Microwave-promoted pure host phase for red emission CaS:Eu^(2+) phosphor from single CaSO_4 precursor and the photoluminescence property

We report a novel approach to obtaining a classical blue-green excitable CaS：Eu2＋ phosphor with desired red emission by microwave （MW） firing procedure in the absence of adding elemental sulphur. The disturbing effect of MW electro- magnetic field on decomposition of CaSO4 into CaS activated by europium is distinctly observed to give pure host phase without adding any elemental sulphur and carbon. The host phase evolution is observed to be highly dependent on the variation of applied MW power from X-ray diffraction （XRD） patterns and the corresponding photoluminescence （PL）, and a maximum PL intensity at 1100 W of MW power is acquired for the obtained purer host phase. The non-thermal and non-equilibrium effects by MW are revealed to correlate with the interaction between polar structure of the host and applied electromagnetic field. The results demonstrate an optional procedure to prepare this red-emitting phosphor in an effective, environment-friendly and scalable approach for phosphor production in the application of bio-illumination for plant cultivation and artificial photosynthesis.

Dual excitable upconversion nanoparticle@polydopamine nanocomposite with intense red emission and efficient photothermal generation

Integration of strong upconversion emission with deep tissue penetration and stable photothermal generation is of great significance for imaging-guided photothermal therapy under infrared excitation.Herein,the NaYF_(4):Yb^(3+),Ho^(3+),Ce^(3+)@NaGdF_(4):Yb^(3+),Nd^(3+)@NaGdF_(4)core-shell-shell upconversion nanoparticles(UCNPs) with increasing Ce^(3+)doping concentration were firstly synthesized,in which the size manipulation,enhanced red to green emission intensity ratio(IR/IG),980 and 808 nm dual-modal excitations,as well as improved total upco nversion emission intensity can be achieved.After the coating of polydopamine(PDA) through dopamine spontaneous polymerization on the UCNPs surface under alkaline condition,the obtained UCNP@PDA nanocomposites show efficient photothermal effect under 808 nm excitation,while the thickness variation of PDA can be indicated by the upconversion spectra under 980 nm excitation.Interestingly,the photothermal effect of the UCNP@PDA nanocomposites with high IR/IGratio is mo re stable with PDA thickness variation,which bene fits from the structure design that allows PDA to simultaneously absorb the visible emission from inside UCNPs and the external 808 nm infrared light.Further in vitro cytotoxicity assay and photothermal therapy demonstrate that the UCNP@PDA nanocomposite has good biocompatibility and ability to kill tumor cells by photothermal effect under 808 nm excitation.This research may provide a nanoplatform for integrating deep bioimaging with highly stable photothermal therapy without the sacrifice of radiative transitions of rare earth ions.

Fluorine-defects induced solid-state red emission of carbon dots with an excellent thermosensitivity

Up to date,solid-state carbon dots(CDs)with bright red fluorescence have scarcely achieved due to aggregation-caused quenching(ACQ)effect and extremely low quantum yield in deep-red to near infrared region.Here,we report a novel fluorine-defects induced solid-state red fluorescence(λ_(em)=676 nm,the absolute fluorescence quantum yields is 4.17%)in fluorine,nitrogen and sulfur co-doped CDs(F,N,S-CDs),which is the first report of such a long wavelength emission of solid-state CDs.As a control,CDs without fluorine-doping(N,S-CDs)show no fluorescence in solid-state,and the fluorescence quantum yield/emission wavelength of N,S-CDs in solution-state are also lower/shorter than that of F,N,S-CDs,which is mainly due to the F-induced defect traps on the surface/edge of F,N,S-CDs.Moreover,the solid-state F,N,S-CDs exhibit an interesting temperature-sensitive behavior in the range of 80-420 K,with the maximum fluorescence intensity at 120 K,unveiling its potential as the temperature-dependent fluorescent sensor and the solid-state light-emitting device adapted to multiple temperatures.

