Photoluminescence Emission Properties Research Articles

Effect of different BaO contents on the photoluminescence properties of the Eu2+-doped high thermal stability Sr3−xBaxMgSi2O8 phosphors

In this study, 0.015 Eu[Formula: see text]-doped Sr[Formula: see text]BaxMgSi2O8 ([Formula: see text], 0.3, 0.6, 0.9) were used as compositions to find the effect of BaO content on their photoluminescence excitation (PLE) and photoluminescence emission (PL) properties. They were sintered at 1400°C in a reduction atmosphere of 95% N[Formula: see text]% H2 to form blue phosphors. X-ray diffraction pattern and SEM observation were used to analyze their crystal properties, and a fluorescence spectrophotometer was used to analyze their PLE and PL properties. After conducting a thorough analysis, our research primarily encompasses four significant research themes. First, SEM observations revealed that synthesized Eu[Formula: see text]-doped Sr[Formula: see text]BaxMgSi2O8 phosphors exhibit the formation of whisker-like structures. Therefore, the whisker-like structures in all the Eu[Formula: see text]-doped Sr[Formula: see text]BaxMgSi2O8 phosphors were analyzed using the HRTEM and its equipped EDS to find how BaO content influenced both the quantity and fineness of these whiskers. Second, we examined the impact of BaO content on the PLE and PL emission intensities of the Eu[Formula: see text]-doped Sr[Formula: see text]BaxMgSi2O8 phosphors across a temperature range from room temperature to 210°C. This investigation aimed to uncover the effects of BaO content and temperature on the thermal stability of the Eu[Formula: see text]-doped Sr[Formula: see text]BaxMgSi2O8 phosphors. Lastly, our fourth important investigation involved reorganizing the PLE spectra of the Eu[Formula: see text]-doped Sr[Formula: see text]BaxMgSi2O8 phosphors with the energy band as the x-axis. The Gaussian fitting function was applied to analyze the excitation spectra and discern the influence of BaO content on the value of the Stokes shift.

Photoswitchable optoelectronic properties of 2D MoSe2/diarylethene hybrid structures

The ability to modulate optical and electrical properties of two-dimensional (2D) semiconductors has sparked considerable interest in transition metal dichalcogenides (TMDs). Herein, we introduce a facile strategy for modulating optoelectronic properties of monolayer MoSe2 with external light. Photochromic diarylethene (DAE) molecules formed a 2-nm-thick uniform layer on MoSe2, switching between its closed- and open-form isomers under UV and visible irradiation, respectively. We have discovered that the closed DAE conformation under UV has its lowest unoccupied molecular orbital energy level lower than the conduction band minimum of MoSe2, which facilitates photoinduced charge separation at the hybrid interface and quenches photoluminescence (PL) from monolayer flakes. In contrast, open isomers under visible light prevent photoexcited electron transfer from MoSe2 to DAE, thus retaining PL emission properties. Alternating UV and visible light repeatedly show a dynamic modulation of optoelectronic signatures of MoSe2. Conductive atomic force microscopy and Kelvin probe force microscopy also reveal an increase in conductivity and work function of MoSe2/DAE with photoswitched closed-form DAE. These results may open new opportunities for designing new phototransistors and other 2D optoelectronic devices.

Toward Broadband Photodetection: Band Alignment and Interlayer Charge Transfer in 2D Transition Metal Dichalcogenides/3D-Ga2O3 Hybrid-Dimensional Heterostructures.

Recently, various transition metal dichalcogenides (TMDs)/Ga2O3 heterostructures have emerged as excellent candidates for the development of broadband photodetection, exhibiting various merits such as broadband optical absorption, efficient interlayer carrier transfer, a relatively simple fabrication process, and potential for flexibility. In this work, vertically stacked MoSe2/Ga2O3, WS2/Ga2O3, and WSe2/Ga2O3 heterostructures were experimentally synthesized, all exhibiting broadband light absorption, spanning at least from 200 to 800 nm. The absorption coefficients of these TMDs/Ga2O3 heterostructures are significantly improved compared to those of individual Ga2O3 films. The superior performance can be attributed to the type-I band alignment and efficient interlayer carrier transfer, which result from various band offsets along with the different doping conditions of the TMD layers, leading to distinct photoluminescence (PL) emission properties. Through a detailed analysis of the excitation-power-dependent PL spectra, we offer an in-depth discussion of the interlayer carrier transfer mechanism in the TMDs/Ga2O3 heterostructures. Regarding interlayer coupling effects, the shift of the EF of TMD layers plays a crucial role in modulating their trion emission properties. These findings suggest that these three TMDs/Ga2O3 heterostructures have great potential in broadband photodetection, and our in-depth physical mechanism analysis lays a solid foundation for a new device design.

