Intense Emission Peak Research Articles

Fluorescence detection of superoxide anion with CsPbBr3 perovskite quantum dots in aqueous media

Among reactive oxygen species, the superoxide radical anion (O2−) is of particular interest due to its involvement in oxidative stress-related diseases and environmental pollutants. Through solution-phase strategy mediated by ligands, colloidal spherical and water-stable perovskite quantum dots (PQDs) of cesium lead bromide (CsPbBr3) were fabricated by functionalizing with D-tartaric acid (D-TA) (namely, CsPbBr3@D-TA PQDs), exhibiting exceptional photoluminescence quantum yield of 29.88 % and intense emission peak at 522 nm when excited at 380 nm. The as-fabricated CsPbBr3@D-TA PQDs showed strong durability and displayed bright green fluorescence when exposed to 365 nm UV radiation. The emission peak of CsPbBr3 PQDs at 522 nm was completely quenched by O2−, showing wider linear range from 0.125 to 25 µM with a detection limit of 39.82 nM. Moreover, CsPbBr3@D-TA PQDs were also applied for bio-imaging of yeast cells. The CsPbBr3@D-TA PQDs-based fluorescence approach holds great potential for sensing of O2− in real samples.

Synthesis and tunable luminescence properties of SrY₂O₄:Dy³⁺ phosphors

In this study, SrY₂O₄:Dy³⁺ phosphors were synthesized using the solid-state reaction method and evaluated after heat treatment at 1300 °C for 5 h. XRD analysis confirmed the orthorhombic structure of SrY₂O₄ with residual Y₂O₃ present. The addition of Dy³⁺ ions caused lattice expansion, impacting grain size and crystallinity. SEM images showed that the phosphor particles had irregular shapes with minimal size variation, although they tended to agglomerate due to high-temperature heat treatment. Optical analysis revealed significant absorption and emission peaks, with a strong excitation band in the 200–306 nm range and prominent sharp peaks in the 306–480 nm range, particularly at a 0.5 mol% doping concentration. Emission spectra indicated the highest intensity at 0.5 mol% Dy³⁺ concentration, with intensity decreasing due to concentration quenching at higher levels. Thermal stability tests showed peak emission intensity at 70 °C, with stability maintained up to 190 °C before notable thermal quenching. Chromaticity coordinates remained within the warm white region at both temperatures. This study provides detailed insights into the effects of Dy³⁺ doping on the structural, optical, and thermal properties of SrY₂O₄ phosphors. Compared to previous studies on rare-earth-doped SrY₂O₄ phosphors, this work is the first to systematically explore the substitution of Y³⁺ ions with Dy³⁺ ions until full replacement. The study not only confirmed that the highest emission intensity occurs at 0.5 mol% Dy³⁺ concentration, but also demonstrated that Dy³⁺-doped SrY₂O₄ phosphors exhibit excellent thermal stability, with emission stability maintained below 150 °C. These findings expand the potential applications of Dy³⁺-doped SrY₂O₄ phosphors, particularly in high-temperature environments and solid-state lighting.

Effect of inorganic compound size on the relative gain of polymer-based optical waveguide amplifiers

Polymer based waveguide amplifiers are the key devices to improve the performance of integrated communication systems. However, due to their comparatively low relative gain, their widespread practical application has been limited. In polymer based optical waveguide amplifiers, the size of inorganic compounds in the composite gain media has a significant impact on the gain performance of the amplifier. Up to now, there has been limited research on the size influence of inorganic compound on the gain variation in organic polymer based optical waveguide amplifiers. In this study, a series of NaLu0.8-xYxF4: Yb, Er-PMMA composite polymer were used as gain media to prepare organic waveguide amplifiers working in the C-band (1530–1565 nm). The size of NaLu0.8-xYxF4: Yb, Er compounds varies between 20 nm and 150 nm. In the polymer based optical waveguide amplifiers, variations in the size of the inorganic NaLu0.8-xYxF4:Yb,Er compound affects not only the C-band emission intensity but also the relative gain. When the size of the inorganic compound is 65 nm, the composite gain media exhibits the maximum emission peak intensity at 1550 nm and the corresponding device achieves a maximum relative gain of 19.3 dB/cm. Our results show that the size of inorganic compounds affects the variation of luminescence intensity and ultimately the gain of waveguide amplifiers. The gain of future polymer optical waveguide amplifiers can be improved by this method.

