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Scanning near-field optical microscopy (SNOM or NSOM) is the technique with the highest lateral optical resolution available today, while infrared (IR) spectroscopy has a high chemical specificity. Combining SNOM with a tunable IR source produces a unique tool, IR-SNOM, capable of imaging distributions of chemical species with a 100 nm spatial resolution. We present in this paper boron nitride (BN) thin film images, where IR-SNOM shows the distribution of hexagonal and cubic phases within the sample. Exciting potential applications in biophysics and medical sciences are illustrated with SNOM images of the distribution of different chemical species within cells. We present in this article images with resolutions of the order of λ/60 with SNOM working with infrared light. With our SNOM setup, we routinely get optical resolutions between 50 and 150 nm, regardless of the wavelength of the light used to illuminate the sample.

The advent of scanning near-field optical microscopy (SNOM) has augmented at a microscopic level the usefulness of optical spectroscopy in the region between 300 nm and 10 mum. Two-dimensional imaging of chemical constituents makes this a very attractive and powerful new approach. In this paper we show SNOM results obtained in several geometrical configurations on boron clusters in silicon, Li clusters embedded in a LiF sample and BN growth on silicon. We also show some results on the wavelength dependence of the reflectivity (R) in the near infrared (IR) of biological cells in liquid environment with the observation of the local fluorescence. The SNOM images revealed features that were not present in the corresponding shear-force (SF) images and which were due to localized changes in the bulk properties of the sample. The size of the smallest detected features clearly demonstrated that near-field conditions were reached both in the visible and infrared region. (C) 2004 Elsevier B.V. All rights reserved.

We studied the effect of the interaction of electromagnetic radiation with human keratinocytes (HaCaT), at low (50 Hz, 1 mT) frequency using both atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) techniques. AFM analysis showed modifications in shape and morphology in exposed cells, while SNOM indirect immunofluorescence analysis revealed an increase of segregation of β4 integrin (an adhesion marker) in the cell membrane of the same cells, suggesting that a higher percentage of the exposed cells shows a modified pattern of this adhesion marker.

The morphological changes of murine hematopoietic 32D Cl3-A cell line, in which apoptosis was induced by deprivation of interleukin-3 (IL-3) from the culture medium, were studied through air operating atomic force microscopy. The subtraction of IL-3 determines the appearing of blebs on plasma membrane and cell fragmentation in several residual bodies. Areas of strong contrast in the friction images, which are nearly absent in control and necrotic cells, were detected with percentage that peaks at 6 h of IL-3 deprivation. These are the results revealing that transient modification of the plasma membrane accompanies the first steps of apoptosis pathway.

The morphological changes induced in (RuPc)2 gas sensing thin films by hydration and de-hydration processes were investigated. Prior to this study a preliminary characterization was performed by conductivity measurements upon exposure to NO2 gas fluxes, to verify the electrical sensing response of the films. This response was correlated to the bulk morphological modification of the films. Subsequently, the effect of external moisture on the morphological stability of the films was addressed. This morphological characterization of the films was performed by using the energy dispersive X-ray reflectivity (EDXR) and atomic force microscopy (AFM) techniques, both ex situ and in situ, i.e. under operating conditions, during exposure of these films to 100% of relative humidity. The measurements allowed an accurate observation of both the surface morphology (i.e. its roughness obtained independently by EDXR and AFM). Moreover bulk evolution of the films was obtained by in situ EDXR and the morphological changes allowed to retrieve information on the water uptake dynamics. Moreover, the reversibility of the water/film interaction was studied and correlated to the sensing properties of the (RuPc)2.

Mediante la microscopia a scansione ad effetto Tunnel viene osservata la struttura molecolare del DNA. Vengono evidenziati i gruppi fosfati e le basi dei solchi minori(minor grooves) mentre la struttura del profondo solco maggiore(major groove) risulta non risolta. Viene descritto il metodo usato chiamato convenzionalmentebarrier height mode insieme al metodo topografico convenzionale e vengono dati alcuni dettagli dell’apparecchiatura sperimentale. Il DNA e stato preparato da soluzione acquosa fissandolo a un substrato di oro mediante la molecola organica Tris 1-Aziridinyl Phosphine Oxide (TAPO).

We report on the use of thermal annealing to improve the behavior of NO2 gas-sensing ruthenium phthalocyanine films at high temperatures. The approach used, based on the study of the effect of temperature on the film morphology, makes use of in situ energy dispersive X-ray reflectometry and atomic force microscopy. The results show that the morphological changes, induced by high working temperatures, strongly affect the material sensing ability. Furthermore, we demonstrate that the film morphology may be stabilized by thermal annealing treatments, thus enhancing the sensor performances in terms of response times and the capability to work at high temperatures.

Scanning near-field optical microscopy (SNOM) makes it routinely possible to overcome the fundamental diffraction limit of standard (far-field) microscopy. Recently, aperture-based infrared SNOM performed in the spectroscopic mode, using the Vanderbilt University free electron laser, started delivering spatially-resolved information on the distribution of chemical species and on other laterally-fluctuating properties. The practical examples presented here show the great potential of this new technique both in materials science and in life sciences. (C) 2004 Elsevier B.V. All rights reserved.

Uncoated DNA molecules marked with an activated tris(l-aziridinyl) phosphine oxide (TAPO) solution were deposited on gold substrates and imaged in air with the use of a high-resolution scanning tunneling microscope (STM). Constant-current and gap-modulated STM images show clear evidence of the helicity of the DNA structure: pitch periodicity ranges from 25 to 35 angstroms, whereas the average diameter is 20 angstroms. Molecular structure within a single helix turn was also observed.

Infrared scanning near-field optical microscopy (IR-SNOM) is an extremely powerful analytical instrument since it combines IR spectroscopy's high chemical specificity with SNOM's high spatial resolution. In order to do this in the infrared, specialty chalcogenide glass fibers were fabricated and their ends tapered to generate SNOM probes. The fiber tips were installed in a modified near-field microscope and both inorganic and biological samples illuminated with the tunable output from a free-electron laser located at Vanderbilt University. Both topographical and IR spectral images were simultaneously recorded with a resolution of similar to 50 and similar to 100 nm, respectively. Unique spectroscopic features were identified in all samples, with spectral images exhibiting resolutions of up to lambda/60, or at least 30 times better than the diffraction limited lens-based microscopes. We believe that IR-SNOM can provide a very powerful insight into some of the most important biomedical research topics.