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. 2022 Dec 24;186:108329. doi: 10.1016/j.microc.2022.108329

One-step synthesis of triethanolamine-capped Pt nanoparticle for colorimetric and electrochemiluminescent immunoassay of SARS-CoV spike proteins

Xiaolan Yang a, Xiangyu Li a, Qingguo He a, Yanbin Ding b, Bin Luo a, Qiuju Xie a, Jiahao Chen a, Yue Hu c, Zhaohong Su a, Xiaoli Qin a,⁎
PMCID: PMC9789547  PMID: 36590823

Graphical abstract

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Keywords: Platinum nanoparticles, Triethanolamine, Colorimetry, Electrochemiluminescence, Immunoassay

Abstract

Platinum nanoparticles (PtNPs) have been attracted worldwide attention due to their versatile application potentials, especially in the catalyst and sensing fields. Herein, a facile synthetic method of triethanolamine (TEOA)-capped PtNPs (TEOA@PtNP) for electrochemiluminescent (ECL) and colorimetric immunoassay of SARS-CoV spike proteins (SARS-CoV S-protein, a target detection model) is developed. Monodisperse PtNPs with an average diameter of 2.2 nm are prepared by a one-step hydrothermal synthesis method using TEOA as a green reductant and stabilizer. TEOA@PtNPs can be used as a nanocarrier to combine with antigen by the high-affinity antibody, which leads to a remarkable inhibition of electron transfer efficiency and mass transfer processes. On the basis of its peroxidase-like activity and easy-biolabeling property, the TEOA@PtNP can be used to establish a colorimetric immunosensor of SARS-CoV S-protein thought catalyzing the reaction of H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB). Especially, the Ru(bpy)32+ ECL reaction is well-achieved with the TEOA@PtNPs due to their great conductivity and loading abundant TEOA co-reactants, resulting in an enhancing ECL signal in immunoassay of SARS-CoV S-protein. As a consequence, two proposed methods could achieve sensitive detection of SARS-CoV S-protein in wide ranges, the colorimetric and ECL detection limits were as low as 8.9 fg /mL and 4.2 fg /mL (S/N = 3), respectively. We believe that the proposed colorimetric and ECL immunosesors with high sensitivity, good reproducibility, and good stability will be a promising candidate for a broad spectrum of applications.

1. Introduction

Coronaviruses, as a large family of RNA viruses, can infect many mammalian and avian species, including human, which generally induce mild infection in humans [1], [2]. But the novel human coronaviruses, such as severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2, can cause intense respiratory illness and death [3], [4]. For example, SARS-CoV-2, a sister virus of SARS-CoV, gives rise to the new coronavirus disease 2019 (COVID-19), has caused over 5 million deaths and infected more than 400 million people until now [5], [6]. Short of the effective treatment, the convenient, rapid and sensitive detection methods for early diagnosis to control pandemic are of great importance [7], [8], [9]. Real-time polymerase chain reaction (RT-PCR) test, as a current standard method for SARS-CoV or SARS-CoV-2 diagnosis, is widely used in most medical centers because of its high specificity and precision [10]. Although RT-PCR is considered as a reliable detection method, it requires laboratory infrastructure and expensive instrumentation to complete the tests [11]. Therefore, developing the rapid, convenient and sensitive diagnostic tests for pandemic are urgently needed.

