One pot synthesis of TiO2:Eu3+ hierarchical structures as a highly specific luminescent sensing probe for the visualization of latent fingerprints

In the present work, TiO₂:Eu³⁺ (1 mol%–11 mol%) nano powders (NPs) were prepared via a facile one-pot hydrothermal method by using Epigallocatechin Gallate (EGCG) as bio-surfactant. The optimized TiO₂:Eu³⁺ (5 mol%) NPs can be used as fluorescent labeling agent for visualizing of latent fingerprints (LFPs) on various porous and non-porous surfaces. The obtained results exhibit well defined ridge details with high sensitivity, selectivity, and low background hindrance which show greater advantages as compared to conventional powders. We demonstrated the viability of high-performance security labels thorough excellent luminescence for practical anti-mimetic applications. Morphology of the prepared samples is highly dependent on pH, concentration of the bio-surfactant, temperature and time durations. Photoluminescence (PL) emission spectra exhibit intense red emission at ～ 615 nm due to electric dipole transition (⁵D₀→⁷F₂). Photometric (CIE and CCT) results clearly show the intense warm red emission of the optimized samples. Therefore, this work offers a superior and universal luminescent label, which can be applied to visualize miniature LFPs particulars for individualization and consequently display great prospective in forensic investigation.     

Flux blended synthesis of novel Y2O3:Eu3+ sensing arrays for highly sensitive dual mode detection of LFPs on versatile surfaces

In the present communication,various fluxes blended Y_2 O_3:Eu~(3+)(5 mol%) nanopowders(NPs) were successfully fabricated by solution combustion method.PXRD pattern confirms body-centered cubic structure of the prepared samples.Energy band gap(Eg) of the fabricated products was estimated and is found to be in the range of 3.13-3.32 eV.Photoluminescence(PL) emission spectra exhibit sharp and intense peaks at ～579,592,614,657,704 nm corresponding to ~5 D_0→~7 F_J(J = 0,1,2,3 and 4) transitions of Eu~(3+) ions.Significance of fluxes for enhancing the PL emissions was extensively studied.Photometric studies of the prepared samples are located in pure red region.Optimized NPs were explored as a novel sensing agent for visualization of latent fingerprints(LFPs) on various surfaces including porous,semiporous and non-porous surfaces followed by powder dusting technique.Various experiments including aging,temperature,scratching and aquatic fresh water treatment tests were performed to evaluate applicability of the fabricated NPs.Visualized LFPs exhibit well defined ridge details including most authenticated sweat pores are also revealed with high sensitivity,selectivity,little background hindrance and less toxicity.Aforementioned results evidence that the method and fabricated NPs can be considered to be simple,rapid and economical and provide novel sensing platform for LFPs visualization in prospective forensic applications.     

Green mediated synthesis of lanthanum doped zinc oxide: Study of its structural,optical and latent fingerprint application

The present paper summarises the synthesis of La³⁺ doped zinc oxide nanoparticles using Aloe vera gel by solution combustion method and the characterization using a powder X-ray diffractometer (PXRD), a transmission electron microscope (TEM), an X-ray photometric spectrometer (XPS), a Raman spectrometer and their applications in optical devices and latent fingerprinting. PXRD pattern confirms the crystallite size of La³⁺ doped ZnO varies from 13 to 20 nm. Crystallite size varies inversely with doping concentration. Photoluminescence properties are found to be the maximum for 2 mol% doping concentration. PL spectra extends the use of ZnO:La³⁺ nanoparticles in blue green LED. These nanoparticles also have superior property as a fluorescent labels in fingerprints.     

