Luminescence Performance Research Articles

Ligand Engineering of Inorganic Lead Halide Perovskite Quantum Dots toward High and Stable Photoluminescence.

The ligand engineering of inorganic lead halide perovskite quantum dots (PQDs) is an indispensable strategy to boost their photoluminescence stability, which is pivotal for optoelectronics applications. CsPbX3 (X = Cl, Br, I) PQDs exhibit exceptional optical properties, including high color purity and tunable bandgaps. Despite their promising characteristics, environmental sensitivity poses a challenge to their stability. This article reviews the solution-based synthesis methods with ligand engineering. It introduces the impact of factors like humidity, temperature, and light exposure on PQD's instability, as well as in situ and post-synthesis ligand engineering strategies. The use of various ligands, including X- and L-type ligands, is reviewed for their effectiveness in enhancing stability and luminescence performance. Finally, the significant potential of ligand engineering for the broader application of PQDs in optoelectronic devices is also discussed.

Effect of hydrophobic modification and dosage of long afterglow phosphors on the properties of self-luminescent cement-based materials

Both the hydrolysis instability of original long afterglow phosphors (OLP) and limited amount of reflective powders (RP) degraded the luminescent performance of self-luminescent cement-based materials (SLCM). This study novelty proposed a solution by coating organosilicon layer on the OLP surface to create hydrophobic effect for enhancing its water resistance. Furthermore, compared with typical SLCM with low content of LP and RP, SLCM mixtures were prepared through replacing cement by LP and containing higher volume of RP according to the modified Andreasen and Andersen (A&A) model. The effects of dosage and surface modification of LP on the strength, hydration kinetics, luminescent performance, phase composition and microstructure of SLCM were examined. Hydrophobic LP (HLP) achieved similar crystal structure but changed its surface morphology as well as enhanced its water resistance. Introduction of the OLP into SLCM was liable to generate the hydrolysis products. HLP performed better in generating more hydration products but less hydrolysis products, thus formed a compact microstructure and enhanced the thermal stability. Hydration kinetics revealed that the hydrolysis reaction of OLP decreased the heat of hydration, while the hydration process was promoted by HLP. Higher dosage of LP after hydrophobic modification in SLCM helped in obtaining a better luminescent performance but caused a drastic reduction in strength. Overall, the optimal dosage of HLP in SLCM including higher volume of RP was more effective in achieving a superior luminescent performance without degrading the strength.

Gold Nanoclusters Whose Photoluminescent Properties are Dynamically Tunable by Modulating the Assembly Pathway Complexity.

Modulating the assembly pathway is an indispensable strategy for optimizing the performance of optical materials. However, implementing this strategy is nontrivial for metal nanocluster building blocks, due to the limited functional modification of nanoclusters and complexity of their emission mechanism. In this report, we demonstrate that a gold nanocluster modified by 4,6-diamino-2-pyrimidinethiol (DPT-AuNCs) self-assembles into two distinct aggregation structures in methanol (MeOH)/water mixed solvent, thus exhibiting pathway complexity. Kinetic studies show that DPT-AuNCs firstly assembles into non-luminescent nanofibers (kinetically controlled), which further transforms into strongly luminescent microflowers (thermodynamically controlled). In-depth analysis of the assembly mechanism reveals that the transformation of aggregation structures involves the disassembly of nanofibers and a subsequent nucleation-growth process. Temperature-dependent photoluminescence (PL) spectroscopy and infrared (IR) measurements reveal that inter-cluster hydrogen bonding bridged by solvent molecules and C-H⋅⋅⋅π interaction are the key factors for emission enhancement. The photoluminescent property of DPT-AuNCs can be controlled by varying the cosolvent in water, enabling DPT-AuNCs to distinguish different kind of alcohols, particularly the isomerism n-propanol (NPA) and isopropanol (IPA). Additionally, the addition of seeds effectively regulate the assembly kinetics of DPT-AuNCs. This study advances our understanding of assembly pathways and improves the luminescent performance of nanoclusters (NCs).

