Towards Room Temperature Thermochromic Coatings with controllable NIR-IR modulation for solar heat management & smart windows applications

Solar heat management & green air-conditioning are among the major technologies that could mitigate heat islands phenomenon while minimizing significantly the CO2 global foot-print within the building & automotive sectors. Chromogenic materials in general, and thermochromic smart coatings especially are promising candidates that consent a noteworthy dynamic solar radiation Infrared (NIR-IR) regulation and hence an efficient solar heat management especially with the expected increase of the global seasonal temperature. Within this contribution, two major challenging bottlenecks in vanadium oxide based smart coatings were addressed. It is validated for the first time that the NIR-IR modulation of the optical transmission (∆TTRANS = T(T〈TMIT) - T(T〉TMIT) of Vanadium oxide based smart coatings can be controlled & tuned. This upmost challenging bottle-neck controllability/tunability is confirmed via a genuine approach alongside to a simultaneous drastic reduction of the phase transition temperature TMIT from 68.8 °C to nearly room temperature. More precisely, a substantial thermochromism in multilayered V2O5/V/V2O5 stacks equivalent to that of standard pure VO2 thin films but with a far lower transition temperature, is reported. Such a multilayered V2O5/V/V2O5 thermochromic system exhibited a net control & tunability of the optical transmission modulation in the NIR-IR (∆TTRANS) via the nano-scaled thickness' control of the intermediate Vanadium layer. In addition, the control of ∆TTRANS is accompanied by a tremendous diminution of the thermochromic transition temperature from the elevated bulk value of 68.8 °C to the range of 27.5-37.5 ºC. The observed remarkable and reversible thermochromism in such multilayered nano-scaled system of V2O5/V/V2O5 is likely to be ascribed to a noteworthy interfacial diffusion, and an indirect doping by alkaline ions diffusing from the borosilicate substrate. It is hoped that the current findings would contribute in advancing thermochromic smart window technology and their applications for solar heat management in glass windows in general, skyscraper especially & in the automotive industry. If so, this would open a path to a sustainable green air-conditioning with zero-energy input.

Room temperature bio-engineered multifunctional carbonates for CO2 sequestration and valorization

This contribution reports, for the first time, on an entirely green bio-engineering approach for the biosynthesis of single phase crystalline 1-D nano-scaled calcite CaCO3. This was validated using H2O as the universal solvent and natural extract of Hyphaene thebaica fruit as an effective chelating agent. In this room temperature green process, CaCl2 and CO2 are used as the unique source of Ca and CO3 respectively in view of forming nano-scaled CaCO3 with a significant shape anisotropy and an elevated surface to volume ratio. In terms of novelty, and relatively to the reported scientific and patented literature in relation to the fabrication of CaCO3 by green nano-chemistry, the current cost effective room temperature green process can be singled out as per the following specificities: only water as universal solvent is used, No additional base or acid chemicals for pH control, No additional catalyst, No critical or supercritical CO2 usage conditions, Only natural extract of thebaica as a green effective chelating agent through its phytochemicals and proper enzematic compounds, room Temperature processing, atmospheric pressure processing, Nanoscaled size particles, and Nanoparticles with a significant shape anisotropy (1-D like nanoparticles). Beyond and in addition to the validation of the 1-D synthesis aspect, the bio-engineered CaCO3 exhibited a wide-ranging functionalities in terms of highly reflecting pigment, an effective nanofertilizer as well as a potential binder in cement industry.

Insights into the precipitation kinetics of CaCO3 particles in the presence of polystyrene sulfonate using in situ small-angle X-ray scattering

The formation of calcium carbonate (CaCO3) nanoparticles (NPs) in the presence of polystyrene sulfonate (PSS) as an additive was examined by time-resolved small-angle X-ray scattering (SAXS) in a flow system that mimics experimental conditions used at home facilities where the precipitation can be achieved in a beaker. The experiments were carried out at low concentrations to remain in the dilute regime. A model-independent analysis was performed using the Porod invariant which defines the scale factor, leaving only the distribution of radii as the adjustable parameter. The presence of the PSS additive strongly retards the precipitation of CaCO3 NPs. The formation of NPs reaches a state of equilibrium after a few minutes. Here, it is shown that the concentration of precursors at a fixed PSS concentration plays a key role in determining the size of the NPs obtained. A full analysis of the SAXS patterns was carried out using the Hurd-Flower model to account for the weaker intensity decay than the classical Porod behaviour. The temporal evolution of the particle radii was determined. Wide-angle X-ray scattering experiments carried out simultaneously show that the particles formed have the structure of vaterite with growth consistent with the evolution of the Porod invariant.

