Pt-Decorated Boron Nitride Nanosheets as Artificial Nanozyme for

Research Article Cite This: ACS Appl. Mater. Interfaces 2019, 11, 22102−22112

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Pt-Decorated Boron Nitride Nanosheets as Artificial Nanozyme for Detection of Dopamine Mariia N. Ivanova,*,† Ekaterina D. Grayfer,*,† Elena E. Plotnikova,†,‡ Lidiya S. Kibis,‡,§ Gitashree Darabdhara,∥,⊥ Purna K. Boruah,∥,⊥ Manash R. Das,*,∥,⊥ and Vladimir E. Fedorov†,‡ †

Nikolaev Institute of Inorganic Chemistry SB RAS, Acad. Lavrentiev Prosp. 3, Novosibirsk 630090, Russian Federation Novosibirsk State University, Pirogova Str. 2, Novosibirsk 630090, Russian Federation § Boreskov Institute of Catalysis SB RAS, Acad. Lavrentiev Prosp. 5, Novosibirsk 630090, Russian Federation ∥ Advanced Materials Group, Materials Sciences and Technology Division, CSIR-North East Institute of Science and Technology, Jorhat 785006, India ⊥ Academy of Scientific and Innovative Research, CSIR-NEIST Campus, Jorhat 785006, India

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S Supporting Information *

ABSTRACT: Over the past decade, nanosized metal oxides, metals, and bimetallic particles have been actively researched as enzyme mimetic nanomaterials. However, the common issues with individual nanoparticles (NPs) are stabilization, reproducibility, and blocking of active sites by surfactants. These problems promote further studies of composite materials, where NPs are spread on supports, such as graphene derivatives or dichalcogenide nanosheets. Another promising type of support for NPs is the few-layered hexagonal boron nitride (hBN). In this study, we develop surfactant-free nanocomposites containing Pt NPs dispersed on chemically modified hydrophilic hBN nanosheets (hBNNSs). Ascorbic acid was used as a reducing agent for the chemical reduction of the Pt salt in the presence of hBNNS aqueous colloid, resulting in Pt/hBNNS nanocomposites, which were thoroughly characterized with X-ray diffraction, transmission electron microscopy, dynamic light scattering, and X-ray photoelectron and infrared spectroscopies. Similar to graphene oxide binding the metal NPs more efficiently than pure graphene, hydrophilic hBNNSs well stabilize Pt NPs, with particle size down to around 8 nm. We further demonstrate for the first time that Pt/hBNNS nanocomposites exhibit peroxidase-like catalytic activity, accelerating the oxidation of the classical colorless peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to its corresponding blue-colored oxidized product in the presence of H2O2. Kinetic and mechanism studies involving terephthalic acid and isopropanol as a fluorescent probe and an •OH radical scavenger, respectively, proved that Pt/hBNNSs assist H2O2 decomposition to active oxygen species (•OH), which are responsible for TMB oxidation. The Pt/hBNNS nanocomposite-assisted oxidation of TMB provides an effective platform for the colorimetric detection of dopamine, an important biomolecule. The presence of increased amounts of dopamine gradually inhibits the catalytic activity of Pt/hBNNSs for the oxidation of TMB by H2O2, thus enabling selective sensing of dopamine down to 0.76 μM, even in the presence of common interfering molecules and on real blood serum samples. The present investigation on Pt/hBNNSs contributes to the knowledge of hBN-based nanocomposites and discovers their new usage as nanomaterials with good enzyme-mimicking activity and dopamine-sensing properties. KEYWORDS: peroxidase-like activity, enzyme mimetics, nanoparticle decoration, boron nitride nanosheets, platinum nanoparticles

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INTRODUCTION

The use of nanomaterials as enzyme mimetics is a growing area of research all over the world.1 Although natural enzymes as biological catalysts have the benefits of substrate specificity, © 2019 American Chemical Society

Received: March 7, 2019 Accepted: May 24, 2019 Published: May 24, 2019 22102

DOI: 10.1021/acsami.9b04144 ACS Appl. Mater. Interfaces 2019, 11, 22102−22112

Research Article

ACS Applied Materials & Interfaces

Scheme 1. Design of the Pt/hBNNS Nanocomposites: (i) Chemical Treatment of Bulk hBN with H2O2 Resulting in the Formation of Chemically Modified Water-Soluble hBNNSs; (ii) Decoration of the Functionalized hBNNSs with Pt NPs Achieved by the Reduction of the Pt Precursor Salt with Ascorbic Acid

wide range of applications is envisaged for hBN-based nanocomposites, including catalysis,29−35 surface-enhanced Raman spectroscopy,36,37 immunosensing,38,39 electrochemical biosensors for hydrogen peroxide40 and glucose,41 antibacterial water treatment,42,43 antioxidation material,44 and so forth. hBN has a range of advantageous properties that promote its use as a support for NPs. It is thermally conductive, stable at high temperatures (up to 800 °C in air), mechanically resistant, and inert toward the action of most acids, bases, and oxidants. Very recent research shows that metal-free hBN may even have its own catalytic activity in several processes.45−48 On the other hand, it has an inert surface, a low surface area in the bulk state, and, consequently, lack of interaction with metal precursors, as opposed to carbon nanomaterials or oxides, such as Al2O3, SiO2, and so forth. To profit from hBN’s attractive properties mentioned above, researchers need to overcome difficulties related to its inertness. One important recent development consists in liquid-phase exfoliation of hBN through ultrasonication, yielding colloid dispersions of thin hBN nanosheets (hBNNSs), which are further used for deposition of metal NPs. Bulk hBN may be ultrasonically exfoliated in organic solvents,49 such as ethanol, isopropanol,33 dimethylformamide,43 ethylene glycol,31 or poly(ethylene glycol),30 and even in water,36,40,42 especially after chemical modification50 or with the help of surfactants.51,52 To render hBNNSs more chemically active and able to bind with metal atoms, they may be noncovalently or covalently functionalized before the introduction of the metal salt. To achieve the noncovalent functionalization, hBN is dispersed in a surfactant water solution,51,52 which is a good strategy to achieve highly concentrated dispersions; but it has the drawbacks of surfactants blocking the potential catalytically active sites or metal-anchoring sites. Covalent functionalization implies attachment of certain surface functional groups,28 such as −OH in hydroxylated hBN (OH−hBN), often prepared through H2O2 treatment.29,50 In spite of the growing number of important findings described above, the use of hBN in composites with metals is still in its infancy and needs further research to uncover more synthetic approaches to effectively anchor metal NPs on its inert surface, to achieve higher loadings of NPs, to control their size, and to broaden their application areas. In this study, we report surfactant-free deposition of Pt NPs on the chemically functionalized surfaces of hBNNSs and, for the first time,

