Multicolor Emission Research Articles

Achieving color-tunable persistent afterglow from ultralong polyacrylamide-based room-temperature phosphorescence materials through phosphorescence Förster resonance energy transfer

Polymer-based pure organic room-temperature phosphorescence (RTP) materials have received widespread attention due to their great application prospects in many fields. However, the reports about polymer-based multicolor RTP materials were still rare. Herein, a series of monochromatic PAM-based RTP materials are constructed by facilely doping boric acid derivatives into polyacrylamide (PAM) matrices. Due to the strong intermolecular hydrogen-bonding interaction, 4-carboxyphenylboronic acid (CPBA) doped system PAM/CPBA achieves an ultralong RTP lifetime of 753 ms with a naked-eye visible blue afterglow up to 12 s. Significantly, PAM/CPBA as energy donor and the commercial fluorescent dye fluorescein (FL) or rhodamine B (RhB) as energy acceptor are used to fabricated ternary doping systems to achieve multicolor afterglow emission through phosphorescence Förster resonance energy transfer (FRET). The afterglow colors of PAM/CPBA/FL and PAM/CPBA/RhB can be easily adjusted from blue to yellow or purple by changing the doping content of FL or RhB. Inspiringly, a nearly white afterglow emission from the quaternary doping system PAM/CPBA/RhB/FL is achieved by varying the amount of FL content. Furthermore, the prepared PAM-based binary and ternary doping RTP materials can be applied in the field of information encryption.

Colorful visualization detection of near-infrared light enabled by an upconversion device with a color-tunable quantum dot light-emitting unit

Color-tunable near-infrared (NIR)-to-visible upconversion devices (UCDs) that correlate the NIR power intensity with the visible emission color are highly desired and hold promise for interactive signal visualization in intelligent optoelectronic devices. In this work, solution-processed color-tunable UCDs integrating a NIR sensing photodetector unit and a color-tunable quantum dot (QD) light-emitting unit are demonstrated. We mixed the red and green QDs in a single emissive layer (EML) for multi-color emission from the UCDs, which is quite different from the previously reported work that used multiple EMLs with different colors. The image color of the resulting color-tunable UCDs can be modulated by bias voltage and driving current and shows a wide color-span range from red to green as the NIR intensity increases. Finally, we present a qualitative correlation between the incident NIR power intensity and the visible emission color, which enables colorful visualization detection of NIR light.

Highly Sensitive Optical Manometer Based on the Visible Emissions of Ce3+‐Doped La6Sr4(SiO4)6F2 Multisite Phosphors

AbstractFor overcoming the unsatisfactory sensitivity of optical manometers and the susceptibility of manometric parameters to temperature changes, a series of Ce3+‐doped La6Sr4(SiO4)6F2 phosphors with multicolor emissions are developed. Excited by 375 nm, the resultant compounds exhibit asymmetric and broad emission bands, which can be easily deconvoluted into two peaks originating from seven to ninefold coordinated Ce3+ sites, where their intensities are dependent on the excitation wavelength. Through analyzing the pressure‐related luminescence intensity ratio (LIR) derived from these two Ce3+ sites, it is clear that the final manometer exhibits an unprecedentedly high relative sensitivity of ≈ 425% GPa−1 at 0.76 GPa (the highest value reported to date). As pressure increases, the emitting color tunes from yellow to blue, resulting in the possibility of visual pressure sensing. Furthermore, based on the color coordinates of the phosphor material, its pressure sensing capability is discussed, in which the maximum sensitivities are 24.38 and 27.74% GPa−1 at 0.76 GPa, when x‐coordinate and y‐coordinate are employed, respectively. Additionally, the LIR value is only slightly affected by temperature, leading to a thermal invariability manometric factor (TIMF) > 400 K GPa−1. The findings indicate that Ce3+‐doped La6Sr4(SiO4)6F2 phosphors are good luminescent candidates for optical and visual multi‐mode manometers.

Multicolor emission tuning of ZnS@SiO2-Eu3+ composite as potential application in light-emitting devices

Multicolor emission tuning of ZnS@SiO2-Eu3+ composite as potential application in light-emitting devices

Experimental capabilities for liquid jet samples at sub-MHz rates at the FXE Instrument at European XFEL.