Numerical investigation of vacuum ultra-violet emission in Ar/O2 inductively coupled plasmas

Abstract Controlling fluxes of vacuum ultraviolet (VUV) radiation is important in a number of industrial and biomedical applications of low pressure plasma sources because, depending on the process, VUV radiation may be desired, required to a certain degree, or unwanted. In this work, the emission of VUV radiation from O atoms is investigated in low-pressure Ar/O2 inductively coupled plasmas via numerical simulations. For this purpose, a self-consistent Ar/O2 plasma-chemical reaction scheme has been implemented in a zero dimensional plasma chemical kinetics model and is used to investigate VUV emission from excited O atoms (3s 5S 2 0 and 3s 3S 1 0 ) at 130 and 135 nm. The model is extensively compared with experimental measurements of absolute VUV emission intensities, electron densities and Ar excited state densities. In addition, oxygen VUV emission intensities are investigated as a function of pressure, Ar/O2 mixture, and power deposition and the dominant reaction pathways leading to oxygen VUV emission are identified and described. In general terms, absolute oxygen VUV emission intensities increase with power and oxygen fraction over the ranges investigated and peak emission intensities are found for pressures between 5–50 Pa. The emission is dominated by the 130 nm resonance line from the decay of the O(3s 3S 1 0 ) state to the ground state. Besides, at low pressure (0.3–1 Pa), the flux of oxygen VUV photons to surfaces is much lower than that of positive ions, whereas oxygen VUV fluxes dominate at higher pressure, ≳ 5–50 Pa depending on O2 fraction. Finally, oxygen atom fluxes to surfaces are, in general, larger than those of VUV photons for the parameter space investigated.

Machine Learning-Assisted Near-Infrared Spectral Fingerprinting for Macrophage Phenotyping.

Spectral fingerprinting has emerged as a powerful tool that is adept at identifying chemical compounds and deciphering complex interactions within cells and engineered nanomaterials. Using near-infrared (NIR) fluorescence spectral fingerprinting coupled with machine learning techniques, we uncover complex interactions between DNA-functionalized single-walled carbon nanotubes (DNA-SWCNTs) and live macrophage cells, enabling in situ phenotype discrimination. Utilizing Raman microscopy, we showcase statistically higher DNA-SWCNT uptake and a significantly lower defect ratio in M1 macrophages compared to M2 and naive phenotypes. NIR fluorescence data also indicate that distinctive intraendosomal environments of these cell types give rise to significant differences in many optical features, such as emission peak intensities, center wavelengths, and peak intensity ratios. Such features serve as distinctive markers for identifying different macrophage phenotypes. We further use a support vector machine (SVM) model trained on SWCNT fluorescence data to identify M1 and M2 macrophages, achieving an impressive accuracy of >95%. Finally, we observe that the stability of DNA-SWCNT complexes, influenced by DNA sequence length, is a crucial consideration for applications, such as cell phenotyping or mapping intraendosomal microenvironments using AI techniques. Our findings suggest that shorter DNA-sequences like GT6 give rise to more improved model accuracy (>87%) due to increased active interactions of SWCNTs with biomolecules in the endosomal microenvironment. Implications of this research extend to the development of nanomaterial-based platforms for cellular identification, holding promise for potential applications in real time monitoring of in vivo cellular differentiation.

Biosynthesis of copper nanoclusters for fluorescence detection of bilirubin in biofluids.

Copper nanoclusters (Cu NCs) have shown significant attention in sensing of molecular and ionic species. In this work, a single-step biosynthetic approach was introduced for the preparation of fluorescent Cu NCs using Holarrhena pubescens (H.pubescens) leaves extract as a template. The synthesized H.pubescens-Cu NCs act as a nanomolecular probe for the detection of bilirubin in biofluids. The synthesized H.pubescens-Cu NCs displayed highest fluorescence intensity at 454 nm, when excited at 330 nm. Importantly, selective detection of bilirubin was obtained by introducing H.pubescens-Cu NCs as a simple molecular probe. The interaction of bilirubin and H.pubescens-Cu NCs resulted in a remarkable decrease in the emission peak intensity. The developed H.pubescens-Cu NCs-based bilirubin molecular probe has a wide linear range of 0.5-20.00 μM with the limit of detection of 30.54 nM for bilirubin. The promising application of H.pubescens-Cu NCs-based molecular probe was assessed by assaying bilirubin in spiked biofluids.

