Stellachi Nanoparticles

Copyright 2015 American Chemical Society (ACS). All Rights Reserved.



1. Contact angle and adsorption energies of nanoparticles at the air-liquid interface determined by neutron reflectivity andmolecular dynamics

By Reguera, Javier; Ponomarev, Evgeniy; Geue, Thomas; Stellacci, Francesco; Bresme, Fernando; Moglianetti, MauroFrom Nanoscale (2015), 7(13), 5665-5673. Language: English, Database: CAPLUS, DOI:10.1039/C5NR00620A

Understanding how nanomaterials interact with interfaces is essential to control their self-assembly as well as theiroptical, electronic, and catalytic properties. We present here an exptl. approach based on neutron reflectivity (NR) thatallows the in situ measurement of the contact angles of nanoparticles adsorbed at fluid interfaces. Because our methodprovides a route to quantify the adsorption and interfacial energies of the nanoparticles in situ, it circumvents problemsassocd. with existing indirect methods, which rely on the transport of the monolayers to substrates for further anal. Weillustrate the method by measuring the contact angle of hydrophilic and hydrophobic gold nanoparticles, coated withperdeuterated octanethiol (d-OT) and with a mixt. of d-OT and mercaptohexanol (MHol), resp. The contact angles werealso calcd. via atomistic mol. dynamics (MD) computations, showing excellent agreement with the exptl. data. Ourmethod opens the route to quantify the adsorption of complex nanoparticle structures adsorbed at fluid interfacesfeaturing different chem. compns.~0 Citings

2. Comparative STM studies of mixed ligand monolayers on gold nanoparticles in air and in 1-phenyloctaneBy Ong, Quy Khac; Zhao, Shun; Reguera, Javier; Biscarini, Fabio; Stellacci, FrancescoFrom Chemical Communications (Cambridge, United Kingdom) (2014), 50(72), 10456-10459. Language: English,Database: CAPLUS, DOI:10.1039/C4CC04114C

Scanning tunnelling microscopy (STM) studies have found stripe-like domains on gold nanoparticles (NPs) coated withcertain binary mixts. of ligand mols. The majority of these NPs' properties have been investigated for particles insolvents. Yet, most STM studies are for NPs in a dry state. Images of the same particles in air and liq. have not beenobtained yet. In this work, a judicious choice of ligand mols. led to NPs with close-to-ideal STM imaging conditions in airand in 1-phenyloctane (PO). Large datasets under both conditions were acquired and rapidly evaluated through powerspectral d. (PSD) anal. The result is a quant. comparison of stripe-like domains in air and PO on the same NPs. PSDanal. dets. a characteristic length-scale for these domains of 1.0 nm in air and in PO showing persistence of stripeddomains in these two media. A length scale of 0.7 nm for homo-ligand NPs was found.~1 Citing

3. Change of Luminescence Properties of Europium Ions Captured by Mixed-Ligand Silver NanoparticlesBy Cho, Eun Seon; Yokoyama, Takahiro; Ertem, Elif; Stellacci, FrancescoFrom Israel Journal of Chemistry (2014), 54(5-6), 708-711. Language: English, Database: CAPLUS,DOI:10.1002/ijch.201400069

We present herein silver nanoparticles about 4 nm in diam. coated with a binary mixt. of 1-octanethiol and 2-(2-{2-[(6-mercaptohexyl)oxy]ethoxy}ethoxy)ethanol. These particles show an affinity towards optically active Eu3+ ions. The effectof the nanoparticle on the characteristic emission peaks of Eu3+ is investigated. We use the variation in emission spectraof the ion to establish its binding to the nanoparticles.~0 Citings

4. A general mechanism for intracellular toxicity of metal-containing nanoparticlesBy Sabella, Stefania; Carney, Randy P.; Brunetti, Virgilio; Malvindi, Maria Ada; Al-Juffali, Noura; Vecchio, Giuseppe;Janes, Sam M.; Bakr, Osman M.; Cingolani, Roberto; Stellacci, Francesco; et alFrom Nanoscale (2014), 6(12), 7052-7061. Language: English, Database: CAPLUS, DOI:10.1039/c4nr01234h

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The assessment of the risks exerted by nanoparticles is a key challenge for academic, industrial, and regulatorycommunities worldwide. Exptl. evidence points towards significant toxicity for a range of nanoparticles both in vitro andin vivo. Worldwide efforts aim at uncovering the underlying mechanisms for this toxicity. Here, we show that theintracellular ion release elicited by the acidic conditions of the lysosomal cellular compartment - where particles areabundantly internalized - is responsible for the cascading events assocd. with nanoparticles-induced intracellular toxicity.We call this mechanism a "lysosome-enhanced Trojan horse effect" since, in the case of nanoparticles, the protectivecellular machinery designed to degrade foreign objects is actually responsible for their toxicity. To test our hypothesis,we compare the toxicity of similar gold particles whose main difference is in the internalization pathways. We show thatparticles known to pass directly through cell membranes become more toxic when modified so as to be mostlyinternalized by endocytosis. Furthermore, using expts. with chelating and lysosomotropic agents, we found that thetoxicity mechanism for different metal contg. NPs (such as metallic, metal oxide, and semiconductor NPs) is mainlyassocd. with the release of the corresponding toxic ions. Finally, we show that particles unable to release toxic ions(such as stably coated NPs, or diamond and silica NPs) are not harmful to intracellular environments.~14 Citings

5. Scanning tunneling microscopy and small angle neutron scattering study of mixed monolayer protected goldnanoparticles in organic solvents

By Moglianetti, Mauro; Ong, Quy Khac; Reguera, Javier; Harkness, Kellen M.; Mameli, Marta; Radulescu, Aurel;Kohlbrecher, Joachim; Jud, Corinne; Svergun, Dmitri I.; Stellacci, FrancescoFrom Chemical Science (2014), 5(3), 1232-1240. Language: English, Database: CAPLUS, DOI:10.1039/c3sc52595c

When a binary mixt. of ligand mols. is used to coat gold nanoparticles, stripe-like domains can occur. Thesenanodomains confer nanoparticles unique structure-dependent properties. The domain structure has been characterizedprimarily using scanning tunneling microscopy (STM) in air and in vacuum. Here we show the first STM images ofstriped nanoparticles in a solvent, 1-phenyloctane. We achieve stable imaging conditions on dodecanethiol-hexanethiol(C12 : C6) 2 : 1 protected gold nanoparticles. These features are persistent across many images and retain theirdirection and overall morphol. when recorded at different scan angles. We also perform small angle neutron scattering(SANS) on two hybrid C6 : C12 nanoparticle samples dissolved in chloroform. The hybrid nanoparticles have the samecompn. and size distribution as samples imaged with STM, but one of the two ligands (either C6 or C12) is deuterated.Low resoln. models reconstructed ab initio by simultaneous fitting of the SANS data reveal striped patterns of C6 andC12 on the gold surface. We use image anal. to quant. compare STM and SANS data, achieving remarkable agreement.This is the first paper to compare evidence of the existence of stripe-like domains for particles in soln. using twoindependent techniques, and we believe that a combination of STM and SANS could become a major approach tocharacterize mixed ligand nanomaterials in soln.~6 Citings

6. Nanoscale Topography and Chemistry Affect Embryonic Stem Cell Self-Renewal and Early DifferentiationBy LaPointe, Vanessa L. S.; Fernandes, Ana Tiago; Bell, Nia C.; Stellacci, Francesco; Stevens, Molly M.From Advanced Healthcare Materials (2013), 2(12), 1644-1650. Language: English, Database: CAPLUS,DOI:10.1002/adhm.201200382

