Synchronously Polishing the Lead-Rich Surface and Passivating Surface Defects of CsPb(Br/I)3 Quantum Dots for High-Performance Pure-Red PeLEDs.

Mixed-halide CsPb(Br/I)3 perovskite quantum dots (QDs) are regarded as one of the most promising candidates for pure-red perovskite light-emitting diodes (PeLEDs) due to their precise spectral tuning property. However, the lead-rich surface of these QDs usually results in halide ion migration and nonradiative recombination loss, which remains a great challenge for high-performance PeLEDs. To solve the above issues, we employ a chelating agent of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid hydrate (DOTA) to polish the lead-rich surface of the QDs and meanwhile introduce a new ligand of 2,3-dimercaptosuccinic acid (DMSA) to passivate surface defects of the QDs. This synchronous post-treatment strategy results in high-quality CsPb(Br/I)3 QDs with suppressed halide ion migration and an improved photoluminescence quantum yield, which enables us to fabricate spectrally stable pure-red PeLEDs with a peak external quantum efficiency of 23.2%, representing one of the best performance pure-red PeLEDs based on mixed-halide CsPb(Br/I)3 QDs reported to date.

High Efficiency and Low Roll-Off Pure-Red Perovskite LED Enabled by Simultaneously Inhibiting Auger and Trap Recombination of Quantum Dots.

CsPbI3 perovskite quantum dots (QDs) could achieve pure-red emission by reducing their size, but the increased exciton binding energy (EB) and surface defects for the small-sized QDs (SQDs) cause severe Auger and trap recombinations, thus worsening their electroluminescence (EL) performance. Herein, we utilize the dangling bonds of the SQDs as a driving force to accelerate KI dissolution to solve its low solubility in nonpolar solvents, thereby allowing K+ and I- to bond to the surface of SQDs. The EB of the SQDs was decreased from 305 to 51 meV because of the attraction of K+ to electrons, meanwhile surface vacancies were passivated by K+ and I-. The Auger and trap recombinations were simultaneously suppressed by this difunctional ligand. The SQD-based light-emitting diode showed a stable pure-red EL peak of 639 nm, an external quantum efficiency of 25.1% with low roll-off, and a brightness of 5934 cd m-2.

Hydrophobic Mn-Doped Solid-State Red-Emitting Carbon Nanodots with AIE Effect and Their Hydrogel Composites for Color-Changing Anticounterfeiting.

The aggregation-caused quenching has always limited the high concentration and solid-state applications of carbon nanodots. While the aggregation-induced emission effect, dominated by intramolecular motion, may be an effective means to solve this problem. Here, hydrophobic solid-state red-light carbon nanodots (M-CDs) with 95% yield are synthesized by a one-step hydrothermal method using 2,2'-dithiodibenzoic acid as the carbon source and manganese acetate as the dopant source. The disulfide bond of 2,2'-dithiodibenzoic acid serves as the symmetry center of molecular rotation and Mn catalyzes the synthesis of M-CDs, which promotes the formation of the central graphitic carbon structure. The M-CDs/agar hydrogel composites can achieve fluorescence transition behavior because of the special fluorescence transition properties of M-CDs. When this composite hydrogel is placed in water, water molecules contact with M-CDs through the network structure of the hydrogels, making the aggregated hydrogels of M-CDs fluorescence orange-red under 365 nm excitation. While in dimethyl sulfoxide, water molecules in the hydrogels network are replaced and the M-CDs fluoresce blue when dispersed, providing a potential application in information encryption. In addition, high-performance monochromatic light-emitting diode (LED) devices are prepared by compounding M-CDs with epoxy resin and coating them on 365 nm LED chips.

Highly Efficient Far-Red Emitting Mg21Ca4Na4(PO4)18: Ce3+, Eu3+ Luminescent Glasses: A Novel Approach Towards Plant Cultivation Technologies.

