Anthraquinone-Polyaniline-Integrated Textile Platforms for In Situ Electrochemical Production of Hydrogen Peroxide for Microbial Deactivation

Hydrogen peroxide (H2O2) is a versatile and effective disinfectant against common pathogenic bacteria such as Escherichia coli (E. coli). Electrochemical H2O2 generation has been studied in the past, but a lack of studies exists on miniaturized electrochemical platforms for the on-demand synthesis of H2O2 for antibacterial applications. In this article, a chemically modified cotton textile platform capable of in situ H2O2 production is demonstrated for E. coli deactivation. The cotton textile was modified by layer-by-layer coating with conductive carbon nanotubes/cellulose nanocrystals (CNT/CNC) and a polymer of polyaniline (PANI) decorated with anthraquinone (AQ), designated as the AQ@PANI@CNT/CNC@textile antibacterial patch. The AQ@PANI@CNT/CNC@textile antibacterial textile patch H2O2 production capabilities were evaluated using both electrochemical and colorimetric methods. The AQ@PANI@CNT/CNC@textile antibacterial patch electrochemically produced H2O2 concentrations up to 209 ± 25 µM over a 40 min period and displayed a log reduction of 3.32 for E. coli over a period of 2 h. The AQ@PANI@CNT/CNC@textile antibacterial patch offers promise for use as a self-disinfecting pathogen control platform.