Adherent cells respond to a wide range of substrate cues, including chem., topog., hydrophobicity, and surface energy.The cell-substrate interface is therefore an important design parameter in regenerative medicine and tissue engineeringapplications, where substrate cues are used to influence cell behavior. Thin films comprising 4.5 nm (av. diam.) goldnanoparticles coated with a mixt. of two alkanethiols can confer hemispherical topog. and specific chem. to bulksubstrates. The behavior of murine embryonic stem cells (ESCs) on the thin films can then be compared with theirbehavior on self-assembled monolayers of the same alkanethiols on vapor-deposited gold, which lack the topog.features. Cells cultured both with and without differentiation inhibitors are characterized by immunofluorescence for Oct4and qPCR for Fgf5, Foxa2, Nanog, Pou5f1, and Sox2. Nanoscale chem. and topog. are found to influence stem celldifferentiation, particularly the early differentiation markers, Fgf5 and Foxa2. Nanoscale topog. also affects Oct4localization, whereas the chem. compn. of the substrate does not have an effect. It is demonstrated for the first time thatESCs can sense topog. features established by 4.5 nm particles, and these findings suggest that nanoscale chem. andtopog. can act synergistically to influence stem cell differentiation. This study furthers the understanding of the effects ofthese substrate properties, improving our ability to design materials to control stem cell fate.~5 Citings

7. Gold nanoparticles protected by fluorinated ligands for 19F MRI

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By Boccalon, Mariangela; Franchi, Paola; Lucarini, Marco; Delgado, Juan Jose; Sousa, Fernanda; Stellacci,Francesco; Zucca, Ileana; Scotti, Alessandro; Spreafico, Roberto; Pengo, Paolo; et alFrom Chemical Communications (Cambridge, United Kingdom) (2013), 49(78), 8794-8796. Language: English,Database: CAPLUS, DOI:10.1039/c3cc44572k

Gold nanoparticles coated with fluorinated ligands (F-MPCs) present features suitable for 19F MRI as obsd. fromphantom expts. Cellular uptake, by HeLa cells, and toxicity of fluorescent dye-decorated F-MPCs are presented togetherwith their ability to bind hydrophobic mols. allowing for a potential combination of targeting, delivery and imaging features.~6 Citings

8. Colloidal Stability of Self-Assembled Monolayer-Coated Gold Nanoparticles: The Effects of Surface Compositional andStructural Heterogeneity

By Huang, Rixiang; Carney, Randy P.; Stellacci, Francesco; Lau, Boris L. T.From Langmuir (2013), 29(37), 11560-11566. Language: English, Database: CAPLUS, DOI:10.1021/la4020674

Surface heterogeneity plays an important role in controllingcolloidal phenomena. This study studied the self-aggregationand bacterial adsorption of self-assembled monolayer coatedgold nanoparticles (AuNPs) with different surface compositionaland structural heterogeneity. Evaluation was performed onAuNPs coated with (1) one ligand with charged terminals(MUS), (2) two homogeneously distributed ligands with resp.charged and nonpolar terminals (brOT) and (3) two ligands withresp. charged and nonpolar terminals with stripe-likedistribution (OT). The brOT particles have less neg.electrophoretic mobility (EPM) values, smaller crit. coagulationconcn. (CCC) and larger adsorption rate on Escherichia colithan that of AuNPs with homogeneously charged groups, ingood agreement with DLVO predictions. Although the ligandcompn. on the surface of AuNPs is the same, OT particleshave less neg. EPM values and faster rate of bacterialadsorption, but much larger CCC compared to brOT. Thedeviation of OT particles from brOT and MUS in their self-aggregation behavior reflects the effects of surfaceheterogeneity on elec. double layer structures at the interface.Results from the present study demonstrated that, besideschem. compn., organization of ligands on particle surface isimportant in detg. their colloidal stability.

~5 Citings

9. Protein-nanoparticle interactions: the effects of surface compositional and structural heterogeneity are scaledependent

By Huang, Rixiang; Carney, Randy P.; Stellacci, Francesco; Lau, Boris L. T.From Nanoscale (2013), 5(15), 6928-6935. Language: English, Database: CAPLUS, DOI:10.1039/c3nr02117c

Nanoparticles (NPs) in the biol. environment are exposed to a large variety and concn. of proteins. Proteins are knownto adsorb in a corona' like structure on the surface of NPs. In this study, we focus on the effects of surface compositionaland structural heterogeneity on protein adsorption by examg. the interaction of self-assembled monolayer coated goldNPs (AuNPs) with two types of proteins: ubiquitin and fibrinogen. This work was designed to systematically investigatethe role of surface heterogeneity in nanoparticle-protein interaction. We have chosen the particles as well as the proteinsto provide different types (in distribution and length-scale) of heterogeneity. The goal was to unveil the role ofheterogeneity and of its length-scale in the particle-protein interaction. Dynamic light scattering and CD spectroscopywere used to reveal different interactions at pH above and below the isoelec. points of the proteins, which is related tothe charge heterogeneity on the protein surface. At pH 7.4, there was only a monolayer of proteins adsorbed onto theNPs and the secondary structure of proteins remained intact. At pH 4.0, large aggregates of nanoparticle-proteincomplexes were formed and the secondary structures of the proteins were significantly disrupted. In terms of interactionthermodn., results from isothermal titrn. calorimetry showed that ubiquitin adsorbed differently onto (1) AuNPs withcharged and nonpolar terminals organized into nano-scale structure (66-34 OT), (2) AuNPs with randomly distributedterminals (66-34 brOT), and (3) AuNPs with homogeneously charged terminals (MUS). This difference in adsorptionbehavior was not obsd. when AuNPs interacted with fibrinogen. The results suggested that the interaction between theproteins and AuNPs was influenced by the surface heterogeneity on the AuNPs, and this influence depends on the scaleof surface heterogeneity and the size of the proteins.

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~12 Citings

10. Determination of monolayer-protected gold nanoparticle ligand-shell morphology using NMRBy Liu, Xiang; Yu, Miao; Kim, Hyewon; Mameli, Marta; Stellacci, FrancescoFrom Nature Communications (2012), 3(Nov.), 2155/1-2155/9. Language: English, Database: CAPLUS,DOI:10.1038/ncomms2155

It is accepted that the ligand shell morphol. of nanoparticles coated with a monolayer of mols. can be partly responsiblefor important properties such as cell membrane penetration and wetting. When binary mixts. of mols. coat ananoparticle, they can arrange randomly or sep. into domains, for example, forming Janus, patchy or striped particles.To date, there is no straightforward method for the detn. of such structures. Here we show that a combination of one-dimensional and two-dimensional NMR can be used to det. the ligand shell structure of a series of particles covered withaliph. and arom. ligands of varying compn. This approach is a powerful way to det. the ligand shell structure of patchyparticles; it has the limitation of needing a whole series of compns. and ligands' combinations with NMR peaks well sepd.and whose shifts due to the surrounding environment can be large enough.~3 Citings

11. Electrical Method to Quantify Nanoparticle Interaction with Lipid BilayersBy Carney, Randy P.; Astier, Yann; Carney, Tamara M.; Voitchovsky, Kislon; Jacob Silva, Paulo H.; Stellacci,FrancescoFrom ACS Nano (2013), 7(2), 932-942. Language: English, Database: CAPLUS, DOI:10.1021/nn3036304

Understanding as well as rapidly screening the interaction ofnanoparticles with cell membranes is of central importance forbiol. applications such as drug and gene delivery. Recently, wehave shown that "striped" mixed-monolayer-coated goldnanoparticles spontaneously penetrate a variety of cellmembranes through a passive pathway. Here, we report anelec. approach to screen and readily quantify the interactionbetween nanoparticles and bilayer lipid membranes.Membrane adsorption is monitored through the capacitiveincrease of suspended planar lipid membranes upon fusionwith nanoparticles. We adopt a Langmuir isotherm model tocharacterize the adsorption of nanoparticles by bilayer lipidmembranes and ext. the partition coeff., K, and the std. freeenergy gain by this spontaneous process, for a variety of sizesof cell-membrane-penetrating nanoparticles. We believe thatthe method presented here will be a useful qual. and quant.tool to det. nanoparticle interaction with lipid bilayers andconsequently with cell membranes.

