Novel Functionalization of Boron-Doped Diamond by Microwave

Article pubs.acs.org/JPCC

Novel Functionalization of Boron-Doped Diamond by Microwave Pulsed-Plasma Polymerized Allylamine Film R. Bogdanowicz,*,† M. Sawczak,‡ P. Niedzialkowski,§ P. Zieba,§ B. Finke,∥ J. Ryl,⊥ J. Karczewski,# and T. Ossowski§ †

Department of Metrology and Optoelectronics, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, 11/12 G. Narutowicza Str., 80-233 Gdansk, Poland ‡ Polish Academy of Sciences, The Szewalski Institute of Fluid-Flow Machinery, 14 Fiszera Str., 80-231 Gdansk, Poland § Analytical Chemistry, Faculty of Chemistry, University of Gdansk, 63 Wita Stwosza Str., 80-952 Gdansk, Poland ∥ Leibniz Institute for Plasma Science and Technology (INP), Felix-Hausdorff-Str. 2, D-17489 Greifswald, Germany ⊥ Department of Electrochemistry, Corrosion and Material Engineering, Gdansk University of Technology, 11/12 Narutowicza Str., 80-233 Gdansk, Poland # Faculty of Applied Physics and Mathematics, Gdansk University of Technology, 11/12 G. Narutowicza Str., 80-233 Gdansk, Poland

ABSTRACT: We report the novel modification of a hydrogen-terminated polycrystalline boron-doped electrode with a microwave pulsed-plasma polymerized allylamine. Boron-doped diamond (BDD) was coated with a very thin layer of adherent cross-linked, pinhole- and additive-free allylamine plasma polymer (PPAAm) resistant to hydrolysis and delamination and characterized by a high density of positively charged amino groups. The pulsed microwave plasma was applied to improve the cross-linking degree and bonding of the plasma polymeric films to boron-doped diamond. The amine-treated BDD films were assessed by advanced surface analytical techniques, such as X-ray photoelectron spectroscopy (XPS), FT-IR, scanning electron microscopy (SEM), laser-induced fluorescence, and water contact angle measurements. The amine-modified Si/BDD surface was functionalized with selected organic molecules containing a carboxylic group in the presence of coupling agents such as diisopropylcarbodiimide (DIC). The anthraquinone derivatives Boc-Lys(AQ)−OH and peptide anthraquinone derivatives of dendrimers were used as electroactive agents for characterization by cyclic voltammetry (CV). The fluorescence reference standards Rhodamine 110 and Fmoc-Trp(Boc)−OH were selected for fluorescence studies.

1. INTRODUCTION The outstanding electrochemical properties of boron-doped diamond (BDD), including wide potential window, low background current, and extreme stability, together with its inherent biocompatibility and chemical inertness make the conductive BDD thin films an interesting candidate for the substrate of third-generation biosensors.1,2 The specificity, sensitivity, and fast response of biosensors based on BDD electrodes have attracted the interest of many research groups.3−9 The BDD electrodes are mostly prepared by the microwave plasma enhanced-chemical vapor deposition (MW PE-CVD) method, and the as-grown surfaces of BDD films are hydrogen-terminated (H-BDD). © 2014 American Chemical Society

The lack of chemically reactive groups precludes the attachment of organic compounds to the surface. Thus, major efforts in BDD electrodes used in biosensors essentially involve elaborate surface modification steps to impart chemical functional groups for the covalent coupling of organic compounds.10 The surfaces of BDD electrodes can be modified in different ways including chemical,11−14 photochemical,15 and, in the case of doped diamond, electrochemical concepts.16,17 Received: January 13, 2014 Revised: March 7, 2014 Published: March 21, 2014 8014

dx.doi.org/10.1021/jp5003947 | J. Phys. Chem. C 2014, 118, 8014−8025

The Journal of Physical Chemistry C

Article

Table 1. Structure of Organic Compounds Used to Functionalize the BDD−PPAAm Surface

any carbon chain. However, in another work Zhuang et al.3 showed that the successful TFAAA grafting onto the diamond surface using UV illumination needs approximately 24 h. Nevertheless, the influence of UV illumination on BDD electronic structure, causing photoejection of electrons from the diamond surface into the liquid phase,18,34 complicates the grafting procedure and is time-consuming. The plasma-assisted surface functionalization and plasma polymer deposition offer great advantages of direct diamond and BDD amination. The reactive plasma process activates the BDD surface enabling highly efficient grafting of amines compared to other chemical or photochemical methods.35−37 Moreover, the so-called plasma polymerization is an attractive method to synthesize thin organic films referred to as “plasma polymer films” (PPFs). PPFs display, among other properties, strong adherence on numerous surfaces, good mechanical properties, and high thermal resistance.38 Allylamine has been chosen as a molecular precursor for film deposition on the basis of the good retention of amino groups.39,40 Saini et al.41 demonstrated the spontaneous adsorption of a water-soluble polymer containing a pendant primary amine along its backbone (PPAAm) to detonation diamond nanoparticles (DNDs). These authors successfully used the PPAAmcoated diamond as an adsorbent for solid-phase extraction (SPE). Moreover, allylamine (H2CCH−CH2−NH2) has been extensively studied.38 The plasma polymer deposition is a well-suited technique for the preparation of a defined interface layer for the covalent immobilization of biologically active molecules. Plasma polymerization of allylamine can yield,

Among the chemical and electrochemical modification methods of the diamond surface, photochemical functionalization is the widely used one.15,18 Among the several steps that are involved in a typical photochemical grafting procedure of organic compounds onto the diamond surface, bonding of the functional groups such as −OH (hydroxyl), 19 −NH 2 (amine),3,20−22 −COOH (carboxyl),23,24 and −CFx components (graphite fluoride)25,26 has been investigated most frequently. The most widely used approach to functionalizing the diamond film surface with organic compounds (R) or metal nanoparticles (NPs) is an amine functionality introduced to the surface. So far, several amination methods of the diamond surface have been proposed.10,21,27,28 Generally, amine-terminated BDD electrodes could be obtained by modification using several methods: (I) etching a hydrogen-terminated BDD surface by NH3 plasma in a specific reactor,28 (II) chemical modification of an oxidized BDD surface with (3-aminopropyl) triethoxysilane,29 (III) photochemical reaction of amino molecules containing a vinyl group with a hydrogen-terminated BDD surface by free radical mechanism,30 and (IV) diazonium functionalization of 4nitrobenzenediazoniumtetrafluoroborate with hydrogen-terminated BDD electrodes by combined chemical and electrochemical processes.31−33 However, it should be noted that besides the direct NH3 attachment most of the abovementioned attachment methods involve the usage of long carbon-chain linker molecules. Zhang et al.21 developed the direct photochemical amination (attaching −NH2) of the diamond surface; the linker is thus the shortest one, without 8015



Article

Table 2. Structure of Redox-Active Peptide Dendrimers

novel functionalization of boron-doped diamond (BDD) by a microwave-excited pulsed-plasma polymerized allylamine film (PPAAm). The details of microwave plasma process and the physicochemical properties of the PPAAm surface are given in refs 44, 49, and 50. A continuous wave (cw) Ar plasma was applied for surface activation to improve the bonding of the plasma polymeric films to diamond,38 followed by the deposition of PPAAm by the pulsed-plasma polymerization of allylamine. Subsequently, the primary amino groups of the aminemodified Si/BDD surface were coupled with selected organic molecules containing a carboxylic group (rhodamine 110 chloride, Fmoc-Trp(Boc)−OH and antraquinone derivatives) as model compounds (see Tables 1 and 2) in the presence of coupling agents such as diisopropylcarbodiimide (DIC). The induced surface modifications were characterized by advanced surface analytical techniques. Moreover, the laser fluorescence spectroscopy measurements and the electrochemical characteristics of the processed BDD electrodes were obtained.