efficiency, and selectivity, they are also associated with disadvantages, such as denaturation and sensitivity to environmental changes and their time-consuming preparation processes, along with purification and storage.2 Hence, nanomaterials are envisaged as artificial enzyme mimetics that are stable, practical, efficient, and selective. Yan et al. in 2007 pioneered the work in that direction by investigating Fe3O4 nanoparticles (NPs) as peroxidase mimics similar to natural peroxidase and capable of catalyzing the oxidation of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to produce a blue color reaction in the presence of H2O2.3 This simple cost-effective colorimetric assay was further investigated in several biosensing applications, including detection of biological molecules such as glucose,4 H2O2,5 amino acids,6 dopamine (DA),7,8 and so forth. DA is one such biomolecule that acts as a neurotransmitter and plays a major role in hormonal, renal, and central nervous systems.8,9 Changes in the concentration of DA lead to neurological syndromes, such as schizophrenia, Alzheimer’s, Parkinson’s, and Huntington’s diseases. Thus, developing rapid methods for its detection is highly important. Because of simple operational techniques and low cost, the colorimetric method can be effectively used for DA detection. Over the last few years, different nanomaterials have been actively investigated as enzyme mimics for the colorimetric detection of biological molecules. In particular, many inorganic NPs, for example, Au,4,10 Ag,11 Pt,12,13 Co3O4@NiO,14 and so forth, exhibit peroxidase-like catalytic activity. Often NPs of metals or metal compounds are deposited on a support surface to improve stability and dispersibility and to avoid the use of stabilizers, which may have a detrimental influence on the catalytic and sensing properties of NPs. Examples of such nanocomposites include magnetite/graphene,5,15 CuS-decorated reduced graphene oxide (rGO) nanosheets,16 Pt/GO,17 Ni/rGO,7 NiCo2S4/rGO,18 and so forth. In addition to graphene-based nanocomposites,8 thin sheets of molybdenum disulfide were used as supports for bimetallic AuPd19 and PtAg20 NPs efficient as peroxidase mimics and sensors for glucose and H2O2 and as electrochemical sensors for DA (Pt/MoS2).21 At the same time, until now, nanocomposites with another interesting graphene analogue, fewlayered hexagonal boron nitride (hBN), have been very little explored as enzyme mimetics.22 Two-dimensional hBN nowadays attracts considerable attention,23−28 in particular, as a support for various NPs. A 22103


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Detection of DA. Typically, freshly prepared aqueous solutions of DA hydrochloride of various concentrations (2−100 μM) were added into the reaction mixture containing sodium acetate buffer (pH 4.0), TMB solution (0.5 M, 250 μL), Pt/hBNNSs (7 mg/L), and H2O2 (50 μL). The entire reaction mixture was incubated for 20 min, and the successive change in the blue color was observed by varying the DA concentration. Selectivity of Our Designed Sensor toward DA Detection. To understand the selectivity of our designed sensor toward DA detection, Pt/hBNNSs-5 was utilized to detect different interferences, such as ascorbic acid, uric acid, lactose, fructose, glucose, L-cysteine, and glutathione, separately. The experimental conditions were similar to the DA detection reactions. However, optimum DA detection was carried out in 50 μM DA concentration, which was 10 times lower than the concentration of other interferences. The selectivity of DA was determined after comparing the absorbance changes of DA and other interference molecules. Further, we conducted additional experiments for the detection of L-cysteine, glutathione, and ascorbic acid in the presence of N-ethylmaleimide (NEM) as a masking agent (concentration of NEM was 500 μM, keeping the concentrations of all other chemicals the same) to diminish the inhibition effect of these molecules toward TMB oxidation. Detection of DA in Real Samples. The practical applicability of the designed sensor in the detection of DA was analyzed in human blood serum samples using the standard addition method. For performing the experiment, human blood serum samples obtained from human volunteers at the CSIR-NEIST Clinical Centre were pretreated by high-speed refrigerated centrifuge at 4000 rpm, and the supernatant was separated and stored under refrigeration at 4 °C. Then, the samples were diluted 10 times with deionized water, and a calibration plot was obtained by allowing the serum samples to undergo spiking with standard DA solution. After that, the TMB solution (0.5 M, 250 μL), Pt/hBNNSs-5 (7 mg/L), and H2O2 (50 μL) were added to the serum samples. The concentration of DA was determined from the calibration plot after knowing the absorbance changes of the serum samples at 652 nm.

explore the enzymatic peroxidase-like catalytic activity of the resulting hybrids toward the oxidation of peroxidase substrate TMB in the presence of H2O2. This oxidation process is inhibited by DA and, thus, functions as an important podium for the colorimetric detection of DA.

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EXPERIMENTAL SECTION

Preparation of hBNNSs. Functionalized hBN samples were prepared by treatment with H2O2 (30%), as described in our previous report.50 In a typical procedure, bulk hBN (150 mg) was put into a cylindrical Teflon-coated autoclave (rated pressure 2−3 atm). H2O2 (30%, 30 mL) was added to the autoclave and ultrasonicated for 15 min and then thermostated in a water bath for 20 h at 80 °C. After the reaction, the solid phase of the mixture was separated by centrifugation, washed twice with water followed by ethanol, and then dried at 50 °C to a constant mass. To obtain colloidal dispersion containing hBNNSs, the resulting product was dispersed in water by ultrasonication for 15 h (1000 mL of water added to 100 mg of functionalized hBN). Synthesis of Pt/hBNNS Nanocomposites. The overall process design is presented in Scheme 1. K2PtCl4 water solution was added to a colloidal dispersion of hBNNSs in water to achieve the calculated amount of Pt in nanocomposites of about 5, 10, and 15 wt % (designated as Pt/hBNNSs-5, Pt/hBNNSs-10, and Pt/hBNNSs-15, respectively). The mixture of Pt precursor and hBNNSs was stirred at room temperature for 30 min, and then the reaction mixture was heated up to 80 °C. The 100-fold excess of ascorbic acid solution was added to the mixture and then heated further for 1 h. During the heating, the color of the mixture changed from white to light gray, which indicated the formation of Pt NPs. The higher the Pt content, the darker the color of the sample and the higher the mass uptake. The Pt/BNNSs remained in colloidal state for more than 3 days, so, when necessary, KCl solution was added to coagulate the dispersion. Electrolyte addition led to full agglomeration of the colloid within 3− 5 h. The solid phase of the mixture was separated by centrifugation, washed twice with water followed by ethanol, and then dried at 50 °C to a constant mass. Peroxidase-like Catalytic Activity of Pt/hBNNS Nanocomposites. The peroxidase-like catalytic activity of the Pt/hBNNS nanocomposites was analyzed through the oxidation of the chromogenic peroxidase substrate TMB (250 μL, 0.5 M) by H2O2 (50 μL) in sodium acetate buffer (0.2 M, 3 mL, pH 4) in the presence of the Pt/hBNNs catalyst (7 mg/L). The incubation of the entire reaction suspension for 20 min was followed by the emergence of the blue TMB oxidation product with a characteristic peak at 652 nm in the ultraviolet−visible (UV−vis) spectrum.53 The catalyst concentration, pH, and temperature effects on the peroxidase-like catalytic activity were analyzed to determine the optimum conditions. The kinetics of the catalytic reaction was examined with respect to the change in the absorbance (at 652 nm) at a time by varying the initial concentration of either TMB or H2O2 and keeping the other concentration constant. The typical Michaelis−Menten curves for Pt/ hBNNS nanocomposites were obtained at a certain concentration range of TMB or H2O2. Michaelis−Menten constant (Km) and maximum velocity (Vmax) were obtained using the Lineweaver−Burk double reciprocal plot

ij K yzi 1 y ij 1 yz 1 zz = jjj m zzzjjjj zzzz + jjj zz j Vmax z [S] j ν k {k { k Vmax {

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RESULTS AND DISCUSSION Synthesis and Characterization of Pt/hBNNS Nanocomposites. Pristine bulk hBN is chemically inert, while effective interaction of the support surface with a metal precursor in solution requires the presence of active sites, such as defects or functional groups, as well as a developed surface area. It is reported that the degree of oxygen functionalization of the support governs NP nucleation and growth mechanisms, as oxygen functional groups are responsible for the electrostatic interactions with charged precursors in solution.54 Therefore, to simplify the loading of Pt NPs onto the hBNNS surface, we conducted chemical modification and exfoliation of bulk hBN powder following our previously developed method that combines solvothermal treatment of hBN bulk powder in a water/H2O2 medium and sonication of the functionalized product in water.50 Hydrogen peroxide is an effective, wasteavoiding oxidant, which adds hydrophilic functional groups (predominantly, −OH) to the hBN surface,50,55 thus facilitating its exfoliation into aqueous colloids of chemically modified hBNNSs (shown in Scheme 1). The resulting functionalized hBNNSs in solutions preserve their hexagonal structures, but become thinner (down to few layers) and more chemically active to bind the metal precursors. To decorate hBNNSs with Pt NPs, a calculated amount of K2PtCl4 (5, 10, 15 wt %) was added to the hBNNS colloids and allowed to sorb on hBNNSs, followed by reduction with ascorbic acid (shown in Scheme 1). Ascorbic acid (vitamin C) was selected as a nonhazardous natural and eco-friendly reducing agent often used for the preparation of free-standing

