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We prepared a new extraction chromatography resin by coating a diglycolamide (DGA) ligand having three DGA moieties tethered to a triaza-9-crown-3 scaffold (TAM-3-DGA) on an inert solid support. This resin was evaluated for the separation of actinides and lanthanides from moderate acid solutions of 0.01–6 M HNO3. The distribution coefficient (Kd) values for trivalent and tetravalent actinides (Am3+, Np4+, and Pu4+) on the resin were large enough (>1 × 104mL/g) between 2 and 6 M HNO3for its real application in separating these minor actinides. The metal ion sorption mechanism studied for Eu3+and Pu4+indicated the existence of a chemisorption phenomenon. The sorption energies for Eu3+and Pu4+were 12.1 ± 0.72 and 18.5 ± 0.5 kJ/mol, respectively. The resin capacity was 13.9 ± 0.3 mg of Eu3+and 11.7 ± 0.4 mg of Pu4+per g of the resin, corresponding to the formation of a 1:1 metal/ligand complex for the Eu3+ion and a 1:2 metal/ligand complex for the Pu4+ion. The sorbed Eu3+and Pu4+ions from the resin phase were effectively eluted with complexing reagents like HEDTA and oxalic acid, respectively. The column capacity was ∼80% of the batch equilibrium value for both Eu3+and Pu4+ions.

Raman-based sensors represent a promising solution to enable both detection and fingerprinting of anionic pollutants in the water distribution network. Due to the weak nature of Raman scattering, a signal intensity enhancement mechanism, such as surface enhanced Raman spectroscopy (SERS), is required. Given the combination of SERS being a first layer effect and the low affinity for metallic surfaces shown by anions, functionalization of the SERS substrates using positively charged self-assembled monolayers (SAMs) is required to guarantee a strong SERS signal. In this work, the performance of three thiol-based coatings, namely, 2-mercapto-4-methyl-pyrimidine, cysteamine, and 2-dimethyl-amino-ethanethiol, is systematically compared for the detection of nitrite, nitrate, and perchlorate ions in water. For each coating, the limit of detection of those analytes is studied in combination with commercial SERS substrates. Cysteamine-coated SERS substrates are shown to provide the lowest limit of detection for the three analytes of this study. Evaluation of this coating on real drinking water samples is reported.

Lamellar Multilayer Gratings (LMG) offer improved resolution for soft-x-ray (SXR) monochromatization, while maintaining a high reflection efficiency in comparison to conventional multilayer mirrors (MM). We previously used a Coupled-Waves Approach (CWA) to calculate SXR diffraction by LMGs and identified a single-order regime in which the incident wave only excites a single diffraction order. We showed that in this regime the angular width of the zeroth-order diffraction peak simply scales linearly with (lamel-to-period ratio) without loss of peak reflectivity. However, the number of bi-layers must then be increased by a factor of 1/. Optimal LMG resolution and reflectivity is obtained in this single-order regime, requiring grating periods of only a few hundred nm, lamel widths < 100nm and lamel heights > 1m [1]. For the fabrication of LMGs with these dimensions, we use a novel process based on UV-NanoImprint Lithography (UV-NIL) and Bosch-type Deep Reactive Ion Etching (DRIE). Successful fabrication of LMGs with periods down to 200nm, line widths of 60nm and multilayer stack heights of 1m is demonstrated. SXR reflectivity measurements were performed on these LMGs at the PTB beamline at the BESSYII synchrotron facility. The measurements demonstrate an improvement in resolution by a factor 3,5 compared to conventional MMs. Further analysis of the SXR reflectivity measurements is currently being performed.

