A new carbazole based fluorescent probe with AIE characteristic for detecting and imaging hydrazine in living cells, mungbean sprouts, Arabidopsis thaliana, and practical samples.

In this study, we report a new carbazole-malononitrile fluorescent probe CBC with an interesting aggregation-induced emission (AIE) characteristic. Probe CBC could rapidly and selectively detect hydrazine (N2H4) in ～100% aqueous media, and also exhibit an exceedingly low detection limit of 6.3 nM for sensitively detecting N2H4. The sensing mechanism of CBC towards N2H4 has been well demonstrated through the spectra of 1H NMR, HRMS and FTIR. Interestingly, probe CBC was applied to visualize and detect gaseous and aqueous N2H4 with sensitive color changes. Importantly, probe CBC was applied to effectively detect N2H4 in practical samples such as soil, human serum, human urine, plants, foods and beverages, as well as sensitively sense and image N2H4 in biological systems including living mungbean sprouts, Arabidopsis thaliana, and HeLa cells.

New dual-responsive fluorescent sensor for hypochlorite and cyanide sensing and its imaging application in live cells and zebrafish.

Excessive levels of cyanide (CN-) and hypochlorite (ClO-) anions are the significant threats to the human health and the environment. Thus, great efforts have been to design and synthesize molecular sensors for the simple, instantaneous and efficient detecting environmentally and biologically important anions. Currently, developing a single molecular sensor for multi-analyte sensing is still a challenging task. In our present work, we developed a new molecular sensor (3TM) based on oligothiophene and Meldrum's acid units for detecting cyanide and hypochlorite anions in biological, environmental and food samples. The detecting ability of 3TM has been examined to various testing substances containing amino acids, reactive oxygen species, cations and anions, showing its high selectivity, excellent sensitivity, short response time (ClO-: 30 s, CN-: 100 s), and broad pH working range (4-10). The detection limits were calculated as 4.2 nM for ClO- in DMSO/H2O (1/8, v/v) solution and 6.5 nM for CN- in DMSO/H2O (1/99, v/v) solution. Sensor 3TM displayed sharp turn-on fluorescence increasement (555 nm, 435 nm) and sensitive fluorescence color changes caused by CN-/ClO-, which is ascribed to the nucleophilic addition and oxidation of ethylenic linkage by cyanide and hypochlorite, respectively. Moreover, sensor 3TM was applied for hypochlorite and cyanide detecting in real-world water, food samples and bio-imaging in live cells and zebrafish. To our knowledge, the developed 3TM sensor is the seventh single-molecular sensor for simultaneous and discriminative detecting hypochlorite and cyanide in food, biological and aqueous environments using two distinct sensing modes.

A dual-responsive fluorescent turn-on sensor for sensitively detecting and bioimaging of hydrazine and hypochlorite in biofluids, live-cells, and plants.

Hydrazine (N2H4) and hypochlorite (ClO-) are extremely harmful to the public health, so it is vitally necessary to detect them in living system. Herein, we developed a new phenthiazine-thiobarbituric acid based dual-analyte responsive fluorescent sensor PT for visually distinguishing and detecting N2H4 and ClO-. PT underwent N2H4/ClO--induced CC breakage, achieving olive-drab/brilliant green fluorescence lighting-up response towards N2H4/ClO- with superb specifity, ultra-sensitivity (detection limit: 15.4 nM for N2H4, 13.7 nM for ClO-), and ultra-fast response (N2H4: <15 s, ClO-: <20 s). The mechanisms for sensing N2H4 and ClO- were investigated with support of spectral measurements and DFT investigation. Sensor based paper-strip/silica-gel device was developed for in-field supervision and on-site monitoring of gaseous and aqueous N2H4 and ClO- solution. In addition, the PT was also applied for quantitatively detecting N2H4 and ClO- in soil, food, plants and bio-fluids. Moreover, PT was utilized to visualize exogenous N2H4 and ClO- in living plants and live-cells, demonstrating this sensor utilized as a powerful tool to detect N2H4 and ClO- in biological fields.

Highly sensitive fluorescent sensor for hypochlorite in nearly 100% aqueous solution and its application for live-cell, plant and zebrafish imaging.

