NiO-Carbon Nanocomposite Derived from Metal

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Hierarchical CuO/NiO-Carbon Nanocomposite Derived from Metal Organic Framework on Cello Tape for the Flexible and High Performance Non-enzymatic Electrochemical Glucose Sensors V Archana, Yang Xia, Ruyi Fang, and G Gnana Kumar ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b05980 • Publication Date (Web): 20 Feb 2019 Downloaded from http://pubs.acs.org on February 21, 2019

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ACS Sustainable Chemistry & Engineering

Hierarchical CuO/NiO-Carbon Nanocomposite Derived from Metal Organic Framework on Cello Tape for the Flexible and High Performance Non-enzymatic Electrochemical Glucose Sensors V. Archana,†,‫ ך‬Yang Xia,‡,‫ ך‬Ruyi Fang,‡ and G. Gnana kumar,†,* †School

of Chemistry, Madurai Kamaraj University,Madurai-625021, Tamil Nadu, India

‡College

of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou, 310014, China

ABSTRACT: The orchestrated network of octahedron shaped Cu organic framework is developed via a simple aging protocol and the partial cation swap reactions between Cu and Ni nodes in the Cu2-paddle wheel units of Cu-MOF generates Cu-Ni-MOF with similar octahedron morphology. Exploiting Cu-Ni-MOF as a template, the uniformly disseminated and tightly pinned CuO/NiO spherical nanoparticles with hieararchical carbon is developed under controlled thermal and atmospheric conditions. The MOFs and metal oxide-carbon nanocomposites coated over the cello tapes (CTs) are exploited as electrochemical sensor probes for non-enzymatic glucose sensing. It effectively tackles the impediments of existing glucose sensor probes including time consumption, high cost, monotonous electrode cleaning and modification processes, and use of swellable inactive binders. Owing to the subsistence of interconnected network and synergistic effect of bimetallic oxides, CuO/NiO-C expedites the considerable electrocatalytic behaviour toward glucose sensing. Furthermore, the fabricated CuO/NiO-C/CT extends its exertion towards the diagnosis of glucose in human serum samples. This flexible electrochemical sensor probes allow the device to endure deformation with high efficacy, opening an exciting avenue for the evolution of

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cost-efficient, binder-free, reliable, flexible, and eco-friendly sensing platforms for the development of futuristic electrochemical sensor devices. Keywords: Octahedron, Metal organic framework, Sacrificial-template synthesis, Hierarchical porous architecture, Cello tape *Corresponding Author : *G.Gnana kumar : E-mail: [email protected] ‫ך‬

Both the authors are equally contributed.


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INTRODUCTION The abnormal level of glucose in human blood may cause metabolic disorders including diabetes mellitus, eye defects, endocrine syndrome, cardiovascular disease etc.,1 The regular monitoring of glucose level prioritizes the prevention of aforementioned life-threatening diseases.2 Hence, the development of reliable, cost-efficient, and high performance sensing devices for the precise and expeditious detection of glucose is considered to be a prodigious scientific-technological importance in clinical research, bio-processing, and food industries. In this context, several approaches such as chemiluminescence,3 colorimetry,4 mass spectrometry,5 and surface-enhanced Raman scattering6 have been exploited for the proficient detection of glucose. Of numerous types of methods, non-enzymatic electrochemical technique has acquired boundless attention due to its distinctive features including simplicity, affordable cost, sensitivity, expeditious response time, lower limit of detection, long-term stability, rapid detection, selectivity etc.,7-9 The versatile nature of transition metal nanocatalysts endorses its potentiality to use as catalysts for non-enzymatic detection of glucose. However, the high cost, narrow linear range, low sensitivity, surface poisoning, and sluggish oxidation kinetics are the remaining conspicuous major challenges of transition metal nanocatalysts.10 Hence, it is conspicuous to design the electrocatalytic materials with high activity and exquisite geometry for the development of futuristic glucose sensors. Recently, metal organic frameworks (MOF) have been discretely aspired as customtailored catalysts in a number of electrochemical applications owing to its well defined configuration, large surface area, and tunable pore volume.11,12 In specific, Cu-MOF has received an unique prominence, attributed to the orientation of catalytically active lewis acid coordination sites on the interior of pore walls and the large accessibility to the guest molecules.13,14 Sun et al., reported the rational non-enzymatic glucose sensing properties of Cu-MOF under alkaline conditions. However, the glucose oxidation mechanism involved at 3 ACS Paragon Plus Environment


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the above prepared nanostructures were not detailed with the aid of significant cyclic voltammetric studies and the conflict analytical parameters obtained between the amperometric and differential pulse voltammetry techniques uncertain their practical utility.15 On the other side, Cu-MOF modified carbon paste electrode (CPE) showed the intrinsically limited catalytic activity toward glucose electrooxidation, owing to the large particle size (200 µm) and lower surface area. Furthermore, this report has not detailed their relevance in real sample analysis, which does not authenticate the reliability of a relevant system.16 From the aforementioned efforts, it is clear that the high sensitivity of Cu-MOF towards moisture restraints its stability, lowering its electrochemical activity towards glucose oxidation. This intrinsic handicap of Cu-MOF could be conquered with the isomorphic substitution of Cu nodes with Ni nodes, which could promote the tolerance towards moisture and proliferate the active sites.17 However, the chelation of metal nodes with an inert organic ligand and the inadequate overlap between Π orbitals of organic ligands and d orbitals of Cu2+/Ni2+ ions may limit the electrical conductivity, leading to the sluggish glucose oxidation kinetics.18 To this end, the conversion of MOF into metal/metal oxide nanoparticles embedded carbon frameworks is an ultimate strategy for the effectual glucose sensing performace via the improved mass and electron transfer processes.19 If the metal oxide-carbon architecture conserves the parent morphology of MOF during the pyrolysis process, it will be valuable to improve the understanding of the influence of a chemical strutuctre toward glucose sensing by circumventing the morphological influences. Although the metal oxide-carbon nanocomposites derived from MOFs are exploited as catalysts in oxygen evolution reaction (OER),20 hydrogen evolution reaction (HER),21 and water splitting,22 their intrinsic impacts in the non-enzymatic electrochemical glucose detection is not detailed, which massively limits


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the opportunities for improving the electrochemical performance of a glucose sensor at a fundamental level. On the other side, the fabrication of conventional non-enzymatic glucose detection probes entails certain hindrances including the utilization of expensive glassy carbon23 and noble metal24-26 (e.g., Pt and Au) electrodes, monotonous electrode cleaning and catalyst loading processes, blockage of active sites via binder utilization, crack or peel off the catalyst layer, and surface poisoning due to the adsorbed intermediate species. Hence, it is important to direct the research efforts towards the development of cost-efficient and simplified electrode fabrication processes. Furthermore, the modern health care systems require flexible, stretchable, and portable non-enzymatic glucose sensing devices, requiring the development of free-standing and flexible electrodes without compromising the electrochemical performance under deformation or bending conditions. Accordingly, we develop and report here the Cu-MOF / Cu/Ni-MOF coated cellotape (CT) as easily disposable, freestanding, and cost- efficienct probe for flexible non-enzymatic glucose sensors and address their challenges toward glucose sensing by converting them into carbon encased metal oxide nanoparticles. EXPERIMENTAL SECTION Materials. Benzene 1,3,5- tricarboxylic acid (BTC) (AR, >95.0%), copper nitrate ((Cu(NO3)2), >99%), nickel nitrate ((Ni(NO3)2), 98.0%), methanol (HPLC & Spectroscopy grade, 99.8%), sodium hydroxide (NaOH (pellet), AR, >98.5%), and glucose (Ar, >99.5%), fructose (Fru, AR, ≥99%), acetaminophen (AP, AR, ≥99%), maltose (Mal, AR, ≥99%), uric acid (UA, HPLC, ≥99%), sucrose (Suc, AR, ≥99%), lactose (Lac, AR, ≥99%), galactose (Gal, AR, ≥99%), citric acid (CA, AR, ≥99.5%), mannose (Man, AR, ≥99%), xylose (Xyl, AR, ≥99%), sodium chloride (NaCl, AR, ≥99.5%), dopamine (DA, AR, ≥99%), ascorbic acid (AA, AR, ≥99.5%) and urea (U, AR, ≥99%) were obtained from sigma Aldrich and directly utilized without further purification. 5 ACS Paragon Plus Environment


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Preparation of Cu/Ni-MOF, Cu-MOF, and Ni-MOF. 3.5 mM Cu(NO3)2 and 3.5 mM Ni(NO3)2 in methanol was gradually added with 4 mM BTC solution and kept at room temperature until the completion of Cu/Ni-MOF precipitation. The resultant Cu-NiMOF was retrieved via centrifugation and washed with methanol and dried at 80 °C. For a comparison, Cu-MOF and Ni-MOF were synthesized by treating 7 mM Cu(NO3)2 and 7 mM Ni(NO3)2, respectively, with 4 mM BTC. Preparation of metal oxide-carbon composites. The calcination of Cu/Ni-MOF, CuMOF, and Ni-MOF in a tubular furnace at 430 °C for 8 h under nitrogen (N2) atmosphere with a ramping rate of 5 °C min-1, generate, respectively, the CuO/NiO-C, CuO-C, and NiO-C. The resultant nanostructures were subsequently washed with ethanol and de-ionized water and dried. Modification

of

CT

with

nanostructures.

