Multicolor Photoluminescence Research Articles

Regulation of Local Site Structures to Stabilize Mixed-Valence Eu2+/3+ under a Reducing Atmosphere for Multicolor Photoluminescence.

Co-doping mixed-valence Eu2+/3+ in a single-phase phosphor is an efficient method to realize the emission color regulation, which holds great potential for anticounterfeiting and ratiometric temperature sensing. Here, the mixed-valence Eu-doped Sr1.95+xLi1-xSi1-xAlxO4F (0 ≤ x ≤ 0.25) phosphors were designed and prepared under a reducing atmosphere. The correlation of local phase structures and luminescence properties was discussed. Replacing Si4+-Li+ ion pairs with Al3+-Sr2+ ion pairs compresses the Sr sites occupied by Eu2+, and it stabilizes Eu3+ in a reducing atmosphere and leads to the coexistence of Eu2+ and Eu3+ in single-phase Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu (0 ≤ x ≤ 0.25) phosphors. Based on the wavelength-dependent luminescence color behaviors of Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors, the fluorescent anticounterfeit papers/patterns containing Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors were the same as ordinary paper under ambient conditions. However, the hidden colors or images can be read out with green-orange luminescence under 365/300 nm light excitation. Benefiting from the diverse thermal response emission behaviors of Eu2+ (530 nm) and Eu3+ (703 nm), Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors exhibit temperature sensing performances, with the maximum absolute and relative sensitivity being 0.0294 K-1 at 573 K and 0.83% K-1 at 348 K. More importantly, Sr1.95+xLi1-xSi1-xAlxO4F:0.05Eu phosphors showed excellent stability in humid, acid, and alkali environments, which contributed to applying mixed-valence Eu2+/3+-doped Sr1.95+xLi1-xSi1-xAlxO4F to the fields of multicolor anticounterfeiting and noncontact optical thermometry.

Dopant concentration induced tuning of emission in Eu3+-doped zirconia nanoparticles

Eu3+-doped zirconia has been considered an efficient phosphor material due to its multi-colour emissive photoluminescence properties. Tuning of emission colour is possible by changing the Eu3+-ions concentration and excitation wavelength. The influence of Eu3+-ions and excitation wavelength on the emission intensity, asymmetric ratio, CIE coordinates, and Judd-Ofelt parameters of the Eu3+-doped zirconia nanophosphors have been explored in this work. Ultra-fine nano-sized particles of pure tetragonal zirconia were observed when the samples were calcined under an argon atmosphere at 800 °C. The expansion and distortion of tetragonal zirconia has been confirmed from XRD and Raman Spectra of Eu3+-doped zirconia samples, respectively. The XPS analysis suggested elemental composition and incorporation of trivalent state of Eu-ions in Eu3+-doped zirconia sample calcined under argon calcination condition. Further, emission spectra of Eu3+-doped zirconia samples have been investigated at the excitation wavelength of 240 nm, 393 nm, and 463 nm. The emission spectra of 3 mol % and 6 mol % Eu3+-doped zirconia samples revealed several emission peaks in the range of 580–710 nm corresponding to the Eu3+-ions transition of 5D0 → 7Fj (=0 to 4). However, due to lower emission intensity, these transitions were not clearly visible up to 1 mol % Eu3+-ions. The CIE coordinates confirmed the tuning of emission colour in Eu3+-doped zirconia nanophosphor at different excitation wavelengths. The Judd-Ofelt parameters also suggested that the Eu3+-doped zirconia may be utilized for better optical gain. So, nano-sized Eu3+-doped zirconia phosphor materials may consider as a potential candidate for different luminescence applications.

Nanotechnology-Assisted, Single-Chromophore-Based White-Light-Emitting Organic Materials with Bioimaging Properties.

