Yongdong Jin

Multifunctional nanoparticles as coupled contrast agents

Engineering compact imaging probes with highly integrated modalities is a key focus in bionanotechnology and will have profound impact on molecular diagnostics, imaging and therapeutics. However, combining multiple components on a nanometre scale to create new imaging modalities unavailable from individual components has proven to be challenging. In this paper, we demonstrate iron oxide and gold-coupled core-shell nanoparticles (NPs) with well-defined structural characteristics (for example, size, shell thickness and core-shell separation) and physical properties (for example, electronic, magnetic, optical, thermal and acoustic). The resulting multifunctional nanoprobes not only offer contrast for electron microscopy, magnetic resonance imaging and scattering-based imaging but, more importantly, enable a new imaging mode, magnetomotive photoacoustic imaging, with remarkable contrast enhancement compared with photoacoustic images using conventional NP contrast agents.

Plasmonic fluorescent quantum dots

Combining multiple discrete components into a single multifunctional nanoparticle could be useful in a variety of applications. Retaining the unique optical and electrical properties of each component after nanoscale integration is, however, a long-standing problem. It is particularly difficult when trying to combine fluorophores such as semiconductor quantum dots with plasmonic materials such as gold, because gold and other metals can quench the fluorescence. So far, the combination of quantum dot fluorescence with plasmonically active gold has only been demonstrated on flat surfaces. Here, we combine fluorescent and plasmonic activities in a single nanoparticle by controlling the spacing between a quantum dot core and an ultrathin gold shell with nanometre precision through layer-by-layer assembly. Our wet-chemistry approach provides a general route for the deposition of ultrathin gold layers onto virtually any discrete nanostructure or continuous surface, and should prove useful for multimodal bioimaging, interfacing with biological systems, reducing nanotoxicity, modulating electromagnetic fields and contacting nanostructures.

Spectrally Tunable Leakage-Free Gold Nanocontainers

Drug delivery with precise spatial and temporal control is of broad current interest in biology and medicine. Despite recent advances achieved by combining drugs or drug carriers with NIR light responsive plasmonic nanomaterials, existing technologies are not capable of preventing drug leakage or degradation. We report a new class of monodisperse gold nanocontainer that can stably encapsulate cargo molecules, yet is compact in size and tunable in spectral responses.

Structural and optical properties of TiO2 thin film and TiO2+2 wt.% ZnFe2O4 composite film prepared by r.f. sputtering

Abstract Amorphous TiO2 thin films and TiO2/ZnFe2O4 composite films were deposited by r.f. magnetron sputtering. The influence of post-deposition annealing on the structural and optical properties was studied. It was established that the anatase single phase exists between 250 and 800°C for the TiO2 thin films, and between 450 and 650°C for the composite films. The absorption edge of TiO2 thin films and composite films exhibits a blue shift with decreasing annealing temperature. The absorption edge of composite films has moved to visible spectrum range, and a very large red shift occurs in comparison with TiO2 thin films.

Synthesis of gold nanoplates by aspartate reduction of gold chloride

Single crystal nanoplates with thickness less than 30 nm, characterized by hexagonal and truncated triangular shapes bounded mainly by [111] facets, were obtained in large quantities by aspartate reduction of gold chloride.

DNA-templated assembly and electropolymerization of aniline on gold surface

Abstract Biomolecule template gives new opportunities for the fabrication of novel materials with special features. Here we report a route to the formation of DNA–polyaniline (PAn) complex, using immobilized DNA as a template. A gold electrode was first modified with monolayer of 2-aminoethanethiol by self-assembly. Thereafter, by simply immersing the gold electrode into DNA solution, DNA molecules can be attached onto the gold surface, followed by the DNA-templated assembly and electropolymerization of protonated aniline. The electrostatic interactions between DNA and aniline can keep the aniline monomers aligning along the DNA strands. Investigations by surface plasmon resonance (SPR), electrochemistry and reflection–absorption UV/Vis–Near IR spectroscopy substantially convince that PAn can be electrochemically grown around DNA template on gold surface. This work may be provides fundamental aspects for building PAn nanowires with DNA as template on solid surface if DNA molecules can be individually separated and stretched.

