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Co-reactant free novel self-enhanced solid-state ECL platform of polyluminol-gold nanocomposite for highly selective and sensitive signal-on detection of Hg2+ ion
Chikkili Venkateswara Raju1,2 and Shanmugam Senthil Kumar1,2*
1Electrodics and Electro Catalysis Division, CSIR-Central Electrochemical Research Institute (CECRI), Karaikudi - 630 003, Tamilnadu, India.
2Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, Uttar Pradesh, India.
*Corresponding author
HYPERLINK "mailto:ssenthilmugam@gmail.com"ssenthilmugam@gmail.com; HYPERLINK "mailto:ssenthilkumar@cecri.res.in" ssenthilkumar@cecri.res.in
Fig. S1. Repetitive CVs of 1.5 mM HAuCl4 (A) in 0.5 M H2SO4 at the scan rate of 0.1 V/s. CV of AuNPs/GCE (B) in 0.5 M H2SO4 at a scan rate of 0.1 V/s.
Fig. S2. CV of PL/GCE (A) and (PL-Au)nano/GCE (B) in 0.5 M H2SO4 at the scan rate of 0.1 V/s.
Fig. S3. Cyclic voltammogram of (PL-Au)nano/GCE in 0.5 M H2SO4 at the scan rate of 0.1 V/s.
Table S1. Current density (j) and Charge (Q) of PL/GCE and (PL-Au)nano/GCE comparison table.
Composite j/mA.cm-2
oxidation reduction Charge (Q) in C
oxidation reductionPL/GCE
(PL-Au)nano/GCE 0.044 0.05
0.13 0.19 25 29
127 131
1. XPS analysis
The XPS survey spectrum of (PL-Au)nano/GCE was shown in Fig. S4, which shows the presence of Au, C, O and N elements, evidencing the existence of luminol along with the gold. Fig. S5 shows the high resolution XPS spectrum of (PL-Au)nano/GCE composite before (Fig. S5A,B) and after etching (Fig. S5C,D) of composite film. The Au binding energies were obtained at 83.78 eV and 87.48 eV (Fig. 1E,F) which corresponds to the 4f7/2 and 4f5/2 respectively ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1021/acssuschemeng.8b00503","ISSN":"2168-0485","abstract":"An eco-friendly and economic efficient approach has been developed for the photoinduced synthesis of more stable AuNPs using an aqueous extract of Croton bonplandianum (AEC) as a reducing and capping agent. The reaction mixture of AEC and HAuCl4.xH2O, when exposed to sunlight turned purple which primarily confirmed the biosynthesis of AuNPs. The biosynthesis was monitored using UV-vis spectroscopy which exhibited a sharp SPR band at 530 nm after 16 min of sunlight exposure. The parameters affecting the synthesis of AuNPs such as sunlight exposure, AEC inoculum dose, and HAuCl4.xH2O concentration were also optimized. The HR-TEM study revealed that, as the metal ion concentrations increased, the average size and anisotropic nature of the AuNPs increased. The X-ray diffraction pattern of AuNPs synthesized confirmed the formation of face-centered cubic crystal lattice of metallic gold. The involvement of polyphenolics in the synthesis of AuNPs was confirmed by comparing the FTIR analysis of pure tannic acid, AEC, and pre- and postannealed AuNPs. The XPS analysis corroborated the presence of two individual peaks attributed to the Au 4f7/2 and Au 4f5/2 binding energies which corresponded to the presence of metallic gold. The AuNPs thus obtained showed peroxidase-like mimicking activity which catalyzed the oxidation of TMB to oxTMB with the development of blue color and absorption spectra at 652 nm. However, the presence of GSH caused further reduction of oxTMB. This detection experiment showed an excellent l i n e a r r e l a t i o n s h i p b e t w e e n 1 a n d 4 0 M w i t h a l i m i t o f d e t e c t i o n o f 0 . 