Halloysite nanotubes coated with magnetic nanoparticles

Co nanoparticles were assembled on the surface of halloysite nanotubes (HNTs) to prepare one-dimensional magnetic Co-HNTs via electroless deposition. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDXS) and vibrating sample magnetometer (VSM). The cobalt nanoparticles of 3–7 nm in size were uniformly deposited on the surface of the nanotubes. The remanent magnetization (M_r), saturation magnetization (M_s) and coercivity (H_c) values of the Co-HNTs were 13.9 emu/g, 27.05 emu/g and 1659 O_e, respectively, larger than that of the pure Co nanoparticles (580.72 O_e). A mechanism of the deposition of the magnetic nanoparticles on the surface of the halloysite nanotubes is suggested. Co-HNTs showed an interesting potential in the field of magnetic devices.     

A general and efficient method for decorating graphene sheets with metal nanoparticles based on the non-covalently functionalized graphene sheets with hyperbranched polymers

Multipyrene terminated hyperbranched polyglycidol (mPHP) has been synthesized and used to non-covalently functionalize pristine graphene sheets (GSs) through π-π stacking interactions. Mediated by the mPHP layer, a variety of metal nanoparticles (Au, Ag and Pt) were in situ generated and deposited onto the surface-modified GS, yielding versatile GS/mPHP/metal nanohybrids. As typical examples, by simply controlling the concentration of HAuCl(4) used, Au nanostructures ranging from isolated spheres to a continuous film were created and coated onto the surface-modified GS. The studies on the fluorescence properties of resulting GS/mPHP/Au hybrid nanostructures reveal that the GS and controllable content of Au components in the hybrids can effectively quench the fluorescence emission of mPHP in a controlled manner. Further investigation indicates that GS/mPHP/Au hybrids are promising surface enhanced Raman scattering (SERS) substrates. The SERS activities of these hybrids depend on the contents and form of the Au. The GS/mPHP/Au hybrid containing continuous Au films exhibits the strongest SERS activity. GS/mPHP/Au hybrids are also used as efficient heterogeneous catalysts for the reduction of 4-NP, and demonstrate excellent catalytic performance. The detailed reaction kinetics and the reusability of such catalysts have also been investigated.     

Graphene nano-cutting using biologically derived metal nanoparticles

We have developed a novel technique to cut graphene films using catalytic metal nanoparticles derived from ferritin, which is one of the proteins that contain a constant amount of Fe oxide in its inner core. For site-selective adsorption of ferritin molecules to sapphire surfaces that are partially covered with graphene films, two methods, dipping and spin-coating, were used. Graphene films were etched by the Fe-catalytic reaction with hydrogen gas at elevated temperatures. It was found that ferritin adsorption sites are controlled by graphene film edges, atomic steps of the sapphire substrate, and solution condition such as molecular concentration and ionic strength. We demonstrate that high density nanoribbons can be fabricated by using the uniformly-sized catalyst nanoparticles derived from ferritin and the aligned etching technique guided by the atomic structures of the substrate surface.     

Theranostic magnetic nanoparticles

Early detection and treatment of disease is the most important component of a favorable prognosis. Biomedical researchers have thus invested tremendous effort in improving imaging techniques and treatment methods. Over the past decade, concepts and tools derived from nanotechnology have been applied to overcome the problems of conventional techniques for advanced diagnosis and therapy. In particular, advances in nanoparticle technology have created new paradigms for theranostics, which is defined as the combination of therapeutic and diagnostic agents within a single platform. In this Account, we examine the potential advantages and opportunities afforded by magnetic nanoparticles as platform materials for theranostics. We begin with a brief overview of relevant magnetic parameters, such as saturation magnetization, coercivity, and magnetocrystalline anisotropy. Understanding the interplay of these parameters is critical for optimizing magnetic characteristics needed for effective imaging and therapeutics, which include magnetic resonance imaging (MRI) relaxivity, heat emission, and attractive forces. We then discuss approaches to constructing an MRI nanoparticle contrast agent with high sensitivity. We further introduce a new design concept for a fault-free contrast agent, which is a T1 and T2 dual mode hybrid. Important capabilities of magnetic nanoparticles are the external controllability of magnetic heat generation and magnetic attractive forces for the transportation and movement of biological objects. We show that these functions can be utilized not only for therapeutic hyperthermia of cancer but also for controlled release of cancer drugs through the application of an external magnetic field. Additionally, the use of magnetic nanoparticles to drive mechanical forces is demonstrated to be useful for molecular-level cell signaling and for controlling the ultimate fate of the cell. Finally, we show that targeted imaging and therapy are made possible by attaching a variety of imaging and therapeutic components. These added components include therapeutic genes (small interfering RNA, or siRNA), cancer-specific ligands, and optical reporting dyes. The wide range of accessible features of magnetic nanoparticles underscores their potential as the most promising platform material available for theranostics.     