One of the exciting developments in contemporary luminescence research is the development of rare earth triggered luminescent glasses, which are a type of lanthanide activated luminous material. For the first time, Ce3+, Eu3+ activated/co-activated Mg21Ca4Na4(PO4)18 orthophosphate glasses have been synthesized using the proposed work's melt quenching technique. The proposed glass sample's XRD pattern has an amorphous character, although its most prominent peak matches data from the Mg21Ca4Na4(PO4)18 standard ICSD database. FT-IR analysis was used to analyze the proposed glass sample's vibrational characteristics. Co-activated Mg21Ca4Na4(PO4)18 glass exhibits large emission peaks under UV excitations that cover the far red area during a photoluminescence examination. These outcomes demonstrate the proposed sample's value in applications such as WLEDs and plant cultivation.

Carbon dots with enhanced red emission for ratiometric sensing and encryption applications.

The excitation-dependent emission properties of carbon dots (Cdots) are extensively reported, but their red emission is often weak, limiting their wider application. Here we introduce ethidium bromide, as a functional precursor with red emission, to enhance the red emission for Cdots, with comparable intensity at a broad wavelength range to multi-emission Cdots (M-Cdots). We found that Cdots prepared with ethidium bromide/ethylenediamine exhibited strong blue and red emission at 440 and 615 nm, with optimal excitation at 360 and 470 nm as M-Cdots, respectively, but the Cdots from single ethidium bromide (EB-Cdots) possessed weak red emission. M-Cdots exhibited a broad absorption band at 478 nm, but a band blue-shifted to 425 nm was observed for EB-Cdots, while no absorption was observed at 478-425 nm for the Cdots prepared with citric acid and ethylenediamine. Thus, we proposed that C=O and C=N formed a π-conjugation structure as the absorption band at 478 nm for the red emission of M-Cdots, as also confirmed with the excitation at 470 nm. Moreover, the π-conjugation structure is fragile and sensitive to harsh conditions, so red emission was difficult to observe for the Cdots prepared with citric acid/ethylenediamine or single ethidium bromide. M-Cdots possess two centers for blue and red emission with different structures. The dual emission was therefore used for ratiometric sensing with dichromate (Cr2O72-) and formaldehyde (HCHO) as the targets using the intensity ratio of the emissions at 615 and 440 nm. Due to the comparable intensity at a broad wavelength range, we designed encryption codes with five excitations at 360, 400, 420, 450, and 470 nm as the inputs, and the emission colors were used for information decoding. Thus, we determined why red emission was difficult to realize for Cdots, and our results could motivate the design of red-emission Cdots for extensive applications.

Promising deep-red emitting Cr3+-doped SrAl12O19 phosphors for plant growth LEDs.

Recently, deep-red-emitting phosphors that can be excited by ultraviolet (UV) and near-ultraviolet (NUV) light have been extensively investigated for plant growth LED applications. However, due to the harmful effects of these high-energy rays on plants, violet- or blue-excited deep-red-emitting phosphors are considered a more appropriate solution. In this work, SrAl12O19:Cr3+ phosphors were synthesized using a simple solid-state reaction, revealing a strikingly sharp deep-red emission band centered at 694 nm and effective excitation by violet light. The optimal SrAl12O19:1.0%Cr3+ phosphor, annealed at 1500°C, exhibits an extended lifetime of 0.549 ms, an energy activation level of 0.239 eV, a good quantum efficiency (QE) of 36.2%, and superior color purity at 100%. Further, an LED prototype with a precise absorption spectrum for far-red phytochrome (Pfr) has been demonstrated. These results indicate that the synthesized SrAl12O19:1.0%Cr3+ phosphors could be used as a promising deep-red-emitting phosphor for plant growth LED.

Exploring the role of neutral ligands in modulating the photoluminescence of samarium complexes with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione.

