Mechanistic Understanding of Oxygen Activation on Bulk Au(111) Surface Using Tip-Enhanced Raman Spectroscopy

Gaining mechanistic understanding of oxygen activation on metal surfaces is a topical area of research in surface science. However, direct investigation of on-surface oxidation processes at the nanoscale and the empirical validation of oxygen activation pathways remain challenging for the conventional analytical tools. In this study, we applied tip-enhanced Raman spectroscopy (TERS) to gain mechanistic insights into oxygen activation on bulk Au(111) surface. Specifically, oxidation of 4-aminothiophenol (4-ATP) to 4-nitrothiophenol (4-NTP) on Au(111) surface was investigated using hyperspectral TERS imaging. Nanoscale TERS images revealed a markedly higher oxidation efficiency in disordered 4-ATP adlayers compared to the ordered adlayers signifying that the oxidation of 4-ATP molecules proceeds via interaction with the on-surface oxidative species. These results were further validated via direct oxidation of the 4-ATP adlayers with H2O2 solution. Finally, TERS measurements of oxidized 4-ATP adlayers in the presence of H2O18 provided the first empirical evidence for the generation of oxidative species on bulk Au(111) surface via water-mediated activation of molecular oxygen. This study expands our mechanistic understanding of oxidation chemistry on bulk Au surface by elucidating the oxygen activation pathway.

Boosting Cathode Activity and Anode Stability of Lithium-Sulfur Batteries with Vigorous Iodic Species Triggered by Nitrate

Lithium-sulfur (Li-S) battery with a sulfurized polyacrylonitrile cathode is a promising alternative to Li-ion systems. However, the sluggish charge transfer of cathode and accumulation of inactive Li on anode remain persistent challenges. An advanced electrolyte additive with function towards both cathode and anode holds great promise to address these issues. Herein, we present a new strategy to boost sulfur activity and rejuvenate dead Li simultaneously. In the polar electrolyte containing I2-LiNO3 additives, I3 -/IO3 - are triggered significantly by the reaction between NO3 - and I- ions. The I3 -/IO3 - are reactive to insulated Li2S product of cathode and inactive Li on anode, thus accelerating the conversion reaction of sulfur and recovering Li sources back to battery cycling. The in situ/ex situ spectroscopic and morphologic monitoring reveal the crucial role of iodine in promoting Li2S dissociation and inhibiting dendritic Li growth. With the modified electrolyte, the symmetric Li||Li cells deliver a lifespan of 4000 h with an overpotential less than 12 mV at 0.5 mA cm-2. For Li-S cells, 100 % capacity retention up to thousands of cycles and enhanced rate capability are available. This work demonstrates a feasible strategy on electrolyte engineering for practical applications of Li-S batteries.

Active Sites in Cr(III)-Based Ethylene Polymerization Catalysts from Machine-Learning-Supported XAS and EPR Spectroscopy

The ethylene polymerization Phillips catalyst has been employed for decades and is central to the polymer industry. While Cr(III) alkyl species are proposed to be the propagating sites, there is so far no direct experimental evidence for such proposal. In this work, by coupling Surface organometallic chemistry, EPR spectroscopy, and machine learning-supported XAS studies, we have studied the electronic structure of well-defined silica-supported Cr(III) alkyls and identified the presence of several surface species in high and low-spin states, associated with different coordination environments. Notably, low-spin Cr(III) sites are shown to participate in ethylene polymerization, indicating that similar Cr(III) alkyl species could be involved in the related Phillips catalyst.

