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Regioselective chemical reactions and structural transformations of two-dimensional (2D) layered transition-metal chalcogenide (TMC) nanocrystals are described. Upon exposure of 2D TiS(2) nanodiscs to a chemical stimulus, such as Cu ion, selective chemical reaction begins to occur at the peripheral edges. This edge reaction is followed by ion diffusion, which is facilitated by interlayer nanochannels and leads to the formation of a heteroepitaxial TiS(2)-Cu(2)S intermediate. These processes eventually result in the generation of a single-crystalline, double-convex toroidal Cu(2)S nanostructure. Such 2D regioselective chemical reactions also take place when other ionic reactants are used. The observations made and chemical principles uncovered in this effort indicate that a general approach exists for building various toroidal nanocrystals of substances such as Ag(2)S, MnS, and CdS.

The conversion of electromagnetic energy into heat by nanoparticles has the potential to be a powerful, non-invasive technique for biotechnology applications such as drug release, disease treatment and remote control of single cell functions, but poor conversion efficiencies have hindered practical applications so far. In this Letter, we demonstrate a significant increase in the efficiency of magnetic thermal induction by nanoparticles. We take advantage of the exchange coupling between a magnetically hard core and magnetically soft shell to tune the magnetic properties of the nanoparticle and maximize the specific loss power, which is a gauge of the conversion efficiency. The optimized core-shell magnetic nanoparticles have specific loss power values that are an order of magnitude larger than conventional iron-oxide nanoparticles. We also perform an antitumour study in mice, and find that the therapeutic efficacy of these nanoparticles is superior to that of a common anticancer drug.

Two-dimensional crystals, single sheets of layered materials, often show distinct properties desired for optoelectronic applications, such as larger and direct band gaps, valley- and spinorbit effects. Being atomically thin, the low amount of material is a bottleneck in photophysical and photochemical applications. Here, we propose the formation of stacks of two-dimensional crystals intercalated with small surfactant molecules. We show, using first principles calculations, that already the very short surfactant methyl amine electronically decouples the layers. We demonstrate the indirect-direct band gap transition characteristic for Group 6 transition metal dichalcogenides experimentally by observing the emergence of a strong photoluminescence signal for ethoxide-intercalated WSe2 and MoSe2 multilayered nanoparticles with lateral size of about 10 nm and beyond. The proposed hybrid materials offer the highest possible density of the two-dimensional crystals with electronic properties typical for monolayers. Variation of the surfactant's chemical potential allows fine-tuning of electronic properties and potentially elimination of trap states caused by defects.

Nowadays, attempts to use nanoparticles for medical applications are on the rise. However, the effect of nanoparticles in the body has not been clarified. In this study, we aimed to examine the pharmacokinetics of magnetized nanoparticles. FITC conjugated SA-MnMEIO nanoparticles were prepared for the purpose of tracing. Nanoparticles (15 nm diameter) were injected into the tail vein of BALB/c mice at a dose of 20 mg (Mn+Fe)/kg. A mouse was housed in a metabolic cage and sacrificed serially up to 14 days for the sampling of blood and tissues from various organs (i.e., heart, kidney, liver, and spleen). The concentration of nanoparticles was measured by detecting FITC using spectrofluorophotometer. Nanoparticles showed a half-life of 8.20 h. The fluorescence intensities of nanoparticles in tissues showed different time-dependent patterns among different organs. In the heart and the liver, the fluorescence intensities increased up to 2 weeks of observation, while those in the kidney and the spleen decreased. The results indicate that nanoparticles have unique pharmacokinetic characteristics and suggest that pharmacokinetic study is essential for the development of new nanoparticles for medical use.

