Porous YAG:Nd3+ Fibers with Excitation and Emission in the Human “NIR Optical Window” as Luminescent Drug Carriers

The design and preparation of luminescent drug carriers has been a prosperous area of research for many years. However, the excitation and/or emission wavelength of such luminescent drug carriers haven′t been optimized in the so‐called human “near infrared (NIR) optical window”, thus restricting their practical applications. Herein, we report the synthesis of electrospun porous YAG:Nd³⁺ (neodymium‐doped yttrium aluminum garnet) fibers with both excitation and emission in the “NIR optical window” as luminescent drug carriers. The YAG:Nd³⁺ porous fibers were characterized by SEM, TEM, XRD, scanning transmission electron microscopy–energy‐dispersive X‐ray spectroscopy (STEM‐EDX), and photoluminescence (PL). Ibuprofen (IBU) was used as a model drug to evaluate the drug‐loading capacities and release profiles of the samples. BMSCs (bone mesenchymal stem cells) were used as model human cells to investigate cytotoxicity. Our results indicated that the YAG:Nd³⁺ fibers possessed a fine, irregularly porous fibrous morphology with an average diameter of 378 nm. The florescence of the sample (1064 nm) could be excited over a wide wavelength range in the NIR region. During the release process of IBU in simulated body fluid (SBF), along with the dissolving of the drug, the solvent entered into the pores, and the emission intensity of the YAG:Nd³⁺ fibers at 1064 nm decreased gradually, owing to a quenching effect of the hydroxy groups, thus provided an approach to track and monitor drug release. In addition, cytotoxicity investigations revealed that these YAG:Nd³⁺ fibers were biocompatible with human cells. Consequently, the porous YAG:Nd³⁺ fibers are a promising material for applications as advanced drug carriers.     

Preparation of luminescent and mesoporous Eu3+/Tb3+ doped calcium silicate microspheres as drug carriers via a template route

Luminescent and mesoporous Eu(3+)/Tb(3+) doped calcium silicate microspheres (LMCS) were synthesized by using mesoporous silica spheres as the templates. The LMCS and drug-loaded samples were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N(2) adsorption/desorption, and photoluminescence (PL) spectra. The results reveal that the LMCS have uniform spherical morphology with a diameter around 400 nm and the mesopore size of 6 nm. The prepared samples exhibit little cytotoxicity at concentrations below 5 mg mL(-1) via MTT assay. In addition, drug storage/release properties of the LMCS were demonstrated for ibuprofen (IBU). The obtained LMCS can be used to encapsulate drugs and release them. Under excitation by UV light, the IBU-loaded samples still show the characteristic (5)D(0)-(7)F(1-3) emission lines of Eu(3+) and the characteristic (5)D(4)-(7)F(3-6) emission lines of Tb(3+). The PL intensity of Eu(3+) in the drug carrier system increases with the cumulative released amount of IBU, making the drug release able to be tracked or monitored by the change of luminescence of Eu(3+). The LMCS reported here with mesoporous structure, good biocompatibility and luminescent property can be a promising drug delivery carrier.     

Preparation and Optical Properties of Submicron SiO2 Spheres Doped with YAG:Nd3+ Nanocrystallites

The sol-gel technology has been applied to obtain SiO₂ spheres of submicron size. The spheres have been doped with YAG:Nd³⁺ nanocrystallites. The nanocrystallites have been obtained from aqueous solutions of citric acid, yttrium, aluminum and neodymium chlorides. The obtained gels have been heated up to 800°C. Emission spectra as well as the excited state lifetimes have been measured at room and liquid nitrogen temperatures. The structural characterization has been performed by means of transmission and scanning electron microscopies (TEM, SEM) and powder diffraction (XRD) measurements. We have observed that the YAG:Nd³⁺ nanocrystallites demonstrate pronounced dependence of the emission intensities on the excitation power as compared to the YAG:Nd³⁺ crystallites embedded into the submicron SiO₂ spheres. The results suggest that silica spheres/YAG:Nd³⁺ composites are expected to be good hosts for microlaser systems.     

