Bright Green Emission Research Articles

Utilization of Judd-Ofelt theory to assess the photophysical properties of β-keto carboxylate Tb(III) complexes with heterocyclic secondary sensitizer

One binary and five ternary green glowing Tb(III) complexes with β-keto acid as primary sensitizer and heterocyclic aromatic system as secondary sensitizer, were synthesised by an eco-friendly method and characterized via various spectroscopic techniques. The assessment of photoluminescent properties in solid complexes and in solution phase with DMSO as solvent, revealed the bright green emission of complexes on irradiation of UV light due to 5D4 → 7F5 transition, whose intensity persistently increased on insertion of secondary sensitizer. Higher relative quantum yield in ternary complexes communicated the contribution of secondary sensitizers in enhancement of luminescence. Judd-Ofelt parameters (Ω2, Ω4, Ω6) were evaluated from NIR absorption spectra of complexes. Higher Ω2 value in complexes demonstrated the higher covalence character and asymmetry around Tb(III) ion. Radiative, nonradiative transition probabilities, radiative life time, branching ratios and luminescence efficiency were also estimated. Complex T6 reported to have 72.5% efficiency which signalizes superb luminescence performance of this complex. Colorimetric parameters were obtained in solid as well as solution form. Exquisite color purity and CCT value > 4000 K established these complexes as cold green light source. Band gap energy and Urbach band tail, obtained via nonlinear fitting of absorption coefficient, turned out to be in semiconductor range thus can have materiality in various photonic devices. The large value of stimulated emission cross section and narrow full width at half maxima (FWHM) of 5D4 → 7F5 emission peak suggested the prospective use of synthesised complexes as laser media for green color lasers.

Single‐Layer Sheets of Alkylammonium Lead Iodide Perovskites with Tunable and Stable Green Emission for White Light‐Emitting Devices

AbstractRecently, metal halide perovskites have attracted considerable interest as highly emissive phosphors for use in white light‐emitting diodes (WLEDs). In perovskites, the migration of halide anions between green‐emitting bromide (e.g., CsPbBr3) and red‐emitting iodide (e.g., CsPbI3) materials is one obstacle to application. Here perovskite WLEDs that do not suffer from the anion exchange problem are reported: this is done by developing green‐emitting single‐layer sheets of (RNH3)2PbI4 (R = C18H35–, C12H25–, and C8H17–) and uniting these with red‐emitting CsPbI3 perovskite quantum dots (QDs). It relies on self‐assembly from ligand‐capped CsPbI3 nanocrystals to form single‐layer sheets of (C18H35NH3)2PbI4: via judicious selection of alkylamines and alkyl acids, (RNH3)2PbI4 single‐layer sheets that exhibit bright and stable green emission with well‐defined single‐layer thickness are produced. Emission from 505, 512 to 536 nm is tuned and a narrow (<20 nm) linewidth is retained. Perovskite LEDs that produce white light with chromaticity coordinates (0.32, 0.33) and color gamut that reaches 117% National Television System Committee (NTSC) in the International Commission on Illumination (CIE) 1931 color space are demonstrated.

Photoluminescence and Lasing of Cs4PbBr6 Micro‐Flakes and Micro‐Flowers with Embedded CsPbBr3 Nanocrystals

Herein, a controlled synthesis route with precise growth tunability of perovskite Cs4PbBr6 micro‐flakes and micro‐flowers with embedded CsPbBr3 nanocrystals (Cs4PbBr6@CsPbBr3) is elaborated. This room‐temperature synthesis scheme initiates the nucleation and growth process of the majority crystalline phase of Cs4PbBr6 with a few CsPbBr3 impurities as confirmed by the X‐ray diffraction studies. The microstructures and shape control are further investigated by scanning electron microscopy (SEM) and the high‐resolution transmission electron microscopy (HRTEM). The results depict hexagonal Cs4PbBr6 micro‐flakes with embedded CsPbBr3 that can spontaneously self‐assemble into micro‐flowers with varying external conditions. This approach gives access to perovskite semiconductors with both structural and excellent optical properties by correlating the dimensionality with quantum confinement effects. The photoluminescence, absorption, and time‐resolved photoluminescence spectroscopy confirm that such as‐synthesized materials exhibit bright green emission with an optical bandgap of 2.3 eV. Lasing action is obtained under an excitation wavelength of 400 nm at 10 K where the light intensity and lifetime are examined at different pump fluences. There exist two linear regions corresponding to spontaneous emission and lasing, respectively. The lower lasing threshold of 27 μJ cm−2 per pulse is obtained and the corresponding Q factor is estimated to be 1090.

