Nanostructures in Hydrogen Peroxide Sensing

THP as a sensor for the electrochemical detection of H2O2

Hydrogen peroxide (H2O2) detection is paramount in biological and clinical domains due to its pivotal role in various physiological and pathological processes. This molecule is a crucial metabolite and effector in cellular redox mechanisms, influencing diverse cellular signaling pathways and bolstering the body's defense mechanisms against infection and oxidative stress. Organic molecule-based electrodes present unique advantages such as operational versatility and scalability, rendering them attractive candidates for sensor development across diverse fields encompassing food safety, healthcare, and environmental monitoring. This study explores the electrochemical properties of a tris(3-hydroxypyridin-4-one) THP, which has been unexplored in electrochemical sensing. Leveraging THP's chelating properties, we aimed to develop an electrochemical probe for hydrogen peroxide detection. Our investigations reveal promising results, with the developed sensor exhibiting a low limit of detection (LOD) of 144 nM, underscoring its potential utility in sensitive and selective H2O2 detection applications. In addition, the new sensor was also tested on fetal bovine serum (FBS) to emphasize future applications on biological matrices. This research signifies a significant stride in advancing electrochemical sensor technologies for hydrogen peroxide detection with several novelties related to the usage of THP, such as high sensitivity and selectivity, performance in biological matrices, repeatability, stability, and reproducibility, economical and practical advantages. This research opens new avenues for enhanced biomedical diagnostics and therapeutic interventions.

Laser-assembled conductive 3D nanozyme film-based nitrocellulose sensor for real-time detection of H2O2 released from cancer cells

In this work, a nanostructured conductive film possessing nanozyme features was straightforwardly produced via laser-assembling and integrated into complete nitrocellulose sensors; the cellulosic substrate allows to host live cells, while the nanostructured film nanozyme activity ensures the enzyme-free real-time detection of hydrogen peroxide (H2O2) released by the sames. In detail, a highly exfoliated reduced graphene oxide 3D film decorated with naked platinum nanocubes was produced using a CO2-laser plotter via the simultaneous reduction and patterning of graphene oxide and platinum cations; the nanostructured film was integrated into a nitrocellulose substrate and the complete sensor was manufactured using an affordable semi-automatic printing approach. The linear range for the direct H2O2 determination was 0.5-80 μM (R2 = 0.9943), with a limit of detection of 0.2 μM. Live cell measurements were achieved by placing the sensor in the culture medium, ensuring their adhesion on the sensors' surface; two cell lines were used as non-tumorigenic (Vero cells) and tumorigenic (SKBR3 cells) models, respectively. Real-time detection of H2O2 released by cells upon stimulation with phorbol ester was carried out; the nitrocellulose sensor returned on-site and real-time quantitative information on the H2O2 released proving useful sensitivity and selectivity, allowing to distinguish tumorigenic cells. The proposed strategy allows low-cost in-series semi-automatic production of paper-based point-of-care devices using simple benchtop instrumentation, paving the way for the easy and affordable monitoring of the cytopathology state of cancer cells.

Advanced Functional Materials for Electrochemical and Biosensors

Modern science and technology are central to the smooth running of daily life [...].

Combining plasmonic and electrochemical biosensing methods

The idea of combining electrochemical (EC) and plasmonic biosensor methods was introduced almost thirty years ago and the potential of electrochemical-plasmonic (EC-P) biosensors has been highlighted ever since. Despite that, the use of EC-P biosensors in analytics has been rather limited so far and the search for unique applications of the EC-P method continues. In this paper, we review the advances in the field of EC-P biosensors and discuss the features and benefits they can provide. In addition, we identify the main challenges for the development of EC-P biosensors and the limitations that prevent EC-P biosensors from more widespread use. Finally, we review applications of EC-P biosensors for the investigation and quantification of biomolecules, and for the study of biomolecular and cellular processes.

Sensitive detection of extracellular hydrogen peroxide using plasmon-enhanced electrochemical activity on Pd-tipped Au nanobipyramids

The fabrication of electroactive nanostructures with high electron concentration and specific electron transport is crucial for electrochemical sensing. In this study, a plasmon-enhanced electrochemical sensor has been developed for the detection of extracellular hydrogen peroxide (H2O2) from cancer cells, utilizing Pd-tipped Au nanobipyramids (PTA NBPs) as the electrocatalysts. Plasmonic PTA NBPs were synthesized by depositing Pd nanoparticles onto the tips of Au nanobipyramids (Au NBPs). Under excitation of localized surface plasmon resonance (LSPR), the PTA NBPs generate high-energy electron-hole pairs (e-/h+) on their surface. The generated electrons (e-) significantly enhance the electrochemical reduction of H2O2. Based on this, a plasmon-enhanced H2O2 electrochemical sensor is constructed with high sensitivity (986.57 μA mM-1 cm-2), low detection limit (0.02 μM), wide linear range (0.1 μM to 980 μM), and good stability and repeatability. Moreover, this sensor also enables the measurement of extracellular H2O2 derived from cancer cells (MCF-7), highlighting its potential applications in cellular biology and biomedical research.

