14 results on '"gold seeds"'
Search Results
2. Gold-seeded Lithium Niobate Nanoparticles: Influence of Gold Surface Coverage on Second Harmonic Properties
- Author
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Rachael Taitt, Mathias Urbain, Zacharie Behel, Ana-María Pablo-Sainz-Ezquerra, Iryna Kandybka, Eloïse Millet, Nicolas Martinez-Rodriguez, Christelle Yeromonahos, Sandrine Beauquis, Ronan Le Dantec, Yannick Mugnier, Pierre-François Brevet, Yann Chevolot, and Virginie Monnier
- Subjects
lithium niobate ,gold seeds ,plasmon ,second harmonic generation ,surface ,hyperpolarizability ,Chemistry ,QD1-999 - Abstract
Hybrid nanoparticles composed of an efficient nonlinear optical core and a gold shell can enhance and tune the nonlinear optical emission thanks to the plasmonic effect. However the influence of an incomplete gold shell, i.e., isolated gold nano-islands, is still not well studied. Here LiNbO3 (LN) core nanoparticles of 45 nm were coated with various densities of gold nano-seeds (AuSeeds). As both LN and AuSeeds bear negative surface charge, a positively-charged polymer was first coated onto LN. The number of polymer chains per LN was evaluated at 1210 by XPS and confirmed by fluorescence titration. Then, the surface coverage percentage of AuSeeds onto LN was estimated to a maximum of 30% using ICP-AES. The addition of AuSeeds was also accompanied with surface charge reversal, the negative charge increasing with the higher amount of AuSeeds. Finally, the first hyperpolarizability decreased with the increase of AuSeeds density while depolarization values for Au-seeded LN were close to the one of bare LN, showing a predominance of the second harmonic volumic contribution.
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- 2021
- Full Text
- View/download PDF
3. Seeds mediated synthesis of giant gold particles on the glass surface.
- Author
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Vasko, A. A., Borodinova, T. I., Marchenko, O. A., and Snegir, S. V.
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MOLECULAR electronics ,GLASS coatings ,GOLD ,PARTICLES ,SURFACE coatings - Abstract
Herein, we present the protocols of synthesis of two types of gold particles which are in the great interest for the purpose of molecular electronics. The first type is the flat prisms with a triangular/hexagonal shape and a lateral size up to ~ 80 µm. They were synthesized directly on a glass surface pretreated with (3-aminopropyl)-triethoxysilane molecules. The second type of particles was synthesized with using gold seeds with diameter of 18 nm. These seeds were deposited on a glass surface coated with APTES. The resulted three-dimensional structures with a form close to spherical increase in size up to 0.5–0.08 µm. Moreover, these particles grew up separately and did not merge during 48 h of synthesis. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
4. Gold-seeded Lithium Niobate Nanoparticles: Influence of Gold Surface Coverage on Second Harmonic Properties
- Author
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Ana-María Pablo-Sainz-Ezquerra, Mathias Urbain, Iryna Kandybka, Rachael Taitt, Yannick Mugnier, Christelle Yeromonahos, Yann Chevolot, Zacharie Behel, Ronan Le Dantec, Virginie Monnier, Nicolas Martinez-Rodriguez, Sandrine Beauquis, Pierre-François Brevet, Eloïse Millet, Institut des Nanotechnologies de Lyon (INL), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-École supérieure de Chimie Physique Electronique de Lyon (CPE)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), INL - Chimie et Nanobiotechnologies (INL - C&N), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-École Centrale de Lyon (ECL), Laboratoire SYstèmes et Matériaux pour la MEcatronique (SYMME), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Institut Lumière Matière [Villeurbanne] (ILM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Optique non linéaire et interfaces (ONLI), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL)
- Subjects
