Science.gov

Sample records for au nanoparticles immobilized

  1. Immobilization of Prussian Blue nanoparticles onto thiol SAM modified Au electrodes for electroanalytical or biosensor applications.

    PubMed

    Miao, Yuqing; Chen, Jianrong; Wu, Xiaohua; Fang, Keming; Jia, Aiping; Liu, Jiwei

    2007-08-01

    Poly(vinylpyrrolidone) (PVP)-protected Prussian Blue (PB) nanoparticles were prepared by simply mixing FeCI3 and K4Fe(CN)6 with absence or presence of HCI or/and KCI in water solution. The obtained PB nanoparticles were immobilized onto thiol self-assembled monolayer (SAM) modified Au electrodes. L-cysteine (Cys) and 1,8-octanedithiol (ODT) were compared as a bridge between the gold surface and the PB nanoparticles. The results show that PB prepared from the initial solution with KCI gives preferred electrochemical response and that Cys/Au shows improved immobilization effect of PB than ODT/Au. The obtained PB/Cys/Au electrodes exhibit electrocatalytic activity toward H2O2 reduction and DL-homocysteine (HCys) oxidation. Glucose oxidase (GOX) was immobilized onto PB modified electrode to explore the potentials for the design of oxidase-based biosensors. It is possible to anchor PB nanoparticles and develop their application on electroanalysis and biosensing.

  2. Synergistic catalysis of metal-organic framework-immobilized Au-Pd nanoparticles in dehydrogenation of formic acid for chemical hydrogen storage.

    PubMed

    Gu, Xiaojun; Lu, Zhang-Hui; Jiang, Hai-Long; Akita, Tomoki; Xu, Qiang

    2011-08-10

    Bimetallic Au-Pd nanoparticles (NPs) were successfully immobilized in the metal-organic frameworks (MOFs) MIL-101 and ethylenediamine (ED)-grafted MIL-101 (ED-MIL-101) using a simple liquid impregnation method. The resulting composites, Au-Pd/MIL-101 and Au-Pd/ED-MIL-101, represent the first highly active MOF-immobilized metal catalysts for the complete conversion of formic acid to high-quality hydrogen at a convenient temperature for chemical hydrogen storage. Au-Pd NPs with strong bimetallic synergistic effects have a much higher catalytic activity and a higher tolerance with respect to CO poisoning than monometallic Au and Pd counterparts. PMID:21761819

  3. Fabrication of quantum dot/silica core-shell particles immobilizing Au nanoparticles and their dual imaging functions

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yoshio; Matsudo, Hiromu; Li, Ting-ting; Shibuya, Kyosuke; Kubota, Yohsuke; Oikawa, Takahiro; Nakagawa, Tomohiko; Gonda, Kohsuke

    2016-03-01

    The present work proposes preparation methods for quantum dot/silica (QD/SiO2) core-shell particles that immobilize Au nanoparticles (QD/SiO2/Au). A colloid solution of QD/SiO2 core-shell particles with an average size of 47.0 ± 6.1 nm was prepared by a sol-gel reaction of tetraethyl orthosilicate in the presence of the QDs with an average size of 10.3 ± 2.1 nm. A colloid solution of Au nanoparticles with an average size of 17.9 ± 1.3 nm was prepared by reducing Au3+ ions with sodium citrate in water at 80 °C. Introduction of amino groups to QD/SiO2 particle surfaces was performed using (3-aminopropyl)-triethoxysilane (QD/SiO2-NH2). The QD/SiO2/Au particles were fabricated by mixing the Au particle colloid solution and the QD/SiO2-NH2 particle colloid solution. Values of radiant efficiency and computed tomography for the QD/SiO2/Au particle colloid solution were 2.23 × 107 (p/s/cm2/sr)/(μW/cm2) at a QD concentration of 8 × 10-7 M and 1180 ± 314 Hounsfield units and an Au concentration of 5.4 × 10-2 M. The QD/SiO2/Au particle colloid solution was injected into a mouse chest wall. Fluorescence emitted from the colloid solution could be detected on the skin covering the chest wall. The colloid solution could also be X-ray-imaged in the chest wall. Consequently, the QD/SiO2/Au particle colloid solution was found to have dual functions, i.e., fluorescence emission and X-ray absorption in vivo, which makes the colloid solution suitable to function as a contrast agent for dual imaging processes.

  4. Direct electrochemistry of laccase immobilized on au nanoparticles encapsulated-dendrimer bonded conducting polymer: application for a catechin sensor.

    PubMed

    Rahman, Md Aminur; Noh, Hui-Bog; Shim, Yoon-Bo

    2008-11-01

    The direct electrochemistry of laccase was promoted by Au nanoparticle (AuNP)-encapsulated dendrimers (Den), which was applied for the detection of catechin. To increase the electrical properties, AuNPs were captured in the interiors of the dendrimer (Den-AuNPs) as opposed to attachment at the periphery of dendrimer. To prepare Den-AuNPs, the Au(III) ions were first coordinated in the interior of dendrimer with nitrogen ligands and then reduced to form AuNPs. The size of AuNPs encapsulated within the interior of the dendrimer was determined to be 1.7 +/- 0.4 nm. AuNPs-encapsulated dendrimers were then used to covalently immobilize laccase (PDATT/ Den(AuNPs)/laccase) through the formation of amide bonds between carboxylic acid groups of the dendrimer and the amine groups of laccase. Each layer of the PDATT/Den(AuNPs)/laccase probe was characterized using CV, EIS, QCM, XPS, SEM, and TEM. The PDATT/Den(AuNPs)/laccase probe displayed a well-defined direct electron-transfer (DET) process of laccase. The quasi-reversible redox peak of the Cu redox center of the laccase molecule was observed at -0.03/+0.13 V vs Ag/AgCl, and the electron-transfer rate constant was determined to be 1.28 s (-1). A catechin biosensor based on the electrocatalytic process by direct electrochemistry of laccase was developed. The linear range and the detection limit in the catechin analysis were determined to be 0.1-10 and 0.05 +/- 0.003 microM, respectively. Interference effects from various phenolic and polyphenolic compounds were also studied, and the general applicability of the biosensor was evaluated by selective analysis of real samples of catechin.

  5. Enhanced surface plasmon resonance by Au nanoparticles immobilized on a dielectric SiO2 layer on a gold surface.

    PubMed

    Jung, Jaeyeon; Na, Kyunga; Lee, Jonghwan; Kim, Ki-Woo; Hyun, Jinho

    2009-09-28

    This paper introduces strategies for enhancement of a surface plasmon resonance (SPR) signal by adopting colloidal gold nanoparticles (AuNPs) and a SiO(2) layer on a gold surface. AuNPs on SiO(2) on a gold surface were compared with an unmodified gold surface and a SiO(2) layer on a gold surface with no AuNPs attached. The modified surfaces showed significant changes in SPR signal when biomolecules were attached to the surface as compared with an unmodified gold surface. The detection limit of AuNPs immobilized on a SPR chip was 0.1 ng mL(-1) for the prostate-specific antigen (PSA), a cancer marker, as measured with a spectrophotometer. Considering that the conventional ELISA method can detect approximately 10 ng mL(-1) of PSA, the strategy described here is much more sensitive (approximately 100 fold). The enhanced shift of the absorption curve resulted from the coupling of the surface and particle plasmons by the SiO(2) layer and the AuNPs on the gold surface.

  6. Immobilization of myoglobin on Au nanoparticle-decorated carbon nanotube/polytyramine composite as a mediator-free H2O2 and nitrite biosensor

    NASA Astrophysics Data System (ADS)

    Vilian, A. T. Ezhil; Veeramani, Vediyappan; Chen, Shen-Ming; Madhu, Rajesh; Kwak, Cheol Hwan; Huh, Yun Suk; Han, Young-Kyu

    2015-12-01

    A novel composite film was designed for use as a highly selective mediator-free amperometric biosensor, and a method was created for accomplishing direct electrochemistry of myoglobin on a multi-walled carbon nanotube and tyramine-modified composite decorated with Au nanoparticles on a glassy carbon electrode. The ultraviolet-visible and electrochemical impedance spectroscopy results showed that myoglobin retained its native conformation in the interaction with Au-PTy-f-MWCNT. The surface coverage of Mb-heme-Fe(II)/(III) immobilized on Au-PTy-f-MWCNT and the heterogeneous electron-transfer rate constant were 2.12 × 10-9 mol cm-2 and 4.86 s-1, respectively, indicating a higher loading capacity of the nanocomposite for direct electron transfer of Mb onto the electrode surface. The proposed Mb/Au-PTy-f-MWCNT biofilm exhibited excellent electrocatalytic behavior toward the reduction of H2O2 and the oxidation of nitrite with linear ranges of 2 to 5000 μM and 1 to 8000 μM and lower detection limits of 0.01 μM and 0.002 μM, respectively. An apparent Michaelis-Menten constant of 0.12 mM indicated that the Mb immobilized on the Au-PTy-f-MWCNT film retained its native activity. This biosensor can be successfully applied to detect H2O2 and nitrite in disinfectant cream, eye drops, pickle juice, and milk samples.

  7. Immobilization of myoglobin on Au nanoparticle-decorated carbon nanotube/polytyramine composite as a mediator-free H2O2 and nitrite biosensor

    PubMed Central

    Vilian, A. T. Ezhil; Veeramani, Vediyappan; Chen, Shen-Ming; Madhu, Rajesh; Kwak, Cheol Hwan; Huh, Yun Suk; Han, Young-Kyu

    2015-01-01

    A novel composite film was designed for use as a highly selective mediator-free amperometric biosensor, and a method was created for accomplishing direct electrochemistry of myoglobin on a multi-walled carbon nanotube and tyramine-modified composite decorated with Au nanoparticles on a glassy carbon electrode. The ultraviolet-visible and electrochemical impedance spectroscopy results showed that myoglobin retained its native conformation in the interaction with Au-PTy-f-MWCNT. The surface coverage of Mb-heme-Fe(II)/(III) immobilized on Au-PTy-f-MWCNT and the heterogeneous electron-transfer rate constant were 2.12 × 10−9 mol cm−2 and 4.86 s−1, respectively, indicating a higher loading capacity of the nanocomposite for direct electron transfer of Mb onto the electrode surface. The proposed Mb/Au-PTy-f-MWCNT biofilm exhibited excellent electrocatalytic behavior toward the reduction of H2O2 and the oxidation of nitrite with linear ranges of 2 to 5000 μM and 1 to 8000 μM and lower detection limits of 0.01 μM and 0.002 μM, respectively. An apparent Michaelis-Menten constant of 0.12 mM indicated that the Mb immobilized on the Au-PTy-f-MWCNT film retained its native activity. This biosensor can be successfully applied to detect H2O2 and nitrite in disinfectant cream, eye drops, pickle juice, and milk samples. PMID:26672985

  8. Flow-injection amperometric determination of glucose using a biosensor based on immobilization of glucose oxidase onto Au seeds decorated on core Fe₃O₄ nanoparticles.

    PubMed

    Samphao, Anchalee; Butmee, Preeyanut; Jitcharoen, Juthamas; Švorc, Ľubomír; Raber, Georg; Kalcher, Kurt

    2015-09-01

    An amperometric biosensor based on chemisorption of glucose oxidase (GOx) on Au seeds decorated on magnetic core Fe3O4 nanoparticles (Fe3O4@Au) and their immobilization on screen-printed carbon electrode bulk-modified with manganese oxide (SPCE{MnO2}) was designed for the determination of glucose. The Fe3O4@Au/GOx modified SPCE{MnO2} was used in a flow-injection analysis (FIA) arrangement. The experimental conditions were investigated in amperometric mode with the following optimized parameters: flow rate 1.7 mL min(-1), applied potential +0.38 V, phosphate buffer solution (PBS; 0.1 mol L(-1), pH 7.0) as carrier and 3.89 unit mm(-2) enzyme glucose oxidase loading on the active surface of the SPCE. The designed biosensor in FIA arrangement yielded a linear dynamic range for glucose from 0.2 to 9.0 mmol L(-1) with a sensitivity of 2.52 µA mM(-1) cm(-2), a detection limit of 0.1 mmol L(-1) and a quantification limit of 0.3 mmol L(-1). Moreover, a good repeatability of 2.8% (number of measurements n=10) and a sufficient reproducibility of 4.0% (number of sensors n=3) were achieved. It was found that the studied system Fe3O4@Au facilitated not only a simpler enzyme immobilization but also provided wider linear range. The practical application of the proposed biosensor for FIA quantification of glucose was tested in glucose sirup samples, honeys and energy drinks with the results in good accordance with those obtained by an optical glucose meter and with the contents declared by the producers. PMID:26003689

  9. Gold and silver nanoparticles for biomolecule immobilization and enzymatic catalysis

    NASA Astrophysics Data System (ADS)

    Petkova, Galina A.; Záruba, Кamil; Žvátora, Pavel; Král, Vladimír

    2012-06-01

    In this work, a simple method for alcohol synthesis with high enantiomeric purity was proposed. For this, colloidal gold and silver surface modifications with 3-mercaptopropanoic acid and cysteamine were used to generate carboxyl and amine functionalized gold and silver nanoparticles of 15 and 45 nm, respectively. Alcohol dehydrogenase from Thermoanaerobium brockii (TbADH) and its cofactor (NADPH) were physical and covalent (through direct adsorption and using cross-linker) immobilized on nanoparticles' surface. In contrast to the physical and covalent immobilizations that led to a loss of 90% of the initial enzyme activity and 98% immobilization, the use of a cross-linker in immobilization process promoted a loss to 30% of the initial enzyme activity and >92% immobilization. The yield of NADPH immobilization was about 80%. The best results in terms of activity were obtained with Ag-citr nanoparticle functionalized with carboxyl groups (Ag-COOH), Au-COOH(CTAB), and Au-citr functionalized with amine groups and stabilized with CTAB (Au-NH2(CTAB)) nanoparticles treated with 0.7% and 1.0% glutaraldehyde. Enzyme conformation upon immobilization was studied using fluorescence and circular dichroism spectroscopies. Shift in ellipticity at 222 nm with about 4 to 7 nm and significant decreasing in fluorescence emission for all bioconjugates were observed by binding of TbADH to silver/gold nanoparticles. Emission redshifting of 5 nm only for Ag-COOH-TbADH bioconjugate demonstrated change in the microenvironment of TbADH. Enzyme immobilization on glutaraldehyde-treated Au-NH2(CTAB) nanoparticles promotes an additional stabilization preserving about 50% of enzyme activity after 15 days storage. Nanoparticles attached-TbADH-NADPH systems were used for enantioselective ( ee > 99%) synthesis of ( S)-7-hydroxy-2-tetralol.

  10. Electrochemical responses and electrocatalysis at single au nanoparticles.

    PubMed

    Li, Yongxin; Cox, Jonathan T; Zhang, Bo

    2010-03-10

    Steady-state electrochemical responses have been obtained at single Au nanoparticles using Pt nanoelectrodes. A Au single-nanoparticle electrode (SNPE) is constructed by chemically immobilizing a single Au nanoparticle at a SiO(2)-encapsulated Pt disk nanoelectrode, which was previously modified by an amine-terminated silane. The Au SNPE has been characterized by transmission electron microscopy, underpotential deposition of Cu, and steady-state cyclic voltammetry. It has been found that the presence of a single Au nanoparticle enhances the electron transfer from the Pt nanoelectrode to the redox molecules, and the voltammetric response at the Au SNPE depends on the size of the Au nanoparticle. The Au SNPE has been utilized to examine the oxygen-reduction reaction in a KOH solution to explore the feasibility of measuring the electrocatalytic activity at a single-nanoparticle level. It has been shown that the electrocatalytic activity of single Au nanoparticles can be directly measured using SNPEs, and the electrocatalytic activity is dependent on the size of the Au nanoparticles. This study can help to understand the structure-function relationship in nanoparticle-based electrocatalysis.

  11. Self-assembly of thiolated cyanine aggregates on Au(111) and Au nanoparticle surfaces

    NASA Astrophysics Data System (ADS)

    Menéndez, Guillermo O.; Cortés, Emiliano; Grumelli, Doris; Méndez de Leo, Lucila P.; Williams, Federico J.; Tognalli, Nicolás G.; Fainstein, Alejandro; Vela, María Elena; Jares-Erijman, Elizabeth A.; Salvarezza, Roberto C.

    2012-01-01

    Heptamethinecyanine J-aggregates display sharp, intense fluorescence emission making them attractive candidates for developing a variety of chem-bio-sensing applications. They have been immobilized on planar thiol-covered Au surfaces and thiol-capped Au nanoparticles by weak molecular interactions. In this work the self-assembly of novel thiolated cyanine (CNN) on Au(111) and citrate-capped AuNPs from solutions containing monomers and J-aggregates has been studied by using STM, XPS, PM-IRRAS, electrochemical techniques and Raman spectroscopy. Data show that CNN species adsorb on the Au surfaces by forming thiolate-Au bonds. We found that the J-aggregates are preferentially adsorbed on the Au(111) surface directly from the solution while adsorbed CNN monomers cannot organize into aggregates on the substrate surface. These results indicate that the CNN-Au interaction is not able to disorganize the large J-aggregates stabilized by π-π stacking to optimize the S-Au binding site but it is strong enough to hinder the π-π stacking when CNNs are chemisorbed as monomers. The optical properties of the J-aggregates remain active after adsorption. The possibility of covalently bonding CNN J-aggregates to Au planar surfaces and Au nanoparticles controlling the J-aggregate/Au distance opens a new path regarding their improved stability and the wide range of biological applications of both CNN and AuNP biocompatible systems.Heptamethinecyanine J-aggregates display sharp, intense fluorescence emission making them attractive candidates for developing a variety of chem-bio-sensing applications. They have been immobilized on planar thiol-covered Au surfaces and thiol-capped Au nanoparticles by weak molecular interactions. In this work the self-assembly of novel thiolated cyanine (CNN) on Au(111) and citrate-capped AuNPs from solutions containing monomers and J-aggregates has been studied by using STM, XPS, PM-IRRAS, electrochemical techniques and Raman spectroscopy. Data show

  12. Immobilization of bovine catalase onto magnetic nanoparticles.

    PubMed

    Doğaç, Yasemin İspirli; Teke, Mustafa

    2013-01-01

    The scope of this study is to achieve carrier-bound immobilization of catalase onto magnetic particles (Fe₃O₄ and Fe₂O₃NiO₂ · H₂O) to specify the optimum conditions of immobilization. Removal of H2O2 and the properties of immobilized sets were also investigated. To that end, adsorption and then cross-linking methods onto magnetic particles were performed. The optimum immobilization conditions were found for catalase: immobilization time (15 min for Fe₃O₄; 10 min for Fe2O₃NiO₂ · H₂O), the initial enzyme concentration (1 mg/mL), amount of magnetic particles (25 mg), and glutaraldehyde concentration (3%). The activity reaction conditions (optimum temperature, optimum pH, pH stability, thermal stability, operational stability, and reusability) were characterized. Also kinetic parameters were calculated by Lineweaver-Burk plots. The optimum pH values were found to be 7.0, 7.0, and 8.0 for free enzyme, Fe₃O₄-immobilized catalases, and Fe₂O₃NiO₂ · H₂O-immobilized catalases, respectively. All immobilized catalase systems displayed the optimum temperature between 25 and 35°C. Reusability studies showed that Fe₃O₄-immobilized catalase can be used 11 times with 50% loss in original activity, while Fe2O₃NiO₂ · H₂O-immobilized catalase lost 67% of activity after the same number of uses. Furthermore, immobilized catalase systems exhibited improved thermal and pH stability. The results transparently indicate that it is possible to have binding between enzyme and magnetic nanoparticles.

  13. 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.

  14. Electrochemical activity of glucose oxidase on a poly(ionic liquid) - Au nanoparticle composite.

    SciTech Connect

    Lee, S.; Ringstrand, B. S.; Stone, D. A.; Firestone, M. A.

    2012-01-01

    Glucose oxidase (GOx) adsorbed on an ionic liquid-derived polymer containing internally organized columns of Au nanoparticles exhibits direct electron transfer and bioelectrocatalytic properties towards the oxidation of glucose. The cationic poly(ionic liquid) provides an ideal substrate for the electrostatic immobilization of GOx. The encapsulated Au nanoparticles serve to both promote the direct electron transfer with the recessed enzyme redox centers and impart electronic conduction to the composite, allowing it to function as an electrode for electrochemical detection.

  15. Using supported Au nanoparticles as starting material for preparing uniform Au/Pd bimetallic catalysts

    SciTech Connect

    Villa, Alberto; Prati, Laura; Su, Dangshen; Wang, Di; Veith, Gabriel M

    2010-01-01

    One of the best methods for producing bulk homogeneous (composition) supported bimetallic AuPd clusters involves the immobilization of a protected Au seed followed by the addition of Pd. This paper investigates the importance of this gold seed in controlling the resulting bimetallic AuPd clusters structures, sizes and catalytic activities by investigating three different gold seeds. Uniform Au-Pd alloy were obtained when a steric/electrostatic protecting group, poly(vinyl alcohol) (PVA), was used to form the gold clusters on activated carbon (AC). In contrast Au/AC precursors prepared using Au nanoparticles with only electrostatic stabilization (tetrakis(hydroxypropyl)phosphonium chloride (THPC)), or no stabilization (magnetron sputtering) produced inhomogeneous alloys and segregation of the gold and palladium. The uniform alloyed catalyst (Pd{at}Au{sub PVA}/AC) is the most active and selective catalyst, while the inhomogenous catalysts are less active and selective. Further study of the PVA protected Au clusters revealed that the amount of PVA used is also critical for the preparation of uniform alloyed catalyst, their stability, and their catalytic activity.

  16. S-shaped SU-8 optical waveguide immobilized with gold nanoparticles for trace detection of explosives

    NASA Astrophysics Data System (ADS)

    Bharadwaj, Reshma; Tripathi, Rakesh; Prabhakar, Amit; Mukherji, Soumyo

    2013-09-01

    In this study, we report a miniaturized optical sensor for direct detection of vapors of nitro-based explosives using gold nanoparticle (AuNP) coated SU-8 polymer optical waveguides. S-shaped waveguide geometry was chosen due its enhanced evanescent field sensitivity. Light was coupled into the waveguide structure to evanescently excite the localized surface plasmon resonance (LSPR) modes of the immobilized AuNP. The AuNP were functionalized with 4- mercaptobenzoic acid (4-MBA) which acts as the receptor for nitro-based explosives. The AuNP coated SU-8 optical waveguide sensor demonstrated an ability to detect 10 parts per billion (ppb) concentration of explosive analytes.

  17. Collision-spike sputtering of Au nanoparticles

    SciTech Connect

    Sandoval, Luis; Urbassek, Herbert M.

    2015-08-06

    Ion irradiation of nanoparticles leads to enhanced sputter yields if the nanoparticle size is of the order of the ion penetration depth. While this feature is reasonably well understood for collision-cascade sputtering, we explore it in the regime of collision-spike sputtering using molecular-dynamics simulation. For this specific case of 200-keV Xe bombardment of Au particles, we show that collision spikes lead to abundant sputtering with an average yield of 397 ± 121 atoms compared to only 116 ± 48 atoms for a bulk Au target. Only around 31% of the impact energy remains in the nanoparticles after impact; the remainder is transported away by the transmitted projectile and the ejecta. The sputter yield of supported nanoparticles is estimated to be around 80% of that of free nanoparticles due to the suppression of forward sputtering.

  18. Collision-spike sputtering of Au nanoparticles

    DOE PAGES

    Sandoval, Luis; Urbassek, Herbert M.

    2015-08-06

    Ion irradiation of nanoparticles leads to enhanced sputter yields if the nanoparticle size is of the order of the ion penetration depth. While this feature is reasonably well understood for collision-cascade sputtering, we explore it in the regime of collision-spike sputtering using molecular-dynamics simulation. For this specific case of 200-keV Xe bombardment of Au particles, we show that collision spikes lead to abundant sputtering with an average yield of 397 ± 121 atoms compared to only 116 ± 48 atoms for a bulk Au target. Only around 31% of the impact energy remains in the nanoparticles after impact; the remaindermore » is transported away by the transmitted projectile and the ejecta. The sputter yield of supported nanoparticles is estimated to be around 80% of that of free nanoparticles due to the suppression of forward sputtering.« less

  19. Collision-spike Sputtering of Au Nanoparticles.

    PubMed

    Sandoval, Luis; Urbassek, Herbert M

    2015-12-01

    Ion irradiation of nanoparticles leads to enhanced sputter yields if the nanoparticle size is of the order of the ion penetration depth. While this feature is reasonably well understood for collision-cascade sputtering, we explore it in the regime of collision-spike sputtering using molecular-dynamics simulation. For the particular case of 200-keV Xe bombardment of Au particles, we show that collision spikes lead to abundant sputtering with an average yield of 397 ± 121 atoms compared to only 116 ± 48 atoms for a bulk Au target. Only around 31 % of the impact energy remains in the nanoparticles after impact; the remainder is transported away by the transmitted projectile and the ejecta. The sputter yield of supported nanoparticles is estimated to be around 80 % of that of free nanoparticles due to the suppression of forward sputtering.

  20. Ambient, rapid and facile deposition of polymer brushes for immobilization of plasmonic nanoparticles

    NASA Astrophysics Data System (ADS)

    Yilmaz, Hatice; Pekdemir, Sami; Ipekci, Hasan H.; Kiremitler, N. Burak; Hancer, Mehmet; Onses, M. Serdar

    2016-11-01

    The immobilization of nanoparticles (NPs) is of great interest to many technological applications and scientific fields. Methods to immobilize NPs either lack the uniformity, robustness and controllability or require complex and impractical preparation techniques. This paper aims in closing this gap by presenting practical routes in preparation of poly(2-vinyl pyridine) (P2VP) brush grafted silicon oxide terminated substrates for immobilization of NPs. Here, we demonstrate that hydroxyl-terminated P2VP can be deposited using different coating techniques and grafted in air at processing times as short as a few minutes. The grafted P2VP brushes can immobilize spherical Au nanoparticles that are 20 nm in diameter, on the surface of substrates with densities as high as ∼600 particles/μm2. The density of the immobilized NPs can be further tuned with the grafting conditions and duration of the particle treatment. More than 80% of the grafted brushes and Au NPs remain on the substrate following abrasion tests proving mechanical robustness of the coatings. The immobilized Au NPs can impart surface enhanced Raman scattering effects in sensing of molecules, illustrating a representative use of the presented platform.

  1. Mimetic biomembrane-AuNPs-graphene hybrid as matrix for enzyme immobilization and bioelectrocatalysis study.

    PubMed

    Wang, Tianshu; Liu, Jiyang; Ren, Jiangtao; Wang, Jin; Wang, Erkang

    2015-10-01

    A hybrid composite constructed of phospholipids bilayer membrane, gold nanoparticles and graphene was prepared and used as matrices for microperoxidase-11 (MP11) immobilization. The direct electrochemistry and corresponding bioelectrocatalysis of the enzyme electrode was further investigated. Phospholipid bilayer membrane protected gold nanoparticles (AuNPs) were assembled on polyelectrolyte functionalized graphene sheets through electrostatic attraction to form a hybrid bionanocomposite. Owing to the biocompatible microenvironment provided by the mimetic biomembrane, microperoxidase-11 entrapped in this matrix well retained its native structure and exhibited high bioactivity. Moreover, the AuNPs-graphene assemblies could efficiently promote the direct electron transfer between the immobilized MP11 and the substrate electrode. The as-prepared enzyme electrode presented good direct electrochemistry and electrocatalytic responses to the reduction of hydrogen peroxide (H2O2). The resulting H2O2 biosensor showed a wide linear range (2.0×10(-5)-2.8×10(-4) M), a low detection limit (2.6×10(-6) M), good reproducibility and stability. Furthermore, this sensor was used for real-time detection of H2O2 dynamically released from the tumor cells MCF-7 in response to a pro-inflammatory stimulant. PMID:26078181

  2. Conjugating folate on superparamagnetic Fe3O4@Au nanoparticles using click chemistry

    NASA Astrophysics Data System (ADS)

    Shen, Xiaofang; Ge, Zhaoqiang; Pang, Yuehong

    2015-02-01

    Gold-coated magnetic core@shell nanoparticles, which exhibit magneto-optical properties, not only enhance the chemical stability of core and biocompatibility of surface, but also provide a combination of multimodal imaging and therapeutics. The conjugation of these tiny nanoparticles with specific biomolecules allows researchers to target the desired location. In this paper, superparamagnetic Fe3O4@Au nanoparticles were synthesized and functionalized with the azide group on the surface by formation of self-assembled monolayers. Folate (FA) molecules, non-immunogenic target ligands for cancer cells, are conjugated with alkyne and then immobilized on the azide-terminated Fe3O4@Au nanoparticles through copper(I)-catalyzed azide-alkyne cycloaddition (click reaction). Myelogenous leukemia K562 cells were used as a folate receptor (FR) model, which can be targeted and extracted by magnetic field after interaction with the Fe3O4@Au-FA nanoparticles.

  3. Click Chemistry Immobilization of Antibodies on Polymer Coated Gold Nanoparticles.

    PubMed

    Finetti, Chiara; Sola, Laura; Pezzullo, Margherita; Prosperi, Davide; Colombo, Miriam; Riva, Benedetta; Avvakumova, Svetlana; Morasso, Carlo; Picciolini, Silvia; Chiari, Marcella

    2016-07-26

    The goal of this work is to develop an innovative approach for the coating of gold nanoparticles (AuNPs) with a synthetic functional copolymer. This stable coating with a thickness of few nanometers provides, at the same time, stabilization and functionalization of the particles. The polymeric coating consists of a backbone of polydimethylacrylamide (DMA) functionalized with an alkyne monomer that allows the binding of azido modified molecules by Cu(I)-catalyzed azide/alkyne 1,3-dipolar cycloaddition (CuAAC, click chemistry). The thin polymer layer on the surface stabilizes the colloidal suspension whereas the alkyne functions pending from the backbone are available for the reaction with azido-modified proteins. The reactivity of the coating is demonstrated by immobilizing an azido modified anti-mouse IgG antibody on the particle surface. This approach for the covalent binding of antibody to a gold-NPs is applied to the development of gold labels in biosensing techniques.

  4. Au nanoparticles films used in biological sensing

    NASA Astrophysics Data System (ADS)

    Rosales Pérez, M.; Delgado Macuil, R.; Rojas López, M.; Gayou, V. L.; Sánchez Ramírez, J. F.

    2009-05-01

    Lactobacillus para paracasei are used commonly as functional food and probiotic substances. In this work Au nanoparticles self-assembled films were used for Lactobacillus para paracasei determination at five different concentrations. Functionalized substrates were immersed in a colloidal solution for one and a half hour at room temperature and dried at room temperature during four hours. After that, drops of Lactobacillus para paracasei in aqueous solution were put into the Au nanoparticles film and let dry at room temperature for another two hours. Infrared spectroscopy in attenuated total reflectance sampling mode was used to observe generation peaks due to substrate silanization, enhancement of Si-O band intensity due to the Au colloids added to silanized substrate and also to observe the enhancement of Lactobacillus para paracasei infrared intensity of the characteristic frequencies at 1650, 1534 and 1450 cm-1 due to surface enhancement infrared absorption.

  5. Influence of Surfactant Bilayers and Substrate Immobilization on the Refractive Index Sensitivity of Anisotropic Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Shahjamali, Mohammad; Large, Nicolas; Martinsson, Erik; Zaraee, Negin; Schatz, George; Aili, Daniel; Mirkin, Chad

    2015-03-01

    Shape-controlled synthesis of gold nanoparticles (AuNPs) generally involves the use of surfactants to regulate the nucleation growth process and to obtain colloidally stable AuNPs. The surfactants adsorb on the NP surface making further functionalization difficult and therefore limit their practical use in many applications such as bio- and molecular sensing, surface-enhanced spectrosopies, and NP assembly. Herein, we report on how cetyltrimethylammonium (CTAX, X =Cl-, Br-) , a common surfactant used in anisotropic AuNPs synthesis, affectsthe nanoparticle sensitivity to local dielectric environment changes and limitsrefractometric plasmonic sensing. We experimentally and theoretically show that the CTAX bilayer significantly reduces the refractive index (RI) sensitivity of anisotropic AuNPs such as flat and concave nanocubes, nanorods, and nanoprisms. We show that the RI sensitivity can be improvedby up to 40% by removing the CTAXfrom immobilized AuNPs using oxygen plasma treatment. The substrate effect on the RI sensitivity caused by NP immobilization isalso investigated. The strategy presented herein is a simple andeffective method to improvethe RI sensitivity of CTAX-stabilized AuNPs, thus increasing their potential in nanoplasmonic sensingand in biomedical applications.

  6. Acetylcholinesterase immobilized onto PEI-coated silica nanoparticles.

    PubMed

    Tumturk, Hayrettin; Yüksekdag, Hazer

    2016-01-01

    Polyethyleneimine (PEI) coated-silica nanoparticles were prepared by the Stöber method. The formation and the structure of the nanoparticles were characterized by ATR-FT-IR spectroscopy and transmission electron microscopy (TEM). TEM images of the silica and PEI-coated nanoparticles revealed that they were well dispersed and that there was no agglomeration. The acetylcholineesterase enzyme was immobilized onto these nanoparticles. The effects of pH and temperature on the storage stability of the free and immobilized enzyme were investigated. The optimum pHs for free and immobilized enzymes were determined as 7.0 and 8.0, respectively. The optimum temperatures for free and immobilized enzymes were found to be 30.0 and 35.0°C, respectively. The maximum reaction rate (Vmax) and the Michaelis-Menten constant (Km) were investigated for the free and immobilized enzyme. The storage stability of acetylcholinesterase was increased when immobilized onto the novel PEI-coated silica nanoparticles. The reuse numbers of immobilized enzyme were also studied. These hybrid nanoparticles are desirable as carriers for biomedical applications.

  7. Immobilization strategy for enhancing sensitivity of immunosensors: L-Asparagine-AuNPs as a promising alternative of EDC-NHS activated citrate-AuNPs for antibody immobilization.

    PubMed

    Raghav, Ragini; Srivastava, Sudha

    2016-04-15

    This paper addresses the question - Is EDC-NHS activated gold nanoparticles modified electrode surface the best available option for antibody immobilization for immunosensor fabrication? Is there any other alternative covalent immobilization strategy for orthogonal orientation of antibody, ensuring enhanced sensitivity of immunosensors? Does EDC-NHS activation of carboxyl functionalized nanoparticles surface really leads to orthogonal or directed immobilization of antibody? Gold nanoparticles synthesized using L-Asparagine as reducing and stabilization agent were employed for orthogonal immobilization of antibody for immunosensor fabrication. Anti-CA125 antibody was used as a model system for immunosensor fabrication. A comparative evaluation of immunosensors fabricated using L-Asparagine stabilized gold nanoparticles and citrate stabilized gold nanoparticles via different immobilization strategies/chemistries was done. The three strategies involved immobilization of Anti-CA125 antibody - (1) after EDC-NHS activation of citrate stabilized gold nanoparticles, (2) directly onto citrate stabilized gold nanoparticles and (3) directly onto L-Asparagine stabilized gold nanoparticles modified electrode surfaces. Comparative evaluation of Impedimetric response characteristics showed 2.5 times increase in sensitivity (349.36 Ω/(IU/mL)/cm(2)) in case of third strategy as compared to first (147.53 Ω/(IU/mL)/cm(2)) and twice that of second strategy (166.24 Ω/(IU/mL)/cm(2)). Additionally, an extended dynamic range of 0-750 IU/mL was observed while for others it was up to 500 IU/mL. Amino acid coated gold nanoparticles ensured orthogonal immobilization, lesser randomization, with 88% of active antibody available for antigen binding as opposed to other two strategies with less than 30% active antibody.

  8. Preparation of well-dispersed gold/magnetite nanoparticles embedded on cellulose nanocrystals for efficient immobilization of papain enzyme.

    PubMed

    Mahmoud, Khaled A; Lam, Edmond; Hrapovic, Sabahudin; Luong, John H T

    2013-06-12

    A nanocomposite consisting of magnetite nanoparticles (Fe3O4NPs) and Au nanoparticles (AuNPs) embedded on cellulose nanocrystals (CNCs) was used as a magnetic support for the covalent conjugation of papain and facilitated recovery of this immobilized enzyme. Fe3O4NPs (10-20 nm in diameter) and AuNPs (3-7 nm in diameter) were stable and well-dispersed on the CNC surface. Energy-dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used to evaluate the surface composition and structure of CNC/Fe3O4NPs/AuNPs. The nanocomposite was successfully used for the immobilization and separation of papain from the reaction mixture. The optimal enzyme loading was 186 mg protein/g CNC/Fe3O4NPs/AuNPs, significantly higher than the value reported in the literature. The activity of immobilized papain was studied by electrochemical detection of its specific binding to the Thc-Fca-Gly-Gly-Tyr-Arg inhibitory sequence bound to an Au electrode. The immobilized enzyme retained 95% of its initial activity after 35 days of storage at 4 °C, compared to 41% for its free form counterpart.

  9. Photosynthetic electron transport system promotes synthesis of Au-nanoparticles.

    PubMed

    Shabnam, Nisha; Pardha-Saradhi, P

    2013-01-01

    In this communication, a novel, green, efficient and economically viable light mediated protocol for generation of Au-nanoparticles using most vital organelle, chloroplasts, of the plant system is portrayed. Thylakoids/chloroplasts isolated from Potamogeton nodosus (an aquatic plant) and Spinacia oleracea (a terrestrial plant) turned Au³⁺ solutions purple in presence of light of 600 µmol m⁻² s⁻¹ photon flux density (PFD) and the purple coloration intensified with time. UV-Vis spectra of these purple colored solutions showed absorption peak at ∼545 nm which is known to arise due to surface plasmon oscillations specific to Au-nanoparticles. However, thylakoids/chloroplasts did not alter color of Au³⁺ solutions in dark. These results clearly demonstrated that photosynthetic electron transport can reduce Au³⁺ to Au⁰ which nucleate to form Au-nanoparticles in presence of light. Transmission electron microscopic studies revealed that Au-nanoparticles generated by light driven photosynthetic electron transport system of thylakoids/chloroplasts were in range of 5-20 nm. Selected area electron diffraction and powder X-ray diffraction indicated crystalline nature of these nanoparticles. Energy dispersive X-ray confirmed that these nanoparticles were composed of Au. To confirm the potential of light driven photosynthetic electron transport in generation of Au-nanoparticles, thylakoids/chloroplasts were tested for their efficacy to generate Au-nanoparticles in presence of light of PFD ranging from 60 to 600 µmol m⁻² s⁻¹. The capacity of thylakoids/chloroplasts to generate Au-nanoparticles increased remarkably with increase in PFD, which further clearly demonstrated potential of light driven photosynthetic electron transport in reduction of Au³⁺ to Au⁰ to form nanoparticles. The light driven donation of electrons to metal ions by thylakoids/chloroplasts can be exploited for large scale production of nanoparticles. PMID:23976990

  10. Photosynthetic electron transport system promotes synthesis of Au-nanoparticles.

    PubMed

    Shabnam, Nisha; Pardha-Saradhi, P

    2013-01-01

    In this communication, a novel, green, efficient and economically viable light mediated protocol for generation of Au-nanoparticles using most vital organelle, chloroplasts, of the plant system is portrayed. Thylakoids/chloroplasts isolated from Potamogeton nodosus (an aquatic plant) and Spinacia oleracea (a terrestrial plant) turned Au³⁺ solutions purple in presence of light of 600 µmol m⁻² s⁻¹ photon flux density (PFD) and the purple coloration intensified with time. UV-Vis spectra of these purple colored solutions showed absorption peak at ∼545 nm which is known to arise due to surface plasmon oscillations specific to Au-nanoparticles. However, thylakoids/chloroplasts did not alter color of Au³⁺ solutions in dark. These results clearly demonstrated that photosynthetic electron transport can reduce Au³⁺ to Au⁰ which nucleate to form Au-nanoparticles in presence of light. Transmission electron microscopic studies revealed that Au-nanoparticles generated by light driven photosynthetic electron transport system of thylakoids/chloroplasts were in range of 5-20 nm. Selected area electron diffraction and powder X-ray diffraction indicated crystalline nature of these nanoparticles. Energy dispersive X-ray confirmed that these nanoparticles were composed of Au. To confirm the potential of light driven photosynthetic electron transport in generation of Au-nanoparticles, thylakoids/chloroplasts were tested for their efficacy to generate Au-nanoparticles in presence of light of PFD ranging from 60 to 600 µmol m⁻² s⁻¹. The capacity of thylakoids/chloroplasts to generate Au-nanoparticles increased remarkably with increase in PFD, which further clearly demonstrated potential of light driven photosynthetic electron transport in reduction of Au³⁺ to Au⁰ to form nanoparticles. The light driven donation of electrons to metal ions by thylakoids/chloroplasts can be exploited for large scale production of nanoparticles.

  11. Site-selective immobilization of gold nanoparticles on graphene sheets and its electrochemical properties

    NASA Astrophysics Data System (ADS)

    Lee, Jea Uk; Lee, Wonoh; Yoon, Sang Su; Kim, Jungwook; Byun, Joon Hyung

    2014-10-01

    The site-selective attachment of metal nanoparticles (NPs) on graphene surface is highly desirable for various applications such as electrochemical sensors and catalysts. Here, we present a simple and effective synthetic approach for the site-selective immobilization of gold NPs (AuNPs) on either basal planes or edges of graphene sheets. The basic principle of this approach is to use cyteamine linker with reactive amine and thiol functional groups at each end, where the amine groups at one end covalently bind to functional groups presented on edges and/or basal planes of chemically synthesized graphene sheets, and the thiol groups at the other end assemble onto pre-synthesized AuNPs through thiol-Au interaction. Due to the difference in the spatial distribution of functional groups presented on graphene oxide (GO) and reduced graphene oxide (rGO) sheets, most of AuNPs are homogeneously immobilized on the basal planes of the cysteamine-functionalized graphene oxide (GO-SH) sheets, whereas AuNPs are selectively attached at the edge parts of the cysteamine-functionalized reduced graphene oxide (rGO-SH) sheets. Raman signals of GO-SH/Au hybrid films with the high content of AuNPs in the hybrids are clearly increased owing to the formation of the charge-transfer complex between AuNPs and GO-SH sheets, exhibiting surface-enhanced Raman scattering (SERS) activity. Furthermore, rGO-SH/Au hybrids enhance the electrochemical activity of modified glassy carbon electrodes owing to the synergetic effects of electrical conduction by the restored aromatic structure of rGO sheets and percolated network of AuNPs along the graphene edges

  12. Au-nanoparticles grafted on plasma treated PE

    NASA Astrophysics Data System (ADS)

    Švorčík, V.; Chaloupka, A.; Řezanka, P.; Slepička, P.; Kolská, Z.; Kasálková, N.; Hubáček, T.; Siegel, J.

    2010-03-01

    Polyethylene (PE) surface was treated with Ar plasma. Activated surface was grafted from methanol solution of 1,2-ethanedithiol. Then the sample was immersed into freshly prepared colloid solution of Au-nanoparticles. Finally Au layer was sputtered on the samples. Properties of the modified PE were studied using various methods: AFM, EPR, RBS and nanoindentation. It was shown that the plasma treatment results in degradation of polymer chain (AFM) and creation of free radicals by EPR. After grafting with dithiol, the concentration of free radicals declines. The presence of Au and S in the surface layer after the coating with Au-nanoparticles was proved by RBS. Plasma treatment changes PE surface morphology and increases surface roughness, too. Another significant change in surface morphology and roughness was observed after deposition of Au-nanoparticles. Nanoindentation measurements show that the grafting with Au-nanoparticles increases adhesion of subsequently sputtered Au layer.

  13. (Au/PANA/PVAc) nanofibers as a novel composite matrix for albumin and streptavidin immobilization.

    PubMed

    Golshaei, Rana; Guler, Zeliha; Sarac, Sezai A

    2016-03-01

    A novel electrospun nanofiber mat (Au/PANA/PVAc) consists of (Gold/Poly Anthranilic acid) (Au/PANA) core/shell nanostructures as a support material for protein immobilization that was developed and characterized by electrochemical impedance spectroscopy. In the core/shells, PANA served carboxyl groups (-COOH) for covalent protein immobilization and Au enhanced the electrochemical properties by acting as tiny conduction centers to facilitate electron transfer. Covalent immobilization of albumin and streptavidin as model proteins onto the (Au/PANA/PVAc) nanofibers was carried out by using 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxyl succinimide (NHS) activation. PVAc nanofibers were compared with Au/PANA/PVAc nanofibers before and after protein immobilization. The successful covalent binding of both albumin and streptavidin onto (Au/PANA/PVAc) nanofibers was confirmed by FTIR-ATR, Electron Microscopy/Energy-Dispersive X-ray Spectroscopy SEM/EDX and Electrochemical impedance spectroscopy (EIS). The nanofibers became resistive due to protein immobilization and the higher charge transfer resistance was observed after higher amount of protein was immobilized. PMID:26706530

  14. Purification, immobilization, and characterization of nattokinase on PHB nanoparticles.

    PubMed

    Deepak, Venkataraman; Pandian, Suresh babu Ram Kumar; Kalishwaralal, Kalimuthu; Gurunathan, Sangiliyandi

    2009-12-01

    In this study, nattokinase was purified from Bacillus subtilis using ion exchange chromatography and immobilized upon polyhydroxybutyrate (PHB) nanoparticles. A novel strain isolated from industrial dairy waste was found to synthesize polyhydroxyalkanoates (PHA) and the strain was identified as Brevibacterium casei SRKP2. PHA granules were extracted from 48 h culture and the FT-IR analysis characterized them as PHB, a natural biopolymer from B. casei. Nanoprecipitation by solvent displacement technique was used to synthesize PHB nanoparticles. PHB nanoparticles were characterized using transmission electron microscopy and particle size ranged from 100-125 nm. Immobilization of nattokinase upon PHB nanoparticles resulted in a 20% increase in the enzyme activity. Immobilization also contributed to the enhanced stability of the enzyme. Moreover, the activity was completely retained on storage at 4 degrees C for 25 days. The method has proven to be highly simple and can be implemented to other enzymes also.

  15. Characterization of protein-immobilized polystyrene nanoparticles using impedance spectroscopy.

    PubMed

    Park, Soo-In; Lee, Sang-Yup

    2014-10-01

    A novel approach for characterization of non-conductive protein-immobilized nanoparticles using AC impedance spectroscopy combined with conductive atomic force microscopy was examined. As AC impedance spectroscopy can provide information on diverse electrical properties such as capacitance and inductance, it is applicable to the characterization of non-conductive substances. Several non-conductive protein-immobilized polystyrene nanoparticles were analyzed using AC impedance spectroscopy, and their impedance spectra were used as markers for nanoparticle identification. Analyses of impedance signals using an electrical circuit model established that the capacitance and inductance of each nanoparticle changed with the adsorbed protein and that impedance spectral differences were characteristic properties of the proteins. From this study, AC impedance spectroscopy was shown to be a useful tool for characterization of non-conductive nanoparticles and is expected to be applicable to the development of sensors for nanomaterials. PMID:25942903

  16. Magnetic nanoparticles coated with polyaniline to stabilize immobilized trypsin

    NASA Astrophysics Data System (ADS)

    Maciel, J. C.; D. Mercês, A. A.; Cabrera, M.; Shigeyosi, W. T.; de Souza, S. D.; Olzon-Dionysio, M.; Fabris, J. D.; Cardoso, C. A.; Neri, D. F. M.; C. Silva, M. P.; Carvalho, L. B.

    2016-12-01

    It is reported the synthesis of magnetic nanoparticles via the chemical co-precipitation of Fe 3+ ions and their preparation by coating them with polyaniline. The electronic micrograph analysis showed that the mean diameter for the nanoparticles is ˜15 nm. FTIR, powder X-ray diffraction and Mössbauer spectroscopy were used to understand the chemical, crystallographic and 57Fe hyperfine structures for the two samples. The nanoparticles, which exhibited magnetic behavior with relatively high spontaneous magnetization at room temperature, were identified as being mainly formed by maghemite ( γFe2O3). The coated magnetic nanoparticles (sample labeled "mPANI") presented a real ability to bind biological molecules such as trypsin, forming the magnetic enzyme derivative (sample "mPANIG-Trypsin"). The amount of protein and specific activity of the immobilized trypsin were found to be 13±5 μg of protein/mg of mPANI (49.3 % of immobilized protein) and 24.1±0.7 U/mg of immobilized protein, respectively. After 48 days of storage at 4 ∘C, the activity of the immobilized trypsin was found to be 89 % of its initial activity. This simple, fast and low-cost procedure was revealed to be a promising way to prepare mPANI nanoparticles if technological applications addressed to covalently link biomolecules are envisaged. This route yields chemically stable derivatives, which can be easily recovered from the reaction mixture with a magnetic field and recyclable reused.

  17. Fabrication of nanoelectrode ensembles by electrodepositon of Au nanoparticles on single-layer graphene oxide sheets.

    PubMed

    Wang, Zhijuan; Zhang, Juan; Yin, Zongyou; Wu, Shixin; Mandler, Daniel; Zhang, Hua

    2012-04-21

    Nanoelectrode ensembles (NEEs) have been fabricated by the electrodeposition of Au nanoparticles (AuNPs) on single-layer graphene oxide (GO) sheets coated on a glassy carbon electrode (GCE). The fabricated NEEs show a typical sigmoidal shaped voltammetric profile, arising from the low coverage density of AuNPs on GCE and large distance among them, which can be easily controlled by varying the electrodeposition time. As a proof of concept, after the probe HS-DNA is immobilized on the NEEs through the Au-S bonding, the target DNA is detected with the methylene blue intercalator. Our results show that the target DNA can be detected as low as 100 fM, i.e. 0.5 amol DNA in 5 μL solution.

  18. Exfoliation restacking route to Au nanoparticle-clay nanohybrids

    NASA Astrophysics Data System (ADS)

    Paek, Seung-Min; Jang, Jae-Up; Hwang, Seong-Ju; Choy, Jin-Ho

    2006-05-01

    A novel gold-pillared aluminosilicate (Au-PILC) were synthesized with positively charged gold nanoparticles capped by mercaptoammonium and exfoliated silicate layers. Gold nanoparticles were synthesized by NaBH4 reduction of AuCl4- in the presence of N,N,N-Trimethyl (11-mercaptoundecyl)ammonium (HS(CH2)11NMe3+) protecting ligand in an aqueous solution, and purified by dialysis. The resulting positively charged and water-soluble gold nanoparticles were hybridized with exfoliated silicate sheets by electrostatic interaction. The formation of Au clay hybrids could be easily confirmed by the powder X-ray diffraction with the increased basal spacing of clay upon insertion of Au nanoparticles. TEM image clearly revealed that the Au particles with an average size of 4 nm maintain their structure even after intercalation. The Au nanoparticles supported by clay matrix were found to be thermally more stable, suggesting that the Au nanoparticles were homogeneously protected with clay nanoplates. The present synthetic route could be further applicable to various hybrid systems between metal nanoparticles and clays.

  19. Selective protein immobilization onto gold nanoparticles deposited under vacuum on a protein-repellent self-assembled monolayer.

    PubMed

    Peissker, Tobias; Deschaume, Olivier; Rand, Danielle R; Boyen, Hans-Gerd; Conard, Thierry; Van Bael, Margriet J; Bartic, Carmen

    2013-12-10

    The immobilization of proteins on flat substrates plays an important role for a wide spectrum of applications in the fields of biology, medicine, and biochemistry, among others. An essential prerequisite for the use of proteins (e.g., in biosensors) is the conservation of their biological activity. Losses in activity upon protein immobilization can largely be attributed to a random attachment of the proteins to the surface. In this study, we present an approach for the immobilization of proteins onto a chemically heterogeneous surface, namely a surface consisting of protein-permissive and protein-repellent areas, which allows for significant reduction of random protein attachment. As protein-permissive, i.e., as protein-binding sites, ultra pure metallic nanoparticles are deposited under vacuum onto a protein-repellent PEG-silane polymer layer. Using complementary surface characterization techniques (atomic force microscopy, quartz crystal microbalance, and X-ray photoelectron spectroscopy) we demonstrate that the Au nanoparticles remain accessible for protein attachment without compromising the protein-repellency of the PEG-silane background. Moreover, we show that the amount of immobilized protein can be controlled by tuning the Au nanoparticle coverage. This method shows potential for applications requiring the control of protein immobilization down to the single molecule level.

  20. Optimizing immobilization of avidin on surface-modified magnetic nanoparticles: characterization and application of protein-immobilized nanoparticles.

    PubMed

    Yang, Tao; Sun, Shuguo; Ma, Meihu; Lin, Qinlu; Zhang, Lin; Li, Yan; Luo, Feijun

    2015-10-01

    A simple optimization method of immobilization of avidin on magnetic nanoparticles (MNPs)' surface was proposed in this study. The avidin-immobilized MNPs were then developed and used to immobilize a model enzyme [Horseradish peroxidase (HRP)]. The loading capacity (LC) and activity of avidin-immobilized MNPs were optimized through selecting the most appropriate nanoparticle's size and shape, glutaraldehyde concentration, cross-linking reaction time, ultrasonic processing time, and initial concentration of avidin. The LC under optimized conditions was 63.37 ± 1.29 mg avidin/g MNPs, and the immobilized protein was still able to maintain its high biological activity of 10.86 ± 0.13 U/mg (biotin-binding activity of nature avidin was 14.1 U/mg) and better thermal stability compared to free avidin. A highly reusable, stable, and easily recovered immobilized HRP was obtained using MNPs as carriers. The immobilized HRP was reused repeatedly more than 9 times and retained more than 65 % of its original activity. PMID:26224655

  1. Covalent immobilization of molecularly imprinted polymer nanoparticles on a gold surface using carbodiimide coupling for chemical sensing.

    PubMed

    Kamra, Tripta; Chaudhary, Shilpi; Xu, Changgang; Montelius, Lars; Schnadt, Joachim; Ye, Lei

    2016-01-01

    One challenging task in building (bio)chemical sensors is the efficient and stable immobilization of receptor on a suitable transducer. Herein, we report a method for covalent immobilization of molecularly imprinted core-shell nanoparticles for construction of robust chemical sensors. The imprinted nanoparticles with a core-shell structure have selective molecular binding sites in the core and multiple amino groups in the shell. The model Au transducer surface is first functionalized with a self-assembled monolayer of 11-mercaptoundecanoic acid. The 11-mercaptoundecanoic acid is activated by treatment with carbodiimide/N-hydroxysuccinimide and then reacted with the core-shell nanoparticles to form amide bonds. We have characterized the process by studying the treated surfaces after each preparation step using atomic force microscopy, scanning electron microscopy, fluorescence microscopy, contact angle measurements and X-ray photoelectron spectroscopy. The microscopy results show the successful immobilization of the imprinted nanoparticles on the surface. The photoelectron spectroscopy results further confirm the success of each functionalization step. Further, the amino groups on the MIP surface were activated by electrostatically adsorbing negatively charged Au colloids. The functionalized surface was shown to be active for surface enhanced Raman scattering detection of propranolol. The particle immobilization and surface enhanced Raman scattering approach described here has a general applicability for constructing chemical sensors in different formats.

  2. Novel functionalized fluorescent polymeric nanoparticles for immobilization of biomolecules

    NASA Astrophysics Data System (ADS)

    Jain, Swati; Chattopadhyay, Sruti; Jackeray, Richa; Abid, C. K. V. Zainul; Singh, Harpal

    2013-07-01

    Novel, size controlled fluorescent polymeric nanoparticles (FPNP) were synthesized having acetoacetoxy functionality on the surface for immobilization of biomolecules which can be utilized as biomarkers and labels in fluoroimmunoassays. Core-shell nanoparticles of poly(styrene, St-methyl methacrylate, MMA-acetoacetoxy ethyl methacrylate, AAEM), stabilized by various concentrations of surfactant, sodium lauryl sulphate (SLS), were obtained by facile miniemulsion co-polymerization encapsulated with pyrene molecules in their hydrophobic core. Analytical, spectroscopic and imaging characterization techniques revealed the formation of stable, monodisperse, spherical nano sized particles exhibiting high luminescence properties. Particles with 1% SLS (S1) showed good dispersion stability and fluorescence intensity and were chosen as ideal candidates for further immobilization studies. Steady state fluorescence studies showed 10 times higher fluorescence intensity of S1 nanoparticles than that of pyrene solution in solvent-toluene at the same concentration. Environmental factors such as pH, ionic strength and time were found to have no effect on fluorescence intensity of FPNPs. Surface β-di-ketone groups were utilized for the covalent immobilization of enzyme conjugated antibodies without any activation or pre-treatment of nanoparticles.Novel, size controlled fluorescent polymeric nanoparticles (FPNP) were synthesized having acetoacetoxy functionality on the surface for immobilization of biomolecules which can be utilized as biomarkers and labels in fluoroimmunoassays. Core-shell nanoparticles of poly(styrene, St-methyl methacrylate, MMA-acetoacetoxy ethyl methacrylate, AAEM), stabilized by various concentrations of surfactant, sodium lauryl sulphate (SLS), were obtained by facile miniemulsion co-polymerization encapsulated with pyrene molecules in their hydrophobic core. Analytical, spectroscopic and imaging characterization techniques revealed the formation of stable

  3. Highly sensitive determination of hydroxylamine using fused gold nanoparticles immobilized on sol-gel film modified gold electrode.

    PubMed

    Kannan, P; John, S Abraham

    2010-03-24

    We are reporting the highly sensitive determination of hydroxylamine (HA) using 2-mercapto-4-methyl-5-thiazoleacetic acid (TAA) capped fused spherical gold nanoparticles (AuNPs) modified Au electrode. The fused TAA-AuNPs were immobilized on (3-mercaptopropyl)-trimethoxysilane (MPTS) sol-gel film, which was pre-assembled on Au electrode. The immobilization of fused TAA-AuNPs on MPTS sol-gel film was confirmed by UV-vis absorption spectroscopy and atomic force microscopy (AFM). The AFM image showed that the AuNPs retained the fused spherical morphology after immobilized on sol-gel film. The fused TAA-AuNPs on MPTS modified Au electrode were used for the determination of HA in phosphate buffer (PB) solution (pH=7.2). When compared to bare Au electrode, the fused AuNPs modified electrode not only shifted the oxidation potential of HA towards less positive potential but also enhanced its oxidation peak current. Further, the oxidation of HA was highly stable at fused AuNPs modified electrode. Using amperometric method, determination of 17.5 nM HA was achieved for the first time. Further, the current response of HA increases linearly while increasing its concentration from 17.5 nM to 22 mM and a detection limit was found to be 0.39 nM (S/N=3). The present modified electrode was also successfully used for the determination of 17.5 nM HA in the presence of 200-fold excess of common interferents such as urea, NO(2)(-), NH(4)(+), oxalate, Mn(2+), Na(+), K(+), Mg(2+), Ca(2+), Ba(2+) and Cu(2+). The practical application of the present modified electrode was demonstrated by measuring the concentration of HA in ground water samples.

  4. Gold nanoparticles-immobilized, hierarchically ordered, porous TiO2 nanotubes for biosensing of glutathione.

    PubMed

    Mers, Sv Sheen; Kumar, Elumalai Thambuswamy Deva; Ganesh, V

    2015-01-01

    Glutathione (GSH) is vital for several functions of our human body such as neutralization of free radicals and reactive oxygen compounds, maintaining the active forms of vitamin C and E, regulation of nitric oxide cycle, iron metabolism, etc. It is also an endogenous antioxidant in most of the biological reactions. Given the importance of GSH, a simple strategy is proposed in this work to develop a biosensor for quantitative detection of GSH. This particular biosensor comprises of gold nanoparticles (Au NPs)-immobilized, hierarchically ordered titanium dioxide (TiO2) porous nanotubes. Hexagonally arranged, honeycomb-like nanoporous tubular TiO2 electrodes are prepared by using a simple electrochemical anodization process by applying a constant potential of 30 V for 24 hours using ethylene glycol consisting of ammonium fluoride as an electrolytic medium. Structural morphology and crystalline nature of such TiO2 nanotubes are analyzed using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Interestingly, nanocomposites of TiO2 with Au NPs is prepared in an effort to alter the intrinsic properties of TiO2, especially tuning of its band gap. Au NPs are prepared by a well-known Brust and Schiffrin method and are immobilized onto TiO2 electrodes which act as a perfect electrochemical sensing platform for GSH detection. Structural characterization and analysis of these modified electrodes are performed using FESEM, XRD, and UV-visible spectroscopic studies. GSH binding events on Au NPs-immobilized porous TiO2 electrodes are monitored by electrochemical techniques, namely, cyclic voltammetry (CV) and chronoamperometry (CA). Several parameters such as sensitivity, selectivity, stability, limit of detection, etc are investigated. In addition, Au NPs dispersed in aqueous medium are also explored for naked-eye detection of GSH using UV-visible spectroscopy in order to compare the performance of the proposed sensor. Our studies clearly indicate

  5. Nanoshells made easy: improving Au layer growth on nanoparticle surfaces.

    PubMed

    Brinson, Bruce E; Lassiter, J Britt; Levin, Carly S; Bardhan, Rizia; Mirin, Nikolay; Halas, Naomi J

    2008-12-16

    The growth of a continuous, uniform Au layer on a dielectric nanoparticle is the critical step in the synthesis of nanoparticles such as nanoshells or nanorice, giving rise to their unique geometry-dependent plasmon resonant properties. Here, we report a novel, streamlined method for Au layer metallization on prepared nanoparticle surfaces using carbon monoxide as the reducing agent. This approach consistently yields plasmonic nanoparticles with highly regular shell layers and is immune to variations in precursor or reagent preparation. Single particle spectroscopy combined with scanning electron microscopy reveal that thinner, more uniform shell layers with correspondingly red-shifted optical resonances are achievable with this approach. PMID:19360963

  6. Polymer-assisted iron oxide magnetic nanoparticle immobilized keratinase

    NASA Astrophysics Data System (ADS)

    Konwarh, Rocktotpal; Karak, Niranjan; Rai, Sudhir Kumar; Mukherjee, Ashis Kumar

    2009-06-01

    Nanotechnology holds the prospect for avant-garde changes to improve the performance of materials in various sectors. The domain of enzyme biotechnology is no exception. Immobilization of industrially important enzymes onto nanomaterials, with improved performance, would pave the way to myriad application-based commercialization. Keratinase produced by Bacillus subtilis was immobilized onto poly(ethylene glycol)-supported Fe3O4 superparamagnetic nanoparticles. The optimization process showed that the highest enzyme activity was noted when immobilized onto cyanamide-activated PEG-assisted MNP prepared under conditions of 25 °C and pH 7.2 of the reaction mixture before addition of H2O2 (3% w/w), 2% (w/v) PEG6000 and 0.062:1 molar ratio of PEG to FeCl2·4H2O. Further statistical optimization using response surface methodology yielded an R2 value that could explain more than 94% of the sample variations. Along with the magnetization studies, the immobilization of the enzyme onto the PEG-assisted MNP was characterized by UV, XRD, FTIR and TEM. The immobilization process had resulted in an almost fourfold increase in the enzyme activity over the free enzyme. Furthermore, the immobilized enzyme exhibited a significant thermostability, storage stability and recyclability. The leather-industry-oriented application of the immobilized enzyme was tested for the dehairing of goat-skin.

  7. The effect of Au amount on size uniformity of self-assembled Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, S.-H.; Wang, D.-C.; Chen, G.-Y.; Chen, K.-Y.

    2008-03-01

    The self-assembled fabrication of nanostructure, a dreaming approach in the area of fabrication engineering, is the ultimate goal of this research. A finding was proved through previous research that the size of the self-assembled gold nanoparticles could be controlled with the mole ratio between AuCl4- and thiol. In this study, the moles of Au were fixed, only the moles of thiol were adjusted. Five different mole ratios of Au/S with their effect on size uniformity were investigated. The mole ratios were 1:1/16, 1:1/8, 1:1, 1:8, 1:16, respectively. The size distributions of the gold nanoparticles were analyzed by Mac-View analysis software. HR-TEM was used to derive images of self-assembled gold nanoparticles. The result reached was also the higher the mole ratio between AuCl4- and thiol the bigger the self-assembled gold nanoparticles. Under the condition of moles of Au fixed, the most homogeneous nanoparticles in size distribution derived with the mole ratio of 1:1/8 between AuCl4- and thiol. The obtained nanoparticles could be used, for example, in uniform surface nanofabrication, leading to the fabrication of ordered array of quantum dots.

  8. Thermal and photoinduced reduction of ionic Au(III) to elemental Au nanoparticles by dissolved organic matter in water: possible source of naturally occurring Au nanoparticles.

    PubMed

    Yin, Yongguang; Yu, Sujuan; Liu, Jingfu; Jiang, Guibin

    2014-01-01

    Naturally occurring Au nanoparticles (AuNPs) have been widely observed in ore deposits, coal, soil, and environmental water. Identifying the source of these naturally occurring AuNPs could be helpful for not only the discovery of Au deposits through advanced exploration methods, but also the elucidation of the biogeochemical cycle and environmental toxicity of ionic Au and engineered AuNPs. Here, we investigated the effect of natural/simulated sunlight and heating on the reduction of ionic Au by ubiquitous dissolved organic matter (DOM) in river water. The reductive process probed by X-ray photoelectron spectroscopy revealed that phenolic, alcoholic, and aldehyde groups in DOM act as reductive sites. Long-time exposure with thermal and photoirradiation induced the further fusion and growth of AuNPs to branched Au nanostructure as precipitation. The formation processes and kinetics of AuNPs were further investigated using humic acid (HA) as the DOM model, with comprehensive characterizing methods. We have observed that HA can reduce ionic Au(III) complex (as chloride or hydroxyl complex) to elemental Au nanoparticles under sunlight or heating. In this process, nearly all of the Au(III) could be reduced to AuNPs, in which HA serves as not only the reductive agent, but also the coating agent to stabilize and disperse AuNPs. The size and stability of AuNPs were highly dependent on the concentration ratio of Au(III) to HA. These results imply that, besides biological processes, this thermal or photochemical reduction process is another possible source of naturally occurring AuNPs in natural environments, which possibly has critical impacts on the transport and transformation of Au and engineered AuNPs.

  9. a High-Performance Glucose Biosensor Based on Zno Nanorod Arrays Modified with AU Nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, Gong; Lei, Yang; Yan, Xiaoqin

    2012-08-01

    An amperometric glucose biosensor based on vertically aligned ZnO nanorod (NR) arrays modified with Au nanoparticles (NPs) was constructed in a channel-limited way. Au NPs with diameters in the range of 8-10 nm have been successfully synthesized by photoreduction method and were uniformly loaded onto the surface of ZnO NRs that was hydrothermally deposited on the Fluorine doped SnO2 conductive glass (FTO) via electrostatic self-assembly technique. The morphology and structure of Au/ZnO NR arrays were characterized by field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectrum analyzer (XPS). The electrocatalytic properties of glucose oxidase (GOD)- immobilized Au/ZnO NR arrays were evaluated by amperometry. Compared with the biosensor based on ZnO NR arrays, the resulting Au/ZnO NR arrays modified biosensor exhibited an expanded linear range from 3 μM to 3 mM with the detection limit of 30 nM and a smaller Michaelis-Menten constant of 0.7836 mM. All these results suggest that the Au NPs can greatly improve the biosensing properties of ZnO NR arrays and therefore Au/ZnO NR arrays provide a promising material for the biosensor designs and other biological applications.

  10. Enzymatic deposition of Au nanoparticles on the designed electrode surface and its application in glucose detection.

    PubMed

    Zhang, Hongfang; Liu, Ruixiao; Sheng, Qinglin; Zheng, Jianbin

    2011-02-01

    This paper reported the enzymatic deposition of Au nanoparticles (AuNPs) on the designed 3-mercapto-propionic acid/glucose oxidase/chitosan (MPA/GOD/Chit) modified glassy carbon electrode and its application in glucose detection. Chit served as GOD immobilization matrix and interacted with MPA through electrostatic attraction. AuNPs, without nano-seeds presented on the electrode surface, was produced through the glucose oxidase catalyzed oxidation of glucose. The mechanism of production of AuNPs was confirmed to be that enzymatic reaction products H(2)O(2) in the solution reduce gold complex to AuNPs. The characterizations of the electrode modified after each assembly step was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Scanning electron microscopy showed the average particle size of the AuNPs is 40nm with a narrow particle size distribution. The content of AuNPs on the electrode surfaces was measured by differential pulse stripping voltammetry. The electrochemical signals on voltammogram showed a linear increase with the glucose concentration in the range of 0.010-0.12mM with a detection limit of 4μM. This provided a method to the determination of glucose. PMID:21115279

  11. Biosynthesis of Au, Ag and Au-Ag nanoparticles using edible mushroom extract

    NASA Astrophysics Data System (ADS)

    Philip, Daizy

    2009-07-01

    Integration of green chemistry principles to nanotechnology is one of the key issues in nanoscience research. There is growing need to develop environmentally benign metal nanoparticle synthesis process that do not use toxic chemicals in the synthesis protocols to avoid adverse effects in medical applications. Here, it is a report on extracellular synthesis method for the preparation of Au, Ag and Au-Ag nanoparticles in water, using the extract of Volvariella volvacea, a naturally occurring edible mushroom, as reducing and protecting agents. Gold nanoparticles of different sizes (20-150 nm) and shapes from triangular nanoprisms to nearly spherical and hexagonal are obtained by this novel method. The size and shape of gold nanoparticles are also found to depend on temperature of the extract. The silver nanoparticles are spherical with size ˜15 nm. There is increased productivity of nanoparticles as shown by sharp and intense surface plasmon resonance bands for the nanoparticles prepared using an excess of the extract. The Au-Ag nanoparticles prepared by co-reduction has only one plasmon band due to alloying of the constituents. All the synthesized nanoparticles are found to be photoluminescent and are highly crystalline as shown by SAED and XRD patterns with fcc phase oriented along the (1 1 1) plane. FTIR measurements were carried out to identify the possible biomolecules responsible for capping and efficient stabilization of the nanoparticles. It is found that Au nanoparticles are bound to proteins through free amino groups and silver nanoparticles through the carboxylate group of the amino acid residues. The position and intensity of the emission band is found to depend on composition of the nanoparticles indicating the possible use in therapeutic applications.

  12. Electrochemically deposited chitosan hydrogel for horseradish peroxidase immobilization through gold nanoparticles self-assembly.

    PubMed

    Luo, Xi-Liang; Xu, Jing-Juan; Zhang, Qing; Yang, Gong-Jun; Chen, Hong-Yuan

    2005-07-15

    A new strategy for immobilization of horseradish peroxidase (HRP) has been presented by self-assembling gold nanoparticles on chitosan hydrogel modified Au electrode. From a mildly acidic chitosan solution, a chitosan film is electrochemically deposited on Au electrode surface via a negative voltage bias. This process is accompanied by the hydrogen evolution reaction, and the released hydrogen gas made the deposited chitosan film with porous structure, which facilitates the assembly of gold nanoparticles and HRP. The resulting substrates were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The immobilized HRP displayed an excellent catalytic property to the reduction of H2O2 in the presence of methylene blue mediator. The resulting biosensor (HRP-modified electrode) showed a wide dynamic range of 8.0 microM-15 mM H2O2, and the linear ranges were 8.0 microM-0.12 mM and 0.50-12 mM, with a detection limit of 2.4 microM estimated at a signal-to-noise ratio of 3. Moreover, the biosensor remained about 85% of its original sensitivity after four weeks' storage.

  13. Spin Polarization and Quantum Spins in Au Nanoparticles

    PubMed Central

    Li, Chi-Yen; Karna, Sunil K.; Wang, Chin-Wei; Li, Wen-Hsien

    2013-01-01

    The present study focuses on investigating the magnetic properties and the critical particle size for developing sizable spontaneous magnetic moment of bare Au nanoparticles. Seven sets of bare Au nanoparticle assemblies, with diameters from 3.5 to 17.5 nm, were fabricated with the gas condensation method. Line profiles of the X-ray diffraction peaks were used to determine the mean particle diameters and size distributions of the nanoparticle assemblies. The magnetization curves M(Ha) reveal Langevin field profiles. Magnetic hysteresis was clearly revealed in the low field regime even at 300 K. Contributions to the magnetization from different size particles in the nanoparticle assemblies were considered when analyzing the M(Ha) curves. The results show that the maximum particle moment will appear in 2.4 nm Au particles. A similar result of the maximum saturation magnetization appearing in 2.3 nm Au particles is also concluded through analysis of the dependency of the saturation magnetization MP on particle size. The MP(d) curve departs significantly from the 1/d dependence, but can be described by a log-normal function. Magnetization can be barely detected for Au particles larger than 27 nm. Magnetic field induced Zeeman magnetization from the quantum confined Kubo gap opening appears in Au nanoparticles smaller than 9.5 nm in diameter. PMID:23989607

  14. Microwave synthesis of Au nanoparticles as promising SERS substrates

    NASA Astrophysics Data System (ADS)

    Wang, Lan; Feng, Shangyuan; Liu, Nenrong; Lei, Jinping; Lin, Hongxin; Sun, Liqing; Chen, Rong

    2012-11-01

    A novel method for rapidly synthesized Au colloidal under microwave irradiation was present in this paper. Size of the Au nanoparticles varied from 10 nm to 60 nm along with varying mol fractions by chloroauric acid solution reduced with sodium citrate. The prepared Au nanoparticles were characterized by transmission electron microscope (TEM) and ultraviolet-visible (UV-Vis) spectrophotometer. It is found that the nanoparticle size and shape are highly dependent on the reaction time and the molar ratios of the reducing agent. By the SERS measurements of R6G, 4-MBA and Crystal violet, this Au colloid is shown to be an excellent SERS substrate with good stability. As the fabrication process of this SERS substrate is simple and inexpensive, this method may be used in large-scale preparation of substrates that can serve as an ideal SERS substrate in biomedical application.

  15. Synthesis and characterization of Ni-Au bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Nik Roselina, N. R.; Azizan, A.; Hyie, Koay Mei; Murad, Mardziah Che; Abdullah, Abdul Hakim

    2015-04-01

    Bimetallic structure of nanoparticles is of great interest due to their extraordinary properties, especially in combining the specialty of the core and its shell. This work reports the effect of pH on the synthesis of Ni-Au (nickel-gold) bimetallic nanoparticles. The synthesis involves a two-step process where Ni nanoparticles were first synthesized using polyol method with hydrazine as the reducing agent. This was followed by the process of reducing AuCl4- to Au in the solution containing pre-prepared Ni to form Ni-Au bimetallic nanoparticles using sodium citrate as the reducing agent. The results obtained from Transmission Electron Microscopy (TEM) show that the process can possibly produce either core-shell structure, or mixture of Ni and Au nanoparticles. Magnetic property of core-shell structure investigated using Vibrating Sample Magnetometer (VSM) demonstrated typical characteristic of ferromagnetic with an increased magnetization as compared to Ni nanoparticles. The saturation magnetization (Ms) and coercivity (Hc) were obtained as 19.1 emu/g and 222.3 Oe, respectively.

  16. Unravelling Thiol's Role in Directing Asymmetric Growth of Au Nanorod-Au Nanoparticle Dimers.

    PubMed

    Huang, Jianfeng; Zhu, Yihan; Liu, Changxu; Shi, Zhan; Fratalocchi, Andrea; Han, Yu

    2016-01-13

    Asymmetric nanocrystals have practical significance in nanotechnologies but present fundamental synthetic challenges. Thiol ligands have proven effective in breaking the symmetric growth of metallic nanocrystals but their exact roles in the synthesis remain elusive. Here, we synthesized an unprecedented Au nanorod-Au nanoparticle (AuNR-AuNP) dimer structure with the assistance of a thiol ligand. On the basis of our experimental observations, we unraveled for the first time that the thiol could cause an inhomogeneous distribution of surface strains on the seed crystals as well as a modulated reduction rate of metal precursors, which jointly induced the asymmetric growth of monometallic dimers.

