In this work we briefly describe the most relevant features of WSXM, a freeware scanning probe microscopy software based on MS-Windows. The article is structured in three different sections: The introduction is a perspective on the importance of software on scanning probe microscopy. The second section is devoted to describe the general structure of the application; in this section the capabilities of WSXM to read third party files are stressed. Finally, a detailed discussion of some relevant procedures of the software is carried out.

https://nanoed.tul.cz/pluginfile.php/1608/mod_resource/content/1/view.pdf

WSXM: a software for scanning probe microscopy and a tool for nanotechnology.

TOPICAL REVIEW: Applications of magnetic nanoparticles in biomedicine

http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

High-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)3, with 1,2-hexadecanediol in the presence of oleic acid and oleylamine leads to monodisperse magnetite (Fe3O4) nanoparticles. Similarly, reaction of Fe(acac)3 and Co(acac)2 or Mn(acac)2 with the same diol results in monodisperse CoFe2O4 or MnFe2O4 nanoparticles. Particle diameter can be tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth. The as-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD. Further, Fe3O4 can be oxidized to Fe2O3, as evidenced by XRD, NEXAFS spectroscopy, and SQUID magnetometry. The hydrophobic nanoparticles can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made. These iron oxide nanoparticles and their dispersions in various media have great potential in magnetic nanodevice and biomagnetic applications.

Monodisperse MFe2O4 (M = Fe, Co, Mn) Nanoparticles

The physical principles underlying some current biomedical applications of magnetic nanoparticles are reviewed. Starting from well-known basic concepts, and drawing on examples from biology and biomedicine, the relevant physics of magnetic materials and their responses to applied magnetic fields are surveyed. The way these properties are controlled and used is illustrated with reference to (i) magnetic separation of labelled cells and other biological entities; (ii) therapeutic drug, gene and radionuclide delivery; (iii) radio frequency methods for the catabolism of tumours via hyperthermia; and (iv) contrast enhancement agents for magnetic resonance imaging applications. Future prospects are also discussed.

https://iopscience.iop.org/article/10.1088/0022-3727/36/13/201/pdf

Applications of magnetic nanoparticles in biomedicine

A biosensor based on magnetoresistance technology.

https://apps.dtic.mil/sti/pdfs/ADA481221.pdf

The BARC biosensor applied to the detection of biological warfare agents.

This paper describes the design of, and the effects of basic environmental parameters on, a microelectromechanical (MEMS) hydrogen sensor. The sensor contains an array of 10 micromachined cantilever beams. Each cantilever is 500 μm wide×267 μm long×2 μm thick and has a capacitance readout capable of measuring cantilever deflection to within 1 nm. A 20-nm-thick coating of 90% palladium–10% nickel bends some of the cantilevers in the presence of hydrogen. The palladium–nickel coatings are deposited in ultra-high-vacuum (UHV) to ensure freedom from a “relaxation” artifact apparently caused by oxidation of the coatings. The sensor consumes 84 mW of power in continuous operation, and can detect hydrogen concentrations between 0.1 and 100% with a roughly linear response between 10 and 90% hydrogen. The response magnitude decreases with increasing temperature, humidity, and oxygen concentration, and the response time decreases with increasing temperature and hydrogen concentration. The 0–90% response time of an unheated cantilever to 1% hydrogen in air is about 90 s at 25 °C and 0% humidity.

Design and performance of a microcantilever-based hydrogen sensor

A low-cost, low-power volatile organic compound (VOC) sensor has been constructed from an array of micromachined parallel-plate capacitors. The sensor has demonstrated detection of many VOCs well below the lower explosive limits and could be used in industrial leak monitoring applications or for homeland defense. In place of a standard dielectric, the individual capacitors were filled with selectively absorbing polymers. Absorption of a target vapor alters the permittivity of the polymers and thereby changes the capacitance of the elements in the array. A variety of polymers have been used, including polyethylene-co-vinylacetate, which was sensitive to nonpolar hydrocarbons, and siloxanefluoro alcohol, which was highly sensitive to polar VOCs and chemical warfare agent simulants. The response magnitude for each element depends on a combination of different phenomenon such as the dielectric constant of the analyte and polymer swelling. The measured sensitivity of the sensor to most VOCs was found to be in the low parts per million (ppm) range. The response magnitude from one capacitor to the next is reproducible to within 3.2% at 20 °C. The sensor typically responded within a second but frequently required 5–10 min to reach equilibrium. Response times could likely be substantially improved with an optimized capacitor structure that contains a decreased gap between the plates and provisions for more rapid vapor exchange.

Chemicapacitive microsensors for volatile organic compound detection

We are developing a sensor capable of detecting biological species such as cells, proteins, toxins, and DNA at concentrations as low as 10−18 M. The force amplified biological sensor will take advantage of the high sensitivity of force microscope cantilevers to detect the presence of as little as one superparamagnetic particle bound to a cantilever by a sandwich immunoassay technique. The device, which will ultimately be small enough for hand‐held use, will perform an assay in about 10 min. Lock‐in detection and use of a reference cantilever will provide a high degree of vibration immunity. An array of ten or more cantilevers will provide greater sensitivity and the capability to detect multiple species simultaneously. The force amplified biological sensor also offers the potential of distinguishing and studying chemical species via its ability to measure binding forces.

David R. Baselt

Papers

A biosensor based on magnetoresistance technology.

The BARC biosensor applied to the detection of biological warfare agents.

Design and performance of a microcantilever-based hydrogen sensor

Chemicapacitive microsensors for volatile organic compound detection

Biosensor based on force microscope technology