Low adhesion, non-wetting phosphonate self-assembled monolayer films formed on copper oxide surfaces

Atto-Scale Noise Near-Infrared Organic Photodetectors Enabled by Controlling Interfacial Energetic Offset through Enhanced Anchoring Ability

The near-infrared (NIR) sensor technology is crucial for various applications such as autonomous driving and biometric tracking. Silicon photodetectors (SiPDs) are widely used in NIR applications; however, their scalability is limited by their crystalline properties. Organic photodetectors (OPDs) have attracted attention for NIR applications owing to their scalability, low-temperature processing, and notably low dark current density (JD), which is similar to that of SiPDs. However, the still high JD (at NIR band) and few measurements of noise equivalent powers (NEPs) pose challenges for accurate performance comparisons. This study addresses these issues by quantitatively characterizing the performance matrix and JD generation mechanism using electron-blocking layers (EBLs) in OPDs. The energy offset at an EBL/photosensitive layer interface determines the thermal activation energy and directly affects JD. A newly synthesized EBL (3PAFBr) substantially enhances the interfacial energy barrier by forming a homogeneous contact owing to the improved anchoring ability of 3PAFBr. As a result, the OPD with 3PAFBr yields a noise current of 852 aA (JD = 12.3 fA cm⁻2 at V → -0.1 V) and several femtowatt-scale NEPs. As far as it is known, this is an ultralow of JD in NIR OPDs. This emphasizes the necessity for quantitative performance characterization.

Thermal Stability and Orthogonal Functionalization of Organophosphonate Self-Assembled Monolayers as Potential Liners for Cu Interconnect

In this study, we investigated the thermal stabilities of butylphosphonic acid (BPA) and aminopropyltriethoxysilane (APTES) self-assembled monolayers (SAM) on a Si substrate. The thermal desorption and the thermal cleavage of the BPA and APTES SAM film on the Si substrate were studied by X-ray photoelectron spectroscopy (XPS) upon thermal treatment from 50 to 550 °C. XPS analyses show that the onset of the thermal desorption of the APTES monolayer occurs at 250 °C and the APTES SAM completely decomposed at 400 °C. Conversely, BPA SAM on Si shows that the onset of thermal desorption occurs at 350 °C, and the BPA SAM completely desorbed at approximately 500 °C. Our study revealed that the organophosphonate SAM is a more stable SAM in modifying the dielectric sidewalls of a Cu interconnect when compared to organosilane SAM. To overcome the spontaneous reaction of the organophosphonate film on the metal substrate, a simple orthogonal functionalization method using thiolate SAM as a sacrificial layer was also demonstrated in this study.

Zwitterionic Copolymer-Regulated Interfacial Polymerization for Highly Permselective Nanofiltration Membrane

A highly permselective nanofiltration membrane was engineered via zwitterionic copolymer assembly regulated interfacial polymerization (IP). The copolymer was molecularly synthesized using single-step free-radical polymerization between 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-aminoethyl methacrylate hydrochloride (AEMA) (P[MPC-co-AEMA]). The dynamic network of P[MPC-co-AEMA] served as a regulator to precisely control the kinetics of the reaction by decelerating the transport of piperazine toward the water/hexane interface, forming a polyamide (PA) membrane with ultralow thickness of 70 nm, compared to that of the pristine PA (230 nm). Concomitantly, manipulating the phosphate moieties of P[MPC-co-AEMA] integrated into the PA matrix enabled the formation of ridge-shaped nanofilms with loose internal architecture exhibiting enhanced inner-pore interconnectivity. The resultant P[MPC-co-AEMA]-incorporated PA membrane exhibited a high water permeance of 15.7 L·m^-2·h^-1·bar^-1 (more than 3-fold higher than that of the pristine PA [4.4 L·m^-2·h^-1·bar^-1]), high divalent salt rejection of 98.3%, and competitive mono-/divalent ion selectivity of 52.9 among the state-of-the-art desalination membranes.

The nature of self-assembled octadecylphosphonic acid (ODPA) layers on copper substrates

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.

Synthesis of fluorinated phosphorus-containing copolymers and their immobilization and properties on stainless steel

A series of fluorinated-phosphonic acid methacrylates were synthesized by free radical polymerization using heptadecafluorodecyl methacrylate (HDFDMA) and (dimethoxyphosphoryl) methyl methacrylate (DMPMM) monomers for potential application as anti-corrosion coatings. The dimethyl protecting groups were then hydrolyzed, giving phosphonic acid groups that are able to stably bind onto metal oxide surfaces. The copolymers were then immobilized as a monolayer film to the surface of 316L stainless steel by treatment of dilute solutions in trifluoroacetic acid for 30 minutes followed by rinsing. The surfaces were analyzed using various techniques and contact angles as high as 128° were recorded for some copolymer functionalized surfaces. Results also demonstrated that the polymer films proved stable to hydrolysis over several weeks of immersion in water.