Ultrasensitive Nonenzymatic Real-Time Hydrogen Peroxide Monitoring Using Gold Nanoparticle-Decorated Titanium Dioxide Nanotube Electrodes

An amperometric enzyme-free hydrogen peroxide (H₂O₂) sensor was developed by catalytically stabilizing active gold nanoparticles (Au NPs) of 4-5 nm on a porous titanium dioxide nanotube (TiO₂ NTs) electrode. The Au NPs were homogeneously distributed on anatase TiO₂ NTs with an outer diameter of ~102 nm, an inner diameter of ~60 nm, and a wall of thickness of ~40 nm. The cyclic voltammogram of the composite electrode showed a pair of redox peaks characterizing the electrocatalytic reduction of H₂O₂. The entrapping of Au NPs on TiO₂ NTs prevented aggregation and facilitated good electrical conductivity and electron transfer rate, thus generating a wide linear range, a low detection limit of ~104 nM, and high sensitivity of ~519 µA/mM, as well as excellent selectivity, reproducibility, repeatability, and stability over 60 days. Furthermore, excellent recovery and relative standard deviation (RSD) were achieved in real samples, which were tap water, milk, and Lactobacillus plantarum bacteria, thereby verifying the accuracy and potentiality of the developed nonenzymatic sensor.

Development of PEGylated Cu nanoclusters: A nontoxic, multifunctional colloidal system for bioimaging and peroxide sensing

This study introduces the development of blue-emitting colloidal Cu NCs through a novel and easy PEGylation method using different functional groups, including -SH and -COOH. The surface functionalization controls the size, cellular toxicity, and emission properties of Cu NCs. The combination of PEG, thiol, and carboxylic groups protects the particle surface from aggregation and oxidation. Among the samples, CAGP (Surface modified Cu NCs with -SH-COOH-PEG combination) emerges as an amazing candidate with the lowest toxicity and enhanced blue emission properties. The bright blue fluorescence emission from Hela cells after treatment with CAGP demonstrated this property. It also has excellent peroxide sensing potential, with a detection limit of 1.4 μM. Because of their excellent bioimaging and peroxide sensing properties, these Cu NCs could be a promising candidate for cellular oxidative stress sensing applications with high clinical relevance.

Improved Electrochemical Hydrogen Peroxide Detection Using a Nickel(II) Phthalimide-Substituted Porphyrazine Combined with Various Carbon Nanomaterials

A metal-free porphyrazine derivative with peripheral phthalimide substituents was metallated with a nickel(II) ion. The purity of the nickel macrocycle was confirmed using HPLC, and characterized by MS, UV-VIS, and 1D (¹H, ¹³C) and 2D (¹H-¹³C HSQC, ¹H-¹³C HMBC, ¹H-¹H COSY) NMR techniques. The novel porphyrazine was combined with various carbon nanomaterials, such as carbon nanotubes-single walled (SWCNTs) and multi-walled (MWCNTs), and electrochemically reduced graphene oxide (rGO), to create hybrid electroactive electrode materials. The carbon nanomaterials' effect on the electrocatalytic properties of nickel(II) cations was compared. As a result, an extensive electrochemical characterization of the synthesized metallated porphyrazine derivative on various carbon nanostructures was carried out using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). An electrode modified with carbon nanomaterials GC/MWCNTs, GC/SWCNTs, or GC/rGO, respectively, was shown to have a lower overpotential than a bare glassy carbon electrode (GC), allowing for the measurement of hydrogen peroxide in neutral conditions (pH 7.4). It was shown that among the tested carbon nanomaterials, the modified electrode GC/MWCNTs/Pz3 exhibited the best electrocatalytic properties in the direction of hydrogen peroxide oxidation/reduction. The prepared sensor was determined to enable a linear response to H₂O₂ in concentrations ranging between 20-1200 µM with the detection limit of 18.57 µM and sensitivity of 14.18 µA mM^-1 cm^-2. As a result of this research, the sensors produced here may find use in biomedical and environmental applications.

Highly Sensitive and Selective Graphene Nanoribbon Based Enzymatic Glucose Screen-Printed Electrochemical Sensor

A simple, sensitive, cost effective, and reliable enzymatic glucose biosensor was developed and tested. Nitrogen-doped heat-treated graphene oxide nanoribbons (N-htGONR) were used for modification of commercially available screen-printed carbon electrodes (SPCEs), together with MnO₂ and glucose oxidase. The resulting sensors were optimized and used to detect glucose in a wide linear range (0.05-5.0 mM) by a simple amperometric method, where the limit of detection was determined to be 0.008 mM. (lifetime), and reproducibility studies were also carried out and yielded favorable results. The sensor was then tested against potential interfering species present in food and beverage samples before its application to real matrix. Spiked beer samples were analyzed (with glucose recovery between 93.5 and 103.5%) to demonstrate the suitability of the developed sensor towards real food and beverage sample applications.

