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Orally targeted drug delivery for treating colonic diseases has attracted much attention because this method can be used as a better alternative to conventional administration of high drug doses, which usually exposes patients to serious systemic toxicity. Here, a pH-responsive nano-in-micro composite as a drug-delivery vehicle for the targeted therapy of inflammatory bowel disease (IBD) is designed and prepared using a one-step droplet microfluidic method with a water-in-oil-in-water manner. The microcapsules, encapsulating both free drugs and drug-loaded nanoparticles (NPs), appear as bowl-shaped spheres with a non-uniform shell thickness. Under colonic pH, the thin concave lamella of the HPMCAS-based shells rapidly ruptures and releases the inner free drug to achieve burst drug release for a sufficiently high and effective concentration of the drug. Subsequently, the gradual decomposition of PLGA-based drug-loaded NPs results in sustained drug release. The sequential burst–sustained drug release is consistent with the pharmacokinetics and medication needs of IBD. In vitro inflammation inhibition experiments further reveal that the nano-in-micro microcapsules can quickly alleviate the inflammatory response at the site of inflammation by reducing the intracellular ROS level and the expression of proinflammatory cytokines. These results demonstrate the success of the targeted drug-delivery model with the function of sequential burst–sustained drug release for IBD therapy.

In this study, we have designed and synthesized a novel ‘AND’ logic based fluorescence probe,1-(3′,6′-bis((tert-butyldiphenylsilyl)oxy)-3-oxospiro (isoindoline-1,9′-xanthen)-2-yl)-3-phenylthiourea (FPSi), for the rapid (3 min) simultaneous detection of F− and Hg2+ in DMSO/H2O solution (7:3, v/v). The FPSi probe, synthesized over three steps starting from commercially available fluorescein, was constructed by attaching tert-butyldiphenylsilyl and thiosemicarbazide (as the specific identification groups for F− and Hg2+) to the skeleton of fluorescein, respectively. FPSi produced no fluorescence response towards the addition of F− or Hg2+ separately. However, when the probe was exposed to a solution containing both F− and Hg2+, there was a significant yellow-green fluorescence. FPSi demonstrated an excellent selectivity towards both F− and Hg2+ in the presence of interfering substances. The results of TOF-MS-EI analysis indicated that the response of FPSi towards F− and Hg2+ was mainly aroused by the F− promoted cleavage of Si–O bond, and Hg2+ triggered an irreversible desulfurization reaction leading to the spiral ring opening. Furthermore, the FPSi probe has been successfully used to detect F− and Hg2+ ions in tap water and cropland soil.

Filamenting temperature-sensitive mutant Z (FtsZ) is recognized as a promising target for new antibiotics development because of its high conservatism and pivotal role in the bacteria cell division. The aromatic heterocyclic scaffold of indole is known showing merit medical functions in antiviral and antimicrobial. In the present study, a series of 1-methylquinolinium derivatives, which were integrated with an indole fragment at its 2-position and a variety of amino groups (cyclic or linear, mono- or di-amine) at the 4-position were synthesized and their antibacterial activities were evaluated. The results of antibacterial study show that the representative compounds can effectively inhibit the growth of testing strains including MRSA and VRE, with MIC values of 1–4 μg/mL by bactericidal mode. The mode of action assays revealed that c2 can effectively disrupt the rate of GTP hydrolysis and dynamic polymerization of FtsZ, and thus inhibits bacterial cell division and then causes bacterial cell death. In addition, the result of resistance generation experiment reveals that c2 is not likely to induce resistance in S. aureus.

Stimuli-responsive organic luminescence-switching materials have attracted much attention for a decade. Most of the reported examples display a reversible two-color luminescence switching, and multicolor-switching materials remain extremely rare. Herein, we report a simple organic molecule, 4,4'-(9,9-dimethyl-9H-fluorene-2,7-diyl)dipyridine (MFDP), which exhibits three different crystal polymorphs (V-MFDP, B-MFDP and G-MFDP) with different luminescent colors. Furthermore, the three crystal polymorphs show a reversible tricolor fluorescent switching from violet to blue and to green upon physical stimuli. The single-crystal structures of the three polymorphs were obtained, and the results indicate that the stimuli-responsive properties of the three polymorphs come from the different stacking modes induced by intermolecular interactions. The competition between weak π-π stacking and weak hydrogen bonding is the main reason for the the phase transformations among the three crystal polymorphs.

New fluorescent dyes derivatized on a classical thiazole orange framework are able to show unexpectedly strong interaction signal and unusual binding selectivity with different structures of nucleic acid, particularly when bound with double-stranded DNA or G-quadruplex DNA. The present study reveals that these small binding ligands simply bearing an additional amino side group on its parent molecule of thiazole orange have almost no background fluorescence in solution. Conversely, they are able to produce an extremely strong yellow emission signal upon interaction with targeting nucleic acids in live cells. The induced fluorescence intensity was approximately 10–15 times stronger than that of thiazole orange. The dyes are therefore excellent fluorescent stains for bio-sensing and bio-imaging applications. It is particularly suitable for fluorescence microscopy experiments requiring very low working concentration (0.25 μM or less) targeting nucleic acids. This was demonstrated using pu27 G-quadruplex DNA, which has a low limit of detection (LOD = 3–4 nM) while thiazole orange was much higher (LOD = 48.7 nM) under the same conditions. In addition, it was found that structural modification on the quinolinium scaffold of thiazole orange was less effective than modification on the benzothiazole moiety. The findings of the present study provide important information for structural advancement of small molecules based on the widely used thiazole orange skeleton, resulting in analogues that are able to achieve higher sensitivity and selectivity for targeting at a specific class of nucleic acids. Computational docking studies were also conducted to illustrate the interaction behaviors of the dyes with different DNA structures.