0 1 3 M . I n a d d i t i o n t o t h i s , t h e s i g n i f i c a n t r e c o v e r y o f G S H f r o m h u m a n b l o o d s e r u m a d v o c a t e d t h a t t h e d e v e l o p e d s y s t e m w a s s i m p l e a n d s e n s i t i v e f o r t h e r e a l s a m p l e a n a l y s i s . " , " a u t h o r " : [{"dropping-particle":"","family":"Kumar","given":"Vijay","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Bano","given":"Daraksha","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Singh","given":"Devendra Kumar","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Mohan","given":"Sweta","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Singh","given":"Vikas Kumar","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Hasan","given":"Syed Hadi","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"ACS Sustainable Chemistry & Engineering","genre":"research-article","id":"ITEM-1","issue":"6","issued":{"date-parts":[["2018","6","4"]]},"page":"7662-7675","publisher":"American Chemical Society","title":"Size-Dependent Synthesis of Gold Nanoparticles and Their Peroxidase-Like Activity for the Colorimetric Detection of Glutathione from Human Blood Serum","type":"article-journal","volume":"6"},"uris":["http://www.mendeley.com/documents/?uuid=57768df2-5c77-4f4d-a291-caedc9817a55"]}],"mendeley":{"formattedCitation":"1","plainTextFormattedCitation":"1","previouslyFormattedCitation":"1"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}1. We observed two peaks for O1s at 532.1 eV and 532.9 eV (Fig. S5A) which are related to C=O and C-O-C binding energies. The N1s spectrum (Fig. S5B) also shows two peaks at 399.1 eV and 400.2 eV respectively. These peaks are due to the presence of amide nitrogen and benzenoid nitrogen respectively ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1088/2053-1591/3/9/095020","ISSN":"2053-1591","abstract":"Heteroatom doped carbon dots (CDs) possess many unique properties and have attracted increasing attention. The precursor is vital for the preparation of highly fluorescent heteroatom doped CDs. Herein, 1, 3-bis(carboxymethyl)imidazolium chloride ([Im(AH)2]Cl, a COOH-functional ionic liquid) and aminoethylethanolamine (AEEA) were firstly used as precursors to prepare nitrogendoped carbon dots (N-CDs) by a simple one-step pyrolysis approach. The effects of reaction time, temperature, and mass ratio of precursors on the quantum yield (QY) of N-CDs were investigated. The prepared N-CDs are spherical morphology with an average diameter of 2.4 nm, and have blue fluorescence with aQY of 23.2% and excitation-dependent emission behavior. They also possess good water solubility and fluorescent stability. In addition, based on the obtained N-CDs, a sensing method of free chlorine detection in acidic water system was introduced. The proposed method has good sensitivity and selectivity to free chlorine, and exhibits a nice linear response in the concentration range from 0.2 to 22 Mwith a detection limit of 0.15M. Furthermore, this sensing method was successfully applied to detect free chlorine of tap water with satisfactory recovery (97%-103%), suggesting it has the potential application in water quality monitoring.","author":[{"dropping-particle":"","family":"Wang","given":"Congyue","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wang","given":"Chunfeng","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sun","given":"Dong","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Li","given":"Aoqi","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Chen","given":"Yujuan","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Zhuo","given":"Kelei","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Materials Research Express","id":"ITEM-1","issue":"9","issued":{"date-parts":[["2016","9","16"]]},"page":"095020","publisher":"IOP Publishing","title":"Facile synthesis of nitrogen-doped carbon dots from COOH-functional ionic liquid and their sensing application in selective detection of free chlorine","type":"article-journal","volume":"3"},"uris":["http://www.mendeley.com/documents/?uuid=fbcdb966-2562-4b9d-8af1-fec6dac3ff95"]},{"id":"ITEM-2","itemData":{"DOI":"10.1016/j.electacta.2018.01.165","ISBN":"9881045770","ISSN":"00134686","abstract":"A method is described to form robust composite supercapacitor electrodes consisting of polyaniline (PANI)-graphene (GNS) and PANI-MoS2 nanosheets wherein composites are formed by Layer by Layer (LbL) deposition. PANI layer consisting of 1015 nm particle size was formed by LLIRT, while GNS and MoS2 layers were formed by modified LLIRT. A special feature of