Nm For Nd3 Research Articles

Rare earth Nd3+-doped organic-inorganic hybrid perovskite quantum dots for white LED

Lead halide perovskite quantum dots (QDs) have garnered significant attention due to their tunable band gaps, unique quantum confinement effects, and high photoluminescence quantum yields (PLQYs). Among them, Organic-inorganic QDs make them promising candidates for optoelectronic devices such as quantum dot light-emitting diodes (QLEDs), solar cells, lasers, and photodetectors. However, the toxicity of lead (Pb) has raised environmental and health concerns, hindering their industrial application. To alleviate concerns about heavy metals Pb, extensive research has been conducted on B-site doping and the development of lead-free perovskites. Herein, we firstly developed B-site doping strategy on organic-inorganic hybrid perovskite QDs via rare-earth elements. Neodymium (III) (Nd3+) doped FAPbBr3 QDs were prepared through the ligand-assisted reprecipitation method at room temperature. The B-site doping strategy could alleviate the heavy metal problem of Pb and modulate the band gap of FAPbBr3 QDs facilely. The results demonstrated that increasing the concentration of Nd³⁺ can change the emission of FAPbBr₃ QDs from pure green to deep blue. Specifically, we achieved highly pure blue emission (∼438 nm) with a full width at half maximum (FWHM) of 13 nm for Nd³⁺-doped FAPbBr₃ QDs. Time-resolved photoluminescence (TRPL) spectroscopy revealed a decrease in the lifetime of FAPbBr₃ QDs from 22.86 to 15.46 ns as the doping concentration increased. Additionally, we fabricated a white LED (WLED) utilizing blue-emitting Nd³⁺-doped FAPbBr₃, green-emitting FAPbBr₃ QDs, and red QDs, achieving a white emission color coordinate of (0.33, 0.36). This study pioneers the application of B-site rare-earth doping in organic-inorganic hybrid perovskite QDs, demonstrating that B-site composition engineering is a reliable strategy to further exploit the perovskite family for wider optoelectronic applications.

Spectroscopic and magneto-optical properties of novel bifunctional Nd,Er:CeF3 crystal

In this study, we report a successful Bridgman growth of Nd3+ and Er3+ co-doped CeF3 (Nd,Er:CeF3) single crystal with a size of Ø25 mm × 30 mm. The absorption and fluorescence characteristics of the Nd,Er:CeF3 crystal were studied systematically. The results show that the fluorescence emission peaks were positioned at 547, 669, 1062.6, and 1542.6 nm, respectively. The fluorescence lifetimes centered at 1062.6 and 1542.6 nm for Nd3+ and Er3+ were 0.313 and 1.12 ms, respectively. Meanwhile, the spectroscopic properties of Nd,Er:CeF3 crystals were investigated based on the Judd–Ofelt theory. Notably, the magneto-optical performance of the Nd,Er:CeF3 crystal was investigated for the first time. The Verdet constants of the Nd,Er:CeF3 crystal at 532, 632.8, 1064, and 1310 nm are 220.3, 142.4, 40.7, and 23.1 rad T−1 m−1, respectively, which are significantly higher than those of undoped CeF3 and traditional Tb3Ga5O12. The results show that Nd,Er:CeF3 is a bifunctional crystal with potential applications in laser and magneto-optical fields.

Comparison of rare earths doping (neodymium and samarium) on structural and magnetic properties of Ni–Zn–Bi nanoferrites

