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Microfluidics technology has been extensively applied in biochemical analysis and medical diagnostics, where precise and efficient control of microfluids is crucial. However, existing passive microfluidic control methods (e.g., microchannels) and active strategies (e.g., optical, thermal, magnetic field, and electrokinetic manipulation) are often hindered by complex device structures and operational uncertainties. Surface acoustic wave (SAW) microfluidic manipulation offers a promising alternative, providing flexible and efficient digital microfluidic control through the modulation of input signals. Nevertheless, the intrinsic hydrophilicity of substrates such as LiNbO 3 results in inefficient microfluidic driving and jetting, primarily due to high surface tension. In this study, we employed chemical vapor deposition (CVD) to coat LiNbO 3 substrates with 1H,1H,2H,2H-Perfluorododecyltrichlorosilane (FDTS) self-assembled monolayers (SAMs), creating hydrophobic surfaces with a contact angle of approximately 120°. In comparison to commercially available Glaco hydrophobic coatings, which reduce SAW amplitude by approximately threefold and increase substrate temperature by up to 1.5 times, FDTS SAMs exhibit negligible impact on SAW properties. Furthermore, when compared to untreated SAW devices, FDTS SAMs-coated devices demonstrated a sixfold increase in droplet driving speed under low power input (e.g., 0.5 W), enabling faster and more precise liquid jetting at velocities reaching 5 m/s. This work highlights the potential of FDTS SAMs in enhancing the performance of SAW-driven microfluidic devices, particularly in applications requiring high-efficiency droplet manipulation. [Display omitted] • Enhanced Microfluidic Performance: FDTS SAMs on LiNbO 3 improve SAW-driven droplet speed sixfold. • Minimal Impact on Device Characteristics: FDTS SAMs preserve SAW amplitude and temperature stability. • Improved Droplet Ejection: FDTS SAMs facilitate smaller droplet ejection with a liquid column speed up to 5 m/s. [ABSTRACT FROM AUTHOR]

• The nature of the back-filler affects the organization of molecular anchor in binary SAMs. • SAM composition results in different water states in the submembrane region of tBLMs. • The choice of back-filler affects the 2D viscosity of the tBLMs. • Long-chain back-fillers in tBLMs enchance sensitivity in pore-forming toxin biosensor. Tethered bilayer lipid membranes (tBLMs) with two different molecular architectures were investigated in the context of their utility for biosensing of pore-forming toxins (PFTs). The different architectures were achieved by using two back-filler molecules of different chain length to act as surface diluents for the molecular anchors [20-tetradecyloxy-3,6,9,12,15,18,22-heptaoxahexatricontane-1-thiol (WC14)] that ensure immobilization of the phospholipid bilayers on a solid conductive (metal, such as gold) support. The back-filler molecules were β-mercaptoethanol (BME) and HS(CH 2) 3 (CH 2 CH 2 O) 5 H thiol (C 3 EO 5 H). In the case of BME, the submembrane space separating solid surface from attached bilayer (typically 1–2 nm thick) is populated with the ice-like, presumably low entropy and low dielectric constant water, however, the water fraction in the submembrane is high. Much bulkier C 3 EO 5 H back-filler renders less space for water in the submembrane, however, it is populated with more mobile water molecules resulting in higher dielectric constant. These two opposing effects result in similar submembrane specific conductances, i.e., the specific electrochemical impedance spectral (EIS) characteristics of the tBLMs and their variation, upon exposure to and reorganization with, the pore-forming toxin (PFT), alpha-hemolysin, occur in the same frequency range for both back-fillers. Significantly, the sensitivity of the C 3 EO 5 H-containing tBLMs to PFT is approximately 7–8 times higher than that of the BME-containing surface constructs. At least two physical phenomena contribute to this difference. The bulkier C 3 EO 5 H back-fillers facilitate the formation of nanoclusters of the molecular anchors, WC14, with cluster sizes ranging from 20 to 120 nm. These highly anchor-clustered, "patchy" tBLMs, consequently exhibit other domains devoid, or nearly so, of anchors, resulting in lowering the tBLM global 2-D viscosity by a factor of 3. Thus, a major conclusion of this study is that lower tBLM 2D fluidity increases the sensitivity of tBLMs to PFTs. [ABSTRACT FROM AUTHOR]

• Mesoionic carbenes (MICs) are used for the first time to modify surfaces. In comparison to NHCs, MICs offer more versatility to immobilize functional groups since they are covalently grafted by click chemistry. • We demonstrate the approach by presenting results with 5 molecules bearing different functional groups, including 3 electroactive ones (no study in this domain features that many substrates). • A wide range of spectroscopic techniques are used: X-ray photoelectron Spectroscopy, infrared Spectroscopy, and even Tip-Enhanced Raman Spectroscopy which provides a local analysis of the surface (once again, no corresponding study has included such a variety of analyses for surface characterization). • The monitoring of MIC grafting as a function of electrode immersion time could be simply performed by cyclic voltammetry. • We demonstrate that reversible exchange reactions are possible between MICs and dodecanethiol on gold surfaces, opening the route for mixed assemblies. Significant progress has been made over the last decades in surface functionalization of coinage metals using thiols and more recently N-heterocyclic carbenes. As shown in this work, mesoionic carbenes (MICs) provide straightforward access to a novel class of surface ligands including electroactive ones and thus materials. Importantly, MICs are easily accessed from triazolium salts (TS) onto which functional groups may be attached with little synthetic effort. Here, we present a library of TS that were further converted, in situ , into MICs and grafted onto gold surfaces. The modified surfaces were thoroughly characterized by advanced spectroscopic methods such as XPS, infrared and Tip-Enhanced Raman Spectroscopy. Through cyclic voltammetry at 100 Vs-1, we could evaluate the surfacic concentration of the grafted molecules for electroactive MICs. We also prepared mixed MIC/thiol self-assembled monolayers, which opens the route to multifunctional surfaces. Triazolium salts bearing redox active or Raman responsive pendant functional arms are easily synthesized through Click Chemistry followed by N3-quaternization. These salts are applied as mesoionic carbene (MIC) precursors for the formation of active self-assembled monolayers (SAMs) on gold surfaces. Ligand grafting on gold was confirmed by cyclic voltammetry (CV), XPS, Raman and TERS spectroscopies. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Neutral impact collision ion scattering spectroscopy (NICISS) is used to measure the energy loss in organic self-assembled monolayers (SAMs) on Au using Ne+ with low kinetic energies from 3 to 5 keV. With increasing film thickness, the energy loss of the projectiles increases because the projectile experiences more collisions with target atoms. Through comparing Monte-Carlo simulations with the NICISS experiments, it was found that contributions from nuclear stopping for Ne+ were significantly larger than for He+ mainly due to the stronger contribution of small-angle scattering of Ne+ making Ne NICISS unsuitable for depth profiling at energies of 5 keV or lower. The measured Ne+ electronic stopping in SAMs is small despite the large atomic number of Ne. Comparing experiments and DFT calculations shows that the latter accurately reproduce stopping powers for Ne+, while SRIM overestimates the stopping power. This contrasts He+ ions, where DFT and SRIM align closely with experiments. [ABSTRACT FROM AUTHOR]