(1)

where ν = initial velocity and [S] = substrate concentration. Km is the concentration of the substrate at which the reaction rate is half of Vmax. The lower the Km value, the stronger the affinity between the substrate and the enzyme. Fluorescent probing to detect hydroxyl radicals (•OH): typically, 50 μL of H2O2 was added to a solution containing 0.5 mM terephthalic acid (TA) and 7 mg/L Pt/hBNNSs-5 and incubated in 0.2 mM sodium acetate buffer (pH 4.0) at 35 °C. 22104


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Figure 1. (a) XRD patterns of hBNNSs, Pt/hBNNSs-5, Pt/hBNNSs-10, and Pt/hBNNSs-15, (b) high-resolution XPS B1s spectrum of Pt/ hBNNSs-5, (c) high-resolution XPS N1s spectrum of Pt/hBNNSs-5, and (d) high-resolution XPS Pt4f spectrum of Pt/hBNNSs-5.

Figure 2. TEM images of (a,b) functionalized soluble hBNNSs and (c,d) Pt/hBNNSs-5 nanocomposite. (e) particle size distribution curve of Pt/ hBNNSs-5.

and supported NPs. The white mixture gradually turned gray within a few minutes, indicating the reduction of platinum precursor to metallic Pt NPs. A large excess of the reducing agent ensured that the NP growth occurred homogeneously. Meanwhile, the exfoliated state of hBNNSs provided a relatively large area to accommodate Pt NPs. Figure 1a shows the typical X-ray diffraction (XRD) patterns for hBNNSs, Pt/hBNNSs-5, Pt/hBNNSs-10, and Pt/hBNNSs-

15. The XRD pattern of pure hBNNSs displays diffraction peaks at 2θ values of 26.6°, 41.6°, 43.7°, 50.1°, 55.1°, 75.9°, and 82.2° corresponding to the (002), (100), (101), (102), (004), (110), and (112) crystallographic planes of hBN, respectively [JCPDS card no. 00-009-0012]. The diffraction patterns of Pt/hBNNSs-5, Pt/hBNNSs-10, and Pt/hBNNSs15 contain additional reflexes at 39.7°, 46.2°, 67.7°, and 81.5° corresponding to the (111), (200), (220), and (311) 22105


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Figure 3. Catalytic TMB oxidation under different experimental conditions: (a) different catalytic systems, that is, in the presence of Pt/hBNNSs-5 alone (line 1), H2O2 alone (line 2), and both H2O2 and Pt/hBNNSs-5 (line 3) (acetate buffer: 0.2 M, pH 4, TMB: 0.5 M, catalyst: 7 mg/L, H2O2: 50 μL and temperature: 25 °C); (b) varying catalyst loading (acetate buffer: 0.2 M, pH 4, TMB: 0.5 mM, H2O2: 50 μL and temperature: 25 °C); (c) varying pH of the solution (TMB: 0.5 mM, catalyst: 7 mg/L, H2O2: 50 μL and temperature: 25 °C); and (d) varying temperature (acetate buffer: 0.2 M, pH 4, TMB: 0.5 mM, catalyst: 7 mg/L and H2O2: 50 μL).

supported by Fourier transform infrared (FTIR) spectroscopy data (Figure S2). In addition, the hydrophilicity imparted to bulk hBN by chemical treatment also constitutes an indirect but important proof of its functionalization. Samples containing higher amounts of Pt appear to bear fewer oxygen groups, as followed from their deteriorated colloidal stability. This may be well-explained by the concomitant reduction of O groups during catalyst preparation or their screening with Pt NPs. Transmission electron microscopy (TEM) images of hBNNSs and Pt/hBNNS nanocomposites are shown in Figure 2. As expected,50 the functionalized hBNNSs exist in colloids in the form of thin sheets with sizes of several hundred nanometers [TEM images in Figure 2a,b and atomic force microscopy (AFM) image in Figure S3]. The TEM images of Pt/hBNNSs-5 (Figure 2c,d) exhibit the hBNNS-supported Pt NPs with average sizes of 8.5 ± 0.2 nm, as followed from the particle size distribution curve (Figure 2e), which are comparable with the crystalline sizes (9.4 nm) of Pt NPs obtained from the XRD pattern. Some Pt particles were agglomerated into more complex structures of 20−25 nm in size for Pt/hBNNSs-5 (Figure 2c,d) and 30−40 nm in size for Pt/hBNNSs-10 and Pt/hBNNSs-15 (Figure S4). Dynamic light scattering (DLS) data were collected to support the TEM findings and better understand the nature of the particles in colloids (as TEM deals with deposited samples). The data confirmed that, overall, the hydrodynamic diameters of the colloidal nanosheets lie in the range of several hundreds of nanometers. However, for samples with higher loading of Pt, colloidal stability problems emerge (Figure S5). The destabilization may be caused by factors such as (i) increased weight of the particles and (ii) decreased number of functional hydrophilic groups at the hBNNS surface, as they are involved

crystallographic planes of face-centered cubic Pt NPs, respectively [JCPDS card no. 00-001-1190]. The intensities of these peaks increase with increasing amount of Pt in the samples from Pt/hBNNSs-5 to Pt/hBNNSs-15. The d-spacing values and crystalline sizes were obtained by using PDXL software. The d-spacing values in the composites were found to be 3.343 (002), 2.170 (100), 2.068 (101), 1.819 (102), 1.667 (004), 1.253 (110), and 1.173 Å (112) for the hBN phase and 2.267 (111), 1.963 (200), 1.383 (220), and 1.180 Å (311) for the Pt phase, as calculated from the data for Pt/hBNNSs-5. Broad diffraction peaks reflect the small average particle size, as expected for well-dispersed NPs. The crystalline sizes of the Pt NPs in Pt/hBNNSs-5 were estimated as 9.4 nm from its XRD pattern by the Scherrer equation. Therefore, the XRD data analysis clearly evidences the successful loading of various amounts of Pt NPs onto hBNNSs. X-ray photoelectron spectroscopy (XPS) survey spectrum (Figure S1a,b) reveals that the main elements in all samples are B, N, O, and Pt (for Pt-loaded samples). Pt/hBNNS samples are characterized by symmetrical B1s and N1s peaks located at 190.5 and 398.1 eV, respectively, in accordance with previously obtained values for hBN50 (Figure 1b,c). The high-resolution Pt 4f spectrum exhibits one main Pt 4f doublet with Eb(Pt 4f7/2) = 71.3 eV, typical for metallic platinum (Figure 1d).56 The following relative atomic percentage ratios of B, N, O, and Pt have been obtained: 49.6/47.7/2.6/0 for hBNNSs; 50.4/ 46.5/2.7/0.4 for Pt/hBNNSs-5; 46.9/49.7/2.8/0.7 for Pt/ hBNNSs-10; and 46.7/49.2/3.2/1.0 for Pt/hBNNSs-15. The estimated Pt content in Pt/hBNNS samples is within reasonable agreement with the theoretically calculated amount used in the experimental procedure. The oxygen found in the XPS spectra (one symmetrical peak located at 532.4 eV, Figure S1c) may be due to OH functional groups, surface contaminations, or adsorbed water. These findings are 22106


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Figure 4. Steady-state kinetic assay of Pt/hBNNSs-5 by varying the (a) TMB concentration at a constant H2O2 concentration (H2O2: 50 mM, acetate buffer: 0.2 M, pH 4, catalyst: 7 mg/L and temperature: 25 °C) and (b) H2O2 concentration at a constant TMB concentration (TMB: 0.5 mM, acetate buffer: 0.2 M, pH 4, catalyst: 7 mg/L and temperature: 25 °C). The inset shows the corresponding Lineweaver−Burk plots, which were obtained using the Michaelis−Menten equation.

