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To probe the effects of deposition temperature on the formation and structural order of self-assembled monolayers (SAMs) on Au(111) prepared by vapor deposition of 2-(2-methoxyethoxy)ethanethiol (CH3O(CH2)2O(CH2)2SH, EG2) for 24 h, we examined the surface structure and electrochemical behavior of the resulting EG2 SAMs using scanning tunneling microscopy (STM) and cyclic voltammetry (CV). STM observations clearly revealed that EG2 SAMs vapor-deposited on Au(111) at 298 K were composed of a disordered phase on the entire Au surface, whereas those formed at 323 K showed improved structural order, showing a mixed phase of ordered and disordered phases. Moreover, at 348 K, uniform and highly ordered EG2 SAMs on Au(111) were formed with a (2 × 3√3) packing structure. CV measurements showed sharp reductive desorption (RD) peaks at −0.818, −0.861, and −0.880 V for EG2 SAM-modified Au electrodes formed at 298, 323, and 348 K, respectively. More negative potential shifts of RD peaks with increasing deposition temperature are attributed to an increase in van der Waals interactions between EG2 molecular backbones resulting from the improved structural quality of EG2 SAMs. Our results obtained herein provide new insights into the formation and thermally driven structural order of oligo(ethylene glycol)-terminated SAMs vapor-deposited on Au(111). [ABSTRACT FROM AUTHOR]

Molecular diodes usually exhibit fixed current values at a specific bias and achieve sizable rectification ratio (RR) at voltages of ≈1.0 V. Here, a series of custom‐designed molecular films of ferrocenyl/ruthenocenyl‐substituted biphenylthiolates and fluorenethiolates on Au (111) is presented, which exhibit a distinctly different behavior. When embedded into two‐terminal junctions, they show two different conduction states, with a high conductivity state at a negative bias and a low conductivity state upon applying a sufficiently high positive bias. Comparing the current values for these two states, an effective RR of more than 1000 is obtained, a value comparable to the best performing molecular diodes but attained already at particularly low voltages. Significantly, the switching between the conduction states is reversible and the initial, high conductivity state can be recovered by the application of a negative bias. The proposed explanation for these observations is the bias‐induced switching of the junction to a metastable state comprising oxidized ferrocenyl/ruthenocenyl entities, which are characterized by less delocalized frontier orbitals and cause the formation of a significant potential barrier within the junction. It is hypothesized that this state can be stabilized by structural changes in the monolayers, affecting also their coupling to the top electrode. [ABSTRACT FROM AUTHOR]

For organic thin‐film transistors (OTFTs) made of solution processed stacks of organic semiconductor and dielectric materials, it is a grand challenge to eliminate the leakage current paths. With a top‐gate bottom‐contact structure, this work introduces a strong dipole interfacial layer made of self‐assembled monolayer (SAM) molecules at metal‐semiconductor contacts to suppress minority carrier injection for low leakage and stable operation, while not affecting majority carrier injection. Both gate insulator (GI) leakage and parasitic leakage in the device architecture are also effectively suppressed with a sputtering‐resistant polymer GI layer and photolith patterned OSC islands, respectively. The devices present a decent mobility with a typical value of 1.98 cm2 V–1 s–1, record‐low leakage current at 10–18 A µm−1 and large ON/OFF ratio (>1010) in a wide gate voltage range (100 V), reaching the theoretical limit and also the best level of inorganic counterparts despite much lower processing temperature (120 °C). Manufacturability of the material stack is verified on a 200 mm × 200 mm substrate and the fabricated 4.7 in. active‐matrix organic light‐emitting diode display, integrating more than 150 000 OTFTs, can be operated at ultra‐low frame‐rate (0.1 Hz) for power saving. [ABSTRACT FROM AUTHOR]

A high-performance indium oxide (In2O3)-based thin-film transistor (TFT) was prepared with aluminum oxide/fluorinated self-assembled monolayer (Al2O3/F-SAM) double-gate dielectric layer. The Al2O3/F-SAM double gate dielectric layer improved the performance of the In2O3-based TFT by reducing the device leakage current. In addition, devices with a double-gate dielectric layer show improved stability under negative bias stress testing compared to devices with a single gate dielectric layer (Al2O3), shifting a threshold voltage by only 0.4 V. These results suggest that the Al2O3/F-SAM double-layer gate dielectric layer can enhance the performance of In2O3-based TFTs. Furthermore, it can be used to improve the performance of other metal oxide-based devices by minimizing the leakage current at low operating voltages at low cost. [ABSTRACT FROM AUTHOR]

Cleavage of DNA at noncanonical recognition sequences by restriction endonucleases (star activity) in bulk solution can be promoted by global experimental parameters, including enzyme or substrate concentration, temperature, pH, or buffer composition. To study the effect of nanoscale confinement on the noncanonical behaviour of BamHI, which cleaves a single unique sequence of 6 bp, we used AFM nanografting to generate laterally confined DNA monolayers (LCDM) at different densities, either in the form of small patches, several microns in width, or complete monolayers of thiol-modified DNA on a gold surface. We focused on two 44-bp DNAs, each containing a noncanonical BamHI site differing by 2 bp from the cognate recognition sequence. Topographic AFM imaging was used to monitor end-point reactions by measuring the decrease in the LCDM height with respect to the surrounding reference surface. At low DNA densities, BamHI efficiently cleaves only its cognate sequence while at intermediate DNA densities, noncanonical sequence cleavage occurs, and can be controlled in a stepwise (on/off) fashion by varying the DNA density and restriction site sequence. This study shows that endonuclease action on noncanonical sites in confined nanoarchitectures can be modulated by varying local physical parameters, independent of global chemical parameters. [ABSTRACT FROM AUTHOR]

Polymer and carbon nanotube composites have aroused extensive attention for thermoelectric materials owing to the combination of low thermal conductivity of polymer and high electrical conductivity of carbon nanotubes. Surface properties of the substrate are of great importance for the charge transport behaviors of semiconducting thin films, which are less explored in thermoelectric applications. Herein, self‐assembled monolayers (SAMs) are used to modify the substrate for thermoelectric polymer composites. The trifluoromethyl (CF3)‐terminated SAM is beneficial for an improved electrical conductivity; while the SAM with amino group is found to improve their Seebeck coefficient and decrease the electrical conductivity. As a result, polymer composites on CF3‐SAM‐modified substrate show a high room‐temperature power factor of 285 µW m−1 K−2 and a large output power of 2.36 µW for thermoelectric generator at a temperature gradient of 50 K. This work demonstrates that surface modification by SAMs is a promising strategy for improving performance of thermoelectric materials and devices. [ABSTRACT FROM AUTHOR]

