CdSe/CdS-Quantum-dots-quantum-rods (QDQRs) with an aspect ratio of ∼6 are prepared via the seeded growth method, encapsulated within a shell of crosslinked poly(isoprene)-block-poly(ethylene glycol) (PI-b-PEG) diblock copolymer, and transferred from the organic phase into aqueous media. Their photoluminescence quantum yield (PLQY) of 78% is not compromised by the phase transfer. Within a period of two months the PLQY of QDQRs in aqueous solution at neutral pH decreases only slightly (to ∼65%). The two-photon (TP) action cross sections of QDQRs (∼105 GM) are two orders of magnitude higher than those of CdSe/CdS/ZnS-core/shell/shell quantum dots (QDs, ∼103 GM) with comparable diameter (∼5 nm). After applying PI-b-PEG encapsulated QDQRs onto the small intestinal mucosa of mice in vivo, their strong red fluorescence can easily be observed by two-photon laser scanning microscopy (TPLSM) and clearly distinguished from autofluorescent background. Our results demonstrate that PI-b-PEG encapsulated CdSe/CdS-QDQRs are excellent probes for studying the uptake and fate of nanoparticles by two-photon imaging techniques in vivo.

We present a simple solution processed synthesis route for GaAs nanocrystals (NCs) with narrow size distribution and high crystallinity using wet chemical methods and commercially available inexpensive precursors with reduced toxicity. The reaction pathway can be described in three steps, starting with a transmetalation reaction between the gallium(III) halide precursor GaCl3 and the reduction agent n-butyllithium. At elevated temperatures elemental gallium is released in this process and enables the formation of GaAs NCs with magnesium arsenide (Mg3As2) as the arsenic source. We obtained a variety of different III–V semiconductor NCs including GaAs, InP, InAs, and GaP using this transmetalation reaction pathway.Keywords: colloidal nanoparticles; gallium arsenide; III−V nanocrystals; indium phosphide; quantum dots;

The neural cell adhesion molecule L1 is involved in nervous system development and promotes regeneration in animal models of acute and chronic injury of the adult nervous system. To translate these conducive functions into therapeutic approaches, a 22-mer peptide that encompasses a minimal and functional L1 sequence of the third fibronectin type III domain of murine L1 was identified and conjugated to gold nanoparticles (AuNPs) to obtain constructs that interact homophilically with the extracellular domain of L1 and trigger the cognate beneficial L1-mediated functions. Covalent conjugation was achieved by reacting mixtures of two cysteine-terminated forms of this L1 peptide and thiolated poly(ethylene) glycol (PEG) ligands (∼2.1 kDa) with citrate stabilized AuNPs of two different sizes (∼14 and 40 nm in diameter). By varying the ratio of the L1 peptide–PEG mixtures, an optimized layer composition was achieved that resulted in the expected homophilic interaction of the AuNPs. These AuNPs were stable as tested over a time period of 30 days in artificial cerebrospinal fluid and interacted with the extracellular domain of L1 on neurons and Schwann cells, as could be shown by using cells from wild-type and L1-deficient mice. In vitro, the L1-derivatized particles promoted neurite outgrowth and survival of neurons from the central and peripheral nervous system and stimulated Schwann cell process formation and proliferation. These observations raise the hope that, in combination with other therapeutic approaches, L1 peptide-functionalized AuNPs may become a useful tool to ameliorate the deficits resulting from acute and chronic injuries of the mammalian nervous system.

The polymer encapsulation of quantum dots via seeded emulsion polymerization is a powerful method for the preparation of extraordinarily stable fluorescent particles and furthermore allows simple and straightforward in situ functionalization of the polymeric shell. Both features are inevitable for the application of quantum dots as targetable fluorescent probes in advanced biomedical studies. In particular, polymer encapsulated quantum dots showed only marginal loss of quantum yields when exposed to Cu2+ ions, which under nonoptimized conditions completely quenched quantum dot fluorescence. This will allow the application of copper-catalyzed click chemistry. Furthermore, by simple addition of functional surfactants or functional monomers during the seeded emulsion polymerization process, a broad range of in situ functionalized polymer-coated quantum dots were obtained. This was demonstrated by purposeful modulation of the zeta potential encapsulated of quantum dots and conjugation of dyestuff. Successful functionalization was unequivocally proven by total reflection X-ray fluorescence.

Herein we demonstrate that seeded emulsion polymerization is a powerful tool to produce multiply functionalized PEO coated iron oxide nanocrystals. Advantageously, by simple addition of functional surfactants, functional monomers, or functional polymerizable linkers—solely or in combinations thereof—during the seeded emulsion polymerization process, a broad range of in situ functionalized polymer-coated iron oxide nanocrystals were obtained. This was demonstrated by purposeful modulation of the zeta potential of encapsulated iron oxide nanocrystals and conjugation of a dyestuff. Successful functionalization was unequivocally proven by TXRF. Furthermore, the spatial position of the functional groups can be controlled by choosing the appropriate spacers. In conclusion, this methodology is highly amenable for combinatorial strategies and will spur rapid expedited synthesis and purposeful optimization of a broad scope of nanocrystals.

We report a novel approach of seeded emulsion polymerization in which nanocrystals are used as seeds. Ultrasmall biocompatible polymer-coated nanocrystal with sizes between 15 and 110 nm could be prepared in a process that avoids any treatment with high shear forces or ultrasonication. The number of nanocrystals per seed, the size of the seeds, and the shell thickness can be independently adjusted. Single encapsulated nanocrystals in ultrasmall nanobeads as well as clusters of nanocrystals can be obtained. Polysorbat-80 was used as surfactant. It consists of poly(ethylene glycol) (PEG) chains, giving the particles outstanding biofunctional characteristics such as a minimization of unspecific interactions.