray diffraction (XRD) and transmission electron micrographs (TEM). The Fourier transform infrared spectroscopy (FT-IR) studies were used to examine the network structure characteristics of silicates in the glass matrices. The XRD and TEM results suggest that the Pr3+ ions are progressively incorporated into the SrF2 nanocrystals in the GC with increase in time of thermal treatment at 650°C, corresponding to the first crystallization temperature of the glass. The obtained visible emissions of Pr3+-doped GC are several times enhanced than that in the glass and the lifetime of the 3P0 level of the Pr3+ ions in glass and GC are found to be 7 and 12μs, respectively. Therefore, the enhanced visible emission and lifetimes in GC are due to the incorporation of Pr3+ ions into the lower phonon energy of SrF2 nanocrystals in the GCs. Moreover, the smaller difference in ionic radius between the added trivalent ions (Pr3+) and Sr2+ induces the larger enhancement of luminescence intensity in the GC. Hence, these enhanced visible luminescence properties indicate that the present glass and GC could be useful for photonic device applications.

Syntheses and Characterization of Three Coordination Polymers of Zinc(II) and Cadmium(II) with Dicarboxylates and Bis(thiabendazole) Ligands

Three d10 coordination polymers formulated as [Zn(L1)2(mip)]n (1), [Zn(L1)(2,6-ndc)]n (2) and [Cd(L2)0.5(bpdc)]n (3) (L1 = 1,1′-(1,3-propanediyl)bis(thiabendazole), L2 = 1,1′-(1,6-hexanediyl)bis(thiabendazole), H2mip = 5-methylisophthalic acid, 2,6-H2ndc = 2,6-naphthalenedicarboxylic acid, H2bpdc = 4,4′-biphenyldicarboxylic acid) were hydrothermally synthesized. Complexes 1–3 were characterized by elemental analysis, IR spectroscopy, X-ray powder diffraction analysis, and single crystal X-ray diffraction. Complexes 1 and 2 present different chain structures, both of them are extended into 2D supramolecular architectures via C–H···O hydrogen bonds, while 3 is a three-fold interpenetrating three-dimensional framework with binodal 4,4-connected mog topology. The thermal stability, UV–visible spectroscopy and luminescence properties of complexes 1–3 were also examined. Furthermore, complex 3 exhibits relatively positive catalytic activity towards the degradation of methyl orange in a Fenton-like process.

Optical spectra of Dy3+-doped GdVO4 and Ca3Sc2Ge3O12 crystals and evaluation of the Ω2/Ω6 ratio as a quality factor for the classification of Dy3+-activated crystalline hosts

The room temperature absorption spectra of Dy3+-doped GdVO4 and Ca3Sc2Ge3O12 crystals have been measured and analysed in the framework of the Judd–Ofelt Theory. The calculated intensity parameters have then been correlated with the intensities of the emission bands in the yellow and blue region. The analysis has then been extended to a number of host lattices using literature data, and a general empirical model has been proposed, correlating the Ω2/Ω6 and the yellow to blue (Y/B) ratio in order to define a criterion for predicting the visible luminescence properties of the Dy-activated crystalline materials.

Visible and near-infrared luminescence of polycatenated cationic pyridinone lanthanide networks

A series of isomorphic lanthanide coordination polymers [Ln(III)(MBP)2(NO3)2(Br)·2C3H6O] [Ln=Eu, Tb, Er, Yb, and Gd; MBP=N,N′-methylene-bis(pyridin-4-one)] featuring polycatenated sql cationic network and incorporated bromide counter ion were prepared. Their visible and near-infrared (NIR) luminescence properties were characterized by steady-state excitation and emission spectra, as well as luminescence lifetimes and quantum yields. The D 2d dodecahedron coordination geometry causes visible light excitations and strongly monochromatic emissions. The external heavy-atom environment induces remarkable enhancement on the NIR emissions. The sensitization processes are revealed by analyzing the electronic properties of MBP ligand.

Rare-Earth-Based Nanoparticles with Simultaneously Enhanced Near-Infrared (NIR)-Visible (Vis) and NIR-NIR Dual-Conversion Luminescence for Multimodal Imaging.

Multifunctional NaGdF4 :Yb(3+),Er(3+),Nd(3+) @NaGdF4 :Nd(3+) core-shell nanoparticles (called Gd:Yb(3+),Er(3+),Nd(3+) @Gd:Nd(3+) NPs) with simultaneously enhanced near-infrared (NIR)-visible (Vis) and NIR-NIR dual-conversion (up and down) luminescence (UCL/DCL) properties were successfully synthesized. The resulting core-shell NPs simultaneously emitted enhanced UCL at 522, 540, and 660 nm and DCL at 980 and 1060 nm under the excitation of a 793 nm laser. The enhanced UCL and DCL can be explained by complex energy-transfer processes, Nd(3+) →Yb(3+) →Er(3+) and Nd(3+) →Yb(3+) , respectively. The effects of Nd(3+) concentration and shell thickness on the UCL/DCL properties were systematically investigated. The UCL and DCL properties of NPs were observed under the optimal conditions: a shell Nd(3+) content of 20 % and a shell thickness of approximately 5 nm. Moreover, the Gd:Yb(3+) ,Er(3+) ,Nd(3+) @Gd:20 % Nd(3+) NPs exhibited remarkable magnetic resonance imaging (MRI) properties similar to that of a clinical agent, Omniscan. Thus, the core-shell NPs with excellent UCL/DCL/magnetic resonance imaging (MRI) properties have great potential for both in vitro and in vivo multimodal bioimaging.