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Dec 1999

Volume 70, Issue 12, pp. 4457-4738

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High resolution surface plasmon resonance spectroscopy

N. J. Tao, S. Boussaad, W. L. Huang, R. A. Arechabaleta, and J. D’Agnese

Rev. Sci. Instrum. 70, 4656 (1999); http://dx.doi.org/10.1063/1.1150128 (5 pages) | Cited 37 times

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A method for detecting surface plasmon resonance with high resolution ( ∼ 10−5 degrees or ∼ 10−8 refractive index units) and fast response time (1 μs) is described. In the method, light is focused through a prism onto a metal film on which molecules to be detected are adsorbed. The total internal reflection of the incident light is collected with a bicell photodetector instead of a single cell or an array of photodetectors that are widely used in previous works. The ratio of the differential signal to the sum signal of the bicell photodetector provides an accurate measurement of shift in surface plasmon resonance angle caused by the adsorption of molecules onto the metal films or by conformational changes in the adsorbed molecules. Using the method, we have studied subtle conformational changes in redox protein, cytochrome c, due to an electron transfer reaction. © 1999 American Institute of Physics.
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87.64.-t Spectroscopic and microscopic techniques in biophysics and medical physics
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.60.Gz Photodetectors (including infrared and CCD detectors)
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

A high pressure fiber-optic reactor with charge-coupled device array ultraviolet-visible spectrometer for monitoring chemical processes in supercritical fluids

Fred Hunt, Hiroyuki Ohde, and C.M. Wai

Rev. Sci. Instrum. 70, 4661 (1999); http://dx.doi.org/10.1063/1.1150129 (7 pages) | Cited 7 times

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A versatile spectroscopic reaction monitoring system for high-pressure liquids and supercritical fluids is described. The cell is designed to be attached to a charge-coupled device array ultraviolet-visible spectrometer via fiber optics, and has been shown to be capable of monitoring high speed reactions and rate of dissolution of a variety of compounds. The design is simple, inexpensive, rugged, and self-aligning. The cell has been tested up to 300 atm and 100 °C without failure. © 1999 American Institute of Physics.  
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
07.60.Rd Visible and ultraviolet spectrometers
82.53.-k Femtochemistry
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
82.20.Pm Rate constants, reaction cross sections, and activation energies
42.79.Pw Imaging detectors and sensors
07.60.Vg Fiber-optic instruments

The use of a special work station for in situ measurements of highly reactive electrochemical systems by atomic force and scanning tunneling microscopes

Yair Cohen and Doron Aurbach

Rev. Sci. Instrum. 70, 4668 (1999); http://dx.doi.org/10.1063/1.1150130 (8 pages) | Cited 14 times

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In this article, we describe a special homemade workstation in which highly reactive electrochemical systems, such as lithium electrodes in polar aprotic systems, can be measured in situ by both atomic force microscopy and scanning tunneling microscopy (STM). The workstation includes an evacuable glovebox that maintains a pure atmosphere in which the microscopes are located, thus enabling measurements in a highly pure argon atmosphere. The system is based on a compact and functional evacuable glovebox which is placed in a special construction which provides full protection against vibrations. This is obtained by suspending the box by flexible cords during the experiments, while all the piping connections are removed. The concept of an evacuable glovebox, which can be back-filled by a pure atmosphere, enables measurements to be performed under a pure inert atmosphere, eliminating the need for noisy gas purification systems. Pure solutions and highly reactive electrode materials are introduced into this glovebox by the use of a transfer method, based on a hermetically sealed transfer vessel and a special vacuum chamber in the glovebox. Preliminary results demonstrated that high-quality imaging of reactive electrochemical systems can be obtained using this system. A procedure for the preparation of STM tips is also described. © 1999 American Institute of Physics.
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07.79.Lh Atomic force microscopes
07.79.Cz Scanning tunneling microscopes
07.30.Kf Vacuum chambers, auxiliary apparatus, and materials
82.47.-a Applied electrochemistry
06.60.Ei Sample preparation (including design of sample holders)
82.45.-h Electrochemistry and electrophoresis

A versatile computer-controlled pulsed nuclear quadrupole resonance spectrometer

Gregory Fisher, Ernesto MacNamara, Robert E. Santini, and Daniel Raftery

Rev. Sci. Instrum. 70, 4676 (1999); http://dx.doi.org/10.1063/1.1150131 (6 pages) | Cited 2 times

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A new, pulsed nuclear quadrupole resonance (NQR) spectrometer capable of performing a variety of pulsed and swept experiments is described. The spectrometer features phase locked, superheterodyne detection using a commercial spectrum analyzer and a fully automatic, computer-controlled tuning and matching network. The tuning and matching network employs stepper motors which turn high power air gap capacitors in a “moving grid” optimization strategy to minimize the reflected power from a directional coupler. In the duplexer circuit, digitally controlled relays are used to switch different lengths of coax cable appropriate for the different radio frequencies. A home-built pulse programmer card controls the timing of radio frequency pulses sent to the probe, while data acquisition and control software is written in Microsoft Quick Basic. Spin-echo acquisition experiments are typically used to acquire the data, although a variety of pulse sequences can be employed. Scan times range from one to several hours depending upon the step resolution and the spectral range required for each experiment. Pure NQR spectra of NaNO2 and 3-aminopyridine are discussed. © 1999 American Institute of Physics.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.05.Dz Control systems
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