Structural Confinement and Energetic Matching Synergistic Effect toward a High-Energy Transfer Efficiency and a Significant Red Emission Enhancement in a Eu2+,Ln3+ Co-doped Sr9LiMn(PO4)7 Whitlockite Phosphor.

Despite an encouraging progress, Mn2+-activated red phosphors suffer from an insufficient emission intensity and a bad color purity. Thus, it is necessary to find a new strategy to realize a bright red emission through highly efficient Mn2+ sensitization. Herein, manipulating Eu2+-sensitized Sr9LiMn(PO4)7 (SLMP) composition by Ln3+ heterovalent substitution is proved to be able to substantially gain a tremendous Mn2+ emission enhancement and result in a dominant red Mn2+ emission. It is found that the emission enhancement ratio is proportional to the order of lanthanide contraction. Notably, Tb3+ doping realizes a 427-fold rise in the integrated emission intensity compared with the SLMP host, which is close to the theoretical maximum of 500. An underlying mechanism for Mn2+ red emission enhancement is proposed, which is attributed to a high-energy transfer probability from Eu2+ to Mn2+ via Ln3+-induced further structural confinement plus an energetic match effect. Meanwhile, homovalent (Ca2+) substitution could precisely tailor Mn2+ emitting color from orange-red to deep red. A warm-white LED device with a low color temperature of 3394 K, a high color-rendering index of 90.2, and suitable CIE coordinates of (0.403, 0.373) is fabricated using optimized phosphor SLMP:Eu2+, Tb3+. These results might reveal a new strategy to develop new red-emitting phosphors with a bright and highly purified red Mn2+ emission.

Synthesis, molecular docking, and evaluation of antibacterial activity of 1,2,4-triazole-norfloxacin hybrids.

A series of 1,2,4-triazole-norfloxacin hybrids was designed, synthesized, and evaluated for in vitro antibacterial activity against common pathogens. All the newly synthesized compounds were characterized by Fourier-transform infrared spectrophotometry, proton and carbon nuclear magnetic resonance, and electrospray ionization-mass spectrometry. Representative compounds from each step of the synthesis were further characterized by X-ray crystallography. Many of the compounds synthesized exhibited antibacterial activity superior to that of norfloxacin toward both, gram-positive and gram-negative bacteria. The toxicity of the 1,2,4-triazole-norfloxacin hybrids toward bacterial cells was 32-512 times higher than that toward mouse fibroblast cells. Moreover, hemolysis was not observed at concentrations of 64 µg/mL, suggesting good biocompatibility. Molecular docking showed a least binding energy of -9.4 to -9.7 kcal/mol, and all compounds were predicted to show remarkable affinity for the bacterial topoisomerase IV.

Ultrahigh-Energy-Transfer Efficiency and Efficient Mn2+ Red Emission Realized by Structural Confinement in Ca9LiMn(PO4)7:Eu2+,Tb3+ Phosphor.

Structural confinement on Eu2+-Mn2+ optical centers is an effective strategy to boost Mn2+ red emission. On the basis of the Ca9LiMn(PO4)7 (CLMP) host with a compact Eu2+-Mn2+ distance of ∼3.5 Å, a pure and intense Mn2+ red emission without seeing Eu2+ emission is realized, indicating that an ultrahigh energy transfer (ET) could be induced by a structural confinement effect. It is found that the Mn2+ emission intensity and quantum efficiency could be further improved by a Tb3+ bridging effect, which offers extra energy levels to reduce the energetic mismatch between the excited states of Eu2+ and Mn2+. The optimal sample CLMP:0.02Eu2+,0.90Tb3+ shows a promising performance in terms of high color purity (93.9%), high quantum efficiency (QE = 51.2%), and good thermal stability (70% of the room-temperature value at 373 K). All of the results demonstrate that CLMP:Eu2+,Tb3+ phosphor is a promising red-light-emitting-diode phosphor, and the structural confinement effect should be developed as a general strategy to enhance the ET efficiency for a pure and efficient emission.

Photosensitizers with aggregation-induced far-red/near-infrared emission for versatile visualization and broad-spectrum photodynamic killing of pathogenic microbes.