White-light-emitting (WLE) organic materials, especially small molecules comprising a single chromophoric unit, have received much attention due to their tremendous use in modern-day electronic devices and biomaterials. They can increase the efficiency and lifetime of devices compared to the currently used combination approach. Herein, we explored a small symmetric push-pull organic molecule Hexyl-TCBD with a single 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) chromophoric unit containing urea as a key functional group on an acceptor-donor∼donor-acceptor (A-D∼D-A) backbone for its ability to show white-light emission in solution as well as in the solid state. The luminescence was absent in the solid state due to the H-bonding- and π-stacking-driven quenching processes, while emission behavior in solution was tunable with variable CIE chromaticity index values via hydrogen (H)-bonding-governed disaggregation phenomena. Translation of WLE from the Hexyl-TCBD solution to a solid state was demonstrated by utilizing nonemissive polystyrene (80 wt % with respect to the chromophore) as the matrix to obtain WLE nanofibers (made by the electrospun technique) via segregating the molecules. The optical microscopy study validated the WLE nanofibers. The presence of multicolor photoluminescence, including white light, could be fine-tuned through various excitation wavelengths, solvent polarities, and polystyrene matrices. Furthermore, the detailed photophysical studies, including lifetime measurements, indicated that the inherent intramolecular charge transfer (ICT) bands of Hexyl-TCBD exhibit better ICT state stabilization by space charge distribution through the modulation of H-bonding between urea groups. Finally, a cytotoxicity study was performed for Hexyl-TCBD on normal and cancer cell lines using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay to explore bioimaging applications in biosystems. MTT results revealed significant toxicity toward cancer cells, whereas normal cells exhibited good biocompatibility.

Supramolecular photoswitch with white-light emission based on bridged bis(pillar[5]arene)s

White light-emitting (WLE) switches have greatly promising and worthy applications in the field of controllable lighting, display, and sensing. Here, we unprecedentedly construct a photocontrollable light-harvesting supramolecular nanoassembly (G/H@NiR) with rarely switchable white light emission, which comprised oligo(phenylenevinylene)-bridged pillar[5]arenes (H), photochromic diarylethene (G), and Nile red (NiR), through host–guest complexation. In the nanosystem, color-tunable photoluminescence such as cyan, orange red, and especially white with chromaticity coordinates (0.33, 0.34) is achieved through altering the proportions of the energy donor (H in assembly G/H) and acceptor center (NiR). Importantly, G, acting as a modulator, can controllably change the energy-transfer (ET) pathway between H and NiR, when the G/H@NiR nanoassembly was exposed to distinct light, achieving reversible switching of multicolor photoluminescence including white-light emission. In addition, the designed intelligent supramolecular assembly G/H@NiR with captivating characteristics has extremely valuable application as erasable multicolor fluorescent inks to be filled in the groove of a three-dimensional model and further form a high-security-level chromatic anticounterfeiting quick response (QR) code, which can be completely hidden and revealed under stimulation of distinct light. Besides, the erasable fluorescent inks can also be used to record data information in mixed fiber film, which can be completely wiped off and rerecord by distinct light. The study provides a controllable supramolecular light-harvesting strategy (the photo-modulating ET pathway in the light-harvesting process) for developing photo-responsive intelligent photoluminescence materials, particularly photosensitive WLE materials, possessing potential applications in photosensitive lighting and display, multicolor imaging, light-manipulative data storage, and high-security-level anticounterfeiting.

Self‐fluorescent polymers for bioimaging

AbstractSelf‐fluorescent polymers with different fluorescent chromophores have attracted considerable attention in the field of fluorescence bioimaging due to their tunable topologies and compositions, which render high fluorescence intensity and multicolor photoluminescence. In this Review, recent advances into the construction of self‐fluorescent polymers via the integration of conventional fluorescent chromophores, such as fluorescent dyes and conjugated polymers, and nonconventional heteroatom‐containing chromophores are summarized. In addition, the classification and bonding modes of fluorescent chromophores in polymer backbones, fluorescence mechanisms, and multicolor photoluminescence are discussed. Finally, the promising applications of self‐fluorescent polymers for fluorescence bioimaging are highlighted.