On the trapping of neutrons in Fabry–Pérot nano-structures and potential applications for cold neutron lifetime Investigations

Correlated to the neutron total reflection phenomenon is the so-called frustrated total reflection, also known as neutron channeling, observed with both thermal and cold neutrons. Within this contribution, such a phenomenon is validated in various additional distinctive Fabry–Pérot nano-resonating configurations; namely in: (i) dual reflection and transmission neutron Fabry–Pérot nano-resonator (Ni/V/Ni/Si substrate), (ii) isotope-based neutron Fabry–Pérot nano-resonator (58Ni/62Ni/58Ni/Silicon substrate), and (iii) multilayered neutron Fabry–Pérot nano-resonator of 8 superposed (B4C/Ti/B4C) single nano-resonators. While such Fabry–Pérot nano-resonators allow effective neutron trapping, the precision of the trapping time of free neutrons in such nano-resonators is governed by the Heisenberg uncertainty and hence offers, a priori, an additional attractive precise approach for potential lifetime investigations. Depending on the configuration of the Fabry–Pérot nano-resonators and the available cold neutron beam, the trapping time is found to be within the temporal regime of 3 to 19 ps. While the main intention of this contribution is to validate the possibility of trapping cold neutrons in nano-structured Fabry–Pérot resonators with a picosecond precision in various configurations, it is hoped that these preliminary results will attract the interest of the neutron lifetime community specifically and the neutron scattering community in general. The potential integration of such trapping method into the bottle or beam methods would elucidate the origin of the difference in neutron lifetime between the two approaches.

Mercury goes Solid at room temperature at nanoscale and a potential Hg waste storage

While room temperature bulk mercury is liquid, it is solid in its nano-configuration (Ønano-Hg ≤ 2.5 nm). Conjugating the nano-scale size effect and the Laplace driven surface excess pressure, Hg nanoparticles of Ønano-Hg ≤ 2.4 nm embedded in a 2-D turbostratic Boron Nitride (BN) host matrix exhibited a net crystallization at room temperature via the experimentally observed (101) and (003) diffraction Bragg peaks of the solid Hg rhombohedral α-phase. The observed crystallization is correlated to a surface atomic ordering of 7 to 8 reticular atomic plans of the rhombohedral α-phase. Such a novelty of size effect on phase transition phenomena in Hg is conjugated to a potential Hg waste storage technology. Considering the vapor pressure of bulk Hg, Room Temperature (RT) Solid nano-Hg confinement could represent a potential green approach of Hg waste storage derived from modern halogen efficient light technology.

From Khoi-San indigenous knowledge to bioengineered CeO2 nanocrystals to exceptional UV-blocking green nanocosmetics

Single phase CeO₂ nanocrystals were bio-synthesized using Hoodia gordonii natural extract as an effective chelating agent. The nanocrystals with an average diameter of 〈Ø〉 ~ 5-26 nm with 4⁺ electronic valence of Ce displayed a remarkable UV selectivity and an exceptional photostability. The diffuse reflectivity profile of such CeO₂ exhibited a unique UV selectivity, in a form of a Heaviside function-like type profile in the solar spectrum. While the UV reflectivity is significantly low; within the range of 0.7%, it reaches 63% in the VIS and NIR. Their relative Reactive Oxygen Species (ROS) production was found to be < 1 within a wide range of concentration (0.5-1000 μg/ml). This exceptional photostability conjugated to a sound UV selectivity opens a potential horizon to a novel family of green nano-cosmetics by green nano-processing.

From Himba indigenous knowledge to engineered Fe2O3 UV-blocking green nanocosmetics

This contribution reports on the physical properties of the natural Namibian red Ochre used by the Himba Community in a form of a formulation, so called Otjize as a skin protective and beauty cream. The morphological and crystallographic studies of this red ochre validated its nano-scaled dominating phase of rhombohedral α-Fe₂O₃ nanocrystals with an additional hydrolized oxide component in a form of γ-FeOOH. The optical investigations showed that such a red ochre exhibits an exceptional UV filtration and a significant IR reflectivity substantiating its effectiveness as an effective UV-blocking & solar heat IR reflector in support of the low skin cancer rate within the Namibian Himba community. In addition, such nanocrystals exhibited a non-negligible antibacterial response against E. Coli & S. Aurus. This study seems confirming the effectiveness of the indigenous Otjize as an effective skin UV protection cream with a sound antimicrobial efficacy against e-Coli & S-Aurus.