Facile Tailoring of Metal-Organic Frameworks for Förster Resonance Energy Transfer-Driven Enhancement in Perovskite Photovoltaics.

Förster resonance energy transfer (FRET) has demonstrated its potential to enhance the light energy utilization ratio of perovskite solar cells by interacting with metal-organic frameworks (MOFs) and perovskite layers. However, comprehensive investigations into how MOF design and synthesis impact FRET in perovskite systems are scarce. In this work, nanoscale HIAM-type Zr-MOF (HIAM-4023, HIAM-4024, and HIAM-4025) is meticulously tailored to evaluate FRET's existence and its influence on the perovskite photoactive layer. Through precise adjustments of amino groups and acceptor units in the organic linker, HIAM-MOFs are synthesized with the same topology, but distinct photoluminescence (PL) emission properties. Significant FRET is observed between HIAM-4023/HIAM-4024 and the perovskite, confirmed by spectral overlap, fluorescence lifetime decay, and calculated distances between HIAM-4023/HIAM-4024 and the perovskite. Conversely, the spectral overlap between the PL emission of HIAM-4025 and the perovskite's absorption spectrum is relatively minimal, impeding the energy transfer from HIAM-4025 to the perovskite. Therefore, the HIAM-4023/HIAM-4024-assisted perovskite devices exhibit enhanced EQE via FRET processes, whereas the HIAM-4025 demonstrates comparable EQE to the pristine. Ultimately, the HIAM-4023-assisted perovskite device achieves an enhanced power conversion efficiency (PCE) of 24.22% compared with pristine devices (PCE of 22.06%) and remarkable long-term stability under ambient conditions and continuous light illumination.

Structural and optical properties of Mg doped TiO2 nanoparticles synthesized by sol-gel method

Pure and doped titanium oxide (TiO2) nanoparticles with various atomic wt% (0 %, 3 %, 5 % and 7 %) of Mg were prepared by sol-gel method followed by the calcination at 100 °C for 12 h to investigate structural, optical and photoluminescence properties of TiO2 nanoparticles. Subsequently prepared samples annealed at 400 °C for 2 h for crystallization. Eventually, as prepared samples have been characterized using X ray diffractometer, scanning electron microscopy (SEM), Fourier transform Infrared Spectroscopy (FTIR), UV–Visible spectroscopy and Photoluminescence spectroscopy. XRD analysis shows that, prepared samples are crystalline in nature with exhibit of mixed phase (Rutile and Anatase) of TiO2. The crystallite size obtained around 12.0 nm of pure TiO2 nanoparticles. As increase in the doping concentration crystallite size was reduced to 6.76 nm. SEM images demonstrate the uniform growth of nanoparticles. Doping offering the tuning the energy band gap of TiO2. Photoluminescence spectra observed near UV to visible region. The intensity of Photoluminescence emission enhanced with increase of Mg doping at various concentration. Band gap and photoluminescence emission properties of doped TiO2, can be useful for optoelectronic applications and as Photo catalyst. The possible mechanism of coordination for different properties for TiO2 nanoparticles with various doping concentration have been well discussed.

Experimental and theoretical studies of pH-responsive iridium(III) complexes of azole and N-heterocyclic carbene ligands.

