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Sample records for protonated nanoparticle surface

  1. Surface Protonics Promotes Catalysis

    NASA Astrophysics Data System (ADS)

    Manabe, R.; Okada, S.; Inagaki, R.; Oshima, K.; Ogo, S.; Sekine, Y.

    2016-12-01

    Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics.

  2. Surface Protonics Promotes Catalysis

    PubMed Central

    Manabe, R.; Okada, S.; Inagaki, R.; Oshima, K.; Ogo, S.; Sekine, Y.

    2016-01-01

    Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando–IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application. Methane was activated by proton collision at the Pd–CeO2 interface, based on the inverse kinetic isotope effect. Proton conduction on the catalyst surface plays an important role in methane activation at low temperature. This report is the first describing promotion of the catalytic reaction by surface protonics. PMID:27905505

  3. Surface modification of Fe2TiO5 nanoparticles by silane coupling agent: Synthesis and application in proton exchange composite membranes.

    PubMed

    Salarizadeh, Parisa; Javanbakht, Mehran; Pourmahdian, Saeed; Bagheri, Ahmad; Beydaghi, Hossein; Enhessari, Morteza

    2016-06-15

    Modifying surfaces of nanoparticles with silane coupling agent provides a simple method to alter their surface properties and improve their dispersibility in organic solvents and polymer matrix. Fe2TiO5 nanoparticles (IT) were modified with 3-aminopropyltriethoxysilane (APTES) as novel reinforcing filler for proton exchange membranes. The main operating parameters such as reaction time (R.T), APTES/IT and triethylamine (TEA)/IT ratios have been optimized for maximum grafting efficiency. The optimum conditions for R.T, APTES/IT and TEA/IT ratios were 6h, 4 and 0.3 respectively. It was observed that the APTES/IT and TEA/IT ratios were the most significant parameters affecting the grafting percentage. Modified nanoparticles were characterized using FT-IR, TGA, SEM, TEM and XRD techniques. Effects of modified nanoparticles in proton exchange membrane fuel cells (PEMFC) were evaluated. The resulting nanocomposite membranes exhibited higher proton conductivity in comparison with pristine SPPEK and SPPEK/IT membranes. This increase is attributed to connectivity of the water channels which creates more direct pathways for proton transport. Composite membrane with 3% AIT (6.46% grafting amount) showed 0.024 S cm(-1) proton conductivity at 25 °C and 149 mW cm(-2) power density (at 0.5V) at 80 °C which were about 243% and 51%, respectively higher than that of pure SPPEK.

  4. Final Report: The Impact of Carbonate on Surface Protonation, Electron Transfer and Crystallization Reactions in Iron Oxide Nanoparticles and Colloids

    SciTech Connect

    Dixon, David Adams

    2013-07-02

    This project addresses key issues of importance in the geochemical behavior of iron oxides and in the geochemical cycling of carbon and iron. For Fe, we are specifically studying the influence of carbonate on electron transfer reactions, solid phase transformations, and the binding of carbonate to reactive sites on the edges of particles. The emphasis on carbonate arises because it is widely present in the natural environment, is known to bind strongly to oxide surfaces, is reactive on the time scales of interest, and has a speciation driven by acid-base reactions. The geochemical behavior of carbonate strongly influences global climate change and CO{sub 2} sequestration technologies. Our goal is to answer key questions with regards to specific site binding, electron transfer reactions, and crystallization reactions of iron oxides that impact both the geochemical cycling of iron and CO{sub 2} species. Our work is focused on the molecular level description of carbonate chemistry in solution including the prediction of isotope fractionation factors. We have also done work on critical atmospheric species.

  5. Improving proton therapy by metal-containing nanoparticles: nanoscale insights

    PubMed Central

    Schlathölter, Thomas; Eustache, Pierre; Porcel, Erika; Salado, Daniela; Stefancikova, Lenka; Tillement, Olivier; Lux, Francois; Mowat, Pierre; Biegun, Aleksandra K; van Goethem, Marc-Jan; Remita, Hynd; Lacombe, Sandrine

    2016-01-01

    The use of nanoparticles to enhance the effect of radiation-based cancer treatments is a growing field of study and recently, even nanoparticle-induced improvement of proton therapy performance has been investigated. Aiming at a clinical implementation of this approach, it is essential to characterize the mechanisms underlying the synergistic effects of nanoparticles combined with proton irradiation. In this study, we investigated the effect of platinum- and gadolinium-based nanoparticles on the nanoscale damage induced by a proton beam of therapeutically relevant energy (150 MeV) using plasmid DNA molecular probe. Two conditions of irradiation (0.44 and 3.6 keV/μm) were considered to mimic the beam properties at the entrance and at the end of the proton track. We demonstrate that the two metal-containing nanoparticles amplify, in particular, the induction of nanosize damages (>2 nm) which are most lethal for cells. More importantly, this effect is even more pronounced at the end of the proton track. This work gives a new insight into the underlying mechanisms on the nanoscale and indicates that the addition of metal-based nanoparticles is a promising strategy not only to increase the cell killing action of fast protons, but also to improve tumor targeting. PMID:27143877

  6. Proton NMR studies of functionalized nanoparticles in aqueous environments

    NASA Astrophysics Data System (ADS)

    Tataurova, Yulia Nikolaevna

    in high-resolution NMR spectra. This technique is selective for protons on the surface organic functional groups due to their motional averaging in solution. In this study, 1H solution NMR spectroscopy was used to investigate the interface of the organic functional groups in D2O. The pKa for these functional groups covalently bound to the surface of nanoparticles was determined using an NMR-pH titration method based on the variation in the proton chemical shift for the alkyl group protons closest to the amine group with pH. The adsorption of toxic contaminants (chromate and arsenate anions) on the surface of functionalized silicalite-1 and mesoporous silica nanoparticles has been studied by 1H solution NMR spectroscopy. With this method, the surface bound contaminants are detected. The analysis of the intensity and position of these peaks allows quantitative assessment of the relative amounts of functional groups with adsorbed metal ions. These results demonstrate the sensitivity of solution NMR spectroscopy to the electronic environment and structure of the surface functional groups on porous nanomaterials.

  7. Proton Dynamics on Goethite Nanoparticles and Coupling to Electron Transport

    SciTech Connect

    Zarzycki, Piotr P.; Smith, Dayle MA; Rosso, Kevin M.

    2015-04-14

    The surface chemistry of metal oxide particles is governed by the charge that develops at the interface with aqueous solution. Mineral transformation, biogeochemical reactions, remediation, and sorption dynamics are profoundly affected in response. Here we report implementation of replica-exchange constant-pH molecular dynamics simulations that use classical molecular dynamics for exploring configurational space and Metropolis Monte Carlo walking through protonation space with a simulated annealing escape route from metastable configurations. By examining the archetypal metal oxide, goethite (α-FeOOH), we find that electrostatic potential gradients spontaneously arise between intersecting low-index crystal faces and across explicitly treated oxide nanoparticles at a magnitude exceeding the Johnson–Nyquist voltage fluctuation. Fluctuations in adsorbed proton density continuously repolarize the surface potential bias between edge-sharing crystal faces, at a rate slower than the reported electron–polaron hopping rate in goethite interiors. This suggests that these spontaneous surface potential fluctuations will control the net movement of charge carriers in the lattice.

  8. Gold Nanoparticles-Enhanced Proton Exchange Membrane (PEM) Fuel Cell

    NASA Astrophysics Data System (ADS)

    Li, Hongfei; Pan, Cheng; Liu, Ping; Zhu, Yimei; Adzic, Radoslav; Rafailovich, Miriam

    Proton exchange membrane fuel cells have drawn great attention and been taken as a promising alternated energy source. One of the reasons hamper the wider application of PEM fuel cell is the catalytic poison effect from the impurity of the gas flow. Haruta has predicted that gold nanoparticles that are platelet shaped and have direct contact with the metal oxide substrate to be the perfect catalysts of the CO oxidization, yet the synthesis method is difficult to apply in the Fuel Cell. In our approach, thiol-functionalized gold nanoparticles were synthesized through two-phase method developed by Brust et al. We deposit these Au particles with stepped surface directly onto the Nafion membrane in the PEM fuel cell by Langmuir-Blodgett method, resulting in over 50% enhancement of the efficiency of the fuel cell. DFT calculations were conducted to understand the theory of this kind of enhancement. The results indicated that only when the particles were in direct surface contact with the membrane, where AuNPs attached at the end of the Nafion side chains, it could reduce the energy barrier for the CO oxidation that could happen at T<300K.

  9. Enhanced proton treatment in mouse tumors through proton irradiated nanoradiator effects on metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Ki; Seo, Seung-Jun; Kim, Hong-Tae; Kim, Ki-Hong; Chung, Myung-Hwan; Kim, Kye-Ryung; Ye, Sung-Jun

    2012-12-01

    The impact of protons on metallic nanoparticles (MNPs) produces the potent release of MNP-induced secondary electrons and characteristic x-rays. To determine the ability of secondary radiations to enhance proton treatment, the therapeutic irradiation of tumors was investigated in mice receiving 100-300 mg MNPs/kg intravenously prior to single dose, 10-41 Gy, proton irradiation. A proton beam was utilized to irradiate nanoparticles with a single Bragg peak set to occur inside a tumor volume (fully absorbed) or to occur after the beam had traversed the entire body. The dose-dependent increase in complete tumor regression (CTR) was 37-62% in the fully-absorbed irradiation group or 50-100% in the traversing irradiation group, respectively, compared with the proton-alone control mice (p < 0.01). One year survival was 58-100% versus 11-13% proton alone. The dose-dependent increase of intracellular reactive oxygen species level was 12-36% at 10 Gy compared with the proton-alone control cell. Therapeutic effective drug concentration that led to 100% CTR with a proton dose of 31 Gy was measured either 41 µg Au/g tissue or 59 µg Fe/g tissue. MNP-based proton treatment increased not only percent CTR and survival in vivo but also ROS generation in vitro, suggesting tumor dose enhancement from secondary radiation as one potent pathway of therapeutic enhancement.

  10. Protonation and Deprotonation on Water's Surface

    NASA Astrophysics Data System (ADS)

    Colussi, A. J.; Enami, S.; Stewart, L.; Hoffmann, M. R.

    2010-12-01

    How the acidity of bulk water (pHbulk) regulates the degree of protonation of Brönsted acids and bases on water surfaces facing hydrophobic media is a key unresolved issue in chemistry and biology. We addressed experimentally the important case of the air/water interface and report the strikingly dissimilar pHbulk-dependences of the protonation/deprotonation of aqueous versus gaseous n-hexanoic acid (HxOH) determined on the surface of aqueous microjets by online electrospray mass spectrometry. We confirm that HxOH(aq) is deprotonated at pHbulk > pKa(HxOH) = 4.8, but find that the deprotonation of HxOH(g) into interfacial HxO-(s) displays two equivalence points at pHbulk ~ 2.5 and ~ 10.0. The weak base HxOH(aq) (pKa(HxOH2+) < - 4) is barely protonated at pHbulk > 1, whereas HxOH(g) is significantly protonated to HxOH2+(s) on pHbulk < 4 water, as expected from the proton affinities PA(HxOH) > PA(H2O) of gas-phase species. The exceptionally large kinetic isotope effect for the protonation of HxOH(g) on D2O/H2O: KIE = HxOH2+/HxODH+ ~ 100, is ascribed to a desolvated transition state. Since ion creation at the interface via proton transfer between H2O itself and neutral species is thermodynamically disallowed i.e., HxOH(g) is actually deprotonated by interfacial OH-(s), whereas Me3N(g) is hardly protonated by H3O+(s) on pHbulk ~ 4 - 8 water (Enami et al., J. Phys. Chem. Lett. 2010, 1, 1599) we conclude that [OH-(s)] > [H3O+(s)] above pHbulk ~ 4, at variance with inferences drawn from spectroscopic signatures or model calculations of water’s surface.

  11. Surface-coupled proton exchange of a membrane-bound proton acceptor.

    PubMed

    Sandén, Tor; Salomonsson, Lina; Brzezinski, Peter; Widengren, Jerker

    2010-03-02

    Proton-transfer reactions across and at the surface of biological membranes are central for maintaining the transmembrane proton electrochemical gradients involved in cellular energy conversion. In this study, fluorescence correlation spectroscopy was used to measure the local protonation and deprotonation rates of single pH-sensitive fluorophores conjugated to liposome membranes, and the dependence of these rates on lipid composition and ion concentration. Measurements of proton exchange rates over a wide proton concentration range, using two different pH-sensitive fluorophores with different pK(a)s, revealed two distinct proton exchange regimes. At high pH (> 8), proton association increases rapidly with increasing proton concentrations, presumably because the whole membrane acts as a proton-collecting antenna for the fluorophore. In contrast, at low pH (< 7), the increase in the proton association rate is slower and comparable to that of direct protonation of the fluorophore from the bulk solution. In the latter case, the proton exchange rates of the two fluorophores are indistinguishable, indicating that their protonation rates are determined by the local membrane environment. Measurements on membranes of different surface charge and at different ion concentrations made it possible to determine surface potentials, as well as the distance between the surface and the fluorophore. The results from this study define the conditions under which biological membranes can act as proton-collecting antennae and provide fundamental information on the relation between the membrane surface charge density and the local proton exchange kinetics.

  12. Biological modeling of gold nanoparticle enhanced radiotherapy for proton therapy

    NASA Astrophysics Data System (ADS)

    Lin, Yuting; McMahon, Stephen J.; Paganetti, Harald; Schuemann, Jan

    2015-05-01

    Gold nanoparticles (GNPs) have shown potential as a radiosensitizer for radiation therapy using photon beams. Recently, experimental studies have been carried out using proton beams showing the GNP enhanced responses in proton therapy. In this work, we established a biological model to investigate the change in survival of irradiated cells due to the radiosensitizing effect of gold nanoparticles. Results for proton, megavoltage (MV) photon and kilovoltage (kV) photon beams are compared. For each particle source, we assessed various treatment depths, GNP cellular uptakes and sizes. We showed that kilovoltage photons caused the highest enhancement due to the high interaction probability between GNPs and kV photons. The cell survival fraction can be significantly reduced for both proton and MV photon irradiations if GNPs accumulate in the cell. For instance, the sensitizer enhancement ratio (SER) is 1.33 for protons in the middle of a spread out Bragg peak for 1 µM of internalized 50 nm GNPs. If the GNPs can all be internalized into the cell nucleus, the SER for proton therapy increases from 1.33 to 1.81. The results also show that for the same mass of GNPs in the cells, one can expect the greatest sensitization by smaller GNPs, i.e. a SER of 1.33 for 1 µM of internalized 50 nm GNPs and a SER of 3.98 for the same mass of 2 nm GNPs. We concluded that if the GNPs cannot be internalized into the cytoplasm, no GNP enhancement will be observed for proton treatment. Meanwhile, proton radiotherapy can potentially be enhanced with GNPs if they can be internalized into cells, and especially the cell nucleus.

  13. AQUEOUS PROTONATION PROPERTIES OF AMPHOTERIC NANOPARTICLES

    EPA Science Inventory

    A divergence is predicted between the acidity behavior of charged sites on micron sized colloidal particles and nanoparticles. Utilizing the approximate analytical solution to the Poisson-Boltzmann equation published by Ohshima et al. (1982), findings from the work included: 1):...

  14. Surface proton transport of fully protonated poly(aspartic acid) thin films on quartz substrates

    NASA Astrophysics Data System (ADS)

    Nagao, Yuki; Kubo, Takahiro

    2014-12-01

    Thin film structure and the proton transport property of fully protonated poly(aspartic acid) (P-Asp100) have been investigated. An earlier study assessed partially protonated poly(aspartic acid), highly oriented thin film structure and enhancement of the internal proton transport. In this study of P-Asp100, IR p-polarized multiple-angle incidence resolution (P-MAIR) spectra were measured to investigate the thin film structure. The obtained thin films, with thicknesses of 120-670 nm, had no oriented structure. Relative humidity dependence of the resistance, proton conductivity, and normalized resistance were examined to ascertain the proton transport property of P-Asp100 thin films. The obtained data showed that the proton transport of P-Asp100 thin films might occur on the surface, not inside of the thin film. This phenomenon might be related with the proton transport of the biological system.

  15. Water-soluble core/shell nanoparticles for proton therapy through particle-induced radiation

    NASA Astrophysics Data System (ADS)

    Park, Jeong Chan; Jung, Myung-Hwan; Kim, Maeng Jun; Kim, Kye-Ryung

    2015-02-01

    Metallic nanoparticles have been used in biomedical applications such as magnetic resonance imaging (MRI), therapy, and drug delivery systems. Metallic nanoparticles as therapeutic tools have been demonstrated using radio-frequency magnetic fields or near-infrared light. Recently, therapeutic applications of metallic nanomaterials combined with proton beams have been reported. Particle-induced radiation from metallic nanoparticles, which can enhance the therapeutic effects of proton therapy, was released when the nanoparticles were bombarded by a high-energy proton beam. Core/shell nanoparticles, especially Au-coated magnetic nanoparticles, have drawn attention in biological applications due to their attractive characteristics. However, studies on the phase transfer of organic-ligand-based core/shell nanoparticles into water are limited. Herein, we demonstrated that hydrophobic core/shell structured nanomaterials could be successfully dispersed in water through chloroform/surfactant mixtures. The effects of the core/shell nanomaterials and the proton irradiation on Escherichia coli (E. coli) were also explored.

  16. Anomalous surface diffusion of protons on lipid membranes.

    PubMed

    Wolf, Maarten G; Grubmüller, Helmut; Groenhof, Gerrit

    2014-07-01

    The cellular energy machinery depends on the presence and properties of protons at or in the vicinity of lipid membranes. To asses the energetics and mobility of a proton near a membrane, we simulated an excess proton near a solvated DMPC bilayer at 323 K, using a recently developed method to include the Grotthuss proton shuttling mechanism in classical molecular dynamics simulations. We obtained a proton surface affinity of -13.0 ± 0.5 kJ mol(-1). The proton interacted strongly with both lipid headgroup and linker carbonyl oxygens. Furthermore, the surface diffusion of the proton was anomalous, with a subdiffusive regime over the first few nanoseconds, followed by a superdiffusive regime. The time- and distance dependence of the proton surface diffusion coefficient within these regimes may also resolve discrepancies between previously reported diffusion coefficients. Our simulations show that the proton anomalous surface diffusion originates from restricted diffusion in two different surface-bound states, interrupted by the occasional bulk-mediated long-range surface diffusion. Although only a DMPC membrane was considered in this work, we speculate that the restrictive character of the on-surface diffusion is highly sensitive to the specific membrane conditions, which can alter the relative contributions of the surface and bulk pathways to the overall diffusion process. Finally, we discuss the implications of our findings for the energy machinery.

  17. Evaluation of the local dose enhancement in the combination of proton therapy and nanoparticles

    SciTech Connect

    Martínez-Rovira, I. Prezado, Y.

    2015-11-15

    Purpose: The outcome of radiotherapy can be further improved by combining irradiation with dose enhancers such as high-Z nanoparticles. Since 2004, spectacular results have been obtained when low-energy x-ray irradiations have been combined with nanoparticles. Recently, the same combination has been explored in hadron therapy. In vitro studies have shown a significant amplification of the biological damage in tumor cells charged with nanoparticles and irradiated with fast ions. This has been attributed to the increase in the ionizations and electron emissions induced by the incident ions or the electrons in the secondary tracks on the high-Z atoms, resulting in a local energy deposition enhancement. However, this subject is still a matter of controversy. Within this context, the main goal of the authors’ work was to provide new insights into the dose enhancement effects of nanoparticles in proton therapy. Methods: For this purpose, Monte Carlo calculations (GATE/GEANT4 code) were performed. In particular, the GEANT4-DNA toolkit, which allows the modeling of early biological damages induced by ionizing radiation at the DNA scale, was used. The nanometric radial energy distributions around the nanoparticle were studied, and the processes (such as Auger deexcitation or dissociative electron attachment) participating in the dose deposition of proton therapy treatments in the presence of nanoparticles were evaluated. It has been reported that the architecture of Monte Carlo calculations plays a crucial role in the assessment of nanoparticle dose enhancement and that it may introduce a bias in the results or amplify the possible final dose enhancement. Thus, a dosimetric study of different cases was performed, considering Au and Gd nanoparticles, several nanoparticle sizes (from 4 to 50 nm), and several beam configurations (source-nanoparticle distances and source sizes). Results: This Monte Carlo study shows the influence of the simulations’ parameters on the local

  18. Preparation of proton conducting membranes containing bifunctional titania nanoparticles

    NASA Astrophysics Data System (ADS)

    Aslan, Ayşe; Bozkurt, Ayhan

    2013-07-01

    Throughout this work, the synthesis and characterization of novel proton conducting nanocomposite membranes including binary and ternary mixtures of sulfated nano-titania (TS), poly(vinyl alcohol) (PVA), and nitrilotri(methyl phosphonic acid) (NMPA) are discussed. The materials were produced by means of two different approaches where in the first, PVA and TS (10-15 nm) were admixed to form a binary system. The second method was the ternary nanocomposite membranes including PVA/TS/NMPA that were prepared at several compositions to get PVA-TS-(NMPA) x . The interaction of functional nano particles and NMPA in the host matrix was explored by FT-IR spectroscopy. The homogeneous distribution of bifunctional nanoparticles in the membrane was confirmed by SEM micrographs. The spectroscopic measurements and water/methanol uptake studies suggested a complexation between PVA and NMPA, which inhibited the leaching of the latter. The thermogravimetry analysis results verified that the presence of TS in the composite membranes suppressed the formation of phosphonic acid anhydrides up to 150 °C. The maximum proton conductivity has been measured for PVA-TS-(NMPA)3 as 0.003 S cm-1 at 150 °C.

  19. Surface patterning of nanoparticles with polymer patches

    SciTech Connect

    Choueiri, Rachelle M.; Galati, Elizabeth; Thérien-Aubin, Héloïse; Klinkova, Anna; Larin, Egor M.; Querejeta-Fernández, Ana; Han, Lili; Xin, Huolin L.; Gang, Oleg; Zhulina, Ekaterina B.; Rubinstein, Michael; Kumacheva, Eugenia

    2016-08-24

    Patterning of colloidal particles with chemically or topographically distinct surface domains (patches) has attracted intense research interest. Surface-patterned particles act as colloidal analogues of atoms and molecules serve as model systems in studies of phase transitions in liquid systems, behave as ‘colloidal surfactants’ and function as templates for the synthesis of hybrid particles. The generation of micrometre- and submicrometre-sized patchy colloids is now efficient but surface patterning of inorganic colloidal nanoparticles with dimensions of the order of tens of nanometres is uncommon. Such nanoparticles exhibit size- and shape-dependent optical, electronic and magnetic properties, and their assemblies show new collective properties. At present, nanoparticle patterning is limited to the generation of two-patch nanoparticles and nanoparticles with surface ripples or a ‘raspberry’ surface morphology. We demonstrate nanoparticle surface patterning, which utilizes thermodynamically driven segregation of polymer ligands from a uniform polymer brush into surface-pinned micelles following a change in solvent quality. Patch formation is reversible but can be permanently preserved using a photocrosslinking step. The methodology offers the ability to control the dimensions of patches, their spatial distribution and the number of patches per nanoparticle, in agreement with a theoretical model. The versatility of the strategy is demonstrated by patterning nanoparticles with different dimensions, shapes and compositions, tethered with various types of polymers and subjected to different external stimuli. Furthermore, these patchy nanocolloids have potential applications in fundamental research, the self-assembly of nanomaterials, diagnostics, sensing and colloidal stabilization.

  20. Surface patterning of nanoparticles with polymer patches

    NASA Astrophysics Data System (ADS)

    Choueiri, Rachelle M.; Galati, Elizabeth; Thérien-Aubin, Héloïse; Klinkova, Anna; Larin, Egor M.; Querejeta-Fernández, Ana; Han, Lili; Xin, Huolin L.; Gang, Oleg; Zhulina, Ekaterina B.; Rubinstein, Michael; Kumacheva, Eugenia

    2016-10-01

    Patterning of colloidal particles with chemically or topographically distinct surface domains (patches) has attracted intense research interest. Surface-patterned particles act as colloidal analogues of atoms and molecules, serve as model systems in studies of phase transitions in liquid systems, behave as ‘colloidal surfactants’ and function as templates for the synthesis of hybrid particles. The generation of micrometre- and submicrometre-sized patchy colloids is now efficient, but surface patterning of inorganic colloidal nanoparticles with dimensions of the order of tens of nanometres is uncommon. Such nanoparticles exhibit size- and shape-dependent optical, electronic and magnetic properties, and their assemblies show new collective properties. At present, nanoparticle patterning is limited to the generation of two-patch nanoparticles, and nanoparticles with surface ripples or a ‘raspberry’ surface morphology. Here we demonstrate nanoparticle surface patterning, which utilizes thermodynamically driven segregation of polymer ligands from a uniform polymer brush into surface-pinned micelles following a change in solvent quality. Patch formation is reversible but can be permanently preserved using a photocrosslinking step. The methodology offers the ability to control the dimensions of patches, their spatial distribution and the number of patches per nanoparticle, in agreement with a theoretical model. The versatility of the strategy is demonstrated by patterning nanoparticles with different dimensions, shapes and compositions, tethered with various types of polymers and subjected to different external stimuli. These patchy nanocolloids have potential applications in fundamental research, the self-assembly of nanomaterials, diagnostics, sensing and colloidal stabilization.

  1. Comparing gold nano-particle enhanced radiotherapy with protons, megavoltage photons and kilovoltage photons: a Monte Carlo simulation.

    PubMed

    Lin, Yuting; McMahon, Stephen J; Scarpelli, Matthew; Paganetti, Harald; Schuemann, Jan

    2014-12-21

    Gold nanoparticles (GNPs) have shown potential to be used as a radiosensitizer for radiation therapy. Despite extensive research activity to study GNP radiosensitization using photon beams, only a few studies have been carried out using proton beams. In this work Monte Carlo simulations were used to assess the dose enhancement of GNPs for proton therapy. The enhancement effect was compared between a clinical proton spectrum, a clinical 6 MV photon spectrum, and a kilovoltage photon source similar to those used in many radiobiology lab settings. We showed that the mechanism by which GNPs can lead to dose enhancements in radiation therapy differs when comparing photon and proton radiation. The GNP dose enhancement using protons can be up to 14 and is independent of proton energy, while the dose enhancement is highly dependent on the photon energy used. For the same amount of energy absorbed in the GNP, interactions with protons, kVp photons and MV photons produce similar doses within several nanometers of the GNP surface, and differences are below 15% for the first 10 nm. However, secondary electrons produced by kilovoltage photons have the longest range in water as compared to protons and MV photons, e.g. they cause a dose enhancement 20 times higher than the one caused by protons 10 μm away from the GNP surface. We conclude that GNPs have the potential to enhance radiation therapy depending on the type of radiation source. Proton therapy can be enhanced significantly only if the GNPs are in close proximity to the biological target.

  2. Comparing gold nano-particle enhanced radiotherapy with protons, megavoltage photons and kilovoltage photons: a Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Lin, Yuting; McMahon, Stephen J.; Scarpelli, Matthew; Paganetti, Harald; Schuemann, Jan

    2014-12-01

    Gold nanoparticles (GNPs) have shown potential to be used as a radiosensitizer for radiation therapy. Despite extensive research activity to study GNP radiosensitization using photon beams, only a few studies have been carried out using proton beams. In this work Monte Carlo simulations were used to assess the dose enhancement of GNPs for proton therapy. The enhancement effect was compared between a clinical proton spectrum, a clinical 6 MV photon spectrum, and a kilovoltage photon source similar to those used in many radiobiology lab settings. We showed that the mechanism by which GNPs can lead to dose enhancements in radiation therapy differs when comparing photon and proton radiation. The GNP dose enhancement using protons can be up to 14 and is independent of proton energy, while the dose enhancement is highly dependent on the photon energy used. For the same amount of energy absorbed in the GNP, interactions with protons, kVp photons and MV photons produce similar doses within several nanometers of the GNP surface, and differences are below 15% for the first 10 nm. However, secondary electrons produced by kilovoltage photons have the longest range in water as compared to protons and MV photons, e.g. they cause a dose enhancement 20 times higher than the one caused by protons 10 μm away from the GNP surface. We conclude that GNPs have the potential to enhance radiation therapy depending on the type of radiation source. Proton therapy can be enhanced significantly only if the GNPs are in close proximity to the biological target.

  3. Platinum Attachments on Iron Oxide Nanoparticle Surfaces

    SciTech Connect

    Palchoudhury, Soubantika; Xu, Yaolin; An, Wei; Turner, C. H.; Bao, Yuping

    2010-04-30

    Platinum nanoparticles supported on metal oxide surfaces have shown great potential as heterogeneous catalysts to accelerate electrochemical processes, such as the oxygen reduction reaction in fuel cells. Recently, the use of magnetic supports has become a promising research topic for easy separation and recovery of catalysts using magnets, such as Pt nanoparticles supported on iron oxide nanoparticles. The attachment of Pt on iron oxide nanoparticles is limited by the wetting ability of the Pt (metal) on ceramic surfaces. A study of Pt nanoparticle attachment on iron oxide nanoparticle surfaces in an organic solvent is reported, which addresses the factors that promote or inhibit such attachment. It was discovered that the Pt attachment strongly depends on the capping molecules of the iron oxide seeds and the reaction temperature. For example, the attachment of Pt nanoparticles on oleic acid coated iron oxide nanoparticles was very challenging, because of the strong binding between the carboxylic groups and iron oxide surfaces. In contrast, when nanoparticles are coated with oleic acid/tri-n-octylphosphine oxide or oleic acid/oleylamine, a significant increase in Pt attachment was observed. Electronic structure calculations were then applied to estimate the binding energies between the capping molecules and iron ions, and the modeling results strongly support the experimental observations.

  4. Enhanced relative biological effectiveness of proton radiotherapy in tumor cells with internalized gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Polf, Jerimy C.; Bronk, Lawrence F.; Driessen, Wouter H. P.; Arap, Wadih; Pasqualini, Renata; Gillin, Michael

    2011-05-01

    The development and use of sensitizing agents to improve the effectiveness of radiotherapy have long been sought to improve our ability to treat cancer. In this letter, we have studied the relative biological effectiveness of proton beam radiotherapy on prostate tumor cells with and without internalized gold nanoparticles. The effectiveness of proton radiotherapy for the killing of prostate tumor cells was increased by approximately 15%-20% for those cells containing internalized gold nanoparticles.

  5. Enhanced relative biological effectiveness of proton radiotherapy in tumor cells with internalized gold nanoparticles

    SciTech Connect

    Polf, Jerimy C.; Gillin, Michael; Bronk, Lawrence F.; Driessen, Wouter H. P.; Arap, Wadih; Pasqualini, Renata

    2011-05-09

    The development and use of sensitizing agents to improve the effectiveness of radiotherapy have long been sought to improve our ability to treat cancer. In this letter, we have studied the relative biological effectiveness of proton beam radiotherapy on prostate tumor cells with and without internalized gold nanoparticles. The effectiveness of proton radiotherapy for the killing of prostate tumor cells was increased by approximately 15%-20% for those cells containing internalized gold nanoparticles.

  6. Mercury's Surface Magnetic Field Determined from Proton-Reflection Magnetometry

    NASA Technical Reports Server (NTRS)

    Winslow, Reka M.; Johnson, Catherine L.; Anderson, Brian J.; Gershman, Daniel J.; Raines, Jim M.; Lillis, Robert J.; Korth, Haje; Slavin, James A.; Solomon, Sean C.; Zurbuchen, Thomas H.; Zuber, Maria T.

    2014-01-01

    Solar wind protons observed by the MESSENGER spacecraft in orbit about Mercury exhibit signatures of precipitation loss to Mercury's surface. We apply proton-reflection magnetometry to sense Mercury's surface magnetic field intensity in the planet's northern and southern hemispheres. The results are consistent with a dipole field offset to the north and show that the technique may be used to resolve regional-scale fields at the surface. The proton loss cones indicate persistent ion precipitation to the surface in the northern magnetospheric cusp region and in the southern hemisphere at low nightside latitudes. The latter observation implies that most of the surface in Mercury's southern hemisphere is continuously bombarded by plasma, in contrast with the premise that the global magnetic field largely protects the planetary surface from the solar wind.

  7. Impact of nanoparticle size and shape on selective surface segregation in polymer nanocomposites

    SciTech Connect

    Mutz, M; Holley, Daniel W; Baskaran, Durairaj; Mays, Jimmy; Dadmun, Mark D

    2012-01-01

    A study of the impact of the size and shape of a nanoparticle on the evolution of structure and surface segregation in polymer nanocomposite thin films is presented. This is realized by monitoring the evolution of structure with thermal annealing and equilibrium depth profile of a deuterated polystyrene/ protonated polystyrene bilayer in the presence and absence of various nanoparticles. For the three shapes examined, sheet-like graphene, cylindrical carbon nanotubes, and spherical soft nanoparticles, the presence of the nanoparticles slowed the inter-diffusion of the polymers in the thin film. The larger nanoparticles slowed the polymer motion the most, while the smaller spherical nanoparticles also significantly inhibited polymer chain diffusion. At equilibrium, the soft spherical nanoparticles, which are highly branched, segregate to the air surface, resulting in a decrease in the excess deuterated PS at the surface. The graphene sheets and single walled carbon nanotubes, on the other hand, enhanced the dPS segregation to the air surface. The graphene sheets were found to segregate to the silicon surface, due to their higher surface energy. Interpretation of these results indicates that entropic factors drive the structural development in the nanocomposite thin films containing the spherical nanoparticles, while a balance of the surface energies of the various components (i.e. enthalpy) controls the thin film structure formation in the polymer-carbon nanoparticle nanocomposites.

  8. Surface patterning of nanoparticles with polymer patches

    DOE PAGES

    Choueiri, Rachelle M.; Galati, Elizabeth; Thérien-Aubin, Héloïse; ...

    2016-08-24

    Patterning of colloidal particles with chemically or topographically distinct surface domains (patches) has attracted intense research interest. Surface-patterned particles act as colloidal analogues of atoms and molecules serve as model systems in studies of phase transitions in liquid systems, behave as ‘colloidal surfactants’ and function as templates for the synthesis of hybrid particles. The generation of micrometre- and submicrometre-sized patchy colloids is now efficient but surface patterning of inorganic colloidal nanoparticles with dimensions of the order of tens of nanometres is uncommon. Such nanoparticles exhibit size- and shape-dependent optical, electronic and magnetic properties, and their assemblies show new collective properties.more » At present, nanoparticle patterning is limited to the generation of two-patch nanoparticles and nanoparticles with surface ripples or a ‘raspberry’ surface morphology. We demonstrate nanoparticle surface patterning, which utilizes thermodynamically driven segregation of polymer ligands from a uniform polymer brush into surface-pinned micelles following a change in solvent quality. Patch formation is reversible but can be permanently preserved using a photocrosslinking step. The methodology offers the ability to control the dimensions of patches, their spatial distribution and the number of patches per nanoparticle, in agreement with a theoretical model. The versatility of the strategy is demonstrated by patterning nanoparticles with different dimensions, shapes and compositions, tethered with various types of polymers and subjected to different external stimuli. Furthermore, these patchy nanocolloids have potential applications in fundamental research, the self-assembly of nanomaterials, diagnostics, sensing and colloidal stabilization.« less

  9. Surface patterning of nanoparticles with polymer patches

    PubMed Central

    Choueiri, Rachelle M.; Galati, Elizabeth; Thérien-Aubin, Héloïse; Klinkova, Anna; Larin, Egor M.; Querejeta-Fernández, Ana; Han, Lili; Xin, Huolin L.; Gang, Oleg; Zhulina, Ekaterina B.; Rubinstein, Michael; Kumacheva, Eugenia

    2016-01-01

    Patterning of colloidal particles with chemically or topographically distinct surface domains (patches) has attracted intense research interest1–3. Surface-patterned particles act as colloidal analogues of atoms and molecules4,5, serve as model systems in studies of phase transitions in liquid systems6, behave as ‘colloidal surfactants’7 and function as templates for the synthesis of hybrid particles8. The generation of micrometre- and submicrometre-sized patchy colloids is now efficient9–11, but surface patterning of inorganic colloidal nanoparticles with dimensions of the order of tens of nanometres is uncommon. Such nanoparticles exhibit size- and shape-dependent optical, electronic and magnetic properties, and their assemblies show new collective properties12. At present, nanoparticle patterning is limited to the generation of two-patch nanoparticles13–15, and nanoparticles with surface ripples16 or a ‘raspberry’ surface morphology17. Here we demonstrate nanoparticle surface patterning, which utilizes thermodynamically driven segregation of polymer ligands from a uniform polymer brush into surface-pinned micelles following a change in solvent quality. Patch formation is reversible but can be permanently preserved using a photocrosslinking step. The methodology offers the ability to control the dimensions of patches, their spatial distribution and the number of patches per nanoparticle, in agreement with a theoretical model. The versatility of the strategy is demonstrated by patterning nanoparticles with different dimensions, shapes and compositions, tethered with various types of polymers and subjected to different external stimuli. These patchy nanocolloids have potential applications in fundamental research, the self-assembly of nanomaterials, diagnostics, sensing and colloidal stabilization. PMID:27556943

  10. Surface complexation of Pb(II) by hexagonal birnessite nanoparticles

    SciTech Connect

    Kwon, K.; Refson, K.; Sposito, G.

    2010-10-15

    Natural hexagonal birnessite is a poorly-crystalline layer type Mn(IV) oxide precipitated by bacteria and fungi which has a particularly high adsorption affinity for Pb(II). X-ray spectroscopic studies have shown that Pb(II) forms strong inner-sphere surface complexes mainly at two sites on hexagonal birnessite nanoparticles: triple corner-sharing (TCS) complexes on Mn(IV) vacancies in the interlayers and double edge-sharing (DES) complexes on lateral edge surfaces. Although the TCS surface complex has been well characterized by spectroscopy, some important questions remain about the structure and stability of the complexes occurring on the edge surfaces. First-principles simulation techniques such as density functional theory (DFT) offer a useful way to address these questions by providing complementary information that is difficult to obtain by spectroscopy. Following this computational approach, we used spin-polarized DFT to perform total-energy-minimization geometry optimizations of several possible Pb(II) surface complexes on model birnessite nanoparticles similar to those that have been studied experimentally. We first validated our DFT calculations by geometry optimizations of (1) the Pb-Mn oxyhydroxide mineral, quenselite (PbMnO{sub 2}OH), and (2) the TCS surface complex, finding good agreement with experimental structural data while uncovering new information about bonding and stability. Our geometry optimizations of several protonated variants of the DES surface complex led us to conclude that the observed edge-surface species is very likely to be this complex if the singly-coordinated terminal O that binds to Pb(II) is protonated. Our geometry optimizations also revealed that an unhydrated double corner-sharing (DCS) species that has been proposed as an alternative to the DES complex is intrinsically unstable on nanoparticle edge surfaces, but could become stabilized if the local coordination environment is well-hydrated. A significant similarity exists

  11. Surface complexation of Pb(II) by hexagonal birnessite nanoparticles

    NASA Astrophysics Data System (ADS)

    Kwon, Kideok D.; Refson, Keith; Sposito, Garrison

    2010-12-01

    Natural hexagonal birnessite is a poorly crystalline layer type Mn(IV) oxide precipitated by bacteria and fungi which has a particularly high adsorption affinity for Pb(II). X-ray spectroscopic studies have shown that Pb(II) forms strong inner-sphere surface complexes mainly at two sites on hexagonal birnessite nanoparticles: triple corner-sharing (TCS) complexes on Mn(IV) vacancies in the interlayers and double edge-sharing (DES) complexes on lateral edge surfaces. Although the TCS surface complex has been well characterized by spectroscopy, some important questions remain about the structure and stability of the complexes occurring on the edge surfaces. First-principles simulation techniques such as density functional theory (DFT) offer a useful way to address these questions by providing complementary information that is difficult to obtain by spectroscopy. Following this computational approach, we used spin-polarized DFT to perform total-energy-minimization geometry optimizations of several possible Pb(II) surface complexes on model birnessite nanoparticles similar to those that have been studied experimentally. We first validated our DFT calculations by geometry optimizations of (1) the Pb-Mn oxyhydroxide mineral, quenselite (PbMnO 2OH), and (2) the TCS surface complex, finding good agreement with experimental structural data while uncovering new information about bonding and stability. Our geometry optimizations of several protonated variants of the DES surface complex led us to conclude that the observed edge-surface species is very likely to be this complex if the singly coordinated terminal O that binds to Pb(II) is protonated. Our geometry optimizations also revealed that an unhydrated double corner-sharing (DCS) species that has been proposed as an alternative to the DES complex is intrinsically unstable on nanoparticle edge surfaces, but could become stabilized if the local coordination environment is well-hydrated. A significant similarity exists in

  12. Modes of interaction between inorganic engineered nanoparticles and biological and abiotic surfaces

    NASA Astrophysics Data System (ADS)

    Schaumann, G. E.; Abraham, P. M.; Dabrunz, A.

    2012-04-01

    Engineered nanoparticles aging and transformation pathways in natural environmental systems are linked with their attachment to surfaces of organisms, plant leaves, biofilms, soil or sediment particles. In this study we investigated attachment of nAg0 and nTiO2 to plant leaves and organic and inorganic model surfaces and daphnia with the objective to understand the physicochemistry behind these interactions as well as potential ecological effects linked with this attachment. Surface-nanoparticle interactions were investigated in well-defined sorption studies and compared to conditions in in ecotoxicological test systems. Model surfaces were chosen to cover a wide range of intermolecular interactions considering van-der Waals interactions as well as proton donor and acceptor interactions. The nanoparticle-surface complexes were analysed with microscopic techniques including optical microscopy, environmental scanning electron microscopy and atomic force microscopy (AFM) as well as with respect to physicochemical interactions. While deposition of nanoparticles in ecotoxicological test systems is often determined by aggregation, and toxicity may be induced by physical effects, sorption of nanoparticle from stable suspensions is controlled by the chemical nature of the model surfaces as well as by the surfaces accessible for the nanoparticles. The current results show that attachment is determined by an intensive interplay between physicochemical nanoparticle-surface interactions, aggregation stability and physical characteristics. This interplay will mutually affect the ecological relevance, including further fate, transport and effects of the nanoparticles in the environment.

  13. Nanoparticle Based Surface-Enhanced Raman Spectroscopy

    SciTech Connect

    Talley, C E; Huser, T R; Hollars, C W; Jusinski, L; Laurence, T; Lane, S M

    2005-01-03

    Surface-enhanced Raman scattering is a powerful tool for the investigation of biological samples. Following a brief introduction to Raman and surface-enhanced Raman scattering, several examples of biophotonic applications of SERS are discussed. The concept of nanoparticle based sensors using SERS is introduced and the development of these sensors is discussed.

  14. Nanoparticle-based PARACEST agents: the quenching effect of silica nanoparticles on the CEST signal from surface-conjugated chelates.

    PubMed

    Evbuomwan, Osasere M; Merritt, Matthew E; Kiefer, Garry E; Dean Sherry, A

    2012-01-01

    Silica nanoparticles of average diameter 53 ± 3 nm were prepared using standard water-in-oil microemulsion methods. After conversion of the surface Si-OH groups to amino groups for further conjugation, the PARACEST agent, EuDOTA-(gly)₄ (-) was coupled to the amines via one or more side-chain carboxyl groups in an attempt to trap water molecules in the inner-sphere of the complex. Fluorescence and ICP analyses showed that approximately 1200 Eu(3+) complexes were attached to each silica nanoparticle, leaving behind excess protonated amino groups. CEST spectra of the modified silica nanoparticles showed that attachment of the EuDOTA-(gly)₄ (-) to the surface of the nanoparticles did not result in a decrease in water exchange kinetics as anticipated, but rather resulted in a complete elimination of the normal Eu(3+) -bound water exchange peak and broadening of the bulk water signal. This observation was traced to catalysis of proton exchange from the Eu(3+) -bound water molecule by excess positively charged amino groups on the surface of the nanoparticles.

  15. Possible Albedo Proton Signature of Hydrated Lunar Surface Layer

    NASA Astrophysics Data System (ADS)

    Schwadron, N.; Wilson, J. K.; Looper, M. D.; Jordan, A.; Spence, H. E.; Blake, J. B.; Case, A. W.; Iwata, Y.; Kasper, J. C.; Farrell, W. M.; Lawrence, D. J.; Livadiotis, G.; Mazur, J. E.; Petro, N. E.; Pieters, C. M.; Robinson, M. S.; Smith, S. S.; Townsend, L. W.; Zeitlin, C. J.

    2015-12-01

    We find evidence for a surface layer of hydrated material in the lunar regolith using "albedo protons" measured by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high-energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and cannot be accounted for by either heavy element enrichment (e.g., enhanced Fe abundance), or by deeply buried (> 50 cm) hydrogenous material. The latitudinal distribution of albedo protons does not correlate with that of epithermal or high-energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in a thin (~ 1-10 cm) layer of hydrated regolith near the surface that is more prevalent near the poles. The CRaTER instrument thus provides critical measurements of volatile distributions within lunar regolith and potentially, with similar sensors and observations, at other bodies within the Solar System.

  16. Surface, structural and tensile properties of proton beam irradiated zirconium

    NASA Astrophysics Data System (ADS)

    Rafique, Mohsin; Chae, San; Kim, Yong-Soo

    2016-02-01

    This paper reports the surface, structural and tensile properties of proton beam irradiated pure zirconium (99.8%). The Zr samples were irradiated by 3.5 MeV protons using MC-50 cyclotron accelerator at different doses ranging from 1 × 1013 to 1 × 1016 protons/cm2. Both un-irradiated and irradiated samples were characterized using Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD) and Universal Testing Machine (UTM). The average surface roughness of the specimens was determined by using Nanotech WSxM 5.0 develop 7.0 software. The FESEM results revealed the formation of bubbles, cracks and black spots on the samples' surface at different doses whereas the XRD results indicated the presence of residual stresses in the irradiated specimens. Williamson-Hall analysis of the diffraction peaks was carried out to investigate changes in crystallite size and lattice strain in the irradiated specimens. The tensile properties such as the yield stress, ultimate tensile stress and percentage elongation exhibited a decreasing trend after irradiation in general, however, an inconsistent behavior was observed in their dependence on proton dose. The changes in tensile properties of Zr were associated with the production of radiation-induced defects including bubbles, cracks, precipitates and simultaneous recovery by the thermal energy generated with the increase of irradiation dose.

  17. Nanoparticle-textured surfaces from spin coating.

    PubMed

    Weiss, R A; Zhai, X; Dobrynin, A V

    2008-05-20

    Rough surfaces composed of discrete but relatively uniform nanoparticles were prepared from a lightly sulfonated polystyrene ionomer by spin coating from tetrahydrofuran (THF) or a THF/methanol mixture onto a silica surface. The particle morphology is consistent with the spinodal decomposition of the film surface occurring during spin coating. The particles are well wetted to the silica, and if heated for a long time above the ionomer's glass-transition temperature, the particles flow and coalesce into a smooth, homogeneous film.

  18. Immobilization of Polymeric Luminophor on Nanoparticles Surface

    NASA Astrophysics Data System (ADS)

    Bolbukh, Yuliia; Podkoscielna, Beata; Lipke, Agnieszka; Bartnicki, Andrzej; Gawdzik, Barbara; Tertykh, Valentin

    2016-04-01

    Polymeric luminophors with reduced toxicity are of the priorities in the production of lighting devices, sensors, detectors, bioassays or diagnostic systems. The aim of this study was to develop a method of immobilization of the new luminophor on a surface of nanoparticles and investigation of the structure of the grafted layer. Monomer 2,7-(2-hydroxy-3-methacryloyloxypropoxy)naphthalene (2,7-NAF.DM) with luminophoric properties was immobilized on silica and carbon nanotubes in two ways: mechanical mixing with previously obtained polymer and by in situ oligomerization with chemisorption after carrier's modification with vinyl groups. The attached polymeric (or oligomeric) surface layer was studied using thermal and spectral techniques. Obtained results confirm the chemisorption of luminophor on the nanotubes and silica nanoparticles at the elaborated synthesis techniques. The microstructure of 2,7-NAF.DM molecules after chemisorption was found to be not changed. The elaborated modification approach allows one to obtain nanoparticles uniformly covered with polymeric luminophor.

  19. Refracting surface plasmon polaritons with nanoparticle arrays.

    PubMed

    Radko, Ilya P; Evlyukhin, Andrey B; Boltasseva, Alexandra; Bozhevolnyi, Sergey I

    2008-03-17

    Refraction of surface plasmon polaritons (SPPs) by various structures formed by a 100-nm-period square lattice of gold nanoparticles on top of a gold film is studied by leakage radiation microscopy. SPP refraction by a triangular-shaped nanoparticle array indicates that the SPP effective refractive index increases inside the array by a factor of approximately 1.08 (for the wavelength 800 nm) with respect to the SPP index at a flat surface. Observations of SPP focusing and deflection by circularly shaped areas as well as SPP waveguiding inside rectangular arrays are consistent with the SPP index increase deduced from the SPP refraction by triangular arrays. The SPP refractive index is found to decrease slightly for longer wavelengths within the wavelength range of 700-860 nm. Modeling based on the Green's tensor formalism is in a good agreement with the experimental results, opening the possibility to design nanoparticle arrays for specific applications requiring in-plane SPP manipulation.

  20. Hydrophobic Silsesquioxane Nanoparticles and Nanocomposite Surfaces (POSTPRINT)

    DTIC Science & Technology

    2006-05-04

    Fluorinated Polyhedral Oligomeric Silsesquioxanes are hydrophobic nanoparticles. One compound, FD8T8, is ultrahydrophobic, possessing a water contact ... angle of 154 deg. This is believed to be the most hydrophobic and lowest surface tension crystalline substance known. Analysis of the x-ray crystal

  1. Water-Mediated Proton Hopping on an Iron Oxide Surface

    SciTech Connect

    Merte, L. R.; Peng, Guowen; Bechstein, Ralf; Rieboldt, Felix; Farberow, Carrie A.; Grabow, Lars C.; Kudernatsch, Wilhelmine; Wendt, Stefen; Laegsgaard, E.; Mavrikakis, Manos; Besenbacher, Fleming

    2012-05-18

    The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H3O+-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO2(110), where water dissociation is a key step in proton diffusion.

  2. RAPID COMMUNICATION: Surface vertical deposition for gold nanoparticle film

    NASA Astrophysics Data System (ADS)

    Diao, J. J.; Qiu, F. S.; Chen, G. D.; Reeves, M. E.

    2003-02-01

    In this rapid communication, we present the surface vertical deposition (SVD) method to synthesize the gold nanoparticle films. Under conditions where the surface of the gold nanoparticle suspension descends slowly by evaporation, the gold nanoparticles in the solid-liquid-gas junction of the suspension aggregate together on the substrate by the force of solid and liquid interface. When the surface properties of the substrate and colloidal nanoparticle suspension define for the SVD, the density of gold nanoparticles in the thin film made by SVD only depends on the descending velocity of the suspension surface and on the concentration of the gold nanoparticle suspension.

  3. Pt nanoparticle-dispersed graphene-wrapped MWNT composites as oxygen reduction reaction electrocatalyst in proton exchange membrane fuel cell.

    PubMed

    Aravind, S S Jyothirmayee; Ramaprabhu, Sundara

    2012-08-01

    Chemical and electrical synergies between graphite oxide and multiwalled carbon nanotube (MWNT) for processing graphene wrapped-MWNT hybrids has been realized by chemical vapor deposition without any chemical functionalization. Potential of the hybrid composites have been demonstrated by employing them as electrocatalyst supports in proton exchange membrane fuel cells. The defects present in the polyelectrolyte, which have been wrapped over highly dispersed MWNT, act as anchoring sites for the homogeneous deposition of platinum nanoparticles. Single-cell proton exchange membrane fuel cells show that the power density of the hybrid composite-based fuel cells is higher compared to the pure catalyst-support-based fuel cells, because of enhanced electrochemical reactivity and good surface area of the nanocomposites.

  4. Transmutable nanoparticles with reconfigurable surface ligands

    NASA Astrophysics Data System (ADS)

    Kim, Youngeun; Macfarlane, Robert J.; Jones, Matthew R.; Mirkin, Chad A.

    2016-02-01

    Unlike conventional inorganic materials, biological systems are exquisitely adapted to respond to their surroundings. Proteins and other biological molecules can process a complex set of chemical binding events as informational inputs and respond accordingly via a change in structure and function. We applied this principle to the design and synthesis of inorganic materials by preparing nanoparticles with reconfigurable surface ligands, where interparticle bonding can be programmed in response to specific chemical cues in a dynamic manner. As a result, a nascent set of “transmutable nanoparticles” can be driven to crystallize along multiple thermodynamic trajectories, resulting in rational control over the phase and time evolution of nanoparticle-based matter.

  5. In vitro cytotoxicity of surface modified bismuth nanoparticles.

    PubMed

    Luo, Yang; Wang, Chaoming; Qiao, Yong; Hossain, Mainul; Ma, Liyuan; Su, Ming

    2012-10-01

    This paper describes in vitro cytotoxicity of bismuth nanoparticles revealed by three complementary assays (MTT, G6PD, and calcein AM/EthD-1). The results show that bismuth nanoparticles are more toxic than most previously reported bismuth compounds. Concentration dependent cytotoxicities have been observed for bismuth nanoparticles and surface modified bismuth nanoparticles. The bismuth nanoparticles are non-toxic at concentration of 0.5 nM. Nanoparticles at high concentration (50 nM) kill 45, 52, 41, 34 % HeLa cells for bare nanoparticles, amine terminated bismuth nanoparticles, silica coated bismuth nanoparticles, and polyethylene glycol (PEG) modified bismuth nanoparticles, respectively; which indicates cytotoxicity in terms of cell viability is in the descending order of amine terminated bismuth nanoparticles, bare bismuth nanoparticles, silica coated bismuth nanoparticles, and PEG modified bismuth nanoparticles. HeLa cells are more susceptible to toxicity from bismuth nanoparticles than MG-63 cells. The simultaneous use of three toxicity assays provides information on how nanoparticles interact with cells. Silica coated bismuth nanoparticles can damage cellular membrane yet keep mitochondria less influenced; while amine terminated bismuth nanoparticles can affect the metabolic functions of cells. The findings have important implications for caution of nanoparticle exposure and evaluating toxicity of bismuth nanoparticles.

  6. WE-G-BRE-02: Biological Modeling of Gold Nanoparticle Radiosensitization for Proton Therapy

    SciTech Connect

    Lin, Y; Paganetti, H; Schuemann, J

    2014-06-15

    Purpose: The aim of this work is to investigate the radiosensitization effect of gold nanoparticles (GNP) in a proton beam. A computational model was built using the Local Effect Model (LEM) to predict the biological outcome of gold nanoparticle (GNP) sensitization. We present the results using a clinical proton beam, 6MV photon beam and two kilovoltage photon beams. Methods: First, Monte Carlo simulations were carried out using TOPAS (TOol for PArticle Simulation) to obtain the spatial dose distribution in the vicinity of GNPs. The dose distribution was then used as an input for LEM, which predicts dose-response curves for high linear energy transfer radiation using the track structure. The cell survival curves were evaluated for three particle sources (proton beam, MV photon beam and kV photon beam), various treatment depths for each particle source, various GNP uptakes and two different GNP sizes. Results: For proton therapy, the GNP sensitization effect is highly dependent on the treatment depth due to the energy-dependent interaction probability. We predict that if GNPs can be taken up by the cell nucleus, proton therapy can be significantly enhanced. If GNPs are only internalized into the cytoplasm, proton therapy can still be enhanced by GNPs and if GNPs are not internalized into cells, there will be no direct damage to the nucleus. For the same GNP uptake and concentration, the cell survival at 2Gy is reduced by 80% using kilovoltage photons, 50% using protons and only 2% using clinical MV photons. Finally, for the same weight of GNPs taken up by the cells, 10 nm GNPs causes 3 times more damage than 50 nm GNPs. Conclusion: We showed that GNPs have potential to be used to enhance radiation therapy for clinical proton beams.

  7. Surface energy of metal alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Takrori, Fahed M.; Ayyad, Ahmed

    2017-04-01

    The measurement of surface energy of alloy nanoparticles experimentally is still a challenge therefore theoretical work is necessary to estimate its value. In continuation of our previous work on the calculation of the surface energy of pure metallic nanoparticles we have extended our work to calculate the surface energy of different alloy systems, namely, Co-Ni, Au-Cu, Cu-Al, Cu-Mg and Mo-Cs binary alloys. It is shown that the surface energy of metallic binary alloy decreases with decreasing particle size approaching relatively small values at small sizes. When both metals in the alloy obey the Hume-Rothery rules, the difference in the surface energy is small at the macroscopic as well as in the nano-scale. However when the alloy deviated from these rules the difference in surface energy is large in the macroscopic and in the nano scales. Interestingly when solid solution formation is not possible at the macroscopic scale according to the Hume-Rothery rules, it is shown it may form at the nano-scale. To our knowledge these findings here are presented for the first time and is challenging from fundamental as well as technological point of views.

  8. Characterization of surface hydrophobicity of engineered nanoparticles.

    PubMed

    Xiao, Yao; Wiesner, Mark R

    2012-05-15

    The surface chemistry of nanoparticles, including their hydrophobicity, is a key determinant of their fate, transport and toxicity. Engineered NPs often have surface coatings that control the surface chemistry of NPs and may dominate the effects of the nanoparticle core. Suitable characterization methods for surface hydrophobicity at the nano-scale are needed. Three types of methods, surface adsorption, affinity coefficient and contact angle, were investigated in this study with seven carbon and metal based NPs with and without coatings. The adsorption of hydrophobic molecules, Rose Bengal dye and naphthalene, on NPs was used as one measure of hydrophobicity and was compared with the relative affinity of NPs for octanol or water phases, analogous to the determination of octanol-water partition coefficients for organic molecules. The sessile drop method was adapted for measuring contact angle of a thin film of NPs. Results for these three methods were qualitatively in agreement. Aqueous-nC(60) and tetrahydrofuran-nC(60) were observed to be more hydrophobic than nano-Ag coated with polyvinylpyrrolidone or gum arabic, followed by nano-Ag or nano-Au with citrate-functionalized surfaces. Fullerol was shown to be the least hydrophobic of seven NPs tested. The advantages and limitations of each method were also discussed.

  9. Paper surfaces for metal nanoparticle inkjet printing

    NASA Astrophysics Data System (ADS)

    Öhlund, Thomas; Örtegren, Jonas; Forsberg, Sven; Nilsson, Hans-Erik

    2012-10-01

    The widespread usage of paper and board offer largely unexploited possibilities for printed electronics applications. Reliability and performance of printed devices on comparatively rough and inhomogenous surfaces of paper does however pose challenges. Silver nanoparticle ink has been deposited on ten various paper substrates by inkjet printing. The papers are commercially available, and selected over a range of different types and construction. A smooth nonporous polyimide film was included as a nonporous reference substrate. The substrates have been characterized in terms of porosity, absorption rate, apparent surface energy, surface roughness and material content. The electrical conductivity of the resulting printed films have been measured after drying at 60 °C and again after additional curing at 110 °C. A qualitative analysis of the conductivity differences on the different substrates based on surface characterization and SEM examination is presented. Measurable parameters of importance to the final conductivity are pointed out, some of which are crucial to achieve conductivity. When certain criteria of the surfaces are met, paper media can be used as low cost, but comparably high performance substrates for metal nanoparticle inks in printed electronics applications.

  10. Investigation of gold nanoparticle radiosensitization mechanisms using a free radical scavenger and protons of different energies.

    PubMed

    Jeynes, J C G; Merchant, M J; Spindler, A; Wera, A-C; Kirkby, K J

    2014-11-07

    Gold nanoparticles (GNPs) have been shown to sensitize cancer cells to x-ray radiation, particularly at kV energies where photoelectric interactions dominate and the high atomic number of gold makes a large difference to x-ray absorption. Protons have a high cross-section for gold at a large range of relevant clinical energies, and so potentially could be used with GNPs for increased therapeutic effect.Here, we investigate the contribution of secondary electron emission to cancer cell radiosensitization and investigate how this parameter is affected by proton energy and a free radical scavenger. We simulate the emission from a realistic cell phantom containing GNPs after traversal by protons and x-rays with different energies. We find that with a range of proton energies (1-250 MeV) there is a small increase in secondaries compared to a much larger increase with x-rays. Secondary electrons are known to produce toxic free radicals. Using a cancer cell line in vitro we find that a free radical scavenger has no protective effect on cells containing GNPs irradiated with 3 MeV protons, while it does protect against cells irradiated with x-rays. We conclude that GNP generated free radicals are a major cause of radiosensitization and that there is likely to be much less dose enhancement effect with clinical proton beams compared to x-rays.

  11. Spatial distributions of dose enhancement around a gold nanoparticle at several depths of proton Bragg peak

    NASA Astrophysics Data System (ADS)

    Kwon, Jihun; Sutherland, Kenneth; Hashimoto, Takayuki; Shirato, Hiroki; Date, Hiroyuki

    2016-10-01

    Gold nanoparticles (GNPs) have been recognized as a promising candidate for a radiation sensitizer. A proton beam incident on a GNP can produce secondary electrons, resulting in an enhancement of the dose around the GNP. However, little is known about the spatial distribution of dose enhancement around the GNP, especially in the direction along the incident proton. The purpose of this study is to determine the spatial distribution of dose enhancement by taking the incident direction into account. Two steps of calculation were conducted using the Geant4 Monte Carlo simulation toolkit. First, the energy spectra of 100 and 195 MeV protons colliding with a GNP were calculated at the Bragg peak and three other depths around the peak in liquid water. Second, the GNP was bombarded by protons with the obtained energy spectra. Radial dose distributions were computed along the incident beam direction. The spatial distributions of the dose enhancement factor (DEF) and subtracted dose (Dsub) were then evaluated. The spatial DEF distributions showed hot spots in the distal radial region from the proton beam axis. The spatial Dsub distribution isotropically spread out around the GNP. Low energy protons caused higher and wider dose enhancement. The macroscopic dose enhancement in clinical applications was also evaluated. The results suggest that the consideration of the spatial distribution of GNPs in treatment planning will maximize the potential of GNPs.

  12. Surface Faceting and Reconstruction of Ceria Nanoparticles.

    PubMed

    Yang, Chengwu; Yu, Xiaojuan; Heißler, Stefan; Nefedov, Alexei; Colussi, Sara; Llorca, Jordi; Trovarelli, Alessandro; Wang, Yuemin; Wöll, Christof

    2017-01-02

    The surface atomic arrangement of metal oxides determines their physical and chemical properties, and the ability to control and optimize structural parameters is of crucial importance for many applications, in particular in heterogeneous catalysis and photocatalysis. Whereas the structures of macroscopic single crystals can be determined with established methods, for nanoparticles (NPs), this is a challenging task. Herein, we describe the use of CO as a probe molecule to determine the structure of the surfaces exposed by rod-shaped ceria NPs. After calibrating the CO stretching frequencies using results obtained for different ceria single-crystal surfaces, we found that the rod-shaped NPs actually restructure and expose {111} nanofacets. This finding has important consequences for understanding the controversial surface chemistry of these catalytically highly active ceria NPs and paves the way for the predictive, rational design of catalytic materials at the nanoscale.

  13. Exogenous control over intracellular acidification: Enhancement via proton caged compounds coupled to gold nanoparticles.

    PubMed

    Carbone, Marilena; Sabbatella, Gianfranco; Antonaroli, Simonetta; Remita, Hynd; Orlando, Viviana; Biagioni, Stefano; Nucara, Alessandro

    2015-11-01

    The pH regulation has a fundamental role in several intracellular processes and its variation via exogenous compounds is a potential tool for intervening in the intracellular processes. Proton caged compounds (PPCs) release protons upon UV irradiation and may efficiently provoke intracellular on-command acidification. Here, we explore the intracellular pH variation, when purposely synthesized PCCs are coupled to gold nanoparticles (AuNPs) and dosed to HEK-293 cells. We detected the acidification process caused by the UV irradiation by monitoring the intensity of the asymmetric stretching mode of the CO(2) molecule at 2343 cm(-1). The comparison between free and AuNPs functionalized proton caged compound demonstrates a highly enhanced CO(2) yield, hence pH variation, in the latter case. Finally, PCC functionalized AuNPs were marked with a purposely synthesized fluorescent marker and dosed to HEK-293 cells. The corresponding fluorescence optical images show green grains throughout the whole cytoplasm.

  14. LET-dependent radiosensitization effects of gold nanoparticles for proton irradiation

    NASA Astrophysics Data System (ADS)

    Li, Sha; Penninckx, Sébastien; Karmani, Linda; Heuskin, Anne-Catherine; Watillon, Kassandra; Marega, Riccardo; Zola, Jerome; Corvaglia, Valentina; Genard, Geraldine; Gallez, Bernard; Feron, Olivier; Martinive, Philippe; Bonifazi, Davide; Michiels, Carine; Lucas, Stéphane

    2016-11-01

    The development of new modalities and protocols is of major interest to improve the outcome of cancer treatment. Given the appealing physical properties of protons and the emerging evidence of biological relevance of the use of gold nanoparticles (GNPs), the radiosensitization effects of GNPs (5 or 10 nm) have been investigated in vitro in combination with a proton beam of different linear energy transfer (LET). After the incubation with GNPs for 24 h, nanoparticles were observed in the cytoplasm of A431 cells exposed to 10 nm GNPs, and in the cytoplasm as well as the nucleus of cells exposed to 5 nm GNPs. Cell uptake of 0.05 mg ml-1 of GNPs led to 0.78 pg Au/cell and 0.30 pg Au/cell after 24 h incubation for 10 and 5 nm GNPs respectively. A marked radiosensitization effect of GNPs was observed with 25 keV μm-1 protons, but not with 10 keV μm-1 protons. This effect was more pronounced for 10 nm GNPs than for 5 nm GNPs. By using a radical scavenger, a major role of reactive oxygen species in the amplification of the death of irradiated cell was identified. All together, these results open up novel perspectives for using high-Z metallic NPs in protontherapy.

  15. WE-G-BRE-04: Gold Nanoparticle Induced Vasculature Damage for Proton Therapy: Monte Carlo Simulation

    SciTech Connect

    Lin, Y; Paganetti, H; Schuemann, J

    2014-06-15

    Purpose: The aim of this work is to investigate the gold nanoparticle (GNP) induced vasculature damage in a proton beam. We compared the results using a clinical proton beam, 6MV photon beam and two kilovoltage photon beams. Methods: Monte Carlo simulations were carried out using TOPAS (TOol for PArticle Simulation) to obtain the spatial dose distribution in close proximity to GNPs up to 20μm distance. The spatial dose distribution was used as an input to calculate the additional dose deposited to the blood vessels. For this study, GNP induced vasculature damage is evaluated for three particle sources (proton beam, MV photon beam and kV photon beam), various treatment depths for each particle source, various GNP uptakes and three different vessel diameters (8μm, 14μm and 20μm). Results: The result shows that for kV photon, GNPs induce more dose in the vessel wall for 150kVp photon source than 250kVp. For proton therapy, GNPs cause more dose in the vessel wall at shallower treatment depths. For 6MV photons, GNPs induce more dose in the vessel wall at deeper treatment depths. For the same GNP concentration and prescribed dose, the additional dose at the inner vessel wall is 30% more than the prescribed dose for the kVp photon source, 15% more for the proton source and only 2% more for the 6MV photon source. In addition, the dose from GNPs deceases sharper for proton therapy than kVp photon therapy as the distance from the vessel inner wall increases. Conclusion: We show in this study that GNPs can potentially be used to enhance radiation therapy by causing vasculature damage using clinical proton beams. The GNP induced damage for proton therapy is less than for the kVp photon source but significantly larger than for the clinical MV photon source.

  16. [Experiment and analyse on the effect of magnetic nanoparticles upon relaxation time of proton in molecular recognition by MRI].

    PubMed

    Hu, Lili; Song, Tao; Yang, Wenhui; Wang, Ming; Zhang, Fang; Tao, Chunjing

    2007-06-01

    To research on the effect of three different magnetic nanoparticles upon relaxation time of proton. The detection by magnetic resonance imaging (MRI) indicates that there is the effect of marked difference to right control experiment and to analyze the difference from theory. The result discloses that will be able to perform the experiment of molecular recognition using magnetic nanoparticles later.

  17. Surface-enhanced Raman scattering of coumarin 343 on silver colloidal nanoparticles

    NASA Astrophysics Data System (ADS)

    Hussain, Shafqat; Pang, Yoonsoo

    2016-09-01

    Surface-enhanced Raman scattering (SERS) of coumarin 343 (C343) adsorbed on silver colloidal nanoparticles reduced by sodium citrate was investigated and the surface adsorption geometry of C343 on Ag was sought by optimizing C343-Ag complexes for neutral and deprotonated C343 molecules in the DFT simulations. The SERS of C343 showed a number of spectral changes upon solution pH change. We found that deprotonated C343 adsorbs on the Ag nanoparticles through the carboxylate group keeping a perpendicular geometry to the surface. When protonated, the adsorption geometry of C343 is changed into more or less flat to the surface as the cyclic ester group becomes a preferred surface adsorption site.

  18. Surface spin polarization induced ferromagnetic Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Shih, Po-Hsun; Li, Wen-Hsien; Wu, Sheng Yun

    2016-05-01

    We report on the observation of ferromagnetic spin polarized moments in 4.5 nm Ag nanoparticles. Both ferromagnetic and diamagnetic responses to an applied magnetic field were detected. The spin polarized moments shown under non-linear thermoinduced magnetization appeared on the surface atoms, rather than on all the atoms in particles. The saturation magnetization departed substantially from the Bloch T3/2-law, showing the existence of magnetic anisotropy. The Heisenberg ferromagnetic spin wave model for Ha-aligned moments was then employed to identify the magnetic anisotropic energy gap of ~0.12 meV. Our results may be understood by assuming the surface magnetism model, in which the surface atoms give rise to polarized moments while the core atoms produce diamagnetic responses.

  19. Nanoparticle-based etching of silicon surfaces

    DOEpatents

    Branz, Howard [Boulder, CO; Duda, Anna [Denver, CO; Ginley, David S [Evergreen, CO; Yost, Vernon [Littleton, CO; Meier, Daniel [Atlanta, GA; Ward, James S [Golden, CO

    2011-12-13

    A method (300) of texturing silicon surfaces (116) such to reduce reflectivity of a silicon wafer (110) for use in solar cells. The method (300) includes filling (330, 340) a vessel (122) with a volume of an etching solution (124) so as to cover the silicon surface 116) of a wafer or substrate (112). The etching solution (124) is made up of a catalytic nanomaterial (140) and an oxidant-etchant solution (146). The catalytic nanomaterial (140) may include gold or silver nanoparticles or noble metal nanoparticles, each of which may be a colloidal solution. The oxidant-etchant solution (146) includes an etching agent (142), such as hydrofluoric acid, and an oxidizing agent (144), such as hydrogen peroxide. Etching (350) is performed for a period of time including agitating or stirring the etching solution (124). The etch time may be selected such that the etched silicon surface (116) has a reflectivity of less than about 15 percent such as 1 to 10 percent in a 350 to 1000 nanometer wavelength range.

  20. Underpotential deposition: From planar surfaces to nanoparticles

    NASA Astrophysics Data System (ADS)

    Oviedo, O. A.; Vélez, P.; Macagno, V. A.; Leiva, E. P. M.

