Urea Assisted Combustion Synthesis Research Articles

Urea-assisted combustion synthesis and nearly zero-thermal-quenching luminescence of highly efficient phosphate phosphor

Exploring green-emitting phosphors with high efficiency and thermostability is a significant issue for enhancing lighting and display quality. In this report, we adopted a facile urea-assisted combustion method to rapidly synthesize terbium-activated NaLaP4O12 (NLPO) powder with high crystallinity. The activators Tb3+ are incorporated into the NLPO lattice via equivalently replacing La3+ ions. Excited at 368 nm, it presents a bright green-emitting performance with high internal quantum efficiency, coming from the dominant 5D4→7F5 transitions of Tb3+. The green-emitting content quenching is controlled by the dipole–dipole interaction. Meanwhile, the emission in response to temperature reveals that the nearly zero-thermal-quenching is induced by the high activation energy barrier (0.31 eV) and suitable structure rigidity. Finally, the light emitting diodes are encapsulated using the studied material, manifesting that it would be a prospective green-emitting candidate. The research shows a guide for developing the terbium-activated phosphors with high luminescence efficiency and excellent thermostability.

Simple fabrication of novel Sm3+ doped BaGd2ZnO5 nanophosphors for flexible displays, improved data security applications, and solid-state lighting applications

In the present work, Urea-assisted combustion synthesis of BaGd2ZnO5:Sm3+ nanophosphors (BGZO:Sm NPs) with orthorhombic symmetry and cool white light luminance. According to the morphological study, the agglomerated particles had non-uniform shapes and crystallite sizes between 30 and 40 nm. The decay lifetime and quantum efficiency are found to be 0.387 ms and 51.4%, respectively. PL emission spectra can gather details about the orange-red emanation from produced NPs since they have a fine peak at 601 nm. Studies on photoluminescence (PL) also demonstrate that exchange-type interrelations are the primary mechanism for the non-radiative relaxing of energy. Finally, outstanding luminous performance is demonstrated by CIE color coordinates (0.5601, 0.3421), color purity (71%), and 1,376 K color-associated temperature (CCT). The multilevel characteristics of the phosphor-attached latent fingerprint (LFP) could be clearly identified in 404 nm light. An optimal observational environment is established by the sharp color contrast between the lines of the valley and ridge. Additionally, the impact of the NP utilized on various substrates for the visualization of LFPs is investigated. The findings demonstrate that the NP is a strong candidate for LFP visualization. Here, a flexible light-emitting material made of polydimethylsiloxane (PDMS) is used as the basis for an anti-counterfeiting (AC) method. Eventually, the ideal sample-convert PDMS flexible films with simple operation and good reusability are created, and their security level is further increased by the collaboration of colorful and distinctive characters.

Influence of synthesis conditions on structural and spectroscopic properties of the K2SrP2O7 pyrophosphate doped with the Eu3+ and Eu2+ ions

This study is focused on the synthesis condition influence related to structural and spectroscopic properties of the potassium strontium pyrophosphate (K2SrP2O7) co-doped with Eu3+ and Eu2+ ions. The experimental parameters of the urea assisted combustion synthesis were optimized by temperature and time of calcination as well as reduction atmosphere composition. The obtained materials were structurally characterized using the X-Ray Powder Diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Spectroscopic properties were determined by emission spectra, excitation spectra, luminescence kinetics and luminescence temperature quenching measurements. It was found that increasing concentration of Eu3+ ions caused an increase of spectroscopic factors, which correspond to the relative integrated luminescence intensities of 5D0–7FJ transitions as well as structural defects. Moreover, the successful Eu2+ ion incorporation was proven by optical spectroscopic measurements, which showed the allowed f-d transitions.