The implementation of high‐resolution polymer templates fabricated by capillary force lithography (CFL) is explored both in nanoimprint lithography (NIL) and in the wet‐etching of metals. Several different thermoplastic and UV‐curable polymers and types of substrates are incorporated into the general CFL procedure to meet the diverging requirements of these two applications. The mechanical stability of UV‐curable templates for imprinting in polymers, as examined by atomic force microscopy (AFM), and their anti‐adhesive properties are excellent for application in NIL. The conditions for curing the UV‐curable polymer are optimized in order to obtain high‐stability polymer templates. Gold patterns on silicon with a lateral resolution of 150 nm are fabricated by subsequent lift‐off in acetone. Similar patterns with a lateral resolution of 100 nm are fabricated using templates of thermoplastic polymers on gold layers on silicon as an etch mask. The transfer of stamp residues during CFL with these polymer templates is proven by X‐ray photoelectron spectroscopy (XPS) and AFM friction analysis. For poly(methylmethacrylate) (PMMA), the presence of large amounts of silicon‐containing residues is found to compromise the processability of the resulting template in subsequent O2reactive‐ion etching (RIE) treatment. The extent of silicon contamination is up to six times less for polystyrene (PS). At this level, the etch performance of the PS etch mask is not affected, as was the case for PMMA. Accurate downscaling of the lateral dimensions of the resulting metal patterns by several factors with respect to the dimensions of the PS etch mask is achieved by over‐etching of the gold. Overall, the results in this paper demonstrate the potential of CFL templates as tools for high‐resolution soft lithography.

The fabrication of three-dimensional (3D) nanostructures, which have sub-100 nm dimensions in all three directions that can be changed independently for each dimension, is a key issue of nanotechnology. E-beam writing can provide high-resolution two-dimensional (2D) nanopatterns, but implementation of pattern replication methods for rapid reproduction of a master and self-assembly, to provide patterned growth of structures, is essential for the development of more general and versatile 3D nanofabrication methodologies. Here the integration of top-down nanoimprint lithography (NIL) and bottom-up layer-by-layer self-assembly (LBL-SA) are described for the preparation of 3D hybrid nanostructures. NIL provided down to sub-100nm poly(methylmethacrylate) (PMMA) structures. These were employed to fabricate patterned self-assembled monolayers of cyclodextrin (CD) host molecules on silicon oxide. The consecutive LBL-SA with adamantyl guest-functionalized dendrimers and CD-modified gold nanoparticles resulted in patterned multilayer structures with thicknesses of 3-30 nm. The x, ycontrol by NIL and the zcontrol (albeit the same height for all nanostructures simultaneously) by LBL-SA ultimately allowed the fabrication of circular structures with a radius of 25 nm and a thickness of 20 nm. The integration of the two methods has thus yielded a versatile 3D nanofabrication methodology comprising 10-40 process steps.

A fundamental understanding of multivalency can have a profound influence on bottom-up nanofabrication. For this purpose, three different types of ferrocenyl (Fc) functionalized dendrimers of generations 1−5 with various spacer groups were adsorbed at self-assembled monolayers (SAMs) of heptathioether-functionalized β-cyclodextrin (βCD) on gold. The dendrimers formed kinetically stable supramolecular assemblies at the βCD host surface having up to eight multivalent supramolecular interactions, but could be efficiently removed from the host surface by electrochemical oxidation of the Fc end groups. Dendrimer desorption and re-adsorption could be repeated a number of times without significant decomposition of the system. The stoichiometries of the dendrimers at the surface were determined using cyclic voltammetry (CV). These were quantitatively confirmed for the lower generations by surface plasmon resonance (SPR) titrations of the dendrimers to the βCD SAM. Measuring CV and SPR simultaneously gave crucial mechanistic information on the electrochemically induced desorption of the dendrimers from the host surface. The redox-active dendrimers effectively blocked the host surface for binding other molecules, e.g. adamantyl-functionalized dendrimers, but electrochemically induced release of the blocking layer revealed the host surface to which the adamantyl dendrimers could then bind.

Nanoimprint lithography (NIL) is used as a tool to pattern self‐assembled monolayers (SAMs) on silicon substrates because of its ability to pattern in the micrometer and nanometer ranges. The polymer template behaves as a physical barrier preventing the formation of a SAM in the covered areas of the substrate. After polymer removal, SAM patterns are obtained. The versatility of the method is shown in various nanofabrication schemes. Substrates are functionalized with a second type of silane adsorbate. Pattern enhancement via selective electrostatic attachment of carboxylate‐functionalized particles is achieved. Further applications of the NIL‐patterned substrates include template‐directed adsorption of particles, as well as the fabrication of electrodes on top of a SAM.

