Single-Molecule Reaction and Characterization by Vibrational Excitation

Yousoo Kim, Tadahiro Komeda, and Maki Kawai

Phys. Rev. Lett. 89, 126104 – Published 3 September 2002

Abstract

Controlled chemical reaction of single trans-2-butene molecules on the Pd(110) surface was realized by dosing tunneling electrons from the tip of a scanning tunneling microscope at 4.7 K. The reaction product was identified as a 1,3-butadiene molecule by inelastic electron tunneling spectroscopy. Threshold voltage for the reaction is $\sim 365 m V$ , which coincides with the vibrational excitation of the C-H stretching mode. The reaction was ascertained to be caused by C-H bond dissociation by multiple vibrational excitations of the C-H stretching mode via inelastic electron tunneling process.

Received 9 April 2002

DOI:https://doi.org/10.1103/PhysRevLett.89.126104

Authors & Affiliations

Yousoo Kim, Tadahiro Komeda, and Maki Kawai^*

RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan

^*The author to whom correspondence should be sent. Email address: maki@postman.riken.go.jp

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 89, Iss. 12 — 16 September 2002

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
STM images of (a) trans-2-butene and (b) 1,3-butadiene molecules ( $area = 45 \times 45 Å^{2}$ , $V_{s} = - 300 m V$ , $I_{t} = 1.00 n A$ ). Schematic representation of the adsorption site of (c) trans-2-butene and (d) 1,3-butadiene molecule on Pd(110), respectively. STM images of coadsorbed surface ( $area = 20 \times 20 Å^{2}$ , $V_{s} = - 200 m V$ , $I_{t} = 0.86 n A$ ) (e) before and (f) after dosing tunneling electrons on a target molecule of trans-2-butene marked with an arrow in (e). The trans-2-butene, reaction product, and 1,3-butadiene molecules are labeled $T$ , $P$ , and $B$ , respectively, in (f).Reuse & Permissions
Figure 2
(a) Vibrational spectra obtained for the clean Pd(110) surface (dashed line) and trans-2-butene (solid line) by STM-IETS taken at a gap resistance of $1 G Ω$ with a $14.1 m V_{r m s}$ ac modulation at 397 Hz. The spectra are averages of four scans from $- 400$ to $+ 400 m V$ . (b) Vibrational spectra for trans-2-buten (upper line) and trans-2-buten- $d_{8}$ (lower line) after background subtraction. The change in conductance for the peaks at $\pm 366 m V$ (268 mV) is 6% (5%) at positive sample bias, and 7% (3%) at negative sample bias, for the C-H (C-D) stretching mode of trans-2-butene (trans-2-butene- $d_{8}$ ). (c) Vibrational spectra for trans-2-butene (curve $T$ ), reaction product (curve $P$ ), and 1,3-butadiene (curve $B$ ) shown in Fig. 1f, respectively. The spectra were taken at a gap resistance of $200 M Ω$ within the range of 0 and 230 mV, in the region where the dehydrogenation does not occur, and $1.5 G Ω$ within the range of 300 and 400 mV.Reuse & Permissions
Figure 3
(a) Reaction yield per electron for trans-2-butene and trans-2-butene- $d_{8}$ as a function of sample bias voltage under constant tunneling current of 32 nA. Dotted lines represent the slopes of the data. Reaction rate ( $R$ ) as a function of tunneling current ( $I$ ) for various applied sample bias voltages for (b) trans-2-butene and (c) trans-2-butene- $d_{8}$ . Solid lines are the results of least squares fits to the data, whose slopes for applied bias voltages correspond to powers ( $n$ ) in nonlinear power-law dependence, $R \propto I^{n}$ . In (b), $n = 2.23$ , 1.96, 2.09, and 1.45 for 370, 400, 600, and 800 mV, respectively. In (c), $n = 3.06$ , 2.19, 2.21, and 1.36 for 400, 600, 800, and 1000 mV, respectively.Reuse & Permissions
Figure 4
Schematic representation of vibrational heating and dehydrogenation using a truncated one-dimensional harmonic oscillator. The potential well includes two C-H and three C-D vibrational states following the reaction orders determined from the experimental results (Figs. 3b, 3c). Representative types of vibrational transition for applied basis are considered as follows: (a) 370, 400, 600 mV and (b) 800 mV for C-H, (c) 400 mV, (d) 600, 800 mV, and (e) 1000 mV for C-D.Reuse & Permissions

Physical Review Letters