Effect of addition of trifluoroacetic acid on the photophysical properties and photoreactions of aromatic imides

The UV and IR spectra of N-methyl-1,8-naphthalimide in benzene showed a two-step consecutive complexation (hydrogen bond formation) with trifluoroacetic acid (TFA). The equilibrium constant K₁ for the first complexation in benzene was determined from the UV spectrum to be 48 M⁻¹. The fluorescence intensities of the imide in benzene were found to be remarkably enhanced by the addition of TFA. Furthermore, photochemical cyclobutane formation of the imide with styrene in benzene was enhanced by the addition of TFA. Enhancement of the fluorescence intensity and the photoreaction of the imide by complexation with TFA was explained by a decrease of the efficiency of the intersystem crossing from ¹(ππ^∗) to ³(nπ^∗), that results from an increase in the energy of the ³(nπ^∗) level due to the complexation.     

基于马鞍形环八四噻吩的复合纳米材料的制备及发光性能

由于环八四噻吩具有独特的"马鞍形"空间结构和光电性质,因此受到越来越多的关注.环八四噻吩(COThs)共有14种同分异构体,其中COTh-1是一类特殊的聚集诱导发光体系,但仅在四氢呋喃等少数有机溶剂中有一定的溶解度,发光强度较弱,限制了这类材料的应用.多孔二氧化硅纳米材料具有比表面积大、孔体积大、粒径可调、生物相容性好...     

Stable Near-infrared-emitting Radical Nanoparticles for Fluorescence Imaging

Stable neutral luminescent radicals with unpaired electrons exhibit unique spin-allowed doublet-doublet transitions, which has attracted significant attention. Although they are pure organic molecules without metal ions thus thought to have low biological toxicity, the application of luminescent radicals to bioimaging has rarely been reported. Here, a stable radical with efficient near-infrared(NIR) emission and good photostability was designed and synthesized. After being wrapped into nanoparticles, it was applied to cell fluorescence imaging. The cytotoxicity experiments suggested that the nanoparticles have remarkable biocompatibility and excellent stability. An NIR fluorescent signal was successfully observed in the cytoplasm of HCT116 cells. The experimental results gave the first example of NIR emitting radical nanoparticles for cell fluorescence imaging and proved the feasibility of the application of luminescent radicals to fluorescence imaging.     

Chiral Deep Eutectic Solvents Enable Full-Color and White Circularly Polarized Luminescence from Achiral Luminophores

Herein, chiral deep eutectic solvents (DES) are prepared by lauric acid as hydrogen bond donors (HBD) and chiral menthol as hydrogen bond acceptors (HBA). When achiral fluorescent molecules are dopedin the menthol-based chiral DES, they emit circularly polarized luminescence (CPL) with handedness controlled by the molecular chirality (l or d ) of menthol. Remarkably, the strategy is universal and a series of achiral fluorescent molecules can be endowed with CPL activity, showing a full-color and white CPL upon appropriate mixing, which paves the way to prepare white CPL materials. Interestingly, CPL appears only in a certain temperature range in the DES. Variable-temperature spectra and other characterization methods reveal that the H-bond network in the chiral DES plays an important role in inducing CPL. This work unveils how the interior structure as well as the hydrogen-bond network of a chiral DES can transfer its chirality to achiral luminophores for the first time and realizes a full-color and white CPL in a DES.     

Modified,Amorphous Titania—A Hybrid Semiconductor for Detoxification and Current Generation by Visible Light

Amorphous, microporous TiO ₂ hybrid semiconductors modified with transition metals induce generation of a photocurrent and photocatalytic degradation of the water contaminant 4-chlorophenol through photoinduced charge separation (the postulated mechanism is shown in the picture, Ar=4-ClC₆H₄). In contrast to the previously known crystalline titania photocatalysts, which are active only when excited with UV light, the amorphous semiconductors modified with platinum, rhodium, and gold chloride enable both processes also with visible light.     

