Thickness and Beyond. Exploiting Spectroscopic Ellipsometry and Atomic Force Nanolithography for the Investigation of Ultrathin Interfaces of Biologic Interest

Parisse, Pietro; Solano, Ilaria; Magnozzi, Michele; Bisio, Francesco; Casalis, Loredana; Cavalleri, Ornella; Canepa, M.

doi:10.1007/978-3-319-75895-4_4

Cited by 5 publications

(7 citation statements)

References 155 publications

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“…This interface layer allows simulating the negative

values in the NIR region. The Au optical constants, which showed good agreement with literature, were obtained by inversion of the spectra of bare substrates [ 65 ], as done in previous papers [ 58 ].…”

Section: Resultssupporting

confidence: 80%

“…As can be observed in Figure 4 ,

values in the NIR (far from molecular resonances) and

values in the near UV are definitely larger for C 6 -ssDNA SAMs deposited in 1 M NaCl buffer with respect to SAMs deposited in 1 mM NaCl buffer. According to previous reports [ 45 , 58 ], these features are associated to the film optical thickness, a quantity depending on refractive index and thickness, that is higher for 1 M NaCl C 6 -ssDNA samples.…”

Section: Resultsmentioning

confidence: 82%

“…

and

spectra exhibit also some typical properties of difference spectra of thiolate SAMs on gold [ 58 ]. In particular,

spectra present a relative maximum ( Figure 4 a) around 500 nm, at the high reflectivity threshold of gold; in the same wavelength region,

spectra ( Figure 4 b) show a well-defined transition to lower values with a minimum around 600 nm [ 59 , 60 ].…”

Section: Resultsmentioning

confidence: 99%

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Morphological and Mechanical Characterization of DNA SAMs Combining Nanolithography with AFM and Optical Methods

et al. 2020

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The morphological and mechanical properties of thiolated ssDNA films self-assembled at different ionic strength on flat gold surfaces have been investigated using Atomic Force Microscopy (AFM). AFM nanoshaving experiments, performed in hard tapping mode, allowed selectively removing molecules from micro-sized regions. To image the shaved areas, in addition to the soft contact mode, we explored the use of the Quantitative Imaging (QI) mode. QI is a less perturbative imaging mode that allows obtaining quantitative information on both sample topography and mechanical properties. AFM analysis showed that DNA SAMs assembled at high ionic strength are thicker and less deformable than films prepared at low ionic strength. In the case of thicker films, the difference between film and substrate Young’s moduli could be assessed from the analysis of QI data. The AFM finding of thicker and denser films was confirmed by X-Ray Photoelectron Spectroscopy (XPS) and Spectroscopic Ellipsometry (SE) analysis. SE data allowed detecting the DNA UV absorption on dense monomolecular films. Moreover, feeding the SE analysis with the thickness data obtained by AFM, we could estimate the refractive index of dense DNA films.

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“…This interface layer allows simulating the negative

Section: Resultssupporting

confidence: 80%

“…As can be observed in Figure 4 ,

values in the NIR (far from molecular resonances) and

Section: Resultsmentioning

confidence: 82%

“…

and

spectra exhibit also some typical properties of difference spectra of thiolate SAMs on gold [ 58 ]. In particular,

spectra present a relative maximum ( Figure 4 a) around 500 nm, at the high reflectivity threshold of gold; in the same wavelength region,

spectra ( Figure 4 b) show a well-defined transition to lower values with a minimum around 600 nm [ 59 , 60 ].…”

Section: Resultsmentioning

confidence: 99%

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Morphological and Mechanical Characterization of DNA SAMs Combining Nanolithography with AFM and Optical Methods

et al. 2020

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“… 30 , 31 To the best of our knowledge, there are no studies on the influence of crosslinking on the swelling/collapsing behavior of PNIPAM brushes, partly as determining the accurate brush heights in the solution is challenging. 32 , 33 It should be noted that the degree of swelling is expected to depend on the geometry and orientation of the chains. For instance, in a brush on a planar surface (compared to a gel in 3D), there is only one spatial dimension available for expansion.…”