The Femtosecond X-ray Experiments (FXE) instrument at the European X-ray Free-Electron Laser (EuXFEL) provides an optimized platform for investigations of ultrafast physical, chemical and biological processes. It operates in the energy range 4.7-20 keV accommodating flexible and versatile environments for a wide range of samples using diverse ultrafast X-ray spectroscopic, scattering and diffraction techniques. FXE is particularly suitable for experiments taking advantage of the sub-MHz repetition rates provided by the EuXFEL. In this paper a dedicated setup for studies on ultrafast biological and chemical dynamics in solution phase at sub-MHz rates at FXE is presented. Particular emphasis on the different liquid jet sample delivery options and their performance is given. Our portfolio of high-speed jets compatible with sub-MHz experiments includes cylindrical jets, gas dynamic virtual nozzles and flat jets. The capability to perform multi-color X-ray emission spectroscopy (XES) experiments is illustrated by a set of measurements using the dispersive X-ray spectrometer in von Hamos geometry. Static XES data collected using a multi-crystal scanning Johann-type spectrometer are also presented. A few examples of experimental results on ultrafast time-resolved X-ray emission spectroscopy and wide-angle X-ray scattering at sub-MHz pulse repetition rates are given.

Photo-induced tunable luminescence from an aggregated amphiphilic ethylene-pyrene derivative in aqueous media

An amphiphilic derivative with a large Stokes shift by introducing flexible hydrophilic long chains into a rigid ethylene-pyrene compound have been successfully synthesized. The alkylated compound exhibited a notable change in charge distribution, facilitating cation-π interactions. Through the process of amphiphilic self-assembly, the formation of highly ordered aggregates enabled effective photo-dimerization under 449 nm LED irradiation. Notably, this photo-responsive technology not only exhibited advanced multi-color emission effects, including white light emission but also exhibited environmentally friendly behavior in the aqueous phase.

Temperature-triggered boron-doped carbon nanoparticles-labeled polyethylene terephthalate with dual emission for double-level fluorescence anti-counterfeiting

The sustainable applications of plastics are extremely challenging in the field of environment. Here, a facile synthesis of temperature-triggered fluorescence platform composed of boron-doped carbon nanoparticles (BCNPs) and polyethylene terephthalate (PET) was proposed as a convenient way to reuse PET plastic products. Notably, the fluorescence of this platform was tuned by incubation temperature and suitable for double-level anti-counterfeiting by utilizing significant difference of fluorescence emission upon 365 and 254 nm excitations, respectively. With a long-term heating regulation, multi-fluorescence emissions could be obtained as fluorescent codes. The fluorescence was assigned that blue emission originated from PET state and red emission derived from surface state of BCNPs. The red emission was enhanced with the increase of temperature, which was the formation mechanism of varied fluorescence. The multi-color emission performance was also validated using slices cut from PET bottle to demonstrate practicability of the platform. The adjustable fluorescence performance made the platform had good anti-counterfeiting ability, which provided a new way for the reuse of PET.

Four-coordinate boron luminophores with N,O-heterobiaryl chelating ligands. Synthesis, structure and photoluminescent properties

Sixteen four-coordinate boron complexes based on N,O-heterobiaryl chelating ligands have been obtained and characterized. These compounds exhibited the multicolor emission with good quantum yields, large Stokes shifts (up to 4987 cm−1), and relatively long fluorescence lifetimes in solution and solid state. The manipulation with structural fragments both in heterocyclic and naphthol moieties showed the prospects for tuning of the absorbance and emitting characteristics. The data of the photo- and chemical stability of the complexes allow us to recommend their use in the study of biological systems.

Self-healing luminescent polyurethane with ultrahigh toughness resulting from lanthanide-bipyridine segment and hydrogen bonds

Synthesis and manufacturing a new generation of luminescent elastomers that simultaneously features self-healing efficiency with superior mechanical properties remains a challenge due to the compromise between toughness and self-healing ability. Here, a new class of transparent luminescent materials was synthesized via coordinating lanthanide (Ln3+) to bipyridine (Bpy) units introduced into the polymer backbone prepared by polymerization of Polytetramethylene ether glycol (PTMEG) and 4-methylenedicyclohexyl diisocyanate (HMDI). Relying on collaborative reinforcement of a great number of loosely packed Ln3+-ligand coordination bonds and hydrogen bonds (H-bonds), the prepared luminescent polymers showed an ultrahigh toughness of 373.12 MJ m−3 and a mechanical ultrahigh strength of 33.73 MPa. In addition, the multi-color emission behavior of the luminescent materials can be simply adjusted via tailoring the molar ratio of Eu3+/Tb3+. The luminescent self-healing materials can reversibly respond to acid-base vapor because of protonation/deprotonation of Bpy ligands. We believe luminescent polymers obtained by us with excellent mechanical properties and luminescence off/on switching ability show great potential applications as acid-base detector.

