Two three-dimensional coordination polymers as fluorescence probes for the detection of nitrobenzene, tetracycline, fluazinam and their application in green pepper.

Two coordination polymers (CPs), [Zn5(L)2(phen)5](1) and [Cd2(HL)(2,2-bpy)(H2O)3](2), were synthesized by using 2',3,3',5,5'-Diphenyl ether pentacarboxylic acid (H5L), phenanthroline (phen), and 2,2'-bipyridine (2,2'-bpy) under hydrothermal conditions. The L5- ligand adopts the µ6-к2: к2: к1: к1: к1: к1 mode in 1 and the µ5-к2: к2: к2: к2: к1 mode in 2. Sensing experiments show that 1 and 2 are fluorescence probes with high sensitivity and rapid detection of nitro explosives, antibiotics, and pesticides. In order to verify the ability of 2 to detect FLU in actual samples, we performed a spiked recovery experiment in green pepper water. The spiked recoveries were 97.77-101.18 %. Interestingly, because H5L is not completely deprotonated in 2, there is abundant hydrogen bonding, which makes the fluorescence quenching rate higher and the detection limit lower. The possible fluorescence quenching mechanism of 1 and 2 can be explained by their UV-VIS absorption spectra and orbital energy levels.

A terphenyl derivative-based colorimetric-fluorimetric probe for the detection of lysine and arginine and their bioimaging.

Lysine (Lys) and arginine (Arg) play a crucial role in the human diets, medical diagnostics, and functional biomaterial synthesis. The imbalance of intake for these two amino acids causes various diseases. Although many analytical techniques have been reported for the detection of amino acids, there are still some issues such as the need for bulky instruments, professional operators, sensitivity to be improved, and real-time detection. Here, a novel colorimetric-fluorimetric probe based on a terphenyl derivative (TPT) has been synthesized for the precise detection of Lys and Arg. In the EtOH-H2O solution of TPT, the NH2 group at the chain end of Lys/Arg undergoes a nucleophilic addition reaction with CN groups of benzothiazole groups of the probe TPT, which breaks the initial long-conjugated system of the probe molecule. As a result, blue shifts can be observed for both UV-vis absorption spectra and fluorescence spectra, accompanying with color changes of the TPT solution. The UV-vis absorption peak of TPT solution shifts from âˆ¼410 nm to âˆ¼325 nm, and the solution color changes from light-yellow to colorless. The fluorescence emission shifts from âˆ¼580 nm to âˆ¼470 nm and the bright-yellow TPT solution changes to blue under the irradiation of 365 nm UV light. For colorimetric method, the limits of detection (LoD) are 0.82 µM and 0.90 µM for Lys and Arg, respectively. For fluorimetric method, they are 2.02 nM and 1.62 nM for Lys and Arg, respectively. In addition, TPT has good selectivity and anti-interference for Lys and Arg. The synthesized probe TPT has been successfully used for the precise detection of Lys and Arg in drugs and for fluorescence imaging of living cells. This work demonstrates that terphenyl-based derivatives are promising organic probes for the detection of Lys and Arg, providing a new way for designing other amino acids probes.

Cu(I)-Catalyzed Highly Regioselective C-H Amidation of Quinoline N-Oxides with Dioxazolones.

A Cu(I)-catalyzed highly regioselective synthesis of 2-acetamidequinoline N-oxides using dioxazolones with quinoline N-oxides has been reported. The reaction possesses mild reaction conditions and excellent functional group compatibility. Furthermore, the addition of hydrochloric acid promotes the decomposition of copper complexes, which is beneficial for postprocessing.

A multifunctional sensor for detecting tetracycline, 4-nitrophenol, and pesticides.

