Maximum Emission Peak Research Articles

Novel fluorescent sensor based on triazole-pyridine derivative for selective detection of mercury (II) ions in different real water samples: Experimental and DFT calculations

Toxic heavy metals, particularly mercury II ions, must be selectively detected in industrial effluent to restrict their percentage and thereby aid in environmental protection. The present study describes the synthesis of 6-(4-(4-(5-cyano-6-oxo-4-styryl)-1,6-dihydropyridin-2-yl)-5-methyl-1H-1,2,3-triazol-1-yl)phenyl)-2-oxo-4-styryl)-1,2-dihydropyridine-3-carbonitrile (TOHC) and its ability as a novel selective fluorescent probe for the detection of mercury II ions in different real water samples. The structure of the prepared TOHC was confirmed by both FTIR and 1HNMR analysis, while crystal structure and thermal stability was investigated using XRD and TGA techniques. The optical properties of TOHC were investigated using both UV–vis and fluorescence spectroscopy at different pH values. Its luminescent properties obtained when TOHC is excited by a wavelength equal to 424 nm, where a maximum emission peak has observed at a wavelength equal to 466.6 nm. Moreover, using Stern-Volmer equation indicate that there is a good correlation between the concentration of Hg2+ ions and the fluorescence intensity of TOHC accompanied with high quenching rate equal to 2.24 x 104 mol−1.L. Selectivity of TOHC toward Hg2+ ions was confirmed by the assistance of fifteen different metal cations. In addition, Job’s Plot method and UV–vis spectroscopy were used to estimate the stoichiometry as well as understand the quenching mechanism between TOHC sensor and Hg2+ ions. The applicability of TOHC sensor for the detection of Hg2+ ions in real samples was further validated using five different real water samples and exhibited excellent results. Lastly, DFT calculations were conducted to provide atomistic insights into the chemical interaction between Hg(II) and TOHC sensor.

Novel fluorescent probes based on sulfur and nitrogen co-doped carbon dots for determination of three N-substituted phenothiazine derivatives in dosage forms

In the current work, sulfur and nitrogen co-doped carbon dots (S,N-CDs) as simple, sensitive, and selective turn-off fluorescent nanosensors were utilized for analysis of three phenothiazine derivatives, including acetophenazine (APZ), chlorpromazine (CPH), and promethazine (PZH). S,N-CDs were synthesized through a green one-pot microwave-assisted technique using widely available precursors (thiourea and ascorbic acid). HRTEM, EDX, FTIR spectroscopy, UV–Vis absorption spectroscopy, and fluorescence spectroscopy were used to characterize the as-synthesized CDs. When excited at 330 nm, the carbon dots produced a maximum emission peak at 410 nm. The cited drugs statically quenched the S,N-CDs fluorescence as revealed by the Stern-Volmer equation. The current method represents the first spectrofluorimetric approach for the determination of the studied drugs without the need for chemical derivatization or harsh reaction conditions. The importance of the proposed work is magnified as the cited drugs do not have any fluorescent properties. The fluorescence of the developed sensor exhibited a linear response to APZ, CPH, and PZH in the concentration ranges of 5.0–100.0, 10.0–100.0, and 10.0–200.0 μM with detection limits of 1.53, 1.66, and 2.47 μM, respectively. The developed fluorescent probes have the advantages of rapidity and selectivity for APZ, CPH, and PZH analysis in tablets with acceptable % recoveries of (98.06–101.66 %). Evaluation of the method's greenness was performed using the Complementary Green Analytical Procedure Index (ComplexGAPI) and Analytical GREEnness metric (AGREE) metrics, indicating that the method is environmentally friendly. Validation of the proposed method was performed according to ICHQ2 (R1) guidelines.

Optical properties of pure and Sn-doped β-Ga2O3 single crystals grown by optical float zone technique

High-quality single crystals of both pure and Sn:β-Ga2O3 single crystals weregrown using the optical floating zone technique and a comprehensive study of its luminescence and scintillation properties was carried out. The pure and Sn:β-Ga2O3 grown crystals were oriented along (100) by Laue diffraction pattern and its monoclinic structure was confirmed using a single crystal XRD. X-ray induced luminescence spectrum shows a maximum emission peak at 365 nm. The cut off wavelength was observed around 258 nm and the optical band gap was calculated to be 4.64 eV from UV–Vis-NIR transmission spectroscopy. The room temperature Raman spectra were recorded and the various vibration modes were investigated. Low temperature (10 to 300 K) and high temperature (325 to 675 K) TL measurements were carried out on X-ray irradiated crystals and its TL kinetic parameters such as activation energy (eV) and frequency factor (S) were calculated. Scintillation decay time profiles were measured for both pure and Sn-doped crystals under 137Cs γ-ray excitation. The calculated scintillation light output is 2300 Ph/5.5 Mev for Sn:β-Ga2O3 crystal under α-particle excitation from 241Am radiation source.

