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This article reports on the synthesis and physical properties of crystalline ZnO:Cr3+ nanophosphors by a low-temperature combustion route using a natural seed extract of Cicer arietinum as the fuel. The obtained product of ZnO:Cr3+ through the C. arietinum seed extract was investigated through various characterization techniques. It was evident that morphology was highly dependent on the concentration of seed extract. Emission spectra show two main intense characteristic peaks recorded at ~593 and ~688 nm which indicate that the optimized ZnO:Cr3+ nanophosphor was highly useful for red-lightemitting devices. The synthesized nanophosphors exhibit a significant antioxidant activity against the scavenging of DPPH-free radicals. [ABSTRACT FROM AUTHOR]

A series of Eu 3+ (1–7 mol %) doped Y 2 SiO 5 red nanophosphors were prepared by eco-friendly combustion route using Calotropis gigantea latex as a fuel. The obtained nanophosphors were calcined at 1000 °C and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman studies, UV–Visible and photoluminescence (PL) spectroscopic techniques. PXRD were used to determine the structure of the phosphors, showing that the product was monoclinic phase of X1 type Y 2 SiO 5 having a phase group P2 1/c n. 14. The PL properties of samples exhibited an intense broad red emission band upon excitation with 397 nm, with a peak at 612 nm, color coordinates of (0.5866, 0.4026), and average correlated color temperature ~2018.5 K. Based on Judd–Ofelt (J–O) theory, the intensity parameters ( Ω 2 and Ω 4 ) were evaluated from the emission spectra of Y 2 SiO 5 : Eu 3+ (1–7 mol %) nanophosphors. The registered trend ( Ω 2 < Ω 4 ) reveals the relatively high symmetry environment around the rare earth ion (RE) site in Y 2 SiO 5 as compared to other host matrix. The results show that prepared samples were compared with the commercially available compound and founds as par to the commercial compound hence it may be used as a potential red phosphors for near UV excited White LEDs applications. [ABSTRACT FROM AUTHOR]

Sm3+ (1.0 –11.0 mol %) doped SrAl 2 O 4 nanopowders were synthesized by ultrasonication followed by propellant chemistry technique using Aloe Vera (A.V.) extract as a surfactant/fuel. The prepared sample's average crystallite size of ∼ 30.0–32.0 nm was estimated. The surface morphology of the samples showed better porosity with nanorods networked to obtain superstructures. Diffused reflection spectral analysis showed that the prepared samples have an optical energy band gap of 5.22 to 5.6 eV, where the increased concentration of Sm3+ decreased the E g value of the SrAl 2 O 4 : Sm3+ (1.0 – 11.0 mol%). Samples showed intense orange-red emission upon excited with 372 nm. Thereafter CIE and CCT values explain that the prepared nanophosphors (NPs) are highly advantageous for the production of red or excited with 372 nm orange emitting diodes in optoelectronics for display devices and WLED applications. SrAl 2 O 4 : Sm3+ (5.0 mol %) NPs were considered to study the LFPs. Hence, the synthesized NPs will give an efficient outlook to visualize ridge patterns in LFPs investigations and anti-counterfeiting applications, which were studied by considering different material surfaces. [ABSTRACT FROM AUTHOR]

