Discipline of Chemistry , Indian Institute of Technology Indore , Simrol, Khandwa Road , Indore - 453552 , M.P. India.
Langmuir. 2019 Sep 10;35(36):11764-11773. doi: 10.1021/acs.langmuir.9b01783. Epub 2019 Aug 26.
Fabrication and precise control of the physicochemical properties of multifunctional organic-inorganic hybrid nanocomposites find great importance in various research fields. Herein, we report the fabrication of a new class of luminescent hybrid coacervate droplets from CdTe quantum dots (QDs) and a poly(diallyldimethylammonium chloride) (PDADMAC) aqueous mixture. The colloidal stability of these droplets has been explored over wide ranges of composition, pH, and ionic strength. Although these hybrid droplets are quite stable in a low-ionic-strength medium (<100 mM NaCl) and neutral/basic pH (pH >6.5), they are unstable in a higher-ionic-strength medium (>100 mM NaCl) and acidic pH (pH <5.5). Our findings indicate specific electrostatic interactions between negatively charged QDs and positively charged PDADMAC behind the observed coacervation. They exhibit the preferential sequestration of organic dyes and serum albumins. The intrinsic luminescent properties of these hybrid droplets have been explored using confocal laser scanning microscopy (CLSM) and epifluorescence microscopy. CLSM reveals the formation of intrinsically luminescent hybrid droplets. In addition, mixed two-color luminescent droplets have been fabricated by simultaneously mixing green- and red-emitting QDs with PDADMAC aqueous solution. Epifluorescence imaging reveals highly photostable and nonbleaching photoluminescence (PL) from individual droplets as a consequence of efficient surface passivation by polymeric chains of PDADMAC. Moreover, using two-photon (2P) confocal imaging we have shown that these hybrid droplets are ideal candidates for 2P confocal imaging applications. The present study can be easily extended to fabricate a wide range of hybrid droplets with various inorganic counterparts having unique optoelectronic properties, which will further expand their applicability in nanocatalysis, bioimaging, and biosensing.
多功能有机-无机杂化纳米复合材料的制备和精确控制在各个研究领域都具有重要意义。在此，我们报告了一种新型发光杂化凝聚液滴的制备，该液滴由碲化镉量子点（QDs）和聚二烯丙基二甲基氯化铵（PDADMAC）水溶液组成。研究了这些液滴在广泛的组成、pH 值和离子强度范围内的胶体稳定性。尽管这些杂化液滴在低离子强度介质（<100 mM NaCl）和中性/碱性 pH 值（pH>6.5）下相当稳定，但在高离子强度介质（>100 mM NaCl）和酸性 pH 值（pH<5.5）下不稳定。我们的研究结果表明，观察到凝聚作用背后存在带负电荷的 QDs 和带正电荷的 PDADMAC 之间的特定静电相互作用。它们表现出对有机染料和血清白蛋白的优先螯合。使用共聚焦激光扫描显微镜（CLSM）和荧光显微镜研究了这些杂化液滴的固有发光特性。CLSM 揭示了具有固有发光性的杂化液滴的形成。此外，通过同时将绿色和红色发射 QD 与 PDADMAC 水溶液混合，制备了混合双色发光液滴。荧光成像揭示了单个液滴具有高度稳定且不发生漂白的光致发光（PL），这是由于 PDADMAC 聚合物链对表面的有效钝化。此外，使用双光子（2P）共聚焦成像，我们已经证明这些杂化液滴是 2P 共聚焦成像应用的理想候选者。本研究可以很容易地扩展到制备具有各种具有独特光电性能的无机对应物的各种杂化液滴，这将进一步扩大它们在纳米催化、生物成像和生物传感中的应用。
