Carbohydrates-Derived Nitrogen-Doped Hierarchical Porous Carbon

Subscriber access provided by University of Sunderland

Article

Carbohydrates-Derived Nitrogen-Doped Hierarchical Porous Carbon for Ultrasensitive Detection of 4-Nitrophenol Lingling Hu, Fei Peng, Dehua Xia, Huanjunwa He, Chun He, Zekun Fang, Jingling Yang, Shuanghong Tian, Virender K. Sharma, and Dong Shu ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b05169 • Publication Date (Web): 29 Oct 2018 Downloaded from http://pubs.acs.org on October 31, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 38 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

ACS Sustainable Chemistry & Engineering

Carbohydrates-Derived Nitrogen-Doped Hierarchical Porous Carbon for Ultrasensitive Detection of 4-Nitrophenol Lingling Hu, † Fei Peng, † Dehua Xia, *,†,‡ Huanjunwa He, † Chun He,*, †, ‡ Zekun Fang, † Jingling Yang, † Shuanghong Tian, †,‡ Virender K. Sharma, *, § and Dong Shu ∞

† School

of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou,

510275, China ‡

Guangdong Provincial Key Laboratory of Environmental Pollution Control and

Remediation Technology, Guangzhou, 510275, China §

Department of Environmental and Occupational Health, School of Public Health, Texas

A&M University, College Station, Texas 77843, U.S.A. ∞

Key Lab of Technology on Electrochemical Energy Storage and Power Generation in

Guangdong Universities, School of Chemistry and Environment, South China Normal University, Guangzhou, 510006, China

*

Corresponding author: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China. Email address: [email protected] (D.H. Xia); [email protected] (C. He); [email protected] (V.K. Sharma) 1

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

ABSTRACT A facile, cost-effective approach to obtain sensor electrode materials with excellent electrochemical performance for sensitive and fast detection of 4-nitrophenol (4-NP) is of great importance to environment and human health. Herein, a smart strategy was proposed for fabrication of nitrogen-doped hierarchical porous carbon (NPC) material with large surface area and unique hierarchical porous structure derived from conveniently available carbohydrates via a facile process. NPC combined with chitosan (CTS) was used to modify indium-tin oxide (ITO) electrode, referred to CTS/NPC/ITO electrode, in which CTS was acted as dispersant and immobilization reagent. Based on the optimum conditions, 4-NP was successfully deposited on CTS/NPC/ITO electrode and the cathodic deposit of 4-NP showed reversible characteristics in a potential range between -0.22 to -0.00 V as well as high ionic-electronic conductivity. Moreover, the electrochemical reaction kinetics and mechanism of 4-NP were explored in detail by CVs, FTIR spectra and LC-MS. The response sensitivities of the electrode for 4-NP were obtained as 4.85 µA µM-1, 2.212 µC µM-1, and 0.118 µA µM-1 (RSD ~ 5%) while detection limits (S/N) = 3) were 27.55, 30.10, and 5.44 µM by applying cyclic voltammetry (CV), chronocoulometry, and differential pulse voltammetry (DPV), respectively. The results were presented to demonstrate that CTS/NPC/ITO electrode had excellent reproducibility, repeatability, good stability and high selectivity for detecting 4-NP in real water samples. Keywords: Cathodic deposit, Electrochemical detection, Nitrogen-doped hierarchical porous carbon, Reaction kinetics, 4-nitrophenol

2


Page 2 of 38

Page 3 of 38 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


INTRODUCTION Nitrogen-containing aromatic compounds like nitrobenzene, nitrotoluenes, and nitrophenols are widely used in industrial manufacturing, e.g. in the production of pesticides, drugs, and dyes and in the leather production as a fungicide.1-2 These compounds ultimately release to environment in which they remain for a long period of time and have therefore been found in freshwater and in marine environments.3 Among the numerous nitro-compounds in environment, 4-nitrophenol (4-NP) is highly toxic, which can damage liver, kidney and human blood as well as the central nervous system.4 Therefore, 4-NP is considered as one of the priority pollutants by United States Environmental Protection Agency, which has set the allowable limit of 60 ppb in drinking water.3, 5 It is imperative to develop a simple and a highly sensitive method to detect 4-NP in water.6 Conventional identification and quantification techniques for determining 4-NP include high-performance liquid chromatography (HPLC),7 liquid chromatography–mass spectrometry (LC–MS),8 gas chromatography–mass spectrometry (GC–MS),9 and fluorescence measurement.10

However, these methods are

time-consuming, involve enormous instrumentation, and require complex sample pretreatment steps, thus unsuitable for routine monitoring of 4-NP in water.11 In contrast, the electrochemical methods have a great potential for environmental analysis because they are usually simple, inexpensive, and rapid as well as sufficiently sensitive for a large-scale monitoring.12-13 The electrochemical response intensity towards 4-NP is extremely dependent on the surface properties and composition of electrode materials.14 Therefore, an approach has been done for designs of new electrochemical sensors capable to provide better surface properties to detect of 4-NP in terms of selectivity, sensitivity,

3



reliability, low cost, and ease of fabrication and use.15 Carbon materials including porous carbon and nanocarbons such as carbon nanotubes, nanofibers, graphene, etc., have been widely used as electrode materials for diverse application in fields of energy conversion devices (e.g. solar cells, fuel cells, supercapacitors, and batteries) and sensor fabrication.16-18 By far, the properties of nanocarbons are well-documented, however, porous carbon, especially activated porous carbon, remains the first choice because of the merits of low cost and easy preparation.19-20 Large surface area and unique pore structure of porous carbon are two key parameters for an ideal electrode to develop electrochemical sensors and biosensors, since they can provide plenty of active sites and help reactant/product transfer.21 For example, Fu et al. has successfully synthesized graphitic mesoporous carbon membrane with dimensionally networked nanotunnels and applied as monolithic matrix for electrochemical sensing.22 Silva et al. reported that porous diamond-like carbon (DLC) electrode was highly sensitive and presented low limits for sensing hormones, neurotransmitters, and endocrine Disruptors.23 Consequently, a wide range of porous carbon synthesis routes have been developed, including using a metallic compound as a template, employing expensive zeolites or silica oxides as a sacrificial scaffold, carbonizing polypyrrole microsheets and cross-linking of terephthalonitrile monomers to produce a carbon precursor.24-28 However, the uneconomic carbon sources, templates and complicated preparation processes used for mass production of porous carbon materials are highly challenging. Carbohydrates, common natural products, which are consisted of carbon, oxygen, and hydrogen, are largely synthesized by plants through photosynthesis (billion tons per year). They are abundant, environmentally-benign, and easily accessible.

