Physics and Chemistry of Nanoclusters

Dr Lauro Oliver Paz-Borbón1

oliver_paz@fisica.unam.mx

1Physics Institute National Autonomous University of Mexico (UNAM)

Seoul, South Korea 11th November 2016

THIS: Theory of Hetero- Interfaces and Surfaces Winter School

a little bit about me..

PhD in Chemistry University of Birmingham Birmingham, UKProf. Dr. Roy Johnston

Postdoc Fritz-Haber Institute Berlin Berlin, GermanyProf. Dr. Matthias Scheffler

Researcher Chalmers University of Technology Gothenburg, SwedenProf. Dr. Henrik Grönbeck

Postdoc King’s College London London, UKDr. Francesca Baletto

Assistant Professor Physics Institute, UNAM Mexico City, Mexico

Oliver Paz Borbón

Email: oliver_paz@fisica.unam.mx

UNAM @ Mexico City

Course aims

“A bird’s eye view to nanoclusters!”

- History and background

- Physical and Chemical properties of nanoclusters

- Computational tools

Much of nanoscience and many nanotechnologies

are concerned with producing new

or enhanced materials.

https://t2.ftcdn.net/jpg/00/47/19/61/500_F_47196194_uaPhX5mywIr1GZtwAzsveCUtRHyFN1z8.jpg

Nature Nanotechnology 4, 538 (2009) www.nature.com/naturenanotechnology

Nanopapers

A nanometer is a unit of spatial measurement that is 10-9

meter, or one billionth of a meter.

Definitions

https://www.hdiac.org/sites/default/files/image_upload/CS_Figure1.png

Nanomaterial is an object that has at least one dimension in the nanometer scale approximately 1-100nm.

Nanomaterials classification

http://eng.thesaurus.rusnano.com/upload/iblock/dfc/nanomaterial1.jpg

Classification is based on the number of dimensions, which are not confined to the nanoscale range (<100 nm).

Historical Background

How it all started!

Richard P. Feynman, “There’s Plenty of Room at the Bottom” [1]

[1] Published on Caltech’s Engineering and Science Magazine (1960)

APS Meeting at Caltech, December 1959

Professor Norio Taniguchi (Tokyo University of Science) was the first one to use the term nanotechnology (1974)

K. Eric Drexler: Ph.D. work was the first doctoral degree on the topic of molecular nanotechnology.

Probe microscopy

In 1981, the Scanning Tunnelling Microscope (STM), was developed by Gerd Binning and Heinrich Rohrer, working at IBM Zurich.

Nobel in Physics (1986): Ruska, Binning and Rohrer

http://www.nobelprize.org/nobel_prizes/physics/laureates/1986/binnig-lecture.pdf

Si(111)- 7x7 surface reconstruction.

https://en.wikipedia.org/wiki/Scanning_tunneling_microscope

Au(100)

Carbon nanotube

Si(111)7x7

Pt @ HOPG

http://web.physik.uni-rostock.de/cluster/beams/forschung_en.htm

Probe microscopy

Fullerenes

http://www.wiley-vch.de/books/sample/3527331972_c01.pdf

The first fullerene molecule to be discovered, buckminsterfullerene (C60), was prepared in 1985 at Rice University via graphite vaporisation at low pressure (Harold Kroto, Nobel 1996)

Advances in interface and colloid science

Aqueous colloidal gold

Around 1850s, Michael Faraday discovered colloidal “ruby” gold while investigating the properties of light and matter.

Intense red colour is obtained for Au particles < 100 nm; or blue/purple for larger ones.

Advances in interface and colloid science

Lycurgus Cup (4th-century Roman glass cage cup)

M e d i e v a l a r t i s a n s w h e r e o n e o f t h e fi r s t nanotechnologists, as they made stained glass by mixing gold chloride into molten glass.

http://www.wiley-vch.de/books/sample/3527331972_c01.pdf

Key paper in (nano)cluster history! four distinct abundance maxima in their mass spectra of Na clustersat W = 2, 7, 19, and 38.

ISSPIC XVIII - International Symposium on Small Particles and Inorganic Clusters

Richard Smelley presents work on C60’s!

Gathers more than 200 scientist within the field!

vs.

icosahedral Au144(SR)60

Decahedral Au144(SR)60

state-of-the-art!

(Metal) Nanoclusters and nanoalloys

General properties

Nanoclusters

- Clusters can be defined as :

- Agglomerates of a few to millions of atoms or molecules.

