Yellow-green Emission Research Articles

Multicolor-Luminescence Including White Light by Photomodulation of Supramolecular Assemblies in Aqueous Media.

Photo-responsive supramolecular systems offer intriguing functional aspects which have led to their applications in diverse fields such as optoelectronics and biomedicine. However, the modulation of the luminescence output in a spatiotemporal fashion by photo-controlled transformation still remains a challenging task. Herein, we report the controlled regulation of the emission color of supramolecular assemblies of amphiphilic cyanostilbenes (CSs) in water through in situ photomodulation employing UV and sunlight. Due to their aggregation-induced emission (AIE) features, the CS chromophores in the supramolecular assemblies exhibited bright greenish-yellow emission. Photoirradiation predominantly led to the formation of a cyclized product exhibiting aggregation-caused quenching (ACQ) features and having efficient cyan-blue emission in water but severely quenched emission in the solid state. Hence, starting from a unicomponent scaffold, photomodulation provided tunable emission ranging from greenish-yellow to cyan-blue including white light in water. Furthermore, using the contrasting AIE and ACQ behavior of the components in the photoirradiated mixtures, we were able to design rewritable fluorescent inks and encryption in solid films indicating the practical utility of these systems.

Wearable Natural Rubber Latex Gloves with Curcumin for Torn Glove Detection in Clinical Settings.

Glove tear or perforation is a common occurrence during various activities that require gloves to be worn, posing a significant risk to the wearer and possibly others. This is vitally important in a clinical environment and particularly during surgical procedures. When a glove perforation occurs (and is noticed), the glove must be replaced as soon as possible; however, it is not always noticeable. The present article is focused on the design and development of a novel fluorescence-based sensing mechanism, which is integrated within the glove topology, to help alert the wearer of a perforation in situ. We hypothesized that natural rubber gloves with curcumin infused would yield fluorescence when the glove is damaged, particularly when torn or punctured. The glove design is based on double-dipping between Natural Rubber Latex (NRL) and an inner layer of latex mixed with curcumin, which results in a notable bright yellow-green emission when exposed to UV light. Curcumin (Cur) is a phenolic chemical found primarily in turmeric that fluoresces yellowish-green at 525 nm. The tear region on the glove will glow, indicating the presence of a Cur coating/dipping layer beneath. NRL film is modified by dipping it in a Cur dispersion solution mixed with NRL for the second dipping layer. Using Cur as a filler in NRL also has the distinct advantage of allowing the glove to be made stronger by evenly distributing it throughout the rubber phase. Herein, the optimized design is fully characterized, including physicochemical (fluorescence emission) and mechanical (tensile and tear tests) properties, highlighting the clear potential of this novel and low-cost approach for in situ torn glove detection.

Synthesis, Crystal Structures, and Density Functional Theory Studies of Two Salt Cocrystals Containing Meldrum's Acid Group.

Two salt cocrystals, C31H34N4O8 (DDD) and C17H20N2O8 (MDD), were synthesized and their structures were determined by single-crystal X-ray diffraction. DDD is made up of one (C13H13O8)− anion, one (C9H11N2)+ cation, and one 5,6-dimethyl-1H-benzo[d]imidazole molecule. MDD consists of one (C4H7N2)+ cation and one (C13H13O8)− anion. DDD and MDD belong to the monoclinic, P21/c space group and triclinic, P-1 space group, respectively. A 1D-chained structure of DDD was constituted by N–H···N and N–H···O hydrogen bonds. However, a 1D-chained structure of MDD was bridged by N–H···O hydrogen bonds. Their density functional theory-optimized geometric structures with a B3LYP/6-311G(d,p) basis set fit well with those of crystallographic studies. By calculating their thermodynamic properties, the correlation equations of C0p,m, S0m, H0m, and temperature T were obtained. By comparing the experimental electronic spectra with the calculated electronic spectra, it is found that the PBEPBE/6-311G(d,p) method can simulate the UV–Vis spectra of DDD and MDD. In addition, the fluorescence spectra in the EtOH solution analysis show that the yellowish-green emission occurs at 570 nm (λex = 310 nm) for DDD and the purplish-blue emission occurs at 454 nm (λex = 316 nm) for MDD.

