One material, many possibilities via enrichment of luminescence in La2Zr2O7:Tb3+ nanophosphors for forensic stimuli aided applications.

Engineering a single material with multidirectional applications is crucial for improving productivity, low cost, flexibility, least power consumption, etc. To achieve these requirements, novel design structures and high-performance materials are in urgent need. Lanthanide-doped nanophosphors have the greatest strengths and ability in order to tune their applications in various dimensions. However, applications of nanophosphor in latent fingerprints visualization, anti-counterfeiting, and luminescent gels/films are still in their infancy. This study demonstrated a simple strategy to enhance the luminescence of Tb3+ (1-11 mol %) doped La2Zr2O7 nanophosphors by conjugating various fluxes via a simple solution combustion route. The photoluminescence emission spectra reveal intense peaks at ~ 491, 546, 587, and 622 nm, which arises from 5D4 → 7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions, respectively. The highest emission intensity was achieved in the NH4Cl flux assisted nanophosphor as compared to NaBr and NH4F assisted samples. The colorimetric images of fingerprints visualized using the optimized nanophosphor on forensic related surfaces exhibit level -III ridge details, including sweat pores, the width of the ridges, bifurcation angle, and the successive distance between sweat pores, etc. These results are decisive parameters that clearly support the statement "no two persons have ever been found to have the same fingerprints". The anti-counterfeiting security ink was formulated using optimized nanophosphor and various patterns were designed by simple screen printing and dip pen technologies. The encoded information was decrypted only under ultraviolet 254 nm light. All the designed patterns are exhibit not just what it looks/feel like and how better it works. As a synergetic contribution of enhanced luminescence of the prepared nanophosphor, the green-emissive films were fabricated, which display excellent flexibility, uniformity, and transparency in the normal and ultraviolet 254 nm light illumination. The aforementioned results revealed that the prepared NH4Cl flux-assisted La2Zr2O7: Tb3+(7 mol %) NPs are considered to be the best candidate for multi-dimensional applications.

Aggregation induced emission based active conjugated imidazole luminogens for visualization of latent fingerprints and multiple anticounterfeiting applications.

Aggregation-induced emission based organic heterocyclic luminogens bearing conjugated electronic structures showed much attention due to its excellent fluorescence in aggregation state. In this communication, a novel conjugated blue light emitting imidazole molecule is synthesized by one pot multicomponent reaction route is reported for the first time. The prepared molecule exhibits a strong fluorescence in aggregation state with exceptional properties, such as high purity, inexpensive, eco-friendly, large scale production, high photostability, etc. By considering these advantages, a new fluorescence based platform has been setup for in-situ visualization of latent fingerprints and its preservation by spray method followed by Poly(vinyl alcohol) masking. A clear and well defined fluorescence fingerprint images are noticed on variety of surfaces by revealing level 1-3 ridge features upon ultraviolet 365 nm light exposure. The dual nature of binding specificity as well as excellent fluorescence properties permits the visualization of latent fingerprints for longer durations (up to 365 days) with superior contrast, high sensitivity, efficiency, selectivity and minimal background hindrance. We further fabricated unclonable invisible security ink for various printing modes on valuable goods for protection against forging. The developed labels are displaying uniform distribution of ink and exceptional stability under various atmospheric environments. The development of long preservative information using aggregation-induced emission based luminogen opens up a new avenue in advanced forensic and data security applications.

Surface functionalized inorganic phosphor by grafting organic antenna for long term preservation of latent fingerprints and data-security applications.

Creative advancements are enormously sought for the advanced forensic and data security in modern era. Herein, fabrication of Bovine Serum Albumin (BSA) functionalized Gd2O3:Eu3+ (5 mol %) nanopowders dispersed in a poly(vinyl alcohol) (PVA) matrix for long term preservation and visualization of latent fingerprints, as well as printing. Efficient intramolecular energy transfers from coordinated ligand to the doped Eu3+ ions, called the antenna effect was precisely organized by grafting organic molecule, resultant to an enhanced photoluminescence emission. On this basis, the masking of PVA/Gd2O3:Eu3+ (5 mol %)@BSA solution on a latent fingerprints results a flexible transparent film; a highly stable fingerprint images with well-defined ridge characteristics was developed on the film, which enabling personal individualization. Interestingly, the followed latent fingerprints development technique was non-destructive and stored long duration up to 1 year on filtrating and non-filtrating surfaces. The same mechanism was also validated by utilized for application of PVA/Gd2O3:Eu3+ (5 mol %)@BSA nanocomposites in dip pen and intaglio printing. Hence, the prepared nanocomposites signify an competent method towards long preservative fingerprints as well as great performance for data security operations. This work endorses a prospective paradigm for luminescence enhancement and its applications in advanced forensic science.