Bacterial infections due to biofilms account for up to 80% of bacterial infections in humans. With the increased use of antibiotic treatments, indwelling medical devices, disinfectants, and longer hospital stays, antibiotic resistant infections are sharply increasing. Annual deaths are predicted to outpace cancer and diabetes combined by 2050. In the past two decades, both chemical and physical strategies have arisen to combat biofilm formation on surfaces. One such promising chemical strategy is the formation of a self-assembled monolayer (SAM), due to its small layer thickness, strong covalent bonds, typically facile synthesis, and versatility. With the goal of combating biofilm formation, the SAM could be used to tether an antibacterial agent such as a small-molecule antibiotic, nanoparticle, peptide, or polymer to the surface, and limit the agent's release into its environment. This review focuses on the use of SAMs to inhibit biofilm formation, both on their own and by covalent grafting of a biocidal agent, with the potential to be used in indwelling medical devices. We conclude with our perspectives on ongoing challenges and future directions for this field. [ABSTRACT FROM AUTHOR]

Polymer solar cell (PSC) has been developed vastly in the past decade due to the advantages of low cost, lightweight, mechanical flexibility, versatility of chemical design and synthesis, semitransparency, and solution processing. The performance and lifetime of PSCs are highly dependent on the properties of both active materials and their interfaces. The combination of the versatility of organic chemistry and the multitude of well‐understood ligand–metal interactions allows self‐assembled monolayers (SAMs) of organic molecules to direct control over the electronic and chemical properties at the inorganic–organic interfaces. Thus, SAMs are an attractive pathway to reconcile interfaces with tunable interface properties in PSCs. Hence, this review describes the application of SAMs in PSCs at different interfaces. First, SAMs as alternatives of traditional transporting materials to reduce the barrier at indium tin oxide (ITO)/active layer interface due to the ability of tuning work function of ITO electrode are discussed. Second, the modifications of metal oxide by SAMs to control the electrical contacts at transporting layer/active layer interface are described. Third, tailoring the properties of the donor/acceptor interface by SAMs to improve the performance of PSCs are summarized. Finally, perspectives and challenges are pointed out for developing highly stable and high‐performance PSCs by applying SAMs. [ABSTRACT FROM AUTHOR]

In recent years, area‐selective atomic layer deposition (AS‐ALD) has attracted increasing interest for its applications in back‐end interconnect processes, and selective deposition of Al2O3 is of particular interest because Al2O3 can serve as an etch hard mask. However, Al2O3 is one of the most difficult ALD systems to block. In this work, a strategy is presented to enhance the blocking ability of dodecanethiol (DDT) self‐assembled monolayers (SAMs) against Al2O3 ALD. It is shown that by conducting DDT deposition on a slightly oxidized Cu surface, which is mainly composed of Cu2O, rather than on a freshly acid‐etched Cu surface, which mainly consists of metallic Cu, the quality of the DDT SAM can be improved. It is further shown that the DDT SAMs formed on Cu2O‐covered Cu substrates are about 3–4 times more effective in blocking Al2O3 than that on acid‐etched Cu surfaces when ALD is performed under subsaturation condition. However, as the Cu oxidation process continues, CuO is formed and the blocking ability of DDT degrades. Finally, selective Al2O3 deposition on DDT‐treated Cu/low‐k patterns using the combined strategy of Cu oxidation and subsaturation conditions achieves selectivity of 0.99 after 4 nm of Al2O3 ALD. [ABSTRACT FROM AUTHOR]

We report here a facile method of modulating the lengthscales of self-organized dewetting of polystyrene thin films by varying the extent of silane grafting on the substrate. The self-assembled monolayers (SAM) of octadecyltrichlorosilane (OTS) were grafted on glass substrates by exposing them to different doses of OTS vapors in a controlled, low pressure environment. Measurement of water contact angles on the modified glass surfaces showed that the contact angles could be continuously increased from 40° to 70° by increasing the time of exposure to the OTS vapors from a few minutes to several hours. Polystyrene (PS) thin films were spin coated on the modified glass substrates and water-solvent mixture induced dewetting of the PS thin films was carried out, where the dewetting kinetics depended on the spreadability of water on the surface. We observed a reduction in the length scales of the dewetting, i.e. the wavelength of instability (λ) and droplet size (d), by increasing the extent of OTS exposure. The λ for a 50 nm thick PS film decreased from 12 to 4 µm while the droplet diameter (d) also decreased, from 2.5 to 1.6 µm. [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]

This paper presents an investigation of atomic force microscopy (AFM) in the force-distance mode for self-assembled monolayers (SAM) by means of molecular dynamics modeling methods. A model system of SAM of biphenyldithiol (BPDT) on a gold substrate and a gold tip with a diameter of 10 nm were used. This work has reproduced the general behavior of force–distance curves in similar systems observed in experimental studies. The impact of the structural order (i.e., standing up ordered, disordered and striped phases) on the attractive and repulsive molecular interactions and conformations were revealed. The ordered SAM in standing up phase has the highest adhesive force and the striped phase has the lowest. The adhesive forces as a function of the tip-surface distance exhibit some unique and distinct features. An AFM induced ordering for both disordered and striped phases is reported. [ABSTRACT FROM AUTHOR]

Self-assembled monolayers (SAMs) are emerging as materials that are candidates of barriers used in back-end-of–line interconnects of integrated circuits for future generations. In this study, SAMs were formed on the SiO2 and porous SiOCH (p-SiOCH) films by using decyltrimethoxysilane (DTMOS) precursor in vapor phase at a temperature of 100 °C. The effects of the formation of SAMs at the surfaces of SiO2 and p-SiOCH films on the electrical characteristics were characterized and compared. With O2 plasma irradiation, SAMs could successfully form on both SiO2 and p-SiOCH films, thereby enhancing the adhesion and dielectric breakdown field. In the p-SiOCH films, SAMs sealed the surface pores and had higher coverage, promoting the effectiveness of the Cu barrier. In the Cu/porous low-k integrated interconnects for advanced technological nodes, therefore, SAMs are promising emerging materials acting as a barrier and adhesive. On the other hand, for SiO2 films, SAMs weakened the barrier; however, they can act as an interfacial adhesion enhancer. [ABSTRACT FROM AUTHOR]