Four eight-coordinated luminescent samarium complexes of type [Sm(hfpd)3L2] and [Sm(hfpd)3L'] [where hfpd = 1,1,1,5,5,5-Hexafluoro-2,4-pentanedione L = tri-octyl-phosphine oxide (TOPO) and L' = 1,10-phenanthroline (phen), neocuproine (neoc) and bathocuproine (bathoc) were synthesized via a stoichiometrically controlled approach. This allows for precise control over the stoichiometry of the complexes, leading to reproducible properties. This investigation focuses on understanding the impact of secondary ligands on the luminescent properties of these complexes. Infrared (IR) spectra provided information about the molecular structures, whereas 1H and 13C nuclear magnetic resonance (NMR) spectra confirmed these structural details along with the coordination of ligands to trivalent Sm ion. The UV-vis spectra revealed the molar absorption coefficient and absorption bands associated with the hfpd ligand and photoluminescence (PL) spectroscopy demonstrated intense orange-red emission (648 nm relative to 4G5/2 → 6H9/2) from the complexes. The Commission Internationale de l'Éclairage (CIE) triangles indicated that the complexes emitted warm orange red light with color coordinates (x, y) ranging from (0.62, 0.36) to (0.40, 0.27). The investigation of the band gap as well as color parameters confirms the utility of these complexes in displays and LEDs.

A Red-Emission Fluorescent Probe for Intracellular Biothiols and Hydrogen Sulfide Imaging in Living Cells.

This research centers on the development and synthesis of a longwave fluorescence probe, labeled as 60T, designed for the simultaneous detection of hydrogen sulfide, cysteine/homocysteine, and glutathione. The probe showcases a swift response, good linearity range, and heightened sensitivity, boasting that the detection limits of the probe for Cys, Hcy, GSH and H2S were 0.140, 0.202, 0.259 and 0.396 µM, respectively. Notably, its efficacy in monitoring thiol status changes in live MCF-7 cells is underscored by a substantial decrease in fluorescence intensity upon exposure to the thiol trapping reagent, N-ethyl maleimide (NEM). With an impressive red emission signal at 630 nm and a substantial Stokes shift of 80 nm, this probe exhibits remarkable sensitivity and selectivity for biothiols and H2S, indicating promising applications in the diagnosis and surgical navigation of relevant cancers.

Nucleophilic Reaction-Enabled Chloride Modification on CsPbI3 Quantum Dots for Pure Red Light-Emitting Diodes with Efficiency Exceeding 26 .

High-performance pure red perovskite light-emitting diodes (PeLEDs) with an emission wavelength shorter than 650 nm are ideal for wide-color-gamut displays, yet remain an unprecedented challenge to progress. Mixed-halide CsPb(Br/I)3 emitter-based PeLEDs suffer spectral stability induced by halide phase segregation and CsPbI3 quantum dots (QDs) suffer from a compromise between emission wavelength and electroluminescence efficiency. Here, we demonstrate efficient pure red PeLEDs with an emission centered at 638 nm based on PbClx -modified CsPbI3 QDs. A nucleophilic reaction that releases chloride ions and manipulates the ligand equilibrium of the colloidal system is developed to synthesize the pure red emission QDs. The comprehensive structural and spectroscopic characterizations evidence the formation of PbClx outside the CsPbI3 QDs, which regulates exciton recombination and prevents the exciton from dissociation induced by surface defects. In consequence, PeLEDs based on PbClx -modified CsPbI3 QDs with superior optoelectronic properties demonstrate stable electroluminescence spectra at high driving voltages, a record external quantum efficiency of 26.1 %, optimal efficiency roll-off of 16.0 % at 1000 cd m-2 , and a half lifetime of 7.5 hours at 100 cd m-2 , representing the state-of-the-art pure red PeLEDs. This work provides new insight into constructing the carrier-confined structure on perovskite QDs for high-performance PeLEDs.

Red Emission Carbon Nanoparticles Which Can Simultaneously Responding to Hypochlorite and pH.

