Tunable Photoluminescence Properties Research Articles

Achieving Luminous Efficiency Enhancement and Near‐Infrared Emission in Moisture‐Stable 0D Zinc‐Based Halides

AbstractZero‐dimensional (0D) metal halides are attractive due to their structure‐dependent and tunable photoluminescence properties. Herein, a new 0D organic–inorganic hybrid Zn‐based halide, (C4H12N2)ZnBr4, featuring a long‐term stable crystal structure and moisture‐stable PL emission under various extreme conditions is reported. A strong electron–phonon coupling effect enables the Zn‐based halide to display highly efficient blue light at 472 nm with a large Stokes shift of 7385 cm−1. Intriguingly, heterovalent substitution of Cu+‐Zn2+ further enhances the photoluminescence quantum efficiency to 60% as the introduction of Cu+ effectively suppresses the nonradiative recombination process. Besides, the formation of twisted [SbBr4]− tetrahedra via Sb3+‐Zn2+ substitution help to achieve a broadband near‐infrared (NIR) emission (760 nm) with full width at half maxima (FWHM) of 203 nm, enabling the potential applications in night‐vision and nondestructive fruit damage inspection. Detailed structural and optical analyses are used to investigate the photophysical processes of different self‐trapped exciton (STE) emission for pristine and Cu+/Sb3+‐doped 0D metal halides. These findings advance the understanding of spectral regulation mechanism via heterovalent substitution and initiate more exploitation of luminescent metal halides for emerging applications.

Excited-state intramolecular proton transfer (ESIPT) salicylaldehyde Schiff bases: ratiometric sensing of ammonia and biologically relevant ions in solution and solid state

ABSTRACT The intricate molecular architecture of ESIPT salicylaldehyde Schiff bases facilitates dynamic processes, inducing tunable photoluminescent properties. Notably, their halochromic nature, exhibiting colour changes in response to external stimuli, adds a vibrant dimension to their molecular repertoire. This sensitivity extends to environmental factors, making them valuable indicators for alterations in surroundings. The compound (E)-N’-(3,5-dibromo-2-hydroxybenzylidene)-4-methylbenzohydrazide (PTBH) demonstrates exceptional sensitivity to ammonia, enabling real-time detection (LOD = 0.14 nM) in both solution (ratiometric) and the solid state. Moreover, their metal chelation capability allows simultaneous sensing of Mg2+ and Fe2+ ions, addressing environmental hazards. Exploiting molecular recognition, the fluorescent probe serves as sensors for amino acids, opening new avenues in biomedical diagnostics. The study introduces a novel solid-state emissive Schiff base, highlighting its stimuli-responsive photoluminescent properties and diverse applications, emphasising its potential in intelligent fluorescent materials for analytical and sensing technologies.

Synthesis, Characterization and Photophysical Properties of a New Family of Rare-Earth Cluster-Based Metal-Organic Frameworks.

In this work, nine new rare-earth metal-organic frameworks (RE-MOFs, where RE=Lu(III), Yb(III), Tm(III), Er(III), Ho(III), Dy(III), Tb(III), Gd(III), and Eu(III)) isostructural to Zr-MOF-808 are synthesized, characterized, and studied regarding their photophysical properties. Materials with high crystallinity and surface area are obtained from a reproducible synthetic procedure that involves the use of two fluorinated modulators. At the same time, these new RE-MOFs display tunable photoluminescent properties due to efficient linker-to-metal energy transfer promoted by the antenna effect, resulting in a series of RE-MOFs displaying lanthanoid-based emissions spanning the visible and near-infrared regions of the electromagnetic spectrum.

Facile Light-Driven Synthesis of Highly Luminous Sulfur Quantum Dots for Fluorescence Sensing and Cell Imaging.