Focused electron beam-induced processing is a versatile method for the fabrication of metallic nanostructures with arbitrary shape, in particular, on top of two-dimensional (2D) organic materials, such as self-assembled monolayers (SAMs). Two methods, namely electron beam-induced deposition (EBID) and electron beam-induced surface activation (EBISA) are studied with the precursors Fe(CO)5 and Co(CO)3NO on SAMs of 1,1′,4′,1′′-terphenyl-4-thiol (TPT). For Co(CO)3NO only EBID leads to deposits consisting of cobalt oxide. In the case of Fe(CO)5 EBID and EBISA yield deposits consisting of iron nanocrystals with high purity. Remarkably, the EBISA process exhibits a strong time dependence, which is analyzed in detail for different electron doses. This time dependence is a new phenomenon, which, to the best of our knowledge, was not reported before. The electron-induced cross-linking of the SAM caused by the cleavage of C–H bonds and the subsequent formation of new C–C bonds between neighboring molecules also seems to play a crucial role in the EBISA process. Previous studies showed that iron nanostructures fabricated on top of a cross-linked SAM on Au/mica can be transferred to solid substrates and grids without any changes, aside from oxidation. Here we demonstrate that iron as well as cobalt oxide structures on top of a cross-linked SAM on Ag/mica do change more significantly. The Fe(NO3)3 solution used for etching of the Ag layer also dissolves the cobalt oxide structures and causes dissolution and reduction of the iron structures. These results demonstrate that the fabrication of hybrids of metallic nanostructures onto organic 2D materials is an intrinsically complex procedure. The interactions among the metallic deposits, the substrate for the growth of the SAM, and the associated etching/dissolving agent need to be considered and further studied.

Abstract Surface‐anchored metal‐organic frameworks (surMOFs) integrate nanoporous supramolecular MOF materials directly into architectures for applications such as gas storage, chemical sensing, and energy storage. Layer‐by‐layer solution‐phase deposition of the MOF‐14 components (1,3,5‐tris(4‐carboxyphenyl)benzene and copper (II) dimers, respectively) produces a porous and conformal film on carboxyl‐terminated self‐assembled monolayers (SAMs). In this research, the formation of ultrathin (less than 25 nm) surMOF films on codeposited bicomponent SAMs and microcontact printed SAMs is investigated by atomic force microscopy, ellipsometry, infrared spectroscopy, and contact angle goniometry. SAMs composed of methyl‐terminated alkanethiols assembled on gold substrates inhibit surMOF formation, whereas carboxyl‐terminated alkanethiols promote MOF‐14‐based film growth. To tune the density of carboxyl groups that anchor the film, methyl‐ and carboxyl‐terminated alkanethiols of varying concentrations are codeposited on gold. This systematic study demonstrates how surMOF film formation and morphology are impacted by these SAMs with mixed surface functionalities. Chemical patterning methods for SAMs, such as microcontact printing (μCP), commonly have mixed chemical functionalities within certain regions of the pattern. Insights gained regarding how mixed surface functionalities affect surMOF film formation are applied herein to optimize the μCP method to produce chemically patterned SAMs that selectively direct surMOF assembly to produce high‐quality surMOF film features.

We map buried hydrogen-bonding networks within self-assembled monolayers of 3-mercapto-N-nonylpropionamide on Au{111}. The contributing interactions include the buried S-Au bonds at the substrate surface and the buried plane of linear networks of hydrogen bonds. Both are simultaneously mapped with submolecular resolution, in addition to the exposed interface, to determine the orientations of molecular segments and directional bonding. Two-dimensional mode-decomposition techniques are used to elucidate the directionality of these networks. We find that amide-based hydrogen bonds cross molecular domain boundaries and areas of local disorder.

Translating sticky biological molecules-such as mussel foot proteins (MFPs)-into synthetic, cost-effective underwater adhesives with adjustable nano- and macroscale characteristics requires an intimate understanding of the glue's molecular interactions. To help facilitate the next generation of aqueous adhesives, we performed a combination of surface forces apparatus (SFA) measurements and replica-exchange molecular dynamics (REMD) simulations on a synthetic, easy to prepare, Dopa-containing peptide (MFP-3s peptide), which adheres to organic surfaces just as effectively as its wild-type protein analog. Experiments and simulations both show significant differences in peptide adsorption on CH3-terminated (hydrophobic) and OH-terminated (hydrophilic) self-assembled monolayers (SAMs), where adsorption is strongest on hydrophobic SAMs because of orientationally specific interactions with Dopa. Additional umbrella-sampling simulations yield free-energy profiles that quantitatively agree with SFA measurements and are used to extract the adhesive properties of individual amino acids within the context of MFP-3s peptide adhesion, revealing a delicate balance between van der Waals, hydrophobic, and electrostatic forces.

The surface functionalization of oxide-free hydrogen-terminated silicon (Si−H) enables predictably tuning its electronic properties, by incorporating tailored functionality for applications such as photovoltaics, biosensing and molecular electronics devices. Most of the available chemical functionalization approaches require an external radical initiator, such as UV light, heat or chemical reagents. Here, we report forming organic monolayers on Si–H surfaces using molecules comprising terminal alcohol (–OH) groups. Self-assembled monolayer (SAM) formation is spontaneous, requires no external stimuli–and yields Si–O–C covalently bound monolayers. The SAMs were characterized by X-ray photoelectron spectroscopy (XPS) to determine the chemical bonding, by X-ray reflectometry (XRR) to determine the monolayers thicknesses on the surface and by atomic force microscopy (AFM) to probe surface topography and surface roughness. The redox activity and the electrochemical properties of the SAMs were studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The availability and the ease of incorporating OH groups in organic molecules, makes this spontaneous grafting as a reliable method to attach molecules to Si surfaces in applications ranging from sensing to molecular electronics where incorporating radical initiator setups is not accessible.

The wide use of copper is limited by its rapid oxidation. Main oxidation mitigation approaches involve alloying or surface passivation technologies. However, surface alloying often modifies the physical properties of copper, while surface passivation is characterized by limited thermal and chemical stability. Herein, we demonstrate an electrochemical approach for surface‐anchoring of an N‐heterocyclic carbene (NHC) nanolayer on a copper electrode by electro‐deposition of alkyne‐functionalized imidazolium cations. Water reduction reaction generated a high concentration of hydroxide ions that induced deprotonation of imidazolium cations and self‐assembly of NHCs on the copper electrode. In addition, alkyne group deprotonation enabled on‐surface polymerization by coupling surface‐anchored and solvated NHCs, which resulted in a 2 nm thick NHC‐nanolayer. Copper film coated with a NHC‐nanolayer demonstrated high oxidation resistance at elevated temperatures and under alkaline conditions. [ABSTRACT FROM AUTHOR]

