Integrated atomic force microscopy and x-ray irradiation for in situ characterization of radiation-induced processes

Abstract

Understanding radiation-induced chemical and physical transformations at material interfaces is important across diverse fields, but experimental approaches are often limited to either ex situ observations or in situ electron microscopy or synchrotron-based methods, in which cases the radiation type and dose are inextricably tied to the imaging basis itself. In this work, we overcome this limitation by demonstrating integration of an x-ray source with an atomic force microscope to directly monitor radiolytically driven interfacial chemistry at the nanoscale. We illustrate the value of in situ observations by examining effects of radiolysis on material adhesion forces in aqueous solution as well as examining the production of alkali nitrates at the interface between an alkali halide crystal surface and air. For the examined salt–air interface, direct visualization under flexible experimental conditions greatly extends prior observations by enabling the transformation process to be followed comprehensively from source-to-sink with mass balance quantitation. Our novel rad-atomic force microscope opens doors into understanding the dynamics of radiolytically driven mass transfer and surface alteration at the nanoscale in real-time.

Direct Measurement of Mineral Dissolution Enhanced by X-ray Irradiation

“…As such, care was taken to ensure consistent image quality, often requiring frequent AFM probe changes when tip convolution increased or tip artifacts became apparent. An X-ray source was chosen as the irradiation method due to its small footprint relative to other sources, allowing for integration with the AFM while allowing for freedom of experimental conditions as described in detail in previous work. , The cell was positioned so that the X-ray source was aligned with the center of the TiO 2 substrate with a separation of ∼3 mm (Figure S1). The dose rate experienced by particles was estimated by irradiating thin radiochromic films (HD-V2 Gafchromic film, International Specialty Products) at full power (12 Watt, 20 kV), as described in previous work, and determined to be reduced to 0.80 kGy/h due to attenuation through the TiO 2 substrate, resulting in a total dose of 6.4 kGy. , A custom cooling system allowed for precise control over the cooling rate of the X-ray source such that the temperature fluctuation measured in the fluid cell was limited to <1 °C during irradiation.…”

“…AFM studies can enable quantitative insights into morphology change, nucleation and growth or step retreat rates, and volume increase or loss of individual or ensembles of particles under a variety of conditions. − Recently, high-resolution AFM has been used to characterize anisotropic step retreat rates for individual gibbsite particles in situ in NaOH solutions . The current study complements this prior work by exploiting a unique atomic force microscope equipped with an integrated X-ray source that enables particle dissolution to be studied with irradiation on or off, both in situ during imaging and ex situ by irradiating while not imaging and then returning to the same particles for detailed characterization. , This AFM platform uniquely enables direct measurements of irradiation effects on the dissolution of individual particles under controlled solution conditions that can be compared with dissolution under identical conditions without irradiation.…”

“…10 The current study complements this prior work by exploiting a unique atomic force microscope equipped with an integrated X-ray source that enables particle dissolution to be studied with irradiation on or off, both in situ during imaging and ex situ by irradiating while not imaging and then returning to the same particles for detailed characterization. 11,12 This AFM platform uniquely enables direct measurements of irradiation effects on the dissolution of individual particles under controlled solution conditions that can be compared with dissolution under identical conditions without irradiation.…”

“…An Xray source was chosen as the irradiation method due to its small footprint relative to other sources, allowing for integration with the AFM while allowing for freedom of experimental conditions as described in detail in previous work. 11,12 The cell was positioned so that the X-ray source was aligned with the center of the TiO 2 substrate with a separation of ∼3 mm (Figure S1). The dose rate experienced by particles was estimated by irradiating thin radiochromic films (HD-V2 Gafchromic film, International Specialty Products) at full power (12 Watt, 20 kV), as described in previous work, and determined to be reduced to 0.80 kGy/h due to attenuation through the TiO 2 substrate, resulting in a total dose of 6.4 kGy.…”

“…The dose rate experienced by particles was estimated by irradiating thin radiochromic films (HD-V2 Gafchromic film, International Specialty Products) at full power (12 Watt, 20 kV), as described in previous work, and determined to be reduced to 0.80 kGy/h due to attenuation through the TiO 2 substrate, resulting in a total dose of 6.4 kGy. 11,12 A custom cooling system allowed for precise control over the cooling rate of the X-ray source such that the temperature fluctuation measured in the fluid cell was limited to <1 °C during irradiation.…”