Fluorescent carbon dots for highly sensitive diosmetin sensing

In this paper, a single signal fluorescent sensor of nitrogen-doped carbon dots (N-CQDs) was established for the micro-determination of diosmetin. In this determination platform, the as-developed N-CQDs with yellow fluorescence were prepared through a facile hydrothermal method with p-phenylenediamine and ascorbic acid as the precursors containing nitrogen and carbon. The as-developed N-CQDs had a classical surface structure and surprising fluorescence stability. The maximum excitation and emission peaks were located at 372 and 528 nm, respectively. Under the optimal sensing conditions, the as-prepared N-CQDs held preeminent immunity towards possible interfering substances. The determination platform’s fluorescence intensity was quenched because of the static quenching and inner filter effect. The fluorescence weakening changes displayed an attractive linear relationship with diosmetin in range of 0.5–150 μM, and the linear equation was ln(F0/F) = 0.014[Q]–0.055 with the R2 of 0.9975 and the detection limit of 0.049 μM. The determination platform could be applied for the trace detection of diosmetin in river water and bovine serum samples. The corresponding recovery rate was 94.8 %–108.8 %, exhibiting that it was a facile and efficient fluorescence sensing strategy.

Ce3+-Activated SrLu2Al3ScSiO12 Cyan-Green-Emitting Garnet-Structured Inorganic Phosphor Materials toward Application in Blue-Chip-Based Phosphor-Converted Solid-State White Lighting.

Phosphor-converted white-light-emitting diodes (WLEDs) with superhigh color rendering index (CRI) are the ongoing pursuit of next-generation solid-state lighting. One of the most important challenges is the limited improvement in CRI on account of the absence of a cyan component in the typical commercial combination. Here, a bright broad-band cyan-green-emitting phosphor with cubic garnet structure, SrLu2Al3ScSiO12:Ce3+ (SLASSO:Ce3+), was successfully reported, which can compensate for the absence of cyan cavity in the 480-520 nm blue-green emission region. With 439 nm blue-light irradiation, the as-fabricated SLASSO:Ce3+ phosphor yields a broad-band cyan-green emission with the maximum emission peak positioned at 525 nm and an appropriate full width at half-maximum (fwhm) of 111 nm, capable of providing more cyan emission component without sacrificing green emission. Meanwhile, the optimal SLASSO:2%Ce3+ phosphor features CIE color coordinates of (0.3254, 0.5470) with cyan-green hue, along with a high internal quantum efficiency of up to 93%. Additionally, thermal stability measurements at different temperatures reveal that the luminescence emission intensity of the proposed phosphor retains 44% of its original integral emission intensity at 423 K with respect to room temperature, while also demonstrating an excellent color stability (ΔE = 5.4 × 10-3). This work shows that the highly efficient SLASSO:Ce3+ garnet phosphor can be utilized as a potential cyan-green-emitting phosphor for filling the cyan gap, resulting in the construction of a high-quality warm WLED with high CRI for "human-centric" sunlight-like full-spectrum solid-state illumination.

Tuning the fluorescence emission of water-stable CsPb(Br/I)3 perovskite nanocrystal probes for naked-eye visual detection of mercury ion

All-inorganic cesium lead halide perovskite nanocrystals (PNCs) have rarely been reported in analytical chemistry, especially in water environment analysis, due to their high susceptibility to environmental conditions. Herein, we investigate and report a method of visual detection of Hg2+ concentration in aqueous solution using CsPb(Br/I)3 PNCs. In this strategy, three kinds of CsPb(Br/I)3 PNCs with FL emission peaks of 551 nm, 591 nm, and 617 nm were used to detect Hg2+, and it was found that Hg2+ can quench the fluorescence of CsPb(Br/I)3 PNCs and blue-shift the maximum FL emission peak. We also found that the Hg2+ concentration has a good linear relationship with the fluorescence quenching rate (I0/I) and FL emission peak shift (Δλ) of CsPb(Br/I)3 PNCs. With the red-shift of the probe FL emission peak, the detected concentration range of Hg2+ gradually expanded. Therefore, the possibility of detecting Hg2+ concentration without huge equipment was detailed by examining the red (R), green (G), and blue (B) values of photographs of CsPb(Br/I)3 PNCs with Hg2+. Under a 365 nm ultraviolet (UV) lamp, the solution color of CsPb(Br/I)3 PNCs emission peaks at 591 nm gradually changes from orange to green with the increase of Hg2+ concentration, which has an excellent visualization effect. The method presented here has the potential to establish a new analytical method for the visual detection of Hg2+ in aqueous environments, and may also facilitate the application of all-inorganic cesium lead halide perovskite nanocrystals for analytical detection in aqueous environments.