First-principles calculations were carried out to study the structural and electronic properties of hydrocarbon chains of self-assembled monolayers with hydrogen dissociation. It was found that the incoming hydrogen could lead to the formation of H2 molecules by stripping the nearby hydrogen atoms in the chains and thereby leave the neighboring carbon atoms to be free radicals. Two parallel hydrocarbon chains with dangling bonds can form a direct C-C bond, i.e., cross-linking happens between the two chains, which is ascribed to a charge accumulation in the cross-linking region. The polymerization of short molecules into long hydrocarbon chains through a different cross-linking mode is also discussed. [ABSTRACT FROM AUTHOR]

BACKGROUND: There is a lack of perfect vascular system in tissue-engineered bone, among which vascularization is the key to limit its wide application. Appropriate matrix chemistry and fluid shear stress stimulation can promote the proliferation, differentiation and function of vascular endothelial cells, and guide the design and fabrication of scaffold materials. OBJECTIVE: To explore the effects of different chemical functional groups and fluid shear stress （FSS） on human umbilical vein endothelial cells, in order to find an efficient combination of material chemistry and fluid shear stress on human umbilical vein endothelial cells. METHODS: Self assembled monolayers with OH,CH3 and NH2 as end functional groups were prepared as matrix materials and blank glass as control.Human umbilical vein endothelial cells were seeded on the surface of four groups of glasses.The release of ATP within 15 minutes after culture and NO within 1 hour after culture was detected.The expression of endothelial nitric oxide synthase protein was detected by western blotting. The formation of focal adhesion and F-actin was observed by laser confocalicro scopy. Human umbilical vein endothelial cells were seeded on the surface of four groups of glasses. When the cells fused to 80%,they were loaded with 1.5 N/m² FSS for 1 hour. ATP release was detected within 15 minutes after loading, and NO release was detected within 1hour after loading. The expression of endothelial nitric oxide synthase was detected by western blotting after loading for 1 hour. RESULTS AND CONCLUSION:（1） Chemical stimulation had no effect on the release of ATP or NO, but FSS could increase the release of ATP and NO, and the expression of endothelial nitric oxide synthase. When FSS and material chemistry acted simultaneously, the expression of ATP and NO was closely related to material chemistry. The release of ATP and NO and the expression of endothelial nitric oxide synthase were highest in NH2-FSS group, followed by FSS group, and those in the CH3-FSS and OH-FSS groups were lowest.（2） Laser confocal microscope showed that a large number of focal adhesions and cytoskeleton protein F-actin could be detected in the NH2 group, followed by control group; those were least in the CH3 and OH groups.（3） The results showed that the combination of NH2 functional group and FSS produced high-efficiency response to shear stress, and the mechanism may be the formation of optimal focal adhesion and F-actin on NH2 surface [ABSTRACT FROM AUTHOR]

Photoresponsivity is a fundamental process that constitutes optoelectronic devices. In molecular junction devices, one of the most adopted strategies is to employ photoactive molecules that can undergo conformational change upon light illumination as the conduction channel. However, such devices suffer from their relatively low photoresponsivity, long switching time, and unidirectional switching. In this study, the authors employed organohalide perovskite (OHP)/graphene heterojunction as a photoactive electrode that acted a source of photo‐generated carriers collected as photocurrent in self‐assembled monolayer (SAM)‐based molecular junctions. This hybrid device architecture of perovskite/graphene/SAM allows the molecular junctions to attain a high photoresponsivity with molecules that have intrinsically little photoresponse. The authors elucidate the role of the molecular SAM in enhancing the photoresponsivity by systematically examining the transport and charge transfer processes at the graphene/SAM interface via molecules with different intrinsic dipole moments. This, corroborated with a theoretical analysis, reveals the origin of the observed photoresponsivity as light‐induced coupling between the SAM and the OHP/graphene electrode within the orbital‐mediated resonant tunnelling transport regime. These findings advance the understanding of photo‐induced charge transport in molecular junctions with heterointerfaces, providing a road‐map for designing high‐performance molecular optoelectronic devices based on hybrid device architecture. [ABSTRACT FROM AUTHOR]

Previous work (Manzi et al. in Tribol Lett 69:147, 2021) proposed a tip–molecular interaction for calculating the friction of organic overlayers that consisted of a parabolic potential that extended to some cut-off distance when the energy reached a value of E sld 0 , which represents an activation barrier for the detachment of the tip from the molecular terminus. A proposed advantage of such a potential was that it could be coupled to other degrees of freedom of the system. A method for accomplishing this is described here for the interaction between a tip and a compliant molecular chain to model the velocity, temperature, and chain-length dependences of the friction force. Analytical equations are derived for constant force sliding, such as in a ball-on-flat tribometer, and for compliant sliding, such as in an atomic force microscopy (AFM) experiment. The analytic models provided good fits to the chain-length dependence of the friction of carboxylate self-assembled monolayers (SAMs) on copper measured in an ultrahigh vacuum tribometer as part of this work and for alkyl thiolate SAMs on gold measured by an AFM taken from the literature. The results indicate that the commonly observed decrease in friction with increasing chain length has a component that is due to geometrical effects, as well as the possible participation of interchain van der Waals’ interactions that are commonly invoked as being responsible for the friction reduction. [ABSTRACT FROM AUTHOR]

Herein, we report a combined strategy encompassing electrochemical and X-ray photoelectron spectroscopy (XPS) experiments to investigate self-assembled monolayer (SAM) conformational reorganization onto an electrode surface due to the application of an electrical field. In particular, 3-mercaptopriopionic acid SAM (3MPA SAM) modified gold electrodes are activated with a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHSS) (EDC-NHSS) mixture by shortening the activation time, from 2 h to 15/20 min, labelled as Protocol-A, -B and -C, respectively. This step, later followed by a deactivation process with ethanolamine (EA), plays a key role in the reaction yields (formation of N-(2-hydroxyethyl)-3-mercaptopropanamide, NMPA) but also in the conformational rearrangement observed during the application of the electrical field. This study aims at explaining the high performance (i.e., single-molecule detection at a large electrode interface) of bioelectronic devices, where the 3MPA-based SAM structure is pivotal in achieving extremely high sensing performance levels due to its interchain interaction. Cyclic voltammetry (CV) experiments performed in K4Fe(CN)6:K3Fe(CN)6 for 3MPA SAMs that are activated/deactivated show similar trends of anodic peak current (IA) over time, mainly related to the presence of interchain hydrogen bonds, driving the conformational rearrangements (tightening of SAMs structure) while applying an electrical field. In addition, XPS analysis allows correlation of the deactivation yield with electrochemical data (conformational rearrangements), identifying the best protocol in terms of high reaction yield, mainly related to the shorter reaction time, and not triggering any side reactions. Finally, Protocol-C's SAM surface coverage, determined by CV in H2SO4 and differential pulse voltammetry (DPV) in NaOH, was 1.29 * 1013 molecules cm−2, being similar to the bioreceptor surface coverage in single-molecule detection at a large electrode interface. [ABSTRACT FROM AUTHOR]

