The Langmuir-Blodgett (LB) technique is known as an elegant method for fabrication of well-defined layered structures with molecular level precision. Since its discovery the LB method has made an indispensable contribution to surface science, physical chemistry, materials chemistry and nanotechnology. However, recent trends in research might suggest the decline of the LB method as alternate methods for film fabrication such as layer-by-layer (LbL) assembly have emerged. Is LB film technology obsolete? This review is presented in order to challenge this preposterous question. In this review, we summarize recent research on LB and related methods including (i) advanced design for LB films, (ii) LB film as a medium for supramolecular chemistry, (iii) LB technique for nanofabrication and (iv) LB involving advanced nanomaterials. Finally, a comparison between LB and LbL techniques is made. The latter reveals the crucial role played by LB techniques in basic surface science, current advanced material sciences and nanotechnologies.

25th anniversary article: what can be done with the Langmuir-Blodgett method? Recent developments and its critical role in materials science.

Chemical and biological sensors have found their niche among modern analytical instruments when real-time determination of the concentration of specific sample constituents is required. Development of sensors with new capabilities is driven by the ever-expanding monitoring needs of a wide variety of species in gases and liquids. On the basis of a variety of definitions of sensors, 1-3 here we will accept that a chemical or biological sensor is an analytical device that utilizes a chemically or biologically responsive sensing layer to recognize a change in a single or multiple chemical or biological parameters of a measured environment and to convert this information into an analytically useful signal. In a sensor device, a sensing material is applied onto a suitable physical transducer to convert a change in a property of a sensing material into a suitable physical signal. The obtained signal from a single transducer or an array of transducers is further processed to provide useful information about the identity and concentration of species in the sample. The energy transduction principles that have been employed for chemical and biological sensing involve radiant, electrical, mechanical, and thermal types of energy. 4,5 Specific sensing concepts are further implemented with each energy transduction. Sensors based on radiant energy of transduction can employ intensity, wavelength, polarization, phase, or time resolution detection. Sensors based on electrical energy of transduction can employ conductometric, potentiometric, or amperometric detection. Sensors based on mechanical energy of transduction can employ gravimetric or viscoelastic detection. Sensors based on thermal energy of transduction can employ calorimetric or pyroelectric detection. Hyphenated techniques in sensing are of significant importance and combine several transduction techniques in one sensor. 6,7 In addition to a sensing material layer and a transducer, a modern sensor system often incorporates other important components such as sample introduction and data processing components. In contrast to sensing based on intrinsic analyte properties (e.g., spectroscopic, dielectric, thermal), indirect sensing utilizes a responsive sensing material. 2,5,8-13 This approach dramatically expands the range of detected species, improves sensor performance (e.g., analyte detection limits), and is more straightforwardly adaptable for miniaturization. 6,14-33

Combinatorial and high-throughput development of sensing materials: the first 10 years.

Single-molecule measurement techniques have illuminated unprecedented details of chemical behavior, including observations of the motion of a single molecule on a surface, and even the vibration of a single bond within a molecule. Such measurements are critical to our understanding of entities ranging from single atoms to the most complex protein assemblies. We provide an overview of the strikingly diverse classes of measurements that can be used to quantify single-molecule properties, including those of single macromolecules and single molecular assemblies, and discuss the quantitative insights they provide. Examples are drawn from across the single-molecule literature, ranging from ultrahigh vacuum scanning tunneling microscopy studies of adsorbate diffusion on surfaces to fluorescence studies of protein conformational changes in solution.

Electrons, Photons, and Force: Quantitative Single-Molecule Measurements from Physics to Biology

Resistless nanofabrication by stencil lithography

Direct conversion of mesoporous crystalline fullerene C70 microtubes into mesoporous graphitic carbon microtubes by heat treatment at high temperature (2000 °C) with retention of the initial one-dimensional tubular morphology is reported. The walls of the resulting graphitic carbon microtubes are composed of ordered conjugated sp2 carbon with a robust mesoporous framework structure. Cyclic voltammetry and chronopotentiometry (charge–discharge) measurements revealed that this new carbon material exhibits high specific capacitance ca. 212.2 F g−1 at a scan rate of 5 mV s−1 and 184.6 F g−1 at current density 0.5 A g−1. Furthermore, the material showed high rate performance. These results demonstrate that mesoporous graphitic carbon microtubes derived from the π-electron carbon source fullerene C70 can be a promising electrode material for application in high performance electrochemical supercapacitors.

