The design and fabrication of three-dimensional multifunctional architectures from the appropriate nanoscale building blocks, including the strategic use of void space and deliberate disorder as design components, permits a re-examination of devices that produce or store energy as discussed in this critical review. The appropriate electronic, ionic, and electrochemical requirements for such devices may now be assembled into nanoarchitectures on the bench-top through the synthesis of low density, ultraporous nanoarchitectures that meld high surface area for heterogeneous reactions with a continuous, porous network for rapid molecular flux. Such nanoarchitectures amplify the nature of electrified interfaces and challenge the standard ways in which electrochemically active materials are both understood and used for energy storage. An architectural viewpoint provides a powerful metaphor to guide chemists and materials scientists in the design of energy-storing nanoarchitectures that depart from the hegemony of periodicity and order with the promise--and demonstration--of even higher performance (265 references).

This manuscript describes the stepwise, ligand-directed assembly, characterization, and prospective applications of three-dimensional Au and Ag nanoparticle, multlilayered films. Films were prepared by successive treatments of a Au nanoparticle monolayer with a bifunctional cross-linker and colloidal Au or Ag solutions. Changes in film electrical and optical properties are reported for a series of bifunctional cross-linkers of varying molecular lengths. Interestingly, these films exhibit Beer's law behavior despite the presence of strong interparticle optical coupling. Multilayer films with greater than six exposures to 2-mercaptoethylamine and Au colloid were highly conductive and resembled bulk Au in appearance. In contrast, films of similar particle coverage generated using a longer cross-linker (1,6-hexanedithiol) exhibited higher transmission in the near-infrared region and exhibited a reduced conductivity. Measurement of the multilayer morphology with atomic force microscopy , electrostatic force microscopy, and field emission scanning electron microscopy revealed a porous, discontinuous morphology composed of large, continuous regions of aggregated nanoparticles. This, in turn, results in a surface roughness contribution to surface plasmon scattering and surface-enhanced Raman scattering observed for Au, Au/Ag, and Ag colloid multilayers. Particulate multilayer films made using horseradish peroxidase as a cross-linker remained enzymatically active, even beneath three layers of colloidal Au. Multilayers could also be prepared on surfaces patterned by microcontact printing. These data show how Au colloid multilayers grown in solution are a viable alternative to evaporated metal films for a number of applications.

The preparation, characterization, and electrochemical properties of two types of conductive Au films are described. Both films are made entirely by wet chemical procedures. In the first, successive treatment of a Au colloid monolayer/glass substrate with (i) 2-mercaptoethylamine and (ii) colloidal Au in solution leads to systematic buildup of a Au colloid multilayer. After seven to eight layers of Au nanoparticles have been deposited, the multilayers become conductive. Cyclic voltammograms of several different redox couples show that the peak-to-peak separation decreases as the number of layers increases. In the second type of film, a solution of hydroxylamine and Au3+ are used to selectively enlarge the size of a preimmobilized colloidal Au monolayer. Once the particles coalesce, the resulting film can be used to generate voltammograms with narrow peak separations. The ability to form conductive Au films using entirely wet-chemical steps may be valuable for fabrication of electrodes with complex shapes.

