Atomic Precision Research Articles

Engineering Qubits in Silicon with Atomic Precision.

Engineering Qubits in Silicon with Atomic Precision.

Photochemical Route for Synthesizing Atomically Precise Metal Nanoclusters from Disulfide.

Practical approaches to the synthesis of atomically precise metal nanoclusters are in high demand as they provide the structural basis for investigating nanomaterials' structure-property correlations with atomic precision. The Brust-Schiffrin method has been widely used, while the essential reductive ligands (e.g., thiols) limit the application of this method for synthesizing metal nanoclusters with specific frameworks and surface ligands. In this work, we developed a photochemical route for synthesizing atomically precise metal nanoclusters by applying disulfide, which is a widely available, stable, and environmentally friendly sulfur source. This method enables the construction of structurally diverse metal nanoclusters and especially features the synthesis of PhS-protected metal nanoclusters that were not easily achieved previously and the gram-scale synthesis. A reduction-oxidation cascade mechanism has been revealed for the photochemical route. This work is expected to open up new opportunities for metal nanocluster synthesis and will contribute to the practical applications of this kind of nanomaterial.

Atomic-scale tailoring of chemisorbed atomic oxygen on epitaxial graphene for graphene-based electronic devices

Graphene, with its unique band structure, mechanical stability, and high charge mobility, holds great promise for next-generation electronics. Nevertheless, its zero bandgap challenges the control of current flow through electrical gating, consequently limiting its practical applications. Recent research indicates that atomic oxygen can oxidize epitaxial graphene in a vacuum without causing unwanted damage. In this study, we have investigated the effects of chemisorbed atomic oxygen on the electronic properties of epitaxial graphene using scanning tunneling microscopy (STM). Our findings reveal that oxygen atoms effectively modify the electronic states of graphene, resulting in a bandgap at its Dirac point. Furthermore, we demonstrate that it is possible to selectively induce desorption or hopping of oxygen atoms with atomic precision by applying appropriate bias sweeps with an STM tip. These results suggest the potential for atomic-scale tailoring of graphene oxide, enabling the development of graphene-based atomic-scale electronic devices.

1,3-DEHYDROADAMANTANE AND ITS DERIVATIVES: A VERSATILE SYNTHETIC PLATFORM FOR PREPARATION OF FUNCTIONAL COMPOUNDS WITH A CAGE STRUCTURE. A REVIEW

A promising strategy for the synthesis of a functional compounds with framework structure is using of 1,3‑dehydroadamantane (tetracyclo[3.3.1.1.3,7.0.1,3]decane, 1,3-DHA, bridging [3.3.1]propellane) and its derivatives, which are able to restoration of adamantane structure in their reactions. The review provides information on the methods for the synthesis of 1,3-DHA, spectral characteristics, probable intermediates generated from propellanes, and the advantages of using – low-stage syntheses of hardly available adamantine derivatives, atomic precision, and “green chemistry”. The reactions of 1,3-DHA with a wide range of organic compounds are considered, a comparative assessment of its reactivity with respect to CH-, NH-, OH- and SH-acids, as well as arenes, hydantoins, and heterocyclic compounds is carried out. New chemo- and regioselective methods for the one-step introduction of a 1-adamantyl group into the molecules of various substrates are classified. Particular attention is paid to the reactions of 1,3-DHA with various C–H acids, which make it possible to easily form C–CAd bonds to obtain hard-to-reach adamantane derivatives. The influence of pKa of the substrate on the selectivity of the reactions was shown. Low-step methods for the synthesis of new adamantane derivatives, which have shown high activity as hsEH epoxide hydrolase inhibitors and antitumor agents, are described.

Visualization of molecular stacking using low-energy electron microscopy

The design of metal-organic interfaces with atomic precision enables the fabrication of highly efficient devices with tailored functionality. The possibility of fast and reliable analysis of molecular stacking order at the interface is of crucial importance, as the interfacial stacking order of molecules directly influences the quality and functionality of fabricated organic-based devices. Dark-field (DF) imaging using Low-Energy Electron Microscopy (LEEM) allows the visualization of areas with a specific structure or symmetry. However, distinguishing layers with different stacking orders featuring the same diffraction patterns becomes more complicated. Here we show that the top layer shift in organic molecular bilayers induces measurable differences in spot intensities of respective diffraction patterns that can be visualized in DF images. Scanning Tunneling Microscopy (STM) imaging of molecular bilayers allowed us to measure the shift directly and compare it with the diffraction data. We also provide a conceptual diffraction model based on the electron path differences, which qualitatively explains the observed phenomenon.

