Aggregation-caused Quenching Effect Research Articles

Smart Nanoassembly Enabling Activatable NIR Fluorescence and ROS Generation with Enhanced Tumor Penetration for Imaging-Guided Photodynamic Therapy.

Fluorescence imaging-guided photodynamic therapy (FIG-PDT) holds promise for cancer treatment, yet challenges persist in poor imaging quality, phototoxicity, and insufficient anti-tumor effect. Herein, a novel nanoplatform, LipoHPM, designed to address these challenges, is reported. This approach employs an acid-sensitive amine linker to connect a biotin-modified hydrophilic polymer (BiotinPEG) with a new hydrophobic photosensitizer (MBA), forming OFF-state BiotinPEG-MBA (PM) micelles via an aggregation-caused quenching (ACQ) effect. These micelles are then co-loaded with the tumor penetration enhancer hydralazine (HDZ) into pH-sensitive liposomes (LipoHPM). Leveraging the ACQ effect, LipoHPM is silent in both fluorescence and reactive oxygen species (ROS) generation during blood circulation but restores both properties upon disassembly. Following intravenous injection in tumor-bearing mice, LipoHPM actively targets tumor cells overexpressing biotin-receptors, contributing to enhanced tumor accumulation. Upon cellular internalization, LipoHPM disassembles within lysosomes, releasing HDZ to enhance tumor penetration and inhibit tumor metastasis. Concurrently, the micelles activate fluorescence for tumor imaging and boost the production of both type-I and type-II ROS for tumor eradication. Therefore, the smart LipoHPM synergistically integrates near-infrared emission, activatable tumor imaging, robust ROS generation, efficient anti-tumor and anti-metastasis activity, successfully overcoming limitations of conventional photosensitizers and establishing itself as a promising nanoplatform for potent FIG-PDT applications.

Over 30% external quantum efficiency for doping-free D-A-type thermally activated delayed fluorescence organic light-emitting diodes

The application of doping-free emitting layers in organic light-emitting diodes (OLEDs) device fabrication has attracted extensive attention due to the simplified process and the low cost. Meanwhile, the application of interfacially doping layer (or ultrathin emissive layer, UEML) with a thickness below 1 nm showed great potential in achieving high device efficiency by reducing the aggregation-caused quenching (ACQ) effect, which was usually observed in neat film and highly doped dopant-host system. This work developed a simple molecular design strategy via peripheral decoration of TADF emissive core with multiple shielding groups (t-butyl and aryl units) to effectively alleviate the intermolecular interaction and the ACQ effect. The resulting OLEDs based on BIPH-TPA exhibited a record-setting external quantum efficiency (EQE) of 15.8 % at 640 nm with a conventional doping-free configuration (25 nm). Furthermore, the ultrathin doping-free (0.2 nm) OLEDs based on NA-TPA achieved unprecedented EQE of 33.1 % at 620 nm. The outstanding EL performance clearly demonstrated promising potential of this molecular design strategy for the exploration of doping-free OLEDs.

Fluorophor Embedded MOFs Steering Gas Ultra‐Recognition

AbstractThin‐film fluorescent sensors play critical roles in the gas sensing field. However, fluorescent sensing materials for practical applications are limited, because of the aggregation‐caused quenching (ACQ) effect and photobleaching. This study investigates a host–guest thin‐film fluorescence sensor by incorporating a fluorescent probe into a metal–organic framework (MOF). The fluorescent molecule Me4BOPHY‐1 acts as a recognition probe for the neurotoxin analog diethylchlorophosphite (DCP). The MOF (ZIF‐8) provides nanocavities for the confinement of guest molecules, which reduces the self‐aggregation of fluorescent molecules and pre‐enriches the target gas. By applying ZIF‐8 framework to disperse the fluorescent molecules, the ACQ effect of Me4BOPHY‐1 can be effectively overcome. The fluorescence quantum efficiency of the molecules is increased from 0.76% to 19.72%, which enables its ability for gas sensing with a fast response time of 3 s and a detection limit as low as 1.13 ppb. Besides, the MOF facilitates selectivity enhancement through the confinement effect, weakening the sensing response to the interference of HCl. Moreover, the confinement effect also ensures high photo‐stability as well as thermal stability. It can maintain fluorescence intensity under 4800 s’ laser irradiation. Thus, the host–guest design strategy offers a thin‐film fluorescence gas sensor with high 3S (sensitivity, selectivity, and stability) toward neurotoxin analytes.