The scanning tunneling microscopy (STM) technique was employed to investigate the adlayer structure and morphology of Self-assembled monolayers (SAMs) fabricated from terphenylmethanethiol (TP1) molecules on Au(111) by preparing from an ethanolic solution at room temperature and subsequently annealed at various temperatures, reaching up to 468 K. Upon heat treatment, the TP1 adlayer exhibited a sequence of distinct structural phases characterized by varying molecular arrangements, namely α, β, γ, δ, ε, σ, and θ, emerging successively for both the as-prepared and annealed samples. The progressive transformation from α → β → γ → δ → ε → σ → α → θ phases, driven by escalating annealing temperatures, entailed a gradual decrease in molecular packing density until the transition from γ → δ, followed by a subsequent increase leading to the formation of the most densely packed molecular network with molecules standing almost upright, referred to as the α phase, which is the same phase observed for non-heat-treated films. Interestingly, the desorption process for the annealed SAMs occurred from the densest packing TP1 molecular structure of the α phase, contrary to those of biphenyl-based organothiol and n -alkanethiol SAMs where desorption takes place from lying-down striped phases. Almost all TP1 molecules were desorbed at an annealing temperature of 468 K, leading to a significant alteration in the surface structure. During the annealing process, our results showed that the gold surface underwent remarkable changes, including the disappearance of the vacancy islands and the emergence of surface cracks in the form of trenches, along with the formation of rounded monoatomic gold islands with a densely packed α phase. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Biodegradable SAMs for supporting stBLM. • Real-time monitoring of electrode modification and stBLM fabrication. • Gramicidin A integrates with membrane and retains its ion-channel function. • EIS and SEIRAS validate membrane integrity. • Potential applications in biomedicine. The utilization of biomimetic membranes supported by advanced self-assembled monolayers is gaining attraction as a promising sensing tool. Biomimetic membranes offer exceptional biocompatibility and adsorption capacity upon degradation, transcending their role as mere research instruments to open new avenues in biosensing. This study focused on anchoring a sparsely tethered bilayer lipid membrane onto a self-assembled monolayer composed of a biodegradable polymer, functionalized with poly(ethylene glycol)-cholesterol moieties, for lipid membrane integration. Real-time monitoring via quartz crystal microbalance, coupled with characterization using surface-enhanced infrared absorption spectroscopy and electrochemical impedance spectroscopy, provided comprehensive insights into each manufacturing phase. The resulting lipid layer, along with transmembrane pores formed by gramicidin A, exhibited robust stability. Electrochemical impedance spectroscopy analysis confirmed membrane integrity, successful pore formation, and consistent channel density. Notably, gramicidin A demonstrated sustained functionality as an ion channel upon reconstitution, with its functionality being effectively blocked and inhibited in the presence of calcium ions. These findings mark significant strides in developing intricate biodegradable nanomaterials with promising applications in biomedicine. [ABSTRACT FROM AUTHOR]

[Display omitted] • ITO surface was modified with 4-nitro benzoic acid (NBA). • NBA induces the dipole layer on the ITO surface. • ITO/NBA shows higher optical transmittance than ITO/PEDOT:PSS substrate. • Photovoltaics device with ITO/NBA substrate showed higher J SC (efficiency) than ITO/PEDOT:PSS. Benefit of small molecule self-assembled monolayers as a buffer layer at the light entering electrode in a photovoltaic device improves the transparency. This results in improved J SC , as a result increased photovoltaics performance. In This work, 4-nitro benzoic acid (NBA) was investigated as an ITO work function modifier, in place of PEDOT:PSS, both in organic and perovskite photovoltaics. Self-assembled monolayer of NBA helps in work function reduction of ITO. Self-assembled monolayer of NBA forms a permanent dipole on the ITO surface consequently increases WF. Using NBA as an ITO work function modifier does not influence the device V OC. From obtained results it is noted that light absorption enhancement is the primary factor for PCE improvement. Results indicates that NBA can be used as work function modifier both in organic–inorganic hybrid perovskite photovoltaics and organic photovoltaics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Optimization of fabrication procedure for high-quality phosphonate SAMs on aluminum. • Phosphate SAMs protect efficiently aluminum substrate from oxidation and degradation. • Phosphate SAMs exhibit much higher hydrolytic and aging stability compared to carboxylates. • Thermal stability limit of phosphate SAMs is by ∼250 K higher compared to carboxylates. Modification of metal oxide surfaces by self-assembled monolayers (SAMs) is attracting growing attention. Carboxylic (CA) and phosphonic (PA) acids are most popular anchoring groups in this context, applied to create hydrophobic coatings, biosensors, and organic field-effect transistors. The efficiency of these devices is crucially affected by the structural quality and stability of the SAM. In this context, we studied the effect of the preparation procedure (solvent, incubation time, and temperature) on the quality of PA SAMs on naturally oxidized aluminum. We demonstrate formation of PA SAMs matching structural quality of archetypical alkanethiols on gold. Next, we compare their stability with analogous CA SAMs. Our data show that PA SAMs not only exhibit much higher hydrolytic stability but are also capable to protect aluminum substrate from oxidation and degradation. Importantly, even small improvement of the PA SAMs quality, translates into enormous increase of their hydrolytic stability crucial for majority of applications. Finally, we demonstrate that the thermal stability of PA on oxidized aluminum is by ∼250 K higher than CA SAMs, and by ∼200 K higher than for thiols on gold, which makes PA SAMs an excellent candidate for organic electronics, where overheating problems and high-temperature fabrication procedures are common issues. [ABSTRACT FROM AUTHOR]

Disposable screen-printed gold electrodes (SPAuEs) are used for the development of numerous immunosensors owing to their ease of modification with biorecognition molecules. A major limitation in the development of SPAuEs based biosensors is the single-use of the electrodes leading to higher costs for sensor development, whereas multiple measurements can affect the sensor stability and reproducibility. Especially, label-free electrochemical impedance spectroscopy (EIS) based SPAuEs sensors are prone to signal drift resulting in false-positive or false-negative data questioning the reliability of the assay. We found that repeated EIS measurements on SPAuEs in ferri- and ferrocyanide solution yielded a significant increase in resistance to charge transfer (R ct) value (positive signal drift) even in a control solution (without the target analyte). The positive signal drift follows the typical pattern of a concentration-dependent calibration curve, rendering repeated measurement error-prone for sensing purposes. In this study, it is shown that the incubation of the SPAuEs in nitrogen purged deaerated phosphate buffered saline (N-PBS) minimized this signal drift in repeated/multiple EIS measurements. This method was then used to develop a peptide-based EIS biosensor for the detection of Vancomycin, a last-line antibiotic used for the treatment of severe multidrug-resistant bacterial infection. This protocol can be followed for the biosensing of other clinically important biomarkers. [Display omitted] • Effect of washing and incubation steps in multiple EIS measurements were evaluated. • Peptide modified screen printed gold electrode showed positive signal drift in multiple EIS measurements. • Incubation of gold electrode in deaerated phosphate buffer minimized this signal drift. • This method is used for label-free detection of vancomycin in 0.5-200 µg/ml. [ABSTRACT FROM AUTHOR]

