Shaowei Chen Ph.D.

Chen, Shaowei
Position Department / Business Unit
Associate Professor of Chemistry Chen Research Group, Department of Chemistry
Institution Disciplines
University of California Nanoparticles Chemistry
City State / Provence
Santa Cruz California
Country Website
USA link
Fax
(831) 459-2935
Our strategy is to employ a series of chemical as well as physical manipulations to shed light onto the molecular origin of these unprecedented electrochemical phenomena. Currently there are three major research projects in my laboratory:

Rectification of Nanoparticle Quantized Charge Transfer. This research project is mainly focused on the electrochemical investigations of chemical rectification of nanoparticle quantized capacitance charging in aqueous media. We used alkanethiolate-protected gold nanoparticles as the illustrating example. In (low-dielectric) organic media (e.g., CH2Cl2), the particle surface assemblies exhibited a series of well-defined voltammetric peaks in both negative and positive electrode potentials that were ascribed to the quantized charging to the particle molecular capacitance. In contrast, in aqueous solutions containing “soft” anions, the quantized charging features were observed only at positive potentials whereas in the negative potential regime, the current was featureless and significantly suppressed. That is, the current at positive potentials was significantly greater than that in the negative potential regime. Consequently, the overall voltammetric response was very similar to that of a molecular diode or current rectifier. Quantized charging was not observed when the electrolyte solutions contained only “hard” ions. The key finding of these studies is that simple ion chemistry can be exploited to gate electron transfer at nanoscale interfaces, a behavior analogous to that of a semiconductor field-effect transistor.

Solid-State Electronic Conductivity of Nanoparticle Ensembles.In this project, we examine the electron transfer chemistry of nanoparticles assemblies in solid state. These include transition-metal as well as semiconductor nanoparticles. We employ self-assembling and Langmuir-Blodgett techniques to fabricate nanoparticle organized assemblies and investigate the effects of interparticle interactions, photoexcitation, as well as chemical environments on the conductivity properties of the ensemble structures. For metal nanoparticles, we found that by deliberate control of the interparticle separation, lateral single electron transfer could be achieved; whereas for semiconductor particles, the electronic conductivity could be drastically enhanced by photoexcitation with the photon energies greater than the ensemble effective bandgap. Comparative studies are also carried out with scanning probe microscopic measurements (e.g., AFM, STM, and LFM). Such activities may be of fundamental importance to molecular electronics as well as photovoltaic applications.

Magnetoelectrochemistry of Nanoparticle Quantized Charging.We also study these nanoscale electron transfer processes in the context of an external magnetic field. Our goal is two folds: to investigate the magnetic properties of nanoparticle molecules at varied charge states and their effects on the corresponding electron transfer dynamics.

Education

B.S. University of Science and Technology of China, 1991; M.S. Cornell University, 1993; Ph.D. Cornell University, 1996

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