Luminescent Ink Research Articles

Er doped layered perovskites with dual mode luminescent behavior and tunable multicolor upconversion emission

Er3+ doped BST nanoparticles with Aurivillius layered structure are synthesized through common solid-state method. Photoluminescence spectroscopy has shown that these oxides are capable of emitting light under UV (366 nm) and IR (980 nm) source. The effect of Er3+ to Yb3+ concentration ratio on upconversion emission are investigated and possible upconversion and energy transfer mechanisms are suggested based on the number of photons participating in UC process. Shift in the upconversion emission from green to red region is visualized by CIE chromaticity diagram. The superiority of coexistence of stoke and anti-stoke emission in a single host lattice with a single activator ion, besides to tunability of UC luminescence only by controlling sensitizer/activator ratio are very interesting features which can be used to produce dual mode multicolor luminescent ink with high security level against forgery.

A Record Chromophore Density in High-Entropy Liquids of Two Low-Melting Perylenes: A New Strategy for Liquid Chromophores.

Liquid chromophores constitute a rare but intriguing class of molecules that are in high demand for the design of luminescent inks, liquid semiconductors, and solar energy storage materials. The most common way to achieve liquid chromophores involves the introduction of long alkyl chains, which, however, significantly reduces the chromophore density. Here, strategy is presented that allows for the preparation of liquid chromophores with a minimal increase in molecular weight, using the important class of perylenes as an example. Two synergistic effects are harnessed: (1) the judicious positioning of short alkyl substituents, and (2) equimolar mixing, which in unison results in a liquid material. A series of 1‐alkyl perylene derivatives is synthesized and it is found that short ethyl or butyl chains reduce the melting temperature from 278 °C to as little as 70 °C. Then, two low‐melting derivatives are mixed, which results in materials that do not crystallize due to the increased configurational entropy of the system. As a result, liquid chromophores with the lowest reported molecular weight increase compared to the neat chromophore are obtained. The mixing strategy is readily applicable to other π‐conjugated systems and, hence, promises to yield a wide range of low molecular weight liquid chromophores.

Synthesis of Lanthanide-Ion-Doped NaYF4 RGB Up-Conversion Nanoparticles for Anti-Counterfeiting Application

Well-defined and mono-dispersed lanthanide-ion-doped NaYF4 up-conversion nanoparticles (UCNPs) were synthesized via thermal decomposition using lanthanide oleate as the precursor. By rational selecting the dopant pairs of the doped lanthanide ions (Y3+, Yb3+, Er3+ and Tm3+) with accurate molar ratios, three-primary-color (RGB) UCNPs which exhibited green (UCNPs-G), blue (UCNPs-B) and red (UCNPs-R) fluorescence, respectively, were prepared. The X-ray diffraction (XRD) patterns showed that the three UCNPs were purely hexagonal-phase NaYF4 crystals. Transmission electron microscopy (TEM) images revealed that the synthesized UCNPs exhibited well-defined nanosphere morphology with uniform size distribution. The average diameters were 23.95±3.35 nm for UCNPs-G, 20.63±2.59 nm for UCNPs-B, and 19.24±2.37 nm for UCNPs-R, respectively. After surface modification employing polyacrylic acid (PAA) as modifier, the obtained UCNPs were converted to be hydrophilic, which can be used as fillers to construct luminescent polymer films and luminescent ink in anti-counterfeiting application.

Synthesis of ZnS–Mn nano-luminescent pigment for ink applications

In the present study, ZnS–Mn nano-luminescent pigments were synthesized, using co-precipitation method. Polyvinylpyrrolidine (PVP) surface modifier and Mn dopant concentrations were considered as affecting parameters. The luminescent ink was loaded with two different concentrations of pigments. The obtained ink was silk-screened on different types of fabrics mainly treated cotton, cotton and nylon. Structure, microstructure, luminescent properties of nano-pigments, inks and fabrics and also rheological properties of the inks were investigated. The results showed that the ceramic ink prepared with nano-luminescent pigment had high photoluminescence (PL) intensity. Moreover, the optimum concentrations of Mn and PVP for obtaining maximum PL intensity were found as 2 and 5 wt%, respectively. SEM images of fabrics indicated that nanoparticles were loaded, nonuniformly, on the fibers. The treated linen and nylon fabrics showed maximum and minimum PL intensity, respectively, due to ink penetration depth in the fabrics. Furthermore, washing fastness estimated for all fabrics was in the proper range.