Multi-targets detection has obtained much attention because this sensing mode can realize the detection of multi-targets simultaneously, which is helpful for biomedical analysis. Carbon nanoparticles have attracted extensive attention due to their superior optical and chemical properties, but there are few reports about red emission carbon nanoparticles for simultaneous detection of multi-targets. In this paper, a red emission fluorescent carbon nanoparticles were prepared by 1, 2, 4-triaminobenzene dihydrochloride at room temperature. The as-prepared red emission fluorescent carbon nanoparticles exhibited strong emission peak located at 635 nm with an absolute quantum yield up to 24%. They showed excellent solubility, high photostability and good biocompatibility. Furthermore, it could sensitively and selectively response to hypochlorite and pH, thus simultaneous detection of hypochlorite and pH was achieved by combining the red emission fluorescent carbon nanoparticles with computational chemistry. The formation mechanisms of red emission fluorescent carbon nanoparticles and their response to hypochlorite and pH were investigated, respectively.

Recent advances of organic emitters in deep-red light-emitting electrochemical cells.

Light-emitting electrochemical cells (LECs) are kind of easily fabricated and low-cost light-emitting devices that can efficiently convert electric power to light energy. Compared with blue and green LECs, the performance of deep-red LECs is limited by the high non-radiative rate of emitters in long-wavelength region. While various organic emitters with deep-red emission have been developed to construct high-performance LECs, including polymers, metal complexes, and organic luminous molecules (OLMs), but this is seldom summarized. Therefore, we overview the recent advances of organic emitters with emission at the deep-red region for LECs, and specifically highlight the molecular design approach and electrochemiluminescence performance. We hope that this review can act as a reference for further research in designing high-performance deep-red LECs.

High-Efficiency Pure-Red Perovskite Quantum-Dot Light-Emitting Diodes.

It is still challenging to achieve high-efficiency pure-red (620-650 nm wavelength) perovskite light-emitting diodes (PeLEDs). Herein, we report pure-red PeLEDs with Commission Internationale de l'Eclairage coordinates (0.703, 0.297) meeting the Rec. 2020, an external quantum efficiency of 20.8%, and a luminance of 3775 cd/m2. This design is based on the strong quantum confinement CsPbI3 quantum dots (QDs) capped by composite ligands of 3-phenyl-1-propylamine and tetrabutylammonium iodide. This strategy stabilized the structure of the strong-confined QDs and reduced the influence of the electric field-induced Stark effect on the PeLEDs. Furthermore, the exciton binding energy of the QDs was decreased by the composited ligands to suppress Auger recombination within the devices. Additionally, the valence-band maximum of the QDs was lifted to match the hole-transport layer, thus balancing charge injection in the PeLEDs. Our device also demonstrated a stable electroluminescence spectrum and a lifetime of 5.6 times longer than the control device.

Lighting-Up the Far-Red Fluorescence of RNA-Selective Dyes by Switching from Ortho to Para Position.

Fluorescence imaging is constantly searching for new far-red emitting probes whose turn-on response is selective upon the interaction with specific biological targets. Cationic push-pull dyes could indeed respond to these requirements due to their intramolecular charge transfer (ICT) character, by which their optical properties can be tuned, and their ability to interact strongly with nucleic acids. Starting from the intriguing results recently achieved with some push-pull dimethylamino-phenyl dyes, two isomers obtained by switching the cationic electron acceptor head (either a methylpyridinium or a methylquinolinium) from the ortho to the para position have been scrutinized for their ICT dynamics, their affinity towards DNA and RNA, and in vitro behavior. By exploiting the marked fluorescence enhancement observed upon complexation with polynucleotides, fluorimetric titrations were employed to evaluate the dyes' ability as efficient DNA/RNA binders. The studied compounds exhibited in vitro RNA-selectivity by localizing in the RNA-rich nucleoli and within the mitochondria, as demonstrated by fluorescence microscopy. The para-quinolinium derivative showed some modest antiproliferative effect on two tumor cell lines as well as improved properties as an RNA-selective far-red probe in terms of both turn-on response (100-fold fluorescence enhancement) and localized staining ability, attracting interest as a potential theranostic agent.

Investigation into Red Emission and Its Applications: Solvatochromic N-Doped Red Emissive Carbon Dots with Solvent Polarity Sensing and Solid-State Fluorescent Nanocomposite Thin Films.

