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The lunar surface is directly and continuously exposed to Galactic Cosmic ray (GCR) particles and Solar energetic particles (SEPs) due to the lack of atmosphere and lunar magnetic field. These charged particles interact with the lunar surface materials producing secondary radiations such as neutrons and gamma rays. In a departure from precise GCR and SEP data, we estimated the effective dose equivalent at the lunar surface and in a lunar lava tube in this paper by using PHITS, a Monte Carlo simulation tool. The effective dose equivalent due to GCR particles at the lunar surface reached 416.0 mSv yr−1 and that due to SEPs reached 2190 mSv/event. On the other hand, the vertical hole of the lava tube provides significant radiation protection. The exposure by GCR particles at the bottom of the vertical hole with a depth of 43 m was found to be below 30 mSv yr−1 while inside a horizontal lava tube, the value was less than 1 mSv yr−1 which is the reference value for human exposure on the Earth. We expect that the lunar holes will be useful components in the practical design of a lunar base to reduce radiation risk and to expand mission terms.

A facile method to synthesize WO 3 ·H 2 O square nanoplates via a mild aging (50°C) of ion-exchanged precursor was developed. The ion-exchanged precursor was prepared by passing the sodium tungstate solution (Na 2 WO 4 ) through a protonated cationexchange resin, and used as impurity-free acidified solution (H 2 WO 4 ) for synthesizing WO 3 ·H 2 O nanoplates. No shape-directing additive was employed. It was observed that the yellow particles were precipitated under aging at 50°C. After aging for 8 h, the precipitated particles were characterized as the WO 3 ·H 2 O nanoplates, and their morphological evolution to square platelet proceeded with an increase of aging time. After aging for 24 h, the WO 3 ·H 2 O square nanoplates were predominantly synthesized. The square nanoplates consisted of a few or several stacked thin layers (thickness, ³10 nm/layer), and provided the well-defined {010} facet for two dominantly exposed surfaces and {101} side facets. Their lateral dimension reached several hundreds of nanometers. It is thus demonstrated that the mild aging (50°C) of the ion-exchanged precursor is a simple and impurity-free synthetic route for WO 3 ·H 2 O square nanoplates. In addition, the monoclinic WO 3 nanoplates were successfully obtained by dehydration-induced topochemical transformation of the WO 3 ·H 2 O nanoplates.

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