Effect of substituted 2,2′-bipyridine derivatives on luminescence characteristics of green emissive terbium complexes: Spectroscopic and optical analysis

Heteroleptic ternary terbium complexes with general representation as [Tb(acac)3 L] have been prepared through single step path with acetylacetone (acac) as chromophoric and substituted 2,2ꞌ-bipyridine as auxiliary (L) moieties. The synthesized complexes are characterized systematically through elemental, spectroscopic and thermogravimetric analyses. The infra-red and proton nuclear magnetic resonance spectra are consistent with the formation of complexes. Green emission is observed for the synthesized terbium complexes in solid form and in dichloromethane (DCM) solvent due to 5D4→7F5 transition. The chromaticity parameters have estimated high color purity of the complexes and their coordinates positioned in the green region of the CIE triangle. The singlet and triplet state energy of 2,2ꞌ-bipyridine (Bpy) and 2,2′-bipyridine dihydrobromide (DBr) show the efficient sensitization of Tb3+ ion in synthesized complexes by respective ligands. The bright green emission and the values of band gap indicate the utilization of synthesized complexes in the fabrication of displays.

Amplification of circularly polarized luminescence from chiral cyclometalated platinum(II) complexes by the formation of excimer

Circularly polarized organic light-emitting diodes (CP-OLEDs) have raised increasing interests owing to their potential application in next-generation displays. In this work, by introducing chiral alkyl chain into tridentate chelating ligand 2,6-bis(N-alkylbenzimidazol-2’-yl)benzene, three chiral Pt(II) complexes are successfully designed and synthesized. All the complexes exhibited bright green emission in dilute acetonitrile solution, while strong yellow-orange emission in highly concentrated solution. However, when these complexes are doped into polymer polymethyl methacrylate, the green emission stemmed from the intrinsic single molecule would be changed into red emission from excimer through adjusting the doping levels. More importantly, the CPL signals could be amplified by an order of magnitude in comparison with solution state. Furthermore, the monochrome devices based on these complexes were successfully fabricated, and achieved good device performances with the maximum luminance of up to 1720 cd m−2 and electroluminescence dissymmetry values of around 2.6 × 10−3. These results indicate that such design strategy for Pt(II) complexes with tridentate cyclometalled ligands would be important for the development of high-performance CP-OLEDs.

Evolutions of the optical properties in green-emitting MAPbBr3 perovskite nanoplatelets/polymethyl methacrylate (PMMA) composite films for light-emitting diode applications

Organometal halide perovskites have been gaining tremendous attention for their potential application as optoelectronic devices, owing to their excellent optical and electronic properties. This work fabricated MAPbBr3/PMMA composite film with bright green emission via a simple drop-casting method. It is found that when MAPbBr3 were combined with PMMA, PL peak position and edge absorption spectra exhibit a redshift phenomenon. Comprehensive characterizations using x-ray diffraction (XRD) and transmission electron microscope (TEM) suggested that this phenomenon possibly corresponded to the dielectric screening and strain of perovskite crystal induced by the presence of PMMA. Understanding this redshift phenomenon could be beneficial for developing high color purity optoelectronic devices. A potential application of the prepared film as a green down-converter is also demonstrated. Applying the MAPbBr3/PMMA film on a UV LED has successfully generated green color at (0.21, 0.71), close to the green color standards, i.e., NTSC 1953 and Adobe RGB 98. This result suggests that MAPbBr3 perovskite nanoplatelets/PMMA composite films have great potential for light-emitting device applications.

