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To develop a convenient method for sensitive and selective determination of Ce3+ in aqueous phase with complicated matrices, a carbon paste electrode (CPE) modified with ion imprinted polymers (IIPs) were fabricated. The polymers were prepared by precipitation polymerization using Ce3+ as template, allyl phenoxyacetate (APA) as monomer, ethylene glycol dimethacrylate (EGDMA) as crosslinker and azobisisobutyronitrile (AIBN) as initiator under the molar ratio of Ce3+, APA and EGDMA as 1:4:40, respectively. Ce3+ was detected directly by differential pulse adsorptive stripping voltammetry (DPASV) and its oxidation peak appears at about 0.93 V. All parameters affecting the sensor's response are optimized and a calibration curve is plotted at a linear range of 1.0 × 10−6–1.0 × 10−5 mol/L and 1.0 × 10−5–2.0 × 10−4 mol/L with the detection limit of 1.5 × 10−7 mol/L. All other rare earth ions have no interference with the determination of Ce3+ even at a concentration 500 times higher than that of Ce3+. This sensor was successfully applied to determination of Ce3+ in two catalyst sample solutions with RSD≤3.3% (n = 5) and recoveries in the range of 99.2%–106.5% at our optimal conditions.

To solve the problem that the ion-imprinted membrane modified on glassy carbon electrode (GCE) usually easily falls off, a screen printed electrode (SPE) which has a relative rough surface than GCE, was selected as the base electrode for preparation of an ion-imprinted sensor for determination of Eu(III). The sensor was obtained by modifying SPE successively with carboxylic multiwalled carbon nanotubes (MWCNs-COOH) as signal amplifying element and Eu(III) ion-imprinted membrane (Eu(III)-IIM) as specific recognition material. To avoid damaging SPE by thermal initiation, the Eu(III)-IIM was prepared via radical photopolymerization at 380 nm using azobisisobutyronitrile (AIBN) as initiator. Differential pulse adsorptive stripping voltammetry (DPASV) was used for determination of Eu3+ by the obtained sensor. After the detection condition was optimized in detail, the sensor showed a linear response to Eu3+ in the concentration range of 1.0 × 10−7–1.0 × 10−3 mol L−1 with the detection limit of 4.0 × 10−8 mol L−1. The obtained sensor possesses of good regeneration, stability and practicability, it can maintain more than 95% of its original response after used more than 30 times or stored in the water for two months. The satisfactory results with the relative standard deviation (RSD) of less than 3.5% (n = 5) were obtained for the determination of europium in water samples by the novel sensor.

As a result of the increasing applications in different fields, europium has become a threat to the environment and human health. Thus, it is necessary to develop a simple and rapid method for determination of europium in trace level. In this paper, a sensor for determination of Eu3+ was established by modifying a screen printed electrode (SPE) successively with poly catechol as signal amplifying element and Eu(III) ion-imprinted membrane fabricated by sol-gel method as the recognition material. After the factors influenced the sensitivity of the sensor for Eu3+ was optimized in detail, Eu3+ can be determined by differential pulse adsorptive stripping voltammetry (DPASV) in the concentration range of 3.0 × 10−7–1.0 × 10−3 mol L−1 with the detection limit of 1.0 × 10−7 mol L−1. The fabricated sensor owns outstanding selectivity, perfect stability and good regeneration. 50-fold excess concentration of rare earth ions such as Ce3+, Tb3+, Ho3+, Dy3+, Er3+, Gd3+, Pr3+, Nd3+, Yb3+ and 100-fold excess concentration of other metal ions such as Fe3+, Ni3+, Cu2+, Zn2+ and Co2+ have no influence on the determination of 1.0 × 10−5 mol L−1 Eu3+. The obtained sensor, which can maintain >90% of its original response after used >60 times or stored in the water for 2 months, has been satisfactorily used to detect Eu3+ in water samples with the relative standard deviation (RSD) of