A novel iridium complex [(dfppy)2Ir(ttz), Ir complex] was synthesized via decarboxylic reaction of ancillary ligand with the iridium complex dimer containing dichloro-bridged bond, the decarboxylation-coordination reaction for the synthesis of Ir complex firstly is found. The single crystal structure, thermally stability, UV–vis absorption, photoluminescence, electrochemistry, and electroluminescent performances of the Ir complex were investigated. Blue and orange-red emissions can be observed for the Ir complex in dichloromethane and OLED with low emissive efficiencies, respectively. We explored the reason for the poor emissive performance. In addition, the luminescent mechanism of (dfppy)2Ir(ttz) was also studied through DFT/TD-DFT calculations.

Stimuli-response organic solid-state luminescence switching materials are attracting increasing interest due to their smart photophysical properties. In this study, a morpholine-modified naphthalic anhydride derivative, 4-(4-morpholinyl)naphthalic anhydride (MBC), was synthesized and studied. Its two crystal polymorphs, MBC-G and MBC-O, were obtained under different crystallization conditions. These two distinct crystals show significantly different solid-state luminescence behaviors: a green emission at 535 nm for MBC-G, and an orange emission at 572 nm for MBC-O. Upon fiercely grinding the MBC-G crystal or melting and then quickly cooling it, a phase transition occurs from MBC-G to MBC-O, accompanied by a fluorescence change from green to orange. The reverse transformation from MBC-O to MBC-G can be achieved by recrystallization. The X-ray single crystal structures show that the green emission should be attributed to molecular J-aggregation in the crystal packing, and the orange emission may originate from molecular H-aggregation. This switchable color nature gives MBC the promising candidate for potential smart anti-counterfeiting and light-emitting materials.

The ongoing poisoning of agricultural products has pushed the security problem to become an important issue. Among them, exceeding the standard rate of pesticide residues is the main factor influencing the quality and security of agricultural products. Monitoring pesticide residues and developing simple, yet ultrasensitive detection systems for pesticide residues are urgently needed. In this study, we successfully developed a novel rhodamine derivative as fluorescent and colorimetric chemosensor R-G for the rapid, selective and ultrasensitive detection of glyphosate pesticide residue in aqueous solution. Through a Cu2+-indicator displacement strategy, glyphosate can displace an indicator (R-G) from a Cu2+-indicator complex due to its strong affinity to bind with Cu2+ to give a turn-on fluorescence and distinct color change. Moreover, a test strip was also fabricated to achieve a facile detection of glyphosate pesticide. To demonstrate the possibility of practical applications, glyphosate was detected on the surface of cabbage and in a spiked soil sample. The detection limit of 4.1 nM and the response time of 2 min indicate that the method is enough sensitive and rapid to detect the glyphosate residue at or below levels that pose a health risk.

Hypochlorous acid plays a very important role in living cells, because it can resist microorganism attack and has a lethal effect on pathogens. The unnormal generation of ClO- can cause tissue damage and corresponding diseases. Detection of ClO- is very necessary in biological systems. In this article, we respectively hybridized the two different water-soluble coumarin (7-hydroxycoumarin and 7-diethylaminocoumarin) fluorophores with a longer-wavelength emissive rhodamine fluorophore to construct an intergrant, and then isothiocyanate was modified with the intergrant to recognized ClO-. The two ratiometric fluorescent probes RHClO-1 and RHClO-2 were developed for ClO- detecting with high selectivity and sensitivity. Especially, the probe RHClO-2 has lower detection limit (42 nM) for ClO- in 5 s. What's more, the probe RHClO-2 was successfully used in monitoring endogenous ClO- in living cells.

Triarylboron-based Lewis acids as fluoride sensors face a stimulating academic challenge because of the high hydration enthalpy of fluoride, and are usually influenced by a competing response for cyanide ion. Herein, we present a new triarylborane functionalized by a metal-ion ligand, di-(2-picolyl)-N-(2-quinolinylmethyl)amine, with subsequent metalation. In aqueous solution, this triarylborane (QB) can capture fluoride and cyanide anions through chelation induced by the synergy of boron and metal ions. Moreover, this triarylborane moiety acts as a fluorescent reporter of the binding, allowing for discrimination between fluoride and cyanide anions through dual-channel fluorescence changes. The different chelation models and fluorogenic responses of this sensor toward F- and CN- were verified by the single-crystal structures of 2-to-2 adduct for KCN and 1-to-1 for KF.

The cell permeable small fluorescent organic molecules possessing RNA-specific binding property were synthesized for the study of structural influence on two determining factors of binding affinity and specificity. Similar investigations are scarce in the field of RNA-specific binding ligand development based on a systematic structural change of small molecules. The newly developed and structurally simple ligands show much higher RNA-binding affinity (equilibrium binding constant: PI1, K = 4.50 × 105 M−1; PI2, K = 4.48 × 105 M−1) than that of a well-studied RNA-selective dye E36 (K = 0.89 × 105 M−1) by the introduction of an aminoethylpiperidine group on the quinolinium scaffold. In addition, the in vivo study of live cell imaging (human prostate cancer cells) indicated that these small molecules are able to provide strong interaction signals when binding with RNA in the region of nucleolus and cytoplasm. The interaction specificity of the molecule towards RNA is found much higher than other types of nucleic acids, which was further supported by the digest tests with ribonuclease (RNase). The experimental results of the present study not only provide important cues on the fluorescent signaling, binding affinity, and specificity advancement with the small RNA-specific binding ligands through structurally refinement of molecular scaffolds, but also give complementary information in searching lead ligands for targeting RNA sequence using high-throughput compound screening techniques and molecular modeling studies.