~14 Citings

12. Dynamic cellular uptake of mixed-monolayer protected nanoparticlesBy Carney, Randy P.; Carney, Tamara M.; Mueller, Marie; Stellacci, FrancescoFrom Biointerphases (2012), 7(1-4), 17. Language: English, Database: CAPLUS, DOI:10.1007/s13758-011-0017-3

Nanoparticles (NPs) are gaining increasing attention for potential application in medicine; consequently, studying theirinteraction with cells is of central importance. Both ligand arrangement and compn. on gold nanoparticles play a crucialrole in their cellular internalization. Previosly shown that 66-34OT nanoparticles coated with stripe-like domains ofhydrophobic (octanethiol, OT, 34%) and hydrophilic (11-mercaptoundecane sulfonate, MUS, 66%) ligands permeatedthrough the cellular lipid bilayer via passive diffusion, in addn. to endo-/pino-cytosis. NP internalization by DC2.4, 3T3,and HeLa cells were analyzed at two temps. and multiple time points. Four NPs that differ in their surface structures andligand compns. and report on their cellular internalization by intracellular fluorescence quantification. Using confocallaser scanning microscopy we have found that all three cell types internalize the 66-34OT NPs more than particlescoated only with MUS, or particles coated with a very similar coating but lacking any detectable ligand shell structure, or'striped' particles but with a different compn. (34-66OT) at multiple data points.

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~13 Citings

13. New mixed ligand coated platinum nanoparticles for heterogeneous catalytic applicationsBy Ghosh, Anirban; Stellacci, Francesco; Kumar, RajivFrom Catalysis Today (2012), 198(1), 77-84. Language: English, Database: CAPLUS,DOI:10.1016/j.cattod.2012.03.079

A series of platinum nanoparticles was prepd. for the first time in presence of one hydrophobic ligand and one hydrophilicligand contg. terminal sulfonic acid headgroup. This mixed ligand combination causes stripe-like domains circumscribingthe nanoparticles, thereby enhancing the catalytic efficiency compared to single ligand coated Pt nanocatalysts. Thiscould be achieved by strategically replacing the hydrophilic ligand (3-mercaptopropane-1-sulfonic acid or MPSA) withhydrophobic ligands (linear alkanethiols like 1-octanethiol or OT) on the surface of the nanoparticles. Apart from theligand compn., the metallic core of the nanocomposite also influences the catalytic efficiency of the ligand shell through asynergistic effect. Herein we report the effects of ligand shell compn. and structure on the efficiency of thenanocomposites on catalytic acylation reactions. Quite high conversion of benzyl alc. to benzyl acetate (with >99%selectivity) was obsd. when acetic acid was used as the acetylating reagent and MPSA-OT-Pt as nanocatalyst at 80 C.The turnover frequency of reaction using MPSA-OT-Pt nanocatalyst was found to be an order of magnitude higher thanthat using well known solid acid catalyst zeolite USY under identical reaction conditions. Further, the selectivity towardbenzyl acetate using USY was 80%, the remaining 20% being dibenzylether. It was also found that the MPSA-OT-Ptnanocatalyst system shows higher activity than gold nanoparticles coated with same set of ligands (such as MPSA-OT-Au nanocatalyst). Addnl., the effects of changing the substrate (such as 1-butanol) and the acylating agent (such aspropionic acid) were also studied.~5 Citings

14. Molecular dynamics study of the effects of nanoscale surface patterning on the interfacial properties of mixed-monolayer protected nanoparticles

By Jiang, Hao; Stellacci, Francesco; Glotzer, Sharon C.From Abstracts of Papers, 243rd ACS National Meeting & Exposition, San Diego, CA, United States, March 25-29,2012 (2012), PHYS-5. Language: English, Database: CAPLUS

Recent expts. have shown that surface structure has significant influence on the interfacial properties of substratesprotected by mixed surfactant monolayers. Interestingly, the total work of adhesion of a monolayer-protectednanoparticle (NP) varies non-monotonically with the size of the striped surface domains of the hydrophilic andhydrophobic coating mols. We investigated the mol. mechanisms of this non-monotonic behavior using mol. dynamics(MD) simulations. Our simulations revealed that the mol. organization of the interfacial water is substantially affected bythe sizes of the hydrophobic and hydrophilic domains on the NP surface. When the size of the hydrophobic domains issmall ( < 1 nm), bridge-like hydrogen-bonded water structures are formed across these domains, stabilizing the waterinterface and increasing the water d. in the regions immediately above the domains. At the same time, due to theentropic effect, water mols. are driven away from the hydrophilic domains as the domain size decreases, decreasing theinterfacial water d. These two competing effects, both of which depend on domain size, combine in a complex way toresult in the non-monotonic dependence of interfacial energy and work of adhesion on the size of surface domains. Wealso investigate via MD simulations the application of these nanoparticles to sensors and show how interfacialmechanisms give rise to sensitive selectivity.~0 Citings

15. Oligonucleotide Delivery by Cell-Penetrating "Striped" NanoparticlesBy Jewell, Christopher M.; Jung, Jin-Mi; Atukorale, Prabhani U.; Carney, Randy P.; Stellacci, Francesco; Irvine, DarrellJ.From Angewandte Chemie, International Edition (2011), 50(51), 12312-12315, S12312/1-S12312/8. Language:English, Database: CAPLUS, DOI:10.1002/anie.201104514

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When mixed self-assembled monolayers of dislike mols. are used to coat AuNPs, nanoscale domains spontaneouslyform in the particles' ligand shell. In particular, "stripe-like" domains form for ca. 1:1 binary mixed ligand compns. Theformation of these domains provides AuNPs with structure-dependent properties. We recently reported the unexpectedfinding that highly water-sol. striped NPs coated with sulfonate- and methylterminated ligands are capable of penetratingthe plasma membrane of cells through non-endocytic energy-independent mechanisms, in contrast to AuNPs bearingsimilar ligands in random configurations, which are only endocytosed. Given our finding that membrane penetration ishighly sensitive to ligand arrangement, a major question raised by this study was whether the membrane penetrationmechanism would support the transport of AuNP-conjugated drug cargos into cells, esp. large, membrane-impermeablehydrophilic macromols. that are the most challenging agents for drug delivery. Here we report on the cellular uptake ofstriped NPs (and non-striped control NPs) conjugated with thiolterminated DNA oligonucleotides (ODNs), in order toanswer this fundamental question and det. how cell entry of striped particles is influenced by cargo size and structure.~31 Citings

16. Determination of nanoparticle size distribution together with density or molecular weight by 2D analyticalultracentrifugation

By Carney, Randy P.; Kim, Jin Young; Qian, Huifeng; Jin, Rongchao; Mehenni, Hakim; Stellacci, Francesco; Bakr,Osman M.From Nature Communications (2011), 2(June), 1338/1-1338/8, S1338/1-S1338/3. Language: English, Database:CAPLUS, DOI:10.1038/ncomms1338

Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Theircores are often polydisperse and coated by a stabilizing shell that varies in size and compn. No single technique cancharacterize both the size distribution and the nature of the shell. Advances in anal. ultracentrifugation allow for the extn.of the sedimentation (s) and diffusion coeffs. (D). Here an approach is reported to transform the s and D distributions ofnanoparticles in soln. into precise mol. wt. (M), d. (pp), and particle diam. (dp) distributions M for mixts. of discretenanocrystals is found within 4% of the known quantities. The accuracy and the d. information achieved on nanoparticlesare unparalleled. A single exptl. run is sufficient for full nanoparticle characterization, without the need for stds. or otherauxiliary measurements. The method is of general applicability and its limitations are discussed.~3 Citings