CT

derived

from

local

shop

(surface resistance < 103 ohm cm-1) was washed with methanol under ultrasonication process to eradicate the impurities over its surface. The pre-cleaned CT was dipped into the homogeneous dispersion of prepared MOFs/metal oxide-carbon nanostructures in methanol (2 mg mL-1) for 24 h and dried at 60 °C for further characterizations. Cu-MOF, Ni-MOF, Cu/Ni-MOF, CuO-C, NiO-C and CuO/NiO-C coated CTs are represented, respectively, as Cu-MOF/CT, Ni-MOF/CT, Cu/Ni-MOF/CT, CuO-C/CT, NiO-C/CT, and CuO/NiO-C/CT. The geometric area of CT employed for the above process is 1.2 × 1.2 cm2 and the mass loading maintained for the catalysts on CTs was 1 mg cm-2. Materials Characterizations. The surface morphological features and microstructures of prepared MOFs and the corresponding calcined materials were evaluated with SEM (JSM5410LV, 15 kV) and TEM (JEM-2010, 100 keV. The crystal phase and structure of prepared materials were scrutinized with X-ray Powder Diffractometer (XRD, ARL, EQUINOX 300L

with Cu-Kα radiation of λ = 1.54 Å).

XPS (Kratos Amicus with 6

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monochromated Al Kɑ (1486.6 eV) as an X-ray source functioning at 15 kV ) was used to analyse the surface chemical species of prepared materials. Raman spectra of prepared nanostrucutres were evaluated with 632.8 nm He-Ne laser equipped Raman spectrometer (HORIBA-LabRAM-HR). FT-IR Spectroscopy (JY-HR800) was employed further to characterize the surface functionalities. The four-probe technique was exploited with an Agilent semiconductor parameter analyzer (Agilent 4156C) to estimate the electrical conductivities of prepared materials. Electrochemical characterizations. The electrochemical responses of prepared materials were evaluated with CHI-650D electrochemical workstation at room temperature in a conventional three electrode cell consisting of Platinum (Pt) wire as an auxiliary electrode, Ag/AgCl as a reference electrode, and electrocatalyst modified CT as a working electrode. The three electrode cell assembly was placed in 0.1 M NaOH solution to record the voltammetric responses of prepared materials at 100 mV s-1 in the absence and presence of 5 mM glucose. The amperometric response of CuO/NiO-C/CT was examined in 0.1 M NaOH solution with the consecutive addition of different concentrations of glucose at an applied potential of 0.65 V vs. Ag/AgCl. RESULTS AND DISCUSSION Morphological Analysis. SEM images of Cu-MOF reveal the octahedron morphology with an average diameter of 2.5-3 µm, constituted with the well-defined eight sharp triangular faces (Figure 1a and b). The medial edge length of triangular faces of fcc type crystal is found to be 2.33 µm. Under ultrasonication process, methanol (CH3OH) is decomposed into CH3● and OH● radicals and the produced OH● radical abstracts H● radical from CH3OH and produces H2O and CH2OH● radical. Then the CH2OH● is further decomposed into H● radical and formaldehyde.27-29 CH3OH → CH3● + OH●

(1) 7



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OH● + CH3OH → H2O + CH2OH●

(2)

CH2OH● → CH2O + H●

(3)

Cu2+ ions from Cu(NO3)2 precursor is initially reduced into Cu+ ions with the aid of H●, followed by the Cu+ redox reaction, generating the Cu0 and Cu2+. Cu2+ + H● → Cu+ + H+

(4)

2Cu+ → Cu0 + Cu2+

(5)

In the presence of water molecules, Cu(NO3)2 generates Cu(H2O)62+ ions and NO3- ions. Upon the ultrasonication process, the redox reaction between Cu0 and Cu2+ forms Cu2O, which is then converted into Cu2(OH)3NO3 with the support of NO3-, H+, and OH● radicals. Cu(NO3)2 + 6H2O ↔ Cu(H2O)62+ + 2NO3-

(6)

Cu2+ + Cu0 + H2O → Cu2O + 2H+

(7)

Cu2O + 2OH. + NO3- + H+ → Cu2(OH)3NO3

(8)

The formed Cu2(OH)3(NO3) is aggregated with the aid of surface adsorbed BTC, owing to the facile intercalation of BTC into Cu2(OH)3(NO3) with the replacement of NO3- anions, serving as an initiator for the polymerisation reaction. Finally, the carboxylate groups of BTC is intercalated and self-oriented with Cu2+ nanocrystals, yielding the polycrystalline Cu-MOF.30,31 The formation of Cu-MOF is contrived with the assembling of dimeric Cu(II) paddle wheel units and tritopic organic ligands as shown in Figure 2a. The dimeric Cu(II) paddle wheel units are comprehended with two adjacent Cu(II) atoms assembled with four carboxylate groups from four organic ligands and two water molecules, respectively, in the equatorial and axial positions. Each neighbouring Cu(II) units are bridged with four carboxylate groups of four organic ligands, leading to the formation of four-connected rectangular nodes. Furthermore, the three deprotonated COO- groups of each organic ligands coordinate with three dimeric Cu(II) units that constructs 3-connected triangle nodes. In the 8 ACS Paragon Plus Environment

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equatorial plane of octahedron morphology, the paddlewheel units are assembled like a square and the formed Cu-MOF framework is comprised of two divergent nanocages with small pore openings.32 In the formation of Cu/Ni-MOF, Ni2+ ions are successfully incorporated into the Cu-MOF framework (Figure 2b) with the partial substitution of Ni(II) units in the dimeric Cu(II) paddlewheel units, which preserves the identical octahedron morphology (Figure 1c and d).33 Upon calcination at 430 °C, Cu-MOF and Cu/Ni-MOF are converted, respectively, into the CuO-C and CuO/NiO-C composites via the pyrolysis of organic ligands and the oxidation of metal nodes. The SEM images of CuO-C (Figure 1e and f) and CuO/NiO-C (Figure 1g and h) composites reveal the uniform octahedron shape inherited from the parent MOFs with slightly reduced mean diameter of 1-2 µm, which is due to the shrinkage effect achieved via the carbonization of organic ligands. The surface and bulk of the octahedron morphology of CuO-C and CuO/NiO-C composites are constituted with the tightly pinned spherical particles with an average diameter of 20 nm. Under an inert atmosphere, the pyrolysis process of MOF leads to the conversion of metallic ions into the respective metal nanoparticles. Upon the further progression of a reaction, the oxygen molecules liberated from organic ligands of MOF oxidize the metal nanoparticles into metal oxide nanoparticles. Meanwhile, the carbon atoms in organic ligand are converted into hierarchical carbon matrix, which is useful in retaining the octahedron morphology of CuO-C and CuO/NiO-C composites (Figure 2c).34 The calcination temperature involved in the conversion of prepared MOFs into their relevant metal oxide/C composites was optimized through the thermogravimetric analysis pattern of Cu/Ni-MOF (Figure S1). During the calcination process, Cu/Ni-MOF demonstrates the first weight loss at 100º C, owing to the evaporation of adsorbed water molecules.35 The major weight loss of Cu/Ni-MOF is observed at 430 ºC, which is due to the decomposition of organic ligands into benzene, hydrogen, carbon dioxide, and carbon monoxide gases.35 No 9 ACS Paragon Plus Environment