- Can be made of one single atom (or molecule) or two or more different species.

Ru3Sn3 Pt49Au49Pt2

Roy Johnston, Dalton Trans. , 2003, 4193

Nanoclusters

- Clusters can be studied in:

- Gas-phase (“free-cluster”) - Supported on a substrate (such as silica, TiO2 and MgO) or in an inert

matrix. - Passivated by ligands (the cluster surface is stabilised by surfactant

molecules)

Pt6@CeO2(111)Pt6

gas-phase

lateral view top view Au102(para- mercaptobenzoic acid)44.

http://www.pnas.org/content/105/27/9157.figures-only

- Have different segregation mixing patterns, i.e. the chemical ordering between the two metals.

- Segregation dependance on bond strength, surface energy, overall cluster size, charge transfer, strength of binding to ligands/substrate, specific electronic effects, etc..

- Bimetallic clusters can:

Nanoclusters

Julius Jellinek, Faraday Discuss., 2008, 138, 11–35

Nanoclusters

HRTEM image of Ni-Pt nanoparticle (ca. 3nm)

HRTEM Pd-Au @ C film

(ca. 8 nm)

http://phys.org/news/2012-02-world-smallest-atomic-valentine.htmlhttp://physics.utsa.edu/Faculty/Yacaman/Yacaman.html

- Present a wide variety of structures: varying from non-crystalline (e.g. decahedral, icosahedral), to crystalline arrangements (e.g. fcc-type bulk-like fragments).

- Due to their size, clusters can:

gas-phase Pt-Pd

FCC-like

gas-phase Pt-Pd

Decahedral

Nanoclusters

http://www.nanoalloy.eu/attachments/article/114/Structure_Ferrando_1.pdf

Nanoclusters

It is difficult to unambiguously define a cluster as being small, medium or large in size!

http://w0.rz-berlin.mpg.de/imprs-cs/download/2012clusterchem.pdf

- Present physico-chemical properties which make them differ from bulk metals.

- Successive fragmentation of a macroscopic piece of a bulk metal will induce a transition to a microscopic insulating particle.

Nanoclusters

http://www.chm.bris.ac.uk/webprojects2002/etan/Webpages/theory.htm

- Due to their size, (metal) clusters can:

- Emergence of new properties e.g.: magnetic, optical / luminescence, chemical / catalytic

- Effects at the (sub)nano-scale quantum confinement large surface/volume ratio, structural changes

- Have a large number of atoms occupying surface sites, where the morphology of the cluster is essential in determining their catalytic properties, with many reactions taking place on nanoparticle surface

Nanoclusters

- Due to their size, (metal) clusters:

Nanoclusters

- For a fixed size, clusters can display:- A wide variety of structural isomers!

- They refer to different structures, having different energies, for a given size (and same chemical for bimetallic clusters).

Pt6@MgO(100) Global minima

0.0 eV

Pt6@MgO(100) 0.5 eV

higher in energy!

Nanoclusters

- For a fixed size, clusters can (also) display:- The existence of homotops in bimetallic nanoalloys (e.g. Pd-Pt, Pd-

Au, Ag-Pt,Ag-Au)

- This leads to different cluster geometrical structures, compositions, structures, geometries!

Study of 40-atom Pt–Au clusters using a combined empirical potential-density

functional approach

Dung T. Tran, Roy L. Johnston

Published 9 March 2011.DOI: 10.1098/rspa.

2010.0562

Overall technological applications…

Heterogenous Catalysis

Nanoclusters applicationsNovel metal nanocatalysts for emission control systems (gasoline and diesel).

Three-way catalysts

Improved oxygen reduction reaction at at hydrogen fuel cell cathode using novel metal nanocatalyst

Nanomaterials applications

https://4wheelonlineblog.files.wordpress.com/2014/11/mirai2.jpg

• Future transportation applications

• Nanobiosystems, medical, health applications

Researchers have developed an imaging technology (PET-MRI) to measure the amount of an antibody-nanoparticle complex that accumulates specifically in atherosclerotic plaque to monitor the development of plaque as well as its disappearance following treatment.