Medical diagnosis of early form of disease relies on the effective quantitative detection of patient biomarkers, so various testing technologies, such as enzyme-linked immunosorbent assay (ELISA) [12], [13], surface plasmon resonance (SPR) [14], [15] and fluorescence analysis [16], have been widely employed in disease diagnosis. Among numerous analytic methods, electrochemiluminescent (ECL) [17], [18], [19] and colorimetric [20], [21] methods hold promise for achieving sensitive, widespread and facile disease diagnosis due to their high selectivity and high noise-to-signal. To obtain an ideal assay performance, multifarious nanomaterials have been utilized over the past few decades for immobilization of the biomolecule recognition elements and receiving a good response in various assay applications [22], [23]. Particularly, metal nanomaterials have attracted great research interests in the fields of fuel cells [24], food safety [25], [26], environmental monitoring and disease diagnostics [27], [28]. Among various reported approaches [29], [30], [31], platinum nanoparticle (PtNP) is one of the most important metal nanomaterials due to their excellent catalytic activity, stability and analytical performances [32], [33]. Thus, PtNPs have been well-applied for versatile applications, such as catalysis [34], electrochemical applications [35] and chemical sensing [36], [37]. Especially, in comparison with natural peroxidase, PtNPs possess outstanding advantages of low cost, tunable catalytic activities, flexibility structure design, a wide range of pH and temperature [38]. For example, Pedone et al. designed an approach based on the enzyme-mimetic properties of PtNPs for colorimetric determination of total antioxidant level in saliva [39]. Zhuo and co-workers reported a sensitive determination for micro RNA let-b7 using the rubrene (Rub) filled mesoporous silica nanospheres as ECL emitters, dissolved O2 as coreactant and PtNPs as coreaction accelerators [40]. It is well known that the size of PtNP is crucial to its catalytic, optical and electronic properties and resulting applications. Scientists have obtained insight into the effects of size-induced electron energy quantization in ultra-small metal nanoparticles on catalysis [41], and these results suggest that PtNPs in a typical range of 1–10 nm can significantly enhance catalytic performance [38]. Therefore, this work attempted to design a novel PtNP with a dimension of sub-5 nm for highly sensitive ECL and colorimetric sensing.

Triethanolamine (TEOA) not only is a hopeful coreactant in ECL systems due to its low cost, less toxicity and great solubility in aqueous solution, but also is a good reducing and stabilizing agent to prepare monodisperse metal nanoparticles [42]. Herein, we describe a simple and convenient synthesis of novel TEOA-capped PtNPs (TEOA@PtNPs) and their application in developing colorimetric and ECL immunoassay, as shown in Scheme 1 . The TEOA@PtNPs were prepared by one pot hydrothermal method with TEOA as a reducing agent and stabilizer. The TEOA@PtNPs were characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet–visible spectroscopy (UV–vis) and X-ray photoelectron spectroscopy (XPS). The synthesized TEOA@PtNPs with an average size of approximately 2.2 nm show a strong catalytic activity toward the reaction of H2O2 and 3,3′,5,5′-tetramethylbenzidine (TMB) [43]. Impressively, with a collaborative strategy combined with the advantages of PtNPs and coreactant-enhanced ECL effect, TEOA@PtNPs modified electrode shows a high ECL response in the aqueous solution. Hence, on the basis of its peroxidase-like property and a high coreactant loading capacity, by employing the SARS-CoV S-protein as a target detection model, the fabricated colorimetric and ECL immunosensor both presented a wide linear detection range, a high sensitivity and an excellent selectivity in complex matrix of actual serum samples, which demonstrated the potential applicability of the proposed method in other biomarker analyses and clinical diagnosis.

Scheme 1.

Scheme 1

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Schematic diagram of the synthesis of TEOA@PtNPs (1); Colorimetric strategy for detection of SARS-CoV S protein by TEOA@PtNPs (2); Fabrication of the ECL immunoassay system for SARS-CoV S-protein detection (3).

2. Experiment

2.1. Instruments and reagents

All chemicals and apparatus used in this paper are exhibited in the Experimental section of the Supporting Information.

2.2. Experimental procedure

2.2.1. Synthesis of the TEOA @ PtNPs and anti-SARS-TEOA@PtNPs

Firstly, 18 mL of ultrapure water was added into a 50 mL round bottom flask and heated to 180 °C in an oil bath. Secondly, 5.1 mL of TEOA (0.075 mol/L) solution and 100 μL of chloroplatinic acid (H2PtCl6, 0.077 mol/L) solution were added under a quick stir. After the reaction solution refluxed at 180 °C for 3 h, the TEOA@PtNPs were formed when the solution changed from light yellow to light brown, and finally to brown black (Scheme 1).

8 mL TEOA@PtNPs solution was mixed with 400 μL 0.5 mg/mL anti-SARS and kept stirring at 4 °C overnight, then the antibody could be strongly adsorbed on the PtNPs surface. The anti-SARS-TEOA@PtNPs were collected by centrifugation and washed with 10 mM phosphatic buffer solution (PBS, pH 7.4) three times. Finally, the precipitant was dispersed in 20 mL 1 % bovine serum protein (BSA) and stored at 4 °C before use.

