Different strategies for functionalization of diamond surfaces

Nitridation of diamond(111) surface by density functional theory

Density functional theory was employed to examine the adsorption and thermal evolution of nitrogen species on diamond(111) impacted by microwave N2 plasma. On bare domains of diamond, as represented by the models of C(111)-2 × 1 and graphite-like C(111), N2(ad) is identified as the major surface species; the desorption of N2(ad) proceeds on both models via a concerted process of breaking two C-N bonds. By contrast, there is evidence of the formation of (NH)2(ad) via the insertion reaction of microwave N2 plasma on hydrogenated domains of diamond, as represented by the models of C(111)-2 × 1-H and C(111)-1 × 1-H. Interestingly, contrasting dynamics of desorption of (NH)2(ad) are presented on these two models, that is, via sequential breaking of two C-N bonds on C(111)-2 × 1-H and via concerted breaking of both C-N bonds on C(111)-1 × 1-H. Our results demonstrate that the observed diversity of surface nitrogen species in composition, bonding, vibration, and desorption in prior experiments is linked to domains of a variety of surface terminations and reconstructions on diamond(111).

Significant thermal rectification induced by phonon mismatch of functional groups in a single-molecule junction

Single-molecule junctions (SMJs) may bring exotic physical effects. In this work, a significant thermal rectification effect is observed in a cross-dimensional system, comprising a diamond, a single-molecule junction, and a carbon nanotube (CNT). The molecular dynamics simulations indicate that the interfacial thermal resistance varies with the direction of heat flow, the orientation of the crystal planes of the diamond, and the length of the CNT. We find that the thermal rectification ratio escalates with the length of the CNT, achieving a peak value of 730% with the CNT length of 200 nm. A detailed analysis of phonon vibrations suggests that the primary cause of thermal rectification is the mismatched vibrations between the biphenyl and carbonyl groups. This discovery may offer theoretical insights for both the experimental exploration and practical application of SMJs in efficient thermal management strategy for high power and highly integrated chips.

Heteroatom Functionalization of H-Terminated Diamond Surfaces

Diamond surface functionalization has received significant research interest recently. Specifically, H-termination has been widely adopted because it endows the diamond surface with negative electron affinity and the hole carrier is injected in the presence of surface transfer dopants. Exploring different functional groups' attachment on diamond surfaces and their impact on the electronic structure, using wet and dry chemical approaches, would hence be of interest in engineering diamond as a semiconductor. Here, we report the functionalization of the H-terminated diamond surface with nitrogen and sulfur heteroatoms. Surface characterization of functionalized diamond surfaces shows that these groups are well-distributed and covalently bonded to diamonds. Four chemical functional groups (-SH, -S-S-, -S-O, and -S=O) were found on the sulfurized diamond surface, and two groups (-NH2 and =NH) upon amination. We also report co-functionalization of surface with N and S (N-S), where sulfurization promotes sequential amination efficiency with reduced exposure time. Electrical measurement shows that heteroatom-modified diamond surfaces possess higher conductivity than H-terminated diamonds. Density functional theory (DFT) shows that upon functionalization with various N/S ratios, the conduction band minimum and valence band maximum downshift, which lowers the bandgap in comparison to an H-terminated diamond. These observations suggest the possibility of heteroatom functionalizations with enhanced surface electrical conductivity on the diamond that are useful for various electronic applications.