A new ICT type D-π-A structured chemosensor DTB derived from a bithiophene-benzothiazole derivative has been synthesized. Sensor DTB showed a colorimetric and fluorometric dual-signaling response to hypochlorite (ClO-) in EtOH/HEPES solution (1/99, V/V, pH = 7.4, nearly 100% aqueous solution). Sensor DTB exhibited well specificity, high sensitivity and rapidity (<1 min) for ClO- with a detection limit of 25 nM. Sensor DTB features remarkable color changes and significant fluorescence "turn-on" response (ca. 45 fold) after treating with ClO-. Comprehensive analyses by 1H NMR, TLC, FTIR, HRMS, UV-vis, fluorescence and DFT illustrated that ClO- reacted with the CC bond of DTB, generating fluorophore 2T-CHO, leading to strong blue fluorescence. Interestingly, DTB loaded colorimetric test strips were established for rapid and real-time visual detection of ClO-. Furthermore, the DTB was successfully applied to quantitatively and sensitively detect ClO- in 84 disinfectant, bio-fluids (human serum and urine) and actual water samples. Importantly, the biocompatible DTB has been employed for visualizing and bioimaging ClO- in mung bean sprouts, Arabidopsis, live cells and zebrafish. These investigations demonstrate that DTB has great potentials for detecting ClO- in various biosystems and environments. This work would offer a new idea for developing multifunctional sensors with better performance for chemo/biosensors.

Improving the Performance of ZnS Photocatalyst in Degrading Organic Pollutants by Constructing Composites with Ag2O.

ZnS is a promising photocatalyst in water purification, whereas its low photon efficiency and poor visible-light response restrict its application. Constructing composites may help solve these problems. In this work, Ag2O was introduced to ZnS for the first time based on their energy band characteristics to form a novel ZnS/Ag2O composite photocatalyst. In the model reaction of degrading methylene blue, the as-designed catalyst exhibited high catalytic activity among a series of ZnS-based composite photocatalysts under similar conditions. The catalytic rate constant was up to 0.138 min-1, which is 27.4- and 15.6-times higher than those of ZnS and Ag2O. This composite degraded 92.4% methylene blue in 50 min, while the ratios were 31.9% and 68.8% for ZnS and Ag2O. Catalytic mechanism study based on photoluminescence and radical-scavenging experiments revealed that the enhanced photocatalytic activity was attributed to the composite structure of ZnS/Ag2O. The structure not only facilitated the separation and transmission of photogenerated carriers but also extended the light response range of the catalyst. The as-designed ZnS/Ag2O composite is promising in degrading organic pollutants in water.

Self-Luminescent Lanthanide Metal-Organic Frameworks as Signal Probes in Electrochemiluminescence Immunoassay.

The successful use of electrochemiluminescence (ECL) in immunoassay for clinical diagnosis requires development of novel ECL signal probes. Herein, we report lanthanide (Ln) metal-organic frameworks (LMOFs) as ECL signal emitters in the ECL immunoassay. The LMOFs were prepared from precursors containing Eu (III) ions and 5-boronoisophthalic acid (5-bop), which could be utilized to adjust optical properties. Investigations of ECL emission mechanisms revealed that 5-bop was excited with ultraviolet photons to generate a triplet-state, which then triggered Eu (III) ions for red emission. The electron-deficient boric acid decreased the energy-transfer efficiency from the triplet-state of 5-bop to Eu (III) ions; consequently, both were excited with high-efficiency at single excitation. In addition, by progressively tailoring the atomic ratios of Ni/Fe, NiFe composites (Ni/Fe 1:1) were synthesized with more available active sites, enhanced stability, and excellent conductivity. As a result, the self-luminescent europium LMOFs displayed excellent performance characteristics in an ECL immunoassay with a minimum detectable limit of 0.126 pg mL-1, using Cytokeratins21-1 (cyfra21-1) as the target detection model. The probability of false positive/false negative was reduced dramatically by using LMOFs as signal probes. This proposed strategy provides more possibilities for the application of lanthanide metals in analytical chemistry, especially in the detection of other disease markers.

New thiophene hydrazide dual-functional chemosensor: Colorimetric sensor for Cu2+ & fluorescent sensor for Al3.

A new thiophene hydrazide derivative TSB was synthesized and utilized as naked-eye colorimetric sensor for Cu2+ by the color changed from colorless to yellow as well as green fluorescent turn on sensor for Al3+ in DMSO/H2O (1/1, V/V) solution. The dual-functional chemosensor TSB for Cu2+/Al3+ sensing displayed excellent properties of special selectivity, superior sensitivity, outstanding anti-interference performance, instantaneous response, wide pH working range and good reversibility. The detection limits of TSB for Cu2+/Al3+ were determined as low as 46.5 nM and 32.7 nM, respectively. The 1:1 binding mode of TSB with Cu2+/Al3+ was proved by spectrometric titrations, Job's plots, FTIR, 1H NMR and HRMS analysis. Moreover, chemosensor TSB was successfully utilized for detection of Cu2+ and Al3+ in real environmental water and food samples with high reliability, demonstrating its practical applicability.