  17. Counterion-Mediated Assembly of Spherical Nucleic Acid-Au Nanoparticle Conjugates (SNA-AuNPs)

    NASA Astrophysics Data System (ADS)

    Kewalramani, Sumit; Moreau, Liane; Guerrero-García, Guillermo; Mirkin, Chad; Olvera de La Cruz, Monica; Bedzyk, Michael; Afosr Muri Team

    2015-03-01

    Controlled crystallization of colloids from solution has been a goal of material scientists for decades. Recently, nucleic acid functionalized spherical Au nanoparticles (SNA-AuNPs) have been programmed to assemble in a wide variety of crystal structures. In this approach, the assembly is driven by Watson-Crick hybridization between DNAs coating the AuNPs. Here, we show that counterions can induce ordered assembly of SNA-AuNPs in bulk solutions, even in the absence of base pairing interactions. The electrostatics-driven assembly of spherical nucleic acid-Au nanoparticle conjugates (SNA-AuNPs) is probed as a function of counterion concentration and counterion valency [ +1 (Na+) or +2 (Ca2+) ] by in situ solution X-ray scattering. Assemblies of AuNPs capped with single-stranded (ss-) or double-stranded (ds-) DNA are examined. SAXS reveals disordered (gas-like) --> face-centered-cubic (FCC) --> glass-like phase transitions with increasing solution ionic strength. These studies demonstrate how non-base-pairing interactions can be tuned to create crystalline assemblies of SNA-AuNPs. The dependence of the inter-SNA-AuNP interactions on counterion valency and stiffness of the DNA corona will be discussed.

  18. Fe/Au Core-Shell Nanoparticles for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Sra, Amandeep; Leslie-Pelecky, Diandra

    2009-10-01

    The physical properties of nanoparticles, including size, composition and surface chemistry, greatly influence biological and pharmacological properties and, ultimately, their clinical applications. Superparamagnetic iron oxide nanoparticles are widely used for applications such as MRI contrast agents, drug delivery via magnetic targeting and hyperthermia due to their chemical stability and biocompatibility; however, enhancing the saturation magnetization (Ms) of nanoparticles would produce greater sensitivity. Our design strategy involves a bottom-up wet chemistry approach to the synthesis of Fe nanoparticles. Specific advantages of Fe are the high value of Ms (210 emu/g in bulk) coupled with low toxicity; however, Fe nanoparticles must be protected from oxidation, which causes a dramatic reduction in Ms. To circumvent oxidation, Fe nanoparticles are coated with a Au shell that prevents the oxidation of the magnetic core and also provides the nanoparticles with plasmonic properties for optical stimulation. Ligands of various functionalities can be introduced through the well established Au-thiol surface chemistry for different biomedical applications while maintaining the magnetic functionality of the Fe core. In this presentation, we will discuss the physical, chemical and magnetic properties of our Fe/Au nanoparticles and their resistance to oxidation.

  19. Gold nanoparticles supported on mesoporous silica: origin of high activity and role of Au NPs in selective oxidation of cyclohexane

    PubMed Central

    Wu, Pingping; Bai, Peng; Yan, Zifeng; Zhao, George X. S.

    2016-01-01

    Homogeneous immobilization of gold nanoparticles (Au NPs) on mesoporous silica has been achieved by using a one-pot synthesis method in the presence of organosilane mercapto-propyl-trimethoxysilane (MPTMS). The resultant Au NPs exhibited an excellent catalytic activity in the solvent-free selective oxidation of cyclohexane using molecular oxygen. By establishing the structure-performance relationship, the origin of the high activity of mesoporous supported Au catalyst was identified to be due to the presence of low-coordinated Au (0) sites with high dispersion. Au NPs were confirmed to play a critical role in the catalytic oxidation of cyclohexane by promoting the activation of O2 molecules and accelerating the formation of surface-active oxygen species. PMID:26729288

  20. Gold nanoparticles supported on mesoporous silica: origin of high activity and role of Au NPs in selective oxidation of cyclohexane

    NASA Astrophysics Data System (ADS)

    Wu, Pingping; Bai, Peng; Yan, Zifeng; Zhao, George X. S.

    2016-01-01

    Homogeneous immobilization of gold nanoparticles (Au NPs) on mesoporous silica has been achieved by using a one-pot synthesis method in the presence of organosilane mercapto-propyl-trimethoxysilane (MPTMS). The resultant Au NPs exhibited an excellent catalytic activity in the solvent-free selective oxidation of cyclohexane using molecular oxygen. By establishing the structure-performance relationship, the origin of the high activity of mesoporous supported Au catalyst was identified to be due to the presence of low-coordinated Au (0) sites with high dispersion. Au NPs were confirmed to play a critical role in the catalytic oxidation of cyclohexane by promoting the activation of O2 molecules and accelerating the formation of surface-active oxygen species.

  1. Co-immobilization of gold nanoparticles with glucose oxidase to improve bioelectrocatalytic glucose oxidation

    NASA Astrophysics Data System (ADS)

    Aquino Neto, Sidney; Milton, Ross D.; Crepaldi, Laís B.; Hickey, David P.; de Andrade, Adalgisa R.; Minteer, Shelley D.

    2015-07-01

    Recently, there has been much effort in developing metal nanoparticle catalysts for fuel oxidation, as well as the development of enzymatic bioelectrocatalysts for fuel oxidation. However, there has been little study of the synergy of hybrid electrocatalytic systems. We report the preparation of hybrid bioanodes based on Au nanoparticles supported on multi-walled carbon nanotubes (MWCNTs) co-immobilized with glucose oxidase (GOx). Mediated electron transfer was achieved by two strategies: ferrocene entrapped within polypyrrole and a ferrocene-modified linear poly(ethylenimine) (Fc-LPEI) redox polymer. Electrochemical characterization of the Au nanoparticles supported on MWCNTs indicate that this catalyst exhibits an electrocatalytic response for glucose even in acidic conditions. Using the redox polymer Fc-LPEI as the mediator, voltammetric and amperometric data demonstrated that these bioanodes can efficiently achieve mediated electron transfer and also indicated higher catalytic currents with the hybrid bioelectrode. From the amperometry, the maximum current density (Jmax) achieved with the hybrid bioelectrode was 615 ± 39 μA cm-2, whereas the bioanode employing GOx only achieved a Jmax of 409 ± 26 μA cm-2. Biofuel cell tests are consistent with the electrochemical characterization, thus confirming that the addition of the metallic species into the bioanode structure can improve fuel oxidation and consequently, improve the power generated by the system.

  2. Conjugating folate on superparamagnetic Fe{sub 3}O{sub 4}@Au nanoparticles using click chemistry

    SciTech Connect

    Shen, Xiaofang Ge, Zhaoqiang; Pang, Yuehong

    2015-02-15

    Gold-coated magnetic core@shell nanoparticles, which exhibit magneto-optical properties, not only enhance the chemical stability of core and biocompatibility of surface, but also provide a combination of multimodal imaging and therapeutics. The conjugation of these tiny nanoparticles with specific biomolecules allows researchers to target the desired location. In this paper, superparamagnetic Fe{sub 3}O{sub 4}@Au nanoparticles were synthesized and functionalized with the azide group on the surface by formation of self-assembled monolayers. Folate (FA) molecules, non-immunogenic target ligands for cancer cells, are conjugated with alkyne and then immobilized on the azide-terminated Fe{sub 3}O{sub 4}@Au nanoparticles through copper(I)-catalyzed azide-alkyne cycloaddition (click reaction). Myelogenous leukemia K562 cells were used as a folate receptor (FR) model, which can be targeted and extracted by magnetic field after interaction with the Fe{sub 3}O{sub 4}@Au–FA nanoparticles. - Graphical abstract: Self-assembled azide-terminated group on superparamagnetic Fe{sub 3}O{sub 4}@Au nanoparticles followed by click reaction with alkyne-functionalized folate, allowing the nanoparticles target folate receptor of cancer cells. - Highlights: • Azidoundecanethiol was coated on the superparamagnetic Fe{sub 3}O{sub 4}@Au nanoparticles by forming self-assembled monolayers. • Alkyne-terminated folate was synthesized from a reaction between the amine and the carboxylic acid. • Conjugation of Fe{sub 3}O{sub 4}@Au nanoparticles with folate was made by copper-catalyzed azide-alkyne cycloaddition click chemistry.

  3. Gold nanoparticle (AuNPs) and gold nanopore (AuNPore) catalysts in organic synthesis.

    PubMed

    Takale, Balaram S; Bao, Ming; Yamamoto, Yoshinori

    2014-04-01

    Organic synthesis using gold has gained tremendous attention in last few years, especially heterogeneous gold catalysis based on gold nanoparticles has made its place in almost all organic reactions, because of the robust and green nature of gold catalysts. In this context, gold nanopore (AuNPore) with a 3D metal framework is giving a new dimension to heterogeneous gold catalysts. Interestingly, AuNPore chemistry is proving better than gold nanoparticles based chemistry. In this review, along with recent advances, major discoveries in heterogeneous gold catalysis are discussed.

  4. Detection of glucose using immobilized bienzyme on cyclic bisureas-gold nanoparticle conjugate.

    PubMed

    Mathew, Manjusha; Sandhyarani, N

    2014-08-15

    A highly sensitive electrochemical glucose sensor has been developed by the co-immobilization of glucose oxidase (GOx) and horseradish peroxidase (HRP) onto a gold electrode modified with biocompatible cyclic bisureas-gold nanoparticle conjugate (CBU-AuNP). A self-assembled monolayer of mercaptopropionic acid (MPA) and CBU-AuNP was formed on the gold electrode through a layer-by-layer assembly. This modified electrode was used for immobilization of the enzymes GOx and HRP. Both the HRP and GOx retained their catalytic activity for an extended time, as indicated by the low value of Michaelis-Menten constant. Analytical performance of the sensor was examined in terms of sensitivity, selectivity, reproducibility, lower detection limit, and stability. The developed sensor surface exhibited a limit of detection of 100nM with a linear range of 100nM to 1mM. A high sensitivity of 217.5μAmM(-1)cm(-2) at a low potential of -0.3V was obtained in this sensor design. Various kinetic parameters were calculated. The sensor was examined for its practical clinical application by estimating glucose in human blood sample. PMID:24835425

  5. Immobilization of a catalytic DNA molecular beacon on Au for Pb(II) detection.

    PubMed

    Swearingen, Carla B; Wernette, Daryl P; Cropek, Donald M; Lu, Yi; Sweedler, Jonathan V; Bohn, Paul W

    2005-01-15

    A Pb(II)-specific DNAzyme fluorescent sensor has been modified with a thiol moiety in order to immobilize it on a Au surface. Self-assembly of the DNAzyme is accomplished by first adsorbing the single-thiolated enzyme strand (HS-17E-Dy) followed by adsorption of mercaptohexanol, which serves to displace any Au-N interactions and ensure that DNA is bound only through the S-headgroup. The preformed self-assembled monolayer is then hybridized with the complementary fluorophore-containing substrate strand (17DS-Fl). Upon reaction with Pb(II), the substrate strand is cleaved, releasing a fluorescent fragment for detection. Fluorescence intensity may be correlated with original Pb(II) concentration, and a linear calibration was obtained over nearly four decades: 10 microM > or = [Pb(II)] > or = 1 nM. The immobilized DNAzyme is a robust system; it may be regenerated after cleavage, allowing multiple sensing cycles. In addition, drying of fully assembled DNAzyme before reaction with Pb(II) does not significantly affect analytical performance. These results demonstrate that, in comparison with solution-based schemes, immobilization of the DNAzyme sensor onto a Au surface lowers the detection limit (from 10 to 1 nM), maintains activity and specificity, and allows sensor regeneration and long-term storage. Realization of Pb(II) detection through an immobilized DNAzyme is the first important step toward creation of a stand-alone, portable Pb(II) detection device such as those immobilizing DNAzyme recognition motifs in the nanofluidic pores of a microfluidic-nanofluidic hybrid multilayer device.

  6. Heatless synthesis of well dispersible Au nanoparticles using pectin biopolymer.

    PubMed

    Ahmed, Hanan B; Zahran, M K; Emam, Hossam E

    2016-10-01

    Due to its potency to utilize in enormous applications, preparation of nanogold is of interest. Moreover, getting of highly dispersed nanogold with small size is extremely needful in specific fields. Herein, Au nanocolloid was prepared using alkali catalyzed pectin biopolymer. Pectin was concurrently used as reductant for Au ions and stabilizer for the produced Au nanoparticles (AuNPs). Reducing sugars were evaluated in the colloidal solution reflecting the role alkali in catalytic degradation of pectin to produce much powerful reducing moieties. The obtained Au nanocolloid was monitored via changing in color, UV-visible spectral and transmission electron microscopy. Using of NaOH as strong alkali achieving rapid rate of degradation reaction, resulted in 0.45g/L reducing sugars from 0.2g/L pectin which produced AuNPs with mean size of 6.5nm. In case of Na2CO3 which attained slow degradation rate led to, slightly low reducing sugar content (0.41g/L), fabricated comparatively size of AuNPs (7.5nm). In both cases, well distributed AuNPs was obtained with suitable stabilization up to 5 months and Na2CO3 exhibited higher stability. The current successful method used to produce small sized AuNPs with high dispersion is an innovative, one-step, easily, costless, energy saving and eco-friendly method.

  7. Heatless synthesis of well dispersible Au nanoparticles using pectin biopolymer.

    PubMed

    Ahmed, Hanan B; Zahran, M K; Emam, Hossam E

    2016-10-01

    Due to its potency to utilize in enormous applications, preparation of nanogold is of interest. Moreover, getting of highly dispersed nanogold with small size is extremely needful in specific fields. Herein, Au nanocolloid was prepared using alkali catalyzed pectin biopolymer. Pectin was concurrently used as reductant for Au ions and stabilizer for the produced Au nanoparticles (AuNPs). Reducing sugars were evaluated in the colloidal solution reflecting the role alkali in catalytic degradation of pectin to produce much powerful reducing moieties. The obtained Au nanocolloid was monitored via changing in color, UV-visible spectral and transmission electron microscopy. Using of NaOH as strong alkali achieving rapid rate of degradation reaction, resulted in 0.45g/L reducing sugars from 0.2g/L pectin which produced AuNPs with mean size of 6.5nm. In case of Na2CO3 which attained slow degradation rate led to, slightly low reducing sugar content (0.41g/L), fabricated comparatively size of AuNPs (7.5nm). In both cases, well distributed AuNPs was obtained with suitable stabilization up to 5 months and Na2CO3 exhibited higher stability. The current successful method used to produce small sized AuNPs with high dispersion is an innovative, one-step, easily, costless, energy saving and eco-friendly method. PMID:27212212

  8. Rational Design of Nanoparticle Platforms for "Cutting-the-Fat": Covalent Immobilization of Lipase, Glycerol Kinase, and Glycerol-3-Phosphate Oxidase on Metal Nanoparticles.

    PubMed

    Aggarwal, V; Pundir, C S

    2016-01-01

    The aggregates of nanoparticles (NPs) are considered better supports for the immobilization of enzymes, as these promote enzyme kinetics, due to their unusual but favorable properties such as larger surface area to volume ratio, high catalytic efficiency of certain immobilized enzymes, non-toxicity of some of the nanoparticle matrices, high stability, strong adsorption of the enzyme of interest by a number of different approaches, and faster electron transportability. Co-immobilization of multiple enzymes required for a multistep reaction cascade on a single support is more efficient than separately immobilizing the corresponding enzymes and mixing them physically, since products of one enzyme could serve as reactants for another. These products can diffuse much more easily between enzymes on the same particle than diffusion from one particle to the next, in the reaction medium. Thus, co-immobilization of enzymes onto NP aggregates is expected to produce faster kinetics than their individual immobilizations on separate matrices. Lipase, glycerol kinase, and glycerol-3-phosphate oxidase are required for lipid analysis in a cascade reaction, and we describe the co-immobilization of these three enzymes on nanocomposites of zinc oxide nanoparticles (ZnONPs)-chitosan (CHIT) and gold nanoparticles-polypyrrole-polyindole carboxylic acid (AuPPy-Pin5COOH) which are electrodeposited on Pt and Au electrodes, respectively. The kinetic properties and analytes used for amperometric determination of TG are fully described for others to practice in a trained laboratory. Cyclic voltammetry, scanning electron microscopy, Fourier transform infra-red spectra, and electrochemical impedance spectra confirmed their covalent co-immobilization onto electrode surfaces through glutaraldehyde coupling on CHIT-ZnONPs and amide bonding on AuPPy/Pin5COOH. The combined activities of co-immobilized enzymes was tested amperometrically, and these composite nanobiocatalysts showed optimum activity

  9. Theoretical studies of acrolein hydrogenation on Au20 nanoparticle

    NASA Astrophysics Data System (ADS)

    Li, Zhe; Chen, Zhao-Xu; He, Xiang; Kang, Guo-Jun

    2010-05-01

    Gold nanoparticles play a key role in catalytic processes. We investigated the kinetics of stepwise hydrogenation of acrolein on Au20 cluster model and compared with that on Au(110) surface. The rate-limiting step barrier of CC reduction is about 0.5 eV higher than that of CO hydrogenation on Au(110) surface. On Au20 nanoparticle, however, the energy barrier of the rate-determining step for CC hydrogenation turns out to be slightly lower than the value for the CO reduction. The selectivity difference on the two substrate models are attributed to different adsorption modes of acrolein: via the CC on Au20, compared to through both CC and CO on Au(110). The preference switch implies that the predicted selectivity of competitive hydrogenation depends on substrate model sensitively, and particles with more low-coordinated Au atoms than flat surfaces are favorable for CC hydrogenation, which is in agreement with experimental result.

  10. A new strategy for the controlled deposition of gold nanoparticle aggregates on two-dimensional polystyrene arrays and its application in glucose oxidase immobilization.

    PubMed

    Xia, Yuetong; Li, Jinru; Jiang, Long

    2012-07-01

    Nano/microstructures play an important role in nanoparticle applications. This paper describes an innovative strategy to fabricate a variety of gold nanoparticle aggregates (AuNPs) on large-scale arrays of up to ∼1 cm(2) made from polystyrene (PS). A dendritic surfactant, C18N3, has multi-amine head groups that can control the thickness of a double layer adsorbed on the PS sphere surface in a pH-dependent manner. Controlling the pH and immersion time in the C18N3 solution allows the morphology of AuNPs deposited on the PS spheres (PS@AuNP) to be regulated. The influence of nano/microstructures on the activity enhancement of glucose oxidase (GOD) was investigated. The results indicated that well-ordered PS@AuNP arrays performed much better in the specific activity enhancement of GOD compared with free GOD and GOD immobilized on PS arrays. Furthermore, it was observed that the immobilized GOD on 2D PS@AuNP arrays maintained a highly improved operational stability compared to free GOD. The mechanism behind this effect is discussed. For practical applications, prepared PS@AuNP arrays can be used as an effective chip for GOD immobilization and application. PMID:22498366

  11. Gold nanoparticles-immobilized, hierarchically ordered, porous TiO2 nanotubes for biosensing of glutathione

    PubMed Central

    Mers, SV Sheen; Kumar, Elumalai Thambuswamy Deva; Ganesh, V

    2015-01-01

    Glutathione (GSH) is vital for several functions of our human body such as neutralization of free radicals and reactive oxygen compounds, maintaining the active forms of vitamin C and E, regulation of nitric oxide cycle, iron metabolism, etc. It is also an endogenous antioxidant in most of the biological reactions. Given the importance of GSH, a simple strategy is proposed in this work to develop a biosensor for quantitative detection of GSH. This particular biosensor comprises of gold nanoparticles (Au NPs)-immobilized, hierarchically ordered titanium dioxide (TiO2) porous nanotubes. Hexagonally arranged, honeycomb-like nanoporous tubular TiO2 electrodes are prepared by using a simple electrochemical anodization process by applying a constant potential of 30 V for 24 hours using ethylene glycol consisting of ammonium fluoride as an electrolytic medium. Structural morphology and crystalline nature of such TiO2 nanotubes are analyzed using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Interestingly, nanocomposites of TiO2 with Au NPs is prepared in an effort to alter the intrinsic properties of TiO2, especially tuning of its band gap. Au NPs are prepared by a well-known Brust and Schiffrin method and are immobilized onto TiO2 electrodes which act as a perfect electrochemical sensing platform for GSH detection. Structural characterization and analysis of these modified electrodes are performed using FESEM, XRD, and UV-visible spectroscopic studies. GSH binding events on Au NPs-immobilized porous TiO2 electrodes are monitored by electrochemical techniques, namely, cyclic voltammetry (CV) and chronoamperometry (CA). Several parameters such as sensitivity, selectivity, stability, limit of detection, etc are investigated. In addition, Au NPs dispersed in aqueous medium are also explored for naked-eye detection of GSH using UV-visible spectroscopy in order to compare the performance of the proposed sensor. Our studies clearly indicate

  12. Gold nanoparticles-immobilized, hierarchically ordered, porous TiO2 nanotubes for biosensing of glutathione.

    PubMed

    Mers, Sv Sheen; Kumar, Elumalai Thambuswamy Deva; Ganesh, V

    2015-01-01

    Glutathione (GSH) is vital for several functions of our human body such as neutralization of free radicals and reactive oxygen compounds, maintaining the active forms of vitamin C and E, regulation of nitric oxide cycle, iron metabolism, etc. It is also an endogenous antioxidant in most of the biological reactions. Given the importance of GSH, a simple strategy is proposed in this work to develop a biosensor for quantitative detection of GSH. This particular biosensor comprises of gold nanoparticles (Au NPs)-immobilized, hierarchically ordered titanium dioxide (TiO2) porous nanotubes. Hexagonally arranged, honeycomb-like nanoporous tubular TiO2 electrodes are prepared by using a simple electrochemical anodization process by applying a constant potential of 30 V for 24 hours using ethylene glycol consisting of ammonium fluoride as an electrolytic medium. Structural morphology and crystalline nature of such TiO2 nanotubes are analyzed using field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). Interestingly, nanocomposites of TiO2 with Au NPs is prepared in an effort to alter the intrinsic properties of TiO2, especially tuning of its band gap. Au NPs are prepared by a well-known Brust and Schiffrin method and are immobilized onto TiO2 electrodes which act as a perfect electrochemical sensing platform for GSH detection. Structural characterization and analysis of these modified electrodes are performed using FESEM, XRD, and UV-visible spectroscopic studies. GSH binding events on Au NPs-immobilized porous TiO2 electrodes are monitored by electrochemical techniques, namely, cyclic voltammetry (CV) and chronoamperometry (CA). Several parameters such as sensitivity, selectivity, stability, limit of detection, etc are investigated. In addition, Au NPs dispersed in aqueous medium are also explored for naked-eye detection of GSH using UV-visible spectroscopy in order to compare the performance of the proposed sensor. Our studies clearly indicate

  13. Photocatalysis enhancement of Au/BFO nanoparticles using plasmon resonance of Au NPs

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Cai, Zhongyang; Ma, Xueming

    2015-12-01

    BiFeO3 (BFO) nanoparticles was synthesized via sol-gel technique, and successfully loaded with small sizes of gold nanoparticles (Au NPs) by impregnation-reduction method to extremely enhance the BFO photocatalytic activity. The obviously stronger optical absorption of Au/BFO observed from the UV-vis diffuse reflectance spectrum confirmed that the surface plasmon resonance (SPR) effect occured on the surface of Au NPs. And the surface plasmon-induced localized electric field could allow the formation of electron/hole pairs in the near surface region of BFO which can migrate to the surface without undergoing electron/hole (e-/h+) pair recombination. The more electrons and holes formed, the more ·OH will be generated to decompose the CR solution. When the gold loading in Au/BFO nanoparticles is 3.36 wt%, the obtained Au/BFO catalyst exhibits best photocatalytic activity evaluated by photocatalysis degradation of Congo red (CR) solution under the visible light irradiation.

  14. On the stability of AuFe alloy nanoparticles.

    PubMed

    Velasco, V; Pohl, D; Surrey, A; Bonatto-Minella, A; Hernando, A; Crespo, P; Rellinghaus, B

    2014-05-30

    AuFe nanoparticles with mean diameters d p  = 13.2 nm have been prepared by inert-gas condensation. Conventional and high-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy investigations show that the particles are mostly icosahedra. Scanning transmission electron microscopy-energy-dispersive x-ray spectroscopy and scanning transmission electron microscopy-electron energy-loss spectroscopy show that the as-grown particles exhibit a core-shell structure. The shell is mainly composed of an amorphous FeO layer. Although Fe and Au are immiscible in the bulk, the particle cores are found to be homogeneously mixed at the atomic level with a local composition of around Au84Fe16 (at.%). AuFe nanoparticles exhibit a complex magnetic structure in which the core behaves as a spin glass with a freezing temperature of 35 K, whereas the amorphous FeO shell behaves as a ferro-ferrimagnetic system. On annealing above 300 °C, the AuFe icosahedra phases separate into their elemental constituents. Hence the as-grown AuFe icosahedra are metastable, thereby implying that the bulk phase diagram also applies for nanoscopic materials.

  15. Hydrogen peroxide biosensor based on hemoglobin immobilized at graphene, flower-like zinc oxide, and gold nanoparticles nanocomposite modified glassy carbon electrode.

    PubMed

    Xie, Lingling; Xu, Yuandong; Cao, Xiaoyu

    2013-07-01

    In this work, a highly sensitive hydrogen peroxide (H2O2) biosensor based on immobilization of hemoglobin (Hb) at Au nanoparticles (AuNPs)/flower-like zinc oxide/graphene (AuNPs/ZnO/Gr) composite modified glassy carbon electrode (GCE) was constructed, where ZnO and Au nanoparticles were modified through layer-by-layer onto Gr/GCE. Flower-like ZnO nanoparticles could be easily prepared by adding ethanol to the precursor solution having higher concentration of hydroxide ions. The Hb/AuNPs/ZnO/Gr composite film showed a pair of well-defined, quasi-reversible redox peaks with a formal potential (E(0)) of -0.367 V, characteristic features of heme redox couple of Hb. The electron transfer rate constant (k(s)) of immobilized Hb was 1.3 s(-1). The developed biosensor showed a very fast response (<2 s) toward H2O2 with good sensitivity, wide linear range, and low detection limit of 0.8 μM. The fabricated biosensor showed interesting features, including high selectivity, acceptable stability, good reproducibility, and repeatability along with excellent conductivity, facile electron mobility of Gr, and good biocompatibility of ZnO and AuNPs. The fabrication method of this biosensor was simple and effective for determination of H2O2 in real samples with quick response, good sensitivity, high selectivity, and acceptable recovery.

  16. Glucose biosensor based on glucose oxidase immobilized at gold nanoparticles decorated graphene-carbon nanotubes.

    PubMed

    Devasenathipathy, Rajkumar; Mani, Veerappan; Chen, Shen-Ming; Huang, Sheng-Tung; Huang, Tsung-Tao; Lin, Chun-Mao; Hwa, Kuo-Yuan; Chen, Ting-Yo; Chen, Bo-Jun

    2015-10-01

    Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV-vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of -0.40 V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5 × 10(-10) mol cm(-2) and 3.36 s(-1), respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10 μM - 2 mM with LOD of 4.1 μM, (2) 2 mM - 5.2 mM with LOD of 0.95 mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible.

  17. Glucose biosensor based on glucose oxidase immobilized at gold nanoparticles decorated graphene-carbon nanotubes.

    PubMed

    Devasenathipathy, Rajkumar; Mani, Veerappan; Chen, Shen-Ming; Huang, Sheng-Tung; Huang, Tsung-Tao; Lin, Chun-Mao; Hwa, Kuo-Yuan; Chen, Ting-Yo; Chen, Bo-Jun

    2015-10-01

    Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV-vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of -0.40 V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5 × 10(-10) mol cm(-2) and 3.36 s(-1), respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10 μM - 2 mM with LOD of 4.1 μM, (2) 2 mM - 5.2 mM with LOD of 0.95 mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible. PMID:26215343

  18. Cell adhesion and proliferation on polyethylene grafted with Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Kasálková, N. Slepičková; Slepička, P.; Kolská, Z.; Sajdl, P.; Bačáková, L.; Rimpelová, S.; Švorčík, V.

    2012-02-01

    Plasma treatment and subsequent Au nano-particles grafting of polyethylene (PE) lead to changes in surface morphology, roughness and wettability, significantly increasing the attractiveness of the material for cells. The PE samples were exposed to argon plasma. Plasma modified PE was chemically grafted by immersion to biphenyldithiol and consequently into solution of Au nano-particles. Changes in chemical structure of the modified PE were studied using X-ray Photoelectron Spectroscopy (XPS) and electrokinetic analysis ( ζ-potential). The surface wettability of the modified PE samples was examined by measurement of the contact angle by standard goniometry. The surface morphology of the plasma modified PE and that grafted with Au nano-particles was studied by Atomic Force Microscopy (AFM). The modified PE samples were seeded with rat vascular smooth muscle cells (VSMCs) and their adhesion and proliferation were studied. Chemically bounded biphenyldithiol increases the number of the incorporated gold nano-particles and changes sample surface properties. The presence of the biphenyldithiol and the gold nano-particles on the PE surface influences dramatically adhesion and proliferation of VSMCs.

  19. Determination of Anthracene on Ag-Au Alloy Nanoparticles/Overoxidized-Polypyrrole Composite Modified Glassy Carbon Electrodes

    PubMed Central

    Mailu, Stephen N.; Waryo, Tesfaye T.; Ndangili, Peter M.; Ngece, Fanelwa R.; Baleg, Abd A.; Baker, Priscilla G.; Iwuoha, Emmanuel I.

    2010-01-01

    A novel electrochemical sensor for the detection of anthracene was prepared by modifying a glassy carbon electrode (GCE) with over-oxidized polypyrrole (PPyox) and Ag-Au (1:3) bimetallic nanoparticles (Ag-AuNPs). The composite electrode (PPyox/Ag-AuNPs/GCE) was prepared by potentiodynamic polymerization of pyrrole on GCE followed by its overoxidation in 0.1 M NaOH. Ag-Au bimetallic nanoparticles were chemically prepared by the reduction of AgNO3 and HAuCl4 using C6H5O7Na3 as the reducing agent as well as the capping agent and then immobilized on the surface of the PPyox/GCE. The nanoparticles were characterized by UV-visible spectroscopy technique which confirmed the homogeneous formation of the bimetallic alloy nanoparticles. Transmission electron microscopy showed that the synthesized bimetallic nanoparticles were in the range of 20–50 nm. The electrochemical behaviour of anthracene at the PPyox/Ag-AuNPs/GCE with Ag: Au atomic ratio 25:75 (1:3) exhibited a higher electrocatalytic effect compared to that observed when GCE was modified with each constituent of the composite (i.e., PPyox, Ag-AuNPs) and bare GCE. A linear relationship between anodic current and anthracene concentration was attained over the range of 3.0 × 10−6 to 3.56 × 10−4 M with a detection limit of 1.69 × 10−7 M. The proposed method was simple, less time consuming and showed a high sensitivity. PMID:22163419

  20. Metal-immobilized magnetic nanoparticles for cytochrome C purification from rat liver.

    PubMed

    Perçin, Işık; Karakoç, Veyis; Ergün, Bahar; Denizli, Adil

    2016-01-01

    Cu(2+) -immobilized magnetic poly(hydroxyethylmethacrylate-N-methacryloyl-(l)-histidinemethylester) (mPHEMAH) nanoparticles were prepared by surfactant-free emulsion polymerization for cytochrome C (cyt C) purification from rat liver. Elemental analysis, atomic force microscopy, zeta sizer, and vibrating sample magnetometer were used to characterize mPHEMAH nanoparticles. In addition to these characterization steps, surface area, average particle size, and size distribution of mPHEMAH nanoparticles were determined. Quantity of immobilized Cu(2+) was measured using atomic absorption spectrophotometry. N-Methacryloyl-(l)-histidinemethylester and Cu(2+) content of mPHEMAH nanoparticles were 0.18 mmol/g polymer and 0.11 mmol/g polymer, respectively. Specific surface area of Cu(2+) -immobilized mPHEMAH nanoparticles was 1180 m(2) /g. Effect of initial cyt C concentration, pH, temperature, and ionic strength on cyt C adsorption onto Cu(2+) -immobilized mPHEMAH nanoparticles was investigated. Maximum cyt C adsorption capacity of Cu(2+) -immobilized mPHEMAH nanoparticles was 311.9 mg/g polymer. Maximum adsorption was obtained at pH 8.0 and 4 °C. Cu(2+) -immobilized mPHEMAH nanoparticles were used ten times with 4.1% decrease in adsorption capacity. In the last stage, Cu(2+) -immobilized mPHEMAH nanoparticles were used to purify cyt C from rat liver tissue, and the purity of desorbed fractions was controlled by SDS-PAGE.

  1. Surface segregation phenomena in extended and nanoparticle surfaces of Cu-Au alloys

    NASA Astrophysics Data System (ADS)

    Li, Jonathan; Wang, Guofeng; Zhou, Guangwen

    2016-07-01

    Using density functional theory (DFT) and Monte Carlo (MC) simulations, we studied the surface segregation phenomena of Au atoms in the extended and nanoparticle surfaces of Cu-Au alloys. Our MC simulations predicted significant Au enrichment in the outermost layer of (111) and (100) extended surfaces, and Au enrichment in the two outermost layers of (110) extended surfaces. The equilibrium Cu-Au nanoparticles were predicted to develop into an Au-enriched shell structure, where Au atoms preferably segregate to the (100) facets while Cu atoms are mainly located on the (111) facet of the nanoparticles. Our simulation predictions agree with experimental measurements.

  2. Magnetic mesoporous silica nanoparticles: fabrication and their laccase immobilization performance.

    PubMed

    Wang, Feng; Guo, Chen; Yang, Liang-rong; Liu, Chun-Zhao

    2010-12-01

    Newly large-pore magnetic mesoporous silica nanoparticles (MMSNPs) with wormhole framework structures were synthesized for the first time by using tetraethyl orthosilicate as the silica source and amine-terminated Jeffamine surfactants as template. Iminodiacerate was attached on these MMSNPs through a silane-coupling agent and chelated with Cu(2+). The Cu(2+)-chelated MMSNPs (MMSNPs-CPTS-IDA-Cu(2+)) showed higher adsorption capacity of 98.1 mg g(-1)-particles and activity recovery of 92.5% for laccase via metal affinity adsorption in comparison with MMSNPs via physical adsorption. The Michaelis constant (K(m)) and catalytic constant (k(cat)) of laccase immobilized on the MMSNPs-CPTS-IDA-Cu(2+) were 3.28 mM and 155.4 min(-1), respectively. Storage stability and temperature endurance of the immobilized laccase on MMSNPs-CPTS-IDA-Cu(2+) increased significantly, and the immobilized laccase retained 86.6% of its initial activity after 10 successive batch reactions operated with magnetic separation.

  3. Improving biohydrogen production using Clostridium beijerinckii immobilized with magnetite nanoparticles.

    PubMed

    Seelert, Trevor; Ghosh, Dipankar; Yargeau, Viviane

    2015-05-01

    In order to supplement the need for alternative energy resources within the near future, enhancing the production of biohydrogen with immobilized Clostridium beijerinckii NCIMB8052 was investigated. Magnetite nanoparticles were functionalized, with chitosan and alginic acid polyelectrolytes using a layer-by-layer method, to promote bacterial attachment. Cultivating C. beijerinckii with these nanoparticles resulted in a shorter lag growth phase and increased total biohydrogen production within 100-ml, 250-ml and 3.6-L reactors compared with freely suspended organisms. The greatest hydrogen yield was obtained in the 250-ml reactor with a value of 2.1 ± 0.7 mol H2/mol glucose, corresponding to substrate conversion and energy conversion efficiencies of 52 ± 18 and 10 ± 3 %, respectively. The hydrogen yields obtained using the immobilized bacteria are comparable to values found in literature. However, to make this process viable, further improvements are required to increase the substrate and energy conversion efficiencies.

  4. Assembling Bare Au Nanoparticles at Positively Charged Templates

    PubMed Central

    Wang, Wenjie; Zhang, Honghu; Kuzmenko, Ivan; Mallapragada, Surya; Vaknin, David

    2016-01-01

    In-situ X-ray reflectivity (XRR) and grazing incidence X-ray small-angle scattering (GISAXS) reveal that unfunctionalized (bare) gold nanoparticles (AuNP) spontaneously adsorb to a cationic lipid template formed by a Langmuir monolayer of DPTAP (1,2-dihexadecanoyl-3-trimethylammonium-propane) at vapor/aqueous interfaces. Analysis of the XRR yields the electron density profile across the charged-interfaces along the surface normal showing the AuNPs assemble with vertical thickness comparable to the particle size. The GISAXS analysis indicates that the adsorbed mono-particle layer exhibits short-range in-plane correlations. By contrast, single-stranded DNA-functionalized AuNPs, while attracted to the positively charged surface (more efficiently with the addition of salt to the solution), display less in-plane regular packing compared to bare AuNPs. PMID:27225047

  5. Assembling Bare Au Nanoparticles at Positively Charged Templates

    NASA Astrophysics Data System (ADS)

    Wang, Wenjie; Zhang, Honghu; Kuzmenko, Ivan; Mallapragada, Surya; Vaknin, David

    2016-05-01

    In-situ X-ray reflectivity (XRR) and grazing incidence X-ray small-angle scattering (GISAXS) reveal that unfunctionalized (bare) gold nanoparticles (AuNP) spontaneously adsorb to a cationic lipid template formed by a Langmuir monolayer of DPTAP (1,2-dihexadecanoyl-3-trimethylammonium-propane) at vapor/aqueous interfaces. Analysis of the XRR yields the electron density profile across the charged-interfaces along the surface normal showing the AuNPs assemble with vertical thickness comparable to the particle size. The GISAXS analysis indicates that the adsorbed mono-particle layer exhibits short-range in-plane correlations. By contrast, single-stranded DNA-functionalized AuNPs, while attracted to the positively charged surface (more efficiently with the addition of salt to the solution), display less in-plane regular packing compared to bare AuNPs.

  6. Assembling Bare Au Nanoparticles at Positively Charged Templates

    DOE PAGES

    Wang, Wenjie; Zhang, Honghu; Kuzmenko, Ivan; Mallapragada, Surya; Vaknin, David

    2016-05-26

    In-situ X-ray reflectivity (XRR) and grazing incidence X-ray small-angle scattering (GISAXS) reveal that unfunctionalized (bare) gold nanoparticles (AuNP) spontaneously adsorb to a cationic lipid template formed by a Langmuir monolayer of DPTAP (1,2-dihexadecanoyl-3-trimethylammonium-propane) at vapor/aqueous interfaces. Analysis of the XRR yields the electron density profile across the charged-interfaces along the surface normal showing the AuNPs assemble with vertical thickness comparable to the particle size. The GISAXS analysis indicates that the adsorbed mono-particle layer exhibits short-range in-plane correlations. By contrast, single-stranded DNA-functionalized AuNPs, while attracted to the positively charged surface (more efficiently with the addition of salt to the solution), displaymore » less in-plane regular packing compared to bare AuNPs.« less

  7. Au/Pd core-shell nanoparticles with varied hollow Au cores for enhanced formic acid oxidation

    NASA Astrophysics Data System (ADS)

    Hsu, Chiajen; Huang, Chienwen; Hao, Yaowu; Liu, Fuqiang

    2013-03-01

    A facile method has been developed to synthesize Au/Pd core-shell nanoparticles via galvanic replacement of Cu by Pd on hollow Au nanospheres. The unique nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, and electrochemical measurements. When the concentration of the Au solution was decreased, grain size of the polycrystalline hollow Au nanospheres was reduced, and the structures became highly porous. After the Pd shell formed on these Au nanospheres, the morphology and structure of the Au/Pd nanoparticles varied and hence significantly affected the catalytic properties. The Au/Pd nanoparticles synthesized with reduced Au concentrations showed higher formic acid oxidation activity (0.93 mA cm-2 at 0.3 V) than the commercial Pd black (0.85 mA cm-2 at 0.3 V), suggesting a promising candidate as fuel cell catalysts. In addition, the Au/Pd nanoparticles displayed lower CO-stripping potential, improved stability, and higher durability compared to the Pd black due to their unique core-shell structures tuned by Au core morphologies.

  8. Au/Pd core-shell nanoparticles with varied hollow Au cores for enhanced formic acid oxidation.

    PubMed

    Hsu, Chiajen; Huang, Chienwen; Hao, Yaowu; Liu, Fuqiang

    2013-03-01

    A facile method has been developed to synthesize Au/Pd core-shell nanoparticles via galvanic replacement of Cu by Pd on hollow Au nanospheres. The unique nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet-visible spectroscopy, and electrochemical measurements. When the concentration of the Au solution was decreased, grain size of the polycrystalline hollow Au nanospheres was reduced, and the structures became highly porous. After the Pd shell formed on these Au nanospheres, the morphology and structure of the Au/Pd nanoparticles varied and hence significantly affected the catalytic properties. The Au/Pd nanoparticles synthesized with reduced Au concentrations showed higher formic acid oxidation activity (0.93 mA cm-2 at 0.3 V) than the commercial Pd black (0.85 mA cm-2 at 0.3 V), suggesting a promising candidate as fuel cell catalysts. In addition, the Au/Pd nanoparticles displayed lower CO-stripping potential, improved stability, and higher durability compared to the Pd black due to their unique core-shell structures tuned by Au core morphologies.

  9. Au/Pd core-shell nanoparticles with varied hollow Au cores for enhanced formic acid oxidation

    PubMed Central

    2013-01-01

    A facile method has been developed to synthesize Au/Pd core-shell nanoparticles via galvanic replacement of Cu by Pd on hollow Au nanospheres. The unique nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, and electrochemical measurements. When the concentration of the Au solution was decreased, grain size of the polycrystalline hollow Au nanospheres was reduced, and the structures became highly porous. After the Pd shell formed on these Au nanospheres, the morphology and structure of the Au/Pd nanoparticles varied and hence significantly affected the catalytic properties. The Au/Pd nanoparticles synthesized with reduced Au concentrations showed higher formic acid oxidation activity (0.93 mA cm-2 at 0.3 V) than the commercial Pd black (0.85 mA cm-2 at 0.3 V), suggesting a promising candidate as fuel cell catalysts. In addition, the Au/Pd nanoparticles displayed lower CO-stripping potential, improved stability, and higher durability compared to the Pd black due to their unique core-shell structures tuned by Au core morphologies. PMID:23452438

  10. Hollow PDA-Au nanoparticles-enabled signal amplification for sensitive nonenzymatic colorimetric immunodetection of carbohydrate antigen 125.

    PubMed

    Zhao, Yan; Zheng, Yiqun; Zhao, Caiyun; You, Jinmao; Qu, Fengli

    2015-09-15

    A novel colorimetric immunoassay was designed for the sensitive detection of carbohydrate antigen 125 (CA125). The success of this immunoassay relies on the use of hollow polydopamine-gold nanoparticles (PDA-Au) for signal amplification to achieve sensitive nonenzymatic colorimetric detection. In particular, PDA-Au was used as a stable and sensitive label and aminated-Fe3O4 magnetic nanoparticles (Fe3O4 NPs) were employed to immobilize capture antibody (Ab1) and acted as a separable immunosensing probe. PDA-Au exhibited high catalytic performance towards p-nitrophenol reduction and thus resulted in significant color change and UV/vis signal variations. The immunoassay was performed based on sandwich protocol. As compared to pure Au nanoparticles, the signal amplification and sensitivity of PDA-Au-based assay was significantly improved. For instance, the dynamic range of the developed colorimetric immunoassay for CA125 was 0.1-100 U/mL with a detection limit of 0.1 U/mL at S/N=3. In addition, this immunoassay was also tested for the analysis of clinical serum samples, which demonstrated its potential for practical diagnostic applications.

  11. Photochromic reaction of the diarylethene derivative on Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Takahashi, Ryoji; Kaneko, Satoshi; Fujii, Shintaro; Kiguchi, Manabu

    2015-03-01

    We have studied the photochromic reaction of the diarylethene derivative on Au nanoparticles using the incoherent excitation as a function of the wavelength of the irradiation light with the aim to clarify the effect of metal nanoparticles on the reaction yield. The photochemical reaction was suppressed by the Au nanoparticles under the irradiation of light whose wave length was shorter than 700 nm, while photochemical reaction was enhanced by the irradiation of light whose wavelength was longer than 750 nm via two-photon absorption process. The suppression of the photochemical reaction could be explained by the quenching of the excited state via radiative and non-radiative decay through energy or charge transfer to the metal substrate (e.g. electron-hole pair formation, surface plasmon excitation, formation of induced-dipole induced-dipole coupling), and the absorption of light by the Au nanoparticle. Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam.

  12. Preparation of graphene oxide-based surface plasmon resonance biosensor with Au bipyramid nanoparticles as sensitivity enhancer.

    PubMed

    Zhang, Jia; Sun, Ying; Wu, Qiong; Gao, Yan; Zhang, Hua; Bai, Yu; Song, Daqian

    2014-04-01

    A sensitive and selective wavelength-modulation surface plasmon resonance (SPR) biosensor based on graphene oxide (GO) and Au bipyramids (AuBPs) is reported for determination of bovine IgM. GO sheets with lengths of 100-300 nm are synthesized and assembled on amine-modified Au film. The large surface area and abundant functional groups of GO allow the efficient immobilization of antibody. AuBPs are nanoparticles with a penta-twinned crystal structure, which have a sharp localized surface plasmon resonance (LSPR) band because of their high monodispersity. In the optimal conditions, the GO-based biosensor with AuBPs as sensitivity enhancers shows a satisfactory response to bovine IgM in the concentration range of 0.03-32 μg mL(-1). For contrast, traditional biosensor, GO-based biosensor and GO-based biosensor with Au nanorods (AuNRs) as sensitivity enhancers for antigen detection were also investigated. Consequently, the as-prepared GO sheets function as promising support for antibody and GO-based SPR biosensor using AuBPs as enhancers has the highest sensitivity among the four types of biosensors.

  13. Ultrasensitive electrochemical sensor for Hg(2+) by using hybridization chain reaction coupled with Ag@Au core-shell nanoparticles.

    PubMed

    Li, Zongbing; Miao, Xiangmin; Xing, Ke; Peng, Xue; Zhu, Aihua; Ling, Liansheng

    2016-06-15

    A novel electrochemical biosensor for Hg(2+) detection was reported by using DNA-based hybridization chain reaction (HCR) coupled with positively charged Ag@Au core-shell nanoparticles ((+)Ag@Au CSNPs) amplification. To construct the sensor, capture probe (CP ) was firstly immobilized onto the surface of glass carbon electrode (GCE). In the presence of Hg(2+), the sandwiched complex can be formed between the immobilized CP on the electrode surface and the detection probe (DP) modified on the gold nanoparticles (AuNPs) based on T-Hg(2+)-T coordination chemistry. The carried DP then opened two ferrocene (Fc) modified hairpin DNA (H1 and H2) in sequence and propagated the happen of HCR to form a nicked double-helix. Numerous Fc molecules were formed on the neighboring probe and produced an obvious electrochemical signal. Moreover, (+)Ag@Au CSNPs were assembly onto such dsDNA polymers as electrochemical signal enhancer. Under optimal conditions, such sensor presents good electrochemical responses for Hg(2+) detection with a detection limit of 3.6 pM. Importantly, the methodology has high selectivity for Hg(2+) detection. PMID:26852203

  14. Ultrasensitive electrochemical sensor for Hg(2+) by using hybridization chain reaction coupled with Ag@Au core-shell nanoparticles.

    PubMed

    Li, Zongbing; Miao, Xiangmin; Xing, Ke; Peng, Xue; Zhu, Aihua; Ling, Liansheng

    2016-06-15

    A novel electrochemical biosensor for Hg(2+) detection was reported by using DNA-based hybridization chain reaction (HCR) coupled with positively charged Ag@Au core-shell nanoparticles ((+)Ag@Au CSNPs) amplification. To construct the sensor, capture probe (CP ) was firstly immobilized onto the surface of glass carbon electrode (GCE). In the presence of Hg(2+), the sandwiched complex can be formed between the immobilized CP on the electrode surface and the detection probe (DP) modified on the gold nanoparticles (AuNPs) based on T-Hg(2+)-T coordination chemistry. The carried DP then opened two ferrocene (Fc) modified hairpin DNA (H1 and H2) in sequence and propagated the happen of HCR to form a nicked double-helix. Numerous Fc molecules were formed on the neighboring probe and produced an obvious electrochemical signal. Moreover, (+)Ag@Au CSNPs were assembly onto such dsDNA polymers as electrochemical signal enhancer. Under optimal conditions, such sensor presents good electrochemical responses for Hg(2+) detection with a detection limit of 3.6 pM. Importantly, the methodology has high selectivity for Hg(2+) detection.

  15. Fabrication of conducting polymer micro/nanostructures coated with Au nanoparticles for electrochemical sensors.

    PubMed

    An, Taechang; Choi, WooSeok; Lee, Eunjoo; Cho, Seong J; Lim, Geunbae

    2012-06-01

    Polypyrrole (PPy) micro/nanostructures coated with Au nanoparticles were prepared by electropolymerization and electro-deposition. Two types of PPy structures, micro-embossed and nanowire forest, were synthesized on patterned gold electrodes using different aqueous solutions, and Au nanoparticles were coated onto the PPy micro/nanostructure surface. The size of the Au nanoparticles ranged from 10 to 100 nm, and the maximum density of the nanoparticles was 73 particles/microm2. The small size and high density of the Au nanoparticles were achieved by optimizing the deposition time and chloroauric acid (HAuCl4) concentration. Cyclic voltammograms of ferrocyanide oxidation showed that the PPy micro/nanostructures coated with Au nanoparticles exhibit good electrochemical activity. These high-performance electrodes can be used in electrochemical sensors because the Au nanoparticles enhance electron transfer and provide a binding site for biomarker molecules, such as DNA, protein, and aptamers.

  16. Heterostructured Au/Pd-M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity.

    PubMed

    Lutz, Patrick S; Bae, In-Tae; Maye, Mathew M

    2015-10-14

    The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had high activity attributed to the porous nature of the platinum domains. PMID:26351824

  17. 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

  18. Titanium dental implants surface-immobilized with gold nanoparticles as osteoinductive agents for rapid osseointegration.

    PubMed

    Heo, Dong Nyoung; Ko, Wan-Kyu; Lee, Hak Rae; Lee, Sang Jin; Lee, Donghyun; Um, Soong Ho; Lee, Jung Haeng; Woo, Yi-Hyung; Zhang, Lijie Grace; Lee, Deok-Won; Kwon, Il Keun

    2016-05-01

    Gold nanoparticles (GNPs) are quite attractive materials for use as osteogenic agents due to their potential effects on the stimulation of osteoblast differentiation. In this study, an osseo-integrated titanium (Ti) implant surface coated with GNPs was used for promotion of bone regeneration. We prepared a silanized Ti surface by chemical treatment of (3-Mercaptopropyl) trimethoxysilane (MPTMS) and immobilized the GNP layer (Ti-GNP) on their surfaces via Au-S bonding. The GNP layer is uniformly immobilized on the surface and the layer covers the titanium oxide surface well, as confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The Ti-GNP was used to investigate the effectiveness of this system both in vitro and in vivo. The in vitro results showed that the Ti-GNP significantly enhances the osteogenic differentiation with increased mRNA expression of osteogenic differentiation specific genes in human adipose-derived stem cells (ADSCs). Furthermore, the in vivo results showed that Ti-GNP had a significant influence on the osseous interface formation. Through these in vitro and vivo tests, we found that Ti-GNP can be useful as osseo-integration inducing dental implants for formation of an osseous interface and maintenance of nascent bone formation. PMID:26874978

  19. Titanium dental implants surface-immobilized with gold nanoparticles as osteoinductive agents for rapid osseointegration.

    PubMed

    Heo, Dong Nyoung; Ko, Wan-Kyu; Lee, Hak Rae; Lee, Sang Jin; Lee, Donghyun; Um, Soong Ho; Lee, Jung Haeng; Woo, Yi-Hyung; Zhang, Lijie Grace; Lee, Deok-Won; Kwon, Il Keun

    2016-05-01

    Gold nanoparticles (GNPs) are quite attractive materials for use as osteogenic agents due to their potential effects on the stimulation of osteoblast differentiation. In this study, an osseo-integrated titanium (Ti) implant surface coated with GNPs was used for promotion of bone regeneration. We prepared a silanized Ti surface by chemical treatment of (3-Mercaptopropyl) trimethoxysilane (MPTMS) and immobilized the GNP layer (Ti-GNP) on their surfaces via Au-S bonding. The GNP layer is uniformly immobilized on the surface and the layer covers the titanium oxide surface well, as confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The Ti-GNP was used to investigate the effectiveness of this system both in vitro and in vivo. The in vitro results showed that the Ti-GNP significantly enhances the osteogenic differentiation with increased mRNA expression of osteogenic differentiation specific genes in human adipose-derived stem cells (ADSCs). Furthermore, the in vivo results showed that Ti-GNP had a significant influence on the osseous interface formation. Through these in vitro and vivo tests, we found that Ti-GNP can be useful as osseo-integration inducing dental implants for formation of an osseous interface and maintenance of nascent bone formation.

  20. Nucleation-Suppressed Phase Stabilization in Fe–Au Nanoparticles

    SciTech Connect

    Mukherjee, P.; Jiang, Xiujuan; Wu, Yaqiao; Kramer, Matthew J.; Shield, J. E.

    2013-10-18

    Four nanoparticle compositions, Fe–21, 35, 47, and 67 at. % Au, have been prepared to study the phase stability and solid-state transformation in confined Fe–Au nanoalloys. The formation of two phases, predicted from bulk thermodynamics, has been suppressed in all compositions. Instead, a single phase solid solution forms after heat treatment at 600 °C and slow cooling. However, bulk phase relationships, signified by the precipitation of α-Fe upon cooling, was observed in larger particles (>20 nm) with composition Fe–35 at. % Au. The suppression of the phase transformation/precipitation in small particles is explained thermodynamically, as the free energy decrease associated with the phase transformation does not exceed the increase in energy due to the introduction of an interphase interface (grain boundary) within the cluster. A general equation has been derived to predict the critical cluster size below which transformations are inhibited, which agrees well with the observed experimental results.

  1. Esterases immobilized on aminosilane modified magnetic nanoparticles as a catalyst for biotransformation reactions.

    PubMed

    Alex, Deepthy; Mathew, Abraham; Sukumaran, Rajeev K

    2014-09-01

    Magnetite nanoparticles were prepared by reacting ferrous and ferric salts in presence of aqueous ammonia. The magnetic nanoparticles (MNPs) were amino functionalized by treating with 3-aminopropyl triethoxy silane (APTES) and was coupled with glutaraldehyde. A novel solvent tolerant esterase from Pseudozyma sp. NII 08165 was immobilized on the MNPs through covalent bonding to the glutaraldehyde. The magnetite nanoparticles had a size range of 10-100 nm, confirmed by DLS. Lipases immobilized on MNPs were evaluated for biotransformation reactions including synthesis of ethyl acetate and transesterification of vegetable oil for producing biodiesel. The MNP immobilized esterase had prolonged shelf life and there was no loss in enzyme activity. PMID:24968816

  2. Esterases immobilized on aminosilane modified magnetic nanoparticles as a catalyst for biotransformation reactions.

    PubMed

    Alex, Deepthy; Mathew, Abraham; Sukumaran, Rajeev K

    2014-09-01

    Magnetite nanoparticles were prepared by reacting ferrous and ferric salts in presence of aqueous ammonia. The magnetic nanoparticles (MNPs) were amino functionalized by treating with 3-aminopropyl triethoxy silane (APTES) and was coupled with glutaraldehyde. A novel solvent tolerant esterase from Pseudozyma sp. NII 08165 was immobilized on the MNPs through covalent bonding to the glutaraldehyde. The magnetite nanoparticles had a size range of 10-100 nm, confirmed by DLS. Lipases immobilized on MNPs were evaluated for biotransformation reactions including synthesis of ethyl acetate and transesterification of vegetable oil for producing biodiesel. The MNP immobilized esterase had prolonged shelf life and there was no loss in enzyme activity.

  3. Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer.

    PubMed

    Namura, Kyoko; Suzuki, Motofumi; Nakajima, Kaoru; Kimura, Kenji

    2013-04-01

    Efficient photoacoustic emission from Au nanoparticles on a porous SiO(2) layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO(2)/SiO(2)/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO(2) layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO(2) layer (0.93). The contribution of the porous SiO(2) layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature. PMID:23571958

  4. Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer.

    PubMed

    Namura, Kyoko; Suzuki, Motofumi; Nakajima, Kaoru; Kimura, Kenji

    2013-04-01

    Efficient photoacoustic emission from Au nanoparticles on a porous SiO(2) layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO(2)/SiO(2)/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO(2) layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO(2) layer (0.93). The contribution of the porous SiO(2) layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature.

  5. Preparation and characterization of a thermostable enzyme (Mn-SOD) immobilized on supermagnetic nanoparticles.

    PubMed

    Song, Chongfu; Sheng, Liangquan; Zhang, Xiaobo

    2012-10-01

    Superoxide dismutase (SOD) has been widely applied in medical treatments, cosmetic, food, agriculture, and chemical industries. In industry, the immobilization of enzymes can offer better stability, feasible continuous operations, easy separation and reusing, and significant decrease of the operation costs. However, little attention has focused on the immobilization of the SOD, as well as the immobilization of thermostable enzymes. In this study, the recombinant thermostable manganese superoxide dismutase (Mn-SOD) of Thermus thermophilus wl was purified and covalently immobilized onto supermagnetic 3-APTES-modified Fe(3)O(4)@SiO(2) nanoparticles using glutaraldehyde method to prepare the Mn-SOD bound magnetic nanoparticles. The Mn-SOD nanoparticles were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer analysis. The results indicated that the diameter of Mn-SOD nanoparticles was 40 (± 5) nm, and its saturation magnetization value was 27.9 emu/g without remanence or coercivity. By comparison with the free Mn-SOD, it was found that the immobilized Mn-SOD on nanoparticles exhibited better resistance to temperature, pH, metal ions, enzyme inhibitors, and detergents. The results showed that the immobilized Mn-SOD on nanoparticles could be reused ten times without significant decrease of enzymatic activity. Therefore, our study presented a novel strategy for the immobilization of thermostable Mn-SOD and for the application of thermostable enzymes. PMID:22237672

  6. Au and Ag/Au double-shells hollow nanoparticles with improved near infrared surface plasmon and photoluminescence properties.

    PubMed

    Ghosh Chaudhuri, Rajib; Paria, Santanu

    2016-01-01

    Metallic hollow nanoparticles have been continuously drawing researcher's attention because of their excellent improved performance compare to the spherical particles in catalysis, photonics, information storage, surface-enhanced Raman scattering, and sensors applications. In this article we demonstrate a novel route for the synthesis of single and double-shells Au and Ag/Au bimetallic hollow nanoparticles using elemental sulfur as a sacrificial core. We also investigate the optical properties of these new hollow particles and compare with that of pure spherical nanoparticles. The surface plasmon resonance spectra of solid Au, hollow single shell Au, and double shells Ag/Au nanoparticles show that there is gradual shifting of Au peak position towards the higher wavelengths for these three nanoparticles respectively. A similar observation was also found for photoluminescence spectra. In case of double-shells Ag/Au hollow nanoparticles the emission spectrum shifts towards the NIR region with significant higher intensity, which is beneficial for in vivo biomedical applications of these particles.

  7. Immobilization and Characterization of Penicillin G Acylase (PGA) Immobilized on Magnetic Ni₀.₅Zn₀.₅Fe₂O₄ Nanoparticles.

    PubMed

    Liu, Ruijiang; Fan, Jiawen; Zhang, Yewang; Wang, Peng; Shen, Xiangqian

    2016-01-01

    Magnetic Ni₀.₅Zn₀.₅Fe₂O₄ nanoparticles were prepared via the solution combustion process and their microstructure and magnetic properties were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The as-prepared magnetic Ni₀.₅Zn₀.₅Fe₂O₄ nanoparticles are characterized with average grain size of about 20 nm and magnetization of 90.3 Am²/kg. The surface of magnetic Ni₀.₅Zn₀.₅Fe₂O₄ nanoparticles was modified by use of sodium silicate and N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride, and the penicillin G acylase (PGA) was successfully immobilized on the surface-modified magnetic Ni₀.₅Zn₀.₅Fe₂O₄ nanoparticles. The results show that the activity for the immobilized PGA is affected less by pH and temperature than that for the free PGA, and the immobilized PGA exhibits a high effective activity, good stability of enzyme catalyst. This immobilized PGA on magnetic Ni₀.₅Zn₀.₅Fe₂O₄ nanoparticles can be separated from the solution by the external magnetic field for cyclic utilization, and they could retain about 70% of initial enzyme activity after 11 consecutive operations. The kinetic parameters (Km and Vmax) were determined, and the value of Km for the immobilized PGA (204.53 mmol/L) is higher than that of the free enzyme (3.50 mmol/L), while Vmax (1.93 mmol/min) is also larger than that of the free enzyme (0.838 mmol/min). PMID:27398443

  8. Synthesis and characterization of cysteine functionalized silver nanoparticles for biomolecule immobilization.

    PubMed

    Upadhyay, Lata Sheo Bachan; Verma, Nishant

    2014-11-01

    A facile method for the aqueous phase synthesis of cysteine-functionalized silver nanoparticles by potato extract has been reported in the present work. These functionalized nanoparticles were then used for the covalent immobilization of a biomolecule, alkaline phosphatase, on its surface through carbodiimide coupling. Different reaction parameters such as cysteine concentration, reducing agent concentration, temperature, pH and reaction time were varied during the nanoparticles' formation, and their effects on plasmon resonance were studied using Ultraviolet-visible spectroscopy. Fourier transform infrared spectroscopy was used to confirm the surface modification of silver nanoparticles by cysteine and the particle size analysis was done using particle size analyzer, which showed the average nanoparticles' size of 61 nm for bare silver nanoparticles and 201 nm for the enzyme-immobilized nanoparticles. The synthesized nanoparticles were found to be highly efficient for the covalent immobilization of alkaline phosphatase on its surface and retained 67% of its initial enzyme activity (9.44 U/mg), with 75% binding efficiency. The shelf life of the enzyme-nanoparticle bioconjugates was found to be 60 days, with a 12% loss in the initial enzyme activity. With a simple synthesis strategy, high immobilization efficiency and enhanced stability, these enzyme-coated nanoparticles have the potential for further integration into the biosensor technology. PMID:24760173

  9. 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.

  10. Structure analysis of bimetallic Co-Au nanoparticles formed by sequential ion implantation

    NASA Astrophysics Data System (ADS)

    Chen, Hua-jian; Wang, Yu-hua; Zhang, Xiao-jian; Song, Shu-peng; chen, Hong; Zhang, Ke; Xiong, Zu-zhao; Ji, Ling-ling; Dai, Hou-mei; Wang, Deng-jing; Lu, Jian-duo; Wang, Ru-wu; Zheng, Li-rong

    2016-08-01

    Co-Au alloy Metallic nanoparticles (MNPs) are formed by sequential ion implantation of Co and Au into silica glass at room temperature. The ion ranges of Au ions implantation process have been displayed to show the ion distribution. We have used the atomic force microscopy (AFM) and transmission electron microscopy (TEM) to investigate the formation of bimetallic nanoparticles. The extended X-ray absorption fine structure (EXAFS) has been used to study the local structural information of bimetallic nanoparticles. With the increase of Au ion implantation, the local environments of Co ions are changed enormously. Hence, three oscillations, respectively, Co-O, Co-Co and Co-Au coordination are determined.

  11. Urease immobilized fluorescent gold nanoparticles for urea sensing.

    PubMed

    Parashar, Upendra Kumar; Nirala, Narsingh R; Upadhyay, Chandan; Saxena, P S; Srivastava, Anchal

    2015-05-01

    We report a surfactant-free synthesis of monodispersed gold nanoparticles (AuNPs) with average size of 15 nm. An approach for visual and fluorescent sensing of urea in aqueous solution based on shift in surface plasmon band (SPB) maxima as well as quench in fluorescence intensity. To enable the urea detection, we functionalized the thiol-capped gold nanoparticles with urease, the enzyme specific to urea using carbodiimide chemistry. The visible color changed of the gold colloidal solution from red to blue (or purple); this was evident from quenching in absorbance and fluorescence intensity, is the principle applied here for the sensing of urea. The solution turns blue when the urea concentration exceeds 8 mg/dL which reveals visual lower detection limit. The lower detection limits governed by the fluorescence quenching were found 5 mg/dL (R(2) = 0.99) which is highly sensitive and selective compared to shift in SPB maxima. The approach depicted here seems to be important in clinical diagnosis.

  12. The impact of immobile zones on the transport and retention of nanoparticles in porous media

    NASA Astrophysics Data System (ADS)

    Molnar, Ian L.; Gerhard, Jason I.; Willson, Clinton S.; O'Carroll, Denis M.

    2015-11-01

    Nanoparticle transport and retention within porous media is treated by conceptualizing the porous media as a series of independent collectors (e.g., Colloid Filtration Theory). This conceptualization assumes that flow phenomena near grain-grain contacts, such as immobile zones (areas of low flow), exert a negligible influence on nanoparticle transport and assumes that retention and release of particles depends only on surface chemistry. This study investigated the impact of immobile zones on nanoparticle transport and retention by employing synchrotron X-ray computed microtomography (SXCMT) to examine pore-scale silver nanoparticle distributions during transport through three sand columns: uniform iron oxide, uniform quartz, and well-graded quartz. Extended tailing was observed during the elution phase of all experiments suggesting that hydraulic retention in immobile zones, not detachment from grains, was the source of tailing. A numerical simulation of fluid flow through an SXCMT data set predicted the presence of immobile zones near grain-grain contacts. SXCMT-determined silver nanoparticle concentrations observed that significantly lower nanoparticle concentrations existed near grain-grain contacts throughout the duration of all experiments. In addition, the SXCMT-determined pore-scale concentration gradients were found to be independent of surface chemistry and grain size distribution, suggesting that immobile zones limit the diffusive transport of nanoparticles toward the collectors. These results suggest that the well-known overprediction of nanoparticle retention by traditional CFT may be due to ignoring the influences of grain-grain contacts and immobile zones. As such, accurate prediction of nanoparticle transport requires consideration of immobile zones and their influence on both hydraulic and surface retention.

  13. Application of electrochemical impedance spectroscopy for monitoring allergen-antibody reactions using gold nanoparticle-based biomolecular immobilization method.

    PubMed

    Huang, Haizhen; Liu, Zhigang; Yang, Xiurong

    2006-09-15

    Gold nanoparticles were used to enhance the immobilization amount and retain the immunoactivity of recombinant dust mite allergen Der f2 immobilized on a glassy carbon electrode (GCE). The interaction between allergen and antibody was studied by electrochemical impedance spectroscopy (EIS). Self-assembled Au colloid layer (ø=16nm) deposited on (3-mercaptopropyl)trimethoxysilane (MPTS)-modified GCE offered a basis to control the immobilization of allergen Der f2. The impedance measurements were based on the charge transfer kinetics of the [Fe(CN)(6)](3-/4-) redox pair, compared with bare GCE, the immobilization of allergen Der f2 and the allergen-antibody interaction that occurred on the electrode surface altered the interfacial electron transfer resistance and thereby slowed down the charge transfer kinetics by reducing the active area of the electrode or by preventing the redox species in electrolyte solution from approaching the electrode. The interactions of allergen with various concentrations of monoclonal antibody were also monitored through the change of impedance response. The results showed that the electron transfer resistance increased with increasing concentrations of monoclonal antibody. PMID:16836968

  14. Enzymatic biosensor of horseradish peroxidase immobilized on Au-Pt nanotube/Au-graphene for the simultaneous determination of antioxidants.

    PubMed

    Wu, Long; Yin, Wenmin; Tang, Kun; Li, Dian; Shao, Kang; Zuo, Yunpeng; Ma, Jing; Liu, Jiawei; Han, Heyou

    2016-08-24

    A new electrochemical method has been proposed for the simultaneous determination of butylated hydroxyanisole (BHA) and propyl gallate (PG) in food matrices based on enzymatic biosensors. Spiny Au-Pt nanotubes (SAP NTs) was first synthesized and demonstrated to exhibit intrinsic peroxidase and catalase-like activity. The structure of SAP NTs provides large surface area and favorable medium for electron transfer, on which HRP were immobilized and acted as enzymatic biosensor for the simultaneous detection of BHA and PG. The results revealed that BHA and PG both have well-defined oxidation waves with peak potentials of 624 and 655 mV, respectively. Under the optimal conditions, the method behaved satisfactory analytical performance towards BHA and PG with a wide linear range of 0.3-50 mg L(-1) and 0.1-100 mg L(-1), as well as a detection limit of 0.046 mg L(-1) and 0.024 mg L(-1) (3σ/slope), respectively. Besides, the proposed method exhibits good sensitivity, stability and reproducibility, providing an alternative to fabricate electrode and construct sensitive biosensors. PMID:27497001

  15. Photocatalytic hybrid Au/ZnO nanoparticles assembled through a one-pot method.

    PubMed

    Manna, Joydeb; Vinod, T P; Flomin, Kobi; Jelinek, Raz

    2015-12-15

    Growth of metal domains on semiconductor nanoparticles is known to enhance their photocatalytic properties. We prepared ZnO nanoparticles decorated with metallic Au domains through a new one-pot microwave-based strategy. The synthetic route utilized microwave-heating of a mixture of only three components: Zn(2+) salt, Au(SCN)4(-) which served as a precursor for metallic gold, and Tris base. The Tris molecules had a dual role in the process, both shaping the morphology of the ZnO particles, as well as constituting docking and nucleation sites for the Au(SCN)4(-) ions. The Au complex subsequently underwent spontaneous crystallization/reduction without co-addition of reducing or stabilizing agents, yielding Au nanoparticles attached to the ZnO surface. We show that the hybrid Au/ZnO nanoparticles exhibited enhanced photocatalytic properties compared to the plain ZnO nanoparticles. PMID:26319327

  16. Reduced graphene oxide supported Au nanoparticles as an efficient catalyst for aerobic oxidation of benzyl alcohol

    NASA Astrophysics Data System (ADS)

    Yu, Xianqin; Huo, Yujia; Yang, Jing; Chang, Sujie; Ma, Yunsheng; Huang, Weixin

    2013-09-01

    Various Au/C catalysts were prepared by Au nanoparticels supported on different carbonaceous supports including reduced graphene oxide (RGO), activated carbon (AC) and graphite (GC) using sol-immobilization method. Au/RGO shows a much higher activity than Au/AC and Au/GC in the liquid phase aerobic oxidation of benzyl alcohol. The superior catalytic performance of Au/RGO may be related to the presence of surface O-containing functional groups and moderate graphite character of RGO supports.

  17. Application of Molecular Imprinted Magnetic Fe3O4@SiO2 Nanoparticles for Selective Immobilization of Cellulase.

    PubMed

    Tao, Qing-Lan; Li, Yue; Shi, Ying; Liu, Rui-Jiang; Zhang, Ye-Wang; Guo, Jianyong

    2016-06-01

    Magnetic Fe3O4@SiO2 nanoparticles were prepared with molecular imprinting method using cellulase as the template. And the surface of the nanoparticles was chemically modified with arginine. The prepared nanoparticles were used as support for specific immobilization of cellulase. SDS-PAGE results indicated that the adsorption of cellulase onto the modified imprinted nanoparticles was selective. The immobilization yield and efficiency were obtained more than 70% after the optimization. Characterization of the immobilized cellulase revealed that the immobilization didn't change the optimal pH and temperature. The half-life of the immobilized cellulase was 2-fold higher than that of the free enzyme at 50 degrees C. After 7 cycles reusing, the immobilized enzyme still retained 77% of the original activity. These results suggest that the prepared imprinted nanoparticles have the potential industrial applications for the purification or immobilization of enzymes. PMID:27427671

  18. Application of Molecular Imprinted Magnetic Fe3O4@SiO2 Nanoparticles for Selective Immobilization of Cellulase.

    PubMed

    Tao, Qing-Lan; Li, Yue; Shi, Ying; Liu, Rui-Jiang; Zhang, Ye-Wang; Guo, Jianyong

    2016-06-01

    Magnetic Fe3O4@SiO2 nanoparticles were prepared with molecular imprinting method using cellulase as the template. And the surface of the nanoparticles was chemically modified with arginine. The prepared nanoparticles were used as support for specific immobilization of cellulase. SDS-PAGE results indicated that the adsorption of cellulase onto the modified imprinted nanoparticles was selective. The immobilization yield and efficiency were obtained more than 70% after the optimization. Characterization of the immobilized cellulase revealed that the immobilization didn't change the optimal pH and temperature. The half-life of the immobilized cellulase was 2-fold higher than that of the free enzyme at 50 degrees C. After 7 cycles reusing, the immobilized enzyme still retained 77% of the original activity. These results suggest that the prepared imprinted nanoparticles have the potential industrial applications for the purification or immobilization of enzymes.

  19. Covalent Immobilization of Bacillus licheniformis γ-Glutamyl Transpeptidase on Aldehyde-Functionalized Magnetic Nanoparticles

    PubMed Central

    Chen, Yi-Yu; Tsai, Ming-Gen; Chi, Meng-Chun; Wang, Tzu-Fan; Lin, Long-Liu

    2013-01-01

    This work presents the synthesis and use of surface-modified iron oxide nanoparticles for the covalent immobilization of Bacillus licheniformis γ-glutamyl transpeptidase (BlGGT). Magnetic nanoparticles were prepared by an alkaline solution of divalent and trivalent iron ions, and they were subsequently treated with 3-aminopropyltriethoxysilane (APES) to obtain the aminosilane-coated nanoparticles. The functional group on the particle surface and the amino group of BlGGT was then cross-linked using glutaraldehyde as the coupling reagent. The loading capacity of the prepared nanoparticles for BlGGT was 34.2 mg/g support, corresponding to 52.4% recovery of the initial activity. Monographs of transmission electron microscopy revealed that the synthesized nanoparticles had a mean diameter of 15.1 ± 3.7 nm, and the covalent cross-linking of the enzyme did not significantly change their particle size. Fourier transform infrared spectroscopy confirmed the immobilization of BlGGT on the magnetic nanoparticles. The chemical and kinetic behaviors of immobilized BlGGT are mostly consistent with those of the free enzyme. The immobilized enzyme could be recycled ten times with 36.2% retention of the initial activity and had a comparable stability respective to free enzyme during the storage period of 30 days. Collectively, the straightforward synthesis of aldehyde-functionalized nanoparticles and the efficiency of enzyme immobilization offer wide perspectives for the practical use of surface-bound BlGGT. PMID:23443161

  20. Synthesis of triangular Au core-Ag shell nanoparticles

    SciTech Connect

    Rai, Akhilesh; Chaudhary, Minakshi; Ahmad, Absar; Bhargava, Suresh; Sastry, Murali . E-mail: msastry@tatachemicals.com

    2007-07-03

    In this paper, we demonstrate a simple and reproducible method for the synthesis of triangular Au core-Ag shell nanoparticles. The triangular gold core is obtained by the reduction of gold ions by lemongrass extract. Utilizing the negative charge on the gold nanotriangles, silver ions are bound to their surface and thereafter reduced by ascorbic acid under alkaline conditions. The thickness of the silver shell may be modulated by varying the pH of the reaction medium. The formation of the Au core-Ag shell triangular nanostructures has been followed by UV-vis-NIR Spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurements. The sharp vertices of the triangles coupled with the core-shell structure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules.