Enhanced color rendering index and thermal stability of Ca2GdNbO6: Dy3+ phosphors by co-doping Sm3+ ions

Nowadays, white light-emitting diodes (WLEDs) converted from single-phase white light-emitting phosphors are a popular subject in solid-state lighting. Dy3+ is one of the most widely used activator ions in single-phase white light-emitting phosphors. However, its application in solid-state lighting is limited due to the lack of a red light component. Therefore, this work synthesized single-phase white light-emitting Ca2GdNbO6: 0.05Dy3+, ySm3+ (CGNO: 0.05Dy3+, ySm3+) phosphors with a double perovskite structure. A detailed study was conducted on the occupancy of co-doped Dy3+-Sm3+ ions in the CGNO lattice and the microstructure of the sample. Simultaneously, the luminescence performance, concentration quenching mechanism, energy transfer, and thermal stability of CGNO:0.05Dy3+, ySm3+ phosphors were discussed. The results indicate that the phosphors have stable physical and chemical properties and excellent optical properties. Under 363 nm excitation, emission peaks of both Dy3+ and Sm3+ were observed in the emission spectrum, indicating that Sm3+ compensates for the insufficient red light component in the samples. In addition, the CIE chromaticity coordinates (CIE) of the CGNO: 0.05Dy3+, ySm3+ samples and the luminescence stability in water were studied. Finally, a WLED device with a high color rendering index Ra = 85.4) and low correlated color temperature (CCT = 3135 K) was prepared by combining a 365 nm chip with the CGNO: 0.05Dy3+, 0.05Sm3+ phosphor. The research confirmed that single-phase white light-emitting CGNO: 0.05Dy3+, ySm3+ phosphors have potential application prospects in the field of WLEDs.

Syntheses, crystal structures, luminescence properties and Hirshfeld surface analyses of two mononuclear 2,2′:6′,2′’-terpyridine lanthanide complexes with different β-diketones

Six ternary lanthanide complexes with different β-diketones as primary “antenna” ligand and 2,2’:6’,2’’-terpyridine as neutral ancillary ligand, namely [Ln(hfac)3(tpy)] [Ln(III) = Eu (1), Gd (2), Tb (3); hfac = hexafluoroacetylacetone; tpy = 2,2’:6’,2’’-terpyridine] and [Ln(btfa)3(tpy)] [Ln(III) = Eu (4), Gd (5), Tb (6); btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione], were synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, single crystal X-ray diffraction and powder X-ray diffraction. The three-dimensional Hirshfeld surface map and two-dimensional fingerprint analysis reveal that the substitution of hfac with btfa result in the decrease of the H···F/F···H and F···F interactions and the increase of the C···H/H···C and H···H interactions. Solid-state luminescence investigations indicate that the Eu(III) complexes (1-Eu and 4-Eu) and the Tb(III) complexes (3-Tb and 6-Tb) display the characteristic lanthanide-centered luminescence upon UV excitations. 1-Eu and 4-Eu emit red light at CIE: 0.6827, 0.3172 and CIE: 0.6819, 0.3179 with the quantum yields (QY) of 78.70 % and 68.85 % and the lifetimes (τ) of 0.768 and 0.808 ms, respectively. 3-Tb and 6-Tb emit green light at CIE: 0.2677, 0.7221 and CIE: 0.2680, 0.7217 with the QY values of 7.56 % and 1.38 % and the τ values of 0.076 and 0.022 ms, respectively. For the Eu(III) complexes, the substitution of hfac by btfa makes the QY value lower from 78.70 % to 68.85 % and slightly prolong the τ value from 0.768 to 0.808 ms, while for the Tb(III) complexes, both of the QY and τ values decrease. The results suggest that the structures of the primary β-diketone ligands could affect the luminescence performances such as QY and τ values of the Eu(III) and Tb(III) complexes.

