Chemical Properties Of Nanoparticles Research Articles

Effect of Surface Related Organic Vibrational Modes in Luminescent Upconversion Dynamics of Rare Earth Ions Doped Nanoparticles

Physical and chemical properties of nanoparticles are known to be subject to the surface factors. For their biological/biomedical applications, typically, surface of the nanoparticles has to be modified which inevitably affects their performance. In this work we have studied the interaction between the surface related organic vibrational modes and the luminescent centers--rare earth ions--in one of the most efficient luminescence upconversion nanosystems--NaYF4. Specifically, the surface quenching centers, the surface related luminescent centers, as well as the role of shell properties, are investigated spectroscopically. Our results demonstrate that the surface related high-frequency vibrational modes can be critical to the spectral properties of the nanosystems once the surface is not well separated from the discrete luminescent centers.

An introduction to nanoscience and nanotechnology

Preface. Acknowledgments. Nanotechnology Time Line. Introduction. 0.1 Incremental Nanotechnology. 0.2 Evolutionary Nanotechnology. 0.3 Radical Nanotechnology. 0.4 Bottom-Up/Top-Down Nanotechnology. References. 1 Size Matters. 1.1 The Fundamental Importance of Size. 1.2 The Magnetic Behavior of Nanoparticles. 1.3 The Mechanical Properties of Nanostructured Materials. 1.4 The Chemical Properties of Nanoparticles. 1.5 Nanoparticles Interacting with Living Systems. Problems. References. 2 Nanoparticles Everywhere. 2.1 Nanoparticles in the Atmosphere. 2.2 Atmospheric Nanoparticles and Health. 2.3 Nanoparticles and Climate. 2.4 Marine Aerosol. 2.5 Nanoparticles in Space. Problems. References. 3 Carbon Nanostructures: Bucky Balls and Nanotubes. 3.1 Why Carbon? 3.2 Discovery of the First Fullerene - C60. 3.3 Structural Symmetry of the Closed Fullerenes. 3.4 Smaller Fullerenes and Shrink-Wrapping Atoms. 3.5 Larger Fullerenes. 3.6 Electronic Properties of Individual Fullerenes. 3.7 Materials Produced by Assembling Fullerenes (Fullerites and Fullerides). 3.8 Discovery of Carbon Nanotubes. 3.9 Structure of SWNTs. 3.10 Electronic Properties of SWNTs. 3.11 Electronic Transport in Carbon Nanotubes. 3.12 Mechanical Properties of Nanotubes. 3.13 Thermal Conductivity of Nanotubes. 3.14 Carbon Nanohorns. 3.15 Carbon Nanobuds and Pea Pods. Problems. References. 4 The Nanotechnology Toolkit. 4.1 Making Nanostructures Using Bottom-up Methods. 4.2 Making Nanostructures Using Top-Down Methods. 4.3 Combining Bottom-up and Top-Down Nanostructures. 4.4 Imaging, Probing and Manipulating Nanostructures. Problems. References. 5 Single-Nanoparticles Devices. 5.1 Data Storage on Magnetic Nanoparticles. 5.2 Quantum Dots. 5.3 Nanoparticles as Transistors. 5.4 Carbon Nanoelectronics. Problems. References. 6 Magic Beacons and Magic Bullets: The Medical Applications of Functional Nanoparticles. 6.1 Nanoparticles Interacting with Living Organisms. 6.2 Treatment of Tumours by Hyperthermia. 6.3 Medical Diagnosis and Theranostics Using Nanomaterials. Problems. References. 7 Radical Nanotechnology. 7.1 Locomotion for Nanobots and Nanofactories. 7.2 On-Board Processing for Nanomachines. 7.3 Medical Nanobots. 7.4 Molecular Assembly. References. 8 Prodding the Cosmic Fabric. 8.1 Zero-Point Energy of Space. 8.2 The Casimir Force. 8.3 The Casimir Force in Nanomachines. References. Glossary. Index.

The Special Features of the Electronic Structure of Imperfect and Interacting Low-Dimensional Nanoparticles

A new method for constructing analytic exactly solvable models of the electronic structure of imperfect and interacting low-dimensional nanoparticles is suggested. The method uses the approach based on multiple scattering theory. It allows characteristic equations to be written specifying the contributions of exchange interactions between separate atoms, nanoparticle fragments, or interacting nanoparticles. The possibilities of the method are demonstrated for the example of one-dimensional and quasi-one-dimensional finite regular structures with monovacancies and isolated attached atoms and diatomic molecules. We also consider regular structures composed of two interacting low-dimensional nanoparticles. The general characteristic of the electronic spectra of the systems under consideration is qualitative changes in the system of energy levels and electron density distributions as a result of the formation of defects or new bonds between subsystems. These changes can substantially influence all the physical and chemical properties of nanoparticles.

Self-Assembled Biodegradable Nanoparticles Developed by Direct Dialysis for the Delivery of Paclitaxel

The main objective of this study was to obtain self-assembled biodegradable nanoparticles by a direct dialysis method for the delivery of anticancer drug. The in vitro cellular particle uptake and cytotoxicity to C6 glioma cell line were investigated. Self-assembled anticancer drugs--paclitaxel-loaded poly(D,L-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLA) nanoparticles--were achieved by direct dialysis. The physical and chemical properties of nanoparticles were characterized by various state-of-the-art techniques. The encapsulation efficiency and in vitro release profile were measured by high-performance liquid chromatography. Particle cellular uptake was studied using confocal microscopy, microplate reader, and flow cytometry. In addition, the cytotoxicity of this drug delivery system was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on C6 glioma cell line to predict the possible dose response of paclitaxel-loaded PLGA and PLA nanoparticles. PLGA and PLA nanoparticles with or without vitamin E tocopherol polyethylene glycol succinate (TPGS) as an additive were obtained, in which the sustained release of paclitaxel of more than 20 days was achieved. The coumarin6-loaded PLGA and PLA nanoparticles could penetrate the C6 glioma cell membrane and be internalized. The cytotoxicity of paclitaxel-loaded nanoparticles seemed to be higher than that of commercial Taxol after 3 days incubation when paclitaxel concentrations were 10 and 20 microg/ml. Direct dialysis could be employed to achieve paclitaxel-loaded PLGA and PLA nanoparticles, which could be internalized by C6 glioma cells and enhance the cytotoxicity of paclitaxel because of its penetration to the cytoplasm and sustained release property.

Ag nanoparticles on highly ordered pyrolytic graphite (HOPG) surfaces studied using STM and XPS

Ag nanoparticles grown on low- and high-defect HOPG surfaces were characterized using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Much stronger interactions between Ag and highly defective HOPG surfaces were found compared to those of low-defect HOPG surfaces. We demonstrate that Ag nanoparticles can be prepared on HOPG with relatively narrow size distributions, allowing investigations on size-dependent changes of electronic and chemical properties of nanoparticles. XPS studies reveal that the Ag 3d states converge to the bulk properties at a much larger particles size range (above 6 nm in diameter in 5 nm in height) compared to other previous results obtained from different substrates, which can be attributed to either inefficient final state screening and/or different particle geometry. Stronger Ag–W-oxide interactions were observed for Ag nanoparticles compared to Ag bulk crystals using XPS.