Silica nanoparticles functionalized with β-cyclodextrin (CD) host molecules (5) have been prepared by reacting carboxylic active ester-terminated silica nanoparticles (4) with CD heptamine. Silica nanoparticles functionalized with glucosamine (6), having similar surface properties as 5 but lacking the host−guest recognition motif, were used to perform blank experiments. The CD-functionalized silica nanoparticles 5 were determined by TEM to be 55 ± 6 nm in size. They exhibited pH-dependent aggregation, which is explained by the presence of free amino and carboxylic acid groups on the particle surface, which was corroborated by zeta potential measurements. The functionalization with CD was further confirmed by host−guest studies in solution and at CD-functionalized silicon substrates. The addition of an adamantyl-terminated dendrimer, capable of multivalent host−guest binding with CD, led to strong aggregation of the CD particles 5, but not of the glucosamine-functionalized 6. Furthermore, 5 gave strong adsorption to CD monolayers on silicon onto which adamantyl-terminated dendrimers were adsorbed, whereas 6 did not. The good discrimination between dendrimer-covered and uncovered areas of the CD monolayer substrates allowed the directed self-assembly of the silica particles 5 onto dendrimer-patterned areas created by microcontact printing.

Spreading in microcontact printing refers to the process or processes by which the ink molecules end up in the parts of the substrate that are adjacent to the contacted areas but which are not contacted themselves. This has been investigated for different inking concentrations of 16-mercaptohexadecanoic acid (MHDA). Spreading of MHDA takes place with retention of a well-defined demarcation. Feature sizes can be controlled by varying the contact times. Spreading, however, only takes place beyond a certain threshold concentration. For low ink concentrations the edges of stamp features dominate the ink transfer. For these low concentrations the extent of this edge dominance depends strongly on ink concentration rather than on contact time. These observations indicate a dominant role of the stamp surface in the processes of pattern formation and spreading.

Monolayers of β-cyclodextrin host molecules have been prepared on SiO2 surfaces. An ordered and stable cyano-terminated monolayer was modified in three consecutive surface reactions. First, the cyanide groups were reduced to their corresponding free amines using Red Al as a reducing agent. Second, 1,4-phenylene diisothiocyanate was used to react with the amine monolayer where it acts as a linking molecule, exposing isothiocyanates that can be derivatized further. Finally, per-6-amino β-cyclodextrin was reacted with these isothiocyanate functions to yield a monolayer exposing β-cyclodextrin. All monolayers were characterized by contact angle measurements, ellipsometric thickness measurements, Brewster angle Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry, which indicate the formation of a densely packed cyclodextrin surface. It was demonstrated that the β-cyclodextrin monolayer could bind suitable guest molecules in a reversible manner. A fluorescent molecule (1), equipped with two adamantyl groups for complexation, was adsorbed onto the host monolayer from solution to form a monolayer of guest molecules. Subsequently, the guest molecules were desorbed from the surface by competition with increasing β-cyclodextrin concentration in solution. The data were fitted using a model. An intrinsic binding constant of 3.3 ± 1 × 10⁵ M^-1 was obtained, which corresponds well to previously obtained results with a divalent guest molecule on β-cyclodextrin monolayers on gold. In addition, the number of guest molecules bound to the host surface was determined, and a surface coverage of ca. 30% was found.