Copper(II) Oxide Nanoparticles Embedded within a PEDOT Matrix for Hydrogen Peroxide Electrochemical Sensing

The aim of this study is the preparation of nanostructured copper(II) oxide-based materials (CuONPs) through a facile additive-free polyol procedure that consists of the hydrolysis of copper(II) acetate in 1,4-butane diol and its application in hydrogen peroxide sensing. The nonenzymatic electrochemical sensor for hydrogen peroxide determination was constructed by drop casting the CuONP sensing material on top of a glassy carbon electrode (GCE) modified by a layer of poly(3,4-ethylenedioxythiophene) conducting polymer (PEDOT). The PEDOT layer was prepared on GCE using the sinusoidal voltage method. The XRD pattern of the CuONPs reveals the formation of the monoclinic tenorite phase, CuO, with average crystallite sizes of 8.7 nm, while the estimated band gap from UV-vis spectroscopy is of 1.2 eV. The SEM, STEM, and BET analyses show the formation of quasi-prismatic microaggregates of nanoparticles, with dimensions ranging from 1 µm up to ca. 200 µm, with a mesoporous structure. The developed electrochemical sensor exhibited a linear response toward H₂O₂ in the concentration range from 0.04 to 10 mM, with a low detection limit of 8.5 μM of H₂O₂. Furthermore, the obtained sensor possessed an excellent anti-interference capability in H₂O₂ determination in the presence of interfering compounds such as KNO₃ and KNO₂.

Electrochemical Quantification of H2O2 Released by Airway Cells Growing in Different Culture Media

Quantification of oxidative stress is a challenging task that can help in monitoring chronic inflammatory respiratory airway diseases. Different studies can be found in the literature regarding the development of electrochemical sensors for H2O2 in cell culture medium to quantify oxidative stress. However, there are very limited data regarding the impact of the cell culture medium on the electrochemical quantification of H2O2. In this work, we studied the effect of different media (RPMI, MEM, DMEM, Ham's F12 and BEGM/DMEM) on the electrochemical quantification of H2O2. The used electrode is based on reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) and was obtained by co-electrodeposition. To reduce the electrode fouling by the medium, the effect of dilution was investigated using diluted (50% v/v in PBS) and undiluted media. With the same aim, two electrochemical techniques were employed, chronoamperometry (CH) and linear scan voltammetry (LSV). The influence of different interfering species and the effect of the operating temperature of 37 °C were also studied in order to simulate the operation of the sensor in the culture plate. The LSV technique made the sensor adaptable to undiluted media because the test time is short, compared with the CH technique, reducing the electrode fouling. The long-term stability of the sensors was also evaluated by testing different storage conditions. By storing the electrode at 4 °C, the sensor performance was not reduced for up to 21 days. The sensors were validated measuring H2O2 released by two different human bronchial epithelial cell lines (A549, 16HBE) and human primary bronchial epithelial cells (PBEC) grown in RPMI, MEM and BEGM/DMEM media. To confirm the results obtained with the sensor, the release of reactive oxygen species was also evaluated with a standard flow cytometry technique. The results obtained with the two techniques were very similar. Thus, the LSV technique permits using the proposed sensor for an effective oxidative stress quantification in different culture media and without dilution.

Flexible Sensors for Hydrogen Peroxide Detection: A Critical Review

Hydrogen peroxide (H₂O₂) is a common chemical used in many industries and can be found in various biological environments, water, and air. Yet, H₂O₂ in a certain range of concentrations can be hazardous and toxic. Therefore, it is crucial to determine its concentration at different conditions for safety and diagnostic purposes. This review provides an insight about different types of sensors that have been developed for detection of H₂O₂. Their flexibility, stability, cost, detection limit, manufacturing, and challenges in their applications have been compared. More specifically the advantages and disadvantages of various flexible substrates that have been utilized for the design of H₂O₂ sensors were discussed. These substrates include carbonaceous substrates (e.g., reduced graphene oxide films, carbon cloth, carbon, and graphene fibers), polymeric substrates, paper, thin glass, and silicon wafers. Many of these substrates are often decorated with nanostructures composed of Pt, Au, Ag, MnO₂, Fe₃O₄, or a conductive polymer to enhance the performance of sensors. The impact of these nanostructures on the sensing performance of resulting flexible H₂O₂ sensors has been reviewed in detail. In summary, the detection limits of these sensors are within the range of 100 nM-1 mM, which makes them potentially, but not necessarily, suitable for applications in health, food, and environmental monitoring. However, the required sample volume, cost, ease of manufacturing, and stability are often neglected compared to other detection parameters, which hinders sensors' real-world application. Future perspectives on how to address some of the substrate limitations and examples of application-driven sensors are also discussed.