Exploring single rare earth doped nanophosphor for efficient white emission through codoping of Na+ and Bi3+ ions into Dy3+ activated LaPO4

Using the simple hydrothermal technique, high-purity nanocrystalline Na+ and Bi3+ co-doped Dy3+ activated LaPO4 was effectively prepared. The structural characterisation of the prepared samples was carried out using XRD, EDS, SEM and FTIR analysis. The existence of Na+, Dy3+, La3+, P5+, O2– and Bi3+ was demonstrated using EDS analysis. The direct band gap value of 4.72 eV is obtained from UV visible absorption spectrum and infer that the doped samples are suitable for optical applications. The photoluminescence excitation spectrum monitored at 474 nm and 570 nm emission, the Na+ and Bi3+ co-doped Dy3+ activated LaPO4 exhibit narrow, and intense characteristics f-f peak of Dy3+ ion at 349 nm, 363 nm, 386 nm and 452 nm. Photoluminescence emission spectrum, monitored under 349 nm, 363 nm and 386 nm shows high intense sharp blue emission peaks of Dy3+ with stark splitting at 475 nm, 478 nm, and 486 nm, yellow emission at 571 nm and 580 nm and a very feeble peak at 658 nm in the red region. When the sample is excited at 452 nm only a yellow band is present. Since the intensity of blue and yellow emission in this host matrix is so high and nearly equal, it is appropriate for cool white emission under 350 nm, 363 nm and 386 nm (near UV) excitation and under 452 nm (blue LED) excitation the prepared phosphor may emerge as highly efficient warm white light emitter suitable for general solid-state lighting applications, which can be further confirmed by CIE chromaticity analysis of the prepared sample. In photoluminescence excitation and emission spectra intensities of peaks of the samples with Bi3+ are more intense, this confirms the positive impact of co-doping of Bi3+ into the sample. The Q value from the Dexter’s formula is calculated as an average of 6.4 and is very close to 6 indicates that the interaction is dipole − dipole, which causes the non-radiative energy migration among the Dy3+ ions in the sample. The lifetime of characteristic yellow emission of Dy3+ in the Na+ and Bi3+ co-doped Dy3+ activated LaPO4 host matrix monitored under 350 nm is calculated as 0.642 ms from decay analysis, fitted by a bi-exponential function. The results support the idea that co-doping of Bi3+ and Na+ into the LaPO4:Dy3+ matrix could emerge as a potential white light emitting phosphor for phosphor-converted white LED application.

Optical Characteristics of a New Molecular Complex: "Nafion-Colloidal CdSe/CdS/ZnS Nanocrystals".

Here, the optical properties of the Nafion polymer membrane containing colloidal CdSe/CdS/ZnS nanocrystals embedded by diffusion have been studied. The CdSe/CdS/ZnS nanocrystals have a core/shell/shell appearance. All experiments were carried out at room temperature (22 ± 2) °C. A toluene solution was used to provide mobility to the active sulfone groups of the Nafion membrane and to embed the nanocrystals inside the membrane. The diffusion process of colloidal CdSe/CdS/ZnS nanocrystals into Nafion proton exchange membrane has resulted in a new molecular complex "Nafion-colloidal CdSe/CdS/ZnS nanocrystals". The kinetics of the nanocrystals embedding into the membrane matrix was investigated using luminescence analysis and absorption spectroscopy techniques. The embedding rate of CdSe/CdS/ZnS nanocrystals into the Nafion polymer membrane was approximately 4·10-3 min-1. The presence of new luminescence centers in the membrane was proved independently by laser emission spectroscopy. The luminescence spectrum of the resulting molecular complex contains intensity maxima at wavelengths of 538, 588, 643 and 700 nm. The additional luminescence maximum observed at the 643 nm wavelength was not recorded in the original membrane, solvent or in the spectrum of the semiconductor nanoparticles. The luminescence maximum of the colloidal CdSe/CdS/ZnS nanocrystals was registered at a wavelength of 634 nm. The intensity of the luminescence spectrum of the membrane with embedded nanocrystals was found to be higher than the intensity of the secondary emission peak of the initial nanocrystals, which is important for the practical use of the "Nafion-colloidal nanocrystals" complex in optical systems. The lines contained in the luminescence spectrum of the membrane, which has been in solution with colloidal nanocrystals for a long time, registered upon its drying, show the kinetics of the formation of the molecular complex "Nafion membrane-nanocrystals". Colloidal nanocrystals located in the Nafion matrix represent an analog of a luminescent transducer.

