Scanning probe technique

Three-dimensional, atomic-scale images of conducting surfaces can be obtained using a scanning tunneling microscope [14,290,334,354,369-381]. It is based on the quantum mechanical tunneling of electrons. The electron clouds of the outermost 

STM can be apphed even under electrochemical conditions, i.e., when both the tip and the sample are immersed in the electrolyte of the cell, and the sample is the working electrode, the surface of which is to be investigated. 

AFM is very similar to STM in terms of its directional translation system and its arrangement, and it also has the ability to produce atomic-scale images of the surface [328,361,369,372,382-385]. However, in this case, the electronic conductivity of the sample is not important because interatomic forces between the tip and tte 

Using AFM, van der Waals forces, electrostatic interactions between ions, frie-tion, elasticity and plasticity can all be measured. 

The polymer film thickness and the solvent swelling of the polymer can be estimated by AFM, as has been demonstrated by Wu and Chang [383] in the case of poly(o-pheitylenediamine). 

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The lubricant properties of alkanethiols and fluorinated alkanes have been studied extensively by scanning probe techniques [163]. In agreement with experiments on LB monolayers it was found that the fluorocarbon monolayers show considerably higher friction than the corresponding hydrocarbon monolayers [164, 165 and 166] even though the fluorocarbons are known to have the lowest surface free energy of all organic materials. 

Additional suggested resources for the reader include introductory articles on scanning probe techniques for materials properties measurement [82,83J. A comprehensive manual describing various surface preparation techniques, experimental procedures and instrumentation is also a good resource [84J, although the more recent modulation based techniques are not covered. Key textbooks include Johnson s on contact mechanics [51J and Israelachvili s on surface forces [18J, as well as a treatment of JKR/DMT issues by Maugis [85J. 

Three scanning probe techniques are described in more detail below the scanning tunneling microscope, the atomic force microscope, and the friction force microscope. 

Alessandrini A, Comi S, Facci P (2006) Unravelling single metalloprotein electron transfer by scanning probe techniques. Phys Chem Chem Phys 8 4383 1397... 

The concept of resolution in AFM is different from radiation-based microscopies because AFM imaging is a three-dimensional imaging technique. There is an important distinction between images resolved by wave optics and those resolved by scanning probe techniques. The former is limited by diffraction, whereas the latter is limited primarily by apical probe geometry and sample geometry. Usually the width of a DNA molecule is loosely used as a measure of resolution, because it has a known diameter of 2.0 nm in its B form. 

The scanning probe techniques readily achieve subnanometer resolution and can sometimes even visualize atoms, provided the following requirements are satisfied ... 

The chemical composition of the IF phase deviates only very slightly, if at all, from the composition of the bulk layered compound. Deviations from stoichiometry can only occur in the cap of the nanotube. In fact, even the most modem analytical techniques, like scanning probe techniques and high (spatial) resolution electron energy loss spectroscopy, are unable to resolve such a tiny deviation from the stoichiometry, like the excess or absence of a single Mo (W) or S (Se) atom in the nanotube cap. 

S. Prokhorova, for skillful measurements with scanning probe techniques. This work was financially supported by the Deutsche Forschungsgemeinschaft (SH 46/2-1), Graduiertenkol-leg-328 Molecular organization and dynamics on surfaces and interfaces . 

When the first edition was published in 1992, the resolution of the acoustic microscope techniques used at the time was controlled by the wavelength. In practice the frequency-dependent attenuation of the acoustic wave in the coupling fluid sets a lower limit to the wavelength, and therefore to the resolution, of about 1 pm for routine applications. Since then scanning probe techniques with nanometre scale resolution have been developed along the lines of the atomic force microscope. This has resulted in the development of the ultrasonic force microscopy techniques, in which the sample is excited by... 

Explain how scanning probe techniques can be modified to provide spectroscopic information. 

The term feedback mode refers to the coupling of heterogeneous reactions at the specimen and the UME and not to an electronic control principle as commonly used in other scanning probe techniques to maintain a constant sample-probe distance. 

Combined scanning probe techniques 932 Compartmentalized surfaces 921 Competitive immunoassay el80 Composite electrodes 145 material 916 Concanavalin A 313, 317 Conducting polymer 44, 73 based ISE 74 Conductivity e62 Conductometric transducers 241 Conjugate 650 polymer 74... 

Other Modes and Scanning Probe Techniques Useful for Polymers... 

Key questions ahead of us concern new concepts for addressing individual molecular switches and the construction of more complex systems which incorporate several switchable functions. Advances in scanning - probe techniques and single molecule spectroscopy as well as supramolecular chemistry will play an important role in this endeavor. 

The techniques involved are single-molecule spectroscopy including optical (fluorescence) methods and single-molecule mechanical manipulation including scanning probe techniques (e.g., force measurements). 

Combining Surface Enhanced Raman Spectroscopy and Nanoscale Scanning Probe Techniques... 

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