In this work, a NIR emitting dye, p-toluenesulfonate (IR-813) was explored as a model precursor to develop red emissive carbon dots (813-CD) with solvatochromic behavior with a red-shift observed with increasing solvent polarity. The 813-CDs produced had emission peaks at 610 and 698 nm, respectively, in water with blue shifts of emission as solvent polarity decreased. Subsequently, 813-CD was synthesized with increasing nitrogen content with polyethyleneimine (PEI) to elucidate the change in band gap energy. With increased nitrogen content, the CDs produced emissions as far as 776 nm. Additionally, a CD nanocomposite polyvinylpyrrolidone (PVP) film was synthesized to assess the phenomenon of solid-state fluorescence. Furthermore, the CDs were found to have electrochemical properties to be used as an additive doping agent for PVP film coatings.

Two Novel Neutral Cyclometalated Iridium(III) Complexes Based on 10,11,12,13-Tetrahydrodibenzo[a,c]phenazine for Efficient Red Electroluminescence.

Two novel neutral phosphorescent iridium(III) complexes (Ir1 and Ir2) were rationally designed and synthesized with high yields using 10,11,12,13-tetrahydrodibenzo[a,c]phenazine as the main ligand. The two complexes showed bright-red phosphorescence (625 nm for Ir1, and 620 nm for Ir2, in CH2Cl2), high-luminescence quantum efficiency (0.32 for Ir1, and 0.35 for Ir2), obvious solvatochromism and good thermostability. Then, they were used to fabricate high-efficiency red OLEDs via vacuum evaporation; the maximum current efficiency, power efficiency, and external quantum efficiency of the red devices based on Ir1 and Ir2 are 13.47/15.22 cd/A, 10.35/12.26 lm/W, and 10.08/7.48%, respectively.

Red Emissive Double Aza[7]helicenes with Antiaromaticity / Aromaticity Switching via the Redox-Induced Radical Cation and Dication Species.

We herein present the synthetic approach to a new antiaromatic double aza[7]helicene C that features NN-embedded polycyclic aromatic hydrocarbons (PAHs). This heteroatom-doped helicene showed a rarely obtained long-wavelength emission and far-red circularly polarized luminescence (CPL) in the solid state. These optical and chiroptical properties could be ascribed to both the NN-PAH core structure and the further extension through angular ring fusions. Such a unique electronic structure also culminated in facile chemical oxidations of neutral C to the positively charged chiral radical (C⋅+ ) and dication species (C2+ ). Interestingly, DFT computations revealed that the pyridazine central core showed an antiaromaticity-to-aromaticity switching, in contrast to the inversed transition for the helical periphery in cationic states. The reported approaches are anticipated to lead to the development of further redox-active chiral systems for potential applications in chiroptoelectronics, spintronics as well as fluorescent bioimaging.

Hyperbranched Polyborosiloxanes: Non-traditional Luminescent Polymers with Red Delayed Fluorescence.

Non-traditional fluorescent polymers have attracted significant attention for their excellent biocompatibility and diverse applications. However, designing and preparing non-traditional fluorescent polymers that simultaneously possess long emission wavelengths and long fluorescence lifetime remains challenging. In this study, a series of novel hyperbranched polyborosiloxanes (P1-P4) were synthesized. As the electron density increases on the monomer diol, the optimal emission wavelengths of the P1-P4 polymers gradually red-shift to 510, 570, 575, and 640 nm, respectively. In particular, P4 not only exhibits red emission but also demonstrates delayed fluorescence with a lifetime of 9.73 µs and the lowest critical cluster concentration (1.76 mg/mL). The experimental results and theoretical calculations revealed that the synergistic effect of dual heteroatom-induced electron delocalization and through-space O⋅⋅⋅O and O⋅⋅⋅N interaction was the key factor contributing to the red-light emission with delayed fluorescence. Additionally, these polymers showed excellent potential in dual-information encryption. This study provides a universal design strategy for the development of unconventional fluorescent polymers with both delayed fluorescence and long-wavelength emission.

Boron-Dipyrromethene-Based Fluorescent Emitters Enable High-Performance Narrowband Red Organic Light-Emitting Diodes.