Sunlight-driven mechanoluminescent composite coating materials based on trap modulation for stress sensing

Nighttime driving safety is a key focus in transportation research due to accidents caused by drivers' inability to clearly see road obstacles, leading to delayed or incorrect decisions. To address this, the use of mechanoluminescent materials on surfaces like roads and buildings offers a potential solution for better object contour detection in poor visibility. This study investigates the use of SrAl2O4 as a phosphor matrix, exploring its luminescence characteristics and the effects of doping with Eu2+ and Dy3+. The optimal doping ratios were determined to be 2 % Eu and 1 % Dy by trap modulation, producing phosphors with significant mechanical luminescence and a prolonged afterglow. Spectroscopic analysis and image assessment demonstrated a visible afterglow lasting up to 60 min, along with impressive mechanical luminescence performance. By combining the developed SrAl2O4:Eu2+, Dy3+ phosphor-based coating with polydimethylsiloxane, a real-time surface stress sensing system was devised utilizing digital camera and other optical sensors. This advancement facilitates the visualization of stresses in complex or confined environments, potentially improving nighttime driving safety through enhanced object contour detection.

Synthesis and Performance of Deep-Red Phosphorescent Iridium Complexes with Pyrone as an Auxiliary Ligand.

Two bis-cyclometalated heteroleptic iridium complexes incorporating 1-phenylisoquinoline (piq) as the main cyclometalating ligand and 3-hydroxy-2-methyl-4-pyrone (ma) or 2-ethyl-3-hydroxy-4H-pyran-4-one (ema) as the auxiliary ligand, namely Ir(piq)2(ma) (Ir-1) and Ir(piq)2(ema) (Ir-2), were developed and applied as deep-red phosphors in organic light-emitting diodes (OLEDs). The two auxiliary ligands had similar influences on the photophysical, electrochemical, and electroluminescent properties of the iridium complexes. Ir(piq)2(ma) (Ir-1) showed better luminescence performance in a simple phosphorescent OLED compared to the traditional red iridium complex Ir(piq)2(acac) and exhibited a current efficiency of 9.39 cd A-1 (EQE of 12.09%). In contrast, Ir(piq)2(ema) exhibited an efficiency of 8.6 cd A-1 (EQE of 10.19%).

Enhanced red emission of MgAl2O4: Cr3+/Mn4+ phosphor co-doped with alkali metal ions

A series of MgAl2O4: Cr, Mn, M (M = Li, Na, K) red phosphors were prepared by solution combustion combined with subsequently annealing treatment. The influence of Cr3+ or Mn4+ single-doping, Cr3+ and Mn4+ double-doping and alkali metal ions co-doping on the luminescence performance of MgAl2O4 phosphors were systematically investigated. XRD and SEM were used to characterize the composition and morphology of the phosphors, and the optical absorption, photoluminescent excitation, photoluminescent emission, fluorescence lifetime and chromaticity coordinate were performed to characterize their luminescence properties. Compared with Cr3+ or Mn4+ single-doped MgAl2O4 phosphors, Cr3+ and Mn4+ double-doped ones can achieve red light emission under a wide range of excitation from ultraviolet to visible light. Co doping with alkali metal ion Li enhances the fluorescence intensity and lifetime of MgAl2O4: Cr, Mn phosphors.

Study on the photoluminescence performance and thermal sensitivity of (Y,Gd)2O3:Tb3+,Dy3+,Tm3+ phosphors

Using ammonia as a precipitation agent, (Y,Gd)2O3:Tb3+x,Dy3+y,Tm3+z phosphors were synthesized by the co-precipitation method. In order to improve the luminescence performance of the luminescent center Tb3+, Tb3+-Dy3+ co-doping and Tb3+-Dy3+-Tm3+ tri-doping were successively carried out, and the optimal component formulations were determined by the controlled variable method (x = 0.03, y = 0.005, z = 0.001). XRD results showed that the sample has a cubic phase Y2O3 structure with good crystalline properties. SEM results revealed that the samples have a unique micro morphology of small ball aggregation. The effects of doping concentration of Dy3+ and Tm3+ on the luminescence properties of Tb3+ were systematically investigated. The energy transfer mechanism among the three ions of Tb3+-Dy3+-Tm3+ was demonstrated by photoluminescence spectroscopy, and the main interaction modes between ions were elucidated. In addition, the matrix lattice environment can change the thermal stability properties of phosphors. In this paper, the temperature characteristics of Y2O3:Tb3+,Dy3+,Tm3+ phosphors are expected to be changed by microtuning the Y2O3 matrix lattice with the introduction of Gd3+. The fluorescence intensity ratio (FIR) and thermal sensitivity indicated that Gd3+ has good temperature sensitivity, and its introduction can effectively improve the temperature sensing performance of the phosphors, which has a wide range of applications in optical temperature measurement sensors.