Time-resolved optical emission spectrometry of Q-switched Nd:YAG laser-induced plasmas from copper targets in air at atmospheric pressure

Q-switched Nd:YAG laser induced plasma from a copper target was studied by time-gated optical multichannel analyser. The features of the spectra such as the plasma background, the type of lines of the solid sample (singlet-doublet, doublet-singlet, doublet-doublet, quadruplet-doublet, quadruplet-quadruplet), the buffer gas, the intensity-time dependence and the line broadening of the neutral and ionic lines are described. Nitrogen, oxygen ion and metal oxide emission, self-absorption, pressure and Stark broadening is predominant at the onset of plasma formation. A time delay is required to reach the best analytical performance.     

Spectral Parameters of Nd^3＋ inthe Nd^3＋：GdMgB5O10 Crystal

1 INTRODUCTION With the development of diode-pumped solid-statelasers, the search of more efficient materials for diode-pumped solid-state lasers is becoming more and moreimportant. The good laser materials should have thefeatures of large absorption coefficient and large ab-sorption line widths, as well as large emission crosssection at the emission wavelength. In the past years,a number of Nd3 -doped crystals, such as Nd3 :YVO4 , Nd3 :YAG[2], Nd3 :KLW[3] and Nd3 : [1]YAP…     

Azulene-moiety-based ligand for the efficient sensitization of four near-infrared luminescent lanthanide cations: Nd3+, Er3+, Tm3+, and Yb3+

The ML(4) complexes formed by reaction between the bidentate azulene-based ligand diethyl 2-hydroxyazulene-1,3-dicarboxylate (HAz) and several lanthanide cations (Pr(3+), Nd(3+), Gd(3+), Ho(3+), Er(3+), Tm(3+), Yb(3+), and Lu(3+)) have been synthesized and characterized by elemental analysis, FT-IR vibrational spectroscopy and electrospray ionization mass spectroscopy. Spectrophotometric titrations have revealed that four Az(-) ligands react with one lanthanide cation to form the ML(4) complex in solution. Studies of the luminescence properties of these ML(4) complexes demonstrated that Az(-) is an efficient sensitizer for four different near-infrared emitting lanthanide cations (Nd(3+), Er(3+), Tm(3+), and Yb(3+)); the resulting complexes have high quantum yield values in CH(3)CN. The near-infrared emission arising from Tm(3+) is especially interesting for biologic imaging and bioanalytical applications since biological systems have minimal interaction with photons at this wavelength. Hydration numbers, representing the number of water molecules bound to the lanthanide cations, were obtained through luminescence lifetime measurements and indicated that no molecules of water/solvent are bound to the lanthanide cation in the ML(4) complex in solution. The four coordinated ligands protect well the central luminescent lanthanide cation against non-radiative deactivation from solvent molecules.     

A strategy to protect and sensitize near-infrared luminescent Nd3+ and Yb3+: organic tropolonate ligands for the sensitization of Ln(3+)-doped NaYF4 nanocrystals

A strategy to sensitize and protect near-infrared (NIR) emitting Nd3+ and Yb3+ is presented. Combining protection provided by the inorganic matrix of NaYF4 nanocrystals and sensitization from tropolonate ligands capped on their surface, the lanthanide cation centered luminescence was observed through the ligand excitation. The extended lanthanide luminescence lifetimes indicate the success of this strategy.     

Terbium hybrid particles with spherical shape as luminescent probe for detection of Cu2+ and Fe3+ in water

A novel green emissive terbium inorganic-polymeric hybrid particle was designed and this material could detect cations in water. Polyvinyl alcohol as an amphiphilic surfactant rendered the powders dispersible in water with regular round shape (10-20 μm). Interestingly, we noticed that not only Cu(2+) (detection limit 10(-4)M) but also Fe(3+) (detection limit 10(-4) M) can give rise to emission quenching to this target material in comparison with K(+), Na(+), Fe(2+), Mn(2+), Pd(2+), Cd(2+) and Co(2+) (10(-3) mol L(-1)). We regarded that the coordination interactions between ligand and metal ions resulted in these quenching processes. Additionally, it was found that the sensing material can be repeatedly used at least 5 cycles. More importantly, this novel material demonstrated higher thermal-stability in aqueous media than pure silica hybrid material.     

