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Condensed films of functional luminophores dominated by the magnitude and dimensionality of the intermolecular interactions play important roles in sensing performance. However, controlling the molecular assembly and regulating photophysical properties remain challenging. In this study, a new luminophore, ortho‐PBI‐Au, was synthesized by anchoring a cyclometalated alkynyl‐gold(III) unit at the ortho‐position of perylene bisimide. An unprecedented T‐type packing model driven by weak Au‐π interaction and Au−H bonds was observed, laying foundation for striking properties of the luminophore. Controlled assembly of ortho‐PBI‐Au at the air‐water interface, realized using the classical Langmuir–Schaeffer technique, afforded the obtained luminescent films with different packing structures. With an optimized film, sensitive, selective, and rapid detection of a hazardous new psychoactive substance, phenylethylamine (PEA), was achieved. The detection limit, response time, and recovery time were <4 ppb, <1 s, and <5 s, respectively, surpassing the performance of the PEA sensors known thus far. The relationship between the characters of films and the sensing performance was systematically examined by grey relational analysis (GRA). The present study suggests that designing novel molecular aggregation with definite adlayer structure is a crucial strategy to enhance the sensing performance, which could be favorable for the film‐based fluorescent sensors. [ABSTRACT FROM AUTHOR]

In typical protein–nanoparticle surface interactions, the biomolecule surface binding and consequent conformational changes are intermingled with each other and are pivotal to the multiple functional properties of the resulting hybrid bioengineered nanomaterial. In this review, we focus on the peculiar properties of the layer formed when biomolecules, especially proteins and peptides, face two-dimensional (2D) nanomaterials, to provide an overview of the state-of-the-art knowledge and the current challenges concerning the biomolecule coronas and, in general, the 2D nano-biointerface established when peptides and proteins interact with the nanosheet surface. Specifically, this review includes both experimental and simulation studies, including some recent machine learning results of a wide range of nanomaterial and peptide/protein systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reactions can be utilized to install adlayers/monolayers on top of small molecule organic semiconductors. • XPS & ellipsometry suggest the surface initializes a ring-opening reaction with the epoxide. • Reaction conditions optimized to avoid thin-film degradation; found to be compatible with OLEDs. Adlayers are often placed at metal-on-organic interfaces as a common strategy to alleviate damage during metal deposition by thermal evaporation. Methods of chemically installing adlayers have been recently demonstrated on organic semiconductors that address these interfacial issues while providing many secondary benefits. Chemical installation has yet to be attempted at the cathode-electron transport layer (ETL) interface within organic light-emitting devices (OLEDs), offering a powerful option to optimize electron injection, improve surface wetting, and reduce metal penetration. Here, a reaction between TPBi (2,2′,2′'-(1,2,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) and propylene oxide results in a controllable 1–3 nm thick layer of propylene oxide as shown by high-resolution X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX). The reactive addition of the adlayer at temperatures below 40℃ does not affect the morphology of the thin film and reaches a high degree of coverage within 3 h. Integration of this layer into a phosphorescent OLED does not introduce any significant negative impact on device function. This result opens up the possibility of introducing further specific functionality into the adlayer to engineer OLED performance. [ABSTRACT FROM AUTHOR]

Adsorption of compounds with exposed aromatic C-nitroso groups on metal surfaces provides a way for fabrication of self-assembled bilayers (SABs) owing to ability of these compounds to dimerize to azodioxides. Here, we have investigated the possibility of self-assembly and dimerization of sulfur-containing aromatic dinitroso derivatives on an Au(111) surface by using polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), atomic force microscopy (AFM), scanning tunneling microscopy (STM), ellipsometry and water contact angle goniometry. While aromatic dinitroso derivatives are present as E -isomeric oligomers in solid state, PM-IRRAS spectra of their adlayers on gold surface revealed the presence of signals characteristic for nitroso monomers and E -azodioxy dimers. AFM and STM images of molecular adlayers showed the appearance of separate domains on an Au(111) surface suggesting formation of monolayer and bilayer-type structures. These results were further corroborated by ellipsometry measurements, which pointed to the presence of a non-uniform molecular adlayer covering gold surface. Comparison with previously studied systems of mononitroso derivatives indicates that adsorption of aromatic dinitroso derivatives on gold surface results in the formation of less ordered adlayers probably due to the steric hindrance of meta -situated nitroso groups. [ABSTRACT FROM AUTHOR]

