MoSIx nanowires functionalization for molecular-scale connectivity

Mihaela – Irina PloscaruJozef Stefan Institute

SLONANO 2007

www.mo6.com

MoSIx nanowires

Vrbanic et al., Nanotechnology 15, 635 (2004)

1μm

bundles of nanowires having a diameter from 1 µm down to 20 nm and a length of up to 5 mm ;

easily disperse in low diameter bundles in organic solvents like isopropanol, methanol, ethanol, acetone, etc. and even H2O ;

one step synthesis - wool like appearance;

XRD measurements – individual nanowires are composed of Mo6 octahedral clusterssurrounded by S or I atoms and connected by bridging anions of S

S atoms

Mo atoms

I atoms

A. Meden et al., Nanotechnology 16, 1578 (2005)

V. Nicolosi et al., Adv. Matter 19, 543 (2007)

Structure of MoSIx nanowires

EXAFS measurements – the distance between Mo atoms is d=2.63 Å

Mo-Mo 2.63 Å

Connectivity of MoSIx nanowires

A. Meden et al., Nanotechnology 16, 1578 (2005)

V. Nicolosi et al., Adv. Matter 19, 543 (2007)

Au colloidAu-Au 2.88 Å

MoSIx nanowireMo-Mo 2.63 Å

S atom

functionalization of nanowires with gold; the presence of S in the structure of the nanowires ; S and Au like each other – covalent bond.

gold has a fcc crystalline structure with an Au-Au atom distance of about 2.88 Å

Sample preparation

dispersion of the nanowires in IPA or water at concentration c=0.1 mg/ml;(V. Nicolosi et al., Chem. Phys. Lett. 425, 89 (2006))

AFM studies of the dispersed nanowires;

AuNPs provided by BBI International company;

AFM studies of the AuNPs;

MoSIx nanowires mixed with AuNPs and left for 3 days at 4 ºC to react.

AuNPs reproducibly attach to the MoSIx nanowires; we have single attachment: one AuNP at the end of the

nanowire; we have also seen multiple attachments: 2 nanowires attached

to one gold cluster or 3 nanowires attached to one gold cluster.

AFM analysis of functionalized nanowires

M.I. Ploscaru et al., Nanoletters 7, 1445 (2007)

Multi terminal-connections: distribution

three terminal connectors

two terminal connectors

schematic representation of 2 terminal-connections and AFM image; nanowires of ~ 0.5 nm connected to ~3 nm gold colloid.

schematic representation of 3 terminal-connections and AFM image; nanowires of ~ 1 nm, 1.5 nm and 2 nm connected to ~ 5 nm gold colloid.

3 terminals

2 terminals

3 terminal-connections - narrow distribution centered at around 120º angle;

2 terminal-connections - broad distribution with angles ranging from 80º to 180º.

the normals of a two (111) planes and one (100) plane form an angle of approximately 120º.

the projection of the normals of three (111) planes form a 120º angle.

Possible connectivity of the multi terminal-connectors

search for planes that can form 120º

between each other; truncate the corners; we obtain a cluster formed of

combination of (111) and (100) planes.

Control experiments with Ag nanoparticles

AuNPs attach to MoSIx nanowires; we have single and also multiple attachments.

sample was prepared as for Au attachment;

non-attachment of AgNPs; the repulsion forces between

the negatively charged colloids and negatively charged nanowires could not be surpassed.

Protein functionalization I

5 nm AuNP covered by thyroglobulin

thyroglobulinMoSIx nanowire

disulfide bonds

protein of high molecular mass (660 kDa) and with surface rich in disulfide bonds

dispersion of nanowires in water – mixed with gold clusters and thyroglobulin;

the solution was left to react in fridge for 3 days and then analyzed under the AFM ;

direct attachment of the protein to the nanowire; the gold clusters attached on the protein.

Protein functionalization II

thyroglobulin functionalized MoSIx nanowires

GFP functionalized nanowires

Possible applications in bio-nano technology

1. nanocircuits

2. biosensors

3. photodetection

GFP can be used as a marker; fluoresces in the lower green

portion of the visible spectrum;(Excitation max=488 nm; Emission max=507 nm)

molecular recognition

MoSIx nanowires

proteins

buffer solution

gold-nanowire networks for possible future devices

MoSIx nanowires

gold colloids

gold pads

D. VengustM. UplaznikJ. StrleA. MrzelD. Mihailovic

S. Jenko KokaljD. Turk