Microwave-assisted one-pot synthesis of carbon dots from biomass: Fe(III) ion sensing and in-situ methylene blue reduction catalytic activity

In this study, zero-dimensional fluorescent carbon dots were synthesized from affordable organic bio-precursors derived from chayote seeds using a one-pot microwave-assisted carbonization process. These biomass-derived carbon dots display excellent fluorescence properties, with an average size of approximately 3.3 nm and a fluorescence quantum yield about 9.56 %. The fluorescence emission spectra were recorded at different excitation peaks, with the highest intensity emission peak observed at 387 nm with an excitation wavelength of 320 nm. These carbon dots effectively detect Fe3+ ions, with a detection limit of 4.5 µmol. Carbon dots show strong catalytic reduction activity against a reduction of Methylene Blue dye, achieving an 81 % reduction in a short period. These biomass-derived carbon dots presents sustainable and promising option for applications in metal sensing and catalytic degradation.

Photoluminescence of Sm3+ and Eu3+ co-doped La2O3–Ga2O3 glasses fabricated by an aerodynamic levitation furnace

A series of transparent (1-y)La2O3–Ga2O3-ySm2O3-xEu2O3 (where x = 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, and y = 0, 0.04) were successfully synthesized using a containerless solidification process. Co-doping with Sm3+ and Eu3+ enhanced the energy absorption of Eu3+, notably improving the characteristic emission peak 5D0-7F2 of Eu3+. The peak emission intensity for y = 0.04 was observed at x = 0.08, attributable to the concentration quenching of Eu3+ ions. As the concentration of Eu3+ increased, the energy transfer effect on emission intensity diminished. Attributed to the energy transfer between Sm3+ and Eu3+, Sm3+ may primarily serve as the sensitizer, and Eu3+ as the activator. According to the Dexter theory, which suggests that the interaction between activator ions and their adjacent ions is the primary mechanism of energy transfer and quenching among Eu3+ ions and adjacent ions, an increase in Eu3+ concentration leads to a decrease in the distance between Eu3+ and adjacent ions, strengthening their interaction, and potentially inducing concentration quenching. Furthermore, with an increase in Eu3+ concentration, the CIE chromaticity coordinates for the samples co-doped with Sm3+ and Eu3+ shifted significantly, enhancing the color purity of the emitted light and bringing it closer to the NTSC color standard coordinates (0.67, 0.33).

Red and green fluorescent carbon dots for highly effective ultraviolet radiation screening and sensing

Carbon dots (CDs) have attracted intense attention because of their excellent optical properties, low toxicity, and biocompatibility. CDs have a great potential to be used as fluorescent sensors and ultraviolet (UV)-blocking materials. In this research, CDs were synthesized by the hydrothermal method using mangosteen leaves as a precursor. A CD aqueous solution exhibited bright green (G-CDs) and red (R-CDs) fluorescence with naked-eye observation under UV irradiation. The maximum fluorescence emission peak intensities of G-CDs and R-CDs were observed at 312 nm and 671 nm under excitation wavelengths of 275 nm and 410 nm, respectively. The absorbance spectra of CDs are shown in the UV range of 200–400 nm. The transmission spectra indicate that the G-CD solution screens UVB and UVC, while R-CDs are an excellent block for all UVA, UVB, and UVC. The average UV-shielding efficiencies of R-CDs and G-CDs are 97.4 %, and 56.1%, respectively. Furthermore, the R-CDs have a tendency to screen high-energy blue light. FTIR results display functional groups of organic substance on CD surfaces showing that the CDs have good biocompatibility with organics and biological materials. Moreover, nanocomposite films of CDs and polyvinyl alcohol (PVA) polymer (CDs/PVA) were prepared using a drop-casting method. In the polymerized state, R-CDs/PVA and G-CDs/PVA exhibit significant improvements in average UV ray blockage of 100.0%, and 83.8% enhancement, respectively. It is noteworthy that PVA combined with R-CDs achieves complete UV ray blocking. Furthermore, the emissions from both CD solution and CDs/PVA under UV radiation cover the regions of red, green, and blue emission. Hence, this work demonstrates the performance of R-CDs- and G-CDs-based platforms that show a high potential for UV-shielding and sensing applications.