Introduction
Hydrogen peroxide (H 2 O 2 ) is an environmentally friendly oxidant used in a wide range of applications, including energy production, chemical synthesis, wastewater treatment, and bioremediation [1,2]. Additionally, it may act as a bacterial and viral pathogenic disinfectant [3,4]. As a disinfectant, H 2 O 2 causes the oxidation of proteins, cleavage of nucleic acids, and dissociation of the 70S ribosomal subunits and denatures a pathogens cell wall [4]. Due to the 2020 COVID-19 pandemic, there is renewed interest in the use of H 2 O 2 for the deactivation of pathogens. For example, some studies have examined the usage of H 2 O 2 for the sterilization and reuse of personal protective equipment (PPE) to address global shortages and for environmental conservation motivations [5][6][7][8]. However, sterilized surgical masks and respirators must adhere to strict FDA guidelines of having a log reduction of ≥3 of both 2 g positive and 2 g negative vegetative bacteria [8]. Recent studies report that 0.5% H 2 O 2 cooling aerosol sprays were found to be highly effective in reducing the viral coronavirus load on used face masks [9,10]. Because of its inherent disinfectant capabilities , the development of new methods for on-demand H 2 O 2 production is an important area of research.
The standard method of H 2 O 2 production includes a complex anthraquinone (AQ)based process [11]. In this process, AQ undergoes hydrogenation and oxidation in the presence of a nickel or palladium catalyst, yielding H 2 O 2 as a byproduct, which is then distilled and concentrated [1,11]. However, this process requires a high energy input, produces large amounts of waste, presents the risk of explosions, and is not suitable for producing small, on-demand quantities of H 2 O 2 for integration into PPE [11]. To overcome  [1]. Additionally, Xue et al. developed a carbon-and nitrogen-doped TiO 2 electrode capable of converting H 2 O into H 2 O 2 at a rate of 0.29 µmol·L −1 ·cm −2 ·h −1 , with a faradaic efficiency of 8% [2]. In a different approach, an electrocatalyst comprising polyaniline (PANI) and AQ has been developed to catalyze the reduction of O 2 into H 2 O 2 [12].
Utilizing an electrosynthesis flow cell, H 2 O 2 was generated at a rate of 1.80 mol·g −1 ·hr −1 , with a faradaic efficiency of 95.8%, making their platform a promising new technology [12].
Both PANI and AQ are capable of generating H 2 O 2 on the cathode when immersed in an electrochemical cell [12,13]. When PANI is oxidized from its leucoemeraldine form to its emeraldine form, it electrocatalyzes the reduction of oxygen via a 2e − oxygen reduction reaction (ORR) transition, shown in Equations (1) and (2) [12,13].
A 2e − ORR may also be catalyzed via AQ, and this reaction is a more kinetically favorable pathway than that afforded via PANI [14,15]. At the cathode, AQ reduces to its semiquinone form, which then catalyzes the reduction of oxygen to the superoxide anion radical (O 2 ·− ), which becomes protonated to form H 2 O 2 ( Figure 1) [14,15]. It is hypothesized that the integration of AQ into the PANI network will likely dramatically enhance the efficiency of H 2 O 2 production [14,15]. amounts of waste, presents the risk of explosions, and is not suitable for producing small, on-demand quantities of H2O2 for integration into PPE [11]. To overcome these drawbacks, electrochemical methods for H2O2 production have been explored. For instance, electrochemical technologies have utilized metal catalysts, such as platinum, to produce H2O2 [1]. Additionally, Xue et al. developed a carbon-and nitrogen-doped TiO2 electrode capable of converting H2O into H2O2 at a rate of 0.29 µmol·L −1 ·cm −2 ·h −1 , with a faradaic efficiency of 8% [2]. In a different approach, an electrocatalyst comprising polyaniline (PANI) and AQ has been developed to catalyze the reduction of O2 into H2O2 [12]. Utilizing an electrosynthesis flow cell, H2O2 was generated at a rate of 1.80 mol·g −1 ·hr −1 , with a faradaic efficiency of 95.8%, making their platform a promising new technology [12]. Both PANI and AQ are capable of generating H2O2 on the cathode when immersed in an electrochemical cell [12,13]. When PANI is oxidized from its leucoemeraldine form to its emeraldine form, it electrocatalyzes the reduction of oxygen via a 2e − oxygen reduction reaction (ORR) transition, shown in Equations (1) and (2) [12,13].
A 2e − ORR may also be catalyzed via AQ, and this reaction is a more kinetically favorable pathway than that afforded via PANI [14,15]. At the cathode, AQ reduces to its semiquinone form, which then catalyzes the reduction of oxygen to the superoxide anion radical (O2 ·− ), which becomes protonated to form H2O2 ( Figure 1) [14,15]. It is hypothesized that the integration of AQ into the PANI network will likely dramatically enhance the efficiency of H2O2 production [14,15]. While effective, metal electrocatalysts are susceptible to anodic degradation and may require regeneration between uses [2]. Furthermore, the creation and integration of a miniaturized electrochemical H2O2-producing device for bacterial and viral disinfection remain a challenge. This study demonstrates a layer-by-layer (LbL) assembly of a cotton textile substrate integrated with layers of conductive carbon nanotube (CNT)/cellulose nanocrystal (CNC) composite and PANI decorated with AQ (AQ@PANI@CNT/CNC@textile). The AQ@PANI@CNT/CNC@textile platform has been successfully tested for electrochemical production of H2O2 for E. coli deactivation. The H2O2 production capabilities of the AQ@PANI@CNT/CNC@textile antibacterial patch were quantified using cyclic voltammetry (CV) and colorimetric methods. The H2O2-generating AQ@PANI@CNT/CNC@textile While effective, metal electrocatalysts are susceptible to anodic degradation and may require regeneration between uses [2]. Furthermore, the creation and integration of a miniaturized electrochemical H 2 O 2 -producing device for bacterial and viral disinfection remain a challenge. This study demonstrates a layer-by-layer (LbL) assembly of a cotton textile substrate integrated with layers of conductive carbon nanotube (CNT)/cellulose nanocrystal (CNC) composite and PANI decorated with AQ (AQ@PANI@CNT/CNC@textile). The AQ@PANI@CNT/CNC@textile platform has been successfully tested for electrochemical production of H 2 O 2 for E. coli deactivation. The H 2 O 2 production capabilities of the AQ@PANI@CNT/CNC@textile antibacterial patch were quantified using cyclic voltammetry (CV) and colorimetric methods. The H 2 O 2-generating AQ@PANI@CNT/CNC@textile holds promise for potential integration into masks or other wearable devices for in situ disinfection.