Realizing ultra-pure red emission with Sn-based lead-free perovskites

Light-emitting diodes(LEDs)are key for the development of next-generation displays for ultra-high-definition television.Alternative materials beyond organic LEDs are required to meet the color purity standards,while retaining low processing cost and environmental friendliness.Liang and colleagues report in Advanced Science that two-dimensional(2D)tin halide perovskite—efficiently stabilized by H3PO2 incorporation—has great promise for ultra-pure red LEDs.

Polyetherimide functionalized carbon dots with enhanced red emission in aqueous solution for bioimaging

Red emissive carbon dots(CDs)are highly desired for biological applications.However,serious luminescence quenching of red emissive CDs in aqueous solution greatly hinders their application in high performance biological imaging.Herein,we reported a facile strategy to realize enhanced red emission of CDs in aqueous solution by surface modification with polyetherimide(PEI)via microwave heating method.High photoluminescence quantum yield(PLQY)of 25%was realized from the PEI functionalized CDs(CDs@PEI)in aqueous solution.The proposed PEI functionalization strategy not only protects the red emission against water molecules quenching,but also reverses the surface charges from negativity to positivity to promote cellular uptake of CDs,leading to clear cell imaging in red fluorescence region.More important,CDs@PEI exhibits much better photostability than commercial red emissive dye(MitoT racker red)in cell fluorescent imaging.Potential application of CDs@PEI on fast staining of cells for clonogenic assay has also been demonstrated.

TCNQ-based organic cocrystal integrated red emission and n-type charge transport

Simultaneously realizing the optical and electrical properties of organic materials is always challenging.Herein,a convenient and promising strategy for designing organic materials with integrated optoelectronic properties based on cocrystal engineering has been put forward.By selecting the fluorene(Flu)and the 7,7′,8,8′-tetracyanoquinodimethane(TCNQ)as functional constituents,the Flu-TCNQ cocrystal prepared shows deep red emission at 702 nm,which is comparable to the commercialized red quantum dot.The highest electron mobility of organic field-effect transistor(OFET)based on Flu-TCNQ is 0.32 cm^(2)V^(−1)s^(−1).Spectroscopic analysis indicates that the intermolecular driving force contributing to the co-assembly of Flu-TCNQ is mainly charge transfer(CT)interaction,which leads to its different optoelectronic properties from constituents.

Effects of charge compensation on red emission in CaYAl_3O_7:Eu^(3+) phosphor

Monovalent ions Li＋, Na＋, and K＋, as charge compensators, are introduced into CaYA1307： M （M = Eu3＋, Ce~＋） in this letter. Their crystal phases and photoluminescence properties of different alkali metal ions doped in CaYA1307 are investigated. In addition, the influence of charge compensation ion Li＋ which has a more obvious role in improving luminescence intensity on CaYA1307： Eu3＋ phosphor is intentionally discussed in detail and a possible mechanism of charge compensation is given. The enhancement of red emission centered at 618 nm belonging to Eu3＋ is achieved by adding alkali metal ion Li＋ under 393-nm excitation.

Bright Red Organic Electroluminescent Devices Based on a Soluble Rare Earth Complex Eu(TTA)_3 Phen

An Electroluminescent device with PVK film doped with Eu(TTA)_(3) Phen and PBD was fabricated.The device structure of glass substrate/indium tin oxide/PPV/PVK∶Eu(TTA)3 Phen∶PBD/Alq_(3)/Al was employed.A sharply red electroluminescence with a maximum luminance of 56.8 cd/m^(2)at 48 V was achieved.

Red/NIR emission carbonized polymer dots based on citric acid-benzoylurea and their application in lymph nodes imaging

Identification of lymph nodes(LNs)is critical for studies of the structure,the role in disease development,and the efficacy of disease treatment.Carbonized polymer dots(CPDs)are expected to be potential LNs-targeted imaging agents due to their excellent properties with special structure,better photoluminescence(PL)and great biocompatibility.Herein,a red/near infrared(NIR)emission CPDs(RCPDs)with one and two-photon bioimaging based on citric acid(CA)and benzoylurea(BU)are prepared.Notably,the RCPDs are capable of targeting LNs for imaging.Lymphocyte homing has been demonstrated to be the cellular mechanism of RCPDs target LNs imaging.This work has developed a new nanomaterial for targeted imaging of LNs,while the biological applications of CPDs have been expanded and deepened.

