Stanislaus S Wong

Publications of Stanislaus S Wong

• Highly Enhanced Electrocatalytic Oxygen Reduction Performance Observed in Bimetallic Palladium-Based Nanowires Prepared under Ambient, Surfactantless Conditions.

  Authors: Christopher Koenigsmann, Eli Sutter, Thomas A Chiesa, Radoslav R Adzic, Stanislaus S Wong

  Nano letters. 03/2012;

  We have employed an ambient, template-based technique that is simple, efficient, and surfactantless to generate a series of bimetallic Pd(1-x)Au(x) and Pd(1-x)Pt(x) nanowires with control overWe have employed an ambient, template-based technique that is simple, efficient, and surfactantless to generate a series of bimetallic Pd(1-x)Au(x) and Pd(1-x)Pt(x) nanowires with control over composition and size. Our as-prepared nanowires maintain significantly enhanced activity toward oxygen reduction as compared with commercial Pt nanoparticles and other 1D nanostructures, as a result of their homogeneous alloyed structure. Specifically, Pd(9)Au and Pd(4)Pt nanowires possess oxygen reduction reaction (ORR) activities of 0.49 and 0.79 mA/cm(2), respectively, which are larger than the analogous value for commercial Pt nanoparticles (0.21 mA/cm(2)). In addition, core-shell Pt∼Pd(9)Au nanowires have been prepared by electrodepositing a Pt monolayer shell and the corresponding specific, platinum mass, and platinum group metal mass activities were found to be 0.95 mA/cm(2), 2.08 A/mg(Pt), and 0.16 A/mg(PGM), respectively. The increased activity and catalytic performance is accompanied by improved durability toward ORR.

• Efficient charge separation in multidimensional nanohybrids.

  Authors: Xiaohui Peng, James A Misewich, Stanislaus S Wong, Matthew Y Sfeir

  Nano letters. 11/2011; 11(11):4562-8.

  We report unidirectional charge transfer in multidimensional nanohybrids, consisting of a quantum dot, an electronically active molecular linker, and a carbon nanotube. After covalent attachment toWe report unidirectional charge transfer in multidimensional nanohybrids, consisting of a quantum dot, an electronically active molecular linker, and a carbon nanotube. After covalent attachment to the nanotube, only emission consistent with the negatively charged quantum dot exciton ion rather than the neutral exciton is observed, showing nearly monoexponential recombination kinetics and an average lifetime of 3.5 ns. Using kinetic models, we explain how charge transfer is biased at the expense of other decay pathways.

• Ambient surfactantless synthesis, growth mechanism, and size-dependent electrocatalytic behavior of high-quality, single crystalline palladium nanowires.

  Authors: Christopher Koenigsmann, Alexander C Santulli, Eli Sutter, Stanislaus S Wong

  ACS nano. 08/2011; 5(9):7471-87.

  In this report, we utilize the U-tube double diffusion device as a reliable, environmentally friendly method for the size-controlled synthesis of high-quality, single crystalline Pd nanowires. TheIn this report, we utilize the U-tube double diffusion device as a reliable, environmentally friendly method for the size-controlled synthesis of high-quality, single crystalline Pd nanowires. The nanowires grown in 200 and 15 nm polycarbonate template pores maintain diameters of 270 ± 45 nm and 45 ± 9 nm, respectively, and could be isolated either as individual nanowires or as ordered free-standing arrays. The growth mechanism of these nanowires has been extensively explored, and we have carried out characterization of the isolated nanowires, free-standing nanowire arrays, and cross sections of the filled template in order to determine that a unique two-step growth process predominates within the template pores. Moreover, as-prepared submicrometer and nanosized wires were studied by comparison with ultrathin 2 nm Pd nanowires in order to elucidate the size-dependent trend in oxygen reduction reaction (ORR) electrocatalysis. Subsequently, the desired platinum monolayer overcoating was reliably deposited onto the surface of the Pd nanowires by Cu underpotential deposition (UPD) followed by galvanic displacement of the Cu adatoms. The specific and platinum mass activity of the core-shell catalysts was found to increase from 0.40 mA/cm(2) and 1.01 A/mg to 0.74 mA/cm(2) and 1.74 A/mg as the diameter was decreased from the submicrometer size regime to the ultrathin nanometer range.

