Hollow dodecahedral Zn0.3Cd0.7S@NiCo-mixed metal oxide p-n heterojunction with high-efficiency photocatalytic hydrogen production activity.

The growing demand for clean and sustainable energy has driven extensive research into efficient photocatalysts for hydrogen production. However, many semiconductor photocatalysts in this field still face the challenges such as wide band gap, limited visible light absorption, and inefficient separation and transport of photoinduced charges. In this study, nickel-cobalt layered double hydroxide (NiCo-LDH) was synthesized using an "etch-and-grow" method with zeolitic imidazolate framework-67 (ZIF-67) as a sacrificial template, followed by high-temperature calcination to produce nickel-cobalt mixed metal oxide (NiCo-MMO). Zn0.3Cd0.7S quantum dots were used to modify NiCo-MMO resulting in a hollow dodecahedral Zn0.3Cd0.7S@NiCo-MMO composite photocatalyst. In hydrogen production performance test, the optimized Zn0.3Cd0.7S@NiCo-MMO exhibited excellent performance (8177.5 µmol·g-1·h-1) and demonstrated good cycling stability. The hollow dodecahedral structure of the Zn0.3Cd0.7S@NiCo-MMO enhanced the light trapping ability and provided large surface area. The p-n heterojunction formed within Zn0.3Cd0.7S@NiCo-MMO accelerated carrier separation and transfer, effectively inhibited the recombination of photogenerated electrons and holes, and significantly improved the hydrogen production activity.

CdSe-Decorated Flowerlike CaMoO4 Microspheres with Enhanced Hydrogen Production Activity.

Photocatalytic hydrogen production technology from water is a more effective and promising method to solve energy and environmental crises. In this work, flowerlike CaMoO4 microspheres were successfully synthesized by an ultrasonic precipitation method and modified with variable concentrations of CdSe NCs. CdSe/CaMoO4 microspheres showed increased light absorption ability, larger relative surface area, lower electrochemical impedance, and longer fluorescence lifetime. The photocatalytic hydrogen production rate of CdSe/CaMoO4 microspheres could reach up to 10 162.33 µmol g-1 h-1. The constructed type-I heterostructure improved the separation of photogenerated electrons and inhibited the rapid recombination of photogenerated electrons and holes, thus enhancing the photocatalytic hydrogen production performance. CdSe/CaMoO4 with high hydrogen production activity would be an efficient photocatalyst for hydrogen production applications.

Photoresponsive Conjugated Microporous Polymer Films Fabricated by Electrochemical Deposition for Controlled Release.

Stable controlled release system, conjugated microporous polymers (CMPs) with stimuli-responsive properties can be ideal structures because their 3D microporous matrix structure and possible stimulated response provide inherent switchable acceptor sites to capture and release guest molecules. Herein, the in situ electrochemical deposition of precursors (DTCzAzo) is utilized to construct highly crosslinked photoresponsive CMP films, which can reversibly undergo the trans-to-cis isomerization alternately with irradiation by 355 and 480 nm laser beams. The size of pores in CMP films changes tremendously during the process of trans-cis photoisomerization, to controllably capture, conserve, and release the guest molecules.

Optical anisotropy and sign reversal in layer-by-layer assembled films from chiral nanoparticles.

Chiral anisotropy and related optical effects at the nanoscale represent some of the most dynamic areas of nanomaterials today. Translation of optical activity of chiral semiconductor and metallic nanoparticles (NPs) into optoelectronic devices requires preparation of thin films from chiral NPs on both flat and curved surfaces. In this paper we demonstrate that chiral NP films can be made via layer-by-layer assembly (LBL) using negatively charged chiral CdS NPs, stabilized by d- and l-cysteine and positively charged polyelectrolytes, as building blocks. LBL coatings from NPs combine simplicity of preparation and strong optical activity. Circular extinction measurements using circular dichroism instruments indicate that the film possess four chiroptical bands at 280, 320, 350, and 390 nm. The latter two bands at 390 and 350 nm are associated with the band gap transitions (chiral excitons), while the former two are attributed to transitions involving surface ligands. When NPs are assembled in LBL films, the rotatory activity and the sign for circular extinction associated with the electronic transition in the inorganic core of the NPs is conserved. However, this is not true for circular extinction bands at short wavelengths: the sign of the rotatory optical activity is reversed. This effect is attributed to the change of the conformation of surface ligands in the polyelectrolyte matrix, which was confirmed both by semi-empirical and density functional (DFT) quantum mechanical calculations. Circular dichroism spectra calculated using a DFT algorithm closely match the experimental spectra of CdS NPs. These findings indicate that the spectroscopic methods sensitive to chirality of the surface ligands can be used to investigate fine structural changes in the surface layer of nanocolloids. Strong rotatory optical activity of nanostructured semiconductor films opens the possibilities for new polarization-based optical devices.

Glucose-functionalized Au nanoprisms for optoacoustic imaging and near-infrared photothermal therapy.

