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Well-defined recyclable Pd- and Rh-bipyridyl group-impregnated SBA-15 catalysts were prepared for C-C bond coupling reaction and selective hydrogenation reactions, respectively. These SBA-15 derived ligands for the catalysts were prepared by direct and indirect co-condensation method using bipyridyl-linked methallylsilane. This indirect method, involving methoxysilane generated from methallylsilane shows higher loading efficiency of transition metal catalysts on SBA-15 than the direct use of methallylsilane.

Nanoscale dynamic processes such as the diffusion of ions within solid-state structures are critical for understanding and tuning material properties in a wide range of areas, such as energy storage and conversion, catalysis, and optoelectronics. In the generation of new types of nanocrystals (NCs), diffusion-mediated ion exchange reactions have also been proposed as one of the most effective transformational strategies. However, retaining the original morphology and crystal structure of metal oxide NCs has been challenging because of Kirkendall void formation, and there has been no success, especially for anion exchange. Here we show that with the aid of an oxygen extracting reagent (OER), anion diffusion is dramatically accelerated and morphology-conserving anion exchange without Kirkendall void formation is possible. In the case of the conversion of Fe

Controlled lateral quantum confinement in single-layer transition-metal chalcogenides (TMCs) can potentially combine the unique properties of two-dimensional (2D) exciton with the size-tunability of exciton energy, creating the single-layer quantum dots (SQDs) of 2D TMC materials. However, exploring such opportunities has been challenging due to the limited ability to produce well-defined SQDs with sufficiently high quality and size control, in conjunction with the commonly observed inconsistency in the optical properties. Here, we report an effective method to synthesize high-quality and size-controlled SQDs of WSe2 via multilayer quantum dots (MQDs) precursors, which enables grasping a clear picture of the role of lateral confinement on the optical properties of the 2D exciton. From the single-particle optical spectra and polarization anisotropy of WSe2 SQDs of varying sizes in addition to their ensemble data, we reveal how the properties of 2D exciton in single-layer TMCs evolve with increasing lateral...

Achieving a molecular level understanding of chemical reactions on the surface of solid-state nanomaterials is important, but challenging. For example, the fully saturated basal plane is believed to be practically inert and its surface chemistry has been poorly explored, while two-dimensional (2D) layered transition-metal chalcogenides (TMCs) display unique reactivities due to their unusual anisotropic nature, where the edges consisting of unsaturated metals and chalcogens are sites for key chemical reactions. Herein, we report the use of Lewis acids/bases to elucidate the chemical reactivity of the basal plane in 2D layered TMCs. Electrophilic addition by Lewis acids (i.e., AlCl3) selectively onto sulfides in the basal plane followed by transmetalation and subsequent etching affords nanopores where such chemical activations are initiated and propagated from the localized positions of the basal plane. This new method of surface modification is generally applicable not only to various chemical compositions...

Nanoparticle clusters (NPCs) have attracted significant interest owing to their unique characteristics arising from their collective individual properties. Nonetheless, the construction of NPCs in a structurally well-defined and size-controllable manner remains a challenge. Here we demonstrate a strategy to construct size-controlled NPCs using the DNA-binding zinc finger (ZnF) protein. Biotinylated ZnF was conjugated to DNA templates with different lengths, followed by incubation with neutravidin-conjugated nanoparticles. The sequence specificity of ZnF and programmable DNA templates enabled a size-controlled construction of NPCs, resulting in a homogeneous size distribution. We demonstrated the utility of magnetic NPCs by showing a three-fold increase in the spin-spin relaxivity in MRI compared with Feridex. Furthermore, folate-conjugated magnetic NPCs exhibited a specific targeting ability for HeLa cells. The present approach can be applicable to other nanoparticles, finding wide applications in many areas such as disease diagnosis, imaging, and delivery of drugs and genes.