• Enhanced electrocatalytic performance of processed, ultrathin, supported Pd-Pt core-shell nanowire catalysts for the oxygen reduction reaction.

  Authors: Christopher Koenigsmann, Alexander C Santulli, Kuanping Gong, Miomir B Vukmirovic, Wei-ping Zhou, Eli Sutter, Stanislaus S Wong, Radoslav R Adzic

  Journal of the American Chemical Society. 06/2011; 133(25):9783-95.

  We report on the synthesis, characterization, and electrochemical performance of novel, ultrathin Pt monolayer shell-Pd nanowire core catalysts. Initially, ultrathin Pd nanowires with diameters ofWe report on the synthesis, characterization, and electrochemical performance of novel, ultrathin Pt monolayer shell-Pd nanowire core catalysts. Initially, ultrathin Pd nanowires with diameters of 2.0 ± 0.5 nm were generated, and a method has been developed to achieve highly uniform distributions of these catalysts onto the Vulcan XC-72 carbon support. As-prepared wires are activated by the use of two distinctive treatment protocols followed by selective CO adsorption in order to selectively remove undesirable organic residues. Subsequently, the desired nanowire core-Pt monolayer shell motif was reliably achieved by Cu underpotential deposition followed by galvanic displacement of the Cu adatoms. The surface area and mass activity of the acid and ozone-treated nanowires were assessed, and the ozone-treated nanowires were found to maintain outstanding area and mass specific activities of 0.77 mA/cm(2) and 1.83 A/mg(Pt), respectively, which were significantly enhanced as compared with conventional commercial Pt nanoparticles, core-shell nanoparticles, and acid-treated nanowires. The ozone-treated nanowires also maintained excellent electrochemical durability under accelerated half-cell testing, and it was found that the area-specific activity increased by ~1.5 fold after a simulated catalyst lifetime.

• Correlating titania morphology and chemical composition with dye-sensitized solar cell performance.

  Authors: Alexander C Santulli, Christopher Koenigsmann, Amanda L Tiano, Donald DeRosa, Stanislaus S Wong

  Nanotechnology. 06/2011; 22(24):245402.

  We have investigated the use of various morphologies, including nanoparticles, nanowires, and sea-urchins of TiO(2) as the semiconducting material used as components of dye-sensitized solar cellsWe have investigated the use of various morphologies, including nanoparticles, nanowires, and sea-urchins of TiO(2) as the semiconducting material used as components of dye-sensitized solar cells (DSSCs). Analysis of the solar cells under AM 1.5 solar irradiation reveals the superior performance of hydrothermally derived nanoparticles, by comparison with two readily available commercial nanoparticle materials, within the DSSC architecture. The sub-structural morphology of films of these nanostructured materials has been directly characterized using SEM and indirectly probed using dye desorption. Furthermore, the surfaces of these nanomaterials were studied using TEM in order to visualize their structure, prior to their application within DSSCs. Surface areas of the materials have been quantitatively analyzed by collecting BET adsorption and dye desorption data. Additional investigation using open circuit voltage decay measurements reveals the efficiency of electron conduction through each TiO(2) material. Moreover, the utilization of various chemically distinctive titanate materials within the DSSCs has also been investigated, demonstrating the deficiencies of using these particular chemical compositions within traditional DSSCs.

• Quantitatively probing the means of controlling nanoparticle assembly on surfaces.

  Authors: Jonathan M Patete, Xiaohui Peng, Joseph M Serafin, Stanislaus S Wong

  Langmuir : the ACS journal of surfaces and colloids. 05/2011; 27(10):5792-805.