Assembling Surface Molecular Sierpiński Triangle Fractals via K+-Invoked Electrostatic Interaction.

Molecular Sierpiński triangles (STs), a family of elegant and well-known fractals, can be prepared on surfaces with atomic precision. Up to date, several kinds of intermolecular interactions such as hydrogen bond, halogen bond, coordination, and even covalent bond have been employed to construct molecular STs on metal surfaces. Herein a series of defect-free molecular STs have been fabricated via electrostatic attraction between potassium cations and electronically polarized chlorine atoms in 4,4″-dichloro-1,1':3',1″-terphenyl (DCTP) molecules on Cu(111) and Ag(111). The electrostatic interaction is confirmed both experimentally by scanning tunneling microscopy and theoretically by density functional theory calculations. These findings illustrate that electrostatic interaction can serve as an efficient driving force to construct molecular fractals, which enriches our toolbox for the bottom-up fabrication of complex functional supramolecular nanostructures.

Photochemical Synthesis of Atomically Precise Ag Nanoclusters.

Photochemical methods are effective for controllable synthesis of silver nanoparticles with specific sizes and shapes. Whether they are capable of fabricating Ag nanoclusters (NCs) with atomic precision is yet to be proved. In this work, we synthesize an atomically precise Ag NC, [Ag25(4-MePhC≡C)20(Dpppe)3](SbF6)3 (Ag25), via a process mediated by visible light. Its total structure is determined by X-ray crystallography. The investigation of the mechanism reveals that the formation of Ag25 is triggered by a photoinduced electron-transfer (PET) process. An electron of certain amines is excited by light with wavelength shorter than 455 nm and transferred to Ag+. The amine is oxidized to the corresponding amine N-oxide. Such a PET process is supported by experimental and density functional theory studies. To expand the application scope of the photochemical method, another three NCs, [Ag19(4-tBuPhC≡C)14(Dpppe)3](SbF6)3 (Ag19), [Ag32(4-tBuPhC≡C)22(Dppp)4](SbF6)3 (Ag32), and bimetallic [Ag22Au3(4-tBuPhC≡C)20(Dpppe)3](SbF6)3 (Ag22Au3), are produced by replacing certain ingredients. Furthermore, since the formation of Ag19 can be regarded as a photochromatic process, a facile amine visual detection method is also presented based on this mechanism.

Proton-Coupled Electron Transfer at the Surface of Polyoxovanadate-Alkoxide Clusters.

ConspectusProton-coupled electron transfer (PCET) is a fundamental process involved in all areas of chemistry, with relevance to biological transformations, catalysis, and emergent energy storage and conversion technologies. Early observations of PCET were reported by Meyer and co-workers in 1981 while investigating the proton dependence of reduction of a molecular ruthenium oxo complex. Since that time, this conceptual framework has grown to encompass an enormous scope of charge transfer and compensation reactions. In this Account, we will discuss ongoing efforts in the Matson Laboratory to understand the fundamental thermodynamics and kinetics of PCET processes at the surface of a series of Lindqvist-type polyoxovanadate clusters. This project aims to provide atomistic resolution of net H atom uptake and transfer at the surfaces of transition-metal oxide materials.First, we discuss our efforts aimed at understanding PCET at metal oxide surfaces using the Lindqvist-type polyoxovanadate-alkoxide (POV-alkoxide) cluster [nBu4N]2[V6O13(TRIOLNO2)2]. These clusters reversibly bind H atom equivalents at bridging oxide sites, mirroring the proposed uptake and release of e-/H+ pairs at transition-metal oxide surfaces. Summarized results include the measurement of bond dissociation free energies of surface hydroxide moieties (BDFE(O-H)) as well as mechanistic analyses that verify concerted proton electron transfer as the operative pathway for PCET at the surface of POV-alkoxide clusters.Next, we discuss net proton and H atom uptake at the surface of reduced variants of the Lindqvist-type POV-alkoxide cluster, [V6O7(OR)12]n (R = Me, Et; n = -2, -1, 0, + 1). In the case of these low-valent POV-alkoxide clusters, nucleophilic bridging sites are kinetically inhibited by functionalization of the cluster surface with organic ligands. This molecular modification enables site-selectivity in proton and H atom uptake to terminal oxide sites. The impact of reaction site and cluster electronics on reaction driving force of PCET is explored, with core electron density playing a critical role in dictating thermodynamics of H atom uptake and transfer. Additional work described here contrasts the kinetics of PCET at terminal oxide sites to the reactivity observed at bridging oxides in POV-alkoxide clusters.Overall, this Account summarizes our foundational knowledge regarding the assessment of PCET reactivity at the surfaces of molecular metal oxides. Drawing analogies between POV-alkoxide clusters and nanoscopic metal oxide materials provide design principles for the advancement of materials applications with atomic precision. These complexes are additionally highlighted as tunable redox mediators in their own right; our studies demonstrate how cluster surface reactivities can be optimized by modifying electronic structure and surface functionalities.

