Self-assembled films of cholesterol were prepared on Au(111) surface and characterized by STM at ... more Self-assembled films of cholesterol were prepared on Au(111) surface and characterized by STM at nanometric level. In dependence of the concentration, two type of films were observed: one in the form of molecular monolayer and second with molecules organized in the square boxes, as a building blocks of the assembly layer. Both arrangements were characterized in great details which offers new insides into determination of molecular position, conformation and mechanism of the film growth. Accommodation of the cholesterol into the self-assembly layers was explained by help of molecular models developed in this study. The obtained finding are interesting from the fundamental as well from the technological point of view, in terms of better understanding of the process related to the functionalization of the metallic surface, and future design of the nano-scale devices (i.e. bio-medical sensors).
Auger electron angular distributions yield images of surface atomic and molecular structure. Angu... more Auger electron angular distributions yield images of surface atomic and molecular structure. Angular distribution Auger microscopy (ADAM) produces silhouettes of near-surface atoms by illuminating them with Auger electrons originating from atoms located deeper in the solid. The silhouettes are then observed by measurement and display of the complete angular distribution of Auger electrons. The locations and shapes of these silhouettes directly reveal the relative positions of atoms near the surface, and also provide important new information regarding the interaction of electrons with matter. Interpretation of ADAM images is straightforward in terms of atoms behaving as point emitters and spherical scatterers of Auger electrons. Consequently, ADAM is an exciting new technique for structural characterization of materials surfaces, thin films, molecular layers and crystals, and also for fundamental studies of electron physics, provided that certain important experimental criteria are met. We will illustrate the ADAM technique by describing its recent application to determination of the structure of metal single-crystal surfaces and epitaxial atomic layers.
In-situ scanning tunneling microscopy (STM) and ex-situ low-energy electron diffraction (LEED) ha... more In-situ scanning tunneling microscopy (STM) and ex-situ low-energy electron diffraction (LEED) have been employed to characterize an iodine-coated Au(11 1) electrode surface in perchloric acid solution in the absence ofiodide ions. Iodine forms a well-ordered monolayer with two distinguished sets of incommensurate lattices (phases): a centered rectangular c(p x 43R-30") phase and a "rotated hexagonal" ("rot-hex") phase in the range of electrode potentials between 0.3 and 1.4 V vs a reversible hydrogen electrode (RHE). Both lattices become more compressed with increasing electrode potential. The (4 3 x 43)R30" phase was found to have the most open structure for the iodine monolayer on the Au(ll1) surface. Uniaxial compression of the c(p x d3R-30") phase (p decreases from 3 to ca. 2.5) resulting from an increase in electrode potential was successfully observed by LEED. In the range ofthe electrode potential between 0.5 and 1.2 Vvs RHE, LEED and in-situ STM measurements indicate a small change in the p value around 2.5. Isometrical electrocompression of the rot-hex-I phase was successfully monitored using in-situ STM by following changes in Moire patterns resulting from an increase in electrode potential. A detailed characterization of the rot-hex-I phase was achieved with the aid of computer-simulated STM images. The reversible phase transition between c(p x d3R-30") and rot-hex occurred at potentials more positive than ca. 1.3 V vs RHE. Atomic size vacancies were observed at the early stages of electrooxidation of the rot-hex-iodine adlayer.
We describe a new approach for biomaterial patterning, viz, masked ion beam lithography. Poly (me... more We describe a new approach for biomaterial patterning, viz, masked ion beam lithography. Poly (methyl methacrylate) (PMMA) film was used as a model system and subjected to Ca + and P + ion implantations through masks. Ca + ion implantation was performed at an energy of 85 keV with a fluence of 1x10 14 ions/cm 2. P + ion implantation was done at an energy of 85 keV with fluences of 1x10 15 and 1x10 16 ions/cm 2. Arrays of holes were generated during these processes. AFM showed that the depth of the holes is in the nanoscale region. The surface hydrophobicity of the exposed PMMA films was investigated by contact angle measurement. The results indicated that ion implantation changed the surface hydrophobicity.
Microstructures of low carbon steel are ferrite (Fe-␣) and pearlite (alternate mixture of Fe-␣ an... more Microstructures of low carbon steel are ferrite (Fe-␣) and pearlite (alternate mixture of Fe-␣ and Fe 3 C) and each one has its own oxidation mechanism. These two phases were identified using in situ electrochemical scanning tunneling microscopy (EC-STM). Real time images were obtained during the immersion of 1018 carbon steel probes in 0.642 M H 3 BO 3 and 0.1 M NaOH, pH 7.8. Two different corrosion mechanisms (oxide characteristics) were identified and correlated with the observed surface changes.