Tunable Circularly Polarized Luminescence by Confining Dye Molecules within Chiral Layered Metal–Organic Framework

AbstractCircularly polarized luminescence (CPL) active materials have attracted widespread attention because of their potential applications. Nonetheless, it is still a great challenge to fabricate CPL materials with both high fluorescence quantum efficiency (Φ) and high luminescent asymmetry factor (glum). According to the unique structure characteristics of chiral layered metal–organic frameworks (CLMOFs), herein a novel strategy to construct high‐performance CPL materials, by utilizing the confinement effect of CLMOFs is developed. Conjugate dye molecules, such as fluorescent brighteners, fluorescein, and rhodamine B, which are readily subjected to aggregation‐caused quenching (ACQ) effect, are successfully intercalated into CLMOF matrix, affording blue, yellow–green, and red CPL, respectively. Both high Φ and glum values of up to 91% and 0.069 are obtained, owing to the distinct confinement effect of CLMOFs. After confining dye molecules within CLMOF, the ACQ effect is effectively inhibited, which is beneficial for fluorescence enhancement; simultaneously, the chirality transfer from CLMOF matrix to dyes by controlling their arrangement in the chiral confinement microenvironment, leading to the high glum values. Based on the full‐color and strong CPL, a multi‐dimensional code system is proposed. This work paves a new avenue to design and assemble CPL materials with high Φ and glum, which can be widely adopted.

Doping/breath figure method triggered reversible diethylchlorophosphate vapor sensing

Aggregation-caused quenching (ACQ) is the key reason why thin-film fluorescence sensing studies have lagged. A facile two-step strategy combining doping with breath figure method (BF) is capable to suppress the ACQ effect without sacrificing the sensing property of the molecule. In this work, two long-wavelength fluorescent probes, Me4BOPHY-1 and Me4BOPHY-2, were synthesized by introducing one or two diethylaminophenyl group in the α-position of Me4BOPHY. Upon addition diethylchlorophosphate (DCP) to the solution of the probes, the initial intramolecular charge transfer (ICT) process is restrained. Thus, the intense fluorescence from Me4BOPHY core was released together with a dramatical color change. As the typical ACQ probes, Me4BOPHY-1 and Me4BOPHY-2 can’t be used in vapor-detection directly due to their weak fluorescence in the solid-phase. By means of being doped with polystyrene solution and being spin-coated under the optimal relative humidity conditions, porous films for DCP vapor detection were prepared with a high detection performance of a 162-ppb low detection limit. Moreover, it is exciting that these films show two outstanding characters of anti-interference to HCl gas and reversibility, which have not been reported in previous studies. This work breaks the application boundary of ACQ materials and provides an inspiration for the development of thin-film fluorescence sensors.

Porous Complex-Mediated Dual Emission of Porphyrins for the Electrochemiluminescence Bioassay.

Although porphyrins make up a promising class of electrochemiluminescence (ECL) luminophors, their aggregation-caused quenching (ACQ) characteristics lead to inferior ECL efficiency (ΦECL). Furthermore, current application of porphyrins is limited to cathodic emission. This work creatively exploited a cage-like porous complex (referred to as SWU-1) as the microreactor to recede the ACQ effect while modulating dual ECL emission of meso-tetra(4-carboxyphenyl)porphine (TCPP), which self-assembled with SWU-1 to form TCPP@SWU-1 nanocapsules (TCPP@SWU-1 NCs). As the microreactor, SWU-1 not only effectively constrained TCPP aggregation to improve electron-hole recombination efficiency but also improved stability of anion and cation radicals, thus significantly enhancing the dual emission of TCPP. Compared with TCPP aggregates, the resulting TCPP@SWU-1 NCs exhibited significantly enhanced anodic and cathodic emission, and their ΦECL was increased by 8.7-fold and 3.9-fold, respectively. Furthermore, black hole quencher-2 (BHQ2) can simultaneously quench anodic and cathodic signals. TCPP@SWU-1 NCs coupling BHQ2 conveniently achieved an ECL ratio detection of miRNA-126, and the limit of detection (S/N = 3) was 4.1 aM. This work pioneered the development of the cage-like porous complex SWU-1 as the microreactor to alleviate defects of the ACQ effect and mediate dual emission of TCPP. The coupling of dual-emitting TCPP@SWU-1 NCs and dual-function moderator BHQ2 created a novel single-luminophor-based ratio system for bioanalysis and provided a promising ECL analysis approach for miRNA-126.

