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496 results on '"Johansson, Leena-Sisko"'

43. Gold Au(I)6 Clusters with Ligand‐Derived Atomic Steric Locking: Multifunctional Optoelectrical Properties and Quantum Coherence.

Author

Chandra, Sourov, Sciortino, Alice, Das, Susobhan, Ahmed, Faisal, Jana, Arijit, Roy, Jayoti, Li, Diao, Liljeström, Ville, Jiang, Hua, Johansson, Leena‐Sisko, Chen, Xi, Nonappa, Cannas, Marco, Pradeep, Thalappil, Peng, Bo, Ras, Robin H. A., Sun, Zhipei, Ikkala, Olli, and Messina, Fabrizio

Subjects
QUANTUM coherence, GOLD clusters, ATOMIC clusters, THIRD harmonic generation, CHARGE transfer, FIELD-effect devices, GOLD nanoparticles
Abstract

An atomically precise ultrasmall Au(I)6 nanocluster where the six gold atoms are complexed by three sterically interlocking stabilizing ligands is reported, allowing a unique combination of efficient third harmonic generation (THG), intense photoluminescence quantum yield (35%), ultrafast quantum coherence, and electron accepting properties. The reaction of 6‐(dibutylamino)‐1,3,5‐triazine‐2,4‐dithiol (TRZ) with HAuCl4 leads to complexation by thiolation. However, intriguingly, another reduction step is needed to form the centrosymmetric Au(I)6TRZ3 clusters with the multifunctional properties. Here, ascorbic acid is employed as a mild reducing agent, in contrast to the classic reducing agents, like NaBH4 and NaBH3CN, which often produce mixtures of clusters or gold nanoparticles. Such Au(I)6 nanocluster films produce very strong THG response, never observed for nanoclusters. The clusters also produce brilliant single and multiphoton luminescence with exceptional stability. Density functional theory calculations and femtosecond transient absorption studies suggest ultrafast ligand‐to‐metal charge transfer, quantum coherence with long decoherence time 200–300 fs, and fast propagation of excitation from the core to the surrounding solvent. Finally, novel electron‐accepting ground state properties allow p‐doping of 2D field‐effect transistor devices. Summarizing, the potential of ultrasmall sterically interlocked Au(I) clusters, i.e., complexes allowed by the new sequential reduction protocol, towards multifunctional devices, fast photoswitches, and quantum colloidal devices is shown. [ABSTRACT FROM AUTHOR]

Published
2023
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46. Design and Testing of a Bending‐Resistant Transparent Nanocoating for Optoacoustic Cochlear Implants

Author

Griffo, Alessandra, Liu, Yingying, Mahlberg, Riitta, Alakomi, Hanna-Leena, Johansson, Leena-Sisko, Milani, Roberto, Department of Bioproducts and Biosystems, VTT Technical Research Centre of Finland, Aalto-yliopisto, and Aalto University

Subjects
interfaces, lcsh:Chemistry, Full Paper, silanes, thin films, lcsh:QD1-999, antifouling coatings, surface chemistry, Full Papers, implantable devices
Abstract

A nanosized coating was designed to reduce fouling on the surface of a new type of cochlear implant relying on optoacoustic stimulation. This kind of device imposes novel design principles for antifouling coatings, such as optical transparency and resistance to significant constant bending. To reach this goal we deposited on poly(dimethylsiloxane) a PEO-based layer with negligible thickness compared to the curvature radius of the cochlea. Its antifouling performance was monitored upon storage by quartz crystal microbalance, and its resistance upon bending was tested by fluorescence microscopy under geometrical constraints similar to those of implantation. The coating displayed excellent antifouling features and good stability, and proved suitable for further testing in real-environment conditions.

Published
2019
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48. Core‐Selective Silver‐Doping of Gold Nanoclusters by Surface‐Bound Sulphates on Colloidal Templates: From Synthetic Mechanism to Relaxation Dynamics.

Author

Chandra, Sourov, Sciortino, Alice, Shandilya, Shruti, Fang, Lincan, Chen, Xi, Nonappa, Jiang, Hua, Johansson, Leena‐Sisko, Cannas, Marco, Ruokolainen, Janne, Ras, Robin H. A., Messina, Fabrizio, Peng, Bo, and Ikkala, Olli

Subjects
GOLD clusters, SULFATES, QUANTUM efficiency, DENSITY functional theory, SILVER sulfide, PHOTOLUMINESCENCE
Abstract

Ultra‐small luminescent gold nanoclusters (AuNCs) have gained substantial interest owing to their low photobleaching and high biocompatibility. While the substitution of silver for gold at the central core of AuNCs has shown significant augmentation of photoluminescence with enhanced photostability, selective replacement of the central atom by silver is, however, energetically inhibited. Herein, a new strategy for in situ site‐selective Ag‐doping exclusively at the central core of AuNCs using sulphated colloidal surfaces as the templates is presented. This approach exceedingly improves the photoluminescence quantum efficiency of AuNCs by eliminating nonradiative losses in the multi‐step relaxation cascade populating the emissive state. Density functional theory predicts the mechanism of specific doping at the central core, endorsing the preferential bonding between Ag+ ions and sulphates in water. Finally, the generic nature of the templating concept to allow core‐specific doping of nanoclusters is unraveled. [ABSTRACT FROM AUTHOR]

Published
2023
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