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Hypothesis Although protein adsorption at an interface is very common and important in biology and biotechnology, it is still not fully understood – mainly due to the intricate balance of forces that ultimately control it. In food processing (and medicine), controlling and manipulating protein adsorption, as well as avoiding protein adsorption (biofilm formation or membrane fouling) by the production of protein-resistant surfaces is of substantial interest. A major factor conferring resistance towards protein adsorption to a surface is the presence of tightly bound water molecules, as is the case in oligo ethylene glycol (OEG)-terminated self-assembled monolayers (SAMs). Due to strong attractive protein-protein and protein-surface interactions observed in systems containing trivalent salt ions, we hypothesize that these conditions may lead to a breakdown of protein resistance in OEG SAMs. Experiments We studied the adsorption behavior of BLG in the presence of a lanthanum(III) chloride (LaCl3) at concentrations of 0, 0.1, 0.8 and 5.0 mM on normally protein resistant triethylene glycol-termianted (EG3) SAMs on a gold surface. We used quartz-crystal microbalance with dissipation (QCM-D) and neutron reflectivity (NR) to characterize the morphology of the interfacial region of the SAM. Findings We demonstrate that the protein resistance of the EG3 SAM breaks down beyond a threshold salt concentration c ∗ and mirrors the bulk behaviour of this system, showing reduced adsorption beyond a second critical salt concentration c ∗ ∗ . These results demonstrate for the first time the controlled switching of the protein-resistant properties of this type of SAM by the addition of trivalent salt.

Hypothesis Achievement of superlubricity is an effective method to reduce friction and wear, which has a prominent influence on the operational efficiency and lifetime of a device. However, some burning issues still remain to be solved for the practical applications of superlubricity, such as the poor load-bearing capacity, especially in liquid superlubricity. Therefore, exploring an effective method to enhance the superlubricity performance is essential to accelerate the application of superlubricity. Experiments The friction properties between two different self-assembled monolayers (SAMs)—a perfluorocarbon SAM and a hydrocarbon SAM—and graphite in water were explored and compared by atomic force microscopy (AFM). Findings Enhanced superlubricity performance due to the fluorination was observed. Specifically, we observed an approximately 85% reduction of the friction coefficient after fluorination, and superlubricity was achieved with extremely low friction coefficient of 0.0003. Moreover, 2.4-fold greater load-bearing capacity of the superlubricity was obtained after fluorination. The molecular origin of the superlubricity enhancement by fluorination was revealed by molecular dynamics (MD) simulations, indicating that the greater load-bearing capacity of the perfluorocarbon SAM was ascribed to the enhanced interaction between the water and SAM by fluorination to form a more robust layered water structure confined in the contact zone, which played a pivotal role in the superlubricity.

Hypothesis The self-assembly of amphiphilic molecules onto solid substrates can result both in the formation of monolayers and multilayers. However, on oxidized and non-oxidized copper (Cu), only monolayer formation was reported for phosphonic acids possessing one phosphate head group. Here, the adsorption of octadecylphosphonic acid (ODPA) on Cu substrates through a self-assembly process was investigated with the initial hypothesis of monolayer formation. Experiments The relative amount of ODPA adsorbed on a Cu substrate was determined by infrared reflection/absorption spectroscopy (IRRAS) and by atomic force microscopy (AFM) investigations before and after ODPA deposition. X-ray photoelectron spectroscopy (XPS) with sputtering was used to characterize the nature of the layers. Findings The results show that the thickness of the ODPA layer increased with deposition time, and after 1 h a multilayer film with a thickness of some tens of nm was formed. The film was robust and required long-time sonication for removal. The origin of the film robustness was attributed to the release of Cu ions, resulting in the formation of Cu-ODPA complexes with Cu ions in the form of Cu(I). Preadsorbing a monolayer of octadecylthiol (ODT) onto the Cu resulted in no ODPA adsorption, since the release of Cu(I) ions was abolished.

The tuning of charge carriers in graphene is essential for its realization as high-performance electrode in various electronic and optoelectronic devices. In this study, we used chemical doping approach to alter the electronic properties of chemical vapor deposition (CVD) grown single-layer graphene (SLG) via coating of octadecyltrimethoxysilane (OTS) self-assembled monolayer (SAM). Raman spectra and electrical measurements showed that the OTS treatment on SLG induces p-type doping. The Raman peaks positions and the values of I2D/IG were examined for pristine and OTS doped graphene, which revealed the charge transfer from graphene to OTS molecules. The electrical characterization demonstrated that the OTS treatment can significantly shift the charge neutrality point towards the right side, which confirmed the p-type doping. This study suggests that the electronic properties of CVD-grown graphene could be modulated by OTS treatment and provides a promising idea for the development of graphene-based electronic devices.