inter alia, primary amine (−NH2) functional groups which promote the covalent immobilization with biomolecules such as proteins, collagen, and DNA.42−44 Although most of the previous studies on plasma polymerization focus on continuous discharge to meet the increasing demand for surface functionalization of solid substrates, the pulsed discharge technique has emerged in the plasma polymerization, leading to structurally well-defined polymer repeat units.45 Hamerli et al.46 reported that the atomic N/C ratio of carbon single bonded to nitrogen is 13.9%, while for carbon in imine or nitrile groups it is 8.8% in the case of plasma-polymerized allylamine fabricated at 400 W microwave power and 50% duty cycle. Although different plasma generation devices are used, it can be inferred that the higher the effective discharge power and the higher the τoff, the more functional nitric groups can be retained. Szunerits et al.47 reported on direct amination of hydrogenterminated diamond surfaces using radiofrequency plasmas of mixtures of He + 5% NH3. The treatment of the hydrogenated BDD surface with He/NH3 plasma led to the formation of an aminated surface. Remes et al.28 performed nanocrystalline diamond (NCD) surface functionalization in RF plasma with a standard excitation frequency of 13.56 MHz. These authors stated that plasma promotes a direct chemical reaction between the diamond surface and the plasma-induced gas radicals containing the primary amino group −NH2. For an improved hemocompatibility of 316L stainless steel, Yang et al.22 developed a facile and effective approach for fabricating a pulsed-RF-plasma polymeric allylamine (P-PPAm) film that possesses a high cross-linking degree and a high density of amine groups, which is used for subsequent bonding of heparin. Due to efficient covalent bonding with the amine-active BDD substrate and electrochemical stability of BDD, the resulting BDD electrode exhibits a good performance in terms of dynamic range of detection, sensitivity, and long-term stability in derivative detection.48 However, research on the covalent immobilization of organic compounds on BDD using microwave pulsed-plasma polymeric film for sensing applications has not been reported until now. Therefore, the objective of the present paper is to investigate a

2. EXPERIMENTAL SECTION 2.1. Si/BDD Electrode Deposition. Si/BDD electrodes were synthesized in an MW PE-CVD system (Seki Technotron AX5200S) on p-type Si wafers with (100) orientation. Substrates were seeded by sonication in nanodiamond suspension (crystallite size of 5−10 nm) for 2 h.51−53 Finally, the substrates were dried under a stream of nitrogen. The substrate temperature was kept at 1000 °C during the deposition process. During the first step, the substrates were etched in hydrogen plasma for 3 min. Excited plasma was ignited by microwave radiation (2.45 GHz).54−56 The plasma microwave power, optimized for diamond synthesis, was kept at 1300 W. The gas mixture ratio was 1% of the molar ratio of CH4−H2 at gas volume of 300 sccm of total flow rate. The base pressure was about 10−6 Torr, and the process pressure was kept at 50 Torr. All samples were doped by using a diborane (B2H6) dopant precursor; [B]/[C] ratio was 10 000 ppm in the plasma (BDD10). The time of polycrystalline layer growth was 6 h, which resulted in the thickness of deposited films of approximately 2 μm. 8016



Article

Figure 1. Schema of functionalization on the diamond surface by organic molecules. Note: The design of the plasma-polymerized surface with PPAAm is only idealized. In addition to primary amino groups −NH2, imines NH, nitriles CN, or acid amides OC−N are found.

Au films were deposited on a glass substrate as a reference and then coated with PPAAm. In this way FT-IRRAS measurements of minimal PPAAm film thicknesses (∼30 nm) were possible. The spectra were obtained at the spectral resolution of 4 cm−1, number of scans 32, in the wavenumber region 4000− 600 cm−1. 2.4. Si/BDD/PPAAm Functionalization. Reagents. Rhodamine 110 chloride and Fmoc-Trp(Boc)−OH were purchased from Sigma-Aldrich Co. Boc-Lys(AQ)−OH and peptide anthraquinone derivatives of dendrimers were obtained by a method described previously61[P. Niedziałkowski, T. Ossowski, unpublished data]. All used solvents were HPLC grade, while all the other reagents were analytical grade. All wet chemical work was done under a laminar flow box in a clean room. Sample Preparation. Polycrystalline diamond layers modified by PPAAm were used for chemical modification with selected organic molecules (see Figure 1). In the case of BocLys(AQ)−OH and Fmoc-Trp(Boc)−OH (1 mM), these compounds were mixed with diisopropylcarbodiimide (DIC) (1.5 mM) and 1-hydroxybenzotriazole (HOBt) (1 mM) in 10 mL of dichloromethane and dimethylformamide (1:1, v/v) mixture in the presence of triethylamine (2 mM). In the case of Rhodamine 110 and the anthraquinone peptide dendrimer (0.5 mM), both these compounds were separately mixed with diisopropylcarbodiimide (DIC) (0.5 mM) and catalytic amounts of 4-(dimethylamino)pyridine (DMAP) and dissolved in 5 mL of a dichloromethane and dimethylformamide (1:2, v/v) mixture in the presence of triethylamine (2 mM). Amine-terminated BDD was immersed in the solutions of four reaction mixtures and left at room temperature for 24 h under a helium atmosphere. Next, the sample was removed from the solution, washed with dimethylformamide, dichloromethane, methanol, water, and methanol, and dried under a stream of nitrogen. Rhodamine 110 chloride belongs to the family of fluorescent dyes widely known as Rhodamines which are applied in fluorescence microscopy and dye laser. Furthermore, Rhodamines are used as fluorescence reference standards and to design fluorescent sensors, while in molecular biology they are employed in many techniques for monitoring biomolecules in living systems and detecting numerous analytes. FmocTrp(Boc)−OH, a commercially available amino acid derivative, was selected as a fluorescent moiety commonly used in peptide synthesis by Fmoc strategy on the solid phase.62 This amino acid anchored on a BDD surface can serve in the future as a primary amino acid for the synthesis of longer peptides on this modified surface. Anthraquinone derivatives Boc-Lys(AQ)−OH and peptide anthraquinone derivatives of dendrimers based on lysine containing four anthraquinone units were used as electroactive agents63−65 to characterize and investigate the processes at chemically modified electrodes by cyclic voltammetry.