Ultra-High-Sensitive Temperature Sensing Based on Er3+ and Yb3+ Co-Doped Lead-Free Double Perovskite Microcrystals

Fluorescence intensity ratio (FIR) thermometry, a new contactless temperature measurement, can achieve accurate measurements in a harsh environment. In this work, all-inorganic lead-free Cs2AgInCl6: Er-Yb and Cs2AgBiCl6: Er-Yb microcrystals emit bright green up-conversion emission, which are synthesized by precipitation at a low temperature (80 °C). In up-conversion emission, FIR of the 2H11/2 → 4I15/2 band to the 4S3/2 → 4I15/2 band exhibits temperature dependence, which can be used as the temperature measurement parameter, so-called FIR thermometry. Moreover, the theoretically accurate measurement range is from 100 to 600 K, achieving maximum absolute sensitivities from 0.0130 to 0.0113 K-1, respectively. The principle of up-conversion and high sensitivity is well explained by calculating the partial density of states. Compared to the reported thermometry materials based on the FIR method, the prepared all-inorganic lead-free Cs2AgInCl6: Er-Yb and Cs2AgBiCl6: Er-Yb microcrystals show outstanding temperature measurement width and sensitivity, becoming a potential candidate for high-sensitivity optical temperature sensors.

Incorporation of Perovskite Nanocrystals into Polymer Matrix for Enhanced Stability in Biological Media: In Vitro and In Vivo Studies.

The outstanding optical properties and multiphoton absorption of lead halide perovskites make them promising for use as fluorescence tags in bioimaging applications. However, their poor stability in aqueous media and biological fluids significantly limits their further use for in vitro and in vivo applications. In this work, we have developed a universal approach for the encapsulation of lead halide perovskite nanocrystals (PNCs) (CsPbBr3 and CsPbI3) as water-resistant fluorescent markers, which are suitable for fluorescence bioimaging. The obtained encapsulated PNCs demonstrate bright green emission at 510 nm (CsPbBr3) and red emission at 688 nm (CsPbI3) under one- and two-photon excitation, and they possess an enhanced stability in water and biological fluids (PBS, human serum) for a prolonged period of time (1 week). Further in vitro and in vivo experiments revealed enhanced stability of PNCs even after their introduction directly into the biological microenvironment (CT26 cells and DBA mice). The developed approach allows making a step toward stable, low-cost, and highly efficient bioimaging platforms that are spectrally tunable and have narrow emission.

Green Synthesis of Phosphorescent Carbon Dots for Anticounterfeiting and Information Encryption.

Room-temperature phosphorescent (RTP) carbon dots (CDs) have promising applications in bioimaging, anticounterfeiting, and information encryption owing to their long lifetimes and wide Stokes shifts. Numerous researchers are interested in developing highly bright RTP CDs using environmentally friendly and safe synthesis processes (e.g., natural raw materials and zero-pollution production pathways). In this study, we successfully synthesized RTP CDs using a hydrothermal process employing natural vitamins as a raw material, ethylenediamine as a passivator, and boric acid as a phosphorescent enhancer, which is referred to as phosphorescent CD (PCD). The PCDs exhibit both bright blue fluorescence emission and green RTP emission, with a phosphorescence lifetime as long as 293 ms and an excellent green afterglow visible to the naked eye for up to 7.0 s. The total quantum yield is 12.69%. The phosphorescence quantum yield (PQY) is up to 5.15%. Based on the RTP performance, PCDs have been successfully employed for anticounterfeiting and information protection applications. The results of this study provide a green strategy for the scalable synthesis of RTP materials, which is a practical method for the fabrication of RTP materials with high efficiency and long afterglow lifetimes.

Bright green emission non-conjugated polymer dots: pH trigged hydrogel for specific adsorption of anionic dyes and visual detection of tert-butylhydroquinone

In recent years, non-conjugated polymer dots (PDs) have attracted considerable interests due to their fundamental importance and potential applications in diverse areas. Herein, we synthesized the green emissive non-conjugated PT PDs with polyethyleneimine (PEI) and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as precursors in one-pot at room temperature with the quantum yield at 25%. Surprisingly, PT PDs solutions could be transformed to hydrogels by pH alteration. By characterization, PT PDs hydrogels performed porous structure with large surface area and positively charged functional groups. Anionic dyes could be easily adsorbed into PT PDs hydrogels through multiple electrostatic interactions. In addition, PT PDs could specifically detect tert-butylhydroquinone (TBHQ) with a low detection limit (27 µM), suggesting their high sensitivity. More importantly, the developed method was successfully applied the detection of TBHQ in the peanut oil, implicating their practical application.

