A stoichiometric imprinted chelating resin for selective recognition of copper(II) ions in aqueous media

This work reports the preparation of a new copper(II) ion-imprinted polymer (IIP) material, using 5,6;14,15-dibenzo-1,4-dioxa-8,12-diazacyclopentadecane-5,14-diene (DBDA15C4) and 2-vinylpyridine (VP) as a non-vinylated chelating agent and a functional vinyl monomer, respectively. The Cu²⁺ ion can form stable complexes with DBDA15C4 and VP. The stoichiometries of Cu²⁺-DBDA15C4 and ternary Cu²⁺-DBDA15C4-VP complexes were elucidated using conductometric and spectrophotometric methods, and found to be Cu²⁺(DBDA15C4), Cu²⁺(DBDA15C4)₂ and Cu²⁺(DBDA15C4)(VP)₂. The results obtained from solution studies were also supported by ab initio theoretical calculations. The resulting ternary complex Cu²⁺(DBDA15C4)(VP)₂ was copolymerized with ethyleneglycoldimethacrylate, as a cross-linking monomer, via bulk polymerization method. The imprinted copper ion was removed from the polymeric matrix by 0.1 M HNO₃. The Cu²⁺-imprinted polymer particles were characterized by IR spectroscopy and elemental analysis. Optimum pH range for rebinding of Cu²⁺ on the IIP and equilibrium binding time were 7.0-7.5 and 45 min, respectively. Sorbent capacity and enrichment factor for Cu²⁺ were obtained as 75.3 ± 1.9 μmol g⁻¹ and 100, respectively. In selectivity study, it was found that imprinting results in increased affinity of the material toward Cu²⁺ ion over other competitor metal ions with the same charge and close ionic radius. The prepared IIPs were repeatedly used and regenerated for five times without a significant decrease in polymer binding affinities.     

Synthesis of poly(4-vinylpyridine) and block copoly (4-vinylpyridine-b-styrene) by atom transfer radical polymerization using 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazamacrocyclotetradecane as ligand

Poly(4-vinylpyridine) (P4VP) and block copolymer, poly(4-vinylpyridine-b-styrene) (P4VP-b-PSt) were prepared by atom transfer radical polymerization (ATRP) using 1-phenylethyl chloride as initiator, CuCl and 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazamacrocyclotetradecane (Me₆[14]aneN₄) as catalyst and ligand. The polymerization of 4VP was carried out in 2-propanol at 40 °C. GPC and NMR studies show that the plot of ln([4VP]₀/[4VP]) against the reaction time is linear, and the molecular weight of the resulting P4VP increased linearly with the conversion. Within 3 h, the conversion can reach almost 90%. P4VP-b-PSt amphiphilic block copolymer with low polydispersity index (M_w/M_n ≈ 1.2) is also obtained by ATRP of St in DMF at 110 °C using P4VP-Cl as macroinitiator, CuCl/ Me₆[14]aneN₄ as catalyst.     

Temperature-dependent six-photon upconversion fluorescence of Er

Yb³⁺/Er³⁺ codoped β-NaYF₄ microcrystals were synthesized through a facile EDTA-assisted hydrothermal method. Under 980 nm excitation, 244, 256, and 276 nm upconversion (UC) emissions were observed in NaYF₄:Yb³⁺/Er³⁺ microcrystals, which were assigned to the ²I_11/2 → ⁴I_15/2, ⁴D_7/2 → ⁴I_15/2, and ⁴G_9/2 → ⁴I_15/2 transitions of Er³⁺ ions, respectively. Successive energy transfers (ETs) from Yb³⁺ to Er³⁺ played crucial roles in populating the high-energy states of Er³⁺ ions. Power dependence analysis exhibited that 244 and 256 nm UC emissions came from six-photon processes. Temperature-dependent UC emissions of ⁴D_7/2 → ⁴I_15/2 and ²I_11/2 → ⁴I_15/2 transitions of Er³⁺ were discussed and the nonradiative relaxation (NR) process of ²I_11/2 → ⁴D_7/2 was confirmed.     