Size-Transformable Superoxide-Triggered Nanoreporters for Crosstalk-Free Dual Fluorescence/Chemiluminescence Imaging and Urinalysis in Living Mice

Chemiluminescence imaging has been recognized as a valuable tool for ultrasensitive detection of physio-pathological events through elimination of background autofluorescence. However, most chemiluminescent nanoprobes suffer from shallow imaging depths and slow clearance from living bodies, which impede their use in clinical settings. We herein report size-transformable nanoreporters (ADN1 and ADN2) that could be activated at disease site by superoxide anion (O₂⋅⁻) to trigger nanostructure disassembly into renal excretable fluorescent fragments as well as chemiluminescence turn-on for crosstalk-free duplex chemo-fluorescence imaging and in vitro urinalysis. In peritonitis mouse model, we demonstrate that the representative nanoreporter ADN1 spontaneously accumulates at the disrupted peritoneum and is cleaved by upregulated O₂⋅⁻ to initiate depolymerization and result in red chemiluminescence at 620 nm, enabling sensitive detection of peritonitis at least 19 h earlier than gold standard histological assays. Additionally, the incorporation of a near-infrared (NIR) dye into ADN1 results in ADN2 exhibiting intense and red-shifted chemiluminescence at ≈800 nm, which permits early detection of deeply seated diseases such as drug-induced hepatotoxicity. This study thus showcases a modular design strategy that is not only applicable to developing versatile chemiluminescent nanoprobes with switchable pharmacokinetics for early disease diagnosis, but also promising for future clinical translations.     

高灵敏检测葡萄糖的新型荧光纳米传感器

构建了一种用于高灵敏检测葡萄糖的新型荧光纳米传感器.在辣根过氧化物酶(HRP)的催化下,H2O2氧化3,3′,5,5′-四甲基联苯胺(TMB),生成具有强吸光性质的TMB多聚体,导致1-氧-1H-非那烯-2,3-二腈(1-Oxo-1H-phenalene-2,3-dicarbonitrile, OPD)分子的荧光发生淬灭,基于此实现H2O2的定量检测,线性范围分别为0.05~0.80 μmol/L和1~10 μmol/L,检出限(3σ)为0.02 μmol/L.由于葡萄糖氧化酶(Gox)可催化葡萄糖分解产生H2O2,基于此可以实现葡萄糖分子的定量检测,线性范围分别为0.1~3.0 μmol/L和4.0~30 μmol/L, 检出限(3σ)为0.02 μmol/L.将本方法用于实际血清样品中葡萄糖的定量检测,结果与临床检测结果相符.     

Fluorescence turn-on probe for biothiols: intramolecular hydrogen bonding effect on the Michael reaction

Weakly fluorescent coumarinyl enones are rapidly transformed into strongly fluorescent molecules through the Michael addition reaction of a thiol group, where an intramolecular hydrogen bond plays a critical role in the reaction rate. The molecular probe (3) with an ortho hydroxyl group to a carbonyl group exhibits a rapid response toward GSH owing to the stabilization of the possible oxyanion intermediate by a preferable intramolecular hydrogen bond. Probe 1 with an o-hydroxyl group also showed a moderately enhanced reaction rate with GSH and soluble in HEPES buffer to exhibit a highly selective and sensitive fluorescence turn-on response toward biothiols.     

A Protocol for Activated Bioorthogonal Fluorescence Labeling and Imaging of 4-Hydroxyphenylpyruvate Dioxygenase in Plants

4-Hydroxyphenylpyruvate dioxygenase (HPPD) plays a crucial role in the synthesis of nutrients needed to maintain optimal plant growth. Its level is closely linked to the extent of abiotic stress experienced by plants. Moreover, it is also the target of commercial herbicides. Therefore, labeling of HPPD in plants not only enables visualization of its tissue distribution and cellular uptake, it also facilitates assessment of abiotic stress of plants and provides information needed for the development of effective environmentally friendly herbicides. In this study, we created a method for fluorescence labeling of HPPD that avoids interference with the normal growth of plants. In this strategy, a perylene-linked dibenzyl-cyclooctyne undergoes strain-promoted azide-alkyne cycloaddition with an azide-containing HPPD ligand. The activation-based labeling process results in a significant emission enhancement caused by the change in the fluorescent forms from an excimer to a monomer. Notably, this activated bioorthogonal strategy is applicable to visualizing HPPD in Arabidopsis thaliana, and assessing its response to multiple abiotic stresses. Also, it can be employed to monitor in vivo levels and locations of HPPD in crops. Consequently, the labeling strategy will be a significant tool in investigations of HPPD-related abiotic stress mechanisms, discovering novel herbicides, and uncovering unknown biological functions.     