New "naked-eye" colori/fluorimetric "turn-on" chemosensor: Ultrafast and ultrasensitive detection of hydrazine in ∼100% aqueous solution and its bio-imaging in living cells.

A new oligothiophene derivative (3TY) was synthesized, and used as a highly selective hydrazine (N2H4) chemosensor in ∼100% aqueous solution with "naked-eye" colorimetric and "turn-on" fluorimetric response. This chemosensor 3TY enabled ultrafast and ultrasensitive detection of hydrazine with ultralow detection limit of 1.45 nM (0.04 ppb) in a wide sensing pH range from 6 to 10. The sensing mechanism of 3TY toward hydrazine was strongly and fully confirmed. More importantly, colorimetric paper test strip and solid support silica are easily prepared by 3TY for on-site and real-time detection of hydrazine. Furthermore, 3TY displays many potential applications for detecting N2H4 in environmental water and human urine along with bio-imaging in living HeLa cells.

Bithiophene-based fluorescent sensor for highly sensitive and ultrarapid detection of Hg2+ in water, seafood, urine and live cells.

Using Hg2+-promoted deprotection reaction, we have developed a new fluorescent turn-on sensor 2TS based on bithiophene fluorophore for Hg2+ detection. The sensing mechanism of 2TS towards Hg2+ was strongly proved by 1H NMR, FTIR, HRMS, UV-vis and fluorescence spectra. Remarkly, 2TS towards Hg2+ in 100% aqueous solution shows high sensitivity with a low detection limit of 19 nM, superior selectivity and ultra-rapid response of 20 s during a wide sensing pH range from 4 to 10. Taking advantage of the excellent properties, the low-cost sensor 2TS-based filter paper/TLC test strips were fabricated for visual, immediate and quantitative detection of Hg2+ in water, proving its applicability towards sensitive in-situ and on-site detection. Meanwhile, 2TS showed high analytical performance for Hg2+ detection in water, seafood as well as human urine samples. Moreover, thanks to the good water solubility, negligible cytotoxicity, good biocompatibility and cell-membrane permeability, 2TS was further applied to effectively image Hg2+ in live cells. Furthermore, the developed sensor 2TS acted as good fluorescent display material for Hg2+ with obvious color change.

High Specific Surface Area TiO2 Nanospheres for Hydrogen Production and Photocatalytic Activity.

TiO2 nanospheres with high specific surface area and good crystallinity were prepared by a hydrothermal method using urea as the capping agent and isopropanol as the solvent. The capping agent effectively controlled the morphology of TiO2 nanospheres and led to improved crystallinity. Using a solvent with a long carbon chain, such as isopropanol, also promoted the formation of TiO2 nanospheres. TiO2 nanospheres with different morphologies were prepared by adjusting the amount of urea. It was found that when TiO2-0.6 was used as the photocatalyst, highest rates of degradation of both methylene blue and rhodamine B under ultraviolet-visible light were observed. Moreover TiO2-0.6 also had the largest hydrogen production efficiency among the different TiO2 samples tested. Thus, TiO2 nanospheres have great development potential and application prospects in environmental management and new modes of energy utilization.

A highly selective and sensitive dual-mode sensor for colorimetric and turn-on fluorescent detection of cyanide in water, agro-products and living cells.

A new highly selective and sensitive dual-mode sensor 3TD based on the conjugate of oligothiophene and barbituric acid moiety was developed for colorimetric and turn-on fluorescent detection of CN─. The sensor 3TD exhibited high specificity towards CN─ by interrupting its own ICT producing thereupon a large blue-shift in UV-Vis spectrum and remarkable "turn-on" fluorescence emission. The detection limit was 2.26 × 10─7 M, which is quite lower than the permissible level of CN─ in drinking water according to the WHO. The fluorescent detection of CN─ was well demonstrated by filter paper strips and silica coated TLC plates. Moreover, the sensor was also used to detect CN─ in environmental water and agro-products with satisfactory results. Most importantly, in terms of these advantages of colorimetric and turn-on fluorescent dual-mode, immediate response, excellent selectivity, high sensitivity, low cytotoxicity, and good biocompatibility, the sensor 3TD was successfully applied into CN- imaging in living cells, demonstrating its excellent value in practical application.

