There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

1. Introduction 20642. Synthesis of Magnetic Nanoparticles 20662.1. Classical Synthesis by Coprecipitation 20662.2. Reactions in Constrained Environments 20682.3. Hydrothermal and High-TemperatureReactions20692.4. Sol-Gel Reactions 20702.5. Polyol Methods 20712.6. Flow Injection Syntheses 20712.7. Electrochemical Methods 20712.8. Aerosol/Vapor Methods 20712.9. Sonolysis 20723. Stabilization of Magnetic Particles 20723.1. Monomeric Stabilizers 20723.1.1. Carboxylates 20733.1.2. Phosphates 20733.2. Inorganic Materials 20733.2.1. Silica 20733.2.2. Gold 20743.3. Polymer Stabilizers 20743.3.1. Dextran 20743.3.2. Polyethylene Glycol (PEG) 20753.3.3. Polyvinyl Alcohol (PVA) 20753.3.4. Alginate 20753.3.5. Chitosan 20753.3.6. Other Polymers 20753.4. Other Strategies for Stabilization 20764. Methods of Vectorization of the Particles 20765. Structural and Physicochemical Characterization 20785.1. Size, Polydispersity, Shape, and SurfaceCharacterization20795.2. Structure of Ferro- or FerrimagneticNanoparticles20805.2.1. Ferro- and Ferrimagnetic Nanoparticles 20805.3. Use of Nanoparticles as Contrast Agents forMRI20825.3.1. High Anisotropy Model 20845.3.2. Small Crystal and Low Anisotropy EnergyLimit20855.3.3. Practical Interests of Magnetic NuclearRelaxation for the Characterization ofSuperparamagnetic Colloid20855.3.4. Relaxation of Agglomerated Systems 20856. Applications 20866.1. MRI: Cellular Labeling, Molecular Imaging(Inﬂammation, Apoptose, etc.)20866.2.

Magnetic Iron Oxide Nanoparticles: Synthesis, Stabilization, Vectorization, Physicochemical Characterizations, and Biological Applications

Photoinduced reactivity of titanium dioxide

Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.

Nano‐photocatalytic Materials: Possibilities and Challenges

Doping is a widely applied technological process in materials science that involves incorporating atoms or ions of appropriate elements into host lattices to yield hybrid materials with desirable properties and functions. For nanocrystalline materials, doping is of fundamental importance in stabilizing a specific crystallographic phase, modifying electronic properties, modulating magnetism as well as tuning emission properties. Here we describe a material system in which doping influences the growth process to give simultaneous control over the crystallographic phase, size and optical emission properties of the resulting nanocrystals. We show that NaYF(4) nanocrystals can be rationally tuned in size (down to ten nanometres), phase (cubic or hexagonal) and upconversion emission colour (green to blue) through use of trivalent lanthanide dopant ions introduced at precisely defined concentrations. We use first-principles calculations to confirm that the influence of lanthanide doping on crystal phase and size arises from a strong dependence on the size and dipole polarizability of the substitutional dopant ion. Our results suggest that the doping-induced structural and size transition, demonstrated here in NaYF(4) upconversion nanocrystals, could be extended to other lanthanide-doped nanocrystal systems for applications ranging from luminescent biological labels to volumetric three-dimensional displays.

Simultaneous phase and size control of upconversion nanocrystals through lanthanide doping

Ferroelectric SbNbO4, antiferroelectric BiNbO4 and their solid solutions have been synthesized in the ceramic form through high temperature solid state reactions. X-ray diffraction and dielectric measurements have been carried out to investigate the structural and dielectric properties of this system as a function of both temperature and concentration. These studies indicate the presence of at least two concentration-dependent structural phase transitions. This is also corroborated by Raman scattering measurements on the entire system. Soft modes and other vibrational properties of the solid solution are discussed.

Structural, dielectric and vibrational properties of the stibiotantalite (Sb1-xBix)NbO4 system for 0 ≤ x ≤ 1

We report the synthesis of nanoembedded biphasic alloy particles of In - Sn near eutectic alloy compositions embedded in an aluminium matrix by rapid solidification processing. Detailed transmission electron microscopy indicates that the two phases present at room temperature in as-synthesized samples are beta and gamma phases with tetragonal and hexagonal crystal structures, respectively. These co-exist with a small amount of single phase In or Sn particles with sizes less than 10 nm. Low temperature magnetization measurements indicate a superconducting transition temperature of 5 K, suggesting complete decomposition of the beta-phase at small sizes and at low temperature. The small particles show type II behavior with a critical field $Hc_{1}$ approximate to 44 G and two values for $Hc_{2}$ of 250 and 1000 G, respectively. These values are considerably lower than those observed in bulk In - Sn alloys.

Synthesis, transformation and superconductivity of dual phase In–Sn alloy nanoparticles embedded in an Al matrix

In this paper, we present the results of studies on ion emission characteristics of a laser plasma produced from a copper nano-particle layer of 1–3 mm thickness coated over polished surface of a solid copper target. Laser intensityof 10 13 –10 14 W/cm 2 was produced on the targets by a 2 J Nd:glass laser having a variable pulse duration of 300–800 ps. Nano-particle size wasin the range of 15–25 nm. Ion emission from the nano-particle plasma was compared with plasma generated from apolished copper target. Ion emission from the nano-structured target was observed to depend on the polarization of theincident laser beam. This effect was stronger for a shorter laser pulse. X-ray emission was measured in the soft andhard X-ray region (0.7 to 8 keV) using various X-ray ﬁlters. A nano-particle coated target is found to yield a largerﬂux as well as velocity of ions as compared to polished target when the laser polarization is parallel to the planecontaining target normal and detector axis. However, no X-ray enhancement has been observed in the wavelengthrange 1.5 to 20 A˚ .Keywords: Ion emission; Laser-plasma interaction; Laser-plasma; Nano-particles

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0263034608000487

Laser plasma interaction in copper nano-particle targets

We have measured the resistance and magnetoresistance of several bulk polycrystalline colossal magnetoresistive materials and epitaxial thin films. In all the polycrystalline materials we observed a much larger magnetoresistance compared to single crystals and epitaxial thin films at temperatures below the ferromagnetic transition temperature. We also observed a field dependent increase in resistance at low temperatures in all the polycrystalline samples. The significance of these results with respect to spin polarised tunnelling is discussed.

Spin polarised tunnelling in granular polycrystalline colossal magnetoresistive manganites

We examine enhanced hard x-ray emission (20 - 200 keV) from plasmas produced on nanoparticles coated optically polished copper surface under different prepulse conditions. We observe that enhancement reduces with increasing prepulse intensity. The dynamics of the process is seen to be in the ps regime. We attribute this to preplasma formation on nanoparticles and subsequent modification/destruction of the nanostructure layer before the arrival of the main pulse. It is suggested that high-contrast ultrashort pulses are essential for nanoparticles to function as yield enhancers.

Pushan Ayyub

Papers

Structural, dielectric and vibrational properties of the stibiotantalite (Sb1-xBix)NbO4 system for 0 ≤ x ≤ 1

Synthesis, transformation and superconductivity of dual phase In–Sn alloy nanoparticles embedded in an Al matrix

Laser plasma interaction in copper nano-particle targets

Spin polarised tunnelling in granular polycrystalline colossal magnetoresistive manganites

Role of prepulses in the interaction of intense, ultrashort lasers with “structured” surfaces