Recently a memristor ( Chua, L. O. IEEE Trans. Circuit Theory 1971 , 18 , 507 ), the fourth fundamental passive circuit element, has been demonstrated as thin film device operations ( Strukov, D. B.; Snider, G. S.; Stewart, D. R.; Williams, R. S. Nature (London) 2008 , 453 , 80 ; Yang, J. J.; Pickett. M. D.; Li, X.; Ohlberg, D. A. A.; Stewart, D. R.; Williams, R. S. Nat. Nanotechnol. 2008 , 3 , 429 ). A new addition to the memristor family can be nanoparticle assemblies consisting of an infinite number of monodispersed, crystalline magnetite (Fe(3)O(4)) particles. Assembly of nanoparticles that have sizes below 10 nm, exhibits at room temperature a voltage-current hysteresis with an abrupt and large bipolar resistance switching (R(OFF)/R(ON) approximately 20). Interestingly, observed behavior could be interpreted by adopting an extended memristor model that combines both a time-dependent resistance and a time-dependent capacitance. We also observed that such behavior is not restricted to magnetites; it is a general property of nanoparticle assemblies as it was consistently observed in different types of spinel structured nanoparticles with different sizes and compositions. Further investigation into this new nanoassembly system will be of importance to the realization of the next generation nanodevices with potential advantages of simpler and inexpensive device fabrications.

The structure of nano-crystalline MnFe2O4 was determined and refined with electron powder diffraction data employing the Rietveld refinement technique. A nano-crystalline sample (with average crystal size of about 10.9 nm) was characterized by selected area electron diffraction in an energy-filtering transmission electron microscope operated at 120 kV. All reflection intensities were extracted from a digitized image plate using the program ELD and then used in the course of structure refinements employing the program FULLPROF for the Rietveld analysis. The final structure was refined in space group Fd-3m (# 227) with lattice parameters a=8.3413(7) A. The reliability factors of the refinement are RF=7.98% and RB=3.55%. Comparison of crystallographic data between electron powder diffraction data and reference data resulted in better agreement with ICSD-56121 rather than with ICSD-28517 which assumes an initial structure model.

Doped up: The incorporation of Zn(2+) dopants in tetrahedral sites leads to the successful magnetism tuning of spinel metal ferrite nanoparticles (see picture). (Zn(0.4)Mn(0.6))Fe(2)O(4) nanoparticles exhibit the highest magnetization value among the metal ferrite nanoparticles. Such high magnetism results in the largest MRI contrast effects (r2=860 mm(-1) s(-1)) reported to date and also huge hyperthermic effects.

Two-dimensional (2D) layered nanostructures have received increasing interest due to their unique nanoscale phenomena and their potential applications ranging from electronics and energy to catalysis. Recent investigation has revealed that laterally confined layered nanocrystals (LCLN) have remarkably enhanced electrochemical properties compared to their bulk counterparts owing to nanoscale characteristics that include large surface areas, finite lateral sizes, and enhanced open-edge morphologies. Among the variety of layered materials that have been described, tin sulfides are of particular interest because of their unique structural properties. SnS2 has a layered CdI2-type structure, composed of tin atoms sandwiched between two layers of hexagonally disposed closepacked sulfur atoms. The 2D layered characteristics of this substance are revealed in alkali metal intercalation phenomena, and by investigating anisotropy of properties such as electric and photoelectric conductivity. Owing to their large theoretical capacities for battery applications, bulk or micron sized tin-based materials have been extensively studied as possible alternatives for commercially available carbon electrodes. However, the main drawback of this system has been stemming from the large volume changes and accompanying sharp decrease in capacity that occur during electrochemical cycles. Aifantis et al. have reported that active sites with spherical and smaller volume fraction could improve electrochemical properties of anode materials from the view point of fracture mechanics. Other researchers also have reported that nanoscale tin sulfide-based materials would lead to an improvement in the cycling stability of these systems. Especially, layered SnS2 nanoplates with swelling tolerant hosting spaces and enhanced guest accessibility would provide enhanced diffusion for Li ion, and lead to the formation of Li-Sn alloy during the cycle, and improve the

Synthetische magnetische Nanopartikel (MNP) werden in der Biomedizin immer haufiger als Sonden eingesetzt. Dies gilt besonders fur die Anwendung in der Kernspintomographie (Magnetic Resonance Imaging, MRI). Diese Nanopartikel sind von ahnlicher Grose wie biologische Funktionseinheiten. Deshalb und wegen ihrer einzigartigen magnetischen Eigenschaften eignen sie sich zur molekularen Bildgebung. Dieser Aufsatz gibt einen Uberblick zu neuartigen MNP-Sonden, mit denen biologische Ereignisse auf molekularer und zellularer Ebene empfindlich und spezifisch nachgewiesen werden konnen.