Boron-Doped Diamond Electrodes: Fundamentals for Electrochemical Applications

Boron-doped diamond (BDD) electrodes have emerged as next-generation electrode materials for various applications in electrochemistry such as electrochemical sensors, electrochemical organic synthesis, CO₂ reduction, ozone water generation, electrochemiluminescence, etc. An optimal BDD electrode design is necessary to realize these applications. The electrochemical properties of BDD electrodes are determined by important parameters such as (1) surface termination, (2) surface orientation, and (3) boron doping level.In this Account, we discuss how these parameters contribute to the function of BDD electrodes. First, control of the surface termination (hydrogen/oxygen) is described. The electrochemical conditions such as the solution pH and the application potential were studied precisely. It was confirmed that an acidic solution and the application of negative potential accelerate hydrogenation, and the mechanism behind this is discussed. For oxygenation, we directly observed changes in surface functional groups by in situ attenuated total reflection infrared spectroscopy and electrochemical X-ray photoelectron spectroscopy measurements.Next, the difference in surface orientation was examined. We prepared homoepitaxial single-crystal diamond electrodes comprising (100) and (111) facets with similar boron concentrations and resistivities and evaluated their electrochemical properties. Experimental results and theoretical calculations revealed that (100)-oriented single-crystal BDD has a wider space charge layer than (111)-oriented BDD, resulting in a slower response. Furthermore, isolated single-crystal microparticles of BDD with exposed (100) and (111) crystal facets were grown, and we studied the electrochemical properties of the respective facets by combination with hopping-mode scanning electrochemical cell microscopy.We also systematically investigated how the boron concentration and sp² species affect the electrochemical properties. The results showed that the appropriate composition (boron and sp² species level) is dependent on the application. The transmission electron microscopy images and electron energy loss spectra of highly boron-doped BDD are shown, and the relationship between the composition and electrochemical properties is discussed. Finally, we investigated in detail the effect of the sp² component on low-doped BDD. Surprisingly, although the sp² component is usually expected to induce a narrowing of the potential window and an increase in the charging current, low-doped BDD showed the opposite trend depending on the degree of sp² carbon.The results and discussion presented in this Account will hopefully promote a better understanding of the fundamentals of BDD electrodes and be useful for the optimal development of electrodes for future applications.

Good Choice of Electrode Material as the Key to Creating Electrochemical Sensors-Characteristics of Carbon Materials and Transparent Conductive Oxides (TCO)

The search for new electrode materials has become one of the goals of modern electrochemistry. Obtaining electrodes with optimal properties gives a product with a wide application potential, both in analytics and various industries. The aim of this study was to select, from among the presented electrode materials (carbon and oxide), the one whose parameters will be optimal in the context of using them to create sensors. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were used to determine the electrochemical properties of the materials. On the other hand, properties such as hydrophilicity/hydrophobicity and their topological structure were determined using contact angle measurements and confocal microscopy, respectively. Based on the research carried out on a wide group of electrode materials, it was found that transparent conductive oxides of the FTO (fluorine doped tin oxide) type exhibit optimal electrochemical parameters and offer great modification possibilities. These electrodes are characterized by a wide range of work and high chemical stability. In addition, the presence of a transparent oxide layer allows for the preservation of valuable optoelectronic properties. An important feature is also the high sensitivity of these electrodes compared to other tested materials. The combination of these properties made FTO electrodes selected for further research.

Single-Step Fabrication Method toward 3D Printing Composite Diamond-Titanium Interfaces for Neural Applications

Owing to several key attributes, diamond is an attractive candidate material for neural interfacing electrodes. The emergence of additive-manufacturing (AM) of diamond-based materials has addressed multiple challenges associated with the fabrication of diamond electrodes using the conventional chemical vapor deposition (CVD) approach. Unlike the CVD approach, AM methods have enabled the deposition of three-dimensional diamond-based material at room temperature. This work demonstrates the feasibility of using laser metal deposition to fabricate diamond-titanium hybrid electrodes for neuronal interfacing. In addition to exhibiting a high electrochemical capacitance of 1.1 mF cm^-2 and a low electrochemical impedance of 1 kΩ cm² at 1 kHz in physiological saline, these electrodes exhibit a high degree of biocompatibility assessed in vitro using cortical neurons. Furthermore, surface characterization methods show the presence of an oxygen-rich mixed-phase diamond-titanium surface along the grain boundaries. Overall, we demonstrated that our unique approach facilitates printing biocompatible titanium-diamond site-specific coating-free conductive hybrid surfaces using AM, which paves the way to printing customized electrodes and interfacing implantable medical devices.

Nanostructured diamond for biomedical applications

Nanostructured forms of diamond have been recently considered for use in a variety of medical devices due to their unusual biocompatibility, corrosion resistance, hardness, wear resistance, and electrical properties. This review considers several routes for the synthesis of nanostructured diamond, including chemical vapor deposition, hot filament chemical vapor deposition, microwave plasma-enhanced chemical vapor deposition, radio frequency plasma-enhanced chemical vapor deposition, and detonation synthesis. The properties of nanostructured diamond relevant to medical applications are described, including biocompatibility, surface modification, and cell attachment properties. The use of nanostructured diamond for bone cell interactions, stem cell interactions, imaging applications, gene therapy applications, and drug delivery applications is described. The results from recent studies indicate that medical devices containing nanostructured diamond can provide improved functionality over existing materials for the diagnosis and treatment of various medical conditions.