A series of nine luminescent iridium(III) complexes with pH-responsive imidazole and benzimidazole ligands have been prepared and characterized. The first series of complexes were of the form [Ir(ppy)2(N^N)]+ or [Ir(ppy)2(C^N)]+ (where ppy is 2-phenylpyridine and N^N is 2-(2-pyridyl)imidazole or 2-(2-pyridyl)benzimidazole and C^N represents a pyridyl-triazolylidene-based N-heterocyclic carbene ligand). For these complexes, the benzimidazole group was either unsubstituted or substituted with electron-withdrawing (Cl) or electron-donating (Me) groups. The second series of complexes were of the form [Ir(phbim)2(N^N)]+ or [Ir(phbim)2(C^N)]+ (where phbim is 2-phenylbenzimidazole and N^N is either 2,2'-bipyridine or 1,10-phenanthroline and C^N is either a pyridyl-imidazolylidene or pyridyl-triazolylidene N-heterocyclic carbene ligand). UV-visible and photoluminescence pH titration studies showed that changing the protonation state of these complexes results in significant changes in the photoluminescence emission properties. The pKa values of prepared complexes were estimated from the spectroscopic pH titration data and these values show that the nature of the pH-sensitive ligands (either main or ancillary ligands) resulted in a significant capacity to modulate the pKa values for these compounds with values ranging from 5.19-11.22. Theoretical investigations into the nature of the electronic transitions for the different protonation states of compounds were performed and the results were consistent with the experimental results.

Quantum Yield of the Emission of Carbon Quantum Dots: Tricks Due to Solvent Polarity and Excitation Dynamics

Carbon quantum dots (CQDs) are recognized as promising fluorescent nanomaterials possessing high thermal stability, tuned photoluminescence, along with the low cost of their production. Quantum yield (QY) of photoluminescence (PL) of CQDs is known to vary largely depending on the synthetic procedures/ chemical composition of CQDs, but there is still no unique approach for explanation of the nature and QY of PL emission of CQDs. Particularly, an accompanying effect of the solvent environment on QY of the PL emission is paid less attention. In this work, we compare photophysical properties of CQDs synthesized by different methods that resulted in the different composition of CQDs. First, fluoralkylated CQDs (Fluocar® Nano) doped with F, N and O heteroatoms, were synthesized via solvothermal method using urea, anhydrous citric acid and 3-(trifluoromethyl) aniline as precursors. Second, hydrophilic CQDs were obtained by liquid-phase synthesis procedure using sucrose (“standard” CQDs). Depending on the synthesis procedure the PL emission properties were tuned according to the polarity of solvent the CQDs were dispersed in. It was found that QY of PL emission of Fluocar® Nano has a much stronger magnitude and absolute dependence on the solvent polarity compared to “standard” CQDs. Fluocar® Nano demonstrated QY of PL emission as high as 93% in dioxane and as low as 30% in aqueous dispersion, whereas QY of the “standard” CQDs varied within 0.7-2.3% when relative solvent polarities ranged from 0.164 to 1.0; however, their relative changes depending on the solvent polarity were similar (Fig.1). Dynamics of the PL emission during first minute of excitation in the form of PL relaxation to some saturated value was also strong for Fluocar® Nano dispersed in less polar solvents, while the emission was stable in a strongly polar aqueous medium. Tentative conclusion was made that the surface of CQDs plays a crucial role in tuning the PL emission, providing different concentration of surface traps that become gradually fed during excitation and different interactions of CQD and polar solvents, respectively. Figure 1

Exchangeable Self‐Assembled Lanthanide Antennas for PLIM Microscopy

AbstractLanthanides have unique photoluminescence (PL) emission properties, including very long PL lifetimes. This makes them ideal for biological imaging applications, especially using PL lifetime imaging microscopy (PLIM). PLIM is an inherently multidimensional technique with exceptional advantages for quantitative biological imaging. Unfortunately, due to the required prolonged acquisitions times, photobleaching of lanthanide PL emission currently constitutes one of the main drawbacks of PLIM. In this study, we report a small aqueous‐soluble, lanthanide antenna, 8‐methoxy‐2‐oxo‐1,2,4,5‐tetrahydrocyclopenta[de]quinoline‐3‐phosphonic acid, PAnt, specifically designed to dynamically interact with lanthanide ions, serving as exchangeable dye aimed at mitigating photobleaching in PLIM microscopy in cellulo. Thus, self‐assembled lanthanide complexes that may be photobleached during image acquisition are continuously replenished by intact lanthanide antennas from a large reservoir. Remarkably, our self‐assembled lanthanide complex clearly demonstrated a significant reduction of PL photobleaching when compared to well‐established lanthanide cryptates, used for bioimaging. This concept of exchangeable lanthanide antennas opens new possibilities for quantitative PLIM bioimaging.