Intense single-band red upconversion emission in BiOCl:Er3+ layered semiconductor via co-doping Ho3+

Exploring a new tuning way to facilely realize single-band red emission in trivalent rare-earth ions(RE3+) doped upconversion(UC) materials is still desirable.In this work,the intense single-band red emission is achieved by co-doping only Ho3+in the BiOCl:Er3+ under 1550 nm excitation.In the BiOCl layered host,co-doping Ho3+can further enhance the red emission and simultaneously suppress the green emission of Er3+,and thus obviously improve the red-to-green(R/G) ratio.It is found that Ho3+does not se rve as ene rgy trapping through the 5 I6 state as in traditional UC materials but acts as ET bridge(4 S3/2,2 H11/2(Er3+)→5 F4,5 S2(Ho3+)→4 F9/2(Er3+)).The tuning mechanism of Ho3+is discussed in detail and further confirms through a comparative experiment.Our research gives an unusual perspective to tune the UC behavior of Er3+through co-doping Ho3+,which might be inspiring for achievement of single-band red UC emission.

Aggregation-induced emission:Red and near-infrared organic light-emitting diodes

Red and near-infrared(NIR)organic light-emitting diodes(OLED)have gained remarkable interest due to their numerous applications.However,the construction of highly emissive emitters is hampered by the energy-gap law and aggregation-caused quenching(ACQ)effect.Whereas,aggregationinduced emission(AIE)materials could avoid the undesirable ACQ effect and emit bright light in aggregated state,which is one class of the most promising materials to fabricate high-performance OLED with a high external quantum efficiency and low efficiency roll-off.This review summarizes recent advances in red and NIR OLED with AIE property,including the traditional fluorescence,thermally activated delayed fluorescence,and hybridized local and charge transfer compounds.Meanwhile,the emphasis attention is paid to the molecular design principles,as well as the molecular structure-photophysical characteristics.We also briefly further outlook the challenges and perspective of red and NIR AIE luminogens.

Energy transfer relation of a novel Ce^(3+)/Pr^(3+)/Eu^(3+) co-doped Sr_(2.975-x)La_xAlO_(4+x)F_(1-x) solid solution phosphor

The photoluminescence properties and energy transfer of a new Ce3＋/pr3＋/Eu3＋ co-doped solid-solution composi- tion of Sr2.975-xLaxAlO4＋xF1-x （LSAF） phosphor are investigated. Upon doping Pr3＋ into lattices of LSAF：Ce host, a shoulder emission peak is observed at about 620 nm, owing to the transition of 1D2 →3H4. Addition of Eu3＋ to LSAF：Ce3＋, Pr3＋ phosphor results in a sharp emission peaked at 675 nm for the 5D0 →TF3 transition and an increase of the intensity of red emission for Pr3＋ with increasing Eu3＋ concentration. The pathways of energy transfer among Ce3＋, Pr3＋, and Eu3＋ are proposed to be responsible for color addition of a red component to the primary yellow emission, enabling a potential adjustable color for blue excitable warm white.