Self-standing non-noble metal (Ni–Fe) oxide nanotube array anode catalysts with synergistic reactivity for high-performance water oxidation

The oxygen evolution reaction (OER) is coupled with a number of important cathodic processes, for instance water splitting for hydrogen production and other energy storage devices based on O2–H2O chemistries such as metal–air batteries and unitized regenerative fuel cells, but they are limited by the slow kinetics. Attempts to solve this problem have received wide attention recently. However, accessing and stabilizing high-oxidation-state catalytically active species to further improve the high performance for the OER has been considered a huge challenge. Here, we report a Ni–Fe oxide-based nanotube array electrode, novel in design, with strong durability and excellent and synergistically enhanced catalytic performance for the OER. The OER electrode, with a nanotube array nanostructure, shows the remarkable features of a small overpotential of 0.28 V, favourable electrode kinetics and high stability, comparing favorably with the reported performances of the best OER electrocatalysts (IrO2), which is attributed to the formation and stabilization of the favourable OER catalytically active species NiOOH that is produced and reinforced by the introduction of Fe into nanostructured materials. This feasible strategy affords a new strategy for the development of effective and robust OER electrodes.

Significantly Enhancing Supercapacitive Performance of Nitrogen-doped Graphene Nanosheet Electrodes by Phosphoric Acid Activation

In this work, we present a new method to synthesize the phosphorus, nitrogen contained graphene nanosheets, which uses dicyandiamide to prevent the aggregation of graphene oxide and act as the nitrogen precursor, and phosphoric acid (H3PO4) as the activation reagent. We have found that through the H3PO4 activation, the samples exhibit the remarkably enhanced supercapacitive performance, and depending on the amount of H3PO4 introduced, the specific capacitance of the samples is gradually increased from 7.6 to 244.6 F g(-1). Meanwhile, the samples also exhibit the good rate capability and excellent stability (up to 10 000 cycles). Through the transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller analyses, H3PO4 treatment induced large pore volume and phosphorus related function groups in the product are assumed to response for the enhancement.

Bacteriorhodopsin/Ag Nanoparticle-Based Hybrid Nano-Bio Electrocatalyst for Efficient and Robust H2 Evolution from Water

Searching for novel hybrid electrocatalysts with high activity and strong durability for a direct electrochemical hydrogen evolution reaction (HER) is extremely desirable but still remains a significant challenge. Herein, we report a novel solid carbon cloth-supported hybrid nano-bio electrocatalyst, decorated with Ag nanoparticles and proton-pumping bacteriorhodopsin (bR) (Ag/bR/CP) that were prepared by in situ electroless deposition and vesicle fusion technology, respectively. When applied as a hydrogen evolution cathode, the Ag/bR/CP shows a low onset overpotential of 63 mV, good durability (no detectable change in its catalytic activity for up to 1000 cycles in alkaline media), and enhanced HER performance under 550 nm irradiation, attributed to the activation of Ag and synergistic effects following light absorption, demonstrated by photoelectrochemical measurements.

Graphene Oxide-Supported Ag Nanoplates as LSPR Tunable and Reproducible Substrates for SERS Applications with Optimized Sensitivity.

Nanoparticles and nanohybrids with well-defined structures, along with tunable localized surface plasmon resonance (LSPR) properties and optimized sensitivity, are crucial and highly desired for surface-enhanced Raman spectroscopy (SERS) applications. In this article, we report on a very promising and flexible SERS platforms with a tunable LSPR response and sensitivity based on Ag nanoplates and graphene oxide (GO). The SERS detection sensitivity can be easily optimized and significantly improved by fine-tuning the LSPR band of the Ag nanoplate/GO substrates (to enhance the SERS response) during sample preparation. We applied the as-prepared SERS platform for sensitive SERS detection of 4-mercaptobenzoic acid and 4-aminothiophenol and found that the SERS signal varied markedly (by ∼10-15-fold) with the fine-tuning of the LSPR band. The SERS enhancement factor of the Ag nanoplate/GO complexes was more than 10(4) times larger than that obtained using spherical Ag nanoparticles. The as-prepared Ag nanoplate/GO platforms, because of their excellent stability and tunable LSPR properties, will find promising practical SERS applications.