Hybrid Titanium dioxide/Poly(3-hexylthiophene) heterojunction solar cells have gained research interest as they have the potential to become cost-effective solar technology in the future. Limited power conversion efficiencies of about 5–6% have been reported so far, and an enhancement in efficiency was achieved through the engineering of the interface between Titanium dioxide (TiO2) and Poly(3-hexylthiophene) (P3HT). Evolution of this solar cell technology is relatively slow-moving due to the complex features of the metal oxide-polymer system and the limited understanding of the technology. In this review, we focus on recent developments in interface modified hybrid Titanium dioxide/Poly(3-hexylthiophene) solar cells, provide a short discussion on the working principle, device structure with interface modifiers, and summarize various types of interface modifiers studied to enhance the photovoltaic performance of hybrid TiO2/P3HT heterojunction solar cells. Further, we discuss the key factors influencing the power conversion efficiency and the role of a variety of interface modifiers in this regard. Finally, the challenges and perspectives related to hybrid TiO2/P3HT heterojunction solar cells are also explored. [ABSTRACT FROM AUTHOR]

Metal oxides (MOXs), in the form of nanowires, have proved to be an excellent active sensing layer of chemoresistive sensors due to their unique physical/chemical properties such as single crystallinity, exceptional electrical properties, and so on. Indeed, MOXs nanowires‐based gas sensors show fast dynamic response with excellent reproducibility, stability, and reactivity toward various gas analytes. However, their limited selectivity and high operation temperature that lead to high power consumption are still major issues that need to be addressed. To improve these characteristics, researchers nowadays are working in the direction of modifying nanowires with different strategies. These strategies include nanowires heterostructures, decoration with particles (metals and metal oxides), core–shell structures, and surface functionalization with self‐assembled monolayers and modification with graphene (pristine and oxidized). By employing these strategies, nanowires sensing performances, especially their selectivity, sensitivity, and response, can immensely enhance. Hence, in this review article, the above‐mentioned strategies to improve the sensing performance of MOXs nanowires are reviewed. Attention is paid to underlying sensing mechanisms and improved sensing characteristics. In addition, MOXs gas sensing mechanism, working principle of conductometric gas sensors, and different synthesis techniques, used to modify nanowires, are also briefly discussed. [ABSTRACT FROM AUTHOR]

We demonstrate a strategy to directly map and quantify the effects of dipole formation on electrical transports and noises in the self-assembled monolayers (SAMs) of molecular wires. In this method, the SAM patterns of fluorinated molecules with dipole moments were prepared on conducting substrates, and a conducting probe in contact-mode atomic force microscopy was utilized to map currents and noises through the probe on the molecular patterns. The maps were analyzed to extract the characteristic parameters of dipolar noises in SAMs, and the results were compared with those of hydrogenated molecular patterns without dipole moments. At rather low bias conditions, the fluorinated molecular junctions exhibited a tunneling conduction and a resistance value comparable to that of the hydrogenated molecules with a six-times-longer length, which was attributed to stronger dipoles formation in fluorinated molecules. Interestingly, conductance (G) in different regions of fluorinated molecular patterns exhibited a strong correlation with a noise power spectral density of SI/I2 like SI/I2 ∝ G−2, which can be explained by enhanced barrier fluctuations produced by the dipoles of fluorinated molecules. Furthermore, we observed that the noise power spectral density of fluorinated molecules showed an anomalous frequency (f) dependence like SI/I2 ∝ 1/f1.7, possibly due to the slowing down of the tunneling of carriers from increased barrier fluctuations. In rather high bias conditions, conductions in both hydrogenated and fluorinated molecules showed a transition from tunneling to thermionic charge transports. Our results provide important insights into the effects of dipoles on mesoscopic transport and resistance-fluctuation in molecules and could have a significant impact on the fundamental understanding and applications in this area. [ABSTRACT FROM AUTHOR]

Tethered‐liquid perfluorocarbon (TLP) coatings show promise for blood‐contacting medical device applications to reduce blood adhesion and delay thrombosis. However, their fabrication and longevity under external fluid flow is not well characterized. A vapor phase silanization reaction leading to the formation of tethered‐perfluorocarbon (TP) layers containing large bumpy aggregates, 300 ± 200 nm thick, on top of an underlying 35 ± 15 nm thick uniform coating is reported. The vapor phase method compares favorably to the well‐established liquid phase deposition to reproducibly create slippery coatings on silicon and polystyrene with very low water sliding angles (2° ± 1°), without the need to control humidity conditions. The TP layer retains perfluorinated lubricants up to 20 000 s–1, using a cone‐and‐plate rheometer, with the higher viscosity lubricant perfluoroperhydrophenanthrene being more resistant to depletion than perfluorodecalin. TLP infused with either of the lubricants effectively reduces adhesion of fibrin from human whole blood relative to TP and control hydrophilic and hydrophobic surfaces. The combination of highly fluorinated TP coatings grafted from the vapor phase to create nanoscale structured surfaces infused with higher viscosity lubricant may be the most suitable combination for clinical applications of liquid‐infused surfaces to reduce thrombosis in blood‐contacting medical devices under flow. [ABSTRACT FROM AUTHOR]

Abstract Artificial receptor‐based protein assays have various attractive features such as a long‐term stability, a low‐cost production process, and the ease of tuning the target specificity. However, such protein sensors are still immature compared with conventional immunoassays. To enhance the application potential of synthetic sensing materials, organic field‐effect transistors (OFETs) are some of the suitable platforms for protein assays because of their solution processability, durability, and compact integration. Importantly, OFETs enable the electrical readout of the protein recognition phenomena of artificial receptors on sensing electrodes. Thus, we believe that OFETs functionalized with artificial protein receptors will be a powerful tool for the on‐site analyses of target proteins. In this Minireview, we summarize the recent progress of the OFET‐based protein assays including the rational design strategies for devices and sensing materials.

