https://is.muni.cz/el/1431/podzim2006/C7780/um/Read/2711172/SAM_str_grwth_ProgSurfSci00_151.pdf

Structure and growth of self-assembling monolayers

Self-assembled monolayers (SAMs) of alkanethiols and dialkanethiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology. Despite the progress made in the knowledge of these fascinating two-dimensional molecular systems, there are still several “hot topics” that deserve special attention in order to understand and to control their physical and chemistry properties at the molecular level. This critical review focuses on some of these topics, including the nature of the molecule–gold interface, whose chemistry and structure remain elusive, the self-assembly process on planar and irregular surfaces, and on nanometre-sized objects, and the chemical reactivity and thermal stability of these systems in ambient and aqueous solutions, an issue which seriously limits their technological applications (375 references).

Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system

In this Review, we aim to provide an updated summary of the research related to hollow micro- and nanostructures, covering both their synthesis and their applications. After a brief introduction to the definition and classification of the hollow micro-/nanostructures, we discuss various synthetic strategies that can be grouped into three major categories, including hard templating, soft templating, and self-templating synthesis. For both hard and soft templating strategies, we focus on how different types of templates are generated and then used for creating hollow structures. At the end of each section, the structural and morphological control over the product is discussed. For the self-templating strategy, we survey a number of unconventional synthetic methods, such as surface-protected etching, Ostwald ripening, the Kirkendall effect, and galvanic replacement. We then discuss the unique properties and niche applications of the hollow structures in diverse fields, including micro-/nanocontainers and rea...

Synthesis, Properties, and Applications of Hollow Micro-/Nanostructures

Impedance biosensors are a class of electrical biosensors that show promise for point-of-care and other applications due to low cost, ease of miniaturization, and label-free operation. Unlabeled DNA and protein targets can be detected by monitoring changes in surface impedance when a target molecule binds to an immobilized probe. The affinity capture step leads to challenges shared by all label-free affinity biosensors; these challenges are discussed along with others unique to impedance readout. Various possible mechanisms for impedance change upon target binding are discussed. We critically summarize accomplishments of past label-free impedance biosensors and identify areas for future research.

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Label-Free Impedance Biosensors: Opportunities and Challenges.

Sensor technology has an important effect on many aspects in our society, and has gained much progress, propelled by the development of nanoscience and nanotechnology. Current research efforts are directed toward developing high-performance gas sensors with low operating temperature at low fabrication costs. A gas sensor working at room temperature is very appealing as it provides very low power consumption and does not require a heater for high-temperature operation, and hence simplifies the fabrication of sensor devices and reduces the operating cost. Nanostructured materials are at the core of the development of any room-temperature sensing platform. The most important advances with regard to fundamental research, sensing mechanisms, and application of nanostructured materials for room-temperature conductometric sensor devices are reviewed here. Particular emphasis is given to the relation between the nanostructure and sensor properties in an attempt to address structure-property correlations. Finally, some future research perspectives and new challenges that the field of room-temperature sensors will have to address are also discussed.

Nanostructured Materials for Room-Temperature Gas Sensors

Multi-wall carbon nanotubes (MWNT) were functionalised in an oxygen-based atmosphere by an inductively coupled RF-plasma at 13.56 MHz. X-ray photoelectron spectroscopy analysis showed that the chemical composition of the nanotube surface depends on the plasma conditions used. The MWNT were then deposited onto microhotplate gas sensor substrates by the drop coating method, A well-adhered thick-film of carbon nanotubes mesh (similar to 17 mu m) was obtained after annealing in air. The influence of the different plasma conditions on the responsiveness of gas sensors fabricated with the functionalised MWNT was studied, The gas sensing properties were investigated both experimentally and theoretically for NO2, and NH3 at room temperature. (c) 2005 Elsevier B.V. All rights reserved.

Oxygen functionalisation of MWNT and their use as gas sensitive thick-film layers

Monolayers of n-dodecanethiol molecules on surfaces of polycrystalline nickel electrochemically pretreated are obtained by immersion either in pure n-dodecanethiol or in a solution of the mercaptan in absolute ethanol. The influence of the electrochemical pretreatment on the quality of the organic layer has been studied by contact angle measurements, electrochemistry, and X-ray photoelectron spectroscopy. It is found that n-dodecanethiol monolayers directly adsorbed on nickel surfaces without electrochemical pretreatment are of poor quality and exhibit a significant proportion of the thiols oxidized into sulfonates and sulfinates. On the contrary, the electrochemical pretreatment leads to monolayers with significantly improved physicochemical properties such as better chemical stability, resistance to electrochemical oxidation, and molecular order.

Self-Assembled Monolayers of n-Dodecanethiol on Electrochemically Modified Polycrystalline Nickel Surfaces

Nanoscaled interdigitated electrodes (IDEs) are developed for the purpose of being used as miniature and sensitive affinity biosensors. Because of the ease to derivatise its surface, oxidized Ti is chosen as an electrode material on a SiO2 substrate. For proof of principle, oxidized and non-oxidized Ti IDEs are characterised in salt solutions and the immobilisation of glucose oxidase is monitored using impedance spectroscopy. Beside transducer development and demonstration, tailored bio interfaces are a prerequisite for the development of sensitive affinity biosensors. Therefore, a characterisation of immobilisations (based on silanisations) on TiO2 and SiO2 is conducted. For this study, different analytical techniques are identified and evaluated. The use of these techniques will enable a thorough characterisation of immobilisation processes, ultimately leading to miniature and sensitive affinity biosensors.

Nanoscaled interdigitated titanium electrodes for impedimetric biosensing

Active layers for gas sensing applications have been obtained by adding oxygen plasma functionalised multi-walled carbon nanotubes (MWCNTs) to WO3 and using the drop-coating deposition method. Scanning electron micrographs showed that MWCNTs are well dispersed on the WO3 matrix. X-ray photoelectron analysis showed that by adding MWCNTs to the WO3 films the contribution of the doublet related with surface defects to the total W 4f signal increased. This gives evidence that the surface area of WO3 films increases due to the addition of MWCNTs to the film. Two different ratios of MWCNTs in WO3 (1/100 and 1/1000) were considered and the response of these sensors towards toxic gases such as nitrogen dioxide, carbon monoxide and ammonia was compared with that of WO3 and MWCNTs gas sensors. The results indicate that the detection at ambient temperature of these toxic gases using WO3-based gas sensors can be highly improved by dispersing an adequate quantity of MWCNTs into the WO3 matrix. A possible mechanism explaining the behaviour of hybrid sensors is introduced.

WO3 films modified with functionalised multi-wall carbon nanotubes: Morphological, compositional and gas response studies

http://ematweb.cmi.ua.ac.be/emat/pdf/1470.pdf

J.J. Pireaux

Papers

Oxygen functionalisation of MWNT and their use as gas sensitive thick-film layers

Self-Assembled Monolayers of n-Dodecanethiol on Electrochemically Modified Polycrystalline Nickel Surfaces

Nanoscaled interdigitated titanium electrodes for impedimetric biosensing

WO3 films modified with functionalised multi-wall carbon nanotubes: Morphological, compositional and gas response studies

Metal-decorated multi-wall carbon nanotubes for low temperature gas sensing