• Binding energy of 3 polymorphs on thiol self-assembled monolayers is calculated. • Anhydrous theophylline has a larger binding energy than monohydrate form. • Binding energy of l -serine or fumaric acid polymorphs shows no obvious difference. • Experiments verify the performance of binding energy calculations. • Molecular modeling is an effective tool to study the selective crystallization. A screening method for selective polymorphic crystal growth was proposed using molecular modeling as an assistant tool in this work. Three typical pharmaceutical polymorphic crystals which are theophylline, l -serine and fumaric acid were chosen as case studies to investigate their selective growth on self-assembled monolayer (SAM) prepared by depositing 3-mercaptopropionic acid (MPA) on gold. Molecular modeling was applied to analyze the arrangement of MPA molecules on the surface, as well as to value the binding energy between these three crystal faces with MPA SAM. The simulation results were used to predict the effect of SAM on the two dimensional selective growth of the polymorphic crystals, and crystallization experiments were carried out to verify the modeling prediction. The results indicate that MPA SAM can directionally induce the nucleation of polymorphic crystals by geometric and chemical interactions matching. Molecular modeling can be as an effective assistant tool to reveal the matching degree, which can give valuable suggestions on the polymorphic drug design. [ABSTRACT FROM AUTHOR]

This paper describes the electrochemical behaviour of self-assembled monolayers (SAMs) of n-alkanethiolates with Fc groups inserted at 14 different positions along the alkyl chain (SC n FcC 13-n , n = 0–13) studied by cyclic voltammetry. The electronic and supramolecular structures of the SAMs have been fully characterised and all molecules are standing up, allowing for precise control over the position of the Fc unit within the SAM as a function of n revealing the shape of the electrostatic potential profile across the SAMs. The potential profile is highly non-linear due to electronic changes in the nature of the Fc—electrode interaction for small values of n < 5, and supramolecular changes for large values of n = 11–13. For intermediate values of n = 5–11, the potential drop is linear and the data can be fitted to a model developed by White and Smith. The electrochemical behaviour was dominated by a one-step reversible redox-process, but the presence of a shoulder indicates that the Fc units are present in different microenvironments resulting from the mismatch in size between the Fc units and the alkyl chains. Other features, including peak splitting, peak broadening, and peak shifts, can be related to changes in the electronic and supramolecular structure of the SAM revealed by molecular dynamics simulations and spectroscopy. For small values of n < 5, electronic effects dominate and the peak oxidation waves are shifted anodically (∼150 mV) and broadened (full width at half maximum of up to 220 mV) because the Fc units hybridise with the Au electrode (for n < 3) or interact with the Au electrode via van der Waals interactions (n = 4, 5). For intermediate values of n = 5–11, supramolecular effects direct the packing structure of the SAMs and clear odd-even effects are observed. For large values of n = 11–13, the top alkyl chains are liquid-like in character and do not block the Fc units from the electrolyte. [ABSTRACT FROM AUTHOR]

Nickel modified rhodanine (Rh) self-assembled monolayer films (Rh-SAM/Ni) were fabricated on copper from 10.0 mM Rh containing methanol. The films were characterized with the help of scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX) techniques. The methanol oxidation activity of the Rh-SAM/Ni electrode was tested in 1.0 M methanol containing 0.1 M KOH solution using many electrochemical techniques. The results indicated that well-ordered and very homogeneously distributed Rh-SAM films were assembled over the copper surface. The rate of methanol electrooxidation reaction can be enhanced by modifying copper surface with Rh-SAM/Ni multi-layer film. The enhanced activity was related to increasing active sites over the surface for adsorption and oxidation of methanol as well as facilitating oxidation or desorption of adsorpted intermediates of the process. It was suggested that the Rh-SAM layer could be a candidate supporting material for fabricating direct methanol fuel cell (DMFCs) anodes. Adherence, compact and well-assembled Rh-SAM-Ni multilayer films were assembled on copper surface and tested as anode electrode (or substrate) for the oxidation of methanol in alkaline media. Image 1 • Very well-distributed and compact Rh-SAM films were assembled on Cu. • The films were modified by small amount of Ni electrodeposition. • Rh-SAM films enhances oxidation rate of methanol electrooxidation in alkaline media. • Modifying Rh-SAM by deposition of Ni provide superior methanol oxidation activity. • Rh-SAM-Ni multilayer film provides good electrochemical stability and low poisoning effect of CO ads. [ABSTRACT FROM AUTHOR]

Abstract The change in orientation of 2-, 3-, and 4-sulfanylbenzonitrile (SBN) self assembled monolayers (SAMs) with respect to electrochemical potential was studied using surface-enhanced Raman spectroscopy (SERS). Being able to understand monolayer orientation under potential control has important applications in both sensors and molecular electronics, where orientation can affect sensitivity and electron transfer respectively. We characterise the vibrations of all three monolayers using a combination of experimental and density function theory (DFT) calculated spectra. The results reveal that the SERS intensities of both in plane (IP) and out of plane (OOP) modes of the aromatic ring and nitrile group are reversibly changed by potential, indicating an orientation change via variations in the tilt and/or twist angles. At more negative potentials the nitrile group of all three SAMs is more perpendicular to the electrode surface and at more positive potentials it is more parallel, governed by an electrostatic interaction between the nitrile group and the electrode surface. Additional effects of the applied potential are observed for the orientation of the ring with respect to the electrode surface through aromatic ring-surface π interactions, confirmed by examination of the effects of the applied potential on the peak width of the C C ring breathing mode. [ABSTRACT FROM AUTHOR]