We measured the size- and shape-dependent compressibility of the TiO2 anatase nanoparticles using monochromatic synchrotron X-ray powder diffraction and high-pressure diamond-anvil cell techniques....

Nanoscale distance-dependent phenomena, such as Forster resonance energy transfer, are important interactions for use in sensing and imaging, but their versatility for bioimaging can be limited by undesirable photon interactions with the surrounding biological matrix, especially in in vivo systems. Here, we report a new type of magnetism-based nanoscale distance-dependent phenomenon that can quantitatively and reversibly sense and image intra-/intermolecular interactions of biologically important targets. We introduce distance-dependent magnetic resonance tuning (MRET), which occurs between a paramagnetic 'enhancer' and a superparamagnetic 'quencher', where the T1 magnetic resonance imaging (MRI) signal is tuned ON or OFF depending on the separation distance between the quencher and the enhancer. With MRET, we demonstrate the principle of an MRI-based ruler for nanometre-scale distance measurement and the successful detection of both molecular interactions (for example, cleavage, binding, folding and unfolding) and biological targets in in vitro and in vivo systems. MRET can serve as a novel sensing principle to augment the exploration of a wide range of biological systems.

nanosheetcrystalsfromthe tungsten oxide rods. The reaction between the carbondisulfide and hexadecylamine generates in situ hydrogendisulfideandhexadecylisothiocyanateviaN-hexadecyldithio-carbamate as a transient species [Eq.(1); see also Figures S1and S2 in the Supporting Information], and subsequent

Nanoparticles have the potential to revolutionize current bio-medical diagnostic and therapeutic methods. For example, magnetic nanoparticles with unique superparamagnetism are emerging as next-generation probes for high performance magnetic resonance (MR) imaging. Their enhanced properties and nanoscale controllability in terms of size, composition, surface states, and magnetic spin structure have allowed for the highly sensitive and target-specific MR imaging of various biological systems including cancer detection, cell trafficking, and angiogenesis. On the other hand, viruses can be utilized as excellent delivery vehicles due to their facile cellular transfection and gene expression efficacies within their target cells. Such excellent properties of viruses offer promising prospects for gene therapy of genetic diseases and cancers, as well as for the genetic engineering of cells. Despite these prospects, a lack of understanding of their biological behaviors including in vivo migration, molecular recognition, gene delivery, and ultimate fate following their desired biofunctional applications limits their further development. There have been previous studies in the development of nanoparticle probing systems for viruses including virus-gold and virus-quantum dot nanoparticle systems. However, their utilization in the probing of viral gene delivery has not been investigated so far. Recently, Gd-based MR contrast agent-coated viruses were developed, but their functional behaviors including targetrecognition, cellular transfection, and gene delivery capabilities have not been demonstrated partly due to the intrinsically low sensitivity of Gd-based MR contrast agents. Our strategy is to hybridize the virus with magnetic nanoparticles into a single nanoparticle system with the dual-functional capabilities of target-specific MR imaging and gene delivery. Specifically, we fabricate hybrid nanoparticles of “enhanced green fluorescent protein (eGFP) promoter genecontaining adenovirus” and “manganese-doped magnetism engineered iron oxide (abbreviated as MnMEIO) nanoparticle”. As the viral gene delivery vector, we selected adenoviruses. Adenoviruses are known to be highly effective for transferring double-stranded DNAs to various cell types. Along with a gene delivery capability, adenoviruses possess targetspecificity to the cells with overexpression of Coxsackievirus B adenovirus receptor (CAR) which is known to facilitate the binding and intrusion of adenoviruses to the host cells. As the magnetic nanoparticle component we selected manganese-doped magnetism-engineered iron oxide (MnFe2O4, MnMEIO) nanoparticles, since it is known that MnMEIO exhibits exceptional MR contrast effects (R2 (=1/T2) value of 358 sec mM) and therefore is advantageous as probes for ultra-sensitive MR imaging. Briefly, the thermal reaction of manganese chloride (MnCl2) and iron tris(2,4-pentadionate) in hot organic solvents containing oleic acid and oleylamine capping molecules yielded hydrophobically capped MnMEIO nanoparticles. Their water-solubility and biocompatibility were attained by introducing 2,3-dimercaptosuccinic acids to the nanoparticle surface. Nanoparticles obtained were 12 nm with a high sizemonodispersity (r < 7%) and possessed single crystallinity, and a saturation magnetization value of 110 emu g (Mn+Fe). Hybridization of adenoviruses with MnMEIO nanoparticles was performed through a slight modification of a literature method, as follows. First, the capsid lysine residues of the adenoviruses were converted to maleimide groups by reacting them with sulfo-succinimidyl(4-N-maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC) cross-linkers. These groups were allowed to react with a large stoichiometric amount of MnMEIO nanoparticles, which resulted in the formation of adenovirus-MnMEIO hybrid nanoparticles by way of the nucleophilic addition of a surface thiol group of MnMEIO to the C O M M U N IC A IO N