Highly Luminescent Inks: Aggregation‐Induced Emission of Copper–Iodine Hybrid Clusters

AbstractAggregation‐induced emission (AIE) is an attractive phenomenon in which materials display strong luminescence in the aggregated solid states rather than in the conventional dissolved molecular states. However, highly luminescent inks based on AIE are hard to be obtained because of the difficulty in finely controlling the crystallinity of AIE materials at nanoscale. Herein, we report the preparation of highly luminescent inks via oil‐in‐water microemulsion induced aggregation of Cu–I hybrid clusters based on the highly soluble copper iodide‐tris(3‐methylphenyl)phosphine (Cu4I4(P‐(m‐Tol)3)4) hybrid. Furthermore, we can synthesize a series of AIE inks with different light‐emission colors to cover the whole visible spectrum range via a facile ligand exchange processes. The assemblies of Cu–I hybrid clusters with AIE characteristics will pave the way to fabricate low‐cost highly luminescent inks.

Highly Luminescent Inks: Aggregation-Induced Emission of Copper-Iodine Hybrid Clusters.

Aggregation-induced emission (AIE) is an attractive phenomenon in which materials display strong luminescence in the aggregated solid states rather than in the conventional dissolved molecular states. However, highly luminescent inks based on AIE are hard to be obtained because of the difficulty in finely controlling the crystallinity of AIE materials at nanoscale. Herein, we report the preparation of highly luminescent inks via oil-in-water microemulsion induced aggregation of Cu-I hybrid clusters based on the highly soluble copper iodide-tris(3-methylphenyl)phosphine (Cu4 I4 (P-(m-Tol)3 )4 ) hybrid. Furthermore, we can synthesize a series of AIE inks with different light-emission colors to cover the whole visible spectrum range via a facile ligand exchange processes. The assemblies of Cu-I hybrid clusters with AIE characteristics will pave the way to fabricate low-cost highly luminescent inks.

Highly stable CsPbBr3@SiO2 nanocomposites prepared via confined condensation for use as a luminescent ink.

We have firstly prepared CsPbBr3@SiO2 nanocomposites with a spherical morphology and diameters less than 125 nm via confined condensation into polystyrene. The obtained CsPbBr3@SiO2 exhibits high stability in polar solvents and can be used as a solution-processable luminescent ink.

Combustion Synthesis of MgSiO3: Eu3+ (1-11 mol %) Nanophosphor: Detection of Eccrine Latent Fingerprints and Anti-Counterfeiting Applications

MgSiO3: Eu3+ (1-11 mol %) nanophosphors were synthesized by solution combustion route. The final product was well characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Photoluminescence (PL) etc. The main objective of the present work was first to fabricate highly luminescent nanophosphor for revelation of latent fingerprints and also to develop luminescent ink for anticounterfeiting applications. Presently the fingerprints developed by using conventional powders have several disadvantages including low sensitivity, high background hindrance, complicated procedure and high toxicity. To encounter this challenge, we explored the optimized MgSiO3: Eu3+ (9 mol %) nanophosphor for detection of latent fingerprints and luminescent anti-counterfeiting ink. Photoluminescence studies of MgSiO3: Eu3+ (1-11 mol %) exhibited the peaks 5D0 → 7FJ (J = 1, 2, 3 and 4) transitions. The CIE and CCT studies indicate that the present phosphor could be highly promising red component for possible applications in the field of white light emitting diodes