Next-Generation Diamond Electrodes for Neurochemical Sensing: Challenges and Opportunities

Carbon-based electrodes combined with fast-scan cyclic voltammetry (FSCV) enable neurochemical sensing with high spatiotemporal resolution and sensitivity. While their attractive electrochemical and conductive properties have established a long history of use in the detection of neurotransmitters both in vitro and in vivo, carbon fiber microelectrodes (CFMEs) also have limitations in their fabrication, flexibility, and chronic stability. Diamond is a form of carbon with a more rigid bonding structure (sp3-hybridized) which can become conductive when boron-doped. Boron-doped diamond (BDD) is characterized by an extremely wide potential window, low background current, and good biocompatibility. Additionally, methods for processing and patterning diamond allow for high-throughput batch fabrication and customization of electrode arrays with unique architectures. While tradeoffs in sensitivity can undermine the advantages of BDD as a neurochemical sensor, there are numerous untapped opportunities to further improve performance, including anodic pretreatment, or optimization of the FSCV waveform, instrumentation, sp2/sp3 character, doping, surface characteristics, and signal processing. Here, we review the state-of-the-art in diamond electrodes for neurochemical sensing and discuss potential opportunities for future advancements of the technology. We highlight our team's progress with the development of an all-diamond fiber ultramicroelectrode as a novel approach to advance the performance and applications of diamond-based neurochemical sensors.

Infrared Absorption Spectroscopy of Albumin Binding with Amine-Containing Plasma Polymer Coatings on Nanoporous Diamond Surfaces

Nanocrystalline diamond (NCD) layers functionalized with amine-containing functional groups have generated considerable interest as biocompatible substrates for attachment of biomolecules and cells with a view to biosensor and tissue engineering applications. Here we prepare nanoporous diamond layers with the surfaces modified by hydrogen plasma, oxygen plasma, and conformal 7 nm amine-containing plasma polymer (PP). Immobilization of bovine serum albumin (BSA) molecules is characterized on such surfaces. Grazing angle reflectance infrared spectroscopy as well as X-ray photoelectron spectroscopy show that concentration of amine-containing bonds after BSA exposure depends on the type of NCD surface modification. AFM measurements reveal that BSA proteins are physisorbed on H- and O-terminated diamond surfaces in different thicknesses and morphology. When the diamond layers are coated with the amine-containing PP, BSA molecules assume similar thickness and morphology, and their adhesion is significantly increased on both types of the diamond surfaces.

Conductive diamond: synthesis, properties, and electrochemical applications

This review summarizes systematically the growth, properties, and electrochemical applications of conductive diamond.

Electrochemical properties of fluorinated boron-doped diamond electrodes via fluorine-containing plasma treatment

It was systematically demonstrated that the electrochemical properties of fluorinated boron-doped diamond electrodes could be attributed to interfacial band bending.

Laser-Induced Periodic Surface Structures (LIPSS) on Heavily Boron-Doped Diamond for Electrode Applications

Diamond is known as a promising electrode material in the fields of cell stimulation, energy storage (e.g., supercapacitors), (bio)sensing, catalysis, etc. However, engineering its surface and electrochemical properties often requires costly and complex procedures with addition of foreign material (e.g., carbon nanotube or polymer) scaffolds or cleanroom processing. In this work, we demonstrate a novel approach using laser-induced periodic surface structuring (LIPSS) as a scalable, versatile, and cost-effective technique to nanostructure the surface and tune the electrochemical properties of boron-doped diamond (BDD). We study the effect of LIPSS on heavily doped BDD and investigate its application as electrodes for cell stimulation and energy storage. We show that quasi-periodic ripple structures formed on diamond electrodes laser-textured with a laser accumulated fluence of 0.325 kJ/cm² (800 nm wavelength) displayed a much higher double-layer capacitance of 660 μF/cm² than the as-grown BDD (20 μF/cm²) and that an increased charge-storage capacity of 1.6 mC/cm² (>6-fold increase after laser texturing) and a low impedance of 2.74 Ω cm² turn out to be appreciable properties for cell stimulation. Additional morphological and structural characterization revealed that ripple formation on heavily boron-doped diamond (2.8 atom % [B]) occurs at much lower accumulated fluences than the 2 kJ/cm² typically reported for lower doping levels and that the process involves stronger graphitization of the BDD surface. Finally, we show that the exposed interface between sp² and sp³ carbon layers (i.e. the laser-ablated diamond surface) revealed faster kinetics than the untreated BDD in both ferrocyanide and RuHex mediators, which can be used for electrochemical (bio)sensing. Overall, our work demonstrates that LIPSS is a powerful single-step tool for the fabrication of surface-engineered diamond electrodes with tunable material, electrochemical, and charge-storage properties.

