Ronny Kürsteiner

Last Name

Kürsteiner

First Name

Ronny

ORCID

0000-0002-4208-1078

Organisational unit

03917 - Burgert, Ingo / Burgert, Ingo

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Publications 1 - 8 of 8

Formation of Iron (Hydr)Oxide Nanoparticles with a pH-Clock
Kürsteiner, Ronny; Ding, Yong; Ritter, Maximilian; et al. (2022)
Nanomaterials
We demonstrate the autonomous synthesis of iron (hydr)oxide (green rust, magnetite, and lepidocrocite) nanoparticles by precipitating iron(II) ions using hydroxide ions generated in situ with the methylene glycol-sulfite (MGS) reaction, a pH-clock. We show that the nature of the products can be predetermined by tuning the initial iron(II) concentration.
Iron-Catalyzed Laser-Induced Graphitization Enabling Current Collector-Free Electrodes With Spatially Tunable Iron/Iron Oxide Phases
Dreimol, Christopher; Edberg, Jesper; Kürsteiner, Ronny; et al. (2025)
Advanced Materials
Iron-catalyzed laser-induced graphitization (IC-LIG) represents an eco-efficient alternative to traditional carbon electrode manufacturing. Combining a bio-based tannic acid-iron precursor ink with CO₂ laser treatment results in sheet resistance of 23.59 ± 1.2 Ω square⁻¹ on renewable substrates. Varying the tannic-acid-to-iron ratio (TA:Fe), the rheology of the precursor ink can be tuned, enabling versatile application techniques, including spray coating, screen printing, and direct-ink-writing (DIW). Subsequent laser-treatment enables the formation of functional IC-LIG electrodes for all application methods, while even thick DIW-printed layers (260 μm) result in complex, conductive electrode patterns. Laser post-treatment expands design possibilities by locally tuning iron phases, such as converting γ-iron to magnetite. The unidirectional laser-treatment results in a layered arrangement, forming a multilayer electrode with a highly graphitized top layer serving as a current collector substitute, and an underlying composite of iron-rich nanoparticles embedded in a porous graphitic foam, acting as a hybrid electrode. Electrochemical analysis reveals double-layer capacitor behavior at low TA:Fe ratios, while higher ratios demonstrate increased redox activity and pseudo-capacitive characteristics. Achieving stable capacities of 15 mF cm⁻² with a 1 M NaCl electrolyte over 5000 cycles underscores the potential of IC-LIG electrodes as a sustainable solution for advanced energy storage devices and beyond.
Salt-In-Wood Piezoelectric Power Generators with Circular Materials Design for High-Performance Sustainable Energy Harvesting
Garemark, Jonas; Ritter, Maximilian; Dreimol, Christopher; et al. (2025)
Advanced Functional Materials
The nanowatt-level power density of current biobased piezoelectric energy harvesters restricts their applicative potential for the efficient conversion of biomechanical energy. A high-performing, fully renewable piezoelectric device incorporating green piezo-active Rochelle salt in a laser-drilled wood template is demonstrated to form ordered crystal pillar arrays by melt crystallization. Investigating the effect of different crystal pillar configurations on the piezoelectric response, a shearing design (45 degrees-oriented pillars) shows potential of up to 30 V and a current of 4 mu A - corresponding to a 10-fold power increase compared to single-crystalline Rochelle salt. A concept of direct laser graphitization on the crystal surfaces are demonstrated using a fully renewable ink to create electrodes of low resistance (36 Omega sq-1). The entire device can be disassembled, fully recycled, and reused. This nanogenerator outperforms state-of-the-art biobased ones and competes with conventional lead-based devices in power generation while showing a significantly lower environmental footprint, as indicated by life-cycle assessment.
Acid Autocatalysis Best Served Hot: The Chlorate–Sulfite–Gluconolactone System as a Thermochemical Clock
Kürsteiner, Ronny; Panzarasa, Guido (2023)
ChemSystemsChem
The autonomous activation of acid-autocatalyzed sulfite-halogenate (iodate, bromate, chlorate) reactions is programmed using slow acid generators (delta-gluconolactone GL, and 1,3-propanesultone PrS). A remarkable correlation is found between the pH- and temperature-time profiles, especially for the chlorate-sulfite-GL system. Further optimization of the latter resulted in a chemical system able to generate sudden temperature and pH changes after a tailorable induction time, that is a "thermochemical clock".