Eu2+-doped microporous aluminosilicate Ca-chabazite Ca1.9Al3.8Si8.2O24 phosphor: synthesis and characterization of potential blue phosphor for NUV wLED

Near-UV (NUV)-excitable blue-light-emitting Eu2+ ions-doped Ca-chabazite Ca1.9Al3.8Si8.2O24 phosphor was synthesized by facile urea-assisted combustion synthesis method. Prepared materials were characterized by X-ray diffraction (XRD) study, scanning Electron Microscopy (SEM), and photoluminescence (PL) spectroscopy. The Eu2+-doped Ca1.9Al3.8Si8.2O24 calcium aluminosilicate phosphor exhibited intense and broad emission in the blue region. CIE chromaticity coordinates were plotted and obtained values were compared with standard NTSC coordinates. Electron vibration interaction (EVI) parameters such as Huang Rhy’s factor (S) and effective phonon energy (ħω) were calculated to determine the strength of electron–phonon coupling. The prepared mineral-based blue-emitting Near-UV-excitable phosphor may prove to be a potential candidate as a blue component for the white light emitting diode (wLED).

Super porous TiO2 photocatalyst: Tailoring the agglomerate porosity into robust structural mesoporosity with enhanced surface area for efficient remediation of azo dye polluted waste water

The low surface area of TiO2 (50 m2g-1 - Degussa P25) due to randomly oriented, agglomerated nanostructures and charge carrier recombination tendency, has till date been its major limitation for photocatalytic remediation of polluted wastewater. This study presents an innovative process to design super porous TiO2 nanostructures with high effective surface area (238 m2g-1), robust, structurally ordered mesoporosity via a simple sol-gel assisted reflux method. Detailed material characterization studies suggest that the higher degree of intermolecular ligation in novel templates such as butanetetracarboxylic or tricarballylic acid modified titanium hydroxide gels resulted in retainment of the porous structure during the urea assisted combustion synthesis. The induction of robust structural porosity is accompanied by a reduction in pore size distribution, an increase in pore volume leading to significantly higher total surface area of the synthesized TiO2. Detailed investigation of dye adsorption kinetics and photocatalytic degradation kinetics, complemented by kinetic modeling analysis confirmed that the super porous TiO2 with robust mesoporous structure outperforms the rest of synthesized TiO2 catalyst (having only agglomerate porosity) in terms of its superior adsorption capacity, faster diffusion kinetics and photocatalytic activity for degradation of Amaranth dye. Thus, the super porous TiO2 shows promising potential for application in sustainable photocatalytic technology for remediation of wastewater contaminated with azo dyes.

Investigation of Pyrophosphates KYP2O7Co-Doped with Lanthanide Ions Useful for Theranostics.

Diphosphate compounds (KYP2O7) co-doped with Yb3+ and Er3+ ions were obtained by one step urea assisted combustion synthesis. The experimental parameters of synthesis were optimized using an experimental design approach related to co-dopants concentration and heattreatment as well as annealing time. The obtained materials were studied with theinitial requirements showing appropriate morphological (X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM)) and spectroscopic properties (emission, luminescence kinetics). Moreover, the effect of Er3+ and Yb3+ ions doped KYP2O7 on morphology, proliferative and metabolic activity and apoptosis in MC3T3-E1 osteoblast cell line and 4B12osteoclasts cell line was investigated. Furthermore, the expression of the common pro-osteogenic markers in MC3T3-E1 osteoblast as well as osteoclastogenesis related markers in 4B12 osteoclasts was evaluated. The extensive in vitro studies showed that KYP2O7 doped with 1 mol% Er3+ and 20 mol% Yb3+ ions positively affected the MC3T3-E1 and 4B12 cells activity without triggering their apoptosis. Moreover, it was shown that an activation of mTOR and Pi3k signaling pathways with 1 mol% Er3+, 20 mol% Yb3+: KYP2O7 can promote the MC3T3-E1 cells expression of late osteogenic markers including RUNX and BMP-2. The obtained data shed a promising light for KYP2O7 doped with Er3+ and Yb3+ ions as a potential factors improving bone fracture healing as well as in bioimaging (so-called in theranostics).

Urea Assisted Combustion Synthesis of LiFePO4/C Nano composite Cathode Material for Lithium Ion Battery Storage System