Exchangeable Self-Assembled Lanthanide Antennas for PLIM Microscopy.

Lanthanides have unique photoluminescence (PL) emission properties, including very long PL lifetimes. This makes them ideal for biological imaging applications, especially using PL lifetime imaging microscopy (PLIM). PLIM is an inherently multidimensional technique with exceptional advantages for quantitative biological imaging. Unfortunately, due to the required prolonged acquisitions times, photobleaching of lanthanide PL emission currently constitutes one of the main drawbacks of PLIM. In this study, we report a small aqueous-soluble, lanthanide antenna, 8-methoxy-2-oxo-1,2,4,5-tetrahydrocyclopenta[de]quinoline-3-phosphonic acid, PAnt, specifically designed to dynamically interact with lanthanide ions, serving as exchangeable dye aimed at mitigating photobleaching in PLIM microscopy in cellulo. Thus, self-assembled lanthanide complexes that may be photobleached during image acquisition are continuously replenished by intact lanthanide antennas from a large reservoir. Remarkably, our self-assembled lanthanide complex clearly demonstrated a significant reduction of PL photobleaching when compared to well-established lanthanide cryptates, used for bioimaging. This concept of exchangeable lanthanide antennas opens new possibilities for quantitative PLIM bioimaging.

Optical and structural characterization of CsPb(I1-xBrx)3 nanomaterials prepared by the mechanochemical method

Hybrid organic-inorganic lead halide perovskites (LHP) are gaining considerable attention due to their wide range of potential applications, particularly as an active layer in solar cells and light-emitting devices owing to their excellent light-harvesting and photoluminescence emission properties. Considering their high color purity and color-tunability, high photoluminescence quantum yield (PLQY), easy fabrication, and cost-efficiency, LHP are promising candidates to compete with the traditional active layer in solid-state lighting. The PL emission of CsPbX3 (X = I, Br, Cl) covers the entire visible range from 400 to 730 nm and can be easily tuned via halide replacement in the I ↔ Br ↔ Cl series. In this work, photoluminescence (PL), luminescence excitation, UV/VIS/NIR absorption, structural and morphological properties of CsPb(I1-xBrx)3 (x = 0–1) nanosized powders prepared by the mechanochemical synthesis method is investigated at 80K and room temperature. A narrow PL peak with full width at half maximum (FWHM) = 16.5 and 6.6 nm was observed at room temperature and 80K from CsPbBr3, respectively. The relation between structure and optical properties of nanopowders is discussed. It is shown that the halide exchange mechanism is an effective approach for fabrication of defect-free materials.

Preparation of N-A Cysteine-capped CdTe/CdS/ZnS core/shell/shell QDs as a Selective Probe for Detecting Damaged DNA

In this study, NAC-capped CdTe/CdS/ZnS core/double shell QDs were synthesized in an aqueous medium to investigate their utility in distinguishing normal DNA from mutated DNA extracted from biological samples. Following the interaction between the synthesized QDs with DNA extracted from leukemia cases (represents damaged DNA) and that of healthy donors (represents undamaged DNA), differential fluorescent emission maxima and intensities were observed. It was found that damaged DNA from leukemic cells DNA-QDs conjugates at 585 nm while intact DNA (from healthy subjects) DNA–QDs conjugates at 574 nm. The obtained results from the optical analyses indicate that the prepared QDs could be utilized as probe for detecting disrupted DNA that is associated with a number of diseases including malignancies. Additionally, the manufactured NAC-CdTe core with CdS shell and ZnS shell QDs were further characterized by high-resolution transmission using field emission scanning electron microscopy (FESEM), energy dispersive X-ray fluorescence (EDX), X-ray diffraction (XRD), infrared spectrum (IR), UV-vis absorbance, photoluminescence (PL) and absorbency intensity using the fully automatic ELISA. The XRD results revealed the formation of NAC-CdTe/CdS/ZnS QDs with a grain size of 5.7 nm. While EDX assay emphasizes the compound content of Cd, S, Zn and Te elements. Whereas SEM test’s findings propose the spherical size of NAC- CdTe/CdS/ZnS QDs within the range of 10–40 nm. The demonstrated mono-dispersed lattice structure of NAC-CdTe core with CdS shell and ZnS shell QDs has superior PL emission properties at [Formula: see text] of [Formula: see text]600 nm and UV-Vis absorption bands at 350 nm. Overall, this study suggests that the synthesized QDs could be employed in developing optical biosensors for a variety of biomedical applications to improve early detection of diseases marked by damaged DNA profile including cancers.