Synthesis and optical properties of novel Gd3+-doped BaZn2(PO4)2 glass-ceramics for radiation detection applications

45P₂O₅–15BaO–25ZnO–15B₂O₃ glasses doped with different concentrations (0 mol%, 0.1 mol%, 0.25 mol%, 0.5 mol%, and 0.75 mol%) of Gd³⁺ were prepared by a melt-quenching method and treated to fabricate glass-ceramics containing BaZn₂(PO₄)₂ crystals by controllable crystallization. The structural, optical, and dosimetric properties were investigated. FTIR spectra indicate that the glasses are composed of [PO₄], [BO₃], and [BO₄] basic structural units. The XRD pattern analysis indicates that the samples contain BaZn₂(PO₄)₂ crystals. In the photoluminescence (PL) spectra, two emission bands are observed at 307 and 313 nm due to the ⁶P_5/2→⁸S_7/2 and ⁶P_7/2→⁸S_7/2 transitions of Gd³⁺, respectively. The OSL dosimetric properties of glass-ceramics were studied further under beta radiation of ⁹⁰Sr. The optimal Gd³⁺ doping concentration of 0.5 mol% was determined. The fading of the OSL signal shows that the CW-OSL signal of Gd³⁺-doped BaZn₂(PO₄)₂ glass-ceramics decays by about 58.95% within 120 h, and the intensity remains stable thereafter. The thermoluminescence (TL) curve has three peaks at 164, 240, and 344 °C. Minimum detectable dose (MDD) of the 0.5 mol% Gd³⁺-doped BaZn₂(PO₄)₂ glass-ceramics was calculated as 0.675 mGy. The samples also exhibit good signal reusability and a broad linear dose-response range (0.3–500 Gy). Results show the excellent dosimetric properties of Gd³⁺-doped BaZn₂(PO₄)₂ glass-ceramics and their potential application in radiation dosimetry.     

Rapid visualization of latent fingerprints using novel CaSiO3:Sm3+ nanophosphors fabricated via ultrasound route

Latent fingerprints (LFPs) were the most significant identification method for individualization. Most commonly available fingerprints (FPs) in crime spot investigation were latent and patent types. Generally,LFPs were invisible and thus the effective visualization technique necessitates for the analysis of such FPs. In the past years, many traditional visualization techniques have been employed, but suffered with low resolution, sensitivity, contrast and high background noise. To overcome such limitations, we synthesized Sm~(3+) doped CaSiO_3 nanophosphors (NPs) via an ultrasound irradiation route using mimosa pudica (m. p.)leaves extract as a bio-surfactant. The morphological behavior of the prepared samples was extensively studied by varying the concentration of the m. p. extract, ultrasound irradiation duration, pH level of the precursor solution and sonication power. The photoluminescence (PL) emission spectra exhibit characteristic peaks at～561,601 and 647 nm, which were attributed to~5G_(5/2)→~6H_J(J=5/2,7/2 and 9/2) transitions of Sm~(3+) ions.The Judd-Ofelt(J-O) intensity parameters and other radiative properties were estimated using PL data. The Commission International de I'Eclairage (CIE) color coordinates were positioned in orange-red region shows average correlated color temperature (CCT) value of～3576 K. The optimized samples can be used as a labeling agent for the visualization of LFPs on various porous and non-porous surfaces under normal light irradiation. The visualized FPs reveals well defined ridge characteristics, namely whorl, loop,arch, bifurcation, eye, island, bridge, sweat pores, etc, with high sensitivity, selectivity, low contrast and background hindrance. Aforementioned results evidence that the prepared CaSiO_3:Sm~(3+) NPs were promising luminescent materials for solid state lighting and forensic applications.     

Synthesis and luminescent properties of Ba3Y3.88Gd0.12O9:Eu3+ phosphors with enhanced red emission

