Thienopyrimidine-derived multifunctional fluorescence sensor for the detection of Cu2+, Fe3+, and PPi in different solvents.

Hydrazine substituted thienopyrimidine, a new fluorophore, was used to synthesize a novel Schiff base R1 as a chemosensor via the condensation with p-formyltriphenylamine, and the structure was confirmed using nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) analysis. When treated with Cu2+ in dimethylsulfoxide (DMSO)/H2O buffer, R1 showed a phenomenon of fluorescence quenching, which was reversible with the action of ethylenediaminetetraacetic acid (EDTA). When treated with Fe3+ in dimethylformamide (DMF)/H2O buffer, R1 exhibited the same phenomenon, but fluorescence was recovered with inorganic pyrophosphate (PPi) quantitatively. The complexation ratios for R1-Cu2+ and R1-Fe3+ were both 1:2, which were manifested by MS titrations and corresponding Job's plots. The limits of detection of R1 for Cu2+ and Fe3+ were 3.11 × 10-8 and 1.24 × 10-7 M, respectively. The sensing mechanism of R1 toward Cu2+ and Fe3+ was confirmed using density functional theory calculations and electrostatic potential analysis. Test strips of R1 were fabricated successfully for on-site detection of Cu2+ and Fe3+. In addition, R1 was applied to recognize Cu2+ and Fe3+ in actual water samples with satisfactory recovery.

A comparative study of two thienopyrimidine Schiff base probes for sequential monitoring of Ga3+ and Pd2.

Two Schiff base probes (S1 and S2) were prepared and synthesized by incorporating thienopyrimidine into salicylaldehyde or 3-ethoxysalicylaldehyde individually, with the aim of detecting Ga3+ and Pd2+ sequentially. Upon chelation with Ga3+, S1 and S2 exhibited fluorescence enhancement in DMSO/H2O buffer. Both S1-Ga3+ and S2-Ga3+ were quenched by Pd2+. The limit of detection for S1 in response to Ga3+ and Pd2+ was 2.86 × 10-7 and 4.4 × 10-9 M, respectively. For S2, the limit of detection for Ga3+ and Pd2+ was 4.15 × 10-8 and 3.0 × 10-9 M, respectively. Furthermore, the complexation ratios of both S1 and S2 with Ga3+ and Pd2+ were determined to be 1:2 through Job's plots, ESI-MS analysis, and theoretical calculations. Two molecular logic gates were constructed, leveraging the response behaviors of S1 and S2. Moreover, the potential utility of S1 and S2 for monitoring Ga3+ and Pd2+ in domestic water was verified.

Electrochemical aptasensor based on gold nanoparticle decorated Ti3C2Tx nanocomposites for chloramphenicol detection.

Using gold (Au) nanoparticle decorated Ti3C2Tx (Ti3C2Tx-Au) nanocomposites, a highly sensitive electrochemical aptasensor for the effective detection of chloramphenicol has been developed. As a two-dimensional layered material, the prepared composite not only provides high surface area, good conductivity, and thermal stability but also substantial binding sites for aptamers with high sensitivity and selectivity for the accurate determination of chloramphenicol. Interestingly, the conductivity and active sites were enhanced by freeze-drying Ti3C2Tx and in situ formation of Ti3C2Tx-Au nanocomposite. The fabricated aptasensor exhibited a very low detection limit (S/N ≥ 3) of 13.18 fg mL-1 with a linear range of 1 ~ 700 pg mL-1 and correlation coefficient of 0.9992. The fabricated aptasensor demonstrated an excellent reproducibility, repeatability, long-term stability, and high selectivity toward chloramphenicol. Further, the aptasensor was applied to real milk samples, and the recoveries were ranged from 98.93 to 101.93%.

Synthesis of Triblock Polycarboxylate Superplasticizers with Well-Defined Structure and Its Dispersing Performance in ß-Hemihydrate Gypsum.