Due to the distinctiveness and perseverance of the friction ridges in fingerprints (FPs), latent fingerprints (LFPs) and lip prints (LPs) are two most significant types of evidence at crime scene. Therefore, it is essential in forensic science to develop a reliable method to detect LFPs and LPs. Traditional detection methods still face a number of difficulties, such as limited sensitivity, low contrast, strong background, and complex processing stages. We proposed a method for visualization of LFPs and LPs by utilizing La 2 CaZnO 5 :Dy3+ (1–5 mol %) (LCZO: Dy) phosphor using a solution combustion method. The crystal structure, phase purity, particle morphology, photoluminescence (PL) properties of the resulting phosphors were then characterized in detail. SEM images suggested that the obtained phosphors are non-uniform shapes and agglomerated to big particles. The photophysical properties of Dy3+ doped phosphors are analyzed by exploiting their photoluminescence excitation (PLE) and emission profiles. The emission profiles of all the doped samples exhibit sharp emission lines centred at ∼481, 573, and 667 nm, which are ascribed to 4F 9/2 → 6H 15/2 , 4F 9/2 → 6H 13/2 , and 4F 9/2 → 6H 11/2 intra configurational transitions of Dy3+ ion, correspondingly. The optimum doping concentration of LCZO: Dy phosphor was 4 mol%, and the dominant factor of concentration quenching effect is the nearest-neighbor ions interaction. The chromaticity coordinates of International Committee LCZO: Dy were located in the yellow color area. In addition, LCZO: 4Dy phosphor can well visualize the LFP image and LP image. The levels 1–3 features of fingerprint and groove pattern of lip print can be easily recognised with high resolution and contrast. The experimental results showed La 2 CaZnO 5 :Dy3+ can be well applied to advanced forensic investigation. • For the first time, a La 2 CaZnO 5 :Dy 3+ (1–5 mol%) phosphors was prepared via solution combustion method. • Using La 2 CaZnO 5 :Dy 3+ phosphor, latent fingerprint minutiae features can be identified. • La 2 CaZnO 5 :Dy 3+ phosphor is also used as a prominent candidate in lip print Applications. [ABSTRACT FROM AUTHOR]

Abstract Structural and luminescence properties of SrTiO 3 : Pr3+: A+ (A+: Li, Na, K) nanophosphors were synthesized by simple sonochemical route. Prepared products were well-characterized for their optical and structural properties. Surface morphology of the prepared samples were studied with the influential parameters such as surfactant concentration, sonication time, temperature, pH and compared the effect with normal mechanical stirring. Morphology was highly dependent on the experimental parameters. The predicted growth mechanism to obtain superstructures of the samples prepared by sonochemical method was discussed. Photoluminescence (PL) studies exhibit characteristic emission peaks of Pr3+ ions in the range 500–750 nm. The highest PL intensity was obtained for 5 mol% of Pr3+ doped samples. Further, co-doping with Li+, Na+ and K+ ions into Pr3+ activated SrTiO 3 phosphor led to an enhancement in luminescence intensity by reducing the parity restriction of electric dipole transitions. As a consequence of suitable local distortion of the crystal field surrounding to the Pr3+ activator ions. The maximum PL intensity was observed for Li+ (1 wt%) co-doped SrTiO 3 :Pr3+ (5 mol%) samples. Furthermore, Li+ ion was the best charge compensator, because of it reduced the defects emission and also increased the emission intensity of Pr3+ significantly. Prepared phosphors exhibit short lifetime, good quantum efficiency; excellent color purity which is near to the NTSC standards. Prepared fluorescent powders were used as a dusting powder for the rapid visualization of latent fingerprints under UV light of 254 nm. From the reported results it is evident that the optimized prepared samples are suitable for solid state lighting and advanced forensic investigation applications. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Eu2+ doped Sr 2 MgSi 2 O 7 nanophosphors (SMSO:Eu2+ NPs) have been synthesized by using solid-state reaction method. As Eu2+ concentration increases, energy transfer (ET) between Eu2+ ions dominated attributed to dipole-dipole (d-d) interaction. Besides, temperature-dependent photoluminescence (PL) of optimized SMSO:7Eu2+ NPs is investigated. The emission shifts towards blue with increased temperature. From the temperature-dependent emission, the activation energy, is ∼0.40 eV. CIE coordinate is (0.1476, 0.1141) with CCT value of 3633 K. The optimized phosphor is used to detect LFPs on various surfaces. The level I-III features are clearly identified under UV 365 nm excitation. Several pores properties namely pore size, shape, number, position, type and pore inter-distance are analyzed in detail. The anti-counterfeiting results clearly showed the enhanced intensity owing to its nano-size, reduced light dispersion and increased light absorption. The overall results clearly suggest the optimized SMSO:7Eu2+ NPs are promising luminescent platform for nUV light-emitting diode (LED) and latent fingerprint (LFP) applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to the outstanding optical qualities, stimulation-responsive luminous materials have drawn a lot of attention in the anti-counterfeiting application. In this work, the feasibility of applying BaLa 2 ZnO 5 :Bi3+ (BLZO:Bi3+) (0.5–4.0 mol%) phosphor, to multiple stimuli anti-counterfeiting (AC) and latent fingerprint visualization (LFP) is explored and discussed. The prepared luminous security ink from the optimized phosphor is effectively used for the multiple stimuli AC under 325, 355 and 375 nm excitation wavelengths. The results show that the fabricated luminous security ink is highly stable in ultraviolet (UV) light, various chemical environments, and ambient conditions. In addition, powder dusting method is utilized for LFPs detection on porous, non-porous and semi-porous surfaces under different excitation wavelengths. The multilevel features of the phosphor-attached LFP could be identified clearly in all the surfaces. The high-resolution LFPs imaging by scanning electron microscope (SEM) pictures, providing us more precise details on the width, distance, distribution, and forms of fingerprint (FP) pores. All the results reveal that the phosphor is a good potential choice for AC and LFP detection. [Display omitted] • At excitation wavelengths of 325, 355, and 375 nm, the BLZO:Bi3+ phosphor can produce blue, baby blue, and blue-green light. • latent fingerprints clearly captured by using the optimized phosphor in powder dusting method. • The application of the prepared luminous security ink for multiple stimuli anti-counterfeiting has been effectively proven. • Results show that luminous security ink is highly stable in UV light, various chemical environments, and ambient conditions. [ABSTRACT FROM AUTHOR]

