A simple paper-based nickel nanocluster-europium mixed ratio fluorescent probe for rapid visual sensing of tetracyclines.

In this work, a ratiometric fluorometric sensor based on nickel nanoclusters (NiNCs)-europium complex (NiNCs-Eu3+) was constructed for the highly selectivity detection of tetracyclines (TCs) in water samples. In the presence of TCs, the blue fluorescence of the sensor NiNCs-Eu3+ was quenched at 430 nm and the characteristic red fluorescence of Eu3+-TCs appeared at 620 nm because of the combined help of inner filter effect (IFE) and antenna effect. Under the optimized conditions (100 mM Eu3+ (100 µL); temperature (25℃); reaction time (10 min), HEPES buffer solution (pH = 7.0)), the sensor offered a wide detection range of tetracycline (TC) and oxytetracycline (OTC) from 0.1 to 50 µM with the detection limit (LOD) of 25 nM and 21 nM, respectively. Moreover, the sensor was able to detect of TC and OTC in tap and lake water with high recovery rate (89.10%-97.60%). In addition, the portable paper-based sensor was constructed using filter paper embedded with NiNCs-Eu3+. The distinct fluorescent color of the paper-based sensor varied from bright blue to red against different concentrations of TC and OTC. These above findings demonstrated the potential for wide application of as-prepared ratio metric fluorescence sensor for visual detection of TCs in water samples.

A molecularly imprinted gel photonic crystal sensor for recognition of chiral amino acids.

A new type of photonic crystal gel molecularly imprinted sensor (MIPHs) was synthesized for the visible chiral recognition of amino acids. The color of MIPHs was changed from green to red when it exposured to various l-pyroglutamic acid concentration (0.05-1.0mmoL/L). Thanks to sensitive reflectance of photonic crystal and high selectivity of MIPs, the constructed MIPHs exhibited good performance towards l-pyroglutamic acid in terms of fast response time (3 min) and low detection limit (LOD) (2.4 µmol/L). Besides, MIPHs was found to have good selectivity toward l-pyroglutamic acid in the presence of interference group with similar structures such as d-pyroglutamic acid, l-tryptophan, l-phenylalanine, and l-proline. In light of these findings, the MIPHs can be used for highly selective recognition of l-pyroglutamic acid. It is expected that our work is able to provide a new roadmap for the chiral identification and separation of amino acids.

Construction of novel luminescent thermometers based on dual-emission centers of rare-earth and bismuth ions.

Optical thermometry based on fluorescence intensity ratio (FIR) technology has several advantages for industrial and medical applications such as remote signaling, non-invasiveness, and excellent spatial resolution. Here, an approach to the construction of luminescent thermometers is proposed based on high-temperature solid-state reactions through doping of rare earth (RE) elements (e.g., samarium (Sm3+) or europium (Eu3+)) into Ca2Y0.97Bi0.03SbO6 (CYBS) phosphors. The tuning of the CYBS:Eu3+ and CYBS:Sm3+ ratios in the phosphors provided a wide range of color changes from purplish blue to red and from purplish blue to pink, respectively. The superiority of optical thermometer is validated by higher values of absolute sensitivity (Sa) and relative sensitivity (Sr). As such, both phosphors exhibit excellent temperature sensing performance with Sa/Sr values (at 483 K) of 4.945 × 10-2/0.968 × 10-2 K-1 (CYBS:0.05Eu3+) and 2.964 × 10-2/0.864 × 10-2 K-1 (CYBS:0.05 Sm3+). Thus, RE-doped CYBS materials with color tuning properties and superior temperature sensing performance are recommended for the construction of novel luminescent optical thermometers.

Single-crystal ordered macroporous metal-organic framework as support for molecularly imprinted polymers and their integration in membrane formant for the specific recognition of zearalenone.

Zearalenone is a fungal contaminant that is widely present in grains. Here, a novel molecularly imprinted membrane based on SOM-ZIF-8 was developed for the rapid and highly selective identification of zearalenone in grain samples. The molecularly imprinted membrane was prepared using polyvinylidene fluoride, cyclododecyl 2,4-dihydroxybenzoate as a template and SOM-ZIF-8 as a carrier. The factors influencing the extraction of zearalenone using this membrane, including the solution pH, extraction time, elution solvent, elution time, and elution volume, were studied in detail. The optimized conditions were 5 mL of sample solution at pH 6, extraction time of 45 min, 4 mL of acetonitrile:methanol = 9:1 as elution solvent, and elution time of 20 min. This method displayed a good linear range of 12-120 ng/g (R2  = 0.998) with the limits of detection and quantification of this method are 1.7 and 5.5 ng/g, respectively. In addition, the membrane was used to selectively identify zearalenone in grain samples with percent recoveries ranging from 87.9 to 101.0% and relative standard deviation of less than 6.6%. Overall, this study presents a simple and effective chromatographic pretreatment method for detecting zearalenone in food samples.

