Red Long-lasting Phosphorescence Research Articles

Red long lasting phosphorescence of Eu3+ doped BiOCl semiconducting polycrystals

AbstractThe exploration of novel long lasting red phosphors is still of importance due to expected commercial applications and scientific interests. In this work, we reported the red long lasting phosphorescence (LLP) from Eu3+ doped BiOCl semiconductor polycrystals. The LLP property of the red phosphor is relatively weak due to less trap density, but the excitation band of LLP stems from the energy gap transition of semiconductor, offering experimental evidence for energy transfer between BiOCl semiconductor and Eu3+ ions. Although the afterglow duration of Eu3+ doped BiOCl was short temporarily, this work may open a novel kind of red LLP phosphors.

Red long lasting phosphorescence in Ca2Ge7O16:Sm3+ via persistent energy transfer from the host to Sm3+

A red long-lasting phosphorescence phosphor Ca2Ge7O16:Sm3+ was synthesized by a high temperature solid state reaction. The persistent energy transfer process from Ca2Ge7O16 host to Sm3+ was confirmed to be much more efficient than that in the photoluminescence process. The color of the persistent luminescence could be adjusted from blue to red with increasing concentration of Sm3+ accordingly. Based on the analysis of the thermoluminescence curves, it was found that Sm3+ doped Ca2Ge7O16 also provided a possibility to be a kind of photo-storage phosphor. Detailed mechanism were studied and illustrated.

Influence of sulfuretted temperature on the luminescent properties of Y2O2S:Eu3+, Mg2+, Ti4+ nanoarrays by EDTA complexing sol–gel template method

Y2O3:Eu3+, Mg2+, Ti4+ nanotube arrays were prepared by sol–gel template method using EDTA (Ethylene Diamine Tetraacetic Acid) as complexing agent to serve as precursor. Long-lasting phosphors Y2O2S:Eu3+, Mg2+, Ti4+ nanotube arrays were obtained by calcinating the precursor in the CS2 atmosphere. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and photoluminescence spectroscopy were used to investigate the effects of sulfuretted temperature on the crystal characteristics, morphology and luminescent properties of Y2O2S:Eu3+, Mg2+, Ti4+ nanoarrays. The results of XRD and EDS reveal that the main phase of sample is Y2O2S when the sulfuretted temperature is 700–850 °C, and the ratio of element Y and S of the sample is very close to 2:1. The SEM observations show that the obtained Y2O2S:Eu3+, Mg2+, Ti4+ nanotube arrays are of uniform size. From the spectrum, the main emission peak lies at 626nm under the 320nm excitation, which is ascribed to the transition of Eu3+ ion from 5D0 to 7F2. After irradiation with 365nm UV (Ultraviolet) radiation for 10min, the phosphor emitted red long-lasting phosphorescence which could last for about 17min (⩾1 mcd/m2).

Synthesis and characterization of Y2O2S:Eu3+, Mg2+, Ti4+ nanotubes via hydrothermal method

We reported an effective method to synthesize Y2O2S:Eu3+, Mg2+, Ti4+ nanotubes. The Y(OH)3 doped with Eu3+, Mg2+ and Ti4+ ions by hydrothermal method serves as the precursor. The red long-lasting phosphor Y2O2S:Eu3+, Mg2+, Ti4+ nanotubes were obtained by means of calcinating the precursor in CS2 atmosphere. The samples were examined using X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) and illuminometer. The results of XRD revealed that the phase of sample was Y2O2S when the sulfuretted temperature reached 750°C. SEM observations showed that the phosphors with diameters of 200–400nm and lengths of 2–3μm inherited the tube-like shape from the precursor after calcination in CS2 atmosphere. Under 325nm UV excitation, the samples exhibited the strongest red emission at 625nm, which corresponded to transition from 5D0 to 7F2 level of Eu3+ ion. After irradiation with 365nm UV (Ultraviolet) radiation for 10min, the nanotubes emitted red long-lasting phosphorescence which could last for about 870s (≥1mcd/m2). And the red-emitting long-lasting phosphorescence was attributed to the persistent energy transfer from the traps to the Ti4+ and Mg2+ ions.

