MoSIx nanowires functionalization for molecular-scale connectivity

1
MoSIx nanowires functionalization for
molecular-scale connectivity
Mihaela Irina Ploscaru Jozef Stefan Institute
SLONANO 2007
2
MoSIx nanowires

• one step synthesis - wool like appearance

• 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

3
Structure of MoSIx nanowires

• XRD measurements individual nanowires are
  composed of Mo6 octahedral clusters
• surrounded by S or I atoms and connected by
  bridging anions of S

A. Meden et al., Nanotechnology 16, 1578
(2005) V. Nicolosi et al., Adv. Matter 19, 543
(2007)

• EXAFS measurements the distance between Mo
  atoms is d2.63 Å

4
Connectivity of MoSIx nanowires

• 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

A. Meden et al., Nanotechnology 16, 1578
(2005) V. Nicolosi et al., Adv. Matter 19, 543
(2007)
5
Sample preparation

• dispersion of the nanowires in IPA or water at
  concentration c0.1 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.

6
AFM analysis of functionalized nanowires

• 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.

M.I. Ploscaru et al., Nanoletters 7, 1445 (2007)
7
Multi terminal-connections distribution

• schematic representation of 2 terminal-connection
  s and AFM image
• nanowires of 0.5 nm connected to 3 nm gold
  colloid.

• 3 terminal-connections - narrow distribution
  centered at around 120º angle
• 2 terminal-connections - broad distribution with
  angles ranging from 80º to 180º.

• schematic representation of 3 terminal-connection
  s and AFM image
• nanowires of 1 nm, 1.5 nm and 2 nm connected
  to 5 nm gold colloid.

8
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.

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

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

9
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.

10
Protein functionalization I

• 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.

11
Protein functionalization II

• GFP functionalized nanowires

• thyroglobulin functionalized MoSIx nanowires

12
Possible applications in bio-nano technology
1. nanocircuits

• gold-nanowire networks for possible future
  devices

2. biosensors

• molecular recognition

3. photodetection

• GFP can be used as a marker
• fluoresces in the lower green portion
• of the visible spectrum
• (Excitation max488 nm Emission max507 nm)

13
(No Transcript)