Finally, we investigated the influence of the Pt content in the catalyst on its activity (Figure S6). Among three Pt-decorated samples, the best results were achieved in the case of Pt/ hBNNSs-5, which may be due to better dispersion of smaller NPs and their tendencies to agglomerate, as their loading increases. Another reason could be that Pt/hBNNSs-10 and Pt/hBNNSs-15 samples are less stable in colloids, as was observed in DLS experiments (Figure S5), and part of the catalyst does not work because of precipitation. As Pt/ hBNNSs-5 is the best sample in terms of efficiency and cost, it was used for further catalytic studies. As for the Pt-free pure hBNNSs, they too have some appreciable catalytic activity, even in the absence of Pt NPs on their surfaces (Figure S6). Here, we note that until very recently, in catalytic studies, hBN has been used simply as a support. However, new data proved that it may possess some catalytic active sites, especially after modification. For example, oxygen functionalities at the edges45−47 and defects48 in hBN are proposed to be responsible for catalytic oxidative dehydrogenation of light alkanes and electrochemical CO2 reduction. Here, we deal with soluble functionalized hBNNSs and observe for the first time their moderate activity for oxidation of TMB as a peroxidase substrate in the presence of H2O2. Thus, the use of hBNNSs for stabilization of Pt NPs has a benefit of additional catalytic activity of the support, acting as a co-catalyst. Kinetics of TMB Oxidation. The kinetics of TMB oxidation using Pt/hBNNSs-5 was studied through the steady-state kinetics measurement by changing the concentration of either TMB or H 2 O 2 while keeping the concentration of other reagents constant. The obtained values of absorbance were converted to the concentration of the blue product using the Beer Lambert’s law

in anchoring of a large number of Pt NPs and/or removed during reduction. Aggregated morphology may come from the attachment of the particles nucleated in solution to the particles deposited on the surface. Numerous reports contain evidence that agglomerates of NPs may have interesting catalytic properties, quite different from the properties of both bulk and welldispersed structures. Two examples of this situation are agglomerated Pt NPs on a glassy carbon support57 and Pt/ Pd/graphene complex hybrids58 that showed improved electrocatalytic properties, supposedly, due to the increased concentration of surface defects in such structures. We further show that the Pt/hBNNSs prepared in this work also possess promising catalytic properties in the enzyme-like oxidation of TMB by H2O2. Peroxidase-like Catalytic Activity and Optimization of Reaction Conditions. The peroxidase-like catalytic activity of the Pt/hBNNS nanocomposites was analyzed through the oxidation of peroxidase substrate TMB in the presence of H2O2, and the progress of the reaction was determined by studying the change in the absorbance at 652 nm characteristic of the oxidized TMB (oxTMB) product. From Figure 3a, it is clearly seen that negligible TMB oxidation occurs in the presence of the TMB−H2O2 system, whereas no oxidation takes place in the TMB−Pt/hBNNSs-5 system. However, when both H2O2 and TMB are employed, considerable TMB oxidation happens. Thus, it is clear that the presence of both H2O2 and Pt/hBNNSs-5 is required for the oxidation of TMB. We optimized various experimental conditions for the TMB oxidation reaction, including catalyst loading (Figure 3b), pH (Figure 3c), and temperature (Figure 3d). It was shown that the catalyst amount has a significant effect on the oxidation of TMB. As the concentration of Pt/ hBNNSs-5 grew from 1 to 7 mg/L, the maximum absorbance at 652 nm also grew remarkably. However, further increasing the concentration of the Pt/hBNNSs-5 nanocomposite to 12 mg/L led to a decrease in the absorbance at 652 nm, implying decreased TMB oxidation. As seen from Figure 3c, the catalytic oxidation of TMB is also pH-dependent, and pH = 4 was found to be the optimum pH for the excellent activity of Pt/ hBNNSs-5 for TMB oxidation. Moreover, the effect of temperature of the reaction medium on the catalytic activity of Pt/hBNNSs-5 was investigated in the temperature range 25−45 °C, and it was found that the maximum absorbance was obtained at 25 °C. Thus, 7 mg/L Pt/hBNNSs-5, pH = 4, and t = 25 °C were selected as the optimal conditions for efficient oxidation of TMB.

A = εoxTMB × c × L

where εoxTMB = 39 000 M−1 cm−1 at 652 nm.51 Typical Michaelis−Menten curves are displayed in Figure 4a,b for TMB and H2O2 as substrates in a particular concentration range. Kinetic parameters Km and Vmax were calculated using Lineweaver−Burk double reciprocal plots (Figure 4a,b insets). The constant Km is an important parameter, which gives the binding affinity between the substrate and the enzyme. From the Lineweaver−Burk plot, the Km values of 0.21 and 9.2 mM were obtained for TMB and H2O2, respectively, indicating a high affinity of TMB toward Pt/hBNNSs-5. Using hBNNSs alone, the Km values of 0.42 and 12.2 mM were obtained for 22107


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Figure 5. (a) Fluorescence emission spectra of TA (line 1), TA + Pt/hBNNSs-5 (line 2), TA + H2O2 (line 3), and TA + Pt/hBNNSs-5 + H2O2 (line 4) and (b) effect of isopropanol on the peroxidase-like catalytic activity of the Pt/hBNNSs-5 nanocomposite (acetate buffer: 0.2 M, pH 4, TMB: 0.5 M, catalyst: 7 mg/L, H2O2: 50 μL and temperature: 25 °C).

Scheme 2. Schematic Illustration of the Possible Mechanism of TMB oxidation by H2O2 in the presense of Pt/hBNNSs: (i) TMB Adsorption on the Catalyst Surface; (ii) H2O2 Radical Decomposition onto Pt NPs; (iii) Newly Formed •OH Radical Species Diffuse to Oxidize TMB through One-Electron Process into Blue-Colored oxTMB Product (Cation Free-Radical TMB+•, Which Exists in Rapid Equilibrium with the Charge-Transfer Complex of TMB with the Diimine Derivative of TMB)

TMB and H2O2, respectively (Figure S7). The lower Km value achieved by using the Pt/hBNNSs-5 nanocomposite as compared to hBNNSs alone indicates a better substrate affinity of Pt/hBNNSs-5. Mechanism of Peroxidase Mimetic Activity of Pt/ hBNNS Nanocomposites. It is generally accepted that peroxidase-assisted TMB oxidation proceeds through the formation of •OH radicals from H2O2.1 To confirm that our catalysts Pt/hBNNSs operate in the same manner, we conducted the fluorescent probe and scavenger addition experiments. First, the process of •OH radical-driven oxidation of the nonfluorescent TA to highly fluorescent 2-hydroxyterephthalic acid54 was used to study the formation of •OH from H2O2 by the Pt/hBNNSs-5 catalyst. Figure 5a shows that the TA molecule alone does not exhibit any fluorescent behavior (line 1), but the presence of H2O2 and Pt/hBNNSs-5 greatly affects the oxidation of TA to 2-hydroxyterepthalic acid and manifests in maximum emission at 426 nm (line 4). Apparently, the system H2O2 + Pt/hBNNSs-5 generates the highest amount of •OH. Their formation was further verified by introducing isopropanol as the scavenger of •OH radicals.59 To the reaction mixture containing TMB, H2O2, and Pt/ hBNNSs-5, isopropanol (0.1 mmol L−1) was added, keeping the other conditions same. Isopropanol modifies the reaction course and lowers the rate of peroxidase activity of the Pt/ hBNNSs-5 nanocomposite nearly 3 times (Figure 5b). Therefore, it may be clearly seen that the •OH radicals act