Technology ,IRON-OXIDE ,General Chemical Engineering ,Chemistry, Multidisciplinary ,Lithium niobate ,Analytical chemistry ,Nanoparticle ,hyperpolarizability ,02 engineering and technology ,01 natural sciences ,lcsh:Chemistry ,chemistry.chemical_compound ,plasmon ,ZNO ,General Materials Science ,chemistry.chemical_classification ,Physics ,lithium niobate ,Polymer ,[CHIM.MATE]Chemical Sciences/Material chemistry ,OPTICAL-PROPERTIES ,021001 nanoscience & nanotechnology ,[SDV.BBM.BP]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Chemistry ,Physical Sciences ,Science & Technology - Other Topics ,0210 nano-technology ,Materials science ,[PHYS.PHYS.PHYS-BIO-PH]Physics [physics]/Physics [physics]/Biological Physics [physics.bio-ph] ,Materials Science ,Hyperpolarizability ,Materials Science, Multidisciplinary ,1ST HYPERPOLARIZABILITY ,NANOWIRES ,010402 general chemistry ,Article ,Physics, Applied ,X-ray photoelectron spectroscopy ,surface ,Surface charge ,Nanoscience & Nanotechnology ,Plasmon ,Science & Technology ,second harmonic generation ,Second-harmonic generation ,gold seeds ,[INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation ,0104 chemical sciences ,chemistry ,lcsh:QD1-999 ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,CLUSTERS ,GENERATION - Abstract
Hybrid nanoparticles composed of an efficient nonlinear optical core and a gold shell can enhance and tune the nonlinear optical emission thanks to the plasmonic effect. However the influence of an incomplete gold shell, i.e., isolated gold nano-islands, is still not well studied. Here LiNbO3 (LN) core nanoparticles of 45 nm were coated with various densities of gold nano-seeds (AuSeeds). As both LN and AuSeeds bear negative surface charge, a positively-charged polymer was first coated onto LN. The number of polymer chains per LN was evaluated at 1210 by XPS and confirmed by fluorescence titration. Then, the surface coverage percentage of AuSeeds onto LN was estimated to a maximum of 30% using ICP-AES. The addition of AuSeeds was also accompanied with surface charge reversal, the negative charge increasing with the higher amount of AuSeeds. Finally, the first hyperpolarizability decreased with the increase of AuSeeds density while depolarization values for Au-seeded LN were close to the one of bare LN, showing a predominance of the second harmonic volumic contribution. ispartof: NANOMATERIALS vol:11 issue:4 ispartof: location:Switzerland status: published
- Published
- 2021
5. Fiducial marker implantation in prostate radiation therapy: Complication rates and technique.
- Author
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Fawaz, Z.S., Yassa, M., Nguyen, D.H., and Vavassis, P.
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PROSTATE cancer treatment , *FIDUCIAL markers (Imaging systems) , *CANCER periodicals , *DISEASE complications , *HEMORRHAGE - Abstract
Purpose This study aims to report the complication rate from the transrectal ultrasound-guided implantation of gold seed markers in prostate radiotherapy, as well as describing the technique used. Materials and methods Between May 2010 and December 2012, 169 patients with localized prostate cancer had an intraprostatic fiducial marker implantation under transrectal ultrasound guidance. The procedure included prophylactic antibiotic therapy, fleet enema, implantation performed by trained radiation oncologists at our center prior to image-guided radiotherapy. Toxicity occurring between implantation and subsequent radiotherapy start date was assessed. The following parameters were analyzed via medical chart review: antibiotic therapy, anticoagulant interruption, bleeding, pain, prostate volume, number of markers implanted, post-implantation complications and delay before starting radiotherapy. Results Of the 169 men, 119 (70.4%) underwent insertion of 4 fiducial markers and the other 50 (29.6%) had 3. The procedure was well-tolerated. There was no interruption of the implantation with regards to pain or hemorrhage. No grade 3 or 4 complications were observed. Seed migration rate was 0.32%, for the migration of 2 markers on 626 implanted. Mean prostate volume was 38 cm 3 (range: 10–150 cm 3 ). Two patients (1.18%) developed a urinary tract infection following the procedure: prostate volume of 25 and 65 cm 3 , four gold seed markers implanted, urinary tract infection resistant to prophylactic antibiotherapy, and treated with antibiotics specific to their infection as determined on urine culture. Conclusion Transrectal fiducial marker implantation for image-guided radiotherapy in prostate cancer is a well-tolerated procedure without major associated complications. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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6. Synthesis of uniform and stable silver nanoparticles by a gold seed-mediated growth approach in a buffer system.