Suppressing ACQ of molecular photosensitizers by distorting the conjugated-plane for enhanced tumor photodynamic therapy.

Non-AIE-type molecular photosensitizers (PSs) suffer from the aggregation-caused-quenching (ACQ) effect in an aqueous medium due to the strong hydrophobic and π-π interactions of their conjugated planes, which significantly hinders the enhancement of tumor photodynamic therapy (PDT). So far, some ionic PSs have been reported with good water-solubility, though the ACQ effect can still be induced in a biological environment rich in ions, leading to unsatisfactory in vivo delivery and fluorescence imaging performance. Hence, designing molecular PSs with outstanding anti-ACQ properties in water is highly desirable, but it remains a tough challenge for non-AIE-type fluorophores. Herein, we demonstrated a strategy for the design of porphyrin-type molecular PSs with remarkable solubility and anti-ACQ properties in an aqueous medium, which was assisted by quantum chemical simulations. It was found that cationic branched side chains can induce serious plane distortion in diphenyl porphyrin (DPP), which was not observed for tetraphenyl porphyrin (TPP) with the same side chains. Moreover, the hydrophilicity of the chain spacer is also crucial to the plane distortion for attaining the desired anti-ACQ properties. Compared to ACQ porphyrin, anti-ACQ porphyrin displayed type-I ROS generation in hypoxia and much higher tumor accumulation efficacy by blood circulation, leading to highly efficient in vivo PDT for hypoxic tumors. This study demonstrates the power of sidechain chemistry in tuning the configuration and aggregation behaviors of porphyrins in water, offering a new path to boost the performance of PSs to fulfill the increasing clinical demands on cancer theranostics.

Polymorphism and Light-Driven Forward Movement of TPE Derivative Micro-Crystal due to ArH-pi Interactions Difference.

Aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) are two classes of opposite luminescence phenomena. It is almost impossible to show both AIE and ACQ effect simultaneously by the same molecule. However, here we report that a simple TPE derivative TAP-TPE grows into both AIE crystals and ACQ ones. It is found that equatorial, contact distance-longer and weak ArH-π interactions exist in AIE crystals while vertical, contact distance-shorter and strong ArH-π interactions appear in ACQ crystals. Theoretical calculation of electron density on the interaction atoms unveils that ACQ crystals have much larger change in electron density than AIE ones, suggesting that the intermolecular electron transfer aroused by the strong ArH-π hydrogen bonds leads to ACQ phenomenon. This result provides a new insight into the emission mechanism in aggregation state. Interestingly, due to the ArH-pi interactions difference, only one of five kinds of crystals shows rapid photochromism, and can act as multimode anti-counterfeiting materials. Very exceptionally, for the first time we find that the photochromic micrometric rod-like crystal even makes forward rolling movement as it repeatedly bends and straightens by responding to on and off of the ultraviolet light irradiation, displaying potential for photo-actuator and light-driven micro-vehicle.

