@article{DoeringGrigorievTapioetal.2022, author = {Doering, Ulrike and Grigoriev, Dmitry and Tapio, Kosti and Bald, Ilko and B{\"o}ker, Alexander}, title = {Synthesis of nanostructured protein-mineral-microcapsules by sonication}, series = {Soft matter}, volume = {18}, journal = {Soft matter}, number = {13}, publisher = {Royal Society of Chemistry}, address = {London}, issn = {1744-6848}, doi = {10.1039/d1sm01638e}, pages = {2558 -- 2568}, year = {2022}, abstract = {We propose a simple and eco-friendly method for the formation of composite protein-mineral-microcapsules induced by ultrasound treatment. Protein- and nanoparticle-stabilized oil-in-water (O/W) emulsions loaded with different oils are prepared using high-intensity ultrasound. The formation of thin composite mineral proteinaceous shells is realized with various types of nanoparticles, which are pre-modified with Bovine Serum Albumin (BSA) and subsequently characterized by EDX, TGA, zeta potential measurements and Raman spectroscopy. Cryo-SEM and EDX mapping visualizations show the homogeneous distribution of the densely packed nanoparticles in the capsule shell. In contrast to the results reported in our previous paper,(1) the shell of those nanostructured composite microcapsules is not cross-linked by the intermolecular disulfide bonds between BSA molecules. Instead, a Pickering-Emulsion formation takes place because of the amphiphilicity-driven spontaneous attachment of the BSA-modified nanoparticles at the oil/water interface. Using colloidal particles for the formation of the shell of the microcapsules, in our case silica, hydroxyapatite and calcium carbonate nanoparticles, is promising for the creation of new functional materials. The nanoparticulate building blocks of the composite shell with different chemical, physical or morphological properties can contribute to additional, sometimes even multiple, features of the resulting capsules. Microcapsules with shells of densely packed nanoparticles could find interesting applications in pharmaceutical science, cosmetics or in food technology.}, language = {en} } @article{SchuermannTitovEbeletal.2022, author = {Sch{\"u}rmann, Robin and Titov, Evgenii and Ebel, Kenny and Kogikoski Junior, Sergio and Mostafa, Amr and Saalfrank, Peter and Milosavljević, Aleksandar R. and Bald, Ilko}, title = {The electronic structure of the metal-organic interface of isolated ligand coated gold nanoparticles}, series = {Nanoscale Advances}, volume = {4}, journal = {Nanoscale Advances}, number = {6}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2516-0230}, doi = {10.1039/d1na00737h}, pages = {1599 -- 1607}, year = {2022}, abstract = {Light induced electron transfer reactions of molecules on the surface of noble metal nanoparticles (NPs) depend significantly on the electronic properties of the metal-organic interface. Hybridized metal-molecule states and dipoles at the interface alter the work function and facilitate or hinder electron transfer between the NPs and ligand. X-ray photoelectron spectroscopy (XPS) measurements of isolated AuNPs coated with thiolated ligands in a vacuum have been performed as a function of photon energy, and the depth dependent information of the metal-organic interface has been obtained. The role of surface dipoles in the XPS measurements of isolated ligand coated NPs is discussed and the binding energy of the Au 4f states is shifted by around 0.8 eV in the outer atomic layers of 4-nitrothiophenol coated AuNPs, facilitating electron transport towards the molecules. Moreover, the influence of the interface dipole depends significantly on the adsorbed ligand molecules. The present study paves the way towards the engineering of the electronic properties of the nanoparticle surface, which is of utmost importance for the application of plasmonic nanoparticles in the fields of heterogeneous catalysis and solar energy conversion.}, language = {en} } @article{SchuermannNagelJuergensenetal.2022, author = {Sch{\"u}rmann, Robin and Nagel, Alessandro and Juergensen, Sabrina and Pathak, Anisha and Reich, Stephanie and Pacholski, Claudia and Bald, Ilko}, title = {Microscopic understanding of reaction rates observed in plasmon chemistry of nanoparticle-ligand systems}, series = {The journal of physical chemistry : C, Nanomaterials and interfaces}, volume = {126}, journal = {The journal of physical chemistry : C, Nanomaterials and interfaces}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.2c00278}, pages = {5333 -- 5342}, year = {2022}, abstract = {Surface-enhanced Raman scattering (SERS) is an effective and widely used technique to study chemical reactions induced or catalyzed by plasmonic substrates, since the experimental setup allows us to trigger and track the reaction simultaneously and identify the products. However, on substrates with plasmonic hotspots, the total signal mainly originates from these nanoscopic volumes with high reactivity and the information about the overall consumption remains obscure in SERS measurements. This has important implications; for example, the apparent reaction order in SERS measurements does not correlate with the real reaction order, whereas the apparent reaction rates are proportional to the real reaction rates as demonstrated by finite-difference time-domain (FDTD) simulations. We determined the electric field enhancement distribution of a gold nanoparticle (AuNP) monolayer and calculated the SERS intensities in light-driven reactions in an adsorbed self-assembled molecular monolayer on the AuNP surface. Accordingly, even if a high conversion is observed in SERS due to the high reactivity in the hotspots, most of the adsorbed molecules on the AuNP surface remain unreacted. The theoretical findings are compared with the hot-electron-induced dehalogenation of 4-bromothiophenol, indicating a time dependency of the hot-carrier concentration in plasmon-mediated reactions. To fit the kinetics of plasmon-mediated reactions in plasmonic hotspots, fractal-like kinetics are well suited to account for the inhomogeneity of reactive sites on the substrates, whereas also modified standard kinetics model allows equally well fits. The outcomes of this study are on the one hand essential to derive a mechanistic understanding of reactions on plasmonic substrates by SERS measurements and on the other hand to drive plasmonic reactions with high local precision and facilitate the engineering of chemistry on a nanoscale.}, language = {en} } @article{EbelBald2022, author = {Ebel, Kenny and Bald, Ilko}, title = {Low-energy (5-20 eV) electron-induced single and double strand breaks in well-defined DNA sequences}, series = {The journal of physical chemistry letters / American Chemical Society}, volume = {13}, journal = {The journal of physical chemistry letters / American Chemical Society}, number = {22}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.2c00684}, pages = {4871 -- 4876}, year = {2022}, abstract = {Ionizing radiation is used in cancer radiation therapy to effectively damage the DNA of tumors. The main damage is due to generation of highly reactive secondary species such as low-energy electrons (LEEs). The accurate quantification of DNA radiation damage of well-defined DNA target sequences in terms of absolute cross sections for LEE-induced DNA strand breaks is possible by the DNA origami technique; however, to date, it is possible only for DNA single strands. In the present work DNA double strand breaks in the DNA sequence 5'-d(CAC)(4)/5'd(GTG)(4) are compared with DNA single strand breaks in the oligonucleotides 5'-d(CAC)(4) and 5'-d(GTG)(4) upon irradiation with LEEs in the energy range from 5 to 20 eV. A maximum of strand break cross section was found around 7 and 10 eV independent of the DNA sequence, indicating that dissociative electron attachment is the underlying mechanism of strand breakage and confirming previous studies using plasmid DNA.}, language = {en} }