Cyanine based ratio fluorescent probe and its application in hypochlorite detection

Hypochlorite (ClO−), a weakly acidic reactive oxygen species, plays a crucial role in antibacterial and anti-inflammatory defense mechanisms. However, elevated levels of ClO− or disruptions in endogenous sites can lead to tissue damage and various diseases including cardiovascular disease, neuronal degeneration, and arthritis. To address this, the development of a specific fluorescent probe with a built-in self-calibration ratio mode for the analysis and biological imaging of ClO− is essential. In this study, a cyanine-based fluorescent probe (Cy-H) was designed for ratiometric fluorescent detection of ClO−, utilizing its aggregation behavior as a novel approach in this field. Upon exposure to ClO−, the phenolic hydroxyl group in probe Cy-H was oxidized into benzoquinone, leading to the formation of cyanine products that displayed a strong tendency to aggregate. As a result, the maximum emission peak of the probe shifted from 700 nm to 485 nm. Notably, a linear relationship was observed between the peak intensity ratio (I485/I700) and the concentration of hypochlorite, with a limit of detection (LOD) of 0.49 μM. Furthermore, this probe was successfully employed for imaging analysis of hypochlorite in living cells and zebrafish.

A pH-regulated fluorescence covalent organic framework for quantitative water content detection in methanol

In this paper, we designed and synthesized a two-dimensional fluorescent covalent organic framework (TAPB-DMTP-COF) for the precise determination of H2O content in methanol. The COF was synthesized using two typical monomers by grinding method, which significantly reduced the synthesis time. By adjusting the pH value of the COF suspension to 4.0, the portion of the COF material structure is disrupted, thereby mitigating π-π stacking and resolving the aggregation-caused quenching (ACQ) effect. Consequently, the non-fluorescent TAPB-DMTP-COF exhibited blue-purple fluorescence emission in methanol. At the same time, it is observed that in the presence of H2O, there is a red shift in the maximum fluorescence emission peak of TAPB-DMTP-COF, which correlates with the H2O content within a specific range. Notably, this redshift demonstrates a linear relationship with H2O content from 4% to 80% in methanol. Our work presents novel insights for efficient analysis and detection of H2O content in methanol and could be used for H2O detection in other organic solvents.

Cobalt oxyhydroxide nanosheet-modulated ratiometric fluorescence platform for the selective detection of malachite green in fish.

A ratiometric fluorescence platform was developed based on the cobalt oxyhydroxide (CoOOH) nanosheet-modulated fluorescence response of blue emissive copper nanoclusters (Cu NCs) and yellow emissive o-phenylenediamine (OPD). CoOOH nanosheets showed dual function of strong absorption and oxidation ability, which can effectively quench the blue fluorescence of Cu NCs, with an excitation and emission peak maximum at 390 and 450nm, respectively, and transfer the OPD into yellow fluorescence products, with an excitation and emission peak maximum at 390 and 560nm, respectively. Upon introducing butyrylcholinesterase (BChE) and its substrates, CoOOH nanosheets were decomposed into Co2+, and malachite green (MG) showed strong inhibition ability to this process. This resulted in the obvious difference on the ratio of blue and yellow fluorescence recorded on the system in the presence and absence of MG, which was utilized for the quantitative detection of MG, with a limit of detection of 0.140μM and a coefficient of variation of 3.5%. Thefluorescence ratiometric assay showed excellent detection performances in practical sample analysis.

Elucidating photocycle in large Stokes shift red fluorescent proteins: Focus on mKeima.

