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Two-dimensional (2D) luminescent materials have received tremendous attention for their intrinsic properties and promising practical applications. Achieving 2D luminescent materials with high photoluminescence (PL) efficiency is still a great challenge. Here, ultrathin metal-free 2D luminescent nanosheets of 2,5,8-triamino-tri- s -triazine (melem) are synthesized through a facile liquid exfoliation process assisted by ultrasound. The as-obtained melem nanosheets distribute in the size range from a few nanometers to around 150 nm with a thickness of about 5 to 6 atomic layers. Melem nanosheets exhibit efficient blue emission with a PL efficiency as high as 77.09%, much higher than the heavily explored 2D luminescent g-C 3 N 4 nanosheets. The high efficiency of melem nanosheets comes from the absence of atom vacancies and the low carrier mobility. Benefiting from the easy synthesis, good stability, low cell toxicity, and high efficiency, melem nanosheets are successfully applied as bioimaging materials on human breast cancer cells, requiring no extra treatments such as surface coating or functionalization. These metal-free 2D luminescent melem nanosheets hold great potential for various applications including bioimaging and other biorelated applications.

Yb3+ doped lead‐free double perovskites (DPs) with near‐infrared (NIR)‐emitting have attracted extensive attention due to their wide application prospects. Unfortunately, they still suffer from weak NIR emission due to undesirable resonance energy transfer between the sensitizers and Yb3+ ions. Herein, a new effective NIR‐emitting DP is developed by co‐doping Sb3+ and Yb3+ into Cs2AgInCl6. Experiments and theoretical calculations reveal that induced by co‐doping Sb3+ ions, the self‐trapped excitation (STE) emission intensity of Cs2AgInCl6 is greatly enhanced by 240 times, and the STE emission shifts from 600 nm to 660 nm, which contributes to a larger spectral overlap between STE emission and the absorption of Yb3+ ions. As a result, the absolute NIR photoluminescence quantum yield reaches an unprecedented 50% in lead‐free DPs via high‐efficiency STE sensitization (>30%). The excellent optical performance of Cs2AgInCl6: Sb, Yb with high ambient, thermal and light stability makes it suitable for application in night‐vision devices. Moreover, an ingenious dual‐modal optical information encryption based on the combination of visible and NIR fluorescence printing patterns utilizing Cs2AgInCl6: Sb and Cs2AgInCl6: Sb, Yb respectively is successfully demonstrated. This study provides inspiration for designing highly efficient NIR‐emitting Ln3+‐doped DPs and illustrates their great potential in versatile optoelectronic applications. [ABSTRACT FROM AUTHOR]

Reticulated copolymer host pillar[5]arene cross-linked with poly(dimethylsiloxane) (PDMS) was synthesized for the facile construction of a double network cross-linked elastomer upon noncovalently cross-linking with tetraphenyethylene (TPE)-based tetratopic guests through host–guest interactions. The obtained sample strips had better mechanical properties and luminescence capabilities. [ABSTRACT FROM AUTHOR]

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The applications of afterglow particles for photodynamic activation and biological imaging have become a topical research area. For these applications, it is critical to have water soluble nanoparticles. However, the synthesis of water soluble afterglow nanoparticles like Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ is a challenging issue because most afterglow materials are very complicated in composition that cannot be synthesized by simple chemical routes. Here, for the first time, Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ water soluble and stable nanoparticles are synthesize using a modified Sol-Gel method followed by the grinding and coating with APTES. The surface coating of the afterglow with APTES and the conjugation with PpIX and folic acid not only improve their water solubility but also enhance the PpIX luminescence by 10 times. More importantly, these strategies make it possible to produce singlet oxygen under X-ray irradiation, which is a very important result for deep cancer treatment. In addition, the surface coating and conjugation largely increase the cell uptake and greatly reduce their dark cytotoxicity. All these results indicate the methods reported here for afterglow nanoparticle synthesis, coating and conjugation are successful, and consequently, the prepared Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ /PPIX/Folic acid nano-conjugates are promising for X-ray induced photodynamic therapy on cancer treatment. [ABSTRACT FROM AUTHOR]

