Accurate
onsite profiling of fluoroquinolone antibiotics (FQs)
is of vital significance for ensuring food safety and estimating environmental
pollution. Here, we propose a smartphone-based QD ratiometric fluorescence-sensing
system to precisely report the level of FQs. As a proof of concept,
we chose gatifloxacin (GFLX, a typical member of FQs) as the model
for the analytical target, which could effectively trigger the fluorescence
color variation of QDs from bright yellow-green (∼557 nm) to
blue (∼448 nm) through the photoinduced electron-transfer (PET)
process, thus yielding an evident ratiometric response. Based on this,
the level of GFLX can be reported within a wide linear range from
0.85 nM to 3.6 μM. Moreover, this assay owns a high sensitivity
with a low detection limit of 0.26 nM for GFLX and a quick sample-to-answer
monitoring time of 5.0 min, manifesting that this platform could be
fully qualified for onsite requirements. Interestingly, this portable
device has successfully been applied for the onsite detection of GFLX
in real food (i.e., milk and drinking water) and
environmental (i.e., fish-farming water) samples
with acceptable results. This developed platform offers a great promise
for the point-of-care detection of FQ residues in practical application
with the merits of being label-free, low-cost, and rapid, thus opening
a new pathway for the onsite evaluation of food safety and environmental
health.
To estimate the photo-oxidation aging performance of PVC-coated membrane material in atmospheric conditions under tensile stresses, the relationship between physical and mechanical properties under accelerated weathering test and outdoor weathering test is studied with the same cumulative UV radiation energy. And then, both tensile strength and whiteness index were measured and compared to characterize the property change of membrane material after aging under four different tensile stresses (0%, 5%, 10% and 20% of the breaking strength), respectively. In addition, FTIR spectrometry was applied to characterize the chemical components of the samples under different weathering conditions, and the carbonyl index was extracted. The results show that there were significant differences of tensile strength and carbonyl index between two kinds of aging conditions, whereas with the increasing tensile stresses, the whiteness index represented a consistent increasing deviation of accelerated weathering from the outdoor weathering. However, the relationship have been built between both whiteness index and tensile strength retention of accelerated weathering and those of outdoor weathering conditions after a Schwarzschild’s modification. Therefore, the service lifespan of PVC-coated membrane materials can be evaluated by accelerated weathering tests under tensile stresses.
Abstract-Monodisperse crosslinked polystyrene (PS) hollow core microspheres were successfully synthesized by two-step dispersion polymerization. The effects of the reaction parameters such as the crosslinking agent concentration, the initiator concentration and the monomer concentration on the particle sizes and size distribution were investigated. The results demonstrated that when the crosslinking agent concentration was low, the hollow microspheres had serious collapse, while the polymer particles became polydisperse with highly concentrated crosslinking agent. When increasing the initiator concentrations, particles with larger sizes and wider size distribution were obtained. If the initial monomer (styrene) weight fraction was too low, the honeycomb hollow ball or even solid particles would be formed, while if the monomer concentration was too high, the hollow microspheres appeared collapsed or ruptured.
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