Large Stokes shift red fluorescent proteins (LSS-RFPs) are genetically encoded and exhibit a significant difference of a few hundreds of nanometers between their excitation and emission peak maxima (i.e., the Stokes shift). These LSS-RFPs (absorbing blue light and emitting red light) feature a unique photocycle responsible for their significant Stokes shift. The photocycle associated with this LSS characteristic in certain RFPs is quite perplexing, hinting at the complex nature of excited-state photophysics. This article provides a brief review on the fundamental mechanisms governing the photocycle of various LSS-RFPs, followed by a discussion on experimental results on mKeima emphasizing its relaxation pathways which garnered attention due to its >200 nm Stokes shift. Corroborating steady-state spectroscopy with computational studies, four different forms of chromophore of mKeima contributing to the cis-trans conformers of the neutral and anionic forms were identified in a recent study. Furthering these findings, in this account a detailed discussion on the photocycle of mKeima, which encompasses sequential excited-state isomerization, proton transfer, and subsequent structural reorganization involving three isomers, leading to an intriguing temperature and pH-dependent dual fluorescence, is explored using broadband femtosecond transient absorption spectroscopy.

A new multi-functional Cd(II)-organic framework as a platform for high selective fluorescence sensing and dye adsorption

A new three-dimensional porous MOF: {[Cd4(L)2(H2O)6]·(H2O)13·[(H2N(Me)2]2}n was synthesized by solvothermal reaction of 2,4-di(2′,4′-dicarboxyphenyl) benzoic acid ligand with Cd(Ⅱ) metal ion. Cd-MOF has a unique Cd-O metal oxygen chain structure. Metal oxygen chains are connected by ligands to form a three-dimensional porous structure. The solid-state fluorescence spectrum of Cd-MOF shows that the maximum emission peak is at 408 nm. Further liquid fluorescence sensing studies show that the complex can effectively and selectively detect Fe3+, CrO42- and Cr2O72− in aqueous solution with detection limit of 1.77 × 10−4 M, 1.08 × 10−3 M and 1.86 × 10−4 M, respectively, and can be reused five times, so it is a potential fluorescence recognition probe material. The fluorescence quenching mechanism of the system was discussed in detail. At the same time, in the study of the adsorption of dye molecules, it is found that the Cd-MOF has good adsorption capacity for methyl green and methylene blue and can also be used as an excellent dye separation material to selectively adsorb and separate mixed anion and cationic dyes.

A novel ratiometric peptide-based fluorescent probe for sequential detection of Hg2+ and S2− ions and its application in living cells and zebrafish imaging

A new ratiometric peptide-based fluorescent probe DWPH was designed and synthesized, comprising dansyl fluorophore as a fluorescent dye, and tripeptide backbone (Trp-Pro-His-NH2) as a recognition group. The addition of Hg2+ caused the maximum emission peak of DWPH to blue shift from 560 nm to 510 nm. DWPH exhibited large Stokes shift (230 nm), satisfactory water solubility (100 % aqueous medium), good selectivity (only Hg2+), high sensitivity (24.6 nM), rapid response (within 50 s) and strong anti-interference ability for Hg2+ detection over a wide pH range (7–11). Additionally, the complex DWPH-Hg2+ as a relay response probe could also be applied to S2− according to displacement approach. Notably, the detection limit for S2− was calculated as 23.3 nM, exhibiting that DWPH showed great potential for environmental monitoring and bioimaging. In addition, DWPH were successfully used to determine Hg2+ and S2− in living cells and zebrafish based on excellent permeability and low cytotoxicity. What’s more, the gradient concentration color changes of Hg2+ and S2− were combined with the smartphone APP to obtain red–green–blue (RGB) values, thus enabling rapid semi-quantitative detection of Hg2+ and S2− without expensive instruments.

Multiway Decomposition Followed by Reconvolution of Fluorescence Time Decay Data.

The use of time-resolved emission spectroscopy (TRES) is increasing as these instruments become more available, and the prices are decreasing, especially with the development of cheaper LED light sources. In this article, we propose a new methodology for analyzing TRES data. It combines two existing methods: PARAFAC and reconvolution. PARAFAC is a soft modeling curve resolution technique which has been extensively applied to steady-state fluorescence data, and reconvolution is the most common method for fitting TRES data. The proposed method is compared to two well-established methods of analyzing these data, namely, global reconvolution and tail fitting. In addition, we compare our approach with the SLICING method proposed in 2021 by Devos et al. which is also based on a soft model, but does not include the reconvolution step. All of these methods follow the assumption that the measured fluorescence signal is a linear combination of the underlying fluorophores. The comparison is based on a measured TRES data set with a mixture of three fluorophores and two sets of simulated data sets with up to four fluorophores. The results show that global fitting works well as long as the signal-to-noise ratio (SNR) is high (more than 15 dB), independent of the spacing between the emission peak maxima. SLICING does not give as good estimates of the time decay, mainly due to the challenge of defining the tail. Our proposed method gives robust and accurate results, outperforming the other techniques in cases with broad instrument response functions and high noise levels with SNRs down to 5 dB.

