Assessing water quality in the Dong Nai River (Vietnam): implications for sustainable management and pollution control.

Dong Nai River provides essential water resources for millions of people across 11 provinces and cities in Vietnam. However, the different pollution sources such as household, farming, and industrial operations have caused the river water quality to deteriorate over the past decade. To gain a comprehensive understanding of the river's surface water quality, this study employed the water quality index (WQI) across 12 different sampling sites. In total,144 water samples with 11 parameters were analyzed in accordance with the Vietnamese standard 08:2015/MONRE. Results revealed a range of surface water quality, from poor to good according to the VN-WQI (Vietnamese standard), and a medium even bad level in some months according to the NS-WQI (American standard). The study also identified temperature, coliform, and dissolved oxygen (DO) as strong contributors to WQI values (VN_WQI standard). Principal component analysis/factor analysis was used to determine pollution sources, with the results highlighting agricultural and domestic activities as the main contributors to river pollution. In conclusion, this study underscores the importance of effective planning and management of infrastructure zoning and local activities to improve the river's surface water quality and surrounding areas, as well as safeguard the well-being of the millions who depend on it.

Systematic synthesis of different-sized AgInS2/GaSxnanocrystals for emitting the strong and narrow excitonic luminescence.

This paper presents for the first time the systematic synthesis of AgInS2(AIS) nanocrystals (NCs) with different sizes of 2.6-6.8 nm just by controlling only the reaction temperature. The synthesis of AIS core NCs was carried out in 2 steps: (i) synthesis of Ag2S NCs and then (ii) partial exchange of Ag+with In3+in the template Ag2S NCs. For step (i), Ag2S NCs of different sizes were synthesized by reaction of the Ag and S precursors at different temperatures of 30 °C to 130 °C, for the same reaction time of 30 min. For step (ii), AIS NCs were created by the exchange of Ag+with In3+at 120 °C for 60 min. Finally, GaSxwas shelled on AIS core NCs to produce the AgInS2/GaSxcore/shell structures. The synthesized AIS/GaSxNCs demonstrate the clear excitonic absorptions and strong, narrow excitonic luminescence peaking at 530-606 nm depending on the size of AIS core NCs.