Synthesis of tertiary-butyl acrylate polymers and preparation of diblock copolymers using atom transfer radical polymerization

The synthesis of tert-butyl acrylate by atom transfer radical polymerization (ATRP) is reported. This polymer was prepared using FeCl₂ · 4H₂O(PPh₃)₂ catalyst system in conjunction with methyl 2-bromopropionate as initiator, in bulk and in solution using acetone as a solvent. The addition of solvent was necessary in order to decrease the polymerization rate and to afford low polydispersity polymers. The number-average molecular weights of the resulting polymers increased in direct proportion to the monomer conversion, and the polydispersities (M_w/M_n) were as low as 1.2. In addition, the preparation of an AB diblock copolymer of poly (n-butyl methacrylate)-block-poly (tert-butyl acrylate) by ATRP is reported. The resulting polymers and copolymers were characterized by means of size exclusion chromatography and ¹H-NMR Spectroscopy.     

Towards understanding monomer coordination in atom transfer radical polymerization: synthesis of [Cu(PMDETA)(π-M)][BPh4] (M = methyl acrylate, styrene, 1-octene, and methyl methacrylate) and structural studies by FT-IR and H NMR spectroscopy and X-ray crystallography

Cu^I complexes of the form [Cu^I(PMDETA)(π-M)][BPh₄] (where PMDETA = N,N,N′,N″,N″-pentamethyldiethylenetriamine, and M = vinyl monomer) were synthesized and isolated from solution as crystals with methyl acrylate (MA), styrene (Sty), and 1-octene (Oct). The interaction of the CC double bond of the vinyl monomer with Cu^I was characterized via FT-IR and ¹H NMR spectroscopy and single crystal X-ray crystallography. A fourth complex with methyl methacrylate (MMA) was synthesized and characterized spectroscopically, but no crystals suitable for X-ray structure analysis could be obtained. In all complexes, PMDETA acts as a tridentate ligand, while the pseudotetrahedral coordination geometry around Cu^I is completed by a π-interaction with the CC double bond of M in the presence of a non-coordinating counter-ion. A decrease in CC IR stretching frequencies of Δν(CC) = −110, −80, −109, and −127 cm⁻¹ for complexes with MA, Sty, Oct, and MMA, respectively, was observed upon coordination. No significant change in CC bond length was seen in the crystal structure for complexes with MA and Oct while a slight lengthening was observed for the Sty complex. The upfield shift of the vinyl proton resonances indicated the presence of significant π-back-bonding.     

Preparation and characterization of a thermoresponsive gigaporous medium for high-speed protein chromatography

A high-speed thermoresponsive medium was developed by grafting poly(N-isopropylacrylamide-co-butyl methacrylate) (P(NIPAM-co-BMA)) brushes onto gigaporous polystyrene (PS) microspheres via surface-initiated atom transfer radical polymerization (ATRP) technique, which has strong mechanical strength, good chemical stability and high mass transfer rate for biomacromolecules. The gigaporous structure, surface chemical composition, static protein adsorption, and thermoresponsive chromatographic properties of prepared medium (PS–P(NIPAM-co-BMA)) were characterized in detail. Results showed that the PS microspheres were successfully grafted with P(NIPAM-co-BMA) brushes and that the gigaporous structure was robustly maintained. After grafting, the nonspecific adsorption of proteins on PS microspheres was greatly reduced. A column packed with PS–P(NIPAM-co-BMA) exhibited low backpressure and significant thermo-responsibility. By simply changing the column temperature, it was able to separate three model proteins at the mobile phase velocity up to 2167 cm h⁻¹. In conclusion, the thermoresponsive polymer brushes grafted gigaporous PS microspheres prepared by ATRP are very promising in ‘green’ high-speed preparative protein chromatography.     

