Scanning Quantum Dot Microscopy

Interactions between atomic and molecular objects are to a large extent defined by the nanoscale electrostatic potentials which these objects produce. We introduce a scanning probe technique that enables three-dimensional imaging of local electrostatic potential fields with sub-nanometer resolution. Registering single electron charging events of a molecular quantum dot attached to the tip of a (qPlus tuning fork) atomic force microscope operated at 5 K, we quantitatively measure the quadrupole field of a single molecule and the dipole field of a single metal adatom, both adsorbed on a clean metal surface. Because of its high sensitivity, the technique can record electrostatic potentials at large distances from their sources, which above all will help to image complex samples with increased surface roughness.Comment: main text: 5 pages, 4 figures, supplementary information file: 4 pages, 2 figure

The Ocean Biomolecular Observing Network (OBON)

Ocean life-from viruses to whales-is built from "biomolecules." Biomolecules such as DNA infuse each drop of ocean water, grain of sediment, and breath of ocean air. The Ocean Biomolecular Observing Network (OBON) is developing a global collaboration that will allow science and society to understand ocean life like never before. The program will transform how we sense, harvest, protect, and manage ocean life using molecular techniques, as it faces multiple stresses including pollution, habitat loss, and climate change. It will also help communities detect biological hazards such as harmful algal blooms and pathogens, and be a key component of next-generation ocean observing systems. OBON will encourage continuous standardization and intercalibration of methods and data interoperability to help enhance and future-proof capabilities. OBON's objectives are: 1) to build a coastal-to-open ocean multi-omics biodiversity observing system; 2) to develop and transfer capacity between partners; 3) to enhance marine ecosystem digitization and modelling and 4) to coordinate action on pressing scientific, management, and policy questions

Autonomous robotic nanofabrication with reinforcement learning

The ability to handle single molecules as effectively as macroscopic building-blocks would enable the construction of complex supramolecular structures inaccessible to self-assembly. The fundamental challenges obstructing this goal are the uncontrolled variability and poor observability of atomic-scale conformations. Here, we present a strategy to work around both obstacles, and demonstrate autonomous robotic nanofabrication by manipulating single molecules. Our approach employs reinforcement learning (RL), which finds solution strategies even in the face of large uncertainty and sparse feedback. We demonstrate the potential of our RL approach by removing molecules autonomously with a scanning probe microscope from a supramolecular structure -- an exemplary task of subtractive manufacturing at the nanoscale. Our RL agent reaches an excellent performance, enabling us to automate a task which previously had to be performed by a human. We anticipate that our work opens the way towards autonomous agents for the robotic construction of functional supramolecular structures with speed, precision and perseverance beyond our current capabilities.Comment: 3 figure

Overestimate of Committed Warming

Palaeoclimate variations are an essential component in constraining future projections of climate change as a function of increasing anthropogenic greenhouse gases. The Earth System Sensitivity (ESS) describes the multi-millennial response of Earth (in terms of global mean temperature) to a doubling of CO2 concentrations. A recent study used a correlation of inferred temperatures and radiative forcing from greenhouse gases over the past 800,000 years to estimate the ESS from present day CO2 is about 9 degrees C, and to imply a long-term commitment of 3-7 degrees C even if greenhouse gas levels remain at present-day concentrations. However, we demonstrate that the methodology of ref. 2 does not reliably estimate the ESS in the presence of orbital forcing of ice age cycles and therefore conclude that the inferred present-day committed warming is considerably overestimated

Hydrogen-doped Brookite TiO2 Nanobullets Array as a Novel Photoanode for Efficient Solar Water Splitting

As a representative photocatalyst for photoelectrochemical solar water splitting, TiO2 has been intensively studied but most researches have focused on the rutile and anatsase phases because brookite, another important crystalline polymorph of TiO2, rarely exists in nature and is difficult to synthesize. In this work, hydrogen doped brookite (H:brookite) nanobullet arrays were synthesized via a well-designed solution reaction for the first time. H:brookite shows highly improved PEC properties with excellent stability, enhanced photocurrent, and significantly high Faradaic efficiency for overall solar water splitting. To support the experimental data, ab initio density functional theory calculations were also conducted. At the interstitial doping site that has minimum formation energy, the hydrogen atoms act as shallow donors and exist as H+. which has the minimum formation energy among three states of hydrogen (H+. H0, and H-). The calculated density of states of H:brookite shows a narrowed bandgap and an increased electron density compared to the pristine brookite. The combined experimental and theoretical results provide frameworks for the exploration of the PEC properties of doped brookite and extend our knowledge regarding the undiscovered properties of brookite of TiO2.ope

Electrostatic potentials of atomic nanostructures at metal surfaces quantified by scanning quantum dot microscopy

The discrete and charge-separated nature of matter — electrons and nuclei — results in local electrostatic fields that are ubiquitous in nanoscale structures and relevant in catalysis, nanoelectronics and quantum nanoscience. Surface-averaging techniques provide only limited experimental access to these potentials, which are determined by the shape, material, and environment of the nanostructure. Here, we image the potential over adatoms, chains, and clusters of Ag and Au atoms assembled on Ag(111) and quantify their surface dipole moments. By focusing on the total charge density, these data establish a benchmark for theory. Our density functional theory calculations show a very good agreement with experiment and allow a deeper analysis of the dipole formation mechanisms, their dependence on fundamental atomic properties and on the shape of the nanostructures. We formulate an intuitive picture of the basic mechanisms behind dipole formation, allowing better design choices for future nanoscale systems such as single-atom catalysts

Field deployment of a man-portable stand-off laser-induced breakdown spectrometer: A preliminary report on the expedition to the Cumbre Vieja volcano (La Palma, Spain, 2021)

This paper reports on the expedition to the Cumbre Vieja volcano (Canary Islands, Spain) in November 2021 to assess stand-off laser-induced breakdown spectroscopy for real-time measurements of the lava streams from a safe point. The paper provides insight on the analytical approach to the problem, the rationale of the instrument design and construction carried out in three weeks, the experience with the new-born instrument at the volcano and the preliminary results. Despite the subtle spectral differences among the samples and the signal variability induced by the strong wind gusts at site, a statistical approach to data processing such as PCA, made possible to extract sufficient information and provide a robust classification tool.We express our sincere gratitude to the Spanish Unidad Militar de Emergencias (UME) for providing essential support, security, and expertise at the field. We would like to thank Carlos Malag ́on (Astro- shop, M ́alaga, Spain) for donating the telescope used in the stand-off LIBS instrument, to the personnel of the Chemical Analysis Area and the Machine Shop of the Central Facility for Research Support (SCAI-UMA) and to Profs. E.R. Losilla and A. Cabeza (Dept. Química Inorgánica, Cristalografía y Mineralogía, UMA) and D. Marrero (Dept. Física Aplicada I, UMA) for their valuable comments and advice with the surrogate samples. This work has been partially supported by the I Plan Propio de Investigaci ́on de la Universidad de M ́alaga, the Extraordinary Funding (RD 1078/2021, 7th December, Núm. 293 Sec. I. P ́ag. 150,995) and PID2020-113407RB-I00 granted by the Spanish Ministry of Science and Innovation (MICINN). Funding for open access charge: Universidad de Málaga / CBU