as main reactive species in the studied peroxidase-like enzymatic reaction. In the absence of H2O2, which is the main source of •OH, the catalyst Pt/hBNNSs-5 is inefficient in the promotion of TA oxidation (Figure 5a, line 2). On the other hand, even in the absence of the catalyst, some oxidation of TA may take place (Figure 5a, line 3). However, although •OH radical formation occurs, no TMB oxidation was observed in this system (Figure 3a, line 2), which proves the indispensability of the Pt/ hBNNSs-5 catalyst for this process. Its role consists in providing active surface sites for adsorption and interaction of the reagents TMB and H2O2. The first step of the process is supposed to be H2O2 and TMB adsorption [processes (i) and (ii) in Scheme 2] on the catalyst surface. In the absence of Pt, hBNNSs may catalyze the reaction to some degree (Figure S6), but better affinities of the substrates to the catalyst’s surface may be achieved when they are decorated with Pt, as evidenced by the kinetic studies discussed above. Pt NPs are well-known for their ability to accelerate H2O2 radical decomposition [process (ii) in Scheme 2]; so, the newly formed •OH radical species diffuse to oxidize TMB into blue-colored cation free-radical TMB+•, which exists in rapid equilibrium with the charge-transfer complex of TMB with the diimine derivative of TMB (oxTMB) [process (iii) in Scheme 2].53 In this way, the catalyst increases the surface electron density and mobility. Therefore, this study provides ample proof for the importance of both active generation of • OH and the accessible catalytic surface. 22108


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Figure 6. (a) UV−vis spectra of the oxTMB product in the presence of different concentrations of DA and (b) plot of the absorbance values at 652 nm vs different concentrations of DA (the inset shows the linear calibration plot at different concentrations of DA in the reaction system) (acetate buffer: 0.2 M, pH 4, TMB: 0.5 M, catalyst: 7 mg/L, H2O2: 50 μL and temperature: 25 °C).

Table 1. Comparison between the Performance of Various Nanomaterials Reported as DA Sensorsa sample no.

materials

methods

linear range (μM)

1 2 3 4 5 6 7 8 9

Ag/rGO Au/rGO Co−Fe3O4/graphene CuS/rGO Au NPs Ag NPs Cu2+ Co3O4@NiO Pt/hBNNSs-5

electrochemical florescent based colorimetric colorimetric colorimetric colorimetric colorimetric colorimetric colorimetric

10−800 5−250 0.5−50 2−100 2.5−20 3.2−20 1−50 1−1000 2−55

catalyst loading

0.5 g/L 0.04 g/L

1.5 mM 3 g/L 0.007 g/L

LOD (μM)

ref

5.4 3 0.08 0.48 2.50 1.20 1.00 1.21 0.76

61 62 15 16 63 64 65 14 present study

a

More data may be found in relevant reviews.1,8,9

Sensitivity and Selectivity of Pt/hBNNS Nanocomposites for DA Detection. Inspired by the peroxidase-like activity of the Pt/hBNNS nanocomposites, we used the Pt/ hBNNSs-5−TMB−H2O2 system for sensitive colorimetric detection of DA, which is one of the important catecholamine neuromodulators in the central nervous system. The oxidation of the TMB molecule was studied by varying the concentrations of DA starting from 0 to 100 μM (Figure 6a,b). The strong UV−vis absorption peak at 652 nm related to the blue oxTMB product decreases with increase in the concentration of DA, indicating the inhibition of the catalytic activity of the Pt/hBNNS nanocomposites. The suppression of the TMB oxidation was attributed to the consumption of hydroxyl radicals for the reaction with DA, resulting in the decrease of the number of available hydroxyl radicals in the reaction mixture for oxidation of the TMB molecule.60 It has been found that a linear relationship exists between the absorbance at 652 nm and DA concentration in the range of 2−50 μM (inset in Figure 6b). Beyond 60 μM of DA, the absorbance at 652 nm decreases considerably, and the curve deviates from linearity. The limit of detection (LOD) for DA is estimated from the standard DA calibration curve as LOD = 3S/K at the signal-to-noise ratio of 3, where “S” is the standard deviation of experimental data (n = 12) and “K” is the slope of the linear calibration plot of the reaction system. The R2 value obtained for the curve is found to be 0.999 and is indicated in the inset of Figure 6b. The calculated LOD from this linear regression was found to be 0.76 μM, which is comparable or superior to some of the previously reported DA-sensing reactions, as presented in Table 1. Analyzing the results in Table 1, one should also keep in mind that it is not so straightforward to compare results from various laboratories, as there are many changing parameters. Some papers report lower

LODs than those obtained here, however, we may note that the catalyst loading (0.007 g/L) and Pt content (∼5% wt) concentration were very low in our case, while in some other reports, the metal content reaches dozens of percents.15,21,61 This makes our reported colorimetric detection technique favorable for relatively inexpensive and easy detection of DA. The selectivity studies of the designed sensor for the detection of DA, ascorbic acid, glutathione, L-cysteine, uric acid, glucose, lactose, and fructose are shown in Figure 7a,b. We find that in the presence of DA, the absorbance at 652 nm decreased substantially, whereas most of the other interfering molecules brought no obvious change in absorbance, even after increasing their concentration to 10 fold to that of DA. To some extent ascorbic acid, L-cysteine, and glutathione also inhibited the TMB oxidation reaction. In the practical analysis, such interference can be removed by using NEM as a masking reagent for thiols.10,18 The detection of L-cysteine, glutathione, and ascorbic acid in the presence of NEM is presented in the Supporting Information (Figure S8). NEM helps to eliminate the interference caused by glutathione and L-cysteine. Indeed, we observed no significant decrease in absorbance at 652 nm (related to blue oxTMB). Otherwise, slight inhibition of TMB oxidation was observed in the presence of NEM for ascorbic acid as compared to glutathione and L-cysteine because of the absence of thiols. Further optimization of the masking procedure should be possible and will be investigated in future. Overall, the Pt/hBNNSs-5 system exhibited good selectivity toward determination of DA. Finally, we demonstrate the practical applicability of the designed sensor for detection of DA in real human blood serum samples. The detailed method is discussed in the Experimental Section. The accuracy of the method was obtained by determining the recoveries of the standard DA 22109


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pristine graphene. These surfactant-free water-soluble Pt/ hBNNSs nanocomposites were found to exhibit good peroxidase-like catalytic activity in the oxidation of TMB with H2O2, owing to their effectiveness in generating active radicals •OH. Pt/hBNNSs are also good candidates for selective colorimetric detection of DA, as DA is found to gradually inhibit the catalytic activity of Pt/hBNNSs. The detection of DA is in a linear range from 2 to 50 μM, with the detection limit down to 0.76 μM, that is, with a low Pt loading in the catalyst and low catalyst concentration in the detecting solution. As hBN-based materials have only recently been recognized to have potential in catalysis and were hardly investigated as enzyme mimics until now, our work provides a further base for their development as catalysts, enzyme mimics, and candidates for use in clinical diagnostics.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.9b04144. Material and characterization techniques, XPS survey and O1s spectra, FTIR, AFM, TEM, and DLS data, catalytic activity of Pt-free hBNNSs, Pt/BNNSs-10 and 15 in TMB oxidation with H2O2, and kinetic studies for Pt-free hBNNSs (PDF)

Figure 7. Selectivity of Pt/hBNNSs-5 toward DA detection in comparison to the other interfering molecules: (a) bar diagrams showing absorbance at 652 nm (concentration of DA 50 μM and other interfering molecules 500 μM) and (b) the corresponding snap shots.