2.2.2. Colorimetric analysis of SARS-CoV S-protein

200 μL 0.5 μg/mL anti-SARS was added to the micropore of a 96-well microtitter plate and incubated at 37 °C overnight. Then the micropore was washed 3 times with 10 mM PBS (pH 7.4). After that, 300 μL 1 % BSA was dropped into each pore and incubated at 37 °C for 2 h to block nonspecific binding sites. After washing 3 times with 10 mM PBS (pH 7.4), 200 μL of different concentrations of antigens were added to each pore and incubated at 37 °C for 2 h. And 200 μL anti-SARS-TEOA@PtNPs were added into each pore and incubated at 37 °C for 2 h. Finally, the pore was also rinsed 3 times with 10 mM PBS (pH 7.4).

To achieve colorimetric detections, 200 μL PBS (100 mM, pH 4.3) containing 10 mM TMB and 10 mL 50 mM H2O2 was injected into each pore and incubated for 15 min at room temperature. Next the absorbance of the mixture was measured by a microplate reader (SpectraMax M5e) at the wavelength of 652 nm.

2.2.3. ECL analysis of SARS-CoV S-protein

First, 5 mL TEOA@PtNPs was mixed with 4 mL Chitosan (CS, 0.5 %) solution and stirred for 2 h and waiting for experiment. As shown in Scheme 1, 30 μL CS-dispersed TEOA@PtNPs solution was cast on the treated glassy carbon electrode (GCE) [44] and dried at room temperature. Then, 6 μL glutaraldehyde (GA, 2.5 %) solution was rapidly dropped to the CS-TEOA@PtNPs/GCE modified electrode for 2 h. After being washed with 10 mM PBS (pH 7.4), 6 μL of 0.5 mg/mL anti-SARS (Ab) was added to the GA/CS-TEOA@PtNPs/GCE electrode and incubated overnight in a humid environment at 4 °C. The excess Ab was removed with 10 mM PBS (pH 7.4). Then, the resulting electrode was incubated with 3 % BSA at 4 °C for 1 h to block the non-specific binding sites (BSA/Ab/GA/CS-TEOA@PtNPs/GCE). After washing with 10 mM PBS (pH 7.4), the electrode was incubated with different concentrations of antigens or serum at 37 °C for 2 h (antigen/BSA/Ab/GA/CS-TEOA@PtNPs/GCE). After several buffer washes, the obtained immunosensors was tested in 0.1 M PBS (pH 7.0) containing 100 μM Ru(bpy)3 2+ from 0 to 1.35 V and the photomultiplier tube (PMT) at 800 V.

3. Results and discussion

3.1. Characterization of TEOA@PtNPs

In this work, The TEOA@PtNPs were easily synthesized via a one-step method (Scheme 1(1)). The TEOA was used as the stabilizer and reductant for the growth of PtNPs. After synthesis, the morphology of the nanoparticles was firstly characterized by TEM. Figs. 1 and 2 and Fig. S1 show the TEOA@PtNPs synthesized using different molar ratios of TEOA/H2PtCl6 and different reaction temperatures. As evidenced by TEM images, the uniform spherical-shaped PtNPs were undoubtedly obtained after the mixture of TEOA and H2PtCl6 (n TEOA: n H2PtCl6 = 50:1) solution was heated to 140 °C for 3 h. Moreover, from the UV–vis spectroscopy (Fig. S2), it can be seen that a broad absorption peak of H2PtCl6 between 200 nm and 300 nm presents, which is the characteristic absorption peak of platinum group metal ions in the ultraviolet–visible region [45]. But it disappeared after the synthesis reaction finishing, proving that H2PtCl6 has reacted completely. Besides, as shown in Fig. 2 g-h, the TEOA@PtNPs possess distinct lattice fringes (the lattice distance is about 0.206 nm) and the average diameter of PtNPs is 2.2 nm. In addition, the energy-dispersive X-ray (EDX) (Fig. 2i) spectroscopic analysis demonstrates that the Pt, C and O elements in the sample, further corroborating the successful formation of the dispersed TEOA@PtNPs.

Fig. 1.

Fig. 1

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TEM images of TEOA@PtNPs formation at the different molar ratios of TEOA and H2PtCl6. From (a) to (f), the molar ratio of TEOA and H2PtCl6 are 20:1, 30:1, 40:1, 50:1, 60:1 and 80:1, respectively. All the reaction temperatures are 140 °C and the reaction times are 3 h.

Fig. 2.