Targeted imaging and tumor therapy using nanomaterials has stimulated research interest recently, but the high cytotoxicity and low cellular uptake of nanomaterials limit their bioapplication. In this paper, glucose (Glc) was chosen to functionalize Au nanoprisms (NPrs) for improving the cytotoxicity and cellular uptake of Au@PEG-Glc NPrs into cancer cells. Glucose is a primary source of energy at the cellular level and at cellular membranes for cell recognition. A coating of glucose facilitates the accumulation of Au@PEG-Glc NPrs in a tumor region much more than Au@PEG NPrs. Due to the high accumulation and excellent photoabsorbing property of Au@PEG-Glc NPrs, enhanced optoacoustic imaging of a tumor in vivo was achieved, and visualization of the tumor further guided cancer treatment. Based on the optical-thermal conversion performance of Au@PEG-Glc NPrs, the tumor in vivo was effectively cured through photothermal therapy. The current work demonstrates the great potential of Au@PEG-Glc NPrs in optoacoustic imaging and photothermal cancer therapy in future.

Correction: Glucose-functionalized Au nanoprisms for optoacoustic imaging and near-infrared photothermal therapy.

Correction for 'Glucose-functionalized Au nanoprisms for optoacoustic imaging and near-infrared photothermal therapy' by Jishu Han et al., Nanoscale, 2016, DOI: 10.1039/c5nr06261f.

Anomalously Fast Diffusion of Targeted Carbon Nanotubes in Cellular Spheroids.

Understanding transport of carbon nanotubes (CNTs) and other nanocarriers within tissues is essential for biomedical imaging and drug delivery using these carriers. Compared to traditional cell cultures in animal studies, three-dimensional tissue replicas approach the complexity of the actual organs and enable high temporal and spatial resolution of the carrier permeation. We investigated diffusional transport of CNTs in highly uniform spheroids of hepatocellular carcinoma and found that apparent diffusion coefficients of CNTs in these tissue replicas are anomalously high and comparable to diffusion rates of similarly charged molecules with molecular weights 10000× lower. Moreover, diffusivity of CNTs in tissues is enhanced after functionalization with transforming growth factor ß1. This unexpected trend contradicts predictions of the Stokes-Einstein equation and previously obtained empirical dependences of diffusivity on molecular mass for permeants in gas, liquid, solid or gel. It is attributed to the planar diffusion (gliding) of CNTs along cellular membranes reducing effective dimensionality of diffusional space. These findings indicate that nanotubes and potentially similar nanostructures are capable of fast and deep permeation into the tissue, which is often difficult to realize with anticancer agents.

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.

Phase-pure FeSe(x) (x = 1, 2) nanoparticles with one- and two-photon luminescence.

Iron chalcogenides hold considerable promise for energy conversion and biomedical applications. Realization of this promise has been hindered by the lack of control over the crystallinity and nanoscale organization of iron chalcogenide films. High-quality nanoparticles (NPs) from these semiconductors will afford further studies of photophysical processes in them. Phase-pure NPs from these semiconductors can also serve as building blocks for mesoscale iron chalcogenide assemblies. Herein we report a synthetic method for FeSe(x) (x = 1, 2) NPs with a diameter of ca. 30 nm that satisfy these needs. The high crystallinity of the individual NPs was confirmed by transmission electron microscopy (TEM) and energy-dispersive X-ray analysis. TEM tomography images suggest pucklike NP shapes that can be rationalized by bond relaxation at the NP edges, as demonstrated in large-scale atomic models. The prepared FeSe(x) NPs display strong photoluminescence with a quantum yield of 20%, which was previously unattainable for iron chalcogenides. Moreover, they also show strong off-resonant luminescence due to two-photon absorption, which should be valuable for biological applications.

Employing aqueous CdTe quantum dots with diversified surface functionalities to discriminate between heme (Fe(II)) and hemin (Fe(III)).

The discrimination of ferrous and ferric states in the human body is one of the basic issues for disease control and prevention because Fe(II) and Fe(III) are a crucial redox pair during the process of material and energy metabolism. Herein, aqueous CdTe quantum dots (QDs) with diversified surface functionalities are applied to discriminate between heme (Fe(II)) and hemin (Fe(III)) by virtue of their difference in quenching QD fluorescence. In aqueous media, the interaction between QDs and heme/hemin mainly involves electrostatic interaction, which is greatly determined by the surface functionalities of the QDs. Thus, by combining the different fluorescence quenching behavior of carboxyl- and/or hydroxyl-functionalized QDs, heme and hemin are discriminated between. In comparison to the discrimination using QDs with single surface functionality, the current method has improved reliability and accuracy.

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.

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.

Manipulating the growth of aqueous semiconductor nanocrystals through amine-promoted kinetic process.

In the conventional procedure of the preparation of aqueous semiconductor nanocrystals (NCs), the growth of NCs was mainly through the thermodynamics-favored Ostwald ripening process. It required additional energy to promote NC growth, such as reflux, hydrothermal method, microwave irradiation, and sonochemical synthesis. Energy-promoted growth usually led to the decomposition of mercapto-ligands and therewith decreased the quality of NCs. Consequently, in this study, the growth of aqueous semiconductor NCs was designed through an amine-promoted kinetic process, which efficiently shortened the growth duration and avoided the decomposition of ligands, thus providing a universal method for preparing various aqueous binary and ternary NCs.