Graphene decoration with metal nanoparticles: towards easy integration for sensing applications

A simple and versatile method for the decoration of CVD grown graphene with metal nanoparticles is presented. The mechanism of nanoparticle formation is galvanic displacement resulting in physically adsorbed clusters. The single layer graphene obtained by this method can be easily transferred. Integration onto a gas sensing transducer is presented as proof of concept.     

Polysulfones tethered with benzimidazole

Benzimidazole units have been grafted onto a polysulfone (PSU) backbone via long alkyl thio-ether chains using a two-step procedure. In the first step, lithiated PSU was reacted with 10-undecenoyl chloride to graft PSU with undecenoyl side chains. The second step involved a free-radical thiol-ene coupling reaction between the CC bonds of the pendant undecenoyl chains and 2-(2-benzimidazolyl)ethanethiol. In this reaction, all the CC bonds were converted into thio-ether linkages without any detectable structural degradation, as confirmed by ¹H NMR spectroscopy and size-exclusion chromatography. The procedure constitutes a convenient and general pathway to attach functional or mesogenic groups to PSU via long flexible spacers. Thermogravimetry showed that the benzimidazole-functionalized polymers were stable up to 250 °C under nitrogen atmosphere, and that the first degradation step was attributed to the cleavage of the thio-ether bond. While the grafting of the undecenoyl side chains was found to significantly decrease the glass transition temperature (T_g), the subsequent tethering of the benzimidazole only slightly increased the T_g of the grafted PSU backbone. The concentration of benzimidazole was probably too low for the formation of a percolating benzimidazole domain. This explains the quite modest proton conductivity measured under completely dry conditions, e.g. 34 nS/cm at 180 °C for a polymer functionalized with 1.7 benzimidazole units per repeating unit of PSU.     

Graphene oxide shell-isolated Ag nanoparticles for surface-enhanced Raman scattering

An efficient surface enhanced Raman scattering (SERS) substrate has been developed based on Ag nanoparticle-decorated graphene oxide (GO). The structure of Ag@GO hybrid material was confirmed by X-ray diffraction, transmission and scanning electron microscopy. The as-prepared substrate exhibited the enhancement ability of SERS toward various aromatic dyes, such as Rhodamine 6G, Rhodamine B, and crystal violet. The enhanced Raman signals could be due to the presence of an ultrathin GO shell with 2.8 nm in thickness. In particular, the GO shell could efficient to maintain chemical and optical stability, and improved biocompatibility for this SERS-activity material.     

Preparation of water-soluble magnetic nanoparticles with controllable silica coating

This work provides a general method for preparing monodisperse,water-soluble and paramagnetic magnetic nanoparticles which are easy to be modified.Firstly,magnetic silica with core-shell structure was prepared according to a previous work.Then,the magnetic silica was treated with alkali solution to afford magnetic nanoparticles.With the increase of calcination temperature for the preparation of magnetic silica,the crystallinity and the magnetic responsibility of magnetic silica strengthened,meanwhile,the corresponding magnetic nanoparticles kept monodisperse without any aggregation.The magnetic nanoparticles are comprised of cobalt ferrite and a silica coating.The silica coating on the cobalt ferrite facilitates the magnetic nanoparticles well-dissolved and monodisperse in water,and easily modified.     