New design of highly sensitive AIE based fluorescent imidazole derivatives: Probing of sweat pores and anti-counterfeiting applications.

A novel aggregation induced emission based 2-(1-(3, 5-bis(trifluoromethyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl) phenol (4) (IMD) fluorescent tags (FTs) was designed by simple acid catalyzed five-member N-heterocyclic ring forming reaction process. Powder X-ray diffraction results showed mechanofluorochromic properties of IMD FTs are easily reversible under external force due to the decrease in crystallinity. These IMD FTs also exhibits strong cyan-blue luminescence in solid state with high quantum efficiency. Detailed investigation of latent fingerprints (LFPs) showed permanent, immutable and unique pores that are distributed on the ridges. The visualization of such sweat pores opens new avenue in the field of forensic science. Hence, the prepared IMD FTs exhibit excellent Lipophicity (LP) properties, which endorse its possible applications for the visualization of sweat pores present in the LFPs. The LFPs visualized by IMD FTs exhibit excellent efficiency, sensitivity, selectivity, low background hindrance and less toxicity. The obtained result evident that the prepared FT and followed technique opens possible applications for the visualization of LFPs on various porous/semi-porous/non-porous surfaces under UV 365 nm light.

New design of highly sensitive and selective MoO3:Eu3+ micro-rods: Probing of latent fingerprints visualization and anti-counterfeiting applications.

Red colour light emitting Eu3+ ions activated MoO3 nanophosphors (NPs) were prepared through an ultrasound assisted sonochemical method using Aloe Vera (A.V.) gel as a bio-surfactant. Properties like crystal structure, morphology, optical band gap, luminescent properties, radiative parameters of prepared samples and their use in latent fingerprint (LFPs) visualization were reported. Powder X-ray diffraction results revealed the single orthorhombic crystal structure of the prepared samples, which specifies effective substitution of dopant ions. Morphology of NPs exhibits the hexagonal rod-like structures with size of ∼10 nm. Photoluminescence (PL) emission spectra exhibited sharp, intense peaks at ∼539 nm, 593 nm, 615 nm, 651 nm and 702 nm attributed to 5D0 → 7F0, 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4 transitions of Eu3+ ions respectively. Judd-Ofelt (J-O) theory was used to estimate the PL intensity parameters and Eu-O ligand behavior. The International Commission on Illumination coordinates of the prepared samples located in the pure red region. The optimized sample can be explored as a novel sensing material for the visualization of LFPs on various surfaces under 254 nm UV light. Clear level-3 patterns (sweat pores) were observed in the LFPs and their decay was very slow compared to the LFPs obtained from commercial powders. The photometric characterization of the prepared samples reveals the suitability of the MoO3:Eu3+ NPs for pure red emission in light-emitting diode, better visualization of LFPs and anti-counterfeiting applications.

SiO2@LaOF:Eu3+ core-shell functional nanomaterials for sensitive visualization of latent fingerprints and WLED applications.

For the first time, intense red color composite of SiO2@LaOF:Eu3+ core-shell nanostructures (NS) were fabricated via facile solvothermal method followed by thermal treatment. The obtained core-shell particles display better spherical shape and non-agglomeration with a narrow size distribution. Photoluminescence (PL) emission spectra exhibits intense peaks at ∼593 nm, 611 nm, 650 nm corresponds to 5D0 → 7FJ (J = 0, 1 and 2) Eu3+ transitions respectively. The spectral intensity parameters and Eu-O ligand behaviors are estimated by means of Judd-Ofelt (J-O) theory. CIE co-ordinates are found to be (x = 0.63, y = 0.36) which is very close to standard NTSC values (x = 0.67, y = 0.33). CCT value is ∼3475 K which is less than 5000 K, as a result this phosphor is suitable for warm light emitting diodes. The optimized core-shell SiO2 (coat III)@LaOF:Eu3+ (5 mol%) was used as a fluorescent labeling marker for the visualization of latent fingerprints on both porous and non-porous surfaces. Obtained fingerprints are highly sensitive and selective also no background hindrance which enables level-I to level-III fingerprint ridge characteristics. Observed results indicate that the significant improvement in luminescence of coreshell NS can be explored as a sensitive functional nanopowder for advanced forensic and solid state lightning applications.

Blue light emitting Y2O3:Tm3+ nanophosphors with tunable morphology obtained by bio-surfactant assisted sonochemical route.