CNT/CNC H 2 O 2 Sensor Electrode Fabrication
The CNT/CNC sensor electrode for H 2 O 2 detection and the CNT/CNC/Ag (Ag/AgCl) reference needle were fabricated as described previously [16,17]. Briefly, stainless steel hypodermic needles were oxidized via immersion in piranha solution consisting of concentrated H 2 SO 4 and 30% H 2 O 2 in a 1:1 (v/v) ratio for 4 h, then washed with DI water and air dried. The oxidized needles were then silylated via immersion in a solution comprising 3-(trimethoxysilyl) propyl methacrylate (TPM)/DI water/methanol (2:1:8 v/v/v) for 4 hrs, then washed with DI water and air dried. To fabricate the CNT/CNC sensor electrode, the silylated needles were infused with a homogenous suspension comprising 1 mg·mL −1 CNT/4 mg·mL −1 CNC at a flow rate of 15 µL·min −1 at 80 • C. Homogenous CNT/CNC suspensions were first prepared by sonicating 1 mg·mL −1 CNT/4 mg·mL −1 CNC in DI water for 3 h [17]. To fabricate the in-house Ag/AgCl reference needle, silylated needles were infused with a 1 mg·mL −1 CNT/4 mg·mL −1 CNC/5 mg·mL −1 Ag nanoparticle suspension (in DI water) at a flow rate of 15 µL·min −1 . The needles were then immersed in 2 mL of sodium hypochlorite bleach overnight at room temperature and rinsed with DI water.

AQ@PANI@CNT/CNC@Textile Antibacterial Patch Fabrication
To fabricate the antibacterial patch, an 8 × 8 cm cotton textile obtained from a local store was drop cast with 8 mL of a 1 mg·mL −1 CNT/4 mg·mL −1 CNC suspension and dried on a hot plate at 50 • C. The PANI microparticles were produced by mixing 50 mL of 0.2 M aniline (in 1 M H 2 SO 4 ) and 50 mL of 0.25 M APS initiator in an ice bath at 4 • C. The resulting PANI microparticle suspension was then centrifuged (4000 rpm, 15 min) and rinsed with DI water three times before being dried in a dehydrator at 70 • C. A 20 mg·mL −1 solution comprising dried PANI microparticles (in DI water) was sonicated for 3 h to create a homogenous suspension. A total of 8 mL of the 20 mg·mL −1 PANI suspension was drop cast onto the CNT/CNC@textile patch and air dried. Lastly, the PANI@CNT/CNC@textile patch was cut into 4 × 4 cm squares. To integrate AQ into the PANI@CNT/CNC@textile patches, 1.5 mL of 0.5 M 2,6-diaminoanthraquinone (in DMSO) was drop cast onto the patch surface and air dried to yield the AQ@PANI@CNT/CNC@textile antibacterial patches. The AQ was similarly drop cast onto the CNT/CNC@textile patches to yield AQ@CNT/CNC@textile patches. After air drying, the patches were gently rinsed in a beaker of DI water to remove any excess AQ. A 0.3 × 1.0 cm strip of copper tape was wrapped around one corner of each patch to serve as an electrical connection.

Characterization of AQ@PANI@CNT/CNC@Textile Antibacterial Patch
Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), voltammetric, and Raman spectroscopy techniques were used to characterize the AQ@PANI@CNT/CNC@textile antibacterial patch. FTIR spectra were recorded using a Bruker Tensor 27 FTIR instrument fitted with diamond attenuated total reflectance (ATR). SEM images were acquired from a Zeiss Sigma 300 VP field emission SEM. EIS was performed by immersing different patches in 25 mM potassium ferricyanide (in 0.1 M KCl) as a standard redox probe in a three-electrode electrochemical cell, with an in-house fabricated Ag/AgCl reference needle, and a platinum counter electrode. EIS data were acquired in the frequency range of 20.0 Hz-1 MHz at 6.00 mV of sinusoidal amplitude. CV was used to determine the electroactive surface area of the different patches. The CV was performed by immersing each patch in 25 mM potassium ferricyanide (in 0.1 M KCl) in a three-electrode electrochemical cell, using an Ag/AgCl reference needle and a platinum counter electrode. A Palmsens 4 potentiostat equipped with PSTrace software was used for all electrochemical measurements.