Ultrasensitive fluorogenic chemosensor based on ESIPT phenomenon for selective determination of Cu2+ ion in aqueous system and its application in environmental samples and biological imaging

A new fluorometric sensor based on salicylideneaniline derivative for the detection of Cu2+ ion in aqueous media was developed and synthesized. The sensor showed strong absorption and fluorescence emission in an aqueous system through ESIPT and ICT characters. The greenish yellow fluorescence emission quenching and color change from bright yellow to pale yellow were observed after complexation with Cu2+via the chelation-enhanced quenching (CHEQ) process. The sensor can recognize Cu2+ ion with high sensitivity and specificity over potential interfering ions as well as a low detection limit of 0.87 ppb, which was lower than the limit level concentration of Cu2+ in drinking water by the United States Environmental Protection Agency (U.S. EPA) and World Health Organization (WHO). The Job's plot, X-ray Absorption Spectroscopy (XAS), and 1H NMR illustrated the chelating mode between PS and Cu2+ ion in 1:1 stoichiometric complexation. The DFT calculations revealed ligand-to-metal charge transfer (LMCT) phenomena upon the Cu2+ binding of PS. Moreover, this fluorescence sensor was successfully employed for analyzing Cu2+ concentration in real water samples as well as living cells.

Greenish-yellow emission from rare-earth free Li+ doped zinc vanadate phosphor

In this article, we present synthesis and spectral study of Zn(3-x)Lix(VO4)2 (x = 0, 0.01, 0.02, 0.03) samples. The orthorhombic phase of all the samples is validated by their XRD pattern. The crystallinity of Zn3(VO4)2 is improved by doping Li+ ions and is supported by the augmentation in crystallite size. The absorption band of the phosphors covers the near-UV region. The XPS analysis ascertains the V+5 oxidation state of vanadium thereby confirming the single-phase of the phosphors. The Li+ ion doping enhances the broadband excitation in the near UV region and emission band of Zn3(VO4)2 in the visible region with stokes shift of 9517.3 cm−1. The increased PL lifetime of the emission bands is observed after Li+ ion doping. The calculated activation energy of Li+ doped Zn3(VO4)2 phosphor is 0.29 eV and there is a 44% loss of emission intensity at 150 °C. Thus, with the broadband near-UV excitation and greenish-yellow emission, the Li+ doped zinc vanadate phosphor can be utilized with near-UV LED chips for the realization of white light.

Encapsulation of AIEgens within Metal–Organic Framework toward High‐Performance White Light‐Emitting Diodes

AbstractWhite light‐emitting diodes (WLEDs) have a wide range of applications in display and illumination, however, it is still challenging to achieve efficient solid‐state white light‐emitting (WLE) materials due to the conventional quenching effect. Herein, a strategy of encapsulating aggregation‐induced emission luminogens (AIEgens) into the pores of metal–organic framework (MOF) to achieve high‐performance WLED is proposed. Two cationic dyes, 2,3,4,5‐tetrakis(4‐methoxyphenyl)oxazol‐3‐ium (MOTPO) and 1‐methyl‐4‐(4‐(1,2,2‐triphenylvinyl)phenyl)pyridin‐1‐ium (TPEPy) with bright blue and yellowish green emissions, respectively, are synthesized and successfully incorporated into the pore of anionic MOF ZJU‐28. The synergy of AIE characteristics and confinement effect within hybrid material result in an enhanced emission signal in comparison to each of the individual components. The single‐phase WLE material with Commission International de L'Eclairage coordinates of (0.35, 0.34) and the quantum efficiency of 64.9% is realized by optimizing the ratio between the two guests, which is almost the best among the reported WLE MOF composites to date. The resulting WLED demonstrates the maximum external quantum efficiency of 12.67% accompanied by the excellent color‐rendering index and correlated color temperature of 86 and 4076 K, respectively. Moreover, the WLE flexible film is also achieved. This work will provide new insights and strategies for the design of efficient WLEDs in the future.