D-A structured high efficiency solid luminogens with tunable emissions： Molecular design and photophysical properties

Fabrication of efficient solid luminogens with tunable emission is both fundamentally significant and technically important. Herein, based on our previous strategy for the construction of efficient and multifunctional solid luminogens through the combination of diverse aggregation-induced emission （ALE） units with other functional moieties, a group of luminophores with electron donor-acceptor （D-A） structure and typical intramolecular charge transfer （ICT） characteristics, namely CZ-DCDPP, DPA-DCDPP and DBPA-DCDPP were synthesized and investigated. The presence of twisting and AlE-active 2,3- dicyano-S,6-diphenylpyrazine （DCDPP） moiety endows them highly emissive in the solid states, whereas the introduction of arylamines with varied electron-donating capacity and different conjugation render them with tunable solid emissions from green to red. While CZ-DCDPP and DPA-DCDPP solids exhibit distinct mechanochromism, both DPA-DCDPP and DBPA-DCDPP solids can generate efficient red emission. Owing to their high efficiency, remarkable thermal and morphological stabilities and moreover red emission, they are promising for diverse optoelectronic and biological applications.

Highly selective and turn-on fluorescence probe with red shift emission for naked-eye detecting Al^(3+)and Ga^(3+)based on metal-organic framework

A novel ZnII-based metal-organic framework with the formula of{[Zn_(2)(BBIP)_(2)(NDC)_(2)]·H_(2)O}n(JXUST-5)derived from 3,5-bis(benzimidazol-1-yl)pyridine(BBIP)and 1,4-naphthalenedicarboxylic acid(H_(2)NDC)has been synthesized.The adjacent Zn^(II)ions are linked through two BBIP ligands to form a[Zn_(2)(BBIP)_(2)]secondary building unit(SBU).The neighbouring SBUs are further connected by NDC^(2-)withμ2-η^(1):η^(1)andμ2-η^(1):η^(1):η^(1)bridging modes to form a two-dimensional(2D)framework.Topological analysis shows that JXUST-5 could be simplified as an uninodal fes topology with a point symbol of{4.8^(2)}.Furthermore,the 2D framework net could be extended through C-H···πinteraction to form the three-dimensional supramolecular structure.Luminescent experiments suggest that JXUST-5 could selectively and sensitively recognize Al^(3+)and Ga^(3+)through fluorescence enhancement effect along with a relatively large red shift.The detection limits for Al^(3+)and Ga^(3+)are 0.17 and 0.69 ppm,respectively.Interestingly,the sensing process for both Al^(3+)and Ga^(3+)could be directly observed with naked eyes under 365 nm UV lamp.Notably,JXUST-5 could be recycled at least five times as a fluorescent sensor toward Al^(3+)and Ga^(3+),which is the second example of turn-on MOF based fluorescent sensor toward Ga^(3+).

Generating long-wavelength absorption bands with enhanced deep red fluorescence and photothermal performance in fused carbon dots aggregates

Carbon dots(CDs)with long-wavelength absorptions and emissions are highly desired for biological applications.Herein,we report a new supra-CDs strategy to construct long-wavelength absorption bands based on fused CDs aggregates(f-CDAs)through a concentration-induced interparticle dehydration process among green emissive CDs(r-CDs)under solvothermal treatment.The obtained fused f-CDAs exhibit an obvious absorption band in 550-700 nm and significantly enhanced deep red fluorescence in N,N-dimethylformamide with photoluminescence quantum yields of 15.6% and high photothermal conversion efficiency up to 26.1%in water.Benefiting from the high photothermal performance,in vivo tumor photothermal therapy has been realized via intratumoral injection of f-CDAs under 655 nm laser irradiated at 0.5 W/cm^(2).

Synthesis and enhanced photoluminescence properties of red emitting divalent ion(Ca^(2+))doped Eu:Y_(2)O_(3)nanophosphors for optoelectronic applications