Fluoroalkyl thiols and alkyl thiols are widely used as low surface energy reagents for the preparation of superhydrophobic surfaces and corrosion resistant surfaces. Although the corrosion resistance of thiol-induced superhydrophobic surfaces has been well addressed previously, few studies have devoted to revealing the difference of fluoroalkyl thiol and alkyl thiol modified surfaces towards anti-corrosion. In this work, two types of superhydrophobic surfaces were prepared by respectively coating self-assembled monolayers (SAMs) of 1 H,1 H,2 H,2 H-perfluorodecanethiol (PFDT) and 1-dodecanethiol (DDT) on femtosecond laser engineered copper substrates. The formation mechanism of the SAMs was explained by analyzing the surface chemical composition. The water contact angle of the PFDT and DDT modified surfaces were measured to be 157.7° and 154.6°, respectively. Electrochemical tests showed that both SAMs significantly reduced the corrosion current density (I corr) and corrosion rate of the copper surfaces, while simultaneously increased the charge transfer resistance (R ct) value by an order of magnitude compared to the pristine copper surface. The surface with PFDT SAM had the smallest I corr and its R ct value was about 1.5 times larger than that with the DDT SAM. These results confirmed that both the SAMs enhanced the anti-corrosion properties of the copper surfaces, and the PFDT SAM was proved to be more effective. Furthermore, the anti-corrosion durability of the PFDT and DDT modified surfaces were compared after exposing them to salt, acid, and alkali solutions for 12 h, and the results showed that the surfaces maintained to be hydrophobic and anti-corrosive, and the PFDT induced superhydrophobic surface indicated better durability. Our results demonstrated that thiols SAMs could significantly improve the anti-corrosion property of structured metal surfaces, and that fluoroalkyl thiol was more desired for long-term anti-corrosive applications in comparison with alkyl thiol. [Display omitted] • Superhydrophobic surfaces were prepared by laser ablation and thiols self-assembly. • As-prepared superhydrophobic surfaces exhibited excellent corrosion resistance. • Anti-corrosive properties of self-assembled fluoroalkyl and alkyl thiols were compared. • Fluoroalkyl thiol induced surfaces are more desired for long-term anti-corrosion. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is a highly flammable and toxic gas to humans and animals, that's why its detection and monitoring are crucial. A promising technique to develop a robust and cheap gas sensor, operating at room temperature, is Localized Surface Plasmon Resonance (LSPR) sensing. However, LSPR sensing of inorganic gas molecules, such as CO, is challenging due to their extremely small differences in refractive indices. In this work, a nanoplasmonic thin film, composed of Au NPs semi-embedded in a CuO matrix (Au:CuO) was functionalized with a silane self-assembled monolayer (APTES molecule) that enhanced the sensitivity of the film to a mixture of CO (50 ppm) in Argon. Three different concentrations of APTES (0.1 %, 1.0 %, and 5.0 %) were silanized on Au:CuO thin film surface, and all the functionalized Au:CuO thin films showed better sensing results than bare Au:CuO thin film. The functionalized Au:CuO thin film with 0.1 % of APTES revealed the best sensing characteristics. Its sensitivity was almost 3 times higher than that of the unmodified Au:CuO thin film. Au:CuO thin films functionalized with APTES are potentially relevant to developing sensitive and selective LSPR sensors for the detection of inorganic gases such as CO, in harsh environments. • Plasmonic Au nanoparticles in CuO thin film were prepared for gas sensing. • Au:CuO sensor is able to distinguish refractive index changes of inert gases. • Functionalization with APTES monolayers enhance sensitivity to CO. [ABSTRACT FROM AUTHOR]

• Oxazine fluorophores ATTO655, ATTO680 and ATTO700 are electroactive. • ATTO655 exhibits very good performance in E-DNA sensing. • Good ssDNA vs dsDNA discrimination achieved by careful assessment of the ET rate. The electrochemical properties of three oxazine fluorophores, ATTO655, ATTO680 and ATTO700 have been investigated at gold electrodes. They display a reversible or quasi-reversible voltammetric behaviour involving either a 2e−, 2H+ or a 2e−, 1H+ redox process depending on the pH, at a formal potential located in the stability range of thiolate self-assembled monolayers (E°' ≈ −0.33 V vs. Ag|AgCl|3M KCl at pH 7.2). The performance of ATTO655 as redox label for electrochemical nucleic acid sensing was evaluated in a typical E-DNA configuration. The redox label has no detrimental impact on the folding of DNA, as shown with the i-motif forming sequence investigated here. An electron transfer rate constant around 40 s−1 was determined, which is comparable to the values reported for the popular methylene blue label. Hybridisation experiments show a significant signal variation between ssDNA and dsDNA, though it is emphasised that the sign and amplitude of the variation are highly dependent on the electrochemical parameters such as the frequency in square wave voltammetry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of the substituent position on the surface and interface characteristics of dichloro-substituted benzenethiolate SAMs on Au(1 1 1 1) • Structural order and uniformity were highest in the order of 2,4-DCBT, 3,4-DCBT, and 3,5-DCBT SAMs. • Seebeck coefficient (S) increased in the order of 3,4-DCBT (4.6 ± 0.1 μV/K) < 2,4-DCBT (5.0 ± 0.4 μV/K) < 3,5-DCBT (5.2 ± 0.1 μV/K) • The trend of S values was qualitatively consistent with that of the work function change (Δ Φ) of the SAMs. The surface structures, electrochemical behaviors, work function changes, and thermopower of dichloro-substituted benzenethiolate self-assembled monolayers (SAMs) on gold surfaces prepared by vapor deposition were investigated using scanning tunneling microscopy (STM), cyclic voltammetry, Kelvin probe force microscopy, and thermoelectric junction measurements to understand the effects of their substituent positions. STM observations revealed that the adsorption of 2,4-dichlorobenzenethiol (2,4-DCBT) on Au(1 1 1) at 363 K for 1 h led to the formation of short-range ordered domains with a (5 × 6√7)R20° structure, while the SAMs formed at 363 K for 4 h consisted of long-range well-ordered domains with a (√3 × 5) structure. 3,4-Dichlorobenzenethiol (3,4-DCBT) SAMs showed coexistence of partial ordered domains and a disordered phase, while 3,4-DCBT SAMs showed fully disordered phases regardless of deposition time. Moreover, the Seebeck coefficient (S) increased in the order of 3,4-DCBT (4.6 ± 0.1 μV/K) < 2,4-DCBT (5.0 ± 0.4 μV/K) < 3,5-DCBT (5.2 ± 0.1 μV/K). Interestingly, the trend of S values was qualitatively consistent with that of the work function change (Δ Φ) of the SAMs. The reductive desorption behavior, work function shifts, and thermopower of aromatic thiolate SAMs were significantly modified by the structural order and direction of molecular dipoles of dichloro-substituted benzenethiols. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Surface vibrational spectroscopies, PM-IRRAS and SERS, give direct insight into anion binding by self-assembled monolayers. • Three surface-attached, charge neutral diamidocarbazoles were demonstrated to act as sulphate anion receptors. • The relative sulphate binding affinities of the metal-supported receptors were estimated from the PM-IRRAS studies. • Partial hydrolysis of the amide bonds in the surface-attached receptors was observed in aqueous solutions. Abstract In this paper we demonstrate the applicability of surface vibrational spectroscopy techniques in sensing sulphate anions, using self-assembled monolayers of hydrogen bonding receptors. Three uncharged, diamidocarbazole receptors were synthesised and attached to gold and silver surfaces via one or two disulphide arms. Their ability to bind anions on the metal surfaces was investigated with polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and surface enhanced Raman scattering (SERS) spectroscopy. Contrary to other techniques applied in optical sensors, such as UV–vis absorption, fluorescence or surface plasmon resonance, surface vibrational spectroscopy techniques used in this work not only display spectral changes proportional to the concentration of sulphate, but also provide an insight into the state of the receptor monolayer and its interactions with the analyte. While SERS measurements confirm the formation of anion-receptor complexes on metal surfaces, PM-IRRAS spectra were further employed to quantify the optical response of the sensor. The system can detect SO 4 2− anions within a concentration range of 10-6 – 10-1 M (in acetonitrile). An effect of the hydrogen bonds formed at the binding site of the diamidocarbazole molecules on the symmetry of sulphate anions is observed, which ultimately proves the anion-receptor binding. [ABSTRACT FROM AUTHOR]