Vacuum Ultraviolet Spectroscopic Properties in Gd3+-Eu3+ Ions Pair Doped MYF4 (M = Li, Na, and K)

LiYF4, NaYF4, and KYF4 doped with Gd3+-Eu3+ ion pairs synthesised by soft route (wet) chemical technique tracked by Reactive Atmosphere Process (RAP). The phase purity of every synthesized material is verified using the X-ray Diffraction (XRD) method. The photoluminescence excitation (PLE) and photoluminescence emission (PL) properties are examined in ultra-violet (UV) and vacuum ultraviolet (VUV) regions. A new type of photon harvesting (cutting) process is studied in the synthesized phosphors. The Quantum Cutting (QC) is observed only in host LiYF4 doped with Gd3+-Eu3+ Phosphor.

Synthesis, Characterization, Photoluminescence Emission and Antibacterial Properties of Some Schiff Base Derivatives of Substituted Salicylaldehyde

Schiff bases such as 4-{[(2-hydroxyphenyl) methylidene]amino} benzoic acid analogues (SB1-SB3) have been produced by the condensation of mole equivalent of 4-amino benzoic acid and various substituted salicylaldehyde. It has given good yield. The synthesized compounds (SB1-SB3) were analyzed by FT-IR, 1H-NMR and Mass spectroscopy techniques. Light emitting properties of the compounds have been studied by photoluminescence (PL) and diffuse reflectance (DR) spectra. Photoluminescence spectra of the compounds SB1-SB3 revealed that these molecules emit light from bright yellow to orange red color following exposure to UV light. From diffuse reflectance spectra, the measured optical band energy for SB1-SB3 was found to be 2.14eV, 2.06eV and 2.26eV respectively. The 3D surface view of scanning electron microscope (SEM) of SB1-SB3 have also been studied. This study revealed that Schiff base derivatives of 4-amino benzoic acid analogue molecules become promising material for light emitting devices. Antibacterial study of these compounds by Kirby-Bauer diffusion method revealed the antibacterial activity . This showed these compounds can be used as antibacterial compounds.

Origin of Broad Emission Induced by Rigid Aromatic Ditopic Cations in Low-Dimensional Metal Halide Perovskites.

The development of broadband emitters based on metal halide perovskites (MHPs) requires the elucidation of structure-emission property correlations. Herein, we report a combined experimental and theoretical study on a series of novel low-dimensional lead chloride perovskites, including ditopic aromatic cations. Synthesized lead chloride perovskites and their bromide analogues show both narrow and broad photoluminescence emission properties as a function of their cation and halide nature. Structural analysis shows a correlation between the rigidity of the ditopic cations and the lead halide octahedral distortions. Density functional theory calculations reveal, in turn, the pivotal role of octahedral distortions in the formation of self-trapped excitons, which are responsible for the insurgence of broad emission and large Stokes shifts together with a contribution of halide vacancies. For the considered MHP series, the use of conventional octahedral distortion parameters allows us to nicely describe the trend of emission properties, thus providing a solid guide for further materials design.