Influence on Red Long-Lasting Phosphorescence due to Different Doping Concentrations of ZnGa<sub>2</sub>O<sub>4</sub>:Cr<sup>3+</sup>

High temperature solid state reaction has been used to prepare the new red long-lasting phosphorescence (LLP) material ZnGa2O4:Cr3+ with different doping concentration. The afterglow properties of the samples have been investigated. Our study has shown that ZnGa2O4 samples without Cr3+ doping have blue-green afterglow. While the blue-green afterglow has disappeared and the red long-lasting phosphorescence according to the Cr3+ luminescence center covering 650 nm-750 nm has been observed when Cr3+ has been doped. In terms of brightness and decay time of the afterglow, the red afterglow and the blue-green afterglow have been entirely different. In this article the influence on LLP due to different doping concentrations of ZnGa2O4:Cr3+ has been discussed and the possible LLP mechanism has been proposed.

Long-lasting phosphorescence functionalization of mesoporous silica nanospheres by CaTiO3:Pr3+ for drug delivery

Long-lasting phosphorescence functionalization of the ordered mesoporous silica nanospheres (MSNs) was realized by depositing a CaTiO3:Pr3+ phosphor layer on its surface via the Pechini sol–gel process, resulting in the formation of the MSNs@CaTiO3:Pr3+ composite material. This material, which combines the mesoporous structure of MSNs and the red long-lasting phosphorescence property of CaTiO3:Pr3+, can be used as a novel functional drug delivery system. The results indicate that a CaTiO3:Pr3+ layer can be synthesized when the annealing temperature reaches 600°C and impurity phases start to appear when the annealing temperature reaches 800°C or higher. The specific surface area of MSNs@CaTiO3:Pr3+ decreases along with the increase of annealing temperature. The MSNs@CaTiO3:Pr3+ sample synthesized at 700°C has appropriate phosphorescence intensity and enough specific surface area (306m2/g) to load drug molecules. The as-synthesized MSNs@CaTiO3:Pr3+ composite material can be tracked in vivo by optical imaging in 12min after peritoneal injection. The quercetin-loaded MSNs@CaTiO3:Pr3+ system still shows the red phosphorescence of Pr3+ (614nm) after UV irradiation and possesses sustained drug release property. In addition, the phosphorescence intensity of Pr3+ increases with an increase in the cumulative released amount of quercetin in the system, making the extent of drug release easily identifiable, trackable, and monitorable by the change of phosphorescence. Our research supplies a new way to fabricate in vivo visible drug delivery system.

Influence of sulfuretted temperature on the luminescent properties of Y2O2S:Eu3+, Mg2+, Ti4+ nanoarrays

Y2O3:Eu3+, Mg2+, Ti4+ nanotube arrays were firstly prepared via sol–gel template method to serve as precursor. Long-lasting phosphors Y2O2S:Eu3+, Mg2+, Ti4+ nanotube arrays were obtained by calcinating the precursor in the CS2 atmosphere. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and photoluminescence spectroscopy were used to investigate the effects of sulfuretted temperature on the crystal characteristics, morphology and luminescent properties of Y2O2S:Eu3+, Mg2+, Ti4+ nanoarrays. The results of XRD and EDS reveal that the main phase of sample is Y2O2S when the sulfuretted temperature rises to 850°C, and the ratio of element Y and S of the sample is very close to 2:1. The SEM observations show that the obtained Y2O2S:Eu3+, Mg2+, Ti4+ nanotube arrays are of uniform size. From the spectrum, the main emission peak lies at 626nm under the 320nm excitation, which is ascribed to the transition of Eu3+ ion from 5D0 to 7F2. After irradiation with 365nm UV (Ultraviolet) radiation for 10min, the phosphor emitted red long-lasting phosphorescence which could last for about 3min (≥1mcd/m2).

