Monodispersive size-controlled gold nanoplates were synthesized with high purity from the reduction of hydrogen tetrachloroaurate by reduced amount of sodium citrate, which kinetically controls the reaction pathway, in the presence of poly(vinyl pyrrolidone) (PVP). With the insufficient addition of the reductant, the molar ratio of sodium citrate and PVP relative to hydrogen tetrachloroaurate played an important role in determining the geometric shape and size of the product. These nanoplates were single crystals with planar width of 80-500 nm and thickness of 10-40 nm, exhibiting strong surface plasmon absorption in the near-infrared (NIR) region of 700-2000 nm. The gold nanoplates were used as the synthetically provided nanoblocks to fabricate single-crystalline nanocomponents, such as a nanoscaled gear or a nanoscaled letter.

Ultrasensitive, label-free, and real-time prostate-specific antigen (PSA) sensor was developed using n-type silicon nanowire-based structures configured as field-effect transistors using the conventional “top-down” semiconductor processes. Specific binding of PSA with antibody of PSA (anti-PSA) immobilized on the Si surface through covalent linkage leads to a conductivity change in response to variations of electric field at the surface. The conductance changes depending on PSA concentrations and pH values in solution according to isoelectric point of PSA provide the evidence of the real-time detection of 1fg∕ml PSA. The authors also explored the sensitivity of PSA immunodetection depending on both Si–field-effect transistors (FET) dimensions and doping concentrations to provide strategy for fabrication of an ultrasensitive Si-FET biosensor.

The surface of gold nanorods is coated with thickness-controlled silver by reducing AgCl 4 3exclusively on the metallic surface to form Au core Ag shell nanorods and then restored by selectively removing the silver coating. Au core Ag shell nanorods show much sharper, stronger, and shorter-wavelengthed surface plasmon absorption than gold nanorods. However, the absorption wavelength is much longer than the one calculated for pure Ag nanorods. This means that the core-shell structure of Au core Ag shell nanorods must be explicitly taken into account in these calculations.

The excited-state tautomerization dynamics of 7-hydroxyquinoline encapsulated in beta-cyclodextrin is compared with that in pure water by measuring isotope-dependent fluorescence kinetics as well as absorption and emission spectra. The normal species tautomerizes stepwise via forming anionic intermediate species in both systems. However, the enol-deprotonation time (40 ps in water) becomes as large as 170 ps whereas the imine-protonation time of the anionic intermediate (160 ps in water) becomes as short as 85 ps in beta-cyclodextrin. The slow formation and the fast decay of the anionic species are attributed to the unstability of the charged species in hydrophobic cages. Encapsulation can be utilized to enhance fluorescence enormously and to accelerate selective reactions by retarding other processes.

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Nanostructured materials having functional properties have been extensively studied recently. [1][2][3][4][5][6] In particular, metal nanostructures attract considerable attention scientifically as well as industrially, because they have possible uses in diverse applications such as catalysis, devices, transistors, and optoelectronics. [7][8][9][10][11] Nanoclusters and colloids of noble metals exhibit characteristic optical and physical properties that are substantially different from those of the corresponding bulk metals, thus attracting a great deal of interest. [12][13][14][15][16][17] They show strong absorption bands in the visible region due to the surface plasmon oscillation modes of conduction electrons. Thus, the optical properties of platinum, palladium, silver, and gold nanoparticles have received considerable attention. [18][19][20][21][22] In addition, core/shell and alloy bimetallic nanoparticles can exhibit peculiar electronic, optical, and catalytic properties that are absent in the corresponding monometallic nanoparticles. [18][19][20][23][24][25] Their optical and physical properties are reported to be tunable by varying their structure and/or their composition. [18][19][20][21][22][24][25] Nanoparticles show a decrease of melting temperature and thermal conductivity with a decrease in size. [17,19,[25][26][27][28][29] This dependence of melting temperature on size is not restricted to any particular materials; rather, it encompasses a wide variety of materials from metals to semiconductors and molecular organic crystals. [17,19,[25][26][27][28][29] The thermal conductivity of nanoparticles was also observed to decrease rapidly with a decrease in size, reaching a value of less than one third of the bulk value. [26] The dependence of melting temperatures on metals has also been exploited to fabricate or alter metal nanocomposites optically. [13,17,19,25] We have recently reported that the mutual transposition of the core and the shell of a Au@Pt core/ shell nanosphere can be obtained by exciting the surface plasmon resonances of platinum with picosecond laser pulses to form a new reversed core/shell Pt@Au nanosphere.[25]Nanomaterials having hollow interiors have attracted increasing interest recently because of their specific structures, interesting properties that differ from their solid counterparts, [1,10,18,21] and wide applications in chemistry, biotechnology, and materials science. [30][31][32][33][34] Hollow nanospheres have a broad range of potential uses in the fields of pharmaceutics, catalysis, and precipitation processes against a variety of sacrificial templates. [35][36][37][38] They are commonly prepared by coating the surfaces of colloidal particles with thin layers of desired materials, followed by the selective removal of the colloidal templates through calcination, wet chemical etching, or galvanic replacement. [10,18,21,[30][31][32][33][34][35][36][37][38] However, the removal of the templates often damages the spherical structures. [35][36][37] Herein we present a new optic...

Integrated nanogap electrodes with separations of several nanometers were fabricated by a simple and highly reproducible method of surface-catalyzed chemical deposition. By this method, multifingered nanogap electrodes of a few nanometers in separation were fabricated with a good yield (over 90%). The fabrication was achieved by immersing the initial gap electrodes obtained by conventional e-beam lithography into a stock solution containing Au ions and a mild reducing agent. After the surface-catalyzed chemical deposition, a rather wide initial gap distance of 18–52nm was decreased to a few nanometers, showing a much narrower distribution (centered at 3.3nm).

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