The four-step pretreatment of deposited BDD/Si electrodes was applied to obtain H-terminated surface and etch sp2 phase impurities, as reported elsewhere.57−59 For all Si/BDD samples, the diamond surface was acid and hydrogen plasma cleaned. First, metallic impurities were dissolved in hot aqua regia (HNO3:HCl/1:3), followed by removal of organic impurities by hot “piranha” solution (H2O2:H2SO4/1:3) at 90 °C. Microwave hydrogen plasma treatment was performed using 1000 W microwave power and 300 sccm of hydrogen gas flow for 10 min. Thus, the BDD surface was made predominantly hydrogen-terminated.58,59 2.2. Si/BDD Electrode Modified with Allylamine (Si/ BDD/PPAAm). Si/BDD electrodes were used as substrates for the surface functionalization in all experiments. A commercial microwave (MW) plasma reactor (2.45 GHz; V55G, Plasma Finish, Schwedt, Germany) was employed for the deposition of a thin film of PPAAm onto the Si/BDD surface. The procedure was carried out in two steps: (1) Si/BDD electrodes were activated by a continuous wave Ar-plasma (800 W, 50 Pa, 100 sccm Ar) followed by (2) the plasma polymerization of the monomer allylamine (AAm) (VWR International GmbH, Darmstadt, Germany), using a MW excited (2.45 GHz, 600 W), pulsed (duty cycle of 0.15 at a pulse length of 2 s), low-pressure (p = 50 Pa) gas-discharge plasma for 144 s effective. Allylamine was fed from a liquid handling system, which was carefully purified of air by evacuating and purging with N2 prior to use. Argon was applied as a carrier gas (50 sccm Ar). The substrate was located in a downstream plasma position, 9 cm from the plasma source. Different values of PPAAm film thickness were obtained by reducing the treatment time (144 s/72 s/36 s). The chemical modification with selected organic molecules was performed immediately after PPAAm deposition. 2.3. Surface Analysis of PPAAm: XPS, FT-IR. XPS. The elemental surface composition and chemical binding properties of the surfaces were determined by high-resolution scanning Xray photoelectron spectroscopy (XPS) with the monochromatic Al Kα source (Escalab 250Xi, ThermoFisher Scientific). Charge neutralization was implemented. Spectra were recorded with an energy step size of 0.1 eV at a pass energy of 15 eV for highly resolved C 1s and N 1s peaks. A chemical derivatization was applied for the quantification of amino groups since amino groups do not lead to significant shifts in the binding energy of the C 1s and N 1s electrons. Amino groups were reacted with 4-trifluoromethylbenzaldehyde (TFBA, Sigma−Aldrich, Steinheim, Germany) at 40 °C for 2 h in a saturated gas phase. FT-IR. The chemical composition and molecular structure of PPAAm thin films were analyzed by means of FT-IRRAS (Fourier transform-infrared reflection−absorption spectroscopy)60 (FT-IR Type: Spectrum One, Perkin-Elmer, Germany). The IRRAS unit of the FT-IR spectrometer in the sample compartment used parallel-polarized light at an incidence angle of 75°. For improving the sensitivity of the FT-IR measurement 8017



Article

Figure 2. SEM microimages obtained from the surfaces of (A) hydrogen-terminated Si/BDD electrode and (B) PPAAm-modified Si/BDD electrode.

2.5. Characterization of the Functionalized Si/BDD/ PPAAm Electrode. The film morphology was investigated by Schottky field emission scanning electron microscopy (FEI Quanta FEG 250) with an ET secondary electron detector. Photographs were taken under high vacuum conditions. The beam accelerating voltage was kept at 20 kV. The spectroscopic properties of the samples were investigated by means of laser-induced fluorescence spectroscopy (LIF). The excitation at the UV or visible spectral range was applied depending on the type of diamond functionalization. For the UV range, the 375 nm/9 mW semiconductor laser (CUBE, Coherent) was used. For the visible range, the 532 nm Nd:YAG SHG laser (Millenia, Spectra Physics) operating at the power level of 0.2 W was applied as an excitation source. Both lasers were operating at the continuous mode. The excitation beam was falling on the sample surface at an angle of 45 degrees. The intensity of laser radiation on the sample surface was at the level of 300 and 600 mW/cm2 for the UV and visible range laser, respectively. The fluorescence signal was collected perpendicular to the sample surface using a microscope objective and focused on the entrance of the optical fiber. In the detection path the band-pass filters (GG44, Schott) for UV excitation and (OG570, Schott) for visible excitation were used for blocking the laser radiation. The fluorescence spectra were analyzed using a 0.3 m monochromator (SR303i, Andor) equipped with 600 grooves/mm grating and recorded using an ICCD detector (DH740, Andor). The water contact angles were measured by the sessile drop method (drop volume ∼0.5 μL) using a DIGIDROP contact angle meter (GBX Instrumentation Scientifique, Romance, France). The determination of the angle between the solid surface and the tangent of the drop was performed by computer control. Three measurements were performed on each surface, and arithmetic means and standard deviations were calculated by using the Origin 6.1 software package (OriginLab Corp., Northampton, USA). The electrochemical investigations of reference oxidation/ reduction systems Fe(CN)63−/4−, Fe2+/3+, and quinone/hydroquinone (Q/H 2Q) were carried out in 0.5 M Na2SO4 containing Fe(CN)63−/4− (5/5 mM), Fe2+/3+ (5/5 mM), and Q/H2Q (5/5 mM). The electrochemical experiments were carried out in an undivided electrolytic cell equipped with

anodes made from BDD with the [B]/[C] ratio = 2000 (BDD2) or [B]/[C] = 10 000 (BDD10). Stainless steel was used as a cathode and Ag/AgCl (0.1 M KCl) as a reference electrode. The anode and cathode elements were flat pieces with the active surface area equal to 4 cm2. In all cases, the distance between the electrodes was 1 cm. The experiments were performed at constant current densities, i.e., 2.5 and 5 mA cm−2 for BDD10 and BDD2, respectively. The applied current densities were close to the limiting current density as suggested in the literature.66 The temperature of the solution in the electrolytic cell (V = 0.1 L) was kept constant by a thermostat and a magnetic stirrer. The potential was applied with an Autolab potentiostat/galvanostat PGSTAT30 (Eco Chemie B.V., The Netherlands) controlled with General Purpose Electrochemical System (GPES 4.9) software.

3. RESULTS 3.1. Analysis of the Si/BDD/PPAAm Electrode Surface. The image of the surface of the hydrogen-terminated Si/BDD electrode made by scanning electron microscopy is shown in Figure 2a. It reveals a nanocrystalline structure with the uniformly distributed crystallites whose sizes are hundreds of nanometers. Sharp edges and boundaries are clearly visible. The structure of the PPAAm-modified Si/BDD electrode (see Figure 2b) is characterized by ovoid shapes. Figure 2b clearly shows that PPAAm is homogeneously distributed over the entire BDD surface. The measurements of surface wettability (Table 3) revealed a significant decrease in the water contact angle after modification with PPAAm. It is well-known that untreated hydrogen-terminated boron-doped diamond surfaces are typically characterized by water contact angles in the hydrophobic range between 80 and 100° which increase with increasing boron concentration.67−69 PPAAm surfaces display the water contact angle values of about 50°. 50 The functionalization of the BDD surface with PPAAm results in water contact angles between 65 and 56°, which decrease with increasing PPAAm film thickness amounting to an average decrease of approximately 20%. The sum of the electrostatic attraction forces on the Si/BDD surface decreases with increasing thickness of PPAAm film. It should be noted that the microwave plasma treatment may lead to additional effects 8018



Article

Table 3. Water Contact Angle Measurementsa sample

PPAAm thickness (nm)

organic compound

Si/BDD Si/BDD/PPAAm BDD10-12 12 no modification BDD10-25 25 no modification BDD10-50 50 no modification Si/BDD/PPAAm/R-(organic compound) Amino Acids BDD10-50-R110 50 Rhodamine 110 BDD10-50-TRP 50 Fmoc-Trp(Boc)−OH Quinones BDD-50-LYSAQ 50 Boc-Lys(AQ)−OH BDD-50-3G 50 anthraquinone peptide dendrimers H-BDD10

-

the strong cross-linking of PPAAm and therefore a strongly reduced solubility in aqueous media. In Table 4 the main vibrational bands observed in the FTIR spectra of freshly deposited PPAAm thin films are listed. It can

contact angle (o) 80

Table 4. Main Vibrational FT-IRRAS Bands in the Observed Spectrum of Freshly Deposited PPAAm