4


Page 4 of 38

Page 5 of 38 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


Converting these carbohydrates to high value-added functional carbon materials seems to be a sensible approach for environmental sustainability.29-30 Pomelo peel is a sustainable, inexpensive and abundant resource supplied by nature. Usually, it is considered as agricultural wastes and often directly discarded in garbage dump in south china, which is harmful to environment. In fact, pomelo peel contains large quantity of carbohydrates, which is usually considered as an ideal carbon precursor to produce porous carbon. Futhermore, it could also provide an excellent platform for further optimizing the structure and properties of derived carbon since the middle white layer of pomelo peel possesses superior absorption capacity toward organic and inorganic solutions due to its sponge-like structure.30-31 Therefore, pomelo peel could be optimized to offer a good way for facile, sustainable and low-cost development of metal-free porous carbon electrode materials. Recently, it is reported that doping of heteroatoms (e.g. nitrogen, sulfur, phosphorus) into carbon materials is an efficient method to improving its chemical activity and electronic property.24, 32-34 Among these heteroatoms, nitrogen is considered as a peerless dopant since it could significantly improve the surface wettability and conductivity of carbon materials, thus enhancing electrochemical performances and possessing long-term stability.30, 35-37 To date, some researchers have successfully synthesized nitrogen-doped carbon materials using pomelo peel as carbon precursor. The nitrogen-doped carbon materials possessed many advantages including the excellent chemical stability, high surface area, versatile structures, high conductivity, and relatively low cost. Yuan et al. displayed a nitrogen-doped nanoporous carbon derived from waste pomelo peel, which showed excellent performance for the oxygen reduction reaction.21 Qu et al. and Xiao et

5



Page 6 of 38

al. reported the nitrogen doped carbon modified electrodes derived from pomelo peel possessed a remarkably large capacitance with good rate capability and excellent long-term cycling stability.30,

35

Li et al. found that N-doped carbon microspheres

(NCMSs) derived from pomelo peel was a superhydrophilic adsorbent, which had ultrastrong adsorption capacities for water-soluble contaminants.38 To our knowledge, in our study, NPC derived from pomelo peel was firstly used as electrode materials to fabricate electrochemical sensor for detecting contaminants. In this study, our strategy is to develop a facile and sustainable approach to synthetize N-doped porous carbons (NPC) derived from pomelo peel with abundant active sites, excellent electron and reactant transfer rate, thus fabricating ultrasensitive electrochemical sensor for 4-NP detection. Chitosan (CTS) is a biocompatible polymer, which contains a large number of amino and hydroxyl groups,

39

and under specific

conditions it is able to form highly water swellable hydrogels and have the excellent membrane forming ability.40 For these reasons, CTS could increase the bonding effect between NPC and ITO electrode, subsequently leading to decrease electron transfer resistance and increase response current. This paper thus proposes combining NPC with CTS to modify ITO electrode, called CTS/NPC/ ITO electrode, to electrochemical detection of 4-NP in water samples. The novelty of the CTS/NPC/ITO electrode as a sensor was demonstrated herein by (i) preparing and characterizing NPC and CTS/NPC/ITO electrode; (ii) investigating the voltammetric behavior, electrochemical reaction kinetics and mechanism of 4-NP on CTS/NPC/ITO electrode; (iii) examining the reproducibility, stability, and sensitivity of CTS/NPC/ITO electrode for detecting 4-NP using three electrochemical techniques,

6


Page 7 of 38 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


including CV, chronocoulometry, and DPV; (iv) establishing the feasibility of the developed sensor to detect 4-NP in real water samples.

RESULTS AND DISCUSSION Physicochemical properties of NPC The synthetic NPC was derived from pomelo peel precursor through hydrothermal and activation processes. Figure 1a shows a diagrammatic drawing to expound the synthetic process (see Text S1 for preparation details). Pomelo peel mainly consists of abundant small cellulose fibers to form sponge-like structure (Fig. S1). Due to its sponge-like structure, pomelo peel has a strong adsorption capacity, which could favor to adsorb melamine. Thus, it is believed that nitrogen-doped porous carbon material could be obtained from carbonization of pomelo peel after adsorbing melamine. Fig. 1b showed that NPC consisted of a large number of ultrafine spherical carbon particles, which were connected to each other to form porous structure. The TEM images in Fig. 1c also confirmed porous carbon frameworks of NPC. The unique porous structures were beneficial to increase the surface area of NPC material, thus providing more active sites to effectively improve the electrochemical activity towards 4-NP. The NPC was further studied by XRD and Raman spectroscopy. As shown in Fig. 1d, XRD pattern of NPC exhibited two broad peaks at 2θ of 24.5° and 43.5°, which could be ascribed to the (002) and (100) index planes of amorphous carbon.31 The Raman spectra (Fig. S2) showed two separate characteristic bands of D-band peak at 1350 cm-1 and G-band peak at 1600 cm-1. The D/G intensity ratio intensity was approximating to 1, which further indicated the amorphous carbon in NPC in agree with the Raman results of

7



honeycomb-like porous carbon.19 The BET surface area and pore structure of NPC samples were determined using N2 adsorption-desorption isotherms. Fig. 1e showed the curve exhibited a type-I sorption isotherm with steep uptakes below P/P0 = 0.05, confirming the presence of abundant micropores. In addition, the obscure hysteresis loop indicated the existence of mesopores and macropores, confirming the formation of hierarchical porous structure in NPC with pore size distribution entered at 1.8 and 9 nm. NPC also possessed high BET surface area (1071 m2 g-1) and high pore volume (0.60 cm3 g-1). NPC with hierarchical porous structure, high surface area and high pore volume would provide a favorable path for electrolyte penetration and transportation.35-36, 41 Thus, it is expected that NPC as an electrode material could show a high electrochemical property for electrochemical sensing of 4-NP. The chemical state in the carbonaceous matrices was studied by XPS analysis. The high-resolution C 1s XPS spectrum displayed four peaks at 284.7 eV, 285.4 eV, 286.5 eV and 289.1 eV for NPC, which was referred as C–C, C–N, C–O and O-C=O, respectively (Fig. 1f).19, 21 Similarly, the high-resolution N 1s spectra (Fig. 1g) can be fitted into four peaks located at 398.6, 400.3, 401.3 and 404.3 eV, attributed to pyridinic-N, pyrrolic-N, graphitic-N and oxidic-N, respectively.21, 24 The N binding configuration was mainly in the form of pyridinic-N, pyrrolic-N, graphitic-N, which have been reported as active sites for electrochemical reaction, thus enhancing electrochemical properties of porous carbon.42 Furthermore, these oxygen and nitrogen functional groups could also improve the wettability of the NPC-based electrodes in the aqueous electrolytes.19

Electrochemical properties of CTS/NPC/ITO electrodes

8


Page 8 of 38

Page 9 of 38 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


The CVs of bare electrode, CTS/PC/ITO electrode and CTS/NPC/ITO electrode at the scan rate of 0.1 V s −1 in 50 mM NaCl were investigated. Compared with CV spectra of bare electrode and CTS/PC/ITO electrode (Fig. S3), the CTS/NPC/ITO electrode showed the excellent electrochemical activity toward 4-NP. The electrochemical properties of CTS/NPC/ITO electrode were further investigated in 0.4 mM 4-NP/50 mM NaCl solution at pH 7.0 by CVs shown in Fig. 2a. The response current of PC/ITO electrode increased significantly compared to the bare ITO. When CTS was introduced, the voltammetric response of CTS/PC/ITO electrode was further slightly increased. CTS was a dispersant and immobilization reagent, which can decrease electron transfer resistance and then increase the response current. Compared with the former three electrodes, the voltammetric response of CTS/NPC/ITO increased significantly, indicating that NPC possessed an excellent electrochemical activity toward 4-NP. The extra performance was attributed to the cooperative synergistic effect, including good accessibility to reactant benefiting from hierarchical porous structure as well as highly active sites deriving from nitrogen doping.21 Next, the electrochemical reversible behavior of electrodes was evaluated by performing CVs of ITO and CTS/NPC/ITO electrodes in 0.05 mM K3[Fe(CN)6] and K4[Fe(CN)6] solutions containing 50 mM NaCl as the supporting electrolyte. The 1st to 20th CVs of ITO and CTS/NPC/ITO electrodes for Fe3+/Fe2+ redox pair were observed (Fig. 2b). A pair of well-defined redox peaks can be seen at the ITO electrode with peak-to-peak separation (ΔEp) of 140 mV and the ratio between anodic and cathodic peak currents (Ipa/Ipc) was ~ 1. When electrode was modified with CTS/NPC materials, the peak currents of redox peaks increased by 8% compared to that of ITO electrode.