Highly Selectivity Molecularly Imprinted Fluorescence Sensor Based on Carbon Quantum Dots for the Determination of Anthraquinones.

Due to the complexity of traditional Chinese medicines (TCMs), it is very important to develop a method that can recognize anthraquinones, the active ingredients in TCMs, with high selectivity. Here, a molecularly imprinted fluorescence sensor was coated on the surface of carbon quantum dots (CDs). Allobarbital was used as functional monomer for this application using theoretical calculations and was successfully synthesized and characterized. The template molecule chrysophanol was combined with the functional monomer allobarbital using a hydrogen bond array. Then, a series of adsorption experiments were performed to study the specific recognition of anthraquinones by the prepared sensors. The results showed that the prepared sensor had a good linear response to concentrations of chrysophanol in the concentration range 0.5 mg · L-1 to 8.0 mg · L-1, a low detection limit (5.0 µg · L-1), high stability, and a short response time (20 min). Additionally, the obtained fluorescence sensor was successfully applied to selectively recognize anthraquinones in TCMs with recoveries of 90.1% to 101.7%. The prepared sensor displays excellent sensitivity and high selectivity towards anthraquinones, mainly due to the specific hydrogen binding sites for the target molecules. Overall, this fluorescence sensor can selectively recognize anthraquinones in TCMs, and provide a method for quality monitoring and rational utilization of TCMs.

Synthesis of a Molecularly Imprinted Polymer on NH2-MIL-101(Cr) for Specific Recognition of Diclofenac Sodium.

A novel molecularly imprinted polymer material based on the metal-organic framework NH2-MIL-101(Cr) (MOF-MIP) was prepared. The synthesized MOF-MIP was characterized by IR, XRD, SEM and N2 absorption. The characterization results displayed that the MOF-MIP which exhibited an octahedral shape had good dispersibility, good thermal stability and a high surface area. Subsequently, the adsorption behavior of MOF-MIP to diclofenac sodium (DS) in aqueous solution was examined. A series of adsorption experiments demonstrated that the MOF-MIP had high transfer mass rates and high sensitivity and selectivity for DS. Then the MOF-MIP was used as the adsorbent of dispersive micro-solid phase extraction (DMSPE) for the detection of DS in urine. Under optimum conditions, the average recovery of DS ranged from 88.3 to 101.6% with RSD of 5.6%. The described method provides a rapid route for determination of DS in human urine.

Highly sensitive α-amanitin sensor based on molecularly imprinted photonic crystals.

α-amanitin is the most toxic amanita in mushrooms with lethal dose to humans around 0.1 mg. Kg-1. Hence, early identification of the poison would improve survival rates and prevent lethal poisoning cases. In this study, molecularly imprinted photonic crystal (MIPC) sensor was prepared by combining molecular imprinting with photonic crystal templates and tested towards the detection of α-amanitin. In this process, synthesized moiety of α-amanitin was utilized as template, dispersed SiO2 colloidal photonic crystal as carrier, methacrylic acid (MAA) as functional monomer, and ethylene glycol dimethacrylate (EDGMA) as crosslinker. The adsorption behavior of MIPC towards α-amanitin in ethanol solution showed shifts in diffraction peaks of MIPC upon binding with α-amanitin molecules. The reflection peak wavelength varied linearly with α-amanitin concentration according to the correlation formula: λ = 15.417c+489.17 (R2 = 0.9985). The recognition process was accompanied by gradual color change in MIPC film. The prepared MIPC sensor possessed wide linear range (10-9-10-3 mg L-1), change in visual color, low detection limit (10-10 mg L-1), short response time (2 min), and good reusability. The MIPC film was then tested towards the detection of α-amanitin in real biological samples (mushroom, urine, and serum) and showed reasonable shift in diffraction peaks and color change upon soaking in solutions spiked with α-amanitin at 10-6 mg L-1 and 10-3 mg L-1, suggesting the suitability of the film for the rapid identification of α-amanitin in complex sample matrices. Overall, the proposed sensor looks promising for the rapid identification of α-amanitin in clinical analysis and food poisoning.

Synthesis of MOF-199/CNTs Nanocomposite for Selective Adsorption and Determination of Nonsteroidal Anti-Inflammatory Drugs in Human Urine.

