Synthesis and single-molecule imaging of highly mobile adamantane-wheeled nanocars

Formation and Manipulation of Diatomic Rotors at the Symmetry-Breaking Surfaces of a Kagome Superconductor

Construction of diatomic rotors, which is crucial for artificial nanomachines, remains challenging due to surface constraints and limited chemical design. Here we report the construction of diatomic Cr-Cs and Fe-Cs rotors where a Cr or Fe atom switches around a Cs atom at the Sb surface of the newly discovered kagome superconductor CsV3Sb5. The switching rate is controlled by the bias voltage between the rotor and scanning tunneling microscope (STM) tip. The spatial distribution of rates exhibits C2 symmetry, possibly linked to the symmetry-breaking charge orders of CsV3Sb5. We have expanded the rotor construction to include different transition metals (Cr, Fe, V) and alkali metals (Cs, K). Remarkably, designed configurations of rotors are achieved through STM manipulation. Rotor orbits and quantum states are precisely controlled by tuning the inter-rotor distance. Our findings establish a novel platform for the controlled fabrication of atomic motors on symmetry-breaking quantum materials, paving the way for advanced nanoscale devices.

Nanopore actuation of a DNA-tracked nanovehicle

As a kind of nanomachine that has great potential for applications in nanoscale sensing and manipulation, nanovehicles with unique shapes and functions have received extensive attention in recent years. Different from the existing common method of using synthetic chemistry to design and manufacture a nanovehicle, here we theoretically report a molecularly assembled DNA-tracked nanovehicle that can move on a solid-state surface using molecular dynamics simulations. A graphene membrane with four nanopores acts as the chassis of the nanoscale vehicle, and two circular ssDNAs across the nanopores serve as the wheels. The electroosmotic flows induced by independently charged nanopores with different surface charge densities under external electric fields were found to be the main power to actuate the controlled rotary motion of circular ssDNAs across every two nanopores. By tuning the rotary speed of each circular ssDNA, the linear and turning movements of the designed nanovehicle were realized. The designed nanovehicle makes it possible to have access to almost everywhere in the human body, which would lead to significant breakthroughs in the fields of nanoscale surgery, drug delivery and so on. The research not only enriches the family of nanorobots, but also opens another way for designing nanovehicles.

Design and Manipulation of a Minimalistic Hydrocarbon Nanocar on Au(111)

Nanocars are carbon-based single-molecules with a precise design that facilitates their atomic-scale control on a surface. The rational design of these molecules is important in atomic and molecular-scale manipulation to advance the development of molecular machines, as well as for a better understanding of self-assembly, diffusion and desorption processes. Here, we introduce the molecular design and construction of a collection of minimalistic nanocars. They feature an anthracene chassis and four benzene derivatives as wheels. After sublimation and adsorption on an Au(111) surface, we show controlled and fast manipulation of the nanocars along the surface using the tip of a scanning tunneling microscope (STM). The mechanism behind the successful displacement is the induced dipole created over the nanocar by the STM tip. We utilized carbon monoxide functionalized tips both to avoid decomposition and accidentally picking the nanocars up during the manipulation. This strategy allowed thousands of maneuvers to successfully win the Nanocar Race II championship.

Investigation of fullerene motion on thermally activated gold substrates with different shapes

In the current study, the regime of motion of fullerene molecules on substrates with different shapes at a range of specific temperatures has been investigated. To do so, the potential energy of fullerene molecules was analyzed using the classical molecular dynamics method. C₂₀, C₃₆, C₅₀, C₆₀, C₇₂, C₇₆, C₈₀, and C₉₀ fullerene molecules were selected due to their spherical shapes with different sizes. In addition, to completely analyze the behavior of these molecules, different gold substrates, including flat, concave, the top side of the step (upward step), and the downside of the step (downward step) substrates, were considered. Specifying the regime of the motion at different temperatures is one of the main goals of this study. For this purpose, we have studied the translational and rotational motions of fullerene molecules independently. In the first step of the investigation, Lennard-Jones potential energy of fullerene molecules was calculated. Subsequently, the regime of motion of different fullerenes has been classified, based on their displacement and sliding velocity. Our findings indicated that C₆₀ is appropriate in less than [Formula: see text] of the conditions. However, C₂₀, C₇₆ and C₈₀ molecules were found to be appropriate candidates in most cases in different conditions while they were incompetent only in seven situations. As far as a straight-line movement is considered, the concave geometry demonstrated a better performance compared to the other substrates. In addition, C₇₂ indicated less favorable performance concerning the range of movement and diffusion coefficients. All in all, our investigation helps to understand the performance of different fullerene molecules on gold substrates and find their probable application, especially as a wheel in nano-machine structures.