When the inkjet printer jets inks, the nozzle of head plate is easily getting wet due to low surface energy of ink, high jetting frequency and high plate surface energy. As a result, non-ejection or diagonal ejection of ink occurs at the time of jetting, which causes non-uniform inkjet printing issues. To solve this problem, in current study, a selective hydrophobic coating of the inkjet head plate was applied using a microcontact printing (μCP) to enhance the uniformity of printing. Due to the characteristics of μCP, the hydrophobic self-assembled-monolayer was selectively deposited only on the surface of the head plate except the inside of the nozzle, which increases the contact angle of the inkjet head plate up to 105.45 ± 2.30°. This selective hydrophobic coating effectively decreases a jetting off-angle of the inkjet printer (Dimatix SG-1024) by ∼ 30 % while maintaining the same meniscus pressure and ink drop velocity as the unmodified conventional printer. The hydrophobic coating produced through this work has a facile regenerability, which is suitable for practical usage in inkjet printer. Furthermore, this method will increase the head life-time by reducing the frequency of the head plate care.

A systematic study of the application of self-assembly monolayers (SAMs) onto electron and hole transporting layers for perovskite solar cells (PSCs) stability is reported. Cs0.05FA0.83MA0.17Pb(I0.87Br0.13)3 (FMC) perovskite films were deposited onto tin oxide (SnO2) and nickel oxide (NiOx) layers that were functionalized with ethylphosphonic acid (EPA) and 4-bromobenzoic acid (BBA) SAMs. X-ray diffractometry measurements were performed on these films shortly after they were deposited. The diffractograms agree with the positions reported in the literature for the crystal structure of the FMC. The results show that the deposition of SAMs on the metal oxide layers yields positive improvements in the FMC film stability and in the device stability when using FMC as the active layer. The work shows that by adopting SAMs, the long-term stability of PSCs cells under accelerated test conditions can be enhanced, and this provides one step on the way to making this technology a commercial reality.

Despite the many advances that have been made in using anionic surfactants to disperse and sort single-walled carbon nanotubes (SWNTs) for optoelectronic applications, one-pot methods for deposition of SWNTs in a diameter (dt) and position controlled manner from as-dispersed sample are essential. Here, we designed and prepared flavin-containing self-assembled monolayers (flavin-SAMs) that can be used to assemble dt-selective individualized SWNT networks directly from SWNT dispersions by using the widely-used anionic surfactant. For a given glass substrate, the dimethallylsilane-linked azide, along with surface immobilization was employed to have Click reaction with terminal acetylene tethered to flavin group known to have strong affinity with SWNT. As demonstrated by atomic force microscopy and other methods, along successful assembly of individualized networks, the SWNTs are either fully or partially wrapped in a dt selective manner by isoalloxazine moieties tethered to the surface, displaying Langmuir isotherm adsorption behaviors in a dipping method dependent manner. The assembled SWNT network secures photoluminescence and electrical conductivity albeit its intimacy to underlying substrate and near monolayer coverage of SWNT network, respectively, and, furthermore, preferentially takes place on flavin-SAM over hydrophobic surface.

Cellular interactions with the microenvironment are mediated by ligand-receptor bonds. Such ligand-receptor bond dynamics is known to be heavily dependent on the loading rate. However, the physiologically-relevant loading rate of living cells remains unknown. Here, using a quartz crystal microbalance (QCM), we developed a bulk-force sensing platform to semi-quantitatively detect the rate of cellular force application during early stages of cell adhesion and spreading. Atop an Au-coated quartz crystal, covalently linked self-assembled monolayers (SAM) were used to immobilize cyclic-RGDfK peptides that can interact with the αvβ3 integrins on cells. The QCM detects the changes in resonant frequency of the vibrating crystal due to the cellular activity/probing (force application) on the QCM surface. The corresponding changes in mass on the surface, proportional to the rate of force application, arise from the cellular interactions with the functionalized surface were calculated. The loading rate of living cells was found to be ∼80–115 pN/s. Collectively, our results revealed a fundamental feature of cell adhesion and spreading providing valuable information regarding cellular interactions with the extracellular matrix.