Sulfur quantum dots (SQDs) are emerging fluorescent nanomaterials, whereas most of the methods for synthesizing SQDs are limited to thermal synthesis. In this study, we report the first case of a light-driven strategy for facile synthesis of SQDs and further applied the SQDs for fluorescence cell imaging. The light-driven synthesis strategy only utilized Na2S as the sulfur source and nano-TiO2 as the photosensitizer. Under ultraviolet illumination, the nano-TiO2 photosensitizer generated a large number of •O2- and •OH to oxidize S2- to Sx2- and further to elemental sulfur, which could be obtained as monodispersed SQDs after etching by H2O2. The prepared SQDs exhibit excellent tunable photoluminescence properties, superior stability, and a uniform small size, with particle diameters in the range of 0.5-4 nm, and the fluorescence absolute quantum yield is as high as 27.8%. Meanwhile, the prepared SQDs also exhibited extreme biocompatibility and stability, and we further applied it for intracellular imaging and Hg2+ sensing with satisfactory results. In comparison to the widely reported thermal synthesis, the light-driven synthesis method is greener and simpler, opening a new way for the preparation of biocompatible SQDs.

Tuning of photoluminescence properties: Impact of Pr-doping in SrTiO3 crystallites

Materials having deep blue emission characteristics with a CIEy chromaticity value less than 0.1 are highly desired. Here we incorporated Pr3+ into the Sr2+ site of the Sr1-x PrxTiO3 (x=0.05, 0.075, 0.10, 0.125, 0.15, 0.20) to quench the typical red photoluminescence (PL) emission in Pr-doped compounds and tune it to a blue-emitting system. XRD analysis and structural refinement demonstrate transition from cubic to tetragonal symmetry at Pr concentrations of, x≥0.1. The contribution of oxygen vacancies in emission mechanism was investigated through XPS analysis. High-resolution FE-SEM analysis of morphological features revealed the creation of tiny grains with the appearance of micro pebbles. Under 380 nm UV illumination a narrow-band blue emission peak FWHM of 19.3 nm was obtained at 428 nm for x=0.05. CIE plots were used to examine the quality of emission peaks and samples show CIEy less than 0.1. This blue emission is crucial for lighting and display applications.

Functional and ultrastretchable thermoplastic elastomeric materials: Influence of carbon dots on fluorescence, dielectric and mechanical properties

AbstractCarbon dots (CDs) are an interesting nanomaterial due to their tunable photoluminescence and other functional properties. Herein, by introducing amine‐functionalized CDs nanoparticles onto macromolecular chains of maleic anhydride grafted styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) via a possible ring‐opening reaction of anhydride with amine, a mechanically robust and ultrastretchable thermoplastic elastomeric materials with fluorescence and dielectric functionality was developed. The amine‐functionalized CDs nanoparticles were synthesized from pyrene precursor by hydrothermal treatment. The transmission electron micrograph, Raman, Fourier transform infrared, and x‐ray photoelectron spectra confirmed the formation of highly crystalline graphitized structure of the CDs nanoparticles. Fluorescence and UV–Vis spectroscopy were used to evaluate the optical properties of the developed materials. The developed CDs/SEBS‐g‐MA nanocomposites exhibited strong intense green fluorescence compared with the pure SEBS‐g‐MA film. The thermal stability of the developed nanocomposites was improved by an increase of the Tmax by about 18°C. In addition, the developed composite showed high stretchability (strain at break ~1000%), good mechanical strength, and dielectric properties (room temperature dielectric constant ~5.2). The enhanced dielectric property of the developed composites may be due to the space charge accumulation and induced interfacial polarization at the filler–matrix interface.

