Blue light-induced rare-earth free phosphors for the highly sensitive and selective imaging of latent fingerprints based on enhanced hydrophobic interaction

The demand for in-situ detection of latent fingerprints(LFPs)in ways of high sensitivity,high selectivity,high contrast,low cost and user-friendly is still urgent.To overcome this challenge,a moisture-stable,red-emitting fluoride phosphor K_(3)AlF_(6):Mn^(4+)(KAF:Mn^(4+))with an organic hydrophobic skin was prepared.The phosphor has a uniform and superfine morphology with excellent luminescence properties.More importantly,this non-ultraviolet(UV)or non-near infrared(NIR)induced phosphor was proved to be an ideal fluorescent label for LFP imaging,which is both friendly for touch DNA analysis and compatible to forensic light sources.The well-defined ridge details with little background interference on various surfaces were presented by the oleic acid(OA)modified KAF:Mn^(4+)(KAF:Mn^(4+)-OA)phosphor in few seconds using the powder dusting method.To confirm the high selectivity of KAF:Mn^(4+)-OA for LFP imaging,an efficient quantitative evaluation method is proposed with the aid of ImageJ&Origin software.Due to the superiority of the Mn^(4+)-doped fluoride for the rapid imaging of LFPs in terms of lowcost,high compatibility and good availability,it is expected to be a promising candidate for forensic science as well as fluorescence imaging in other fields instead of rare earth luminescent materials.

A comparison research on replacements of Ba^(2+)by Lu^(3+)and Ba^(2+)-Si^(4+)by Lu^(3+)-Al^(3+)in BaSi_(2)O_(2)N_(2):Eu phosphors

As a cyan-emitting oxonitridosilicate phosphor,BaSi_(2)O_(2)N_(2):Eu^(2+)can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba^(2+)by Lu^(3+)and Ba^(2+)-Si^(4+)by Lu^(3+)-Al^(3+)can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu^(3+)doping,the internal quantum efficiencyηIQE Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)is 24.08%higher than that of Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+).After Al^(3+)co-doping,theηIQE is further increased by 10.31%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).When the temperature rises to 473 K,the luminescence intensity of Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+)maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba_(0.97)Si_(2)O_(2)N_(2):0.03 Eu^(2+),while the luminescence intensity of Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)keeps 73.87%of the initial value,which increases by18.52%compared to Ba_(0.925)Si_(2)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+).The mechanisms for luminescence and thermal stability improvement are proposed.The Ba_(0.925)Si_(1.97)O_(2)N_(2):0.03 Eu^(2+),0.045 Lu^(3+),0.03 Al^(3+)cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu^(2+)red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi_(2)O_(2)N_(2):Eu^(2+),Lu^(3+),Al^(3+)phosphor has great application prospect in the field of full-spectrum lighting.

Synthesis and photoluminescent properties of Sm^(3+)-activated La_(3)Si_(6)N_(11)as an orange-red emitting phosphor

A series of Sm^(3+)-doped La_(3)Si_(6)N_(11)phosphor materials we re synthesized by a high temperature solid-state reaction method.The crystal structure,micro structure,photoluminescence properties,decay curves as well as thermal quenching properties of the as-prepared phosphors were investigated systematically.The excitation spectra contain a wide asymmetric band below 350 nm originating from the host absorption,several sharp excitation peaks in the range of 300-550 nm corresponding to f-f transition of Sm^(3+).Under the excitation of 369 and 414 nm light,the phosphors exhibit strong narrow-band orangered emission peaked at 605 nm.The average decay time of La_(2.99)Si_(6)N_(11):0.01 Sm^(3+)sample is fitted to be0.38 ms and the CIE coordinates were calculated to be(0.6105,0.3833).For water resistance,La_(3)Si_(6)N_(11):Sm^(3+)is better than K_(2)SiF_(6):Mn^(4+)phosphor.After soaking in deionized water for 300 min,the La_(3)Si_(6)N_(11):Sm^(3+)sample retains approximately 80%of its initial relative emission intensity.When the temperature rises to 423 K(150℃),the emission intensity of La_(2.99)Si_(6)N_(11):0.01 Sm^(3+)sample remains 85%in co mparison to that of room tempe rature.The activation energy was calculated to be 0.63253 eV,which is higher than those of Sm^(3+)-activated oxide phosphors,indicating that the phosphor has relatively good thermal stability.