  1. Oxidation of Chlorpromazine by Lipoxygenase Immobilized on Magnetic Fe3O4 Nanoparticles.

    PubMed

    Ding, Wenwu; Hou, Zhaosheng; Che, Zhenming; Li, Mingyuan; Chen, Xianggui; Zhang, Junqing; Zhang, Qikun

    2016-06-01

    In this work, soybean lipoxygenase enzyme was immobilized on the magnetic Fe3O4 nanoparticles to oxidate chlorpromazine (CPZ). The physicochemical properties of the nanoparticles were characterized with transmission electronic microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA), and the magnetic properties were detected by a vibrating sample magnetometer (VSM). The TEM images indicated the surface and the size of the immobilized enzyme were much rougher and thicker than those of the naked particles. The analyses of XRD patterns showed that the structure of the magnetic nanoparticles had no significant change while the nanoparticles also exhibited higher superparamagnetism at room temperature. Compared to free enzyme or the enzyme immobilized with other methods, the optimal pH, temperature and H2O2 concentration for the activity of immobilized enzyme did not have great changes, but the immobilized enzyme was more stable and less sensitive to the change of the influence factors than free counterpart. The immobilized enzyme could be recovered easily by magnetic separation and could be reused for many times in the process of CPZ oxidation. The results obtained by simulating the model of Michaelis-Menten indicated that the reaction of CPZ oxidation followed Michaelis-Menten kinetics and the enzyme still retained its affinity for CPZ while the enzyme was immobilized. PMID:27427602

  2. Reversible immobilization of BSA on Cu-chelated PAMAM dendrimer modified iron oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Demir, M.; Şenel, M.; Baykal, A.

    2014-09-01

    In this study, polyamidoamine (PAMAM) dendrimer coated superparamagnetite nanoparticles were synthesized by growing of PAMAM on amino-silane coated iron oxide nanoparticles. The PAMAM modified superparamagnetite nanoparticles were used as reversible protein immobilization host materials. During the reversible immobilization studies the effect of different metal ions such as; Cu+2, Zn+2, Co+2, Ni+2 on immobilization efficiency of BSA were evaluated. The maximum BSA adsorption capacity of the PAMAM-MNP- Cu+2 beads was observed to be 52.84 mg/g (BSA/PAMAM-MNP) at pH 7.0. Various characteristics of immobilized BSA such as; effect of generation, effect of pH, BSA concentration, temperature, salt concentration and reusability of PAMAM-MNP were evaluated.

  3. Surface modification of magnetite nanoparticles using gluconic acid and their application in immobilized lipase.

    PubMed

    Sui, Ying; Cui, Yu; Nie, Yong; Xia, Guang-Ming; Sun, Guo-Xin; Han, Jing-Tian

    2012-05-01

    Superparamagnetic magnetite nanoparticles (SMN) were surface-modified with gluconic acid (GLA) to improve their hydrophilicity and bio-affinity. Gluconic acid was successfully coated on the surface of magnetite nanoparticles and characterized using Fourier transform infrared spectroscopy (FT-IR). With water-soluble carbodiimide (EDC) as the coupling reagent, lipase was successfully immobilized onto the hydroxyl-functionalized magnetic nanoparticles. The immobilized lipase had better resistance to temperature and pH inactivation in comparison to the free form and hence widened the reaction pH and temperature range. Thermostability and storage stability of the enzyme improved upon covalent immobilization. Immobilized lipase showed higher activity after recycling when compared to the free one and could be recovered by magnetic separation.

  4. Gold surfaces and nanoparticles are protected by Au(0)-thiyl species and are destroyed when Au(I)-thiolates form.

    PubMed

    Reimers, Jeffrey R; Ford, Michael J; Halder, Arnab; Ulstrup, Jens; Hush, Noel S

    2016-03-15

    The synthetic chemistry and spectroscopy of sulfur-protected gold surfaces and nanoparticles is analyzed, indicating that the electronic structure of the interface is Au(0)-thiyl, with Au(I)-thiolates identified as high-energy excited surface states. Density-functional theory indicates that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)-thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s-d hybridization and charge polarization effects that perturbatively mix in some Au(I)-thiolate character. A simple method for quantifying these contributions is presented, revealing that a driving force for nanoparticle growth is nobleization, minimizing Au(I)-thiolate involvement. Predictions that Brust-Schiffrin reactions involve thiolate anion intermediates are verified spectroscopically, establishing a key feature needed to understand nanoparticle growth. Mixing of preprepared Au(I) and thiolate reactants always produces Au(I)-thiolate thin films or compounds rather than monolayers. Smooth links to O, Se, Te, C, and N linker chemistry are established.

  5. Phenolics impart Au(3+)-stress tolerance to cowpea by generating nanoparticles.

    PubMed

    Shabnam, Nisha; Pardha-Saradhi, P; Sharmila, P

    2014-01-01

    While evaluating impact of Au nanoparticles on seed germination and early seedling growth of cowpea, HAuCl4 was used as control. Seedlings of cowpea raised in HAuCl4, even at concentration as high as 1 mM, did not show any suppression in growth. Accordingly, Au(3+), despite being a heavy metal, did not alter levels of stress markers (viz. proline and malondialdehyde) in cowpea. Interestingly, cowpea turned clear pale yellow HAuCl4 solutions colloidal purple during the course of seed germination and seedling growth. These purple colloidal suspensions showed Au-nanoparticle specific surface plasmon resonance band in absorption spectra. Transmission electron microscopic and powder X-ray diffraction investigations confirmed presence of crystalline Au-nanoparticles in these purple suspensions. Each germinating seed of cowpea released ∼35 nmoles of GAE of phenolics and since phenolics promote generation of Au-nanoparticles, which are less/non toxic compared to Au(3+), it was contemplated that potential of cowpea to withstand Au(3+) is linked to phenolics. Of the different components of germinating seed of cowpea tested, seed coat possessed immense power to generate Au-nanoparticles, as it was the key source of phenolics. To establish role of phenolics in generation of Au-nanoparticles (i) seed coat and (ii) the incubation medium in which phenolics were released by germinating seeds, were tested for their efficacy to generate Au-nanoparticles. Interestingly, incubation of either of these components with Au(3+) triggered increase in generation of Au-nanoparticles with concomitant decrease in phenolics. Accordingly, with increase in concentration of Au(3+), a proportionate increase in generation of Au-nanoparticles and decrease in phenolics was recorded. In summary, our findings clearly established that cowpea possessed potential to withstand Au(3+)-stress as the phenolics released by seed coat of germinating seeds possess potential to reduce toxic Au(3+) to form non

  6. Rhodamine B immobilized on hollow Au-HMS material for naked-eye detection of Hg2+ in aqueous media.

    PubMed

    Zhang, Na; Li, Gang; Cheng, Zhuhong; Zuo, Xiujin

    2012-08-30

    A simple, effective method has been demonstrated to immobilize Rhodamine B (RhB) probes on mesoporous silica (Au-HMS). The prepared chemosensor (Au-HMS-Probe) was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-vis spectrum and Fourier transform infrared spectroscopy (FT-IR). Further application of Au-HMS-Probe in sensing Hg(2+) was confirmed by fluorescence titration experiment. Au-HMS-Probe afforded "turn-on" fluorescence enhancement and displayed high brightness in water, and it also showed excellent selectivity for Hg(2+) over alkali (Na(+), K(+)), alkaline earth (Mg(2+), Ca(2+)) and other heavy metal ions (Ag(+), Cd(2+), Co(2+), Pb(2+), Ni(2+), Cu(2+), Fe(2+)). Importantly, Au-HMS-Probe could be regenerated by treatment with tetrapropylammonium hydroxide solution.

  7. Solvent-induced desorption of alkanethiol ligands from Au nanoparticles.

    PubMed

    Huang, Yuanyuan; Liu, Wei; Cheng, Hao; Yao, Tao; Yang, Lina; Bao, Jie; Huang, Ting; Sun, Zhihu; Jiang, Yong; Wei, Shiqiang

    2016-06-21

    Removing surfactants from a colloidal metal nanoparticle surface is necessary for their realistic applications, and how they could be stripped is a subject of active investigation. Here, we report a solvent-induced desorption of dodecanethiol ligands from the gold nanoparticle surface, and traced this desorption process using a combination of in situ X-ray absorption fine structure (XAFS) and Raman spectroscopic techniques. In situ analysis results reveal that the solvent exchange of ethanol with tetrahydrofuran (THF) can effectively remove dodecanethiol ligands while keeping the particle morphology unchanged. Upon increasing the THF/ethanol ratio from 0 : 1 to 5 : 1, the surface coverage of thiol on the Au surface is reduced from 0.47 to 0.07, suggesting the depletion of ligands first from the nanoparticle facet sites, then from the edge sites, while the ligands at the corner sites are intact. This work enriches our knowledge on surfactant removal and may pave the way towards preparing surface-clean nanoparticles for practical applications. PMID:27241025

  8. Visible light photoactivity of TiO2 loaded with monometallic (Au or Pt) and bimetallic (Au/Pt) nanoparticles

    NASA Astrophysics Data System (ADS)

    Gołąbiewska, Anna; Lisowski, Wojciech; Jarek, Marcin; Nowaczyk, Grzegorz; Zielińska-Jurek, Anna; Zaleska, Adriana

    2014-10-01

    TiO2 modified with monometallic (Au or Pt) and bimetallic (Au/Pt) nanoparticles have been prepared using a water-in-oil microemulsion system (water/AOT/cyclohexane) followed by calcination step. The effect of metal ratio, reducing agent type (NaBH4 or N2H4), TiO2 matrix type (P-25, ST-01, TiO-5, TiO2 nanotubes or TiO2 obtained by TIP hydrolysis) as well as calcination temperature (from 350 to 650 °C) were systematically investigated. Obtained photocatalysts were characterized by UV-vis diffuse-reflectance spectroscopy (DRS), BET surface area measurements, scanning transmission microscopy (STEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity under visible light (λ > 420 nm) has been estimated in phenol degradation reaction in aqueous phase. The results showed that phenol degradation rate under visible light in the presence of TiO2 loaded with Au/Pt nanoparticles differed from 0.7 to 2.2 μmol dm-3 min-1 for samples prepared using different reducing agent. Sodium borohydride (NaBH4) favors formation of smaller Au/Pt nanoparticles and higher amount gold in Au/Pt is in the form of electronegative species (Auδ-) resulted in higher photoactivity. TiO2 obtained by TIP hydrolysis in microemulsion system seems to be the best support for Au/Pt nanoparticles from all among investigated matrix. It was also observed that enhancement of calcination temperature from 450 to 650 °C resulted in rapid drop of Au/Pt-TiO2 photoactivity under visible light due to surface area shrinkage, crystal structure change and probably change in Au/Pt nanoparticles morphology.

  9. Multifunctional hybrid Fe2O3-Au nanoparticles for efficient plasmonic heating

    DOE PAGES

    Murph, Simona E. Hunyadi; Larsen, George K.; Lascola, Robert J.

    2016-02-20

    We describe the synthesis and properties of multifunctional Fe2O3-Au nanoparticles produced by a wet chemical approach and investigate their photothermal properties using laser irradiation. Here, the composite Fe2O3-Au nanoparticles retain the properties of both materials, creating a multifunctional structure with excellent magnetic and plasmonic properties.

  10. Immobilization of Lipase by Adsorption Onto Magnetic Nanoparticles in Organic Solvents.

    PubMed

    Shi, Ying; Liu, Wei; Tao, Qing-Lan; Jiang, Xiao-Ping; Liu, Cai-Hong; Zeng, Sha; Zhang, Ye-Wang

    2016-01-01

    In order to improve the performance of lipase in organic solvents, a simple immobilization method was developed by adsorption of lipase onto Fe₃O₄@ SiO₂magnetic nanoparticles in organic solvent. Among the solvents tested, toluene was found to be the most effective solvent for the immobilization. A maximum immobilization yield of 97% and relative activity of 124% were achieved in toluene at 30 °C. The optimal temperature, enzyme loading and water activity were 30 °C, 1.25 mg/mg support and 0.48 aw, respectively. The residual activity of immobilized lipase was 67% after 10 cycles of use. The advantages of the immobilized lipase including easy recovery, high stability, and enhanced activity of immobilized lipase in organic solvents show potential industrial applications in anhydrous solvents. PMID:27398494

  11. Core-size-dependent catalytic properties of bimetallic Au/Ag core-shell nanoparticles.

    PubMed

    Haldar, Krishna Kanta; Kundu, Simanta; Patra, Amitava

    2014-12-24

    Bimetallic core-shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core-shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core-shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV-vis study confirm the formation of core-shell nanoparticles. We have examined the catalytic activity of these core-shell nanostructures in the reaction between 4-nitrophenol (4-NP) and NaBH4 to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core-shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core-shell nanoparticles, and the Au100/Ag bimetallic core-shell nanoparticle is found to be 12-fold more active than that of the pure Au nanoparticles with 100 nm diameter. Thus, the catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core-shell structure, and the rate is dependent on the size of the core of the nanoparticles.

  12. Growth of textured thin Au coatings on iron oxide nanoparticles with near infrared absorbance

    PubMed Central

    Ma, L L; Borwankar, A U; Willsey, B W; Yoon, K Y; Tam, J O; Sokolov, K V; Feldman, M D; Milner, T E; Johnston, K P

    2013-01-01

    A homologous series of Au-coated iron oxide nanoparticles, with hydrodynamic diameters smaller than 60 nm was synthesized with very low Auto-iron mass ratios as low as 0.15. The hydrodynamic diameter was determined by dynamic light scattering and the composition by atomic absorption spectroscopy and energy dispersive x-ray spectroscopy (EDS). Unusually low Au precursor supersaturation levels were utilized to nucleate and grow Au coatings on iron oxide relative to formation of pure Au nanoparticles. This approach produced unusually thin coatings, by lowering autocatalytic growth of Au on Au, as shown by transmission electron microscopy (TEM). Nearly all of the nanoparticles were attracted by a magnet indicating a minimal amount of pure Au particles The coatings were sufficiently thin to shift the surface plasmon resonance (SPR) to the near infrared (NIR), with large extinction coefficients., despite the small particle hydrodynamic diameters, observed from dynamic light scattering to be less than 60 nm. PMID:23238021

  13. Superparamagnetic silica nanoparticles with immobilized metal affinity ligands for protein adsorption

    NASA Astrophysics Data System (ADS)

    Ma, Zhiya; Guan, Yueping; Liu, Huizhou

    2006-06-01

    Superparamagnetic silica-coated magnetite (Fe 3O 4) nanoparticles with immobilized metal affinity ligands were prepared for protein adsorption. First, magnetite nanoparticles were synthesized by co-precipitating Fe 2+ and Fe 3+ in an ammonia solution. Then silica was coated on the Fe 3O 4 nanoparticles using a sol-gel method to obtain magnetic silica nanoparticles. The condensation product of 3-Glycidoxypropyltrimethoxysilane (GLYMO) and iminodiacetic acid (IDA) was immobilized on them and after charged with Cu 2+, the magnetic silica nanoparticles with immobilized Cu 2+ were applied for the adsorption of bovine serum albumin (BSA). Scanning electron micrograph showed that the magnetic silica nanoparticles with an average size of 190 nm were well dispersed without aggregation. X-ray diffraction showed the spinel structure for the magnetite particles coated with silica. Magnetic measurement revealed the magnetic silica nanoparticles were superparamagnetic and the saturation magnetization was about 15.0 emu/g. Protein adsorption results showed that the nanoparticles had high adsorption capacity for BSA (73 mg/g) and low nonspecific adsorption. The regeneration of these nanoparticles was also studied.

  14. Biomolecule-based formaldehyde resin microspheres loaded with Au nanoparticles: a novel immunoassay for detection of tumor markers in human serum.

    PubMed

    Lu, Wenbo; Qian, Chen; Bi, Liyan; Tao, Lin; Ge, Juan; Dong, Jian; Qian, Weiping

    2014-03-15

    A surfactant-free and template-free method for the high-yield synthesis of biomolecule (serotonin)-based formaldehyde resin (BFR) microspheres is proposed for the first time. The colloidal microspheres loaded with Au nanoparticles (AuNPs) prepared by a convenient in-situ synthesis of AuNPs on BFR (AuNPs/BFR) microsphere surface show good stability. AuNPs/BFR microspheres not only favor the immobilization of antibody but also facilitate the electron transfer. It is found that the resultant AuNPs/BFR microspheres can be designed to act as a sensitive label-free electrochemical immunosensor for carcinoembryonic antigen (CEA) determination. The immunosensor is prepared by immobilizing capture anti-CEA on AuNPs/BFR microspheres assembled on thionine (TH) modified glassy carbon electrode (GCE). TH acts as the redox probe. Under the optimized conditions, the linear range of the proposed immunosensor is estimated to be from 25 pg/mL to 2000 pg/mL (R=0.998) and the detection limit is estimated to be 3.5 pg/mL at a signal-to-noise ratio of 3. The prepared immunosensor for detection of CEA shows high sensitivity, reproducibility and stability. Our study demonstrates that the immunosensor can be used for the CEA detection in humans serum. PMID:24176971

  15. Biomolecule-based formaldehyde resin microspheres loaded with Au nanoparticles: a novel immunoassay for detection of tumor markers in human serum.

    PubMed

    Lu, Wenbo; Qian, Chen; Bi, Liyan; Tao, Lin; Ge, Juan; Dong, Jian; Qian, Weiping

    2014-03-15

    A surfactant-free and template-free method for the high-yield synthesis of biomolecule (serotonin)-based formaldehyde resin (BFR) microspheres is proposed for the first time. The colloidal microspheres loaded with Au nanoparticles (AuNPs) prepared by a convenient in-situ synthesis of AuNPs on BFR (AuNPs/BFR) microsphere surface show good stability. AuNPs/BFR microspheres not only favor the immobilization of antibody but also facilitate the electron transfer. It is found that the resultant AuNPs/BFR microspheres can be designed to act as a sensitive label-free electrochemical immunosensor for carcinoembryonic antigen (CEA) determination. The immunosensor is prepared by immobilizing capture anti-CEA on AuNPs/BFR microspheres assembled on thionine (TH) modified glassy carbon electrode (GCE). TH acts as the redox probe. Under the optimized conditions, the linear range of the proposed immunosensor is estimated to be from 25 pg/mL to 2000 pg/mL (R=0.998) and the detection limit is estimated to be 3.5 pg/mL at a signal-to-noise ratio of 3. The prepared immunosensor for detection of CEA shows high sensitivity, reproducibility and stability. Our study demonstrates that the immunosensor can be used for the CEA detection in humans serum.

  16. Optical properties of ion-beam-synthesized Au nanoparticles in SiO2 matrix

    NASA Astrophysics Data System (ADS)

    Hsieh, Chang-Lin; Oyoshi, Keiji; Chao, Der-Sheng; Tsai, Hsu-Sheng; Hong, Wei-Lun; Takeda, Yoshihiko; Liang, Jenq-Horng

    2016-05-01

    In recent years, gold (Au) nanoparticles have been synthesized via various methods and used in optical and biomedical detection. Au nanoparticles contain some remarkable dimension-dependent optical properties due to surface plasmon resonance (SPR) in Au nanoparticles which causes high absorption in visible light regions. Since SPR in well-crystallized Au nanoparticles can enhance the local electromagnetic field, it is thus expected that greater efficiency in the photoluminescence (PL) originating from oxygen deficiency centers (ODC) can be achieved in Au-implanted SiO2 matrix. In order to demonstrate the enhancement of PL, Au nanoparticles were formed in SiO2 film using ion beam synthesis and their optical and microstructural properties were also investigated in this study. The results revealed that a clear absorption peak at approximately 530 nm was identified in the UV-Vis spectra and was attributed to SPR induced by Au nanoparticles in SiO2. The SPR of Au nanoparticles is also dependent on thermal treatment conditions, such as post-annealing temperature and ambient. The Au nanoparticle-containing SiO2 film also displayed several distinctive peaks at approximately 320, 360, 460, and 600 nm in the PL spectra and were found to be associated with ODC-related defects and non-bridging oxygen hole centers (NBOHC) in SiO2. In addition, the PL peak intensities increased as post-annealing temperature increased, a finding contradictory to the defect recovery but highly consistent with the SPR tendency. A maximum PL emission was achieved when the Au-implanted SiO2 film was annealed at 1100 °C for 1 h under N2. Therefore, the existence of Au nanoparticles in SiO2 film can induce SPR effects as well as enhance PL emission resulting from defect-related luminescence centers.

  17. Metanephrine neuroendocrine tumor marker detection by SERS using Au nanoparticle/Au film sandwich architecture.

    PubMed

    Boca, Sanda; Farcau, Cosmin; Baia, Monica; Astilean, Simion

    2016-02-01

    Neuroendocrine tumors, such as pheochromocytoma or paraganglioma, are dangerous tumors that constitute a potential threat for a large number of patients. Currently, the biochemical diagnosis of neuroendocrine tumors is based on measurement of the direct secretory products of the adrenomedullary-sympathetic system or of their metabolites, such as catecholamines or their metanephrine derivatives, from plasma or urine. The techniques used for analysis of plasma free metanephrines, i.e. high-performance liquid chromatography or high-performance liquid chromatography coupled with mass-spectrometry are technically-demanding and time consuming, which limit their availability. Here we demonstrate a simple, fast and low-cost method for detecting metanephrine by Surface Enhanced Raman Scattering (SERS). The protocol consists in using evaporation-induced self-assembly of gold (Au) nanoparticles incubated with the analyte, on planar gold films. The assembly process produces regions with a dense distribution of both inter-particle gaps and particle-film gaps. Finite-difference time-domain simulations confirm that both kinds of gaps are locations of enhanced electromagnetic fields resulting from inter-particle and particle-film plasmonic coupling, useful for SERS amplification. Metanephrine vibrational bands assignment was performed according to density functional theory calculations. Metanephrine metabolite was detected in liquid at concentration levels lower than previously reported for other similar metabolites. The obtained results demonstrate that the Au nanoparticle/Au film exhibits noticeable SERS amplification of the adsorbed metabolite and can be used in the design of efficient, stable SERS-active substrates for the detection and identification of specific tumor markers.

  18. Metanephrine neuroendocrine tumor marker detection by SERS using Au nanoparticle/Au film sandwich architecture.

    PubMed

    Boca, Sanda; Farcau, Cosmin; Baia, Monica; Astilean, Simion

    2016-02-01

    Neuroendocrine tumors, such as pheochromocytoma or paraganglioma, are dangerous tumors that constitute a potential threat for a large number of patients. Currently, the biochemical diagnosis of neuroendocrine tumors is based on measurement of the direct secretory products of the adrenomedullary-sympathetic system or of their metabolites, such as catecholamines or their metanephrine derivatives, from plasma or urine. The techniques used for analysis of plasma free metanephrines, i.e. high-performance liquid chromatography or high-performance liquid chromatography coupled with mass-spectrometry are technically-demanding and time consuming, which limit their availability. Here we demonstrate a simple, fast and low-cost method for detecting metanephrine by Surface Enhanced Raman Scattering (SERS). The protocol consists in using evaporation-induced self-assembly of gold (Au) nanoparticles incubated with the analyte, on planar gold films. The assembly process produces regions with a dense distribution of both inter-particle gaps and particle-film gaps. Finite-difference time-domain simulations confirm that both kinds of gaps are locations of enhanced electromagnetic fields resulting from inter-particle and particle-film plasmonic coupling, useful for SERS amplification. Metanephrine vibrational bands assignment was performed according to density functional theory calculations. Metanephrine metabolite was detected in liquid at concentration levels lower than previously reported for other similar metabolites. The obtained results demonstrate that the Au nanoparticle/Au film exhibits noticeable SERS amplification of the adsorbed metabolite and can be used in the design of efficient, stable SERS-active substrates for the detection and identification of specific tumor markers. PMID:26820563

  19. The on-bead digestion of protein corona on nanoparticles by trypsin immobilized on the magnetic nanoparticle.

    PubMed

    Hu, Zhengyan; Zhao, Liang; Zhang, Hongyan; Zhang, Yi; Wu, Ren'an; Zou, Hanfa

    2014-03-21

    Proteins interacting with nanoparticles would form the protein coronas on the surface of nanoparticles in biological systems, which would critically impact the biological identities of nanoparticles and/or result in the physiological and pathological consequences. The enzymatic digestion of protein corona was the primary step to achieve the identification of protein components of the protein corona for the bottom-up proteomic approaches. In this study, the investigation on the tryptic digestion of protein corona by the immobilized trypsin on a magnetic nanoparticle was carried out for the first time. As a comparison with the usual overnight long-time digestion and the severe self-digestion of free trypsin, the on-bead digestion of protein corona by the immobilized trypsin could be accomplished within 1h, along with the significantly reduced self-digestion of trypsin and the improved reproducibility on the identification of proteins by the mass spectrometry-based proteomic approach. It showed that the number of identified bovine serum (BS) proteins on the commercial Fe3O4 nanoparticles was increased by 13% for the immobilized trypsin with 1h digestion as compared to that of using free trypsin with even overnight digestion. In addition, the on-bead digestion of using the immobilized trypsin was further applied on the identification of human plasma protein corona on the commercial Fe3O4 nanoparticles, which leads the efficient digestion of the human plasma proteins and the identification of 149 human plasma proteins corresponding to putative critical pathways and biological processes.

  20. Heterostructured Au/Pd-M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

    NASA Astrophysics Data System (ADS)

    Lutz, Patrick S.; Bae, In-Tae; Maye, Mathew M.

    2015-09-01

    The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had high activity attributed to the porous nature of the platinum domains.The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had

  1. Highly efficient antibody immobilization with multimeric protein Gs coupled magnetic silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Lee, J. H.; Choi, H. K.; Chang, J. H.

    2011-10-01

    This work reports the immobilization of monomeric, dimeric and trimer protein Gs onto silica magnetic nanoparticles for self-oriented antibody immobilization. To achieve this, we initially prepared the silica-coated magnetic nanoparticle having about 170 nm diameters. The surface of the silica coated magnetic nanoparticles was modified with 3- aminopropyl-trimethoxysilane (APTMS) to chemically link to multimeric protein Gs. The conjugation of amino groups on the SiO2-MNPs to cysteine tagged in multimeric protein Gs was performed using a sulfo-SMCC coupling procedure. The binding efficiencies of monomer, dimer and trimer were 77 %, 67 % and 55 % respectively. However, the efficiencies of antibody immobilization were 70 %, 83 % and 95 % for monomeric, dimeric and trimeric protein G, respectively. To prove the enhancement of accessibility by using multimeric protein G, FITC labeled goat-anti-mouse IgG was treated to mouse IgG immobilized magnetic silica nanoparticles through multimeric protein G. FITC labeled goat anti-mouse IgGs were more easily bound to mouse IgG immobilized by trimeric protein G than others. Finally protein G bound silica magnetic nanoparticles were utilized to develop highly sensitive immunoassay to detect hepatitis B antigen.

  2. Immobilized protease on the magnetic nanoparticles used for the hydrolysis of rapeseed meals

    NASA Astrophysics Data System (ADS)

    Jin, Xin; Li, Ju-Fang; Huang, Ping-Ying; Dong, Xu-Yan; Guo, Lu-Lu; Yang, Liang; Cao, Yuan-Cheng; Wei, Fang; Zhao, Yuan-Di; Chen, Hong

    2010-07-01

    (3-aminopropl) triethoxysilaneand modified magnetic nanoparticles with the average diameter of 25.4 nm were synthesized in water-phase co-precipitation method. And then these nanoparticles were covalently coupled with alkaline protease as enzyme carrier by using 1,4-phenylene diisothlocyanate as coupling agent. Experiments showed that the immobilized protease can keep the catalytic bioactivity, which can reach to 47.8% when casein was served as substrate. Results showed that the catalytic activity of immobilized protease on these magnetic nanoparticles could retain 98.63±2.37% after 60 days. And it is more stable than the free protease during the shelf-life test. The enzyme reaction conditions such as optimum reaction temperature and pH are the same as free protease. Furthermore, mix-and-separate experiments showed that the immobilized protease could be recycled through the magnetic nanoparticles after the biocatalysis process. When the rapeseed meals were used as substrate, the degree of hydrolysis of immobilized alkaline protease achieved 9.86%, while it was 10.41% for the free protease. The macromolecular proteins of rapeseed meals were hydrolyzed by immobilized protease into small molecules such as polypeptides or amino acids. Thus, a novel efficient and economic way for the recycling of enzymes in the application of continuous production of active peptides was provided based on these magnetic nanoparticles.

  3. Facile and high-efficient immobilization of histidine-tagged multimeric protein G on magnetic nanoparticles

    PubMed Central

    2014-01-01

    This work reports the high-efficient and one-step immobilization of multimeric protein G on magnetic nanoparticles. The histidine-tagged (His-tag) recombinant multimeric protein G was overexpressed in Escherichia coli BL21 by the repeated linking of protein G monomers with a flexible linker. High-efficient immobilization on magnetic nanoparticles was demonstrated by two different preparation methods through the amino-silane and chloro-silane functionalization on silica-coated magnetic nanoparticles. Three kinds of multimeric protein G such as His-tag monomer, dimer, and trimer were tested for immobilization efficiency. For these tests, bicinchoninic acid (BCA) assay was employed to determine the amount of immobilized His-tag multimeric protein G. The result showed that the immobilization efficiency of the His-tag multimeric protein G of the monomer, dimer, and trimer was increased with the use of chloro-silane-functionalized magnetic nanoparticles in the range of 98% to 99%, rather than the use of amino-silane-functionalized magnetic nanoparticles in the range of 55% to 77%, respectively. PMID:25593554

  4. Design and Preparation of Supported Au Catalyst with Enhanced Catalytic Activities by Rationally Positioning Au Nanoparticles on Anatase.

    PubMed

    Wang, Liang; Wang, Hong; Rice, Andrew E; Zhang, Wei; Li, Xiaokun; Chen, Mingshu; Meng, Xiangju; Lewis, James P; Xiao, Feng-Shou

    2015-06-18

    A synergistic effect between individual components is crucial for increasing the activity of metal/metal oxide catalysts. The greatest challenge is how to control the synergistic effect to obtain enhanced catalytic performance. Through density functional theory calculations of model Au/TiO2 catalysts, it is suggested that there is strong interaction between Au nanoparticles and Ti species at the edge/corner sites of anatase, which is favorable for the formation of stable oxygen vacancies. Motivated by this theoretical analysis, we have rationally prepared Au nanoparticles attached to edge/corner sites of anatase support (Au/TiO2-EC), confirmed by their HR-TEM images. As expected, this strong interaction is well characterized by Raman, UV-visible, and XPS techniques. Very interestingly, compared with conventional Au catalysts, Au/TiO2-EC exhibits superior catalytic activity in the oxidations using O2. Our approach to controlling Au nanoparticle positioning on anatase to obtain enhanced catalytic activity offers an efficient strategy for developing more novel supported metal catalysts.

  5. Design and Preparation of Supported Au Catalyst with Enhanced Catalytic Activities by Rationally Positioning Au Nanoparticles on Anatase.

    PubMed

    Wang, Liang; Wang, Hong; Rice, Andrew E; Zhang, Wei; Li, Xiaokun; Chen, Mingshu; Meng, Xiangju; Lewis, James P; Xiao, Feng-Shou

    2015-06-18

    A synergistic effect between individual components is crucial for increasing the activity of metal/metal oxide catalysts. The greatest challenge is how to control the synergistic effect to obtain enhanced catalytic performance. Through density functional theory calculations of model Au/TiO2 catalysts, it is suggested that there is strong interaction between Au nanoparticles and Ti species at the edge/corner sites of anatase, which is favorable for the formation of stable oxygen vacancies. Motivated by this theoretical analysis, we have rationally prepared Au nanoparticles attached to edge/corner sites of anatase support (Au/TiO2-EC), confirmed by their HR-TEM images. As expected, this strong interaction is well characterized by Raman, UV-visible, and XPS techniques. Very interestingly, compared with conventional Au catalysts, Au/TiO2-EC exhibits superior catalytic activity in the oxidations using O2. Our approach to controlling Au nanoparticle positioning on anatase to obtain enhanced catalytic activity offers an efficient strategy for developing more novel supported metal catalysts. PMID:26266615

  6. Control of the spatial distribution and crystal orientation of self-organized Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Yasukawa, Yukiko; Liu, Xiaoxi; Shirsath, Sagar E.; Suematsu, Hisayuki; Kotaki, Yukio; Nemoto, Yoshihiro; Takeguchi, Masaki; Morisako, Akimitsu

    2016-09-01

    Ordered, two-dimensional, self-organized Au nanoparticles were fabricated using radiofrequency (RF) magnetron sputtering. The particles were uniformly spherical in shape and ultrafine in size (3-7 nm) and showed an ultrahigh density in the order of ˜1012 inch-2. A custom-developed sputtering apparatus that employs low sputtering power density and a minimized sputtering time (1 min) was used to markedly simplify the preparation conditions for Au nanoparticle fabrication. The spatial distribution of Au nanoparticles was rigorously controlled by placing a Ta interfacial layer between the Au nanoparticles and substrate as well as by post-annealing samples in an Ar atmosphere after the formation of Au nanoparticles. The interfacial layer and the post-annealing step caused approximately 40% of the Au nanoparticles on the substrate surface to orient in the (111) direction. This method was shown to produce ultrafine Au nanoparticles showing an ultrahigh surface density. The crystal orientation of the nanoparticles can be precisely controlled with respect to the substrate surface. Therefore, this technique promises to deliver tunable nanostructures for applications in the field of high-performance electronic devices.

  7. Control of the spatial distribution and crystal orientation of self-organized Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Yasukawa, Yukiko; Liu, Xiaoxi; Shirsath, Sagar E.; Suematsu, Hisayuki; Kotaki, Yukio; Nemoto, Yoshihiro; Takeguchi, Masaki; Morisako, Akimitsu

    2016-09-01

    Ordered, two-dimensional, self-organized Au nanoparticles were fabricated using radiofrequency (RF) magnetron sputtering. The particles were uniformly spherical in shape and ultrafine in size (3–7 nm) and showed an ultrahigh density in the order of ∼1012 inch–2. A custom-developed sputtering apparatus that employs low sputtering power density and a minimized sputtering time (1 min) was used to markedly simplify the preparation conditions for Au nanoparticle fabrication. The spatial distribution of Au nanoparticles was rigorously controlled by placing a Ta interfacial layer between the Au nanoparticles and substrate as well as by post-annealing samples in an Ar atmosphere after the formation of Au nanoparticles. The interfacial layer and the post-annealing step caused approximately 40% of the Au nanoparticles on the substrate surface to orient in the (111) direction. This method was shown to produce ultrafine Au nanoparticles showing an ultrahigh surface density. The crystal orientation of the nanoparticles can be precisely controlled with respect to the substrate surface. Therefore, this technique promises to deliver tunable nanostructures for applications in the field of high-performance electronic devices.

  8. Asymmetric photoelectric property of transparent TiO2 nanotube films loaded with Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Liang, Wei; Liu, Yiming; Zhang, Wanggang; Zhou, Diaoyu; Wen, Jing

    2016-11-01

    Semitransparent composite films of Au loaded TiO2 nanotubes (TNT-Au) were prepared by sputtering Au nanoparticles on highly transparent TiO2 nanotubes films, which were fabricated directly on FTO glasses by anodizing the Ti film sputtered on the FTO glasses. Compared with pure TNT films, the prepared TNT-Au films possessed excellent absorption ability and high photocurrent response and improved photocatalytic activity under visible-light irradiation. It could be concluded that Au nanoparticles played important roles in improving the photoelectrochemical performance of TNT-Au films. Moreover, in this work, both sides of TNT-Au films were researched and compared owing to theirs semitransparency. It was firstly found that the photoelectric activity of TNT-Au composite films with back-side illumination was obviously superior to front-side illumination.

  9. Improvement of thermal stability of polypropylene using DOPO-immobilized silica nanoparticles

    PubMed Central

    Dong, Quanxiao; Ding, Yanfen; Wen, Bin; Wang, Feng; Dong, Huicong; Zhang, Shimin

    2014-01-01

    After the surface silylation with 3-methacryloxypropyltrimethoxysilane, silica nanoparticles were further modified by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The immobilization of DOPO on silica nanoparticles was confirmed by Fourier transform infrared spectroscopy, UV–visible spectroscopy, magic angle spinning nuclear magnetic resonance, and thermogravimetric analysis. By incorporating the DOPO-immobilized silica nanoparticles (5 wt%) into polypropylene matrix, the thermal oxidative stability exhibited an improvement of 62 °C for the half weight loss temperature, while that was only 26 °C increment with incorporation of virgin silica nanoparticles (5 wt%). Apparent activation energies of the polymer nanocomposites were estimated via Flynn–Wall–Ozawa method. It was found that the incorporation of DOPO-immobilized silica nanoparticles improved activation energies of the degradation reaction. Based on the results, it was speculated that DOPO-immobilized silica nanoparticles could inhibit the degradation of polypropylene and catalyze the formation of carbonaceous char on the surface. Thus, thermal stability was significantly improved. PMID:24729654

  10. A novel electrochemical sensor based on magneto Au nanoparticles/carbon paste electrode for voltammetric determination of acetaminophen in real samples.

    PubMed

    Haghshenas, Esmaeel; Madrakian, Tayyebeh; Afkhami, Abbas

    2015-12-01

    An electrochemical magneto Au nanoparticles/carbon paste electrodes (MAuNP/CPE) which is used for the determination of acetaminophen (AC) in real samples was developed. Initially, Au nanoparticles were immobilized at the surface of Fe3O4 (AuNPs@Fe3O4), which was used as a sorbent for capturing AC molecules. After adding AuNPs@Fe3O4 to the AC solution and stirring for 20 min, the AuNPs@Fe3O4 was gathered on the magneto electrode based on its magnetic field. The AC molecules which became adsorbed at AuNPs@Fe3O4 were analyzed by differential pulse voltammetry (DPV). For characterization and investigation of the performance of AuNPs@Fe3O4 and MAuNPs/CPE, various methods, including scanning electron microscopy, X-ray diffraction, UV-Vis spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and DPV were used. Under the optimized conditions, the anodic peak current was linear to the concentration of AC in the range of 0.1 to 70.0μmol L(-1) with the detection limit of 4.5×10(-2)μmol L(-1). This method was also successfully used to detect the concentration of AC in pharmaceutical formulations and human serum samples. In addition, the proposed magneto sensor exhibited good reproducibility, long-term stability and fast current response. PMID:26354256

  11. A novel electrochemical sensor based on magneto Au nanoparticles/carbon paste electrode for voltammetric determination of acetaminophen in real samples.

    PubMed

    Haghshenas, Esmaeel; Madrakian, Tayyebeh; Afkhami, Abbas

    2015-12-01

    An electrochemical magneto Au nanoparticles/carbon paste electrodes (MAuNP/CPE) which is used for the determination of acetaminophen (AC) in real samples was developed. Initially, Au nanoparticles were immobilized at the surface of Fe3O4 (AuNPs@Fe3O4), which was used as a sorbent for capturing AC molecules. After adding AuNPs@Fe3O4 to the AC solution and stirring for 20 min, the AuNPs@Fe3O4 was gathered on the magneto electrode based on its magnetic field. The AC molecules which became adsorbed at AuNPs@Fe3O4 were analyzed by differential pulse voltammetry (DPV). For characterization and investigation of the performance of AuNPs@Fe3O4 and MAuNPs/CPE, various methods, including scanning electron microscopy, X-ray diffraction, UV-Vis spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and DPV were used. Under the optimized conditions, the anodic peak current was linear to the concentration of AC in the range of 0.1 to 70.0μmol L(-1) with the detection limit of 4.5×10(-2)μmol L(-1). This method was also successfully used to detect the concentration of AC in pharmaceutical formulations and human serum samples. In addition, the proposed magneto sensor exhibited good reproducibility, long-term stability and fast current response.

  12. Thermal stability of bimetallic Au/Fe nanoparticles in silica matrix

    SciTech Connect

    Pannu, Compesh Singh, Udai B. Hooda, Sonu Kabiraj, D. Avasthi, D. K.

    2014-04-24

    Thin silica film containing Au and Fe bimetallic nanoparticles were prepared by atom beam cosputtering. The samples were annealed at different temperatures from 400 to 800° C to study the thermal stability of bimetallic nanoparticles using X ray diffraction. It is observed that at 800° C strong structural rearrangement took place leading to thermal decomposition of bimetallic nanoparticles.

  13. Nanoscale mapping of plasmon and exciton in ZnO tetrapods coupled with Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Bertoni, Giovanni; Fabbri, Filippo; Villani, Marco; Lazzarini, Laura; Turner, Stuart; van Tendeloo, Gustaaf; Calestani, Davide; Gradečak, Silvija; Zappettini, Andrea; Salviati, Giancarlo

    2016-01-01

    Metallic nanoparticles can be used to enhance optical absorption or emission in semiconductors, thanks to a strong interaction of collective excitations of free charges (plasmons) with electromagnetic fields. Herein we present direct imaging at the nanoscale of plasmon-exciton coupling in Au/ZnO nanostructures by combining scanning transmission electron energy loss and cathodoluminescence spectroscopy and mapping. The Au nanoparticles (~30 nm in diameter) are grown in-situ on ZnO nanotetrapods by means of a photochemical process without the need of binding agents or capping molecules, resulting in clean interfaces. Interestingly, the Au plasmon resonance is localized at the Au/vacuum interface, rather than presenting an isotropic distribution around the nanoparticle. On the contrary, a localization of the ZnO signal has been observed inside the Au nanoparticle, as also confirmed by numerical simulations.

  14. Nanoscale mapping of plasmon and exciton in ZnO tetrapods coupled with Au nanoparticles.

    PubMed

    Bertoni, Giovanni; Fabbri, Filippo; Villani, Marco; Lazzarini, Laura; Turner, Stuart; Van Tendeloo, Gustaaf; Calestani, Davide; Gradečak, Silvija; Zappettini, Andrea; Salviati, Giancarlo

    2016-01-01

    Metallic nanoparticles can be used to enhance optical absorption or emission in semiconductors, thanks to a strong interaction of collective excitations of free charges (plasmons) with electromagnetic fields. Herein we present direct imaging at the nanoscale of plasmon-exciton coupling in Au/ZnO nanostructures by combining scanning transmission electron energy loss and cathodoluminescence spectroscopy and mapping. The Au nanoparticles (~30 nm in diameter) are grown in-situ on ZnO nanotetrapods by means of a photochemical process without the need of binding agents or capping molecules, resulting in clean interfaces. Interestingly, the Au plasmon resonance is localized at the Au/vacuum interface, rather than presenting an isotropic distribution around the nanoparticle. On the contrary, a localization of the ZnO signal has been observed inside the Au nanoparticle, as also confirmed by numerical simulations. PMID:26754789

  15. Nanoscale mapping of plasmon and exciton in ZnO tetrapods coupled with Au nanoparticles

    PubMed Central

    Bertoni, Giovanni; Fabbri, Filippo; Villani, Marco; Lazzarini, Laura; Turner, Stuart; Van Tendeloo, Gustaaf; Calestani, Davide; Gradečak, Silvija; Zappettini, Andrea; Salviati, Giancarlo

    2016-01-01

    Metallic nanoparticles can be used to enhance optical absorption or emission in semiconductors, thanks to a strong interaction of collective excitations of free charges (plasmons) with electromagnetic fields. Herein we present direct imaging at the nanoscale of plasmon-exciton coupling in Au/ZnO nanostructures by combining scanning transmission electron energy loss and cathodoluminescence spectroscopy and mapping. The Au nanoparticles (~30 nm in diameter) are grown in-situ on ZnO nanotetrapods by means of a photochemical process without the need of binding agents or capping molecules, resulting in clean interfaces. Interestingly, the Au plasmon resonance is localized at the Au/vacuum interface, rather than presenting an isotropic distribution around the nanoparticle. On the contrary, a localization of the ZnO signal has been observed inside the Au nanoparticle, as also confirmed by numerical simulations. PMID:26754789

  16. Nanoscale mapping of plasmon and exciton in ZnO tetrapods coupled with Au nanoparticles

    DOE PAGES

    Bertoni, Giovanni; Fabbri, Filippo; Villani, Marco; Lazzarini, Laura; Turner, Stuart; Van Tendeloo, Gustaaf; Calestani, Davide; Gradečak, Silvija; Zappettini, Andrea; Salviati, Giancarlo

    2016-01-12

    Metallic nanoparticles can be used to enhance optical absorption or emission in semiconductors, thanks to a strong interaction of collective excitations of free charges (plasmons) with electromagnetic fields. Herein we present direct imaging at the nanoscale of plasmon-exciton coupling in Au/ZnO nanostructures by combining scanning transmission electron energy loss and cathodoluminescence spectroscopy and mapping. The Au nanoparticles (~30 nm in diameter) are grown in-situ on ZnO nanotetrapods by means of a photochemical process without the need of binding agents or capping molecules, resulting in clean interfaces. Interestingly, the Au plasmon resonance is localized at the Au/vacuum interface, rather than presentingmore » an isotropic distribution around the nanoparticle. Moreover, on the contrary, a localization of the ZnO signal has been observed inside the Au nanoparticle, as also confirmed by numerical simulations.« less

  17. Modification of TiO2 by Bimetallic Au-Cu Nanoparticles for Wastewater Treatment

    PubMed Central

    Hai, Zibin; Kolli, Nadia EL; Uribe, Daniel Bahena; Beaunier, Patricia; José-Yacaman, Miguel; Vigneron, Jackie; Etcheberry, Arnaud; Sorgues, Sébastien; Colbeau-Justin, Christophe; Chen, Jiafu; Remita, Hynd

    2016-01-01

    Au, Cu and bimetallic Au-Cu nanoparticles were synthesized on the surface of commercial TiO2 compounds (P25) by reduction of the metal precursors with tetrakis (hydroxymethyl) phosphonium chloride (THPC) (0.5 % in weight). The alloyed structure of Au-Cu NPs was confirmed by HAADF-STEM, EDS, HRTEM and XPS techniques. The photocatalytic properties of the modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV-visible irradiation. The modification by the metal nanoparticles induces an increase in the photocatalytic activity. The highest photocatalytic activity is obtained with Au-Cu/TiO2 (Au/Cu 1:3). Their electronic properties have been studied by time resolved microwave conductivity (TRMC) to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification with Au, Cu and Au-Cu nanoparticles plays a role in charge-carrier separations increasing the activity under UV-light. Indeed, the metal nanoparticles act as a sink for electron, decreasing the charge carrier recombination. The TRMC measurements show also that the bimetallic Au-Cu nanoparticles are more efficient in electron scavenging than the monometallic Au and Cu ones. PMID:27274844

  18. Rationalization of Au concentration and distribution in AuNi@Pt core-shell nanoparticles for oxygen reduction reaction

    SciTech Connect

    An, Wei; Liu, Ping

    2015-09-18

    Improving the activity and stability of Pt-based core–shell nanocatalysts for proton exchange membrane fuel cells while lowering Pt loading has been one of the big challenges in electrocatalysis. Here, using density functional theory, we report the effect of adding Au as the third element to enhance the durability and activity of Ni@Pt core–shell nanoparticles (NPs) during the oxygen reduction reaction (ORR). Our results show that the durability and activity of a Ni@Pt NP can be finely tuned by controlling Au concentration and distribution. For a NiAu@Pt NP, the durability can be greatly promoted by thermodynamically favorable segregation of Au to replace the Pt atoms at vertex, edge, and (100) facets on the shell, while still keeping the ORR activity on the active Pt(111) shell as high as that of Ni@Pt nanoparticles. Such behavior strongly depends on a direct interaction with the Ni interlayer. The results not only highlight the importance of interplay between surface strain on the shell and the interlayer–shell interaction in determining the durability and activity but also provide guidance on how to maximize the usage of Au to optimize the performance of core–shell (Pt) nanoparticles. As a result, such understanding has allowed us to discover a novel NiAu@Pt nanocatalyst for the ORR.

  19. Rationalization of Au concentration and distribution in AuNi@Pt core-shell nanoparticles for oxygen reduction reaction

    DOE PAGES

    An, Wei; Liu, Ping

    2015-09-18

    Improving the activity and stability of Pt-based core–shell nanocatalysts for proton exchange membrane fuel cells while lowering Pt loading has been one of the big challenges in electrocatalysis. Here, using density functional theory, we report the effect of adding Au as the third element to enhance the durability and activity of Ni@Pt core–shell nanoparticles (NPs) during the oxygen reduction reaction (ORR). Our results show that the durability and activity of a Ni@Pt NP can be finely tuned by controlling Au concentration and distribution. For a NiAu@Pt NP, the durability can be greatly promoted by thermodynamically favorable segregation of Au tomore » replace the Pt atoms at vertex, edge, and (100) facets on the shell, while still keeping the ORR activity on the active Pt(111) shell as high as that of Ni@Pt nanoparticles. Such behavior strongly depends on a direct interaction with the Ni interlayer. The results not only highlight the importance of interplay between surface strain on the shell and the interlayer–shell interaction in determining the durability and activity but also provide guidance on how to maximize the usage of Au to optimize the performance of core–shell (Pt) nanoparticles. As a result, such understanding has allowed us to discover a novel NiAu@Pt nanocatalyst for the ORR.« less

  20. Plasmonic interactions and optical forces between Au bypyramidal nanoparticle dimers.

    SciTech Connect

    Nome, R. A.; Guffey, M. J.; Scherer, N. F.; Gray, S. K.; Univ. of Chicago

    2009-04-23

    Interparticle forces that can be driven by applied (optical) fields could lead to the formation of new particle arrangements when assembled in arrays. Furthermore, the potentially large interactions and large local fields associated with plasmon excitations in anisotropic nanoparticles can lead to enhanced nonlinear responses and applications for sensing. These and other applications would benefit from simulations of spectra and forces arising from plasmonic interactions. We present the results of rigorous three-dimensional, finite-difference, time-domain calculations of near- and far-field properties of pairs of Au bipyramidal nanoparticles in three different configurations: side-by-side, head-to-tail, and face-on. The absorption and scattering spectra depend strongly on the geometry as well as on the interparticle separation, as intuitively expected from a dipole coupling picture. Bipyramidal dimers in head-to-tail and face-on geometries exhibit an increasingly red-shifted (longitudinal) plasmon resonance with decreasing separation, whereas side-by-side dimers exhibit a blue shift. Large resonant field enhancements at the gap between particles in a head-to-tail configuration indicate the strong coupling of plasmonic modes. The Maxwell stress tensor formalism is employed to calculate the optical force one particle exerts on the other. Both significant attraction and weak repulsion can be obtained, depending on the relative arrangement of the particles. The force between bipyramids in the head-to-tail configuration can be greater than 10 times the force between pairs of Au nanospheres with the same volume. Experimental linear scattering spectra of particles trapped using the plasmon-resonance-based optical trapping method are found to be consistent with two particles trapped in the side-by-side configuration.

  1. Antimicrobial Properties of Lysosomal Enzymes Immobilized on NH₂Functionalized Silica-Encapsulated Magnetite Nanoparticles.

    PubMed

    Bang, Seung Hyuck; Sekhon, Simranjeet Singh; Cho, Sung-Jin; Kim, So Jeong; Le, Thai-Hoang; Kim, Pil; Ahn, Ji-Young; Kim, Yang-Hoon; Min, Jiho

    2016-01-01

    The immobilization efficiency, antimicrobial activity and recovery of lysosomal enzymes on NH2 functionalized magnetite nanoparticles have been studied under various conditions. The immobi- lization efficiency depends upon the ratio of the amount of enzyme and magnetite and it shows an increase with magnetite concentration which is due to the presence of amine group at the magnetite surface that leads to a strong attraction. The optimized reaction time to immobilize the lysosomal enzymes on magnetite was determined by using a rolling method. The immobilization efficiency increases with reaction time and reached a plateau after 5 minutes and then remained constant for 10 minutes. However, after 30 minutes the immobilization efficiency decreased to 85%, which is due to the weaker electrostatic interactions between magnetite and detached lysosomal enzymes. The recovery and stability of immobilized lysosomal enzymes has also been studied. The antimicrobial activity was almost 100% but it decreased upon reuse and no activity was observed after its reuse for seven times. The storage stability of lysosomal enzymes as an antimicrobial agent was about 88%, which decreased to 53% after one day and all activity of immobilized lysosomal enzymes was maintained after five days. Thus, the lysosomal enzymes immobilized on magnetite nanoparticles could potentially be used as antimicrobial agents to remove bacteria. PMID:27398573

  2. Antimicrobial Properties of Lysosomal Enzymes Immobilized on NH₂Functionalized Silica-Encapsulated Magnetite Nanoparticles.

    PubMed

    Bang, Seung Hyuck; Sekhon, Simranjeet Singh; Cho, Sung-Jin; Kim, So Jeong; Le, Thai-Hoang; Kim, Pil; Ahn, Ji-Young; Kim, Yang-Hoon; Min, Jiho

    2016-01-01

    The immobilization efficiency, antimicrobial activity and recovery of lysosomal enzymes on NH2 functionalized magnetite nanoparticles have been studied under various conditions. The immobi- lization efficiency depends upon the ratio of the amount of enzyme and magnetite and it shows an increase with magnetite concentration which is due to the presence of amine group at the magnetite surface that leads to a strong attraction. The optimized reaction time to immobilize the lysosomal enzymes on magnetite was determined by using a rolling method. The immobilization efficiency increases with reaction time and reached a plateau after 5 minutes and then remained constant for 10 minutes. However, after 30 minutes the immobilization efficiency decreased to 85%, which is due to the weaker electrostatic interactions between magnetite and detached lysosomal enzymes. The recovery and stability of immobilized lysosomal enzymes has also been studied. The antimicrobial activity was almost 100% but it decreased upon reuse and no activity was observed after its reuse for seven times. The storage stability of lysosomal enzymes as an antimicrobial agent was about 88%, which decreased to 53% after one day and all activity of immobilized lysosomal enzymes was maintained after five days. Thus, the lysosomal enzymes immobilized on magnetite nanoparticles could potentially be used as antimicrobial agents to remove bacteria.

  3. Synthesis and optical properties of Au decorated colloidal tungsten oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Tahmasebi, Nemat; Mahdavi, Seyed Mohammad

    2015-11-01

    In this study, colloidal tungsten oxide nanoparticles were fabricated by pulsed laser ablation of tungsten target using the first harmonic of a Nd:YAG laser (1064 nm) in deionized water. After ablation, a 0.33 g/lit HAuCl4 aqueous solution was added into as-prepared colloidal nanoparticles. In this process, Au3+ ions were reduced to decorate gold metallic state (Au0) onto colloidal tungsten oxide nanoparticles surface. The morphology and chemical composition of the synthesized nanoparticles were studied by AFM, XRD, TEM and XPS techniques. UV-Vis analysis reveals a distinct absorption peak at ∼530 nm. This peak can be attributed to the surface plasmon resonance (SPR) of Au and confirms formation of gold state. Moreover, X-ray photoelectron spectroscopy reveals that Au ions' reduction happens after adding HAuCl4 solution into as-prepared colloidal tungsten oxide nanoparticles. Transmission electron microscope shows that an Au shell has been decorated onto colloidal WO3 nanoparticles. Noble metal decorated tungsten oxide nanostructure could be an excellent candidate for photocatalysis, gas sensing and gasochromic applications. Finally, the gasochromic behavior of the synthesized samples was investigated by H2 and O2 gases bubbling into the produced colloidal Au/WO3 nanoparticles. Synthesized colloidal nanoparticles show excellent coloration contrast (∼80%) through NIR spectra.

  4. Preparation and application of polymer-grafted magnetic nanoparticles for lipase immobilization

    NASA Astrophysics Data System (ADS)

    Yong, Yang; Bai, Yongxiao; Li, Yanfeng; Lin, Lei; Cui, Yanjun; Xia, Chungu

    Functionalized superparamagnetic particles were prepared by graft polymerization of glycidyl methacrylate and methacryloxyethyl trimethyl ammonium chloride onto the surface of modified-Fe 3O 4 nanoparticles. The resultant particles were characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometry. The results indicate that the polymer chains had been effectively grafted onto the surface of Fe 3O 4 nanoparticles. The functionalized particles remained dispersive and superparamagnetic. Lipase was immobilized on the magnetic particles under mild conditions by electrostatic adsorption and covalent binding with the activity recovery up to 70.4%. The immobilized lipase had better thermal stability compared to free lipase.

  5. Bioelectrochemistry of non-covalent immobilized alcohol dehydrogenase on oxidized diamond nanoparticles.

    PubMed

    Nicolau, Eduardo; Méndez, Jessica; Fonseca, José J; Griebenow, Kai; Cabrera, Carlos R

    2012-06-01

    Diamond nanoparticles are considered a biocompatible material mainly due to their non-cytotoxicity and remarkable cellular uptake. Model proteins such as cytochrome c and lysozyme have been physically adsorbed onto diamond nanoparticles, proving it to be a suitable surface for high protein loading. Herein, we explore the non-covalent immobilization of the redox enzyme alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae (E.C.1.1.1.1) onto oxidized diamond nanoparticles for bioelectrochemical applications. Diamond nanoparticles were first oxidized and physically characterized by X-ray diffraction (XRD), FT-IR and TEM. Langmuir isotherms were constructed to investigate the ADH adsorption onto the diamond nanoparticles as a function of pH. It was found that a higher packing density is achieved at the isoelectric point of the enzyme. Moreover, the relative activity of the immobilized enzyme on diamond nanoparticles was addressed under optimum pH conditions able to retain up to 70% of its initial activity. Thereafter, an ethanol bioelectrochemical cell was constructed by employing the immobilized alcohol dehydrogenase onto diamond nanoparticles, this being able to provide a current increment of 72% when compared to the blank solution. The results of this investigation suggest that this technology may be useful for the construction of alcohol biosensors or biofuel cells in the near future.

  6. Facile synthesis of PtAu alloy nanoparticles with high activity for formic acid oxidation

    SciTech Connect

    Zhang, Sheng; Shao, Yuyan; Yin, Geping; Lin, Yuehe

    2010-02-15

    We report the facile synthesis of carbon supported PtAu alloy nanoparticles with high electrocatalytic activity as the anode catalyst for direct formic acid fuel cells (DFAFCs). PtAu alloy nanopaticles are synthesized by co-reducing HAuCl4 and H2PtCl6 with NaBH4 in the presence of sodium citrate and then the nanoparticles are deposited on Vulcan XC-72R carbon support (PtAu/C). The obtained catalysts are characterized with X-ray diffraction (XRD) and transmission electron microscope (TEM), which reveal PtAu alloy formation with an average diameter of 4.6 nm. PtAu/C exhibits 8 times higher catalytic activity toward formic acid oxidation than Pt/C. The enhanced activity of PtAu/C catalyst is attributed to noncontinuous Pt sites formed in the presence of the neighbored Au sites, which promotes direct oxidation of formic acid by avoiding poison CO.

  7. Au nanoparticles on graphitic petal arrays for surface-enhanced Raman spectroscopy

    SciTech Connect

    Rout, Chandra Sekhar; Kumar, Anurag; Xiong Guoping; Fisher, Timothy S.; Irudayaraj, Joseph

    2010-09-27

    We report a unique substrate for surface-enhanced Raman scattering (SERS) based on Au nanoparticle-decorated, thin graphitic petals. The petals were grown on Si substrates by microwave plasma chemical vapor deposition without catalyst, followed by Au nanoparticle decoration on the oxygen plasma-treated petals by electrodeposition. The substrates possess high surface area and sharp nanoscale features that enable high SERS sensitivity to detect 1x10{sup -7} M rhodamine 6G in methanol solution. The obtained SERS enhancement is comparable to the best values reported in the literature and is determined to result from high surface area and increased density of Au nanoparticles on the petal surfaces.

  8. Immobilization of uranium by biomaterial stabilized FeS nanoparticles: Effects of stabilizer and enrichment mechanism.

    PubMed

    Shao, Dadong; Ren, Xuemei; Wen, Jun; Hu, Sheng; Xiong, Jie; Jiang, Tao; Wang, Xiaolin; Wang, Xiangke

    2016-01-25

    Iron sulfide (FeS) nanoparticles have been recognized as effective scavengers for multi-valent metal ions. However, the aggregation of FeS nanoparticles in aqueous solution greatly restricts their application in real work. Herein, different biomaterial-FeS nanoparticles were developed for the in-situ immobilization of uranium(VI) in radioactive waste management. TEM images suggested that sodium carboxymethyl cellulose (CMC) and gelatin can effectively suppress the aggregation of FeS nanoparticles in aqueous solutions. The resulting CMC-FeS and gelatin-FeS were stable in aqueous solutions and showed high adsorption capacity for U(VI). Specially, gelatin-FeS showed the best performance in U(VI) adsorption-reduction immobilization under experimental conditions. The maximum enrichment capacity of U(VI) on CMC-FeS and gelatin-FeS at pH 5.0 and 20 °C achieved to ∼430 and ∼556 mg/g, respectively. Additionally, gelatin-FeS and CMC-FeS nanoparticles presented excellent tolerance to environmental salinity. The immobilized U(VI) on the surfaces of CMC-FeS and gelatin-FeS remained stable more than one year. These findings highlight the possibility of using ggelatin-FeS for efficient immobilization of U(VI) from radioactive wastewater.

  9. Immobilization of uranium by biomaterial stabilized FeS nanoparticles: Effects of stabilizer and enrichment mechanism.

    PubMed

    Shao, Dadong; Ren, Xuemei; Wen, Jun; Hu, Sheng; Xiong, Jie; Jiang, Tao; Wang, Xiaolin; Wang, Xiangke

    2016-01-25

    Iron sulfide (FeS) nanoparticles have been recognized as effective scavengers for multi-valent metal ions. However, the aggregation of FeS nanoparticles in aqueous solution greatly restricts their application in real work. Herein, different biomaterial-FeS nanoparticles were developed for the in-situ immobilization of uranium(VI) in radioactive waste management. TEM images suggested that sodium carboxymethyl cellulose (CMC) and gelatin can effectively suppress the aggregation of FeS nanoparticles in aqueous solutions. The resulting CMC-FeS and gelatin-FeS were stable in aqueous solutions and showed high adsorption capacity for U(VI). Specially, gelatin-FeS showed the best performance in U(VI) adsorption-reduction immobilization under experimental conditions. The maximum enrichment capacity of U(VI) on CMC-FeS and gelatin-FeS at pH 5.0 and 20 °C achieved to ∼430 and ∼556 mg/g, respectively. Additionally, gelatin-FeS and CMC-FeS nanoparticles presented excellent tolerance to environmental salinity. The immobilized U(VI) on the surfaces of CMC-FeS and gelatin-FeS remained stable more than one year. These findings highlight the possibility of using ggelatin-FeS for efficient immobilization of U(VI) from radioactive wastewater. PMID:26448488

  10. Direct imaging Au nanoparticle migration inside mesoporous silica channels.

    PubMed

    Liu, Zhengwang; Che, Renchao; Elzatahry, Ahmed A; Zhao, Dongyuan

    2014-10-28

    Supported metal nanoparticle (NP) catalysts have been widely used in many industry processes and catalytic reactions. Catalyst deactivation is mainly caused by the sintering of supported metal NPs. Hence, understanding the metal NPs' sintering behaviors has great significance in preventing catalyst deactivation. Here we report the metal particle migration inside/between mesochannels by scanning transmission electron microscopy and electron energy loss spectroscopy via an in situ TEM heating technique. A sintering process is proposed that particle migration predominates, driven by the difference of gravitational potential from the height of the uneven internal surface of the mesopores; when the distance of the gold nanoparticles with a size of about 3 and 5 nm becomes short after migration, the coalescence process is completed, which is driven by an "octopus-claw-like" expansion of a conduction electron cloud outside the Au NPs. The supports containing an abundance of micropores help to suppress particle migration and coalescence. Our findings provide the understanding toward the rational design of supported industrial catalysts and other nanocomposites with enhanced activity and stability for applications such as batteries, catalysis, drug delivery, gas sensors, and solar cells.

  11. Sonochemical synthesis of (3-aminopropyl)triethoxysilane-modified monodispersed silica nanoparticles for protein immobilization

    SciTech Connect

    Shen, Shou-Cang; Ng, Wai Kiong; Chia, Leonard; Dong, Yuan-Cai; Tan, Reginald B.H.

    2011-10-15

    Graphical abstract: 3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by rapid sonochemical co-condensation to achieve high capability for protein immobilization. Highlights: {yields} Amino-modified monodispersed silica nanoparticles were synthesized by rapid co-condensation. {yields} Strong positive charge was created by aminopropyl-modification. {yields} Capability for immobilization of negatively charged protein was enhanced. {yields} Electrostatic interaction between proteins and surface contributed to the enhanced adsorption. -- Abstract: 3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by a rapid sonochemical co-condensation synthesis procedure. The chemical nature of surface organic modifier on the obtained modified silica nanoparticle was characterized by {sup 13}C and {sup 29}Si MAS Nuclear Magnetic Resonance (NMR) spectroscopies, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)- differential scanning calorimetry (DSC). Due to the strengthened positive surface charge of the silica nanoparticles by the modification with aminopropyl groups, the capability for bovine serum albumin (BSA) adsorption was significantly increased as compared with bare silica nanoparticles. 80 mg/g BSA was adsorbed on modified silica nanoparticles, whereas only 20 mg/g BSA could be loaded on pure silica nanoparticles. The enhanced positive surface charge repelled proteins with net positive charge and the modified silica nanoparticles exhibited negligible adsorption of lysozyme, thus a selective adsorption of proteins could be achieved.

  12. Enzyme:nanoparticle bioconjugates with two sequential enzymes: stoichiometry and activity of malate dehydrogenase and citrate synthase on Au nanoparticles.

    PubMed

    Keighron, Jacqueline D; Keating, Christine D

    2010-12-21

    We report the synthesis and characterization of bioconjugates in which the enzymes malate dehydrogenase (MDH) and/or citrate synthase (CS) were adsorbed to 30 nm diameter Au nanoparticles. Enzyme:Au stoichiometry and kinetic parameters (specific activity, k(cat), K(M), and activity per particle) were determined for MDH:Au, CS:Au, and three types of dual-activity MDH/CS:Au bioconjugates. For single-activity bioconjugates (MDH:Au and CS:Au), the number of enzyme molecules adsorbed per particle was dependent upon the enzyme concentration in solution, with multilayers forming at high enzyme:Au solution ratios. The specific activity of adsorbed enzyme increased with increasing number adsorbed per particle for CS:Au, but was less sensitive to stoichiometry for MDH:Au. Dual activity bioconjugates were prepared in three ways: (1) by adsorption of MDH followed by CS, (2) by adsorption of CS followed by MDH, and (3) by coadsorption of both enzymes from the same solution. The resulting bioconjugates differed substantially in the number of enzyme molecules adsorbed per particle, the specific activity of the adsorbed enzymes, and also the enzymatic activity per particle. Bioconjugates formed by adding CS to the Au nanoparticles before MDH was added exhibited higher specific activities for both enzymes than those formed by adding the enzymes in the reverse order. These bioconjugates also had 3-fold higher per-particle sequential activity for conversion of malate to citrate, despite substantially fewer copies of both enzymes present.

  13. Ultrasensitive and selective electrochemical diagnosis of breast cancer based on a hydrazine-Au nanoparticle-aptamer bioconjugate.

    PubMed

    Zhu, Ye; Chandra, Pranjal; Shim, Yoon-Bo

    2013-01-15

    Human epidermal growth factor receptor 2 (HER2) and HER2-overexpressing breast cancer cells were detected using an electrochemical immunosensor combined with hydrazine and aptamer-conjugated gold nanoparticles (AuNPs). The sensor probe was fabricated by covalently immobilizing anti-HER2 onto a nanocomposite layer that was composed of self-assembled 2,5-bis(2-thienyl)-1H-pyrrole-1-(p-benzoic acid) (DPB) on AuNPs. The hydrazine-AuNP-aptamer bioconjugate, where the hydrazine reductant was directly attached onto AuNPs to avoid the nonspecific deposition of silver on the sensor surface, was designed and used to reduce silver ion for signal amplification selectively. The silver-stained target cells were visualized easily by the bare eye and an optical microscope, and the cells were quantitatively analyzed using stripping voltammetry. The parameters affecting the analytical response were optimized. The proposed sensor was capable of differentiating between HER2-positive breast cancer cells and HER2-negative cells. This method exhibited an excellent diagnosis method for the ultrasensitive detection of SK-BR-3 breast cancer cells in human serum samples with a detection limit of 26 cells/mL.

  14. Shaping of Au nanoparticles embedded in various layered structures by swift heavy ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Dawi, E. A.; ArnoldBik, W. M.; Ackermann, R.; Habraken, F. H. P. M.

    2016-10-01

    We present a novel method to extend the ion-beam induced shaping of metallic nanoparticles in various layered structures. Monodisperse Au nanoparticles having mean diameter of 30 nm and their ion-shaping process is investigated for a limited number of experimental conditions. Au nanoparticles were embedded within a single plane in various layered structures of silicon nitride films (Si3N4), combinations of oxide-nitride films (SiO2-Si3N4) and amorphous silicon films (a-Si) and have been sequentially irradiated at 300 K at normal incidence with 50 and 25 MeV Ag ions, respectively. Under irradiation with heavy Ag ions and with sequential increase of the irradiation fluence, the evolution of the Au peak derived from the Rutherford Backscattering Spectrometry show broadening in Au peak, which indicates that the Au becomes distributed over a larger depth region, indicative of the elongation of the nanoparticles. The latter is observed almost for every layer structure investigated except for Au nanoparticles embedded in pure a-Si matrix. The largest elongation rate at all fluences is found for the Au nanoparticles encapsulated in pure Si3N4 films. For all irradiation energy applied, we again demonstrate the existence of both threshold and saturation fluences for the elongation effects mentioned.

  15. pH-dependent immobilization of urease on glutathione-capped gold nanoparticles.

    PubMed

    Garg, Seema; De, Arnab; Mozumdar, Subho

    2015-05-01

    Urease is a nickel-dependent metalloenzyme that catalyzes the hydrolysis of urea to form ammonia and carbon dioxide. Although the enzyme serves a significant role in several detoxification and analytical processes, its usability is restricted due to high cost, availability in small amounts, instability, and a limited possibility of economic recovery from a reaction mixture. Hence, there is a need to develop an efficient, simple, and reliable immobilization strategy for the enzyme. In this study, the carboxyl terminated surface of glutathione-capped gold nanoparticles have been utilized as a solid support for the covalent attachment of urease. The immobilization has been carried out at different pH conditions so as to elucidate its effect on the immobilization efficiency and enzyme bioactivity. The binding of the enzyme has been quantitatively and qualitatively analyzed through techniques like ultraviolet-visible spectroscopy, intrinsic steady state fluorescence, and circular dichorism. The bioactivity of the immobilized enzyme was investigated with respect to the native enzyme under different thermal conditions. Recyclability and shelf life studies of the immobilized enzyme have also been carried out. Results reveal that the immobilization is most effective at pH of 7.4 followed by that in an acidic medium and is least in alkaline environment. The immobilized enzyme also exhibits enhance activity in comparison to the native form at physiological temperature. The immobilized urease (on gold glutathione nanoconjugates surface) can be effectively employed for biosensor fabrication, immunoassays and as an in vivo diagnostic tool in the future.

  16. Covalent immobilization of molecularly imprinted polymer nanoparticles using an epoxy silane.

    PubMed

    Kamra, Tripta; Chaudhary, Shilpi; Xu, Changgang; Johansson, Niclas; Montelius, Lars; Schnadt, Joachim; Ye, Lei

    2015-05-01

    Molecularly imprinted polymers (MIPs) can be used as antibody mimics to develop robust chemical sensors. One challenging problem in using MIPs for sensor development is the lack of reliable conjugation chemistry that allows MIPs to be fixed on transducer surface. In this work, we study the use of epoxy silane to immobilize MIP nanoparticles on model transducer surfaces without impairing the function of the immobilized nanoparticles. The MIP nanoparticles with a core-shell structure have selective molecular binding sites in the core and multiple amino groups in the shell. The model transducer surface is functionalized with a self-assembled monolayer of epoxy silane, which reacts with the core-shell MIP particles to enable straightforward immobilization. The whole process is characterized by studying the treated surfaces after each preparation step using atomic force microscopy, scanning electron microscopy, fluorescence microscopy, contact angle measurements and X-ray photoelectron spectroscopy. The microscopy results show that the MIP particles are immobilized uniformly on surface. The photoelectron spectroscopy results further confirm the action of each functionalization step. The molecular selectivity of the MIP-functionalized surface is verified by radioligand binding analysis. The particle immobilization approach described here has a general applicability for constructing selective chemical sensors in different formats.

  17. Enzyme-free surface plasmon resonance aptasensor for amplified detection of adenosine via target-triggering strand displacement cycle and Au nanoparticles.

    PubMed

    Yao, Gui-Hong; Liang, Ru-Ping; Huang, Chun-Fang; Zhang, Li; Qiu, Jian-Ding

    2015-04-29

    Herein, we combine the advantage of aptamer technique with the amplifying effect of an enzyme-free signal-amplification and Au nanoparticles (NPs) to design a sensitive surface plasmon resonance (SPR) aptasensor for detecting small molecules. This detection system consists of aptamer, detection probe (c-DNA1) partially hybridizing to the aptamer strand, Au NPs-linked hairpin DNA (Au-H-DNA1), and thiolated hairpin DNA (H-DNA2) previously immobilized on SPR gold chip. In the absence of target, the H-DNA1 possessing hairpin structure cannot hybridize with H-DNA2 and thereby Au NPs will not be captured on the SPR gold chip surface. Upon addition of target, the detection probe c-DNA1 is forced to dissociate from the c-DNA1/aptamer duplex by the specific recognition of the target to its aptamer. The released c-DNA1 hybridizes with Au-H-DNA1 and opens the hairpin structure, which accelerate the hybridization between Au-H-DNA1 and H-DNA2, leading to the displacement of the c-DNA1 through a branch migration process. The released c-DNA1 then hybridizes with another Au-H-DNA1 probe, and the cycle starts anew, resulting in the continuous immobilization of Au-H-DNA1 probes on the SPR chip, generating a significant change of SPR signal due to the electronic coupling interaction between the localized surface plasma of the Au NPs and the surface plasma wave. With the use of adenosine as a proof-of-principle analyte, this sensing platform can detect adenosine specifically with a detection limit as low as 0.21 pM, providing a simple, sensitive and selective protocol for small target molecules detection. PMID:25847158

  18. Organosulfur-functionalized Au, Pd, and Au-Pd nanoparticles on 1D silicon nanowire substrates: preparation and XAFS studies.

    PubMed

    Zhang, Peng; Zhou, Xingtai; Tang, Yuanhong; Sham, Tsun Kong

    2005-08-30

    A hybrid preparative method was developed to prepare organosulfur-functionalized Au nanoparticles (NPs) on silicon nanowires (SiNWs) by reacting HAuCl(4) with SiNW in the presence of thiol. A number of organosulfur molecules-dodecanethiol, hexanethiol, 1,6-hexanedithiol, and tiopronin-were used to functionalize the Au surface. Size-selected NPs ranging from 1.6 to 7.5 nm were obtained by varying the S/Au ratio and the concentration of HAuCl(4). This method was further extended to the preparation Pd and Pd-Au bimetallic NPs on SiNWs. The morphology of the metal nanostructures was examined by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The local structure and bonding of the SiNW-supported metal nanostructures were studied using X-ray absorption fine structures (XAFS) [including both X-ray near-edge structures (XANES) and extended X-ray absorption fine structures (EXAFS)] at the Au L(3)-, Pd K-, S K-, and Si K-edges. It was also found that the annealing of the thiol-capped Au NPs up to 500 degrees C transforms the surface of the thiol-capped NPs to gold sulfide, as identified using Au L(3)- and S K-edge XANES. We also illustrate that this preparative approach can be used to form size-controllable Au NPs on carbon nanotubes. PMID:16114963

  19. Preparation and characterization of carboxyl functionalization of magnetite nanoparticles for oligonucleotide immobilization

    NASA Astrophysics Data System (ADS)

    Kim, Min-Jung; Jang, Dae-Hwan; Choa, Yong-Ho

    2010-05-01

    Fe3O4 nanoparticles prepared by the co-precipitation of Fe2+ and Fe3+ with NH4OH were simply modified by the carboxylic acid group of 3-thiopheneacetic acid (3TA) and meso-2,3-dimercaptosuccinic acid (DMSA). These functionalized Fe3O4 nanoparticles when coated with 3TA and DMSA have increased hydrophilic properties, thus causing them to be well dispersed in aqueous solutions. Then oligonucleotides (5'-AGC T-Amine-3') were immobilized on the carboxylic acid group-modified Fe3O4 nanoparticles. They were characterized by using FT-IR, XRD and TEM. The concentration of the oligonucleotide-modified Fe3O4 nanoparticles was investigated using a UV-vis spectrometer and compared to that of Fe3O4 nanoparticles without any surface modification. The Fe3O4 nanoparticles were spherical and the particle sizes were approximately 10 nm. The immobilizing efficiencies of the Fe3O4 nanoparticles modified with 3TA and DMSA were higher than those of the non-functionalized Fe3O4 nanoparticles.