Porous organic polymer nanotubes as luminescent probe for highly selective and sensitive detection of Fe<Superscript>3+</Superscript>

Two porous organic polymer nanotubes (PNT-2 and PNT-3) were synthesized via Ni-catalyzed Yamamoto reaction, using 2,4,6-tris-(4-bromo-phenyl)-[1,3,5]-triazine (TBT) as one monomer, and 2,7-dibromopyrene (DBP) or 1,3,6,8-tetrabromopyrene (TBP) as another monomer. The scanning electron microscope (SEM) images show that both PNT-2 and PNT-3 possess clear hollow tube structures. Luminescent measurements indicate that both PNT-2 and PNT-3 can serve as luminescent probe for highly selective and sensitive detection of Fe³⁺ by luminescent quenching effect. Absorption competition quenching (ACQ) mechanism is also proposed to explain luminescent quenching behavior, i.e., the overlap of the UV-spectra between Fe³⁺ and PNTs causes the energy competition, and therefore leads to luminescent quenching. Moreover, both PNT-2 and PNT-3 still show high selectivity and sensitivity for sensing Fe³⁺ in 10% ethanol aqueous solution, which means that the two porous PNTs are promising candidates as luminescent probes for detecting Fe³⁺ in practical applications.     

Optical absorption and near infrared emission properties of Nd3+ ions in alkali lead tellurofluoroborate glasses

Nd³⁺ doped H₃BO₃–PbO–TeO₂–RF (R = Li, Na and K) glasses were prepared through melt quenching technique. Optical absorption and near infrared (NIR) fluorescence spectra were recorded at room temperature. The spectral intensities were analyzed in terms of the Judd–Ofelt (J–O) parameters (Ω_λ = 2, 4, 6). The covalency effect of Nd–O bond on the J–O parameters was estimated from the relative absorbance ratio (R) between ⁴I_9/2 → ⁴F_7/2 and ⁴I_9/2 → ⁴S_3/2 transitions. The effect of Nd–O covalency on the Ω₄ and Ω₆ intensity parameters as well as on the spontaneous emission probabilities (A_R) was discussed. Lomheim and Shazer hybrid method was applied to determine the fluorescence branching ratios (β_R) of each emission transition from the ⁴F_3/2 metastable level to its lower lying levels. The evaluated total radiative transition probabilities (A_T), stimulated emission cross-sections (σ_e) and gain bandwidth parameters (σ_e × Δλ_P) were compared with the earlier reports.     

Feasibility of depth profiling of Zn-based coatings by laser ablation inductively coupled plasma optical emission and mass spectrometry using infrared Nd:YAG and ArF* lasers

The feasibility of depth profiling of zinc-coated iron sheets by laser ablation (LA) was studied using an Nd:YAG laser (1064 nm) with inductively coupled plasma optical emission spectrometry (ICP-OES), and an excimer ArF* laser (193 nm) with a beam homogenizer. The latter was coupled to an ICP with mass spectrometry (ICP-MS). Fixed-spot ablation was applied. Both LA systems were capable of providing depth profiles that approach the profiles obtained by glow discharge optical emission spectroscopy (GD-OES) and electron probe X-ray microanalysis (EPXMA). For Nd:YAG laser an artefact consisting of zinc depth profile signal tailing appeared, enlarging thus erroneously diffusional coating–substrate interface profile. However, the ArF* system partially reduced but not suppressed that phenomenon. For both LA systems the Fe signal from the substrate increased with depth as expected and reached a plateau. The depth resolution (depth range corresponding to 84%–16% change in the full signal) achieved was several micrometers. Ablation rate was found to depend on ablation spot area at constant irradiance. Consequently, ablated volume per shot dependence on pulse energy exhibits deviation from linear course.     

