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Abstract Neodymium activated strontium zinc aluminate (Sr 3 ZnAl 2 O 7 :x%Nd3+) nanophosphor was synthesized using the sol-gel technique whereby the Nd3+erscript> concentration was varied in the range 0 ≤ x ≤ 2. The effect of Nd3+ concentration on the structure, particle morphology and photoluminescence properties of Sr 3 ZnAl 2 O 7 were investigated. The X-ray diffraction (XRD) results revealed that all samples resembled the mixture of both ZnAl 2 O 4 and Sr 3 Al 2 O 6 cubic structures. Nd3+ doping influenced the crystallite sizes of the prepared phosphor materials. The energy dispersive X-ray spectroscopy (EDS) results confirmed the presence of all expected elements in the composition. Scanning electron microscopy (SEM) revealed that as the Nd3+ concentration increased the surface morphology changed to smooth mountain-like structures. The ultraviolet–visible (UV–Vis) diffuse reflection spectroscopy showed that the band gap of Sr 3 ZnAl 2 O 7 can be tuned from 2.74 to 2.95 eV by increasing the Nd3+ concentration. When the host is excited above the bandgap (374 nm), broad emission attributed to defects occurs with the maximum near 585 nm. Doped samples excited in this manner do not exhibit additional luminescence due to the Nd3+ ions, but in contrast there is a small dip in the defect emission band near 585 nm due to absorption attributed to Nd3+ ions. Characteristic infrared emissions of Nd3+ ions at 885, 1064 and 1340 nm were observed by directly exciting the Nd3+ ions at 585 nm (4I 9/2 → 5G 5/2 + 2G 7/2) and were attributed to 4F 3/2 → 4I 9/2, 4I 11/2 and 4I 13/2 transitions, respectively. The Commission Internationale de l'Eclairage (CIE) coordinates results showed that the orange emission colour is from the host. [ABSTRACT FROM AUTHOR] more...

Copper selenide (Cu 2 Se) thin films have been deposited on glass slide substrates using the chemical bath deposition technique at room temperature. The films were annealed at 250 °C in an air atmosphere at different time intervals. The X-ray diffraction revealed that the Cu 2 Se films have a face-centered berzelianite cubic structure. The estimated average crystallite sizes were found to be 45 nm. X-ray Photoelectron Spectroscopy showed binding energy peaks corresponding to the Cu 2 Se. Scanning electron microscopy results showed that the morphology of the Cu 2 Se thin films consists of spherical particles. Energy dispersive spectroscopy confirmed the presence of Cu and Se. The Ultraviolet–visible spectroscopy results showed that the energy bandgap of the films ranges between 1.52 and 1.25 eV. Photoluminescence results showed emissions from the Cu 2 Se defects at around 2.27, 2.40, 2.68, and 2.96 eV. It was found that the emission intensity increased up to 3 h and then decreased with an increase in annealing time. • Cu2Se thin films were prepared for the first time using CBD method. • There are limited reports on the synthesis of Cu2Se thin films via CBD and the effectsof annealing time has not been investigated. • XRD disclosed a face-centred berzelianite cubic structure. • PL revealed that the optimum annealing time is 3 h. • Coordinates position for all samples falls within the light greenish-blue region of theCIE diagram. [ABSTRACT FROM AUTHOR] more...

In this work the novel poly (ε-caprolactone) (PCL)/ZnO: Ce3+, Eu3+ nanocomposites have been prepared through the solution casting method using acetophenone as solvent. The properties of the final composites were investigated by XRD, SEM, TGA, DSC, UV and PL. Diffraction patterns showed crystalline peaks at Bragg angles 2θ = 21.3° and 23.6° for PCL and the nanocomposite. Nanosphosphors are clearly dispersed and seem to have occupied PCL micro-cavities with expected elemental composition. The degree of crystallinity and overall thermal stability of the PCL nanocomposites are lower than of the pristine polymer. UV–vis transmittance spectra of the PCL showed absorption edge at lower wavelengths than all nanocomposites and nanopowders. There is an apparent improvement in the luminescent properties of the solution casted nanocomposites. In fact, the luminescence intensity of the co-doped nanocomposite samples has increased roughly10 times compared to PCL. • The PCL/phosphor nanocomposites were successfully prepared through the solution casting method, using acetophenone as the solvent. • Estimated D values suggest that powders tend to attract each other within the nanocomposites. • DSC showed an increase in the amorphous regions in PCL. • TGA revealed a decrease in the thermal stability of the nanocomposites. • UV–Vis–NIR absorption spectroscopy exhibits red shift in the nanocomposites. [ABSTRACT FROM AUTHOR] more...