In this work, a novel AaBAb-type triblock polycarboxylate superplasticizers (PCEs) with well defined molecular structures were designed and synthesized, firstly, by reversible addition-fragmentation chain transfer (RAFT) polymerization, to explore the structure-property relationship PCEs in the ß-hemihydrate gypsum (ß-HH) system. Three PCEs with the same molecular weight and different structure were obtained by changing the feed ratio of the RAFT agent, initiator, and monomer. The effect of the chemical structure of PCEs on their dispersing property and water reduction capacity were assessed in gypsum by measuring the flowability of pastes and the adsorption ability of PCEs on gypsum. Results showed that among three PCEs, when the monomer ratio is 5:1 and a:b = 1:1, PCE-1 exhibited a higher working efficiency, verifying the contribution of regulating structural parameters to the improvement in performances of gypsum paste, because PCE-1 showed the strongest binding capacity with calcium ions due to the relatively equal amount of carboxyl groups at both ends. The AaBAb-type PCEs provide a special advantage over the conventional comb polymer to understand the relation between the structure and property of PCEs, and a direction for further development of PCEs of high performance.

High-sensitive ferrocene labeled aptasensor for the detection of Mucin 1 by tuning the sequence constitution of complementary probe.

A strand displacement-based "signal-off" electrochemical aptasensor is reported for the detection of Mucin 1 (MUC 1) based on a high original signal. Different from the conventional "signal-off" electrochemical biosensors where electrochemical substances are dispersed in electrolyte solution, here the current signal was generated by the complementary probe (CP) associated with ferrocene (Fc) labeled aptamer (Apt.-Fc). Because Apt.-Fc and MUC 1 have a higher affinity, Apt.-Fc dissociates from CP in the presence of MUC 1, resulting in a reduction of detection current signal generated by oxidation of labeled Fc. In this system, high detection signal is necessary to improve the sensor's performance. For this aim, a strategy is proposed for changing the modalities of electron transport and the quantity of Apt.-Fc introduced by simply tuning the sequence constitution of CP. As expected, a high detection current signal was obtained after selecting CP(Apt.-Fc)-TTT as the optimal CP. The aptasensor was then employed to detect MUC 1, and satisfactory detection results with a low detection limit (LOD) of 0.087 pM (S/N = 3), good specificity, good stability, and feasibility of detection of MUC 1 in artificial serum (recovery of 92-101%, RSD of 1.36-5.23%) were obtained.

A sensitive electrochemical DNA sensor for detecting Helicobacter pylori based on accordion-like Ti3C2Tx: a simple strategy.

A novel electrochemical DNA sensor was designed to detect Helicobacter pylori based on accordion-like Ti3C2Tx. Here the multilayer Ti3C2Tx obtained by DMSO delamination was used to modify the glass carbon electrode, with a large specific surface area and excellent conductivity. Au nanoparticles were supported on the modified electrode and worked as an effective carrier to fix the capture probe (cpDNA) with sulfhydryl group through the firm binding of Au-S bond. Such an accordion-like Ti3C2Tx structure provides an ultrahigh electroactive surface area and ample binding sites for accommodating Au nanoparticles, which is advantageous for the signal amplification during the detection. And further, the sandwich structure formed by hybridizing cpDNA with target DNA sequence (tDNA) and rpDNA (rpDNA is a strand of DNA that can be base-paired with the tested tDNA) increases greatly the current signal and enhances the sensitivity of the electrochemical DNA sensor. Under optimal conditions, the developed electrochemical DNA sensor showed a wide linear range from 10-11 to 10-14 M and a low detection limit of 1.6 × 10-16 M and exhibited good sensitivity, reproducibility, and stability. A novel electrochemical DNA sensor with simple sandwich structure was designed to detect H. pylori based on accordion-like Ti3C2Tx.

Expression and Biochemical Characterization of a Novel Marine Chitosanase from Streptomyces niveus Suitable for Preparation of Chitobiose.