Excellent magnetic properties in ferrites are required for high-frequency applications and for wastewater treatment. Thus, the present study shows the comparison of magnetic and structural properties of Nd and Sm substituted Ni–Zn–Bi ferrites with the series Ni0.5Zn0.5Bi0.04NdxFe1.96–xO4 (with step size 0.002) and Ni0.5Zn0.5Bi0.04SmxFe1.96–xO4 (with step size 0.02) prepared using citrate precursor method. The impact of the substitution of rare earth ions (Nd and Sm) on magnetic properties of the synthesized samples is observed using a vibrating sample magnetometer (VSM). The saturation magnetization values enhance considerably from 52 to 58 emu/g for Nd3+ ions and 39 to 57 emu/g for Sm3+ ions, thus, making these materials magnetically hard. Further, the higher value of coercivity is also observed ranging from 133 to 167 Oe for Nd3+ ions and 81 to 155 Oe for Sm3+ ions. The shape of hysteresis loops indicates a super paramagnetic and ferromagnetic behavior in the obtained samples. The squareness ratio value is <0.5, suggesting the uniaxial anisotropy of particles and hence, these ferrites are suitable for microwave-absorbing and in permanent magnetic materials. The X-ray diffraction (XRD) pattern shows the formation of pure cubic crystallites, where, lattice parameters range from 0.840 to 0.839 nm and from 0.838 to 0.839 nm for Nd3+ and Sm3+ ions substitution, respectively. The crystallite size ranges between 28.63 to 29.89 nm and 18.33 to 26.23 nm, for substitution of Nd3+ and Sm3+ ions, respectively. Field emission scanning electron microscopy (FESEM) shows the formation of homogeneous grains, whereas, energy dispersive spectrometer (EDS) counts describe the purity of the samples. The Sm concentration x = 0.10 has the maximum surface area with value of 42.6 m2/g which proves to be having good data storage application due to high surface area. The zero-field cooled (ZFC) and field cooled (FC) data show that Nd-doped Ni–Zn–Bi nanoferrites show superparamagnetic behaviour in the room temperature range which makes them suitable for practical applications.

Novel Nd3+ and Ho3+ co-doped multifunctional CeF3 crystal for laser and magneto-optical applications

In this study, a 1.5 at.% Nd3+ and 0.5 at.% Ho3+ co-doped CeF3 (Nd,Ho:CeF3) single crystal was successfully grown by the vertical Bridgman method. The absorption and fluorescence characteristics of the fabricated crystal were evaluated. The spectroscopic properties of the Nd,Ho:CeF3 crystal were investigated based on the Judd–Ofelt (J–O) theory. The parameters Ω2, Ω4, and Ω6 of Ho3+ were fitted as 0.338 × 10−20, 0.731 × 10−20, and 0.350 × 10−20 cm2, respectively. The fluorescence lifetimes centered at 1064 and 1970 nm for Nd3+ and Ho3+ were 261 and 47 μs, respectively. Notably, the magneto-optical performance of the Nd,Ho:CeF3 crystal was investigated for the first time. The measured Verdet constants of Nd,Ho:CeF3 at 532, 632.8, 1064, 1310, and 1550 nm were 228.0, 154.7, 42.4, 29.1, and 18.5 rad·T−1·m−1, respectively, which were significantly larger than those of pure CeF3 and traditional Tb3Ga5O12. The results demonstrated that Nd,Ho:CeF3 crystals can be applied in both lasers and magneto-optical devices.

High laser performance of an Al3+ and Nd3+-codoping in sodium-borotellurite glass for NIR broadband laser application

The main spectroscopic properties of Nd3+ ions immersed in an oxide glass with composition 59B2O3–10TeO2–30Na2O–1Al2O3:1Nd2O3 (in mol%) has been studied by X-ray diffraction, EDS, SEM, luminescence, transmission, FTIR and Raman spectroscopies. Very high values of the main spectroscopic parameters of Nd3+ ions were determined from the Ωt intensity parameters according to Judd-Ofelt formalism. The 4F3/2 → 4I11/2 NIR transition at 1060 nm of Nd3+ ions is evaluated from the relevant laser parameters reporting a very high quantum efficiency (95%), large effective bandwidth (36 nm), high laser performance quality (9.19 × 10−24 cm2·s) and low saturation intensity (2.04 × 108 W/m2). The excellent non-linear properties of Nd3+ ions are attributed to a microcrystallization inside the glass induced by Al3+ and Nd3+-codoping and a high sodium concentration which intensified the ligand field strengths around Nd3+ ions. Such microcristallization is verified by the presence of several crystalline peaks observed in the FTIR and Raman spectra and identified as Al–O and Te–O linkage vibrations in α-Al2O3 and α-TeO2 phases. As a consequence, a significant reduction of free hydroxyls is appreciated at the midinfrared region in both spectra. Whereas the presence of graphite was detected in the Raman spectrum at 2450 and 2889 cm−1. The great centrosymmetric loss of the Nd3+-sites is indicated by a high value of the Ω2 parameter (36.98 × 10−20 cm2) and confirmed by matched vibrational modes displayed in the deconvoluted Raman and FTIR spectra from 370 to 1750 cm−1 according to the Mutual Exclusion Rule for non-centrosymmetric point groups. The X-ray pattern of the Nd3+-doped oxide glass shows three different amorphous phases generated by delocalized and localized 4f-electrons indicating coexistence of ionic and covalent oxide-metal bonds as characteristic of the invert glasses. However, the compositional parameters confirmed a preferentially covalent domain of oxide-metal bonds as well as presence of crystalline phase, being both structural characteristics consistent with the Judd-Ofelt, transmission, FTIR and Raman results. Finally, the radiative properties are compared with those reported for other Nd3+-activated aluminate glasses suggesting that Al3+ and Nd3+-codoped sodium-borotellurite glass has a great potential for NIR broadband laser application.