• PLA/SiO2:Sr2+: Tb3+ composites were successfully synthesized by melt mixing and characterized. • TEM and XRD were used to determine the physical properties. • The thermal properties of the composites were determined using DSC and TGA. • Photoluminescent behavior of the composites was studied with laser PL. • All the samples emit in the blue vertex as shown by the CIE results. SiO 2 :0.4% Sr2+, x% Tb3+ (0 ≤ x ≤ 0.5) nanophosphor powders were prepared by sol-gel method. The powder samples were dispersed into the PLA polymer matrix through melt mixing method and compression molding to prepare the nanophosphor polymer composite. X-ray diffraction (XRD) patterns showed broad peaks with the position of the peaks shifting and more separating with an increase in Tb3+ concentration. The transmission electron microscope (TEM) images showed darker patches with the introduction of the nanophosphor, which indicates the incorporation of phosphor particles into PLA polymer. Differential scanning calorimeter (DSC) results revealed that the composites show an increase in the cold crystallization temperature (T cc) and slight decrease in the glass transition temperature (T g) as compared to the PLA. Thermogravimetric analysis (TGA) results showed that the thermal stability of the composites show an initial decrease with the incorporation of the fillers, but they become more thermally stable with higher Tb concentration in the fillers. Ultraviolet visible spectroscopy (UV–vis) results showed the decrease in transmittance for the composite compared to the PLA polymer. The photoluminescence (PL) results showed that the incorporation of the Sr2+doped SiO 2 only affected the luminescence intensity, while co-doping with the incorporation of the Sr2+ and Tb3+ ions induced the emissions peaks at 487, 543, 582 and 621 nm, which could be attributed to the 5D 4 → 7F 3 , 7F 4 , 7F 5 , and 7F 6 transitions of Tb3+, respectively. The main aim of this study was to fabricate the light emitting polymer-based material. [Display omitted] [ABSTRACT FROM AUTHOR] more...

Abstract Nanophosphor powders of the mixed phases of ZnAl 2 O 4 /ZnO/SrAl 2 O 4 /Sr 3 Al 2 O 6 (ZZSS) doped with Tb3+ (ZZSS:0.025%Tb3+) were successfully prepared by sol-gel technique. The effect of the annealing period at a fixed annealing temperature (1000 °C) and dopant concentration (0.025% Tb3+) on the structure and photoluminescence properties was investigated. X-ray diffraction results revealed that the crystallite size was influenced by the annealing period. Scanning electron microscopy showed that varying the annealing period influenced the particle morphology of the prepared nanophosphor material. High resolution transmission electron microscopy confirmed that the prepared material is on the nanoscale. The photoluminescence results showed that the ZZSS emits at 585 nm when excited at 374 nm, which is attributed to the defects centres within the ZnO phase. The Tb3+ doped samples showed emissions peaks at 545, 590 and 623 nm which were attributed to the 4f transitions of Tb3+, specifically 5D 4 → 7F J (J = 5, 4, 3). Increasing the annealing period up to 5.4 h led to luminescence enhancements, while a further increase led to quenching. The Commision Internationale de l'Eclairage coordinates showed that the greenish emission colour could be tuned by varying the annealing period. Highlights • The prepared nanophosphor resembles the mix phases of ZnAl 2 O 4 /ZnO/SrAl 2 O 4 /Sr 3 Al 2 O 6. • Annealing period influences the crystallite sizes of the prepared nanophosphor. • The morphology was greatly influenced by annealing period. • Photoluminescence (PL) results showed 5.4 h as the optimum annealing period of the prepared nanophosphor. • The greenish colour from terbium can be enhanced by varying the annealing period. [ABSTRACT FROM AUTHOR] more...