Quantitative nanotomography of amorphous and polycrystalline samples using coherent X-ray diffraction

This article presents a combined approach where quantitative forward-scattering coherent diffraction imaging (CDI) is supported by crystal diffraction using 8.1 keV synchrotron X-ray radiation. The method allows the determination of the morphology, mass density and crystallinity of an isolated microscopic specimen. This approach is tested on three homogeneous samples made of different materials with different degrees of crystallinity. The mass density and morphology are revealed using three-dimensional coherent diffraction imaging with a resolution better than 36 nm. The crystallinity is extracted from the diffraction profiles measured simultaneously with coherent diffraction patterns. The presented approach extends CDI to structural characterization of samples when crystallinity aspects are of interest.

X-ray nanotomography of coccolithophores reveals that coccolith mass and segment number correlate with grid size

Coccolithophores of the Noëlaerhabdaceae family are covered by imbricated coccoliths, each composed of multiple calcite crystals radially distributed around the periphery of a grid. The factors that determine coccolith size remain obscure. Here, we used synchrotron-based three-dimensional Coherent X-ray Diffraction Imaging to study coccoliths of 7 species of Gephyrocapsa, Emiliania and Reticulofenestra with a resolution close to 30 nm. Segmentation of 45 coccoliths revealed remarkable size, mass and segment number variations, even within single coccospheres. In particular, we observed that coccolith mass correlates with grid perimeter which scales linearly with crystal number. Our results indirectly support the idea that coccolith mass is determined in the coccolith vesicle by the size of the organic base plate scale (OBPS) around which R-unit nucleation occurs every 110–120 nm. The curvation of coccoliths allows inference of a positive correlation between cell nucleus, OBPS and coccolith sizes.

Coccolithophores are one of the most abundant phytoplankton and calcifying organisms, well-known to produce intricate calcareous exoskeletons made of coccoliths. Here the authors show, by using X-ray nanotomography, the dependence of the grid size on the calcite nucleation site number and on the mass of coccoliths.

In-Situ X-ray Tomography Study of Cement Exposed to CO2 Saturated Brine

For successful CO₂ storage in underground reservoirs, the potential problem of CO₂ leakage needs to be addressed. A profoundly improved understanding of the behavior of fractured cement under realistic subsurface conditions including elevated temperature, high pressure and the presence of CO₂ saturated brine is required. Here, we report in situ X-ray micro computed tomography (μ-CT) studies visualizing the microstructural changes upon exposure of cured Portland cement with an artificially engineered leakage path (cavity) to CO₂ saturated brine at high pressure. Carbonation of the bulk cement, self-healing of the leakage path in the cement specimen, and leaching of CaCO₃ were thus directly observed. The precipitation of CaCO₃, which is of key importance as a possible healing mechanism of fractured cement, was found to be enhanced in confined regions having limited access to CO₂. For the first time, the growth kinetics of CaCO₃ under more realistic well conditions have thus been estimated quantitatively. Combining the μ-CT observations with scanning electron microscopy resulted in a detailed understanding of the processes involved in the carbonation of cement.

Densification and depression in glass transition temperature in polystyrene thin films

Ellipsometry and X-ray reflectivity were used to characterize the mass density and the glass transition temperature of supported polystyrene (PS) thin films as a function of their thickness. By measuring the critical wave vector (qc) on the plateau of total external reflection, we evidence that PS films get denser in a confined state when the film thickness is below 50 nm. Refractive indices (n) and electron density profiles measurements confirm this statement. The density of a 6 nm (0.4 gyration radius, Rg) thick film is 30% greater than that of a 150 nm (10Rg) film. A depression of 25 °C in glass transition temperature (Tg) was revealed as the film thickness is reduced. In the context of the free volume theory, this result seems to be in apparent contradiction with the fact that thinner films are denser. However, as the thermal expansion of thinner films is found to be greater than the one of thicker films, the increase in free volume is larger for thin films when temperature is raised. Therefore, the free volume reaches a critical value at a lower Tg for thinner films. This critical value corresponds to the onset of large cooperative movements of polymer chains. The link between the densification of ultrathin films and the drop in their Tg is thus reconciled. We finally show that at their respective Tg(h) all films exhibit a critical mass density of about 1.05 g/cm(3) whatever their thickness. The thickness dependent thermal expansion related to the free volume is consequently a key factor to understand the drop in the Tg of ultrathin films.