  20. Effect of experimental conditions on size control of Au nanoparticles synthesized by atmospheric microplasma electrochemistry.

    PubMed

    Huang, Xunzhi; Li, Yongsheng; Zhong, Xiaoxia

    2014-01-01

    Atmospheric microplasma electrochemistry was utilized to synthesize Au nanoparticles (NPs). The synthesized Au NPs were investigated as a function of reduction current, solution temperature, and stirring (or not) by using ultraviolet-visible (UV-Vis) absorbance and transmission electron microscopy (TEM). It was illustrated that high current promoted the growth of Au NPs with small size, and more Au NPs with large size were synthesized as a rise of temperature. The Au NPs often with small size were synthesized as a result of stirring. The production rate, the electrostatic repulsion, and the residence time of the Au NPs at the interfacial region play an important role in the growth of Au NPs. The results shed light upon the roadmap to control the size and particle size distribution (PSD) of Au NPs synthesized by atmospheric microplasma electrochemistry. PMID:25364315

  1. Hybrid nanoparticle architecture for cellular uptake and bioimaging: direct crystallization of a polymer immobilized with magnetic nanoparticles on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Depan, D.; Misra, R. D. K.

    2012-09-01

    We describe here the success of an innovative approach of direct immobilization of magnetic nanoparticles (MNPs) onto carbon nanotubes (CNTs). The approach involved functionalization of magnetic nanoparticles and consequent covalent linkage to a copolymer (PE-b-PEG). Next, the immobilized magnetic nanoparticles on the copolymer were directly crystallized on the long axis of CNTs, where the interfacial adhesion comes from electrostatic and van der Waals interaction. The intracellular trafficking of a hybrid nanoparticle system [(PE-b-PEG)-MNP-CNT-FITC] in HeLa cells was monitored using a fluorescent marker, FITC, conjugated to the nanoparticle system. The distribution of the nanoparticle system inside cells was studied by fluorescence microscopy in a time and dose dependent manner, and it was observed that the nanoparticles are located in the cytoplasm and no apparent cell death was observed at the concentration studied. Also, the effect of an externally applied magnetic field on actin cytoskeleton, cell morphology and intracellular uptake of iron was studied. The approach described here is promising for simultaneous imaging and monitoring intracellular uptake.

  2. Hybrid nanoparticle architecture for cellular uptake and bioimaging: direct crystallization of a polymer immobilized with magnetic nanoparticles on carbon nanotubes.

    PubMed

    Depan, D; Misra, R D K

    2012-10-21

    We describe here the success of an innovative approach of direct immobilization of magnetic nanoparticles (MNPs) onto carbon nanotubes (CNTs). The approach involved functionalization of magnetic nanoparticles and consequent covalent linkage to a copolymer (PE-b-PEG). Next, the immobilized magnetic nanoparticles on the copolymer were directly crystallized on the long axis of CNTs, where the interfacial adhesion comes from electrostatic and van der Waals interaction. The intracellular trafficking of a hybrid nanoparticle system [(PE-b-PEG)-MNP-CNT-FITC] in HeLa cells was monitored using a fluorescent marker, FITC, conjugated to the nanoparticle system. The distribution of the nanoparticle system inside cells was studied by fluorescence microscopy in a time and dose dependent manner, and it was observed that the nanoparticles are located in the cytoplasm and no apparent cell death was observed at the concentration studied. Also, the effect of an externally applied magnetic field on actin cytoskeleton, cell morphology and intracellular uptake of iron was studied. The approach described here is promising for simultaneous imaging and monitoring intracellular uptake.

  3. Silica nanoparticles for micro-particle imaging velocimetry: fluorosurfactant improves nanoparticle stability and brightness of immobilized iridium(III) complexes.

    PubMed

    Lewis, David J; Dore, Valentina; Rogers, Nicola J; Mole, Thomas K; Nash, Gerard B; Angeli, Panagiota; Pikramenou, Zoe

    2013-11-26

    To establish highly luminescent nanoparticles for monitoring fluid flows, we examined the preparation of silica nanoparticles based on immobilization of a cyclometalated iridium(III) complex and an examination of the photophysical studies provided a good insight into the Ir(III) microenvironment in order to reveal the most suitable silica nanoparticles for micro particle imaging velocimetry (μ-PIV) studies. Iridium complexes covalently incorporated at the surface of preformed silica nanoparticles, [Ir-4]@Si500-Z, using a fluorinated polymer during their preparation, demonstrated better stability than those without the polymer, [Ir-4]@Si500, as well as an increase in steady state photoluminescence intensity (and therefore particle brightness) and lifetimes which are increased by 7-fold compared with nanoparticles with the same metal complex attached covalently throughout their core, [Ir-4]⊂Si500. Screening of the nanoparticles in fluid flows using epi-luminescence microscopy also confirm that the brightest, and therefore most suitable particles for microparticle imaging velocimetry (μ-PIV) measurements are those with the Ir(III) complex immobilized at the surface with fluorosurfactant, that is [Ir-4]@Si500-Z. μ-PIV studies demonstrate the suitability of these nanoparticles as nanotracers in microchannels.

  4. Immobilization of β-d-galactosidase from Kluyveromyces lactis on functionalized silicon dioxide nanoparticles: characterization and lactose hydrolysis.

    PubMed

    Verma, Madan Lal; Barrow, Colin James; Kennedy, J F; Puri, Munish

    2012-03-01

    β-D-Galactosidase (BGAL) from Kluyveromyces lactis was covalently immobilized to functionalized silicon dioxide nanoparticles (10-20 nm). The binding of the enzyme to the nanoparticles was confirmed by Fourier transform-infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Functionalized nanoparticles showed 87% immobilization yield. Soluble and immobilized enzyme preparation exhibited pH-optima at pH 6.5 and 7.0, respectively, with temperature optima at 35 and 40°C, respectively. Michaelis constant (K(m)) was 4.77 and 8.4mM for free and immobilized BGAL, respectively. V(max) for the soluble and immobilized enzyme was 12.25 and 13.51 U/ml, respectively. Nanoparticle immobilized BGAL demonstrated improved stability after favoring multipoint covalent attachment. Thermal stability of the immobilized enzyme was enhanced at 40, 50 and 65°C. Immobilized nanoparticle-enzyme conjugate retained more than 50% enzyme activity up to the eleventh cycle. Maximum lactose hydrolysis by immobilized BGAL was achieved at 8h.

  5. Growth of Au@Pt coreshell nanoparticles: Probed by in-situ XANES and UV-visible spectroscopy

    NASA Astrophysics Data System (ADS)

    Nayak, C.; Bhattacharyya, K.; Tripathi, A. K.; Jha, S. N.; Bhattacharyya, D.; Sahoo, N. K.

    2016-05-01

    Au@Pt core shell nanoparticles have been synthesized by reducing Au and Pt chloride precursors with Block Co-polymer and Ascorbic acid. The growth and nucleation of Au@Pt nanoparticles have been investigated by in-situ time resolved XANES measurement which gives the evolution of the reduction process of the precursors. Linear combination fitting of the XANES spectra has been carried out to find the fraction of Au and Pt cations reduced at a particular reaction time. UV-Visible spectroscopy is used as a complementary technique which gives the changes in the Au SPR peak as Au@Pt core shell nanoparticles are formed.

  6. Core-shell Au@Pd nanoparticles with enhanced catalytic activity for oxygen reduction reaction via core-shell Au@Ag/Pd constructions

    PubMed Central

    Chen, Dong; Li, Chengyin; Liu, Hui; Ye, Feng; Yang, Jun

    2015-01-01

    Core-shell nanoparticles often exhibit improved catalytic properties due to the lattice strain created in these core-shell particles. Herein, we demonstrate the synthesis of core-shell Au@Pd nanoparticles from their core-shell Au@Ag/Pd parents. This strategy begins with the preparation of core-shell Au@Ag nanoparticles in an organic solvent. Then, the pure Ag shells are converted into the shells made of Ag/Pd alloy by galvanic replacement reaction between the Ag shells and Pd2+ precursors. Subsequently, the Ag component is removed from the alloy shell using saturated NaCl solution to form core-shell Au@Pd nanoparticles with an Au core and a Pd shell. In comparison with the core-shell Au@Pd nanoparticles upon directly depositing Pd shell on the Au seeds and commercial Pd/C catalysts, the core-shell Au@Pd nanoparticles via their core-shell Au@Ag/Pd templates display superior activity and durability in catalyzing oxygen reduction reaction, mainly due to the larger lattice tensile effect in Pd shell induced by the Au core and Ag removal. PMID:26144550

  7. Electrochemical Deposition and Re-oxidation of Au at Highly Oriented Pyrolytic Graphite. Stabilization of Au Nanoparticles on the Upper Plane of Step Edges

    SciTech Connect

    Pinhero, Patrick Joseph; Lister, Tedd Edward; Boxley, Chett J.; White, Henry S.

    2003-10-01

    The electrochemical deposition and reoxidation of Au on the basal plane of highly oriented pyrolytic graphite (HOPG) immersed in a 5 mM AuCl4-/6 M LiCl solution is reported. Scanning electron microscopy (SEM) and ex-situ atomic force microscopy (AFM) demonstrate that Au nanoparticles, ~3.3 nm in height and ~10 nm in diameter, are deposited at times less than ~1 s. The density of nanoparticles, 6 × 109 cm-2, is of the same order of magnitude as the surface point defect density, suggesting that point defects act as nucleation sites for Au electrodeposition. A small subset of the Au nanoparticles (~7%) continues to grow between 1 and 50 s, reaching a height of ~150 nm and a diameter of ~300 nm. At times greater than 50 s, the larger particles coalesce to yield a surface comprised of a low density (~2 × 106 cm-2) of micrometer-size Au crystallites surrounded by Au nanoparticles. Double potential step chronocoulometric experiments demonstrate that the electrodeposition of Au is chemically irreversible, a finding supported by SEM and AFM observations of Au nanoparticles and larger crystallites on the surface after long periods of reoxidation (>3600 s). Au nanoparticles are observed to be preferentially deposited on the upper plane of step edges, a consequence of the nonuniform surface electron density that results from relaxation of the graphite lattice near steps.

  8. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles.

    PubMed

    Chaffin, Elise; O'Connor, Ryan T; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ∼410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods. PMID:27497571

  9. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaffin, Elise; O'Connor, Ryan T.; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ˜410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods.

  10. Dependence of SERS enhancement on the chemical composition and structure of Ag/Au hybrid nanoparticles.

    PubMed

    Chaffin, Elise; O'Connor, Ryan T; Barr, James; Huang, Xiaohua; Wang, Yongmei

    2016-08-01

    Noble metal nanoparticles (NPs) such as silver (Ag) and gold (Au) have unique plasmonic properties that give rise to surface enhanced Raman scattering (SERS). Generally, Ag NPs have much stronger plasmonic properties and, hence, provide stronger SERS signals than Au NPs. However, Ag NPs lack the chemical stability and biocompatibility of comparable Au NPs and typically exhibit the most intense plasmonic resonance at wavelengths much shorter than the optimal spectral region for many biomedical applications. To overcome these issues, various experimental efforts have been devoted to the synthesis of Ag/Au hybrid NPs for the purpose of SERS detections. However, a complete understanding on how the SERS enhancement depends on the chemical composition and structure of these nanoparticles has not been achieved. In this study, Mie theory and the discrete dipole approximation have been used to calculate the plasmonic spectra and near-field electromagnetic enhancements of Ag/Au hybrid NPs. In particular, we discuss how the electromagnetic enhancement depends on the mole fraction of Au in Ag/Au alloy NPs and how one may use extinction spectra to distinguish between Ag/Au alloyed NPs and Ag-Au core-shell NPs. We also show that for incident laser wavelengths between ∼410 nm and 520 nm, Ag/Au alloyed NPs provide better electromagnetic enhancement than pure Ag, pure Au, or Ag-Au core-shell structured NPs. Finally, we show that silica-core Ag/Au alloy shelled NPs provide even better performance than pure Ag/Au alloy or pure solid Ag and pure solid Au NPs. The theoretical results presented will be beneficial to the experimental efforts in optimizing the design of Ag/Au hybrid NPs for SERS-based detection methods.

  11. Immobilization of Lipases on Alkyl Silane Modified Magnetic Nanoparticles: Effect of Alkyl Chain Length on Enzyme Activity

    PubMed Central

    Wang, Jiqian; Meng, Gang; Tao, Kai; Feng, Min; Zhao, Xiubo; Li, Zhen; Xu, Hai; Xia, Daohong; Lu, Jian R.

    2012-01-01

    Background Biocatalytic processes often require a full recycling of biocatalysts to optimize economic benefits and minimize waste disposal. Immobilization of biocatalysts onto particulate carriers has been widely explored as an option to meet these requirements. However, surface properties often affect the amount of biocatalysts immobilized, their bioactivity and stability, hampering their wide applications. The aim of this work is to explore how immobilization of lipases onto magnetite nanoparticles affects their biocatalytic performance under carefully controlled surface modification. Methodology/Principal Findings Magnetite nanoparticles, prepared through a co-precipitation method, were coated with alkyl silanes of different alkyl chain lengths to modulate their surface hydrophobicity. Candida rugosa lipase was then directly immobilized onto the modified nanoparticles through hydrophobic interaction. Enzyme activity was assessed by catalytic hydrolysis of p-nitrophenyl acetate. The activity of immobilized lipases was found to increase with increasing chain length of the alkyl silane. Furthermore, the catalytic activities of lipases immobilized on trimethoxyl octadecyl silane (C18) modified Fe3O4 were a factor of 2 or more than the values reported from other surface immobilized systems. After 7 recycles, the activities of the lipases immobilized on C18 modified nanoparticles retained 65%, indicating significant enhancement of stability as well through hydrophobic interaction. Lipase immobilized magnetic nanoparticles facilitated easy separation and recycling with high activity retaining. Conclusions/Significance The activity of immobilized lipases increased with increasing alkyl chain length of the alkyl trimethoxy silanes used in the surface modification of magnetite nanoparticles. Lipase stability was also improved through hydrophobic interaction. Alkyl silane modified magnetite nanoparticles are thus highly attractive carriers for enzyme immobilization

  12. Superparamagnetic Au-Fe3O4 nanoparticles: one-pot synthesis, biofunctionalization and toxicity evaluation

    NASA Astrophysics Data System (ADS)

    Pariti, A.; Desai, P.; Maddirala, S. K. Y.; Ercal, N.; Katti, K. V.; Liang, X.; Nath, M.

    2014-09-01

    Superparamagnetic Au-Fe3O4 bifunctional nanoparticles have been synthesized using a single step hot-injection precipitation method. The synthesis involved using Fe(CO)5 as iron precursor and HAuCl4 as gold precursor in the presence of oleylamine and oleic acid. Oleylamine helps in reducing Au3+ to Au0 seeds which simultaneously oxidizes Fe(0) to form Au-Fe3O4 bifunctional nanoparticles. Triton® X-100 was employed as a highly viscous solvent to prevent agglomeration of Fe3O4 nanoparticles. Detailed characterization of these nanoparticles was performed by using x-ray powder diffraction, transmission electron microscopy, scanning tunneling electron microscopy, UV-visible spectroscopy, Mössbauer and magnetometry studies. To evaluate these nanoparticles’ applicability in biomedical applications, L-cysteine was attached to the Au-Fe3O4 nanoparticles and cytotoxicity of Au-Fe3O4 nanoparticles was tested using CHO cells by employing MTS assay. L-cysteine modified Au-Fe3O4 nanoparticles were qualitatively characterized using Fourier transform infrared spectroscopy and Raman spectroscopy; and quantitatively using acid ninhydrin assay. Investigations reveal that that this approach yields Au-Fe3O4 bifunctional nanoparticles with an average particle size of 80 nm. Mössbauer studies indicated the presence of Fe in Fe3+ in A and B sites (tetrahedral and octahedral, respectively) and Fe2+ in B sites (octahedral). Magnetic measurements also indicated that these nanoparticles were superparamagnetic in nature due to Fe3O4 region. The saturation magnetization for the bifunctional nanoparticles was observed to be ˜74 emu g-1, which is significantly higher than the previously reported Fe3O4 nanoparticles. Mössbauer studies indicated that there was no significant Fe(0) impurity that could be responsible for the superparamagnetic nature of these nanoparticles. None of the investigations showed any presence of other impurities such as Fe2O3 and FeOOH. These Au-Fe3O4 bifunctional

  13. Temperature-independent formation of Au nanoparticles in ionic liquids by arc plasma deposition

    NASA Astrophysics Data System (ADS)

    Hatakeyama, Yoshikiyo; Kimura, Satoshi; Kameyama, Tatsuya; Agawa, Yoshiaki; Tanaka, Hiroyuki; Judai, Ken; Torimoto, Tsukasa; Nishikawa, Keiko

    2016-08-01

    An effective preparation method of Au nanoparticles (NPs) is presented, wherein an arc plasma deposition technique is combined with ionic liquids (ILs) used as capture media. This method requires no chemical reaction. By selecting ILs, size-controlled Au NPs are produced easily and on a massive scale.

  14. Immobilization and kinetics of catalase on calcium carbonate nanoparticles attached epoxy support.

    PubMed

    Preety; Hooda, Vinita

    2014-01-01

    A novel hybrid epoxy/nano CaCO3 composite matrix for catalase immobilization was prepared by polymerizing epoxy resin in the presence of CaCO3 nanoparticles. The hybrid support was characterized using scanning electron microscopy and Fourier transform infrared spectroscopy. Catalase was successfully immobilized onto epoxy/nano CaCO3 support with a conjugation yield of 0.67 ± 0.01 mg/cm(2) and 92.63 ± 0.80 % retention of activity. Optimum pH and optimum temperature of free and immobilized catalases were found to be 7.0 and 35 °C. The value of Km for H2O2 was higher for immobilized enzyme (31.42 mM) than native enzyme (27.73 mM). A decrease in Vmax value from 1,500 to 421.10 μmol (min mg protein)(-1) was observed after immobilization. Thermal and storage stabilities of catalase improved immensely after immobilization. Immobilized enzyme retained three times than the activity of free enzyme when kept at 75 °C for 1 h and the half-life of enzyme increased five times when stored in phosphate buffer (0.01 M, pH 7.0) at 5 °C. The enzyme could be reused 30 times without any significant loss of its initial activity. Desorption of catalase from the hybrid support was minimum at pH 7.0.

  15. Dual immobilization and magnetic manipulation of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Yang, S. Y.; Jian, Z. F.; Horng, H. E.; Hong, Chin-Yih; Yang, H. C.; Wu, C. C.; Lee, Y. H.

    By suitably bio-functionalizing the surfaces, magnetic nanoparticles are able to bind specific biomolecules, and may serve as vectors for delivering bio-entities to target tissues. In this work, the synthesis of bio-functionalized magnetic nanoparticles with two kinds of bio-probes is developed. Here, the stem cell is selected as a to-be-delivered bio-entity and infarcted myocardium is the target issue. Thus, cluster designation-34 (CD-34) on stem cell and creatine kinase-MB (CK-MB) (or troponin I) on infarcted myocardium are the specific biomolecules to be bound with bio-functionalized magnetic nanoparticles. In addition to demonstrating the co-coating of two kinds of bio-probes on a magnetic nanoparticle, the feasibility of manipulation on bio-functionalized magnetic nanoparticles by external magnetic fields is investigated.

  16. A combined experimental and computational study of AuPd nanoparticles

    NASA Astrophysics Data System (ADS)

    Bruma, Alina

    The thesis is focused on the investigation of structural properties of AuPd nanoparticles via theoretical and experimental studies. For the first system, the 98-atom AuPd nanoclusters, a theoretical analysis has been employed to study the energetics and segregation effects and to assess how typical is the Leary Tetrahedron (LT). Although this motif is the most stable at the empirical level, it loses stability at the DFT level against FCC or Marks Decahedron. The second system is the Au24Pd1 nanoclusters. Theoretically, by performing a search at the DFT level using Basin Hopping Monte Carlo, we identified pyramidal cage structures as putative global minima, where Pd sits in the core and Au occupies surface positions. The Lowdin analysis emphasized charge transfer between Pd and Au, explaining the enhanced catalytic activity with respect to Au25 clusters. Experimentally, STEM has been employed for the structural characterization of Au24Pd1 clusters supported on Multiwall Carbon Nanotubes. Whenever possible, we have tried to link the experimental analysis to the theoretical findings. The third system has been the evaporated AuPd nanoparticles. We observed that the annealing process led to the formation of L12 ordered phases as well as layered and core-shell structures. This study aimed to bring an insight on the segregation and energetics effects of AuPd nanoparticles with potential applications in nanocatalysis.

  17. UV Spectra of Amino Acid Immobilized at Nanoparticles Formation through Nanosphere Lithography (NSL) by Plasma Treatment

    SciTech Connect

    Mohamad, Farizan; Agam, Mohd Arif; Nur, Hadi

    2011-05-25

    The modifying of nanospheres structures by plasma treatments to the fabricated nanoparticles arrays by Nanosphere Lithography (NSL) techniques to create Periodic Particles Arrays (PPAs) with different size, shape and orientation. Spectra of amino acid that immobilized to the nanoparticles arrays under Ultra Violet (UV) spectrums were studied. The PPAs with different sizes, shapes and orientation were fabricated by plasma treatment of 5 sec, 7 sec and 10 sec to the Polystyrene Nanosphere (PSN). Plasma treatment will effect to the PSN including etching part of the PSN to produce a much bigger channel to the single layer template of the PSN. Metal was deposited at interstitial sites between of the polymer balls and later removed by dissolving them in organic solvent, leaving a hexagonal pattern of metal structures at the interstitial sites. The nanoparticles immobilized with the standard amino acid, which later investigated under UV spectrums. The spectrums shows the possibilities use as biosensor devices.

  18. Synthesis of tripodal catecholates and their immobilization on zinc oxide nanoparticles

    PubMed Central

    Klitsche, Franziska; Ramcke, Julian; Migenda, Julia; Hensel, Andreas; Vossmeyer, Tobias; Weller, Horst

    2015-01-01

    Summary A common approach to generate tailored materials and nanoparticles (NPs) is the formation of molecular monolayers by chemisorption of bifunctional anchor molecules. This approach depends critically on the choice of a suitable anchor group. Recently, bifunctional catecholates, inspired by mussel-adhesive proteins (MAPs) and bacterial siderophores, have received considerable interest as anchor groups for biomedically relevant metal surfaces and nanoparticles. We report here the synthesis of new tripodal catecholates as multivalent anchor molecules for immobilization on metal surfaces and nanoparticles. The tripodal catecholates have been conjugated to various effector molecules such as PEG, a sulfobetaine and an adamantyl group. The potential of these conjugates has been demonstrated with the immobilization of tripodal catecholates on ZnO NPs. The results confirmed a high loading of tripodal PEG-catecholates on the particles and the formation of stable PEG layers in aqueous solution. PMID:26124871

  19. Immobilization of selenite in soil and groundwater using stabilized Fe-Mn binary oxide nanoparticles.

    PubMed

    Xie, Wenbo; Liang, Qiqi; Qian, Tianwei; Zhao, Dongye

    2015-03-01

    Stabilized Fe-Mn binary oxide nanoparticles were synthesized and tested for removal and in-situ immobilization of Se(IV) in groundwater and soil. A water-soluble starch or food-grade carboxymethyl cellulose (CMC) was used as a stabilizer to facilitate in-situ delivery of the particles into contaminated soil. While bare and stabilized nanoparticles showed rapid sorption kinetics, starch-stabilized Fe-Mn offered the greatest capacity for Se(IV). The Langmuir maximum capacity was determined to be 109 and 95 mg-Se/g-Fe for starch- and CMC-stabilized nanoparticles, respectively, and the high Se(IV) uptake was observed over the typical groundwater pH range of 5-8. Column breakthrough tests indicated that the stabilized nanoparticles were deliverable in a model sandy soil while non-stabilized particles were not. When a Se(IV)-spiked soil was treated in situ with the nanoparticles, >90% water leachable Se(IV) was transferred to the nanoparticle phase, and thereby immobilized as the particles were retained in the downstream soil matrix. The nanoparticle amendment reduced the TCLP (toxicity characteristic leaching procedure) leachability and the California WET (waste extraction test) leachability of Se(IV) by 76% and 71%, respectively. The technology holds the potential to fill a major technology gap in remediation of metals-contaminated soil and groundwater.

  20. Solvent Control of Surface Plasmon-Mediated Chemical Deposition of Au Nanoparticles from Alkylgold Phosphine Complexes.

    PubMed

    Muhich, Christopher L; Qiu, Jingjing; Holder, Aaron M; Wu, Yung-Chien; Weimer, Alan W; Wei, Wei David; McElwee-White, Lisa; Musgrave, Charles B

    2015-06-24

    Bottom-up approaches to nanofabrication are of great interest because they can enable structural control while minimizing material waste and fabrication time. One new bottom-up nanofabrication method involves excitation of the surface plasmon resonance (SPR) of a Ag surface to drive deposition of sub-15 nm Au nanoparticles from MeAuPPh3. In this work we used density functional theory to investigate the role of the PPh3 ligands of the Au precursor and the effect of adsorbed solvent on the deposition process, and to elucidate the mechanism of Au nanoparticle deposition. In the absence of solvent, the calculated barrier to MeAuPPh3 dissociation on the bare surface is <20 kcal/mol, making it facile at room temperature. Once adsorbed on the surface, neighboring MeAu fragments undergo ethane elimination to produce Au adatoms that cluster into Au nanoparticles. However, if the sample is immersed in benzene, we predict that the monolayer of adsorbed solvent blocks the adsorption of MeAuPPh3 onto the Ag surface because the PPh3 ligand is large compared to the size of the exposed surface between adsorbed benzenes. Instead, the Au-P bond of MeAuPPh3 dissociates in solution (Ea = 38.5 kcal/mol) in the plasmon heated near-surface region followed by the adsorption of the MeAu fragment on Ag in the interstitial space of the benzene monolayer. The adsorbed benzene forces the Au precursor to react through the higher energy path of dissociation in solution rather than dissociatively adsorbing onto the bare surface. This requires a higher temperature if the reaction is to proceed at a reasonable rate and enables the control of deposition by the light induced SPR heating of the surface and nearby solution.

  1. Synthesis and immobilization of silver nanoparticles on aluminosilicate nanotubes and their antibacterial properties

    NASA Astrophysics Data System (ADS)

    Ipek Yucelen, G.; Connell, Rachel E.; Terbush, Jessica R.; Westenberg, David J.; Dogan, Fatih

    2016-04-01

    A novel colloidal method is presented to synthesize silver nanoparticles on aluminosilicate nanotubes. The technique involves decomposition of AgNO3 solution to Ag nanoparticles in the presence of aluminosilicate nanotubes at room temperature without utilizing of reducing agents or any organic additives. Aluminosilicate nanotubes are shown to be capable of providing a unique chemical environment, not only for in situ conversion of Ag+ into Ag0, but also for stabilization and immobilization of Ag nanoparticles. The synthesis strategy described here could be implemented to obtain self-assembled nanoparticles on other single-walled metal oxide nanotubes for unique applications. Finally, we demonstrated that nanotube/nanoparticle hybrid show strong antibacterial activity toward Gram-positive Staphylococcus epidermidis and Gram-negative Escherichia coli.

  2. Au nanoparticle-functionalised WO3 nanoneedles and their application in high sensitivity gas sensor devices.

    PubMed

    Vallejos, Stella; Stoycheva, Toni; Umek, Polona; Navio, Cristina; Snyders, Rony; Bittencourt, Carla; Llobet, Eduard; Blackman, Christopher; Moniz, Savio; Correig, Xavier

    2011-01-01

    A new method of synthesising nanoparticle-functionalised nanostructured materials via Aerosol Assisted Chemical Vapour Deposition (AACVD) has been developed. Co-deposition of Au nanoparticles with WO(3) nanoneedles has been used to deposit a sensing layer directly onto gas sensor substrates providing devices with a six-fold increase in response to low concentrations of a test analyte (ethanol). PMID:21103469

  3. Effect of Au nano-particle aggregation on the deactivation of the AuCl3/AC catalyst for acetylene hydrochlorination

    PubMed Central

    Dai, Bin; Wang, Qinqin; Yu, Feng; Zhu, Mingyuan

    2015-01-01

    A detailed study of the valence state and distribution of the AuCl3/AC catalyst during the acetylene hydrochlorination deactivation process is described and discussed. Temperature-programmed reduction and X-ray photoelectron spectral analysis indicate that the active Au3+ reduction to metallic Au0 is one reason for the deactivation of AuCl3/AC catalyst. Transmission electron microscopy characterization demonstrated that the particle size of Au nano-particles increases with increasing reaction time. The results indicated that metallic Au0 exhibits considerable catalytic activity and that Au nano-particle aggregation may be another reason for the AuCl3/AC catalytic activity in acetylene hydrochlorination. PMID:25994222

  4. Evaluation of nanoparticle-immobilized cellulase for improved ethanol yield in simultaneous saccharification and fermentation reactions

    SciTech Connect

    Lupoi, Jason; Smith, Emily

    2011-12-01

    Ethanol yields were 2.1 (P = 0.06) to 2.3 (P = 0.01) times higher in simultaneous saccharification and fermentation (SSF) reactions of microcrystalline cellulose when cellulase was physisorbed on silica nanoparticles compared to enzyme in solution. In SSF reactions, cellulose is hydrolyzed to glucose by cellulase while yeast simultaneously ferments glucose to ethanol. The 35 C temperature and the presence of ethanol in SSF reactions are not optimal conditions for cellulase. Immobilization onto solid supports can stabilize the enzyme and promote activity at non-optimum reaction conditions. Mock SSF reactions that did not contain yeast were used to measure saccharification products and identify the mechanism for the improved ethanol yield using immobilized cellulase. Cellulase adsorbed to 40 nm silica nanoparticles produced 1.6 times (P = 0.01) more glucose than cellulase in solution in 96 h at pH 4.8 and 35 C. There was no significant accumulation (<250 {mu}g) of soluble cellooligomers in either the solution or immobilized enzyme reactions. This suggests that the mechanism for the immobilized enzyme's improved glucose yield compared to solution enzyme is the increased conversion of insoluble cellulose hydrolysis products to soluble cellooligomers at 35 C and in the presence of ethanol. The results show that silica-immobilized cellulase can be used to produce increased ethanol yields in the conversion of lignocellulosic materials by SSF.

  5. Comparative study of immobilized Trametes versicolor laccase on nanoparticles and kaolinite.

    PubMed

    Hu, Xiaoke; Zhao, Xueheng; Hwang, Huey-Min

    2007-01-01

    Laccase from Trametes versicolor was immobilized on nanoparticles and kaolinite by physical adsorption or chemical covalence in which the supporters were activated by cross-linked with glutaraldehyde. Thermal and pH stabilities of immobilized laccase on these different supporters were compared. The degradation efficiencies of these immobilized laccases on oxidation of benzo[a]pyrene (BaP) were also compared. The results showed that the immobilized laccases on nanoparticles were more stable in resisting pH and thermal changes. After 48h oxidation, laccase immobilized on kaolinite using the covalent coupling method showed a higher efficiency of oxidation with the BaP residue of 23% in the presence of 1mM HBT and with BaP residue of 37% in 1mM ABTS as the mediator. The results also exhibited a significant inhibition by 1% surfactant Tween 80. According to the HPLC analysis, the oxidation products including 1,6-benzo[a]pyrene quinone, 3,6-benzo[a]pyrene quinone and 6,12-benzo[a]pyrene quinone were identified.

  6. A sensitive electrochemiluminescence immunosensor based on luminophore capped Pd@Au core-shell nanoparticles as signal tracers and ferrocenyl compounds as signal enhancers.

    PubMed

    Liu, Yuting; Wang, Haijun; Xiong, Chengyi; Yuan, Yali; Chai, Yaqin; Yuan, Ruo

    2016-07-15

    In this work, N-(aminobutyl)-N-(ethylisoluminol) (ABEI), an analogue of luminol, is served as both the reductant and luminescence reagent to synthesize ABEI capped Pd@Au core-shell nanoparticles (ABEI-Pd@AuNPs). The nanoparticles not only exhibit inherent electrochemiluminescence (ECL) property, but also possess advantages of noble-metal nanomaterials such as outstanding electronic property, high specific surface area and good biocompatibility. In order to enhance the luminescence efficiency, ferrocene monocarboxylic acid (Fc) as catalyzer is grafted on the surface of ABEI-Pd@AuNPs with the aid of l-cysteine (l-Cys). When the Fc is electrochemically oxidized to ferricinium cation species (Fc(+)), the decomposition of H2O2 which existed in detection solution can be catalyzed by Fc(+) to generate oxygen-related free radicals, resulting effective signal amplification for ABEI-H2O2 system. For potential applications, the Pd@Au core-shell nanoparticles bifunctionalized by ABEI and catalyzer are employed as nano-carriers to immobilize detection antibody (Ab2). Based on sandwiched immunoreactions, a "signal-on" ECL immunosensor is developed for detection of human collagen type IV (Col IV), a potential biomarker associated with diabetic nephropathy. Consequently, the proposed immunosensor provides a wide linear detection ranging from 1pgmL(-1) to 10ngmL(-1) with a relatively low detection limit of 0.3pgmL(-1) (S/N=3). PMID:26985586

  7. Electrochemiluminescence immunosensor using poly(l-histidine)-protected glucose dehydrogenase on Pt/Au bimetallic nanoparticles to generate an in situ co-reactant.

    PubMed

    Xiao, Lijuan; Chai, Yaqin; Wang, Haijun; Yuan, Ruo

    2014-08-21

    In this work, Pt/Au bimetallic nanoparticles (Pt/Au NPs) were used as nanocarriers to develop an electrochemiluminescence (ECL) immunosensor for sensitive cardiac troponin I (cTnI) detection, coupling with enzyme-based signal amplification. First, gold nanoparticles modified Ru(phen)3(2+)-doped silica nanoparticles (Au@RuSiO2 NPs) with numerous luminophores were used as a platform, potentially increasing the signal intensity. Second, Pt/Au NPs with large surface area and rich surface atoms were a superior matrix for the immobilization of numerous antibodies (Ab2), poly(l-histidine) (PLH) and glucose dehydrogenase (GDH). More importantly, the PLH-protected GDH exhibited excellent enzymatic activity for the oxidation of glucose accompanied by the reduction of NAD(+) to NADH. The in situ generated NADH acted as a co-reactant of Ru(phen)3(2+), significantly enhancing the ECL signal. In this manner, the designed immunosensor displayed high sensitivity for the detection of cTnI in the range of 0.010 ng mL(-1) to 10 ng mL(-1) with a detection limit of 3.3 pg mL(-1) (S/N = 3). The proposed strategy holds a new promise for highly sensitive bioassays for application in clinical analyses. PMID:24940578

  8. Sintering behavior of spin-coated FePt and FePtAu nanoparticles

    NASA Astrophysics Data System (ADS)

    Kang, Shishou; Jia, Zhiyong; Zoto, I.; Reed, D.; Nikles, David E.; Harrell, J. W.; Thompson, Gregory; Mankey, Gary; Krishnamurthy, Vemuru V.; Porcar, L.

    2006-04-01

    FePt and [FePt]95Au5 nanoparticles with an average size of about 4 nm were chemically synthesized and spin coated onto silicon substrates. Samples were subsequently thermally annealed at temperatures ranging from 250 to 500 °C for 30 min. Three-dimensional structural characterization was carried out with small-angle neutron scattering (SANS) and small-angle x-ray diffraction (SAXRD) measurements. For both FePt and [FePt]95Au5 particles before annealing, SANS measurements gave an in-plane coherence length parameter a=7.3 nm, while SAXRD measurements gave a perpendicular coherence length parameter c=12.0 nm. The ratio of c/a is about 1.64, indicating the as-made particle array has a hexagonal close-packed superstructure. For both FePt and FePtAu nanoparticles, the diffraction peaks shifted to higher angles and broadened with increasing annealing temperature. This effect corresponds to a shrinking of the nanoparticle array, followed by agglomeration and sintering of the nanoparticles, resulting in the eventual loss of positional order with increasing annealing temperature. The effect is more pronounced for FePtAu than for FePt. Dynamic coercivity measurements show that the FePtAu nanoparticles have both higher intrinsic coercivity and higher switching volume at the same annealing temperature. These results are consistent with previous studies that show that additive Au both lowers the chemical ordering temperature and promotes sintering.

  9. Optical properties of Ag nanoparticle-polymer composite film based on two-dimensional Au nanoparticle array film

    PubMed Central

    2014-01-01

    The nanocomposite polyvinyl pyrrolidone (PVP) films containing Ag nanoparticles and Rhodamine 6G are prepared on the two-dimensional distinctive continuous ultrathin gold nanofilms. We investigate the optical properties and the fluorescence properties of silver nanoparticles-PVP polymer composite films influenced by Ag nanoparticles and Au nanoparticles. Absorption spectral analysis suggests that the prominently light absorption in Ag nanowire/PVP and Ag nanowire/PVP/Au film arises from the localized surface plasmon resonance of Ag nanowire and Au nanofilm. The enhanced fluorescence is observed in the presence of Ag nanowire and Au nanofilm, which is attributed to the excitation of surface plasmon polariton resonance of Ag nanowire and Au nanofilm. The gold nanofilm is proven to be very effective fluorescence resonance energy transfer donors. The fabricated novel structure, gold ultrathin continuous nanofilm, possesses high surface plasmon resonance properties and prominent fluorescence enhancement effect. Therefore, the ultrathin continuous gold nanofilm is an active substrate on nanoparticle-enhanced fluorescence. PMID:24685186

  10. Plasmon-enhanced photoelectrochemical water splitting using au nanoparticles decorated on hematite nanoflake arrays.

    PubMed

    Wang, Lei; Zhou, Xuemei; Nguyen, Nhat Truong; Schmuki, Patrik

    2015-02-01

    Hematite nanoflake arrays were decorated with Au nanoparticles through a simple solution chemistry approach. We show that the photoactivity of Au-decorated Fe2 O3 electrodes for photoelectrochemical water oxidation can be effectively enhanced in the UV/Visible region compared with the bare Fe2 O3 . Au-nanoparticle-decorated Fe2 O3 nanoflake electrodes exhibit a significant cathodic shift of the onset potential up to 0.6 V [vs. reversible hydrogen electrode (RHE)], and a two times increase in the water oxidation photocurrent is achieved at 1.23 VRHE . A maximum photocurrent of 2.0 mA cm(-2) at 1.6 VRHE is obtained in 1 M KOH under AM 1.5 (100 mW cm(-2) ) conditions. The enhancement in photocurrent can be attributed to the Au nanoparticles acting as plasmonic photosensitizers that increase the optical absorption.

  11. A highly efficient phase transfer method for preparing alkylamine-stabilized Ru, Pt, and Au nanoparticles.

    PubMed

    Yang, J; Lee, Jim Yang; Deivaraj, T C; Too, Heng-Phon

    2004-09-01

    A highly efficient phase-transfer method was developed to prepare alkylamine-stabilized nanoparticles of several noble metals. This method involved first mixing the metal hydrosols and an ethanol solution of dodecylamine and then extracting the dodecylamine-stabilized metal nanoparticles into toluene. The efficiency of this phase-transfer method was nearly 100%. Alkylamine-stabilized Ru, Pt, and Au nanoparticles 3.45, 4.33, and 7.89 nm in diameter, respectively, could be prepared this way. The self-assembly of dodecylamine-stabilized Pt and Au particles was also detected by transmission electron microscopy (TEM).

  12. Protein Viability on Au Nanoparticles during an Electrospray and Electrostatic-Force-Directed Assembly Process

    DOE PAGES

    Mao, Shun; Lu, Ganhua; Yu, Kehan; Chen, Junhong

    2010-01-01

    We study the protein viability on Au nanoparticles during an electrospray and electrostatic-force-directed assembly process, through which Au nanoparticle-antibody conjugates are assembled onto the surface of carbon nanotubes (CNTs) to fabricate carbon nanotube field-effect transistor (CNTFET) biosensors. Enzyme-linked immunosorbent assay (ELISA) and field-effect transistor (FET) measurements have been used to investigate the antibody activity after the nanoparticle assembly. Upon the introduction of matching antigens, the colored reaction from the ELISA and the change in the electrical characteristic of the CNTFET device confirm that the antibody activity is preserved during the assembly process.

  13. Enantiomeric separations of chiral pharmaceuticals using chirally modified tetrahexahedral Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Shukla, N.; Yang, D.; Gellman, A. J.

    2016-06-01

    Tetrahexahedral (THH, 24-sided) Au nanoparticles modified with D- or L-cysteine (Cys) have been used as enantioselective separators of the chiral pharmaceutical propranolol (PLL) in solution phase. Polarimetry has been used to measure the rotation of linearly polarized light by solutions containing mixtures of PLL and Cys/THH-Au NPs with varying enantiomeric excesses of each. Polarimetry yields clear evidence of enantiospecific adsorption of PLL onto the Cys/THH-Au NPs. This extends prior work using propylene oxide as a test chiral probe, by using the crystalline THH Au NPs with well-defined facets to separate a real pharmaceutical. This work suggests that chiral nanoparticles, coupled with a density separation method such as centrifugation, could be used for enantiomeric purification of real pharmaceuticals. A simple robust model developed earlier has also been used to extract the enantiospecific equilibrium constants for R- and S-PLL adsorption onto the D- and L-Cys/THH-Au NPs.

  14. Au nanoparticle sensitized ZnO nanopencil arrays for photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Wang, Tuo; Lv, Rui; Zhang, Peng; Li, Changjiang; Gong, Jinlong

    2014-11-01

    This paper describes the synthesis of Au nanoparticle sensitized ZnO nanopencil arrays on F-doped SnO2 substrates by an aqueous chemical growth and subsequent photoreduction method. The Au-ZnO nanopencil arrays yield a photocurrent of ~1.5 mA cm-2 at 1 V versus Ag/AgCl. The enhanced photocurrent is attributed to the surface plasmon resonance effect of Au nanoparticles and the prolonged lifetime of the photo-generated electron-hole pairs. The improved stability of ZnO is due to the plasmon resonance energy transfer process enabled by the Au nanoparticles, which enhances the electric field intensity in a small, well-defined location of the ZnO semiconductor.This paper describes the synthesis of Au nanoparticle sensitized ZnO nanopencil arrays on F-doped SnO2 substrates by an aqueous chemical growth and subsequent photoreduction method. The Au-ZnO nanopencil arrays yield a photocurrent of ~1.5 mA cm-2 at 1 V versus Ag/AgCl. The enhanced photocurrent is attributed to the surface plasmon resonance effect of Au nanoparticles and the prolonged lifetime of the photo-generated electron-hole pairs. The improved stability of ZnO is due to the plasmon resonance energy transfer process enabled by the Au nanoparticles, which enhances the electric field intensity in a small, well-defined location of the ZnO semiconductor. Electronic supplementary information (ESI) available: Illustrative schematic of PEC measurements, XPS of ZnO nanorods and nanopencils. See DOI: 10.1039/c4nr03735a

  15. Preparation of photoreactive phospholipid polymer nanoparticles to immobilize and release protein by photoirradiation.

    PubMed

    Chen, Weixin; Inoue, Yuuki; Ishihara, Kazuhiko

    2015-11-01

    Photoreactive and cytocompatible polymer nanoparticles for immobilizing and releasing proteins were prepared. A water-soluble and amphiphilic phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA)-co-4-(4-(1-methacryloyloxyethyl)-2-methoxy-5-nitrophenoxy) butyric acid (PL)) (PMB-PL) was synthesized. The PMB-PL underwent a cleavage reaction at the PL unit with photoirradiation at a wavelength of 365 nm. Additionally, the PMB-PL took polymer aggregate in aqueous medium and was used to modify the surface of biodegradable poly(L-lactic acid) (PLA) nanoparticle as an emulsifier. The morphology of the PMB-PL/PLA nanoparticle was spherical and approximately 130 nm in diameter. The carboxylic acid group in the PL unit could immobilize proteins by covalent bonding. The bound proteins were released by a photoinduced cleavage reaction. Within 60s, up to 90% of the immobilized proteins was released by photoirradiation. From these results and with an understanding of the fundamental properties of MPC polymers, we concluded that PMB-PL/PLA nanoparticles have the potential to be used as smart carriers to deliver proteins to biological systems, such as the inside of living cells.

  16. Size and Surface Effect of Gold Nanoparticles (AuNPs) in Nanogold-Assisted Pcr

    NASA Astrophysics Data System (ADS)

    Huang, Jiehuan; Zhang, Xiaodong; Wang, Chunmei; Wang, Lihua; Li, Haikuo; Cao, Xueyan; Zhang, Aili; Li, Xueling; Fan, Chunhai; Hu, Jun

    Recently, gold nanoparticles (AuNPs) were reported to increase the specificity and efficiency of the polymerase chain reaction (PCR). In this paper, we tested the enhancement of AuNPs with five different sizes on the specificity of two-round PCR. The results showed that, except 5.02 nm AuNPs, the AuNPs that could achieve the similar enhancement happened to have nearly the same total surface area. The surface effect seems to be the key factor of nanogold-assisted PCR.

  17. In situ immobilization of palladium nanoparticles in microfluidic reactors and assessment of their catalytic activity.

    PubMed

    Lin, Rui; Freemantle, Ruel G; Kelly, Nicholas M; Fielitz, Thomas R; Obare, Sherine O; Ofoli, Robert Y

    2010-08-13

    We report on the synthesis and characterization of catalytic palladium nanoparticles (Pd NPs) and their immobilization in microfluidic reactors fabricated from polydimethylsiloxane (PDMS). The Pd NPs were stabilized with D-biotin or 3-aminopropyltrimethoxysilane (APTMS) to promote immobilization inside the microfluidic reactors. The NPs were homogeneous with narrow size distributions between 2 and 4 nm, and were characterized by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and x-ray diffraction (XRD). Biotinylated Pd NPs were immobilized on APTMS-modified PDMS and glass surfaces through the formation of covalent amide bonds between activated biotin and surface amino groups. By contrast, APTMS-stabilized Pd NPs were immobilized directly onto PDMS and glass surfaces rich in hydroxyl groups. Fourier transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectroscopy (XPS) results showed successful attachment of both types of Pd NPs on glass and PDMS surfaces. Both types of Pd NPs were then immobilized in situ in sealed PDMS microfluidic reactors after similar surface modification. The effectiveness of immobilization in the microfluidic reactors was evaluated by hydrogenation of 6-bromo-1-hexene at room temperature and one atmosphere of hydrogen pressure. An average first-run conversion of 85% and selectivity of 100% were achieved in approximately 18 min of reaction time. Control experiments showed that no hydrogenation occurred in the absence of the nanocatalysts. This system has the potential to provide a reliable tool for efficient and high throughput evaluation of catalytic NPs, along with assessment of intrinsic kinetics.

  18. Fe impurities weaken the ferromagnetic behavior in Au nanoparticles.

    PubMed

    Crespo, P; García, M A; Fernández Pinel, E; Multigner, M; Alcántara, D; de la Fuente, J M; Penadés, S; Hernando, A

    2006-10-27

    In this Letter, we report on a crucial experiment showing that magnetic impurities reduce the ferromagnetic order temperature in thiol-capped Au glyconanoparticles (GNPs). The spontaneous magnetization of AuFe GNPs exhibits a fast decrease with temperature that contrasts with the almost constant value of the magnetization observed in Au NPs. Moreover, hysteresis disappears below 300 K. Both features indicate that Fe impurities reduce the high local anisotropy field responsible for the ferromagnetic behavior in Au GNPs. As a consequence, the amazing ferromagnetism in Au NPs should not be associated with the presence of magnetic impurities.

  19. Phase decomposition of AuFe alloy nanoparticles embedded in silica matrix under swift heavy ion irradiation

    NASA Astrophysics Data System (ADS)

    Pannu, Compesh; Bala, Manju; Singh, U. B.; Srivastava, S. K.; Kabiraj, D.; Avasthi, D. K.

    2016-07-01

    AuFe alloy nanoparticles embedded in silica matrix are synthesized using atom beam sputtering technique and subsequently irradiated with 100 MeV Au ions at various fluences ranging from 1 × 1013 to 6 × 1013 ions/cm2. The X-ray diffraction, absorption spectroscopy, X-ray photo electron spectroscopy and transmission electron microscopy results show that swift heavy ion irradiation leads to decomposition of AuFe alloy nanoparticles from surface region and subsequent reprecipitation of Au and Fe nanoparticles occur. The process of phase decomposition and reprecipitation of individual element nanoparticles is explained on the basis of inelastic thermal spike model.

  20. Controlled growth and multi-photon luminescence of hexagonal arrays of Au nanoparticles on anodic aluminum oxide templates

    NASA Astrophysics Data System (ADS)

    Li, Jian-Bo; Yu, Ying; Peng, Xiao-Niu; Yang, Zhong-Jian; Zhou, Zhang-Kai; Zhou, Li

    2012-06-01

    Au nanoparticles were deposited onto anodic aluminum oxide (AAO) templates by using a rotating sputtering technique. Interestingly, hexagonal arrays of Au nanoparticles were obtained at an appropriate rotating rate and deposition time. Strong three-photon luminescence was observed from the hexagonally arrayed Au nanoparticles, which is attributed to the strong enhancements of local electromagnetic fields at both excitation and emission wavelengths. Our findings provide a new method to prepare Au nanoparticle arrays with large field enhancements and could have prospective applications in plasmonic nanodevices, such as surface-enhanced Raman scattering substrates, and biosensors.

  1. Amperometric immunosensor for α-fetoprotein antigen in human serum based on co-immobilizing dinuclear copper complex and gold nanoparticle doped chitosan film

    NASA Astrophysics Data System (ADS)

    Gan, Ning; Meng, Ling Hua; Wang, Feng

    2009-09-01

    A sensitive amperometric immunosensor for α-fetoprotein (AFP), a tumor marker for the diagnosis of hepatocellular carcinoma (HCC), was constructed, The immunosensor is prepared by co-immobilizing [Cu2(phen)2Cl2] (μ-Cl)2 (CuL), nano-Au/Chitosan(Chit) composite, horseradish peroxidase (HRP) and AFP antibody(anti-AFP) on a glassy carbon electrode (GCE). Firstly, CuL was irreversibly absorb on GCE electrode through π-π stacking interaction; then nano-Au/Chit composite was immobilized onto the electrode because of its excellent membrane-forming ability, finally HRP and anti-AFP was adsorbed onto the surface of the gold nanoparticles to construct GCE | CuL/nanoAu-chit/HRP/anti-AFP immunosensor. The preparation procedure of the electrode was characterized by electrochemical and spectroscopy method. The results showed that this immunosensor exhibited an excellent electrocatalytic response to the reduction of hydrogen peroxide (H2O2) without the aid of an electron mediator, offers a high-sensitivity (1710 nA · ng-1 · ml-1) for the detection of AFP and has good correlation for detection of AFP in the range of 0.2 to 120.0 ng/ml with a detection limit of 0.05 ng/ml. The biosensor showed high selectivity as well as good stability and reproductivity.

  2. Highly sensitive electrochemiluminescenc assay of acetylcholinesterase activity based on dual biomarkers using Pd-Au nanowires as immobilization platform.

    PubMed

    Ye, Cui; Wang, Min-Qiang; Zhong, Xia; Chen, Shihong; Chai, Yaqin; Yuan, Ruo

    2016-05-15

    One-dimensional Pd-Au nanowires (Pd-Au NWs) were prepared and applied to fabricate an electrochemiluminescence (ECL) biosensor for the detection of acetylcholinesterase (AChE) activity. Compared with single-component of Pd or Au, the bimetallic nanocomposite of Pd-Au NWs offers a larger surface area for the immobilization of enzyme, and displays superior electrocatalytic activity and efficient electron transport capacity. In the presence of AChE and choline oxidase (ChOx), acetylcholine (ATCl) is hydrolyzed by AChE to generate thiocholine, then thiocholine is catalyzed by ChOx to produce H2O2 in situ, which serves as the coreactant to effectively enhance the ECL intensity in luminol-ECL system. The detection principle is based on the inhibited AChE and reactivated AChE as dual biomarkers, in which AChE was inhibited by organophosphorus (OP) agents, and then reactivated by obidoxime. Such dual biomarkers method can achieve credible evaluation for AChE activity via providing AChE activity before and after reactivation. The liner range for AChE activity detection was from 0.025 U L(-1) to 25 KU L(-1) with a low detection limit down to 0.0083 U L(-1). PMID:26686921

  3. Highly sensitive electrochemiluminescenc assay of acetylcholinesterase activity based on dual biomarkers using Pd-Au nanowires as immobilization platform.

    PubMed

    Ye, Cui; Wang, Min-Qiang; Zhong, Xia; Chen, Shihong; Chai, Yaqin; Yuan, Ruo

    2016-05-15

    One-dimensional Pd-Au nanowires (Pd-Au NWs) were prepared and applied to fabricate an electrochemiluminescence (ECL) biosensor for the detection of acetylcholinesterase (AChE) activity. Compared with single-component of Pd or Au, the bimetallic nanocomposite of Pd-Au NWs offers a larger surface area for the immobilization of enzyme, and displays superior electrocatalytic activity and efficient electron transport capacity. In the presence of AChE and choline oxidase (ChOx), acetylcholine (ATCl) is hydrolyzed by AChE to generate thiocholine, then thiocholine is catalyzed by ChOx to produce H2O2 in situ, which serves as the coreactant to effectively enhance the ECL intensity in luminol-ECL system. The detection principle is based on the inhibited AChE and reactivated AChE as dual biomarkers, in which AChE was inhibited by organophosphorus (OP) agents, and then reactivated by obidoxime. Such dual biomarkers method can achieve credible evaluation for AChE activity via providing AChE activity before and after reactivation. The liner range for AChE activity detection was from 0.025 U L(-1) to 25 KU L(-1) with a low detection limit down to 0.0083 U L(-1).

  4. Light-Induced Reversible Self-Assembly of Gold Nanoparticles Surface-Immobilized with Coumarin Ligands.

    PubMed

    He, Huibin; Feng, Miao; Chen, Qidi; Zhang, Xinqi; Zhan, Hongbing

    2016-01-18

    A novel light-induced reversible self-assembly (LIRSA) system is based on the reversible photodimerization and photocleavage of coumarin groups on the surface of gold nanoparticles (AuNPs) in THF solution. Facilitated by coumarin groups, light irradiation at 365 nm triggers the stable assembly of monodisperse AuNPs; the resulting self-assembly system can be disassembled back to the disassembled state by a relatively short exposure to benign UV light. The reversible self-assembly cycle can be repeated 4 times. A specific concentration range of coumarin ligand and the THF solvent were identified to be the two predominant factors that contribute to the LIRSA of AuNPs. This is the first successful application of reversible photodimerization based on a coumarin derivative in the field of AuNP LIRSA. This LIRSA system may provide unique opportunities for the photoregulated synthesis of many adjustable nanostructures and devices.

  5. Gold Nanoparticles Doped with (199) Au Atoms and Their Use for Targeted Cancer Imaging by SPECT.

    PubMed

    Zhao, Yongfeng; Pang, Bo; Luehmann, Hannah; Detering, Lisa; Yang, Xuan; Sultan, Deborah; Harpstrite, Scott; Sharma, Vijay; Cutler, Cathy S; Xia, Younan; Liu, Yongjian

    2016-04-20

    Gold nanoparticles have been labeled with various radionuclides and extensively explored for single photon emission computed tomography (SPECT) in the context of cancer diagnosis. The stability of most radiolabels, however, still needs to be improved for accurate detection of cancer biomarkers and thereby monitoring of tumor progression and metastasis. Here, the first synthesis of Au nanoparticles doped with (199)Au atoms for targeted SPECT tumor imaging in a mouse triple negative breast cancer (TNBC) model is reported. By directly incorporating (199)Au atoms into the crystal lattice of each Au nanoparticle, the stability of the radiolabel can be ensured. The synthetic procedure also allows for a precise control over both the radiochemistry and particle size. When conjugated with D-Ala1-peptide T-amide, the Au nanoparticles doped with (199)Au atoms can serve as a C-C chemokine receptor 5 (CCR5)-targeted nanoprobe for the sensitive and specific detection of both TNBC and its metastasis in a mouse tumor model.

  6. Au-ZnO hybrid nanoparticles exhibiting strong charge-transfer-induced SERS for recyclable SERS-active substrates.

    PubMed

    Liu, Liping; Yang, Haitao; Ren, Xiao; Tang, Jin; Li, Yongfeng; Zhang, Xiangqun; Cheng, Zhaohua

    2015-03-12

    Flower-shaped Au-ZnO hybrid nanoparticles have been prepared via seeding growth and subsequent wet-chemical etching of Au-ZnO core-shell nanoparticles. The etched Au-ZnO hybrid nanoparticles have shown a stronger surface-enhanced Raman scattering (SERS) signal of the nontotally symmetric (b2) vibrational modes of PATP molecules than Au nanoparticles alone, which is attributed to the chemical enhancement effect of the ZnO layer which is greatly excited by the localized surface plasmon resonance (LSPR) of Au cores. Further, the mechanism of the LSPR-enhanced charge transfer (CT) effect has been proved by the SERS spectra of PATP molecules excited using different laser sources from 325 to 785 nm. Moreover, the photocatalytic experimental results indicated that Au-ZnO hybrid nanoparticles are promising as biologically compatible and recyclable SERS-active platforms for different molecular species.

  7. Supramolecular immobilization of redox enzymes on cyclodextrin-coated magnetic nanoparticles for biosensing applications.

    PubMed

    Díez, Paula; Villalonga, Reynaldo; Villalonga, María L; Pingarrón, José M

    2012-11-15

    Mono-6-formyl-β-cyclodextrin moieties were attached to (3-aminopropyl)triethoxysilane-coated superparamagnetic Fe(3)O(4) nanoparticles by reductive alkylation with NaBH(3)CN. The oligosaccharide-capped core-shell nanoparticles were employed as support for the supramolecular immobilization of two different adamantane-modified enzymes, tyrosinase and xanthine oxidase, through host-guest interactions. The enzyme-modified nanomaterial was further used to magnetically modify carbon paste electrodes for constructing amperometric biosensors toward cathecol and xanthine. The tyrosinase and xanthine oxidase based biosensors showed excellent electroanalytical behaviours, with linear ranges of 100 nM-12 μM cathecol and 5.0-120 μM xanthine, sensitivities of 12 mA/M and 130 mA/M, and low detection limits of 22 nM and 2.0 μM, respectively. The supramolecular nature of the immobilization approach was confirmed by electroanalytical methods.

  8. Structural studies of Au-Pd bimetallic nanoparticles by a genetic algorithm method

    NASA Astrophysics Data System (ADS)

    Shao, Gui-Fang; Tu, Na-Na; Liu, Tun-Dong; Xu, Liang-You; Wen, Yu-Hua

    2015-06-01

    Metallic nanoparticles have attracted particular interests due to their excellent electronic, catalytic and optical properties over the past decades. Atomic-level understanding of structural characteristics of metallic nanoparticles is of great importance for their syntheses and applications because the structural characteristics strongly determine their chemical and physical properties. In this article, we systematically investigated the structural stability and structural features of Au-Pd nanoparticles by using the genetic algorithm with the quantum correction Sutton-Chen potentials. Layered coordinate ranking method and an effective fitness function have been introduced into the genetic algorithm to enhance its searching ability of low-energy configurations. Here were addressed eight representative nanoshapes including single-crystalline and multiple-twinned structures. The results reveal that the developed genetic algorithm exhibits superior searching ability. In all polyhedra, the truncated octahedron possessed the best stability, while the icosahedron did the worst. Moreover, segregation of Au to the surface and that of Pd to the core were disclosed in these polyhedral Au-Pd nanoparticles. Particularly, for Au composition of 50%, the optimized structures of Au-Pd nanoparticles were predicted to exhibit core-shell structures.

  9. Visual detection of organophosphorus pesticides represented by mathamidophos using Au nanoparticles as colorimetric probe.

    PubMed

    Li, Hongkun; Guo, Jiajia; Ping, Hong; Liu, Lurui; Zhang, Minwei; Guan, Fengrui; Sun, Chunyan; Zhang, Qian

    2011-12-15

    With citrate-coated Au nanoparticles as colorimetric probe, a novel visual method for rapid assay of organophosphorus pesticides has been developed. The assay principle is based on catalytic hydrolysis of acetylthiocholine into thiocholine by acetylcholinesterase, which induces the aggregation of Au nanoparticles and the color change from claret-red to purple or even grey. The original plasmon absorption of Au nanoparticles at 522 nm decreases, and simultaneously, a new absorption band appears at 675 nm. The irreversible inhibition of organophosphorus pesticides on acetylcholinesterase prevents aggregation of Au nanoparticles. Under optimum conditions, the absorbance at 522 nm of Au nanoparticles is related linearly to the concentration of mathamidophos in the range of 0.02-1.42 μg/mL with a detection limit of 1.40 ng/mL. This colorimetric method has been successfully utilized to detect mathamidophos in vegetables with satisfactory results. The proposed colorimetric assay exhibits good reproducibility and accuracy, providing a simple and rapid method for the analysis of organophosphorus pesticides.

  10. Design, synthesis and characterization of functionalized SCK nanoparticles and functionalized biocompatible surfaces: Construction platforms for nanoparticle assembly and biomacromolecule immobilization

    NASA Astrophysics Data System (ADS)

    Qi, Kai

    This dissertation focuses on the design, synthesis and characterization of biotin-functionalized shell crosslinked knedel-like (SCK) nanoparticles, biotin-functionalized polymer brush surfaces, and their utilization as construction platforms for the study of streptavidin-mediated nanoparticle assembly. SCKs are a class of nano-objects, originating from the self-assembly of amphiphilic block copolymers. Their synthesis and functionalization were accomplished beginning from the synthesis of block copolymers via living radical polymerization techniques, and extending to supramolecular assembly and polymer modification reactions. The regioselective placement of biotin units on the surface of SCK nanoparticles was achieved via two synthetic methods: mixed micelle formation with chain-end biotinylated block copolymers and their non-biotinylated analog followed by shell crosslinking reactions; and post-preparation functionalization reactions of SCKs with biotinylated molecules. Both methods enabled facile control of the degree of biotinylation. The resulting SCK nanoparticles were characterized thoroughly and the bioavailability of the biotin moieties present on the SCK surface was determined. These biotinylated SCK nanoparticles were used as building blocks for the preparation of streptavidin-mediated nanoparticle assemblies upon well-defined biotinylated substrates. Chain-end biotinylated polymer brushes served as well-defined substrates for nanoparticle assembly. These functionalized polymer brush surfaces were prepared by a grafting-from technique utilizing nitroxide mediated polymerization (NMP). Functionalized initiators were synthesized and covalently immobilized on the surface in patterns by contact molding that allowed for the preparation of nano-patterned polymer brush surfaces via NMP. The biotinylated polymer brush surfaces were characterized thoroughly and used to immobilize streptavidin. Subsequent attachment of biotinylated SCKs led to the formation of

  11. Photoluminescence enhancement in few-layer WS{sub 2} films via Au nanoparticles

    SciTech Connect

    Choi, Sin Yuk; Yip, Cho Tung; Li, Guang-Can; Lei, Dang Yuan; Fung, Kin Hung; Yu, Siu Fung E-mail: jh.hao@polyu.edu.hk; Hao, Jianhua E-mail: jh.hao@polyu.edu.hk

    2015-06-15

    Nano-composites of two-dimensional atomic layered WS{sub 2} and Au nanoparticles (AuNPs) have been fabricated by sulfurization of sputtered W films followed by immersing into HAuCl{sub 4} aqueous solution. The morphology, structure and AuNPs distribution have been characterized by electron microscopy. The decorated AuNPs can be more densely formed on the edge and defective sites of triangle WS{sub 2}. We have compared the optical absorption and photoluminescence of bare WS{sub 2} and Au-decorated WS{sub 2} layers. Enhancement in the photoluminescence is observed in the Au-WS{sub 2} nano-composites, attributed to localized surface plasmonic effect. This work provides the possibility to develop photonic application in two-dimensional materials.

  12. Biosensing capability of gold-nanoparticle- immobilized three-dimensionally ordered macroporous film

    NASA Astrophysics Data System (ADS)

    Chen, H.-H.; Suzuki, H.; Sato, O.; Gu, Z.-Z.

    2005-11-01

    A new type of biosensor was fabricated by coating gold nanoparticles onto a film with a three-dimensionally ordered macroporous (3DOM) structure. It was found that the localized surface plasmon resonance of the immobilized nanoparticles changes with the infiltration medium inside the voids of the 3DOM film and the surface-adsorbed compounds. Application of this type of film to the real-time detection of immunoreaction was demonstrated. It is anticipated that this kind of film will have applications in label-free biosensors.

  13. Enhanced surface plasmon resonance with the modified catalytic growth of Au nanoparticles.

    PubMed

    Yang, Xiaohai; Wang, Qing; Wang, Kemin; Tan, Weihong; Li, Huimin

    2007-01-15

    The catalytic growth of Au nanoparticles (AuNPs) has been employed in several analytical methods for improving the detection sensitivity, or integrated with the enzyme reactions for the quantitative detection of the respective substrates. However, the catalytic growth of Au nanoparticles do not work in some situations, such as surface plasmon resonance (SPR), electrochemistry, where metal matrices were used, because metal matrices used in these techniques, e.g. Au, are susceptible to metal deposition, which increased the background seriously. In this work, a SiO(2) layer was vapor-deposited on the gold film. The inhibition of metal deposition by this SiO(2) layer was investigated by SPR sensor. The results showed that the SiO(2) layer could avoid the deposition of metal on Au film. With the low background achieved by SiO(2)-coated Au films, sensitive detection of DNA hybridization using the catalytic growth of Au nanoparticles enhanced SPR was demonstrated. The work described here maybe helpful for the development of sensitive bioanalytical methods.

  14. Effects of the proximity of Au nanoparticles on magnetic and transport properties of LSMO ultrathin layers

    SciTech Connect

    Brivio, S.; Magen Dominguez, Cesar; Sidorenko, A; Petti, D.; Cantoni, M.; Finazzi, M; Ciccacci, F; Renzi, R; Varela del Arco, Maria; Picozzi, S.; Bertacco, R.

    2010-01-01

    The effect of the proximity of Au nanoparticles on the transport and magnetic properties of ultrathin La2/3Sr1/3MnO3 (LSMO) films has been investigated. We find a huge increase of the resistivity of the manganite (by four orders of magnitude for a Au nominal thickness of 2 nm), which is accompanied by a strong decrease of the Curie temperature. A combined scanning transmission electron microscopy and electron energy loss spectroscopy (STEM-EELS) analysis shows that interfaces are coherent and atomically sharp, and that the structural quality is very high. On the other end, a strong reduction of the Mn oxidation state is seen upon Au capping. NMR data show a strong attenuation of the double exchange signal upon formation of Au nanoparticles. Ab-initio calculations indicate a negligible influence of Au on LSMO at an ideal interface, with the LSMO surface magnetic and electronic properties essentially unchanged upon creation of the Au/LSMO interface. In view of these calculations, the experimental results cannot be explained in terms of purely electrostatic effects induced by the proximity of a noble metal. Here we propose that the main driving force underlying the observed change in physical properties is the high reactivity of Au nanoparticles which can locally pump oxygen from the manganite, thus favouring a phase separation ensuing from O inhomogeneity which deteriorates the transport and electrical properties.

  15. Interaction of Mesotetrakis (2,6,dimethoxyphenol) Porphyrin with AuTiO2 Nanoparticles: A Spectroscopic Approach.

    PubMed

    Revathi, R; Rameshkumar, A; Sivasudha, T

    2016-06-01

    The combination of nanoparticles with the photosensitizing molecules will assist in developing new approach for their biological applications. In this paper work, we have studied the interaction of photosensitising mesotetrakis (2,6,dimethoxyphenol) porphyrin molecule (P1) with AuTiO2 nanoparticles using absorption, fluorescence and time resolved measurements. An isosbestic point is appeared in the absorption spectrum of P1 on increasing the concentration of AuTiO2 nanoparticles indicates the interaction of P1 with AuTiO2 nanoparticles. Static type of quenching is observed in the fluorescence quenching measurement which is confirmed through lifetime measurements. Energy level calculations and Rehm Weller methods confirms the electron transfer mechanism from the excited P1 to the AuTiO2 nanoparticles. The observed effective binding and electron transfer property of porphyrin with AuTiO2 nanoparticles has great potential to be applied in the field of photodynamic therapy.

  16. Interaction of Mesotetrakis (2,6,dimethoxyphenol) Porphyrin with AuTiO2 Nanoparticles: A Spectroscopic Approach.

    PubMed

    Revathi, R; Rameshkumar, A; Sivasudha, T

    2016-06-01

    The combination of nanoparticles with the photosensitizing molecules will assist in developing new approach for their biological applications. In this paper work, we have studied the interaction of photosensitising mesotetrakis (2,6,dimethoxyphenol) porphyrin molecule (P1) with AuTiO2 nanoparticles using absorption, fluorescence and time resolved measurements. An isosbestic point is appeared in the absorption spectrum of P1 on increasing the concentration of AuTiO2 nanoparticles indicates the interaction of P1 with AuTiO2 nanoparticles. Static type of quenching is observed in the fluorescence quenching measurement which is confirmed through lifetime measurements. Energy level calculations and Rehm Weller methods confirms the electron transfer mechanism from the excited P1 to the AuTiO2 nanoparticles. The observed effective binding and electron transfer property of porphyrin with AuTiO2 nanoparticles has great potential to be applied in the field of photodynamic therapy. PMID:27427692

  17. Influence of the S-Au Bond Strength on the Magnetic Behavior of S-Capped Au Nanoparticles

    NASA Astrophysics Data System (ADS)

    Vázquez, María J. Rodríguez; Rivas, José; López-Quintela, M. Arturo; Mosquera, Antonio Mouriño; Torneiro, Mercedes

    Recently, large permanent atomic magnetic moments have been found in Au nanoparticles capped with thiols. It is assumed that the formation of localized Au-S bonds at the particle surface induces the damping of the surface plasmon resonance and the appearance of a ferromagnetic-like behavior. In this work we will show for the first time that thioethers can also induce both phenomena, i.e., the damping of the plasmon band and the appearance of permanent magnetic moments. Furthermore, we have studied the influence of the Au-S bond strength on both phenomena using two different synthesized thioether ligands. It will be shown that, although both ligands can induce a complete damping of the plasmon band, only with one of the ligands (the one corresponding to the stronger S-Au bond) the appearance of a ferromagnetic-like order is observed. This is an indication of the extreme sensitivity of the magnetism on the strength of the charge transfer at the S-Au bond.

  18. Immobilized Silver Nanoparticles on Chitosan with Special Surface State-Enhanced Antimicrobial Efficacy and Reduced Cytotoxicity.

    PubMed

    He, Miao; Lu, Liying; Zhang, Jinchi; Li, Danzhen

    2015-09-01

    Immobilized chitosan-Ag nanoparticles (CTS-Ag NPs) with special surface state have been synthesized successfully through immobilizing Ag NPs on the amino-enriched surface of CTS by reducing Ag (I) in situ. The antimicrobial efficiency and potency of CTS-Ag NPs against Escherichia coli and Staphylococcus aureus were studied. Our results reveal that surface-immobilized CTS-Ag NPs show better antimicrobial efficacy than several other reported monodisperse colloidal Ag NPs, because the unique surface state of our CTS-Ag NPs leads to both "contact killing" and "ion mediated killing" functions. Due to the synergetic effect of CTS and Ag NPs, the immobilized CTS-Ag NPs present a broader antimicrobial spectrum and a more effective antifungal activity against Monilia albican. In addition, CTS as an environment friendly dispersant can help to reduce the cytotoxicity of Ag NPs on higher organisms. The immobilized CTS-Ag NPs are stable and can maintain good disinfection potential after 6 months' shelf-time. PMID:26716197

  19. Characterization and immobilization of trypsin on tannic acid modified Fe3O4 nanoparticles.

    PubMed

    Atacan, Keziban; Özacar, Mahmut

    2015-04-01

    Fe3O4 nanoparticles (NPs) were synthesized by co-precipitating Fe2+ and Fe3+ in an ammonia solution. Fe3O4 NPs functionalized with tannic acid were prepared. After functionalization process, trypsin enzyme was immobilized on these Fe3O4 NPs. The influence of pH, temperature, thermal stability, storage time stability and reusability on non-covalent immobilization was studied. The properties of Fe3O4 and its modified forms were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), UV-vis spectrometer (UV) and X-ray diffraction (XRD), magnetization and zeta potential measurements. The immobilized enzyme was slightly more stable than the free enzyme at 45°C. According to the results, the activity of immobilized trypsin was preserved 55% at 45°C after 2 h and 90% after 120 days storage. In addition, the activity of the immobilized trypsin was preserved 40% of its initial activity after eight times of successive reuse. PMID:25686792

  20. Improvement of the stability and activity of immobilized glucose oxidase on modified iron oxide magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Abbasi, Mahboube; Amiri, Razieh; Bordbar, Abdol-Kalegh; Ranjbakhsh, Elnaz; Khosropour, Ahmad-Reza

    2016-02-01

    Immobilized proteins and enzymes are widely investigated in the medical field as well as the food and environmental fields. In this study, glucose oxidase (GOX) was covalently immobilized on the surface of modified iron oxide magnetic nanoparticles (MIMNs) to produce a bioconjugate complex. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to the size, shape and structure characterization of the MIMNs. Binding of GOX to these MIMNs was confirmed by using FT-IR spectroscopy. The stability of the immobilized and free enzyme at different temperature and pH values was investigated by measuring the enzymatic activity. These studies reveal that the enzyme's stability is enhanced by immobilization. Further experiments showed that the storage stability of the enzyme is improved upon binding to the MIMNs. The results of kinetic measurements suggest that the effect of the immobilization process on substrate and product diffusion is small. Such bioconjugates can be considered as a catalytic nanodevice for accelerating the glucose oxidation reaction for biotechnological purposes.

  1. On-chip enzymatic microreactor using trypsin-immobilized superparamagnetic nanoparticles for highly efficient proteolysis.