    2015-01-01

    An overview is given of selected theoretical, experimental and computer simulation research on thermodynamic modeling applied to the metal underpotential deposition. Focus is made mainly on the last 20 years. The upd-theory on planar surfaces is revisited and the thermodynamic framework is extended to consider underpotential deposition on nanoparticles and to include anion coadsorption, solvation and double layer charging. Results from molecular dynamics and Monte Carlo simulations are shown for systems of experimental interest. At the end some perspectives for further advanced modeling of the present problem are given.

  1. The impacts of surface polarity on the solubility of nanoparticle.

    PubMed

    Zhu, Jianzhuo; Ou, Xinwen; Su, Jiguo; Li, Jingyuan

    2016-07-28

    In order to study the dependence of water solubility and hydration behavior of nanoparticles on their surface polarity, we designed polar nanoparticles with varying surface polarity by assigning atomic partial charge to the surface of C60. The water solubility of the nanoparticle is enhanced by several orders of magnitude after the introduction of surface polarity. Nevertheless, when the atomic partial charge grows beyond a certain value (qM), the solubility continuously decreases to the level of nonpolar nanoparticle. It should be noted that such qM is comparable with atomic partial charge of a variety of functional groups. The hydration behaviors of nanoparticles were then studied to investigate the non-monotonic dependence of solubility on the surface polarity. The interaction between the polar nanoparticle and the hydration water is stronger than the nonpolar counterpart, which should facilitate the dissolution of the nanoparticles. On the other hand, the surface polarity also reduces the interaction of hydration water with the other water molecules and enhances the interaction between the nanoparticles which may hinder their dispersion. Besides, the introduction of surface polarity disturbs and even rearranges the hydration structure of nonpolar nanoparticle. Interestingly, the polar nanoparticle with less ordered hydration structure tends to have higher water solubility.

  2. Enhancing surface coverage and growth in layer-by-layer assembly of protein nanoparticles.

    PubMed

    Mohanta, Vaishakhi; Patil, Satish

    2013-10-29

    Thin films of bovine serum albumin (BSA) nanoparticles are fabricated via layer-by-layer assembly. The surface of BSA nanoparticles have two oppositely acting functional groups on the surface: amine (NH2) and carboxylate (COO(-)). The protonation and deprotonation of these functional groups at different pH vary the charge density on the particle surface, and entirely different growth can be observed by varying the nature of the complementary polymer and the pH of the particles. The complementary polymers used in this study are poly(dimethyldiallylammonium chloride) (PDDAC) and poly(acrylic acid) (PAA). The assembly of BSA nanoparticles based on electrostatic interaction with PDDAC suffers from the poor loading of the nanoparticles. The assembly with PAA aided by a hydrogen bonding interaction shows tremendous improvement in the growth of the assembly over PDDAC. Moreover, the pH of the BSA nanoparticles was observed to affect the loading of nanoparticles in the LbL assembly with PAA significantly.

  3. Phospholipids and glycolipids mediate proton containment and circulation along the surface of energy-transducing membranes.

    PubMed

    Yoshinaga, Marcos Y; Kellermann, Matthias Y; Valentine, David L; Valentine, Raymond C

    2016-10-01

    Proton bioenergetics provides the energy for growth and survival of most organisms in the biosphere ranging from unicellular marine phytoplankton to humans. Chloroplasts harvest light and generate a proton electrochemical gradient (proton motive force) that drives the production of ATP needed for carbon dioxide fixation and plant growth. Mitochondria, bacteria and archaea generate proton motive force to energize growth and other physiologies. Energy transducing membranes are at the heart of proton bioenergetics and are responsible for catalyzing the conversion of energy held in high-energy electrons→electron transport chain→proton motive force→ATP. Whereas the electron transport chain is understood in great detail there are major gaps in understanding mechanisms of proton transfer or circulation during proton bioenergetics. This paper is built on the proposition that phospho- and glyco-glycerolipids form proton transport circuitry at the membrane's surface. By this proposition, an emergent membrane property, termed the hyducton, confines active/unbound protons or hydronium ions to a region of low volume close to the membrane surface. In turn, a von Grotthuß mechanism rapidly moves proton substrate in accordance with nano-electrochemical poles on the membrane surface created by powerful proton pumps such as ATP synthase.

  4. Surface modification of magnetic nanoparticles in biomedicine

    NASA Astrophysics Data System (ADS)

    Chu, Xin; Yu, Jing; Hou, Yang-Long

    2015-01-01

    Progress in surface modification of magnetic nanoparticles (MNPs) is summarized with regard to organic molecules, macromolecules and inorganic materials. Many researchers are now devoted to synthesizing new types of multi-functional MNPs, which show great application potential in both diagnosis and treatment of disease. By employing an ever-greater variety of surface modification techniques, MNPs can satisfy more and more of the demands of medical practice in areas like magnetic resonance imaging (MRI), fluorescent marking, cell targeting, and drug delivery. Project supported by the National Natural Science Foundation of China (Grant Nos. 51125001 and 51172005), the Natural Science Foundation of Beijing,China (Grant No. 2122022), the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No. 81421004), and the Doctoral Program of the Education Ministry of China (Grant No. 20120001110078).

  5. Surface functionalization of dopamine coated iron oxide nanoparticles for various surface functionalities

    NASA Astrophysics Data System (ADS)

    Sherwood, Jennifer; Xu, Yaolin; Lovas, Kira; Qin, Ying; Bao, Yuping

    2017-04-01

    We present effective conjugation of four small molecules (glutathione, cysteine, lysine, and Tris(hydroxymethyl)aminomethane) onto dopamine-coated iron oxide nanoparticles. Conjugation of these molecules could improve the surface functionality of nanoparticles for more neutral surface charge at physiological pH and potentially reduce non-specific adsorption of proteins to nanoparticles surfaces. The success of conjugation was evaluated with dynamic light scattering by measuring the surface charge changes and Fourier transform infrared spectroscopy for surface chemistry analysis. The stability of dopamine-coated nanoparticles and the ability of conjugated nanoparticles to reduce the formation of protein corona were evaluated by measuring the size and charge of the nanoparticles in biological medium. This facile conjugation method opens up possibilities for attaching various surface functionalities onto iron oxide nanoparticle surfaces for biomedical applications.

  6. Local dose enhancement of proton therapy by ceramic oxide nanoparticles investigated with Geant4 simulations.

    PubMed

    McKinnon, Sally; Guatelli, Susanna; Incerti, Sebastien; Ivanchenko, Vladimir; Konstantinov, Konstantin; Corde, Stéphanie; Lerch, Michael; Tehei, Moeava; Rosenfeld, Anatoly

    2016-12-01

    Nanoparticles (NPs) have been shown to enhance X-ray radiotherapy and proton therapy of cancer. The effectiveness of radiation damage is enhanced in the presence of high atomic number (high-Z) NPs due to increased production of low energy, higher linear energy transfer (LET) secondary electrons when NPs are selectively internalized by tumour cells. This work quantifies the local dose enhancement produced by the high-Z ceramic oxide NPs Ta2O5 and CeO2, in the target tumour, for the first time in proton therapy, by means of Geant4 simulations. The dose enhancement produced by the ceramic oxides is compared against gold NPs. The energy deposition on a nanoscale around a single nanoparticle of 100nm diameter is investigated using the Geant4-DNA extension to model particle interactions in the water medium. Enhancement of energy deposition in nano-sized shells of water, local to the NP boundary, ranging between 14% and 27% was observed for proton energies of 5MeV and 50MeV, depending on the NP material. Enhancement of electron production and energy deposition can be correlated to the direct DNA damage mechanism if the NP is in close proximity to the nucleus.

  7. The effect of polymer coatings on proton transverse relaxivities of aqueous suspensions of magnetic nanoparticles.

    PubMed

    Carroll, Matthew R J; Huffstetler, Phillip P; Miles, William C; Goff, Jonathon D; Davis, Richey M; Riffle, Judy S; House, Michael J; Woodward, Robert C; St Pierre, Timothy G

    2011-08-12

    Iron oxide magnetic nanoparticles are good candidates for magnetic resonance imaging (MRI) contrast agents due to their high magnetic susceptibilities. Here we investigate 19 polyether-coated magnetite nanoparticle systems comprising three series. All systems were synthesized from the same batch of magnetite nanoparticles. A different polyether was used for each series. Each series comprised systems with systematically varied polyether loadings per particle. A highly significant (p < 0.0001) linear correlation (r = 0.956) was found between the proton relaxivity and the intensity-weighted average diameter measured by dynamic light scattering in the 19 particle systems studied. The intensity-weighted average diameter measured by dynamic light scattering is sensitive to small number fractions of larger particles/aggregates. We conclude that the primary effect leading to differences in proton relaxivity between systems arises from the small degree of aggregation within the samples, which appears to be determined by the nature of the polymer and, for one system, the degree of polymer loading of the particles. For the polyether coatings used in this study, any changes in relaxivity from differences in water exclusion or diffusion rates caused by the polymer are minor in comparison with the changes in relaxivity resulting from variations in the degree of aggregation.

  8. Effects of surface chemistry and size on iron oxide nanoparticle delivery of oligonucleotides

    NASA Astrophysics Data System (ADS)

    Shen, Christopher

    The discovery of RNA interference and the increasing understanding of disease genetics have created a new class of potential therapeutics based on oligonucleotides. This therapeutic class includes antisense molecules, small interfering RNA (siRNA), and microRNA modulators such as antagomirs (antisense directed against microRNA) and microRNA mimics, all of which function by altering gene expression at the translational level. While these molecules have the promise of treating a host of diseases from neurological disorders to cancer, a major hurdle is their inability to enter cells on their own, where they may render therapeutic effect. Nanotechnology is the engineering of materials at the nanometer scale and has gained significant interest for nucleic acid delivery due to its biologically relevant length-scale and amenability to multifunctionality. While a number of nanoparticle vehicles have shown promise for oligonucleotide delivery, there remains a lack of understanding of how nanoparticle coating and size affect these delivery processes. This dissertation seeks to elucidate some of these factors by evaluating oligonucleotide delivery efficiencies of a panel of iron oxide nanoparticles with varying cationic coatings and sizes. A panel of uniformly-sized nanoparticles was prepared with surface coatings comprised of various amine groups representing high and low pKas. A separate panel of nanoparticles with sizes of 40, 80, 150, and 200 nm but with the same cationic coating was also prepared. Results indicated that both nanoparticle surface coating and nanoparticle hydrodynamic size affect transfection efficiency. Specific particle coatings and sizes were identified that gave superior performance. The intracellular fate of iron oxide nanoparticles was also tracked by electron microscopy and suggests that they function via the proton sponge effect. The research presented in this dissertation may aid in the rational design of improved nanoparticle delivery vectors for

  9. The proton collecting function of the inner surface of cytochrome c oxidase from Rhodobacter sphaeroides.

    PubMed

    Marantz, Y; Nachliel, E; Aagaard, A; Brzezinski, P; Gutman, M

    1998-07-21

    The experiments presented in this study address the problem of how the cytoplasmic surface (proton-input side) of cytochrome c oxidase interacts with protons in the bulk. For this purpose, the cytoplasmic surface of the enzyme was labeled with a fluorescein (Flu) molecule covalently bound to Cys223 of subunit III. Using the Flu as a proton-sensitive marker on the surface and phiOH as a soluble excited-state proton emitter, the dynamics of the acid-base equilibration between the surface and the bulk was measured in the time-resolved domain. The results were analyzed by using a rigorous kinetic analysis that is based on numeric integration of coupled nonliner differential rate equations in which the rate constants are used as adjustable parameters. The analysis of 11 independent measurements, carried out under various initial conditions, indicated that the protonation of the Flu proceeds through multiple pathways involving diffusion-controlled reactions and proton exchange among surface groups. The surface of the protein carries an efficient system made of carboxylate and histidine moieties that are sufficiently close to each other as to form a proton-collecting antenna. It is the passage of protons among these sites that endows cytochrome c oxidase with the capacity to pick up protons from the buffered cytoplasmic matrix within a time frame compatible with the physiological turnover of the enzyme.

  10. Acellular assessments of engineered-manufactured nanoparticle biological surface reactivity

    EPA Science Inventory

    It is critical to assess the surface properties and reactivity of engineered-manufactured nanoparticles (NPs) as these will influence their interactions with biological systems, biokinetics and toxicity. We examined the physicochemical properties and surface reactivity of metal o...

  11. Surface-modified multifunctional MIP nanoparticles

    PubMed Central

    Moczko, Ewa; Poma, Alessandro; Guerreiro, Antonio; de Vargas Sansalvador, Isabel Perez; Caygill, Sarah; Canfarotta, Francesco; Whitcombe, Michael J.; Piletsky, Sergey

    2015-01-01

    The synthesis of core-shell molecularly imprinted polymer nanoparticles (MIP NPs) has been performed using a novel solid-phase approach on immobilised templates. The same solid phase also acts as protective functionality for high affinity binding sites during subsequent derivatisation/shell formation. This procedure allows for the rapid synthesis, controlled separation and purification of high-affinity materials, with each production cycle taking just 2 hours. The aim of this approach is to synthesise uniformly-sized imprinted materials at the nanoscale which can be readily grafted with various polymers without affecting their affinity and specificity. For demonstration purposes we grafted anti-melamine MIP NPs with coatings which introduce the following surface characteristics: high polarity (PEG methacrylate); electro-activity (vinyl ferrocene); fluorescence (eosin acrylate); thiol groups (pentaerythritol tetrakis(3-mercaptopropionate)). The method has broad applicability and can be used to produce multifunctional imprinted nanoparticles with potential for further application in the biosensors, diagnostics and biomedical fields and as an alternative to natural receptors. PMID:23503559

  12. Sum Frequency Vibrational Spectroscopy (SFVS) of Water and Hydroxyls on the Corundum (1-102) surface: Acid-base properties from direct observation of protonation states

    NASA Astrophysics Data System (ADS)

    Waychunas, G.; Sung, J.; Shen, R.

    2010-12-01

    SFVS is a powerful tool for quantitative measurement of protonated functional groups on mineral surfaces. We demonstrate this for the Corundum (1-102) interface where the orientation and nature of surface hydroxyls on the dry neutral surface can be obtained and compared with Crystal Truncation Rod (CTR) models for the surface termination and most likely functional groups, effectively allowing testing of such models. A scheme for describing the hydrogen bonding among these protonated groups is found to be consistent with surface symmetry and the particular vibrational frequencies observed. The addition of water to the interface alters the hydrogen bonding of the hydroxyls and introduces water-functional group hydrogen bonding. Direct measurement of the SFVS hydroxyl and water band amplitudes can be used to test expected pKa values, and hence link acid-base properties to precise molecular surface entities. The analysis methodology can be applied to analogous nanoparticle surfaces, though with some limitations.

  13. Probing and repairing damaged surfaces with nanoparticle-containing microcapsules

    NASA Astrophysics Data System (ADS)

    Kratz, Katrina; Narasimhan, Amrit; Tangirala, Ravisubhash; Moon, Sungcheal; Revanur, Ravindra; Kundu, Santanu; Kim, Hyun Suk; Crosby, Alfred J.; Russell, Thomas P.; Emrick, Todd; Kolmakov, German; Balazs, Anna C.

    2012-02-01

    Nanoparticles have useful properties, but it is often important that they only start working after they are placed in a desired location. The encapsulation of nanoparticles allows their function to be preserved until they are released at a specific time or location, and this has been exploited in the development of self-healing materials and in applications such as drug delivery. Encapsulation has also been used to stabilize and control the release of substances, including flavours, fragrances and pesticides. We recently proposed a new technique for the repair of surfaces called `repair-and-go'. In this approach, a flexible microcapsule filled with a solution of nanoparticles rolls across a surface that has been damaged, stopping to repair any defects it encounters by releasing nanoparticles into them, then moving on to the next defect. Here, we experimentally demonstrate the repair-and-go approach using droplets of oil that are stabilized with a polymer surfactant and contain CdSe nanoparticles. We show that these microcapsules can find the cracks on a surface and selectively deliver the nanoparticle contents into the crack, before moving on to find the next crack. Although the microcapsules are too large to enter the cracks, their flexible walls allow them to probe and adhere temporarily to the interior of the cracks. The release of nanoparticles is made possible by the thin microcapsule wall (comparable to the diameter of the nanoparticles) and by the favourable (hydrophobic-hydrophobic) interactions between the nanoparticle and the cracked surface.

  14. Porous Collagen Scaffold Reinforced with Surfaced Activated PLLA Nanoparticles

    PubMed Central

    Xu, Cancan; Lu, Wei; Bian, Shaoquan; Liang, Jie; Fan, Yujiang; Zhang, Xingdong

    2012-01-01

    Porous collagen scaffold is integrated with surface activated PLLA nanoparticles fabricated by lyophilizing and crosslinking via EDC treatment. In order to prepare surface-modified PLLA nanoparticles, PLLA was firstly grafted with poly (acrylic acid) (PAA) through surface-initiated polymerization of acrylic acid. Nanoparticles of average diameter 316 nm and zeta potential −39.88 mV were obtained from the such-treated PLLA by dialysis method. Porous collagen scaffold were fabricated by mixing PLLA nanoparticles with collagen solution, freeze drying, and crosslinking with EDC. SEM observation revealed that nanoparticles were homogeneously dispersed in collagen matrix, forming interconnected porous structure with pore size ranging from 150 to 200 μm, irrespective of the amount of nanoparticles. The porosity of the scaffolds kept almost unchanged with the increment of the nanoparticles, whereas the mechanical property was obviously improved, and the degradation was effectively retarded. In vitro L929 mouse fibroblast cells seeding and culture studies revealed that cells infiltrated into the scaffolds and were distributed homogeneously. Compared with the pure collagen sponge, the number of cells in hybrid scaffolds greatly increased with the increment of incorporated nanoparticles. These results manifested that the surface-activated PLLA nanoparticles effectively reinforced the porous collagen scaffold and promoted the cells penetrating into the scaffold, and proliferation. PMID:22448137

  15. The electrochemisty of surface modified <10 nm metal oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Roberts, Joseph J. P.

    Chapter One provides a general introduction of the research on metal oxide nanoparticles (MOx), highlighting their synthesis, surface modification, and functionalization. Emphasis is given to the different synthetic route for producing small (<10 nm) MOx nanoparticles with narrow size distributions. Different methods for modifying their surface with small organic molecules are discussed with focus given to silanes and phosphates. Furthermore, functionalizing surface modified nanoparticles for specific functions is addressed, with markers for analytically relevant nanoscale quantification being the primary focus. Chapter Two describes in detail the thermal degradation synthesis used for the generation of small MOx nanoparticles. It demonstrates the versatile of the synthesis by successfully synthesizing ZrO 2 and IrO2 nanoparticles. Preliminary work involving the formation of Bi2S3, Bi2O3, and RuO2 nanomaterials is also addressed. The solvothermal synthesis of indium tin oxide (ITO) is also shown for comparison to ITO produced by thermal degradation. Chapter Three details the surface modification of ITO nanoparticles and subsequent electrochemical tagging with a ferrocene moiety. ITO nanoparticles were synthesized via thermal degradation. These nanoparticles underwent a ligand exchange with a covalently binding mondentate silane terminated with a primary amine. Acyl chloride coupling between the amine and chlorocarbonylferrocene provided an electrochemical tag to quantify the level of surface modification. Electrochemisty of the quasi-diffusing nanoparticles was evaluated via cyclic voltammetry (CV), chronoamperometry (CA), and mircodisk electrode (microE) experiments. Chapter Four investigates spectroscopic tagging of ITO and ZrO2 nanoparticles as well as electrochemical tagging of ZrO 2 and IrO2 nanoparticles. An unbound azo-dye was synthesized and attempts were made to attach the dye to the surface of ITO nanoparticles. Imine couple between a spectroscopic tag

  16. Investigating the Interaction of Water Vapour with Aminopropyl Groups on the Surface of Mesoporous Silica Nanoparticles.

    PubMed

    Paul, Geo; Musso, Giorgia Elena; Bottinelli, Emanuela; Cossi, Maurizio; Marchese, Leonardo; Berlier, Gloria

    2017-04-05

    The interaction of water molecules with the surface of hybrid silica-based mesoporous materials is studied by (29) Si, (1) H and (13) C solid-state NMR and IR spectroscopy, with the support of ab initio calculations. The surface of aminopropyl-grafted mesoporous silica nanoparticles is studied in the dehydrated state and upon interaction with controlled doses of water vapour. Former investigations described the interactions between aminopropyl and residual SiOH groups; the present study shows the presence of hydrogen-bonded species (SiOH to NH2 ) and weakly interacting "free" aminopropyl chains with restricted mobility, together with a small amount of protonated NH3(+) groups. The concentration of the last-named species increased upon interaction with water, and this indicates reversible and fast proton exchange from water molecules to a fraction of the amino groups. Herein, this is discussed and explained for the first time, by a combination of experimental and theoretical approaches.

  17. SU-E-J-247: A Simulation of X-Ray Emission with Gold Nanoparticle Irradiated by Energetic Proton Beam

    SciTech Connect

    Newpower, M; Ahmad, S; Chen, Y

    2014-06-01

    Purpose: To investigate the proton induced X-ray emissions in gold-water mixture materials. Methods: In this study a Monte Carlo simulation was created using the GEANT4 toolkit (version 4.9.6). The geometry in this setup includes a 2 cm × 2 cm × 2 cm target, a scoring sphere (radius = 10 cm) and a 65 MeV planar proton source (2 cm × 2 cm). Four concentrations of a gold-water solution were irradiated with 5×10{sup 5} incident protons at a distance of 0.5 cm perpendicular to the surface of the target. The solutions of gold-water mixture had 10%, 5%, 1% and 0.5% of gold by mass, respectively. The number of photon emitting for the target was counted in the scoring sphere for the energy range of 0-86.0 keV in 0.1 keV bins. For this study the reference physics list PhysListEmStandard was used together with the x-ray fluorescence, Auger electron and PIXE (particle induced xray emission) options enabled. The range cuts for photons and electrons were set at 0.5 mm and 1.0 mm, respectively. Results: In the energy spectra of emitting X-ray fluorescence, peaks from gold K shell characteristic x-rays (68.8 and 66.9 keV) were observed. The number of counts under the peaks of Ka1 and Ka2 was found to increase with the increasing of the gold concentrations in the mixture materials. The X-ray yields (for both Ka1 and Ka2) when fitted with least-square method as a function of gold concentration demonstrate a linear dependency with R{sup 2} > 0.96. The Ka1yield per incident proton was found to be 0.0016 for 10% gold-water mixture solutions. Conclusion: This preliminary study with PIXE technique with gold nanoparticle has demonstrated potentials for its utilization in the development of range and dose verification methodology that is currently of great interest in the field of proton radiation therapy.

  18. Interaction of surface-modified silica nanoparticles with clay minerals

    NASA Astrophysics Data System (ADS)

    Omurlu, Cigdem; Pham, H.; Nguyen, Q. P.

    2016-11-01

    In this study, the adsorption of 5-nm silica nanoparticles onto montmorillonite and illite is investigated. The effect of surface functionalization was evaluated for four different surfaces: unmodified, surface-modified with anionic (sulfonate), cationic (quaternary ammonium (quat)), and nonionic (polyethylene glycol (PEG)) surfactant. We employed ultraviolet-visible spectroscopy to determine the concentration of adsorbed nanoparticles in conditions that are likely to be found in subsurface reservoir environments. PEG-coated and quat/PEG-coated silica nanoparticles were found to significantly adsorb onto the clay surfaces, and the effects of electrolyte type (NaCl, KCl) and concentration, nanoparticle concentration, pH, temperature, and clay type on PEG-coated nanoparticle adsorption were studied. The type and concentration of electrolytes were found to influence the degree of adsorption, suggesting a relationship between the interlayer spacing of the clay and the adsorption ability of the nanoparticles. Under the experimental conditions reported in this paper, the isotherms for nanoparticle adsorption onto montmorillonite at 25 °C indicate that adsorption occurs less readily as the nanoparticle concentration increases.

  19. Exogenous control over intracellular acidification: Enhancement via proton caged compounds coupled to gold nanoparticles and an alternative pathway with DMSO

    PubMed Central

    Carbone, Marilena; Sabbatella, Gianfranco; Antonaroli, Simonetta; Remita, Hynd; Orlando, Viviana; Biagioni, Stefano; Nucara, Alessandro

    2016-01-01

    Proton caged compounds exhibit a characteristic behavior when directly dosed into cells or being coupled to gold nanoparticles prior to the dosing. When irradiated in the near ultraviolet region, they release protons that interact with intracellular HCO3− to yield H2CO3. The dissociation of carbonic acid, then, releases CO2 that can be distinctively singled out in infrared spectra. In the process of searching a pathway to augment the intracellular uptake of proton caged compounds, we probed the association of 1-(2-nitrophenyl)-ethylhexadecyl sulfonate (HDNS) with DMSO, an agent to enhance the membrane permeability. We found out a different UV-induced protonation mechanism that opens up to new conduits of employing of proton caged compounds. Here, we report the infrared data we collected in this set of experiments. PMID:26870760

  20. Exogenous control over intracellular acidification: Enhancement via proton caged compounds coupled to gold nanoparticles and an alternative pathway with DMSO.

    PubMed

    Carbone, Marilena; Sabbatella, Gianfranco; Antonaroli, Simonetta; Remita, Hynd; Orlando, Viviana; Biagioni, Stefano; Nucara, Alessandro

    2016-03-01

    Proton caged compounds exhibit a characteristic behavior when directly dosed into cells or being coupled to gold nanoparticles prior to the dosing. When irradiated in the near ultraviolet region, they release protons that interact with intracellular HCO3 (-) to yield H2CO3. The dissociation of carbonic acid, then, releases CO2 that can be distinctively singled out in infrared spectra. In the process of searching a pathway to augment the intracellular uptake of proton caged compounds, we probed the association of 1-(2-nitrophenyl)-ethylhexadecyl sulfonate (HDNS) with DMSO, an agent to enhance the membrane permeability. We found out a different UV-induced protonation mechanism that opens up to new conduits of employing of proton caged compounds. Here, we report the infrared data we collected in this set of experiments.

  1. Surface Characterization of Nanoparticles: critical needs and significant challenges

    PubMed Central

    Baer, D. R.

    2013-01-01

    There is a growing recognition that nanoparticles and other nanostructured materials are sometimes inadequately characterized and that this may limit or even invalidate some of the conclusions regarding particle properties and behavior. A number of international organizations are working to establish the essential measurement requirements that enable adequate understanding of nanoparticle properties for both technological applications and for environmental health issues. Our research on the interaction of iron metal-core oxide-shell nanoparticles with environmental contaminants and studies of the behaviors of ceria nanoparticles, with a variety of medical, catalysis and energy applications, have highlighted a number of common nanoparticle characterization challenges that have not been fully recognized by parts of the research community. This short review outlines some of these characterization challenges based on our research observations and using other results reported in the literature. Issues highlighted include: 1) the importance of surfaces and surface characterization, 2) nanoparticles are often not created equal – subtle differences in synthesis and processing can have large impacts; 3) nanoparticles frequently change with time having lifetime implications for products and complicating understanding of health and safety impacts; 4) the high sensitivity of nanoparticles to their environment complicates characterization and applications in many ways; 5) nanoparticles are highly unstable and easily altered (damaged) during analysis. PMID:25342927

  2. Proton Radii of B12-17 Define a Thick Neutron Surface in B17

    NASA Astrophysics Data System (ADS)

    Estradé, A.; Kanungo, R.; Horiuchi, W.; Ameil, F.; Atkinson, J.; Ayyad, Y.; Cortina-Gil, D.; Dillmann, I.; Evdokimov, A.; Farinon, F.; Geissel, H.; Guastalla, G.; Janik, R.; Kimura, M.; Knöbel, R.; Kurcewicz, J.; Litvinov, Yu. A.; Marta, M.; Mostazo, M.; Mukha, I.; Nociforo, C.; Ong, H. J.; Pietri, S.; Prochazka, A.; Scheidenberger, C.; Sitar, B.; Strmen, P.; Suzuki, Y.; Takechi, M.; Tanaka, J.; Tanihata, I.; Terashima, S.; Vargas, J.; Weick, H.; Winfield, J. S.

    2014-09-01

    The first determination of radii of point proton distribution (proton radii) of B12-17 from charge-changing cross sections (σCC) measurements at the FRS, GSI, Darmstadt is reported. The proton radii are deduced from a finite-range Glauber model analysis of the σCC. The radii show an increase from B13 to B17 and are consistent with predictions from the antisymmetrized molecular dynamics model for the neutron-rich nuclei. The measurements show the existence of a thick neutron surface with neutron-proton radius difference of 0.51(0.11) fm in B17.

  3. Application of Surface Chemical Analysis Tools for Characterization of Nanoparticles

    PubMed Central

    Baer, DR; Gaspar, DJ; Nachimuthu, P; Techane, SD; Castner, DG

    2010-01-01

    The important role that surface chemical analysis methods can and should play in the characterization of nanoparticles is described. The types of information that can be obtained from analysis of nanoparticles using Auger electron spectroscopy (AES); X-ray photoelectron spectroscopy (XPS); time of flight secondary ion mass spectrometry (TOF-SIMS); low energy ion scattering (LEIS); and scanning probe microscopy (SPM), including scanning tunneling microscopy (STM) and atomic force microscopy (AFM), are briefly summarized. Examples describing the characterization of engineered nanoparticles are provided. Specific analysis considerations and issues associated with using surface analysis methods for the characterization of nanoparticles are discussed and summarized, along with the impact that shape instability, environmentally induced changes, deliberate and accidental coating, etc., have on nanoparticle properties. PMID:20052578

  4. A universal surface complexation framework for modeling proton binding onto bacterial surfaces in geologic settings

    USGS Publications Warehouse

    Borrok, D.; Turner, B.F.; Fein, J.B.

    2005-01-01

    Adsorption onto bacterial cell walls can significantly affect the speciation and mobility of aqueous metal cations in many geologic settings. However, a unified thermodynamic framework for describing bacterial adsorption reactions does not exist. This problem originates from the numerous approaches that have been chosen for modeling bacterial surface protonation reactions. In this study, we compile all currently available potentiometric titration datasets for individual bacterial species, bacterial consortia, and bacterial cell wall components. Using a consistent, four discrete site, non-electrostatic surface complexation model, we determine total functional group site densities for all suitable datasets, and present an averaged set of 'universal' thermodynamic proton binding and site density parameters for modeling bacterial adsorption reactions in geologic systems. Modeling results demonstrate that the total concentrations of proton-active functional group sites for the 36 bacterial species and consortia tested are remarkably similar, averaging 3.2 ?? 1.0 (1??) ?? 10-4 moles/wet gram. Examination of the uncertainties involved in the development of proton-binding modeling parameters suggests that ignoring factors such as bacterial species, ionic strength, temperature, and growth conditions introduces relatively small error compared to the unavoidable uncertainty associated with the determination of cell abundances in realistic geologic systems. Hence, we propose that reasonable estimates of the extent of bacterial cell wall deprotonation can be made using averaged thermodynamic modeling parameters from all of the experiments that are considered in this study, regardless of bacterial species used, ionic strength, temperature, or growth condition of the experiment. The average site densities for the four discrete sites are 1.1 ?? 0.7 ?? 10-4, 9.1 ?? 3.8 ?? 10-5, 5.3 ?? 2.1 ?? 10-5, and 6.6 ?? 3.0 ?? 10-5 moles/wet gram bacteria for the sites with pKa values of 3

  5. Asymmetric light reflectance from metal nanoparticle arrays on dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Huang, K.; Pan, W.; Zhu, J. F.; Li, J. C.; Gao, N.; Liu, C.; Ji, L.; Yu, E. T.; Kang, J. Y.

    2015-12-01

    Asymmetric light reflectance associated with localized surface plasmons excited in metal nanoparticles on a quartz substrate is observed and analyzed. This phenomenon is explained by the superposition of two waves, the wave reflected by the air/quartz interface and that reflected by the metal nanoparticles, and the resulting interference effects. Far field behavior investigation suggests that zero reflection can be achieved by optimizing the density of metal nanoparticles. Near field behavior investigation suggests that the coupling efficiency of localized surface plasmon can be additionally enhanced by separating the metal NPs from substrates using a thin film with refractive index smaller than the substrate. The latter behavior is confirmed via surface-enhanced Raman spectroscopy studies using metal nanoparticles on Si/SiO2 substrates.

  6. Asymmetric light reflectance from metal nanoparticle arrays on dielectric surfaces.

    PubMed

    Huang, K; Pan, W; Zhu, J F; Li, J C; Gao, N; Liu, C; Ji, L; Yu, E T; Kang, J Y

    2015-12-18

    Asymmetric light reflectance associated with localized surface plasmons excited in metal nanoparticles on a quartz substrate is observed and analyzed. This phenomenon is explained by the superposition of two waves, the wave reflected by the air/quartz interface and that reflected by the metal nanoparticles, and the resulting interference effects. Far field behavior investigation suggests that zero reflection can be achieved by optimizing the density of metal nanoparticles. Near field behavior investigation suggests that the coupling efficiency of localized surface plasmon can be additionally enhanced by separating the metal NPs from substrates using a thin film with refractive index smaller than the substrate. The latter behavior is confirmed via surface-enhanced Raman spectroscopy studies using metal nanoparticles on Si/SiO2 substrates.

  7. Molecular Statics Calculations of Proton Binding to Goethite Surfaces: Thermodynamic Modeling of the Surface Charging and Protonation of Goethite in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Felmy, Andrew R.; Rustad, James R.

    1998-01-01

    Molecular statics calculations of proton binding at the hydroxylated faces of goethite are used to guide the development of a thermodynamic model which describes the surface charging properties of goethite in electrolyte solutions. The molecular statics calculations combined with a linear free energy relation between the energies of the hydroxylated surface and the aqueous solvated surface predict that the acidity constants for most singly (aqua or hydroxo), doubly (μ-hydroxo), and triply (μ 3-hydroxo or μ 3-oxo) coordinated surface sites all have similar values. This model which binds protons to the goethite 110 and 021 faces satisfactorily describes the surface charging behavior of goethite, if pair formation between bulk electrolyte species, i.e., Na +, Cl -, and NO 3-, is included in the model. Inclusion of minor species of quite different charging behavior (designed to describe the possible presence of defect species) did not improve our predictions of surface charge since the protonation of the major surface sites changed when these minor species were introduced into the calculations thereby negating the effect of small amounts of defect species on the overall charging behavior. The final thermodynamic model is shown to be consistent with the surface charging properties of goethite over a range of pH values, NaNO 3, and NaCl concentrations.

  8. Quantitative investigation of physical factors contributing to gold nanoparticle-mediated proton dose enhancement

    NASA Astrophysics Data System (ADS)

    Cho, Jongmin; Gonzalez-Lepera, Carlos; Manohar, Nivedh; Kerr, Matthew; Krishnan, Sunil; Cho, Sang Hyun

    2016-03-01

    Some investigators have shown tumor cell killing enhancement in vitro and tumor regression in mice associated with the loading of gold nanoparticles (GNPs) before proton treatments. Several Monte Carlo (MC) investigations have also demonstrated GNP-mediated proton dose enhancement. However, further studies need to be done to quantify the individual physical factors that contribute to the dose enhancement or cell-kill enhancement (or radiosensitization). Thus, the current study investigated the contributions of particle-induced x-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), Auger and secondary electrons, and activation products towards the total dose enhancement. Specifically, GNP-mediated dose enhancement was measured using strips of radiochromic film that were inserted into vials of cylindrical GNPs, i.e. gold nanorods (GNRs), dispersed in a saline solution (0.3 mg of GNRs/g or 0.03% of GNRs by weight), as well as vials containing water only, before proton irradiation. MC simulations were also performed with the tool for particle simulation code using the film measurement setup. Additionally, a high-purity germanium detector system was used to measure the photon spectrum originating from activation products created from the interaction of protons and spherical GNPs present in a saline solution (20 mg of GNPs/g or 2% of GNPs by weight). The dose enhancement due to PIXE/PIGE recorded on the films in the GNR-loaded saline solution was less than the experimental uncertainty of the film dosimetry (<2%). MC simulations showed highly localized dose enhancement (up to a factor 17) in the immediate vicinity (<100 nm) of GNRs, compared with hypothetical water nanorods (WNRs), mostly due to GNR-originated Auger/secondary electrons; however, the average dose enhancement over the entire GNR-loaded vial was found to be minimal (0.1%). The dose enhancement due to the activation products from GNPs was minimal (<0.1%) as well. In conclusion, under the

  9. Quantitative investigation of physical factors contributing to gold nanoparticle-mediated proton dose enhancement.

    PubMed

    Cho, Jongmin; Gonzalez-Lepera, Carlos; Manohar, Nivedh; Kerr, Matthew; Krishnan, Sunil; Cho, Sang Hyun

    2016-03-21

    Some investigators have shown tumor cell killing enhancement in vitro and tumor regression in mice associated with the loading of gold nanoparticles (GNPs) before proton treatments. Several Monte Carlo (MC) investigations have also demonstrated GNP-mediated proton dose enhancement. However, further studies need to be done to quantify the individual physical factors that contribute to the dose enhancement or cell-kill enhancement (or radiosensitization). Thus, the current study investigated the contributions of particle-induced x-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), Auger and secondary electrons, and activation products towards the total dose enhancement. Specifically, GNP-mediated dose enhancement was measured using strips of radiochromic film that were inserted into vials of cylindrical GNPs, i.e. gold nanorods (GNRs), dispersed in a saline solution (0.3 mg of GNRs/g or 0.03% of GNRs by weight), as well as vials containing water only, before proton irradiation. MC simulations were also performed with the tool for particle simulation code using the film measurement setup. Additionally, a high-purity germanium detector system was used to measure the photon spectrum originating from activation products created from the interaction of protons and spherical GNPs present in a saline solution (20 mg of GNPs/g or 2% of GNPs by weight). The dose enhancement due to PIXE/PIGE recorded on the films in the GNR-loaded saline solution was less than the experimental uncertainty of the film dosimetry (<2%). MC simulations showed highly localized dose enhancement (up to a factor 17) in the immediate vicinity (<100 nm) of GNRs, compared with hypothetical water nanorods (WNRs), mostly due to GNR-originated Auger/secondary electrons; however, the average dose enhancement over the entire GNR-loaded vial was found to be minimal (0.1%). The dose enhancement due to the activation products from GNPs was minimal (<0.1%) as well. In conclusion, under the currently

  10. Mapping and Quantifying Surface Charges on Clay Nanoparticles.

    PubMed

    Liu, Jun; Gaikwad, Ravi; Hande, Aharnish; Das, Siddhartha; Thundat, Thomas

    2015-09-29

    Understanding the electrical properties of clay nanoparticles is very important since they play a crucial role in every aspect of oil sands processing, from bitumen extraction to sedimentation in mature fine tailings (MFT). Here, we report the direct mapping and quantification of surface charges on clay nanoparticles using Kelvin probe force microscopy (KPFM) and electrostatic force microscopy (EFM). The morphology of clean kaolinite clay nanoparticles shows a layered structure, while the corresponding surface potential map shows a layer-dependent charge distribution. More importantly, a surface charge density of 25 nC/cm(2) was estimated for clean kaolinite layers by using EFM measurements. On the other hand, the EFM measurements show that the clay particles obtained from the tailings demonstrate a reduced surface charge density of 7 nC/cm(2), which may be possibly attributed to the presence of various bituminous compounds residing on the clay surfaces.

  11. Assembly of surface engineered nanoparticles for functional materials

    NASA Astrophysics Data System (ADS)

    Yu, Xi

    Nanoparticles are regarded as exciting new building blocks for functional materials due to their fascinating physical properties because of the nano-confinement. Organizing nanoparticles into ordered hierarchical structures are highly desired for constructing novel optical and electrical artificial materials that are different from their isolated state or thermodynamics random ensembles. My research integrates the surface chemistry of nanoparticles, interfacial assembly and lithography techniques to construct nanoparticle based functional structures. We designed and synthesized tailor-made ligands for gold, semiconductor and magnetic nanoparticle, to modulate the assembly process and collective properties of the assembled structures, by controlling the key parameters such as particle-interface interaction, dielectric environments and inter-particle coupling etc. Top-down technologies such as micro contact printing, photolithography and nanoimprint lithography are used to guide the assembly into arbitrarily predesigned structures for potential device applications.

  12. Surfactant assisted surface studies of zinc sulfide nanoparticles

    NASA Astrophysics Data System (ADS)

    Shahi, Ashutosh K.; Pandey, B. K.; Swarnkar, R. K.; Gopal, R.

    2011-09-01

    We report a simple soft chemical method for the synthesis of ZnS nanoparticles using varying concentration of cationic surfactant CTAB and examine its surface properties. Powder X-ray diffraction, UV-vis spectroscopy, photoluminescence spectroscopy, selective area electron diffraction, and transmission electron microscopy are used to characterize the as prepared ZnS nanoparticles. XRD and TEM measurements show the size of polydispersed ZnS nanoparticles is in the range of 2-5 nm with cubic phase structure. The photoluminescence spectrum of ZnS nanoparticles exhibits four fluorescence emission peaks centered at 387 nm, 412 nm, 489 nm and 528 nm showing the application potential for the optical devices. In Raman spectra of ZnS nanoparticles, the modes around 320, 615 and 700 cm-1 are observed.

  13. Tailoring nanoparticle surface monolayers for biomolecular recognition and delivery applications

    NASA Astrophysics Data System (ADS)

    Agasti, Sarit S.

    Engineering the interfaces between biomolecules and nanomaterials is central to the creation of materials for diverse areas of biomedical applications, including therapy, sensing and imaging. The goal of this research has been oriented toward the tailoring of the interfaces through the atomic level control provided by the organic synthesis. By employing a synergistic approach in the research, combining colloids, surface science, organic synthesis and biology, gold nanoparticles with tailored monolayers have been developed for bio-applications. This thesis illustrates the design and synthesis of these surface functionalized gold nanoparticles and their use in protein surface recognition and delivery systems for therapeutic applications. For protein surface recognition, we have fabricated gold nanoparticles bearing a diversity of amino acids termini and studied their interactions with proteins to elucidate the parameters affecting their interactions and catalytic behavior. In therapeutic applications, we have demonstrated the use of organically tailored nanoparticles for the creation of delivery systems featuring tunable stability and regulated drug release. Additionally, gold nanoparticles functionalized with molecular recognition motif have been used to demonstrate host-guest chemistry inside the living cells for the activation of therapeutic gold nanoparticles.

  14. A bioinspired strategy for surface modification of silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Tian, Jianwen; Zhang, Haoxuan; Liu, Meiying; Deng, Fengjie; Huang, Hongye; Wan, Qing; Li, Zhen; Wang, Ke; He, Xiaohui; Zhang, Xiaoyong; Wei, Yen

    2015-12-01

    Silica nanoparticles have become one of the most promising nanomaterials for a vast of applications. In this work, a novel strategy for surface modification of silica nanoparticles has been developed for the first time via combination of mussel inspired chemistry and Michael addition reaction. In this procedure, thin polydopamine (PDA) films were first coated on the bare silica nanoparticles via self-polymerization of dopamine in alkaline condition. And then amino-containing polymers were introduced onto the PDA coated silica nanoparticles through Michael addition reaction, that are synthesized from free radical polymerization using poly(ethylene glycol) methyl methacrylate (PEGMA) and N-(3-aminopropyl) methacrylamide (NAPAM) as monomers and ammonium persulfate as the initiator. The successful modification of silica nanoparticles was evidenced by a series of characterization techniques. As compared with the bare silica nanoparticles, the polymers modified silica nanoparticles showed remarkable enhanced dispersibility in both aqueous and organic solution. This strategy is rather simple, effective and versatile. Therefore, it should be of specific importance for further applications of silica nanoparticles and will spark great research attention of scientists from different fields.

  15. Nanosensors based on functionalized nanoparticles and surface enhanced raman scattering

    DOEpatents

    Talley, Chad E.; Huser, Thomas R.; Hollars, Christopher W.; Lane, Stephen M.; Satcher, Jr., Joe H.; Hart, Bradley R.; Laurence, Ted A.

    2007-11-27

    Surface-Enhanced Raman Spectroscopy (SERS) is a vibrational spectroscopic technique that utilizes metal surfaces to provide enhanced signals of several orders of magnitude. When molecules of interest are attached to designed metal nanoparticles, a SERS signal is attainable with single molecule detection limits. This provides an ultrasensitive means of detecting the presence of molecules. By using selective chemistries, metal nanoparticles can be functionalized to provide a unique signal upon analyte binding. Moreover, by using measurement techniques, such as, ratiometric received SERS spectra, such metal nanoparticles can be used to monitor dynamic processes in addition to static binding events. Accordingly, such nanoparticles can be used as nanosensors for a wide range of chemicals in fluid, gaseous and solid form, environmental sensors for pH, ion concentration, temperature, etc., and biological sensors for proteins, DNA, RNA, etc.

  16. First application of proton reflection magnetometry with MESSENGER to estimate Mercury's surface magnetic field strength (Invited)

    NASA Astrophysics Data System (ADS)

    Winslow, R. M.; Johnson, C. L.; Anderson, B. J.; Gershman, D. J.; Raines, J. M.; Lillis, R. J.; Korth, H.; Slavin, J. A.; Solomon, S. C.

    2013-12-01

    We present the first use of proton reflection magnetometry, a novel adaptation of electron reflectometry, to estimate Mercury's surface field strength. We use measurements of protons by MESSENGER's Fast Imaging Plasma Spectrometer (FIPS) in 8-s integration times. Because of the limited field of view of FIPS, we average pitch-angle distributions by accumulating proton data from multiple integration periods and orbits over selected geographical regions. Proton loss cones are evident in both the northern hemisphere cusp region as well as on the nightside at low latitudes in the southern hemisphere. The existence of the loss cones provides confirmation of proton precipitation to the surface in these regions. The loss cone pitch-angle cut-offs are gradual rather than sharp, which we attribute in part to wave-particle scattering causing pitch-angle diffusion. Fitting diffusion curves to the pitch-angle distributions yields estimates of both the cut-off pitch angle, αc, and an average Dαt, where Dα is the pitch-angle diffusion coefficient and t is the diffusion time. The in-situ magnetic field together with αc provide an estimate of the surface magnetic field strength. The results are within 10% of a magnetospheric model for the surface field at the mapped surface locations, but are systematically lower than the model predictions. This discrepancy is consistent with the presence of near-surface plasma, which locally lowers the actual total magnetic field at the surface but is not included in the vacuum-field magnetospheric model. As consistency checks, we have confirmed that the loss cone size decreases with increasing altitude and that the surface magnetic field strength increases with increasing latitude. Our results confirm the offset dipole structure at the surface and demonstrate that proton reflection magnetometry is a practical method for inferring the surface magnetic field strength at Mercury. Further observations may resolve regional-scale structure in the

  17. Magnetic nanoparticles: surface effects and properties related to biomedicine applications.

    PubMed

    Issa, Bashar; Obaidat, Ihab M; Albiss, Borhan A; Haik, Yousef

    2013-10-25

    Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10-100 μm), viruses, genes, down to proteins (3-50 nm). The optimization of the nanoparticles' size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents.

  18. Anisotropic Nanoparticles and Anisotropic Surface Chemistry.

    PubMed

    Burrows, Nathan D; Vartanian, Ariane M; Abadeer, Nardine S; Grzincic, Elissa M; Jacob, Lisa M; Lin, Wayne; Li, Ji; Dennison, Jordan M; Hinman, Joshua G; Murphy, Catherine J

    2016-02-18

    Anisotropic nanoparticles are powerful building blocks for materials engineering. Unusual properties emerge with added anisotropy-often to an extraordinary degree-enabling countless new applications. For bottom-up assembly, anisotropy is crucial for programmability; isotropic particles lack directional interactions and can self-assemble only by basic packing rules. Anisotropic particles have long fascinated scientists, and their properties and assembly behavior have been the subjects of many theoretical studies over the years. However, only recently has experiment caught up with theory. We have begun to witness tremendous diversity in the synthesis of nanoparticles with controlled anisotropy. In this Perspective, we highlight the synthetic achievements that have galvanized the field, presenting a comprehensive discussion of the mechanisms and products of both seed-mediated and alternative growth methods. We also address recent breakthroughs and challenges in regiospecific functionalization, which is the next frontier in exploiting nanoparticle anisotropy.

  19. Gold nanoparticle induced vasculature damage in radiotherapy: Comparing protons, megavoltage photons, and kilovoltage photons

    PubMed Central

    Lin, Yuting; Paganetti, Harald; McMahon, Stephen J.; Schuemann, Jan

    2015-01-01

    Purpose: The purpose of this work is to investigate the radiosensitizing effect of gold nanoparticle (GNP) induced vasculature damage for proton, megavoltage (MV) photon, and kilovoltage (kV) photon irradiation. Methods: Monte Carlo simulations were carried out using tool for particle simulation (TOPAS) to obtain the spatial dose distribution in close proximity up to 20 μm from the GNPs. The spatial dose distribution from GNPs was used as an input to calculate the dose deposited to the blood vessels. GNP induced vasculature damage was evaluated for three particle sources (a clinical spread out Bragg peak proton beam, a 6 MV photon beam, and two kV photon beams). For each particle source, various depths in tissue, GNP sizes (2, 10, and 20 nm diameter), and vessel diameters (8, 14, and 20 μm) were investigated. Two GNP distributions in lumen were considered, either homogeneously distributed in the vessel or attached to the inner wall of the vessel. Doses of 30 Gy and 2 Gy were considered, representing typical in vivo enhancement studies and conventional clinical fractionation, respectively. Results: These simulations showed that for 20 Au-mg/g GNP blood concentration homogeneously distributed in the vessel, the additional dose at the inner vascular wall encircling the lumen was 43% of the prescribed dose at the depth of treatment for the 250 kVp photon source, 1% for the 6 MV photon source, and 0.1% for the proton beam. For kV photons, GNPs caused 15% more dose in the vascular wall for 150 kVp source than for 250 kVp. For 6 MV photons, GNPs caused 0.2% more dose in the vascular wall at 20 cm depth in water as compared to at depth of maximum dose (Dmax). For proton therapy, GNPs caused the same dose in the vascular wall for all depths across the spread out Bragg peak with 12.7 cm range and 7 cm modulation. For the same weight of GNPs in the vessel, 2 nm diameter GNPs caused three times more damage to the vessel than 20 nm diameter GNPs. When the GNPs were attached

  20. Gold nanoparticle induced vasculature damage in radiotherapy: Comparing protons, megavoltage photons, and kilovoltage photons

    SciTech Connect

    Lin, Yuting Paganetti, Harald; Schuemann, Jan; McMahon, Stephen J.

    2015-10-15

    Purpose: The purpose of this work is to investigate the radiosensitizing effect of gold nanoparticle (GNP) induced vasculature damage for proton, megavoltage (MV) photon, and kilovoltage (kV) photon irradiation. Methods: Monte Carlo simulations were carried out using tool for particle simulation (TOPAS) to obtain the spatial dose distribution in close proximity up to 20 μm from the GNPs. The spatial dose distribution from GNPs was used as an input to calculate the dose deposited to the blood vessels. GNP induced vasculature damage was evaluated for three particle sources (a clinical spread out Bragg peak proton beam, a 6 MV photon beam, and two kV photon beams). For each particle source, various depths in tissue, GNP sizes (2, 10, and 20 nm diameter), and vessel diameters (8, 14, and 20 μm) were investigated. Two GNP distributions in lumen were considered, either homogeneously distributed in the vessel or attached to the inner wall of the vessel. Doses of 30 Gy and 2 Gy were considered, representing typical in vivo enhancement studies and conventional clinical fractionation, respectively. Results: These simulations showed that for 20 Au-mg/g GNP blood concentration homogeneously distributed in the vessel, the additional dose at the inner vascular wall encircling the lumen was 43% of the prescribed dose at the depth of treatment for the 250 kVp photon source, 1% for the 6 MV photon source, and 0.1% for the proton beam. For kV photons, GNPs caused 15% more dose in the vascular wall for 150 kVp source than for 250 kVp. For 6 MV photons, GNPs caused 0.2% more dose in the vascular wall at 20 cm depth in water as compared to at depth of maximum dose (Dmax). For proton therapy, GNPs caused the same dose in the vascular wall for all depths across the spread out Bragg peak with 12.7 cm range and 7 cm modulation. For the same weight of GNPs in the vessel, 2 nm diameter GNPs caused three times more damage to the vessel than 20 nm diameter GNPs. When the GNPs were attached

  1. Proton radii of neutron-rich B isotopes and neutron surface thickness in 17B

    NASA Astrophysics Data System (ADS)

    Kanungo, Rituparna; Estrade, Alfredo; Horiuchi, Wataru

    2014-09-01

    As the neutron to proton asymmetry increases nuclei develop exotic structures such as neutron skin and halo. It is important to investigate how this asymmetry affects the proton distribution. The matter and proton radii have started unfolding a complete picture of the halo. For two-neutron halos the correlation between the halo neutrons and their distance from the core can be derived to define the average halo geometry. The proton radii are crucial information to extract the neutron skin thickness to constrain the equation of state of asymmetric nuclear matter. Very limited information is available on the proton radii of very neutron-rich nuclei. In this presentation, we will describe the new technique of extracting proton radii from charge changing cross sections using relativistic beams at GSI, Germany. The presentation will show first measurements of proton radii of the neutron-rich boron isotopes. The implications of the results in understanding the neutron surface thickness in the Borromean 17B and its possible halo structure will be discussed. As the neutron to proton asymmetry increases nuclei develop exotic structures such as neutron skin and halo. It is important to investigate how this asymmetry affects the proton distribution. The matter and proton radii have started unfolding a complete picture of the halo. For two-neutron halos the correlation between the halo neutrons and their distance from the core can be derived to define the average halo geometry. The proton radii are crucial information to extract the neutron skin thickness to constrain the equation of state of asymmetric nuclear matter. Very limited information is available on the proton radii of very neutron-rich nuclei. In this presentation, we will describe the new technique of extracting proton radii from charge changing cross sections using relativistic beams at GSI, Germany. The presentation will show first measurements of proton radii of the neutron-rich boron isotopes. The implications

  2. Chemical analysis of surface oxygenated moieties of fluorescent carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Huang, Jie; Deming, Christopher P.; Song, Yang; Kang, Xiongwu; Zhou, Zhi-You; Chen, Shaowei

    2012-01-01

    Water-soluble carbon nanoparticles were prepared by refluxing natural gas soot in concentrated nitric acid. The surface of the resulting nanoparticles was found to be decorated with a variety of oxygenated species, as suggested by spectroscopic measurements. Back potentiometric titration of the nanoparticles was employed to quantify the coverage of carboxylic, lactonic, and phenolic moieties on the particle surface by taking advantage of their vast difference of acidity (pKa). The results were largely consistent with those reported in previous studies with other carbonaceous (nano)materials. Additionally, the presence of ortho- and para-quinone moieties on the nanoparticle surface was confirmed by selective labelling with o-phenylenediamine, as manifested in X-ray photoelectron spectroscopy, photoluminescence, and electrochemical measurements. The results further supported the arguments that the surface functional moieties that were analogous to 9,10-phenanthrenequinone were responsible for the unique photoluminescence of the nanoparticles and the emission might be regulated by surface charge state, as facilitated by the conjugated graphitic core matrix.

  3. Multiplicity fluctuations of net protons on the hydrodynamic freeze-out surface

    NASA Astrophysics Data System (ADS)

    Jiang, Lijia; Li, Pengfei; Song, Huichao

    2016-12-01

    This proceeding briefly summarizes our recent work on calculating the correlated fluctuations of net protons on the hydrodynamic freeze-out surface near the QCD critical point. For both Poisson and Binomial baselines, our calculations could roughly reproduce the energy dependent cumulant C4 and κσ2 of net protons, but always over-predict C2 and C3 due to the positive contributions from the static critical fluctuations.

  4. SU-E-T-577: Obliquity Factor and Surface Dose in Proton Beam Therapy

    SciTech Connect

    Das, I; Andersen, A; Coutinho, L

    2015-06-15

    Purpose: The advantage of lower skin dose in proton beam may be diminished creating radiation related sequalae usually seen with photon and electron beams. This study evaluates the surface dose as a complex function of beam parameters but more importantly the effect of beam angle. Methods: Surface dose in proton beam depends on the beam energy, source to surface distance, the air gap between snout and surface, field size, material thickness in front of surface, atomic number of the medium, beam angle and type of nozzle (ie double scattering, (DS), uniform scanning (US) or pencil beam scanning (PBS). Obliquity factor (OF) is defined as ratio of surface dose in 0° to beam angle Θ. Measurements were made in water phantom at various beam angles using very small microdiamond that has shown favorable beam characteristics for high, medium and low proton energy. Depth dose measurements were performed in the central axis of the beam in each respective gantry angle. Results: It is observed that surface dose is energy dependent but more predominantly on the SOBP. It is found that as SSD increases, surface dose decreases. In general, SSD, and air gap has limited impact in clinical proton range. High energy has higher surface dose and so the beam angle. The OF rises with beam angle. Compared to OF of 1.0 at 0° beam angle, the value is 1.5, 1.6, 1,7 for small, medium and large range respectively for 60 degree angle. Conclusion: It is advised that just like range and SOBP, surface dose should be clearly understood and a method to reduce the surface dose should be employed. Obliquity factor is a critical parameter that should be accounted in proton beam therapy and a perpendicular beam should be used to reduce surface dose.

  5. DNA surface modified gadolinium phosphate nanoparticles as MRI contrast agents.

    PubMed

    Dumont, Matthieu F; Baligand, Celine; Li, Yichen; Knowles, Elisabeth S; Meisel, Mark W; Walter, Glenn A; Talham, Daniel R

    2012-05-16

    Oligonucleotide modified gadolinium phosphate nanoparticles have been prepared and their magnetic resonance relaxivity properties measured. Nanoparticles of GdPO4·H2O were synthesized in a water/oil microemulsion using IGEPAL CO-520 as surfactant, resulting in 50 to 100 nm particles that are highly dispersible and stable in water. Using surface modification chemistry previously established for zirconium phosphonate surfaces, the particles are directly modified with 5'-phosphate terminated oligonucleotides, and the specific interaction of the divalent phosphate with Gd(3+) sites at the surface is demonstrated. The ability of the modified nanoparticles to act as MRI contrast agents was determined by performing MR relaxivity measurements at 14.1 T. Solutions of nanopure water, Feridex, and Omniscan (FDA approved contrast agents) in 0.25% agarose were used for comparison and control purposes. MRI data confirm that GdPO4·H2O nanoparticles have relaxivities (r1, r2) comparable to those of commercially available contrast agents. In addition, the data suggest that biofunctionalization of the surface of the nanoparticles does not prevent their function as MRI contrast agents.

  6. Magnetic Nanoparticles: Surface Effects and Properties Related to Biomedicine Applications

    PubMed Central

    Issa, Bashar; Obaidat, Ihab M.; Albiss, Borhan A.; Haik, Yousef

    2013-01-01

    Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10–100 μm), viruses, genes, down to proteins (3–50 nm). The optimization of the nanoparticles’ size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents. PMID:24232575

  7. Investigation of Surface Coatings on Silver Nanoparticles by Surface Enhanced Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Kühn, Melanie; Ivleva, Natalia P.; Niessner, Reinhard; Baumann, Thomas

    2013-04-01

    The behavior of engineered inorganic nanoparticles (EINP) in the environment is strongly affected by their surface properties. Once introduced in the aquatic or terrestric environment, the nanoparticle surface may be altered by weathering or the formation of a coating. These changes influence the interactions of the nanoparticle with natural surfaces or interfaces as well as with other particles. Natural organic matter for example is known to have a stabilizing effect on most nanoparticles. Therefore the assessment of the fate and transport of nanoparticles in the environment requires a precise knowledge of the influence of the coating and its modifications under natural conditions. A suitable tool for the investigation of coatings on silver nanoparticles is surface enhanced Raman spectroscopy (SERS). Although silver nanoparticles themselves do not have a distinct Raman signal, the Raman signal of adsorbed or nearby substances is enhanced by a factor of 103 - 106. This leads to a considerably higher sensitivity of SERS in comparison to normal Raman microscopy. Therefore, coatings on silver nanoparticles should be accessible via the SERS effect. As a first step, plain and citrate stabilized silver nanoparticles were mixed with different natural coating substances (polygalacturonic acid, seaweed extract, and humic substances) and filtered with a polycarbonate filter to remove excessive coating material. Afterwards, the nanoparticles were redispersed from the filter by ultrasonification. This washing procedure was repeated three times while always maintaining the same concentration of nanoparticles. SERS spectra were recorded after each washing step with a LabRAM HR Raman mircospectrometer (Horiba Scientific, Japan, ? = 633 nm, 20x water-immersion-objective, measurement time 10 s). First results indicate the formation of a stabilizing layer around the nanoparticles after contact with humic substances, thus providing experimental evidence to the stabilization of EINP

  8. Microscale Heat Transfer Transduced by Surface Plasmon Resonant Gold Nanoparticles

    PubMed Central

    Roper, D. Keith; Ahn, W.; Hoepfner, M.

    2008-01-01

    Visible radiation at resonant frequencies is transduced to thermal energy by surface plasmons on gold nanoparticles. Temperature in ≤10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value. This value increased in proportion to incident laser power and in proportion to nanoparticle content at low concentration. Heat input to the system by nanoparticle transduction of resonant irradiation equaled heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat by microvolume suspensions of gold nanoparticles was determined by applying an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Measured values of transduction efficiency were increased from 3.4% to 9.9% by modulating the incident continuous wave irradiation. PMID:19011696

  9. Quantitatively Probing the Means of Controlling Nanoparticle Assembly on Surfaces

    SciTech Connect

    Patete, J.m.; Wong, S.; Peng, X.; Serafin, J.M.

    2011-05-17

    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 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.

  10. Existence of a proton transfer chain in bacteriorhodopsin: participation of Glu-194 in the release of protons to the extracellular surface.

    PubMed

    Dioumaev, A K; Richter, H T; Brown, L S; Tanio, M; Tuzi, S; Saito, H; Kimura, Y; Needleman, R; Lanyi, J K

    1998-02-24

    Glu-194 near the extracellular surface of bacteriorhodopsin is indispensable for proton release to the medium upon protonation of Asp-85 during light-driven transport. As for Glu-204, its replacement with glutamine (but not aspartate) abolishes both proton release and the anomalous titration of Asp-85 that originates from coupling between the pKa of this buried aspartate and those of the other acidic groups. Unlike the case of Glu-204, however, replacement of Glu-194 with aspartate raises the pKa for proton release. In Fourier transform infrared spectra of the E194D mutant a prominent positive band is observed at 1720 cm-1. It can be assigned from [4-13C]aspartate and D2O isotope shifts to the C&dbd;O stretch of protonated Asp-194. Its rise correlates with proton transfer from the retinal Schiff base to Asp-85. Its decay coincides with the appearance of a proton at the surface, detected under similar conditions with fluorescein covalently bound to Lys-129 and with pyranine. Its amplitude decreases with increasing pH, with a pKa of about 9. We show that this pKa is likely to be that of the internal proton donor to Asp-194, the Glu-204 site, before photoexcitation, while 13C NMR titration indicates that Asp-194 has an initial pKa of about 3. We propose that there is a chain of interacting residues between the retinal Schiff base and the extracellular surface. After photoisomerization of the retinal the pKa's change so as to allow (i) Asp-85 to become protonated by the Schiff base, (ii) the Glu-204 site to transfer its proton to Asp-194 in E194D, and therefore to Glu-194 in the wild type, and (iii) residue 194 to release the proton to the medium.

  11. Surface functionalized magnetic nanoparticles for cancer therapy applications

    NASA Astrophysics Data System (ADS)

    Wydra, Robert John

    Despite recent advances, cancer remains the second leading cause of deaths in the United States. Magnetic nanoparticles have found various applications in cancer research as drug delivery platforms, enhanced contrast agents for improved diagnostic imaging, and the delivery of thermal energy as standalone therapy. Iron oxide nanoparticles absorb the energy from an alternating magnetic field and convert it into heat through Brownian and Neel relaxations. To better utilize magnetic nanoparticles for cancer therapy, surface functionalization is essential for such factors as decreasing cytotoxicity of healthy tissue, extending circulation time, specific targeting of cancer cells, and manage the controlled delivery of therapeutics. In the first study, iron oxide nanoparticles were coated with a poly(ethylene glycol) (PEG) based polymer shell. The PEG coating was selected to prevent protein adsorption and thus improve circulation time and minimize host response to the nanoparticles. Thermal therapy application feasibility was demonstrated in vitro with a thermoablation study on lung carcinoma cells. Building on the thermal therapy demonstration with iron oxide nanoparticles, the second area of work focused on intracellular delivery. Nanoparticles can be appropriately tailored to enter the cell and deliver energy on the nanoscale eliminating individual cancer cells. The underlying mechanism of action is still under study, and we were interested in determining the role of reactive oxygen species (ROS) catalytically generated from the surface of iron oxide nanoparticles in this measured cytotoxicity. When exposed to an AMF, the nanoscale heating effects are capable of enhancing the Fenton-like generation of ROS determined through a methylene blue degradation assay. To deliver this enhanced ROS effect to cells, monosaccharide coated nanoparticles were developed and successfully internalized by colon cancer cell lines. Upon AMF exposure, there was a measured increase in

  12. Surface Proton Hopping and Coupling Pathway of Water Oxidation on Cobalt Oxide Catalyst

    NASA Astrophysics Data System (ADS)

    Pham, Hieu; Cheng, Mu-Jeng; Frei, Heinz; Wang, Lin-Wang

    We propose an oxidation pathway of water splitting on cobalt oxide surface with clear thermodynamic and kinetic details. The density-functional theory studies suggest that the coupled proton-electron transfer is not necessarily sequential and implicit in every elementary step of this mechanistic cycle. Instead, the initial O-O bond could be formed by the landing of water molecule on the surface oxos, which is then followed by the dispatch of protons through the hopping manner and subsequent release of di-oxygen. Our theoretical investigations of intermediates and transition states indicate that all chemical conversions in this pathway, including the proton transfers, are possible with low activation barriers, in addition to their favorable thermodynamics. Our hypothesis is supported by recent experimental observations of surface superoxide that is stabilized by hydrogen bonding to adjacent hydroxyl group, as an intermediate on fast-kinetics catalytic site.

  13. Proton magnetic resonance study of diamond nanoparticles decorated by transition metal ions

    NASA Astrophysics Data System (ADS)

    Panich, A. M.; Altman, A.; Shames, A. I.; Osipov, V. Yu; Aleksenskiy, A. E.; Vul', A. Ya

    2011-03-01

    We report on a 1H NMR study of diamond nanoparticles decorated by copper and cobalt. Increase in the 1H relaxation rate under decoration results from the interactions of hydrogen nuclear spins of the surface hydrocarbon and hydroxyl groups with paramagnetic copper and cobalt ions. This finding reveals the appearance of paramagnetic Cu2+ or Co2+ ions on the detonation nanodiamond (DND) surface rather than as a separate phase, which is consistent with the 13C NMR data of the same samples. Our results shed light on the mechanism of ion incorporation. A topological model for relative position of paramagnetic Cu2+ or Co2+ ions and hydrogen atoms on the DND surface is suggested. An application of the studied nanomaterials in the field of biomedicine is discussed.

  14. Control surface wettability with nanoparticles from phase-change materials

    NASA Astrophysics Data System (ADS)

    ten Brink, G. H.; van het Hof, P. J.; Chen, B.; Sedighi, M.; Kooi, B. J.; Palasantzas, G.

    2016-12-01

    The wetting state of surfaces can be controlled physically from the highly hydrophobic to hydrophilic states using the amorphous-to-crystalline phase transition of Ge2Sb2Te5 (GST) nanoparticles as surfactant. Indeed, contact angle measurements show that by increasing the surface coverage of the amorphous nanoparticles the contact angle increases to high values ˜140°, close to the superhydrophobic limit. However, for crystallized nanoparticle assemblies after thermal annealing, the contact angle decreases down to ˜40° (significantly lower than that of the bare substrate) leading to an increased hydrophilicity. Moreover, the wettability changes are also manifested on the capillary adhesion forces by being stronger for the crystallized GST state.

  15. Sustainable environmental nanotechnology using nanoparticle surface modification.

    EPA Science Inventory

    Reactive nanomaterials used for environmental remediation require surface modification to make them mobile in the subsurface. Nanomaterials released into the environment inadvertently without an engineered surface coating will acquire one (e.g. adsorption of natural organic matt...

  16. Nonlinear surface plasma wave induced target normal sheath acceleration of protons

    SciTech Connect

    Liu, C. S.; Tripathi, V. K. Shao, Xi; Liu, T. C.

    2015-02-15

    The mode structure of a large amplitude surface plasma wave (SPW) over a vacuum–plasma interface, including relativistic and ponderomotive nonlinearities, is deduced. It is shown that the SPW excited by a p-polarized laser on a rippled thin foil target can have larger amplitude than the transmitted laser amplitude and cause stronger target normal sheath acceleration of protons as reported in a recent experiment. Substantial enhancement in proton number also occurs due to the larger surface area covered by the SPW.

  17. Assembly of responsive-shape coated nanoparticles at water surfaces

    NASA Astrophysics Data System (ADS)

    Lane, J. Matthew D.; Grest, Gary S.

    2014-04-01

    Nanoparticle (NP) assembly and aggregation can be controlled using a variety of organic coatings that bind to the nanoparticle surface and alter its affinity for solvent and other particles. We show that surprisingly simple short chain polymer coatings can be effectively used to selectively control the aggregation of very small nanoparticles by taking advantage of the environment-responsive shape produced by the coating's spontaneous asymmetry on high-curvature nanoparticles. Using extremely long molecular dynamics simulations of alkanethiol coated Au nanoparticles, we show that varying the terminal groups of a nanoparticle coating dramatically alters the coating shape at the water liquid-vapor interface, producing very different assembly morphologies. NPs with CH3-terminated coatings assemble into short linear groupings with a highly aligned structure at early time and then form more disordered clusters as these linear groupings further assemble. NPs with COOH-terminated coatings assemble into dimers and disordered clumps with no preferred alignment at short time and longer disordered chains of particles at longer times. We also find that the responsive shape of the coating continues to adapt to local environment during assembly. The orientations of chains within NP coatings are significantly different when the NPs are arranged in aggregates than when they are isolated.

  18. Excited State Potential Energy Surfaces of Polyenes and Protonated Schiff Bases.

    PubMed

    Send, Robert; Sundholm, Dage; Johansson, Mikael P; Pawłowski, Filip

    2009-09-08

    The potential energy surface of the (1)Bu and (1)A' states of all-trans-polyenes and the corresponding protonated Schiff bases have been studied at density functional theory and coupled cluster levels. Linear polyenes and protonated Schiff bases with 4 to 12 heavy atoms have been investigated. The calculations show remarkable differences in the excited state potential energy surfaces of the polyenes and the protonated Schiff bases. The excited states of the polyenes exhibit high torsion barriers for single-bond twists and low torsion barriers for double-bond twists. The protonated Schiff bases, on the other hand, are very flexible molecules in the first excited state with low or vanishing torsion barriers for both single and double bonds. Calculations at density functional theory and coupled cluster levels yield qualitatively similar potential energy surfaces. However, significant differences are found for some single-bond torsions in longer protonated Schiff bases, which indicate a flaw of the employed time-dependent density functional theory methods. The close agreement between the approximate second and third order coupled cluster levels indicates that for these systems calculations at second order coupled cluster level are useful in the validation of results based on time-dependent density functional theory.