The exploration of photosensitizers with aggregation-induced emission (AIE PSs) for efficient visualization and broad-spectrum photodynamic killing of pathogenic microbes is a significant task. Herein, two far-red/near-infrared AIE-active PSs (TBTPy and TBTCy) were attained to show efficient Type I and Type II ROS generation, benefiting from the efficient ISC processes. The attained AIE PSs, especially TBTPy with bright emission, showed advantages in discriminating G+ bacteria over G- bacteria, and distinguishing dead E. coli from lived one. Both TBTPy and TBTCy have the capacity of broad-spectrum photodynamic killing of pathogenic microbes in vitro with considerable safety for mammalian cells. Antimicrobial mechanism is found to be changing osmotic pressure of cytoplasm in E. coli, causing cell deformation and destruction of S. aureus and C. albicans. In vivo anti-infection experiment demonstrated AIE PSs can accelerate the healing process of the burned wounds on rats infected by methicillin-resistant S. aureus (MRSA) or E. coli, indicating their potential to treat tertiary burns in clinical application. Therefore, the attained AIE PSs hold great promise as antimicrobial candidates in infective therapeutic application.

High-efficient and pH-sensitive orange luminescence from silicon-doped carbon dots for information encryption and bio-imaging.

The exploration of carbon dots (CDs) with high quantum yield, facile synthesis path and satisfying output for their multiple applications remains a challenge. Thus, a silicon-doped orange-emitting carbon dots (O-CDs) is synthesized via a one-step hydrothermal method o-phenylenediamine and ethyl orthosilicate as raw materials. The O-CDs exhibits a bright and non-excitation-dependent emission peaking at 580 nm, and the corresponding quantum yield could be greatly boosted from 39.2 % to 64.1 % by silicon doping. The obtained O-CDs possess good biocompatibility and promising luminescence stability with varying solvents, ionic concentrations and temperatures. Its bio-imaging ability is performed by incubating zebrafish embryos with O-CDs aqueous solution, and clear in-vivo fluorescent images are obtained. Furthermore, due to its high-efficient and specific pH-sensitive emission with excellent dispersibility, the O-CDs can be used as a fluorescent ink for dual-model data encry/decryption in both hand-writing and stamp printing. Therefore, the as-prepared O-CDs show the potential as promising candidate for biomedical diagnosis, data encryption, and anti-counterfeiting.

Pb(II) detection and versatile bio-imaging of green-emitting carbon dots with excellent stability and bright fluorescence.

Green-emitting carbon dots (G-CDs) were synthesized via a simple and green hydrothermal method using betaine hydrochloride and sulfadiazine as carbon and nitrogen sources, respectively. Excellent luminescence stability with varying pH, salt concentrations, temperature is found with excitation-independent emission. G-CDs can be successfully used for the detection of Pb(ii) in the range of 0-200 µM. There was good linear relationship between the Pb(ii) concentration and G-CD fluorescence intensity with a correlation coefficient of 0.993, and the limit of detection (LOD) was 3.0174 µmol L-1. Due to its good biocompatibility, G-CDs can be successfully applied to zebrafish imaging as well as cell imaging, and the results show that G-CDs is more suitable for the zebrafish embryo imaging. Our results suggested that the obtained G-CDs can be used as multifunctional probes, highlighting their potential in different biological studies.

Tunable photoluminescence and energy transfer of Sr9LiMg(PO4)7: Ce3+/Tb3+/Mn2+ phosphors.

The Ce3+/Tb3+/Mn2+ activated color-tunable phosphors Sr9LiMg(PO4)7 (SLMP) were prepared by solid-state reaction with post-annealing treatment. The structural, static and time-resolved luminescent properties are studied in detail. XRD pattern showed the pure trigonal phase of Sr9LiMg(PO4)7 at an annealing temperature of 1300 °C. Ce3+-doped SLMP phosphor exhibits near-ultraviolet emission with peak-wavelength at 380 nm. Efficient Ce3+-Tb3+/Mn2+ energy transfer process is demonstrated by luminescence spectrum and luminescence lifetimes of as-prepared samples. The emitting-color of SLMP: Ce3+/Tb3+/Mn2+ was tunable through changing Ce3+/Tb3+/Mn2+ ratio. Emission peak intensity of SLMP: Ce3+, Tb3+ phosphor shows good thermal stability with rising temperature. These results suggest its great potential as luminescent materials with good performance for UV-excitable applications.