Graphene oxide coupled with gold nanoparticles for localized surface plasmon resonance based gas sensor

An optical gas sensor was prepared by depositing graphene oxide flakes over a monolayer of gold nanoparticles, chemically attached to a functionalized fused silica substrate. The coupling between flakes and nanoparticles lead to optical changes upon exposure to different gases: in particular, we observed a shift of the surface plasmon resonance band in presence of both reducing and oxidizing gases. This effect can be explained in terms of a strong gold–graphene interaction and specifically of electron transfer between the gold nanoparticles and the two-dimensional sheet of the sp²-hybridized carbons of graphene oxide.     

Structural,magnetic and electric properties of ZrO2 tapes decorated with magnetic nanoparticles

We produced ZrO₂ ceramic tape decorated with magnetic nanoparticles through tape casting technique. The green and sintered magnetic tapes were characterized by XRD, SEM, EDS, magnetic measurements, and I–V curves. We investigated the changes in the structural, magnetic and electrical properties, after the sintering process, and discussed the connections between them. The magnetic properties, performed in a wide range of external magnetic field and temperature, show magnetite phase for the magnetic nanoparticles governing the magnetic and electric properties of the green tape. On the other hand, for the sintered tape, the increase in the hematite phase led to remarkable changes in the magnetic and electrical properties. The electrical characterization reflects the observed changes in the structural properties after the sintering process. Additionally, the main advantages of the ceramic tapes decorated with magnetic nanoparticles reside in the possibility of producing functional thin ceramic materials that are easily moldable for electronic devices applications.     

Electrical and magnetic properties of Polystyrene doped with Iron nanoparticles

Summary Polymer composites have recently received a considerable amount of scientific and technological interest, because their properties can be properly controlled, choosing the adequate doped particles, their size and concentrations, and the synthesis conditions. In this work we report the synthesis and characterization of a polystyrene (PS) matrix doped with different concentrations of iron nanoparticles. X-ray diffraction and transmission electron microscopy were used to characterize the structure of the samples. The behaviour of the d.c. electrical conductivity (σ_dc) and the complex permittivity (ε*=ε^′-iε^′′) as a function of frequency (100 Hz–10 MHz) reflects the important effect of the iron nanoparticles concentration in the sample properties. A percolation threshold in the conductivity was observed at a critical concentration of iron nanoparticles. A noticeable increase in the saturation magnetization and coercivity is observed with the rise of the iron nanoparticles concentration, being thisbehaviour also noticed in the remanent magnetization. A rise of the initial a.c. susceptibility with the iron concentration is also observed.     

Nanocomposite polyHIPEs with magnetic nanoparticles: Preparation and heating effect

Emulsion templating of high internal phase emulsions (HIPEs) was used to synthesise microcellular poly(styrene-co-divinylbenzene) magnetic nanoparticle composites with open, interconnected, porous structures. The emulsions were stabilised by a combination of a surfactant and maghemite/magnetite (uncoated or coated with oleic acid) nanoparticles and then cured thermally. Up to 23 wt% (with regards to complete composite mass) of magnetic nanoparticles were incorporated into the polymer matrix. Composite polymers exhibited magnetic properties with a saturation magnetisation of 13 emu/g and a substantial heating effect at the AC magnetic field of 3.8 kA/m and a frequency of 104 kHz. A nanocomposite polyHIPE sample with coated nanoparticles exhibited a higher hyperthermia effect. Samples retained typical polyHIPE morphology with cavity diameters of approx. 8 μm and interconnecting pores of around 0.8 μm in diameter. Compared to styrene/divinylbenzene polyHIPEs without nanoparticles, the openness (interconnecting pore size to cavity size ratio) was slightly reduced. Materials were characterised with gas adsorption porosimetry, XRD, TGA/DSC, SEM, TEM.     

