以昇陳

The rational design and synthesis of the first fluorogenic Phe-based BODIPY amino acids, and their application to produce peptide-based agents for rapid and wash-free labelling of fungal cells is described. This technology has been exploited to develop a sensitive and low-cost fluorescence-based assay for the detection of Candida albicans in human urine using simple benchtop spectrophotometers.

Abstract

Fungal infections caused by Candida species are among the most prevalent in hospitalized patients. However, current methods for the detection of Candida fungal cells in clinical samples rely on time-consuming assays that hamper rapid and reliable diagnosis. Herein, we describe the rational development of new Phe-BODIPY amino acids as small fluorogenic building blocks and their application to generate fluorescent antimicrobial peptides for rapid labelling of Candida cells in urine. We have used computational methods to analyse the fluorogenic behaviour of BODIPY-substituted aromatic amino acids and performed bioactivity and confocal microscopy experiments in different strains to confirm the utility and versatility of peptides incorporating Phe-BODIPYs. Finally, we have designed a simple and sensitive fluorescence-based assay for the detection of Candida albicans in human urine samples.

Nature Communications, Published online: 24 February 2022; doi:10.1038/s41467-022-28701-1

Constructing ultraviolet lasing is of great significance for basic research and medical use. Here the authors present a strategy for generating ultraviolet lasing through a tandem upconversion process with ultralarge anti-Stokes shift (1260 nm).

This review emphasizes five strategies for enhancing the fluorescence brightness of fluorophores when the absorption/emission wavelength of the fluorophore is red-shifted to the near-infrared (NIR) region. And the latest NIR high-brightness fluorophore biological imaging is introduced.

Abstract

Due to the merits of decreased photon attenuation, autofluorescence, and scattering, the near-infrared (NIR, 700–1700 nm) region is an important window in the field of biomedicine, such as in vivo fluorescence imaging, in which both the optical detection depth and the resolution/contrast have been significantly improved. In particular, for second NIR (NIR-II, 1000–1700 nm) dyes, biological tissues have almost no background interference. Typical fluorophores have excellent spectral performance and rich functional modification sites and can be optimized into NIR dyes for bioimaging. However, as the absorption/emission wavelength of fluorophores redshift to NIR, it is challenging to keep fluorophores with satisfying brightness. Therefore, for the purpose of increasing the absorption/emission wavelength of dye while promoting its brightness, it is necessary to study the structure–property relationship of the dyes. This review introduces the influences of fluorophores’ structure on their photophysical properties, summarizes the strategies for maintaining high fluorescence brightness along with redshifted absorption/emission wavelengths, and the latest advances of highly fluorescent brightness dyes. Finally, the opportunities and challenges in this emerging field are also provided. The authors aim to provide insightful design guidelines and clear overview of highly bright NIR fluorescent dyes, which might trigger new ideas and applications.

Publication date: 15 May 2022

Source: Chemical Engineering Journal, Volume 436

Author(s): Huiqin Wang, Bingjie Zhao, Chao Qu, Chunbo Duan, Zhe Li, Peng Ma, Peng Chang, Chunmiao Han, Hui Xu

Nature Photonics, Published online: 24 February 2022; doi:10.1038/s41566-022-00958-4

New dopant and host materials yield a deep blue phosphorescent organic light-emitting diode with a lifetime exceeding 1,000 h.

Two donor–acceptor (DA) covalent organic frameworks (COFs) show high crystallinity, good porosity, and excellent stability, which are incorporated into the FAPbI₃ layer of perovskite solar cells. The highest power-conversion efficiency observed for perovskite solar cells constructed with DA-COFs is 23.19% with excellent humidity stability, which provides a pathway for using DA-COFs to fabricate perovskite solar cells with high efficiency and stability.