9



Page 10 of 38

Moreover, the decrease of ΔEp (72 mV) was observed at the CTS/NPC/ITO electrode, indicating that CTS/NPC/ITO electrode could improve the reversibility of the redox reaction. The effect of scan rates (v) was examined using Fe3+/Fe2+ redox pair (Fig. 2c-d and Fig. S4). The electrochemical active surface area A (cm2) for each electrode was estimated using Randles–Sevcik equation: 43 Ip = 2.69 × 105 n3/2 A D1/2 v1/2 c

(1)

Where Ip is the anodic or cathodic current peak, n is the number of exchanged electrons, D is the diffusion coefficient (6.39 × 10-6 cm2 s-1), and C is the concentration of electro-active species (mol cm-3). The slope values of the plots of Ipa vs v1/2 gave the effective electro-active areas for ITO, CTS/PC/ITO and CTS/NPC/ITO electrodes as 0.0437 cm2, 0.0619 cm2 and 0.0701 cm2, respectively. The result indicated that high surface area and nitrogen doping of NPC were beneficial to increase electrochemical active surface area. The electrochemical impedance spectroscopy (EIS) was further conducted to study the interface properties of electrodes. In general, the diameter of the semicircle part at high frequency was equivalent to charge transfer resistance (RCT), depicting the charge transfer rate through the electrode/electrolyte interface.44 As displayed in Fig. S5, CTS/NPC/ITO electrode exhibited smaller semicircle diameter than that of CTS/PC/ITO electrode, indicating that nitrogen doping has a positive effect on carrier transfer efficiency and electronic conductivity of electrode. Based on these results, CTS/NPC material coating on ITO electrode was able to optimize the properties of electrodes successfully, confirmed by increase in electroactive

10


Page 11 of 38 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


area, carrier transfer efficiency and electronic conductivity as well as improvement in reversibility of the redox reactions. Therefore, CTS/NPC could provide a good opportunity for the modified electrode to detect 4-NP with high selectivity.

Voltammetric behavior of 4-NP on CTS/NPC/ITO electrode Initially, the CVs on CTS/NPC/ITO electrode were obtained in 50 mM NaCl electrolyte solution with and without 0.4 mM 4-NP (Fig. S6). No redox signals were observed without 4-NP, suggesting that the CTS/NPC/ITO was an electrochemically inactive electrode in the selected potential range. Fig. 3a shows multiple CVs on CTS/NPC/ITO electrode in 0.4 mM 4-NP when applying voltage ranged between 0.6 V and -1.4 V at a scan rate of 0.1 V s−1. A distinct reduction peak appeared at -1.182 V (peak I) in the first CV sweep. The reduction peak was attributed to the reduction of 4-NP.45 Following the 10th of multiple CVs, a pair of sharp redox peaks emerged in the potential region along with the new cathodic peak (-0.273 V, peak II) and the anodic peak (-0.025 V, peak III). As successive potential scanning, the reduction peak (peak I) showed a gradual decrease and remained unchanged thereafter. The currents of the redox peaks continuously increased until attain a maximum, indicating the formation of a cathodic deposition layer. Interestingly, when potential scan range was set between 0.6 to -1.2 V (Fig. 3b), the peak II and peak III became smaller than the voltammograms under the potential scan up to −1.4 V. Next, the potential scan range was set between 0.6 to -0.8 V in order to elucidate the origin of the redox pair. Under this voltage range, reduction of nitryl group did not occur. As shown in Fig. 3c, the redox peaks even disappeared in multiple CVs, revealing that

11



Page 12 of 38

the formation of peak I, namely the reduction of 4-NP, was responsible for the appearance of the reversible redox couple. Notably, the response current of peak I was much higher than that of peaks II and III, further suggesting that the cathodic electroreduction of 4-NP likely corresponded to a reaction possessing high electron transfer number.

Kinetic studies of 4-NP on CTS/NPC/ITO electrode The CVs at different potential scan rates were carried out to learn details of peak current and peak potential. The CVs on CTS/NPC/ITO electrode with different potential scan rate in 0.4 mM 4-NP were shown in Fig. 4a. The reduction peak current increased with the increase in scan rate. Significantly, the current was proportional to the square root of scan rate in the range of 0.02 - 0.4 V s-1, indicating that the cathodic reduction of 4-NP on the CTS/NPC/ITO electrode was diffusion-controlled process. The peak potential (Epc) of peak I shifted negatively with increase in the scan rate. There was a linear relationship between Epc and ln v in the studied range and the regression equation was Epc = - 0.0312 lnv - 1.0657 (r2 = 0.99). According to Laviron’s theory, 46 RT / nF was calculated as 0.0312. Based on the assumption that the charge transfer coefficient α was 0.5 for a totally irreversible electrode reaction process,

47

the calculated number of

electrons was ~ 2.0, which suggests that two electrons were involved in the reduction of 4-NP. The influence of the scan rate on the redox peak current and potential was also investigated and the kinetic parameters including charge transfer coefficient (α), number of electrons involved (n), surface coverage (Γ), and reaction rate constant Ks could be experimentally calculated.

12


Page 13 of 38 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


The cathodic deposit of 4-NP, obtained by CVs of 20 cycles, showed pairs of well-defined redox peaks in 0.4 mM 4-NP/50 mM NaCl solution (Fig. 4b). The cathodic peak heights were close to anodic peaks for all the scan rates and simultaneously showed a linear increase as a function of the scan rate from 0.02 to 0.3 V s−1 (inset in Fig. 4b). This suggests that the redox process was a surface-confined process. The regression equation could be written as Ip.a (μA) = 52.639 v + 3.252. The number of electrons involved in the redox reaction at the CTS/NPC/ITO electrode was ascertained by Eq. 2. 48 n  0.0565(E p  E p /2 ) 1

(2)

Where Ep was the peak potential and Ep/2 was the half peak potential. The calculated value of n was ~ 1 (peak III of Fig. 4b was taken as an example to determine n). This suggested that one-electron was involved in the redox process of peaks II and III. The surface coverage for cathodic deposits of 4-NP on the electrode surfaces could be estimated from the slope of Ip.a vs v and using Eq. 3. 46 I p.a 

n2F 2  vA  4 RT

(3)

Where A is the effective area of the electrode (calculated from Eq. 1) and F is Faraday’s constant (95485 C mol-1). The calculation result showed that the surface coverage for cathodic deposits of 4-NP was 8.01 × 10−11 mol cm-2. With the increase of the scan rate, the potential of the reduction peak (peak II) shifted negatively and the potential of the oxidation peak (peak III) shifted positively. The Ep.a varied linearly with ln v and the regression equation was Ep.a = 0.03548 lnv + 0.03575. According to the Laviron’s theory, the relationship between Ep.a and scan rate can be expressed by Eq. 4 47:

