Qingbo Zhang

Bio: Qingbo Zhang is an academic researcher from Rice University. The author has contributed to research in topics: Nanoparticle & Nanoclusters. The author has an hindex of 33, co-authored 49 publications receiving 7265 citations. Previous affiliations of Qingbo Zhang include Massachusetts Institute of Technology & National University of Singapore.

Negligible Particle-Specific Antibacterial Activity of Silver Nanoparticles

Abstract: For nearly a decade, researchers have debated the mechanisms by which AgNPs exert toxicity to bacteria and other organisms. The most elusive question has been whether the AgNPs exert direct “particle-specific” effects beyond the known antimicrobial activity of released silver ions (Ag+). Here, we infer that Ag+ is the definitive molecular toxicant. We rule out direct particle-specific biological effects by showing the lack of toxicity of AgNPs when synthesized and tested under strictly anaerobic conditions that preclude Ag(0) oxidation and Ag+ release. Furthermore, we demonstrate that the toxicity of various AgNPs (PEG- or PVP- coated, of three different sizes each) accurately follows the dose–response pattern of E. coli exposed to Ag+ (added as AgNO3). Surprisingly, E. coli survival was stimulated by relatively low (sublethal) concentration of all tested AgNPs and AgNO3 (at 3–8 μg/L Ag+, or 12–31% of the minimum lethal concentration (MLC)), suggesting a hormetic response that would be counterproductive t...

From Aggregation-Induced Emission of Au(I)–Thiolate Complexes to Ultrabright Au(0)@Au(I)–Thiolate Core–Shell Nanoclusters

Abstract: A fundamental understanding of the luminescence of Au–thiolate nanoclusters (NCs), such as the origin of emission and the size effect in luminescence, is pivotal to the development of efficient synthesis routes for highly luminescent Au NCs. This paper reports an interesting finding of Au(I)–thiolate complexes: strong luminescence emission by the mechanism of aggregation-induced emission (AIE). The AIE property of the complexes was then used to develop a simple one-pot synthesis of highly luminescent Au–thiolate NCs with a quantum yield of ∼15%. Our key strategy was to induce the controlled aggregation of Au(I)–thiolate complexes on in situ generated Au(0) cores to form Au(0)@Au(I)–thiolate core–shell NCs where strong luminescence was generated by the AIE of Au(I)–thiolate complexes on the NC surface. We were able to extend the synthetic strategy to other thiolate ligands with added functionalities (in the form of custom-designed peptides). The discovery (e.g., identifying the source of emission and the s...

The Synthesis of SERS-Active Gold Nanoflower Tags for In Vivo Applications

Abstract: This paper reports a simple, one-pot, template-free synthesis of flower-like Au nanoparticles (three-dimensional branched nanoparticles with more than 10 tips) with high yield and good size monodispersity at room temperature. The size of the Au nanoflowers could be tuned by controlling the composition of the starting reaction mixture. The key synthesis strategy was to use a common Good's buffer, HEPES, as a weak reducing and particle stabilizing agent to confine the growth of the Au nanocrystals in the special reaction region of limited ligand protection (LLP). Time-course measurements by UV-vis spectroscopy and TEM were used to follow the reaction progress and the evolution of the flower-like shape. The Au nanoflowers exhibited strong surface-enhanced effects which were utilized in the design of an efficient, stable, and nontoxic Raman-active tag for in vivo applications.

Graphene-like MoS2/amorphous carbon composites with high capacity and excellent stability as anode materials for lithium ion batteries

Abstract: A facile process to synthesize graphene-like MoS2/amorphous carbon (a-C) composites was developed. MoS2/C composites were firstly prepared by hydrothermal method employing sodium molybdate, sulfocarbamide and glucose as starting materials. The graphene-like MoS2/a-C composites were obtained after annealing at 800 °C in H2/N2. The samples were characterized by XRD, SEM, EDS and HRTEM. It was confirmed that in the composites MoS2 has a structure of single-layer, which is named graphene-like nanostructure. The graphene-like MoS2 nanosheets were uniformly dispersed in amorphous carbon. The interlaminar distance of the adjacent graphene-like MoS2 nanosheets in the composites measured was ∼1.0 nm. The mechanism of the formation of the graphene-like MoS2/a-C composites was investigated. The graphene-like MoS2/a-C composites exhibited high capacity and excellent cyclic stability used as anode materials for Li-ion batteries. The composite prepared by adding 1.0 g of glucose in hydrothermal solution exhibited the highest reversible capacity (962 mAh g−1) and excellent cyclic stability. After 100 cycles, it still retained 912 mAh g−1. The significant improvements in the electrochemical properties of the graphene-like MoS2/a-C composites could be attributed to the graphene-like structure of the MoS2 nanosheets and the synergistic effects of graphene-like MoS2 and amorphous carbon.

Synthesis of highly fluorescent metal (Ag, Au, Pt, and Cu) nanoclusters by electrostatically induced reversible phase transfer.

Abstract: This paper reports a simple and scalable method for the synthesis of highly fluorescent Ag, Au, Pt, and Cu nanoclusters (NCs) based on a mild etching environment made possible by phase transfer via electrostatic interactions. Using Ag as a model metal, a simple and fast (total synthesis time < 3 h) phase transfer cycle (aqueous → organic (2 h incubation) → aqueous) has been developed to process originally polydisperse, nonfluorescent, and unstable Ag NCs into monodisperse, highly fluorescent, and extremely stable Ag NCs in the same phase (aqueous) and protected by the same thiol ligand. The synthetic protocol was successfully extended to fabricate highly fluorescent Ag NCs protected by custom-designed peptides with desired functionalities (e.g., carboxyl, hydroxyl, and amine). The facile synthetic method developed in this study should largely contribute to the practical applications of this new class of fluorescence probes.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Aggregation-Induced Emission: Together We Shine, United We Soar!

Abstract: Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

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.