Atom probe tomography was used to analyze self-assembled monolayer of octanethiol and (1H,1H,2H,2H) perfluoro decanethiol (PFDT) in a mixed and unmixed state on a gold surface. The first part of this report, we have analyzed the two SAMs with a direct comparison, whereas in the second part, a binary mixture of these two SAMs (with a 1:1 ratio) are analyzed. Au was taken as a metal substrate in both cases. It has been observed that, although having similar structure and belongs from the same SAMs group, the sequence of evaporation of both chains appeared significantly different molecular fractions in the first case, while in the mixed phase condition the two SAMs chains were arranged in a patchy domain by forming a small nanoscale cluster on the gold surface. Primarily, this study gives an overall understanding of evaporation sequence and surface morphology of the SAMs in an unmixed and mixed condition on the gold substrate, which may lead to the further design process in various applications.

An efficient and facile strategy for producing core-shell Au@Ag nanorods (NRs) with controllable width and length as excellent surface enhanced Raman scattering (SERS) substrate was proposed. Au nanodipyramids (NDPs) of three various widths were prepared by overgrowth along the radial orientation, and together with Au NDPs as seed, silver was deposited in the axial orientation to successfully obtain core-shell Au@Ag NRs with diverse length (73 nm–157 nm) and width (25 nm–43 nm). The morphology, optical properties and SERS performance of the as-synthesized Au@Ag NRs were investigated systematically. The broadly tunable UV-Vis absorption range for Au@Ag NRs as far as the near-infrared (NR) region was able to be obtained. Furthermore, the SERS property of Au@Ag NRs two-dimensional monolayer was explored by using crystal violet (CV) as Raman probe. The optimal SERS enhancement effect with enhancement factor (EF) as high as 6.13✕105 could be achieved for Au@Ag NRs with wider width and longer length, which was confirmed by the simulation results of electromagnetic (EM) field distribution by FDTD method. Our novel approach provides some facinating insights into adjusting the width of Au@Ag NRs, which also significantly influences the SERS behaviors of the Au@Ag NRs. It allows to fabricating SERS substrate with superior SERS performance compared to previously reported Au@Ag NRs only with tunable length via direct overgrowth. Besides, this as-compounded Au@Ag NRs are expected to have promising application and significant value in other fields.

Immunoassays are important for the diagnosis of many diseases. Efficient methods for the immobilization of the biorecognition elements is a relevant subject because the antibody loading is directly related to the detection range and sensitivity. Here different self-assembled films were explored to take advantage of polar oxygenated groups from graphene oxide (GO) structure. Surface plasmon resonance (SPR) sensors were modified with different GO self-assembled films and compared to the well-established thiol-functionalization with 11-MUA (11- mercaptoundecanoic acid). Self-assembled cysteamine/GO functionalized sensor (Cys-GOSA) provided the highest protein loading (7.66 × 10−12 mol cm−2 against 1.29 × 10−11 mol cm−2 for the traditional thiol-functionalization). The Langmuir-Blodgett (LB) films of GO were composed of aggregates and empty spaces, which hindered the antibody anchoring (around 6.38 × 10−12 to 3.45 × 10−12 mol cm−2). The SPR response of the Cys-GOSA-modified sensor to the 4.0 ng mL−1 PSA was 125% higher than the thiol-functionalized sensor at the same concentration. This result indicates a simple and promising surface modification strategy for many important applications, not limited to SPR sensors, but for all immunoreaction-based assays as enzyme-linked immunosorbent assay (ELISA), electrochemical (e.g. amperometric and impedimetric) and quartz crystal microbalance (QCM) based sensors.

We report results of the studies relating to the fabrication of a surface plasmon resonance (SPR) based label-free immunosensor for real-time monitoring of endothelin-1 (ET-1), a colon cancer biomarker. A gold disk modified with a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (11-MUA) was functionalised via covalent immobilization of monoclonal anti-ET-1 antibodies using EDC-NHS (1-(3-(dimethylamine)-propyl)-3-ethylcarbodiimide hydrochloride, N-hydroxy succinimide) chemistry. This immunosensing platform (ethanolamine/anti-ET-1/11-MUA/Au) was characterized via atomic force microscopy (AFM), contact angle (CA) and Fourier transform infrared (FT-IR) spectroscopic techniques. The fabricated SPR electrode was further used to detect ET-1 in the broad concentration range 2–100 pg mL−1, with a detection limit of 0.30 pg mL−1 and remarkable sensitivity of 2.18 mo pg−1mL. The adsorption mechanism was studied using monophasic model and the values of association (ka) and dissociation (kd) constants for anti-ET-1 and ET-1 binding were calculated to be 4.4 ± 0.4 × 105 M−1 s−1 and 2.04 ± 0.0003 × 10−3 s−1, respectively. The results obtained via analysis of serum samples of colorectal cancer patients were found to be in good agreement with those obtained from enzyme-linked immunosorbent assay (ELISA) technique. Further, electrochemical studies were performed to prove the efficacy of the fabricated platform as a point of care device for the detection of ET-1.