The effect of an inert gas pressure on the structure of selenium thin films has been systematical... more The effect of an inert gas pressure on the structure of selenium thin films has been systematically investigated in the pulsed laser deposition process. The ablated material is deposited on Au (111) gold thin films for its characterization by atomic force microscopy (AFM). Analysis of the surface morphology shows that instead of the formation of a uniform Se thin film on top of Au (111) terraces, as it occurs in high vacuum, the film grows as two dimensional ellipsoid shaped aggregates. The size of these Se aggregates increases significantly with the gas pressure and reaches a maximum at pressures of ∼ 1.5 Torr, and subsequently decreases with further increase of the gas pressure. This effect is probably due to the fact that the kinetic energy of the impinging species decreases as pressure increases, thus impeding diffusion on the substrate surface. However, further increase in the pressure prevents the Se species from being deposited on the substrate resulting in a decrease in size of the aggregates.
Marine Rogoznica lake (RL), an eutrophic and euxinic environment situated at the eastern Adriatic... more Marine Rogoznica lake (RL), an eutrophic and euxinic environment situated at the eastern Adriatic coast was used as a natural laboratory to test the application of atomic force microscopy (AFM) in combination with the electrochemical and high temperature catalytic oxidation (HTCO) measurements for characterization of water column organic matter (OM) and reduced sulfur species (RSS) in relation to seasonal changes of environmental conditions. Water column of RL was explored at the nanoscale by the AFM during the anoxic holomictic event (S1, October 2011) and stratified winter (S2, January 2012) and spring (S3, May 2012) conditions in the oxic and anoxic water samples. Obtained results from the AFM uphold the electrochemical and HTCO measurements, indicating significant difference in the present type of OM during the holomictic, anoxic stress conditions in comparison to the samples collected during the stratification period. Differences in the OM type were discussed in line with the physical and biological processes that occurred in RL during sampling: mixing processes characterized by fast turnover of water layers and biological activity characterized by low (January 2012) and high (May 2012) primary production of diatoms and zooplankton grazing activities.
Kinetics of copper deposition onto an Au(111) surface from sulfuric acid electrolyte, was evaluat... more Kinetics of copper deposition onto an Au(111) surface from sulfuric acid electrolyte, was evaluated using potentiostatic current transients. Measurements were conducted employing a new and nontraditional method, with gold electrode completely free from copper deposit at the beginning of the potential step (i.e., deposition process). The current transients obtained clearly show partial contribution from copper underpotential deposition (UPD) and copper overpotential deposition (OPD) processes. Quantitative evaluation of experimental transients was performed with the recently developed method for theoretical transient computer simulation. Detailed analysis of the kinetic parameters shows that copper UPD could be characterized as a two-dimensional nucleation and growth limited by the lattice incorporation (2D-LI) process and copper OPD as a three-dimensional nucleation process limited by diffusion-controlled growth (3D-DC). The UPD seems to be an inevitable part of the deposition process and takes place prior to OPD, regardless of the potential applied. Therefore, UPD should be treated as an early stage of the deposition process. Furthermore, our results show that the kinetics differs depending on whether deposition is initiated from a clean, bare Au(111) surface or from a gold surface already coated with a copper UPD adlayer. This indicates the role of the UPD process and the UPD adlayer on the course of OPD. Differences observed in deposition kinetics between electrolytic baths at pH 2 and 4 were likely due to adsorption of different sulfate species (sulfate or bisulfate anions) on the copper-deposit-modified Au(111) substrate (UPD, epitaxial monolayer) or bulk deposit adlayer (OPD).
Bulletin of the American Physical Society, Mar 17, 2009
Iztapalapa-Nanostructured silver thin films in a quasipercolated state are used as the starting m... more Iztapalapa-Nanostructured silver thin films in a quasipercolated state are used as the starting morphology for inducing changes in shape and ordering effects by pulsed laser irradiation with a Nd:YAG laser (355 nm) [1,2]. The complex nanostructures are transformed into nanospheres which in turn are ordered in regular patterns when irradiated through a diffractive element such as a slit or a pinhole. The samples are deposited onto TEM grids by the pulsed laser deposition technique. These transformations are subsequently characterized by transmission electron microscopy and by atomic force microscopy. The observed effects are explained using Fresnel diffraction theory. Excellent agreement with the experimental results are obtained. [1] E. Haro-Poniatowski et al. Appl.
