Ion-imprinted Polymer Research Articles

Synthesis and application of a surface ionic imprinting polymer on silica-coated Mn-doped ZnS quantum dots as a chemosensor for the selective quantification of inorganic arsenic in fish.

A novel room temperature phosphorescence chemosensor probe has been successfully developed and applied to the selective detection and quantification of inorganic arsenic (As(III) plus As(V)) in fish samples. The prepared material (IIP@ZnS:Mn QDs) was based on Mn-doped ZnS quantum dots coated with (3-aminopropyl) triethoxysilane and an As(III) ionic imprinted polymer. The novel use of vinyl imidazole as a complexing reagent when synthesizing the ionic imprinted polymer guarantees that both inorganic arsenic species (As(III) and As(V)) can interact with the recognition cavities in the ionic imprinted polymer. After characterization, several studies were performed to enhance the interaction between the targets (As(III) and As(V) ions) and the IIP@ZnS:Mn QDs nanoparticles. The optimization and validation process showed that the composite material offers high selectivity (high imprinting factor) for inorganic arsenic species. The limit of quantification for total inorganic As was 29.6μgkg-1, value lower than the EU/EC regulation limits proposed for other foodstuffs than fish, such as rice. The proposed method is therefore simple, requires short analysis times and offers good sensitivity, precision (inter-day relative standard deviations lower than 10%), and quantitative analytical recoveries. The method has been successfully applied to assess total inorganic arsenic in several fishery products, showing good agreement with the total inorganic arsenic concentration (As(III) plus As(V)) found after applying other advanced and expensive methods such those based on high-performance liquid chromatography hyphenated to inductively coupled plasma-mass spectrometry. Graphical abstract.

Synthesis of surface ion-imprinted polymer for specific detection of thorium under acidic conditions

A fibrous surface ion-imprinted polymer (IIP) was synthesized for thorium removal through direct electron beam radiation using thorium as a template. Polypropylene coated by polyethylene non-woven fabrics (PE/PP) was used as a substrate. The PE/PP non-woven fabrics were irradiated in the presence of the phosphoric monomer (2-HMPA) composed of 2-hydroxyethyl methacrylic phosphoric acid diester (50%) and monoester (50%) emulsified with the crosslinker. Hence, the formation of the three-dimensional IIP-Th crosslinked network and complexation between thorium (template) and 2-HMPA was investigated. The emulsion stability and particle size distribution of emulsion were determined using dynamic light scattering (DLS). Various factors influencing the synthesis of the thorium ion-imprinted (Th-IIP) non-woven PE/PP such as the absorbed radiation dose, monomer concentration, and type of crosslinker were investigated. The IIP-Th was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy–energy-dispersive X-ray (SEM–EDX), and X-ray photoelectron spectroscopy (XPS) and applied as an adsorbent for the removal of thorium using the batch adsorption method. The IIP-Th achieved a maximum distribution coefficient of 3.293 g/L and selectivity ratio (Th(IV)/U(VI)) of 9.5 after 90 min of contact time under acidic conditions. The adsorption kinetics of IIP-Th followed the pseudo-second-order kinetic model for both Th(IV) adsorption and U(VI) adsorption. The synthesized fibrous surface ion-imprinted polymer is a promising candidate for the selective removal of thorium ions from aqueous solution.

Synthesis of Azobenzene-Based Ion-Imprinted Polymers for Selective Removal of Cobalt and Copper Ions from a Mixture of Metal Ions

Azobenzene based metal ion-imprinted polymers (IIPs) were synthesized for selective separation of Co (II) and Cu (II) ions from the mixture of metal ions. After polymerization, cavities for the Co2+ and Cu2+ ions were created in the polymer materials by leaching with hydrochloric acid solution. The synthesized IIPs were characterized by FT-IR, 1 H NMR and elemental analysis. The competitive sorption studies were carried out to evaluate the selectivity of the target metal ions. Interestingly, the observed sorption capacity was pH dependent and maximum sorption was found to be 95.4 and 103.0 mg·g−1 for Co-IIPs and Cu-IIPs at pH 5, respectively. It was observed that the IIPs showed good selectivity to Co (II) and Cu (II) ions in the presence of other bi and trivalent metal ions in solution. Reused capacity was also checked for six times without a significant decrease in binding affinity for IIPs.