Molecular Gears: From Solution to Surfaces

This review highlights the major efforts devoted to the development of molecular gears over the past 40 years, from pioneering covalent bis-triptycyl systems undergoing intramolecular correlated rotation in solution, to the most recent examples of gearing systems anchored on a surface, which allow intermolecular transmission of mechanical power. Emphasis is laid on the different strategies devised progressively to control the architectures of molecular bevel and spur gears, as intramolecular systems in solution or intermolecular systems on surfaces, while aiming at increased efficiency, complexity and functionality.

Locomotion of the C60-based nanomachines on graphene surfaces

We provide a comprehensive computational characterization of surface motion of two types of nanomachines with four C₆₀ "wheels": a flexible chassis Nanocar and a rigid chassis Nanotruck. We study the nanocars' lateral and rotational diffusion as well as the wheels' rolling motion on two kinds of graphene substrates-flexible single-layer graphene which may form surface ripples and an ideally flat graphene monolayer. We find that the graphene surface ripples facilitate the translational diffusion of Nanocar and Nanotruck, but have little effect on their surface rotation or the rolling of their wheels. The latter two types of motion are strongly affected by the structure of the nanomachines instead. Surface diffusion of both nanomachines occurs preferentially via a sliding mechanism whereas the rolling of the "wheels" contributes little. The axial rotation of all "wheels" is uncorrelated.

Light-Activated Organic Molecular Motors and Their Applications

Molecular motors are at the heart of cellular machinery, and they are involved in converting chemical and light energy inputs into efficient mechanical work. From a synthetic perspective, the most advanced molecular motors are rotators that are activated by light wherein a molecular subcomponent rotates unidirectionally around an axis. The mechanical work produced by arrays of molecular motors can be used to induce a macroscopic effect. Light activation offers advantages over biological chemically activated molecular motors because one can direct precise spatiotemporal inputs while conducting reactions in the gas phase, in solution and in vacuum, while generating no chemical byproducts or waste. In this review, we describe the origins of the first light-activated rotary motors and their modes of function, the structural modifications that led to newer motor designs with optimized rotary properties at variable activation wavelengths. Presented are molecular motor attachments to surfaces, their insertion into supramolecular structures and photomodulating materials, their use in catalysis, and their action in biological environments to produce exciting new prospects for biomedicine.

The Structure of Adamantane Clusters: Atomistic vs. Coarse-Grained Predictions From Global Optimization

Candidate structures for the global minima of adamantane clusters, (C₁₀H₁₆)_N, are presented. Based on a rigid model for individual molecules with atom-atom pairwise interactions that include Lennard-Jones and Coulomb contributions, low-energy structures were obtained up to N = 42 using the basin-hopping method. The results indicate that adamantane clusters initially grow accordingly with an icosahedral packing scheme, followed above N = 14 by a structural transition toward face-centered cubic structures. The special stabilities obtained at N = 13, 19, and 38 are consistent with these two structural families, and agree with recent mass spectrometry measurements on cationic adamantane clusters. Coarse-graining the intermolecular potential by averaging over all possible orientations only partially confirm the all-atom results, the magic numbers at 13 and 38 being preserved. However, the details near the structural transition are not captured well, because despite their high symmetry the adamantane molecules are still rather anisotropic.