Novel positive nanocomposite photoresists for X-ray lithography (XRL) and Extreme Ultraviolet lit... more Novel positive nanocomposite photoresists for X-ray lithography (XRL) and Extreme Ultraviolet lithography (EUVL) have been developed. In this work, resists containing acrylate monomers, organic-inorganic hybrid nanoparticles and a photo acid generator (PAG) were prepared by varying the compositions of the components. It was observed that the nanophotoresists were suitable for XRL and EUVL. The new resists exhibit all characteristics for NGL viz. defect free thin film formation <100 nm and show high sensitivity (1.0-1 .2 mJ/cm2) and contrast (y-4.9). This significant increase in sensitivity should lead to an enormous cost reduction of the XRL and EUVL processes as well as high-resolution sub-100 urn features.
Unequal-sphere packing model is applied for the simulation of large number of hexagonal adlayer s... more Unequal-sphere packing model is applied for the simulation of large number of hexagonal adlayer structures with surface coverage between = 1 3 and = 1 on the hexagonal substrate, with atomic radius of the adsorbate and substrate atoms as the only input. Each structure is characterized with respect to collective adlayer properties: the average adlayer height and the adlayer roughness. The distribution of hexagonal arrangements is presented in a special plot, which can be used for identification and characterization of hexagonal adlayers of different surface coverages and atomic registries. The most likely structures are related to the extreme values of our model parameters. The usefulness of this methodology is successfully demonstrated by comparison with some real adsorbate-substrate systems, i.e., halogens and rare gases adsorbed on ͑111͒ surface. Besides the agreement with experimental results, our model offers new insight into the formation of atomic adlayers and detailed analysis of the atomic registry. We believe that our approach will be of use for identification of probable structures among the large number of combinatorial possibilities in theoretical studies and for better interpretation of experimental results ͑i.e., scanning-tunneling microscopy images of atomic adlayers͒.
A simple unequal-sphere packing (USP) model, based on pure geometrical principles, was applied to... more A simple unequal-sphere packing (USP) model, based on pure geometrical principles, was applied to study the centered-rectangular iodine c(p× 3)R30°adlayer on the Au(111) surface, well-known from surface X-ray structure (SXS), low energy electron diffraction (LEED), and scanning tunneling microscopy (STM) experiments. To reproduce the exact patterns observed in experiments, two selective conditionssminimum average adsorbate height and minimum adlayer roughnessswere imposed. As a result, a series of adlayer patterns with c(p× 3)R30°symmetry (2.3 < p < 3), with precise structural details, including atomic registry and identification of the p-bisector as the most likely trajectory for the iodine adatom movement during the so-called uniaxial compression phenomenon, were identified. In addition, using the same model, the difference between the iodine adlayer arranged in hexagonal and centered-rectangular c(p× 3)R30°patterns, as in the case of Pt(111) and Au(111) surfaces, was investigated. Qualitative and quantitative comparison shows that iodine adatoms in these two arrangements differ significantly in atomic registry, distance from the substrate, and the adlayer corrugation. Our findings could be of special interest in the study of the nature of the iodine adatom bonding to different substrates (i.e., Au vs Pt).
Journal of Electroanalytical Chemistry, May 1, 2019
Studies have well documented that mutations in the adenomatous polyposis coli gene (APC) are invo... more Studies have well documented that mutations in the adenomatous polyposis coli gene (APC) are involved in the development of different types of cancer. Therefore, the objective of the present report was to design and construct a sensitive nanostructured genosensor able to detect specific sequences of the APC gene in order to be applied in early carcinogenesis diagnosis. We used screen-printed gold electrodes (SPGE) modified with DNA probes and mercaptoundecanoic acid chemically immobilized on a gold sensor surface. APC complementary DNA sequences were hybridized on the previously immobilized DNA probes. Besides, we tested effects of different intercalating agents, and various temperatures on the hybridization reaction to increase the sensitivity and selectivity of our device. The evaluation of these processes was carried out by means of the cyclic voltammetry technique (CV) to monitor the redox reaction of [Fe(CN) 6 ] 3−/4− on the SPGE-s. The constructed genosensor exhibited an excellent response to identify the APC gene in a concentration range from 100 pM to 100 μM, with 43.92 pM as the limit of detection in the presence of doxorubicin as DNA intercalating agent. The selectivity of the device was tested by using a DNA sequence different from the APC gene, which shows negative response. Considering the importance of APC mutations in the development of tumors in the digestive, urogenital, and mammary tissues, here developed electrochemical genosensor, due to its easy management, short time of response, and high performance, may be useful for early cancer detection.