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other significant weight losses were observed beyond the aforesaid temperature. On the basis of above carbonization process, the calcination temperature for the conversion of MOFs into metal oxide/C composites is optimized to 430 ºC. The obtained Tranmission Electron Microscopy (TEM) images visualize the octahedron morphology with the smooth surface of Cu/Ni-MOF, which are in accordance with the relevant SEM images (Figure 3a and b). The TEM images of CuO/NiO-C unveil that the octahedron surface is constituted with a number of uniform sized and tightly packed spherical particles (Figure 3c-e). The ligand derived carbon layers tightly pin the CuO and NiO nanoparticles and prevents the formation of aggregates. Figure 3f of CuO/NiO-C reveals the crystal lattices of two different metal oxides with the interplanar crystal distances of 0.240 and 0.235 nm, which are indexed, respectively, to the (111) plane of monoclinic CuO and (111) facet of face centered cubic (fcc) NiO.36 The selected-area diffraction patterns of both the Cu/Ni-MOF (inset : Figure 3b) and CuO/NiO-C (inset : Figure 3f) demonstrate the blurred diffraction rings with the random arrangement of bright spots, exposing their polycrystalline structure. High-angle annular dark field scanning TEM (HAADF-STEM) image (Figure 3g) of CuO/NiO-C further confirms the octahedron morphology. The relevant elemental mapping micrographs unambiguously provide evidence for the homogeneous distribution of Cu, Ni, C, and O elements, revealing the successful formation of metal oxidecarbon composite from Cu/Ni-MOF (Figure 3g). The uniform coating of CuO/NiO-C on CT is revealed from the microscopic cross-sectional view of the CuO/NiO-C/CT, which ensures the homogeneous ion diffusion and charge transfer kinetics (Figure S2). XRD Patterns. Cu-MOF exhibits the characteristic diffraction peaks at 11.5, 13.34, 14.92, 17.4, 18.9, 20.1, 21.24, 24.0, 25.8, 29.2, 35.1 and 39.02°, corresponding, respectively, to the (222), (400), (420), (500), (440), (600), (620), (551), (731), (751), (773), and (882) reflection planes (JCPDS-Card No: 00-062-1183) (Figure 4a).32 Bimetallic Cu/Ni-MOF exhibits the 10 ACS Paragon Plus Environment

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similar diffraction peaks (Figure 4b) as that of Cu-MOF, owing to the alike ionic radius of Cu2+ (0.70 A°) and Ni2+ (0.72 A°).37 The presence of carbon in CuO-C is validated from the broad diffraction peak centred between 15-30° (Figure 4c). The characteristic diffraction peaks identified for CuO-C at 32.21, 35.55, 38.77, 48.79, 53.4, 58.21, 61.6, 66.03, 67.95, 72.5, and 75.11° are indexed, respectively, to the (110), (11-1), (111), (20-2), (020), (202), (11-3), (31-1), (220), (311), and (22-2) reflection planes of monoclinic symmetry phase of CuO (space group C2/c) (JCPDS-Card No: 48-1548) (Figure 4c).38 Along with the diffraction patterns of CuO and carbon, CuO/NiO-C demonstrates the fcc structured NiO as evidenced from the (111), (200), (220), (311), and (222) planes, respectively, at 36.2, 42.1, 66.05, 72.2, and 74.9° (JCPDS-Card No: 71-1179) (Figure 4d).39 XPS Analysis. The full scan X-ray photoelectron spectrum (XPS) of CuO/NiO-C demonstrates the presence of C 1s (13.8 at%), O 1s (33.2 at%), Cu 2p (27.9 at%), and Ni 2p (25.1 at%) (Figure 5a).40,41 In the core-level XPS spectrum of Cu 2p (Figure 5b), the peaks centred at 931.6 and 951.5 eV are related, respectively, to the spin-orbit peaks of Cu 2p3/2 and Cu 2p1/2 with an energy separation of 19.9 eV, endorsing the presence of Cu2+ in CuO phase. The satellite peaks found at 940.6 and 960.2 eV are related, respectively, to the Cu 2p3/2 and Cu 2p1/2.42,43 The core level Ni 2p spectrum exhibits the characteristic Ni 2p3/2 and Ni 2p1/2 peaks, respectively, at 853.5 and 870.7 eV with the spin-orbit energy difference of 17.2 eV, demonstrating the existence of Ni2+ in CuO/NiO-C (Figure 5c).42 The satellite peaks related with Ni 2p3/2 and Ni 2p1/2 peaks are located, respectively, at 858.8 and 877.7 eV. The peaks centred at 283.6, 284.4, and 286.6 eV, are analogous, respectively, to the CC/C=C, C-O, and C=O bonds (Figure 5d).44 The at% ratio found between the Cu and Ni is consistent with the molar ratio of Cu2+ and Ni2+ ions maintained in the preparation procedure.



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The O 1s spectrum of CuO/NiO-C (Figure 5e) is splitted into two different peaks at 527.9 and 529.6 eV, which are correlated, respectively, to the oxygen in metal oxide (M = Cu, Ni) and C=O bonds.44 Raman Spectroscopic Studies. The Raman spectrum of Cu-MOF reveals the bands at 1003 and 1601 cm-1, ascribed to the C=C stretching modes of benzene ring. The bands at 730 and 820 cm-1 are associated, respectively, with the out-of-plane ring and out-of-plane ring (C-H) bending vibrations. The Raman active bands at 1462 and 1528 cm-1 correspond, respectively, to the symmetric and asymmetric stretching modes of carboxylate units.45 The bands centred at 283, 434, and 492 cm-1 are assigned to the Cu(II) vibrational modes in CuMOF (Figure 6i(a)).46 In addition to the above characteristic bands, Cu/Ni-MOF demonstrates the new band at 412 cm-1, accredited to the Ni(II) vibrational modes (Figure 6i(b)).47 In contrast, CuO-C derived from Cu-MOF demonstrates the bands at 281, 330, and 605 cm-1, assigned, respectively, to the Ag, Bg’ and Bg” modes of CuO48 and the bands indexed at 1321 and 1586 cm-1 belong to the D and G bands of amorphous carbon in CuO-C (Figure 6i(c)). The presence of NiO in CuO/NiO-C is substantiated from the Raman active bands at 510, 701, and 1090 cm-1, attributed, respectively, to the longitudinal optical (LO) one phonon mode (1P), two phonon excitation (2P) 2TO, and longitudinal optical (2LO) two phonon mode (2P) of NiO (Figure 6i(d)).49 FT-IR Studies. The Fourier Transform Infrared (FT-IR) spectrum of Cu-MOF (Figure 6ii(a)) endorses the characteristic asymmetric and symmetric C=O stretching vibrations of carboxylate groups, respectively, at 1620 and 1381 cm-1.50 The C=C stretching vibrations of Cu-MOF are observed at 1562 and 1445 cm-1. The band at 1713 cm-1 is ascribed to the C=O stretching vibration present in the BTC.51 The coordination of Cu2+ with the carboxylate groups of BTC is identified from the Cu-O stretching vibration at 728 cm-1.52 Along with the slightly shifted characteristic bands of Cu-MOF, Cu/Ni-MOF 12 ACS Paragon Plus Environment

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exhibits the Ni-O stretching vibration at 463 cm-1, ascribed from the coordination of Ni2+ with the carboxylate groups of BTC (Figure 6ii(b)).53 Upon the conversion of Cu-MOF into CuOC, the peaks corresponding to the C=C, C=O, and metal coordinated carboxylate groups are disappeared, and the new peaks appear at 490, 532, and 591 cm-1 are ascribed to the stretching vibrations of Cu-O bond in CuO/C (Figure 6ii(c)).54 The existence of carbonized network in CuO-C is ensured from the C-C and C=C stretching vibrations, respectively, at 1104 and 1625 cm-1. The aforementioned characteristic FT-IR bands of CuO-C are slightly shifted for CuO/NiO-C and the Ni-O stretching vibration is observed at 440 cm-1, enunciating the composite formation of CuO/NiO-C (Figure 6ii(d)).55 Electrochemical Responses of Prepared Nanostructures. The electrochemical behaviour of prepared nanostructures was assessed with the

voltammograms of nanostructures

modified CTs in 0.1 M NaOH at a sweep rate of 100 mV s-1 (Figure 7a). No consequence redox responses and lower back ground currents are perceived in the voltammogrammes of bare CT (Figure S3), Cu-MOF/CT (Figure 7a), Ni-MOF/CT (Figure 7a), and Cu/Ni-MOF/CT (Figure 7a) in 0.1 M NaOH. The electroactive metal species encapsulated with the electroinert organic ligands limits the electron transfer among the metal species in MOF, which limits the electrical conductivity of Cu-MOF (8.4 x 10-7 S cm-1), Ni-MOF (9.2 x 10-7 S cm-1) and Cu/Ni-MOF (1.6 x 10-6 S cm-1) and responsible for the consequent lower back ground current (Figure 7a). On the other side, CuO-C derived

from Cu-MOF demonstrates

the notable redox waves at 0.56 and 0.70 V vs. Ag/AgCl, representing, respectively, the presumable conversion of Cu(II) into Cu(III) under the forward sweep and Cu(III) into Cu(II) at a backward sweep. Meanwhile, NiO-C prepared from Ni-MOF exhibits the Ni(III)/Ni(II) redox couple and the observed redox responses of CuO-C/CT and NiO-C/CT are matched, respectively, with the redox behaviour of CuO and NiO under alkaline conditions56,57, specifying the effective conversion of inactive MOF into the electrochemically active metal 13 ACS Paragon Plus Environment