It is known that bioactivities of chitooligosaccharide (COS) are closely related to the degree of polymerization (DP); therefore, it is essential to prepare COS with controllable DP, such as chitobiose showing high antioxidant and antihyperlipidemia activities. In this study, BLAST, sequence alignment and phylogenetic analysis of characterized glycoside hydrolase (GH) 46 endo-chitosanases revealed that a chitosanase Sn1-CSN from Streptomyces niveus was different from others. Sn1-CSN was overexpressed in E. coli, purified and characterized in detail. It showed the highest activity at pH 6.0 and exhibited superior stability between pH 4.0 and pH 11.0. Sn1-CSN displayed the highest activity at 50 °C and was fairly stable at ≤45 °C. Its apparent kinetic parameters against chitosan (DDA: degree of deacetylation, >94%) were determined, with Km and kcat values of 1.8 mg/mL and 88.3 s-1, respectively. Cu2+ enhanced the activity of Sn1-CSN by 54.2%, whereas Fe3+ inhibited activity by 15.1%. Hydrolysis products of chitosan (DDA > 94%) by Sn1-CSN were mainly composed of chitobiose (87.3%), whereas partially acetylated chitosan with DDA 69% was mainly converted into partially acetylated COS with DP 2-13. This endo-chitosanase has great potential to be used for the preparation of chitobiose and partially acetylated COS with different DPs.

A new sensor based on thieno[2,3-b]quinoline for the detection of In3+ , Fe3+ and F- by different fluorescence behaviour.

Based on thieno[2,3-b]quinoline-2-carbohydrazide and salicylaldehyde, a novel fluorescent probe (L) was designed and synthesized. L could be used as a multifunctional sensor to sequentially detect In3+ and Fe3+ through fluorescence enhancement and fluorescence quenching in DMF/H2 O buffer solutions. At the same time, L had good anti-interference ability, which could still detect In3+ and Fe3+ well in the presence of other metal ions. For F- , it could be detected by enhancing the fluorescence change caused by the introduction of Al3+ . When other anions were present, the detection of F- would not be interfered. The detection limits of In3+ , Fe3+ and F- were 1.16 × 10-10 M, 2.03 × 10-8 M and 7.98 × 10-9 M, respectively. The complexation model and sensing mechanism between L and In3+ , Fe3+ and F- were confirmed by calculating structural optimization and energy optimization using Gaussian 09 software.

A selective "turn-on" sensor for recognizing In3+ and Zn2+ in respective systems based on imidazo[2,1-b]thiazole.

A new simple and easily synthesized multitarget sensor, (E)-N'-(4-(diethylamino)-2-hydroxybenzylidene)imidazo[2,1-b]thiazole-6-carbohydrazide (X), was designed and synthesized using imidazo[2,1-b]thiazole-6-carboxylic acid and 4-(diethylamino)-2-hydroxybenzaldehyde. X could be used as a sensor to detect In3+ in DMF-H2O buffer solution and detect Zn2+ in EtOH-H2O buffer solution through fluorescence enhancement with detection limits of 1.02 × 10-9 M and 5.5 × 10-9 M, respectively. X exhibited an efficient "off-on-off" fluorescence behavior by cyclic addition of metal ions (In3+ and Zn2+) and EDTA. The stoichiometry between X and metal ions (In3+ and Zn2+) was 1 : 1. The binding mode and sensing mechanism of X with metal ions (In3+ and Zn2+) was verified by theoretical calculations using Gaussian 09 based on B3LYP/6-31G(d) and B3LYP/LANL2DZ basis, respectively. Moreover, X could be applied as a potential sensor for the quantitative detection of In3+ and Zn2+ with a satisfactory recovery and relative standard deviation (RSD) in real water samples.

Mesoporous silica hybridized by ordered mesoporous carbon for in-tube solid-phase microextraction.