  As a means of developing a simple, cost-effective, and reliable method for probing nanoparticle behavior, we have used atomic force microscopy to gain a quantitative 3D visual representation of theAs a means of developing a simple, cost-effective, and reliable method for probing nanoparticle behavior, we have used atomic force microscopy to gain a quantitative 3D visual representation of the deposition patterns of citrate-capped Au nanoparticles on a substrate as a function of (a) sample preparation, (b) the choice of substrate, (c) the dispersion solvent, and (d) the number of loading steps. Specifically, we have found that all four parameters can be independently controlled and manipulated in order to alter the resulting pattern and quantity of as-deposited nanoparticles. From these data, the sample preparation technique appears to influence deposition patterns most broadly, and the dispersion solvent is the most convenient parameter to use in tuning the quantity of nanoparticles deposited onto the surface under spin-coating conditions. Indeed, we have quantitatively measured the effect of surface coverage for both mica and silicon substrates under preparation techniques associated with (i) evaporation under ambient air, (ii) heat treatment, and (iii) spin-coating preparation conditions. In addition, we have observed a decrease in nanoparticle adhesion to a substrate when the ethylene glycol content of the colloidal dispersion solvent is increased, which had the effect of decreasing interparticle-substrate interactions. Finally, we have shown that substrates prepared by these diverse techniques have potential applicability in surface-enhanced Raman spectroscopy.

• Effect of morphology of ZnO nanostructures on their toxicity to marine algae.

  Authors: Xiaohui Peng, Shelagh Palma, Nicholas S Fisher, Stanislaus S Wong

  Aquatic toxicology (Amsterdam, Netherlands). 02/2011; 102(3-4):186-96.

  The influence of ZnO nanoparticle morphology on its toxicity for marine diatoms was evaluated. Four ZnO nanoparticle motifs, possessing distinctive sizes and shapes, were synthesized without addingThe influence of ZnO nanoparticle morphology on its toxicity for marine diatoms was evaluated. Four ZnO nanoparticle motifs, possessing distinctive sizes and shapes, were synthesized without adding surfactants. Diameters of ZnO spheres ranged from 6.3 nm to 15.7 nm, and lengths of rod-shaped particles were 242 nm to 862 nm. Their effects on the growth of the marine diatoms, Thalassiosira pseudonana, Chaetoceros gracilis, and Phaeodactylum tricornutum, were determined in laboratory cultures. Between 4.1 and 4.9% of the Zn from all types of nanoparticles dissolved within 72 h and was neither concentration dependent nor morphology dependent. Addition of all nanoparticles at all concentrations tested stopped growth of T. pseudonana and C. gracilis, whereas P. tricornutum was the least sensitive, with its growth rate inversely proportional to nanoparticle concentration. Bioaccumulation of Zn released from nanoparticles in T. pseudonana was sufficient to kill this diatom. The toxicity of rod-shaped particles to P. triocornutum was noted to be greater than that of the spheres. The overall results suggest that toxicity studies assessing the effects of nanoparticles on aquatic organisms need to consider both the dissolution of these particles and the cellular interaction of nanoparticle aggregates.

• Solution-based synthetic strategies for one-dimensional metal-containing nanostructures.

  Authors: Amanda L Tiano, Christopher Koenigsmann, Alexander C Santulli, Stanislaus S Wong

  Chemical communications (Cambridge, England). 11/2010; 46(43):8093-130.

  One-dimensional (1D) nanostructures, such as nanowires, nanotubes, nanorods, and nanoribbons, have attracted significant attention stemming from the plethora of interesting size-dependent and, moreOne-dimensional (1D) nanostructures, such as nanowires, nanotubes, nanorods, and nanoribbons, have attracted significant attention stemming from the plethora of interesting size-dependent and, more importantly, structure-related properties resulting from confinement effects. In particular, the novel properties of 1D nanostructures of metals and metal oxides (binary and ternary) render them as prime candidates for a wide range of applications including the fabrication of nanoscale devices associated with solar cells, energy storage, fuel cells, molecular computing and information storage, medical imaging, diagnosis and detection, drug delivery, sensors and catalysis. Thus, it has been simultaneously necessary and critical to create synthetic protocols for the production of these materials which not only are reliable and reproducible, but also can generate compositionally pure, monodisperse, highly crystalline products of a desired 1D morphology. Solution-based methodologies have demonstrated significant advantages over other approaches, as they are facile, simple, flexible, 'green' by nature, and can be applied to a wide range of nanomaterials with diverse chemical compositions. Moreover, these methods can often be scaled so as to produce large quantities of products which are advantageous from an applications' standpoint. Herein, we present synthetic advances associated with solution-based approaches. Specifically solvothermal/hydrothermal, molten salt, electrospinning, template-directed, solution/one-pot, and sol-gel methodologies are discussed with the primary goal of achieving the reproducible synthesis of 1D motifs of metals, binary metal oxides, and ternary metal oxide systems.