the development is the architecture which is rarely found in the literature wherein singular components are stacked over each other to form a composite. The architecture is found to show strong synergistic effects suitable for high performance supercapacitor applications. The composites were characterized by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) etc. The characterization indicates the formation of composites having uniform distribution of PANI nanoparticles over the 2D nanosheets of GNS and MoS2 respectively. The electrochemical performance of the composites was evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Galvanostatic Charge Discharge (GCD). The composite layer consisting of PANI-GNS alternate layers, showed an excellent specific capacitance (Csp) of 549 F g-1 while PANI-MoS2 alternate layers and PANI layers showed Csp to be (413 F g-1) and (185 F g-1) respectively. It is proposed that Csp stability of the composites is greatly enhanced by the architecture of composite formation through LbL deposition approach. PANI-GNS showed high stability (95% retention of Csp), PANI-MoS2 (94% retention of Csp) as against single component capacitance of PANI (67% retention of Csp). The results reveal the importance of the architecture of composite formation. The architecture of depositing alternate layers of components to form a composite would have special properties leading to synergistic effect in the applications. The present communication is a proof of this concept. It shows the boost in the charge storage resulting in stable robust supercapacitors formation. We predict similar advantages in other applications such as solar energy conversion, sensors, catalysis, etc.","author":[{"dropping-particle":"","family":"Patil","given":"Sagar H.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Gaikwad","given":"Aarti P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Sathaye","given":"Shivaram D.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Patil","given":"Kashinath R.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Electrochimica Acta","id":"ITEM-2","issued":{"date-parts":[["2018","3"]]},"page":"556-568","publisher":"Elsevier Ltd","title":"To form layer by layer composite film in view of its application as supercapacitor electrode by exploiting the techniques of thin films formation just around the corner","type":"article-journal","volume":"265"},"uris":["http://www.mendeley.com/documents/?uuid=98366d59-683c-475d-9bed-39d5322d6e0b"]}],"mendeley":{"formattedCitation":"2,3","plainTextFormattedCitation":"2,3","previouslyFormattedCitation":"2,3"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}2,3. The binding energies of O and N spectrum shows similar before and after etching but the peak intensities were changed. The peak intensities of N 1s and O 1s were decreased after the etching (Fig. S5 C, D). The EDX spectrum of PL/GCE shows carbon, nitrogen, oxygen elements which indicates the presence of lumiol, whereas (PL-Au)nano/GCE (Fig. S6A,B) clearly shows the Au atom along with luminol. In AFM, we observed trace of flakes like structure for PL/GCE. A well defined nano-spheres with uniform size and shape particles were observed for (PL-Au)nano/GCE (Fig. S6 C,D). The fine nano structure of (PL-Au)nano/GCE composite is due to the presence of gold atoms.
Fig. S4. XPS survey spectrum of (PL-Au)nano/GCE composite.
Fig. S5. XPS spectrum of O(1s) and N(1s) of (PL-Au)nano/GCE before etching (A,B) and after etching (C,D) respectively.
Fig. S6. EDX of PL/GCE (A), (PL-Au)nano/GCE(B), AFM images of PL/GCE (C) and (PL-Au)nano/GCE (D).
Fig. S7. Electrochemical impedance studies of GCE, PL/GCE and (PL-Au)nano/GCE in 1 mM Ferricyanide containing 0.1 M PBS. Inset is EIS circuit diagram.
Fig. S8. Repetitive CVs of 1 mM luminol+1.5 mM PtCl42- (A) and 1 mM luminol+1.5 mM AgNO3 (B) in 0.5 M H2SO4. Cyclic voltammograms (B) and its corresponding ECL signals (D) of (PL-Pt)nano/GCE (a), (PL-Ag)nano/GCE (b) in 0.1 M PBS (pH 7.4) at a scan rate of 0.1 V/s.
