KPFM images were recorded using lift mode also known as hover mode operation. In lift mode KPFM, the topography of the sample is measured during the trace scan without an applied potential. During the retrace of the same line, the tip follows the topography measured during the trace pass but offset 50 nm above the surface, and an AC and DC voltage is applied between the tip and sample to nullify the electrostatic interactions.
Increasing the tip-sample separation by 50 nm eliminates the possibility of cross talk between the topography and surface potential measurements. The gold substrates were grounded to eliminate sample charging. Films adsorbed from solution in non-polar liquids.
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J Colloid Sci , 1: — In The Chemistry of organic derivatives of gold and silver. Volume chapter Edited by: Patai S, Rappoport Z. New York: Academic Press; Nucleic Acids Res , — Nat Biotechnol , — Nanotechnology , — Appl Phys Lett , — Appl Surf Sci , — Acc Chem Res , — Langmuir , — Liu GY, Salmeron MB: Reversible displacement of chemisorbed n-alkane thiol molecules on Au surface: an atomic force microscopy study.
Am Chem Soc , — Phys Rev B , — Moores B, Hane F, Eng L, Leonenko Z: Kelvin probe force microscopy in application to biomolecular films: frequency modulation, amplitude modulation, and lift mode. Ultramicroscopy , — Download references. Correspondence to Zoya Leonenko. BM and JS carried out the thiol SAM preparation and nanografting experiments, participated in the manuscript draft preparation. SX participated in nanografting experiments and participated in the manuscript draft preparation. ZL conceived of the study, participated in its design and coordination and finished the final draft of the manuscript.
All authors read and approved the final manuscript. Reprints and Permissions. Moores, B. Nanoscale Res Lett 6, doi Download citation. Search all SpringerOpen articles Search. Abstract Thiol self-assembled monolayers SAMs are widely used in many nano- and bio-technology applications. Background Thiol self-assembled monolayers SAMs are promising for many nano- and bio-technology applications as they offer a reliable method to produce surfaces with desirable properties.
Nano Lett , 3: — Nanoscale Rese Lett , 6: Mohanty P, Landskron K: Simple systematic synthesis of periodic mesoporous organosilica nanoparticles with adjustable aspect ratios. Nanoscale Rese Lett , 4: 1. Small , 3: — Langmuir , — Du X, He JH: Hierarchically mesoporous silica nanoparticles: extraction, amino-functionalization, and their multipurpose potentials.
Small , 5: — Qi ZM, Honma I, Zhou H: Ordered-mesoporous-silica-thin-film-based chemical gas sensors with integrated optical polarimetric interferometry.
Surface Patterning with Colloidal Monolayers
Angew Chem Int Edt , — Macromol Symp , — Science , — ACS Nano , 2: — J Mater Chem , — Chem Soc Rev , — Crooks RM: New organic materials suitable for use in chemical sensor arrays. Acc Chem Res , 5: — Christen K: Novel nanomaterial strips contaminants from waste streams. Environ Sci Technol , AA. Wei LM, Zhang YF: Emulsion polymerization of ethylene from mesoporous silica nanoparticles with vinyl functionalized monolayers.
Crosslinking of floating colloidal monolayers | SpringerLink
Wei LM, Tang T, Huang BT: Novel acidic porous clay heterostructure with highly ordered organic—inorganic hybrid structure: one-pot synthesis of mesoporous organosilica in the galleries of clay. Micropor Mesopor Mater , — Download references. Correspondence to Liangming Wei or Yafei Zhang.
LMW designed the experiment and wrote the manuscript.
Read e-book Surface Patterning with Colloidal Monolayers (Springer Theses)
ZHZ helped analyze the characterization results. All authors read and approved the final manuscript. Reprints and Permissions. Wei, L. Functionalized self-assembled monolayers on mesoporous silica nanoparticles with high surface coverage. Nanoscale Res Lett 7, doi Download citation.
Search all SpringerOpen articles Search. Abstract Mesoporous silica nanoparticles MSNs containing vinyl-, propyl-, isobutyl- and phenyl functionalized monolayers were reported. Background Periodic mesoporous silica materials have been intensively investigated over the last decade due to their ordered structure, large surface area, and well-defined pore size [ 1 , 2 ]. Figure 1. Full size image. Methods The organosilanes vinyl-trichlorsilan, propyl-trichlorsilan, isobutyl-trichlorosilane, and phenyl-trichlorsilan were purchased from Sigma-Aldrich Corporation, St.
Figure 2. It should be noted that, in a limit case, a group of S particles is constituted by a single isolated S particle. As described in Section 2 , on the grounds of this concept of minimum threshold distance, individual entities are identified based on the cardinality of the set of neighbors defined for each S particle j and on the identification of connected components. The set of neighbors contains all the S particles that are within the threshold distance R from the S particle j.