• Size-dependent infrared phonon modes and ferroelectric phase transition in BiFeO3 nanoparticles.

  Authors: Peng Chen, Xiaoshan Xu, Christopher Koenigsmann, Alexander C Santulli, Stanislaus S Wong, Janice L Musfeldt

  Nano letters. 10/2010; 10(11):4526-32.

  One emergent property of ferroelectric nanoparticles is the sized-induced structural distortion to a high-symmetry paraelectric phase at small particle sizes. Finite length scale effects can thus beOne emergent property of ferroelectric nanoparticles is the sized-induced structural distortion to a high-symmetry paraelectric phase at small particle sizes. Finite length scale effects can thus be advantageously employed to elucidate ferroelectric transition mechanisms. In this work, we combine infrared spectroscopy with group theory and lattice dynamics calculations to reveal the displacive nature of the ferroelectric transition in BiFeO3, a room temperature multiferroic. Systematic intensity and frequency trends in selected vibrational modes show that the paraelectric phase is Pm3m and the lowest frequency A1 feature is the soft mode that drives the first order transition. Finite length scale effects are also evident in the electronic structure with a red-shifted band gap in nanoscale BiFeO3 compared with that of the rhombohedral film, a result that can impact the development of ferroelectric photovoltaics and oxide-based electronics. Taken together, these findings demonstrate the foundational importance of size effects for enhancing the rich functionality and broad utility of transition metal oxides.

• Photoelectrochemical behaviour of anatase nanoporous films: effect of the nanoparticle organization.

  Authors: Teresa Lana-Villarreal, Yuanbing Mao, Stanislaus S Wong, Roberto Gómez

  Nanoscale. 09/2010; 2(9):1690-8.

  The photoelectrochemical behaviour of anatase thin films with different nanoarchitectures and the same active surface area (or thickness) has been studied in acidic media in the absence and in theThe photoelectrochemical behaviour of anatase thin films with different nanoarchitectures and the same active surface area (or thickness) has been studied in acidic media in the absence and in the presence of formic acid. The electrodes were composed of either wire-like nanocrystal aggregates or commercial TiO(2) nanoparticles. Cyclic voltammetry in the dark reveals a larger trap concentration in the band gap for the nanoparticulate (NP) electrodes, which can be ascribed to a larger number of intergrain boundaries. Also under illumination, the behaviour for both types of anatase structures significantly differs: water photooxidation arises at more negative potentials for the nanocolumnar (NC) electrodes. In the presence of an efficient hole acceptor such as HCOOH, significantly larger photocurrents were noted for the NC films as compared with those for the NP electrodes, with the photocurrent onset also shifted towards more positive potentials for the latter. These results point to a diminished electron recombination, which can be related with a smaller concentration of intergrain boundaries, together with a more efficient HCOOH hole transfer for the wire-like nanocrystal aggregate architecture. In addition, the oxygen reduction reaction is also favoured in the case of NC electrodes.

• Size-dependent enhancement of electrocatalytic performance in relatively defect-free, processed ultrathin platinum nanowires.

  Authors: Christopher Koenigsmann, Wei-ping Zhou, Radoslav R Adzic, Eli Sutter, Stanislaus S Wong

  Nano letters. 08/2010; 10(8):2806-11.

  We report on the synthesis, characterization, and electrocatalytic performance of ultrathin Pt nanowires with a diameter of less than 2 nm. An acid-wash protocol was employed in order to yield highlyWe report on the synthesis, characterization, and electrocatalytic performance of ultrathin Pt nanowires with a diameter of less than 2 nm. An acid-wash protocol was employed in order to yield highly exfoliated, crystalline nanowires with a diameter of 1.3 +/- 0.4 nm. The electrocatalytic activity of these nanowires toward the oxygen reduction reaction was studied in relation to the activity of both supported and unsupported Pt nanoparticles as well as with previously synthesized Pt nanotubes. Our ultrathin, acid-treated, unsupported nanowires displayed an electrochemical surface area activity of 1.45 mA/cm(2), which was nearly 4 times greater than that of analogous, unsupported platinum nanotubes and 7 times greater than that of commercial supported platinum nanoparticles.