Narrowband organic light-emitting diodes (OLEDs) are receiving significant attention and have demonstrated impressive performance in blue and green OLEDs. However, developing high-performance narrowband red OLEDs remains a highly desired yet challenging task. Herein, we have developed narrowband red fluorescent emitters by utilizing a boron-dipyrromethene (BODIPY) skeleton in combination with a methyl-shield strategy. These emitters exhibit small full-width at half-maxima (FWHM) ranging from 21 nm (0.068 eV) to 25 nm (0.081 eV) and high photoluminescence quantum yields (ΦPL ) ranging from 88.5 % to 99.0 % in toluene solution. Using BODIPY-based luminescent materials as emitters, high-performance narrowband red OLEDs have been assembled with external quantum efficiency as high as 18.3 % at 623 nm and 21.1 % at 604 nm. This work represents, to our knowledge, the first successful case of achieving NTSC pure-red OLEDs with the Commission Internationale de l'Éclairage (CIE) coordinates of [0.67, 0.33] based on conventional fluorescent emitters.

Red-emitting heteroleptic iridium(III) complexes: photophysical and cell labeling study.

Two red-emitting heteroleptic iridium(III) complexes (Ir-p and Ir-q) were synthesized and their photophysical and biological properties were analyzed. After their structures have been confirmed by several techniques, such as 1H NMR, 13C NMR, FT-IR, UV-Vis, and MALDI TOF analyses, their luminescence behavior was investigated in ethanol and PBS (physiological medium, pH ~ 7.4) solutions. Emission spectra of both complexes are dominated by 3MLCT states at room temperature in ethanolic solution, but at 77 K the Ir-q exhibits the 3LC as the dominant emission state. The Ir-q complex shows one of the highest emission quantum yields, 11.5%, for a red emitter based on iridium(III) complexes in aerated PBS solution, with color coordinates (x;y) of (0.712;0.286). Moreover, both complexes display high potential to be used as a biological marker with excitation wavelengths above 400 nm, high water solubility (Ir-p 1838 µmol L-1, Ir-q 7601 µmol L-1), and distinct emission wavelengths from the biological autofluorescence. Their cytotoxicity was analyzed in CHO-k1 cells by MTT assays, and the IC50 was estimated as being higher than 131 µmol L-1 for Ir-p, and higher than 116 µmol L-1 for Ir-q. Concentrations above 70% of viability were used to perform cell imaging by confocal and fluorescence microscopies and the results suggest that the complexes were internalized by the cell membrane and they are staining the cytoplasm region.

Surface engineered bimetallic gold/silver nanoclusters for in situ imaging of mercury ions in living organisms.

Chemical sensing for the sensitive and reliable detection of mercury(II) ions (Hg2+) is of great importance in environmental protection, food safety, and biomedical applications. Due to the bio-enrichment property of Hg2+ in organisms, it is particularly meaningful to develop an effective tool that can in situ and rapidly monitor the level of Hg2+ in living organisms. In this work, we report ligand functionalized gold-silver bimetallic nanoclusters with bright red fluorescence as intracellular probes for imaging Hg2+ in living cells and zebrafish. The bimetallic nanoclusters of DTT-GSH@Au/AgNCs (DG-Au/AgNCs) with strong fluorescence that benefited from the synergistic effect of Au and Ag atoms were obtained through a one-pot synthesis method, incorporating glutathione (GSH) and dithiothreitol (DTT) as the reducers and functionalized ligands. Attractively, the bright red fluorescence of DG-Au/AgNCs could be rapidly and selectively quenched by Hg2+ within 1 min with a very low detection limit of 1.01 nM. Additionally, DG-Au/AgNCs had a great advantage in the detection of Hg2+ in living cells and zebrafish owing to its notably strong red fluorescence at 665 nm, which could avoid effectively auto-fluorescence interference from the organism. Such easily prepared bimetallic fluorescent nanoclusters would be expected to provide a noninvasive and sensitive approach in the detection of heavy metals in situ for environmental protection.