A series of fluorinated-phosphonic acid methacrylates were synthesized by free radical polymerization using heptadecafluorodecyl methacrylate (HDFDMA) and (dimethoxyphosphoryl) methyl methacrylate (DMPMM) monomers for potential application as anti-corrosion coatings.

Molecular Coverage Determines Sliding Wear Behavior of n-Octadecylphosphonic Acid Functionalized Cu-O Coated Steel Disks against Aluminum

The sliding wear behavior of Cu–O coated steel disks functionalized with n-octadecyl-phosphonic acids was evaluated against aluminum in ball-on-disk tribometer experiments. After 5 m of sliding the friction coefficient of the functionalized sample with maximum molecular coverage is ≤0.3 ± 0.1. Surfaces with lower coverage mitigate friction and wear as well exhibiting initially similar low friction coefficients but reveal the breakdown of lubrication for sliding distances <5 m. The length of the low friction sliding distance before breakdown scales with the coverage of n-octadecylphosphonic acids on the Cu–O surface. Coverage hence determines the tribological behavior of the functionalized surface against sliding aluminum. As the coverage is increased, detrimental asperity contacts between the rubbing surfaces are reduced.

Phosphonate and carboxylic acid co-functionalized MoS2 sheets for efficient sorption of uranium and europium: Multiple groups for broad-spectrum adsorption

It is significant to develop novel materials and techniques for efficient removal of radionuclides from radioactive wastes due to the radioactive and chemical toxicity. In this paper, we report a strategy for broad-spectrum adsorption of radionuclides by multiple groups-decorated adsorbents. Specifically, the adsorbents were prepared by grafting diethyl-(4-vinylbenzyl) phosphonate and maleic anhydride copolymers onto molybdenum disulfide sheets for the sorption of uranium(VI) and europium(III). The sorption efficiencies exhibited a dependency on pH, contact time and initial concentrations. The sorption reached the equilibrium within 60 min and followed a pseudo-second-order kinetic model. The maximum sorption capacities of the sorbents were 448.4 mg/g and 171.2 mg/g at pH 4.0 and 298.15 K for uranium(VI) and europium(III), respectively. The sorbent possessed a high efficiency of 98% in five sorption-desorption cycles without damage in chemical structures. XPS spectra showed that the sorption of uranium(VI) and europium(III) on the sorbents were originated from the interaction between multiple groups (such as sulfur, COOH, PO and PO) and uranium/europium. This work demonstrates that the adsorbent can be utilized as a promising material for the separation of broad-spectrum radionuclides from an aqueous solution.

Adsorption Studies of Organophosphonic Acids on Differently Activated Gold Surfaces

In this study, the formation of self-assembled monolayers consisting of three organophosphonic acids (vinyl-, octyl-, and tetradecylphosphonic acid) from isopropanol solutions onto differently activated gold surfaces is studied in situ and in real time using multiparameter surface plasmon resonance (MP-SPR). Data retrieved from MP-SPR measurements revealed similar adsorption kinetics for all investigated organophosphonic acids (PA). The layer thickness of the immobilized PA is in the range of 0.6-1.8 nm corresponding to monolayer-like coverage and correlates with the length of the hydrocarbon chain of the PA molecules. After sintering the surfaces, the PA are irreversibly attached onto the surfaces as proven by X-ray photoelectron spectroscopy and attenuated total reflection infrared and grazing incidence infrared spectroscopy. Potential adsorption modes and interaction mechanisms are proposed.

Fast formation of superhydrophobic octadecylphosphonic acid (ODPA) coating for self-cleaning and oil/water separation

A simple and fast method to prepare robust superhydrophobic octadecylphosphonic acid (ODPA) coating on oxidized copper mesh for self-cleaning and oil/water separation is reported here. The substrate of the copper mesh was first oxidized by simple immersion in an aqueous solution of 1.0 M NaOH and 0.05 M K2S2O8 at room temperature for 30 min, which was then covered with micro- and nanoscale Cu(OH)2 on the surface. Subsequently, the oxidized copper mesh was immersed in 2 × 10(-4) M octadecylphosphonic acid/tetrahydrofuran (ODPA/THF) solution, an ODPA coating formed on the oxidised copper mesh. The ODPA coating formation process takes place rapidly, almost in 1 second, which makes the as-prepared mesh exhibit superhydrophobicity with the water contact angle of approximately 158.9° and superoleophilicity with the oil contact angle of 0°. Moreover, the as-prepared mesh has self-cleaning effect and can be repeatedly used to efficiently separate a series of oil/water mixtures like gasoline/water and diesel/water. Interestingly, straightforward oxidation of a copper substrate produces a "water-removing" type oil/water separation mesh with underwater superoleophobicity, whereas ODPA coating on the oxidized copper mesh produces an "oil-removing" type oil/water separation mesh with superhydrophobicity and superoleophilicity. This interesting conversion results from a small amount of ODPA and takes place very rapidly.