White light phosphors have many potential applications such as solid-state lighting, full color displays, light source for plant growth, and crop improvement. However, most of these phosphors are rare-earth-based materials which are costly and would be facing the challenge of resource issue due to the extremely low abundance of these elements on earth. A new white color composite consisted of a graphitic-phase nitrogen carbon (g-C3N4) treated with nitric acid and copper-cysteamine Cu3Cl(SR)2 is reported herein. Under a single wavelength excitation at 365 nm, these two materials show a strong blue and red luminescence, respectively. It is interesting to find that the white light emission with a quantum yield of 20% can be obtained by mixing these two self-activated luminescent materials at the weight ratio of 1:1.67. Using a 365 nm near-ultraviolet chip for excitation, the composite produces a white light-emitting diode that exhibits an excellent color rendering index of 94.3. These white-emitting materials are environment friendly, easy to synthesize, and cost-effective. More importantly, this will potentially eliminate the challenge of rare earth resources. Furthermore, a single chip is used for excitation instead of a multichip, which can greatly reduce the cost of the devices. [ABSTRACT FROM AUTHOR]

Undoped ZnO, Ce-doped ZnO, and (Li, Ce)-codoped ZnO nanophosphors were prepared by a sol-gel process. The effects of the additional doping with Li ions on the crystal structure, particle morphology, and luminescence properties of Ce-doped ZnO were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy and photoluminescence spectroscopy. The results indicate that the obtained samples are single phase, and a nanorod shaped morphology is observed for (Li, Ce)-codoping. Under excitation with 325 nm light, Ce-doped ZnO phosphors show an ultraviolet emission, a green emission, and a blue emission caused by Zn interstitials. The spectrum of the sample codoped with a proper Li concentration features two additional emissions that can be attributed to the Ce ions. With the increase of the Li doping concentration, the Ce blue luminescence of (Li, Ce)-codoped ZnO is obviously enhanced, which results not only from the increase of the Ce ion concentration itself but also from the energy transfer from the ZnO host material to the Ce ions. This enhancement reaches a maximum at a Li content of 0.02, and then decreases sharply due to the concentration quench. These nanophosphors may promise for application to the visible-light-emitting devices. PACS: 78.55.Et; 81.07.Wx; 81.20.Fw [ABSTRACT FROM AUTHOR]

Abstract: ZnO:Zn films with strong adhesion to the substrate were obtained by evaporating ZnO powders in the mixture of N2 and H2. The ZnO:Zn films produced in the reductive gas showed bright green photoluminescence and n-type conductivity. After the ZnO:Zn films were re-fired in the air, the conductivity and luminescent intensity decrease to less than 1% and about 50% of the initial values, respectively. For the two different types of samples obtained in the reductive gas and in the air, respectively, their point defects showed notable difference as indicated by the measurements of electron spin resonance and X-ray photoelectron spectroscopies. The native defects account for the green-emission while the n-type conductivity is perhaps associated with the hydrogen doping. [Copyright &y& Elsevier]

Abstract: ZnO:Eu3+, Li+ films prepared by the dip-coating method were characterized by photoluminescence (PL) and electroluminescence (EL). When the ZnO:Eu3+, Li+ films were excited using UV light with energy corresponding to the band-to-band excitation of the host matrix, the PL spectra showed emissions from both ZnO and Eu3+ ions, while their EL spectra showed emissions only from Eu3+ ions, and no emission from ZnO could be detected. It is found that the EL emission intensity B is dependent on the applied voltage, B=B o exp(−bV −1/2). With increasing frequency, the EL intensity dramatically increases at lower frequencies (<1000Hz), and then increases gradually at higher frequencies (>1000Hz). [Copyright &y& Elsevier]

Abstract: Europium-doped nanosized zinc gallate phosphors with the nominal formula of ZnGa2−x O4:xEu were synthesized by citrate sol–gel method, and the crystal structure and luminescent properties were investigated by means of X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersive spectrometer (EDS) and photoluminescence (PL). The results indicate that the material consisting of ZnGa2O4:Eu3+ particles exhibits good crystallinity and the particle size varies with the calcining temperature. Changes of peak position and intensity of the excited charge transfer band were observed as the doping concentration and calcining temperature varied. The optimal molar concentration for obtaining the highest photoluminescent intensity for ZnGa2−x O4:xEu phosphors was 6at% (calcined at 1000°C for 5h). [Copyright &y& Elsevier]