13



E p.a  E  o

RT nF

ln v 

RT nF

ln(

nF RTks

)

Page 14 of 38

(4)

Where Eo is the formal standard potential, α is the charge-transfer coefficient, ks is the standard heterogeneous reaction rate constant (s−l). The linear fitting of the data gave a slope of 0.035, from which an estimated value of α was obtained as 0.778 by considering one-electron was involved in the redox reaction. From the intercept, the ks value of 0.36 s−1 was obtained using E0 = - 0.149 V (vs. SCE at pH 7.0). This result indicated a reasonably fast electron transfer between the cathodic deposits of 4-NP and the CTS/NPC/ITO electrode. The ionic-electronic conductivity of cathodic deposits of 4-NP was studied by EIS. Fig. 5 showed the Nyquist plots of CTS/NPC/ITO electrode with cathodic 4-NP deposits in comparison with CTS/NPC/ITO electrode at open circuit potential (Eocp). Randles equivalent circuit, electrolyte solution resistance (RS), charge transfer resistance (RCT), and double layer capacitance (Cd), were used to fit experimental data. The calculated parameters of the simulated equivalent circuit were listed in Table S1. The calculated value of Rct on CTS/NPC/ITO electrode from the EIS measurements was 6780 Ω whereas Rct on CTS/NPC/ITO electrode with cathodic 4-NP deposits was 397 Ω. Such lower charge transfer resistance on CTS/NPC/ITO electrode revealed that the cathodic deposits of 4-NP possessed mixed ionic and electronic conductivity and hence acted as ion-to-electron transducers.49 According to the discussion above, the cathodic deposited layer of 4-NP could be successfully coated on CTS/NPC/ITO electrode by multiple cyclic voltammetry and the deposited layer showed reversible characteristics in the low potential range and also had

14


Page 15 of 38 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


high ionic-electronic conductivity. Moreover, the electron transfer rate for the redox reaction of cathodic 4-NP deposits was fast. Thus, it was reasonable to conclude that the redox current response on CTS/NPC/ITO electrode could easily be used to detect 4-NP with high sensitivity and selectivity. Electrochemical reaction mechanism of 4-NP on CTS/NPC/ITO The number of electrons involved in the electrochemical reaction of 4-NP was carried out in Fig. 4a and b. It was concluded that two electrons were involved in the reduction of 4-NP and one electron was involved in the redox process. In order to identify electrochemical reaction products of 4-NP, the reaction products extracted from the modified electrodes for 10 times were measured by FTIR spectra to examine the characteristic bands. As shown in Fig. S7, the FTIR spectra revealed C=O stretching vibration at 1638 cm-1, N=N stretching vibration at 1480 cm-1 and C-O-C vibration of aromatic series at 1312 cm-1, indicating that the reaction products of 4-NP contained the functional groups of C=O, N=N, C-O-C. Furthermore, the electrochemical reaction products of 4-NP, obtained by chloroform extraction from the CTS/NPC/ITO after CVs of 500 cycles in 0.4 mM 4-NP solution with potential scan range setting between 0.6 to -1.4 V was analyzed by LC-MS. As shown in Fig. 6a, 4-NP standard solution showed a peak at m/z 138. Compared with 4-NP standard solution, three new products with m/z values 276.9, 485.5 and 623.9 were found (Fig. 6b). According to the intensity of the three peaks, the substance with m/z value 485.5 (tetramer) was the main electrochemical reaction product. Based on LC-MS analysis, two electrons involved in 4-NP reduction and one electron involved in the redox process, the scheme for electrochemical reaction of 4-NP could be speculated and the proposed pathway was plotted as shown in Fig. 6c.

15



Firstly, along with the processes of two-electron transfer, the large reduction peak (I) was attributed to the reduction of 4-NP to the corresponding nitrosophenol or benzoquinone monoxime. The intermediate products immediately reacted with each other to form dimer with one benzoquinonyl through polymerization reaction and the process had no electron transfer. As the functional group O-N=N-O in dimer was a strong electron acceptor, the O-H bond of benzene ring was easy to be oxidized at the active site of the modified electrode to benzoquinonyl, which was a reversible reaction with one electron transfering. Finally, the dimer with double benzoquinonyl ((m/z= 276.9) can transform to tetramer (m/z = 485.5) because of the unstable functional group O-N=N-O.

Electrochemical determination of 4-NP on CTS/NPC/ITO electrode Fig. S8 showed a group of CVs, recorded in different concentrations of 4-NP solutions to develop a relationship between the current responses and the concentrations of 4-NP. Under the optimum conditions, the anodic peak current of peak III on the 5th CVs was linearly proportional to the concentration of 4-NP in the range of 0.05 to 0.4 mM (r2 = 0.99). The average response sensitivity of three replicates was 4.85 μA μM-1 with the relative standard deviation (RSD) of 4.6%. The limit of detection (LOD, S/N = 3) was estimated as 27.55 μM. Chronocoulometry method was also employed to directly detect 4-NP. The transient current as a function of time was recorded (Fig. S9). The chronocoulometric response to 4-NP concentration was linear in the concentration range from 0.02 to 0.1 mM (r2 = 0.99). The average response sensitivity of three replicates was 2.212 μC μM-1 with and RSD of 6.3%. The LOD (S/N = 3) was calculated as 30.10 μM.

16


Page 16 of 38

Page 17 of 38 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


Finally, DPV method was carried out using different concentrations of 4-NP solutions (Fig. 7). The ipc was linear with the concentration of 4-NP in the range of 0.002 to 0.4 mM. The response sensitivity of 4-NP was 0.118 μA μM-1 and the RSD was 3.8% (n = 3). The LOD (S/N = 3) was estimated as 5.44 μM. The comparison of three electrochemical detection methods was presented in Table S2. The DPV technique gave the best results in view of LOD (5.44 μM), linear response range (0.002 to 0.4 mM) and RSD (3.8%). However, in terms of the sensitivity, the cyclic voltammetry technique (4.85 μA μM-1) showed better result than the DPV technique (0.118 μA μM-1). Thus, selection parameters would determine which of the three methods may be applied to determine the concentration of 4-NP. Overall, results established successful fabrication of the CTS/NPC/ITO electrode to detect 4-NP. Furthermore, the analytical performance of the present CTS/NPC/ITO based sensor for 4-NP sensing was compared with those of other reported sensors in terms of linear range and LOD. As shown in Table S3, a well-linear range and LOD were attained without employing any nanomaterials or tedious electrode modification process to fabricate CTS/NPC/ITO-based sensor, demonstrating CTS/NPC/ITO could be a promising sensor electrode for electrochemical determination of 4-NP. Durability, stability and selectivity of CTS/NPC/ITO electrode The reproducibility of repeated electrodes was estimated by comparing the oxidation peak current of the cathodic deposit of 0.4 mM 4-NP. The RSD was 5.5% for ten repeated electrode preparations. Repetitive measurements for the same electrode were carried out in 0.4 mM 4-NP solution to evaluate the reusability of CTS/NPC/ITO electrode. Between the repeated measurements, the used electrode was washed by