Abstract

Covalent organic frameworks (COFs) as a new class of crystalline, porous materials have attracted extensive attention in the fields of photocatalytic and photovoltaic applications. Generally, donor–acceptor (DA) structures play an important role in the charge separation efficiency of solar cells. In this study, two DA-COFs with high crystallinity, good porosity, and excellent stability are incorporated into the FAPbI₃ layer of perovskite solar cells. This addition of DA-COFs reduces the defect concentration and shallows the defect state. The donor–acceptor system in COFs also possesses strong charge-transfer pathway, which strongly prevents charge recombination to afford more efficient charge separation efficiency. The highest power-conversion efficiency of perovskite solar cells constructed with DA-COFs is 23.19% with excellent humidity stability of the solar cells. Therefore, this work provides a pathway for using DA-COFs to fabricate perovskite solar cells with higher efficiency and stability.

The first [1+1+1] cycloaddition reaction has been achieved on the Ag(111) surface to afford the aza[3]radialenes. The chlorine substituents in the isocyanides ensured the selectivity and orientational order of the products via the steric hindrance-directed molecular assembly.

Abstract

[3]Radialenes are the smallest carbocyclic structures with unusual topologies and cross-conjugated π-electronic structures. Here, we report a novel [1+1+1] cycloaddition reaction for the synthesis of aza[3]radialenes on the Ag(111) surface, where the steric hindrance of the chlorine substituents guides the selective and orientational assembling of the isocyanide precursors. By combining scanning tunneling microscopy, non-contact atomic force microscopy, and time-of-flight secondary ion mass spectrometry, we determined the atomic structure of the produced aza[3]radialenes. Furthermore, two reaction pathways including synergistic and stepwise are proposed based on density functional theory calculations, which reveal the role of the chlorine substituents in the activation of the isocyano groups via electrostatic interaction.

Strongly electronegative atoms would activate energy transfer tunnels of conjugated polymeric backbones and thus enhance the energy transfer process from the hosts in the backbones to the thermally activated delayed fluorescence units. A simple side chain conjugated polymer with oxygen atoms inserted into the polymeric backbones is reported as a high-performance OLEDs material with low efficiency roll-off.

Abstract

Thermally activated delayed fluorescence (TADF) conjugated polymers are attractive for display and illumination applications owing to their excellent device performance and convenient device fabrication. However, conjugated polymers frequently encounter insufficient energy transfer from hosts to TADF units, lowering device performance. Herein, a strategy for improving light-emitting performances through adjusting the local electronegativity of the polymeric backbones by inserting electron-withdrawing atoms and activating energy transmission channels is proposed. Meanwhile, strongly electronegative atoms also affect the charge-transfer natures (CT) of TADF polymers and minimize the energy difference between the lowest singlet and triplet states, leading to a rapid reverse intersystem crossing process through the vibronic coupling between ¹CT and ³CT with extremely close energy levels. The produced TADF polymer, pBP-PXZ, can achieve an external quantum efficiency (EQE) of 23.11%, exhibiting no roll-off when the luminance is less than 200 cd m⁻² whereas only a 3% EQE decrease at 500 cd m⁻². The EQE can even maintain above 19% under 1000 cd m⁻², which is the highest efficiency among TADF polymer-based organic light-emitting diodes (OLEDs) under high luminance. The study provides a new perspective for designing high-performance OLEDs materials.

In this work, a pure organic phosphor of tris(4-chlorophenyl)phosphine oxide (CPO) with a large energy gap between T₁ and T₂ triplet states is developed. Then, tunable afterglow colors from green to yellow can be achieved due to the different distribution of the triplet excitons from low- and high-lying triplet excited states. Furthermore, high-level anti-counterfeiting tags are successfully prepared.

Abstract

Single molecules with dual persistent luminescence are very rarely explored, in spite of their emerging use in frontier optoelectronic applications. Here, a pure organic phosphor of tris(4-chlorophenyl)phosphine oxide (CPO) possessing a large energy gap between the lowest excited triplet (T₁) and higher excited triplet (T₂) states is reported, which can emit dual persistent room-temperature phosphorescence (RTP) from low- and high-lying triplet excited states. The femtosecond transient absorption experiments and theoretical calculations reveal that the excitons to the T₁ and T₂ states are populated through different pathways. As a result, the distribution of the triplet excitons can be efficiently manipulated by using different excitation energy, and tunable afterglow colors from green to yellow can be achieved. Furthermore, the CPO molecule is successfully applied in the fabrication of high-level anti-counterfeiting tags and flexible 3D objects with curling properties. From these initial discoveries, it is expected that triphenylphosphine derivatives, with their rich chemistry of core-substitution, can provide infinite opportunities in the expansion of organic molecules with high-lying persistent RTP.

