Active straining engineering on self-assembled stacked Ni-based hybrid electrode for ultra-low overpotential

Generating sufficient strains on metal surfaces are highly challenging owing to that most metals can deform plastically to relax the strains on the surfaces.In this work,we developed a facile but highly efficient stacked deposition strategy to in situ activation and reconstruction of NiO/NiOOH on Ni matrix,following with the migration of Fe ions to NiOOH.The Fe sites on the Ni/NiO/NiOOH facilitate the formation of the stable*OH oxygenated intermediates,and the Ni matrix in the catalyst provides the catalyst excellent stability.The oxygen evolution reaction(OER)performance of the stacked NiFe-5 with compressive strain displays the strengthened binding to oxygenated intermediates and superior OER activity,the ultralow overpotentials of 162 versus reversible hydrogen electrode at 10 mA cm^(-2).On the other hand,the Ni-5 without the incorporation of Fe has shown an outstanding hydrogen evolution reaction(HER)activity,affording an overpotential of 47 mV at 10 mA cm^(-2).The NiFe-5‖Ni-5 enables the overall water splitting at a voltage of 1.508 V to achieve 20 mA cm^(-2) with remarkable durability.The stacked deposition strategy improves binding strength of Ni-based catalysts to oxygenated intermediates via generating compressive strain,causing high catalytic activities on OER and HER.

Au@Ag Core-shell Nanorods Self-assembled on Polyelectrolyte Multilayers for Ultra-High Sensitivity SERS Fiber Probes

We demonstrated a chemical process in the fabrication of a SERS fiber probe with an ultrahigh sensitivity.The synthesis was carried out by preparing Au@Ag core-shell nanorods (Au@Ag-NRs) selfassembled on polyelectrolyte (PE) multilayers,for which Au@Ag-NRs were controlled by adjusting the silver layer thickness.The effect of silver layer thickness of Au@Ag-NRs on the SERS performance of the fiber probe was investigated.The SERS fiber probe shows the best performance when the silver layer thickness is controlled at 8.57 nm.Under the condition of optimizing silver layer thickness,the fiber probe exhibits ultra-high sensitivity (i e,10^(-10) M crystalline violet,CV),good reproducibility (i e,RSD of 3.5%) and stability.Besides,electromagnetic field distribution of the SERS fiber probe was also investigated.The strongest enhancement is found within the core of fiber,whereas a weakened electromagnetic field exists in the fiber cladding layer.The SERS fiber probe can be a good candidate in ultra-trace detection for biomedical and environmental areas.

Novel self-assembled films of La-based phosphonate 3-aminopropyltriethoxysilane

Silane coupling reagent (3-aminopropyltriethoxysilane (APTES)) was prepared on single-crystal silicon substrates to form two-dimensional self-assembled monolayer (SAM). The terminal-NH2 groups in the film were in situ phosphorylated to -PO(OH)2 group to endow the film with good chemisorption ability. Then La-based thin films were deposited on phosphorylated APTES-SAM in order to make good use of the chemisorption ability of -PO(OH)2 groups. The thickness of the film was determined with ellipsometer, while phase transformation and surface morphology, surface energy, phase composition were analyzed by means of atomic force microscope (AFM), contact angle measurements and X-ray photoelectron spectroscopy (XPS). The results indicated that the terminal-NH2 groups could be completely transformed into desirable-PO(OH)2 groups after phosphorylation of APTES-SAM. Detailed XPS analysis of the La3+ peaks revealed that lanthanum element existed in the films in different states. As a result, conclusion could be made that lanthanum reacted with -PO(OH)2 groups on the surface of the substrate by chemical bond which would improve the bonding strength between the film and silicon substrate. Since the La-based thin films were well adhered to the silicon substrate, it might find promising application in the surface-modification of single-crystal Si and SiC in microelectromechanical systems (MEMS).

Self-Assembled Al Nanostructure/ZnO Quantum Dot Heterostructures for High Responsivity and Fast UV Photodetector

Light confinement induced by spontaneous near-surface resonance is inherently determined by the location and geometry of metallic nanostructures(NSs),offering a facile and effective approach to break through the limitation of the light-mater interaction within the photoactive layers.Here,we demonstrate high-performance Al NS/ZnO quantum dots(Al/ZnO) heterostructure UV photodetectors with controllable morphologies of the self-assembled Al NSs.The Al/ZnO heterostructures exhibit a superior light utilization than the ZnO/Al heterostructures,and a strong morphological dependence of the Al NSs on the optical properties of the heterostructures.The inter-diffusion of Al atoms into ZnO matrixes is of a great benefit for the carrier transportation.Consequently,the optimal photocurrent of the Al/ZnO heterostructure photodetectors is significantly increased by 275 times to ~1.065 mA compared to that of the pristine ZnO device,and an outstanding photoresponsivity of 11.98 A W-1 is correspondingly achieved under 6.9 MW cm-2 UV light illumination at 10 V bias.In addition,a relatively fast response is similarly witnessed with the Al/ZnO devices,paving a path to fabricate the high-performance UV photodetectors for applications.