Fig. 2

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TEM images of TEOA@PtNPs formation at 100 °C (a), 120 °C (b), 140 °C (c), 160 °C (d), 180 °C (e) and 200 °C (f), respectively. The molar ratio of TEOA/H2PtCl6 is 50:1 and the reaction time is 3 h. (g) The fast Fourier transform diffraction pattern of TEOA@PtNPs and the high resolution TEM pattern of a single TEOA@PtNPs (inset). (h) The histogram of diameter distribution of TEOA@PtNPs. (i) EDX image of TEOA@PtNPs.

The surface chemistry of the as-synthesized sample was detected by XPS and FT-IR. Are shown in Fig. 3 (a–e), the XPS of the C 1s binding energy appears at 284.8 eV (C—C), 286.2 eV (C-OH) and 288.2 eV (O Created by potrace 1.16, written by Peter Selinger 2001-2019 C-O) [46]. The peak centered at 400.0 eV in the N 1s XPS spectra is originated from the C—N bond, and the peak at 531.8 eV in the O 1s XPS spectra is attributed to C—O [47], [48]. The two main peaks at 71.2 eV (Pt 4f7/2) and 74.4 eV (Pt 4f5/2) in the Pt 4f XPS spectra are assigned to metallic Pt0 (Pt0 4f7/2, Pt0 4f5/2), revealing the existence of metallic Pt0 species in TEOA@PtNPs [49]. The metallic Pt0 should be from the reduction of H2PtCl6 and might possess peroxidase-mimicking active sites and high structural stability. According to the FT-IR spectra (Fig. 3f), two similar curves prove that the primary structures of TEOA are maintained in the TEOA@ PtNPs. The obvious peaks at 3318 cm−1 and 1028 cm−1 are ascribed to the hydroxyl groups of TEOA. Compared with TEOA, the decrease of hydroxyl peak at 1080 cm−1 and the appearance of carboxyl peaks at 1635 cm−1 on the TEOA@PtNPs, indicating that hydroxyl group in TEOA can reduce Pt4+ to Pt0 while it is oxidized to carboxyl group. Moreover, the carboxyl groups interaction with the PtNPs surface via O − Pt conjunction can prevent agglomeration and/or unlimited growth of the TEOA@PtNPs [50].

Fig. 3.

Fig. 3

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XPS spectra of TEOA@PtNPs (a) and high-resolution spectra of O 1s (b), N 1s (c), C 1s (d) and Pt 4f (e). (f) The FT-IR spectra of TEOA@PtNPs (black curve) and TEOA (red curve).

3.2. Peroxidase-like activity of TEOA@PtNPs

The colorimetric experiments were utilized to investigate the peroxidase-like activity of the TEOA@PtNPs by its catalysis toward the oxidation of TMB by H2O2 (Scheme 1(2)). Different concentrations of TMB (120 μL, 4–18 mM) and 10 mM of H2O2 (120 μL) were mixed with 3 mL PBS (100 mM, pH 2–8), and then 300 μL TEOA@PtNPs suspension was added to the solution. After incubation at different temperatures for several minutes, the catalytic performance of the TEOA@PtNPs was detected by UV–vis absorption spectroscopy and the absorbance at 652 nm [51]. Under optimization pH (pH = 3, Fig. 4 a), the solution colour changed obviously to blue after addition of TEOA@PtNPs (prepared at 100 °C, Fig. 4b) in the mixture of H2O2 and TMB. Moreover, when the synthesized TEOA@PtNPs (n TEOA: n H2PtCl6 = 30:1) was incubated with the mixture of TMB/ H2O2 at 55 °C (Fig. 4c–d), both the UV–vis spectrum and the solution colour presented remarkable change. Intriguingly, a linear correlation between the difference absorbance (ΔA) and the logarithm of H2O2 concentration (4–18 mM) were observed, and the limit of detection (LOD) was about 2.5 mM (Fig. 4e), showing a great peroxidase-like catalytic performance of TEOA@PtNPs and a sensitivity of this colorimetric method for H2O2 detection.

Fig. 4.