Single-pulse (532 nm, 8 ns) micropatterning of silicon with nanometric surface modulation is demo... more Single-pulse (532 nm, 8 ns) micropatterning of silicon with nanometric surface modulation is demonstrated by irradiating through a diffracting pinhole. The irradiation results obtained at fluences above the melting threshold are characterized by scanning electron and scanning force microscopy and reveal a good agreement with Fresnel diffraction theory. The physical mechanism is identified and discussed on basis of both thermocapillary and chemicapillary induced material transport during the molten state of the surface.
Journal of electroanalytical chemistry and interfacial electrochemistry, Mar 1, 1985
Etudes, par voltammetrie lineaire, de l'influence de l'adsorption du laurylsulfate de Na ... more Etudes, par voltammetrie lineaire, de l'influence de l'adsorption du laurylsulfate de Na sur le processus du titre
... can be tailored by implanting Ca/P ions. This appears to be a promising technique for the fab... more ... can be tailored by implanting Ca/P ions. This appears to be a promising technique for the fabrication of 2D and 3D microstructures on biocompatible polymeric materials. The effects of the pattern geometry and implanted ion ...
International Journal of Nanomedicine, May 1, 2019
In the present study, we investigated the effects of 17β-estradiol (E 2) on membrane roughness an... more In the present study, we investigated the effects of 17β-estradiol (E 2) on membrane roughness and gold nanoparticle (AuNP) uptake in MCF-7 breast cancer cells. Methods: Estrogen receptor (ER)-positive breast cancer cells (MCF-7) were exposed to bare 20 nm AuNPs in the presence and absence of 1×10 −9 M E 2 for different time intervals for up to 24 hrs. The effects of AuNP incorporation and E 2 incubation on the MCF-7 cell surface roughness were measured using atomic force microscopy (AFM). Endocytic vesicle formation was studied using confocal laser scanning microscopy (CLSM). Finally, the results were confirmed by hyperspectral optical microscopy. Results: High-resolution AFM images of the surfaces of MCF-7 membranes (up to 250 nm 2) were obtained. The incubation of cells for 12 hrs with AuNP and E 2 increased the cell membrane roughness by 95% and 30% compared with the groups treated with vehicle (ethanol) or AuNPs only, respectively. This effect was blocked by an ER antagonist (7α,17β-[9-[(4,4,5,5,5-Pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17-diol [ICI] 182,780). Higher amounts of AuNPs were localized inside MCF-7 cells around the nucleus, even after 6 hrs of E 2 incubation, compared with vehicle-treated cells. Endolysosome formation was induced by E 2 , which may be associated with an increase in AuNP-uptake. Conclusions: E 2 enhances AuNP incorporation in MCF-7 cells by modulating of plasma membrane roughness and inducing lysosomal endocytosis. These findings provide new insights into combined nanotherapies and hormone therapies for breast cancer.
Journal of the American Chemical Society, Jul 1, 1988
Adsorption of the following compounds from aqueous solutions at well-defined Pt(11 1) single-crys... more Adsorption of the following compounds from aqueous solutions at well-defined Pt(11 1) single-crystal surfaces has been studied: 2,5-dihydroxythiophenol (DHTP); 2,5-dihydroxy-4-methylbenzyl mercaptan (DMBM); thiophenol (TP); pentafluorothiophenol (PFTP); 2,3,5,6-tetrafluorothiophenol (TFTP4); 2,3,4,5-tetrafluorothiophenol (TFTP2); and benzyl mercaptan (BM). Adsorbed layers formed from DHTP or DMBM were found by cyclic voltammetry to undergo reversible two-electron, two-proton electrochemical oxidation-reduction and were shown to be stable under vacuum. Therefore, the results of surface spectroscopy in ultrahigh vacuum are directly applicable to the liquid-solid and vapor-solid chemistry and electrochemistry of these compounds. Packing density (adsorbed moles per unit area) was measured for each compound by quantitative Auger electron spectroscopy. Packing densities of these compounds display a plateau at adsorbate concentration above 1 mM. Vibrational spectra of the adsorbed layers from these compounds were obtained by electron energy-loss spectroscopy (EELS) and were compared with the infrared (IR) spectra of the parent compounds in KBr. The EELS and IR spectra were quite similar except that the mercaptan hydrogen is lost during adsorption, and EELS de-emphasizes the 0-H stretching modes of phenolic compound such as DHTP and DMBM. Each of these compounds is evidently attached to Pt(11 1) predominantly through the sulfur atom. LEED observations reveal that, except for the DMBM layer which has (2 4 3 X 243)R30° symmetry, these compounds adsorb without long-range ordering with respect to the Pt(11 1) surface, although their large, constant packing densty and attachment through the S atom is evidence that the adsorbed molecules are uniformly oriented.