The sensitive detection and quantification of heavy and transition metal ions are particularly important. Among them, mercury(II) (Hg2+) and silver(I) (Ag+) ions, as the most ubiquitous heavy metal ion pollutants, are difficult to discriminate in the same system because of their similar reactions and coordination abilities. Herein, we designed and synthesized a “turn-on” chemosensor, RBTP, which is an intergrant of rhodol and 2-hydroxy benzothiazole by introducing a benzothiazole unit to the ortho-position of the phenolic hydroxy of rhodol. RBTP showed a sensitive dual-channel fluorescence-enhanced response to Hg2+ and Ag+ at 595 and 520 nm with low detection limits of 0.27 and 0.45 μM, respectively. Studies of their sensing mechanism indicated that the Hg2+-induced orange fluorescence at 595 nm originates from an irreversible Hg2+-promoted oxadiazole forming reaction and the Ag+-induced green fluorescence at 520 nm originates from special molecular packing of the RBTP-Ag+ complex. Furthermore, the potential of probe RBTP as practical biological imaging agents was further confirmed in HepG2 cells. Simultaneously, RBTP exhibited remarkable solid-state luminescence with an aggregation-induced emission (AIE) feature. The AIE mechanism was thoroughly explored using X-ray single-crystal structures and photophysical determinations.

Sialic acid (SA) located at the terminal end of glycans on cell membranes has been shown to play an important yet distinctive role in various biological and pathological processes. Effective methods for the facile, sensitive and in situ analysis of SA on living cell surfaces are of great significance in terms of clinical diagnostics and therapeutics. Here, a new polydiacetylene (PDA) liposome-based sensor system bearing phenylboronic acid (PBA) and 1,8-naphthalimide derived fluorophore moieties was developed as a fluorescence turn-on sensor for the detection of free SA in aqueous solution and the in situ imaging of SA-terminated glycans on living cell surfaces. In the sensor system, three diacetylene monomers, PCDA-pBA, PCDA-Nap and PCDA-EA, were designed and synthesized to construct the composite PDA liposome sensor. The monomer PCDA-pBA modified with PBA molecules was employed as a receptor for SA recognition, while the monomer PCDA-Nap containing a 1,8-naphthalimide derivative fluorophore was used for fluorescence signaling. When the composite PDA liposomes were formed, the energy transfer between the fluorophore and the conjugated backbone could directly quench the fluorescence of the fluorophore. In the presence of additional SA or SA abundant cells, the strong binding of SA with PBA moieties disturbed the pendent side chain conformation, resulting in the fluorescence restoration of the fluorophore. The proposed methods realized the fluorescence turn-on detection of free SA in aqueous solution and the in situ imaging of SA on living MCF-7 cell surfaces. This work provides a new potential tool for simple and selective analysis of SA on living cell membranes.

A promising gold nanorod sensor that demonstrated comparable antibacterial ability, selectively recognized Escherichia coli (E. coli), and used selenol as the recognition group was prepared and applied for foodstuff E.coli detection. We used a sulfhydryl compound linked with fluorescent dye by sulfamide bonds (SH-NB) to modify gold nanorods (GNRs) and fabricate GNRs-SH-NB that can selectively and sensitively detect selenol. Selenol group broke sulfamide bonds, causing the fluorescent dye to fall off from GNRs-SH-NB and exhibit red fluorescence, demonstrating that it can selectively identify E. coli with the unique selenoenzymes or selenoproteins in the bacterium. After the decomposition of GNRs-SH-NB, the obtained GNRs modified by N-heterocyclic sulfhydryl compounds and positively charged fluorescent dyes showed synergistic antibacterial properties. Furthermore, the photothermal effect of GNRs increased the temperature beyond the optimum temperature of E. coli and caused its maladjustment, leading to the death of the bacterium. Thus, GNRs-SH-NB exerted a considerable antibacterial effect against E. coli and accurately detected E. coli in milk, meat, and eggshell. With the low limit of detection, this novel antibacterial sensor GNRs-SH-NB provide a promising method to identify the E. coli and further utilized in food safety field initially.

Organic solid-state luminescence switching materials have attracted increasing interest due to their ability to manifest a reversible solid-state luminescence color change upon physical perturbation without changing the chemical structure of their component molecules. We employed the design strategy of introducing different weak C–H···π interactions into the same molecular system to obtain two metastable solid states and synthesized an o-methylphenyl substituted tetraphenylethene molecule: 1,1,2,2-tetrakis(2′-methyl-[1,1′-biphenyl]−4-yl)-ethene (TMPE). This compound showed typical aggregation-induced emission properties and a crystalline-induced luminous blue-shifted feature. The results of single-crystal structure determination and theoretical calculation indicated that the blue-shift was caused by the large twisted configuration of biphenyl units fixed by the C–H···π interactions in the crystal state. Furthermore, the compound TMPE exhibited reversible stimuli-responsive luminescence color switching between blue emission (459 nm) in the crystal state and green emission (496 nm) in the amorphous state upon fuming, grinding and heating. This work discusses the relationship between the molecular stacking mode and the photophysical properties of the compound. The X-ray single-crystal structures, characterization of the photophysical properties, powder X-ray diffraction and differential scanning calorimetry provide insight into the phase transformation and the luminescence behavior. The obvious luminescent color, high luminescent efficiency and manageable, reversible fluorescence switching give TMPE the potential to be the foundation of a class of smart organic solid luminescence switching materials.