Efficient energy transfer between Nd3+ → Yb3+ codoped Gd2O2S host for NIR emission

Novel near infrared (NIR) emitting phosphor, Gd2O2S codoped with Nd3+ and Yb3+ was synthesized by one step combustion synthesis and characterized with X-ray diffraction, photoluminescence emission, photoluminescence excitation spectra and fluorescence decay measurements. The good connectivity with grains and the semi-sphere line structure was found by TEM. The functional group analysis was carried out by Fourier transform infrared (FTIR) spectroscopic techniques. The prepared phosphor gives emission spectra in NIR region centred at 978 nm for Yb3+ and at 890 nm, 1065 nm, 1320 nm for Nd3+ doped samples. For codped samples the peaks at 890 nm and 1320 nm have been eliminated. The emission was recorded under 800 nm excitation and an efficient Nd3+ → Yb3+ resonant and phonon-assisted energy transfer processes have been observed. It have been studied using steady-state and time-resolved optical spectroscopies. Results indicate that the energy transfer occurs via nonradiative electric dipole–dipole processes and is enhanced with the concentration of Yb3+ acceptor ions, having an efficiency higher than 75% for the glass doped with 1 mol% of Nd2O3 and 4 mol% of Yb2O3.

Er3+-to-dye energy transfer in DNA-coated core and core/shell/shell upconverting nanoparticles with 980 nm and 808 nm excitation of Yb3+ and Nd3.

The capability of upconverting nanoparticles (UCNPs) to convert near infrared (NIR) into visible light has become an important feature for biosensing, imaging, therapy, and their combination. While significant achievements have been accomplished during the last decade developing nanohybrids based on UCNPs as energy donors in Förster resonance energy transfer (FRET) systems, it is still challenging to understand and control FRET from UCNPs to dyes and to adapt the NIR excitation wavelength. Here, we describe the synthesis, characterization, and steady-state and time-resolved FRET analysis of UCNP-DNA nanohybrids, in which dye labelled single stranded (ss)DNA was attached to Yb-Er-co-doped core UCNPs (c-UCNPs) and c-UCNPs with a thin Nd-doped shell and a second thin undoped shell (css-UCNPs). Despite differences in sizes, compositions, donor-acceptor distances, brightness, and excitation wavelength (980 nm for Yb3+ and 808 nm for Nd3+), all UCNP-DNA nanohybrids showed very similar concentration dependent FRET-quenching of UCNP luminescence with efficiencies between 0 and ∼20%. We analyzed luminescence intensities, decay times, and rise times and could show the entanglement of excitation and emission kinetics by simply changing the excitation wavelength from 980 nm to 808 nm for the same css-UCNPs. Time-gated FRET-sensitized dye luminescence showed dye-ssDNA concentration dependence over four orders of magnitude (1 nM to 10 μM), which suggested a possible application to nucleic acid biosensing for both 808 and 980 nm excitation.

Effects of La3+ on the enhancement NIR quantum cutting and UC emissions in Nd3+–Yb3+ co-doped transparent silicate glass-ceramics for solar cells