Self-assembled films of cholesterol were prepared on Au(111) surface and characterized by STM at ... more Self-assembled films of cholesterol were prepared on Au(111) surface and characterized by STM at nanometric level. In dependence of the concentration, two type of films were observed: one in the form of molecular monolayer and second with molecules organized in the square boxes, as a building blocks of the assembly layer. Both arrangements were characterized in great details which offers new insides into determination of molecular position, conformation and mechanism of the film growth. Accommodation of the cholesterol into the self-assembly layers was explained by help of molecular models developed in this study. The obtained finding are interesting from the fundamental as well from the technological point of view, in terms of better understanding of the process related to the functionalization of the metallic surface, and future design of the nano-scale devices (i.e. bio-medical sensors).
Auger electron angular distributions yield images of surface atomic and molecular structure. Angu... more Auger electron angular distributions yield images of surface atomic and molecular structure. Angular distribution Auger microscopy (ADAM) produces silhouettes of near-surface atoms by illuminating them with Auger electrons originating from atoms located deeper in the solid. The silhouettes are then observed by measurement and display of the complete angular distribution of Auger electrons. The locations and shapes of these silhouettes directly reveal the relative positions of atoms near the surface, and also provide important new information regarding the interaction of electrons with matter. Interpretation of ADAM images is straightforward in terms of atoms behaving as point emitters and spherical scatterers of Auger electrons. Consequently, ADAM is an exciting new technique for structural characterization of materials surfaces, thin films, molecular layers and crystals, and also for fundamental studies of electron physics, provided that certain important experimental criteria are met. We will illustrate the ADAM technique by describing its recent application to determination of the structure of metal single-crystal surfaces and epitaxial atomic layers.
In-situ scanning tunneling microscopy (STM) and ex-situ low-energy electron diffraction (LEED) ha... more In-situ scanning tunneling microscopy (STM) and ex-situ low-energy electron diffraction (LEED) have been employed to characterize an iodine-coated Au(11 1) electrode surface in perchloric acid solution in the absence ofiodide ions. Iodine forms a well-ordered monolayer with two distinguished sets of incommensurate lattices (phases): a centered rectangular c(p x 43R-30") phase and a "rotated hexagonal" ("rot-hex") phase in the range of electrode potentials between 0.3 and 1.4 V vs a reversible hydrogen electrode (RHE). Both lattices become more compressed with increasing electrode potential. The (4 3 x 43)R30" phase was found to have the most open structure for the iodine monolayer on the Au(ll1) surface. Uniaxial compression of the c(p x d3R-30") phase (p decreases from 3 to ca. 2.5) resulting from an increase in electrode potential was successfully observed by LEED. In the range ofthe electrode potential between 0.5 and 1.2 Vvs RHE, LEED and in-situ STM measurements indicate a small change in the p value around 2.5. Isometrical electrocompression of the rot-hex-I phase was successfully monitored using in-situ STM by following changes in Moire patterns resulting from an increase in electrode potential. A detailed characterization of the rot-hex-I phase was achieved with the aid of computer-simulated STM images. The reversible phase transition between c(p x d3R-30") and rot-hex occurred at potentials more positive than ca. 1.3 V vs RHE. Atomic size vacancies were observed at the early stages of electrooxidation of the rot-hex-iodine adlayer.
We describe a new approach for biomaterial patterning, viz, masked ion beam lithography. Poly (me... more We describe a new approach for biomaterial patterning, viz, masked ion beam lithography. Poly (methyl methacrylate) (PMMA) film was used as a model system and subjected to Ca + and P + ion implantations through masks. Ca + ion implantation was performed at an energy of 85 keV with a fluence of 1x10 14 ions/cm 2. P + ion implantation was done at an energy of 85 keV with fluences of 1x10 15 and 1x10 16 ions/cm 2. Arrays of holes were generated during these processes. AFM showed that the depth of the holes is in the nanoscale region. The surface hydrophobicity of the exposed PMMA films was investigated by contact angle measurement. The results indicated that ion implantation changed the surface hydrophobicity.
Microstructures of low carbon steel are ferrite (Fe-␣) and pearlite (alternate mixture of Fe-␣ an... more Microstructures of low carbon steel are ferrite (Fe-␣) and pearlite (alternate mixture of Fe-␣ and Fe 3 C) and each one has its own oxidation mechanism. These two phases were identified using in situ electrochemical scanning tunneling microscopy (EC-STM). Real time images were obtained during the immersion of 1018 carbon steel probes in 0.642 M H 3 BO 3 and 0.1 M NaOH, pH 7.8. Two different corrosion mechanisms (oxide characteristics) were identified and correlated with the observed surface changes.