Synthesis of ion-imprinted polymer with gamma irradiation for the adsorption of Tripolyphosphate

One method of separating tripolyphosphate ion uses ion-imprinted polymer. Chitosan-succinate, tripolyphosphate and methylene bis akrilamida (MBA) were used as the complexing polymer, template, and crosslinker agent, respectively. In the first step, Fe(III)-chitosan-succinate-tripolyphospate was formed. In the second step, Fe(III)-chitosan-succinate-tripolyphospate was crosslinked by MBA and irradiated by gamma rays. Then, tripolyphosphate ion was removed with KOH solution to form a selective cavity for tripolyphosphate ion in the ion-imprinted polymer (IIP). Based on the results of this study, the optimum adsorption of tripolyphosphate ion was found at an MBA crosslinker concentration of 1%, pH 2, irradiation dose 20 kGy, and a tripolyphosphate ion concentration of 1 ppm. This study also included experimental adsorption of tripolyphosphate ion on non-imprinted polymer (NIP-MBA) and an evaluation of the effect of interference ions. The resulting adsorption of tripolyphosphate ion on IIP was found to be higher than those of non-imprinted polymer. The adsorption percentages were found to be 94 % for IIP and 14 % for NIP-MBA. Chloride ion (Cl-) provided greater interference in the adsorption process of tripolyphosphate ion compared to carbonate ions. The percent adsorptions of tripolyphosphates were estimated to be 57.71 % in the presence Cl- ion and 68.28 % in the presence CO32−ion.

Selective solid-phase extraction of trace copper ions in an aqueous solution using ion-imprinted polymer

The study represents preparation of chitosan-based Cu(II) ion-imprinted polymer (IIP) and its utilization for selective solid phase extraction and preconcentration of copper in aqueous and real samples. The IIP was prepared by precipitation co-polymerization. The prepared IIP was characterized by different morphological and elemental analytical techniques such as, FT-IR, SEM/EDS, XRD, TGA, and ICP-OES. Then, prepared material was used for extraction of Cu(II) by optimizing different extraction experiments such as effect of pH, sorbent dosages, and contact time. The results showed successful preparation of an ion-imprinted polymer and optimization of extraction parameters for Cu(II) extraction in aqueous and real samples.

A magnetic ion-imprinted polymer composed of silica-coated magnetic nanoparticles and polymerized 4-vinyl pyridine and 2,6-diaminopyridine for selective extraction and determination of lead ions

A novel, sensitive and highly selective magnetic ion-imprinted polymer for facile separation and preconcentration of trace quantities of Pb(ii) ions.

Sensor based on electrosynthesised imprinted polymeric film for rapid and trace detection of copper(II) ions

Herein we report the fabrication, characterisation and application of a novel voltammetric sensor based on an electrosynthesised ion imprinted polymer (IIP) film for the determination of copper(II) in water samples. This sensitive and highly selective sensor was prepared by electropolymerisation of p-phenylenediamine in the presence of Cu2+ as template, combined with the screen-printed technology for the transducer element. Electrochemical methods were used to control the electropolymerisation process, the template removal and the subsequent rebinding. The electrosynthesised film on the surface of screen-printed platinum electrodes was characterised by cyclic voltammetry (CV), scanning electron microscopy (SEM), and FTIR-ATR analysis. The incubation of the IIP-modified electrode with Cu2+ resulted in an increase of the redox properties of the obtained polymer. The performance of the proposed sensor was observed in acetate buffer (50 mM, pH = 5) over the Cu2+ concentration range 0.95–244 nM, with a limit of detection of 2.7 nM. The multivariate approach was employed in order to evaluate the influence of four variables on the sensitivities of the imprinted sensor towards the template. The IIP sensor showed high affinity to copper in comparison with the non-imprinted polymer (NIP). The reproducibility of the sensor was evaluated on five different sensors and it was estimated as 7.75 % (RSD). Selectivity studies were performed against several potential interferents, such as Ni2+, Mn2+, Ag+, Hg2+, Zn2+, Co2+, Pb2+ and Cd2+ ions. The application of the proposed sensor in spiked drinking water revealed a good recovery (95–105 %).