Time-domain Tollens reaction: synthesising silver nanoparticles with the formaldehyde clock
Kürsteiner, Ronny; Ritter, Maximilian; Sologubenko, Alla; et al. (2023)
Nanoscale Advances
The addition of silver(i) ions to the methylene glycol-sulphite (MGS) clock reaction results in the sudden formation of metallic silver nanoparticles. Stable suspensions are obtained in the presence of poly(vinylpyrrolidone). The time delay before the appearance of the particles, as well as their size, decreases with the initial methylene glycol concentration while their monodispersity increases.
Acid Autocatalysis Best Served Hot: The Chlorate-Sulfite-Gluconolactone System as a Thermochemical Clock
Kürsteiner, Ronny; Panzarasa, Guido (2023)
ChemSystemsChem
Iron-Catalyzed Laser-Induced Graphitization – Multiscale Analysis of the Structural Evolution and Underlying Mechanism
Dreimol, Christopher; Kürsteiner, Ronny; Ritter, Maximilian; et al. (2024)
Small
The transition to sustainable materials and eco-efficient processes in commercial electronics is a driving force in developing green electronics. Iron-catalyzed laser-induced graphitization (IC-LIG) has been demonstrated as a promising approach for rendering biomaterials electrically conductive. To optimize the IC-LIG process and fully exploit its potential for future green electronics, it is crucial to gain deeper insights into its catalyzation mechanism and structural evolution. However, this is challenging due to the rapid nature of the laser-induced graphitization process. Therefore, multiscale preparation techniques, including ultramicrotomy of the cross-sectional transition zone from precursor to fully graphitized IC-LIG electrode, are employed to virtually freeze the IC-LIG process in time. Complementary characterization is performed to generate a 3D model that integrates nanoscale findings within a mesoscopic framework. This enabled tracing the growth and migration behavior of catalytic iron nanoparticles and their role during the catalytic laser-graphitization process. A three-layered arrangement of the IC-LIG electrode is identified including a highly graphitized top layer with an interplanar spacing of 0.343 nm. The middle layer contained gamma-iron nanoparticles encapsulated in graphitic shells. A comparison with catalyst-free laser graphitization approaches highlights the unique opportunities that IC-LIG offers and discuss potential applications in energy storage devices, catalysts, sensors, and beyond.
Piezoelectric and Photoconductive Zinc Oxide-Wood Hybrids Obtained by Atomic Layer Deposition
Ritter, Maximilian; Maćkosz, Krzysztof; Garemark, Jonas; et al. (2025)
ACS Nano
The development of sustainable functional wood-based materials for advanced photonic, optical, and energy-harvesting applications is a topic of great priority and scientific interest. Owing to its inherent piezoactivity and photoconductivity, zinc oxide (ZnO) can be of help for all these applications. While previously used for wood-based piezoelectric nanogenerators, its use for enabling wood with photoconductive properties has not yet been demonstrated. Here, we introduce an innovative method to produce ZnO-wood hybrids based on atomic layer deposition (ALD), a technique so far underrepresented in the field of wood functionalization. By a studied combination of ALD, customized sample geometry, structure-retaining delignification, and careful selection of the drying method, we obtained a homogeneous functionalization of a bulk wood scaffold with layers of nanocrystalline ZnO. This approach allowed us to achieve control over the homogeneity, distribution, and coating thickness of the oxide layer. The micro- and nanostructure of the resulting hybrids were investigated by electron microscopy as well as by X-ray diffraction and scattering. The ZnO-wood hybrids show an anisotropic piezoelectric response due to the natural structure of the wood. Moreover, we demonstrate the use of ZnO-functionalized wood for the fabrication of bulk (photo)conductive wood. Upon irradiation with UV light, a significant decrease in resistivity is observed, which increases again upon removal of UV light. Finally, we used the hybrids to fabricate a ZnO-wood replica by thermal removal of the cellulose scaffold. This treatment leaves behind a detailed inorganic wood replica down to the smallest open accessible features such as micrometer-sized wood pits.

Publications 1 - 8 of 8

Ronny Kürsteiner

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