The temperature dependence of dynamics of a soft matter chemisorbed on a solid-liquid interface oscillating at MHz was investigated using a quartz crystal microbalance (QCM). Specifically, the relationship between the temperature and the resonant length of the soft matter was systematically examined, where the resonant length means the molecular length moving with the oscillating solid-liquid interface at MHz. The temperature shift changes the stiffness (shear viscosity and shear elastic modulus) of the soft matter. In the present work, as chemisorbed soft matter, the self-assembled monolayers (SAMs) of mercapto oligo(ethylene oxide) methyl ethers, HS(CH2CH2O)nCH3 (n = 19 and 43) were employed. As a result, we have revealed that temperature changes induce variations in the resonant length from 10.2 (10 °C) to 8.0 nm (35 °C). We also discuss the variation of the resonant length on the basis of the viscosity and elasticity of the SAMs.

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.

The chemical composition of surfaces functionalized with self-assembled monolayers (SAMs) is an important parameter that determines their performance in a broad range of applications, from immobilizing molecular machines to initiation and growth control of MOFs (Metal-Organic Frameworks). In this article, a critical survey of XPS (X-ray photoelectron spectroscopy) and NEXAFS (near edge X-ray absorption fine structure) spectroscopy data for pyridine-functionalized monolayers on gold surfaces is presented to compile correlations that have been indiscernible before. Monolayers with aromatic backbones are compared to monolayers with aliphatic backbones. Monolayers with pyridine end-groups are compared to mixed monolayers formed terpyridine-functionalized by molecules end-groups and non-functionalized molecules. Thiol-oxidation during ageing of the SAMs in air is addressed. And finally, the addressability of the SAMs for the deposition of metal-ions and organic molecules is investigated and compared. This work consequently delivers a comprehensive set of spectroscopic data of (ter-)pyridine-terminated SAMs and their performance as template for the preparation of functional multilayers of macrocycles exhibiting a preferential orientation.

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.

Self-assembled monolayer (SAM) of multiply-alkylated cyclopentenes (MACEs), homologue of the famous hydrocarbon mobile lubricant multiply alkylated cyclopentanes (MACs), was fabricated as self-lubricating film on the surface of the thiol-functionalized silicon wafer (HS-Si) via facile thiol-ene “click” reaction, induced with UV-light or heating. The surface property analysis, including static contact angle and surface roughness, indicated the successful self-assembly. The microtribological tests of the different samples on a UMT-1 tribometer (CETR) in a ball-on-plate contact configuration showed that the SAMs possessed excellent self-lubricating property, in which the SAM H obtained via the heating-induced thiol-ene “click” reaction had the lower friction coefficient and longer tribological durability than the SAM UV one prepared under UV-irradiation. The proposed self-lubricating strategy is expected to be used in the lubrication of micro-/nano-electromechanical systems (MEMSs/NEMSs).

Quantitative atomic force microscope (AFM) measurements are performed by using both unmodified and octadecyltrichlorosilane self-assembled monolayers (OTS-SAMs)-functionalized AFM silicon (Si) tips in contact with the uncoated SiO2 substrate, OTS-SAMs coated SiO2 substrate and SiO2 substrate with graphene (Gr) sheet on its surface, providing six pairs of frictional interfaces. Drastic differences in the adhesion and friction responses of these six pairs of friction interfaces are observed. Lower adhesion force and friction force occur with OTS-SAMs coated on either tips or substrates, and the friction force is ultralow when Gr presented on the substrate with OTS-coated tips sliding against it. The observed ultralow friction is attributed to the hydrophobicity and incommensurate contact between Gr and OTS-SAMs. This work has important impact on designing approaches of friction pairs to achieve ultralow friction.

Since the discovery of organic semiconductors, material and device processing has been enhanced by improvements in carrier injection, carrier mobility, and device stability. However, these improvements are insufficient in the case of organic devices employing organic semiconductor materials. To improve the performance of organic devices, we need better understanding of the carrier injection property at the electrode-organic layer interface. In this paper, we studied carrier injection and accumulation in organic semiconductor by using electrical and optical measurements, i.e., I-V, C-V, AFM, and FTIR measurements. We used 6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) as the organic semiconductor layer. In order to enhance the carrier injection into TIPS-pentacene, we focused on the binding effect of the self-assembled monolayer, i.e., (3-Mercaptopropyl) trimethoxysilane (MPTMS) and pentafluorobenzenethiol (PFBT), deposited on the surface of the substrate.