Slice Visualization for Imaging Nanocluster Transformations.

Metal nanoclusters have served as an emerging class of modular nanomaterials. Several efficient strategies have been proposed for transforming cluster precursors into new nanoclusters with customized structures and enhanced performance. However, such nanocluster transformations have still been in a "blind box" state, meaning that the existing intermediates were hard to track with atomic precision. Herein, we present a "slice visualization" approach for in-depth imaging of the nanocluster transformation from Au1Ag24(SR)18 to Au1Ag30(SR)20. With this approach, two cluster intermediates, namely, Au1Ag26(SR)19 and Au1Ag28(SR)20, were monitored with atomic precision. The four nanoclusters constituted a correlated Au1Ag24+2n (n = 0, 1, 2, and 3) cluster series with comparable structural features─the same Au1Ag12 icosahedral kernel but evolutionary peripheral motif structures. The mechanism of nanocluster structure growth was mapped in detail─insertion of Ag2(SR)1 or Ag-induced assembly of surface subunits. The presented "slice visualization" approach not only contributes an ideal cluster platform for in-depth investigations of structure-property correlations but also hopefully acts as a powerful means for obtaining clear information on nanocluster structure evolution.

Universal quantum control of an atomic spin qubit on a surface

Scanning tunneling microscopy (STM) enables the bottom-up fabrication of tailored spin systems on a surface that are engineered with atomic precision. When combining STM with electron spin resonance (ESR), these single atomic and molecular spins can be controlled quantum-coherently and utilized as electron-spin qubits. Here we demonstrate universal quantum control of such a spin qubit on a surface by employing coherent control along two distinct directions, achieved with two consecutive radio-frequency (RF) pulses with a well-defined phase difference. We first show transformations of each Cartesian component of a Bloch vector on the quantization axis, followed by ESR-STM detection. Then we demonstrate the ability to generate an arbitrary superposition state of a single spin qubit by using two-axis control schemes, in which experimental data show excellent agreement with simulations. Finally, we present an implementation of two-axis control in dynamical decoupling. Our work extends the scope of STM-based pulsed ESR, highlighting the potential of this technique for quantum gate operations of electron-spin qubits on a surface.

Proposition of atomic and close-to-atomic scale manufacturing

Atomic and close-to-atomic scale manufacturing (ACSM) is the core competence of Manufacturing III. Unlike other conceptions or terminologies that only focus on the atomic level precision, ACSM defines a new realm of manufacturing where quantum mechanics plays the dominant role in the atom/molecule addition, migration and removal, considering the uncertainty principle and the discrete nature of particles. As ACSM is still in its infant stage, only little has been systematically elaborated at the core proposition of ACSM by now, hence there is a need to understand its concept and vision. This article elucidates the development of ACSM and clarifies its proposition, which aims to achieve a clearer understanding on ACSM and direct more effective efforts toward this promising area.

Enhanced Optical Gain from Photoactivated Colloidal Quantum Wells

AbstractCadmium chalcogenide colloidal quantum wells (CQWs) are a unique class of optical gain materials that can be precisely engineered in terms of thickness and composition at the atomic level using colloidal atomic layer deposition (c‐ALD). However, the atomic layer deposition is typically performed at room temperature, resulting in low emission efficiency and the need for additional thermal annealing. In this study, ultraviolet (UV) illumination is used to treat the CQWs prepared using c‐ALD and a significant improvement in their photoluminescence is observed, with an irreversible 79‐fold increase. Furthermore, the lasing threshold is reduced to two‐thirds of the untreated samples, enabling whispering gallery mode lasing from the CQW in solution. This research demonstrates an efficient and convenient method for boosting the emission from the CQWs and highlights the advantages of CQWs as optical gain media that can be engineered with atomic precision.

Correlating structural distortions and optical shifts in carboxylate-exchanged CdSe nanoplatelets.