  19. Water-gas-shift reaction on metal nanoparticles and surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Ping; Rodriguez, José A.

    2007-04-01

    Density functional theory was employed to investigate the water-gas-shift reaction (WGS, CO +H2O→H2+CO2) on Au29 and Cu29 nanoparticles seen with scanning tunneling microscopy in model Au /CeO2(111) and Cu /CeO2(111) catalysts. Au(100) and Cu(100) surfaces were also included for comparison. According to the calculations of the authors, the WGS on these systems operate via either redox or associative carboxyl mechanism, while the rate-limiting step is the same, water dissociation. The WGS activity decreases in a sequence: Cu29>Cu(100)>Au29>Au(100), which agrees well with the experimental observations. Both nanoparticles are more active than their parent bulk surfaces. The nanoscale promotion on the WGS activity is associated with the low-coordinated corner and the edge sites as well as the fluxionality of the particles, which makes the nanoparticles more active than the flat surfaces for breaking the O-H bond. In addition, the role of the oxide support during the WGS was addressed by comparing the activity seen in the calculations of the authors for the Au29 and Cu29 nanoparticles and activity reported for X /CeO2(111) and X /ZnO(000ı¯)(X =Cu or Au) surfaces.

  20. Enhanced Cyanate Ester Nanocomposites through Improved Nanoparticle Surface Interactions

    DTIC Science & Technology

    2013-05-09

    Surface Interactions 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Christopher M. Sahagun, Andrew J. Guenthner ...Octyl, hydroxyl, 3- aminopropyltrimethoxy modified silica nanoparticles. (Evonik) Campos; Guenthner ; Haddad; Mabry. Fluoroalkyl-Functionalized

  1. Surface Modified Gadolinium Phosphate Nanoparticles as MRI Contrast Agents

    NASA Astrophysics Data System (ADS)

    Dumont, Matthieu F.; Baligand, Celine; Knowles, Elisabeth S.; Meisel, Mark W.; Walter, Glenn A.; Talham, Daniel R.

    2012-02-01

    Nanoparticles of GdPO4H2O were synthesized in a water/oil microemulsion using IGEPAL CO-520 as surfactant resulting in 50 nm to 100 nm particles that are dispersible and stable in water. Using surface modification chemistry previously established for zirconium phosphonate surfaces,ootnotetext J. Monot et al., J. Am. Chem. Soc. 130 (2008) 6243. the particles are directly modified with 5'-phosphate terminated oligonucleotides, and the specific interaction of the divalent phosphate with Gd^3+ sites at the surface is demonstrated. The ability of the modified nanoparticles to act as MRI contrast agents was determined by performing MR relaxivity measurements at 14 T. Solutions of nanopure water, Feridex and Omniscan (FDA cleared contrast agents) in 0.25% agarose were used for comparison and control purposes. MRI data confirm that GdPO4H2O nanoparticles have relaxivities (r1,r2) comparable to commercially available contrast agents.ootnotetext H. Hifumi et al., J. Am. Chem. Soc. 128 (2006) 15090. In addition, biofunctionalization of the surface of the nanoparticles does not prevent their function as MRI contrast agents.

  2. Characterization of QCM sensor surfaces coated with molecularly imprinted nanoparticles.

    PubMed

    Reimhult, Kristina; Yoshimatsu, Keiichi; Risveden, Klas; Chen, Si; Ye, Lei; Krozer, Anatol

    2008-07-15

    Molecularly imprinted polymers (MIPs) are gaining great interest as tailor-made recognition materials for the development of biomimetic sensors. Various approaches have been adopted to interface MIPs with different transducers, including the use of pre-made imprinted particles and the in situ preparation of thin polymer layers directly on transducer surfaces. In this work we functionalized quartz crystal microbalance (QCM) sensor crystals by coating the sensing surfaces with pre-made molecularly imprinted nanoparticles. The nanoparticles were immobilized on the QCM transducers by physical entrapment in a thin poly(ethylene terephthalate) (PET) layer that was spin-coated on the transducer surface. By controlling the deposition conditions, it was possible to gain a high nanoparticle loading in a stable PET layer, allowing the recognition sites in nanoparticles to be easily accessed by the test analytes. In this work, different sensor surfaces were studied by micro-profilometry and atomic force microscopy and the functionality was evaluated using quartz crystal microbalance with dissipation (QCM-D). The molecular recognition capability of the sensors were also confirmed using radioligand binding analysis by testing their response to the presence of the test compounds, (R)- and (S)-propranolol in aqueous buffer.

  3. Surface Bonding Effects in Compound Semiconductor Nanoparticles: II

    SciTech Connect

    Helen H. Farrell

    2008-07-01

    Small nanoparticles have a large proportion of their atoms either at or near the surface, and those in clusters are essentially all on the surface. As a consequence, the details of the surface structure are of paramount importance in governing the overall stability of the particle. Just as with bulk materials, factors that determine this stability include “bulk” structure, surface reconstruction, charge balance and hybridization, ionicity, strain, stoichiometry, and the presence of adsorbates. Needless to say, many of these factors, such as charge balance, hybridization and strain, are interdependent. These factors all contribute to the overall binding energy of clusters and small nanoparticles and play a role in determining the deviations from an inverse size dependence that we have previously reported for compound semiconductor materials. Using first-principles density functional theory calculations, we have explored how these factors influence particle stability under a variety of conditions.

  4. Controlling the hydrophilicity and contact resistance of fuel cell bipolar plate surfaces using layered nanoparticle assembly

    NASA Astrophysics Data System (ADS)

    Wang, Feng

    Hybrid nanostructured coatings exhibiting the combined properties of electrical conductivity and surface hydrophilicity were obtained by using Layer-by-Layer (LBL) assembly of cationic polymer, silica nanospheres, and carbon nanoplatelets. This work demonstrates that by controlling the nanoparticle zeta (zeta) potential through the suspension parameters (pH, organic solvent type and amount, and ionic content) as well as the assembly sequence, the nanostructure and composition of the coatings may be adjusted to optimize the desired properties. Two types of silica nanospheres were evaluated as the hydrophilic component: X-TecRTM 3408 from Nano-X Corporation, with a diameter of about 20 nm, and polishing silica from Electron Microscopy Supply, with diameter of about 65 nm. Graphite nanoplatelets with a thickness of 5~10nm (Aquadag RTM E from Acheson Industries) were used as electrically conductive filler. A cationic copolymer of acrylamide and a quaternary ammonium salt (SuperflocRTM C442 from Cytec Corporation) was used as the binder for the negatively charged nanoparticles. Coatings were applied to gold-coated stainless steel substrates presently used a bipolar plate material for proton exchange membrane (PEM) fuel cells. Coating thickness was found to vary nearly linearly with the number of polymer-nanoparticle layers deposited while a monotonic increase in coating contact resistance was observed for all heterogeneous and pure silica coatings. Thickness increased if the difference in the oppositely charged zeta potentials of the adsorbing components was enhanced through alcohol addition. Interestingly, an opposite effect was observed if the zeta potential difference was increased through pH variation. This previously undocumented difference in adsorption behavior is herein related to changes to the surface chemical heterogeneity of the nanoparticles. Coating contact resistance and surface wettability were found to have a more subtle dependence on the assembly

  5. Surface-induced dissociation of singly and multiply protonated polypropylenamine dendrimers.

    PubMed

    de Maaijer-Gielbert, J; Gu, C; Somogyi, A; Wysocki, V H; Kistemaker, P G; Weeding, T L

    1999-05-01

    The ease of fragmentation of various charge states of protonated polypropylenamine (POPAM) dendrimers is investigated by surface-induced dissociation. Investigated are the protonated diaminobutane propylenamines [DAB(PA)n] DAB(PA)8 (1+ and 2+), DAB(PA)16 (2+ and 3+), and DAB(PA)32 (3+ and 4+). These ions have been proposed to fragment by charge-directed intramolecular nucleophilic substitution (SNi) reactions. Differences in relative fragment ion abundances between charge states can be related to the occupation of different protonation sites. These positions can be rationalized based on estimates of Coulomb energies and gas-phase basicities of the protonation/fragmentation sites. The laboratory collision energies at which the fragment ion current is approximately 50% of the total ion current were found to increase with the size, but to be independent of charge state of the protonated POPAM dendrimers. It is suggested that intramolecular Coulomb repulsion within the multiply protonated POPAM dendrimers selected for activation does not readily result in easier fragmentation, which is in accordance with the proposed fragmentation mechanism.

  6. Nanoparticle-Based Antimicrobials: Surface Functionality is Critical

    PubMed Central

    Gupta, Akash; Landis, Ryan F.; Rotello, Vincent M.

    2016-01-01

    Bacterial infections cause 300 million cases of severe illness each year worldwide. Rapidly accelerating drug resistance further exacerbates this threat to human health. While dispersed (planktonic) bacteria represent a therapeutic challenge, bacterial biofilms present major hurdles for both diagnosis and treatment. Nanoparticles have emerged recently as tools for fighting drug-resistant planktonic bacteria and biofilms. In this review, we present the use of nanoparticles as active antimicrobial agents and drug delivery vehicles for antibacterial therapeutics. We further focus on how surface functionality of nanomaterials can be used to target both planktonic bacteria and biofilms. PMID:27006760

  7. Cubic versus spherical magnetic nanoparticles: the role of surface anisotropy.

    PubMed

    Salazar-Alvarez, G; Qin, J; Sepelák, V; Bergmann, I; Vasilakaki, M; Trohidou, K N; Ardisson, J D; Macedo, W A A; Mikhaylova, M; Muhammed, M; Baró, M D; Nogués, J

    2008-10-08

    The magnetic properties of maghemite (gamma-Fe2O3) cubic and spherical nanoparticles of similar sizes have been experimentally and theoretically studied. The blocking temperature, T(B), of the nanoparticles depends on their shape, with the spherical ones exhibiting larger T(B). Other low temperature properties such as saturation magnetization, coercivity, loop shift or spin canting are rather similar. The experimental effective anisotropy and the Monte Carlo simulations indicate that the different random surface anisotropy of the two morphologies combined with the low magnetocrystalline anisotropy of gamma-Fe2O3 is the origin of these effects.

  8. Studies on surface plasmon resonance and photoluminescence of silver nanoparticles.

    PubMed

    Smitha, S L; Nissamudeen, K M; Philip, Daizy; Gopchandran, K G

    2008-11-01

    Silver nanoparticles of different sizes were prepared by citrate reduction and characterized by UV-vis absorbance spectra, TEM images and photoluminescence spectra. The morphology of the colloids obtained consists of a mixture of nanorods and spheres. The surface plasmon resonance (SPR) and photoemission properties of Ag nanoparticles are found to be sensitive to citrate concentration. A blue shift in SPR and an enhancement in photoluminescence intensity are observed with increase in citrate concentration. Effect of addition of KCl and variation of pH in photoluminescence was also studied.

  9. Platinum nanoparticles on gallium nitride surfaces: effect of semiconductor doping on nanoparticle reactivity.

    PubMed

    Schäfer, Susanne; Wyrzgol, Sonja A; Caterino, Roberta; Jentys, Andreas; Schoell, Sebastian J; Hävecker, Michael; Knop-Gericke, Axel; Lercher, Johannes A; Sharp, Ian D; Stutzmann, Martin

    2012-08-01

    Platinum nanoparticles supported on n- and p-type gallium nitride (GaN) are investigated as novel hybrid systems for the electronic control of catalytic activity via electronic interactions with the semiconductor support. In situ oxidation and reduction were studied with high pressure photoemission spectroscopy. The experiments revealed that the underlying wide-band-gap semiconductor has a large influence on the chemical composition and oxygen affinity of supported nanoparticles under X-ray irradiation. For as-deposited Pt cuboctahedra supported on n-type GaN, a higher fraction of oxidized surface atoms was observed compared to cuboctahedral particles supported on p-type GaN. Under an oxygen atmosphere, immediate oxidation was recorded for nanoparticles on n-type GaN, whereas little oxidation was observed for nanoparticles on p-type GaN. Together, these results indicate that changes in the Pt chemical state under X-ray irradiation depend on the type of GaN doping. The strong interaction between the nanoparticles and the support is consistent with charge transfer of X-ray photogenerated free carriers at the semiconductor-nanoparticle interface and suggests that GaN is a promising wide-band-gap support material for photocatalysis and electronic control of catalysis.

  10. Reducing ZnO nanoparticle cytotoxicity by surface modification

    NASA Astrophysics Data System (ADS)

    Luo, Mingdeng; Shen, Cenchao; Feltis, Bryce N.; Martin, Lisandra L.; Hughes, Anthony E.; Wright, Paul F. A.; Turney, Terence W.

    2014-05-01

    Nanoparticulate zinc oxide (ZnO) is one of the most widely used engineered nanomaterials and its toxicology has gained considerable recent attention. A key aspect for controlling biological interactions at the nanoscale is understanding the relevant nanoparticle surface chemistry. In this study, we have determined the disposition of ZnO nanoparticles within human immune cells by measurement of total Zn, as well as the proportions of extra- and intracellular dissolved Zn as a function of dose and surface coating. From this mass balance, the intracellular soluble Zn levels showed little difference in regard to dose above a certain minimal level or to different surface coatings. PEGylation of ZnO NPs reduced their cytotoxicity as a result of decreased cellular uptake arising from a minimal protein corona. We conclude that the key role of the surface properties of ZnO NPs in controlling cytotoxicity is to regulate cellular nanoparticle uptake rather than altering either intracellular or extracellular Zn dissolution.Nanoparticulate zinc oxide (ZnO) is one of the most widely used engineered nanomaterials and its toxicology has gained considerable recent attention. A key aspect for controlling biological interactions at the nanoscale is understanding the relevant nanoparticle surface chemistry. In this study, we have determined the disposition of ZnO nanoparticles within human immune cells by measurement of total Zn, as well as the proportions of extra- and intracellular dissolved Zn as a function of dose and surface coating. From this mass balance, the intracellular soluble Zn levels showed little difference in regard to dose above a certain minimal level or to different surface coatings. PEGylation of ZnO NPs reduced their cytotoxicity as a result of decreased cellular uptake arising from a minimal protein corona. We conclude that the key role of the surface properties of ZnO NPs in controlling cytotoxicity is to regulate cellular nanoparticle uptake rather than

  11. NOTE: Comparison of surface doses from spot scanning and passively scattered proton therapy beams

    NASA Astrophysics Data System (ADS)

    Arjomandy, Bijan; Sahoo, Narayan; Cox, James; Lee, Andrew; Gillin, Michael

    2009-07-01

    Proton therapy for the treatment of cancer is delivered using either passively scattered or scanning beams. Each technique delivers a different amount of dose to the skin, because of the specific feature of their delivery system. The amount of dose delivered to the skin can play an important role in choosing the delivery technique for a specific site. To assess the differences in skin doses, we measured the surface doses associated with these two techniques. For the purpose of this investigation, the surface doses in a phantom were measured for ten prostate treatment fields planned with passively scattered proton beams and ten patients planned with spot scanning proton beams. The measured doses were compared to evaluate the differences in the amount of skin dose delivered by using these techniques. The results indicate that, on average, the patients treated with spot scanning proton beams received lower skin doses by an amount of 11.8% ± 0.3% than did the patients treated with passively scattered proton beams. That difference could amount to 4 CGE per field for a prescribed dose of 76 CGE in 38 fractions treated with two equally weighted parallel opposed fields.

  12. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    PubMed Central

    Bhakta, Snehasis; Dixit, Chandra K; Bist, Itti; Jalil, Karim Abdel; Suib, Steven L; Rusling, James F

    2016-01-01

    Understanding of the synthesis kinetics and our ability to modulate medium conditions allowed us to generate nanoparticles via an ultra-fast process. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as precursor and 50% ethanol and sodium hydroxide catalyst. Synthesis is performed under gentle conditions at 20 °C for 20 min Long synthesis time and catalyst-associated drawbacks are most crucial in silica nanoparticle synthesis. We have addressed both these bottlenecks by replacing the conventional Stober catalyst, ammonium hydroxide, with sodium hydroxide. We have reduced the overall synthesis time from 20 to 1/3 h, ~60-fold decrease, and obtained highly monodispersed nanoparticles with 5-fold higher surface area than Stober particles. We have demonstrated that the developed NPs with ~3-fold higher silane can be used as efficient probes for biosensor applications. PMID:27606068

  13. Sodium hydroxide catalyzed monodispersed high surface area silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Bhakta, Snehasis; Dixit, Chandra K.; Bist, Itti; Abdel Jalil, Karim; Suib, Steven L.; Rusling, James F.

    2016-07-01

    Understanding of the synthesis kinetics and our ability to modulate medium conditions allowed us to generate nanoparticles via an ultra-fast process. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as precursor and 50% ethanol and sodium hydroxide catalyst. Synthesis is performed under gentle conditions at 20 °C for 20 min Long synthesis time and catalyst-associated drawbacks are most crucial in silica nanoparticle synthesis. We have addressed both these bottlenecks by replacing the conventional Stober catalyst, ammonium hydroxide, with sodium hydroxide. We have reduced the overall synthesis time from 20 to 1/3 h, ∼60-fold decrease, and obtained highly monodispersed nanoparticles with 5-fold higher surface area than Stober particles. We have demonstrated that the developed NPs with ∼3-fold higher silane can be used as efficient probes for biosensor applications.

  14. Protons are one of the limiting factors in determining sensitivity of nano surface-assisted (+)-mode LDI MS analyses.

    PubMed

    Cho, Eunji; Ahn, Miri; Kim, Young Hwan; Kim, Jongwon; Kim, Sunghwan

    2013-10-01

    A proton source employing a nanostructured gold surface for use in (+)-mode laser desorption ionization mass spectrometry (LDI-MS) was evaluated. Analysis of perdeuterated polyaromatic hydrocarbon compound dissolved in regular toluene, perdeuterated toluene, and deuterated methanol all showed that protonated ions were generated irregardless of solvent system. Therefore, it was concluded that residual water on the surface of the LDI plate was the major source of protons. The fact that residual water remaining after vacuum drying was the source of protons suggests that protons may be the limiting reagent in the LDI process and that overall ionization efficiency can be improved by incorporating an additional proton source. When extra proton sources, such as thiolate compounds and/or citric acid, were added to a nanostructured gold surface, the protonated signal abundance increased. These data show that protons are one of the limiting components in (+)-mode LDI MS analyses employing nanostructured gold surfaces. Therefore, it has been suggested that additional efforts are required to identify compounds that can act as proton donors without generating peaks that interfere with mass spectral interpretation.

  15. Protons are One of the Limiting Factors in Determining Sensitivity of Nano Surface-Assisted (+)-Mode LDI MS Analyses

    NASA Astrophysics Data System (ADS)

    Cho, Eunji; Ahn, Miri; Kim, Young Hwan; Kim, Jongwon; Kim, Sunghwan

    2013-10-01

    A proton source employing a nanostructured gold surface for use in (+)-mode laser desorption ionization mass spectrometry (LDI-MS) was evaluated. Analysis of perdeuterated polyaromatic hydrocarbon compound dissolved in regular toluene, perdeuterated toluene, and deuterated methanol all showed that protonated ions were generated irregardless of solvent system. Therefore, it was concluded that residual water on the surface of the LDI plate was the major source of protons. The fact that residual water remaining after vacuum drying was the source of protons suggests that protons may be the limiting reagent in the LDI process and that overall ionization efficiency can be improved by incorporating an additional proton source. When extra proton sources, such as thiolate compounds and/or citric acid, were added to a nanostructured gold surface, the protonated signal abundance increased. These data show that protons are one of the limiting components in (+)-mode LDI MS analyses employing nanostructured gold surfaces. Therefore, it has been suggested that additional efforts are required to identify compounds that can act as proton donors without generating peaks that interfere with mass spectral interpretation.

  16. Surface plasmon enhanced photoluminescence from copper nanoparticles: Influence of temperature

    SciTech Connect

    Yeshchenko, Oleg A. Bondarchuk, Illya S.; Losytskyy, Mykhaylo Yu.

    2014-08-07

    Anomalous temperature dependence of surface plasmon enhanced photoluminescence from copper nanoparticles embedded in a silica host matrix has been observed. The quantum yield of photoluminescence increases as the temperature increases. The key role of such an effect is the interplay between the surface plasmon resonance and the interband transitions in the copper nanoparticles occurring at change of the temperature. Namely, the increase of temperature leads to the red shift of the resonance. The shift leads to increase of the spectral overlap of the resonance with photoluminescence band of copper as well as to the decrease of plasmon damping caused by interband transitions. Such mechanisms lead to the increase of surface plasmon enhancement factor and, consequently, to increase of the quantum yield of the photoluminescence.

  17. The influence of edge sites on the development of surface charge on goethite nanoparticles: A molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Felmy, Andrew R.

    2005-03-01

    Large-scale molecular simulation of proton accumulations were carried out on (i) (110) and (021) slabs immersed in aqueous solution and (ii) a series of model goethite nanoparticles of dimension 2 to 8 nm with systematically varying acicularity and (110)/(021) surface areas. In the slab systems, the (021) surface exhibits 15% more proton charge per unit area than the (110) surface. In the particulate systems, the acicular particles having the highest (110)/(021) ratio accumulate the most charge, opposite to the trend expected from the slab simulations, indicating that, at length scales on the order of 10 nm, the slab results are not a good indicator of the overall charging behavior of the particles. The primary reason for the discrepancy between the particulate systems and slab systems is the preferential accumulation of protons at acute (110)-(110) intersections. Charge accumulates preferentially in this region because excess proton charge at an asperity is more effectively solvated than at a flat interface.

  18. The Influence of Edge Sites on the Development of Surface Charge on Goethite Nanoparticles: A Molecular Dynamics Investigation

    SciTech Connect

    Rustad, James R.; Felmy, Andrew R.

    2005-03-15

    Large-scale molecular simulation of proton accumulations were carried out on (1) (110) and (021) slabs immersed in aqueous solution and (2) a series of model goethite nanoparticles of dimension 2-8 nm with systematically varying acicularity and (110)/(021) surface areas. In the slab systems, the (021) surface exhibits 15 percent more proton charge/unit area than the (110) surface. In the particulate systems, the acicular particles, having the highest (110)/(021) ratio accumulate the most charge, opposite to the trend expected from the slab simulations, indicating that, at length scales on the order of 10 nm, the slab results are not a good indicator of the overall charging behavior of the particles. The primary reason for the discrepancy between the particulate systems and slab systems is the preferential accumulation of protons at acute (110)-(110) intersections. Charge accumulates preferentially in this region because excess proton charge at an asperity is more effectively solvated than at a flat interface.

  19. Mercury adsorption to gold nanoparticle and thin film surfaces

    NASA Astrophysics Data System (ADS)

    Morris, Todd Ashley

    Mercury adsorption to gold nanoparticle and thin film surfaces was monitored by spectroscopic techniques. Adsorption of elemental mercury to colloidal gold nanoparticles causes a color change from wine-red to orange that was quantified by UV-Vis absorption spectroscopy. The wavelength of the surface plasmon mode of 5, 12, and 31 nm gold particles blue-shifts 17, 14, and 7.5 nm, respectively, after a saturation exposure of mercury vapor. Colorimetric detection of inorganic mercury was demonstrated by employing 2.5 nm gold nanoparticles. The addition of low microgram quantities of Hg 2+ to these nanoparticles induces a color change from yellow to peach or blue. It is postulated that Hg2+ is reduced to elemental mercury by SCN- before and/or during adsorption to the nanoparticle surface. It has been demonstrated that surface plasmon resonance spectroscopy (SPRS) is sensitive to mercury adsorption to gold and silver surfaces. By monitoring the maximum change in reflectivity as a function of amount of mercury adsorbed to the surface, 50 nm Ag films were shown to be 2--3 times more sensitive than 50 nm Au films and bimetallic 15 nm Au/35 nm Ag films. In addition, a surface coverage of ˜40 ng Hg/cm2 on the gold surface results in a 0.03° decrease in the SPR angle of minimum reflectivity. SPRS was employed to follow Hg exposure to self-assembled monolayers (SAMs) on Au. The data indicate that the hydrophilic or hydrophobic character of the SAM has a significant effect on the efficiency of Hg penetration. Water adsorbed to carboxylic acid end group of the hydrophilic SAMs is believed to slow the penetration of Hg compared to methyl terminated SAMs. Finally, two protocols were followed to remove mercury from gold films: immersion in concentrated nitric acid and thermal annealing up to 200°C. The latter protocol is preferred because it removes all of the adsorbed mercury from the gold surface and does not affect the morphology of the gold surface.

  20. Hydrophobic Silsesquioxane Nanoparticles and Nanocomposite Surfaces

    DTIC Science & Technology

    2008-09-23

    structure indicates a large number of Si…F contacts may lead to ultrahydrophobicity. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION...surface tension crystalline substance known. Analysis of the x-ray crystal structure indicates a large number of Si…F contacts may lead to...unlimited 07-473Pre Printed 9/23/2008 6 Figure 3. Water drop on surface of FD8T8 with a contact angle of 154°. Solid State Structures of

  1. Probing cytotoxicity of nanoparticles and organic compounds using scanning proton microscopy, scanning electron microscopy and fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Tong, Yongpeng; Li, Changming; Liang, Feng; Chen, Jianmin; Zhang, Hong; Liu, Guoqing; Sun, Huibin; Luong, John H. T.

    2008-12-01

    Scanning proton microscopy, scanning electron microscopy (SEM) and fluorescence microscopy have been used to probe the cytotoxicity effect of benzo[a]pyrene (BaP), ethidium bromide (EB) and nanoparticles (ZnO, Al 2O 3 and TiO 2) on a T lymphoblastic leukemia Jurkat cell line. The increased calcium ion (from CaCl 2) in the culture medium stimulated the accumulation of BaP and EB inside the cell, leading to cell death. ZnO, Al 2O 3 and TiO 2 nanoparticles, however, showed a protective effect against these two organic compounds. Such inorganic nanoparticles complexed with BaP or EB which became less toxic to the cell. Fe 2O 3 nanoparticles as an insoluble particle model scavenged by macrophage were investigated in rats. They were scavenged out of the lung tissue about 48 h after infection. This result suggest that some insoluble inorganic nanoparticles of PM (particulate matters) showed protective effects on organic toxins induced acute toxic effects as they can be scavenged by macrophage cells. Whereas, some inorganic ions such as calcium ion in PM may help environmental organic toxins to penetrate cell membrane and induce higher toxic effect.

  2. Correlating Humidity-Dependent Ionically Conductive Surface Area with Transport Phenomena in Proton-Exchange Membranes

    SciTech Connect

    He, Qinggang; Kusoglu, Ahmet; Lucas, Ivan T.; Clark, Kyle; Weber, Adam Z.; Kostecki, Robert

    2011-08-01

    The objective of this effort was to correlate the local surface ionic conductance of a Nafion? 212 proton-exchange membrane with its bulk and interfacial transport properties as a function of water content. Both macroscopic and microscopic proton conductivities were investigated at different relative humidity levels, using electrochemical impedance spectroscopy and current-sensing atomic force microscopy (CSAFM). We were able to identify small ion-conducting domains that grew with humidity at the surface of the membrane. Numerical analysis of the surface ionic conductance images recorded at various relative humidity levels helped determine the fractional area of ion-conducting active sites. A simple square-root relationship between the fractional conducting area and observed interfacial mass-transport resistance was established. Furthermore, the relationship between the bulk ionic conductivity and surface ionic conductance pattern of the Nafion? membrane was examined.

  3. SU-E-T-544: Microscopic Dose Enhancement of Gold Nanoparticles in Water for Proton Therapy: A Simulation Study

    SciTech Connect

    Newpower, M; Ahmad, S; Chen, Y

    2015-06-15

    Purpose: To quantify the microscopic dose and linear energy transfer (LET) enhancement of gold nanoparticles (GNPs) in water for proton therapy. Methods: The GEANT4 toolkit (version 10) with low energy electromagnetic classes was used to create a series of simulations where three radii (r=5, 20, 100 nm) of gold nanoparticles (GNPs) were irradiated with 5 × 106 80 MeV protons. A cubic detector (10 × 10 × 10 um, divided in 25 × 25 × 25 voxels) were placed in a water phantom where the GNP rests in the center. The size of incident proton beam was set to be same as the GNPs and perpendicularly aiming to the target. Dose deposited to each voxel were recorded to calculate the overall deposited dose and the dose-averaged LET. The emitted secondary electron spectra were also collected in a spherical customized scorer (radius = 150 nm). Results: The average dose from a single GNP in a cubic water phantom was increased by 0.12 %, 1.12% and 2.3% and the mean dose-averaged LET was increased by 5.87% and 27.67% and 0.31% for GNP radius of 5 nm, 20 nm and 100 nm, respectively. Conclusion: The dose enhancement effect from the presence of a single GNP was qualified in a water phantom. A significant increase in the mean dose-averaged LET was found for 20 nm GNP.

  4. Controlled multiple functionalization of mesoporous silica nanoparticles: homogeneous implementation of pairs of functionalities communicating through energy or proton transfers.

    PubMed

    Noureddine, Achraf; Lichon, Laure; Maynadier, Marie; Garcia, Marcel; Gary-Bobo, Magali; Zink, Jeffrey I; Cattoën, Xavier; Wong Chi Man, Michel

    2015-07-14

    The synthesis of mesoporous silica nanoparticles bearing organic functionalities is strained by the careful adjustment of the reaction parameters, as the incorporation of functional and/or voluminous organosilanes during the sol-gel synthesis strongly affects the final structure of the nanoparticles. In this paper we describe the design of new clickable mesoporous silica nanoparticles as spheres or rods, synthesized by the co-condensation of TEOS with two clickable organosilanes (bearing alkyne and azide groups) and readily multi-functionalizable by CuAAC click chemistry. We show that controlled loadings of clickable functions can be homogeneously distributed within the MSN, allowing us to efficiently click-graft various pairs of functionalities while preserving the texture and morphology of the particles. The homogeneous distribution of the grafted functionalities was probed by FRET experiments between two anchored fluorophores. Moreover, a communication by proton transfer between two functions was demonstrated by constructing a light-actuated nanomachine that works through a proton transfer between a photoacid generator and a pH-sensitive supramolecular nanogate. The activation of the nanomachine enabled the successful release of rhodamine B in buffered solutions and the delivery of doxorubicin in breast cancer cells (MCF-7) upon blue irradiation.

  5. Immobilization of gold nanoparticles on cell culture surfaces for safe and enhanced gold nanoparticle-mediated laser transfection

    NASA Astrophysics Data System (ADS)

    Kalies, Stefan; Heinemann, Dag; Schomaker, Markus; Gentemann, Lara; Meyer, Heiko; Ripken, Tammo

    2014-07-01

    In comparison to standard transfection methods, gold nanoparticle-mediated laser transfection has proven to be a versatile alternative. This is based on its minor influence on cell viability and its high efficiency, especially for the delivery of small molecules like small interfering RNA. However, in order to transfer it to routine usage, a safety aspect is of major concern: The avoidance of nanoparticle uptake by the cells is desired. The immobilization of the gold nanoparticles on cell culture surfaces can address this issue. In this study, we achieved this by silanization of the appropriate surfaces and the binding of gold nanoparticles to them. Comparable perforation efficiencies to the previous approaches of gold nanoparticle-mediated laser transfection with free gold nanoparticles are demonstrated. The uptake of the immobilized particles by the cells is unlikely. Consequently, these investigations offer the possibility of bringing gold nanoparticle-mediated laser transfection closer to routine usage.

  6. Immobilization of gold nanoparticles on cell culture surfaces for safe and enhanced gold nanoparticle-mediated laser transfection.

    PubMed

    Kalies, Stefan; Heinemann, Dag; Schomaker, Markus; Gentemann, Lara; Meyer, Heiko; Ripken, Tammo

    2014-01-01

    In comparison to standard transfection methods, gold nanoparticle-mediated laser transfection has proven to be a versatile alternative. This is based on its minor influence on cell viability and its high efficiency, especially for the delivery of small molecules like small interfering RNA. However, in order to transfer it to routine usage, a safety aspect is of major concern: The avoidance of nanoparticle uptake by the cells is desired. The immobilization of the gold nanoparticles on cell culture surfaces can address this issue. In this study, we achieved this by silanization of the appropriate surfaces and the binding of gold nanoparticles to them. Comparable perforation efficiencies to the previous approaches of gold nanoparticle-mediated laser transfection with free gold nanoparticles are demonstrated. The uptake of the immobilized particles by the cells is unlikely. Consequently, these investigations offer the possibility of bringing gold nanoparticle-mediated laser transfection closer to routine usage.

  7. Composite Nafion/sulfonated zirconia membranes: effect of the filler surface properties on proton transport characteristics

    PubMed Central

    D’Epifanio, Alessandra; Navarra, Maria Assunta; Weise, F. Christoph; Mecheri, Barbara; Farrington, Jaime; Licoccia, Silvia; Greenbaum, Steve

    2009-01-01

    Due to their strong acidity and water affinity, sulfated zirconia nanoparticles were evaluated as inorganic additives in the formation of composite Nafion-based membranes. Two types of sulfated zirconia were obtained according to the preparation experimental conditions. Sulfated zirconia-doped Nafion membranes were prepared by a casting procedure. The properties of the composite membranes were compared with those of an unfilled Nafion membrane obtained by the same preparation method. The water uptake, measured at room temperature in a wide relative humidity range, was higher for the composite membranes, this confirming the hydrophilic nature of the selected additives. The membrane doped by zirconia particles having the highest sulphate group concentration showed the highest water diffusion coefficient in the whole range of temperature and relative humidity investigated due to the presence of SO42− providing extra acid sites for water diffusion. The proton diffusivity calculated from impedance spectroscopy measurements was compared with water self diffusion coefficients measured by NMR Spectroscopy. The difference between proton and water diffusivity became significant only at high humidification levels, highlighting the role of water in the intermolecular proton transfer mechanism. Finally, great improvements were found when using the composite membrane as electrolyte in a fuel cell working at very low relative humidity. PMID:20209115

  8. Surface modification of MoS2 nanoparticles with ionic liquid-ligands: towards highly dispersed nanoparticles.

    PubMed

    Osim, Wilton; Stojanovic, Anja; Akbarzadeh, Johanna; Peterlik, Herwig; Binder, Wolfgang H

    2013-10-18

    Highly dispersible MoS2 nanoparticles have been prepared via surface-modification using a novel tetraethylene glycol-based ionic liquid containing a chelating moiety attached to the cation. The choice of the respective ligand enables the generation of highly dispersible MoS2 nanoparticles with either polar, hydrophobic or "amphiphilic" surfaces, forming highly stable dispersions or microemulsions.

  9. Molecular modeling of the surface charging of hematite. I. The calculation of proton affinities and acidities on a surface

    NASA Astrophysics Data System (ADS)

    Wasserman, Evgeny; Rustad, James R.; Felmy, Andrew R.

    1999-03-01

    Calculation of the energy of a charged defect on a surface in supercell geometry is discussed. An important example of such a calculation is evaluation of surface proton affinities and acidities, as adding or removing a proton creates a charged unit cell. Systems with periodic boundary conditions in three spatial directions and a vacuum gap between slabs are demonstrated to be inadequate for unit cells having non-zero ionic charge and uniform neutralizing background. In such a system the calculated energy diverges linearly with the thickness of the vacuum gap. A system periodic in two directions and finite in the direction perpendicular to the surface (2-D PBC) with the neutralizing background distributed as the surface charge density is free from this problem. Furthermore, the correction for the interaction of the charged defect with its own translational images is needed to speed up the convergence to the infinite dilution limit. The expression for the asymptotic correction for the energy of interaction of a charged defect with its translational images in 2-D PBC geometry has been developed in this study. The asymptotic correction is evaluated as the interaction energy of a 2-D translationally periodic array of point charges located above and below the plate of non-uniform dielectric. This is a generalization of the method of M. Leslie and M.J. Gillan [J. Phys. C, 18 (1985) 973] for the calculation of the energy of a charged defect in bulk crystals. The usefulness of this correction was demonstrated on two test cases involving the calculation of proton affinity and acidity at the (012) surface of hematite. The proposed method is likely to be important in ab initio calculations of the energy effect of the surface protonation reactions, where computational limitations dictate a small size for the unit cell.

  10. Theory of collective proton motion at interfaces with densely packed protogenic surface groups.

    PubMed

    Golovnev, Anatoly; Eikerling, Michael

    2013-01-30

    We present a theoretical study of collective proton transport at a 2D array of end-grafted protogenic surface groups with sulfonic acid head groups. The graft positions of the surface groups form a regular hexagonal lattice. We consider the interfacial array at a high packing density of the surface groups and under minimal hydration with one water molecule added per head group. For these conditions, the stable interfacial conformation consists of a bicomponent lattice of hexagonally ordered sulfonate anions and interstitial hydronium cations. Hydronium ion motion occurs as a travelling solitary wave. We analyse the microscopic parameters of the solitons and study the influence of different potential profiles on the proton motion created by rotation and tilting of sidechains and sulfonate anions. Using soliton solutions of the equation of motion, we establish relations between the energy and mobility of the solitons and the microscopic structural and interaction parameters of the array.

  11. The effect of magnetically induced linear aggregates on proton transverse relaxation rates of aqueous suspensions of polymer coated magnetic nanoparticles.

    PubMed

    Saville, Steven L; Woodward, Robert C; House, Michael J; Tokarev, Alexander; Hammers, Jacob; Qi, Bin; Shaw, Jeremy; Saunders, Martin; Varsani, Rahi R; St Pierre, Tim G; Mefford, O Thompson

    2013-03-07

    It has been recently reported that for some suspensions of magnetic nanoparticles the transverse proton relaxation rate, R(2), is dependent on the time that the sample is exposed to an applied magnetic field. This time dependence has been linked to the formation of linear aggregates or chains in an applied magnetic field via numerical modeling. It is widely known that chain formation occurs in more concentrated ferrofluids systems and that this has an affect on the ferrofluid properties. In this work we examine the relationships between colloidal stability, the formation of these linear structures, and changes observed in the proton transverse relaxation rate of aqueous suspensions of magnetic particles. A series of iron oxide nanoparticles with varying stabilizing ligand brush lengths were synthesized. These systems were characterized with dynamic light scattering, transmission electron microscopy, dark-field optical microscopy, and proton transverse relaxation rate measurements. The dark field optical microscopy and R(2) measurements were made in similar magnetic fields over the same time scale so as to correlate the reduction of the transverse relaxivity with the formation of linear aggregates. Our results indicate that varying the ligand length has a direct effect on the colloidal arrangement of the system in a magnetic field, producing differences in the rate and size of chain formation, and hence systematic changes in transverse relaxation rates over time. With increasing ligand brush length, attractive inter-particle interactions are reduced, which results in slower aggregate formation and shorter linear aggregate length. These results have implications for the stabilization, characterization and potentially the toxicity of magnetic nanoparticle systems used in biomedical applications.

  12. Mars surface radiation exposure for solar maximum conditions and 1989 solar proton events

    NASA Technical Reports Server (NTRS)

    Simonsen, Lisa C.; Nealy, John E.

    1992-01-01

    The Langley heavy-ion/nucleon transport code, HZETRN, and the high-energy nucleon transport code, BRYNTRN, are used to predict the propagation of galactic cosmic rays (GCR's) and solar flare protons through the carbon dioxide atmosphere of Mars. Particle fluences and the resulting doses are estimated on the surface of Mars for GCR's during solar maximum conditions and the Aug., Sep., and Oct. 1989 solar proton events. These results extend previously calculated surface estimates for GCR's at solar minimum conditions and the Feb. 1956, Nov. 1960, and Aug. 1972 solar proton events. Surface doses are estimated with both a low-density and a high-density carbon dioxide model of the atmosphere for altitudes of 0, 4, 8, and 12 km above the surface. A solar modulation function is incorporated to estimate the GCR dose variation between solar minimum and maximum conditions over the 11-year solar cycle. By using current Mars mission scenarios, doses to the skin, eye, and blood-forming organs are predicted for short- and long-duration stay times on the Martian surface throughout the solar cycle.

  13. Gold nanoparticles surface modification using BSA and cysteine

    NASA Astrophysics Data System (ADS)

    Cardoso-Avila, P. E.; Pichardo-Molina, J. L.; Upendra Kumar, K.; Barbosa-Sabanero, G.; Barbosa-Garcia, O.

    2011-08-01

    Metal nanometer-size particles show intriguing optical properties which depend on their shape, size and local environment. For these reasons, these materials have received a lot of attention in different scientific areas, and several applications can be found, for example: fabrication of bio-sensor, electronic devices, catalysis and new drugs. However, in the case of biomedical applications, metallic nanoparticles need to satisfy several requirements: bio-compatibility, stability and functionality. To satisfy these requirements, metallic nanoparticles need to be modified in their surfaces. In this work we report the synthesis and the modification of gold nanoparticles (GNPs) surface. GNPs were fabricated following the Turkevich's method, and the bio-conjugation (surface modification) was done using cysteine and bovine serum albumin (BSA). Our results of Uv-vis spectroscopy show that BSA and cysteine permit to increase the stability of GNPs in presence of NaCl, the stability is function of BSA concentration. Also to verify the bio-conjugation we used Raman spectroscopy and gel electrophoresis.

  14. Nanoparticle-Based Surface Modifications for Microtribology Control and Superhydrophobicity

    NASA Astrophysics Data System (ADS)

    Hurst, Kendall Matthew

    2010-11-01

    The emergence of miniaturization techniques for consumer electronics has brought forth the relatively new and exciting field of microelectromechanical systems (MEMS). However, due to the inherent forces that exist between surfaces at the micro- and nanoscale, scientists and semiconductor manufacturers are still struggling to improve the lifetime and reliability of complex microdevices. Due to the extremely large surface area-to-volume ratio of typical MEMS and microstructured surfaces, dominant interfacial forces exist which can be detrimental to their operational lifetime. In particular, van der Waals, capillary, and electrostatic forces contribute to the permanent adhesion, or stiction , of microfabricated surfaces. This strong adhesion force also contributes to the friction and wear of these silicon-based systems. The scope of this work was to examine the effect of utilizing nanoparticles as the basis for roughening surfaces for the purpose of creating films with anti-adhesive and/or superhydrophobic properties. All of the studies presented in this work are focused around a gas-expanded liquid (GXL) process that promotes the deposition of colloidal gold nanoparticles (AuNPs) into conformal thin films. The GXL particle deposition process is finalized by a critical point drying step which is advantageous to the microelectromechanical systems and semiconductor (IC) industries. In fact, preliminary results illustrated that the GXL particle deposition process can easily be integrated into current MEMS microfabrication processes. Thin films of AuNPs deposited onto the surfaces of silicon-based MEMS and tribology test devices were shown to have a dramatic effect on the adhesion of microstructures. In the various investigations, the apparent work of adhesion between surfaces was reduced by 2-4 orders of magnitude. This effect is greatly attributed to the roughening of the typically smooth silicon oxide surfaces which, in turn, dramatically decreases the "real are of

  15. Proton surface charge determination in Spodosol horizons with organically bound aluminum

    NASA Astrophysics Data System (ADS)

    Skyllberg, Ulf; Borggaard, Ole K.

    1998-05-01

    Net proton surface charge densities were determined in O, E, Bh, and Bs horizons of a sandy till, Spodosol from Denmark, by means of acid-base titration combined with ion adsorption in 0.005 M Ca(NO 3) 2 and independent permanent charge determination. The release of organic anions exceeded the adsorption of NO 3-, resulting in a desorption of anions in all horizons. Data were found to obey the law of balance between surface charges and adsorbed ions only when charges pertaining to Al and organic anions released during the titration experiments were accounted for, in addition to charges pertaining the potential determining ions (PDI) H + and OH - and the index ions Ca 2+ and NO 3-. It was furthermore shown that the point of zero net proton charge (PZNPC) in soils highly depends on the concentration of organically bound Al. Approaches previously used in soils, in which adsorbed Al n+ has been ignored (i.e., considered equivalent to nH + as a PDI), resulted in a PZNPC of 4.1 in the Bs horizon. If instead organically bound Al was accounted for as a counter-ion similar to 3/2Ca 2+, a PZNPC of 2.9 was obtained for the same Bs horizon. Based on PZNPC values estimated by the latter approach, combined with a weak-acid analog, it was shown that organic proton surface charges buffered pH with a similar intensity in the O, E, Bh, and Bs horizons of this study. Because the acidity of Al adsorbed to conjugate bases of soil organic acids is substantially weaker than the acidity of the corresponding protonated form of the organic acids, the point of zero net proton charge (PZNPC) will increase if the concentration of organically adsorbed Al increases at the expense of adsorbed H. This means that PZNPC values determined for soils with unknown concentrations of organically adsorbed Al are highly operational and not very meaningful as references.

  16. Surface passivation of semiconducting oxides by self-assembled nanoparticles

    PubMed Central

    Park, Dae-Sung; Wang, Haiyuan; Vasheghani Farahani, Sepehr K.; Walker, Marc; Bhatnagar, Akash; Seghier, Djelloul; Choi, Chel-Jong; Kang, Jie-Hun; McConville, Chris F.

    2016-01-01

    Physiochemical interactions which occur at the surfaces of oxide materials can significantly impair their performance in many device applications. As a result, surface passivation of oxide materials has been attempted via several deposition methods and with a number of different inert materials. Here, we demonstrate a novel approach to passivate the surface of a versatile semiconducting oxide, zinc oxide (ZnO), evoking a self-assembly methodology. This is achieved via thermodynamic phase transformation, to passivate the surface of ZnO thin films with BeO nanoparticles. Our unique approach involves the use of BexZn1-xO (BZO) alloy as a starting material that ultimately yields the required coverage of secondary phase BeO nanoparticles, and prevents thermally-induced lattice dissociation and defect-mediated chemisorption, which are undesirable features observed at the surface of undoped ZnO. This approach to surface passivation will allow the use of semiconducting oxides in a variety of different electronic applications, while maintaining the inherent properties of the materials. PMID:26757827

  17. Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

    PubMed Central

    2008-01-01

    Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed. PMID:21749733

  18. Surface plasmon resonance optical sensor and antibacterial activities of biosynthesized silver nanoparticles.

    PubMed

    Bindhu, M R; Umadevi, M

    2014-01-01

    Silver nanoparticles were prepared using aqueous fruit extract of Ananas comosus as reducing agent. These silver nanoparticles showed surface plasmon peak at 439 nm. They were monodispersed and spherical in shape with an average particle size of 10 nm. The crystallinity of these nanoparticles was evident from clear lattice fringes in the HRTEM images and bright circular spots in the SAED pattern. The antibacterial activities of prepared nanoparticles were found to be size-dependent, the smaller nanoparticles showing more bactericidal effect. Aqueous Zn(2+) and Cu(4+) selectivity and sensitivity study of this green synthesized nanoparticle was performed by optical sensor based surface plasmon resonance (SPR) at room temperature.

  19. Surface plasmon resonance optical sensor and antibacterial activities of biosynthesized silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Bindhu, M. R.; Umadevi, M.

    2014-03-01

    Silver nanoparticles were prepared using aqueous fruit extract of Ananas comosus as reducing agent. These silver nanoparticles showed surface plasmon peak at 439 nm. They were monodispersed and spherical in shape with an average particle size of 10 nm. The crystallinity of these nanoparticles was evident from clear lattice fringes in the HRTEM images and bright circular spots in the SAED pattern. The antibacterial activities of prepared nanoparticles were found to be size-dependent, the smaller nanoparticles showing more bactericidal effect. Aqueous Zn2+ and Cu4+ selectivity and sensitivity study of this green synthesized nanoparticle was performed by optical sensor based surface plasmon resonance (SPR) at room temperature.

  20. Dynamics of Protonated Peptide Ion Collisions with Organic Surfaces: Consonance of Simulation and Experiment

    SciTech Connect

    Pratihar, Subha; Barnes, George L.; Laskin, Julia; Hase, William L.

    2016-08-18

    In this Perspective mass spectrometry experiments and chemical dynamics simulations are described which have explored the atomistic dynamics of protonated peptide ions, peptide-H+, colliding with organic surfaces. These studies have investigated surface-induced dissociation (SID) for which peptide-H+ fragments upon collision with the surface, peptide-H+ physisorption on the surface, soft landing (SL), and peptide-H+ reaction with the surface, reactive landing (RL). The simulations include QM+MM and QM/MM direct dynamics. For collisions with self-assembled monolayer (SAM) surfaces there is quite good agreement between experiment and simulation in the efficiency of energy transfer to the peptide-H+ ion’s internal degrees of freedom. Both the experiments and simulations show two mechanisms for peptide-H+ fragmentation, i.e. shattering and statistical, RRKM dynamics. Mechanisms for SL are probed in simulations of collisions of protonated dialanine with a perfluorinated SAM surface. RL has been studied experimentally for a number of peptide-H+ + surface systems, and qualitative agreement between simulation and experiment is found for two similar systems.

  1. Electron emission and energy loss in grazing collisions of protons with insulator surfaces

    SciTech Connect

    Gravielle, M. S.; Miraglia, J. E.; Aldazabal, I.; Aumayr, F.; Lederer, S.; Winter, H.

    2007-07-15

    Electron emission from LiF, KCl, and KI crystal surfaces during grazing collisions of swift protons is studied using a first-order distorted-wave formalism. Owing to the localized character of the electronic structure of these surfaces, we propose a model that allows us to describe the process as a sequence of atomic transitions from different target ions. Experimental results are presented for electron emission from LiF and KI and energy loss from KI surfaces. Calculations show reasonable agreement with these experimental data. The role played by the charge of the incident particle is also investigated.

  2. Origin of Surface Canting within Fe3O4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Krycka, K. L.; Borchers, J. A.; Booth, R. A.; Ijiri, Y.; Hasz, K.; Rhyne, J. J.; Majetich, S. A.

    2014-10-01

    The nature of near-surface spin canting within Fe3O4 nanoparticles is highly debated. Here we develop a neutron scattering asymmetry analysis which quantifies the canting angle to between 23° and 42° at 1.2 T. Simultaneously, an energy-balance model is presented which reproduces the experimentally observed evolution of shell thickness and canting angle between 10 and 300 K. The model is based on the concept of Td site reorientation and indicates that surface canting involves competition between magnetocrystalline, dipolar, exchange, and Zeeman energies.

  3. Single-electron induced surface plasmons on a topological nanoparticle

    PubMed Central

    Siroki, G.; Lee, D.K.K.; Haynes, P. D.; Giannini, V.

    2016-01-01

    It is rarely the case that a single electron affects the behaviour of several hundred thousands of atoms. Here we demonstrate a phenomenon where this happens. The key role is played by topological insulators—materials that have surface states protected by time-reversal symmetry. Such states are delocalized over the surface and are immune to its imperfections in contrast to ordinary insulators. For topological insulators, the effects of these surface states will be more strongly pronounced in the case of nanoparticles. Here we show that under the influence of light a single electron in a topologically protected surface state creates a surface charge density similar to a plasmon in a metallic nanoparticle. Such an electron can act as a screening layer, which suppresses absorption inside the particle. In addition, it can couple phonons and light, giving rise to a previously unreported topological particle polariton mode. These effects may be useful in the areas of plasmonics, cavity electrodynamics and quantum information. PMID:27491515

  4. Toward tuning the surface functionalization of small ceria nanoparticles

    SciTech Connect

    Huang, Xing; Wang, Binghui; Grulke, Eric A.; Beck, Matthew J.

    2014-02-21

    Understanding and controlling the performance of ceria nanoparticle (CNP) catalysts requires knowledge of the detailed structure and property of CNP surfaces and any attached functional groups. Here we report thermogravimetric analysis results showing that hydrothermally synthesized ∼30 nm CNPs are decorated with 12.9 hydroxyl groups per nm{sup 2} of CNP surface. Quantum mechanical calculations of the density and distribution of bound surface groups imply a scaling relationship for surface group density that balances formal charges in the functionalized CNP system. Computational results for CNPs with only hydroxyl surface groups yield a predicted density of bound hydroxyl groups for ∼30 nm CNPs that is ∼33% higher than measured densities. Quantitative agreement between predicted and measured hydroxyl surface densities is achieved when calculations consider CNPs with both –OH and –O{sub x} surface groups. For this more general treatment of CNP surface functionalizations, quantum mechanical calculations predict a range of stable surface group configurations that depend on the chemical potentials of O and H, and demonstrate the potential to tune CNP surface functionalizations by varying temperature and/or partial pressures of O{sub 2} and H{sub 2}O.

  5. Geometry and surface controlled formation of nanoparticle helical ribbons

    NASA Astrophysics Data System (ADS)

    Pham, Jonathan; Lawrence, Jimmy; Lee, Dong; Grason, Gregory; Emrick, Todd; Crosby, Alfred

    2013-03-01

    Helical structures are interesting because of their space efficiency, mechanical tunability and everyday uses in both the synthetic and natural world. In general, the mechanisms governing helix formation are limited to bilayer material systems and chiral molecular structures. However, in a special range of dimensions where surface energy dominates (i.e. high surface to volume ratio), geometry rather than specific materials can drive helical formation of thin asymmetric ribbons. In an evaporative assembly technique called flow coating, based from the commonly observed coffee ring effect, we create nanoparticle ribbons possessing non-rectangular nanoscale cross-sections. When released into a liquid medium of water, interfacial tension between the asymmetric ribbon and water balances with the elastic cost of bending to form helices with a preferred radius of curvature and a minimum pitch. We demonstrate that this is a universal mechanism that can be used with a wide range of materials, such as quantum dots, metallic nanoparticles, or polymers. Nanoparticle helical ribbons display excellent structural integrity with spring-like characteristics and can be extended high strains.

  6. Surface-mediated light transmission in metal nanoparticle chains

    NASA Astrophysics Data System (ADS)

    Compaijen, P. Jasper; Malyshev, Victor A.; Knoester, Jasper

    2013-05-01

    We study theoretically the efficiency of the transmission of optical signals through a linear chain consisting of identical and equidistantly spaced silver metal nanoparticles. Two situations are compared: the transmission efficiency through an isolated chain and through a chain in close proximity of a reflecting substrate. The Ohmic and radiative losses in each nanoparticle strongly affect the transmission efficiency of an isolated chain and suppress it to large extent. It is shown that the presence of a reflecting interface may enhance the guiding properties of the array. The reason for this is the energy exchange between the surface plasmon polaritons (SPPs) of the array and the substrate. We focus on the dependence of the transmission efficiency on the frequency and polarization of the incoming light, as well as on the influence of the array-interface spacing. Sometimes the effect of these parameters turns out to be counterintuitive, reflecting a complicated interplay of several transmission channels.

  7. Degradation mechanisms of Platinum Nanoparticle Catalysts in Proton Exchange Membrane Fuel Cells: The Role of Particle Size

    SciTech Connect

    Yu, Kang; Groom, Daniel J.; Wang, Xiaoping; Yang, Zhiwei; Gummalla, Mallika; Ball, Sarah C.; Myers, Deborah J.; Ferreira, Paulo J.

    2014-10-14

    Five membrane-electrode assemblies (MEAs) with different average sizes of platinum (Pt) nanoparticles (2.2, 3.5, 5.0, 6.7, and 11.3 nm) in the cathode were analyzed before and after potential cycling (0.6 to 1.0 V, 50 mV/s) by transmission electron microscopy. Cathodes loaded with 2.2 nm and 3.5 nm catalyst nanoparticles exhibit the following changes during electrochemical cycling: (i) substantial broadening of the size distribution relative to the initial size distribution, (ii) presence of coalesced particles within the electrode, and (iii) precipitation of sub-micron-sized particles with complex shapes within the membrane. In contrast, cathodes loaded with 5.0 nm, 6.7 nm and 11.3 nm size catalyst nanoparticles are significantly less prone to the aforementioned effects. As a result, the electrochemically-active surface area (ECA) of MEA cathodes loaded with 2.2 nm and 3.5 nm nanoparticle catalysts degrades dramatically within 1,000 cycles of operation, while the electrochemically-active surface area of MEA cathodes loaded with 5.0 nm, 6.7 nm and 11.3 nm nanoparticle catalysts appears to be stable even after 10,000 cycles. The loss in MEA performance for cathodes loaded with 2.2 nm and 3.5 nm nanoparticle catalysts appears to be due to the loss in electrochemically-active surface area concomitant with the observed morphological changes in these nanoparticle catalysts

  8. Dopamine Serves as a Stable Surface Modifier for Iron Oxide Nanoparticles

    NASA Astrophysics Data System (ADS)

    Chi, Xiaoqin; Wang, Xiaomin; Hu, Juan; Wang, Lirong; Gao, Jinhao; Zhang, Bei; Zhang, Xixiang

    2013-03-01

    Iron oxide nanoparticles are an important class of nanomaterials in a broad range of biomedical applications because of their superparamagnetism and biocompatibility. The success of biomedical applications of iron oxide nanoparticles relies on the particles' surface functionalization, which requires robust and versatile surface anchors. Here, we report on a detailed examination of the dopamine-based surface modification of iron oxide nanoparticles. We used dopamine (2-(3,4-dihydroxyphenyl)ethylamine) and L-dopa (3,4-dihydroxy-L-phenylalanine) as two surface modifiers and chose Fe2O3 hollow nanoparticles and Fe3O4 nanoparticles as two representative substrates. Optical and TEM images showed that iron oxide nanoparticles dispersed very well in water after surface modification. The analysis of the UV-Vis spectra indicated that dopamine and L-dopa are stable after being immobilized on the surface of iron oxide nanoparticles when the pH value of the environment is about 7. The magnetic properties analysis further showed that the blocking temperature of the dopamine- or L-dopa-decorated iron oxide nanoparticles hardly changed over 20 days, confirming long-term stability of these surface modified nanoparticles. Cell assay indicated that these dopamine- or L-dopa-modified iron oxide nanoparticles were biocompatible. These results confirm that dopamine serves as a stable modifier and a robust anchor to functionalize iron oxide nanoparticles in biomedical applications.

  9. Influence of surface spins on the magnetization of fine maghemite nanoparticles

    SciTech Connect

    Nadeem, K.; Krenn, H.; Szabó, D. V.

    2013-12-16

    Influence of surface spins on magnetization of maghemite nanoparticles have been studied by using SQUID measurements and also comparison done with theoretical simulations. Surface spin disorder arises in these nanoparticles due to the randomness of surface spins. A model of AC-susceptibility has been used to investigate the experimental results. The comparison between experiment and theory signifies the presence of large effective anisotropy and freezing effects on the surface of maghemite nanoparticles. The enhanced effective anisotropy constant of these nanoparticles as compared to bulk maghemite is due to presence of disordered surface spins.

  10. Quantitative evaluation of bioorthogonal chemistries for surface functionalization of nanoparticles.

    PubMed

    Feldborg, Lise N; Jølck, Rasmus I; Andresen, Thomas L

    2012-12-19

    We present here a highly efficient and chemoselective liposome functionalization method based on oxime bond formation between a hydroxylamine and an aldehyde-modified lipid component. We have conducted a systematic and quantitative comparison of this new approach with other state-of-the-art conjugation reactions in the field. Targeted liposomes that recognize overexpressed receptors or antigens on diseased cells have great potential in therapeutic and diagnostic applications. However, chemical modifications of nanoparticle surfaces by postfunctionalization approaches are less effective than in solution and often not high-yielding. In addition, the conjugation efficiency is often challenging to characterize and therefore not addressed in many reports. We present here an investigation of PEGylated liposomes functionalized with a neuroendocrine tumor targeting peptide (TATE), synthesized with a variety of functionalities that have been used for surface conjugation of nanoparticles. The reaction kinetics and overall yield were quantified by HPLC. Reactions were conducted in solution as well as by postfunctionalization of liposomes in order to study the effects of steric hindrance and possible affinity between the peptide and the liposome surface. These studies demonstrate the importance of choosing the correct chemistry in order to obtain a quantitative surface functionalization of liposomes.

  11. Surface Plasmon Mediated Chemical Solution Deposition of Gold Nanoparticles on a Nanostructured Silver Surface

    SciTech Connect

    Qiu, Jingjing; Wu, Yung-Chen; Wang, Yi-Chung; Engelhard, Mark H.; McElwee-White, Lisa; Wei, Wei

    2013-01-01

    Utilizing intrinsic surface properties to direct and control nanostructure growth on a large-scale surface is fundamentally interesting and holds great technological promise. Reported here is a novel "bottom-up" approach to fabricating sub-15 nm Au nanoparticles on a nanostructured Ag surface via a liquid-phase chemical deposition by using localized surface plasmon resonance (SPR) excitation. A molecular thermometry strategy was employed to investigate the SPR-mediated photothermal heating of the Ag film on nanosphere (AgFON) substrate and measured the surface temperature to be above 230 °C, which led to an efficient decomposition of CH3AuPPh3 to form Au nanoparticles on the Ag surface. Particle sizes were tunable between 3 to 10 nm by adjusting the deposition time. Moreover, investigation of the deposition kinetics revealed that the Au nanoparticle deposition was surface-limited by the Ag substrate. This SPR-mediated chemical solution deposition (SPMCSD) strategy should be extendable to the deposition of many other materials for various applications.

  12. Interaction of Biofunctionalized Nanoparticles with Receptors on Cell Surfaces: MC Simulations

    NASA Astrophysics Data System (ADS)

    Dormidontova, Elena; Wang, Shihu

    2015-03-01

    One of the areas of active development of modern nanomedicine is drug/gene delivery and imaging application of nanoparticles functionalized by ligands, aptamers or antibodies capable of specific interactions with cell surface receptors. Being a complex multifunctional system different structural aspects of nanoparticles affect their interactions with cell surfaces and the surface properties of cells can be different (e.g. density, distribution and mobility of receptors). Computer simulations allow a systematic investigation of the influence of multiple factors and provide a unified platform for the comparison. Using Monte Carlo simulations we investigate the influence of the nanoparticle properties (nanoparticle size, polymer tether length, polydispersity, density, ligand energy, valence and density) on nanoparticle-cell surface interactions and make predictions regarding favorable nanoparticle design for achieving multiple ligand-receptor binding. We will also discuss the implications of nanoparticle design on the selectivity of attachment to cells with high receptor density while ``ignoring'' cells with a low density of receptors.

  13. Bacterial growth on a superhydrophobic surface containing silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Heinonen, S.; Nikkanen, J.-P.; Laakso, J.; Raulio, M.; Priha, O.; Levänen, E.

    2013-12-01

    The antibacterial effect of silver can be exploited in the food and beverage industry and medicinal applications to reduce biofouling of surfaces. Very small amount of silver ions are enough to destructively affect the metabolism of bacteria. Moreover, superhydrophobic properties could reduce bacterial adhesion to the surface. In this study we fabricated superhydrophobic surfaces that contained nanosized silver particles. The superhydrophobic surfaces were manufactured onto stainless steel as combination of ceramic nanotopography and hydrophobication by fluorosilane. Silver nanoparticles were precipitated onto the surface by a chemical method. The dissolution of silver from the surface was tested in an aqueous environment under pH values of 1, 3, 5, 7, 9, 11 and 13. The pH value was adjusted with nitric acid and ammonia. It was found that dissolution rate of silver increased as the pH of the solution altered from the pH of de-ionized water to lower and higher pH values but dissolution occurred also in de-ionized water. The antimicrobial potential of this coating was investigated using bacterial strains isolated from the brewery equipment surfaces. The results showed that the number of bacteria adhering onto steel surface was significantly reduced (88%) on the superhydrophobic silver containing coating.

  14. Proton damage effects on GaAs/GaAlAs vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Le Metayer, P.; Gilard, O.; Germanicus, R.; Campillo, D.; Ledu, F.; Cazes, J.; Falo, W.; Chatry, C.

    2003-12-01

    A series of proton irradiations of GaAs/GaAlAs vertical cavity surface emitting lasers (VCSELs) has been carried out for the purpose of assessing the suitability of these devices for space applications. The irradiations were performed on biased and unbiased devices at energies of 30, 40, 50, and 60 MeV. Both current versus voltage (I-V) and optical power versus current (P-I) characteristics were measured before and after each irradiation phase. A simple circuit equivalent model for the VCSEL has been developed to analyze proton damage effects through the extraction of electrical parameters. The current threshold of VCSEL is shown to be the only important parameter modified by a high fluence (up to 1012 protons/cm2) irradiation. Changes in the threshold current show radiation generated recombination centers to be the main cause of degradation. Due to carrier injection annealing related effects, we observed that unbiased devices show the greatest relative threshold increase (between 15% and 20% at 1013 protons/cm2). The threshold current damage factor was also calculated. The analysis of the I-V characteristics shows that in the range of low fluences (1010-1012 protons/cm2) radiation induced ordering effects may compete with the usual radiation degradation that we observed at higher fluences. Consequently, the nonionizing energy loss approach, which is extensively used to predict the degradation of electronic devices under a full spectrum of energetic particles, is deemed to be not yet applicable for prediction of end-of-life performances of VCSELs.

  15. Ferroplasmons: Intense Localized Surface Plasmons in Metal-Ferromagnetic Nanoparticles

    SciTech Connect

    Sachan, Ritesh; Malasi, Abhinav; Ge, Jingxuan; Yadavali, Sagar P; Gangopadhyay, Anup; Krishna, Dr. Hare; Garcia, Hernando; Duscher, Gerd J M; Kalyanaraman, Ramki

    2014-01-01

    Interaction of photons with matter at length scales far below their wavelengths has given rise to many novel phenomena, including localized surface plasmon resonance (LSPR). However, LSPR with narrow bandwidth (BW) is observed only in a select few noble metals, and ferromagnets are not among them. Here, we report the discovery of LSPR in ferromagnetic Co and CoFe alloy (8% Fe) in contact with Ag in the form of bimetallic nanoparticles prepared by pulsed laser dewetting. These plasmons in metal-erromagnetic nanostructures, or ferroplasmons (FP) for short, are in the visible spectrum with comparable intensity and BW to those of the LSPRs from the Ag regions. This finding was enabled by electron energy-loss mapping across individual nanoparticles in a monochromated scanning transmission electron microscope. The appearance of the FP is likely due to plasmonic interaction between the contacting Ag and Co nanoparticles. Since there is no previous evidence for materials that simultaneously show ferromagnetism and such intense LSPRs, this discovery may lead to the design of improved plasmonic materials and applications. It also demonstrates that materials with interesting plasmonic properties can be synthesized using bimetallic nanostructures in contact with each other.

  16. Surface Nucleation in the Freezing of Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Mendez-Villuendas, Eduardo; Bowles, Richard K.

    2007-05-01

    We use molecular simulation to calculate the nucleation free energy barrier for the freezing of a 456 atom gold cluster over a range of temperatures. The results show that the embryo of the solid cluster grows at the vapor-surface interface for all temperatures studied and that the usual classical nucleation model, with the embryo growing in the core of the cluster, is unable to predict the shape of the free energy barrier. We use a simple partial wetting model that treats the crystal as a lens-shaped nucleus at the liquid-vapor interface and find that the line tension plays an important role in the freezing of gold nanoparticles.

  17. Production of excitons in grazing collisions of protons with LiF surfaces: An onion model

    SciTech Connect

    Miraglia, J. E.; Gravielle, M. S.

    2011-12-15

    In this work we evaluate the production of excitons of a lithium fluoride crystal induced by proton impact in the intermediate and high energy regime (from 100 keV to 1 MeV). A simple model is proposed to account for the influence of the Coulomb grid of the target by dressing crystal ions to transform them in what we call onions. The excited states of these onions can be interpreted as excitons. Within this model, total cross section and stopping power are calculated by using the first Born and the continuum distorted-wave (CDW) eikonal initial-state (EIS) approximations. We found that between 7 and 30 excitons per incident proton are produced in grazing collisions with LiF surfaces, becoming a relevant mechanism of inelastic transitions.

  18. In Situ Nanopressing: A General Approach to Robust Nanoparticles-Polymer Surface Structures

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojie; He, Junhui; Jin, Binbin

    2016-09-01

    We report a novel, facile and general approach, in situ nanopressing, to integrate nanoparticles and polymers in a thin film configuration, where both nanoparticles exposure and film robustness are indispensable for applications. By simply pressing silica nanoparticles into a polymer thin film under an external force, we successfully attained a nanoparticles-polymer thin film, where the silica nanoparticles were partly embedded in the polymer thin film. The outstanding characteristic of easy-to-fabricate nanoparticles-polymer thin films combined the properties of both materials, giving excellent antireflective and antifogging properties, as well as enhanced the robustness of composite thin film. This in situ nanopressing may not only provide an alternative to meet the challenge of constructing mechanically robust nanoparticles-polymer thin films that require nanoparticles on the film surface, but also enrich the methodology to integrate nanoparticles and polymers.

  19. In Situ Nanopressing: A General Approach to Robust Nanoparticles-Polymer Surface Structures

    PubMed Central

    Zhang, Xiaojie; He, Junhui; Jin, Binbin

    2016-01-01

    We report a novel, facile and general approach, in situ nanopressing, to integrate nanoparticles and polymers in a thin film configuration, where both nanoparticles exposure and film robustness are indispensable for applications. By simply pressing silica nanoparticles into a polymer thin film under an external force, we successfully attained a nanoparticles-polymer thin film, where the silica nanoparticles were partly embedded in the polymer thin film. The outstanding characteristic of easy-to-fabricate nanoparticles-polymer thin films combined the properties of both materials, giving excellent antireflective and antifogging properties, as well as enhanced the robustness of composite thin film. This in situ nanopressing may not only provide an alternative to meet the challenge of constructing mechanically robust nanoparticles-polymer thin films that require nanoparticles on the film surface, but also enrich the methodology to integrate nanoparticles and polymers. PMID:27642153

  20. Environmentally responsive surface-modified silica nanoparticles for enhanced oil recovery

    NASA Astrophysics Data System (ADS)

    Behzadi, Abed; Mohammadi, Aliasghar

    2016-09-01

    Environmentally responsive surface-modified nanoparticles are colloidal nanoparticles coated with, at least, two physicochemically distinct surface groups. Recent advances in the synthesis and production of nanoparticles have enabled the production of environmentally responsive surface-modified nanoparticles with both hydrophilic and hydrophobic surface groups. These nanoparticles act like colloidal surfactants. In this paper, environmentally responsive surface-modified silica nanoparticles are synthesized and used for enhancement of oil recovery. For this purpose, silica nanoparticles are coated with polyethylene glycol chains as hydrophilic agent and propyl chains as hydrophobic agent at various quantities, and their ability to modulate oil-water interface properties and oil recovery is examined. Oil-water interfacial tension and water surface tension are decreased by 50 % in the presence of silica nanoparticles coated with both agents. Measuring oil-drop contact angle on oil-wetted glass slides and carbonate rock sections, after aging in various surface-modified silica nanofluids, indicates that the wettability of various oil-wetted surfaces is modified from strongly oil-wet to water-wet. Flooding nanofluids to glass micro-models and pore-level investigations demonstrate that surface modification of silica nanoparticles, specially, with both hydrophilic and hydrophobic agents improves considerably their performance in increasing oil recovery and wettability alteration.

  1. Alumoxane/ferroxane nanoparticles for the removal of viral pathogens: the importance of surface functionality to nanoparticle activity.