■

Corresponding Authors

*E-mail: [email protected] (M.N.I.). *E-mail: [email protected] (E.D.G.). *E-mail: [email protected], [email protected] (M.R.D.).

that were added in diluted human serum samples. The recoveries of DA in the human serum sample ranged from 95.6 to 104.3% and are presented in Table 2. Thus, our developed biosensor based on the Pt/hBNNSs-5 nanocomposite could be used effectively to determine DA in real samples.

ORCID

Ekaterina D. Grayfer: 0000-0002-2994-959X Manash R. Das: 0000-0002-6317-7933 Author Contributions

Table 2. DA Concentration Determined in Diluted Human Serum Samples (n = 3)a sample serum 1

serum 2

added DA concentration (μM)

found DA concentration (μM)

RSD

recovery (%)

5 10 15 5 10 15

5.12 10.43 14.76 4.87 10.22 14.34

0.6 4.9 3.3 2.2 0.8 2.6

102.4 104.3 98.4 97.4 102.2 95.6

AUTHOR INFORMATION

The manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The research was supported by the Ministry of Science and Education of the Russian Federation. E.D.G. would like to thank the President of the Russian Federation for the scholarship awarded (cπ-140.2018.1). Authors from the CSIR-NEIST Jorhat acknowledge the Director, CSIR-NEIST for his kind permission for collaboration of this work and also acknowledge the DST, New Delhi for the financial support (DST project no. DST/INT/RUS/RFBR/P-193; CSIRNEIST project no. GPP-0301). G.D. is thankful to the DST, India for providing DST-INSPIRE Fellowship. P.K.B. is thankful to the CSIR, New Delhi for financial assistance from the CSIR-SRF fellowship grant.

a

Since the concentration of DA ranges from nanomols to micromols (10 nM to 1 μM) in the extracellular fluid of the central nervous system, the concentration of DA is very low in real samples and, moreover, as the serum samples have been diluted before spiking, the concentration of DA in the initial samples may be considered nil.

■

CONCLUSIONS In summary, we successfully prepared Pt/hBNNS nanocomposites featuring thin, chemically exfoliated hBNNSs decorated with platinum NPs, following a facile and efficient method, which does not involve toxic or waste-generating chemicals, such as hydrazine. The use of chemically modified hBNNSs promotes effective anchoring of metal precursors to the nanosheet surface, similar to graphene oxide or defective graphene more effectively binding the metal salt ions than

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REFERENCES

(1) Wei, H.; Wang, E. Nanomaterials with Enzyme-Like Characteristics (Nanozymes): Next-Generation Artificial Enzymes. Chem. Soc. Rev. 2013, 42, 6060−6093. (2) Nelson, D. L.; Cox, M. M. Lehninger Principles of Biochemistry; W.H. Freeman & Co Ltd.: New York, 2005; Chapter 6.

22110


Research Article


(21) Chao, J.; Han, X.; Sun, H.; Su, S.; Weng, L.; Wang, L. Platinum Nanoparticles Supported MoS 2 Nanosheet for Simultaneous Detection of Dopamine and Uric Acid. Sci. China: Chem. 2016, 59, 332−337. (22) Zhang, Y.; Wang, Y.-N.; Sun, X.-T.; Chen, L.; Xu, Z.-R. Boron Nitride Nanosheet/CuS Nanocomposites as Mimetic Peroxidase for Sensitive Colorimetric Detection of Cholesterol. Sens. Actuators, B 2017, 246, 118−126. (23) Golberg, D.; Bando, Y.; Huang, Y.; Terao, T.; Mitome, M.; Tang, C.; Zhi, C. Boron Nitride Nanotubes and Nanosheets. ACS Nano 2010, 4, 2979−2993. (24) Rao, C. N. R.; Nag, A. Inorganic Analogues of Graphene. Eur. J. Inorg. Chem. 2010, 4244−4250. (25) Lin, Y.; Connell, J. W. Advances in 2D Boron Nitride Nanostructures: Nanosheets, Nanoribbons, Nanomeshes, and Hybrids with Graphene. Nanoscale 2012, 4, 6908−6939. (26) Zhang, K.; Feng, Y.; Wang, F.; Yang, Z.; Wang, J. Two Dimensional Hexagonal Boron Nitride (2D-hBN): Synthesis, Properties and Applications. J. Mater. Chem. C 2017, 5, 11992−12022. (27) Luo, W.; Yanbin, W.; Emily, H.; Yi, L.; Bao, Y.; Liangbing, H. Solution Processed Boron Nitride Nanosheets: Synthesis, Assemblies and Emerging Applications. Adv. Funct. Mater. 2017, 27, 1701450. (28) Zheng, Z.; Cox, M.; Li, B. Surface Modification of Hexagonal Boron Nitride Nanomaterials: A Review. J. Mater. Sci. 2018, 53, 66− 99. (29) Wang, L.; Sun, C.; Xu, L.; Qian, Y. Convenient Synthesis and Applications of Gram Scale Boron Nitride Nanosheets. Catal. Sci. Technol. 2011, 1, 1119−1123. (30) Zhao, H.; Song, J.; Song, X.; Yan, Z.; Zeng, H. Ag/White Graphene Foam for Catalytic Oxidation of Methanol with High Efficiency and Stability. J. Mater. Chem. A 2015, 3, 6679−6684. (31) Huang, C.; Chen, C.; Ye, X.; Ye, W.; Hu, J.; Xu, C.; Qiu, X. Stable Colloidal Boron Nitride Nanosheet Dispersion and Its Potential Application in Catalysis. J. Mater. Chem. A 2013, 1, 12192−12197. (32) Shen, H.; Duan, C.; Guo, J.; Zhao, N.; Xu, J. Facile in Situ Synthesis of Silver Nanoparticles on Boron Nitride Nanosheets with Enhanced Catalytic Performance. J. Mater. Chem. A 2015, 3, 16663− 16669. (33) Elumalai, G.; Noguchi, H.; Lyalin, A.; Taketsugu, T.; Uosaki, K. Gold Nanoparticle Decoration of Insulating Boron Nitride Nanosheet on Inert Gold Electrode toward an Efficient Electrocatalyst for the Reduction of Oxygen to Water. Electrochem. Commun. 2016, 66, 53− 57. (34) Fu, L.; Lai, G.; Chen, G.; Lin, C.-T.; Yu, A. Microwave Irradiation-Assisted Exfoliation of Boron Nitride Nanosheets: A Platform for Loading High Density of Nanoparticles. ChemistrySelect 2016, 1, 1799−1803. (35) Gao, L.; Wang, Y.; Li, H.; Li, Q.; Ta, N.; Zhuang, L.; Fu, Q.; Bao, X. A Nickel Nanocatalyst within a h-BN Shell for Enhanced Hydrogen Oxidation Reactions. Chem. Sci. 2017, 8, 5728−5734. (36) Lin, Y.; Bunker, C. E.; Fernando, K. A. S.; Connell, J. W. Aqueously Dispersed Silver Nanoparticle-Decorated Boron Nitride Nanosheets for Reusable, Thermal Oxidation-Resistant Surface Enhanced Raman Spectroscopy (SERS) Devices. ACS Appl. Mater. Interfaces 2012, 4, 1110−1117. (37) Dai, P.; Xue, Y.; Wang, X.; Weng, Q.; Zhang, C.; Jiang, X.; Tang, D.; Wang, X.; Kawamoto, N.; Ide, Y.; Mitome, M.; Golberg, D.; Bando, Y. Pollutant Capturing Sers Substrate: Porous Boron Nitride Microfibers with Uniform Silver Nanoparticle Decoration. Nanoscale 2015, 7, 18992−18997. (38) Yang, G.-H.; Shi, J.-J.; Wang, S.; Xiong, W.-W.; Jiang, L.-P.; Burda, C.; Zhu, J.-J. Fabrication of a Boron Nitride-Gold Nanocluster Composite and Its Versatile Application for Immunoassays. Chem. Commun. 2013, 49, 10757−10759. (39) Sharma, M. K.; Narayanan, J.; Pardasani, D.; Srivastava, D. N.; Upadhyay, S.; Goel, A. K. Ultrasensitive Electrochemical Immunoassay for Surface Array Protein, a Bacillus Anthracis Biomarker Using