Wavelength-tunable photoluminescence of CsPbBr3 microcrystal via in situ halogen doping

Lead halide perovskite semiconductors have received significant attention in recent years as promising candidates for optoelectronic applications. Their controllable bandgap in nanostructures (nanocrystals, nanowires) has been widely and successfully investigated. Intentionally manipulating the atomic behavior with dopants in their macroscopic structure with high quality and stability is still challenging. We studied the crystal structure and photoluminescence (PL) behavior of the anion (Cl) doped CsPbBr3 microcrystals. The doped microcrystal with a low doping concentration has shown a large wavelength-tunable PL emission from 535 nm to 457 nm. Two separate emission peaks (blue and green) are carefully studied in the excitation power dependent PL spectra. The doping and excitation endow the perovskite microcrystal adjustable PL emission band and peak intensities, which may serve as a new degree of manipulation freedom in the color-tunable display and functional optoelectronics.

Luminescence properties of Tb3+ -doped sodium phosphate glasses for green laser and X-ray imaging application

Tb3+ doped sodium-gadolinium-aluminum-phosphate glass samples (PGNA) with chemical compositions 30Na2CO3:8Gd2O3:5Al2O3:(57- x)P2O5: x Tb4O7 (where x=0, 0.25, 0.5, 1.0, 2.0, 3.0, 4.0, and 5 mol. %) were manufactured by using adopting the conventional melt quenching technique. The PXRD study of the prepared samples was used to confirm the amorphous structure. FE-SEM, EDS, and FTIR studies were carried out to analyze the elemental and structural characteristics of synthesized glasses. The X-ray induced luminescence spectra were obtained at room temperature and the emission peak at 311 nm corresponding to Gd3+ transition was observed decreasing with the increase of Tb4O7 concentrations, while emission peak intensities corresponding to Tb3+ electronic transitions increased with the concentrations of Tb4O7. The results from the photoluminescence (PL) studies in the UV–Vis–NIR region showed the glasses emitting intense green light with the highest peak at 544 nm under excitations at 220, 272, and 311 nm. The PL emission intensities were found reasonably high under characteristic excitations of both Gd3+ and Tb3+, peaking at 380, 414, 437, 489, 544, 584, and 623 nm, which corresponding to 5D3→7F6,5D3→7F5, 5D3→7F4, 5D4→7F6, 5D4→7F5, 5D4→7F5, 5D4→7F4, 5D4→7F3 transitions, respectively. The decay time of Tb3+ ions has been observed to decrease when the concentration of Tb4O7 increases. The energy transfer from Gd3+ to Tb3+ was found increased with increasing of Tb3+ concentrations. The CIE 1931 chromaticity coordinates of Tb doped PGNA glasses were found to be in the green range, indicating a strong potential for green laser application. The results from X-ray imaging showed that Tb-doped glass scintillators promise of efficient and low-cost solution for X-ray imaging applications.

Study of crystal structure and optical features of single-phase Ba2BiV3O11: Dy3+ nanophosphors for advanced solid-state illuminating applications

Urea-aided solution combustion (SC) method has been employed to generate monoclinic structure-based Dy (III) doped Ba2BiV3O11 nanophosphors. X-ray diffraction (XRD) and the Rietveld refinement techniques confirmed that the developed nanophosphors are crystallized in a monoclinic crystal system with space group as P21/a. The crystallite size was assessed via Scherrer's equation and Williamson-Hall (W–H) plot. SEM and TEM images confirm the agglomerated particle with a non-uniform shape lies in the nano range. An energy dispersive X-ray (EDAX) study is executed to assess various constitute elements and their relative dispersal was analyzed via mapping spectrum. The highly intense emission peak at 577 nm is ascribed to 4F9/2→6H13/2 electronic transition of the Dy3+ ion when energized at 327 nm wavelength. The band gap values for the host matrix and the optimized sample were measured using a DR spectrophotometer. Auzel's model was utilized to establish the values of quantum efficiency (68.21 %), non-radiative rates (597.08 s−1), and intrinsic lifetime (0.7803 ms). Furthermore, PL (photoluminescence) data is exercised to attain chromatic quantities viz. color coordinates (x and y), and correlated color temperature (CCT), which are strongly endorsed for their usage as near UV-based advanced solid-state illuminating devices.