X-Ray Scattering Studies of Multilayer Interfaces

The results of specular and diffuse x-ray scattering studies of multilayers are discussed. We show here that such studies can yield detailed statistical information about the interfacial roughness and morphology. Results on a GaAs/AlAs multilayer are presented and the data is analyzed within the Born approximation.

X-ray analysis of mesoporous silica thin films templated by Brij58 surfactant

The structural optimization of highly mesoporous silica thin film templated with Brij58 is reported in this paper. The best conditions for obtaining well organized films are studied as a function of the concentration of surfactant, the relative humidity (RH) and the aging time of the solutions used in the dip-coating process. We first show on the basis of the results obtained by small angle x-ray scattering (SAXS) experiments on the binary system Brij58/water that the structure of the films determined by grazing incidence (GI) SAXS experiments can be explained according to a specific equation involving the initial masses of the sol constituents. Then the structural properties of the films are investigated by x-ray reflectivity (XRR) and GISAXS before and after removing the surfactant. The mesoporosities and morphology of the films are determined by analyzing the reflectivity curves of the highly ordered silica thin films in the cubic phase.

In situmonitoring by synchrotron radiation of the formation of ZnO nanoparticles by aqueous chemical growth

Synchrotron radiation experiments were carried out during thein situgrowth of ZnO nanoparticles by the aqueous chemical growth technique. The first results of this exploratoryin situgrazing-incidence diffraction (GID) experiment are reported, with emphasis on the difficulties encountered. In particular, it is shown that, whenin situGID experiments are carried out in a 25 mm-long cell, scattering by the solvent dominates. This impedes the observation of the formation of ZnO nanoparticles during the early stages of the growth process. Nevertheless, it is clearly shown that the wurzite hexagonal structure is present in the solution. At a specific concentration, it is shown how the peak intensities and widths of the Bragg peaks evolve as a function of time.

Self-assembled monolayers of bisphosphonates: influence of side chain steric hindrance

Bisphosphonates form self-assembled monolayers (SAMs) spontaneously on stainless steel, silicon, and titanium oxidized surfaces. We used contact angle measurements, atomic force microscopy, and X-ray reflectivity analysis to study the formation of SAMs on a model surface of ultraflat titanium (rms = 0.2 nm). The results were extended to standard materials (mechanically polished titanium, stainless steel, and silicon) and showed that water-soluble bisphosphonic perfluoropolyether can easily form SAMs, with 100% surface coverage and a layer thickness of less than 3 nm. Hydrophobic (water contact angle >110 degrees on stainless steel or titanium) and lipophobic (methylene iodide contact angle >105 degrees on titanium) properties are discussed in terms of industrial applications.

Magnetic behaviour of nickel-cyclam complexes in mesoporous silica: EPR investigations

Electron paramagnetic resonance (EPR) investigations are carried out on mesoporous silica (SBA15) functionalized by Ni-cyclam complexes (1,4,8,11-tetraazacyclotetradecane groups chelating nickel ions). The magnetic behaviour of nickel-cyclam groups, their mutual interactions and dispersions in the mesoporous silica are compared with respect to the doping rates and the synthesis procedures. The spin-spin interactions and the relaxation processes were clarified from the thermal evolution in the temperature range (4 K, 300 K) of the paramagnetic spin susceptibilities and EPR line widths. Thus, the relaxation mechanisms seem marked by the Jahn-Teller effect on the nickel ions mediated by exchange interactions between nearest spins. Isolated Ni-cyclam molecules are involved in some samples while others show the formation of clusters where phonon-assisted one-dimensional (1D) ferromagnetic ordering occurs below 45 K. The performed experiments point out the efficiency of the EPR technique to probe the degree of functionalization of mesoporous silica by Ni-cyclam molecules and to give valuable feedback to improve the synthesis routes.

Reproducibility in X-ray reflectometry: results from the first world-wide round-robin experiment

X-ray reflectometry (XRR) is a well established technique to evaluate quantitatively electron density, thickness and roughness of thin layers. In this paper, results of the first world-wide XRR round-robin experiment, involving 20 laboratories, are presented and discussed. The round-robin experiment was performed within the framework of the VAMAS Project `X-ray reflectivity measurements for evaluation of thin films and multilayers', the aim of which is to produce a `good practice' manual for XRR. The reproducibility of measurements obtained using different equipment has been investigated. The influence of the fitting of the experimental data was shown to be non-negligible compared with the experimental factors. The dynamic intensity range proves to be an important parameter for obtaining a good quality measurement. A simpler test sample which does not develop a surface oxide layer over time is now the subject of a follow-up study.

