Latest ArticlesDuring past few years, the construction of fluorescent metallacycles featuring the fluorescence-resonance energy transfer behavior has attracted extensive attention due to their diverse applications such as real-time monitoring the dynamics of coordination-driven self-assembly, photoswitching fluorescence-resonance energy transfer, and light-controlled generation of singlet oxygen for cancer therapy. This review focuses on the recent advances on the design principles, preparation methods, optical properties, and the wide applications of fluorescent metallacycles with the FRET property.
Room temperature phosphorescence (RTP) generated by small molecules has attracted great attention due to their unique potentials for biosensor, bioimaging and security protection. While, the design of RTP materials is extremely challenging for organic small molecules in non-crystalline solid state. Herein, we report a new strategy for achieving non-crystalline organic small molecules with RTP emission by modifying different phosphors onto diphenylalanine or phenylalanine derivatives. Benefiting from the skeletal structure of the amino acid derivatives, there are intermolecular hydrogen bond formation and rigidification effect, thereby minimizing the intermolecular motions and enhancing their RTP performance
Cytochrome P450 1A1 (CYP1A1), a heme-containing monooxygenase, is of particular importance for human health because of its vital roles in the metabolic activation of pro-carcinogenic compounds to the carcinogens. Deciphering the relevance of CYP1A1 to human diseases and screening of CYP1A1 modulators require reliable tool(s) for probing this key enzyme in complex biological matrices. Herein, a practical and ultrasensitive fluorescence-based assay for real-time sensing CYP1A1 activities in biological systems has been developed, via designing an isoform-specific fluorogenic sensor for CYP1A1 (CHPO). The newly developed fluorogenic substrate for CYP1A1 has been carefully investigated in terms of specificity, sensitivity, precision, quantitative linear range and the anti-interference ability. The excellent selectivity, strong anti-interference ability and fast response kinetics, making the practicability of CHPO-based CYP1A1 activity assay is better than that of most reported CYP1A1 activity assays. Furthermore, CHPO has been successfully used for imaging CYP1A1 activities in living cells and human tissues, as well as for high-throughput screening of CYP1A1 inhibitors using tissue preparations as enzyme sources. Collectively, this study provided a practical fluorogenic sensor for real-time sensing CYP1A1 in complex biological systems, which would strongly facilitate the investigations on the relevance of CYP1A1 to human diseases and promote high-throughput screening of CYP1A1 modulators for biomedical applications.
To realize a fast, easy-operation and precise way using fluorescence probes to quantify analytes is a goal to facilitate detection, especially in situ. Herein, we are reporting an approach which can be generally employed for the differentiation and quantitation of analytes through fluorescence chromaticity and luminosity. Seven representative fluorescent probes, targeting pH, cysteine, hydrogen sulfide, hydrogen peroxide, palladium and hydrazine, were synthesized and tested. Without utilizing costly instrumentations, portable devices were employed to collect data of photographs from the fluorescence samples in responses to different analytes. Subsequently, the photographic images were digitally processed to generate calibration curves between chromaticity/luminosity verse concentrations after mapping to the CIE 1931 xyY standard color space. Good linear calibration curves and quantitative analysis of unknown samples with low errors through the spectral technology demonstrated the reliability of this method. Thus, we showed the analytical method with a simple and on-site constructible/portable device which is promising for applications in more fluorescence probes
For efficient and quantitative DNA detection, fluorescence staining is the most often explored approach, which relies on non-covalent binding of dyes with double stranded DNA (dsDNA). Ethidium bromide (EB) is the most classic DNA stain, but suffers from its high carcinogenicity. A series of less toxic alternatives were developed, many of which contain the core structure of the benzothiazole ring. However, the relationship between the structure and the DNA detection performance was not illustrated. Herein, five benzothiazole dyes, namely thiazole orange, SYBR Green Ⅰ, PicoGreen, SYBR Safe, and thioflavine-T, were compared for DNA detection through direct fluorescence and gel electrophoresis, with particular focus on the structure-performance relationship. It turned out that SYBR Green Ⅰ is currently the best choice for DNA detection. The results in this work may be useful for future DNA-staining dye developments.
In the active layer of organic solar cells (OSCs), the lifetime of triplet excitons is one of the decisive factors in the diffusion length and therefore has important impact on the power conversion efficiency of the devices. Herein, we have investigated singlet excited state relaxation dynamics and their triplet exciton lifetimes of two thiophene-coupled perylene diimides (PDI) dyads (2PDI-Th and fused-2PDI-Th), in order to provide a unique explanation in depth on their different performances in OSC devices. From the transient absorption (TA) spectra, the singlet excitons of 2PDI-Th form excimers in the time scale of 1.5 ps. Then the excimers go into the triplet state via intersystem crossing (ISC). In fused-2PDI-Th, triplet excitons are generated directly from the singlet excited excitons via the efficient ISC. Density functional theory (DFT) calculations further support the formation of excimers. DFT results indicate that 2PDI-Th exhibits an H-typed molecular configuration which is beneficial to form the excimers, while fused-2PDI-Th gives a twisted X-shaped configuration in the optimized ground and excited state. In steady-state emission spectra, 2PDI-Th shows abroad and featureless spectral characteristics of the excimers with a decay time of 840 ps, which is much shorter than those of PDI (5.5 ns) and fused-2PDI-Th (3.3 ns). The triplet lifetime (67 μs) of fused-2PDI-Th is factor of 3 longer than that of 2PDI-Th (22 μs). These results demonstrate that ring-fused structure is an efficient strategy to eliminate excimer formation and prolong the lifetime of triplet excitons, which provides a new insight for design of optoelectronic molecules for high efficiency organic solar cells.