The effect of an inert gas pressure on the structure of selenium thin films has been systematical... more The effect of an inert gas pressure on the structure of selenium thin films has been systematically investigated in the pulsed laser deposition process. The ablated material is deposited on Au (111) gold thin films for its characterization by atomic force microscopy (AFM). Analysis of the surface morphology shows that instead of the formation of a uniform Se thin film on top of Au (111) terraces, as it occurs in high vacuum, the film grows as two dimensional ellipsoid shaped aggregates. The size of these Se aggregates increases significantly with the gas pressure and reaches a maximum at pressures of ∼ 1.5 Torr, and subsequently decreases with further increase of the gas pressure. This effect is probably due to the fact that the kinetic energy of the impinging species decreases as pressure increases, thus impeding diffusion on the substrate surface. However, further increase in the pressure prevents the Se species from being deposited on the substrate resulting in a decrease in size of the aggregates.
Marine Rogoznica lake (RL), an eutrophic and euxinic environment situated at the eastern Adriatic... more Marine Rogoznica lake (RL), an eutrophic and euxinic environment situated at the eastern Adriatic coast was used as a natural laboratory to test the application of atomic force microscopy (AFM) in combination with the electrochemical and high temperature catalytic oxidation (HTCO) measurements for characterization of water column organic matter (OM) and reduced sulfur species (RSS) in relation to seasonal changes of environmental conditions. Water column of RL was explored at the nanoscale by the AFM during the anoxic holomictic event (S1, October 2011) and stratified winter (S2, January 2012) and spring (S3, May 2012) conditions in the oxic and anoxic water samples. Obtained results from the AFM uphold the electrochemical and HTCO measurements, indicating significant difference in the present type of OM during the holomictic, anoxic stress conditions in comparison to the samples collected during the stratification period. Differences in the OM type were discussed in line with the physical and biological processes that occurred in RL during sampling: mixing processes characterized by fast turnover of water layers and biological activity characterized by low (January 2012) and high (May 2012) primary production of diatoms and zooplankton grazing activities.
Kinetics of copper deposition onto an Au(111) surface from sulfuric acid electrolyte, was evaluat... more Kinetics of copper deposition onto an Au(111) surface from sulfuric acid electrolyte, was evaluated using potentiostatic current transients. Measurements were conducted employing a new and nontraditional method, with gold electrode completely free from copper deposit at the beginning of the potential step (i.e., deposition process). The current transients obtained clearly show partial contribution from copper underpotential deposition (UPD) and copper overpotential deposition (OPD) processes. Quantitative evaluation of experimental transients was performed with the recently developed method for theoretical transient computer simulation. Detailed analysis of the kinetic parameters shows that copper UPD could be characterized as a two-dimensional nucleation and growth limited by the lattice incorporation (2D-LI) process and copper OPD as a three-dimensional nucleation process limited by diffusion-controlled growth (3D-DC). The UPD seems to be an inevitable part of the deposition process and takes place prior to OPD, regardless of the potential applied. Therefore, UPD should be treated as an early stage of the deposition process. Furthermore, our results show that the kinetics differs depending on whether deposition is initiated from a clean, bare Au(111) surface or from a gold surface already coated with a copper UPD adlayer. This indicates the role of the UPD process and the UPD adlayer on the course of OPD. Differences observed in deposition kinetics between electrolytic baths at pH 2 and 4 were likely due to adsorption of different sulfate species (sulfate or bisulfate anions) on the copper-deposit-modified Au(111) substrate (UPD, epitaxial monolayer) or bulk deposit adlayer (OPD).
Bulletin of the American Physical Society, Mar 17, 2009
Iztapalapa-Nanostructured silver thin films in a quasipercolated state are used as the starting m... more Iztapalapa-Nanostructured silver thin films in a quasipercolated state are used as the starting morphology for inducing changes in shape and ordering effects by pulsed laser irradiation with a Nd:YAG laser (355 nm) [1,2]. The complex nanostructures are transformed into nanospheres which in turn are ordered in regular patterns when irradiated through a diffractive element such as a slit or a pinhole. The samples are deposited onto TEM grids by the pulsed laser deposition technique. These transformations are subsequently characterized by transmission electron microscopy and by atomic force microscopy. The observed effects are explained using Fresnel diffraction theory. Excellent agreement with the experimental results are obtained. [1] E. Haro-Poniatowski et al. Appl.