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oxide and carbon composite. The electrical conductivity of CuO-C and NiO-C is found, respectively, to be (0.4 S cm-1) and (0.52 S cm-1). CuO/NiO-C/CT reveals the anodic wave at 0.66 vs. Ag/AgCl and two cathodic waves at 0.72 and 0.54 V vs. Ag/AgCl, assigning, respectively, to the Cu(II)/Cu(III) and Ni(II)/Ni(III) redox couples (Figure 7b). The slight shifting in the redox wave potential of CuO/NiO-C composite demonstrates the presence of a complex species. The presence of conducting carbon and bimetallic oxide nanoparticles in CuO/NiO-C promotes the surface energy and electrical conductivity (1.7 S cm-1), which provides the maximum redox current for CuO/NiO-C/CT than those of other studied CTs. The redox responses of CuO/NiO-C/CT were perceived with respective of sweep rates in 0.1 M NaOH vs. Ag/AgCl (Figure 7c). The linear response in the redox wave currents are observed for the sweep rates ranging from 20 to 100 mV s-1, indicating the diffusion controlled progression. Electrocatalytic Activities of Bare CT and Modified CTs toward Glucose Oxidation. The electrochemical function of developed materials towards glucose oxidation was measured with CVs in 5 mM glucose under 0.1 M NaOH at a sweep rate of 100 mV s-1 (Figure 8a). No conspicuous redox process is noticed for bare CT in the presence of glucose, indicating that bare CT has no appreciable electrocatalytic activity towards glucose. CuMOF/CT and Ni-MOF/CT reveal the significant oxidation waves with the presence of 5 mM glucose, owing to the participation, respectively, of Cu(II)/Cu(III) and Ni(II)/Ni(III) redox couples. The non-enzymatic glucose oxidation is further enhanced with the substitution of Ni2+ lattice in the Cu2+ framework of octahedron morphology. It is authenticated from the well defined glucose oxidation wave at 0.78 V vs. Ag/AgCl with an increased Ipa, owing to the participation of Cu(II)/Cu(III) and Ni(II)/Ni(III) redox pairs. The octahedron Cu/Ni-MOF network is comprised with Cu(II) and Ni(II) paddle-wheel units, where the equatorial and axial positions are assembled, respectively, with four carboxylate groups of tritopic organic 14 ACS Paragon Plus Environment

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ligands and water molecules. The comprehensive framework is made up of a large number of open coordination sites with two separate types of cages, providing the auxiliary pathways for charge transfer, facilitating the electrocatalytic glucose oxidation. Upon the conversion of prepared MOFs into their relevant metal oxide-carbon composites, the enhanced glucose oxidation performances are observed. CuO-C/CT and NiOC/CT evince the better resolved anodic waves with enhanced Ipas compared to their parent MOFs. It is attributed to the contribution of excellent electron delivery system associated with Cu(II)/Cu(III) and Ni(II)/Ni(III) redox pairs and conductive carbon matrix. In specific, NiO-C/CT demonstrates the slightly enhanced Ipa over the CuO-C/CT, which is due to the higher electrical conductivity of NiO-C nanoarchitectures. Among the used CTs, CuO/NiOC/CT manifests an excellent electrocatalytic activity towards glucose oxidation. The glucose electrooxidation wave of CuO/NiO-C/CT is remarked at 0.76 V vs. Ag/AgCl with the wellresolved anodic peak, owing to the oxidation of glucose into gluconolactone with the participation of Cu(II)/Cu(III) and Ni(II)/Ni(III) redox couples (Figure 8b). In comparison with Cu, Ni atoms exhibit the lower d-orbital occupancy and an incorporation of Ni into the Cu matrix result the surface d-states in CuO/NiO, which can function as lewis acid sites. These d-states are localized at the Ni sites and are expected to function as adsorption sites for the Lewis bases, which facilitates the adsorption of Lewis bases of glucose via their nonbonded electron pairs.58,59 Thus, the synerigistic effects created between the NiO and CuO in CuO/NiO-C and the hierarchical void spaces formed during the annealing process afford a large number of space sites for the accommodation of analyte, which collectively facilitates the interfacial contact between the analyte and electrode.60 Owing to the resistivity of the agglomeration of nanoparticles, the large surface area is exposed and retained for CuO/NiOC to the analyte, which escalates the adsorption and diffusion of an analyte further, maximizing the utilization rate of an electrolyte.60 The interconnected hierarchical network of 15 ACS Paragon Plus Environment


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CuO and NiO substructures with carbon bestows robust stability along with the shortened electron diffusion passage to surpass the glucose oxidation kinetics.61 The metal oxide nanoparticles assembled in an octahedron shape provides the properly oriented and exposed metallic active sites, which improves the efficient access of diffused anlayte with uniformly implanted active sites. The synergistic effect achieved from the uniform metal nanoparticles and carbon matrices provide efficient surface energy and large interfaces, facilitating the enhanced distribution of bimetallic oxides that improves the charge carrier kinetics for efficient glucose oxidation.61,62 CV responses of CuO/NiO-C/CT are acquired with the addition of different concentration of glucose in 0.1 M NaOH at 100 mV s-1 (Figure 8c). The gradual increment in Ipa with increasing concentration of glucose is witnessed along with the positive shift in the anodic wave potential, indicating the absence of fouling consequences at CuO/NiO-C/CT . The electrokinetics involved in glucose oxidation at CuO/NiO-C/CT is realised as a function of sweep rate ranging from 20-100 mV s-1 in the presence of 5 mM glucose in 0.1 M NaOH (Figure 8d). The enhancement in Ipa with the positive shift in the anodic wave potential is observed with the good linearity between Ipa to the square root of the sweep rate, evincing that the electrokinetics of CuO/NiO-C/CT involves the diffusion controlled process. To appraise the electrochemical stability of CuO/NiO-C, the CV study was performed for CuO/NiO-C/CT in 5 mM glucose with 0.1 M NaOH solution at a scan rate of 100 mV s-1 under successive scans of 100 cycles (Figure S4). After 100 cycles, the peak current response of CuO/NiO-C/CT toward glucose electroxoidation is retained to 90.1 % from its initial (1st cycle) response. The unchanged curve shape and constant Ipa with Epa upon the successive cycles guarantee the eminent electrochemical stability of CuO/NiO-C toward glucose oxidation, which is due to the strongly interlaced CuO/NiO nanoparticles with the carbon


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layers, authenticating the durable application of CuO/NiO-C/CT in glucose sensing under harsh electrochemical regimes. The optimization studies of pH toward the effective glucose oxidation are explored for CuO/NiO-C/CT in the presence of 5 mM glucose over a wide pH range of 5-14 at 100 mV s-1. CuO/NiO-C/CT does not display any obvious peaks at pH 5, owing to the inactivation of the catalytic active sites of CuO/NiO-C (Figure 9a and b). However, the glucose oxidation behaviour is elevated with an increase in the pH ranging from 7 to 13 and the maximum Ipa is perceived at the pH of 13. The maximum number of Cu(II)/Cu(III) and Ni(II)/Ni(III) redox species generated under the pH of 13 facilitates an efficient glucose electrooxidation. The erosion of a reference electrode observed for the pH >13 lowers the electrocatalytic response for CuO/NiO-C/CT towards glucose oxidation63, specifying that the pH of 13 is optimal for an efficient glucose electrooxidation. The flexibility of the prepared CuO/NiO-C/CT was investigated by observing the electrochemical performance at different bending states of angles ranging from 0 to 180o (Figure 9c). CuO/NiO-C/CT shows a negligible impact on Ipa response (Figure 9d) during wide and narrow bending, confirming the excellent flexibility of the fabricated sensor probe. Amperometric Detection of Glucose at CuO/NiO-C/CT. The reliability of CuO/NiOC/CT towards glucose oxidation is further appraised via amperometric current-time (i-t) curve in 0.1 M NaOH at 0.65 V vs. Ag/AgCl (Figure 10a). The amperometric behaviour of CuO/NiO-C/CT towards glucose oxidation demonstrates the well-defined stair case voltammograms and the step by step enhancement in amperometric current response in line with the different concentration of analyte (Figure 10a and inset: Figure 10a). The amperometric response attains a steady-state current within 5 s, unveiling the rapid charge carrier kinetics involved at the glucose electrooxidation process. Furthermore, the linear correlation is accomplished from the diffusion controlled kinetics of glucose oxidation with 17 ACS Paragon Plus Environment


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the concentration ranging from 100 nM to 4.5 mM (Figure 10b). From the calibration plot, the sensitivity towards glucose oxidation is found to be 586.7 µA mM-1 cm-2 with the lower detection limit (LOD) of 37 nM and the LOD is calculated by using the formula of 3sb/S (sbstandard deviation of background current and S-slope of the calibration plot).The porous architecture of CuO/NiO-C renders

abundant channels for the efficient adsorption and

diffusion of glucose to reach the interior catalytic sites.61

The strongly interconnected

networks with the uniform distribution of metal active sites proliferate the electrocatalytic glucose oxidation.61 Thus, the CuO/NiO-C demonstrates excellent electrochemical properties toward glucose oxidation, which outfits the sensing performances of other existing nonenzymatic electrochemical glucose detection reports (Table S1). Interference

Study

of

CuO/NiO-C/CT.