Eu3+-doped tungstate Ba2Lu0.667WO6 was synthesized by the sol-gel method. The X-ray diffraction (XRD) patterns and structural refinement indicate that the matrix Ba2Lu0.667WO6 is trigonal double-perovskite structure. The phosphors were characterized by the scanning electron microscope (SEM), diffuse reflection, photoluminescence spectra and decay curves. It was found that the undoped host shows blue emission. The optimal doping concentration of Ba2Lu0.667WO6:Eu3+ is about 12 mol%. This phosphor can be efficiently excited by near-ultraviolet and blue light to realize the stronger orange-red luminescence. The phosphor presents the dominated 5D0→7F1 transition at a low doping level, and the 5D0→7F2 transition increases its intensity in the Eu3+-heavily doped samples. The host has the ability to converse UV light to blue, orange-red color. The thermal stability of the red-emission was investigated. The high activation energy of Ba2Lu0.667WO6:Eu3+ phosphor is very valuable for the application in W-LED devices. The different luminescence features were discussed on the base of the crystal structure.

Fluorescent solid-state organic materials have been intensively researched in recent years. In this study, two 2-(2-hydroxyphenyl)benzothiazole (HBT) derivatives: phenylethylene-modified HBT (HBT-s-Ph) and diphenylethylene-modified HBT (HBT-d-Ph), were synthesized by facile Suzuki cross-coupling reactions. In toluene solutions, the fluorescence quantum yield (Φf) of HBT-s-Ph is slightly larger than that of HBT-d-Ph, because of the presence of a stronger intramolecular H-bond in HBT-s-Ph than in HBT-d-Ph. In crystalline forms, both of their Φf has substantial improvement, and the Φf of HBT-d-Ph reaches 78%, which is twice that of HBT-s-Ph. The crystal structure revealed that the striking emission enhancement of HBT-d-Ph was attributable to its distinct molecular packing model and the resultant relatively weak intermolecular interactions induced by the single phenyl group cis to the HBT moiety.

Controllable manipulation of fluid flow is crucial for efficient particle separation, which is associated with plenty of biomedical and industrial applications. Microfluidic technologies have achieved promising progress in particle positioning depending on inertial force with or without the help of the Dean effect. Herein, we describe an inertial microfluidic system containing a spiral microchannel for various highly efficient particle separations. We demonstrated that Dean-like secondary flow can be regulated by geometric confinement in the microchannel. On the introduction of a library of micro-obstacles into the spiral microchannels, the resulting linear acceleration of secondary flow can be applied to remarkably enhance particle focusing in time and space. Further, multiple separating and sorting manipulations of particles including polymeric particles, circulating tumor cells, and blood cells, can be successfully accomplished in the dimension-confined spiral channels in a sheathless, high-throughput (typically 3 ml min-1), long-term (at least 4 h), and highly-efficient (up to 99.8% focusing) manner. The methodological achievement pointing to ease-of-use, effective, and high-throughput particle manipulations is useful for both laboratory and commercial developments of microfluidic systems in life and material sciences.

As a commonly known chemical warfare agent, sulfur mustard (SM) is a severe vesicant that can induce grievous blisters on the skin and mucous membranes. Because the onset of SM toxicity is fast, a rapid, sensitive, and accurate method for the detection of SM is necessary. However, designing an effective detection method for SM is challenging because SM does not have any traditional molecular recognition sites. In this study, a fluorescence probe for the detection of SM and an SM simulant (2-chloroethyl ethyl sulfide, CEES) was developed based on the reaction of benzenemethanethiol with the analytes. A non-emissive mercaptomethylphenyl-modified tetraphenylethene (TPE) probe was designed and synthesized. This probe can emit strong fluorescence upon reacting with CEES for 5 minutes in an aqueous solution in the presence of metal ions due to the formation of a sandwich-type complex, which can effectively restrict the rotation of the phenyl rings of TPE. Furthermore, this procedure exhibited high sensitivity for analytes and can be applied to the detection of CEES in soil. As a TPE derivative, this probe also exhibited a reversible solid-state luminescence color switching between blue emission (467 nm) in the crystal state and green emission (516 nm) in the amorphous state upon fuming, grinding and heating. These results indicate that S4 has potential as a multifunctional material of a “smart” luminophor and an AIE-active fluorescent probe for SM.

Although the organic dyes based on excited state intramolecular proton transfer (ESIPT) mechanism have attracted significant attention, the structure-property relationship of ESIPT dyes needs to be further exploited. In this paper, three series of ethynyl-extended regioisomers of 2-(2'-hydroxyphenyl)benzothiazole (HBT), at the 3'-, 4'- and 6-positions, respectively, have been synthesized. Changes in the absorption and emission spectra were correlated with the position and electronic nature of the substituent groups. Although 4'- and 6-substituted HBT derivatives exhibited absorption bands at longer wavelengths, the keto-emission of 3'-substituted HBT derivatives was found at a substantially longer wavelength. The gradual red-shifted fluorescence emission was found for 3'-substituted HBT derivatives where the electron-donating nature of substituent group increased, which was opposite to what was observed for 4'- and 6-substituted HBT derivatives. The results derived from the theoretical calculations were in conformity with the experimental observations. Our study could potentially provide experimental and theoretical basis for designing novel ESIPT dyes that possess unique fluorescent properties.

