Facilities
As a leader in the study of photosynthesis and photobiology, ASU has already amassed considerable resources in the Center for Photosynthesis including our ultrafast laser and microscopy facilities. Both these facilities and the Center for Solid State Electronics Research (CSSER) provide important support to the Center for BioOptical Nanotechnology.
The Center has recently consolidated most the ASU’s ultrafast laser and microscopy facility in the Biodesign Institute where it is used by researchers campus-wide. This is the foremost facilities for the application of ultrafast-laser technology to biology anywhere in the world.
Femtosecond transient absorbance/florescence instruments
The Center’s ultrafast facility is managed by Dr. Su Lin and used by a number of researchers in the ASU Photosynthesis Center and is managed by Dr. Su Lin. Our current instrument is based on a titanium-sapphire, self-mode-locked oscillator generating short pulses at a 100 MHz frequency which are selectively amplified to roughly 1 mJ per pulse in a regenerative amplifier pumped by a kilohertz Nd-YAG laser. This pulse is used either directly to generate pump and probe pulses as described above or it is passed through an optical parametric generator/amplifier to generate excitation wavelengths from about 390 nm through the near IR range (with a gap in the 500 nm range) The pulse width is wavelength-dependent, but for most measurements is about 150 femtoseconds. The repetition rate is 1000 Hz.
The Center has recently expanded their femtosecond system with high sensitivity single wavelength measurement capabilities, ideal for work at low excitation energy and under conditions where small signals are expected. The new system also has the ability to generate two excitation pulses that can be independently varied in both time and wavelength, for multipulse experiments. The light source for this system is an all solid state regeneratively amplified Ti:S laser system (Millennia, Tsunami, spitfire, Spectra Physics). The system provides 1 mJ, 100fs pulses at 1 KHz repetition rate, with a wavelength tuning range from 760-869 nm. The majority of the laser power is used to pump one or two optical 2000 nm with a pulse energy of 5 – 100 uJ, depending on the wavelength and pump power. These pulses are used as the excitation source in pump-probe experiments. About 10 percent of the laser output is focused into a 1 cm flowing water cell to generate a white light continuum beam, covering a wavelength region from 350 – 1500 nm, is split into two identical parts used as probe and reference beams. The probe and reference beams are sent through a monochromator (Acton Research) and either recorder by a dual diaode array system (Princeton Instruments) of individual wavelengths are monitored for high sensitivity single wavelength measurements.
Time-Correlated Single photon counting apparatus
The Center is a major user of a picosecond resolution time-correlated single photon counting system which is operated as part of the Photosynthesis Center ultrafast facility. This system consists of either a dye laser synchronously pumped by an actively mode locked Nd-YAG laser excitation source or a Ti-sapphire pump source both of which give a roughly 70 ps machine response function for detection in the near infrared (limited by the electronics and photomultipliers). Excitation is available from 280 – 315 nm, and the fluorescence detection range is 330 – 110 nm.
Surface Analysis
Shared surface characterization equipment used includes high resolution SEM Rutherford Backscattering/channeling, Auger, and XPS facilities. The capabilities of this proposal will be further enhanced through the use of specialized surface characterization facilities of collaborators at the new Department of Energy Center for Integrated Nanotechnology at Los Alamos Laboratories.
There is also a major facility for optical characterization of surfaces in the recently completed Biodesign Institute building. This consists of a series of microscopes coupled to any of a number of laser systems, both CW and ultrafast. The ultrafast lasers can be used for characterization of solution samples or surfaces. Excitation is available from 280 – 1000 nm from a combination of mode-locked dye lasers and a titanium-sapphire laser, with a pulse width as short as 70 fs. Two of the microscopes associated with these laser systems are set up for multiparameter, single molecule, confocal fluorescence detection using a very high resolution (nanometer) three-dimensional translation stage for scanning. These instruments can monitor a number of fluorescent properties on the surface including fluorescent lifetime via time correlated single photon counting, anisotropy and multiple wavelengths. The fluorescence detection range is 350 – 1100 nm. The microscopes are able to perform normal light microscopy (including DIC) and have a high sensitivity CCD (Cascade). These systems are capable of imaging individual molecules, complexes and cells all via multiparameter, picosecond time-resolved, confocal fluorescence detection. The spatial resolution of these systems is less then 500 nm using linear excitation and roughly 300nm with multi-photon excitation. There is also a large-scale (12-cm2) scanning system (using a 2-mirror galvanometer-based scanner) with lower (20 micron) resolution for detailed imaging of large samples.