Polystyrene films as barrier layers for corrosion protection of copper and copper alloys

Dip-coated polystyrene layers of sub-micrometre thickness (85-500nm) have been applied on copper and copper alloys (aluminium brass, copper-nickel 70/30), as well as on stainless steel 304, and produced an effective barrier against corrosion and adhesion of corrosion-relevant microorganisms. According to the dynamic wettability measurements, the coatings exhibited high advancing (103°), receding (79°) and equilibrium (87°) contact angles, low contact angle hysteresis (6°) and surface free energy (31mJ/m(2)). The corrosion rate of copper-nickel 70/30 alloy samples in 3.5% NaCl was as low as 3.2μm/a (44% of that of the uncoated samples), and in artificial seawater was only 0.9μm/a (29% of that of the uncoated samples). Cell adhesion was studied by fluorescence microscopy, using monoculture of Desulfovibrio alaskensis. The coatings not only decreased the corrosion rate but also markedly reduced the number of bacterial cells adhered to the coated surfaces. The PS coating on copper gave the best result, 2×10(3)cells/cm(2) (1% of that of the uncoated control).

Adsorption of a PEO-PPO-PEO triblock copolymer on metal oxide surfaces with a view to reducing protein adsorption and further biofouling

Abstract Biomolecule adsorption is the first stage of biofouling. The aim of this work was to reduce the adsorption of proteins on stainless steel (SS) and titanium surfaces by modifying them with a poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-PEO triblock copolymer. Anchoring of the central PPO block of the copolymer is known to be favoured by hydrophobic interaction with the substratum. Therefore, the surfaces of metal oxides were first modified by self-assembly of octadecylphosphonic acid. PEO-PPO-PEO preadsorbed on the hydrophobized surfaces of titanium or SS was shown to prevent the adsorption of bovine serum albumin (BSA), fibrinogen and cytochrome C, as monitored by quartz crystal microbalance (QCM). Moreover, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry were used to characterize the surfaces of the SS and titanium after competitive adsorption of PEO-PPO-PEO and BSA. The results show that the adsorption of BSA is well prevented on hydrophobized surfaces, in contrast to the surfaces of native metal oxides.

Corrosion resistant performances of alkanoic and phosphonic acids derived self-assembled monolayers on magnesium alloy AZ31 by vapor-phase method

Alkanoic and phosphonic acid derived self-assembled monolayers (SAMs) were formed on magnesium alloy by the vapor phase method. AFM and XPS studies showed that SAMs were formed on Mg alloy. The chemical and anticorrosive properties of the SAMs prepared on magnesium alloys were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. Water contact angle measurements revealed that, although SA and ISA have the same headgroup to anchor to the magnesium alloy surface, the packing density on the magnesium alloy surface could be considerably different. The contact angle hysteresis of SAMs with a carboxylate headgroup is much larger than that of SAMs with a phosphonic acid group. The XPS O 1s peaks indicated more likely a mix of mono-, bi-, or tridentate binding of phosphonic acid SAM to the oxide or hydroxide surface of the Mg alloy. The electrochemical measurements showed that the phosphonic acid derived SAM had better corrosion resistance compared to alkanoic acid derived SAM. The chemical stability of SAMs modified magnesium alloy was investigated using water contact angle and XPS measurements. The water contact angle and XPS measurements revealed that the molecular density of OP and PFEP on magnesium alloy would be higher than those of SA and ISA on magnesium alloy.

Self-assembled monolayers of thiols and dithiols on gold: new challenges for a well-known system

Self-assembled monolayers (SAMs) of alkanethiols and dialkanethiols on gold are key elements for building many systems and devices with applications in the wide field of nanotechnology. Despite the progress made in the knowledge of these fascinating two-dimensional molecular systems, there are still several "hot topics" that deserve special attention in order to understand and to control their physical and chemistry properties at the molecular level. This critical review focuses on some of these topics, including the nature of the molecule-gold interface, whose chemistry and structure remain elusive, the self-assembly process on planar and irregular surfaces, and on nanometre-sized objects, and the chemical reactivity and thermal stability of these systems in ambient and aqueous solutions, an issue which seriously limits their technological applications (375 references).