Design and spectroscopic study of samarium complexes with tunable photoluminescent properties

The synthesis and characterization of four octacoordinated complexes of [Sm(TFPB)3] with different neutral ligands have been successfully performed. This study aimed to evaluate the potential of neutral ligands in enhancing the emission intensity of Sm(III) ion by investigating their light-emitting characteristics. Dominance of hypersensitive transition 4G5/2 → 6H9/2 is observed which suggests the asymmetry in the vicinity of Sm(III) ion in these complexes, reinforced by asymmetry ratio. Stark-splitting in the magnetic dipole 4G5/2→6H5/2 transition was consistent across most complexes, but [Sm(TFPB)3(topo)2] displayed a different pattern due to monodentate auxiliary moiety, which does not provide as much structural rigidity and stability as found in the other complexes. Various analyses including IR, NMR, CV, TGA, UV and colorimetry, supported possible applications of synthesized complexes in devices based on photonics, sensors, magnets and other technological fields.

Dual-emissive luminescence in OIHMH single crystals: tunable red-green emissions via Mn2+ doping and theoretical insights.

The burgeoning demand for materials with tunable photoluminescence properties for applications has necessitated the exploration of novel luminescent materials. This study presents the synthesis and characterization of a novel 0D organic-inorganic hybrid metal halide (OIHMH) single crystal, C6H14N2CdBr4, which exhibits intriguing luminescent properties upon Mn2+ doping. The introduction of single Mn2+ ions results in a dual-emission, with the unexpected emergence of a red emission peak at 627 nm, in addition to the conventional tetrahedral green emission at 525 nm. This dual-emission is attributed to the distinct inter-tetrahedral distances within the crystal structure of C6H14N2CdBr4 with varying distances between [CdBr4]2- tetrahedra, influencing the spatial distribution and interaction of the [MnBr4]2- tetrahedra. Electron paramagnetic resonance (EPR) spectroscopy and theoretical calculations reveal the 627 nm and 525 nm emissions are attributed to the d-d transition of magnetic coupled Mn2+-Mn2+ pairs and isolated Mn2+ ions, respectively. This study not only advances the understanding of the luminescence mechanisms of Mn2+ but also paves the way for the development of tunable luminescent materials.

Low-Temperature and Catalyst-Free Plasma Synthesis of Plastics-Derived Graphene Quantum Dots

The advanced industrial, social, and technological developments in modern society have rendered the production of around 300 million tons of plastic annually, yet only 50% or even less are being recycled. Moreover, the current recycling process is limited to the conversion of plastic wastes (PWs) into hydrocarbon fuels, which also requires the use of high temperatures and energies, long reaction time, and high-cost platinum-based catalysts. Therefore, there is an urgent need to develop a more sustainable and environmentally friendly method to recycle these PWs and possibly into functional materials for diverse applications.We introduce non-equilibrium and low-temperature microplasma technologies to convert PWs into graphene quantum dots (GQDs) at ambient conditions without any additional toxic chemicals, expensive catalysts, and sophisticated vacuum technologies. The reactive species generated by the plasma enables not only rapid deconstruction of PWs into small hydrocarbons moieties, but also simultaneous reconstruction of nanographene domain and nucleation into GQDs. GQDs are zero-dimensional carbon nanomaterials with unique quantum confinement and edge effects, which are hybridized by sp2 carbon in a honeycomb network. The quantum confinement and edge effects bestow GQDs with unique, tunable, and stable photoluminescence (PL) properties. Coupled with the biocompatibility, low toxicity, large surface area, and chemical inertness, GQDs can be employed in various applications, including imaging, sensing, optoelectronics, drug delivery, catalysis, and energy related applications. Nevertheless, the current syntheses of GQDs still need the use of high temperatures, strong acids or reducing agents, long reaction time, and tedious synthesis procedures.Here the utilization of microplasma enables the degradation and conversion of various plastics into functional GQDs with well-controlled structures in one-step at ambient conditions and catalyst-free manner, alleviating the current drawbacks in the GQDs synthesis. Among various PWs, polyethylene terephthalate-derived GQDs (PET-GQDs) exhibit enticing and bright white emission under 365 nm UV irradiation with a Commission Internationale de l’Eclairage 1931 of (0.29, 0.35). Moreover, the colloidal PET-GQDs can be exploited for heavy metal ions detection with a low limit of detection of 8.4 nM, while the composite film state is usable as sensitive temperature tag from 10 – 80 °C and LED panel. Our work provides an insight into the novel technologies for PWs recycling into functional nanomaterials in cost-effective, scalable, and environmentally friendly way.

