The synthetic chemistry and spectroscopy of sulfur-protected gold surfaces and nanoparticles is analyzed, indicating that the electronic structure of the interface is Au(0)-thiyl, with Au(I)-thiolates identified as high-energy excited surface states. Density-functional theory indicates that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)-thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s-d hybridization and charge polarization effects that perturbatively mix in some Au(I)-thiolate character. A simple method for quantifying these contributions is presented, revealing that a driving force for nanoparticle growth is nobleization, minimizing Au(I)-thiolate involvement. Predictions that Brust-Schiffrin reactions involve thiolate anion intermediates are verified spectroscopically, establishing a key feature needed to understand nanoparticle growth. Mixing of preprepared Au(I) and thiolate reactants always produces Au(I)-thiolate thin films or compounds rather than monolayers. Smooth links to O, Se, Te, C, and N linker chemistry are established.gold-sulfur bonding | synthesis | mechanism | electronic structure | nanoparticle G old self-assembled monolayers (SAMs) and monolayerprotected gold nanoparticles form important classes of systems relevant for modern nanotechnological and sensing applications (1-5). Understanding the chemical nature of these interfaces is critical to the design of new synthesis techniques, the design of new spectroscopic methods to investigate them, and to developing system properties or device applications. Over the last 10 y, great progress has been made in understanding the atomic structures of gold-sulfur interfaces (6). Most discussion (7) has focused on the identification of adatom-bound motifs of the form RS-Au-SR (where R is typically a linear alkyl chain or phenyl group) sitting above a regular Au(111) surface (8-10) or on top of a nanoparticle core of regular geometry (11), Other variant structures have also been either observed, such as polymeric chains such as the trimer RS-Au-SR-Au-SR) (10, 11), or proposed (8,12,13). By considering the four isomers of butanethiol (14), we have shown that alternative structures can also be produced in which RS groups bind directly to an Au(111) surface without gold adatoms. This occurs whenever steric interactions across the adatoms are too strong or steric intermolecular packing forces allow for very high surface coverages if both adatom and directly bound motifs coexist in the same regular SAM (15). The cross-adatom steric effect has also been demonstrated for gold nanoparticles (16), and we have shown that Coulombic interactions between charged tail groups can also inhibit adatom formation (17). SAMs involving adatoms have poor longrange order owing to the surface pitting that is required to deliver gold adatoms, while directly bound motifs lead to regular surfaces (18).There is clearly a delicate balance between the forces that direct these different in...

Mapping the entire frequency bandwidth of brain electrophysiological signals is of paramount importance for understanding physiological and pathological states. The ability to record simultaneously DC-shifts, infraslow oscillations (<0.1Hz), typical LFP signals (0.1-80 Hz) and higher frequencies (80-600 Hz) using the same recording site would particularly benefit preclinical epilepsy research and could provide clinical biomarkers for improved seizure onset zone delineation. However, commonly used metal microelectrode technology suffers from instabilities that hamper the high-fidelity of DC-coupled recordings, which are needed to access signals of very low frequency. Here, we use flexible graphene depth neural probes (gDNP), consisting of a linear array of graphene microtransistors, to concurrently record DC-shifts and high frequency neuronal activity in awake rodents. We show that gDNPs can reliably record and map with high spatial resolution seizures, pre-ictal DC-shifts and seizure associated spreading depolarizations together with higher frequencies through the cortical laminae to the hippocampus in a mouse model of chemically-induced seizures. Moreover, we demonstrate functionality of chronically implanted devices over 10 weeks by recording with high fidelity spontaneous spike-wave discharges and associated infraslow oscillations in a rat model of absence epilepsy. Altogether, our work highlights the suitability of this technology for in vivo electrophysiology research, and in particular epilepsy research, by allowing stable and chronic DC-coupled recordings.

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Micro/Nano robots have shown enormous potential for diverse biomedical applications, such as targeted delivery, in vivo biosensing, minimally invasive surgery and cell manipulation through extending their area of operation to various previously inaccessible locations. The motion of these small-scale robots can be either self-propelled or remotely controlled by some external power sources. However, in order to use them for biomedical applications, optimization of biocompatible propulsion and precise controllability are highly desirable. In this article, the recent progresses about the biocompatible propulsion (e.g. self-propulsion, external stimuli based propulsion and bio-hybrid propulsion) techniques for these micro/nano robotic devices are summarized along with their applications, with a special focus on the advantages and disadvantages of different propulsion techniques. The current challenges and future perspectives of these small-scale devices are discussed in the final section. Highlights This review paper discusses: • The enormous potential of micro/nano robotics for advancing biomedical applications. • The latest development of the biocompatible propulsion techniques. • The future research needed to prompt the widespread adoption of micro/nano robotics in the biomedical sector.

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Application of enzymatic biofuel cells (EBFCs) in wearable or implantable biomedical devices requires flexible and biocompatible electrode materials.

Graphene-based quantum dots (GQDs) are attractive fluorophores due to their excellent photoluminescence properties, water solubility, low cost, and low toxicity. However, the lack of simple, efficient, and environmental-friendly synthesis methods often limits their biological applications. Herein, we explore a novel, one-pot, green synthesis approach for the fabrication of fluorescent GQDs without involving any harsh reagents. Graphene oxide is used as a precursor, and a 2 h hydrothermal synthesis is carried out with assistance of hydrogen peroxide; no further post purification steps are required. The effects of reaction conditions on the characteristics of GQDs are comprehensively investigated. The as-synthesized GQDs show a high photostability and excellent biocompatibility as revealed by cell viability assays for three different cell lines, namely, macrophages, endothelial cells, and a model cancer cell line. The detailed studies of cellular uptake mechanisms suggest that for all of the three cell lines the major internalization route for GQDs is caveolaemediated endocytosis followed by clathrin-mediated endocytosis at a less extent. Our results demonstrate the great potential of the as-synthesized GQDs as fluorescent nanoprobes. The study also provides unique insight into the cell−GQDs interactions, which is highly valuable for bioimaging and other related applications such as diagnostics and drug delivery.

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