A thermally activated reverse internal conversion (TARIC) pathway is proposed, which can achieve effective population transfer from T₁ to T₂ states via conical intersection point. On this basis, the mediated T₂ state facilitates the TADF and triplet−triplet annihilation photon upconversion channel. Benefited from the TARIC pathway, the designed 2′,7′-dichlorofluorescein (DCF) derivative DCF−MPYM−Me photosensitizer presents an excellent upconversion efficiency.

Abstract

Recent years have seen a surge in organic emitters that exhibit thermally activated delayed fluorescence (TADF) behavior owing to their high exciton utilization efficiency, low biological toxicity, etc. However, the existing TADF channel is insufficiently well developed as to design high-performance materials especially in the high-lying triplet state mediated reverse intersystem crossing process. A thermally activated reverse internal conversion (TARIC) pathway is reported here, which can achieve effective population transfer from T₁ to T₂ states via conical intersection point with the barrier of 3.81 kcal mol⁻¹. On this basis, the mediated T₂ state facilitates the TADF and triplet–triplet annihilation photon upconversion (TTA–UC) channel. Furthermore, benefited from the TARIC pathway, the designed 2′,7′-dichlorofluorescein (DCF) derivative DCF−MPYM−Me photosensitizer presents an excellent upconversion efficiency of 13.6%. The high upconversion efficiency is the best performance in purely organic TADF photosensitizers without heavy atoms in TTA−UC systems.

The phenazine group is utilized for the first time to synthesize multicolored thermally activated delayed fluorescence molecules for realizing the emission from deep blue to red. They feature unique hybrid local and charge-transfer-type excited states, ultrahigh exciton utilization efficiencies, and 10.74% maximum external quantum efficiency. These superior performances make them promising candidates for organic light-emitting diodes.

Abstract

A new family of phenazine-based compounds is synthesized to achieve multicolored emission from deep blue (418 nm) to red (625 nm). Emitters have unique hybrid local and charge-transfer excited states for S₁, T₁, T₂, and even higher-layer excited states, respectively, while all emitters possess thermally activated delayed fluorescence (TADF) nature. The rigid structure of phenazine and steric hindrance of donors are sufficiently utilized to suppress the nonradiative consumption, manipulate the configurations of excited states, and regulate the luminescence color. Organic light-emitting diodes exhibit superior multicolored emission with 10.74% external quantum efficiency. Employing such kind of simple-structured and easily synthesized compounds to realize multicolored emission would provide a new strategy for designing high-performance and multicolored TADF materials.

The impacts of bromine atom on delayed fluorescence property are investigated and elucidated. The different positions of bromine atom on molecular backbone cause significant differences in photoluminescence efficiencies and delayed fluorescence lifetimes in solid state, due to different orbital contribution ratios of bromine atom to molecular frontier orbitals and thus varied spin–orbit coupling interactions.

Abstract

Heavy atom effect is beneficial to delayed fluorescence by enlarging spin–orbit coupling (SOC). The introduction of halogen atoms to luminogenic molecules is a widely used approach to realize heavy atom effect, but the positions of halogen atoms may exert quite different impacts on the photophysical properties of the molecules. To confirm this hypothesis, herein, bromine atoms are introduced on a delayed fluorescence luminogen comprised of benzoyl acceptor and phenoxazine and phenylcarbazole donors at different positions. The resultant luminogens show great differences in photoluminescence (PL) efficiencies and delayed fluorescence lifetimes in solid state, which could be attributed to different orbital contribution ratios of bromine atoms to molecular frontier orbitals and thus varied SOC interactions, as revealed by spectroscopy, crystallography, and theoretical calculation. The luminogens with bromine atoms on the phenylcarbazole units hold much better PL properties than those with bromine atoms on other positions, and behave efficiently as emitters in organic light-emitting diodes, furnishing high external quantum efficiencies of up to 28.6% and small efficiency roll-offs. The structure–property relationship gained in this work can provide guidance for the further design of efficient luminescent materials.