(3) Gao, L.; Zhuang, J.; Nie, L.; Zhang, J.; Zhang, Y.; Gu, N.; Wang, T.; Feng, J.; Yang, D.; Perrett, S.; Yan, X. Intrinsic Peroxidase-Like Activity of Ferromagnetic Nanoparticles. Nat. Nanotechnol. 2007, 2, 577−583. (4) Jv, Y.; Li, B.; Cao, R. Positively-Charged Gold Nanoparticles as Peroxidiase Mimic and Their Application in Hydrogen Peroxide and Glucose Detection. Chem. Commun. 2010, 46, 8017−8019. (5) Wei, H.; Wang, E. Fe3O4 Magnetic Nanoparticles as Peroxidase Mimetics and Their Applications in H2O2 and Glucose Detection. Anal. Chem. 2008, 80, 2250−2254. (6) Ray, C.; Dutta, S.; Sarkar, S.; Sahoo, R.; Roy, A.; Pal, T. Intrinsic Peroxidase-Like Activity of Mesoporous Nickel Oxide for Selective Cysteine Sensing. J. Mater. Chem. B 2014, 2, 6097−6105. (7) Kumar, M. K.; Prataap, R. K. V.; Mohan, S.; Jha, S. K. Preparation of Electro-Reduced Graphene Oxide Supported Walnut Shape Nickel Nanostructures, and Their Application to Selective Detection of Dopamine. Microchim. Acta 2016, 183, 1759−1768. (8) Pandikumar, A.; Soon How, G. T.; See, T. P.; Omar, F. S.; Jayabal, S.; Kamali, K. Z.; Yusoff, N.; Jamil, A.; Ramaraj, R.; John, S. A.; Lim, H. N.; Huang, N. M. Graphene and Its Nanocomposite Material Based Electrochemical Sensor Platform for Dopamine. RSC Adv. 2014, 4, 63296−63323. (9) Rasheed, P. A.; Lee, J.-S. Recent Advances in Optical Detection of Dopamine Using Nanomaterials. Microchim. Acta 2017, 184, 1239−1266. (10) Feng, J.-J.; Guo, H.; Li, Y.-F.; Wang, Y.-H.; Chen, W.-Y.; Wang, A.-J. Single Molecular Functionalized Gold Nanoparticles for Hydrogen-Bonding Recognition and Colorimetric Detection of Dopamine with High Sensitivity and Selectivity. ACS Appl. Mater. Interfaces 2013, 5, 1226−1231. (11) Jiang, H.; Chen, Z.; Cao, H.; Huang, Y. Peroxidase-Like Activity of Chitosan Stabilized Silver Nanoparticles for Visual and Colorimetric Detection of Glucose. Analyst 2012, 137, 5560−5564. (12) Liu, Y.; Wu, H.; Chong, Y.; Wamer, W. G.; Xia, Q.; Cai, L.; Nie, Z.; Fu, P. P.; Yin, J.-J. Platinum Nanoparticles: Efficient and Stable Catechol Oxidase Mimetics. ACS Appl. Mater. Interfaces 2015, 7, 19709−19717. (13) Ma, M.; Zhang, Y.; Gu, N. Peroxidase-Like Catalytic Activity of Cubic Pt Nanocrystals. Colloids Surf., A 2011, 373, 6−10. (14) Zhu, Y.; Yang, Z.; Chi, M.; Li, M.; Wang, C.; Lu, X. Synthesis of Hierarchical Co3O4@Nio Core-Shell Nanotubes with a Synergistic Catalytic Activity for Peroxidase Mimicking and Colorimetric Detection of Dopamine. Talanta 2018, 181, 431−439. (15) Hosseini, M.; Aghazadeh, M.; Reza Ganjali, M. A Facile OnePot Synthesis of Cobalt-Doped Magnetite/Graphene Nanocomposite as Peroxidase Mimetics in Dopamine Detection. New J. Chem. 2017, 41, 12678−12684. (16) Dutta, S.; Ray, C.; Mallick, S.; Sarkar, S.; Sahoo, R.; Negishi, Y.; Pal, T. A Gel-Based Approach to Design Hierarchical CuS Decorated Reduced Graphene Oxide Nanosheets for Enhanced Peroxidase-Like Activity Leading to Colorimetric Detection of Dopamine. J. Phys. Chem. C 2015, 119, 23790−23800. (17) Wang, H.; Li, S.; Si, Y.; Zhang, N.; Sun, Z.; Wu, H.; Lin, Y. Platinum Nanocatalysts Loaded on Graphene Oxide-Dispersed Carbon Nanotubes with Greatly Enhanced Peroxidase-Like Catalysis and Electrocatalysis Activities. Nanoscale 2014, 6, 8107−8116. (18) Wang, Y.; Yang, L.; Liu, Y.; Zhao, Q.; Ding, F.; Zou, P.; Rao, H.; Wang, X. Colorimetric Determination of Dopamine by Exploiting the Enhanced Oxidase Mimicking Activity of Hierarchical NiCo2S4RGO Composites. Microchim. Acta 2018, 185, 496. (19) Sun, Z.; Zhao, Q.; Zhang, G.; Li, Y.; Zhang, G.; Zhang, F.; Fan, X. Exfoliated MoS2 Supported Au-Pd Bimetallic Nanoparticles with Core-Shell Structures and Superior Peroxidase-Like Activities. RSC Adv. 2015, 5, 10352−10357. (20) Cai, S.; Han, Q.; Qi, C.; Lian, Z.; Jia, X.; Yang, R.; Wang, C. Pt74Ag26 Nanoparticle-Decorated Ultrathin MoS2 Nanosheets as Novel Peroxidase Mimics for Highly Selective Colorimetric Detection of H2O2 and Glucose. Nanoscale 2016, 8, 3685−3693. 22111