In recent years, due to the abuse of antibiotics, nitro explosives and pesticides, which have caused great harm to the environment and human health, social concerns have prompted researchers to develop more sensitive detection platforms for these pollutants. In this paper, a novel two-dimensional Zn (II) coordination polymer, [Zn(L)0.5(1,2-bimb)]·DMF (1), [H4L=[1,1':4',1''-terphenyl]-2, 2'',4, 4'' -tetracarboxylic acid, 1,2-bimb = 1,2-bis(imidazol-1-ylmethyl)benzene] was synthesized using a hydro-solvothermal method. Among commonly used organic solvents, 1 exhibits significant stability. Fast and efficient fluorescence response can be achieved for tetracycline (TET), 4-nitrophenol (4-NP), fluazinam (FLU), and abamectin benzoate (AMB) with low detection limits. A binary intelligent logic gate device with FLU and AMB as chemical input signals is successfully constructed, which provides a new idea for biochemical detection. In addition, a portable visual test paper has been prepared, which has high sensitivity, good selectivity, and simple operation. It can be used for rapid detection of pollutants in daily life and has broad application prospects. Finally, a detailed discussion was conducted on the fluorescence sensing mechanism of 1 for detecting TET, 4-NP, AMB and FLU.

Synthesis of highly sensitive and multi-response Eu-MOF, fluorescence sensing properties and anti-counterfeiting applications.

A new Europium metal-organic framework (Eu-MOF), namely [Eu(dpa) (H2O)]·0.5(bpy)·4H2O}n (H4dpa = 5-(3,4-dicarboxyphenoxy) isophenic acid, bpy = protonated 4,4'-bipyridine) was synthesized and structurally characterized by elemental analyses, infrared spectroscopy, and X-ray single-crystal diffraction analyses. Eu-MOF shows a three-dimensional network structure based on EuIII ions and (dpa)4- ligands via µ4: η1, η2, η2, η2 coordination mode. Fluorescence analysis shows that Eu-MOF has excellent fluorescence sensing characteristics, which can efficiently and sensitively detect various pollutants in water: the limit of detection (LOD) of ratiometric fluorescence detection of ANI in water was 42.9 nM, which was better than the single-peak detection limit. In addition, the peak detection limits of Eu-MOF for Flu, ORN and NB were 120 nM, 27 nM and 94 nM, respectively. In addition, XPS, LUMO orbital energy level, fluorescence lifetime, ultraviolet absorption and other principles are used to explore the mechanism of fluorescence quenching. Surprisingly, Eu-MOF not only has excellent anti- counterfeiting ability and stability, can be used as anti-counterfeiting material in life, but also has good selectivity to Flu. Eu-MOF has obvious fluorescence quenching effect on Flu on paper under ultraviolet light, which can be used for rapid in situ imaging test paper of pesticide residues.

Responsive photonic hydrogel for colorimetric detection of formaldehyde.

Formaldehyde (FA) can damage DNA, cause liver and kidney dysfunction, and ultimately lead to malignant tumors. Therefore, it is essential to develop a method that can conveniently detect FA with high detection sensitivity. Here, a responsive photonic hydrogel was prepared by embedding three-dimensional photonic crystal (PC) into amino-functionalized hydrogel to construct a colorimetric sensing film for FA. The amino groups on the polymer chains of the photonic hydrogel reacts with FA to increase the crosslinking density of the hydrogel, resulting in its volume shrinkage and a decrease in microsphere spacing of the PC. That causes the reflectance spectra blue-shift of more than 160 nm and color change from red to cyan for the optimized photonic hydrogel, achieving the sensitive, selective and colorimetric detection of FA. The constructed photonic hydrogel shows good accuracy and reliability for practical determination of FA in air and aquatic products, providing a new strategy for designing other target analytes responsive photonic hydrogels.

MOFs-based Fe@YAU-101/GCE electrochemical sensor platform for highly selective detecting trace multiplex heavy metal ions.

The construction of sensors with specific recognition functions can easily, sensitively and efficiently detect heavy metal ions, which is a demand in the field of electrochemical sensing and an important topic in the detection of environmental pollutants. An electrochemical sensor based on MOFs composites was developed for sensing of multiplex metal ions. The large surface area, adjustable porosities and channels in MOFs facilitate successful loading of sufficient quantities highly active units. The active units and pore structures of MOFs are regulated and synergetic with each other to enhance the electrochemical activity of MOFs composites. Thus, the selectivity, sensitivity and reproducibility of MOFs composites have been improved. Fortunately, after characterization, Fe@YAU-101/GCE sensor with strong signal was successfully constructed. In the presence of target metal ions in solution, the Fe@YAU-101/GCE can efficiently and synchronously identify Hg2+, Pb2+, and Cd2+. The detection limits (LOD) are 6.67 × 10-10 M(Cd2+), 3.33 × 10-10 M(Pb2+) and 1.33 × 10-8 M (Hg2+), and are superior to the permissible limits set by the National Environmental Protection Agency. The electrochemical sensor is simple without sophisticated instrumentation and testing processes, hence promising for practical applications.