Near-infrared (NIR) quantum cutting (QC) and upconversion (UC) emission of Nd3+–Yb3+ co-doped in Si–Al–Ba–La transparent silicate glass-ceramics (SGC) were prepared. Influence of La3+ on the enhancement NIR QC and UC emission intensity of the co-doped Nd3+–Yb3+ in SGC were investigated. Thereby, NIR QC and UC emission intensity of the co-doped Nd3+–Yb3+ were increased strongly with increasing concentration of LaF3 from 5 up to 25 mol. %. The value of NIR QC emission intensity of the co-doped Nd3+–Yb3+ band centered at ~890, 947, 1071, 1339 and 1430 nm is maximized when the concentration of LaF3 reaches 25 mol. %. At the same time, with the increasing concentration of Yb3+, NIR QC emission intensity of the co-doped Nd3+–Yb3+ bands centered at ~890, 1071, 1339 and 1430 nm of Nd3+ and 947 nm of Yb3+ were gradually increased and reaches its maximum at 2.5 mol. % Yb3+, then decreased owing to the self-quenching effect. In addition, NIR QC mechanism and energy transfer (ET) processes between 2F5/2 → 2F7/2 transition of Yb3+ and transitions of Nd3+ are discussed.

Ultra-broadband 1.0 μm band emission spectroscopy in Pr3+/Nd3+/Yb3+ tri-doped tellurite glass.

Tellurite glasses doped with trivalent Pr3+, Nd3+ and Yb3+ ions were prepared using conventional high-temperature melt-quenching technique and their optical absorption, near-infrared emission, X-ray diffraction (XRD), Raman spectrum, and differential scanning calorimeter (DSC) curve were measured. Upon excitation at 488 nm, an ultra-broadband near-infrared emission extending from 800 to 1120 nm was found to appear owing to the overlapping of the emission bands centered at 900 and 1035 nm of Pr3+, 880 and 1060 nm of Nd3+ as well as 978 nm of Yb3+, respectively. The energy transfer mechanism among Pr3+, Nd3+ and Yb3+ ions which was responsible for the observed ultra-broadband near-infrared emission was investigated to understand the luminescent phenomena. In addition, Judd-Ofelt theory was applied to predict the radiative properties of doped rare-earth ions, and some important radiative parameters such as radiative transition probability, branching ratio and radiative lifetime were derived. Meanwhile, the structural information of amorphous nature and vibrational units was revealed by the XRD pattern and Raman spectrum. Also, the DSC curve displayed the good thermal stability to resist thermal damage for studied tellurite glass with high glass transition temperature. The results indicate that Pr3+/Nd3+/Yb3+ tri-doped tellurite glass is a promising material for ultra-broadband fiber lasers operating around 1.0 μm near-infrared band.

Spectroscopic analysis of up conversion luminescence in doped halogeno-antimonite glass

The up-conversion emission of Nd3+, Sm3+ and Er3+ has been studied in a new halogeno-antimonite glass with the chemical composition 80 Sb2O3 – 10 ZnBr2 – 10 KCl. Doping concentration was 0.2 mol% of lanthanide (Ln) ions. Rare earths were introduced as fluorides LnF3 that were further converted into oxides. Main physical properties of base glass were measured, including density, thermal expansion, characteristic temperatures, refractive index and optical transmission. The amount of residual hydroxyls was calculated from the OH absorption band around 3000 nm. The recorded up-conversion emission lines are λem = 536 nm for Nd3+ pumped at 805 nm; λem = 563 nm, 600 nm, 631 nm and 645 nm for Sm3+ pumped at 945 nm; λem = 531 nm for Er3+ pumped at 798 nm. Co-doped glass (0.1 Yb3+ + 0.1 Er3+) pumped at 980 nm has three emission lines at 524 nm, 545 nm and 650 nm. Corresponding transitions have been identified and the mechanisms ruling the up-conversion process is discussed. They include excited state absorption (ESA), energy transfer (ET) cooperative energy transfer (CET), emission assisted by phonon (EAP), multiphonon relaxation (MR) and cross- relaxation (CR).

Spectroscopic Properties and Continuous Wave Laser Performances at 1064 nm of Nd3+: LuAG Transparent Ceramic