High-dimensional mixed-valence copper cyanide complexes: Syntheses,structural characterizations and magnetism

Reactions of CuCl₂ with different CN complexes in presence of a neutral ancillary ligand lead to two novel mixed-valence Cu complexes [Cu^II(bpy)Cu^I(CN)₃]_n, 1 (bpy = 2,2′-bipyridine) and {[Cu^II(tn)₂][Cu^I₄(CN)₆]}_n2 (tn = 1,3-diaminopropane). For compound 1, the asymmetric unit involves two Cu ions Cu1 and Cu2 (Cu^I and Cu^II centres, respectively) which strongly differ in their environments. The Cu1 ion presents a CuC₄ pseudo-tetrahedral geometry, while the Cu2 ion presents a CuN₅ slightly distorted square-pyramidal geometry. The extended structure of 1 is generated by three cyano ligands which differ in their coordination modes. One CN group has a μ₃ coordination mode and bridges two Cu^I and one Cu^II ion, while the two other CN groups act as μ₂ bridges leading to a sophisticated 3-D structure. As for 1, the asymmetric unit of 2 involves three crystallographically different Cu ions (Cu1A and Cu1B, presumably Cu^I centres, and Cu2 presumably Cu^II centres). The Cu2 ion presents centrosymmetric CuN₄ coordination environments involving four nitrogen atoms from two bidentate tn ligands; while the Cu1A and Cu1B ions are three coordinated to cyano groups. The structure can be described as formed by 18-membered “[Cu^I(CN)]₆” planar metallocycles that are connected to their six neighbors to generate 2-D sheets; these sheets stack forming infinite hexagonal channels in which the [Cu(tn)₂]²⁺ units are located. Magnetic measurements show an unexpected weak ferromagnetic coupling (θ = 0.239(1) K) of the Cu^II ions through the long and “a priori diamagnetic” –NC–Cu^I–CN– bridges in compound 1 and an essentially paramagnetic behavior in compound 2.     

Copper‐Mediated Controlled/“Living” Radical Polymerization in Polar Solvents: Insights into Some Relevant Mechanistic Aspects

The field of transition‐metal‐mediated controlled/“living” radical polymerization (CLRP) has become the subject of intense discussion regarding the mechanism of this widely‐used and versatile process. Most mechanistic analyses (atom transfer radical polymerization (ATRP) vs. single‐electron transfer living radical polymerization (SET‐LRP)) have been based on model experiments, which cannot correctly mimic the true reaction conditions. We present, for the first time, a determination of the [Cu^IBr]/[L] (L=nitrogen‐based chelating ligand) ratio and the extent of Cu^IBr/L disproportionation during CLRP of methyl acrylate (MA) in dimethylsulfoxide (DMSO) with Cu⁰ wire as a transition‐metal catalyst source. The results suggest that Cu⁰ acts as a supplemental activator and reducing agent of Cu^IIBr₂/L to Cu^IBr/L. More importantly, the Cu^IBr/L species seem to be responsible for the activation of SET‐LRP.     

Atom transfer radical polymerization of styrene initiated by triphenylmethyl chloride

Triphenylmethyl chloride (TPMCl) was employed for the first time as the initiator of atom transfer radical polymerization (ATRP) of styrene in the presence of CuCl/N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) as catalyst and cyclohexanone as solvent. The kinetic plot was first-order with respect to monomer. A linear increase of number average molecular weight (M_n) vs. monomer conversion was observed, and the molecular weight distribution (MWD) was relatively narrow (M_w/M_n = 1.2-1.5). ¹H NMR spectra revealed the ω-Cl group at the chain end. Another two initiators, benzyl chloride (BzCl) and diphenylmethyl chloride (DPMCl), were also employed in contrast with triphenylmethyl chloride to investigate the influence of phenyl numbers on the polymerization.     