Nanomaterials applications

http://www.nano.gov/you/nanotechnology-benefits

https://csb.mgh.harvard.edu/nahrendorfhttp://pubs.acs.org/doi/pdf/10.1021/nn500962q

Past, current and future research on (metal) nanoclusters

- Cluster reactivity at the nanoscale

Activity increases with decreasing size, with most active Au particles reported to have a few nm in diameter

Haruta et al. J. Catal. 115 (1989) 301http://www.fhi-berlin.mpg.de/acnew/department/pages/teaching/pages/teaching__wintersemester__2006_2007/fielicke_clusterchemistry_020207.pdf

Nanoclusters reactivity and catalisis

- Cluster reactivity at the nanoscaleExcellent (nano)-catalyst due to their high surface to volume ratio!

http://www.fhi-berlin.mpg.de/acnew/department/pages/teaching/pages/teaching__wintersemester__2006_2007/fielicke_clusterchemistry_020207.pdf

Nanoclusters reactivity and catalisis

Nanoclusters reactivity and catalisis

Model reaction CO + O2 —> CO2

examined by gas phase ion

chemistry and mass spectrometry techniques

[EXP 1998] [EXP/THEO 2003]

Nanoclusters reactivity and catalisis

[THEO 2012] [EXP/THEO 2014]

Nanoclusters reactivity and catalisis

[EXP/THEO 2016][EXP/THEO 2015]

Nanoclusters reactivity and catalisis

[EXP/THEO 2013][THEO 2016]

Experimental preparationtechniques and characterization

Manufactur ing a t the nanoscale is known as nanomanufacturing.

http://www.nature.com/nrn/journal/v7/n1/images/nrn1827-i1.jpg

Nanomaterials fabrication

“Bottom up” “Top down”

Laser ablationExperimental background

https://en.wikipedia.org/wiki/Physical_vapor_deposition

A small metal target (plate or rod) of bulk material is evaporated by laser ablation.

lnf-wiki.eecs.umich.edu/wiki/images/c/ce/Sputter_Deposition.png

white disk Al2O3

squared substrate SrTiO3

650 °C

plasma explosion

https://en.wikipedia.org/wiki/Pulsed_laser_deposition

Physical vapour deposition (PVD)

https://en.wikipedia.org/wiki/Physical_vapor_deposition

1. Vaporization of the material from a solid source. 2. Transportation of the vapor in vacuum to the substrate surface3. Condensation onto the substrate

Sputting target: Al, Cu, Cr, ZnO, Al2O3,

In2O3, Ti, I, W, Y

lnf-wiki.eecs.umich.edu/wiki/images/c/ce/Sputter_Deposition.png

Au atoms adsorbed on the MgO surface

http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.96.146804http://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=108832720

Experimental background

Sol-Gel Method

Is a method for producing solid materials from small molecules. Typical precursors are metal alkoxides and metal chlorides.

white disk Al2O3

squared substrate SrTiO3

650 °C

plasma explosion

https://en.wikipedia.org/wiki/Sol-gel

Involves the conversion of

monomers into a colloidal solution (sol) that acts as the precursor for

an integrated network (gel)

http://www.photokatalyse.fraunhofer.de/en/Kompetenzen/Schicht_Prozessentwicklung/Sol-Gel-Lacktechnik.html

Experimental background

650 °C

A solution of Ag+ or Au3+ ions is prepared separately.

http://onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.2000.tb01566.x/epdf

The Ag+ or Au3+ precursors are AgNO3

and HAuCl4.3H2O

A suitable ligand for the formation of metal ion complexes is introduced.

Mono dispersed Particles from Solution:

http://education.mrsec.wisc.edu/277.htm

TEM image

Chloroauric acidsilver nitrate

Experimental background

Nanomaterials characterisation

State-of-the-art characterisation of nanoclusters involve a number of experimentaltechniques:

X-ray analysis

Electron microscopy

Scanning probe microscopy

Vibrational spectrometry

Auger-electron microscopy

Mass spectrometry

Optical techniques …

Nanomaterials characterisation:

X-ray diffraction (XRD)

3-D X-ray diffraction image of a truncated octahedra nanoparticle with 200nm diameter

http://phys.org/news/2015-02-x-ray-pulses-uncover-free-nanoparticles.html

X-ray photoemission spectra (XPS)

Phys. Chem. Chem. Phys.,2014, 16, 26645

SLAC - USA

Nanomaterials fabrication

Miguel Yacaman, UTSA, personal communication

(HR) TEM (Transmission Electron Microscopy)

SEM (Scanning Electron Microscopy)

http://www.microscopy.ethz.ch/catalysis.htm

SEM images of Pt particles on alumina.