Luminescence properties of Tb-doped SrAl4O7

In this research terbium-doped strontium aluminate SrAl4O7 samples were synthesized using solid-state synthesis method. X-Ray powder diffraction (XRD) and photoluminescence (PL) measurements were applied for sample characterization. All of them exhibited yellowish-green emission with highest peak at 542 ​nm attributable to 5D4 →7F5 transition. The highest emission intensity was observed in Sr0.98Al4O7:Tb0.02 sample while higher doping levels resulted in decrease of the PL intensities due to concentration quenching. Samples with additional IA group ions for charge compensation were also prepared and their PL properties were measured.

A Fluorescent Linear Conjugated Polymer Constructed from Pillararene and Anthracene.

Over the past few years, conjugated polymers (CPs) have aroused much attention owing to their rigid conjugated structures, which can perform well in light harvesting and energy transfer and offer great potential in materials chemistry. In this article, we fabricate a new luminescent linear CP p(P[5](OTf)2-co-9,10-dea) via the Sonogashira coupling of 9,10-diethynylanthracene and trifluoromethanesulfonic anhydride (OTf) modified pillar[5]arene, generating enhanced yellow-green fluorescence emission at around 552 nm. The reaction condition was screened to get a deeper understanding of this polymerization approach, resulting in an excellent yield as high as 92% ultimately. Besides the optical properties, self-assembly behaviors of the CP in low/high concentrations were studied, where interesting adjustable morphologies from tube to sheet were observed. In addition, the fluorescence performance and structural architecture can be disturbed by the host–guest reorganization between the host CP and the guest adiponitrile, suggesting great potential of this CP material in the field of sensing and detection.

High-efficient yellow-green emission in (TDMP)MnBr4 single crystal with modulation of spin-phonon-charge interactions

In this paper, a new zero-dimensional organic-inorganic hybrid manganese bromide single crystal with high-efficiency yellow-green emission has been synthesized by inserting C6H16N22+ into [MnBr4]2- tetrahedrons lattice, and its PLQY reaches up to 89%. At the same time, the relationship between the emission wavelength and relaxation process under CW laser excitation was investigated in this single crystal, exhibiting different emission colors under continuous-wave laser excitation of different wavelengths. The results show that the distance between the nearest Mn2+ in the lattice is 6.8 Å, this number brings up a very weak ferromagnetic coupling state and a dominant paramagnetic state, which lead to a significant emission band at 550 nm and a weak emission band at about 640 nm when excited by 325 nm laser. The high-level d-d transition at about 400 nm and AFM d-d transition at 458 nm band could be found simultaneously under continuous-wave laser excitation above the bandgap, and the photophysical properties of the multiple emission bands and the microscopic interactions of the spin, carrier, and phonon inside the lattice have been discussed. These findings provide a new direction for Mn-based materials in the field of luminescence and provide ideas for the development of new materials with the microscopic interaction modulation of the spin, carrier, and phonon.

Synthesis and tunable emission from yellow-green to red-orange of Ca3MgSi2O8:Eu3+, Dy3+ phosphor

In this work, Ca3MgSi2O8:R (R = Dy3+, Eu3+, and Eu3+/Dy3+) phosphors are synthesized in air by using the high-emperature solid-state reaction method. The crystal phase, crystal structures, lifetimes, and luminescence properties are investigated. Ca3MgSi2O8:Eu3+ phosphor with excitation at 394 nm emits red-orange light and its emission spectrum covers the region from 575 nm to 720 nm due to the 5D0 → 7F0, 7F1, 7F2, 7F3, and 7F4 transitions of Eu3+ ion. Ca3MgSi2O8:Dy3+ phosphor under excitation at 350 nm exhibits yellow-green emission with four emission bands in the range of 460–500 nm, 550–600 nm, 650–680 nm, and 740–775 nm, which are attribuited to the 4F9/2 → 6H15/2, 6H13/2, 6H11/2, and 6H9/2 transitions of Dy3+ ion, respectively. The energy transfer from Dy3+ to Eu3+ ions in Ca3MgSi2O8:Eu3+, Dy3+ phosphor can be confirmed by the spectral properties. The tunable emission properties of Ca3MgSi2O8:Eu3+, Dy3+ phosphor from yellow-green to red-orange can be fulfilled by the change of the excitation wavelength or the concentration proportion between Dy3+ and Eu3+ ions. The luminous mechanism and energy transfer of Ca3MgSi2O8:Eu3+, Dy3+ phosphor are explained by the energy level diagrams of Eu3+ and Dy3+ ions.