17



dipping in acetone for 10 min to remove the reaction products of 4-NP, followed by thoroughly washing using ethanol and deionized water. Then CVs on the treated electrodes after first cycle to sixth cycle were performed in 50 mM NaCl solution as shown in Fig. S10. It was found that no peak signals were observed in CVs, suggesting that the reaction products of 4-NP were completely removed from CTS/NPC/ITO electrode. As shown in Fig. S11a, there was no significant decrease (6%) in the current response till seven repeated measurements, revealing a good reusability of CTS/NPC/ITO electrode. The long-term stability of CTS/NPC/ITO electrode was investigated by measuring the current response of 0.4 mM 4-NP among 40 days using DPV technique. As shown in Fig. S11b, during the first 20 days, the CTS/NPC/ITO electrode exhibited good stability and the current response maintained 95.1% of its original response. Afterward, 85.4% of the original current response retained after 40 days. Moreover, it was found that the morphology of CTS/NPC/ITO electrode was unchanged after 200 CV sweeps in the potential range between 0.6 to -1.4 V, according to the corresponding SEM images (Fig. S12). These results suggested that the CTS/NPC/ITO electrode displayed a relatively long-term stability. The selectivity of CTS/NPC/ITO on the determination of 4-NP was also studied (the detail was given in Text S2 and Table S4). It was concluded that the inorganic ions and organic compounds, which possibly present in real water samples, had no significant influence on the electrochemical response signals of 4-NP.

Real water samples detection The detection reliability of the fabricated electrode was examined by measuring 4-NP in Guangzhou Zhujiang River water and tap water with the standard addition

18


Page 18 of 38

Page 19 of 38 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


method. The contrast between the HPLC and our method (DPV) in water sample detection was investigated and the obtained results were shown in Table 1. The recoveries of this work were ranged from 94.6% to 102.4% which was in good accordance with the range obtained by the HPLC method. Each of the samples was measured for six times (RDS below 4%), and the average values were adopted, suggesting that CTS/NPC modified electrode was effective and feasible. Thus, the modified electrode can be successfully used for the determination of 4-NP in practical samples.

CONCLUSIONS We herein reported a facile, cost-effective approach to prepare nitrogen-doped hierarchical porous carbon (NPC) as electrochemical sensor materials. The as-obtained NPC material exhibited a unique hierarchical porous structure with abundant micro-/meso-/ macro-pores and high surface area (up to 1071 m2 g-1), favor to the performance of electrochemical sensor. The modified electrode, CTS/NPC/ITO exhibited a high sensitivity and selectivity towards 4-NP. The cathodic deposits layer of 4-NP on the modified electrode formed by multiple sweep voltammetry showed well-defined redox signals in the low potential range and had high ionic-electronic conductivity. Moreover, the electrochemical reaction kinetics and mechanism of 4-NP were explored by CVs, FTIR spectra and LC-MS. Under the optimized conditions of three electroanalytical methods, DPV technique had the widest linear range and lowest detection limit to detect 4-NP. The oxidation peak current in DPV method varied linearly in the range from 0.02-0.4 mM while the response sensitivity and detection limit were

19



0.118 µA µM-1 (RSD = 3.8%) and 5.44 µM (S/N = 3), respectively. Comparatively, CV technique had higher sensitivity to detect 4-NP than that of the DPV method. The anodic peak current in CV varied linearly in the range from 0.05-0.4 mM while the response sensitivity and detection limit were 4.85 µA µM-1 (RSD = 4.6%) and 27.55 µM (S/N = 3), respectively. The modified sensor was able to detect 4-NP in real water samples with good precision. The proposed sensor demonstrated several advantages including easy fabrication, high selectivity, good reproducibility, high stability and low cost.

ASSOCIATED CONTENT Supporting Information Additional details on texts showing experimental section and selectivity of CTS/NPC/ITO electrode, table showing fitting values based on equivalent circuit, tables highlighting the superior performance and high selectivity of CTS/NPC/ITO electrode toward 4-NP sensing, optical microscopy image of pomelo peel, Raman spectra of NPC, CVs and EIS on different electrodes, CVs at different scan rate, CVs with and without 4-NP, FTIR of 4-NP reaction products, 4-NP detection using CV and chronocoulometry methods, CVs on the treated CTS/NPC/ITO electrode after different cycles, repetitive measurements and long-term current response, SEM images of CTS/NPC/ITO electrode after 200 CV sweeps, DPV of 4-NP in the presence of interferents.

ACKNOWLEDGMENTS The authors wish to thank the National Natural Science Foundation of China (No. 51578556, 21876212, 21673086, 41603097), Natural Science Foundation of Guangdong

20


Page 20 of 38

Page 21 of 38 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


Province (No. 2015A030308005, S2013010012927, S2011010003416), Science and Technology Research Programs of Guangdong Province (No. 2014A020216009) for financially supporting this work.

REFERENCES (1) Yan, Z.; Fu, L.; Zuo, X.; Yang, H. Green assembly of stable and uniform silver nanoparticles on 2D silica nanosheets for catalytic reduction of 4-nitrophenol. Appl. Catal. B: Environ. 2018, 226, 23-30, DOI: 10.1016/j.apcatb.2017.12.040. (2) Sarkar, A. K.; Saha, A.; Midya, L.; Banerjee, C.; Mandre, N.; Panda, A. B.; Pal, S. Cross-linked biopolymer stabilized exfoliated titanate nanosheet-supported AgNPs: A green sustainable ternary nanocomposite hydrogel for catalytic and antimicrobial activity. ACS

Sustain.

Chem.

Eng.

2017,

5

(2),

1881-1891,

DOI:

10.1021/acssuschemeng.6b02594. (3) Subashchandrabose, S. R.; Venkateswarlu, K.; Krishnan, K.; Naidu, R.; Lockington, R.; Megharaj, M. Rhodococcus wratislaviensis strain 9: An efficient p-nitrophenol degrader with a great potential for bioremediation. J. Hazard. Mater. 2017, 347, 176-183, DOI: 10.1016/j.jhazmat.2017.12.063. (4) Luo, J.; Gao, Y.; Tan, K.; Wei, W.; Liu, X. Preparation of a magnetic molecularly imprinted graphene composite highly adsorbent for 4-nitrophenol in aqueous medium. ACS

Sustain.

Chem.

Eng.

2016,

4

10.1021/acssuschemeng.6b00367. 21


(6),

3316-3326,

DOI:


(5) Guo, X.; Zhao, F.; Liu, J.; Liu, Z.; Wang, Y. An ultrastable zinc(II)–organic framework as a recyclable multi-responsive luminescent sensor for Cr(III), Cr(VI) and 4-nitrophenol in the aqueous phase with high selectivity and sensitivity. J. Mater. Chem. A 2017, 5 (37), 20035-20043, DOI: 10.1039/c7ta05896a. (6) Li, J.; Kuang, D.; Feng, Y.; Zhang, F.; Xu, Z.; Liu, M. A graphene oxide-based electrochemical sensor for sensitive determination of 4-nitrophenol. J. Hazard. Mater. 2012, 201-202, 250-259, DOI: 10.1016/j.jhazmat.2011.11.076. (7) Mei, M.; Huang, X.; Yu, J.; Yuan, D. Sensitive monitoring of trace nitrophenols in water samples using multiple monolithic fiber solid phase microextraction and liquid chromatographic analysis. Talanta 2015, 134, 89-97, DOI: 10.1016/j.talanta.2014.10.059. (8) Zhang, M.; Chen, X.; Zhou, H.; Murugananthan, M.; Zhang, Y. Degradation of p-nitrophenol by heat and metal ions co-activated persulfate. Chem. Eng. J 2015, 264, 39-47, DOI: 10.1016/j.cej.2014.11.060. (9) Kumar, S.; Singh, S.; Srivastava, V. C. Electro-oxidation of nitrophenol by ruthenium oxide coated titanium electrode: Parametric, kinetic and mechanistic study. Chem. Eng. J. 2015, 263, 135-143, DOI: 10.1016/j.cej.2014.11.051. (10) Yu, J.; Wang, X.; Kang, Q.; Li, J.; Shen, D.; Chen, L. One-pot synthesis of a quantum dot-based molecular imprinting nanosensor for highly selective and sensitive fluorescence detection of 4-nitrophenol in environmental waters. Environ. Sci. Nano 2017, 4 (2), 493-502, DOI: 10.1039/c6en00395h. (11) Singh, S.; Kumar, N.; Kumar, M.; Jyoti; Agarwal, A.; Mizaikoff, B. Electrochemical 22