    PubMed

    Liu, Junyan; Lin, Shuang; Qi, Dawei; Deng, Chunhui; Yang, Pengyuan; Zhang, Xiangmin

    2007-12-28

    An easily replaceable microchip enzymatic microreactor has been fabricated based on the glass microchip with trypsin-immobilized superparamagnetic nanoparticles. Magnetic nanoparticles with small size (50 nm in diameter) and strong magnetism were synthesized. At first, amine-functionalized magnetic nanoparticles with high magnetic responsivity and excellent dispersibility were prepared through a facile one-pot strategy. Then, magnetic nanoparticles were functionalized with numerous aldehyde (-CHO) groups by treating the as-synthesized, amine-functionalized magnetic nanoparticles with glutaraldehyde. Finally, immobilization of trypsin onto the aldehyde-functionalized magnetic nanoparticles was achieved through reaction of the aldehyde groups with amine groups of trypsin. The prepared magnetic nanoparticles were then locally packed onto the glass microchip by the application of a strong magnetic field using a magnet to form an on-chip magnetic nanoparticles packing bed. Capability of the proteolytic microreactor was demonstrated by cytochrome c, bovine serum albumin and myoglobin as model proteins. The digestion products were characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with sequence coverage of 83%, 43% and 79% observed, respectively. Complete protein digestion was achieved in a short time (10 s) under the flow rate of 5 microL/min. These results are expected to open up a new possibility for the proteolysis analysis as well as a new application of magnetic nanoparticles. It is easy to replace the nanoparticles and make the new microreactor. It takes less than 1 min under the condition of extra magnetic to form a new packing bed. The packing bed can be used for at least five times without any treatments. Additionally, since the preparation and surface functionality of magnetic nanoparticles is low-cost and reproducible, the preparation method and application approach of the magnetic nanoparticles may find much

  2. Trimetallic Au/Pt/Rh Nanoparticles as Highly Active Catalysts for Aerobic Glucose Oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Haijun; Cao, Yingnan; Lu, Lilin; Cheng, Zhong; Zhang, Shaowei

    2015-02-01

    This paper reports the findings of an investigation of the correlations between the catalytic activity for aerobic glucose oxidation and the composition of Au/Pt/Rh trimetallic nanoparticles (TNPs) with average diameters of less than 2.0 nm prepared by rapid injection of NaBH4. The prepared TNPs were characterized by UV-Vis, TEM, and HR-TEM. The catalytic activity of the alloy-structured TNPs for aerobic glucose oxidation is several times higher than that of Au monometallic nanoparticles with nearly the same particle size. The catalytic activities of the TNP catalysts were dependent not only on the composition, but also on the electronic structure. The high catalytic activities of the Au/Pt/Rh TNPs can be ascribed to the formed negative-charged Au atoms due to electron donation of Rh neighboring atoms acting as catalytically active sites for aerobic glucose oxidation.

  3. Remarkable enhancement of electrocatalytic activity by tuning the interface of Pd-Au bimetallic nanoparticle tubes.

    PubMed

    Cui, Chun-Hua; Yu, Jin-Wen; Li, Hui-Hui; Gao, Min-Rui; Liang, Hai-Wei; Yu, Shu-Hong

    2011-05-24

    The interface, which formed in a bimetallic system, is a critical issue to investigate the fundamental mechanism of enhanced catalytic activity. Here, we designed unsupported Pd-Au bimetallic nanoparticle tubes with a tunable interface, which was qualitatively controlled by the proportion of Pd and Au nanoparticles (NPs), to demonstrate the remarkably enhanced effect of Pd and Au NPs in electro-oxidation of ethanol. The results demonstrated that the electrocatalytic activity is highly relative to the interface and has no direct relation with individual metal component in the Pd-Au system. This effect helps us in achieving a fundamental understanding of the relationship between their activity and the interface structure and chemical properties and, consequently, is helpful in designing new catalysts with high performances. PMID:21506570

  4. Hydrogen sensing with optical microfibers coated with Pd/Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Monzón-Hernández, David; Luna-Moreno, Donato; Martínez-Escobar, Dalia; Villatoro, Joel

    2010-10-01

    Optical microfibers decorated with PdAu nanoparticles are proposed for fast hydrogen sensing. The microfibers were obtained by simply tapering conventional telecommunications fiber down to dimensions comparable to the wavelength of the guided light. A few millimeters of the microfiber were coated with a PdAu layer in island form by depositing the layer at low evaporation rate (0.1 Å/s). Then the islands were grown with a thermal annealing process until composite nanoparticles were formed. The PdAu nanoparticles deposited on the optical microfibers experience optical and physical changes when they exposed to hydrogen. This gives rise to reversible transmission changes with an unusual pulsed like behavior which is attributed to scattering of the guided light. The devices are promising for detecting low concentrations of hydrogen (up to 8%) at room temperature with response and recovery times on the order of seconds.

  5. Highly sensitive and rapid bacteria detection using molecular beacon-Au nanoparticles hybrid nanoprobes.

    PubMed

    Cao, Jing; Feng, Chao; Liu, Yan; Wang, Shouyu; Liu, Fei

    2014-07-15

    Since many diseases are caused by pathogenic bacterial infections, accurate and rapid detection of pathogenic bacteria is in urgent need to timely apply appropriate treatments and to reduce economic costs. To end this, we designed molecular beacon-Au nanoparticle hybrid nanoprobes to improve the bacterial detection efficiency and sensitivity. Here, we show that the designed molecular beacon modified Au nanoparticles could specifically recognize synthetic DNAs targets and can readily detect targets in clinical samples. Moreover, the hybrid nanoprobes can recognize Escherichia coli within an hour at a concentration of 10(2) cfu/ml, which is 1000-folds sensitive than using molecular beacon directly. Our results show that the molecular beacon-Au nanoparticle hybrid nanoprobes have great potential in medical and biological applications.

  6. Immobilization of arsenate in a sandy loam soil using starch-stabilized magnetite nanoparticles.

    PubMed

    Liang, Qiqi; Zhao, Dongye

    2014-04-30

    This study investigated effectiveness of starch-stabilized magnetite nanoparticles for in situ enhanced sorption and immobilization of arsenate, As(V), in a model sandy loam soil. Batch tests showed that the nanoparticles offered an As(V) distribution coefficient of 10,000 L/g, which is >3 orders of magnitude greater than that for the soil. Batch and column experimental results revealed that the nanoparticle treatment greatly reduced water-leachable As(V) and the leachability of As(V) remaining in the soil per TCLP (Toxicity Characteristic Leaching Procedure) analysis. Column tests showed that water-leachable As(V) from the As(V)-laden soil containing 31.45 mg/kg was reduced by ∼93% and the TCLP leachability by >83% when the soil was treated with 34 pore volumes of a 0.1g-Fe/L of the nanoparticle suspension. While the nanoparticles are deliverable in the soil, the effective travel distance of the nanoparticles can be manipulated by controlling the injection flow rate. Under natural groundwater flow conditions (velocity ≤ 2.4 × 10(-4)cm/s), the delivered nanoparticles are confined within a limited distance (<6.1cm).

  7. Surface functionalization of chitosan-coated magnetic nanoparticles for covalent immobilization of yeast alcohol dehydrogenase from Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Li, Gui-yin; Zhou, Zhi-de; Li, Yuan-jian; Huang, Ke-long; Zhong, Ming

    2010-12-01

    A novel and efficient immobilization of yeast alcohol dehydrogenase (YADH, EC1.1.1.1) from Saccharomyces cerevisiae has been developed by using the surface functionalization of chitosan-coated magnetic nanoparticles (Fe 3O 4/KCTS) as support. The magnetic Fe 3O 4/KCTS nanoparticles were prepared by binding chitosan alpha-ketoglutaric acid (KCTS) onto the surface of magnetic Fe 3O 4 nanoparticles. Later, covalent immobilization of YADH was attempted onto the Fe 3O 4/KCTS nanoparticles. The effect of various preparation conditions on the immobilized YADH process such as immobilization time, enzyme concentration and pH was investigated. The influence of pH and temperature on the activity of the free and immobilized YADH using phenylglyoxylic acid as substrate has also been studied. The optimum reaction temperature and pH value for the enzymatic conversion catalyzed by the immobilized YADH were 30 °C and 7.4, respectively. Compared to the free enzyme, the immobilized YADH retained 65% of its original activity and exhibited significant thermal stability and good durability.

  8. Plasmonic effect of spray-deposited Au nanoparticles on the performance of inverted organic solar cells.

    PubMed

    Chaturvedi, Neha; Swami, Sanjay Kumar; Dutta, Viresh

    2014-09-21

    Gold nanoparticles with varying sizes were prepared by the spray process under an electric field (DC voltages of 0 V and 1 kV applied to the nozzle) for studying their role in inverted organic solar cells (ITO/Au/ZnO/P3HT:PCBM/Ag). The application of electric field during the spray process resulted in a smaller size (35 nm as compared to 70 nm without the electric field) of the nanoparticles with more uniform distribution. This gave rise to a difference in the surface plasmon resonance (SPR) effect created by the gold nanoparticles (Au NPs), which then affected the solar cell performance. The photovoltaic performances of plasmonic inverted organic solar cells (ITO/Au/ZnO/P3HT:PCBM/Ag) using spray-deposited Au and ZnO layers (both at 1 kV) showed improved efficiency. Fast exciton quenching in the P3HT:PCBM layer was achieved by using a spray-deposited Au layer in between ITO and ZnO layers. The absorption spectra and internal power conversion efficiency (IPCE) curve showed that the Au nanoparticles provide significant plasmonic broadband light absorption enhancement which resulted in the enhancement of the JSC value. Maximum efficiency of 3.6% was achieved for the inverted organic solar cell (IOSC) with an exceptionally high short circuit current density of ∼15 mA cm(-2) which is due to the additional photon absorption and the corresponding increase observed in the IPCE spectrum. The spray technique can be easily applied for the direct formation of Au nanoparticles in the fabrication of IOSC with improved performance over a large area.

  9. Molecular imprinting and immobilization of cellulase onto magnetic Fe3O4@SiO2 nanoparticles.

    PubMed

    Li, Yue; Wang, Xiang-Yu; Zhang, Rui-Zhuo; Zhang, Xiao-Yun; Liu, Wei; Xu, Xi-Ming; Zhang, Ye-Wang

    2014-04-01

    Supermagnetic Fe3O4@SiO2 nanoparticles were molecular-imprinted prepared with cellulase as the template. The molecular imprinted nanoparticles were used as support to immobilization of cellulase. The transmission electron microscopy confirmed the core-shell structure and revealed that the size of the nanoparticles was around 10 nm. It was observed that cellulase was immobilized on the nanoparticles successfully from the Fourier transform infrared spectra. The adsorption of cellulase on the nanoparticles was specific and rapid. A high immobilization efficiency of 95% was achieved after the optimization. At 70 degrees C, the half-life of the immobilized cellulase was 3.3-fold of the free enzyme. Compared with the free enzyme, the immobilized cellulase has the same optimal pH, higher optimal temperature, better thermal stability and higher catalytic efficiency. The results strongly suggest that the immobilized cellulase on molecular imprinted Fe3O4@SiO2 has the potential applications in the production of bioethanol, paper and pulp industry, and pharmaceutical industry.

  10. Immobilization of Iron Nanoparticles on Multi Substrates and Its Reduction Removal of Chromium (VI) from Waste Streams

    EPA Science Inventory

    This article describes the in-situ synthesis and immobilization of iron nanoparticles on several substrates at room temperature using NaBH4 as a reducing agent and ascorbic acid as capping agent. The method is very effective in protecting iron nanoparticles from air oxidation for...

  11. Core-shell Au-Pd nanoparticles as cathode catalysts for microbial fuel cell applications

    NASA Astrophysics Data System (ADS)

    Yang, Gaixiu; Chen, Dong; Lv, Pengmei; Kong, Xiaoying; Sun, Yongming; Wang, Zhongming; Yuan, Zhenhong; Liu, Hui; Yang, Jun

    2016-10-01

    Bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions. In this study, we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in microbial fuel cells, which represent a promising technology for wastewater treatment, while directly generating electrical energy. In specific, in comparison with the hollow structured Pt nanoparticles, a benchmark for the electrocatalysis, the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains. The maximum power density generated in a membraneless single-chamber microbial fuel cell running on wastewater with core-shell Au-Pd as cathode catalysts is ca. 16.0 W m‑3 and remains stable over 150 days, clearly illustrating the potential of core-shell nanostructures in the applications of microbial fuel cells.

  12. Core-shell Au-Pd nanoparticles as cathode catalysts for microbial fuel cell applications

    PubMed Central

    Yang, Gaixiu; Chen, Dong; Lv, Pengmei; Kong, Xiaoying; Sun, Yongming; Wang, Zhongming; Yuan, Zhenhong; Liu, Hui; Yang, Jun

    2016-01-01

    Bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions. In this study, we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in microbial fuel cells, which represent a promising technology for wastewater treatment, while directly generating electrical energy. In specific, in comparison with the hollow structured Pt nanoparticles, a benchmark for the electrocatalysis, the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains. The maximum power density generated in a membraneless single-chamber microbial fuel cell running on wastewater with core-shell Au-Pd as cathode catalysts is ca. 16.0 W m−3 and remains stable over 150 days, clearly illustrating the potential of core-shell nanostructures in the applications of microbial fuel cells. PMID:27734945

  13. Synthesis and Characterization of Au@Cu Core-Shell Nanoparticles

    NASA Astrophysics Data System (ADS)

    Khanal, Subarna; Velazquez-Salazar, Jesus; Yacaman, Miguel Jose

    2011-10-01

    The synthesis of bimetallic nanoparticles has become so important in present times due to its diverse applications of nanotechnology. Particularly most of the bimetallic nanoparticles are focused to use in catalysis, plasmonic, magnetic, sensors, and many other applications. In Au/Cu case, the bulk Au and Cu are soluble at all compositions. But the structure of Au/Cu nanoparticles depends on the preparation methods. The structure might be the core shell, alloys or other morphology. Au- Cu core-shell nanocrystals were prepared using a two-step polyol reduction method. First, Au core seeds were prepared by reducing HAuCl4. 4H2O in ethylene glycol (EG) using oil-bath heating in the presence of polyvinylpyrrolidone (PVP) as a polymer surfactant. Then Cu shells were overgrown on Au core seeds by reducing Cu2(OAc)4 in EG with PVP again using oil-bath heating. The morphology is studied by STEM HITACHI S-5500.The resultant crystal structures were characterized using TEM, high-resolution (HR)-TEM and the STEM were using for the study of micro analysis.

  14. Conducting shrinkable nanocomposite based on au-nanoparticle implanted plastic sheet: tunable thermally induced surface wrinkling.

    PubMed

    Greco, Francesco; Bellacicca, Andrea; Gemmi, Mauro; Cappello, Valentina; Mattoli, Virgilio; Milani, Paolo

    2015-04-01

    A thermally shrinkable and conductive nanocomposite material is prepared by supersonic cluster beam implantation (SCBI) of neutral Au nanoparticles (Au NPs) into a commercially available thermo-retractable polystyrene (PS) sheet. Micronanowrinkling is obtained during shrinking, which is studied by means of SEM, TEM and AFM imaging. Characteristic periodicity is determined and correlated with nanoparticle implantation dose, which permits us to tune the topographic pattern. Remarkable differences emerged with respect to the well-known case of wrinkling of bilayer metal-polymer. Wrinkled composite surfaces are characterized by a peculiar multiscale structuring that promises potential technological applications in the field of catalytic surfaces, sensors, biointerfaces, and optics, among others. PMID:25811100

  15. A simple approach to obtain hybrid Au-loaded polymeric nanoparticles with a tunable metal load

    NASA Astrophysics Data System (ADS)

    Luque-Michel, Edurne; Larrea, Ane; Lahuerta, Celia; Sebastian, Víctor; Imbuluzqueta, Edurne; Arruebo, Manuel; Blanco-Prieto, María J.; Santamaría, Jesús

    2016-03-01

    A new strategy to nanoengineer multi-functional polymer-metal hybrid nanostructures is reported. By using this protocol the hurdles of most of the current developments concerning covalent and non-covalent attachment of polymers to preformed inorganic nanoparticles (NPs) are overcome. The strategy is based on the in situ reduction of metal precursors using the polymeric nanoparticle as a nanoreactor. Gold nanoparticles and poly(dl-lactic-co-glycolic acid), PLGA, are located in the core and shell, respectively. This novel technique enables the production of PLGA NPs smaller than 200 nm that bear either a single encapsulated Au NP or several smaller NPs with tunable sizes and a 100% loading efficiency. In situ reduction of Au ions inside the polymeric NPs was achieved on demand by using heat to activate the reductive effect of citrate ions. In addition, we show that the loading of the resulting Au NPs inside the PLGA NPs is highly dependent on the surfactant used. Electron microscopy, laser irradiation, UV-Vis and fluorescence spectroscopy characterization techniques confirm the location of Au nanoparticles. These promising results indicate that these hybrid nanomaterials could be used in theranostic applications or as contrast agents in dark-field imaging and computed tomography.A new strategy to nanoengineer multi-functional polymer-metal hybrid nanostructures is reported. By using this protocol the hurdles of most of the current developments concerning covalent and non-covalent attachment of polymers to preformed inorganic nanoparticles (NPs) are overcome. The strategy is based on the in situ reduction of metal precursors using the polymeric nanoparticle as a nanoreactor. Gold nanoparticles and poly(dl-lactic-co-glycolic acid), PLGA, are located in the core and shell, respectively. This novel technique enables the production of PLGA NPs smaller than 200 nm that bear either a single encapsulated Au NP or several smaller NPs with tunable sizes and a 100% loading

  16. Graphene decorated with PtAu alloy nanoparticles: facile synthesis and promising application for formic acid oxidation

    SciTech Connect

    Zhang, Sheng; Shao, Yuyan; Liao, Honggang; Liu, Jun; Aksay, Ilhan A.; Yin, Geping; Lin, Yuehe

    2011-03-01

    PtAu alloy nanoparticles (~ 3.2 nm in diameter) are synthesized in poly(diallyldimethylammonium chloride) (PDDA) aqueous solution and uniformly dispersed on graphene nanosheets. PtAu/graphene exhibits high electrocatalytic activity and stability for formic acid oxidation, which is attributed to the high dispersion of PtAu nanoparticles and the specific interaction between PtAu and graphene, indicating a promising catalyst for direct formic acid fuel cells. The facile method can be readily extended to the synthesis of other alloy nanoparticles.

  17. Growth of Au nanoparticle films and the effect of nanoparticle shape on plasmon peak wavelength

    SciTech Connect

    Horikoshi, S. Matsumoto, N.; Kato, T.; Omata, Y.

    2014-05-21

    Metal nanoparticles (NPs) exhibit localized surface plasmon resonance (LSPR) and thus have potential for use in a wide range of applications. A facile technique for the preparation of NP films using an electron-cyclotron-resonance plasma sputtering method without a dewetting process is described. Field emission scanning electron microscopy (FE-SEM) observations revealed that the Au NPs grew independently as island-like particles during the first stage of sputtering and then coalesced with one another as sputtering time increased to ultimately form a continuous film. A plasmon absorption peak was observed via optical measurement of absorption efficiency. The LSPR peak shifted toward longer wavelengths (red shift) with an increase in sputtering time. The cause of this plasmon peak shift was theoretically investigated using the finite-difference time-domain calculation method. A realistic statistical distribution of the particle shapes based on FE-SEM observations was applied for the analysis, which has not been previously reported. It was determined that the change in the shape of the NPs from spheroidal to oval or slender due to coalescence with neighbouring NPs caused the LSPR peak shift. These results may enable the design of LSPR devices by controlling the characteristics of the nanoparticles, such as their size, shape, number density, and coverage.

  18. Green synthesis and characterization of Au@Pt core-shell bimetallic nanoparticles using gallic acid

    NASA Astrophysics Data System (ADS)

    Zhang, Guojun; Zheng, Hongmei; Shen, Ming; Wang, Lei; Wang, Xiaosan

    2015-06-01

    In this study, we developed a facile and benign green synthesis approach for the successful fabrication of well-dispersed urchin-like Au@Pt core-shell nanoparticles (NPs) using gallic acid (GA) as both a reducing and protecting agent. The proposed one-step synthesis exploits the differences in the reduction potentials of AuCl4- and PtCl62-, where the AuCl4- ions are preferentially reduced to Au cores and the PtCl62- ions are then deposited continuously onto the Au core surface as a Pt shell. The as-prepared Au@Pt NPs were characterized by transmission electron microscope (TEM); high-resolution transmission electron microscope (HR-TEM); scanning electron microscope (SEM); UV-vis absorption spectra (UV-vis); X-ray diffraction (XRD); Fourier transmission infrared spectra (FT-IR). We systematically investigated the effects of some experimental parameters on the formation of the Au@Pt NPs, i.e., the reaction temperature, the molar ratios of HAuCl4/H2PtCl6, and the amount of GA. When polyvinylpyrrolidone K-30 (PVP) was used as a protecting agent, the Au@Pt core-shell NPs obtained using this green synthesis method were better dispersed and smaller in size. The as-prepared Au@Pt NPs exhibited better catalytic activity in the reaction where NaBH4 reduced p-nitrophenol to p-aminophenol. However, the results showed that the Au@Pt bimetallic NPs had a lower catalytic activity than the pure Au NPs obtained by the same method, which confirmed the formation of Au@Pt core-shell nanostructures because the active sites on the surfaces of the Au NPs were covered with a Pt shell.

  19. In situ biosynthesis of Ag, Au and bimetallic nanoparticles using Piper pedicellatum C.DC: green chemistry approach.

    PubMed

    Tamuly, Chandan; Hazarika, Moushumi; Borah, Sarat Ch; Das, Manash R; Boruah, Manas P

    2013-02-01

    The synthesis of Ag, Au and Ag-Au bimetallic nanoparticles using Piper pedicellatum C.DC leaf extract is demonstrated here. The rapid formation of stable Ag and Au nanoparticles has been found using P. pedicellatum C.DC leaf extract in aqueous medium at normal atmospheric condition. Competitive reduction of Ag(+) and Au(3+) ions present simultaneously in solution during exposure to P. pedicellatum C.DC leaf extract leads to the synthesis of bimetallic Ag-Au nanoparticles in solution. Transmission electron microscopy (TEM) analysis revealed that the Ag nanoparticles predominantly form spherical in shape with the size range of 2.0±0.5-30.0±1.2 nm. In case of Au nanoparticles, the particles are spherical in shape along with few triangular, hexagonal and pentagonal shaped nanoparticles also observed. X-ray diffraction (XRD) studies revealed that the nanoparticles were face centered cubic (fcc) in shape. Fourier transform infrared spectroscopy (FTIR) showed nanoparticles were capped with plant compounds. The chemical constituents, viz. catechin, gallic acid, courmaric acid and protocatechuic acid of the leaf extract were identified which may act as a reducing, stabilizing and capping agent. The expected reaction mechanism in the formation of Ag and Au nanoparticles is also reported. PMID:23107941

  20. In situ biosynthesis of Ag, Au and bimetallic nanoparticles using Piper pedicellatum C.DC: green chemistry approach.

    PubMed

    Tamuly, Chandan; Hazarika, Moushumi; Borah, Sarat Ch; Das, Manash R; Boruah, Manas P

    2013-02-01

    The synthesis of Ag, Au and Ag-Au bimetallic nanoparticles using Piper pedicellatum C.DC leaf extract is demonstrated here. The rapid formation of stable Ag and Au nanoparticles has been found using P. pedicellatum C.DC leaf extract in aqueous medium at normal atmospheric condition. Competitive reduction of Ag(+) and Au(3+) ions present simultaneously in solution during exposure to P. pedicellatum C.DC leaf extract leads to the synthesis of bimetallic Ag-Au nanoparticles in solution. Transmission electron microscopy (TEM) analysis revealed that the Ag nanoparticles predominantly form spherical in shape with the size range of 2.0±0.5-30.0±1.2 nm. In case of Au nanoparticles, the particles are spherical in shape along with few triangular, hexagonal and pentagonal shaped nanoparticles also observed. X-ray diffraction (XRD) studies revealed that the nanoparticles were face centered cubic (fcc) in shape. Fourier transform infrared spectroscopy (FTIR) showed nanoparticles were capped with plant compounds. The chemical constituents, viz. catechin, gallic acid, courmaric acid and protocatechuic acid of the leaf extract were identified which may act as a reducing, stabilizing and capping agent. The expected reaction mechanism in the formation of Ag and Au nanoparticles is also reported.

  1. Biogenic synthesis of Au and Ag nanoparticles by Indian propolis and its constituents.

    PubMed

    Roy, Nayan; Mondal, Samiran; Laskar, Rajibul A; Basu, Saswati; Mandal, Debabrata; Begum, Naznin Ara

    2010-03-01

    In an attempt to find natural, environmentally benign, green-chemical agents for the synthesis of metal nanoparticles, we have demonstrated for the first time the excellent efficiency of ethanol and water extracts of a natural, non-toxic material, Indian propolis and two of its chemical constituents, pinocembrin and galangin in the rapid synthesis of stable Ag and Au nanoparticles having wide spectrum of fascinating morphologies. Both of these two extracts were found to be extremely efficient in the synthesis of Ag and Au nanoparticles under alkaline condition. For a given metal ion precursor, the kinetics of particle synthesis were remarkably similar in all the cases, as it is evident from the absorption spectra monitored over time. Moreover they exhibited similar redox behavior under alkaline condition (pH approximately 10.62). The efficiency of the ethanol and water extracts of Indian propolis towards Ag and Au nanoparticles synthesis was compared with that of naturally occurring hydroxyflavonoids, pinocembrin and galangin isolated from Indian propolis; which are equally efficient in the rapid synthesis of Ag and Au nanoparticles and stabilization of the resultant particles.

  2. Ordered carbohydrate-derived porous carbons immobilized gold nanoparticles as a new electrode material for electrocatalytical oxidation and determination of nicotinamide adenine dinucleotide.

    PubMed

    Hosseini, Hadi; Behbahani, Mohammad; Mahyari, Mojtaba; Kazerooni, Hanif; Bagheri, Akbar; Shaabani, Ahmad

    2014-09-15

    The ordered carbohydrate-derived porous carbons (OC-DPCs) were first functionalized with thiol groups (-SH) and then immobilized with gold nanoparticles (AuNPs). The Au-SH-OC-DPCs were characterized by CHN analysis, transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD). The Au-SH-OC-DPCs were applied for the fabrication of a new electrochemical sensor. The electrocatalytic capabilities of the new sensor were tested by the oxidation of nicotinamide adenine dinucleotide (NADH) in a 0.1 M Robinson buffer solution (pH 7.0) using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV). The Au-SH-OC-DPCs showed a good voltammetric performance in the electrochemical detection of NADH with a low detection limit (1.0 nM), high sensitivity (4.934 μA/μM), and wide linear concentration range (5.0 nM-10 µM).

  3. Engineering plasmon-enhanced Au light emission with planar arrays of nanoparticles.

    PubMed

    Walsh, Gary F; Dal Negro, Luca

    2013-02-13

    By systematically investigating the light emission and scattering properties of arrays of Au nanoparticles with varying size and separation, we demonstrate tunability and control of metal photoluminescence and unveil the critical role of near-field plasmonic coupling for the engineering of active metal nanostructures. We show that the decay of photoexcited electron-hole pairs into localized surface plasmons (LSPs) dramatically modifies the Au emission wavelength, line shape, and quantum efficiency depending both on particles size and separation. In particular, in arrays with near-field coupled nanoparticles we demonstrate broad light scattering and emission spectra that scale differently with respect to nanoparticle size due to the enhanced LSP nonradiative decay caused by near-field interparticle coupling. Our experimental results are fully supported by semianalytical extinction simulations based on rigorous coupled wave analysis, which demonstrate the importance of tuning plasmonic near-field coupling for the engineering of active devices based on light emitting arrays of metallic nanoparticles. PMID:23339774

  4. Study of photodynamic activity of Au@SiO2 core-shell nanoparticles in vitro.

    PubMed

    Meena, K S; Dhanalekshmi, K I; Jayamoorthy, K

    2016-06-01

    Metal-semiconductor core-shell type Au@SiO2 nanoparticles were prepared by Stober's method. They were characterized by absorption, XRD, HR-TEM and EDAX techniques. The resulting modified core-shell nanoparticles shows that the formation of singlet oxygen, which was confirmed by ESR technique. The photohemolysis studies were carried out under two different experimental conditions. It is observed that the photohemolysis increases with concentration as well as light dose. Cell viability of the core-shell nanoparticles against HeLa cell lines were studied by MTT assay method. The outcomes of the present study indicate that, the Au@SiO2 core-shell nanoparticles are extremely stable with a very high photodynamic efficiency under visible light illumination.

  5. Enhanced efficiency of graphene-silicon Schottky junction solar cells by doping with Au nanoparticles

    SciTech Connect

    Liu, X.; Zhang, X. W. Yin, Z. G.; Meng, J. H.; Gao, H. L.; Zhang, L. Q.; Zhao, Y. J.; Wang, H. L.

    2014-11-03

    We have reported a method to enhance the performance of graphene-Si (Gr/Si) Schottky junction solar cells by introducing Au nanoparticles (NPs) onto the monolayer graphene and few-layer graphene. The electron transfer between Au NPs and graphene leads to the increased work function and enhanced electrical conductivity of graphene, resulting in a remarkable improvement of device efficiency. By optimizing the initial thickness of Au layers, the power conversion efficiency of Gr/Si solar cells can be increased by more than three times, with a maximum value of 7.34%. These results show a route for fabricating efficient and stable Gr/Si solar cells.

  6. Enhanced efficiency of graphene-silicon Schottky junction solar cells by doping with Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, X.; Zhang, X. W.; Yin, Z. G.; Meng, J. H.; Gao, H. L.; Zhang, L. Q.; Zhao, Y. J.; Wang, H. L.

    2014-11-01

    We have reported a method to enhance the performance of graphene-Si (Gr/Si) Schottky junction solar cells by introducing Au nanoparticles (NPs) onto the monolayer graphene and few-layer graphene. The electron transfer between Au NPs and graphene leads to the increased work function and enhanced electrical conductivity of graphene, resulting in a remarkable improvement of device efficiency. By optimizing the initial thickness of Au layers, the power conversion efficiency of Gr/Si solar cells can be increased by more than three times, with a maximum value of 7.34%. These results show a route for fabricating efficient and stable Gr/Si solar cells.

  7. Enhancing the stability and antibiofilm activity of DspB by immobilization on carboxymethyl chitosan nanoparticles.

    PubMed

    Tan, Yulong; Ma, Su; Liu, Chenguang; Yu, Wengong; Han, Feng

    2015-09-01

    A β-N-acetyl-glucosaminidase (DspB) from Aggregatibacter actinomycetemcomitans CU1000 has been proved to inhibit and detach the biofilms formed by Staphylococcus epidermidis, Staphylococcus aureus and A. actinomycetemcomitans. However, the application of this enzyme is limited by its poor stability. In the present study, a β-N-acetyl-glucosaminidase encoding gene, dspB, was cloned from A. actinomycetemcomitans HK1651 and expressed in Escherichia coli. The recombinant DspB was loaded on hydrogel nanoparticles, which was prepared by using linoleic acid (LA) modified carboxymethyl chitosan (CMCS) after sonication. The nanoparticles were almost saturated by DspB at 0.3 mg/ml, which gave a loading capacity of 76.7%. The immobilization enhanced thermal stability, storage stability and reusability of DspB significantly. Moreover, it also increased antibiofilm activity due to the dual mechanism, including the improvement of the enzyme stability and the antibiofilm activity of CMCS nanoparticles. PMID:26302845

  8. Evidence of chitosan-mediated reduction of Au(III) to Au(0) nanoparticles under electron beam by using OH˙ and e⁻(aq) scavengers.

    PubMed

    Dang Nguyen Vô, Khoa; Kowandy, Christelle; Dupont, Laurent; Coqueret, Xavier

    2015-03-01

    Selective scavengers of e(-)(aq) and OH˙ radicals were used to investigate the radiolytic synthesis of gold nanoparticles from Au(III) solutions in the presence of chitosan. This reaction does not exclusively follow the direct reduction by solvated electrons. Irradiation generates short-lived and long-lived reductive species derived from chitosan that efficiently convert Au(III) into Au(0) which aggregates to form clusters.

  9. Spectral response of nanocrystalline ZnO films embedded with Au nanoparticles

    SciTech Connect

    Patra, Anuradha; Manivannan, A; Kasiviswanathan, S

    2012-12-01

    The optical response of a two-phase composite consisting of Au nanoparticles (AuNPs) in a nanocrystalline ZnO thin film matrix has been systematically studied and analyzed by the Bergman–Milton spectral density formalism. The real and imaginary parts of the effective dielectric function exhibited anomalous dispersion and absorption, respectively, at the characteristic localized surface plasmon resonance (LSPR) wavelength. A multilayer structure consisting of two AuNP–ZnO composite films separated by a thin ZnO film displayed a twofold increase in the absorption at LSPR (with negligible change in FWHM), which is attributed to the increase in the number density of the AuNPs resulting from the nanocrystalline nature of the ZnO film. The results have been used to correlate the spectral density function to the morphology of AuNPs in a ZnO matrix.

  10. Enhanced Oxygen Reduction Activity In Acid By Tin-Oxide Supported Au Nanoparticle Catalysts

    SciTech Connect

    Baker,W.; Pietron, J.; Teliska, M.; Bouwman, P.; Ramaker, D.; Swider-Lyons, K.

    2006-01-01

    Gold nanoparticles supported on hydrous tin-oxide (Au-SnO{sub x}) are active for the four-electron oxygen reduction reaction in an acid electrolyte. The unique electrocatalytic of the Au-SnO is confirmed by the low amount of peroxide detected with rotating ring-disk electrode voltammetry and Koutecky-Levich analysis. In comparison, 10 wt % Au supported on Vulcan carbon and SnO{sub x} catalysts both produce significant peroxide in the acid electrolyte, indicating only a two-electron reduction reaction. Characterization of the Au-SnO{sub x} catalyst reveals a high-surface area, amorphous support with 1.7 nm gold metal particles. The high catalytic activity of the Au-SnO is attributed to metal support interactions. The results demonstrate a possible path to non-Pt catalysts for proton exchange membrane fuel cell cathodes.

  11. Immobilization of silver nanoparticles synthesized using Curcuma longa tuber powder and extract on cotton cloth for bactericidal activity.

    PubMed

    Sathishkumar, Muthuswamy; Sneha, Krishnamurthy; Yun, Yeoung-Sang

    2010-10-01

    The present study reports the synthesis of silver (Ag) nanoparticles from silver precursor using plant biomaterials, Curcuma longa tuber powder and extract. Water-soluble organics present in the plant materials were mainly responsible for the reduction of silver ions to nano-sized silver particles. pH played a major role in size control of the particles. Silver nanoparticle synthesis was higher in tuber extract compared to powder, which was attributed to the large and easy availability of the reducing agents in the extract. Zeta potential studies showed that the surface charge of the formed nanoparticles was highly negative. The minimum bactericidal concentration (MBC) for Escherichia coli BL-21 strain was found to be 50 mg/L. Immobilization of silver nanoparticles on cotton cloth using sterile water showed better bactericidal activity when compared to polyvinylidene fluoride (PVDF) immobilized cloth, but on consecutive washing the activity reduced drastically in sterile water immobilized cloth. PMID:20541399

  12. Biosynthesis of Au nanoparticles using cumin seed powder extract.

    PubMed

    Sneha, Krishnamurthy; Sathishkumar, Muthuswamy; Lee, Shi Yn; Bae, Min A; Yun, Yeoung-Sang

    2011-02-01

    Cumin seed was investigated for synthesis of gold nanoparticles. Polydispersed particles were obtained at pH 3 and 30 degrees C, and the effect of temperature and pH on synthesis of gold nanoparticles was analyzed. TEM images showed that amount of platelets formed were predominant at lower temperature where as more number of monodispersed spherical particle of size 1-10 nm were perceived at high temperatures. The gold nanoparticles particles formed at higher pH were stable, uniform and spherical in shape. XPS analysis showed the presence of pure gold nanoparticles.

  13. Ethylene binding to Au/Cu alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Gammage, Michael D.; Stauffer, Shannon; Henkelman, Graeme; Becker, Michael F.; Keto, John W.; Kovar, Desiderio

    2016-11-01

    Weak chemisorption of ethylene has been shown to be an important characteristic in the use of metals for the separation of ethylene from ethane. Previously, density functional theory (DFT) has been used to predict the binding energies of various metals and alloys, with Ag having the lowest chemisorption energy amongst the metals and alloys studied. Here Au/Cu alloys are investigated by a combination of DFT calculations and experimental measurements. It is inferred from experiments that the binding energy between a Au/Cu alloy and ethylene is lower than to either of the pure metals, and DFT calculations confirm that this is the case when Au segregates to the particle surface. Implications of this work suggest that it may be possible to further tune the binding energy with ethylene by compositional and morphological control of films produced from Au-surface segregated alloys.

  14. Immobilization of mercury in field soil and sediment using carboxymethyl cellulose stabilized iron sulfide nanoparticles.

    PubMed

    Gong, Yanyan; Liu, Yuanyuan; Xiong, Zhong; Kaback, Dawn; Zhao, Dongye

    2012-07-27

    Mercury (Hg) is one of the most pervasive and bio-accumulative metals in the environment. Yet, effective in situ remediation technologies have been lacking. This study investigated the effectiveness of a class of soil-deliverable FeS nanoparticles for in situ immobilization of Hg in two field-contaminated soils from a New Jersey site and one sediment from an Alabama site. The nanoparticles were prepared using sodium carboxymethyl cellulose (CMC) as a stabilizer. Transmission electron microscopy measurements revealed a particle size of 34.3 ± 8.3 nm (standard deviation), whereas dynamic light scattering gave a hydrodynamic diameter of 222.5 ± 3.2 nm. Batch tests showed that at an FeS-to-Hg molar ratio of 28:1-118:1, the nanoparticles reduced water-leachable Hg by 79%-96% and the TCLP (toxicity characteristic leaching procedure) based leachability by 26%-96%. Column breakthrough tests indicated that the nanoparticles were deliverable in the sediment/soil columns under moderate injection pressure. However, once the external pressure was removed, the delivered nanoparticles remained virtually mobile under typical groundwater flow conditions. When the Hg-contaminated soil and sediment were treated with 52-95 pore volumes of a 500 mg l(-1) FeS nanoparticle suspension, water-leachable Hg was reduced by 90%-93% and TCLP-leachable Hg was reduced by 65%-91%. The results warrant further field demonstration of this promising in situ remediation technology.

  15. Dealloying-based facile synthesis and highly catalytic properties of Au core/porous shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Minho; Ko, Sung Min; Nam, Jwa-Min

    2016-06-01

    Porous nanostructures exhibit excellent catalytic properties due to high surface-to-volume ratio, good surface reactivity and various structural features, but controlling the distribution, size, shape and density of pores and structural features of these particles is highly challenging. Herein, we report a tunable dealloying-based facile synthetic strategy to form highly porous Au core/porous shell nanoparticles (CPS NPs) in high yield by selectively dissolving Ag atoms from Au/Au-Ag core/alloy shell NPs. The CPS NPs exhibit a very short induction time, high conversion rate constant, low activation energy and high turnover frequency due to their catalytically active porous shells containing networked thin ligaments, surface defects, ultra-high porosity and photothermal properties. The CPS NPs are more catalytic Au NPs than other reported Au nanostructures, and the strategy and results open avenues in porous nanostructures and nanocatalysts.Porous nanostructures exhibit excellent catalytic properties due to high surface-to-volume ratio, good surface reactivity and various structural features, but controlling the distribution, size, shape and density of pores and structural features of these particles is highly challenging. Herein, we report a tunable dealloying-based facile synthetic strategy to form highly porous Au core/porous shell nanoparticles (CPS NPs) in high yield by selectively dissolving Ag atoms from Au/Au-Ag core/alloy shell NPs. The CPS NPs exhibit a very short induction time, high conversion rate constant, low activation energy and high turnover frequency due to their catalytically active porous shells containing networked thin ligaments, surface defects, ultra-high porosity and photothermal properties. The CPS NPs are more catalytic Au NPs than other reported Au nanostructures, and the strategy and results open avenues in porous nanostructures and nanocatalysts. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01321j

  16. Experimental study on the coalescence process of SiO2 supported colloidal Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Ruffino, F.; Torrisi, V.; Grimaldi, M. G.

    2015-11-01

    We report on an experimental study of the coalescence-driven grow process of colloidal Au nanoparticles on SiO2 surface. Nanoparticles with 30, 50, 80, 100 nm nominal diameters on a SiO2 substrate were deposited, from solutions, by the drop-casting method. Then, annealing processes, in the 573-1173 K temperature range and 900-3600 s time range, were performed. Using scanning electron microscopy analyses, the temporal evolution of the nanoparticles sizes has been studied. In particular, for all classes of nanoparticles, the experimental-obtained diameters distributions evidenced double-peak shapes (i. e. bimodal distributions): a first peak centered (and unchanged changing the annealing temperature and/or time) at the nominal diameter of the as-deposited nanoparticles, , and a second peak shifting at higher mean diameters, , increasing the annealing temperature and/or time. This observation suggested us a coalescence-driven growth process of a nanoparticles sub-population. As a consequence, the temporal evolution of (for each class of nanoparticles and each annealing temperature), within the well-established particles coalescence theoretical framework, has been analyzed. In particular, by the analyses of the experimental data using relations as prescribed by the theoretical model, a characteristic size-dependent activation energy for the Au nanoparticles coalescence process has been evaluated.

  17. Effect of spherical Au nanoparticles on nanofriction and wear reduction in dry and liquid environments

    PubMed Central

    Maharaj, Dave

    2012-01-01

    Summary Nano-object additives are used in tribological applications as well as in various applications in liquids requiring controlled manipulation and targeting. On the macroscale, nanoparticles in solids and liquids have been shown to reduce friction and wear. On the nanoscale, atomic force microscopy (AFM) studies have been performed in single- and multiple-nanoparticle contact, in dry environments, to characterize friction forces and wear. However, limited studies in submerged liquid environments have been performed and further studies are needed. In this paper, spherical Au nanoparticles were studied for their effect on friction and wear under dry conditions and submerged in water. In single-nanoparticle contact, individual nanoparticles, deposited on silicon, were manipulated with a sharp tip and the friction force was determined. Multiple-nanoparticle contact sliding experiments were performed on nanoparticle-coated silicon with a glass sphere. Wear tests were performed on the nanoscale with AFM as well as on the macroscale by using a ball-on-flat tribometer to relate friction and wear reduction on the nanoscale and macroscale. Results indicate that the addition of Au nanoparticles reduces friction and wear. PMID:23213639

  18. Ion beam shaping of Au nanoparticles in silica: Particle size and concentration dependence

    SciTech Connect

    Dawi, E. A.; Mink, M. P.; Vredenberg, A. M.; Habraken, F. H. P. M.; Rizza, G.

    2009-04-01

    Irradiation with swift heavy ions of spherical Au nanoparticles confined within a silica matrix shapes them into prolate nanorods and nanowires whose principal axes are aligned along the beam direction. In the present paper, we investigate the role that is played by the initial nanoparticle size and concentration in this so-called ion-shaping mechanism. We have produced silica films wherein Au nanoparticles with average diameters of 15, 30, and 45 nm were embedded within a single plane and have irradiated these films at 300 K at normal incidence with 18, 25, and 54 MeV Ag ions. We demonstrate the existence of both threshold and saturation fluences for the elongation effects mentioned. The values of these critical fluences depend both on the ion energy and the initial nanoparticle size. Moreover, we show that 45 nm Au particles are not deformed when irradiated with 18 MeV Ag ions, such that this value corresponds to an energy threshold for the deformation process. As far as the influence of the nanoparticle concentration on the shaping characteristics is concerned, we have found that above the critical irradiation fluence, the deformation effect becomes very sensitive to the initial concentration of the nanoparticles.

  19. Nanoporous Au-based chronocoulometric aptasensor for amplified detection of Pb(2+) using DNAzyme modified with Au nanoparticles.

    PubMed

    Zhang, Chen; Lai, Cui; Zeng, Guangming; Huang, Danlian; Tang, Lin; Yang, Chunping; Zhou, Yaoyu; Qin, Lei; Cheng, Min

    2016-07-15

    The authors herein described an amplified detection strategy employing nanoporous Au (NPG) and gold nanoparticles (AuNPs) to detect Pb(2+) ions in aqueous solution. The thiol modified Pb(2+)-specific DNAzyme was self-assembled onto the surface of the NPG modified electrode for hybridizing with the AuNPs labeled oligonucleotide and for forming the DNA double helix structure. Electrochemical signal, redox charge of hexaammineruthenium(III) chloride (RuHex), was measured by chronocoulometry. Taking advantage of amplification effects of the NPG electrode for increasing the reaction sites of capture probe and DNA-AuNPs complexes for bringing about the adsorption of large numbers of RuHex molecules, this electrochemical sensor could detect Pb(2+) quantitatively, in the range of 0.05-100nM, with a limit of detection as low as 0.012nM. Selectivity measurements revealed that the sensor was specific for Pb(2+) even with interference by high concentrations of other metal ions. This sensor was also used to detect Pb(2+) ions from samples of tap water, river water, and landfill leachate samples spiked with Pb(2+) ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. This simple aptasensor represented a promising potential for on-site detecting Pb(2+) in drinking water. PMID:26921553

  20. Sintering Behavior of Spin-coated FePt and FePtAu Nanoparticles

    SciTech Connect

    Kang, Shishou; Jia, Zhiyong; Zoto, Ilir; Reed, R. C.; Nikles, David E.; Harrell, J. W.; Vemuru, Krishnamurthy V; Porcar, L.

    2006-01-01

    FePt and [FePt]{sub 95}Au{sub 5} nanoparticles with an average size of about 4 nm were chemically synthesized and spin coated onto silicon substrates. Samples were subsequently thermally annealed at temperatures ranging from 250 to 500 C for 30 min. Three-dimensional structural characterization was carried out with small-angle neutron scattering (SANS) and small-angle x-ray diffraction (SAXRD) measurements. For both FePt and [FePt]{sub 95}Au{sub 5} particles before annealing, SANS measurements gave an in-plane coherence length parameter a = 7.3 nm, while SAXRD measurements gave a perpendicular coherence length parameter c = 12.0 nm. The ratio of c/a is about 1.64, indicating the as-made particle array has a hexagonal close-packed superstructure. For both FePt and FePtAu nanoparticles, the diffraction peaks shifted to higher angles and broadened with increasing annealing temperature. This effect corresponds to a shrinking of the nanoparticle array, followed by agglomeration and sintering of the nanoparticles, resulting in the eventual loss of positional order with increasing annealing temperature. The effect is more pronounced for FePtAu than for FePt. Dynamic coercivity measurements show that the FePtAu nanoparticles have both higher intrinsic coercivity and higher switching volume at the same annealing temperature. These results are consistent with previous studies that show that additive Au both lowers the chemical ordering temperature and promotes sintering.

  1. Tuning the SERS Response with Ag-Au Nanoparticle-Embedded Polymer Thin Film Substrates.

    PubMed

    Rao, V Kesava; Radhakrishnan, T P

    2015-06-17

    Development of facile routes to the fabrication of thin film substrates with tunable surface enhanced Raman scattering (SERS) efficiency and identification of the optimal conditions for maximizing the enhancement factor (EF) are significant in terms of both fundamental and application aspects of SERS. In the present work, polymer thin films with embedded bimetallic nanoparticles of Ag-Au are fabricated by a simple two-stage protocol. Ag nanoparticles are formed in the first stage, by the in situ reduction of silver nitrate by the poly(vinyl alcohol) (PVA) film through mild thermal annealing, without any additional reducing agent. In the second stage, aqueous solutions of chloroauric acid spread on the Ag-PVA thin film under ambient conditions, lead to the galvanic displacement of Ag by Au in situ inside the film, and the formation of Ag-Au particles. Evolution of the morphology of the bimetallic nanoparticles into hollow cage structures and the distribution of Au on the nanoparticles are revealed through electron microscopy and energy dispersive X-ray spectroscopy. The localized surface plasmon resonance (LSPR) extinction of the nanocomposite thin film evolves with the Ag-Au composition; theoretical simulation of the extinction spectra provides insight into the observed trends. The Ag-Au-PVA thin films are found to be efficient substrates for SERS. The EF follows the variation of the LSPR extinction vis-à-vis the excitation laser wavelength, but with an offset, and the maximum SERS effect is obtained at very low Au content; experiments with Rhodamine 6G showed EFs on the order of 10(8) and a limit of detection of 0.6 pmol. The present study describes a facile and simple fabrication of a nanocomposite thin film that can be conveniently deployed in SERS investigations, and the utility of the bimetallic system to tune and maximize the EF.

  2. Immobilization of Lipase on Silver Nanoparticles via Adhesive Polydopamine for Biodiesel Production

    PubMed Central

    Dumri, Kanchana; Hung Anh, Dau

    2014-01-01

    Biodiesel production technology is competitive in terms of low cost and alternative source of energy which should be not only sustainable but also environmentally friendly. Designing of the lipase immobilization for biodiesel production has a remarkable impact and is still challenging. In this work, biodiesel production from soybean oil was enhanced and facilitated by using a novel biocatalyst consisting of commercial lipase (EC 3.1.1.3), silver nanoparticles, and polydopamine. Silver nanoparticles (AgNPs) were synthesized with a size range of 10–20 nm. Polydopamine (PD) was delivered by the self-polymerization of dopamine in 10 mM Tris-HCl pH 8.5 and simultaneously coated the AgNPs to form a PD/AgNPs complex. Lipase was immobilized on the PD/AgNPs complex surface via covalent bonds to form a tailor-made biocatalyst consisting of immobilized lipase/PD/AgNPs complex (LPA). The formation and morphology of each composition were characterized by UV-Vis spectroscopy and scanning electron microscope (SEM). Significantly, gas chromatography analysis showed a remarkable biodiesel production yield of 95% by using the LPA complex at 40°C for 6-hours reaction time, whereas the yield was 86% when using free lyophilized lipase. The LPA complex was apparently reusable after 7 batches and the latter conversion rate of soybean oil was decreased by only 27%. PMID:25328685

  3. Electrochemical immunosensor for detecting typical bladder cancer biomarker based on reduced graphene oxide-tetraethylene pentamine and trimetallic AuPdPt nanoparticles.

    PubMed

    Ma, Hongmin; Zhang, Xiaoyue; Li, Xiaojian; Li, Rongxia; Du, Bin; Wei, Qin

    2015-10-01

    A highly sensitive electrochemical immunosensor for detection of typical bladder cancer biomarker-nuclear matrix protein 22 (NMP22) was developed by using reduced graphene oxide-tetraethylene pentamine (rGO-TEPA) and trimetallic AuPdPt nanoparticles (NPs). rGO-TEPA was used as the ideal material for signal amplification and AuPdPt NPs immobilization due to its excellent conductivity and large surface area. An effective platform was constructed for antibodies anchoring by using AuPdPt NPs, which kept the antibodies' high stability and bioactivity. Moreover, AuPdPt NPs could accelerate the electron transfer and enhance the signal response, which assisted by the synergistic effect of the three different metals (Au, Pd and Pt). The proposed immunosensor showed satisfied performance such as simple fabrication, low detection limits (0.01 U/mL), wide linear range (from 0.040 to 20 U/mL), short analysis time (2 min), high stability and selectivity in the detection of NMP22. Furthermore, the proposed immunosensor was employed to test real urine samples with satisfactory results.

  4. Ultrasensitive enzyme-free electrochemical immunoassay for free thyroxine based on three dimensionally ordered macroporous chitosan-Au nanoparticles hybrid film.

    PubMed

    Zhang, Qi; Chen, Xiaojun; Tu, Fulai; Yao, Cheng

    2014-09-15

    The measurement of free thyroxine concentration in serum is considered to be an essential indicator of thyroid function. Here, a novel enzyme-free sandwich electrochemical immunosensor for the detection of FT4 antigen based on the immobilization of primary antibody (Ab1) on three dimensional ordered macroporous chitosan-Au nanoparticles hybrid (3DOM CS-AuNPs) film electrode, and magnetic multiwall carbon nanotubes (MMWCNTs) were used as label of secondary antibody (Ab2). The 3DOM CS-AuNPs film electrode was constructed by one-step electrodeposition of CS-AuNPs composite onto Au electrode with silica opal template. MMWCNTs were prepared by chemical co-precipitation of Fe(2+) and Fe(3+) salts on carboxylated MWCNTs. Ru(bpy)3(2+) labeled anti-FT4 (Ru(bpy)3(2+)-Ab2) was covalently attached to MMWCNTs through the formation of amide bond between the carboxylic groups of MWCNTs and the amine groups of antibody. Under the optimal conditions, FT4 was detected in a concentration range from 0.71 fg mL(-1) to 1.15 pg mL(-1) with a correlation coefficient of 0.998 and a detection limit of 0.20 fg mL(-1). Moreover, the immunosensor showed excellent selectivity, good stability, satisfactory reproducibility and regeneration. Importantly, the developed method was used to assay clinical serum specimens, achieving a good relation with those obtained from the commercialized electrochemiluminescent method.

  5. Fabrication of catalytically active Au/Pt/Pd trimetallic nanoparticles by rapid injection of NaBH{sub 4}

    SciTech Connect

    Zhang, Haijun; Lu, Lilin; Cao, Yingnan; Du, Shuang; Cheng, Zhong; Zhang, Shaowei

    2014-01-01

    Graphical abstract: The synthesis and characterization of 2.0 nm-diameter Au/Pt/Pd nanoparticles are reported. The catalytic activity for glucose oxidation of the nanoparticles is several times higher than that of Au nanoparticles with nearly same size. - Highlights: • PVP-protected Au/Pt/Pd trimetallic nanoparticles (TNPs) of 2.0 nm in diameter were prepared. • The catalytic activity of TNPs is several times higher than that of Au nanoparticles. • Negatively charged Au atoms in the TNPs were confirmed by DFT calculation. - Abstract: Au/Pt/Pd trimetallic nanoparticles (TNPs) with an alloyed structure and an average diameter of about 2.0 nm were prepared via reducing the corresponding ions with rapidly injected NaBH{sub 4}, and characterized by UV–vis, TEM and HR-TEM. The catalytic activity of as-prepared TNPs for the aerobic glucose oxidation is several times higher than that of Au monometallic nanoparticles with about the same average size, which could be attributed to the catalytically active sites provided by the negatively charged Au atoms as a result of the electron donation from the neighboring Pd atoms. This was well supported by the electron density calculations based on the density functional theory.

  6. Enhancing catalytic performance of β-glucosidase via immobilization on metal ions chelated magnetic nanoparticles.

    PubMed

    Chen, Tingting; Yang, Wenjuan; Guo, Yuling; Yuan, Renjun; Xu, Li; Yan, Yunjun

    2014-09-01

    A novel magnetic Fe3O4 nanoparticles (MNPs) coupled with agarose (AMNPs) was synthesized using co-precipitation via alkaline condition and span-80 surfactants in organic solvent. Iminodiacetate was first attached to the MNPs through epichlorohydrin agent and then chelated with metal ions. The morphology and chemical properties of these prepared supports were characterized by scanning electron microscopy (SEM), X-ray power diffraction (XRD), vibrating sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FT-IR). Among them, the Co(2+)-chelated AMNPs (AMNPs-ECH-IDA-Co(2+)) showed the second highest enzyme adsorption capacity of 1.81 mg/g particles, and achieved the largest activity recovery of 117% per protein gram in immobilization of β-glucosidase (BGL). The Michaelis constant (Km) and Vmax of the immobilized BGL were 0.904 mM and 0.057 μmol/min, respectively, and its activation energy was much lower than the free form. Moreover, the immobilized enzyme exhibited enhanced thermostability and operational stability. It still retained more than 90% of its initial activity after being operated for 15 successive batches. This study demonstrates that the immobilized β-glucosidase has a good prospect in industrial applications. PMID:25039060

  7. Enhancing catalytic performance of β-glucosidase via immobilization on metal ions chelated magnetic nanoparticles.

    PubMed

    Chen, Tingting; Yang, Wenjuan; Guo, Yuling; Yuan, Renjun; Xu, Li; Yan, Yunjun

    2014-09-01

    A novel magnetic Fe3O4 nanoparticles (MNPs) coupled with agarose (AMNPs) was synthesized using co-precipitation via alkaline condition and span-80 surfactants in organic solvent. Iminodiacetate was first attached to the MNPs through epichlorohydrin agent and then chelated with metal ions. The morphology and chemical properties of these prepared supports were characterized by scanning electron microscopy (SEM), X-ray power diffraction (XRD), vibrating sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FT-IR). Among them, the Co(2+)-chelated AMNPs (AMNPs-ECH-IDA-Co(2+)) showed the second highest enzyme adsorption capacity of 1.81 mg/g particles, and achieved the largest activity recovery of 117% per protein gram in immobilization of β-glucosidase (BGL). The Michaelis constant (Km) and Vmax of the immobilized BGL were 0.904 mM and 0.057 μmol/min, respectively, and its activation energy was much lower than the free form. Moreover, the immobilized enzyme exhibited enhanced thermostability and operational stability. It still retained more than 90% of its initial activity after being operated for 15 successive batches. This study demonstrates that the immobilized β-glucosidase has a good prospect in industrial applications.

  8. Construction of glutamate biosensor based on covalent immobilization of glutamate oxidase on polypyrrole nanoparticles/polyaniline modified gold electrode.

    PubMed

    Batra, Bhawna; Kumari, Seema; Pundir, Chandra Shekhar

    2014-04-10

    A method is described for construction of a highly sensitive electrochemical biosensor for detection of glutamate. The biosensor is based on covalent immobilization of glutamate oxidase (GluOx) onto polypyrrole nanoparticles and polyaniline composite film (PPyNPs/PANI) electrodeposited onto Au electrode. The enzyme electrode was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 3s at pH 7.5 (0.1 M sodium phosphate) and 35 °C, when operated at 50 mV s⁻¹. It exhibited excellent sensitivity (detection limit as 0.1 nM), fast response time and wider linear range (from 0.02 to 400 μM). Analytical recovery of added glutamate (5 mM and 10 mM) was 95.56 and 97%, while within batch and between batch coefficients of variation were 3.2% and 3.35% respectively. The enzyme electrode was used 100 times over a period of 60 days, when stored at 4 °C. The biosensor measured glutamate level in food stuff, which correlated well with a standard colorimetric method (r=0.99). PMID:24629270

  9. Enrichment of malaria parasites by antibody immobilized magnetic nanoparticles.

    PubMed

    Tangchaikeeree, Tienrat; Jangpatarapongsa, Kulachart; Polpanich, Duangporn; Thiramanas, Raweewan; Pornjarone, Atcharavalai; Udnaen, Somkiat; Udomsangpetch, Rachanee; Tangboriboonrat, Pramuan

    2013-10-01

    The simple and less expensive technique based on magnetic nanoparticles (MNPs) was developed for separation of malaria parasites containing specific antigens. The carboxylated MNPs were chemically bound with anti-P. falciparum IgG antibodies (Ab-MNPs) purified from the plasma of malaria patients and then used for removal of P. falciparum malaria-infected erythrocytes from other non-infected blood cells in malaria culture at a given percent parasitemia. The results from optical microscope showed that all blood stages parasites, i.e., ring, trophozoite and schizont, could be separated from other blood components with high purity (> or = 95%) and yield of 33.5% (the early stages of ring and trophozoite:the schizont stage were 1:1.34). Highly specific interaction between Ab-MNPs and the P. falciparum malaria infected erythrocytes was confirmed by scanning electron microscope. When compared to the centrifugation with Percoll gradient and depletion by sorbitol lysis which are specific to the mature and the ring stages, respectively, our technique would be more useful for production of high quality of parasites to use in malaria pathogenesis or immunological studies, and in detection techniques.

  10. 99mTc radiolabelling of Fe3O4-Au core-shell and Au-Fe3O4 dumbbell-like nanoparticles

    NASA Astrophysics Data System (ADS)

    Felber, M.; Alberto, R.

    2015-04-01

    The development of nanoparticle-based dual-modality probes for magnetic resonance imaging (MRI) and positron emission tomography (PET) or single photon emission computed tomography (SPECT) is increasingly growing in importance. One of the most commonly used radionuclides for clinical SPECT imaging is 99mTc and the labelling of Fe3O4 nanoparticles with 99mTc was shown to be a successful strategy to obtain dual-modality imaging agents. In this work, we focus on gold containing magnetic nanomaterials. The radiolabelling of magnetic Fe3O4-Au core-shell and Fe3O4-Au dumbbell-like nanoparticles with the [99mTc(CO)3]+ fragment is described. The key elements for this 99mTc labelling approach are novel coating ligands, consisting of an anchor for the Au surface, a polyethylene glycol linker and a strong chelator for the [99mTc(CO)3]+ moiety.The development of nanoparticle-based dual-modality probes for magnetic resonance imaging (MRI) and positron emission tomography (PET) or single photon emission computed tomography (SPECT) is increasingly growing in importance. One of the most commonly used radionuclides for clinical SPECT imaging is 99mTc and the labelling of Fe3O4 nanoparticles with 99mTc was shown to be a successful strategy to obtain dual-modality imaging agents. In this work, we focus on gold containing magnetic nanomaterials. The radiolabelling of magnetic Fe3O4-Au core-shell and Fe3O4-Au dumbbell-like nanoparticles with the [99mTc(CO)3]+ fragment is described. The key elements for this 99mTc labelling approach are novel coating ligands, consisting of an anchor for the Au surface, a polyethylene glycol linker and a strong chelator for the [99mTc(CO)3]+ moiety. Electronic supplementary information (ESI) available: Analyses of Fe3O4-Au core-shell nanoparticles; analyses of Au-Fe3O4 dumbbell-like nanoparticles; 99mTc labelling of Fe3O4-Au core-shell nanoparticles; 99mTc complexes; 99mTc labelling of Au-Fe3O4 dumbbell-like nanoparticles; syntheses coating ligands. See

  11. Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction

    NASA Astrophysics Data System (ADS)

    Tan, Lingyu; Li, Lidong; Peng, Yi; Guo, Lin

    2015-12-01

    Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611} high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H2PtCl6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells.

  12. Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction.

    PubMed

    Tan, Lingyu; Li, Lidong; Peng, Yi; Guo, Lin

    2015-12-18

    Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611} high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H2PtCl6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells.

  13. Catalytic Gas-Phase Glycerol Processing over SiO2-, Cu-, Ni- and Fe- Supported Au Nanoparticles

    PubMed Central

    Kapkowski, Maciej; Siudyga, Tomasz; Sitko, Rafal; Lelątko, Józef; Szade, Jacek; Balin, Katarzyna; Klimontko, Joanna; Bartczak, Piotr; Polanski, Jaroslaw

    2015-01-01

    In this study, we investigated different metal pairings of Au nanoparticles (NPs) as potential catalysts for glycerol dehydration for the first time. All of the systems preferred the formation of hydroxyacetone (HYNE). Although the bimetallics that were tested, i.e., Au NPs supported on Ni, Fe and Cu appeared to be more active than the Au/SiO2 system, only Cu supported Au NPs gave high conversion (ca. 63%) and selectivity (ca. 70%) to HYNE. PMID:26580400

  14. FRET controlled photoluminescence in β-In2S3 microflower—Au nanoparticle ensemble

    NASA Astrophysics Data System (ADS)

    Warrier, Anita R.; Parameswaran, Chithra; Bingi, Jayachandra; Vijayan, C.

    2016-06-01

    We report on the exciton–plasmon interaction and fluorescence resonance energy transfer controlled photoluminescence quenching and switching in β-In2S3 microflowers dispersed in Au nanoparticle colloid. The strong resonant interaction of excited β-In2S3 microflowers with the surface plasmons of Au nanoparticles (∼520 nm) lead to shift in the excitonic binding energy (2.4 eV) with a magnitude of ∼50 meV. In the proximity of Au nanoparticles, the broad emission spectrum of β-In2S3 microflowers with prominent peak at wavelength of ∼540 nm is quenched and the peak switches to wavelength of ∼600 nm. We demonstrate that the quenching and switching of emission band depends on the rate of fluorescence resonance energy transfer, extent of spectral overlap and β-In2S3 microflowers (donor)- Au nanoparticles (acceptor) distance. This study opens the wide possibility of fabricating sensors and photonic devices with tunable optical properties.

  15. Air-stable Fe@Au nanoparticles synthesized by the microemulsion's methods

    NASA Astrophysics Data System (ADS)

    Rivas, José; Redondo, Yolanda Piñeiro; Iglesias-Silva, Esther; Vilas-Vilela, J. M.; León, L. M.; López-Quintela, Manuel Arturo

    2013-05-01

    Magnetic particles covered by gold are very important in many biological applications. However, there are not simple methods to produce small (< 5-10 nm) nanoparticles. One of the main reasons for that is the general use of iron oxides as magnetic cores, which have a large crystalline mismatch with gold. The use of Fe would be more appropriate, but its high tendency to oxidation has largely precluded it from being used as a core. Here, we will show that using a simple "one-pot" successive reaction method in microemulsions, can avoid such problems and is able to produce very stable core-shell Fe@Au nanoparticles. With this procedure, nanoparticles of ˜6 nm with a Fe core of 3 nm can easily be obtained. These Fe@Au nanoparticles, with a saturation magnetization of 1.13 emu/g, are very stable even in air after magnetic separation from the solution, which shows the good covering of the Fe core by the Au shell. In this contribution we will report the key parameters, which have to be taken into account, to prepare such stable Fe@Au dispersions and analyze their optical and magnetic properties, as well as their possible applications as biosensors, targeted magnetic separation, etc.

  16. DNA reorientation on Au nanoparticles: label-free detection of hybridization by surface enhanced Raman spectroscopy.

    PubMed

    Papadopoulou, Evanthia; Bell, Steven E J

    2011-10-21

    DNA sequences attached to Au nanoparticles via thiol linkers stand up from the surface, giving preferential enhancement of the adenine ring breathing SERS band. Non-specific binding via the nucleobases reorients the DNA, reducing this effect. This change in intensity on reorientation was utilised for label-free detection of hybridization of a molecular beacon.

  17. Spectroscopic and Physical Characterization of Functionalized Au Nanoparticles: A Multiweek Experimental Project

    ERIC Educational Resources Information Center

    Masson, Jean-Francois; Yockell-Lelièvre, Hélène

    2014-01-01

    A term project was introduced in teaching advanced spectroscopy and notions of nanotechnology to chemistry students at the graduate level (M.Sc. and Ph.D.). This project could also be suited for an honor's thesis at the undergraduate level. Students were assigned a unique combination of nanoparticle synthesis (13 nm Au nanospheres, ~100 nm…

  18. Collagen-chitosan scaffold modified with Au and Ag nanoparticles: Synthesis and structure

    NASA Astrophysics Data System (ADS)

    Rubina, M. S.; Kamitov, E. E.; Zubavichus, Ya. V.; Peters, G. S.; Naumkin, A. V.; Suzer, S.; Vasil'kov, A. Yu.

    2016-03-01

    Nowadays, the dermal biomimetic scaffolds are widely used in regenerative medicine. Collagen-chitosan scaffold one of these materials possesses antibacterial activity, good compatibility with living tissues and has been already used as a wound-healing material. In this article, collagen-chitosan scaffolds modified with Ag and Au nanoparticles have been synthesized using novel method - the metal-vapor synthesis. The nanocomposite materials are characterized by XPS, TEM, SEM and synchrotron radiation-based X-ray techniques. According to XRD data, the mean size of the nanoparticles (NPs) is 10.5 nm and 20.2 nm in Au-Collagen-Chitosan (Au-CollCh) and Ag-Collagen-Chitosan (Ag-CollCh) scaffolds, respectively in fair agreement with the TEM data. SAXS analysis of the composites reveals an asymmetric size distribution peaked at 10 nm for Au-CollCh and 25 nm for Ag-CollCh indicative of particle's aggregation. According to SEM data, the metal-carrying scaffolds have layered structure and the nanoparticles are rather uniformly distributed on the surface material. XPS data indicate that the metallic nanoparticles are in their unoxidized/neutral states and dominantly stabilized within the chitosan-rich domains.

  19. Gold surfaces and nanoparticles are protected by Au(0)–thiyl species and are destroyed when Au(I)–thiolates form

    PubMed Central

    Reimers, Jeffrey R.; Ford, Michael J.; Halder, Arnab; Ulstrup, Jens; Hush, Noel S.

    2016-01-01

    The synthetic chemistry and spectroscopy of sulfur-protected gold surfaces and nanoparticles is analyzed, indicating that the electronic structure of the interface is Au(0)–thiyl, with Au(I)–thiolates identified as high-energy excited surface states. Density-functional theory indicates that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)–thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s–d hybridization and charge polarization effects that perturbatively mix in some Au(I)–thiolate character. A simple method for quantifying these contributions is presented, revealing that a driving force for nanoparticle growth is nobleization, minimizing Au(I)–thiolate involvement. Predictions that Brust–Schiffrin reactions involve thiolate anion intermediates are verified spectroscopically, establishing a key feature needed to understand nanoparticle growth. Mixing of preprepared Au(I) and thiolate reactants always produces Au(I)–thiolate thin films or compounds rather than monolayers. Smooth links to O, Se, Te, C, and N linker chemistry are established. PMID:26929334

  20. Charging effect in Au nanoparticle memory device with biomolecule binding mechanism.

    PubMed

    Jung, Sung Mok; Kim, Hyung-Jun; Kim, Bong-Jin; Yoon, Tae-Sik; Kim, Yong-Sang; Lee, Hyun Ho

    2011-07-01

    Organic memory device having gold nanoparticle (Au NPs) has been introduced in the structure of metal-pentacene-insulator-silicon (MPIS) capacitor device, where the Au NPs layer was formed by a new bonding method. Biomolecule binding mechanism between streptavidin and biotin was used as a strong binding method for the formation of monolayered Au NPs on polymeric dielectric of poly vinyl alcohol (PVA). The self-assembled Au NPs was functioned to show storages of charge in the MPIS device. The binding by streptavidin and biotin was confirmed by AFM and UV-VIS. The UV-VIS absorption of the Au NPs was varied at 515 nm and 525 nm depending on the coating of streptavidin. The AFM image showed no formation of multi-stacked layers of the streptavidin-capped Au NPs on biotin-NHS layer. Capacitance-voltage (C-V) performance of the memory device was measured to investigate the charging effect from Au NPs. In addition, charge retention by the Au NPs storage was tested to show 10,000 s in the C-V curve.

  1. Enhanced antilipopolysaccharide (LPS) induced changes in macrophage functions by Rubia cordifolia (RC) embedded with Au nanoparticles.

    PubMed

    Singh, Ashwani Kumar; Tripathi, Yamini B; Pandey, Nidhi; Singh, D P; Tripathi, Deepshikha; Srivastava, O N

    2013-12-01

    In this paper, we have shown that gold nanoparticles (Au (NPs)) embedded in Rubia cordifolia (RC) matrix (RC-Au (NPs)) exhibit a high therapeutic value relating to its anti-inflammatory characteristics. It was prepared by utilizing the reducing properties of RC to convert HAuCl4 into Au (NPs). In order to compare its effectiveness, with respect to Au (NPs), the latter was synthesized separately by reducing HAuCl4 with lemon extract. These Au (NPs) along with RC-Au (NPs) were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), and UV-visible spectroscopy. The enhancement in anti-inflammatory characteristics was assessed as its inhibitory potential for lipopolysaccharide (LPS)-induced nitric oxide (NO) release, by rat peritoneal macrophages. The RC-Au (NPs) significantly enhanced its potential to inhibit NO release, which was reported in terms of inhibitory concentration for 50% inhibition (IC50=11.98 ng/ml), as compared to either RC extract (IC50=47 × 10(3)ng/ml) or to Au (NPs) (IC50=587.50 ng/ml).

  2. Visible-Light-Induced Effects of Au Nanoparticle on Laccase Catalytic Activity.

    PubMed

    Guo, Sijie; Li, Hao; Liu, Juan; Yang, Yanmei; Kong, Weiqian; Qiao, Shi; Huang, Hui; Liu, Yang; Kang, Zhenhui

    2015-09-23

    A deep understanding of the interaction between the nanoparticle and enzyme is important for biocatalyst design. Here, we report the in situ synthesis of laccase-Au NP (laccase-Au) hybrids and its catalytic activity modulation by visible light. In the present hybrid system, the activity of laccase was significantly improved (increased by 91.2% vs free laccase) by Au NPs. With a short time visible light illumination (λ > 420 nm, within 3 min), the activity of laccase-Au hybrids decreased by 8.1% (vs laccase-Au hybrid without light), which can be restored to its initial one when the illumination is removed. However, after a long time illumination (λ > 420 nm, over 10 min), the catalytic activity of laccase-Au hybrids consecutively decreases and is not reversible even after removing the illumination. Our experiments also suggested that the local surface plasma resonance effect of Au NPs causes the structure change of laccase and local high temperature near the Au NPs. Those changes eventually affect the transportation of electrons in laccase, which further results in the declined activity of laccase.

  3. Enhanced fluorescence by surface plasmon coupling of Au nanoparticles in an organic electroluminescence diode

    NASA Astrophysics Data System (ADS)

    Fujiki, A.; Uemura, T.; Zettsu, N.; Akai-Kasaya, M.; Saito, A.; Kuwahara, Y.

    2010-01-01

    A significant increase in electroluminescence was achieved through coupling with localized surface plasmons in a single layer of Au nanoparticles. We fabricated a thin-film organic electroluminescence diode, which consists of an indium tin oxide (ITO) anode, a Au nanoparticle array, a Cu phthalocyanine hole transport layer, a tris(8-hydroxylquinolianato) aluminum (III) electron transport layer, a LiF electron injection layer, and an Al cathode. The device structure, with size-controlled Au particles embedded on ITO, can be used to realize the optimum distance for exciton-plasmon interactions by simply adjusting the thickness of the hole transport layer. We observed a 20-fold increase in the molecular fluorescence compared with that of a conventional diode structure.

  4. Synthesis and characterization of Au-core Ag-shell nanoparticles from unmodified apoferritin

    SciTech Connect

    Li, T.; Chattopadhyay, S.; Shibata, T.; Cook, R. E.; Miller, J. T.; Suthiwangcharoen, N.; Lee, S.; Winans, R. E.; Lee, B.

    2012-01-01

    Narrow-size distributed, water-soluble Au-core Ag-shell nanoparticles with a size range from 1 to 5 nm are synthesized using unmodified apoferritin as a template. Fast protein liquid chromatography reveals that the nanoparticles are formed inside the apoferritin cavity and are stable in aqueous solution. Electron microscopy shows that the particles are uniform in size and composed of both Au and Ag. In addition, extended X-ray absorption fine structure confirms that the particles have a core-shell structure with a Au core covered with a Ag shell. By varying the loading amounts of the silver precursor, the Ag shell thickness is controlled from one layer to several layers.

  5. Facile synthesis and optical properties of polymer-laced ZnO-Au hybrid nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, XianHong; Zhang, XiaoYan; Cheng, WenZheng; Shao, HongQin; Liu, Xiao; Li, XueMei; Liu, HongLing; Wu, JunHua

    2014-03-01

    Bi-phase dispersible ZnO-Au hybrid nanoparticles were synthesized via one-pot non-aqueous nanoemulsion using the triblock copolymer poly(ethylene glycol)- block-poly(propylene glycol)- block-poly(ethylene glycol) as the surfactant. The characterization shows that the polymer-laced ZnO-Au nanoparticles are monosized and of high crystallinity and demonstrate excellent dispersibility and optical performance in both organic and aqueous medium, revealing the effects of quantum confinement and medium. The findings show two well-behaved absorption bands locating at approximately 360 nm from ZnO and between 520 and 550 nm from the surface plasmon resonance of the nanosized Au and multiple visible fingerprint photoluminescent emissions. Consequently, the wide optical absorbance and fluorescent activity in different solvents could be promising for biosensing, photocatalysis, photodegradation, and optoelectronic devices.