Surface-Enhanced Raman Scattering-Based Surface Chemotaxonomy: Combining Bacteria Extracellular Matrices and Machine Learning for Rapid and Universal Species Identification

Rapid, universal, and accurate identification of bacteria in their natural states is necessary for on-site environmental monitoring and fundamental microbial research. Surface-enhanced Raman scattering (SERS) spectroscopy emerges as an attractive tool due to its molecule-specific spectral fingerprinting and multiplexing capabilities, as well as portability and speed of readout. Here, we develop a SERS-based surface chemotaxonomy that uses bacterial extracellular matrices (ECMs) as proxy biosignatures to hierarchically classify bacteria based on their shared surface biochemical characteristics to eventually identify six distinct bacterial species at >98% classification accuracy. Corroborating with in silico simulations, we establish a three-way inter-relation between the bacteria identity, their ECM surface characteristics, and their SERS spectral fingerprints. The SERS spectra effectively capture multitiered surface biochemical insights including ensemble surface characteristics, e.g., charge and biochemical profiles, and molecular-level information, e.g., types and numbers of functional groups. Our surface chemotaxonomy thus offers an orthogonal taxonomic definition to traditional classification methods and is achieved without gene amplification, biochemical testing, or specific biomarker recognition, which holds great promise for point-of-need applications and microbial research.

Self-Assembled Monolayers of N-Heterocyclic Olefins on Au(111)

Self-assembled monolayers (SAMs) of N-heterocyclic olefins (NHOs) have been prepared on Au(111) and their thermal stability, adsorption geometry, and molecular order were characterized by X-ray photoelectron spectroscopy, polarized X-ray absorption spectroscopy, scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. The strong σ-bond character of NHO anchoring to Au induced high geometrical flexibility that enabled a flat-lying adsorption geometry via coordination to a gold adatom. The flat-lying adsorption geometry was utilized to further increase the surface interaction of the NHO monolayer by backbone functionalization with methyl groups that induced high thermal stability and a large impact on work-function values, which outperformed that of N-heterocyclic carbenes. STM measurements, supported by DFT modeling, identified that the NHOs were self-assembled in dimers, trimers, and tetramers constructed of two, three, and four complexes of NHO-Au-adatom. This self-assembly pattern was correlated to strong NHO-Au interactions and steric hindrance between adsorbates, demonstrating the crucial influence of the carbon-metal σ-bond on monolayer properties.

In situ Observation of Evolving H2 and Solid Electrolyte Interphase Development at Potassium Insertion Materials within Highly Concentrated Aqueous Electrolytes

The solid-electrolyte interphase (SEI) is key to stable, high voltage lithium-ion batteries (LIBs) as a protective barrier that prevents electrolyte decomposition. The SEI is thought to play a similar role in highly concentrated water-in-salt electrolytes (WISEs) for emerging aqueous batteries, but its properties remain unknown. In this work, we utilized advanced scanning electrochemical microscopy (SECM) and operando electrochemical mass spectrometry (OEMS) techniques to gain deeper insight into the SEI that occurs within highly concentrated WISEs. As a model, we focus on a 55 mol/kg K(FSA)0.6 (OTf)0.4 electrolyte and a 3,4,9,10-perylenetetracarboxylic diimide negative electrode. For the first time, our work showed distinctly passivating structures with slow apparent electron transfer rates alike to the SEI found in LIBs. In situ analyses indicated stable passivating structures when PTCDI was stepped to low potentials (≈-1.3 V vs. Ag/AgCl). However, the observed SEI was discontinuous at the surface and H2 evolution occurred as the electrode reached more extreme potentials. OEMS measurements further confirmed a shift in the evolution of detectable H2 from -0.9 V to <-1.4 V vs. Ag/AgCl when changing from dilute to concentrated electrolytes. In all, our work shows a combined approach of traditional battery measurements with in situ analyses for improving characterization of other unknown SEI structures.

