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This investigation first proposed that open-circuit potential vs time ͑OCP-t͒ is a novel nonlinear potential step controlled by redox reaction and nucleation. A novel thermodynamic model of OCP-t is obtained for electroless deposition of Ni on Pd-activated p-type silicon͑100͒. Thermodynamic transient properties such as capacity of double layer C, surface charge density q, interfacial tension ␥, and resistance of chemical reaction Rr are calculated. Results show that the variation of OCP is dependant on the interfacial double layer. The breakdown and rearrangement of the double layer causes surface charge density step, which triggers momentary nucleation of Ni on the substrate. Results also show that reductant pulses would be an effective way to speed nuclei growth.Open-circuit potential vs time ͑OCP-t͒ has been proved a sensitive and effective technique for sensing transient mixed potential at the interface of solid/solution. It has been applied in monitoring the corrosion behavior of metal, 1-3 hydrogen absorption in Pd electrodes, 4 oxygen, 5 carbon monoxide, 6 adsorption in Pt/Pd electrode, and characterization of acrylic hydrogels. 7 Our group also reports its application in electroless deposition of Ag. 8 However, the methodology of OCP-t is still undeveloped. Few papers on the mathematic model of OCP-t are reported. In this work, a novel thermodynamic model of OCP-t is used to propose for electroless deposition. We believe that it would be helpful to understand the process of electroless deposition and develop further applications of OCP-t.Electroless deposition of metal films on silicon such as aluminum, 9 copper, 9-11 silver, 12,13 gold, 14 nickel, 15,16 NiP alloy, 17 NiB alloy, 18 and CuNi alloy 19 have been investigated. The nucleation and reaction mechanisms 16-20 have also been studied. However, the transient information of electroless deposition is still blurry and needs to find a sensitive technique to describe it. OCP-t is an ideal option for this purpose because it can record transient potential of electroless deposition effectively. 8 Other transient techniques controlled by outer circuits such as conventional potential step and current step make it difficult to acquire actual information of electroless deposition.During the electroless deposition process, there are six processes occurring on the surface of samples, which include: ͑i͒ mass transport of ions, ͑ii͒ migration of ions, ͑iii͒ charge or discharge of double layer, ͑iv͒ adsorption or desorption of ions, ͑v͒ chemical reaction, and ͑vi͒ nucleation on the substrate. 21 In this experiment, the mass transport and migration of ions can be ignored because of agitating strongly. NiSO 4 solution and NH 2 NH 2 reductant are selected because their reactions are clear. Amperometric i-t is used to acquire transient current of electroless deposition. Ni film and Pd seed layer are characterized by atomic force microscope ͑AFM͒ and differential pulse voltammetry ͑DPV͒. ExperimentalInstruments and software.-AFM ͑Explorer, Veeco Co., USA͒ in contact mode,...

Carboxylated chitosan (CKCTS) was prepared for the removal of Cd(II), Pb(II), and Cu(II) from aqueous solutions. The effects of experimental parameters such as pH value, initial concentration, contact time and temperature on the adsorption were studied. From the results we can see that the adsorption capacities of Cd(II), Pb(II), and Cu(II) increase with increasing pH of the solution. The kinetic rates were best fitted to the pseudo-second-order model. The adsorption equilibrium data were fitted well with the Langmuir isotherm, which revealed that the maximum adsorption capacities for monolayer saturation of Cd(II), Pb(II), and Cu(II) were 0.555, 0.733 and 0.827 mmol/g, respectively. The adsorption was an exothermic process.

Analytical Chemistry Trust Fund SAC StudentshipsThe Trustees invite proposals from supervisors for research projects likely to make important contributions to the advancement of analytical chemistry in the UK and which are suitable for well qualified postgraduate students. Projects will be assessed particularly on the originality of the research proposed and its application to industrial needs. Applications may be submitted by research supervisors, who must be members of the Analytical Division of The Royal Society of Chemistry of at least 2 years' standing. If any form of equipment grant is likely to be required this should be included in the submission. The allocation of the limited amount of money available for proposals for projects to start in the Autumn term of 1992 will be considered early in that year when a tentative award may be made, subject to the Trustees being satisfied by the Summer of 1992 that a student acceptable to