  6. Inhibition of gold nanoparticles (AuNPs) on pathogenic biofilm formation and invasion to host cells

    PubMed Central

    Yu, Qilin; Li, Jianrong; Zhang, Yueqi; Wang, Yufan; Liu, Lu; Li, Mingchun

    2016-01-01

    Owing to the growing infectious diseases caused by eukaryotic and prokaryotic pathogens, it is urgent to develop novel antimicrobial agents against clinical pathogenic infections. Biofilm formation and invasion into the host cells are vital processes during pathogenic colonization and infection. In this study, we tested the inhibitory effect of Au nanoparticles (AuNPs) on pathogenic growth, biofilm formation and invasion. Interestingly, although the synthesized AuNPs had no significant toxicity to the tested pathogens, Candida albicans and Pseudomonas aeruginosa, the nanoparticles strongly inhibited pathogenic biofilm formation and invasion to dental pulp stem cells (DPSCs). Further investigations revealed that AuNPs abundantly bound to the pathogen cells, which likely contributed to their inhibitory effect on biofilm formation and invasion. Moreover, treatment of AuNPs led to activation of immune response-related genes in DPSCs, which may enhance the activity of host immune system against the pathogens. Zeta potential analysis and polyethylene glycol (PEG)/polyethyleneimine (PEI) coating tests further showed that the interaction between pathogen cells and AuNPs is associated with electrostatic attractions. Our findings shed novel light on the application of nanomaterials in fighting against clinical pathogens, and imply that the traditional growth inhibition test is not the only way to evaluate the drug effect during the screening of antimicrobial agents. PMID:27220400

  7. Selective decoration of Au nanoparticles on monolayer MoS2 single crystals.

    PubMed

    Shi, Yumeng; Huang, Jing-Kai; Jin, Limin; Hsu, Yu-Te; Yu, Siu Fung; Li, Lain-Jong; Yang, Hui Ying

    2013-01-01

    We report a controllable wet method for effective decoration of 2-dimensional (2D) molybdenum disulfide (MoS2) layers with Au nanoparticles (NPs). Au NPs can be selectively formed on the edge sites or defective sites of MoS2 layers. The Au-MoS2 nano-composites are formed by non-covalent bond. The size distribution, morphology and density of the metal nanoparticles can be tuned by changing the defect density in MoS2 layers. Field effect transistors were directly fabricated by placing ion gel gate dielectrics on Au-decorated MoS2 layers without the need to transfer these MoS2 layers to SiO2/Si substrates for bottom gate devices. The ion gel method allows probing the intrinsic electrical properties of the as-grown and Au-decorated MoS2 layers. This study shows that Au NPs impose remarkable p-doping effects to the MoS2 transistors without degrading their electrical characteristics.

  8. Inhibition of gold nanoparticles (AuNPs) on pathogenic biofilm formation and invasion to host cells.

    PubMed

    Yu, Qilin; Li, Jianrong; Zhang, Yueqi; Wang, Yufan; Liu, Lu; Li, Mingchun

    2016-01-01

    Owing to the growing infectious diseases caused by eukaryotic and prokaryotic pathogens, it is urgent to develop novel antimicrobial agents against clinical pathogenic infections. Biofilm formation and invasion into the host cells are vital processes during pathogenic colonization and infection. In this study, we tested the inhibitory effect of Au nanoparticles (AuNPs) on pathogenic growth, biofilm formation and invasion. Interestingly, although the synthesized AuNPs had no significant toxicity to the tested pathogens, Candida albicans and Pseudomonas aeruginosa, the nanoparticles strongly inhibited pathogenic biofilm formation and invasion to dental pulp stem cells (DPSCs). Further investigations revealed that AuNPs abundantly bound to the pathogen cells, which likely contributed to their inhibitory effect on biofilm formation and invasion. Moreover, treatment of AuNPs led to activation of immune response-related genes in DPSCs, which may enhance the activity of host immune system against the pathogens. Zeta potential analysis and polyethylene glycol (PEG)/polyethyleneimine (PEI) coating tests further showed that the interaction between pathogen cells and AuNPs is associated with electrostatic attractions. Our findings shed novel light on the application of nanomaterials in fighting against clinical pathogens, and imply that the traditional growth inhibition test is not the only way to evaluate the drug effect during the screening of antimicrobial agents. PMID:27220400

  9. Evidence for Bioavailability of Au Nanoparticles from Soil and Biodistribution within Earthworms (Eisenia fetida)

    SciTech Connect

    J Unrine; S Hunyadi; O Tsyusko; W Rao; A Shoults-Wilson; P Bertsch

    2011-12-31

    Because Au nanoparticles (NPs) are resistant to oxidative dissolution and are easily detected, they have been used as stable probes for the behavior of nanomaterials within biological systems. Previous studies provide somewhat limited evidence for bioavailability of Au NPs in food webs, because the spatial distribution within tissues and the speciation of Au was not determined. In this study, we provide multiple lines of evidence, including orthogonal microspectroscopic techniques, as well as evidence from biological responses, that Au NPs are bioavailable from soil to a model detritivore (Eisenia fetida). We also present limited evidence that Au NPs may cause adverse effects on earthworm reproduction. This is perhaps the first study to demonstrate that Au NPs can be taken up by detritivores from soil and distributed among tissues. We found that primary particle size (20 or 55 nm) did not consistently influence accumulated concentrations on a mass concentration basis; however, on a particle number basis the 20 nm particles were more bioavailable. Differences in bioavailability between the treatments may have been explained by aggregation behavior in pore water. The results suggest that nanoparticles present in soil from activities such as biosolids application have the potential to enter terrestrial food webs.

  10. Highly active PtAu alloy nanoparticle catalysts for the reduction of 4-nitrophenol.

    PubMed

    Zhang, Jianming; Chen, Guozhu; Guay, Daniel; Chaker, Mohamed; Ma, Dongling

    2014-02-21

    To enhance the catalytic activity of gold nanoparticles (AuNPs) for the hydrogenation of nitro-aromatic chemicals, Pt was introduced into AuNPs to form "bare" PtAu alloy NPs using a physical approach, pulsed laser ablation in liquid (PLAL), on single metal-mixture targets. These PLAL-NPs are deemed to favor catalysis due to the absence of any surfactant molecules on their unique "bare and clean" surface. The PLAL-NPs were facilely assembled onto CeO2 nanotubes (NTs) by simply mixing them without conducting any surface functionalization, representing another advantage of these NPs. Their catalytic activity was assessed in 4-nitrophenol (4-NP) hydrogenation. The reaction catalyzed by alloy-NP/CeO2-NT catalysts demonstrates a remarkably higher reaction rate in comparison with that catalyzed by pure Au and Pt NPs, and other similar Au and Pt containing catalysts reported recently. A "volcano-like" catalytic activity dependence of the alloy NPs on their chemical composition suggests a strong synergistic effect between Au and Pt in the 4-NP reduction, far beyond the simple sum of their individual contributions. It leads to the significantly enhanced catalytic activity of Pt30Au70 and Pt50Au50 alloy NPs, outperforming not only each single constituent, but also their physical mixtures and most recently reported AuNP based nanocatalysts. The favorable d-band center shift of Pt after alloying, and co-operative actions between Pt clusters and nearby Au (or mixed PtAu) sites were proposed as possible mechanisms to explain such a strong synergistic effect on catalysis.

  11. Pressure-induced stiffness of Au nanoparticles to 71 GPa under quasi-hydrostatic loading.

    PubMed

    Hong, Xinguo; Duffy, Thomas S; Ehm, Lars; Weidner, Donald J

    2015-12-01

    The compressibility of nanocrystalline gold (n-Au, 20 nm) has been studied by x-ray total scattering using high-energy monochromatic x-rays in the diamond anvil cell under quasi-hydrostatic conditions up to 71 GPa. The bulk modulus, K0, of the n-Au obtained from fitting to a Vinet equation of state is ~196(3) GPa, which is about 17% higher than for the corresponding bulk materials (K0: 167 GPa). At low pressures (<7 GPa), the compression behavior of n-Au shows little difference from that of bulk Au. With increasing pressure, the compressive behavior of n-Au gradually deviates from the equation of state (EOS) of bulk gold. Analysis of the pair distribution function, peak broadening and Rietveld refinement reveals that the microstructure of n-Au is nearly a single-grain/domain at ambient conditions, but undergoes substantial pressure-induced reduction in grain size until 10 GPa. The results indicate that the nature of the internal microstructure in n-Au is associated with the observed EOS difference from bulk Au at high pressure. Full-pattern analysis confirms that significant changes in grain size, stacking faults, grain orientation and texture occur in n-Au at high pressure. We have observed direct experimental evidence of a transition in compressional mechanism for n-Au at ~20 GPa, i.e. from a deformation dominated by nucleation and motion of lattice dislocations (dislocation-mediated) to a prominent grain boundary mediated response to external pressure. The internal microstructure inside the nanoparticle (nanocrystallinity) plays a critical role for the macro-mechanical properties of nano-Au. PMID:26570982

  12. Hotspots engineering by grafting Au@Ag core-shell nanoparticles on the Au film over slightly etched nanoparticles substrate for on-site paraquat sensing.

    PubMed

    Wang, Chaoguang; Wu, Xuezhong; Dong, Peitao; Chen, Jian; Xiao, Rui

    2016-12-15

    Paraquat (PQ) pollutions are ultra-toxic to human beings and hard to be decomposed in the environment, thus requiring an on-site detection strategy. Herein, we developed a robust and rapid PQ sensing strategy based on the surface-enhanced Raman scattering (SERS) technique. A hybrid SERS substrate was prepared by grafting the Au@Ag core-shell nanoparticles (NPs) on the Au film over slightly etched nanoparticles (Au FOSEN). Hotspots were engineered at the junctions as indicated by the finite difference time domain calculation. SERS performance of the hybrid substrate was explored using p-ATP as the Raman probe. The hybrid substrate gives higher enhancement factor comparing to either the Au FOSEN substrate or the Au@Ag core-shell NPs, and exhibits excellent reproducibility, homogeneity and stability. The proposed SERS substrates were prepared in batches for the practical PQ sensing. The total analysis time for a single sample, including the pre-treatment and measurement, was less than 5min with a PQ detection limit of 10nM. Peak intensities of the SERS signal were plotted as a function of the PQ concentrations to calibrate the sensitivity by fitting the Hill's equation. The plotted calibration curve showed a good log-log linearity with the coefficient of determination of 0.98. The selectivity of the sensing proposal was based on the "finger print" Raman spectra of the analyte. The proposed substrate exhibited good recovery when it applied to real water samples, including lab tap water, bottled water, and commercially obtained apple juice and grape juice. This SERS-based PQ detection method is simple, rapid, sensitive and selective, which shows great potential in pesticide residue and additives abuse monitoring. PMID:27498319

  13. Ellagic Acid Directed Growth of Au-Pt Bimetallic Nanoparticles and Their Catalytic Applications

    NASA Astrophysics Data System (ADS)

    Barnaby, Stacey N.; Sarker, Nazmul H.; Banerjee, Ipsita A.

    2013-02-01

    In this work, we report the facile formation of bimetallic nanoparticles of Au-Pt in the presence of the plant polyphenol ellagic acid (EA). It was found that EA formed micro-fibrillar assemblies, which aggregated into micro-bundles under aqueous conditions. Those micro-bundles acted as templates for the growth of Au nanoparticles, as well as bimetallic Au-Pt nanoparticles biomimetically. At higher concentrations of EA, it was observed that in addition to forming fibrous micro-bundles, columnar assemblies of EA were formed in the presence of the metal nanoparticles. The formation of the assemblies was found to be concentration dependent. It appears that upon binding to metal ions and subsequent formation of the nanoparticles, morphological changes occur in the case of EA assemblies. The morphological changes observed were probed by electron microscopy. Further, the ability of the materials to degrade the toxic aromatic nitro compound 2-methoxy-4-nitroaniline was explored, where 50% degradation was observed within 15 min, indicating that such hybrid materials may have potential applications in environmental remediation.

  14. Structural and Optical Properties of Discrete Dendritic Pt Nanoparticles on Colloidal Au Nanoprisms

    PubMed Central

    2016-01-01

    Catalytic and optical properties can be coupled by combining different metals into nanoscale architectures in which both the shape and the composition provide fine-tuning of functionality. Here, discrete, small Pt nanoparticles (diameter = 3–6 nm) were grown in linear arrays on Au nanoprisms, and the resulting structures are shown to retain strong localized surface plasmon resonances. Multidimensional electron microscopy and spectroscopy techniques (energy-dispersive X-ray spectroscopy, electron tomography, and electron energy-loss spectroscopy) were used to unravel their local composition, three-dimensional morphology, growth patterns, and optical properties. The composition and tomographic analyses disclose otherwise ambiguous details of the Pt-decorated Au nanoprisms, revealing that both pseudospherical protrusions and dendritic Pt nanoparticles grow on all faces of the nanoprisms (the faceted or occasionally twisted morphologies of which are also revealed), and shed light on the alignment of the Pt nanoparticles. The electron energy-loss spectroscopy investigations show that the Au nanoprisms support multiple localized surface plasmon resonances despite the presence of pendant Pt nanoparticles. The plasmonic fields at the surface of the nanoprisms indeed extend into the Pt nanoparticles, opening possibilities for combined optical and catalytic applications. These insights pave the way toward comprehensive nanoengineering of multifunctional bimetallic nanostructures, with potential applications in plasmon-enhanced catalysis and in situ monitoring of chemical processes via surface-enhanced spectroscopy. PMID:27688821

  15. Structural and Optical Properties of Discrete Dendritic Pt Nanoparticles on Colloidal Au Nanoprisms

    PubMed Central

    2016-01-01

    Catalytic and optical properties can be coupled by combining different metals into nanoscale architectures in which both the shape and the composition provide fine-tuning of functionality. Here, discrete, small Pt nanoparticles (diameter = 3–6 nm) were grown in linear arrays on Au nanoprisms, and the resulting structures are shown to retain strong localized surface plasmon resonances. Multidimensional electron microscopy and spectroscopy techniques (energy-dispersive X-ray spectroscopy, electron tomography, and electron energy-loss spectroscopy) were used to unravel their local composition, three-dimensional morphology, growth patterns, and optical properties. The composition and tomographic analyses disclose otherwise ambiguous details of the Pt-decorated Au nanoprisms, revealing that both pseudospherical protrusions and dendritic Pt nanoparticles grow on all faces of the nanoprisms (the faceted or occasionally twisted morphologies of which are also revealed), and shed light on the alignment of the Pt nanoparticles. The electron energy-loss spectroscopy investigations show that the Au nanoprisms support multiple localized surface plasmon resonances despite the presence of pendant Pt nanoparticles. The plasmonic fields at the surface of the nanoprisms indeed extend into the Pt nanoparticles, opening possibilities for combined optical and catalytic applications. These insights pave the way toward comprehensive nanoengineering of multifunctional bimetallic nanostructures, with potential applications in plasmon-enhanced catalysis and in situ monitoring of chemical processes via surface-enhanced spectroscopy.

  16. A click strategy for the immobilization of MacMillan organocatalysts onto polymers and magnetic nanoparticles.

    PubMed

    Riente, Paola; Yadav, Jagjit; Pericàs, Miquel A

    2012-07-20

    A chemically modified, first generation MacMillan imidazolidin-4-one has been anchored onto 1% DVB Merrifield resin and Fe3O4 (5.3 ± 1.4 nm) magnetic nanoparticles through copper-catalyzed alkyne azide cycloaddition (CuAAC) reactions. The resulting immobilized catalysts have been successfully used in the asymmetric Friedel-Crafts alkylation of N-substituted pyrroles with α,β-unsaturated aldehydes. The PS-supported catalyst (B) showed higher catalytic activity and enantioselectivity, while the MNP-supported one (A) showed higher recyclability and could be used in a sequential process with intermediate magnetic decantation. PMID:22758605

  17. Enzyme-free Detection of Hydrogen Peroxide from Cerium Oxide Nanoparticles Immobilized on Poly(4-vinylpyridine) Self-Assembled Monolayers

    SciTech Connect

    Gaynor, James D.; Karakoti, Ajay S.; Inerbaev, Talgat; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Seal, Sudipta; Thevuthasan, Suntharampillai

    2013-05-02

    A single layer of oxygen-deficient cerium oxide nanoparticles (CNPs) are immobilized on microscopic glass slide using poly(4-vinylpyridine) (PVP) self-assembled monolayers (SAMs). A specific colorimetric property of CNPs when reacted with hydrogen peroxide allows for the direct, single-step peroxide detection which can be used in medical diagnosis and explosives detection. Multiple PVP-CNP immobilized layers improve sensitivity of detection and the sensor can be regenerated for reuse.

  18. Fungal biomolecules assisted biosynthesis of Au-Ag alloy nanoparticles and evaluation of their catalytic property.

    PubMed

    Tripathi, Ravi Mani; Gupta, Rohit Kumar; Bhadwal, Akhshay Singh; Singh, Priti; Shrivastav, Archana; Shrivastav, B R

    2015-08-01

    The catalytic reduction of methylene blue was studied using biosynthesised gold-silver (Au-Ag) alloy nanoparticles (NPs). The fungal biomass of Trichoderma harzianum was used as a reducing and stabilising agent in the synthesis of Au-Ag alloy NPs. The synthesised NPs were well characterised by UV-vis spectroscopy, dynamic light scattering, X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The plausible synthesis mechanism involved in the formation of Au-Ag alloy NPs was also discussed with diagrammatic representation. A series of experiments was performed to investigate the catalytic activity of the as-prepared Au-Ag alloy NPs and found that the alloy NPs show excellent catalytic activity. PMID:26224346

  19. Biocompatible D-Penicillamine Conjugated Au Nanoparticles: Targeting Intracellular Free Copper Ions for Detoxification

    PubMed Central

    Kandanapitiye, Murthi S.; Gunathilake, Chamila; Jaroniec, Mietek

    2015-01-01

    High thiophillicicity of the Au-nanoparticle (Au NP) surface leads to covalent attachment of D-penicillamine molecules to Au NPs to form biocompatible D-penicillamine conjugated Au NPs. The latter are highly water-dispersible, exhibit no cytotoxicity, and can readily penetrate the cell membrane to target intracellular free copper ions for selective copper detoxification in the presence of the other divalent essential metal ions including Zn(II), Fe(II), Mn(II), Ca(II), and Mg(II), thus opening up a new avenue for improving the efficacy and pharmacokinetics of D-penicillamine, an important clinical drug currently used to treat the copper overload-related diseases and disorders. PMID:26213624

  20. Polyethylenimine-immobilized core-shell nanoparticles: synthesis, characterization, and biocompatibility test.

    PubMed

    Ratanajanchai, Montri; Soodvilai, Sunhapas; Pimpha, Nuttaporn; Sunintaboon, Panya

    2014-01-01

    Herein, we prepared PEI-immobilized core-shell particles possessing various types of polymer cores via a visible light-induced surfactant-free emulsion polymerization (SFEP) of three vinyl monomers: styrene (St), methyl methacrylate (MMA), and 2-hydroxyethyl methacrylate (HEMA). An effect of monomers on the polymerization and characteristics of resulting products was investigated. Monomers with high polarity can provide high monomer conversion, high percentage of grafted PEI, stable particles with uniform size distribution but less amino groups per particles. All prepared nanoparticles exhibited a core-shell nanostructure, containing PEI on the shell with hydrodynamic size around 140-230nm. For in-vitro study in Caco-2 cells, we found that the incorporation of PEI into these core-shell nanoparticles can significantly reduce its cytotoxic effect and also be able to internalized within the cells. Accordingly, these biocompatible particles would be useful for various biomedical applications, including gene transfection and intracellular drug delivery.

  1. Magnetic solid phase extraction using gold immobilized magnetic mesoporous silica nanoparticles coupled with dispersive liquid-liquid microextraction for determination of polycyclic aromatic hydrocarbons.

    PubMed

    Mehdinia, Ali; Khojasteh, Esmail; Baradaran Kayyal, Tohid; Jabbari, Ali

    2014-10-17

    An efficient magnetic sorbent was introduced for solid phase extraction by incorporation of the gold nanoparticles into the hexagonal lattice of magnetic MCM-41. For the effective incorporation of the gold nanoparticles, magnetic MCM-41 was functionalized with 3-aminopropyltriethoxysilane (APTES), which then interacted with Au atoms through the amine groups. Furthermore, to achieve high pre-concentration factors (PFs), the method was coupled with dispersive liquid-liquid microextraction (DLLME) procedure. Polycyclic aromatic hydrocarbons (PAHs) were used as the model compounds to evaluate the extraction performance of the proposed method. The π-system of PAH compounds and immobilized Au atoms on the surface of the sorbent can cause the electron donor-acceptor interactions. The parameters affecting extraction recovery such as types of the disperser and extraction solvents, pH of the sample solution, and the extraction time were optimized. Under the optimized conditions, the high PFs were obtained in the range 5519-6271 for the target analytes. The kinetic adsorption illustrated that 5 min was sufficient to achieve adsorption equilibrium for PAHs. The evaluations also showed a linearity range 0.01-50 μg L(-1) with the detection limit in the range 0.002-0.004 μg L(-1) for the PAHs. The applicability of the method for the analysis of PAHs in real samples was justified by the extraction of PAHs from seawater samples. The results indicated good recovery efficiencies ranging from 91.4 to 104.2%. PMID:25194625

  2. Magnetic solid phase extraction using gold immobilized magnetic mesoporous silica nanoparticles coupled with dispersive liquid-liquid microextraction for determination of polycyclic aromatic hydrocarbons.

    PubMed

    Mehdinia, Ali; Khojasteh, Esmail; Baradaran Kayyal, Tohid; Jabbari, Ali

    2014-10-17

    An efficient magnetic sorbent was introduced for solid phase extraction by incorporation of the gold nanoparticles into the hexagonal lattice of magnetic MCM-41. For the effective incorporation of the gold nanoparticles, magnetic MCM-41 was functionalized with 3-aminopropyltriethoxysilane (APTES), which then interacted with Au atoms through the amine groups. Furthermore, to achieve high pre-concentration factors (PFs), the method was coupled with dispersive liquid-liquid microextraction (DLLME) procedure. Polycyclic aromatic hydrocarbons (PAHs) were used as the model compounds to evaluate the extraction performance of the proposed method. The π-system of PAH compounds and immobilized Au atoms on the surface of the sorbent can cause the electron donor-acceptor interactions. The parameters affecting extraction recovery such as types of the disperser and extraction solvents, pH of the sample solution, and the extraction time were optimized. Under the optimized conditions, the high PFs were obtained in the range 5519-6271 for the target analytes. The kinetic adsorption illustrated that 5 min was sufficient to achieve adsorption equilibrium for PAHs. The evaluations also showed a linearity range 0.01-50 μg L(-1) with the detection limit in the range 0.002-0.004 μg L(-1) for the PAHs. The applicability of the method for the analysis of PAHs in real samples was justified by the extraction of PAHs from seawater samples. The results indicated good recovery efficiencies ranging from 91.4 to 104.2%.

  3. Enhanced phenol degradation in coking wastewater by immobilized laccase on magnetic mesoporous silica nanoparticles in a magnetically stabilized fluidized bed.

    PubMed

    Wang, Feng; Hu, Yiru; Guo, Chen; Huang, Wei; Liu, Chun-Zhao

    2012-04-01

    The immobilized laccase on magnetic mesoporous silica nanoparticles has been developed for efficient phenol degradation. The degradation rate of phenol by the immobilized laccase was 2-fold higher than that of the free laccase, and the immobilized laccase retained 71.3% of its initial degradation ability after 10 successive batch treatments of coking wastewater. The phenol degradation in the coking wastewater was enhanced in a continuous treatment process by the immobilized laccase in a magnetically stabilized fluidized bed (MSFB) because of good mixing and mass transfer. The degradation rate of phenol maintained more than 99% at a flow rate of less than 450mLh(-1) and decreased slowly to 91.5% after 40h of the continuous operation in the MSFB. The present work indicated that the immobilized laccase on magnetic mesoporous supports together with the MSFB provided a promising avenue for the continuous enzymatic degradation of phenolic compounds in industrial wastewater.

  4. Pulsed-laser-deposited TiO2 nanocrystalline films supporting Au nanoparticles for visible-light-operating plasmonic photocatalysts

    NASA Astrophysics Data System (ADS)

    Yoshida, Takehito; Watanabe, Tei; Kikuchi, Fumito; Tabuchi, Takeru; Umezu, Ikurou; Haraguchi, Masanobu

    2016-05-01

    We have synthesized pulsed-laser-deposited (PLD) TiO2 nanocrystalline films supporting Au nanoparticles. Au films were deposited on the PLD TiO2 nanocrystalline films with the mass thickness of 4 nm. The as-deposited Au films had island structures. After furnace annealing at 300 °C for 180 min in air, the as-deposited island-structured Au films were balled with the mean diameter of 19 nm on the PLD TiO2 nanocrystalline films. We confirmed that the balled Au nanoparticles had the localized surface plasmonic resonance absorption band in the range of 510-600 nm. Photocatalytic activities of the Au-supporting TiO2 nanocrystalline films were evaluated by a methylene blue decomposition method. We clarified that the Au-supporting TiO2 nanocrystalline films demonstrated visible-light-driven photocatalytic activities, under the filtered (490-500 nm) Xe arc lamp irradiation.

  5. Hydrodechlorination Catalysis of Pd-on-Au Nanoparticles Varies with Particle Size

    SciTech Connect

    Pretzer, Lori A.; Song, Hyun J.; Fang, Yu-Lun; Zhao, Zhun; Guo, Neng; Wu, Tianpin; Arslan, Ilke; Miller, Jeffrey T.; Wong, Michael S.

    2013-02-01

    The dependence of bimetallic PdAu catalytic activity on the relative ratios of Pd and Au has been theoretically predicted and experimentally observed for a number of reactions. Trichloroethene (TCE), a common carcinogenic solvent that is difficult to remove from contaminated groundwater in many industrialized nations, can be chemically degraded especially rapidly with Au nanoparticles partially coated with Pd ("Pd-on-Au NPs"). These NPs catalyze the room-temperature water-phase TCE hydrodechlorination (HDC) reaction with activities that follow a volcano-shape dependence on Pd surface coverage. The effect of particle size is not known, though. Pd-on-Au NPs synthesized with 3, 7, and 10 nm Au NPs and Pd surface coverages between 0 and 150% were studied in detail. Volcano-shape dependence on Au particle size and Pd surface coverage was observed, with 7 nm Au NPs with a Pd coverage of 60-70% having the highest TCE HDC activity. Extended x-ray absorption fine-structure spectroscopy (EXAFS) revealed the correlation was strongest between catalytic activity and the presence of non-oxidized Pd ensembles of ~2-3 atoms in contact with ~8-10 Au atoms. Isolated Pd atoms and Pd ensembles were visualized for the first time through aberration-corrected scanning transmission electron microscopy (STEM). This study provides the most direct evidence yet for Pd-on-Au NPs containing 2-dimensional Pd ensembles as the active sites for TCE HDC and likely for other chemical reactions. A portion of the research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. This research was supported by the Laboratory Directed Research and Development program at Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  6. Use of aerosol route to fabricate positively charged Au/Fe3O4 Janus nanoparticles as multifunctional nanoplatforms

    NASA Astrophysics Data System (ADS)

    Byeon, Jeong Hoon; Park, Jae Hong

    2016-10-01

    Gold (Au)-decorated iron oxide (Fe3O4), Au/Fe3O4, Janus nanoparticles were fabricated via the continuous route for aerosol Au incorporation with Fe3O4 domains synthesized in an aqueous medium as multifunctional nanoplatforms. The fabricated nanoparticles were subsequently exposed to 185-nm UV light to generate positive charges on Au surfaces, and their activities were tested in computed tomography (CT) and magnetic resonance (MR) imaging, gene-delivery and photothermal therapy. No additional polymeric coatings of the Janus particles also had a unique ability to suppress inflammatory responses in macrophages challenged with lipopolysaccharide, which may be due to the absence of amine groups.

  7. Direct Evidence for Percolation of Immobilized Polymer Layer around Nanoparticles Accounting for Sol-Gel Transition in Fumed Silica Dispersions.

    PubMed

    Zheng, Zhong; Song, Yihu; Yang, Ruiquan; Zheng, Qiang

    2015-12-22

    Immobilized polymer fractions have been claimed to be of vital importance for sol-gel transitions generally observed in nanoparticle dispersions but remain a matter of debate regarding mechanism and difficulty for prediction. Here we investigate the immobilized layer structures of trifunctionality polyether polyol (PPG) near the surfaces of hydrophilic and hydrophobic fumed silica (FS) nanoparticles to reveal the role of surface chemistry on the molecular dynamics and sol-gel transitions of the dispersions. Using modulated differential scanning calorimetry, we measure the specific heat capacity during glass transition and the enthalpy during cold-crystallization. Comparing with hydrophobic FS that forms a fully immobilized (glassy) layer, we find that hydrophilic FS immobilizes more PPG, forming a partially immobilized outer layer being unable to crystallize next to the inner glassy layer. By correlating the thickness of the glassy layer with half of the minimum spacing between nanoparticles, we directly evidence the percolation of this layer along the nearest neighbor nanoparticles responsible for the sol-gel transition. Using effective volume fraction including the glassy layer, we successfully construct master curves of relative viscosity of both hydrophilic and hydrophobic FS dispersions, pointing to a common sol-gel transition mechanism mediated by the surface chemistry.

  8. Electron emission of Au nanoparticles embedded in ZnO for highly conductive oxide

    SciTech Connect

    Huang, Po-Shun; Lee, Jung-Kun; Hoe Kim, Dong

    2014-04-07

    We investigated the effect of embedded Au nanoparticles (Au NPs) on electrical properties of zinc oxide (ZnO) for highly conductive oxide semiconductor. Au NPs in ZnO films influenced both the structural and electrical properties of the mixture films. The electrical resistivity decreases by as much as five orders of magnitude. This is explained by the electron emission from Au NPs to the ZnO matrix. Temperature-dependent Hall effect measurements show that an electron emission mechanism changes from tunneling to thermionic emission at T = 180 K. The electron mobility in the mixture film is mainly limited by the grain boundaries at lower temperature (80-180 K), and the Au/ZnO heterogeneous interface at higher temperature (180-340 K). In addition to the electron emission, embedded Au NPs alter the ZnO matrix microstructure and improve the electron mobility. Compared to the undoped ZnO film, the carrier concentration of the Au NP-embedded ZnO film can be increased by as much as six orders of magnitude with a small change in the carrier mobility. This result suggests a way to circumvent the inherent tradeoff between the carrier concentration and the carrier mobility in transparent conductive oxide (TCO) materials.

  9. From the Au nano-clusters to the nanoparticles on 4H-SiC (0001)

    PubMed Central

    Li, Ming-Yu; Zhang, Quanzhen; Pandey, Puran; Sui, Mao; Kim, Eun-Soo; Lee, Jihoon

    2015-01-01

    The control over the configuration, size, and density of Au nanoparticles (NPs) has offered a promising route to control the spatial confinement of electrons and photons, as a result, Au NPs with a various configuration, size and density are witnessed in numerous applications. In this work, we investigate the evolution of self-assembled Au nanostructures on 4H-SiC (0001) by the systematic variation of annealing temperature (AT) with several deposition amount (DA). With the relatively high DAs (8 and 15 nm), depending on the AT variation, the surface morphology drastically evolve in two distinctive phases, i.e. (I) irregular nano-mounds and (II) hexagonal nano-crystals. The thermal energy activates adatoms to aggregate resulting in the formation of self-assembled irregular Au nano-mounds based on diffusion limited agglomeration at comparatively low annealing temperature, which is also accompanied with the formations of hillocks and granules due to the dewetting of Au films and surface reordering. At high temperature, hexagonal Au nano-crystals form with facets along {111} and {100} likely due to anisotropic distribution of surface energy induced by the increased volume of NPs. With the small DA (3 nm), only dome shaped Au NPs are fabricated along with the variation of AT from low to elevated temperature. PMID:26354098

  10. Development of morin-conjugated Au nanoparticles: Exploring the interaction efficiency with BSA using spectroscopic methods

    NASA Astrophysics Data System (ADS)

    Yue, Hua-Li; Hu, Yan-Jun; Huang, Hong-Gui; Jiang, Shan; Tu, Bao

    2014-09-01

    In order to enhance its interaction efficiency with biomacromolecules for the usage as a therapeutic agent, we have conjugated morin, an antioxidant activity and anti-tumor drug, with citrate-coated Au nanoparticles (M-C-AuNPs). M-C-AuNPs were prepared by reducing chloroauric acid using trisodium citrate in the boiling condition, and the resulted M-C-AuNPs were characterized by UV-vis absorption spectroscopy, Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. In this article, UV-vis absorption spectroscopy in combination with fluorescence spectroscopy, and circular dichroism (CD) spectroscopy were employed to investigate the interactions between M-C-AuNPs and bovine serum albumin (BSA), C-AuNPs and BSA in a phosphate buffer at pH 7.4. By comparing the quenching constant KSV, effective quenching constant Ka, binding constant Kb and the number of binding sites n, it is clearly suggested that M-C-AuNPs could enhance the binding force of morin with BSA, which would pave the way for the design of nanotherapeutic agents with improved functionality.

  11. From the Au nano-clusters to the nanoparticles on 4H-SiC (0001).

    PubMed

    Li, Ming-Yu; Zhang, Quanzhen; Pandey, Puran; Sui, Mao; Kim, Eun-Soo; Lee, Jihoon

    2015-01-01

    The control over the configuration, size, and density of Au nanoparticles (NPs) has offered a promising route to control the spatial confinement of electrons and photons, as a result, Au NPs with a various configuration, size and density are witnessed in numerous applications. In this work, we investigate the evolution of self-assembled Au nanostructures on 4H-SiC (0001) by the systematic variation of annealing temperature (AT) with several deposition amount (DA). With the relatively high DAs (8 and 15 nm), depending on the AT variation, the surface morphology drastically evolve in two distinctive phases, i.e. (I) irregular nano-mounds and (II) hexagonal nano-crystals. The thermal energy activates adatoms to aggregate resulting in the formation of self-assembled irregular Au nano-mounds based on diffusion limited agglomeration at comparatively low annealing temperature, which is also accompanied with the formations of hillocks and granules due to the dewetting of Au films and surface reordering. At high temperature, hexagonal Au nano-crystals form with facets along {111} and {100} likely due to anisotropic distribution of surface energy induced by the increased volume of NPs. With the small DA (3 nm), only dome shaped Au NPs are fabricated along with the variation of AT from low to elevated temperature.

  12. From the Au nano-clusters to the nanoparticles on 4H-SiC (0001).

    PubMed

    Li, Ming-Yu; Zhang, Quanzhen; Pandey, Puran; Sui, Mao; Kim, Eun-Soo; Lee, Jihoon

    2015-01-01

    The control over the configuration, size, and density of Au nanoparticles (NPs) has offered a promising route to control the spatial confinement of electrons and photons, as a result, Au NPs with a various configuration, size and density are witnessed in numerous applications. In this work, we investigate the evolution of self-assembled Au nanostructures on 4H-SiC (0001) by the systematic variation of annealing temperature (AT) with several deposition amount (DA). With the relatively high DAs (8 and 15 nm), depending on the AT variation, the surface morphology drastically evolve in two distinctive phases, i.e. (I) irregular nano-mounds and (II) hexagonal nano-crystals. The thermal energy activates adatoms to aggregate resulting in the formation of self-assembled irregular Au nano-mounds based on diffusion limited agglomeration at comparatively low annealing temperature, which is also accompanied with the formations of hillocks and granules due to the dewetting of Au films and surface reordering. At high temperature, hexagonal Au nano-crystals form with facets along {111} and {100} likely due to anisotropic distribution of surface energy induced by the increased volume of NPs. With the small DA (3 nm), only dome shaped Au NPs are fabricated along with the variation of AT from low to elevated temperature. PMID:26354098

  13. High electrical conductance enhancement in Au-nanoparticle decorated sparse single-wall carbon nanotube networks.

    PubMed

    McAndrew, Calum F; Baxendale, Mark

    2013-08-01

    We report high electrical conductance enhancement in sparse single-walled carbon nanotube networks by decoration with Au nanoparticles. The optimized hybrid network exhibited a sheet resistance of 650 Ω sq(-1), 1/1500 of the resistance of the host undecorated network, with a negligible optical transmission penalty (>90% transmittance at 550 nm wavelength). The electrical transport at room temperature in the host and decorated networks was dominated by two-dimensional variable range hopping. The high conductance enhancement was due to positive charge transfer from the decorating Au nanoparticles in intimate contact with the host network causing a Fermi energy shift into the high density of states at a van Hove singularity and enhanced electron delocalization relative to the host network which beneficially modifies the hopping parameters in such a way that the network behaves as an integral whole. The effect is most pronounced when the nanoparticle diameter is comparable to the electron mean free path in the bulk material at room temperature and there is minimum nanoparticle agglomeration. For higher than optimal values of nanoparticle coverage or nanoparticle diameter, the conductance enhancement is countered by metallic inclusions in the current pathways that are of higher resistance than the variable range hopping-controlled elements.

  14. Controllable synthesis and characterization of Fe3O4/Au composite nanoparticles

    NASA Astrophysics Data System (ADS)

    Xing, Yan; Jin, Yan-Yan; Si, Jian-Chao; Peng, Ming-Li; Wang, Xiao-Fang; Chen, Chao; Cui, Ya-Li

    2015-04-01

    Fe3O4/Au composite nanoparticles (GoldMag NPs) have received considerable attention because of their advantageous properties arisen from both individual Au and Fe3O4 nanoparticles. Many efforts have been devoted to the synthesis of these composite nanoparticles. Herein, GoldMag NPs were reported to be synthesized by two-step method. Fe3O4 nanoparticles were prepared by co-precipitation and modified by the citric acid, and then citric acid-coated Fe3O4 nanoparticles were used as seeds in sodium citrate solution to reduce the HAuCl4. The size of obtained nanoparticles was geared from 25 to 300 nm by controlling the concentration of reactants. The GoldMag NPs were characterized by UV-vis spectrometer, dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The GoldMag NPs showed good superparamagnetism at room temperature and were well dispersed in water with surface plasmon resonance absorption peak varied from 538 nm to 570 nm.

  15. Immobilizing highly catalytically active Pt nanoparticles inside the pores of metal-organic framework: a double solvents approach.

    PubMed

    Aijaz, Arshad; Karkamkar, Abhi; Choi, Young Joon; Tsumori, Nobuko; Rönnebro, Ewa; Autrey, Tom; Shioyama, Hiroshi; Xu, Qiang

    2012-08-29

    Ultrafine Pt nanoparticles were successfully immobilized inside the pores of a metal-organic framework, MIL-101, without aggregation of Pt nanoparticles on the external surfaces of framework by using a "double solvents" method. TEM and electron tomographic measurements clearly demonstrated the uniform three-dimensional distribution of the ultrafine Pt NPs throughout the interior cavities of MIL-101. The resulting Pt@MIL-101 composites represent the first highly active MOF-immobilized metal nanocatalysts for catalytic reactions in all three phases: liquid-phase ammonia borane hydrolysis, solid-phase ammonia borane thermal dehydrogenation, and gas-phase CO oxidation. PMID:22888976

  16. Facile Synthesis of Au-Coated Magnetic Nanoparticles and Their Application in Bacteria Detection via a SERS Method.

    PubMed

    Wang, Junfeng; Wu, Xuezhong; Wang, Chongwen; Rong, Zhen; Ding, Hongmei; Li, Hui; Li, Shaohua; Shao, Ningsheng; Dong, Peitao; Xiao, Rui; Wang, Shengqi

    2016-08-10

    This study proposes a facile method for synthesis of Au-coated magnetic nanoparticles (AuMNPs) core/shell nanocomposites with nanoscale rough surfaces. MnFe2O4 nanoparticles (NPs) were first modified with a uniform polyethylenimine layer (2 nm) through self-assembly under sonication. The negatively charged Au seeds were then adsorbed on the surface of the MnFe2O4 NPs through electrostatic interaction for Au shell formation. Our newly developed sonochemically assisted hydroxylamine seeding growth method was used to grow the adsorbed gold seeds into large Au nanoparticles (AuNPs) to form a nanoscale rough Au shell. Au-coated magnetic nanoparticles (AuMNPs) were obtained from the intermediate product (Au seeds decorated magnetic core) under sonication within 5 min. The AuMNPs were highly uniform in size and shape and exhibited satisfactory surface-enhanced Raman scattering (SERS) activity and strong magnetic responsivity. PATP was used as a probe molecule to evaluate the SERS performance of the synthesized AuMNPs with a detection limit of 10(-9) M. The synthesized AuMNPs were conjugated with Staphylococcus aureus (S. aureus) antibody for bacteria capture and separation. The synthesized plasmonic AuNR-DTNB NPs, whose LSPR wavelength was adjusted to the given laser excitation wavelength (785 nm), were conjugated with S. aureus antibody to form a SERS tag for specific recognition and report of the target bacteria. S. aureus was indirectly detected through SERS based on sandwich-structured immunoassay, with a detection limit of 10 cells/mL. Moreover, the SERS intensity at Raman peak of 1331 cm(-1) exhibited a linear relationship to the logarithm of bacteria concentrations ranging from 10(1) cells/mL to 10(5) cells/mL. PMID:27420923

  17. Preparation of multi-functionalized Fe3O4/Au nanoparticles for medical purposes.

    PubMed

    del Mar Ramos-Tejada, María; Viota, Julian L; Rudzka, Katarzyna; Delgado, Angel V

    2015-04-01

    In this work, we investigate a route towards the synthesis of multi-functionalized nanoparticles for medical purposes. The aim is to produce magnetite/gold (Fe3O4/Au) nanoparticles combining several complementary properties, specifically, being able to carry simultaneously an antitumor drug and a selected antibody chosen so as to improve specificity of the drug vehicle. The procedure included, firstly, the preparation of Fe3O4 cores coated with Au nanoparticles: this was achieved by using initially the layer-by-layer technique in order to coat the magnetite particles with a three polyelectrolyte (cationic-anionic-cationic) layer. With this, the particles became a good substrate for the growth of the gold layer in a well-defined core-shell structure. The resulting nanoparticles benefit from the magnetic properties of the magnetite and the robust chemistry and the biostability of gold surfaces. Subsequently, the Fe3O4/Au nanoparticles were functionalized with a humanized monoclonal antibody, bevacizumab, and a chemotherapy drug, doxorubicin. Taken together, bevacizumab enhances the therapeutic effect of chemotherapy agents on some kinds of tumors. In this work we first discuss the morphology of the particles and the electrical characteristics of their surface in the successive synthesis stages. Special attention is paid to the chemical stability of the final coating, and the physical stability of the suspensions of the nanoparticles in aqueous solutions and phosphate buffer. We describe how optical absorbance and electrokinetic data provide a follow up of the progress of the nanostructure formation. Additionally, the same techniques are employed to demonstrate that the composite nanoparticles are capable of loading/releasing doxorubicin and/or bevacizumab.

  18. 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

  19. Magnetic switch of permeability for polyelectrolyte microcapsules embedded with Co@Au nanoparticles.

    PubMed

    Lu, Zonghuan; Prouty, Malcolm D; Guo, Zhanhu; Golub, Vladimir O; Kumar, Challa S S R; Lvov, Yuri M

    2005-03-01

    We explored using a magnetic field to modulate the permeability of polyelectrolyte microcapsules prepared by layer-by-layer self-assembly. Ferromagnetic gold-coated cobalt (Co@Au) nanoparticles (3 nm diameter) were embedded inside the capsule walls. The final 5 mum diameter microcapsules had wall structures consisting of 4 bilayers of poly(sodium styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH), 1 layer of Co@Au, and 5 bilayers of PSS/PAH. External alternating magnetic fields of 100-300 Hz and 1200 Oe were applied to rotate the embedded Co@Au nanoparticles, which subsequently disturbed and distorted the capsule wall and drastically increased its permeability to macromolecules like FITC-labeled dextran. The capsule permeability change was estimated by taking the capsule interior and exterior fluorescent intensity ratio using confocal laser scanning microscopy. Capsules with 1 layer of Co@Au nanoparticles and 10 polyelectrolyte bilayers are optimal for magnetically controlling permeability. A theoretical explanation was proposed for the permeability control mechanisms. "Switching on" of these microcapsules using a magnetic field makes this method a good candidate for controlled drug delivery in biomedical applications.

  20. Effect of Au nano-particles doping on polycrystalline YBCO high temperature superconductor

    NASA Astrophysics Data System (ADS)

    Dadras, Sedigheh; Gharehgazloo, Zahra

    2016-07-01

    In this research, we prepared different Au nanoparticles (0.1-2 wt%) doped YBCO high temperature superconductor samples by sol-gel method. To characterize the samples, we used X-Ray diffraction (XRD) and scanning electron microscope (SEM) analysis. Results show the formation of orthorhombic phase of superconductivity for all prepared samples. We observed that by adding Au nanoparticles, the grains' size of the samples reduces from 76 nm to 47 nm as well. The critical current density (Jc) and transition temperature (Tc) were determined using current versus voltage (I-V) and resistivity versus temperature (ρ-T) measurements, respectively. We found that by increasing Au nanoparticles in the compound, in comparison to the pure YBCO sample, the transition temperature, pinning energy and critical current density will increase. Also, the highest Jc is for 1 wt% Au doped YBCO compound that its critical current density is about 8 times more than the Jc of pure one in 0.7 T magnetic field.

  1. Cytocompatibility of Ar + plasma treated and Au nanoparticle-grafted PE

    NASA Astrophysics Data System (ADS)

    Švorčík, V.; Kasálková, N.; Slepička, P.; Záruba, K.; Král, V.; Bačáková, L.; Pařízek, M.; Lisá, V.; Ruml, T.; Gbelcová, H.; Rimpelová, S.; Macková, A.

    2009-06-01

    Polyethylene (PE) was irradiated with inert Ar plasma, and the chemically active PE surface was grafted with Au nanoparticles. The composition and the structure of the modified PE surface were studied using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). Changes in the surface wettability were determined from the contact angle measured in a reflection goniometer. The changes in the surface roughness and morphology were followed by atomic force microscopy (AFM). The modified PE samples were seeded with rat vascular smooth muscle cells (VSMC) or mouse NIH 3T3 fibroblasts, and their adhesion and proliferation were studied. We found that plasma discharge and Au grafting lead to dramatic changes in the surface morphology and roughness of PE. The Au nanoparticles were found not only on the sample surface, but also in the sample interior up to the depth of about 100 nm. In addition, plasma modification of the PE surface, followed with grafting Au-nanoparticles, significantly increased the attractiveness of the PE surface for the adhesion and growth of VSMC, and particularly for mouse embryonic 3T3 fibroblasts.

  2. Gold nanoparticles immobilized on metal-organic frameworks with enhanced catalytic performance for DNA detection.

    PubMed

    Liu, Ya Li; Fu, Wen Liang; Li, Chun Mei; Huang, Cheng Zhi; Li, Yuan Fang

    2015-02-25

    In this work, gold nanoparticles (AuNPs) assembled on the surface of iron based metal-organic frameworks (MOFs), Fe-MIL-88, are facilely prepared through electrostatic interactions using polyethyleneimine (PEI) molecules as linker. The resulting hybrid materials possess synergetic peroxidase-like activity. Because iron based metal-organic frameworks, Fe-MIL-88, exhibits highly peroxidase-like activity, and AuNPs has the distinct adsorption property to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The peroxidase-like activity of Au@Fe-MIL-88 exhibit excellent switchable in response to specific DNA, ssDNA is easily adsorbed on the surface of the Au@Fe-MIL-88 hybrids, resulting in the reduce of the peroxidase-like activity of the hybrids. While it is recovered by the addition of target DNA, and the recovery degree is proportional to the target DNA concentration over the range of 30-150 nM with a detection limit of 11.4 nM. Based on these unique properties, we develop a label-free colorimetric method for DNA hybridization detection. In control experiment, base-mismatched DNA cannot induce recovery of the peroxidase-like activity. This detection method is simple, cheap, rapid and colorimetric.

  3. Gold nanoparticles immobilized on metal-organic frameworks with enhanced catalytic performance for DNA detection.

    PubMed

    Liu, Ya Li; Fu, Wen Liang; Li, Chun Mei; Huang, Cheng Zhi; Li, Yuan Fang

    2015-02-25

    In this work, gold nanoparticles (AuNPs) assembled on the surface of iron based metal-organic frameworks (MOFs), Fe-MIL-88, are facilely prepared through electrostatic interactions using polyethyleneimine (PEI) molecules as linker. The resulting hybrid materials possess synergetic peroxidase-like activity. Because iron based metal-organic frameworks, Fe-MIL-88, exhibits highly peroxidase-like activity, and AuNPs has the distinct adsorption property to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The peroxidase-like activity of Au@Fe-MIL-88 exhibit excellent switchable in response to specific DNA, ssDNA is easily adsorbed on the surface of the Au@Fe-MIL-88 hybrids, resulting in the reduce of the peroxidase-like activity of the hybrids. While it is recovered by the addition of target DNA, and the recovery degree is proportional to the target DNA concentration over the range of 30-150 nM with a detection limit of 11.4 nM. Based on these unique properties, we develop a label-free colorimetric method for DNA hybridization detection. In control experiment, base-mismatched DNA cannot induce recovery of the peroxidase-like activity. This detection method is simple, cheap, rapid and colorimetric. PMID:25702274

  4. Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles.

    PubMed

    Ma, Hui; Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan; Shi, Xiangyang

    2012-04-15

    Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants. PMID:22138171

  5. Enhanced dechlorination of trichloroethylene using electrospun polymer nanofibrous mats immobilized with iron/palladium bimetallic nanoparticles.

    PubMed

    Ma, Hui; Huang, Yunpeng; Shen, Mingwu; Guo, Rui; Cao, Xueyan; Shi, Xiangyang

    2012-04-15

    Fe/Pd bimetallic nanoparticles (NPs) have held great promise for treating trichloroethylene (TCE)-contaminated groundwater, without the accumulation of chlorinated intermediates. However, the conventionally used colloidal Fe/Pd NPs usually aggregate rapidly, resulting in a reduced reactivity. To reduce the particle aggregation, we employed electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) polymer nanofibers as a nanoreactor to immobilize Fe/Pd bimetallic NPs. In the study, the water-stable PAA/PVA nanofibrous mats were complexed with Fe (III) ions via the binding with the free carboxyl groups of PAA for subsequent formation and immobilization of zero-valent iron (ZVI) NPs. Fe/Pd bimetallic NPs were then formed by the partial reduction of Pd(II) ions with ZVI NPs. The formed electrospun nanofibrous mats containing Fe/Pd bimetallic NPs with a diameter of 2.8 nm were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis, and inductively coupled plasma-atomic emission spectroscopy. The Fe/Pd NP-containing electrospun PAA/PVA nanofibrous mats exhibited higher reactivity than that of the ZVI NP-containing mats or colloidal Fe/Pd NPs in the dechlorination of trichloroethylene (TCE), which was used as a model contaminant. With the high surface area to volume ratio, high porosity, and great reusability of the fibrous mats immobilized with the bimetallic NPs, the composite nanofibrous mats should be amenable for applications in remediation of various environmental contaminants.

  6. Novel electrochemical dual-aptamer-based sandwich biosensor using molybdenum disulfide/carbon aerogel composites and Au nanoparticles for signal amplification.

    PubMed

    Fang, Lin-Xia; Huang, Ke-Jing; Liu, Yang

    2015-09-15

    A new electrochemical aptamer biosensor for the platelet-derived growth factor BB (PDGF-BB) detection has been developed based on the signal amplification of MoS2/carbon aerogel composites (MoS2/CA) and sandwich assay. A facile hydrothermal route assisted by L-cysteine was applied to synthesize CA incorporated flower-like MoS2 with the large surface active sites and good conductivity. The electrochemical aptasensor was constructed by sandwiching the PDGF-BB between a glassy carbon electrode modified with thiol-terminated PDGF-BB aptamer-1 (Apt1)/gold nanoparticles (AuNPs)/MoS2/CA and the AuNPs with thiol-terminated PDGF-BB aptamer-2 (Apt2) and 6-ferrocenyl hexanethiol (Fc). Fc-AuNPs-Apt2 acted as tracer and AuNPs/MoS2/CA were utilized as the biosensor platform to immobilize a large amount of capture aptamers, owing to their layered structure and high surface-to-volume ratio. Based on the sandwich format, a dual signal amplification strategy had been successfully developed with a wide linear response in the range of 0.001-10nM and a limit of detection of 0.3 pM. The developed assay demonstrated good selectivity and high sensitivity, indicating potential applications in bioanalysis and biomedicine.

  7. Molecular interactions of different size AuNP-COOH nanoparticles with human fibrinogen.

    PubMed

    Deng, Jun; Sun, Mingcong; Zhu, Jiyu; Gao, Changyou

    2013-09-01

    Protein adsorption influences greatly the performance of materials used in biotechnology and biomedicine. The binding of fibrinogen (Fg) to nanoparticles (NPs) can result in protein unfolding and exposure of cryptic epitopes that subsequently interact with cell surface receptors. The response and its degree are dependent on the size, charge, and concentration of the NPs. In this study the binding kinetics of human Fg to negatively charged 11-mercaptoundecanoic acid-functionalized gold nanoparticles (AuNPs-COOH) ranging from 5.6 to 64.5 nm were examined. The larger NPs bound Fg with a larger number of proteins per square unit and a higher dissociation rate (Kd'), but with decreased affinity. By contrast, the 5.6 nm AuNPs-COOH behaved in a cooperative manner for Fg adsorption. In the presence of excess Fg, only the 64.5 nm AuNPs-COOH showed severe aggregation, whose degree was alleviated in a dilute Fg solution. The Fg is adsorbed through a side-on configuration and both side-on and end-on configurations on the smaller (5.6 and 14.2 nm) and 31.5 nm AuNPs-COOH, respectively. It also retains the native conformation. By contrast, on the 64.5 nm AuNPs-COOH the Fg adopts the end-on configuration and loses most of the secondary structure.

  8. Effect of dielectric spacer layers and substrate on SERS with Au nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Briber, Robert M.; Rabin, Oded

    2015-03-01

    The optical response of a plasmonic nanostructure is often highly dependent on the nature of the underlying substrate. To study the effect of the substrate on surface enhanced Raman scattering (SERS), a series of SERS substrates were fabricated consisting of a hexagonal array of Au nanoparticles self assembled on block copolymer films, a silicon oxide (dielectric) layer and a silicon substrate or an Au substrate. The inter-particle distance and the dielectric layer thickness were controlled. The SERS Enhancement Factors (EF) were calculated by comparing the Raman spectra of 4-aminothiophenol adsorbed on the surface of the Au nanoparticles and in a standard solution. The SERS EF were found to be strongly affected by the inter-particle distance and silicon oxide thickness. Changing the inter-particle spacing induced a 102 variation in the EF, changing the oxide thickness increased EF values by an factor of 10, and changing substrate from Si to Au increased EF by a factor of 10. Maximal enhancement factors were found with oxide layer thicknesses between 30 nm and 50 nm beneath the 30 nm polymer film with Au substrates. This geometry both improved the resonance condition with the probe laser and reduced the absorption by the substrate. This work illustrates that optimization of plasmonic-based sensors should consider both the metallic and the surrounding structures. The Institute for Research in Electronics and Applied Physics (IREAP), University of Maryland, College Park, MD 20742.

  9. Preparation and photocatalytic activity of eccentric Au-titania core-shell nanoparticles by block copolymer templates.

    PubMed

    Li, Xue; Fu, Xiaoning; Yang, Hui

    2011-02-21

    A novel route for a preparation of eccentric Au-titania core-shell nanoparticles using gold nanoparticles (AuNPs) with block copolymer shells as a template is reported. AuNPs with poly(2-vinyl pyridine)-block-poly(ethylene oxide) (PVP-b-PEO) block copolymer shells are first prepared by UV irradiation of the solution of PVP-b-PEO/HAuCl(4) complexes. Then the sol-gel reaction of titanium tetra-isopropoxide (TTIP) selectively on the surfaces of AuNPs leads to Au-titania core-shell composite nanoparticles. The eccentric Au-titania core-shell nanoparticles are obtained from the Au-titania core-shell composite nanoparticles by removal of organic interlayer by UV treatment. Photocatalytic activities of the resulting eccentric core-shell nanoparticles are investigated in terms of the degradation of methylene blue (MB). The results show that the eccentric core-shell structures endow the catalyst with greatly enhanced photocatalytic activity. PMID:21157597

  10. Polyurethane nanoparticles as support for peroxidase immobilization and electrochemical detection of dopamine

    NASA Astrophysics Data System (ADS)

    Creczynski-Pasa, Tánia; Fritzen-Garcia, Maurícia; Oliveira, Ines; Zanetti-Ramos, Betina; Fatibello-Filho, Orlando; Soldi, Valdir; Pasa, André.

    2010-03-01

    Two different carbon paste electrodes were constructed by the immobilization of peroxidase extracted from the pine kernel homogenate (I) or purified HRP (II) on pegylated polyurethane nanoparticles for dopamine detection. The polyurethane nanoparticles were characterized by AFM and DLS (260nm) and, showed good potential as a support material for enzyme immobilization. The best analytical response was obtained for the electrodes containing 2.5 U of peroxidase mg-1 of carbon paste (I) and 0.25 U of HRP mg-1 of carbon paste (II). The analytical curves were linear for dopamine from 9.9x10-5 to 1.6x10-3 mol L-1 with a limit detection of 9.0x10-6 mol L-1 for electrode I and 1.7x10-5 to 1.9x10-3 mol L-1 with a limit detection of 2.0x10-6 mol L-1 for electrode II. The recoveries of dopamine from pharmaceutical are in agreement with the official method.

  11. Tailored functionalization of iron oxide nanoparticles for MRI, drug delivery, magnetic separation and immobilization of biosubstances.

    PubMed

    Hola, Katerina; Markova, Zdenka; Zoppellaro, Giorgio; Tucek, Jiri; Zboril, Radek

    2015-11-01

    In this critical review, we outline various covalent and non-covalent approaches for the functionalization of iron oxide nanoparticles (IONPs). Tuning the surface chemistry and design of magnetic nanoparticles are described in relation to their applicability in advanced medical technologies and biotechnologies including magnetic resonance imaging (MRI) contrast agents, targeted drug delivery, magnetic separations and immobilizations of proteins, enzymes, antibodies, targeting agents and other biosubstances. We review synthetic strategies for the controlled preparation of IONPs modified with frequently used functional groups including amine, carboxyl and hydroxyl groups as well as the preparation of IONPs functionalized with other species, e.g., epoxy, thiol, alkane, azide, and alkyne groups. Three main coupling strategies for linking IONPs with active agents are presented: (i) chemical modification of amine groups on the surface of IONPs, (ii) chemical modification of bioactive substances (e.g. with fluorescent dyes), and (iii) the activation of carboxyl groups mainly for enzyme immobilization. Applications for drug delivery using click chemistry linking or biodegradable bonds are compared to non-covalent methods based on polymer modified condensed magnetic nanoclusters. Among many challenges, we highlight the specific surface engineering allowing both therapeutic and diagnostic applications (theranostics) of IONPs and magnetic/metallic hybrid nanostructures possessing a huge potential in biocatalysis, green chemistry, magnetic bioseparations and bioimaging. PMID:25689073

  12. Immobilized gold nanoparticle sensor for label-free optical detection of biomolecular interactions

    NASA Astrophysics Data System (ADS)

    Nath, Nidhi; Chilkoti, Ashutosh

    2002-06-01

    We present a new label free optical technique to study biomolecular interactions in real time on a surface. This method monitors changes in the absorbance spectrum of a monolayer of gold on glass as a function of biomolecular binding. Gold nanoparticles with a diameter of 13 nm were chemisorbed onto an amine-terminated glass surface. The absorbance spectrum of the monolayer exhibited both a red shift as well as an increase in the absorbance at peak wavelength as a function of bulk solution refractive index. The increase in absorbance at peak wavelength as a function of bulk solution refractive index. The increase in absorbance at 550 nm was employed to study the kinetics of fibrinogen adsorption on the immobilized monolayer. The result obtained with the absorbance sensor were compared with those obtained using conventional SPR. This sensor is attractive because of its simplicity: gold nanoparticles are easily prepared with high reproducibility, they can be easily immobilized on glass, and their absorbance spectrum can be easily measured using widely available UV-vis spectrophotometers. Furthermore, this technique should be easily amenable to the design of chips in an array format for application in hgih-throughput immunoassays and proteomics.

  13. Tailored functionalization of iron oxide nanoparticles for MRI, drug delivery, magnetic separation and immobilization of biosubstances.

    PubMed

    Hola, Katerina; Markova, Zdenka; Zoppellaro, Giorgio; Tucek, Jiri; Zboril, Radek

    2015-11-01

    In this critical review, we outline various covalent and non-covalent approaches for the functionalization of iron oxide nanoparticles (IONPs). Tuning the surface chemistry and design of magnetic nanoparticles are described in relation to their applicability in advanced medical technologies and biotechnologies including magnetic resonance imaging (MRI) contrast agents, targeted drug delivery, magnetic separations and immobilizations of proteins, enzymes, antibodies, targeting agents and other biosubstances. We review synthetic strategies for the controlled preparation of IONPs modified with frequently used functional groups including amine, carboxyl and hydroxyl groups as well as the preparation of IONPs functionalized with other species, e.g., epoxy, thiol, alkane, azide, and alkyne groups. Three main coupling strategies for linking IONPs with active agents are presented: (i) chemical modification of amine groups on the surface of IONPs, (ii) chemical modification of bioactive substances (e.g. with fluorescent dyes), and (iii) the activation of carboxyl groups mainly for enzyme immobilization. Applications for drug delivery using click chemistry linking or biodegradable bonds are compared to non-covalent methods based on polymer modified condensed magnetic nanoclusters. Among many challenges, we highlight the specific surface engineering allowing both therapeutic and diagnostic applications (theranostics) of IONPs and magnetic/metallic hybrid nanostructures possessing a huge potential in biocatalysis, green chemistry, magnetic bioseparations and bioimaging.

  14. Green synthesis and applications of Au-Ag bimetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Meena Kumari, M.; Jacob, John; Philip, Daizy

    2015-02-01

    This paper reports for the first time the synthesis of bimetallic nanoparticles at room temperature using the fruit juice of pomegranate. Simultaneous reduction of gold and silver ions in different molar ratios leads to the formation of alloy as well as core-shell nanostructures. The nanoparticles have been characterized using UV-vis spectroscopy, transmission electron microscopy, Fourier Transform Infrared Spectroscopy and X-ray diffraction. The synthesized alloy particles are used as catalysts in the reduction of 2-, 3-, 4-nitrophenols to the corresponding amines and in the degradation of methyl orange. The reduction kinetics for all the reactions follows pseudo-first order. The rate constants follow the order k4-nitrophenol < k2-nitrophenol < k3-nitrophenol. Thermal conductivity is measured as a function of volume fraction and it is observed that the incorporation of the alloy nanoparticles enhances the thermal conductivity of the base fluid (water) showing nanofluid application. The nitric oxide and hydroxyl radical scavenging activity shown by the nanoparticles promise the potential application in biomedical field.

  15. Green synthesis and applications of Au-Ag bimetallic nanoparticles.

    PubMed

    Meena Kumari, M; Jacob, John; Philip, Daizy

    2015-02-25

    This paper reports for the first time the synthesis of bimetallic nanoparticles at room temperature using the fruit juice of pomegranate. Simultaneous reduction of gold and silver ions in different molar ratios leads to the formation of alloy as well as core-shell nanostructures. The nanoparticles have been characterized using UV-vis spectroscopy, transmission electron microscopy, Fourier Transform Infrared Spectroscopy and X-ray diffraction. The synthesized alloy particles are used as catalysts in the reduction of 2-, 3-, 4-nitrophenols to the corresponding amines and in the degradation of methyl orange. The reduction kinetics for all the reactions follows pseudo-first order. The rate constants follow the order k4-nitrophenolnanoparticles enhances the thermal conductivity of the base fluid (water) showing nanofluid application. The nitric oxide and hydroxyl radical scavenging activity shown by the nanoparticles promise the potential application in biomedical field. PMID:25218228

  16. Oxygen reduction reaction activity and structural stability of Pt-Au nanoparticles prepared by arc-plasma deposition.

    PubMed

    Takahashi, Shuntaro; Chiba, Hiroshi; Kato, Takashi; Endo, Shota; Hayashi, Takehiro; Todoroki, Naoto; Wadayama, Toshimasa

    2015-07-28

    The oxygen reduction reaction (ORR) activity and durability of various Au(x)/Pt100 nanoparticles (where x is the atomic ratio of Au against Pt) are evaluated herein. The samples were fabricated on a highly-oriented pyrolytic graphite substrate at 773 K through sequential arc-plasma depositions of Pt and Au. The electrochemical hydrogen adsorption charges (electrochemical surface area), particularly the characteristic currents caused by the corner and edge sites of the Pt nanoparticles, decrease with increasing Au atomic ratio (x). In contrast, the specific ORR activities of the Au(x)/Pt100 samples were dependent on the atomic ratios of Pt and Au: the Au28/Pt100 sample showed the highest specific activity among all the investigated samples (x = 0-42). As for ORR durability evaluated by applying potential cycles between 0.6 and 1.0 V in oxygen-saturated 0.1 M HClO4, Au28/Pt100 was the most durable sample against the electrochemical potential cycles. The results clearly showed that the Au atoms located at coordinatively-unsaturated sites, e.g. at the corners or edges of the Pt nanoparticles, can improve the ORR durability by suppressing unsaturated-site-induced degradation of the Pt nanoparticles. PMID:26118789

  17. Exchange bias effect in Au-Fe3O4 dumbbell nanoparticles induced by the charge transfer from gold

    DOE PAGES

    Feygenson, Mikhail; Bauer, John C; Gai, Zheng; Marques, Carlos; Aronson, Meigan C.; Teng, Xiaowei; Su, Dong; Stanic, Vesna; Urban, Volker S; Kevin, Beyer; et al

    2015-08-10

    We have studied the origin of the exchange bias effect in the Au-Fe3O4 dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe3O4 nanoparticles (9.8 nm). The magnetization, small-angle neutron scattering, synchrotron x-ray diffraction and scanning transmission electron microscope measurements determined the antiferromagnetic FeO wüstite phase within Fe3O4 nanoparticles, originating at the interface with the Au nanoparticles. The interface between antiferromagnetic FeO and ferrimagnetic Fe3O4 is giving rise to the exchange bias effect. The strength of the exchange bias fields depends on the interfacial area and lattice mismatchmore » between both phases. We propose that the charge transfer from the Au nanoparticles is responsible for a partial reduction of the Fe3O4 into FeO phase at the interface with Au nanoparticles. The Au-O bonds are formed across the interface to accommodate an excess of oxygen released during the reduction of magnetite.« less

  18. Exchange bias effect in Au-Fe3O4 dumbbell nanoparticles induced by the charge transfer from gold

    SciTech Connect

    Feygenson, Mikhail; Bauer, John C.; Gai, Zheng; Marques, Carlos; Aronson, Meigan C.; Teng, Xiaowei; Su, Dong; Stanic, Vesna; Urban, Volker S.; Beyer, Kevin A.; Dai, Sheng

    2015-08-10

    We have studied the origin of the exchange bias effect in the Au-Fe3O4 dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe3O4 nanoparticles (9.8 nm). The magnetization, small-angle neutron-scattering, synchrotron x-ray diffraction, and scanning transmission electron microscope measurements determined the antiferromagnetic FeO wustite phase within Fe3O4 nanoparticles, originating at the interface with the Au nanoparticles. The interface between antiferromagnetic FeO and ferrimagnetic Fe3O4 is giving rise to the exchange bias effect. The strength of the exchange bias fields depends on the interfacial area and lattice mismatch between both phases. We propose that the charge transfer from the Au nanoparticles is responsible for a partial reduction of the Fe3O4 into the FeO phase at the interface with Au nanoparticles. The Au-O bonds are formed, presumably across the interface to accommodate an excess of oxygen released during the reduction of magnetite

  19. Efficient purification of lysozyme from egg white by 2-mercapto-5-benzimidazolesulfonic acid modified Fe3O4/Au nanoparticles.

    PubMed

    Zhu, Xinjun; Zhang, Lianying; Fu, Aiyun; Yuan, Hao

    2016-02-01

    2-Mercapto-5-benzimidazolesulfonic acid (MBISA) modified Fe3O4/Au nanoparticles were synthesized in aqueous solution and characterized by photo correlation spectroscopy (PCS) and vibrating sample magnetometer (VSM). The so-obtained Fe3O4/Au-MBISA nanoparticles were capable of specific adsorbing lysozyme. The maximum amount of lysozyme adsorbed on 1.0mg Fe3O4/Au-MBISA nanoparticles was 346μg. The lysozyme desorption behavior was studied and the lysozyme recovery from Fe3O4/Au-MBISA nanoparticles approached 100% under optimal conditions, and the reusability studies showed that the nanoparticles could maintain about 91% of the initial lysozyme adsorption capacity after 7 repeated adsorption-elution cycles. The Fe3O4/Au-MBISA nanoparticles were used in the purification of lysozyme from chicken egg white, which was verified by a single SDS-PAGE band. Therefore, the obtained Fe3O4/Au-MBISA nanoparticles exhibited excellent performance in the direct purification of lysozyme from egg white.

  20. 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.

  1. Intrinsic heating in optically trapped Au nanoparticles measured by dark-field spectroscopy

    PubMed Central

    Andres-Arroyo, Ana; Wang, Fan; Toe, Wen Jun; Reece, Peter

    2015-01-01

    Assessing the degree of heating present when a metal nanoparticle is trapped in an optical tweezers is critical for its appropriate use in biological applications as a nanoscale force sensor. Heating is necessarily present for trapped plasmonic particles because of the non-negligible extinction which contributes to an enhanced polarisability. We present a robust method for characterising the degree of heating of trapped metallic nanoparticles, using the intrinsic temperature dependence of the localised surface plasmon resonance (LSPR) to infer the temperature of the surrounding fluid at different incident laser powers. These particle specific measurements can be used to infer the rate of heating and local temperature of trapped nanoparticles. Our measurements suggest a considerable amount of a variability in the degree of heating, on the range of 414–673 K/W, for different 100 nm diameter Au nanoparticles, and we associated this with variations in the axial trapping position. PMID:26417530

  2. Apoferritin Nanoparticle: A Novel and Biocompatible Carrier for Enzyme Immobilization with Enhanced Activity and Stability

    SciTech Connect

    Zhang, Youyu; Tang, Zhiwen; Wang, Jun; Wu, Hong J.; Lin, Chiann Tso; Lin, Yuehe

    2011-11-01

    Apoferritin is a nanostructured material with a uniform size and spherical structure, and it has excellent bio-compatibility. In this work, we report the use of apoferritin as a novel and biocompatible carrier for stabilizing enzymes and their activities. We used glucose oxidase (GOx) as a model enzyme. GOx was immobilized on the surface of the apoferritin through a green synthetic approach taking advantage of bioaffinity binding between streptavidin and biotin. As a result, a glucose oxidase-biotin/streptavidin/biotin-apoferritin conjugate (Apo-GOx) was prepared using streptavidin as a bridge. The synthesized Apo-GOx was characterized with transmission electron microscopy, ultraviolet, and fluorescence spectroscopy. The activity and stability of GOx on the surface of the apoferritin were studied in different environments, such as temperature, chemicals, and pH, in comparison with the biotinylated GOx (B-GOx). The results showed that the activity of GOx on the apoferritin surface was significantly enhanced. The thermal and chemical stability of the GOx on the apoferritin was also greatly improved compared to free B-GOx in a solution. It was found that the activity of the GOx on the apoferritin only lost 30% in comparison to a 70% loss of free B-GOx after a 2 h incubation at 50oC. There was almost no decrease in activity for the GOx on the apoferritin as compared to an 80% activity decrease for free B-GOx after 30 min incubation in a 5 M urea solution. Glucose detection was used as a model application for the enzyme immobilization method developed in this work. The GOx immobilized apoferritin nanoparticles exhibited high sensitivity for glucose detection with a detection limit of 3 nM glucose. This work offers a novel approach for immobilizing enzymes with enhanced stability and activity, and this method may find a number of applications, such as in enzyme catalysis, DNA assays and immunoassays.

  3. Immobilization of glucose oxidase using CoFe2O4/SiO2 nanoparticles as carrier

    NASA Astrophysics Data System (ADS)

    Wang, Hai; Huang, Jun; Wang, Chao; Li, Dapeng; Ding, Liyun; Han, Yun

    2011-04-01

    Aminated-CoFe2O4/SiO2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. Glucose oxidase (GOD) was immobilized on CoFe2O4/SiO2 NPs via cross-linking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, cross-linking time of 3 h, solution pH of 7.0 and 0.4 mg GOD (in 3.0 mg carrier). The immobilized GOD showed maximal catalytic activity at pH 6.5 and 40 °C. After immobilization, the GOD exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 80% of its initial activity after the incubation at 50 °C for 25 min, whereas free enzyme had only 20% of initial activity after the same incubation. After kept at 4 °C for 28 days, the immobilized and free enzyme retained 87% and 40% of initial activity, respectively. The immobilized GOD maintained approximately 57% of initial activity after reused 7 times. The KM (Michaelis-Menten constant) values for immobilized GOD and free GOD were 14.6 mM and 27.1 mM, respectively.

  4. Chitosan coated on the layers' glucose oxidase immobilized on cysteamine/Au electrode for use as glucose biosensor.

    PubMed

    Zhang, Yawen; Li, Yunqiu; Wu, Wenjian; Jiang, Yuren; Hu, Biru

    2014-10-15

    A glucose biosensor was developed via direct immobilization of glucose oxidase (GOD) by self-assembled cysteamine monolayer on Au electrode surface followed by coating chitosan on the surface of electrode. In this work, chitosan film was coated on the surface of GOD as a protection film to ensure the stability and biocompatibility of the constructed glucose biosensor. The different application ranges of sensors were fabricated by immobilizing varied layers of GOD. The modified surface film was characterized by a scanning electron microscope (SEM) and the fabrication process of the biosensor was confirmed through electrochemical impedance spectroscopy (EIS) of ferrocyanide. The performance of cyclic voltammetry (CV) in the absence and presence of 25 mM glucose and ferrocenemethanol showed a diffusion-controlled electrode process and reflected the different maximum currents between the different GOD layers. With the developed glucose biosensor, the detection limits of the two linear responses are 49.96 μM and 316.8 μM with the sensitivities of 8.91 μA mM(-1)cm(-2) and 2.93 μA mM(-1)cm(-2), respectively. In addition, good stability (up to 30 days) of the developed biosensor was observed. The advantages of this new method for sensors construction was convenient and different width ranges of detection can be obtained by modified varied layers of GOD. The sensor with two layers of enzyme displayed two current linear responses of glucose. The present work provided a simplicity and novelty method for producing biosensors, which may help design enzyme reactors and biosensors in the future. PMID:24820862

  5. Enabling low amounts of YAG:Ce(3+) to convert blue into white light with plasmonic Au nanoparticles.

    PubMed

    Hussain, Talib; Zhong, Liubiao; Danesh, Mohammad; Ye, Huiqi; Liang, Ziqiang; Xiao, Dong; Qiu, Cheng-Wei; Lou, Chaogang; Chi, Lifeng; Jiang, Lin

    2015-06-21

    We report a new strategy to directly attach Au nanoparticles onto YAG:Ce(3+) phosphor via a chemical preparation method, which yields efficient and quality conversion of blue to yellow light in the presence of a low amount of phosphor. Photoluminescent intensity and quantum yield of YAG:Ce(3+) phosphor are significantly enhanced after Au nanoparticle modification, which can be attributed to the strongly enhanced local surface electromagnetic field of Au nanoparticles on the phosphor particle surface. The CIE color coordinates shifted from the blue light (0.23, 0.23) to the white light region (0.30, 0.33) with a CCT value of 6601 K and a good white light CRI value of 78, which indicates that Au nanoparticles greatly improve the conversion efficiency of low amounts of YAG:Ce(3+) in WLEDs.