How Luminescence Performances of Silicon-Doped Carbon Dots Contribute to Copper-Catalyzed photoATRP?

How Luminescence Performances of Silicon-Doped Carbon Dots Contribute to Copper-Catalyzed photoATRP?

Ion exchange-assisted surface passivation toward highly stable red-emitting fluoride phosphors for light-emitting diodes

A facile and environmentally friendly ion exchange-assisted surface passivation (IASP) strategy is presented for synthesizing red emitting Mn4+-activated fluoride phosphors. A substantial, pristine Mn4+-free shell layer, applied as a coating to Mn4+ doped potassium fluorosilicate K2SiF6:Mn4+ (KSFM) phosphors, enhances both water resistance and luminescence efficiency. The stability test of fluoride in water at ambient temperature and boiling water demonstrates that IASP-treated KSFM phosphors are highly water resistant. Furthermore, both the negative thermal temperature (NTQ) fitting results and the photoluminescence (PL) decay confirm that the IASP process effectively passivates surface defects, leading to enhanced luminescence performance. The maximum internal quantum yield (QYi) of the IASP-KSFM phosphor is 94.24%. A white LED realized a high color rendering index (CRI) of 93.09 and luminous efficiency (LE) of 149.48 lm/W. This work presented a novel technique for the development of stable fluoride phosphors and has the potential to increase the use of KSFM phosphors in plant supplementary lighting systems and white light-emitting diodes.

Eu3+ doped Ca3LiSbO6 and Eu3+, Li+ co-doped Ca3LiSbO6 phosphors for white light-emitting diodes

Novel antimonate Ca3LiSbO6: xEu3+ red phosphor was synthesised using a high-temperature solid-phase reaction. The effect of Eu3+ doping concentration on its crystal structure and luminescence performance was investigated. It was found that Eu3+ was at the inversion symmetry site in the lattice of Ca3LiSbO6. To improve the luminescence performance of Ca3LiSbO6: 0.05Eu3+ red phosphor, Ca3LiSbO6: 0.05Eu3+, xLi + red phosphor was synthesised. The doping of Li + can correct the charge difference generated by the substitution of Ca2+ by Eu3+, reduce the generation of defects, enhance the local symmetry of the luminescence centre of Eu3+, improve the structural rigidity, and thus enhance the luminous intensity of the phosphor. At 423 K, the luminous intensity of this phosphor was 68 % of the initial temperature, which was higher than that of the phosphor without the charge compensator Li+ (60 %), indicating that Li+ improved the thermal stability of the phosphor.

Investigation of TM (TM=Mg, Cu) doping effect on the luminescence performance of CsPbCl3 from a first-principles investigation

The inorganic perovskite CsPbCl3 has raised great concern in recent years due to its great tunability of luminescence properties via impurity doping. However, the blue-emitting mechanism of the impurity-doped CsPbCl3 is unexplored. In this work, we focus on the structural, electronic, and optical properties of CsPb1-x TM x Cl3 (TM=Mg, Cu; x = 0, 0.037, 0.074) based on the first-principles calculations. It is indicated that TM doping decreases the lattice parameter, deforms octahedral structure, and improves the stability of CsPbCl3. The increased direct bandgap values and unique TM energy levels occupation show that the doped systems behave only blue-emitting well. The Mg-s and Cu-3d (eg) states out the bandgaps are close to the valence band edge and conduction band edge respectively, both promoting the carrier radiation recombination. Furthermore, the density of states analyses demonstrates that the enhanced emission of TM-doped CsPbCl3 benefits from the TM different electronic configurations and the different hybridization ways (Mg 3s/Cl 3p, Cu eg/Cl 3p), producing more carriers with increasing x respectively. The obtained optical properties imply that the TM-doped systems exhibit significant optical absorption and high carrier mobilities, promoting excellent luminescence efficiency. Our work explains the blue-emitting mechanism of the TM-doped CsPbCl3, providing a prospective strategy for designing highly efficient blue-emitting devices for optoelectronic applications based on the available parent materials by modulating the bandgap, synergistic relation of impurity energy level and band edge, and optical property.