Molybdenum trioxide (MoO3) thin films prepared by cathodic electrodeposition on indium-tin-oxide coated glass substrates from aqueous peroxo-polymolybdate solutions have been studied as a function of sintering temperature (25-450 °C). Cyclic voltammetry, chronopotentiometry, chronoamperometry, and spectroelectrochemical measurements performed with MoO 3 thin films in 1 M LiClO4/propylene carbonate demonstrate that the electrochemical behavior (Li + insertion/extraction and coloration) is strongly dependent upon thermally induced changes in micro-/nanocrystallinity, which directly influence measured Li + diffusion properties as well as electroinsertion and electrochromic reversibilities. Structural analysis using X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy indicate that films heat treated at 100 °C or less exist as amorphous oxide-hydrates of molybdenum; whereas films heated to 250 °C exist as disordered, mixed-phase materials comprising monoclinic β-MoO 3 and orthorhombic R-MoO3. Crystallization to the more thermodynamically stable orthorhombic R-MoO3 occurs at 350 °C and above. The mixed-phase material exhibits inhomogeneous electrochemical activity, evidenced by the existence of complicated voltammetric and chronoamperometric responses. The effects of sintering temperature on ion insertion and electrocoloration properties are discussed.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is an important technique to characterize many different materials, including synthetic polymers. MALDI mass spectral data can be used to determine the polymer average molecular weights, repeat units, and end groups. The development of solvent-free sample preparation methods has enabled MALDI to analyze insoluble materials and, interestingly, can provide higher-quality mass spectral data. Although the utility of solvent-free sample preparation for MALDI has been demonstrated, the reasons for its success are only now being discovered. In this study, we use microscopy tools to image samples prepared using solvent-free methods to examine the morphology of these samples. The samples are prepared using a simple vortex method. Our results show that the average particle size of typical MALDI matrices is reduced from their original tens to hundreds of micrometers to hundreds of nanometers. This size reduction of the matrix occurs in one minute using the vortex method. We also observe remarkably smooth and homogeneous sample morphologies for the laser to interrogate, especially considering the relatively crude methods used to prepare our samples. [5][6][7][8][9][10]. MALDI can generate important data on the telomer repeat units, end groups, and average molecular weights of these materials. MALDI methods have been developed to address a broad variety of different polymer materials containing different chemistries. One of the key issues in traditional MALDI sample preparation is making true solutions of the analyte and the matrix [9]. Many interesting polymeric analytes are either completely insoluble or present significant challenges in making analytically useful solutions. To address these issues, solvent-free sample preparation methods have been developed. While several groups investigated solventfree sample preparation methods at nearly the same time, the methods developed by Trimpin, Räder, and coworkers have gained widespread use [11][12][13][14][15]. To make the sample preparation step easier, less time consuming, and reduce the risk of cross-contamination, we developed a simple version of the solvent-free sample preparation method, now called the vortex method [16]. Although the utility of solvent-free sample preparation for MALDI has been clearly demonstrated, the investigations into why it works and what impact these data have on our overall understanding of the MALDI process have only recently begun [17,18].To develop increased understanding of the utility of the solvent-free MALDI sample preparation method, we have investigated the morphology of these samples using different imaging experiments-optical imaging [19], scanning electron microscopy (SEM) [20], atomic force microscopy (AFM) [21], and time-of-flight secondary ion mass spectrometry (ToF-SIMS) [22]. Previous work has shown the utility of investigating MALDI sample morphology using imaging methods. We have used SEM to investigate the morphology of electrospray deposited samples [23] ...

A detailed study of electrochemically deposited molybdenum oxide thin films has been carried out after they were sintered at 250 degrees C. Conductive probe atomic force microscopy (CP-AFM), Raman microscopy, and X-ray photoelectron spectroscopy (XPS) techniques were employed to assess the complex structural, electronic, and compositional properties of these films. Spatially resolved Raman microprobe spectroscopy studies reveal that sintered molybdenum oxide is polymorphous and phase segregated with three types of domains observed comprising orthorhombic alpha-MoO3, monoclinic beta-MoO3, and intermixed alpha-/beta-MoO3. CP-AFM studies conducted in concert with Raman microprobe spectroscopy allowed for correlation between specific compositional regions and localized electronic properties. Single point tunneling spectroscopy studies of chemically distinct regions show semiconducting current-voltage (I-V) behavior with the beta-MoO3 polymorph exhibiting higher electronic conductivity than intermixed alpha-/beta-MoO3 or microcrystalline alpha-MoO3 domains. XPS valence level spectra of beta-MoO3 films display a small structured band near the Fermi level, indicative of an increased concentration of oxygen vacancies. This accounts for the greatly enhanced electronic conductivity of beta-MoO3 as these positively charged cationic defects (anion vacancies) act to trap excess electrons. Connections between structural features, electronic properties, and chemical composition are established and discussed. Importantly, this work highlights the value of using spatially resolved techniques for correlating structural and compositional features with electrochemical behaviors of disordered, mixed-phase lithium insertion oxides.

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