65 58 56

wavenumber [cm−1] 3600−3000 2970−2870 2200−2100 1700−1680 1690−1650 1680−1630 1650−1510 f ingerprint region 1465−1375 1250 1100

57 65 70 53

a

The modification of Si/BDD with PPAAm leads to decreased water contact angles, i.e., between 56° and 65° in comparison to the Hterminated Si/BDD surfaces. The functionalization with organic compounds results in a successive shift of the water contact angle values compared to Si/BDD/PPAAm (n = 3).

vibration modes H-bonded OH stretch N−H stretch C−H symm./assym. stretch CN nitrile stretch; CC triple bond stretch CO stretch in acid amides CN stretch, CC stretch OC−N amides N−H deformation C−H, O−H deformation C−N stretch C−O stretch

be concluded that the molecular structure of deposited film reproduces the monomer structure H2CCH−CH2−NH2. The main bands of aliphatic C−H groups, ν-CH2,3 (stretching vibrations), and amines, δ-NH (deformation vibration), can be observed in the regions 2970−2870 cm−1 and 1650−1510 cm−1. The partial transformation of amino groups into amide (1700 cm−1) and nitrile (2300−2200 cm−1) functional groups can be concluded, which confirms our previous observation.44 The XPS was performed to determine the chemical composition for the freshly deposited PPAAm film on the Si/ BDD electrode. High-resolution spectra of the C 1s and N 1s are shown in Figure 4. C 1s exhibits not less than six main components. The strongest peak visible at 284.05 eV is attributable to C−C and C−H bonds at the surface of the highly doped BDD electrode.

which can be useful in improving adhesion. The water contact angles measured on the functionalized surfaces for Rhodamine 110, Fmoc-Trp(Boc)−OH, Boc-Lys(AQ)−OH, and anthraquinone peptide dendrimers equal 57, 65, 70, and 53°, respectively. These results are a direct consequence of the polarity of the examined compounds. The peptide dendrimer is the most polar compound, containing free amine groups of lysine; therefore, the contact angle is the smallest (53°). Boc-Lys(AQ)−OH is the most nonpolar compound containing two groups, i.e., 9,10anthraquinone as the redox-active unit and a protecting group, which is Boc. Similar polarity was displayed by the derivative of tryptophan (Fmoc-Trp(Boc)−OH) because it contains two protecting groups. The contact angle of Rhodamine 110 is comparable to that of the unmodified BDD/PPAAm surface, which results from the chemical nature of these two molecule. The plasma polymerization of allylamine (PPAAm) differs completely from a pure chemical polymerization of allylamine. The process management is different, and more importantly, the surface functionalization is achieved. Whereas one-third of the primary amino groups are deposited by the pure chemical polymerization, only about 3−4% of the primary amino groups are found on the PPAAm surface. This means that the microwave plasma treatment leads to a mixed functionalization primarily due to the presence of amino groups and small amounts of imines and nitriles (see Figure 3). (The surface radicals created in the plasma process react with ambient air after the plasma process has been finished.) A big advantage is

Figure 3. Probable structural formula of the plasma-polymerized allylamine (PPAAm) surface.

Figure 4. High-resolution XPS spectra of C 1s and N 1s peaks for freshly deposited PPAAm. 8019



Article

Table 5. Percentage Contribution of Each C 1s and N 1s Peak for Freshly Deposited PPAAm atomic % peak BE

C−C BDD

C−C aliphatic

C−NH

C−O, CN

NCO

COO

C−N(1)

C−N(2)

CNOH

37.14 284.1

10.13 284.9

15.10 285.8

7.47 286.9

3.69 287.9

0.43 288.7

9.33 398.8

2.67 399.7

0.33 400.6

It has been demonstrated that different [B] doping ranges of BDD polycrystalline film show a different C 1s core level energy range in the XPS spectra.70 Additionally, PPAAm film displays multiple peaks in the C 1s high-resolution spectra in the range from 284.8 to 289.0 eV. The XPS chemical analysis is presented in Table 5. The peak positions are in agreement with previously described PPAAm film deposited on titanium substrates.44 The N 1s peak was fitted by combining different peaks, marked in the plot as −C−N1 and −C−N2, originating from miscellaneous covalent −C−N bonds such as −C−NH2, −C N, CN, −C−N−C, O C−NH2, O C−NHR, and CNOH. Oxygen was also a part of the chemical analysis, contributing 13.72%. 3.2. Functionalization of the Si/BDD/PPAAm Electrode. 3.2.1. Spectroscopic Characterization of Functionalized Si/BDD/PPAAm. The fluorescent properties of modified BDD electrodes are important because of the possibility of the optical readout, for example, in biosensing applications. In this work LIF spectra were studied to confirm the effectiveness of the surface functionalization process as well as to investigate the optical properties of modified BDD. Figure 5 presents LIF

Figure 6. Fluorescence intensity measured for BDD electrodes functionalized with different components; measurements were recorded at 375 and 532 nm laser excitation wavelength.

intensity for each sample was calculated from the Fl = (S − B)· B−1 formula, where S is the integral of fluorescence signal in the analyzed spectral range and B is an integral of signal recorded for the unmodified BDD surface. The fluorescence values Fl were then normalized for each excitation wavelength to enable a comparison of results received for different lasers. On the basis of Figure 6, the optimal excitation wavelength for each sample could be estimated. In the case of the anthraquinone peptide dendrimer (3), Boc-Lys(AQ)−OH (4), and Fmoc-Trp(Boc)−OH (5), the fluorescence signal was relatively strong for both excitation wavelengths. For the first two samples, the excitation wavelength of 532 nm was more efficient, while for Fmoc-Trp(Boc)−OH excitation at 375 nm was preferred. In the case of the sample modified with Rhodamine 110 (2), the intensity of fluorescence was very weak. On the basis of the data presented in Figure 6, the optimal excitation wavelengths were selected for each sample. The fluorescence spectra recorded at these optimal wavelengths are shown in Figure 7. For the excitation at 375 nm, a wide fluorescence band of Fmoc-Trp(Boc)−OH with a maximum near 525 nm was observed (Figure 7a). On the basis of Figure 7b, it can be concluded that the excitation at 532 nm is more efficient for Boc-Lys(AQ)−OH and the anthraquinone peptide dendrimer, which both have their fluorescence bands close to 630 nm. The fluorescence signal recorded for the sample modified with Rhodamine 110 (excitation at 532 nm) is presented in Figure 7c. The observed fluorescence with a maximum at 570 nm was comparable to the signal recorded for the unmodified sample. 3.2.2. Electrochemical Behavior and Stability in Relation to Functionalization. The authors intended to apply the widely used electrochemical systems to characterize the surface of the following modified electrodes: (I) negatively charged [Fe(CN)6]3−/4− which is a one-electron reduction/oxidation system, (II) positively charged Fe2+/Fe3+, and (III) neutrally charged Q/H2Qquinone/hydroquinone. In the case of the BDD electrode modified with plasmapolymerized allylamine (PPAAm), the reduction peak Ec and

Figure 5. LIF spectra of a BDD electrode modified with allylamine (PPAAm).

spectra recorded for BDD electrodes modified with amine for different thickness values of the aminated layer. In the case of the unmodified BDD surface, no measurable fluorescence was detected. For the aminated surface, a wide fluorescence band with a maximum near 525 nm was observed; the band intensity increased with increasing time of plasma polymerization, i.e., with increasing PPAAm thickness. In the next step, the fluorescent properties of aminated BDD electrodes functionalized with Rhodamine 110, Fmoc-Trp(Boc)−OH, Boc-Lys(AQ)−OH, and anthraquinone peptide dendrimers were studied by using the UV (375 nm) and visible (532 nm) excitation range. These wavelengths values were selected because of the availability of inexpensive semiconductor laser sources for the specified spectral ranges, which is important from the point of view of future applications. A comparison of fluorescence intensities recorded for the investigated samples is presented in Figure 6. The fluorescence 8020



Article

derivatives produced the reduction/oxidation process for the [Fe (CN)6]3−/4− model system (see Figure 9).