Molecules at interfaces can exhibit a behavior that is very different from that in bulk phases. In this paper we will analyze one important factor that makes the difference between these two situations. Unlike in bulk situations—which are characterized by a practically constant density and a given type of crystal structure—molecules in a self-assembled monolayer (SAM) adsorbed on a substrate electrode are characterized by a density (coverage) and an ordering that can be widely tuned. The theoretical results presented in this paper indicate that tuning the coverage of SAMs consisting of floppy molecules may have a strong impact on the molecular conformation. Therefore, it may represent a route to achieve interface-driven control over the charge transfer/transport at molecular scale. Specifically, we consider three floppy molecular species—H-(C6H4)2-SH (biphenylmonothiol), HS-(C6H4)2-SH (4,4′-dithiol-1,1′-biphenyl), and NC5H4-C6H4-SH (4-(4-pyridinyl) benzenethiol)—consisting of two benzene or benzene-based rings that can easily rotate relative to each other. Our calculations reveal that, by varying the SAM coverage, the torsional angle can be varied by a factor of two. This reflects itself in a change of conductance over one order of magnitude, a fact that can be exploited in designing molecular switches.

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 SO42− 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.

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.

The topic of intermolecular interactions enhancing electron tunneling between protein residues on biofilm surface has been investigated by some theoretical studies. However, few of experimental studies could confirm this viewpoint. In this work, the Mercaptopropionic acid self-assembled monolayer (MPA SAM) with terminal carboxyl groups was constructed, as a simplified model for functionalized biomimic membrane. The electron tunneling rate constant of ferrocenylmethanol redox process on SAM was obtained from experimental results of scanning electrochemical microscopy. It is found that the electron tunneling across MPA SAM is faster than that of contrastive Methyl mercaptopropionate SAM. This result is attributed to the intermolecular interactions between the redox and MPA molecules. The conditions of lower pH and weaker ion pair effect all benefit the formation of the intermolecular interactions, resulting the enhancement of electron tunneling more obvious. Based on this, this kind of intermolecular interaction is inferred to be intermolecular hydrogen bond. Our work may have contributions to exploring electron tunneling between protein residues on biofilm surface.

Here, the construction and characterization of the first immunosensor for highly sensitive and label free detection of Fig mosaic virus (FMV) is reported. The specific antibody against nucleocapsid of the virus was raised and immobilized at the surface of 11-mercaptoundecanoic acid (MUA) and 3-mercapto propionic acid (MPA) modified gold electrode, via carbodiimide coupling reaction. The immunosensor fabrication steps were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical detection of FMV was conducted using differential pulse voltammetry in ferri/ferrocyanide solution as a redox probe. The proposed immunosensor exhibited high selectivity, good reproducibility and high sensitivity for FMV detection in a range from 0.1 nM to 1 μM with a detection limit of 0.03 nM. Moreover, good results were obtained for determination of FMV in real samples, indicating the feasibility of the developed immunosensor for detection of fig mosaic disease, without the need for molecular (e.g. PCR) amplification.

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 K3[Fe(CN)6]/K4[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 Rct 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.

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.

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 (

Self-assembled monolayers (SAM) are molecular assemblies ordered on a solid surface. In general, they are formed by the reaction of an alkyl-thiol molecule and a gold surface. Alkyl groups do not have additional functionalities in this case. On the other hand, the detailed design of electroactive layers able to be assembled on gold surface can transfer all electrochemical behavior to this surface and thus, an inert surface can have defined and modulated properties. Motivated by this approach, our interest was to evaluate the preferential coordination of the complex [Ru(H4dcbpy)2Cl2] with the 4‑mercapto‑pyridine ligand through the pyridine portion. To achieve this specificity, the ligand was previously attached to the surface of the gold electrode by the thiol portion. Moreover, the electrode modified with the electroactive self-assembled monolayer (E-SAM) was used in sensing of dopamine. Based on the electrochemical studies it was possible to observe that the gold electrode modified with the E-SAM of ruthenium complex (Ru‑4‑mpy‑Au) had an increase in the resistance to charge transfer (Rct = 274 Ω) when compared to the bare gold electrode (Rct = 19 Ω). On the other hand, the charge transfer rate constant is 104 times faster than for the bare gold electrode. These results suggest that the Ru‑4‑mpy‑Au electrode can be used for sensing of molecules through the electrocatalytic process of oxidation. The Ru‑4‑mpy‑Au electrode shows the best results for linear range (0–400 μmol L−1), and the lowest potential of detection (0.2 V vs Ag/AgCl) and limit of detection (3.3 μmol L−1) when compared to the other electrodes that were studied.

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.

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 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.