- Author
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Xin, Junwei, Yin, Xunjun, Chen, Shougang, and Wu, Aiguo
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NANOSTRUCTURED materials synthesis , *SILVER nanoparticles , *BUFFER solutions , *CHEMICAL reactions , *SODIUM borohydride , *REDUCING agents , *HYDROXYLAMINE hydrochloride , *SODIUM hydroxide - Abstract
A seeding growth approach to the preparation of silver nanoparticles with a controllable size was developed. It contained a two-step reaction: the first step was gold seed clusters quickly generated by a chemical reaction using sodium borohydride as a reducing reagent; the second one was controllable silver nanoparticles were grown at the mild condition by using the mixed reducing reagents (hydroxylamine hydrochloride and sodium hydroxide) to form a buffer system. The gold core was beneficial for the crystalline of silver cations to form the nanoparticles and the buffer system which was composed of hydroxylamine hydrochloride and sodium hydroxide, and was helpful for controlling the size and shape of the as-prepared silver nanoparticles. These as-prepared nanoparticles were characterised by X-ray powder diffraction, UV-Vis spectroscopy (UV-Vis) and transmission electron microscopy along with energy dispersive X-ray spectroscopy. The results indicated that the obtained silver nanoparticles are highly crystallised with an average diameter around 10 nm. The content of gold seeds and the mild reaction rate controlled by the buffer system were considered to be key factors in the control of silver nanoparticles’ morphology and size. A possible mechanism of the silver nanoparticles formed was also proposed. [ABSTRACT FROM AUTHOR]
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- 2014
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7. Commissioning of MRI-only based treatment planning procedure for external beam radiotherapy of prostate.
- Author
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KapanEN, Mika, Collan, Juhani, Beule, Annette, Seppälä, Tiina, Saarilahti, Kauko, and TENhunEN, Mikko
- Abstract
In radiotherapy, target tissues are defined best on MR images due to their superior soft tissue contrast. Computed tomography imaging is geometrically accurate and it is needed for dose calculation and generation of reference images for treatment localization. Co-registration errors between MR and computed tomography images can be eliminated using magnetic resonance imaging-only based treatment planning. Use of ionizing radiation can be avoided which is especially important in adaptive treatments requiring several re-scans. We commissioned magnetic resonance imaging-only based procedure for external radiotherapy, treatment planning of the prostate cancer. Geometrical issues relevant in radiotherapy, were investigated including quality assurance testing of the scanner, evaluation of the displacement of skin contour and radiosensitive rectum wall, and detection of intraprostatic fiducial gold seed markers used for treatment localization. Quantitative analysis was carried out for 30 randomly chosen patients. Systematic geometrical errors were within 2.2 mm. The gold seed markers were correctly identified for 29 out of the 30 patients. Positions of the seed midpoints were consistent within 1.3 mm in magnetic resonance imaging and computed tomography. Positional error of rectal anterior wall due to susceptibility effect was minimal. Geometrical accuracy of the investigated equipment and procedure was sufficient for magnetic resonance imaging-only based radiotherapy, treatment planning of the prostate cancer including treatment virtual simulation. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]
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- 2013
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8. Tracking target position variability using intraprostatic fiducial markers and electronic portal imaging in prostate cancer radiotherapy.
- Author
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Munoz, F., Fiandra, C., Franco, P., Guarneri, A., Ciammella, P., Stefanis, P., Rondi, N., Moretto, F., Badellino, S., Iftode, C., Ragona, R., and Ricardi, U.
