Theory is presented for a mathematical model that includes two-dimensional diffusion for the stripping of randomly distributed metal nanoparticles. Theoretical results are compared with the reversible and irreversible limits in the approximate analytical form derived by Brainina and co-workers ( Brainina K. Z. Brainina K. Z. Talanta197118513.. Brainina K. Z. Lesunova R. P. Brainina K. Z. Lesunova R. P. Zh. Anal. Khim.1974291302.. Brainina K. Z. Vydrevich M. B. Brainina K. Z. Vydrevich M. B. J. Electroanal. Chem.19811211.) when considering an average coverage of material across the whole electrode surface instead of the individual particle environments considered in the presented theory. Experimental results are reported for the stripping of different-sized silver nanoparticles (AgNPs) from a basal-plane pyrolytic graphite electrode in 0.1 M NaClO4. Different loadings (as measured by the stripping charge) for each size of nanoparticle were investigated. The theory presented was used to explain the observed experimental trends in stripping peak potential and indicates that the Ag/Ag+ couple has electrochemically reversible kinetics.

The Li/Li+ couple is investigated in the room temperature ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C4mpyrr][NTf2], at a range of temperatures varying from 298 to 318 K.Experiments are conducted using both nickel and platinum microelectrodes. On nickel, a single stripping peak is observed for the stripping of bulk lithium that allowed thermodynamic and kinetic parameters to be extracted via computational simulation. At 298 K, the electrochemical rate constant (k0) ) 1.2 X 10-5 cms-1, the diffusion coefficient (D) ) 4.5 X 10-8 cm2 s-1, the formal potential (E(f)0 ) -3.26 V versus the Fc/Fc+ reference couple, and the transfer coefficient (alpha) = 0.63. On platinum, multiple stripping peaks are observed due to the stripping of Li-Pt alloys in addition to the stripping of bulk lithium. The ratio of the different stripping peaks is found to change with temperature, indicating that Li-Pt alloys are more thermodynamically stable than pure bulk lithium and platinum.

The synthesis of magnetic, monodisperse nanoparticles has attracted great interest in nanoelectronics and nanomedicine. Here we report the fabrication of pure magnetite nanoparticles, less than ten nanometers in size, using the cage-shaped protein apoferritin (Fe(3)O(4)-ferritin). Crystallizable proteins were obtained through careful successive separation methods, including a magnetic chromatography that enabled the effective separation of proteins, including a Fe(3)O(4) nanoparticle (7.9 ± 0.8 nm), from empty ones. Macroscopic protein crystals allowed the fabrication of three-dimensional arrays of Fe(3)O(4) nanoparticles with interparticle gaps controlled by dehydration, decreasing their magnetic susceptibilities and increasing their blocking temperatures through enhanced dipole-dipole interactions.

Cyclic voltammetry experiments were conducted using solutions of Na + ions in 12 different ionic liquids (RTILs) on a nickel microelectrode in order to observe the deposition and stripping of metallic sodium. In most of the liquids the potential window was insufficient to observe the formation and removal of bulk sodium, despite the enlargement of some potential windows in the presence of sodium. However, in the ionic liquids) the deposition and stripping peaks for the bulk sodium were observed, allowing simulation of the current-voltage curves and extraction of kinetic and thermodynamic data, notably the electrochemical rate constant, k 0 , and the formal potential, E f 0 , for the Na/Na + couple. Variable temperature measurements also gave quantitative information on the temperature dependence of E f 0 , dE f 0 /dT. Diffusion coefficients for Na + ions in the three RTILs are also reported. All parameters are compared and contrasted with that of the Li/Li + couple, demonstrating that sodium possesses a more positive E f 0 than lithium in the investigated RTILs, although the difference is markedly less than that in solvents such as water or ammonia.

The voltammetry and kinetics of the Ag|Ag + system (commonly used as a reference electrode material in both protic/aprotic and RTIL solvents) was studied in the room-temperature ionic liquid N-butyl-Nmethylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C 4 mpyrr][NTf 2 ] on a 10 µm diameter Pt electrode. For the three silver salts investigated (AgOTf, AgNTf 2 , and AgNO 3 , where OTf -) trifluoromethanesulfonate, NTf 2 -) bis(trifluoromethylsulfonyl)imide, and NO 3 -) nitrate), the voltammetry gave rise to a redox couple characteristic of a "deposition/stripping" process at the platinum electrode surface. Using potential step chronoamperometry, the diffusion coefficients of AgOTf, AgNTf 2 , and AgNO 3 were found to be 1.05, 1.17, and 5.00 × 10 -11 m 2 s -1 . All three voltammograms were theoretically modeled to reveal surprisingly slow standard electrochemical rate constants, k 0 , of 2.0, 1.5, and 0.19 × 10 -4 cm s -1 respectively for the Ag + |Ag 0 couple. As a potentially faster alternative to the Ag|Ag + system, the voltammetry and kinetics of the TMPD|TMPD +• system (where TMPD ) N,N,N ′,N′-tetramethyl-p-phenylenediamine) was also studied, using neutral TMPD and two TMPD radical cation salts, with BF 4and NTf 2counter anions. Diffusion coefficients for TMPD, TMPD +• BF 4 -, and TMPD +• NTf 2were calculated to be 1.84, 1.35, and 1.43 × 10 -11 m 2 s -1 respectively, and a k 0 value of 2.6-2.8 × 10 -3 cm s -1 was obtained from theoretical fitting of the cyclic voltammetry. This number is an order of magnitude larger than that for the Ag|Ag + system, allowing for the suggestion that the TMPD|TMPD +• system may be more suitable than the Ag|Ag + system as a redox couple for use in reference electrodes for ionic liquids.