On-Surface Synthesis and Characterization of a High-Spin Aza-[5]-Triangulene

Triangulenes are a class of open-shell triangular graphene flakes with total spin increasing with their size. In the last years, on-surface-synthesis strategies have permitted fabricating and engineering triangulenes of various sizes and structures with atomic precision. However, direct proof of the increasing total spin with their size remains elusive. In this work, we report the combined in-solution and on-surface synthesis of a large nitrogen-doped triangulene (aza-[5]-triangulene) on a Au(111) surface, and the detection of its high-spin ground state. Bond-resolved scanning tunneling microscopy images uncovered radical states distributed along the zigzag edges, which were detected as weak zero-bias resonances in scanning tunneling spectra. These spectral features reveal the partial Kondo screening of a high-spin state. Through a combination of several simulation tools, we find that the observed distribution of radical states is explained by a quintet ground state (S=2), instead of the quartet state (S=3/2) expected for the neutral species. This confirms that electron transfer to the metal substrate raises the spin of the ground state. We further provide a qualitative description of the change of (anti)aromaticity introduced by N-substitution, and its role in the charge stabilization on a surface, resulting in an S=2 aza-triangulene on Au(111).

Bulk and Surface Contributions to Ionisation Potentials of Metal Oxides

Determining the absolute band edge positions in solid materials is crucial for optimising their performance in wide-ranging applications including photocatalysis and electronic devices. However, obtaining absolute energies is challenging, as seen in CeO2 , where experimental measurements show substantial discrepancies in the ionisation potential (IP). Here, we have combined several theoretical approaches, from classical electrostatics to quantum mechanics, to elucidate the bulk and surface contributions to the IP of metal oxides. We have determined a theoretical bulk contribution to the IP of stoichiometric CeO2 of only 5.38 eV, while surface orientation results in intrinsic IP variations ranging from 4.2 eV to 8.2 eV. Highly tuneable IPs were also found in TiO2 , ZrO2 , and HfO2 , in which surface polarisation plays a pivotal role in long-range energy level shifting. Our analysis, in addition to rationalising the observed range of experimental results, provides a firm basis for future interpretations of experimental and computational studies of oxide band structures.

Bilayer-Coating Strategy for Hydrophobic Nanoparticles Providing Colloidal Stability, Functionality, and Surface Protection in Biological Media

The surface chemistry of nanoparticles is a key step on the pathway from particle design towards applications in biologically relevant environments. Here, a bilayer-based strategy for the surface modification of hydrophobic nanoparticles is introduced that leads to excellent colloidal stability in aqueous environments and good protection against disintegration, while permitting surface functionalization via simple carbodiimide chemistry. We have demonstrated the excellent potential of this strategy using upconversion nanoparticles (UCNPs), initially coated with oleate and therefore dispersible only in organic solvents. The hydrophobic oleate capping is maintained and a bilayer is formed upon addition of excess oleate. The bilayer approach renders protection towards luminescence loss by water quenching, while the incorporation of additional molecules containing amino functions yields colloidal stability and facilitates the introduction of functionality. The biological relevance of the approach was confirmed with the use of two model dyes, a photosensitizer and a nitric oxide (NO) probe that, when attached to the surface of the UCNPs, retained their functionality to produce singlet oxygen and detect intracellular NO, respectively. We present a simple and fast strategy to protect and functionalize inorganic nanoparticles in biological media, which is important for controlled surface engineering of nanosized materials for theranostic applications.

Resolving the Heat Generated from ZrO2 Atomic Layer Deposition Surface Reactions

In situ pyroelectric calorimetry and spectroscopic ellipsometry were used to investigate surface reactions in atomic layer deposition (ALD) of zirconium oxide (ZrO₂ ). Calibrated and time-resolved in situ ALD calorimetry provides new insights into the thermodynamics and kinetics of saturating surface reactions for tetrakis(dimethylamino)zirconium(IV) (TDMAZr) and water. The net ALD reaction heat ranged from 0.197 mJ cm^-2 at 76 °C to 0.155 mJ cm^-2 at 158 °C, corresponding to an average of 4.0 eV/Zr at all temperatures. A temperature dependence for reaction kinetics was not resolved over the range investigated. The temperature dependence of net reaction heat and distribution among metalorganic and oxygen source exposure is attributed to factors including growth rate, equilibrium surface hydroxylation, and the extent of the reaction. ZrO₂ -forming surface reactions were investigated computationally using DFT methods to better understand the influence of surface hydration on reaction thermodynamics.