Page 22 of 38

Page 23 of 38 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


sensing and remediation of 4-nitrophenol using bio-synthesized copper oxide nanoparticles. Chem. Eng. J. 2017, 313, 283-292, DOI: 10.1016/j.cej.2016.12.049. (12) Khan, M.; Liu, X.; Zhu, J.; Ma, F.; Hu, W.; Liu, X. Electrochemical detection of tyramine with ITO/APTES/ErGO electrode and its application in real sample analysis. Biosens. Bioelectron. 2018, 108, 76-81, DOI: 10.10164/j.bios.2018.02.042. (13) Siara, L. R.; de Lima, F.; Cardoso, C. A. L.; Arruda, G. J. Electrochemically pretreated zeolite-modified carbon-paste electrodes for determination of linuron in an agricultural formulation and water. Electrochim. Acta 2015, 151, 609-618, DOI: 10.1016/j.electacta.2014.11.008. (14) Zhao, L.; Cai, Z.; Yao, Q.; Zhao, T.; Chen, X.; Lin, H.; Xiao, Y. Electropolymerization fabrication of three-dimensional N, P-co-doped carbon network as a flexible electrochemical dopamine sensor. Sensor Actuat. B Chem. 2017, 253, 1113-1119, DOI: 10.1016/j.snb.2017.06.111. (15) Hosseini, H.; Behbahani, M.; Mahyari, M.; Kazerooni, H.; Bagheri, A.; Shaabani, A. Ordered carbohydrate-derived porous carbons immobilized gold nanoparticles as a new electrode material for electrocatalytical oxidation and determination of nicotinamide adenine

dinucleotide.

Biosens.

Bioelectron.

2014,

59,

412-417,

DOI:

10.1016/j.bios.2014.02.046. (16) Zhou, G.; Kim, N. R.; Chun, S. E.; Lee, W.; Um, M. K.; Chou, T. W.; Islam, M. F.; Byun, J. H.; Oh, Y. Highly porous and easy shapeable poly-dopamine derived graphene-coated single walled carbon nanotube aerogels for stretchable wire-type 23



supercapacitors. Carbon 2018, 130, 137-144, DOI: 10.1016/j.carbon.2017.12.123. (17) Yang, Y.; Yang, X.; Yang, Y.; Yuan, Q. Aptamer-functionalized carbon nanomaterials electrochemical sensors for detecting cancer relevant biomolecules. Carbon 2018, 129, 380-395, DOI: 10.1016/j.carbon.2017.12.013. (18) Chen, J.; Mao, Z.; Zhang, L.; Tang, Y.; Wang, D.; Bie, L.; Fahlman, B. D. Direct production of nitrogen-doped porous carbon from urea via magnesiothermic reduction. Carbon 2018, 130, 41-47, DOI: 10.1016/j.carbon.2017.12.125. (19) Liang, Q.; Ye, L.; Huang, Z.; Xu, Q.; Bai, Y.; Kang, F.; Yang, Q. A honeycomb-like porous carbon derived from pomelo peel for use in high-performance supercapacitors. Nanoscale 2014, 6 (22), 13831-13837, DOI: 10.1039/c4nr04541f. (20) Yang, J.; Xu, W.; He, C.; Huang, Y.; Zhang, Z.; Wang, Y.; Hu, L.; Xia, D.; Shu, D. One-step synthesis of silicon carbide foams supported hierarchical porous sludge-derived activated carbon as efficient odor gas adsorbent. J. Hazard. Mater. 2018, 344, 33-41, DOI: 10.1016/j.jhazmat.2017.09.056. (21) Yuan, W.; Feng, Y.; Xie, A.; Zhang, X.; Huang, F.; Li, S.; Zhang, X.; Shen, Y. Nitrogen-doped nanoporous carbon derived from waste pomelo peel as a metal-free electrocatalyst for the oxygen reduction reaction. Nanoscale 2016, 8 (16), 8704-8711, DOI: 10.1039/c6nr00764c. (22) Fu, C.; Yi, D.; Deng, C.; Wang, X.; Zhang, W.; Tang, Y.; Caruso, F.; Wang, Y. A Partially Graphitic Mesoporous Carbon Membrane with Three-Dimensionally Networked Nanotunnels for Ultrasensitive Electrochemical Detection. Chem. Mater. 2017, 29 (12), 24


Page 24 of 38

Page 25 of 38 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


5286-5293, DOI: 10.1021/acs.chemmater.7b01423. (23) Silva, T. A.; Zanin, H.; May, P. W.; Corat, E. J.; Fatibello-Filho, O. Electrochemical performance of porous diamond-like carbon electrodes for sensing hormones, neurotransmitters, and endocrine disruptors. ACS Appl. Mater. Interfaces 2014, 6 (23), 21086-21092, DOI: 10.1021/am505928j. (24) Gao, W.; Feng, X.; Zhang, T.; Huang, H.; Li, J.; Song, W. One-step pyrolytic synthesis of nitrogen and sulfur dual-doped porous carbon with high catalytic activity and good accessibility to small biomolecules. ACS Appl. Mater. Interfaces 2014, 6 (21), 19109-19117, DOI: 10.1021/am505080r. (25) Ying, J.; Li, J.; Jiang, G.; Cano, Z. P.; Ma, Z.; Zhong, C.; Su, D.; Chen, Z. Metal-organic

frameworks

derived

platinum-cobalt

bimetallic

nanoparticles

in

nitrogen-doped hollow porous carbon capsules as a highly active and durable catalyst for oxygen reduction reaction. Appl. Catal. B: Environ. 2018, 225, 496-503, DOI: 10.1016/j.apcatb.2017.11.077. (26) Rajkumar, C.; Veerakumar, P.; Chen, S. M.; Thirumalraj, B.; Liu, S. B. Facile and novel synthesis of palladium nanoparticles supported on a carbon aerogel for ultrasensitive electrochemical sensing of biomolecules. Nanoscale 2017, 9 (19), 6486-6496, DOI: 10.1039/c7nr00967d. (27) Liu, X.; Liu, X.; Sun, B.; Zhou, H.; Fu, A.; Wang, Y.; Guo, Y. G.; Guo, P.; Li, H. Carbon materials with hierarchical porosity: Effect of template removal strategy and study on their electrochemical properties. Carbon 2018, 130, 680-691, DOI: 25



