By using a solid KCl melt in conjunction with an Ag/AgCl component, Vanau et al. 8 were able to fabricate an SSRE designed specifically for beverage industry applications. They found that this SSRE had a wide range of pH use, stable potentials, and small drift potentials (1 mV at room temperature over 3 months time). The reported stability and lifetime of this reference electrode make it particularly applicable for the food industry. In addition to food industry, engine diagnostics are utilizing SSRE to assess efficiency. Oxygen sensors have long been utilizing yttria-stabilized zirconia-based potentiometric components. Recently, Mn-based oxides have been studied to find a suitable SSRE to ensure accurate on-board diagnosis for engines. Miura et al. 9 found Mn 2 O 3 -sensing electrodes to function with excellent sensitivity and has great potential for miniaturization.Rius-Ruiz et al. 10 recently reported a carbon nanotube (CNT)-based SSRE. The most successful design tested utilized a photopolymerized n-butyl acrylate polymer in conjuction with SWCNTs, acting as the transducer layer. This type of transducer layer was often superior to alternative solid transducers, and the resulting SSRE proved insensitive to room lighting. The superior characteristics of this reference electrode as well as its ease of fabrication allow for potential widespread usage in a multitude of systems.Other Papers of Interest. To ensure reference electrodes keep up with current miniaturization trends, it has become challenging to find suitable materials for all potential applications. One such challenging arena is that of steel corrosion monitoring. Muralidharan et al. 11 developed a NiFe 2 O 4 reference electrode due to its superior fabrication cost and ease and its resistance to corrosion. The resulting electrode exhibited stability and low polarization currents in a calcium hydroxide solution, which is commonly used in concrete environments.Shibata et al. 12 examined the stability of an Ag/AgCl reference electrode with the novel salt bridge 1-methyl-3-octylimidazolium bis(trifluoromethanesulfonyl)-amide. This bridge was proposed and found to be superior in order to avoid the interference found using alternate ionic liquid salt bridges, such as KCl, while experimenting in phthalate buffer. Further evaluation of stability is necessary; however, the initial findings suggest this ionic liquid salt bridge is promising. Huang et al. 13 recently developed a working system using a Nafion strip membrane as an ion-conducting bridge, allowing for electrochemical measurements in pure water. By using this bridge, it is possible to avoid potential leaching contaminants and gain higher accuracy.Measuring the electrodeposition of boron melts is a challenge to researchers due to the unknown chemistry of KF-KCl-KBrF 4 . Pal et al. 14 fabricated an Ag/AgCl reference electrode that was found to be reversible and to have suitable stability and nonpolarizability. This will allow for the first available measurements of KF-KCl-KBrF 4 chemistry at high tempera...

Electronic conductivity, σEL, in solid-state films of alkanethiolate monolayer protected Au clusters (Au MPCs) occurs by a bimolecular, electron self-exchange reaction, whose rate constant is controlled by (a) the core-to-core tunneling of electronic charge along alkanethiolate chains and (b) the mixed valency of the MPC cores (e.g., a mixture of cores with different electronic charges). The tunneling mechanism is demonstrated by an exponential relation between the electronic conductivity of Au309(C n )92 MPCs (average composition) and n, the alkanethiolate chainlength, which varies from 4 to 16. The electron tunneling coefficient β n = 1.2/CH2 or, after accounting for alkanethiolate chain interdigitation, βdis = 0.8 Å-1. Quantized electrochemical double layer charging of low polydispersity Au140(C6)53 MPCs was used to prepare solutions containing well-defined mixtures of MPC core electronic charges (such as MPC0 mixed with MPC1+). Electronic conductivities of mixed-valent, solid-state Au140(C6)53 MPC films cast from such solutions are proportional to the concentration product [MPC0][MPC1+], and give a MPC0/1+ electron self-exchange rate constant of ca. 1010 M-1 s-1.

Place-exchange and amide-forming coupling reactions represent two facile and efficient routes to poly-functionalization of water-soluble nanoparticles. In this paper, place-exchange and amide-forming coupling reactions with water-soluble tiopronin-MPCs are described and their products characterized by 1H and 31P NMR, capillary electrophoresis, electrochemistry, and fluorescence spectroscopy. Place-exchange reactions of ligands with tiopronin-MPCs yield products with about half of the ligand exchange expected on the basis of solution stoichiometry and a nonselective exchange and were not noticeably affected by steric encumbrances. Tiopronin-MPCs to which viologens are coupled (avg 36/MPC) adsorb as monolayers on Au electrodes as shown in electrochemical quartz crystal microbalance experiments. Multilayer adsorption occurs on long experimental time scales. The strong adsorption of the viologen-functionalized clusters is ascribed to increased interaction and stability in the viologen reduction products. Capillary electrophoresis experiments with tiopronin-MPCs and viologen-functionalized tiopronin-MPCs reveal a number of separable core size/charge state combinations. Fluorescence measurements show ∼50% quenching of fluorescein upon attachment (avg 3.7/cluster) to tiopronin-MPCs, relative to the monomer under the same conditions. The results of this paper provide a pathway to explore poly-functionalized water-soluble nanoparticles in a variety of applications, including their use as biosensors.

Intensely- and broadly-absorbing nanoparticles (IBANs)of silver protected by arylthiolates were recently synthesized and showed unique optical properties, yet question of their dispersity and their molecular formulas remained. Here IBANs are identified as a superatom complex with a molecular formula of Ag44(SR)304− and an electron count of 18.This molecular character is shared by IBANs protected by 4-fluorothiophenol or 2-naphthalenethiol. The molecular formula and purity is determined by mass spectrometry and confirmed by sedimentation velocity-analytical ultracentrifugation. The data also give preliminary indications of a unique structure and environment for Ag44(SR)304−.

Plants and some types of bacteria demonstrate an elegant means to capitalize on the superabundance of solar energy that reaches our planet with their energy conversion process called photosynthesis. Seeking to harness Nature's optimization of this process, we have devised a biomimetic photonic energy conversion system that makes use of the photoactive protein complex Photosystem I, immobilized on the surface of nanoporous gold leaf (NPGL) electrodes, to drive a photoinduced electric current through an electrochemical cell. The intent of this study is to further the understanding of how the useful functionality of these naturally mass-produced, biological light-harvesting complexes can be integrated with nonbiological materials. Here, we show that the protein complexes retain their photonic energy conversion functionality after attachment to the nanoporous electrode surface and, further, that the additional PSI/electrode interfacial area provided by the NPGL allows for an increase in PSI-mediated electron transfer with respect to an analogous 2D system if the pores are sufficiently enlarged by dealloying. This increase of interfacial area is pertinent for other applications involving electron transfer between phases; thus, we also report on the widely accessible and scalable method by which the NPGL electrode films used in this study are fabricated and attached to glass and Au/Si supports and demonstrate their adaptability by modification with various self-assembled monolayers. Finally, we demonstrate that the magnitude of the PSI-catalyzed photocurrents provided by the NPGL electrode films is dependent upon the intensity of the light used to irradiate the electrodes.