Characterization of Atmospheric Electrical Discharge in Pin-water Configuration at Different NaCl Concentrations

The interaction between a pin-plate and plasma are representing an interest subject in plasma technology and applications. In this research, the influence of added NaCl to distilled water on the discharge characteristics that formed in the gap between pin-water surfaces was investigated in more details. Their electrical and optical characteristics serve as identifiers. It's found that all optical emissions intensity peaks as a results that detected are decreased with increasing of NaCl concentrations (300,400, and 500 mg). As well as, the emission intensity of neutral emission peaks are much higher than that of the ionic emission peaks. The addition of NaCl changes the liquid accessibility, which alters the kinetics of the discharge that forms in the pin-water surface gap. Also, its observed that the NaCl concentrations affected on the I-V characteristics. The data detected that the plasma frequency ((377.1176 - 279.1951)*1011 rad/sec), electron number density ((4.4519 – 2.4401)*1017 cm-3) and electron temperature (2.1537 – 1.663 eV) decreased with increases of NaCl concentrations except the Debye length ((1.6342 – 1.93989)*10-6 cm) shown a different behavior with increase of NaCl concentrations.

Influence of Dy3+ ions on spectroscopic studies of thermally stable telluro zinc phosphate glasses for white light emitting devices

A transparent series of telluro zinc phosphate glasses with varying Dy3+ ion concentrations (BTZPDy) were synthesized using a melt-quenching procedure. The non-crystalline/amorphous form of the BTZPDy glass matrices has been demonstrated via an X-ray diffraction (XRD) profile. As a way of recognizing the proficient usage of the obtained BTZPDy glass matrices in the white light emitting devices, the spectroscopic characteristics such as optical absorption, photoluminescence excitation (PLE) and emission, as well as temperature-dependent photoluminescence (TDPL) were conducted and investigated in detail. The absorption spectrum was determined in the n-UV to NIR range for the as-prepared BTZPDy1.0 glass sample and the optical energy band gap has been assessed via utilizing Tauc’s plot. In the visible range, photoluminescence spectra demonstrate three distinct emission peaks under different n-UV excitations, among which an intense emission peak around 575 nm is related to the 4F9/2 → 6H13/2 transition in the prepared BTZPDy glasses. The color coordinates (x, y) for the prepared BTZPDy1.0 glass were situated in the white light zone of the CIE graph and adjacent to the standard white light region (0.33, 0.33). Furthermore, TDPL spectral studies suggest the excellent thermal stability of BTZPDy glass samples alongside a high value of activation energy. In view of the above results, as-prepared BTZPDy glasses can be utilized for the fabrication of thermally stable white light emitting devices.

Unveiling the Structural and Optical Properties of Samarium Titanates Pyrochlore, Sm2Ti2O7

A magnetic system whose geometry prevents all pairwise spin interactions from being fulfilled simultaneously to minimize the energy is said to be frustrated. These systems are prevalent throughout all disciplines of physical and chemical study. This article reports a detailed structural and optical analysis of such frustrated Sm2Ti2O7 (STO), a pyrochlore structure. The ordered pyrochlore, STO of cubic symmetry, space group Fd3¯m [no. 227], has been synthesized using the standard solid-state reaction method. The Tauc’s plot reveals a direct band gap value of 3.8 eV from ultraviolet-visible reflectance data. Photoluminescence studies for STO using 280 nm excitation wavelength show the most intense emission peak at 395 nm, 468 nm, and other weak emissions at 368 nm, 412 nm, 430 nm, 449 nm, and 514 nm corresponding to the respective electronic transitions, indicates that the materials show photoluminescence properties. However, the unique characteristics of Sm2Ti2O7, including its wide band gap, photoluminescence, and high refractive index, make it a promising candidate for various magneto-optical, solid oxide fuel cell device fabrication applications.