Cysteine (Cys) plays an important role in regulating cellular redox balance. But due to the constant changes in the concentration of Cys in organisms, fast response sensors are urgent required for practical application. In this work, a fluorescent probe with a fast response was developed by linking coumarin derivatives containing α, β-unsaturated ketones to NBD. The PET effect made the system non-fluorescent. When the probe reacted with Cys, the bond between the coumarin derivative and the NBD was cut off, meanwhile a rapid rearrangement and reactive site passivation occurred. Then two fluorophores with the same emission peak are released, among them, strong fluorescence signal of NBD dominated. Thus, although the similar reaction occurred for Hcy, the rate of NBD derivative rearrangement was slow, in a short time, fluorescence signal was still weak. As for GSH, cleavage could occur, but no rearrange within the NBD molecule due to GSH with large volume. Because of strong fluorescent emission, this probe was successfully used in biological imaging about cell and zebrafish. More importantly, the probe was successfully used to evaluate the oxidative stress caused by copper(II) in living cells. This fluorescence strategy and application will provide a new way of studying intracellular oxidative stress processes and damage.
Acetylene black (AB), as a kind of carbon material with large specific surface area, low density, strong electron transferability, is supposed to have great potential for application in advanced oxidation processes (AOPs). In this study, AB was utilized as a peroxydisulfate (PDS) activator for the catalytic degradation of sulfamethoxazole (SMX) in aqueous media. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) techniques, zeta potential and Raman spectra were employed to characterize the features of AB. To verify the excellent performance of AB/PDS systems, a series of control experiments were carried out. Compared to graphite/PDS and biochar/PDS system, AB/PDS system could complete degradation of SMX within 15 min. Besides, the effects of key factors including AB dosage, PDS dosage, initial pH and SMX concentration on SMX degradation in AB/PDS system were elucidated systematically. Furthermore, through the radical quenching experiments, it was proved that singlet oxygen (1O2) was dominantly responsible for the degradation of SMX. Finally, based on the experiment results and comprehensive analysis, a probable reaction mechanism of AB/PDS system for SMX degradation was proposed. This work suggests that AB has a good potential for tackling the hazardous pollutants in environmental remediation.
Efficient generation of singlet oxygen (1O2) by an excitonic energy transfer process is highly desired on a semiconductor photocatalyst for selective oxidation of methyl phenyl sulfide (MPS). Herein, it is demonstrated that a large amount of 1O2 is produced on pristine graphitic carbon nitride (CN) nanosheet compared with bismuth oxybromide (BiOBr) and commercial P25 titanium dioxide (TiO2). This leads to a certain photoactivity of CN for MPS oxidation. The observed ~77% selectivity for CN depends on the competitive results of excitonic energy transfer for 1O2 formation and charge carrier separation for superoxide radical (O2·-) production, which are based on the phosphorescence spectra and electron paramagnetic resonance signals, respectively. Moreover, ultrathin CN nanosheets are synthesized by thermal treatment with the cyanuric acid-melamine hydrogen bonded aggregates as precursors. It is confirmed that the amount of produced 1O2 could be increased by decreasing the thickness of resultant CN nanosheets. The optimized ultrathin CN nanosheet (~4 nm) exhibits excellent photoactivity with high selectivity (~99%). It is suggested that the excitonic energy transfer for 1O2 formation is close related to the intrinsic exciton binding energy and the two-dimensional quantum confinement effect. This work establishes a basic mechanistic understanding on the excitonic processes in CN, and develops a feasible route to design CN-based photocatalysts for efficient 1O2 generation.
Multiple pollutants including pathogenic microorganism contaminations and emerging organic contaminations (EOCs) have shown a growing threat to the environment, especially the natural waters. However, the control and removal of pathogenic microorganism contaminations and EOCs have been greatly limited since limited knowledge of their environmental behaviors. Thus, a novel and efficient photocatalyst Ag2O/BiOBr heterojunction was synthesized and used for removal of multiple pollutants including Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), tetracycline and acetaminophen under visible light. The results showed that there were valid electron transfer pathways between BiOBr and Ag2O, the main electron transfer direction was the BiOBr to Ag2O. Photo-generated electrons were stored in Ag2O and thus separation efficiency between holes and photo-generated electrons was obviously enhanced. Active oxygen species were highly produced and eventually end up with the high efficiency of removal of multiple pollutants. For Ag2O/BiOBr with Ag2O content at 3% (the best performance) under visible light, log decrease of E. coli was 7.16 (removal efficiency was 100%) in 120 min, log decrease of S. aureus was 7.23 (removal efficiency was 100%) in 160 min, C/C0 of tetracycline was 0.06 in 180 min, C/C0 of acetaminophen was 0.17 in 180 min. This work could provide a promising candidate in the actual contaminated natural waters for cleaning multiple pollutants.
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