Photo- and Redox-Driven Artificial Molecular Motors

Directed motion at the nanoscale is a central attribute of life, and chemically driven motor proteins are nature's choice to accomplish it. Motivated and inspired by such bionanodevices, in the past few decades chemists have developed artificial prototypes of molecular motors, namely, multicomponent synthetic species that exhibit directionally controlled, stimuli-induced movements of their parts. In this context, photonic and redox stimuli represent highly appealing modes of activation, particularly from a technological viewpoint. Here we describe the evolution of the field of photo- and redox-driven artificial molecular motors, and we provide a comprehensive review of the work published in the past 5 years. After an analysis of the general principles that govern controlled and directed movement at the molecular scale, we describe the fundamental photochemical and redox processes that can enable its realization. The main classes of light- and redox-driven molecular motors are illustrated, with a particular focus on recent designs, and a thorough description of the functions performed by these kinds of devices according to literature reports is presented. Limitations, challenges, and future perspectives of the field are critically discussed.

Diamondoid Nanostructures as sp3 -Carbon-Based Gas Sensors

Diamondoids, sp³ -hybridized nanometer-sized diamond-like hydrocarbons (nanodiamonds), difunctionalized with hydroxy and primary phosphine oxide groups, enable the assembly of the first sp³ -C-based chemical sensors by vapor deposition. Both pristine nanodiamonds and palladium nanolayered composites can be used to detect toxic NO₂ and NH₃ gases. This carbon-based gas sensor technology allows reversible NO₂ detection down to 50 ppb and NH₃ detection at 25-100 ppm concentration with fast response and recovery processes at 100 °C. Reversible gas adsorption and detection is compatible with 50 % humidity conditions. Semiconducting p-type sensing properties are achieved from devices based on primary phosphine-diamantanol, in which high specific area (ca. 140 m²  g^-1 ) and channel nanoporosity derive from H-bonding.

From the Synthesis of Nanovehicles to Participation in the First Nanocar Race-View from the French Team

This review article presents our accomplished work on the synthesis of molecular triptycene wheels and their introduction into nanovehicles such as wheelbarrows and nanocars, equipped with two and four wheels, respectively. The architecture of nanovehicles is based on polycyclic aromatic hydrocarbons, which provide a potential cargo zone. Our strategy allowed us to obtain planar or curved nanocars, exhibiting different mobilities on metallic surfaces. Our curved nanocar participated in the first nanocar race organized in Toulouse (France) on 28 and 29 April 2017.

Directing the diffusive motion of fullerene-based nanocars using nonplanar gold surfaces

A new method for guiding the motion of fullerene and fullerene-based nanocars is introduced in this paper. The effects of non-flat substrates on the motion of C₆₀, a nanocar and a nanotruck are investigated at different conditions and temperatures. Their behavior is studied using two different approaches: analyzing the variation in potential energy and conducting all-atom classical molecular dynamics simulations. This paper proposes that the use of a stepped substrate will make their motion more predictable and controllable. The results of the simulations show that C₆₀ stays on the top side of the step and cannot jump over the step at temperatures of 400 K and lower. However, at temperatures of 500 K and higher, C₆₀ has sufficient energy to travel to the down side of the step. C₆₀ attaches to the edge and moves just alongside of the edge when it is on the down side of the step. The edge also restricts the motion of C₆₀ alongside the edge and reduces its range of motion. By considering the motion of C₆₀, the general behavior of the nanocar and nanotruck is predictable. The nanocar stays on the top side of the step at temperatures of 400 K and less; at 500 K and higher temperatures, its wheels jump off the edge, and its range of motion is restricted. The relatively rigid chassis of the nanotruck does not allow the free individual motion of the wheels. As a result, the entire nanotruck stays on the top side of the step, even at 600 K. A pathway with the desired route can be fabricated for the motion of C₆₀ and nanocars using the method presented in this paper. This represents a step towards the directional motion of C₆₀ and nanocars.

On-Surface Synthesis and Characterization of Honeycombene Oligophenylene Macrocycles

We report the on-surface formation and characterization of [30]-honeycombene, a cyclotriacontaphenylene, which consists of 30 phenyl rings (C₁₈₀H₁₂₀) and has a diameter of 4.0 nm. This shape-persistent, conjugated, and unsubstituted hexagonal hydrocarbon macrocycle was obtained by solvent-free synthesis on a silver (111) single-crystal surface, making solubility-enhancing alkyl side groups unnecessary. Side products include strained macrocycles with square, pentagonal, and heptagonal shape. The molecules were characterized by scanning tunneling microscopy and density functional theory (DFT) calculations. On the Ag(111) surface, the macrocycles act as molecular quantum corrals and lead to the confinement of surface-state electrons inside the central cavity. The energy of the confined surface state correlates with the size of the macrocycle and is well described by a particle-in-the-box model. Tunneling spectroscopy suggests conjugation within the planar rings and reveals influences of self-assembly on the electronic structure. While the adsorbed molecules appear to be approximately planar, the free molecules have nonplanar conformation, according to DFT.