Synthesis of BiOCl: Eu3+ Microarchitectures and their WLED’s, Fingerprint Detection and Anticounterfeiting Applications

BiOCl: Eu3+(1-9mol %) microarchitectures were synthesized by the solution combustion method by employing Barbituric acid as fuel. The crystal structure, morphologies and luminescence properties of Eu3+doped BiOCl have been systematically investigated by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) and spectroscopy respectively. The prime objective of the current effort was first to fabricate highly luminescent nanophosphor for revelation of latent fingerprints, lips prints including infiltrating and non-filtrating surfaces and also to develop luminescent ink for anticounterfeiting applications. Presently the fingerprints developed by using conventional powders have several disadvantages including low sensitivity, high background hindrance, complicated procedure and high toxicity. To encounter this challenge, we explored the optimized BiOCl:Eu3+(3mol %) nanophosphor for detection of latent fingerprints and luminescent anti-counterfeiting ink. The morphology of the phosphor was tuned by adjusting the concentration of fuel. Photoluminescence studies of BiOCl:Eu3+(1-9mol %) exhibited the peaks 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions. The CIE and CCT characteristics specify that the synthesized nanophosphor might be immensely show potential red factor for promising applications in WLED’s. The BiOCl: Eu3+ (1-9 mol %) nanopowder also showed clear ridge patterns of level I and level II and further showed sharp image of label when observed in the UV light. The results indicated that the present phosphor could be used in both forensic as well as in anti counterfeiting applications.

A Novel Approach to Synthesise a Dual-Mode Luminescent Composite Pigment for Uncloneable High-Security Codes to Combat Counterfeiting.

A strategy is demonstrated to protect valuable items, such as currency, pharmaceuticals, important documents, etc. against counterfeiting, by marking them with luminescent security codes. These luminescent security codes were printed by employing luminescent ink formulated from a cost effective dual-mode luminescent composite pigment of Gd1.7 Yb0.2 Er0.1 O3 and Zn0.98 Mn0.02 S phosphors using commercially available PVC Gold medium. In the composite, Gd1.7 Yb0.2 Er0.1 O3 and Zn0.98 Mn0.02 S account for upconversion and downconversion processes, respectively. The synthesis procedure of the composite involves the admixing of Gd1.7 Yb0.2 Er0.1 O3 nanorods and Zn0.98 Mn0.02 S phosphor, synthesised by hydrothermal and facile solid-state reaction methods, respectively. The structural, morphological, microstructural, and photoluminescent features of Gd1.7 Yb0.2 Er0.1 O3 nanorods, Zn0.98 Mn0.02 S phosphor and composite were characterised by using XRD, SEM, TEM, and photoluminescence (PL) techniques, respectively. The distribution of PL intensity of the printed pattern was examined by using confocal PL mapping microscopy. The obtained results reveal that security codes printed using ink formulated from this bi-luminescent composite pigment provide dual-stage security against counterfeiting.

Ultrasound assisted sonochemically engineered effective red luminescent labeling agent for high resolution visualization of latent fingerprints

Nanoscience and technology finds wide range of benefits in the area of surface based science due to its nano size and high surface area. This offers new potentials in surface-based science comprising latent fingerprint (LFP) and to develop luminescent ink for anti-counterfeiting applications. Due to high backward hindrance, low sensitivity, complicated setup, and poor universality of traditionally developed techniques were main drawbacks for the visualization of LFPs. To overcome these problems, we explored the superstructures (SS) of europium ions doped BaTiO3 nanophosphors (NPs) prepared via sonochemical route with bio-template as surfactant for the detection of LFPs and as an anti-counterfeiting ink. The morphologies of SS were highly dependent on the concentration of Aloe vera (A.V.) gel as well as ultrasound irradiation time. The obtained SS displayed pure red emission which corresponds to the 5D0→7FJ transitions of Eu3+ ions under UV light. The results clearly evident that the optimized BaTiO3:Eu3+ NPs will create a new prospect for research in LFPs visualization and anti-counterfeiting technology.