Electrochemiluminescence enhanced by isolating ACQphores in imine-linked covalent organic framework for organophosphorus pesticide assay

Most of covalent organic frameworks (COFs) are non or weakly emissive due to either the molecular thermal motion-mediated energy dissipation or the aggregation-caused quenching (ACQ) effect. Herein, we synthesize an imine-linked COF (TFPPy-TPh-COF) with high electrochemiluminescence (ECL) emission and the capability of eliminating the ACQ effect and further construct an ECL sensor for malathion detection. The imine-linked COF is obtained by the condensation reaction of (1,1':3′,1″-terphenyl)-4,4″-diamine (TPh) and 1,3,6,8-tetrakis(p-formylphenyl)pyrene (TFPPy), and it has higher ECL efficiency than TFPPy aggregates due to the separation of ACQ luminophores (i.e., TFPPy) from each other by TPh and the restriction of intramolecular motions of TFPPy and TPh to reduce the nonradiative decay. The efficient quenching of ECL is achieved by electrochemiluminescence resonance energy transfer (ERET) from the excited state of the TFPPy-TPh-COF to zeolite imidazolate framework-8 (ZIF-8) and the steric hindrance of ZIF-8. Acetylcholinesterase (AChE) can enzymatically hydrolyze acetylcholine (ACh) to generate acetic acid. The resultant acetic acid can trigger the dissolution of ZIF-8 to produce an enhanced ECL signal. Malathion as an organophosphorus pesticide serves as an AChE inhibitor to prevent the production of acetic acid, inducing the decrease of ECL signal. This sensor displays a limit of detection (LOD) of 2.44 pg/mL and a wide dynamic detection range of 0.01–1000 ng/mL. Furthermore, it can be used to detect other organophosphates pesticides (e.g., methidathion, chlorpyrifos, and paraoxon) and measure malathion in real samples (i.e., pakchoi, lettuce, and apples).

Highly Efficient Doping‐Free Thermally Activated Delayed Fluorescent Organic Light‐Emitting Diodes with an Ultrathin Quasi‐Host‐Guest Emission Layer

AbstractDoping‐free organic light‐emitting diodes (OLEDs) are beneficial to reduce manufacturing costs for mass production, which, however, are limited by the ubiquitous aggregation‐caused quenching (ACQ) effect, especially for thermally activated delayed fluorescence (TADF) emitters with relatively long exciton lifetimes. Herein, two typical TADF emitters pACRS and pACRSO with different sulfur atom valence states are developed, where pACRS with a thioether unit exhibits suppressed intermolecular interaction, alleviated ACQ effect, and higher efficiency in a conventional doping‐free device, in contract to pACRSO with a sulfone unit. It is of interest that comparable efficiencies are achieved for both emitters in doping‐free OLEDs with an ultrathin emission layer (UEML), in which the emitter molecules are deposited onto the surface of the underlying organic layer of host material to form an ultrathin quasi‐host‐guest system with alleviated ACQ effect. Besides, the suppressed trap effect is the key to guarantee the efficiency of UEML‐OLEDs, while different intermolecular interactions of emitters that determine the optimized UEML thickness will affect the efficiency roll‐off. Furthermore, benefiting from the UEML structure, highly efficient doping‐free OLEDs are also successfully achieved for red TADF emitters with stronger intermolecular interactions. Such an UEML strategy meeting efficiency and cost demands holds great promise for doping‐free OLEDs.

Secondary Structure in Overcoming Photosensitizers' Aggregation: α-Helical Polypeptides for Enhanced Photodynamic Therapy.

Aggregation caused quenching (ACQ) effect could severely inhibit the application of hydrophobic photosensitizers (PSs) bearing planar and rigid structures. Most of the reported cases utilized random-coiled polymers for the in vivo delivery of PSs, which would inevitably aggravate ACQ effect due to the flexible chains. In this work, the role of polymers' secondary structures (especially α-helical conformation) in overcoming the PSs' aggregation was systemically investigated based on the design of α-helical polypeptides bearing tetraphenylporphyrin (TPP) side chains. Atomistic molecular dynamics simulation, fluorescence quantum yield and reactive oxygen species (ROS) generation yield were evaluated to demonstrate that α-helical polypeptide backbones could significantly boost both fluorescence quantum yield and ROS by suppressing the π-π stacking interaction between TPP units. The enhanced in vitro and in vivo phototoxicity for helical polypeptides also revealed functions of secondary structures in inhibiting ACQ and improving the membrane activity. Successful in vivo photodynamic therapy (PDT) results in mice bearing H22 tumors showed great potentials for further clinical applications. This article is protected by copyright. All rights reserved.