A solution-phase synthetic protocol to form two-dimensional (2D) single-layer transition-metal chalcogenides (TMCs) has long been sought; however, such efforts have been plagued with the spontaneous formation of multilayer sheets. In this study, we discovered a solution-phase synthetic protocol, called "diluted chalcogen continuous influx (DCCI)", where controlling the chalcogen source influx (e.g., H2S) during its reaction with the transition-metal halide precursor is the critical parameter for the formation of single-layer sheets as examined for the cases of group IV TMCs. The continuous influx of dilute H2S throughout the entire growth period is necessary for large sheet formation through the exclusive a- and b-axial growth processes. By contrast, the burst influx of highly concentrated H2S in the early stages of the growth process forms multilayer TMC nanodiscs. Our DCCI protocol is a new synthetic concept for single-layer TMCs and, in principle, can be operative for wide range of TMC nanosheets.

Overcoming resistance: Heat-treated cancer cells possess a protective mechanism for resistance and survival. Resistance-free apoptosis-inducing magnetic nanoparticles (RAINs) successfully promote hyperthermic apoptosis, obstructing cell survival by triggering two functional units of heat generation and the release of geldanamycin (GM) for heat shock protein (Hsp) inhibition under an alternating magnetic field (AMF).

The intrinsic nature of small-molecule chemotherapeutics, including i) limited aqueous solubility, ii) systemic toxicity due to non-specific whole-body distribution, and iii) potential development of drug resistance after initial administration, compromises their treatment efficacy.[1] Recently, nanoparticle (NP)-based drug delivery systems have been considered as promising alternatives to overcome some of these limitations and begin to resolve obstacles in the disease management in clinical oncology.[2] The intraparticular space of a NP vector can be employed to package drug payloads without constrain associated with their solubility. Further, NP vectors exhibit enhanced permeability and retention (EPR) effects[3] that facilitate the differential uptake, leading to preferential spatio-distribution in tumor.[4] However, conventional NP drug delivery systems tend to passively release drug payloads, limiting the ability to release an effective drug concentration at a desired time window. Therefore, there is a need to develop next-generation NP drug delivery system such as a stimuli-responsive drug release system with a goal of achieving spatio-temporal control, by which an acute level of drug concentration can be delivered at the time point the NP vectors reach maximum tumor accumulation.[5] By doing so, it is expected to dramatically improve therapeutic effects in tumor and effectively reduce systematic toxicity at a minute drug dosage.[6]

Two-dimensional (2D) layered nanostructures are emerging fast due to their exceptional materials properties. While the importance of physical approaches (e.g., guest intercalation and exfoliation) of 2D layered nanomaterials has been recognized, an understanding of basic chemical reactions of these materials, especially in nanoscale regime, is obscure. Here, we show how chemical stimuli can influence the fate of reaction pathways of 2D layered nanocrystals. Depending on the chemical characteristics (Lewis acid ((1)O2) or base (H2O)) of external stimuli, TiS2 nanocrystal is respectively transformed to either a TiO2 nanodisc through a "compositional metathesis" or a TiO2 toroid through multistage "edge-selective structural transformation" processes. These chemical reactions can serve as the new design concept for functional 2D layered nanostructures. For example, TiS2(disc)-TiO2(shell) nanocrystal constitutes a high performance type II heterojunction which not only a wide range solar energy coverage (~80%) with near-infrared absorption edge, but also possesses enhanced electron transfer property.