Abstract A new bioelectronic nose based on a field effect transistor coupled with an aptamer as the sensing element was developed. The gas-to-liquid extraction interface required for appropriate aptamer function was integrated into standard CMOS technology. It was developed with the use of a sacrificial aluminium etching technique combined with surface modifications by silanes for wettability control. As a proof of concept, aptamer Van74 for vanillin was immobilized on the sensitive surface of the ISFET. The developed microsystem can selectively detect vanillin vapor in a concentration range from 2.7 ppt to 0.3 ppm, with a detection limit of 2.7 ppt. The sensor was able to detect vanillin in a gas sample obtained from roasted coffee beans. This outcome provides a foundation for developing a new generation of bioelectronic noses for the detection and discrimination of volatile compounds. Highlights • A novel bioelectronic nose based on the aptamer and ISFET was introduced. • Fabrication of a gas-to-liquid extraction interface was integrated in standard CMOS-technology. • The fabricated bioelectronic nose allowed selective detection of vanillin in coffee aroma. [ABSTRACT FROM AUTHOR]

Abstract Laminin immobilization into diverse biological and synthetic matrices has been explored to replicate the microenvironment of stem cell niches and gain insight into the role of extracellular matrix (ECM) on stem cell behavior. However, the site-specific immobilization of this heterotrimeric glycoprotein and, consequently, control over its orientation and bioactivity has been a challenge that has limited many of the explored strategies to date. In this work, we established an affinity-based approach that takes advantage of the native high affinity interaction between laminin and the human N-terminal agrin (hNtA) domain. This interaction is expected to promote the site-selective immobilization of laminin to a specific substrate, while preserving the exposure of its key bioactive epitopes. Recombinant hNtA (rhNtA) domain was produced with high purity (>90%) and successfully conjugated at its N-terminal with a thiol-terminated poly(ethylene glycol) (PEG) without affecting its affinity to laminin. Self-assembled monolayers (SAMs) of mono-PEGylated rhNtA on gold (mPEG rhNtA-SAMs) were then prepared to evaluate the effectiveness of this strategy. The site-specific immobilization of laminin onto mPEG rhNtA-SAMs was shown to better preserve protein bioactivity in comparison to laminin immobilized on SAMs of thiol-PEG-succinimidyl glutaramide (HS-PEG-SGA), used for the non-selective covalent immobilization of laminin, as evidenced by its enhanced ability to efficiently self-polymerize and mediate cell adhesion and spreading of human neural stem cells. These results highlight the potential of this novel strategy to be used as an alternative to the conventional immobilization approaches in a wide range of applications, including engineered coatings for neuroelectrodes and cell culture, as well as biofunctionalization of 3D matrices. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Functionalization of oxide catalysts with phosphonic acids (PAs) slows dehydrogenation and condensation of alcohols. • PA functionalization of TiO 2 -anatase, CeO 2 and SnO 2 (but not other oxides) enhances alcohol dehydration. • Metal-oxygen bond strength appears to correlate with enhancement of dehydration activity after PA functionalization. Abstract Controlling the near-surface environment of heterogeneous catalysts is of fundamental importance for high selectivity and activity. Self-assembled monolayers (SAMs) are effective tools to control reaction selectivity and activity for both supported noble metal and metal oxide catalysts. We previously demonstrated tunable dehydration activity of alcohols on phosphonic acid-modified, anatase-phase TiO 2. In this work, we investigated the generality of this approach by studying the modification of other metal oxides including Al 2 O 3 , CeO 2 , CuO, Fe 2 O 3 , MgO, rutile-TiO 2 , SnO 2 , V 2 O 5 , WO 3 , ZrO 2 , and ZnO. Modification of these materials with phosphonic acids results in the formation of SAMs on the surface, as determined by infrared spectroscopy; studies of the thermal stability on selected catalysts indicated that the SAMs remained intact up to approximately 400 °C in inert environments. Decomposition of alcohols on these native materials resulted in dehydration, dehydrogenation, and condensation. Upon functionalization with phosphonic acid modifiers, the activity of all pathways decreased significantly, except for dehydration on CeO 2 , anatase-TiO 2 , and SnO 2. We explored the properties of these oxides that may be responsible for this increase in dehydration activity using correlations to bulk properties. This analysis supported the hypothesis that phosphonic acid monolayers act as surface-level dopants for metal oxides of specific metal-oxygen bond strength and oxidation state. [ABSTRACT FROM AUTHOR]

Abstract This paper presents tribological and corrosion properties of perfluoro and alkylphosphonic self-assembled monolayers formed on Ti incorporated carbon coatings. The Ti-DLC incorporated coatings were deposited on Ti6Al4V substrates by Radio Frequency Plasma Enhanced Chemical Vapour Deposition (RF PECVD) method using combination of methane (CH 4) and titanium (IV) isopropoxide (Ti [OCH(CH 3) 2 ] 4) atmospheres. The obtained coatings were subsequently modified by perfluoro and alkylphosphonic self-assembled layers having hydrocarbon or perfluorocarbon chains (DP and PFDP). Presented results show that application of these compounds on the top of Ti-DLC coatings significantly improves their tribological properties. After 1000 m of ball-on-disc test the DP- and PFDP- modified coatings presented low coefficient of friction, showing particularly more stable and lower value in case of PFDP while the unmodified coating was worn out already after 160 m of the test under the same conditions. The corrosion tests show varied results for both modifiers. In the case of PFDP an increased reactivity of the coating is observed, whereas for DP the results prove the anti-corrosive effect of this self-assembled layer. Highlights • Ti-DLC coatings were deposited using Titanium (IV) isopropoxide and CH 4 by RF PECVD method. • Ti-DLC layers were modified by perfluoro and alkylphosphonic self-assembled monolayers. • Corrosion and tribological properties of modified Ti-DLC coatings were examined. • Self-assembled monolayers created on surface of Ti-DLC coating improves its tribologcial and corrosive properties. [ABSTRACT FROM AUTHOR]

Graphical abstract Mixed-solvent precipitation: substrates were immersed in the good solvent of nanoparticles, then poor solvent were continuously dropped into the mixed-solution, after a few minutes, the Self-Assembled Monolayers (Nano-SAMs) were formed on the substrates via nanoparticles precipitation. Highlights • Nanoparticles rapidly form high-coverage and densely-packed Nano-SAMs via this mixed-solvent precipitation method. • Suitable for multiple nanoparticles, regardless of the size and modification of nanoparticle. • Suitable for multiple ultra-flat substrates, regardless of the surface modification and type of substrate. Abstract Nanoparticle self-assembled monolayers (Nano-SAMs) have drawn great attention for their unique applications in many fields such as plasma, surface-enhanced optics, sensors and catalysts. However, how to fabricate high-coverage and densely-packed Nano-SAMs in a limited time is still a challenge, especially for the ultra-thin Nano-SAMs (<10 nm). In this paper, high-coverage and densely-packed ultrathin Nano-SAMs were fabricated by using ultra-small nanoparticles (e.g. nanoclusters and quantum dots) to deposit onto substrates in organic/water mixture via the continuous dropping of organic solvent. Compared with the conventional methods such as the electrophoresis deposition and the soaking method, nanoparticles could formed higher coverage and more densely-packed Nano-SAMs with few defects through a shorter period of time by using this mixed-solvent precipitation method. This mixed-solvent precipitation presents a facile approach to design and construct high-coverage densely-packed Nano-SAMs. [ABSTRACT FROM AUTHOR]