To enhance the extraction performance, a mesoporous silica was modified with ordered mesoporous carbon for solid-phase microextraction. Three stainless-steel wires coated with the mesoporous material were placed in a polyetheretherketone tube for getting an extraction tube. The tube was coupled to high-performance liquid chromatography with diode array detector, and the online analysis system was constructed. Then its extraction performance was evaluated using hydrophobic polycyclic aromatic hydrocarbons, phthalates, and hydrophilic neonicotinoids. The best selectivity was presented for polycyclic aromatic hydrocarbons. Several main conditions were optimized such as sampling volume, sampling rate, methanol concentration in the sample, and desorption time, a rapid and sensitive analytical method was established toward polycyclic aromatic hydrocarbons. The analytical method exhibited wide linear range from 0.017 to 15 µg/L with acceptable correlation coefficients more than 0.9990, limits of detection in 0.005-0.020 µg/L, limits of quantification ranging from 0.017 to 0.066 µg/L as well as large enrichment factors of 377-2314. It was successfully applied to detect trace polycyclic aromatic hydrocarbons in some real water samples including tap water, snow water, and domestic sewage.

Carbon nanotubes functionalized mesoporous silica for in-tube solid-phase microextraction of polycyclic aromatic hydrocarbons.

A mesoporous silica was functionalized by carbon nanotubes to enhance the extraction performance. The mesoporous material was coated on stainless steel wires, and three wires were inserted inside of a polyetheretherketone tube for in-tube solid-phase microextraction. The tube was coupled to high-performance liquid chromatography with diode array detection to obtain online analytical system, then its extraction performance was evaluated using eight polycyclic aromatic hydrocarbons as the targets. In order to good sensitivity and accuracy, four conditions were optimized such as sampling volume, sampling rate, methanol content in the sample, and desorption time. Under the optimum conditions, an online analytical method was established and exhibited low limits of detection from 0.005 to 0.050 µg/L, wide linear range of 0.016-20.00 µg/L with acceptable correlation coefficients in 0.9921-0.9999, as well as large enrichment factors in the range of 311-2412. The method was successfully applied to determine trace polycyclic aromatic hydrocarbons in some real water samples including, two kinds of bottled water, tap water, and river water, a few polycyclic aromatic hydrocarbons were detected but none quantified in these samples.

A Unique Approach to Development of a Multiratiometric Fluorescent Composite Probe for Multichannel Bioimaging.

Ratiometric fluorescent probes have shown great potential for optical sensing and have been widely used for bioimaging. However, due to extremely stringent molecular design, most conventional organic ratiometric fluorescent probes can only achieve one single ratio. Currently, the detection of a target in living systems in a multiratiometric manner is prominently challenging. Therefore, it is of great significance to develop a method to construct the multiratiometric fluorescent probes for accurate quantitative detection of specific small molecules. To address this challenge, we developed a unique multiratiometric composite fluorescent probe. Herein, a new triple-ratiometric fluorescent composite nanoprobe CP@GQDs-OH based on OH-functionalized GQDs (GQDs-OH) and red emission ratiometric fluorescent molecular probe (CP) was prepared through π-π stacking. The novel nanoprobe showed high selectivity for SO2 with three linear ratio changes. Significantly, CP@GQDs-OH was successfully applied for the detection of SO2 in the living cells and zebrafishes by the unprecedented triple-ratiometric fashion.

Ultrasensitive electrochemical detection of ochratoxin A based on signal amplification by one-pot synthesized flower-like PEDOT-AuNFs supported on a graphene oxide sponge.