Temperature control is an important method of self-defense in biological systems. For example, one response mounted by humans in an effort to fight injury, including viral and bacterial infections, involves an increase in body temperature, thus producing the well-recognized symptoms of fever.[1] Today, the idea of using artificial temperature control for disease removal is being realized with the aid of various techniques, such as ultrasound, near-infrared light, and magnetic field by increasing localized temperature in a targeted region.[2] Magnetic nanoparticles have attracted considerable attention for hyperthermia applications owing to their ability to generate heat effectively when exposed to an alternating magnetic field without a penetration depth limit.[3] Hyperthermia, the artificially induced heat treatment of a disease, uses temperatures ranging between 42 °C and 47°C. Generally, a temperature below 45 °C induces apoptotic cell death.[4] As compared to necrosis, apoptosis is a more benign form of “programmed” cell death.[5] Nonliving cells produced as the result of apoptotic process are cleaned by phagocytosis without affecting neighboring normal cells. In contrast, necrosis, typically generated by harsh and high-temperature hyperthermia, is considered relatively harmful because it can be correlated with inflammatory disease and metastasis.[6] However, achieving effective apoptotic hyperthermia is often difficult, as cells typically acquire resistance to induced thermal stress.[7] Repeated exposures to high temperatures with high concentration of magnetic nanoparticles are usually necessary to achieve a useful level of therapeutic efficacy even though the conditions could favor necrotic cell death rather than apoptosis. Because cancer cells are susceptible to heat at about 43 °C, while most normal tissues remain undamaged,[8] hyperthermia using this temperature defines a recognized but unmet goal.

While interesting and unprecedented material characteristics of two dimensionality (2-D) layered nanomaterials are emerging, their reliable synthetic methodologies are not well developed. In this study we demonstrate general applicability of synthetic protocols to a wide range of colloidal 2-D layered transition-metal chalcogenide (TMC) nanocrystals. As distinctly different from other nanocrystals, we discovered that 2-D layered TMC nanocrystals are unstable in the presence of reactive radicals from elemental chalcogen during the crystal formation. We first introduce the synthesis of titanium sulfide and selenide where well-defined single crystallinity and lateral size controllability are verified, and then such synthetic protocols are extended to all of group IV and V transition-metal sulfide (TiS(2), ZrS(2), HfS(2), VS(2), NbS(2), and TaS(2)) and selenide (TiSe(2), ZrSe(3), HfSe(3), VSe(2), NbSe(2), and TaSe(2)) nanocrystals. The use of appropriate chalcogen source is found to be critical for the successful synthesis of 2-D layered TMC nanocrystals. CS(2) is an efficient chalcogen precursor for metal sulfide nanocrystals, whereas elemental Se is appropriate for metal selenide nanocrystals. We briefly discuss the effects of reactive radical characteristics of elemental S and Se on the formation of 2-D layered TMC nanocrystals.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

The chemical pathway responsible for the conversion of the organotitanium compound tetraneopentyltitanium to titanium carbide has been studied under chemical vapor conditions and on single crystals in ultra-high vacuum. For every equivalent of TiNp4 consumed in the deposition process, 3.28 equiv of neopentane and 0.16 equiv of isobutane are produced; other organic species are also formed but in relatively small amounts. About 93% of the carbon and hydrogen originally present in the precursor can be accounted for in these products. Thermolysis of the specifically deuterated analogue Ti(CD2CMe3)4 yields a 2.25:1 ratio of neopentane-d3 and neopentane-d2; this result combined with a kinetic isotope effect of 4.9 at 385 K shows unequivocally that the first step in the deposition pathway under CVD conditions is α-hydrogen abstraction. The α-hydrogen abstraction step produces 1 equiv of neopentane and a titanium alkylidene, which undergoes further α- (and eventually γ-) hydrogen activation processes to generate ...

Studies of the thermolysis of Ti(CH2CMe3)4 in solution have been carried out in parallel with studies of the chemical mechanism responsible for its conversion to titanium carbide under CVD conditions. In hydrocarbon solutions, the neopentyl complex thermolyzes to eliminate 2.1 equiv of neopentane as the principal organic product. A deuterium kinetic isotope effect (kR(H)/kR(D) ) 5.2 ( 0.4) upon deuterating the alkyl groups at the R positions provides clear evidence that the initial step in the thermolysis is an R-hydrogen abstraction reaction to form neopentane. The activation parameters for this R-hydrogen abstraction process are ¢H q ) 21.5 ( 1.4 kcal/mol and ¢S q )- 16.6 ( 3.8 cal/(mol K). The titanium-containing product of this reaction is a titanium alkylidene, which in solution activates C-H bonds of both saturated and unsaturated hydrocarbon solvents such as benzene and cyclohexane. No activation of the C-F bonds of hexafluorobenzene is seen, however. Under special circumstances, a second thermolysis pathway for TiNp4 can be detected, A-hydrogen activation, but this pathway is intrinsically about 25 times slower than the R-hydrogen abstraction process.