Kinetic Monte Carlo simulations of three-dimensional self-assembled quantum dot islands

By three-dimensional kinetic Monte Carlo simulations, the effects of the temperature, the flux rate, the total coverage and the interruption time on the distribution and the number of self-assembled InAs/GaAs(001) quantum dot(QD) islands are studied, which shows that a higher temperature, a lower flux rate and a longer growth time correspond to a better island distribution. The relations between the number of islands and the temperature and the flux rate are also successfully simulated. It is observed that for the total coverage lower than 0.5 ML, the number of islands decreases with the temperature increasing and other growth parameters fixed and the number of islands increases with the flux rate increasing when the deposition is lower than 0.6 ML and the other parameters are fixed.

Characterization of Self-assembled Monolayers on Gold Electrode Using Electrochemical Quartz Crystal Microbalance

The electrochemical quartz crystal microbalance (EQCM) is used to investigate the characteristics of the thiolated self-assembled monolayer(SAM) on gold surface.A 5MHz QCM element serves as both the mass-sensitive sensor and the working electrode of the electrochemical system.The 6-mecapto-1-hexanol and and the 16-mer oligonucleotide with a mercaptohexyl group at the 5'-phosphate end are utilized to form the SAM on the gold electrode.The frequency response of the QCM during cyclic voltammetry (CV) scanning and cbronoamperometry are recorded together with the electrochemical current.The experimental results indicates that the frequency response is more sensitive to the surface coverage.Therefore,the response of the EQCM reveals more details of the SAM on gold electrode.It is especially useful for analysing the immobilization quality,such as probe orientation and coverage,of the SAM.

The Molecular Recognition Characteristics of ω-MercaptoMethoxy Poly(Ethylene Glycol) Self-assembled Monolayer at Gold Electrode and the Detection of Dopamine in Serum

Self assembled monolayers (SAMs) of to-mercapto methoxy poly(ethylene glycol)(MPEG) on gold electrode were used as a means to detect dopamine. Dopamine (DA) had good response at the MPEG film electrode and ascorbic acid (AA) was repelled from the SAMs. TheMPEG film is a biocompatible film, there was no adsorption of biosample and no inactivation atelectrode surface when it was used to detect DA in biosamples.

Recent advances in design and applications of biomimetic self-assembled peptide hydrogels for hard tissue regeneration

The development of natural biomaterials applied for hard tissue repair and regeneration is of great importance,especially in societies with a large elderly population.Self-assembled peptide hydrogels are a new generation of biomaterials that provide excellent biocompatibility,tunable mechanical stability,injectability,trigger capability,lack of immunogenic reactions,and the ability to load cells and active pharmaceutical agents for tissue regeneration.Peptide-based hydrogels are ideal templates for the deposition of hydroxyapatite crystals,which can mimic the extracellular matrix.Thus,peptide-based hydrogels enhance hard tissue repair and regeneration compared to conventional methods.This review presents three major self-assembled peptide hydrogels with potential application for bone and dental tissue regeneration,including ionic self-complementary peptides,amphiphilic(surfactant-like)peptides,and triple-helix(collagen-like)peptides.Special attention is given to the main bioactive peptides,the role and importance of self-assembled peptide hydrogels,and a brief overview on molecular simulation of self-assembled peptide hydrogels applied for bone and dental tissue engineering and regeneration.

Immobilization of antibodies on the self-assembled monolayer by antigen-binding site protection and immobilization kinetic control

The orientation of the biological molecule immobi-lized on a solid surface has been critical in devel-opment of various applications. In this study, ori-entation of antibody was retained by protecting the antigen-binding site of the antibody prior to immo-bilization to -functionalized mixed self-assembled monolayer (SAM) of 12-mercaptododecanoic acid and 1-heptanethiol. More importantly, the number of immobilization bonds formed between each an-tigen-binding site protected antibody molecule and the solid surface was controlled by optimizing the mole fraction of the activated carboxyl group of the linker molecules in the mixed SAM. The amount of antibody used in this study was approximately equivalent to the amount for one monolayer surface coverage. The resulting activity of protected immo-bilized antibody was about 10 fold higher than that of random immobilized

Electrochemical investigation on the film of L-cysteine self-assembled to nanoparticles on a gold electrode

The film contained L-cysteine and gold nanoparticles were provided by self-assembled monolayers (SAMs) and potentiostatic electrodeposition technology on the gold electrode. Two methods were used to study the film: In the first, cyclic voltammetry (CV) was used to inspect the functional groups of the film and the same time hydroquinone was chosen to be a probe molecule in the based solution;secondly, based on analytical technology of scanning electrochemical microscopy (SECM), the heterogeneous rate constant (keff) between solid phase (the modified electrode) and liquid phase (K3Fe(CN)6) was obtained. As a result, the better binary catalysis of hydroquinone was demonstrated and the heterogeneous rate constant (keff) is the greater at 8 h for L-cysteine self-assembled monolayers (SAMs).