Donor-Acceptor structured phenylmethylene pyridineacetonitrile derivative with aggregation-induced emission characteristics: photophysical, mechanofluorochromic and electroluminescent properties

Development of organic luminescent materials which are highly emissive in aggregation state is of great significance in practical applications. In this work, a phenylmethylene pyridineacetonitrile derivative fluorophore p-DBCNPy was synthesized via Knoevenagel condensation in good yield and its structure was characterized. p-DBCNPy exhibited evident aggregation-induced emission (AIE) feature and remarkable solvatochromic effect. The solid powder of p-DBCNPy emitted green fluorescence with a quantum yield of 0.59. Taking the advantages of the high emission efficiency and thermal stability, p-DBCNPy was employed as the light emitting material in an organic light-emitting diode (OLED) device and showed good potential in electroluminescent applications. Moreover, the fluorophore demonstrated reversible mechanochromism behavior which was ascribed to the transformation between the crystalline and amorphous phase. The greenish-yellow emission of p-DBCNPy powder turned orange with a red shift of over 40 nm upon grinding. The results demonstrated the versatilities of phenylmethylene pyridineacetonitrile derivatives in the applications in mechanochromism and optoelectronics.

Heteroctanuclear Au4Ag4 Cluster Complexes of 4,5-Diethynylacridin-9-One with Luminescent Mechanochromism.

Two heteroctanuclear Au4Ag4 cluster complexes of 4,5-diethynylacridin-9-one (H2L) were prepared through the self-assembly reactions of [Au(tht)2](CF3SO3), Ag(tht)(CF3SO3), H2L and PPh3 or PPh2Py (2-(diphenylphosphino)pyridine). The Au4Ag4 cluster consists of a [Au4L4]4− and four [Ag(PPh3)]+ or [Ag(PPh2Py)]+ units with Au4L4 framework exhibiting a twisted paper clip structure. In CH2Cl2 solutions at ambient temperature, both compounds show ligand fluorescence at ca. 463 nm as well as phosphorescence at 650 nm for 1 and 630 nm for 2 resulting from admixture of 3IL (intraligand) of L ligand, 3LMCT (from L ligand to Au4Ag4) and 3MC (metal-cluster) triplet states. Crystals or crystalline powders manifest bright yellow-green phosphorescence with vibronic-structured emission bands at 530 (568sh) nm for complex 1 and 536 (576sh) nm for complex 2. Upon mechanical grinding, yellow-green emission in the crystalline state is dramatically converted to red luminescence centered at ca. 610 nm with a drastic redshift of the emission after crystal packing is destroyed.

Solvent-driven thiol protected luminescent cobalt nanoclusters

The choice of solvent in the wet chemical synthesis of metal nanoclusters plays a critical role in engineering the cluster size, stoichiometry composition, geometric configurations and activity via regulating the adsorption of thiol staple motifs over the core of these nanoclusters. Herein, we report a facile synthesis of thiophenol(TP) stabilized cobalt nanoclusters (CoNCs) in a DMSO medium by chemical reduction method. The significant impact of solvents over CoNCs was explored by altering the chemical environment of NCs with definite volume fractions of polar protic (Chloroform, Acetic acid) and aprotic (DMSO, Acetone) solvents. The tunable H-bonding ability of polar protic solvents with varying dipole moments induces changes in the physicochemical properties of CoNCs. On the other hand, the use of polar aprotic solvents influences the Co(II)-SR staple motifs to aggregate over CoNCs. The stability of CoNCs with aprotic solvent i.e., acetone was accompanied with etching, gives rise to the changes in the molecular composition leading to structure-property changes. The insights on solvent-dependent properties might be from the synergetic factors of hydrogen bonding and hydrophobic interactions between thiol and solvent molecules. The solvent-derived structure-property changes were confirmed using TEM, UV–visible absorption studies, XRD, FT-IR, Raman, MALDI-MS analysis, photoluminescence and lifetime decay studies. The PL emission peak of CoNCs in DMSO observed at 440 nm (blue emission) is red-shifted to 555 nm with greenish-yellow emission, while changing the environment with less polar aprotic acetone as a solvent. In the polar protic solvent environment, the crucial role of H-bonding interactions promotes the emission peak at 562 nm by activating a new emissive state along with 440 nm emission. The cytotoxicity examination of these CoNCs compounds on MCF-7 cells has indicated their biocompatibility and non-toxic property as an alternative agent for bioimaging and biolabeling for research aspects in in-vitro studies. This work addresses the impact of different polar solvent environments and their substantial dependency on the structure-property correlation of aromatic thiol stabilized cobalt nanoclusters and their applicability for cell imaging in biomedical research.