Fig. 4

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Photographs and UV–vis spectra of detection solution in the presence of TEOA@PtNPs. (a) Effects of pH, (b) effects of TEOA@PtNPs synthesized with different temperatures from 100 to 180 °C, (c) effects of incubation temperatures from 15 to 70 °C, (d) effects of TEOA@PtNPs synthesized with different molar ratio of TEOA and H2PtCl6. (e) The photographs (inset) and the liner calibration plot for H2O2 detection using the catalyst of TEOA@PtNPs. (f) The absorbance (inset) and the liner calibration plot for SARS-CoV S-protein detection using TEOA@PtNPs as the peroxidase-like catalyst.

3.3. Analytical performance for SARS-CoV S-protein colorimetric detection

SARS virus is an acute respiratory infectious disease, which is often acute and can cause severe acute respiratory syndrome after infection. It has strong invasiveness and can be rapidly grown and replicated in the lung tissue, causing diffuse damage to the lung [52]. In our work, we used the SARS-CoV S-protein as a model target to develop a colorimetric assay, based on the increase in absorbance at 652 nm because of the peroxidase-like catalytic activity of TEOA@PtNPs. As shown in Fig. S3, the colour of the detection solution become bluer with the increasing SARS-CoV S-protein concentration, indicating more TEOA@PtNPs were integrated due to the affinity interaction of antigens and antibodies. So, a good linear relationship between the ΔA and the logarithm value of SARS-CoV S-protein concentration is presented in a range of 100 fg/mL–10 μg/mL, and the LOD value is about 8.9 fg/mL, calculating from the 3σ of the blank signal and the linear slop (Fig. 4f) [53]. To evaluate the selectivity and specificity of this proposed method for SARS-CoV S-protein detection was examined with immunoglobulin G (IgG), classical swine fever virus (CSFV), foot-and-mouth disease virus (FMDV), and all three. As shown in Fig. S3I-L and Fig. S4, these interfering substances present negligible response, suggesting the high specificity and good discrimination capability of this biosensor.

3.4. Optimization of the ECL conditions

TEOA, as a co-reactant for Ru(bpy)3 2+ ECL systems, shows a positive effect on ECL response due to its electron-withdrawing hydroxyethyl groups [46]. Ru(bpy)3 2+ and TEOA are widely used in ECL systems, and its reaction mechanism has also been reported (Fig. S5) [54], [55]. Thus, to maximize the ECL performance of the prepared TEOA@PtNPs, the experimental conditions including different molar ratios of TEOA and H4PtCl6, different temperatures and times were optimized. As presented in Fig. S6a, the largest ECL response is observed at molar ratios (n TEOA/n H2PtCl6) of 50:1. The ECL responses increased with the prolonged reaction temperature and time, so the reaction condition for synthesized TEOA@PtNPs was chosen at 180 °C for 3 h (Fig. S6b–c). As shown in Fig. S6d, the largest ECL response is obtained at the volume ratio of TEOA@PtNPs/CS of 10:8, and then decreases rapidly with the increase the amount of CS, because the low electrical conductivity of CS might hinder electron-transfer process, resulting in a weak ECL response.

3.5. Electrochemical characterization of the proposed ECL immunosensor

The Cyclic Voltammetry (CV) and electrochemical impedance spectroscopy (EIS) play important roles on investigating the charge-transfer processes at the electrode surface of ECL sensors [56], [57]. As presented in Fig. S7, compared with bare GEC, the TEOA@PtNPs film on GCE improved the electron-transfer at the GCE surface, indicating the good conductivity of the PtNPs. However, the electron transfer resistance (R et) value gradually increases after the modification of CS-TEOA@PtNPs, GC, antibody, BSA and antigen on GCE, because the poor conductivity of CS and the formation of the immune-complex would block the electron transfer of the Fe(CN)6 3-/ Fe(CN)6 4- probe. The experimental results of CV are consistent with those of EIS, proving that the biosensor is successfully fabricated.

3.6. ECL detection of SARS-CoV S-protein

Under the optimized conditions, a label-free ECL immunosensing platform was established for SARS-CoV S-protein determination (Scheme 1(3)). Fig. 5 a exhibits that the ECL intensities decline along with increasing the concentrations of SARS-CoV S-protein, demonstrating that the nonconductive immune complexes block the electron-transfer process. Therefore, the Fig. 5b shows a good linear relationship between the difference ECL intensity (ΔI) and the common logarithm of SARS-CoV S-protein concentration ranging from 10 fg/mL to 10 ng/mL, and the LOD is 4.2 fg/mL (S/N = 3). As shown in Table S1, the LODs of these two methods are lower than or comparable with that of the previous methods.