In this study, BaAl 2 O 4 /MgAl 2 O 4 /MgO:x% Gd3+ (BMM:x% Gd3+) (0 ≤ x ≤ 1.1) mixed phases nanophosphors were prepared for the first-time using sol-gel method. The effect of Gd3+ concentration on the morphology, structure, and optical characteristics were examined. X-ray diffraction (XRD) confirmed the presence of hexagonal (BaAl 2 O 4), cubic (MgAl 2 O 4 and MgO) phases. Varying the Gd3+ concentration has no significant influence on the prepared nanophosphors morphology. Energy dispersive X-ray spectroscopy (EDS) confirmed the presence of the anticipated elementary compositions. Photoluminescence (PL) results showed three emissions peaks located around 312, 616 and 730 nm. The emission peak at 312 nm was ascribed to 6P 7/2 → 6S 7/2 transition in Gd3+ whereas other emission peaks originated from other impurities such as Cr3+. [ABSTRACT FROM AUTHOR] more...

Pristine and octadecylammine (ODA)-capped ZnO nanostructures were synthesized via the homogeneous precipitation method at a bath temperature of 80 °C and annealed in air at 700 °C for 2 h. Various molar concentrations of ODA ranging from 0.3 to 15 mol% ODA were used to study the effect of ODA capping into ZnO nanostructures. The x-ray diffraction (XRD) analyses revealed the hexagonal wurtzite structure for all prepared samples. The estimated average crystallite sizes were found to be in the range of 46–72 nm. It was found that the crystallite sizes increased with an increase in the amount of ODA molar concentration. The surface morphology studied using scanning electron microscopy (SEM) showed flower-like shapes for pristine ZnO and cylindrical nanorods features for ODA-capped ZnO nanostructures. Elemental energy dispersive (EDS) and mapping analysis conducted on the samples shows homogeneous distribution of Zn, O, and C ions. The Ultraviolet-visible diffusion reflectance spectroscopy showed a decrease in the band gap with an increasing of ODA molar concentration. The photoluminescence (PL) results demonstrated that the luminescence intensity increased up to 10 mol% ODA. However, further increase in ODA molar concentration revealed the decrease on the luminescence intensity. The approach in the present study opened a new way to tune band gap and luminescence intensity using ODA. [ABSTRACT FROM AUTHOR] more...

MgAl 2 O 4 and 0.1% Eu 3+ , x% Cr 3+ co-activated nano-phosphors were successfully prepared using the sol-gel method. The co-activator (Cr 3+ ) mol% was varied at a range of 0 ≤ x ≤ 0.15 % . All annealed samples consist of the pure cubic MgAl 2 O 4 structure. Varying the Cr 3+ concentration influenced the surface morphology of the nano-phosphor. The host, 0.1% Cr 3+ and 0.1% Eu 3+ activated nanophosphor emits at different wavelengths. The emission peak at 398 nm is attributed to the defect within the host. The emission peaks at 403, 565 and 694 nm are attributed to arise from the Cr 3+ transitions from 4 T 1 → 4 A, 4 T 2 → 4 A 2 and 2 E → 4 A 2 , respectively. The emission peaks at 574 and 619 nm are respectively attributed to the 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 transitions in the Eu 3+ ion. No evidence of energy transfer was observed. The emission colour could be turned by varying the co-activator concentration and excitation wavelength. [ABSTRACT FROM AUTHOR] more...

