Sol- Gel Synthesis Of Transi3on Metal Doped Silica Nanopar3cles

Transcription

1 Sol- Gel Synthesis Of Transi3on Metal Doped Silica Nanopar3cles Pat Downs Graduate Student Department of Material Science and Engineering Rensselaer Polytechnic Institute, Troy, NY, USA Advisors: Linda Schadler, Richard Siegel, Jonathan Dordick Collaborators: Shyang Shuoh Ao Sealed Air, Na3onal Science Founda3on 2014 Rensselaer Nanotechnology Center Research Symposium Wednesday, October 29, 2014

2 Why Silica & Why A Doped Nanoparticle? Monodisperse silica micro/ nanoparticles have been synthesized since 1968 by Werner Stöber To observe changes in the particle s surface energy Experimentally surface energy vs. concentration is found to vary linearly for bulk surfaces Nanoparticle surface energy has also been found to change dependent on composition A. Kiejna,K.F. Wojciechowski.(1996) Image from: Fromen et al. (2004)

3 Surface Energy Interfacial Energy - Defined as the reversible work required to form or to extend a unit area of interface between a surface and its coexisting fluid plastically l Surface Energy - Unsatisfied bonding potential of atoms at a surface - Linked to hydrophobicity through Young- Dupré contact angle equation - Sessile Drop Water droplet on brass surface l l High degree of error for non-flat surfaces Cannot be applied to solid-solid interactions Kuna et al. Nature Materials 8, (2009) Qi et al. (2000) Aspenes et al. SINTEF Petroleum Research, Bergen, Norway (2009)

4 Experimental Approach Challenge: - Amorphous particles - Monodisperse - Non-modified surface - Particle sizes of nm - Controllable surface energy Average Diameter (nm) Water Concentration (M) Stöber nanoparticle size as a function of water concentration Napierska et al. (2003) O Kelly et al. (2012) Miezele et al. (1985) Morgan et al (2007) Bogush et al (1988)

5 Objectives Synthesize nanoparticles of variable surface energy Determine relation between the adsorption behavior of proteins and nanoparticle surface energy Understand the conformation changes of proteins associated with nanoparticle surface energy Surface Energy?

6 Fe-SiO 2 Nanoparticles 100 nm 100 nm SEM micrograph of amorphous 0.1% Fe doped Silica Nanoparticles synthesized for 20 H Average particle size: 60nm +/- 6nm SEM micrograph of amorphous 1% Fe doped Silica Nanoparticles synthesized for 20H Moran et al. (2001)

7 Results: Ni-SiO2 Nanoparticles 0.5 at% Ni Expected Avg. Size : / nm Avg. Size: /- 3.8 nm 100nm 5 at% Ni Expected 100nm Avg Size: 20 nm +/- 6.7 nm 7.3 +/- 0.3 at% Ni Avg. Size: 18.5 nm +/- 6.4 nm 100nm 20 at% Ni Expected Avg. Size: 24nm +/- 11nm 100nm

8 Ni-SiO2 Nanoparticles Silica 0.5 at% expected Ni synthesized in Methanol for 2 H Avg. Size : / nm Avg. Size: /- 3.8 nm

9 Results: Ni-SiO2 Nanoparticles 85nm Atomic Concentration (at %) Average size: 85 +/- 8nm Expected 20 at% Ni 86nm 81.5nm Intensity (arb.) Al O 0 Ni Si Ni Sputter Time (min) 1.5 Auger Spectra of 2kV ion gun sputtered depth profiles of Ni-SiO2 nanoparticles EDS spectra of Ni-SiO2 nanoparticles on polished aluminum confirming nickel incorporation Ni Ni 3 4 kv

10 Results: Ni-SiO 2 Nanoparticles Counts/sec Binding Energy (ev) XPS Spectra of 10 at% expected Ni- SiO 2 Nanoparticles Expected Nickel Doping Measured Nickel Doping 5 at% / at% 10 at% 7.3 +/- 0.3 at% 20 at% /- 2.1 at% Atomic Concentration (at%) at% Ni 5 at% Ni 10 at% Ni Sputter Time (minutes) Auger Spectra of 2kV ion gun sputtered depth profiles of Ni-SiO 2 nanoparticles

11 Results: Effect of Ammonia Hydroxide and Water Concentration Particle Size (nm) M H 2 O 2 M H 2 O 4 M H 2 O Ammonia Hydroxide [M] Effect of NH 4 OH particle size of expected 20 at% doped nanoparticles Average Diameter (nm) Water Concentration [M] Stöber nanoparticle size as a function of water concentration Bogush et al (1988)

12 Dopant Concentration Effect on Particle Size 1 % Zn Doped Silica Avg. Size: / nm 5 % Zn Doped Silica Avg. Size: / nm 20 % Zn Doped Silica Avg. Size: / nm

13 Dopant Concentration Effect on Particle Size NH4OH [M] Zn (at%) Particle Size (nm) NH4OH [M] Zn (at%) Particle Size (nm) H2O [M] H2O [M] Particle size as a function of H 2 O[M] and Zn Concentration at 4.5 M NH 4 OH Particle size as a function of H 2 O[M] and Zn Concentration at 6.5 M NH 4 OH

14 Results of Zinc Synthesis: Bimodal Distributions 5 % Zn Doped Silica Avg. Size: / nm Avg. Size: / nm 1 % Zn Doped Silica Avg. Size: / nm Avg. Size: / nm Scale Bars are 100nm 10 % Zn Doped Silica Avg. Size: / nm Avg. Size: / nm All Synthesized in Methanol for 2 H with 3M NH4OH

15 Contact Angle of Ni-SiO2 Nanoparticles 0.5 at% Expected Nickel Doped Nanoparticles Average Particle Diameter: /- 5.2 nm Contact Angle: /- 5.6 degrees Silica Nanoparticles Average Particle Diameter: /- 3.3 nm Contact Angle: / degrees

16 Acknowledgements Funding Support Sealed Air Special Thanks: Raymond Dove National Science Foundation Robert Planty Collaborators Shyang Shuo Advisors Linda Schadler Richard Siegel Jon Dordick

17 Conclusions q Fe-SiO 2 Amorphous nanoparticles up to 1 at% Fe were synthesized Concentrations above 1 at% Fe were found to be polydisperse and unstable with rapid oxidation leading to crystalline nanoparticles q Ni-SiO 2 and Zn-SiO 2 q q q q q Amorphous homogenous nickel doped nanoparticles of 18 nm to 200+ nm were synthesized Correlation between particle size, PDI, and NH 4 OH concentration Amorphous Zn doped nanoparticles were synthesized with a slight increase in polydispersity compared to the Ni doped nanoparticles Correlation between Zn concentration and particle size Preliminary data supporting possible changes in surface energy from transition metal content

18 Questions?

19 Temperature-Time Effect on Particle Size 310 Nanoparticle Size (nm) Synthesis Time (minutes) 10% Particle Size (nm) Logarithmic (10% Particle Size (nm)) 5.0% Particle Size (nm) Logarithmic (5.0% Particle Size (nm)) 5.0% Particle Size 55C Logarithmic (5.0% (nm) Particle Size 55C (nm)) 10% Particle Size 55C (nm) Logarithmic (10% Particle Size 55C (nm))

20 Results: Transition Metal Coagulation 30 at% Ni 40 nm Micrograph of Silica-Ca nanoparticles 100 nm Zerroug et al. Journal of Colloid and Interfacial Science