Scanning tunneling microscopy and the atomic structure of solid surfaces

Ogletree, Frank; Salmerón, Miquel

doi:10.1016/0079-6786(90)90002-w

Cited by 37 publications

(6 citation statements)

References 219 publications

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“…In an effort to obtain direct structural information on the aggregation of Chl a in thin films, we have examined monolayers of Chl a transferred onto freshly cleaved graphite (HOPG, ZYB grade, Advanced Ceramics, Lakewood, OH) by scanning tunneling (STM; Nanoscope II STM, Digital Instruments, Santa Barbara, CA) (8,9) and atomic force (AFM) (10, 11) microscopies, i.e. scanning probe microscopy.…”

mentioning

confidence: 99%

Chlorophyll a dimer: A possible primary electron donor for the photosystem II

Boussaad

Tazi

Leblanc

1997

Proc. Natl. Acad. Sci. U.S.A.

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In the photosynthetic membrane, there is a particular aggregated state for the chlorophyll a (Chl a) molecules with a specific arrangement responsible for the high efficiency of energy conversion. Chl a monolayers, transferred onto solid substrates, are systems that potentially can mimic the packing of the in vivo system. The association of Chl a in the monolayer results in the formation of dimers with an average size of 3.00 ؎ 0.15 nm. Considering the organization of the dimers, we assume that P680 is a dimer with the (anti) parallel transition moments of the constituent. The Chl a macrocycles most likely are tilted to each other by 30؇ with respect to the membrane plane.Green plants use light energy, through photosynthesis, to reduce CO 2 and produce carbohydrates. The central unit where this activity takes place, the photosynthetic membrane, is described as a segment of lipid bilayer in which proteinpigment complexes are bound. Two complexes within the photosynthetic membrane are considered the key reaction centers, photosystem I (PS I) and PS II (1). Pigments, such as chlorophyll a (Chl a), located within PS I and PS II, play a major role in the capture of light energy and the subsequent charge transfer that results in CO 2 reduction (2). Chl a has a broad absorption spectrum, and aggregation through selfassembly typically leads to changes in its optical properties (3, 4). Red shifts are commonly observed in in vitro Chl a systems, such as thin films, monolayers, and colloidal dispersions, used as models for the in vivo system (5). One such system, based on the Langmuir-Blodgett (L-B) (6) technique for forming ordered thin films, allows the orientation of molecules in a molecular monolayer at an air͞water interface and the subsequent transfer onto solid substrates. The transferred L-B film is highly packed and well organized, and the use of this technique allows preparation of systems to potentially mimic the in vivo packing of Chl a within the photosynthetic membrane.Numerous attempts have been made to model the arrangement of Chl a to rationalize its high energy conversion efficiency. One model (7) proposed for the primary electron donor of PS I describes the formation of a Chl a dimer held together via water bridges. In this model, the oxygen of one H 2 O molecule is coordinated to the magnesium of a Chl a molecule, while its hydrogen bonds to the keto carbonyl group of a second Chl a molecule. A second H 2 O molecule completes the dimer in the same way. This results in a structure where the distance between the Mg centers is 0.89 nm, and the interplanar separation between the macrocycles is 0.36 nm.In an effort to obtain direct structural information on the aggregation of Chl a in thin films, we have examined monolayers of Chl a transferred onto freshly cleaved graphite (HOPG, ZYB grade, Advanced Ceramics, Lakewood, OH) by scanning tunneling (STM; Nanoscope II STM, Digital Instruments, Santa Barbara, CA) (8, 9) and atomic force (AFM) (10, 11) microscopies, i.e. scanning probe microscopy. Chl a (T...

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mentioning

confidence: 99%

Chlorophyll a dimer: A possible primary electron donor for the photosystem II

Boussaad

Tazi

Leblanc

1997

Proc. Natl. Acad. Sci. U.S.A.

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“…Tunneling from states with a small momentum component parallel to the surface (i. e. close to the center of the surface Brillouin zone) is more probable than from states with larger momentum component parallel to the surface (see e. g. [28,29]). As a result, an ordinarily constant, two-dimensional density of states becomes more weighted close to the band edge.…”

Section: Density Of Statesmentioning

confidence: 99%

Extracting the Rashba splitting from scanning tunneling microscopy measurements

Ast

2015

Journal of Electron Spectroscopy and Related Phenomena

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“…Furthermore, electron tunneling enables STM to probe electron states at different energies at a point or as an image, referred to as scanning tunneling spectroscopy (STS). After almost 40 years, commercially available scanning tunneling microscopes are routinely capable of obtaining a lateral resolution of ≤100 pm and a vertical resolution of 1 pm, which is enough to identify atomic features at the surface. − …”

Section: Operando Surface Science On Single Crystal Catalystsmentioning

confidence: 99%

Operando Surface Characterization on Catalytic and Energy Materials from Single Crystals to Nanoparticles

Choi

Kim

et al. 2020

ACS Nano

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Modern surface science faces two major challenges, a materials gap and a pressure gap. While studies on single crystal surface in ultrahigh vacuum have uncovered the atomic and electronic structures of the surface, the materials and environmental conditions of commercial catalysis are much more complicated, both in the structure of the materials and in the accessible pressure range of analysis instruments. Model systems and operando surface techniques have been developed to bridge these gaps. In this Review, we highlight the current trends in the development of the surface characterization techniques and methodologies in more realistic environments, with emphasis on recent research efforts at the Korea Advanced Institute of Science and Technology. We show principles and applications of the microscopic and spectroscopic surface techniques at ambient pressure that were used for the characterization of atomic structure, electronic structure, charge transport, and the mechanical properties of catalytic and energy materials. Ambient pressure scanning tunneling microscopy and X-ray photoelectron spectroscopy allow us to observe the surface restructuring that occurs during oxidation, reduction, and catalytic processes. In addition, we introduce the ambient pressure atomic force microscopy that revealed the morphological, mechanical, and charge transport properties that occur during the catalytic and energy conversion processes. Hot electron detection enables the monitoring of catalytic reactions and electronic excitations on the surface. Overall, the information on the nature of catalytic reactions obtained with operando spectroscopic and microscopic techniques may bring breakthroughs in some of the global energy and environmental problems the world is facing.

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Scanning tunneling microscopy and the atomic structure of solid surfaces

Cited by 37 publications

References 219 publications

Chlorophyll a dimer: A possible primary electron donor for the photosystem II

Chlorophyll a dimer: A possible primary electron donor for the photosystem II

Extracting the Rashba splitting from scanning tunneling microscopy measurements

Operando Surface Characterization on Catalytic and Energy Materials from Single Crystals to Nanoparticles

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