Helix-constructed polar rare-earth iodate fluoride as a laser nonlinear optical multifunctional material.
ABSTRACT: The first trivalent rare-earth iodate fluoride nonlinear optical (NLO) crystal, Y(IO3)2F (YIF), was successfully designed and synthesized, featuring polarization-favorable helical chains constructed from trans-YO6F2 polyhedra and IO3 groups. It exhibited a suitable balance of a wide transparency range of 0.26-10.0 ?m, high laser damage threshold (LDT) of 39.6 × AgGaS2, and moderate second harmonic generation (SHG) effect of 2 × KDP. A series of doped RE:YIF (RE = Pr, Nd, Dy, Ho, Er, Tm, and Yb) crystals were easily synthesized benefiting from the spring-shaped helix structure, which possess wide absorption and emission peaks as well as long lifetime, especially in the visible and near-infrared regions. Particularly, the remarkable fluorescence properties of Nd and Yb doped YIF crystals are comparable to and even better than those of traditional self-frequency doubling (SFD) crystals such as YAB, YCOB, and GdCOB. Thus, these RE-doped YIF crystals are promising laser SFD crystals. This work also indicated that constructing helical chains should be an effective strategy for the design of inorganic polar materials.
Project description:A new thermographic phosphor based on chromium(III)-doped yttrium aluminum borate (YAB) is obtained as single crystals by high temperature flux growth and as a microcrystalline powder via solution combustion synthesis. The phosphor is excitable both in the blue (lambda(max) 422 nm) and in the red part of the spectrum (lambda(max) 600 nm) and shows bright NIR emission. The brightness of the phosphor is comparable to that of a well-known lamp phosphor Mn(IV)-doped magnesium fluorogermanate. At ambient temperatures, the Cr(III)-doped YAB shows high temperature dependence of the luminescence decay time, which approaches 1% per deg. The material shows no decrease in luminescence intensity at higher temperatures. The new phosphor is particularly promising for applications in temperature-compensated optical chemosensors (including those based on NIR-emitting indicators) and in pressure-sensitive paints.
Project description:Elucidation of upconversion nanoparticles (UCNPs) that can be excited by near-infrared (NIR) light is an interesting topic in the field of photodynamic therapy (PDT). However, the PDT efficiency of conventional UCNPs is limited due to the low quantum yield and overheating effect of the 980 nm light source. In this study, a light source with a wavelength of 808 nm was used as an excitation source for Nd-doped UCNPs to solve the overheating effect. UCNPs with a core@shell structure (NaYF4:Yb,Er,Nd@NaYF4:Yb,Nd) were synthesized to increase the upconversion emission efficiency. Dual-color emitting Er-doped UCNPs and dual photosensitizers (Chlorin e6 and Rose Bengal) were used for enhanced PDT. Each photosensitizer could absorb red and green emissions of the UCNPs to generate reactive oxygen species (ROS), respectively. The ROS generation in a dual photosensitizer system is significantly higher than that in a single photosensitizer system. Additionally, PDT induces immunogenic apoptosis. In this study, by utilizing a highly efficient PDT agent, PDT-induced apoptosis was studied by biomarker analysis.
Project description:Core/shell1/shell2/shell3 structured NaGdF4:Nd/NaYF4/NaGdF4:Nd,Yb,Er/NaYF4 nanocrystals were well designed and synthesized, each of the parts assume respective role and work together to achieve dual-mode upconverting (UC) and downconverting (DC) luminescence upon the low heat effect 800-nm excitation. Nd(3+), Yb(3+), Er(3+) tri-doped NaGdF4:Nd,Yb,Er UC layer [NIR (800 nm)-to-Visible (540 nm)] with a constitutional efficient 800 nm excitable property were achieved for the in-vitro bioimaging with low auto-fluorescence and photo-damage effects. Moreover, typical NIR (800 nm)-to-NIR (860-895 nm) DC luminescence of Nd(3+) has also been realized with this designed nanostructure. Due to the low heat effect, high penetration depth of the excitation and the high efficiency of the DC luminescence, the in-vivo high contrast DC imaging of a whole body nude mouse was achieved. We believe that such dual-mode luminescence NCs will open the door to engineering the excitation and emission wavelengths of NCs and will provide a new tool for a wide variety of applications in the fields of bioanalysis and biomedical.
Project description:This report details spectroscopic characterizations of rare-earth, core-shell nanoparticles decorated with the <i>f</i>-element chelator 3,4,3-LI(1,2-HOPO). Evidence of photon downconversion is corroborated through detailed power dependence measurements, which suggest two-photon decay paths are active in these materials, albeit only representing a minority contribution of the sum luminescence, with emission being dominated by normal, Stokes' shifted fluorescence. Specifically, ultraviolet ligand photosensitization of Nd<sup>3+</sup> ions in a NaGdF<sub>4</sub> host shell results in energy transfer to a Nd<sup>3+</sup>/Yb<sup>3+</sup>-doped NaGdF<sub>4</sub> nanoparticle core. The population and subsequent decay of core, Yb<sup>3+</sup> <sup>2</sup> <i>F</i> <sub>5/2</sub> states result in a spectral shift of 620 nm, manifested in a NIR emission displaying luminescence profiles diagnostic of Yb<sup>3+</sup> and Nd<sup>3+</sup> excited state decays. Emphasis is placed on the generality of this material architecture for realizing ligand-pumped, multi-photon downconversion, with the Nd<sup>3+</sup>/Yb<sup>3+</sup> system presented here functioning as a working prototype for a design principle that may be readily extended to other lanthanide pairs.