Synthesis and characterization of magnetic polyHIPEs with humic acid surface modified magnetic iron oxide nanoparticles

Magnetic macroporous polymer monoliths have been prepared using styrene/divinylbenzene (S/DVB) high internal phase emulsions (HIPEs) as templates. Humic acid surface modified iron oxide magnetic nanoparticles (Fe₃O₄@HA) have been used to prepare magnetic emulsion templates. The effect of magnetic particle concentration has been investigated by changing the ratio of Fe₃O₄@HA nanoparticles in the continuous phase. Highly macroporous polymers with magnetic response were obtained by the removal of the internal phase after the curing of emulsions at 80 °C. Fe₃O₄@HA particles were characterized by XRD and FTIR. The porosity, pore morphology and magnetic properties of the macroporous polymers were characterized as a function of the Fe₃O₄@HA concentration by scanning electron microscopy (SEM), Brunauer–Emmet–Teller (BET) molecular adsorption method and vibrating sample magnetometry (VSM), respectively. BET and VSM measurements demonstrated that the specific surface area and the saturation magnetization of the polymer monoliths were changed according to the Fe₃O₄@HA concentration between 8.77–35.08 m² g^?1 and 0.63–11.79 emu g^?1, respectively. Resulting magnetic monoliths were tested on the adsorption of Hg(II) and atomic absorption spectroscopy (AAS) was used to calculate the adsorption capacities. The maximum adsorption capacity of the magnetic monoliths was calculated to be 20.44 mmol g^?1 at pH 4.     

磁性氧化铁纳米颗粒的研究进展

磁性纳米颗粒是一种多功能性材料,在医学、催化和磁记录材料等领域有着广泛的应用。本文综述了磁性氧化铁纳米颗粒的制备方法,包括共沉淀法、热分解法、微乳液法、水热合成法;改性途径,包括表面活性剂改性、有机聚合物包覆,和硅、碳、金等无机材料包覆的研究现状和最新研究成果,并对其以后的发展方向进行了展望。     

Monodisperse magnetic nanoparticles for biomedical applications

Magnetic nanoparticles that are superparamagnetic with high saturation moment have great potential for biomedical applications. Solution‐phase syntheses have recently been applied to make various kinds of monodisperse magnetic nanoparticles with standard deviation in diameter of less than 10%. However, the surface of these nanoparticles is coated with a layer of hydrocarbon molecules due to the use of lipid‐like carboxylic acid and amine in the syntheses. Surface functionalization leads to the formation of water‐soluble nanoparticles that can be further modified with various biomolecules. Such functionalization has brought about several series of monodisperse magnetic nanoparticle systems that have shown promising applications in protein or DNA separation, detection and magnetic resonance imaging contrast enhancement. The goal of this mini review is to summarize the recent progress in the synthesis and surface modification of monodisperse magnetic nanoparticles and their applications in biomedicine. Copyright © 2007 Society of Chemical Industry     

Monodisperse magnetic nanoparticles for theranostic applications

Effective medical care requires the concurrent monitoring of medical treatment. The combination of imaging and therapeutics allows a large degree of control over the treatment efficacy and is now commonly referred to as "theranostics". Magnetic nanoparticles (NPs) provide a unique nanoplatform for theranostic applications because of their biocompatibility, their responses to the external magnetic field, and their sizes which are comparable to that of functional biomolecules. Recent studies of magnetic NPs for both imaging and therapeutic applications have led to greater control over size, surface functionalization, magnetic properties, and specific binding capabilities of the NPs. The combination of the deep tissue penetration of the magnetic field and the ability of magnetic NPs to enhance magnetic resonance imaging sensitivity and magnetic heating efficiency makes magnetic NPs promising candidates for successful future theranostics. In this Account, we review recent advances in the synthesis of magnetic NPs for biomedical applications such as magnetic resonance imaging (MRI) and magnetic fluid hyperthermia (MFH). Our focus is on iron oxide (Fe(3)O(4)) NPs, gold-iron oxide (Au-Fe(3)O(4)) NPs, metallic iron (Fe) NPs, and Fe-based alloy NPs, such as iron-cobalt (FeCo) and iron-platinum (FePt) NPs. Because of the ease of fabrication and their approved clinical usage, Fe(3)O(4) NPs with controlled sizes and surface chemistry have been studied extensively for MRI and MFH applications. Porous hollow Fe(3)O(4) NPs are expected to have similar magnetic, chemical, and biological properties as the solid Fe(3)O(4) NPs, and their structures offer the additional opportunity to store and release drugs at a target. The Au-Fe(3)O(4) NPs combine both magnetically active Fe(3)O(4) and optically active Au within one nanostructure and are a promising NP platform for multimodal imaging and therapeutics. Metallic Fe and FeCo NPs offer the opportunity for probes with even higher magnetizations. However, metallic NPs are normally very reactive and are subject to fast oxidation in biological solutions. Once they are coated with a layer of polycrystalline Fe(3)O(4) or a graphitic shell, these metallic NPs are more stable and provide better contrast for MRI and more effective heating for MFH. FePt NPs are chemically more stable than Fe and FeCo NPs and have shown great potential as contrast agents for both MRI and X-ray computed tomography (CT) and as robust probes for controlled heating in MFH.     