Polymerized Thermally Activated Delayed‐Fluorescence Small Molecules: Long‐Axis Polymerization Leads to a Nearly Concentration‐Independent Luminescence

AbstractNowadays numerous thermally activated delayed fluorescence (TADF) polymers have been developed for PLEDs to realize high device performance and tunable emission colors. However, they often possess a strong concentration dependence on their luminescence including aggregation‐caused quenching (ACQ) and aggregation‐induced emission (AIE). Herein, we first report a nearly concentration‐independent TADF polymer based on the strategy of polymerized TADF small molecules. It is found that when a donor‐acceptor‐donor (D‐A‐D) type TADF small molecule is polymerized through its long‐axis direction, the triplet state is distributed along the polymeric backbone to effectively suppress the unwanted concentration quenching. Unlike the short‐axis one with an ACQ effect, the photoluminescent quantum yield (PLQY) of the resultant long‐axis polymer remains almost unchanged with the increasing doping concentration. Accordingly, a promising external quantum efficiency (EQE) up to 20 % is successfully achieved in a whole doping control window of 5–100 wt. %.

Polymerized Thermally Activated Delayed-Fluorescence Small Molecules: Long-Axis Polymerization Leads to a Nearly Concentration-Independent Luminescence.

Nowadays numerous thermally activated delayed fluorescence (TADF) polymers have been developed for PLEDs to realize high device performance and tunable emission colors. However, they often possess a strong concentration dependence on their luminescence including aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE). Herein, we first report a nearly concentration-independent TADF polymer based on the strategy of polymerized TADF small molecules. It is found that when a donor-acceptor-donor (D-A-D) type TADF small molecule is polymerized through its long-axis direction, the triplet state is distributed along the polymeric backbone to effectively suppress the unwanted concentration quenching. Unlike the short-axis one with an ACQ effect, the photoluminescent quantum yield (PLQY) of the resultant long-axis polymer remains almost unchanged with the increasing doping concentration. Accordingly, a promising external quantum efficiency (EQE) up to 20 % is successfully achieved in a whole doping control window of 5-100 wt. %.

Enhanced Luminescence of Dye-Decorated ZIF-8 Composite Films via Controllable D-A Interactions for White Light Emission.

Metal-organic frameworks (MOFs) constructed by metal ions/clusters and organic linkers are used to encapsulate fluorescent guest species with aggregation-caused quenching (ACQ) effects to enhance fluorescence properties due to their porous structures and high specific surface areas. However, there would be a problem of matching between MOF pores and guest molecules' sizes. In this paper, amorphous ZIF-8 was modified by carboxyl functional groups (H3BTC-ZIF-8) via introducing the 1,2,4-benzenetricarbonic acid (H3BTC) ligand into the ZIF-8 sol system. Moreover, H3BTC-ZIF-8 was used for the loading of organic fluorescent dyes rhodamine 6G (R6G) and coumarin 151 (C151) to prepare R6G/C151/H3BTC-ZIF-8 composite films. A white-light-emitting composite film (R6G/C151/H3BTC-ZIF-8) with CIE coordinates of (0.323, 0.347) was successfully prepared by compounding fluorescent dyes (R6G and C151) with H3BTC-modified ZIF-8, whose photoluminescence quantum yield (PLQY) can reach 64.0%. It was higher than the PLQY of the composite films prepared by crystalline ZIF-8 (40.2%) or amorphous ZIF-8 without H3BTC (48.0%) compounded with the same concentrations of dyes. The fluorescence enhancement was probably attributed to an increased amount of active sites of H3BTC-modified ZIF-8 interacting with dyes C151 and R6G. This can form hydrogen bonds between H3BTC-ZIF-8 and C151, and weak electron donor-acceptor (D-A) interactions between H3BTC-ZIF-8 and R6G molecules, respectively, thus enhancing the interactions between dyes and ZIF-8 and reducing the ACQ effect existing between dye molecules. Therefore, this strategy could provide an important guidance to develop white-light-emissive materials.

Medium-Ring Strategy Enables Multiple Resonance Emitters with Twisted Geometry and Fast Spin-Flip to Suppress Efficiency Roll-Off.

