Southwest University

About: Southwest University is a education organization based out in Chongqing, China. It is known for research contribution in the topics: Population & Bombyx mori. The organization has 29772 authors who have published 27755 publications receiving 409441 citations. The organization is also known as: Southwest University in Chongqing & SWU.

Carbon quantum dots based ratiometric fluorescence probe for sensitive and selective detection of Cu2+ and glutathione

Abstract: A novel method was established for the ratiometric fluorescence detection of Cu2+ and glutathione (GSH) by carbon quantum dots (CQDs), and it was fabricated through one-pot facile hydrothermal treatment using o-phenylenediamine (OPD) and citric acid as precursors. Based on the selective oxidation reaction of OPD with Cu2+, the detection strategy of Cu2+ was proposed using ratiometric fluorescence probe. The oxidation production (2,3-diaminophenazine) of OPD, obtained through the oxidation reaction of OPD and Cu2+, not only emerged a new emission peak at 562 nm, but also quenched the fluorescence of CQDs with maximum emission at 446 nm. The mechanism was Forster resonance energy transfer (FRET) between CQDs and 2,3-diaminophenazine (oxOPD). Furthermore, the oxidation reaction between Cu2+ and OPD could be inhibited when added GSH into the solution, which could prevent the fluorescence of CQDs being quenched. The sensing system showed high sensitivity toward Cu2+ and GSH in a range of 0.25–10.0 μmol L−1 and 1.0–80.0 μmol L−1 with a detection limit 0.076 μmol L−1 and 0.30 μmol L−1, respectively. Besides, the proposed method could apply to efficient quantification of Cu2+ and GSH in practical samples.

Particles interaction forces and their effects on soil aggregates breakdown

Abstract: A B S T R A C T Soil aggregates profoundly influence soil fertility and environmental problems, and usually improving soil aggregation is the central issue in soil management. Compared with external forces, the internal forces of soil, i.e., surface hydration force, electrostatic force and van der Waals force, may play a crucial role in aggregate formation and stability. However, there are few quantitative investigations on those fundamental issues. In the present work we aim to calculate surface hydration force, electrostatic force and van der Waals force of soil/clay particles in aqueous solution, and then quantitatively evaluate the effects of the three forces on soil/clay aggregates breakdown. There was critical surface potential in particles interaction pressure and aggregates breakdown, and if the surface potential exceeded this critical point, a further increase of the surface potential could not significantly increase particles interaction pressure and aggregate breakdown. The critical surface potentials for particle interaction pressure were 207.0 and 179.7 mV for the soil and montmorillonite, respectively. Our study suggested two steps in aggregate breakdown when dried aggregates were re-wetted: (1) separating soil particles in aggregates to a distance of 1.2–1.4 nm between two adjacent particle surfaces by the surface hydration forces (swelling process); (2) breaking soil aggregates in a way of explosion or dispersion under strong or weak electric field conditions. Surface hydration force played a crucial role in aggregate swelling, and without this repulsive pressure, a dried aggregate could not be dispersed again after re-wetting.