Polydiacetylene (PDA) materials have been adopted as one of the powerful conjugated polymers for sensing applications due to their unique optical properties. In this paper, we present a new PDA liposome-based sensor system with enhanced fluorescent self-amplification by tuning a fluorophore fluorescence emission. In this system, a 1,8-naphthalimide derivative employed as a highly fluorescent fluorophore was incorporated into a PDA supermolecule. During the formation of blue PDA liposomes, the fluorescence emission of the fluorophore can be directly quenched, while thermal-induced phase transition of PDA liposomes from blue to red can readily restore this fluorescence emission. These phenomena could be ascribed to the tunable Förster energy transfer between the excited fluorophore and PDA conjugated framework. To demonstrate the sensing performance of this newly prepared PDA liposome-based sensor, the sensor with fluorescent self-amplification was successfully applied for the detection of cationic surfactants (CS). The results show that the PDA liposomes displayed a distinct color change and fluorescence restoration in the presence of cationic surfactant species, and allowed detection of cationic surfactants with high sensitivity and selectivity. The limit of detection for target CS, such as cetyltrimethylammonium bromide (CTAB), can reach as low as 184 nM. Compared to the traditional methods based on colorimetric PDA liposomes, this newly fabricated PDA sensor system was superior for sensitivity. Thus, our findings offer an avenue for the design and development of new types of PDA sensors with enhanced sensitivity.

An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples.

Electrochemical determination of luteolin and baicalein always needs acidic supporting electrolyte to guarantee good sensitivity. Therefore, most of the reported electrochemical sensors of luteolin and baicalein are unsuitable for detection of neutral actual samples. It is necessary to design a highly sensitive sensor for direct determination of them in neutral conditions. In this study, poly(N-isopropylacrylamide-acrylic acid) hydrogel particles (NIPA/AA) and multiwall carbon nanotubes (MWCNTs) composite modified glassy carbon electrode (GCE) was fabricated by a simple casting method. The voltammetric results showed that the NIPA/AA particle film provided acidic environment for proton-electron coupled reaction in neutral mediums. The near-surface pH of the electrode was related on the loaded amount of the NIPA/AA particles in pH range from 4.2 to 5.9. The voltammetric behaviors of luteolin and baicalein at the NIPA/AA-MWCNTs-GCE were studied by cyclic voltammetry. The peak separations between cathodic and anodic peaks were decreased and peak currents were increased because of decrease in pH and increase in ion conductivity at the local electrode surface. The sensitivity of the electrode was investigated by differential pulse voltammetry. Even under neutral conditions, the plots of the oxidation currents of luteolin and baicalein were dependent linearly on their concentration with detection limit of 14.5 pM and 44.4 pM, respectively. Moreover, the proposed NIPA/AA-MWCNTs-GCE was also successfully applied for determination of luteolin and baicalein in peanut shell, Huang-qin and tomato samples.

We designed and synthesized a tri-(2-picolyl) amine (TPA) functionalized triarylborane, 1-(6-(4-(dimesitylboryl)phenyl)pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine (PB2). The photophysical properties of PB2 were thoroughly explored. Moreover, PB2 can capture CN− and F− in aqueous solution through strong chelation induced by the synergy of a boron atom and metal ion gripped by TPA to display entirely different fluorogenic responses such as fluorescence enhancement for CN− and fluorescence quenching for F−. The results of TOF-MS-EI analysis and theoretical calculations indicate that the complexing of PB2 with CN− formed a 2-to-2 adduct with a stabilized configuration, resulting in strong emission. The complexing of PB2 with F− formed a 1-to-1 adduct with a loose configuration, resulting in weak emission. In pure water, the detection limit of PB2 for CN− is 0.79 μM, and in H2O/THF (1:9 v/v) system, the detection limits of PB2 for CN− and F− can reach 0.39 and 2.12 μM, respectively, indicating its potential application for effective detection and discrimination of CN− and F−.

The development of sensitive colorimetric and fluorescent chemosensors for Cu2+ sensing has gained much attention in recent years because of their potential application in clinical biochemistry and environmental studies. Herein, a novel rhodamine-based chemosensor NRG was constructed, which exhibited high sensitivity and selectivity and a quick response for Cu2+, accompanied by remarkable color and fluorescence changes. Moreover, besides sensing Cu2+, NRG can capture Cu2+ effectively and quickly in aqueous solution. Based on the results, NRG-functionalized gel balls were fabricated and exhibited strong adsorbability and a high adsorption capacity for Cu2+, accompanied by an obvious color change. More interestingly, the gel balls can be recycled after treatment with an EDTA solution. These excellent properties make the gel ball a promising candidate for copper ion purification.