Synthesis and photoluminescence study of KCaPO4:Eu3+ phosphors for solid state lighting

A series of KCaPO4:Eu3+ phosphors was effectively synthesized utilizing a wet chemical method. The photoluminescence excitation and emission properties of the phosphor were investigated. The KCaPO4:Eu3+ phosphor was efficiently excited at 394 nm, and the PL (Photoluminescence) emission spectra were obtained at 591 and 614 nm. Concentration quenching occurred at a Eu3+ ion concentration of 0.5 mol%. The present work suggests that the KCaPO4:Eu3+ phosphors may be a potential candidate as a near-UV (Ultraviolet) convertible material for solid state lighting applications.

Plasmon-Controlled Selective Emission Enhancement of Eu3+ with (Au Core)@(Y(V,P)O4:Eu) Nanostructures.

Plasmonic nanostructures have a capability to control the photoluminescence (PL) emission properties of optical species and thus can dramatically enhance the performances of diverse optical systems and devices. Lanthanide ions typically exhibit multiple PL emission lines. Systematic studies on the plasmon-enabled selective enhancement for the different emission lines of lanthanide ions are still highly desired in order to achieve the fine manipulation on the spectral profile and luminescence intensity ratio (LIR). Herein we report on the synthesis and PL emission properties of monodisperse spherical (Au core)@(Y(V,P)O4:Eu) nanostructures, which integrate the plasmonic and luminescent units into an individual core@shell structure. The localized surface plasmon resonance adjusted through control of the size of the Au nanosphere core enables the systematic modulation of the selective emission enhancement of Eu3+. As revealed by single-particle scattering and PL measurements, the five luminescence emission lines of Eu3+ originating from the 5D0,1 excitation states are affected by the localized plasmon resonance to different extents, which are dependent on both the dipole transition nature and the intrinsic quantum yield of the emission line. Based on the plasmon-enabled tunable LIR, high-level anticounterfeiting and optical temperature measurements for photothermal conversion are further demonstrated. Our architecture design and PL emission tuning results offer many possibilities for constructing multifunctional optical materials by integrating plasmonic and luminescent building blocks into hybrid nanostructures with different configurations.

Helianthus-annuus assisted synthesis of ZrO2 nanoparticles: Enhanced electrochemical, photoluminescent, and optical properties

Cubic-phase ZrO2 nanoparticle (NPs) were synthesized using a cost-effective single-pot green combustion method and Helianthus annuus extract, and their properties were evaluated. Powder X-ray diffraction was used to investigate the purity, crystal structure, and size of the NPs, and the average size of the NPs was determined to be ∼ 25 nm. The internal surface morphology of the NPs with distinct voids and pores were observed using scanning electron microscopy (SEM) Ultraviolet–visible (UV-vis) absorption spectroscopy was used to analyze the optical properties of the as-synthesized ZrO2 NPs, and their energy bandgap was determined to be 4.5 eV. The photoluminescence (PL) spectrum of the cubic-phase ZrO2 NPs presented a broad band in the UV-vis region. The PL emission properties of the ZrO2 NPs were studied by analyzing their emission wavelength at ∼490 nm, and the results revealed that the NPs can be efficiently used for display applications. The electrochemical properties of a graphite–ZrO2 NP electrode was qualitatively analyzed by performing cyclic voltammetry (CV) and electrochemical impedance spectroscopy experiments in a three–electrode system with a 0.1 M KCl solution as the electrolyte. Our results suggested that the NPs can be used to evaluate the thermodynamics of the redox reaction, and their capacitance was determined using the CV curves of a graphite–ZrO2 working electrode at different scan rates in the range of 0.01 ∼ 0.05 V/s at room temperature. Furthermore, the photodegradation rate of Reactive Blue 4 textile dye over the as-prepared ZrO2 NPs reached 97% under UV-vis light irradiation.