We demonstrate a novel magnetophoretic immunoassay of allergen-specific immunoglobulin E (IgE) based on the magnetophoretic deflection velocity of a microbead that is proportional to the associated magnetic nanoparticles under enhanced magnetic field gradient in a microchannel. In this detection scheme, two types of house dust mites, Dermatophagoides farinae (D. farinae) and Dermatophagoides pteronyssinus (D. pteronyssinus), were used as the model allergens. Polystyrene microbeads were conjugated with each of the mite extracts followed by incubation with serum samples. The resulting mixture was then reacted with magnetic nanoparticle-conjugated anti-human IgE for detection of allergen-specific IgE by using sandwich immuno-reactions. A ferromagnetic microstructure combined with a permanent magnet was employed to increase the magnetic field gradient ( approximately 10(4) T/m) in a microfluidic device. The magnetophoretic velocities of microbeads were measured in a microchannel under applied magnetic field, and the averaged velocity was well correlated with the concentration of allergen-specific IgE in serum. From the analysis of pooled sera obtained from 44 patients, the detection limits of the allergen-specific human IgEs for D. farinae and D. pteronyssinus were determined to be 565 (0.045 IU/mL) and 268 fM (0.021 IU/mL), respectively. These values are 1 order of magnitude lower than those by a conventional CAP system. For evaluation of reproducibility and accuracy, unknown sera were subjected to a blind test by using the developed assay system, and they were compared with the CAP system. As a result, coefficient of variance was less than 10%, and the developed method enabled a fast assay with a tiny amount of serum ( approximately 10 microL).

Successful development of ultra-sensitive molecular imaging nanoprobes for the detection of targeted biological objects is a challenging task. Although magnetic nanoprobes have the potential to perform such a role, the results from probes that are currently available have been far from optimal. Here we used artificial engineering approaches to develop innovative magnetic nanoprobes, through a process that involved the systematic evaluation of the magnetic spin, size and type of spinel metal ferrites. These magnetism-engineered iron oxide (MEIO) nanoprobes, when conjugated with antibodies, showed enhanced magnetic resonance imaging (MRI) sensitivity for the detection of cancer markers compared with probes currently available. Also, we successfully visualized small tumors implanted in a mouse. Such high-performance, nanotechnology-based molecular probes could enhance the ability to visualize other biological events critical to diagnostics and therapeutics.

Anorganische Nanokristalle mit gezielt praparierten Formen und Abmessungen haben einzigartige, formabhangige Eigenschaften und sind als Bausteine zur Herstellung von Nanofunktionseinheiten von grosem Interesse. In diesem Aufsatz fassen wir die jungsten Entwicklungen bei der Formkontrolle von kolloidalen Nanokristallen zusammen, wobei der Schwerpunkt auf den wissenschaftlich und technologisch wichtigen Halbleiter- und Metalloxid-Nanokristallen liegt, die sich durch nichthydrolytische Synthesemethoden erhalten lassen. Viele ungewohnliche Strukturmotive wurden entdeckt, darunter Polyeder, Stabchen und Drahte, Scheiben und Prismen sowie komplexere Formen wie verzweigte Stabchen, Sterne, anorganische Dendrimere und Hanteln. Der gegenwartig favorisierte Mechanismus der Formkontrolle wird vorgestellt, ebenso wie richtungsweisende Studien zur Anordnung formkontrollierter Nanokristalle zu geordneten Ubergittern und zur Herstellung hochentwickelter Prototypen von Nanofunktionseinheiten.

