Directional Self-Assembly of Ligand-Stabilized Gold Nanoparticles into Hollow Vesicles through Dynamic Ligand Rearrangement

Hickey, Robert J.,Seo, Myungjoo,Luo, Qingjie,Park, So-Jung American Chemical Society 2015 Langmuir Vol.31 No.14

<P>Here we report a novel approach to prepare all-nanoparticle vesicles using ligand-stabilized gold particles as a building block. Hydroxyalkyl-terminated gold nanoparticles were spontaneously organized into well-defined hollow vesicle-like assemblies in water without any template. The unusual anisotropic self-assembly was attributed to the ligand rearrangement on nanoparticles, which leads to increased hydroxyl group density at the nanoparticle/water interface. One-dimensional strings were formed instead of vesicles with increasing surface ligand density, which supports the hypothesis. The size and the wall thickness of vesicles were controlled by adjusting the concentration of nanoparticles or by adding extra surfactants. The work presented here highlights the dynamic nature of surface ligands on gold particles and demonstrates that the combination of ligand rearrangement and the hydrophobic effect can be used as a versatile tool for anisotropic self-assembly of nanoparticles.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2015/langd5.2015.31.issue-14/la503903n/production/images/medium/la-2014-03903n_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la503903n'>ACS Electronic Supporting Info</A></P>

Size-Controlled Self-Assembly of Superparamagnetic Polymersomes

Hickey, Robert J.,Koski, Jason,Meng, Xin,Riggleman, Robert A.,Zhang, Peijun,Park, So-Jung American Chemical Society 2014 ACS NANO Vol.8 No.1

<P>We report the size-controlled self-assembly of polymersomes through the cooperative self-assembly of nanoparticles and amphiphilic polymers. Polymersomes densely packed with magnetic nanoparticles in the polymersome membrane (magneto-polymersome) were fabricated with a series of different sized iron oxide nanoparticles. The distribution of nanoparticles in a polymersome membrane was size-dependent; while small nanoparticles were dispersed in a polymer bilayer, large particles formed a well-ordered superstructure at the interface between the inner and outer layer of a bilayer membrane. The yield of magneto-polymersomes increased with increasing the diameter of incorporated nanoparticles. Moreover, the size of the polymersomes was effectively controlled by varying the size of incorporated nanoparticles. This size-dependent self-assembly was attributed to the polymer chain entropy effect and the size-dependent localization of nanoparticles in polymersome bilayers. The transverse relaxation rates (<I>r</I><SUB>2</SUB>) of magneto-polymersomes increased with increasing the nanoparticle diameter and decreasing the size of polymersomes, reaching 555 ± 24 s<SUP>–1</SUP> mM<SUP>–1</SUP> for 241 ± 16 nm polymersomes, which is the highest value reported to date for superparamagnetic iron oxide nanoparticles.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-1/nn405012h/production/images/medium/nn-2013-05012h_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn405012h'>ACS Electronic Supporting Info</A></P>

Shape-controlled syntheses of metal oxide nanoparticles by the introduction of rare-earth metals

Song, H. W.,Kim, N. Y.,Park, J. e.,Ko, J. H.,Hickey, R.,Kim, Y. H.,Park, S. J. Royal Society of Chemistry 2017 Nanoscale Vol.9 No.8

<P>Here, we report the size- and shape-controlled synthesis of metal oxide nanoparticles through the introduction of rare-earth metals. The addition of gadolinium oleate in the synthesis of iron oxide nanoparticles induced sphere-to-cube shape changes of nanoparticles and generated iron oxide nanocubes coated with gadolinium. Based on experimental investigations and density functional theory (DFT) calculations, we attribute the shape change to the facet-selective binding of undecomposed gadolinium oleates. While many previous studies on the shape-controlled syntheses of nanoparticles rely on the stabilization of specific crystal facets by anionic surfactants or their decomposition products, this study shows that the interaction between growing transition metal oxide nanoparticles and rare-earth metal complexes can be used as a robust new mechanism for shape-controlled syntheses. Indeed, we demonstrated that this approach was applicable to other transition metal oxide nanoparticles (i.e., manganese oxide and manganese ferrite) and rare earth metals (i.e., gadolinium, europium, and cerium). This study also demonstrates that the nature of metal-ligand bonding can play an important role in the shape control of nanoparticles.</P>