Role of manganese in red long-lasting phosphorescence of manganese-doped diopside for in vivo imaging

Materials with red long-lasting phosphorescence, such as MnII-doped diopsides, can be used for small animal in vivo imaging. CaMgSi2O6:Mn powders with various amounts of Mn were prepared by sol–gel to investigate their long-lasting phosphorescence mechanism. X-ray diffraction, X-ray absorption fine and near-edge structure and electron paramagnetic resonance showed that manganese is quantitatively introduced in the structure as MnII. Most of the Mn doping ions substitute Mg and possess a highly elongated octahedral environment. While photoluminescence and X-ray excited optical luminescence spectra show both orange (585nm) and red (685nm) 4T1 (4G)→6A1 (6S) emission of MnIICa and MnIIMg, respectively, MnIIMg red emission dominates long-lasting phosphorescence and thermally stimulated luminescence spectra. These results point to MnIIMg as the preferential hole trap and recombination center in the long-lasting phosphorescence mechanism. An intense persistent red emission suitable for in vivo imaging probes is obtained for the highest nominal Mn content (7.5%).

A Red Long-Lasting Phosphorescence Material Gd9.33(SiO4)6O2:Sm3+ and Effect of Oxygen Vacancies on Its Performance

A novel red long-lasting phosphorescence material Gd9.33(SiO4)6O2:Sm3+ was reported in this paper. There are two kinds of Gd sites occupied by Sm3+ ions in this host matrix, Gd1 (CN = 9) and Gd2 (CN = 7). The Gd2 site is surrounded by six oxygen atoms bonded to silicon and one free oxygen atom which may be missed easily and then become an oxygen vacancy. A significant sequential enhancement on the afterglow performance of the air-sintered, the vacuum-sintered and the reduction-sintered samples was observed. This improvement could be attributed to the increase of oxygen vacancies acting as sensitizer and electron traps for afterglow, which was investigated with thermoluminescence. It is established that, the traps arising from oxygen defects (oxygen vacancies mostly) are responsible for the afterglow phenomenon of the Gd9.33(SiO4)6O2:Sm3+ phosphor.

Luminescence Properties of Red Long-Lasting Phosphorescence Phosphor AlN:Mn2+

The luminescence properties of red long-lasting phosphorescence phosphor AlN:Mn2+ were reported. Studies show that AlN:Mn2+ phosphors exhibit red emission band in a wavelength range of 570–700 nm centered at ca. 600 nm and FWHM of 43 nm. The concentration quenching of Mn2+ in AlN phosphor is 2.5 mol%. After irradiation under the 254 nm UV light, the afterglow emission of Mn2+ (4T1g(G)-6A1g(S)) can be obviously observed for at least 1 h in the limit of light perception of dark-adapted human eyes (0.32 mcd/m2). Possible mechanism for the afterglow of AlN:Mn2+ phosphor is explained. All the results indicate that the Mn2+-doped AlN phosphor has promising potential of practical applications as a new red-light-emitting afterglow material.

Red long-lasting phosphorescence based on color conversion process

The principle of color conversion process was used to generate red long-lasting phosphorescence (LLP) using SrAl2O4:Eu, Dy (SAO) as primary light source and rhodamine B encapsulated mesoporous silica nanoparticles (MCM-R) as effective color conversion agent. The phosphorescence spectra of MCM-R/SAO hybrid samples show green peaks from 425nm to 550nm and red peaks from 550nm to 700nm, which can be attributed to the phosphorescence of SAO and the fluorescence of MCM-R, respectively. The phosphorescence color can be adjusted from green to red by changing the mass ratio of MCM-R/SAO. When the mass ratio of MCM-R/SAO increases from 0.05 to 1.5, a blue shift for the green peak and a red shift for the red peak of the phosphorescence spectra can be observed and the intensity of the red emission peak increase relatively towards the green one. The phosphorescence decay curves show that MCM-R and SAO have similar decay dynamics and the MCM-R can inherit the LLP properties of SAO. The phosphorescence decay spectra indicate that the MCM-R/SAO hybrid can retain constant and steady visual phosphorescence color. The red phosphorescence can be seen in the dark with naked eyes for more than 5h. So, the red LLP can be successfully achieved based on the principle of color conversion process.