In this work, the Gd³⁺/Eu³⁺ activated Ba₃Y₄O₉ (BYO) phosphors were successfully synthesized via coprecipitation method at 1400 °C. The precursor composition, crystal structure stability, microscopic morphology, photoluminescence (PL)/photoluminescence excitation (PLE) spectra and fluorescence attenuation analysis of the phosphors are discussed in detail. The chemical composition of the precursor was determined by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry (TG) analysis; According to field emission-scanning electron microscopy (FE-SEM) analysis, it is found that the particle size of phosphor is uniform and the agglomeration is few. According to PL/PLE spectra analysis, Ba₃Y_3.28Eu_0.6Gd_0.12O₉ phosphors has the strongest excitation band at 260 nm and the strongest emission band at 614 nm, and the fluorescence intensity of Ba₃Y_3.28Eu_0.6Gd_0.12O₉ is higher than that of Ba₃Y_3.4Eu_0.6O₉. The quenching concentration of Eu³⁺ in Ba₃Y_3.88–4xEu_4xGd_0.12O₉ phosphors is x = 0.15 and the mechanism of quenching concentration of Eu³⁺ is electric dipole-quadrupole type interactions. The lifetime value of Ba₃Y_3.88–4xEu_4xGd_0.12O₉ (x = 0.15) phosphors is 0.686 ms and decreases with the increase of Eu³⁺ content. In addition, the CIE chromaticity diagram of Ba₃Y_3.28Eu_0.6Gd_0.12O₉ phosphors is (0.66, 0.34). Finally, the lamp beads assembled with Ba₃Y_3.28Eu_0.6Gd_0.12O₉ phosphors have an ideal luminous effect. Therefore, the Ba₃Y_3.88–4xEu_4xGd_0.12O₉ phosphors designed in this work may hopefully meet the requirements of various lighting and optical display applications.     

A dual-stimuli-responsive intelligent layered lanthanide hydroxide for application in information security and latent fingerprint identification

With the rapid changes in the field of information, the research and development of optical storage materials with high security and large storage capacity are particularly important in the development of contemporary society. However, conventional memory materials with static fluorescent outputs have the disadvantages of easy simulation and forgery, which limits their practical application in the protection of confidential information. In this research, a dual-stimuli-responsive intelligent fluorescent material based on Tb³⁺ and Eu³⁺ ions doped layered lanthanide hydroxide (LYH:Eu_xTb_1–xDPA) was fabricated, which can realize reversible multi-color luminescence conversion (from green to red) by varying the pH and temperature. Combined with the Morse code and security pattern, the multiple encryption and decryption of confidential information and anti-counterfeiting can also be realized. Therefore, the obtained intelligent fluorescent material has a great application prospect for information security. In addition, due to the excellent color tunability, the material can provide the possibility to obtain potential fingerprints with high contrast and no background interference on different color substrates. The unique dual-stimuli-responsive behavior of this material provides more ingenious design inspiration for the design of multi-color intelligent fluorescent devices.     

Synthesis and luminescent properties of BaGd2O4:Eu3+ phosphors with highly efficient red-emitting

The BaGd_(2-2 x)Eu_(2 x)O_4(BG, x = 0.01-0.09) phosphors were successfully synthesized via the sol-gel method,and BaY_(2-2 y)Eu_(2 y)O_4(BY, y = 0.005-0.07) phosphors were included for comparison. The pure phase BG phosphors with the ordered CaFe_2 O_4-type structure are obtained by annealing at 1300℃ for5 h. The phosphors with uniform particle size of 120 nm and good dispersion display typical Eu~(3+)emission with the strongest peak at 613 nm(~5 D_0→~7 F_2 transition of Eu3+) under optimal excitation band at 262 nm(CTB band). The presence of Gd~(3+) excitation bands on the PLE spectra monitoring the Eu3+emission directly proves an evidence of Gd~(3+)-Eu~(3+) energy transfer. Owing to the concentration quenching, the optimum content of Eu3+ addition is 5 at%(x = 0.05), and the quenching mechanism is determined to be the exchange reaction between Eu3+. All the BG samples have similar color coordinates and temperature of(0.64 ± 0.02, 0.36 ± 0.01) and 2000 ± 100 K,respectively. The lifetime value of BaGd_(1.9)Eu_(0.1)O_4 for 613 nm is fitted to be 2.19 ± 0.01 ms, and the Eu~(3+) concentration does not change the lifetime significantly. Owing to the Gd~(3+)-Eu~(3+) energy transfer, the luminescent intensity of the BaGd_(1.9)Eu_(0.1)O_4 phosphor is better than BY system. The BG system served as a new type of phosphor is expected to be widely used in lighting and display areas.     