We present evidence that the dual emission of β-hydroxy-vinylimine boron compounds consisting of fluorescence and room temperature phosphorescence in solution is caused by the experimental artifact, where bright emission intensity saturates the detection dynamic range of the fluorimeter.

Abstract

A series of β-hydroxy-vinylimine boron compounds 1–7 have been reported to exhibit unique dual emission, consisting of fluorescence and room temperature phosphorescence (RTP) in solution. This finding triggered intensive research of RTP in β-hydroxy-vinylimine boron derivatives. Herein, we show clear evidence that the associated dual emission, especially RTP, is caused by the experimental artifact, where bright emission intensity saturates the detection dynamic range of the fluorimeter.

With the emergence of high-performance non-fullerene acceptors, significant enhancement in power conversion efficiencies (PCEs) of organic solar cells (OSCs) has been achieved. However, the modest open-circuit voltage imposed by relatively large non-radiative recombination energy loss (ΔE ₃) limits further improvement of PCEs. This review summarizes the recent advance in ΔE ₃ of OSCs from material design, morphology manipulation, ternary strategy, and mechanism.

Abstract

Impressive short-circuit current density and fill factor have been achieved simultaneously in single-junction organic solar cells (OSCs) with the emergence of high-performance non-fullerene acceptors. However, the power conversion efficiencies (PCEs) of OSCs still lag behind those of inorganic and perovskite solar cells, mainly due to the modest open-circuit voltage (V _OC) imposed by relatively large energy loss (E _loss). Generally, E _loss in solar cells can be divided into three parts. Among them, ΔE ₁ is inevitable for all photovoltaic cells and depends on the optical bandgap of solar cells, while radiative recombination energy loss, ΔE ₂, in OSCs can approach the negligible value via finely matching donor with acceptor material in the blend. The relatively large non-radiative recombination energy loss, ΔE ₃, becomes the main barrier to further reduce E _loss and thus enhance PCE in non-fullerene acceptor-based OSCs. In this review, the recent studies and achievements about ΔE ₃ in non-fullerene acceptor-based OSCs have been summarized from the aspects of material design, morphology manipulation, ternary strategy, mechanism, and theoretical study. It is hoped that this review helps to get a deep understanding and boost the advance of ΔE ₃ study in OSCs.

Highly efficient deep-blue emitters of TTT-TPA-R (R = H, OMe, and ^t Bu) with a Commission International de I'Eclairage (CIE) coordinate of CIE_y < 0.08 are developed. All these emitters can harvest both singlet and triplet excitons via hot excitons process. The solution processable organic light-emitting diodes achieve the maximum external quantum efficiency of 10.5%.

Abstract

Realizing high efficiency deep blue emission with a Commission international de I'Eclairage (CIE) coordinate of CIE_y < 0.08 is still a big challenge. In this contribution, three molecules, named TTT-TPA-R (R = H, OMe, ^t Bu), using tris(triazolo)triazine (TTT) as the acceptor and triphenylamine derivatives (TPA-R, R = H, OMe, and ^t Bu) as the donor are prepared and characterized. All these emitters show deep/pure blue emission between 420 and 470 nm in the PMMA film, concomitant with the excellent emission efficiency of 80–100%. Both experimental and calculated methods demonstrate that these emitters exhibit a clearly hybridized local and charge-transfer excited state and can harvest both singlet and triplet excitons via reverse intersystem crossing process from the high-lying triplet to singlet states. Therefore, the solution processable deep blue organic light-emitting diodes (OLEDs) achieve a maximum external quantum efficiency (EQE _max) of 10.5% which is the recorded value for the solution processable deep blue OLED based on the “hot exciton” mechanism. Using TTT-TPA-H as the host material, solution-processed phosphorescent OLED based on PO-01 presents the EQE _max of 20.2%. These results pave a novel avenue for designing highly efficient deep blue emitter in solution processable OLED.