Molecular self-assembly is an important aspect of bottom-up approaches for the nanofabrication of functional materials. The self-assembly of smaller-size units like ions has yet to be studied further. The self-adsorption of Bi without applied potential and electrochemical deposition of Bi/Bi were studied and compared through cyclic voltammetry. Both of them exhibit two pairs of redox peaks assigned to the (2 × 2)-Bi adlayer and incommensurate ( p × √3)-2 Bi adlayer. The adsorption of two Bi surface phases is related with the Bi salt concentration and adsorption time. Within a certain concentration or time range, the adsorption approaches to be saturated due to the surface limitation of self-adsorbed surface layers. The (2 × 2)-Bi adlayer firstly adsorbs to the active sites of Au where there is strong interaction between Bi and Au. With the increase of time, more Bi adsorbs onto the unoccupied sites of Au with a relatively weak interaction force to form a denser ( p × √3)-2 Bi layer. A new pair of redox peaks appears for the electrodeposition of the Bi/Bi bulky layer which is easily stripped from the Au surface through a consecutive potential scan. Comparatively speaking, the adsorbed (2 × 2) and ( p × √3)-2 Bi adlayers are stable in the same potential scanning condition due to the strong interaction between the two surface Bi layers and the below Au atoms. Such a controllable self-adsorption of the Bi ultrathin layer on foreign substrates exhibits a potential for the modification of materials in the size of ions. [ABSTRACT FROM AUTHOR]

Abstract: A model for the adsorption-induced static conductivity variation for the adatoms – single layer graphene (SLG) – metal substrate system with account of the dipole–dipole repulsion in the adlayer has proposed. The obtained results have been applied to the H/SLG/W system. Numerical estimations have shown that the effect of the atomic hydrogen monolayer on the epitaxial graphene (SLG/W) conductivity is of the order of . [Copyright &y& Elsevier]

Understanding of the interfacial chemistry of ultrathin polymeric adlayers is fundamentally important in the context of establishing quantitative design rules for the fabrication of nonfouling surfaces in various applications such as biomaterials and medical devices. In this study, seven poly( l-lysine)- graft-poly(2-methyl-2-oxazoline) (PLL-PMOXA) copolymers with grafting density (number of PMOXA chains per lysine residue) 0.09, 0.14, 0.19, 0.33, 0.43, 0.56, and 0.77, respectively, were synthesized and characterized by means of nuclear magnetic resonance spectroscopy (NMR). The copolymers were then adsorbed on NbO surfaces. Optical waveguide lightmode spectroscopy method was used to monitor the surface adsorption in situ of these copolymers and provide information on adlayer masses that were then converted into PLL and PMOXA surface densities. To investigate the relationship between copolymer bulk architecture (as shown by NMR data) and surface coverage as well as surface architecture, time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis was performed. Furthermore, ToF-SIMS method combined with principal component analysis (PCA) was used to verify the protein resistant properties of PLL-PMOXA adlayers, by thorough characterization before and after adlayer exposure to human serum. ToF-SIMS analysis revealed that the chemical composition as well as the architecture of the different PLL-PMOXA adlayers indeed reflects the copolymer bulk composition. ToF-SIMS results also indicated a heterogeneous surface coverage of PLL-PMOXA adlayers with high grafting densities higher than 0.33. In the case of protein resistant surface, PCA results showed clear differences between protein resistant and nonprotein-resistant surfaces. Therefore, ToF-SIMS results combined with PCA confirmed that the PLL-PMOXA adlayer with brush architecture resists protein adsorption. However, low increases of some amino acid signals in ToF-SIMS spectra were detected after the adlayer has been exposed to human serum. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Scanning tunnelling microscopy (STM), cyclic voltammetry (CV) and electron paramagnetic resonance spectroscopy (EPR) were used to investigate the influence of the TMP amine derivative on Au (111). The STM results show that the gold surface covered by the adlayer of the TMP derivative is easily modified (holes formation) after increasing the bias voltage to 0.5V. The CV and EPR results show the electrochemical origin of observed STM topography changes. It is suggested that TMP could be oxidized to the nitroxyl TEMPO radical which adsorbs on Au in the form of an oxoammonium cation. Such an oxoammonium cation at the potential of 0.5V forms a permanent complex of gold and the nitroxyl radical which could be easily desorbed during STM imaging. [Copyright &y& Elsevier]