This work presents the synthesis of Y_(2)O_(3):Eu^(3+),χCa^(2+)(χ=0 mol%,1 mol%,3 mol%,5 mol%,7 mol%,9 mol%,11 mol%)nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic,display,and lighting applications.The X-ray diffraction(XRD)patterns of the proposed nanophosphor reveal its structural properties and crystalline nature.The transmission electron microscope(TEM)results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca^(2+).Fourier transform infrared spectroscopy(FTIR)and Raman vibrations also confirm the presence of Y-O vibration and subsequently explain the crystalline nature,structural properties,and purity of the samples.All the synthesized nanophosphors samples emit intense red emission at 613 nm(~5D_(0)→~7 F_(2))under excitation with 235,394 and 466 nm wavelengths of Eu^(3+)ions.The photoluminescence(PL)emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength,respectively.The emission intensity of Y_(2)O_(3):Eu^(3+),χCa^(2+)(5 mol%)is increased 8-fold as compared to Eu:Y_(2)O_(3).Doping with Ca^(2+)ions enhances the emission intensity of Eu:Y_(2)O_(3)nanopho sphors due to an increase in energy transfer in Ca^(2+)→Eu^(3+)through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix.It is also observed that the optical band gap and the lifetime of the~5D_(0)level of Eu^(3+)ions in Y_(2)O_(3):Eu^(3+),xCa^(2+)nanophosphor sample gets changed with a doping conce ntration of Ca^(2+)ions.Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%,respectively.CIE,CCT,and color purity values(>98%)show an improved red-emitting nanophosphor in the warm region of light,which makes this mate rial superior with a specific potential application for UV-based white LEDs with security ink,display devices,and various other optoelectronics devices.

Bright red electroluminescent devices based on a soluble lanthanide complex Eu(DBM)_3(phen)

Electroluminescent devices with PVK film doped with Eu(DBM)3(phen) and PBD were fabricated. The device structure of glass substrate/indium-tin-oxide/PPV/PVK:Eu(DBM)3-(phen):PBD/Alq3/Al was employed. The emissive layer was formed by spin-casting method. A sharply red electroluminescence with a maximum luminance of 114.4 cd/m2 was achieved at 42 V.

A novel off-on fluorescent probe for specific detection and imaging of cysteine in live cells and in vivo

Cysteine(Cys)plays a pivotal role in many physiological and pathological processes,including detoxification and protein synthesis.The abnormal levels of Cys are linked to many diseases.In this study,a novel red-emitting off-on fluorescent probe Cys-TCF was masterly constructed for discriminative detection of Cys.After a series of experimental assessment,Cys-TCF displayed higher selectivity and sensitivity for Cys over other biothilols with a low detection limit(0.04μmol/L).More notably,the probe was also successfully applied to image Cys in live cells and live zebrafishes with low cytotoxicity.

Oxide ancillary ligand-based europium β-diketonate complexes and their enhanced luminosity

Ternary materials of europium complex with2,2,6,6-tetramethyl-3,5-heptanedione(tmhd) ligand and aqua ligand as ancillary ligands have been prepared and characterized for various optoelectronic characteristics.Reactions of hydrated complex [Eu(tmhd)_(3)(H_(2)O)_(2)] proceeded with triphenylphosphine oxide(TPPO) and pyridine-N-oxide(PNO) ancillary ligands were studied to develop novel complexes. The prepared complexes show good thermal stability. A comparative investigation of preparedmaterials[Eu(tmhd)_(3)(H_(2)O)_(2)],[Eu(tmhd)_(3)(TPPO)_(2)] and [Eu(tmhd)_(3)(PNO)_(2)] was conducted for their luminescent behaviors in order to obtain the role of ancillary ligand in the enhancement of illumination amount generated from europium(Eu^(3+)) ion. Color coordinates of prepared ternary complexes such as[Eu(tmhd)_(3)(H_(2)O)_(2)]with(x = 0.54,y = 0.32),[Eu(tmhd)_(3)(TPPO)_(2)] with(x = 0.56, y = 0.32) and[Eu(tmhd)_(3)(PNO)_(2)] with(x = 0.57, y = 0.33) indicated that these materials exhibited bright red emission in visible region spectrum. The complexes show a proficient energy transport pathway from the ligands to the innermost Eu^(3+)by means of an ancillary ligand-sensitized luminescence process. Interaction between the metal and ligand results in a distinguished effect on quantum efficiency(η) as well as on Judd–Ofelt intensity factor(Ω_(2)) of the prepared materials.