In this present work, we demonstrated economical way to synthesize nano crystalline LiFePO4Olivine structured LiFePO4/C nanocomposite using urea as fuel and sucrose as carbon source were calculated using the total oxidizing and reducing valencies of the components which provide as numerical coefficients for stoichiometric balance so that the equivalent ratio is unity followed by heat treatment at 600 °C for 6 - 10 h, under Ar (90%) and H2 (10%) gas atmosphere.The resultant products are characterized by XRD to know the phase formation and for estimation of the crystallite size. The XRD patterns were collected in steps of 0.02° over the range of 10° ≤2θ ≤80° at room temperature with a constant counting time of 0.1 s per step, From XRD all the powders showing the nano sized crystallite sizes in the range of 40-45nm. The morphologies of the powders were investigated by a scanning electron microscopy (SEM) all samples indicate the agglomeration of powder with highly porous nature in all the samples. The synthesized olivine powders were subjected to thermogravimetric / differential scanning calorimetry (TG-DSC) as the reference material in the temperature range of 25–1000°C with a heating rate of 10°C/min in air and nitrogen atmosphere. Raman spectra were obtained with 514.5 nm Ar-Ion laser radiation at a laser power of 150 mW in the range of 100- 2000cm-1 for a total of 10 scans to increase the signal-to-noise ratio and with 4 cm-1 spectral resolutionwerestudied.

Photoluminescence Properties of Eu3+ and Ce3+ Activated Calcium Chlorophosphate Via Combustion Synthesis Method

Calcium chlorophosphate (Ca2PO4Cl) phosphors, activated by rare earth ions Eu3+ and Ce3+ were prepared by urea assisted combustion synthesis technique and their characterization and luminescent properties were studied. The synthesized phosphors were investigated by powdered XRD, SEM and Photoluminescence characterization (PL) methods. PL excitation spectra of Ca2PO4Cl:Eu3+/Ce3+ phosphor exhibit narrow bands in the near ultra violet (n-UV) range, and the PL emission spectra of Ca2PO4Cl: Eu3+/Ce3+ phosphor shows sharp narrow bands typical of rare earth ions. The bands observed in the PL emission and excitation spectra of Ca2PO4Cl: Eu3+/Ce3+ phosphors can be ascribed to the electronic transitions within 4f configurations of rare earth ions. The excitation peaks for Ca2PO4Cl: Eu3+ is in n-UV range. The obtained results suggest that these phosphors may be favorable for lamp industry.

Synthesis and cytotoxic effects of SrAl_2O_4 persistent luminescence nanoparticles co-doped with Eu^2+/Dy^3+ ions

Persistent luminescence strontium aluminate nanoparticles co-doped with Eu2+ and Dy3+ were prepared by urea-assisted combustion synthesis. Different percentages of co-dopants were evaluated in order to optimize luminescence of the nanophosphor. Luminescence measurements showed that excitation of this green-emitting phosphor occurred within a wide range of wavelengths (254 – 460 nm) while the half-life time of persistent luminescence laid within the seconds regime. Presence of Dy3+ as the co-dopant enhanced the green emission in this interval of time, and the entire decay time occurred in minutes. Crystallinity and morphology were evaluated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. Strontium aluminate co-doped with 1%Eu, and 1%Dy, and 1%Eu, and 3%Dy emitted an intense green signal and long decay time. These crystal nanophosphors displayed sizes of 18 nm and 22 nm, respectively. The cytotoxic effect of nanoparticles was determined by a cell viability test where the tri-methyl-tetrazolium reagent (MTT) was reduced only by metabolically active cells. Different concentrations of bare nanoparticles were tested in a 96-well plate containing 10, 000 cells per well of a human cervix carcinoma cell line (HeLa). Evaluation of cell viability by this cytotoxic assay showed that in most of the cases cell viability was higher than 60% after incubation with bare nanoparticles. Since our bare nanoparticles were not cytotoxic, these results open a broad field of biomedical applications for phosphorescent materials as cell biolabels and imaging research area.

Photoluminescence, size and morphology of red-emitting Gd2O3:Eu3+ nanophosphor synthesized by various methods

Gd2O3:Eu3+ nanoparticles with doping concentration of 5% were prepared by urea-assisted combustion synthesis (UCS), carbohydrazide combustion synthesis (CCS), sucrose-aided combustion synthesis (SCS), glycine combustion synthesis (GCS) and by sol–gel (SG) synthesis. The nanopowders were postannealed at 1000°C for 3h to obtain nanocrystalline phosphor, which was confirmed by X-ray diffraction (XRD). Surface chemical groups were detected by Fourier transform infrared spectroscopy (FTIR). Particle size distribution and morphology images of the synthesized nanoparticles were obtained using transmission electron microscopy (TEM). Average particle size decreased exponentially with an increase in the amount of gases evolved during the synthesis method. Nanoparticles obtained by UCS showed the highest photoluminescence (PL) intensity, and absolute quantum yield (QY). A comparison of the factors affecting optical properties showed that PL intensity, QY and fluorescence lifetime were dependent on crystallite size.