Abstract: An approach to multiparametric characterisation of variable electroactive interfaces based on potentiodynamic electrochemical impedance spectroscopy (PDEIS) [G.A. Ragoisha, A.S. Bondarenko, Electrochim. Acta 50 (2005) 1553] has been extended to atomic multilayer assembly monitoring. The multilayers were formed by successive underpotential deposition of Te, Se and Pb or Cu adlayers on Au, and also by cadmium adlayer deposition on tellurium underlayer supported by gold. These multilayers were characterised in potentiodynamic mode by dependences of ac equivalent circuit parameters on electrode potential. The dependences disclose variations of interfacial double electric layer, charge transfer and diffusion. The dependencies of the characteristic parameters of the Au/Tead/Sead/Pbad composite three-layer have been found to be significantly different from the corresponding dependences of Au/Tead/Pbad and Au/Sead/Pbad bilayers, while Au/Tead/Sead/Cuad has shown much similarity with Au/Sead/Cuad in Faradaic part of ac response. Upd of Pb, Cu and Cd on the chalcogen adlayers has shown irreversibility with especially strong potential shift of adlayer oxidation potential in the case of lead deposition on bi-chalcogen Au/Tead/Sead underlayer. Unlike Pb adlayer, which is formed locally on top of tellurium–selenium bilayer and could be fully dissolved in the anodic scan in the potential range of stability of the chalcogen composite underlayer, copper penetrated into the Au/Tead/Sead bilayer and dissolved incompletely at Cu adlayer oxidation potential. The self-descriptiveness of potential dependences of circuit parameters suggests PDEIS to be a handy tool for layer-by-layer deposition monitoring in electrochemical nanotechnologies. [Copyright &y& Elsevier]

Abstract: In this paper, we compare the properties of SiO2/water interface modified by cetyltrimethylammonium bromide (CTAB) with those of CTAB spherical micelles. The suspension of uniform silica nanoparticles coated with CTAB adlayer was investigated by using a set of acid–base indicators. The study of the colloidal system has been provided using electron microscopy and dynamic light scattering methods; the diameter of the initial SiO2 particles in dried state was ca. 40 nm. The increase in the ζ-potential value of nanoparticles from −34 to +(37–54) mV on going from pure silica suspension to the CTAB-containing system points on the silica surface recharging and formation of surfactant bilayer (or multilayer) on the silica/water interface. To obtain further information about the interfacial surfactant adlayer, the behavior of different indicator dyes has been studied in CTAB-modified SiO2 suspension. Comparison of the indices of apparent ionization constants, i.e., values of phenol red, bromothymol blue, and fluorescein with those determined in CTAB micellar solutions have confirmed the supposition about certain similarity between CTAB-covered silica nanoparticles and common spherical surfactant micelles. However, the experiments on kinetics of bromophenol blue fading, as well as the spectral properties of methyl orange and solvatochromic Reichardt''s indicator and some other data revealed the specificity of surfactant-coated silica nanoparticles, presumably, originating from their surface morphology. [Copyright &y& Elsevier]

Abstract: Successive underpotential deposition of Tead, Cuad and Pbad adlayers in the potentiodynamic mode was used for Tead/Cuad/Pbad atomic three-layer structure assembling on polycrystalline Au support. Layer-by-layer deposition was characterised in each of the stages with potentiodynamic electrochemical impedance spectroscopy (PDEIS) by variations, with the electrode potential E, of double layer pseudocapacitance Q dl, charge transfer resistance R ct and Warburg coefficient A of diffusion impedance. Q dl(E) has shown a strong decrease in the cathodic scan during Te atomic layer deposition on Au, a sharp peak in the subsequent Cuad deposition on Au/Tead and an increase in Pbad deposition on Au/Tead/Cuad. The inverses of charge transfer resistance and Warburg coefficient have shown characteristic maxima in and A −1(E) dependencies in all the three stages of Tead/Cuad/Pbad three-layer assembling. The characteristic features in the dependences on the potential of the ac response parameters compensated for insufficient self-descriptiveness of the dc part of the nonstationary interface response in the layer-by-layer deposition. High information density of PDEIS spectra provides better control of electrochemical processes on nonstationary interfaces and this new opportunity can enable wider use of electrochemical approaches for thin-layer structures preparation. [Copyright &y& Elsevier]