Zero Thermal Quenching Phenomenon of Green Emitting Carbon Dots with High Biocompatibility and Stable Multicolor Biological Imaging in a Hot Environment.

Carbon dots are emerging fluorescent nanomaterials with unique physical and chemical properties and a wide range of applications. Herein, we have designed and successfully synthesized thermally stable green emissive nitrogen-doped carbon dots (NCDs) with a photoluminescent quantum yield of 11.32% through facile solvent-free carbonization. NCDs demonstrated zero thermal quenching upon various temperatures modulating from 20 to 80 °C. The green emissive NCDs perform very stably even after heating them at 80 °C for 1 h. The thermal stability mechanism demonstrates that C═O and C═N functional groups control the particle aggregation and protect the fluorescent hub from photo-oxidation and thermal oxidation. Highly biocompatible CDs exhibit bright, stable, and multicolor emissions in T-ca cells under hot circumstances (25-45 °C). Additionally, NCDs offer long-term stability in the biosystem, as evidenced by the fact that the cell retains its brightness about 70% after prolonging the incubation time to 8 days. Furthermore, the fluorescent NCDs are utilized as in vivo imaging agents in the hot environment as they display bright and thermally stable imaging (27-45 °C) under 488 nm excitation. The results confirmed that the produced thermally stable NCDs could be used in biology and related medical fields that require hot environment imaging.

Synthesis of multicolour luminescent graphitic carbon nitride quantum dots through controlled graphitization and surface states

Carbon nitride quantum dots are important metal free semiconductors due to their controlled optoelectronics and low toxicity. Here the sulphur heteroatom doping of these nanomaterials is achieved by the low cost hydrothermal process leading to a multicolour photoluminescence. A simple change in water/dimethyl sulfoxide ratio as a solvent helps to achieve a wide tunability in photoluminescence, almost from blue, green, yellow to red with a high quantum yield. This change has been accounted for the particle size, bond conjugation, and heteroatom doping of carbon nitride nanoparticles. Due to multicolour emission, benignity and low cost these materials can be the promising candidates for various optoelectronic applications.

Facile preparation of carbon dots with multicolor emission for fluorescence detection of ascorbic acid, glutathione and moisture content

The nitrogen-doped carbon dots (N-CDs) with multicolor emission (green, yellow, and red) were fabricated with naphthalenetetracarboxylic dianhydride as carbon precursor, and different alkylamines as passive agents. The structures of the as-prepared carbon dots were confirmed by the Fourier transform infrared (FT-IR) spectrum, X-ray photoelectron spectroscopy (XPS) spectra, transmission electron microscopy (TEM), Raman spectra, and X-ray diffraction (XRD) pattern. The characterized results and UV–vis absorption spectrum demonstrated that the luminescence variations of different CDs were probably attributed to the difference of N-related states, oxygen-containing groups, and oxidation degree in the CDs structure. Moreover, the green emitting CDs (G-CDs) could be utilized as fluorescent probe for ascorbic acid (AA) detection with detection limit (LOD) of 5 μM. The yellow emitting CDs (Y-CDs) could be used to detect glutathione (GSH) in the range of 1–70 μM with LOD of 0.07 μM. The red emitting CDs (R-CDs) could detect the water content in THF, DMF, acetone, and EtOH with LODs of 0.44%, 0.31%, 0.55% and 0.55%, respectively. Remarkably, G-CDs and Y-CDs can distinguish AA and GSH respectively with high selectivity and accuracy. Finally, the fluorescent probes based on G-CDs and Y-CDs were successfully applied for the AA and GSH determination in vitamin C tablet, grapefruit juice, and GSH whitening serum samples with high reliability and feasibility, which provided the guidance for the selection of AA and GSH supplements.