A "turn-on" inverse opal photonic crystal fluorescent sensing film for detection of cysteine and its bioimaging of living cells.

A "turn-on" inverse opal photonic crystal fluorescent sensing film infiltrated with a coumarin derivative is reported for the reliable and accurate detection of cysteine in human serum and fluorescence imaging of living cells. The coumarin derivative containing allyl ester specifically reacts with cysteine by ammonolysis to generate a fluorescent product whose emission wavelength is at ~ 535 nm, providing a selective fluorescence detection for cysteine. The emitted fluorescence is significantly enhanced due to the slow photon effect derived from the photonic crystal film. This is because the emission wavelength is overlapped with the blue-band edge of the photonic stopband of the selected inverse opal film. The fluorescence enhancement effect endows the prepared inverse opal film with highly sensitive detection with a limit of detection of 3.23 × 10-9 mol/L and a wide linear detection range of 1 × 10-7 - 1 × 10-3 mol/L. A fast response within 30 s toward cysteine is also achieved due to the three-dimensional interconnected macroporous structure with a high-specific surface area of the inverse opal film. The prepared inverse opal fluorescent sensing film has been successfully applied to the detection of cysteine in human serum and bioimaging of living cells. In the diluted human serum, the recoveries for the detection of cysteine were 97.92 - 107.20%, and the relative standard deviations were 2.61-9.04%, demonstrating the potential applicability of the inverse opal fluorescent sensing film to real sample analysis. The method may provide a universal strategy for constructing various photonic crystal fluorescent sensing films by using different fluorescent probes.

Zn-MOFs composites loaded with silver nanoparticles are used for fluorescence sensing pesticides, Trp, EDA and photocatalytic degradation of organic dyes.

The abuse of pesticides, antibiotics, organic solvents, etc., not only deteriorates the ecological environment, but even affects the normal development of organisms, posing a serious threat to global public health.Efficient and sensitive detection of pesticides, antibiotics, organic solvents and so on are very important, but also a challenge to scientists. By depositing Ag nanoparticles on the surface of Zn-MOF (1: {[Zn2(bta)(bpy)(H2O)2]·2H2O}n), a new type of composite material (Ag@1) was successfully synthesized and analyzed by TEM, EDS, XPS, XRD, IR and other characterization methods. Ag@1 can serve as multi-response fluorescence sensor to detect pesticides (fluazinam (FLU) and emamectin benzoate (EMB)), Tryptophan (Trp) and Ethylenediamine (EDA). In particular, Ag@1 showed "turn-off" fluorescence sensing for FLU and EDA, and "turn-on" fluorescence sensing for EMB and Trp. It is worth mentioning that we further explored its analysis of FLU and Trp in real water samples and fetal bovine serum. The recoveries are satisfactory, 97.95 % - 102.39 % and 96.69 % - 101.85 %, respectively. In addition, the photocatalytic performance of Ag@1 was found to be excellent, the degradation rate of methylene blue (MB) reached 86 %, and its degradation mechanism was discussed.

Water-Stable Cd-MOF with fluorescent sensing of Tetracycline, Pyrimethanil, abamectin benzoate and construction of logic gate.

Due to the indiscriminate abuse of pesticides and antibiotics has caused serious threats to the environment and human and animal bodies, the detection of antibiotics and pesticides has attracted widespread attention in recent years. Herein, a novel 2D Cd (II)-MOF, [Cd(L)0.5(1,2-bimb)] (Cd-L-1,2-bimb), [H4L = 1, 1'-ethylbiphenyl -3, 3', 5, 5'- tetracarboxylic acid, 1, 2-bimb = 1, 2-bis[(1H-imidazol-1-yl) methyl] benzene] is synthesized. Cd-L-1,2-bimb has excellent stability in different organic solvents and in the range of pH 1.1-12.5. Cd-L-1,2-bimb exhibits high selectivity, high sensitivity, and fast luminescent response to pesticides [pyrimethanil (PTH, LOD = 2.2 µM) and abamectin benzoate (AMB, LOD = 2.39 µM)] and antibiotic contaminants tetracycline (TET, LOD = 0.13 µM). Cd-L-1,2-bimb displays discriminative fluorescence when detecting AMB and PTH, and is an implication logic gate. Finally, the possible detection mechanism of Cd-L-1,2-bimb toward different pollutants is also further investigated. This MOF-based multifunctional sensor opens up new prospects for environmental monitors.