Direct Arylation of Silicon Nanocrystals with Hexadehydro-Diels-Alder-Derived Benzynes

Colloidal silicon nanocrystals (SiNCs) have garnered significant interest in optoelectronics and biomedical applications. Direct arylation provides pathways to enhance the solution processability of particles and manipulate the photophysical and electronic properties of SiNCs. Unfortunately, existing methods employed to prepare aryl-functionalized SiNCs are based on organometallic coupling or transition-metal-catalyzed strategies, which require metal-based reagents for preactivation or the precursors and complicated post-treatment processes for product purification. Herein, we demonstrate a metal-free method that directly functionalizes SiNCs with aryl-based ligands. We design a series of benzyne derivatives formed from the thermal cyclization of predesigned alkynes, allowing efficient arylation on hydride-terminated silicon surfaces under mild conditions. These aryl-functionalized SiNCs exhibit strong blue emissions with nanosecond-scaled decay, suggesting the formation of a new radiative recombination channel on SiNC surfaces.

Achieving High Single-Pass Carbon Conversion Efficiencies in Durable CO2 Electroreduction in Strong Acids via Electrode Structure Engineering

Acidic CO₂ reduction (CO₂ R) holds promise for the synthesis of low-carbon-footprint chemicals using renewable electricity. However, the corrosion of catalysts in strong acids causes severe hydrogen evolution and rapid deterioration of CO₂ R performance. Here, by coating catalysts with an electrically nonconductive nanoporous SiC-Nafion^TM layer, a near-neutral pH was stabilized on catalyst surfaces, thereby protecting the catalysts against corrosion for durable CO₂ R in strong acids. Electrode microstructures played a critical role in regulating ion diffusion and stabilizing electrohydrodynamic flows near catalyst surfaces. This surface-coating strategy was applied to three catalysts, SnBi, Ag, and Cu, and they exhibited high activity over extended CO₂ R operation in strong acids. Using a stratified SiC-Nafion^TM /SnBi/polytetrafluoroethylene (PTFE) electrode, constant production of formic acid was achieved with a single-pass carbon efficiency of >75 % and Faradaic efficiency of >90 % at 100 mA cm^-2 over 125 h at pH 1.

The Covalent Functionalization of Surface-Supported Graphene: An Update

In the last decade, the use of graphene supported on solid surfaces has broadened its scope and applications, and graphene has acquire a promising role as a major component of high-performance electronic devices. In this context, the chemical modification of graphene has become essential. In particular, covalent modification offers key benefits, including controllability, stability, and the facility to be integrated into manufacturing operations. In this Review, we critically comment on the latest advances in the covalent modification of supported graphene on substrates. We analyze the different chemical modifications with special attention to radical reactions. In this context, we review the latest achievements in reactivity control, tailoring electronic properties, and introducing active functionalities. Finally, we extended our analysis to other emerging 2D materials supported on surfaces, such as transition metal dichalcogenides, transition metal oxides, and elemental analogs of graphene.

A Gemini-Type Superwettable Separator for Consecutive Purification of Water and Oil Phases from Oil-Water Mixtures and Emulsions

Oil pollution results from daily activities and a variety of industries have caused not only severe environmental problems but also wastage of valuable petrochemical resources. Separation based on superwettable materials holds promise; however, practical applications of a single type of superwettable materials were often limited due to their ability in treatment of complicated oil-water systems. Herein, a Gemini-type separator was created through the cooperation of two kinds of superwettable sand particles with opposite wettability, i. e., one is superhydrophobic whereas the other is superhydrophilic. Cooperatively by the two types of superwettable sand, consecutive separation and purification of both water and oil phases from complicated oil-water systems (e. g., water mixed with a lighter or denser oil, water emulsified in oil, oil emulsified in water, and/or a combination of them in one batch) could be achieved with high flux and superior efficiency just in one single operation unit.