Aggregation-induced emission (AIE) has attracted considerable interest in recent years. An understanding of the underlying mechanisms for the AIE phenomena is also of great importance. Here, we synthesized four fluorenone derivatives, which all show typical AIE properties. Their enhanced solid-state luminescence showed a 160 nm red-shift (from 380 to 540 nm) in comparison to their luminescence in dilute tetrahydrofuran (THF) solutions. The single-crystal structure and photophysical properties revealed that the bathochromic luminescence is due to the formation of static excimers. To further demonstrate the AIE mechanism of static excimers, rather than restricted intramolecular rotation (RIR), we designed a diphenylfluorenone-diboronic acid adduct, which can react with d -glucose to create structurally rigid oligomers, resulting in the restriction of intramolecular rotations. The spectral change in the d -glucose titration of the adduct indicated that the bathochromic AIE of these fluorenone compounds cannot possibly be caused by RIR and conformational planarization.

Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) is employed to investigate the electrochemical behavior of adenine molecules on smooth Ag electrodes. To attain this goal, pinhole-free shell-isolated Ag nanoparticles (Ag SHINs) have been synthesized and then used as signal “amplifiers” in the gap-mode configuration (Ag SHINs are coupled with a Ag electrode surface). The as-prepared Ag SHINs exhibit remarkable plasmonic performance under 488, 532, and 633 nm excitations as revealed by finite-difference time-domain (FDTD) simulations and SHINERS experiments. Furthermore, wavelength-dependent SHINERS investigation of adenine on Ag electrodes is excellently combined with the electrochemical technique. With outstanding chemical stability and plasmonic property, the Ag SHINs are extraordinarily suitable for fundamental studies at various electrochemical interfaces.

Copper-free click chemistry has been used to graft quaternized poly(dimethylaminoethyl methacrylate) (QPA) modified with azide to the quantum dots (QDs) derived with dibenzocyclooctynes (DBCO). The success of the quaternary ammonium polymer-modified QDs was confirmed by ultraviolet-visible spectrophotometry (UV-Vis), fluorescence spectroscopy, zeta (ζ) potential, size distribution, and transmission electron microscopy (TEM). The QPA-modified QDs exhibited properties of selective recognition and killing of bacteria. The novelty of this study lies in fact that the synthesis method of the antimicrobial QPA-modified QDs is simple. Moreover, from another standpoint, QPA-modified QDs simultaneously possess abilities of selective recognition and killing of bacteria over mammalian cells, which is very different from the currently designed multifunctional antimicrobial systems composed of complicated systematic compositions.

Hydrogen sulfide (H2S) and sulfite (SO32−) are two important sulfur-containing species that play different and important roles in industrial and biological processes. Accordingly, the development of efficient methods for simple, rapid, sensitive and selective monitoring of H2S and SO32− is of the utmost importance in both environmental and biological sciences. In this study, we developed a new dual functional probe NIR-DNP for discriminative detection of H2S and SO32−. This probe can sense H2S and SO32− via two different approaches, a significant near-infrared fluorescence enhancement and color change from purple to cyan induced by H2S as well as a visible color change from purple to colorless caused by SO32−. The detection limits of the probe NIR-DNP for H2S and SO32− in aqueous solutions were 36.53 nM and 33.33 nM, respectively. Competitive experiments demonstrated that the probe NIR-DNP had a high fluorescence selectivity for H2S and excellent colorimetric selectivity for SO32− over other analytes. The sensing mechanism of the probe toward H2S and SO32− was based on the H2S-induced thiolysis of dinitrophenyl ether and SO32−-induced nucleophilic addition, respectively. Further investigation showed that the probe NIR-DNP could be used to develop an easy-to-prepare and easy-to-detect paper-based test strip for cheap and effective detection of SO32−. Also, the probe NIR-DNP has the potential to image exogenous and endogenous H2S in living cells.

We report a visualized method for the detection of Cu2+ ions, which relies on the Cu(I)-catalyzed 1,3-dipolar cycloaddition of alkynes on the surface of functionalized QDs and azides on the surface of functionalized graphene oxide (GO). This click chemistry process results in self-assembly of GO-N3 sheets into aggregates that can be observed by the naked eye. The catalyst, Cu(I), was conveniently derived from the reduction of Cu(II) in the presence of sodium ascorbate, thereby allowing the reaction to serve as a naked eye method to assay for the presence of Cu2+ ions.

Near-infrared (NIR) fluorophore with one functional group, which can be utilized to conjugate other molecules, could meet various requirements just through structural modification, such as for regulating their subtle equilibrium between hydrophilicity and lipophilicity. Herein, considering the favorable photophysical properties of dicyanomethylene-benzopyran (DCMB) derivatives and the orthogonality of functional groups and the excellent biocompatibility of CuI-catalyzed click chemistry, the synthesis of azido and phenolic hydroxyl-bifunctionalized DCMB-based compound N3-DCMBOH is described, which can conjugate with other molecules by click chemistry. As a preliminary exploration, tert-butyldiphenylsilyl group and alkynyl-contained quaternary ammonium were successively conjugated onto N3-DCMBOH to construct NIR fluorescent sensor QA-DCMBSi for detection of F−. The dramatic absorption band change with 196 nm red shift and distinct NIR fluorescence enhancement at 718 nm, can be attributed to F− mediated cleavage of silicon-oxygen bond to release QA-DCMBOH, which was verified by MS spectrum.