Mechanistic Insights into Cobalt-Catalyzed Regioselective C4-Alkenylation of 3-Acetylindole: A Detailed Theoretical Study.

A detailed mechanistic study of Co(III)-catalyzed C4-alkenylation of 3-acetylindole (1a) was done based on calculations at density functional theory (DFT) and correlated wave function levels. The whole catalytic cycle consists of four steps: C-H activation, olefin insertion, ß-hydride elimination, and regeneration of the catalyst. The theoretical results support olefin insertion as the rate-determining step leading to the experimentally observed regioselectivity of the C4 site over the C2 site. By the analysis of three-dimensional (3D) geometries and the NCl plot, the preference for the C4 site over the C2 site could be attributed to the weaker repulsive interaction between the indole moiety and olefin in the transition states of the olefin insertion step for the former. The reliability of the theoretical mechanistic results is further confirmed through the DFT calculation of other related indole derivatives and olefin substrates.

Ascorbic acid functionalized anti-aggregated Au nanoparticles for ultrafast MEF and SERS detection of tartrazine: an ultra-wide piecewise linear range study.

Tartrazine, as a synthetic food colorant, is harmful to health upon excessive intake. In this study, we developed a simple, sensitive and ultrafast method to detect tartrazine effectively. Specifically, we successfully used ascorbic acid-functionalized anti-aggregated Au nanoparticles (AuNPs) as enhanced substrates to detect tartrazine in drinks using metal enhanced fluorescence (MEF) and surface-enhanced Raman scattering (SERS) piecewise linearly. The fluorescence intensity and Raman signals of the tartrazine solution enhanced after the addition of AuNPs. There was a good linear correlation between the fluorescence intensity and the concentration of tartrazine from 2.0 µM to 40.0 µM, and the limit of detection (LoD) was 15.4 nM. In addition, the Raman intensity also increased linearly with an increase in the concentration of tartrazine in a wide range (1.0 × 10-5 µM to 1.0 × 10-1 µM) and a lower LoD (0.8 pM) was achieved compared with the results from the fluorescence technique. Both fluorescence and SERS can immediately detect tartrazine in drinks after the substrate was mixed with analytes. Hence, the as-prepared anti-aggregated AuNPs as substrate material achieved a highly sensitive, selective and ultrafast detection of tartrazine via fluorescence and Raman techniques in a wide detection range, providing a novel strategy for the detection of food additives.

Information encryption, highly sensitive detection of nitrobenzene, tetracycline based on a stable luminescent Cd-MOF.

A stable luminescent Cd-MOF, formulated as [Cd(L)0.5(4, 4'-bpy)0.5]·H2O (1), (H4L = 1, 1'-ethylbiphenyl -3, 3', 5, 5'- tetracarboxylic acid, 4, 4' -bpy = 4, 4'-bipyridine), is acquired under solvothermal conditions. 1 exhibits stability in the pH range from 1.5 to 12.2 and in different organic solvents. 1 can detect tetracycline and nitrobenzene by fluorescence quenching with high sensitivity and selectivity. The detection limits are 0.14 µM and 14 nM, respectively. Interestingly, 1 can encapsulate Tb3+ and sensitize its characteristic peaks. Moreover, the fluorescent ink is prepared by using the luminescent properties of the Tb3+@Cd-MOF. The light of the fluorescent ink disappears in an acid gas HCl atmosphere and then reappears in an alkaline gas ammonia atmosphere. This phenomenon can be repeated and the reason for this phenomenon is also explained in the article. Therefore, Tb3+@Cd-MOF has huge application potential in information encryption.

Highly selective detecting Aspartic acid, detecting Ornidazole and information encryption and decryption supported by a heterometallic anionic Cd (II)-K (I)-MOF.