17. Mixed-Ligand Nanoparticles as Supramolecular ReceptorsBy Liu, Xiang; Hu, Ying; Stellacci, FrancescoFrom Small (2011), 7(14), 1961-1966. Language: English, Database: CAPLUS, DOI:10.1002/smll.201100386

Mixed-ligand-coated Au nanoparticles were synthesized using a naphthalene-terminated thiol (MNT) ligand andhexanethiol (HT). The mixed ligands self-assemble at the surface of nanoparticles forming a structure that interacts withPAHs through pi-pi interactions. Whereas the corresponding homoligand particles do not interact with PAHs in anydetectable way, the mixed-ligand particles all have good binding ability to PAHs; specifically Au-MNT0.50HT0.50 binds topyrene with a binding const. of 6.49 5.71 104 M-1. Overall, mixed ligand-coated Au nanoparticles are versatilereceptors for various PAHs. These easy-to-synthesize and easy-to-tailor particles can be used potentially for thedetection and clean-up of PAH pollutants.~12 Citings

18. Effect of Composition on the Catalytic Properties of Mixed-Ligand-Coated Gold NanoparticlesBy Ghosh, Anirban; Basak, Soubir; Wunsch, Benjamin H.; Kumar, Rajiv; Stellacci, FrancescoFrom Angewandte Chemie, International Edition (2011), 50(34), 7900-7905, S7900/1-S7900/4. Language: English,Database: CAPLUS, DOI:10.1002/anie.201101821

Effect of compn. on catalytic properties of mixed-ligand-coated gold nanoparticles is discussed, as is esterification ofbenzyl alc with acetic acid with prodn. and kinetics for benzyl acetate.~18 Citings

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19. Artificial Surface-Modified Si3N4 Nanopores for Single Surface-Modified Gold Nanoparticle ScanningBy Astier, Yann; Datas, Lucien; Carney, Randy; Stellacci, Francesco; Gentile, Francesco; DiFabrizio, EnzoFrom Small (2011), 7(4), 455-459. Language: English, Database: CAPLUS, DOI:10.1002/smll.201002113

The use of functionalized Si3N4 nanopores for the detection of neg. charged gold nanoparticles from 2.4 to 8.9 nm diam.is shown. It is possible to detect the surface mol. interactions through ionic current alterations, whether or not the elec.-field driven nanoparticle threads through the pore. This simulation work suggests that electrostatic interactions areessential to create the initial nanoparticle-nanopore interaction. Once a nanoparticle is engaged into the nanopore,Brownian motion theory fits the av. off-current time due to the nanopore interaction with the nanoparticle. This hasdemonstrated that electrostatic forces are essential to create the initial nanoparticle-nanopore interaction. Brownianmotion theory helps clarify the av. off-current time due to the nanopore interaction with the nanoparticle.~12 Citings

20. Wetting of nanometer-scale domainsBy Kuna, Jeffrey J.; Stellacci, Francesco; Mwenifumbo, Steve; Stevens, Molly M.From Polymer Preprints (American Chemical Society, Division of Polymer Chemistry) (2010), 51(1), 16-17. Language:English, Database: CAPLUS

This study showed that there is an almost linear dependence of work of adhesion on surface compn. for particles coatedwith longer hydrophilic and shorter hydrophobic ligand mols. The formation of synthetic surfaces possessingsubnanometer domains using self-assembled monolayers (SAMs) is difficult to achieve on flat surfaces due to thetendency for dissimilar components of a SAM to phase sep. into domains several nanometers across or larger. It wasfound that biocomponent SAMs formed on the surface of a nanoparticle do not undergo conventional phase sepn., butinstead form a stripe-like domains due to the curvature of the underlying surface. In a nanoparticle film system, in whichthe nanoparticles were coated with 6-mercaptohexan-1-ol (MHol) and 1-octanethiol (OT), the work of adhesion and thussurface energy varied non-monotonically with compn. The current hydrophilic ligand, 11-mercaptoundecan-1-ol (MUDol),is longer than the previous system's hydrophilic ligand, MHol, which is of comparable length to the hydrophobic ligand,OT. The increased margin in ligand length may preclude or significantly weaken the mol.-scale wetting effects previouslyhypothesized to exist since it is known there is substantial disorder in a SAM composed of ligands of two differentlengths. The longer length of the hydrophilic ligand would increase the surface hydroxyl flexibility and reduce theconfinement effect. Addnl., the hydrophobic headgroups would be sheltered by the longer hydrophilic ligands, reducingthe cavitation effect.~0 Citings

21. Monolayer-coated surfaces as catalytic platforms for organic reactionsBy Stellacci, Francesco; Wunsch, BenjaminFrom PCT Int. Appl. (2009), WO 2009143406 A2 20091126, Language: English, Database: CAPLUS

This invention provides a method for increasing the activity of catalysts. The method requires the introduction of thecatalyst into nano-structured surfaces. The catalysts are introduced as functional groups in mols. forming a monolayeron a surface. A mixed monolayer of catalyst and inert mols. generates ordered domains of mols. on the surface. Thecatalyst is confined in regions of 0.5 nm to 3 nm in size and is surrounded by an inert material. The presence of suchordered domains that commensurate in size with the reactants, enhance the performance of the catalyst and increasethe rate of the reaction.~0 Citings

22. Statistical analysis of scanning tunneling microscopy images of 'striped' mixed monolayer protected goldnanoparticles

By Hu, Ying; Wunsch, Benjamin H.; Sahni, Sahil; Stellacci, FrancescoFrom Journal of Scanning Probe Microscopy (2009), 4(1), 24-35. Language: English, Database: CAPLUS,DOI:10.1166/jspm.2009.1004

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Recent studies based on scanning tunneling microscopy (STM) have shown that when gold nanoparticles are coatedwith binary mixts. of ligand mols. ribbon-like domains of alternating compn. spontaneously form in the particles ligandshell. The presence of these domains has been linked to many surface properties, such as protein nonspecificadsorption, cell membrane permeation, or soly. Here we present a detailed report on the methods and procedures usedto acquire and analyze STM images of these ligand coated nanoparticles. We develop a novel statistical approach toanalyze the images and differentiate them from images generated by feedback loop artifact. We conclude with adiscussion of the potentials and problems of this technique.~11 Citings

23. Nanoparticles having sub-nanometer featuresBy Stellacci, Francesco; Jackson, Alicia M.From U.S. Pat. Appl. Publ. (2009), US 20090246527 A1 20091001, Language: English, Database: CAPLUS

An article has a surface, at least a portion of which has a local radius of curvature of 1000 nm. The article may be ananoparticle or a surface, a portion of which has a roughness characterized by a radius of curvature of 1000 nm. Amonolayer coating disposed on the surface includes a plurality of ligands organized into ordered domains having acharacteristic size of 10 nm.~2 Citings

24. Monodispersed organic monolayer coated calcium-containing nanoparticlesBy Stellacci, Francesco; Uzun, Oktay; Cox, ShermanFrom PCT Int. Appl. (2009), WO 2009111437 A2 20090911, Language: English, Database: CAPLUS

