『Abstract
　The acidic, non-oxidative dissolution of galena (PbS) nanocrystals has been studied in detail using transmission electron microscopy (TEM) to follow the evolution of the size and shape of the nanocrystals before and after dissolution experiments, X-ray photoelectron spectroscopy (XPS) to follow particle chemistry, and dissolution rate analysis to compare dissolution rates between nanocrystalline and bulk galena. Dissolution characteristics were also studied as a function of nanocrystal access to bulk vs. confined solution due to the degree of proximity of next-nearest grains. Nearly monodisperse galena nanocrystals with an average diameter of 14.4 nm were synthesized for this study, and samples were exposed to pH 3, deoxygenated HCl solutions for up to 3 h at 25℃. Detailed XPS analysis showed the nanocrystals to be free of unwanted contamination, surface complexes, and oxidative artifacts, except for small amounts of lead-containing oxidation species in both pre- and post-dissolution samples which have been observed in fresh, natural bulk galena. Depending on the calculation methods used, galena nanocrystals, under the conditions of our experiments, dissolve at a surface area normalized rate of one to two orders of magnitude faster than bulk galena under similar conditions. We believe that this reflects the higher percentage of reactive surface area on nanocrystalline surfaces vs. surfaces on larger crystals. In addition, it was shown that {111} and {110} faces dissolve faster than {100} faces on nanocrystals, rationalized by the average coordination number of ions on each of these faces. Finally, dissolution was greatly inhibited for galena nanocrystal surfaces that were closely adjacent (1-2 nm, or less) to other nanocrystals, a direct indication of the properties of aqueous solutions and ion transport in extremely confined spaces and relevant to dissolution variations that have been suspected within aggregates.』

1. Introduction
2. Materials and methods
　2.1. Galena synthesis and preparation for dissolution experiments
　2.2. Dissolution experiments
　2.3. characterization of galena nanocrystals
　　2.3.1. X-ray diffraction (XRD)
　　2.3.2. X-ray photoelectron spectroscopy (XPS)
　　2.3.3. Transmission electron microscopy (TEM)
3. Results and discussion
　3.1. Pre-dissolution galena nanocrystals
　　3.1.1. XRD crystal structure and particle size
　　3.1.2. Chemical composition of nanocrystals
　　3.1.3. Pre-dissolution crystal structure and morphology observed by HRTEM
　3.2. Shape and size evolution of post-dissolution PbS nanocrystals
　　3.2.1. Shape evolution
　　3.2.2. Statistical analysis of size evolution
　　3.2.3. HRTEM observations of nanocrystal morphology evolution
　　　3.2.3.1. Isolated nanocrystals
　　　3.2.3.2. Particle clusters
4. Implications
Acknowledgments
Appendix A. Calculation of geometric surface area (AGEO) and AGEO normalized dissolution rate (RGEO)
References