Quantitative SAXS Analysis of the P123/Water/Ethanol Ternary Phase Diagram

The ternary phase diagram of the amphiphilic triblock copolymer PEO-PPO-PEO ((EO)(20)(PO)(70)(EO)(20) commercialized under the generic name P123), water, and ethanol has been investigated at constant temperature (T = 23 degrees C) by small-angle X-ray scattering (SAXS). The microstructure resulting from the self-assembly of the PEO-PPO-PEO block copolymer varies from micelles in solution to various types of liquid crystalline phases such as cubic, 3D hexagonal close packed spheres (HCPS), 2D hexagonal, and lamellar when the concentration of the polymer is increased. In the isotropic liquid phase, the micellar structural parameters are obtained as a function of the water-ethanol ratio and block copolymer concentration by fitting the scattering data to a model involving core-shell form factor and a hard sphere structure factor of interaction. The micellar core, the aggregation number, and the hard sphere interaction radius decrease when increasing the ethanol/water ratio in the mixed solvent. We show that the fraction of ethanol present in the core is responsible for the swelling of the PPO blocks. In the different liquid crystalline phases, structural parameters such as lattice spacing, interfacial area of PEO block, and aggregation number are also evaluated. In addition to classical phases such as lamellar, 2D hexagonal, and liquid isotropic phases, we have observed a two-phase region in which cubic Fm3m and P6(3)mmc (hexagonally close packing of spheres (HCPS)) phases coexist. This appears at 30% (w/w) of P123 in pure water and with 5% (w/w) of ethanol. At 10% (w/w) ethanol, only the HCPS phase remains present.

Multiple glass-transition temperatures in thin supported films of isotactic PMMA as revealed by enhanced Raman scattering

The glass-transition temperature, Tg, of isotactic PMMA thin films has been measured for four thicknesses by enhanced Raman spectroscopy and ellipsometry. This was made possible by inserting a silica spacer layer between the film and the substrate. The use of such a spacer drastically improves the sensitivity of Raman scattering measurements. The improvement in the sensitivity allows us to study phenomena involving changes in molecular dynamics, such as the phase transition, and to probe the existence in very thin films of several thickness-dependent transition temperatures, Tg(h). This in turn is interpreted as the occurrence in the film of a layered structure. The influence of the polymer concentration on the conformation of the surface adsorbed polymer layer and therefore on Tg(h) is discussed.

Substrate-induced modulation of the Raman scattering signals from self-assembled organic nanometric films

Raman scattering signals recorded by microscopy from organic self-assembled monolayers (thin nanometric films of calibrated thickness) on silica substrates were found to be much stronger than those obtained from identical films assembled on bulk silicon substrates. This effect, observed in the backscattering geometry, is shown to result from interferences between the direct and reflected beams (including both the excitation and scattered radiation) in front of a smooth reflecting surface. Strong dependence of the effect on the distance between the sampled monolayer and the bulk silicon substrate allows enhancement of the Raman signals of organic monolayer films on silicon by factors up to approximately 70 by using appropriate silica spacers. The dependence of the Raman signal intensity on film thickness was also studied for thicker nanometric films comprising a series of self-assembled organosilane multilayers on bulk silicon and fused silica substrates, and the predicted deviation from linearity in the case of the silicon substrate is experimentally confirmed.

First in-situ SAXS studies of the mesostructuration of spherical silica and titania particles during spray-drying process

Meso-organisation of SiO2 and TiO2 particles prepared by spray drying have been for the first time analysed through in-situ SAXS. Both processing and chemical parameters are critical to obtain meso-organised spheres.

Structural and magnetic properties of evaporated nanostructured Fe/V multilayers

The structural and magnetic properties of the evaporated Fe/V multilayers with a fixed V-layer thickness (tV = 1.5 nm) and variable Fe layer thicknesses (0.75 nm < or = tFe < or = 6 nm) have been studied by X-ray reflectivity and high-angle X-ray diffraction, conversion-electron Mössbauer spectrometry, and vibrating sample magnetometry. The results show that multilayers are formed with a broad Fe/V interface and pure crystalline bcc-Fe layers in the center of the individual subsystems. The Fe spin orientation is aligned in the film plane in the individual centers as well in the interfacial regions. The interfacial anisotropy constant Ks was estimated to be equal to 0.04 mJ/m2. This parallel magnetic anisotropy is discussed in terms of reduced symmetry effects on the hybridized 3d states.

