The chemical garden, which has been known as the plant-growth-like diffusion of chemicals since the 17th century, has regained much attention in recent years. Significant progress in research not only promoted the understanding of the phenomenon itself but also suggested a prospective method of synthesizing new materials via the chemical garden route. It is extremely important to introduce new characterization techniques to provide more insights into chemical diffusion and element redistribution during the reaction process. The present article describes some successful applications of the realtime X-ray fluorescence (XRF) movie technique to observe each diffusing element. The protagonist of the movie is a chemical garden reaction growing from a seed of calcium salt and ferrous salt mixtures. Through observation by an XRF movie, it has been found that the growth rate and diffusion behavior of calcium and iron are very different. This results in a macroscopic diversity of the element composition in the finally precipitated chemical garden structures. The present research not only reconfirms the potential of fabricating gradient composites through the self-organized chemical garden approach but also demonstrates the attractive achievements of XRF movies. It has been demonstrated that the XRF movie is an indispensable realtime characterization technique for the study of chemical garden reactions or even other related diffusions.

As X-ray fluorescence radiation isotropically spreads from the sample, one of the most important requirements for spectrometers for many years has been a large solid angle. Charge-coupled device (CCD) cameras are quite promising options because they have a fairly large area size, usually larger than 150 mm. The present work has examined the feasibility of a commercially available camera with an ordinary CCD chip (1024 × 1024 pixels, the size of one pixel is 13 μm × 13 μm, designed for visible light) as an X-ray fluorescence detector. As X-ray photons create charges in the CCD chip, reading very quickly the amount is the key for this method. It is very simple if the charges always go into one pixel. As the charges quite often spread to several pixels, and sometimes can be lost, it is important to recover the information by filtering out the unsuccessful events. For this, a simple, versatile, and reliable scheme has been proposed. It has been demonstrated that the energy resolution of the present camera is 150 eV at Mn Kα, and also that its overall achievement in seeing minor elements is almost compatible with conventional X-ray fluorescence detectors. When the CCD camera is combined with a micro-pinhole collimator, full field X-ray fluorescence imaging with a spatial resolution of 20 μm becomes possible. Further feasibility in practical X-ray fluorescence analysis is discussed.

A visible-light digital camera is used for taking ordinary photos, but with new operational procedures it can measure the photon energy in the X-ray wavelength region and therefore see chemical elements. This report describes how one can observe X-rays by means of such an ordinary camera - The front cover of the camera is replaced by an opaque X-ray window to block visible light and to allow X-rays to pass; the camera takes many snap shots (called single-photon-counting mode) to record every photon event individually; an integrated-filtering method is newly proposed to correctly retrieve the energy of photons from raw camera images. Finally, the retrieved X-ray energy-dispersive spectra show fine energy resolution and great accuracy in energy calibration, and therefore the visible-light digital camera can be applied to routine X-ray fluorescence measurement to analyze the element composition in unknown samples. In addition, the visible-light digital camera is promising in that it could serve as a position sensitive X-ray energy detector. It may become able to measure the element map or chemical diffusion in a multi-element system if it is fabricated with external X-ray optic devices. Owing to the camera’s low expense and fine pixel size, the present method will be widely applied to the analysis of chemical elements as well as imaging.

A visible-light camera was used to resolve X-ray fluorescence spectra. Following the installation of a micro-pinhole, simultaneous multi-element X-ray fluorescence movie imaging was conducted in a synchrotron facility.

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Full-field x-ray fluorescence (XRF) imaging is an efficient technique for investigating element composition of a sample and the corresponding spatial distribution. Eliminating scattering x-rays is important for visualizing diluted/trace elements clearly. However, using the linear polarization of synchrotron radiation to remove scattering in full-field XRF imaging has not been feasible for many years because a synchrotron beam is inherently narrow in the direction perpendicular to the polarization and a large imaging area and a low scattering background cannot be simultaneously achieved. In this study, the trade-off was solved by expanding a synchrotron beam in the direction perpendicular to the polarization using an asymmetric-cut Si crystal. Large areas of samples were illuminated. In addition, a collimator plate, which only transmitted scattering x-rays that spread in the polarization direction, was used for imaging. Therefore, the detected scattering intensity was low. The present full-field XRF imaging scheme with a size-expanded polarized synchrotron beam is well suited for visualizing diluted/trace elements. It could be extended to x-ray absorption edge fine structure imaging for analyzing the chemical state of diluted/trace elements in inhomogeneous samples.

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The scattering background in large-area X-ray fluorescence analysis (more than one square centimeter) has been greatly reduced by using highly polarized X-rays and by inserting a collimator plate between the sample and the detector.