Diamond thin films: giving biomedical applications a new shine

Progress made in the last two decades in chemical vapour deposition technology has enabled the production of inexpensive, high-quality coatings made from diamond to become a scientific and commercial reality. Two properties of diamond make it a highly desirable candidate material for biomedical applications: first, it is bioinert, meaning that there is minimal immune response when diamond is implanted into the body, and second, its electrical conductivity can be altered in a controlled manner, from insulating to near-metallic. In vitro, diamond can be used as a substrate upon which a range of biological cells can be cultured. In vivo, diamond thin films have been proposed as coatings for implants and prostheses. Here, we review a large body of data regarding the use of diamond substrates for in vitro cell culture. We also detail more recent work exploring diamond-coated implants with the main targets being bone and neural tissue. We conclude that diamond emerges as one of the major new biomaterials of the twenty-first century that could shape the way medical treatment will be performed, especially when invasive procedures are required.

Fluorination of Boron-Doped Diamond Film Electrodes for Minimization of Perchlorate Formation

This research investigated the effects of surface fluorination on both rates of organic compound oxidation (phenol and terephthalic acid (TA)) and ClO₄^- formation at boron-doped diamond (BDD) film anodes at 22 °C. Different fluorination methods (i.e., electrochemical oxidation with perfluorooctanoic acid (PFOA), radio frequency plasma, and silanization) were used to incorporate fluorinated moieties on the BDD surface, which was confirmed by X-ray photoelectron spectroscopy (XPS). The silanization method was found to be the most effective fluorination method using a 1H,1H,2H,2H-perfluorodecyltrichlorosilane precursor to form a self-assembled monolayer (SAM) on the oxygenated BDD surface. The ClO₄^- formation decreased from rates of 0.45 ± 0.03 mmol m^-2 min^-1 during 1 mM NaClO₃ oxidation and 0.28 ± 0.01 mmol m^-2 min^-1 during 10 mM NaCl oxidation on the BDD electrode to below detectable levels (<0.12 μmoles m^-2 min^-1) for the BDD electrode functionalized by a 1H,1H,2H,2H-perfluorodecyltrichlorosilane SAM. These decreases in rates corresponded to 99.94 and 99.85% decreases in selectivity for ClO₄^- formation during the electrolysis of 10 mM NaCl and 1 mM NaClO₃ electrolytes, respectively. By contrast, the oxidation rates of phenol were reduced by only 16.3% in the NaCl electrolyte and 61% in a nonreactive 0.1 M KH₂PO₄ electrolyte. Cyclic voltammetry with Fe(CN)₆^3-/4- and Fe^3+/2+ redox couples indicated that the long fluorinated chains created a blocking layer on the BDD surface that inhibited charge transfer via steric hindrance and hydrophobic effects. The surface coverages and thicknesses of the fluorinated films controlled the charge transfer rates, which was confirmed by estimates of film thicknesses using XPS and density functional theory simulations. The aliphatic silanized electrode also showed very high stability during OH^• production. Perchlorate formation rates were below the detection limit (<0.12 μmoles m^-2 min^-1) for up to 10 consecutive NaClO₃ oxidation experiments.