In Situ Electrochemical Generation of H 2 O 2 , and Electrochemical and Colorimetric Quantification
To electrochemically generate H 2 O 2 , antibacterial patches were immersed in 10 mL of 0.1 M phosphate buffer (pH 7.0) electrolyte in a three-electrode cell comprising a platinum counter electrode and an Ag/AgCl reference needle for CV application (−1.0 to 1.0 V, 0.25 V·s −1 ).
The H 2 O 2 was electrochemically detected using CV (−1.0 to 1.0 V, 0.1 V·s −1 ) acquired from a CNT/CNC needle sensor running separately within the H 2 O 2 generation cell. The H 2 O 2 detection cell comprised a three-electrode system, with a platinum wire and Ag/AgCl reference needle acting as the counter and reference electrodes, respectively. Faradaic capacitance was determined from the CVs acquired using the CNT/CNC needle sensor and was calculated by averaging the cathodic current within the − 0.50 to 0 V voltage range and dividing it by the scan rate. The ∆capacitance was determined by subtracting the capacitance generated from the blank from that generated from the sample and dividing it by capacitance of the blank.
A colorimetric method was also used to detect H 2 O 2 generation. Briefly, the colorimetric reagent was prepared by combining 0.3681 g of sodium acetate trihydrate, 0.0102 g of 4-aminoantipyrine, 0.0047 g of phenol, 29.4 µL of glacial acetic acid, and D.I water to make 50 mL of solution. In a cuvette, 2 mL of the colorimetric reagent was mixed with 10 µL of 1.1 mg/mL horseradish peroxidase dissolved in D.I water, 500 µL of electrolyte, and brought to a volume of 3 mL using 490 µL of DI water [18]. The absorbance at 505 nm was measured in triplicate using a LabQuest spectrophotometer.

E. coli Deactivation Test Using the Antibacterial Patches
Different antibacterial patch designs were tested for their ability to deactivate E. coli. E. coli K-12 (Z-) cells were streaked on tryptic soy agar (TSA) and incubated at 37 • C for 24 h. Single E. coli colonies were suspended in 0.85% (w/v) sterile saline, and the turbidity was adjusted to match a 0.

Morphological Characterization of Antibacterial Textile Patches
The surface morphologies of the various patches prior to and after E. coli integration were examined using SEM. The CNT/CNC@textile patch, shown in Figure 2a, shows evidence of the nanoporous and stable fiber network characteristic of the overlapping nanofiber structure of the cotton textile and CNT/CNC composite. The addition of PANI to the CNT/CNC@textile enhances patch rigidity. As shown in Figure 2b, the PANI microparticles are distributed on the CNT/CNC and textile fiber network. Figure 2c,d show the AQ@CNT/CNC@textile and the AQ@PANI@CNT/CNC@textile patches following the incorporation of E. coli cells, respectively. AQ is visualized as tiny crystals coated on the surface of the CNT/CNC fiber network, while E. coli cells appear as rounded cylinders (Figure 2c,d). Visually, the density of E. coli cells was higher in the AQ@PANI@CNT/CNC@textile patch, which provides evidence that the integration of the porous PANI coating can trap more bacteria. To confirm the success of the LbL patch assembly, FTIR was acquired at various stages during AQ@PANI@CNT/CNC@textile antibacterial patch fabrication. FTIR spectra from the CNT/CNC@textile patch showed peaks at 1091, 1714, 2910, and 3423 cm −1 (Figure 3), which can be attributed to C-O stretching, C=O stretching, and C-H stretching of the carboxy groups attached to the walls of the functionalized CNTs, and OH stretching of carboxylic acid group, respectively [19,20]. The addition of the PANI layer to the CNT/CNC@textile patch results in two new peaks at 1495 and 1583 cm −1 (Figure 3), which represent the C=C stretching vibrations of the benzenoid and quinoid rings of PANI [21]. Spectra acquired from the AQ@PANI@CNT/CNC@textile antibacterial patch show an additional peak at 1567 cm −1 , which can be attributed to the anthraquinone ring, as well as peaks around 3330, and 3417 cm −1 (Figure 3), which are indicative of the symmetric and asymmetric stretching vibrations of NH 2 group [22].
Polymers 2023, 15, x FOR PEER REVIEW 6 of 12 carboxylic acid group, respectively [19,20]. The addition of the PANI layer to the CNT/CNC@textile patch results in two new peaks at 1495 and 1583 cm −1 (Figure 3), which represent the C=C stretching vibrations of the benzenoid and quinoid rings of PANI [21]. Spectra acquired from the AQ@PANI@CNT/CNC@textile antibacterial patch show an additional peak at 1567 cm −1 , which can be attributed to the anthraquinone ring, as well as peaks around 3330, and 3417 cm −1 (Figure 3), which are indicative of the symmetric and asymmetric stretching vibrations of NH2 group [22].