Ion-imprinted mesoporous silica/magnetic graphene oxide composites functionalized with Schiff-base for selective Cu(II) capture and simultaneously being transformed as a robust heterogeneous catalyst

Ascribing to the risk on public health and environment, as well as the extensive applications of copper, the highly selective capture and effective utilization of the recovered Cu(II) ion by using a multifunctional material are of significant practical interest. However, there remains an arduous challenge to the fulfillment of such tasks. In this study, using the mesoporous silica/magnetic graphene oxide composites (MS/MGO) as the support, 2-((2-(3-(trimethoxysilyl)propylamino)ethylimino)methyl)phenol (TPEMP) bearing Schiff-base as the functional monomer, surface Cu(II) ion-imprinted polymers (Cu(II)-IIPs) were fabricated and applied for the selective capture Cu(II) ion from aqueous media. Additionally, the reuse of the spent Cu(II) loaded adsorbent (SMS/MGO-Cu) to the catalytic application was also explored. The obtained samples were characterized by various techniques. The uptake of Cu(II) by Cu(II)-IIP-2 was tested through the study of pH effect, sorption isotherms and uptake kinetics, selective sorption, adsorbent regeneration. The results indicated the Cu(II)-IIP-2 had high selectivity and faster kinetic over reported adsorbents, with an equilibrium adsorption capacity of 195.3 mg/g at 298 k within 30 min. Sorption isotherms were well described by the Langmuir model, while the uptake kinetics was fitted by the pseudo-second order rate equation. In addition, the Cu(II)-IIP-2 could be recycled six times without any significant loss in adsorption capacity. Importantly, the best catalysis efficiency of SMS/MGO-Cu for the synthesis of 1-methyl-4-(p-tolyloxy)benzene was 95%. These results indicate the Cu(II)-IIP-2 can not only be applied to effectively remove Cu(II) ion from aqueous media, but also be used in heterogeneous catalytic organic synthesis reactions after sorption.

Preparation of highly selective magnetic cobalt ion-imprinted polymer based on functionalized SBA-15 for removal Co2+ from aqueous solutions.

In this research, a novel magnetic cobalt ion imprinted adsorbent (Co(II)-MIIP) was synthesized by use of magnetic SBA-15 core-shell. It was functionalized by dithizone, and after identification by various techniques was used for removal of cobalt from aquatic systems. The uptake of cobalt proceeded very fast and achieved to equilibration within 5min at which 74mgg-1 of cobalt was adsorbed at pH = 8 with adsorbent dose of 0.15g. The ion imprinted sorbent exhibited good selectivity towards cobalt ions. Separation and recovery of the used sorbent was carried out respectively by use of magnetic field and by use of HNO3 (0.1M), and 85% of the initial capacity was obtained after seven 7 regeneration cycles. Different isotherm models, and error analysis were used to evaluate the experimental data. Thermodynamic, and kinetic evaluations showed that sorption process was endothermic, and described by second order kinetic model (R2 > 0.99). The equilibrium was established within five min.

Potential Adsorption of Heavy Metal Ions by Eugenol Compounds and Derivatives through Ion Imprinted Polymer

Research on the potential of Ion Imprinted Polymer (IIP) selective adsorption of heavy metals using eugenol compounds and their derivatives has been carried out. Isolation and synthesis of eugenol derivatives with metal selective active groups and their use as selective metal carriers have been carried out with satisfactory results. Carrier effectiveness can still be improved by methods that focus on the target molecule recognition model. This adsorption method is called Ion Imprinted Polymer (IIP). The main components of IIP are functional monomers, crosslinkers, and target molecules. The use of acrylamide and its derivatives as functional monomers is useful with a lot of success achieved but also invites danger because it includes carcinogenic substances, a nerve poison, and so on. Moreover, the N group, which is an active acrylamide group, and its derivatives are only selective towards borderline metals (HSAB theory). Alternatives that are safe and can increase their selectivity are therefore needed. Eugenol, with its three potential functional groups, is believed to be able to replace the function of acrylamide and its derivatives that can even increase the effectiveness of IIP. The purpose of this study is to determine the potential of eugenol derivatives as selective adsorbents through the IIP method. This synthesis of IIP involved the use of basic ingredients of eugenol and its derivatives (polyeugenol, EOA, polyacetate). Each base material is contacted with a metal template then crosslinked with three kinds of crosslinking agents, namely EGDMA, DVB, and bisphenol. IIP is formed after the metal template is released using acid/HCl. The outcomes obtained demonstrate that the IIP method is able to increase the metal adsorption capacity and that the IIP method for metals is largely determined by the release of metals, which will form a hole for metal entry through adsorption. Poly-Cd-DVB, Eug-Cr-DVB, Poly-Cu-bisphenol, Polyacetate -Cr-DVB are polymer materials that have the potential to make up an IIP.