Fluorescent carbon dots for discriminating cell types: a review.

Carbon dots (CDs) are quasi-spherical carbon nanoparticles with excellent photoluminescence, good biocompatibility, favorable photostability, and easily modifiable surfaces. CDs, serving as fluorescent probes, have emerged as an ideal tool for cellular differentiation owing to their outstanding luminescence performance and tunable surface properties. In this review, we summarize the recent research progress with CDs in the differentiation of cancer/normal cells, Gram-positive/Gram-negative bacteria, and live/dead cells, as well as the cellular differences used for differentiation. Additionally, we summarize the preparation methods, raw materials, and properties of the CDs used for cell discrimination. The differentiation mechanisms and the advantages or limitations of the differentiation methods are also introduced. Finally, we propose several research challenges in this field and future research directions that require extensive investigation. It is hoped that this review will help researchers in the design of new CDs as ideal fluorescent probes for realizing diverse cell differentiation applications.

"Nanoscale electric vehicle" for the patterning of nanomaterials: Selective electrophoretic deposition of programmable silica composite nanoparticles

Colloidal nanocrystals stand at the forefront of various applications given their unique optoelectronic properties and abundant active sites. However, the surface dynamics of nanocrystals make it difficult to avoid performance sacrifices that result from certain processing methods. Here we introduce a general nanoscale electric vehicle (NEV) platform for efficient and lossless manipulation and processing of functional nanomaterials by selective electrophoretic deposition. Dual-ligand modified system comprising charging ligands and anchoring ligands enables NEV to be universally compatible with fine patterning of various nanomaterials such as quantum dots, perovskites, rare-earth compositions or Janus materials. Without performance impairment from additional modifications, the luminescence performance of the nanocrystals improved significantly with the help of NEV to a level comparable to the commercial standard. Furthermore, we demonstrate the capabilities of our approach for display and anti-counterfeiting encryption applications. Our strategy offers a versatile way of creating high-performance nanomaterial devices in a cost-effective and non-destructive manner.

Chiral perovskite-CdSe/ZnS QDs composites with high circularly polarized luminescence performance achieved through additive-solvent engineering.

Chiral perovskite materials are being extensively studied as one of the most promising candidates for circularly polarized luminescence (CPL)-related applications. Balancing chirality and photoluminescence (PL) properties is of great importance for enhancing the value of the dissymmetry factor (glum), and a higher glum value indicates better CPL. Chiral perovskite/quantum dot (QD) composites emerge as an effective strategy for overcoming the dilemma that achieving strong chirality and PL in chiral perovskite while at the same time achieving high glum in this composite is very crucial. Here, we choose diphenyl sulfoxide (DPSO) as an additive in the precursor solution of chiral perovskite to regulate the lattice distortion. How structural variation affects the chiral optoelectronic properties of the chiral perovskite has been further investigated. We find that chiral perovskite/CdSe-ZnS QD composites with strong CPL have been achieved, and the calculated maximum |glum| of the composites increased over one order of magnitude after solvent-additive modulation (1.55 × 10-3 for R-DMF/QDs, 1.58 × 10-2 for R-NMP-DPSO/QDs, -2.63 × 10-3 for S-DMF/QDs, and -2.65 × 10-2 for S-NMP-DPSO/QDs), even at room temperature. Our findings suggest that solvent-additive modulation can effectively regulate the lattice distortion of chiral perovskite, enhancing the value of glum for chiral perovskite/CdSe-ZnS QD composites.