A pH-sensitive ESIPT molecule with aggregation-induced emission and tunable solid-state fluorescence multicolor for anti-counterfeiting and food freshness detection

Achieving stimulus-responsive multicolor solid-state photoluminescence based on a single fluorescence compound has potential applications in anti-counterfeiting labels and visual detection. However, few such organic chromophores have these features and been used in this fields. In this study, multiple pH-sensitive sites were incorporated into a single molecule of succinimide substituted 2-(2′-hydroxyphenyl)Benzothiazole derivative (BTSA) that was Aggregation induced emission (AIE) and Excited state intramolecular proton transfer (ESIPT) active, exhibiting multilevel and highly secured anti-counterfeiting abilities. Under ammonia atmosphere, BTSA exhibits reversible switching between the green and blue fluorescence. By rationally manipulating two stimuli (acid and base), BTSA labels incredibly shows four different emission colors. The multicolor fluorescence changes are irreversible and evidently depend on the order of acid-base added. Together with smartphone that can quickly and accurately identify the multiple colors, BTSA affords a new covert fluorescent anti-counterfeiting technique with high security through the combination of reversible and irreversible fluorescence multicolor changes, as well as order and stimuli-dependent luminescent patterns. In addition, BTSA labels are successfully applied for real-time and visual monitoring the food freshness of pork and shrimp. The molecular design rationale presented here provide a new design strategy for the purposes of multicolor anti-counterfeiting and food freshness detection.

Highly Versatile Upconverting Oxyfluoride-Based Nanophosphor Films.

Fluoride-based compounds doped with rare-earth cations are the preferred choice of materials to achieve efficient upconversion, of interest for a plethora of applications ranging from bioimaging to energy harvesting. Herein, we demonstrate a simple route to fabricate bright upconverting films that are transparent, self-standing, flexible, and emit different colors. Starting from the solvothermal synthesis of uniform and colloidally stable yttrium fluoride nanoparticles doped with Yb3+ and Er3+, Ho3+, or Tm3+, we find the experimental conditions to process the nanophosphors as optical quality films of controlled thickness between few hundreds of nanometers and several micrometers. A thorough analysis of both structural and photophysical properties of films annealed at different temperatures reveals a tradeoff between the oxidation of the matrix, which transitions through an oxyfluoride crystal phase, and the efficiency of the upconversion photoluminescence process. It represents a significant step forward in the understanding of the fundamental properties of upconverting materials and can be leveraged for the optimization of upconversion systems in general. We prove bright multicolor upconversion photoluminescence in oxyfluoride-based phosphor transparent films upon excitation with a 980 nm laser for both rigid and flexible versions of the layers, being possible to use the latter to coat surfaces of arbitrary shape. Our results pave the way toward the development of upconverting coatings that can be conveniently integrated in applications that demand a large degree of versatility.

Supramolecular Pins with Ultralong Efficient Phosphorescence.

Constructing ultralong organic phosphorescent materials possessing a high quantum yield is challenging. Herein, assemblies of purely organic supramolecular pins composed of alkyl-bridged phenylpyridinium salts and cucurbit[8]uril (CB[8]) are reported. Different from "one host with two guests" and "head-to-tail" binding, the binding formation of supramolecular pins is "one host with one guest" and "head-to-head," which overcomes electrostatic repulsion and promotes intramolecular charge transfer. The supramolecular pin 1/CB[8] displays afterglow with high phosphorescence quantum yield (99.38%) after incorporation into a rigid matrix, which is the highest yield reported to date for phosphorescent materials. Moreover, multicolor photoluminescence can be obtained by different excitation wavelengths and ratios of host to guest. Owing to the redshift of the absorption, the supramolecular pins are applied for targeted phosphorescence imaging of mitochondria. This work will provide a reasonable supramolecular strategy to achieve redshifted and efficient phosphorescence both in the solid state and in aqueous solution.

A novel layered rare-earth hydroxides/polyvinyl alcohol hydrogel with multicolor photoluminescence behavior

The layered rare-earth hydroxides LEuxTb1-xHs nanosheets were stably isolated in polyvinyl alcohol (PVA) hydrogels via a freeze–thaw method (x: 0–1) due to the hydrogen bond interactions between LEuxTb1-xHs and PVA. The energy transfer from Tb3+ to Eu3+ and the Eu3+ concentration quenching effect were inhibited in LEuxTb1-xHs/PVA hydrogels, resulting in the independent photoluminescence (PL) emissions of Eu3+ and Tb3+ in and a corresponding multicolor PL.