- Abstract
Copyright of La Radiologia Medica is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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- 2012
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9. Evaluation of implanted gold seeds for breast radiotherapy planning and on treatment verification: A feasibility study on behalf of the IMPORT trialists
- Author
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Coles, Charlotte E., Harris, Emma J., Donovan, Ellen M., Bliss, Peter, Evans, Philip M., Fairfoul, Jamie, Mackenzie, Christine, Rawlings, Christine, Syndikus, Isabel, Twyman, Nicola, Vasconcelos, Joana, Vowler, Sarah L., Wilkinson, Jenny S., Wilks, Robin, Wishart, Gordon C., and Yarnold, John
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BREAST cancer treatment , *CANCER radiotherapy , *LUMPECTOMY , *IMAGE-guided radiation therapy , *CLINICAL trials , *IONIZING radiation - Abstract
Abstract: Background and purpose: We describe a feasibility study testing the use of gold seeds for the identification of post-operative tumour bed after breast conservation surgery (BCS). Materials and Methods: Fifty-three patients undergoing BCS for invasive cancer were recruited. Successful use was defined as all six seeds correctly positioned around the tumour bed during BCS, unique identification of all implanted seeds on CT planning scan and ⩾3 seeds uniquely identified at verification to give couch displacement co-ordinates in 10/15 fractions. Planning target volume (PTV) margin size for four correction strategies were calculated from these data. Variability in tumour bed contouring was investigated with five radiation oncologists outlining five CT datasets. Results: Success in inserting gold seeds, identifying them at CT planning and using them for on-treatment verification was recorded in 45/51 (88%), 37/38 (97%) and 42/43 (98%) of patients, respectively. The clinicians unfamiliar with CT breast planning consistently contoured larger volumes than those already trained. Margin size ranged from 10.1 to 1.4mm depending on correction strategy. Conclusion: It is feasible to implant tumour bed gold seeds during BCS. Whilst taking longer to insert than surgical clips, they have the advantage of visibility for outlining and verification regardless of the ionising radiation beam quality. Appropriate correction strategies enable margins of the order of 5mm as required by the IMPORT trials however, tackling clinician variability in contouring is important. [Copyright &y& Elsevier]
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- 2011
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10. Practical Issues in the Implementation of Image-guided Radiotherapy for the Treatment of Prostate Cancer within a UK Department
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Rimmer, Y.L., Burnet, N.G., Routsis, D.S., Twyman, N., Hoole, A.C.F., Treeby, J., Welford, D., Fairfoul, J., ‘Aho, T., Vowler, S.L., and Benson, R.J.
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RADIOTHERAPY , *PROSTATE cancer , *MEDICAL electronics , *PHYSIOLOGICAL therapeutics - Abstract
ABSTRACT: Aims: To study the feasibility of using implanted gold seeds in combination with a commercial software system for daily localisation of the prostate gland during conformal radiotherapy, and to assess the effect this may have on departmental workload. Materials and methods: Six patients had three gold radio-opaque seeds implanted into the prostate gland before starting a course of radiotherapy. The seeds were identified on daily portal images and an automated online system provided immediate vector analysis of discrepancies between the planned and actual daily position of the intraprostatic seeds. In total, 138 interfractional displacements were analysed. The workload impact for the department was assessed using the basic treatment equivalence model, by comparing measurements of daily treatment session durations with a control group of patients receiving standard conformal radiotherapy, matched for treatment complexity. Results: No acute complications of seed insertion were observed. A number of developmental issues required solutions to be identified before clinical implementation was possible. The standard deviations of the set-up and organ motion systematic errors in the left–right, superior–inferior and anterior–posterior directions were 2.4, 3.0 and 2.5mm, respectively. The standard deviations of the set-up and organ motion random errors calculated were 2.5, 2.9 and 3.7mm. The mean treatment session duration with this daily prostate localisation system was increased by 3min compared with matched controls using standard imaging practice. If all radical prostate patients in our department were to receive image-guided radiotherapy in this way, this would increase machine workload time by 2.2h/day. Conclusions: The implementation of this image-guided system is feasible. No additional linear accelerator modification is required and standard imaging devices can be used. It would be a useful addition to any department''s image-guided radiotherapy developmental strategy. [Copyright &y& Elsevier]
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- 2008
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11. Gold-seeded Lithium Niobate Nanoparticles: Influence of Gold Surface Coverage on Second Harmonic Properties.
