Jean-Claude Bradley

Creating electrical contacts between metal particles using directed electrochemical growth

Electrical connections in microelectronics are usually established by means of photolithography to define the conducting channels. But methods that do not involve lithography have been explored, such as the use of electrodeposition or electropolymerization to grow random structures of conducting material between two electrodes. This approach has been used to make diodes, transistors and signal amplifiers based on conducting polymers. Template-based and thermal plating strategies have also been used to direct the growth of electrically conducting media. One advantage of these approaches over photolithography is the possibility of forming contacts in three dimensions and so achieving enhanced data-processing densities. Previous electrochemical approaches have required that the electrodes to be connected are physically linked to the external voltage source. Here we show that electrodissolution and electrodeposition processes in an applied electric field can be exploited to create directional growth of copper deposits between copper particles that are not connected to an external circuit. Moreover, the particles distort the electric field in such a way as to focus the diffusion of copper ions and consequently the direction of ‘wire’ growth, enabling the particles to be connected to one another in a directional and controllable manner. This suggests that appropriately directed electric fields may be used to connect an array of such particles into an arbitrary circuit pattern.

Open Data, Open Source and Open Standards in chemistry: The Blue Obelisk five years on

BackgroundThe Blue Obelisk movement was established in 2005 as a response to the lack of Open Data, Open Standards and Open Source (ODOSOS) in chemistry. It aims to make it easier to carry out chemistry research by promoting interoperability between chemistry software, encouraging cooperation between Open Source developers, and developing community resources and Open Standards.ResultsThis contribution looks back on the work carried out by the Blue Obelisk in the past 5 years and surveys progress and remaining challenges in the areas of Open Data, Open Standards, and Open Source in chemistry.ConclusionsWe show that the Blue Obelisk has been very successful in bringing together researchers and developers with common interests in ODOSOS, leading to development of many useful resources freely available to the chemistry community.

Treatment of Social Anxiety Disorder Using Online Virtual Environments in Second Life

Over 80% of people with social anxiety disorder (SAD) do not receive any type of treatment, despite the existence of effective evidence-based treatments. Barriers to treatment include lack of trained therapists (particularly in nonmetropolitan areas), logistical difficulties (e.g., cost, time, transportation), concerns regarding social stigma, and fear of negative evaluation from health care providers. Interventions conducted through electronic communication media, such as the Internet, have the potential to reach individuals who otherwise would not have access to evidence-based treatments. Second Life is an online virtual world that holds great promise in the widespread delivery of evidence-based treatments. We assessed the feasibility, acceptability, and initial efficacy of an acceptance-based behavior therapy in Second Life to treat adults with generalized SAD. Participants (n=14) received 12 sessions of weekly therapy and were assessed at pretreatment, midtreatment, posttreatment, and follow-up. Participants and therapists rated the treatment program as acceptable and feasible, despite frequently encountered technical difficulties. Analyses showed significant pretreatment to follow-up improvements in social anxiety symptoms, depression, disability, and quality of life, with effect sizes comparable to previously published results of studies delivering in-person cognitive behavior therapy for SAD. Implications and future directions are discussed.

Contactless Electrodeposition of Palladium Catalysts

Site-selective electrodeposition of catalytically active metals on electrically conducting support particles was achieved by polarization with an electric field in a nonconductive matrix in the presence of metal salt solutions. The transmission electron micrograph shows a graphite particle to which Pd and Au were applied sequentially to opposite ends by reversing the direction of the electric field.

The Spectral Game: leveraging Open Data and crowdsourcing for education

We report on the implementation of the Spectral Game, a web-based game where players try to match molecules to various forms of interactive spectra including 1D/2D NMR, Mass Spectrometry and Infrared spectra. Each correct selection earns the player one point and play continues until the player supplies an incorrect answer. The game is usually played using a web browser interface, although a version has been developed in the virtual 3D environment of Second Life. Spectra uploaded as Open Data to ChemSpider in JCAMP-DX format are used for the problem sets together with structures extracted from the website. The spectra are displayed using JSpecView, an Open Source spectrum viewing applet which affords zooming and integration. The application of the game to the teaching of proton NMR spectroscopy in an undergraduate organic chemistry class and a 2D Spectrum Viewer are also presented.

