For the structure of micelle-encapsulated QDs, QDs are coated in sequence of coordinating ligands, such as hydrophobic surfactants (TOPO and oleic acid), the hydrophobic section of triblock polymer (PPO-(PEO)n-COOH) and hydrophilic section of triblock polymer (PPO-(PEO)n-COOH). The oil-like layer between TOPO/oleic acid with PPO formed a lamellar layer to protect the inner QDs. Meanwhile, the carboxyl group on the PEO surface plays an important role for QDs to maintain the colloidal stability, as well as to provide site for the biomolecule conjugation with the purpose of cell targeting. The micelle-encapsulated QD samples, with or without FA conjugation, can remain well-suspended in aqueous dispersion under pH 7.4, with no aggregation for more than six months at ambient temperature and no loss of any photoluminescence intensity.
Wu et al. reported polysaccharide-based hybrid nanogels that combine functional building blocks for optical pH-sensing, cancer cell imaging, and controlled drug release within a single nanoparticle system for combined diagnosis and therapy. The hybrid nanogels were synthesized by in-situ immobilization of CdSe QDs in the interior of the dual responsive (pH and temperature) hydroxypropylcellulose -poly (acrylic acid) (HPC-PAA) semi-interpenetrating polymer networks. The HPC-PAA-CdSe hybrid nanogels combine a strong trap emission at 741 nm for sensing physicochemical environment in a pH dependent manner and a visible excitonic emission at 592 nm for mouse melanoma B16F10 cell imaging. The hybrid nanogels also provide excellent stability as a drug carrier. They not only provide a high drug loading capacity for a model anticancer drug, temozolomide, but also offer a pH-triggered sustained-release of the drug molecules in the gel network.
Various sizes of manganese-doped cadmium selenide quantum dots (Mn-doped CdSe QDs) synthesized using inverse Micelle technique with organic solvent and surfactant possesses zinc blende structure with physical size ranging from 3 to 14 nm and crystallite size 2.46 to 5.46 nm respectively for 0 to 90 mins samples with narrow size distribution. Mn-doped CdSe QDs observed to growth larger QDs compared to pure CdSe QDs at significantly same reaction times. The lattice parameter compressed with QDs sizes growth due to the introduction of lattice strain due to the incorporation of Mn atoms into CdSe QDs lattice. The Mn-doped CdSe QDs shows a slight blue-shift on absorption and emission spectra’s compared to pure CdSe even though is possessed larger QDs. The band gap structure modification prominently affected by the lattice strain were transition of Stoke`s, Rayleigh to anti-Stoke`s shifts observed as the Mn doped CdSe QDs size growth. The typical red-shift of absorption and emission wavelength observed with growth of QDs sizes. The role of oleic acid acid as a surfactant and capping agent shows in FTIR spectra. The lattice strain tailored the binding energy between the ion prominently on the surface of the QDs with growth of QDs sizes.
Alkyl Chains of Surface Ligands Affect Polytypism of CdSe Nanocrystals and Play an Important Role in the Synthesis of Anisotropic Nanoheterostructures.