Aptamer-Based Carboxyl-Terminated Nanocrystalline Diamond Sensing Arrays for Adenosine Triphosphate Detection

Here, we propose simple diamond functionalization by carboxyl termination for adenosine triphosphate (ATP) detection by an aptamer. The high-sensitivity label-free aptamer sensor for ATP detection was fabricated on nanocrystalline diamond (NCD). Carboxyl termination of the NCD surface by vacuum ultraviolet excimer laser and fluorine termination of the background region as a passivated layer were investigated by X-ray photoelectron spectroscopy. Single strand DNA (amide modification) was used as the supporting biomolecule to immobilize into the diamond surface via carboxyl termination and become a double strand with aptamer. ATP detection by aptamer was observed as a 66% fluorescence signal intensity decrease of the hybridization intensity signal. The sensor operation was also investigated by the field-effect characteristics. The shift of the drain current–drain voltage characteristics was used as the indicator for detection of ATP. From the field-effect characteristics, the shift of the drain current–drain voltage was observed in the negative direction. The negative charge direction shows that the aptamer is capable of detecting ATP. The ability of the sensor to detect ATP was investigated by fabricating a field-effect transistor on the modified NCD surface.

Enhanced H2O2 Production at Reductive Potentials from Oxidized Boron-Doped Ultrananocrystalline Diamond Electrodes

This work investigates the surface chemistry of H₂O₂ generation on a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode. It is motivated by the need to efficiently disinfect liquid waste in resource constrained environments with limited electrical power. X-ray photoelectron spectroscopy was used to identify functional groups on the BD-UNCD electrode surfaces while the electrochemical potentials of generation for these functional groups were determined via cyclic voltammetry, chronocoulometry, and chronoamperometry. A colorimetric technique was employed to determine the concentration and current efficiency of H₂O₂ produced at different potentials. Results showed that preanodization of an as-grown BD-UNCD electrode can enhance the production of H₂O₂ in a strong acidic environment (pH 0.5) at reductive potentials. It is proposed that the electrogeneration of functional groups at oxidative potentials during preanodization allows for an increased current density during the successive electrolysis at reductive potentials that correlates to an enhanced production of H₂O₂. Through potential cycling methods, and by optimizing the applied potentials and duty cycle, the functional groups can be stabilized allowing continuous production of H₂O₂ more efficiently compared to static potential methods.

The Life of Pi Star: Exploring the Exciting and Forbidden Worlds of the Benzophenone Photophore

The widespread applications of benzophenone (BP) photochemistry in biological chemistry, bioorganic chemistry, and material science have been prominent in both academic and industrial research. BP photophores have unique photochemical properties: upon n-π* excitation at 365 nm, a biradicaloid triplet state is formed reversibly, which can abstract a hydrogen atom from accessible C-H bonds; the radicals subsequently recombine, creating a stable covalent C-C bond. This light-directed covalent attachment process is exploited in many different ways: (i) binding/contact site mapping of ligand (or protein)-protein interactions; (ii) identification of molecular targets and interactome mapping; (iii) proteome profiling; (iv) bioconjugation and site-directed modification of biopolymers; (v) surface grafting and immobilization. BP photochemistry also has many practical advantages, including low reactivity toward water, stability in ambient light, and the convenient excitation at 365 nm. In addition, several BP-containing building blocks and reagents are commercially available. In this review, we explore the "forbidden" (transitions) and excitation-activated world of photoinduced covalent attachment of BP photophores by touring a colorful palette of recent examples. In this exploration, we will see the pros and cons of using BP photophores, and we hope that both novice and expert photolabelers will enjoy and be inspired by the breadth and depth of possibilities.

Carbon Substrates: A Stable Foundation for Biomolecular Arrays

Since their advent in the early 1990s, microarray technologies have developed into a powerful and ubiquitous platform for biomolecular analysis. Microarrays consist of three major elements: the substrate upon which they are constructed, the chemistry employed to attach biomolecules, and the biomolecules themselves. Although glass substrates and silane-based attachment chemistries are used for the vast majority of current microarray platforms, these materials suffer from severe limitations in stability, due to hydrolysis of both the substrate material itself and of the silyl ether linkages employed for attachment. These limitations in stability compromise assay performance and render impossible many potential microarray applications. We describe here a suite of alternative carbon-based substrates and associated attachment chemistries for microarray fabrication. The substrates themselves, as well as the carbon-carbon bond-based attachment chemistries, offer greatly increased chemical stability, enabling a myriad of novel applications.