• Mechanism-based tumor-targeting drug delivery system. Validation of efficient vitamin receptor-mediated endocytosis and drug release.

  Authors: Shuyi Chen, Xianrui Zhao, Jingyi Chen, Jin Chen, Larisa Kuznetsova, Stanislaus S Wong, Iwao Ojima

  Bioconjugate chemistry. 05/2010; 21(5):979-87.

  An efficient mechanism-based tumor-targeting drug delivery system, based on tumor-specific vitamin-receptor mediated endocytosis, has been developed. The tumor-targeting drug delivery system is aAn efficient mechanism-based tumor-targeting drug delivery system, based on tumor-specific vitamin-receptor mediated endocytosis, has been developed. The tumor-targeting drug delivery system is a conjugate of a tumor-targeting molecule (biotin: vitamin H or vitamin B-7), a mechanism-based self-immolative linker and a second-generation taxoid (SB-T-1214) as the cytotoxic agent. This conjugate (1) is designed to be (i) specific to the vitamin receptors overexpressed on tumor cell surface and (ii) internalized efficiently through receptor-mediated endocytosis, followed by smooth drug release via glutathione-triggered self-immolation of the linker. In order to monitor and validate the sequence of events hypothesized, i.e., receptor-mediated endocytosis of the conjugate, drug release, and drug-binding to the target protein (microtubules), three fluorescent/fluorogenic molecular probes (2, 3, and 4) were designed and synthesized. The actual occurrence of these processes was unambiguously confirmed by means of confocal fluorescence microscopy (CFM) and flow cytometry using L1210FR leukemia cells, overexpressing biotin receptors. The molecular probe 4, bearing the taxoid linked to fluorescein, was also used to examine the cell specificity (i.e., efficacy of receptor-based cell targeting) for three cell lines, L1210FR (biotin receptors overexpressed), L1210 (biotin receptors not overexpressed), and WI38 (normal human lung fibroblast, biotin receptor negative). As anticipated, the molecular probe 4 exhibited high specificity only to L1210FR. To confirm the direct correlation between the cell-specific drug delivery and anticancer activity of the probe 4, its cytotoxicity against these three cell lines was also examined. The results clearly showed a good correlation between the two methods. In the same manner, excellent cell-specific cytotoxicity of the conjugate 1 (without fluorescein attachment to the taxoid) against the same three cell lines was confirmed. This mechanism-based tumor-targeting drug delivery system will find a range of applications.

• Evaluating cytotoxicity and cellular uptake from the presence of variously processed TiO2 nanostructured morphologies.

  Authors: Jingyi Chen, Hongjun Zhou, Alexander C Santulli, Stanislaus S Wong

  Chemical research in toxicology. 05/2010; 23(5):871-9.

  We evaluated the cytotoxicity of various morphological classes of TiO(2) nanostructures (including 0-D nanoparticles, 1-D nanorods, and 3-D assemblies) toward living cells. These TiO(2)We evaluated the cytotoxicity of various morphological classes of TiO(2) nanostructures (including 0-D nanoparticles, 1-D nanorods, and 3-D assemblies) toward living cells. These TiO(2) nanostructures were modified with fluorescent dye molecules, mediated via a dopamine linkage, in order to facilitate a confocal study of their internalization. Specifically, we noted that both TiO(2) 1-D nanorods and 0-D nanoparticles could internalize into cells after 24 h of incubation time. However, only incubation with TiO(2) 1-D nanorods and 3-D micrometer-scale sea urchin-like assemblies at concentrations of up to 125 microg/mL yielded data suggestive of cell viabilities of close to 100%. Moreover, upon irradiation with UV light for periods of a few minutes at energy densities of up to 1 J/cm(2), we observed up to 60% mortality rates, indicative of the cytotoxic potential of photoirradiated TiO(2) nanostructures due to the generation of reactive oxygen species.

• Ambient large-scale template-mediated synthesis of high-aspect ratio single-crystalline, chemically doped rare-earth phosphate nanowires for bioimaging.

  Authors: Fen Zhang, Stanislaus S Wong

  ACS nano. 01/2010; 4(1):99-112.