A hybrid nanocomposite containing a moisture-resistant surface based on MOF-199 and carbon nanotubes (CNTs) was synthesized. Characterization was undertaken using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The adsorption behavior of the MOF-199/CNTs composite to ibuprofen was then investigated at room temperature. Experimentation revealed that the hybrid absorbent had excellent adsorption capacity for the nonsteroidal anti-inflammatory drug (NSAID), ibuprofen, with maximum adsorption up to 40.8 mg/g. The adsorbent was able to be recycled several times without deactivation. Finally, the MOF-199/CNTs composite was used as the extraction sorbents for selective extraction of ibuprofen, ketoprofen and naproxen in human urine. The results showed successful application of the nanocomposite to NSAID analysis in spiked human urine samples. Recoveries at three concentrations were 89.7-96.8%, 79.3-85.5% and 95.6-97.5% for ibuprofen, ketoprofen and naproxen, respectively. The relative standard deviations (RSDs) were within the range of 2.9-5.3%. The results demonstrated that the MOF-199/CNTs composite is an excellent adsorbent for determination of NSAIDs in spiked urine samples.

Preparation of a molecularly imprinted sensor based on quartz crystal microbalance for specific recognition of sialic acid in human urine.

A novel molecularly imprinted quartz crystal microbalance (QCM) sensor was successfully prepared for selective determination of sialic acid (SA) in human urine samples. To obtain the QCM sensor, we first modified the gold surface of the QCM chip by self-assembling of allylmercaptane to introduce polymerizable double bonds on the chip surface. Then, SA molecularly imprinted polymer (MIP) nanofilm was attached to the modified QCM chip surface. For comparison, we have also characterized the nonmodified and improved surfaces of the QCM sensor by using atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. We then tested the selectivity and detection limit of the imprinted QCM sensor via a series of adsorption experiments. The results show a linear response in the range of 0.025-0.50 µmol L-1 for sialic acid. Moreover, the limit of detection (LOD) of the prepared imprinted QCM sensor was found to be 1.0 nmol L-1 for sialic acid, and high recovery values range from 87.6 to 108.5% with RSD < 8.7 (n = 5) for the spiked urine sample obtained. Overall, this work presents how a novel QCM sensor was developed and used to detect sialic acid in human urine samples. Graphical abstract Specific recognition of sialic acid by the MIP-QCM sensor system.

The molecularly imprinted polymer supported by anodic alumina oxide nanotubes membrane for efficient recognition of chloropropanols in vegetable oils.

A new route to synthesize a covalent interaction-based molecularly imprinted polymer (MIP) material for 3-chloro-1,2-propanediol (3-MCPD) inside the nanopores of anodic alumina oxide (AAO) is presented. A series of adsorption experiments showed MIP had good extraction capacity and selectivity for 3-MCPD. In order to evaluate the usability of the MIP nanotubes membrane, a method combining AAO@MIP membrane extraction with gas chromatography - mass spectrometry (GC-MS) detection was developed for determination of chloropropanols. The limits of detection for the proposed method were 0.072 and 0.13 µg·L-1, respectively, for 3-MCPD and 1,3-DCP. The average recoveries of 3-MCPD and 1,3-DCP spiked oil samples at three concentrations (0.01, 0.05 and 0.1 mg·kg-1) were in the range of 75.6-101.0% with a RSD of 3.3-8.4%, indicating the method would be suitable for determination of chloropropanols in vegetable oils.

Fabrication of a molecularly imprinted polymer immobilized membrane with nanopores and its application in determination of ß2-agonists in pork samples.

In this paper, a method for the synthesis of ractopamine molecularly imprinted polymers (MIPs) nanotube membranes on anodic alumina oxide (AAO) nanopore surface by atom transfer radical polymerization (ATRP) was presented, in which methacrylic acid (MAA) was selected as functional monomer with a polymerization rate of 1:6 between ractopamine and MAA by the computational investigations. The morphology of MIPs nanotube membranes characterized by scanning electron microscope (SEM) suggested a well growth in the AAO nanopore surface. A series of adsorption experiments revealed that the MIPs nanotube membranes showed better extraction capacity and good selectivity for ractopamine and its analogues than that of non-imprinted polymers (NIPs) nanotube membranes. In order to evaluate the usability of the MIPs nanotube membranes, a methodology by combining MIPs nanotube membranes extraction couple with high performance liquid chromatography (HPLC) detection for the determination of ß2-agonists in complex samples was developed. The linear ranges were 10-1000 µg/L for ractopamine, 100-1000 µg/L for clenbuterol, epinephrine and dopamine, and 200-1000 µg/L for terbutaline. The detection limits were within the range of 0.074-0.25 µg/L and the RSDs (n=3) were from 2.8% to 4.3%. The method was successfully applied to the analysis of ß2-agonists in spiked real samples, The recoveries of all the ß2-agonists at the two concentration levels were found to be within the range of 86.3-97.0% and 82.8-95.7%, respectively. The RSDs were within 2.7-5.7%. The results demonstrated that the proposed method is very suitable for the determination of ß2-agonists in pork samples.