Section: Introductionmentioning

confidence: 99%

Tuning the Thermoresponsive Behavior of Surface-Attached PNIPAM Networks: Varying the Crosslinker Content in SI-ATRP

et al. 2021

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The synthesis and thermoresponsive properties of surface-attached poly( N -isopropylacrylamide)- co - N , N ′-methylene bisacrylamide (PNIPAM- co -MBAM) networks are investigated. The networks are formed via SI-ARGET-ATRP (“grafting-from”) on thiol-based initiator-functionalized gold films. This method is reliable, well controlled, fast, and applicable to patterned surfaces ( e.g. , nanopores) for networks with dry thicknesses >20 nm. Surface-attached PNIPAM- co -MBAM gels are swollen below their volume phase transition temperature but above collapse without complete expulsion of water (retain ∼50 vol %). The swelling/collapse transition is studied using complementary SPR and QCMD techniques. The ratio between swollen and collapsed heights characterizes the thermoresponsive behavior and is shown to not depend on network height but to vary with MBAM content. The higher the proportion of the crosslinker, the lower the magnitude of the phase transition, until all responsiveness is lost at 5 mol % MBAM. The temperature range of the transition is broadened for more crosslinked PNIPAM- co -MBAM gels but remains centered around 32 °C. Upon reswelling, less crosslinked networks display sharp transitions, while for those containing ≥3 mol % MBAM, transitions remain broad. This tunable behavior persists for gels on nanostructured gold surfaces. Investigating PNIPAM- co -MBAM networks on gold plasmonic nanowell arrays is a starting point for expanding their scope as thermo-controlled nanoactuators.

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“…Va inoltre osservato che i valori di | δΔ | nel NIR (lontano dalle risonanze molecolari) e i valori δΨ nel vicino UV sono decisamente maggiori per i SAM depositati ad elevata forza ionica. Come discusso in precedenti lavori [30,41], queste caratteristiche sono associate allo spessore ottico del film, una grandezza correlata all'indice di rifrazione e allo spessore del film, che risulta più elevata per i SAM depositati ad elevata forza ionica. I dati SE confermano quindi che la forza ionica del buffer gioca un ruolo significativo nella formazione del SAM.…”

Section: Fig 3 Esperimenti DI Shaving Su Sam Di Dna Preparati a Bassaunclassified

<em>SELF-ASSEMBLY</em> DI DNA SU SUPERFICIE: UNO STUDIO COMBINATO NANOLITOGRAFIA/SPETTROSCOPIA OTTICA

Cavalleri¹

2020

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The self-assembly of organic molecules and biomolecules on inorganic surfaces is a complex process which results from the interplay between different interactions: molecule/molecule, molecule/surface, and molecule/solvent interactions. The interest in the study of molecular self-assembly derives from the possibility to obtain functionalized surfaces that exhibit the functional properties of the deposited (bio) molecules. Self-Assembled Monolayers (SAMs) are indeed widely used in biosensing. SAMs of organosulphur compounds on gold are among the most widely studied SAMs. In the following, a combined approach that couples scanning probe microscopy and spectroellipsometry is discussed and applied to the study of the morphological, mechanical and optical properties of SAMs of DNA single strands. DNA SAMs are a widely investigated system since they can be exploited for the design of DNA microarrays based on the hybridization between complementary DNA strands.

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Thickness and Beyond. Exploiting Spectroscopic Ellipsometry and Atomic Force Nanolithography for the Investigation of Ultrathin Interfaces of Biologic Interest

Cited by 5 publications

References 155 publications

Morphological and Mechanical Characterization of DNA SAMs Combining Nanolithography with AFM and Optical Methods

Morphological and Mechanical Characterization of DNA SAMs Combining Nanolithography with AFM and Optical Methods

Tuning the Thermoresponsive Behavior of Surface-Attached PNIPAM Networks: Varying the Crosslinker Content in SI-ATRP

<em>SELF-ASSEMBLY</em> DI DNA SU SUPERFICIE: UNO STUDIO COMBINATO NANOLITOGRAFIA/SPETTROSCOPIA OTTICA

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