  6. Controlled synthesis and synergistic effects of graphene-supported PdAu bimetallic nanoparticles with tunable catalytic properties

    NASA Astrophysics Data System (ADS)

    Liu, Chang-Hai; Liu, Rui-Hua; Sun, Qi-Jun; Chang, Jian-Bing; Gao, Xu; Liu, Yang; Lee, Shuit-Tong; Kang, Zhen-Hui; Wang, Sui-Dong

    2015-03-01

    Graphene-supported bimetallic nanoparticles are promising nanocatalysts, which can show strong and tunable catalytic activity and selectivity. Herein room-temperature-ionic-liquid-assisted metal sputtering is utilized to synthesize PdAu bimetallic nanoparticles on graphene with bare surface, small size, high surface density and controlled Pd-to-Au ratio. This controllable synthetic approach is green-chemistry compatible and totally free of additives and byproducts. The supported PdAu nanoparticles show excellent catalytic capabilities for both oxidation and reduction reactions, strongly dependent on the Pd-to-Au ratio. A strong correlation among catalytic performance, bimetallic composition and charge redistribution in the PdAu nanoparticles has been demonstrated. The results suggest that sufficient Au d-holes appear to be significant to the catalysis of oxidation reaction, and a metallic Pd surface is critical to the catalysis of reduction reaction. By the present method, the bimetallic combination can be tailored for distinct types of catalytic reactions.Graphene-supported bimetallic nanoparticles are promising nanocatalysts, which can show strong and tunable catalytic activity and selectivity. Herein room-temperature-ionic-liquid-assisted metal sputtering is utilized to synthesize PdAu bimetallic nanoparticles on graphene with bare surface, small size, high surface density and controlled Pd-to-Au ratio. This controllable synthetic approach is green-chemistry compatible and totally free of additives and byproducts. The supported PdAu nanoparticles show excellent catalytic capabilities for both oxidation and reduction reactions, strongly dependent on the Pd-to-Au ratio. A strong correlation among catalytic performance, bimetallic composition and charge redistribution in the PdAu nanoparticles has been demonstrated. The results suggest that sufficient Au d-holes appear to be significant to the catalysis of oxidation reaction, and a metallic Pd surface is critical

  7. Au nanoparticles/poly(caffeic acid) composite modified glassy carbon electrode for voltammetric determination of acetaminophen.

    PubMed

    Li, Tianbao; Xu, Juan; Zhao, Lei; Shen, Shaofei; Yuan, Maosen; Liu, Wenming; Tu, Qin; Yu, Ruijin; Wang, Jinyi

    2016-10-01

    An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples. PMID:27474318

  8. Au nanoparticles/poly(caffeic acid) composite modified glassy carbon electrode for voltammetric determination of acetaminophen.

    PubMed

    Li, Tianbao; Xu, Juan; Zhao, Lei; Shen, Shaofei; Yuan, Maosen; Liu, Wenming; Tu, Qin; Yu, Ruijin; Wang, Jinyi

    2016-10-01

    An Au nanoparticles/poly(caffeic acid) (AuNPs/PCA) composite modified glassy carbon (GC) electrode was prepared by successively potentiostatic technique in pH 7.4 phosphate buffer solution containing 0.02mM caffeic acid and 1.0mM HAuCl4. Electrochemical characterization of the AuNPs/PCA-GC electrode was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical behavior of acetaminophen (AP) at the AuNPs/PCA-GC electrode was also studied by cyclic voltammetry. Compared with bare GC and poly(caffeic acid) modified GC electrode, the AuNPs/PCA-GC electrode was exhibited excellent electrocatalytic activity toward the oxidation of AP. The plot of catalytic current versus AP concentration showed two linear segments in the concentration ranges 0.2-20µM and 50-1000µM. The detection limit of 14 nM was obtained by using the first range of the calibration plot. The AuNPs/PCA-GC electrode has been successfully applied and validated by analyzing AP in blood, urine and pharmaceutical samples.

  9. Dual Transient Bleaching of Au/PbS Hybrid Core/Shell Nanoparticles.

    PubMed

    Kobayashi, Yoichi; Nonoguchi, Yoshiyuki; Wang, Li; Kawai, Tsuyoshi; Tamai, Naoto

    2012-05-01

    We examined the optical response of hybrid Au/PbS core/shell nanoparticles (NPs) using transient absorption spectroscopy. Finite-difference time-domain (FDTD) calculations and transient absorption measurements show that Au/PbS NPs have unique two extinction peaks: the peak at the longer wavelength (∼700 nm) is originated from the plasmon, and that at the shorter wavelength (550 nm) is from the local maximum of the refractive index of PbS. The transient absorption dynamics of Au/PbS NPs excited at 400 nm have clear oscillation behavior, which is assigned to the breathing mode of whole particle. We observed a weak excitation-wavelength dependence of the plasmon band. The time constant of electron-phonon coupling of Au/PbS NPs was obtained by changing the excitation intensity. We show that spectral properties of Au/PbS NPs are strongly altered by the hybrid formations, while their dynamics differ only minimally compared with those of Au NPs. PMID:26288045

  10. A composition and size controllable approach for Au-Ag alloy nanoparticles

    PubMed Central

    2012-01-01

    A capillary micro-reaction was established for the synthesis of Au-Ag alloy nanoparticles (NPs) with a flexible and controllable composition and grain size by tuning the synthesis temperature, the residence time, or the mole ratio of Au3+:Ag+. By extending the residence time from 5 to 900 s, enhancing the temperature from 120°C to 160°C, or decreasing the mole ratio of Au3+:Ag+ from 1:1 to 1:20, the composition of samples was changed continuously from Au-rich to Ag-rich. The particles became large with the increase of the residence time; however, synthesis temperatures showed less effect on the particle size change. The particle size of the Au-Ag alloy NPs with various composition could be kept by adjusting the mole ratio of Au3+:Ag+. TEM observation displayed that the as-obtained NPs were sphere-like with the smallest average size of 4.0 nm, which is half of those obtained by the traditional flask method. PMID:22513005

  11. Efficiency enhancement of polymer solar cells by localized surface plasmon of Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Gao, H. L.; Zhang, X. W.; Yin, Z. G.; Zhang, S. G.; Meng, J. H.; Liu, X.

    2013-10-01

    We demonstrate the improvement of power conversion efficiency (PCE) in bulk heterojunction polymer solar cells based on blended poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester by introducing 40 nm Au nanoparticles (NPs) with various concentrations. The Au NPs were deposited on indium-tin-oxide (ITO) substrates by spin-coating from colloidal solution prior to deposition of poly (3,4-ethylene dioxythiophene:poly (styrene sulfonate) (PEDOT:PSS) buffer layer. It has been found that both short-circuit current density and PCE increase after incorporating Au NPs between ITO and PEDOT:PSS layer, and a suitable area density of Au NPs is required to achieve a maximum enhancement of device efficiency. The PCE of solar cells has been increased from 3.50% to 3.81% with 0.9 wt. % Au NPs. The PCE enhancement is attributed to the localized surface plasmon excitation of Au NPs. The method employed herein is a kind of simple and convenient solution process, and it has great potential in future practical applications.

  12. Investigating the Energy Transfer from Dye Molecules to DNA Stabilized Au Nanoparticles.

    PubMed

    Patel, Arun Singh; Sahoo, Harekrushna; Mohanty, T

    2016-09-01

    Double-stranded DNA stabilized gold nanoparticles (Au NPs) are synthesized by chemical reduction method and characterized with different spectroscopic techniques such as UV-Visible absorption, Fourier transform infrared (FTIR), & circular-dichroism (CD) as well as transmission electron microscopy (TEM). These NPs show absorption maximum at 520 nm and size of most of the particles are of the order of 3.5 ± 1.0 nm. These Au NPs show crystalline nature as confirmed from electron diffraction pattern. The effect of formation of Au NPs on the macromolecule has been studied using infrared and circular dichroism spectroscopy. Formation of NPs causes conformational changes in the DNA molecules. These Au NPs are further used as resonant energy acceptor of fluorescence emission from dye molecules (Rhodamine 6G). The fluorescence intensity of Rhodamine 6G (R6G) is quenched in presence of Au NPs. The effect of DNA molecules on the fluorescence quenching and the rate of energy transfer from R6G molecules to Au NPs have been explored. PMID:27422695

  13. Spherical and polygonal shape of Au nanoparticles coated functionalized polymer microspheres

    NASA Astrophysics Data System (ADS)

    Xu, Ting; Li, Yingzhi; Zhang, Junxian; Qi, Yalong; Zhao, Xin; Zhang, Qinghua

    2015-08-01

    Uniform polystyrene (PS)/polypyrrole (PPy) composite microspheres with well-defined core/shell structures are synthesized by chemical oxidative polymerization. Gold nanoparticles (Au NPs) are successfully coated on the surface of PS/PPy microspheres by means of electrostatic interactions due to the functionalized PPy coatings supplying sufficient amino groups and the additive of mercapto acetic acid. Furthermore, the as-prepared PS/PPy/Au microspheres serving as seeds facilitate Au NPs further growth by in situ reduction in HAuCl4 solution to obtain PS/PPy/Au spheres with the core/shell/shell structure. Morphology observation demonstrates that the monodisperse PS/PPy/Au microspheres compose of uniform cores and the compact coatings containing distinct two layers. X-ray diffraction and X-ray photoelectron spectroscope confirm the existence of PPy and Au on the surface of the composite spheres. This facile approach to preparing metal-coated polymer spheres supplies the potential applications in biosensors, electronics and medical diagnosis.

  14. Raman scattering of 4-aminobenzenethiol sandwiched between Ag nanoparticle and macroscopically smooth Au substrate: effects of size of Ag nanoparticles and the excitation wavelength.

    PubMed

    Kim, Kwan; Choi, Jeong-Yong; Lee, Hyang Bong; Shin, Kuan Soo

    2011-09-28

    A nanogap formed by a metal nanoparticle and a flat metal substrate is one kind of "hot site" for surface-enhanced Raman scattering (SERS). Accordingly, although no Raman signal is observable when 4-aminobenzenethiol (4-ABT), for instance, is self-assembled on a flat Au substrate, a distinct spectrum is obtained when Ag or Au nanoparticles are adsorbed on the pendent amine groups of 4-ABT. This is definitely due to the electromagnetic coupling between the localized surface plasmon of Ag or Au nanoparticle with the surface plasmon polariton of the planar Au substrate, allowing an intense electric field to be induced in the gap even by visible light. To appreciate the Raman scattering enhancement and also to seek the optimal condition for SERS at the nanogap, we have thoroughly examined the size effect of Ag nanoparticles, along with the excitation wavelength dependence, by assembling 4-ABT between planar Au and a variable-size Ag nanoparticle (from 20- to 80-nm in diameter). Regarding the size dependence, a higher Raman signal was observed when larger Ag nanoparticles were attached onto 4-ABT, irrespective of the excitation wavelength. Regarding the excitation wavelength, the highest Raman signal was measured at 568 nm excitation, slightly larger than that at 632.8 nm excitation. The Raman signal measured at 514.5 and 488 nm excitation was an order of magnitude weaker than that at 568 nm excitation, in agreement with the finite-difference time domain simulation. It is noteworthy that placing an Au nanoparticle on 4-ABT, instead of an Ag nanoparticle, the enhancement at the 568 nm excitation was several tens of times weaker than that at the 632.8 nm excitation, suggesting the importance of the localized surface plasmon resonance of the Ag nanoparticles for an effective coupling with the surface plasmon polariton of the planar Au substrate to induce a very intense electric field at the nanogap.

  15. Surface-enhanced raman scattering detection of DNAs derived from virus genomes using au-coated paramagnetic nanoparticles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A magnetic capture-based, surface-enhanced Raman scattering (SERS) assay for DNA detection has been developed which utilizes Au-coated paramagnetic nanoparticles (Au@PMPs) as both a SERS substrate and effective bio-separation reagent for the selective removal of target DNAs from solution. Hybridizat...

  16. Probing Hot Electron Flow Generated on Pt Nanoparticles with Au/TiO2 Schottky Diodes during Catalytic CO Oxidation

    SciTech Connect

    Park, Jeong Y.; Lee, Hyunjoo; Renzas, J. Russell; Zhang, Yawen; Somorjai, G.A.

    2008-05-01

    Hot electron flow generated on colloid platinum nanoparticles during exothermic catalytic carbon monoxide oxidation was directly detected with Au/TiO{sub 2} diodes. Although Au/TiO{sub 2} diodes are not catalytically active, platinum nanoparticles on Au/TiO{sub 2} exhibit both chemicurrent and catalytic turnover rate. Hot electrons are generated on the surface of the metal nanoparticles and go over the Schottky energy barrier between Au and TiO{sub 2}. The continuous Au layer ensures that the metal nanoparticles are electrically connected to the device. The overall thickness of the metal assembly (nanoparticles and Au thin film) is comparable to the mean free path of hot electrons, resulting in ballistic transport through the metal. The chemicurrent and chemical reactivity of nanoparticles with citrate, hexadecylamine, hexadecylthiol, and TTAB (Tetradecyltrimethylammonium Bromide) capping agents were measured during catalytic CO oxidation at pressures of 100 Torr O{sub 2} and 40 Torr CO at 373-513 K. We found that chemicurrent yield varies with each capping agent, but always decreases with increasing temperature. We suggest that this inverse temperature dependence is associated with the influence of charging effects due to the organic capping layer during hot electron transport through the metal-oxide interface.

  17. An enhanced photocatalytic response of nanometric TiO2 wrapping of Au nanoparticles for eco-friendly water applications

    NASA Astrophysics Data System (ADS)

    Scuderi, Viviana; Impellizzeri, Giuliana; Romano, Lucia; Scuderi, Mario; Brundo, Maria V.; Bergum, Kristin; Zimbone, Massimo; Sanz, Ruy; Buccheri, Maria A.; Simone, Francesca; Nicotra, Giuseppe; Svensson, Bengt G.; Grimaldi, Maria G.; Privitera, Vittorio

    2014-09-01

    We propose a ground-breaking approach by an upside-down vision of the Au/TiO2 nano-system in order to obtain an enhanced photocatalytic response. The system was synthesized by wrapping Au nanoparticles (~8 nm mean diameter) with a thin layer of TiO2 (~4 nm thick). The novel idea of embedding Au nanoparticles with titanium dioxide takes advantage of the presence of metal nanoparticles, in terms of electron trapping, without losing any of the TiO2 exposed surface, so as to favor the photocatalytic performance of titanium dioxide. A complete structural characterization was made by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The remarkable photocatalytic performance together with the stability of the nano-system was demonstrated by degradation of the methylene blue dye in water. The non-toxicity of the nano-system was established by testing the effect of the material on the reproductive cycle of Mytilus galloprovincialis in an aquatic environment. The originally synthesized material was also compared to conventional TiO2 with Au nanoparticles on top. The latter system showed a dispersion of Au nanoparticles in the liquid environment, due to their instability in the aqueous solution that clearly represents an environmental contamination issue. Thus, the results show that nanometric TiO2 wrapping of Au nanoparticles has great potential in eco-friendly water/wastewater purification.

  18. In situ formation of well-dispersed palladium nanoparticles immobilized in imidazolium-based organic ionic polymers.

    PubMed

    Zhao, Huaixia; Wang, Yangxin; Wang, Ruihu

    2014-09-25

    A new strategy for in situ generation of well-dispersed palladium nanoparticles (NPs) immobilized in imidazolium-based organic ionic polymers was presented. Without extra addition of palladium species, the as-synthesized ionic polymers showed excellent catalytic activity and good reusability in the hydrogenation of nitroarenes.

  19. Long-timescale dynamics of thiol capped Au nanoparticle clusters at the air-water interface

    NASA Astrophysics Data System (ADS)

    Choudhuri, Madhumita; Datta, Alokmay

    2014-04-01

    A two-dimensional network of thiol-capped Au nanoparticle (AuNP) clusters is self-organized on a Stearic Acid (amphiphilic fatty acid) Langmuir monolayer on water surface. The AuNP clusters are found to form a pattern of connected and enclosed microspaces in the stearic acid template. The network features can be controlled by changing the surface pressure of the monolayer during compression. The two-dimensional dynamics of this network has been studied over a long timescale using Brewster Angle Microscopy (BAM). The dynamics is very slow, indicating the stability of the network system, and is essentially driven by the tendency to lower the number of nodes or joints in the network.

  20. Ultrathin organic bulk heterojunction solar cells: Plasmon enhanced performance using Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Shahin, Shiva; Gangopadhyay, Palash; Norwood, Robert A.

    2012-07-01

    The plasmonic effect of gold nanoparticles (AuNPs) enhances light absorption and, thus, the efficiency of organic bulk heterojunction solar cells with poly (3-hexylthiophene) (P3HT): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as active layer. We report optimization of this enhancement by varying the attachment density of the self-assembled AuNPs on silanized ITO using N1-(3-trimethoxysilylpropyl)diethylenetriamine. Using finite difference time domain simulations, the thicknesses of poly (3,4-ethylenedioxythiophene) (PEDOT): poly (styrenesulfonate) (PSS) and P3HT:PCBM layers were suitably varied to ensure broadband optical absorption enhancement and minimal exciton quenching within the active layer. Our experimental results demonstrate that for solar cell structures with 20% surface coverage, absorption is increased by 65% as predicted by simulations. Further, we show that AuNPs increase the efficiency by 30% and that silanization of ITO positively impacts device performance.

  1. Combined Au-plasmonic nanoparticles with mesoporous carbon material (CMK-3) for photocatalytic water splitting

    SciTech Connect

    Hung, Wei Hsuan E-mail: yinm@sari.ac.cn; Lai, Sz Nian; Su, Cheng Yi; Yin, Min E-mail: yinm@sari.ac.cn; Li, Dongdong; Xue, Xinzhong; Tseng, Chuan Ming

    2015-08-17

    The conventional TiO{sub 2} photoelectrode for water splitting was integrated with ordered mesoporous carbon material (CMK-3) and Au metal nanoparticles (NPs) to improve the photocatalytic efficiency under visible light irradiation. Compared to TiO{sub 2}, Au/TiO{sub 2}-CMK-3 photoelectrode demonstrated over two orders of magnitude enhancement of photocurrent under 532 nm laser irradiation due to the generation of hot electron and near field from Au NPs. Furthermore, the improvement of free carrier transport and additional long-wavelength absorption can be achieved by exploiting the superior conductivity and blackbody-like property of CMK-3. This proposed enhancement mechanism was proved by the measurements of photoluminescence emission spectrum and electrochemical impedance spectroscopy.

  2. Sensitive voltammetric determination of vanillin with an AuPd nanoparticles-graphene composite modified electrode.

    PubMed

    Shang, Lei; Zhao, Faqiong; Zeng, Baizhao

    2014-05-15

    In this work, graphene oxide was reduced to graphene with an endogenous reducing agent from dimethylformamide, and then AuPd alloy nanoparticles were electrodeposited on the graphene film. The obtained AuPd-graphene hybrid film was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and voltammetry. The electrochemical behavior of vanillin was studied using the AuPd-graphene hybrid based electrode. It presented high electrocatalytic activity and vanillin could produce a sensitive oxidation peak at it. Under the optimal conditions, the peak current was linear to the concentration of vanillin in the ranges of 0.1-7 and 10-40 μM. The sensitivities were 1.60 and 0.170 mA mM(-1) cm(-2), respectively; the detection limit was 20 nM. The electrode was successfully applied to the detection of vanillin in vanilla bean, vanilla tea and biscuit samples.

  3. Development of α-polyoxometalate-polypyrrole-Au nanoparticles modified sensor applied for detection of folic acid.

    PubMed

    Babakhanian, Arash; Kaki, Samineh; Ahmadi, Mahtab; Ehzari, Hosna; Pashabadi, Afshin

    2014-10-15

    In this work, electrochemically synthesized gold nanoparticles (AuNPs) and α-polyoxometalate (α-POM) (K7PMO2W9O39 · H2O) were simultaneously doped into electropolymerized polypyrrole (PPy) film using the cyclic voltammetry (CV) technique. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and CVs were used to characterize the composite films. The PPy-α-POM-AuNPs modified gold (Au) electrode was used to determine folic acid (FA) using square-wave voltammetry (SWV). The modified electrode exhibited excellent electrocatalytic ability to the reduction of FA at 0.3 V (vs. SCE) with the electron transfer rate constant (ks) of 1.15 × 10(-19)s(-1). The common coexisting substances showed no interferences on the response of modified electrode to FA. The modified electrode indicated reproducible behavior and a high level stability during the experiments, making it particularly suitable for the analytical purposes.

  4. Au(I)-thiolate nanostructures fabricated by chemical exfoliation and their transformation to gold nanoparticle assemblies.

    PubMed

    Nie, Hui; Li, Minjie; Hao, Yajiao; Wang, Xudong; Gao, Sheng; Yang, Bingjie; Gu, Mengdi; Sun, Linlin; Zhang, Sean Xiao-An

    2014-11-15

    Chemical exfoliation method was applied to transform bulky assemblies of Au(I)-3-mercaptopropionate (MPA) coordination polymer (CP) to nanosheets and nanostrings using sodium citrate as an exfoliator. The exfoliation process and the structural characteristics of the Au(I)-MPA nanosheets and nanostrings were fully investigated by transmission electron microscopy, atomic force microscopy, UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy and so on. As the structural rigidity and stability of the obtained Au(I)-MPA nanosheets, they are ideal precursors for fabrication of water soluble gold nanoparticle assemblies through progressive pyrolysis. This work provides a significant strategy toward the morphology regulation of CP nanostructures and will inspire further development of this research area. PMID:25170603

  5. Fabrication of Au@Ag core-shell nanoparticles using polyelectrolyte multilayers as nanoreactors.

    PubMed

    Zhang, Xin; Wang, Hui; Su, Zhaohui

    2012-11-01

    A new synthetic strategy has been developed for the fabrication of Au-Ag bimetallic core-shell nanoparticles (NPs) using polyelectrolyte multilayers (PEMs) as unique nanoreactors. Bimetallic NPs composed of Au core and Ag shell were successively incorporated into PEMs by repeating anion/cation exchange/reduction cycle multiple times in a stepwise manner. The strategy described here allows for the facile preparation of Au@Ag core-shell NPs with well-controlled core and shell dimensions and geometrically tunable optical properties by simply varying the number of ion-exchange/reduction cycles in the PEM matrix. The strategy can be extended to synthesize in situ other core-shell NPs in polymer matrix.

  6. Electrogenerated chemiluminescence immunosensor for Bacillus thuringiensis Cry1Ac based on Fe3O4@Au nanoparticles.

    PubMed

    Li, Jianping; Xu, Qian; Wei, Xiaoping; Hao, Zaibin

    2013-02-20

    A highly sensitive electrochemiluminescence (ECL) immunosensor for Cry1Ac was fabricated. The primary antibody anti-Cry1Ac was immobilized onto core-shell structural Fe(3)O(4)@Au nanoparticles. The antigen and glucose-oxidase-labeled secondary antibody were then successively combined to form sandwich-type immunocomplexes through a specific interaction. The magnetic particles loaded with sandwich immune complexes were attracted to a magnet-controlled glass carbon electrode (GCE) by an external magnet applied on top of the GCE. ECL was generated by the reaction between luminol and hydrogen peroxide derived from the enzymatic reaction in the presence of glucose. The sensors exhibited high sensitivity and a wide linear range for Bacillus thuringiensis Cry1Ac detection from 0 to 6 ng/mL, as well as a detection limit of 0.25 pg/mL (S/N = 3). The sensor is one of the most sensitive sensors for Cry1Ac, which can be easily renewed and conveniently used. PMID:23317307

  7. Preparation and characterization of Au nanoparticles capped with mercaptocarboranyl clusters.

    PubMed

    Cioran, Ana M; Teixidor, Francesc; Krpetić, Željka; Brust, Mathias; Viñas, Clara

    2014-04-01

    The preparation of 3-4 nm and 10 nm gold nanoparticles capped with neutral carborane-based mercaptocarboranes, via two different preparative routes, is reported. The resulting boron-enriched nanomaterials exhibit complete dispersibility in water, opening the way for the use of these monolayer protected clusters (MPCs) in medical applications, such as boron neutron capture therapy (BNCT). These newly prepared MPCs have been characterized by FTIR, (1)H and (11)B NMR spectroscopy, UV-visible, centrifugal particle sizing (CPS), and, in some cases, inductively coupled plasma atomic emission spectrometry (ICP-AES). Water dispersibility exhibited by these MPCs allowed the study of the cellular uptake by HeLa cells.

  8. Ion-irradiation induced chemical ordering of FePt and FePtAu nanoparticles

    NASA Astrophysics Data System (ADS)

    Seetala, Naidu V.; Harrell, J. W.; Lawson, Jeremy; Nikles, David E.; Williams, John R.; Isaacs-Smith, Tamara

    2005-12-01

    We have studied the effect of ion-beam irradiation on reducing the ordering temperature of FePt and FePtAu nanoparticles. FePt and FePt(Au14%) 4 nm particles dispersed on a Si-substrate were irradiated by 300 keV Al-ions with a dose of 1 × 1016 ions/cm2 at 43 °C using a water-cooled flange in order to minimize the vacancy migration and voids formation within the collision cascades. Partial chemical ordering has been observed in as-irradiated particles with coercivity of 60-130 Oe. Post-irradiation annealing at 220 °C enhanced chemical ordering in FePt nanoparticles with coercivity of 3500 Oe, magnetic anisotropy of 1.5 × 107 erg/cc, and thermal stability factor of 130. A much higher 375 °C post-irradiation annealing was required in FePtAu, presumably because Au atoms were trapped at Fe/Pt lattice sites at lower temperatures. As the annealing temperature increased, anomalous features in the magnetization reversal curves were observed that disappeared at higher annealing temperatures.

  9. Designing Pd-on-Au bimetallic nanoparticle catalysts for trichloroethene hydrodechlorination.

    PubMed

    Nutt, Michael O; Hughes, Joseph B; Michael, S Wong

    2005-03-01

    Alumina-supported palladium (Pd) catalysts have previously been shown to hydrodechlorinate trichloroethene (TCE) and other chlorinated compounds in water, at room temperature, and in the presence of hydrogen. The feasibility of this catalytic technology to remediate groundwater of halogenated compounds can be improved by re-designing the Pd material in order to increase catalytic activity. We synthesized and characterized Pd supported on gold nanoparticles (Au NPs) of different Pd loadings. In all cases, we found that these catalysts were considerably more active than Pd NPs, alumina-supported Pd, ard Pd-black (62.0, 12.2, and 0.42 L x g(Pd)(-1) x min(-1), respectively). There is a synergistic effect of the Pd-on-Au bimetallic structure, with the material with the highest TCE hydrodechlorination activity (943 L x g(Pd)(-1) x min(-1)) comprised of Au NPs partially covered by Pd metal. The Pd-on-Au bimetallic catalyst structure provides a new synthesis approach in improving the catalytic properties of monometallic Pd materials. The resulting nanoparticle-based materials should be highly suitable as hydrodehalogenation and reduction catalysts for the remediation of various organic and inorganic groundwater contaminants.

  10. Impact of surface roughness of Au core in Au/Pd core-shell nanoparticles toward formic acid oxidation - Experiment and simulation

    NASA Astrophysics Data System (ADS)

    Hsu, Chiajen; Huang, Chienwen; Hao, Yaowu; Liu, Fuqiang

    2013-12-01

    The Au/Pd core-shell nanoparticles (NPs) were synthesized via galvanic replacement of Cu by Pd on hollow Au cores by adding different concentrations of Na2SO3 solution. It was found that the higher concentration of Na2SO3 that was used, the rougher the Au nanospheres became. However, the rougher Au surface may cause more defects in the Pd layers and decrease the catalytic abilities. The Au/Pd NPs synthesized using 0 M Na2SO3 (denoted as 0 M-Au/Pd NPs) have the smoothest Pd surface and demonstrate higher formic acid oxidation (FAO) activity (0.714 mA cm-2, normalized to the surface area of Pd) than other Au/Pd NPs and commercial Pd black (0.47 mA cm-2). Additional electrochemical characterization of the 0 M-Au/Pd NPs also demonstrated lower CO-stripping onset and peak potentials, higher stability (8× improvement in stabilized oxidation current), and superior durability (by 1.6×) than the Pd black. In addition, a simple simulation of FAO was adopted to predict the anodic curve by including reaction intermediates of formate and hydroxyl. The 0 M-Au/Pd NPs were found to show higher formate and lower hydroxyl coverage than the Pd black.

  11. Core/shell Au/CuPt nanoparticles and their dual electrocatalysis for both reduction and oxidation reactions.

    PubMed

    Sun, Xiaolian; Li, Dongguo; Ding, Yong; Zhu, Wenlei; Guo, Shaojun; Wang, Zhong Lin; Sun, Shouheng

    2014-04-16

    We report a facile synthesis of monodisperse core/shell 5/1.5 nm Au/CuPt nanoparticles by coreduction of platinum acetylacetonate and copper acetylacetonate in the presence of 5 nm Au nanoparticles. The CuPt alloy effect and core/shell interactions make these Au/CuPt nanoparticles a promising catalyst for both oxygen reduction reaction and methanol oxidation reaction in 0.1 M HClO4 solution. Their specific (mass) reduction and oxidation activities reach 2.72 mA/cm(2) (1500 mA/mg Pt) at 0.9 V and 0.755 mA/cm(2) (441 mA/mg Pt) at 0.8 V (vs reversible hydrogen electrode), respectively. Our studies show that the existence of the Au nanoparticle core not only minimizes the Pt usage but also improves the stability of the Au/CuPt catalyst for fuel cell reactions. The results suggest that the core/shell design is indeed effective for optimizing nanoparticle catalysis. The same concept may be extended to other multimetallic nanoparticle systems, making it possible to tune nanoparticle catalysis for many different chemical reactions.

  12. In vitro and in vivo anti-biofilm effects of silver nanoparticles immobilized on titanium.

    PubMed

    Qin, Hui; Cao, Huiliang; Zhao, Yaochao; Zhu, Cheng; Cheng, Tao; Wang, Qiaojie; Peng, Xiaochun; Cheng, Mengqi; Wang, Jiaxin; Jin, Guodong; Jiang, Yao; Zhang, Xianlong; Liu, Xuanyong; Chu, Paul K

    2014-11-01

    Prevention of periprosthetic infection (PPI) by inhibiting biofilm formation on prostheses is crucial to orthopedic surgery. In this work, silver nanoparticles (Ag NPs) are fabricated in situ and immobilized on titanium by silver plasma immersion ion implantation (PIII). The anti-biofilm activity rendered by the immobilized Ag NPs is assessed using Staphylococcus epidermidis, a biofilm producing strain, in vitro and in vivo. The immobilized Ag NPs show no apparent cytotoxicity but reduce biofilm formation in vitro by inhibiting bacteria adhesion and icaAD transcription. The immobilized Ag NPs offer a good defense against multiple cycles of bacteria attack in vitro, and the mechanism is independent of silver release. Radiographic assessment, microbiological cultures, and histopathological results demonstrate the ability of the functionalized surface against bacterial infection to reduce the risk of implant-associated PPI. PMID:25112937

  13. A general strategy for site-directed enzyme immobilization by using NiO nanoparticle decorated mesoporous silica.

    PubMed

    Ling, Daishun; Gao, Liqian; Wang, Jianpeng; Shokouhimehr, Mohammadreza; Liu, Jiahui; Yu, Yongsheng; Hackett, Michael J; So, Pui-Kin; Zheng, Bo; Yao, Zhongping; Xia, Jiang; Hyeon, Taeghwan

    2014-06-23

    Mesoporous materials have recently gained much attention owing to their large surface area, narrow pore size distribution, and superior pore structure. These materials have been demonstrated as excellent solid supports for immobilization of a variety of proteins and enzymes for their potential applications as biocatalysts in the chemical and pharmaceutical industries. However, the lack of efficient and reproducible methods for immobilization has limited the activity and recyclability of these biocatalysts. Furthermore, the biocatalysts are usually not robust owing to their rapid denaturation in bulk solvents. To solve these problems, we designed a novel hybrid material system, mesoporous silica immobilized with NiO nanoparticles (SBA-NiO), wherein enzyme immobilization is directed to specific sites on the pore surface of the material. This yielded the biocatalytic species with higher activity than free enzyme in solution. These biocatalytic species are recyclable with minimal loss of activity after several cycles, demonstrating an advantage over free enzymes.

  14. Immobilization of invertase on chitosan coated γ-Fe2O3 magnetic nanoparticles to facilitate magnetic separation.

    PubMed

    Waifalkar, P P; Parit, S B; Chougale, A D; Sahoo, Subasa C; Patil, P S; Patil, P B

    2016-11-15

    Industrially important invertase enzyme was immobilized on chitosan coated sol gel derived γ-Fe2O3 magnetic nanoparticles (MNPs) to enable it for repetitive use by magnetic separation. MNPs were characterized by X-ray diffraction (XRD), dynamic light scattering (DLS), field emission scanning electron microscope (FE-SEM), Fourier transform infrared (FTIR) spectrometer and magnetic measurements. FTIR studies confirmed successful immobilization of invertase on MNPs. The ability to convert sucrose into invert syrup was enhanced in immobilized invertase compared to that of free enzyme. Further it was found that invertase immobilized on MNPs (IIMNPs) were more stable at varying pH and temperature conditions. Magnetic separation technique was successfully employed for reuse of the IIMNPs for 20 times without significant loss of activity. PMID:27501039

  15. Bimetallic Ag-Au nanoparticles: Extracting meaningful optical constants from the surface-plasmon extinction spectrum

    NASA Astrophysics Data System (ADS)

    Moskovits, M.; Srnova-Sloufova, I.; Vlckova, B.

    2002-06-01

    We report an approach for extracting the optical constants of bimetallic Ag-Au nanoparticles from the measured surface-plasmon (SP) extinction spectra. The dielectric function of the metal is expressed as an analytic function of the wavelength in which the interband (and all other non-Drude) contributions to the dielectric function are represented by a sum of Lorentz functions. This expression is then used to fit the experimental extinction spectra to appropriate functions based on Mie theory. Three Lorentz functions (plus a Drude term) were found to be sufficient to reproduce the dielectric functions of Ag and Au [P. B. Johnson and R. W. Christy, Phys. Rev. B 6, 4370 (1972)] over the entire 0.6-6.5 eV range reported. With functions of this type, an excellent multiparameter fit of the measured extinction spectrum of colloidal Ag was obtained. Extinction spectra of a series of (Ag)Au hydrosols, prepared by reducing a gold precursor in the presence of previously synthesized silver seed particles with Au mole fractions ranging from 0.1 to 0.8, were measured. The extinction spectra show a single band (attributed to the surface plasmon) for all of the colloids produced, suggesting alloy formation. Transmission electron microscopy (TEM) images, however, indicate clear core-shell contrast for nanoparticles with Au mole fractions 0.4 and higher. With a presumed particle structure consisting of Ag core and Ag/Au alloy shell, very good fits were obtained for all of the measured extinction spectra by using a fitting strategy that restricted the number of parameters allowed to vary freely in the aforementioned dielectric function. The values of the dielectric function of the presumed shells were extracted in this manner as a function of wavelength. For particles with Au mole fraction 0.1-0.3, the results suggest an incompletely formed shell. For particles with higher Au mole fractions, the dielectric function of the shell gradually approaches that of Au. Overall, the results

  16. Enhancing the performance of catalytic AuPt nanoparticles in nonaqueous lithium-oxygen batteries

    NASA Astrophysics Data System (ADS)

    Lu, Meihua; Chen, Dongyun; Xu, Chaohe; Zhan, Yi; Lee, Jim Yang

    2015-07-01

    The deposition of catalytic AuPt (1 : 1) nanoparticles (NPs) into hollow mesoporous nitrogen-doped carbon microspheres (HMCMS) was found to significantly improve the effectiveness of the catalysis of oxygen reactions in nonaqueous lithium-oxygen batteries (LOBs); surpassing the performance of unsupported AuPt NPs or HMCMS in discharge and charge overpotentials (lower), specific capacity and rate performance (higher), and cycle life (longer). Specifically at a typical current density of 100 mA g-1, a LOB with the AuPt/HMCMS cathode catalyst could provide discharge and charge capacities of 6028 and 6000 mA h g-1 respectively and a charge-discharge voltage gap of only 1.27 V. The discharge capacity decreased by 5% when the current density was doubled, and by 23% when the current density was quintupled. The AuPt/HMCMS LOB could be cycled 75 times for a depth of discharge (DOD) of 1000 mA h g-1 without exceeding the charge cut-off voltage of 4.4 V. These measurements indicate that the HMCMS is an outstanding catalyst support to use for increasing the effectiveness of oxygen electrocatalysts in the LOBs.The deposition of catalytic AuPt (1 : 1) nanoparticles (NPs) into hollow mesoporous nitrogen-doped carbon microspheres (HMCMS) was found to significantly improve the effectiveness of the catalysis of oxygen reactions in nonaqueous lithium-oxygen batteries (LOBs); surpassing the performance of unsupported AuPt NPs or HMCMS in discharge and charge overpotentials (lower), specific capacity and rate performance (higher), and cycle life (longer). Specifically at a typical current density of 100 mA g-1, a LOB with the AuPt/HMCMS cathode catalyst could provide discharge and charge capacities of 6028 and 6000 mA h g-1 respectively and a charge-discharge voltage gap of only 1.27 V. The discharge capacity decreased by 5% when the current density was doubled, and by 23% when the current density was quintupled. The AuPt/HMCMS LOB could be cycled 75 times for a depth of discharge (DOD

  17. Horseradish peroxidase-immobilized magnetic mesoporous silica nanoparticles as a potential candidate to eliminate intracellular reactive oxygen species

    NASA Astrophysics Data System (ADS)

    Shen, Yajing; Zhang, Ye; Zhang, Xiang; Zhou, Xiuhong; Teng, Xiyao; Yan, Manqing; Bi, Hong

    2015-02-01

    Horseradish peroxidase-immobilized magnetic mesoporous silica nanoparticles (MMSNs-HRP) have been synthesized by a NHS/EDC coupling between the amino groups of horseradish peroxidase (HRP) and the carboxyl groups on the MMSNs surface. It is found that the immobilized HRP on MMSNs still retain high activity and the MMSNs-HRP can eliminate the reactive oxygen species (ROS) in Chinese hamster ovary (CHO) cells induced by the addition of H2O2 aqueous solution. Further, the fluorescent MMSN-HRP-CD nanoparticles have been prepared by attaching biocompatible, fluorescent carbon dots (CDs) to MMSNs-HRP. We have also investigated the effect of an applied magnetic field on cellular uptake of MMSNs-HRP-CDs and found that the internalization of MMSNs-HRP-CDs by CHO cells could be enhanced within 2 hours under the magnetic field. This work provides us with a novel and efficient method to eliminate ROS in living cells by using HRP-immobilized nanoparticles.Horseradish peroxidase-immobilized magnetic mesoporous silica nanoparticles (MMSNs-HRP) have been synthesized by a NHS/EDC coupling between the amino groups of horseradish peroxidase (HRP) and the carboxyl groups on the MMSNs surface. It is found that the immobilized HRP on MMSNs still retain high activity and the MMSNs-HRP can eliminate the reactive oxygen species (ROS) in Chinese hamster ovary (CHO) cells induced by the addition of H2O2 aqueous solution. Further, the fluorescent MMSN-HRP-CD nanoparticles have been prepared by attaching biocompatible, fluorescent carbon dots (CDs) to MMSNs-HRP. We have also investigated the effect of an applied magnetic field on cellular uptake of MMSNs-HRP-CDs and found that the internalization of MMSNs-HRP-CDs by CHO cells could be enhanced within 2 hours under the magnetic field. This work provides us with a novel and efficient method to eliminate ROS in living cells by using HRP-immobilized nanoparticles. Electronic supplementary information (ESI) available: TEM image of CDs, BET XRD

  18. Immobilization of cellulase on TiO2 nanoparticles by physical and covalent methods: a comparative study.

    PubMed

    Ahmad, Razi; Sardar, Meryam

    2014-08-01

    Immobilization of cellulase from Aspergillus niger on TiO2 nanoparticles was studied by two different approaches--physical adsorption and covalent coupling. A. niger was selected, as it is generally non-pathogenic, is found in nature in the broad range of habitats and produces cellulase extracellulary. For covalent method, TiO2 nanoparticles were modified with aminopropyltriethoxysilane (APTS). The adsorbed and covalently immobilized enzymes showed 76% and 93% activity, respectively, as compared to the free enzyme. The catalytic efficiency V(max)/K(m) increased from 0.4 to 4.0 after covalent attachment, whereas in adsorption method, it increased slightly from 0.4 to 1.2. The covalently-immobilized and adsorbed cellulase lost only 25% and 50% of their activity, respectively after 60 min of incubation at 75 degrees C. The reusability and operational stability data also showed that covalent coupling increased the stability of the enzyme. The presence of enzyme on TiO2 nanoparticles was confirmed by Fourier-transform infrared spectroscopy. The high-resolution transmission electron microscopy (HR-TEM) and atomic force microscopy (AFM) studies indicated aggregation of enzyme when adsorbed on TiO2 surface and a monolayer of enzyme in covalent attachment. In conclusion, covalently attached cellulase retained good activity and thermal stability, as compared to physically adsorbed enzyme. The lower amount of enzyme activity and thermal stability in case of physically adsorbed immobilized enzyme was due to aggregation of the enzyme after adsorption on TiO2 nanoparticles, as revealed by HR-TEM and AFM. Thus, TiO2 nanoparticles could be suitable candidates for immobilization of cellulase for industrial applications like paper, textile, detergent and food industries.

  19. Fabrication and characterization of core-shell magnetic chitosan nanoparticles as a novel carrier for immobilization of Burkholderia cepacia lipase.

    PubMed

    Ghadi, Arezoo; Tabandeh, Fatemeh; Mahjoub, Soleiman; Mohsenifar, Afshin; Roshan, Farid Talebnia; Alavije, Razieh Shafiee

    2015-01-01

    In this study, the chitosan magnetic core-shell nanoparticles (CMNPs) was synthesized and then used as a support for immobilization of lipase. The characteristics of CMNPs, including morphology, topography and spectra type before and after immobilization were determined. The scanning electron micrographs of the CMNPs showed that they were approximately uniform spheres and the distribution chart indicated that the particles have the mean diameter of 100 nm. Kinetic parameters of Km and Vm were calculated as 1.07 mM and 29.43 U/mg for free B. cepacia lipase and 1.29 mM and 25.82 U/mg for immobilized lipase on CMNPs, respectively. The activity of immobilized lipase was 32 U/mg under optimum temperature and pH. CMNP's were used in trasesterification reaction in order to evaluate the activity of the immobilized enzyme compared to the free enzyme. Immobilization of lipase on CMNPs improved stability and total relative activity of the enzyme. It could be concluded that CMNPs be considered as a suitable carrier for enzyme immobilization.

  20. Synthesis of Au nanoparticles decorated graphene oxide nanosheets: noncovalent functionalization by TWEEN 20 in situ reduction of aqueous chloroaurate ions for hydrazine detection and catalytic reduction of 4-nitrophenol.

    PubMed

    Lu, Wenbo; Ning, Rui; Qin, Xiaoyun; Zhang, Yingwei; Chang, Guohui; Liu, Sen; Luo, Yonglan; Sun, Xuping

    2011-12-15

    In this paper, we develop a cost-effective and simple route for the synthesis of Au nanoparticles (AuNPs) decorated graphene oxide (GO) nanosheets using polyoxyethylene sorbitol anhydride monolaurate (TWEEN 20) as a stabilizing agent for GO as well as a reducing and immobilizing agent for AuNPs. The AuNPs assemble on the surface of TWEEN-functionalized GO by the in situ reduction of HAuCl(4) aqueous solution. The morphologies of these composites were characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). It is found that the resultant AuNPs decorated GO nanosheets (AuNPs/TWEEN/GO) exhibit remarkable catalytic performance for hydrazine oxidation. This hydrazine sensor has a fast amperometric response time of less than 3s. The linear range is estimated to be from 5 μM to 3 mM (r=0.999), and the detection limit is estimated to be 78 nM at a signal-to-noise ratio of 3. The AuNPs/TWEEN/GO composites also exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GO supports also enhance the catalytic activity via a synergistic effect.

  1. Beet juice utilization: Expeditious green synthesis of nobel metal nanoparticles (Ag, Au, Pt, and Pd) using microwaves

    EPA Science Inventory

    Metal nanoparticles of Ag, Au, Pt, and Pd were prepared in aqueous solutions via a rapid microwave-assisted green method using beet juice, an abundant sugar-rich agricultural produce, served as both a reducing and a capping reagent. The Ag nanoparticles with capping prepared by b...

  2. One-pot tuning of Au nucleation and growth: from nanoclusters to nanoparticles.

    PubMed

    Lai, Sheng-Feng; Chen, Wen-Chang; Wang, Cheng-Liang; Chen, Hsiang-Hsin; Chen, Shin-Tai; Chien, Chia-Chi; Chen, Yi-Yun; Hung, Wen-Ting; Cai, Xiaoqing; Li, Enrong; Kempson, Ivan M; Hwu, Y; Yang, C S; Tok, Eng-Soon; Tan, Hui Ru; Lin, Ming; Margaritondo, G

    2011-07-01

    We describe a simple and effective method to obtain colloidal surface-functionalized Au nanoparticles. The method is primarily based on irradiation of a gold solution with high-flux X-rays from a synchrotron source in the presence of 11-mercaptoundecanoic acid (MUA). Extensive tests of the products demonstrated high colloidal density as well as excellent stability, shelf life, and biocompatibility. Specific tests with X-ray diffraction, UV-visible spectrometry, visible microscopy, Fourier transform infrared spectroscopy, dark-field visible-light scattering microscopy, and transmission electron microscopy demonstrated that MUA, being an effective surfactant, not only allows tunable size control of the nanoparticles, but also facilitates functionalization. The nanoparticle sizes were 6.45 ± 1.58, 1.83 ± 1.21, 1.52 ± 0.37 and 1.18 ± 0.26 nm with no MUA and with MUA-to-Au ratios of 1:2, 1:1, and 3:1. The MUA additionally enabled functionalization with l-glycine. We thus demonstrated flexibility in controlling the nanoparticle size over a large range with narrow size distribution.

  3. Spectroscopic study of 3-Hydroxyflavone - protein interaction in lipidic bi-layers immobilized on silver nanoparticles.

    PubMed

    Voicescu, Mariana; Ionescu, Sorana; Nistor, Cristina L

    2017-01-01

    The interaction of 3-Hydroxyflavone with serum proteins (BSA and HSA) in lecithin lipidic bi-layers (PC) immobilized on silver nanoparticles (SNPs), was studied by fluorescence and Raman spectroscopy. BSA secondary structure was quantified with a deconvolution algorithm, showing a decrease in α-helix structure when lipids were added to the solution. The effect of temperature on the rate of the excited-state intra-molecular proton transfer and on the dual fluorescence emission of 3-HF in the HSA/PC/SNPs systems was discussed. Evaluation of the antioxidant activity of 3-HF in HSA/PC/SNPs systems was also studied. The antioxidant activity of 3-HF decreased in the presence of SNPs. The results are discussed with relevance to the secondary structure of proteins and of the 3-HF based nano-systems to a topical formulation useful in the oxidative stress process. PMID:27380623

  4. Bioinspired hierarchical nanotubular titania immobilized with platinum nanoparticles for photocatalytic hydrogen production.

    PubMed

    Liu, Xiaoyan; Li, Jiao; Zhang, Yiming; Huang, Jianguo

    2015-05-11

    A bioinspired nanocomposite composed of platinum nanoparticles and nanotubular titania was fabricated in which the titania matter was templated by natural cellulose substance. The composite possesses three- dimensional hierarchical structures, and ultrafine metallic platinum particles with sizes of ca. 2 nm were immobilized uniformly on the surfaces of the titania nanotubes. Such a nanocomposite with 1.06 wt % of platinum content shows the optimal photocatalytic hydrogen production activity from water splitting of 16.44 mmol h(-1)  g(-1) , and excessive loading of platinum results in poorer photocatalytic performance. The structural integrity of the nanocomposite upon cyclic water-splitting processes results in its sufficient photocatalytic stability.

  5. Enzymatic activity of cholesterol oxidase immobilized onto polymer nanoparticles mediated by Congo red.

    PubMed

    Silva, Rubens A; Carmona-Ribeiro, Ana Maria; Petri, Denise F S

    2013-10-01

    Poly(ethylene glycol), PEG, decorated polystyrene (PS) nanoparticles were synthesized and characterized by means of dynamic light scattering (DLS), zeta (ζ) potential measurements, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The adsorption of Congo red (CR) onto PS/PEG particles was evidenced by the decrease of ζ potential values and increase in the particles mean diameter in comparison to bare particles. Cholesterol oxidase (ChOx), the main enzyme in the oxidation of cholesterol, adsorbed onto PS/PEG and PS/PEG/CR particles, as revealed by the increase in the particles mean size and spectrophotometry. The enzymatic activity of free and immobilized ChOx was determined as a function of time by means of a coupled reaction with horseradish peroxidase. The activity of free ChOx decreased with time, while the activity of immobilized ChOx increased with time; after 1h reaction the latter was half of the former. Freeze-drying the ChOx covered PS/PEG/CR particles allowed their storage for at least one month under room conditions without loss of enzymatic activity. Conjugation effects between CR and ChOx or cholesterol evidenced by circular dichroism and spectrophotometry rendered a conformational state of ChOx, such that the enzymatic action was favored. ChOx adsorbed onto PS/PEG presents no enzymatic activity, probably due to ChOx denaturation or unfavorable orientation. Freeze-dried and freshly prepared dispersions of ChOx immobilized onto PS/PEG/CR particles yielded linear response in the cholesterol concentration range of 100mgdL(-1) (lowest limit of normal blood concentration) to 300mgdL(-1) (high risk level).

  6. Unraveling structures of protection ligands on gold nanoparticle Au68(SH)32

    PubMed Central

    Xu, Wen Wu; Gao, Yi; Zeng, Xiao Cheng

    2015-01-01

    New low-energy atomic structures of the thiolate-protected gold nanoparticle Au68(SH)32 are uncovered, where the atomic positions of the Au atoms are taken from the recent single-particle transmission electron microscopy measurement by Kornberg and co-workers, whereas the pattern of thiolate ligands on the gold core is attained on the basis of the generic formulation (or rule) of the “divide and protect” concept. Four distinct low-energy isomers, Iso1 to Iso4, whose structures all satisfy the generic formulation, are predicted. Density-functional theory optimization indicates that the four isomers are all lower in energy by 3 to 4 eV than the state-of-the-art low-energy isomer reported. Further analysis of the optimized structures of Au68(SH)32 shows that the structure of gold core in Iso1 to Iso4 is consistent with the experiment, whereas the positions of a few Au atoms at the surface of gold core are different. The computed optical absorption spectra of the four isomers are consistent with the measured spectrum. Computation of catalytic properties of Au68(SH)32 toward CO oxidation suggests that the magic number cluster can be a stand-alone nanoscale catalyst for future catalytic applications. PMID:26601162

  7. Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

    SciTech Connect

    Herz, A. E-mail: dong.wang@tu-ilmenau.de; Rossberg, D.; Hentschel, M.; Theska, F.; Wang, D. E-mail: dong.wang@tu-ilmenau.de; Schaaf, P.; Friák, M.; Holec, D.; Šob, M.; Schneeweiss, O.

    2015-08-17

    Solid-state dewetting is used to fabricate supersaturated, submicron-sized Au-Ni solid solution particles out of thin Au/Ni bilayers by means of a rapid thermal annealing technique. Phase separation in such particles is studied with respect to their equilibrium crystal (or Wulff) shape by subsequent annealing at elevated temperature. It is found that (100) faceting planes of the equilibrated particles are enriched with Ni and (111) faces with Au. Both phases are considered by quantum-mechanical calculations in combination with an error-reduction scheme that was developed to compensate for a missing exchange-correlation potential that would reliably describe both Au and Ni. The observed phase configuration is then related to the minimization of strongly anisotropic elastic energies of Au- and Ni-rich phases and results in a rather unique nanoparticle composite state that is characterized by nearly uniform value of elastic response to epitaxial strains all over the faceted surface. The same conclusion is yielded also by evaluating bi-axial elastic moduli when employing interpolated experimental elastic constants. This work demonstrates a useful route for studying features of physical metallurgy at the mesoscale.

  8. Direct observation of enhanced plasmon-driven catalytic reaction activity of Au nanoparticles supported on reduced graphene oxides by SERS.

    PubMed

    Liang, Xiu; You, Tingting; Liu, Dapeng; Lang, Xiufeng; Tan, Enzhong; Shi, Jihua; Yin, Penggang; Guo, Lin

    2015-04-21

    Graphene-based nanocomposites have recently attracted tremendous research interest in the field of catalysis due to their unique optical and electronic properties. However, direct observation of enhanced plasmon-driven catalytic activity of Au nanoparticles (NPs) supported on reduced graphene oxides (Au/rGO) has rarely been reported. Herein, based on the reduction from 4-nitrobenzenethiol (4-NBT) to p,p'-dimercaptoazobenzene (DMAB), the catalytic property of Au/rGO nanocomposites was investigated and compared with corresponding Au NP samples with similar size distribution. Our results show that Au/rGO nanocomposites could serve as a good catalytic and analytic platform for plasmon-driven chemical reactions. In addition, systematic comparisons were conducted during power- and time-dependent surface-enhanced Raman scattering (SERS) experiments, which exhibited a lower power threshold and higher catalytic efficiency for Au/rGO as compared to Au NPs toward the reaction. PMID:25793752

  9. The impact of oxygen on the morphology of gas-phase prepared Au nanoparticles

    SciTech Connect

    Pohl, D.; Surrey, A.; Schultz, L.; Rellinghaus, B.

    2012-12-24

    We present an easy procedure for the synthesis of single crystalline gold nanoparticles with a mean diameter of 4 nm using a DC-sputtering in an argon-oxygen gas mixture. Morphology population statistics have been determined to quantify the influence of oxygen. It is found that the particles undergo a structural transition from predominantly icosahedral to single crystalline particles with increasing amount of oxygen. Aberration-corrected high-resolution transmission electron microscopy investigation proves that likewise prepared single crystalline nanoparticles are defect and oxygen free. In contrast, the icosahedral particles prepared with pure argon show the presence of edge dislocations pointing to an energetic disfavoring already at these relatively small particle sizes. This morphology control of clean and uncovered Au nanoparticles provides a high application potential, e.g., for studying the influence of the particle morphology on plasmonic and catalytic properties.

  10. Assembly/Disassembly of DNA-Au Nanoparticles: A Strategy of Intervention

    DOE PAGES

    Lim, I-Im S.; Wang, Lingyan; Chandrachud, Uma; Gal, Susannah; Zhong, Chuan-Jian

    2008-01-01

    This report describes the viability of a strategy for manipulating the assembly/disassembly processes of DNA-Au nanoparticles by molecular intervention. Using the temperature-induced assembly and disassembly processes of DNAs and gold nanoparticles as a model system, the introduction of a molecular recognition probe is demonstrated to lead to the intervention of the assembly/disassembly processes depending on its specific biorecognition. This process can be detected by monitoring the change in the optical properties of gold nanoparticles and their DNA assemblies. Implications of the preliminary results to exploration of the resulting nanostructures for fine-tuning of the interfacial reactivities in DNA-based bioassays and biomaterialmore » engineering are also discussed.« less

  11. Facile nucleation of gold nanoparticles on graphene-based thin films from Au144 molecular precursors

    NASA Astrophysics Data System (ADS)

    Venter, Andrei; Hesari, Mahdi; Shafiq Ahmed, M.; Bauld, Reg; Workentin, Mark S.; Fanchini, Giovanni

    2014-04-01

    We demonstrate a facile and cost effective method to obtain gold nanoparticles on graphene by dispersing Au144 molecular nanoclusters by spin coating them in thin layers on graphene-based films and subsequent annealing in a controlled atmosphere. The graphene-based thin films used for these experiments are prepared by solvent-assisted exfoliation of graphite in water in the presence of ribonucleic acid as a surfactant and by subsequent vacuum filtration of the resulting graphene-containing suspensions. Not only is this method easily reproducible, but it leads to gold nanoparticles that are not dependent in size on the number of graphene layers beneath them. This is a distinct advantage over other methods. Plasmonic effects have been detected in our gold nanoparticle-decorated graphene layers, indicating that these thin films may be useful in applications such as plasmonic solar cells and optical memory devices.

  12. Internalization: acute apoptosis of breast cancer cells using herceptin-immobilized gold nanoparticles

    PubMed Central

    Rathinaraj, Pierson; Al-Jumaily, Ahmed M; Huh, Do Sung

    2015-01-01

    Herceptin, the monoclonal antibody, was successfully immobilized on gold nanoparticles (GNPs) to improve their precise interactions with breast cancer cells (SK-BR3). The mean size of the GNPs (29 nm), as determined by dynamic light scattering, enlarged to 82 nm after herceptin immobilization. The in vitro cell culture experiment indicated that human skin cells (FB) proliferated well in the presence of herceptin-conjugated GNP (GNP–Her), while most of the breast cancer cells (SK-BR3) had died. To elucidate the mechanism of cell death, the interaction of breast cancer cells with GNP–Her was tracked by confocal laser scanning microscopy. Consequently, GNP–Her was found to be bound precisely to the membrane of the breast cancer cell, which became almost saturated after 6 hours incubation. This shows that the progression signal of SK-BR3 cells is retarded completely by the precise binding of antibody to the human epidermal growth factor receptor 2 receptor of the breast cancer cell membrane, causing cell death. PMID:25709498

  13. Development of Antigen-Immobilized Metallothionein Sensor that Exploits Gold Nanoparticle-Based Enhancement of Signal.

    PubMed

    Kim, Namsoo; Son, So-Hee

    2015-08-01

    An antigen-immobilized indirect-competitive immunosensor that detects metallothionein (MT), a potent biomarker of contamination with heavy metals, was developed exploiting enhancement of signal based on an additional binding of gold nanoparticles to an anti-MT antibody through the biotin-avidin interaction. The sensor was constructed by the immobilization of MT at 1 mg/mL on a 9-MHz quartz crystal microbalance and the concentration of the antibody for competitive reaction was optimized as 10 µg/mL based on the degree of sensor response. At this moment, the control response of the sensor obtained with enhancement of signal was 343.8 Hz and was larger than that without enhancement of signal 2.47 fold. The sensor responses decreased gradually with increasing analyte concentrations, and a linear relationship between analyte concentration and sensor response was acquired in the range of 0.005-1 ng/mL MT in double-logarithmic scales with a correlation coefficient (r) of 0.9858. The limit of detection of the present sensor was presumed to be present below 5 pg/mL MT.

  14. Immobilization of nitrate reductase onto epoxy affixed silver nanoparticles for determination of soil nitrates.

    PubMed

    Sachdeva, Veena; Hooda, Vinita

    2015-08-01

    Epoxy glued silver nanoparticles were used as immobilization support for nitrate reductase (NR). The resulting epoxy/AgNPs/NR conjugates were characterized at successive stages of fabrication by scanning electron microscopy and fourier transform infrared spectroscopy. The immobilized enzyme system exhibited reasonably high conjugation yield (37.6±0.01 μg/cm(2)), with 93.54±0.88% retention of specific activity. Most favorable working conditions of pH, temperature and substrate concentration were ascertained to optimize the performance of epoxy/AgNPs/NR conjugates for soil nitrate quantification. The analytical results for soil nitrate determination were consistent, reliable and reproducible. Minimum detection limit of the method was 0.05 mM with linearity from 0.1 to 11.0 mM. The % recoveries of added nitrates (0.1 and 0.2 mM) were<95.0% and within-day and between-day coefficients of variations were 0.556% and 1.63% respectively. The method showed good correlation (R(2)=0.998) with the popular Griess reaction method. Epoxy/AgNPs bound NR had a half-life of 18 days at 4 °C and retained 50% activity after 15 reuses.

  15. Novel microwave-assisted digestion by trypsin-immobilized magnetic nanoparticles for proteomic analysis.

    PubMed

    Lin, Shuang; Yun, Dong; Qi, Dawei; Deng, Chunhui; Li, Yan; Zhang, Xiangmin

    2008-03-01

    In this study, a novel microwave-assisted protein digestion method was developed using trypsin-immobilized magnetic nanoparticles (TIMNs). The magnetic nanoparticles worked as not only substrate for enzyme immobilization, but also excellent microwave irradiation absorber and, thus, improved the efficiency of microwave-assisted digestion greatly. Three standard proteins, bovine serum albumin (BSA), myoglobin, and cytochrome c, were used to optimize the conditions of this novel digestion method. With the optimized conditions, peptide fragments produced in very short time (only 15 s) could be identified successfully by MALDI-TOF-MS. When it was compared to the conventional in-solution digestion (12 h), equivalent or better digestion efficiency was observed. Even when protein quantity was as low as micrograms, this novel digestion method still could digest proteins successfully, while the same samples by conventional in-solution digestion failed. Moreover, with an external magnetic field, the enzyme could be removed easily and reused. It was verified that, after 4 replicate runs, the TIMNs still kept high activity. To further confirm the efficiency of this rapid digestion method for proteome analysis, it was applied to the protein extract of rat liver. Without any preparation and prefractionation processing, the entire proteome digested by TIMNs in 15 s went through LC-ESI-MS/MS direct analysis. The whole shotgun proteomic experiment was finished in only 1 h with the identification of 313 proteins ( p < 0.01). This new application of TIMNs in microwave-assisted protein digestion really opens a route for large-scale proteomic analysis.

  16. Development of therapeutic Au-methylene blue nanoparticles for targeted photodynamic therapy of cervical cancer cells.

    PubMed

    Yu, Jiashing; Hsu, Che-Hao; Huang, Chih-Chia; Chang, Po-Yang

    2015-01-14

    Photodynamic therapy (PDT) involves the cellular uptake of a photosensitizer (PS) combined with oxygen molecules and light at a specific wavelength to be able to trigger cancer cell death via the apoptosis pathway, which is less harmful and has less inflammatory side effect than necrosis. However, the traditional PDT treatment has two main deficiencies: the dark toxicity of the PS and the poor selectivity of the cellular uptake of PS between the target cells and normal tissues. In this work, methylene blue (MB), a known effective PS, combined with Au nanoparticles (NPs) was prepared using an intermolecular interaction between a polystyrene-alt-maleic acid (PSMA) layer on the Au NPs and MB. The Au@polymer/MB NPs produced a high quantum yield of singlet oxygen molecules, over 50% as much as that of free MB, when they were excited by a dark red light source at 660 nm, but without significant dark toxicity. Furthermore, transferrin (Tf) was conjugated on the Au@polymer/MB NPs via an EDC/NHS reaction to enhance the selectivity to HeLa cells compared to 3T3 fibroblasts. With a hand-held single laser treatment (32 mW/cm) for 4 min, the new Au@polymer/MB-Tf NPs showed a 2-fold enhancement of PDT efficiency toward HeLa cells over the use of free MB at 4 times dosage. Cellular staining examinations showed that the HeLa cells reacted with Au@polymer/MB-Tf NPs and the 660 nm light excitation triggered PDT, which caused the cells to undergo apoptosis ("programmed" cell death). We propose that applying this therapeutic Au@polymer/MB-Tf nanoagent is facile and safe for delivery and cancer cell targeting to simultaneously minimize side effects and accomplish a significant enhancement in photodynamic therapeutic efficiency toward next-generation nanomedicine development.

  17. Controlled protein embedment onto Au/Ag core-shell nanoparticles for immuno-labeling of nanosilver surface.

    PubMed

    Lee, In Hwan; Lee, Jeong Min; Jung, Yongwon

    2014-05-28

    Difficulties in stable conjugation of biomolecules to nanosilver surfaces have severely limited the use of silver nanostructures in biological applications. Here, we report a facile antibody conjugation onto gold/silver (Au/Ag) core-shell nanoparticles by stable and uniform embedment of an antibody binding protein, protein G, in silver nanoshells. A rigid helical peptide linker with a terminal cysteine residue was fused to protein G. A mixture of the peptide-fused protein G and space-filling free peptide was reacted with gold nanoparticles (AuNPs) to form a protein G-linked peptide layer on the particle surface. Uniform silver nanoshells were successfully formed on these protein G-AuNPs, while stably embedding protein G-linked peptide layers. Protein G specifically targets the Fc region of an antibody and thus affords properly orientated antibodies on the particle surface. Compared to Au nanoparticles of similar size with randomly adsorbed antibodies, the present immuno-labeled Au/Ag core-shell nanoparticles offered nearly 10-fold higher sensitivities for naked-eye detection of surface bound antigens. In addition, small dye molecules that were bonded to the peptide layer on Au nanoparticles exhibited highly enhanced surface-enhanced Raman scattering (SERS) signals upon Ag shell formation. The present strategy provides a simple but efficient way to conjugate antibodies to nanosilver surfaces, which will greatly facilitate wider use of the superior optical properties of silver nanostructures in biological applications. PMID:24801432

  18. Multifunctional nanocomposites constructed from Fe3O4-Au nanoparticle cores and a porous silica shell in the solution phase.

    PubMed

    Chen, Fenghua; Chen, Qingtao; Fang, Shaoming; Sun, Yu'an; Chen, Zhijun; Xie, Gang; Du, Yaping

    2011-11-01

    This work is directed towards the synthesis of multifunctional nanoparticles composed of Fe(3)O(4)-Au nanocomposite cores and a porous silica shell (Fe(3)O(4)-Au/pSiO(2)), aimed at ensuring the stability, magnetic, and optical properties of magnetic-gold nanocomposite simultaneously. The prepared Fe(3)O(4)-Au/pSiO(2) core/shell nanoparticles are characterized by means of TEM, N(2) adsorption-desorption isotherms, FTIR, XRD, UV-vis, and VSM. Meanwhile, as an example of the applications, catalytic activity of the porous silica shell-encapsulated Fe(3)O(4)-Au nanoparticles is investigated by choosing a model reaction, reduction of o-nitroaniline to benzenediamine by NaBH(4). Due to the existence of porous silica shells, the reaction with Fe(3)O(4)-Au/pSiO(2) core/shell nanoparticles as a catalyst follows second-order kinetics with the rate constant (k) of about 0.0165 l mol(-1) s(-1), remarkably different from the first-order kinetics with the k of about 0.002 s(-1) for the reduction reaction with the core Fe(3)O(4)-Au nanoparticles as a catalyst. PMID:21637876

  19. Au@MnS@ZnS Core/Shell/Shell Nanoparticles for Magnetic Resonance Imaging and Enhanced Cancer Radiation Therapy.

    PubMed

    Li, Meifang; Zhao, Qi; Yi, Xuan; Zhong, Xiaoyan; Song, Guosheng; Chai, Zhifang; Liu, Zhuang; Yang, Kai

    2016-04-20

    Although conventional radiotherapy (RT) has been widely used in the clinic to treat cancer, it often has limited therapeutic outcomes and severe toxic effects. There is still a need to develop theranostic agents with both imaging and RT-enhancing functions to improve the accuracy and efficiency of RT. Herein we synthesize Au@MnS@ZnS core/shell/shell nanoparticles with polyethylene glycol (PEG) functionalization, yielding Au@MnS@ZnS-PEG nanoparticles with great stability in different physiological solutions and no significant cytotoxicity. It is found that Au@MnS@ZnS-PEG nanoparticles can enhance the cancer cell killing efficiency induced by RT, as evidenced by multiple in vitro assays. Owing to the existence of paramagnetic Mn(2+) in the nanoparticle shell, our Au@MnS@ZnS-PEG can be used as a contrast agent for T1-weighted magnetic resonance (MR) imaging, which reveals the efficient accumulation and retention of nanoparticles in the tumors of mice after intravenous injection. Importantly, by exposing tumor-bearing mice that were injected with Au@MnS@ZnS-PEG to X-ray irradiation, the tumor growth can be significantly inhibited. This result shows clearly improved therapeutic efficacy compared to RT alone. Furthermore, no obvious side effect of Au@MnS@ZnS-PEG is observed in the injected mice. Therefore, our work presents a new type of radiosensitizing agent, which is promising for the imaging-guided enhanced RT treatment of cancer.

  20. Iodide-induced organothiol desorption and photochemical reaction, gold nanoparticle (AuNP) fusion, and SERS signal reduction in organothiol-containing AuNP aggregates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gold nanoparticles (AuNPs) have been used extensively as surface-enhanced Raman spectroscopic (SERS) substrates for their large SERS enhancements and widely believed chemical stability. Presented is the finding that iodide can rapidly reduce the SERS intensity of the ligands, including organothiols ...

  1. Graphene functionalized porous Au-paper based electrochemiluminescence device for detection of DNA using luminescent silver nanoparticles coated calcium carbonate/carboxymethyl chitosan hybrid microspheres as labels.

    PubMed

    Li, Meng; Wang, Yanhu; Zhang, Yan; Yu, Jinghua; Ge, Shenguang; Yan, Mei

    2014-09-15

    In the paper, a simple and sensitive electrochemiluminescence (ECL) DNA sensor based on graphene-modified porous Au-paper working electrode (GR/Au-PWE) and calcium carbonate/carboxymethyl chitosan (CaCO3/CMC) hybrid microspheres @ luminescent silver nanoparticles (AgNPs) composites was developed. The GR/Au-PWE with excellent conductivity was successfully prepared for the immobilization of capture probe. The CaCO3/CMC hybrid microspheres were prepared by the precipitation of calcium carbonate in an aqueous solution containing CMC. The AgNPs was synthesized by thermal reduction of silver ions in glycine matrix, taking advantage of the solid-state matrix to control the nucleation and migration of reduced silver atoms. The CaCO3/CMC@AgNPs composites exhibited 3.6 times higher ECL intensity than the pure AgNPs-labeled reporter DNA. Taking advantage of dual-amplification effects, the paper-based DNA sensor could detect the target DNA quantitatively, in the range of 4.0×10(-17)-5.0×10(-11) M, with a limit of detection as low as 8.5×10(-18) M, and perform excellent selectivity. The simple, low-cost, sensitive device could be easily applied for point-of-care testing, public health and environmental monitoring in remote regions, developing or developed countries.

  2. Conversion of Ag nanowires to AgCI nanowires decorated with Au nanoparticles and their photocatalytic activity.

    SciTech Connect

    Sun, Y.; Center for Nanoscale Materials

    2010-02-11

    A two-step approach has been developed to synthesize AgCl nanowires decorated with Au nanoparticles by using Ag nanowires as chemical templates. In the first step, the Ag nanowires are oxidized with FeCl{sub 3} followed by a simultaneous precipitation reaction between Ag{sup +} and Cl{sup -} ions at room temperature, resulting in conversion of the Ag nanowires to AgCl nanowires as well as reduction of Fe{sup 3+} to Fe{sup 2+} ions. In the second step, the Fe{sup 2+} ions generated in the first step reduce Au precursors (e.g., NaAuCl{sub 4}) to deposit Au nanoparticles on the surfaces of the AgCl nanowires, resulting in the formation of AgCl:Au composite nanowires. Because of strong surface plasmon resonance and chemical inertness of Au nanoparticles, the as-synthesized AgCl:Au nanowires exhibit enhanced absorption coefficient in the visible region and enhanced chemical stability to prevent them from degradation and aggregation. These unique properties enable the AgCl:Au nanowires to be used as a class of promising plasmonic photocatalysts driven by visible light. Preliminary results demonstrate these composite nanowires can efficiently decompose organics, such as methylene blue molecules, under illumination of white light.

  3. Synthesis of amino-silane modified superparamagnetic Fe{sub 3}O{sub 4} nanoparticles and its application in immobilization of lipase from Pseudomonas fluorescens Lp1

    SciTech Connect

    Kanimozhi, S.; Perinbam, K.

    2013-05-15

    Highlights: ► Magnetic nanoparticles were synthesized by chemical co-precipitation method. ► Surface was functionalized with amino-silane and used for lipase immobilization. ► Characterized through TEM, SEM, XRD, FT-IR and VSM analysis. ► The functionalization and immobilization did not affect the magnetite properties. ► The immobilized lipase showed greater functional property than free lipase. - Abstract: Superparamagnetic nanoparticles (Fe{sub 3}O{sub 4}–magnetite) were prepared by chemical co-precipitation method and their surface was functionalized with 3-aminopropyltriethoxysilane via silanization reaction to obtain amino functionalized magnetic nanoparticles. The purified lipase from Pseudomonas fluorescens Lp1 was immobilized onto functionalized magnetite using glutaraldehyde as the coupling agent. The characterization of the nanoparticles was done by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, vibrating sample magnetometry and Fourier transformed infrared spectroscopy. The size of the magnetite was measured about 10–30 nm. The results of characterization study revealed the successful immobilization of lipase on to functionalized magnetite. The saturation magnetization of magnetic nanoparticles was found to be 28.34 emu/g whereas the immobilized magnetic nanoparticle was 17.074 emu/g. The immobilized lipase had greater activity at 50 °C and thermal stability upto 70 °C. It exhibited excellent reusability for 4 cycles and storage stability upto 15 days by retaining 75% of its initial activity.

  4. Surface-enhanced Raman scattering in three-dimensional ordered Au nanoparticles in anodic porous alumina matrix

    NASA Astrophysics Data System (ADS)

    Kondo, Toshiaki; Nishio, Kazuyuki; Masuda, Hideki

    2011-12-01

    The fabrication of a three-dimensional (3D) ordered array of metal and/or metal oxide nanoparticles in an anodic porous alumina matrix and the application of a 3D array of Au nanoparticles as a substrate for the measurement of surfaceenhanced Raman scattering (SERS) are discussed. The 3D structure is prepared by a repeated process composed of the formation of nanoholes by the anodization of Al and the subsequent electrochemical deposition of a metal into the holes. The dependence of the SERS intensity on the number of layers of the Au nanoparticle array was examined. In addition, the effect of the gap size between Au nanoparticles was also investigated. The present process allows the fabrication of 3D functional optical devices based on the enhancement of the electric field of incident light.

  5. Immobilization of As(III) in soil and groundwater using a new class of polysaccharide stabilized Fe-Mn oxide nanoparticles.

    PubMed

    An, Byungryul; Zhao, Dongye

    2012-04-15

    A new class of stabilized Fe-Mn binary oxide nanoparticles was prepared with a water-soluble starch or carboxymethyl cellulose (CMC) as a stabilizer. The nanoparticles were characterized and tested with respect to sorption of As(III) and As(V) from water and for immobilization of As(III) in soil. While arsenic sorption capacities were comparable for bare, or stabilized Fe-Mn nanoparticles, particle stabilization enabled the nanoparticles to be delivered into soil for in situ immobilization of arsenite. High As(III) sorption capacity was observed over a broad pH range of 5-9. Column breakthrough tests demonstrated soil mobility of CMC-stabilized nanoparticles. Once delivered, the nanoparticles remain virtually immobile in soil under typical groundwater conditions, serving as a fixed sink for arsenic. When an As(III)-laden soil was treated with CMC-stabilized Fe-Mn at an Fe-to-As molar ratio of 6.5-39, the water leachable arsenic was reduced by 91-96%, and the TCLP leachability was reduced by 94-98%. Column elution tests of an As(III)-laden soil indicated that application of CMC-stabilized Fe-Mn transferred nearly all water-soluble As(III) to the nanoparticle phase. Consequently, As(III) is immobilized as the nanoparticles are immobilized in the soil. The nanoparticle amendment was able to reduce the TCLP leachability of As(III) remaining in the soil bed by 78%.

  6. Spontaneous formation of Au-Pt alloyed nanoparticles using pure nano-counterparts as starters: a ligand and size dependent process.