Abstract 3‑Hydroxy‑N‑(5‑mercapto‑1,3,4‑thiadiazol‑2‑yl) benzamide (HMTB) was synthesized and self-assembled on the surface of gold electrode. The self-assembled monolayer of HMTB (Au-HMTB SAM) so formed was electrochemically characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in the presence of K 3 [Fe(CN) 6 ]/K 4 [Fe(CN) 6 ] as a redox couple and found to be well-assembled free from defects and pinholes. Atomic force microscopy (AFM) was used to examine the morphology of Au-HMTB-SAM and confirmed that the molecules of HMTB form dense and well-packed SAM on gold electrode. The Au-HMTB SAM was applied as a platform for impedimetric sensing of various metal ions by measuring R ct values from the fit of Randles circuit. EIS results indicated that Au-HMTB SAM electrode exhibited a selective impedimetric response towards Co2+ over a wide linear concentration range of 1.0 × 10−10 M to 1.0 × 10−4 M (r2 = 0.991 ± 0.054) at pH = 6 with a detection limit of 2.5 × 10−11 M. The impedimetric sensor selectively respond to Co2+ in the presence of diverse interfering ions such as Na+, K+, Mg2+, Ca2+, Ni2+, Cd2+, Cu2+, Hg2+, Zn2+, Pb2+, Ag+, Fe3+ and Cr3+. The sensor has been successfully applied for estimation of cobalt content in different environmental samples such as water, soil and food crops (wheat and rice). The impedimetric cobalt sensor based on Au-HMTB SAM could serve as a simple, reliable and sensitive method for the electrochemical detection of cobalt(II) in other environmental and biological samples. Graphical abstract Unlabelled Image Highlights • HMTB was synthesized and self-assembled on the surface of gold electrode. • Au-HMTB SAM was characterized by using CV, EIS and AFM. • Au-HMTB SAM was successfully applied as a platform for impedimetric sensing of Co2+ • The sensor could sense Co2+ in a wide concentration range of 1 × 10−10 M to 1 × 10−4 M. [ABSTRACT FROM AUTHOR]

Abstract A highly sensitive flow-injection capacitive immunosensor was developed for detection of the mycotoxin zearalenone (ZEN). Different strategies for immobilization of an anti-ZEN antibody on the surface of a gold electrode, i.e. polytyramine or self-assembled monolayers (SAMs) of 3-mercaptopropionic acid (3-MPA) and lipoic acid (LA), were used and their performances were compared. The LA- and 3-MPA-based systems showed broad linear ranges for ZEN determination, i.e. from 0.010 nM to 10 nM and from 0.020 nM to 10 nM, respectively. Under optimal conditions, the LA-based immunosensor was capable of performing up till 13 regeneration-interaction cycles (with use of glycine HCl, pH 2.4) with a limit of detection (LOD) of 0.0060 nM, equivalent to 1.9 pg mL−1. It also demonstrated a good inter-assay precision (RSD < 10%). However, the tyramine-based capacitive immunosensor showed a bad repeatability (only 4 regeneration-interaction cycles were possible) and inter-assay precision (RSD > 15%) which did not allow sensitive and precise measurements. The LA-based method was compared with a direct ELISA. These results demonstrated that the label-free developed capacitive immunosensor had a better sensitivity and shorter analysis time in comparison with the direct microwell-plate format. Graphical abstract fx1 Highlights • Development of a capacitive immunosensor for the detection of zearalenone (ZEN). • Functionalization of a gold electrode by different immobilization strategies. • Determination and comparison of analytical performances of the different immunosensors. • Comparison of the label-free capacitive immunosensor with a direct ELISA. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Mannich reaction was used to functionalize phenolic molecules permitting their surface immobilization. • The strategy did not compromise the phenol functionality and the biological activity of the immobilized molecules. • The modification and the surface immobilization was confirmed by NMR, XPS, and MALDI-TOF MS. • We showed the immobilized molecules can be functional in an enzyme activity assay. Abstract Various phenol-containing molecules such as flavonoids have a wide range of biological effects including anticancer, antimicrobial, and anti-inflammatory properties, and, therefore, they have become subjects of active research for various medicinal and biological applications. To construct applicable materials incorporated with phenol-containing molecules, strategies for immobilization of phenol-containing molecules on solid substrates are required. Although several immobilization methods have been devised and reported, mostly harnessing phenol functionality, however, development of a general immobilization method has been hampered due to its complicated chemical reactions and low reaction yields on surfaces. Furthermore, the use of phenol as a reaction center may compromise the biological activity of phenol-containing molecules. Here, we describe a simple, fast, and reliable method for the surface immobilization of phenol-containing molecules by introducing chemical functional groups, carboxylic acid, thiol, and azide, while maintaining phenol functionality by way of the Mannich-type condensation reaction. We examined the chemical functionalization of naphthol, tyrosine, and flavanone and their immobilization to the self-assembled monolayers on gold via various surface chemistries: the carbodiimide coupling reaction, Michael addition, and the 'click' reaction. We strongly believe our method can be a general and practical platform for immobilization of various phenol-containing molecules on surfaces of various materials. [ABSTRACT FROM AUTHOR]

Abstract In this work, an Au electrode modified with self-assembled monolayers (SAMs) of 3-thienylphosphonic acid (TPA) was used as a novel functional interface to selectively sense dopamine (DA) in the presence of excess ascorbic acid (AA). Ellipsometry, X-ray photoelectron spectroscopic (XPS) and electrochemical measurements proved the immobilization of TPA on the gold surface. Interestingly, the Au electrode modified with TPA substantially improved the antifouling and renewal capabilities towards the oxidation of dopamine (DA) after 15 days of storage in undeoxygenated phosphate buffer solution (PBS pH 7.4). Moreover, the TPA-SAMs modified Au electrode could afford a selective electrochemical response for the DA oxidation in the presence of ascorbic acid (AA). Based on this result, a high sensitive detection limit of 2.0 × 10−7 M for DA could be obtained in the presence of high concentration of AA. Graphical abstract Unlabelled Image Highlights • Modification of Au electrodes with TPA are obtained by self-assembly method. • TPA plays an important role for the determination of DA. • DA can be determined in the presence of AA at TPA/Au electrode. • A high sensitive detection limit for DA can be obtained by TPA/Au electrode. [ABSTRACT FROM AUTHOR]

Abstract Surface modification of zinc oxide (ZnO) plays a crucial role in enhancing the performance of organic photovoltaics (OPVs) due to its structure defect. Herein, methoxyphenylphosphonic acid (MPPA) modifier is introduced for interface engineering to improve the cell performance. The power conversion efficiency (PCE) of 11% has been achieved based on fullerene-free systems together with a breakthrough in current density. We obtain ZnO with reduced surface defect and lower work function after incorporation of MPPA modifier. Moreover, by analyzing dynamics process of solar cells, we discover MPPA modifier promotes the exciton generation, exciton diffusion, exciton dissociation and charge transport with reduced bimolecular recombination and trap-based recombination loss, leading to better power conversion processes. Highlights • MPPA modifier reduced the surface defect of ZnO, leading to a lower work function. • MPPA modifier optimized the morphology of organic active layer. • MPPA modifier reduced bimolecular recombination and trap-based recombination loss. [ABSTRACT FROM AUTHOR]