In this study, a molecularly imprinted electrochemical sensor based on graphene/Au nanoparticles (G@AuNPs) compound materials and molecularly imprinted membrane (MIM) modified glassy carbon electrodes (GCEs) was developed for the sensitive detection of colchicine in pharmaceuticals and serum (MIM/G@AuNPs/GCE). The film was formed by the in situ polymerization of colchicine-imprinted membranes on the G@AuNPs-modified GCE using methacrylic acid as the functional monomer. The specific surface area, catalytic performance, and electrical conductivity of the electrode increased on account of the formation of G@AuNPs compound materials, thereby improving the sensitivity of the sensor. The MIM as a preconcentrator exhibited chemical selectivity. Under optimal conditions, the MIM/G@AuNPs/GCE sensor exhibited high selectivity and high anti-interference ability. Moreover, good linearity was obtained in the range of 1.2 × 10−8 to 1.2 × 10−6 mol L−1 and 1.2 × 10−6 to 1.0 × 10−4 mol L−1 of colchicine with a detection limit of 4.8 × 10−9 mol L−1. The sensor was successfully applied for the direct determination of colchicine in colchicine tablets and human serum samples, with a relative standard deviation of less than 3.1% (n = 5) and recoveries ranging from 97.5% to 110.0%.

For the aim to detect Ce(III) in food with selectivity, sensitivity and speediness, a electrochemical sensor (Ce(III)-IIM/PC/GCE) was constructed by electropolymerization of a poly-catechol (PC) film on glassy carbon electrode (GCE) followed by modifying a Ce(III) ion-imprinted membrane (IIM) formed with electropolymerization using o-phenylenediamine as monomer. After that, a differential pulse adsorptive stripping voltammetry (DPASV) was developed for determination of Ce(III) by the obtained sensor. Under the optimal conditions, the sensor possesses good reproducibility and storage stability. Furthermore, it can be used directly for determination of Ce(III) in the concentration range of 3.0 × 10− 12–1.0 × 10− 4 mol L− 1 with the limit of detection of 1.0 × 10− 12 mol L− 1. Since over 50-fold excess concentration of Fe3 +, Cu2 + and Ni2 + will produce some interferences in the direct determination of Ce(III), an extraction method was adopted when it be used in food. After extraction of the samples with 1-phenyl-3-methyl-4-benzoyl-5-benzopyrazolone (PMBP), Ce(III) can be determined by Ce(III)-IIM/PC/GCE in the presence of > 500-fold excess concentration of Fe3 +, Cu2 + and Ni2 + with the limit of detection of 4.7 × 10− 9 mol L− 1. The sensor was successfully applied to determine cerium in food after extracted by PMBP with a relative standard deviation (RSD) of

In this study, a magnetic electrochemical sensor, Fe3O4@PDA-DMSA, was triumphantly fabricated by covalently modifying dimercaptosuccinic acid (DMSA) around magnetic polydopamine (Fe3O4@PDA). PDA with many functional groups can act as the starting points for covalent modification with desired molecules, and DMSA containing abundant sulfhydryl and carboxyl groups can be used as an excellent candidate. This magnetic nanocomposite synergistically exhibits several functions (especially high magnetic susceptibility), which can own unique advantages in electrochemical sensing applications. It was employed to enrich target analytes to design a novel electrochemical sensor for reliably monitoring of Pb(II) and Cu(II) in environmental samples, resulting from the specific chelation mechanisms between metal ions and functional groups. X-ray photoelectron spectral data demonstrate the main chelation mechanisms of this process. The synergistic effect among Fe3O4, PDA, and DMSA enhances the electrochemical sensitivity and accelerates the electron transfer. Under optimized conditions, the linear responses to Pb(II) and Cu(II) within the concentration range of 0.5–50 μg L−1 was obtained with the detection limits of 0.1 and 0.2 μg L−1, respectively. The little to no interference generated from common coexisting anions/cations allows the designed sensor to operate in diverse environmental conditions for practical applications. Such method of covalent modification can be used for designing sensitive electrochemical sensors for monitoring heavy metal ions.

The microhardness of micro-level TiC and TiB reinforcements in in-situ synthesized (TiC+TiB)/Ti-6Al-4V composite were investigated independently by spherical nanoindentation. The morphology of indentation on the matrix, reinforcements and the reinforcement / matrix interfaces were characterized by scanning electron microscope (SEM). The influence of cracks on the load-displacement curves and microhardness were analysed and discussed. The microhardness of TiC and TiB were calculated from the load-displacement curves on reinforcements without cracks. The average microhardness of TiC and TiB in this composite were 24.1 and 19.6 GPa, respectively, which agreed with the values in other composites and coatings. These results verified that the nanoindentation method was a very useful method to characterize the microhardness of micron-level reinforcements in discontinuous metal matrix composite.