Light Directed Synthesis and Chemical Patterning of Surfaces
All of the different optical laser scanning instruments described above have also been used for light-directed synthesis of heteropolymers and/or patterning of surfaces. Using the microscopes, patterning resolution down to a few hundred nanometer resolution should be possible. In addition, the Center has recently purchased a micro-mirror array system (MMA) specifically designed by Intelligent Microsystems for patterning molecules on surfaces using the photolabile blocking group chemistry proposal. The excitation is at approximately 30 nm. The micromirror array itself consists of approximately 800,000 individually addressable mirrors imaged onto a roughly 1 by 1.5 cm area. This chemical pattern or heteropolymer synthesis with a resolution of 10-15 microns.
Interface Force Microscopy Laboratory
The Interface Force Microscopy Laboratory (280 sq. ft.) contains a specially designed Interface Force Microscope (IFM) as well as a Park Scientific Instruments UHV STM.AFM. We are collaborating with Bruce Bunker and Jack Houston on IFM and high sensitivity FTIR measurements of molecular monolayers at Sandia National Laboratories as a user member of the DOE Center for Integrated Nanotechnologies (CINT). The Interfacial Force Microscope (IFM) enables intermolecular forces between a functionalized tip and a molecular surface to be directly probed. It is based on a unique design by J.E. Houston at Sandia National Laboratories (1,2) and uses micro-scale silicon self-balancing, force versus distance measurements. By eliminating deflection during force measurement, a quantitative measure over the entire range of force interactions is enabled between the probe tip and surface. We have an IFM at ASU and also use the CINT's specialized facilities. The IFM enables the direct quantitative measurements of the chemical interaction between functionalized sensor surfaces and target molecules tethered to the IFM tip. A liquid-cell chamber and glass tips (as well as conventional metal tips) have been developed for nano-scale molecular measurements. Micro- and nano-scale patterned substrate fabrication and tip development is carried out in the UHV metal deposition laboratory (590 sq. ft.) and in the CSSER clean room facility (see below).
Clean Room and Fabrication Facilities
All of the facilities required to fabricate the SOI MOSFETS and nano-gap electrodes are available in the ASU Center for Solid State Electronics Research. A 4,000 sq. ft. class-100 clean room in CSSER contains equipment that supports semiconductor wafer up to 4-inch) and device processing. Accessories include furnaces for diffusion, annealing, oxidation, rapid thermal processing system, evaporators, and sputtering stations for the deposition of contracts and dielectrics, and several reactive ion etchers, including a deep silicon etch tool. Facilities for computer aided design, mask making, and optical lithography are available. For feature sizes down to 2 nm we can use the recently installed JEOL 6000SF electron beam lithography facility. A Hitachi 5700 Field Emission SEM with a resolution of ~2 nm can be used to image the devices. These laboratories also include facilities for ultra-low current on –wafer probing using a Cascade Summit probe station and purpose build microfluidic stations that allow the monitoring of device behavior as reagents are applied. The Summit probe station is designed for the measurement of sub-picofard capacitance and is well suited for the impedance spectroscopy measurements that we are proposing. Also, there is a nanoimprinting lab as well as a focused ion beam system for fabrication with roughly 20 nm resolution.
Zeiss Scanning Confocal Microscope
The Zeiss Duo is a confocal scanning microscope system that combines high-speed line scanning, high resolution point scanning, DIC, and spectral profiling onto a single platform. The line scan mode is particularly well suited for live cell imaging and can image 120 fps at 512x512 resolution and over an order of magnitude faster for reduced fields of view. There are two and three independent detection channels for the line scan and point scan modules respectively. In addition both scan heads may be used simultaneously with one laser being used for imaging while a second laser is used for bleaching or photoactivation of a region of interest. The spectral resolution is 10.7 nm and a number of laser lines from 405 to 633 are available as excitation sources. The instrument is located in room A193. Contact Doug Daniel regarding training and scheduling. (tel: 965-4608, ddaniel@asu.edu)