The Electronic Origin of the Zeta Potential is Supported by the Redox Mechanism on an Aqueous Dispersion of Exfoliated Graphite

Herein we have proposed that a redox mechanism can produce surface charges and negative zeta potential on an aqueous graphite dispersion. Graphite was kept in contact with a concentrated ammonia aqueous solution, washed, and exfoliated in water, resulting in a dispersion with lyophobic nature. Ammonia treatment did not provide functional groups or nitrogen doping to graphite. Moreover, this material was washed twice before sonication to remove most hydroxide. Therefore, neither functional groups, nitrogen atoms, nor hydroxide excess is responsible for the zeta potential. Kelvin probe force microscopy has shown that the ammonia-treated and exfoliated graphite has higher Fermi level than the water-treated material, indicating that the contact between ammonia and graphite promotes redox reactions that provide electrons to graphite. These electrons raise the Fermi level of graphite and generate the negative zeta potential, consequently, they account for the colloidal stability.

Structure of an Ultrathin Oxide on Pt3 Sn(111) Solved by Machine Learning Enhanced Global Optimization

Determination of the atomic structure of solid surfaces typically depends on comparison of measured properties with simulations based on hypothesized structural models. For simple structures, the models may be guessed, but for more complex structures there is a need for reliable theory-based search algorithms. So far, such methods have been limited by the combinatorial complexity and computational expense of sufficiently accurate energy estimation for surfaces. However, the introduction of machine learning methods has the potential to change this radically. Here, we demonstrate how an evolutionary algorithm, utilizing machine learning for accelerated energy estimation and diverse population generation, can be used to solve an unknown surface structure-the (4×4) surface oxide on Pt₃ Sn(111)-based on limited experimental input. The algorithm is efficient and robust, and should be broadly applicable in surface studies, where it can replace manual, intuition based model generation.

Structure of an Ultrathin Oxide on Pt3Sn(111) Solved by Machine Learning Enhanced Global Optimization

Determination of the atomic structure of solid surfaces typically depends on comparison of measured properties with simulations based on hypothesized structural models. For simple structures, the models may be guessed, but for more complex structures there is a need for reliable theory-based search algorithms. So far, such methods have been limited by the combinatorial complexity and computational expense of sufficiently accurate energy estimation for surfaces. However, the introduction of machine learning methods has the potential to change this radically. Here, we demonstrate how an evolutionary algorithm, utilizing machine learning for accelerated energy estimation and diverse population generation, can be used to solve an unknown surface structure-the (4×4) surface oxide on Pt3Sn(111)-based on limited experimental input. The algorithm is efficient and robust, and should be broadly applicable in surface studies, where it can replace manual, intuition based model generation.

Synthesis and Characterization of peri-Heptacene on a Metallic Surface

The synthesis of long n-peri-acenes (n-PAs) is challenging as a result of their inherent open-shell radical character, which arises from the presence of parallel zigzag edges beyond a certain n value. They are considered as π-electron model systems to study magnetism in graphene nanostructures; being potential candidates in the fabrication of optoelectronic and spintronic devices. Here, we report the on-surface formation of the largest pristine member of the n-PA family, i.e. peri-heptacene (n=7, 7-PA), obtained on an Au(111) substrate under ultra-high vacuum conditions. Our high-resolution scanning tunneling microscopy investigations, complemented by theoretical simulations, provide insight into the chemical structure of this previously elusive compound. In addition, scanning tunneling spectroscopy reveals the antiferromagnetic open-shell singlet ground state of 7-PA, exhibiting singlet-triplet spin-flip inelastic excitations with an effective exchange coupling (J_eff ) of 49 meV.