  A simple and effective template-mediated protocol has been developed for the large-scale, room-temperature preparation of high-aspect-ratio, single-crystalline Tb-doped CePO(4) nanowires, measuringA simple and effective template-mediated protocol has been developed for the large-scale, room-temperature preparation of high-aspect-ratio, single-crystalline Tb-doped CePO(4) nanowires, measuring approximately 12 nm in diameter and over 10 mum in length. Moreover, we also isolated sheaf-like bundles of nanostructures. The synthesis mechanism likely involved a crystal splitting step. The resulting nanowires demonstrated an intense redox-sensitive green photoluminescence, which was exploited, in addition to their inherently high biocompatibility and low toxicity, for potential applications in biological imaging and labeling of cells.

• Water-Dispersible, Multifunctional, Magnetic, Luminescent Silica-Encapsulated Composite Nanotubes.

  Authors: Hongjun Zhou, Jingyi Chen, Eli Sutter, Mikhail Feygenson, M C Aronson, Stanislaus S Wong

  Small (Weinheim an der Bergstrasse, Germany). 12/2009;

  A multifunctional one-dimensional nanostructure incorporating both CdSe quantum dots (QDs) and Fe(3)O(4) nanoparticles (NPs) within a SiO(2)-nanotube matrix is successfully synthesized based on theA multifunctional one-dimensional nanostructure incorporating both CdSe quantum dots (QDs) and Fe(3)O(4) nanoparticles (NPs) within a SiO(2)-nanotube matrix is successfully synthesized based on the self-assembly of preformed functional NPs, allowing for control over the size and amount of NPs contained within the composite nanostructures. This specific nanostructure is distinctive because both the favorable photoluminescent and magnetic properties of QD and NP building blocks are incorporated and retained within the final silica-based composite, thus rendering it susceptible to both magnetic guidance and optical tracking. Moreover, the resulting hydrophilic nanocomposites are found to easily enter into the interiors of HeLa cells without damage, thereby highlighting their capability not only as fluorescent probes but also as possible drug-delivery vehicles of interest in nanobiotechnology.

• Optical nanocrystallography with tip-enhanced phonon Raman spectroscopy.

  Authors: Samuel Berweger, Catalin C Neacsu, Yuanbing Mao, Hongjun Zhou, Stanislaus S Wong, Markus B Raschke

  Nature nanotechnology. 09/2009; 4(8):496-9.

  Conventional phonon Raman spectroscopy is a powerful experimental technique for the study of crystalline solids that allows crystallography, phase and domain identification on length scales down toConventional phonon Raman spectroscopy is a powerful experimental technique for the study of crystalline solids that allows crystallography, phase and domain identification on length scales down to approximately 1 microm. Here we demonstrate the extension of tip-enhanced Raman spectroscopy to optical crystallography on the nanoscale by identifying intrinsic ferroelectric domains of individual BaTiO(3) nanocrystals through selective probing of different transverse optical phonon modes in the system. The technique is generally applicable for most crystal classes, and for example, structural inhomogeneities, phase transitions, ferroic order and related finite-size effects occurring on nanometre length scales can be studied with simultaneous symmetry selectivity, nanoscale sensitivity and chemical specificity.

• Synthesis and characterization of V(2)O(3) nanorods.

  Authors: Alexander C Santulli, Wenqian Xu, John B Parise, Liusuo Wu, M C Aronson, Fen Zhang, Chang-Yong Nam, Charles T Black, Amanda L Tiano, Stanislaus S Wong

  Physical chemistry chemical physics : PCCP. 06/2009; 11(19):3718-26.

  In this work, VO(2) nanorods have been initially generated as reactive nanoscale precursors to their subsequent conversion to large quantities of highly crystalline V(2)O(3) with no detectableIn this work, VO(2) nanorods have been initially generated as reactive nanoscale precursors to their subsequent conversion to large quantities of highly crystalline V(2)O(3) with no detectable impurities. Structural changes in VO(2), associated with the metallic-to-insulating transition from the monoclinic form to the rutile form, have been investigated and confirmed using X-ray diffraction and synchrotron data, showing that the structural transition is reversible and occurs at around 63 degrees C. When this VO(2) one-dimensional sample was subsequently heated to 800 degrees C in a reducing atmosphere, it was successfully transformed into V(2)O(3) with effective retention of its nanorod morphology. We have also collected magnetic and transport data on these systems that are comparable to bulk behavior and consistent with trends observed in previous experiments.