    PubMed

    Maguire-Boyle, Samuel J; Liga, Michael V; Li, Qilin; Barron, Andrew R

    2012-09-21

    A bi-functional nano-composite coating has been created on a porous Nomex® fabric support as a trap for aspirated virus contaminated water. Nomex® fabric was successively dip-coated in solutions containing cysteic acid functionalized alumina (alumoxane) nanoparticles and cysteic acid functionalized iron oxide (ferroxane) nanoparticles to form a nanoparticle coated Nomex® (NPN) fabric. From SEM and EDX the nanoparticle coating of the Nomex® fibers is uniform, continuous, and conformal. The NPN was used as a filter for aspirated bacteriophage MS2 viruses using end-on filtration. All measurements were repeated to give statistical reliability. The NPN fabrics show a large decrease as compared to Nomex® alone or alumoxane coated Nomex®. An increase in the ferroxane content results in an equivalent increase in virus retention. This suggests that it is the ferroxane that has an active role in deactivating and/or binding the virus. Heating the NPN to 160 °C results in the loss of cysteic acid functional groups (without loss of the iron nanoparticle's core structure) and the resulting fabric behaves similar to that of untreated Nomex®, showing that the surface functionalization of the nanoparticles is vital for the surface collapse of aspirated water droplets and the absorption and immobilization of the MS2 viruses. Thus, for virus immobilization, it is not sufficient to have iron oxide nanoparticles per se, but the surface functionality of a nanoparticle is vitally important in ensuring efficacy.

  2. Photophysical properties of luminescent silicon nanoparticles surface-modified with organic molecules via hydrosilylation.

    PubMed

    Miyano, Mari; Kitagawa, Yuichi; Wada, Satoshi; Kawashima, Akira; Nakajima, Ayako; Nakanishi, Takayuki; Ishioka, Junya; Shibayama, Tamaki; Watanabe, Seiichi; Hasegawa, Yasuchika

    2016-01-01

    Luminescent silicon nanoparticles have attracted considerable attention for their potential uses in various applications. Many approaches have been reported to protect the surface of silicon nanoparticles and prevent their easy oxidation. Various air-stable luminescent silicon nanoparticles have been successfully prepared. However, the effect of interactions of the π-electron system with the silicon surface on the excited state properties of silicon nanoparticles is unclear. In this study, we have successfully prepared silicon nanoparticles protected with three organic compounds (styrene, 1-decene, and 1-vinyl naphthalene) and have examined their photophysical properties. The ligand π-electron systems on the silicon surface promoted the light harvesting ability for the luminescence through a charge transfer transition between the protective molecules and silicon nanoparticles and also enhanced the radiative rate of the silicon nanoparticles.

  3. Formation of silicon carbide and diamond nanoparticles in the surface layer of a silicon target during short-pulse carbon ion implantation

    NASA Astrophysics Data System (ADS)

    Remnev, G. E.; Ivanov, Yu. F.; Naiden, E. P.; Saltymakov, M. S.; Stepanov, A. V.; Shtan'ko, V. F.

    2009-04-01

    Synthesis of silicon carbide and diamond nanoparticles is studied during short-pulse implantation of carbon ions and protons into a silicon target. The experiments are carried out using a TEMP source of pulsed powerful ion beams based on a magnetically insulated diode with radial magnetic field B r . The beam parameters are as follows: the ion energy is 300 keV, the pulse duration is 80 ns, the beam consists of carbon ions and protons, and the ion current density is 30 A/cm2. Single-crystal silicon wafers serve as a target. SiC nanoparticles and nanodiamonds form in the surface layer of silicon subjected to more than 100 pulses. The average coherent domain sizes in the SiC particles and nanodiamonds are 12-16 and 8-9 nm, respectively.

  4. Synthesis of water soluble glycine capped silver nanoparticles and their surface selective interaction

    SciTech Connect

    Agasti, Nityananda; Singh, Vinay K.; Kaushik, N.K.

    2015-04-15

    Highlights: • Synthesis of water soluble silver nanoparticles at ambient reaction conditions. • Glycine as stabilizing agent for silver nanoparticles. • Surface selective interaction of glycine with silver nanoparticles. • Glycine concentration influences crystalinity and optical property of silver nanoparticles. - Abstract: Synthesis of biocompatible metal nanoparticles has been an area of significant interest because of their wide range of applications. In the present study, we have successfully synthesized water soluble silver nanoparticles assisted by small amino acid glycine. The method is primarily based on reduction of AgNO{sub 3} with NaBH{sub 4} in aqueous solution under atmospheric air in the presence of glycine. UV–vis spectroscopy, transmission electron microscopy (TEM), X–ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG) and differential thermal analysis (DTA) techniques used for characterization of resulting silver nanoparticles demonstrated that, glycine is an effective capping agent to stabilize silver nanoparticles. Surface selective interaction of glycine on (1 1 1) face of silver nanoparticles has been investigated. The optical property and crystalline behavior of silver nanoparticles were found to be sensitive to concentration of glycine. X–ray diffraction studies ascertained the phase specific interaction of glycine on silver nanoparticles. Silver nanoparticles synthesized were of diameter 60 nm. We thus demonstrated an efficient synthetic method for synthesis of water soluble silver nanoparticles capped by amino acid under mild reaction conditions with excellent reproducibility.

  5. WE-G-BRE-07: Proton Therapy Enhanced by Tumor-Targeting Gold Nanoparticles: A Pilot in Vivo Experiment at The Proton Therapy Center at MD Anderson Cancer Center

    SciTech Connect

    Wolfe, T; Grant, J; Wolfe, A; Gillin, M; Krishnan, S

    2014-06-15

    Purpose: Assess tumor-growth delay and survival in a mouse model of prostate cancer treated with tumor-targeting gold nanoparticles (AuNPs) and proton therapy. Methods: We first examined the accumulation of targeting nanoparticles within prostate tumors by imaging AuNPs with ultrasound-guided photoacoustics at 24h after the intravenous administration of goserelin-conjugated AuNPs (gAuNP) in three mice. Nanoparticles were also imaged at the cellular level with TEM in PC3 cells incubated with gAuNP for 24h. Pegylated AuNPs (pAuNP) were also imaged in vivo and in vitro for comparison. PC3 cells were then implanted subcutaneously in nude mice; 51mice with 8–10mm tumors were included. AuNPs were injected intravenously at 0.2%w/w final gold concentration 24h before irradiation. A special jig was designed to facilitate tumor irradiation perpendicular to the proton beam. Proton energy was set to 180MeV, the radiation field was 18×18cm{sup 2}, and 9cm or 13.5cm thick solid-water compensators were used to position the tumors at either the beam entrance (BE) or the SOBP. Physical doses of 5Gy were delivered to all tumors on a patient beam line at MD Anderson's Proton Therapy Center. Results: The photoacoustic experiment reveled that our nanoparticles leak from the tumor-feeding vasculature and accumulate within the tumor volume over time. Additionally, TEM images showed gAuNP are internalized in cancer cells, accumulating within the cytoplasm, whereas pAuNP are not. Tumor-growth was delayed by 11 or 32days in mice receiving gAuNP irradiated at the BE or the SOBP, relative to proton radiation alone. Survival curves (ongoing experiment) reveal that gAuNPs improved survival by 36% or 74% for tumors irradiated at the BE or SOBP. Conclusion: These important, albeit preliminary, in vivo findings reveal nanoparticles to be potent sensitizers to proton therapy. Further, conjugation of AuNPs to tumor-specific antigens that promote enhanced cellular internalization improved both

  6. Adsorption at cell surface and cellular uptake of silica nanoparticles with different surface chemical functionalizations: impact on cytotoxicity

    NASA Astrophysics Data System (ADS)

    Kurtz-Chalot, A.; Klein, J. P.; Pourchez, J.; Boudard, D.; Bin, V.; Alcantara, G. B.; Martini, M.; Cottier, M.; Forest, V.

    2014-11-01

    Silica nanoparticles are particularly interesting for medical applications because of the high inertness and chemical stability of silica material. However, at the nanoscale their innocuousness must be carefully verified before clinical use. The aim of this study was to investigate the in vitro biological toxicity of silica nanoparticles depending on their surface chemical functionalization. To that purpose, three kinds of 50 nm fluorescent silica-based nanoparticles were synthesized: (1) sterically stabilized silica nanoparticles coated with neutral polyethylene glycol molecules, (2) positively charged silica nanoparticles coated with amine groups, and (3) negatively charged silica nanoparticles coated with carboxylic acid groups. RAW 264.7 murine macrophages were incubated for 20 h with each kind of nanoparticles. Their cellular uptake and adsorption at the cell membrane were assessed by a fluorimetric assay, and cellular responses were evaluated in terms of cytotoxicity, pro-inflammatory factor production, and oxidative stress. Results showed that the highly positively charged nanoparticle were the most adsorbed at cell surface and triggered more cytotoxicity than other nanoparticle types. To conclude, this study clearly demonstrated that silica nanoparticles surface functionalization represents a key parameter in their cellular uptake and biological toxicity.

  7. The influence of size, shape, and surface coating on the stability of aqueous nanoparticle suspensions

    SciTech Connect

    Mulvihill, M.J.; Habas, S.E.; La Plante, I.J.; Wan, J.; Mokari, T.

    2010-09-03

    In response to the rapid development and emerging commercialization of nanoparticles, fundamental studies concerning the fate of nanoparticles in the environment are needed. Precise control over the nanoparticle size, shape, and surface coating of cadmium selenide particles modified with thiolate ligands has been used to analyze the effects of nanoparticle design on their stability in aqueous environments. Nanoparticle stability was quantified using the concept of critical coagulation concentration (CCC) in solutions of sodium chloride. These investigations characterized the instability of the ligand coatings, which varied directly with chain length of the capping ligands. The stability of the ligand coatings were characterized as a function of time, pH, and ionic strength. Ligand dissociation has been shown to be a primary mechanism for nanoparticle aggregation when short-chain (C2-C6) ligands are used in the ligand shell. Stable nanoparticle suspensions prepared with long chain ligands (C11) were used to characterize nanoparticle stability as a function of size and shape. A linear relationship between particle surface area and the CCC was discovered and was found to be independent of nanoparticle shape. Quantitative analysis of nanoparticle size, shape, and surface coating demonstrated the importance of ligand stability and particle surface area for the prediction of nanoparticle stability.

  8. Mucoadhesion of polystyrene nanoparticles having surface hydrophilic polymeric chains in the gastrointestinal tract.

    PubMed

    Sakuma, S; Sudo, R; Suzuki, N; Kikuchi, H; Akashi, M; Hayashi, M

    1999-01-25

    The mucoadhesion of polystyrene nanoparticles having surface hydrophilic polymeric chains in the gastrointestinal (GI) tract was investigated in rats. Radiolabeled nanoparticles were synthesized by adding hydrophobic 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine in the final process of nanoparticle preparation. The radioiodonated diazirine seemed to be incorporated in the hydrophobic polystyrene core of nanoparticles. The incorporation rate was less than 10%, irrespective of nanoparticle type. The diazirine incorporated in nanoparticles exhibited little leakage from them even though they were mixed with a solution corresponding to GI juice. The change in blood ionized calcium concentration after oral administration of salmon calcitonin (sCT) with nanoparticles showed that the in vivo enhancement of sCT absorption by radiolabeled nanoparticles was the same as that by non-labeled nanoparticles. The GI transit rates of nanoparticles having surface poly(N-isopropylacrylamide), poly(vinylamine) and poly(methacrylic acid) chains, which can improve sCT absorption, were slower than that of nanoparticles covered by poly(N-vinylacetamide), which does not enhance sCT absorption at all. These slow transit rates were probably the result of mucoadhesion of nanoparticles. The strength of mucoadhesion depended on the structure of the hydrophilic polymeric chains on the nanoparticle surface. The mucoadhesion of poly(N-isopropylacrylamide) nanoparticles, which most strongly enhanced sCT absorption, was stronger than that of ionic nanoparticles, and poly(N-vinylacetamide) nanoparticles probably did not adhere to the GI mucosa. These findings demonstrated that there is a good correlation between mucoadhesion and enhancement of sCT absorption.

  9. Nitrate Deposition to Surface Snow at Summit, Greenland, Following the 9 November 2000 Solar Proton Event

    NASA Technical Reports Server (NTRS)

    Duderstadt, Katharine A.; Dibb, Jack E.; Schwadron, Nathan A.; Spence, Harlan E.; Jackman, Charles Herbert; Randall, Cora E.; Solomon, Stanley C.; Mills, Michael J.

    2014-01-01

    This study considers whether spurious peaks in nitrate ions in snow sampled at Summit, Greenland from August 2000 to August 2002 are related to solar proton events. After identifying tropospheric sources of nitrate on the basis of correlations with sulfate, ammonium, sodium, and calcium, we use the three-dimensional global Whole Atmosphere Community Climate Model (WACCM) to examine unaccounted for nitrate spikes. Model calculations confirm that solar proton events significantly impact HOx, NOx, and O3 levels in the mesosphere and stratosphere during the weeks and months following the major 9 November 2000 solar proton event. However, SPE-enhanced NOy calculated within the atmospheric column is too small to account for the observed nitrate ion peaks in surface snow. Instead, our WACCM results suggest that nitrate spikes not readily accounted for by measurement correlations are likely of anthropogenic origin. These results, consistent with other recent studies, imply that nitrate spikes in ice cores are not suitable proxies for individual SPEs and motivate the need to identify alternative proxies.

  10. The double effects of silver nanoparticles on the PVDF membrane: Surface hydrophilicity and antifouling performance

    NASA Astrophysics Data System (ADS)

    Li, Jian-Hua; Shao, Xi-Sheng; Zhou, Qing; Li, Mi-Zi; Zhang, Qi-Qing

    2013-01-01

    In this study, silver nanoparticles were used to endow poly(vinylidene fluoride) (PVDF) membrane with excellent surface hydrophilicity and outstanding antifouling performance. Silver nanoparticles were successfully immobilized onto PVDF membrane surface under the presence of poly(acrylic acid) (PAA). The double effects of silver nanoparticles on PVDF membrane, i.e., surface hydrophilicity and anti-fouling performance, were systematically investigated. Judging from result of water static contact measurement, silver nanoparticles had provided a significant improvement in PVDF membrane surface hydrophilicity. And the possible explanation on the improvement of PVDF membrane surface hydrophilicity with silver nanoparticles was firstly proposed in this study. Membrane permeation and anti-bacterial tests were carried out to characterize the antifouling performance of PVDF membrane. Flux recovery ratio (FRR) increased about 40% after the presence of silver nanoparticles on the PVDF membrane surface, elucidating the anti-organic fouling performance of PVDF membrane was elevated by silver nanoparticles. Simultaneously, anti-bacterial test confirmed that PVDF membrane showed superior anti-biofouling activity because of silver nanoparticles. The above-mentioned results clarified that silver nanoparticles can endow PVDF membrane with both excellent surface hydrophilicity and outstanding antifouling performance in this study.

  11. Adsorption of DNA on colloidal Ag nanoparticles: effects of nanoparticle surface charge, base content and length of DNA.

    PubMed

    Abbasian, Sara; Moshaii, Ahmad; Nikkhah, Maryam; Farkhari, Nahid

    2014-04-01

    The adsorption of single and double stranded DNA on colloidal silver nanoparticles has been studied to investigate the effects of surface charge of the nanoparticles, the composition of the oligonucleotide and its length on the adsorption characteristics. The results explain that the nanoparticle surface charge is a key parameter determining the propensity of oligonucleotides to adsorb on nanoparticles. The adsorption also depends on the length and composition of oligonucleotide. The protective effects of both single and double stranded DNA against salt-induced aggregation dramatically increase as the DNA length increases. In contrast to other available reports, we observed that long oligonucleotides (single-stranded and double stranded) can well be adsorbed on the nanoparticles as the short ones leading to almost complete protection of nanoparticles against salt induced aggregation and hence are not suitable for the sensing applications. Finally, the light scattering from the Ag nanoparticles has been simulated and the results compared with the experiments. Our understanding should improve development of colorimetric assays for DNA detection based on aggregation of unmodified metallic nanoparticles.

  12. Tuning surface hydrophilicity/hydrophobicity of hydrocarbon proton exchange membranes (PEMs).

    PubMed

    He, Chenfeng; Mighri, Frej; Guiver, Michael D; Kaliaguine, Serge

    2016-03-15

    The effect of annealing on the surface hydrophilicity of various representative classes of hydrocarbon-based proton exchange membranes (PEMs) is investigated. In all cases, a more hydrophilic membrane surface develops after annealing at elevated temperatures. The annealing time also had some influence, but in different ways depending on the class of PEM. Longer annealing times resulted in more hydrophilic membrane surfaces for copolymerized sulfonated poly(ether ether ketone) (SPEEK-HQ), while the opposite behavior occurred in sulfonated poly(aryl ether ether ketone) (Ph-SPEEK), sulfonated poly(aryl ether ether ketone ketone) (Ph-m-SPEEKK) and sulfonated poly (aryl ether ether nitrile) (SPAEEN-B). Increased surface hydrophilicity upon annealing results from ionic cluster decomposition, according to the "Eisenberg-Hird-Moore model" (EHM). The increased surface hydrophilicity is supported by contact angle (CA) measurements, and the cluster decomposition is auxiliarily supported by probing the level of atomic sulfur (sulfonic acid) within different surface depths using angle-dependent XPS as well as ATR-FTIR. Membrane acidification leads to more hydrophilic surfaces by elimination of the hydrogen bonding that occurs between strongly-bound residual solvent (dimethylacetamide, DMAc) and PEM sulfonic acid groups. The study of physicochemical tuning of surface hydrophilicity/hydrophobicity of PEMs by annealing and acidification provides insights for improving membrane electrode assembly (MEA) fabrication in fuel cell (FC).

  13. The thermodynamics of proton hydration and the electrochemical surface potential of water

    SciTech Connect

    Pollard, Travis P.; Beck, Thomas L.

    2014-11-14

    The free energy change for transferring a single ion across the water liquid/vapor interface includes an electrochemical surface potential contribution. Since this potential is not directly accessible to thermodynamic measurement, several extra-thermodynamic approaches have been employed to infer its sign and magnitude, with a resulting wide spread of values. Here, we examine further the thermodynamics of proton hydration and the electrochemical surface potential of water along three directions: (1) a basic relation of interfacial electrostatics and experimental results on ion distributions near a water/organic interface are employed to infer a solvent contribution to the electrochemical surface potential, (2) a re-analysis is performed of the existing bulk and cluster ion hydration data, and (3) extensive computational modeling is conducted to examine the size dependence of hydration enthalpy differences for the NaF ion pair between the small cluster and the converged bulk limits. The computational studies include classical polarizable models and high-level quantum chemical methods. The new theoretical analysis of existing experimental data and the combined classical/quantum modeling lead to results consistent with our previously derived proton hydration quantities.

  14. Goethite surface reactivity: a macroscopic investigation unifying proton, chromate, carbonate, and lead(II) adsorption.

    PubMed

    Villalobos, Mario; Pérez-Gallegos, Ayax

    2008-10-15

    The goethite surface structure has been extensively studied, but no convincing quantitative description of its highly variable surface reactivity as inversely related to its specific surface area (SSA) has been found. The present study adds experimental evidence and provides a unified macroscopic explanation to this anomalous behavior from differences in average adsorption capacities, and not in average adsorption affinities. We investigated the chromate anion and lead(II) cation adsorption behavior onto three different goethites with SSA varying from 50 to 94 m(2)/g, and analyzed an extensive set of published anion adsorption and proton charging data for variable SSA goethites. Maximum chromate adsorption was found to occupy on average from 3.1 to 9.7 sites/nm(2), inversely related to SSA. Congruency of oxyanion and Pb(II) adsorption behavior based on fractional site occupancy using these values, and a site density analysis suggest that: (i) ion binding occurs to singly and doubly coordinated sites, (ii) proton binding occurs to singly and triply coordinated sites (ranging from 6.2 to 8 total sites/nm(2), in most cases), and (iii) a predominance of (210) and/or (010) faces explains the high reactivity of low SSA goethites. The results imply that the macroscopic goethite adsorption behavior may be predicted without a need to investigate extensive structural details of each specific goethite of interest.

  15. In situ surface characterization and oxygen reduction reaction on shape-controlled gold nanoparticles.

    PubMed

    Hernández, J; Solla-Gullón, J; Herrero, E; Feliu, J M; Aldaz, A

    2009-04-01

    Gold nanoparticles of different shapes/surface structures were synthesized and electrochemically characterized. An in-situ surface characterization of the Au nanoparticles, which was able to obtain qualitative information about the type and relative sizes of the different facets present in the surface of the Au nanoparticles, was carried out by using Pb Under Potential Deposition (UPD) in alkaline solutions as a surface sensitive tool. The results obtained show that the final atomic arrangement on the surface can be different from that expected from the bulk structure of the well-defined shape Au nanoparticles. In this way, the development of precise in-situ methods to measure the distribution of the different sites on the nanoparticle surface, as lead UPD on gold surfaces, is highlighted. Oxygen Reduction Reaction (ORR) was performed on the different Au nanoparticles. In agreement with the particular sensitivity of the oxygen reduction to the presence of Au(100) surface domains, cubic Au nanoparticles show much better electrocatalytic activity for ORR than small spherical particles and long nanorods, in agreement with the presence of a great fraction of (100) terrace sites on the surface of cubic gold nanoparticles.

  16. Tuning nanoparticle structure and surface strain for catalysis optimization.

    PubMed

    Zhang, Sen; Zhang, Xu; Jiang, Guangming; Zhu, Huiyuan; Guo, Shaojun; Su, Dong; Lu, Gang; Sun, Shouheng

    2014-05-28

    Controlling nanoparticle (NP) surface strain, i.e. compression (or stretch) of surface atoms, is an important approach to tune NP surface chemistry and to optimize NP catalysis for chemical reactions. Here we show that surface Pt strain in the core/shell FePt/Pt NPs with Pt in three atomic layers can be rationally tuned via core structural transition from cubic solid solution [denoted as face centered cubic (fcc)] structure to tetragonal intermetallic [denoted as face centered tetragonal (fct)] structure. The high activity observed from the fct-FePt/Pt NPs for oxygen reduction reaction (ORR) is due to the release of the overcompressed Pt strain by the fct-FePt as suggested by quantum mechanics-molecular mechanics (QM-MM) simulations. The Pt strain effect on ORR can be further optimized when Fe in FePt is partially replaced by Cu. As a result, the fct-FeCuPt/Pt NPs become the most efficient catalyst for ORR and are nearly 10 times more active in specific activity than the commercial Pt catalyst. This structure-induced surface strain control opens up a new path to tune and optimize NP catalysis for ORR and many other chemical reactions.

  17. Proton spectral editing in the inhomogeneous radiofrequency field of a surface coil using modified stimulated echoes.

    PubMed

    Lahrech, H; Briguet, A

    1990-11-01

    It is shown that the modified stimulated echo sequence, [theta](+/- x +/- y)-t1-[theta](+ x)-t2/2-[2 theta](+ x)-t2/2- [theta](+ x)-t1-Acq(+/- x +/- y), denoted as MSTE[2 theta]x according to the exciter phase of the 2 theta pulse, is able to perform proton spectral editing without difference spectra. On the other hand, this sequence appears to be suitable for spatial localization. Sensitivity and spatial selectivity of MSTE and conventional stimulated echo sequence (STE) are briefly compared. MSTE is applied to editing lactate in the rat brain using the locally restricted excitation of a surface coil.

  18. Degradation studies of proton-implanted vertical cavity surface emitting lasers

    NASA Astrophysics Data System (ADS)

    Cheng, Y. Michael; Herrick, Robert W.; Petroff, Pierre M.; Hibbs-Brenner, Mary K.; Morgan, Robert A.

    1995-09-01

    We analyze the degradation process of proton-implanted, top-emitting vertical cavity surface emitting lasers using cross-sectional cathodoluminescence. The spatially resolved luminescence characteristics of the active regions, and p- and n-distributed Bragg reflector (DBR) mirrors before and after degradation of the devices are presented. Degradation has been observed not only in the active regions, but also remarkably in the p-DBR mirror stacks. We show that a significant minority carrier population is present in the p mirror under normal operating conditions to drive the degradation observed in the p mirror.

  19. Surface Charge-Switching Polymeric Nanoparticles for Bacterial Cell Wall-Targeted Delivery of Antibiotics

    PubMed Central

    Radovic-Moreno, Aleksandar F.; Lu, Timothy K.; Puscasu, Vlad A.; Yoon, Chris J.; Langer, Robert; Farokhzad, Omid C.

    2013-01-01

    Bacteria have shown a remarkable ability to overcome drug therapy if there is a failure to achieve sustained bactericidal concentration or if there is a reduction in activity in situ. The latter can be caused by localized acidity, a phenomenon that can occur as a result of the combined actions of bacterial metabolism and the host immune response. Nanoparticles (NP) have shown promise in treating bacterial infections, but a significant challenge has been to develop antibacterial NPs that may be suitable for systemic administration. Herein we develop drug-encapsulated, pH-responsive, surface charge-switching poly(D, L-lactic-co-glycolic acid)-b-poly(L-histidine)-b-poly(ethylene glycol) (PLGA-PLH-PEG) nanoparticles for treating bacterial infections. These NP drug carriers are designed to shield nontarget interactions at pH 7.4 but bind avidly to bacteria in acidity, delivering drugs and mitigating in part the loss of drug activity with declining pH. The mechanism involves pH-sensitive NP surface charge-switching, which is achieved by selective protonation of the imidazole groups of PLH at low pH. NP binding studies demonstrate pH-sensitive NP binding to bacteria with a 3.5±0.2 to 5.8±0.1 fold increase in binding to bacteria at pH 6.0 compared to 7.4. Further, PLGA-PLH-PEG-encapsulated vancomycin demonstrates reduced loss of efficacy at low pH, with an increase in minimum inhibitory concentration of 1.3-fold as compared to 2.0-fold and 2.3-fold for free- and PLGA-PEG-encapsulated vancomycin, respectively. The PLGA-PLH-PEG NPs described herein are a first step towards developing systemically administered drug carriers that can target and potentially treat Gram-positive, Gram-negative, or polymicrobial infections associated with acidity. PMID:22471841

  20. Surface charge-switching polymeric nanoparticles for bacterial cell wall-targeted delivery of antibiotics.

    PubMed

    Radovic-Moreno, Aleksandar F; Lu, Timothy K; Puscasu, Vlad A; Yoon, Christopher J; Langer, Robert; Farokhzad, Omid C

    2012-05-22

    Bacteria have shown a remarkable ability to overcome drug therapy if there is a failure to achieve sustained bactericidal concentration or if there is a reduction in activity in situ. The latter can be caused by localized acidity, a phenomenon that can occur as a result of the combined actions of bacterial metabolism and the host immune response. Nanoparticles (NP) have shown promise in treating bacterial infections, but a significant challenge has been to develop antibacterial NPs that may be suitable for systemic administration. Herein we develop drug-encapsulated, pH-responsive, surface charge-switching poly(D,L-lactic-co-glycolic acid)-b-poly(L-histidine)-b-poly(ethylene glycol) (PLGA-PLH-PEG) nanoparticles for treating bacterial infections. These NP drug carriers are designed to shield nontarget interactions at pH 7.4 but bind avidly to bacteria in acidity, delivering drugs and mitigating in part the loss of drug activity with declining pH. The mechanism involves pH-sensitive NP surface charge switching, which is achieved by selective protonation of the imidazole groups of PLH at low pH. NP binding studies demonstrate pH-sensitive NP binding to bacteria with a 3.5 ± 0.2- to 5.8 ± 0.1-fold increase in binding to bacteria at pH 6.0 compared to 7.4. Further, PLGA-PLH-PEG-encapsulated vancomycin demonstrates reduced loss of efficacy at low pH, with an increase in minimum inhibitory concentration of 1.3-fold as compared to 2.0-fold and 2.3-fold for free and PLGA-PEG-encapsulated vancomycin, respectively. The PLGA-PLH-PEG NPs described herein are a first step toward developing systemically administered drug carriers that can target and potentially treat Gram-positive, Gram-negative, or polymicrobial infections associated with acidity.

  1. Laser desorption/ionization from nanostructured surfaces: nanowires, nanoparticle films and silicon microcolumn arrays

    NASA Astrophysics Data System (ADS)

    Chen, Yong; Luo, Guanghong; Diao, Jiajie; Chornoguz, Olesya; Reeves, Mark; Vertes, Akos

    2007-04-01

    Due to their optical properties and morphology, thin films formed of nanoparticles are potentially new platforms for soft laser desorption/ionization (SLDI) mass spectrometry. Thin films of gold nanoparticles (with 12±1 nm particle size) were prepared by evaporation-driven vertical colloidal deposition and used to analyze a series of directly deposited polypeptide samples. In this new SLDI method, the required laser fluence for ion detection was equal or less than what was needed for matrix-assisted laser desorption/ionization (MALDI) but the resulting spectra were free of matrix interferences. A silicon microcolumn array-based substrate (a.k.a. black silicon) was developed as a new matrix-free laser desorption ionization surface. When low-resistivity silicon wafers were processed with a 22 ps pulse length 3×ω Nd:YAG laser in air, SF6 or water environment, regularly arranged conical spikes emerged. The radii of the spike tips varied with the processing environment, ranging from approximately 500 nm in water, to ~2 µm in SF6 gas and to ~5 µm in air. Peptide mass spectra directly induced by a nitrogen laser showed the formation of protonated ions of angiotensin I and II, substance P, bradykinin fragment 1-7, synthetic peptide, pro14-arg, and insulin from the processed silicon surfaces but not from the unprocessed areas. Threshold fluences for desorption/ionization were similar to those used in MALDI. Although compared to silicon nanowires the threshold laser pulse energy for ionization is significantly (~10×) higher, the ease of production and robustness of microcolumn arrays offer complementary benefits.

  2. Surface mineralization and characterization of tobacco mosaic virus biotemplated nanoparticles

    NASA Astrophysics Data System (ADS)

    Freer, Alexander S.

    The genetically engineered tobacco mosaic virus (TMV) has been utilized as a biotemplate in the formation of nanoparticles with the intent of furthering the understanding of the biotemplated nanoparticles formed in the absence of an external reducing agent. Specifically, the work aims to provide better knowledge of the final particle characteristics and how these properties could be altered to better fit the need of functional devices. Three achievements have been accomplished including a method for controlling final particle size, characterizing the resistivity of palladium coated TMV, and the application of TMV as an additive in nanometric calcium carbonate synthesis. Until the last 5 years, formation of metal nanoparticles on the surface of TMV has always occurred with the addition of an external reducing agent. The surface functionalities of genetically engineered TMV allow for the reduction of palladium in the absence of an external reducing agent. This process has been furthered to understand how palladium concentration affects the final coating uniformity and thickness. By confirming an ideal ratio of palladium and TMV concentrations, a uniform coat of palladium is formed around the viral nanorod. Altering the number of palladium coating cycles at these concentrations allows for a controllable average diameter of the final nanorods. The average particle diameter was determined by small angle x-ray scattering (SAXS) analysis by comparing the experimental results to the model of scattering by an infinitely long cylinder. The SAXS results were confirmed through transmission electron microscopy images of individual Pd-TMV nanorods. Secondly, methodologies to determine the electrical resistivity of the genetically engineered TMV biotemplated palladium nanoparticles were created to provide valuable previously missing information. Two fairly common nanoelectronic characterization techniques were combined to create the novel approach to obtain the desired

  3. Measuring melittin uptake into hydrogel nanoparticles with near-infrared single nanoparticle surface plasmon resonance microscopy.

    PubMed

    Cho, Kyunghee; Fasoli, Jennifer B; Yoshimatsu, Keiichi; Shea, Kenneth J; Corn, Robert M

    2015-01-01

    This paper describes how changes in the refractive index of single hydrogel nanoparticles (HNPs) detected with near-infrared surface plasmon resonance microscopy (SPRM) can be used to monitor the uptake of therapeutic compounds for potential drug delivery applications. As a first example, SPRM is used to measure the specific uptake of the bioactive peptide melittin into N-isopropylacrylamide (NIPAm)-based HNPs. Point diffraction patterns in sequential real-time SPRM differential reflectivity images are counted to create digital adsorption binding curves of single 220 nm HNPs from picomolar nanoparticle solutions onto hydrophobic alkanethiol-modified gold surfaces. For each digital adsorption binding curve, the average single nanoparticle SPRM reflectivity response, ⟨Δ%RNP⟩, was measured. The value of ⟨Δ%RNP⟩ increased linearly from 1.04 ± 0.04 to 2.10 ± 0.10% when the melittin concentration in the HNP solution varied from zero to 2.5 μM. No change in the average HNP size in the presence of melittin is observed with dynamic light scattering measurements, and no increase in ⟨Δ%RNP⟩ is observed in the presence of either FLAG octapeptide or bovine serum albumin. Additional bulk fluorescence measurements of melittin uptake into HNPs are used to estimate that a 1% increase in ⟨Δ%RNP⟩ observed in SPRM corresponds to the incorporation of approximately 65000 molecules into each 220 nm HNP, corresponding to roughly 4% of its volume. The lowest detected amount of melittin loading into the 220 nm HNPs was an increase in ⟨Δ%RNP⟩ of 0.15%, corresponding to the absorption of 10000 molecules.

  4. A proton NMR relaxation study of water dynamics in bovine serum albumin nanoparticles.

    PubMed

    Belotti, Monica; Martinelli, Andrea; Gianferri, Raffaella; Brosio, Elvino

    2010-01-14

    Water dynamics and compartmentation in glutaraldehyde cross-linked bovine serum albumin nanoparticles have been investigated by an integrated nuclear magnetic resonance (NMR) protocol based on water relaxation times and self-diffusion coefficients measurements. Multi-exponentially of water relaxation curves has been accounted for according to a diffusive and chemical exchange model (see B. P. Hills, S. F. Takacs and P. S. Belton, Mol. Phys., 1989, 67(4), 903, and Mol. Phys., 1989, 67(4), 913; E. Brosio, M. Belotti and R. Gianferri, in Food Science and Technology: New Research, ed. L. V. Greco and M. N. Bruno, Nova Science Publishers, Hauppauge (NY), 2008) that made it possible to single out water molecules in the molecular spaces in the interior of albumin nanoparticles, in the meso-cavities formed by packed nanoparticles and in the meniscus on top of the nanoparticles suspension. A quantitative rationalization of T(2) values of water different components allowed morphological information to be acquired as for the size of water filled compartments, while self-diffusion coefficient measurements of water excess or fluxed packed nanoparticles suspensions are describers of transport properties of soft biomaterials. The paper reports an NMR approach that can be seen as a general and relevant method to characterize excess-water-swollen soft biomaterials.

  5. A high-throughput and selective method for the measurement of surface areas of silver nanoparticles.

    PubMed

    Agustin, Yuana Elly; Tsai, Shen-Long

    2015-04-21

    A high-throughput and selective method based on biomolecule affinity coordination was employed for measuring nanoparticle surface area in solutions. In this design, silver binding peptides (AgBPs) are immobilized on bacterial cellulose via fusion with cellulose binding domains to capture silver nanoparticles whereas green fluorescent proteins are fused with AgBPs as reporters for surface area quantification.

  6. Plasma-Synthesized Silver Nanoparticles on Electrospun Chitosan Nanofiber Surfaces for Antibacterial Applications.

    PubMed

    Annur, Dhyah; Wang, Zhi-Kai; Liao, Jiunn-Der; Kuo, Changshu

    2015-10-12

    Chitosan nanofibers have been electrospun with poly(ethylene oxide) and silver nitrate, as a coelectrospinning polymer and silver nanoparticle precursor, respectively. The average diameter of the as-spun chitosan nanofibers with up to 2 wt % silver nitrate loading was approximately 130 nm, and there was no evidence of bead formation or polymer agglomeration. Argon plasma was then applied for surface etching and synthesis of silver nanoparticles via precursor decomposition. Plasma surface bombardment induced nanoparticle formation primarily on the chitosan nanofiber surfaces, and the moderate surface plasma etching further encouraged maximum exposure of silver nanoparticles. UV-vis spectra showed the surface plasmon resonance signature of silver nanoparticles. The surface-immobilized nanoparticles were visualized by TEM and were found to have average particle diameters as small as 1.5 nm. Surface analysis by infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the interactions between the silver nanoparticles and chitosan molecules, as well as the effect of plasma treatment on the nanofiber surfaces. Finally, a bacteria inhibition study revealed that the antibacterial activity of the electrospun chitosan nanofibers correspondingly increased with the plasma-synthesized silver nanoparticles.

  7. Surface engineering of gold nanoparticles for in vitro siRNA delivery

    NASA Astrophysics Data System (ADS)

    Zhao, Enyu; Zhao, Zhixia; Wang, Jiancheng; Yang, Chunhui; Chen, Chengjun; Gao, Lingyan; Feng, Qiang; Hou, Wenjie; Gao, Mingyuan; Zhang, Qiang

    2012-07-01

    Cellular uptake, endosomal/lysosomal escape, and the effective dissociation from the carrier are a series of hurdles for specific genes to be delivered both in vitro and in vivo. To construct siRNA delivery systems, poly(allylamine hydrochloride) (PAH) and siRNA were alternately assembled on the surface of 11.8 +/- 0.9 nm Au nanoparticles (GNP), stabilized by denatured bovine serum albumin, by the ionic layer-by-layer (LbL) self-assembly method. By manipulating the outmost PAH layer, GNP-PAH vectors with different surface electric potentials were prepared. Then, the surface potential-dependent cytotoxicity of the resultant GNP-PAH particles was evaluated via sulforhodamine B (SRB) assay, while the surface potential-dependent cellular uptake efficiency was quantitatively analyzed by using the flow cytometry method based on carboxyfluorescein (FAM)-labeled siRNA. It was revealed that the GNP-PAH particles with surface potential of +25 mV exhibited the optimal cellular uptake efficiency and cytotoxicity for human breast cancer MCF-7 cells. Following these results, two more positively charged polyelectrolytes with different protonating abilities in comparison with PAH, i.e., polyethylenimine (PEI), and poly(diallyl dimethyl ammonium chloride) (PDDA), were chosen to fabricate similarly structured vectors. Confocal fluorescence microscopy studies indicated that siRNA delivered by GNP-PAH and GNP-PEI systems was better released than that delivered by the GNP-PDDA system. Further flow cytometric assays based on immunofluorescence staining of the epidermal growth factor receptor (EGFR) revealed that EGFR siRNA delivered by GNP-PAH and GNP-PEI exhibited similar down-regulation effects on EGFR expression in MCF-7 cells. The following dual fluorescence flow cytometry assays by co-staining phosphatidylserine and DNA suggested the EGFR siRNA delivered by GNP-PAH exhibited an improved silencing effect in comparison with that delivered by the commercial transfection reagent

  8. Membrane mimetic surface functionalization of nanoparticles: Methods and applications

    PubMed Central

    Weingart, Jacob; Vabbilisetty, Pratima; Sun, Xue-Long

    2013-01-01

    Nanoparticles (NPs), due to their size-dependent physical and chemical properties, have shown remarkable potential for a wide range of applications over the past decades. Particularly, the biological compatibilities and functions of NPs have been extensively studied for expanding their potential in areas of biomedical application such as bioimaging, biosensing, and drug delivery. In doing so, surface functionalization of NPs by introducing synthetic ligands and/or natural biomolecules has become a critical component in regards to the overall performance of the NP system for its intended use. Among known examples of surface functionalization, the construction of an artificial cell membrane structure, based on phospholipids, has proven effective in enhancing biocompatibility and has become a viable alternative to more traditional modifications, such as direct polymer conjugation. Furthermore, certain bioactive molecules can be immobilized onto the surface of phospholipid platforms to generate displays more reminiscent of cellular surface components. Thus, NPs with membrane-mimetic displays have found use in a range of bioimaging, biosensing, and drug delivery applications. This review herein describes recent advances in the preparations and characterization of integrated functional NPs covered by artificial cell membrane structures and their use in various biomedical applications. PMID:23688632

  9. Nanoparticles and intracellular applications of surface-enhanced Raman spectroscopy

    PubMed Central

    Taylor, Jack; Huefner, Anna; Li, Li; Wingfield, Jonathan

    2016-01-01

    Surface-enhanced Raman spectrocopy (SERS) offers ultrasensitive vibrational fingerprinting at the nanoscale. Its non-destructive nature affords an ideal tool for interrogation of the intracellular environment, detecting the localisation of biomolecules, delivery and monitoring of therapeutics and for characterisation of complex cellular processes at the molecular level. Innovations in nanotechnology have produced a wide selection of novel, purpose-built plasmonic nanostructures capable of high SERS enhancement for intracellular probing while microfluidic technologies are being utilised to reproducibly synthesise nanoparticle (NP) probes at large scale and in high throughput. Sophisticated multivariate analysis techniques unlock the wealth of previously unattainable biomolecular information contained within large and multidimensional SERS datasets. Thus, with suitable combination of experimental techniques and analytics, SERS boasts enormous potential for cell based assays and to expand our understanding of the intracellular environment. In this review we trace the pathway to utilisation of nanomaterials for intracellular SERS. Thus we review and assess nanoparticle synthesis methods, their toxicity and cell interactions before presenting significant developments in intracellular SERS methodologies and how identified challenges can be addressed. PMID:27479539

  10. Surface modification of PLGA nanoparticles via human serum albumin conjugation for controlled delivery of docetaxel

    PubMed Central

    2013-01-01

    Background Poly lactic-co-glycolic acid (PLGA) based nanoparticles are considered to be a promising drug carrier in tumor targeting but suffer from the high level of opsonization by reticuloendothelial system due to their hydrophobic structure. As a result surface modification of these nanoparticles has been widely studied as an essential step in their development. Among various surface modifications, human serum albumin (HSA) possesses advantages including small size, hydrophilic surface and accumulation in leaky vasculature of tumors through passive targeting and a probable active transport into tumor tissues. Methods PLGA nanoparticles of docetaxel were prepared by emulsification evaporation method and were surface conjugated with human serum albumin. Fourier transform infrared spectrum was used to confirm the conjugation reaction where nuclear magnetic resonance was utilized for conjugation ratio determination. In addition, transmission electron microscopy showed two different contrast media in conjugated nanoparticles. Furthermore, cytotoxicity of free docetaxel, unconjugated and conjugated PLGA nanoparticles was studied in HepG2 cells. Results Size, zeta potential and drug loading of PLGA nanoparticles were about 199 nm, −11.07 mV, and 4%, respectively where size, zeta potential and drug loading of conjugated nanoparticles were found to be 204 nm, −5.6 mV and 3.6% respectively. Conjugated nanoparticles represented a three-phasic release pattern with a 20% burst effect for docetaxel on the first day. Cytotoxicity experiment showed that the IC50 of HSA conjugated PLGA nanoparticles (5.4 μg) was significantly lower than both free docetaxel (20.2 μg) and unconjugated PLGA nanoparticles (6.2 μg). Conclusion In conclusion surface modification of PLGA nanoparticles through HSA conjugation results in more cytotoxicity against tumor cell lines compared with free docetaxel and unconjugated PLGA nanoparticles. Albumin conjugated PLGA nanoparticles may

  11. Generation of metal nanoparticles from silver and copper objects: nanoparticle dynamics on surfaces and potential sources of nanoparticles in the environment.

    PubMed

    Glover, Richard D; Miller, John M; Hutchison, James E

    2011-11-22

    The use of silver nanoparticles (AgNPs) in antimicrobial applications, including a wide range of consumer goods and apparel, has attracted attention because of the unknown health and environmental risks associated with these emerging materials. Of particular concern is whether there are new risks that are a direct consequence of their nanoscale size. Identifying those risks associated with nanoscale structure has been difficult due to the fundamental challenge of detecting and monitoring nanoparticles in products or the environment. Here, we introduce a new strategy to directly monitor nanoparticles and their transformations under a variety of environmental conditions. These studies reveal unprecedented dynamic behavior of AgNPs on surfaces. Most notably, under ambient conditions at relative humidities greater than 50%, new silver nanoparticles form in the vicinity of the parent particles. This humidity-dependent formation of new particles was broadly observed for a variety of AgNPs and substrate surface coatings. We hypothesize that nanoparticle production occurs through a process involving three stages: (i) oxidation and dissolution of silver from the surface of the particle, (ii) diffusion of silver ion across the surface in an adsorbed water layer, and (iii) formation of new, smaller particles by chemical and/or photoreduction. Guided by these findings, we investigated non-nanoscale sources of silver such as wire, jewelry, and eating utensils that are placed in contact with surfaces and found that they also formed new nanoparticles. Copper objects display similar reactivity, suggesting that this phenomenon may be more general. These findings challenge conventional thinking about nanoparticle reactivity and imply that the production of new nanoparticles is an intrinsic property of the material that is not strongly size dependent. The discovery that AgNPs and CuNPs are generated spontaneously from manmade objects implies that humans have long been in direct

  12. Molecular modeling of the surface charging of hematite. II. Optimal proton distribution and simulation of surface charge versus pH relationships

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Wasserman, Evgeny; Felmy, Andrew R.

    1999-03-01

    A parameterized classical potential model for the interaction of water and hydroxide with iron oxide was used to calculate the optimal proton arrangement and proton binding energies on the (012) surface of hematite. Energy minimization calculations with the parameterized potential model indicate that approximately 75% of adsorbed water molecules are dissociated on this surface, in agreement with recent TPD and HREELS measurements. Surface protonation/deprotonation energies were calculated from the predicted optimal arrangement of protons on the neutral (012) surface. A supercell geometry with translational symmetry in two dimensions and finite in the third dimension (2-D PBC) was assumed. The calculated surface protonation energies were then used to model the experimentally observed surface-charging curve of hematite in aqueous solution. Excellent agreement was found between the calculated and measured surface charge for ionic strengths ranging from 0.001 to 0.1 M. Our calculations favor the value of 8.5 for the pH of zero charge of hematite over the more recent result of 6.7.

  13. Adsorption study of antibiotics on silver nanoparticle surfaces by surface-enhanced Raman scattering spectroscopy

    NASA Astrophysics Data System (ADS)

    Filgueiras, Aline Luciano; Paschoal, Diego; Dos Santos, Hélio F.; Sant'Ana, Antonio C.

    2015-02-01

    In this work the adsorption of the antibiotics levofloxacin (LV), tetracycline (TC) and benzylpenicillin (BP) on the surface of silver nanoparticles (AgNP) have been investigated through both surface-enhanced Raman scattering (SERS) and UV-VIS-NIR spectroscopies. The SERS spectra were obtained using 1064 nm exciting radiation. Theoretical models for the antibiotic molecules were obtained from DFT calculations, and used in the vibrational assignment. The adsorption geometries were proposed based on the changes in the spectral patterns. The LV compound adsorbs through carboxylate group, TC compound interacts with silver atoms through carbonyl from intermediate ring, and BP compound adsorbs by carbonyl moieties from carboxylate and acyclic amide.

  14. Solar-Wind Protons and Heavy Ions Sputtering of Lunar Surface Materials

    SciTech Connect

    Barghouty, N.; Meyer, Fred W; Harris, Peter R

    2011-01-01

    Lunar surface materials are exposed to {approx}1 keV/amu solar-wind protons and heavy ions on almost continuous basis. As the lunar surface consists of mostly oxides, these materials suffer, in principle, both kinetic and potential sputtering due to the actions of the solar-wind ions. Sputtering is an important mechanism affecting the composition of both the lunar surface and its tenuous exosphere. While the contribution of kinetic sputtering to the changes in the composition of the surface layer of these oxides is well understood and modeled, the role and implications of potential sputtering remain unclear. As new potential-sputtering data from multi-charged ions impacting lunar regolith simulants are becoming available from Oak Ridge National Laboratory's MIRF, we examine the role and possible implications of potential sputtering of Lunar KREEP soil. Using a non-equilibrium model we demonstrate that solar-wind heavy ions induced sputtering is critical in establishing the timescale of the overall solar-wind sputtering process of the lunar surface. We also show that potential sputtering leads to a more pronounced and significant differentiation between depleted and enriched surface elements. We briefly discuss the impacts of enhanced sputtering on the composition of the regolith and the exosphere, as well as of solar-wind sputtering as a source of hydrogen and water on the moon.

  15. Surface chemistry studies of copper and nickel nanoparticles deposited on a titanium dioxide(110) surface

    NASA Astrophysics Data System (ADS)

    Zhou, Jing

    Metal nanoparticles on oxides are important in heterogeneous catalysis due to their unique properties related to size and structure. In this study, supported Cu and Ni nanoparticles on a rutile TiO2(110) surface have been studied as model systems for 'real world' heterogeneous catalysts to understand the relationship between the size and the catalytic properties of the metal particles. All the experiments were carried out under ultrahigh vacuum conditions using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), low energy electron spectroscopy (LEED) and temperature programmed desorption (TPD) techniques. Cu and Ni grow three-dimensional particles on the TiO2(110) surface at temperatures between 295 K and 850 K. The growth of Cu and Ni is similar except that the sintering of Ni particles occurs at higher temperatures. In order to investigate the particle size effect on the catalytic reactivity of the metal particles, different sizes of Cu and Ni particles with uniform size distributions were prepared on titania by varying the metal diffusion rate (D) to deposition flux (F) ratios. The surface chemistry of these supported Cu and Ni nanoparticles was investigated with dimethyl methylphosphonate (DMMP), a simulant for chemical warfare agents and pesticides. TPD studies indicate that DMMP decomposition may be via the methoxy intermediate. The adsorbed DMMP decomposes to CH4, H2CO and H2 on the Cu nanoparticles and films, and to CH4, CO and H2 on the Ni nanoparticles and films between 295 K and 850 K. The decomposition of DMMP on Cu and Ni surfaces is not sensitive to the particle size. However, heating the Ni particles or film before DMMP adsorption causes a decrease in Ni reactivity due to the loss of active sites. The titania support plays an important role in DMMP reaction on Cu surfaces. Finally, in order to relate ultrahigh vacuum studies with real catalytic conditions usually associated with much higher pressures, the role of oxygen on

  16. Energy loss of MeV protons specularly reflected from metal surfaces

    SciTech Connect

    Juaristi, J.I.

    1996-05-01

    A parameter-free model is presented to study the energy loss of fast protons specularly reflected from metal surfaces. The contributions to the energy loss from excitation of valence-band electrons and ionization of localized target-atom electronic states are calculated separately. The former is calculated from the induced surface wake potential using linear response theory and the specular-reflection model, while the latter is calculated in the first Born approximation. The results obtained are in good agreement with available experimental data. However, the experimental qualitative trend of the energy loss as a function of the angle of incidence is obtained when the valence-band electron model is replaced by localized target atom electron states, though with a worse quantitative agreement. {copyright} {ital 1996 The American Physical Society.}

  17. Toxicity of nanoparticle surface coating agents: Structure-cytotoxicity relationship.

    PubMed

    Zhang, Ying; Li, Xiaoping; Yu, Hongtao

    2016-07-02

    Surface coating agents for metal nanoparticles, cationic alkyl ammonium bromides, and anionic alkyl sulfates were tested against human skin keratinocytes (HaCaT) and blood T lymphocytes (TIB-152). The surfactants of short chain (C8) are not cytotoxic, but as chain length increases, their cytotoxicity increases and levels off at C12 for cationic surfactants against both cell lines and for anionic surfactants against the TIB-152, but C14 for anionic surfactants against HaCaT. The cationic surfactants are more toxic than the anionic surfactants for HaCaT; while with similar cytotoxicity for TIB-152 cells. di- and tetra-Alkyl ammonium salts are more cytotoxic than the mono-substituted.

  18. Self-organization of gold nanoparticles on silanated surfaces

    PubMed Central

    Kyaw, Htet H; Sellai, Azzouz; Dutta, Joydeep

    2015-01-01

    Summary The self-organization of monolayer gold nanoparticles (AuNPs) on 3-aminopropyltriethoxysilane (APTES)-functionalized glass substrate is reported. The orientation of APTES molecules on glass substrates plays an important role in the interaction between AuNPs and APTES molecules on the glass substrates. Different orientations of APTES affect the self-organization of AuNps on APTES-functionalized glass substrates. The as grown monolayers and films annealed in ultrahigh vacuum and air (600 °C) were studied by water contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, UV–visible spectroscopy and ultraviolet photoelectron spectroscopy. Results of this study are fundamentally important and also can be applied for designing and modelling of surface plasmon resonance based sensor applications. PMID:26734526

  19. Upconversion Nanoparticles: Synthesis, Surface Modification, and Biological Applications

    PubMed Central

    Wang, Meng; Abbineni, Gopal; Clevenger, April; Mao, Chuanbin; Xu, Shukun

    2011-01-01

    New generation fluorophores, also termed upconversion nanoparticles (UCNPs), have the ability to convert near infrared radiations with lower energy into visible radiations with higher energy via a non-linear optical process. Recently, these UCNPs have evolved as alternative fluorescent labels to traditional fluorophores, showing great potential for imaging and biodetection assays in both in vitro and in vivo applications. UCNPs exhibit unique luminescent properties, including high penetration depth into tissues, low background signals, large Stokes shifts, sharp emission bands, and high resistance to photo-bleaching, making UCNPs an attractive alternative source for overcoming current limitations in traditional fluorescent probes. In this review, we discuss the recent progress in the synthesis and surface modification of rare earth doped UCNPs with a specific focus on their biological applications. PMID:21419877

  20. Analytical performance of molecular beacons on surface immobilized gold nanoparticles of varying size and density.

    PubMed

    Uddayasankar, Uvaraj; Krull, Ulrich J

    2013-11-25

    The high quenching efficiency of metal nanoparticles has facilitated its use as quenchers in molecular beacons. To optimize this system, a good understanding of the many factors that influence molecular beacon performance is required. In this study, molecular beacon performance was evaluated as a function of gold nanoparticle size and its immobilization characteristics. Gold nanoparticles of 4 nm, 15 nm and 87 nm diameter, were immobilized onto glass slides. Each size regime offered distinctive optical properties for fluorescence quenching of molecular dyes that were conjugated to oligonucleotides that were immobilized to the gold nanoparticles. Rigid double stranded DNA was used as a model to place fluorophores at different distances from the gold nanoparticles. The effect of particle size and also the immobilization density of nanoparticles was evaluated. The 4 nm and 87 nm gold nanoparticles offered the highest sensitivity in terms of the change in fluorescence intensity as a function of distance (3-fold improvement for Cy5). The optical properties of the molecular fluorophore was of significance, with Cy5 offering higher contrast ratios than Cy3 due to the red-shifted emission spectrum relative to the plasmon peak. A high density of gold nanoparticles reduced contrast ratios, indicating preference for a monolayer of immobilized nanoparticles when considering analytical performance. Molecular beacon probes were then used in place of the double stranded oligonucleotides. There was a strong dependence of molecular beacon performance on the length of a linker used for attachment to the nanoparticle surface. The optimal optical performance was obtained with 4 nm gold nanoparticles that were immobilized as monolayers of low density (5.7×10(11)particles cm(-2)) on glass surfaces. These nanoparticle surfaces offered a 2-fold improvement in analytical performance of the molecular beacons when compared to other nanoparticle sizes investigated. The principles developed

  1. Gold nanoparticle based surface enhanced fluorescence for detection of organophosphorus agents

    NASA Astrophysics Data System (ADS)

    Dasary, Samuel S. R.; Rai, Uma S.; Yu, Hongtao; Anjaneyulu, Yerramilli; Dubey, Madan; Ray, Paresh Chandra

    2008-07-01

    Organophosphorus agents (OPA) represent a serious concern to public safety as nerve agents and pesticides. Here we report the development of gold nanoparticle based surface enhanced fluorescence (NSEF) spectroscopy for rapid and sensitive screening of organophosphorus agents. Fluorescent from Eu 3+ ions that are bound within the electromagnetic field of gold nanoparticles exhibit a strong enhancement. In the presence of OPA, Eu 3+ ions are released from the gold nanoparticle surface and thus a very distinct fluorescence signal change was observed. We discussed the mechanism of fluorescence enhancement and the role of OPA for fluorescence intensity change in the presence of gold nanoparticles.

  2. Anchoring gold nanoparticles onto a mica surface by oxygen plasma ashing for sequential nanocomponent assembly

    NASA Astrophysics Data System (ADS)

    Takagi, Akihiko; Ojima, Kaoru; Mikamo, Eriko; Matsumoto, Takuya; Kawai, Tomoji

    2007-01-01

    Water-soluble gold nanoparticles were immobilized in both polar (water) and nonpolar (chloroform) liquids on hydrophilic mica surface by oxygen plasma ashing. It is then demonstrated that a DNA with a thiol at an extremity is attached to the immobilized nanoparticles due to the gold-thiol coupling and stretched in the flow direction of the following water rinse. This technique allows a sequential integration of nanoparticles and molecules for various solutions, since the nanoparticles remain on a solid surface rather than dissolve into the solution.

  3. Surface-Enhanced Raman Scattering Nanoparticles as Optical Labels for Imaging Cell Surface Proteins

    NASA Astrophysics Data System (ADS)

    MacLaughlin, Christina M.

    Assaying the expression of cell surface proteins has widespread application for characterizing cell type, developmental stage, and monitoring disease transformation. Immunophenotyping is conducted by treating cells with labelled targeting moieties that have high affinity for relevant surface protein(s). The sensitivity and specificity of immunophenotyping is defined by the choice of contrast agent and therefore, the number of resolvable signals that can be used to simultaneously label cells. Narrow band width surface-enhanced Raman scattering (SERS) nanoparticles are proposed as optical labels for multiplexed immunophenotying. Two types of surface coatings were investigated to passivate the gold nanoparticles, incorporate SERS functionality, and to facilitate attachment of targeting antibodies. Thiolated poly(ethylene glycol) forms dative bonds with the gold surface and is compatible with multiple physisorbed Raman-active reporter molecules. Ternary lipid bilayers are used to encapsulate the gold nanoparticles particles, and incorporate three different classes of Raman reporters. TEM, UV-Visible absorbance spectroscopy, DLS, and electrophoretic light scattering were used characterize the particle coating. Colourimetric protein assay, and secondary antibody labelling were used to quantify the antibody conjugation. Three different in vitromodels were used to investigate the binding efficacy and specificity of SERS labels for their biomarker targets. Primary human CLL cells, LY10 B lymphoma, and A549 adenocarcinoma lines were targeted. Dark field imaging was used to visualize the colocalization of SERS labels with cells, and evidence of receptor clustering was obtained based on colour shifts of the particles' Rayleigh scattering. Widefield, and spatially-resolved Raman spectra were used to detect labels singly, and in combination from labelled cells. Fluorescence flow cytometry was used to test the particles' binding specificity, and SERS from labelled cells was also

  4. Solvothermal synthesis of ceria nanoparticles with large surface areas

    SciTech Connect

    Hosokawa, S.; Shimamura, K.; Inoue, M.

    2011-11-15

    Highlights: {yields} Thermal decomposition of Ce(C{sub 7}H{sub 15}COO){sub 3}.xH{sub 2}O synthesized by solvothermal method. {yields} CeO{sub 2} having an extremely large surface area of 180 m{sup 2}/g. {yields} High catalytic activity of Ru catalyst supported on the CeO{sub 2} having high surface area. -- Abstract: Ceria nanoparticles were obtained by the calcination of precursors synthesised via the solvothermal reaction of cerium acetate. The CeO{sub 2} samples obtained by the thermal decomposition of Ce(C{sub 7}H{sub 15}COO){sub 3}.xH{sub 2}O synthesised by solvothermal reaction in 1,4-butanediol in the presence of octanoic acid had an extremely large surface area of 180 m{sup 2}/g. The Ru catalyst supported on this CeO{sub 2} sample showed a high catalytic activity for benzyl alcohol oxidation.

  5. Surface nature of nanoparticle zinc-titanium oxide aerogel catalysts

    NASA Astrophysics Data System (ADS)

    Wang, Chien-Tsung; Lin, Jen-Chieh

    2008-05-01

    Nanoparticle zinc-titanium oxide materials were prepared by the aerogel approach. Their structure, surface state and reactivity were investigated. Zinc titanate powders formed at higher zinc loadings possessed a higher surface area and smaller particle size. X-ray photoelectron spectroscopy (XPS) revealed a stronger electronic interaction between Zn and Ti atoms in the mixed oxide structure and showed the formation of oxygen vacancy due to zinc doping into titania or zinc titanate matrices. The 8-45 nm aerogel particles were evaluated as catalysts for methanol oxidation in an ambient flow reactor. Carbon dioxide was favorably produced on the oxides with anion defects. Titanium based oxides exhibited a high selectivity to dimethyl ether, so that a strong Lewis acidic character suggested for the catalysts was associated primarily with the Ti 4+ center. Both methanol conversion and dimethyl ether formation rates increased with increasing the zinc content added to the oxide support. Results demonstrate that cubic zinc titanate phases produce new Lewis acid sites having also a higher reactivity and that the nature of the catalytic surface transforms from Lewis acidic to basic characters due to the presence of reactive oxygen vacancies.

  6. Surface functionalized mesoporous silica nanoparticles for intracellular drug delivery

    NASA Astrophysics Data System (ADS)

    Vivero-Escoto, Juan Luis

    Mesoporous silica nanoparticles (MSNs) are a highly promising platform for intracellular controlled release of drugs and biomolecules. Despite that the application of MSNs in the field of intracellular drug delivery is still at its infancy very exciting breakthroughs have been achieved in the last years. A general review of the most recent progress in this area of research is presented, including a description of the latest findings on the pathways of entry into live mammalian cells together with the intracellular trafficking, a summary on the contribution of MSNs to the development of site-specific drug delivery systems, a report on the biocompatibility of this material in vitro andin vivo, and a discussion on the most recent breakthroughs in the synthesis and application of stimuli-responsive mesoporous silica-based delivery vehicles. A gold nanoparticles (AuNPs)-capped MSNs-based intracellular photoinduced drug delivery system (PR-AuNPs-MSNs) for the controlled release of anticancer drug inside of human fibroblast and liver cells was synthesized and characterized. We found that the mesoporous channels of MSNs could be efficiently capped by the photoresponsive AuNPs without leaking the toxic drug, paclitaxel, inside of human cells. Furthermore, we demonstrated that the cargo-release property of this PR-AuNPs-MSNs system could be easily photo-controlled under mild and biocompatible conditions in vitro. In collaboration with Renato Mortera (a visiting student from Italy), a MSNs based intracellular delivery system for controlled release of cell membrane impermeable cysteine was developed. A large amount of cysteine molecules were covalently attached to the silica surface of MSNs through cleavable disulfide linkers. These cysteine-containing nanoparticles were efficiently endocytosed by human cervical cancer cells HeLa. These materials exhibit 450 times higher cell growth inhibition capability than that of the conventional N-acetylcysteine prodrug. The ability to

  7. SU-E-J-139: One Institution’s Experience with Surface Imaging in Proton Therapy

    SciTech Connect

    Zhao, L; Singh, H; Zheng, Y

    2015-06-15

    Purpose: X-ray system is commonly used for IGRT in proton therapy, however image acquisition not only increases treatment time but also adds imaging dose. We studied a 3D surface camera system (AlignRT) performance for proton therapy. Methods: System accuracy was evaluated with rigid phantom under two different camera location configurations. For initial clinical applications, post mastectomy chest wall and partial breast treatments were studied. X-ray alignment was used as our ground truth. Our studies included: 1) comparison of daily patient setup shifts between X-ray alignment and SI calculation; 2) interfractional breast surface position variation when aligning to bony landmark on X-ray; 3) absolute positioning using planning CT DICOM data; 4) shifts for multi-isocenter treatment plan; 5) couch isocentric rotation accuracy. Results: Camera locations affected the system performance. After camera relocation, the accuracy of the system for the rigid phantom was within 1 mm (fixed couch), and 1.5 mm (isocentric rotation). For intrafractional patient positioning, X-ray and AlignRT shifts were highly correlated (r=0.99), with the largest difference (mean ± SD) in the longitudinal direction (2.14 ± 1.02 mm). For interfractional breast surface variation and absolute positioning, there were still larger disagreements between the two modalities due to different focus on anatomical landmarks, and 95% of the data lie within 5mm with some outliers at 7 mm–9 mm. For multi-isocenter shifts, the difference was 1 ± 0.56 mm over an 11 cm shift in longitudinal direction. For couch rotation study, the differences was 1.36 ± 1.0 mm in vertical direction, 3.04 ± 2.11 mm in longitudinal direction, and 2.10 ± 1.66 mm in lateral direction, with all rotation differences < 1.5 degree. Conclusion: Surface imaging is promising for intrafractional treatment application in proton therapy to reduce X-ray frequency. However the interfractional discrepancy between the X-ray and SI

  8. Bacteria-mimicking nanoparticle surface functionalization with targeting motifs

    NASA Astrophysics Data System (ADS)

    Lai, Mei-Hsiu; Clay, Nicholas E.; Kim, Dong Hyun; Kong, Hyunjoon

    2015-04-01

    In recent years, surface modification of nanocarriers with targeting motifs has been explored to modulate delivery of various diagnostic, sensing and therapeutic molecular cargo to desired sites of interest in in vitro bioengineering platforms and in vivo pathologic tissue. However, most surface functionalization approaches are often plagued by complex chemical modifications and effortful purifications. To resolve such challenges, this study demonstrates a unique method to immobilize antibodies that can act as targeting motifs on the surfaces of nanocarriers, inspired by a process that bacteria use for immobilization of the host's antibodies. We hypothesized that alkylated Staphylococcus aureus protein A (SpA) would self-assemble with micelles and subsequently induce stable coupling of antibodies to the micelles. We examined this hypothesis by using poly(2-hydroxyethyl-co-octadecyl aspartamide) (PHEA-g-C18) as a model polymer to form micelles. The self-assembly between the micelles and alkylated SpA became more thermodynamically favorable by increasing the degree of substitution of octadecyl chains to PHEA-g-C18, due to a positive entropy change. Lastly, the mixing of SpA-PA-coupled micelles with antibodies resulted in the coating of micelles with antibodies, as confirmed with a fluorescence resonance energy transfer (FRET) assay. The micelles coated with antibodies to VCAM-1 or integrin αv displayed a higher binding affinity to substrates coated with VCAM-1 and integrin αvβ3, respectively, than other controls, as evaluated with surface plasmon resonance (SPR) spectroscopy and a circulation-simulating flow chamber. We envisage that this bacteria-inspired protein immobilization approach will be useful to improve the quality of targeted delivery of nanoparticles, and can be extended to modify the surface of a wide array of nanocarriers.In recent years, surface modification of nanocarriers with targeting motifs has been explored to modulate delivery of various

  9. Communication: Reactions and adsorption at the surface of silver nanoparticles probed by second harmonic generation.

    PubMed

    Gan, Wei; Gonella, Grazia; Zhang, Min; Dai, Hai-Lung

    2011-01-28

    Even though nanoparticles have dimensions much smaller than the optical wavelength and shapes commonly with inversion symmetry, we show, for the first time, direct experimental evidence that second harmonic generation (SHG) can be detected from the surface layer of metallic nanoparticles, in this case 40 nm radius Ag particles. The SH intensity detected is shown to substantially decrease upon chemical bonding of thiol molecules to the Ag particle surface. The surface generated SH intensity can be used for probing properties and processes at the nanoparticle surface.

  10. Fabrication of condensate microdrop self-propelling porous films of cerium oxide nanoparticles on copper surfaces.

    PubMed

    Luo, Yuting; Li, Juan; Zhu, Jie; Zhao, Ye; Gao, Xuefeng

    2015-04-13

    Condensate microdrop self-propelling (CMDSP) surfaces have attracted intensive interest. However, it is still challenging to form metal-based CMDSP surfaces. We design and fabricate a type of copper-based CMDSP porous nanoparticle film. An electrodeposition method based on control over the preferential crystal growth of isotropic nanoparticles and synergistic utilization of tiny hydrogen bubbles as pore-making templates is adopted for the in situ growth of cerium oxide porous nanoparticle films on copper surfaces. After characterizing their microscopic morphology, crystal structure and surface chemistry, we explore their CMDSP properties. The nanostructure can realize the efficient ejection of condensate microdrops with sizes below 50 μm.

  11. Gold nanoparticle biodistribution: Cell, blood, and tissue interactions as a function of nanoparticle surface properties

    NASA Astrophysics Data System (ADS)

    Shah, Neha B.

    Intravenously injected gold nanoparticles (GNPs) hold a great promise for clinical diagnostic and therapeutic applications. A critical issue in their implementation is incomplete mechanistic understanding of their in vivo biodistribution. Two major limitations in optimizing the biodistribution of NPs are: (1) achieving the highest accumulation at the disease site, and (2) avoiding accumulation in healthy organs including liver and spleen. To overcome these limitations, the interactions of GNPs with biological system must be better understood. The research described in this dissertation sought to advance the field of GNP in vivo biodistribution by elucidating the effects of GNP surface properties such as surface charge, ligand, and polyethylene glycol (PEG) coverage. It was shown that the interactions of GNPs with cells and tissues were a function of their surface properties. A Confocal Raman Microscopy based technique was developed to study GNPs interactions with cells in vitro in fast, label-free, and non-invasive way. It was further shown that GNP surface properties strongly influence their blood circulation time in vivo. It was demonstrated that GNPs interact with circulating blood cells including platelets and monocytes, which may play a role in their clearance from blood stream. Most of the injected dose was shown to accumulate in liver and spleen; however, both organs displayed a different mechanism of uptake and distribution of GNPs. Long-term biodistribution studies further suggested that GNPs were still found in liver and spleen after 4 months, but GNPs showed clearance from liver overtime.

  12. Role of nanoparticle size, shape and surface chemistry in oral drug delivery.

    PubMed

    Banerjee, Amrita; Qi, Jianping; Gogoi, Rohan; Wong, Jessica; Mitragotri, Samir

    2016-09-28

    Nanoparticles find intriguing applications in oral drug delivery since they present a large surface area for interactions with the gastrointestinal tract and can be modified in various ways to address the barriers associated with oral delivery. The size, shape and surface chemistry of nanoparticles can greatly impact cellular uptake and efficacy of the treatment. However, the interplay between particle size, shape and surface chemistry has not been well investigated especially for oral drug delivery. To this end, we prepared sphere-, rod- and disc-shaped nanoparticles and conjugated them with targeting ligands to study the influence of size, shape and surface chemistry on their uptake and transport across intestinal cells. A triple co-culture model of intestinal cells was utilized to more closely mimic the intestinal epithelium. Results demonstrated higher cellular uptake of rod-shaped nanoparticles in the co-culture compared to spheres regardless of the presence of active targeting moieties. Transport of nanorods across the intestinal co-culture was also significantly higher than spheres. The findings indicate that nanoparticle-mediated oral drug delivery can be potentially improved with departure from spherical shape which has been traditionally utilized for the design of nanoparticles. We believe that understanding the role of nanoparticle geometry in intestinal uptake and transport will bring forth a paradigm shift in nanoparticle engineering for oral delivery and non-spherical nanoparticles should be further investigated and considered for oral delivery of therapeutic drugs and diagnostic materials.