Morphology-controlled synthesis, growth mechanism and fluorescence of YF3:Eu3+, Bi3+

In recent years, morphology-controlled synthesis and corresponding property tuning in inorganic materials have attracted considerable attention. In this work, lanthanide luminescent materials of YF3:0.125Eu3+, 0.5%Bi3+ with a variety of well-defined morphologies including spherical, truncated octahedron, octahedron and pseudo-sphere particle have been controllably synthesized via a facile hydrothermal method. Phase structure and morphology of the materials are tuned, and thus fluorescent properties are tailored by changing the synthetic parameters of reaction temperature and dwelling time. With increasing reaction temperature, the materials are transformed from KY3F10 to YF3, and the morphology varies from spherical to octahedron and finally truncated octahedra. When dwelling time increases, the samples also extend from KY3F10 to YF3 and the morphology changes from spherical to octahedron, then truncated octahedra and finally pseudo-sphere particle. The possible growth mechanism for diverse morphologies has been proposed. The fluorescence intensity of the materials is closely related to their morphologic characteristics. The YF3:0.125Eu3+, 0.5%Bi3+ with truncated octahedra synthesized at 200°C for 18h presents the strongest emission intensity because of its less defects sites and large grain size. In addition, it has been demonstrated that the present luminescent materials can be potentially used as the luminescent ink.

Facile combustion based engineering of novel white light emitting Zn 2 TiO 4 :Dy 3+ nanophosphors for display and forensic applications

Abstract Nanomaterials find a wide range of applications in surface based nanoscience and technology. To pass high backward encumbrance, low sensitivity, complicated setup and poor universality in traditional methods for the enhancement of latent fingerprints and display applications, we explored the superstructures of dysprosium (Dy 3+ ) doped Zn 2 TiO 4 via a facile solution combustion route. This method offers new potentials in surface-based science comprising display, latent fingerprint, and luminescent ink for anticounterfeiting applications. The characteristic emissions of intra-4f shell Dy 3+ cations in blue, yellow and red regions corresponding to 4 F 9/2 to 6 H 15/2 , 6 H 13/2 , and 6 H 11/2 transitions respectively, showed white emission, and the Judd–Ofelt theory was used to estimate photometric parameters. The concentration quenching phenomenon is discussed based on possible interactions. Our study reveals a new prospect of using optimized Zn 2 TiO 4 :Dy 3+ nanophosphors for research in display, fingerprint detection, cheiloscopy, anti-counterfeiting technology, ceramic pigment and forensic applications.

Unclonable Security Codes Designed from Multicolor Luminescent Lanthanide-Doped Y2O3 Nanorods for Anticounterfeiting.

The duplicity of important documents has emerged as a serious problem worldwide. Therefore, many efforts have been devoted to developing easy and fast anticounterfeiting techniques with multicolor emission. Herein, we report the synthesis of multicolor luminescent lanthanide-doped Y2O3 nanorods by hydrothermal method and their usability in designing of unclonable security codes for anticounterfeiting applications. The spectroscopic features of nanorods are probed by photoluminescence spectroscopy. The Y2O3:Eu3+, Y2O3:Tb3+, and Y2O3:Ce3+ nanorods emit hypersensitive red (at 611 nm), strong green (at 541 nm), and bright blue (at 438 nm) emissions at 254, 305, and 381 nm, respectively. The SEM and TEM/HRTEM results reveal that these nanorods have diameter and length in the range of 80-120 nm and ∼2-5 μm, respectively. The two-dimensional spatially resolved photoluminescence intensity distribution in nanorods is also investigated by using confocal photoluminescence microscopic technique. Further, highly luminescent unclonable security codes are printed by a simple screen printing technique using luminescent ink fabricated from admixing of lanthanide doped multicolor nanorods in PVC medium. The prospective use of these multicolor luminescent nanorods provide a new opportunity for easily printable, highly stable, and unclonable multicolor luminescent security codes for anti-counterfeiting applications.