Suppressing aggregation-caused quenching (ACQ) effect and reducing device efficiency roll-off are both crucial yet challenging for multi-resonance (MR) emitters. Herein, we put forward a medium-ring strategy to design efficient MR emitters that feature heptagonal tribenzo[b,d,f]azepine (TBA) donors. The highly twisted conformation enlarges the intermolecular distances between the MR-emitting cores, and thus suppresses ACQ effect. Meanwhile, the introduction of heptagonal donors enhances spin-orbital coupling, so as to accelerate reverse intersystem crossing (RISC) process. This medium-ring strategy gives rise to the first example of blue MR emitter that simultaneously possesses radiative decay rate as fast as 108 s-1 and RISC rate as fast as 106 s-1 . Accordingly, DTBA-B2N3 enables to assemble high-performance blue organic light-emitting diodes (OLEDs) with maximum external quantum efficiency (EQEmax ) of 30.9 % and alleviated efficiency roll-off (EQE1000 : 20.5 %).

Medium‐Ring Strategy Enables Multiple Resonance Emitters with Twisted Geometry and Fast Spin‐Flip to Suppress Efficiency Roll‐Off

AbstractSuppressing aggregation‐caused quenching (ACQ) effect and reducing device efficiency roll‐off are both crucial yet challenging for multi‐resonance (MR) emitters. Herein, we put forward a medium‐ring strategy to design efficient MR emitters that feature heptagonal tribenzo[b,d,f]azepine (TBA) donors. The highly twisted conformation enlarges the intermolecular distances between the MR‐emitting cores, and thus suppresses ACQ effect. Meanwhile, the introduction of heptagonal donors enhances spin‐orbital coupling, so as to accelerate reverse intersystem crossing (RISC) process. This medium‐ring strategy gives rise to the first example of blue MR emitter that simultaneously possesses radiative decay rate as fast as 108 s−1 and RISC rate as fast as 106 s−1. Accordingly, DTBA‐B2N3 enables to assemble high‐performance blue organic light‐emitting diodes (OLEDs) with maximum external quantum efficiency (EQEmax) of 30.9 % and alleviated efficiency roll‐off (EQE1000: 20.5 %).

Crystallization‐Induced Enhanced Electrochemiluminescence from a New Tris(bipyridine)ruthenium(II) Derivative

AbstractClassic tris(bipyridine)ruthenium(II) complex (Ru‐bpy) with high electrochemiluminescence (ECL) efficiency still suffers from a serious aggregation‐caused quenching (ACQ) problem, which greatly weakens its ECL efficiency to restrict further applications in solid‐state ECL imaging and light‐emitting devices. Herein, the crystallization‐induced enhanced ECL (CIE‐ECL) of tris(bipyridine)ruthenium(II) derivatives (Ru‐TPE) are reported by decorating Ru‐bpy with inherent aggregation‐induced emission active tetraphenylethene (TPE), which effectively eliminates the detrimentalπ–πstacking interactions and thus helps Ru‐bpy surmount notorious ACQ effect in the aqueous phase. The Ru‐TPE shows negligible ECL emission in solution but produces a strong ECL emission upon crystallization. Surprisingly, the ECL efficiency of Ru‐TPE crystals is 20 and 3 times higher than that of its solution and Ru‐bpy crystals, respectively. Experimental and structural analysis reveals that such a CIE‐ECL effect originates from the restricted intramolecular rotation and ordered molecular packing. Moreover, the high‐resolution ECL imaging of a single Ru‐TPE crystal is successfully demonstrated. This work provides a new design strategy for achieving high efficiency in solid‐state ECL imaging and devices.