  13. Modification of the surface of superparamagnetic iron oxide nanoparticles to enable their safe application in humans

    PubMed Central

    Strehl, Cindy; Maurizi, Lionel; Gaber, Timo; Hoff, Paula; Broschard, Thomas; Poole, A Robin; Hofmann, Heinrich; Buttgereit, Frank

    2016-01-01

    Combined individually tailored methods for diagnosis and therapy (theragnostics) could be beneficial in destructive diseases, such as rheumatoid arthritis. Nanoparticles are promising candidates for theragnostics due to their excellent biocompatibility. Nanoparticle modifications, such as improved surface coating, are in development to meet various requirements, although safety concerns mean that modified nanoparticles require further review before their use in medical applications is permitted. We have previously demonstrated that iron oxide nanoparticles with amino-polyvinyl alcohol (a-PVA) adsorbed on their surfaces have the unwanted effect of increasing human immune cell cytokine secretion. We hypothesized that this immune response was caused by free-floating PVA. The aim of the present study was to prevent unwanted immune reactions by further surface modification of the a-PVA nanoparticles. After cross-linking of PVA to nanoparticles to produce PVA-grafted nanoparticles, and reduction of their zeta potential, the effects on cell viability and cytokine secretion were analyzed. PVA-grafted nanoparticles still stimulated elevated cytokine secretion from human immune cells; however, this was inhibited after reduction of the zeta potential. In conclusion, covalent cross-linking of PVA to nanoparticles and adjustment of the surface charge rendered them nontoxic to immune cells, nonimmunogenic, and potentially suitable for use as theragnostic agents. PMID:27877036

  14. Surface-independent antibacterial coating using silver nanoparticle-generating engineered mussel glue.

    PubMed

    Jo, Yun Kee; Seo, Jeong Hyun; Choi, Bong-Hyuk; Kim, Bum Jin; Shin, Hwa Hui; Hwang, Byeong Hee; Cha, Hyung Joon

    2014-11-26

    During implant surgeries, antibacterial agents are needed to prevent bacterial infections, which can cause the formation of biofilms between implanted materials and tissue. Mussel adhesive proteins (MAPs) derived from marine mussels are bioadhesives that show strong adhesion and coating ability on various surfaces even in wet environment. Here, we proposed a novel surface-independent antibacterial coating strategy based on the fusion of MAP to a silver-binding peptide, which can synthesize silver nanoparticles having broad antibacterial activity. This sticky recombinant fusion protein enabled the efficient coating on target surface and the easy generation of silver nanoparticles on the coated-surface under mild condition. The biosynthesized silver nanoparticles showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria and also revealed good cytocompatibility with mammalian cells. In this coating strategy, MAP-silver binding peptide fusion proteins provide hybrid environment incorporating inorganic silver nanoparticle and simultaneously mediate the interaction of silver nanoparticle with surroundings. Moreover, the silver nanoparticles were fully synthesized on various surfaces including metal, plastic, and glass by a simple, surface-independent coating manner, and they were also successfully synthesized on a nanofiber surface fabricated by electrospinning of the fusion protein. Thus, this facile surface-independent silver nanoparticle-generating antibacterial coating has great potential to be used for the prevention of bacterial infection in diverse biomedical fields.

  15. Dynamics of water confined on the surface of titania and cassiterite nanoparticles

    SciTech Connect

    Ross, Dr. Nancy; Spencer, Elinor; Levchenko, Andrey A.; Kolesnikov, Alexander I; Abernathy, Douglas L; Boerio-Goates, Juliana; Woodfield, Brian; Navrotsky, Alexandra; Li, Guangshe; Wang, Weixing; Wesolowski, David J

    2011-01-01

    We present low-temperature inelastic neutron scattering spectra collected on two metal oxide nanoparticle systems, isostructural TiO2 rutile and SnO2 cassiterite, between 0-550 meV. Data were collected on samples with varying levels of water coverage, and in the case of SnO2, particles of different sizes. This study provides a comprehensive understanding of the structure and dynamics of the water confined on the surface of these particles. The translational movement of water confined on the surface of these nanoparticles is suppressed relative to that in ice-Ih and water molecules on the surface of rutile nanoparticles are more strongly restrained that molecules residing on the surface of cassiterite nanoparticles. The INS spectra also indicate that the hydrogen bond network within the hydration layers on rutile is more perturbed than for water on cassiterite. This result is indicative of stronger water-surface interactions between water on the rutile nanoparticles than for water confined on the surface of cassiterite nanoparticles. These differences are consistent with the recently reported differences in the surface energy of these two nanoparticle systems. The results of this study also support previous studies that suggest that water dissociation is more prevalent on the surface of SnO2 than TiO2.

  16. Targeting and molecular imaging of HepG2 cells using surface-functionalized gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Rathinaraj, Pierson; Lee, Kyubae; Choi, Yuri; Park, Soo-Young; Kwon, Oh Hyeong; Kang, Inn-Kyu

    2015-07-01

    Mercaptosuccinic acid (M)-conjugated gold nanoparticles (GM) were prepared and characterized by transmission electron microscope and dynamic light scattering. M was used to improve the monodispersity and non-specific intracellular uptake of nanoparticles. Lactobionic acid (L) was subsequently conjugated to the GM to target preferentially HepG2 cells (liver cancer cells) that express asialoglycoprotein receptors (ASGPR) on their membrane surfaces and facilitate the transit of nanoparticles across the cell membrane. The mean size of lactobionic acid-conjugated gold nanoparticle (GL) was approximately 10 ± 0.2 nm. Finally, the Atto 680 dye (A6) was coupled to the nanoparticles to visualize their internalization into HepG2 cells. The interaction of surface-modified gold nanoparticles with HepG2 cells was studied after culturing cells in media containing the GM or L-conjugated GM (GL).

  17. [Preparation, characterization and surface-enhanced Raman properties of agarose gel/gold nanoparticles hybrid].

    PubMed

    Ma, Xiao-yuan; Liu, Ying; Wang, Zhou-ping

    2014-08-01

    Agarose gel/gold nanoparticles hybrid was prepared by adding gold nanoparticles to preformed agarose gel. Naniocomposite structures and properties were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV-Vis-NIR absorption spectroscopy. Experimental data indicated a uniform distribution of gold nanoparticles adsorbed on agarose gel network And the excellent optical absorption properties were shown. Based on the swelling-contraction characteristics of agarose gel and the adjustable localized surface plasmon resonance (LSPR) of the gold nanoparticles, the nano-composites were used as surface enhanced Raman scattering (SERS) substrate to detect the Raman signal molecules Nile blue A. Results revealed that the porous structure of the agarose gel provided a good carrier for the enrichment of the gold nanoparticles. The gold nanoparticles dynamic hot-spot effect arising from the agarose gel contraction loss of water in the air greatly enhanced the Raman signal.

  18. Surface engineering of inorganic nanoparticles for imaging and therapy.

    PubMed

    Nam, Jutaek; Won, Nayoun; Bang, Jiwon; Jin, Ho; Park, Joonhyuck; Jung, Sungwook; Jung, Sanghwa; Park, Youngrong; Kim, Sungjee

    2013-05-01

    Many kinds of inorganic nanoparticles (NPs) including semiconductor, metal, metal oxide, and lanthanide-doped NPs have been developed for imaging and therapy applications. Their unique optical, magnetic, and electronic properties can be tailored by controlling the composition, size, shape, and structure. Interaction of such NPs with cells and/or in vivo compartments is critically determined by the surface properties, and sophisticated control over the NP surface is essential to control their fate in biological environments. We review NP surface coating strategies using the categories of small surface ligand, polymer, and lipid. Use of small ligand molecules has the advantage of maintaining the minimal hydrodynamic (HD) size. Polymers can be advantageous in NP anchoring by combining multiple affinity groups. Encapsulation of NPs in polymers, lipids or surfactants can preserve the as-synthesized NPs. NP surface properties and reaction conditions should be carefully considered to obtain a bioconjugate that maintains the physicochemical properties of NP and functionalities of the conjugated biomolecules. We highlight how the surface properties of NPs impact their interactions with cells and in vivo compartments, especially focused on the important surface design parameters such as HD size, surface charge, and targeting. Typically, maximal cellular uptake can take place in the intermediate NP size range of 40-60nm. Clearance of NPs from blood circulation is largely dependent on the degree of uptake by reticuloendothelial system when they are larger than 10nm. When the HD size is below 10nm, NPs show broad distribution over many organs. Reduction of HD size below the limit of renal barrier can achieve fast clearance of NPs. For maximal tumor accumulation, NPs should have long blood circulation time and should be large enough to prevent rapid penetration. NPs are also desired to rapidly clear out from the body after the mission before they cause toxic side effects

  19. Temperature dependence of the effective anisotropies in magnetic nanoparticles with Néel surface anisotropy

    NASA Astrophysics Data System (ADS)

    Yanes, R.; Chubykalo-Fesenko, O.; Evans, R. F. L.; Chantrell, R. W.

    2010-12-01

    We discuss the physical concept of the effective anisotropy in magnetic nanoparticles with surface anisotropy. A recently developed constrained Monte Carlo method allows evaluation of the temperature dependence of the energy surface in the whole temperature range, from which the effective anisotropy is determined. We consider nanoparticles of different shapes with cubic or uniaxial core anisotropy and Néel surface anisotropy. We demonstrate that at low temperatures surface effects can be dominant, leading to an overall cubic effective anisotropy even in spherical nanoparticles with uniaxial core anisotropy. This cubic anisotropy contribution decreases more rapidly with increasing temperature than the uniaxial core anisotropy, leading to a temperature-induced reorientation transition. We discuss the scaling behaviour of the effective anisotropy with magnetization in nanoparticles with surface anisotropy contribution. The scaling exponent deviates from that expected from Callen-Callen theory due to increased fluctuations of the surface spins.

  20. Surface faceting and elemental diffusion behaviour at atomic scale for alloy nanoparticles during in situ annealing

    PubMed Central

    Chi, Miaofang; Wang, Chao; Lei, Yinkai; Wang, Guofeng; Li, Dongguo; More, Karren L.; Lupini, Andrew; Allard, Lawrence F.; Markovic, Nenad M.; Stamenkovic, Vojislav R.

    2015-01-01

    The catalytic performance of nanoparticles is primarily determined by the precise nature of the surface and near-surface atomic configurations, which can be tailored by post-synthesis annealing effectively and straightforwardly. Understanding the complete dynamic response of surface structure and chemistry to thermal treatments at the atomic scale is imperative for the rational design of catalyst nanoparticles. Here, by tracking the same individual Pt3Co nanoparticles during in situ annealing in a scanning transmission electron microscope, we directly discern five distinct stages of surface elemental rearrangements in Pt3Co nanoparticles at the atomic scale: initial random (alloy) elemental distribution; surface platinum-skin-layer formation; nucleation of structurally ordered domains; ordered framework development and, finally, initiation of amorphization. Furthermore, a comprehensive interplay among phase evolution, surface faceting and elemental inter-diffusion is revealed, and supported by atomistic simulations. This work may pave the way towards designing catalysts through post-synthesis annealing for optimized catalytic performance. PMID:26576477

  1. Construction of boundary-surface-based Chinese female astronaut computational phantom and proton dose estimation.

    PubMed

    Sun, Wenjuan; Jia, Xianghong; Xie, Tianwu; Xu, Feng; Liu, Qian

    2013-03-01

    With the rapid development of China's space industry, the importance of radiation protection is increasingly prominent. To provide relevant dose data, we first developed the Visible Chinese Human adult Female (VCH-F) phantom, and performed further modifications to generate the VCH-F Astronaut (VCH-FA) phantom, incorporating statistical body characteristics data from the first batch of Chinese female astronauts as well as reference organ mass data from the International Commission on Radiological Protection (ICRP; both within 1% relative error). Based on cryosection images, the original phantom was constructed via Non-Uniform Rational B-Spline (NURBS) boundary surfaces to strengthen the deformability for fitting the body parameters of Chinese female astronauts. The VCH-FA phantom was voxelized at a resolution of 2 × 2 × 4 mm(3)for radioactive particle transport simulations from isotropic protons with energies of 5000-10 000 MeV in Monte Carlo N-Particle eXtended (MCNPX) code. To investigate discrepancies caused by anatomical variations and other factors, the obtained doses were compared with corresponding values from other phantoms and sex-averaged doses. Dose differences were observed among phantom calculation results, especially for effective dose with low-energy protons. Local skin thickness shifts the breast dose curve toward high energy, but has little impact on inner organs. Under a shielding layer, organ dose reduction is greater for skin than for other organs. The calculated skin dose per day closely approximates measurement data obtained in low-Earth orbit (LEO).

  2. One-step synthesis of silver nanoparticles, nanorods, and nanowires on the surface of DNA network.

    PubMed

    Wei, Gang; Zhou, Hualan; Liu, Zhiguo; Song, Yonghai; Wang, Li; Sun, Lanlan; Li, Zhuang

    2005-05-12

    Here, we describe a one-step synthesis of silver nanoparticles, nanorods, and nanowires on DNA network surface in the absence of surfactant. Silver ions were first adsorbed onto the DNA network and then reduced in sodium borohydride solution. Silver nanoparticles, nanorods, and nanowires were formed by controlling the size of pores of the DNA network. The diameter of the silver nanoparticles and the aspect ratio of the silver nanorods and nanowires can be controlled by adjusting the DNA concentration and reduction time.

  3. Gold Nanoparticles with Externally Controlled, Reversible Shifts of Local Surface Plasmon Resonance Bands

    PubMed Central

    Yavuz, Mustafa S.; Jensen, Gary C.; Penaloza, David P.; Seery, Thomas A. P.; Pendergraph, Samuel A.; Rusling, James F.; Sotzing, Gregory A.

    2010-01-01

    We have achieved reversible tunability of local surface plasmon resonance in conjugated polymer functionalized gold nanoparticles. This property was facilitated by the preparation of 3,4-ethylenedioxythiophene (EDOT) containing polynorbornene brushes on gold nanoparticles via surface-initiated ring-opening metathesis polymerization. Reversible tuning of the surface plasmon band was achieved by electrochemically switching the EDOT polymer between its reduced and oxidized states. PMID:19839619

  4. Strategies in biomimetic surface engineering of nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Gong, Yong-Kuan; Winnik, Françoise M.

    2012-01-01

    Engineered nanoparticles (NPs) play an increasingly important role in biomedical sciences and in nanomedicine. Yet, in spite of significant advances, it remains difficult to construct drug-loaded NPs with precisely defined therapeutic effects, in terms of release time and spatial targeting. The body is a highly complex system that imposes multiple physiological and cellular barriers to foreign objects. Upon injection in the blood stream or following oral administation, NPs have to bypass numerous barriers prior to reaching their intended target. A particularly successful design strategy consists in masking the NP to the biological environment by covering it with an outer surface mimicking the composition and functionality of the cell's external membrane. This review describes this biomimetic approach. First, we outline key features of the composition and function of the cell membrane. Then, we present recent developments in the fabrication of molecules that mimic biomolecules present on the cell membrane, such as proteins, peptides, and carbohydrates. We present effective strategies to link such bioactive molecules to the NPs surface and we highlight the power of this approach by presenting some exciting examples of biomimetically engineered NPs useful for multimodal diagnostics and for target-specific drug/gene delivery applications. Finally, critical directions for future research and applications of biomimetic NPs are suggested to the readers.

  5. Impact of surface defects on the surface charge of gibbsite nanoparticles.

    PubMed

    Klaassen, Aram; Liu, Fei; van den Ende, Dirk; Mugele, Frieder; Siretanu, Igor

    2017-04-06

    We use high resolution Atomic Force Microscopy to study the surface charge of the basal plane of gibbsite nanoparticles, with a lateral resolution of approximately 5 nm, in ambient electrolyte of variable pH and salt content. Our measurements reveal surface charge variations on the basal planes that correlate with the presence of topographic defects such as atomic steps. This surface charge heterogeneity, which increases with increasing pH, suggests that for a pH between 6 and 9 the defect sites display a stronger chemical activity than adjacent, apparently atomically smooth regions of the basal plane. Smooth regions display a slight positive surface charge of ≈0.05e per nm(2) that hardly varies within this pH range. In contrast, near the topographic defects we observe a much lower charge. Considering the size of the interaction area under the probing tip, this implies that at the defect sites the charge density must be negative, ≈-0.1e per nm(2). These measurements demonstrate that surface defects have a large influence on the average surface charge of the gibbsite basal plane. These findings will contribute to understand why surface defects play an important role in various applications, such as fuel cells, chemical synthesis, self-assembly, catalysis and surface treatments.

  6. Reduced Cationic Nanoparticle Cytotoxicity Based on Serum Masking of Surface Potential

    PubMed Central

    McConnell, Kellie I.; Shamsudeen, Sabeel; Meraz, Ismail M.; Mahadevan, Thiruvillamalai S.; Ziemys, Arturas; Rees, Paul; Summers, Huw D.; Serda, Rita E.

    2016-01-01

    Functionalization of nanoparticles with cationic moieties, such as polyethyleneimine (PEI), enhances binding to the cell membrane; however, it also disrupts the integrity of the cell’s plasma and vesicular membranes, leading to cell death. Primary fibroblasts were found to display high surface affinity for cationic iron oxide nanoparticles and greater sensitivity than their immortalized counterparts. Treatment of cells with cationic nanoparticles in the presence of incremental increases in serum led to a corresponding linear decrease in cell death. The surface potential of the nanoparticles also decreased linearly as serum increased and this was strongly and inversely correlated with cell death. While low doses of nanoparticles were rendered non-toxic in 25% serum, large doses overcame the toxic threshold. Serum did not reduce nanoparticle association with primary fibroblasts, indicating that the decrease in nanoparticle cytotoxicity was based on serum masking of the PEI surface, rather than decreased exposure. Primary endothelial cells were likewise more sensitive to the cytotoxic effects of cationic nanoparticles than their immortalized counterparts, and this held true for cellular responses to cationic microparticles despite the much lower toxicity of microparticles compared to nanoparticles. PMID:27301181

  7. Quantitative surface acoustic wave detection based on colloidal gold nanoparticles and their bioconjugates.

    PubMed

    Chiu, Chi-Shun; Gwo, Shangjr

    2008-05-01

    The immobilization scheme of monodispersed gold nanoparticles (10-nm diameter) on piezoelectric substrate surfaces using organosilane molecules as cross-linkers has been developed for lithium niobate (LiNbO3) and silicon oxide (SiO2)/gold-covered lithium tantalate (LiTaO3) of Rayleigh and guided shear horizontal- (guided SH) surface acoustic wave (SAW) sensors. In this study, comparative measurements of gold nanoparticle adsorption kinetics using high-resolution field-emission scanning electron microscopy and SAW sensors allow the frequency responses of SAW sensors to be quantitatively correlated with surface densities of adsorbed nanoparticles. Using this approach, gold nanoparticles are used as the "nanosized mass standards" to scale the mass loading in a wide dynamical range. Rayleigh-SAW and guided SH-SAW sensors are employed here to monitor the surface mass changes on the device surfaces in gas and liquid phases, respectively. The mass sensitivity ( approximately 20 Hz.cm2/ng) of Rayleigh-SAW device (fundamental oscillation frequency of 113.3 MHz in air) is more than 2 orders of magnitude higher than that of conventional 9-MHz quartz crystal microbalance sensors. Furthermore, in situ (aqueous solutions), real-time measurements of adsorption kinetics for both citrate-stabilized gold nanoparticles and DNA-gold nanoparticle conjugates are also demonstrated by guided SH-SAW (fundamental oscillation frequency of 121.3 MHz). By comparing frequency shifts between the adsorption cases of gold nanoparticles and DNA-gold nanoparticle conjugates, the average number of bound oligonucleotides per gold nanoparticle can also be determined. The high mass sensitivity ( approximately 6 Hz.cm2/ng) of guided SH-SAW sensors and successful detection of DNA-gold nanoparticle conjugates paves the way for real-time biosensing in liquids using nanoparticle-enhanced SAW devices.

  8. Molecular statics calculations of proton binding to goethite surfaces: A new approach to estimation of stability constants for multisite surface complexation models

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Felmy, Andrew R.; Hay, Benjamin P.

    1996-05-01

    A new approach to estimating stability constants for proton binding in multisite surface complexation models is presented. The method is based on molecular statics computation of energies for the formation of proton vacancies and interstitials in ideal periodic slabs representing the (100), (110), (010), (001), and (021) surfaces of goethite. Gas-phase energies of clusters representing the hydrolysis products of ferric iron are calculated using the same potential energy functions used for the surface. These energies are linearly related to the hydrolysis constants for ferric iron in aqueous solution. Stability constants for proton binding at goethite surfaces are estimated by assuming the same log K- Δ E relationship for goethite surface protonation reactions. These stability constants predict a pH of zero charge of 8.9, in adequate agreement with measurements on CO 2-free goethite. The estimated stability constants differ significantly from previous estimations based on Pauling bond strength. We find that nearly all the surface oxide ions are reactive; nineteen of the twenty-six surface sites investigated have log Kint between 7.7 and 9.4. This implies a site density between fifteen and sixteen reactive sites/nm for crystals dominated by (110) and (021) crystal faces.

  9. Role of oxygen in wetting of copper nanoparticles on silicon surfaces at elevated temperature

    PubMed Central

    Ghosh, Tapas

    2017-01-01

    Copper nanoparticles have been deposited on silicon surfaces by a simple galvanic displacement reaction, and rapid thermal annealing has been performed under various atmospheric conditions. In spite of the general tendency of the agglomeration of nanoparticles to lower the surface energy at elevated temperatures, our plan-view and cross-sectional transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis shows that the thermal oxidation of the copper nanoparticles and formation of cupric oxide (CuO) on silicon surfaces leads to wetting rather than agglomeration. In contrast, agglomeration has been observed when copper nanoparticles were annealed in a nitrogen environment. The lattice transformation from cubic Cu to monoclinic CuO, and hence the change in surface energy of the particles, assists the wetting process. The occurrence of wetting during the oxidation step implies a strong interaction between the oxidized film and the silicon surface. PMID:28326232

  10. In situ spectroscopy of ligand exchange reactions at the surface of colloidal gold and silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Dinkel, Rebecca; Peukert, Wolfgang; Braunschweig, Björn

    2017-04-01

    Gold and silver nanoparticles with their tunable optical and electronic properties are of great interest for a wide range of applications. Often the ligands at the surface of the nanoparticles have to be exchanged in a second step after particle formation in order to obtain a desired surface functionalization. For many techniques, this process is not accessible in situ. In this review, we present second-harmonic scattering (SHS) as an inherently surface sensitive and label-free optical technique to probe the ligand exchange at the surface of colloidal gold and silver nanoparticles in situ and in real time. First, a brief introduction to SHS and basic features of the SHS of nanoparticles are given. After that, we demonstrate how the SHS intensity decrease can be correlated to the thiol coverage which allows for the determination of the Gibbs free energy of adsorption and the surface coverage.

  11. Effect of surface charge on the cellular uptake of fluorescent magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Kralj, Slavko; Rojnik, Matija; Romih, Rok; Jagodič, Marko; Kos, Janko; Makovec, Darko

    2012-10-01

    We report on the nanoparticle uptake into MCF10A neoT and PC-3 cells using flow cytometry, confocal microscopy, SQUID magnetometry, and transmission electron microscopy. The aim was to evaluate the influence of the nanoparticles' surface charge on the uptake efficiency. The surface of the superparamagnetic, silica-coated, maghemite nanoparticles was modified using amino functionalization for the positive surface charge (CNPs), and carboxyl functionalization for the negative surface charge (ANPs). The CNPs and ANPs exhibited no significant cytotoxicity in concentrations up to 500 μg/cm3 in 24 h. The CNPs, bound to a plasma membrane, were intensely phagocytosed, while the ANPs entered cells through fluid-phase endocytosis in a lower internalization degree. The ANPs and CNPs were shown to be co-localized with a specific lysosomal marker, thus confirming their presence in lysosomes. We showed that tailoring the surface charge of the nanoparticles has a great impact on their internalization.

  12. Determination of the surface area and sizes of supported copper nanoparticles through organothiol adsorption-Chemisorption

    NASA Astrophysics Data System (ADS)

    Ndolomingo, Matumuene Joe; Meijboom, Reinout

    2016-12-01

    The mechanisms involving the nanoparticle surfaces in catalytic reactions are more difficult to elucidate due to the nanoparticle surface unevenness, size distributions, and morphological irregularity. True surface area and particle sizes determination are key aspects of the activity of metal nanoparticle catalysts. Here we report on the organothiol adsorption-based technique for the determination of specific surface area of Cu nanoparticles, and their resultant sizes on γ-Al2O3 supports. Quantification of ligand packing density on copper nanoparticles is also reported. The concentration of the probe ligand, 2-mercaptobenzimidazole (2-MBI) before and after immersion of supported copper catalysts was determined by ultraviolet-visible spectrometry (UV-vis). The amount of ligand adsorbed was found to be proportional to the copper nanoparticles surface area. Atomic absorption spectrometry (AAS), N2-physisorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used for the characterization of the catalysts. A fair agreement was found between particle sizes obtained from ligand adsorption and TEM methods. The catalytic activity of the copper nanoparticles related to their inherent surface area was evaluated using the model reaction of the oxidation of morin by hydrogen peroxide.

  13. Multilayers of oppositely charged SiO2 nanoparticles: effect of surface charge on multilayer assembly.

    PubMed

    Lee, Daeyeon; Gemici, Zekeriyya; Rubner, Michael F; Cohen, Robert E

    2007-08-14

    The growth behavior of all-silica nanoparticle multilayer thin films assembled via layer-by-layer deposition of oppositely charged SiO2 nanoparticles was studied as a function of assembly conditions. Amine-functionalized SiO2 nanoparticles were assembled into multilayers through the use of three different sizes of negatively charged SiO2 nanoparticles. The assembly pH of the nanoparticle suspensions needed to achieve maximum growth for each system was found to be different. However, the surface charge /z/ of the negatively charged silica nanoparticles at the optimal assembly pH was approximately the same, indicating the importance of this parameter in determining the growth behavior of all-nanoparticle multilayers. When /z/ of the negatively charged nanoparticles lies between 0.6z(0) and 1.2z(0) (where z(0) is the pH-independent value of the zeta-potential of the positively charged nanoparticles used in this study), the multilayers show maximum growth for each system. The effect of particle size on the film structure was also investigated. Although nanoparticle size significantly influenced the average bilayer thickness of the multilayers, the porosity and refractive index of multilayers made from nanoparticles of different sizes varied by a small amount. For example, the porosity of the different multilayer systems ranged from 42 to 49%. This study further demonstrates that one-component all-nanoparticle multilayers can be assembled successfully by depositing nanoparticles of the same material but with opposite surface charge.

  14. Surface modification of metal and metal coated nanoparticles to induce clustering

    NASA Astrophysics Data System (ADS)

    Gowda, M. H.; Glembocki, O. J.; Geng, S.; Prokes, S. M.; Garces, N.; Caldwell, J. D.

    2010-08-01

    Surface enhanced Raman scattering (SERS) is a powerful technique for the detection of submonolayer coverage of gold or silver surfaces. The magnitude of the effect and the spectral wavelength of the peak depend on the metal nanoparticles used and its geometry. In this paper we show that the use of chemicals that bind to gold or silver can lead to the clustering of nanoparticles. We used well defined Au nanoparticles in our experiments and add cysteamine to solutions containing the nanoparticles. The plasmonic response of the nanoparticles is measured by transmission Surface Plasmon Resonance (SPR) spectroscopy. We observed significant changes to the SPR spectra that are characteristics of close coupled nanoparticles. The time evolution of these changes indicates the formation of gold nanoparticles clusters. The SERS response of these clustered nanoparticles is observed to red shift from the designed peak wavelength in the green to the red. In addition, the placement of these clusters on dielectric surfaces shifts the SPR even more into the red. The experimental results are supported by calculations of the electromagnetic fields using finite difference methods.

  15. Internal photoemission from plasmonic nanoparticles: comparison between surface and volume photoelectric effects.

    PubMed

    Uskov, Alexander V; Protsenko, Igor E; Ikhsanov, Renat S; Babicheva, Viktoriia E; Zhukovsky, Sergei V; Lavrinenko, Andrei V; O'Reilly, Eoin P; Xu, Hongxing

    2014-05-07

    We study the emission of photoelectrons from plasmonic nanoparticles into a surrounding matrix. We consider two mechanisms of electron emission from the nanoparticles--surface and volume ones--and use models for these two mechanisms which allow us to obtain analytical results for the photoelectron emission rate from a nanoparticle. Calculations have been carried out for a step potential at the surface of a spherical nanoparticle, and a simple model for the hot electron cooling has been used. We highlight the effect of the discontinuity of the dielectric permittivity at the nanoparticle boundary in the surface mechanism, which leads to a substantial (by ∼5 times) increase of the internal photoelectron emission rate from a nanoparticle compared to the case when such a discontinuity is absent. For a plasmonic nanoparticle, a comparison of the two photoeffect mechanisms was undertaken for the first time which showed that the surface photoeffect can in the general case be larger than the volume one, which agrees with the results obtained for a flat metal surface first formulated by Tamm and Schubin in their pioneering development of a quantum-mechanical theory of photoeffect in 1931. In accordance with our calculations, this possible predominance of the surface effect is based on two factors: (i) effective cooling of hot carriers during their propagation from the volume of the nanoparticle to its surface in the scenario of the volume mechanism and (ii) strengthening of the surface mechanism through the effect of the discontinuity of the dielectric permittivity at the nanoparticle boundary. The latter is stronger at relatively lower photon energies and correspondingly is more substantial for internal photoemission than for an external one. We show that in the general case, it is essential to take both mechanisms into account in the development of devices based on the photoelectric effect and when considering hot electron emission from a plasmonic nanoantenna.

  16. Molecular Surface Chemistry by Metal Single Crystals and Nanoparticles from Vacuum to High Pressure.

    SciTech Connect

    Somorjai, Gabor A.; Park, Jeong Y.

    2008-04-05

    Model systems for studying molecular surface chemistry have evolved from single crystal surfaces at low pressure to colloidal nanoparticles at high pressure. Low pressure surface structure studies of platinum single crystals using molecular beam surface scattering and low energy electron diffraction techniques probe the unique activity of defects, steps and kinks at the surface for dissociation reactions (H-H, C-H, C-C, O{double_bond}O bonds). High-pressure investigations of platinum single crystals using sum frequency generation vibrational spectroscopy have revealed the presence and the nature of reaction intermediates. High pressure scanning tunneling microscopy of platinum single crystal surfaces showed adsorbate mobility during a catalytic reaction. Nanoparticle systems are used to determine the role of metal-oxide interfaces, site blocking and the role of surface structures in reactive surface chemistry. The size, shape and composition of nanoparticles play important roles in determining reaction activity and selectivity.

  17. Accelerated CO2 transport on surface of AgO nanoparticles in ionic liquid BMIMBF4

    NASA Astrophysics Data System (ADS)

    Ji, Dahye; Kang, Yong Soo; Kang, Sang Wook

    2015-11-01

    The AgO nanoparticles were utilized for a CO2 separation membrane. The AgO nanoparticles were successfully generated in ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF4) by favorable interaction between the surface of particles and the counteranion of BMIMBF4. The generated AgO nanoparticles were confirmed by TEM, and the average size was 20 nm. Coordinative interactions of dissociated AgO particles with BMIM+BF4- were investigated by FT-Raman spectroscopy. When the ionic liquid BMIMBF4 containing AgO nanoparticles was utilized as a CO2 separation membrane, the separation performance was largely enhanced.

  18. Refractive index measurement of nanoparticles by immersion refractometry based on a surface plasmon resonance sensor

    NASA Astrophysics Data System (ADS)

    Kano, Hiroshi; Iseda, Ayumu; Ohenoja, Katja; Niskanen, Ilpo

    2016-06-01

    Accurate determination of the refractive index of nanoparticles has important ramifications for applications, such as pharmaceuticals, cosmetics, paints, textiles, and inks. We describe a new method to determine the refractive index of nanoparticles by immersion refractometry with a surface plasmon resonance sensor. With this method, the refractive index of the nanoparticles is perfectly matched with that of the surrounding liquid. We demonstrate this method for calcium fluoride nanoparticles that have an average diameter of 100 nm; the results achieve an accuracy of better than 0.002 refractive index units.

  19. Accelerated CO2 transport on surface of AgO nanoparticles in ionic liquid BMIMBF4

    PubMed Central

    Ji, Dahye; Kang, Yong Soo; Kang, Sang Wook

    2015-01-01

    The AgO nanoparticles were utilized for a CO2 separation membrane. The AgO nanoparticles were successfully generated in ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF4) by favorable interaction between the surface of particles and the counteranion of BMIMBF4. The generated AgO nanoparticles were confirmed by TEM, and the average size was 20 nm. Coordinative interactions of dissociated AgO particles with BMIM+BF4− were investigated by FT-Raman spectroscopy. When the ionic liquid BMIMBF4 containing AgO nanoparticles was utilized as a CO2 separation membrane, the separation performance was largely enhanced. PMID:26549605

  20. Surface Structure of Protonated R-Sapphire (1$\\bar{1}$02) Studied by Sum-Frequency Vibrational Spectroscopy

    SciTech Connect

    Sung, Jaeho; Zhang, Luning; Tian, Chuanshan; Waychunas, Glenn A.; Shen, Y. Ron

    2011-03-23

    Sum frequency vibrational spectroscopy was used to study the protonated R-plane (1$\\bar{1}$02 ) sapphire surface. The OH stretch vibrational spectra show that the surface is terminated with three hydroxyl moieties, two from AlOH2 and one from Al2OH functional groups. The observed polarization dependence allows determination of the orientations of the three OH species. The results suggest that the protonated sapphire (1$\\bar{1}$02 ) surface differs from an ideal stoichimetric termination in a manner consistent with previous X-ray surface diffraction (crystal truncation rod) studies. However, in order to best explain the observed hydrogenbonding arrangement, surface oxygen spacing determined from the X-ray diffraction study requires modification.

  1. Surface engineering of macrophages with nanoparticles to generate a cell-nanoparticle hybrid vehicle for hypoxia-targeted drug delivery.

    PubMed

    Holden, Christopher A; Yuan, Quan; Yeudall, W Andrew; Lebman, Deborah A; Yang, Hu

    2010-02-02

    Tumors frequently contain hypoxic regions that result from a shortage of oxygen due to poorly organized tumor vasculature. Cancer cells in these areas are resistant to radiation- and chemotherapy, limiting the treatment efficacy. Macrophages have inherent hypoxia-targeting ability and hold great advantages for targeted delivery of anticancer therapeutics to cancer cells in hypoxic areas. However, most anticancer drugs cannot be directly loaded into macrophages because of their toxicity. In this work, we designed a novel drug delivery vehicle by hybridizing macrophages with nanoparticles through cell surface modification. Nanoparticles immobilized on the cell surface provide numerous new sites for anticancer drug loading, hence potentially minimizing the toxic effect of anticancer drugs on the viability and hypoxia-targeting ability of the macrophage vehicles. In particular, quantum dots and 5-(aminoacetamido) fluorescein-labeled polyamidoamine dendrimer G4.5, both of which were coated with amine-derivatized polyethylene glycol, were immobilized to the sodium periodate-treated surface of RAW264.7 macrophages through a transient Schiff base linkage. Further, a reducing agent, sodium cyanoborohydride, was applied to reduce Schiff bases to stable secondary amine linkages. The distribution of nanoparticles on the cell surface was confirmed by fluorescence imaging, and it was found to be dependent on the stability of the linkages coupling nanoparticles to the cell surface.

  2. Surface charge of gold nanoparticles mediates mechanism of toxicity

    NASA Astrophysics Data System (ADS)

    Schaeublin, Nicole M.; Braydich-Stolle, Laura K.; Schrand, Amanda M.; Miller, John M.; Hutchison, Jim; Schlager, John J.; Hussain, Saber M.

    2011-02-01

    Recently gold nanoparticles (Au NPs) have shown promising biological and military applications due to their unique electronic and optical properties. However, little is known about their biocompatibility in the event that they come into contact with a biological system. In the present study, we have investigated whether modulating the surface charge of 1.5 nm Au NPs induced changes in cellular morphology, mitochondrial function, mitochondrial membrane potential (MMP), intracellular calcium levels, DNA damage-related gene expression, and of p53 and caspase-3 expression levels after exposure in a human keratinocyte cell line (HaCaT). The evaluation of three different Au NPs (positively charged, neutral, and negatively charged) showed that cell morphology was disrupted by all three NPs and that they demonstrated a dose-dependent toxicity; the charged Au NPs displayed toxicity as low as 10 µg ml-1 and the neutral at 25 µg ml-1. Furthermore, there was significant mitochondrial stress (decreases in MMP and intracellular Ca2+ levels) following exposure to the charged Au NPs, but not the neutral Au NPs. In addition to the differences observed in the MMP and Ca2+ levels, up or down regulation of DNA damage related gene expression suggested a differential cell death mechanism based on whether or not the Au NPs were charged or neutral. Additionally, increased nuclear localization of p53 and caspase-3 expression was observed in cells exposed to the charged Au NPs, while the neutral Au NPs caused an increase in both nuclear and cytoplasmic p53 expression. In conclusion, these results indicate that surface charge is a major determinant of how Au NPs impact cellular processes, with the charged NPs inducing cell death through apoptosis and neutral NPs leading to necrosis.Recently gold nanoparticles (Au NPs) have shown promising biological and military applications due to their unique electronic and optical properties. However, little is known about their biocompatibility in the

  3. Demonstration of surface-enhanced Raman scattering by tunable, plasmonic gallium nanoparticles

    PubMed Central

    Wu, Pae C; Khoury, Christopher G.; Kim, Tong-Ho; Yang, Yang; Losurdo, Maria; Bianco, Giuseppe V.; Vo-Dinh, Tuan; Brown, April S.; Everitt, Henry O.

    2009-01-01

    Size-controlled gallium nanoparticles deposited on sapphire are explored as alternative substrates to enhance Raman spectral signatures. Gallium’s resilience following oxidation is inherently advantageous compared to silver for practical ex vacuo, non-solution applications. Ga nanoparticles are grown using a simple, molecular beam epitaxy-based fabrication protocol, and by monitoring their corresponding surface plasmon resonance energy through in situ spectroscopic ellipsometry, the nanoparticles are easily controlled for size. Raman spectroscopy performed on cresyl fast violet (CFV) deposited on substrates of differing mean nanoparticle size represents the first demonstration of enhanced Raman signals from reproducibly tunable self-assembled Ga nanoparticles. Non-optimized aggregate enhancement factors of ~80 were observed from the substrate with the smallest Ga nanoparticles for CFV dye solutions down to a dilution of 10 ppm. PMID:19655747

  4. Synthesis of biomacromolecule-stabilized silver nanoparticles and their surface-enhanced Raman scattering properties

    NASA Astrophysics Data System (ADS)

    Zhang, Danhui; Yang, Houbo

    2013-09-01

    In this work, water soluble silver nanoparticles stabilized by biomacromolecule, were produced through using an aqueous solution of silver nitrate with Bovine Serum Albumin (BSA) under different reducing agents (such as sodium borohydride, hydrazine, N, N-dimethyl formamide) at the room temperature, where BSA provided the main function to form monodispersed silver nanoparticles. UV-vis spectroscopy, Fluorescence spectra, TEM and HR-TEM are used to characterize the BSA-capped silver nanoparticles under different condition. The results show that the formed silver nanoparticles have different size and morphology under the three different reducing agents. Moreover, the fluorescence intensity of BSA was drastically quenched in presence of Ag nanoparticles from the results of fluorescence spectra. Furthermore, the surface-enhanced Raman scattering effects of the formed silver nanoparticles were also displayed and we made a comparison under three different reducing agents.

  5. Surface functionalization of silica-coated magnetic nanoparticles for covalent attachment of cholesterol oxidase

    NASA Astrophysics Data System (ADS)

    Šulek, Franja; Drofenik, Miha; Habulin, Maja; Knez, Željko

    2010-01-01

    A systematic approach towards the fabrication of highly functionalized silica shell magnetic nanoparticles, presently used for enzyme immobilization, is herein fully presented. The synthesis of bare maghemite (γ-Fe 2O 3) nanoparticles was accomplished by thermal co-precipitation of iron ions in ammonia alkaline solution at harsh reaction conditions, respectively. Primary surface engineering of maghemite nanoparticles was successfully performed by the proper deposition of silica onto nanoparticles surface under strictly regulated reaction conditions. Next, the secondary surface functionalization of the particles was achieved by coating the particles with organosilane followed by glutaraldehyde activation in order to enhance protein immobilization. Covalent immobilization of cholesterol oxidase was attempted afterwards. The structural and magnetic properties of magnetic silica nanocomposites were characterized by TEM and vibrating sample magnetometer (VSM) instruments. X-ray diffraction measurements confirmed the spinel structure and average size of uncoated maghemite nanoparticles to be around 20 nm in diameter. SEM-EDS spectra indicated a strong signal for Si, implying the coating procedure of silica onto the particles surface to be successfully accomplished. Fourier transform infrared (FT-IR) spectra analysis confirmed the binding of amino silane molecules onto the surface of the maghemite nanoparticles mediated Si-O-Si chemical bonds. Compared to the free enzyme, the covalently bound cholesterol oxidase retained 50% of its activity. Binding of enzyme onto chemically modified magnetic nanoparticles via glutaraldehyde activation is a promising method for developing biosensing components in biomedicine.

  6. Dual surface plasmon resonances in Ni nanoparticles in silica

    SciTech Connect

    Majhi, Jayanta K.; Kuiri, Probodh K.

    2015-06-24

    We report the observations of two broad absorption bands (at ∼3.5 and ∼6.0 eV) in the optical absorption (OA) spectra of Ni nanoparticles (NPs) in silica. For the calculations of the OA spectra, Maxwell-Garnett type effective medium theory has been used with NP radii in the range of 1 – 50 nm. The peak positions of both the OA bands have been found to shift towards higher energy (blue-shift) with decrease in NP radius. In addition, the OA spectra are found to more sensitive for smaller NPs as compare to larger NPs. These observations are argued as due to the confinement of the mean free path of free electrons in Ni NPs. Based on this, we conclude that the observed OA bands are due to the surface plasmon resonance (SPR) absorptions irrespective of the satisfaction of the criteria of the SPR conditions, thus resolving the unclear understanding of the appearance of two absorption bands in Ni NPs.

  7. Tailoring Surface Roughness by Grafting Nanoparticles to Random Copolymer Films

    NASA Astrophysics Data System (ADS)

    Caporizzo, Matthew; Ezzibdeh, Rami; Composto, Russell

    2013-03-01

    The effect of random copolymer composition on surface attachment and sinking of amine functionalized silica nanoparticles (d =45 nm) is investigated. Films of poly(styrene-ran-tert-butyl acrylate) (StBA) with 37% tBA are converted to poly(S-ran-acrylic acid) (SAA) by annealing for 15h at temperatures ranging from 135C to 200C. The conversion of the tBA ranges from under 10% to 100% and is monitored by ellipsometry and ATR-FTIR. At complete conversion (25 wt% AA), SAA forms nano-phase separated domains that result in particle aggregation within AA rich domains. At lower AA conversion, a disordered polymer morphology leads to grafting sites which are randomly distributed. NPs graft from nearly a complete monolayer to multilayers depending the percent of AA. Both the rate of NP attachment and the maximum loading of NPs into the film scale with the fraction of AA; this behavior is attributed to a reduction in the energetic barrier for the particle to sink into the film with increased swelling (more hydrophilic). A particularly attractive outcome of this systematic study is that optically transparent films with controlled roughness can be routinely prepared. Such films are of interest for investigating biomolecular adsorption and superhydrophobic, clear, non-fouling coatings. Supported by NSF DMR08-32802.

  8. Surface Plasmon-Driven Water Reduction: Gold Nanoparticle Size Matters

    SciTech Connect

    Qian, Kun; Sweeny, Brendan C.; Johnston-Peck, Aaron C.; Niu, Wenxin; Graham, Jeremy O.; DuChene, Joseph S.; Qiu, Jingjing; Wang, Yi-Chung; Engelhard, Mark H.; Su, Dong; Stach, Eric A.; Wei, Wei

    2014-07-16

    Water reduction under two visible light ranges (λ > 400 and λ > 435 nm) was investigated using gold-loaded titanium dioxide (Au-TiO2) with different sizes of Au nanoparticles (NPs). Two different mechanisms have been determined to clarify the specific role of Au NPs in visible light-induced photocatalytic reactions. Our study provides solid evidences showing that Au NPs sizes are essential for the surface plasmon-driven water reduction under λ > 435 nm. More specifically, we have demonstrated that the Au NPs sizes are vital for the SPR mediated electron transfer efficiency and play a critical role in determining the reduction potential of the transferred electrons in the TiO2 conduction band (CB) and their following activities. Our discovery provides a facile way to manipulate the reduction potential of transferred electrons by simply varying the Au NPs sizes, which will greatly facilitate the design of suitable plasmonic photocatalysts for water reduction and other valuable solar-to-fuel reactions.

  9. Surface modification of PLGA nanoparticles to deliver nitric oxide to inhibit Escherichia coli growth

    NASA Astrophysics Data System (ADS)

    Reger, Nina A.; Meng, Wilson S.; Gawalt, Ellen S.

    2017-04-01

    Polymer nanoparticles consisting of poly (DL-lactic-co-glycolic acid) were surface functionalized to deliver nitric oxide. These biodegradable and biocompatible nanoparticles were modified with an S-nitrosothiol molecule, S-nitrosocysteamine, as the nitric oxide delivery molecule. S-nitrosocysteamine was covalently immobilized on the nanoparticle surface using small organic molecule linkers and carbodiimide coupling. Nanoparticle size, zeta potential, and morphology were determined using dynamic light scattering and scanning electron microscopy, respectively. Subsequent attachment of the S-nitrosothiol resulted in a nitric oxide release of 37.1 ± 1.1 nmol per milligram of nanoparticles under physiological conditions. This low concentration of nitric oxide reduced Escherichia coli culture growth by 31.8%, indicating that the nitric oxide donor was effective at releasing nitric oxide even after attachment to the nanoparticle surface. Combining the nitric oxide modified nanoparticles with tetracycline, a commonly prescribed antibiotic for E. coli infections, increased the effectiveness of the antibiotic by 87.8%, which allows for lower doses of antibiotics to be used in order to achieve the same effect. The functionalized nanoparticles were not cytotoxic to mouse fibroblasts.

  10. Surface-Directed Synthesis of Erbium-Doped Yttrium Oxide Nanoparticles within Organosilane Zeptoliter Containers

    PubMed Central

    2015-01-01

    We introduce an approach to synthesize rare earth oxide nanoparticles using high temperature without aggregation of the nanoparticles. The dispersity of the nanoparticles is controlled at the nanoscale by using small organosilane molds as reaction containers. Zeptoliter reaction vessels prepared from organosilane self-assembled monolayers (SAMs) were used for the surface-directed synthesis of rare earth oxide (REO) nanoparticles. Nanopores of octadecyltrichlorosilane were prepared on Si(111) using particle lithography with immersion steps. The nanopores were filled with a precursor solution of erbium and yttrium salts to confine the crystallization step to occur within individual zeptoliter-sized organosilane reaction vessels. Areas between the nanopores were separated by a matrix film of octadecyltrichlorosilane. With heating, the organosilane template was removed by calcination to generate a surface array of erbium-doped yttria nanoparticles. Nanoparticles synthesized by the surface-directed approach retain the periodic arrangement of the nanopores formed from mesoparticle masks. While bulk rare earth oxides can be readily prepared by solid state methods at high temperature (>900 °C), approaches for preparing REO nanoparticles are limited. Conventional wet chemistry methods are limited to low temperatures according to the boiling points of the solvents used for synthesis. To achieve crystallinity of REO nanoparticles requires steps for high-temperature processing of samples, which can cause self-aggregation and dispersity in sample diameters. The facile steps for particle lithography address the problems of aggregation and the requirement for high-temperature synthesis. PMID:25163977

  11. Surface-directed synthesis of erbium-doped yttrium oxide nanoparticles within organosilane zeptoliter containers.

    PubMed

    Englade-Franklin, Lauren E; Morrison, Gregory; Verberne-Sutton, Susan D; Francis, Asenath L; Chan, Julia Y; Garno, Jayne C

    2014-09-24

    We introduce an approach to synthesize rare earth oxide nanoparticles using high temperature without aggregation of the nanoparticles. The dispersity of the nanoparticles is controlled at the nanoscale by using small organosilane molds as reaction containers. Zeptoliter reaction vessels prepared from organosilane self-assembled monolayers (SAMs) were used for the surface-directed synthesis of rare earth oxide (REO) nanoparticles. Nanopores of octadecyltrichlorosilane were prepared on Si(111) using particle lithography with immersion steps. The nanopores were filled with a precursor solution of erbium and yttrium salts to confine the crystallization step to occur within individual zeptoliter-sized organosilane reaction vessels. Areas between the nanopores were separated by a matrix film of octadecyltrichlorosilane. With heating, the organosilane template was removed by calcination to generate a surface array of erbium-doped yttria nanoparticles. Nanoparticles synthesized by the surface-directed approach retain the periodic arrangement of the nanopores formed from mesoparticle masks. While bulk rare earth oxides can be readily prepared by solid state methods at high temperature (>900 °C), approaches for preparing REO nanoparticles are limited. Conventional wet chemistry methods are limited to low temperatures according to the boiling points of the solvents used for synthesis. To achieve crystallinity of REO nanoparticles requires steps for high-temperature processing of samples, which can cause self-aggregation and dispersity in sample diameters. The facile steps for particle lithography address the problems of aggregation and the requirement for high-temperature synthesis.

  12. Antibiofilm surface functionalization of catheters by magnesium fluoride nanoparticles

    PubMed Central

    Lellouche, Jonathan; Friedman, Alexandra; Lahmi, Roxanne; Gedanken, Aharon; Banin, Ehud

    2012-01-01

    The ability of bacteria to colonize catheters is a major cause of infection. In the current study, catheters were surface-modified with MgF2 nanoparticles (NPs) using a sonochemical synthesis protocol described previously. The one-step synthesis and coating procedure yielded a homogenous MgF2 NP layer on both the inside and outside of the catheter, as analyzed by high resolution scanning electron microscopy and energy dispersive spectroscopy. The coating thickness varied from approximately 750 nm to 1000 nm on the inner walls and from approximately 450 nm to approximately 580 nm for the outer wall. The coating consisted of spherical MgF2 NPs with an average diameter of approximately 25 nm. These MgF2 NP-modified catheters were investigated for their ability to restrict bacterial biofilm formation. Two bacterial strains most commonly associated with catheter infections, Escherichia coli and Staphylococcus aureus, were cultured in tryptic soy broth, artificial urine and human plasma on the modified catheters. The MgF2 NP-coated catheters were able to significantly reduce bacterial colonization for a period of 1 week compared to the uncoated control. Finally, the potential cytotoxicity of MgF2 NPs was also evaluated using human and mammalian cell lines and no significant reduction in the mitochondrial metabolism was observed. Taken together, our results indicate that the surface modification of catheters with MgF2 NPs can be effective in preventing bacterial colonization and can provide catheters with long-lasting self-sterilizing properties. PMID:22419866

  13. Air stable colloidal copper nanoparticles: Synthesis, characterization and their surface-enhanced Raman scattering properties

    NASA Astrophysics Data System (ADS)

    Ramani, Thekkathu; Leon Prasanth, K.; Sreedhar, Bojja

    2016-03-01

    Air stable colloidal copper nanoparticles are synthesized by a simple chemical reduction method using octadecylsilane as a reducing agent and octadecylamine as a stabilizing agent in toluene without any inert gas. The formation of nanosized copper was confirmed by its characteristic surface plasmon absorption peaks in UV-visible spectra. The transmission electron microscopic (TEM) images show that the resulting copper nanoparticles are distributed uniformly with a narrow size distribution. The X-ray diffraction (XRD) demonstrated that the obtained copper nanoparticles are single crystalline nanoparticles. Fourier transform infra-red (FT-IR) spectroscopic data suggested that the silane Si-H is responsible for the reduction of copper ions. And also the resulting colloidal copper nanoparticles exhibit large surface-enhanced Raman scattering (SERS) signals.

  14. Enhancing performance and surface antifouling properties of polysulfone ultrafiltration membranes with salicylate-alumoxane nanoparticles

    NASA Astrophysics Data System (ADS)

    Mokhtari, Samaneh; Rahimpour, Ahmad; Shamsabadi, Ahmad Arabi; Habibzadeh, Setareh; Soroush, Masoud

    2017-01-01

    To improve the hydrophilicity and antifouling properties of polysulfone (PS) ultrafiltration membranes, we studied the use of salicylate-alumoxane (SA) nanoparticles as a novel hydrophilic additive. The effects of SA nanoparticles on the membrane characteristics and performance were investigated in terms of membrane structure, permeation flux, solute rejection, hydrophilicity, and antifouling ability. The new mixed-matrix membranes (MMMs) possess asymmetric structures. They have smaller finger-like pores and smoother surfaces than the neat PS membranes. The embedment of SA nanoparticles in the polymer matrix and the improvement of surface hydrophilicity were investigated. Ultrafiltration experiments indicated that the pure-water flux of the new MMMs initially increases with SA nanoparticles loading followed by a decrease at high loadings. Higher BSA solution flux was achieved for the MMMs compared to the neat PS membranes. Membranes with 1 wt.% SA nanoparticles exhibit the highest flux recovery ratio of 87% and the lowest irreversible fouling of 13%.

  15. High-performance heterogeneous catalysis with surface-exposed stable metal nanoparticles.

    PubMed

    Huang, Ning; Xu, Yanhong; Jiang, Donglin

    2014-11-27

    Protection of metal nanoparticles from agglomeration is critical for their functions and applications. The conventional method for enhancing their stability is to cover them with passivation layers to prevent direct contact. However, the presence of a protective shell blocks exposure of the metal species to reactants, thereby significantly impeding the nanoparticles' utility as catalysts. Here, we report that metal nanoparticles can be prepared and used in a surface-exposed state that renders them inherently catalytically active. This strategy is realised by spatial confinement and electronic stabilisation with a dual-module mesoporous and microporous three-dimensional π-network in which surface-exposed nanoparticles are crystallised upon in situ reduction. The uncovered palladium nanoparticles serve as heterogeneous catalysts that are exceptionally active in water, catalyse unreactive aryl chlorides for straightforward carbon-carbon bond formation and are stable for repeated use in various types of cross couplings. Therefore, our results open new perspectives in developing practical heterogeneous catalysts.

  16. Catalytic Properties of Unsupported Palladium Nanoparticle Surfaces Capped with Small Organic Ligands

    PubMed Central

    Gavia, Diego J.

    2015-01-01

    This Minireview summarizes a variety of intriguing catalytic studies accomplished by employing unsupported, either solubilized or freely mobilized, and small organic ligand-capped palladium nanoparticles as catalysts. Small organic ligands are gaining more attention as nanoparticle stabilizers and alternates to larger organic supports, such as polymers and dendrimers, owing to their tremendous potential for a well-defined system with spatial control in surrounding environments of reactive surfaces. The nanoparticle catalysts are grouped depending on the type of surface stabilizers with reactive head groups, which include thiolate, phosphine, amine, and alkyl azide. Applications for the reactions such as hydrogenation, alkene isomerization, oxidation, and carbon-carbon cross coupling reactions are extensively discussed. The systems defined as “ligandless” Pd nanoparticle catalysts and solvent (e.g. ionic liquid)-stabilized Pd nanoparticle catalysts are not discussed in this review. PMID:25937846

  17. Regulating the surface plasmon resonance coupling between Au-nanoparticle and Au-film

    NASA Astrophysics Data System (ADS)

    Wang, Shuang; Li, Kewu; Zhang, Rui; Jing, Ning; Chen, Youhua; Chen, Yuanyuan; Wang, Zhibin

    2017-01-01

    In this paper, we report the coupling between the localized surface plasmon resonance (LSPR) of Au-nanoparticles and surface plasmon resonance (SPR) of the Au-film. According to the conditions for SPR excitation of the classical Kretschmann-Raether structure with 50nm Au thin film, the commonly used classes of spherical Au-nanoparticle is studied and optimized. We used the finite element analysis (COMSOL Multiphysics 5.0), to simulate the coupling. The results from calculation and simulation indicate that the resonant plasmonic coupling between Au-nanoparticles and Au-film could lead to a large field enhancement and thus improve SPR. We demonstrate that the resonant plasmonic coupling could be regulated by the size of nanoparticles, the distance between nanoparticles .

  18. Construction of boundary-surface-based Chinese female astronaut computational phantom and proton dose estimation

    PubMed Central

    Sun, Wenjuan; JIA, Xianghong; XIE, Tianwu; XU, Feng; LIU, Qian

    2013-01-01

    With the rapid development of China's space industry, the importance of radiation protection is increasingly prominent. To provide relevant dose data, we first developed the Visible Chinese Human adult Female (VCH-F) phantom, and performed further modifications to generate the VCH-F Astronaut (VCH-FA) phantom, incorporating statistical body characteristics data from the first batch of Chinese female astronauts as well as reference organ mass data from the International Commission on Radiological Protection (ICRP; both within 1% relative error). Based on cryosection images, the original phantom was constructed via Non-Uniform Rational B-Spline (NURBS) boundary surfaces to strengthen the deformability for fitting the body parameters of Chinese female astronauts. The VCH-FA phantom was voxelized at a resolution of 2 × 2 × 4 mm3for radioactive particle transport simulations from isotropic protons with energies of 5000–10 000 MeV in Monte Carlo N-Particle eXtended (MCNPX) code. To investigate discrepancies caused by anatomical variations and other factors, the obtained doses were compared with corresponding values from other phantoms and sex-averaged doses. Dose differences were observed among phantom calculation results, especially for effective dose with low-energy protons. Local skin thickness shifts the breast dose curve toward high energy, but has little impact on inner organs. Under a shielding layer, organ dose reduction is greater for skin than for other organs. The calculated skin dose per day closely approximates measurement data obtained in low-Earth orbit (LEO). PMID:23135158

  19. Electron-induced Ti-rich surface segregation on SrTiO3 nanoparticles.

    PubMed

    Lin, Yuyuan; Wen, Jianguo; Hu, Linhua; McCarthy, James A; Wang, Shichao; Poeppelmeier, Kenneth R; Marks, Laurence D

    2015-01-01

    Atomic surface structures of nanoparticles are of interest in catalysis and other fields. Aberration-corrected HREM facilitates direct imaging of the surfaces of nanoparticles. A remaining concern of surface imaging arises from beam damage. It is important to identify the intrinsic surface structures and the ones created by electron beam irradiation in TEM. In this study, we performed aberration-corrected HREM and EELS to demonstrate that TiO and bcc type Ti islands form due to intense electron irradiation. The formation of Ti-rich islands is in agreement with previous high temperature annealing experiments on the surfaces of SrTiO3 single crystals.

  20. Surface-enhanced Raman scattering enhancement factor distribution for nanoparticles of arbitrary shapes using surface integral equation method

    NASA Astrophysics Data System (ADS)

    Ying Huang, Shao; Wu, Bae-Ian; Foong, Shaohui

    2013-01-01

    Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT) surface integral equation method is applied for the first time to accurately estimate the surface-enhanced Raman scattering (SERS) enhancement factor distribution for arbitrary nanoparticles and nano-aggregates. It is the first time in literature that the distributions of SERS enhancement factors of nanoparticles of a large variety are reported. It is shown that not every SERS substrate exhibits a long-tail distribution as a dimer consisting of two spheres in close proximity. Generic methods are proposed to evaluate the performance of nanoparticles on SERS substrates. A cumulative distribution is proposed to examine the contributions of hot and warm spots around the nanoparticles. It is used to identify the importance of warm spots on a SERS substrate. A parameter q is proposed to describe the likelihood of a randomly positioned molecule that can be activated. This study provides guidance and insights for the optimization of SERS substrate fabrication techniques.

  1. nanoparticles

    NASA Astrophysics Data System (ADS)

    Andreu-Cabedo, Patricia; Mondragon, Rosa; Hernandez, Leonor; Martinez-Cuenca, Raul; Cabedo, Luis; Julia, J. Enrique

    2014-10-01

    Thermal energy storage (TES) is extremely important in concentrated solar power (CSP) plants since it represents the main difference and advantage of CSP plants with respect to other renewable energy sources such as wind, photovoltaic, etc. CSP represents a low-carbon emission renewable source of energy, and TES allows CSP plants to have energy availability and dispatchability using available industrial technologies. Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 500°C. Their main drawbacks are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve thermal properties of fluids is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. In this work, solar salt used in CSP plants (60% NaNO3 + 40% KNO3) was doped with silica nanoparticles at different solid mass concentrations (from 0.5% to 2%). Specific heat was measured by means of differential scanning calorimetry (DSC). A maximum increase of 25.03% was found at an optimal concentration of 1 wt.% of nanoparticles. The size distribution of nanoparticle clusters present in the salt at each concentration was evaluated by means of scanning electron microscopy (SEM) and image processing, as well as by means of dynamic light scattering (DLS). The cluster size and the specific surface available depended on the solid content, and a relationship between the specific heat increment and the available particle surface area was obtained. It was proved that the mechanism involved in the specific heat increment is based on a surface phenomenon. Stability of samples was tested for several thermal cycles and thermogravimetric analysis at high temperature was carried out, the samples being stable.

  2. Recent advances in synthesis and surface modification of superparamagnetic iron oxide nanoparticles with silica

    NASA Astrophysics Data System (ADS)

    Sodipo, Bashiru Kayode; Aziz, Azlan Abdul

    2016-10-01

    Research on synthesis of superparamagnetic iron oxide nanoparticles (SPION) and its surface modification for biomedical applications is of intense interest. Due to superparamagnetic property of SPION, the nanoparticles have large magnetic susceptibility, single magnetic domain and controllable magnetic behaviour. However, owing to easy agglomeration of SPION, surface modification of the magnetic particles with biocompatible materials such as silica nanoparticle has gained much attention in the last decade. In this review, we present recent advances in synthesis of SPION and various routes of producing silica coated SPION.

  3. Magnetic iron oxide nanoparticles: Synthesis and surface coating techniques for biomedical applications

    NASA Astrophysics Data System (ADS)

    Sun, Sheng-Nan; Wei, Chao; Zhu, Zan-Zan; Hou, Yang-Long; Subbu, S. Venkatraman; Xu, Zhi-Chuan

    2014-03-01

    Iron oxide nanoparticles are the most popular magnetic nanoparticles used in biomedical applications due to their low cost, low toxicity, and unique magnetic property. Magnetic iron oxide nanoparticles, including magnetite (Fe3O4) and maghemite (γ-Fe2O3), usually exhibit a superparamagnetic property as their size goes smaller than 20 nm, which are often denoted as superparamagnetic iron oxide nanoparticles (SPIONs) and utilized for drug delivery, diagnosis, therapy, and etc. This review article gives a brief introduction on magnetic iron oxide nanoparticles in terms of their fundamentals of magnetism, magnetic resonance imaging (MRI), and drug delivery, as well as the synthesis approaches, surface coating, and application examples from recent key literatures. Because the quality and surface chemistry play important roles in biomedical applications, our review focuses on the synthesis approaches and surface modifications of iron oxide nanoparticles. We aim to provide a detailed introduction to readers who are new to this field, helping them to choose suitable synthesis methods and to optimize the surface chemistry of iron oxide nanoparticles for their interests.

  4. Novel mechanochemical approaches for the synthesis of surface-functionalized metal nanoparticles

    NASA Astrophysics Data System (ADS)

    McMahon, Brandon Wade

    A novel mechanochemical milling technique, homogeneous media milling (HMM) is used to generate copious nanoparticles from a metal, parent media. Through the addition of surface-active capping agents, this method removes material from inch-scale parent material, via spallation and abrasion, resulting in gram-scale quantities of nanoparticles. Based on the principal of lowering a materials surface free energy through the chemisorption of a liquid or gaseous reagent, ductile and malleable metals can now be effectively and efficiently reduced to the nano scale. Acetonitrile was discovered to be an exceptionally good reagent for producing active aluminum nanoparticles, and oleic acid could be used to subsequently functionalize the particle surface, rendering them air-stable and hydrocarbon-fuel dispersible. In the interest of generality this process was used to make iron and copper nanoparticles via a similar method. It was discovered that acetonitrile decomposes on the surface of aluminum during HMM, resulting in the liberation of methyl group and hydrogen, which was detected as H2, CH4, and C2H6 in the headspace of the milling jar. Ammonia and methylamine, in gaseous form, are also reported to be highly effective surface-active milling agents for the production of aluminum nanoparticles. Methylamine, in particular, produced active, pyrophoric nanoparticles. For both acetonitrile and methylamine evidence of a stable surface adduct can be detected post milling using X-Ray photoelectron spectroscopy.

  5. Energetics and Dynamics of Fragmentation of Protonated Leucine Enkephalin from Time- and Energy-Resolved Surface-Induced Dissociation Studies

    SciTech Connect

    Laskin, Julia

    2006-07-01

    Dissociation of singly protonated leucine enkephalin (YGGFL) was studied using surface-induced dissociation in a Fourier transform ion cyclotron resonance mass spectrometer specially configured for studying ion activation by collisions with surfaces. The energetics and dynamics of seven primary dissociation channels were deduced from modeling the time- and energy-resolved fragmentation efficiency curves for different fragment ions using an RRKM-based approach developed at the Environmental Molecular Sciences Laboratory (EMSL).

  6. Preparation of transition metal nanoparticles and surfaces modified with (CO) polymers synthesized by RAFT

    DOEpatents

    McCormick, III, Charles L.; Lowe, Andrew B.; Sumerlin, Brent S.

    2006-10-25

    A new, facile, general one-phase method of generating thiol-functionalized transition metal nanoparticles and surface modified by (co)polymers synthesized by the RAFT method is described. The method includes the steps of forming a (co)polymer in aqueous solution using the RAFT methodology, forming a collidal transition metal precursor solution from an appropriate transition metal; adding the metal precursor solution or surface to the (co)polymer solution, adding a reducing agent into the solution to reduce the metal colloid in situ to produce the stabilized nanoparticles or surface, and isolating the stabilized nanoparticles or surface in a manner such that aggregation is minimized. The functionalized surfaces generated using these methods can further undergo planar surface modifications, such as fuctionalization with a variety of different chemical groups, expanding their utility and application.

  7. Preparation of transition metal nanoparticles and surfaces modified with (co)polymers synthesized by RAFT

    DOEpatents

    McCormick, III, Charles L.; Lowe, Andrew B [Hattiesburg, MS; Sumerlin, Brent S [Pittsburgh, PA

    2011-12-27

    A new, facile, general one-phase method of generating thiol-functionalized transition metal nanoparticles and surfaces modified by (co)polymers synthesized by the RAFT method is described. The method includes the steps of forming a (co)polymer in aqueous solution using the RAFT methodology, forming a colloidal transition metal precursor solution from an appropriate transition metal; adding the metal precursor solution or surface to the (co)polymer solution, adding a reducing agent into the solution to reduce the metal colloid in situ to produce the stabilized nanoparticles or surface, and isolating the stabilized nanoparticles or surface in a manner such that aggregation is minimized. The functionalized surfaces generated using these methods can further undergo planar surface modifications, such as functionalization with a variety of different chemical groups, expanding their utility and application.

  8. Preparation of transition metal nanoparticles and surfaces modified with (CO)polymers synthesized by RAFT

    DOEpatents

    McCormick, III., Charles L.; Lowe, Andrew B.; Sumerlin, Brent S.

    2006-11-21

    A new, facile, general one-phase method of generating thio-functionalized transition metal nanoparticles and surfaces modified by (co)polymers synthesized by the RAFT method is described. The method includes the stops of forming a (co)polymer in aqueous solution using the RAFT methodology, forming a colloidal transition metal precursor solution from an appropriate transition metal; adding the metal precursor solution or surface to the (co)polymer solution, adding a reducing agent into the solution to reduce the metal colloid in situ to produce the stabilized nanoparticles or surface, and isolating the stabilized nanoparticles or surface in a manner such that aggregation is minimized. The functionalized surfaces generated using these methods can further undergo planar surface modifications, such as functionalization with a variety of different chemical groups, expanding their utility and application.

  9. New electrocatalysts for unitized regenerative fuel cell: Pt-Ir alloy deposited on the proton exchange membrane surface by impregnation-reduction method.

    PubMed

    Wan, Chieh-Hao; Wu, Chun-Lin; Lin, Meng-Tsun; Shih, Chihhsiong

    2010-07-01

    In this paper, a modified technique to prepare Pt-Ir catalyst layer on the proton exchange membrane (PEM) surface using the impregnation-reduction (IR) method is proposed to improve the electrocatalytic activity as well as the life cycle of the bifunctional oxygen electrode (BOE). The resulted electrocatalysts were characterized by the Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Electron Probe Micro-Analysis (EPMA), and Transmission Electron Microscope (TEM). The electrocatalytic properties of the Pt-Ir layer on PEM surface for the oxygen reduction and water oxidation reactions as well as the life cycle of MEA were investigated. Experimental results showed that the Ir particles were dispersed densely in the platinum layer through the modified IR technique. The atomic ratio of Pt over Ir elements was 9:1, and the resulted thickness of the obtained Pt-Ir catalyst layer was about 1.0 microm. The Pt-Ir catalyst layer was composed of Pt layer doped with Ir nano-particles comprising nano Pt-Ir alloy phase. The large surface area of Ir core with Pt shell particles and the presence of nano Pt-Ir alloy phase led to a higher electrocatalytic activity of BOE. Due to the good binding between the Nafion membrane and the Pt-Ir alloy catalyst, as well as the composite structure of the resulted Pt-Ir, the life cycle of Unitized Regenerative Fuel Cell (URFC) is improved through this novel BOE.

  10. Surface functionalization of titanium dioxide nanoparticles: Photo-stability and reactive oxygen species (ROS) generation

    NASA Astrophysics Data System (ADS)

    Louis, Kacie M.

    Metal oxide nanoparticles are becoming increasingly prevalent in society for applications of sunscreens, cosmetics, paints, biomedical imaging, and photovoltaics. Due to the increased surface area to volume ratio of nanoparticles compared to bulk materials, it is important to know the health and safety impacts of these materials. One mechanism of toxicity of nominally "safe" materials such as TiO 2 is through the photocatalytic generation of reactive oxygen species (ROS). ROS production and ligand degradation can affect the bioavailability of these particles in aqueous organisms. We have investigated ROS generation by functionalized TiO2 nanoparticles and its influence on aggregation and bioavailability and toxicity to zebrafish embryos/larvae. For these studies we investigated anatase TiO2 nanoparticles. For application purposes and solution stability, the TiO2 nanoparticles were functionalized with a variety of ligands such as citrate, 3,4-dihydroxybenzaldehyde, and ascorbate. We quantitatively examined the amount of ROS produced in aqueous solution using fluorescent probes and see that more ROS is produced under UV light than in the dark control. Our measurements show that TiO2 toxicity reaches a maximum for nanoparticles with smaller diameters, and is correlated with surface area dependent changes in ROS generation. In an effort to reduce toxicity through control of the surface and surface ligands, we synthesized anatase nanoparticles of different sizes, functionalized them with different ligands, and examined the resulting ROS generation and ligand stability. Using a modular ligand containing a hydrophobic inner region and a hydrophilic outer region, we synthesized water-stable nanoparticles, via two different chemical reactions, having much-reduced ROS generation and thus reduced toxicity. These results suggest new strategies for making safer nanoparticles while still retaining their desired properties. We also examine the degradation of the different ligands

  11. Environment-mediated structure, surface redox activity and reactivity of ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Sayle, Thi X. T.; Molinari, Marco; Das, Soumen; Bhatta, Umananda M.; Möbus, Günter; Parker, Stephen C.; Seal, Sudipta; Sayle, Dean C.