Electrochemical Characterization of Antibacterial Patches
Different patches were characterized via EIS using 25 mM potassium ferricyanide (in 0.1 M KCl) as the standard redox probe. The Nyquist plots from EIS analysis and associated circuit fittings are shown in Figure 4a and Figure S1, respectively. A low electron transfer resistance (Rct) is desirable for high patch conductivity and effective signal transduction for H2O2 generation [16]. The Rct values determined from the circuit fittings (Figure S1) for the CNT/CNC@textile, PANI@CNT/CNC@textile, AQ@CNT/CNC@textile, and AQ@PANI@CNT/CNC@textile patches are shown in Table 1. The integration of either PANI or AQ to the CNT/CNC@textile patches greatly reduced the Rct, indicative of increased electrical conductivity. When combined, the AQ@PANI@CNT/CNC@textile antibacterial patch demonstrates a reduced Rct compared to the AQ@CNT/CNC@textile patch, owing to the enhanced conductivity afforded to it via the PANI integration. A lower Rct is advantageous for the AQ@PANI@CNT/CNC@textile patches, as it likely results in more effective H2O2 production via enhanced electrical signal transduction.

Electrochemical Characterization of Antibacterial Patches
Different patches were characterized via EIS using 25 mM potassium ferricyanide (in 0.1 M KCl) as the standard redox probe. The Nyquist plots from EIS analysis and associated circuit fittings are shown in Figure 4a and Figure S1, respectively. A low electron transfer resistance (R ct ) is desirable for high patch conductivity and effective signal transduction for H 2 O 2 generation [16]. The R ct values determined from the circuit fittings ( Figure S1) for the CNT/CNC@textile, PANI@CNT/CNC@textile, AQ@CNT/CNC@textile, and AQ@PANI@CNT/CNC@textile patches are shown in Table 1. The integration of either PANI or AQ to the CNT/CNC@textile patches greatly reduced the R ct , indicative of increased electrical conductivity. When combined, the AQ@PANI@CNT/CNC@textile antibacterial patch demonstrates a reduced R ct compared to the AQ@CNT/CNC@textile patch, owing to the enhanced conductivity afforded to it via the PANI integration. A lower R ct is advantageous for the AQ@PANI@CNT/CNC@textile patches, as it likely results in more effective H 2 O 2 production via enhanced electrical signal transduction.   Table 1. The addition of the PANI layer resulted in an increase in the electroactive surface area of the textile patches relative to their non-PANI-integrated counterparts. A high electroactive surface area is desirable for an effective electrochemical platform and lends well to affording a higher capacity for bacterial adsorption. The addition of AQ only slightly reduced the electroactive surface area of the PANI@CNT/CNC@textile patches.

Electrochemical and Colorimetric Quantification of Antibacterial Textile Patch H2O2 Production
Two three-electrode cells were utilized to produce and quantify the H2O2 generated from various chemically modified patches. In the H2O2 generation cell, the patches acted as the working electrode for CV application in phosphate buffer. For the H2O2 detection system, a CNT/CNC sensor electrode was used as the working electrode for CV acquisition in the same electrochemical cell using a different potentiostat [17]. Representative CVs taken from CNT/CNC@textile, PANI@CNT/CNC@textile, and AQ@PANI@CNT/CNC@textile patches acquired during the electrochemical catalysis of H2O2 are shown in Figure S2.
For the capacitive quantification of H2O2, a calibration curve in the range of 0-400 µM H2O2 was used ( Figure S3), where the ∆capacitance was determined using the cathodic peak current found within the −0.5 to 0 V range. Evidently, the CNT/CNC sensor electrode used for H2O2 detection is reliable, displaying a calibration sensitivity of 0.00202 µF·µM −1 ( Figure S3b), with an LOD of 45.4 µM. CVs acquired using the CNT/CNC sensor electrode  Table 1. The addition of the PANI layer resulted in an increase in the electroactive surface area of the textile patches relative to their non-PANI-integrated counterparts. A high electroactive surface area is desirable for an effective electrochemical platform and lends well to affording a higher capacity for bacterial adsorption. The addition of AQ only slightly reduced the electroactive surface area of the PANI@CNT/CNC@textile patches.