ZnS thin films are made by laser driven chemical vapor deposition (CVD) from a single-source precursor, Zn(S{sub 2}COCHMe{sub 2}){sub 2} under vacuum conditions. Photofragments in the gas phase are identified simultaneously by luminescence spectroscopy. The laser selectively activates the initial decomposition of the precursor and drives its conversion to the desired materials under mild conditions. These photolytically produced films are compared to films made by thermal deposition from the same precursor. The deposits from both techniques, characterized by X-ray diffraction, Rutherford backscattering, and X-ray photoelectron spectroscopy, are pure stoichiometric ZnS in the hexagonal phase. Surface morphology differs in shape and granule size. During the laser-driven CVD process, gas-phase photochemical intermediates are identified by luminescence spectroscopy. The luminescent photoproducts are Zn and S{sub 2}, the two elemental components of the final material. Photofragmentation mechanisms leading to ZnS, the luminescent species Zn and S{sub 2}, and the gaseous organic byproducts are discussed. Further characterization of photofragmentation pathways is provided by the trapping of the photoreaction products and by mass spectroscopy. 34 refs., 6 figs.

This study provides an easy and simple method to obtain inorganic nanoparticles that can penetrate the blood–brain barrier, the heavily guarded system in the brain, via cross-linked serum albumin surface coatings. Their intact BBB permeability was confirmed in both in vitro and in vivo tests.

We present a colloidal route for the synthesis of ultrathin ZrS(2) (UT-ZrS(2)) nanodiscs that are ~1.6 nm thick and consist of approximately two unit cells of S-Zr-S. The lateral size of the discs can be tuned to 20, 35, or 60 nm while their thickness is kept constant. Under the appropriate conditions, these individual discs can self-assemble into face-to-face-stacked structures containing multiple discs. Because the S-Zr-S layers within individual discs are held together by weak van der Waals interactions, each UT-ZrS(2) disc provides spaces that can serve as host sites for intercalation. When we tested UT-ZrS(2) discs as anodic materials for Li(+) intercalation, they showed excellent nanoscale size effects, enhancing the discharge capacity by 230% and greatly improving the stability in comparison with bulk ZrS(2). The nanoscale size effect was especially prominent for their performance in fast charging/discharging cycles, where an 88% average recovery of reversible capacity was observed for UT-ZrS(2) discs with a lateral diameter of 20 nm. The nanoscale thickness and lateral size of UT-ZrS(2) discs are critical for fast and reliable intercalation cycling because those dimensions both increase the surface area and provide open edges that enhance the diffusion kinetics for guest molecules.

The immune-response of macrophages is an important area of investigation since it represents the major pathway by which early-stage defense barriers are established in skin, lungs, and mucosal systems to counteract foreign objects. In this study, we have examined the size-dependent inflammatory and toxicological effects of nanostructured silver particles (nano-Ag) on macrophage immune cells.

Achieving high accuracy in the imaging of biological targets is a challenging issue. For MRI, to enhance imaging accuracy, two different imaging modes with specific contrast agents are used; one is a T1 type for a “positive” MRI signal and the other is a T2 type for a “negative” signal. Conventional contrast agents respond only in a single imaging mode and frequently encounter ambiguities in the MR images. Here, we propose a “magnetically decoupled” core−shell design concept to develop a dual mode nanoparticle contrast agent (DMCA). This DMCA not only possesses superior MR contrast effects but also has the unique capability of displaying “AND” logic signals in both the T1 and T2 modes. The latter enables self-confirmation of images and leads to greater diagnostic accuracy. A variety of novel DMCAs are possible, and the use of DMCAs can potentially bring the accuracy of MR imaging of diseases to a higher level.