Acid-Resistant BODIPY Amino Acids for Peptide-Based Fluorescence Imaging of GPR54 Receptors in Pancreatic Islets

The G protein-coupled kisspeptin receptor (GPR54 or KISS1R) is an important mediator in reproduction, metabolism and cancer biology; however, there are limited fluorescent probes or antibodies for direct imaging of these receptors in cells and intact tissues, which can help to interrogate their multiple biological roles. Herein, we describe the rational design and characterization of a new acid-resistant BODIPY-based amino acid (Trp-BODIPY PLUS), and its implementation for solid-phase synthesis of fluorescent bioactive peptides. Trp-BODIPY PLUS retains the binding capabilities of both short linear and cyclic peptides and displays notable turn-on fluorescence emission upon target binding for wash-free imaging. Finally, we employed Trp-BODIPY PLUS to prepare some of the first fluorogenic kisspeptin-based probes and visualized the expression and localization of GPR54 receptors in human cells and in whole mouse pancreatic islets by fluorescence imaging.     

细胞内源性分子辅助荧光信号放大策略及细胞成像

细胞内原位信号放大策略是检测低丰度内源性目标物的有效手段, 但多数信号放大策略依赖于外源性辅助物, 不可避免地改变细胞内微环境, 进而对机体造成一定干扰. 针对此问题, 可利用细胞内源性物质(如金属离子、 核酸、 蛋白酶等)实现原位荧光信号放大, 对不同生物标志物进行荧光成像, 此方法对低丰度靶分子检测及成像具有重要意义. 本文对内源性物质辅助信号放大及细胞内荧光成像相关研究进行了归纳整理, 介绍了内源性核酸、 酶、 蛋白质、 三磷酸腺苷(ATP)和金属离子辅助信号放大策略, 并探讨了其信号放大机理; 总结了内源性物质辅助信号放大探针在低丰度物质检测及成像方面的研究进展; 最后展望了该策略在细胞成像方面的优势及应用前景.     

Covalent Organic Framework for Improving Near-Infrared Light Induced Fluorescence Imaging through Two-Photon Induction

Fluorescent materials exhibiting two-photon induction (TPI) are used for nonlinear optics, bioimaging, and phototherapy. Polymerizations of molecular chromophores to form π-conjugated structures were hindered by the lack of long-range ordering in the structure and strong π–π stacking between the chromophores. Reported here is the rational design of a benzothiadiazole-based covalent organic framework (COF) for promoting TPI and obtaining efficient two-photon induced fluorescence emissions. Characterization and spectroscopic data revealed that the enhancement in TPI performance is attributed to the donor-π-acceptor-π-donor configuration and regular intervals of the chromophores, the large π-conjugation domain, and the long-range order of COF crystals. The crystalline structure of TPI-COF attenuates the π–π stacking interactions between the layers, and overcomes aggregation-caused emission quenching of the chromophores for improving near-infrared two-photon induced fluorescence imaging.     

用荧光光谱和共振光散射光谱研究甲硝唑与牛血清白蛋白的相互作用

用荧光光谱和共振光散射光谱对甲硝唑与牛血清白蛋白的作用进行了对比研究, 测定了该反应的结合常数、结合位点数. 探讨了甲硝唑对牛血清白蛋白荧光和共振光散射猝灭的机理． 利用热力学参数确定了分子间的作用力性质；根据非辐射能量转换机制, 确定了甲硝唑-牛血清白蛋白间的结合距离. 采用同步荧光技术考察了甲硝唑对牛血清白蛋白构象的影响．     

Hydrogen Bonds Strengthened Metal-Free Perovskite for Degradable X-ray Detector with Enhanced Stability,Flexibility and Sensitivity