Electrochemical and Colorimetric Quantification of Antibacterial Textile Patch H 2 O 2 Production
Two three-electrode cells were utilized to produce and quantify the H 2 O 2 generated from various chemically modified patches. In the H 2 O 2 generation cell, the patches acted as the working electrode for CV application in phosphate buffer. For the H 2 O 2 detection system, a CNT/CNC sensor electrode was used as the working electrode for CV acquisition in the same electrochemical cell using a different potentiostat [17]. Representative CVs taken from CNT/CNC@textile, PANI@CNT/CNC@textile, and AQ@PANI@CNT/CNC@textile patches acquired during the electrochemical catalysis of H 2 O 2 are shown in Figure S2.
For the capacitive quantification of H 2 O 2 , a calibration curve in the range of 0-400 µM H 2 O 2 was used ( Figure S3), where the ∆capacitance was determined using the cathodic peak current found within the −0.5 to 0 V range. Evidently, the CNT/CNC sensor electrode used for H 2 O 2 detection is reliable, displaying a calibration sensitivity of 0.00202 µF·µM −1 ( Figure S3b), with an LOD of 45.4 µM. CVs acquired using the CNT/CNC sensor electrode during H 2 O 2 production from the various patches and the resulting plots of the time trend of ∆capacitance are shown in Figures S4 and S5, respectively. No H 2 O 2 was produced via the CNT/CNC@textile patch, evident by the poor linear signal response (R 2 = 0.0564) ( Figure S5). H 2 O 2 production rates determined by capacitive quantification were 4.19 and 7.20 µM·min −1 for the PANI@CNT/CNC@textile and AQ@PANI@CNT/CNC@textile patches, respectively (Figure 5a). Additionally, the total concentration of H 2 O 2 generated from the PANI@CNT/CNC@textile and AQ@PANI@CNT/CNC@textile patches after 32 min of CV application was 173 and 209 µM, respectively (Figure 5a). PANI@CNT/CNC@textile patch produced H2O2 at a rate of 1.01 µM·min (Figure 5b). For the AQ@PANI@CNT/CNC@textile patch, H2O2 production occurred very slowly in the first 16 min before increasing linearly at a rate of 9.54 µM·min −1 . The total concentration of H2O2 after 32 min of CV application was determined to be 36.8 and 143 µM for PANI@CNT/CNC@textile and AQ@PANI@CNT/CNC@textile patches, respectively ( Figure  5b). Both quantification methods indicate that the integration of AQ into PANI@CNT/CNC@textile patches improves both the rate of and total H2O2 production (Figure 5). However, capacitive detection is likely more accurate due to a higher calibration sensitivity. Mechanistically, H2O2 is generated from O2 via a 2e − ORR assisted by the AQ@PANI@CNT/CNC@textile antibacterial patch [1]. AQ acts as the primary catalyst for the OOR reaction, while PANI acts as a conductive surface for the attachment of AQ and contributes additional catalytic activity [1]. Therefore, the greater rates of H2O2 production for the AQ@PANI@CNT/CNC@textile antibacterial patches relative to the PANI@CNT/CNC@textile can be attributed to the enhanced catalytic activity imparted by the AQ layer [1]. Generally, the AQ@PANI@CNT/CNC@textile patch produces either lower or similar amounts of H2O2 compared to other methods (Table 2). However, the AQ@PANI@CNT/CNC@textile patch is flexible, lends well for wearability, and is an ideal platform for integration into medical PPE for self-disinfection via on-demand electrochemical H2O2 generation. A colorimetric assay was used as an additional method to quantify H 2 O 2 production [18]. The presence of H 2 O 2 was indicated by the absorbance peak at 505 nm, and this detection method had a calibration sensitivity of 4.53 × 10 −4 µM −1 ( Figure S6), with a LOD of 59.5 µM. The resulting absorption spectra and timed trends in absorbance (@ 505 nm) for H 2 O 2 generation from AQ@PANI@CNT/CNC@textile and PANI@CNT/CNC@textile patches are shown in Figures S7 and S8, respectively. Using the colorimetric assay, the PANI@CNT/CNC@textile patch produced H 2 O 2 at a rate of 1.01 µM·min −1 (Figure 5b). For the AQ@PANI@CNT/CNC@textile patch, H 2 O 2 production occurred very slowly in the first 16 min before increasing linearly at a rate of 9.54 µM·min −1 . The total concentration of H 2 O 2 after 32 min of CV application was determined to be 36.8 and 143 µM for PANI@CNT/CNC@textile and AQ@PANI@CNT/CNC@textile patches, respectively ( Figure 5b). Both quantification methods indicate that the integration of AQ into PANI@CNT/CNC@textile patches improves both the rate of and total H 2 O 2 production ( Figure 5). However, capacitive detection is likely more accurate due to a higher calibration sensitivity.
Mechanistically, H 2 O 2 is generated from O 2 via a 2e − ORR assisted by the AQ@PANI@CNT/CNC@textile antibacterial patch [1]. AQ acts as the primary catalyst for the OOR reaction, while PANI acts as a conductive surface for the attachment of AQ and contributes additional catalytic activity [1]. Therefore, the greater rates of H 2 O 2 production for the AQ@PANI@CNT/CNC@textile antibacterial patches relative to the PANI@CNT/CNC@textile can be attributed to the enhanced catalytic activity imparted by the AQ layer [1]. Generally, the AQ@PANI@CNT/CNC@textile patch produces either lower or similar amounts of H 2 O 2 compared to other methods (Table 2). However, the AQ@PANI@CNT/CNC@textile patch is flexible, lends well for wearability, and is an ideal platform for integration into medical PPE for self-disinfection via on-demand electrochemical H 2 O 2 generation.