Solid surface vs. liquid surface: nanoarchitectonics, molecular machines, and DNA origami

Comparisons of science and technology between these solid and liquid surfaces would be a good navigation for current-to-future developments.

Carbon nanotubes dispersed in aqueous solution by ruthenium(ii) polypyridyl complexes

Cationic ruthenium(ii) polypyridyl complexes with appended pyrene groups have been synthesized and used to disperse single-walled carbon nanotubes (SWCNT) in aqueous solutions. To this end, planar pyrene groups enable association by means of π-stacking onto carbon nanotubes and, in turn, the attachment of the cationic ruthenium complexes. Importantly, the ionic nature of the ruthenium complexes allows the formation of stable dispersions featuring individualized SWCNTs in water as confirmed in a number of spectroscopic and microscopic assays. In addition, steady-state photoluminescence spectroscopy was used to probe the excited state interactions between the ruthenium complexes and SWCNTs. These studies show that the photoluminescence of both, that is, of the ruthenium complexes and of SWCNTs, are quenched when they interact with each other. Pump-probe transient absorption experiments were performed to shed light onto the nature of the photoluminescence quenching, showing carbon nanotube-based bands with picosecond lifetimes, but no new bands which could be unambigously assigned to photoinduced charge transfer process. Thus, from the spectroscopic data, we conclude that quenching of the photoluminescence of the ruthenium complexes is due to energy transfer to proximal SWCNTs.

Nanoarchitectonics for Dynamic Functional Materials from Atomic-/Molecular-Level Manipulation to Macroscopic Action

Objects in all dimensions are subject to translational dynamism and dynamic mutual interactions, and the ability to exert control over these events is one of the keys to the synthesis of functional materials. For the development of materials with truly dynamic functionalities, a paradigm shift from "nanotechnology" to "nanoarchitectonics" is proposed, with the aim of design and preparation of functional materials through dynamic harmonization of atomic-/molecular-level manipulation and control, chemical nanofabrication, self-organization, and field-controlled organization. Here, various examples of dynamic functional materials are presented from the atom/molecular-level to macroscopic dimensions. These systems, including atomic switches, molecular machines, molecular shuttles, motional crystals, metal-organic frameworks, layered assemblies, gels, supramolecular assemblies of biomaterials, DNA origami, hollow silica capsules, and mesoporous materials, are described according to their various dynamic functions, which include short-term plasticity, long-term potentiation, molecular manipulation, switchable catalysis, self-healing properties, supramolecular chirality, morphological control, drug storage and release, light-harvesting, mechanochemical transduction, molecular tuning molecular recognition, hand-operated nanotechnology.

Unimolecular Submersible Nanomachines. Synthesis, Actuation, and Monitoring

Unimolecular submersible nanomachines (USNs) bearing light-driven motors and fluorophores are synthesized. NMR experiments demonstrate that the rotation of the motor is not quenched by the fluorophore and that the motor behaves in the same manner as the corresponding motor without attached fluorophores. No photo or thermal decomposition is observed. Through careful design of control molecules with no motor and with a slow motor, we found using single molecule fluorescence correlation spectroscopy that only the molecules with fast rotating speed (MHz range) show an enhancement in diffusion by 26% when the motor is fully activated by UV light. This suggests that the USN molecules give ∼9 nm steps upon each motor actuation. A non-unidirectional rotating motor also results in a smaller, 10%, increase in diffusion. This study gives new insight into the light actuation of motorized molecules in solution.

Synthesis of Functionalized Mono-, Bis-, and Trisethynyltriptycenes for One-Dimensional Self-Assembly on Surfaces

This paper describes the synthesis of triptycene-based building blocks that are able to interact through hydrogen bonds to form one-dimensional self-assembled motifs on surfaces. We designed 9,10-diethynyltriptycene derivatives functionalized at the ethynyl end groups by a variety of hydrogen-bonding groups for homomolecular recognition and complementary building blocks for heteromolecular recognition. We also present the synthesis of bis- and trisethynyltriptycenes with terminal alkyne functional groups available for on-surface azide-alkyne cycloaddition reaction to expand the potential of the triptycene building block.