    PubMed

    Usón, Laura; Sebastian, Victor; Mayoral, Alvaro; Hueso, Jose L; Eguizabal, Adela; Arruebo, Manuel; Santamaria, Jesus

    2015-06-14

    In this work we investigate the formation of PtAu monodisperse alloyed nanoparticles by ageing pure metallic Au and Pt small nanoparticles (sNPs), nanoparticle size <5 nm, under certain conditions. We demonstrate that those bimetallic entities can be obtained by controlling the size of the initial metallic sNPs separately prepared and by selecting their appropriate capping agents. The formation of this spontaneous phenomenon was studied using HR-STEM, EDS, ionic conductivity, UV-Vis spectroscopy and cyclic voltammetry. Depending on the type of capping agent used and the size of the initial Au sNPs, three different materials were obtained: (i) AuPt bimetallic sNPs showing a surface rich in Au atoms, (ii) segregated Au and Pt sNPs and (iii) a mixture of bimetallic nanoparticles as well as Pt sNPs and Au NPs. Surface segregation energies and the nature of the reaction environment are the driving forces to direct the distribution of atoms in the bimetallic sNPs. PtAu alloyed nanoparticles were obtained after 150 h of reaction at room temperature if a weak capping agent was used for the stabilization of the nanoparticles. It was also found that Au atoms diffuse towards Pt sNPs, producing a surface enriched in Au atoms. This study shows that even pure nanoparticles are prone to be modified by the surrounding nanoparticles to give rise to new nanomaterials if atomic diffusion is feasible. PMID:25985914

  7. Enhancement of superconducting Tc (33 K) by entrapment of FeSe in carbon coated Au-Pd17Se15 nanoparticles.

    PubMed

    Mishra, Sukhada; Song, Kai; Ghosh, Kartik C; Nath, Manashi

    2014-03-25

    FeSe has been an interesting member of the Fe-based superconductor family ever since the discovery of superconductivity in this simple binary chalcogenide. Simplicity of composition and ease of synthesis has made FeSe, in particular, very lucrative as a test system to understand the unconventional nature of superconductivity, especially in low-dimensional models. In this article we report the synthesis of composite nanoparticles containing FeSe nanoislands entrapped within an ent-FeSe-Pd16Se15-Au nanoparticle and sharing an interface with Pd17Se15. This assembly exhibits a significant enhancement in the superconducting Tc (onset at 33 K) accompanied by a noticeable lattice compression of FeSe along the <001> and <101> directions. The Tc in FeSe is very sensitive to application of pressure and it has been shown that with increasing external pressure Tc can be increased almost 4-fold. In these composite nanoparticles reported here, immobilization of FeSe on the Pd17Se15 surface contributes to increasing the effect of interfacial pressure, thereby enhancing the Tc. The effect of interfacial pressure is also manifested in the contraction of the FeSe lattice (up to 3.8% in <001> direction) as observed through extensive high-resolution TEM imaging. The confined FeSe in these nanoparticles occupied a region of approximately 15-25 nm, where lattice compression was uniform over the entire FeSe region, thereby maximizing its effect in enhancing the Tc. The nanoparticles have been synthesized by a simple catalyst-aided vapor transport reaction at 800 °C where iron acetylacetonate and Se were used as precursors. Morphology and composition of these nanoparticles have been studied in details through extensive electron microscopy. PMID:24494773

  8. Rhombic Coulomb diamonds in a single-electron transistor based on an Au nanoparticle chemically anchored at both ends

    NASA Astrophysics Data System (ADS)

    Azuma, Yasuo; Onuma, Yuto; Sakamoto, Masanori; Teranishi, Toshiharu; Majima, Yutaka

    2016-02-01

    Rhombic Coulomb diamonds are clearly observed in a chemically anchored Au nanoparticle single-electron transistor. The stability diagrams show stable Coulomb blockade phenomena and agree with the theoretical curve calculated using the orthodox model. The resistances and capacitances of the double-barrier tunneling junctions between the source electrode and the Au core (R1 and C1, respectively), and those between the Au core and the drain electrode (R2 and C2, respectively), are evaluated as 4.5 MΩ, 1.4 aF, 4.8 MΩ, and 1.3 aF, respectively. This is determined by fitting the theoretical curve against the experimental Coulomb staircases. Two-methylene-group short octanedithiols (C8S2) in a C8S2/hexanethiol (C6S) mixed self-assembled monolayer is concluded to chemically anchor the core of the Au nanoparticle at both ends between the electroless-Au-plated nanogap electrodes even when the Au nanoparticle is protected by decanethiol (C10S). This is because the R1 value is identical to that of R2 and corresponds to the tunneling resistances of the octanedithiol chemically bonded with the Au core and the Au electrodes. The dependence of the Coulomb diamond shapes on the tunneling resistance ratio (R1/R2) is also discussed, especially in the case of the rhombic Coulomb diamonds. Rhombic Coulomb diamonds result from chemical anchoring of the core of the Au nanoparticle at both ends between the electroless-Au-plated nanogap electrodes.

  9. Regional selective construction of nano-Au on Fe3O4@SiO2@PEI nanoparticles by photoreduction

    NASA Astrophysics Data System (ADS)

    Zhou, Ying; Ping, Tuo; Maitlo, Inamullah; Wang, Bowen; Yasir Akram, Muhammad; Nie, Jun; Zhu, Xiaoqun

    2016-05-01

    A magnetically separatable catalyst Fe3O4@SiO2@PEI@Au (gold) nanoparticle was successfully constructed by a novel regional selective photoreduction method. Based on the photolysis mechanism of a type II photoinitiator, through controlling the distribution of polyethylene imine (PEI), Au nanoparticles about 10 nm, which are only on the surface of the Fe3O4@SiO2@PEI nanoparticle, could be photoreduced due to the PEI acting as a coordinating agent, capping agent, and photoreducing agent simultaneously. The small size Au nanoparticles endow the catalyst with a high catalytic performance toward the reduction of 4-nitroaniline to 4-aminophenol by NaBH4. In addition, magnetic Fe3O4@SiO2@PEI@Au nanoparticles could easily be recovered and could be reused at least six times still keeping catalytic efficiency higher than 95%, which contributes to their high stability and magnetization. Furthermore, compared to another reported approach, this method showed great regional selectivity of reducing metal nanoparticles by controlling the distribution of the PEI. Taking advantage of the regional selectivity of the photoreducing method could also be used to fabricate other metal nanoparticles as catalysts for various reactions.

  10. Modeling the Effect of pH and Temperature for Cellulases Immobilized on Enzymogel Nanoparticles.

    PubMed

    Samaratunga, Ashani; Kudina, Olena; Nahar, Nurun; Zakharchenko, Andrey; Minko, Sergiy; Voronov, Andriy; Pryor, Scott W

    2015-06-01

    Production costs of cellulosic biofuels can be lowered if cellulases are recovered and reused using particulate carriers that can be extracted after biomass hydrolysis. Such enzyme recovery was recently demonstrated using enzymogel nanoparticles with grafted polymer brushes loaded with cellulases. In this work, cellulase (NS50013) and β-glucosidase (Novozyme 188) were immobilized on enzymogels made of poly(acrylic acid) polymer brushes grafted to the surface of silica nanoparticles. Response surface methodology was used to model effects of pH and temperature on hydrolysis and recovery of free and attached enzymes. Hydrolysis yields using both enzymogels and free cellulase and β-glucosidase were highest at the maximum temperature tested, 50 °C. The optimal pH for cellulase enzymogels and free enzyme was 5.0 and 4.4, respectively, while both free β-glucosidase and enzymogels had an optimal pH near 4.4. Highest hydrolysis sugar concentrations with cellulase and β-glucosidase enzymogels were 69 and 53 % of those with free enzymes, respectively. Enzyme recovery using enzymogels decreased with increasing pH, but cellulase recovery remained greater than 88 % throughout the operating range of pH values less than 5.0 and was greater than 95 % at pH values below 4.3. Recovery of β-glucosidase enzymogels was not affected by temperature and had little impact on cellulase recovery.

  11. Synthesis and surface immobilization of antibacterial hybrid silver-poly(l-lactide) nanoparticles

    NASA Astrophysics Data System (ADS)

    Taheri, Shima; Baier, Grit; Majewski, Peter; Barton, Mary; Förch, Renate; Landfester, Katharina; Vasilev, Krasimir

    2014-08-01

    Infections associated with medical devices are a substantial healthcare problem. Consequently, there has been increasing research and technological efforts directed toward the development of coatings that are capable of preventing bacterial colonization of the device surface. Herein, we report on novel hybrid silver loaded poly(L-lactic acid) nanoparticles (PLLA-AgNPs) with narrowly distributed sizes (17 ± 3 nm) prepared using a combination of solvent evaporation and mini-emulsion technology. These particles were then immobilized onto solid surfaces premodified with a thin layer of allylamine plasma polymer (AApp). The antibacterial efficacy of the PLLA-AgNPs nanoparticles was studied in vitro against both gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria. The minimal inhibitory concentration values against Staphylococcus epidermidis and Escherichia coli were 0.610 and 1.156 μg · mL-1, respectively. The capacity of the prepared coatings to prevent bacterial surface colonization was assessed in the presence of Staphylococcus epidermidis, which is a strong biofilm former that causes substantial problems with medical device associated infections. The level of inhibition of bacterial growth was 98%. The substrate independent nature and the high antibacterial efficacy of coatings presented in this study may offer new alternatives for antibacterial coatings for medical devices.

  12. Antimicrobial chitosan-PVA hydrogel as a nanoreactor and immobilizing matrix for silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Agnihotri, Shekhar; Mukherji, Soumyo; Mukherji, Suparna

    2012-09-01

    Hydrogels are water-insoluble crosslinked hydrophilic networks capable of retaining a large amount of water. The present work aimed to develop a novel chitosan-PVA-based hydrogel which could behave both as a nanoreactor and an immobilizing matrix for silver nanoparticles (AgNPs) with promising antibacterial applications. The hydrogel containing AgNPs were prepared by repeated freeze-thaw treatment using varying amounts of the crosslinker, followed by in situ reduction with sodium borohydride as a reducing agent. Characterization studies established that the hydrogel provides a controlled and uniform distribution of nanoparticles within the polymeric network without addition of any further stabilizer. The average particle size was found to be 13 nm with size distribution from 8 to 21 nm as per HR-TEM studies. Swelling studies confirmed that higher amount of crosslinker and silver incorporation inside the gel matrices significantly enhanced the porosity and chain entanglement of the polymeric species of the hydrogel, respectively. The AgNP-hydrogel exhibited good antibacterial activity and was found to cause significant reduction in microbial growth ( Escherichia coli) in 12 h while such activity was not observed for the hydrogel without AgNPs.

  13. Modeling the Effect of pH and Temperature for Cellulases Immobilized on Enzymogel Nanoparticles.

    PubMed

    Samaratunga, Ashani; Kudina, Olena; Nahar, Nurun; Zakharchenko, Andrey; Minko, Sergiy; Voronov, Andriy; Pryor, Scott W

    2015-06-01

    Production costs of cellulosic biofuels can be lowered if cellulases are recovered and reused using particulate carriers that can be extracted after biomass hydrolysis. Such enzyme recovery was recently demonstrated using enzymogel nanoparticles with grafted polymer brushes loaded with cellulases. In this work, cellulase (NS50013) and β-glucosidase (Novozyme 188) were immobilized on enzymogels made of poly(acrylic acid) polymer brushes grafted to the surface of silica nanoparticles. Response surface methodology was used to model effects of pH and temperature on hydrolysis and recovery of free and attached enzymes. Hydrolysis yields using both enzymogels and free cellulase and β-glucosidase were highest at the maximum temperature tested, 50 °C. The optimal pH for cellulase enzymogels and free enzyme was 5.0 and 4.4, respectively, while both free β-glucosidase and enzymogels had an optimal pH near 4.4. Highest hydrolysis sugar concentrations with cellulase and β-glucosidase enzymogels were 69 and 53 % of those with free enzymes, respectively. Enzyme recovery using enzymogels decreased with increasing pH, but cellulase recovery remained greater than 88 % throughout the operating range of pH values less than 5.0 and was greater than 95 % at pH values below 4.3. Recovery of β-glucosidase enzymogels was not affected by temperature and had little impact on cellulase recovery. PMID:25935220

  14. Achieving Selective and Efficient Electrocatalytic Activity for CO2 Reduction Using Immobilized Silver Nanoparticles.

    PubMed

    Kim, Cheonghee; Jeon, Hyo Sang; Eom, Taedaehyeong; Jee, Michael Shincheon; Kim, Hyungjun; Friend, Cynthia M; Min, Byoung Koun; Hwang, Yun Jeong

    2015-11-01

    Selective electrochemical reduction of CO2 is one of the most sought-after processes because of the potential to convert a harmful greenhouse gas to a useful chemical. We have discovered that immobilized Ag nanoparticles supported on carbon exhibit enhanced Faradaic efficiency and a lower overpotential for selective reduction of CO2 to CO. These electrocatalysts were synthesized directly on the carbon support by a facile one-pot method using a cysteamine anchoring agent resulting in controlled monodispersed particle sizes. These synthesized Ag/C electrodes showed improved activities, specifically decrease of the overpotential by 300 mV at 1 mA/cm(2), and 4-fold enhanced CO Faradaic efficiency at -0.75 V vs RHE with the optimal particle size of 5 nm compared to polycrystalline Ag foil. DFT calculations enlightened that the specific interaction between Ag nanoparticle and the anchoring agents modified the catalyst surface to have a selectively higher affinity to the intermediate COOH over CO, which effectively lowers the overpotential. PMID:26447349

  15. Impedimetric Aptasensor for Ochratoxin A Determination Based on Au Nanoparticles Stabilized with Hyper-Branched Polymer

    PubMed Central

    Evtugyn, Gennady; Porfireva, Anna; Stepanova, Veronika; Kutyreva, Marianna; Gataulina, Alfiya; Ulakhovich, Nikolay; Evtugyn, Vladimir; Hianik, Tibor

    2013-01-01

    An impedimetric aptasensor for ochratoxin A (OTA) detection has been developed on the base of a gold electrode covered with a new modifier consisting of electropolymerized Neutral Red and a mixture of Au nanoparticles suspended in the dendrimeric polymer Botlorn H30®. Thiolated aptamer specific to OTA was covalently attached to Au nanoparticles via Au-S bonding. The interaction of the aptamer with OTA induced the conformational switch of the aptamer from linear to guanine quadruplex form followed by consolidation of the surface layer and an increase of the charge transfer resistance. The aptasensor makes it possible to detect from 0.1 to 100 nM of OTA (limit of detection: 0.02 nM) in the presence of at least 50 fold excess of ochratoxin B. The applicability of the aptasensor for real sample assay was confirmed by testing spiked beer samples. The recovery of 2 nM OTA was found to be 70% for light beer and 78% for dark beer. PMID:24287535

  16. Plasmon resonance-based optical trapping of single and multiple Au nanoparticles.

    SciTech Connect

    Toussaint, K. C.; Liu, M.; Pelton, M.; Pesic, J.; Guffey, M.; Guyot-Sionnest, P.; Scherer, N. F.; Univ. of Chicago

    2007-01-01

    The plasmon resonance-based optical trapping (PREBOT) method is used to achieve stable trapping of metallic nanoparticles of different shapes and composition, including Au bipyramids and Au/Ag core/shell nanorods. In all cases the longitudinal plasmon mode of these anisotropic particles is used to enhance the gradient force of an optical trap, thereby increasing the strength of the trap potential. Specifically, the trapping laser is slightly detuned to the long-wavelength side of the longitudinal plasmon resonance where the sign of the real component of the polarizability leads to an attractive gradient force. A second (femtosecond pulsed) laser is used to excite two-photon fluorescence for detection of the trapped nanoparticles. Two-photon fluorescence time trajectories are recorded for up to 20 minutes for single and multiple particles in the trap. In the latter case, a stepwise increase reflects sequential loading of single Au bipyramids. The nonlinearity of the amplitude and noise with step number are interpreted as arising from interactions or enhanced local fields among the trapped particles and fluctuations in the arrangements thereof.

  17. Electrocatalytic oxidation of small organic molecules on Pt-Au nanoparticles supported by POMAN-MWCNTs

    NASA Astrophysics Data System (ADS)

    Dong, Qi-Zhi; Li, Li-Li; Chen, Qian-Shan; Guo, Can-Cheng; Yu, Gang

    2015-08-01

    Poly ( o-methoxyaniline) and multi-wall carbon nanotube composite (POMAN-MWCNT) films were deposited onto the platinum (Pt) electrode surface by cyclic voltammetry (CV). Then, platinum and gold (Au) nano-particles were deposited by CV and the double potential deposition method to modify the composite film on the Pt electrode. The morphology of the composite film was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and its electrocatalytic activity toward methanol and formaldehyde oxidation was studied by CV and other electrochemical methods. The results demonstrated that Pt-Au/POMAN-MWCNTs obtained by the double potential deposition method had a much higher catalytic activity and better anti-poisoning property for electrooxidation of methanol and formaldehyde. The improved catalytic performance could be attributed to the uniformly distribution of duel-metal nanoparticles and the synergistic effect between Pt and Au metals. The abstract should briefly state the problem or purpose of the research, indicate the methodology used, summarize the principal findings and major conclusions.

  18. Structural patterns at all scales in a nonmetallic chiral Au133(SR)52 nanoparticle

    PubMed Central

    Zeng, Chenjie; Chen, Yuxiang; Kirschbaum, Kristin; Appavoo, Kannatassen; Sfeir, Matthew Y.; Jin, Rongchao

    2015-01-01

    Structural ordering is widely present in molecules and materials. However, the organization of molecules on the curved surface of nanoparticles is still the least understood owing to the major limitations of the current surface characterization tools. By the merits of x-ray crystallography, we reveal the structural ordering at all scales in a super robust 133–gold atom nanoparticle protected by 52 thiolate ligands, which is manifested in self-assembled hierarchical patterns starting from the metal core to the interfacial –S–Au–S– ladder-like helical “stripes” and further to the “swirls” of carbon tails. These complex surface patterns have not been observed in the smaller nanoparticles. We further demonstrate that the Au133(SR)52 nanoparticle exhibits nonmetallic features in optical and electron dynamics measurements. Our work uncovers the elegant self-organization strategies in assembling a highly robust nanoparticle and provides a conceptual advance in scientific understanding of pattern structures. PMID:26601152

  19. Study of faceted Au nanoparticle capped ZnO nanowires: antireflection, surface enhanced Raman spectroscopy and photoluminescence aspects

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Juluri, R. R.; Guha, P.; Sathyavathi, R.; Dash, Ajit; Jena, B. K.; Satyam, P. V.

    2015-02-01

    We report a single step growth process of faceted Au nanoparticles (NPs) on highly c-axis oriented ZnO nanowires (NWs) and report that a system with a lower antireflection coefficient also showed higher surface enhanced Raman spectroscopy (SERS) enhanced factors. Well-dispersed Au NPs are grown on silicon substrate using a thin film-in-air-annealing method (using 1 nm and 5 nm thick Au films on silicon and subsequent annealing in air at 800 °C) wherein enhanced oxide growth at the Au-Si interface was used to inhibit inter-diffusion to avoid Au-Si alloy formation (Au/SiOx/Si). These substrates are used to grow aligned ZnO NWs using a high temperature (≈900 °C) chemical vapour deposition method. Depending on the size and areal density of initial catalytic Au NPs, the resultant photoluminescence, reflectance characteristics, and effectiveness as SERS substrates of the faceted Au NP capped ZnO NWs coatings are systematically studied. The highly oriented and faceted Au NPs on ZnO NWs have been used as free standing SERS substrates to detect sub-micro molar crystal violet molecules with an analytical enhancement factor (AEF) of ≥104 and with high repeatability. The substrate with high-density Au-ZnO heterostructures (5 nm Au case) found to have larger AEF, very low reflectance (≈0.75%) and more green emission.

  20. Strong interactions between Au nanoparticles and TiO2 mesocrystal: highly selective photocatalytic reduction of nitroarenes

    NASA Astrophysics Data System (ADS)

    Yan, Ziran; Chen, Qifeng; Xia, Ping; Ma, Wenxin; Ren, Baosheng

    2016-01-01

    Au/TiO2 mesocrystals (Au/TMCs) were synthesized via a template-free solvothermal approach, followed with in situ photoreduction of gold chloride tetrahydrate for deposition of Au nanoparticles (AuNPs). The microstructure and components of the photocatalysts were characterized with various techniques. The results indicated that the AuNPs selectively anchored on the (101) facet of TiO2 mesocrystals (TMCs). More interestingly, the strong interactions occurred between AuNP and TMC support, due to the formation of a close Schottky heterointerface, combined with Ti-O-Au chemical bonds partially formed. Unexpectedly, it was found that the AuNPs typically aligned with their [111] direction, parallelling to the [101] direction of TMC in many cases. Au/TMCs exhibited high selectivity and activity for the transformation of nitroarenes to corresponding azoxyarenes, which could be attributed to not only the plasmonic effect of AuNPs and the unique superstructure of TMC, but also the highly strong interaction between AuNPs and TMCs through the close Schottky heterointerface.

  1. CO2-Responsive Polymer-Functionalized Au Nanoparticles for CO2 Sensor.

    PubMed

    Ma, Ying; Promthaveepong, Kittithat; Li, Nan

    2016-08-16

    Metallic nanoparticles (NPs) coated with stimuli-responsive polymers (SRPs) exhibit tunable optical properties responding to external stimuli and show promising sensing applications. We present a new CO2-responsive polymer, poly(N-(3-amidino)-aniline) (PNAAN), coated gold NPs (AuNPs) synthesized by directly reducing HAuCl4 with a CO2-responsive monomer N-(3-amidino)-aniline (NAAN). The amidine group of PNAAN can be protonated into a hydrophilic amidinium group by dissolved CO2 (dCO2). This induces the PNAAN to swell and detach from the AuNP surface, resulting in AuNP aggregation and color change. By monitoring the UV absorbance change of AuNPs, a sensitive dCO2 sensor with a linear range of 0.0132 to 0.1584 hPa and a limit of detection (LOD) of 0.0024 hPa is developed. This method shows dramatic improvement in sensitivity and convenience of sample preparation compared with the previously reported dCO2 sensor. PMID:27459645

  2. Enhancing the performance of catalytic AuPt nanoparticles in nonaqueous lithium-oxygen batteries.

    PubMed

    Lu, Meihua; Chen, Dongyun; Xu, Chaohe; Zhan, Yi; Lee, Jim Yang

    2015-08-14

    The deposition of catalytic AuPt (1 : 1) nanoparticles (NPs) into hollow mesoporous nitrogen-doped carbon microspheres (HMCMS) was found to significantly improve the effectiveness of the catalysis of oxygen reactions in nonaqueous lithium-oxygen batteries (LOBs); surpassing the performance of unsupported AuPt NPs or HMCMS in discharge and charge overpotentials (lower), specific capacity and rate performance (higher), and cycle life (longer). Specifically at a typical current density of 100 mA g(-1), a LOB with the AuPt/HMCMS cathode catalyst could provide discharge and charge capacities of 6028 and 6000 mA h g(-1) respectively and a charge-discharge voltage gap of only 1.27 V. The discharge capacity decreased by 5% when the current density was doubled, and by 23% when the current density was quintupled. The AuPt/HMCMS LOB could be cycled 75 times for a depth of discharge (DOD) of 1000 mA h g(-1) without exceeding the charge cut-off voltage of 4.4 V. These measurements indicate that the HMCMS is an outstanding catalyst support to use for increasing the effectiveness of oxygen electrocatalysts in the LOBs. PMID:26165186

  3. Monodisperse Au nanoparticles for selective electrocatalytic reduction of CO2 to CO.

    PubMed

    Zhu, Wenlei; Michalsky, Ronald; Metin, Önder; Lv, Haifeng; Guo, Shaojun; Wright, Christopher J; Sun, Xiaolian; Peterson, Andrew A; Sun, Shouheng

    2013-11-13

    We report selective electrocatalytic reduction of carbon dioxide to carbon monoxide on gold nanoparticles (NPs) in 0.5 M KHCO3 at 25 °C. Among monodisperse 4, 6, 8, and 10 nm NPs tested, the 8 nm Au NPs show the maximum Faradaic efficiency (FE) (up to 90% at -0.67 V vs reversible hydrogen electrode, RHE). Density functional theory calculations suggest that more edge sites (active for CO evolution) than corner sites (active for the competitive H2 evolution reaction) on the Au NP surface facilitates the stabilization of the reduction intermediates, such as COOH*, and the formation of CO. This mechanism is further supported by the fact that Au NPs embedded in a matrix of butyl-3-methylimidazolium hexafluorophosphate for more efficient COOH* stabilization exhibit even higher reaction activity (3 A/g mass activity) and selectivity (97% FE) at -0.52 V (vs RHE). The work demonstrates the great potentials of using monodisperse Au NPs to optimize the available reaction intermediate binding sites for efficient and selective electrocatalytic reduction of CO2 to CO.

  4. Two-dimensional ZnO ultrathin nanosheets decorated with Au nanoparticles for effective photocatalysis

    NASA Astrophysics Data System (ADS)

    Hu, Jin; You, Ning; Yu, Zhe; Zhou, Gang; Xu, Xiaoyong

    2016-08-01

    Two-dimensional (2D) materials, especially the inorganic 2D nanosheets (NSs), are of particular interest due to their unique structural and electronic properties, which are favorable for photoelectronic applications such as photocatalysis. Here, we design and fabricate the ultrathin 2D ZnO NSs decorated with Au nanoparticles (AuNPs), though molecular modelling 2D hydrothermal growth and followed by surface modification are used as an effective photocatalyst for photocatalytic organic dye degradation and hydrogen production. The ultrathin 2D nature enables ultrahigh atom ratio near surface to proliferate the active sites, and the Au plasmon plays a promoting role in the visible-light absorption and photogenerated charge separation, thus integrating the synergistic benefits to boost the redox reactions at catalyst/electrolyte interface. The AuNPs-decorated ZnO NSs yield the impressive photocatalytic activities such as the dye degradation rate constant of 7.69 × 10-2 min-1 and the hydrogen production rate of 350 μmol h-1 g-1.

  5. CO2-Responsive Polymer-Functionalized Au Nanoparticles for CO2 Sensor.

    PubMed

    Ma, Ying; Promthaveepong, Kittithat; Li, Nan

    2016-08-16

    Metallic nanoparticles (NPs) coated with stimuli-responsive polymers (SRPs) exhibit tunable optical properties responding to external stimuli and show promising sensing applications. We present a new CO2-responsive polymer, poly(N-(3-amidino)-aniline) (PNAAN), coated gold NPs (AuNPs) synthesized by directly reducing HAuCl4 with a CO2-responsive monomer N-(3-amidino)-aniline (NAAN). The amidine group of PNAAN can be protonated into a hydrophilic amidinium group by dissolved CO2 (dCO2). This induces the PNAAN to swell and detach from the AuNP surface, resulting in AuNP aggregation and color change. By monitoring the UV absorbance change of AuNPs, a sensitive dCO2 sensor with a linear range of 0.0132 to 0.1584 hPa and a limit of detection (LOD) of 0.0024 hPa is developed. This method shows dramatic improvement in sensitivity and convenience of sample preparation compared with the previously reported dCO2 sensor.

  6. Au nanoparticle/graphene nanocomposite as a platform for the sensitive detection of NADH in human urine.

    PubMed

    Govindhan, Maduraiveeran; Amiri, Mona; Chen, Aicheng

    2015-04-15

    Here we report on a facile, rapid, sensitive, selective and highly stable electrochemical sensing platform for β-nicotinamide adenine dinucleotide (NADH) based on uncapped Au nanoparticle/reduced graphene oxide (rGO) nanocomposites without the aid of any redox mediators and enzymes. The Au nanoparticle/rGO composite sensing platform was directly formed on a glassy carbon electrode through an in situ electrochemical reduction of GO and Au(3+) with a 100% usage of the precursors. The as-prepared Au nanoparticle/rGO composites demonstrated excellent direct electrocatalytic oxidation toward NADH, providing a large electrochemical active surface area as well as a favorable environment for electron transfer from NADH to the electrode via the enhanced mobility of charge carriers. The Au nanoparticle/rGO composites offered a ~2.3 times higher electrocatalytic current density with a negative shift of 112mV, in comparison to Au nanoparticles. The sensor developed in this study displayed a high sensitivity of 0.916µA/µMcm(2) and a wide linear range of from 50nM to 500µM with a limit of detection of 1.13nM (S/N=3). The interferences from the common interferents such as glutathione, glucose, ascorbic acid and quanine were negligible. The prepared sensor was further tested for the determination of NADH in human urine samples, showing the Au nanoparticle/rGO nanocomposites simultaneously formed by one-step electrochemical reduction have promising biomedical applications. PMID:25499660

  7. Impact of temperature-induced coalescence on SERS properties of Au nanoparticles deposited on GaN nano-columns

    NASA Astrophysics Data System (ADS)

    Dzięcielewski, Igor; Smalc-Koziorowska, Julita; Bańkowska, Małgorzata; Sochacki, Tomasz; Khachapuridze, Alexandr; Weyher, Jan

    2016-08-01

    Nanostructured GaN surfaces sputtered with Au provide very promising and reproducible platforms for surface enhanced Raman scattering (SERS). The enhancement factor (EF) in SERS is expected to depend strongly on the local metal (Au) surface structure (size, distribution and morphology). Herein we show how temperature-induced coalescence followed by recrystallization of Au on GaN nano-columns occurs well below the melting point of gold. This process is reflected in SEM, TEM images and SERS spectra of Au/GaN - bound p-mercaptobenzoic acid (4-MBA), a model Raman scatterer. SERS signals of 4-MBA bound to Au/GaN reach minimum for platforms exposed to t = 350 °C before regaining the intensity when annealed in the range of 450-900 °C. The results have been discussed in the light of the nature of SERS active sites - so called "hot spots" and structure of Au nanoparticles.

  8. Double Detection of Mycotoxins Based on SERS Labels Embedded Ag@Au Core-Shell Nanoparticles.

    PubMed

    Zhao, Yuan; Yang, Yaxin; Luo, Yaodong; Yang, Xuan; Li, Manli; Song, Qijun

    2015-10-01

    A sensitive surface-enhanced Raman scattering (SERS) signal dependent double detection of mycotoxins is achieved for the first time, without the aid of nucleic acid amplification strategies. SERS labels embedded Ag@Au core-shell (CS) nanoparticles (NPs) as novel SERS tags are successfully prepared through a galvanic replacement-free deposition. SERS tags produce stable and quantitative SERS signal, emerging from the plasmonic coupling at the junction of Ag core and Au shell. SERS tags engineered Raman aptasensors are developed for the double detection of ochratoxin A (OTA) and aflatoxin B1 (AFB1) in maize meal. The limits of detection (LODs) are as low as 0.006 ng/mL for OTA and 0.03 ng/mL for AFB1. The developed protocol can be extended to a large set of different SERS tags for the sensitive detection of multiple targets that possess different lengths of aptamers.

  9. [Au5Mes5]: improved gram-scale synthesis and its use as a convenient precursor for halide-free supported gold nanoparticles.

    PubMed

    Siddiqi, G; Mougel, V; Copéret, C

    2015-08-28

    A simple one-step and gram-scale synthesis of [Au5Mes5] from AuCl3 was developed, and this molecular precursor was used to generate Au nanoparticles on SiO2 and Al2O3. While [Au5Mes5] does not react with surface silanols and is only physisorbed, its incipient wetness impregnation followed by H2 treatment leads to a narrow size distribution of 1.4 nm Au nanoparticles. In contrast, [Au5Mes5] reacts with partially dehydroxylated Al2O3 to directly yield 1 nm Au nanoparticles along with adsorbed species. A subsequent treatment under hydrogen leads to a narrow size distribution of smaller 0.8 nm Au particles. PMID:26200206

  10. Glucose oxidase/colloidal gold nanoparticles immobilized in Nafion film on glassy carbon electrode: Direct electron transfer and electrocatalysis.

    PubMed

    Zhao, Shuang; Zhang, Kai; Bai, Yu; Yang, Weiwei; Sun, Changqing

    2006-10-01

    The direct electron transfer of glucose oxidase (GOD) was achieved based on the immobilization of GOD/colloidal gold nanoparticles on a glassy carbon electrode by a Nafion film. The immobilized GOD displayed a pair of well-defined and nearly reversible redox peaks with a formal potential (Eo ') of -0.434 V in 0.1 M pH 7.0 phosphate buffer solution and the response showed a surface-controlled electrode process. The dependence of Eo ' on solution pH indicated that the direct electron transfer reaction of GOD was a two-electron-transfer coupled with a two-proton-transfer reaction process. The experimental results also demonstrated that the immobilized GOD retained its electrocatalytic activity for the oxidation of glucose. So the resulting modified electrode can be used as a biosensor for detecting glucose. PMID:16556513

  11. Highly narrow nanogap-containing Au@Au core-shell SERS nanoparticles: size-dependent Raman enhancement and applications in cancer cell imaging.

    PubMed

    Hu, Chongya; Shen, Jianlei; Yan, Juan; Zhong, Jian; Qin, Weiwei; Liu, Rui; Aldalbahi, Ali; Zuo, Xiaolei; Song, Shiping; Fan, Chunhai; He, Dannong

    2016-01-28

    Cellular imaging technologies employing metallic surface-enhanced Raman scattering (SERS) tags have gained much interest toward clinical diagnostics, but they are still suffering from poor controlled distribution of hot spots and reproducibility of SERS signals. Here, we report the fabrication and characterization of high narrow nanogap-containing Au@Au core-shell SERS nanoparticles (GCNPs) for the identification and imaging of proteins overexpressed on the surface of cancer cells. First, plasmonic nanostructures are made of gold nanoparticles (∼15 nm) coated with gold shells, between which a highly narrow and uniform nanogap (∼1.1 nm) is formed owing to polyA anchored on the Au cores. The well controlled distribution of Raman reporter molecules, such as 4,4'-dipyridyl (44DP) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), are readily encoded in the nanogap and can generate strong, reproducible SERS signals. In addition, we have investigated the size-dependent SERS activity of GCNPs and found that with the same laser wavelength, the Raman enhancement discriminated between particle sizes. The maximum Raman enhancement was achieved at a certain threshold of particle size (∼76 nm). High narrow nanogap-containing Au@Au core-shell SERS tags (GCTs) were prepared via the functionalization of hyaluronic acid (HA) on GCNPs, which recognized the CD44 receptor, a tumor-associated surface biomarker. And it was shown that GCTs have a good targeting ability to tumour cells and promising prospects for multiplex biomarker detection. PMID:26701141

  12. Immobilization of carboxypeptidase from Sulfolobus solfataricus on magnetic nanoparticles improves enzyme stability and functionality in organic media

    PubMed Central

    2014-01-01

    Background Superparamagnetic iron oxide nanoparticles (MNP) offer several advantages for applications in biomedical and biotechnological research. In particular, MNP-based immobilization of enzymes allows high surface-to-volume ratio, good dispersibility, easy separation of enzymes from the reaction mixture, and reuse by applying an external magnetic field. In a biotechnological perspective, extremophilic enzymes hold great promise as they often can be used under non-conventional harsh conditions, which may result in substrate transformations that are not achievable with normal enzymes. This prompted us to investigate the effect of MNP bioconjugation on the catalytic properties of a thermostable carboxypeptidase from the hyperthermophilic archaeon Sulfolobus solfataricus (CPSso), which exhibits catalytic properties that are useful in synthetic processes. Results CPSso was immobilized onto silica-coated iron oxide nanoparticles via NiNTA-His tag site-directed conjugation. Following the immobilization, CPSso acquired distinctly higher long-term stability at room temperature compared to the free native enzyme, which, in contrast, underwent extensive inactivation after 72 h incubation, thus suggesting a potential utilization of this enzyme under low energy consumption. Moreover, CPSso conjugation also resulted in a significantly higher stability in organic solvents at 40°C, which made it possible to synthesize N-blocked amino acids in remarkably higher yields compared to those of free enzyme. Conclusions The nanobioconjugate of CPSso immobilized on silica-coated magnetic nanoparticles exhibited enhanced stability in aqueous media at room temperature as well as in different organic solvents. The improved stability in ethanol paves the way to possible applications of immobilized CPSso, in particular as a biocatalyst for the synthesis of N-blocked amino acids. Another potential application might be amino acid racemate resolution, a critical and expensive step in

  13. Site-specific immobilization of a (His)6-tagged acetylcholinesterase on nickel nanoparticles for highly sensitive toxicity biosensors.

    PubMed

    Ganesana, Mallikarjunarao; Istarnboulie, Georges; Marty, Jean-Louis; Noguer, Thierry; Andreescu, Silvana

    2011-12-15

    This paper reports site-specific affinity immobilization of (His)6-tagged acetylcholinesterase (AChE) onto Ni/NiO nanoparticles for the development of an electrochemical screen-printed biosensor for the detection of organophosphate pesticides. The method is based on the specific affinity binding of the His-tagged enzyme to oxidized nickel nanoparticle surfaces in the absence of metal chelators. This approach allows stable and oriented attachment of the enzyme onto the oxidized nickel through the external His residue in one-step procedure, allowing for fast and sensitive detection of paraoxon in the concentration range from 10(-8) to 10(-13) M. A detection limit of 10(-12) M for paraoxon was obtained after 20 min incubation. This method can be used as a generic approach for the immobilization of other His-tagged enzymes for the development of biosensors. PMID:21937214

  14. Synthesis and characterization of Au102(p-MBA)44 nanoparticles.

    PubMed

    Levi-Kalisman, Yael; Jadzinsky, Pablo D; Kalisman, Nir; Tsunoyama, Hironori; Tsukuda, Tatsuya; Bushnell, David A; Kornberg, Roger D

    2011-03-01

    The synthesis of Au(102)(p-MBA)(44) nanoparticles on a preparative scale in high yield is described. Various analytical methods are shown to give results consistent with the composition and known structure of the particles, showing the preparation is essentially homogeneous, and attesting to the validity of the methods as well. Derivatization of the particles with proteins and DNA is demonstrated, and conditions are described for imaging individual particles by cryo-EM at low electron dose, close to focus, conditions optimal for recording high-resolution details.

  15. Control of shell thickness in silica-coating of Au nanoparticles and their X-ray imaging properties.

    PubMed

    Kobayashi, Yoshio; Inose, Hiromitsu; Nakagawa, Tomohiko; Gonda, Kohsuke; Takeda, Motohiro; Ohuchi, Noriaki; Kasuya, Atsuo

    2011-06-15

    This paper describes a performance of precise control of shell thickness in silica-coating of Au nanoparticles based on a sol-gel process, and an investigation into X-ray imaging properties for the silica-coated Au (Au/SiO(2)) particles. The Au nanoparticles with a size of 16.9±1.2 nm prepared through a conventional citrate reduction method were used as core particles. The Au nanoparticles were silica-coated with a sol-gel reaction using tetraethylorthosilicate (TEOS) as a silica source, sodium hydroxide (NaOH) as a catalyst, and (3-aminopropyl) trimethoxysilane (APMS) as a silane coupling agent. An increase in TEOS concentration resulted in an increase in shell thickness. Under certain concentrations of Au, H(2)O, NaOH, and APMS, the Au/SiO(2) particles with silica shell thickness of 6.0-61.0 nm were produced with varying TEOS concentration. Absorption peak wavelength of surface plasmon resonance of the Au/SiO(2) colloid solution depended on silica shell thickness, which agreed approximately with the predictions by Mie theory. The as-prepared colloid solution could be concentrated up to an Au concentration of 0.19 M with salting-out and centrifugation. The concentrated colloid solution showed an X-ray image with high contrast, and a computed tomography value for the colloid solution with an Au concentration of 0.129 M was achieved 1329.7±52.7 HU. PMID:21458820

  16. Photocatalytic activity of erbium-doped TiO{sub 2} nanoparticles immobilized in macro-porous silica films

    SciTech Connect

    Castaneda-Contreras, J.; Maranon-Ruiz, V.F.; Chiu-Zarate, R.; Perez-Ladron de Guevara, H.; Rodriguez, R.; Michel-Uribe, C.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Erbium-doped TiO{sub 2} nanoparticles were immobilized on macro-porous silica films. Black-Right-Pointing-Pointer The films were obtained by a phase separation process. Black-Right-Pointing-Pointer The samples exhibited photo-catalytic activity under visible light. Black-Right-Pointing-Pointer The sensitization of TiO{sub 2} was attributed to a red shift in the TiO{sub 2} band-gap. -- Abstract: A macro-porous silica film served as mechanical support to immobilize TiO{sub 2} nanoparticles, which were doped with erbium. The films and the nanoparticles were prepared by sol-gel route. The nanoparticles exhibited photocatalytic activity under visible light. We obtained a degradation rate of methylene blue that followed first order kinetics. The sensitization of the nanoparticles to visible light was attributed to a red shift in the band-gap of the TiO{sub 2} due to the addition of erbium ions.

  17. Electronic structure of thiolate-covered gold nanoparticles: Au102(MBA)44.

    PubMed

    Li, Yan; Galli, Giulia; Gygi, François

    2008-09-23

    We present first principles, density functional theory (DFT) calculations of the structural and electronic properties of thiolate-protected gold nanoparticles [Au(102)(MBA)(44) ] that have been recently crystallized and measured by X-ray diffraction. Our calculations yield structural properties in very good agreement with experiment and reveal the impact of thiolate adsorption on both the surface geometry and the electronic structure of the gold core; in particular, within DFT we observe the emergence of an energy gap of about 0.5 eV, upon MBA adsorption. Using a localized orbital analysis, we characterize the electron distribution in the nanoparticle and provide insight into the bonding of thiolates on curved gold surfaces.

  18. An experimental study of thermal diffusivity of Au nanoparticles: effects of concentration particle size

    NASA Astrophysics Data System (ADS)

    Shahriari, Esmaeil; Moradi, Mohammad; Raeisi, Morteza

    2016-06-01

    In this article, Au nanoparticles in polyvinylpyrrolidone (PVP) solution were prepared by gamma radiation at different concentrations. The solutions were irradiated at doses of 50 kGy for making different sizes. The average sizes of particle in the prepared samples were measured using the nanophox machine. A dual-beam mode-mismatched thermal lens (TL) method was used to investigate the effect of thermal diffusivity of samples. The TL measurement was carried out using a green diode laser (wavelength 532 nm, 60 mW) and a He-Ne laser (wavelength 632.8 nm, 0.5 mW) for excitation source and probe beam, respectively. The results showed that the thermal diffusivity of samples enhances with the growth of particle size and density of solutions. This increment can be attributed to phonon scattering at interface of particles-liquid and contact between the nanoparticles and surrounded liquid.

  19. Configuration of microbially synthesized Pd-Au nanoparticles studied by STEM-based techniques

    NASA Astrophysics Data System (ADS)

    Tran, D. T.; Jones, I. P.; Preece, J. A.; Johnston, R. L.; Deplanche, K.; Macaskie, L. E.

    2012-02-01

    Bimetallic Pd-Au particles synthesized using Desulfovibrio desulfuricans bacteria are characterized using scanning transmission electron microscopy (STEM) with a high-angle annular dark field (HAADF) detector combined with energy dispersive x-ray (EDX) silicon drift detector (SDD) elemental mapping and plasmon electron energy-loss spectroscopy (EELS). When combined with EDX, theoretical considerations or EELS, the atomic-number contrast (Z-contrast) provided by HAADF-STEM is effective in characterizing the compositional configuration of the bimetallic nanoparticles. Homogeneous mixing and complex segregations have been found for different particles in this work. The EELS study has also found different behaviours corresponding to surface plasmon resonances in different regions of a single particle due to its heterogeneity and anisotropy. HAADF-STEM tomography has been performed to obtain three-dimensional (3D) visualization of the nanoparticles.

  20. Au and Pt nanoparticle supported catalysts tailored for H-2 production: From models to powder catalysts

    DOE PAGES

    T. D. Nguyen-Phan; Baber, A. E.; Rodriguez, J. A.; Senanayake, S. D.

    2015-12-10

    The use of metal nanoparticles (NPs), including Au and Pt, supported over oxides has been pivotal, and is ever increasing in enabling catalytic reactions which target the production of hydrogen. We review here the most recent works pertaining to the fundamental understanding of the structure, morphology, growth, characterization, and intrinsic phenomenological properties of Au– and Pt– based catalysts that influence the reactivity and selectivity to target hydrogen production. We draw on surface science and theoretical methods of model and powder catalysts using high resolution imaging, spectroscopy, scattering experiments, and theoretical studies. Based on these insights we identify key aspects ofmore » studies of supported metal nanoparticle (NP) catalysts for several reactions. The main focus of this review is on the intersection of catalytic chemistry related to the water-gas shift (WGS), oxygenate steam reforming (OSR), and solarassisted reactions (SAR).« less

  1. Critical island-size, stability, and morphology of 2D colloidal Au nanoparticle islands.

    PubMed

    Hubartt, Bradley C; Amar, Jacques G

    2015-01-14

    The critical island-size, stability, and morphology of 2D colloidal Au nanoparticle islands formed during drop-drying are studied using an empirical potential which takes into account core-core, ligand-ligand, and ligand-solvent interactions. Good agreement with experiment is obtained for the dependence of the critical island-size on nanoparticle diameter. Our results for the critical length-scale for smoothing via edge-diffusion are also consistent with the limited facet size and island-relaxation observed in experiments. In addition, the relatively high rate of monomer diffusion on an island as well as the low barrier for interlayer diffusion are consistent with experimental observations that second-layer growth does not occur until after the first layer is complete.

  2. Au and Pt nanoparticle supported catalysts tailored for H-2 production: From models to powder catalysts

    SciTech Connect

    T. D. Nguyen-Phan; Baber, A. E.; Rodriguez, J. A.; Senanayake, S. D.

    2015-12-10

    The use of metal nanoparticles (NPs), including Au and Pt, supported over oxides has been pivotal, and is ever increasing in enabling catalytic reactions which target the production of hydrogen. We review here the most recent works pertaining to the fundamental understanding of the structure, morphology, growth, characterization, and intrinsic phenomenological properties of Au– and Pt– based catalysts that influence the reactivity and selectivity to target hydrogen production. We draw on surface science and theoretical methods of model and powder catalysts using high resolution imaging, spectroscopy, scattering experiments, and theoretical studies. Based on these insights we identify key aspects of studies of supported metal nanoparticle (NP) catalysts for several reactions. The main focus of this review is on the intersection of catalytic chemistry related to the water-gas shift (WGS), oxygenate steam reforming (OSR), and solarassisted reactions (SAR).

  3. Micro-optical coherence tomography tracking of magnetic gene transfection via Au-Fe3O4 dumbbell nanoparticles

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Liu, Xinyu; Wei, Chao; Xu, Zhichuan J.; Sim, Stanley Siong Wei; Liu, Linbo; Xu, Chenjie

    2015-10-01

    Heterogeneous Au-Fe3O4 dumbbell nanoparticles (NPs) are composed of Au NPs and Fe3O4 NPs that bring in optical and magnetic properties respectively. This article reports the engineering of Au-Fe3O4 NPs as gene carriers for magnetic gene transfection as well as contrast agents for micro-optical coherence tomography (μOCT). As a proof-of-concept, Au-Fe3O4 NPs are used to deliver the green fluorescent protein to HEK 293T cells and their entrance into the cells is monitored through μOCT.Heterogeneous Au-Fe3O4 dumbbell nanoparticles (NPs) are composed of Au NPs and Fe3O4 NPs that bring in optical and magnetic properties respectively. This article reports the engineering of Au-Fe3O4 NPs as gene carriers for magnetic gene transfection as well as contrast agents for micro-optical coherence tomography (μOCT). As a proof-of-concept, Au-Fe3O4 NPs are used to deliver the green fluorescent protein to HEK 293T cells and their entrance into the cells is monitored through μOCT. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05459a

  4. Novel Au/La-SrTiO3 microspheres: superimposed effect of gold nanoparticles and lanthanum doping in photocatalysis.

    PubMed

    Wang, Guannan; Wang, Pei; Luo, He-Kuan; Hor, T S Andy

    2014-07-01

    Novel multielement Au/La-SrTiO(3) microspheres were synthesized by a solvothermal method using monodisperse gold and La-SrTiO(3) nanocrystals as building blocks. The porous Au/La-SrTiO(3) microspheres had a large surface area of 94.6 m(2)  g(-1). The stable confined Au nanoparticles demonstrated strong surface plasmon resonance effect, leading to enhanced absorption in a broad UV/Vis/NIR range. Doping of rare-earth metal La also broadened the absorption band to the visible region. Both the conduction and valence bands of Au/La-SrTiO(3) microspheres thus show favorable potential for proton reduction under visible light. The superimposed effect of Au nanoparticles and La doping in Au/La-SrTiO(3) microspheres led to high photocurrent density in photoelectrochemical water splitting and good photocatalytic activity in photodegradation of rhodamine B. The photocatalytic activities are in the order of the following: Au/La-SrTiO(3) microspheres>Au/SrTiO(3) microspheres>La-SrTiO(3) microspheres>SrTiO(3) microspheres.

  5. Treatment of landfill leachate using immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO₂ nanoparticles.

    PubMed

    Hu, Liang; Zeng, Guangming; Chen, Guiqiu; Dong, Haoran; Liu, Yutang; Wan, Jia; Chen, Anwei; Guo, Zhi; Yan, Ming; Wu, Haipeng; Yu, Zhigang

    2016-01-15

    This study investigated the performance of immobilized Phanerochaete chrysosporium loaded with nitrogen-doped TiO2 nanoparticles in the treatment of raw landfill leachate with a very low biodegradability ratio (BOD5/COD) of 0.09. The effects of various operating parameters, such as initial chemical oxygen demand (COD) concentration, pH, temperature, and biosorbent dosage, were evaluated with respect to the removal efficiency of total organic carbon (TOC) and ammonia nitrogen (NH3-N). For the immobilized biosorbents, an optimum pH of 6.0 for TOC and 7.0 for NH3-N were found suitable for TOC and NH3-N removal at temperature of 37°C, respectively. The most superior removal efficiencies of TOC and NH3-N of landfill leachate were over 75% and 74% in 72 h at an initial COD concentration of 200 mg L(-1), respectively. In addition, heavy metals were partly removed by the immobilized biosorbents during the process of landfill leachate treatment. The species and mass percentage of organic compounds in landfill leachate after the treatment were found to have considerably declined according to the gas chromatography coupled with mass spectrometry (GC-MS) system. These results indicate that the immobilized P. chrysosporium loaded with nitrogen-doped TiO2 nanoparticles could be a convenient and efficient method for the treatment of landfill leachate. PMID:26355412

  6. Propitious Immobilization of Gold Nanoparticles on Poly(dimethylsiloxane) Substrate for Local Surface Plasmon Resonance Based Biosensor

    NASA Astrophysics Data System (ADS)

    Trung, Nguyen Ba; Yoshikawa, Hiroyuki; Tamiya, Eiichi; Viet, Pham Hung; Takamura, Yuzuru; Ashahi, Tsuyoshi

    2012-03-01

    In this work, a simple method for fabricating gold nanoparticle (AuNP) layer on a poly(dimethylsiloxane) (PDMS) substrate based on electrostatic deposition of AuNP colloid onto a chemically-modified PDMS surface using 3-aminopropyltriethoxysilane (γ-APTES) was developed. AuNPs of 100 nm diameter were successfully dispersed and deposited onto the chemically-modified PDMS surface. The morphology and optical property of the AuNP layer were examined by atomic force microscopy (AFM) and UV-visible absorption spectroscopy, respectively. It was found that the prepared AuNP layer on PDMS could work as a localized surface plasma resonance (LSPR) sensor. The sensing characteristics were examined by changing the refractive index of solution surrounding the AuNP and antigen-antibody events on the AuNP surface. Changes in absorbance intensity and peak wavelength shift of the LSPR band were both clearly observed. The developed technique can hopefully expand the applications of PDMS for not only micro channel fabrication, but also sensing construction for easier and simpler preparation of microfluidic biosensors, which were then applied for immunoassays and other biochemical analyses.

  7. Tailoring the electrical properties of MoS2 field effect transistors by depositing Au nanoparticles and alkanethiol molecules.

    PubMed

    Cho, Kyungjune; Jeong, Hyunhak; Kim, Tae-Young; Pak, Jinsu; Kim, Jae-Keun; Choi, Barbara Yuri; Lee, Takhee

    2016-05-11

    We fabricated and characterized MoS2 field effect transistors. First, we measured the electrical properties of MoS2 field effect transistors (FETs) that were made with mechanically exfoliated MoS2 flakes. Then, we deposited Au nanoparticles on the MoS2 channel and measured the electrical properties. We observed whether the source-drain current increased or decreased after the Au particles were deposited. The deposited Au particles either formed an extra current path and increased the current or behaved as charge-withdrawing sites and decreased the current. Next, we deposited alkanethiol molecules on the Au particles to reduce the work function of the Au. Alkanethiol molecules are known to form a self-assembled monolayer on the Au surface, and the electric dipole moment of the molecules causes the work function of the Au to decrease. Au particles can capture electrons from the MoS2 channel due to their high work function. However, the decreased work function of the Au particles subjected to alkanethiol treatment could cause captured electrons to be released from the Au particles to MoS2. Therefore, the current increased after alkanethiol treatment. This study may provide useful methods to utilize surface treatments with particles and molecules to tailor the electrical properties of MoS2-based FETs.

  8. Use of aerosol route to fabricate positively charged Au/Fe3O4 Janus nanoparticles as multifunctional nanoplatforms

    PubMed Central

    Byeon, Jeong Hoon; Park, Jae Hong

    2016-01-01

    Gold (Au)-decorated iron oxide (Fe3O4), Au/Fe3O4, Janus nanoparticles were fabricated via the continuous route for aerosol Au incorporation with Fe3O4 domains synthesized in an aqueous medium as multifunctional nanoplatforms. The fabricated nanoparticles were subsequently exposed to 185-nm UV light to generate positive charges on Au surfaces, and their activities were tested in computed tomography (CT) and magnetic resonance (MR) imaging, gene-delivery and photothermal therapy. No additional polymeric coatings of the Janus particles also had a unique ability to suppress inflammatory responses in macrophages challenged with lipopolysaccharide, which may be due to the absence of amine groups. PMID:27713519

  9. The deposition of Au-Pt core-shell nanoparticles on reduced graphene oxide and their catalytic activity

    NASA Astrophysics Data System (ADS)

    Cui, Xiu; Wu, Shengnan; Jungwirth, Scott; Chen, Zhibing; Wang, Zhenghua; Wang, Lun; Li, Yongxin

    2013-07-01

    Au-Pt core-shell nanoparticles have been synthesized on a reduced graphene oxide (RGO) surface by an under-potential deposition (UPD) redox replacement technique, which involves redox replacement of a copper UPD monolayer by {{PtCl}}_{4}^{2-} that could be reduced and deposited simultaneously. Scanning electron microscopy (SEM) and electrochemical methods have been used to characterize the graphene decorated with Au-Pt core-shell nanoparticles. The electrochemical experiments show that the materials exhibit excellent catalytic activity towards the oxygen reduction reaction and the methanol oxidation reaction. It is believed that the high-performance of this new catalyst is due to the ultrathin Pt shell on the Au nanoparticles surface and the oxygen-containing functional groups on the RGO surface.

  10. Horseradish peroxidase-immobilized magnetic mesoporous silica nanoparticles as a potential candidate to eliminate intracellular reactive oxygen species.

    PubMed

    Shen, Yajing; Zhang, Ye; Zhang, Xiang; Zhou, Xiuhong; Teng, Xiyao; Yan, Manqing; Bi, Hong

    2015-02-21

    Horseradish peroxidase-immobilized magnetic mesoporous silica nanoparticles (MMSNs-HRP) have been synthesized by a NHS/EDC coupling between the amino groups of horseradish peroxidase (HRP) and the carboxyl groups on the MMSNs surface. It is found that the immobilized HRP on MMSNs still retain high activity and the MMSNs-HRP can eliminate the reactive oxygen species (ROS) in Chinese hamster ovary (CHO) cells induced by the addition of H2O2 aqueous solution. Further, the fluorescent MMSN-HRP-CD nanoparticles have been prepared by attaching biocompatible, fluorescent carbon dots (CDs) to MMSNs-HRP. We have also investigated the effect of an applied magnetic field on cellular uptake of MMSNs-HRP-CDs and found that the internalization of MMSNs-HRP-CDs by CHO cells could be enhanced within 2 hours under the magnetic field. This work provides us with a novel and efficient method to eliminate ROS in living cells by using HRP-immobilized nanoparticles. PMID:25587910

  11. Metallic/bimetallic magnetic nanoparticle functionalization for immobilization of α-amylase for enhanced reusability in bio-catalytic processes.

    PubMed

    Singh, Vishal; Rakshit, Kanak; Rathee, Shweta; Angmo, Stanzin; Kaushal, Shimayali; Garg, Pankaj; Chung, Jong Hoon; Sandhir, Rajat; Sangwan, Rajender S; Singhal, Nitin

    2016-08-01

    Novel magnetic nanoparticles coated with silica and gold were synthesized for immobilization of α-amylase enzyme and characterized with Fourier transform infrared spectroscopy, transmission electron microscopy. Effect of various limiting factors such as substrate concentration, temperature, and pH on the catalytic activity of enzyme was investigated. The optimum pH for free and immobilized enzyme was found unaffected (7.0), whereas optimum temperature for the enzyme activity was increased from 60°C for free enzyme to 80°C for immobilized counterpart. The gains in catalytic attributes concomitant to ease of recovery of the enzyme reflect the potential of the approach and the product to be useful for the enzymatic bioprocessing. The Michaelis-Menten constant (Km) value of the immobilized α-amylase was higher than that of free α-amylase, whereas maximum velocity (Vmax), and turn over number (Kcat), values were almost similar. Immobilized α-amylase maintained 60% of the enzyme activity even after recycling ten times. PMID:27176673

  12. Immobilization of β-galactosidase from Lactobacillus plantarum HF571129 on ZnO nanoparticles: characterization and lactose hydrolysis.

    PubMed

    Selvarajan, E; Mohanasrinivasan, V; Subathra Devi, C; George Priya Doss, C

    2015-09-01

    β-Galactosidase from Lactobacillus plantarum HF571129 was immobilized on zinc oxide nanoparticles (ZnO NPs) using adsorption and cross-linking technique. Immobilized β-galactosidase showed broad-spectrum pH optima at pH 5-7.5 and temperature 50-60 °C. Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) showed that β-galactosidase successfully immobilized onto supports. Due to the limited diffusion of high molecular weight substrate, K m of immobilized enzyme slightly increased from 6.64 to 10.22 mM, while V max increased from 147.5 to 192.4 µmol min(-1) mg(-1) as compared to the soluble enzyme. The cross-linked adsorbed enzyme retained 90 % activity after 1-month storage, while the native enzyme showed only 74 % activity under similar incubation conditions. The cross-linked β-galactosidase showed activity until the seventh cycle and maintained 88.02 % activity even after the third cycle. The activation energy of thermal deactivation from immobilized biocatalyst was 24.33 kcal/mol with a half-life of 130.78 min at 35 °C. The rate of lactose hydrolysis for batch and packed bed was found to be 0.023 and 0.04 min(-1).

  13. Time-dependent growth of crystalline Au0-nanoparticles in cyanobacteria as self-reproducing bioreactors: 2. Anabaena cylindrica

    PubMed Central

    Rösken, Liz M; Cappel, Felix; Körsten, Susanne; Fischer, Christian B; Schönleber, Andreas; van Smaalen, Sander; Geimer, Stefan; Beresko, Christian; Ankerhold, Georg

    2016-01-01

    Summary Microbial biosynthesis of metal nanoparticles as needed in catalysis has shown its theoretical ability as an extremely environmentally friendly production method in the last few years, even though the separation of the nanoparticles is challenging. Biosynthesis, summing up biosorption and bioreduction of diluted metal ions to zero valent metals, is especially ecofriendly, when the bioreactor itself is harmless and needs no further harmful reagents. The cyanobacterium Anabaena cylindrica (SAG 1403.2) is able to form crystalline Au0-nanoparticles from Au3+ ions and does not release toxic anatoxin-a. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and laser-induced breakdown spectroscopy (LIBS) are applied to monitor the time-dependent development of gold nanoparticles for up to 40 hours. Some vegetative cells (VC) are filled with nanoparticles within minutes, while the extracellular polymeric substances (EPS) of vegetative cells and the heterocyst polysaccharide layer (HEP) are the regions, where the first nanoparticles are detected on most other cells. The uptake of gold starts immediately after incubation and within four hours the average size remains constant around 10 nm. Analyzing the TEM images with an image processing program reveals a wide distribution for the diameter of the nanoparticles at all times and in all regions of the cyanobacteria. Finally, the nanoparticle concentration in vegetative cells of Anabaena cylindrica is about 50% higher than in heterocysts (HC). These nanoparticles are found to be located along the thylakoid membranes. PMID:27335727

  14. Time-dependent growth of crystalline Au(0)-nanoparticles in cyanobacteria as self-reproducing bioreactors: 2. Anabaena cylindrica.

    PubMed

    Rösken, Liz M; Cappel, Felix; Körsten, Susanne; Fischer, Christian B; Schönleber, Andreas; van Smaalen, Sander; Geimer, Stefan; Beresko, Christian; Ankerhold, Georg; Wehner, Stefan

    2016-01-01

    Microbial biosynthesis of metal nanoparticles as needed in catalysis has shown its theoretical ability as an extremely environmentally friendly production method in the last few years, even though the separation of the nanoparticles is challenging. Biosynthesis, summing up biosorption and bioreduction of diluted metal ions to zero valent metals, is especially ecofriendly, when the bioreactor itself is harmless and needs no further harmful reagents. The cyanobacterium Anabaena cylindrica (SAG 1403.2) is able to form crystalline Au(0)-nanoparticles from Au(3+) ions and does not release toxic anatoxin-a. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and laser-induced breakdown spectroscopy (LIBS) are applied to monitor the time-dependent development of gold nanoparticles for up to 40 hours. Some vegetative cells (VC) are filled with nanoparticles within minutes, while the extracellular polymeric substances (EPS) of vegetative cells and the heterocyst polysaccharide layer (HEP) are the regions, where the first nanoparticles are detected on most other cells. The uptake of gold starts immediately after incubation and within four hours the average size remains constant around 10 nm. Analyzing the TEM images with an image processing program reveals a wide distribution for the diameter of the nanoparticles at all times and in all regions of the cyanobacteria. Finally, the nanoparticle concentration in vegetative cells of Anabaena cylindrica is about 50% higher than in heterocysts (HC). These nanoparticles are found to be located along the thylakoid membranes. PMID:27335727

  15. Phosphate removal and recovery from water using nanocomposite of immobilized magnetite nanoparticles on cationic polymer.

    PubMed

    Abo Markeb, Ahmad; Alonso, Amanda; Dorado, Antonio David; Sánchez, Antoni; Font, Xavier

    2016-08-01

    A novel nanocomposite (NC) based on magnetite nanoparticles (Fe3O4-NPs) immobilized on the surface of a cationic exchange polymer, C100, using a modification of the co-precipitation method was developed to obtain magnetic NCs for phosphate removal and recovery from water. High-resolution transmission electron microscopy-energy-dispersive spectroscopy, scanning electron microscopy , X-ray diffraction, and inductively coupled plasma optical emission spectrometry were used to characterize the NCs. Continuous adsorption process by the so-called breakthrough curves was used to determine the adsorption capacity of the Fe3O4-based NC. The adsorption capacity conditions were studied under different conditions (pH, phosphate concentration, and concentration of nanoparticles). The optimum concentration of iron in the NC for phosphate removal was 23.59 mgFe/gNC. The sorption isotherms of this material were performed at pH 5 and 7. Taking into account the real application of this novel material in real water, the experiments were performed at pH 7, achieving an adsorption capacity higher than 4.9 mgPO4-P/gNC. Moreover, Freundlich, Langmuir, and a combination of them fit the experimental data and were used for interpreting the influence of pH on the sorption and the adsorption mechanism for this novel material. Furthermore, regeneration and reusability of the NC were tested, obtaining 97.5% recovery of phosphate for the first cycle, and at least seven cycles of adsorption-desorption were carried out with more than 40% of recovery. Thus, this work described a novel magnetic nanoadsorbent with properties for phosphate recovery in wastewater. PMID:26849360

  16. Volcano-like behavior of Au-Pd core-shell nanoparticles in the selective oxidation of alcohols.

    PubMed

    Silva, Tiago A G; Teixeira-Neto, Erico; López, Núria; Rossi, Liane M

    2014-01-01

    Gold-palladium (AuPd) nanoparticles have shown significantly enhanced activity relative to monometallic Au and Pd catalysts. Knowledge of composition and metal domain distributions is crucial to understanding activity and selectivity, but these parameters are difficult to ascertain in catalytic experiments that have primarily been devoted to equimolar nanoparticles. Here, we report AuPd nanoparticles of varying Au:Pd molar ratios that were prepared by a seed growth method. The selective oxidation of benzyl alcohol was used as a model reaction to study catalytic activity and selectivity changes that occurred after varying the composition of Pd in bimetallic catalysts. We observed a remarkable increase in catalytic conversion when using a 10:1 Au:Pd molar ratio. This composition corresponds to the amount of Pd necessary to cover the existing Au cores with a monolayer of Pd as a full-shell cluster. The key to increased catalytic activity derives from the balance between the number of active sites and the ease of product desorption. According to density functional theory calculations, both parameters are extremely sensitive to the Pd content resulting in the volcano-like activity observed.

  17. Fabrication and bioproperties of raspberry-type hybrid nanoparticles of Au-thioethyl pendant ligand@chitosan.

    PubMed

    Huang, Bin; Tong, Fengyu; Chen, Yeting; Zhu, Qinshu; Xing, Lei; Lv, Mengqi; Mao, Chun; Lu, Zuhong; Shen, Jian

    2013-01-01

    Synthesis of nanoparticles with desired size/morphology has enormous importance, especially in the compelling field of nanotechnology. In this case, a novel kind of raspberry-type hybrid nanoparticles was prepared by hybridization of chitosan (CS) with thioethyl pendant ligand (TPL) modified Au nanoparticles (Au-TPL@CS NPs). Such method was based on ionic gelation using sodium tripolyphosphate as a counterion. The blood compatibility of Au-TPL@CS NPs was characterized by coagulation tests, plasma recalcification time, hemolysis assay, morphological changes of red blood cells (RBCs) and complement activation in vitro. The results showed that Au-TPL@CS NPs exhibited good blood compatibility. The possible underlying mechanism was also present. Finally, the direct electron transfer reactivity of the Hemoglobin/Au-TPL@CS NPs/multi-walled carbon nanotubes/glassy carbon electrode was investigated with cyclic voltammetry measurements. The biosensor exhibited a good electrocatalytic activity to the reduction of H2O2. Such new type of Au-TPL@CS NPs provides a promising platform of biological system for early illness detection and treatment in future.

  18. Electrochemical sensing platform for L-CySH based on nearly uniform Au nanoparticles decorated graphene nanosheets.

    PubMed

    Xu, Fugui; Wang, Fan; Yang, Duanguang; Gao, Yong; Li, Huaming

    2014-05-01

    In this study, Au nanoparticles decorated graphene nanosheets were prepared using poly(vinylpyrrolidone) (PVP) covalently functionalized graphene oxide and chloroauric acid as template and Au precursor, respectively. Both the density and the size of Au nanoparticles deposited on the surface of graphene could be adjusted by the PVP grafting density. The graphene-Au hybrid nanosheets were then applied to fabricate a highly sensitive l-cysteine (L-CySH) electrochemical sensing platform. The cyclic voltammetry results showed that the modified glassy carbon electrode with graphene-Au hybrid nanosheets exhibited strong catalytic activity toward the electrooxidation of L-CySH. The current exhibited a widely linear response ranging from 0.1 to 24 μM with a low detection limit under the optimized conditions. The detection limit of L-CySH could reach as low as 20.5 nM (S/N=3). The enhanced electrochemical performance of the fabricated sensor was attributed to the combination of the excellent conductivity of graphene and strong catalytic property of uniform Au nanoparticles.

  19. Volcano-like Behavior of Au-Pd Core-shell Nanoparticles in the Selective Oxidation of Alcohols

    PubMed Central

    Silva, Tiago A. G.; Teixeira-Neto, Erico; López, Núria; Rossi, Liane M.

    2014-01-01

    Gold-palladium (AuPd) nanoparticles have shown significantly enhanced activity relative to monometallic Au and Pd catalysts. Knowledge of composition and metal domain distributions is crucial to understanding activity and selectivity, but these parameters are difficult to ascertain in catalytic experiments that have primarily been devoted to equimolar nanoparticles. Here, we report AuPd nanoparticles of varying Au:Pd molar ratios that were prepared by a seed growth method. The selective oxidation of benzyl alcohol was used as a model reaction to study catalytic activity and selectivity changes that occurred after varying the composition of Pd in bimetallic catalysts. We observed a remarkable increase in catalytic conversion when using a 10:1 Au:Pd molar ratio. This composition corresponds to the amount of Pd necessary to cover the existing Au cores with a monolayer of Pd as a full-shell cluster. The key to increased catalytic activity derives from the balance between the number of active sites and the ease of product desorption. According to density functional theory calculations, both parameters are extremely sensitive to the Pd content resulting in the volcano-like activity observed. PMID:25042537

  20. Volcano-like behavior of Au-Pd core-shell nanoparticles in the selective oxidation of alcohols.

    PubMed

    Silva, Tiago A G; Teixeira-Neto, Erico; López, Núria; Rossi, Liane M

    2014-01-01

    Gold-palladium (AuPd) nanoparticles have shown significantly enhanced activity relative to monometallic Au and Pd catalysts. Knowledge of composition and metal domain distributions is crucial to understanding activity and selectivity, but these parameters are difficult to ascertain in catalytic experiments that have primarily been devoted to equimolar nanoparticles. Here, we report AuPd nanoparticles of varying Au:Pd molar ratios that were prepared by a seed growth method. The selective oxidation of benzyl alcohol was used as a model reaction to study catalytic activity and selectivity changes that occurred after varying the composition of Pd in bimetallic catalysts. We observed a remarkable increase in catalytic conversion when using a 10:1 Au:Pd molar ratio. This composition corresponds to the amount of Pd necessary to cover the existing Au cores with a monolayer of Pd as a full-shell cluster. The key to increased catalytic activity derives from the balance between the number of active sites and the ease of product desorption. According to density functional theory calculations, both parameters are extremely sensitive to the Pd content resulting in the volcano-like activity observed. PMID:25042537

  1. Fabrication of two-dimensional Au at FePt core-shell nanoparticle arrays by photochemical metal deposition

    SciTech Connect

    Haertling, Thomas; Uhlig, Tino; Olk, Phillip; Eng, Lukas M.; Seidenstuecker, Axel; Wiedwald, Ulf; Han Luyang; Plettl, Alfred; Ziemann, Paul; Bigall, Nadja C.; Eychmueller, Alexander

    2010-05-03

    In this report, we experimentally demonstrate that single platinum nanoparticles exhibit the necessary catalytic activity for the optically induced reduction of H[AuCl{sub 4}] complexes to elemental gold. This finding is exploited for the parallel Au encapsulation of FePt nanoparticles arranged in a self-assembled two-dimensional array. Magnetic force microscopy reveals that the thin gold layer formed on the FePt particles leads to a strongly increased long-term stability of their magnetization under ambient conditions.

  2. Plasmonic Au nanoparticles embedding enhances the activity and stability of CdS for photocatalytic hydrogen evolution

    SciTech Connect

    Yu, Guiyang; Wang, Xiang; Cao, Jungang; Wu, Shujie; Yan, Wenfu; Liu, Gang

    2016-01-01

    A composite photocatalyst of embedding plasmonic Au nanoparticle into CdS (Au@CdS) was prepared with a cysteine-assisted hydrothermal approach. This structure could take fully advantage of electromagnetic fields at the surface of the Au nanoparticles under visible light illumination. The photocatalytic hydrogen evolution activity of CdS could be significantly improved. Without the use of any other metal or metal oxide as cocatalysts, the quantum efficiency can reach 12.1 % over 0.5%Au@CdS at 420 nm. When using 0.1%Pt as a cocatalyst, the quantum efficiency of 0.5%Au@CdS can be further improved to 45.6%. This efficiency can be maintained more than 100 h in the test 12 days, exhibiting a relatively high stability. Photoluminescence (PL) characterization shows that the formation rate of photoexcited e-/h+ was dramatically increased when Au nanoparticles were embedded into CdS. Time-resolved PL measurement shows that Au@CdS also has a longer luminescence lifetime than that of CdS, reflecting that the photoexcited electrons in Au@CdS be with much longer lifetime to reduce H+ forming H2. All these enhancements can be attributed to the effective energy transfer between the Au surface and CdS due to the well matched composite nanostructure. Dr. Xiang Wang gratefully acknowledges the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division for the support of this work.

  3. Au@Ag/Au nanoparticles assembled with activatable aptamer probes as smart ``nano-doctors'' for image-guided cancer thermotherapy

    NASA Astrophysics Data System (ADS)

    Shi, Hui; Ye, Xiaosheng; He, Xiaoxiao; Wang, Kemin; Cui, Wensi; He, Dinggeng; Li, Duo; Jia, Xuekun

    2014-07-01

    Although nanomaterial-based theranostics have increased positive expectations from cancer treatment, it remains challenging to develop in vivo ``nano-doctors'' that provide high-contrast image-guided site-specific therapy. Here we designed an activatable theranostic nanoprobe (ATNP) via self-assembly of activatable aptamer probes (AAPs) on Au@Ag/Au nanoparticles (NPs). As both quenchers and heaters, novel Au@Ag/Au NPs were prepared, showing excellent fluorescence quenching and more effective near-infrared photothermal therapy than Au nanorods. The AAP comprised a thiolated aptamer and a fluorophore-labeled complementary DNA; thus, the ATNP with quenched fluorescence in the free state could realize signal activation through target binding-induced conformational change of the AAP, and then achieve on-demand treatment under image-guided irradiation. By using S6 aptamer as the model, in vitro and in vivo studies of A549 lung cancer verified that the ATNP greatly improved imaging contrast and specific destruction, suggesting a robust and versatile theranostic strategy for personalized medicine in future.Although nanomaterial-based theranostics have increased positive expectations from cancer treatment, it remains challenging to develop in vivo ``nano-doctors'' that provide high-contrast image-guided site-specific therapy. Here we designed an activatable theranostic nanoprobe (ATNP) via self-assembly of activatable aptamer probes (AAPs) on Au@Ag/Au nanoparticles (NPs). As both quenchers and heaters, novel Au@Ag/Au NPs were prepared, showing excellent fluorescence quenching and more effective near-infrared photothermal therapy than Au nanorods. The AAP comprised a thiolated aptamer and a fluorophore-labeled complementary DNA; thus, the ATNP with quenched fluorescence in the free state could realize signal activation through target binding-induced conformational change of the AAP, and then achieve on-demand treatment under image-guided irradiation. By using S6 aptamer as

  4. DNA origami based Au-Ag-core-shell nanoparticle dimers with single-molecule SERS sensitivity

    NASA Astrophysics Data System (ADS)

    Prinz, J.; Heck, C.; Ellerik, L.; Merk, V.; Bald, I.

    2016-03-01

    DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 1010, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled.DNA origami nanostructures are a versatile tool to arrange metal nanostructures and other chemical entities with nanometer precision. In this way gold nanoparticle dimers with defined distance can be constructed, which can be exploited as novel substrates for surface enhanced Raman scattering (SERS). We have optimized the size, composition and arrangement of Au/Ag nanoparticles to create intense SERS hot spots, with Raman enhancement up to 1010, which is sufficient to detect single molecules by Raman scattering. This is demonstrated using single dye molecules (TAMRA and Cy3) placed into the center of the nanoparticle dimers. In conjunction with the DNA origami nanostructures novel SERS substrates are created, which can in the future be applied to the SERS analysis of more complex biomolecular targets, whose position and conformation within the SERS hot spot can be precisely controlled. Electronic supplementary information (ESI) available: Additional information about materials and methods, designs of DNA origami templates, height profiles, additional SERS spectra, assignment of DNA

  5. Understanding the effect of ultrathin AuPd alloy shells of irregularly shaped Au@AuPd nanoparticles with high-index facets on enhanced performance of ethan