Self-activated phosphor Ba2V2O7 microrods were prepared by the hydrothermal reaction method. Structural refinement was conducted on the basis of the X-ray diffraction (XRD) measurements. The morphological properties of the sample were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical elements of the microrods were determined by energy dispersive spectrometry (EDS) measurements. The Ba2V2O7 microrods have a big length–diameter ratio with a diameter of 10–50 μm and length of 0.5–2 μm. The UV-vis optical absorption of the Ba2V2O7 microrods shows a direct allowed electronic transition with a band energy of 3.22 eV. The photoluminescence properties were studied such as emission and excitation spectra, the decay curve and lifetime, color coordinates and the absolute internal quantum efficiency (η). Notably, the Ba2V2O7 microrods present bright luminescence with a high quantum efficiency of 47.5%. It is suggested that Ba2V2O7 microrods could be used for efficient lighting and displays. Moreover, Ba2V2O7 microrods show scintillating properties, which were confirmed by X-ray excited luminescence (XEL) at room temperature. The morphological characteristics of the microrods could also have the potential to greatly reduce the cost of fabricating flexible lighting devices.

Smart organic luminescence materials that exhibit a reversible stimuli-responsive change of luminescence color in the solid state without changing the chemical structure of their component molecules have attracted increasing interest. We employed the design strategy of introducing different weak interactions into the same molecular system to synthesize 2,7-bis(2′-methyl-[1,1′-biphenyl]-4-yl)-fluorenone (MPF). Two crystal polymorphs of MPF, green-yellow crystal G-MPF and orange crystal O-MPF, were obtained through culturing the single crystal under the different crystallization conditions of diffusing diethyl ether into its respective tetrahydrofuran or CH2Cl2 solution. Both of the two crystal polymorphs exhibit high luminous efficiency and reversible stimuli-responsive solid-state luminescence color switching. Upon heating the green crystal G-MPF or grinding the orange crystal O-MPF, their emission reversibly changes between green at 530 nm and orange at 570 nm. The X-ray single-crystal structures, characterization of the photophysical properties, powder X-ray diffraction and differential scanning calorimetry provide insight into the phase transformation and the luminescence behavior. The results indicate that the green emission of G-MPF originates from molecular J-aggregation and the orange emission of O-MPF originates from static excimers. This work discusses the relationship between the molecular stacking mode and the photophysical properties, and demonstrates a molecular design strategy to obtain stimuli-responsive organic solid-state luminescence switching materials.

In this work, we designed and synthesized four symmetric and asymmetric thienyl-substituted fluorenone compounds, which all exhibited typical AIE properties. Besides a high solid-state fluorescence quantum yield, the enhanced luminescence of their solid-state powders showed a 170 nm red-shift (from 380 to 550 nm) in comparison with the luminescence of their dilute tetrahydrofuran solutions. The photophysical properties and single-crystal structure, combined with the theoretical calculation, revealed that the bathochromic luminescence is due to the formation of static excimers.

β-BiNbO4 with a high temperature triclinic form was prepared via a high-temperature solid-state reaction ceramic method. Structural refinement and surface characteristic studies were performed. The optical absorption, and electronic calculation of the band structures and density of states were also studied. β-BiNbO4 ceramic has an indirect transition with a band energy of 3.05 eV. The valence band is dominated by O-2p states whereas the conduction band has predominantly Nb 4d and Bi 6s character. The intrinsic luminescence properties of β-BiNbO4 were reported, and present a blue emission band peak at 435 nm under the excitation of UV light. The β-BiNbO4 ceramic presents scintillation properties under high energy irradiation. The luminescence was studied via the combinations of the color centers, band calculation and energy transfer from NbO6 to Bi(3+) in the lattices. The thermal quenching and activation energy for the luminescence were reported. β-BiNbO4 has potential applications in photoluminescence and scintillation materials.

Pb2+ and Cd2+ are the most ubiquitous heavy metal ion pollutants, and they have aroused much attention due to their irreversible and significant damage to human organ. In this work, a new fluorescein-based “OR-AND” logic gate colorimetric probe 3′,6′-bis((tert-butyldiphenylsilyl)oxy)-2-(2-((2-hydroxyphenyl)imino)ethylidene)aminspiro[isoindoline-1,9′-xanthen]-3-one (FP) was designed and synthesized via attaching 2-(2-((2-hydroxyphenyl)imino)ethylidene)amino and tert-butyldiphenylsilyl to fluorescein as the specific identification groups. This sensor can rapidly and sensitively discriminate Pb2+ and Cd2+ by utilizing F− as an auxiliary reagent. When Pb2+ or Cd2+ was added into the FP solution, the absorption band at 533 nm increased and the peak at 374 nm decreased, the color changed from colorless to pale-purple, resulting in a ratiometric spectral change. However, adding fluoride ion to the FP solution containing Pb2+ or Cd2+ resulted in a distinct phenomenon in which the pale purple color fades out to colorless for a Pb2+-containing solution and deepen to dark purple for a Cd2+-containing solution, which is attributable to the different coordination mechanisms. In aqueous solution, the detection limits of FP can reach 0.42 μM for Pb2+ and 0.53 μM for Cd2+. The probe exhibited rapid responses for these analytes. Moreover, FP was successfully used to rapidly detect trace amounts of hazardous Pb2+ and Cd2+ in tap water with good relative recovery and the relative standard deviations (RSD) were 1.8% for Pb2+ and 0.3% for Cd2+, providing a novel approach for detecting Pb2+ and Cd2+ in practical application.