Abstract Self‐assembled monolayers (SAMs) are becoming widely utilized as hole‐selective layers in high‐performance p‐i‐n architecture perovskite solar cells. Ultrasonic spray coating and airbrush coating are demonstrated here as effective methods to deposit MeO‐2PACz; a carbazole‐based SAM. Potential dewetting of hybrid perovskite precursor solutions from this layer is overcome using optimized solvent rinsing protocols. The use of air‐knife gas‐quenching is then explored to rapidly remove the volatile solvent from an MAPbI3 precursor film spray‐coated onto an MeO‐2PACz SAM, allowing fabrication of p‐i‐n devices with power conversion efficiencies in excess of 20%, with all other layers thermally evaporated. This combination of deposition techniques is consistent with a rapid, roll‐to‐roll manufacturing process for the fabrication of large‐area solar cells.

Abstract Tethered‐liquid perfluorocarbon (TLP) coatings show promise for blood‐contacting medical device applications to reduce blood adhesion and delay thrombosis. However, their fabrication and longevity under external fluid flow is not well characterized. A vapor phase silanization reaction leading to the formation of tethered‐perfluorocarbon (TP) layers containing large bumpy aggregates, 300 ± 200 nm thick, on top of an underlying 35 ± 15 nm thick uniform coating is reported. The vapor phase method compares favorably to the well‐established liquid phase deposition to reproducibly create slippery coatings on silicon and polystyrene with very low water sliding angles (2° ± 1°), without the need to control humidity conditions. The TP layer retains perfluorinated lubricants up to 20 000 s–1, using a cone‐and‐plate rheometer, with the higher viscosity lubricant perfluoroperhydrophenanthrene being more resistant to depletion than perfluorodecalin. TLP infused with either of the lubricants effectively reduces adhesion of fibrin from human whole blood relative to TP and control hydrophilic and hydrophobic surfaces. The combination of highly fluorinated TP coatings grafted from the vapor phase to create nanoscale structured surfaces infused with higher viscosity lubricant may be the most suitable combination for clinical applications of liquid‐infused surfaces to reduce thrombosis in blood‐contacting medical devices under flow.

Cu-Cu direct interconnects are highly desirable for the microelectronic industry as they allow for significant reductions in the size and spacing of microcontacts. The main challenge associated with using Cu is its tendency to rapidly oxidize in air. This research paper describes a method of Cu passivation using a self-assembled monolayer (SAM) to protect the surface against oxidation. However, this approach faces two main challenges: the degradation of the SAM at room temperature in the ambient atmosphere and the monolayer desorption technique prior to Cu-Cu bonding. In this paper, the systematic investigation of these challenges and their possible solutions are presented. The methods used in this study include thermocompression (TC) bonding, X-ray photoelectron spectroscopy (XPS), shear strength testing, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results indicate nearly no Cu oxidation (4 at.%) for samples with SAM passivation in contrast to the bare Cu surface (27 at.%) after the storage at −18 °C in a conventional freezer for three weeks. Significant improvement was observed in the TC bonding with SAM after storage. The mean shear strength of the passivated samples reached 65.5 MPa without storage. The average shear strength values before and after the storage tests were 43% greater for samples with SAM than for the bare Cu surface. In conclusion, this study shows that Cu-Cu bonding technology can be improved by using SAM as an oxidation inhibitor, leading to a higher interconnect quality.

The effect of solution pH on the formation and surface structure of 2-pyrazinethiolate (2-PyzS) self-assembled monolayers (SAMs) formed by the adsorption of 2-mercaptopyrazine (2-PyzSH) on Au(111) was investigated using scanning tunneling microscopy (STM) and X-ray photoelectron microscopy (XPS). Molecular-scale STM observations clearly revealed that 2-PyzS SAMs at pH 2 had a short-range ordered phase of (2√3 × √21)R30° structure with a standing-up adsorption structure. However, 2-PyzS SAMs at pH 8 had a very unique long-range ordered phase, showing a "ladder-like molecular arrangement" with bright repeating rows. This ordered phase was assigned to the (3 × √37)R43° structure, consisting of two different adsorption structures: standing-up and tilted adsorption structures. The average arial density of 2-PyzS SAMs on Au(111) at pH 8 was calculated to be 49.47 Å 2 /molecule, which is 1.52 times more loosely packed compared to the SAMs at pH 2 with 32.55 Å 2 /molecule. XPS measurements showed that 2-PyzS SAMs at pH 2 and pH 8 were mainly formed through chemical interactions between the sulfur anchoring group and the Au(111) substrates. The proposed structural models of packing structures for 2-PyzS SAMs on Au(111) at different pHs are well supported by the XPS results. The results of this study will provide new insights into the formation, surface structure, and molecular orientation of SAMs by N-heteroaromatic thiols with pyrazine molecular backbone on Au(111) at the molecular level.

The research on photonic synapses holds immense promise for various applications, such as robotics and artificial intelligence. Pursuing lightweight, miniaturized, and low-energy consumption designs is crucial for enhancing efficiency and adaptability in evolving technological environments. To achieve this goal, this work designs a series of conjugated self-assembled molecules with photoactive pyrene, benzo-naphthol-thiophene (BNT), perylene, and benzothieno-benzothiophene cores to develop ultrathin (<3 nm) charge-trapping self-assembled monolayers (SAMs). The highly crystalline BNT forms an orderly arrangement with the semiconducting channel, further exhibiting distinguished current contrast stability (∼10 8 ) and synaptic features, including paired-pulse facilitation (153%), ultralow energy consumption (28.9 aJ), and short/long-term plasticity. The device successfully demonstrates the emulation of human learning behavior and the self-protection mechanism against ultraviolet radiation utilizing crystalline and conjugated SAMs with different charge traps. Additionally, the capability of background denoising is evidenced by the high recognition accuracy (∼90%) for the preprocessed images. This study not only strengthens the diverse functionality of SAMs in optoelectronic devices but also highlights the significant potential of device miniaturization for biomimetic applications, making it a crucial contribution to the field.

The photovoltaic performance of inverted perovskite solar cells (PSCs) relies on effectively managing the interface between the hole extraction layer and the light-absorbing perovskite layer. In this study, we have synthesised (4-(3,6-bis(methylthio)-9H-carbazol-9-yl)butyl)phosphonic acid (MeS-4PACz), which forms a self-assembled monolayer (SAM) on the fluorine-doped tin oxide (FTO) electrode. The molecule's methylthio substituents generate a favourable interfacial dipole moment and interact with the perovskite layer. This interaction results in well-aligned energy levels among the FTO/SAM/perovskite layers, promoting efficient hole extraction and significantly reducing carrier recombination losses. Additionally, the methylthio groups passivate iodide vacancies and interact with Pb 2+ ions of the perovskite, reducing defect-induced trap states and enhancing the crystalline growth of the perovskite layer. Consequently, inverted PSCs incorporating MeS-4PACz achieve a power conversion efficiency of 25.13 %, along with outstanding photostability., (© 2024 Wiley-VCH GmbH.)