• Carbon nanotube-nanocrystal heterostructures.

  Authors: Xiaohui Peng, Jingyi Chen, James A Misewich, Stanislaus S Wong

  Chemical Society reviews. 05/2009; 38(4):1076-98.

  The importance of generating carbon nanotube-nanoparticle heterostructures is that these composites ought to take advantage of and combine the unique physical and chemical properties of both carbonThe importance of generating carbon nanotube-nanoparticle heterostructures is that these composites ought to take advantage of and combine the unique physical and chemical properties of both carbon nanotubes and nanoparticles in one discrete structure. These materials have potential applicability in a range of diverse fields spanning heterogeneous catalysis to optoelectronic device development, of importance to chemists, physicists, materials scientists, and engineers. In this critical review, we present a host of diverse, complementary strategies for the reliable synthesis of carbon nanotube-nanoparticle heterostructures using both covalent as well as non-covalent protocols, incorporating not only single-walled and multi-walled carbon nanotubes but also diverse classes of metallic and semiconducting nanoparticles (221 references).

• Functionalized single-walled carbon nanotubes as rationally designed vehicles for tumor-targeted drug delivery.

  Authors: Jingyi Chen, Shuyi Chen, Xianrui Zhao, Larisa V Kuznetsova, Stanislaus S Wong, Iwao Ojima

  Journal of the American Chemical Society. 01/2009; 130(49):16778-85.

  A novel single-walled carbon nanotube (SWNT)-based tumor-targeted drug delivery system (DDS) has been developed, which consists of a functionalized SWNT linked to tumor-targeting modules as well asA novel single-walled carbon nanotube (SWNT)-based tumor-targeted drug delivery system (DDS) has been developed, which consists of a functionalized SWNT linked to tumor-targeting modules as well as prodrug modules. There are three key features of this nanoscale DDS: (a) use of functionalized SWNTs as a biocompatible platform for the delivery of therapeutic drugs or diagnostics, (b) conjugation of prodrug modules of an anticancer agent (taxoid with a cleavable linker) that is activated to its cytotoxic form inside the tumor cells upon internalization and in situ drug release, and (c) attachment of tumor-recognition modules (biotin and a spacer) to the nanotube surface. To prove the efficacy of this DDS, three fluorescent and fluorogenic molecular probes were designed, synthesized, characterized, and subjected to the analysis of the receptor-mediated endocytosis and drug release inside the cancer cells (L1210FR leukemia cell line) by means of confocal fluorescence microscopy. The specificity and cytotoxicity of the conjugate have also been assessed and compared with L1210 and human noncancerous cell lines. Then, it has unambiguously been proven that this tumor-targeting DDS works exactly as designed and shows high potency toward specific cancer cell lines, thereby forming a solid foundation for further development.

• A facile and mild synthesis of 1-D ZnO, CuO, and alpha-Fe(2)O(3) nanostructures and nanostructured arrays.

  Authors: Hongjun Zhou, Stanislaus S Wong

  ACS nano. 06/2008; 2(5):944-58.

  ZnO nanowires, CuO nanowires, and alpha-Fe(2)O(3) nanotubes as well as their corresponding arrays have been successfully synthesized via a low cost, generalizable, and simplistic template method.ZnO nanowires, CuO nanowires, and alpha-Fe(2)O(3) nanotubes as well as their corresponding arrays have been successfully synthesized via a low cost, generalizable, and simplistic template method. Diameters of one-dimensional (1-D) metal oxide nanostructures ( approximately 60-260 nm), measuring micrometers in length, can be reliably and reproducibly controlled by the template pore channel dimensions. Associated vertically aligned arrays have been attached to the surfaces of a number of geometrically significant substrates, such as curved plastic and glass rod motifs. The methodology reported herein relies on the initial formation of an insoluble metal hydroxide precursor, initially resulting from the reaction of the corresponding metal solution and sodium hydroxide, and its subsequent transformation under mild conditions into the desired metal oxide nanostructures. Size- and shape-dependent optical, magnetic, and catalytic properties of as-prepared 1-D metal oxides were investigated and noted to be mainly comparable to or better than the associated properties of the corresponding bulk oxides. A plausible mechanism for as-observed wire and tube-like motifs is also discussed.