To enhance the sensitivity of an aptasensor, a novel strategy was designed to develop an electrochemical aptasensor based on poly(3,4-ethylenedioxy thiophene)-gold nanoflower (PEDOT-AuNF) composites supported on a three-dimensional graphene oxide sponge (GOS). GOS with a three-dimensional sponge-like porous structure, exhibiting excellent electrical conductivity and a large surface area, provided the first amplification of the electrochemical signal for ochratoxin A (OTA) detection. PEDOT-AuNFs, synthesized by an ionic liquid-assisted one-pot method, presented a peculiar hierarchical flower-like structure, a high electroactive surface area, and more binding sites for immobilizing the aptamer molecules by the Au-S bonds. When PEDOT-AuNFs were supported on the surface of GOS by the interaction of the π-π packing between PEDOT and graphene oxide, a synergistic effect was produced to provide the second amplification for the aptasensor. PEDOT-AuNFs/GOS provided an ultrasensitive detection technique by multiple signal amplification for the electrochemical sensing of OTA. Consequently, this strategy not only endowed the aptasensor with high sensitivity but also needed no complicated signal amplification. The electrochemical sensor was fabricated successfully on a glassy carbon electrode to detect OTA with a linear response in the range of 0.01-20 ng L-1 and a limit of detection of 4.9 pg L-1. Moreover, it displayed good specificity, reproducibility and stability. The utilization of the proposed aptasensor for the quantitative determination of OTA in wine indicates that it can find promising applications in detecting OTA and even other mycotoxins in foodstuffs.

A fluorescent sensor for Zn(2+) and NO2(-) based on the rational control of C[double bond, length as m-dash]N isomerization.

A new strategy for the ultrasensitive sensing of cations and anions based on the control of C[double bond, length as m-dash]N isomerization has been developed. Imine-derived ligand is non-fluorescent due to the C[double bond, length as m-dash]N isomerization process, whereas its ternary complex with ZnCl2 is moderately fluorescent because of the partial inhibition of C[double bond, length as m-dash]N isomerization. Such a ternary complex can give a remarkable fluorescence increase when it interacts with nitrite because of the much more efficient suppression of C[double bond, length as m-dash]N isomerization. This modulation process of C[double bond, length as m-dash]N isomerization can thus be used for the highly selective detection of Zn(2+) and NO2(-) in an aqueous solution.

A new Schiff base derived from 5-(thiophene-2-yl)oxazole as "off-on-off" fluorescence sensor for monitoring indium and ferric ions sequentially and its application.

A new Schiff base sensor (E)-N'-((8-hydroxy-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl)methylene)-5-(thiophen-2-yl)oxazole-4-carbohydrazide (TOQ) was synthesized and found to emit yellowish green fluorescence upon introduction of In3+. Furthermore, the resulting complex TOQ-In3+ was quenched selectively by Fe3+. The detection limits of TOQ for In3+ and Fe3+ were 1.75 × 10-10 M and 8.45 × 10-9 M, respectively. The complex stoichiometry of TOQ with target ions was determined to be 1:2 via Job's plot analysis, which further was verified by ESI-MS titration and theoretical calculations. Moreover, TOQ can be used for the determination of target ions in environmental water samples. A portable paper sensor of TOQ was successfully developed for detecting In3+ to assess its applicability.

[Flow-injection chemiluminescence determination of trace copper on-line separation and enrichment by ion imprinted polymer].

In the present study, Cu(II)-imprinted polymer was prepared and used as an effective method for separation and enrichment of Cu (II) ion in samples. An on-line preconcentration and extraction flow-injection system using solid phase extraction (SPE) column packed with prepared ion imprinted polymer (IIP) was set up. The column was eluted with a mixture of ethanol and H2 SO4 after preconcentration. A sensitive and simple chemiluminescence (CL) method using flow-injection has been developed for the determination of copper. The method is based on the fact that traces of Cu(II) exert a catalytic action on the oxidation between morin by KMnO4 solution. After optimizing the different experimental parameters, a calibration graph was obtained over the concentration range of 0 to 10 microg x mL(-1) for Cu(II) and r = 0.996 8. The detection limit is 0.001 2 microg x mL(-1). The recoveries are between 95% and 105% and the standard relative deviations (RSD) are less than 3% at 4.0 microg x mL(-1) (n = 9) level was obtained. The new chemiluminescence determination for copper has been established. The method can be satisfactorily applied to the determination of copper in sample.