The Chemistry of Cu3 N and Cu3 PdN Nanocrystals

The precursor conversion chemistry and surface chemistry of Cu₃ N and Cu₃ PdN nanocrystals are unknown or contested. Here, we first obtain phase-pure, colloidally stable nanocubes. Second, we elucidate the pathway by which copper(II) nitrate and oleylamine form Cu₃ N. We find that oleylamine is both a reductant and a nitrogen source. Oleylamine is oxidized by nitrate to a primary aldimine, which reacts further with excess oleylamine to a secondary aldimine, eliminating ammonia. Ammonia reacts with Cu^I to form Cu₃ N. Third, we investigated the surface chemistry and find a mixed ligand shell of aliphatic amines and carboxylates (formed in situ). While the carboxylates appear tightly bound, the amines are easily desorbed from the surface. Finally, we show that doping with palladium decreases the band gap and the material becomes semi-metallic. These results bring insight into the chemistry of metal nitrides and might help the development of other metal nitride nanocrystals.

Surface Chemistry Impact on the Light Absorption by Colloidal Quantum Dots

At the size scale at which quantum confinement effects arise in inorganic semiconductors, the materials' surface-to-volume ratio is intrinsically high. This consideration sets surface chemistry as a powerful tool to exert further control on the electronic structure of the inorganic semiconductors. Among the materials that experience the quantum confinement regime, those prepared via colloidal synthetic procedures (the colloidal quantum dots - and wires and wells, too -) are prone to undergo surface reactions in the solution phase and thus represent an ideal framework to study the ensemble impact of surface chemistry on the materials' electronic structure. It is here discussed such an impact at the ground state by using the absorption spectrum of the colloidal quantum dots as a descriptor. The experiments show that the chemical species (the ligands) at the colloidal quantum dot surface induce changes to the optical band gap, the absorption coefficient at all wavelengths, and the ionization potential. These evidences point to a description of the colloidal quantum dot (the ligand/core adduct) as an indecomposable species, in which the orbitals localized on the ligands and the core mix in each other's electric field. This description goes beyond conventional models that conceive the ligands on the basis of pure electrostatic arguments (i. e., either as a dielectric shell or as electric dipoles) or as a mere potential energy barrier at the core boundaries.

Alternative view of oxygen reduction on porous carbon electrocatalysts: the substance of complex oxygen-surface interactions

Electrochemical oxygen reduction reaction (ORR) is an important energy-related process requiring alternative catalysts to expensive platinum-based ones. Although recently some advancements in carbon catalysts have been reported, there is still a lack of understanding which surface features might enhance their efficiency for ORR. Through a detailed study of oxygen adsorption on carbon molecular sieves and using inelastic neutron scattering, we demonstrated here that the extent of oxygen adsorption/interactions with surface is an important parameter affecting ORR. It was found that both the strength of O₂ physical adsorption in small pores and its specific interactions with surface ether functionalities in the proximity of pores positively influence the ORR efficiency. We have shown that ultramicropores and hydrophobic surface rich in ether-based groups and/or electrons enhance ORR on carbon electrocatalysts and the performance parameters are similar to those measured on Pt/C with the number of electron transfer equal to 4.

Bridging the Gap in the Mechanistic Understanding of Electrocatalysis via In Situ Characterizations

Electrocatalysis offers a promising strategy to take advantage of the increasingly available and affordable renewable energy for the sustainable production of fuels and chemicals. Attaining this promise requires a molecular level insight of the electrical interface that can be used to tailor the selectivity of electrocatalysts. Addressing this selectivity challenge remains one of the most important areas in modern electrocatalytic research. In this Perspective, we focus on the use of in situ techniques to bridge the gap in the fundamental understanding of electrocatalytic processes. We begin with a brief discussion of traditional electrochemical techniques, ex situ measurements and in silico analysis. Subsequently, we discuss the utility and limitations of in situ methodologies, with a focus on vibrational spectroscopies. We then end by looking ahead toward promising new areas for the application of in situ techniques and improvements to current methods.

