Zhi-Yuan Li

Bio: Zhi-Yuan Li is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Nanocages & Photothermal therapy. The author has an hindex of 8, co-authored 9 publications receiving 2870 citations. Previous affiliations of Zhi-Yuan Li include Institute for Systems Biology & Lawrence Berkeley National Laboratory.

Gold nanocages: bioconjugation and their potential use as optical imaging contrast agents.

Abstract: Gold nanocages of <40 nm in dimension have been synthesized using the galvanic replacement reaction between Ag nanocubes and HAuCl4 in an aqueous solution. By controlling the molar ratio between Ag and HAuCl4, the gold nanocages could be tuned to display surface plasmon resonance peaks around 800 nm, a wavelength commonly used in optical coherence tomography (OCT) imaging. OCT measurements on phantom samples indicate that these gold nanocages have a moderate scattering cross-section of ∼8.10 × 10-16 m2 but a very large absorption cross-section of ∼7.26 × 10-15 m2, suggesting their potential use as a new class of contrast agents for optical imaging. When bioconjugated with antibodies, the gold nanocages have also been demonstrated for specific targeting of breast cancer cells.

Gold Nanocages: Engineering Their Structure for Biomedical Applications

Abstract: The galvanic replacement reaction between a Ag template and HAuCl4 in an aqueous solution transforms 30-200 mn Ag nanocubes into Au nanoboxes and nanocages (nanoboxes with porous walls). By controlling the molar ratio of Ag to HAuCl4, the extinction peak of resultant structures can be continuously tuned from the blue (400 nm) to the near-infrared (1200 nm) region of the electromagnetic spectrum. These hollow An nanostructures are characterized by extraordinarily large cross sections for both absorption and scattering. Optical coherence tomography measurements indicate that the 36 nm nanocage has a scattering cross-section of similar to 0.8 X 10(-15) m(2) and an absorption cross-section of similar to 7.3 X 10(-15) m(2). The absorption cross-section is more than five orders of magnitude larger than those of conventional organic dyes. Exposure of Au nanocages to a camera flash resulted in the melting and conversion of Au nanocages into spherical particles due to photothermal heating. Discrete-di poleapproximation calculations suggest that the magnitudes of both scattering and absorption cross-sections of An nanocages can be tailored by controlling their dimensions, as well as the thickness and porosity of their walls. This novel class of hollow nanostructures is expected to find use as both a contrast agent for optical imaging in early stage tumor detection and as a therapeutic agent for photothermal cancer treatment.

Optical properties of Pd-Ag and Pt-Ag nanoboxes synthesized via galvanic replacement reactions.

Abstract: Silver nanocubes dispersed in water were transformed into Pd−Ag or Pt−Ag nanoboxes by adding either Na2PdCl4 or Na2PtCl4 By controlling the amount of noble metal salt added, and therefore the molar ratio of Na2PdCl4 or Na2PtCl4 to Ag, we could tune the surface plasmon resonance peak of the nanostructures across the entire visible spectrum, from 440 to 730 nm Replacement of Ag with Pd resulted in the formation of a nanobox composed of a Pd−Ag alloy single crystal, but the nanobox formed after replacement of Ag with Pt was instead composed of distinct Pt nanoparticles DDA calculations suggest that both nanoboxes absorb light strongly, with Qabs/Qsca ≈ 5 After galvanic replacement, Pd−Ag and Pt−Ag nanostructures remain SERS active, suggesting their use as a SERS probe for studying the dependence of interfacial chemistry on composition

Size-dependence of surface plasmon resonance and oxidation for Pd nanocubes synthesized via a seed etching process.

Abstract: Pd nanocubes between 8 and 50 nm in size were synthesized at the same concentration of Na2PdCl4 precursor by controlling the number of seeds formed in the nucleation stage. Increasing the concentration of FeCl3, an oxidative etchant for Pd, reduced the number of seeds and led to formation of larger Pd nanocubes. The larger nanocubes exhibited surface plasmon resonance peaks in the visible region, the locations of which matched with the results of the discrete dipole approximation calculation. While the nanocubes of 25 and 50 nm in size oxidized in air to form Pd@PdO core-shell structures, the 8-nm nanocubes were stable in air for over 90 days.

Corrosion‐Based Synthesis of Single‐Crystal Pd Nanoboxes and Nanocages and Their Surface Plasmon Properties

Abstract: Corrosion can be broadly defined as "the damage to metalcaused by reactions with its environment," and may take place in manydifferent forms such as pitting, crevice etching, intergranular exchange,galvanic replacement, and dealloying. Although corrosion is generallyundesirable (automobile corrosion alone costs $16 billion annually!), itcan be exploited as a versatile route to porous structures such as metalmembranes. While many solution-phase methods have been developed forsynthesizing nanoparticles with well controlled shapes, it is still agreat challenge to generate hollow nanostructures without involvingexotic templates.

Nanocarriers as an emerging platform for cancer therapy

Abstract: Nanotechnology has the potential to revolutionize cancer diagnosis and therapy. Advances in protein engineering and materials science have contributed to novel nanoscale targeting approaches that may bring new hope to cancer patients. Several therapeutic nanocarriers have been approved for clinical use. However, to date, there are only a few clinically approved nanocarriers that incorporate molecules to selectively bind and target cancer cells. This review examines some of the approved formulations and discusses the challenges in translating basic research to the clinic. We detail the arsenal of nanocarriers and molecules available for selective tumour targeting, and emphasize the challenges in cancer treatment.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

Abstract: Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Determining the size and shape dependence of gold nanoparticle uptake into mammalian cells.

Abstract: We investigated the intracellular uptake of different sized and shaped colloidal gold nanoparticles. We showed that kinetics and saturation concentrations are highly dependent upon the physical dimensions of the nanoparticles (e.g., uptake half-life of 14, 50, and 74 nm nanoparticles is 2.10, 1.90, and 2.24 h, respectively). The findings from this study will have implications in the chemical design of nanostructures for biomedical applications (e.g., tuning intracellular delivery rates and amounts by nanoscale dimensions and engineering complex, multifunctional nanostructures for imaging and therapeutics).

Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine

Abstract: The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photothermal therapeutic applications, is based on the optical properties of the nanoparticles. We use Mie theory and discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold nanospheres, silica−gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions. A systematic quantitative study of the various trends is presented. By increasing the size of gold nanospheres from 20 to 80 nm, the magnitude of extinction as well as the relative contribution of scattering to the extinction rapidly increases. Gold nanospheres in the size range commonly employed (∼40 nm)...

Hollow Micro-/Nanostructures: Synthesis and Applications**

Abstract: Hollow micro-/nanostructures are of great interest in many current and emerging areas of technology. Perhaps the best-known example of the former is the use of fly-ash hollow particles generated from coal power plants as partial replacement for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro-/nanostructures. We present a comprehensive overview of synthetic strategies for hollow structures. These strategies are broadly categorized into four themes, which include well-established approaches, such as conventional hard-templating and soft-templating methods, as well as newly emerging methods based on sacrificial templating and template-free synthesis. Success in each has inspired multiple variations that continue to drive the rapid evolution of the field. The Review therefore focuses on the fundamentals of each process, pointing out advantages and disadvantages where appropriate. Strategies for generating more complex hollow structures, such as rattle-type and nonspherical hollow structures, are also discussed. Applications of hollow structures in lithium batteries, catalysis and sensing, and biomedical applications are reviewed.