A transparent 2 at% Nd3+-doped Lu3Al5O12 (LuAG) ceramic was fabricated by using tape-casting method and solid-state sintering technology. Based on the room temperature absorption spectrum, the three J–O intensity parameters were calculated with Judd–Ofelt analysis, and then, the radiative transition rates and branching ratios of transitions from 4 F 3/2 manifold to the ${}^4{{\rm {\mathbf I}}_{ \mathbf{{J}^{\prime}}}}$ ( $\mathbf{{ J}^{\prime}} = 13/2,\;11/2,\;9/2$ ) lower lying multiple manifolds were determined. The quantum efficiency of 80.4% was evaluated from the measured fluorescence lifetime and the radiative lifetime of the ${}^4{{\mathbf F}_{3/2 }}$ manifold state. Also, the inter-Stark energy levels of the $4{{{\mathbf I}}_{\boldsymbol{J^{\prime}}}}$ manifolds were performed, and the peak emission cross sections of the ${}^4{\mathbf{F}_{3/2 }} \to {}^4{{{\mathbf {I}}}_{\mathbf{{ J}^{\prime}}}}$ intermanifold transitions were determined. The total emission cross section for ${}^4{\mathbf{F}_{3/2 }} \to $ ${}^4{\mathbf{I}_{9/2 }}$ , ${}^4{\mathbf{I}_{11/2 }}$ , and ${}^4{\mathbf{I}_{13/2 }}$ transitions was calculated to be $7.41 \times {10^{ - 20}} {{\rm c}}{{{\rm m}}^2}$ , $29.83 \times {10^{ - 20}} {{\rm c}}{{{\rm m}}^2}$ , and $10.53 \times {10^{ - 20}} {{\rm c}}{{{\rm m}}^2}$ , respectively. Finally, under an 808 nm diode laser pumping, the continuous wave laser performances of the Nd:LuAG transparent ceramic were investigated.

Simultaneous dual-wavelength laser operation at 937 and 1062 nm in Nd3+:Gd3Ga5O12

Diode-end-pumped continuous-wave (cw) simultaneous dual-wavelength laser operation at 937 and 1062 nm in a single Nd3+:Gd3Ga5O12 (Nd:GGG) crystal was demonstrated. A total output power of 1.12 W at the two fundamental wavelengths was achieved at incident pump power of 17.6 W. The optical-to-optical conversion was up to 6.4% with respect to the incident pump power. To the best of our knowledge, this is first work on cw simultaneous dual-wavelength operation at 937 and 1062 nm in Nd:GGG crystal.

Scintillation properties of Nd3+, Tm3+, and Er3+ doped LuF3 scintillators in the vacuum ultra violet region

In order to develop novel vacuum ultra violet (VUV) emitting scintillators, we grew Nd 0.5%, Tm 0.5%, and Er 0.5% doped LuF3 scintillators by the μ-pulling down method, because LuF3 has a very wide band gap and Nd3+, Tm3+, and Er3+ luminescence centers show fast and intense 5d–4f emission in VUV region. Transmittance and X-ray induced radioluminescence were studied in these three samples using our original spectrometer made by Bunkou-Keiki company. In the VUV region, transmittance of 20–60% was achieved for all the samples. The emission peaks appeared at approximately 180, 165, and 164 nm for Nd3+, Tm3+, and Er3+ doped LuF3, respectively. Using PMT R8778 (Hamamatsu), we measured their light yields under 241Am α-ray excitation. Compared with Nd:LaF3 scintillator, which has 33 photoelectrons/5.5 MeV α, Nd:LuF3 and Tm:LuF3 showed 900±90 and 170±20 ph/5.5 MeV-α, respectively. Only for the Nd doped one, we can detect 137Cs 662 keV γ-ray photoabsorption peak and the light yield of 1200±120 ph/MeV was measured. We also investigated their decay time profiles by picosecond pulse X-ray equipped streak camera, and the main decay component of Nd:LuF3 turned out to be 7.63 ns.

Simultaneous dual-wavelength CW laser operation at 1064 and 930 nm in Nd3+:YAlO3

A dual-wavelength continuous-wave (CW) diode end-pumped Nd3+:YAlO3 (Nd:YAP) laser that generates simultaneous laser action at the wavelengths 1064 and 930 nm is demonstrated. A total output power of 2.15 W (1.57 W at 1064 nm and 0.58 W at 930 nm) for the dual-wavelength was achieved at the incident pump power of 17.8 W with optical conversion efficiency of 12.1%. The M 2 values for 930 and 1064 nm lights were found to be around 1.21 and 1.32, respectively.