Abstract: ZnO sol was prepared and ZnO monolayer film and nanosized ZnO/polyaniline (PAN) multylayer films were coated on polished Al foil using the layer-by-layer self-assembly method. UV–vis absorbance, reflection and photoluminescence spectroscopy were obtained to investigate the luminescent properties of the samples. The ZnO sol has a single excitation peak in the UV (ultraviolet) region and a single emission peak in the green region. The excitation spectra of ZnO monolayer film and ZnO/PAN multylayer films show a continuous wide band without evident peak, and the emission spectra consist of three parts with peaks in UV, blue and green region, respectively. [Copyright &y& Elsevier]

Long afterglow phosphor Y2O2S:Gd,Eu,Ti,Mg was synthesized by a gas absorption method and the effect of Ti4+ and Mg2+ ions doping on the luminescent properties was also investigated. Single phase Y2O2S can be obtained by calcining the oxide mixture in a graphite crucible absorbed with sulfur. Ti4+ and Mg2+ ions decrease the luminescent intensity of the phosphor, but either Ti4+ or Mg2+ ion doping results in red long afterglow. A strong thermoluminescence peak appears when codoping Ti4+ and Mg2+ ions in the phosphor. [Copyright &y& Elsevier]

A new phosphor Ca12Al14O33:Nd,Eu was synthesized by a traditional solid-state reaction method and the luminescent properties were investigated. The phosphors are well crystallized by calcination at 1200 °C. The excitation and the emission spectra show the characteristic broadband of the Eu2+ ion and the emission light is indigo. Doping Nd3+ ion in the phosphor results in indigo long afterglow phosphorescence (the time for the phosphorescence intensity to decrease to 10% of its initial value is about 50 s) when the excitation light is cut off. The emission intensity decreases with the increase of Nd3+ ion concentration. Whereas, the phosphorescence intensity and afterglow time improve when the concentration of Nd3+ ion increases. [Copyright &y& Elsevier]

Metal nitrate aqueous solution was mixed with citric acid to synthesize the red emission nanometer Y2O3:Eu phosphor by simple sol–gel processing. Structure characterization of the phosphor was carried out by XRD and TEM. The samples are mostly amorphous when the dry gel is calcined below 500 °C and crystallize completely at 600 °C, and the crystallity increases with increasing calcining temperature. The mean particle size increases from about 10 to 50 nm when the calcining temperature increases from 600 to 900 °C, while that calcined at 1250 °C is about 100 nm. The luminescence property of the phosphor was analyzed by measuring the excitation and emission spectra. The luminescence intensity increases when the calcining temperature increases and luminescence intensity is higher than that prepared by solid-state reaction method when the concentration of Eu3+ and the calcining temperature are the same. [Copyright &y& Elsevier]

Abstract: In this paper, ZnO sol and nanosized film were prepared at low temperature, and effect of Tb3+ doping on the luminescent properties was investigated. ZnO sol and film show yellow emission with peak at about 533nm under excitation of UV light. If Tb3+ is doped in ZnO sol and film, energy transfer from ZnO to Tb3+ ion takes place, and the emission of Tb3+ can be obviously detected. Energy diagram was schematically drawn to illustrate the luminescent mechanism of ZnO:Tb. [Copyright &y& Elsevier]

Abstract: Zn1−x Mg x O pellets were synthesized using traditional solid-reaction method and luminescent properties were investigated. ZnO doped with MgO reveals long afterglow emission that can last for more than 10min after the samples were sintered in sealed crucible above a certain temperature. The emission spectra of Zn1−x Mg x O (0< x <1) can be Gaussian fit to two peaks, and the relative intensity of the two emission peaks alters with increasing the sintering temperature. The position of the two emission peaks shows slight red shift when the sintering temperature increases from 1100 to 1250°C and remains unchanged even though the sintering temperature is further increased. The emission peak in the green region is similar with the single emission band of ZnO, while that in the orange region is related to the long-lasting phosphorescence. [Copyright &y& Elsevier]

Abstract: Based on the matrix of alkali-earth-aluminate, the luminous gem is artificially manufactured, doped with Eu2+ as activator and Dy3+ as hole trap. The morphology and crystal structure of the luminous gem are analyzed by scan electron microscopy (SEM) and X-ray diffraction (XRD). The excitation and emission spectra of the gem are broad band, and the main emission band is around 514nm. The decay times of the artificial luminous gem and the long afterglow phosphor are measured. The results indicate that the artificial luminous gem has high initial luminescent brightness and slow decay process. The gem could glow continuously for over 25h in the darkness after absorbs natural light. They have high degree of hardness and no radioactivity just like “night shinning jewel”. This product can have great potential applications in jewelry industry. [Copyright &y& Elsevier]