White light excitation of the near infrared Er3+ emission in exchanged zeolite sensitised by oxygen vacancies

A new material based on Er(3+)-exchanged zeolite L crystals, in which oxygen vacancies have been generated, is proposed as an efficient emitter in the near infrared third telecommunication window. The rare earth ions photoluminescence is efficiently generated by energy transfer from the excited oxygen vacancies, which act as wide range light harvesters. The proposed material can be excited in the whole Near UV-VIS-NIR spectral range from 355 to 700 nm, thus representing the first step toward versatile, zeolite based NIR sources that can be excited with white light.     

Electronic polarizability and Judd-Ofelt parameters of Nd3+ and Er3+ ions in transparent crystallized glasses with nonlinear optical Ba2 TiSi2O8 nanocrystals

Transparent crystallized glasses consisting of nonlinear optical Ba(2)TiSi(2)O(8) nanocrystals are prepared in Eu(2)O(3)-, Nd(2)O(3)-, and Er(2)O(3)-doped 40BaO-20TiO(2)-40SiO(2) glasses by a conventional heat treatment method in order to clarify the optical properties of rare-earth (RE) ions in nanocrystals. The electronic polarizabilities of crystallized glasses are evaluated from the values of density and refractive index, and are found to decrease due to nanocrystallization, which indicates that the chemical bonding state in the crystallized glasses is more covalent compared to the precursor glasses. It is proposed from x-ray diffraction analyses and photoluminescence spectra of Eu(3+) ions that RE ions such as Nd(3+) and Eu(3+) are incorporated into Ba(2)TiSi(2)O(8) nanocrystals. The Judd-Ofelt parameters, Omega(t) (t=2, 4, and 6), of Nd(3+) and Er(3+) ions are evaluated from optical absorption spectra. It is observed that the Omega(2) parameter of Nd(3+) and Er(3+) increases largely due to nanocrystallization, suggesting that the site symmetry of Nd(3+) and Er(3+) ions in nanocrystallized glasses is largely distorted due to their incorporations into the Ba(2+) sites in Ba(2)TiSi(2)O(8) nanocrystals. The change in the Omega(4) and Omega(6) parameters due to nanocrystallization is small. It is proposed that nonlinear optical Ba(2)TiSi(2)O(8) nanocrystals including RE ions would have a high potential as active optical materials.     

Analysis of graphitized cast irons by optical emission spectroscopy: matrix effects in the glow discharge and the spark excitation

Graphite has a substantially lower sputtering rate in glow discharge than have the other structural components of graphitized cast irons, which leads to a structure-related matrix effect, consisting of an increasing relative surface coverage by graphite of the sample surface during the initial stage of the GD-OES analysis, and, consequently, to an increasing carbon signal intensity. This effect exists inherently in any multicomponent system with different sputtering rates of the components and should be taken into account in GD-OES quantification. A simple theory is presented to describe quantitatively the changes in relative contributions of different phases to the flux of the sputtered material entering the discharge and a formula is presented, expressing elemental intensity changes as a function of sputtering rates and stoichiometry of the structural components.After reaching the steady state, there are no substantial differences in the GD-OES signal response of the analyzed elements between the graphitic and the white cast irons. To reach this steady state, long preburn times and high sputtering rates have to be used. In the spark atomization/excitation, there are very strong and complex structure-related matrix effects, which make the analysis of graphitic cast irons by spark excitation impossible.     

Synthesis and properties of the TTA/Gd2O3: Eu3+ luminescent system

Journal of Sol-Gel Science and Technology - Hybrid materials based on lanthanide ions or lanthanide-doped nanostructured particles have received a lot of recent attention because organic ligands...     