- Author
-
Taitt, Rachael, Urbain, Mathias, Behel, Zacharie, Pablo-Sainz-Ezquerra, Ana-María, Kandybka, Iryna, Millet, Eloïse, Martinez-Rodriguez, Nicolas, Yeromonahos, Christelle, Beauquis, Sandrine, Le Dantec, Ronan, Mugnier, Yannick, Brevet, Pierre-François, Chevolot, Yann, Monnier, Virginie, and Ueno, Kosei
- Subjects
- *
LITHIUM niobate , *GOLD nanoparticles , *SURFACE charges , *SECOND harmonic generation - Abstract
Hybrid nanoparticles composed of an efficient nonlinear optical core and a gold shell can enhance and tune the nonlinear optical emission thanks to the plasmonic effect. However the influence of an incomplete gold shell, i.e., isolated gold nano-islands, is still not well studied. Here LiNbO3 (LN) core nanoparticles of 45 nm were coated with various densities of gold nano-seeds (AuSeeds). As both LN and AuSeeds bear negative surface charge, a positively-charged polymer was first coated onto LN. The number of polymer chains per LN was evaluated at 1210 by XPS and confirmed by fluorescence titration. Then, the surface coverage percentage of AuSeeds onto LN was estimated to a maximum of 30% using ICP-AES. The addition of AuSeeds was also accompanied with surface charge reversal, the negative charge increasing with the higher amount of AuSeeds. Finally, the first hyperpolarizability decreased with the increase of AuSeeds density while depolarization values for Au-seeded LN were close to the one of bare LN, showing a predominance of the second harmonic volumic contribution. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
12. Avaliação do uso de 'sementes' de ouro e ultrassom no tratamento do câncer por hipertermia
- Author
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BARROS, André Luiz de Souza, SILVA, Teresinha Gonçalves da, and NASCIMENTO, Silene Carneiro do
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Cancer,Hipertemia, Sementes de Ouro,Ultrasson, Doxorrubicina ,Cancer ,Hyperthermia ,Gold seeds ,Ultrasound ,Doxorubicin - Abstract
CNPQ O câncer é tratado, atualmente, como uma epidemia global e apesar dessa grande expressividade epidemiológica a base terapêutica utilizada no combate ao câncer limita-se a quimioterapia, a radioterapia e a cirurgia. Esses tratamentos apresentam uma série de limitações e efeitos adversos. Hipertermia é uma proposta de tratamento de câncer onde as células do tumor são afetadas pela elevação da temperatura local de acordo com a temperatura e o tempo de exposição à fonte de calor. O objetivo desse trabalho foi testar os efeitos da hipertermia obtidos através de uma técnica baseada no uso do ultrassom para irradiar sementes de ouro inseridas no interior de tumores sólidos. Neste sentido, o presente trabalho avaliou a eficácia desta técnica em modelos computacionais, in vitro e pré-clínicos. Para definir a forma geométrica e a difusão de calor da semente de ouro, foi utilizado um código computacional com base na equação de difusão de calor. A partir dos parâmetros definidos teoricamente foi elaborada uma técnica cirúrgica para confirmação pré-clínica e foram realizadas terapias conjuntas usando doxorrubicina. Os resultados das simulações computacionais mostraram que as sementes com 0,8x10mm e 1x 10mm, irradiadas durante 600s com frequência 1,5 MHz produziram uma taxa de geração de calor igual a 6 x 106 W/m3. No modelo de tratamento por dose única os animais foram irradiados durante 30 min com a frequência de 1MHz e as temperaturas foram avaliadas nas regiões centrais e periféricas do tumor. Os resultados obtidos no tratamento por dose única mostraram que o aumento na temperatura foi capaz de produzir necrose coagulativa em 81,9 ±7,2% da área total do tumor. No tratamento por três doses, os animais foram irradiados durante 15min com intervalos de 5 dias. Os resultados apresentados pelos animais tratados com três doses mostraram taxa de inibição tumoral igual a 84.7%. A associação do prétratamento com sementes de ouro irradiadas com ultrassom e doxorrubicina reduziu a IC50 desse fármaco em cerca de 50% em cultura de células e apresentou 87% de inibição tumoral contra o carcinoma de Ehrlich. Podemos concluir, a partir dos nossos resultados, que a hipertermia produzida pela irradiação de sementes de ouro com ultrassom é um método eficaz na