Nanopatterned Thermoresponsive Functionalization of Substrates via Nanosphere Lithography
Connected components can be identified by constructing a binary image from the coordinates of S particle centroids by drawing discs of radius equal to half of the selected threshold distance centered on such coordinates. Isolated particles, dimers and chains are first identified with the sole cardinality of the set of neighbors. In this way, each of the individual entities constitutes a connected component; the particles whose centroids belong to the same connected component are regarded as part of the same entity.
A final check based on the concept of neighborhood is carried out into the clusters thus identified; clusters made up of particles all having only two nearest neighbors are classified as loops. Figure 2 a reports groups of particles color-coded according to whether they were categorized as isolated particles, dimers, chains, clusters classified as loops and clusters other than the loops identified from the examples of SEM images acquired at variable particle number ratio.
For an increasing S particle concentration, the number of isolated S particles decreases, while the number of S particles involved in other groups comprising more than one particle appears to rise. Figure 3 shows a close-up of SEM images on which a color-coded representation of S particles according to the previous classification is superposed. As visible, very diverse entities were found in our assemblies, even with strongly anisotropic characteristics, such as chains and clusters.
Our procedure allows the identification of clusters in more disordered and sparse assemblies, which is not affordable with methods used for the individuation of more crystalline clusters with nearly hexagonal or square symmetry. Such techniques are based, for instance, on setting specific thresholds on diverse combinations of different parameters, such as the magnitude of the bond orientational order parameter, of the bond length deviation i.
However, the groups of S particles identified in our assemblies are far from exhibiting a compact and uniform distribution and, hence, traditional tools for cluster identification would not be adequate in this case. Even a recently developed technique used to distinguish between low-density gas and high-density phases without specific assumptions on their symmetry [ 41 ] is not applicable for the sparse and anisotropic assemblies encountered in our experiments: in fact, it relies on the regularity of the Voronoi cells and implies a more isotropic distribution of particles in contrast to the highly anisotropic characteristics of the entities occurring in our assemblies and clusters of larger size in comparison to those detected in these experiments.
Subsequently, the average number of particles composing chains, loops and clusters other than loops was investigated Figure 2 c. As apparent, a rise in the S particle concentration does not entail a significant upturn in the size of loops, which means that loops observed in our assemblies are formed by only few particles independently of the particle number ratio.
For a deeper insight into the characteristics of groups identified as clusters other than loops, we determined the percentage of S particles involved in different size classes. In this case, the thresholds for the definition of the different size classes were selected as 7 corresponding to the size of a cluster formed by a particle surrounded by a single shell of nearest neighbors in a hexagonal arrangement and 19 corresponding to the size of a cluster made up of one particle and two shells of nearest neighbors in a hexagonal arrangement.
The latter value was deemed as the minimum size of a grain in other works [ 55 ]. As observed, at such moderately low S particle concentrations, L particles still preserve a dense packing, preventing the formation of large S particle clusters. For this purpose, we used an analysis based on Minkowski functionals.
Minkowski functionals or measures are a set of topological and geometrical descriptors useful for the characterization of spatial patterns as they provide morphological measures for size, shape and connectivity in D dimensions. Minkowski functionals are computed for patterns constructed starting from the coordinates of the particle centroids by placing a cover disc with radius R m at each couple of coordinates similarly to what we have previously shown in the procedure for the identification of clusters [ 56 , 57 ].
In two dimensions, as in our case, there are three functionals that can be computed from such patterns, i. The Minkowski functionals are evaluated by varying R m , giving rise to a curve characteristic of a given particle configuration [ 56 , 57 , 58 ]. The dependence on R m of such measures can cast light on the actual morphology of a colloidal assembly.
As such, they have been used, for instance, in the analysis of crystalline, hexatic and liquid phases in single-sized colloidal assemblies [ 57 ], or in the investigation of binary assemblies of superparamagnetic particles by computing them for the sole L particles and for the sole S particles [ 56 ]. Particularly interesting for the purpose of morphological analysis is the Euler characteristic normalized to the number of particles.
The trends resemble those observed for binary assemblies of superparamagnetic particles reported in previous studies [ 56 ], and confirm the gradual loss of the hexagonal order of L particles in favor of the coexistence of different symmetries. Such a trend has been ascribed to the anisotropic character of S particle groupings [ 56 ]. However, the analysis of all the S particles hides the features of individual S particle clusters and does not allow one to discern if such a trend is related to the shape of the individual clusters as separate independent entities or only to the formation of holes due to overlap of discs built around particles belonging to different entities.
As explained, our goal consists in the description of the morphology of such clusters as individual entities. In this sense, we need to focus individually on each cluster. As a matter of fact, a global analysis of all S particles could bury the specific features of the individual clusters under the collective characteristics of the whole S particle patterns because connected components and holes would result from the overlap of all the entities previously identified, i.