Thermoluminescence and kinetic parameters of synthesised BaAl2O4(Dy) phosphor irradiated with gamma and mega-voltage radiation

Dy doped BaAl2O4 powder sample was successfully synthesised by urea assisted combustion synthesis route. Post preparation calcination was done at 700°C for 1h. The formation of compound was confirmed by powder X-ray diffraction (PXRD).The estimated particle size was found to be ∼30.51nm by using Debye Scherer's formula. The high-resolution scanning electron microscope (SEM) micrograph shows the presence of several micro and nano-particles within the grain. Thermal behaviour of prepared powder sample was studied using thermogravimetric analysis (TGA). It has been confirmed that the prepared phosphor was thermally stable up to 800°C. Thermoluminescence (TL) analysis of prepared sample was carried out after the irradiation with Co-60 gamma rays, 6-mega voltage (MV) and 16MV photon beams. Glow curves of the prepared BaAl2O4 (Dy:1%) sample were similar in shape irrespective of incident energy and radiation type. The low and high intensity peak in each curve was appeared at around 108°C and 305°C, respectively. No appreciable shift in peak positions has been observed. The trapping parameters, namely activation energy (E), order of kinetics (b) and frequency factor (s) have been determined using glow curve shape (Chen's) method. The activation energy as well as frequency factor increases with increase in the energy of incident radiation. Energy dependence has been observed in the present phosphor due to Compton's scattering, dominates at this energy range. It has been observed that peak of each glow curves of the sample irradiated with gamma and mega-voltage photons, lies within ±5°C. This phosphor can be utilised for display technology as well as radiation dosimetry, especially where the need for tissue equivalent material is not a constraint. Low cost, less time consuming and high yield are some important key factors of this method over other synthesis techniques.

Synthesis and characterization of spinel LiMn2O4 nanoparticles by urea assisted combustion synthesis

Synthesis and characterization of spinel LiMn2O4 nanoparticles by urea assisted combustion synthesis

A feasibility study on SnO2/NiFe2O4 nanocomposites as anodes for Li ion batteries

The SnO2/NiFe2O4 nanocomposite samples with varying concentration of SnO2 such as 5wt.% and 10wt.% were synthesized via urea assisted combustion synthesis. The kinetics of the combustion reactions were studied using thermo gravimetry analysis and from which the compound formation temperature of all the samples were observed to be below 400°C. From the morphological analysis the grain size of NiFe2O4, 5wt.% SnO2/NiFe2O4 and 10wt.% SnO2/NiFe2O4 samples were observed to be around 1.7, 2.3 and 3.5μm. The chrono potentiometry analyses of the samples were performed against lithium metal electrode. The capacity retention was found to be higher for composite with 10wt.% SnO2. The discharge capacity of 10wt.% SnO2 sample with respect to Li metal and LiMn2O4 electrode was observed to be around 980mAh/g and 138mAh/g respectively.

Hybrid supercapacitor with nano-TiP2O7 as intercalation electrode

Nano-size (≤100nm) TiP2O7 is prepared by the urea assisted combustion synthesis, at 450 and 900°C. The compound is characterized by powder X-ray diffraction, Rietveld refinement, high resolution transmission electron microscopy and surface area methods. Lithium cycling properties by way of galvanostatic cycling and cyclic voltammetry (CV) showed a reversible and stable capacity of 60 (±3)mAhg−1 (0.5mole of Li) up to 100 cycles, when cycled at 15mAg−1 between 2–3.4V vs. Li. Non-aqueous hybrid supercapacitor, TiP2O7 (as anode) and activated carbon (AC) (as cathode) has been studied by galvanostatic cycling and CV in the range, 0–3 V at 31mAg−1 and exhibited a specific discharge capacitance of 29 (±1)Fg−1stable in the range, 100–500 cycles. The Ragone plot shows a deliverable maximum of 13Whkg−1 and 371Wkg−1 energy and power density, respectively.