Effect of dopant (Li+, Mg2+ and Bi3+) on the photoluminescence emission intensity of Eu3+ doped CaAl2O4 phosphor: Application to white LEDs

In this work, we have investigated the photoluminescence (PL) emission properties of Eu3+ doped CaAl2O4 in the presence of singly, doubly and triply ionized dopant ions i.e., Li+, Mg2+ and Bi3+ ions. The phosphor samples were synthesized by the high-temperature solid-state reaction process at 1473 K. The crystalline phase, crystallinity and surface morphology of Li+, Mg2+ and Bi3+ ions doped 0.01Eu3+:CaAl2O4 phosphor were examined and confirmed by X-Ray diffraction (XRD) and scanning electron microscope (SEM) measurements. The different vibrational groups and their corresponding vibrational frequencies were measured by Fourier transform infrared (FTIR) technique. The 0.01Eu3+:CaAl2O4 phosphor emits intense red emission at 616 nm on excitations with 393 nm (Eu3+ line) and by the charge transfer band (Eu3+-O2-) at 262 nm. The overall PL emission intensity of 0.01Eu3+:CaAl2O4 phosphor on excitation with 393 nm is found to increase almost 2.8 times in the presence of Li+ than other dopants. The emission intensity are increased in case of Li+ and Mg2+ doping due to crystallinity, charge compensation and the asymmetry created around the Eu3+ ions in the phosphors matrix. However, in case of Bi3+ ion, the emission intensity decreases on 393 nm excitation. In the presence of Bi3+ ion the intense red emission is observed due to energy transfer from Bi3+ (3P1→1S0) to Eu3+ ion on λexc = 294 nm. The lifetime study were carried in each case which are in accordance with the PL emission behaviour of Li+, Mg2+ and Bi3+ ions doped 0.01Eu3+:CaAl2O4 phosphor. The CIE color coordinates, correlated color temperature (CCT) and color purity have been calculated, which shows highly pure red color in the warm light region. The 0.01Eu3+:0.10Li+:CaAl2O4 phosphor may be used in displays devices, photonic devices, solid state lighting as red light emitting source.

Atomically precise deposition of (Er0.1Y0.9)2SiO5 combined with digitally processed DC sputtering and non-radical oxidation

(Er0.1Y0.9)2SiO5 (EYSO) crystalline thin film is expected as one of highly optical gain media for silicon photonics. Layer-by-layer deposition for the directed crystallization has been attempted to achieve a compact waveguide amplifier. In this study, atomically precise deposition (APD) of EYSO as the layer-by-layer approach was demonstrated by combination with digitally processed DC sputtering and nonradical oxidation. The crystalline phase was targeted at the C2/c space group of the monoclinic EYSO, and the directed crystallization of EYSO based on the APD process was confirmed by x-ray diffraction measurements. The nonradical oxidation effect on the improvement of the crystallinity of EYSO was also discussed through photoluminescence (PL) measurements. It was revealed that the APD process improved the Er-related PL emission properties of EYSO, suggesting a remarkable reduction in oxygen vacancies that act as the nonradiative center. Consequently, the decay time reaches 2.5 ms close to the radiative lifetime of Er ion in EYSO.

Excitation-independent deep-blue emitting carbon dots with 62% emission quantum efficiency and monoexponential decay profile for high-resolution fingerprint identification

Reaching emissive nanomaterials at short wavelengths with a high quantum efficiency (QE) is an attractive task for researchers. This is more demanding in carbon dots (CDs) with diverse applications that usually emit photons at wavelengths around 450–620 nm. In this study, deep blue-emissive doped-CDs (d-CDs) with high photoluminescence (PL) QE up to 62% and excitation-independent properties were prepared via a short-time microwave irradiation method. The prepared CDs showed simultaneous amorphous and crystalline features, with average sizes of 4.75 nm and bright emission color located at 422 nm. It was found that the presence of sulfur-related dopant levels plays a key role in emission properties in such a way that the PL signal drops significantly in the absence of N-acetyl-l-cysteine (NAC) as a dopant source. On the other hand, the trisodium citrate dihydrate (TSC) was selected as a carbon source to form the main carbon skeleton without it no emission was recorded. Monoexponential-fitted recombination trend with an average lifetime of about 10 ns also confirmed excellent PL emission properties with uniform energy levels and minimized defect-contributing recombinations. The practical use of the as-prepared N, S-doped CDs was assessed in fingerprint detection indicating a bright and clear scheme for both core and termination regions of the fingerprint. Simplicity, cost-effectiveness, high-product yield, low toxicity, along with high/stable PL quantum efficiency in deep-blue wavelengths, and demonstrated ability for fingerprint purposes, support the prospective application of these dual doped-CDs for sensing and bioimaging applications.