Enabling efficient NIR-II luminescence in lithium-sublattice core–shell nanocrystals towards Stark sublevel based nanothermometry

The luminescence in the second near-infrared(NIR-II)spectral region(1,000–1,700 nm)has recently attracted great attention for emerging biological applications owing to its merit of deep tissue bioimaging and high spatiotemporal resolution.However,it still remains a challenge to achieve the highly efficient NIR-II emissions of lanthanides in nanomaterials.Herein,we report an ideal design of sensitizing lithium sublattice core–shell nanocrystals for efficient NIR-II emission properties from a set of lanthanide emitters including Er3+,Tm3+,Ho3+,Pr3+,and Nd3+.In particular,the typical NIR-II emission of Er3+at 1.5μm was greatly enhanced by further manipulating the energy transfer via Er3+–Ce3+cross-relaxation,and the quantum yield can reach up to 35.74%under 980 nm excitation(12.5 W·cm−2),which is the highest value to the best of our knowledge.The 808 nm responsive efficient NIR-II emission was also enabled at the single-particle level through rational core–shell–shell structure design.Moreover,the lithium-sublattice provides an obvious spectral Stark-splitting feature,which can be used in the ultrasensitive NIR-II nanothermometer with relative sensitivity of 0.248%K−1 and excellent thermal cycling stability.These results open a door to the research of new kinds of efficient NIR-II luminescent materials,showing great promise in various frontier fields such as deep tissue nanothermometry and in vivo bioimaging.

Energy transfer and cross-relaxation induced multicolor upconversion emissions in Er^3+/Tm^3+/Yb^3+ doped double perovskite La2ZnTiO6 phosphors

Investigation on the bright and stable upconversion(UC)phosphors with multicolor emissions is fundamental and significant for the frontier applications of display and tempe rature probe.He re,dive rse emitting colors with blue,cyan and yellowish green,which are caused by the energy transfer and crossrelaxation processes,are obtained by altering Er^3+,Tm^3+and Yb^3+concentrations in Er3+singly,Er^3+-Tm^3+-Yb^3+co-and tri-doped double perovskite La2ZnTiO6(LZT)phosphors synthesized by a simple solid-state reaction.In addition,excellent infrared emission at 801 nm located at"first biological windo w"is collected in Tm^3+-Yb^3+co-doped phosphors.Meanwhile,the temperature sensing properties based on the thermally coupled levels((^2H11/2)/(^4S3/2))of Er3+ions were analyzed from 298 to 573 K of LZT:0.15 Er^3+/0.10 Yb^3+phosphor,demonstrating that the maximal sensitivity value is about56×10^-4 K^-1 at 448 K.All these results imply that this kind of UC material has potential applications in display,bioimaging and optical device.

Ce^(3+) doped BaLu_(2)Al_(2)Ga_(2)SiO_(12)——A novel blue-light excitable cyan-emitting phosphor with ultra-high quantum efficiency and excellent stability for full-spectrum white LEDs

It is well known that cyan-emitting phosphors play a very important role in full-spectrum white LEDs.A large number of cyan-emitting phosphors have been reported in the past few years,however,most of them can only be effectively excited by near-ultraviolet light.There are very few cyan-emitting phosphors that can be intensively excited by blue light(440 and 470 nm).Here,a novel blue-light excitable cyan-emitting phosphor BaLu_(1.95)Ce_(0.05)Al_(2)Ga_(2)SiO_(12)with excellent performance is reported.The cyan phosphor has a cubic structure in space group Ia3^(-)d with a=1.205379(3)nm,which can be easily obtained through a solid-state reaction pathway.The emission peak of the cyan phosphor is located at 500 nm and its internal quantum efficiency is as high as 90.01%when excited at 455 nm at 25℃.The cyan phosphor exhibits superior resistance against thermal quenching of luminescence,and its intensity at 125℃is as strong as 92.14%of the intensity at room temperature.Meanwhile,it also shows an outstanding resistance against water,where its luminescence intensity is hardly changed after being immersed in pure water for 528 h.The white LED lamp prepared by employing the obtained BaLu_(1.95)-Ce_(0.05)Al_(2)Ga_(2)SiO_(12)as cyan phosphor displays remarkable optical properties with CCT=4441 K,Ra=93.7,CRI=90.4 and CIE 1931(x,y)as(x=0.3648,y=0.3752).The experimental results demonstrate that BaLu_(1.95)Ce_(0.05)Al_(2)Ga_(2)SiO_(12)is a promising cyan-emitting phosphor with great application potential in full-spectrum white LEDs.