Nanoscale topography influences polymer surface diffusion

Using high-throughput single-molecule tracking, we studied the diffusion of poly(ethylene glycol) chains at the interface between water and a hydrophobic surface patterned with an array of hexagonally arranged nanopillars. Polymer molecules displayed anomalous diffusion; in particular, they exhibited intermittent motion (i.e., immobilization and "hopping") suggestive of continuous-time random walk (CTRW) behavior associated with desorption-mediated surface diffusion. The statistics of the molecular trajectories changed systematically on surfaces with pillars of increasing height, exhibiting motion that was increasingly subdiffusive and with longer waiting times between diffusive steps. The trajectories were well-described by kinetic Monte Carlo simulations of CTRW motion in the presence of randomly distributed permeable obstacles, where the permeability (the main undetermined parameter) was conceptually related to the obstacle height. These findings provide new insights into the mechanisms of interfacial transport in the presence of obstacles and on nanotopographically patterned surfaces.

The functionalization of nanodiamonds (diamondoids) as a key parameter of their easily controlled self-assembly in micro- and nanocrystals from the vapor phase

We detail herein readily accessible processes to control previously unobserved robust self-assemblies of nanodiamonds (diamondoids) in micro- and nanocrystals from their mild vapor deposition. The chemical functionalization of uniform and discernible nanodiamonds was found to be a key parameter, and depending on the type of functional group (hydroxy, fluorine, etc.) and its position on the diamondoid, the structure of the discrete deposits can vary dramatically. Thus, well-defined anisotropic structures such as rod, needle, triangle or truncated octahedron shapes can be obtained, and self-assembled edifices of sizes ranging from 20 nm to several hundred micrometers formed with conservation of a similar structure for a given diamondoid. Key thermodynamic data including sublimation enthalpy of diamondoid derivatives are reported, and the SEM of the self-assemblies coupled with EDX analyses and XRD attest the nature and purity of nanodiamond crystal deposits. This attractive method is simple and outperforms in terms of deposit quality dip-coating methods we used. This vapor phase deposition approach is expected to allow for an easy formation of diamondoid nanoobjects on different types of substrates.

Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains

This experimental work aims at probing current-induced forces at the atomic scale. Specifically it addresses predictions in recent work regarding the appearance of run-away modes as a result of a combined effect of the non-conservative wind force and a 'Berry force'. The systems we consider here are atomic chains of Au and Pt atoms, for which we investigate the distribution of break down voltage values. We observe two distinct modes of breaking for Au atomic chains. The breaking at high voltage appears to behave as expected for regular break down by thermal excitation due to Joule heating. However, there is a low-voltage breaking mode that has characteristics expected for the mechanism of current-induced forces. Although a full comparison would require more detailed information on the individual atomic configurations, the systems we consider are very similar to those considered in recent model calculations and the comparison between experiment and theory is very encouraging for the interpretation we propose.

Design, synthesis and photophysical studies of dipyrromethene-based materials: insights into their applications in organic photovoltaic devices

This review article presents the most recent developments in the use of materials based on dipyrromethene (DPM) and azadipyrromethenes (ADPM) for organic photovoltaic (OPV) applications. These chromophores and their corresponding BF2-chelated derivatives BODIPY and aza-BODIPY, respectively, are well known for fluorescence-based applications but are relatively new in the field of photovoltaic research. This review examines the variety of relevant designs, synthetic methodologies and photophysical studies related to materials that incorporate these porphyrinoid-related dyes in their architecture. The main idea is to inspire readers to explore new avenues in the design of next generation small-molecule and bulk-heterojunction solar cell (BHJSC) OPV materials based on DPM chromophores. The main concepts are briefly explained, along with the main challenges that are to be resolved in order to take full advantage of solar energy.