Multiphoton light emission in barium stannate perovskites driven by oxygen vacancies, Eu3+ and La3+: accessing the role of defects and local structures.

Defect engineering in perovskites has been found to be the most efficient approach to manipulate their performance in ultraviolet-to-visible photon conversion. Under UV irradiation, BaSnO3 exhibited multicolor photoluminescence (MCPL) in the bluish white region. Its origin has not been well studied in the literature and has been probed in this work using synchrotron radiation, positron annihilation and density functional theory. To achieve desirable performance of doped BaSnO3 in optoelectronics, it is imperative to have correct information on the dopant local site, doping induced defect evolution and efficacy of host to dopant energy transfer (HDET). Extended X-ray absorption fine structure (EXAFS) showed that Eu3+ ions stabilize at both Ba2+ and Sn4+ sites consistent with the highly negative formation energy of around -6.26 eV. Eu3+ doping leads to an intense 5D0→7F1 orange emission and a feeble 5D0→7F2 red emission and an internal quantum yield (IQY) of ∼21% mediated by ET from the defect level of EuBa and EuSn sites to the valence band maximum (VBM). X-ray absorption near edge structure (XANES) ruled out any role of Sn2+ in the PL of BaSnO3 or Eu2+ in the PL of BaSnO3:Eu3+. Interestingly, when co-doped, Eu3+ stabilizes at Sn4+ sites whereas La3+ stabilizes at Ba2+ sites with a formation energy value of -6.44 eV. Based on the asymmetry ratio in emission spectra, it was found that La3+ ions lead to lowering of symmetry around Eu3+ due to increased vacancies and structural distortions, and also suppress the luminescence IQY. We have performed experimental positron annihilation lifetime spectroscopy (PALS) to probe the defects in BaSnO3 in pristine samples and on doping/co-doping. The positron lifetimes for saturation trapping of positrons in various kinds of defects envisaged in BaSnO3 and in the defect free system were calculated using the MIKA Doppler program. Such deep insight into the effect of local structures, dopant sites, defect evolution, ET, etc. on the optical properties of BaSnO3 is expected to provide very deep insight for material scientists into the fabrication of perovskite-based optoelectronic and light-emitting devices.

Light-emitting MXene quantum dots

MXene (M_{<italic>n</italic>+1}X_{<italic>n</italic>}) is an emerging class of layered two-dimensional (2D) materials, which are derived from their bulk-state MAX phase (M_{<italic>n</italic>+1}AX_{<italic>n</italic>}, where M: early transition metal, A: group element 13 and 14, and X: carbon and/or nitrogen). MXenes have found wide-ranging applications in energy storage devices, sensors, catalysis, etc. owing to their high electronic conductivity and wide range of optical absorption. However, the absence of semiconducting MXenes has limited their applications related to light emission. Research has shown that quantum dots (QDs) derived from MXene (MQDs) not only retain the properties of the parent MXene but also demonstrate significant improvement on light emission and quantum yield (QY). The optical properties and photoluminescence (PL) emission mechanisms of these light-emitting MQDs have not been comprehensively investigated. Recently, work on light-emitting MQDs has shown good progress, and MQDs exhibiting multi-color PL emission along with high QY have been fabricated. The synthesis methods also play a vital role in determining the light emission properties of these MQDs. This review provides an overview of light-emitting MQDs and their synthesis methods, optical properties, and applications in various optical, sensory, and imaging devices. The future prospects of light-emitting MQDs are also discussed to provide an insight that helps to further advance the progress on MQDs.

Dinuclear Triple-Stranded Helicates Composed of Tetradentate Ligands with Aluminum(III) Chromophores: Optical Resolution and Multi-color Circularly Polarized Luminescence Properties.