Understanding the Role of Surface Heterogeneities in Electrosynthesis Reactions

In this perspective, we highlight the role of surface heterogeneity in electrosynthesis reactions. Heterogeneities may come in the form of distinct crystallographic facets, boundaries between facets or grains, or point defects. We approach this topic from a foundation of surface science, where signatures from model systems provide understanding of observations on more complex and higher-surface-area materials. In parallel, probe-based techniques can inform directly on spatial variation across electrode surfaces. We call attention to the role spectroscopy can play in understanding the impact of these heterogeneities in electrocatalyst activity and selectivity, particularly where these surface features have effects extending into the electrolyte double layer.

A Molecular-Scale Approach to Rare-Earth Beneficiation: Thinking Small to Avoid Large Losses

Separating rare-earth-element-rich minerals from unwanted gangue in mined ores relies on selective binding of collector molecules at the interface to facilitate froth flotation. Salicylhydroxamic acid (SHA) exhibits enhanced selectivity for bastnäsite over calcite in microflotation experiments. Through a multifaceted approach, leveraging density functional theory calculations, and advanced spectroscopic methods, we provide molecular-level mechanistic insight to this selectivity. The hydroxamic acid moiety introduces strong interactions at metal-atom surface sites and hinders subsurface-cation stabilization at vacancy-defect sites, in calcite especially. Resulting from hydrogen-bond-induced interactions, SHA lies flat on the bastnäsite surface and shows a tendency for multilayer formation at high coverages. In this conformation, SHA complexation with bastnäsite metal ions is stabilized, leading to advanced flotation performance. In contrast, SHA lies perpendicular to the calcite surface due to a difference in cationic spacing. We anticipate that these insights will motivate rational design and selection of future collector molecules for enhanced ore beneficiation.

Soap Bubble Pollination

Natural and artificial flower pollination are critical processes in the life cycle of flowering plants. Declines in the number of global pollinator insects, the heavy labor of conducting artificial pollination manually, and the rising cost of pollen grains are considered to be significant worldwide problems. Here we show that chemically functionalized soap bubbles exhibit effective and convenient delivery of pollen grains to the targeted flowers thanks to their stickiness, softness, high flexibility, and enhancement of pollen activity. By exploring the physicochemical properties of functional soap bubbles, we could prepare mechanically stabilized soap bubbles capable of withstanding the windmills produced by robotic pollination. An unmanned aerial vehicle equipped with a soap bubble maker was autonomously controlled to pollinate flowers. Such technology of automatic intelligent robotic pollination with functional soft materials would lead to innovative agricultural systems that can tackle the global issues of pollination.

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Developed soap bubbles exhibit various biological and physicochemical properties

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The soap bubbles allow effective flower pollination

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A flying robot equipped with a bubble maker can be used for autonomous pollination

One-Step Direct Fixation of Atmospheric CO2 by Si-H Surface in Solution

The efficient conversion of carbon dioxide (CO₂) into useful chemicals has important practical significance for environmental protection. Until now, direct fixation of atmospheric CO₂ needs first extraction from the atmosphere, an energy-intensive process. Silicon (or Si-H surface), Earth-abundant, low-cost and non-toxic, is a promising material for heterogeneous CO₂ chemical fixation. Here we report one-step fixing of CO₂ directly from the atmosphere to a paraformaldehyde-like polymer by Si-H surface at room temperature. With the assistance of HF, commercial silicon powder was used as a heterogeneous reducing agent, for converting gaseous CO₂ to a polymer of fluorine substituted polyoxymethylene and hydroxyl substituted polyoxymethylene alternating copolymer (F-POM). Making use of the Si-H surface toward the fixation of atmospheric gaseous CO₂ is a conceptually distinct and commercially interesting strategy for making useful chemicals and environmental protection.