Influence of a chelating agent on optical and morphological properties of YAG: Tb3+ phosphors prepared by the sol-gel process

Chemical modifications are widely used in sol-gel method in order to control the mechanisms involved during hydrolysis-condensation and polymerization processes. In this paper, the influence of acetylaceton (acac) used as a chelating agent in the synthesis of undoped and Tb³⁺-doped Y₃Al₅O₁₂ (YAG) powders and sols, has been investigated. Its effects on samples crystallization and morphology have been studied by means of high-temperature X-ray diffraction (HTXRD), thermal analysis (DTA-TG), infrared (IR) and Raman spectroscopies, transmission electron microscopy (TEM) and laser granulometry. It was shown that acetylaceton enhances the structural organization of YAG compound. Moreover, acac-modified powders exhibit much smaller particles than unmodified ones. Optical study has also been achieved on doped samples. Laser induced luminescence spectra and fluorescence decays of Tb³⁺ ions show that acac affects the optical properties of YAG: Tb³⁺ for any types of samples (sol, xerogel or crystallized powder). Powders demonstrate a better luminescence yield without acetylaceton, whereas stabilized sols are more efficient than unstabilized ones.     

Dendrimers as Nd3+ ligands: Effect of Generation on the Efficiency of the Sensitized Lanthanide Emission

We have designed two novel dendrimers with cyclam cores with appended poly(amido amine) (PAMAM) dendrons, decorated at the periphery with four and eight dansyl chromophores, respectively. The photophysical properties of the dendrimers and their Nd³⁺ complexes have been investigated. The energy‐transfer efficiency to the lanthanide ions from these dendrimers has been studied as a function of the generation. It has been observed that an increase in the dendrimer generation as well as the number of amide units enhances the energy transfer to the lanthanide ion.     

Oxoclusters of the lanthanides begin to resemble solid-state materials at very small cluster sizes: structure and NIR emission from Nd(III)

The reaction of Nd(SePh)3 with SeO2 and Hg in pyridine gives the dodecanuclear cluster [(py)18Nd12O6Se4(Se2)4(SePh)4(Se2Ph)2Hg2(SePh)4][(Hg(SePh)3]2. In this compound the 12 Nd(III) ions are stacked in four sets of Nd3, with pairs of tetrahedral oxo ligands separating the Nd3 planes and Se, SeSe, SePh, pyridine, and HgSePh groups encapsulating the oxo core. Both the Nd-O bond lengths and the geometries about the oxo ions are remarkably similar to those found in solid-state Nd2O3. Near-IR emission experiments indicate that the cluster emission properties are less intense than those of highly emissive (DME)2Nd(SC6F5)3 or (THF)8Nd8O2Se2(SePh)16 but brighter than the nonemissive solid-state compound Nd2O3. Intensity variations are interpreted in terms of concentration quenching and phonon relaxation.     

Yb3+ as an origin of the strong anti-Stokes luminescence in NIR FT-Raman spectra of some lanthanide sesquioxides

Strong anti-Stokes bands observed in FT-Raman spectra of Y2O3, Gd2O3 and Lu2O3 are explained by NIR luminescence of Yb3+ impurities present in sesquioxides after the excitation with the 1064 nm line of an Nd:YAG laser. Samples of Y2O3:Yb, Ga2O3:Yb, CeO2:Yb, Gd2O3:Yb and Lu2O3:Yb were prepared by solution combustion synthesis procedure using urea. All materials were investigated by FT-Raman and FT-NIR spectroscopy and characterized by X-ray powder diffraction.     

Calculation of ligand-field and Stark sub-levels in laser crystals Nd~(3+):KY(WO_4)_2 and Nd~(3+):KGd(WO_4)_2

The parameters of ligand field of laser crystal Na~(3+):KY(WO_4)_2 and Nd~(3+):KGd(WO_4)_2are obtained by a scheme which involved intermediate coupling and ligand field interaction.Thecalculated Stark-levels are in good agreement with the experimental values.