destruição de tumores sólidos e pode ser usado como um eficiente adjuvante na quimioterapia O câncer é tratado, atualmente, como uma epidemia global e apesar dessa grande expressividade epidemiológica a base terapêutica utilizada no combate ao câncer limita-se a quimioterapia, a radioterapia e a cirurgia. Esses tratamentos apresentam uma série de limitações e efeitos adversos. Hipertermia é uma proposta de tratamento de câncer onde as células do tumor são afetadas pela elevação da temperatura local de acordo com a temperatura e o tempo de exposição à fonte de calor. O objetivo desse trabalho foi testar os efeitos da hipertermia obtidos através de uma técnica baseada no uso do ultrassom para irradiar sementes de ouro inseridas no interior de tumores sólidos. Neste sentido, o presente trabalho avaliou a eficácia desta técnica em modelos computacionais, in vitro e pré-clínicos. Para definir a forma geométrica e a difusão de calor da semente de ouro, foi utilizado um código computacional com base na equação de difusão de calor. A partir dos parâmetros definidos teoricamente foi elaborada uma técnica cirúrgica para confirmação pré-clínica e foram realizadas terapias conjuntas usando doxorrubicina. Os resultados das simulações computacionais mostraram que as sementes com 0,8x10mm e 1x 10mm, irradiadas durante 600s com frequência 1,5 MHz produziram uma taxa de geração de calor igual a 6 x 106 W/m3. No modelo de tratamento por dose única os animais foram irradiados durante 30 min com a frequência de 1MHz e as temperaturas foram avaliadas nas regiões centrais e periféricas do tumor. Os resultados obtidos no tratamento por dose única mostraram que o aumento na temperatura foi capaz de produzir necrose coagulativa em 81,9 ±7,2% da área total do tumor. No tratamento por três doses, os animais foram irradiados durante 15min com intervalos de 5 dias. Os resultados apresentados pelos animais tratados com três doses mostraram taxa de inibição tumoral igual a 84.7%. A associação do prétratamento com sementes de ouro irradiadas com ultrassom e doxorrubicina reduziu a IC50 desse fármaco em cerca de 50% em cultura de células e apresentou 87% de inibição tumoral contra o carcinoma de Ehrlich. Podemos concluir, a partir dos nossos resultados, que a hipertermia produzida pela irradiação de sementes de ouro com ultrassom é um método eficaz na destruição de tumores sólidos e pode ser usado como um eficiente adjuvante na quimioterapia
- Published
- 2015
13. Shape-Controlled Gold Nanoparticle Synthesis
- Author
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ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE, Cramer, Hailey E, Giri, Lily, Griep, Mark H, Karna, Shashi P, ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE, Cramer, Hailey E, Giri, Lily, Griep, Mark H, and Karna, Shashi P
- Abstract
At the nanoscale, the optical, electrical, and catalytic properties of a material depend on its size and shape. Therefore, synthesis of nanoparticles with controlled size and shape is important for their application in biosensors, photonics, and other optoelectronic devices. Whereas the effect of size on the properties of nanoparticles has been extensively studied in the past two decades, similar studies on the shape of nanoparticles have received little attention. The specific goals of this research are to synthesize nanoparticles with desired shapes and investigate their structure-property relationships. Recently, we successfully synthesized colloidal gold (Au), silver (Ag), and mixed Au Ag nanoparticles using aqueous chemistry. The particles exhibited a mixture of shapes, including spheres, rods, and prisms. In the present work, we synthesize Au nanorods, nanospheres, and nanotriangles using a wet-chemical, seed-mediated growth method employing the surfactant cetyltrimethylammonium bromide as a growth-directing micellar template. It was possible to obtain these shapes through precise tuning of thermodynamic and kinetic parameters and the addition of small concentrations of halide and metal ions. Characterization of the particles was performed using tunneling electron microscopy, energy-dispersive spectroscopy, ultraviolet-visible spectroscopy, and dynamic light scattering., The original document contains color images.