A bovine serum albumin and squaraine dye assembly fluorescent probe for pepsin detection

Gastroesophageal reflux disease (GERD) is a highly prevalent condition. Screening for GERD remains a great challenge due to the non-specific nature of the symptoms. Now, salivary pepsin detection has become an effective tool for diagnosing GERD due to its non-invasive and highly specific advantages. However, the diagnosis of GERD by detecting pepsin in saliva still has factors such as long reaction time, poor selectivity, and low detection sensitivity, which need to be improved. In this work, bovine serum albumin (BSA) and a squaraine dye (SQ) were employed to build a BSA-SQ assembly with a fluorescent “on-off” change for rapid and sensitive detection of pepsin. In a Gly-HCl (pH = 2.6) buffer system, SQ had a significant aggregation caused-quenching (ACQ) effect. As SQ was embedded in the cavity of BSA, this improved its dispersion and inhibited the ACQ effect of SQ, resulting in enhanced fluorescence of the system. At this stage, pepsin catalyzed the hydrolysis of BSA, leading to the aggregation of SQ and the quenching of the fluorescence of BSA-SQ. The high catalytic activity of pepsin makes BSA-SQ suitable for the qualitative and quantitative detection of pepsin, showing a good linear relationship in the range of 0.5–40 μg/mL with a detection limit of 97 ng/mL. Finally, the use of this fluorescent probe method to detect pepsin in human saliva showed results consistent with conventional ELISA methods with relative errors between 0.4 and 5.5 %, confirming the great potential of BSA-SQ for the rapid diagnosis of GERD.

The effect of alkoxyl groups on the photoproperties of meta-octasubstituted tetraphenyl porphyrins

• . Installing substituent groups with different lengths/sizes and conformations at the meta-octa-substituted position of meso-tetraphenyl porphyrin. • . H 2 T(OHE) 2 PP with longer and branched alkoxyl chains effectively suppressed aggregation-caused quenching effect. • . H 2 T(OH) 2 PP in solid state shows the naked-eye visible fluorescence, making its practical applications possible. The emission of most organic fluorescent molecules in aggregation states decays or fades, as interpreted by the aggregation-caused quenching (ACQ) effect, because the excited state energy is depleted via nonradiative channels when chromophores stack together. However, most fluorescent materials are utilized in the solid state, and hence it is vital to tune the chromophore stacking mode for modulating the photoluminescence properties. In this work, the meso-tetraphenyl porphyrin was taken as the parent chromophore unit to investigate the substituent-group effect on the luminescence properties of porphyrin-based complexes. The selected substituent groups (-OH, -OMe and 2-ethylhexyloxy) with different lengths/sizes and conformations were installed at the meta-octa-substituted position of meso-tetraphenyl porphyrin. The distance of porphyrin chromophores was regulated by the substituent chain. It was found that in the solid or aggregate state, porphyrin with longer and branched alkoxyl chains effectively suppressed the π-π stacking interaction, maintained the photoluminescence property of the porphyrin chromophore as in its dilute solution and overcame the ACQ effect. In contrast, porphyrin with a shorter alkoxyl chain, for example, the methoxyl group, affords a weak emission property in the solid state, and the substituent hydroxyl group leads to the complete quenching of the emission in the solid-state due to the close stacking of porphyrin rings.

Structural modification of NIR-II fluorophores for angiography beyond 1300 nm: Expanding the xanthene universe

Fluorescence bioimaging via the second near-infrared (NIR-II) window can provide precise images with a low background signal due to attenuated absorption and scattering in biological tissues. However, it is challenging to realize organic fluorophores' absorption/emission wavelength beyond 1300 nm depending on their intrinsic emission of monomers. Reducing parasitic aggregation caused quenching (ACQ) effect is expected as an efficient strategy to achieve fluorescence bioimaging in an ideal region. Herein, two NIR-II xanthene fluorophores (CM1 and CM2) with different side chains on identical skeletons were synthesized. Besides, their corresponding assemblies (CM1 NPs and CM2 NPs) were subsequently prepared, which exhibited distinct spectroscopic properties. Notably, CM2 NPs exhibited a significantly reduced ACQ effect with maximal absorption/emission extended to 1235/1250 nm. Molecular dynamics simulations revealed that intermolecular hydrogen bond, π-π interaction, and CH-π interaction of CM2 were essential for the reduced ACQ effect. In vivo hindlimb angiography showed that CM2 NPs could distinguish the neighboring artery and vein in high resolution. Besides, CM2 NPs could achieve angiography beyond 1300 nm and even resolve capillaries as small as 0.23 mm. This study provides a new strategy for reducing the ACQ effect by controlling different side chains of NIR-II xanthene dyes for angiography beyond 1300 nm.