A highly stable heterometallic MOF, {[(Me2NH2)2]·[Cd2K2(L)2(H2O)]}n (H4L = terphenyl-2, 2', 4, 4'-tetracarboxylic acid) (1), was synthesized. 1 featuring one-dimensional channels can efficiently detect Aspartic acid with a low limit of detection (LOD) value (2.5 µM). More interestingly, 1 can encapsulate Eu3+ and sensitize the visible-emitting characteristic fluorescence of Eu3+ in aqueous solution. Then, Eu3+@CdK-MOF is found to be an excellent fluorescence sensor for the detection of Ornidazole (ODZ) and the portable ODZ test paper is also successfully designed. Eu3+@CdK-MOF can also be used as fluorescent ink to write some words. The words can be hidden when treated with acid vapor and then the words can be restored when treated with alkaline vapor. More importantly, the hidden information can be read repeatedly. Therefore, this reversible light-emitting and reusable property have great potential for development in information encryption and decryption and information storage.

Europium(III) Complex-Functionalized SiO2@mTiO2 Nanospheres for Al3+-Modulated Multicolor Emission.

A europium(III) hybrid material Eu(tta)3bpdc-SiO2@mTiO2 (Htta = 2-thenoyltrifluoroacetone, H2bpdc = 2,2'-bipyridine-3,3'-dicarboxylic acid) was successfully designed and synthesized by the covalent grafting complex Eu(tta)3bpdc to SiO2@mTiO2 core-shell nanosphere. The FT-IR, PXRD, XPS, TEM, HRTEM, SAED, TGA and PL were performed to characterize these materials. The results indicate that core-shell nanosphere structure and anatase crystallites of SiO2@mTiO2 are retained well after grafting the europium complex. Hybrid material Eu(tta)3bpdc-SiO2@mTiO2 displays uniform nanosphere structure, bright red color and long lifetime, which can serve as a multicolor emission material modulated by using Al3+ ions via the cation exchange approach under a single-wavelength excitation. To the best of our knowledge, this work is the first multicolor emissive sensor for Al3+ ions based on the lanthanide hybrid material.

Fluorescence Sensing of Formaldehyde and Acetaldehyde Based on Responsive Inverse Opal Photonic Crystals: A Multiple-Application Detection Platform.

Formaldehyde (FA) and acetaldehyde (AcH) used as common chemicals in many fields are carcinogenic. The presently reported detection methods usually need expensive instruments, professional technicians, and time-consuming processes, and the detection sensitivity still needs further improvement. Herein, we report a highly effective fluorescence (FL) sensing film for FA and AcH based on naphthalimide derivative-infiltrated responsive SiO2 inverse opal photonic crystals (PCs), establishing a practically multiple-application detection platform for FA and AcH in air, aquatic products, and living cells. Nucleophilic addition products between the amine group of the naphthalimide derivative and aldehydes emit strong FL at ∼550 nm, realizing selective FL detection for FA and AcH. The emitted FL can be enhanced remarkably because of the slow photon effect of PCs, in which the FL wavelength is located at the stopband edge of PCs. A highly sensitive detection for FA and AcH with limits of detection of 10.6 and 7.3 nM, respectively, is achieved, increasing 3 orders of magnitude compared with that in the solution system. Additionally, the interconnected three-dimensional microporous inverse opal structure endows the sensor with a rapid response within 1 min. Furthermore, the as-prepared PC sensor can be reused by simple washing in an acidic aqueous solution. The sensing system can be used as a FL multi-detection platform for FA and AcH in air, aqueous solution, and living cells. This FL sensing approach based on small organic molecule-functionalized PCs is universally available to develop various sensors for target analytes by designing new functional organic compounds.

Dense π-stacking of flexible ligands fixed in interpenetrating Zn(ii) MOF exhibiting long-lasting phosphorescence and efficient carrier transport.

Three-fold interpenetrating Zn(ii) MOF with the dense π-stacking of flexible ligands exhibit long-lived phosphorescence emission up to 91 ms at room temperature. Photoelectric measurements show efficient electro-hole separation based on the long lifetime of triplet state exciton.

A novel rhodamine-based colorimetric and fluorometric probe for simultaneous detection of multi-metal ions.