New chiroptical chromophores, dinuclear triple-stranded helicates, composed of tetradentate ligands with aluminum(III) ions, are described. These are synthesized in two steps using inexpensive pyrrole derivatives, hydrazine, and aluminum chloride. These molecular architectures (ALPHY) show multi-color (cyan, yellow, and orange) photoluminescence in solution and in the solid-state, which depends on the substituents of the ligands. The photoluminescence quantum yields of helicates were up to 54 %. The right-handed (P) and left-handed (M) helicates are so stable that they do not undergo racemization in some solvents and are mirror images according to circular dichroism and circularly polarized luminescence (CPL) with an absolute luminescence dissymmetry factor (glum ) of up to the 10-3 order. Mixing the different helicates produces white-light emission with CPL characters. This study offers a glimpse into the potential applications of chromophores with diverse photophysical properties.

Colour-tunable ultralong-lifetime room temperature phosphorescence with external heavy-atom effect in boron-doped carbon dots

• Boron-doped carbon dots (BDs) are prepared from citric acid and boric acid. • BDs possesses high PLQY (40.4%) and PQY (23.5%), together with long afterglow lifetime (1.17 s). • BD-X was obtained from citric acid, boric acid and KX (X = Cl, Br and I). • BD-X exhibits extraordinarily high PQY of 34.4% and untralong afterglow lifetime of 2.61 s. • BDs and BD-X are successfully employed for anti-counterfeiting and information encryption. Color-tunable ultralong-lifetime room temperature phosphorescence (URTP) materials have become powerful candidates for the extensive applications of optoelectronics, information encryption, anti-counterfeiting and sensing. Nevertheless, it hard to prepare URTP luminophores with both long afterglow lifetime and high phosphorescence quantum yield (PQY) under ambient conditions. Herein, we developed a convenient, rapid and gram-scale method to successfully obtain a series of URTP boron-doped carbon dots (BDs, named as BD50, BD100, BD150 and BD300, respectively), utilizing boric acid (BA, 3 g) and citric acid (CA, 50, 100, 150 and 300 mg) as precursers. BD50 shows prominent multi-colour emissive photoluminescence (PL) and phosphorescence, with extraordinarily high PL quantum yield (PLQY, 40.4%) and PQY (23.5%). Moreover, BD50 exhibits bright yellow-green afterglow, with lifetime as high as 1.17 s. What worth more to joy and encourage is that significant improvements in PQY and lifetime were achieved by introducing halide ions into BDs, due to external heavy-atom effect (EHE). BD-X (X = Cl, Br and I) possesses high PQY and long lifetime (up to 34.4% and 2.61 s). Based on the unique RTP performance of BDs and BD-X, these URTP luminophores are successfully applied to anti-counterfeiting and information encryption. This work contributes to develop smart materials with ultralong afterglow and high phosphorescence efficiency.

Highly Efficient Amide Michael Addition and Its Use in the Preparation of Tunable Multicolor Photoluminescent Polymers.

The amide bond is one of the most pivotal functional groups in chemistry and biology. It is also the key component of proteins and widely present in synthetic materials. The majority of studies have focused on the formation of the amide group, but its postmodification has scarcely been investigated. Herein, we successfully develop the Michael additions of amide to acrylate, acrylamide, or propiolate in the presence of phosphazene base at room temperature. This amide Michael addition is much more efficient when the secondary amide instead of the primary amide is used under the same conditions. This reaction was applied to postfunctionalize poly(methyl acrylate-co-acrylamide), P(MA-co-Am), and it is shown that the amide groups of P(MA-co-Am) could be completely modified by N,N-dimethylacrylamide (DMA). Interestingly, the resulting copolymer exhibited tailorable fluorescence with emission wavelength ranging from 380 to 613 nm, which is a desired property for luminescent materials. Moreover, the emissions of the copolymer increased with increasing concentration in solution for all excitation wavelengths from 320 to 580 nm. Therefore, this work not only develops an efficient t-BuP4-catalyzed amide Michael addition but also offers a facile method for tunable multicolor photoluminescent polymers, which is expected to find a wide range of applications in many fields, such as in anticounterfeiting technology.