Research Article

ACS Applied Materials & Interfaces Au−Pd Nanocrystals Loaded on Boron-Nitride Nanosheets as Catalytic Labels. Biosens. Bioelectron. 2016, 80, 442−449. (40) Yang, G.-H.; Abulizi, A.; Zhu, J.-J. Sonochemical Fabrication of Gold Nanoparticles−Boron Nitride Sheets Nanocomposites for Enzymeless Hydrogen Peroxide Detection. Ultrason. Sonochem. 2014, 21, 1958−1963. (41) Li, Q.; Luo, W.; Su, L.; Chen, J.; Chou, K.-C.; Hou, X. An Amperometric Glucose Enzyme Biosensor Based on Porous Hexagonal Boron Nitride Whiskers Decorated with Pt Nanoparticles. RSC Adv. 2016, 6, 92748−92753. (42) Roy, A. K.; Byoungnam, P.; Kang Seok, L.; Sung Young, P.; Insik, I. Boron Nitride Nanosheets Decorated with Silver Nanoparticles through Mussel-Inspired Chemistry of Dopamine. Nanotechnology 2014, 25, 445603. (43) Gao, G.; Mathkar, A.; Martins, E. P.; Galvão, D. S.; Gao, D.; Autreto, P. A. d. S.; Sun, C.; Cai, L.; Ajayan, P. M. Designing Nanoscaled Hybrids from Atomic Layered Boron Nitride with Silver Nanoparticle Deposition. J. Mater. Chem. A 2014, 2, 3148−3154. (44) Fan, D.; Zhou, Q.; Lv, X.; Jing, J.; Ye, Z.; Shao, S.; Xie, J. Synthesis, Thermal Conductivity and Anti-Oxidation Properties of Copper Nanoparticles Encapsulated within Few-Layer h-BN. Ceram. Int. 2018, 44, 1205−1208. (45) Grant, J. T.; Carrero, C. A.; Goeltl, F.; Venegas, J.; Mueller, P.; Burt, S. P.; Specht, S. E.; McDermott, W. P.; Chieregato, A.; Hermans, I. Selective Oxidative Dehydrogenation of Propane to Propene Using Boron Nitride Catalysts. Science 2016, 354, 1570− 1573. (46) Shi, L.; Wang, D.; Song, W.; Shao, D.; Zhang, W.-P.; Lu, A.-H. Edge-Hydroxylated Boron Nitride for Oxidative Dehydrogenation of Propane to Propylene. ChemCatChem 2017, 9, 1788−1793. (47) Shi, L.; Wang, D.; Lu, A.-H. A Viewpoint on Catalytic Origin of Boron Nitride in Oxidative Dehydrogenation of Light Alkanes. Chin. J. Catal. 2018, 39, 908−913. (48) Tang, S.; Zhou, X.; Zhang, S.; Li, X.; Yang, T.; Hu, W.; Jiang, J.; Luo, Y. Metal-Free Boron Nitride Nanoribbon Catalysts for Electrochemical CO2 Reduction: Combining High Activity and Selectivity. ACS Appl. Mater. Interfaces 2019, 11, 906−915. (49) Coleman, J. N.; Lotya, M.; O’Neill, A.; Bergin, S. D.; King, P. J.; Khan, U.; Young, K.; Gaucher, A.; De, S.; Smith, R. J.; Shvets, I. V.; Arora, S. K.; Stanton, G.; Kim, H.-Y.; Lee, K.; Kim, G. T.; Duesberg, G. S.; Hallam, T.; Boland, J. J.; Wang, J. J.; Donegan, J. F.; Grunlan, J. C.; Moriarty, G.; Shmeliov, A.; Nicholls, R. J.; Perkins, J. M.; Grieveson, E. M.; Theuwissen, K.; McComb, D. W.; Nellist, P. D.; Nicolosi, V. Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials. Science 2011, 331, 568−571. (50) Nazarov, A. S.; Demin, V. N.; Grayfer, E. D.; Bulavchenko, A. I.; Arymbaeva, A. T.; Shin, H.-J.; Choi, J.-Y.; Fedorov, V. E. Functionalization and Dispersion of Hexagonal Boron Nitride (h-BN) Nanosheets Treated with Inorganic Reagents. Chem.−Asian J. 2012, 7, 554−560. (51) Smith, R. J.; King, P. J.; Lotya, M.; Wirtz, C.; Khan, U.; De, S.; O’Neill, A.; Duesberg, G. S.; Grunlan, J. C.; Moriarty, G.; Chen, J.; Wang, J.; Minett, A. I.; Nicolosi, V.; Coleman, J. N. Large-Scale Exfoliation of Inorganic Layered Compounds in Aqueous Surfactant Solutions. Adv. Mater. 2011, 23, 3944−3948. (52) Yao, Y.; Lin, Z.; Li, Z.; Song, X.; Moon, K.-S.; Wong, C.-p. Large-Scale Production of Two-Dimensional Nanosheets. J. Mater. Chem. 2012, 22, 13494−13499. (53) Josephy, P. D.; Mason, R. P.; Eling, T. Cooxidation of the Clinical Reagent 3, 5, 3′ 5′-Tetramethylbenzidine by Prostaglandin Synthase. Cancer Res. 1982, 42, 2567−2570. (54) Goncalves, G.; Marques, P. A. A. P.; Granadeiro, C. M.; Nogueira, H. I. S.; Singh, M. K.; Grácio, J. Surface Modification of Graphene Nanosheets with Gold Nanoparticles: The Role of Oxygen Moieties at Graphene Surface on Gold Nucleation and Growth. Chem. Mater. 2009, 21, 4796−4802. (55) Zhi, C. Y.; Bando, Y.; Terao, T.; Tang, C. C.; Kuwahara, H.; Golberg, D. Chemically Activated Boron Nitride Nanotubes. Chem. Asian J. 2009, 4, 1536−1540.

(56) Porsgaard, S.; Merte, L. R.; Ono, L. K.; Behafarid, F.; Matos, J.; Helveg, S.; Salmeron, M.; Roldan Cuenya, B.; Besenbacher, F. Stability of Platinum Nanoparticles Supported on SiO2/Si(111): A High-Pressure X-Ray Photoelectron Spectroscopy Study. ACS Nano 2012, 6, 10743−10749. (57) Maillard, F.; Schreier, S.; Hanzlik, M.; Savinova, E. R.; Weinkauf, S.; Stimming, U. Influence of Particle Agglomeration on the Catalytic Activity of Carbon-Supported Pt Nanoparticles in Co Monolayer Oxidation. Phys. Chem. Chem. Phys. 2005, 7, 385−393. (58) Guo, S.; Dong, S.; Wang, E. Three-Dimensional Pt-on-Pd Bimetallic Nanodendrites Supported on Graphene Nanosheet: Facile Synthesis and Used as an Advanced Nanoelectrocatalyst for Methanol Oxidation. ACS Nano 2009, 4, 547−555. (59) Naghavi, K.; Saion, E.; Rezaee, K.; Yunus, W. M. M. Influence of Dose on Particle Size of Colloidal Silver Nanoparticles Synthesized by Gamma Radiation. Radiat. Phys. Chem. 2010, 79, 1203−1208. (60) Slivka, A.; Cohen, G. Hydroxyl Radical Attack on Dopamine. J. Biol. Chem. 1985, 260, 15466−15472. (61) Kaur, B.; Pandiyan, T.; Satpati, B.; Srivastava, R. Simultaneous and Sensitive Determination of Ascorbic Acid, Dopamine, Uric Acid, and Tryptophan with Silver Nanoparticles-Decorated Reduced Graphene Oxide Modified Electrode. Colloids Surf., B 2013, 111, 97−106. (62) Li, W.; Ma, L.; Wu, B.; Zhang, Y.; Li, Z. A Chemically Reduced Graphene Oxide−Au Nanocage Composite for the Electrochemical Detection of Dopamine and Uric Acid. Anal. Methods 2017, 9, 3819− 3824. (63) Baron, R.; Zayats, M.; Willner, I. Dopamine-, L-Dopa-, Adrenaline-, and Noradrenaline-Induced Growth of Au Nanoparticles: Assays for the Detection of Neurotransmitters and of Tyrosinase Activity. Anal. Chem. 2005, 77, 1566−1571. (64) Nezhad, M. R. H.; Tashkhourian, J.; Khodaveisi, J.; Khoshi, M. R. Simultaneous Colorimetric Determination of Dopamine and Ascorbic Acid Based on the Surface Plasmon Resonance Band of Colloidal Silver Nanoparticles Using Artificial Neural Networks. Anal. Methods 2010, 2, 1263−1269. (65) Wang, H.-B.; Li, Y.; Dong, G.-L.; Gan, T.; Liu, Y.-M. A Convenient and Label-Free Colorimetric Assay for Dopamine Detection Based on the Inhibition of the Cu(II)-Catalyzed Oxidation of a 3,3′,5,5′-Tetramethylbenzidine−H2O2 System. New J. Chem. 2017, 41, 14364−14369.

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