We report on the fabrication of thermoresponsive poly(N-isopropylacrylamide) nanogel-based dual fluorescent sensors for temperature and Hg2+ ions, and the effects of thermo-induced nanogel collapse on the detection sensitivity of Hg2+ ions. Near-monodisperse thermoresponsive nanogels were prepared via emulsion polymerization of N-isopropylacrylamide (NIPAM) and a novel 1,8-naphthalimide-based polarity-sensitive and Hg2+-reactive fluorescent monomer (NPTUA, 3). At room temperature, PNIPAM nanogels labeled with a single type of naphthalimide-based dye (NPTUA) can act as ratiometric Hg2+ probes at the nanomolar level. Upon heating above the phase transition temperature, the fluorescence intensity of NPTUA-labeled nanogels in the absence of Hg2+ exhibit ∼3.4-fold increase due to that NPTUA moieties are now located in a more hydrophobic microenvironment. Moreover, it was observed that the detection sensitivity to Hg2+ can be further improved above the nanogel phase transition temperature. At a nanogel concentration of 0.05 g L−1 and in the same Hg2+ concentration range (0–3.0 equiv.), ∼10 fold and ∼57 fold increase in fluorescence emission intensity ratio changes can be achieved at 25 and 40 °C, respectively.
我们报告了基于热致伸缩性聚(N-异丙基
丙烯酰胺)纳米凝胶的温度和 Hg2+ 离子双荧光传感器的制备,以及热致纳米凝胶塌缩对 Hg2+ 离子检测灵敏度的影响。通过乳液聚合 N-isopropylacryl
AMide (NIP
AM) 和一种新型 1,8-naphthalimide 基极性敏感型 Hg2+ 反应荧光单体 (N
PTUA, 3) 制备了近单分散热致塌缩纳米凝胶。在室温下,用一种
萘二甲
酰亚胺染料(N
PTUA)标记的
PNIP
AM 纳米凝胶可作为纳摩尔级的 Hg2+ 比率探针。当加热到相变温度以上时,在没有 Hg2+ 的情况下,N
PTUA 标记的纳米凝胶的荧光强度会增加 3.4 倍,这是因为 N
PTUA 分子现在位于更疏
水的微环境中。此外,还观察到在纳米凝胶相变温度以上,对 Hg2+ 的检测灵敏度会进一步提高。当纳米凝胶浓度为 0.05 g L-1 时,在相同的 Hg2+ 浓度范围(0-3.0 等当量)内,25 °C 和 40 °C 时的荧光发射强度比变化分别增加了 10 倍和∼57 倍。