Effect of monomer molecular flow on electrode surface on the structure of poly(α-tetrathiophene) obtained by anodic polymerization

Different structures have been found for poly(α-tetrathiophene) [poly(α-4TF)] electrosynthesized on Pt by anodic oxidation of 1.0 mM monomer solutions in media such as 45:35:20 (v/v/v) acetonitrile/THF/DMF, 45:35:20 (v/v/v) acetonitrile/ethanol/DMF and 72:28 (v/v) acetonitrile/DMF containing 0.1 M LiClO₄; as well as 72:28 (v/v) acetonitrile/DMF with 0.1 M NaClO₃, under dynamic and static conditions at 25 °C. In all cases the polymer was generated by chronoamperometry at 1.000 V vs. Ag∣AgCl, corresponding to the first oxidation peak detected by cyclic voltammetry. Uniform, adherent, insoluble and black polymer films were obtained under these conditions. The resulting structures have been elucidated by combining the information of their IR spectrum, n_ox-value and doping level of the counterion. The degree of crosslinking of every polymer has been quantified and related to the molecular flow of monomer on the Pt electrode. A monomer concentration flow between 4 × 10⁻⁶ and 5 × 10⁻⁶ mmol cm⁻² s⁻¹ was determined as the limiting value below which the polymer grows with crosslinking. This value corresponds to the electropolymerization rate of α-4TF by Pt area unit at 25 °C.     

Insight into the ATRP rate controlling ability of initiator structure: Micromolecular,macromolecular, and immobilized initiators

The equilibrium constant (K_ATRP) is a key factor for ensuring a successful atom transfer radical polymerization (ATRP), which guarantees a controlled process with predictable product properties. In this work, the effect of initiator type (i.e., micromolecular, macromolecular, and immobilized initiator) on the ATRP kinetics was studied through a developed mathematical model. It was validated thoroughly via experiments using fluorinated monomer (2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) as model component. The results show that the activity and deactivity of the copper(I) chlorine/1,1,4,7,7‐pentamethyldiethylenetriamine (Cu^ICl/PMDETA) heterogeneous catalytic complex is the highest for ethyl 2‐bromoisobutyrate (Eib‐Br), lower for bromo‐poly(styrene) (PS‐Br), and the lowest for bromo‐aminopropyl functionalized SiO₂ (SiO₂‐APTS‐Br). The initiation system of Eib‐Br with Cu^ICl/4,4′‐dinonyl‐2,2′‐bipyridyl (dNbpy) has relatively lower activating ability, but the polymerization keeps controllable by its higher deactivating ability. In addition, this homogeneous catalytic system (Cu^ICl/dNbpy) is facile for further implementing the developed model to guide for the preparation of fluorinated gradient copolymers by semi‐batch ATRP. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2228–2238     

Synthesis and properties of polymer brushes composed of poly(diphenylacetylene) main chain and poly(ethylene glycol) side chains

Novel cylindrical polymer brushes consisting of poly(diphenylacetylene) main chain and poly(poly(ethylene glycol) methyl ether monomethacrylate) (PPEGMA) side chains were synthesized by the diphenylacetylene macromonomer or side chain initiated atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether monomethacrylate (PEGMA) from an bromo isobutyryl-bearing poly(diphenylacetylene) (poly(BrDPA)) method. The diphenylacetylene macromonomer, namely, DPA-PPEGMA, were prepared by the ATRP of PEGMA from bromo isobutyryl-bearing diphenylacetylene. DPA-PPEGMA was polymerized successfully with WCl₆-Ph₄Sn catalyst to give high molecular weight polymer brushes poly(DPA-PPEGMA). Meanwhile, polymer brushes (PDPA-g-PPEGMA) were obtained by ATRP of PEGMA from poly(BrDPA). The molecular weight of the side chains of PPEGMA could be controlled simply by modulating the ATRP time. The macromonomer and polymer brushes are soluble in nonpolar solvents such as toluene and chloroform. The polymers of poly(BrDPA) and poly(DPA-PPEGMA) absorb in the longer wavelength region, with two peaks at around 370 and 414 nm. The polymers are thermally stable and exhibit double crystallization and melting peaks during the cooling and heating scans.     

The Effect of [CuI]/[CuII] Ratio on the Kinetics and Conformation of Polyelectrolyte Brushes by Atom Transfer Radical Polymerization

Summary: The atom transfer radical polymerization of [2‐(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) has been studied under different [Cu^I]/[Cu^II] ratios. The reaction kinetics is followed by ellipsometry and quartz crystal microbalance and it was found that the reaction speed influences the grafting density of the polymer brushes. High [Cu^I]/[Cu^II] ratios, i.e., fast polymerizations, lead to less dense polymer brushes.