Potential of Y2Sn2O7:Eu3+, Dy3+ Inorganic Nanophosphors in Latent Fingermark Detection

In this work, we investigated the potential of Eu3+/Dy3+-codoped Y2Sn2O7 fluorescent nanophosphors to visualize latent fingermarks. We prepared these nanophosphors with various doping concentrations by the conventional coprecipitation reaction. The crystal structure, morphology, luminescence properties, and energy transfer mechanisms were studied. The crystalline phase was characterized by X-ray diffraction and crystal structure refinement using the Rietveld method. XRD measurements showed that the samples crystallized in the pure single pyrochlore phase with few more peaks originated from secondary phases and impurities generated during phosphor production, and that Eu3+ ions occupied D3d symmetry sites. The average crystallite size after mechanical grinding was less than 100 nm for all compositions. The optical characterization showed that, when excited under 532 nm, the Eu3+/Dy3+-codoped Y2Sn2O7 samples’ main intense emission peaks were located at 580–707 nm, corresponding to the 5D0→7Fj (j = l, 2, 3, and 4) transitions of europium. In fact, the 5D0→7F2 hypersensitive transition is strongly dependent on the local environment and was quite weak in Eu3+:Y2Sn2O7 at low Eu3+ doping levels. We found that the presence of Dy3+ as a codopant permitted enhancing the emission from this transition. The calculated PL CIE coordinates for the synthesized nanophosphors were very close to those of the reddish-orange region and only slightly dependent on the doping level. Various surfaces, including difficult ones (wood and ceramic), were successfully tested for latent fingerprint development with the prepared Eu3+/Dy3+-codoped Y2Sn2O7 fluorescent nanophosphor powder. Thanks to the high contrast obtained, fingerprint ridge patterns at all three levels were highlighted: core (level 1) islands, bifurcation, and enclosure (level 2), and even sweat pores (level 3).

Dynamic optical information encoding strategy of flexible thin films based on Ba2SiO4 phosphor for ultra-long storage time

Nowadays, state-of-the-art for optical data storage (ODS) have emerged as a leader in the competition of data storage technologies. However, the development of optical storage technology based on optically stimulated luminescence (OSL) encounter the serious problems, of single storage mode and easily decoding. In this study, a series of Ba2SiO4 (denoted as BS): Eu2+, Ln3+ (Ln = Dy, Ho) phosphors with adjustable trap distributions (trap depths of 0.6–0.8 eV) have been developed by high-temperature solid-phase method and exhibit intense green emission peak located at 504 nm under excitation of 360 nm. Typically, BS: 0.02Eu2+, 0.02Ho3+ phosphor owns a shallow trap depth of 0.696 eV and BS: 0.02Eu2+, 0.02Dy3+ phosphor shows a deep trap depth of 0.81 eV. Interestingly, the flexible optical information storage film prepared by BS: 0.02Eu2+, 0.02Ho3+ phosphor through spin-coating technique can storage the “National Water Conservation Logo” pattern under NUV irradiation and reappear even after more than 60 days at 75 °C. Subsequently, multimodal anti-counterfeiting strategy is proposed by BS: Eu2+, Ln3+ (Ln = Dy, Ho) phosphors with adjustable trap depths and the flexible information coding device with high transmittance has been developed, in which encrypted message of “HELLO” and “86068” can be recognized at 75 °C and 130 °C, respectively. This work not only lays the foundation for realizing the durability of optical information storage, but also provides high security with multiple levels of retrievability.

Color point tuning for Ce3+ and Tb3+ activated Sr5(BO3)3F phosphors

Color-tunable luminescence in phosphors can be achieved in a number of ways. In this study, a series of Ce3+/Tb3+ singly doped and (Ce3+,Tb3+) doubly doped Sr5(BO3)3F (SBOF) phosphors, having color point tuning properties, were synthesized by solid-state reaction. The emission color can be adjustable in two ways: by means of changing Ce3+ concentration or doubly doping Ce3+ and Tb3+ ions. The variation in the Ce3+ concentration in Ce3+ singly doped SBOF shows a red shift of the emission. The red shift can be assigned to energy transfer between Ce3+ ions at different sites. In the SBOF:Ce3+,Tb3+ samples, adjustable emission from blue to green can also be obtained by changing Tb3+ doping concentration when Ce3+ content is fixed under UV excitation. This is due to the energy transfer process from Ce3+ to Tb3+ in SBOF:Ce3+,Tb3+ phosphors. Moreover, the characteristic emission peak intensity of Tb3+ in the co-doped sample is enhanced by about 40 times compared with the single-doped Tb3+ phosphor under near-ultraviolet excitation. The potential application of this green-emitting phosphor in UV chip excited white LED was evaluated.