Synthesis and coordinative layer-by-layer deposition of pyridine-functionalized gold nanoparticles and tetralactam macrocycles on silicon substrates

Immobilization of catalytic virus-like particles in a flow reactor

A functional microfluidic reactor is constructed by the immobilization of gold containing virus-based protein cages that catalyze the reduction of nitro-arenes with high efficiency.

Pillar[5]arene-Based Supramolecular Plasmonic Thin Films for Label-Free, Quantitative and Multiplex SERS Detection

Novel plasmonic thin films based on electrostatic layer-by-layer (LbL) deposition of citrate-stabilized Au nanoparticles (NPs) and ammonium pillar[5]arene (AP[5]A) have been developed. The supramolecular-induced LbL assembly of the plasmonic nanoparticles yields the formation of controlled hot spots with uniform interparticle distances. At the same time, this strategy allows modulating the density and dimensions of the Au aggregates, and therefore the optical response, on the thin film with the number of AuNP-AP[5]A deposition cycles. Characterization of the AuNP-AP[5]A hybrid platforms as a function of the deposition cycles was performed by means of visible-NIR absorption spectroscopy, and scanning electron and atomic force microscopies, showing larger aggregates with the number of cycles. Additionally, the surface enhanced Raman scattering efficiency of the resulting AuNP-AP[5]A thin films has been investigated for three different laser excitations (633, 785, and 830 nm) and using pyrene as Raman probe. The best performance was shown by the AuNP-AP[5]A film obtained with two deposition cycles ((AuNP-AP[5]A)₂) when excited with a 785 laser line. The optical response and SERS efficiency of the thin films were also simulated using the M³ solver and employing computer aided design models built based on SEM images of the different films. The use of host molecules as building blocks to fabricate (AuNP-AP[5]A)₂) films has enabled the ultradetection, in liquid and gas phase, of low molecular weight polyaromatic hydrocarbons, PAHs, with no affinity for gold but toward the hydrophobic AP[5]A cavity. Besides, these plasmonic platforms allowed achieving quantitative detection within certain concentration regimes. Finally, the multiplex sensing capabilities of the AuNP-AP[5]A)₂ were evaluated for their ability to detect in liquid and gas phase three different PAHs.

Photocontrolled On-Surface Pseudorotaxane Formation with Well-Ordered Macrocycle Multilayers

The photoinduced pseudorotaxane formation between a photoresponsive axle and a tetralactam macrocycle was investigated in solution and on glass surfaces with immobilized multilayers of macrocycles. In the course of this reaction, a novel photoswitchable binding station with azobenzene as the photoswitchable unit and diketopiperazine as the binding station was synthesized and studied by NMR and UV/Vis spectroscopy. Glass surfaces have been functionalized with pyridine-terminated SAMs and subsequently with multilayers of macrocycles through layer-by-layer self assembly. A preferred orientation of the macrocycles could be confirmed by NEXAFS spectroscopy. The photocontrolled deposition of the axle into the surface-bound macrocycle-multilayers was monitored by UV/Vis spectroscopy and led to an increase of the molecular order, as indicated by more substantial linear dichroism effects in angle-resolved NEXAFS spectra.

Anion-induced palladium nanoparticle formation during the on-surface growth of molecular assemblies

We demonstrate a process that results in the formation of palladium nanoparticles during the assembly of molecular thin films. These nanoparticles are embedded in the films and are generated by a chemical reaction of the counter anions of the molecular components with the metal salt that is used for cross-linking these components.

A photoswitchable rotaxane operating in monolayers on solid support

A novel photoswitchable rotaxane was synthesised and its switching behaviour in solution and on solid support was studied.

Principal component analysis (PCA)-assisted time-of-flight secondary-ion mass spectrometry (ToF-SIMS): a versatile method for the investigation of self-assembled monolayers and multilayers as precursors for the bottom-up approach of nanoscaled devices

The production of high-quality self-assembled monolayers (SAMs) followed by layer-by-layer (LbL) self-assembly of macrocycles is essential for nanotechnology applications based on functional surface films. To help interpret the large amount of data generated by a standard ToF-SIMS measurement, principal component analysis (PCA) was used. For two examples, the advantages of a combination of ToF-SIMS and PCA for quality control and for the optimization of layer-by-layer self-assembly are shown. The first example investigates how different cleaning methods influence the quality of SAM template formation. The second example focuses on the LbL self-assembly of macrocycles and the corresponding stepwise surface modification.

Synthetic approach towards ‘click’ modified chalcone based organotriethoxysilanes; UV-Vis study

The efficient linkage of a conjugate chalcone to n-propyltriethoxysilanes via a 1,2,3-triazole is reported. The synthesis involves a Claisen–Schmidt condensation followed by a copper(i) catalyzed azide–alkyne cycloaddition (CuAAC) reaction.