The systematic assembly of nanoscale constituents into highly ordered superlattices is of significant interest because of the potential of their multifunctionalities and the discovery of new collective properties. However, successful observations of such superlattice-associated nanoscale phenomena are still elusive. Here, we present magnetic superlattices of Co and Fe 3 O 4 nanoparticles with multidimensional symmetry of either AB (NaCl) or AB 2 (AlB 2 ). The discovery of significant enhancement (≈25 times) of ferrimagnetism is further revealed by forming previously undescribed superlattices of magnetically soft–hard Fe 3 O 4 @CoFe 2 O 4 through the confined geometrical effect of thermally driven intrasuperlattice phase transition between the nanoparticulate components.

Although multicomponent core-shell type nanomaterials are one of the highly desired structural motifs due to their simultaneous multifunctionalities, the fabrication strategy for such nanostructures is still in a primitive stage. Here, we present a redox-transmetalation process that is effective as a general protocol for the fabrication of high quality and well-defined core-shell type bimetallic nanoparticles on the sub-10 nm scale. Various core-shell type nanomaterials including Co@Au, Co@Pd, Co@Pt, and Co@Cu nanoparticles are fabricated via transmetalation reactions. Compared to conventional sequential reduction strategies, this transmetalation process has several advantages for the fabrication of core-shell type nanoparticles: (i) no additional reducing agent is needed and (ii) spontaneous shell layer deposition occurs on top of the core nanoparticle surface and thus prevents self-nucleation of secondarily added metals. We also demonstrate the versatility of these core-shell structures by transferring Co@Au nanoparticles from an organic phase to an aqueous phase via a surface modification process. The nanostructures, magnetic properties, and reaction byproducts of these core-shell nanoparticles are spectroscopically characterized and identified, in part, to confirm the chemical process that promotes the core-shell structure formation.

Inorganic nanocrystals with certain geometries exhibit unique shape dependent phenomena and subsequent utilization of them as building blocks for the key components of nanodevices is of huge interest. Architecture of these nanocrystals can be simply classified by their dimensionalities: zero-dimensional (0D) quantum dots including spheres, cubes, and tetrahedrons, one-dimensional nanorods and wires, two-dimensional (2D) nanodiscs and plates, and other advanced shapes such as rod-based multipods and nanostars. Among them, one-dimensional (1D) structures are of current interest in materials chemistry not only because they exhibit novel optical properties arising from dimensional anisotropy, but also because they can be utilized as key materials in addressable two-terminal circuits for nanodevice applications. We describe here the current studies on a variety of one-dimensional semiconductor and metal oxide nano-building blocks obtained by liquid phase colloidal synthetic methods. Several mechanisms and critical parameters for nanocrystal shape guiding processes are carefully examined. Once we understand the guiding laws of nanocrystals growth, many new nano-building blocks will easily be tailored for the discovery of novel phenomena and also further exciting advancement of nanoscience and nanotechnology.

The unique properties of magnetic nanocrystals provide them with high potential as key probes and vectors in the next generation of biomedical applications. Although superparamagnetic iron oxide nanocrystals have been extensively studied as excellent magnetic resonance imaging (MRI) probes for various cell trafficking, gene expression, and cancer diagnosis, further development of in vivo MRI applications has been very limited. Here, we describe in vivo diagnosis of cancer, utilizing a well-defined magnetic nanocrystal probe system with multiple capabilities, such as small size, strong magnetism, high biocompatibility, and the possession of active functionality for desired receptors. Our magnetic nanocrystals are conjugated to a cancer-targeting antibody, Herceptin, and subsequent utilization of these conjugates as MRI probes has been successfully demonstrated for the monitoring of in vivo selective targeting events of human cancer cells implanted in live mice. Further conjugation of these nanocrystal probes with fluorescent dye-labeled antibodies enables both in vitro and ex vivo optical detection of cancer as well as in vivo MRI, which are potentially applicable for an advanced multimodal detection system. Our study finds that high performance in vivo MR diagnosis of cancer is achievable by utilizing improved and multifunctional material properties of iron oxide nanocrystal probes.