The

anti-interference

ability

of

an

electrochemical probe is a conspicious analytical parameter for their practical applications. Under physiological environment, the influence of interference is generally obtained from the electroactive organic species, which are easily oxidizable at an applied working potential. The normal glucose level in human serum (3-8 mM) is notably higher than those of the competing redox pairs of UA (0.33 mM) and AA (0.125 mM).57 However, the electron transfer rate of above competing species is comparable with glucose, which may stimulate their equivalent electrooxidation response with glucose. Hence, the impact of potential interfering endogeneous species such as AA, UA, CA, DA, AP, U, KCl, and NaCl at a concentration of 0.15 mM against the successive addition of 1.5 mM glucose was assessed with an amperometric technique at 0.65 V vs. Ag/AgCl in 0.1 M NaOH (Figure 10c). The steady-state amperogram of CuO/NiO-C/CT evinces the trivial current response towards the interfering species compared to glucose. Under alkaline conditions, the iso-electric point of CuO-NiO is observed to be ∼9.75-10.25,36 specifying their negative charges. While, UA and AA loss protons under alkaline conditions, generating negative charges on its surface. It 18 ACS Paragon Plus Environment

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provides robust repelling activity against the negatively charged CuO and NiO, which limits the elctrooxidation response of UA and AA at CuO/NiO-C/CT. The excellent antiinterference activity is also observed for CuO/NiO-C/CT against the commonly found reducing sugars including Lac, Suc, Fru, Gal, Man, Xyl, and Mal. It is also clear that the amperometric response of CuO/NiO-C/CT toward glucose electrooxidation is not affected with the pre-addition of endogeneous interfering species, specifying the excellent specifity of CuO/NiO-C/CT for glucose sensing. Chloride Poisoning. In general, the adequate contact of metal nanostructures with Cl- ions loses its electrochemical activity with the metal-Cl complex formation.64 In practical sensing applications, the exposure of Cl- ions with an analyte is unavoidable, which urges the exploration of Cl- poisoning effect for the fabricated sensor probes. Hence, the amperometric i-t curve experiment was accomplished for CuO/NiO-C/CT by stimulating the 0.1 M NaCl with 0.1 M NaOH, followed by the addition of glucose at various concentrations. No obvious changes in the amperometric responses of CuO/NiO-C/CT in NaCl containing glucose validate the excellent resistivity of prepared CuO/NiO-C against Cl- poisoning (Figure 10d). Reproducibility, Repeatability, and Stability Studies. The prolonged electrochemical stability of developed sensor probe was authenticated by monitoring i-t amperometric response of CuO/NiO-C/CT towards 5 mM glucose in 0.1 M NaOH at 0.65 V vs. Ag/AgCl for 56 days. The retention current of about 92.8 % from its initial amperometric response is observed at 56th day of experiment, endorsing the eminent stability of the fabricated CuO/NiO-C/CT (Figure S5). No significant changes observed between the digital photographs of the virgin and 56 days operated CuO/NiO-C/CT (inset : Figure S5) rule out the disintegration of CT and peel-off the catalyst layer from CT, illustrating the robust contact stability of CuO/NiO-C with CT. Furthermore, the current response of seven fabricated CuO/NiO-C/CTs toward glucose sensing was assessed under similar conditions 19 ACS Paragon Plus Environment


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and the obtained RSD in the range of 3.3 % prompts the satisfied electrode-to-electrode reproducibility of the system. The replication of freshly fabricated different CuO/NiO-C/CTs was scrutinized under similar conditions by 10 successive assessments. The peak current response of CuO/NiO-C/CTs unveils the RSD of 2.9 % for ten measurements, exhibiting the adequate replication of fabricated sensors. Real Sample Analysis. The analytical feasibility of fabricated CuO/NiO-C towards glucose diagnosis was corroborated with human serum samples collected from a healthy volunteer and processed in accordance with the guidelines of research ethics. The gathered serum sample was diluted with 0.1 M NaOH to probe the amperometric i-t response of CuO/NiO-C towards the known concentration of glucose at 0.65 V vs. Ag/AgCl. As projected in Table 1, the recovery (97.5 - 103.8 %) and relative standard deviation (2.33 - 2.78 %) obtained for glucose spiked in blood serum at CuO/NiO-C is in good endorsement with ACCU-CHEK Active gluconometer (Table 1). The analytical consequence of constructed CuO/NiO-C reinforces its potential glucose sensing capability with high reproducibility and precision towards the on-site applications. CONCLUSIONS Highly symmetric, octahedron shaped, and hierarchical porous CuO/NiO-C architecture was developed by using a Cu/Ni-MOF as a sacrificial template. The close proximity of Cu2+-Ni2+ ions and organic ligands in Cu/Ni-MOF facilitated the formation of CuO-NiO metal naoparticles with tightly pinned carbon architectures, which enhanced the electrochemical stability via the strongly interconnected networks. The peculiar environment of metal oxides enabled the versatility in creating a large exposed area for the facile diffusion of an analyte and rapid electron transportation to reinforce the electrooxidation of glucose with excellent sensitivity and specificity. Thus, this study complements the environmentally benign and short processing synthetic conditions, binder-free modification of sensor probes with the 20 ACS Paragon Plus Environment

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easily available, self standing, and disposable CT, availability of hierarchcial cavities, and cardinal insights of synergies and ceaseless electron flow architecture, which collectively pave avenues for the evolution of cost-efficient, flexible, and durable glucose sensing systems.

ASSOCIATED CONTENT Supporting Information Cross sectional image of CuO/NiO-C/CT, CVs of bare CT in the presence and absence of glucose, electrochemical stability profile of CuO/NiO-C, and comparison table. Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS This study was supported by the Science and Engineering Research Board, New Delhi, India, Major Project Grant No. EMR/2015/000912. Y.Xia acknowledges the financial supports from National Natural Science Foundation of China (Grant No. 21403196) and Natural Science Foundation of Zhejiang Province (Grant No. LY17E020010).



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REFERENCES (1) Choudhary, M.; Shukla, S. K.; Taher, A.; Siwal, S.; Mallick, K. Organic-Inorganic Hybrid Supramolecular Assembly: An Efficient Platform for Nonenzymatic Glucose Sensor. ACS Sustain. Chem. Eng. 2014, 2, 2852−2858, DOI: 10.1021/sc500613q. (2) Zhu, H.; Li, L.; Zhou, W.; Shao, Z.; Chen, X. Advances in Non-enzymatic Glucose Sensors Based on Metal Oxides. J. Mater. Chem. B 2016, 4, 7333-7349, DOI: 10.1039/c6tb02037b. (3) Xie, J. X.; Chen, W. J.; Wu, X. X.; Wu, Y. Y.; Lin, H. Enhanced Luminol Chemiluminescence by Co-Fe LDH Nanoplates and its Application in H2O2 and Glucose detection. Anal. Methods 2017, 9, 974-979, DOI: 10.1039/C6AY02731H. (4) Jin, L.; Meng, Z.; Zhang, Y.; Cai, S.; Zhang, Z.; Li, C.; Shang, L.; Shen, Y. Ultrasmall Pt Nanoclusters as Robust Peroxidase Mimics for Colorimetric Detection of Glucose in Human

Serum.

ACS

Appl.

Mater.

Inter.

