This paper describes a facile method that generates dimers of Ag nanospheres by etching Ag nanocubes with Fe(NO 3 ) 3 in ethanol with the assistance of poly(vinyl pyrrolidone) (PVP). During the etching process, the corners and edges of the Ag nanocubes were truncated off to generate spherical particles, accompanied by dimerization as a result of reduction in colloidal stability due to the addition of ionic species. Both ethanol and PVP play an important role in the etching and dimerization processes. By starting with Ag nanocubes of different sizes, we obtained welldefined dimers of Ag spheres 40, 63, and 80 nm in diameter with percentages of dimerization >60%. Since this approach can be used to fabricate dimers of Ag nanospheres with a range of different sizes, it allows for a systematic study of the hot-spot phenomenon in SERS. By correlating with SEM imaging, we measured the SERS enhancement factors for individual dimers from the three different samples, and an average value of 3.9×10 7 , 9.3×10 7 , and 1.7×10 8 was obtained, respectively.

Progress in practical applications of large, passively collected data sets is often hindered by the lack of appropriate analytical tools or the proprietary nature of applicable software. One of the most widely used data sources in the United States is truck GPS data that are commercially available from a few sources nationwide. Although many large GPS data sets are used in the development of tour-based truck models, the development of a fairly general approach to data analysis and processing that can be readily applied to various GPS data sets without need of proprietary software is still of interest. First, this paper presents a set of tools and techniques used to transform low-frequency truck GPS data available from commercial sources into complete trajectories on the network, that is, sequences of links constituting continuous paths traversed by each truck, with corresponding time stamps on each of the nodes. For this exercise, only open-source software was used, and the algorithm implementation was released as an open-source tool under a business-friendly license. Second, use of the truck GPS data was expanded beyond the standard extraction of trip matrices and estimation of tour models. Additional applications include select link analysis, time-of-day analysis, and trajectory data visualization.

Hotspots können die Empfindlichkeit der oberflächenverstärkten Raman‐Streuung (SERS) stark erhöhen, doch erklärt werden konnte dieses Phänomen bisher nicht. Eine neue Strategie (siehe Bild) setzt auf das Plasmaätzen, um an Hotspots zwischen zwei Silbernanowürfeln adsorbierte SERS‐aktive Moleküle zu isolieren und gezielt zu untersuchen.magnified image

Although catalytic processes mediated by surface plasmon resonance (SPR) excitation have emerged as an ew frontier in catalysis,t he selectivity of these processes remains poorly understood. Here,t he selectivity of the SPR-mediated oxidation of p-aminothiophenol (PATP) employing Au NPs as catalysts was controlled by the choice of catalysts (Au or TiO 2 -Au NPs) and by the modulation of the charge transfer from UV-excited TiO 2 to Au.W hen Au NPs were employed as catalyst, the SPR-mediated oxidation of PATP yielded p,pdimercaptobenzene (DMAB). When TiO 2 -Au NPs were employed as catalysts under both UV illumination and SPR excitation, p-nitrophenol (PNTP) was formed from PATP in as ingle step.I nterestingly,P NTP molecules were further reduced to DMAB after the UV illumination was removed. Our data showthat control over charge-transfer processes may play an important role to tune activity,product formation, and selectivity in SPR-mediated catalytic processes.

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