Since inorganic nanocrystals exhibit unique shape-dependent nanoscale properties and can be utilized as basic building blocks for futuristic nanodevices, a systematic study on the shape control of these nanocrystals remains an important subject in materials and physical chemistry. In this feature article, we overview the recent progress on the synthetic development of symmetry-controlled colloidal nanocrystals of semiconductor and metal oxide, which are prepared through nonhydrolytic chemical routes. We describe their shape-guiding processes and illustrate the detailed key factors controlling their growth by examining various case studies of zero-dimensional spheres and cubes, one-dimensional rods, and quasi multidimensional structures such as disks, multipods, and stars. Specifically, the crystalline phase of nucleating seeds, surface energy, kinetic vs thermodynamic growth, and selective adhesion processes of capping ligands are found to be most crucial for the determination of the nanocrystal shape.

In this paper, we describe an easy and reliable method for the production of patterned monolayers of Co nanoparticles. A two-dimensional monolayer of Co nanoparticles is fabricated by spreading a nanoparticle solution over an air-water interface and then transferring it to a hydrophobic substrate by using the Langmuir-Blodgett (LB) method. Transmission electron microscopy (TEM) was used to show that, with increasing surface pressure, the Co nanoparticles become well-organized into a Langmuir monolayer with a hexagonal close-packed structure. By controlling the pH of the subphase, it was found that a monolayer of Co nanoparticles with long-range order could be obtained. Further, by transferring the Langmuir monolayer onto a poly(dimethoxysilane) (PDMS) mold, the selective micropatterning of the Co nanoparticles could be achieved on a patterned electronic circuit. The electronic transport properties of the Co nanoparticles showed the ohmic I-V curve.

We present a new strategy to fabricate a monolayer assembly of Br-terminated Co nanoparticles on functionalized Si surfaces by using chemical covalent bonding and microcontact printing method. Self-assembled monolayers (SAMs) of the Co nanoparticles formed on the hydroxyl-terminated Si surface exhibit two-dimensional island networks with locally ordered arrays via covalent linkage between nanoparticles and surface. On the other hand, SAMs of the nanoparticles on the aminopropyl-terminated Si surface show an individual and random distribution over an entire surface. Furthermore, we have fabricated striped architectures of Co nanoparticles using a combination of microcontact printing and covalent linkage. Microcontact printing of octadecyltrichlorosilane and selective covalent linkage between nanoparticles and functionalized Si surfaces lead to a hybrid nanostructure with selectively assembled nanoparticles stripes on the patterned functionalized Si surfaces.

The structure, magnetism, and phase transition of core-shell type CoPt nanoparticles en route to solid solution alloy nanostructures are systematically investigated. The characterization of Co(core)Pt(shell) nanoparticles obtained by a "redox transmetalation" process by transmission electron microscopy (TEM) and, in particular, X-ray absorption spectroscopy (XAS) provides clear evidence for the existence of a core-shell type bimetallic interfacial structure. Nanoscale phase transitions of the Co(core)Pt(shell) structures toward c-axis compressed face-centered tetragonal (fct) solid solution alloy CoPt nanoparticles are monitored at various stages of a thermally induced annealing process and the obtained fct nanoalloys show a large enhancement of their magnetic properties with ferromagnetism. The relationship between the nanostructures and their magnetic properties is in part elucidated through the use of XAS as a critical analytical tool.

We introduce a novel strategy to fabricate a bifunctional monolayer assembly of Co nanoparticles on a Si(111) surface via the covalent linkage of terminal functional groups between the Si surface and the nanoparticles. The Br-terminated Co nanoparticles that are assembled on the aminopropyl-terminated Si surface show an individual and random distribution over an entire surface. Furthermore, we have fabricated a selective patterned monolayer assembly of Co nanoparticles using a combination of microcontact printing and covalent linkage: the Br-terminated Co nanoparticles attached on only aminopropyl-terminated regions but not on the octadecyl-terminated regions that consist of nonfunctional alkyl groups.