Nano layered ion imprinted polymer based electrochemical sensor and sorbent for Mn (II) ions from real samples

In this study, a multiwalled carbon nanotube based ion-imprinted polymer was prepared for the sensing and extraction of manganese ion. The binding sites for adsorption of Mn(II) ion were synthesized by free radical polymerization. For the comparison purpose ion imprinted polymer without using MWCNT was also prepared (MWCNT-NIP). To find out importance of MWCNT, ion imprinted polymer without MWCNT was also synthesized (IIP and NIP). The synthesized polymers were characterized by FT-IR, XRD, TEM, EDAX, and TGA. An electrochemical sensor was made by modifying a platinum electrode with MWCNT-IIP. The electrochemical response of the nanostructures modified platinum electrode were investigated and optimized. The limit of detection of the electrochemical sensor was investigated using DPV, it was found to be 0.0138 µM. The applicability of the modified electrochemical sensor was effectively applied for the sensing and extraction of Mn(II) ion from real samples collected from lake water, fertilizers, and mining effluents. The Mn(II) ion imprinted MWCNT-IIP exhibit Langmuir adsorption isotherm and pseudo-second-order kinetics which proposed homogenous monolayer formation of imprinting sites on the polymer sorbent. The selectivity studies were carried out using imprinted and non-imprinted polymers, the imprinted sorbent shows high selectivity and specificity towards Mn(II) ion than other metal ions.

A novel electrochemical sensor based on ion imprinted polymer and gold nanomaterials for nitrite ion analysis in exhaled breath condensate

Human Exhaled Breath Condensate (EBC) contains markers of several inflammatory diseases. Its analysis is of interest to a number of researchers. Nitrite ions (NO2-), which are widely used in our daily lives, are nevertheless among these indicators. In this study, a simple, fast, portable, non-invasive and cheap electrochemical sensor is developed for the analysis of the nitrite profile in EBC. In this regard, sodium nitrite (NaNO2) was first immobilized on self-assembled 2-aminothiophenol (2-ATP) on a screen-printed gold electrode (Au-SPE). Then, a polymer matrix composed of polyvinyl alcohol (PVA) crosslinked with glutaraldehyde (GA) was combined with gold nanoparticles (Au-NPs) to cover the modified Au-SPE and complete the fabrication of the Ion Imprinted Polymer (IIP) sensor. The electrochemical behaviour of the sensor was monitored using Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Differential Pulse Voltammetry (DPV) methods, while the morphology and chemical composition of its layers were observed by infrared Fourier transform (FTIR), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy coupled with energy dispersion X-Ray spectroscopy (SEM-EDS) techniques. In addition, after a successful control test using a Non-Imprinted Ion Polymer (NIIP) sensor, the obtained results demonstrated satisfactory sensitivity and selectivity to nitrite compared to co-existing interfering substances in EBC, such as nitrate, acetate and ammonium nitrate. Under improved experimental conditions, the nitrite IIP sensor exhibits responses proportional to nitrite concentrations (R2 = 0.96) over a concentration range of 0.5–50 μg mL−1 with a detection limit (LOD) of 4 μmol L−1 (signal-to-noise ratio S/N = 3). The proposed approach was well applied for the nitrite determination in EBC samples with a relative standard deviation (RSD = 4%) and could open clinical applications in respiratory medicine.

Application of Ion Exchange, Solvent Extraction, and Ion-Imprinted Methods for Separation of 203Pb

Lead-203 was produced by proton bombardment of natural thallium target. For producing 203Pb, natTl was electroplated on copper backing as target and was bombarded by energetic proton beam. After bombardment, the target was dissolved in 1 M HNO3. Ion exchange, solvent extraction, and nanomagnetic ion-imprinted polymer methods were used for separating 203Pb from thallium. The separation efficiency of these methods was studied. γ-Ray spectroscopy was applied for evaluating 203Pb and others radionuclides. The separation efficiency was determined from the γ-ray spectra. The separation efficiency of the methods using ion exchange, solvent extraction, and nanomagnetic ion-imprinted adsorbent was 98, 99.3, and 96.4%, respectively.