Metal-free perovskites (MFPs) with flexible and degradable properties have been adopted in flexible X-ray detection. For now, figuring out the key factors between structure and device performance are critical to guide the design of MFPs. Herein, MPAZE-NH₄I₃ ⋅ H₂O was first designed and synthesized with improved structural stability and device performance. Through theoretical calculations, the introducing methyl group benefits modulating tolerance factor, increases dipole moment and strengthens hydrogen bonds. Meanwhile, H₂O increases the hydrogen bond formation sites and synergistically realizes the band nature modulation, ionic migration inhibition and structural stiffness optimization. Spectra analysis also proves that the improved electron-phonon coupling and carrier recombination lifetime contribute to enhanced performance. Finally, a flexible and degradable X-ray detector was fabricated with the highest sensitivity of 740.8 μC Gy_air⁻¹ cm⁻² and low detection limit (0.14 nGy_air s⁻¹).     

Fluorescence staining and confocal laser scanning microscopy study of hydrogen-bonded poly(vinylpyrrolidone)/poly(acrylic acid) film

Poly(vinylpyrrolidone) (PVPON) and poly(acrylic acid) (PAA) were layer-by-layer (LBL) assembled to prepare the thin films based on hydrogen-bonding complexation. The hydrogen-bonded PVPON/PAA films were incubated in acidic, neutral and basic vapors separately. To study the morphologies after incubation, the films were stained by pH-sensitive fluorescent dyes using chemical and physical ways, and investigated with confocal laser scanning microscope (CLSM). The chemical way (labeling) was covalently linking fluoresceinamine (FAM) to some monomer units of PAA while the physical way was adsorbing rhodamine B (RB) molecules from dilute solution. Atomic force microscope (AFM) was combined with CLSM to find that after incubation in neutral or basic vapor the hydrogen-bonded PVPON/PAA films form porous structure and the pores are through the whole film.     

基于核酸适配体的荧光法检测水胺硫磷和丙溴磷

建立了基于适配体的农药水胺硫磷和丙溴磷的荧光检测方法.采用可特异性识别水胺硫磷和丙溴磷、且5 '端标记荧光基团FAM的核酸适配体(F-ssDNA),与3 '末端标记猝灭基团DABCYL的短链序列(Q-ssDNA)互补杂交形成双链结构,荧光基团的荧光被淬灭,荧光信号很弱;此时加入靶分子,特异性结合核酸适配体,引起互补短链序列从双链结构中解离,使适配体荧光信号增强,基于此可实现水胺硫磷、丙溴磷的定量检测.优化后的检测条件为:将终浓度为25 nmol/L F-ssDNA与50 nmol/L Q-ssDNA在25℃孵育20 min,使二者杂交形成双链适配体探针复合物,加入等体积的农药样品孵育60 min,然后检测体系的荧光信号变化值△I.在最佳条件下,△I与水胺硫磷和丙溴磷的浓度均在50～ 500 μmol/L范围内呈线性关系.水胺硫磷的检出限(LOD,3σ)为11.4 μmol/L,相对标准偏差(RSD)为5.8％(n=10);丙溴磷的检出限为14.0 μmol/L,RSD为4.9％(n=l0).用于实际水样中两种农药的检测,加标回收率为85.8％ ～95.3％.     

荧光特性双层自组装膜电极及电化学性能研究

以半胱胺酸为中介,利用荧光试剂1＿萘胺二乙酸钠(NADA)和DL＿半胱胺酸(Cys)的静电吸引作用,将荧光试剂NADA间接组装在金电极表面,形成自组装双层膜电极NADA/Cys/Au,该双层膜电极对金属离子具有荧光识别和电化学传感功能,本文着重研究了双层膜电极NADA/Cys/Au的电化学性能,并将其用于超痕量铜离子和镍离子的电化学分析连续测定.     