Surface-coated nanoparticles of LaF3 and LaPO4 doped with the luminescent trivalent lanthanide ions Eu³⁺, Nd³⁺, Er³⁺, Pr³⁺, Ho³⁺, and Yb³⁺ have been prepared. These ions emit in the visible and in the near-infrared part of the electromagnetic spectrum. The ions Nd³⁺, Er³⁺, Pr³⁺, and Ho³⁺ are the main focus in this research because they show emissions in telecommunication windows. The Yb³⁺ ion is of interest because it can be used as a sensitizer for Er³⁺. The Eu³⁺ ion has been used as a probe for the structural environment of the luminescent ion. It is shown that these lanthanide ions are incorporated in the inorganic host of the particles and that the particles are dispersable in organic solvents. The luminescent lifetimes of the ions are increased by orders of magnitude compared to organic complexes, with values ranging from several microseconds for Pr³⁺ and Ho³⁺, up to about 200 μs for Nd³⁺, and 1 ms for Er³⁺. This increase in the luminescence lifetime is indicative of an effective shielding of the lanthanide ions from nonradiative decay of the excited state by the high-energy vibrations of the solvents and the coordinated organic ligands. A model is proposed to describe the nonexponential behavior of the luminescence decay by quenching from outside the particle. It uses two fit parameters, kR, a parameter describing the luminescence decay rate in the absence of surface quenching, and C, a parameter describing the sensitivity toward quenching. Using this model, the luminescence decays can be fitted very well, and factors influencing the luminescence lifetime like concentration quenching and solvent effects can be described accurately.

Nanostencils (shadow masks with submicrometer apertures in a thin silicon nitride membrane) are promising tools for the facile one‐step generation of nanopatterns of various materials by physical vapor deposition. Evaporation through a shadow mask is accompanied by gradual clogging of the apertures due to adhesion of evaporated material. In order to reduce this effect, nanostencils were coated with alkyl and perfluoroalkyl self‐assembled monolayers (SAMs). The formation and properties of SAMs on planar silicon nitride substrates were studied by contact angle goniometry, X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The SAMs are stable under evaporation of gold at various angles. SAM‐coated nanostencils showed considerably less adhesion of gold compared to bare SixNystencils.

Gradual clogging of the apertures of nanostencils used as miniature shadow masks in metal evaporations can be reduced by coating the stencil with self-assembled monolayers (SAM). This is quantified by the dimensions (height and volume) of gold features obtained by nanostencil evaporation as measured by scanning electron microscopy (SEM) and atomic force microscopy (AFM). An increase in material deposition through the apertures by more than 100% can be achieved with SAM-coated stencils, which increases their lifetime.

The rupture forces of individual β-cyclodextrin (β-CD)−ferrocene host−guest complexes in an aqueous medium were measured by dynamic single molecule force spectroscopy using an atomic force microscope (AFM). The thiol-derivatized ferrocene guest was immobilized in self-assembled monolayers on gold-coated AFM tips, while the heptasulfide β-CD host was self-assembled onto atomically flat Au(111) substrates. The effects of the alkyl spacer length of the ferrocene adsorbates, the relative concentration of ferrocene in the mixed monolayer on the AFM tip, and the unloading rate on the observed molecular unbinding events were studied. Depending on the concentration of ferrocene moieties on the AFM tip, multiple or predominantly single pull-off events were observed. A statistical analysis showed that the observed rupture forces are integer multiples of one fundamental force quantum of 55 ± 10 pN, which is attributed to the rupture of a single host−guest complex. This force quantum is found to be independent of the number of interacting host−guest pairs, independent of the spacer length, and independent of the unloading rate. These results indicate that the host−guest complex rupture forces were probed under conditions of thermodynamic equilibrium.

Poly(propylene imine) (PPI) dendrimers of generations 1−5 have been derivatized with dialkyl sulfide chains. On water, these dendrimers form stable LB films with densely packed alkyl chains pointing to the air and cores exposed to the aqueous solution. Self-assembly of the same dendrimers from solution onto a gold surface leads to a flattened orientation of the molecules on the surface, as shown by high contact angle hystereses, high electrochemical capacitances, and low charge transfer resistances. X-ray photoelectron spectroscopy data indicate that the formation of the flattened structure can be attributed to adsorption to the gold surface of not only part of the sulfide moieties in the alkyl chains, but also part of the tertiary amines in the core. The electrochemically determined surface coverages of ferrocene-modified dendritic wedges (with similar molecular structures as those of the dialkyl sulfide PPI dendrimers) confirm the proposed flattened, surface-spread dendritic structure. In contrast, LB films of the sulfide PPI dendrimers that were transferred onto gold appear to largely remain their original, densely packed state, as for these films smaller contact angle hystereses and higher charge transfer resistances are measured than those observed for the monolayers prepared by self-assembly from solution. Additionally, the electrochemical capacitances of the transferred LB films point to a layer thickness comparable to the thickness of a densely packed didecylsulfide monolayer. The results in this study demonstrate that different surface architectures can be prepared of the same compounds by solely varying the preparation procedure.

