Kinetically controlled fabrication of gold nanorods and investigation of their thermal stability via in-situ TEM heating

Size controlled CTAB-capped AuNRs with various aspect ratios (ARs) ranging from 1.63±0.13 to 4.12±0.25 were synthesized following a modified seed-mediated method. Their thermal stability was examined by in-situ TEM heating. The results revealed a structural change from rods to spheres with increasing temperature. At lower temperatures 600ºC, particles became increasingly spherical. This behaviour occurred at temperatures lower than the melting point of bulk gold supporting a surface diffusion mechanism with material diffusing from the tips and redepositing at the middle of the rods. The rate of change in AR appeared to increase for thinner AuNRs

Synthesis and Characterization of Gold Nanostructures for Healthcare Applications

Functionalized gold nanostructures with well-defined geometry and controlled optical properties can potentially play an important role in healthcare applications such as biosensing, photocatalysis, drug delivery, photothermal therapy and imaging due to their unique properties. This thesis aims to develop a novel Au nanostructure for healthcare applications, using an effective synthesis protocol in order to produce a suitable Au nanostructure with NIR absorption, high thermal stability and low toxicity. Well-controlled, reproducible Au nanostructures with NIR absorption spectra, including gold nanoparticles (NPs), nanorods (NRs), nanobipyramids (NBPs) and nanotriangles (NTs) have been synthesised using a wet-chemical synthesis approach and characterized using dynamic light scattering and transmission electron microscopy. The optical and plasmonic properties of the Au nanostructures were investigated using uv-vis spectroscopy, finite element modelling (FEM) and STEM/low-loss EELS analysis was employed. EELS results exhibited good agreement with uv-vis spectra and FEM modeling and revealed the size- and shape-dependent plasmonic properties and showed that NIR absorption can be altered by increasing the curvature of particles. The thermal stability of Au nanostructures, which is important for photothermal therapy applications, was investigated using in-situ TEM heating. It was found that the thermal stability of Au nanostructures decreased in the order : AuNPs > AuNTs > AuNBPs > AuNRs. The proposed useful temperature ranges whereby heating does not significantly affect the optical properties were up to 100ºC, 200ºC, 800ºC, for CTAB-capped AuNRs, CTAB-capped AuNBPs and CTAC-stabilized AuNTs, respectively. The thermal stability of particles was increased by surface functionalization of the NPs from a CTAB coating, through a PSS coating and finally to a silica coating. Thermal deformation arose from curvature-driven surface diffusion. Finally, the biocompatibility of Au nanostructures, in terms of the effect of size, morphology, and surface coating, was investigated by their electrochemical interaction with a model membrane based on DOPC on an Hg/Pt electrode. Only smaller Au nanostructures with a diameter of ca. 20 nm exhibited a significant interaction. However, the effect of the surface coating was found to be a more significant effect with the order of interaction with the model membrane ranging from CTAB > PSS > CTAC > citrate coated Au nanostructures. Thus overall, potential biocompatible candidates for healthcare applications are proposed to be citrate-, PSS- or silica-coated gold nanostructures with NIR absorption and dimensions larger than approximately 20-25 nm.

A Scalable Middleware Solution for Advanced Wide Area Web Services

To alleviate scalability problems in the Web, many researchers concentrate on how to incorporate advanced caching and replication techniques. Many solutions incorporate object-based techniques. In particular, Web resources are considered as distributed objects offering a well-defined interface. We argue that most proposals ignore two important aspects. First, there is little discussion on what kind of coherence should be provided. Proposing specific caching or replication solutions makes sense only if we know what coherence model they should implement. Second, most proposals treat all Web resources alike. Such a one-size-fits-all approach will never work in a wide-area system. We propose a solution in which Web resources are encapsulated in physically distributed shared objects. Each object should encapsulate not only state and operations, but also the policy by which its state is distributed, cached, replicated, migrated, etc

One‐Step Preparation of Biocompatible Gold Nanoplates with Controlled Thickness and Adjustable Optical Properties for Plasmon‐Based Applications

The ability to synthesize plasmonic nanomaterials with well‐defined structures and tailorable size is crucial for exploring their potential applications. Gold nanoplates (AuNPLs) exhibit appealing structural and optical properties, yet their applications are limited by difficulties in thickness control. Other challenges include a narrow range of tunability in size and surface plasmon resonance, combined with a synthesis conventionally involving cytotoxic cetyltrimethylammonium (CTA) halide surfactant. Here, a one‐step, high‐yield synthesis of single‐crystalline AuNPLs is developed, based on the combined use of two structure‐directing agents, methyl orange and FeBr3, which undergo preferential adsorption onto different crystalline facets of gold. The obtained AuNPLs feature high shape homogeneity that enables mesoscopic self‐assembly, broad‐range tunability of dimensions (controlled thickness from ≈7 to ≈20 nm, accompanied by modulation of the edge length from ≈150 nm to ≈2 µm) and plasmonic properties. These merits, coupled with a preparation free of CTA‐halide surfactants, have facilitated the exploration of various uses, especially in bio‐related areas. For example, they are demonstrated as biocompatible photothermal agents for cell ablation in NIR I and NIR II windows. This work paves the way to the innovative fabrication of anisotropic plasmonic nanomaterials with desired attributes for wide‐ranging practical applications

Optimal methods for coordinated en-route web caching for tree networks

Web caching is an important technology for improving the scalability of Web services. One of the key problems in coordinated enroute Web caching is to compute the locations for storing copies of an object among the enroute caches so that some specified objectives are achieved. In this article, we address this problem for tree networks, and formulate it as a maximization problem. We consider this problem for both unconstrained and constrained cases. The constrained case includes constraints on the cost gain per node and on the number of object copies to be placed. We present dynamic programming-based solutions to this problem for different cases and theoretically show that the solutions are either optimal or convergent to optimal solutions. We derive efficient algorithms that produce these solutions. Based on our mathematical model, we also present a solution to coordinated enroute Web caching for autonomous systems as a natural extension of the solution for tree networks. We implement our algorithms and evaluate our model on different performance metrics through extensive simulation experiments. The implementation results show that our methods outperform the existing algorithms of either coordinated enroute Web caching for linear topology or object placement (replacement) at individual nodes only.Keqiu Li, Hong Shen, Francis Y. L. Chin, Si Qing Zhen

World Wide Web Caching for Internet in Thailand

World Wide Web (WWW) is one of the hottest application on the Internet. Most of WWW sites are abroad and require traffic through Thailand's international gateways. The deployment of WWW caching infrastructure in Thailand's Internet will decrease the redundance of international traffic and decrease the respond time dramatically. WWW objects which were previously accessed will be stored in local caches and remain available locally to other users for further utilization without having to go the original source. A hierarchically structured WWW caching seems to be the best choice for Thailand's Internet. Harvest WWW cache is intended to be used as a building block due to its superior performance and hierarchical caching support. 1 Introduction WWW is the fastest growing applications on the Internet. Recently, the WWW traffic volume has surpassed the FTP traffic volume which used to be the largest portion of the Internet traffic. [9] The key to the success of WWW is its user-friendly and gr..

Adaptation-Aware Web Caching: Caching in the Future Pervasive Web

In the upcoming world of Pervasive Computing, content adaptation is an essential concept to meet the heterogeneous requirements of web users using various web access technologies. However, content adaptation interferes with the effectiveness of web caching. Leveraging the advantages of web caching even in the world of Pervasive Computing is the subject of this paper. We presen