Synthetic magnetic nanoparticles (MNPs) are emerging as versatile probes in biomedical applications, especially in the area of magnetic resonance imaging (MRI). Their size, which is comparable to biological functional units, and their unique magnetic properties allow their utilization as molecular imaging probes. Herein, we present an overview of recent breakthroughs in the development of new synthetic MNP probes with which the sensitive and target-specific observation of biological events at the molecular and cellular levels is possible.

Co@Pt-Au nanoparticles, which have enhanced magnetism and high stability in aqueous media, are utilized in conjunction with MRI to monitor the structural evolution of Abeta assemblies, especially Abeta protofibrils in the early reversible stages.

Magnetic nanoparticles exhibit unique nanoscale properties and their utilization for various magnetic systems is of significant interest. Especially, heterostructured magnetic nanoparticles are emerging as next-generation materials due to their synergistically enhanced magnetism and potential multifunctionalities. Herein, we overview the recent advances in the development of magnetic nanoparticles with a focus on multicomponent heterostructured nanoparticles including alloys, core-shells, and binary superlattices synthesized via nonhydrolytic methods. Their multifunctionalites and high performance capabilities are demonstrated for applications in high density magnetic storages, chemical catalysis, and biomedical separation and diagnostics.

Hybrid nanoparticles are of significant interest primarily because of their innate multifunctional capabilities. These capabilities can be exploited when hybrid nanoparticles are used for applications in the biomedical sciences in particular, where they are utilized as multimodal nanoplatforms for sensing, imaging, and therapy of biological targets. However, the realization of their biomedical applications has been difficult, in part because of a lack of high quality hybrid nanoparticles which possess high aqueous colloidal stability and biocompatibility while retaining their multifunctionalities. Here, we present the development of inorganic heterodimer nanoparticles of FePt-Au with multifunctional capabilities including catalytic growth effects, magnetic resonance (MR) contrast effects, optical signal enhancing properties, and high colloidal stability and biocompatibility. Their multimodal capabilities for biological detection are demonstrated through their utilizations in the patterned biochip based detection of avidin-biotin interaction as well as in molecular MR imaging of neuroblastoma cells.

Inorganic nanocrystals with tailored geometries exhibit unique shape-dependent phenomena and subsequent utilization of them as building blocks for the fabrication of nanodevices is of significant interest. Herein, we review the recent developments in the shape control of colloidal nanocrystals with a focus on the scientifically and technologically important semiconductor and metal oxide nanocrystals obtained by nonhydrolytic synthetic methods. Many structurally unprecedented motifs have been discovered including polyhedrons, rods and wires, plates and prisms, and other advanced shapes such as branched rods, stars, inorganic dendrites, and dumbbells. The currently proposed shape-guiding mechanisms are presented and the important pioneering studies on the assembly of shape-controlled nanocrystals into ordered superlattices and the fabrication of prototype advanced nanodevices are discussed.

Co@Pt nanoparticles as a bifunctional nanoplatform system for the hydrogenation of various unsaturated organic molecules under mild conditions and also for magnetic separation and recycling are demonstrated.

High-quality biocompatible magnetic iron oxide (Fe3O4) nanocrystals were developed through a ligand exchange process of hydrophobically capped nanocrystals with hydrophilic molecules. By simple modulation of the nanocrystal surface ligand charge properties, we have been able to prepare magnetic nanocrystals with excellent intracellular labeling capabilities that efficiently label a variety of cell types without the need for additional transport facilitating agents. The excellent intracellular labeling capability of the newly developed cationic WSIO has further led to successful MRI monitoring of the migration of neural stem cells in rat spinal cord. The magnetic nanocrystals developed here have great potential in applications for labeling of various cell types and also the monitoring of cell-based medical treatments and cancer metastasis.