Abstract: Bis(octakis(octyloxy) phthalocyaninato) europium(III) (Eu[Pc(OC8H17)8]2) adlayers were self-assembled on the gold surface by means of an improved self-assembling technique. The cyclic voltammograms (CVs) of the Eu[Pc(OC8H17)8]2-modified single-crystalline and poly-crystalline gold electrodes in perchloric acid displayed two pairs of redox waves due to the successive removal or addition of electrons from or to the ligand-based orbitals. The effect of Eu[Pc(OC8H17)8]2 adlayers on the electron transfer rate at electrode/solution interface was investigated by using Fe(CN)6 3−/4− couple as the redox probe. The redox behavior of Eu[Pc(OC8H17)8]2 adlayers and their accelerating effect on the electron transfer are closely associated with the electronic delocalization of rare earth sandwich complexes. However, in most cases, the Eu[Pc(OC8H17)8]2 adlayers were found to have inhibition role to complicated electrochemical reactions taking place on the gold surface, such as the gold substrate oxidation, the electrochemical reduction of oxygen, the electrochemical oxidation of ascorbic acid (Vitamin C) and the underpotential deposition (UPD) of silver. [Copyright &y& Elsevier]

Abstract: The underpotential deposition (UPD) of silver and lead on Au(111) was performed sequentially to produce a thin composite layer. Ag was deposited underpotentially in 1mM Ag2SO4 and 0.1M H2SO4 at 0.400V and 0.010V vs. Ag wire. The results of cyclic voltammetry carried out on this Ag/Au(111) electrode in a Pb2+ electrolyte with 0.1M HClO4 indicated contributions from both Au and Ag substrates. In situ STM images showed that the UPD of Pb on Ag/Au(111) had an unusual multilayer morphology. Cyclic Voltammetry was also used to demonstrate the stability and presence of the Ag adlayer in the Pb2+ electrolyte. In the presence of sodium nitrate, this composite system exhibits a catalytic effect on nitrate reduction that is not observed for Au(111), Ag/Au(111), Pb/Au(111), Ag(111), or Pb/Ag(111). Our results demonstrate that the Ag–Pb/Au(111) composite system has an enhanced catalytic effect on nitrate reduction. [Copyright &y& Elsevier]

Cyclic voltammetry and chronoamperometry have been employed for the preparation and characterization of noble metal electrode substrates modified with bismuth adlayers. The influence of bismuth ad-atoms on the electrocatalytic activity of the resulting platinum and gold modified electrode was investigated toward the electrooxidation of several sugar acid molecules in moderately alkaline medium. A direct comparative study regarding the catalytic activity between platinum and gold electrodes has been carried out in order to obtain useful information on the electrooxidation mechanism of sugar acids. It is found that different pre-adsorption processes of analyte on the platinum and gold electrodes were involved giving rise to different adsorption states in the oxide region and double region of potentials, respectively. The bismuth adsorbed species acts as a true catalyst on the direct electrooxidation pathway, providing the oxygen necessary for the oxidation of organic molecules adsorbed on the PtOx or Au sites in the oxide and double region, respectively. [Copyright &y& Elsevier]

A simple solution of an inverse problem of reconstruction of thickness, permittivity and surface coverage of an adlayer disposed on the surface of a channel optical waveguide is proposed and substantiated theoretically. It is shown that the reconstruction errors for the parameters of the adlayer can be minimized by a choice of the channel waveguide parameters. The application of the procedure to biochemical sensors is considered. [ABSTRACT FROM AUTHOR]

Understanding the growth mechanism of adlayer graphene is key to preparing a large-area uniform and continuous bilayer or multilayer graphene film, which is essential for electronic and photonic device applications. We synthesized high-quality single-layer graphene (SLG) film with numerous adlayer grains on liquid copper by controllable chemical vapor deposition (CVD). By adjusting parameters related to hydrogen and methane flow, we confirmed a competitive relationship between the etching and the growth of the adlayer, and they can reach dynamic equilibrium during the CVD process. Through the reasonable design of growth time, more details about adlayer growth were revealed. The etched defect is used as the center of carbon injection to grow adlayer under the first layer. For the first time, this research proposes and proves the growth mechanism of etching controlled adlayer growth, which opens a new door for the controllable synthesis of bilayer or multilayer graphene. [Display omitted] • We revealed the competitive relationship between the adlayer growth and growth-based etching in the LPCVD process. • The center of first layer, the adlayer and the etching originate from the same nucleation point. • A possible growth mechanism for adlayer graphene was proposed. [ABSTRACT FROM AUTHOR]