Construction of a novel GQD based ratiometric fluorescent composite probe for viscosity detection.

Herein, a novel ratiometric fluorescent composite nanoprobe RV-1@GQDs-OH was developed based on OH-functionalized GQDs (GQDs-OH) and molecular probe (RV-1) viaπ-π stacking. Compared with the conventional "on-off" viscosity probes, RV-1@GQDs-OH can be successfully applied in living systems for the ratiometric detection of viscosity changes in the viscosity range of 0-600 cP.

Surface Modification of Bentonite with Polymer Brushes and Its Application as an Efficient Adsorbent for the Removal of Hazardous Dye Orange I.

Poly(2-(dimethylamino)ethyl methacrylate)-grafted bentonite, marked as Bent-PDMAEMA, was designed and prepared by a surface-initiated atom transfer radical polymerization method for the first time in this study. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) were applied to characterize the structure of Bent-PDMAEMA, which resulted in the successful synthesis of Bent-PDMAEMA. As a cationic adsorbent, the designed Bent-PDMAEMA was used to remove dye Orange I from wastewater. The adsorption property of Bent-PDMAEMA for Orange I dye was investigated under different experimental conditions, such as solution pH, initial dye concentration, contact time and temperature. Under the optimum conditions, the adsorption amount of Bent-PDMAEMA for Orange I dye could reach 700 mg·g-1, indicating the potential application of Bent-PDMAEMA for anionic dyes in the treatment of wastewater. Moreover, the experimental data fitted well with the Langmuir model. The adsorption process obeyed pseudo-second-order kinetic process mechanism.

Ultra-Highly Efficient Removal of Methylene Blue Based on Graphene Oxide/TiO2/Bentonite Sponge.

An ultra-highly efficient Graphene Oxide/TiO2/Bentonite (GO/TiO2/Bent) sponge was synthesized using an in situ hydrothermal method. GO/TiO2/Bent sponge with a GO mass concentration of 10% exhibited the highest treatment efficiency of methylene blue (MB), combining adsorption and photocatalytic degradation, and achieved a maximum removal efficiency of 100% within about 70 min. To further prove the ultra-high removal capacity of the sponge, the concentration of MB in water increased to ten times the original concentration. At so high a MB concentration, the removal rate was still as high as 80% in 90 min. The photocatalytic mechanism of GO/TiO2/Bent sponge was discussed through XPS, PL and radicals quenching experiments. Here Bent can immobilize TiO2 and react with a photo-generated hole to increase the amount of hydroxyl radical; effectively enhancing the degradation of MB.GO sponge enlarges the sensitivity range of TiO2 to visible light by increasing the charge separation of TiO2 and reducing the recombination of photo-generated electron-hole pairs. Additionally, GO sponge with an interconnected porous structure provides an effective platform to immobilize TiO2/bent and makes them be easily recovered. The as-prepared sponge develops a simple and cost-effective strategy to realize the ultra-highly efficient treatment of dyes in wastewater.

Bentonite Modified by Allylamine Polymer for Adsorption of Amido Black 10B.

The main object of this work is to remove Amido black 10B using a new type of bentonite-based adsorbent with cationic groups by the modification of polyallyl amines between the interlayers of bentonite. Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy were used to characterize the functionalized bentonite. A series of batch adsorption experiments were performed. The maximum adsorption amount was 144.08 mg g-1 when the pH was 2 and the contact time was 120 min. In addition, the equilibrium isotherm data were analyzed using Langmuir and Freundlich isotherm models, while only the Langmuir model could provide a high correlation. Therefore, this study provided a new functionalized bentonite as a low-cost adsorbent for dye removal from water.