Plot of the frequency change of wet brushes on a QCM crystal (Δf) versus the dry thickness of brushes synthesized at different [Cu^I]/[Cu^II] ratios.     

Reverse atom transfer radical polymerisation (RATRP) of methacrylates using copper(I)/pyridinimine catalysts in conjunction with AIBN

N-n-Propyl-2-pyridylmethanimine, 1, N-n-octyl-2-pyridylmethanimine, 2, N-n-lauryl-2-pyridylmethanimine, 3, and N-n-octadecyl-2-pyridylmethanimine, 4 have been used in conjunction with copper(II) bromide and azo initiators for the reverse atom transfer radical polymerisation of a range of methacrylates. AIBN to Cu^IIBr₂ ratios of 0.5:1, 0.75:1 and 1:1 give PMMA with M_n 11 500 g mol⁻¹ (PDi = 1.24) (at 22% conversion), 12 500 g mol⁻¹ (PDi = 1.06) (at 83% conversion) and 10 900 g mol⁻¹ (PDi = 1.11) (at 84% conversion), respectively. A Cu^IIBr₂ complex is demonstrated to be needed at the start of the reaction for good control over molecular weight and polydispersity as reactions using Cu(I)Br as catalyst yielded PMMA of M_n 31 000 g mol⁻¹ (PDi = 2.90), reactions with no copper yield PMMA of M_n 33 000 g mol⁻¹ (PDi = 2.95). The RATRP of styrene was carried out using Cu^IIBr₂ as catalyst. AIBN to Cu^IIBr₂ ratio of 0.5:1, 0.75:1 and 1:1 gave PS with M_n = 12 400 g mol⁻¹ (PDi = 1.27) at low conversion, M_n = 15 500 g mol⁻¹ (PDi = 1.11) and 12 400 g mol⁻¹ (PDi = 1.38), respectively at ∼85% conversion. A series of block copolymers of MMA with BMA, BzMA and DMEAMA (15 600 g mol⁻¹ (PDi = 1.18), 13 300 g mol⁻¹ (PDi = 1.14) 15 300 g mol⁻¹ (PDi) = 1.16), using a PMMA macroinitiator were prepared. Emulsion polymerisation of MMA using [initiator]:[Cu^(II)Br₂] ratio = 0.5:1 with Brij surfactant gave a linear increase of M_n with respect to conversion, final M_n = 112 800 g mol⁻¹ (PDi = 1.42). Further reactions were carried out with [initiator]:[Cu^(II)Br₂] ratio = 0.75:1 and 1:1. Both giving PMMA with M_n ∼ 32 000 g mol⁻¹ (PDi ∼ 2.4). These reactions exhibit no control, this is because the azo initiator is present in excess and all of the monomer is consumed by a free radical polymerisation as opposed to a controlled reaction. Particle size analysis (DLS) showed the particle size between 160 and170 nm in all cases.     

Characterization and optimization of poly(glycidyl methacrylate-co-styrene) synthesized by atom transfer radical polymerization

Styrene (S) and glycidyl methacrylate (GMA) copolymers were synthesized by atom transfer radical polymerization (ATRP) under different conditions. The effect of initiators, ligands, solvents, and temperature to the linear first-order kinetics and polydispersity index (PDI) was investigated for bulk polymerization. First-order kinetics was observed between linearly increasing molecular weight versus conversion and low polydispersities (PDI) were achieved for ethyl 2-bromo isobutyrate (EBiB) as an initiator and N,N′,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA)/CuBr as a catalyst. The copolymers with different compositions were synthesized using different in-feed ratios of monomers. Copolymers composition was calculated from ¹H NMR spectra which were further confirmed by quantitative ¹³C{¹H} NMR spectra. The monomer reactivity ratios were obtained with the help of Mayo-Lewis equation using genetic algorithm method. The values of reactivity ratios for glycidyl methacrylate and styrene monomers are r_G = 0.73 and r_S = 0.42, respectively.     