The binary monolayer system of 2-naphthalenethiol (2NT) and octanethiol (OT) was prepared on the surface of Au(111) and structurally characterized by scanning tunneling microscopy (STM) in ambient conditions. X-ray photoelectron spectroscopy (XPS) was conducted for elemental analysis of the adsorbates present in each monolayer. Both the sequence of deposition and the concentration of the 2NT solution used were varied. The mixed monolayer systems formed various surface structures, including the formation of novel packing of 2NT which are observed when the lower concentration of 2NT is adsorbed onto a pre-existing OT monolayer.

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.

Non-fullerene organic solar cells (OSCs) have attracted great attention due to their advantages such as tunable energy levels, reduced energy loss, strong light absorption. Here, three small molecules with polar functional groups were utilized to modify the surface of zinc oxide (ZnO) electron transport layer through self-assembled monolayers (SAMs) formation. Inverted non-fullerene OSCs with PBDB-T:ITIC blend as active layer based on the ZnO with SAMs modification showed enhanced device performance (10.90%) compared to that without SAM treatment (10.03%). The ultraviolet photoelectron spectroscopy results revealed that the SAMs could lower the surface work function of ZnO, allowing for better electron extraction. The analysis results of J-V characteristics under different light illumination intensities suggested more efficient charge dissociation and weaker trap-assisted bimolecular recombination in the devices with SAMs modification. Our work provides an effective approach to modify the ZnO surface for efficient non-fullerene OSCs.

There are fewer researches on the effect of functional group position change on device performance for highly efficient perovskite solar cell. In this work, we take pyridinesulfonic acid as an example, and study the effect of the isomeride: 2- and 3-pyridinesulfonic acid self-assembled monolayer on device performance for highly efficient perovskite solar cell. The efficiency of control device is 14.65% (Hysteresis Index = 0.31) under illumination of a simulated sunlight (AM 1.5G, 100 mW cm−2). Through use of the 3-pyridinesulfonic acid self-assembled monolayer, the device exhibits striking improvements to reach the efficiency of 16.88% (Hysteresis Index = 0.02), which constitutes an enhancement compared to those of 2-pyridinesulfonic acid self-assembled monolayer modified device (16.54%, Hysteresis Index = 0.02). The enhanced photovoltaic performances can be attributed to the larger perovskite grain sizes, and easier passivation of electron transporting layer/perovskite interface, which promote the charge separation, transport and collection.

In this work, we report on the effect of amino-terminated self-assembled monolayers (SAMs) on the growth and adhesion of copper on a dielectric surface in ultra-high vacuum. The nucleation and adhesion of copper is studied for a range of self-assembled monolayers both with and without nitrogen containing terminal groups, and as a function chain length using X-ray photoelectron spectroscopy, dynamic water contact angle, sheet resistance, and adhesion testing measurements. In-situ X-ray photoelectron spectroscopy studies of ultra-thin copper films show that the presence of nitrogen significantly improves the nucleation of copper to the surface, particularly those coated with long chain SAMs. However, upon thermal annealing short chain amino-terminated SAMs retain much of the deposited copper while significant desorption occurs for longer chains. Results consistent with these observations are obtained during conventional tape test measurements to determine adhesion. As such, for CMOS interconnect applications which require copper trenches with a nano-scale cross section, short chain SAMs offer excellent nucleation and adhesion, as well as the potential to act as a pore-sealant for low-k materials, without impacting significantly on the cross-sectional area of the copper lines.

In actual industrial processes, in addition to separation of just water and oil, separation of multiphase liquids and separation of organic solvents are also required. Here, we demonstrate successful multiphase liquid separation by simply applying different coating materials to aluminum meshes with a hierarchical microcubic and nanohole structure. A gravity-driven multiphase separation system was designed using these meshes as the separation media, and it showed high collection rate (99%) and high content ratio (95%). The fabricated separation system could sequentially separate liquids with surface tension of ≤21.6, 21.6–32.0, and ≥32.0 mN/m by choosing a filter with the proper surface energy. Given the small differences in the surface tension of the liquids used in this study, the separation system with a surface-energy-controlled filter can be an impressive tool to separate numerous liquid mixtures.

Cu Cu bonding process is intensively investigated nowadays because of the possibility of obtaining fine-pitch interconnects in 3D stacks for efficient electronic and sensing applications. These interconnects possess high shear strength, as well as excellent electrical and thermal conductivity compared to commonly used solder joints. The bottleneck of Cu Cu bonding technology is the rapid oxidation of Cu and adsorption of a contamination layer upon exposure to air. This effect can be strongly reduced by using self-assembled monolayers (SAMs) as temporary protective coatings on Cu substrates. The results of X-ray photoelectron spectroscopy (XPS) yielded a drastic decrease in oxidation rate of both sputtered and electroplated Cu surfaces during storage of passivated samples at −40 °C for 7 days. The results of infrared spectroscopic ellipsometry (IRSE) showed that after 10 days of air exposure at room temperature the long-chain 1-hexadecanethiol (C16) SAMs appear to still remain on the Cu surface and to have much slower oxidation rate in comparison to the short-chain 1-hexanethiol (C6) SAMs. Therefore, we can make a conclusion that the application of long-chain alkanethiols or storage of passivated samples at low temperature can provide a long-term oxidation protection for Cu surfaces stored in air.

