Novel ultra-wideband fluorescence material:Defect state control based on nickel-doped semiconductor QDs embedded in inorganic glasses

In recent years,the development of an environmentally friendly quantum dots(QDs)embedded luminous solid by a simple method has attracted considerable attention.In this study,semiconductor ZnS QDs were successfully prepared in an inorganic matrix of amorphous glass,which yielded beneficial broadband emission in the long-wavelength region of the visible range.The strong red emission belonged to the defect state energy level of the ZnS QDs,which could be enhanced by incorporation of nickel ions into the fixed matrix to regulate the defects state.The novel material had a small self-absorption,wide excitation and emission ranges,and thus potential applications in light-conversion devices,luminescent solar concentrators,and solar cell cover glasses.

Energy transfer and 2 μm emission in Tm^(3+)/Ho^(3+) co-doped(Y_(0.87)La_(0.1)Zr_(0.03))_2O_3 nanopowders

（Y0.87La0.1Zr0.03）2O3 nanopowders doped with various concentrations of Tm^3＋ and Ho^3＋ were prepared by the citrate method. The standard cubic Y2O3 phase can be matched in the Tm^3＋/Ho^3＋ co-doped（Y0.87La0.1Zr0.03）2 O3 nanopowders. The nanopowders exhibit average particle sizes of 40,60, 80 and 100 nm after calcinated at 900,1000,1100 and 1200℃,respectively. The energy transfer from Tm^3＋ to Ho^3＋ and the optimum fluorescence emission around 2 μm were investigated. Results indicate that the emission bands at around 1.86 and 1.95 μm correspond to 3 F4→3 H6 transition of Tm^3＋ and 5 I7→5 I8 transition of Ho^3＋, respectively.Better spectral properties were achieved in Tm^3＋/Ho^3＋ co-doped（Y0.87La0.1Zr0.03）2O3 nanopowders with the average size of 100 nm obtained at the conditions of the treatment of precursors calcinated at 1200 ℃ for 2 h doped with 1.5 mol% Tm^3＋ and 1 mol% Ho^3＋.

Luminescent and thermometric properties of dual emitting Eu^(2+)/Sm^(3+) co-doped Sr_(4)La(PO_(4))_(3)O phosphor based on energy transfer

Eu^(2+)/Sm^(3+)co-doped dual-emitting Sr_(4)La(PO_(4))_(3)O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and temperature-dependent luminescence properties of Eu^(2+)/Sm^(3+)co-doped Sr_(4)La(PO_(4))_(3)O phosphors were researched and analyzed in detail.The blue emission of Eu^(2+)and the red emission of Sm^(3+)can work together as FIR signals.Based on the different response characteristics of these two ion emissions to temperature,Sr_(4)La(PO_(4))_(3)O:Eu^(2+)/Sm^(^(3+))phosphor achieves the relative sensitivity of0.48384%/K and a wide range of temperature measurements from room temperature to 573 K.The results reveal that the Sr_(4)La(PO_(4))_(3)O:Eu^(2+)/Sm^(3+)phosphor has application prospect in the field of high temperature optical thermometry.The energy transfer mechanism is proved to be the dipole-dipole interaction between Eu^(2+)and Sm^(3+)ions.

Emission tunable of Mg_(0.695)Si_(0.695)Al_(1.39)O_(3.65)N_(0.35):Eu^(2+),Mn^(2+) oxynitride phosphors via energy transfer for WLEDs

A series of Eu^(2+)doped and Eu^(2+)/Mn^(2+) co-doped Mg_(0.695)Si_(0.695)Al_(1.39)O_(3.65)N_(0.35)(MSAON) phosphors were synthesized by solid-state reaction at a lower temperature of 1500℃.The crystal morphology and structure of MSAON host were characterized by SEM,TEM and XRD.The quantum yield(QY) for Eu^(2+)doped MSAON phosphors was measured as high as 62%,indicating the excellent luminous efficiency.For the Eu^(2+)/Mn^(2+)co-doped MSAON phosphor,the photoluminescence spectrum and delay curves reveal the efficient energy transfer(ET) process from Eu^(2+)to Mn^(2+)ions.Meanwhile,the corresponding energy transfer efficiency,critical distance and mechanism are discussed in detail.Temperature-dependent emission spectrum shows the thermal and color stabilities.The emission color of MSAON:Eu^(2+),Mn^(2+)phosphors could be tuned from blue through white to red via varying the concentration of Mn^(2+) ions.White-light-emitting diodes(WLEDs) were successfully fabricated by encapsulating the phosphors in nUV LED(365 nm) devices obtaining white light with color rendering index(CRI) as high as 87.7.The results reveal that the MSAON:Eu^(2+),Mn^(2+)phosphors could have potential application in the field of n-UV WLEDs.

An optical thermometer with high sensitivity and superior signal discriminability based on dual-emitting Ce^(3+)/Eu^(2+)co-doped La5Si2BO13 thermochromic phosphor

A novel non-contact optical thermometer,qualified with high sensitivity and temperature resolution,is urgently needed for temperature measuring of micro devices,moving objects and specific severe environments.Hence,a series of dual-emitting La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphors were synthesized.The two ions show diverse responses with the changing in temperature.The variational emissions of Ce^(3+)and Eu^(2+)can be converted to FIR(fluorescence intensity ratio)signals.The maximal absolute sensitivity Sa and relative sensitivity Sr reach up to 0.07526%/K and 3.2241%/K,respectively.It is worthy noting that the Sa and Sr possess the same variation tendency and both have high values in the low temperature region(293-373 K),showing the great temperature measuring property especially in low temperature region.The temperature sensing characteristics are superior to the results of most previous reports.The energy transfer(ET)process is certified to occur from Ce^(3+)to Eu^(2+)ions.These studies indicate that La_(5)Si_(2)BO_(13):Ce^(3+),Eu^(2+)phosphor could have a good prospect for optical thermometry.

Upconversion luminescence, intrinsic optical bistability,and optical thermometry in Ho3+/Yb3+: BaMoO4 phosphors

Ho^3+/Yb^3+: BaMoO4 phosphors with different concentrations were fabricated by a gel combustion method.The upconversion(UC) luminescence, intrinsic optical bistability, and the corresponding mechanisms were reported for the present system. The optical thermometric properties based on red(^5F5→^5I8) and green(^5F4/^5S2→^5I8) emissions were studied. The sensing sensitivities could be tuned by manipulating the cooperative energy transfer process. The highest absolute sensitivity was 99 × 10^-4 K^-1 at 573 K, which is larger than that of many previous UC materials.