Advanced forensic applications and optoelectronics both heavily rely on rare earth (RE) element activated luminous phosphor materials. We have used a single-phase green-emitting Sr 9 Al 6 O 18 :Er3+ (1–11 mol%) (SAO:Er) nanophosphor to detect latent fingerprints (LFPs) and white light-emitting diodes (w-LEDs). The X-ray diffraction and Rietveld refinement were used to examine crystallographic data. The phosphors showed vivid-green luminescence when stimulated by 378 nm, a near ultraviolet (nUV). The concentration of Er3+ ions is observed to affect the photoluminescence emission (PLE) intensity, reaching its highest value for 5 mol% doping. The optimized phosphor is used in latent finger print (LFP), lip print (LP) and anti-counterfeiting (AC) applications. Under 378 nm excitation, multilevel features of the phosphor-attached LFPs could be clearly identified. The high colour contrast between the ridge and valley lines made for an excellent observation. We have developed simple brush and screen-printing methods for creating a variety of patterns using our custom anti-counterfeit security ink. In addition to this, the obtained AC tags exhibit high resolution and long-term durability. These characteristics clearly demonstrated that the current phosphor is an excellent luminescent material for data storage applications. • Green-emitting Sr 9 Al 6 O 18 :Er3+ nanophosphors were obtained by solution combustion. • Vivid-green luminescence was obtained when stimulated by 378 nm near ultraviolet. • The prepared fluorescent ink is highly beneficial for high-end security encryption. • Anti-counterfeiting labels exhibit high resolution and long-term durability. [ABSTRACT FROM AUTHOR]

Synthesis of Eu 3+ doped Y 2 O 3 nanophosphors via modified sonochemical method was presented. Morphologies of the prepared products were analyzed with respect to the influential parameters during the preparation time. The photoluminescence (PL) emission spectra exhibits several peaks at ∼537 nm, 598 nm, 613 nm and 662 nm attributed to 5 D 0 → 7 F J ( J = 0, 1–3) transitions of Eu 3+ ions in the host lattice. The types of energy transfer between the Eu 3+ ions were responsible for concentration quenching confirms the electric dipole–quadrupole interaction among the ions. The Judd-Ofelt intensity parameters and other radiative properties were estimated by using PL emission spectra. The photometric characteristics of the prepared samples indicate that the color co-ordinates were tune towards pure red emission with color purity of ∼88%. The results signified that the prepared Y 2 O 3 :Eu 3+ was a potential amber phosphor for solid state and LED’s applications. [ABSTRACT FROM AUTHOR]