2017,

9,

10027-10033,

DOI:

10.1021/acsami.7b01616. (5) Chen, R.; Xu, W.; Xiong, C.; Zhou, X.; Xiong, S.; Nie, Z.; Mao, L.; Chen, Y.; Chang, H.-C. High-Salt-Tolerance Matrix for Facile Detection of Glucose in Rat Brain Microdialysates by MALDI Mass Spectrometry. Anal. Chem. 2011, 84, 465-469, DOI: 10.1021/ac202438a. (6) Hu, Y.; Cheng, H.; Zhao, X.; Wu, J.; Muhammad, F.; Lin, S.; He, J.; Zhou, L.; Zhang, C.; Deng, Y.; Wang, P.; Zhou, Z.; Nie, S.; Wei, H. Surface-Enhanced Raman Scattering Active Gold Nanoparticles with Enzyme-Mimicking Activities for Measuring Glucose and Lactate in Living Tissues. ACS Nano 2017, 11, 5558-5566, DOI: 10.1021/acsnano.7b00905. (7) Niu, X.; Li, X.; Pan, J.; He, Y.; Qiu, F.; Yan, Y. Recent Advances in Non-enzymatic Electrochemical Glucose Sensors Based on Nonprecious Transition Metal Materials: Opportunitiesand Challenges. RSC Adv. 2016, 6, 84893, DOI: 10.1039/c6ra12506a. 22 ACS Paragon Plus Environment

Page 23 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(8) Shu, Y.; Li, B.; Chen, J.; Xu, Q.; Pang, H.; Hu, X. Facile Synthesis of Ultrathin Nickel-Cobalt Phosphate 2D Nanosheets with Enhanced Electrocatalytic Activity for Glucose Oxidation. ACS Appl. Mater. Inter. 2018, 10, 2360-2367, DOI: 10.1021/acsami.7b17005. (9) Naik, K. K.; Gangan, A.; Chakraborty, B.; Nayak, S. K.; Rout, C. S. Enhanced Nonenzymatic Glucose-Sensing Properties of Electrodeposited NiCo2O4–Pd Nanosheets: Experimental and DFT Investigations. ACS Appl. Mater. Inter. 2017, 9, 23894-23903, DOI: 10.1021/acsami.7b02217. (10) Zhu, J.; Jiang, J.; Liu, J.; Ding, R.; Li, Y.; Ding, H.; Feng, Y.; Wei, G.; Huang, X. CNT-Network Modified Ni Nanostructured Arrays for High Performance Non-enzymatic Glucose Sensors. RSC Adv. 2011, 1, 1020-1025, DOI: 10.1039/c1ra00280e. (11) Kung, C.-W.; Otake, K.; Buru, C. T.; Goswami, S.; Cui, Y.; Hupp, J. T.; Spokoyny, A. M.; Farha, O. K. Increased Electrical Conductivity in a Mesoporous Metal–Organic Framework Featuring Metallacarboranes Guests. J. Am. Chem. Soc. 2018, 140, 3871-3875, DOI: 10.1021/jacs.8b00605. (12) Xu, Y.; Li, Q.; Xue, H.; Pang, H. Metal-Organic Frameworks for Direct Electrochemical Applications. Coordination Chem. Rev. 2018, 376,

292–318, DOI:

10.1016/j.ccr.2018.08.010. (13) Cirujano, F. G.; Xamena, F. X. L.; Corma, A. MOFs as Multifunctional Catalysts: One-Pot Synthesis of Menthol from Citronellal over a Bifunctional MIL-101 Catalyst. Dalt. Trans. 2012, 41, 4249-4254, DOI: 10.1039/c2dt12480g. (14) Liu, Y.; Zhang, Y.; Chena, J.; Pang, H. Copper Metal–Organic Framework Nanocrystal for Plane Effect Nonenzymatic Electro-catalytic Activity of Glucose. Nanoscale, 2014, 6, 10989-10994, DOI: 10.1039/c4nr03396e.



Page 24 of 42

(15) Sun, Y.; Li, Y.; Wang, N.; Xu, Q. Q.; Xu, L.; Lin, M. Copper‐Based Metal‐Organic Framework for Non‐enzymatic Electrochemical Detection of Glucose. Electroanal. 2018, 30, 474-478, DOI: 10.1002/elan.201700629. (16) Zhang, D.; Zhang, J.; Zhang, R.; Shi, H.; Guo, Y.; Guo, X.; Li, S.; Yuan, B. 3D Porous Metal-Organic Framework as an Efficient Electrocatalyst for Nonenzymatic Sensing Application. Talanta 2015, 144, 1176-1181, DOI: 10.1016/j.talanta.2015.07.091. (17) Tan, K.; Nijem, N.; Canepa, P.; Gong, Q.; Li, J.; Thonhauser, T.; Chabal, Y. J. Stability and Hydrolyzation of Metal Organic Frameworks with Paddle-Wheel SBUs upon Hydration. Chem. Mater. 2012, 24, 3153-3167, DOI: 10.1021/cm301427w. (18) Talin, A. A.; Centrone, A.; Ford, A. C.; Foster, M. E.; Stavila, V.; Haney, P.; Kinney, R. A.; Szalai, V.; Gabaly, F. E.; Yoon, H. P.; Leonard, F.; Allendorf, M. D. Tunable Electrical Conductivity in Metal-Organic Framework Thin-Film Devices. Science 2014, 343, 66-69, DOI: 10.1126/science.1246738. (19) Yang, L.; Zeng, X.; Wang, W.; Cao, D. Recent Progress in MOF‐Derived, Heteroatom‐Doped Porous Carbons as Highly Efficient Electrocatalysts for Oxygen Reduction Reaction in Fuel Cells. Adv. Funct. Mater. 2018, 28, 1704537-1704557, DOI: 10.1002/adfm.201704537. (20) Xu, Y.; Li, B.; Zheng, S.; Wu, P.; Zhan, J.; Xue, H.; Xu, Q.; Pang, H. Ultrathin TwoDimensional Cobalt-Organic Framework Nanosheets for High-Performance Electrocatalytic Oxygen Evolution. J. Mater. Chem. A 2018, 6, 22070-22076, DOI: 10.1039/c8ta03128b. (21) Jahan, M.; Liu, Z.; Loh, K. P. A Graphene Oxide and Copper-Centered Metal Organic Framework Composite as a Tri- Functional Catalyst for HER, OER, and ORR. Adv. Funct. Mater. 2013, 23, 5363-5372, DOI: 10.1002/adfm.201300510. (22) Liu, M.-R.; Hong, Q.-L.; Li, Q.-H.; Du, Y.; Zhang, H.-X.; Chen, S.; Zhou, T.; Zhang, J. Cobalt Boron Imidazolate Framework Derived Cobalt Nanoparticles Encapsulated in B/N 24 ACS Paragon Plus Environment

Page 25 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Codoped Nanocarbon as Efficient Bifunctional Electrocatalysts for Overall Water Splitting. Adv. Funct. Mater. 2018, 28, 1801136-1801144, DOI: 10.1002/adfm.201801136. (23) Chen, L. Y.; Fujita, T.; Ding, Y.; Chen, M. W. A Three-Dimensional Gold-Decorated Nanoporous Copper Core-Shell Composite for Electrocatalysis and Nonenzymatic Biosensing. Adv. Funct. Mater. 2010, 20, 2279–2285, DOI: 10.1002/adfm.201000326. (24) Niu, X. H.; Shi, L. B.; Zhao, H. L.; Lan, M. B. Advanced Strategies for Improving the Analytical Performance of Pt-Based Nonenzymatic Electrochemical Glucose Sensors: A Minireview. Analytical Methods. 2016, 8, 1755-1764, DOI: 10.1039/c5ay03181h. (25) Park, J.-G.; Akhtar, M. S.; Li, Z. Y.; Cho, D.-S.; Lee, W.; Yang, O.-B. Application of Single Walled Carbon Nanotubes as Counter Electrode for Dye Sensitized Solar Cells. Electrochim. Acta 2012, 85, 600–604, DOI: 10.1016/j.electacta.2012.07.110. (26) Zhong, G.-X.; Zhang, W.-X.; Sun, Y.-M.; Wei, Y.-Q.; Lei, Y.; Peng, H.-P.; Liu, A.L.; Chen, Y.-Z.; Lin, X.-H. A Nonenzymatic Amperometric Glucose Sensor Based on Three Dimensional Nanostructure Gold Electrode. Sens. Actuat. B. Chem. 2015, 212, 72-77, DOI: 10.1016/j.snb.2015.02.003. (27) Krishna, C. M.; Lion, Y.; Kondo, T.; Riesz, P. Thermal Decomposition of Methanol in the Sonolysis of Methanol-Water Mixtures. Spin-Trapping Evidence for Isotope Exchange Reactions. J. Phys. Chem. 1987, 91, 5847-5850, DOI: 10.1021/j100307a007. (28) Buttner, J.; Gutierrez, M.; Henglein, A. Sonolysis of Water-Methanol Mixtures. J. Phys. Chem. 1991, 95, 1528-1530, DOI: 10.1021/j100157a004. (29) Aronowitz, D.; Naegeli, W.; Glassman, I. Kinetics of the Pyrolysis of Methanol. J. Phys. Chem. 1977, 81, 25, DOI: 10.1021/j100540a037. (30) Li, M.; Dinca, M. On the Mechanism of MOF-5 Formation under Cathodic Bias. Chem. Mater. 2015, 27, 3203−3206, DOI: 10.1021/acs.chemmater.5b00899.