Antibacterial Efficacy of AQ@PANI@CNT/CNC@Textile Antibacterial Patch
The ability of the AQ@PANI@CNT/CNC@textile antibacterial patch to deactivate E. coli bacteria was tested. CV was performed on E. coli-integrated CNT/CNC@textile, PANI@CNT/CNC@textile, and AQ@PANI@CNT/CNC@textile patches immersed in phosphate buffer, and samples taken from the electrochemical cells at various times were grown on LB agar plates and counted ( Figure S9). The CNT/CNC@textile patch showed very little antibacterial activity, demonstrated by the large number of E. coli colonies formed from it at any point during CV application ( Figure S9). Antibacterial activities of PANI@CNT/CNC@textile and AQ@PANI@CNT/CNC@textile patches were evaluated numerically using a log reduction (Figure 6), calculated by taking the log of the colony forming units (CFU) after 0 min of CV application divided by the CFU after a given time of CV application. After 2 h of CV application, the E. coli-integrated AQ@PANI@CNT/CNC@textile antibacterial patch, and the log reduction was 3.32, whereas that of the PANI@CNT/CNC patch was less than 0.500 ( Figure 6). As such, the FDA Tier 3 standard for reusable face masks (log reduction ≥ 3) [8] is satisfied via the AQ@PANI@CNT/CNC@textile antibacterial patch, and its antibacterial activity correlates with an approximate 99.9% reduction in E. coli bacteria over 2 h. This suggests that the AQ@PANI@CNT/CNC@textile patch may be useful for integration into face coverings or masks for enhanced microbe deactivation and sanitization [28].

Conclusions
The AQ@PANI@CNT/CNC@textile antibacterial patch described in this study produced H2O2 in amounts up to 209 ± 25 µM. Although this concentration of H2O2 is lower than that reported in other studies conducted using PANI and AQ electrocatalysts [12], bacterial deactivation tests showed a log reduction of 3.32 for E. coli after 2 h of electro-

Conclusions
The AQ@PANI@CNT/CNC@textile antibacterial patch described in this study produced H 2 O 2 in amounts up to 209 ± 25 µM. Although this concentration of H 2 O 2 is lower than that reported in other studies conducted using PANI and AQ electrocatalysts [12], bacterial deactivation tests showed a log reduction of 3.32 for E. coli after 2 h of electrochemical H 2 O 2 generation. These results are indicative of strong antibacterial activity, and the textile-based antibacterial patch has great potential to be integrated into PPE or face coverings for enhanced protection against pathogens. Overall, this study outlines a promising textile-based technology that may be further optimized for controlling various pathogens in food-safety-and health-related applications.