Effective role of Co-dopants (Dy3+, Sm3+) on Tunable multicolour emission of Tb3+ doped telluroborate glasses for Natural White light applications

In the current work the efficacy of incorporation of Dy3+ and Sm3+ ions into Tb3+ doped new telluroborate glass as well as their interactions was investigated. In this study, Tb3+ ions were employed as activators and sensitizers for both Dy3+ and Sm3+ ions emissions, which emanate from the excited states of Dy3+ (4F9/2) and Sm3+ (4G5/2) ions through a non-radiative energy transfer process. To validate the emission gamut of the prepared glasses, distinct emission colours were inspected with the CIE 1931 chromaticity analysis and the appropriate correlated colour temperature (CCT) values were estimated. The emission decay profile relating to the Tb3+ ions (5D4 state) of the glasses was investigated. The energy transfer efficiency, which stems from Tb3+ ion to Dy3+ and Sm3+ ions were found to be 49 and 54% respectively. The IH model was successfully used to analyse the interaction mechanism.

Multicolor Emission of Organic Microcrystals with Charge Transfer Interactions through Cocrystal Engineering

Multicolor Emission of Organic Microcrystals with Charge Transfer Interactions through Cocrystal Engineering

Highly fluorescent N, F co-doped carbon dots with tunable light emission for multicolor bio-labeling and antibacterial applications

Carbon dots (CDs) have emerged as potential biomaterials for bioimaging and antimicrobial applications. However, the lack of tunable long-wavelength emission performance and imprecise antibacterial mechanism limit their practical application. Thus, developing versatile CDs that combine outstanding optical performance and excellent antibacterial activity is of great practical significance. Herein, we prepared a novel nitrogen and fluorine co-doped CDs (N, F-CDs) from o-phenylenediamine and 2,3,5,6-tetrafluoroterephthalic acid, which exhibit high fluorescence quantum yield of 52.2%, large Stokes shift of 112 nm, as well tunable multicolor emission light from blue to red region. Thanks to the high biocompatibility and excellent photostability, the N, F-CDs were successfully implemented to multicolor biolabeling of mammalian cells, protozoan cells and plant cells. Moreover, the negatively charged N, F-CDs hold inherent efficient antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). By thoroughly studying the underlying antibacterial mechanisms at the molecular level through real-time quantitative PCR assay, we found the expression of related genes was notably down-regulated, further demonstrated that N, F-CDs against two bacterial strains had distinct target pathways. Our work provides a new reference for developing highly fluorescent multicolor CDs, and may facilitate the design and application of CDs-based nanomaterials in biological environment.

Red InGaN Micro-LEDs on Silicon Substrates: Potential for Multicolor Display and Wavelength Division Multiplexing Visible Light Communication

Red micro light-emitting diodes (micro-LEDs) on silicon substrates are crucial for the realization of large-scale, high-quality, low-cost micro-LED displays, and are also beneficial for high-speed visible light communication (VLC). In this letter, micro-LEDs with different sizes were fabricated. The maximum light output power density of the 20 μm pixel can reach 3.36 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is 14 times higher than that of the largest pixel (150 μm). By adjusting the pixel size and injection current, a direct color shift from red to green can be observed. Moreover, multicolor emission with uniform brightness can be realized by adjusting duty cycle, which has broad application prospect in monolithic, multicolor displays. Despite the significant blue shift phenomenon, the peak wavelength of all pixels is still greater than 630 nm at the current density of 100 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which means that red light can be emitted in a large current density range to meet various application scenarios requiring different driving conditions. We have realized red, yellow and green micro-LED transmitters on Si substrate by changing the driving current density and modulation bandwidth up to 533.15 MHz is achieved when emitting green light. This is the report of red-emission micro-LEDs on Si substrates for visible light communication for the first time. And we proposed a proof-of-concept monolithic, multicolor wavelength division multiplexing scheme that achieved a total allowable transmission data rate of 2.35 Gbps. Such micro-LED is expected to be applied in multicolor displays, high-speed multi-channel VLC, color-tunable light sources, etc. In particular, due to its high integration and miniaturization, it is expected to be used in future practical application scenarios such as wearable communication devices and smartwatches.

Sulfonium-cation-containing aggregation-induced emission block copolymers: self-assembly, multicolor emission, and detection for DNA polyplexes