Silver/silicon nanostructure for surface-enhanced fluorescence of Ln3+ (LnNd, Ho, and Er)

The surface-enhanced fluorescence of lanthanide ions (neodymium ions Nd3+, holmium ions Ho3+, and erbium ions Er3+) owing to resonant plasmons oscillation on the surface of Ag/Si nanostructure was described. In the presence of Ag/Si nanomaterials, the fluorescence peaks were significantly enhanced, which resulted in a typical 185-fold enhancement at 592 nm for Nd3+, 82-fold at 550 nm for Ho3+, and 80-fold at 533 nm for Er3+ at the concentration of 0.05 M. This Ag/Si nanostructure had larger enhancement factor than that caused by unsupported Ag nanoparticles, which might be attributed to the local field overlap originated from the closed and fixed Ag nanoparticles on silicon nanowires.

Absorption cross-sections of Cr4+:YAG at 946 and 914 nm

Abstract The ground and excited state absorption cross-sections of the Cr4+:YAG saturable absorber at the 4F3/2–4I9/2 transition wavelengths of Nd3+ (946 nm for Nd3+:YAG, 914 nm for Nd3+:YVO4) are measured by a pump–probe method.

Laser emission at 1077 nm in Nd3+-doped calcium aluminosilicate glass

Laser emission at 1077 nm (4F3/2→4I11/2) was demonstrated in Nd3+-doped low silica content calcium aluminosilicate (LSCA) glass under 810-nm pumping by a Ti:sapphire laser. The slope efficiency of the laser emission was found to be 34% with a 20-mW threshold power. The excited-state absorption (ESA) and stimulated emission were measured between 850 and 1520 nm. The results showed two ESA bands from 931 to 1070 nm (4F3/2→2D3/2,2G9/2,4G11/2,2K15/2) and from 1160 to 1414 nm (4F3/2,4G9/2 → 4G7/2,2K13/2). The stimulated emission for the laser transition was found to be 45-nm broad with a peak value of 1.8×10-20 cm2. Thermal and mechanical properties of the LSCA glass were compared to the ED-2 and LHG-8 glasses. While the mechanical properties of the LSCA glass are superior to those of the commercial glasses, its temperature coefficient of optical path length is the highest among the three hosts.

Near-Infrared and Visible Luminescence from Terphenyl-Based Lanthanide(III) Complexes Bearing Amido and Sulfonamido Pendant Arms

A series of m-terphenyl-based ligands bearing three coordinating oxyacetate and two amido or two sulfonamido groups, (1a-b)H3 and (2)H3, respectively, have been synthesized and characterized. The structures of the corresponding neutral complexes have been studied using 1H-NMR spectroscopy and luminescence experiments. The photophysical properties of the (1a-b)Eu, (2)Eu, (1a)Tb, and (2)Tb complexes have been studied to determine the structure of the first coordination sphere in methanol. The first coordination sphere consists of eight donor atoms provided by the ligand (three chelating oxyacetate groups and two amide or sulfonamide oxygens), and one methanol molecule. The (1a)Dy and (1a)Sm complexes exhibited sensitized luminescence in the visible spectral region, but the luminescence intensity was very sensitive to quenching by C-H groups. The near-infrared emitting (1a)Ln and (2)Ln complexes exhibited sensitized luminescence at wavelengths (at 880, 1060, and 1330 nm for Nd3+, at 980 nm for Yb3+, and at 1550 nm for Er3+) of interest for applications in optical telecommunication devices. The luminescence lifetimes of these complexes in DMSO and [D6]DMSO are in the range of microseconds. The luminescent state of the NIR emitting lanthanide ions is very efficiently quenched by high frequency oscillators (such as C-H groups) in the solvent and the ligand.

Near-Infrared and Visible Luminescence from Terphenyl-Based Lanthanide(III) Complexes Bearing Amido and Sulfonamido Pendant Arms

A series of m-terphenyl-based ligands bearing three coordinating oxyacetate and two amido or two sulfonamido groups, (1a-b)H3 and (2)H3, respectively, have been synthesized and characterized. The structures of the corresponding neutral complexes have been studied using 1H-NMR spectroscopy and luminescence experiments. The photophysical properties of the (1a-b)Eu, (2)Eu, (1a)Tb, and (2)Tb complexes have been studied to determine the structure of the first coordination sphere in methanol. The first coordination sphere consists of eight donor atoms provided by the ligand (three chelating oxyacetate groups and two amide or sulfonamide oxygens), and one methanol molecule. The (1a)Dy and (1a)Sm complexes exhibited sensitized luminescence in the visible spectral region, but the luminescence intensity was very sensitive to quenching by C-H groups. The near-infrared emitting (1a)Ln and (2)Ln complexes exhibited sensitized luminescence at wavelengths (at 880, 1060, and 1330 nm for Nd3+, at 980 nm for Yb3+, and at 1550 nm for Er3+) of interest for applications in optical telecommunication devices. The luminescence lifetimes of these complexes in DMSO and [D6]DMSO are in the range of microseconds. The luminescent state of the NIR emitting lanthanide ions is very efficiently quenched by high frequency oscillators (such as C-H groups) in the solvent and the ligand.