OZONE SENSING PROPERTIES OF THERMALLY EVAPORATED In2O3-BASED THIN FILMS

K. ARSHAK,G. HICKEY,E. FORDE,J. HARRIS 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2008 NANO Vol.3 No.4

Ozone sensing properties of mixed oxides of In2O3, ZnO, and SnO2 in the form of thin films are explored. Exposure to ozone causes defects in the materials, and subsequently causes changes in the materials properties. In this work, a cost-effective, room temperature, real-time ozone monitoring device has been developed. The fabricated sensors are capable of detecting threshold ozone safety levels proposed by the World Health Organization (WHO) while operating at room temperature. Room temperature operation offers many advantages over high temperature operation, such as reduced power consumption, reduced fabrication costs, and ease of implementation into portable devices, such as laptops and mobile phones. The fabrication of these sensors was carried out by means of an Edwards E306A Coating System. Various mixtures of In2O3, ZnO, and snO2 were deposited in a rectangular pattern on top of copperinterdigitated electrodes. X-ray Photo Spectroscopy (XPS) analysis showed that there were levels of impurities in the sensor samples, which were dependant on the fabrication process and parameters. XPS analysis also gave a detailed account of the shifts in binding energies of the thin oxide layers. The results presented show that the highest response to environmentally relevant ozone concentrations is achieved with a very thin sensing layer and a high deposition rate. The performance of the sensors has been investigated and compared.

SUNSHINE, EARTHSHINE AND CLIMATE CHANGE: II. SOLAR ORIGINS OF VARIATIONS IN THE EARTH’S ALBEDO

P.R.Goode,E.Pall,V.Yurchyshyn,J.Qiu,J.Hickey,P.Monta?esRodriguez,M.-C.Chu,E.Kolbe,C.T.Brown,S.E.Koonin 한국천문학회 2003 Journal of The Korean Astronomical Society Vol.36 No.2

SUNSHINE, EARTHSHINE AND CLIMATE CHANGE: II. SOLAR ORIGINS OF VARIATIONS IN THE EARTH'S ALBEDO

GOODE P. R.,PALLE E.,YURCHYSHYN V.,QIU J.,HICKEY J.,RODRIGUEZ P. MONTANES,CHU M.-C.,KOLBE E.,BROWN C.T.,KOONIN S.E. The Korean Astronomical Society 2003 Journal of The Korean Astronomical Society Vol.36 No.suppl1

There are terrestrial signatures of the solar activity cycle in ice core data (Ram & Stoltz 1999), but the variations in the sun's irradiance over the cycle seem too small to account for the signature (Lean 1997; Goode & Dziembowski 2003). Thus, one would expect that the signature must arise from an indirect effect(s) of solar activity. Such an indirect effect would be expected to manifest itself in the earth's reflectance. Further, the earth's climate depends directly on the albedo. Continuous observations of the earthshine have been carried out from Big Bear Solar Observatory since December 1998, with some more sporadic measurements made during the years 1994 and 1995. We have determined the annual albedos both from our observations and from simulations utilizing the Earth Radiation Budget Experiment (ERBE) scene model and various datasets for the cloud cover, as well as snow and ice cover. With these, we look for inter-annual and longer-term changes in the earth's total reflectance, or Bond albedo. We find that both our observations and simulations indicate that the albedo was significantly higher during 1994-1995 (activity minimum) than for the more recent period covering 1999-2001 (activity maximum). However, the sizes of the changes seem somewhat discrepant. Possible indirect solar influences on the earth's Bond albedo are discussed to emphasize that our earthshine data are already sufficiently precise to detect, if they occur, any meaningful changes in the earth's reflectance. Still greater precision will occur as we expand our single site observations to a global network.