Effective and simultaneous detection of multi-metal ions has been achieved by a colorimetric and fluorometric probe (REHBA) synthesized from rhodamine hydrazide and polyhydroxyl aromatic aldehyde. REHBA can serve as a colorimetric detector for Cu2+ and Co2+, and a fluorometric probe for Pb2+. The colorless solution of REHBA changes to pink for Cu2+/Co2+ and shows a remarkable fluorescence for Pb2+. The further differentiation of Cu2+ and Co2+ depends on whether the colorimetric response of REHBA is reversible upon addition of ethylene diamine tetraacetic acid. The response is reversible for Cu2+, while it is not for Co2+. The spirolactam ring-opening in REHBA and the formation of REHBA-metal complexes with binding stoichiometric ratio of 1:1 are responsible for the UV-visible and fluorescence behaviors. REHBA shows excellent selectivity, anti-interference and good sensitivity. The limit of detection of Cu2+, Co2+ and Pb2+ is 0.11 µM, 0.88 µM and 0.73 µM, respectively. In addition, REHBA has been applied to recognize Pb2+ in living cells by fluorescence image and Cu2+, Co2+ and Pb2+ in real water samples, indicating that REHBA is a potential candidate for multi-metal-ions detection.

Temperature-humidity dual regulation of a single-core-double-shell microcapsule fabricated by electrostatic-assembly and chemical precipitation.

Humidity and temperature control materials have attracted increasing attention due to their energy saving and intelligent regulation of human comfort in the field of interior building and clothing. Phase change microcapsules have been widely used, however, most of which focus on temperature regulation without humidity control. In this work, we report a novel temperature-humidity dual regulation microcapsule with single-core-double-shell structure. FT-IR and XRD measurements confirmed that the shell materials were successfully fabricated on the paraffin core via electrostatic-assembly and the subsequent chemical precipitation method. SEM, TEM and optical microscope photos showed that the microcapsules were spherical morphology with layer-by-layer shells at a diameter around 2-5 µm. The SiO2 shell was aggregated from nano-sized particles and formed a loose and porous micro-structure, supported by the result of N2 adsorption-desorption isotherms. In addition, the synergistic effect of hydrophilic and porous loose (chitosan/GO/chitosan)-SiO2 double shells endowed the microcapsules with humidity regulation. The constructed microcapsules showed temperature regulation behavior due to its phase change performance of paraffin and good thermal durability after 10 thermal cycles. They also showed stable humidity regulation performance after repeated adsorption/desorption. The simulation experiments of temperature and humidity regulation indicated that the microcapsule could keep the temperature and humidity in a stable range. The as-prepared microcapsules have outstanding temperature and humidity regulation properties, showing an application prospects in energy-saving fields.

A novel multi-purpose Zn-MOF fluorescent sensor for 2,4-dinitrophenylhydrazine, picric acid, La3+ and Ca2+: Synthesis, structure, selectivity, sensitivity and recyclability.

A new three-dimensional luminescence Zn-MOF sensor with the molecular formula [Zn4(µ3-OH)2(ptptc)1.5(DMA)(H2O)2]·2DMA (complex 1) for the selective sensing of 2,4-dinitrophenylhydrazine (2,4-DNPH), picric acid (PA), La3+ and Ca2+ has been synthesized from terphenyl-3,3',5,5'-tetracarboxylic acid (H4ptptc) and zinc nitrate under solvothermal conditions. XRD analysis reveals that complex 1 crystallizes in monoclinic system P21/n space group and consists of a three-dimensional network with one-dimensional channels, which are expected to facilitate the diffusion, concentration and detection processes. Real-time fluorescence quenching responses and good reversibility were observed in the fluorescence titration experiments with nano-molar scale detection limits for 2,4-dinitrophenylhydrazine (2,4-DNPH, 100 nM) and picric acid (PA, 500 nM). Noticeable emission band shift from 365 nm to 420 nm was observed when treated complex 1 with La3+ and a new emission band centered at 475 nm appeared when treated complex 1 with Ca2+ in the metal ions sensing experiments. In virtue of its high selectively, good sensitively and recyclability complex 1 could be a promising fluorescent sensor for explosives and metal ions.