    2013-06-01

    Nanomaterials, with potential application as bio-medicinal agents, exploit the chemical properties of a solid, with the ability to be transported (like a molecule) to a variety of bodily compartments. However, the chemical environment can change significantly the structure and hence properties of a nanomaterial. Accordingly, its surface reactivity is critically dependent upon the nature of the (biological) environment in which it resides. Here, we use Molecular Dynamics (MD) simulation, Density Functional Theory (DFT) and aberration corrected TEM to predict and rationalise differences in structure and hence surface reactivity of ceria nanoparticles in different environments. In particular we calculate reactivity `fingerprints' for unreduced and reduced ceria nanoparticles immersed in water and in vacuum. Our simulations predict higher activities of ceria nanoparticles, towards oxygen release, when immersed in water because the water quenches the coordinative unsaturation of surface ions. Conversely, in vacuum, surface ions relax into the body of the nanoparticle to relieve coordinative unsaturation, which increases the energy barriers associated with oxygen release. Our simulations also reveal that reduced ceria nanoparticles are more active towards surface oxygen release compared to unreduced nanoceria. In parallel, experiment is used to explore the activities of ceria nanoparticles that have suffered a change in environment. In particular, we compare the ability of ceria nanoparticles, in an aqueous environment, to scavenge superoxide radicals compared to the same batch of nanoparticles, which have first been dried and then rehydrated. The latter show a distinct reduction in activity, which we correlate to a change in the redox chemistry associated with moving between different environments. The reactivity of ceria nanoparticles is therefore not only environment dependent, but is also influenced by the transport pathway or history required to reach the particular

  12. Environment-mediated structure, surface redox activity and reactivity of ceria nanoparticles.

    PubMed

    Sayle, Thi X T; Molinari, Marco; Das, Soumen; Bhatta, Umananda M; Möbus, Günter; Parker, Stephen C; Seal, Sudipta; Sayle, Dean C

    2013-07-07

    Nanomaterials, with potential application as bio-medicinal agents, exploit the chemical properties of a solid, with the ability to be transported (like a molecule) to a variety of bodily compartments. However, the chemical environment can change significantly the structure and hence properties of a nanomaterial. Accordingly, its surface reactivity is critically dependent upon the nature of the (biological) environment in which it resides. Here, we use Molecular Dynamics (MD) simulation, Density Functional Theory (DFT) and aberration corrected TEM to predict and rationalise differences in structure and hence surface reactivity of ceria nanoparticles in different environments. In particular we calculate reactivity 'fingerprints' for unreduced and reduced ceria nanoparticles immersed in water and in vacuum. Our simulations predict higher activities of ceria nanoparticles, towards oxygen release, when immersed in water because the water quenches the coordinative unsaturation of surface ions. Conversely, in vacuum, surface ions relax into the body of the nanoparticle to relieve coordinative unsaturation, which increases the energy barriers associated with oxygen release. Our simulations also reveal that reduced ceria nanoparticles are more active towards surface oxygen release compared to unreduced nanoceria. In parallel, experiment is used to explore the activities of ceria nanoparticles that have suffered a change in environment. In particular, we compare the ability of ceria nanoparticles, in an aqueous environment, to scavenge superoxide radicals compared to the same batch of nanoparticles, which have first been dried and then rehydrated. The latter show a distinct reduction in activity, which we correlate to a change in the redox chemistry associated with moving between different environments. The reactivity of ceria nanoparticles is therefore not only environment dependent, but is also influenced by the transport pathway or history required to reach the particular

  13. Pattern formation in fatty acid-nanoparticle and lipid-nanoparticle mixed monolayers at water surface

    NASA Astrophysics Data System (ADS)

    Choudhuri, M.; Datta, A.; Iyengar, A. N. Sekar; Janaki, M. S.

    2015-06-01

    Dodecanethiol-capped gold nanoparticles (AuNPs) are self-organized in two different amphiphilic monolayers one of which is a single-tailed fatty acid Stearic acid (StA) and the other a double-tailed lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). In the StA-AuNP film the AuNPs self-organize to form an interconnected network of nanoclusters on compression while in the DMPC-AuNP film the AuNPs aggregate to form random, isolated clusters in the film. The long time evolution of the films at constant surface pressure reveals ring structures in the former and diffusion limited aggregates in the latter that with time evolve into an irregular porous maze of AuNPs in the DMPC film. The difference in structure of the AuNP patterns in the two films can be attributed to a difference in the lipophilic interactions between the NPs and the amphiphilic molecules. The mean square intensity fluctuations f(ln) calculated along a typical line for the 2D structures in both the films at initial and final stages of long time evolution reflect the structural changes in the films over time.

  14. Enhancing the magnetic anisotropy of maghemite nanoparticles via the surface coordination of molecular complexes

    PubMed Central

    Prado, Yoann; Daffé, Niéli; Michel, Aude; Georgelin, Thomas; Yaacoub, Nader; Grenèche, Jean-Marc; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe; Arrio, Marie-Anne; Cartier-dit-Moulin, Christophe; Sainctavit, Philippe; Fleury, Benoit; Dupuis, Vincent; Lisnard, Laurent; Fresnais, Jérôme

    2015-01-01

    Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest—and more attractive—systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm γ-Fe2O3 nanoparticles with the [CoII(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination—without nanoparticle aggregation and without complex dissociation—of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude. PMID:26634987

  15. Fluorescent silica nanoparticles with chemically reactive surface: Controlling spatial distribution in one-step synthesis.

    PubMed

    Vera, María L; Cánneva, Antonela; Huck-Iriart, Cristián; Requejo, Felix G; Gonzalez, Mónica C; Dell'Arciprete, María L; Calvo, Alejandra

    2017-06-15

    The encapsulation of fluorescent dyes inside silica nanoparticles is advantageous to improve their quality as probes. Inside the particle, the fluorophore is protected from the external conditions and its main emission parameters remains unchanged even in the presence of quenchers. On the other hand, the amine-functionalized nanoparticle surface enables a wide range of applications, as amino groups could be easily linked with different biomolecules for targeting purposes. This kind of nanoparticle is regularly synthesized by methods that employ templates, additional nanoparticle formation or multiple pathway process. However, a one-step synthesis will be an efficient approach in this sort of bifunctional hybrid nanoparticles. A co-condensation sol-gel synthesis of hybrid fluorescent silica nanoparticle where developed. The chemical and morphological characterization of the particles where investigated by DRIFTS, XPS, SEM and SAXS. The nanoparticle fluorescent properties were also assessed by excitation-emission matrices and time resolved experiments. We have developed a one-pot synthesis method that enables the simultaneous incorporation of functionalities, the fluorescent molecule and the amino group, by controlling co-condensation process. An exhaustive characterization allows the definition of the spatial distribution of the fluorescent probe, fluorescein isothiocyanate, inside the particle and reactive amino groups on the surface of the nanoparticle with diameter about 100nm.

  16. Non-lithographic SERS substrates: tailoring surface chemistry for Au nanoparticle cluster assembly.

    PubMed

    Adams, Sarah M; Campione, Salvatore; Caldwell, Joshua D; Bezares, Francisco J; Culbertson, James C; Capolino, Filippo; Ragan, Regina

    2012-07-23

    Near-field plasmonic coupling and local field enhancement in metal nanoarchitectures, such as arrangements of nanoparticle clusters, have application in many technologies from medical diagnostics, solar cells, to sensors. Although nanoparticle-based cluster assemblies have exhibited signal enhancements in surface-enhanced Raman scattering (SERS) sensors, it is challenging to achieve high reproducibility in SERS response using low-cost fabrication methods. Here an innovative method is developed for fabricating self-organized clusters of metal nanoparticles on diblock copolymer thin films as SERS-active structures. Monodisperse, colloidal gold nanoparticles are attached via a crosslinking reaction on self-organized chemically functionalized poly(methyl methacrylate) domains on polystyrene-block-poly(methyl methacrylate) templates. Thereby nanoparticle clusters with sub-10-nanometer interparticle spacing are achieved. Varying the molar concentration of functional chemical groups and crosslinking agent during the assembly process is found to affect the agglomeration of Au nanoparticles into clusters. Samples with a high surface coverage of nanoparticle cluster assemblies yield relative enhancement factors on the order of 10⁹ while simultaneously producing uniform signal enhancements in point-to-point measurements across each sample. High enhancement factors are associated with the narrow gap between nanoparticles assembled in clusters in full-wave electromagnetic simulations. Reusability for small-molecule detection is also demonstrated. Thus it is shown that the combination of high signal enhancement and reproducibility is achievable using a completely non-lithographic fabrication process, thereby producing SERS substrates having high performance at low cost.

  17. Development of fluorescent thermoresponsive nanoparticles for temperature monitoring on membrane surfaces.

    PubMed

    Santoro, S; Sebastian, V; Moro, A J; Portugal, C A M; Lima, J C; Coelhoso, I M; Crespo, J G; Mallada, R

    2017-01-15

    In this work, tris(phenantroline)ruthenium(II) chloride (Ru(phen)3) was immobilized in silica nanoparticles prepared according to the Stöber method. Efforts were devoted on the optimization of the nano-thermometer in terms of size, polydispersity, intensity of the emission and temperature sensitivity. In particular, the immobilization of the luminophore in an external thin shell made of silica grown in a second step on bare silica nanoparticles allowed producing fluorescent monodisperse silica nanoparticles (420±20nm). A systematic study was addressed to maximize the intensity of the emission of the fluorescent nanoparticles by adjusting the concentration of Ru(phen)3(2+) in the shell from 0.2 to 24wt.%, whereas the thickness of the shell is affected by the amount of silica precursor employed. The luminescent activity of the doped nanoparticles was found to be sensitive to the temperature. In fact, the intensity of the emission linearly decreased by increasing the temperature from 20°C to 65°C. The thermoresponsive nanoparticles were functionalized with long aliphatic chains in order to obtain hydrophobic nanoparticles. The developed nanoparticles were immobilized via dip-coating procedure on the surface of hydrophobic porous membranes, such as Polyvinylidene fluoride (PVDF) prepared via Non-Solvent Induced Phase Separation (NIPS), providing local information about the membrane surface temperature.

  18. Surface modification of permalloy (Ni80Fe20) nanoparticles for biomedical applications

    NASA Astrophysics Data System (ADS)

    Qin, Gaowu W.; Darain, Farzana; Wang, Hui; Dimitrov, Krassen

    2011-01-01

    We report a simple and novel method for surface biofunctionalization onto recently reported Ni80Fe20 permalloy nanoparticles ( 71 nm) and the immobilization of a model protein, IgG from human serum. The strategy of protein immobilization involved attachment of histidine-tagged streptavidin to the Ni80Fe20 nanoparticles via a non-covalent ligand binding followed by biotinylated human IgG binding on the nanoparticle surface using the specific high affinity avidin-biotin interaction. The biofunctionalization of Ni80Fe20 permalloy nanoparticles was confirmed by Fourier Transform InfraRed (FTIR) spectroscopy and protein denaturing gel electrophoresis (lithium dodecyl sulfate-polyacrylamide gel electrophoresis, LDS-PAGE). This protocol for surface functionalization of the novel nanometer-sized Ni80Fe20 permalloy particles with biological molecules could open diverse applications in disease diagnostics and drug delivery.

  19. Probing protein adsorption on a nanoparticle surface using second harmonic light scattering.

    PubMed

    Das, A; Chakrabarti, A; Das, P K

    2016-09-21

    A new application of second harmonic light scattering to probe protein physisorption on a gold nanoparticle surface in aqueous buffer is reported. The free energies of adsorption, the number of protein molecules adsorbed on the surface and the binding affinity of a moderate size protein, alcohol dehydrogenase (ADH), and a small protein, insulin, have been determined using the change in the second harmonic scattered light signal as a function of binding. Four different size gold nanoparticles from 15 to 60 nm were used to determine the effect of size on the free energy change, the affinity constant and the number of protein molecules adsorbed on the surface. All were shown to increase with an increase in size. The binding can be reversed by centrifugation, and the protein molecules can be desorbed quantitatively. The application of this method for studying thermodynamic parameters of weakly interacting biomolecules with nanoparticles for nanoparticle based diagnostic and therapeutic formulations is important.

  20. Preliminary investigations into surface molecularly imprinted nanoparticles for Helicobacter pylori eradication

    PubMed Central

    Han, Jiaying; Sun, Yinjing; Hou, Jiapeng; Wang, Yuyan; Liu, Yu; Xie, Cao; Lu, Weiyue; Pan, Jun

    2015-01-01

    This paper reports investigations into the preparation and characterization of surface molecularly imprinted nanoparticles (SMINs) designed to adhere to Helicobacter pylori (H. pylori). Imprinted nanoparticles were prepared by the inverse microemulsion polymerization method. A fraction of Lpp20, an outer membrane protein of H. pylori known as NQA, was chosen as template and modified with myristic acid to facilitate its localization on the surface of the nanoparticles. The interaction between these SMINs with the template NQA were evaluated using surface plasmon resonance (SPR), change in zeta potential and fluorescence polarization (FP). The results were highly consistent in demonstrating a preferential recognition of the template NQA for SMINs compared with the control nanoparticles. In vitro experiments also indicate that such SMINs are able to adhere to H. pylori and may be useful for H. pylori eradication. PMID:26713273

  1. Synthesis and surface functionalization of silica nanoparticles for nanomedicine

    PubMed Central

    Liberman, Alexander; Mendez, Natalie; Trogler, William C.; Kummel, Andrew C.

    2014-01-01

    There are a wide variety of silica nanoformulations being investigated for biomedical applications. Silica nanoparticles can be produced using a wide variety of synthetic techniques with precise control over their physical and chemical characteristics. Inorganic nanoformulations are often criticized or neglected for their poor tolerance; however, extensive studies into silica nanoparticle biodistributions and toxicology have shown that silica nanoparticles may be well tolerated, and in some case are excreted or are biodegradable. Robust synthetic techniques have allowed silica nanoparticles to be developed for applications such as biomedical imaging contrast agents, ablative therapy sensitizers, and drug delivery vehicles. This review explores the synthetic techniques used to create and modify an assortment of silica nanoformulations, as well as several of the diagnostic and therapeutic applications. PMID:25364083

  2. Segregation of Fischer-Tropsch reactants on cobalt nanoparticle surfaces.

    PubMed

    Lewis, E A; Le, D; Jewell, A D; Murphy, C J; Rahman, T S; Sykes, E C H

    2014-06-21

    Using scanning tunnelling microscopy, we have visualized the segregation of carbon monoxide and hydrogen, the two reactants in Fischer-Tropsch synthesis, on cobalt nanoparticles at catalytically relevant coverages. Density functional theory was used to interrogate the relevant energetics.

  3. Synthesis and surface functionalization of silica nanoparticles for nanomedicine

    NASA Astrophysics Data System (ADS)

    Liberman, Alexander; Mendez, Natalie; Trogler, William C.; Kummel, Andrew C.

    2014-09-01

    There are a wide variety of silica nanoformulations being investigated for biomedical applications. Silica nanoparticles can be produced using a wide variety of synthetic techniques with precise control over their physical and chemical characteristics. Inorganic nanoformulations are often criticized or neglected for their poor tolerance; however, extensive studies into silica nanoparticle biodistributions and toxicology have shown that silica nanoparticles may be well tolerated, and in some case are excreted or are biodegradable. Robust synthetic techniques have allowed silica nanoparticles to be developed for applications such as biomedical imaging contrast agents, ablative therapy sensitizers, and drug delivery vehicles. This review explores the synthetic techniques used to create and modify an assortment of silica nanoformulations, as well as several of the diagnostic and therapeutic applications.

  4. Active Tumor Permeation and Uptake of Surface Charge-Switchable Theranostic Nanoparticles for Imaging-Guided Photothermal/Chemo Combinatorial Therapy

    PubMed Central

    Hung, Chia-Chian; Huang, Wen-Chia; Lin, Yi-Wen; Yu, Ting-Wei; Chen, Hsin-Hung; Lin, Sung-Chyr; Chiang, Wen-Hsuan; Chiu, Hsin-Cheng

    2016-01-01

    To significantly promote tumor uptake and penetration of therapeutics, a nanovehicle system comprising poly(lactic-co-glycolic acid) (PLGA) as the hydrophobic cores coated with pH-responsive N-acetyl histidine modified D-α-tocopheryl polyethylene glycol succinate (NAcHis-TPGS) is developed in this work. The nanocarriers with switchable surface charges in response to tumor extracellular acidity (pHe) were capable of selectively co-delivering indocyanine green (ICG), a photothermal agent, and doxorubicin (DOX), a chemotherapy drug, to tumor sites. The in vitro cellular uptake of ICG/DOX-loaded nanoparticles by cancer cells and macrophages was significantly promoted in weak acidic environments due to the increased protonation of the NAcHis moieties. The results of in vivo and ex vivo biodistribution studies demonstrated that upon intravenous injection the theranostic nanoparticles were substantially accumulated in TRAMP-C1 solid tumor of tumor-bearing mice. Immunohistochemical examination of tumor sections confirmed the active permeation of the nanoparticles into deep tumor hypoxia due to their small size, pHe-induced near neutral surface, and the additional hitchhiking transport via tumor-associated macrophages. The prominent imaging-guided photothermal therapy of ICG/DOX-loaded nanoparticles after tumor accumulation induced extensive tumor tissue/vessel ablation, which further promoted their extravasation and DOX tumor permeation, thus effectively suppressing tumor growth. PMID:26909107

  5. Size control of silica nanoparticles and their surface treatment for fabrication of dental nanocomposites.

    PubMed

    Kim, J W; Kim, L U; Kim, C K

    2007-01-01

    Nearly monodispersed silica nanoparticles having a controlled size from 5 to 450 nm were synthesized via a sol-gel process, and then the optimum conditions for the surface treatment of the synthesized silica nanoparticles with a silane coupling agent (i.e., 3-methacryloxypropyltrimethoxysilane (gamma-MPS)) were explored to produce dental composites exhibiting enhanced adhesion and dispersion of silica nanoparticles in the resin matrix. The particle size was increased by increasing amounts of the catalyst (NH4OH) and silica precursor (tetraethylorthosilicate, TEOS) and by decreasing the amount of water in the reaction mixtures regardless of solvents used for the synthesis. The particle size prepared by using ethanol as a solvent was significantly larger than that prepared by using methanol as a solvent when the composition of the reaction mixture was fixed. The nanosized particles in the 5-25 nm range were aggregated. The amount of grafted gamma-MPS on the surface of the synthesized silica nanoparticles was dependent on the composition of the reaction mixture when an excess amount of gamma-MPS was used. When surface treatment was performed at optimum conditions found here, the amount of the grafted gamma-MPS per unit surface area of the silica nanoparticles was nearly the same regardless of the particle size. Dispersion of the silica particles in the resin matrix and interfacial adhesion between silica particles and resin matrix were enhanced when surface treated silica nanoparticles were used for preparing dental nanocomposites.

  6. Surface chemistry of cadmium sulfide magic-sized clusters: a window into ligand-nanoparticle interactions.

    PubMed

    Nevers, Douglas R; Williamson, Curtis B; Hanrath, Tobias; Robinson, Richard D

    2017-03-02

    Optoelectronic properties of nanoparticles are intimately coupled to the complex physiochemical interplay between the inorganic core and the organic ligand shell. Magic-sized clusters, which are predominately surface atoms, provide a promising avenue to clarify these critical surface interactions. Whereas these interactions impact the surface of both nanoparticles and magic-sized clusters, we show here that only clusters manifest a shift in the excitonic peak by up to 0.4 eV upon solvent or ligand treatment. These results highlight the utility of the clusters as a probe of ligand-surface interactions.

  7. Deposition of Cu Nanoparticles on the Surface of Metallic Aluminum

    NASA Astrophysics Data System (ADS)

    Lescinskis, A.; Katkevics, J.; Erts, D.; Viksna, A.

    2012-08-01

    Deposition of Cu particles by electrolysis at constant electrode potential and by internal electrolysis methods was investigated. The composition of deposited material was confirmed by optical and scanning electron microscope methods. Combination of electrolysis at constant electrode potential with internal electrolysis method was found most effective for fabrication of nanoparticle arrays. Single crystalline Cu particles are fabricated by internal electrolysis, while polycrystalline ones obtained by combined chronopotentiometric and internal electrolysis methods. The formation mechanism of Cu nanoparticles is described.

  8. Nanoparticle generation and interactions with surfaces in vacuum systems

    NASA Astrophysics Data System (ADS)

    Khopkar, Yashdeep

    Extreme ultraviolet lithography (EUVL) is the most likely candidate as the next generation technology beyond immersion lithography to be used in high volume manufacturing in the semiconductor industry. One of the most problematic areas in the development process is the fabrication of mask blanks used in EUVL. As the masks are reflective, there is a chance that any surface aberrations in the form of bumps or pits could be printed on the silicon wafers. There is a strict tolerance to the number density of such defects on the mask that can be used in the final printing process. Bumps on the surface could be formed when particles land on the mask blank surface during the deposition of multiple bi-layers of molybdenum and silicon. To identify, and possibly mitigate the source of particles during mask fabrication, SEMATECH investigated particle generation in the VEECO Nexus deposition tool. They found several sources of particles inside the tool such as valves. To quantify the particle generation from vacuum components, a test bench suitable for evaluating particle generation in the sub-100 nm particle size range was needed. The Nanoparticle test bench at SUNY Polytechnic Institute was developed as a sub-set of the overall SEMATECH suite of metrology tools used to identify and quantify sources of particles inside process tools that utilize these components in the semiconductor industry. Vacuum valves were tested using the test bench to investigate the number, size and possible sources of particles inside the valves. Ideal parameters of valve operation were also investigated using a 300-mm slit valve with the end goal of finding optimized parameters for minimum particle generation. SEMATECH also pursued the development of theoretical models of particle transport replicating the expected conditions in an ion beam deposition chamber assuming that the particles were generated. In the case of the ion beam deposition tool used in the mask blank fabrication process, the ion

  9. Luminescence Decay Dynamics and Trace Biomaterials Detection Potential of Surface-Functionalized Nanoparticles

    PubMed Central

    Cheng, Kwan H.; Aijmo, Jacob; Ma, Lun; Yao, Mingzhen; Zhang, Xing; Como, John; Hope-Weeks, Louisa J.; Huang, Juyang; Chen, Wei

    2009-01-01

    We have studied the luminescence decay and trace biomaterials detection potential of two surface-functionalized nanoparticles, poly(ethylene glycol) bis(carboxymethyl) ether-coated LaF3:Ce,Tb (~20 nm) and thioglycolic acid-coated ZnS/Mn (~5 nm). Upon UV excitation, these nanoparticles emitted fluorescence peaking at 540 and 597 nm, respectively, in solution. Fluorescence imaging revealed that these nanoparticles targeted the trace biomaterials from fingerprints that were deposited on various nonporous solid substrates. Highly ordered, microscopic sweat pores within the friction ridges of the fingerprints were labeled with good spatial resolutions by the nanoparticles on aluminum and polymethylpentene substrates, but not on glass or quartz. In solution, these nanoparticles exhibited multicomponent fluorescence decays of resolved lifetimes ranging from nano-to microseconds and of average lifetimes of ~24 and 130 µs for the coated LaF3:Ce,Tb and ZnS:Mn, respectively. The long microsecond-decay components are associated with the emitters at or near the nanocrystal core surface that are sensitive to the size, surface-functionalization, and solvent exposure of the nanoparticles. When the nanoparticles were bound to the surface of a solid substrate and in the dried state, a decrease in the microsecond decay lifetimes was observed, indicative of a change in the coating environment of the nanocrystal surface upon binding and solvent removal. The average decay lifetimes for the surface-bound ZnS:Mn in the dried state were ~60, 30, and 11 µs on quartz, aluminum, and polymethylpentene, respectively. These values were still 2 orders of magnitude longer than the typical fluorescence decay background of most substrates (e.g., ~0.36 µs for polymethylpentene) in trace forensic evidence detections. We conclude that coated ZnS: Mn nanoparticles hold great promise as a nontoxic labeling agent for ultrasensitive, time-gated, trace evidence detections in nanoforensic applications

  10. Inexpensive approach for production of high-surface-area silica nanoparticles from rice hulls biomass.

    PubMed

    Palanivelu, Rajagounder; Padmanaban, Periasamy; Sutha, Sadhasivam; Rajendran, Venkatachalam

    2014-12-01

    In this study, we prepared amorphous and crystalline silica nanoparticles from rice hulls biomass using pyrolysis technique at different processing temperatures such as 923, 973, 1023, 1073, 1123 and 1173 K. X-ray fluorescence studies show that the purity of all the synthesised silica nanoparticles is in the range of 98-99.7%. X-ray diffraction studies reveal that amorphous silica nanoparticles are formed at 923-1023 K, whereas crystalline particles at 1073-1173 K. Morphology and microstructure of silica nanoparticles are studied by scanning electron and transmission electron microscopes. Silica nanoparticles obtained at different processing temperatures yield particle size in the range of 6-100 nm. Chemical composition and surface functionalities of the particles are examined by energy-dispersive X-ray diffraction and Fourier transform infrared spectroscopic studies. The developed method effectively uses rice hulls biomass as a green natural source in the synthesis of amorphous and crystalline silica nanoparticles with high-specific surface area. The optimised processing temperature (1023 K) enables amorphous silica nanoparticles to have high-specific surface area of 538 m(2)g(-1).

  11. Enhanced optical second harmonic generation in hybrid polymer nanoassemblies based on coupled surface plasmon resonance of a gold nanoparticle array

    NASA Astrophysics Data System (ADS)

    Ishifuji, Miki; Mitsuishi, Masaya; Miyashita, Tokuji

    2006-07-01

    Effective utilization of coupled surface plasmon resonance from gold nanoparticles was demonstrated experimentally for optoelectronic applications based on second-order nonlinear optics. Hybrid polymer nanoassemblies were constructed by manipulating gold nanoparticle arrays with nonlinear optical active polymer nanosheets to investigate the second harmonic generation. The gold nanoparticle arrays were assembled on heterodeposited polymer nanosheets. The second harmonic light intensity was enhanced by a factor of 8. The observed enhancement was attributed to coupling of surface plasmons between two adjacent gold nanoparticles, thereby enhancing the surface electromagnetic field around the nanoparticles at the fundamental light wavelength (1064nm).

  12. Measuring binding kinetics of aromatic thiolated molecules with nanoparticles via surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Devetter, Brent M.; Mukherjee, Prabuddha; Murphy, Catherine J.; Bhargava, Rohit

    2015-05-01

    Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this study, we report the development of surface-enhanced Raman spectroscopy (SERS) as a method to monitor the kinetics of gold-thiolate bond formation on colloidal gold nanoparticles. A theoretical model combining SERS enhancement with the Beer-Lambert law is proposed to explain ensemble scattering and absorption effects in colloids during chemisorption. In order to maximize biological relevance and signal reproducibility, experiments used to validate the model focused on maintaining nanoparticle stability after the addition of water-soluble aromatic thiolated molecules. Our results indicate that ligand exchange on gold nanoparticles follow a first-order Langmuir adsorption model with rate constants on the order of 0.01 min-1. This study demonstrates an experimental spectroscopic method and theoretical model for monitoring binding kinetics that may prove useful for designing novel probes.Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this

  13. Graphene oxide-Fe{sub 3}O{sub 4} nanoparticle composite with high transverse proton relaxivity value for magnetic resonance imaging

    SciTech Connect

    Venkatesha, N.; Srivastava, Chandan; Poojar, Pavan; Geethanath, Sairam; Qurishi, Yasrib

    2015-04-21

    The potential of graphene oxide–Fe{sub 3}O{sub 4} nanoparticle (GO-Fe{sub 3}O{sub 4}) composite as an image contrast enhancing material in magnetic resonance imaging has been investigated. Proton relaxivity values were obtained in three different homogeneous dispersions of GO-Fe{sub 3}O{sub 4} composites synthesized by precipitating Fe{sub 3}O{sub 4} nanoparticles in three different reaction mixtures containing 0.01 g, 0.1 g, and 0.2 g of graphene oxide. A noticeable difference in proton relaxivity values was observed between the three cases. A comprehensive structural and magnetic characterization revealed discrete differences in the extent of reduction of the graphene oxide and spacing between the graphene oxide sheets in the three composites. The GO-Fe{sub 3}O{sub 4} composite framework that contained graphene oxide with least extent of reduction of the carboxyl groups and largest spacing between the graphene oxide sheets provided the optimum structure for yielding a very high transverse proton relaxivity value. It was found that the GO-Fe{sub 3}O{sub 4} composites possessed good biocompatibility with normal cell lines, whereas they exhibited considerable toxicity towards breast cancer cells.

  14. Sorption of untreated and humic acid coated silver nanoparticles to environmental and model surfaces

    NASA Astrophysics Data System (ADS)

    Abraham, Priya M.; Baumann, Thomas; Schaumann, Gabriele E.

    2014-05-01

    The environmental fate of engineered nanoparticles is controlled their colloidal stability and their interaction with different environmental surfaces. Little is known about sorption of nanoparticles to environmental surfaces under quasi-equilibrium conditions. Nevertheless, sorption isotherms may also be a valuable means of studying nanoparticle-sorbent interactions. We investigated sorption of engineered silver nanoparticles (nAg) from stable and unstable suspensions in presence and absence of natural organic matter (NOM) to model surfaces (sorbents with specific chemical functional groups) and environmental materials (plant leaves and sand). Morphology and nanomechanical parameters of the surfaces covered with nanoparticles were assessed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The sorption of nAg from stable suspensions and in absence of NOM was non-linear and best described by a Langmuir model, where Langmuir coefficients varied with sorbent surface chemistry, which suggests monolayer sorption (Abraham et al. 2013). For nAg sorption from an unstable suspension, the sorption isotherms did not follow any classical sorption models, suggesting interplay between aggregation and sorption (Abraham et al. 2013). In contrast, sorption was strongly suppressed and exhibited linear sorption isotherms in the presence of NOM. The difference in sorption isotherms suggests predominance of different sorption mechanisms depending on presence or absence of NOM, which can be only partly explained by the NOM coating alone. On the basis of the current results, a partial release of NOM coating for sorption of certain surfaces cannot be excluded. The validity of the Langmuir isotherm suggests monolayer sorption, which can be explained by the blocking effect due to electrostatic repulsion of individual nanoparticles. In unstable suspensions, aggregates are instead formed in suspension, formed on the surface and then sorbed, or formed in both ways

  15. Catechol-functionalized adhesive polymer nanoparticles for controlled local release of bone morphogenetic protein-2 from titanium surface.

    PubMed

    Lee, Hong Jae; Koo, Ahn Na; Lee, Suk Won; Lee, Myung Hyun; Lee, Sang Cheon

    2013-09-10

    We report on a novel surface functionalization approach to equip the titanium (Ti) surfaces with osteogenic properties. A key feature of the approach is the treatment of the Ti surfaces with Ti-adhesive nanoparticles that can stably load and controllably release bone morphogenetic protein-2 (BMP-2). Ti-adhesive nanoparticles were prepared by self-assembly of a catechol-functionalized poly(amino acid) diblock copolymer, catechol-poly(L-aspartic acid)-b-poly(L-phenylalanine) (Cat-PAsp-PPhe). The nanoparticles consist of Ti-adhesive peripheral catechol groups, anionic PAsp shells, and PPhe inner cores. Field-emission scanning electron microscopy (Fe-SEM) images showed that the Ti-adhesive nanoparticles could be uniformly immobilized on Ti surfaces. X-ray photoelectron spectroscopy (XPS) confirmed the successful anchoring of nanoparticles onto Ti surfaces. After surface immobilization of the nanoparticles, the static water contact angle of the Ti substrate decreased from 75.3° to 50.0° or 36.4°, depending on the surface nanoparticle. Fluorescence microscopic analysis showed that BMP-2 could be effectively incorporated onto the Ti surface with adhesive nanoparticles. BMP-2 was controllably released for up to 40 days. The Ti substrate functionalized with BMP-2-incorporated nanoparticles significantly promoted attachment, proliferation, spreading, and alkaline phosphatase (ALP) activity of human adipose-derived stem cell (hADSC). The catechol-functionalized adhesive nanoparticles may be applied to various medical devices to create surfaces for improved performance.

  16. Surface protonation at the rutile (110) interface: explicit incorporation of solvation structure within the refined MUSIC model framework.

    PubMed

    Machesky, Michael L; Predota, Milan; Wesolowski, David J; Vlcek, Lukas; Cummings, Peter T; Rosenqvist, Jörgen; Ridley, Moira K; Kubicki, James D; Bandura, Andrei V; Kumar, Nitin; Sofo, Jorge O

    2008-11-04

    The detailed solvation structure at the (110) surface of rutile (alpha-TiO2) in contact with bulk liquid water has been obtained primarily from experimentally verified classical molecular dynamics (CMD) simulations of the ab initio-optimized surface in contact with SPC/E water. The results are used to explicitly quantify H-bonding interactions, which are then used within the refined MUSIC model framework to predict surface oxygen protonation constants. Quantum mechanical molecular dynamics (QMD) simulations in the presence of freely dissociable water molecules produced H-bond distributions around deprotonated surface oxygens very similar to those obtained by CMD with nondissociable SPC/E water, thereby confirming that the less computationally intensive CMD simulations provide accurate H-bond information. Utilizing this H-bond information within the refined MUSIC model, along with manually adjusted Ti-O surface bond lengths that are nonetheless within 0.05 A of those obtained from static density functional theory (DFT) calculations and measured in X-ray reflectivity experiments (as well as bulk crystal values), give surface protonation constants that result in a calculated zero net proton charge pH value (pHznpc) at 25 degrees C that agrees quantitatively with the experimentally determined value (5.4+/-0.2) for a specific rutile powder dominated by the (110) crystal face. Moreover, the predicted pHznpc values agree to within 0.1 pH unit with those measured at all temperatures between 10 and 250 degrees C. A slightly smaller manual adjustment of the DFT-derived Ti-O surface bond lengths was sufficient to bring the predicted pHznpcvalue of the rutile (110) surface at 25 degrees C into quantitative agreement with the experimental value (4.8+/-0.3) obtained from a polished and annealed rutile (110) single crystal surface in contact with dilute sodium nitrate solutions using second harmonic generation (SHG) intensity measurements as a function of ionic strength

  17. Surface Protonation at the Rutile (110) Interface: Explicit Incorporation of Solvation Structure within the Refined MUSIC Model Framework

    SciTech Connect

    Machesky, Michael L.; Predota, M.; Wesolowski, David J

    2008-11-01

    The detailed solvation structure at the (110) surface of rutile ({alpha}-TiO{sub 2}) in contact with bulk liquid water has been obtained primarily from experimentally verified classical molecular dynamics (CMD) simulations of the ab initio-optimized surface in contact with SPC/E water. The results are used to explicitly quantify H-bonding interactions, which are then used within the refined MUSIC model framework to predict surface oxygen protonation constants. Quantum mechanical molecular dynamics (QMD) simulations in the presence of freely dissociable water molecules produced H-bond distributions around deprotonated surface oxygens very similar to those obtained by CMD with nondissociable SPC/E water, thereby confirming that the less computationally intensive CMD simulations provide accurate H-bond information. Utilizing this H-bond information within the refined MUSIC model, along with manually adjusted Ti-O surface bond lengths that are nonetheless within 0.05 {angstrom} of those obtained from static density functional theory (DFT) calculations and measured in X-ray reflectivity experiments (as well as bulk crystal values), give surface protonation constants that result in a calculated zero net proton charge pH value (pHznpc) at 25 C that agrees quantitatively with the experimentally determined value (5.4 {+-} 0.2) for a specific rutile powder dominated by the (110) crystal face. Moreover, the predicted pH{sub znpc} values agree to within 0.1 pH unit with those measured at all temperatures between 10 and 250 C. A slightly smaller manual adjustment of the DFT-derived Ti-O surface bond lengths was sufficient to bring the predicted pH{sub znpc} value of the rutile (110) surface at 25 C into quantitative agreement with the experimental value (4.8 {+-} 0.3) obtained from a polished and annealed rutile (110) single crystal surface in contact with dilute sodium nitrate solutions using second harmonic generation (SHG) intensity measurements as a function of ionic

  18. Directed assembly of Au nanoparticles onto planar surfaces via multiple hydrogen bonds.

    PubMed

    Zirbs, Ronald; Kienberger, Ferry; Hinterdorfer, Peter; Binder, Wolfgang H

    2005-08-30

    We have developed a new concept to effect nanoparticle binding on surfaces by use of directed, specific molecular interactions. Hamilton-type receptors displaying a binding strength of approximately 10(5) M(-)(1) were covalently fixed onto self-assembled monolayers via Sharpless-type "click" reactions, thus representing an efficient method to control the densities of ligands over a range from low to complete surface coverage. Au nanoparticles covered with the matching barbituric acid receptors bound with high selectivity onto this surface by a self-assembly process mediated by multiple hydrogen bonds. The binding process was investigated with atomic force microscopy. Moderate control of particle density was achieved by controlling the receptor density on the self-assembled monolayer surface. The method opens a general approach to nanoparticle and small object binding onto patterned surfaces.

  19. Examining metal nanoparticle surface chemistry using hollow-core, photonic-crystal, fiber-assisted SERS.

    PubMed

    Eftekhari, Fatemeh; Lee, Anna; Kumacheva, Eugenia; Helmy, Amr S

    2012-02-15

    In this Letter, we demonstrate the efficacy of hollow core photonic crystal fibers (HCPCFs) as a surface-enhanced Raman spectroscopy (SERS) platform for investigating the ligand exchange process on the surface of gold nanoparticles. Raman measurements carried out using this platform show the capability to monitor minute amounts of surface ligands on gold nanoparticles used as an SERS substrate. The SERS signal from an HCPCF exhibits a tenfold enhancement compared to that in a direct sampling scheme using a cuvette. Using exchange of cytotoxic cetyltrimethylammonium bromide with α-methoxy-ω-mercaptopoly(ethylene glycol) on the surface of gold nanorods as an exemplary system, we show the feasibility of using HCPCF SERS to monitor the change in surface chemistry of nanoparticles.

  20. Cytotoxicity of surface-functionalized silicon and germanium nanoparticles: the dominant role of surface charges.

    PubMed

    Bhattacharjee, Sourav; Rietjens, Ivonne M C M; Singh, Mani P; Atkins, Tonya M; Purkait, Tapas K; Xu, Zejing; Regli, Sarah; Shukaliak, Amber; Clark, Rhett J; Mitchell, Brian S; Alink, Gerrit M; Marcelis, Antonius T M; Fink, Mark J; Veinot, Jonathan G C; Kauzlarich, Susan M; Zuilhof, Han

    2013-06-07

    Although it is frequently hypothesized that surface (like surface charge) and physical characteristics (like particle size) play important roles in cellular interactions of nanoparticles (NPs), a systematic study probing this issue is missing. Hence, a comparative cytotoxicity study, quantifying nine different cellular endpoints, was performed with a broad series of monodisperse, well characterized silicon (Si) and germanium (Ge) NPs with various surface functionalizations. Human colonic adenocarcinoma Caco-2 and rat alveolar macrophage NR8383 cells were used to clarify the toxicity of this series of NPs. The surface coatings on the NPs appeared to dominate the cytotoxicity: the cationic NPs exhibited cytotoxicity, whereas the carboxylic acid-terminated and hydrophilic PEG- or dextran-terminated NPs did not. Within the cationic Si NPs, smaller Si NPs were more toxic than bigger ones. Manganese-doped (1% Mn) Si NPs did not show any added toxicity, which favors their further development for bioimaging. Iron-doped (1% Fe) Si NPs showed some added toxicity, which may be due to the leaching of Fe(3+) ions from the core. A silica coating seemed to impart toxicity, in line with the reported toxicity of silica. Intracellular mitochondria seem to be the target for the toxic NPs since a dose-, surface charge- and size-dependent imbalance of the mitochondrial membrane potential was observed. Such an imbalance led to a series of other cellular events for cationic NPs, like decreased mitochondrial membrane potential (ΔΨm) and ATP production, induction of ROS generation, increased cytoplasmic Ca(2+) content, production of TNF-α and enhanced caspase-3 activity. Taken together, the results explain the toxicity of Si NPs/Ge NPs largely by their surface characteristics, provide insight into the mode of action underlying the observed cytotoxicity, and give directions on synthesizing biocompatible Si and Ge NPs, as this is crucial for bioimaging and other applications in for

  1. Correlations between neutrons and protons near the Fermi surface and Qα of superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Liu, Min; Wu, Xizhen; Meng, Jie

    2016-01-01

    The shell corrections and shell gaps in nuclei are systematically studied with the latest Weizsäcker-Skyrme (WS4) mass model. We find that most of asymmetric nuclei with (sub)shell closures locate along the shell stability line (SSL), N =1.37 Z +13.5 , which might be due to a strong correlation between neutrons and protons near the Fermi surface. The double magicity of nuclei 46Si and 78Ni is predicted according to the corresponding shell gaps, shell corrections, and nuclear deformations. The unmeasured superheavy nuclei, 296118 and 298120, with relatively large shell gaps and shell corrections, also locate along the SSL, whereas the traditional magic nucleus 298Fl evidently deviates from the line. The α -decay energies of superheavy nuclei with Z =113 -126 are simultaneously investigated by using the WS4 model together with the radial basis function corrections. For superheavy nuclei with large shell corrections, the smallest α -decay energy for elements Z =116 , 117, and 118 in their isotope chains locates at N =178 rather than 184.

  2. Carbon monoxide protonation in condensed phases and bonding to surface superacidic Brønsted centers.

    PubMed

    Stoyanov, Evgenii S; Malykhin, Sergei E

    2016-02-14

    Using infrared (IR) spectroscopy and density functional theory (DFT) calculations, interaction of CO with the strongest known pure Brønsted carborane superacids, H(CHB11Hal11) (Hal = F, Cl), was studied. CO readily interacted at room temperature with H(CHB11F11) acid, forming a mixture of bulk salts of formyl and isoformyl cations, which were in equilibrium An(-)H(+)CO COH(+)An(-). The bonding of CO to the surface Brønsted centers of the weaker acid, H(CHB11Cl11), resulted in breaking of the bridged H-bonds of the acid polymers without proton transfer (PT) to CO. The binding occurred via the C atom (blue shift ΔνCO up to +155-167 cm(-1), without PT) or via O atom (red shift ΔνCO up to -110 cm(-1), without PT) always simultaneously, regardless of whether H(+) is transferred to CO. IR spectra of all species were interpreted by B3LYP/cc-pVQZ calculations of the simple models, which adequately mimic the ability of carborane acids to form LH(+)CO, LH(+)CO, COH(+)L, and COH(+)L compounds (L = bases). The CO bond in all compounds was triple. Acidic strength of the Brønsted centers of commonly used acid catalysts, even so-called superacidic catalysts, is not sufficient for the formation of the compounds studied.

  3. Gelatin-stabilized copper nanoparticles: Synthesis, morphology, and their surface-enhanced Raman scattering properties

    NASA Astrophysics Data System (ADS)

    Zhang, Danhui; Yang, Houbo

    2013-04-01

    Gelatin-stabilized spherical-shaped copper nanoparticles are synthesized by a simple chemical reaction. The synthesis is performed by the reduction of copper (II) salt with hydrazine in aqueous solution under atmospheric air in the presence of gelatin as capping agent. Advantages of the synthetic method include its production of water dispersible copper nanoparticles at room temperature under no inert atmosphere and making the synthesis more environmental friendly. The synthesized copper nanoparticles are investigated by UV-vis spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and transmission electron microscopy (TEM). The results demonstrate that the amount of gelatin is important for the formation of the copper nanoparticles. The resulting colloidal copper nanoparticles exhibit large surface-enhanced Raman scattering (SERS) signals.

  4. Synthesis of surface bound silver nanoparticles on cellulose fibers using lignin as multi-functional agent.

    PubMed

    Hu, Sixiao; Hsieh, You-Lo

    2015-10-20

    Lignin has proven to be highly effective "green" multi-functional binding, complexing and reducing agents for silver cations as well as capping agents for the synthesis of silver nanoparticles on ultra-fine cellulose fibrous membranes. Silver nanoparticles could be synthesized in 10min to be densely distributed and stably bound on the cellulose fiber surfaces at up to 2.9% in mass. Silver nanoparticle increased in sizes from 5 to 100nm and became more polydispersed in size distribution on larger fibers and with longer synthesis time. These cellulose fiber bound silver nanoparticles did not agglomerate under elevated temperatures and showed improved thermal stability. The presence of alkali lignin conferred moderate UV absorbing ability in both UV-B and UV-C regions whereas the bound silver nanoparticles exhibited excellent antibacterial activities toward Escherichia coli.

  5. Surface enhanced Raman scattering, antibacterial and antifungal active triangular gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Smitha, S. L.; Gopchandran, K. G.

    2013-02-01

    Shape controlled syntheses of gold nanoparticles have attracted a great deal of attention as their optical, electronic, magnetic and biological properties are strongly dependent on the size and shape of the particles. Here is a report on the surface enhanced Raman scattering (SERS) activity of Cinnamomum zeylanicum leaf broth reduced gold nanoparticles consisting of triangular and spherical like particles, using 2-aminothiophenol (2-ATP) and crystal violet (CV) as probe molecules. Nanoparticles prepared with a minimum leaf broth concentration, having a greater number of triangular like particles exhibit a SERS activity of the order of 107. The synthesized nanoparticles exhibit efficient antibacterial activity against the tested gram negative bacterium Escherichia coli and gram positive bacterium Staphylococcus aureus. Investigations on the antifungal activity of the synthesized nanoparticles against Aspergillus niger and Fusarium oxysporum positive is also discussed.

  6. Surface modification of nanoparticles enables selective evasion of phagocytic clearance by distinct macrophage phenotypes

    NASA Astrophysics Data System (ADS)

    Qie, Yaqing; Yuan, Hengfeng; von Roemeling, Christina A.; Chen, Yuanxin; Liu, Xiujie; Shih, Kevin D.; Knight, Joshua A.; Tun, Han W.; Wharen, Robert E.; Jiang, Wen; Kim, Betty Y. S.

    2016-05-01

    Nanomedicine is a burgeoning industry but an understanding of the interaction of nanomaterials with the immune system is critical for clinical translation. Macrophages play a fundamental role in the immune system by engulfing foreign particulates such as nanoparticles. When activated, macrophages form distinct phenotypic populations with unique immune functions, however the mechanism by which these polarized macrophages react to nanoparticles is unclear. Furthermore, strategies to selectively evade activated macrophage subpopulations are lacking. Here we demonstrate that stimulated macrophages possess higher phagocytic activities and that classically activated (M1) macrophages exhibit greater phagocytic capacity than alternatively activated (M2) macrophages. We show that modification of nanoparticles with polyethylene-glycol results in decreased clearance by all macrophage phenotypes, but importantly, coating nanoparticles with CD47 preferentially lowers phagocytic activity by the M1 phenotype. These results suggest that bio-inspired nanoparticle surface design may enable evasion of specific components of the immune system and provide a rational approach for developing immune tolerant nanomedicines.

  7. Surface spin-glass in cobalt ferrite nanoparticles dispersed in silica matrix

    NASA Astrophysics Data System (ADS)

    Zeb, F.; Sarwer, W.; Nadeem, K.; Kamran, M.; Mumtaz, M.; Krenn, H.; Letofsky-Papst, I.

    2016-06-01

    Surface effects in cobalt ferrite (CoFe2O4) nanoparticles dispersed in a silica (SiO2) matrix were studied by using AC and DC magnetization. Nanoparticles with different concentration of SiO2 were synthesized by using sol-gel method. Average crystallite size lies in the range 25-34 nm for different SiO2 concentration. TEM image showed that particles are spherical and elongated in shape. Nanoparticles with higher concentration of SiO2 exhibit two peaks in the out-of-phase ac-susceptibility. First peak lies in the high temperature regime and corresponds to average blocking temperature of the nanoparticles. Second peak lies in the low temperature regime and is attributed to surface spin-glass freezing in these nanoparticles. Low temperature peak showed SiO2 concentration dependence and was vanished for large uncoated nanoparticles. The frequency dependence of the AC-susceptibility of low temperature peak was fitted with dynamic scaling law which ensures the presence of spin-glass behavior. With increasing applied DC field, the low temperature peak showed less shift as compared to blocking peak, broaden, and decreased in magnitude which also signifies its identity as spin-glass peak for smaller nanoparticles. M-H loops showed the presence of more surface disorder in nanoparticles dispersed in 60% SiO2 matrix. All these measurements revealed that surface effects become strengthen with increasing SiO2 matrix concentration and surface spins freeze in to spin-glass state at low temperatures.

  8. Effect of surface structure on the dynamic magnetic response in Ni-Zn ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Poddar, P.; Swaminathan, R.

    2005-03-01

    Surface magnetic spin structure plays a dominant role in determining the effective anisotropy in magnetic nanostructures. To probe the anisotropy in nanoparticle systems, we have developed an RF transverse susceptibility technique based on a resonant tunnel-diode oscillator (TDO). Transverse susceptibility measurements were performed on NiZn ferrite nanoparticles (synthesized using a RF induction plasma torch) over a wide temperature range (10K to 300K) and magnetic fields (-10kOe to 10kOe). As-synthesized polydisperse nanoparticles showed broad peaks at the characteristic anisotropy fields that are attributed to the presence of both the (100) and (111) surfaces and their respective surface anisotropy contributions. The peak positions and heights were found to be sensitive to the particle size dispersion and surface magnetic spin structure. The polydisperse particles were coated with oleic acid and size-selected using ultra-centrifugation. The anisotropy peaks are conspicuously absent in the size-selected smaller nanoparticles. This is understood within the framework of a surface structure model based on isotropic canted triangular spin structures on the dominant (111) surfaces in the smallest nanoparticles. Work at USF supported by NSF through Grant No. CTS-0408933. RS and MEM thank the Institute of Complex Engineering Systems (ICES), CMU for support.

  9. Does seed size and surface anatomy play role in combating phytotoxicity of nanoparticles?

    PubMed

    Jain, Navin; Bhargava, Arpit; Pareek, Vikram; Sayeed Akhtar, Mohd; Panwar, Jitendra

    2017-03-01

    Rapid utilization of nano-based products will inevitably release nanoparticles into the environment with unidentified consequences. Plants, being an integral part of ecosystem play a vital role in the incorporation of nanoparticles in food chain and thus, need to be critically assessed. The present study assesses the comparative phytotoxicity of nanoparticle, bulk and ionic forms of zinc at different concentrations on selected plant species with varying seed size and surface anatomy. ZnO nanoparticles were chosen in view of their wide spread use in cosmetics and health care products, which allow their direct release in the environment. The impact on germination rate, shoot & root length and vigour index were evaluated. A concentration dependent inhibition of seed germination as well as seedling length was observed in all the tested plants. Due to the presence of thick cuticle on testa and root, pearl millet (xerophytic plant) was found to be relatively less sensitive to ZnO nanoparticles as compared to wheat and tomato (mesophytic plants) with normal cuticle layer. No correlation was observed between nanoparticles toxicity and seed size. The results indicated that variations in surface anatomy of seeds play a crucial role in determining the phytotoxicity of nanoparticles. The present findings significantly contribute to assess potential consequences of nanoparticle release in environment particularly with major emphasis on plant systems. It is the first report which suggests that variations observed in phytotoxicity of nanoparticles is mainly due to the predominant differences in size and surface anatomy of tested plant seeds and root architecture. Effect of various concentrations of nano ZnO, bulk ZnO and zinc sulphate on the growth of pearl millet (A), tomato (B) and wheat (C) seedlings.

  10. Surface NMR measurement of proton relaxation times in medium to coarse-grained sand aquifer.

    PubMed

    Shushakov, O A

    1996-01-01

    A surface NMR investigation of groundwater in the geomagnetic field is under study. To detect the surface NMR a wire loop with a diameter of about 100 m, being an antenna for both an exciting field source and the NMR signal receiver, is laid out on the ground. A sinusoidal current pulse with a rectangular envelope is passed through the loop to excite the NMR signal. The carrier frequency of the oscillating current in this pulse is equal to the Larmor frequency of protons in the Earth's magnetic field. The current amplitude is changed up to 200 amps and the pulse duration is fixed and is equal to 40 ms. The exciting pulse is followed by an induction emf signal caused by the Larmor nuclear precession in geomagnetic field. The relaxation times T1, T2, and T2* were measured by the surface NMR for both groundwater in medium to coarse-grained sand at borehole and for bulk water under the ice surface of frozen lake. To determine T1, a longitudinal interference in experiments with repeated pulses was measured. A sequence with equal period between equal excitation pulses was used. The relaxation times T1, T2, measured for bulk water under the ice of the Ob reservoir were 1.0 s and 0.7 s, respectively. To estimate an influence of dissolved oxygen T1 of the same water at the same temperature was measured by lab NMR with and without pumping of oxygen. The relaxation time T1 measured for water in the medium to coarse-grained sand is 0.65 s. The relaxation time T2 estimated by spin echo sequence is found to be equal to 0.15 s. The relaxation time T2* is found to be about 80 ms. This result contradicts published earlier phenomenological correlation between relaxation time T2* and grain size of water-bearing rock. This could be as a result of unsound approach based on grain size or influence of paramagnetic impurities.

  11. Role of surface ligands in nanoparticle permeation through a model membrane: a coarse-grained molecular dynamics simulations study

    NASA Astrophysics Data System (ADS)

    Song, Bo; Yuan, Huajun; Jameson, Cynthia J.; Murad, Sohail

    2012-09-01

    How nanoparticles interact with biological membranes is of significant importance in determining the toxicity of nanoparticles as well as their potential applications in phototherapy, imaging and gene/drug delivery. It has been shown that such interactions are often determined by nanoparticle physicochemical factors such as size, shape, hydrophobicity and surface charge density. Surface modification of the nanoparticle offers the possibility of creating site-specific carriers for both drug delivery and diagnostic purposes. In this work, we use coarse-grained molecular dynamic simulations to explore the permeation characteristics of ligand-coated nanoparticles through a model membrane. We compare permeation behaviors of ligand-coated nanoparticles with bare nanoparticles to provide insights into how the ligands affect the permeation process. A series of simulations is carried out to validate a coarse-grained model for nanoparticles and a lipid membrane system. The minimum driving force for nanoparticles to penetrate the membrane and the mechanism of nanoparticle-membrane interaction were investigated. The potential of the mean force profile, nanoparticle velocity profile, force profile and density profiles (planar and radial) were obtained to explore the nanoparticle permeation process. The structural properties of both nanoparticles and lipid membrane during the permeation, which are of considerable fundamental interest, are also studied in our work. The findings described in our work will lead to a better understanding of nanoparticle-lipid membrane interactions and cell cytotoxicity and help develop more efficient nanocarrier systems for intracellular delivery of therapeutics.

  12. Covalent attachment of nanoparticles to copolymer surfaces to control structure-property relationships

    NASA Astrophysics Data System (ADS)

    McConnell, Marla D.

    Interest in functional nanoparticles has increased in recent years, because their small size gives them unique properties. Surface assembly of nanoparticles is particularly appealing, because it can create surfaces with tunable wetting and optical properties. This thesis presents a novel method for the covalent assembly of silica nanoparticles on random copolymer films via covalent bonding, and the subsequent analysis of the wetting and optical properties of these functionalized surfaces. First, the kinetics of the covalent attachment of amine-modified silica nanoparticles to poly(styrene-ran-acrylic acid) were investigated. The surface swelling of the copolymer films upon exposure to reaction solvents was studied with in situ AFM. The films' surface roughness controlled the nanoparticle attachment kinetics, as well as the final nanoparticle coverage. For particle diameters on the order of the roughness features, 70% surface coverage was achieved, while particles with diameters much larger than the surface features reached only 30% coverage. The wetting properties of the nanoparticle surfaces were investigated as a function of particle coverage and diameter. At low coverages of small particles, the surfaces exhibited Wenzel-type wetting behavior. At high particle coverages, the surfaces showed Cassie-type wetting. Finally, the particles were observed to sink into the polymer film with increasing reaction time. This sinking, as well as the magnitude of the contact angles achieved at high particle coverages, led to the hypothesis that polymer chains wet onto the surface of the silica particles. Core-shell Janus particles were prepared by electrostatic assembly of gold nanoparticles on the unprotected surfaces of the silica particles. The plasmon resonance absorption of the gold particles underwent a red shift upon formation of closely-packed networks on the silica particle surfaces. By applying gold, chromium, and gold:palladium coatings to the Janus particles and

  13. Optically Evolved Assembly Formation in Laser Trapping of Polystyrene Nanoparticles at Solution Surface.

    PubMed

    Wang, Shun-Fa; Kudo, Tetsuhiro; Yuyama, Ken-Ichi; Sugiyama, Teruki; Masuhara, Hiroshi

    2016-11-29

    Assembling dynamics of polystyrene nanoparticles by optical trapping is studied with utilizing transmission/reflection microscopy and reflection microspectroscopy. A single nanoparticle assembly with periodic structure is formed upon the focused laser irradiation at solution surface layer and continuously grows up to a steady state within few minutes. By controlling nanoparticle and salt concentrations in the colloidal solution, the assembling behavior is obviously changed. In the high concentration of nanoparticles, the assembly formation exhibits fast growth, gives large saturation size, and leads to dense packing structure. In the presence of salt, one assembly with the elongated aggregates was generated from the focal spot and 1064 nm trapping light was scattered outwardly with directions, while a small circular assembly and symmetrical expansion of the 1064 nm light were found without salt. The present nanoparticle assembling in optical trapping is driven through multiple scattering in gathered nanoparticles and directional scattering along the elongated aggregates derived from optical association of nanoparticles, which dynamic phenomenon is called optically evolved assembling. Repetitive trapping and release processes of nanoparticles between the assembly and the surrounding solution always proceed, and the steady state at the circular assembly formed by laser trapping is determined under optical and chemical equilibrium.

  14. Laser trapping and assembling of nanoparticles at solution surface studied by reflection micro-spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Shun-Fa; Yuyama, Ken-ichi; Suigiyama, Teruki; Masuhara, Hiroshi

    2015-08-01

    We present the laser power dependent behavior of optical trapping assembling of 208-nm polystyrene (PS) nanoparticles at the solution surface layer. The assembling dynamics is examined by reflection microspectroscopy as well as transmission and backscattering imaging. The transmission imaging shows that the laser irradiation at the solution surface layer forms a nanoparticle assembly, whose diameter becomes large with the increase in the laser power. The backscattering image of the assembly gives structural color, meaning that nanoparticles are periodically arranged over the whole assembly region. In reflection microspectroscopy, one band appears at long wavelength and is gradually shifted to the short wavelength with the irradiation. After the blue shift, the reflection band is located at the shorter wavelength under the laser irradiation at the higher power. We discuss these spectral changes from the viewpoint of the inter-particle distance determined by the dynamic balance between attractive optical force and repulsive electrostatic force among nanoparticles.

  15. Surface properties, simultaneous photocatalytic and magnetic activities of Ni2FeVO6 nanoparticles

    NASA Astrophysics Data System (ADS)

    Qiao, Xuebin; Huang, Yanlin; Cheng, Han; Seo, Hyo Jin

    2015-12-01

    Nickel-ferro-vanadium oxide Ni2FeVO6 nanoparticles were prepared by the sol-gel film coating and subsequent sintering method. The phase formation was investigated X-ray polycrystalline diffraction (XRD) measurement. The surface characteristics were measured by scanning electron microscope (SEM), transmission electron microscopy (TEM), specific surface area, energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). This vanadate has a narrow band-gap energy of 1.784 eV. The investigations concluded that Ni2FeVO6 nanoparticles have photocatalytic ability under visible-light irradiation. The ferromagnetic behavior of the nanoparticles was confirmed by the magnetic hysteresis loops. The nanoparticles can be magnetically recoverable after photocatalytic reactions. The photocatalytic activities were discussed on the base of the multivalent cations in crystal lattices.

  16. Solubility studies of inorganic-organic hybrid nanoparticle photoresists with different surface functional groups.

    PubMed

    Li, Li; Chakrabarty, Souvik; Jiang, Jing; Zhang, Ben; Ober, Christopher; Giannelis, Emmanuel P

    2016-01-21

    The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists.

  17. Modeling Nanoparticle Targeting to a Vascular Surface in Shear Flow Through Diffusive Particle Dynamics.

    PubMed

    Peng, Bei; Liu, Yang; Zhou, Yihua; Yang, Longxiang; Zhang, Guocheng; Liu, Yaling

    2015-12-01

    Nanoparticles are regarded as promising carriers for targeted drug delivery and imaging probes. A fundamental understanding of the dynamics of polymeric nanoparticle targeting to receptor-coated vascular surfaces is therefore of great importance to enhance the design of nanoparticles toward improving binding ability. Although the effects of particle size and shear flow on the binding of nanoparticles to a vessel wall have been studied at the particulate level, a computational model to investigate the details of the binding process at the molecular level has not been developed. In this research, dissipative particle dynamics simulations are used to study nanoparticles with diameters of several nanometers binding to receptors on vascular surfaces under shear flow. Interestingly, shear flow velocities ranging from 0 to 2000 s(-1) had no effect on the attachment process of nanoparticles very close to the capillary wall. Increased binding energy between the ligands and wall caused a corresponding linear increase in bonding ability. Our simulations also indicated that larger nanoparticles and those of rod shape with a higher aspect ratio have better binding ability than those of smaller size or rounder shape.

  18. Surface modification of PLGA nanoparticles by carbopol to enhance mucoadhesion and cell internalization.

    PubMed

    Surassmo, Suvimol; Saengkrit, Nattika; Ruktanonchai, Uracha Rungsardthong; Suktham, Kunat; Woramongkolchai, Noppawan; Wutikhun, Tuksadon; Puttipipatkhachorn, Satit

    2015-06-01

    Mucoadhesive poly (lactic-co-glycolic acid) (PLGA) nanoparticles having a modified shell-matrix derived from polyvinyl alcohol (PVA) and Carbopol (CP), a biodegradable polymer coating, to improve the adhesion and cell transfection properties were developed. The optimum formulations utilized a CP concentration in the range of 0.05-0.2%w/v, and were formed using modified emulsion-solvent evaporation technique. The resulting CP-PLGA nanoparticles were characterized in terms of their physical and chemical properties. The absorbed CP on the PLGA shell-matrix was found to affect the particle size and surface charge, with 0.05% CP giving rise to smooth spherical particles (0.05CP-PLGA) with the smallest size (285.90 nm), and strong negative surface charge (-25.70 mV). The introduction of CP results in an enhancement of the mucoadhesion between CP-PLGA nanoparticles and mucin particles. In vitro cell internalization studies highlighted the potential of 0.05CP-PLGA nanoparticles for transfection into SiHa cells, with uptake being time dependent. Additionally, cytotoxicity studies of CP-PLGA nanoparticles against SiHa cancer cells indicated that low concentrations of the nanoparticles were non-toxic to cells (cell viability >80%). From the various formulations studied, 0.05CP-PLGA nanoparticles proved to be the optimum model carrier having the required mucoadhesive profile and could be an alternative therapeutic efficacy carrier for targeted mucosal drug delivery systems with biodegradable polymer.

  19. Formation of metastable tetragonal zirconia nanoparticles: Competitive influence of the dopants and surface state

    SciTech Connect

    Gorban, Oksana; Synyakina, Susanna; Volkova, Galina; Gorban, Sergey; Konstantiova, Tetyana; Lyubchik, Svetlana

    2015-12-15

    The effect of the surface modification of the nanoparticles of amorphous and crystalline partially stabilized zirconia by fluoride ions on stability of the metastable tetragonal phase was investigated. Based on the DSC, titrimetry and FTIR spectroscopy data it was proven that surface modification of the xerogel resulted from an exchange of the fluoride ions with the basic OH groups. The effect of the powder pre-calcination temperature before modification on the formation of metastable tetragonal phase in partially stabilized zirconia was investigated. It was shown that the main factor of tetragonal zirconia stabilization is the state of nanoparticles surface at pre-crystallization temperatures.

  20. Functionalized Magnetic Nanoparticles for the Detection and Quantitative Analysis of Cell Surface Antigen

    PubMed Central

    Shahbazi-Gahrouei, Daryoush; Abdolahi, Mohammad; Zarkesh-Esfahani, Sayyed Hamid; Laurent, Sophie; Sermeus, Corine; Gruettner, Cordula

    2013-01-01

    Cell surface antigens as biomarkers offer tremendous potential for early diagnosis, prognosis, and therapeutic response in a variety of diseases such as cancers. In this research, a simple, rapid, accurate, inexpensive, and easily available in vitro assay based on magnetic nanoparticles and magnetic cell separation principle was applied to identify and quantitatively analyze the cell surface antigen expression in the case of prostate cancer cells. Comparing the capability of the assay with flow cytometry as a gold standard method showed similar results. The results showed that the antigen-specific magnetic cell separation with antibody-coated magnetic nanoparticles has high potential for quantitative cell surface antigen detection and analysis. PMID:23484112

  1. Catechol versus bisphosphonate ligand exchange at the surface of iron oxide nanoparticles: towards multi-functionalization

    NASA Astrophysics Data System (ADS)

    Guénin, Erwann; Lalatonne, Yoann; Bolley, Julie; Milosevic, Irena; Platas-Iglesias, Carlos; Motte, Laurence

    2014-11-01

    We report an investigation of the ligand exchange at the surface of iron oxide nanoparticles in water. For this purpose we compared two strong chelating agents on the iron oxide surface containing catechol and bisphosphonate moieties. Interactions between the coating agents (catechol/bisphosphonate) and the nanoparticle's surface were studied by FTIR and DFT calculations. Ligand exchange experiments were performed using sonication and the exchange yield was characterized by FTIR and EDX. This methodology allowed introducing bisphosphonates with various functionalities (alkyne or biotin) permitting multi-functionalization.

  2. Identifying low-coverage surface species on supported noble metal nanoparticle catalysts by DNP-NMR

    SciTech Connect

    Johnson, Robert L.; Perras, Frédéric A.; Kobayashi, Takeshi; Schwartz, Thomas J.; Dumesic, James A.; Shanks, Brent H.; Pruski, Marek

    2015-11-20

    DNP-NMR spectroscopy has been applied to enhance the signal for organic molecules adsorbed on γ-Al2O3-supported Pd nanoparticles. In addition, by offering >2500-fold time savings, the technique enabled the observation of 13C-13C cross-peaks for low coverage species, which were assigned to products from oxidative degradation of methionine adsorbed on the nanoparticle surface.

  3. Solubility studies of inorganic-organic hybrid nanoparticle photoresists with different surface functional groups

    NASA Astrophysics Data System (ADS)

    Li, Li; Chakrabarty, Souvik; Jiang, Jing; Zhang, Ben; Ober, Christopher; Giannelis, Emmanuel P.

    2016-01-01

    The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists.The solubility behavior of Hf and Zr based hybrid nanoparticles with different surface ligands in different concentrations of photoacid generator as potential EUV photoresists was investigated in detail. The nanoparticles regardless of core or ligand chemistry have a hydrodynamic diameter of 2-3 nm and a very narrow size distribution in organic solvents. The Hansen solubility parameters for nanoparticles functionalized with IBA and 2MBA have the highest contribution from the dispersion interaction than those with tDMA and MAA, which show more polar character. The nanoparticles functionalized with unsaturated surface ligands showed more apparent solubility changes after exposure to DUV than those with saturated ones. The solubility differences after exposure are more pronounced for films containing a higher amount of photoacid generator. The work reported here provides material selection criteria and processing strategies for the design of high performance EUV photoresists. Electronic supplementary

  4. Identifying low-coverage surface species on supported noble metal nanoparticle catalysts by DNP-NMR

    DOE PAGES

    Johnson, Robert L.; Perras, Frédéric A.; Kobayashi, Takeshi; ...

    2015-11-20

    DNP-NMR spectroscopy has been applied to enhance the signal for organic molecules adsorbed on γ-Al2O3-supported Pd nanoparticles. In addition, by offering >2500-fold time savings, the technique enabled the observation of 13C-13C cross-peaks for low coverage species, which were assigned to products from oxidative degradation of methionine adsorbed on the nanoparticle surface.

  5. Molecular Theory Studies of Polymer/Nanoparticle Blends Near Surfaces

    NASA Astrophysics Data System (ADS)

    McGarrity, Erin; Frischknecht, Amalie; Mackay, Michael

    2007-03-01

    Recent experimental results have shown that nanoparticles added to supported thin polymer films can inhibit dewetting by migrating to the substrate. To better understand this phenomenon, we use a classical density functional theory developed by Tripathi and Chapman. The effects of nanoparticle radius and density are examined. Preliminary results for hard-particle hard-chain systems indicate that regular layered structures emerge when a critical density is reached and the particles displace the polymers near the substrate. The effects of particle and polymer attractions and substrate potentials are currently being studied. We also compare our results to molecular simulations.

  6. FDTD/TDSE study of surface-enhanced infrared absorption by metal nanoparticles.

    SciTech Connect

    Chang, S.-H.; Schatz, G. C.; Gray, S. K.; Chemistry; Northwestern Univ.; National Cheng-Kung Univ.

    2006-01-01

    We study surface-enhanced infrared absorption, including multiphoton processes, due to the excitation of surface plasmons on metal nanoparticles. The time-dependent Schroedinger equation and finite-difference time-domain method are self-consistently coupled to treat the problem.

  7. Recent advances on surface engineering of magnetic iron oxide nanoparticles and their biomedical applications.

    PubMed

    Gupta, Ajay Kumar; Naregalkar, Rohan R; Vaidya, Vikas Deep; Gupta, Mona

    2007-02-01

    Magnetic nanoparticles with appropriate surface coatings are increasingly being used clinically for various biomedical applications, such as magnetic resonance imaging, hyperthermia, drug delivery, tissue repair, cell and tissue targeting and transfection. This is because of the nontoxicity and biocompatibility demand that mainly iron oxide-based materials are predominantly used, despite some attempts to develop 'more magnetic nanomaterials' based on cobalt, nickel, gadolinium and other compounds. For all these applications, the material used for surface coating of the magnetic particles must not only be nontoxic and biocompatible but also allow a targetable delivery with particle localization in a specific area. Magnetic nanoparticles can bind to drugs and an external magnetic field can be applied to trap them in the target site. By attaching the targeting molecules, such as proteins or antibodies, at particles surfaces, the latter may be directed to any cell, tissue or tumor in the body. In this review, different polymers/molecules that can be used for nanoparticle coating to stabilize the suspensions of magnetic nanoparticles under in vitro and in vivo situations are discussed. Some selected proteins/targeting ligands that could be used for derivatizing magnetic nanoparticles are also explored. We have reviewed the various biomedical applications with some of the most recent uses of magnetic nanoparticles for early detection of cancer, diabetes and atherosclerosis.

  8. Surface treated titanium dioxide nanoparticles as inorganic UV filters in sunscreen products.

    PubMed

    Veronovski, Nika; Lešnik, Maja; Lubej, Andrej; Verhovšek, Dejan

    2014-01-01

    TiO(2) nanoparticles were used in this research as an inorganic UV absorber for preparation of a sunscreen that ensures optically transparent films with adequate SPF. TiO(2) nanoparticles in rutile crystal form, produced in Cinkarna Celje, were used in this research. The elementary principle of the nanograde TiO(2) production is the sulphate synthesis process, which is upgraded for the synthesis of final nano product. TiO(2) nanoparticles were subsequently surface modified by coating with sodium silicate as the source of silica. The resulting silica coated TiO(2) nanoparticles were examined by scanning (SEM) and transmission electron microscopy (TEM). Uniform particles distribution and homogeneous amorphous coatings, formed in heterogeneous nucleation of silica molecules on the surface of TiO(2) nanoparticles, were observed. Sun-protection factor (SPF) of 28 was determined for sunscreen with incorporated 9.0 wt. % TiO(2) nanoparticles, surface treated with 5.0 wt. % silica according to the "Method for the In Vitro Determination of UVA Protection Provided by Sunscreen Products".

  9. Surface effects in the magnetic properties of crystalline 3 nm ferrite nanoparticles chemically synthesized

    NASA Astrophysics Data System (ADS)

    Lima, E.; De Biasi, E.; Mansilla, M. Vasquez; Saleta, M. E.; Effenberg, F.; Rossi, L. M.; Cohen, R.; Rechenberg, H. R.; Zysler, R. D.