Among organic small molecules, hydrogen peroxide (H2O2) and hydrazine (NH2NH2) often cause concern because they are widely used in biological and chemical industries. Here, we present a novel probe RH-1 for colorimetric detection of NH2NH2 and fluorescent imaging of H2O2. In this probe, rhodamine was used as the main skeleton due to its favorable spectroscopic performance and stable absorption. Importantly, a benzoic acid group is present in the rhodamine skeleton, which can react with NH2NH2 by amidation. The rhodamine skeleton can also be modified with chromogens to detect H2O2. Results showed that RH-1 can be used for colorimetric detection of NH2NH2 and fluorescent monitoring of H2O2 with high selectivity and sensitivity. The detection limits for NH2NH2 and H2O2 were 0.27 and 0.16 μM, respectively. Moreover, RH-1 can fluorescently image H2O2 in living cells with low cytotoxicity.

New generation of antibacterial agents are urgently needed in order to fight the emergence of multidrug-resistant bacteria. FtsZ is currently identified as a promising target for new types of antimicrobial compounds development because of its conservative characteristics and its essential role played in bacterial cell division. In the present study, the antibacterial activity of a series of benzofuroquinolinium derivatives was investigated. The results show that the compounds possess potent antibacterial activity against drug resistant pathogens including MRSA, VREF and NDM-1 Escherichia coli. Biological studies reveal that the compound is an effective inhibitor that is able to suppress FtsZ polymerization and GTPase activity and thus stopping the cell division and causing cell death. More importantly, this series of compounds shows low cytotoxicity on mammalian cells and therefore they could be new chemotypes for the development of new antibacterial agents targeting the cell-division protein FtsZ.

In this paper, we introduced a new sensor for detecting sulfur mustard (SM) and its simulant through the functionalization of a rhodol chromophore with benzothiazole, followed by thionation of the spirolactam. The synthesized chemodosimeter (RHBT) exhibited an obvious green-yellow fluorescence enhancement and chromogenic change from colorless to fuchsia in the presence of SM and its simulant stimuli, which is based on the spirothiolactam ring opening of rhodol induced by the synergy of S-alkylation of thiolactam and the excited state intramolecular proton transfer (ESIPT) of rhodol-benzothiazole. Furthermore, the chemodosimeter was successfully demonstrated for the rapid detection of SM and its simulant in solution, soil and air at ambient temperature, indicating its potential application for on-site detection of sulfur mustard.

The increasing incidence of multidrug resistant bacterial infection renders an urgent need for the development of new antibiotics. To develop small molecules disturbing FtsZ activity has been recognized as promising approach to search for antibacterial of high potency systematically. Herein, a series of novel quinolinium derivatives were synthesized and their antibacterial activities were investigated. The compounds show strong antibacterial activities against different bacteria strains including MRSA, VRE and NDM-1 Escherichia coli. Among these derivatives, a compound bearing a 4-fluorophenyl group (A2) exhibited a superior antibacterial activity and its MICs to the drug-resistant strains are found lower than those of methicillin and vancomycin. The biological results suggest that these quinolinium derivatives can disrupt the GTPase activity and dynamic assembly of FtsZ, and thus inhibit bacterial cell division and then cause bacterial cell death. These compounds deserve further evaluation for the development of new antibacterial agents targeting FtsZ.

Herein, we designed and synthesized a luminophor, Rh-F, which is an intergrant of rhodol and 2-hydroxy benzothiazole by introducing a benzothiazole unit onto the ortho-position of the phenolic hydroxy of rhodol. Rh-F exhibited excellent fluorescence properties such as a large Stokes shift (>180 nm) and the synergistic effect of aggregation-induced emission (AIE) and an excited state intramolecular proton transfer (ESIPT) feature. The AIE/ESIPT mechanism was thoroughly explored using X-ray single-crystal structures and photophysical determinations. Furthermore, Rh-F showed a sensitive fluorescence response to Fe2+ with low detection limits of 115.2 nM and high selectivity. Studies of its sensing mechanism indicated that the Fe2+-induced blue-green fluorescence-quenched at 525 nm originates from an irreversible Fe2+ chelate with the oxygen atom of the hydroxyl group and the N atom of the benzothiazole moiety. This blocked the ESIPT process of Rh-F which resulted in the quenching of the fluorescence sensor for Rh-F.

C3-symmetric truxene and triindole have been widely used to design the branched optoelectronic molecules. However, most of them exhibit high luminous efficiency in the solution and quenched luminescence in the solid state. Here, we respectively chose alkylated truxene and triindole as the central core, 2-methylphenyl as the peripheral functional groups to synthesize three branched compounds. Their photophysical properties have been explored combining with the theoretical calculation. The three compounds exhibit good solubility and high solid-state fluorescence quantum yields. The absorption and emission peaks of triindole compound exhibit apparent red-shift in comparison with those of truxene compounds, which indicates triindole more highly electron delocalization than truxene. The single-crystal structure shows that alkylation of the central core and branched steric bulkiness of these molecules effectively reduce the intermolecular π⋯π stacking and avoid the non-radiative transition of these molecules from excited state to ground state in the solid state.

In this paper, we designed and synthesized a novel TBET-based ratiometric fluorescent chemodosimeter, RH-Au, for Au(3+). It was found that the probe RH-Au displayed highly selective, sensitive and naked-eye detection upon the addition of Au(3+). The probe RH-Au can be used in the pH range 6.0-7.5 and the detection limit was determined to be as low as 2.91 nM (0.57 ppb). We also demonstrated a successful application of imaging Au(3+) in living cells using RH-Au.