A hydrothermal atomic force microscope for imaging in aqueous solution up to 150 °C

Abstract

We present the design of a contact atomic force microscope (AFM) that can be used to image solid surfaces in aqueous solution up to 150 °C and 6 atm. The main features of this unique AFM are: (1) an inert gas pressurized microscope base containing stepper motor for coarse advance and the piezoelectric tube scanner; (2) a chemically inert membrane separating these parts from the fluid cell; (3) a titanium fluid cell with fluid inlet–outlet ports, a thermocouple port, and a sapphire optical window; (4) a resistively heated ceramic booster heater for the fluid cell to maintain the temperature of solutions sourced from a hydrothermal bomb; and (5) mass flow control. The design overcomes current limitations on the temperature and pressure range accessible to AFM imaging in aqueous solutions. Images taken at temperature and pressure are presented, demonstrating the unit-cell scale (<1 nm) vertical resolution of the AFM under hydrothermal conditions.

Protein Crystal Growth Under High Pressure

“…Direct observations of individual elementary steps on protein crystal surfaces have been carried out mainly by atomic force microscopy (AFM) (Durbin & Carlson, 1992;Durbin et al, 1993;McPherson et al, 2000). However, AFM does not work under high pressure (> 6 atm) at the present stage (Higgins et al, 1998). Besides, the scan of a cantilever would potentially affect the soft surfaces of protein crystals.…”

A high-pressure atomic force microscope for imaging in supercritical carbon dioxide

“…A Nanoscope TM IIIa Multimode AFM system (Bruker AXS, Santa Barbara, CA) was utilized to operate the scCO 2 AFM and, as similar to the HAFM, 15 we have tapped into the piezoelectric scanner, the stepper motor and the optical head control signals from the Multimode AFM base to produce a functional apparatus. This new apparatus is designed to operate in contact mode imaging only.…”

“…For a number of mineral systems (e.g., oxides and silicates), rates of dissolution and growth reactions at room temperature are too slow to be measured by conventional in situ atomic force microscope (AFM) instrumentation. In 1998, Higgins et al developed the hydrothermal AFM 15 so as to gain access to mineral growth and dissolution rates in aqueous media at elevated temperatures and concomitant mildly increased pressures. That development allowed researchers to measure otherwise slow reaction rates more efficiently, for minerals such as magnesite, [16][17][18] barite, 19 plagioclase feldspars, 20 and phyllosilicates.…”

“…Here we report the development of a high-pressure scCO 2 AFM that enables in situ analysis of solid surfaces at pressures up to 100 atm at temperatures up to ∼350 K. This instrument is based on the hydrothermal AFM 15 and incorporates a number of similar features. The hydrothermal AFM can operate at pressures up to ∼10 atm, though a second generation hydrothermal AFM developed by Jordan and Astilleros 24 has the capacity to operate at pressures up to 50 atm.…”

The ReactorAFM: Non-contact atomic force microscope operating under high-pressure and high-temperature catalytic conditions

“…The easiest approach is to operate a standard AFM in an environmental chamber, 13,14 but this severely limits the operating temperature range and choice of gases (e.g., no corrosive gases). A more advanced approach uses a high-pressure flow cell that is separated from the piezo of the AFM scanner by a flexible membrane, to operate up to 423 K and 6 bar in liquids, 15 or up to 350 K and 100 atm in supercritical CO 2 . 16 These two instruments are limited to static AFM (i.e., contact mode) and constant temperature (long equilibration times), but could in principle be applied to catalytic systems.…”