Jishu Han

Coating urchinlike gold nanoparticles with polypyrrole thin shells to produce photothermal agents with high stability and photothermal transduction efficiency.

Photothermal therapy using inorganic nanoparticles (NPs) is a promising technique for the selective treatment of tumor cells because of their capability to convert the absorbed radiation into heat energy. Although anisotropic gold (Au) NPs present an excellent photothermal effect, the poor structural stability during storage and/or upon laser irradiation still limits their practical application as efficient photothermal agents. With the aim of improving the stability, in this work we adopted biocompatible polypyrrole (PPy) as the shell material for coating urchinlike Au NPs. The experimental results indicate that a several nanometer PPy shell is enough to maintain the structural stability of NPs. In comparison to the bare NPs, PPy-coated NPs exhibit improved structural stability toward storage, heat, pH, and laser irradiation. In addition, the thin shell of PPy also enhances the photothermal transduction efficiency (η) of PPy-coated Au NPs, resulting from the absorption of PPy in the red and near-infrared (NIR) regions. For example, the PPy-coated Au NPs with an Au core diameter of 120 nm and a PPy shell of 6.0 nm exhibit an η of 24.0% at 808 nm, which is much higher than that of bare Au NPs (η = 11.0%). As a primary attempt at photothermal therapy, the PPy-coated Au NPs with a 6.0 nm PPy shell exhibit an 80% death rate of Hela cells under 808 nm NIR laser irradiation.

Quantum-Dot-Induced Self-Assembly of Cricoid Protein for Light Harvesting

Stable protein one (SP1) has been demonstrated as an appealing building block to design highly ordered architectures, despite the hybrid assembly with other nano-objects still being a challenge. Herein, we developed a strategy to construct high-ordered protein nanostructures by electrostatic self-assembly of cricoid protein nanorings and globular quantum dots (QDs). Using multielectrostatic interactions between 12mer protein nanoring SP1 and oppositely charged CdTe QDs, highly ordered nanowires with sandwich structure were achieved by hybridized self-assembly. QDs with different sizes (QD1, 3-4 nm; QD2, 5-6 nm; QD3, ∼10 nm) would induce the self-assembly protein rings into various nanowires, subsequent bundles, and irregular networks in aqueous solution. Atomic force microscopy, transmission electron microscopy, and dynamic light scattering characterizations confirmed that the size of QDs and the structural topology of the nanoring play critical functions in the formation of the superstructures. Furthermore, an ordered arrangement of QDs provides an ideal scaffold for designing the light-harvesting antenna. Most importantly, when different sized QDs (e.g., QD1 and QD3) self-assembled with SP1, an extremely efficient Förster resonance energy transfer was observed on these protein nanowires. The self-assembled protein nanostructures were demonstrated as a promising scaffold for the development of an artificial light-harvesting system.

Fabrication of CdTe nanoparticles-based superparticles for an improved detection of Cu2+ and Ag+

Detection of highly toxic and bioaccumulative heavy metal ions using fluorescent semiconductor nanoparticles (NPs) has stimulated recent research interests, but the separation of NPs after detection has failed to be achieved. In this paper, fluorescent CdTe NPs-based superparticles (SPs) were fabricated using oil droplets in microemulsion as templates. By controlling the experimental variables, SPs with different fluorescence and composition were obtained. In particular, CdTe/Fe3O4 binary SPs simultaneously exhibited strong fluorescence and magnetism, thus achieving the separation of SPs. These CdTe-based SPs showed an improved detection of Cu2+ and Ag+.

One-pot, seedless synthesis of flowerlike Au–Pd bimetallic nanoparticles with core-shell-like structure via sodium citrate coreduction of metal ions

Bimetallic nanoparticles (NPs) comprised of gold (Au) and palladium (Pd) are promising catalysts in accelerating a variety of chemical reactions. The further performance enhancement greatly depends on the current efforts to create the synthetic methodology for optimizing NP morphology and structure. Here we report a one-pot and seedless synthesis of Au–Pd bimetallic NPs via citrate coreduction of Au and Pd ions. Due to the higher capacity of citrate in reducing Au ions, the nucleation of Au NPs is more favored than that of Pd. Consequently, the current system permits the production of bimetallic NPs with core-shell-like structure, namely an Au-rich core and Pd-rich shell. Moreover, the morphology of the as-synthesized NPs is also determined by the experimental variables, such as the Au-to-Pd feed ratio, dosage of sodium citrate, and charging sequence. With a good control of the nucleation and growth process, flowerlike Au–Pd bimetallic NPs with core-shell-like structures are synthesized. These flowerlike bimetallic NPs are the best in catalyzing formic acid oxidation and Suzuki coupling reaction in comparison to the Au–Pd bimetallic NPs with other morphologies.