Quasi-2D nanomaterials such as semiconducting nanoplatelets (NPLs) have drawn considerable interest due to their tunable optical properties and large surface to volume ratios. Cadmium selenide (CdSe) NPLs are of particular fundamental interest since their thicknesses can be controlled with atomic precision using well-established solution-phase synthetic techniques. Additionally, their large surface area makes them especially susceptible to changes in the identity of the capping ligands and, therefore, good model systems for understanding surface chemistry. In the current work, we explore the role of these ligands in altering the lattice parameters and optical properties of CdSe NPLs. We build on prior research that has employed varying binding groups, including thiols, phosphonic acids, and halides, to demonstrate ligand-dependent optical bandgap changes and concomitant lattice distortions as determined by powder x-ray diffraction (PXRD). Our work investigates the correlations between ligand-induced optical and structural changes with a series of ligands that maintain a consistent carboxylic acid binding group, thus allowing us to probe secondary ligand effects. We perform ligand exchanges on oleic acid-capped CdSe NPLs with benzoic acids, cinnamic acids, and cyclohexanecarboxylic acid. In all cases, the optical bandgap decreases upon ligand exchange, and a correlated expansion in the thickness of the NPLs is observed via PXRD. We also observe that the benzoic acids produce larger optical and structural distortions than the cinnamic acids. We show that the optical and structural correlation is nearly quantitatively described by quantum confinement effects, with the thicker quantum wells exhibiting smaller energy gaps.

Photoresponse of Solution-Synthesized Graphene Nanoribbon Heterojunctions on Diamond Indicating Phototunable Photodiode Polarity

Graphene nanoribbon heterostructures and heterojunctions have attracted interest as next-generation molecular diodes with atomic precision. Their mass production via solution methods and prototypical device integration remains to be explored. Here, the bottom-up solution synthesis and characterization of liquid-phase-processable graphene nanoribbon heterostructures (GNRHs) are demonstrated. Joint photoresponsivity measurements and simulations provide evidence of the structurally defined heterostructure motif acting as a type-I heterojunction. Real-time, time-dependent density functional tight-binding simulations further reveal that the photocurrent polarity can be tuned at different excitation wavelengths. Our results introduce liquid-phase-processable, self-assembled heterojunctions for the development of nanoscale diode circuitry and adaptive hardware.

Green Synthesis Magnetite (Fe3O4) Nanoparticles from Rhus Coriaria extract: A Characteristic Comparison with a Conventional Chemical Method.

In recent years, nanotechnology has become one of the most important and exciting avant-gardes, without exception, in all fields of science. Through nanotechnology, novel materials and devices can be industrialized with atomic precision. In general, there are three main methods for synthesizing NPs: Chemical, physical and biological, or green methods. However, the conventional chemical and physical methods include the use of toxic chemicals that are toxic in nature and using pricy devices, which leads to the development of new methods using nontoxic and eco-friendly materials. These eco-friendly methods use biological systems, microorganisms, and plant-based materials as reducing, capping, and stabilizing agents to synthesize NPs. In this study, iron oxide (Fe3O4) NPs have been synthesized using a green method, a Rhus Coriaria extract, and a conventional chemical method. A comparison between these two methods is conducted to validate the importance of the biological method. This study demonstrates, as we expected, by utilizing different characterization techniques, that the synthesized green Fe3O4 NPs, in general, possess better and enhanced properties than the chemical method. This difference is evident in the aggregation status, capping and stabilizing agents around the NPs, magnetic and thermal properties, and stability of NPs. These results, in turn, highlight the importance of the available phytochemical in the Rhus Coriaria extract as a suitable candidate for biosynthesizing Fe3O4 NPs.

Atomically Precise Clusters: Chemical Evolution of Molecular Matter at the Nanoscale

The chemistry of nanoparticles with atomic precision has become a subject of interest due to the unique physical and chemical properties of these systems in comparison to their bulk counterparts. Nanoparticles typically contain thousands of atoms, arranged in a specific fashion. There is a need to bridge the gap between single atoms and nanoparticles to understand the size evolution of matter. This regime, composed of a few atoms, is called nanoclusters having size in the range of 1 to 3 nm, with a precise number of atoms, with well-defined structure and properties. Most of studied materials in this class are composed of noble metals. Various techniques, including UV/vis spectroscopy, mass spectrometry, and single crystal XRD, reveal their molecular nature. Their unique electronic properties can be used for applications in the fields of catalysis, sensing, magnetism, medicinal, bio-imaging, etc. This article touches upon the basics of nanoclusters, their synthesis, characterization, atomic structures, and supramolecular arrangements. We hope that this work provides a brief understanding of nanoclusters and inspires young scientists to conduct research in the chemistry of clusters.