Fig. 5.

Fig. 5

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ECL responses (a) and the corresponding calibrating plot (b) of the biosensor toward different concentrations of SARS-CoV S-protein. (c) Stability of the biosensor toward 1 pg/mL, 1 ng/mL and 10 ng/mL SARS-CoV S-protein based on continuous cyclic scanning (6 times) in 0.1 M PBS (pH 7.0) solution containing 100 μM Ru(bpy)32+. Scan potential: 0–1.35 V. Scan rate: 100 mV/s. PMT = 800 V.

3.7. Reproducibility, selectivity and stability of the ECL biosensor

To investigate the purpose of the potential application, the proposed immunosensor were incubated with 1 pg/mL, 1 ng/mL and 10 ng/mL SARS-CoV S-protein, respectively, and then continuously scanned for 6 cycles. As shown in Fig. 5c, the corresponding relative standard deviations (RSDs) of ECL signals are 4.6 %, 3.6 % and 4.0 %, respectively, indicating the satisfying reliability and good stability. Moreover, five individual measurements for 100 fg/mL and 100 pg/mL SARS-CoV S-protein were conducted to investigate the reproducibility. The corresponding RSD values are 1.39 % and 2.96 % (Fig. S8), indicating the ECL approach has a great repeatability. As presented in Fig. S9, the interference proteins, including IgG, CSFV and FMDV, all show low ECL responses, proving that this biosensor has excellent selectivity to the SARS-CoV S-protein.

3.8. Detection of SARS-CoV S-protein in serum samples

The potential application of this ECL method for the detection of SARS-CoV S-protein was further investigated by analyzing serum samples. The standard addition experiments were carried out by adding different concentrations of SARS-CoV S-protein into 10 % blank human serum samples (Fig. S10). Table S2 presents that the recoveries range from 97.8 % to 102 % with the RSDs from 0.25 % to 6.47 %. These good results demonstrate that this ECL method possesses great practicability in clinical human serum samples.

4. Conclusions

In summary, we develop a facile and one-step synthesis of TEOA-capped PtNPs for colorimetric and ECL immunosensing of SARS-CoV S-protein. The TEOA is used as the reducing agent and stabilizer, resulting in the TEOA@PtNPs with good dispersibility, high stability and great peroxidase-like catalytic performance. Moreover, the TEOA@PtNPs are used as peroxidase mimic to establish a colorimetric sensor for sensitive determination of SARS-CoV S-protein. Meanwhile, the TEOA@PtNPs possess a large number of coreactant molecules capped on the PtNPs surface, which can produce a great ECL response with Ru(bpy)3 2+. Thus, an ultrasensitive ECL strategy for the detection of SARS-CoV S-protein is also successfully developed. The cost-effective TEOA@PtNPs not only provide an alternative for colorimetric sensing applications and clinical analyses, but also open a new avenue for the promising application of PtNPs in the field of ECL biosensing.

CRediT authorship contribution statement

Xiaolan Yang: Data curation, Formal analysis, Investigation, Writing – original draft. Xiangyu Li: Data curation, Writing – original draft. Qingguo He: Visualization, Software. Yanbin Ding: Supervision. Bin Luo: Formal analysis, Software. Qiuju Xie: Supervision. Jiahao Chen: Supervision. Yue Hu: Investigation. Zhaohong Su: Visualization, Investigation, Software. Xiaoli Qin: Conceptualization, Methodology, Validation, Writing – review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This research was funded by the National Natural Science Foundation of China (22004034), Natural Science Foundation of Hunan Province (China) (2020JJ5226, 2020JJ4346), Science Foundation of Hunan Agricultural University (540499818007), Foundation of Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle (ES202180064), and Undergraduate Innovation and Entrepreneurship Training Program of Hunan Province (s202210537082). The authors would like to thank Shiyanjia Lab (www.shiyanjia.com) for supporting TEM and XPS tests. X. Yang, X. Li and Q. He contributed equally to this work.

Footnotes

Appendix A

Supplementary data to this article can be found online at https://doi.org/10.1016/j.microc.2022.108329.

Appendix A. Supplementary data

The following are the Supplementary data to this article:

Supplementary data 1
mmc1.docx (2.8MB, docx)

Data availability

The authors are unable or have chosen not to specify which data has been used.

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