Modified sonochemical route was used to prepare Y2O3:Tm3+ (1-11mol%) nanophosphor using Mimosa pudica (M.P.) leaves extract as bio-surfactant. The prepared samples were exhibited high crystalline nature with various morphologies. This was due to sonochemical experimental reaction took place between cavitation bubbles and nearby solution. The average crystallite sizes of the prepared samples were about 15nm to 21nm as obtained from PXRD and TEM analysis. The ultraviolet visible absorption spectra showed prominent bands with an energy gap varied from 5.73eV to 5.84eV. Photoluminescence (PL) emission spectra shows the prominent blue light emission peak at ~456nm attributed to 1D2→3F4 transitions of Tm3+ ions. Judd-Ofelt intensity parameters were estimated by using PL emission spectra. The photometric characteristics of the prepared compounds were very close to the blue color of NTSC standards. So the results were fruitful in making use of Y2O3:Tm3+ nanophosphor as an alternative material for effective blue component in WLED's.

Dual color emitting Eu doped strontium orthosilicate phosphors synthesized by bio-template assisted ultrasound for solid state lightning and display applications.

A novel Sr2SiO4:Eu (1-5mol %) superstructures (SS) were synthesized using bio-sacrificial A.V. gel assisted ultrasound method. Powder X-ray diffraction patterns confirmed the presence of both α and ß phase formation. It was evident that the morphological growth was highly reliant on A.V. gel concentration, sonication time, pH and sonication power. The formation mechanisms for different hierarchical SS were proposed. From diffuse reflectance spectra, the energy band gap was estimated and found to be ∼4.70-5.11eV. The photoluminescence emission spectra for the excitation at 392nm, shows characteristic emission peaks at 593, 613, 654 and 702nm which were attributed to 5D0→7F0, 7F1,7F2 and 7F3 transitions of Eu3+ ions respectively. Conversely, when the samples were subjected to the heat treatment at 850°C for 3h under argon atmosphere, display an intense broad emission peak with two de-convoluted peaks at 490 and 550nm due to 4f65d1→4f1 (8S7/2) transitions of Eu2+ ions. The concentration quenching phenomenon was discussed which attributes to energy transfer, electron-phonon coupling and ion-ion interaction. The Judd-Ofelt intensity parameters and other radiative properties were estimated by using emission spectra. The CIE chromaticity coordinate values of Sr2SiO4:Eu2+ and Eu3+ nanophosphors were located in green and red regions respectively. The calculated CCT and CRI values specify that the present phosphor can be fairly useful for both green and red components of white LED's. Luminescence decay and quantum yield suggest the suitability of this phosphor as an efficient luminescent medium for light emitting diodes. Overall, the results elucidated a rapid, environmentally benign, cost-effective and convenient method for Sr2SiO4:Eu3+ synthesis and for the possible applications such as solid state lighting and display devices.

Novel EGCG assisted ultrasound synthesis of self-assembled Ca2SiO4:Eu(3+) hierarchical superstructures: Photometric characteristics and LED applications.

This paper reports for the first time ultrasound, EGCG assisted synthesis of pure and Eu(3+) (1-5mol%) activated Ca2SiO4 nanophosphors having self-assembled superstructures with high purity. The shape, size and morphology of the product were tuned by controlling influential parameters. It was found that morphology was highly dependent on EGCG concentration, sonication time, pH and sonication power. The probable formation mechanism for various hierarchical superstructures was proposed. The PL studies of Ca2SiO4:Eu(3+) phosphors can be effectively excited by the near ultraviolet (UV) (396nm) light and exhibited strong red emission around 613nm, which was attributed to the Eu(3+) ((5)D0→(7)F2) transition. The concentration quenching phenomenon was explained based on energy transfer between defect and Eu(3+) ions, electron-phonon coupling and Eu(3+)-Eu(3+) interaction. The Judd-Ofelt intensity parameters and radiative properties were estimated by using PL emission spectra. The photometric studies indicate that the obtained phosphors could be a promising red component for possible applications in the field of white light emitting diodes.

Effective fingerprint recognition technique using doped yttrium aluminate nano phosphor material.

First time the yttrium aluminate nanoparticles are used to improve the fingerprint quality. Eco-friendly green combustion process is used to synthesize YAlO3:Sm(3+) (0.5-11mol%) nanophosphor using green tea leaf extract as non-toxic and eco-friendly fuel. Powder X-ray diffraction study confirms the orthorhombic phase. The average sizes of the crystallites were found to be in the range 20-35nm. The emission peaks centered at 564, 601 and 647nm is attributed to 4f-4f (4)G5/2→(6)HJ=5/2,7/2,9/2 forbidden transitions of Sm(3+) ions. Judd-Ofelt theory is applied to experimental data for providing qualitative support by determining J-O intensity parameters. The Commission International De I-Eclairage chromaticity co-ordinates are very close to National Television System Committee standard value of white emission (x=0.296, y=0.237). Further, correlated color temperature is found to be ∼11,900K. A simple, fast, highly sensitive and low-cost method for the detection and enhancement of fingermarks in a broad range of surfaces is developed and constitutes an alternative to traditional luminescent powders.