The surfactant-mediated shape evolution of titanium dioxide anatase nanocrystals in nonaqueous media was studied. The shape evolves from bullet and diamond structures to rods and branched rods. The modulation of surface energies of the different crystallographic faces through the use of a surface selective surfactant is the key parameter for the shape control.

Carbon nanotubes (CNTs) were grown from Co nanoparticles by thermal chemical vapor deposition using C 2 H 2 , H 2 , and Ar gases. The diameters of CNTs were limited by the sizes of the catalytic Co nanoparticles. From 5 nm Co nanoparticles, very long and straight CNTs with diameters below 5 nm were grown. C 2 H 2 was so effective as the carbon feedstock that the required amount of C 2 H 2 was only 0.1% of the total amount of gases to grow CNTs from 5 nm Co nanoparticles. For 8 nm Co nanoparticles, a long enough pretreatment time was essential in growing dense CNTs.

The systematic shape control of colloidal nanocrystals including one-dimensional (1D) nanorods remains a key issue in the “bottom–up” approach of nanoscience. Here, we examine the anisotropic structural evolution of various semiconductor nanocrystals and systematically elucidate the key growth parameters for their shape control. The crystalline phase of nucleating seeds and kinetic growth regimes controlled by changing growth parameters are crucial for the determination of the 1D nanocrystal geometry.

Shape- and dopant-controlled magnetic semiconductor nanocrystals have been achieved by the thermolysis of nonpyrophoric and less reactive single molecular precursors under a monosurfactant system. Reaction parameters governing both the intrinsic crystalline phase and the growth regime (kinetic vs thermodynamic) are found to be important for the synthesis of various shapes of MnS nanocrystals that include cubes, spheres, 1-dimensional (1-D) monowires, and branched wires (bipods, tripods, and tetrapods). Obtained nanowires exhibit enhanced optical and magnetic properties compared to those of 0-D nanospheres. Proper choice of molecular precursors and kinetically driven low-temperature growth afford dopant controlled 1-D Cd1-xMn(x)S nanorods at high levels (up to approximately 12%) of Mn, which is supported by repeated surface exchange experiments and X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) analyses.

We introduce cubic magnetic nanoparticles as an effective tool for precise and ultrafast control of mechanosensitive cells. The temporal resolution of our system is ∼1000 times faster than previously used magnetic switches and is comparable to the current state-of-the-art optogenetic tools. The use of a magnetism-gated switch reported here can address the key challenges of studying mechanotransduction in biological systems. The cube-shaped magnetic nanoparticles are designed to bind to components of cellular membranes and can be controlled with an electromagnet to exert pico-Newtons of mechanical force on the cells. The cubic nanoparticles can thus be used for noncontact mechanical control of the position of the stereocilia of an inner ear hair cell, yielding displacements of tens of nanometers, with sub-millisecond temporal resolution. We also prove that such mechanical stimulus leads to the influx of ions into the hair cell. Our study demonstrates that a magnetic switch can yield ultrafast temporal resolution, and has capabilities for remote manipulation and biological specificity, and that such magnetic system can be used for the study of mechanotransduction processes of a wide range of sensory systems.

Simple and effective generation of transition metal chalcogenides (TMCs) in a single-layer form has been a challenging task. Here we present a tandem molecular intercalation (TMI) as a new exfoliation concept for producing single-layer TMCs from multi-layer colloidal TMC nanostructures in solution phase. TMI requires tandem Lewis base intercalates, where short 'initiator' molecules first intercalate into TMCs to open up the interlayer gap, and the long 'primary' molecules then bring the gap to full width so that a random mixture of intercalates overcomes the interlayer force. Spontaneous exfoliation then yields single-layer TMCs. The TMI process is uniquely advantageous because it works in a simple one-step process under safe and mild conditions (that is, room temperature without sonication or H-2 generation). With the appropriate intercalates, we have successfully generated single-layer nanostructures of group IV (TiS2, ZrS2), group V (NbS2) and VI (WSe2, MoS2) TMCs.

