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

Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field.

Carbon quantum dots and their applications

Fluorescent carbon-based materials have drawn increasing attention in recent years owing to exceptional advantages such as high optical absorptivity, chemical stability, biocompatibility, and low toxicity. These materials primarily include carbon dots (CDs), nanodiamonds, carbon nanotubes, fullerene, and fluorescent graphene. The superior properties of fluorescent carbon-based materials distinguish them from traditional fluorescent materials, and make them promising candidates for numerous exciting applications, such as bioimaging, medical diagnosis, catalysis, and photovoltaic devices. Among all of these materials, CDs have drawn the most extensive notice, owing to their early discovery and adjustable parameters. However, many scientific issues with CDs still await further investigation. Currently, a broad series of methods for obtaining CD-based materials have been developed, but efficient one-step strategies for the fabrication of CDs on a large scale are still a challenge in this field. Current synthetic methods are mainly deficient in accurate control of lateral dimensions and the resulting surface chemistry, as well as in obtaining fluorescent materials with high quantum yields (QY). Moreover, it is important to expand these kinds of materials to novel applications. Herein, a facile and highoutput strategy for the fabrication of CDs, which is suitable for industrial-scale production (yield is ca. 58%), is discussed. The QY was as high as ca. 80%, which is the highest value recorded for fluorescent carbon-based materials, and is almost equal to fluorescent dyes. The polymer-like CDs were converted into carbogenic CDs by a change from low to high synthesis temperature. The photoluminescence (PL) mechanism (high QY/PL quenching) was investigated in detail by ultrafast spectroscopy. The CDs were applied as printing ink on the macro/micro scale and nanocomposites were also prepared by polymerizing CDs with certain polymers. Additionally, the CDs could be utilized as a biosensor reagent for the detection of Fe in biosystems. The CDs were prepared by a hydrothermal method, which is described in the Supporting Information (Figure 1a; see also the Supporting Information, Figure S1). The reaction was conducted by first condensing citric acid and ethylenediamine, whereupon they formed polymer-like CDs, which were then carbonized to form the CDs. The morphology and structure of CDs were confirmed by analysis. Figure 1b shows transmission electron microscopy (TEM) images of the CDs, which can be seen to have a uniform dispersion without apparent aggregation and particle diameters of 2–6 nm. The sizes of CDs were also measured by atomic force microscopy (AFM; Figure S2), and the average height was 2.81 nm. From the high-resolution TEM, most particles are observed to be amorphous carbon particles without any lattices; rare particles possess well-resolved lattice fringes. With such a low carbon-lattice-structure content, no obvious D or G bands were detected in the Raman spectra of the CDs (Figure S3). The XRD patterns of the CDs (Figure 1c) also displayed a broad peak centered at 258 (0.34 nm), which is also attributed to highly disordered carbon atoms. Moreover, NMR spectroscopy (H and C) was employed to distinguish sp-hybridized carbon atoms from sp-hybridized carbon atoms (Figure S4). In the H NMR spectrum, sp carbons were detected. In the C NMR spectrum, signals in the range of 30–45 ppm, which correspond to aliphatic (sp) carbon atoms, and signals from 100–185 ppm, which are indicative of sp carbon atoms, were observed. Signals in the range of 170– 185 ppm, which correspond to carboxyl/amide groups, were also present. In the FTIR analysis of CDs, the following were observed: stretching vibrations of C OH at 3430 cm 1 and C H at 2923 cm 1 and 2850 cm , asymmetric stretching vibrations of C-NH-C at 1126 cm , bending vibrations of N H at 1570 cm , and the vibrational absorption band of C=O at 1635 cm 1 (Figure S5). Moreover, the surface groups were also investigated by XPS analysis (Figure 1d). C1s analysis revealed three different types of carbon atoms: graphitic or aliphatic (C=C and C C), oxygenated, and nitrous (Table S1). In the UV/Vis spectra, the peak was focused on 344 nm in an aqueous solution of CDs. In the fluorescence spectra, CDs have optimal excitation and emission wavelengths at 360 nm and 443 nm, and show a blue color under a hand-held UV lamp (Figure 2a). Excitation-dependent PL behavior was [*] S. Zhu, Q. Meng, Prof. J. Zhang, Y. Song, Prof. K. Zhang, Prof. B. Yang State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University Changchun, 130012 (P. R. China) E-mail: byangchem@jlu.edu.cn

Highly Photoluminescent Carbon Dots for Multicolor Patterning, Sensors, and Bioimaging

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Graphene, a single layer of graphite, possesses a unique two-dimensional structure, high conductivity, superior electron mobility and extremely high specific surface area, and can be produced on a large scale at low cost. Thus, it has been regarded as an important component for making various functional composite materials. Especially, graphene-based semiconductor photocatalysts have attracted extensive attention because of their usefulness in environmental and energy applications. This critical review summarizes the recent progress in the design and fabrication of graphene-based semiconductor photocatalysts via various strategies including in situ growth, solution mixing, hydrothermal and/or solvothermal methods. Furthermore, the photocatalytic properties of the resulting graphene-based composite systems are also discussed in relation to the environmental and energy applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation and photocatalytic disinfection. This critical review ends with a summary and some perspectives on the challenges and new directions in this emerging area of research (158 references).

Graphene-based semiconductor photocatalysts

Shape-controlled synthesis of Cu2O nanocrystals assisted by Triton X-100

Growth of single-crystal magnetite nanowires from Fe3O4 nanoparticles in a surfactant-free hydrothermal process

A novel microemulsion process was introduced for the large-scale synthesis of uniform Ag4SiW12O40 nanowires with an average diameter of about 8?nm and length of up to 10??m. The ageing time of the reaction mixture played an important role in controlling the morphology of the products, and the interaction between ethanol and AOT (sodium bis-(2-ethyexylsulfosuccinate)) can be used to illustrate the formation of the nanowires. The products were characterized by IR, TEM and XRD techniques.

https://iopscience.iop.org/article/10.1088/0957-4484/15/1/010/pdf

Synthesis and characterization of polyoxometalate nanowires based on a novel microemulsion process

A series of high performance Ag@Ag salts photocatalysts were designed and fabricated. The photocatalytic abilities of this kind of catalysts can be tuned by altering the negative charged ions (Cl−, Br−, I−, CrO42−, PO43−, PW12O403−, and SiW12O404−): higher stability and higher charged anions lead to the stronger photocatalytic ability.

Suoyuan Lian

Papers

Shape-controlled synthesis of Cu2O nanocrystals assisted by Triton X-100

Growth of single-crystal magnetite nanowires from Fe3O4 nanoparticles in a surfactant-free hydrothermal process

Synthesis and characterization of polyoxometalate nanowires based on a novel microemulsion process

Tuning metal@metal salt photocatalytic abilities by different charged anions.

Surfactant-assisted solvothermal preparation of submicrometer-sized hollow hematite particles and their photocatalytic activity