10.1016/j.carbon.2018.01.046. (28) Li, S.; Zhang, X.; Huang, Y. Zeolitic imidazolate framework-8 derived nanoporous carbon as an effective and recyclable adsorbent for removal of ciprofloxacin antibiotics from water. J. Hazard. Mater. 2017, 321, 711-719, DOI: 10.1016/j.jhazmat.2016.09.065. (29) Hu, Z.; Shen, Z.; Yu, J. C. Converting carbohydrates to carbon-based photocatalysts for environmental treatment. Environ. Sci. Technol. 2017, 51 (12), 7076-7083, DOI: 10.1021/acs.est.7b00118. (30) Qu, G.; Jia, S.; Wang, H.; Cao, F.; Li, L.; Qing, C.; Sun, D.; Wang, B.; Tang, Y.; Wang, J. Asymmetric supercapacitor based on porous N-doped carbon derived from pomelo peel and NiO arrays. ACS Appl. Mater. Interfaces 2016, 8 (32), 20822-20830, DOI: 10.1021/acsami.6b06630. (31) Hong, K.; Qie, L.; Zeng, R.; Yi, Z.; Zhang, W.; Wang, D.; Yin, W.; Wu, C.; Fan, Q.; Zhang, W.; Huang, Y. Biomass derived hard carbon used as a high performance anode material for sodium ion batteries. J. Mater. Chem. A 2014, 2 (32), 12733-12738, DOI: 10.1039/c4ta02068e. (32) Cui, L.; Wu, J.; Ju, H. Nitrogen-doped porous carbon derived from metal-organic gel for electrochemical analysis of heavy-metal ion. ACS Appl. Mater. Interfaces 2014, 6 (18), 16210-16216, DOI: 10.1021/am504367t. (33) Li, S.; Wang, L.; Zhang, X.; Chai, H.; Huang, Y. A Co, N co-doped hierarchically porous carbon hybrid as a highly efficient oxidase mimetic for glutathione detection. Sensor Actuat. B Chem. 2018, 264, 312-319, DOI: 10.1016/j.snb.2018.03.015. 26


Page 26 of 38

Page 27 of 38 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


(34) Chen, Q.; Liang, C.; Zhang, X.; Huang, Y. High oxidase-mimic activity of Fe nanoparticles embedded in an N-rich porous carbon and their application for sensing of dopamine. Talanta 2018, 182, 476-483, DOI: 10.1016/j.talanta.2018.02.032. (35) Xiao, K.; Ding, L.-X.; Chen, H.; Wang, S.; Lu, X.; Wang, H. Nitrogen-doped porous carbon derived from residuary shaddock peel: a promising and sustainable anode for high energy density asymmetric supercapacitors. J. Mater. Chem. A 2016, 4 (2), 372-378, DOI: 10.1039/c5ta08591h. (36) Travlou, N. A.; Bandosz, T. J. N-doped polymeric resin-derived porous carbons as efficient ammonia removal and detection media. Carbon 2017, 117, 228-239, DOI: 10.1016/j.carbon.2017.02.099. (37) Hao, J.; Huang, Y.; He, C.; Xu, W.; Yuan, L.; Shu, D.; Song, X. ； Meng, T. Bio-templated fabrication of three-dimensional network activated carbons derived from mycelium pellets for supercapacitor applications. Sci. Rep. 2018, 8, 562, DOI: 10.1038/s41598-017-18895-6. (38) Li, J.; Bai, H.; Li, X.; Li, W.; Zhai, J.; Li, M.; Xi, G. Hierarchical porous carbon microspheres with superhydrophilic surface for efficient adsorption and detection of water-soluble contaminants. J. Mater. Chem. A 2018, 6 (25), 12153-12161, DOI: 10.1039/c8ta02143k. (39) Thakur, V. K.; Thakur, M. K. Recent Advances in Graft Copolymerization and Applications of Chitosan: A Review. ACS Sustain. Chem. Eng. 2014, 2 (12), 2637-2652, DOI: 10.1021/sc500634p. 27



Page 28 of 38

(40) Zanini, V. I. P.; Giménez, R. E.; Pérez, O. E. L.; Mishima, B. A. L. D.; Borsarelli, C. D. Enhancement of amperometric response to tryptophan by proton relay effect of chitosan adsorbed on glassy carbon electrode. Sensor Actuat. B Chem. 2015, 209, 391-398, DOI: 10.1016/j.snb.2014.11.087. (41) Hei, Y.; Li, X.; Zhou, X.; Liu, J.; Sun, M.; Sha, T.; Xu, C.; Xue, W.; Bo, X.; Zhou, M.

Electrochemical

meso-macroporous

sensing

carbons.

platform Anal.

Chim.

based

on

Acta.

kelp-derived

2017,

1003,

hierarchical 16-25,

DOI:

10.1016/j.aca.2017.12.007. (42) Shi, J.; Zhou, X.; Xu, P.; Qiao, J.; Chen, Z.; Liu, Y. Nitrogen and sulfur Co-doped mesoporous carbon materials as highly efficient electrocatalysts for oxygen reduction reaction. Electrochim. Acta 2014, 145, 259-269, DOI: 10.10 16/j.electacta.2014.08.091. (43) Libansky, M.; Zima, J.; Barek, J.; Reznickova, A.; Svorcik, V.; Dejmkova, H. Basic electrochemical properties of sputtered gold film electrodes. Electrochim. Acta 2017, 251, 452-460, DOI: 10.1016/j.electacta.2017.08.048. (44) Saraf M.; Natarajan, K.; Mobin, S. M. Robust nanocomposite of nitrogen-doped reduced graphene oxide and MnO2 nanorods for high-performance supercapacitors and nonenzymatic peroxide sensors. ACS Sustain. Chem. Eng. 2018, 6 (8), 10489-10504, DOI: 10.1021/acssuschemeng.8b01845. (45) Deng, P.; Xu, Z.; Feng, Y.; Li, J. Electrocatalytic reduction and determination of p-nirophenol on acetylene black paste electrode coated with salicylaldehyde-modified chitosan. Sensor Actuat. B Chem. 2012, 168, 381-389, DOI: 10.1016/j.snb.2012.04.041. 28


Page 29 of 38 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


(46) Eguílaz, M.; Villalonga, R.; Rivas, G. Electrochemical biointerfaces based on carbon nanotubes-mesoporous silica hybrid material: bioelectrocatalysis of hemoglobin and biosensing

appication.

Biosens.

Bioelectron.

2018,

111,

144-151,

DOI:

10.1016/j.bios.2018.04.004. (47) Ciszewski, A.; Sron, K.; Stepniak, I.; Milczarek, G. Nickel (II) lignosulfonate as precursor for the deposition of nickel hydroxide nanoparticles on a glassy carbon electrode for oxidative electrocatalysis. Electrochim. Acta 2014, 134, 355-362, DOI: 10.1016/j.electacta.2014.04.152. (48) Nazarov, B.; Larionova, E.; Stromberg, A.; Antipenko, I. Theory of the reversible electrode process in case of cyclic voltammetry at finite thickness film electrode. Electrochem. Commun. 2007, 9 (8), 1936-1944, DOI: 10.1016/j.elecom.2007.04.014. (49) El-Rahman, M. K. A.; Rezk, M. R.; Mahmoud, A. M.; Elghobashy, M. R. Design of a stable solid-contact ion-selective electrode based on polyaniline nanoparticles as ion-to-electron transducer for application in process analytical technology as a real-time analyzer. Sensor Actuat. B Chem. 2015, 208, 14-21, DOI: 10.1016/j.snb.2014.11.009.