Page 26 of 42

(31) Zheng, C.; Greer, H. F.; Chiang, C.-Y.; Zhou. W. Microstructural Study of the Formation Mechanism of Metal–Organic Framework MOF-5. CrystEngComm 2014, 16, 1064–1070, DOI: 10.1039/c3ce41291a. (32) Saraf, M.; Rajak, R.; Mobin, S. M. A Fascinating Multitasking Cu-MOF/rGO Hybrid for High Performance Supercapacitors and Highly Sensitive and Selective Electrochemical Nitrite Sensors. J. Mater. Chem. A 2016, 4, 16432-16445, DOI: 10.1039/c6ta06470a. (33) Gotthardt, M. A.; Schoch, R.; Wolf, S.; Bauer, M.; Kleist, W. Synthesis and Characterization of Bimetallic Metal–Organic Framework Cu–Ru-BTC with HKUST-1 Structure. Dalt. Trans. 2015, 44, 2052-2056, DOI: 10.1039/c4dt02491e. (34) Sun, D.; Ye, L.; Sun, F.; García, H.; Li, Z. From Mixed-Metal MOFs to CarbonCoated Core–Shell Metal Alloy@ Metal Oxide Solid Solutions: Transformation of Co/NiMOF-74 to CoxNi1–x @ Co yNi1–y O@ C for the Oxygen Evolution Reaction. Inorg. Chem. 2017, 56, 5203-5209, DOI: 10.1021/acs.inorgchem.7b00333. (35) Yang, Y.; Shukla, P.; Wang, S.; Rudolph, V.; Chenc, X.-M.; Zhu, Z. Significant Improvement of Surface Area and CO2 Adsorption of Cu–BTC via Solvent Exchange Activation. RSC Adv. 2013, 3, 17065, DOI:10.1039/C3RA42519C. (36) Ding, R.; Liu, J.; Jiang, J.; Zhu, J.; Huang, X. Mixed Ni–Cu-Oxide Nanowire Array on Conductive Substrate and its Application as Enzyme-Free Glucose Sensor. Anal. Methods 2012, 4, 4003-4008, DOI: 10.1039/c2ay25792k. (37) Hu, J.; Yu, H.; Dai, W.; Yan, X.; Hu, X.; Huang, H. Enhanced Adsorptive Removal of Hazardous Anionic Dye “Congo Red” by a Ni/Cu Mixed-Component Metal–Organic Porous Material. RSC Adv. 2014, 4, 35124-35130, DOI: 10.1039/c4ra05772d. (38) Wu, R.; Qian, X.; Yu, F.; Liu, H.; Zhou, K. Wei. J.; Huang, Y. MOF-Templated Formation of Porous CuO Hollow Octahedra for Lithium-Ion Battery Anode Materials. J. Mater. Chem. A. 2013, 1, 11126-11129, DOI: 10.1039/c3ta12621h. 26 ACS Paragon Plus Environment

Page 27 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(39) Dong, C.; Xiao, X.; Chen, G.; Guan, H.; Wang, Y.; Djerdj, I. Porous NiO Nanosheets Self-Grown on Alumina Tube Using a Novel Flash Synthesis and Their Gas Sensing Properties. RSC Adv. 2015, 5, 4880-4885, DOI: 10.1039/C4RA13025A. (40) Siva, G.; Aziz, M. A.; Gnana kumar, G. Engineered Tubular Nanocomposite Electrocatalysts Based on CuS for High-Performance, Durable Glucose Fuel Cells and Their Stack.

ACS

Sustainable

Chem.

Eng.

2018,

6,

5929−5939,

DOI:

10.1021/acssuschemeng.7b04326. (41) Ma, J.; Yin, L.; Ge, T. 3D Hierarchically Mesoporous Cu-Doped NiO Nanostructures as High-Performance Anode Materials for Lithium Ion Batteries. CrystEngComm. 2015, 17, 9336-9347, DOI: 10.1039/c5ce00818b. (42) Balamurugan, J.; Thanh, T. D.; Heo S. B.; Kim, N. H.; Lee, J. H. Novel Route to Synthesis of N-Doped Graphene/Cu–Ni Oxide Composite for High Electrochemical Performance. Carbon 2015, 94, 962-970, DOI: 10.1016/j.carbon.2015.07.087. (43) Dubal, D. P.; Gund, G. S.; Holze, R.; Jadhav, H. S.; Lokhande, C. D.; Park, C.-J. Surfactant-Assisted Morphological Tuning of Hierarchical CuO Thin Films for Electrochemical

Supercapacitors.

Dalt.

Trans.

2013,

42,

6459-6467,

DOI:

10.1039/c3dt50275a. (44) Wang, L.; Xing, H.; Gao, S.; Ji, X.; Shen, Z. Porous Flower-like NiO@Graphene Composites with Superior Microwave Absorption Properties, J. Mater. Chem. C 2017, 5, 2005-2014, DOI: 10.1039/c6tc05179k. (45) Biemmi, E.; Darga, A.; Stock, N.; Bein, T. Direct Growth of Cu3(BTC)2(H2O)3·xH2O Thin Films on Modified QCM-Gold Electrodes–Water Sorption Isotherms. Micropor. Mesopor. Mater. 2008, 114, 380-386, DOI: 10.1016/j.micromeso.2008.01.024. (46) Prestipino, C.; Regli, L.; Vitillo, J. G.; Bonino, F.; Damin, A.; Lamberti, C.; Zecchina, A.; Solari, P. L.; Kongshaug K. O.; Bordiga, S. Local Structure of Framework Cu(II) in 27 ACS Paragon Plus Environment


Page 28 of 42

HKUST-1 Metallorganic Framework: Spectroscopic Characterization upon Activation and Interaction with Adsorbates. Chem. Mater. 2006, 18, 1337-1346, DOI: 10.1021/cm052191g. (47) Bonino,

F.;

Chavan,

S.;

Vitillo,

J.

G.;

Groppo,

E.;

Agostini,

G.;

Lamberti, C.; Dietzel, P. D. C.; Prestipino, C.; Bordiga, S. Local Structure of CPO-27-Ni Metallorganic Framework upon Dehydration and Coordination of NO. Chem. Mater. 2008, 20, 4957–4968, DOI: 10.1021/cm800686k. (48) Tsai, C.-H.; Fei, P.-H.; Lin, C.-M.; Shiu, S.-L. CuO and CuO/Graphene Nanostructured Thin Films as Counter Electrodes for Pt-Free Dye-Sensitized Solar Cells. Coatings 2018, 8, 21-33, DOI: 10.3390/coatings8010021. (49) Adhikari, S.; Madras, G. Role of Ni in Hetero-Architectured NiO/Ni Composites for Enhanced Catalytic Performance. Phys. Chem. Chem. Phys. 2017, 21, 13895-13908, DOI: 10.1039/C7CP01332A. (50) Lucena, F. R. S.; de Araujo, L. C.; Rodrigues, M. D.; da Silva, T. G.; Pereira, V. R.; Militao, G. C.; Fontes, D. A. F.; Rolim-Neto, P. J.; da Silva, F. F.; Nascimento, S. C. Induction of Cancer Cell Death by Apoptosis and Slow Release of 5-Fluoracil from MetalOrganic Frameworks Cu-BTC. Biomed. Pharmacother. 2013, 67, 707-713, DOI: 10.1016/j.biopha.2013.06.003. (51) Li, Y.; Miao, J.; Sun, X.; Xiao, J.; Li, Y.; Wang, H.; Xia, Q.; Li, Z. Mechanochemical Synthesis of Cu-BTC@GO with Enhanced Water Stability and Toluene Adsorption Capacity. Chem. Eng. J. 2016, 298, 191-197, DOI: 10.1016/j.cej.2016.03.141. (52) Kumar, R. S.; Kumar, S. S.; Kulandainathan, M. A. Efficient Electrosynthesis of Highly Active Cu3(BTC)2-MOF and its Catalytic Application to Chemical Reduction. Micropor. Mesopor. Mater. 2013, 168, 57-64, DOI: 10.1016/j.micromeso.2012.09.028. (53) Sherino, B.; Mohamad, S.; Halim, S. N. A.; Manan, N. S. A. Electrochemical Detection of Hydrogen Peroxide on a New Microporous Ni–Metal Organic Framework 28 ACS Paragon Plus Environment