Role of crystal defects in red long-lasting phosphorescence of CaMgSi2O6:Mn diopsides

CaMgSi2O6:Mn diopsides are used for in vivo long-lasting phosphorescence (LLP) imaging. Trapping defects involved in the LLP mechanism were investigated. On annealing Mn-doped diopsides at 1100 °C in an Ar–H2 atmosphere, Ca EXAFS/XANES and electron paramagnetic resonance (EPR) evidenced paramagnetic oxygen vacancies while X-ray diffraction, Mn XANES and EPR revealed SiO2 formation and significant evaporation of the Mn dopant. A thermally stimulated luminescence (TSL) peak at 475 K ascribed to electron trapping at oxygen vacancies was found responsible for LLP at RT. Most intense red LLP suitable for in vivo imaging was achieved by a trade-off between a high MnII content (favourable to MnIIMg red over MnIICa orange luminescence) and the formation of oxygen vacancies favourable to LLP and luminescence light yield. Mn XANES revealed an effective charge larger than 2+ for MnII, in line with the role of hole trap in the LLP mechanism. Compounds annealed at lower temperatures (800 °C and 900 °C) in Ar–H2 showed smaller particle size (60–70 nm) and maximum Mn content but poor luminescence and LLP due to surface quenching defects.

Synthesis of a New Red Long Persistent Phosphor Sr2ZnSi2O7: Eu3+, Lu3+ via Sol–Gel Method and Investigation of its Luminescence

A novel red long persistent phosphor of Sr2ZnSi2O7: Eu3+, Lu3+ was successfully synthesized with sol–gel method. Its properties were systematically characterized by X-ray diffraction(XRD), luminescence, afterglow decay curves and thermoluminescence (TL) spectra. The red phosphor showed one emission peak at 616.9nm, which is attributed to the typical 5D0–7F2 transition of Eu3+ ions as luminescent centers in Sr2ZnSi2O7 host. Lu3+ as a sensitized ion played an important role in enhancing the long afterglow performance of Sr2ZnSi2O7: Eu3+, Lu3+. Under UV light irradiation, this phosphor showed obvious red long-lasting phosphorescence that can be clearly seen with naked eyes in a dark room for over 20s after the irradiation source has been removed. Thermoluminescence (TL) measurement showed that Lu3+ co-dopan can reduce the trap depth of the title phosphor to obtain suitable ones.

Red long-lasting phosphorescence (LLP) in β-TCP type Ca 9.5Mn(PO 4) 7 compounds

Mn-ion doped calcium phosphates namely Ca 5(PO 4) 3(OH) hydroxyapatite (HAP), β-Ca 3(PO 4) 2 (β-TCP) as well as Ca 9.5Mn(PO 4) 7 whitlockite were synthesized and the optical properties of the Mn 2+ cations were investigated. Annealing under reducing atmosphere enhances the emission of the divalent manganese species. Electron paramagnetic resonance (EPR) and optical spectroscopies confirm that Mn 2+ ions are the active species. Orange and red emissions occur respectively for the Mn:HAP and Mn:TCP. For this latter, long-lasting phosphorescence (LLP) coming from the Mn 2+ emission ( 4T 1 → 6A 1 transition) is observed at 640 nm but it appears that the traps depths are either two shallow or too deep to lead to an efficient long-lasting emission.

Synthesis and characterization of Y 2O 2S:Eu 3+, Mg 2+, Ti 4+ nanorods via a solvothermal routine

Y 2O 2S:Eu 3+, Mg 2+, Ti 4+ nanorods were prepared by a solvothermal procedure. Rod-like Y(OH) 3 was firstly synthesized by hydrothermal method to serve as the precursor. Y 2O 2S:Eu 3+, Mg 2+, Ti 4+ powders were obtained by calcinating the precursor at CS 2 atmosphere. The Y 2O 2S:Eu 3+, Mg 2+, Ti 4+ phosphor with diameters of 30–50 nm and lengths up to 200–400 nm inherited the rod-like shape from the precursor after calcined at CS 2 atmosphere. The Y 2O 2S:Eu 3+, Mg 2+, Ti 4+ nanorods showed hexagonal pure phase, good dispersion and exhibited bright red luminescence. After irradiation by 265 or 325 nm for 5 min, the phosphor emitted red long-lasting phosphorescence, and the phosphorescence could be seen with the naked eyes in the dark clearly for more than 1 h after the irradiation source was removed. It was considered that the long-lasting phosphorescence was due to the persistent energy transfer from the traps to the Ti 4+ and Mg 2+ ions to generate the red-emitting long-lasting phosphorescence.

