The projection X-ray microscope utilized a very small X-ray source emitted from a thin (0.1-3 μm) target metal film
excited by the focused electron beam of a scanning electron microscope (SEM). When an object is placed just below the
target metal film, the diverging X-rays enlarge the shadow of the object. Because no X-ray optics such as a zone-plate is
used, the focal depth is, in principle, infinitely large. We exploited this to apply projection X-ray microscopy to
three-dimensional (3-D) structure analysis by means of cone-beam computed tomography (CT).
A small arthropod (<i>Pseudocneorhinus bifasciatus</i>, 5 mm in length) was examined for CT study. The projection images
were recorded at 3-degree increments over the whole range (360°) of a stepping-motor-controlled sample rotator. The
3-D reconstructed image was calculated to be 256 x 256 x 256 (5 μm) voxel data. The reconstructed 3-D image showed
in detail the internal structure of an opaque object.
Trial for element mapping using projection X-ray microscope is also performed by developing a new target exchanger.
This apparatus enables exchange of metal targets without leaking vacuum of SEM. By taking images using Kα line from
nickel and cobalt targets, distribution of iron, which has absorption edge between two Kα lines, can be shown.
Distribution of less than 10 μm iron particles is distinguished from cobalt particles. This system would be applicable for
3-D element analysis.
One of the important points in synthesis of nano-particles (NPs) is regulation of the size of particles. Use of a protein cavity as a grow field of NP is one candidate procedure to make the size uniform. Here fabrication of nanometric aluminium and indium particles using protein, ferritin, are described. Aluminium NPs were observed as nano-crystals however indium NPs were amorphous. The indium NPs thus formed have uniform spherical shape with diameter of 6.6 ± 0.5 nm, while aluminium NPs were somewhat irregular in shape with about 6 nm diameter. At some special condition, proteins are going to crystallize and that would provide regularly arranged sites for NPs. This means crystallization of proteins provides regular array of NPs. Regular two-dimensional (2D) arrays of indium nanoparticles are successfully produced by crystallising ferritin with indium NP (In-ferritin) on a solid surface using the denatured protein film method or direct spreading. The lattice constant of NP arrays obtained by the denatured protein film method is 13.3 nm with hexagonal packing, and arrays of more than 4 μm<sup>2</sup> in area can be obtained by transfer onto silicon wafer. Square lattice with spacing of 9.3 nm is also obtained by direct spreading of salt free In-ferritin on solid surface. The square lattice is expect to be bilayer because spacing of 9.3 nm cannot be performed by monolayer.
We have applied projection X-ray microscope for three- dimensional (3D) structure analysis by means of cone-beam computed tomography. The projection images of small insect, Omiscus Porcellio, were recorded in every 1 degree for whole direction (360 degree) with a stepping motor controlled sample rotator. The images were recorded with cooled CCD camera (HAMAMATSU C4880) which detect X-ray directly. The 3D image was reconstructed from cone-beam projections using back-projection algorithm. The resolution of the reconstructed 3D image (256 x 256 x 256 pixels) was about 20 micrometers . The digestive organs were clearly visualized in 3D.