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Atmospheric CO₂ is fixed with HF-treated silicon powders via one-step method

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The product is fluorine substituted polymer (F-POM)

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The fixation process is monitored by in situ infrared studies and mass spectra

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The mechanism on the direct CO₂ fixation by Si-H surface is proposed

Modification of TiO2 Nanoparticles with Organodiboron Molecules Inducing Stable Surface Ti3+ Complex

As one of the most promising semiconductor oxide materials, titanium dioxide (TiO₂) absorbs UV light but not visible light. To address this limitation, the introduction of Ti³⁺ defects represents a common strategy to render TiO₂ visible-light responsive. Unfortunately, current hurdles in Ti³⁺ generation technologies impeded the widespread application of Ti³⁺ modified materials. Herein, we demonstrate a simple and mechanistically distinct approach to generating abundant surface-Ti³⁺ sites without leaving behind oxygen vacancy and sacrificing one-off electron donors. In particular, upon adsorption of organodiboron reagents onto TiO₂ nanoparticles, spontaneous electron injection from the diboron-bound O²⁻ site to adjacent Ti⁴⁺ site leads to an extremely stable blue surface Ti³⁺‒O^−· complex. Notably, this defect generation protocol is also applicable to other semiconductor oxides including ZnO, SnO₂, Nb₂O₅, and In₂O₃. Furthermore, the as-prepared photoelectronic device using this strategy affords 10³-fold higher visible light response and the fabricated perovskite solar cell shows an enhanced performance.

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Organodiborons are used to reshape the surface electronic state of semiconductor oxides

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Diboron adsorption leads to spontaneous charge transfer and reduced surface metal ions

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Photodetector based on diboron material affords 10³ fold higher visible light response

A Metal-free Click Chemistry Approach for the Assembly and Probing of Biomolecules

Probing of biomolecular complexes by single-molecule force spectroscopy (SMFS) methods including AFM requires proper and suitable coupling methods for immobilization of biomolecules onto the AFM tip and the surface. The use of flexible tethers for the coupling process has dual advantages. First, they allow the specific immobilization of interacting molecules, and second, their flexibility facilitates the proper orientation of the interacting partners. Recently, we developed an approach termed Flexible Nano Array (FNA) in which interacting partners are located on the same polymeric FNA molecule separated by a flexible segment with a defined length. In this paper, we modified the FNA tether approach by incorporating click chemistry with non-metal modification. FNA was synthesized using DNA synthesis chemistry, in which phosphoramidite (PA) spacers containing six ethylene glycol units were used instead of nucleoside triphosphates. During the synthesis, two T modifiers conjugated to two dibenzocyclooctyl (DBCO) residues were incorporated at selected positions within the FNA. The DBCO functionality allows for coupling azide labeled biomolecules via click chemistry. Amyloid peptide Aβ(14-23) terminated with azide was incorporated into the FNA and the reaction was controlled with mass-spectrometry. Assembly of tethered Aβ(14-23) peptides into dimers was characterized by AFM force spectroscopy experiments in which the AFM tip functionalized with FNA terminated with biotin probed a streptavidin-coated mica surface. The formation of the peptide dimer was verified with force spectroscopy that showed the appearance of a specific fingerprint for dimer dissociation followed by a rupture event for the biotin-streptavidin link. The developed approach is capable of multiple probing events to allow the collection of a large set of data for a quantitative analysis of the force spectroscopy events.

Rapid and Facile Microwave-Assisted Surface Chemistry for Functionalized Microarray Slides

We describe a rapid and facile method for surface functionalization and ligand patterning of glass slides based on microwave-assisted synthesis and a microarraying robot. Our optimized reaction enables surface modification 42-times faster than conventional techniques and includes a carboxylated self-assembled monolayer, polyethylene glycol linkers of varying length, and stable amide bonds to small molecule, peptide, or protein ligands to be screened for binding to living cells. We also describe customized slide racks that permit functionalization of 100 slides at a time to produce a cost-efficient, highly reproducible batch process. Ligand spots can be positioned on the glass slides precisely using a microarraying robot, and spot size adjusted for any desired application. Using this system, we demonstrate live cell binding to a variety of ligands and optimize PEG linker length. Taken together, the technology we describe should enable high-throughput screening of disease-specific ligands that bind to living cells.