Quantum Dot-Based Hybrid Coacervate Nanodroplets for Ultrasensitive Detection of Hg²⁺

Abstract

Multifunctional organic–inorganic hybrid materials with inherent optical, electrical, and/or magnetic properties find tremendous importance in various fields such as sensing, photovoltaics, therapeutics, bioimaging, and light-emitting devices. Herein, we have fabricated membrane-free organic–inorganic hybrid luminescent coacervate nanodroplets and utilized them toward ultrasensitive detection and efficient removal of mercuric ions (Hg2+) simultaneously. The self-assembly of negatively charged mercaptosuccinic acid (MSA) capped CdTe quantum dots (QDs) in the presence of positively charged poly­(diallyl­dimethyl­ammonium chloride) (PDADMAC) leads to the formation of luminescent nanodroplets with average size of 430 ± 20 nm. Selective luminescence quenching of these nanodroplets has been observed only in the presence of Hg2+. It has also been observed that the presence of other metal ions does not interfere in the sensing process. Our findings reveal that Hg2+ ions specifically associate with the porous structure of these nanodroplets via electrostatic interactions with the free carboxylate groups of MSA ligands at the surface of CdTe QDs and undergo photoinduced electron transfer (PET) with photoexcited QDs. The limit of detection (LOD) for Hg2+ sensing with our present system is estimated to be 1.32 nM (0.26 ppb), which is significantly lower than most of the earlier reported self-assembled materials. Moreover, these hybrid nanodroplets efficiently sequester trace quantities of Hg2+ from contaminated water. The overall performance of our present system toward Hg2+ remediation is superior over most of the earlier reported hybrid nanocomposites in terms of fast uptake kinetics (within 15 min), ultrasensitive detection (LOD 0.26 ppb), and high sequestration efficiency (98.3%). With regard to our present findings in particular, the tailorability of surface ligands and inorganic nanoparticles in hybrid nanodroplets provide great advantage for the development of multifunctional nanomaterials for a diverse range of applications.

Robust Anionic LnIII–Organic Frameworks: Chemical Fixation of CO2, Tunable Light Emission, and Fluorescence Recognition of Fe3+

“…Moreover, the CO 2 isosteric heat of adsorption ( Q st ) fitted by using the virial equation (Figure S5) for the CO 2 isotherms measured at 273 and 293 K was 26.75 kJ mol –1 at zero loading and equivalent to the values of MAF-25 (26.3 kJ mol –1 ), InOF-1 (29 kJ mol –1 ), etc. It should be noted that the strong charge-density cations of Eu III in 1-Eu serving as the Lewis acidic sites will play an important role in host–guest interaction, as discussed by Zhao et al Meanwhile, there was evidence that the exposed coordinated oxygen atoms as unorthodox Lewis basic sites also could form stronger dipole–dipole interactions with the CO 2 quadrupole. − However, there was an indispensable fact that the comparatively low amount of CH 4 also could be adsorbed with the values of 17.3 and 9.8 cm 3 g –1 at 273 and 298 K, respectively. In order to check the adsorption selectivity between CO 2 and CH 4 , the ideal adsorbed solution theory (IAST) calculation by the dual-site Langmuir–Freundlich equation for fitting the single-component adsorption isotherm parameters determined that the selectivity coefficient of CO 2 /CH 4 (50:50, v/v) was 14 in at 100 kPa under 298 K, which proved that the separation of CO 2 from natural gas was quite straightforward and feasible (Figure S6).…”

Specific Loading and In Vitro Controlled Release of a Ru-Based Hydrophobically Encapsulated Model Anticancer Drug inside Nanoassemblies toward Stimuli-Responsive Drug Delivery

“…42 Previously, we developed a unique class of coacervates from negatively charged ligand-capped inorganic q u a n t u m d o t s a n d p o s i t i v e l y c h a r g e d p o l y -(diallyldimethylammonium chloride) (PDADMAC) in aqueous media. 43,44 These hybrid coacervates exhibit high colloidal stability in a broad range of pH and ionic strength values along with highly stable inherent luminescence. 43 Moreover, using biocompatible carbon dots (CDs) and PDADMAC, we demonstrated the applicability of CD-based coacervates toward theranostic applications.…”

Ionic-Group Dependence of Polyelectrolyte Coacervate Phase Behavior

“…Complex coacervation is liquid–liquid phase separation (LLPS) when two oppositely charged polyelectrolytes are mixed in an aqueous solution, which is mainly attributed to the electrostatic interaction and entropic gain by counterion release . Complex coacervates, polymer-rich phases generated by the LLPS, have drawn increasing attention because of their large potential applications for stimuli-responsive materials in various areas, including drug delivery, encapsulation, , sensing, and underwater adhesives . Recently, much attention has been paid to polyelectrolyte complexation in the process of biological phenomena, including the formation of membrane-less organelles in cells and the compaction of DNA by the electrostatic interaction between histones and the DNA backbone. , …”