Molecular Bridge Engineering for Tuning Quantum Electronic Transport and Anisotropy in Nanoporous Graphene

Recent advances on surface-assisted synthesis have demonstrated that arrays of nanometer wide graphene nanoribbons can be laterally coupled with atomic precision to give rise to a highly anisotropic nanoporous graphene structure. Electronically, this graphene nanoarchitecture can be conceived as a set of weakly coupled semiconducting 1D nanochannels with electron propagation characterized by substantial interchannel quantum interferences. Here, we report the synthesis of a new nanoporous graphene structure where the interribbon electronic coupling can be controlled by the different degrees of freedom provided by phenylene bridges that couple the conducting channels. This versatility arises from the multiplicity of phenylene cross-coupling configurations, which provides a robust chemical knob, and from the interphenyl twist angle that acts as a fine-tunable knob. The twist angle is significantly altered by the interaction with the substrate, as confirmed by a combined bond-resolved scanning tunneling microscopy (STM) and ab initio analysis, and should accordingly be addressable by other external stimuli. Electron propagation simulations demonstrate the capability of either switching on/off or modulating the interribbon coupling by the corresponding use of the chemical or the conformational knob. Molecular bridges therefore emerge as efficient tools to engineer quantum transport and anisotropy in carbon-based 2D nanoarchitectures.

Collective Quantum Magnetism in Nitrogen-Doped Nanographenes.

The emergence of quantum magnetism in nanographenes provides ample opportunities to fabricate purely organic devices for spintronics and quantum information. Although heteroatom doping is a viable way to engineer the electronic properties of nanographenes, the synthesis of doped nanographenes with collective quantum magnetism remains elusive. Here, a set of nitrogen-doped nanographenes (N-NGs) with atomic precision are fabricated on Au(111) through a combination of imidazole [2+2+2]-cyclotrimerization and cyclodehydrogenation reactions. High-resolution scanning probe microscopy measurements reveal the presence of collective quantum magnetism for nanographenes with three radicals, with spectroscopic features which cannot be captured by mean-field density functional theory calculations but can be well reproduced by Heisenberg spin model calculations. In addition, the mechanism of magnetic exchange interaction of N-NGs has been revealed and compared with their counterparts with pure hydrocarbons. Our findings demonstrate the bottom-up synthesis of atomically precise N-NGs which can be utilized to fabricate low-dimensional extended graphene nanostructures for realizing ordered quantum phases.

Spin Polarization of Polyalanine Molecules in 2D and Dimer-Row Assemblies Adsorbed on Magnetic Substrates: The Role of Coupling, Chirality, and Coordination.

Propagation of electrons along helical molecules adsorbed on surfaces comes along with a robust spin polarization effect called chirality induced spin selectivity CISS. However, experiments on the molecular scale that allow a true correlation of spin effects with the molecular structure are quite rare. Here we have studied the structure of self-assembled chiral molecules and the electronic transmission and spin polarization of the current through the system by means of ambient scanning tunneling microscopy and spectroscopy in heterostructures of various α-helix polyalanine-based molecules (PA) adsorbed on Al2O3/Pt/Au/Co/Au substrates with perpendicular magnetic anisotropy. We have found a phase separation of the molecules into well-ordered enantiopure 2D hexagonal phases and quasi-1D heterochiral-dimer structures, which allows for the analysis of the spin polarization with almost atomic precision of PA in different phases. The spin polarization reaches up to 75% for chemisorbed molecules arranged in a hexagonal phase. On the contrary, for weakly coupled PA molecules without cysteine anchoring groups in a quasi-1D phase, a spin polarization of around 50% was found. Our results show that both the intermolecular interaction as well as the coupling to the substrate are important and point out that collective effects within the molecules and at the interfaces are required to achieve a high chiral induced spin selectivity.

Tuning metal/superconductor to insulator/superconductor coupling via control of proximity enhancement between NbSe2 monolayers

The interplay between charge transfer and electronic disorder in transition-metal dichalcogenide multilayers gives rise to superconductive coupling driven by proximity enhancement, tunneling and superconducting fluctuations, of a yet unwieldy variety. Artificial spacer layers introduced with atomic precision change the density of states by charge transfer. Here, we tune the superconductive coupling between monolayers from proximity-enhanced to tunneling-dominated. We correlate normal and superconducting properties in tailored multilayers with varying SnSe layer thickness (). From high-field magnetotransport the critical fields yield Ginzburg–Landau coherence lengths with an increase of cross-plane (), trending towards two-dimensional superconductivity for . We show cross-overs between three regimes: metallic with proximity-enhanced coupling (), disordered-metallic with intermediate coupling () and insulating with Josephson tunneling (). Our results demonstrate that stacking metal mono- and dichalcogenides allows to convert a metal/superconductor into an insulator/superconductor system, prospecting the control of two-dimensional superconductivity in embedded layers.