The production of methanol from the electrochemical reduction of CO 2 is a promising method of mitigating climate change while simultaneously producing a useful liquid fuel. In this study, we design self-assembled monolayers (SAMs) of thiols on metal and metal oxide electrodes that operate via cooperative catalysis between the thiolated surface sites and exposed electrode defect sites. This defect-driven mechanism enables the fabrication of SAM-modified ZnO electrodes that yield methanol with an extraordinarily high Faradaic efficiency of up to 92%. To understand the origin of this high selectivity, we study the effect of the chain length of the alkanethiols, different tail functional groups, and applied voltages on catalyst performance. These results combined with density functional theory calculations give a detailed atomic-level understanding of catalyst operation. Furthermore, the SAM linkage tolerates CO 2 reduction conditions, and the catalyst's excellent selectivity for methanol remains high after 10 h of continuous conversion. Taken together, these findings with SAM-based electrodes convey a new and facile design strategy for the creation of highly selective CO 2 reduction electrocatalysts.

The inherent large HOMO-LUMO gap of alkyl thiol (CnS) self-assembled monolayers (SAMs) has limited their application in molecular electronics. This work demonstrates significant enhancement of mechano-electrical sensitivity in CnS SAMs by external compression, achieving a gauge factor (GF) of approximately 10 for C10S SAMs. This GF surpasses values reported for conjugated wires and DNA strands, highlighting the potential of CnS SAMs in mechanosensitive devices. Conductive atomic force microscopy (cAFM) investigations reveal a strong dependence of GF on the alkyl chain length in probe/CnS/Au junctions. This dependence arises from the combined influence of molecular tilting and probe penetration, facilitated by the low Young's modulus of alkyl chains. Theoretical simulations corroborate these findings, demonstrating a shift in the electrode Fermi level toward the molecular resonance region with increasing chain length and compression. Introducing a rigid graphene interlayer prevents probe penetration, resulting in a GF that is largely independent of the alkyl chain length. This highlights the critical role of probe penetration in maximizing mechano-electrical sensitivity. These findings pave the way for incorporating CnS SAMs into mechanosensitive and mechanocontrollable molecular electronic devices, including touch-sensitive electronic skin and advanced sensor technologies. This work demonstrates the potential of tailoring mechanical and electrical properties of SAMs through molecular engineering and interface modifications for optimized performance in specific applications.

Two-dimensional graphene has emerged as a promising competitor to silicon in the post-Moore era due to its superior electrical, optical, and thermal properties. However, graphene undergoes a strong degradation in its in-plane thermal conductivity when it is coupled to an amorphous substrate. Meanwhile, the weak van der Waals interaction between graphene and the dielectric substrate leads to high interfacial thermal resistance. Severe challenges in the device's heat dissipation rise, resulting in elevated hotspot and deteriorated electrical performance. Here, we applied self-assembled monolayers (SAMs) to modify the interface between graphene and the oxide substrate and mitigate the thermal issues in the device. The -NH 2 terminated SAM demonstrates enhanced interfacial coupling strength between graphene and substrate, increasing the interfacial thermal conductance. The -CH 3 terminated SAM effectively suppresses the substrate phonon scattering, preserving the high in-plane thermal conductivity of graphene. Particularly, the -NH 2 terminated SAM significantly enhances the heat dissipation efficacy of graphene field-effect transistors and alleviates the self-heating issues. Enhancements of 28.1% and 48.2% were observed in the devices' current-carrying capacity and maximum power density , respectively. Our research provides a highly attractive platform for incorporating SAMs to improve thermal management in two-dimensional electronic devices.

Self-assembled monolayers (SAMs) are emerging as platform technology for a myriad of applications, yet they still possess varied spatial stability and predictability issues as their properties are heavily dependent on subtle structural features. Reducing entropy within such a system serves as one of many potential solutions to increase order and therefore coherence/precision in measured properties. Here we explore controlled thermal annealing to improve edge disorders in SAMs and significantly reduce data variance. Using both odd- and even-numbered n-alkanethiol SAMs on Au, we observe statistically significant difference in the contact angles between edge and center. Thermal annealing at 40 °C significantly narrows differences between edges and centre of the SAM, albeit with significant reduction in the parity dependent odd-even effect. This study provides a pathway to improve SAMs consistency through minimal external perturbation as reflected by the minimization of odd-even effect as SAMs become increasingly ordered., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

Voltage-responsive biosensors capable of monitoring real-time adsorption behavior of biological analytes onto electroactive surfaces offer attractive strategies for disease detection, separations, and other adsorption-dependent analytical techniques. Adsorption of biological analytes onto electrically switchable surfaces can be modelled using neutravidin and biotin. Here, we report self-assembled monolayers formed from voltage-switchable biotinylated molecules on gold surfaces with tunable sensitivity to neutravidin in response to applied voltages. By using electrochemical quartz crystal microbalance (EQCM), we demonstrated real-time switchable behavior of these bio-surfaces and investigate the range of sensitivity by varying the potential of the same surfaces from -400 mV to open circuit potential (+155 mV) to +300 mV. We compared the tunability of the mixed surfaces to bare Au surfaces, voltage inert surfaces, and switchable biotinylated surfaces. Our results indicate that quartz crystal microbalance allows real-time changes in analyte binding behavior, which enabled observing the evolution of neutravidin sensitivity as the applied voltage was shifted. EQCM could in principle be used in kinetic studies or to optimize voltage-switchable surfaces in adsorption-based diagnostics., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)

Here, a unique crossbar architecture is designed and fabricated, incorporating vertically integrated self-assembled monolayers in electronic devices. This architecture is used to showcase 100 individual vertical molecular junctions on a single chip with a high yield of working junctions and high device uniformity. The study introduces a transfer approach for patterned liquid-metal eutectic alloy of gallium and indium top electrodes, enabling the creation of fully flexible molecular devices with electrical functionalities. The devices exhibit excellent charge transport performance, sustain a high rectification ratio (>10 3 ), and stable endurance and retention properties, even when the devices are significantly bent. Furthermore, Boolean logic gates, including OR and AND gates, as well as half-wave and full-wave rectifying circuits, are successfully implemented. The unique design of the flexible molecular device represents a significant step in harnessing the potential of molecular devices for high-density integration and possible molecule-based computing., (© 2024 Wiley‐VCH GmbH.)