Determination of Phenolic Compounds in Environmental Water by HPLC Combination with On-Line Solid-Phase Extraction Using Molecularly Imprinted Polymers.

A novel molecularly imprinted polymer (MIP) was synthesized using halloysite nanotubes (HNT) as matrix, ß-cyclodextrin (ß-CD) and methyl propyl acid (MAA) as functional monomers, and 2,4,6-TCP as template molecule by graft copolymerization. Infrared spectroscopy and transmission electron microscopy (TEM) were used to characterize the as-synthesized imprinted polymer. The selective recognizability of the MIP towards four phenolic analogs were determined and the recognition coefficients for 2,4,6-TCP, 2,6-DCP, 4-CP and phenol were found to be 2.17, 1.85, 2.02 and 1.36, respectively. Using as the packing material of solid-phase extraction, the imprinted polymer has been applied to on-line extraction of the four phenolic compounds in environmental water. The corresponding analytical methods to determine these four phenolic compounds have been developed. Good linear relationships were obtained over the range of 0.05-5.0 mg x L(-1). The average recoveries for spiked samples were in the range of 74.8-97.2%, and the detection limits for 2,4,6-TCP, 2,6-DCP, p-chlorophenol, phenol were 0.19, 0.20, 0.75, 0.73 mg x L(-1), respectively. The method is rapid, accurate and high selectivity. It was feasible for the determination of trace level phenolic compounds in environmental samples.

[Preparation of microcystin-LR molecularly imprinted polymer coated stir bar and its adsorptive performances].

An effective method for the preparation of magnetic molecularly imprinted polymers (MIPs) on attapulgite (ATP) using microcystin-LR (MC-LR) as template molecule through reversible addition fragmentation chain transfer (RAFT) radical polymerization was reported. A novel MIPs stir bar sorptive extraction (SBSE) coating was prepared by sol-gel method. The structure and morphology of MIPs were characterized by infrared spectroscopy (IR) and transmission electron microscopy (TEM). The adsorption performance of SBSE coated with MC-LR was studied by high performance liquid chromatography (HPLC). The results showed that under the optimized experimental conditions, the present method has high selectivity to MC-LR. A good linearity was achieved for MC-LR over the range of 0.010-5.0 mg/L and the limit of detection (S/N = 3) was found to be as low as 0.27 µg/L. The proposed method was successfully applied to the determination of MC-LR in water samples. The average recoveries ranged from 83.33% to 100.07% with the relative standard deviations (RSDs) of 1.40%-9.17% at three spiked levels (20, 40 and 80 µg/L). The developed method is rapid, selective and sensitive, and adapts to the analysis of trace MC in water samples.

[Determination of three phenolic compounds in water samples by solid phase extraction with microemulsion liquid chromatography].

A method for the determination of phenol, bisphenol A (BPA), 2,4-dichlorophenol in water samples based on solid-phase extraction with microemulsion liquid chromatography (MELC) was established. The water sample was acidified, and then cleaned-up by a C18 solid phase extraction cartridge. The separation was carried out on an Inertsil C18 (150 mm x 4.6 mm, 5 microm) with a gradient elution using a microemulsion (consisting of 3.0% sodium dodecyl sulfate (SDS), 6.0% butyl alcohol, 0.8% n-heptane, 90.2% (water + 0.5% acetic acid)) and acetonitrile as mobile phases at a flow rate of 1.0 mL/min and a detection wavelength of 280 nm. The detection limits (S/N = 3) of phenol, BPA, 2,4-dichlorophenol were 0.74, 8.0, 8.0 microg/L, respectively. Good linearities were achieved for the target compounds over the range of 0.1 - 10 mg/L. The spiked recoveries of three phenolic compounds in blank water samples) were 82.7%, 87.8%, 82.6% for phenol, BPA, 2,4-dichlorophenol respectively. The recoveries of target compounds in real water samples ranged from 85.7% to 113.2%. The developed method is simple, selective, sensitive and applicable for the analysis of environmental water samples.