A fast, highly selective and sensitive colorimetric and fluorescent sensor for Cu2+ and its application in real water and food samples.

A new oligothiophene functionalized Schiff base sensor 3TDC has been successfully designed and synthesized. Sensor 3TDC exhibited "naked-eye" colorimetric and selective "on-off" fluorescence response toward Cu2+ with high selectivity and sensitivity within a wide pH range. The binding ratio of the sensor 3TDC and Cu2+ was determined to be 1:1 through fluorescence titration, Job's plot, 1H NMR titration, FTIR and DFT studies. The detection limit is calculated to be as low as 2.81 × 10-8 M, which is much lower than the allowable level of Cu2+ in drinking water set by U.S. Environmental Protection Agency (~20 µM) and the World Health Organization (~30 µM). The binding constant (Ka) of Cu2+ to sensor 3TDC was found to be 2.52 × 104 M-1. Sensor 3TDC for Cu2+ detection exhibited fast fluorescence response within 30 s and high anti-interference performance. Moreover, sensor 3TDC could be used as an effective fluorescent sensor for detecting Cu2+ ions in various real water and food samples with good accuracy and high precision.

Novel thiophene-based colorimetric and fluorescent turn-on sensor for highly sensitive and selective simultaneous detection of Al3+ and Zn2+ in water and food samples and its application in bioimaging.

A novel bifunctional thiophene-based Schiff base TS as a colorimetric and fluorescent turn-on sensor for rapid and simultaneous detection of Al3+ and Zn2+ ions with high selectivity and sensitivity has been developed. The sensor shows remarkable fluorescence enhancement response for Al3+ and Zn2+ over a broad pH range with good anti-interference capability, which accompanied with an obvious color change easily detected by naked eyes. Sensor TS can detect as low as 3.7 × 10-9 M for Al3+ and 3.0 × 10-8 M for Zn2+, whereas respective association constants are 1.16 × 104 M-1 and 2.08 × 104 M-1. With the help of fluorescence titration and Job's plot, the stoichiometric ratio of TS with Al3+/Zn2+ was determined to be 1:1. The sensing mechanism of sensor TS with Al3+/Zn2+ based on the chelation-enhanced fluorescence (CHEF) was analyzed in detail through 1H NMR titration, FTIR, HRMS and DFT studies. Moreover, sensor TS has been applied to the detection of Al3+ and Zn2+ in real environmental water and food samples as well as the filter paper-based test strips. Furthermore, sensor TS has good cell-permeability and can be used to selectively sense intracellular Al3+ and Zn2+ by bioimaging.

Synthesis, photophysical and electrochemical properties of a new star-shaped molecule with a 1,3,5-triethynylbenzene core and diketopyrrolopyrrole arms.

A new star-shaped small molecule BDPP-1 based on 1,3,5-triethynylbenzene as a core and diketopyrrolopyrrole (DPP) as rigid arms have been successfully designed and synthesized. The thermal stability, photophysical and electrochemical properties were explored. The synthesized star-shaped small molecule BDPP-1 exhibited excellent solubility, high thermal stability, broad and strong absorption, narrow band gap and appropriate molecular levels. Moreover, the photoinduced charge separation process between the synthesized donor and acceptor PC61BM was evaluated by the fluorescence quenching experiment, revealing that the donor material BDPP-1 possessed efficient photoinduced charge separation performance. These detailed investigations on the structure-property relationship of the novel star-shaped molecule revealed that BDPP-1 is a prospective candidate as a donor material for organic photovoltaic materials.

A highly selective colorimetric and ratiometric fluorescent probe for instantaneous sensing of Hg2+ in water, soil and seafood and its application on test strips.

A new simple and efficient oligothiophene-based colorimetric and ratiometric fluorescent probe has been developed for highly sensitive and fast detection of Hg2+ in water, soil and seafood. The probe 5-(1,3-dithiolan-2-yl)-2,2':5',2″-terthiophene 3 TS can selectively detect Hg2+ via the Hg2+-promoted deprotection reaction of thioacetals, which caused a remarkable color change from colorless to yellow and a strong fluorescence enhancement with emission color varying from blue to yellow, enabling naked-eye detection of Hg2+. The probe shows high sensitivity with the detection limit down to 1.03 × 10-8 M. Visual color changes of 3 TS were observed on filter paper and TLC testing strips when they were impregnated on testing strips and immersed in Hg2+ solution. Moreover, the probe 3 TS has been successfully used to rapidly detect trace amounts of hazardous Hg2+ ions in tap, distilled, river and lake water, cropland soil, fish, shrimp and kelp samples with acceptable results and good recoveries.