A method for the synthesis of monodispersed, org.-monolayer coated, calcium-contg. nanoparticles is presented. Abiphasic liq. system comprises an aq. phase of bare particles and an org. phase contg. org. mols. with carboxylic acidend group is mixed. The carboxylic acid group binds to the surface of the calcium-contg. particles and the particles arecoated with a monolayer of org. mols. The exposed surface of the coated particles is more hydrophobic than the surfaceof the bare particle and the particles are extd. to the org. phase. The process changes the geometry of the particles anddecreases the size distribution in a population of particles. Acid neutralizers tablets (antacids) and acid neutralizingprocesses in natural water reservoirs and in industrial water are important for the relief of acid assocd. pain for peoplewith ulcers or with gastroesophageal reflux disease, or acid indigestion. Calcium carbonate is often used as an antacid.~2 Citings

25. The role of phase separated nanodomains in the solubility of mixed-monolayer-protected metal nanoparticlesBy Centrone, Andrea; Penzo, Erika; Jackson, Alicia M.; Stellacci, FrancescoFrom AIChE Annual Meeting, Conference Proceedings, Philadelphia, PA, United States, Nov. 16-21, 2008 (2008),187/1-187/2. Language: English, Database: CAPLUS

We present that, when Au nanoparticles are coated with a binary mixt. of immiscible ligands, ordered ribbon-like domainsof alternating compn. spontaneously form and that their width is comparable to the size of a single solvent mol. Whenribbon-like domains arise in the ligand shell, the enthalpy of mixing for mixed ligand nanoparticles depends on thedomain spacing (which can be varied through the stoichiometric ratio of the ligands used in the synthesis). Probably theligand shell domains favor the wetting of the different solvents when their sizes and chem. groups match the solventmols. size and chem. functionality thus contributing to the total nanoparticle soly.~0 Citings

26. Electrophysiological study of single gold nanoparticle/-hemolysin complex formation: a nanotool to slow downssDNA through the -hemolysin nanopore

By Astier, Yann; Uzun, Oktay; Stellacci, FrancescoFrom Small (2009), 5(11), 1273-1278. Language: English, Database: CAPLUS, DOI:10.1002/smll.200801779

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Single-monolayer-protected gold nanoparticles can be captured in the -hemolysin nanopore (see image). Single-nanopore ion conductance studies of the nanoparticle/nanopore complex are described. The effect of the nanoparticlesize, charge, and surface coating on ssDNA threading speed through the nanopore/nanoparticle complex is discussed.~9 Citings

27. Surface-structure-regulated cell-membrane penetration by monolayer-protected nanoparticlesBy Verma, Ayush; Uzun, Oktay; Hu, Yuhua; Hu, Ying; Han, Hee-Sun; Watson, Nicki; Chen, Suelin; Irvine, Darrell J.;Stellacci, FrancescoFrom Nature Materials (2008), 7(7), 588-595. Language: English, Database: CAPLUS, DOI:10.1038/nmat2202

Nanoscale objects are typically internalized by cells into membrane-bounded endosomes and fail to access the cytosoliccell machinery. Whereas some biomacromols. may penetrate or fuse with cell membranes without overt membranedisruption, no synthetic material of comparable size has shown this property yet. Cationic nano-objects pass through cellmembranes by generating transient holes, a process assocd. with cytotoxicity. Studies aimed at generating cell-penetrating nanomaterials have focused on the effect of size, shape and compn. Here, we compare membranepenetration by two nanoparticle isomers' with similar compn. (same hydrophobic content), one coated with subnanometrestriations of alternating anionic and hydrophobic groups, and the other coated with the same moieties but in a randomdistribution. We show that the former particles penetrate the plasma membrane without bilayer disruption, whereas thelatter are mostly trapped in endosomes. Our results offer a paradigm for analyzing the fundamental problem of cell-membrane-penetrating bio- and macro-mols. The structural organization of surface groups on nanoparticles is proven tobe important for cell membrane penetration. Nanoparticles coated with alternating ribbon-like arrangements ofhydrophobic and anionic ligands penetrate membranes without causing disruption. These design rules may haveimplications for toxicity issues and drug delivery applications of nanomaterials. The structural organization of surfacegroups on nanoparticles is proven to be important for cell membrane penetration. Nanoparticles coated with alternatingribbon-like arrangements of hydrophobic and anionic ligands penetrate membranes without causing disruption. Thesedesign rules may have implications for toxicity issues and drug delivery applications of nanomaterials.~511 Citings

28. Effect of Ligand Shell Structure on the Interaction between Monolayer-Protected Gold NanoparticlesBy Hu, Ying; Uzun, Oktay; Dubois, Cedric; Stellacci, FrancescoFrom Journal of Physical Chemistry C (2008), 112(16), 6279-6284. Language: English, Database: CAPLUS,DOI:10.1021/jp709895z

Here the authors present a comparative anal. of 2 types of equally monodisperse Au nanoparticles (8 nm in diam.), onecoated only with dodecanethiol ligands and the other coated with a mixt. of dodecanethiol and 4-methylbenzenethiolligands. The former particles ('homoligand') have a homogeneous coating, while the latter ones ('rippled') show a striatedstructure composed of phase-sepd. ribbon-like domains of alternating compn. A combined scanning tunneling and TEMstudy shows that homoligand nanoparticles interdigitate into one another less than rippled particles and readily formhexagonally packed supracrystals, while rippled particles are trapped in more disordered glassy arrangements.~20 Citings

29. Fabrication of water soluble chains using divalent metal nanoparticlesBy Uzun, Oktay; Stellacci, FrancescoFrom Abstracts of Papers, 235th ACS National Meeting, New Orleans, LA, United States, April 6-10, 2008 (2008),PMSE-141. Language: English, Database: CAPLUS

Nanostructured materials reveal unique electronic and optical properties that are related to their size and shape. Theycan simultaneously provide scaffolds for devices and serve as building blocks for the creation of two- and three-dimensional systems. The existing methodologies for the fabrication of nanoparticle assemblies are less establishedthan what conventional mol. synthesis can offer. We developed a new approach that is based on the functionalization ofthe polar singularities that must form when a curved surface is coated with ordered monolayers, such as a phase-sepd.mixt. of ligands. This simple method can allow us to place reactive mols. specifically at two diametrically opposedpositions in the mol. coating of metal nanoparticles and thus, creating nanoparticle based bi-functional reactivemonomers.

~0 Citings

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30. Fabrication of water soluble chains using divalent metal nanoparticlesBy Uzun, Oktay; Stellacci, FrancescoFrom PMSE Preprints (2008), 98, 230-231. Language: English, Database: CAPLUS

Nanostructured materials reveal unique electronic and optical properties that are related to their size and shape. Theycan simultaneously provide scaffolds for devices and serve as building blocks for the creation of two- and three-dimensional systems. The existing methodologies for the fabrication of nanoparticle assemblies are less establishedthan what conventional mol. synthesis can offer. We developed a new approach that is based on the functionalization ofthe polar singularities that must form when a curved surface is coated with ordered monolayers, such as a phase-sepd.mixt. of ligands. This simple method can allow us to place reactive mols. specifically at two diametrically opposedpositions in the mol. coating of metal nanoparticles and thus, creating nanoparticle based bi-functional reactivemonomers.