An organic ferroelectric material poly(vinylidene fluoride):dabcoHReO₄ as a perovskite dopant can be partially polarized by the built-in electric field of perovskite solar cell (pero-SC) itself, which produces an additional electric field, thus promoting the charge-carrier transportation. A promising 24.23% power conversion efficiency (PCE) (certified PCE of 23.45%) and robust operational stability are obtained.

Abstract

The built-in electric field (BEF) intensity of silicon heterojunction solar cells can be easily enhanced by selective doping to obtain high power conversion efficiencies (PCEs), while it is challenging for perovskite solar cells (pero-SCs) because of the difficulty in doping perovskites in a controllable way. Herein, an effective method is reported to enhance the BEF of FA_0.92MA_0.08PbI₃ perovskite by doping an organic ferroelectric material, poly(vinylidene fluoride):dabcoHReO₄ (PVDF:DH) with high polarizability, that can be driven even by the BEF of the device itself. The polarization of PVDF:DH produces an additional electric field, which is maintained permanently, in a direction consistent with that of the BEF of the pero-SC. The BEF superposition can more sufficiently drive the charge-carrier transport and extraction, thus suppressing the nonradiative recombination occurring in the pero-SCs. Moreover, the PVDF:DH dopant benefits the formation of a mesoporous PbI₂ film, via a typical two-step processing method, thereby promoting perovskite growth with high crystallinity and a few defects. The resulting pero-SC shows a promising PCE of 24.23% for a 0.062 cm² device (certified PCE of 23.45%), and a remarkable PCE of 22.69% for a 1 cm² device, along with significantly improved moisture resistances and operational stabilities.

Nature Chemistry, Published online: 07 February 2022; doi:10.1038/s41557-021-00861-5

Nanometre-sized polyaromatic hydrocarbons (nanographenes) have been largely explored as single-layer systems. Now a C64 nanographene comprising a planar core decorated with four terphenyl–imide moieties at its periphery has been shown to assemble with coronene to form bi- and trilayer host–guest complexes in solution, as well as tetra-, hexa- and multilayer stacks in the crystalline state.

A stepwise Förster resonance energy transfer (FRET) process with an intermediate dye is presented, which provides a universal strategy for tuning the luminescence peak by a large margin. Therefore, bright NIR luminescence with a lifetime up to 0.2 s at 810 nm is achieved based on a new triphenylene-dye-doped polymer (TP@PVA) with a blue phosphorescence of 3.29 s.

Abstract

Organic near infrared (NIR) persistent-luminescence systems with bright and long-lived emission are highly valuable for applications in communication, imaging, and sensors. However, realizing these materials (especially lifetime over 0.1 s) is a challenge, mainly because of non-radiative quenching of their long-lived excitons. Herein, a universal strategy of stepwise Förster resonance energy transfer (FRET) for a bright NIR system with remarkable persistent luminescence (up to 0.2 s at 810 nm) is presented, based on a new triphenylene-dye-doped polymer (triphenylene-2-ylboronic acid@poly(vinyl alcohol) (TP@PVA)) with a persistent blue phosphorescence of 3.29 s. This persistent NIR luminescence is demonstrated for application not only in NIR anti-counterfeiting but also NIR bioimaging with penetrating a piece of skin as thick as 2.0 mm. By co-doping a red dye (such as Nile red) and an NIR dye Cyanine 7 (Cy7) into this doped PVA film, the shortage of spectral overlap between TP emission and Cy7 absorbance is successfully solved, through a stepwise FRET process involving triplet to singlet (TS)-FRET from TP to the intermediate red dye and then singlet to singlet (SS)-FRET to Cy7. It is noted that the efficiency of the upper TS-FRET is enhanced significantly by the lower SS-FRET, leading to high efficiencies for the continuous FRETs.