Electrochemical CO 2 reduction can convert waste emissions into dense liquid fuels compatible with existing energy infrastructure. High-rate electrocatalytic conversion of CO 2 to ethanol has been achieved in membrane electrode assembly (MEA) electrolyzers; however, ethanol produced at the cathode is transported, via electroosmotic drag and diffusion, to the anode, where it is diluted and may be oxidized. The ethanol concentrations that result on both the cathodic and anodic sides are too low to justify the energetic and financial cost of downstream separation. Here, we present a porous catalyst adlayer that facilitates the evaporation of ethanol into the cathode gas stream and reduces the water transport, leading to a recoverable stream of concentrated ethanol. The adlayer is comprised of ethylcellulose-bonded carbon nanoparticles and forms a porous, electrically conductive network on the surface of the copper catalyst that slows the transport of water to the gas channel. We achieve the direct production of an ethanol stream of 12.4 wt %, competitive with the concentration of current industrial ethanol production processes.

Ionic self-assembly of charged molecular building blocks relies on the interplay between long-range electrostatic forces and short-range, often cooperative, supramolecular interactions, yet has been seldom studied in two dimensions at the solid-liquid interface. Here, we demonstrate anion-driven switching of two-dimensional (2D) crystal structure at the Au(111)/octanoic acid interface. Using scanning tunneling microscopy (STM), three organic salts with identical polyaromatic cation (PQPC 6 ) but different anions (perchlorate, anthraquinonedisulfonate, benzenesulfonate) are shown to form distinct, highly ordered self-assembled structures. Reversible switching of the supramolecular arrangement is demonstrated by in situ exchange of the anion on the pre-formed adlayer, by changing the concentration ratio between the incoming and outgoing anion. Density functional theory (DFT) calculations reveal that perchlorate is highly mobile in the adlayer, and corroborate why this anion is only resolved transiently in STM. Surprisingly, the templating effect of the anion persists even where it does not become part of the adlayer 2D fabric, which we ascribe to differences in stabilization of cation conformations by the anion. Our results provide important insight into the structuring of mixed anion-cation adlayers. This is essential in the design of tectons for ionic self-assembled superstructures and biomimetic adaptive materials and valuable also to understand adsorbate-adsorbate interactions in heterogeneous catalysis.+ ) but different anions (perchlorate, anthraquinonedisulfonate, benzenesulfonate) are shown to form distinct, highly ordered self-assembled structures. Reversible switching of the supramolecular arrangement is demonstrated by in situ exchange of the anion on the pre-formed adlayer, by changing the concentration ratio between the incoming and outgoing anion. Density functional theory (DFT) calculations reveal that perchlorate is highly mobile in the adlayer, and corroborate why this anion is only resolved transiently in STM. Surprisingly, the templating effect of the anion persists even where it does not become part of the adlayer 2D fabric, which we ascribe to differences in stabilization of cation conformations by the anion. Our results provide important insight into the structuring of mixed anion-cation adlayers. This is essential in the design of tectons for ionic self-assembled superstructures and biomimetic adaptive materials and valuable also to understand adsorbate-adsorbate interactions in heterogeneous catalysis., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The surface cleansing treatment of non-natural cleavage planes of semiconductors is usually performed in vacuum using ion sputtering and subsequent annealing. In this Research Article, we report on the evolution of surface atomic structure caused by different ways of surface treatment as monitored by in situ core-level photoemission measurements of Cd-4d and Te-4d atomic levels and reflection high-energy electron diffraction (RHEED). Sputtering of surface increases the density of the dangling bonds by 50%. This feature and the less than ideal ordering can be detrimental to device applications. An effective approach is employed to improve the quality of this surface. One monolayer (ML) of Te grown by the method of molecular beam epitaxy (MBE) on the target surface with heating at 300 °C effectively improves the surface quality as evidenced by the improved sharpness of RHEED pattern and a reduced diffuse background in the spectra measured by high-resolution ultraviolet photoemission spectroscopy (HRUPS). Calculations have been performed for various atomic geometries by employing first-principles geometry optimization. In conjunction with an analysis of the core level component intensities in terms the layer-attenuation model, we propose a "vacancy site" model of the modified 1 ML-Te/CdTe(111)A (2 × 2) surface.