Project description:Cysteine-functionalized chitosan magnetic nano-based particles were synthesized for the sorption of light and heavy rare earth (RE) metal ions (La(III), Nd(III) and Yb(III)). The structural, surface, and magnetic properties of nano-sized sorbent were investigated by elemental analysis, FTIR, XRD, TEM and VSM (vibrating sample magnetometry). Experimental data show that the pseudo second-order rate equation fits the kinetic profiles well, while sorption isotherms are described by the Langmuir model. Thermodynamic constants (?G°, ?H°) demonstrate the spontaneous and endothermic nature of sorption. Yb(III) (heavy RE) was selectively sorbed while light RE metal ions La(III) and Nd(III) were concentrated/enriched in the solution. Cationic species RE(III) in aqueous solution can be adsorbed by the combination of chelating and anion-exchange mechanisms. The sorbent can be efficiently regenerated using acidified thiourea.
Project description:There is increasing interest in rare earth (RE) doped nanoparticles (NPs) due to their sharp absorption and photoluminescence (PL) in the near infrared (NIR) spectral region. These NIR based nanoparticles (NPs) could allow biological imaging at substantial depths with enhanced contrast and high spatial resolution due to the absence of auto fluorescence in biological samples under infrared excitation. Here, we present the highly efficient infrared photoluminescence in GdF?:Nd(3+) nanoparticles under 800 nm excitation within the hydrodynamic size limitations for bio-applications. The downconversion (Stokes emission) absolute quantum yields (QY) in powder, polymaleic anhydride-alt-1-octadicene (PMAO) coated powder and colloidal solutions have been investigated. QY measurements have revealed that downconversion (Stokes emission) QYs of approximately 5 ± 2 nm sized GdF?:1% Nd(3+) colloidal NPs are 2000 times higher than those of efficient upconversion (UC) particles NaYF?:20% Er/2% Yb of the same size. Furthermore, the utility of these NIR emitting nanoparticles for bioimaging probes has been demonstrated by confocal imaging and spectroscopic study.
Project description:Rare earth Nd3+ ion-doped Ca12Al14O33 single crystals were grown at a rate of 1 mm/h by the floating zone technique in an oxygen atmosphere. The Nd concentration in the central area of the as-grown crystals was higher than that in the peripheral area due to the highly concave growth interface shape. The average Nd concentration in the as-prepared parallelepiped slices of ?6 × 3 × 2 mm3 for electride fabrication was ?0.093 ± 0.011 atom % Nd in contrast to the nominal 0.1 atom % Nd concentration. The Nd-doped C12A7:Nd single crystalline electride prepared by thermal treatment with a Ti metal at 1100 °C for 48 h induced an insulator-metal transition with the highest conductivity of approximately 1165 S/cm. These annealing conditions provide an approach to completely remove clathrated oxide ions from the crystallographic cages, leading to the formation of C12A7:Nd(e -) and C12A7:e - electrides with high-density electrons (?2.4 ± 0.2 × 1021 and ?1.8 ± 0.1 × 1021 cm-3) localized in the cages. The carrier mobility at room temperature in C12A7:Nd(e -) was very similar to that in C12A7:e -, even though it was very high at temperatures below ?150 K.
Project description:Transparent single crystals of two new iodates K3Sc(IO3)6 and KSc(IO3)3Cl have been synthesized hydrothermally. Single-crystal X-ray diffraction was used to determine their crystal structures. Both compounds crystallize in non-centrosymmetric space groups. The compound K3Sc(IO3)6 crystallizes in the orthorhombic space group Fdd2. The crystal structure is made up of [ScO6] octahedra, [IO3] trigonal pyramids, and [KO8] distorted cubes. The compound KSc(IO3)3Cl crystallizes in the trigonal space group R3. The building blocks are [ScO6] octahedra, [KO12] polyhedra, and [IO3] trigonal pyramids. The Cl- ions act as counter ions and reside in tunnels in the crystal structure. The second harmonic generation (SHG) measurements at room temperature, using 1064 nm radiation, on polycrystalline samples show that the SHG intensities of K3Sc(IO3)6 and KSc(IO3)3Cl are around 2.8 and 2.5 times that of KH2PO4 (KDP), respectively. In addition, K3Sc(IO3)6 and KSc(IO3)3Cl are phase-matchable at the fundamental wavelength of 1064 nm. The large anharmonicity in the optical response of both compounds is further supported by an anomalous temperature dependence of optical phonon frequencies as well as their enlarged intensities in Raman scattering. The latter corresponds to a very large electronic polarizability.
Project description:Multifunctional integration on single upconversion nanoparticles (UCNPs), such as the simultaneous achievement of imaging, sensing, and therapy, will be extremely attractive in various application fields. Herein, we demonstrated that single core/shell NaGdF<sub>4</sub>:Yb/Er-based UCNPs (<10 nm) with a highly Yb<sup>3+</sup> or Nd<sup>3+</sup> doped shell simultaneously exhibited good upconversion luminescence (UCL), temperature sensing, and photothermal conversion properties under 980 or 808 nm excitation, respectively. The spatial separation between the emission/sensing core and the heating shell was able to tailor the competition between the light and heat generation processes, and hence higher UCL efficiency and enhanced heating capability were achieved by introducing the rational core/shell design. Especially, Nd<sup>3+</sup>-sensitized core/shell nanoparticles were excitable to the laser at a more biocompatible wavelength of 808 nm, and hence the heating effect of water was greatly minimized. The heating and sensing capabilities of Nd<sup>3+</sup>-sensitized core/shell UCNPs with smaller sizes (<10 nm) were confirmed in aqueous environment under single 808 nm laser excitation, implying their promising applications in imaging-guided and temperature-monitored photothermal treatments.