Fluorescent and ratiometric humidity sensor based on cyano-substituted oligo(p-phenylene)/silica gel hybrid materials

We have synthesized a kind of cyano-substituted oligo(p-phenylene) hybrid materials by Knoevenagel condensation reaction, which can be used as ratiometric relative humidity (RH) sensor. When the RH increased from 5 % to 90 %, the maximum emission peak of C1-3/SG gradually redshifted from 530 nm to 575 nm with the fluorescence changed from green to orange. This phenomenon can be attributed to the water vapor induced aggregation of dyes on the matrix. The non-covalent force between the dyes and the silica gel could be adjusted by altering the structures of the dyes, and the RH sensing property of the final hybrid materials could be further regulated. R2-3/SG hybrid fabricated by R2 with large steric isooctyl groups possessed indiscernible RH sensing properties, while the R1-3/SG without hydrogen bond interactions between dyes and substrate was more susceptible to water vapor. The surface properties and specific surface area of the substrate were critical for RH sensing. RH sensing properties were not presented for the substrates without hydroxyl groups or low specific surface area such as PET or PP fibers. Moreover, we have prepared a kind of C1 loaded paper strips, which exhibited potentially ability in anticounterfeiting application.

Development of red phosphor Li8CaLa2Ta2O13:Eu3+ for WLEDs and anti-counterfeiting applications

A set of novel red phosphors Li8CaLa2Ta2O13:xEu3+ (LCLTO:xEu3+) were successfully prepared using a solid-state reaction method. The properties of the prepared samples, including phase purity, elemental composition, and morphology, were systematically investigated using X-ray diffraction, scanning electron microscopy, and diffuse reflectance spectroscopy analyses. The 610 nm maximum emission peak is attributed to the 5D0→7F2 transition of Eu3+ ion under 394 nm irradiation. Among all the LCLTO:xEu3+ phosphors, LCLTO:0.6Eu3+ showed the strongest emission intensity because of the concentration quenching effect of the electric dipole–dipole interaction among the Eu3+ ions, which was also demonstrated by the decay curves. Remarkably, the emission intensity of the optimal LCLTO:0.6Eu3+ phosphor, which exhibited a high internal quantum efficiency of 49.30% and excellent color purity of 96.79%, was approximately 2.29 times higher than that of commercial Y2O3:Eu3+ red phosphors. The thermal stability of the LCLTO:0.6Eu3+ sample with good color stability was meticulously investigated. The fabricated white-light-emitting diode (WLED) exhibited a superior color-rendering index of Ra = 82 and chromaticity coordinates of (0.3260, 0.3639), suggesting that LCLTO:0.6Eu3+ has potential applicability in developing efficient and high-quality WLEDs. Moreover, the prepared LCLTO:0.6Eu3+/PDMS composite film demonstrated exceptional flexural resistance and chemical stability, indicating considerable promise for practical anti-counterfeiting applications.

Graphene quantum dots based fluorescent biosensor for nitrogen detection of urea fertilizer

A simple and fast fabrication of fluorescent biosensor based on graphene quantum dots (GQDs) for agricultural application is presented. Graphene oxide was used as a starting material for GQDs synthesis by hydrothermal method. Optical properties and morphology of the synthesized GQDs were characterized by UV-Vis, photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). The results showed that the synthesized GQDs exhibited spherical shape with their average diameter of 5.70 nm. The UV-Vis and PL spectra showed typical adsorption peak and maximum emission peak of the synthesized GQDs at 330 nm and 472 nm, respectively. To study sensing performance of fluorescent biosensor for nitrogen detection, aqueous solution of GQDs was mixed with different concentrations of nitrogen solution. According to PL spectra result, it is found that PL intensity of GQDs solution significantly increased corresponding to higher concentrations of nitrogen solution. This result suggests that fluorescent biosensor based on GQDs may be an alternative technique for primary nutrient detection in soils.