Highly luminescent lead bromine perovskite via fast and eco-friendly water-assisted mechanochemical method

All-inorganic cesium lead halide perovskite nanocrystals (CPeNCs) have aroused tremendous research attention due to their excellent photophysical properties. Here, we report an eco-friendly and fast water-assisted mechanochemical synthesis of CsPbBr3 perovskite functionalized by oleic acid (OA) and hydroxyl groups (OH). Owing to the water exfoliation and mechanical shearing force, the CsPbBr3 bulks quickly transformed into rectangular CsPbBr3 particles in 10 min with a bright green emission (λem = 525 nm) and a high photoluminescence quantum yield (PLQY) up to 53%. Impressively, the functionalized CsPbBr3 retains their bright green emission in ethanol after 360 days, showing high ethanol resistance. Thus, an alcohol solubility and easy film-forming transparent polymer of polyvinyl butyral (PVB) is directly employed to encapsulate functionalized CsPbBr3 in ethanol solution. The obtained CsPbBr3/PVB composite film shows excellent water resistance, whose photoluminescence intensity drops only 20% after 60 h in water. The composite film was demonstrated as color converter layers of white light-emitting diodes device with color coordinates of (0.329, 0.321). This work not only offers a green synthesis method for perovskite fluorescent material, but also helps to address their long-term stability in polar solvents towards their various applications.

Selective detection of iron (III) using salicylic acid capped Tb3+-doped CaF2 colloidal nanoparticles

Lanthanide (Ln3+) doped nanoparticles (NPs) possess sharp luminescence peaks with long excited state lifetimes. In this manuscript we have utilized these features for the selective detection of Fe3+ ions through resonance energy transfer approach. This is achieved using salicylic acid (SA) capped Tb3+-doped CaF2 (SA@CaF2:Tb3+) NPs. These nanoparticles exhibit bright green color emission upon ultraviolet (U.V.) excitation due to the strong energy transfer from the salicylic acid molecules to Tb3+ ions. An enhancement in the green emission intensity close to 40 times is noted. Upon addition of ferric ions, the emission intensity of the green emission is greatly reduced. The spectral overlap of the SA emission with the absorption of the analyte is assumed to be the reason for the selective quenching of the luminescence intensity. As a consequence, the overall energy transfer efficiency from salicylic acid to terbium ions (Tb3+) is reduced resulting in the lowering of Tb3+ emission intensity. The calculated detection limit for the ferric ions is 8.7 μM. The selective decrease in the green emission intensity upon Fe3+ is confirmed by the introduction of other cations like Ni2+, Mn2+, Cu2+, Co2+, Cr2+, Pb2+, Zn2+ and Mg2+ resulting hardly in any alteration to the Tb3+ emission intensity. This work clearly directs that the resonance energy transfer (RET) using Tb3+-doped NPs can be used as a technique to detect ferric ions.

Terbium (III)-based Metallacrowns with aggregation-induced emission feature coupled with cu (II) for fluorescence detection of cysteine

The Metallacrowns (MCs) composed of repeated [Metal-N-O] subunits are a type of new material, but the MCs have not been developed and utilized in analytical applications. This essay reports on a new kind of terbium(III)-based Metallacrowns (Tb-MCs) with aggregation-induced emission (AIE) feature to build a sensing platform. It is first time that Tb-MCs are able to aggregate to larger aggregates in water along with a bright green emission, so that the property makes it possible to apply in biosensing. Thereafter, the AIE of Tb-MCs can be quenched effectively by Cu2+. Based on the high affinity of thiol to Cu2+, cysteine (Cys) recovers the fluorescence of Tb-MCs in the presence of Cu2+. There is a good linear range varying from 0.02 to 20 μM with a low limit of detection (LOD) 9.67 nM of Cys. In the end, this novel probe is also successfully applied to the determination of Cys in human serum with satisfactory results.

