A novel Ni2+ ion-imprinted polymer (IIP) was synthesized through a precipitation polymerization technique using itaconic acid (as functional monomer) and ethylene glycol dimethacrylate (as cross-linking agent). NIP was next used to construct a Ni2+ ion-selective membrane electrode through dispersing its particles in a poly (vinyl chloride)(PVC) based membrane plasticized with dibutylphthalate. The electrode revealed a Nernstian response of 24. 2± 0. 5 mV decade-1 to Ni2+ from 1. 0×10-5 to 1. 0×10-1 mol L-1 and had a lower detection limit of 5. 0×10-6 mol L-1. A control electrode based on non-imprinted polymer (NIP) was also prepared and evaluated, and found to be insensitive to the analyte ions in aqueous media. The satisfactory qualities of the developed IIP sensor make it a suitable candidate for the determination of Ni2+ ions.

The present research discusses the structure stabilizing and protecting effects of Ni2+ against suicide-peroxide inactivation of horseradish peroxidase (HRP). Suicide inactivation of HRP by hydrogen peroxide (3 mM) was monitored by measuring change in the absorbance of the colored product (tetraguaiacol) of the catalytic reaction cycle at 470 nm. Progress curves of the catalytic reaction cycle were obtained at 27 oC, phosphate buffer (5 mM), pH 7.0. The corresponding kinetic parameters (e.g., initial enzyme activity (a o) and the apparent rate constant (ki) of suicide inactivation of HRP by peroxide) were evaluated using a kinetic equation derived in this study. Comparative activatory and inhibitory effects of Ni2+ on the kinetics of suicide-peroxide inactivation of HRP are discussed.

Cross-linking starch microsphere (CSM) is a derivative of crude starch and has been studied and applied widely in the fields of medicine and sanitary devices. In our studies we have found that starch microsphere has good adsorption performance to metal ions in water. In this work, a type of cross-linking starch microsphere has been synthesized by reversed phase suspension method using soluble starch as raw material with N,N'-methylenebisacrylamide as a cross-linking agent. The observation through scanning electron microscopy (SEM) shows that CSM is a homogeneous mixture of spherical particulates with heterogeneous surface with particles' average diameter of about 50  mm. The structure characteristics of carbonyl group and second acylamide in Fourier transform infrared spectroscopy spectrogram of CSM demonstrates that the soluble starch is definitely cross-linked with N,N'-methylenebisacrylamide. The synthetic analysis of X-ray diffraction indicates that the cross-linking function decreases the crystallinity of CSM compared with that of soluble starch. The adsorption capacity of CSM towards Cu2+, Co2+, and Ni2+ increases with the increase in metal ion concentration, and by lowering the temperature, adsorption can be accelerated. The adsorption behaviour of CSM in different temperatures is in agreement with the Freundlich isothermal equation. The research results show that the adsorption process is exothermic, can proceed spontaneously, with the adsorption force mainly derived from enthalpy changes. The thermodynamic parameters of adsorption process show that the adsorption behaviour of CSM towards Cu2+, Co2+, and Ni2+ is of a physical type.

Nickel ions are toxic to the environment and they are also relevant in biology. Fluorescence sensing is a sensitive method and metal sensing can be carried out employing cheaper and easy-to-synthesize molecules that possess fluorescence emission. Therefore, the development of newer and simply-synthesized chemosensor molecules for nickel ions in aqueous media is required. We report, in this paper, a simple semicarbazone derivative of a piperidin-4-one as a nickel ion sensor in water. The compound forms a 1: 1 stoichiometric complex with nickel ions. The association constant value is 4. 04 × 104 mol-1 dm3. The nickel ion-selectivity of the compound is explored employing UV-Vis and fluorescence spectroscopy. Ni2+ ion-chelation enhances the fluorescence of the chemosensor molecule. The Ni2+ detection limit of the chemosensor was 1 × 10-7 mol dm-3. The compound also forms a 1: 2 inclusion complex with β,-cyclodextrin. The structure of the complex is proposed. Host: guest complex formation of β,-cyclodextrin with the piperidin-4-one derivative results in the interference of the host molecule with the chelation of Ni2+ ions. As an extension of the application of the piperidin-4-one derivative, we demonstrate the Ni(II) ion filtration by incorporating the compound with a polysulfone film.