One-step formation of bifunctionnal aryl/alkyl grafted films on conducting surfaces by the reduction of diazonium salts in the presence of alkyl iodides

The formation of partial perfluoroalkyl or alkyl radicals from partial perfluoroalkyl or alkyl iodides (ICH2CH2C6F13 and IC6H13) and their reaction with surfaces takes place at low driving force (∼-0.5 V/SCE) when the electrochemical reaction is performed in acetonitrile in the presence of diazonium salts (ArN2(+)), at a potential where the latter is reduced. By comparison to the direct grafting of ICH2CH2C6F13, this corresponds to a gain of ∼2.1 V in the case of 4-nitrobenzenediazonium. Such electrochemical reaction permits the modification of gold surfaces (and also carbon, iron, and copper) with mixed aryl-alkyl groups (Ar = 3-CH3-C6H4, 4-NO2-C6H4, and 4-Br-C6H4, R = C6H13 or (CH2)2-C6F13). These strongly bonded mixed layers are characterized by IRRAS, XPS, ToF-SIMS, ellipsometry, water contact angles, and cyclic voltammetry. The relative proportions of grafted aryl and alkyl groups can be varied along with the relative concentrations of diazonium and iodide components in the grafting solution. The formation of the films is assigned to the reaction of aryl and alkyl radicals on the surface and on the first grafted layer. The former is obtained from the electrochemical reduction of the diazonium salt; the latter results from the abstraction of an iodine atom by the aryl radical. The mechanism involved in the growth of the film provides an example of complex surface radical chemistry.

Photochromism-induced amplification of critical current density in superconducting boron-doped diamond with an azobenzene molecular layer

A key issue in molecular electronics is the control of electronic states by optical stimuli, which enables fast and high-density data storage and temporal-spatial control over molecular processes. In this article, we report preparation of a photoswitchable superconductor using a heavily boron-doped diamond (BDD) with a photochromic azobenzene (AZ) molecular layer. BDDs electrode properties allow for electrochemical immobilization, followed by copper(I)-catalyzed alkyne-azide cycloaddition (a "click" reaction). Superconducting properties were examined with magnetic and electrical transport measurements, such as field-dependent isothermal magnetization, temperature-dependent resistance, and the low-temperature voltage-current response. These measurements revealed reversible amplification of the critical current density by 55% upon photoisomerization. This effect is explained as the reversible photoisomerization of AZ inducing an inhomogeneous electron distribution along the BDD surface that renormalizes the surface pinning contribution to the critical current.

Visible-light sensitization of boron-doped nanocrystalline diamond through non-covalent surface modification

The boron-doped diamond electrode is efficiently sensitized with a light-harvesting molecule using a facile and versatile synthetic method.

Diamond nanowires: fabrication, structure, properties, and applications

C(sp(3) )C-bonded diamond nanowires are wide band gap semiconductors that exhibit a combination of superior properties such as negative electron affinity, chemical inertness, high Young's modulus, the highest hardness, and room-temperature thermal conductivity. The creation of 1D diamond nanowires with their giant surface-to-volume ratio enhancements makes it possible to control and enhance the fundamental properties of diamond. Although theoretical comparisons with carbon nanotubes have shown that diamond nanowires are energetically and mechanically viable structures, reproducibly synthesizing the crystalline diamond nanowires has remained challenging. We present a comprehensive, up-to-date review of diamond nanowires, including a discussion of their synthesis along with their structures, properties, and applications.

Diamond nanowires modified with poly[3-(pyrrolyl)carboxylic acid] for the immobilization of histidine-tagged peptides

Coating boron-doped diamond nanowires (BDD NWs) with a conducting polymer, poly[3-(pyrrolyl)carboxylic acid], has been reported. Polymer coating was achieved through electropolymerization of 3-(pyrrolyl)carboxylic acid at the electrode interface by amperometrically biasing the BDD NWs interface until a predefined charge has passed. The poly[3-(pyrrolyl)carboxylic acid] modified BDD NWs (PPA-BDD NWs) were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Using a deposition charge of 11 mC cm(-2) resulted in a thin polymer film deposition. The availability of the carboxylic groups of the polymer coated BDD NWs electrode was demonstrated through copper ion (Cu(2+)) chelation. The resulting complex was successfully used for the site-specific immobilization of histidine-tagged peptides. The binding process was followed by electrochemical impedance spectroscopy (EIS). The Cu(2+)-chelated PPA-BDD NWs interface showed peptide loading capability comparable to those of commercially available interfaces and can be easily regenerated several times using ethylenediaminetetraacetic acid (EDTA).