Figure 9. Experimental cyclic voltammograms of BDD electrodes in an aqueous solution of [Fe(CN)6]3−/4− (5 mM) in Na2SO4 (0.5 M). PPAAm-modified electrodes which have been functionalized with organic compounds; scan rate 100 mV s−1. Figure 7. LIF spectra recorded for BDD electrodes functionalized with Rhodamine 110, Fmoc-Trp(Boc)−OH, Boc-Lys(AQ)−OH, and anthraquinone peptide dendrimer.

Due to the low value of ΔE, the best reversibility of the redox system has been obtained for [Fe(CN)6]3−/4−. For Fe2+/3+ and quinone/hydroquinone, we observed higher separation of the anodic (Epa) and cathodic (Epc) peaks (see Figure 10). This indicates the irreversibility of the electrochemical process and more hindrance for electron transfer across the allyamine coating. Comparing the three electrochemical reaction models, we were able to determine how the structure of the electrode coating affects the transfer of electrons. We have chosen positively (Fe2+/3+), negatively ([Fe(CN)6]3−/4−), and neutrally (Q/H2Q) charged redox systems. At the BDD10-50-TRP electrode, the oxidation (Ea = 0.765 V) and reduction (Ec = −0.216 V) processes in quinone occur for different values compared to the potential of the unmodified electrode (Figure 10). A significant increase in the height of oxidation/reduction peaks for the quinone/hydroquinone system was observed in comparison to other redox systems used in the experiment. This was due to the fact that the reactions in the quinone/ hydroquinone system are based on the two-electron transfer mechanism. The results of the redox process in the Fe2+/3+ system indicate that the oxidation peaks of Fe2+/3+ occur at similar potential values at BDD10-TRP-50 and H-BDD10 electrodes (1.184 and 1.175 V, respectively). However, the reduction peak at the electrode modified with tryptophan is shifted to more positive potential (Ec = −0.319 V) compared to the unmodified electrode (Ec = −0.616 V). This indicates that the introduction of a tryptophan derivative on the outer surface of the electrode significantly influenced the given redox system. However, this influence was much smaller than in the case of the allylamine surface modified with rhodamine, lysine derivatives, and the anthraquinone peptide dendrimer. The electrochemical activity of PPAAm-modified electrodes (BDD10-50-X) was compared to the unmodified electrode surface (H-BDD10) using reduction potentials appointed as (Ea + Ec)/2 = Ef0. The redox potential of [Fe(CN)6]3−/4− for both the unmodified BDD electrode and the BDD10-TRP electrode modified with L-tryptophan was 0.136 V. On other electrodes

oxidation peak Ea associated with the oxidation and reduction of the reference system [Fe(CN)6]3−/4− were not observed in 0.5 M Na2SO4 solution (see Figure 8). The modification of

Figure 8. Experimental cyclic voltammograms of BDD electrodes in an aqueous solution of [Fe(CN)6]3−/4− (5 mM) in Na2SO4 (0.5 M). H-terminated electrode (constant line) and the electrode modified with 50 nm of PPAAm (dotted line); scan rate 100 mV s−1.

BDD with allylamine (BDD10-50) causes the current to decrease from 100−180 μA to 10−20 μA compared to unmodified BDD (H-BDD10). The allyamine layer deposited on the BDD electrode creates an insulating barrier layer, and protonation of the primary amino groups was not detected. Moreover, the small change in solution pH (pH 7 ± 2) had no significant effect on the electrode processes. Similar results were obtained when the experiment was carried out with other reference systems, i.e., Fe2+/3+ and quinone/hydroquinone. However, only the [Fe(CN)6]3−/4− redox process is presented in this paper. The surface of the BDD electrode modified with plasmapolymerized allylamine (PPAAm) that has been subsequently functionalized with amino acids and 9,10-anthraquinone 8021



Article

Figure 10. Experimental cyclic voltammograms of H-BDD-10 and BDD10-50-TRP electrodes in an aqueous solution of [Fe(CN)6]3−/4− (5 mM), Fe2+/3+ (5 mM), and Q/H2Q (5 mM) in Na2SO4 (0.5 M); scan rate 100 mV s−1.

Table 6. Electrochemical Parameters of the Reaction of [Fe(CN)6]3−/4− on the Surface of Modified BDD Electrodes sample H-BDD10 BDD10-50-R110 BDD10-50-TRP BDD-50-LYSAQ BDD-50-3G a

functionalization as-deposited fluorescent dye amino acid 9,10-anthraquinone, amino acid 9,10-anthraquinone, peptide dendrimers

Epc (V)

Epa (V)

−0.044 −0.008 −0.080 −0.017 −0.026

0.316 0.244 0.352 0.253 0.253

Ef0a (V) 0.136 0.118 0.136 0.118 0.114

Ic (A) −1.320 −2.982 −1.075 −3.203 −2.878

× × × × ×

k0 (cm·s−1)

Ia (A) −4

10 10−4 10−4 10−4 10−4

1.725 3.391 1.331 3.554 3.212

× × × × ×

−4

10 10−4 10−4 10−4 10−4

2.89 6.72 2.49 6.31 6.70

× × × × ×

10−4 10−4 10−4 10−4 10−4

Ef0 = (Epa + Epc)/2.

modified with amino acid and quinoid derivatives, the oxidation−reduction Ef0 process occurred slightly easier with a shift toward more positive values, i.e., 0.118, 0.118, and 0.113 V for BDD10-50-R110, BDD-50-LYSAQ, and BDD-50-3G, respectively (see Table 6). The studies performed on diamond electrodes and modified diamond electrodes show that ΔE is higher than 120 mV, which means that the behavior of the [Fe(CN)6]3−/4− redox system can be regarded as quasi-reversible. Therefore the standard electrochemical rate constants ko can be estimated by the method described by Nicolson, i.e., by analyzing the change of ΔE versus scan rate71 (see Figure 11). Assuming the equal diffusion of oxygenated and reduced species DR = D0 = 7.0 × 10−6 cm/s and by using the relationship between ΔE and V, the reaction constants ko for a one-step one-electron process were calculated. The slowest electrochemical electron transfer ko was observed for the unmodified BDD electrode and BDD electrode modified with an L-tryptophan derivative; the respective values were 2.89 × 10−4 and 2.49 × 10−4 cm/s. For BDD modified with Rhodamine 110, the anthraquinoid amino acid derivative (Boc-LysAQ), and Dendrimere G3, the obtained values were similar (6.5 ± 0.2 × 10−4 cm/s) and higher than that observed for the unmodified BDD electrode. In the case of a BDD electrode functionalized with Rhodamine 110, anthraquinone peptide dendrimer, and BocLys(AQ)−OH, the values of cathodic and anodic current for redox reaction in the [Fe(CN)6]3−/4− system were similar (Ic, Ia = 3 ± 0.2 × 10−4 A). For the BDD10-50-TRP electrode and the

Figure 11. Cyclic voltammograms of BDD electrode functionalized with Rhodamine 110 (BDD10-50-R110) in an aqueous solution of [Fe(CN)6]3−/4− (5 mM) in Na2SO4 (0.5 M) for different scan rates.

unmodified H-BDD10 electrode, significantly lower currents were observed, i.e., 1 × 10−4 and 1.3 × 10−4, respectively.

