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Characterization of thiol-functionalized oligo(phenylene-ethynylene)-protected Au nanoparticles by scanning tunneling microscopy and spectroscopy
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10.1063/1.4747720
/content/aip/journal/apl/101/8/10.1063/1.4747720
http://aip.metastore.ingenta.com/content/aip/journal/apl/101/8/10.1063/1.4747720
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Figures

Image of FIG. 1.
FIG. 1.

(a) Chemical structure of thiol-functionalized OPE, 1,4-bis-(3-mercapto-phenylethynyl)benzene, ligand molecule. (b) Schematic drawing of the double-barrier tunneling junctions. Junction 1 is the tunneling barrier between STM-tip and Au core, which consists of a vacuum layer and OPE ligand, and junction 2 is the tunneling barrier between the Au core and Au(111) surface, which consists of only the OPE ligand.

Image of FIG. 2.
FIG. 2.

Comparison between SEM and STM images of chemisorbed OPE-protected Au nanoparticles on Au(111) substrate. (a)–(c) and (d)–(e) are the SEM and STM images, respectively, of the sample prepared by immersion in a 0.16 nM DMF solution of OPE-protected Au nanoparticle for 10 min. (b) and (c) are magnified images of the square area (A and B, respectively) of (a). The size of (b) and (d) is 150 × 150 nm2 and the size of (c) and (e) is 100 × 100 nm2. The STM images for (d) and (e) were obtained with set-point currents of 20 pA and sample bias voltages of −1.8 V and 1.5 V, respectively.

Image of FIG. 3.
FIG. 3.

Stochastic switching behaviors of OPE-protected Au nanoparticle, observed using STM. (a) STM images obtained with a sample bias voltage of −1.5 V, set point current of 10 pA, and image size of 35 × 35 nm2. (b) Successive STM images of single OPE-protected Au nanoparticle were acquired at 7 -, 15 -, 25 -, 32 -, 47 -, 59 -, and 80-min intervals from the image A. (c) is the cross-sectional profile of the Au nanoparticle in Fig. 3(b) (black solid lines and blue broken lines represent as A and B, respectively).

Image of FIG. 4.
FIG. 4.

Tunneling current versus sample bias voltage characteristics in STM-tip/vacuum/OPE ligand/Au core/OPE ligand/Au(111). (a)–(f) show the linear plots and the corresponding semi-logarithmic plots. Solid lines represent the experimental results and broken lines represent the theoretical I(V) curves calculated using the orthodox theory. The values of the evaluated parameter are as follows: (a) C 1 = 0.039 aF, C 2 = 0.062 aF, R 1 = 71 GΩ, R 2 = 12 GΩ, and Q 0 = −0.06e; (b) C 1 = 0.053 aF, C 2 = 0.079 aF, R 1 = 194 GΩ, R 2 = 11 GΩ, and Q 0 = −0.023e; (c) C 1 = 0.084 aF, C 2 = 0.15 aF, R 1 = 44.6 GΩ, R 2 = 15 GΩ, and Q 0 = −0.15e; (d) C 1 = 0.056 aF, C 2 = 0.067 aF, R 1 = 32 GΩ, R 2 = 10 GΩ, and Q 0 = −0.061e; (e) C 1 = 0.045 aF, C 2 = 0.091 aF, R 1 = 21.9 GΩ, R 2 = 8 GΩ, and Q 0 = 0.147e; (f) C 1 = 0.068 aF, C 2 = 0.046 aF, R 1 = 17.5 GΩ, R 2 = 7.5 GΩ, and Q 0 = 0.114e, where e is the unit charge.

Image of FIG. 5.
FIG. 5.

Set-point current (I set) dependence of tunneling resistances (a) R 1, and (b) R 2 for OPE-protected Au nanoparticles. Open and closed circles represent the evaluated values of R 1 and R 2, respectively. (a) Solid line indicates the power law R 1∝1/Iset when I set R 1 = 2 V. (b) The solid and the dashed lines show the power law relationship I set R 1 = 2 V (R 1/R 2 = 1) and I set R 2 = 0.04 V (R 1/R 2 = 50), respectively. The average values of R 2 for OPE-protected Au nanoparticles are 15 GΩ when I set ≤ 20 pA.

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/content/aip/journal/apl/101/8/10.1063/1.4747720
2012-08-23
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Characterization of thiol-functionalized oligo(phenylene-ethynylene)-protected Au nanoparticles by scanning tunneling microscopy and spectroscopy
http://aip.metastore.ingenta.com/content/aip/journal/apl/101/8/10.1063/1.4747720
10.1063/1.4747720
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