An unprecedented phosphonic acid with a vinylene-bridged fluoroalkyl chain (-C6F12-CH=CH-C6F13) was synthesized and characterized. This compound comprises the perfluorohexyl (C6F13) group, which allows the exclusion of the use and formation of bioaccumulative perfluorooctanoic-acid-related compounds (i.e., compounds containing the (C7F15)C moiety). Self-assembled monolayers (SAMs) of the novel phosphonic acid were formed on indium-tin oxide and stainless steel substrates by solution deposition. The surface properties, formation kinetics, and thermal stabilities of the SAMs were investigated by X-ray photoelectron spectroscopy, contact angle measurements, and atomic force microscopy. Compared to the SAMs of known fluorinated phosphonic acids containing CnF2n+1 groups (n = 4, 6, 8), the SAM of this novel phosphonic acid bearing the -C6F12-CH=CH-C6F13 group showed a high uniformity, a lower surface energy, and a lower contact angle hysteresis. In addition, the novel phosphonic acid allowed the rapid modification of metal oxide surfaces and imparted a superior thermal stability compared to conventional fluorinated phosphonic acids. Therefore, this phosphonic acid bearing a vinylene-bridged fluoroalkyl chain is a promising candidate for improving both surface modification and environmental properties in comparison with conventional analogs having long perfluoroalkyl chains.

Uranium, as a naturally radioactive actinide element, plays a significant role in the nuclear industry. It is reasonably necessary to develop a fast and efficient approach for uranyl ions detection. In consideration of the practical application, fluorescent film sensor exhibits great advantages of convenience, ease of being made into portable devices, etc. Herein, a new film senor towards uranyl ion has been designed and fabricated via drawing into an AIE-active (aggregation-induced emission) tetraphenylethene moiety and a carbamoylphosphine oxide chelate moiety through a self-assembled monolayer on quartz glass. Fluorescence spectra measurements demonstrated that the film sensor could be used for detecting UO22+ in a simple way with the range of 0–0.5 μM, and the calculated limit of detection was as low as 32 nM. On the basis of the results from XPS, NMR, MS, time-resolved fluorescence spectra and absorption spectra measurements, the fluorescence quenching was arising from the UO22+ located around the tetraphenylethene molecules under the ground state. Furthermore, the film sensor exhibit higher selectivity toward UO22+ than the other metal ions. These results suggest that the film sensor can be applied as a convenient sensor for the UO22+ detection.

Three surface modifiers consisting of three parts were synthesized to fabricate photo-patternable self-assembled monolayers (SAMs) on inorganic materials for pattern-transformation; the first part is the one that binds to the surface of metal oxides (trialkoxysilane or phosphonic acid with an amino group at the end), the second is an o-nitrobenzyl (ONB) linker that protects the amino group, and the third is a hydrophobic polyhedral oligomeric silsesquioxane (POSS) that is connected to the linker. The immobilized silicon wafer with a silane coupling agent or indium tin oxide with the phosphonic acid became nearly as hydrophobic as the silicon surface-modified with perfluoroalkyl agents. After photoirradiation, the second and third parts (ONB linker with the POSS moiety) were removed and the modified surfaces became hydrophilic owing to the appearance of amino groups. This was confirmed using the contact angle of water and X-ray photoelectron spectroscopy data. Silver nano-ink or 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene was selectively deposited on the photo-irradiated region using a mask.

A new hybrid of favorable orientated cytochrome c (cyt c) and a 1-Pyreneacetic acid (PA) functionalized graphene (Gr) on Au electrode (AuE) was prepared. In the hybrid system, Gr was functionalized with (PA) molecule through π-π interaction (PA-Gr). Afterward the PA-Gr attached to the AuE via Thionalide self-assembled monolayer (SAM), then conjugated with cyt c. The AuE/SAM/PA-Gr/cyt c hybrid system was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) techniques. SECM approach curves were applied to measure the standard tunneling electron transfer (ET) and bimolecular rate constants which were 56.6 s-1 and 1×109cm3mol-1s-1, respectively.