For the first time, X-ray excited luminescence of Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ , an efficient persistent phosphor with good potential for lighting, biological imaging and photodynamic activation, is reported in this paper. A modified Sol-Gel method is used to synthesize Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ phosphors and their luminescence properties are highly associated with the synthesis conditions. The dependences of the X-ray excited optical luminescence and persistent luminescence of Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ on the reaction pH, temperature, ratio of Eu/Dy, and the calcination duration time are investigated and the association of the luminescence behaviors with the synthesis conditions is explored as a good strategy to optimize the phosphors for practical applications. [ABSTRACT FROM AUTHOR]

Herein, enhanced red emission (670 nm) of Mg 0.1 Zn 0.9 O phosphors was obtained through the localized surface plasmon (LSP) resonance of Ag nanoparticles following an enhancement in the local electric field, as demonstrated through experimental and theoretical studies. Interestingly, with an increase in the Ag doping amount (x), the intensity of the red emission increased, reaching a maximum at x = 0.1%, followed by a decrease due to plasmon reabsorption and a reduction in the degree of overlap between the excitation peak of Ag-Mg 0.1 Zn 0.9 O and the LSP resonance absorption peak of Ag nanoparticles. Additionally, an enhanced white fluorescence was observed from Ag-Mg 0.1 Zn 0.9 O phosphors prepared via a two-stage annealing process. These findings will be useful in the development of display devices with a high emission efficiency. [ABSTRACT FROM AUTHOR]

La 0.2 Y 1.8 O 3 is a new and promising scintillator which is based on the host material without doping. Here the time gated X-ray excited optical luminescence is measured by using the excitation energy below, above and at the La L 3 -edge. A relatively slow and broad emission with peak at 415 nm has been observed as the dominant emission. Also, a weak emission at 360 nm is observed at the fast window, associated with the recombination of trapped excitons in Y 2 O 3 host. The observations show that the broad emission at 415 nm is most likely due to the recombination of trapped excitons associated with the La 3+ doping into Y 2 O 3 sites. [ABSTRACT FROM AUTHOR]

The red long persistent phosphor (LPP) β-Zn3(PO4)2: Mn2+,Dy3+ is precipitated by addition of NH4OH to an aqueous or HNO3 solution of ZnO, MnCO3, (NH4)2HPO4, and Dy2O3 followed by sintering in a thermal-carbon reducing atmosphere (corundum crucible, 1223 K, 3 h). [ABSTRACT FROM AUTHOR]

Abstract: A simple and low-cost approach is presented to tune the visible emission of Mg-doped ZnO phosphors obtained in a two-stage annealing process. The products of this process were characterized via X-ray diffraction, scanning electron microscopy and fluorescence measurements. The results indicate that the second annealing time has a significant influence on the particle size and structure of the samples, and the visible emission of Mg-doped ZnO phosphors is tunable in a wide range from blue to red by changing the second annealing time. The defect emission of phosphors exhibiting strong dependence on annealing time suggests that visible emission would be more consistent with intrinsic defects than extrinsic defects. White emission was obtained for the phosphors annealed in a carbon monoxide reducing atmosphere for 30, 60, 180 and 300min. The Commission International de l’Eclairage chromaticity of the 60-min annealed sample was determined to be (x =0.27, y =0.34), and T c was observed to be 8929K. [Copyright &y& Elsevier]

Abstract: Chromium-doped zinc gallate powder is synthesized via a solid-state reaction and subsequently deposited as a thin film on quartz substrates by using a pulsed laser deposition technique under two different deposition conditions. The films are characterized with X-ray diffraction, scanning electron microscopy, UV–vis spectrophotometry and luminescent measurements. As the oxygen pressure is changed from 0 to 1Pa, we find that the grain size gets smaller, the crystallinity improves, the band-gap energy increases, the excitation peaks of the charge transfer band exhibit a remarkable blue-shift from 263 to 247nm and the intensity of the red emission (694nm) is enhanced. The results suggest that the structural and luminescent properties of ZnGa2O4:Cr3+ thin film phosphors are improved by deposition at an oxygen pressure of 1Pa. [Copyright &y& Elsevier]

Mg-doped ZnO phosphors are obtained from a previously described precursor gel by annealing in air at 850 °C for 3 h followed by a second annealing step in a CO reducing atmosphere at 850 °C for different times (10, 30, 60, 180, and 399 min). [ABSTRACT FROM AUTHOR]