Crystal and Species Engineering with Semi‐Flexible Nitrogen Containing Organic Cations: Generation of [H13O6]+ Ions with the Unfavoured Unbranched Topology by Enclosing Hydrochloric Acid in a Porous Inorganic‐Organic Hybrid Material

The reaction of rhodium(III) chloride trihydrate with 1, 4‐diazacycloheptane in concentrated hydrochloric acid results in the formation of tris(1, 4‐diazoniacycloheptane) hexaaquahydrogen(1+) bis(hexachlororhodate(III)) chloride, [C₅H₁₄N₂]₃[H₁₃O₆][RhCl₆]₂Cl ( 1 ). Dark red crystals of 1 are obtained by diffusion‐controlled crystallization at room temperature. Slow evaporation of the mother liquor over a period of several days yields a few tiny crystals of the bis(1, 4‐diazoniacycloheptane) hexachlororhodate(III) chloride hydrate, [C₅H₁₄N₂]₂[RhCl₆]Cl ˙ 1.75 H₂O ( 2 ), as red thin squared plates. In the context of crystal engineering, compounds 1 and 2 are inorganic‐organic hybrid materials built up from octahedral [RhCl₆]^3‐, simple Cl^‐ and semi‐flexible heterocyclic 1, 4‐diazoniacycloheptane ions, incorporating either the [H₁₃O₆]⁺ and further Cl^‐ ions or portions of simple water molecules. Both compounds crystallize in the space group type P2₁/c. Compound 1 contains isolated [H₁₃O₆]⁺ ions with a linear chain‐like configuration enclosed in the cavities of the inorganic‐organic framework. The presence of a strong central O···H···O hydrogen bond within the [H₁₃O₆]⁺ ions in 1 is confirmed by the short O···O separation of 2.47Å and by characteristic IR absorption bands at 1626 (s), ～ 1250 (m) and 668 (m) cm^‐1. During the thermal decomposition, compound 1 looses at first five equivalents of water and one equivalent of hydrochloric acid in a two‐step process at 37 °C and 67 °C. This is followed by the decomposition of the 1, 4‐diazoniacycloheptane cations and the hexachlororhodate(III) anions, starting at 190 °C and proceeding intensified at 240 °C.     

Insights into the Aggregation Behaviour of a Benzoselenadiazole-Based Compound and Generation of White Light Emission

We have designed and synthesized the benzoselenadiazole (BDS) based donor-acceptor-donor (D-A-D) π-conjugated compound 4,7-di((E)styryl)benzo[2,1,3]selenadiazole ( 1 ). A single-crystal study of 1 shows J-type molecular aggregation in the solid state. The crystal packing of 1 shows head-to-head dimeric intermolecular assembly via Se⋅⋅⋅N interactions while staircase-type interlock molecular packing has occurred via Se⋅⋅⋅π interaction. The staircase-type interlock packing of dimeric molecular arrangement induces sheet-type, herringbone type architecture along crystallographic a axis and ab plane via CH⋅⋅⋅π interactions. Interestingly, the J-type aggregation of 1 in solid state changes to H-type aggregation upon UV-irradiation. Moreover, our spectroscopic findings in solution state reveal H-type of aggregation of 1 in 90 % aqueous THF. We have further demonstrated white light emission in the binary mixture of 1 and 1-pyrenemethanol ( 2 ) in 90 % aqueous THF. Our study reveals solvent specific co-assembly of H-aggregated 1 and 2 in 90 % aqueous THF solution, which shows white light emissive properties with the Commission Internationale de l'Eclairage (CIE) chromaticity coordinates (0.32, 0.31). The observed white light emission arises mainly due to the combination of red light from H-aggregated 1 , blue light from monomeric 2 and green light from excimers of 2 .     

Photo- and Electrochemical Cobalt Catalysed Hydrogen Atom Transfer for the Hydrofunctionalisation of Alkenes

Catalytic hydrogen atom transfer from metal-hydrides to alkenes allows feedstock olefins to be used as alkyl radical precursors. The chemoselectivity of this process makes it an attractive synthetic tool and as such it has been regularly used in synthesis of complex molecules. However, onwards reactivity is limited by compatibility with the conditions which form the key metal-hydride species. Now, through the merger with photocatalysis or electrochemistry, milder methods are emerging which can unlock entirely new reactivity and offer perspectives on expanding these methods in unprecedented directions. This review outlines the most recent developments in electro- and photochemical cobalt catalysed methods and offers suggestions on the future outlook.