Abtract The initial attachment and subsequent biofilm formation of electroactive bacteria Shewanella putrefaciens CN32 was investigated to clarify the influence of organic conditioning layers. A selection of macromolecules and self‐assembled monolayers (SAMs) of different chain lengths and functional groups were prepared and characterized by means of infrared spectroscopy in terms of their chemistry. Surface energy and Zeta (ζ‐) potential of the conditioning layers was determined with contact angle and streaming current measurements. Among the studied surface parameters, a high polar component and a high ratio of polar‐to‐disperse components of the surface energy has emerged as a successful indicator for the inhibition of the initial settlement of S. putrefaciens on stainless steel AISI 304 surfaces. Considering the negative surface charge of planktonic S. putrefaciens cells, and the strong inhibition of cell attachment by positively charged polyethylenimine (PEI) conditioning layers, our results indicate that electrostatic interactions do play a subordinate role in controlling the attachment of this microorganism on stainless steel AISI 304 surfaces. For the biofilm formation, the organization of the SAMs affected the local distribution of the biofilms. The formation of three‐dimensional and patchy biofilm networks was promoted with increasing disorder of the SAMs.

Organic electronic devices rely on the performance of polymers that are used as active layers. Poly-(3,4-ethylenedioxythiophene) (PEDOT) is one of the most studied polymers for organic electronic devices and especially bioelectronics. Because charge carriers move along the polymer backbone (anisotropic charge transport), one of the key challenges is controlling orientation of the polymer in thin films, hence increasing the transport performance. Here, we introduce a method for the oriented growth of PEDOT chains on nanometer-thick self-assembled monolayer (SAM)-modified gold electrodes. We show that, when the gold layer is covered with a SAM that is active for polymer chain growth, a more crystalline film is obtained compared to the surface having a nonactive SAM. We used a nitric acid oxidant to perform the polymerization, which overcomes temperature incompatibility between the gold-supported thiolate monolayers and the polymerization. We characterize the chemical nature and physical properties of the oriented PEDOT film. Reaction conditions and ease of processing appeal especially to organic electronic device applications where surface modification can play a critical role. [ABSTRACT FROM AUTHOR]

To understand the electrical and charge transport phenomena in either single or large‐scale molecular junctions, direct current (DC) measurements are mainly utilized. The current–voltage data obtained from DC measurements on molecular junctions (MJs) are employed to infer charge transport parameters, including barrier height, contact resistance, attenuation factor (β), and underlying transport mechanisms. However, DC measurements can not separate the individual electrical components, as it produces a total current that flows in the molecular junctions. Contact resistance obtained from the DC measurements by extrapolating plot of resistance versus chain length can not make exact value. In addition, defected SAMs‐based MJs or junctions having a protective layer, DC measurements alone can predict neither proper electrical values nor the correct transport mechanisms and it lacks frequency response. Electrical impedance spectroscopy (EIS) along with the circuit model enables the identification of individual electrical components of the molecular junctions and faultless contact resistance values that facilitate the model of actual transport mechanisms. In this Review, the working principle of electrical impedance spectroscopy and circuit modeling to digitize the experimental results on various molecular junctions, is discussed. Overall, the EIS technique can serve as an excellent analytical tool for the proper electrical characterization that is highly desirable for molecular electronics. [ABSTRACT FROM AUTHOR]

An abrupt increase of CH3-groups brightness as well as CH2-groups modulation along alkyl skeleton were observed in scanning tunneling microscopy (STM) images of n-alkanes monolayers on graphite. Analysis of STM-patterns demonstrates that both effects strongly depend on deformations of molecules and scanning conditions. We have observed that due to deformations, the monolayer is going to be compressed, thus methylene units protrude away from the surface forming a corrugated structure. Moreover, the distance between adjacent lamellae narrows, leading to the absence of furrows and, in particular, to a significant increasing of tunneling current from peripheral groups. The whole monolayer has been conserving its anomalous brightness for a few hours. Moreover, when the scanning conditions are changed, the monolayer could undergo an instantaneous reordering from the structure with increased brightness to the uniform one. [ABSTRACT FROM AUTHOR]

A surface‐confined redox reaction triggers the formation of single bilayer membranes from small unilamellar vesicles of anionic or zwitterionic phospholipids onto gold surfaces modified with a ferrocene‐terminated self‐assembled monolayer (SAM). The ion pairing association of the charged lipid headgroups with the electrogenerated cationic ferroceniums drives the assembly of the phospholipids on the SAM surface to produce solid‐supported bilayers of high surface coverage (≳90%) from gel‐ or fluid‐phase forming phospholipids within minutes at room temperature. The redox‐mediated strategy reported in this work is a conceptual advance in the preparation of solid‐supported lipid bilayers. It is fast, compatible with negatively‐charged and zwitterionic phospholipids, insensitive to the phase state of the phospholipid in the vesicle precursor, and not limited to hydrophilic surfaces. [ABSTRACT FROM AUTHOR]

We introduce an efficient method for the immobilization of phenolic compounds, based on 1,2,4,‐triazoline‐3,5‐dione (TAD), which selectively reacts with phenolic compounds at the α position to the phenolic hydroxyl group, ensuring intact phenol functionality, and therefore, maintaining the biological activity of the phenolic compound. We prepared self‐assembled monolayers on gold that presented urazole (the reduced form of TAD) as the terminal group and which were activated electrochemically without treatment with chemical oxidants, allowing on‐demand activation and in situ immobilization of the phenolic compounds. We examined the immobilization of various phenolic compounds and verified the surface chemistry using electrochemistry and mass spectrometry. The proposed method is simple and straightforward and does not require complicated protocols and reagents, and thus, it can be a general and practical platform for the immobilization of phenol‐containing molecules on the surfaces of various materials. [ABSTRACT FROM AUTHOR]

The dielectric behavior of organic materials at molecular dimensions can be vastly different than their bulk counterparts and therefore it is important to investigate and control the dielectric response of molecular‐scale materials for a large variety of applications. Large‐area molecular junctions are explored to study the charge transport mechanisms with unprecedented detail and to demonstrate novel functionalities. Therefore, large‐area molecular junctions are, in principle, a promising platform to study the dielectric effects at the molecular scale. This review summarizes recent progress on the measurements and understanding of the dielectric behavior of molecular systems and how they behave differently from their bulk properties. This review introduces, briefly, the concepts of impedance spectroscopy (IS) and how this technique can be applied to study the dielectric response of solid‐state large‐area molecular junctions. This analysis gives new insights in the factors that determine the dielectric constant of monolayers (including collective electrostatic effects and how the dielectric constant increases with monolayer thickness), how IS gives new insights into the role of defects, and the factors that contribute to the molecule–electrode contact resistance. This review ends with an outlook highlighting interesting future directions. [ABSTRACT FROM AUTHOR]