4. CONCLUSIONS The microwave pulsed-plasma polymerized allylamine (PPAAm) method can be used to prepare directly amineterminated BDD/Si electrode surfaces. SEM images showed that PPAAm is homogeneously distributed over the whole BDD surface. FT-IR results showed that the molecular structure of deposited film reproduces the monomer structure H2CCH−CH2−NH2. 8022



Article

For the unmodified BDD surface, no measurable fluorescence was observed. In the case of the aminated surface, a wide fluorescence band was observed; its intensity increased with increasing time of plasma polymerization. The fluorescence signal recorded on the electrodes modified with anthraquinone peptide dendrimer, Boc-Lys(AQ)−OH, and Fmoc-Trp(Boc)− OH was relatively strong. In the case of modification with Rhodamine 110, the intensity of fluorescence was weak. The BDD electrode coated with plasma-polymerized allylamine (PPAAm) did not display the transfer of electrons from the diamond surface to the [Fe (CN)6]3−/4− redox system. A further functionalization of the BDD electrode surface with anthraquinones and peptide derivatives activated the surface toward the electron transfer reaction. The BDD-(PPAAm) electrodes modified with peptide and quinone compounds displayed the accelerated rate of electron transfer for the [Fe(CN)6]3−/4− redox system. Except for the electrode modified with an L-tryptophan derivative, the reaction rate constant ko for the modified electrodes was higher than that of the as-deposited electrode (H-BDD10).

■

Electrodes Modified with Boron-doped Diamond. Sens. Actuators, B 2013, 189, 30−36. (6) Su, L.; Qiu, X.; Guo, L.; Zhang, F.; Tung, C. Amperometric Glucose Sensor Based on Enzyme-modified Boron-doped Diamond Electrode by Cross-linking Method. Sens. Actuators, B 2004, 99, 499− 504. (7) Zhou, Y. L.; Tian, R. H.; Zhi, J. F. Amperometric Biosensor Based on Tyrosinase Immobilized on a Boron-doped Diamond Electrode. Biosens. Bioelectron. 2007, 22, 822−828. (8) Yu, Y.; Zhou, Y.; Wu, L.; Zhi, J. Electrochemical Biosensor Based on Boron-Doped Diamond Electrodes with Modified Surfaces. Int. J. Electrochem. 2011, 2012. (9) Bogdanowicz, R.; Fabiańska, A.; Golunski, L.; Sobaszek, M.; Gnyba, M.; Ryl, J.; Darowicki, K.; Ossowski, T.; Janssens, S. D.; Haenen, K.; et al. Influence of the Boron Doping Level on the Electrochemical Oxidation of the Azo Dyes at Si/BDD Thin Film Electrodes. Diamond Relat. Mater. 2013, 39, 82−88. (10) Szunerits, S.; Boukherroub, R. Different Strategies for Functionalization of Diamond Surfaces. J. Solid State Electrochem. 2008, 12, 1205−1218. (11) Ando, T.; Nishitani-Gamo, M.; Rawles, R. E.; Yamamoto, K.; Kamo, M.; Sato, Y. Chemical Modification of Diamond Surfaces Using a Chlorinated Surface as an Intermediate State. Diamond Relat. Mater. 1996, 5, 1136−1142. (12) Tsubota, T.; Hirabayashi, O.; Ida, S.; Nagaoka, S.; Nagata, M.; Matsumoto, Y. Chemical Modification of Hydrogenated Diamond Surface Using Benzoyl Peroxides. Phys. Chem. Chem. Phys. 2002, 4, 806−811. (13) Nakamura, T.; Ishihara, M.; Ohana, T.; Koga, Y. Chemical Modification of Diamond Powder Using Photolysis of Perfluoroazooctane. Chem. Commun. 2003, 900−901. (14) Liu, Y.; Gu, Z.; Margrave, J. L.; Khabashesku, V. N. Functionalization of Nanoscale Diamond Powder: Fluoro-, Alkyl-, Amino-, and Amino Acid-Nanodiamond Derivatives. Chem. Mater. 2004, 16, 3924−3930. (15) Strother, T.; Knickerbocker, T.; Russell; Butler, J. E.; Smith, L. M.; Hamers, R. J. Photochemical Functionalization of Diamond Films. Langmuir 2002, 18, 968−971. (16) Kuo, T.-C.; McCreery, R. L.; Swain, G. M. Electrochemical Modification of Boron-Doped Chemical Vapor Deposited Diamond Surfaces with Covalently Bonded Monolayers. Electrochem. Solid-State Lett. 1999, 2, 288−290. (17) Goeting, C. H.; Marken, F.; Gutiérrez-Sosa, A.; Compton, R. G.; Foord, J. S. Electrochemically Induced Surface Modifications of Borondoped Diamond Electrodes: An X-ray Photoelectron Spectroscopy Study. Diamond Relat. Mater. 2000, 9, 390−396. (18) Nichols, B. M.; Butler, J. E.; Russell; Hamers, R. J. Photochemical Functionalization of Hydrogen-Terminated Diamond Surfaces: A Structural and Mechanistic Study. J. Phys. Chem. B 2005, 109, 20938−20947. (19) Notsu, H.; Fukazawa, T.; Tatsuma, T.; Tryk, D. A.; Fujishima, A. Hydroxyl Groups on Boron-Doped Diamond Electrodes and Their Modification with a Silane Coupling Agent. Electrochem. Solid-State Lett. 2001, 4, H1−H3. (20) Torrengo, S.; Miotello, A.; Minati, L.; Bernagozzi, I.; Ferrari, M.; Dipalo, M.; Kohn, E.; Speranza, G. The Role of Oxygen in the One Step Amination Process of Nanocrystalline Diamond Surface. Diamond Relat. Mater. 2011, 20, 990−994. (21) Zhang, G.-J.; Song, K.-S.; Nakamura, Y.; Ueno, T.; Funatsu, T.; Ohdomari, I.; Kawarada, H. DNA Micropatterning on Polycrystalline Diamond via One-Step Direct Amination. Langmuir 2006, 22, 3728− 3734. (22) Yang, Z.; Wang, J.; Luo, R.; Maitz, M. F.; Jing, F.; Sun, H.; Huang, N. The Covalent Immobilization of Heparin to Pulsed-plasma Polymeric Allylamine Films on 316L Stainless Steel and the Resulting Effects on Hemocompatibility. Biomaterials 2010, 31, 2072−2083. (23) Yang, J.-H.; Song, K.-S.; Zhang, G.-J.; Degawa, M.; Sasaki, Y.; Ohdomari, I.; Kawarada, H. Characterization of DNA Hybridization

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +48 58 347 1503. Fax: +48 58 347 18 48. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors gratefully acknowledge financial support from the Polish National Science Center (NCN) under Grant No. 2011/ 03/D/ST7/03541, the National Centre for Research and Development (NCBiR) under project No. LIDER/20/91/L-2/ 10, and the University of Gdansk within the project supporting young scientists and PhD students No. 538-8210-B020-13. The DS funds of the Faculty of Electronics, Telecommunications and Informatics of the Gdansk University of Technology are also acknowledged. Authors would like to thank Michał Sobaszek for fruitful discussions and productive research collaboration. The excellent technical assistance of Urte Kellner and Uwe Lindemann (INP e.V., Greifswald, Germany) is kindly acknowledged.