We demonstrate a novel synthetic scheme that can be used to control the crystalline phase and shape of GaP semiconductor nanocrystals. Our study shows that steric effects of surfactant ligands can modulate the crystalline phases and control the shapes of nanocrystals. The shape of the nanocrystals obtained varies from zero-dimensional spheres to one-dimensional rods via controlling the ratio between primary and tertiary alkylamines. III-V semiconductors (in our case: GaP) under 10 nm in width are first reported, and unique optical properties due to shape anisotropy are also observed.

Since the use of magnetic nanocrystals as probes for biomedical system is attractive, it is important to develop optimal synthetic protocols for high-quality magnetic nanocrystals and to have the systematic understanding of their nanoscale properties. Here we present the development of a synthetically controlled magnetic nanocrystal model system that correlates the nanoscale tunabilities in terms of size, magnetism, and induced nuclear spin relaxation processes. This system further led to the development of high-performance nanocrystal-antibody probe systems for the diagnosis of breast cancer cells via magnetic resonance imaging.

Shape- and size-controlled synthesis of single-crystalline maghemite (gamma-Fe2O3) nanocrystals are performed by utilizing a solution-based one-step thermolysis method. Modulating the growth parameters, such as the type and amount of capping ligands as well as the growth time, is shown to have a significant effect on the overall shape and size of the obtained nanocrystals and on the ripening process itself. The resulting shapes of the novel structures are diverse, including slightly faceted spheres, diamonds, prisms, and hexagons, all of which are in fact truncated dodecahedron structures with different degrees of truncation along the {111}, {110}, or {100} faces. Spherical nanocrystals are easily assembled into the three-dimensional superlattices, demonstrating the uniformity of these nanocrystals. The size-dependent magnetic properties are examined, and large hexagon-shaped gamma-Fe2O3 nanocrystals are shown to be ferrimagnetic at room temperature.

We demonstrate a novel synthetic scheme that can be used to differentially guide the shape of PbS semiconductor nanocrystals. Our study first demonstrates the discovery of single-crystalline star-shaped nanocrystals as novel transient species. We then carefully probe their shape evolution toward other novel nanostructures (e.g., tadpole-, L-, T-, cross-shapes, highly faceted star shapes, truncated octahedrons and cubes, etc.) and systematically elucidate the key parameters that control these final structures. In principle, through programming these growth parameters, the desired architecture of building blocks of other kinds of nano materials can be constructed.

A simple one-pot synthesis of size and shape controlled ZnTe nanocrystals using a monomeric molecular precursor, [Zn(TePh)2][TMEDA], has been studied by varying the growth temperature or the templating surfactants.

One-step size-controlled synthesis of ZnSe quantum dots is studied and the obtained QDs are luminescent with the emission wavelength varying over a wide range (up to 100 nm) depending on the particle size; the single-molecular precursor is an air-stable bis(phenylselenolato)zinc N,N,N′,N′-tetramethylethylenediamine (TMEDA) complex, which effectively affords different sizes of ZnSe QDs depending on growth temperatures.

A magnetic field is successfully utilized to induce the fabrication of size controllable one-dimensional (1-D) supercrystals which are composed of a highly crystalline assembly of fcc-packed cobalt nanoparticles; the anisotropy associated supercrystal magnetism is enhanced with four times higher coercivity than that of randomly aggregated nanoparticles.

Remarkable selectivity is achieved in the cleavage of benzyl ethers using ball-shaped palladium nanocatalysts, Pd@MCM-48, in an MCM-48 matrix. The unique nanocatalysts not only feature unprecedented complete hydrogenolysis selectivity of a benzyl ether over hydrogenation of a double bond, but also demonstrate selective cleavage of unsubstituted benzyl ether over substituted benzyl ethers.