A single-phase full-color phosphor Sr2Ca2La(PO4)3O:Eu2+,Tb3+,Mn2+: Photoluminescence and energy transfer

A single-phase full-color emitting phosphor Sr₂Ca₂La(PO₄)₃O:Eu²⁺,Tb³⁺,Mn²⁺ was synthesized by the high temperature solid-state method. The phase formation, luminescence properties, thermal stability, and energy transfer from Eu²⁺ to Tb³⁺ and Eu²⁺ to Mn²⁺ in Sr₂Ca₂La(PO₄)₃O were investigated in details. Tunable emission color from blue to blueish green or orange can be observed under 365 nm near-ultraviolet excitation based on the energy transfer from Eu²⁺ to Tb³⁺ or Mn²⁺ ions by varying the ratio of Eu²⁺/Tb³⁺ or Eu²⁺/Mn²⁺ ions. White light was obtained with chromaticity coordinates of (0.3558, 0.3500) in the Sr₂Ca₂La(PO₄)₃O:0.04Eu²⁺,0.08Tb³⁺,0.40Mn²⁺ phosphor, suggesting their potential applications in white light emitting diodes.     

Electrochemical Studies of Effect of Eu~(3 ) on Adenosine-5′-Diphosphate at Mercury Electrode

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Rational design of monovalent ions (Li,Na,K) co-doped ZnAl_2O_4:Eu~(3+) nanocrystals enabling versatile robust latent fingerprint visualization

Alkali metal ions(M~+ = Na~+,Li~+,K~+) co-doped ZnAl_2O_4:Eu~(3+)(5 mol%)(ZAE) nanopowders(NPs) were prepared via solution combustion route using Mimosa pudica(MP) leaves extract as a fuel. PXRD results of co-doped samples enhance the crystallinity and grain growth. Photoluminescence(PL) of the prepared ZAE and ZAE:M~+(M~+ = Na~+, Li~+, K~+) NPs shows intense emission peaks in the range of 550-750 nm and ascribed to ~5D_0→~7F_J(J=0-4) transitions of Eu~(3+) ions, respectively. A 2-fold enhancement in PL intensity was observed in Li~+ co-doped samples. The optimized ZnAl_2O_4:Eu~(3+)(5 mol%), Li~+(1 wt%)(ZAEL)NPs were used to visualize LFPs on various porous, semi-porous and non-porous surfaces through robust powder dusting technique. The visualized latent fingerprints(LFPs) reveal well defined level 1-3 ridge characteristics under several tests such as fingerprint aging and fresh water treatment for various time durations. The obtained results clearly evidence that the prepared NPs are quite useful for multifunctional applications such as advanced forensic and solid state lightning.     

In vivo optical bioimaging by using Nd-doped LaF_3 luminescent nanorods in the second near-infrared window

Fluorescent imaging in the second near-infrared(NIR-Ⅱ, 1000-1700 nm) region has attracted enormous research interest due to its advantages of unprecedentedly improved imaging sensitivity and spatial resolution. Herein, high quality NIR-Ⅱ emissive LaF_3:Nd~(3+) nanorods(NRs) with hexagonal phase structure and controlled size were synthesized by a hydrothermal method. And the Nd~(3+) doping induced NIRⅡ luminescent intensity evolution was studied, In vivo NIR-Ⅱ bioimaging and real-time tracking reveal that these LaF3:Nd~(3+) NRs are mainly accumulated in liver and spleen. Moreover, in vivo toxicity assessment demonstrates that LaF_3:Nd~(3+) NRs feature low biotoxicity and good biocompatibility in living animals. Therefore, the NIR-Ⅱ emitting hexagonal phase LaF_3 NRs with controlled size are promising probes for optical bioimaging.     