Discriminating Cr(III) and Cr(VI) using aqueous CdTe quantum dots with various surface ligands

The discrimination of Cr(III) and Cr(VI) is considered as one of the important analytical issues for environmental protection and disease prevention, because Cr(III) and Cr(VI) have different physiological effects and toxicities. Low cost, highly sensitive fluorescent sensors are highly demanded. Herein we report a facile and feasible method for discriminating Cr(III) and Cr(VI) by employing the aqueous CdTe quantum dots (QDs) with different surface ligands by virtue of their difference in quenching QD fluorescence. The QD fluorescence quenching by Cr(III)/Cr(VI) is mainly affected by electrostatic interaction, which is greatly determined by the surface functionalities of QDs. Thus, by combining the different fluorescence quenching behavior of carboxyl-, hydroxyl-, and/or amino-functionalized QDs, Cr(III) and Cr(VI) are discriminated. In comparison to the discrimination using the QDs with single surface functionality, the current method indicates improved reliability and accuracy.

Gold nanoparticle superstructures with enhanced photothermal effect

Gold (Au) nanomaterials are promising photothermal therapeutic agents for the selective treatment of tumor cells. Further development of correlated techniques greatly depends on the current efforts to enhance the photothermal performance by fabricating novel Au architectures. In this work, water-dispersible spherical superstructures are constructed from original hydrophobic Au nanoparticles (NPs) in place of oil droplets in microemulsion as the templates. Different from the previous reports, Pluronic F127, a nonionic triblock copolymers of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide), is employed as the capping agent to directly make the superstructures biocompatible. However, due to the nonionic nature, it is difficult to control the size and morphology of Au superstructures using F127 alone. Additional positive surfactants, such as octadecyl-p-vinylbenzyldimethylammonium chloride, are necessary to assist Au superstructure formation in a controlled manner. The as-prepared Au superstructures, which possess enhanced absorption the in red and near-infrared region, exhibit more efficient photothermal behavior in comparison to individual Au NPs.

Versatile fabrication of water-dispersible nanoparticle–amphiphilic copolymer composite microspheres with specific functionalities

In this paper, we demonstrated a versatile approach for fabricating water-dispersible nanoparticle (NP)–polymer composite microspheres from amphiphilic poly(ethylene glycol) diglycidyl-grafted poly(maleic anhydride-alt-octadecene) (PMAO-g-PEG) and various NPs with specific functionalities. Depending on the surface polarity of the NPs, the microspheres were fabricated either via two step phase transfers for water soluble NPs or one step phase transfer for oil-soluble ones. For example, aqueous luminescent CdTe NPs were first transferred to chloroform by dimethyldioctadecylammonium bromide modification, and subsequently transferred back to water using PMAO-g-PEG, thus producing luminescent microspheres. Due to the protection of the polymer, the luminescence stability of the NPs under acidic conditions was significantly improved, permitting the detection of Ag+ and Cu2+ over a broader pH range.

Binary superparticles from preformed Fe3O4 and Au nanoparticles

Binary superparticles (SPs) from various functional nanoparticles are fabricated using oil droplets in microemulsion as templates. The structural stability of SPs is further improved by polymer decoration. This protocol provides a facile and flexible approach to integrate multifunctionalities in nanometre-sized spheres with long term stability.

Polymer-mediated growth of fluorescent semiconductor nanoparticles in preformed nanocomposites

In this study, we investigated the size and photoluminescence (PL) evolution of CdTe nanoparticles (NPs) in different polymer media under thermal annealing. A quick growth and maintenance of strong PL were observed. By analyzing the transmission electron microscopy (TEM) images of NPs in polymer media, we discovered that the size evolution of NPs was the combination of Ostwald ripening and dynamic coalescence throughout the growth process. Moreover, the experimental results also revealed that the nature of polymers determined the dynamic coalescence of NPs from three aspects; the mobility of polymer chains, the compatibility of NPs with polymer media, and the interaction between NPs and polymer network. Thus by altering the glass transition temperature (T(g)) of polymers, the molar mass (M(n)) of the polymers, the phase separation of NPs in polymer media, as well as the interaction between NPs and polymers, the growth rate of NPs was controllable.