In this work, an amperometric sensor was developed for the selective recognition and sensitive determination of palladium in complex matrices using a glassy carbon electrode (GCE) modified with a novel ion-imprinted membrane (IIM) and graphene. Graphene enhanced the sensor's electron transfer and sensitivity. The electrode surface was first directly modified with graphene through the electrodeposition of graphene oxide. An ion-imprinted polymer membrane was subsequently synthesized on this modified surface via in situ polymerization in acetonitrile using allylurea (NAU) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linking agent, and azobisisobutyronitrile as an initiator at a molar ratio of template (PdCl2) to NAU to EGDMA of 1:4:40. Amperometric i-t curves were measured for the determination of palladium. The designed modified electrode was shown a linear response to Pd(II) ions in the range of 2.0 × 10− 8–2.0 × 10− 4 mol L− 1 of Pd(II) ion with a detection limit of 6.4 × 10− 9 mol L− 1. Metal ions present at concentrations 15 times higher than that of Pd(II) did not interfere with the determination of Pd(II). The sensor was successfully applied to determine palladium in catalyst and plant samples with a relative standard deviation (RSD) of less than 3.3% (n = 5) and recoveries in the range of 99.2–106.5%.

In this study, Fe3O4@PDA@MnO2 core-shell magnetic nanocomposites were synthesized for the first time, and used to enrich target analyte to construct an electrochemical sensor for sensitive detection of trace Pb(II) in the environmental samples. A dense polydopamine (PDA) coating was firstly formed on the surface of Fe3O4 to ensure high stability because the developed method is employed under strongly acidic conditions. Then a high adsorption capacity MnO2 shell can be simply introduced to the surface of the PDA as a result of the redox activity between PDA and KMnO4. Differential pulse voltammetry (DPV) was applied for determining target metal ions. Chemical and electrochemical factors, including quantity of Fe3O4@PDA@MnO2 nanocomposites, preconcentration solutions pH, preconcentration time and supporting electrolytes, were optimized. Under excellent conditions, the designed sensor demonstrated a linear response to Pb(II) within the range of 0.1–150 μg L−1 and with a detection limit of 0.03 μg L−1. The proposed methodology exhibited excellent performance in selectivity, sensitivity and long-term stability, and was also successfully applied to determine Pb(II) in the real water samples. This study suggested that Fe3O4@PDA@MnO2 nanocomposites are a better alternative to Pb(II) analysis resulting from its low cost, low toxicity, strong adsorption, and good reproducibility.

A rhodium (III) ion carbon paste electrode (CPE) based on an ion imprinted polymer (IIP) as a new modifying agent has been prepared and studied. Rh(III) ion imprinted polymer was synthesized by copolymerization of acrylamide-Rh(III) complex and ethylene glycol dimethacrylate according to the precipitation polymerization. Acrylamide acted as both functional monomer and complexing agent to create selective coordination sites in a cross-linked polymer. The ion imprinted carbon paste electrode (IIP-CPE) was prepared by mixing rhodium IIP-nanoparticles and graphite powder in n-eicosane as an adhesive and then embedding them in a Teflon tube. Amperometric i-t curve method was applied as the determination technique. Several parameters, including the functional monomer, molar ratio of template, monomer and cross-linking agent, the amounts of IIP, the applied potential, the buffer solution and pH have been studied. According to the results, IIP-CPE showed a considerably higher response in comparison with the electrode embedded with non-imprinted polymer (NIP), indicating the formation of suitable recognition sites in the IIP structure during the polymerization stage. The introduced electrode showed a linear range of 1.00×10-8~3.0×10-5 mol·L-1 and detection limit of 6.0 nmol L-1 (S/N = 3). The IIP-CPE was successfully applied for the trace rhodium determination in catalyst and plant samples with RSD of less than 3.3% (n = 5) and recoveries in the range of 95.5~102.5%.