Page 29 of 42 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Material-Carbon Paste Electrode. Sens. Actuat. B Chem. 2018, 254, 1148–1156, DOI: 10.1016/j.snb.2017.08.002. (54) Shinde, S. K.; Dubal, D. P.; Ghodake, G. S.; Gomez-Romero, P.; Kim, S.; Fulari, V. J. Influence of Mn Incorporation On the Supercapacitive Properties of Hybrid CuO/Cu(OH)2 Electrodes. RSC Adv. 2015, 5, 30478-30484, DOI: 10.1039/c5ra01093d. (55) Behnoudnia, F.; Dehghani, H. Anion Effect on the Control of Morphology for NiC2O4·2H2O Nanostructures as Precursors for Synthesis of Ni(OH)2 and NiO Nanostructures and their Application for Removing Heavy Metal Ions of Cadmium(II) and Lead(II). Dalton Trans. 2014, 43, 3471-3478, DOI: 10.1039/c3dt52049h. (56) Xia, L.; Xu, L.; Song, J.; Xu, R.; Liu, D.; Dong, B.; Song, H. CdS Quantum Dots Modified

CuO

Inverse

Opal

Electrodes

for

Ultrasensitive

Electrochemical

and

Photoelectrochemical Biosensor. Sci. Rep. 2015, 5, 10838 (1-12), DOI: 10.1038/srep10838. (57) Gao, Z.; Han, Y.; Wang, Y.; Xu, J.; Song, Y.; One-Step to Prepare Self-Organized Nanoporous NiO/TiO2 Layers and its Use in Non-Enzymatic Glucose Sensing. Sci. Rep. 2013, 3, 3323 (1-7), DOI: 10.1038/srep03323. (58) Yeo, I.-H.; Johnson, D. C. Electrochemical Response of Small Organic Molecules at Nickel–Copper Alloy Electrodes. J. Electroanalyt. Chem. 2001, 495, 110–119, DOI: 10.1016/S0022-0728(00)00401-0. (59) Yeo, I.-H.; Johnson, D. C. Anodic response of glucose at copper-based alloy electrodes.

J.

Electroanalyt.

Chem.

2000,

484,

157–163,

DOI:

10.1016/S0022-

0728(00)00072-3. (60) Wu, R.; Qian, X.; Rui, X.; Liu, H.; Yadian, B.; Zhou, K.; Wei, J.; Yan, Q.; Feng, X.Q.; Long, Y.; Wang, L.; Huang, Y. Zeolitic Imidazolate Framework 67‐Derived High Symmetric Porous Co3O4 Hollow Dodecahedra with Highly Enhanced Lithium Storage Capability. Small 2014, 10, 1932-1938, DOI: 10.1002/smll.201303520. 29 ACS Paragon Plus Environment


Page 30 of 42

(61) Li, H.; Liang, M.; Sun, W.; Wang, Y. Bimetal–Organic Framework: One‐Step Homogenous Formation and its Derived Mesoporous Ternary Metal Oxide Nanorod for High‐Capacity, High‐Rate, and Long‐Cycle‐Life Lithium Storage. Adv. Func. Mater. 2016, 26, 1098-1103, DOI: 10.1002/adfm.201504312. (62) Chawla, M.; Randhawa, J. K.; Siril, P. F. Calcination Temperature as a Probe to Tune the Non-Enzymatic Glucose Sensing Activity of Cu-Ni Bimetallic Nanocomposites. New. J. Chem. 2017, 41, 4582–4591, DOI: 10.1039/c6nj03920k. (63) Babu, K. J.; Sheet, S.; Lee, Y. S.; Gnana kumar, G: Three-Dimensional Dendrite Cu−Co/Reduced Graphene Oxide Architectures on a Disposable Pencil Graphite Electrode as an Electrochemical Sensor for Nonenzymatic Glucose Detection. ACS Sustainable Chem. Eng. 2018, 6, 1909-1918, DOI: 10.1021/acssuschemeng.7b03314. (64) Chen, X. M.; Lin, Z. J.; Chen, D. J.; Ji, T. T.; Cai, Z. M.; Wang, X. R.; Chen, X.; Chen, G. N.; Oyama, M. Nonenzymatic Amperometric Sensing of Glucose by Using Palladium Nanoparticles Supported on Functional Carbon Nanotubes. Biosens. Bioelectron 2010, 25, 1803-1808, DOI: 10.1016/j.bios.2009.12.035.


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Figure 1. SEM images of (a and b) Cu-MOF, (c and d) Cu/Ni-MOF, (e and f) CuO-C, and (g and h) CuO/NiO-C.



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Figure 2. Molecular structure of (a) Cu-MOF and (b) Cu/Ni-MOF, and (c) formation mechanism of CuO/NiO-C from Cu/Ni-MOF.


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Figure 3. TEM images of (a and b) Cu/Ni-MOF with the inset in (b) showing the SAED pattern and (c-e) CuO/NiO-C, (f) HR-TEM image of CuO/NiO-C with the inset in (f) showing the SAED pattern, and (g) HAADF-STEM image of CuO/NiO-C and the corresponding elemental mapping images.



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Figure 4. XRD patterns of (a) Cu-MOF, (b) Cu/Ni-MOF, (c) CuO-C, and (d) CuO/NiO-C.


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Figure 5. (a) XPS full scan spectrum of CuO/NiO-C and the deconvoluted spectrum of (b) Cu 2p, (c) Ni 2p, (d) C 1s, and (e) O 1s.



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Figure 6. (i) Raman and (ii) FT-IR spectra of (a) Cu-MOF, (b) Cu/Ni-MOF, (c) CuO-C, and (d) CuO/NiO-C.


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Figure 7. (a) CVs of studied CTs in 0.1 M NaOH at a scan rate of 100 mV s-1, (b) activation mechanism of CuO/NiO-C/CT with NaOH solution, and (c) CVs of CuO/NiO-C/CT in 0.1 M NaOH at different scan rates with the inset in (c) showing the calibration plot of peak current vs. square root of scan rate.



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Figure 8. (a) CVs of studied CTs in the presence of 5 mM glucose in 0.1 M NaOH at a scan rate of 100 mV s-1, (b) glucose electrooxidation mechanism at CuO/NiO-C/CT, (c) CVs of CuO/NiO-C/CT with the different concentration of glucose in 0.1 M NaOH at at a scan rate of 100 mV s-1, and (d) CVs of CuO/NiO-C/CT with 5 mM glucose in 0.1 M NaOH as a function of scan rates with the inset in (d) showing the calibration plot of peak current vs. square root of at a scan rate.


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Figure 9. (a) CuO/NiO-C/CT‘s CVs with 5 mM glucose under various pH levels at 100 mV s-1, (b) the corresponding plot of pH vs. Ipa, and (c) the CVs of CuO/NiO-C/CT at different bending angles with 5 mM glucose in 0.1 M NaOH at a scan rate of 100 mV s-1, and the corresponding peak current density as a function of different bending angles of CuO/NiO-C/CT with the inset in (d) showing the digitial photographs of CuO/NiO-C/CT at different bending angles.



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Figure 10. (a) CuO/NiO-C/CT’s amperometric behaviour upon the successive injection of glucose at 0.65 V vs. Ag/AgCl with the inset (a) showing the amperometric behaviour of CuO/NiO-C/CT towards 100-900 nM glucose, (b) calibration plot of CuO/NiO-C/CT’s amperometric responses with respective of glucose concentration, (c) interfernce test of CuO/NiO-C/CT with the addition of of 0.15 mM interfering species and 1.5 mM glucose at 0.65 V vs. Ag/AgCl in 0.1 M NaOH, and (d) amperometric behaviour of CuO/NiO-C/CT in 0.1 M NaOH solution with the successive addition of glucose in the absence and presence of 0.1 M NaCl at 0.65 V vs. Ag/AgCl with the inset in (d) showing the amperometric behaviour of CuO/NiO-C/CT towards 100-900 nM glucose.


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Table 1. Electrochemical detection of glucose in human serum samples at CuO/NiO-C/CT.

Glucose concentration Original serum sample (mM)

9.6

aDetermined

Diluted serum sample (mM)

2.0

Glucose added (µM)

Glucose found (mM) RSDb (%)

Recovery (%)

Gluco metera

Proposed method

0

2.05

1.95

2.33

97.5

100

2.12

2.18

2.47

103.8

300

2.31

2.38

2.61

103.5

500

2.58

2.57

2.74

102.8

700

2.72

2.77

2.78

102.6

by ACCU-CHEK Active glucometer. bRelative standard deviation of four

measurements.



FOR TABLE OF CONTENTS USE ONLY

Hierarchical NiO/CuO-Carbon nanocomposite derived from metal organic framework on disposable cello tape is explored as a binder free probe for high performance non-enzymatic glucose sensors.


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NiO-Carbon Nanocomposite Derived from Metal

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