2. Concentration effect of luminol and HAuCl4.3H2O
We deposited (PL-Au)nano on GCE surface by changing the luminol and HAuCl4.3H2O concentrations and effectively studied the ECL experiments. Initially by taking 1 mM luminol as constant we changed the HAuCl4.3H2O concentrations from 0.125 to 2 mM during the deposition (PL-Au)nano/GCE composite.
Fig. S9. Cyclic voltammograms (A) of (PL-Au)nano/GCE after 20 cycles in 0.5 M H2SO4 after composite formation in 0.5 M H2SO4 + 0.125 (a), 0.25 (b), 0.375 (c), 0.5 (d), 1 (e), 1.5 (f) and 2 mM (g) HAuCl4 at a scan rate of 0.1 V/s, (B) corresponding calibration curve, (C) Corresponding ECL responses of (PL-Au)nano/GCE in 0.1 M PBS (pH 7.4) and (D) ECL calibration curve.
Fig. S9A indicates the CV of (PL-Au)nano/GCE in 0.5 M H2SO4 at 0.1 V/s at various HAuCl4.3H2O concentrations from 0.125 to 2 mM (Fig. S10A (a-g)), which is used during the deposition of composite. We find that the oxidation and reduction current of (PL-Au)nano/GCE increases and attains a limiting value of 1.5 mM of HAuCl4.3H2O, after that there is no change in current even at 2 mM. The derivative plot of concentration versus peak current shows in Fig. S9B. Fig. S9C is corresponding ECL signals of (PL-Au)nano/GCE in O2-saturated 0.1 M PBS (pH 7.4). As like CV, observed ECL intensity of (PL-Au)nano/GCE (Fig. S9C (a-g)) also increases and reaches maximum when HAuCl4.3H2O is 1.5 mM. The derivative plot for ECL intensity vs. concentration plot was shown in Fig. S9D. Further by keeping 1.5 mM HAuCl4.3H2O as constant we changed the luminol concentration (Fig. S10A) from 1 to 3 mM, which can be used during the cycling, and its corresponding ECL curves (Fig. S10B) in O2 saturated 0.1 M PBS (pH 7.4). This result reveals that there is no more change of peak current in CV and ECL signals were observed by changing luminol concentration during cycling in 0.5 M H2SO4 at 0.1 V/s.
Fig. S10. (A) Cyclic voltammograms of (PL-Au)nano/GCE in 0.5 M H2SO4 after 20 cycles in 1.5 mM HAuCl4 + 1 mM luminol, 1.5 mM HAuCl4 + 2 mM luminol and 1.5 mM HAuCl4 + 3 mM luminol at a scan rate of 0.1 V/s. (B) corresponding ECL in 0.1 M PBS (pH 7.4).
Fig. S11. ECL response (A) of (PL-Au)nano/GCE at various Hg2+ concentrations 0, 10, 30, 50, 70, 90, 110, 130 and 150 nM, its calibration curve (B) in O2 saturated 0.1 M PBS (pH7.4) at 0.1 V/s.
Fig. S12. ECL signals of PL/GCE at various Hg2+ concentration 0 to 20 nM in 0.1 M PBS (pH 7.4).
Fig. S13. The linear plot between Hg2+ concentration and absorbance obtained from AAS.
Table S2. Hg2+ ion detection and recovery (%) in tap water and serum samples by using AAS technique.
SampleConcentration
Spiked (nM) found (nM)Recovery (% n=3)
Tap water
Serum
30 28.8
50 48.8
30 30.2
50 50.2
96
97.6
100.6
100.4
3. References
ADDIN Mendeley Bibliography CSL_BIBLIOGRAPHY 1. Kumar, V. et al. Size-Dependent Synthesis of Gold Nanoparticles and Their Peroxidase-Like Activity for the Colorimetric Detection of Glutathione from Human Blood Serum. ACS Sustain Chem Eng 6, 76627675 (2018).
2. Wang, C. et al. Facile synthesis of nitrogen-doped carbon dots from COOH-functional ionic liquid and their sensing application in selective detection of free chlorine. Mater. Res. Express 3, 095020 (2016).
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