Novel copper complexes based on the thiocyanate bridge - Synthesis, X-ray studies and magnetic properties

Three novel compounds {[Cu(bpzm)(SCN)][Cu(bpzm)(MeOH)][Cu(SCN)₄]}_n (1a), {[Cu₂(bpzm)₂(μ-SCN)(SCN)₃]}_n (1b) and [Cu₂(μ-SCN)₂(SCN)₂(dpa)₂] (2) have been obtained in one-step self-assembly reaction of copper dichloride, a suitable N-N ligand (bis(pyrazol-1-yl)methane and 2,2′-dipyridylamine) and ammonium thiocyanate. For the reaction involving bis(pyrazol-1-yl)methane, an unprecedented in situ reduction of some Cu(II) ions to Cu(I) has been observed. The compound {[Cu(bpzm)(SCN)][Cu(bpzm)(MeOH)][Cu(SCN)₄]}_n (1a) belongs to a relatively scarce group of mixed-valence Cu^II/Cu^I coordination polymers with interesting polymeric architecture. It creates infinite two-dimensional structure consisting of layers extending along crystallographic plane (0 0 1), in which the cations [Cu^II(bpzm)(SCN)]⁺ and [Cu^II(bpzm)(MeOH)]²⁺ are connected by ions [Cu^I(SCN)₄]³⁻ through single end-to-end thiocyanato bridges. Structure 1b consists two crystallographically independent chains. The chain A has a zig-zag form and extends along the crystallographic direction [0 0 1], whereas the second chain is linear and runs along the crystallographic direction [0 1 0]. The structure 2 consists of dinuclear [Cu₂(dpa)₂(μ-SCN)₂(SCN)₂] units. Variable-temperature magnetic susceptibility measurements show very weak antiferromagnetic interactions between the paramagnetic centres Cu(II) centers inside the crystal lattices of three novel compounds.     

Atom transfer radical polymerization of a novel quinoline derivative monomer and fluorescent property

A novel functional monomer incorporating quinoline derivative moiety as the side group, 2-[4-(2,7,7-trimethyl-3-ethoxycarbonyl-5-oxo-1,4,5,6,7,8-hexhydricquinoline)phenoxyl] ethylmethacrylate (HQPEMA), was synthesized and polymerized utilizing atom transfer radical polymerization (ATRP) technique. 2-(4-Chloromethylphenyl)benzoxazole (CMPB) and CuCl/PMDETA were used as the initiator and catalyst, respectively. GPC, ¹H NMR and fluorescent emission spectroscopy were conducted for characterization of polymers. The linear increase of number average molecular weight (M_n) versus conversion and the relatively narrow molecular weight distribution (M_w/M_n) of the obtained polymers confirmed that ATRP of HQPEMA was carried out successfully. In addition, the fluorescence “structural self-quenching effect” was observed in the DMF solution of the monomer HQPEMA, which bearing both electron-donating chromophore group and electron-accepting CC bond. We also found that the fluorescence properties of the newly obtained polymers containing quinoline chromophore depended on both the monomer concentration in solution and the polarity of solvents. The emission of the polymer film showed that the emission peak maxima of the polymer film shifted 50 nm towards high wavelength with respect to the polymer in DMF solution due to the intermolecular or intramolecular interactions of the polymer chains.     

Nickel(II) and copper(II) complexes of unsymmetrical tetradentate reduced Schiff base ligands