Up-conversion luminescence of a violet color from sol-gel derived Nd3+:SiO2+Al2O3 glasses

Solid-state up-conversion lasers are found to be practical alternatives to frequency doubling techniques for the conversion of infrared radiation into visible light. Several applications, such as under-water optical communications and biomedical sensors, await the development of compact, efficient room-temperature devices that can operate at wavelengths not commonly obtainable by conventional laser sources. Such up-conversion lasers are considered as possible solutions to immediate technological problems. Trivalent rare-earth ions doped in different glasses and in certain crystals demonstrate up-conversion emissions in the visible wavelength range. The 4fn electronic level structures of these ions provide many long-lived intermediate levels, which could be populated using infrared radiation. These levels, together with some meta-stable higher lying levels, give rise to strong visible emissions [1]. Over the past few years, up-conversion emission (violet color) from Nd3+ ions has been reported in a variety of glasses based on certain chlorides, fluoroindate, fluorogallate, fluorozirconate, multi-component oxides and heavy metals [2–7]. In all these neodymium glasses, the up-conversion emissions are due to their low vibration frequencies and small phonon energy, and they are all synthesized by conventional melting methods. It is commonly believed that the Nd3+ in silica glasses cannot emit the up-conversion emission. In the literature, some researchers have stated that they did not observe violet up-conversion emission from the Nd3+doped silica glasses [6]. In addition, conventional silica fibers are not efficient in generating up-conversion signals from Nd3+ because of their large phonon frequencies. However, in our present work, we have indeed observed a relatively strong up-conversion emission in violet (399 nm) color upon excitation with a yellow light (580 nm) from Nd3+ : SiO2+Al2O3 glasses prepared by the sol-gel process. This short paper reports, for the first time, up-conversion emission in Nd3+ doped SiO2 based sol-gel glasses. Following the conventional sol-gel process [8], tetraethylorthosilicate (TEOS) was diluted in ethanol (EtOH) and water, with HCl added as a catalyst. The mole ratio of TEOS to EtOH to H2O was 1 : 8 : 8. The solution was allowed to a hydrolyze at 60 ◦C for an hour. Al(NO3)3·9H2O and Nd(NO3)3·6H2O were used as the precursors of Al2O3 and Nd2O3 respectively. They were dissolved in EtOH in separate beakers and then added drop-by-drop into the pre-hydrolyzed TEOS solution. The end solutions were stirred at room temperature in a sealed bottle for a period of one week. Dried gels were thus obtained by removing the cover of the bottle and leaving the gel in the open air for several days. A high temperature treatment was carried out on all these dried gels in an electric furnace at 1000 ◦C for about 12.5 h, and were kept there for about 5 h, and then cooled down to room temperature gradually. Based on our previous results on the laser transition (F3/2→ I11/2) properties at 1064 nm of Nd3+ doped Al3+ co-doped silica [9], we have analyzed three samples for upconversion emissions at various Nd3+ concentrations. The mole ratio of each of the chemicals used was as follows: 100SiO2 : 10AlO1.5 : xNdO1.5 (x = 0.1, 0.5 and 1.0). The up-conversion emission spectra were measured by using a Spex Fluorolog-3 spectrofluorometer, attached with a 1934D3 phosphorimeter. This system employs the Datamax software package for acquiring the spectrum and the decay curve data. The source of excitation was a xenon flash lamp. The measured data pertaining to the luminescence were corrected for the detector. Fig. 1 shows the up-conversion emission spectra of the three samples studied under excitation at 580 nm. An intense violet emission peak at 399 nm has been observed in all these samples. Three additional weaker fluorescent transitions at 342 nm, 372 nm and 452 nm have also been found. Referring to the energy diagram of Fig. 2, the emissions correspond to transitions: D3/2 → I9/2 (∼342 nm), D3/2 → I11/2 and