Photocurrent generators derived from non-covalently assembled soft-matter molecular system

It is rather difficult to design a multilayer photocurrent generator system on the ITO electrode, however, the preparation of thin film with high surface concentration of donor units is indispensable in order to achieve high conversion efficiency. The polymer film of porphyrin bearing pyroles on the electrode was prepared by the potential sweep method. It was indicated that the self-aggregation can be suppressed by encapsulation of the porphyrin unit in the cavity of macro-cyclic host molecule, cyclodextrin. We established the non-equilibrium host-guest system with porphyrins and cyclodextrins for the first time. The photocurrent density and the quantum yield in the porphyrin-cyclodextrin system are remarkably improved. It was demonstrated that the high quantum yield, perhaps 25 times larger, arises from the isolation of the porphyrin unit by cyclodextrin through host-guest interactions.     

Graphene films decorated with metal sulfide nanoparticles for use as counter electrodes of dye-sensitized solar cells

The composite films of metal sulfide (MS, M = Ni, Co) nanoparticles (NPs)/graphene films were proposed to be novel transparent conductive oxide- and platinum (Pt)-free counter electrodes with high electrocatalytic activity for dye-sensitized solar cells (DSSCs). Such DSSCs show higher photovoltaic conversion efficiencies of 5.25% (NiS/graphene) and 5.04% (CoS/graphene), compared with 5.00% for (Pt/fluorine-doped tin oxide). The excellent DSSC efficiencies are mainly due to the superior electrocatalytic activity of the MS and graphene films, and highly electrical properties of graphene films (9.57 Ω/sq). The excellent charge transfer between MS NPs and graphene films is due to the unique MS NPs and high surface area graphene structure. The graphene films were directly grown on dielectric SiO₂ substrates by chemical vapor deposition. MS NPs were uniformly implanted on the graphene films by dip coating of MS precursors M(C₃H₅OS₂)₂, and further annealed at 400 °C for 30 min under Ar.     

Graphene oxide impregnated with iron oxide nanoparticles for the removal of atrazine from the aqueous medium

ABSTRACT

The present study proposes development of an adsorbent based on combination of graphene oxide (GO) and iron oxide (α-γ-Fe₂O₃) nanoparticles for atrazine removal from water. The synthesized adsorbent (GO@ α-γ-Fe₂O₃) was characterized using different techniques. Magnetic measurements proved that the adsorbent has superparamagnetic characteristics, thus facilitating its magnetic separation from the working suspensions. The maximum adsorption capacity was 42.5 mg g^?1. The Langmuir isotherm and the pseudo-second order kinetic models correlated adequately with the experimental data. The thermodynamic data showed that atrazine adsorption was spontaneous, endothermic and thermodynamically favorable.     

新型氨基化磁性纳米粒子的合成

通过嫁接方法在包有二氧化硅的纳米CoFe2O4磁粒表面进行氨基化修饰,制备出一种可用于生物医学领域的新型氨基化纳米磁粒,采用TGA-DTA,IR,VSM和Zeta-potential等测定方法,对氨基化和未氨基化的CoFe2O4纳米粒子进行了表征。元素分析结果显示,有0.98 mmol/g的有机分子固定在纳米粒子表面;红外和热分析数据显示,带氨基的有机分子嫁接到磁粒表面的二氧化硅壳层上;Zeta电位数据也显示,带氨基的有机分子嫁接到纳米磁粒表面;样品的磁性参数显示,氨基化纳米磁粒仍具有好的磁学性能。