29



Page 30 of 38

Table 1. Determination results of 4-NP in water samples and recovery value.

Samples

Add. (μM)

This method Detection

Recovery

(μM)

HPLC method RSD Detection Recovery

RSD

(%)

(%)

(μM)

(%)

(%)

River water 1

40

37.8

94.6

3.25

38.7

96.75

3.51

River water 2

60

58.4

97.3

2.30

61.1

101.8

3.02

River water 3

120

122.9

102.4

2.75

121.8

101.5

2.36

Tap water 1

40

38.6

96.5

3.75

39.2

98.0

3.59

Tap water 2

60

59.3

98.9

2.83

59.6

99.3

3.25

Tap water 3

120

120.8

100.7

2.08

120.5

100.4

3.15

30


Page 31 of 38

(a)

(d)

(c) Intensity (a.u.)

(b)

100 nm 0

(e)

(f)

10

20

30

40

Intensity (a.u.)

dV/dlog(D) (cm 3 /g )

1.5 1.2

200

0.9 0.6

100

C-N (285.4) C-O (286.2) O-C=O (289.1)

0.3

60

70

80

90

(g)

C-C (284.7)

Pyrrolic-N (400.3)

Pyridinic-N (398.6)

300

50

2θ (degree)

Graphitic-N (401.3)

Intensity (a.u.)

400

Volume Adsorbed (cm3/g)

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


N-Oxide (404.4)

0.0

0

0

0.0

0.2

0.4

20 40 60 80 100 Pore Diameter (nm)

0.6

0.8

Relative Pressure (P/P0)

1.0

280

282

284

286

288

290

Binding energy (eV)

292

394

396

398

400

402

404

Binding energy (eV)

406

408

Fig. 1. (a) Schematic for preparation procedure of CTS/NPC/ITO; (b) SEM image, (c) TEM image, (d) XRD pattern, (e) N2 adsorption-desorption isotherms, (f) high-resolution C1s XPS spectrum and (g) high-resolution N 1s XPS spectrum of as-prepared NPC material.

31



CTS/NPC/ITO

(b)

ITO

100

0

Current (A)

Current (A)

200

(a)

75

-75 ITO PC/ITO CTS/PC/ITO CTS/NPC/ITO

-150

0

-100

-225 -1.5

1000

-0.5

0.0

0.5

Potential (V)

1.0

0.0

(c)

900

1000

600 300 0.2

0

0.4

v1/2

0.6

(1)

500

0.2

0.4

(d)

1200 900 600 300

0.2

0.4

v1/2

0.6

0 (1)

-500

-500

0.6

Potential (V)

1500

1500

Current (A)

Ip.a (A

500

-1.0

Ip.a (A)

-2.0

Current (A)

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

Page 32 of 38

-1000 (7)

(7) -0.2

0.0

0.2

0.4

Potential (V)

-1500

0.6

-0.2

0.0

0.2

Potential (V)

0.4

0.6

Fig. 2. (a) CVs for ITO, PC/ITO, CTS/PC/ITO and CTS/NPC/ITO in 0.4 mM 4-NP /50 mM

NaCl

solution;

(b)

CVs

for

ITO

and

CTS/NPC/ITO

in

0.05

mM

K3[Fe(CN)6]/K4[Fe(CN)6]; (c) CVs for ITO and (d) CVs for CTS/NPC/ITO electrode in 0.05 mM K3[Fe(CN)6]/K4[Fe(CN)6] at different scan rate (v = 0.02-0.4 V s −1) ( The inset indicated the relation of anodic peak current with the square root of scan rate).

32


Page 33 of 38

200

(a)

III

Current (A)

0 1

II

-200 10 -400

I

10

1

-600 -1.5

-1.0

-0.5

0.0

0.5

Potential (V)

100

III

1.0

(b)

Current (A)

0 II

1

-100 10 -200 -300 -1.5

-1.0

-0.5

0.0

Potential (V)

0.5

1.0

(c)

100

Current (A)

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


0

-100

-200 -1.0

-0.5

0.0

0.5

1.0

Potential (V)

Fig. 3. CVs for CTS/NPC/ITO electrode in 0.4 mM 4-NP/50 mM NaCl solution at different scan potential range of (a) -1.4 to 0.6 V, (b) -1.2 to 0.6 V and (c) -0.8 to 0.6 V (v = 0.1 V s−1).

33



400

(a)

Ep.c (V)

-0.9 -1.0

III

-1.1

Current (A)

-4

-3

0

-2

lnv

-200

-1

II

(1)

120

-400 I -600 -1.5

160

Ip.c (A )

200

80 40

0.2

(7)

-1.0

-0.5

0.0

Potential (V)

0.4

0.6

v1/2 0.5

1.0

300

(b)

Ep.a (V)

0.00

200 100

-0.05

III

-0.10 -4

-3

-2 lnv

-1

0 1

-100

60

Ip.a (A)

Current (A)

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

Page 34 of 38

40

-200

5

II

20 0.0

-300 -0.8

-0.6

-0.4

-0.2

0.0

0.2

Potential (V)

0.1

0.2 -1

v (Vs )

0.4

0.6

0.3

0.8

Fig. 4. (a) CVs of 4-NP and (b) CVs of cathodic deposits of 4-NP on CTS/NPC/ITO electrode at different scan rate (v = 0.02-0.4 V s − 1) ( The insets are the relation of peak currents and peak potentials with scan rate).

34


Page 35 of 38

30

20

-Z'' (kW)

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


10 CTS/NPC/ITO with cathodic 4-NP deposits CTS/NPC/ITO

0

0

5

10

15

Z' (kW)

20

25

30

Fig. 5. EIS Nyquist plots of CTS/NPC/ITO electrode and CTS/NPC/ITO electrode with cathodic 4-NP deposits in 50 mM NaCl under open circuit conditions.

35



100

138

80 60 40 20 0

485.5

100

(a)

Relative abundance

Relative abundance

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

Page 36 of 38

80 100 120 140 160 180 200 220 240 260

m/z

(b)

80 623.9

60 40 20 138.3 0

100

276.9

200

300

400

500

600

700

800

m/z

(c)

Fig. 6. LC-MS spectra of (a) 4-NP and (b) the reaction products extracted from the modified electrodes for 10 times; (c) Reaction process of 4-NP on CTS/NPC/ITO.

36


Page 37 of 38

200

10

175 150 60

1

50

125 100

I p.a (A )

Current (A)

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


40 30 20 10 0

-0.5

0

100

-0.4

200 300 C4-NP (µM)

-0.3

400

-0.2

-0.1

0.0

0.1

0.2

Potential (V)

Fig. 7. DPV for CTS/NPC/ITO electrode under different 4-NP concentration. The insert is the relation of anodic peak current with 4-NP concentration.

37



TOC art

Converting waste natural biomass into porous carbon and developing a fast and sensitive sensor to detect 4-nitrophenol is a sustainable technology.

38


Page 38 of 38

Carbohydrates-Derived Nitrogen-Doped Hierarchical Porous Carbon

Recommend Documents