Bioinspired Synthesis of Reduced Graphene Oxide-Wrapped Geobacter sulfurreducens as a Hybrid Electrocatalyst for Efficient Oxygen Evolution Reaction

Doping/decorating of graphene or reduced graphene oxide (rGO) with heteroatoms provides a promising route for the development of electrocatalysts which will be useful in many technologies, including water splitting. However, current doping approaches are complicated, not eco-friendly, and not cost-effective. Herein, we report the synthesis of doped/decorated rGO for oxygen evolution reaction (OER) using a simple approach that is cost-effective, sustainable, and easy to scale up. The OER catalyst was derived from the reduction of GO by an exo-electron-transferring bacterium, Geobacter sulfurreducens. Various analytical tools indicate that OER active elements such as Fe, Cu, N, P, and S decorate the rGO flakes. The hybrid catalyst (i.e., Geobacter/rGO) produces a geometric current density of 10 mA cm–2 at an overpotential of 270 mV versus the reversible hydrogen electrode with a Tafel slope of 43 mV dec–1 and possesses high durability, as evidenced through 10 h of stability testing. Electrochemical analyses suggest the importance of Fe and its possible role as an active site for OER. Overall, this work represents a simple approach toward the development of an earth-abundant, eco-friendly, and highly active OER electrocatalyst for various applications such as solar fuel production, rechargeable metal–air batteries, and microbial electrosynthesis

Roadmap on optical sensors

Optical sensors and sensing technologies are playing a more and more important role in our modern world. From micro-probes to large devices used in such diverse areas like medical diagnosis, defence, monitoring of industrial and environmental conditions, optics can be used in a variety of ways to achieve compact, low cost, stand-off sensing with extreme sensitivity and selectivity. Actually, the challenges to the design and functioning of an optical sensor for a particular application requires intimate knowledge of the optical, material, and environmental properties that can affect its performance. This roadmap on optical sensors addresses different technologies and application areas. It is constituted by twelve contributions authored by world-leading experts, providing insight into the current state-of-the-art and the challenges their respective fields face. Two articles address the area of optical fibre sensors, encompassing both conventional and specialty optical fibres. Several other articles are dedicated to laser-based sensors, micro- and nano-engineered sensors, whispering-gallery mode and plasmonic sensors. The use of optical sensors in chemical, biological and biomedical areas is discussed in some other papers. Different approaches required to satisfy applications at visible, infrared and THz spectral regions are also discussed

Precision synthesis : designing hot spots over hot spots via selective gold deposition on silver octahedra edges

A major challenge in plasmonic hot spot fabrication is to efficiently increase the hot spot volumes on single metal nanoparticles to generate stronger signals in plasmon-enhanced applications. Here, the synthesis of designer nanoparticles, where plasmonic-active Au nanodots are selectively deposited onto the edge/tip hot spot regions of Ag nanoparticles, is demonstrated using a two-step seed-mediated precision synthesis approach. Such a “hot spots over hot spots” strategy leads to an efficient enhancement of the plasmonic hot spot volumes on single Ag nanoparticles. Through cathodoluminescence hyperspectral imaging of these selective edge gold-deposited Ag octahedron (SEGSO), the increase in the areas and emission intensities of hot spots on Ag octahedra are directly visualized after Au deposition. Single-particle surface-enhanced Raman scattering (SERS) measurements demonstrate 10-fold and 3-fold larger SERS enhancement factors of the SEGSO as compared to pure Ag octahedra and non-selective gold-deposited Ag octahedra (NSEGSO), respectively. The experimental results corroborate well with theoretical simulations, where the local electromagnetic field enhancement of our SEGSO particles is 15-fold and 1.3-fold stronger than pure Ag octahedra and facet-deposited particles, respectively. The growth mechanisms of such designer nanoparticles are also discussed together with a demonstration of the versatility of this synthetic protocol

Roadmap on optical sensors

Published 18 December 2023Optical sensors and sensing technologies are playing a more and more important role in our modern world. From micro-probes to large devices used in such diverse areas like medical diagnosis, defense, monitoring of industrial and environmental conditions, optics can be used in a variety of ways to achieve compact, low cost, stand-off sensing with extreme sensitivity and selectivity. Actually, the challenges to the design and functioning of an optical sensor for a particular application requires intimate knowledge of the optical, material, and environmental properties that can affect its performance. This roadmap on optical sensors addresses different technologies and application areas. It is constituted by twelve contributions authored by world-leading experts, providing insight into the current state-of-the-art and the challenges their respective fields face. Two articles address the area of optical fiber sensors, encompassing both conventional and specialty optical fibers. Several other articles are dedicated to laser-based sensors, micro- and nano-engineered sensors, whispering-gallery mode and plasmonic sensors. The use of optical sensors in chemical, biological and biomedical areas is discussed in some other papers. Different approaches required to satisfy applications at visible, infrared and THz spectral regions are also discussed.Mário F S Ferreira, Gilberto Brambilla, Luc Thévenaz, Xian Feng, Lei Zhang, Misha Sumetsky, Callum Jones, Srikanth Pedireddy, Frank Vollmer, Peter D Dragic, Ori Henderson-Sapir, David J Ottaway, Elodie Strupiechonski, Goretti G Hernandez-Cardoso, Arturo I Hernandez-Serrano, Francisco J González, Enrique Castro Camus, Alexis Méndez, Paola Saccomandi, Qimin Quan, Zhongcong Xie, Björn M Reinhard and Max Die

Inflating hollow nanocrystals through a repeated Kirkendall cavitation process

Owing to their unique properties, hollow metal nanocrystals demonstrate greater catalytic promise than their solid counterparts. Here the authors produce hollow and inflated palladium nanocrystals with thin shells via a repeated Kirkendall cavitation process, and demonstrate their activity for formic acid oxidation