Graphical abstract Rhodanine self-assembled monolayer (Rh-SAM) films were prepared on copper specimens in different solvents, characterized and applied as corrosion protection agents in 3.5% NaCl solution. Highlights • Rhodanine self-assembled monolayer films were prepared on copper specimens in different solvents. • Compact and homogenously distributed films were assembled on copper surface. • Appearance, electrochemical and physical properties of films depend on preparation conditions. • The best film was obtained in 10 mM after 24 h film formation time when methanol was used as solvent. • The films have very good corrosion inhibition efficiency in 3.5% NaCl solution. Abstract Rhodanine self-assembled monolayer (Rh-SAM) films were prepared on copper specimens in different solvents. The assembled films were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR) and contact angle measurements. The inhibition efficiency of the films against copper corrosion in 3.5% NaCl solution was studied using electrochemical impedance spectroscopy (EIS), potantodynamic polarization (PP) and linear polarization resistance (LPR) techniques. It was found that very well-ordered and almost homogenously distributed Rh-SAM films were assembled on the copper surface. The appearance, electrochemical and physical properties of the films were depending on preparation conditions. The SAM films reduce greatly the corrosion rate of copper in 3.5% NaCl solution. Their protection ability depends on the type of solvent. The best film for this aim was obtained in 10 mM Rh after 24 h film formation time when methanol was used as solvent. The high corrosion protection ability of the films was assigned to the formation of a compact and protective structure over the copper surface. Assembling SAM films of this healthy compound and their application for corrosion protection has not been reported yet and is very original. [ABSTRACT FROM AUTHOR]

C-reactive protein (CRP) is a crucial biomarker of cardiovascular diseases and for its detection both optical and electrochemical techniques were applied. This study concerns the application of DNA aptamer as recognition layer for CRP detection. For that purpose aptamer immobilization method on gold surface was selected and the content of receptor layer was optimized to ensure an efficient binding to target protein. The quality of the monolayer was verified by the application of chronocoulometry and atomic force microscopy. Using thiolated aptamers provided the formation of layers of highest density and stability. The square-wave voltammetry experiments performed in the presence of methylene blue redox indicator revealed a linear response of aptasensor towards CRP in the range from 1 to 100 pM. Moreover, a DNA aptamer – based sensor showed good selectivity towards C-reactive protein in comparison to interfering proteins including BSA and IgE. Finally, the analysis of CRP in serum sample was conducted using the developed aptasensor. [ABSTRACT FROM AUTHOR]

A hexadecane-1,1-bisphosphonic acid monolayer was grafted on the surface of muscovite mica via a simple self-assembled method. The result of AFM showed that the height of the bisphosphonate SAMs was about 2.40 nm, corresponding to both monolayer-like coverage and the hydrocarbon chain length. TOF-SIMS indicated that the reaction between bisphosphonic acid and silicon was took place on the surface of mica substrate. It can be proved from IR, AFM, XPS, and TOF-SIMS that the alkylbisphosphonate SAM was bonded to the mica with the mode of double-tridentate attachment. In addition, organobisphosphonate SAM possessed excellent orderliness and stability, which provides a theoretical basis for its efficient application in the field of organic modification. [ABSTRACT FROM AUTHOR]

Stable functionalization of semiconductor surfaces is a prerequisite for all-semiconductor mid-IR biophotonics. This work demonstrates the adsorption of phosphonic acids on oxygen plasma activated GaSb and InAsSb surfaces. X-ray photoelectron spectroscopy shows that oxygen plasma treatment, used to activate the investigated III–V surfaces, increases the surface oxide layer beyond its native oxide thickness. Phosphonates with different terminal groups, either ethylene glycol or fluorinate carbon terminated groups, allow to modify the hydrophobicity of the surfaces and to protect the surfaces by an anti-fouling cover layer. Infrared spectroscopy indicates partial deprotonation of the phosphonic acid and thus phosphonate bonding to the surfaces. Adsorption of phosphonates on an all-semiconductor mid-IR plasmonic grating structure is detected by a shift and by a shape modulation of the plasmonic resonance peak. Compared with molecule adsorption on flat mirror-like layers a ten-fold signal enhancement is found. The adsorbed molecules are stable upon baking at 120° C, ultrasonic cleaning with organic solvents and storage for several weeks at ambient conditions. These results show that stable functionalization of InAsSb and GaSb surfaces by phosphonate monolayers is possible. All-semiconductor enhanced plasmonic sensing in the mid-IR was demonstrated. [ABSTRACT FROM AUTHOR]

Hybrid organic/inorganic interfaces could pave the way to chemically designed or new multifunctional electronic devices, in particular in the spintronics field where, for instance, the interfacial spin polarization can be tuned through chemical interactions and surface modifications. We report herein, for the very first time, the assays of self-assembled monolayers (SAMs) formation on Mn 5 Ge 3 surface. Interestingly, Mn 5 Ge 3 is a ferromagnetic metal possessing interesting features for spintronics such as a high Curie temperature, a capability to grow epitaxially on Ge germanium that is a key point for integration in the mainstream Si technology. Mn 5 Ge 3 thin films are synthesized by molecular beam epitaxy under ultra-vacuum condition. We studied the Mn 5 Ge 3 surface prior to deposition of SAMs, meaning the surface exposed to air and different solvents, by XPS and contact angle measurements leading to the value of the surface tension of this surface. Then SAMs of octanethiol and perfluorodecanethiol are formed on Mn 5 Ge 3 surface at room temperature. The best experimental conditions to form the SAMs are found for an immersion time of 36 h and a concentration of 4 mM. [ABSTRACT FROM AUTHOR]

In the present paper we describe a simple method to immobilize amino cyclodextrins (CDs) and methylated-amino cyclodextrins on gold surfaces. We also report on the effect that the presence of methyl groups in the broader rim of the cyclodextrin causes on the interaction with the guest molecule bentazon. By means of electrochemical measurements, X-ray photoelectron spectroscopy and contact angle experiments we have demonstrated that the CDs attach covalently to the gold surfaces by amide bond formation and that the CD cavity is oriented opposite to the gold surface. We have shown that methylated-CD/Au modified surfaces are more sensitive towards the recognition of the herbicide bentazon than the non-methylated variants. The association constants for the corresponding interactions of the immobilized CD with the guest molecule have been determined from surface plasmon resonance experiments. The magnitudes of these constants (30.8 ± 1.0 M −1 and 80.5 ± 4.2 M −1 for amino-CD and methylated-amino cyclodextrins, respectively) are consistent with the change of hydrophobicity caused by methyl groups. The results demonstrate the feasibility of using CD-gold modified surfaces to encapsulate herbicides such as bentazon within the macrocyclic receptor without necessity of carrying out the experiments in solution. [ABSTRACT FROM AUTHOR]