Two new reduced Schiff base ligands, [HL¹ = 4-{2-[(pyridin-2-ylmethyl)-amino]-ethylimino}-pentan-2-one and HL² = 4-[2-(1-pyridin-2-yl-ethylamino)-ethylimino]-pentan-2-one] have been prepared by reduction of the corresponding tetradentate unsymmetrical Schiff bases derived from 1:1: 1 condensation of 1,2-ethanediamine, acetylacetone and pyridine-2-carboxaldehyde/2-acetyl pyridine. Four complexes, [Ni(L¹)]ClO₄ (1), [Cu(L¹)]ClO₄ (2), [Ni(L²)]ClO₄ (3), and [Cu(L²)]ClO₄ (4) with these two reduced Schiff base ligands have been synthesized and structurally characterized by X-ray crystallography. The mono-negative ligands L¹ and L² are chelated in all four complexes through the four donor atoms to form square planar nickel(II) and copper(II) complexes. Structures of 3 and 4 reveal that enantiomeric pairs are crystallized together with opposite chirality in the nitrogen and carbon atoms. The two Cu^II complexes (2 and 4) exhibit both irreversible reductive (Cu^II/Cu^I; E_pc, −1.00 and −1.04 V) and oxidative (Cu^II/Cu^III; E_pa, +1.22 and +1.17 V, respectively) responses in cyclic voltammetry. The electrochemically generated Cu^I species for both the complexes are unstable and undergo disproportionation.     

Synthesis and characterization of novel ion-imprinted polymeric nanoparticles for very fast and highly selective recognition of copper(II) ions

This work reports the preparation of new Cu²⁺ ion-imprinted polymeric nanoparticles using 1-hydroxy-4-(prop-2′-enyloxy)-9,10-anthraquinone (AQ) as a vinylated chelating agent. The Cu²⁺ ion found to form a stable 1:1 complex with AQ in methanol solution. The resulting Cu²⁺-AQ complex was copolymerized with ethyleneglycol dimethacrylate, as a cross-linking monomer, via precipitation polymerization method. The imprint copper ion was removed from the polymeric matrix using a 0.1 mol L⁻¹ HNO₃ solution. The Cu²⁺-imprinted polymeric nanoparticles were characterized by IR spectroscopy, scanning electron microscopy (SEM) and N₂ adsorption-desorption isotherms. The SEM micrographs showed colloidal nanoparticles of 60-100 nm in diameter and slightly irregular in shape. Optimum pH for maximum sorption was 7.0. Sorption and desorption of Cu²⁺ ion on the IIP nanoparticles were quite fast and achieved completely over entire investigated time periods of 2-30 min. Maximum sorbent capacity and enrichment factor of the prepared IIP for Cu²⁺ were 73.8 μmol g⁻¹ and 56.5, respectively. The relative standard deviation and limit of detection (C_LOD = 3S_b/m) of the method were evaluated as 2.6% and 0.1 ng mL⁻¹, using inductively coupled plasma-atomic emission spectrometry, respectively. It was found that the imprinting technology results in increased affinity of the prepared material toward Cu²⁺ ion over other metal ions with the same charge and close ionic radius. The relative standard deviations for six and twenty replicates with the same nanoparticles were found to be 1.7% and 2.1%, respectively.     

Fluorometric method for the determination of hydrogen peroxide and glucose with Fe3O4 as catalyst

In this paper, we utilized the instinct peroxidase-like property of Fe₃O₄ magnetic nanoparticles (MNPs) to establish a new fluorometric method for determination of hydrogen peroxide and glucose. In the presence of Fe₃O₄ MNPs as peroxidase mimetic catalyst, H₂O₂ was decomposed into radical that could quench the fluorescence of CdTe QDs more efficiently and rapidly. Then the oxidization of glucose by glucose oxidase was coupled with the fluorescence quenching of CdTe QDs by H₂O₂ producer with Fe₃O₄ MNPs catalyst, which can be used to detect glucose. Under the optimal reaction conditions, a linear correlation was established between fluorescence intensity ratio I₀/I and concentration of H₂O₂ from 1.8 × 10⁻⁷ to 9 × 10⁻⁴ mol/L with a detection limit of 1.8 × 10⁻⁸ mol/L. And a linear correlation was established between fluorescence intensity ratio I₀/I and concentration of glucose from 1.6 × 10⁻⁶ to 1.6 × 10⁻⁴ mol/L with a detection limit of 1.0 × 10⁻⁶ mol/L. The proposed method was applied to the determination of glucose in human serum samples with satisfactory results.