Publications of Pierre Colson
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See detailExperimental Design applied to spin coating of 2D colloidal crystal masks : a relevant method?
Colson, Pierre ULiege; Cloots, Rudi ULiege; Henrist, Catherine ULiege

in Langmuir (2011), 27(21), 12800-12806

Monolayers of colloidal spheres are used as masks in nanosphere lithography (NSL) for the selective deposition of nanostructured layers. Several methods exist for the formation of the self-organized ... [more ▼]

Monolayers of colloidal spheres are used as masks in nanosphere lithography (NSL) for the selective deposition of nanostructured layers. Several methods exist for the formation of the self-organized particles monolayers, among which spin coating appears to be very promising. However, a spin coating process is defined by several parameters like several ramps, rotation speeds and durations. All parameters influence the spreading and drying of the droplet containing the particles. Moreover, scientists are confronted to the formation of numerous defects in spin coated layers, limiting well-ordered areas to a few µm2. So far, empiricism mainly ruled the world of nanoparticles self-organization by spin coating and much of the literature is experimentally based. Therefore, the development of experimental protocols to control the ordering of particles is a major goal for further progress in NSL. We applied experimental design to spin coating, to evaluate the efficiency of this method to extract and model the relationships between the experimental parameters and the degree of ordering in the particles monolayers. A set of experiments was generated by the MODDE software and applied to the spin coating of latex suspension (diam. 490 nm). We calculated the ordering by a homemade image analysis tool. The results of Partial Least Squares (PLS) modeling show that the proposed mathematical model only fits data from strictly monolayers but is not predictive for new sets of parameters. We submitted the data to Principal Component Analysis (PCA) that was able to explain 91% of the results when based on strictly monolayers samples. PCA shows that the ordering was positively correlated to the ramp time and negatively correlated to the first rotation speed. We obtain large defect-free domains with the best set of parameters tested in this study. This protocol leads to areas of 200 µm2, which has never been reported so far. [less ▲]

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See detailWell Shaped Mn(3)O(4) Nano-octahedra with Anomalous Magnetic Behavior and Enhanced Photodecomposition Properties
Li, Yu; Tan, Haiyan; Yang, Xiao-Yu et al

in Small : Nano Micro (2011), 7(4), 475-483

Very uniform and well shaped Mn(3)O(4) nano-octahedra are synthesized using a simple hydrothermal method under the help of polyethylene glycol (PEG200) as a reductant and shape-directing agent. The nano ... [more ▼]

Very uniform and well shaped Mn(3)O(4) nano-octahedra are synthesized using a simple hydrothermal method under the help of polyethylene glycol (PEG200) as a reductant and shape-directing agent. The nano-octahedra formation mechanism is monitored. The shape and crystal orientation of the nanoparticles is reconstructed by scanning electron microscopy and electron tomography, which reveals that the nano-octahedra only selectively expose {101} facets at the external surfaces. The magnetic testing demonstrates that the Mn(3)O(4) nano-octahedra exhibit anomalous magnetic properties: the Mn(3)O(4) nano-octahedra around 150 nm show a similar Curie temperature and blocking temperature to Mn(3)O(4) nanoparticles with 10 nm size because of the vertical axis of [001] plane and the exposed {101} facets. With these Mn(3)O(4) nano-octahedra as a catalyst, the photodecomposition of rhodamine B is evaluated and it is found that the photodecomposition activity of Mn(3)O(4) nano-octahedra is much superior to that of commercial Mn(3)O(4) powders. The anomalous magnetic properties and high superior photodecomposition activity of well shaped Mn(3)O(4) nano-octahedra should be related to the special shape of the nanoparticles and the abundantly exposed {101} facets at the external surfaces. Therefore, the shape preference can largely broaden the application of the Mn(3)O(4) nano-octahedra. [less ▲]

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See detailElaboration of Magnetic Nanodots by Nanosphere Lithography : a Computerized Method for Order Quantification
Colson, Pierre ULiege; Cloots, Rudi ULiege; Henrist, Catherine ULiege

Conference (2008, December 01)

Nanosphere lithography (NSL) is an ideal inexpensive fabrication tool for producing regular, nearly homogenous arrays of nanoparticules with different sizes. There are many different methods for the ... [more ▼]

Nanosphere lithography (NSL) is an ideal inexpensive fabrication tool for producing regular, nearly homogenous arrays of nanoparticules with different sizes. There are many different methods for the fabrication of the latex monolayer based on electrophoresis, the controlled evaporation of a solvent from the suspension containing latex particles, spincoating etc… We focused our work on this last method. The main problem with formation of 2D latex monolayers is that there are always a high number of different structural defects such as: point defects (vacancies), line defects (dislocations) and also many disordered areas. The influence of the different spincoating parameters on the amount of defects was determined by image analysis of SEM micrographies from the different samples. FePt and Co films were deposited onto quartz substrates through the polystryrene monolayers by magnetron sputtering. The nanopsheres were removed by sonication in toluene. Post-deposition annealing treatment was performed under reductive atmosphere for the FePt nanodots in order to transform the as-deposited chemically disoredered face-centered cubic (fcc) structure into the chemically ordered face-centered tetragonal (fct) phase (L10-phase). DRX , SEM and MFM analysis were performed on the different samples. [less ▲]

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See detailCovalent binding of antitumor benzoacronycines to double-stranded DNA induces helix opening and the formation of single-stranded DNA: Unique consequences of a novel DNA-bonding mechanism
David-Cordonnier, MH; Laine, W; Lansiaux, A et al

in Molecular Cancer Therapeutics (2005), 4(1), 71-80

The majority of DNA-binding small molecules known thus far stabilize duplex DNA against heat denaturation. A high, drug-induced increase in the melting temperature (T-m) of DNA is generally viewed as a ... [more ▼]

The majority of DNA-binding small molecules known thus far stabilize duplex DNA against heat denaturation. A high, drug-induced increase in the melting temperature (T-m) of DNA is generally viewed as a good criterion to select DNA ligands and is a common feature of several anticancer drugs such as intercalators (e.g., anthracyclines) and alkylators (e.g., ecteinascidin 743). The reverse situation (destabilization of DNA to facilitate its denaturation) may be an attractive option for the identification of therapeutic agents acting on the DNA structure. We have identified the tumor-active benzoacronycine derivative S23906-1 [(+/-)-cis-1, 2-diacetoxy-6-methoxy-3,3,14-trimethyl 1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2]acridin-7- one] as a potent DNA alkylating agent endowed with a helicase-like activity. Using complementary molecular approaches, we show that covalent binding to DNA of the diacetate compound S23906-1 and its monoacetate analogue S28687-1 induces a marked destabilization of the double helix with the formation of alkylated ssDNA. The DNA-bonding properties and effects on DNA structure of a series of benzoacronycine derivatives, including the dicarbamate analogue S29385-1, were studied using complementary biochemical (electromobility shift assay, nuclease S1 mapping) and spectroscopic (fluorescence and T-m measurements) approaches. Alkylation of guanines in DNA by S28687-1 leads to a local denaturation of DNA, which becomes susceptible to cleavage by nuclease S1 and significantly decreases the T-m of DNA. The drug also directly alkylates single-strand DNA, but mass spectrometry experiments indicate that guanines in duplexes are largely preferred over single-stranded structures. This molecular study expands the repertoire of DNA-binding mechanisms and provides a new dimension for DNA recognition by small molecules. [less ▲]

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