Synthesis, characterization, and application of β-cyclodextrin-based ion-imprinted polymer for selective sequestration of Cr(VI) ions from aqueous media: Kinetics and isotherm studies

Toxic chromium(VI) is a menace to the environment and humans. Its tendency to transform into chromium(III) complicates its removal. An ion-imprinted polymer (IIP) synthesized by encapsulating 1,5′-diphenylcarbazide (DPC) ligand into the β-cyclodextrin cavities then held into position by 4-vinylpyridine and ethylene glycol dimethacrylate functional monomers (γ-MPS/β-CD/DPC/VP) were employed to investigate Cr(VI) removal efficacy. The corresponding non-imprinted polymer was also prepared, but the template ion was omitted. The inclusion of DPC ligand into the polymeric matrix was responsible for the pronounced selectivity observed due to the high affinity of DPC towards Cr(VI). Characteristic peaks at 3318, 1718, 1258 and 940 cm−1 apportioned to the –OH, CO, C–N, and Si–O–CH3 functional groups were observed in the FTIR spectra. The maximum Langmuir adsorption capacity obtained at 25 °C was 15.61 mg/g for IIP. The optimum solid/liquid ratio achieved at equilibrium time (240 min) was 10 g/L. The IIP selectivity order was Cr(VI)>Cr(III)>Co(II)>Zn(II)>Ni(II).

Preparation of thermo-sensitive surface ion-imprinted polymers based on multi-walled carbon nanotube composites for selective adsorption of lead(II) ion

A novel thermo-sensitive lead ion-imprinted polymers (IIPs) based on multi-walled carbon nanotubes(MWCNTs) was prepared by reverse suspension polymerization, using chitosan (CS), hydroxyethyl methacrylate and N-isopropylacrylamide as the polymeric monomers, Pb(II) as the template and glutaraldehyde as the crosslinking agent. The chemical structure, morphology and magnetic properties were characterized by Fourier transform infrared spectrometer(FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), thermogravimetry (TGA), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The adsorption properties of IIPs were investigated by ultraviolet spectrophotometr (UV–vis) and atomic absorption spectrophotometry (AAS). The results showed that IIPs had obvious temperature sensitivity, and the adsorption capacity and the adsorption equilibrium time of imprinted polymers could be controlled by changing the temperature. The maximum adsorption capacity of IIPs for Pb2+ reached 83.20 mg/g at 35 ℃. The adsorption process was more in accord with the pseudo second-order kinetic and the Langmuir isotherm adsorption model. The selectivity coefficients of Pb2+/Cu2+, Pb2+/Cd2+, Pb2+/Zn2+ and Pb2+/Ni2+ were 15.66, 59.50, 24.79 and 20.52, respectively, indicating that IIPs had excellent selective adsorption for Pb2+. In addition, IIPs was recycled 6 times, and the adsorption capacity was not obviously reduced. The electrochemical properties of ion-imprinted carbon paste electrodes (CPE/IIPs) were characterized by cyclic voltammetry (CV), and CPE/IIPs exhibited excellent electrochemical performance.

Rapid and selective extraction of trace amount of Pb(II) in aqueous samples using a magnetic ion-imprinted polymer and detection by flame atomic absorption spectrometry

A magnetic Pb(II) ion-imprinted polymer was synthesized using magnetic Fe3O4@SiO2 nanospheres as supporter, n-benzoyl-n-phenyl hydroxylamine as ligand, 4-vinyl pyridine as monomer, ethylene glycol dimethacrylate as crosslinker and 2,2′-azobis(isobutyronitrile) as the initiator. The template was removed from the polymer using 4 mL of HCl (2 mol L-1). The chemical structure, morphology-particle size, elemental analysis, thermal behavior and magnetic properties of the sorbent were evaluated using Fourier-transform infrared spectroscopy, scanning electron microscopy & ImageJ software - Energy dispersive X-ray system, thermal gravimetric analysis and vibrating sample magnetometry. Various parameters such as pH, equilibrium extraction time, temperature and the eluent were optimized. The results showed the sorbent adsorption capacity was 92.3 mg g-1 in pH 6.0 media, equilibrium time of 7 min at 40 °C. Calibration linearity was 2-150 µg L-1 with detection limit of 0.3 µg L-1. The prepared sorbent had high selectivity and was successfully applied to the removing of lead in real samples.

Ultrasonic-assisted micro solid phase extraction of arsenic on a new ion-imprinted polymer synthesized from chitosan-stabilized pickering emulsion in water, rice and vegetable samples.

Pickering emulsion polymerization has been employed for the Ultrasonic assisted-micro solid phase extraction (UA-µSPE) of ultra trace arsenic species by a new magnetic ion imprinted polymer (MIIP) prior to hydride generation atomic absorption spectrometry. 2-acetyl benzofuran thiosemicarbazone (2-ABT) as a new chelating agent and core- shell hydrophobic magnetic nanoparticles was synthesized and the polymerization was carried out at the presence of arsenic - ligand complex, crosslinker, monomer, initiator, stabilizing agent and water-oil emulsion magnetic carrier. In second step, the nanoparticles and polymers were characterized. The analytical parameters such as pH, amount of polymer and ultrasonic time were selected and optimozed by Plackett-Burman and Box-Behnken designs respectively. Linear dynamic range, detection limit and relative standard deviation were 0.01-85.000 µg·L-l, 0.003 µg·L-l, and 3.21%, respectively. The proposed preconcentration procedure was successfully applied to the determination of arsenic ion in a wide range of food samples with different and complex matrixes.