Effect of protonation on the photophysical properties of 4-substituted and 4,7-disubstituted quinazoline push-pull chromophores

White-light emission from single molecular systems has attracted a great deal of attention due to their advantages over multicomponent emitters. Azaheterocyclic push-pull derivatives have been demonstrated to be white emitters by combining neutral and protonated forms in the appropriate ratio, although limited cases of white-light emission have been reported from quinazoline derivatives. Herein, we describe a series of push-pull 4-substituted and 4,7-disubstituted quinazolines that show white photoluminescence both in solution and in the solid state. All of the materials were prepared by straightforward Suzuki–Miyaura cross-coupling reactions and the compounds exhibited remarkable emission solvatochromism. In some cases the presence of acid prompted the appearance of emission bands of complementary colors. Thus, multicolor photoluminescence, including white light, could be finely tuned by the controlled protonation of the electron-deficient quinazoline ring.

Ring-in-Ring(s) Complexes Exhibiting Tunable Multicolor Photoluminescence.

One ring threaded by two other rings to form a non-intertwined ternary ring-in-rings motif is a challenging task in noncovalent synthesis. Constructing multicolor photoluminescence systems with tunable properties is also a fundamental research goal, which can lead to applications in multidimensional biological imaging, visual displays, and encryption materials. Herein, we describe the design and synthesis of binary and ternary ring-in-ring(s) complexes, based on an extended tetracationic cyclophane and cucurbit[8]uril. The formation of these complexes is accompanied by tunable multicolor fluorescence outputs. On mixing equimolar amounts of the cyclophane and cucurbit[8]uril, a 1:1 ring-in-ring complex is formed as a result of hydrophobic interactions associated with a favorable change in entropy. With the addition of another equivalent of cucurbit[8]uril, a 1:2 ring-in-rings complex is formed, facilitated by additional ion-dipole interactions involving the pyridinium units in the cyclophane and the carbonyl groups in cucurbit[8]uril. Because of the narrowing in the energy gaps of the cyclophane within the rigid hydrophobic cavities of cucurbit[8]urils, the binary and ternary ring-in-ring(s) complexes emit green and bright yellow fluorescence, respectively. A series of color-tunable emissions, such as sky blue, cyan, green, and yellow with increased fluorescence lifetimes, can be achieved by simply adding cucurbit[8]uril to an aqueous solution of the cyclophane. Notably, the smaller cyclobis(paraquat-p-phenylene), which contains the same p-xylylene linkers as the extended tetracationic cyclophane, does not form ring-in-ring(s) complexes with cucurbit[8]uril. The encapsulation of this extended tetracationic cyclophane by both one and two cucurbit[8]urils provides an incentive to design and synthesize more advanced supramolecular systems, as well as opening up a feasible approach toward achieving tunable multicolor photoluminescence with single chromophores.

Unique Growth Pathway in Solution-Solid-Solid Nanowires: Cubic to Hexagonal Phase Transformation.

Solution–solid–solid (SSS) nanowires can be catalyzed by superionic Ag2S via ion diffusion. Here, we synthesize ZnS nanowires of the wurtzite crystal structure and heterostructures via a low-temperature growth pathway. Single-crystalline ZnS nanowires were produced by varying reaction time and temperature (120–200 °C) via thermal decomposition of a single-source precursor, Zn(DDTC)2. A phase transformation (zinc blende → wurtzite) was observed during the synthesis with a three-step growth pathway proposed. Temperature-controlled phase transformation facilitates oriented attachment into a 1D nanowire, followed by helical epitaxial and lateral growths during ripening. Additionally, the CdS–ZnS heterostructured nanowires can be obtained after introducing the Cd(DDTC)2 precursor. ZnS nanowires of defined diameters (5–10 nm) are served as backbones to grow heterostructures of ternary semiconductors with multicolor photoluminescence (450–800 nm). Structural and optical characterizations (PL, 2D PLE, and TCSPC) are investigated to confirm origins of broadband emission from multiple lifetimes (0.5–12 ns) for exciton recombination in heterostructures. Our study demonstrates this unique growth pathway for SSS nanowire synthesis under mild, facile, and atmospheric conditions.