Blue polyimides for high-performance solution-processable organic light-emitting diodes

Blue light-emitting materials with excellent film-forming ability, superior morphological stability, outstanding color purity, and high device efficiency are in urgent demand for new-generation display and solid-state lighting devices fabricated by low-cost wet processing. However, their current performances are far from satisfactory. Herein, two polyimide (PI)-based blue polymers are first precisely constructed and synthesized through a “Hinge-type Linking” strategy. A small molecular is introduced into the PI backbone via non-conjugated aliphatic imide ring linker. These polymers not only show superb thermal stability and morphological stability, but also maintain narrowband blue emission. Furthermore, PIs are prepared by polycondensation method, precipitated and purified in ethanol solvent, which avoids the use of metal catalysts. The resulting solution-processable devices achieve high performance with a maximum external quantum efficiency (EQE) of 9.94 % and maximum emission peak at 460 nm. To the best of our knowledge, this is the first time that solution-processable polymer light-emitting diodes (PLEDs) based on the “hot exciton” mechanism achieving splendid performance with maximum EQE close to 10 %. The superior performance is attributed to the validity of the “Hinge-type Linking” strategy in PLEDs, opening up a new avenue for PLED development and application.

A novel reaction-based ratiometric fluorescent probe with large Stokes shift for the detection of Hg2+ in river sample

Based on Hg2+-promoted desulfurization-hydrolysis of the diphenylphosphinothioate moiety, a novel ratiometric fluorescent probe 1 for Hg2+ using hemicyanine as the fluorophore was designed and synthesized. In sensing of Hg2+, the maximum fluorescence emission and absorption peaks of 1 shifted from 450 nm to 504 nm and from 351 nm to 376 nm, respectively, accompanied by color change from colorless to green under illumination with a 365 nm UV lamp. 1 not only exhibited remarkable change in the ratios of both absorbance (A376 nm/A351 nm) and fluorescence intensity (F504 nm/F450 nm), but also had large Stokes shift, fast response, excellent sensitivity, and high selectivity for Hg2+. Furthermore, 1 was successfully applied for Hg2+ detection in river water sample.

PVK-based LEDs doped by cadmium sulphide nanocrystals coated by mixed thiophenol and 1-decanethiol

Nanoparticles capped with more than one ligand have great potential to improve the properties of optoelectronic devices. To discuss this possibility, we synthesized cadmium sulphide nanocrystals coated by two different ligands, 1-decanethiol and thiophenol. In addition, as a reference, cadmium sulphide nanocrystals coated with thiophenol were synthesized. Photoluminescence and UV–Vis absorption measurements indicated that the maximum emission peaks of both cadmium sulphide nanoparticles were located around 600 nm and the absorption edges showed the existence of two different types of crystalline structure, cubic zinc blende and wurzite-type hexagonal. But the nanoparticles with both ligands had higher emission intensity than nanocrystals coated only by thiophenol. Finally, hybrid light-emitting devices have been manufactured with the following structure: Indium Tin Oxide/Poly(3,4-ethylenedi-oxythiophene): poly(styrene sulfonate)/poly(9-vinylcarbazole): cadmium sulphide/Aluminum. These devices presented an active layer composed of poly(9-vinylcarbazole) doped by cadmium sulphide nanocrystals coated only by thiophenol in one case and with thiophenol and 1-decanethiol in the other case. The inclusion of nanocrystals in the active layer increased the current density of these devices. In addition, the solubility in chlorobenzene of nanoparticles with both ligands was improved, due to the presence of 1-decanethiol on their surface. Moreover, the presence of the second ligand intensified the influence of nanoparticles in electroluminescence measurements compared to cadmium sulfide nanocrystals without 1-decanethiol.

Red and Near Infrared Emissive Bis‐Tridentate Ir(III) Phosphors for Organic Light Emitting Diodes

AbstractEfficient saturated red and near‐infrared (NIR) emissive materials are needed in the development of organic light‐emitting diodes (OLEDs), with applications extending beyond flat panel displays and lighting luminaries. Toward this aim, a series of bis‐tridentate Ir(III) complexes (3a ‒ 3c and 4a ‒ 4c) are designed and synthesized, showing emission spanning the region of 601‒694 nm in degassed toluene. Their emission tuning is mainly achieved using monoanionic chromophoric chelates, L1H for red and L2H for deep‐red and NIR, where the extended π‐conjugation and electron deficient N atoms are introduced synergistically. Moreover, three ancillary chelates, X1H2, X2H2, and X3H2, delivered a secondary influence via varied donor strength to the central Ir(III) atom. The resulting red and deep‐red OLED devices exhibit maximum (max.) external quantum efficiencies (EQEs) of 21.4% and 18.1% with peak maximum at 620 and 666 nm, respectively. More impressively, the device based on 4b delivers a NIR emission peak maximum at 702 nm with a maximum EQE of 10.0%.