The development of technology related to forensic is still beneficial and requires for continued research and the implementation of evaluation procedures. In this context, the current work focuses on the production of blue light emitting La 2 Zr 2 O 7 nanophosphors (LZO) (NPs) doped with Ce3+ ions and surface modified with oleyl amine (OA) are employed for data security and latent fingerprint imaging applications. The formation of the pure pyrochlore phase is confirmed from powder X-ray diffraction (PXRD). The structural analysis is performed from Rietveld refinement. Scanning electron microscope (SEM) and transmission electron microscopy are used to study the surface morphology and crystallite size estimation respectively. Photoluminescence (PL) emission spectra exhibit all the characteristic emission peaks of Ce3+ ions. The surface modified NPs by OA exhibited 2-fold enhancement in the emission intensity as compared to unmodified NPs, which is due to effective intramolecular energy transfers from coordinated ligands to the activated Ce3+ ions, called the antenna effect. The most trustworthy proof of a person's identity can be found in the ridge characteristics revealed by the observed latent fingerprints employing surface modified nanophosphor. The chemical bonding between the nanophosphor and chemical components contained in the fingerprints, which enables the majority of authenticated sweat pores, further confirmed by high resolution photographs of formed latent fingerprints. The NPs which have OA grafted onto them can be made into security ink that can be used to create hidden inscriptions with a basic brush technique as well as screen print and decoded under 283 nm light illumination. The features of the NPs, which is a real-time option for latent fingerprint formation and anti-counterfeiting technologies are significantly improved by the surface modification technique. • A series of La 2 Zr 2 O 7 : Ce3+ NPs were synthesized through a combustion synthesis method. • Optimized sample was further surface modified by utilizing OA as a surface modifier. • Surface modified NPs may be used for visualization of latent fingerprints and anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

A series of neodymium ions activated yttrium aluminate nanophosphors of various concentrations were synthesized by solution combustion method using oxalyl dihydrazide as a fuel. The crystal structure, optical energy gap, luminescent properties and Judd-Ofelt analysis were carried out. The use of the phosphor in revealing/enhancing the fingerprints quality was investigated in detail. The powder X-ray diffraction results confirmed the orthorhombic phase for the prepared samples. From diffuse reflectance spectra, estimated energy gap was found to be in range of 5.38–5.80 eV. The photoemission profile of YAlO 3 : Nd 3+ exhibit a blue emission upon 364 nm excitation. Further, the prepared materials were used for enhancing the quality of latent fingerprint technique. The present method was facile and robust for visualization of fingerprint with enhanced sensitivity, low glare light and high efficiency on various surfaces. The demonstrated results on facile detection of fingerprints virtually on any surfaces using YAlO 3 :Nd 3+ nanophosphors are versatile tool which hold great promise for practical applications on forensic sciences. [ABSTRACT FROM AUTHOR]

A new class of ceramic pigments based on orthorhombic Thulium (Tm 3+ ) doped YAlO 3 nanophosphors are synthesized by a simple and efficient low temperature solution combustion method using oxalyl dihydrazide (ODH) as fuel. The phosphors exhibit bright blue emission upon 359 nm excitation. Judd–Ofelt ( J–O ) theory is applied to a series of Tm 3+ doped phosphors based on their emission spectra. CIE chromaticity co-ordinates confirm blue emission of the phosphor. The prepared nano-phosphor was successful in developing latent fingerprint from various forensic relevant materials. A preliminary investigation of their anti-counterfeiting performance has been made, and the results indicate that the color emitting capability and high concealment makes this nanophosphor can provide a strengthened and more reliable anti-counterfeiting effect. As a result the optimized YAlO 3 :Tm 3+ (3 mol%) phosphor is quite useful for potential application of pigments of desired color, solid state lighting, latent fingerprint, display and anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

First time the yttrium aluminate nanoparticles are used to improve the fingerprint quality. Eco-friendly green combustion process is used to synthesize YAlO 3 :Sm 3+ (0.5–11 mol%) 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 20–35 nm. The emission peaks centered at 564, 601 and 647 nm is attributed to 4f–4f 4 G 5 / 2 → 6 H J = 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 ∼11,900 K. 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. [ABSTRACT FROM AUTHOR]