    2010-11-01

    We have systematically studied the magnetic properties of ferrite nanoparticles with 3, 7, and 11 nm of diameter with very narrow grain size distributions. Samples were prepared by the thermal decomposition of Fe(acac)3 in the presence of surfactants giving nanoparticles covered by oleic acid. High resolution transmission electron microscopy (HRTEM) images and XRD diffraction patterns confirms that all samples are composed by crystalline nanoparticles with the spinel structure expected for the iron ferrite. ac and dc magnetization measurements, as well in-field Mössbauer spectroscopy, indicate that the magnetic properties of nanoparticles with 11 and 7 nm are close to those expected for a monodomain, presenting large MS (close to the magnetite bulk). Despite the crystalline structure observed in HRTEM images, the nanoparticles with 3 nm are composed by a magnetically ordered region (core) and a surface region that presents a different magnetic order and it contains about 66% of Fe atoms. The high saturation and irreversibility fields in the M(H ) loops of the particles with 3 nm together with the misalignment at 120 kOe in the in-field Mössbauer spectrum of surface component indicate a high surface anisotropy for the surface atoms, which is not observed for the core. For T <10 K, we observe an increase in the susceptibility and of the magnetization for former sample, indicating that surface moments tend to align with applied field increasing the magnetic core size.

  10. Nanoparticle-protein interactions: a thermodynamic and kinetic study of the adsorption of bovine serum albumin to gold nanoparticle surfaces.

    PubMed

    Boulos, Stefano P; Davis, Tyler A; Yang, Jie An; Lohse, Samuel E; Alkilany, Alaaldin M; Holland, Lisa A; Murphy, Catherine J

    2013-12-03

    Investigating the adsorption process of proteins on nanoparticle surfaces is essential to understand how to control the biological interactions of functionalized nanoparticles. In this work, a library of spherical and rod-shaped gold nanoparticles (GNPs) was used to evaluate the process of protein adsorption to their surfaces. The binding of a model protein (bovine serum albumin, BSA) to GNPs as a function of particle shape, size, and surface charge was investigated. Two independent comparative analytical methods were used to evaluate the adsorption process: steady-state fluorescence quenching titration and affinity capillary electrophoresis (ACE). Although under favorable electrostatic conditions kinetic analysis showed a faster adsorption of BSA to the surface of cationic GNPs, equilibrium binding constant determinations indicated that BSA has a comparable binding affinity to all of the GNPs tested, regardless of surface charge. BSA was even found to adsorb strongly to GNPs with a pegylated/neutral surface. However, these fluorescence titrations suffer from significant interference from the strong light absorption of the GNPs. The BSA-GNP equilibrium binding constants, as determined by the ACE method, were 10(5) times lower than values determined using spectroscopic titrations. While both analytical methods could be suitable to determine the binding constants for protein adsorption to NP surfaces, both methods have limitations that complicate the determination of protein-GNP binding constants. The optical properties of GNPs interfere with Ka determinations by static fluorescence quenching analysis. ACE, in contrast, suffers from material compatibility issues, as positively charged GNPs adhere to the walls of the capillary during analysis. Researchers seeking to determine equilibrium binding constants for protein-GNP interactions should therefore utilize as many orthogonal techniques as possible to study a protein-GNP system.

  11. Controlled Assembly of Viral Surface Proteins into Biological Nanoparticles

    NASA Astrophysics Data System (ADS)

    Nakatani-Webster, Eri

    In recent years, therapeutic use of engineered particles on the 1-1,000 nm scale has gained popularity; these nanoparticles have been developed for use in drug delivery, gene therapy, vaccine preparation, and diagnostics. Often, viral proteins are utilized in the design of such species, and outlined here are completed studies on the in vitro assembly of nanoparticles derived from two very different viral systems. The incorporation of the human immunodeficiency virus (HIV) envelope glycoprotein precursor gp160 into phospholipid bilayer nanodiscs is discussed as a potential platform for vaccine design; efforts were successful, however yield currently limits the practical application of this approach. The utility of bacteriophage lambda procapsids and virus-like particles in therapeutic nanoparticle design is also outlined, as are efforts toward the structural and thermodynamic characterization of a urea-triggered capsid maturation event. It is demonstrated that lambda virus-like particles can be assembled from purified capsid and scaffolding proteins, and that these particles undergo urea-triggered maturation and in vitro decoration protein addition similar to that seen in lambda procapsids. The studies on lambda provided materials for the further development of nanoparticles potentially useful in a clinical setting, as well as shedding light on critical viral assembly and maturation events as they may take place in vivo.

  12. Synthesis and surface engineering of iron oxide nanoparticles for biomedical applications.

    PubMed

    Gupta, Ajay Kumar; Gupta, Mona

    2005-06-01

    Superparamagnetic iron oxide nanoparticles (SPION) with appropriate surface chemistry have been widely used experimentally for numerous in vivo applications such as magnetic resonance imaging contrast enhancement, tissue repair, immunoassay, detoxification of biological fluids, hyperthermia, drug delivery and in cell separation, etc. All these biomedical and bioengineering applications require that these nanoparticles have high magnetization values and size smaller than 100 nm with overall narrow particle size distribution, so that the particles have uniform physical and chemical properties. In addition, these applications need special surface coating of the magnetic particles, which has to be not only non-toxic and biocompatible but also allow a targetable delivery with particle localization in a specific area. To this end, most work in this field has been done in improving the biocompatibility of the materials, but only a few scientific investigations and developments have been carried out in improving the quality of magnetic particles, their size distribution, their shape and surface in addition to characterizing them to get a protocol for the quality control of these particles. Nature of surface coatings and their subsequent geometric arrangement on the nanoparticles determine not only the overall size of the colloid but also play a significant role in biokinetics and biodistribution of nanoparticles in the body. The types of specific coating, or derivatization, for these nanoparticles depend on the end application and should be chosen by keeping a particular application in mind, whether it be aimed at inflammation response or anti-cancer agents. Magnetic nanoparticles can bind to drugs, proteins, enzymes, antibodies, or nucleotides and can be directed to an organ, tissue, or tumour using an external magnetic field or can be heated in alternating magnetic fields for use in hyperthermia. This review discusses the synthetic chemistry, fluid stabilization and

  13. Excited-state intramolecular proton transfer to carbon atoms: nonadiabatic surface-hopping dynamics simulations.

    PubMed

    Xia, Shu-Hua; Xie, Bin-Bin; Fang, Qiu; Cui, Ganglong; Thiel, Walter

    2015-04-21

    Excited-state intramolecular proton transfer (ESIPT) between two highly electronegative atoms, for example, oxygen and nitrogen, has been intensely studied experimentally and computationally, whereas there has been much less theoretical work on ESIPT to other atoms such as carbon. We have employed CASSCF, MS-CASPT2, RI-ADC(2), OM2/MRCI, DFT, and TDDFT methods to study the mechanistic photochemistry of 2-phenylphenol, for which such an ESIPT has been observed experimentally. According to static electronic structure calculations, irradiation of 2-phenylphenol populates the bright S1 state, which has a rather flat potential in the Franck-Condon region (with a shallow enol minimum at the CASSCF level) and may undergo an essentially barrierless ESIPT to the more stable S1 keto species. There are two S1/S0 conical intersections that mediate relaxation to the ground state, one in the enol region and one in the keto region, with the latter one substantially lower in energy. After S1 → S0 internal conversion, the transient keto species can return back to the S0 enol structure via reverse ground-state hydrogen transfer in a facile tautomerization. This mechanistic scenario is verified by OM2/MRCI-based fewest-switches surface-hopping simulations that provide detailed dynamic information. In these trajectories, ESIPT is complete within 118 fs; the corresponding S1 excited-state lifetime is computed to be 373 fs in vacuum. Most of the trajectories decay to the ground state via the S1/S0 conical intersection in the keto region (67%), and the remaining ones via the enol region (33%). The combination of static electronic structure computations and nonadiabatic dynamics simulations is expected to be generally useful for understanding the mechanistic photophysics and photochemistry of molecules with intramolecular hydrogen bonds.

  14. Highly water-dispersible surface-modified Gd(2)O(3) nanoparticles for potential dual-modal bioimaging.

    PubMed

    Hu, Zhangjun; Ahrén, Maria; Selegård, Linnéa; Skoglund, Caroline; Söderlind, Fredrik; Engström, Maria; Zhang, Xuanjun; Uvdal, Kajsa

    2013-09-16

    Water-dispersible and luminescent gadolinium oxide (GO) nanoparticles (NPs) were designed and synthesized for potential dual-modal biological imaging. They were obtained by capping gadolinium oxide nanoparticles with a fluorescent glycol-based conjugated carboxylate (HL). The obtained nanoparticles (GO-L) show long-term colloidal stability and intense blue fluorescence. In addition, L can sensitize the luminescence of europium(III) through the so-called antenna effect. Thus, to extend the spectral ranges of emission, europium was introduced into L-modified gadolinium oxide nanoparticles. The obtained EuIII-doped particles (Eu:GO-L) can provide visible red emission, which is more intensive than that without L capping. The average diameter of the monodisperse modified oxide cores is about 4 nm. The average hydrodynamic diameter of the L-modified nanoparticles was estimated to be about 13 nm. The nanoparticles show effective longitudinal water proton relaxivity. The relaxivity values obtained for GO-L and Eu:GO-L were r1=6.4 and 6.3 s−1 mM−1 with r2/r1 ratios close to unity at 1.4 T. Longitudinal proton relaxivities of these nanoparticles are higher than those of positive contrast agents based on gadolinium complexes such as Gd-DOTA, which are commonly used for clinical magnetic resonance imaging. Moreover, these particles are suitable for cellular imaging and show good biocompatibility.

  15. On the protonation of oxo- and hydroxo-groups of the goethite (α-FeOOH) surface: A FTIR spectroscopic investigation of surface O H stretching vibrations

    NASA Astrophysics Data System (ADS)

    Boily, Jean-François; Felmy, Andrew R.

    2008-07-01

    The O-H stretching region of goethite particles evaporated at different levels of acidity was investigated by Attenuated Total Reflectance (ATR)-Fourier Transform InfraRed (FTIR) spectroscopy. Two-dimensional IR Correlation Spectroscopy was used to identify correlations between different sets of discrete surface OH stretches and a Multivariate Curve Resolution analysis was used to resolve the predominant spectral components. Two dominant groups of hydroxyls were identified on the basis of their differences in proton affinity. Group I hydroxyls appear as two 3698/3541 and 3660/3490 cm -1 band pairs. Group II hydroxyls are manifested through the 3648 and 3578 cm -1 bands at greater levels of surface proton loading. There is consequently no correlation between O-H stretching frequencies and proton affinity. Groups I and II were assigned to mostly singly- (-OH) and doubly- (μ-OH) coordinated hydroxyls, respectively. Stretches arising from triply-coordinated (μ 3-OH) are proposed to be embedded within the dominant O-H band of bulk goethite. The possibility that these sites contribute to Group I and II hydroxyls should, however, not be entirely dismissed without further investigations. A reexamination of Temperature Programmed Desorption (TPD)-FTIR data of one goethite sample evaporated from alkaline conditions [Boily J.-F., Szanyi J., Felmy A. R. (2006) A combined FTIR and TPD study on the bulk and surface dehydroxylation and decarbonation of synthetic goethite. Geochim. Cosmochim. Acta70, 3613-3624] provided further constraints to this band assignment by providing clues to the network of surface hydrogen bonds. Important cooperative effects between hydrogen-bonded surface hydroxyls are suggested to play a crucial role on the variations of the position and intensity of discrete O-H stretching bands as a function of protonation level and temperature.

  16. On the protonation of oxo- and hydroxo- groups of the goethite (α-FeOOH) surface: A FTIR spectroscopic investigation of surface O-H stretching vibrations.

    SciTech Connect

    Boily, Jean F; Felmy, Andrew R

    2008-06-01

    The O–H stretching region of goethite particles evaporated at different levels of acidity was investigated by Attenuated Total Reflectance (ATR)-Fourier Transform InfraRed (FTIR) spectroscopy. Two-dimensional IR Correlation Spectroscopy was used to identify correlations between different sets of discrete surface OH stretches and a Multivariate Curve Resolution analysis was used to resolve the predominant spectral components. Two dominant groups of hydroxyls were identified on the basis of their differences in proton affinity. Group I hydroxyls appear as two 3698/3541 and 3660/3490 cm-1 band pairs. Group II hydroxyls are manifested through the 3648 and 3578 cm-1 bands at greater levels of surface proton loading. There is consequently no correlation between O–H stretching frequencies and proton affinity. Groups I and II were assigned to mostly singly- (–OH) and doubly- (μ-OH) coordinated hydroxyls, respectively. Stretches arising from triply-coordinated (μ3-OH) are proposed to be embedded within the dominant O–H band of bulk goethite. The possibility that these sites contribute to Group I and II hydroxyls should, however, not be entirely dismissed without further investigations. A reexamination of Temperature Programmed Desorption (TPD)-FTIR data of one goethite sample evaporated from alkaline conditions [Boily J.-F., Szanyi J., Felmy A. R. (2006) A combined FTIR and TPD study on the bulk and surface dehydroxylation and decarbonation of synthetic goethite. Geochim. Cosmochim. Acta70, 3613–3624] provided further constraints to this band assignment by providing clues to the network of surface hydrogen bonds. Important cooperative effects between hydrogen-bonded surface hydroxyls are suggested to play a crucial role on the variations of the position and intensity of discrete O–H stretching bands as a function of protonation level and temperature.

  17. Surface chemistry and size influence the release of model therapeutic nanoparticles from poly(ethylene glycol) hydrogels

    NASA Astrophysics Data System (ADS)

    Hume, Stephanie L.; Jeerage, Kavita M.

    2013-05-01

    Nanoparticles have emerged as promising therapeutic and diagnostic tools, due to their unique physicochemical properties. The specific core and surface chemistries, as well as nanoparticle size, play critical roles in particle transport and interaction with biological tissue. Localized delivery of therapeutics from hydrogels is well established, but these systems generally release molecules with hydrodynamic radii less than 5 nm. Here, model nanoparticles with biologically relevant surface chemistries and diameters between 10 and 35 nm are analyzed for their release from well-characterized hydrogels. Functionalized gold nanoparticles or quantum dots were encapsulated in three-dimensional poly(ethylene glycol) hydrogels with varying mesh size. Nanoparticle size, surface chemistry, and hydrogel mesh size all influenced the release of particles from the hydrogel matrix. Size influenced nanoparticle release as expected, with larger particles releasing at a slower rate. However, citrate-stabilized gold nanoparticles were not released from hydrogels. Negatively charged carboxyl or positively charged amine-functionalized quantum dots were released from hydrogels at slower rates than neutrally charged PEGylated nanoparticles of similar size. Transmission electron microscopy images of gold nanoparticles embedded within hydrogel sections demonstrated uniform particle distribution and negligible aggregation, independent of surface chemistry. The nanoparticle-hydrogel interactions observed in this work will aid in the development of localized nanoparticle delivery systems.

  18. Assessing the Potential for Drug-Nanoparticle Surface Interactions To Improve Drug Penetration into the Skin.

    PubMed

    Cai, X J; Woods, A; Mesquida, P; Jones, S A

    2016-04-04

    There is continued debate as to how nanomaterials enhance the passive diffusion of drugs through the skin. This study examined if drug-nanoparticle surface interactions, which occurred during topical application, had the capability to enhance percutaneous penetration. Atomic force microscopy force adhesion measurements were used to demonstrate that a model drug, tetracaine, strongly adsorbed to the surface of a negatively charged carboxyl-modified polystyrene nanoparticle (NanoPSCOOH) through both its methyl and amine functionalities (up to a 6- and 16-fold greater adhesion force respectively compared with the CH3-CH3 control). These drug-particle adhesion forces were significantly reduced (p < 0.05) to values that were lower than the CH3-CH3 control measurements when tetracaine interacted with a silica nanoparticle (NanoSiO2). This reduction in adhesion was attributed to the lower surface charge of the NanoSiO2 (ca. -23 mV) compared to the NanoPSCOOH (ca. -40 mV), which diminished the electrostatic interactions between positive amine of tetracaine and the negative particle. Mixing NanoPSCOOH with tetracaine on the skin retarded percutaneous drug penetration compared to the control (tetracaine saturated solution without nanoparticles), but the NanoSiO2, which still adsorbed the tetracaine, produced a 3.6-fold enhancement in percutaneous penetration compared to the same control. These data demonstrated the capability of moderate nanoparticle surface interactions that occurred within the application vehicle to promote drug percutaneous penetration.

  19. Surface decoration of carbon nanosheets with amino-functionalized organosilica nanoparticles

    NASA Astrophysics Data System (ADS)

    Baikousi, M.; Dimos, K.; Bourlinos, A. B.; Zbořil, R.; Papadas, I.; Deligiannakis, Y.; Karakassides, M. A.

    2012-02-01

    Carbonaceous nanosheets decorated with amino-functionalized organosilica nanoparticles have been synthesized by a direct pyrolysis of betaine at 400 °C in air, followed by a simple surface treatment with ([3-(2-aminoethylamino) propyl]trimethoxysilane under reflux conditions. Both pristine and organosilica modified carbon nanosheets (OMCNs), were characterized by Fourier-transform infrared (FTIR), Raman, and electron paramagnetic resonance (EPR) spectroscopies, transmission electron microscopy and thermal analysis methods. The experimental data reveal a dramatic increase in the number of radical centers on the surface of the developed OMCN hybrid. The organosilica nanoparticles, ranging in size between 3 and 15 nm, are spherical and homogenously anchored on the surface of carbon nanosheets. The formation of Csbnd Osbnd Si bridges between carbon sheets and the organosilica nanoparticles has been supported by FTIR and EPR. These nanoparticles are bound to the nanosheet surface together with individual functional organosilane groups at a spacing of about 4 Å distance. The final hybrid is the complex nanosystem composed of 2D carbon nanosheets, spherical organosilica nanoparticles and immobilized amino organosilane molecules.

  20. Physicochemical properties of surface charge-modified ZnO nanoparticles with different particle sizes

    PubMed Central

    Kim, Kyoung-Min; Choi, Mun-Hyoung; Lee, Jong-Kwon; Jeong, Jayoung; Kim, Yu-Ri; Kim, Meyoung-Kon; Paek, Seung-Min; Oh, Jae-Min

    2014-01-01

    In this study, four types of standardized ZnO nanoparticles were prepared for assessment of their potential biological risk. Powder-phased ZnO nanoparticles with different particle sizes (20 nm and 100 nm) were coated with citrate or L-serine to induce a negative or positive surface charge, respectively. The four types of coated ZnO nanoparticles were subjected to physicochemical evaluation according to the guidelines published by the Organisation for Economic Cooperation and Development. All four samples had a well crystallized Wurtzite phase, with particle sizes of ∼30 nm and ∼70 nm after coating with organic molecules. The coating agents were determined to have attached to the ZnO surfaces through either electrostatic interaction or partial coordination bonding. Electrokinetic measurements showed that the surface charges of the ZnO nanoparticles were successfully modified to be negative (about −40 mV) or positive (about +25 mV). Although all the four types of ZnO nanoparticles showed some agglomeration when suspended in water according to dynamic light scattering analysis, they had clearly distinguishable particle size and surface charge parameters and well defined physicochemical properties. PMID:25565825

  1. Durable superhydrophobic and antireflective surfaces by trimethylsilanized silica nanoparticles-based sol-gel processing.

    PubMed

    Manca, Michele; Cannavale, Alessandro; De Marco, Luisa; Aricò, Antonino S; Cingolani, Roberto; Gigli, Giuseppe

    2009-06-02

    We present a robust and cost-effective coating method to fabricate long-term durable superhydrophobic andsimultaneouslyantireflective surfaces by a double-layer coating comprising trimethylsiloxane (TMS) surface-functionalized silica nanoparticles partially embedded into an organosilica binder matrix produced through a sol-gel process. A dense and homogeneous organosilica gel layer was first coated onto a glass substrate, and then, a trimethylsilanized nanospheres-based superhydrophobic layer was deposited onto it. After thermal curing, the two layers turned into a monolithic film, and the hydrophobic nanoparticles were permanently fixed to the glass substrate. Such treated surfaces showed a tremendous water repellency (contact angle = 168 degrees ) and stable self-cleaning effect during 2000 h of outdoor exposure. Besides this, nanotextured topology generated by the self-assembled nanoparticles-based top layer produced a fair antireflection effect consisting of more than a 3% increase in optical transmittance.

  2. Polyaspartamide derivative nanoparticles with tunable surface charge achieve highly efficient cellular uptake and low cytotoxicity.

    PubMed

    Xu, Min; Zhao, Yuefang; Feng, Min

    2012-08-07

    Cationic nanocarrier mediated intracellular therapeutic agent delivery acts as a double-edged sword: the carriers promote cellular uptake, but interact nonspecifically and strongly with negatively charged endogenic proteins and cell membranes, which results in aggregates and high cytotoxicity. The present study was aimed at exploring zwitterionic polyaspartamide derivative nanoparticles for efficient intracellular delivery with low cytotoxicity. Poly(aspartic acid) partially grafted tetraethylenepentamine (PASP-pg-TEPA) with different isoelectric points (IEPs) was synthesized. The PASP-pg-TEPA formed zwitterionic nanoparticles with an irregular core and a well-defined shell structure in aqueous medium. Their particle size decreased from about 300 to 80 nm with an increase of the IEP from 7.5 to 9.1. The surface charge of the PASP-pg-TEPA nanoparticles could be tuned from positive to negative with a change of the pH of the medium. The nanoparticles with an IEP above 8.5 exhibited good stability under simulated physiological conditions. It was noted that the zwitterionic PASP-pg-TEPA nanoparticles displayed highly efficient cellular uptake in HeLa cells (approximately 99%) in serum-containing medium and did not adversely affect the cell viability at concentrations up to 1 mg/mL. Furthermore, thermodynamic analysis using isothermal titration calorimetry provided direct evidence that these zwitterionic nanoparticles had low binding affinities for serum protein. Therefore, the zwitterionic PASP-pg-TEPA nanoparticles could overcome limitations of cationic nanocarriers and achieve efficient intracellular delivery with low cytotoxicity.

  3. Io's surface composition based on reflectance spectra of sulfur/salt mixtures and proton-irradiation experiments

    NASA Technical Reports Server (NTRS)

    Nash, D. B.; Fanale, F. P.

    1977-01-01

    Available full-disk reflectance spectra of Io in the range 0.3 to 2.5 microns have been used to determine a surface compositional model for Io that is consistent with Io's other known chemical and physical properties. Results indicate that the surface of Io contains abundant dehydrated salts of high Na, Mg, and Fe(3+) content such as bloedite and ferrous iron sulfate. Experiments were performed studying the irradiation damage effects from low-energy proton bombardment, since Io is immersed in Jupiter's magnetosphere.

  4. Design strategy of surface decoration for efficient delivery of nanoparticles by computer simulation

    PubMed Central

    Ding, Hong-ming; Ma, Yu-qiang

    2016-01-01

    Understanding the role of surface decoration of nanoparticles in protein adsorption and cellular uptake is of great importance in biomedicine. Here, by using dissipative particle dynamics simulations, we take two typical coating polymers (i.e., hydrophilic and zwitterionic polymers) as an example, and systematically investigate their effect on cellular delivery of hydrophobic and charged nanoparticles (in the presence of serum protein). Our results show that though two types of polymers are charge-neutral and can both reduce the protein adsorption, there exist some differences between their ability of protein resistance, especially in the case of positively charged nanoparticles. Besides, it is found that the coating polymers may also greatly decrease the cellular uptake efficiency of nanoparticles. Nevertheless, and importantly, since the zwitterionic polymers may become positively charged under low pH environments, the nanoparticle can attach onto cell membrane more firmly than that coated with hydrophilic polymers, which can further enhance the active targeting of nanoparticles. Finally, we also provide the design maps for surface decoration to achieve efficient cellular delivery. These results can help better understand how to keep the balance between protein resistance and cell targeting, which may give some useful guidelines on optimal design of future nanomaterials in drug delivery. PMID:27226273

  5. Chemical dynamics simulations of energy transfer, surface-induced dissociation, soft-landing, and reactive-landing in collisions of protonated peptide ions with organic surfaces.

    PubMed

    Pratihar, Subha; Barnes, George L; Hase, William L

    2016-07-07

    There are two components to the review presented here regarding simulations of collisions of protonated peptide ions peptide-H(+) with organic surfaces. One is a detailed description of the classical trajectory chemical dynamics simulation methodology. Different simulation approaches are used, and identified as MM, QM + MM, and QM/MM dependent on the potential energy surface used to represent the peptide-H(+) + surface collision. The second are representative examples of the information that may be obtained from the simulations regarding energy transfer and peptide-H(+) surface-induced dissociation, soft-landing, and reactive-landing for the peptide-H(+) + surface collisions. Good agreement with experiment is obtained for each of these four collision properties. The simulations provide atomistic interpretations of the peptide-H(+) + surface collision dynamics.

  6. Surface-enhanced Raman scattering sensor for theophylline determination by molecular imprinting on silver nanoparticles.

    PubMed

    Liu, Ping; Liu, Renyong; Guan, Guijian; Jiang, Changlong; Wang, Suhua; Zhang, Zhongping

    2011-10-21

    A surface-enhanced Raman scattering (SERS)-based sensor for the determination of theophylline (THO) has been developed by imprinting the target molecules on the surface of silver nanoparticles. The desired recognition sites are generated after template removal and homogeneous distribution on the silver nanoparticles that have been incorporated within polymer matrix by the in situ reduction of theophylline-silver complexes, providing molecular recognition ability and SERS active surfaces. The theophylline molecules, complementary to the shape, size, and functionality of the recognition cavities, can selectively bind to the recognition sites at the surface of silver nanoparticles driven by the formation of hydrogen bonding and surface coordination. It has been demonstrated that the SERS signals of the theophylline molecules captured on the surface of the silver nanoparticles have a good reproducibility and a dose-response relationship to the target analytes, showing the potential for reliable identification and quantification of the bioactive compound. The molecular imprinting-based SERS sensor, like antibodies or enzymes, also possesses the ability to distinguish theophylline from the closely related structure caffeine due to the variations of molecular size and shape as well as the different affinity to silver ions.

  7. Highly hydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles.

    PubMed

    Tiraferri, Alberto; Kang, Yan; Giannelis, Emmanuel P; Elimelech, Menachem

    2012-09-26

    Thin-film composite polyamide membranes are state-of-the-art materials for membrane-based water purification and desalination processes, which require both high rejection of contaminants and high water permeabilities. However, these membranes are prone to fouling when processing natural waters and wastewaters, because of the inherent surface physicochemical properties of polyamides. The present work demonstrates the fabrication of forward osmosis polyamide membranes with optimized surface properties via facile and scalable functionalization with fine-tuned nanoparticles. Silica nanoparticles are coated with superhydrophilic ligands possessing functional groups that impart stability to the nanoparticles and bind irreversibly to the native carboxyl moieties on the membrane selective layer. The tightly tethered layer of nanoparticles tailors the surface chemistry of the novel composite membrane without altering the morphology or water/solute permeabilities of the membrane selective layer. Surface characterization and interfacial energy analysis confirm that highly hydrophilic and wettable membrane surfaces are successfully attained. Lower intermolecular adhesion forces are measured between the new membrane materials and model organic foulants, indicating the presence of a bound hydration layer at the polyamide membrane surface that creates a barrier for foulant adhesion.

  8. Surface faceting and elemental diffusion behaviour at atomic scale for alloy nanoparticles during in situ annealing

    DOE PAGES

    Chi, Miaofang; Wang, Chao; Lei, Yinkai; ...

    2015-11-18

    The catalytic performance of nanoparticles is primarily determined by the precise nature of the surface and near-surface atomic configurations, which can be tailored by post-synthesis annealing effectively and straightforwardly. Understanding the complete dynamic response of surface structure and chemistry to thermal treatments at the atomic scale is imperative for the rational design of catalyst nanoparticles. Here, by tracking the same individual Pt3Co nanoparticles during in situ annealing in a scanning transmission electron microscope, we directly discern five distinct stages of surface elemental rearrangements in Pt3Co nanoparticles at the atomic scale: initial random (alloy) elemental distribution; surface platinum-skin-layer formation; nucleation ofmore » structurally ordered domains; ordered framework development and, finally, initiation of amorphization. Furthermore, a comprehensive interplay among phase evolution, surface faceting and elemental inter-diffusion is revealed, and supported by atomistic simulations. Furthermore, this work may pave the way towards designing catalysts through post-synthesis annealing for optimized catalytic performance.« less

  9. Magnetic domains and surface effects in hollow maghemite nanoparticles

    SciTech Connect

    Cabot, Andreu; Alivisatos, A. Paul; Puntes, Victor; Balcells, Lluis; Iglesias, Oscar; Labarta, Amilcar

    2008-09-30

    In the present work, we investigate the magnetic properties of ferrimagnetic and non-interacting maghemite hollow nanoparticles obtained by the Kirkendall effect. From the experimental characterization of their magnetic behavior, we find that polycrystalline hollow maghemite nanoparticles exhibit low blocked-to-superparamagnetic transition temperatures, small magnetic moments, significant coercivities and irreversibility fields, and no magnetic saturation on external magnetic fields up to 5 T. These results are interpreted in terms of the microstructural parameters characterizing the maghemite shells by means of atomistic Monte Carlo simulations of an individual spherical shell. The model comprises strongly interacting crystallographic domains arranged in a spherical shell with random orientations and anisotropy axis. The Monte Carlo simulation allows discernment between the influence of the polycrystalline structure and its hollow geometry, while revealing the magnetic domain arranggement in the different temperataure regimes.

  10. Utilizing the photothermal effect for releasing molecules from the surfaces of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Samsam Bakhtiari, Amir Bahman

    Nanomaterials, with unique physical and chemical properties, have the potential to help in the development of drug delivery systems. Some of these properties can be attributed to the nanoscale dimension of these materials. By masking, targeting, and release of a therapeutic agent, these nanomaterials can provide a delivery system that would reduce side effects. Gold nanoparticles have been studied as a candidate for the drug delivery system. These materials can be decorated with molecules that have a thermally responsive reaction (i.e., Diels-Alder). In addition, gold nanoparticles when irradiated with a right wavelength of light produce heat. Consequently, the generated heat from nanoparticles causes a retro-Diels-Alder reaction, which release a segment of molecule (i.e., payload) from gold surfaces. This controlled release mechanism is a novel method to take advantage of the properties inherent in gold nanoparticles and have the potential to be used in drug delivery system.

  11. Using Response Surface Methodology in Synthesis of Ultrafine Copper Nanoparticles by Electrolysis

    NASA Astrophysics Data System (ADS)

    Tamilvanan, A.; Balamurugan, K.; Ponappa, K.; Madhan Kumar, B.

    2016-02-01

    Electrolysis is a method used for producing copper (Cu) nanoparticles at faster rate and at low cost in ambient conditions. The property of Cu nanoparticles prepared by electrolysis depends on their process parameters. The influence of selected process parameters such as copper sulfate (CuSo4) concentration, electrode gap and electrode potential difference on particle size was investigated. To optimize these parameters response surface methodology (RSM) was used. Cu nanoparticles prepared by electrolysis were characterized by using X-ray diffraction (XRD) and scanning electron microscope (SEM). After reviewing the results of analysis of variance (ANOVA), mathematical equation was created and optimized parameters for producing Cu nanoparticles were determined. The results confirm that the average size of Cu particle at the optimum condition was found to be 17nm and they are hexagonal in shape.

  12. Temperature-induced processes for size-selected metallic nanoparticles on surfaces

    NASA Astrophysics Data System (ADS)

    Bettermann, H.; Werner, M.; Getzlaff, M.

    2017-01-01

    The melting behavior of Iron-Nickel alloy nanoparticles on W(110) was studied under UHV conditions as a function of heating temperature and heating duration. These particles were found to be stable at 423 K without evaporation or diffusion taking place. Unrolling carpet behavior occurs at higher temperatures. This creates ramified islands around the nanoparticles. Ostwald ripening at higher temperatures or longer heating times is creating compact islands. The melting of these nanoparticles opens the possibility for thin film growth of FeNi alloys. The formation of monolayer high islands is a strong contrast to Fe, Co, and FeCo alloy nanoparticles which are dominated by direct evaporation, single atom surface diffusion and anisotropic spreading.

  13. Nanoparticle technology for treatment of Parkinson's disease: the role of surface phenomena in reaching the brain.

    PubMed

    Leyva-Gómez, Gerardo; Cortés, Hernán; Magaña, Jonathan J; Leyva-García, Norberto; Quintanar-Guerrero, David; Florán, Benjamín

    2015-07-01

    The absence of a definitive treatment for Parkinson's disease has driven the emerging investigation in the search for novel therapeutic alternatives. At present, the formulation of different drugs on nanoparticles has represented several advantages over conventional treatments. This type of multifunctional carrier, owing to its size and composition, has different interactions in biological systems that can lead to a decrease in ability to cross the blood-brain barrier. Therefore, this review focuses on the latest advances in obtaining nanoparticles for Parkinson's disease and provides an overview of technical aspects in the design of brain drug delivery of nanoparticles and an analysis of surface phenomena, a key aspect in the development of functional nanoparticles for Parkinson's disease.

  14. Magnetic nanoparticle (MNP) enhanced biosensing by surface plasmon resonance (SPR) for portable devices

    NASA Astrophysics Data System (ADS)

    Wang, Jianlong; Zhu, Zanzan; Munir, Ahsan; Zhou, H. Susan

    2010-04-01

    The use of magnetic nanparticles in microfluidic systems is emerging and is receiving growing attention due to the synergistic advantages of microfluidics and magnetic nanoparticles. Biomagnetic separation techniques based on magnetic nanoparticles are becoming increasingly important with a wide range of possible applications. However, the separation products are difficult to be detected by general method due to the small size of MNPs. Here, we demonstrate magnetic nanoparticles can greatly enhance the signal of surface plasmon resonance spectroscopy (SPR). Features of MNPs-aptamer conjugates as a powerful amplification reagent for ultrasensitive immunoassay are explored for the first time. Our results confirm that MNPs is a powerful sandwich element and an excellent amplification reagent for SPR based sandwich immunoassay and SPR has a great potential for the detection of magnetic nanoparticles-based separation products.

  15. Revisiting 30 years of biofunctionalization and surface chemistry of inorganic nanoparticles for nanomedicine

    PubMed Central

    Conde, João; Dias, Jorge T.; Grazú, Valeria; Moros, Maria; Baptista, Pedro V.; de la Fuente, Jesus M.

    2014-01-01

    In the last 30 years we have assisted to a massive advance of nanomaterials in material science. Nanomaterials and structures, in addition to their small size, have properties that differ from those of larger bulk materials, making them ideal for a host of novel applications. The spread of nanotechnology in the last years has been due to the improvement of synthesis and characterization methods on the nanoscale, a field rich in new physical phenomena and synthetic opportunities. In fact, the development of functional nanoparticles has progressed exponentially over the past two decades. This work aims to extensively review 30 years of different strategies of surface modification and functionalization of noble metal (gold) nanoparticles, magnetic nanocrystals and semiconductor nanoparticles, such as quantum dots. The aim of this review is not only to provide in-depth insights into the different biofunctionalization and characterization methods, but also to give an overview of possibilities and limitations of the available nanoparticles. PMID:25077142

  16. Triply surface-plasmon resonant four-wave mixing imaging of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Masia, Francesco; Langbein, Wolfgang; Watson, Peter; Borri, Paola

    2011-03-01

    We have developed a novel multiphoton microscopy technique not relying on (and hence not limited by) fluorescence emission, which exploits the third-order nonlinearity called four-wave mixing of gold nanoparticles in resonance with their surface Plasmon. The coherent, transient and resonant nature of this signal allows its detection free from backgrounds that limit other contrast methods for gold nanoparticles. We show detection of single 10nm gold nanoparticles with low excitation intensities, corresponding to negligible average thermal heating. Owing to the the third-order nonlinearity we measure a transversal and axial resolution of 140nm and 470nm respectively, better than the one-photon diffraction limit. We also show high-contrast imaging of gold-labels down to 5nm size in Golgi structures of HepG2 cells at useful imaging speeds (10 kHz pixel rate). Thermal dissociation of gold nanoparticles from their bonding sites when varying the excitation intensity is also investigated.

  17. Effects of para-substituents of styrene derivatives on their chemical reactivity on platinum nanoparticle surfaces

    NASA Astrophysics Data System (ADS)

    Hu, Peiguang; Chen, Limei; Deming, Christopher P.; Lu, Jia-En; Bonny, Lewis W.; Chen, Shaowei

    2016-06-01

    Stable platinum nanoparticles were successfully prepared by the self-assembly of para-substituted styrene derivatives onto the platinum surfaces as a result of platinum-catalyzed dehydrogenation and transformation of the vinyl groups to the acetylene ones, forming platinum-vinylidene/-acetylide interfacial bonds. Transmission electron microscopic measurements showed that the nanoparticles were well dispersed without apparent aggregation, suggesting sufficient protection of the nanoparticles by the organic capping ligands, and the average core diameter was estimated to be 2.0 +/- 0.3 nm, 1.3 +/- 0.2 nm, and 1.1 +/- 0.2 nm for the nanoparticles capped with 4-tert-butylstyrene, 4-methoxystyrene, and 4-(trifluoromethyl)styrene, respectively, as a result of the decreasing rate of dehydrogenation with the increasing Taft (polar) constant of the para-substituents. Importantly, the resulting nanoparticles exhibited unique photoluminescence, where an increase of the Hammett constant of the para-substituents corresponded to a blue-shift of the photoluminescence emission, suggesting an enlargement of the HOMO-LUMO band gap of the nanoparticle-bound acetylene moieties. Furthermore, the resulting nanoparticles exhibited apparent electrocatalytic activity towards oxygen reduction in acidic media, with the best performance among the series of samples observed with the 4-tert-butylstyrene-capped nanoparticles due to an optimal combination of the nanoparticle core size and ligand effects on the bonding interactions between platinum and oxygen species.Stable platinum nanoparticles were successfully prepared by the self-assembly of para-substituted styrene derivatives onto the platinum surfaces as a result of platinum-catalyzed dehydrogenation and transformation of the vinyl groups to the acetylene ones, forming platinum-vinylidene/-acetylide interfacial bonds. Transmission electron microscopic measurements showed that the nanoparticles were well dispersed without apparent

  18. Surface engineering of Co and FeCo nanoparticles for biomedical application

    NASA Astrophysics Data System (ADS)

    Behrens, Silke; Bönnemann, Helmut; Matoussevitch, Nina; Gorschinski, Angelika; Dinjus, Eckhard; Habicht, Wilhelm; Bolle, Jens; Zinoveva, Svetlana; Palina, Natalie; Hormes, Josef; Modrow, Hartwig; Bahr, Stephan; Kempter, Volker

    2006-09-01

    Monodisperse Co, Fe, and FeCo nanoparticles are prepared via thermal decomposition of metal carbonyls in the presence of aluminium alkyls, yielding air-stable magnetic metal nanoparticles after surface passivation. The particles are characterized by electron microscopy (SEM, TEM, ESI), electron spectroscopy (MIES, UPS, and XPS) and x-ray absorption spectroscopy (EXAFS). The particles are peptized by surfactants to form stable magnetic fluids in various organic media and water, exhibiting a high volume concentration and a high saturation magnetization. In view of potential biomedical applications of the particles, several procedures for surface modification are presented, including peptization by functional organic molecules, silanization, and in situ polymerization.

  19. Preparation, Surface Properties, and Therapeutic Applications of Gold Nanoparticles in Biomedicine.

    PubMed

    Panahi, Yunes; Mohammadhosseini, Majid; Nejati-Koshki, Kazem; Abadi, Azam Jafari Najaf; Moafi, Hadi Fallah; Akbarzadeh, Abolfazl; Farshbaf, Masoud

    2017-02-01

    Gold nanoparticles (AuNPs) due to their unique properties and manifold surface functionalities have been applied in bio-nanotechnology. The application of GNPs in recent medical and biological research is very extensive. Especially it involves applications such as detection and photothermalysis of microorganisms and cancer stem cells, biosensors; optical bio-imaging and observing of cells and these nanostructures also serve as practical platforms for therapeutic agents. In this review we studied all therapeutic applications of gold nanoparticles in biomedicine, synthesis methods, and surface properties.

  20. Correlation Between Surface Chemistry and Electrocatalytic Properties of Monodisperse Pt(x)Ni(1-x) Nanoparticles

    SciTech Connect

    Wang, Chao; Chi, Miaofang; Wang, Guofeng; Van der Vliet, Dennis; Li, Dongguo; More, Karren Leslie; Wang, Hsien-Hua; Schlueter, John; Markovic, Nenad; Stamenkovic, Vojislav

    2011-01-01

    Monodisperse and homogeneous Pt{sub x}Ni{sub 1-x} alloy nanoparticles of various compositions are synthesized via an organic solution approach in order to reveal the correlation between surface chemistry and their electrocatalytic properties. Atomic-level microscopic analysis of the compositional profile and modeling of nanoparticle structure are combined to follow the dependence of Ni dissolution on the initial alloy composition and formation of the Pt-skeleton nanostructures. The developed approach and acquired knowledge about surface structure-property correlation can be further generalized and applied towards the design of advanced functional nanomaterials.

  1. Effect of fullerenol surface chemistry on nanoparticle binding-induced protein misfolding

    NASA Astrophysics Data System (ADS)

    Radic, Slaven; Nedumpully-Govindan, Praveen; Chen, Ran; Salonen, Emppu; Brown, Jared M.; Ke, Pu Chun; Ding, Feng

    2014-06-01

    Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and dynamics of ubiquitin. We found that all derivatives bound to the model protein. Specifically, the more hydrophilic nanoparticles with a higher number of hydroxyl groups bound to the surface of the protein via hydrogen bonds, which stabilized the protein without inducing large conformational changes in the protein structure. In contrast, fullerene derivatives with a smaller number of hydroxyl groups buried their hydrophobic surface inside the protein, thereby causing protein denaturation. Overall, our results revealed a distinct role of surface chemistry on nanoparticle-protein binding and binding-induced protein misfolding.Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and

  2. Surface enhanced Raman scattering study of the antioxidant alkaloid boldine using prismatic silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Herrera, M. A.; Jara, G. P.; Villarroel, R.; Aliaga, A. E.; Gómez-Jeria, J. S.; Clavijo, E.; Garrido, C.; Aguayo, T.; Campos Vallette, M. M.

    2014-12-01

    Prismatic silver nanoparticles (PNps) were used in the surface enhanced Raman scattering (SERS) study of the antioxidant alkaloid boldine (5,6,6a,7-tetrahydro-1,10-dimethoxy-6-methyl-4H-dibenzo[de,g]quinoline-2,9-diol). Prismatic and quasi-spherical (QsNps) silver nanoparticles were synthesized and characterized by UV-Vis spectra, topographic profile (AFM) and zeta potential measurements. Raman and infrared (IR) spectra of the boldine were registered. Theoretical model calculations of the boldine onto the Ag surface predict a nearly coplanar orientation of the benzo[de]quinoline moiety and non-bonded interactions (electrostatic).

  3. Signal enhancement of surface plasmon resonance based on gold nanoparticle-antibody complex for immunoassay.

    PubMed

    Lee, Woochang; Oh, Byung-Keun; Kim, Yong-Wan; Choi, Jeong-Woo

    2006-11-01

    In the immunoassay based on surface plasmon resonance (SPR) system, the signal enhancement was done by means of the conjugate of gold (Au) nanoparticle-antibody fragment. Antibody fragment was prepared for the improved immobilization based on Au-thiol interaction. Through the ellipsometric analysis on surface, the conjugation between Au and antibody fragment was performed in the oriented manner. The optimal fabrication conditions such as concentration and incubation time were determined for the constant size of the fabricated nanoparticle-antibody conjugate. Through the plot of SPR angle difference versus antigen concentration, the linear correlation was achieved, of which the detection limit was 100 fg/ml.

  4. Durable, superoleophobic polymer–nanoparticle composite surfaces with re-entrant geometry via solvent-induced phase transformation

    NASA Astrophysics Data System (ADS)

    Brown, Philip S.; Bhushan, Bharat

    2016-02-01

    Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices.

  5. Durable, superoleophobic polymer–nanoparticle composite surfaces with re-entrant geometry via solvent-induced phase transformation

    PubMed Central

    Brown, Philip S.; Bhushan, Bharat

    2016-01-01

    Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices. PMID:26876479

  6. High-speed collision of copper nanoparticle with aluminum surface: Molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Pogorelko, Victor V.; Mayer, Alexander E.; Krasnikov, Vasiliy S.

    2016-12-01

    We investigate the effect of the high-speed collision of copper nanoparticles with aluminum surface by means of molecular dynamic simulations. Studied diameter of nanoparticles is varied within the range 7.2-22 nm and the velocity of impact is equal to 500 or 1000 m/s. Dislocation analysis shows that a large quantity of dislocations is formed within the impact area. Overall length of dislocations is determined, first of all, by the impact velocity and by the size of incident copper nanoparticle, in other words, by the kinetic energy of the nanoparticle. Dislocations occupy the total volume of the impacted aluminum single crystal layer (40.5 nm in thickness) in the form of intertwined structure in the case of large kinetic energy of the incident nanoparticle. Decrease in the initial kinetic energy or increase in the layer thickness lead to restriction of the penetration depth of the dislocation net; formation of separate dislocation loops is observed in this case. Increase in the initial system temperature slightly raises the dislocation density inside the bombarded layer and considerably decreases the dislocation density inside the nanoparticle. The temperature increase also leads to a deeper penetration of the copper atoms inside the aluminum. Additional molecular dynamic simulations show that the deposited particles demonstrate a very good adhesion even in the case of the considered relatively large nanoparticles. Medium energy of the nanoparticles corresponding to velocity of about 500 m/s and elevated temperature of the system about 700-900 K are optimal parameters for production of high-quality layers of copper on the aluminum surface. These conditions provide both a good adhesion and a less degree of the plastic deformation. At the same time, higher impact velocities can be used for combined treatment consisting of both the plastic deformation and the coating.

  7. Enteric trimethyl chitosan nanoparticles containing hepatitis B surface antigen for oral delivery.

    PubMed

    Farhadian, Asma; Dounighi, Naser Mohammadpour; Avadi, Mohammadreza

    2015-01-01

    Oral vaccination is the preferred route of immunization. However, the degradative condition of the gastrointestinal tract and the higher molecular size of peptides pose major challenges in developing an effective oral vaccination system. One of the most excellent methods used in the development of oral vaccine delivery system relies on the entrapment of the antigen in polymeric nanoparticles. In this work, trimethyl chitosan (TMC) nanoparticles were fabricated using ionic gelation teqnique by interaction hydroxypropyl methylcellulose phthalate (HPMCP), a pH-sensitive polymer, with TMC and the utility of the particles in the oral delivery of hepatitis B surface antigen (HBsAg) was evaluated employing solutions that simulated gastric and intestinal conditions. The particle size, morphology, zeta potential, loading capacity, loading efficiency, in vitro release behavior, structure, and morphology of nanoparticles were evaluated, and the activity of the loaded antigen was assessed. Size of the optimized TMC/HPMCP nanoparticles and that of the antigen-loaded nanoparticles were 85 nm and 158 nm, respectively. Optimum loading capacity (76.75%) and loading efficiency (86.29%) were achieved at 300 µg/mL concentration of the antigen. SEM images revealed a spherical shape as well as a smooth and near-homogenous surface of nanoparticles. Results of the in vitro release studies showed that formulation with HPMCP improved the acid stability of the TMC nanoparticles as well as their capability to preserve the loaded HBsAg from gastric destruction. The antigen showed good activity both before and after loading. The results suggest that TMC/HPMCP nanoparticles could be used in the oral delivery of HBsAg vaccine.

  8. Surface plasma resonant effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells

    PubMed Central

    2013-01-01

    In this study, we prepared different shapes of gold nanoparticles by seed-mediated growth method and applied them on the photoelectrodes of dye-sensitized solar cells (DSSCs) to study the surface plasma resonant (SPR) effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells. The analyses of field emission scanning electron microscopy show that the average diameter of the spherical gold nanoparticles is 45 nm, the average length and width of the short gold nanorods were 55 and 22 nm, respectively, and the average length and width of the long gold nanorods were 55 and 14 nm, respectively. The aspect ratio of the short and long gold nanorods was about 2.5 and 4, respectively. The results of ultraviolet–visible absorption spectra show that the absorption wavelength is about 540 nm for spherical gold nanoparticles, and the absorption of the gold nanorods reveals two peaks. One is about 510 to 520 nm, and the other is about 670 and 710 nm for the short and long gold nanorods, respectively. The best conversion efficiency of the dye-sensitized solar cells with spherical gold nanoparticles and short and long gold nanorods added in is 6.77%, 7.08%, and 7.29%, respectively, and is higher than that of the cells without gold nanoparticles, which is 6.21%. This result indicates that the effect of gold nanoparticles on the photoelectrodes can increase the conductivity and reduce the recombination of charges in the photoelectrodes, resulting in the increase of conversion efficiency for DSSCs. In addition, the long gold nanorods have stronger SPR effect than the spherical gold nanoparticles and short gold nanorods at long wavelength. This may be the reason for the higher conversion efficiency of DSSCs with long gold nanorods than those of the cells with spherical gold nanoparticles and short gold nanorods. PMID:24172147

  9. Effect of net surface charge on physical properties of the cellulose nanoparticles and their efficacy for oral protein delivery.

    PubMed

    Song, Yongbo; Chen, Lingyun

    2015-05-05

    Both net positively and negatively charged cellulose-based nanoparticles were prepared from oppositely charged carboxymethylcellulose (CMC) and quaternized cellulose (QC). Effect of surface charge on efficacy of cellulose nanoparticles for delivering both positively and negatively charged proteins was investigated. Lysozyme (LYS) and bovine serum albumin (BSA), which possess positive and negative charge at physiological pH respectively, were used as models. The results revealed that high encapsulation efficiency (67.7% and 85.1%) could be achieved when negatively charged protein was encapsulated in positively charged nanoparticles, or positively charged protein was encapsulated in negatively charged nanoparticles. Proteins encapsulated in optimal cellulose nanoparticles could be sustainably released and no obvious protein denaturation was detected. Both net positively and negatively charged nanoparticles exhibited low cytotoxicity due to cellulose's good biocompatibility. Not only net positively charged nanoparticles demonstrated high cellular uptake efficiency, but also net negatively charged nanoparticles showed somewhat efficient cellular uptake.

  10. Cytotoxicity of surface-functionalized silicon and germanium nanoparticles: the dominant role of surface charges

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Sourav; Rietjens, Ivonne M. C. M.; Singh, Mani P.; Atkins, Tonya M.; Purkait, Tapas K.; Xu, Zejing; Regli, Sarah; Shukaliak, Amber; Clark, Rhett J.; Mitchell, Brian S.; Alink, Gerrit M.; Marcelis, Antonius T. M.; Fink, Mark J.; Veinot, Jonathan G. C.; Kauzlarich, Susan M.; Zuilhof, Han

    2013-05-01

    Although it is frequently hypothesized that surface (like surface charge) and physical characteristics (like particle size) play important roles in cellular interactions of nanoparticles (NPs), a systematic study probing this issue is missing. Hence, a comparative cytotoxicity study, quantifying nine different cellular endpoints, was performed with a broad series of monodisperse, well characterized silicon (Si) and germanium (Ge) NPs with various surface functionalizations. Human colonic adenocarcinoma Caco-2 and rat alveolar macrophage NR8383 cells were used to clarify the toxicity of this series of NPs. The surface coatings on the NPs appeared to dominate the cytotoxicity: the cationic NPs exhibited cytotoxicity, whereas the carboxylic acid-terminated and hydrophilic PEG- or dextran-terminated NPs did not. Within the cationic Si NPs, smaller Si NPs were more toxic than bigger ones. Manganese-doped (1% Mn) Si NPs did not show any added toxicity, which favors their further development for bioimaging. Iron-doped (1% Fe) Si NPs showed some added toxicity, which may be due to the leaching of Fe3+ ions from the core. A silica coating seemed to impart toxicity, in line with the reported toxicity of silica. Intracellular mitochondria seem to be the target for the toxic NPs since a dose-, surface charge- and size-dependent imbalance of the mitochondrial membrane potential was observed. Such an imbalance led to a series of other cellular events for cationic NPs, like decreased mitochondrial membrane potential (ΔΨm) and ATP production, induction of ROS generation, increased cytoplasmic Ca2+ content, production of TNF-α and enhanced caspase-3 activity. Taken together, the results explain the toxicity of Si NPs/Ge NPs largely by their surface characteristics, provide insight into the mode of action underlying the observed cytotoxicity, and give directions on synthesizing biocompatible Si and Ge NPs, as this is crucial for bioimaging and other applications in for example

  11. The mechanisms for nanoparticle surface diffusion and chain self-assembly determined from real-time nanoscale kinetics in liquid

    SciTech Connect

    Woehl, Taylor J.; Prozorov, Tanya

    2015-08-20

    The mechanisms for nanoparticle self-assembly are often inferred from the morphology of the final nanostructures in terms of attractive and repulsive interparticle interactions. Understanding how nanoparticle building blocks are pieced together during self-assembly is a key missing component needed to unlock new strategies and mechanistic understanding of this process. Here we use real-time nanoscale kinetics derived from liquid cell transmission electron microscopy investigation of nanoparticle self-assembly to show that nanoparticle mobility dictates the pathway for self-assembly and final nanostructure morphology. We describe a new method for modulating nanoparticle diffusion in a liquid cell, which we employ to systematically investigate the effect of mobility on self-assembly of nanoparticles. We interpret the observed diffusion in terms of electrostatically induced surface diffusion resulting from nanoparticle hopping on the liquid cell window surface. Slow-moving nanoparticles self-assemble predominantly into linear 1D chains by sequential attachment of nanoparticles to existing chains, while highly mobile nanoparticles self-assemble into chains and branched structures by chain–chain attachments. Self-assembly kinetics are consistent with a diffusion-driven mechanism; we attribute the change in self-assembly pathway to the increased self-assembly rate of highly mobile nanoparticles. Furthermore, these results indicate that nanoparticle mobility can dictate the self-assembly mechanism and final nanostructure morphology in a manner similar to interparticle interactions.

  12. The mechanisms for nanoparticle surface diffusion and chain self-assembly determined from real-time nanoscale kinetics in liquid

    DOE PAGES

    Woehl, Taylor J.; Prozorov, Tanya

    2015-08-20

    The mechanisms for nanoparticle self-assembly are often inferred from the morphology of the final nanostructures in terms of attractive and repulsive interparticle interactions. Understanding how nanoparticle building blocks are pieced together during self-assembly is a key missing component needed to unlock new strategies and mechanistic understanding of this process. Here we use real-time nanoscale kinetics derived from liquid cell transmission electron microscopy investigation of nanoparticle self-assembly to show that nanoparticle mobility dictates the pathway for self-assembly and final nanostructure morphology. We describe a new method for modulating nanoparticle diffusion in a liquid cell, which we employ to systematically investigate themore » effect of mobility on self-assembly of nanoparticles. We interpret the observed diffusion in terms of electrostatically induced surface diffusion resulting from nanoparticle hopping on the liquid cell window surface. Slow-moving nanoparticles self-assemble predominantly into linear 1D chains by sequential attachment of nanoparticles to existing chains, while highly mobile nanoparticles self-assemble into chains and branched structures by chain–chain attachments. Self-assembly kinetics are consistent with a diffusion-driven mechanism; we attribute the change in self-assembly pathway to the increased self-assembly rate of highly mobile nanoparticles. Furthermore, these results indicate that nanoparticle mobility can dictate the self-assembly mechanism and final nanostructure morphology in a manner similar to interparticle interactions.« less

  13. Understanding electric field-enhanced transport for the measurement of nanoparticles and their assembly on surfaces

    NASA Astrophysics Data System (ADS)

    Tsai, De-Hao

    The goal of this dissertation is to understand the synthesis, characterization, and integration of nanoparticles and nanoparticle-based devices by electric field-enhanced transport of nanoparticles. Chapter I describes the factors used for determining particle trajectories and found that electric fields provide the directional electrostatic force to overcome other non-directional influences on particle trajectories. This idea is widely applied in the nanoparticle classification, characterization, and assembly onto substrate surfaces as investigated in the following chapters. Chapter 2 presents a new assembly method to position metal nanoparticles delivered from the gas phase onto surfaces using the electrostatic force generated by biased p-n junction patterned substrates. Aligned deposition patterns of metal nanoparticles were observed, and the patterning selectivity quantified. A simple model accounting for the generated electric field, and the electrostatic, van der Waals, and image forces was used to explain the observed results. Chapter 2.2 describes a data set for particle size resolved deposition, from which a Brownian dynamics model for the process can be evaluated. Brownian motion and fluid convection of nanoparticles, as well as the interactions between the charged nanoparticles and the patterned substrate, including electrostatic force, image force and van der Waals force, are accounted for in the simulation. Using both experiment and simulation the effects of the particle size, electric field intensity, and the convective flow on coverage selectivity have been investigated. Coverage selectivity is most sensitive to electric field, which is controlled by the applied reverse bias voltage across the p-n junction. A non-dimensional analysis of the competition between the electrostatic and diffusion force is found to provide a means to collapse a wide range of process operating conditions and an effective indicator or process performance. Directed assembly of

  14. Quantum well intermixing technique using proton implantation for carrier confinement of vertical-cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Moriwaki, Shouhei; Saitou, Minoru; Miyamoto, Tomoyuki

    2016-08-01

    We investigated quantum well intermixing (QWI) using proton implantation to form the carrier confinement structure in the active layer of a vertical-cavity surface-emitting laser (VCSEL). The required potential barrier height is discussed referring to the result of numerical analysis. The bandgap change due to the QWI was investigated experimentally for various quantum well structures, proton dose densities, and thermal annealing conditions. A potential barrier height of 30 meV was observed using a high-indium and thin-well structure. High crystalline quality was confirmed by photoluminescence intensity measurement, even after the QWI process, and the lasing of the fabricated QWI-VCSEL was observed without any deterioration. The proposed technique would be effective in improving the device performance in a simple fabrication process.

  15. Palladium nanoparticles on hierarchical carbon surfaces: A new architecture for robust nano-catalysts

    NASA Astrophysics Data System (ADS)

    Vijwani, Hema; Mukhopadhyay, Sharmila M.

    2012-12-01

    Surface activity of heterogeneous catalysts can be enhanced if their sizes are reduced to nanometers. However, loose nanomaterials pose potential health and environmental risks. This issue has been addressed by attachment of palladium nanoparticles on multi-scale hierarchical carbon supports that have exceptionally high surface area per volume. The supports consist of porous carbon foam whose surface has been either chemically functionalized, or morphologically altered by grafting of carbon-nanotubes. It is seen that whereas chemical functionalization does provide some increase in nano-catalyst loading, morphological modification is significantly more powerful. It has the potential to create orders of magnitude increase in catalytic activity within the same overall volume. The synthesis techniques have been investigated in sufficient detail to provide significant control over the density and size of nanoparticles. Abundant distribution of nanoparticles is observed even within the deeper pores of the microcellular foam. The nanoparticles are seen to be metallic Pd having face centered cubic structure. Additionally, the nano-particles and nanotubes are durable, and remain attached to the base support after long periods of rapid rotation in water. These robust hybrid structures show promise in future applications such as sensors, water purification systems, fuel cell electrodes and hydrogen storage sponges.

  16. Directed Self-assembly of Nanoparticles at the Polymer Surface by Highly Compressible Supercritical Carbon Dioxide

    SciTech Connect

    M Asada; P Gin; M Endoh; S Satija; T Taniguchi; T Koga

    2011-12-31

    We report a versatile route for self-assembly of polymer-soluble nanoparticles at the polymer surface using highly compressible supercritical carbon dioxide (scCO{sub 2}). Polystyrene and poly(methyl methacrylate)-based nanocomposite thin films with functionalized polyhedral oligomeric silsesquioxane and phenyl C{sub 61} butyric acid methyl ester nanoparticles were prepared on Si substrates and exposed to scCO{sub 2} at different pressures under the isothermal condition of 36 C. The resultant structures could be then preserved by the vitrification process of the glassy polymers via quick pressure quench to atmospheric pressure and subsequently characterized by using various surface sensitive experimental techniques in air. We found that the surface segregation of these nanoparticles is induced in the close vicinity of P = 8.2 MPa where the excess absorption of the fluid into the polymers maximizes. However, when the film thickness becomes less than about 4R{sub g} thick (where R{sub g} is the radius of polymer gyration), the uniform dispersion of the nanoparticles is favorable instead even at the same CO{sub 2} conditions. We clarify that the phase transition is correlated with the emergence of a concentration gradient of the fluid at the polymer/CO{sub 2} interface and is a general phenomenon for different polymer-nanoparticle interactions.

  17. Near-field Light Scattering Techniques for Measuring Nanoparticle-Surface Interaction Energies and Forces

    PubMed Central

    O'Dell, Dakota; Adam, Ian S.; DiPaolo, Brian; Sabharwal, Manit; Shi, Ce; Hart, Robert; Earhart, Christopher; Erickson, David

    2015-01-01

    Nanoparticles are quickly becoming commonplace in many commercial and industrial products, ranging from cosmetics to pharmaceuticals to medical diagnostics. Predicting the stability of the engineered nanoparticles within these products a priori remains an important and difficult challenge. Here we describe our techniques for measuring the mechanical interactions between nanoparticles and surfaces using near-field light scattering. Particle-surface interfacial forces are measured by optically “pushing” a particle against a reference surface and observing its motion using scattered near-field light. Unlike atomic force microscopy, this technique is not limited by thermal noise, but instead takes advantage of it. The integrated waveguide and microfluidic architecture allow for high-throughput measurements of about 1000 particles per hour. We characterize the reproducibility of and experimental uncertainty in the measurements made using the NanoTweezer surface instrument. We report surface interaction studies on gold nanoparticles with 50 nm diameters, smaller than previously reported in the literature using similar techniques. PMID:26855473

  18. Evolution of the Surface Science of Catalysis from Single Crystals to Metal Nanoparticles under Pressure

    SciTech Connect

    Somorjai, Gabor A.; Park, Jeong Y.

    2008-03-06

    Vacuum studies of metal single crystal surfaces using electron and molecular beam scattering revealed that the surface atoms relocate when the surface is clean (reconstruction) and when it is covered by adsorbates (adsorbate induced restructuring). It was also discovered that atomic steps and other low coordination surface sites are active for breaking chemical bonds (H-H, O=O, C-H, C=O and C-C) with high reaction probability. Investigations at high reactant pressures using sum frequency generation (SFG)--vibrational spectroscopy and high pressure scanning tunneling microscopy (HPSTM) revealed bond breaking at low reaction probability sites on the adsorbate-covered metal surface, and the need for adsorbate mobility for continued turnover. Since most catalysts (heterogeneous, enzyme and homogeneous) are nanoparticles, colloid synthesis methods were developed to produce monodispersed metal nanoparticles in the 1-10 nm range and controlled shapes to use them as new model catalyst systems in two-dimensional thin film form or deposited in mesoporous three-dimensional oxides. Studies of reaction selectivity in multipath reactions (hydrogenation of benzene, cyclohexene and crotonaldehyde) showed that reaction selectivity depends on both nanoparticle size and shape. The oxide-metal nanoparticle interface was found to be an important catalytic site because of the hot electron flow induced by exothermic reactions like carbon monoxide oxidation.

  19. Dispersion of ceria nanoparticles on γ-alumina surface functionalized using long chain carboxylic acids

    NASA Astrophysics Data System (ADS)

    Ledwa, Karolina Anna; Kępiński, Leszek

    2017-04-01

    Dispersion and stability of nanoparticles on a support is determined by the interaction between these phases. In case of hydrophobic nanoparticles (e.g. synthesized by reverse microemulsion method) the interaction with hydrophilic support (e.g. γ-Al2O3) is weak and agglomeration as well as poor resistance to sintering may cause problems. The bonding of the particles to the support may be effectively strengthened by proper modification of the support, e.g. by adsorption of hydrophobic compounds on its surface. In this work decanoic, myristic, stearic and oleic acid were used for the first time to cover γ-Al2O3 surface in order to enhance the dispersion of ceria nanoparticles deposited afterward by impregnation on such support. TGA and FTIR methods revealed that at monolayer coverage (1.1-2.5 molecules per nm2) the acid molecules are firmly bounded to the alumina surface. Morphology, textural properties, phase composition and reducibility of the CeO2/γ-Al2O3 samples were investigated using TEM, SEM, BET, XRD and H2-TPR methods. It has been shown that deposition of CeO2 nanoparticles on γ-Al2O3 surface covered with all studied acids enhances its dispersion, stability and reducibility. The most effective modification of the γ-Al2O3 surface was obtained at loading of 2.3 molecules of decanoic acid per nm2 of the support.

  20. Evolution of the surface science of catalysis from single crystals to metal nanoparticles under pressure

    NASA Astrophysics Data System (ADS)

    Somorjai, Gabor A.; Park, Jeong Y.

    2008-05-01

    Vacuum studies of metal single crystal surfaces using electron and molecular beam scattering revealed that the surface atoms relocate when the surface is clean (reconstruction) and when it is covered by adsorbates (adsorbate-induced restructuring). It was also discovered that atomic steps and other low coordination surface sites are active for breaking chemical bonds (H-H, O O, C-H, C O, and C-C) with high reaction probability. Investigations at high reactant pressures using sum frequency generation—vibrational spectroscopy and high pressure scanning tunneling microscopy revealed bond breaking at low reaction probability sites on the adsorbate-covered metal surface and the need for adsorbate mobility for continued turnover. Since most catalysts (heterogeneous, enzyme, and homogeneous) are nanoparticles, colloid synthesis methods were developed to produce monodispersed metal nanoparticles in the 1-10nm range and controlled shapes to use them as new model catalyst systems in two-dimensional monolayer film or deposited in mesoporous three-dimensional oxides. Studies of reaction selectivity in multipath reactions (hydrogenation of benzene, cyclohexene, and crotonaldehyde) showed that the reaction selectivity depends on both nanoparticle size and shape. The oxide-metal nanoparticle interface was found to be an important catalytic site that is associated with the hot electron flow induced by exothermic reactions such as carbon monoxide oxidation.

  1. Beauty is skin deep: a surface monolayer perspective on nanoparticle interactions with cells and bio-macromolecules.

    PubMed

    Saha, Krishnendu; Bajaj, Avinash; Duncan, Bradley; Rotello, Vincent M

    2011-07-18

    Surface recognition of biosystems is a critical component in the development of novel biosensors and delivery vehicles, and for the therapeutic regulation of biological processes. Monolayer-protected nanoparticles present a highly versatile scaffold for selective interaction with bio-macromolecules and cells. Through the engineering of the monolayer surface, nanoparticles can be tailored for surface recognition of biomolecules and cells. This review highlights recent progress in nanoparticle-bio-macromolecule/cellular interactions, emphasizing the effect of the surface monolayer structure on the interactions with proteins, DNA, and cell surfaces. The extension of these tailored interactions to hybrid nanomaterials, biosensing platforms, and delivery vehicles is also discussed.

  2. Nanoantioxidant-driven plasmon enhanced proton-coupled electron transfer

    NASA Astrophysics Data System (ADS)

    Sotiriou, Georgios A.; Blattmann, Christoph O.; Deligiannakis, Yiannis

    2015-12-01

    Proton-coupled electron transfer (PCET) reactions involve the transfer of a proton and an electron and play an important role in a number of chemical and biological processes. Here, we describe a novel phenomenon, plasmon-enhanced PCET, which is manifested using SiO2-coated Ag nanoparticles functionalized with gallic acid (GA), a natural antioxidant molecule that can perform PCET. These GA-functionalized nanoparticles show enhanced plasmonic response at near-IR wavelengths, due to particle agglomeration caused by the GA molecules. Near-IR laser irradiation induces strong local hot-spots on the SiO2-coated Ag nanoparticles, as evidenced by surface enhanced Raman scattering (SERS). This leads to plasmon energy transfer to the grafted GA molecules that lowers the GA-OH bond dissociation enthalpy by at least 2 kcal mol-1 and therefore facilitates PCET. The nanoparticle-driven plasmon-enhancement of PCET brings together the so far unrelated research domains of nanoplasmonics and electron/proton translocation with significant impact on applications based on interfacial electron/proton transfer.Proton-coupled electron transfer (PCET) reactions involve the transfer of a proton and an electron and play an important role in a number of chemical and biological processes. Here, we describe a novel phenomenon, plasmon-enhanced PCET, which is manifested using SiO2-coated Ag nanoparticles functionalized with gallic acid (GA), a natural antioxidant molecule that can perform PCET. These GA-functionalized nanoparticles show enhanced plasmonic response at near-IR wavelengths, due to particle agglomeration caused by the GA molecules. Near-IR laser irradiation induces strong local hot-spots on the SiO2-coated Ag nanoparticles, as evidenced by surface enhanced Raman scattering (SERS). This leads to plasmon energy transfer to the grafted GA molecules that lowers the GA-OH bond dissociation enthalpy by at least 2 kcal mol-1 and therefore facilitates PCET. The nanoparticle-driven plasmon

  3. Surface modified PLGA nanoparticles for brain targeting of Bacoside-A.

    PubMed

    Jose, S; Sowmya, S; Cinu, T A; Aleykutty, N A; Thomas, S; Souto, E B

    2014-10-15

    The present paper focuses on the development and in vitro/in vivo characterization of nanoparticles composed of poly-(D,L)-Lactide-co-Glycolide (PLGA) loading Bacoside-A, as a new approach for the brain delivery of the neuroprotective drug for the treatment of neurodegenerative disorders (e.g. Alzheimer Disease). Bacoside-A-loaded PLGA nanoparticles were prepared via o/w emulsion solvent evaporation technique. Surface of the nanoparticles were modified by coating with polysorbate 80 to facilitate the crossing of the blood brain barrier (BBB), and the processing parameters (i.e. sonication time, the concentration of polymer (PLGA) and surfactant (polysorbate 80), and drug-polymer ratio) were optimized with the aim to achieve a high production yield. Brain targeting potential of the nanoparticles was evaluated by in vivo studies using Wistar albino rats. The nanoparticles produced by optimal formulation were within the nanosized range (70-200 nm) with relatively low polydispersity index (0.391 ± 1.2). The encapsulation efficiency of Bacoside-A in PLGA nanoparticles was 57.11 ± 7.11%, with a drug loading capacity of 20.5 ± 1.98%. SEM images showed the spherical shape of the PLGA nanoparticles, whereas their low crystallinity was demonstrated by X-ray studies, which also confirmed no chemical interactions between the drug and polymer molecules. The in vitro release of Bacoside-A from the PLGA nanoparticles followed a sustained release pattern with a maximum release of up to 83.04 ± 2.55% in 48 h. When compared to pure drug solution (2.56 ± 1.23 μg/g tissue), in vivo study demonstrated higher brain concentration of Bacoside-A (23.94 ± 1.74 μg/g tissue) suggesting a significant role of surface coated nanoparticles on brain targeting. The results indicate the potential of surface modified PLGA nanoparticles for the delivery of Bacoside-A to the brain.