• The prepared nanophosphor resembles the monoclinic CaAl 2 O 4. • Annealing period influences the crystallite sizes of the prepared nanophosphor. • The morphology was greatly influenced by annealing period. • Photoluminescence (PL) results showed 6.9 h as the optimum annealing period of the prepared nanophosphor. • The energy band gap and the greenish colour from samarium can be tuned by varying the annealing period. We report on the variation of annealing period (AP) in the range 1–8 h on samarium doped calcium aluminate (CaAl 2 O 4 :0.1%Sm3+) powders prepared by sol-gel method. The effect of AP was investigated on the structure, morphology and optical properties of the powders. The X-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS) findings showed that Sm3+ ions were successfully doped into CaAl 2 O 4. XRD confirmed that AP does not have any effect on the phase of the prepared nanopowders, hence all the samples have a monoclinic structure. Scanning electron microscope (SEM) showed that as AP increases the particles became more agglomerated and smoother. The energy band gap (E g) was affected by the increase in AP. Ultraviolet-visible (UV–vis) diffuse reflection spectroscopy demonstrated that E g can be tuned between 5.56 and 5.71 eV. The photoluminescence (PL) emission spectrum upon excitation of 403 nm displayed ten emission peaks located at around (559, 564 and 576), (601 and 608), (643, 648, 653 and 662) and 708 nm. These emission peaks can be ascribed to the 4G 5/2 → 6H 5/2 , 4G 5/2 → 6H 7/2 , 4G 5/2 →6H 9/2 and 4G 5/2 →6H 11/2 transitions of Sm3+ ion, respectively. It further showed that the optimum luminescence intensity occurred for AP = 7 h. The Commission Internationale de l'Eclairage (CIE) analysis revealed that AP has tuned the emission colour from greenish to orange-red. The results indicate that the prepared nanopowders can potentially be used in the orange/red emitting phosphors. [ABSTRACT FROM AUTHOR] more...

This paper reports on the effects of varying the Cu2+ doping concentration on the structure, morphology and optical properties of the BaAl 2 O 4 phosphor. BaAl 2 O 4 :x% Cu2+ (0 ≤ x ≤ 1) series were successfully synthesized via citrate sol-gel method. The X-ray diffraction (XRD) results revealed that the prepared phosphor sample consist of a single phase hexagonal structure. The presence of Ba, Al, O and Cu were confirmed by the energy dispersive X-ray spectroscopy (EDS). Scanning electron microscope (SEM) revealed that the morphology of the prepared samples highly depends on the Cu2+ concentration. Transmission electron microscopy (TEM) results revealed the hollow tubular and nano-nature of the crystallite sizes. When the un-doped sample was excited at 283 nm, the photoluminescence (PL) results revealed six emission peaks located at 420, 435, 457, 521, 612 and 722 nm, which were attributed to the intrinsic intra band gap defects within the BaAl 2 O 4 (host). The emission at 425 nm observed for the BaAl 2 O 4 :Cu2+ samples was attributed to the 3d84s1 → 3d9 transition in Cu2+ ion. The optimum doping Cu2+ concentration was found to be 0.075% Cu2+. Critical energy transfer distance (R c) of Cu2+ ions was found to be 12.01 Å, which suggested that the multipole-multipole interaction was the main reason for the luminescence quenching. The International Commission on Illumination (CIE) colour showed that the bluish emission colour of the prepared samples depends on the excitation wavelength and Cu2+ concentration. Thermo stimulated luminescence (TSL) of the host material showed the presence of both the swallow and deep traps respectively located at 75 and 240 °C. • Hexagonal nanocrystalline BaAl 2 O 4 :x% Cu2+ (0 ≤ x ≤ 1) phosphor powders were succesfully prepared via the citrate sol-gel technique. • Photoluminescence emission intensity of the powder sample was dependent on the Cu2+ concentration. • Both emissions from the host and Cu2+ were observed. • The Commission on Illumination color coordinate evidently showed that the bluish emission depends on the Cu2+ concentration. • Themoluminescence results showed the precence of both the shallow and deep level tranps in BaAl 2 O 4 : Cu2+ phosphor material. [ABSTRACT FROM AUTHOR] more...

A series of SiO 2 (host), SiO 2 :0.4 mol% Sr2+ singly doped and SiO 2 :0.4 mol% Sr2+: x mol% Tb3+ co-doped (where x = 0.04, 0.08, 0.1, 0.4 and 0.5) phosphors was successfully prepared using the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), ultraviolet–visible (UV–vis) spectroscopy and photoluminescence (PL) were used to determine the structural, morphological and optical properties of the samples. The XRD results showed that all of the samples were amorphous, while EDS confirmed the presence of the expected elements. PL results confirmed energy transfer from the SiO 2 (host) to Tb3+. The highest emission intensity was observed for the co-doped sample containing 0.4 mol% Tb3+. The CIE coordinates showed that the emission colour of the samples could be tuned from blue to green by varying the Tb3+ concentration. [ABSTRACT FROM AUTHOR] more...