Preparation,structure, luminescence properties of europium doped zinc spinel structure green-emitting phosphor ZnAl2O4:Eu2+

The Zn_(1-x)Al_2 O_4:xEu~(2+) phosphor powders were synthesized by the solid-state reaction method.The synthesis temperature for ZnAl_2 O_4 was optimized,whereas the phase structure,TEM images,photoluminescence(PL) properties,the concentration quenching mechanism,the fluorescence decay curves,as well as the CIE chromaticity coordinates of the samples were investigated in details.Under the excitation at 379 nm,the phosphor exhibits an asymmetric broad-band green emission with a peak at 532 nm,which is ascribed to the 5 d-4 f transition of Eu2+.When the doping concentration of Eu2+ ions is 0.01,the luminescence intensity of the sample reaches the maximum value.It is further proved that the exchange interaction results in the concentration quenching of Eu2+ in the Zn_(1-x)Al_2 O_4:xEu~(2+) phosphor powders.The thermal quenching property of ZnAl_2 O_4:Eu~(2+)phosphor was investigated and the quantum efficiency(QE) values of the selected Zn_(0.99)Al_2 O_4:0.01 Eu~(2+) phosphor was measured and determined as 54.85%.The lifetime of the optimized sample Zn_(0.99)Al_2 O_4:0.01 Eu~(2+) is 3.0852 μs and the CIE coordinate of the sample was calculated as(0.3323,0.5538) with high-color-purity green emission.All properties indicate that the green-emitting ZnAl_2 O_4:Eu~(2+) phosphor powder has potential application in white LEDs.     

Red-emitting CaWO4:Eu3+,Tm3+ phosphor for solid-state lighting: Luminescent properties and morphology evolution

CaWO₄:xEu³⁺,yTm³⁺crystals were obtained by facile synthesis at low temperature by the microwaveassisted hydrothermal method(MAH).The phase formation,morphology,luminescent properties and ene rgy transfer were investigated.The X-ray diffraction(XRD)re sults show the formation of a scheelitelike tetragonal structure without the presence of secondary phases.The growth mechanism of hierarchical micro structures based on self-assembly and Ostwald-ripening processes was evaluated,obtaining different types of morphologies.The luminescence spectra of CaWO₄:Eu³⁺,Tm³⁺at 325 nm excitation show the predominance of red emission at the 5 D0→7 F2(Eu³⁺)transition at 624 nm.This feature signals dominant behavior of the electric dipole type.The presence of Tm³⁺is notably evident in the absorption spectra by the related excitation transitions:3 H6→1 G4,3 H6→3 F3 and 3 H6→3 H4.Color parameters are discussed to characterize CaWO₄:Eu³⁺,Tm³⁺emission.The study of the emission spectrum as a function of the concentration of Eu³⁺(x mol%)and Tm³⁺(y mol%)indicates that the CaWO₄:Eu³⁺,Tm³⁺phosphors show stronger red emission intensity and exhibit the CIE value of x=0.63 and y=0.35.The photoluminescence results show 97%high color purity for CaWO₄:4 mol%Eu³⁺,a high CRI(92%)and a low CCT of 1085 K.These results demonstrate that the CaWO₄:Eu³⁺,Tm³⁺red phosphors are promising as color converters for application in white light-emitting diodes and display devices.     

Eu2+-doped Sr5(PO4)3Br blue-emitting phosphor with high color purity for near-UV-pumped white light-emitting diodes

Eu²⁺-doped bromophosphateapatite Sr₅(PO₄)₃Br phosphors were synthesized by the conventional high-temperature solid-state reaction. The crystal structure and luminescence properties of the phosphors, as well as their thermal stability and CIE chromaticity coordinates were systematically investigated. Photoluminescence spectra of Sr₅(PO₄)₃Br:Eu²⁺ exhibit a single blue emission at 450 nm under the excitation of 345 nm, which is ascribed to the 4f–5d transition of Eu²⁺. The phosphor shows very good thermal stability. The CIE color coordinates are very close to those of BaMgAl₁₀O₁₇:Eu²⁺ (BAM). All the properties indicate that the blue-emitting Sr₅(PO₄)₃Br:Eu²⁺ phosphor has potential application in white LEDs.     