/pdf/mesoporous-graphitic-carbon-microtubes-derived-from-3g09wv63qo.pdf

Mesoporous graphitic carbon microtubes derived from fullerene C70 tubes as a high performance electrode material for advanced supercapacitors

In the research of advanced materials based on nanoscience and nanotechnology, it is often desirable to measure nanoscale local electrical conductivity at a designated position of a given sample. For this purpose, multiple-probe scanning probe microscopes (MP-SPMs), in which two, three or four scanning tunneling microscope (STM) or atomic force microscope (AFM) probes are operated independently, have been developed. Each probe in an MP-SPM is used not only for observing high-resolution STM or AFM images but also for forming an electrical contact enabling nanoscale local electrical conductivity measurement. The world's first double-probe STM (DP-STM) developed by the authors, which was subsequently modified to a triple-probe STM (TP-STM), has been used to measure the conductivities of one-dimensional metal nanowires and carbon nanotubes and also two-dimensional molecular films. A quadruple-probe STM (QP-STM) has also been developed and used to measure the conductivity of two-dimensional molecular films without the ambiguity of contact resistance between the probe and sample. Moreover, a quadruple-probe AFM (QP-AFM) with four conductive tuning-fork-type self-detection force sensing probes has been developed to measure the conductivity of a nanostructure on an insulating substrate. A general-purpose computer software to control four probes at the same time has also been developed and used in the operation of the QP-AFM. These developments and applications of MP-SPMs are reviewed in this paper.

Development and Application of Multiple-Probe Scanning Probe Microscopes

Four-terminal electrical measurement is realized on a microscopic structure in air, without a lithographic process, using a home-built quadruple-scanning-probe force microscope (QSPFM). The QSPFM has four probes whose positions are individually controlled by obtaining images of a sample in the manner of atomic force microscopy (AFM), and uses the probes as contacting electrodes for electrical measurements. A specially arranged tuning fork probe (TFP) is used as a self-detection force sensor to operate each probe in a frequency modulation AFM mode, resulting in simultaneous imaging of the same microscopic feature on an insulator using the four TFPs. Four-terminal electrical measurement is then demonstrated in air by placing each probe electrode in contact with a graphene flake exfoliated on a silicon dioxide film, and the sheet resistance of the flake is measured by the van der Pauw method. The present work shows that the QSPFM has the potential to measure the intrinsic electrical properties of a wide range of microscopic materials in situ without electrode fabrication.

https://iopscience.iop.org/article/10.1088/0957-4484/22/28/285205/pdf

A quadruple-scanning-probe force microscope for electrical property measurements of microscopic materials.

We expand the range of applications of a tuning fork probe (TFP) in frequency-modulation atomic force microscopy (FM-AFM) by attaching a long metal tip at a certain angle. By the combined flexure of the metal tip and the tuning fork prong, this TFP can change the direction of the detectable force by switching the resonance frequency, which has not been realized with conventional TFPs with short tips. The oscillatory behavior of the tip apex of the TFP is predicted by computer simulations and is experimentally confirmed with scanning electron microscope. FM-AFM operations using this TFP are performed in various environments, i.e., in ultrahigh vacuum, air, and water. FM-AFM images obtained at an atomic step of highly oriented pyrolytic graphite in air show a clear difference depending on the excitation frequency. It is also revealed that the higher order flexural modes of this TFP are advantageous for FM-AFM in water due to the reduction in the degree of hydrodynamic damping.

Angled long tip to tuning fork probes for atomic force microscopy in various environments

A method for combinatorial fabrication and characterization of organic/inorganic thin film devices in UHV.

Over the past decade, multiple-scanning-probe microscope systems with independently controlled probes have been developed for nanoscale electrical measurements. We developed a quadruple-scanning-probe tunneling microscope (QSPTM) that can determine and control the probe position through scanning-probe imaging. The difficulty of operating multiple probes with submicrometer precision drastically increases with the number of probes. To solve problems such as determining the relative positions of the probes and avoiding of contact between the probes, we adopted sample-scanning methods to obtain four images simultaneously and developed an original control system for QSPTM operation with a function of automatic positional recognition. These improvements make the QSPTM a more practical and useful instrument since four images can now be reliably produced, and consequently the positioning of the four probes becomes easier owing to the reduced chance of accidental contact between the probes.

Seiji Higuchi

Papers

Development and Application of Multiple-Probe Scanning Probe Microscopes

A quadruple-scanning-probe force microscope for electrical property measurements of microscopic materials.

Angled long tip to tuning fork probes for atomic force microscopy in various environments

A method for combinatorial fabrication and characterization of organic/inorganic thin film devices in UHV.

Multiple-scanning-probe tunneling microscope with nanoscale positional recognition function