Amphiphilic aggregation-induced emission (AIE) polymers have emerged as highly attractive materials that exhibit the synergistic effect of functional polymeric self-assemblies with AIE luminogens. In this study, we design and synthesize block copolymers containing sulfonium cations and a hydrophobic tetraphenylethene (TPE) unit. These copolymers exhibit distinct self-assembly behaviors with AIE, polyplex formation with DNA, and tunable color emissions. Amphiphilic block copolymer PMTEAMe+Cl--b-PATPE, consisting of 4-(1,2,2-triphenylvinyl)phenyl acrylate (ATPE) and cationized 2-(methylthio)ethyl acrylate (MTEAMe+Cl-), was synthesized via reversible addition–fragmentation chain transfer polymerization, followed by cationization. Self-assembled structures containing TPE-aggregated cores and cationic PMTEAMe+Cl- shells and their emission behaviors were investigated. By introducing charged fluorescent dyes (Rose Bengal and Rhodamine B) into aqueous solutions of amphiphilic PMTEAMe+Cl--b-PATPE, we observed a shift in the emission color from blue to orange/red, which was attributed to the electrostatic interactions and fluorescence resonance energy transfer between the dyes and the copolymers. The emission color and intensity were also governed by polyplex formation between the negatively charged DNA and the positively charged sulfonium segments in the shell, depending on the charged states of the dyes. This system provides a method for efficient visual detection of DNA polyplex formation using multicolor fluorescent coding.

Nonlinear Metal–Organic Framework Crystals for Efficient Multicolor Coherent Optical Emission

AbstractNon‐centrosymmetric metal–organic frameworks (MOFs) have recently emerged as a promising class of coordination polymers for nonlinear optics and light conversion. Nevertheless, achieving high endurance and efficiency for the light conversion within the whole visible range by a single crystal of MOF remains a challenge. This article reports on the design of two non‐centrosymmetric MOFs based on a 1,3,5‐benzenetricarboxylic acid ligand and Er/Co ions, providing an efficient and simultaneous multiple second and third optical harmonic generations (SHG, THG) from 400 to 750 nm with a high endurance (over 100 cycles or 3 h of continuous operation). Optical experiments and quantum chemical modeling of the MOF single crystals confirm the polarization and chemistry‐dependent efficiency of SHG and THG, associated with the varied MOFs' symmetry and dipole moment. The observed coherent light conversion within the whole visible range by MOF single crystals at ambient conditions makes it possible to achieve the multicolor (up to three) coherent emission required for modern laser technologies, making MOFs highly competitive and sustainable materials for nonlinear optics.

Optimizing scalable synthesis of high-quality FeSe quantum dot in organic and aqueous states

A typical layered transition metal chalcogenide nanostructure, FeSe quantum dots (QDs) have recently begun to attract for their unique optical properties, i.e., multicolored excitation dependent emission (MEDE) property that breaks conventional Kasha - Vavilov rule as well as their potential applications in biological, and optical/electronic sensing and imaging. In this article, we present robust and optimized protocols for the scalable synthesis of FeSe QDs either in aqueous or organic syntheses. The synthesis conditions were carefully compared to obtain insistent synthesis parameters, e.g., solvents, precursors, stabilizers, pH, temperature, concentration, and reaction time after reproduction experiments. Furthermore, post-treatment procedures, i.e., phase transition and PEGylation are also optimized for further potential environmental and biological applications. In the scale-up experiments, a 5-liter reactor was utilized to produce approximately 55 g of QDs per batch, showing a robust optical MEDE property. The most optimized experimental condition reached quantum yield (QY) up to 60 % at the typical synthesis conditions of pH 9.0, 95 °C for 4 h of reflux, and the production yield of ca. 20%. These high fluorescent QDs can be potentially applied for biological fluorophores as well as next-generation QD displays.

Photoinduced multi-color emission of naphthalenediimide radical in different solvents and dynamic anti-counterfeiting film

Developing innovative materials with environmentally stable 1,4,5,8-Naphthalene diimide radicals (NDI−) emissions is significant. In this work, we have successfully constructed an NDI-based material 2-NDI (N, N′-bis(2-butyric acid)-1,4,5,8-naphthalene diimide) that emits strong fluorescence in solvents and polymethyl methacrylate (PMMA) upon irradiation. The radical 2-NDI− exhibits multi-color emission in different solvent systems, and the fluorescence emission is concentration-dependent. It is worth noting that it exhibits a rare dynamic fluorescence in DMF solvent, with the fluorescence color changing from yellow-green to orange and finally to white. Theoretical calculations show that the fluorescence is derived from the Dn-D0 vertical emission of 2-NDI− monomer and excimer. Owing to the outstanding free radical fluorescence emission properties, various films (PMMA systems) based on 2-NDI in different solvents have been successfully made to be applied in multiple dynamic information anti-counterfeiting and encryption. This work achieved simple and stable fluorescence emission based on NDI−, making it a potential candidate for practical applications and providing a new platform for the future design of NDI-based photochromic materials.