~0 Citings

31. Relationship Between Structure and Solubility of Thiol-Protected Silver Nanoparticles and AssembliesBy Bauer, Christina A.; Stellacci, Francesco; Perry, Joseph W.From Topics in Catalysis (2008), 47(1-2), 32-41. Language: English, Database: CAPLUS, DOI:10.1007/s11244-007-9032-5

The soly. of alkylthiol-coated Ag nanoparticles and the energetics of the ligand disordering were studied. Calorimetrymeasurements provided correlations between the nature of the ligands and the enthalpy of the ligand disordering, whichhave guided the improvement of nanoparticle soly. and dispersion in org. media.~22 Citings

32. Entropy-Mediated Patterning of Surfactant-Coated Nanoparticles and SurfacesBy Singh, Chetana; Ghorai, Pradip K.; Horsch, Mark A.; Jackson, Alicia M.; Larson, Ronald G.; Stellacci, Francesco;Glotzer, Sharon C.From Physical Review Letters (2007), 99(22), 226106/1-226106/4. Language: English, Database: CAPLUS,DOI:10.1103/PhysRevLett.99.226106

The authors perform atomistic and mesoscale simulations to explain the origin of exptl. obsd. stripelike patterns formedby immiscible ligands coadsorbed on the surfaces of Au and Ag nanoparticles. When the conformational entropy gainedvia this morphol. is sufficient, microphase-sepd. stripelike patterns form. When the entropic gain is not sufficient, theauthors instead predict bulk phase-sepd. Janus particles. The authors also show corroborating exptl. results that confirmsimulational predictions that stripes form on flat surfaces as well as on curved nanoparticle surfaces.~10 Citings

33. Nanoparticles having sub-nanometer featuresBy Stellacci, Francesco; Jackson, Alicia M.From PCT Int. Appl. (2007), WO 2007100787 A2 20070907, Language: English, Database: CAPLUS

An article has a surface, at least a portion of which has a local radius of curvature of 1000 nm. The article may be ananoparticle or a surface, a portion of which has a roughness characterized by a radius of curvature of 1000 nm. Amonolayer coating disposed on the surface includes a plurality of ligands organized into ordered domains having acharacteristic size of 10 nm.~0 Citings

34. Divalent Metal Nanoparticles

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By DeVries, Gretchen A.; Brunnbauer, Markus; Hu, Ying; Jackson, Alicia M.; Long, Brenda; Neltner, Brian T.; Uzun,Oktay; Wunsch, Benjamin H.; Stellacci, FrancescoFrom Science (Washington, DC, United States) (2007), 315(5810), 358-361. Language: English, Database: CAPLUS,DOI:10.1126/science.1133162

Nanoparticles can be used as the building blocks for materials such as supracrystals or ionic liqs. However, they lack theability to bond along specific directions as atoms and mols. do. We report a simple method to place target mols.specifically at two diametrically opposed positions in the mol. coating of metal nanoparticles. The approach is based onthe functionalization of the polar singularities that must form when a curved surface is coated with ordered monolayers,such as a phase-sepd. mixt. of ligands. The mols. placed at these polar defects have been used as chem. handles toform nanoparticle chains that in turn can generate self-standing films.~432 Citings

35. Low temperature scanning tunneling microscopy images of 'rippled' mixed monolayer protected nanoparticlesBy Jackson, Alicia M.; Miwa, Jill; Rosei, Federico; Stellacci, FrancescoFrom Polymer Preprints (American Chemical Society, Division of Polymer Chemistry) (2006), 47(2), 864-865.Language: English, Database: CAPLUS

Nanoparticles of Au coated with a mixt. of 1-nonanethiol and mercaptohexanol (molar ratio: 2:1) were prepd. using aslight variation of the Schiffrin method. The ligand shell ordering in the samples was studied at low temp. and UHVconditions using a high-resoln. scanning tunneling microscope. The microstructure of the coated Au nanoparticles isdepicted and described. Some of the nanoparticles form highly defined ribbon-like domains or ripples. The data for theripple spacing measured with the UHV HR-STM are nearly identical with data obtained in a DI multimode Nanoscope IIIaSTM under ambient conditions.~0 Citings

36. From Homoligand- to Mixed-Ligand- Monolayer-Protected Metal Nanoparticles: A Scanning Tunneling MicroscopyInvestigation

By Jackson, Alicia M.; Hu, Ying; Silva, Paulo Jacob; Stellacci, FrancescoFrom Journal of the American Chemical Society (2006), 128(34), 11135-11149. Language: English, Database:CAPLUS, DOI:10.1021/ja061545h

The ligand shell that coats, protects, and imparts a large no. ofproperties to gold nanoparticles is a 2-D self-assembledmonolayer wrapped around a 3-D metallic core. Here wepresent a study of the mol. packing of ligand shells on goldnanoparticles based on the anal. of scanning tunnelingmicroscopy (STM) images. We discuss methods for optimalnanoparticle sample prepn. in relation to STM imagingconditions. We show that the packing of a self-assembledmonolayer composed solely of octanethiols on goldnanoparticles depends on the particle's diam. with an av.headgroup spacing of 5.4 , which is different from that ofsimilar monolayers formed on flat Au(111) surfaces (5.0 ). Inthe case of nanoparticles coated with mixts. of ligands-knownto phase sep. into randomly shaped and ordered domains onflat surfaces-we find that phase sepn. leads to the formation ofconcentric, ribbonlike domains of alternating compn. Thespacing of these domains depends on the ligand shell compn.We find that, for a given compn., the spacing increases withdiam. in a manner characterized by discontinuous transitions at"crit." particle sizes. We discuss possible interpretations for theobsd. trends in our data.

~128 Citings

37. Size fractionation of metal nanoparticles by membrane filtration

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By Akthakul, Ariya; Hochbaum, Allon I.; Stellacci, Francesco; Mayes, Anne M.From Advanced Materials (Weinheim, Germany) (2005), 17(5), 532-535. Language: English, Database: CAPLUS,DOI:10.1002/adma.200400636

A thin film composite nanofiltration membrane was fabricated by coating a conventional ultrafiltration membrane with aself-assembling amphiphilic graft copolymer. The membranes were used in the fractionation of gold nanoparticles toachieve a well-defined particle cutoff diam. and decreased size dispersion.~76 Citings

38. Ligand coated metal nanoparticles new tools for nanofabrication and for fluorescence imagingBy Stellacci, Francesco; Perry, Joseph W.From Abstracts, 31st Northeast Regional Meeting of the American Chemical Society, Saratoga Springs, NY, UnitedStates, June 15-18 (2003), 65. Language: English, Database: CAPLUS

Ligand-coated metal nanoparticles are powerful new materials for nano-electronic and photonic applications. They canbe readily synthesized and their stability and soly. allows them to be cast in complex composite materials or self-assembled into ordered films. It will be demonstrated that it is possible to induce the growth of these nanoparticles withthe proper excitation conditions. More importantly, conductive metal features can be obtained in composite materialsconsisting of a polymer matrix doped with ligand-coated metal nanoparticles, suitable reducing dyes, and metal salts, viaeither linear or non-linear optical excitation. 3D silver, copper and gold structures fabricated using two-photon absorptionthat are characterized with various techniques will be presented. The synthesis and characterization of silvernanoparticles with fluorescent chromophores covalently bond to their metallic core will be presented. The fluorescenceproperties of these particles and of their fractal aggregates will be compared. It will be shown that chromophores self-assembled on metal nanoparticle fractal clusters can show two-photon induced fluorescence enhancements as high asfive orders of magnitude.".~0 Citings

39. One- and two-photon induced growth of ligand coated nanoparticles for 2 + 3D metal patterningBy Stellacci, Francesco; Bauer, Christina A.; Meyer-Friedrichsen, Timo; Wenseleers, Wim; Alain, Valerie; Kuebler,Stephen M.; Pond, Stephanie J.; Zhang, Yadong; Marder, Seth R.; Perry, Joseph W.From Proceedings of SPIE-The International Society for Optical Engineering (2002), 4809(Nanoscale Optics andApplications), 62-68. Language: English, Database: CAPLUS, DOI:10.1117/12.453771