Synthesis and tunable photoluminescence properties of Er3+/Eu3+ co-doped Na5La(MoO4)4 phosphors

The tunable emission characteristics of Er3+ doped and Er3+/Eu3+ co-doped Na5La(MoO4)4 phosphors prepared via high-temperature solid phase method were investigated. The microstructure of the modified phosphor was studied by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy, and its luminescence properties were analyzed by photoluminescence excitation and photoluminescence spectra. The energy transfer mechanism of Er3+ ions to Eu3+ ions was investigated by changing the concentration of Eu3+ ions to induce the spectral changes, and the photoluminescence decay lifetime was measured to validate the findings. Notably, under excitation at 380 nm, the co-doped phosphors exhibited tunable emission ranging from green to orange-red. Furthermore, Na5La(MoO4)4:0.04Er3+/0.04Eu3+ phosphor, when combined with a 380 nm chip, achieved desired warm white light emission. These promising results underscore the potential application of Na5La(MoO4)4:0.04Er3+/0.04Eu3+ phosphor in solid-state lighting.

Preparation of multicolor carbon quantum dots by hydrothermal method and their functionalization applications

Carbon quantum dots (CQDs) have become a popular research topic because of their many unique virtues, especially the significance of tunable photoluminescence properties. However, the synthesis of multicolor CQDs is still at an exploratory stage, and there are many dilemmas that have not yet been well resolved, such as long-wavelength emission and solid-state luminescence. Here, we selected suitable carbon and dopant sources as precursors for the synthesis of CQDs through the rational design of the experiments in an aqueous system, and the as-prepared CQDs possessed blue, green, yellow and red emissions, with optimal emissions of approximately 475 nm, 530 nm, 580 nm, and 645 nm, respectively. Furthermore, the corresponding PLQYs were 30.13 %, 36.84 %, 39.16 % and 21.36 %, respectively. It was found that the redshift of the emission wavelengths can be attributed to the synergistic effect of the increase in the sp2 conjugate size and the surface states. To conquer the aggregation caused quenching (ACQ) of CQDs and realize the solid-state luminescence of CQDs, we successfully prepared solid-state fluorescent films and solid-state phosphors. Finally, multicolor CQDs were successfully applied to prepare monochromatic and white light-emitting diodes (WLEDs). The adopted green synthesis technology can provide a good technical support for the future development of CQDs synthesis.

Magnetically driven nanorobots based on peptides nanodots with tunable photoluminescence for rapid scavenging reactive α-dicarbonyl species and effective blocking of advanced glycation end products.

The present work constructed magnetically driven nanorobots by conjugating the photoluminescent β-alanine-histidine (β-AH) nanodots to superparamagnetic nanoparticles (SPNPs) for simultaneously sensitive determination and fast trapping RDS in food processing, achieving efficient regulation of advanced glycation end products (AGEs) risk. Bio-derivative β-AH nanodots with orderly self-assembly nanostructure and tunable photoluminescent properties served as both biorecognition elements to effectively bind and scavenge the reactive α-dicarbonyl species (RDS), as well as the indicator with sensitive fluorescence response in the food matrix. The magnetically driven nanorobots with excellent biosafety of endogenous dipeptides displayed a high binding capacity of 80.12mgg-1 with ultrafast equilibrium time. Furthermore, the magnetically driven nanorobots achieved rapid removal of the RDS with the manipulation of the external magnetic field, which enabled intercepting AGEs generation without byproducts residual as well as ease-of-operation. This work provided a promising strategy with biosafety and versatility for both accurate determination and efficient removal of hazards.