Octahedron vacancy induced luminescence improvement of double perovskite type phosphors LaMg2/3-xNb1/3O3:Mn4+ with multifunctional applications

Near infrared (NIR) phosphors have been booming as promising candidates for agriculture due to the adjustable spectrum and excellent match with the dyes of the plants. Here, Mn4+ activated double perovskite LaMg2/3Mn1/3O3 NIR phosphor was prepared, which showed high match with the absorption spectra of phytochrome PFR. Concentration of Mg2+ was decreased to create octahedron vacancy into the lattice to improve the luminescence performance. Structure and luminescence variation of the phosphors LaMg2/3-xNb1/3O3:Mn4+ along with the increased vacancy concentration were carried out. Relative sensitivity Sr of the optimized LaMg0.57Nb0.33O3:Mn4+ reaches 3.109 % and exhibits great application potential in temperature sensor. Both the NIR light emitting diode (LED) and white LED were fabricated by using this double perovskite NIR phosphor and applied to the cultivation of dragon fruit as light compensation. The dragon fruits matured faster than those without any light compensation. These results confirm the great application potential of this double perovskite NIR phosphor in temperature sensor and plant cultivation.

Enhancement of luminescent and photocatalytic performance of hydrothermally synthesized ZnS NPs using Ce as defect regulator

Using the hydrothermal technique, we synthesised ZnS and Ce-doped ZnS nanoparticles with various doping concentrations (0.5, 1, 2.5, and 5 wt%). X-ray diffraction (XRD) analysis indicated that pure ZnS nanoparticles exhibited a cubic phase, but when doped with Ce, the phase changed to wurtzite. The phase transition in the doped ZnS nanoparticles was also verified by Raman spectroscopy. In the photoluminescence (PL) spectra, however, no transitions matching to the dopant were identified, the overall luminous behaviour of the nanoparticles may still be influenced by the luminescence of the host material. Morphological examinations were carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed information about the size, shape, and distribution of the nanoparticles. The presence of Ce was further confirmed by Energy-dispersive x-ray spectroscopy (EDAX). The visible light photocatalytic activity of the nanoparticles was examined, and it was observed that the photocatalytic efficiency initially increased with doping concentration and then decreased. For 99% degradation efficiency, a doping concentration of 1% was determined to be optimal. The success of the synthesis and characterisation of Ce-doped ZnS nanoparticles is highlighted in this work, which demonstrates their phase change, shape, elemental composition, and photocatalytic activity. the findings give important insights into the possible uses of these nanoparticles in photocatalysis and other domains like optoelectronics.

Nonstoichiometry-Induced Self-Activated Phosphors for Dynamic Anti-counterfeiting Applications.

Optical signals with distinctive properties, such as contactless, fast response, and high identification, are harnessed to realize advanced anti-counterfeiting. However, the simultaneous attainment of multi-color, -temporal, and -modal luminescence performance remains a compelling and imperative pursuit. In our work, a temperature/photon-responded dynamic self-activated luminescence originating from nonstoichiometric Zn2GeO4 is developed with the modulation of intrinsic defects. The increased concentration of oxygen vacancies (VO••) contributes to an enhanced recombination of ZnGe″-VO••, ultimately improving the self-activated luminescence performance. Additionally, the photoluminescence (PL) color of the representative Zn2.2GeO4 sample changes from green to blue-white with the increased ultraviolet (UV) irradiation time. Concurrently, the emission color undergoes a variation from blue to green as the ambient temperature raises from 280 to 420 K. Remarkably, green long persistent luminescence (LPL) and photostimulated luminescence (PSL) behaviors are observed. Herein, this study elucidates a sophisticated anti-counterfeiting approach grounded in the dynamic luminescent attributes of nonstoichiometric Zn2GeO4, presenting a promising frontier for the evolution of anti-counterfeiting technologies.

Crystal growth and spectroscopic analysis of Ho,Pr:BaF2 crystal for 3 μm mid-infrared emission

Ho-doped and Ho,Pr co-doped BaF2 crystals were grown using the temperature gradient technique. The absorption spectra, fluorescence spectra, and fluorescence lifetimes were measured and analyzed. For Ho-doped BaF2, 1.0 at.% Ho:BaF2 showed the best luminescence performance in the 3 μm band. After co-doping with Pr3+, the lower-level lifetime of Ho3+ ions in the 3 μm band was significantly reduced, while the upper laser level lifetime was minimally affected, indicating that Pr3+ ions can be effectively used as a deactivating ion of Ho3+ ions in the BaF2 matrix. For 1.5 at.% Ho, 0.1 at.% Pr:BaF2, the lifetime ratio of the upper and lower levels was 0.47, effectively realizing population inversion.