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Self-assembled monolayers (SAMs) of 2-aminoethanethiol (AET) or 1,6-hexanedithiol (HDT) are formed on Au and Ag substrates, and colloidal Au (13.6 ( 2.0 nm diameter) and Ag (30.0 ( 10 nm diameter) nanoparticles are deposited onto these SAM surfaces. The resulting multilayered nanostructures, prepared with different combinations of the substrate, SAM, and nanoparticles, are studied with surface plasmon resonance (SPR) measurements. Under certain circumstances, the SPR sensitivity of the bare metal is considerably enhanced by the presence of the metal particles. Both the occurrence and the degree of this effect depend strongly on the choice of the combination of materials in the multilayered system. The substrate/SAM/nanoparticles systems that exhibit the enhanced SPR sensitivity include Au/AET/Au, Au/HDT/Au, Au/AET/Ag, and Ag/AET/Ag. On the other hand, the effects of the nanoparticles are relatively week for Au/HDT/Ag, Ag/HDT/Ag, Ag/ AET/Au, and Ag/HDT/Au. The observed system-selective nature of the nanoparticle induced SPR enhancement is discussed using Fresnel equations in a six-phase model. The results demonstrate how the interactions within and among the different components of a nanoparticle based SPR sensor affect the performance of such a sensor. These results also demonstrate the potential utility of the SPR technique in the investigation of structural and optical properties of self-assembled nanostructured materials.

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This review discusses recent developments in the areas of fabrication, certain types of optical characterization, and applications of a selected class of chemically assembled nanomaterials, namely i) gold and silver nanoparticles deposited onto optically transparent glass substrates; ii) thiol‐functionalized self‐assembled monolayers (SAMs); iii) chemically stabilized gold and silver nanoparticles (monolayer protected clusters, MPCs); and iv) MPCs linked to metallic substrates and adsorbates. Six linear optical techniques for the characterization of these materials are discussed: transmission localized surface plasmon resonance spectroscopy, T‐LSPR; propagating surface plasmon resonance spectroscopy, P‐SPR; polarization‐selective Fourier transform infrared reflection absorption spectroscopy, PS‐FTIRRAS; polarization‐modulation Fourier transform infrared reflection absorption spectroscopy, PM‐FTIRRAS; surface‐enhanced infrared reflection absorption spectroscopy, SEIRRAS; and infrared ellipsometry. The review focuses particularly on providing a unified treatment of these six optical techniques by using a relatively simple stratified multilayer model.

Using Au nanoparticles, it is possible under certain experimental conditions to considerably enhance the sensitivity of a conventional surface plasmon resonance (SPR) device. In this report, we examine the mechanism of this enhancement and discuss the experimental factors that are crucial to the performance of such a nanoparticle based SPR device. Among these factors, the surface plasmon-supporting metal substrate plays a major role. We demonstrate this by comparing experimental SPR data for Au and Ag substrates. In both cases, ∼25-30 nm diameter Au particles are attached to the substrate metal via a sandwiched monolayer of 1,6-hexanedithiol. The width and the efficiency of SPR for both substrates are affected by the Au particles. However, the particle-induced shift in the SPR angle is observed only for the Au substrate. This observation is explained in terms of competitive effects of propagating surface plasmons in the substrate metal and localized surface plasmons in the Au nanoparticles.In recent years, the SPR imaging technique has been successfully employed for immunosensing and for thickness measurements of ultrathin (2-20 Å) films. [1][2][3] In a typical SPR device, the sample layer is adsorbed onto a metal film, and the total attenuated reflection (ATR) efficiency, R, of the metal is measured as a function of the incidence angle, θ, of a probe light beam. The behavior of R is determined by the propagating surface plasmon polariton (SPP) modes at the metal/sample interface. In the absence of the sample, the R-θ plot (SPR plot) exhibits a dip at the angle, θ p , where the condition for SPR (resonance in SPP oscillations) is satisfied. In the presence of the sample layer(s), θ p shifts to a new value, and this shift is analyzed to determine the thickness (amount) and/or the dielectric function (chemical properties) of the sample. 4,5 Usually, the width, position and height of the SPR plot, as well as the fractional reflectivity change, (∆R/R) p , at the SPR angle are also modified in the presence of the adsorbed sample. These latter changes can provide additional information about the sample. However, often the sensitivity of the SPR device is limited by small shifts in θ p and (∆R/R) p . An effort to overcome the limitations of conventional SPR imaging have been recently reported by Lyon et al. 6,7 The discussion of our present communication focuses on the SPR device proposed by these authors. They use a gold nanoparticle-modified device, where an organic self-assembled monolayer (SAM) is sandwiched between a gold film and a layer of colloidal gold particles (in the 10-60 nm diameter range). The experimental sample is adsorbed on top on to the Au nanoparticles. The Au particles enhance the magnitude of ∆θ p , and at the same time, introduce an additional change in (∆R/R) p . These particles have their own

We report the synthesis and characterization of a series of imidazolium iodide ionic liquids (ILs) containing monomethoxy-terminated poly(ethylene glycol) (mPEG), and n-alkyl groups. These PEGylated ILs contain 7, 12, or 16 ethylene glycol units in the side chains, and are designed as potential electrolytes for energy conversion and storage devices such as dye-sensitized solar cells, supercapacitors, and Li ion batteries. The thermophysical (density, viscosity, and the temperatures of glass-transition, crystallization and melting) and electrochemical (nonfaradaic window, and capacitor leakage resistance) properties of the ILs, that are critical to these targeted applications, are studied using an array of techniques. 1-Alkyl-3-methylimidazolium iodide ILs are synthesized and characterized in parallel with the PEGylated ILs, to compare how the electrolyte properties of the two systems are affected by their detailed molecular structures, and especially by the ether oxygen atoms. The mPEG side chains show strong intramolecular interactions with the imidazolium ring, weakening Coulombic interactions between the imidazolium cation and the iodide anion. The PEGylated ILs, therefore, exhibit conductivities of the order of 0.1 mS cm -1 (25 °C) despite their relatively high viscosities, and support a temperature-independent electrochemical window of about 2 V, demonstrating their suitability for extended temperature applications.

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