Migration of luminescent ink components, a new approach for ink dating

Many inks of wet stamps and of writing instruments such as ballpoint pens, felt-tip pens or roller pens contain luminescent components. Optical comparison of two or more unknown inks with the aid of IR-camera systems is a standard method in questioned document examination. It has been observed, that these components may migrate within the paper and especially along the stroke of an intersected line with another ink. In this study we describe and discuss the migration of these components.We could show that migration data can be used for ink dating.

UV light-switchable transparent polymer films and invisible luminescent inks based on carbon dots and lanthanide complexes

We present a simple approach for the preparation of UV light-switchable transparent composite polymer films and invisible luminescent inks based on the combination of carbon dots (CDs) and trisdipicolinate lanthanide complexes.

Influence of Nanosized Silicon Oxide on the Luminescent Properties of ZnO Nanoparticles

For practical use of nanosized zinc oxide as the phosphor its luminescence quantum yields should be maximized. The aim of this work was to enhance luminescent properties of ZnO nanoparticles and obtain high-luminescent ZnO/SiO2composites using simpler approaches to colloidal synthesis. The luminescence intensity of zinc oxide nanoparticles was increased about 3 times by addition of silica nanocrystals to the source solutions during the synthesis of ZnO nanoparticles. Then the quantum yield of luminescence of the obtained ZnO/SiO2composites is more than 30%. Such an impact of silica is suggested to be caused by the distribution of ZnO nanocrystals on the surface of silica, which reduces the probability of separation of photogenerated charges between the zinc oxide nanoparticles of different sizes, and as a consequence, there is a significant increase of the luminescence intensity of ZnO nanoparticles. This way of increasing nano-ZnO luminescence intensity facilitates its use in a variety of devices, including optical ultraviolet and visible screens, luminescent markers, antibacterial coatings, luminescent solar concentrators, luminescent inks for security printing, and food packaging with abilities of informing consumers about the quality and safety of the packaged product.

Preparation and Characterization of Y2O3, Sio2 Doped By Eu2O3 as Luminescent Ink

Preparation and Characterization of Y2O3, Sio2 Doped By Eu2O3 as Luminescent Ink

Inkjet printable luminescent Eu3+-TiO2 doped in sol gel matrix for paper tagging.

Europium (III) with different concentrations (0.2, 0.4 and 0.8 %)-TiO(2) doped silica composite systems were sensitized by sol-gel method. Different spectroscopic and microscopic tools characterized the composites. The Europium ion incorporated into the liquid silica-titania solution acts as red light emission center in the luminescent materials. This luminescent nano composite pigment has great potential of application in preparing luminescent ink. Inkjet printer loaded with the prepared ink to show its potential usage as tagging material performed the printing test on a white paper.

A New Anti‐Counterfeiting Feature Relying on Invisible Luminescent Full Color Images Printed with Lanthanide‐Based Inks

Europium and terbium trisdipicolinate complexes are inkjet printed onto paper with commercially available desktop inkjet printers. Together with a commercial blue luminescent ink, the red‐emitting luminescent ink containing europium and the green‐emitting luminescent ink containing terbium are used to reproduce accurate full color images that are invisible under white light and appear under a 254 nm UV light. Such invisible luminescent images are attractive anti‐counterfeiting security features. The luminescent prints have a color range (gamut) nearly as wide as the gamut of a standard sRGB display. The gamut of the luminescent prints is determined by relying on a simple model predicting the relative spectral radiant emittances of any printed luminescent color halftone. The model is also used to establish the correspondence between the surface coverages of the printed luminescent inks and the emitted color of these luminescent halftones. The accuracy of the spectral prediction model is very good and can be rationalized by the absence of quenching when the luminescent lanthanide complexes are printed in superposition with the other luminescent materials.