水分散超支化共轭聚合物纳米粒子的制备及其对苦味酸的高灵敏荧光检测

Water-dispersed Hyperbranched Conjugated Polymer Nanoparticles for Highly Sensitive Fluorescent Detection of Picric Acid

采用Suzuki细乳液聚合以及后功能化反应,制备了季铵盐末端的水分散超支化共轭聚合物纳米粒子(HCPN-QA),用于高灵敏度和高选择性的检测2,4,6-三硝基苯酚(PA).带正电荷的季铵盐端基以及疏水的超支化共轭聚合物核心,使HCPN-QA对水中呈酸性的PA产生静电吸引与疏水富集的协同作用,产生高度灵敏的荧光猝灭响应,检测限达到0.18μg/L,猝灭常数达到6.36×10~7 L/mol,相比于有机相分散的超支化共轭聚合物纳米粒子HCPN-OMe,HCPN-QA检测限低了4个数量级,猝灭常数高出3个数量级.通过研究HCPN-QA粒径对PA检测灵敏度的影响,发现纳米粒子粒径对PA的检测灵敏度影响很小.并且,HCPN-QA对PA的猝灭响应显著高于TNT及其他硝基爆炸物,表现出很好的选择性以及竞争选择性.此外,HCPN-QA检测试纸对PA固体颗粒的检测表现出很高的灵敏度,检测限达到66 pg/mm^2.

Water-dispersed hyperbranched conjugated polymer nanoparticles（HCPN-QA） with quaternary ammonium salt as terminal groups were prepared by Suzuki polymerization in miniemulsion,followed by post-functionalization reaction,for highly sensitive and selective sensing of picric acid（PA） in aqueous solutions.By taking advantage of the positively charged quaternary ammonium salt terminal groups and hydrophobic cavities inside the hyperbranched core,bright blue emissive HCPN-QA can efficiently bind with PA in water by electrostatic attraction and hydrophobic encapsulation interaction,leading to highly efficient fluorescence quenching.The quenching constant of HCPN-QA was 6.36 ×10^7 L/mol,which was three orders higher than that of its organic solution-dispersed hyperbranched conjugated polymer nanoparticle analogue（HCPN-OMe）.HCPN-QA was capable of sensing PA in water with a detection limit of 7.8 × 10～（-10） mol/L（0.18 μg/L）,which was four orders of magnitude lower than that of HCPN-OMe（0.34 mg/L）.Meanwhile,this value was also lower than the maximum permissible level（1 μg/L） for PA in drinking water set by World Health Organization（WHO）.Moreover,by decreasing the amount of surfactants during the polymerization,nanoparticles with small diameter were obtained for further studying the relationship between particle size and the sensitivity for PA sensing.The fluorescent titration study indicated that particle size of HCPN-QA had little effect on the sensitivity for PA sensing.Furthermore,by combining electrostatic attraction and hydrophobic encapsulation interaction,HCPN-QA also showed much higher fluorescence quenching response to PA over other analytes,including 2,4,6-trinitrotoluene（TNT）,2,4-dinitrotoluene（DNT）,nitrobenzene,cyclotetramethylenetetranitramine（HMX）,1,3,5-trinitro-1,3,5-triazinane（RDX）,nitromethane,ammonium nitrate,chlorobenzene,toluene and phenol in water.Especially,HCPN-QA showed nearly 60-fold higher quenching constant for PA than that of TNT,indicating that HCPN-QA had not only a high sensitivity,but also a good selectivity for PA sensing.In addition,contact mode detection was further performed using fluorescent paper strips based on HCPN-QA for naked eye detection of PA with a detection limit of 66 pg/mm^2.