One-step hydrothermal synthesis of fluorescent silicon nanoparticles for sensing sulfide ions and cell imaging

We have presented a hydrothermal approach for synthesizing fluorescent silicon nanoparticles (F-SiNPs) with yellow-green emission. The obtained F-SiNPs exhibited excellent stability and good biocompatibility. By virtue of the specific reaction between S2- and 5,5′-dithiobis-(2-nitrobenzoic acid) (DTNB), colorimetric assay of S2- was realized with a good linear range of 0–100 μM. The colorimetric detection system could be further combined with F-SiNPs to construct a probe for fluorescence turn-off sensing S2- in aqueous solution due to inner filter effect. In the fluorescent detection system, a good linearity with S2- concentration in the range of 0–50 μM was accomplished. And as low as 0.1 μM S2- was successfully detected. Moreover, the F-SiNPs displayed low cytotoxicity and good biocompatibility, and was further utilized for cell imaging. These results demonstrated the promising applications of F-SiNPs in S2- analysis and bioimaging.

Luminescence properties of Yb3+ and Er3+ co-doped into Gd2O3:Bi3+ phosphor powder

Yb3+ and Er3+ co-doped Gd2O3:Bi3+ phosphor were prepared via a combustion method. The structural properties and surface morphology of the phosphors were studied with X-ray diffraction and a scanning electron microscope. UV–visible absorption, photoluminescence and cathodoluminescence (CL) spectra were also investigated. The optical bandgap of Gd2O3 increased with additional doping. The visible emission confirmed that the Gd2O3:Bi3+ co-doped with Yb3+ is located in the blue and green band regions related to the Bi3+ in the S6 and C2 symmetry sites. The near-infrared (NIR) down-conversion (DC) emission intensity increased upon increasing the Yb3+ concentration. The visible Bi3+ emission was reduced when adding a higher Yb3+ ion concentration while the NIR emission increased due to the energy transfer from the Bi3+ to the Yb3+ ions. UV-Vis energy excitation photons were successfully converted into NIR photons. The up-conversion (UC) visible emission spectra of Gd2O3:Bi3+ co-doped Er3+ consisted of two strong green, weak red and NIR emission bands. The 980 nm infrared excitation was successfully converted into UV-Vis emission. The CL emission spectra confirmed blue emission bands assigned to the 3P1 → 1S0 transitions of the Bi3+ ions and the green-yellow emission bands corresponded to an overlap between the 3P1 → 1S0 transitions of the Bi3+ ions and the 2H11/2, 4S3/2 → 4I15/2 transitions of the Er3+ ions. A significant enhancement of the emission intensities of Yb3+ and Er3+ ions was observed after Bi3+ doping. The results indicated that Gd2O3 materials based on the Bi3+–Yb3+ and Bi3+–Er3+ couples may be possible phosphors for improving photovoltaic conversion efficiency via spectral modification utilizing the DC and UC processes.