  4. Oligolayer-coated nanoparticles: impact of surface topography at the nanobio interface.

    PubMed

    Wurster, Eva-Christina; Liebl, Renate; Michaelis, Stefanie; Robelek, Rudolf; Wastl, Daniel S; Giessibl, Franz J; Goepferich, Achim; Breunig, Miriam

    2015-04-22

    Layer-by-layer coating of nanoparticles with a layer number in the single-digit range has gained increasing attention in the field of nanomedicinal research. However, the impact of using various polyelectrolytes on oligolayer formation and, more importantly, their influence on the interaction with the biological system has not often been considered in the past. Hence, we investigated the polyelectrolyte deposition profiles and resulting surface topographies of up to three polyelectrolyte layers on a flat gold sensor surface using three different polycations, namely, poly(ethylene imine) (PEI), poly(allylamine hydrochloride) (PAH), and poly(diallylammonium chloride) (PD), each in combination with poly(styrenesulfonate) (PSS). Surface plasmon resonance spectroscopy and atomic force microscopy revealed that the PEI/PSS pair in particular showed a so-called overshoot phenomenon, which is associated with partial polyelectrolyte desorption from the surface. This is also reflected by a significant increase in the surface roughness. Then, after having transferred the oligolayer assembly onto nanoparticles of ∼32 nm, we realized that quite similar surface topographies must have emerged on a curved gold surface. A major finding was that the extent of surface roughness contributes significantly to the fashion by which the oligolayer-coated nanoparticles interact with serum proteins and associate with cells. For example, for the PEI/PSS system, both the surface roughness and protein adsorption increased by a factor of ∼12 from the second to third coating layer and, at the same time, the cell association massively decreased to only one-third. Our study shows that surface roughness, along with other particle properties such as size, shape, zeta potential, and hydrophobicity, is another decisive factor for nanoparticles in a biological context, which has indeed been discussed previously but has not to date been investigated for oligolayers.

  5. Nanoparticle Properties and Synthesis Effects on Surface-Enhanced Raman Scattering Enhancement Factor: An Introduction

    PubMed Central

    2015-01-01

    Raman spectroscopy has enabled researchers to map the specific chemical makeup of surfaces, solutions, and even cells. However, the inherent insensitivity of the technique makes it difficult to use and statistically complicated. When Raman active molecules are near gold or silver nanoparticles, the Raman intensity is significantly amplified. This phenomenon is referred to as surface-enhanced Raman spectroscopy (SERS). The extent of SERS enhancement is due to a variety of factors such as nanoparticle size, shape, material, and configuration. The choice of Raman reporters and protective coatings will also influence SERS enhancement. This review provides an introduction to how these factors influence signal enhancement and how to optimize them during synthesis of SERS nanoparticles. PMID:25884017

  6. Prediction of Surface and pH-Specific Binding of Peptides to Metal and Oxide Nanoparticles

    NASA Astrophysics Data System (ADS)

    Heinz, Hendrik; Lin, Tzu-Jen; Emami, Fateme Sadat; Ramezani-Dakhel, Hadi; Naik, Rajesh; Knecht, Marc; Perry, Carole C.; Huang, Yu

    2015-03-01

    The mechanism of specific peptide adsorption onto metallic and oxidic nanostructures has been elucidated in atomic resolution using novel force fields and surface models in comparison to measurements. As an example, variations in peptide adsorption on Pd and Pt nanoparticles depending on shape, size, and location of peptides on specific bounding facets are explained. Accurate computational predictions of reaction rates in C-C coupling reactions using particle models derived from HE-XRD and PDF data illustrate the utility of computational methods for the rational design of new catalysts. On oxidic nanoparticles such as silica and apatites, it is revealed how changes in pH lead to similarity scores of attracted peptides lower than 20%, supported by appropriate model surfaces and data from adsorption isotherms. The results demonstrate how new computational methods can support the design of nanoparticle carriers for drug release and the understanding of calcification mechanisms in the human body.

  7. Acute and subchronic toxicity analysis of surface modified paclitaxel attached hydroxyapatite and titanium dioxide nanoparticles.

    PubMed

    Venkatasubbu, Gopinath Devanand; Ramasamy, S; Gaddam, Pramod Reddy; Kumar, J

    2015-01-01

    Nanoparticles are widely used for targeted drug delivery applications. Surface modification with appropriate polymer and ligands is carried out to target the drug to the affected area. Toxicity analysis is carried out to evaluate the safety of the surface modified nanoparticles. In this study, paclitaxel attached, folic acid functionalized, polyethylene glycol modified hydroxyapatite and titanium dioxide nanoparticles were used for targeted drug delivery system. The toxicological behavior of the system was studied in vivo in rats and mice. Acute and subchronic studies were carried out. Biochemical, hematological, and histopathological analysis was also done. There were no significant alterations in the biochemical parameters at a low dosage. There was a small change in alkaline phosphatase (ALP) level at a high dosage. The results indicate a safe toxicological profile.

  8. Surface modification of iron oxide nanoparticles and their conjuntion with water soluble polymers for biomedical application

    NASA Astrophysics Data System (ADS)

    Thanh Huong, Nguyen; Thi Kieu Giang, Lam; Thanh Binh, Nguyen; Minh, Le Quoc

    2009-09-01

    Superparamagnetic iron oxide nanoparticles (SPION) coated with suitable bio-compatible substances have been used in biomedicine, particularly in magnetic resonance imaging (MRI), tissue engineering, and hyperthermia and drug delivery. In this study, we describe the synthesis of SPION and its surface modification for in-vitro experiments. The particle diameter and structure were estimated by FESEM, TEM, XRD analyses. The saturation magnetization was characterized. SPION with a mean size of 12 nm have been prepared under N2 atmosphere, with support of natural polymeric starch, by controlling chemical coprecipitation of magnetite phase from aqueous solutions containing suitable salts ratios of Fe2+ and Fe3+. The surface of SPION-nanoparticles was treated with a coordinatable agent for higher dispersion ability in water and remaining the superparamagnetic behavior. The prepared iron oxide nanoparticles were coated with starch, dextran, PEG or MPEG to extend the application potential in the quite different engineering field of nano biomedicine.

  9. In vitro and in vivo anticancer activity of surface modified paclitaxel attached hydroxyapatite and titanium dioxide nanoparticles.

    PubMed

    Venkatasubbu, G Devanand; Ramasamy, S; Reddy, G Pramod; Kumar, J

    2013-08-01

    Targeted drug delivery using nanocrystalline materials delivers the drug at the diseased site. This increases the efficacy of the drug in killing the cancer cells. Surface modifications were done to target the drug to a particular receptor on the cell surface. This paper reports synthesis of hydroxyapatite and titanium dioxide nanoparticles and modification of their surface with polyethylene glycol (PEG) followed by folic acid (FA). Paclitaxel, an anticancer drug, is attached to functionalized hydroxyapatite and titanium dioxide nanoparticles. The pure and functionalised nanoparticles are characterised with XRD, TEM and UV spectroscopy. Anticancer analysis was carried out in DEN induced hepatocarcinoma animals. Biochemical, hematological and histopathological analysis show that the surface modified paclitaxel attached nanoparticles have an higher anticancer activity than the pure paclitaxel and surface modified nanoparticles without paclitaxel. This is due to the targeting of the drug to the folate receptor in the cancer cells.

  10. Wetting of nanofluids with nanoparticles of opposite surface potentials on pristine CVD graphene

    NASA Astrophysics Data System (ADS)

    Lee, Woorim; Kihm, Kenneth David; Park, Jae Sung; Lee, Woomin; Kim, Honggoo; Lee, Changhyuk; Cheon, Sosan; Lim, Gyumin

    2016-07-01

    Comparative wettability studies of graphene are conducted for two different nanofluids with opposite surface potentials of +53 mV (45-nm alumina nanoparticles) and -45 mV (28-nm silica nanoparticles), respectively. Aged graphene surface, which has adsorbed abundant hydrocarbon contaminants, shows weak hydrophobicity of about 90° wetting angles for both nanofluids for the tested volume concentration range from 0 to 10 %. For pristine graphene surfaces, however, the contact angle of alumina nanofluids continually increases from 50° to 70° for the same volume concentration increase, but the contact angle of silica nanofluids shows first increase of up to about 1 % concentration and then remains nearly unchanged with further increasing concentration. Since the nanoparticle-graphene interaction at the solid-liquid (SL) interface is expected to be the most crucial in determining the nanofluid wetting angles, the corresponding surface energy γ_{{SL}} is examined from elaboration of F_{{DLVO}}, the Derjaguin-Landau-Verwey-Overbeek force. The magnitudes of both the repulsive F_{{DLVO}} on the alumina nanoparticles and the attractive F_{{DLVO}} on the silica nanoparticles show rapid decreases up to 1 % volume concentration and exhibit slower decreases thereafter. The reduced repulsive F_{{DLVO}} of the alumina nanoparticle drives the increasing aggregation of nanoparticles on the SL interface with increasing concentration, thus increasing the SL interfacial energy γ_{{SL}}. On the contrary, the reduced attractive F_{{DLVO}} on the silica nanoparticle retards their aggregation on the SL interface with increasing concentration and slows the increase in γ_{{SL}}, eventually settling on the saturated level of γ_{{SL}} from a certain concentration onwards. These distinctive behaviors of γ_{{SL}} are consistent with the measured contact angles that gradually increase with increasing concentration for the positive surface potential (alumina), but initially increase and then

  11. Nanoparticle self-structuring in a nanofluid film spreading on a solid surface.

    PubMed

    Nikolov, Alex; Kondiparty, Kirti; Wasan, Darsh

    2010-06-01

    Liquids containing nanoparticles (nanofluids) exhibit different spreading or thinning behaviors on solids than liquids without nanoparticles. Previous experiments and theoretical investigations have demonstrated that the spreading of nanofluids on solid surfaces is enhanced compared to the spreading of base fluids without nanoparticles. However, the mechanisms for the observed enhancement in the spreading of nanofluids on solid substrates are not well understood. The complex nature of the interactions between the particles in the nanofluid and with the solid substrate alters the spreading dynamics [Wasan, D. T.; Nikolov, A. D. Nature 2003, 423, 156]. Here, we report, for the first time, the results of an experimental observation of nanoparticles self-structuring in a nanofluid film formed between an oil drop and a solid surface. Using a silica-nanoparticle aqueous suspension (with a nominal diameter of 19 nm and 10 vol %) and reflected light interferometry, we show the nanoparticle layering (i.e., stratification) phenomenon during film thinning on a smooth hydrophilic glass surface. Our experiments revealed that the film thickness stability on a solid substrate depends on the film size (i.e., the drop size). A film formed from a small drop (with a high capillary pressure) is thicker and contains more particle layers than a film formed from a large drop (with a lower capillary pressure). The data for the film-meniscus contact angle verses film thickness (corresponding to the different number of particle layers) were obtained and used to calculate the film structural energy isotherm. These results may provide a better understanding of the complex phenomena involved in the enhanced spreading of nanofluids on solid surfaces.

  12. Surface Degradation and Nanoparticle Release of a Commercial Nanosilica/Polyurethane Coating Under UV Exposure.

    PubMed

    Jacobs, Deborah S; Huang, Sin-Ru; Cheng, Yu-Lun; Rabb, Savelas A; Gorham, Justin M; Krommenhoek, Peter J; Yu, Lee L; Nguyen, Tinh; Sung, Lipiin

    2016-09-01

    Many coatings properties such as mechanical, electrical, and ultra violet (UV) resistance are greatly enhanced by the addition of nanoparticles, which can potentially increase the use of nanocoatings for many outdoor applications. However, because polymers used in all coatings are susceptible to degradation by weathering, nanoparticles in a coating may be brought to the surface and released into the environment during the life cycle of a nanocoating. Therefore, the goal of this study is to investigate the process and mechanism of surface degradation and potential particle release from a commercial nanosilica/polyurethane coating under accelerated UV exposure. Recent research at the National Institute of Standards and Technology (NIST) has shown that the matrix in an epoxy nanocomposite undergoes photodegradation during exposure to UV radiation, resulting in surface accumulation of nanoparticles and subsequent release from the composite. In this study, specimens of a commercial polyurethane (PU) coating, to which a 5 mass % surface treated silica nanoparticles solution was added, were exposed to well-controlled, accelerated UV environments. The nanocoating surface morphological changes and surface accumulation of nanoparticles as a function of UV exposure were measured, along with chemical change and mass loss using a variety of techniques. Particles from the surface of the coating were collected using a simulated rain process developed at NIST, and the collected runoff specimens were measured using inductively coupled plasma-optical emission spectroscopy (ICP-OES) to determine the amount of silicon released from the nanocoatings. The results demonstrated that the added silica nanoparticle solution decreased the photodegradation rate (i.e., stabilization) of the commercial PU nanocoating. Although the degradation was slower than the previous nanosilica epoxy model system, the degradation of the PU matrix resulted in accumulation of silica nanoparticles on the

  13. Surface modification and bioconjugation of FeCo magnetic nanoparticles with proteins.

    PubMed

    Wang, Wei; Jing, Ying; He, Shihai; Wang, Jian-Ping; Zhai, Jian-Ping

    2014-05-01

    Magnetic Fe70Co30 nanoparticles with a cubic shape and a mean size of 15±1.5 nm were fabricated using a magnetron-sputtering-based gas phase condensation deposition method. The particles had a high saturation magnetization of 220 emu/g, which is much higher than that of commercially available iron oxide nanoparticles. The FeCo nanoparticles were modified by 3-aminopropyltriethoxy silane and subsequently activated by glutaraldehyde, leading to successful attachment of aldehyde groups onto nanoparticle surfaces. Three proteins, namely streptavidin, PAPP-A antibody and Nectin-4 antibody, were immobilized on glutaraldehyde activated FeCo nanoparticles, and their loading levels were quantitatively evaluated. Our results show that loading capabilities are 95 μg of streptavidin, 128 μg of PAPP-A, and 125 μg of Nectin-4 antibody per milligram of FeCo nanoparticles, and that the three immobilized proteins retain their binding bioactivity. The protein-FeCo conjugates may find valuable applications involving magnetic separation and purification of proteins and cells, and the magnetic detection of biomolecules.

  14. Synthesis of surface protein-imprinted nanoparticles endowed with reversible physical cross-links.

    PubMed

    Yang, Chongchong; Yan, Xianming; Guo, Hao; Fu, Guoqi

    2016-01-15

    Researches on protein molecularly imprinted polymers have been challenged by the difficulties in facilitating biomacromolecular transfer, in particular upon the template removal step, and enhancing their recognition performance. Addressing these issues, herein we report synthesis of core–shell structured surface protein-imprinted nanoparticles with reversible physical cross-links formed in the imprinted nanoshells. The imprinted layers over nanoparticle supports are fabricated via aqueous precipitation polymerization (PP) of di(ethylene glycol) methyl ether methacrylate (MEO2MA), a thermo-responsive monomer bearing no strong H-bond donor, and other functional and cross-linking monomers. During polymerization, physical cross-links together with chemical cross-links are in site produced within the imprinted shells based on hydrophobic association among the PMEO2MA, favoring formation of high-quality imprints. While cooled appropriately below the polymerization temperature, these physical cross-links can be dissociated rapidly, thus facilitating removal of the embedded template. For proof of this concept, lysozyme-imprinted nanoparticles were synthesized at 37 °C over the nanoparticles functionalized with carboxylic and vinyl groups. The template removal from the imprinted nanoparticles was readily achieved by washing with a dilute acidic detergent solution at 4 °C. As-prepared imprinted nanoparticles showed greatly higher imprinting factor and specific rebinding than obtained with the same recipe but by solution polymerization (SP). Moreover, such imprinted nanomaterials exhibited satisfactory rebinding selectivity, kinetics and reusability.

  15. Selective chromofluorogenic sensing of heparin by using functionalised silica nanoparticles containing binding sites and a signalling reporter.

    PubMed

    Climent, Estela; Calero, Pilar; Marcos, M Dolores; Martínez-Máñez, Ramón; Sancenón, Félix; Soto, Juan

    2009-01-01

    Heparin detective: Silica nanoparticles functionalised with ion-channel scaffolds were prepared and used for the chromofluorogenic sensing of heparin in aqueous environments (see figure). The surface of the nanoparticles was functionalised with polyamines (binding sites) and thiols. The reaction of a dye (squaraine) with the surface thiol groups was selectively inhibited by the coordination of heparin with the partly protonated polyamines.

  16. Significance of surface charge and shell material of superparamagnetic iron oxide nanoparticle (SPION) based core/shell nanoparticles on the composition of the protein corona.

    PubMed

    Sakulkhu, Usawadee; Mahmoudi, Morteza; Maurizi, Lionel; Coullerez, Geraldine; Hofmann-Amtenbrink, Margarethe; Vries, Marcel; Motazacker, Mahdi; Rezaee, Farhad; Hofmann, Heinrich

    2015-02-01

    As nanoparticles (NPs) are increasingly used in many applications their safety and efficient applications in nanomedicine have become concerns. Protein coronas on nanomaterials' surfaces can influence how the cell "recognizes" nanoparticles, as well as the in vitro and in vivo NPs' behaviors. The SuperParamagnetic Iron Oxide Nanoparticle (SPION) is one of the most prominent agents because of its superparamagnetic properties, which is useful for separation applications. To mimic surface properties of different types of NPs, a core-shell SPION library was prepared by coating with different surfaces: polyvinyl alcohol polymer (PVA) (positive, neutral and negative), SiO2 (positive and negative), titanium dioxide and metal gold. The SPIONs with different surfaces were incubated at a fixed serum : nanoparticle surface ratio, magnetically trapped and washed. The tightly bound proteins were quantified and identified. The surface charge has a great impact on protein adsorption, especially on PVA and silica where proteins preferred binding to the neutral and positively charged surfaces. The importance of surface material on protein adsorption was also revealed by preferential binding on TiO2 and gold coated SPION, even negatively charged. There is no correlation between the protein net charge and the nanoparticle surface charge on protein binding, nor direct correlation between the serum proteins' concentration and the proteins detected in the coronas.

  17. Atomic scale deformation in the solid surface induced by nanoparticle impacts

    NASA Astrophysics Data System (ADS)

    Xu, J.; Luo, J. B.; Lu, X. C.; Wang, L. L.; Pan, G. S.; Wen, S. Z.

    2005-06-01

    Nanoparticle impacts on an ultra-smooth surface always occur in nano-machining processes, such as polishing of a monocrystalline silicon wafer, which is an important process in the manufacture of semiconductors. A fundamental understanding of nanoparticle impacts on a solid surface is important to control and prevent the deformation of the surface. In this study, a cylindrical liquid jet containing de-ionized water and SiO2 nanoparticles impacts obliquely on a single crystal silicon surface at a speed of 50 m s-1. The microstructure of the impacted surface was examined using a high resolution transmission electron microscope, an atomic force microscope, etc. Some crystal defects, lattice distortion, grain refinement and rotation of grains in the surface layer of the silicon wafer after exposure for 30 s have been observed. However, when the exposure time is extended to 10 min, an amorphous layer containing crystal grains is exhibited in the subsurface, and many craters, scratches and atom pileups can be found in the surface.

  18. Thin Films of Uniform Hematite Nanoparticles: Controls on Surface Hydrophobicity and Self-Assembly

    SciTech Connect

    Wang, Wei; Liang, Liyuan; Johs, Alexander; Gu, Baohua

    2008-01-01

    In this study we show that uniform hematite ( -Fe2O3) nanoparticle thin films with controlled layer thickness can be formed by Langmuir-Blodgett (LB) monolayer deposition on surface areas of several square centimeters. The technique involves synthesis of uniform hematite nanoparticles by forced hydrolysis and surface modifications for increased hydrophobicity to bring the particles to the air-water interface. Methods of thermal treatment, stepped solvent exchange, and oleate surfactant coating were studied for their effectiveness in increasing hydrophobicity by removing surface adsorbed water and OH groups and were subsequently validated by Fourier-transform infrared (FTIR) spectral analysis. Surface pressure-area ( -A) and surface pressure-time ( -t) isotherms indicate that the stability of the particle monolayer at the air-water interface depends on the method of surface modification. Thermal evaporation treatment was found to produce thin films of hematite nanoparticles with the greatest uniformity and surface coverage as characterized by UV-visible spectroscopic, scanning electron microscopic (SEM) and atomic force microscopic (AFM) analyses.

  19. Nanodisco Balls: Control over Surface versus Core Loading of Diagnostically Active Nanocrystals into Polymer Nanoparticles

    PubMed Central

    2015-01-01

    Nanoparticles of complex architectures can have unique properties. Self-assembly of spherical nanocrystals is a high yielding route to such systems. In this study, we report the self-assembly of a polymer and nanocrystals into aggregates, where the location of the nanocrystals can be controlled to be either at the surface or in the core. These nanospheres, when surface decorated with nanocrystals, resemble disco balls, thus the term nanodisco balls. We studied the mechanism of this surface loading phenomenon and found it to be Ca2+ dependent. We also investigated whether excess phospholipids could prevent nanocrystal adherence. We found surface loading to occur with a variety of nanocrystal types including iron oxide nanoparticles, quantum dots, and nanophosphors, as well as sizes (10–30 nm) and shapes. Additionally, surface loading occurred over a range of polymer molecular weights (∼30–3000 kDa) and phospholipid carbon tail length. We also show that nanocrystals remain diagnostically active after loading onto the polymer nanospheres, i.e., providing contrast in the case of magnetic resonance imaging for iron oxide nanoparticles and fluorescence for quantum dots. Last, we demonstrated that a fluorescently labeled protein model drug can be delivered by surface loaded nanospheres. We present a platform for contrast media delivery, with the unusual feature that the payload can be controllably localized to the core or the surface. PMID:25188401

  20. Nanoparticles to increase adhesive properties of biologically secreted materials for surface affixing.

    PubMed

    Zhang, Mingjun; Liu, Maozi; Bewick, Sharon; Suo, Zhiyong

    2009-06-01

    Surface adhesion in nature has been the focus of intense study over the past few years. Nevertheless, research in this field has primarily concentrated on understanding the chemical aspects of adhesion. While scientists have been able to determine some of the molecular structures present in the adhesives secreted by surface climbing or surface affixing biological systems such as mussels and barnacles, the fundamental adhesion mechanisms used by these systems are still unknown. This research paper focuses on the nano-scale morphological similarities of adhesive materials secreted from marine mussels, barnacles and ivy. We discovered that marine mussels secrete large amounts of adhesive materials in the form of nanoparticles for surface adhesion. This is in keeping with our previous work, which indicated a similar phenomenon for ivy. Both studies concur with earlier research on marine barnacles, polychaetes and sea stars. Taken together, these results indicate that nanoparticles are used by natural, biological systems to increase surface adhesion. These nanoparticle surface adhesion mechanisms have important implications in terms of engineering surface adhesive materials and devices.

  1. Low absorption losses of strongly coupled surface plasmons in nanoparticle assemblies.

    PubMed

    Chang, Wei-Shun; Willingham, Britain A; Slaughter, Liane S; Khanal, Bishnu P; Vigderman, Leonid; Zubarev, Eugene R; Link, Stephan

    2011-12-13

    Coupled surface plasmons in one-dimensional assemblies of metal nanoparticles have attracted significant attention because strong interparticle interactions lead to large electromagnetic field enhancements that can be exploited for localizing and amplifying electromagnetic radiation in nanoscale structures. Ohmic loss (i.e., absorption by the metal), however, limits the performance of any application due to nonradiative surface plasmon relaxation. While absorption losses have been studied theoretically, they have not been quantified experimentally for strongly coupled surface plasmons. Here, we report on the ohmic loss in one-dimensional assemblies of gold nanoparticles with small interparticle separations of only a few nanometers and hence strong plasmon coupling. Both the absorption and scattering cross-sections of coupled surface plasmons were determined and compared to electrodynamic simulations. A lower absorption and higher scattering cross-section for coupled surface plasmons compared to surface plasmons of isolated nanoparticles suggest that coupled surface plasmons suffer smaller ohmic losses and therefore act as better antennas. These experimental results provide important insight for the design of plasmonic devices.

  2. Relationships between number, surface area, and mass concentrations of different nanoparticles in workplaces.

    PubMed

    Zou, Hua; Zhang, Qunwei; Xing, Mingluan; Gao, Xiangjing; Zhou, Lifang; Tollerud, David J; Tang, Shichuang; Zhang, Meibian

    2015-08-01

    No consistent metric for measuring exposure to nanoparticles has yet been agreed upon internationally. This study seeks to examine the relationship between the number concentration (NC), surface area concentration (SAC), and mass concentration (MC) of nanoparticles in workplaces. Real-time NC20-1000 nm, SAC10-1000 nm, and respirable MC100-1000 nm were determined for different nanoparticles. Concentration ratio (CR, activity: background), exposure ranking (ER), and between-metric correlation coefficients (R) were used to analyze the relationships between the three metrics. The ratio of cumulative percentage by number (APN) and cumulative percentage by mass (APM) was used to analyze whether the nanoparticle number is predominant, as compared with the nanoparticle mass. The CRs of NC20-1000 nm and SAC10-1000 nm for different nanoparticles at the corresponding work sites were higher than those of respirable MC100-1000 nm. The ERs of NC20-1000 nm for nano-Fe2O3 and nano-Al2O3 were the same as those of SAC10-1000 nm, but were inconsistent with those of respirable MC100-1000 nm. The order of correlation coefficients between NC20-1000 nm, SAC10-1000 nm, and respirable MC100-1000 nm was: RSAC and NC > RSAC and MC > RNC and MC. The ratios of APN and APM for nano-Al2O3 and grinding-wheel particles (less than 100 nm) at the same work site were 2.03 and 1.65, respectively. NC and SAC metrics are significantly distinct from the MC in characterizing exposure to airborne nanoparticles. Simultaneous measurements of the NC, SAC, and MC should be conducted as part of nanoparticle exposure assessment strategies and epidemiological studies.

  3. Manganese Phosphate Self-assembled Nanoparticle Surface and Its application for Superoxide Anion Detection

    PubMed Central

    Shen, Xiaohui; Wang, Qi; Liu, Yuhong; Xue, Wenxiao; Ma, Lie; Feng, Shuaihui; Wan, Mimi; Wang, Fenghe; Mao, Chun

    2016-01-01

    Quantitative analysis of superoxide anion (O2·−) has increasing importance considering its potential damages to organism. Herein, a novel Mn-superoxide dismutase (MnSOD) mimics, silica-manganous phosphate (SiO2-Mn3(PO4)2) nanoparticles, were designed and synthesized by surface self-assembly processes that occur on the surface of silica-phytic acid (SiO2-PA) nanoparticles. The composite nanoparticles were characterized by fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electronic microscopy (SEM), electron diffraction pattern, energy dispersive spectroscopy (EDS) and elemental mapping. Then the electrochemical measurements of O2·− based on the incorporation of SiO2-Mn3(PO4)2 onto the surface of electrodes were performed, and some satisfactory results were obtained. This is the first report that manganous phosphate (Mn3(PO4)2) nanoparticles with shape-controlled, but not multilayer sheets, were utilized for O2·− detection. The surface self-assembly technology we proposed will offer the ideal material to construct more types biosensor and catalytic system for its nanosized effect. PMID:27357008

  4. Microstructure and micromorphology of Cu/Co nanoparticles: Surface texture analysis

    NASA Astrophysics Data System (ADS)

    Ţălu, Ştefan; Bramowicz, Miroslaw; Kulesza, Slawomir; Ghaderi, Atefeh; Dalouji, Vali; Solaymani, Shahram; Khalaj, Zahra

    2016-09-01

    This paper analyses the three-dimensional (3-D) surface texture of Cu/Co thin films deposited by DC-Magnetron sputtering method on the silicon substrates. The prepared Cu/Co nanoparticles were used as research materials. Three groups of samples were deposited on silicon substrates in the argon atmosphere and gradually cooled down to room temperature. The crystalline structures and elemental compositions were analyzed by X-ray diffraction (XRD) spectrum with conventional Bragg-Brentano geometry. X-ray diffraction profile indicates that Co and Cu interpenetrating crystalline structures are formed in these films. The sample surface images were recorded using atomic force microscopy (AFM) and analyzed by means of the fractal geometry. Statistical, fractal and functional surface properties of prepared samples were computed to describe major characteristics of the spatial surface texture of Cu/Co nanoparticles. Presented deposition method is a versatile, costeffective, and simple method to synthesize nano- and microstructures of Cu/Co thin films. This type of 3-D morphology allows to understand the structure/property relationships and to investigate defect-related properties of Cu/Co nanoparticles. Presented results confirm the possibility of preparing high-quality Cu/Co nanoparticles via DC-Magnetron sputtering method on silicon substrates.

  5. Cellular Stress Response to Engineered Nanoparticles: Effect of Size, Surface Coating, and Cellular Uptake

    EPA Science Inventory

    CELLULAR STRESS RESPONSE TO ENGINEERED NANOPARTICLES: EFFECT OF SIZE, SURFACE COATING, AND CELLULAR UPTAKE RY Prasad 1, JK McGee2, MG Killius1 D Ackerman2, CF Blackman2 DM DeMarini2 , SO Simmons2 1 Student Services Contractor, US EPA, RTP, NC 2 US EPA, RTP, NC The num...

  6. All-nanoparticle layer-by-layer surface modification of micro- and ultrafiltration membranes.

    PubMed

    Escobar-Ferrand, Luis; Li, Diya; Lee, Daeyeon; Durning, Christopher J

    2014-05-20

    Layer-by-layer (LbL) deposition using primarily inorganic silica nanoparticles is employed for surface modification of polymeric micro- and ultrafiltration (MF/UF) membranes to produce novel thin film composite (TFC) membranes intended for nanofiltration (NF) and reverse osmosis (RO) applications. A wide variety of porous substrate membranes with different surface characteristics are successfully employed. This report gives detailed results for polycarbonate track etched (PCTE), polyethersulfone (PES), and sulfonated PES (SPEES) MF/UF substrates. Both spherical (cationic/anionic) and eccentric elongated (anionic) silica nanoparticles are deposited using conditions similar to those in prior works for solid substrates (e.g., Lee et al.). Appropriate selection of the pH for anionic and cationic particle deposition enables construction of nanoparticle-only layers 100-1200 nm in thickness atop the original porous membrane substrates. The surface layer thickness appears to vary linearly with the number of bilayers deposited, i.e., with the number of anionic/cationic deposition cycles. The deposition process is optimized to eliminate drying-induced cracking and improve mechanical durability via thickness control and postdeposition hydrothermal treatment. "Dead-end" permeation tests using dextran standards reveal the hydraulic characteristics and separations capability for the PCTE-based TFC membranes. The results show that nanoparticle-based LbL surface modification of MF and UF rated media can produce TFC membranes with NF capabilities.

  7. SURFACE CHEMISTRY INFLUENCE CANCER KILLING EFFECT OF TiO2 NANOPARTICLES

    PubMed Central

    Thevenot, Paul; Cho, Jai; Wavhal, Dattatray; Timmons, Richard B.; Tang, Liping

    2008-01-01

    Photocatalyzed TiO2 nanoparticles have been shown to eradicate cancer cells. However the required in situ introduction of UV light limits the use of such a therapy in patients. In the present study, the non-photocatalyic anti-cancer effect of surface functionalized TiO2 was examined. Nanoparticles bearing -OH, -NH2, or –COOH surface groups, were tested for their effect on in vitro survival of several cancer and control cell lines. The cells tested included B16F10 melanoma, Lewis lung carcinoma (LLC), JHU prostate cancer cells, and 3T3 fibroblasts. Cell viability was observed to depend on particle concentrations, cell types, and surface chemistry. Specifically, -NH2 and -OH groups exhibited significantly higher toxicity than -COOH. Microscopic and spectrophotometric studies revealed nanoparticle-mediated cell membrane disruption leading to cell death. The results suggest that functionalized TiO2, and presumably other nanoparticles, may be surface engineered for targeted cancer therapy. PMID:18502186

  8. Cell and nanoparticle transport in tumour microvasculature: the role of size, shape and surface functionality of nanoparticles

    PubMed Central

    Lian, Yanping; Zhang, Lucy T.; Aldousari, Saad M.; Hedia, Hassan S.; Asiri, Saeed A.; Liu, Wing Kam

    2016-01-01

    Through nanomedicine, game-changing methods are emerging to deliver drug molecules directly to diseased areas. One of the most promising of these is the targeted delivery of drugs and imaging agents via drug carrier-based platforms. Such drug delivery systems can now be synthesized from a wide range of different materials, made in a number of different shapes, and coated with an array of different organic molecules, including ligands. If optimized, these systems can enhance the efficacy and specificity of delivery compared with those of non-targeted systems. Emerging integrated multiscale experiments, models and simulations have opened the door for endless medical applications. Current bottlenecks in design of the drug-carrying particles are the lack of knowledge about the dispersion of these particles in the microvasculature and of their subsequent internalization by diseased cells (Bao et al. 2014 J. R. Soc. Interface 11, 20140301 (doi:10.1098/rsif.2014.0301)). We describe multiscale modelling techniques that study how drug carriers disperse within the microvasculature. The immersed molecular finite-element method is adopted to simulate whole blood including blood plasma, red blood cells and nanoparticles. With a novel dissipative particle dynamics method, the beginning stages of receptor-driven endocytosis of nanoparticles can be understood in detail. Using this multiscale modelling method, we elucidate how the size, shape and surface functionality of nanoparticles will affect their dispersion in the microvasculature and subsequent internalization by targeted cells. PMID:26855759

  9. Effect of silica nanoparticles with variable size and surface functionalization on human endothelial cell viability and angiogenic activity

    NASA Astrophysics Data System (ADS)

    Guarnieri, Daniela; Malvindi, Maria Ada; Belli, Valentina; Pompa, Pier Paolo; Netti, Paolo

    2014-02-01

    Silica nanoparticles could be promising delivery vehicles for drug targeting or gene therapy. However, few studies have been undertaken to determine the biological behavior effects of silica nanoparticles on primary endothelial cells. Here we investigated uptake, cytotoxicity and angiogenic properties of silica nanoparticle with positive and negative surface charge and sizes ranging from 25 to 115 nm in primary human umbilical vein endothelial cells. Dynamic light scattering measurements and nanoparticle tracking analysis were used to estimate the dispersion status of nanoparticles in cell culture media, which was a key aspect to understand the results of the in vitro cellular uptake experiments. Nanoparticles were taken up by primary endothelial cells in a size-dependent manner according to their degree of agglomeration occurring after transfer in cell culture media. Functionalization of the particle surface with positively charged groups enhanced the in vitro cellular uptake, compared to negatively charged nanoparticles. However, this effect was contrasted by the tendency of particles to form agglomerates, leading to lower internalization efficiency. Silica nanoparticle uptake did not affect cell viability and cell membrane integrity. More interestingly, positively and negatively charged 25 nm nanoparticles did not influence capillary-like tube formation and angiogenic sprouting, compared to controls. Considering the increasing interest in nanomaterials for several biomedical applications, a careful study of nanoparticle-endothelial cells interactions is of high relevance to assess possible risks associated to silica nanoparticle exposure and their possible applications in nanomedicine as safe and effective nanocarriers for vascular transport of therapeutic agents.

  10. Characterization of localized surface plasmon resonance transducers produced from Au25 nanoparticle multilayers

    PubMed Central

    Vaccarello, Paul; Tran, Linh; Meinen, Julia; Kwon, Chuhee; Abate, Yohannes; Shon, Young-Seok

    2012-01-01

    This article reports the preparation of gold plasmonic transducers using a nanoparticle self-assembly/heating method and the characterization of the films using scattering-type scanning near-field optical microscopy (s-SNOM). Nanoparticle-polymer multilayer films were prepared by the layer-by-layer assembly on glass slides by alternating exposures to monodisperse Au25 nanoparticles and ionic polymer linkers. Thermal evaporation of organic matters from the nanoparticle-polymer multilayer films at 600 °C allowed the nanoparticles to coalescence and form nanostructured films. Characterization of the nanostructured films generated from Au25 nanoparticles using atomic force microscopy (AFM) showed that the films have rounded, small, island-like morphologies (d: 30-50 nm) with a pit in the center of many islands. However, further characterizations with s-SNOM revealed that the produced nanoislands contain a single gold cluster in a pit surrounded by donut-shaped dielectric species. Formation of such a structure is thought to be resulted from the embedding of gold clusters under the reorganized polysiloxane binder coatings and glass surfaces during heat treatment of the Au25 nanoparticle multilayer films. The nanostructured films displayed strong surface plasmon resonance bands in UV-vis spectra with a peak absorbance occurring at ~545-550 nm. The optical sensing capability of the films was examined using D-glucose-functionalized gold island films with the interaction of Concanavalin A (ConA). The result showed that the adsorption of ConA on island films causes a large change in the LSPR band intensity. PMID:22822292

  11. Surface-modified gatifloxacin nanoparticles with potential for treating central nervous system tuberculosis

    PubMed Central

    Marcianes, Patricia; Negro, Sofia; García-García, Luis; Montejo, Consuelo; Barcia, Emilia; Fernández-Carballido, Ana

    2017-01-01

    A new nanocarrier is developed for the passage of gatifloxacin through the blood–brain barrier to treat central nervous system tuberculosis. Gatifloxacin nanoparticles were prepared by nanoprecipitation using poly(lactic-co-glycolic acid) (PLGA) 502 and polysorbate 80 or Labrafil as surface modifiers. The evaluation of in vivo blood–brain barrier transport was carried out in male Wistar rats using rhodamine-loaded PLGA nanoparticles prepared with and without the surface modifiers. At 30 and 60 minutes after administration, nanoparticle biodistribution into the brain (hippocampus and cortex), lungs, and liver was studied. The results obtained from the cerebral cortex and hippocampus showed that functionalization of rhodamine nanoparticles significantly increased their passage into the central nervous system. At 60 minutes, rhodamine concentrations decreased in both the lungs and the liver but were still high in the cerebral cortex. To distinguish the effect between the surfactants, gatifloxacin-loaded PLGA nanoparticles were prepared. The best results corresponded to the formulation prepared with polysorbate 80 with regard to encapsulation efficiency (28.2%), particle size (176.5 nm), and ζ-potential (−20.1 mV), thereby resulting in a promising drug delivery system to treat cerebral tuberculosis. PMID:28331318

  12. Effect of Surface Treated Silicon Dioxide Nanoparticles on Some Mechanical Properties of Maxillofacial Silicone Elastomer

    PubMed Central

    Zayed, Sara M.; Alshimy, Ahmad M.; Fahmy, Amal E.

    2014-01-01

    Current materials used for maxillofacial prostheses are far from ideal and there is a need for novel improved materials which mimic as close as possible the natural behavior of facial soft tissues. This study aimed to evaluate the effect of adding different concentrations of surface treated silicon dioxide nanoparticles (SiO2) on clinically important mechanical properties of a maxillofacial silicone elastomer. 147 specimens of the silicone elastomer were prepared and divided into seven groups (n = 21). One control group was prepared without nanoparticles and six study groups with different concentrations of nanoparticles, from 0.5% to 3% by weight. Specimens were tested for tear strength (ASTM D624), tensile strength (ASTM D412), percent elongation, and shore A hardness. SEM was used to assess the dispersion of nano-SiO2 within the elastomer matrix. Data were analyzed by one-way ANOVA and Scheffe test (α = 0.05). Results revealed significant improvement in all mechanical properties tested, as the concentration of the nanoparticles increased. This was supported by the results of the SEM. Hence, it can be concluded that the incorporation of surface treated SiO2 nanoparticles at concentration of 3% enhanced the overall mechanical properties of A-2186 silicone elastomer. PMID:25574170

  13. Dissecting the structure of surface stabilizer on the dispersion of inorganic nanoparticles in aqueous medium

    NASA Astrophysics Data System (ADS)

    Ding, Yong; Yu, Zongzhi; Zheng, Junping

    2017-03-01

    Dispersing inorganic nanoparticles in aqueous solutions is a key requirement for a great variety of products and processes, including carriers in drug delivery or fillers in polymers. To be highly functional in the final product, inorganic particles are required to be finely dispersed in nanoscale. In this study, silica was selected as a representative inorganic particle. Surface stabilizers with different chain length and charged group were designed to reveal the influence of electrostatic and van der Waals forces between silica and stabilizer on the dispersion of silica particles in aqueous medium. Results showed surface stabilizer with longer alkyl chain and charged group exerted best ability to deaggregate silica, leading to a hydrodynamic size of 51.1 nm. Surface stabilizer designing with rational structure is a promising solution for deagglomerating and reducing process time and energy. Giving the designability and adaptability of surface stabilizer, this method is of potential for dispersion of other inorganic nanoparticles.

  14. Direct surface engineering of silicon nanoparticles prepared by collinear double-pulse ns laser ablation

    NASA Astrophysics Data System (ADS)

    Mahdieh, M. H.; Momeni, A.

    2017-01-01

    In this paper we study the photoluminescence properties of colloidal silicon nanoparticles (Si NPs) in distilled water, with the aim of clarifying the role of surface characteristics on the emission properties. We will show that double-pulse ns laser ablation (DPLA) of a silicon target in water with different inter-pulse delay times of i.e. 5 and 10 ns can result in production of colloidal Si NPs with different PL emission intensities at the visible spectral range of 550-650 nm. The results reveal that DPLA process at the different delay times can induce different oxide related surface characteristics on the Si NPs through the direct surface engineering of the nanoparticles. A detailed analysis of the PL emissions using the stochastic quantum confinement model explained that the different emission behaviors of the colloids are associated with the oxide-related surface states which are contributed as radiative centers in the PL process.

  15. Silica Supported Ceria Nanoparticles: A Hybrid Nanostructure To Increase Stability And Surface Reactivity Of Nano-crystalline Ceria

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Varga, Tamas; Thevuthasan, Suntharampillai

    2014-01-21

    The mixed oxidation state (3+/4+) of ceria nanoparticles of smaller sizes make them attractive materials for their catalytic antioxidant biological properties. However the unmodified smaller ceria nanoparticles are limited in their use due to particles agglomeration and reduced surface chemical reactivity in the solutions used to disperse the nanoparticles. This work describes an effort to stabilize small ceria nanoparticles, retaining their desired activity, on a larger stable silica support. The ceria nanoparticles attached to silica was synthesized by a solution synthesis technique in which the surface functional groups of silica nanoparticles were found to be essential for the formation of smaller ceria nanoparticles. The surface chemical and vibrational spectroscopy analysis revealed cerium–silicate (Ce-O-Si) covalent bond linkage between silica and cerium oxide nanoparticles. The colloidal properties (agglomerate particle size and suspension stability) of ceria attached to silica was significantly improved due to inherent physico-chemical characteristics of silica against random collision and gravitation settling as opposed to unmodified ceria nanoparticles in solution. The bio-catalytic activity of ceria nanoparticles in the 3+ oxidation state was not found to be limited by attachment to the silica support as measured by free radical scavenging activity in different biological media conditions.

  16. Localized surface plasmon resonance-based hybrid Au-Ag nanoparticles for detection of Staphylococcus aureus enterotoxin B

    NASA Astrophysics Data System (ADS)

    Zhu, Shaoli; Du, ChunLei; Fu, Yongqi

    2009-09-01

    A triangular hybrid Au-Ag nanoparticles array was proposed for the purpose of biosensing in this paper. Constructing the hybrid nanoparticles, an Au thin film is capped on the Ag nanoparticles which are attached on glass substrate. The hybrid nanoparticles array was designed by means of finite-difference and time-domain (FDTD) algorithm-based computational numerical calculation and optimization. Sensitivity of refractive index of the hybrid nanoparticles array was obtained by the computational calculation and experimental detection. Moreover, the hybrid nanoparticles array can prevent oxidation of the pure Ag nanoparticles from atmosphere environment because the Au protective layer was deposited on top of the Ag nanoparticles so as to isolate the Ag particles from the atmosphere. We presented a novel surface covalent link method between the localized surface plasmon resonance (LSPR) effect-based biosensors with hybrid nanoparticles array and the detected target molecules. The generated surface plasmon wave from the array carries the biological interaction message into the corresponding spectra. Staphylococcus aureus enterotoxin B (SEB), a small protein toxin was directly detected at nanogramme per milliliter level using the triangular hybrid Au-Ag nanoparticles. Hence one more option for the SEB detection is provided by this way.

  17. Investigation on the adsorption characteristics of anserine on the surface of colloidal silver nanoparticles.

    PubMed

    Thomas, S; Maiti, N; Mukherjee, T; Kapoor, S

    2013-08-01

    The surface-enhanced Raman scattering (SERS) studies of anserine (beta-alanyl-N-methylhistidine) was carried out on colloidal silver nanoparticles to understand its adsorption characteristics. The experimentally observed Raman bands were assigned based on the results of DFT calculations. The studies suggest that the interaction of anserine is primarily through the carboxylate group with the imidazole ring in an upright position with respect to the silver surface. Concentration dependent SERS studies suggest a change in orientation at sub-monolayer concentration.

  18. Assessment of airborne nanoparticles present in industry of aluminum surface treatments.

    PubMed

    Santos, R J; Vieira, M T

    2017-03-01

    Conventional industrial processes are emission sources of unintended nanoparticles which are potentially harmful for the environment and human health. The aim of this study is to assess airborne nanoparticle release from aluminum surface treatment processes in various workplaces. Two direct reading instruments, a scanning mobility particle sizer to measure size distribution and a nanoparticle surface area monitoring to measure the surface area of particles deposited in the human lung, were employed to perform area monitoring. The lacquering paint was the process which released the highest concentration of particles from 10-487 nm (7.06 × 10(6) particles/cm(3)). The lacquering baths process emitted particles of the largest average size (76.9 nm) and the largest surface area deposited in the human lung (167.4 µm(2)/cm(3)). Conversely, the anodizing bath process generated particles of the smallest average size (44.3 nm) and the lowest human lung-deposited surface area (1.2 µm(2)/cm(3)). The total number of particles and the surface area can only be fairly correlated for environments in which the surface area presented higher values. The transmission electron microscopy analysis confirmed the presence of aluminum oxide particles of different dimensions near the LB and AB areas and polymeric-based particles near the LP areas. The findings of this study indicated that lacquering and anodizing surface treatments are indeed responsible for the emission of airborne nanoparticles. It also highlights the importance of control strategies as a means of protecting workers' health and environment.

  19. Highly transparent superhydrophobic surfaces from the coassembly of nanoparticles (≤100 nm).

    PubMed

    Karunakaran, Raghuraman G; Lu, Cheng-Hsin; Zhang, Zanhe; Yang, Shu

    2011-04-19

    We report a simple and versatile approach to creating a highly transparent superhydrophobic surface with dual-scale roughness on the nanoscale. 3-Aminopropyltrimethoxysilane (APTS)-functionalized silica nanoparticles of two different sizes (100 and 20 nm) were sequentially dip coated onto different substrates, followed by thermal annealing. After hydrophobilization of the nanoparticle film with (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane for 30 min or longer, the surface became superhydrophobic with an advancing water contact angle of greater than 160° and a water droplet (10 μL) roll-off angle of less than 5°. The order of nanoparticles dip coated onto the silicon wafer (i.e., 100 nm first and 20 nm second or vice versa) did not seem to have a significant effect on the resulting apparent water contact angle. In contrast, when the substrate was dip coated with monoscale nanoparticles (20, 50, and 100 nm), a highly hydrophobic surface (with an advancing water contact angle of up to 143°) was obtained, and the degree of hydrophobicity was found to be dependent on the particle size and concentration of the dip-coating solution. UV-vis spectra showed nearly 100% transmission in the visible region from the glass coated with dual-scale nanoparticles, similar to the bare one. The coating strategy was versatile, and superhydrophobicity was obtained on various substrates, including Si, glass, epoxy resin, and fabrics. Thermal annealing enhanced the stability of the nanoparticle coating, and superhydrophobicity was maintained against prolonged exposure to UV light under ambient conditions.

  20. Surface plasmon-driven water reduction: gold nanoparticle size matters.

    PubMed

    Qian, Kun; Sweeny, Brendan C; Johnston-Peck, Aaron C; Niu, Wenxin; Graham, Jeremy O; DuChene, Joseph S; Qiu, Jingjing; Wang, Yi-Chung; Engelhard, Mark H; Su, Dong; Stach, Eric A; Wei, Wei David

    2014-07-16

    Water reduction under two different visible-light ranges (λ > 400 nm and λ > 435 nm) was investigated in gold-loaded titanium dioxide (Au-TiO2) heterostructures with different sizes of Au nanoparticles (NPs). Our study clearly demonstrates the essential role played by Au NP size in plasmon-driven H2O reduction and reveals two distinct mechanisms to clarify visible-light photocatalytic activity under different excitation conditions. The size of the Au NP governs the efficiency of plasmon-mediated electron transfer and plays a critical role in determining the reduction potentials of the electrons transferred to the TiO2 conduction band. Our discovery provides a facile method of manipulating photocatalytic activity simply by varying the Au NP size and is expected to greatly facilitate the design of suitable plasmonic photocatalysts for solar-to-fuel energy conversion.

  1. Impact of poly(lactic-co-glycolic acid) nanoparticle surface charge on protein, cellular and haematological interactions.

    PubMed

    Pillai, Gopikrishna J; Greeshma, M M; Menon, Deepthy

    2015-12-01

    The initial interactions of nanoparticles with biomolecules have a great influence on its toxicity, efficacy, biodistribution and clearance. The present work is an attempt to understand the impact of surface charge of polymeric nanoparticles on its plasma protein and cellular interactions. Negative, near-neutral and positively charged poly(lactic-co-glycolic acid) [PLGA] nanoparticles were prepared using casein, poly(vinyl alcohol) and poly(ethylene imine) respectively, as surface stabilizers. A significant temporal variation in the hydrodynamic diameter of PLGA nanoparticles was observed in the presence of plasma proteins, which correlated with the amount of proteins adsorbed to each surface. Positively charged particles displayed the maximum size variation and protein adsorption. Cellular uptake of differentially charged nanoparticles was also concurrent with the quantity of adsorbed proteins, though there was no significant difference in their cytotoxicity. Haematological interactions (haemolysis and plasma coagulation times) of positively charged nanoparticles were considerably different from near-neutral and negative nanoparticles. Collectively, the results point to the interplay between plasma protein adsorption and cellular interactions of PLGA nanoparticles, which is governed by its surface charge, thereby necessitating a rational design of nanoparticles.

  2. Conservative fluctuational-electromagnetic interaction of a conducting nanoparticle with a smooth surface of condensed medium

    NASA Astrophysics Data System (ADS)

    Dedkov, G. V.; Kyasov, A. A.

    2007-05-01

    General expressions for a conservative force of the fluctuational-electromagnetic interaction between a neutral spherical conducting nanoparticle and a smooth surface of condensed medium are obtained for the first time with allowance for both electric and magnetic components. The results of calculations performed for a copper particle interacting with a copper surface show that the contribution of the magnetic components is predominating for all distances from the surface exceeding the particle radius R. The contribution due to the near-surface modes, which is proportional to the temperature and inversely proportional to the cube of the distance, is predominating at distances above ˜10 R.

  3. Regulation of Macrophage Recognition through the Interplay of Nanoparticle Surface Functionality and Protein Corona.

    PubMed

    Saha, Krishnendu; Rahimi, Mehran; Yazdani, Mahdieh; Kim, Sung Tae; Moyano, Daniel F; Hou, Singyuk; Das, Ridhha; Mout, Rubul; Rezaee, Farhad; Mahmoudi, Morteza; Rotello, Vincent M

    2016-04-26

    Using a family of cationic gold nanoparticles (NPs) with similar size and charge, we demonstrate that proper surface engineering can control the nature and identity of protein corona in physiological serum conditions. The protein coronas were highly dependent on the hydrophobicity and arrangement of chemical motifs on NP surface. The NPs were uptaken in macrophages in a corona-dependent manner, predominantly through recognition of specific complement proteins in the NP corona. Taken together, this study shows that surface functionality can be used to tune the protein corona formed on NP surface, dictating the interaction of NPs with macrophages.

  4. Aqueous Aggregation Behavior of Engineered Superparamagnetic Iron Oxide Nanoparticles: Effects of Oxidative Surface Aging.

    PubMed

    Li, Wenlu; Lee, Seung Soo; Mittelman, Anjuliee M; Liu, Di; Wu, Jiewei; Hinton, Carl H; Abriola, Linda M; Pennell, Kurt D; Fortner, John D

    2016-12-06

    For successful aqueous-based applications, it is necessary to fundamentally understand and control nanoparticle dispersivity and stability over a range of dynamic conditions, including variable ionic strengths/types, redox chemistries, and surface ligand reactivity/degradation states (i.e., surface aging). Here, we quantitatively describe the behavior of artificially aged, oleic acid (OA) bilayer coated iron oxide nanoparticles (IONPs) under different scenarios. Hydrogen peroxide (H2O2), used here as a model oxidant under both dark and light ultraviolet (UVA) conditions, was employed to "age" materials, to varying degrees, without increasing ionic strength. Short-term stability experiments indicate that OA-IONPs, while stable in the dark, are effectively destabilized when exposed to UVA/H2O2/•OH based oxidation processes. Compared to bicarbonate, phosphate (1.0 mM) has a net stabilizing effect on OA-IONPs under oxidative conditions, which can be attributed to (surface-based) functional adsorption. Corresponding aggregation kinetics in the presence of monovalent (Na(+)) and divalent cations (Ca(2+)) show that attachment efficiencies (α) are strongly dependent on the cation concentrations/types and degree of surface aging. Taken together, our findings directly highlight the need to understand the critical role of particle surface transformation(s), via oxidative aging, among other routes, with regard to the ultimate stability and environmental fate of surface functionalized engineered nanoparticles.

  5. Proton Coupled Electron Transfer Reactions at the Surface of Metal Oxide Nanomaterials

    NASA Astrophysics Data System (ADS)

    Braten, Miles N.

    Nanostructured metal oxide materials are found in many products and processes in our society today, but they play a particularly important role in the conversion and storage of energy. The materials are used as catalysts and redox active supports in devices such as dye sensitized solar cells, solid oxide fuel cells, and flow batteries, where they transfer and store electrons and charge balancing cations. Oftentimes electron transfer is modulated by the cations and when the cation is a proton, these redox reactions are known as proton coupled electron transfer (PCET) reactions. The work described in this dissertation focuses on understanding the PCET reactivity of nanocrystalline metal oxide materials. Chapter 1 introduces the concept of PCET and provides background information on the zinc oxide (ZnO) nanocrystals (NCs) which the majority of the research is focused on. Chapter 2 examines the chemistry that occurs during the photoreduction of ZnO NCs. Chapter 3 describes experiments probing how ZnO NC capping ligand concentration and NC size modulate PCET reaction rates. Chapter 4 describes experiments that compare the PCET reactivity of ZnO NCs with different numbers of electrons and protons stored on them. Chapter 5 describes attempts to observe the electrochemical reduction of ZnO NCs attached to gold electrodes. Finally, Chapter 6 contains attempts to identify a nanostructured metal oxide alkane oxidation catalyst for use in fuel cell.

  6. Local Charge Injection and Extraction on Surface-Modified Al2O3 Nanoparticles in LDPE.

    PubMed

    Borgani, Riccardo; Pallon, Love K H; Hedenqvist, Mikael S; Gedde, Ulf W; Haviland, David B

    2016-09-14

    We use a recently developed scanning probe technique to image with high spatial resolution the injection and extraction of charge around individual surface-modified aluminum oxide nanoparticles embedded in a low-density polyethylene (LDPE) matrix. We find that the experimental results are consistent with a simple band structure model where localized electronic states are available in the band gap (trap states) in the vicinity of the nanoparticles. This work offers experimental support to a previously proposed mechanism for enhanced insulating properties of nanocomposite LDPE and provides a powerful experimental tool to further investigate such properties.

  7. Surface-Enhanced Raman Spectroscopy Sensors From Nanobiosilica With Self-Assembled Plasmonic Nanoparticles

    PubMed Central

    Ren, Fanghui; Campbell, Jeremy; Rorrer, Gregory L.; Wang, Alan X.

    2014-01-01

    We present an innovative surface-enhanced Raman spectroscopy (SERS) sensor based on a biological-plasmonic hybrid nanostructure by self-assembling silver (Ag) nanoparticles into diatom frustules. The photonic-crystal-like diatom frustules provide a spatially confined electric field with enhanced intensity that can form hybrid photonic-plasmonic modes through the optical coupling with Ag nanoparticles. The experimental results demonstrate 4–6× and 9–12× improvement of sensitivities to detect the Raman dye for resonance and nonresonance SERS sensing, respectively. Such low-cost and high-sensitivity SERS sensors have significant potentials for label-free biosensing. PMID:25309113

  8. Redox induced protonation of heme propionates in cytochrome c oxidase: Insights from surface enhanced resonance Raman spectroscopy and QM/MM calculations.

    PubMed

    Sezer, Murat; Woelke, Anna-Lena; Knapp, Ernst Walter; Schlesinger, Ramona; Mroginski, Maria Andrea; Weidinger, Inez M

    2017-02-01

    Understanding the coupling between heme reduction and proton translocation in cytochrome c oxidase (CcO) is still an open problem. The propionic acids of heme a3 have been proposed to act as a proton loading site (PLS) in the proton pumping pathway, yet this proposal could not be verified by experimental data so far. We have set up an experiment where the redox states of the two hemes in CcO can be controlled via external electrical potential. Surface enhanced resonance Raman (SERR) spectroscopy was applied to simultaneously monitor the redox state of the hemes and the protonation state of the heme propionates. Simulated spectra based on QM/MM calculations were used to assign the resonant enhanced CH2 twisting modes of the propionates to the protonation state of the individual heme a and heme a3 propionates respectively. The comparison between calculated and measured H2OD2O difference spectra allowed a sound band assignment. In the fully reduced enzyme at least three of the four heme propionates were found to be protonated whereas in the presence of a reduced heme a and an oxidized heme a3 only protonation of one heme a3 propionates was observed. Our data supports the postulated scenario where the heme a3 propionates are involved in the proton pathway.

  9. Facile in situ characterization of gold nanoparticles on electrode surfaces by electrochemical techniques: average size, number density and morphology determination.

    PubMed

    Wang, Ying; Laborda, Eduardo; Salter, Chris; Crossley, Alison; Compton, Richard G

    2012-10-21

    A fast and cheap in situ approach is presented for the characterization of gold nanoparticles from electrochemical experiments. The average size and number of nanoparticles deposited on a glassy carbon electrode are determined from the values of the total surface area and amount of gold obtained by lead underpotential deposition and by stripping of gold in hydrochloric acid solution, respectively. The morphology of the nanoparticle surface can also be analyzed from the "fingerprint" in lead deposition/stripping experiments. The method is tested through the study of gold nanoparticles deposited on a glassy carbon substrate by seed-mediated growth method which enables an easy control of the nanoparticle size. The procedure is also applied to the characterization of supplied gold nanoparticles. The results are in satisfactory agreement with those obtained via scanning electron microscopy.

  10. Surface modification of oleylamine-capped Ag-Cu nanoparticles to fabricate low-temperature-sinterable Ag-Cu nanoink

    NASA Astrophysics Data System (ADS)

    Kim, Na Rae; Jong Lee, Yung; Lee, Changsoo; Koo, Jahyun; Lee, Hyuck Mo

    2016-08-01

    By treating oleylamine (OA)-capped Ag-Cu nanoparticles with tetramethylammonium hydroxide (TMAH), we obtained metal nanoparticles that are suspended in polar solvents and sinterable at low temperatures. The simple process with ultra sonication enables synthesis of monodispersed and high purity nanoparticles in an organic base, where the resulting nanoparticles are dispersible in polar solvents such as ethanol and isopropyl alcohol. To investigate the surface characteristics, we conducted Fourier-transform infrared and zeta-potential analyses. After thermal sintering at 200 °C, which is approximately 150 °C lower than the thermal decomposition temperature of OA, an electrically conductive thin film was obtained. Electrical resistivity measurements of the TMAH-treated ink demonstrate that surface modified nanoparticles have a low resistivity of 13.7 × 10-6 Ω cm. These results confirm the prospects of using low-temperature sinterable nanoparticles as the electrode layer for flexible printed electronics without damaging other stacked polymer layers.

  11. Altering protein surface charge with chemical modification modulates protein-gold nanoparticle aggregation

    NASA Astrophysics Data System (ADS)

    Jamison, Jennifer A.; Bryant, Erika L.; Kadali, Shyam B.; Wong, Michael S.; Colvin, Vicki L.; Matthews, Kathleen S.; Calabretta, Michelle K.

    2011-02-01

    Gold nanoparticles (AuNP) can interact with a wide range of molecules including proteins. Whereas significant attention has focused on modifying the nanoparticle surface to regulate protein-AuNP assembly or influence the formation of the protein "corona," modification of the protein surface as a mechanism to modulate protein-AuNP interaction has been less explored. Here, we examine this possibility utilizing three small globular proteins—lysozyme with high isoelectric point (pI) and established interactions with AuNP; α-lactalbumin with similar tertiary fold to lysozyme but low pI; and myoglobin with a different globular fold and an intermediate pI. We first chemically modified these proteins to alter their charged surface functionalities, and thereby shift protein pI, and then applied multiple methods to assess protein-AuNP assembly. At pH values lower than the anticipated pI of the modified protein, AuNP exposure elicits changes in the optical absorbance of the protein-NP solutions and other properties due to aggregate formation. Above the expected pI, however, protein-AuNP interaction is minimal, and both components remain isolated, presumably because both species are negatively charged. These data demonstrate that protein modification provides a powerful tool for modulating whether nanoparticle-protein interactions result in material aggregation. The results also underscore that naturally occurring protein modifications found in vivo may be critical in defining nanoparticle-protein corona compositions.

  12. Toxicity of bare and surfaced functionalized iron oxide nanoparticles towards microalgae.

    PubMed

    Toh, Pey Yi; Tai, Wan Yii; Ahmad, Abdul Latif; Lim, Jit Kang; Chan, Derek Juinn Chieh

    2016-01-01

    This study investigates the toxicity of bare iron oxide nanoparticles (IONPs) and surface functionalization iron oxide nanoparticles (SF-IONPs) to the growth of freshwater microalgae Chlorella sp. This study is important due to the increased interest on the application of the magnetic responsive IONPs in various fields, such as biomedical, wastewater treatment, and microalgae harvesting. This study demonstrated that the toxicity of IONPs was mainly contributed by the indirect light shading effect from the suspending nanoparticles which is nanoparticles concentration-dependent, direct light shading effect caused by the attachment of IONPs on cell and the cell aggregation, and the oxidative stress from the internalization of IONPs into the cells. The results showed that the layer of poly(diallyldimethylammonium chloride) (PDDA) tended to mask the IONPs and hence eliminated oxidative stress toward the protein yield but it in turn tended to enhance the toxicity of IONPs by enabling the IONPs to attach on cell surfaces and cause cell aggregation. Therefore, the choice of the polymer that used for surface functionalize the IONPs is the key factor to determine the toxicity of the IONPs.

  13. Thiol-reactive amphiphilic block copolymer for coating gold nanoparticles with neutral and functionable surfaces.

    PubMed

    Chen, Hongwei; Zou, Hao; Paholak, Hayley J; Ito, Masayuki; Qian, Wei; Che, Yong; Sun, Duxin

    2014-04-21

    Nanoparticles designed for biomedical applications are often coated with polymers containing reactive functional groups, such as -COOH and -NH2, to conjugate targeting ligands or drugs. However, introducing highly charged surfaces promotes binding of the nanoparticles to biomolecules in biological systems through ionic interactions, causing the nanoparticles to aggregate in biological environments and consequently undergo strong non-specific binding to off-target cells and tissues. Developing a unique polymer with neutral surfaces that can be further functionalized directly would be critical to develop suitable nanomaterials for nanomedicine. Here, we report a thiol-reactive amphiphilic block copolymer poly(ethylene oxide)-block-poly(pyridyldisulfide ethylmeth acrylate) (PEO-b-PPDSM) for coating gold nanoparticles (AuNPs). The resultant polymer-coated AuNPs have almost neutral surfaces with slightly negative zeta potentials from -10 to 0 mV over a wide pH range from 2 to 12. Although the zeta potential is close to zero we show that the PEO-b-PPDSM copolymer-coated AuNPs have both good stability in various physiological conditions and reduced non-specific adsorption of proteins/biomolecules. Because of the multiple pyridyldisulfide groups on the PPDSM block, these individually dispersed nanocomplexes with an overall hydrodynamic size around 43.8 nm can be directly functionalized via disulfide-thiol exchange chemistry.

  14. Fabrication of sticky and slippery superhydrophobic surfaces via spin-coating silica nanoparticles onto flat/patterned substrates.

    PubMed

    Cho, Kuan-Hung; Chen, Li-Jen

    2011-11-04

    Silica nanoparticles were spin-coated onto a flat/patterned (regular pillar-like) substrate to enhance the surface roughness. The surface was further modified by a self-assembled fluorosilanated monolayer. The advancing/receding contact angle and sliding angle measurements were performed to determine the wetting behavior of a water droplet on the surface. It is interesting to find that a transition from a Wenzel surface to a sticky superhydrophobic surface is observed due to the spin-coating silica nanoparticles. A slippery superhydrophobic surface can be further obtained after secondary spin-coating with silica nanoparticles to generate a multi-scale roughness structure. The prepared superhydrophobic substrates should be robust for practical applications. The adhesion between the substrate and nanoparticles is also examined and discussed.

  15. Size and surface chemistry of nanoparticles lead to a variant behavior in the unfolding dynamics of human carbonic anhydrase

    NASA Astrophysics Data System (ADS)

    Nasir, Irem; Lundqvist, Martin; Cabaleiro-Lago, Celia

    2015-10-01

    The adsorption induced conformational changes of human carbonic anhydrase I (HCAi) and pseudo wild type human carbonic anhydrase II truncated at the 17th residue at the N-terminus (trHCAii) were studied in presence of nanoparticles of different sizes and polarities. Isothermal titration calorimetry (ITC) studies showed that the binding to apolar surfaces is affected by the nanoparticle size in combination with the inherent protein stability. 8-Anilino-1-naphthalenesulfonic acid (ANS) fluorescence revealed that HCAs adsorb to both hydrophilic and hydrophobic surfaces, however the dynamics of the unfolding at the nanoparticle surfaces drastically vary with the polarity. The size of the nanoparticles has opposite effects depending on the polarity of the nanoparticle surface. The apolar nanoparticles induce seconds timescale structural rearrangements whereas polar nanoparticles induce hours timescale structural rearrangements on the same charged HCA variant. Here, a simple model is proposed where the difference in the timescales of adsorption is correlated with the energy barriers for initial docking and structural rearrangements which are firmly regulated by the surface polarity. Near-UV circular dichorism (CD) further supports that both protein variants undergo structural rearrangements at the nanoparticle surfaces regardless of being ``hard'' or ``soft''. However, the conformational changes induced by the apolar surfaces differ for each HCA isoform and diverge from the previously reported effect of silica nanoparticles.The adsorption induced conformational changes of human carbonic anhydrase I (HCAi) and pseudo wild type human carbonic anhydrase II truncated at the 17th residue at the N-terminus (trHCAii) were studied in presence of nanoparticles of different sizes and polarities. Isothermal titration calorimetry (ITC) studies showed that the binding to apolar surfaces is affected by the nanoparticle size in combination with the inherent protein stability. 8-Anilino

  16. Characterization of size, surface charge, and agglomeration state of nanoparticle dispersions for toxicological studies

    NASA Astrophysics Data System (ADS)

    Jiang, Jingkun; Oberdörster, Günter; Biswas, Pratim

    2009-01-01

    Characterizing the state of nanoparticles (such as size, surface charge, and degree of agglomeration) in aqueous suspensions and understanding the parameters that affect this state are imperative for toxicity investigations. In this study, the role of important factors such as solution ionic strength, pH, and particle surface chemistry that control nanoparticle dispersion was examined. The size and zeta potential of four TiO2 and three quantum dot samples dispersed in different solutions (including one physiological medium) were characterized. For 15 nm TiO2 dispersions, the increase of ionic strength from 0.001 M to 0.1 M led to a 50-fold increase in the hydrodynamic diameter, and the variation of pH resulted in significant change of particle surface charge and the hydrodynamic size. It was shown that both adsorbing multiply charged ions (e.g., pyrophosphate ions) onto the TiO2 nanoparticle surface and coating quantum dot nanocrystals with polymers (e.g., polyethylene glycol) suppressed agglomeration and stabilized the dispersions. DLVO theory was used to qualitatively understand nanoparticle dispersion stability. A methodology using different ultrasonication techniques (bath and probe) was developed to distinguish agglomerates from aggregates (strong bonds), and to estimate the extent of particle agglomeration. Probe ultrasonication performed better than bath ultrasonication in dispersing TiO2 agglomerates when the stabilizing agent sodium pyrophosphate was used. Commercially available Degussa P25 and in-house synthesized TiO2 nanoparticles were used to demonstrate identification of aggregated and agglomerated samples.

  17. Broadband tunability of surface plasmon resonance in graphene-coating silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhe, Shi; Yang, Yang; Lin, Gan; Zhi-Yuan, Li

    2016-05-01

    Graphene decorated nanomaterials and nanostructures can potentially be used in military and medical science applications. In this article, we study the optical properties of a graphene wrapping silica core-shell spherical nanoparticle under illumination of external light by using the Mie theory. We find that the nanoparticle can exhibit surface plasmon resonance (SPR) that can be broadly tuned from mid infrared to near infrared via simply changing the geometric parameters. A simplified equivalent dielectric permittivity model is developed to better understand the physics of SPR, and the calculation results agree well qualitatively with the rigorous Mie theory. Both calculations suggest that a small radius of graphene wrapping nanoparticle with high Fermi level could move the SPR wavelength of graphene into the near infrared regime. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204365 and 11434017) and the National Basic Research Program of China (Grant No. 2013CB632704).

  18. Surface-Induced First-Order Transition in Athermal Polymer-Nanoparticle Blends

    NASA Astrophysics Data System (ADS)

    McGarrity, E. S.; Frischknecht, A. L.; Frink, L. J. D.; Mackay, M. E.

    2007-12-01

    We investigate the phase behavior of athermal polymer-nanoparticle blends near a substrate. We apply a recent fluids density functional theory of Tripathi and Chapman to a simple model of the blend as a mixture of hard spheres and freely jointed hard chains, near a hard wall. We find that there is a first-order phase transition in which the nanoparticles expel the polymer from the surface to form a monolayer. The nanoparticle transition density depends on the length of the polymer and the overall bulk density of the system. The effect is due both to packing entropy effects related to size asymmetry between the components and to the polymer configurational entropy. The simplicity of the system allows us to understand the so-called “entropic-push” observed in experiments.

  19. Silicon and germanium nanoparticles with tailored surface chemistry as novel inorganic fiber brightening agents.

    PubMed

    Deb-Choudhury, Santanu; Prabakar, Sujay; Krsinic, Gail; Dyer, Jolon M; Tilley, Richard D

    2013-07-31

    Low-molecular-weight organic molecules, such as coumarins and stilbenes, are used commercially as fluorescent whitening agents (FWAs) to mask photoyellowing and to brighten colors in fabrics. FWAs achieve this by radiating extra blue light, thus changing the hue and also adding to the brightness. However, organic FWAs can rapidly photodegrade in the presence of ultraviolet (UV) radiation, exacerbating the yellowing process through a reaction involving singlet oxygen species. Inorganic nanoparticles, on the other hand, can provide a similar brightening effect with the added advantage of photostability. We report a targeted approach in designing new inorganic silicon- and germanium-based nanoparticles, functionalized with hydrophilic (amine) surface terminations as novel inorganic FWAs. When applied on wool, by incorporation in a sol-gel Si matrix, the inorganic FWAs improved brightness properties, demonstrated enhanced photostability toward UV radiation, especially the germanium nanoparticles, and also generated considerably lower levels of reactive oxygen species compared to a commercial stilbene-based organic FWA, Uvitex NFW.