Novel positive nanocomposite photoresists for X-ray lithography (XRL) and Extreme Ultraviolet lit... more Novel positive nanocomposite photoresists for X-ray lithography (XRL) and Extreme Ultraviolet lithography (EUVL) have been developed. In this work, resists containing acrylate monomers, organic-inorganic hybrid nanoparticles and a photo acid generator (PAG) were prepared by varying the compositions of the components. It was observed that the nanophotoresists were suitable for XRL and EUVL. The new resists exhibit all characteristics for NGL viz. defect free thin film formation <100 nm and show high sensitivity (1.0-1 .2 mJ/cm2) and contrast (y-4.9). This significant increase in sensitivity should lead to an enormous cost reduction of the XRL and EUVL processes as well as high-resolution sub-100 urn features.
Unequal-sphere packing model is applied for the simulation of large number of hexagonal adlayer s... more Unequal-sphere packing model is applied for the simulation of large number of hexagonal adlayer structures with surface coverage between = 1 3 and = 1 on the hexagonal substrate, with atomic radius of the adsorbate and substrate atoms as the only input. Each structure is characterized with respect to collective adlayer properties: the average adlayer height and the adlayer roughness. The distribution of hexagonal arrangements is presented in a special plot, which can be used for identification and characterization of hexagonal adlayers of different surface coverages and atomic registries. The most likely structures are related to the extreme values of our model parameters. The usefulness of this methodology is successfully demonstrated by comparison with some real adsorbate-substrate systems, i.e., halogens and rare gases adsorbed on ͑111͒ surface. Besides the agreement with experimental results, our model offers new insight into the formation of atomic adlayers and detailed analysis of the atomic registry. We believe that our approach will be of use for identification of probable structures among the large number of combinatorial possibilities in theoretical studies and for better interpretation of experimental results ͑i.e., scanning-tunneling microscopy images of atomic adlayers͒.
A simple unequal-sphere packing (USP) model, based on pure geometrical principles, was applied to... more A simple unequal-sphere packing (USP) model, based on pure geometrical principles, was applied to study the centered-rectangular iodine c(p× 3)R30°adlayer on the Au(111) surface, well-known from surface X-ray structure (SXS), low energy electron diffraction (LEED), and scanning tunneling microscopy (STM) experiments. To reproduce the exact patterns observed in experiments, two selective conditionssminimum average adsorbate height and minimum adlayer roughnessswere imposed. As a result, a series of adlayer patterns with c(p× 3)R30°symmetry (2.3 < p < 3), with precise structural details, including atomic registry and identification of the p-bisector as the most likely trajectory for the iodine adatom movement during the so-called uniaxial compression phenomenon, were identified. In addition, using the same model, the difference between the iodine adlayer arranged in hexagonal and centered-rectangular c(p× 3)R30°patterns, as in the case of Pt(111) and Au(111) surfaces, was investigated. Qualitative and quantitative comparison shows that iodine adatoms in these two arrangements differ significantly in atomic registry, distance from the substrate, and the adlayer corrugation. Our findings could be of special interest in the study of the nature of the iodine adatom bonding to different substrates (i.e., Au vs Pt).
Journal of Electroanalytical Chemistry, May 1, 2019
Studies have well documented that mutations in the adenomatous polyposis coli gene (APC) are invo... more Studies have well documented that mutations in the adenomatous polyposis coli gene (APC) are involved in the development of different types of cancer. Therefore, the objective of the present report was to design and construct a sensitive nanostructured genosensor able to detect specific sequences of the APC gene in order to be applied in early carcinogenesis diagnosis. We used screen-printed gold electrodes (SPGE) modified with DNA probes and mercaptoundecanoic acid chemically immobilized on a gold sensor surface. APC complementary DNA sequences were hybridized on the previously immobilized DNA probes. Besides, we tested effects of different intercalating agents, and various temperatures on the hybridization reaction to increase the sensitivity and selectivity of our device. The evaluation of these processes was carried out by means of the cyclic voltammetry technique (CV) to monitor the redox reaction of [Fe(CN) 6 ] 3−/4− on the SPGE-s. The constructed genosensor exhibited an excellent response to identify the APC gene in a concentration range from 100 pM to 100 μM, with 43.92 pM as the limit of detection in the presence of doxorubicin as DNA intercalating agent. The selectivity of the device was tested by using a DNA sequence different from the APC gene, which shows negative response. Considering the importance of APC mutations in the development of tumors in the digestive, urogenital, and mammary tissues, here developed electrochemical genosensor, due to its easy management, short time of response, and high performance, may be useful for early cancer detection.