Distinct patterns of all-trans retinoic acid dependent expression of HOXB and HOXC homeogenes in human embryonal and small-cell lung carcinoma cell lines

The expression patterns of the class I homeogenes HOXB and HOXC clusters in the presence of retinoic acid (RA) were studied in two human small-cell lung cancer (SCLC) cell lines and compared to that of NT2/D1 embryonal carcinoma cells. Contrasting with the sequential 3'-5' induction of the HOX genes observed after RA treatment of embryonic NT2/D1 cells, in the SCLC cells the responding genes (induced or down-regulated) were interspersed with insensitive genes (expressed or unexpressed), while no genomic alteration affected the corresponding clusters. These findings imply that HOX gene regulatory mechanisms are altered in non-embryonic SCLC cells, perhaps reflecting their ability to respond to more diversified stimuli, in relation with their origin from adult tissues.

DNA hypomethylation in breast cancer: an independent parameter of tumor progression?

The global DNA methylation status was investigated on a series of 59 breast cancers by Southern blotting, using methylation sensitive restriction enzymes. By comparison to control DNA, almost all tumor DNAs were found globally hypomethylated. However, the demethylation was variable from tumor to tumor. Compared to other biological parameters, the methylation did not correlate with chromosome alterations, steroid hormone receptor status, or histopathological grading. Tumors which appeared to be the most evolved for other parameters were only mildly hypomethylated, whereas tumors with strongly hypomethylated DNA corresponded to those with slight alterations of the other parameters. Thus, DNA hypomethylation is a consistent characteristic of breast cancer, but its variations may not correlate with tumor progression of most breast cancers.

Comparison of fixation procedures for fluorescent quantitation of DNA content using image cytometry

DNA quantitation using fluorescent dyes is of interest in image cytometry in that it is nondestructive in its mode of staining and is compatible with techniques such as FISH and immunofluorescence, allowing multicolor analysis of a wide range of cellular markers of interest. Optimal preparation techniques were sought using human peripheral blood lymphocytes and fine needle samples of breast carcinomas. Unfixed (air-dried only), ethanol, ethanol/acetic acid, and paraformaldehyde/ethanol fixations were tested. Unfixed or fixed cells were placed on slides as a drop or by cytocentrifugation, stained with 4',6-diamidino-2-phenylindole dihydrochloride and DNA content was measured using image analysis. Histogram quality was evaluated using G0G1 peak coefficient of variation, and compared to those generated by flow cytometry. Drop preparations of ethanol/acetic acid fixed and cytospin preparations of paraformaldehyde/ethanol fixed cells appeared to give the best histograms for image analysis, which were inferior in quality to those generated by flow cytometry. Comparison of breast carcinoma histograms generated by flow and image showed the same DNA aneuploid populations but with slightly higher DNA indices measured by image analysis.

A High-Energy Monochromatic Laue (MonoLaue) X-ray Diffuse Scattering Study of KMnF3 using an Image Plate

The technique of high-energy monochromatic Laue X-ray scattering using image plates to record the diffraction patterns is presented. A tunable wiggler beamline is used as an X-ray source. It is shown that such experimental conditions present many advantages over conventional tube sources and photographic films. A study of diffuse scattering in the perovskite compound KMnF3 is presented to illustrate this in a qualitative way.

Scanning ion analytical microscopy for high-resolution detection of 5-bromo-2'-deoxyuridine incorporation in metaphase chromosomes

We investigated the possibilities of using scanning ion analytical microscopy (SIAM) to detect bromine in human metaphase chromosomes. The experiments were performed after incorporation of the thymidine analogue, 5-bromo-2'-deoxyuridine (BrdU), into the DNA or by in situ hybridization of a BrdU-labelled probe for the subcentromeric repeated DNA sequences. The possibilities offered by this microanalytical method were compared with immunofluorescent staining techniques. Well-defined maps of bands containing bromide were obtained with metaphase chromosomes that had incorporated BrdU during the late S-phase. Their patterns were similar to the labelling obtained by immunofluorescence. In addition, SIAM reveals the presence of bromine within constitutive heterochromatic regions in which BrdU is poorly detected by immunofluorescence. The comparison of the 12C14N, 31P and 81Br maps of controls and fluorescence plus Giemsa (FPG) metaphase chromosomes shows the loss of bromide from DNA during this treatment. SIAM emerges as a new powerful microanalytical technology for investigating chromosome structure further.