Single rotating molecule-machines: nanovehicles and molecular motors

In the last decade many molecular machines with controlled molecular motions have been synthesized. In the present review chapter we will present and discuss our contribution to the field, in particular through some examples of rotating molecular machines that have been designed, synthesized, and studied in our group. After starting by explaining why it is so important to study such machines as single molecules, we will focus on two families of molecular machines, nanovehicles and molecular motors. The first members of the nanovehicle family are molecules with two triptycenes as wheels: the axle and the wheelbarrow. Then come the four-wheel nanocars. Since triptycene wheels are not very mobile on metallic surfaces, alternative wheels with a bowl-shape structure have also been synthesized and studied on surfaces. The molecular motors are built around ruthenium organometallic centers and have a piano-stool geometry with peripheric ferrocenyl groups.

Control of active semiconducting layer packing in organic thin film transistors through synthetic tailoring of dielectric materials

The influence of dielectric material's property on the solid state structure packing of active semiconducting layer in OTFTs has been carefully studied by employing a whole new family of dielectric materials based on the rigid, tetrahedral bulky moleculei.e.adamantane, a smallest cage structure of diamond.

Motor proteins and molecular motors: how to operate machines at the nanoscale

Several classes of biological molecules that transform chemical energy into mechanical work are known as motor proteins or molecular motors. These nanometer-sized machines operate in noisy stochastic isothermal environments, strongly supporting fundamental cellular processes such as the transfer of genetic information, transport, organization and functioning. In the past two decades motor proteins have become a subject of intense research efforts, aimed at uncovering the fundamental principles and mechanisms of molecular motor dynamics. In this review, we critically discuss recent progress in experimental and theoretical studies on motor proteins. Our focus is on analyzing fundamental concepts and ideas that have been utilized to explain the non-equilibrium nature and mechanisms of molecular motors.

Directional molecular sliding at room temperature on a silicon runway

The design of working nanovehicles is a key challenge for the development of new devices. In this context, 1D controlled sliding of molecules on a silicon-based surface is successfully achieved by using an optimized molecule-substrate pair. Even though the molecule and surface are compatible, the molecule-substrate interaction provides a 1D template effect to guide molecular sliding along a preferential surface orientation. Molecular motion is monitored by STM experiments under ultra-high vacuum at room temperature. Molecule-surface interactions are elucidated by semi-empirical calculations.

Extending single molecule fluorescence observation time by amplitude-modulated excitation

We present a hardware-based method that can improve single molecule fluorophore observation time by up to 1500% and super-localization by 47% for the experimental conditions used. The excitation was modulated using an acousto-optic modulator (AOM) synchronized to the data acquisition and inherent data conversion time of the detector. The observation time and precision in super-localization of four commonly used fluorophores were compared under modulated and traditional continuous excitation, including direct total internal reflectance excitation of Alexa 555 and Cy3, non-radiative Förster resonance energy transfer (FRET) excited Cy5, and direct epi-fluorescence wide field excitation of Rhodamine 6G. The proposed amplitude-modulated excitation does not perturb the chemical makeup of the system or sacrifice signal and is compatible with multiple types of fluorophores. Amplitude-modulated excitation has practical applications for any fluorescent study utilizing an instrumental setup with time-delayed detectors.

Molecule concept nanocars: chassis, wheels, and motors?

The design, synthesis, and running of a molecular nanovehicle on a surface assisted by proper nanocommunication channels for feeding and guiding the vehicle now constitute an active field of research and are no longer a nano-joke. In this Perspective, we describe how this field began, its growth, and problems to be solved. Better molecular wheels, a molecular motor with its own gears assembling for torque transmission must be mounted on (i.e., chemically bonded to) a good molecular chassis for the resulting covalently constructed molecular nanovehicle to run on a surface in a controlled manner at the atomic scale. We propose a yearly molecule concept nanocar contest to boost molecular nanovehicle research.

Improved analysis for determining diffusion coefficients from short, single-molecule trajectories with photoblinking

Two maximum likelihood estimation (MLE) methods were developed for optimizing the analysis of single-molecule trajectories that include phenomena such as experimental noise, photoblinking, photobleaching, and translation or rotation out of the collection plane. In particular, short, single-molecule trajectories with photoblinking were studied, and our method was compared to existing analytical techniques applied to simulated data. The optimal method for various experimental cases was established, and the optimized MLE method was applied to a real experimental system: single-molecule diffusion of fluorescent molecular machines known as nanocars.