High-reliability all-fiber FIR temperature sensor using LiGd(WO4)2:Er3+/Yb3+ phosphors

Rare earth doped LiGd(WO4)2 phosphors have been prepared by solid sintering technology. The dominant 4G5/2→6H9/2 emission of Sm3+ ions suggests that Sm3+ ions occupy the non-centrosymmetric lattices in LGWO:Sm3+ phosphors. Under the excitation at 980 nm laser, bright green upconversion emissions at 531 nm and 553 nm were detected in LGWO:Er3+/Yb3+ phosphor, which was used to build a high-reliability temperature sensor based on fluorescence intensity ratio (FIR) technology. The calibration curve between FIR and temperature was established at the temperature range of 258–423 K. The highest absolute sensitivity was 0.0137 K−1 at 423 K and the standard deviation of multiple temperature measurements at 313 K was only 0.108%. Experimental data show that this material can be used for the all-fiber temperature sensors.

Preparation and photoluminescent characteristics of green Tb(III) complexes with β-diketones and N donor auxiliary ligands

This paper presents four octa coordinated ternary terbium complexes based on 2-benzoylacetophenone (BAP) and other auxiliary ligands. For characterization purpose, elemental analysis, electrochemical study, thermal analysis and spectroscopic investigations were carried out in detail. Optical band gap (3–4 eV) of complexes was determined from Tauc’s relation. Upon excitation in UV region, emission spectra of complexes demonstrate peaks of Tb3+ ion at ∼616 nm, 589 nm, 548 nm, and 492 nm, attributed to 5D4 → 7FJ (J = 3 to 6) respectively due to energy transfer from ligand to Tb(III) ion via antenna effect. Peak at 548 nm corresponding to 5D4 → 7F5 is responsible for bright green emission of synthesized terbium complexes. CIE color coordinates and color purity further corroborate the green emission of Tb3+ complexes. The complexes were found to be quite stable as studied by thermal analysis. The outcomes of characterizations have demonstrated that these complexes could behave as good contenders in lighting systems and displays owing to their photometric characteristics.

Spectroscopic and optical investigation of 1,10-phenanthroline based Tb(III) β-diketonate complexes

A series of luminescent ternary terbium complexes based on fluorinated ligand 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (TFNB) and other auxiliary ligands were synthesized and explored. Optical and photophysical characteristics of complexes were examined spectroscopically. Thermal and electrochemical behavior of complexes is also reported. In emission spectra of complexes, four characteristic peaks of Tb3+ ion at 492 nm, 548 nm, 586 nm and 615 nm accredited to 5D4 → 7FJ (J = 6–3) transitions appeared upon excitation in UV region. Most intense peak at 548 nm is accountable for bright green emission of ternary complexes. Color purity and CIE parameters also suggest the green luminous behavior of complexes. Our investigation has revealed that the synthesized complexes could be used in preparing lighting system, OLEDs and display devices owing to their luminescent characteristics.

Improved electric-field-induced strain and strong photoluminescence properties in novel Er3+-modified 0.93Bi0.5Na0.5TiO3-0.07BaTiO3 multifunctional ceramics

Recently, the progress of electronic devices toward miniaturization has strongly promoted development of multifunctional materials possessing multiple desirable properties. In this study, we develop and fabricate 0.93Bi0.5Na0.5TiO3-0.07BaTiO3-xEr multifunctional ceramics which show simultaneously considerable electric-field-induced strain and bright green light emission properties. With the introduction of Er3+, the ceramics gradually transform from non-ergodic relaxor phase to ergodic relaxor phase which could reversibly transform to ferroelectric phase under the electric field. As a result, with improving Er3+ content, the shape of the polarization-electric field loops of the ceramics become pinched, and it is obvious that the negative strain disappears while the positive strain gradually increases and reaches a maximum value 0.46% at x = 1.2 mol%. Besides, After the ceramics are poled, the light emission peak are greatly enhanced attributed to the decreased crystal symmetry and increased domain size, and is the strongest at x = 1.2 mol%. These results indicate that 0.93Bi0.5Na0.5TiO3-0.07BaTiO3-xEr ceramics are good candidates for developing multifunctional optoelectronic devices.