Multifunctional ratiometric fluorescent sensing platform constructed by grafting various response groups on carbon dots with bromine active site for biosensing and bioimaging

Multifunctional sensing platform with the advantages of simplicity, convenience and efficiency is critical to the improvement of application in biosensing and bioimaging. However, the lack of easily modified scaffold materials seriously hinders its various responsive sensing development. To solve this issue, a novel kind of carbon dots (namely rCDs) with easily modified bromine substitution site was developed by one-step solvothermal treatment of citric acid, ethylenediamine and 4-bromo-1,8-naphthalic anhydride. Benefiting from the maintained structure of naphthalimide structure with bromine substitution site to contribute responsive yellow-green fluorescence emission and the stable blue fluorescence emission from citric acid and ethylenediamine, dual emissive ratiometric sensors based on rCDs could be conveniently fabricated by avoiding the combination of two components with distinct emission wavelength together. As proof, three ratiometric fluorescent probes for sensing formaldehyde (rCDs-FA), HSO3- (rCDs-HSO3-) and pH (rCDs-pH) featuring high stability, selectivity and biocompatibility were simply prepared. Moreover, the as-obtained probes were successfully applied to monitor dynamic variations of formaldehyde, HSO3- and pH changes in living cells. Taken together, the established multifunctional ratiometric fluorescent sensing platform could be simply and effectively regulated through changing the grafted response groups. This work would provide a universal method to design more biosensing or bioimaging platforms by adjusting response groups in the future.

Self-recovering mechanochromic luminescence of the derivatives of benzanthrone and carbazole: Towards damage-resistive information recording and security probes

Discovery of organic luminophores with unique properties typically leads to new applications of such emitters in the field of organic optoelectronics. The example is demonstrated in this study. One of the newly synthesized mechanochromic derivatives of benzanthrone and carbazole demonstrates ability of self-regulation of its solid-state structure and related light-emitting properties. This compound shows intensive green emission peaking at 537 nm in the initial state, weak yellowish green emission peaking at 557 nm after mechanical treatment which self-recovers back to intensive green emission with the intensity maximum at 539 nm. The processes are completely reversible. They include the following set of states: highly emissive state → damaged weak-emissive state → self-recovering → recovered highly emissive state. The developed compound is a very rare example of materials which can be used for security probes or data/code writing with recovering ability after mechanical damage. Variety of experimental studies including spectroscopy of thermally annealed samples and single crystal and powder diffraction X-ray analysis revealed the ability of the developed derivatives of benzanthrone and carbazole to form different polymorphs and aggregates in solid-state responsible for their multicolour mechanochromic emission.

Lattice-site engineering in ZnGa2O4:Cr3+ through Li+ doping for dynamic luminescence and advanced optical anti-counterfeiting

Doping Li+ resulted in oxygen vacancies and green-yellow emission. Changing the excitation wavelength/temperature yielded varied visible/NIR lights and afterglows, which contributed to a dynamic luminescence.

A coumarin coupled tetraphenylethylene based multi-targeted AIEgen for cyanide ion and nitro explosive detection, and cellular imaging.

A coumarin coupled tetraphenylethylene based AIEgen (TPE-Lac) with an intense greenish-yellow emission has been synthesized and utilized for multipurpose sensing and imaging applications. TPE-Lac acts as a sensitive sensor for the detection of cyanide ions (CN-) with an immediate turn-off response in the presence of many other interfering cations and anions. The limit of detection (LOD) was as low as 33 nM, which is well below the permissible limit set by the World Health Organization (WHO). Cyanide detection in the solid phase was successfully demonstrated by drop-casting the solution of the TPE-Lac probe on TLC plates and measuring and analysing the fluorescence response by ImageJ analysis. TPE-Lac was further employed in the detection of explosive nitroaromatics in solution and solid phases. Also, TPE-Lac was found suitable as an imaging agent and could easily percolate into live H520 cells giving bright fluorescence from the intra-cellular region. Easy and cost-effective synthesis, fast response and low LODs are some of the advantages of this AIEgen over available molecular probes for the same purpose.

Benzothiadiazole-based fluorophores as efficient non-doped emitters for solution-processed organic light-emitting diodes

New HLCT fluorophores are synthesized and successfully applied as non-doped emissive layers in solution-processed double-layered OLEDs. These devices exhibit intense yellow-green emission colors with superior performance.