The Electrochemistry of Cytochrome c at a Viologen-thiol Self-Assembled Monolayer

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Electrochemical Impedance Study of Schiff Base by Means of Self-assembled Monolayer

In this work, the self-assembled monolayer of Schiff base was first investigated using electrochemical impedance spectroscopy (EIS). The complexation of Cu2+ with the Schiff base was also detected with EIS method. The approximate linear relationship between Cu2+ and the reaction resistance (Rr) was observed. All the results suggest that the electrochemical property of Schiff base could be studied conveniently by means of forming self-assembled monolayer.

The Intermolecular Interaction in Self-Assembled Monolayers on Gold Electrode

The intermolecular interaction in an azobenzene self-assembled monolayers (SAMs) ongold electrode was investigated by controlling the assembling time and using mixed self-assembledtechniques, and the variation of apparent electron transfer rate constant (ks) of azobenzene SAMswith different molecular packing density is repofted.

Characterization of Formation Kinetics of Self-Assembled Thiol Monolayers on Gold by Electrochemical Impedance Spectroscopy

Self-assembled monolayers of octadecanethiol (ODT) on gold have been studied by electrochemical impedance spectroscopy (EIS). The fractional coverage has been examined as a function of immersion time of Au in ODT deposition solution. The fractional coverage exhibits two distinct adsorption steps: an initial rapid step followed by a slow one. The fractional coverage of ODT monolayer increases sharply from zero to more than 99% of its maximum within the first minute. However, it takes a day for the fractional coverage to approach its final value.

Fluorescence spectra of colloidal self-assembled CdSe nano-wire on substrate of porous Al2O3/Au nanoparticles

We present a self-assembly method to prepare array nano-wires of colloidal CdSe quantum dots on a substrate of porous Al2 O3 film modified by gold nanoparticles. The photoluminescence(PL) spectra of nanowires are in situ measured by using a scanning near-field optical microscopy(SNOM) probe tip with 100-nm aperture on the scanning near-field optical microscope. The results show that the binding sites from the edge of porous Al2 O3 nanopores are combined with the carboxyl of CdSe quantum dots’ surface to form an array of CdSe nanowires in the process of losing background solvent because of the gold nanoparticles filling the nano-holes of porous Al2 O3 film. Compared with the area of nonself-assembled nano-wire, the fluorescence on the Al2 O3/Au/CdSe interface is significantly enhanced in the self-assembly nano-wire regions due to the electron transfer conductor effect of the gold nanoparticles’ surface. In addition, its full width at half maximum(FWHM) is also obviously widened. The method of enhancing fluorescence and energy transfer can widely be applied to photodetector, photocatalysis, optical display, optical sensing, and biomedical imaging, and so on.

Improvement of Performance of HfS_2 Transistors Using a Self-Assembled Monolayer as Gate Dielectric

This work details a study based on HfS_(2 )transistors utilizing an n-octadecylphosphonic acid-based self-assembled monolayer(SAM)as the gate dielectric.The fabrication of the SAM-based two-dimensional(2D)material transistor is simple and can be used to improve the quality of the interface of air-sensitive 2D materials.In comparison to HfS_(2) transistors utilizing a conventional Al_2O_(3) gate insulator by atomic layer deposition,HfS_(2) transistors utilizing an SAM as the gate dielectric can reduce the operation region from 4 V to 2 V,enhance the field-effect mobility from 0.03 cm^2/Vs to 0.75 cm^2/Vs,improve the sub-threshold swing from 404 m V/dec to 156 m V/dec,and optimize the hysteresis to 0.03 V,thus demonstrating improved quality of the semiconductor/insulator interface.

Assessment of Defects and Collapsed Sites in Self-Assembled Alkanethiol Monolayer on Gold by Cyclic Voltammetry and A.C.Impedance

Self-assembly of octadecyl mercaptan on gold was investigated by cyclic voltammetry(CV) and electrochemical impedance spectroscopy (EIS). Results of CV experiments show thatthere are no structUral defects exposed directly to the redox couple in solution, but EISexperiments indicate that collapsed sites exist in the monolayer. A method to estimate the degree ofdisorder in the Au/thiol monolayer surface is proposed by using admittance plane plot.

The Channel Behavior of Gramicidin D in the Self-assembled Monolayer

It was found for the first time that gramicidin D (GD) molecules can be incorporated intothe ODM monolayer which is self-assembled on the surface of the gold electrode and formmonovalent canon channels.

A MEMS Based Amperometric Immunosensor with Self-assembled Monolayers Immobilization Technique

Based on MEMS technology,immunosensor with an'Au,Pt,Pt'three-microelectrode system enclosed in a SU-8 micro pool was fabricated.Employing SAMs technique,the Au electrode was modified by cysteamine(Cys)to assemble gold nanopanicles(nanogold)layer,subsequently,a layer of protein G(PG)was immobilized on nanogold layer to further capture antibody orientedly.Compared with the immunosensors using bulky gold electrode and direct PG binding to electrode immobilization technique for antibody,it has attractive advantages,such as miniaturization,good compatibility,broad linear range for human immunoglobulin(HIgG)and easy to be designed into array.