Color‐Tunable Carbon Dots with Aggregation‐Induced Emission Constructed by FRET between Surface Luminescence Centers

AbstractAs a class of new fluorescent materials, carbon dots (CDs) have drawn widespread attention by virtue of their tunable photoluminescence (PL), excellent biocompatibility, and novel physicochemical properties. Unfortunately, in solid state, most CDs experience serious aggregation‐caused quenching (ACQ). In this work, color‐tunable CDs with aggregation‐induced emission (AIE) are prepared by simply changing the filling ratio of the autoclave. The obtained CDs show dual emission (green/red) in solid state, and the fluorescent color can be tuned from green to red. These CDs all exhibit blue fluorescence in dilute solution, and aggregation‐induced redshift behaviors are observed when the CDs form aggregates. Structural and optical characterizations prove that blue fluorescence is contributed by the carbon cores, whereas the green/red emission is attributed to the surface groups. Multicolor fluorescence is caused by increased fluorescence resonance energy transfer (FRET) efficiency among the dual emission (green/red) peaks from g‐CDs to r‐CDs. Surprisingly, delayed fluorescence (DF) of CDs are brightened by inserting the CDs into poly(vinyl alcohol) (PVA) films, which can be easily recognized by the naked eyes with a lifetime up to ms. Finally, owing to the unique AIE and DF properties, the four CDs can be applied to multimodal advanced anti‐counterfeiting and information encryption.

Synthesis and characterization of ZnGa2O4:Cr3+Ge3+ compounds with tunable photoluminescence properties

Synthesis and characterization of ZnGa2O4:Cr3+Ge3+ compounds with tunable photoluminescence properties

Tunable photoluminescence properties and non-contact thermometry of Bi3+, Sm3+ co-doped YVO4 phosphors

Tunable photoluminescence properties and non-contact thermometry of Bi3+, Sm3+ co-doped YVO4 phosphors

Self-Assembly and Mechanochromism Behavior of Gold(I) Supramolecular Cluster

Aurophilicity interaction has played a crucial role in the controllable self-assembly of polynuclear clusters with high nuclear structures and tunable photoluminescence properties. We proposed a multi-component synergistic self-assembly strategy for the controlled synthesis of a hexadeca-nuclei gold(I) supramolecular cluster through spontaneous ligand substitution and conformation rearrangement driven by AuI···AuI bonding interactions. In supramolecular cluster 12+·2BF4–, multi-components could be highly accurately aggregated together when thiolate-chloride/phosphine coordination exchange reactivity is partially activated by changing the stoichiometric ratio between digold(I) corners, dppmAu2Cl2, and ditopic linkers, trithiocyanuric salt. Mass spectra confirmed the stepwise self-assembly mechanism in solution, which was also supported by crystallographic data. Supramolecular cluster 12+·2BF4– displayed intense emission properties either in the solid state or in solution. Moreover, cluster 12+·2BF4– exhibited a reversible mechanochromic luminescence behavior in the crystalline state and aggregation-caused blue-shifted emission in solution. Hence, emissive gold(I) cluster with strong aurophilicity interactions has great potential value in the fluorescence imaging for 3D printing hydrogels.

Enhanced stability and tunable photoluminescence in Mn2+-doped one-dimensional hybrid lead halide perovskites for high-performance white light emitting diodes.