■

REFERENCES

(1) Nebel, C. E.; Yang, N.; Uetsuka, H.; Osawa, E.; Tokuda, N.; Williams, O. Diamond Nano-wires, a New Approach Towards Next Generation Electrochemical Gene Sensor Platforms. Diamond Relat. Mater. 2009, 18, 910−917. (2) Qureshi, A.; Kang, W. P.; Davidson, J. L.; Gurbuz, Y. Review on Carbon-derived, Solid-state, Micro and Nano Sensors for Electrochemical Sensing Applications. Diamond Relat. Mater. 2009, 18, 1401− 1420. (3) Zhuang, H.; Srikanth, V. V. S. S.; Jiang, X.; Aronov, I.; Wenclawiak, B. W.; Luo, J.; Ihmels, H. Elucidation of Different Steps Involved in Allylamine Functionalization of the Diamond Surface and Its Polymerization by Time-of-Flight Secondary Ion Mass Spectrometry. Chem. Mater. 2010, 22, 4414−4418. (4) Zhou, Y.; Zhi, J. The Application of Boron-doped Diamond Electrodes in Amperometric Biosensors. Talanta 2009, 79, 1189− 1196. (5) Bogdanowicz, R.; Czupryniak, J.; Gnyba, M.; Ryl, J.; Ossowski, T.; Sobaszek, M.; Siedlecka, E. M.; Darowicki, K. Amperometric Sensing of Chemical Oxygen Demand at Glassy Carbon and Silicon 8023



Article

on Partially Aminated Diamond by Aromatic Compounds. Langmuir 2006, 22, 11245−11250. (24) Härtl, A.; Schmich, E.; Garrido, J. A.; Hernando, J.; Catharino, S. C. R.; Walter, S.; Feulner, P.; Kromka, A.; Steinmüller, D.; Stutzmann, M. Protein-modified Nanocrystalline Diamond Thin Films for Biosensor Applications. Nat. Mater. 2004, 3, 736−742. (25) Ray, M. A.; Tyler, T.; Hook, B.; Martin, A.; Cunningham, G.; Shenderova, O.; Davidson, J. L.; Howell, M.; Kang, W. P.; McGuire, G. Cool Plasma Functionalization of Nano-crystalline Diamond Films. Diamond Relat. Mater. 2007, 16, 2087−2089. (26) Denisenko, A.; Romanyuk, A.; Pietzka, C.; Scharpf, J.; Kohn, E. Electronic Surface Barrier Properties of Fluorine-terminated Borondoped Diamond in Electrolytes. Surf. Sci. 2011, 605, 632−637. (27) Zou, Y. S.; He, L. L.; Zhang, Y. C.; Li, Z. X.; Wang, H. P.; Gu, L.; Tu, C. J.; Zeng, H. B. Construction and Surface Enhanced Raman Scattering Activity of Gold Nanoparticles Array on Boron Doped Diamond Film. Mater. Chem. Phys. 2013, 141, 816−821. (28) Remes, Z.; Choukourov, A.; Stuchlik, J.; Potmesil, J.; Vanecek, M. Nanocrystalline Diamond Surface Functionalization in Radio Frequency Plasma. Diamond Relat. Mater. 2006, 15, 745−748. (29) Notsu, H.; Tatsuma, T.; Fujishima, A. Tyrosinase-modified Boron-doped Diamond Electrodes for the Determination of Phenol Derivatives. J. Electroanal. Chem. 2002, 523, 86−92. (30) Yang, W.; Auciello, O.; Butler, J. E.; Cai, W.; Carlisle, J. A.; Gerbi, J. E.; Gruen, D. M.; Knickerbocker, T.; Lasseter, T. L.; Russell, J. N.; et al. DNA-modified Nanocrystalline Diamond Thin-films as Stable, Biologically Active Substrates. Nat. Mater. 2002, 1, 253−257. (31) Zhong, Y. L.; Loh, K. P.; Midya, A.; Chen, Z.-K. Suzuki Coupling of Aryl Organics on Diamond. Chem. Mater. 2008, 20, 3137−3144. (32) Nebel, C. E.; Yang, N.; Uetsuka, H.; Osawa, E.; Tokuda, N.; Williams, O. Diamond Nano-wires, a New Approach Towards Next Generation Electrochemical Gene Sensor Platforms. Diamond Relat. Mater. 2009, 18, 910−917. (33) Dauphas, S.; Corlu, A.; Guguen-Guillouzo, C.; Ababou-Girard, S.; Lavastre, O.; Geneste, F. Covalent Immobilization of Antibodies on Electrochemically Functionalized Carbon Surfaces. New J. Chem. 2008, 32, 1228−1234. (34) Nebel, C. E.; Shin, D.; Takeuchi, D.; Yamamoto, T.; Watanabe, H.; Nakamura, T. Photochemical Attachment of Amine Linker Molecules on Hydrogen Terminated Diamond. Diamond Relat. Mater. 2006, 15, 1107−1112. (35) Keen, I.; Broota, P.; Rintoul, L.; Fredericks, P.; Trau, M.; Grøndahl, L. Introducing Amine Functionalities on a Poly(3hydroxybutyrate-co-3-hydroxyvalerate) Surface: Comparing the Use of Ammonia Plasma Treatment and Ethylenediamine Aminolysis. Biomacromolecules 2006, 7, 427−434. (36) Krueger, A.; Lang, D. Functionality Is Key: Recent Progress in the Surface Modification of Nanodiamond. Adv. Funct. Mater. 2012, 22, 890−906. (37) Luong, J. H. T.; Male, K. B.; Glennon, J. D. Boron-doped Diamond Electrode: Synthesis, Characterization, Functionalization and Analytical Applications. Analyst 2009, 134, 1965−1979. (38) Denis, L.; Cossement, D.; Godfroid, T.; Renaux, F.; Bittencourt, C.; Snyders, R.; Hecq, M. Synthesis of Allylamine Plasma Polymer Films: Correlation Between Plasma Diagnostic and Film Characteristics. Plasma Processes Polym. 2009, 6, 199−208. (39) Förch, R.; Zhang, Z.; Knoll, W. Soft Plasma Treated Surfaces: Tailoring of Structure and Properties for Biomaterial Applications. Plasma Processes Polym. 2005, 2, 351−372. (40) Kühn, G.; Retzko, I.; Lippitz, A.; Unger, W.; Friedrich, J. Homofunctionalized Polymer Surfaces Formed by Selective Plasma Processes. Surf. Coat. Technol. 2001, 142−144, 494−500. (41) Saini, G.; Yang, L.; Lee, M. L.; Dadson, A.; Vail, M. A.; Linford, M. R. Amino-Modified Diamond as a Durable Stationary Phase for Solid-Phase Extraction. Anal. Chem. 2008, 80, 6253−6259. (42) Basarir, F.; Cuong, N.; Song, W.-K.; Yoon, T.-H. Surface Modification via Plasma Polymerization of Allylamine for Antibody Immobilization. Macromol. Symp. 2007, 249−250, 61−66.