Development of epoxy/rice straw-based cellulose nanowhiskers composite smart coating immobilized with rare-earth doped aluminate: Photoluminescence and anticorrosion properties for sustainability

Novel epoxy resin (E)/CNW nanocomposite coatings were developed with different total contents of rare-earth doped aluminate nanoparticles (REA NPs). The produced epoxy-cellulose nanowhiskers-rare earth doped aluminate nanoparticles (E-CNW-REA) coatings were applied onto mild steel. The epoxy/CNW nanocomposite coatings were characterized by X-ray fluorescence analysis (XRF), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXA), transmission electron microscope (TEM) and infrared spectra (FT-IR). Both colorimetric properties and transparency of the nanocomposite coatings were proved by exploring UV–Vis absorption spectroscopy and CIE Lab parameters. The hardness and superhydrophobic properties were also explored. The photoluminescent transparent coatings showed an excitation at 365 nm, and a bright green emission wavelength at 517 nm under UV light. The corrosion protection performance of the coated mild steel samples soaked in an aqueous solution of sodium chloride (3.5%) was investigated using electrochemical impedance spectroscopy (EIS). The coatings with CNW were found to have anti-corrosion properties. Moreover, the nanocomposite coating with CNW (1 w%) was monitored to exhibit the most pronounced long-persistent photoluminescence for 60 min in the dark. The photoluminescent coatings exhibited highly durable long-lasting phosphorescence. Thus, the current strategy can be considered as a simple promising technology for industrial production of anti-corrosive, superhydrophobic and long-persistent phosphorescent.

In situ interfacial passivation with an arylphosphine oxide and phosphonate electron transporting layer for efficient all-solution-processed PeQLEDs.

Perovskite quantum dot light-emitting diodes (PeQLEDs) have emerged as a promising candidate for high-quality lightings and displays, where an electron transporting layer (ETL) is required to achieve balanced charge transport and thus high performance. However, the ETL is often thermally-deposited under vacuum, since the low-cost solution process would damage the underlying perovskite quantum dots (PeQDs). Here, we demonstrate efficient all-solution-processed PeQLEDs based on arylphosphine oxide (SPPO13) and phosphonate (TPPO) as the ETL. Benefitting from the coordination between PO and exposed Pb atoms, in situ interfacial passivation occurs during the solution deposition of SPPO13 or TPPO on PeQDs. As a result, bilayer films (PeQDs/ETL) exhibit improved photoluminescence quantum yields and prolonged lifetimes compared with single layer PeQDs. Correspondingly, all-solution-processed PeQLEDs are fabricated successfully via an orthogonal solvent strategy, revealing bright green emission with a promising current efficiency of 24.1 cd A-1 (12.1 lm W-1, 6.47%) and CIE coordinates of (0.12, 0.79).

11-Mercaptoundecanoic Acid-Functionalized Carbon Dots As a Ratiometric Optical Probe for Doxorubicin Detection

A ratiometric optical dual-mode probe was first designed for the detection of doxorubicin (DOX) based on 11-mercaptoundecanoic acid-functionalized carbon dots (MUA-CDs). The carbon dots (CDs) were synthesized via hydrothermal carbonization of m-phenylenediamine and p-aminobenzoic acid, and then it was reacted with 11-mercaptoundecanoic acid by the amide reaction to obtain the MUA-CDs. The as-synthesized MUA-CDs have a high fluorescence quantum yield (59.4%) with bright green emission. Based on a specific electrostatic interaction and the fluorescence resonance energy transfer (FRET) between MUA-CDs and DOX, a ratiometric optical dual-mode probe was constructed for the detection of DOX with good selectivity, high sensitivity, and excellent anti-interference performance. When DOX was mixed the MUA-CDs, the fluorescence of the MUA-CDs at 513 nm decreased, while the fluorescence at 590 nm increased. With this information, a ratiometric fluorescent method was established to determine DOX with a linear range and limit of detection (LOD) of 0.25–19.96 and 0.66 μM and 50.33–80.88 and 0.23 μM, respectively. Meanwhile, the color of the MUA-CDs varied from colorless to dark yellow in the presence of DOX, and therefore, a ratiometric colorimetric method was applied to determine DOX in a range of 2.50–29.80 μM with a LOD of 0.75 μM. Finally, the as-constructed probe was successfully used to determine DOX in serum, urine, and live cells with satisfactory results. This work will contribute to the specific design of functional CDs and broaden the application of functional CDs in analytical detection and biological imaging.