- Published
- 2013
14. Synthesis and characterization of silicon nanowires, silicon nanorods, and magnetic nanocrystals
- Author
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Heitsch, Andrew Theron
- Subjects
- Silicon nanowires, Silicon nanorods, Iron platinum nanocrystals, SLS growth, Dodecylamine, Magnetic nanocrystals, Gold seeds, Trisilane, Nanocrystals, Nanowires, Nanorods
- Abstract
Silicon nanowires, silicon nanorods, and magnetic nanocrystals have shown interesting size, shape, mechanical, electronic, and/or magnetic properties and many have proposed their use in exciting applications. However, before these materials can be applied, it is critical to fully understand their properties and how to synthesize them economically and reproducibly. Silicon nanowires were synthesized in high boiling point ambient pressure solvents using gold and bismuth nanocrystals seeds and trisilane as the silicon precursor. Reactions temperatures as low as 410°C were used to promote the solution-liquid-solid (SLS) growth of silicon nanowires. The silicon nanowires synthesis was optimized to produce 5 mg of silicon nanowires with average diameters of 30 nm and lengths exceeding 2 [mu]m by adjusting the silicon to gold ratio in the injection mixture and reaction temperature. Silicon nanorods were synthesized using a solution-based arrested-SLS growth approach where gold seeds, trisilane, and a dodecylamine were vital to the success. Dodecylamine was found to prevent gold seed coalescence at high temperatures -- creating small diameter rods -- and bond to the crystalline silicon surface -- preventing silicon nanorod aggregation. Furthermore, an etching strategy was developed using an emulsion of aqua regia and chloroform to remove the gold seeds from the silicon nanorods tip. A thin silicon shell surrounding the gold seed of the silicon nanorod was subsequently observed. Multifunctional colloidal core-shell nanoparticles of iron platinum or iron oxide encapsulated in fluorescent dye doped silica shells were also synthesized. The as-prepared magnetic nanocrystals are initially hydrophobic and were coated with a uniform silica shell using a microemulsion approach. These colloidal heterostructures have the potential to be used as dual-purpose tags, exhibiting a fluorescent signal that could be combined with enhanced magnetic resonance imaging contrast. Compositionally-ordered, single domain, antiferromagnetic L1₂ FePt₃ and ferromagnetic L1₀ FePt nanocrystals were synthesized by coating colloidally-grown Pt-rich or stoichiometricly equal Fe-Pt nanocrystals with thermally-stable SiO₂ and annealing at high temperature. Without the silica coating, the nanocrystals transform predominately into the L1₀ FePt phase due to interparticle diffusion of Fe and Pt atoms. Magnetization measurements of the L1₂ FePt₃ nanocrystals revealed two antiferromagnetic transitions near the bulk Neél temperatures of 100K and 160K. Combining L1₂ FePt₃ nanocrystals with L1₀ FePt nanocrystals was found to produce a constriction in field-dependent magnetization loops that has previously been observed near zero applied field in ensemble measurements of single domain silica-coated L1₀ FePt nanocrystals. Dipole interactions between FePt@SiO₂ nanoparticles with varying SiO₂ shell thickness was also explored.
- Published
- 2010
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