Single-pulse (532 nm, 8 ns) micropatterning of silicon with nanometric surface modulation is demo... more Single-pulse (532 nm, 8 ns) micropatterning of silicon with nanometric surface modulation is demonstrated by irradiating through a diffracting pinhole. The irradiation results obtained at fluences above the melting threshold are characterized by scanning electron and scanning force microscopy and reveal a good agreement with Fresnel diffraction theory. The physical mechanism is identified and discussed on basis of both thermocapillary and chemicapillary induced material transport during the molten state of the surface.
Journal of electroanalytical chemistry and interfacial electrochemistry, Mar 1, 1985
Etudes, par voltammetrie lineaire, de l'influence de l'adsorption du laurylsulfate de Na ... more Etudes, par voltammetrie lineaire, de l'influence de l'adsorption du laurylsulfate de Na sur le processus du titre
... can be tailored by implanting Ca/P ions. This appears to be a promising technique for the fab... more ... can be tailored by implanting Ca/P ions. This appears to be a promising technique for the fabrication of 2D and 3D microstructures on biocompatible polymeric materials. The effects of the pattern geometry and implanted ion ...
International Journal of Nanomedicine, May 1, 2019
In the present study, we investigated the effects of 17β-estradiol (E 2) on membrane roughness an... more In the present study, we investigated the effects of 17β-estradiol (E 2) on membrane roughness and gold nanoparticle (AuNP) uptake in MCF-7 breast cancer cells. Methods: Estrogen receptor (ER)-positive breast cancer cells (MCF-7) were exposed to bare 20 nm AuNPs in the presence and absence of 1×10 −9 M E 2 for different time intervals for up to 24 hrs. The effects of AuNP incorporation and E 2 incubation on the MCF-7 cell surface roughness were measured using atomic force microscopy (AFM). Endocytic vesicle formation was studied using confocal laser scanning microscopy (CLSM). Finally, the results were confirmed by hyperspectral optical microscopy. Results: High-resolution AFM images of the surfaces of MCF-7 membranes (up to 250 nm 2) were obtained. The incubation of cells for 12 hrs with AuNP and E 2 increased the cell membrane roughness by 95% and 30% compared with the groups treated with vehicle (ethanol) or AuNPs only, respectively. This effect was blocked by an ER antagonist (7α,17β-[9-[(4,4,5,5,5-Pentafluoropentyl)sulfinyl]nonyl]estra-1,3,5(10)-triene-3,17-diol [ICI] 182,780). Higher amounts of AuNPs were localized inside MCF-7 cells around the nucleus, even after 6 hrs of E 2 incubation, compared with vehicle-treated cells. Endolysosome formation was induced by E 2 , which may be associated with an increase in AuNP-uptake. Conclusions: E 2 enhances AuNP incorporation in MCF-7 cells by modulating of plasma membrane roughness and inducing lysosomal endocytosis. These findings provide new insights into combined nanotherapies and hormone therapies for breast cancer.
Journal of the American Chemical Society, Jul 1, 1988
Adsorption of the following compounds from aqueous solutions at well-defined Pt(11 1) single-crys... more Adsorption of the following compounds from aqueous solutions at well-defined Pt(11 1) single-crystal surfaces has been studied: 2,5-dihydroxythiophenol (DHTP); 2,5-dihydroxy-4-methylbenzyl mercaptan (DMBM); thiophenol (TP); pentafluorothiophenol (PFTP); 2,3,5,6-tetrafluorothiophenol (TFTP4); 2,3,4,5-tetrafluorothiophenol (TFTP2); and benzyl mercaptan (BM). Adsorbed layers formed from DHTP or DMBM were found by cyclic voltammetry to undergo reversible two-electron, two-proton electrochemical oxidation-reduction and were shown to be stable under vacuum. Therefore, the results of surface spectroscopy in ultrahigh vacuum are directly applicable to the liquid-solid and vapor-solid chemistry and electrochemistry of these compounds. Packing density (adsorbed moles per unit area) was measured for each compound by quantitative Auger electron spectroscopy. Packing densities of these compounds display a plateau at adsorbate concentration above 1 mM. Vibrational spectra of the adsorbed layers from these compounds were obtained by electron energy-loss spectroscopy (EELS) and were compared with the infrared (IR) spectra of the parent compounds in KBr. The EELS and IR spectra were quite similar except that the mercaptan hydrogen is lost during adsorption, and EELS de-emphasizes the 0-H stretching modes of phenolic compound such as DHTP and DMBM. Each of these compounds is evidently attached to Pt(11 1) predominantly through the sulfur atom. LEED observations reveal that, except for the DMBM layer which has (2 4 3 X 243)R30° symmetry, these compounds adsorb without long-range ordering with respect to the Pt(11 1) surface, although their large, constant packing densty and attachment through the S atom is evidence that the adsorbed molecules are uniformly oriented.
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