Luminescence properties of a new Mn 2+-activated red long-afterglow phosphor

A new phosphor, CaZnGe 2O 6:Mn 2+, which emits red long-lasting phosphorescence centered at 648 nm upon UV light excitation, is prepared by the conventional high-temperature solid-state method and its luminescent properties are systematically investigated in this paper. XRD, photoluminescence, thermoluminescence spectra and afterglow decay curve are used to characterize the synthesized phosphor. This phosphor is well crystallized by calcination at 1150 °C for 3 h and possesses excellent performance. The color coordinate values of this phosphor are x=0.64, y=0.26 under 250 nm UV light excitation. Under 250-nm UV light irradiation, this phosphor shows obvious long-lasting phosphorescence that can be seen with the naked eye in the dark clearly after the irradiation source has been removed for more than 3 h. The possible mechanism of this red-light-emitting long-afterglow phosphor is also investigated based on the experiment results.

A kinetics model of red long-lasting phosphorescence in MgSiO3:Eu2+, Dy3+, Mn2+

Abstract In this work, a red long-lasting phosphor: MgSiO 3 :Eu 2+ , Dy 3+ , Mn 2+ was prepared by sol–gel method. The XRD pattern of this phosphor is indexed on a proto-enstatite structure (JCPDS No. 11-0273). Its red long-lasting phosphorescence was confirmed and attributed to the Mn 2+ emission. In MgSiO 3 :Eu 2+ , Dy 3+ , Mn 2+ , the functions of co-doped Eu 2+ and Dy 3+ ions are affirmed as sensitizers and trap centers, respectively. Further TL study was taken on the trap centers introduced by Dy 3+ , including fitting of trap depths and frequency factors. Moreover, a long-lasting phosphorescence model of MgSiO 3 :Eu 2+ , Dy 3+ , Mn 2+ was suggested.

One-dimensional hollow SrS nanostructure with red long-lasting phosphorescence

A novel one-dimensional (1D) hollow nanostructure of SrS:Eu 2+, Dy 3+ with red long lasting phosphorescence was successfully fabricated by a soft template method followed by annealing treatment at 900 °C. The 1D nanostructures are 60–100 nm in diameter and several hundreds nanometers in length. The TEM image indicates that the 1D nanostructure could be considered to be assembled in lines by lots of nano-hollow spheres. The properties of photoluminescence and afterglow of the 1D nanostructure were also investigated and discussed.

Blue and red long lasting phosphorescence (LLP) in β-Zn 3(PO 4) 2:Mn 2+,Zr 4+

Multi-color long lasting phosphorescent (LLP) phenomenon in β-Zn 3(PO 4) 2:Mn 2+,Zr 4+ was systematically investigated. It is found that the red ( λ Em=616 nm) LLP performance of Mn 2+ such as brightness and duration is largely improved, and that the blue ( λ Em=475 nm) LLP of Zr 4+ with lower intensity appears when Zr 4+ ions are co-doped into the matrix. The fluorescence, phosphorescence and thermoluminescence (TL) spectra show that Mn 2+ ion is solely expected as a luminescent center, while Zr 4+ ion not only acts as a luminescent center, but also induces an electron trap (Trap Zr) associated with a TL peak at 344 K. The trap depth for Trap Zr is 0.25 eV, while that for the intrinsic trap is 0.38 eV, associated with a dominant peak at 385 K for Zn 3(PO 4) 2:Mn 2+. The Zr 4+-induced trap with suitable depth is responsible for the improvement of the red LLP of Mn 2+ ion and the appearance of the blue LLP of Zr 4+ ion. The LLP mechanism is also investigated.

Photostimulated Red Long-lasting Phosphorescence in β-Zn[sub 3](PO[sub 4])[sub 2]:Mn[sup 2+],Ga[sup 3+

Photostimulated red long-lasting phosphorescence in β-Zn3(PO 4 ) 2 :Mn 2 + ,Ga 3 + was observed and investigated by fluorescence, phosphorescence, and thermoluminescence spectra. The present sample emits intense red long-lasting phosphorescence after irradiation by 254 nm UV light. The red long-lasting phosphorescence appears once again after further excitation by 365 nm UV light when the sample is kept in the dark for 24 h, and the 254 nm UV light-induced long-lasting phosphorescence cannot be detected. A mechanism responsible for the photostimulated long-lasting phosphorescence is proposed.