(43) Puleo, D. .; Kissling, R. .; Sheu, M.-S. A Technique to Immobilize Bioactive Proteins, Including Bone Morphogenetic Protein-4 (BMP-4), on Titanium Alloy. Biomaterials 2002, 23, 2079−2087. (44) Finke, B.; Luethen, F.; Schroeder, K.; Mueller, P. D.; Bergemann, C.; Frant, M.; Ohl, A.; Nebe, B. J. The Effect of Positively Charged Plasma Polymerization on Initial Osteoblastic Focal Adhesion on Titanium Surfaces. Biomaterials 2007, 28, 4521−4534. (45) Wang, X.; Wang, J.; Yang, Z.; Leng, Y.; Sun, H.; Huang, N. Structural Characterization and Mechanical Properties of Functionalized Pulsed-plasma Polymerized Allylamine Film. Surf. Coat. Technol. 2010, 204, 3047−3052. (46) Hamerli, P.; Weigel, T.; Groth, T.; Paul, D. Surface Properties of and Cell Adhesion onto Allylamine-plasma-coated Polyethylenterephtalat Membranes. Biomaterials 2003, 24, 3989−3999. (47) Szunerits, S.; Jama, C.; Coffinier, Y.; Marcus, B.; Delabouglise, D.; Boukherroub, R. Direct Amination of Hydrogen-terminated Boron Doped Diamond Surfaces. Electrochem. Commun. 2006, 8, 1185−1190. (48) Zhou, Y. L.; Tian, R. H.; Zhi, J. F. Amperometric Biosensor Based on Tyrosinase Immobilized on a Boron-doped Diamond Electrode. Biosens. Bioelectron. 2007, 22, 822−828. (49) Finke, B.; Hempel, F.; Testrich, H.; Artemenko, A.; Rebl, H.; Kylián, O.; Meichsner, J.; Biederman, H.; Nebe, B.; Weltmann, K.-D.; et al. Plasma Processes for Cell-adhesive Titanium Surfaces Based on Nitrogen-containing Coatings. Surf. Coat. Technol. 2011, 205 (Supplement 2), S520−S524. (50) Finke, B.; Schröder, K.; Ohl, A. Structure Retention and Water Stability of Microwave Plasma Polymerized Films From Allylamine and Acrylic Acid. Plasma Processes Polym. 2009, 6, S70−S74. (51) Bogdanowicz, R.; Ryl, J.; Darowicki, K.; Kosmowski, B. B. Ellipsometric Study of Oxide Formation on Cu Electrode in 0.1 M NaOH. J. Solid State Electrochem. 2009, 13, 1639−1644. (52) Janssens, S. D.; Pobedinskas, P.; Vacik, J.; Petráková, V.; Ruttens, B.; D’Haen, J.; Nesládek, M.; Haenen, K.; Wagner, P. Separation of Intra- and Intergranular Magnetotransport Properties in Nanocrystalline Diamond Films on the Metallic Side of the Metal− insulator Transition. New J. Phys. 2011, 13, 083008. (53) Gajewski, W.; Achatz, P.; Williams, O. A.; Haenen, K.; Bustarret, E.; Stutzmann, M.; Garrido, J. A. Electronic and Optical Properties of Boron-doped Nanocrystalline Diamond Films. Phys. Rev. B 2009, 79, 045206. (54) Bogdanowicz, R.; Gnyba, M.; Wroczyński, P.; Kosmowski, B. B. Optoelectronic System for Monitoring of Thin Diamond Layers Growth. J. Optoelectron. Adv. Mater. 2010, 12, 1660−1665. (55) Bogdanowicz, R. Investigation of H2:CH4 Plasma Composition by Means of Spatially Resolved Optical Spectroscopy. Acta Phys. Pol., A 2008, 114, A33−A38. (56) Bogdanowicz, R.; Gnyba, M.; Wroczyński, P. Optoelectronic Monitoring of Plasma Discharge Optimized for Thin Diamond Film Synthesis. J. Phys. IV (Proc.) 2006, 137, 57−60. (57) Codognoto, L.; Machado, S. A. S.; Avaca, L. A. Square Wave Voltammetry on Boron-doped Diamond Electrodes for Analytical Determinations. Diamond Relat. Mater. 2002, 11, 1670−1675. (58) Suffredini, H. B.; Pedrosa, V. A.; Codognoto, L.; Machado, S. A. S.; Rocha-Filho, R. C.; Avaca, L. A. Enhanced Electrochemical Response of Boron-doped Diamond Electrodes Brought on by a Cathodic Surface Pre-treatment. Electrochim. Acta 2004, 49, 4021− 4026. (59) Medeiros, R. A.; Rocha-Filho, R. C.; Fatibello-Filho, O. Simultaneous Voltammetric Determination of Phenolic Antioxidants in Food Using a Boron-doped Diamond Electrode. Food Chem. 2010, 123, 886−891. (60) Greenler, R. G. Infrared Study of Adsorbed Molecules on Metal Surfaces by Reflection Techniques. J. Chem. Phys. 2004, 44, 310−315. (61) Szymańska, A.; Ossowski, T.; Łankiewicz, L. Synthesis and Photophysical Properties of L-N E-(9,10-dioxo-9,10-dihydroanthracen-1-yl)-lysine, Dabcyl-like Chromophore for Peptide Studies. Lett. Pept. Sci. 2002, 9, 193−196. 8024



Article

(62) Wang, Q.; Vasilescu, A.; Subramanian, P.; Vezeanu, A.; Andrei, V.; Coffinier, Y.; Li, M.; Boukherroub, R.; Szunerits, S. Simultaneous Electrochemical Detection of Tryptophan and Tyrosine Using Borondoped Diamond and Diamond Nanowire Electrodes. Electrochem. Commun. 2013, 35, 84−87. (63) Niedziałkowski, P.; Ossowski, T.; Majewski, R.; Nowakowska, Z.; Schroeder, G. Thiol-functionalized Anthraquinones: Mass Spectrometry and Electrochemical Studies. Monatsh. Chem. 2011, 142, 1121−1129. (64) Kowalczyk, A.; Nowicka, A. M.; Jurczakowski, R.; Niedzialkowski, P.; Ossowski, T.; Stojek, Z. New Anthraquinone Derivatives as Electrochemical Redox Indicators for the Visualization of the DNA Hybridization Process. Electroanalysis 2010, 22, 49−59. (65) Czupryniak, J.; Niedziałkowski, P.; Karbarz, M.; Ossowski, T.; Stojek, Z. Lysine and Arginine Oligopeptides Tagged with Anthraquinone: Electrochemical Properties. Electroanalysis 2012, 24, 975−982. (66) Tsantaki, E.; Velegraki, T.; Katsaounis, A.; Mantzavinos, D. Anodic Oxidation of Textile Dyehouse Effluents on Boron-doped Diamond Electrode. J. Hazard. Mater. 2012, 207−208, 91−96. (67) Kawarada, H. Hydrogen-terminated Diamond Surfaces and Interfaces. Surf. Sci. Rep. 1996, 26, 205−259. (68) Girard, H.; Simon, N.; Ballutaud, D.; Herlem, M.; Etcheberry, A. Effect of Anodic and Cathodic Treatments on the Charge Transfer of Boron Doped Diamond Electrodes. Diamond Relat. Mater. 2007, 16, 316−325. (69) Takeuchi, D.; Kato, H.; Ri, G. S.; Yamada, T.; Vinod, P. R.; Hwang, D.; Nebel, C. E.; Okushi, H.; Yamasaki, S. Direct Observation of Negative Electron Affinity in Hydrogen-terminated Diamond Surfaces. Appl. Phys. Lett. 2005, 86, 152103−152103−3. (70) Ghodbane, S.; Ballutaud, D.; Omnès, F.; Agnès, C. Comparison of the XPS Spectra from Homoepitaxial {111}, {100} and Polycrystalline Boron-doped Diamond Films. Diamond Relat. Mater. 2010, 19, 630−636. (71) Nicholson, R. S. Theory and Application of Cyclic Voltammetry for Measurement of Electrode Reaction Kinetics. Anal. Chem. 1965, 37, 1351−1355.

8025


Novel Functionalization of Boron-Doped Diamond by Microwave

Recommend Documents