Ligand-coated metallic nanoparticles are powerful new materials for nanoelectronic and photonics applications. Theycan be readily synthesized and their stability and soly. allows them to be cast in complex composite materials or self-assembled into quasi-ordered films. The authors demonstrate that, in the presence of reducing dyes with a large two-photon cross-section and metal salts, it is possible to induce the growth of metal nanoparticles in composite films underoptical excitation or irradn. with electrons. The authors demonstrate further that continuous metal structures can beobtained via laser irradn. of the composites and that, with two-photon excitation, 3D structures can be fabricated. Silver,copper, and gold microstructures have been fabricated via two-photon excitation. The compn. of the authors polymericprecursor is described in detail. In order to achieve highly-homogeneous solid-state solns. of nanoparticles dissolved inpoly(vinylcarbazole) (PVK), the authors synthesized tailor-made nanoparticles on which the authors have introduced amixt. of carbazoyl-terminated octylthiol and simple octylthiols. Preliminary expts. on electron-beam lithog. show that thinfilms of nanoparticles doped with suitable dyes and metal salts are efficient precursors form metal structures.~4 Citings

40. Ultrabright supramolecular beacons based on the self-assembly of two-photon chromophores on metal nanoparticlesBy Stellacci, Francesco; Bauer, Christina A.; Meyer-Friedrichsen, Timo; Wenseleers, Wim; Marder, Seth R.; Perry,Joseph W.From Journal of the American Chemical Society (2003), 125(2), 328-329. Language: English, Database: CAPLUS,DOI:10.1021/ja0281277

Silver nanoparticles coated with a self-assembled layer of 2500 chromophoric alkylthiol ligands, that exhibit a huge perparticle two-photon absorption cross section (2.7 10-45 cm4 s photon-1) and a high fluorescence quantum yield (0.33),are reported. Polyfunctionalized variants of these nanoparticles have been produced that show reasonable soly. inwater/ethanol mixts. By virtue of the large no. of tethered chromophores, these particles act as strongly two-photonabsorbing nanobeacons and may have applications in fluorescence imaging and sensing.

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~67 Citings

41. Five orders-of-magnitude enhancement of two-photon absorption for dyes on silver nanoparticle fractal clustersBy Wenseleers, Wim; Stellacci, Francesco; Meyer-Friedrichsen, Timo; Mangel, Timo; Bauer, Christina A.; Pond,Stephanie J. K.; Marder, Seth R.; Perry, Joseph W.From Journal of Physical Chemistry B (2002), 106(27), 6853-6863. Language: English, Database: CAPLUS,DOI:10.1021/jp014675f

Strong enhancement of the two-photon absorption of org. mols. near silver nanoparticle fractal clusters has been obsd.and has been exploited to yield composite materials with very strong two-photon absorption and two-photon-excitedfluorescence properties. Measurements on cluster films coated with a chromophoric polymer or with thiol-boundchromophores give spatially-averaged enhancements of 1000 and 20,000, resp. Two-photon fluorescence microscopystudies show that the enhancements are spatially inhomogeneous, with peak-enhancement factors of 10,000(polymer/cluster) and 160,000 (thiol chromophore/cluster), and excitation frequency-dependent. These results are inaccord with theor. predictions of local-field effects due to strong localization of collective plasmon modes in fractal metalclusters, and demonstrate an approach to ultrasensitive two-photon processes.~149 Citings

42. Laser and electron-beam induced growth of nanoparticles for 2D and 3D metal patterningBy Stellacci, Francesco; Bauer, Christina A.; Meyer-Friedrichsen, Timo; Wenseleers, Wim; Alain, Valerie; Kuebler,Stephen M.; Pond, Stephanie J. K.; Zhang, Yadong; Marder, Seth R.; Perry, Joseph W.From Advanced Materials (Weinheim, Germany) (2002), 14(3), 194-198. Language: English, Database: CAPLUS,DOI:10.1002/1521-4095(20020205)14:33.0.CO;2-W

Defined continuous metal patterns were grown by laser or electron beam irradn. of composite materials contg. thecorresponding metal nanoparticles. Excitation by 1- or 2-photon absorption resulted in 1-step laser writing of continuousAg, Cu, and Au metal microstructures in 1D, 2D, and 3D patterns. The electron beam irradn. of ultrathin films of a dye-attached-metal nanoparticle composite allowed for high-sensitive writing of lines and pads demonstrating the applicabilityof such materials for direct electron beam lithog. of a metal. The samples were investigated by SEM, TEM , and opticalabsorption spectroscopy. A polymer/nanocomposite material for the direct writing of Ag metal was designed andfabricated based on the photoreductive growth of the nanoparticles. It consisted of AgBF4 as a precursor for the metalnanoparticles, a photoreducing dye (I; R1 = R2 = C11H23) as the sensitizer, ligand-coated Ag nanoparticles as seeds (I;R1 = Me, R2 = C11H22SH) and polyvinylcarbazole as the host polymer and sacrificial reducing agent.

~130 Citings

43. Contact angle and adsorption energies of nanoparticles at the air-liquid interface determined by neutron reflectivityand molecular dynamics

By Reguera Javier; Ponomarev Evgeniy; Geue Thomas; Stellacci Francesco; Bresme Fernando; Moglianetti MauroFrom Nanoscale (2015), 7(13), 5665-73, Language: English, Database: MEDLINE

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Copyright 2015 U.S. National Library of Medicine.



Understanding how nanomaterials interact with interfaces is essential to control their self-assembly as well as theiroptical, electronic, and catalytic properties. We present here an experimental approach based on neutron reflectivity(NR) that allows the in situ measurement of the contact angles of nanoparticles adsorbed at fluid interfaces. Becauseour method provides a route to quantify the adsorption and interfacial energies of the nanoparticles in situ, itcircumvents problems associated with existing indirect methods, which rely on the transport of the monolayers tosubstrates for further analysis. We illustrate the method by measuring the contact angle of hydrophilic andhydrophobic gold nanoparticles, coated with perdeuterated octanethiol (d-OT) and with a mixture of d-OT andmercaptohexanol (MHol), respectively. The contact angles were also calculated via atomistic molecular dynamics(MD) computations, showing excellent agreement with the experimental data. Our method opens the route to quantifythe adsorption of complex nanoparticle structures adsorbed at fluid interfaces featuring different chemicalcompositions.

~0 Citings

44. Protein-nanoparticle interactions: the effects of surface compositional and structural heterogeneity are scaledependent

By Huang Rixiang; Carney Randy P; Stellacci Francesco; Lau Boris L TFrom Nanoscale (2013), 5(15), 6928-35, Language: English, Database: MEDLINENanoparticles (NPs) in the biological environment are exposed to a large variety and concentration of proteins.Proteins are known to adsorb in a 'corona' like structure on the surface of NPs. In this study, we focus on the effects ofsurface compositional and structural heterogeneity on protein adsorption by examining the interaction of self-assembled monolayer coated gold NPs (AuNPs) with two types of proteins: ubiquitin and fibrinogen. This work wasdesigned to systematically investigate the role of surface heterogeneity in nanoparticle-protein interaction. We havechosen the particles as well as the proteins to provide different types (in distribution and length-scale) of heterogeneity.The goal was to unveil the role of heterogeneity and of its length-scale in the particle-protein interaction. Dynamic lightscattering and circular dichroism spectroscopy were used to reveal different interactions at pH above and below theisoelectric points of the proteins, which is related to the charge heterogeneity on the protein surface. At pH 7.4, therewas only a monolayer of proteins adsorbed onto the NPs and the secondary structure of proteins remained intact. AtpH 4.0, large aggregates of nanoparticle-protein complexes were formed and the secondary structures of the proteinswere significantly disrupted. In terms of interaction thermodynamics, results from isothermal titration calorimetryshowed that ubiquitin adsorbed differently onto (1) AuNPs with charged and nonpolar terminals organized into nano-scale structure (66-34 OT), (2) AuNPs with randomly distributed terminals (66-34 brOT), and (3) AuNPs withhomogeneously charged terminals (MUS). This difference in adsorption behavior was not observed when AuNPsinteracted with fibrinogen. The results suggested that the interaction between the proteins and AuNPs was influencedby the surface heterogeneity on the AuNPs, and this influence depends on the scale of surface heterogeneity and thesize of the proteins.