Preparation of highly efficient ion-imprinted polymers with Fe3O4 nanoparticles as carrier for removal of Cr(VI) from aqueous solution

Fe3O4 magnetic nanoparticles were prepared by hydrothermal synthesis and their surface was modified by the sol-gel method. Polymers imprinted with magnetic Cr (VI) were prepared by using Cr2O72− as template ion, 4-vinyl pyridine (4-VP) as monomer, isopropanol as solvent and Fe3O4 as matrix. The effects of solvent type, amount of Cr (VI) addition and volume of crosslinking agent on the adsorption properties of the imprinted polymers were investigated. The polymers were characterized by Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). The adsorption equilibrium was reached within 50 min, and the maximum adsorption capacity was 201.55 mg·g−1. The adsorption process conformed to the Langmuir model, and the results of kinetic fitting showed that the pseudo-first-order kinetic model applied. In the Cr2O72−/AlF4− and Cr2O72−/CrO42− competitive systems, the imprinted polymer showed good selectivity to the template ions, with relative selectivity factors of 6.91 and 5.99, respectively. When the imprinted polymer was reused 6 times, the adsorption capacity decreased by only 8.2%, demonstrating good reusability.

Facile and efficient removal of Pb(II) from aqueous solution by chitosan-lead ion imprinted polymer network

A new chitosan based imprinted polymer was prepared by copolymerization of 4-Vinylpyridine (VP) as a functional monomer and N,N′-Methylenebisacrylamide (MBA) as a crosslinker in the presence of Potassium peroxodisulfate (KPS) as an initiator to eliminate Pb(II) from aqueous solutions. The template ions were removed from ion imprinted polymer (IIPs) particles by leaching with 0.1 M nitric acid (HNO3) that leaves cavities in the particles with the capability of selective extraction of the Pb(II) ions. Some properties of the bioadsorbent were further identified using Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Thermal Gravimetric Analysis (TGA). In addition, the equilibrium adsorption data were examined through Langmuir and Freundlich isotherm models and it was found that adsorption data fit well with the Freundlich isotherm. The competitive adsorption studies clearly showed that the Pb(II)-IP has a much higher adsorption capacity for Pb(II) than the non-imprinted polymer (NIP) with the same chemical composition; furthermore, it has excellent selectivity for the targeted ion. In addition, the studies regarding the regeneration and reuse studies revealed that the Pb(II)-IP beads showed no significant decrease in their adsorption capacities.

Selective fluorescence sensor based on ion-imprinted polymer-modified quantum dots for trace detection of Cr(VI) in aqueous solution.

A new fluorescence sensor (QDs-IIP), based on ion-imprinted polymers (IIP) as recognition element and Mn-doped ZnS quantum dots (QDs) as fluorophore, was synthesized for the selective and sensitive determination of hexavalent chromium (Cr(VI)) ions. The QD was first coated by SiO2 layer, and then modified with Cr(VI)-imprinted polymer. Several parameters affecting fluorescence intensity such as tetraethylorthosilicate (TEOS) volume, ZnS:Mn@SiO2 amount, and radiation time were investigated and optimized. The QDs-IIP was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscope (TEM), and scanning electron microscope (SEM). Furthermore, the fluorescence quenching mechanism was investigated by using UV-VIS and fluorescence spectrophotometer, and it was found that internal filtration effect was the main fluorescence quenching mechanism. The relative fluorescence intensity (F0/F) increased linearly with the increase of Cr(VI) concentration in the range of 20μgL-1-1.0mgL-1. The QDs-IIP sensor showed high recognition selectivity for Cr(VI) in comparison with the QDs-NIP sensor with an imprinting factor (IF) of 2.53, and it could be reused 5 times. In addition, an analytical method of Cr(VI) based on the QDs-IIP sensor was established with a limit of detection of 5.48μgL-1, and was then applied to actual water samples with satisfactory results. Therefore, QDs-IIP can be deemed as a practicable fluorescent sensor for trace Cr(VI) detection. Graphical abstract.