Compared with current vacuum-deposited multilayer organic light-emitting diodes (OLEDs), solution-processed simplified-structured OLEDs are more appealing by merits of low costs and promising potentials in large-area OLEDs. Nevertheless, it remains challenging due to intermixing between adjacent organic layers. Herein, indium tin oxide (ITO) surface was deposited with molybdenum trioxide (MoO3) and then modified with self-assembled monolayer (SAM) of pentafluorobenzyl phosphonic acid. The SAM modification process made the MoOx film rich in oxygen vacancies, which ensured effective hole injection from the hybrid modified ITO directly to the emitting layer. This strategy facilitates HTL-free OLEDs and then completely avoids interlayer intermixing. Using the hybrid modified ITO as anode, HTL-free solution-processed green phosphorescent OLED was prepared and achieved a maximum current efficiency of 63.24 cd A−1 and a maximum external quantum efficiency of 18.18%. Meanwhile, preferable operational stability than standard multilayer OLEDs was obtained. For red phosphorescent OLED, a maximum external quantum efficiency of 17.49% was achieved. This work proposed a new way of adjusting cation valence to improve hole injection, contributing to solution-processed OLED fabrication.

Whereas modification of individual interfaces in organic photovoltaic (OPV) devices by self-assembled monolayers (SAMs) is a well-established procedure, simultaneous engineering of several interfaces therein represents still a challenge, with an open outcome. In this context, in the present study, we test a dual modification approach by the example of a model OPV device, featuring in particular indium tin oxide (ITO) cathode, ZnO cathode buffer layer (CBL), and a polymer heterojunction active layer (AL). The dual modification involved both ITO/ZnO and ZnO/AL interfaces, which were engineered with several SAMs bearing electron-withdrawing and electron-donating tail groups. Characterization of these interfaces and the CBL suggests that the major effects of the SAM-engineering were optimization of the interfacial electrical contacts and interfacial dipole as well as improved morphology of the CBL and lower density of defects therein. Interestingly, at the single interface modification, a larger positive effect was achieved with the –OCH3 terminated SAM than with the –CF3 decorated one. In contrast, at the dual modification, an inverse effect was observed, with a better performance of the –CF3 termination, pointing to a complex synergetic mechanism. Significantly, the dual modification resulted in a noticeably larger improvement of the photovoltaic characteristics of the OPV devices as compared to the standard approach, manifesting the advantages of the dual strategy.

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.

A short chain peptide is covalently attached to an evaporated gold electrode to form a biocompatible self-assembled monolayer (SAM) surface. The peptide is designed to optimize the interfacial interaction of horse heart cytochrome c (cytc) through the electrostatic interaction of the carboxylate group on the terminal amino acid glutamate and the amine on lysine in cytc. Cytc exhibits quasi-reversible voltammetry and is stable on the time scale of the experiments. Marcus theory is used to calculate the electron transfer rates, which are ~5 times faster for cytc/peptide/Au compared to cytc/11-mercaptoundecanoic acid/Au SAMs of similar chain length. The formal potentials also shift for the cytc/peptide system ~20 mV more positive than cytc adsorbed to 11-mercaptoundecanoic acid-SAM/Au electrodes.

We demonstrated a homeotropic liquid crystal (LC) alignment state on fluorinated self-assembled monolayers (FSAMs) deposited by gas-phase method as a function of deposition time. The gas-phase method to deposit FSAMs was simple process and cost-effective. Contact angle data and surface energy analyses of the FSAMs showed that film formation occurs, and showed a correlation with the homeotropic alignment of LC molecules on the FSAMs. Stable LC alignments on FSAMs were achieved at deposition time over 60 min. In addition, high transparency and thermal stability of FSAM further enhanced its possibility as a LC alignment layer.

The chemical composition of self-assembled monolayers on the surface of pyrolytic-coke particles were examined by a variety of characteristic tests and the results revealed that aliphatic hydrocarbons are incorporated as self-assembled monolayers on the surface of pyrolytic coke particles. The self-assembled monolayers are responsible for particulate agglomeration of pyrolytic-cokes in hot quench water and fouling propensity. The size distribution of agglomerated particles was observed by scanning electron microscopy representing the merged agglomerated particles by self-assembled monolayer. Energy-dispersive X-ray spectra revealed no heteroatoms in the chemical structure of self-assembled monolayer, while BET technique highlighted the active role of micropores to adsorb the self-assembled monolayers. Particle size analysis revealed the agglomeration process of coke fines from id: 1–5 μm to 10–40 μm. Such agglomeration increases the risk of plugging and restriction of heat transfer in process equipments. The results revealed that a reliable solution to overcome the fouling problem is preventing the formation of self-assembled monolayers.