~3 Citings

45. Electrical method to quantify nanoparticle interaction with lipid bilayersBy Carney Randy P; Astier Yann; Carney Tamara M; Voitchovsky Kislon; Jacob Silva Paulo H; Stellacci FrancescoFrom ACS nano (2013), 7(2), 932-42, Language: English, Database: MEDLINEUnderstanding as well as rapidly screening the interaction of nanoparticles with cell membranes is of centralimportance for biological applications such as drug and gene delivery. Recently, we have shown that "striped" mixed-monolayer-coated gold nanoparticles spontaneously penetrate a variety of cell membranes through a passive pathway.Here, we report an electrical approach to screen and readily quantify the interaction between nanoparticles and bilayerlipid membranes. Membrane adsorption is monitored through the capacitive increase of suspended planar lipidmembranes upon fusion with nanoparticles. We adopt a Langmuir isotherm model to characterize the adsorption ofnanoparticles by bilayer lipid membranes and extract the partition coefficient, K, and the standard free energy gain bythis spontaneous process, for a variety of sizes of cell-membrane-penetrating nanoparticles. We believe that themethod presented here will be a useful qualitative and quantitative tool to determine nanoparticle interaction with lipidbilayers and consequently with cell membranes.

~3 Citings

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46. Determination of monolayer-protected gold nanoparticle ligand-shell morphology using NMRBy Liu Xiang; Yu Miao; Kim Hyewon; Mameli Marta; Stellacci FrancescoFrom Nature communications (2012), 31182, Language: English, Database: MEDLINEIt is accepted that the ligand shell morphology of nanoparticles coated with a monolayer of molecules can be partlyresponsible for important properties such as cell membrane penetration and wetting. When binary mixtures ofmolecules coat a nanoparticle, they can arrange randomly or separate into domains, for example, forming Janus,patchy or striped particles. To date, there is no straightforward method for the determination of such structures. Herewe show that a combination of one-dimensional and two-dimensional NMR can be used to determine the ligand shellstructure of a series of particles covered with aliphatic and aromatic ligands of varying composition. This approach is apowerful way to determine the ligand shell structure of patchy particles; it has the limitation of needing a whole seriesof compositions and ligands' combinations with NMR peaks well separated and whose shifts due to the surroundingenvironment can be large enough.

~0 Citings

47. Determination of nanoparticle size distribution together with density or molecular weight by 2D analyticalultracentrifugation

By Carney Randy P; Kim Jin Young; Qian Huifeng; Jin Rongchao; Mehenni Hakim; Stellacci Francesco; Bakr OsmanMFrom Nature communications (2011), 2335, Language: English, Database: MEDLINENanoparticles are finding many research and industrial applications, yet their characterization remains a challenge.Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No singletechnique can characterize both the size distribution and the nature of the shell. Advances in analyticalultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report anapproach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density((P)) and particle diameter (d(p)) distributions. M for mixtures of discrete nanocrystals is found within 4% of theknown quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A singleexperimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliarymeasurements. We believe that our method is of general applicability and we discuss its limitations.

~7 Citings

48. Surface-structure-regulated cell-membrane penetration by monolayer-protected nanoparticlesBy Verma Ayush; Uzun Oktay; Hu Yuhua; Hu Ying; Han Hee-Sun; Watson Nicki; Chen Suelin; Irvine Darrell J; StellacciFrancescoFrom Nature materials (2008), 7(7), 588-95, Language: English, Database: MEDLINENanoscale objects are typically internalized by cells into membrane-bounded endosomes and fail to access thecytosolic cell machinery. Whereas some biomacromolecules may penetrate or fuse with cell membranes without overtmembrane disruption, no synthetic material of comparable size has shown this property yet. Cationic nano-objectspass through cell membranes by generating transient holes, a process associated with cytotoxicity. Studies aimed atgenerating cell-penetrating nanomaterials have focused on the effect of size, shape and composition. Here, wecompare membrane penetration by two nanoparticle 'isomers' with similar composition (same hydrophobic content),one coated with subnanometre striations of alternating anionic and hydrophobic groups, and the other coated with thesame moieties but in a random distribution. We show that the former particles penetrate the plasma membranewithout bilayer disruption, whereas the latter are mostly trapped in endosomes. Our results offer a paradigm foranalysing the fundamental problem of cell-membrane-penetrating bio- and macro-molecules.

~93 Citings

49. Entropy-mediated patterning of surfactant-coated nanoparticles and surfacesBy Singh Chetana; Ghorai Pradip K; Horsch Mark A; Jackson Alicia M; Larson Ronald G; Stellacci Francesco; GlotzerSharon CFrom Physical review letters (2007), 99(22), 226106, Language: English, Database: MEDLINE

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We perform atomistic and mesoscale simulations to explain the origin of experimentally observed stripelike patternsformed by immiscible ligands coadsorbed on the surfaces of gold and silver nanoparticles. We show that when theconformational entropy gained via this morphology is sufficient, microphase-separated stripelike patterns form. Whenthe entropic gain is not sufficient, we instead predict bulk phase-separated Janus particles. We also showcorroborating experimental results that confirm our simulational predictions that stripes form on flat surfaces as well ason curved nanoparticle surfaces.

~2 Citings

50. Divalent metal nanoparticlesBy Devries Gretchen A; Brunnbauer Markus; Hu Ying; Jackson Alicia M; Long Brenda; Neltner Brian T; Uzun Oktay;Wunsch Benjamin H; Stellacci FrancescoFrom Science (New York, N.Y.) (2007), 315(5810), 358-61, Language: English, Database: MEDLINENanoparticles can be used as the building blocks for materials such as supracrystals or ionic liquids. However, theylack the ability to bond along specific directions as atoms and molecules do. We report a simple method to placetarget molecules specifically at two diametrically opposed positions in the molecular coating of metal nanoparticles.The approach is based on the functionalization of the polar singularities that must form when a curved surface iscoated with ordered monolayers, such as a phase-separated mixture of ligands. The molecules placed at these polardefects have been used as chemical handles to form nanoparticle chains that in turn can generate self-standing films.

~2 Citings

51. From homoligand- to mixed-ligand- monolayer-protected metal nanoparticles: a scanning tunneling microscopyinvestigation

By Jackson Alicia M; Hu Ying; Silva Paulo Jacob; Stellacci FrancescoFrom Journal of the American Chemical Society (2006), 128(34), 11135-49, Language: English, Database: MEDLINEThe ligand shell that coats, protects, and imparts a large number of properties to gold nanoparticles is a 2-D self-assembled monolayer wrapped around a 3-D metallic core. Here we present a study of the molecular packing ofligand shells on gold nanoparticles based on the analysis of scanning tunneling microscopy (STM) images. Wediscuss methods for optimal nanoparticle sample preparation in relation to STM imaging conditions. We show that thepacking of a self-assembled monolayer composed solely of octanethiols on gold nanoparticles depends on theparticle's diameter with an average headgroup spacing of 5.4 A, which is different from that of similar monolayersformed on flat Au(111) surfaces (5.0 A). In the case of nanoparticles coated with mixtures of ligands-known to phaseseparate into randomly shaped and ordered domains on flat surfaces-we find that phase separation leads to theformation of concentric, ribbonlike domains of alternating composition. The spacing of these domains depends on theligand shell composition. We find that, for a given composition, the spacing increases with diameter in a mannercharacterized by discontinuous transitions at "critical" particle sizes. We discuss possible interpretations for theobserved trends in our data.

~2 Citings

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