Thioether derivatives with 1–4 thioether moieties were used as inks in microcontact printing on gold for the reproduction of patterns as they combine good monolayer quality with synthetic versatility, and high molecular weights. Self‐assembled monolayers (SAMs) on gold of compounds 1and 2had a quality comparable to SAMs of decanethiol, both regarding monolayer order and etch resistance. Etch resistances of SAMs of 3and 4were lower. Resulting structures after etching of patterned SAMs using 1, 2, and 3were of good quality for patterns with feature sizes on the same stamp ranging from 1–200 μm. Patterns of 4were not reproduced. Overall, compounds 1and 2are good candidates for low‐diffusion inks.

The insertion process of individual dendrimer sulfide 1 molecules into self-assembled monolayers (SAMs) of 11-mercapto-1-undecanol has been investigated by atomic force microscopy (AFM), wettability, and electrochemical measurements. Immersion of 11-mercapto-1-undecanol SAMs in solutions of increasing concentrations of 1 leads to an increase in the number of dendrimer molecules inserted into the thiol layer. Similarly, longer contact times of the original SAM with the solvent (dichloromethane) also lead to a higher number of inserted dendrimers. However, 11-mercapto-1-undecanol monolayers prepared by immersion into 1 mM solutions of the thiol for 2, 5, 10, 30, 60, 120, and 180 min, followed by a 60 min exposure to a solution of dendrimer 1 did not show significant differences in the number of inserted dendrimers. This indicates that the initial layer quality is not a determining factor for the insertion process. A mechanism consisting of rapid dissociation of surface thiols, possibly as disulfides, followed by slow dendrimer adsorption, is proposed. The rate-determining step of the process is the insertion of the individual dendrimer molecules. For the dissociation step, first-order kinetics for the fraction of covered substrate versus time of exposure to solvent was found, with a rate constant, k, of (8.0 ± 1.5) × 10^-4 min^-1.

The surfactant behavior of the water-soluble calix[4]arene 1, which has carboxylate groups at the upper rim and two phenyl groups at the lower rim, and its complexation to γ-cyclodextrin were studied. The critical micelle concentration (cmc) of 1 and of tetrapropoxycalix[4]arenetetracarboxylate 2 are 35 and 650 μM, respectively. The stabilities of the 1:1 inclusion complexes of γ-cyclodextrin with 1 and 2 are 1.3 × 10⁴ and 1.5 × 10³ M^-1, respectively. The stability of the former complex was derived from a calorimetric titration under conditions where 1 is largely micellized. A minimization routine is described for determining the heat contributions of demicellization and complexation. The association of 1 to γ-cyclodextrin is enthalpy-driven, which, together with the high K value and the 1:1 binding stoichiometry, indicates that both pendant phenyl rings of 1 are included in the γ-cyclodextrin cavity.

A new deprotection procedure in the synthesis of (partially) phosphate-methylated oligodeoxynucleotides has been developed, involving treatment of fully protected DNA fragments with methanolic potassium carbonate. It is shown that base deprotection can be accomplished in potassium carbonate/methanol without aftecting the methyl phosphotriesters. This methodology enables us to synthesize, both in solution and on a solid support, DNA fragments which are phosphate-methylated at defined positions. The solid phase synthesis, however, turns out to be accompanied by considerable demethylation of the phosphotriesters. It is demonstrated that this demethylation does not occur during the deprotection or work-up procedure. Furthermore, it was found that the latter side-reaction is suppressed when the standard capping procedure with acetic anhydride is included.