Highly sensitive oligothiophene-phenylamine-based dual-functional fluorescence "turn-on" sensor for rapid and simultaneous detection of Al3+ and Fe3+ in environment and food samples.

Developing low-cost and efficient sensors for rapid, selective and sensitive detection of the transition metal ions in environmental and food science is very important. In this study, a novel dual-functional fluorescent "turn-on" sensor 3TP based on oligothiophene-phenylamine Schiff base has been synthesized for discrimination and simultaneous detection of both Al3+ and Fe3+ ions with high selectivity and anti-interference over other metal ions. Sensor 3TP displayed a very fast fluorescence-enhanced response towards Al3+ and Fe3+ ions with low detection limits (0.177µM for Al3+ and 0.172µM for Fe3+) and wide pH response range (4.0-12.0). The Al3+/Fe3+ sensing mechanisms were investigated by fluorescence experiments, 1H NMR titrations, FT-IR and ESI-MS spectra. Importantly, sensor 3TP was served as an efficient solid material for the highly sensitive and selective detection of Fe3+ on TLC plates. Moreover, the sensor 3TP has been successfully used to detect trace Al3+ and Fe3+ in environment and food samples with satisfactory results and good recoveries, revealing a convenient, reliable and accurate method for Al3+ and Fe3+ analysis in real samples.

Highly selective and sensitive determination of Cu2+ in drink and water samples based on a 1,8-diaminonaphthalene derived fluorescent sensor.

A new simple and efficient fluorescent sensor L based on 1,8­diaminonaphthalene Schiff-base for highly sensitive and selective determination of Cu2+ in drink and water has been developed. This Cu2+-selective detection over other tested metal ions displayed an obvious color change from blue to colorless easily detected by naked eye. The detection limit is determined to be as low as 13.2 nM and the response time is very fast within 30 s. The 1:1 binding mechanism was well confirmed by fluorescence measurements, IR analysis and DFT calculations. Importantly, this sensor L was employed for quick detection of Cu2+ in drink and environmental water samples with satisfactory results, providing a simple, rapid, reliable and feasible Cu2+-sensing method.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu2+ in ~100% aqueous media and application to real samples.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu2+ was developed. Sensor ADA showed high selectivity and sensitivity toward Cu2+ in ~100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu2+ recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8nM, which is much lower than the allowable level of Cu2+ in drinking water set by U.S. Environmental Protection Agency (~20µM) and the World Health Organization (~30µM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu2+ with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field.

A dual-responsive colorimetric and fluorescent chemosensor based on diketopyrrolopyrrole derivative for naked-eye detection of Fe3+ and its practical application.

A novel dual-responsive colorimetric and fluorescent chemosensor L based on diketopyrrolopyrrole derivative for Fe3+ detection was designed and synthesized. In presence of Fe3+, sensor L displayed strong colorimetric response as amaranth to rose pink and significant fluorescence enhancement and chromogenic change, which served as a naked-eye indicator by an obvious color change from purple to red. The binding constant for L-Fe3+ complex was found as 2.4×104 with the lower detection limit of 14.3nM. The sensing mechanism was investigated in detail by fluorescence measurements, IR and 1H NMR spectra. Sensor L for Fe3+ detection also exhibited high anti-interference performance, good reversibility, wide pH response range and instantaneous response time. Furthermore, the sensor L has been used to quantify Fe3+ ions in practical water samples with good recovery.

Oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor: Sensing ability, TD-DFT calculations and its application as an efficient solid state sensor.

An oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor 3 T-2CN was reported. Sensor 3 T-2CN showed both naked-eye recognition and ratiometric fluorescence response for CN- with an excellent selectivity and high sensitivity. The sensing mechanism based on the nucleophilic attack of CN- on the vinyl CC bond has been successfully confirmed by the optical measurements, 1H NMR titration, FT-IR spectra as well as the DFT/TD-DFT calculations. Moreover, the detection limit was calculated to be 0.19µM, which is much lower than the maximum permission concentration in drinking water (1.9µM). Importantly, test strips (filter paper and TLC plates) containing 3 T-2CN were fabricated, which could act as a practical and efficient solid state optical sensor for CN- in field measurements.