R. H. Bernhardt

Bio: R. H. Bernhardt is an academic researcher. The author has contributed to research in topics: Scanning tunneling microscope & Electrochemical scanning tunneling microscope. The author has an hindex of 3, co-authored 4 publications receiving 450 citations.

Imaging alkane layers at the liquid/graphite interface with the scanning tunneling microscope

Abstract: We have directly imaged n‐alkane layers adsorbed at the liquid/graphite interface using a scanning tunneling microscope. The layers possessed a high degree of two‐dimensional ordering. The adsorbate was observed to enhance the tunneling current, and the atomic structure of the images was dominated by features associated with the substrate. These systems are excellent vehicles for studies concerning the imaging mechanism of adsorbed organic layers because of their stability and simplicity.

Observation of highly ordered, two‐dimensional n‐alkane and n‐alkanol structures on graphite

Abstract: We have directly imaged n‐alkane and n‐alkanol layers at the liquid–graphite interface using a scanning tunneling microscope (STM). The layers possessed a high degree of two‐dimensional ordering, and the adsorbate was observed to enhance the tunneling current. The results of this study agree with calorimetric and surface mass measurements, and show that these macroscopic measurements can aid in the selection of systems suitable for imaging with the STM.

Mechanisms for the deposition of nanometer‐sized structures from organic fluids using the scanning tunneling microscope

Abstract: We have formed nanometer‐sized structures on graphite surfaces by the application of voltage pulses to the tunneling tip of a scanning tunneling microscope. This work pursues a line of a study initiated by Foster et al. [Nature 331, 324 (1988)]. The structures we formed in this way range from 1 nm2 to at least 100 nm2 in size. We have successfully formed these structures using a variety of tip materials (W, PtIr) and methods of manufacture (etched, ion milled, mechanically formed).We have formed structures in air, and in the presence of dimethyl phthalate and decane. We have observed a 3–4 V threshold for structure formation. We have not observed any strong dependence on pulse length in the range of 200 ns to 2 μs. Monitoring the current and tip position as a function of time proved to be a useful diagnostic technique. A likely mechanism for the formation of these structures is the deposition of tip material onto the surface.

STM Imaging of Physisorbed Molecules at the Liquid/Graphite Interface

Abstract: We have directly imaged n‐alkane and n‐alkanol layers at the liquid/graphite interface using a scanning tunneling microscope. The layers possessed a high degree of two‐dimensional ordering and the adsorbate was observed to enhance the tunneling current. Both commensurate and incommensurate adsorption was observed. Tip‐molecule forces and thermal motion of the adsorbed molecules are also discussed.

Two-dimensional supramolecular self-assembly probed by scanning tunneling microscopy

Abstract: Supramolecular chemistry has a very large impact on chemistry of current interest and the use of non-covalent but directional forces is appealing for the construction of 'supramolecular architectures'. The invention of scanning probe microscopy techniques has opened new doorways to study these concepts on surfaces. This review deals with recent progress in the study of two-dimensional supramolecular self-assembly on surfaces probed by scanning tunneling microscopy, with a special emphasis on structure, dynamics and reactivity of hydrogen bonded systems.

Self-assembly at the liquid/solid interface: STM reveals.

Abstract: The liquid/solid interface provides an ideal environment to investigate self-assembly phenomena, and scanning tunneling microscopy (STM) is the preferred methodology to probe the structure and the properties of physisorbed monolayers on the nanoscale. Physisorbed monolayers are of relevance in areas such as lubrication, patterning of surfaces on the nanoscale, and thin film based organic electronic devices, to name a few. It's important to gain insight in the factors which control the ordering of molecules at the liquid/solid interface in view of the targeted properties. STM provides detailed insight into the importance of molecule-substrate (epitaxy) and molecule-molecule interactions (hydrogen bonding, metal complexation, and fluorophobic/fluorophilic interactions) to direct the ordering of both achiral and chiral molecules on the atomically flat surface. By controlling the location and orientation of functional groups, chemical reactions can be induced at the liquid/solid interface, via external stimul...

Two-dimensional porous molecular networks of dehydrobenzo[12]annulene derivatives via alkyl chain interdigitation.

Abstract: The self-assembly of a series of hexadehydrotribenzo[12]annulene (DBA) derivatives has been scrutinized by scanning tunneling microscopy (STM) at the liquid−solid interface. First, the influence of core symmetry on the network structure was investigated by comparing the two-dimensional (2D) ordering of rhombic bisDBA 1a and triangular DBA 2a (Figure 1). BisDBA 1a forms a Kagome network upon physisorption from 1,2,4-trichlorobenzene (TCB) onto highly oriented pyrolytic graphite (HOPG). Under similar experimental conditions, DBA 2a shows the formation of a honeycomb network. The core symmetry and location of alkyl substituents determine the network structure. The most remarkable feature of the DBA networks is the interdigitation of the nonpolar alkyl chains: they connect the π-conjugated cores and direct their orientation. As a result, 2D open networks with voids are formed. Second, the effect of alkyl chain length on the structure of DBA patterns was investigated. Upon increasing the length of the alkyl c...

Biological atomic force microscopy: what is achieved and what is needed

Abstract: Biological atomic force microscopy (AFM) has become a rapidly developing interdisciplinary field of research in recent years. Not only has the technique, including instrumentation and specimen preparation methods, become increasingly sophisticated, but also its applications have encompassed a broad range of interesting subjects in biology. In this review, we present an extensive overview of the current status of biological AFM, including both the instrumentation and the application of AFM. In addition, we discuss the major problems that have yet to be fully resolved and present our analysis of the various factors involved. The published results so far clearly demonstrate the great potential of AFM in structural research and the ability of AFM to make unique contributions to our comprehension of various biological processes.