Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

/pdf/self-assembled-monolayers-of-thiolates-on-metals-as-a-form-1neb0hj3k4.pdf

Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

Recent years have seen a renewed interest in the harvesting and conversion of solar energy. Among various technologies, the direct conversion of solar to chemical energy using photocatalysts has received significant attention. Although heterogeneous photocatalysts are almost exclusively semiconductors, it has been demonstrated recently that plasmonic nanostructures of noble metals (mainly silver and gold) also show significant promise. Here we review recent progress in using plasmonic metallic nanostructures in the field of photocatalysis. We focus on plasmon-enhanced water splitting on composite photocatalysts containing semiconductor and plasmonic-metal building blocks, and recently reported plasmon-mediated photocatalytic reactions on plasmonic nanostructures of noble metals. We also discuss the areas where major advancements are needed to move the field of plasmon-mediated photocatalysis forward.

Plasmonic-metal nanostructures for efficient conversion of solar to chemical energy

-phenylenevinylene)s L4. Fluorene-Based Conjugated Polymers L4.1. Fluorene-Based Copolymers ContainingElectron-Rich MoietiesM4.2. Fluorene-Based Copolymers ContainingElectron-Deﬁcient MoietiesN4.3. Fluorene-Based Copolymers ContainingPhosphorescent ComplexesQ5. Carbazole-Based Conjugated Polymers R5.1. Poly(2,7-carbazole)-Based Polymers R5.2. Indolo[3,2-

https://ir.nctu.edu.tw:443/bitstream/11536/6508/1/000271856900020.pdf

Synthesis of Conjugated Polymers for Organic Solar Cell Applications

/pdf/aryl-aryl-bond-formation-one-century-after-the-discovery-of-1jdyxlkwix.pdf

Aryl-aryl bond formation one century after the discovery of the Ullmann reaction.

This is the report of a DOE-sponsored workshop organized to discuss the status of our understanding of charge-transfer processes on the nanoscale and to identify research and other needs for progress in nanoscience and nanotechnology. The current status of basic electron-transfer research, both theoretical and experimental, is addressed, with emphasis on the distance-dependent measurements, and we have attempted to integrate terminology and notation of solution electron-transfer kinetics with that of conductance analysis. The interface between molecules or nanoparticles and bulk metals is examined, and new research tools that advance description and understanding of the interface are presented. The present state-of-the-art in molecular electronics efforts is summarized along with future research needs. Finally, novel strategies that exploit nanoscale architectures are presented for enhancing the efficiences of energy conversion based on photochemistry, catalysis, and electrocatalysis principles.

Charge Transfer on the Nanoscale: Current Status

It is now established that hexagonally ordered domain structures can be formed in anodic alumina films by repeated anodization and stripping of the porous oxide. We find that the domain size is a linear function of time and increases with temperature. The pore density is initially high but decreases with anodizing time, as dominant pores deepen. Very small pores exist in native oxide in air or nucleate after electropolishing. Pore growth may start when the electric field increases at the pore bottoms, and acid dissolves the oxide locally.

On the Growth of Highly Ordered Pores in Anodized Aluminum Oxide

Unimolecular electrical rectification in hexadecylquinolinium tricyanoquinodimethanide

Unimolecular electrical rectifiers.

In 1959, the late Richard P. Feynman proposed, in his usual witty way, that there was “plenty of room at the bottom”, i.e., that atomic and molecular dimensions had not yet been exploited in information storage.1 In electronic technology, what was initially called “microminiaturization” did provide fantastic economies of scale, cost, and speed: the integrated circuits (IC) introduced by Noyce and Kilby were the beginning of this trend. It was observed that the scale of ICs or “computer chips” has halved, at first every 2 years, then every 18 months;2 this brought a concomitant increase in computing speed (“VAX on a chip”, then “Cray on a chip”) and an astonishing decrease in unit cost. However, there is trouble ahead. Circuit designers talk about “design rules”, the closest distance between adjacent electronic components in the IC. These design rules define the clock cycle, which is the time required to travel between the furthest components on the chip: shorter cycles mean faster computing. These design rules have now crept down to about 180 nm commercially. If photolithography is used, the design rules are limited, by Rayleigh’s criterion,3 to about one-half the wavelength of light used. Capacitative coupling between components and heat dissipation are perennial headaches. Three-dimensional integration (rather than planar integration) has remained an elusive goal. To achieve better performance, i.e., going to design rules of 100 nm or below, requires abandoning UV radiation and resorting to X-ray or electron beam lithography, with much higher error rates. At 50 nm, an even more drastic limit sets in: one can no longer “dope” Si uniformly. Present projections are that this 50 nm “silicon wall” will be reached by the year 2005.4 The idea of using molecules as electronic devices has gained attention and respectability in the past quarter century. By chemical insertion of electron-donating or electron-withdrawing groups, molecules can become oneelectron donors (D) or one-electron acceptors (A). To work properly, the oxidation or reduction of these molecules must be chemically reversible. In group IV chemistry (today, group 14: Si, Ge), one dopes a crystal of Ge or Si with dilute concentrations of interstitial or substitutional electron-rich elements (group V, or 15: N, P, As, etc.) to achieve an “n-doped” material. To make a “p-doped” crystal, one dopes with group III (or 13: Al, Ga, In, etc.). Thus, “D” corresponds to “n”, and “A” corresponds to “p”. By accosting a micrometer-thick film of organic D molecules to a micrometer-thick film of an organic A molecules, one gets a microscopic DA rectifier (one-way conductor) of electrical current, equivalent to an inorganic pn rectifier.5 In the 1960s, and particularly in the early 1970s, organic charge-transfer crystals and conducting polymers yielded organic equivalents of inorganic electronic systems: semiconductors, metals, superconductors, batteries, etc.6 But this wave of “me-too-ism” did not create a new technology: the organic systems did not perform better, or less expensively, than their inorganic counterparts. The two niche areas that survived are liquid crystal displays and (maybe) light-emitting diodes based on conducting polymers. In the early 1980s, sparked by three scientific conferences organized by the late Forrest L. Carter, the idea of “molecular electronics”, that is, electronic devices consisting solely of molecules, gained large-scale interest.7-9 Aficionados of biological processes started talking about “biomolecular electronics”. The term “molecular electronics” was extended to all electronic properties of polymers, crystals, etc.swhat we might call “large-scale molecular electronics”. This field, as outlined above, has not fared well in the marketplace. A persistent view has been that unimolecular, or “oligomolecular”,10,11 or “molecular-scale” 12 electronics have a very bright future, just as the new millennium begins. Molecules, with their 1-3 nm sizes, should step in where inorganic chemistry finally fails. Thus, unimolecular electronics will come to the rescue: they will finally find a central role in electronic technology.

Robert M. Metzger

Papers

Charge Transfer on the Nanoscale: Current Status

On the Growth of Highly Ordered Pores in Anodized Aluminum Oxide

Unimolecular electrical rectification in hexadecylquinolinium tricyanoquinodimethanide

Unimolecular electrical rectifiers.

Electrical rectification by a molecule : the advent of unimolecular electronic devices