Encryption and authentication of security patterns by ecofriendly multi-color photoluminescent inks containing oxazolidine-functionalized nanoparticles

Counterfeiting of confidential documents has been a costly challenge for banks, companies, and customers. Encryption of invisible security marks, such as barcodes, quick response codes, and logos, in national or international confidential documents by high-security anticounterfeiting inks is the most significant solution for counterfeiting problems. Ecofriendly multi-color photoluminescent anticounterfeiting inks based on highly-fluorescent polymer nanoparticles functionalized with new oxazolidine derivatives were developed for the fast and facile encryption of security labels on cellulosic documents, such as paper currency, passport, and certificate. Depending on the polarity of functionalized polymer nanoparticles, a wide range of colors and fluorescence emissions were observed as a result of polar-polar interactions between the oxazolidine molecules and surface functional groups of the nanoparticles. The fluorescent polymer nanoparticles showed spherical, vesicular, and cauliflower-like morphologies resulted from different surface functional groups. Functional polymer nanoparticles displayed high stability and printability on cellulosic substrates due to hydrogen bonding interactions. The highly-fluorescent polymer nanoparticles were also used to prepare anticounterfeiting inks with different colors and fluorescence emissions. All the ecofriendly polymeric anticounterfeiting inks were loaded to stamps with specific marks, and then applied to different confidential documents. Printed labels displayed highly intense fluorescence emission in different colors (green, orange, pink, and purple depending on the matrix polarity) under UV irradiation (365 nm). These water-based multi-color fluorescent anticounterfeiting inks with highly intense, bright, and sensitive fluorescence emission have potential applications in encryption and authentication of security patterns.

Tunable dual fluorescence emissions with high photoluminescence quantum yields modulated by Na ion dispersion method for purely solid state N-doped carbon dots

In this work, we reported a facile Na ion dispersion (NID) method for simply preparing a series of purely solid state N-doped carbon dots (NCDots) with tunable photoluminescence from blue to yellow light. We demonstrated for the first time that tunable multicolor photoluminescence is ascribed as dual fluorescence emissions modulated by the ratio between surface state (SS) and core state (CS) of NCDots, respectively. Moreover, we revealed that the emission of CS is determined by heterocycle N and the emission of SS is related to amino N and Na ion. Furthermore, the common aggregation caused quenching (ACQ) phenomenon of solid state CDots is efficiently inhibited by introducing NID effect. Therefore, photoluminescence quantum yield (PLQY) of our purely solid state NCDots could be up to 80.7 %, to the best of our knowledge, which is the highest PLQY for the purely solid state CDots until now. This work paves the way for the development of purely solid state CDots with high PLQY and tunable multicolor photoluminescence and applications in optoelectronic device and cell imaging fields.

Multiresponsive Luminescence Materials: Richer Color Than Chameleon Materials

AbstractDeveloping light‐harvesting materials with tunable emission colors is highly desirable in applications requiring a specific color on‐demand. The modulation in material composition, structures, and polymerization can provide a useful tool for producing a wide range of emission colors. However, controlling the color gamut in a ready‐made material remains a formidable challenge. Here, several germinate‐based phosphors are reported that provide precise dynamic emission color tuning in the visible color range through the optical multiplexing of lanthanides and other ion dopants, such as lead (Pb2+) and manganese (Mn2+). The emission gamut of the developed germinate‐based materials in the full visible color range can be tuned on demand by adjusting the excitation wavelength, thereby allowing dynamic synergistic multicolor, multitemporal, and multimodal integration with ready‐made materials. The multicolored photoluminescence property of the developed phosphors is related to the different interaction modes of dopants in the crystals. Furthermore, the applications of color‐tunable phosphors in multicolor display and anticounterfeiting are demonstrated. These findings provide valuable insights toward developing next‐generation smart luminescent materials and sensors.