Analytical expressions describing the electrochemical impedance spectrum of a metallic electrode modified with an acid thiol monolayer, that undergoes a potential-induced proton transfer, have been derived from an electrostatic model of the interface. The frequency dispersion of the electrode impedance is described by an equivalent circuit that bears some similarities with that associated with a surface redox process. Good agreement is found between the theoretical predictions and the impedance of a Au(111) electrode modified with a 11-mercaptoundecanoic monolayer recorded as a function of ac frequency, dc potential and surface concentration of electrochemically active carboxylic groups. The same thermodynamic and kinetic parameter values are obtained from independent analysis of the voltammetric and impedimetric responses, except in the case of the reorganization energy for proton transfer, which seems to be affected by a slow potential-induced reorientation and dissociation of the external acid groups of the monolayer. [ABSTRACT FROM AUTHOR]

The fabrication of hybrid nanoassemblies involving sulfure-modified photochromic derivatives (SMPDs) on the gold nanoparticles (AuNPs) was carried out to investigate the influence of AuNPs surface plasmons on the SMPDs photoisomerization. The size of the AuNPs obtained was <30 nm in average diameter. Upon irradiation by alternating UV and Vis light, a reversible photochemical isomerization along with bathochromic shift in the absorption band takes place on the surface of the AuNPs in analogy with free SMPDs in solutions. Furthermore, in some cases a significant quenching of photochromic reactivity was observed due to the excited energy transfer from the photochromic molecules to the AuNPs core. [ABSTRACT FROM AUTHOR]

We demonstrate mirror-finished superhydrophobic aluminum surfaces fabricated via the formation of anodic alumina nanofibers and subsequent modification with self-assembled monolayers (SAMs). High-density anodic alumina nanofibers were formed on the aluminum surface via anodizing in a pyrophosphoric acid solution. The alumina nanofibers became tangled and bundled by further anodizing at low temperature because of their own weight, and the aluminum surface was completely covered by the long falling nanofibers. The nanofiber-covered aluminum surface exhibited superhydrophilic behavior, with a contact angle measuring less than 10°. As the nanofiber-covered aluminum surface was modified with n-alkylphosphonic acid SAMs, the water contact angle drastically shifted to superhydrophobicity, measuring more than 150°. The contact angle increased with the applied voltage during pyrophosphoric acid anodizing, the anodizing time, and the number of carbon atoms contained in the SAM molecules modified on the alumina nanofibers. By optimizing the anodizing and SAM-modification conditions, superhydrophobic behavior could be achieved with only a brief pyrophosphoric acid anodizing period of 3 min and subsequent simple immersion in SAM solutions. The superhydrophobic aluminum surface exhibited a high reflectance, measuring approximately 99% across most of the visible spectrum, similar to that of an electropolished aluminum surface. Therefore, our mirror-finished superhydrophobic aluminum surface based on anodic alumina nanofibers and SAMs can be used as a reflective mirror in various optical applications such as concentrated solar power systems. [ABSTRACT FROM AUTHOR]

Assembling monolayers between ITO electrode and the overlying organic layers is an important way to obtain high-performance organic light-emitting diodes (OLEDs). Herein, self-assembling monolayers (SAMs) based on pentafluorobenzylphosphonic acid (F 5 BPA) and heneicosafluorododecylphosphonic acid (HF 21 DPA) were formed on ITO surfaces. The work function of ITO was elevated from 4.82 eV to 5.20 eV and 5.81 eV by introduction of F 5 BPA and HF 21 DPA, respectively, which could facilitate hole transport into the device, and therefore improve charge balance in OLEDs. In addition, the water contact angles of ITO also increased from 46.45° to 87.09° and 110.6°, respectively, which could contribute to better-matched interfacial surface energy, and prevent the interface incompatibility. The surface properties of ITO after modification were also studied by using X-ray photoelectron spectroscopy, atomic force microscope and UV–visible spectra measurements. Besides, compared with the OLEDs using bare ITO anodes, the SAM-modified devices showed improved brightness (29245.49 cd/m 2 ), higher luminous efficiency (6.09 cd/A), and smaller turn-on voltage (2.8 V). This promising approach provides a simple route for the fabrication of highly efficient OLEDs. [ABSTRACT FROM AUTHOR]

A comprehensive experimental investigation of the influence of the chain length on the electric field induced proton transfer at α,ω-mercaptoalkanecarboxylic acids self-assembled monolayers (SAMs) is conducted by means of voltammetric and electrochemical impedance spectroscopic measurements. The chain length has a significant impact on the total protonation/deprotonation charge and on the kinetics of the phenomenon. The results are discussed in light of existing theoretical models describing this electric field driven protonation/deprotonation process. Characteristic proton transfer frequencies were independently determined by impedance spectroscopy and by scan rate dependent voltammetric analyses. The two types of measurements are in mutual agreement and show that the protonation/deprotonation slows down as the chain length increases. [ABSTRACT FROM AUTHOR]

Thin polycrystalline copper films of low surface roughness and low electrical resistivity were deposited by physical vapor deposition onto mica at room temperature and in thicknesses ranging from 10 to 80 nm. The crystalline orientation of the films was mainly in the [111] direction, with a surface roughness of under 8.0 nm for thicker films. The copper films were coated with dodecanethiol (DDT), CH 3 (CH 2 ) 10 HS by direct immersion into a millimolar solution of the molecules in ethanol for 20 h. Self-Assembled monolayers (SAMs) formation was observed based on XPS studies. The results showed that DDT-SAMs were an effective barrier against the oxidation of the metallic surface, and the resistivity increased between 15% and 70% over the bulk value, depending on the film thickness. [ABSTRACT FROM AUTHOR]

Self-assembled monolayers (SAMs) of N-heterocyclic carbenes (NHCs) on metal substrates are currently one of the most promising systems in context of molecular-scale engineering of surfaces and interfaces, crucial for numerous applications. Interest in NHC SAMs is mainly driven by their assumingly higher thermal stability compared to thiolate SAMs most broadly used at the moment. Most of the NHC SAMs utilize imidazolium as an anchoring group for linking molecules to the metal substrate via carbene C atom. It is well established in the literature that standing up and stable NHC SAMs are built only when using bulky side groups attached to nitrogen heteroatoms in imidazolium moiety, which, however, leads to monolayers exhibiting much lower packing density compared to thiolate SAMs. Here, by combined X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and temperature-programmed secondary ion mass spectrometry analysis, we demonstrate that using NHCs with small methyl side groups in combination with simple, solution-based preparation leads to the formation of aromatic monolayers exhibiting at least doubled surface density, upright molecular orientation, and ultra-high thermal stability compared to the NHC SAMs reported before. These parameters are crucial for most applications, including, in particular, molecular and organic electronics, where aromatic SAMs serve either as a passive element for electrode engineering or as an active part of organic field effect transistors and novel molecular electronics devices. [Display omitted] • Extraordinary high thermal stability of NHC SAMs by a suitable molecular design. • Upright molecular orientation in NHC-SAMs for the maximum impact of surface functionalization. • NHC SAMs with exceptionally high packing density for efficient surface engineering. [ABSTRACT FROM AUTHOR]