Pt

4Pt5

HR-STEM

STM (Scanning Tunneling Microscopy)

Ag particle supported on ZnO Pt atoms supported on Al2O3

Pt7 on TiO2

Nat Nanotechnol. 2015 Jul;10(7):577-88. doi: 10.1038/nnano.2015.140.

Nanomaterials fabrication

Infrared spectroscopy (IR)

Exploits the fact that molecules absorb specific frequencies that are characteristic of their structure. These absorptions are resonant frequencies

http://onlinelibrary.wiley.com/doi/10.1002/chem.201304586/full

http://www.wag.caltech.edu/home/jang/genchem/infrared.htmhttp://fel.fhi-berlin.mpg.de/

Schematic view of the dual-target dual-laser ablation source for the production

of metal clusters +

mass selection

Computational tools for (metal) nanoclusters

Atomistic modelling can reduce the cost and accelerate the time scales of understanding and developing novel materials. http://www.icams.de/content/research/index.html

Computational Modelling

Computational Modelling

http://www.icmr.ucsb.edu/programs/summer-school-2013/LeSar%20UCSB%20Summer%20School.pdf

How do we create models?

Think before you compute!

Electronic Structure Methods

LDA Local Density Approx.

GGA Generalised Gradient Approx.

meta-GGA

hybrids

RPA

Density Laplacian

Exact exchange

Exact exchange + correlation

V xc

acc

urac

yan

d C

PU ti

me!

Density Functional Theory (DFT) is the current electronic structure workhorse via High-Performance Computing (HPC) calculations.

Quantum Chemistry (Hartree-Fock theory)

Single reference: Møller-Plesset (MP)

Conf. interaction (CI) Coupled cluster (CC)

…

Computational Materials Modeling

Density Functional Theory (DFT)

LDA GGA

Hybrids …

Tight binding …

Time dependent DFT … Interatomic potentials

Pair potentials (Lennard-Jones)

Morse potential Gupta many-body

…

Molecular Dynamics Classical

Born-Oppenheimer Car-Parinello

…

Computational Methodologies

*Does not include ALL techniques!

QM/MM methods Development of force fields

…

Global optimizations (genetic algorithm) + atomistic level potentials + DFT simulations of < 100 atom size gas-phase clusters - with Dr. Roy Johnston (UniBham) [1]

Other research lines @ IFUNAM

[1] Rossi, Ellaby, Paz-Borbón, Atanasov, Baletto, submitted J. Phys.: Condens. Matter (2016)

Atomistic (classical) Molecular Dynamics simulations of > 500 atom size supported clusters - with Dr. Francesca Baletto (KCL) [1]

Other research lines @ IFUNAM

LoDiS MD manual

Kevin Rossi, Francesca Baletto

⇤

Physics Department,

King’s College London, WC2R 2LS,

UK

⇤ francesca.baletto@kcl.ac.uk

[1] Rossi, Ellaby, Paz-Borbón, Atanasov, Baletto, submitted J. Phys.: Condens. Matter (2016)

+

metal

atom-atom

Metal atom-oxide

Main objetive

Andrés López BSc Thesis

c) Our own Basin Hopping-DFT (Python3.4 code + Quantum Espresso, eventually + LODIS-MD) implementation for global optimization of (oxide) supported metal clusters

[1] López-Martínez, Garzón, Grönbeck, Posada-Amarillas, Paz-Borbón, in preparation (2016)

Main objetive c) Our own Basin Hopping-DFT (Python3.4 code + Quantum Espresso, eventually + LODIS-MD) implementation for global optimization of (oxide) supported metal clusters

…@ γ-Al2O3 …@ TiO2

… open GitHub link for the community :D

Pt @ CeO2 (111) (PBE+U, Ueffec = 4.5 eV)

Dr Francesca Baletto (KCL)Dr Henrik Grönbeck (Chalmers)Dr Miguel José Yacaman (UTSA)

Project IA102716

SC16-1-IG-78 SC15-1-IG-82

Dr Carlos Villagomez (IFUNAM)Mr Andres Lopez (IFUNAM)

Dr Ignacio Garzón (IFUNAM)

Dr Alvaro Posada (UniSonora)

CPU-time (1,600,000 hrs)

AcknowledgementsCollaborators: Funding:

Dr Gabriela Diaz (IFUNAM)

Dr Aloysius Soon (Yonsei)