Chaorui Xue

Dual photoluminescence centers from inorganic-salt-functionalized carbon dots for ratiometric pH sensing

A controlled and effective strategy for synthesizing carbon dots (CDs) with dual photoluminescence (PL) peaks is presented in this report which involved employing coal-based CDs as seeds, and using appropriate diammonium phosphate (DAP) as a modifying agent. The formation of dual PL color CDs (D-CDs) mainly depends on the reaction temperature and thermally induced surface remodification of coal-based CDs with DAP. The origin of dual PL peak emissions is attributed to the presence of grafted N- and P-related groups on CDs through DAP functionalization. The synthesized D-CDs show a distinct pH-sensitive behavior under optimized laboratory conditions. Accordingly, a fluorescent ratiometric probe is developed based on these CDs for the detection of pH distribution and variation over a broad range in a complex system with interfering metal ions.

Fluoride doped SrTiO3/TiO2 nanotube arrays with a double layer walled structure for enhanced photocatalytic properties and bioactivity

Anodized TiO2 nanotube arrays have important applications in the area of photocatalysis and biomedicine. In this study, with the aim of improving the photocatalytic and biomedical properties of TiO2 nanotube arrays, we prepared both single and double layer walled TiO2 nanotube arrays and subjected them to hydrothermal treatment in strontium acetate solution. It was found that fluoride doped SrTiO3/TiO2 nanotube arrays could be formed after hydrothermal treatment without the failure of the single and double layer walled structure. In the case of fluoride doped SrTiO3/TiO2 nanotube arrays with a double layer walled structure, doping of fluoride induced a visible light response, formation of SrTiO3 benefited the separation of photogenerated electron–hole pairs, and the double layer walled structure led to an enlarged surface area. Due to the synergetic effect of above three factors, the fluoride doped double layer walled SrTiO3/TiO2 nanotube arrays demonstrated the highest photocatalytic activity under ultraviolet, visible and simulated solar light irradiation. The degradation rates of methylene blue solution are 0.13 h−1, 0.26 h−1 and 0.53 h−1 respectively. Moreover, ability to induce hydroxylapatite formation on the surface was also examined through an immersing test in simulated body fluid. The results indicated that SrTiO3, doped fluoride and a double layer walled structure could stimulate the hydroxylapatite formation by providing a larger number of hydroxyl ions, hydroxyl radicals and reactive initiation sites, thus the fluoride doped double layer walled SrTiO3/TiO2 nanotube arrays also exhibited the best ability to form hydroxylapatite on the surface.