Transition-metal chalcogenide (TMC) nanoflakes of composition MX2 (where M=Ti, Zr and Hf; X=S and Se) crystallize preferentially in equilateral hexagons and exhibit a pronounced lateral quantum confinement. The hexagonal shape of octahedral (1T) TMC nanoflakes is the result of charge localization at the edges/vertices and the resulting Coulomb repulsion. Independent of their size, all nanoflakes have the Mn X2n-2 stoichiometry and thus an unoxidized metal center which results in dopant states. These states become relevant for small nanoflakes and lead to metallic character, but for larger nanoflakes (>6 nm) the 2D monolayer properties dominate. Finally, coordination of Lewis bases at the nanoflake edges has no significant effect on the electronic structure of these species confirming the viability of colloidal synthetic approaches.

Stem-cell-based therapies have attracted considerable interest in regenerative medicine and oncological research. However, a major limitation of systemic delivery of stem cells is the low homing efficiency to the target site. Here, we report a serendipitous finding that various iron-based magnetic nanoparticles (MNPs) actively augment chemokine receptor CXCR4 expression of bone-marrow-derived mesenchymal stem cells (MSCs). On the basis of this observation, we designed an iron-based nanocluster that can effectively label MSCs, improve cell homing efficiency, and track the fate of the cells in vivo. Using this nanocluster, the labeled MSCs were accurately monitored by magnetic resonance imaging and improved the homing to both traumatic brain injury and glioblastoma models as compared to unlabeled MSCs. Our findings provide a simple and safe method for imaging and targeted delivery of stem cells and extend the potential applications of iron-based MNPs in regenerative medicine and oncology.

Our study presents the preparation of well-defined Pd nanoballs and nanowires using the different pore size of cubic and hexagonal shaped MCM type mesoporous silicate materials as matrix templates. The synthesis involves loading the organometallic precursor into template matrix via chemical vapor infiltration (CVI), followed by mild thermal decomposition to generate Pd metals self-organized inside the template. For Pd@MCM-48, the Pd metal forms spherical domains (-38 nm) consisting of three dimensionally interconnected into Pd arrays; for Pd@SBA-15 and Pd@MCM-41, the Pd metal forms of one-dimensional wires. Etching out the matrix produces porous Pd nanoballs (pore sizes of ∼ 1.5 - 2.0 nm) with retaining original domain sizes of ∼38 nm; similarly Pd@SBA-15 and Pd@MCM-41 afford freestanding Pd nanowires. In addition, phase transition behavior and melting point depression of the Pd nanowires is studied.

Mesoporous silica nanoparticles are useful nanomaterials that have demonstrated the ability to contain and release cargos with mediation by gatekeepers. Magnetic nanocrystals have the ability to exhibit hyperthermic effects when placed in an oscillating magnetic field. In a system combining these two materials and a thermally sensitive gatekeeper, a unique drug delivery system can be produced. A novel material that incorporates zinc-doped iron oxide nanocrystals within a mesoporous silica framework that has been surface-modified with pseudorotaxanes is described. Upon application of an AC magnetic field, the nanocrystals generate local internal heating, causing the molecular machines to disassemble and allowing the cargos (drugs) to be released. When breast cancer cells (MDA-MB-231) were treated with doxorubicin-loaded particles and exposed to an AC field, cell death occurred. This material promises to be a noninvasive, externally controlled drug delivery system with cancer-killing properties.

This review focuses on the gas phase photochemical fragmentation processes of coordination compounds that are precursors for the laser driven synthesis of solid-state materials such as thin films and nanoclusters from the gas phase. Specific emphasis is placed on the identification of photofragments by luminescence spectroscopy during the deposition process. In several cases, results from mass spectroscopy and from photofragmentation under the collision-free conditions of a molecular beam are included to clarify the identifications and mechanisms. Detailed experimental measurements have been made on metal diketonates, metal amides, metal xanthates and metal thiocarbamates. These compounds are useful as molecular precursors for the synthesis of thin films and nanoparticles of metals, binary and ternary materials, and semiconductor films.

Metallic palladium films are prepared at 10-2 Torr by 308 nm irradiation of gaseous (2-methylallyl)(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato) palladium. Gas-phase luminescence spectra recorded dur...