Organic-inorganic hybrid low-dimensional lead halides have garnered significant interest in the realm of solid-state optical materials due to their unique properties and potential applications. In this study, we report the synthesis, characterization and application of Mn2+-doped one-dimensional (1D) [AEP]PbCl5·H2O hybrid lead halide perovskites with tunable photoluminescence properties. The Mn2+ doping leads to a redshift of the dominant emission wavelength from 463 nm to 630 nm, with the optimal doping concentration resulting in an enhanced photoluminescence quantum yield (PLQY) from less than 1% to 8.96%. The structural and optical stability of these doped perovskites have been thoroughly investigated revealing excellent performance under humid and high-temperature conditions. Perovskite-PVP composite films exhibit high crystallization and bright orange-red emission under UV excitation. Furthermore, we demonstrate the successful fabrication of a white LED device using the Mn2+-doped perovskite in combination with commercial green and blue phosphors. The fabricated LED exhibits a high color rendering index (CRI) of 87.2 and stable electroluminescence performance under various operating currents and extended operation times. Our findings highlight the potential of Mn2+-doped 1D hybrid lead halide perovskites as efficient and stable phosphors for high-performance white light emitting diodes and other optoelectronic applications.

Renal clearing carbon dots-based near-infrared fluorescent super-small nanoprobe for renal imaging

Real-time renal imaging is indispensable for monitoring kidney-related disease processes and evaluating the nephrotoxicity of nanoprobes. Owing to their small size, tunable photoluminescence properties, and low biotoxicity, carbon dots (CDs) are widely employed as nanoprobes for imaging-guided disease diagnosis. However, the preparation of near-infrared CDs is a stupendous challenging. Here, CDs with near-infrared fluorescence (NIR-CDs) were prepared by one-pot pyrolysis and were comprehensively evaluated for real-time renal imaging. The NIR-CDs possessed super-small size (1.8 ± 0.2 nm) and high quantum yield (14.3% in aqueous solution) at 696 nm. NIR-CDs exhibited high-efficiency renal clearance at 24 h post-treatment (97.47–99.27% ID) via glomerular filtration. The irreversible clearance of NIR-CDs enables effective real-time monitoring of kidney function in the normal and acute kidney injury (AKI) mouse models. Consequently, NIR-CDs can be utilized for imaging analyses of impaired kidney function, pioneering a serviceable guideline for neoapplications of NIR-CDs.

High quality germanate phosphor La(2-x-y)Ge2O7: Tb3+, Eu3+for WLED applications

White light emitting diodes (WLEDs), as the fourth generation of new light source, has the advantages of light weight, small size, low energy consumption, fast response speed and convenient use, but their poor thermal stability, high correlation color temperature (CCT) and low color rendering (Ra) limit their large-scale application of high-power WLED. In this work, we report the preparation of WLEDs by combining rare earth ions Tb3+-Eu3+ with La2Ge2O7, which exhibits tunable photoluminescence properties and excellent thermal stability. The detailed study shows that the layered structure of the material is conducive to efficient energy transfer (ET) between Tb3+ (sensitizer) and Eu3+ (activator), and effectively inhibits the luminescence attenuation caused by concentration quenching. Based on this, the doping ratio of Tb3+/Eu3+ in the phosphor is controlled and the phosphor is combined with blue chip to obtain excellent white light (CCT = 3955 K). The light efficiency (87 lm w−1) is comparable to that of commercial phosphors, and there is no significant decrease after continuous operation for 1000 h, which provides a good candidate material for the preparation of high-power WLED.

Synthesis of CdSe and CdSe/ZnS Quantum Dots with Tunable Crystal Structure and Photoluminescent Properties

Mastery over the structure of nanocrystals is a powerful tool for the control of their fluorescence properties and to broaden the range of their applications. In this work, the crystalline structure of CdSe can be tuned by the precursor concentration and the dosage of tributyl phosphine, which is verified by XRD, photoluminescence and UV-vis spectra, TEM observations, and time-correlated single photon counting (TCSPC) technology. Using a TBP-assisted thermal-cycling technique coupled with the single precursor method, core–shell QDs with different shell thicknesses were then prepared. The addition of TBP improves the isotropic growth of the shell, resulting in a high QY value, up to 91.4%, and a single-channel decay characteristic of CdSe/ZnS quantum dots. This work not only provides a facile synthesis route to precisely control the core–shell structures and fluorescence properties of CdSe nanocrystals but also builds a link between ligand chemistry and crystal growth theory.