Electric field directed construction of diodes using free-standing three-dimensional components

A process of making an electric current rectifying device using spatially coupled bipolar electrochemical deposition includes (a) placing at least two electrically conductive substrates, which may be a source of electrically conductive material, or a separate source of electrically conductive material, together with at least one semiconductor into an environment capable of conducting electricity and containing electrodes; (b) aligning the substrates and the semiconductor with respect to the electrodes such that the electrodes are not in contact with the substrates or the semiconductor and such that the material will form a conductive structure between and in contact with the substrates and the semiconductor when an electric field is applied between the electrodes; (c) to form a first electrically conductive structure between and in contact with a first of the substrates and the semiconductor; (d) reversing the polarity of the voltage to form a second electrically conductive structure.

Contactless Tip‐Selective Electrodeposition of Palladium onto Carbon Nanotubes and Nanofibers

Abstract Palladium was electrodeposited onto the tips of isolated carbon nanofibers and carbon nanopipes using an electric field. The amount of Pd deposited on the tips was controlled by varying the field application time. The morphology obtained varied from agglomerate of small particles that just covers the end of the nanotube to large ramified deposits that grow off the tip of the nanotube. The influence of the orientation of the carbon nanostructures with respect to the applied electric field and the quantity of the metal deposited is discussed. Electron microscopy was used to characterize the morphology and location of the deposits.

Pulsed Bipolar Electrodeposition of Palladium onto Graphite Powder

The pulsed bipolar electrodeposition of palladium onto 1-2 μm graphite particles was investigated. The amount of palladium deposited was strongly correlated with field intensity, showing an abrupt increase at 2-3 kV/cm. The electrodeposition was successful for frequencies ranging from 500 Hz to 20 kHz, and the amount of deposited palladium was independent of the frequency used. These results demonstrate that the preparation of bipolar electrodeposited catalysts can be achieved within a very large frequency window. Palladium surface area measurements indicate an increase in dispersion with increasing frequency. Sonication of the graphite prior to deposition leads to significantly greater palladium dispersion. Electron microscopy characterization reveals three types of growth: surface-bound, ramified, and amorphous. The surface-bound growth appears as spherical deposits on the order of 5 nm in both dc and pulsed-field experiments. The ramified deposits consist of interconnected 25-50 nm diam spherical structures extending from the graphite particles and appear in the samples prepared at all studied frequencies.

Ion transport and deposit growth in spatially coupled bipolar electrochemistry

In spatially coupled bipolar electrochemistry, electrodissolution and electrodeposition processes in an applied electric field are exploited to create directional growth of copper deposits between two copper discs, not physically linked to an external voltage source. Here, we study the electric field in the whole cell through theoretical modeling, and ion transport in the interdisc region using optical and particle image velocimetry techniques. Their combined effect on incubation time and deposit morphology is assessed. Both the electric field and ion transport in the interdisc region are crucial factors in the characteristics of the interconnection. The model simulations reveal that the electric field is almost an order of magnitude larger in the region between discs as compared with the mean field value. Measurements and simulations show that the incubation time scales linearly with the inverse of the electric field, an indication that in this period, migration is the dominant transport mode. Experiments reveal that after branching develops, convection plays a relevant role as well, the contact growing linearly in time, with a change of the time/length slope at half the interdisc gap.

Chemistry in second life.

This review will focus on the current level on chemistry research, education, and visualization possible within the multi-user virtual environment of Second Life. We discuss how Second Life has been used as a platform for the interactive and collaborative visualization of data from molecules and proteins to spectra and experimental data. We then review how these visualizations can be scripted for immersive educational activities and real-life collaborative research. We also discuss the benefits of the social networking affordances of Second Life for both chemists and chemistry students.