Extended X-ray Absorption Fine Structure Study of Eu-Doped BaPbO_3

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Multi-site occupancies and luminescence properties of cyan-emitting Ca9-xNaGd2/3(PO4)7:Eu2+phosphors for white light-emitting diodes

Cyan-emitting Ca₉NaGd_2/3(PO₄)₇:Eu²⁺phosphors were synthesized via high temperature solid-state route.X-ray powder diffraction(XRD)and scanning electron microscopy(SEM)were used to verify the phase and morphology of the Ca₉NaGd_2/3(PO₄)₇:Eu²⁺(CNGP:Eu²⁺)phosphors.The as-obtained phosphor exhibits a broad excitation band of 250-420 nm,which is near the ultraviolet region.An intense asymmetric cyan emission at 496 nm corresponds to the 5 d-4 f transition of Eu²⁺.The multiplesite luminescent properties of Eu²⁺ions in CNGP benefit from versatile structure ofβ-Ca3(PO4)2 compounds.The effective energy transfer distance is 5.46 nm(through the spectral overlap calculation),validating that the resonant energy migration type is via dipole-dipole interaction mechanism.Compared to the initial one at room temperature,the luminescent intensity of CNGP:Eu²⁺phosphor can maintain 77%as it is heated up to 420 K.A white light-emitting diode(WLED)with excellent luminesce nt properties was successfully fabricated.Moreover,the CIE chromaticity coordinates of fabricated WLED driven by changing current just change slightly.     

Physicochemical properties of Li3Ba2La3(MoO4)8:Eu,Tb red-emitting phosphor for solid state white lamps

In this work,combustion synthesis was used for the first time to fabricate a phosphor material with red emission for applications in solid-state white-light lamps.We synthesized a material with emission wavelength at λ_em=617 nm,excited under long UV-blue wavelength based on Eu³⁺,Tb³⁺-activated molybdates Li₃Ba₂(La_1-x-yEu_xTb_y)₃(MoO₄)₈ with 0 ≤ x ≤1 and 0 ≤ y ≤ 1.A series of pow...     

Preparation and luminescence properties of orange-red Ba3Y4O9:Sm3+ phosphors

A novel orange-red emitting Ba₃Y₄O₉:Sm³⁺ phosphors were prepared by a high temperature solid-state reaction in air. X-ray diffraction (XRD), photoluminescence spectra, fluorescence decay and temperature-dependent emission spectra were utilized to characterize the structure and luminescence properties. The results show that the excitation spectrum includes a series of linear peaks at 350, 367, 382, 410, 424, 445, 470 and 495 nm, respectively. Under 410 nm excitation, the emission peaks were located at 574 nm (⁴G_5/2—⁶H_5/2), 608 nm (⁴G_5/2—⁶H_7/2), 659 nm (⁴G_5/2—⁶H_9/2) and 722 nm (⁴G_5/2—⁶H_11/2), respectively. The concentration quenching occurs when x equals 0.08 for Ba₃Y_4–xO₉:xSm³⁺ phosphor and its mechanism is ascribed to the dipole–dipole interaction. The chromaticity coordinates of Ba₃Y_3.92O₉:0.08Sm³⁺ phosphor are in the orange-red region. The temperature-dependent study shows that this phosphor has excellent luminescence thermal-stability. And the luminescence intensity of Ba₃Y_3.92O₉:0.08Sm³⁺ phosphor at 473 K only declines by about 25.75% of its initial intensity. The experimental data indicate that Ba₃Y₄O₉:Sm³⁺ phosphor may be promising as an orange-red emitting phosphor for white light emitting diodes.     

VUV photoluminescence properties of KSrPO4:Dy3+ phosphor

White-light-emitting phosphors based on phosphate host matrix, KSrPO_4 doped with Dy~(3+), were prepared by solid state reaction and their VUV luminescent properties were firstly investigated. The excitation band peaking at 125-153 nm corresponding to the absorption of PO_4~(3-) group exhibits very strong absorption. The phosphors emit warm-white luminescence under vacuum ultraviolet excitation of 147 nm, which consists of three main emission peaks located at 475, 570 and 662 nm, respectively.According to the luminescence and color chromaticity of the optimal sample KSrPO_4:1 mol%Dy~(3+),1.3 mol%Li~+, it can be a potential candidate for mercury-free fluorescent lamps.