Pt–Pd Bimetallic Aerogel as High-Performance Electrocatalyst for Nonenzymatic Detection of Hydrogen Peroxide

Hydrogen peroxide (H2O2) plays an indispensable role in the biological, medical, and chemical fields. The development of an effective H2O2 detecting method is of great importance. In the present work, a series of PtxPdy bimetallic aerogels and Pt, Pd monometallic aerogels were controllably synthesized by one-step gelation method. Their morphologies and compositions were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and so forth. These aerogels were used as nonenzyme electrocatalysts for the detection of H2O2. The cyclic voltammetric and amperometric results demonstrated that the performance of the metal aerogels showed volcano-type behavior, with the Pt50Pd50 aerogel sitting on top. The Pt50Pd50 aerogel-based electrochemical sensor exhibited excellent comprehensive performance, with a low overpotential of −0.023 V vs. Ag/AgCl, a broad linear range from 5.1 to 3190 μM (R2 = 0.9980), and a high sensitivity of 0.19 mA mM−1 cm−2, in combination with good anti-interference ability and stability. A comprehensive study indicated that the superior sensing performance of the Pt50Pd50 aerogel is closely related to its optimized d-band center and larger cumulative pore volume. This work first applied Pt–Pd bimetallic aerogels into the detection of H2O2 and shows the promising application of noble metal aerogels in the electrochemical sensing area.

A non-enzymatic electrochemical hydrogen peroxide sensor based on copper oxide nanostructures

This article describes the synthesis of nanostructured copper oxide on copper wires and its application for the detection of hydrogen peroxide. Copper oxide petal nanostructures were obtained by a one-step hydrothermal oxidation method. The resulting coating is uniform and dense and shows good adhesion to the wire surface. Structure, surface, and composition of the obtained samples were studied using field-emission scanning electron microscopy along with energy-dispersive spectroscopy and X-ray diffractometry. The resulting nanostructured samples were used for electrochemical determination of the H2O2 content in a 0.1 M NaOH buffer solution using cyclic voltammetry, differential pulse voltammetry, and i-t measurements. A good linear relationship between the peak current and the concentration of H2O2 in the range from 10 to 1800 μM was obtained. The sensitivity of the obtained CuO electrode is 439.19 μA·mM-1. The calculated limit of detection is 1.34 μM, assuming a signal-to-noise ratio of 3. The investigation of the system for sensitivity to interference showed that the most common interfering substances, that is, ascorbic acid, uric acid, dopamine, NaCl, glucose, and acetaminophen, do not affect the electrochemical response. The real milk sample test showed a high recovery rate (more than 95%). According to the obtained results, this sensor is suitable for practical use for the qualitative detection of H2O2 in real samples, as well as for the quantitative determination of its concentration.

Prussian Blue/Carbon Nanotube Sensor Spread with Gelatin/Zein Glaze: A User-Friendly Modification for Stable Interference-Free H2O2 Amperometry

We report the production and characterization of effective amperometric sensors for cathodic hydrogen peroxide (H₂O₂) detection. The proposed electrodes involve a combination of a H₂O₂-signaling Prussian Blue (PB)/carbon nanotube (CNT) layer with a glaze of the biopolymers gelatin (top) and zein (beneath) for protection against PB leakage. The sandwich-type sensor was constructed through simple "drop and dry" steps with (1) suspensions of the CNTs in a soluble PB solution, (2) zein in ethanol, and (3) gelatin in water, applied sequentially to the carbon working electrode disk of a screen-printed carbon electrode (SPCE) platform. The PB in the signaling layer acted as the electrocatalyst for H₂O₂ reduction at -150 mV vs Ag/AgCl/3 M KCl, enabling cathodic H₂O₂ amperometry with good target proportionality. Calibration trials confirmed the linearity of the response up to 700 μM (R² > 0.998), with a sensitivity of 0.425 μA μM^-1 cm^-2 and a practical detection limit of 1 μM. Quantification of H₂O₂ in model and real samples with gelatin-zein-PB/CNT-SPCEs had a recovery of close to 100% of the true value. Since they are easily and cheaply made and yield accurate target assessments, gelatin-zein-PB/CNT-SPCEs are an ideal tool for electrochemical H₂O₂ analyses in human body fluids, health care products, and samples from industries that use H₂O₂ as a bleach and germicide. Workers with little experience in sensor fabrication and limited funding will particularly benefit from utilization of the proposed H₂O₂ probes, which as well as being used in H₂O₂ testing also have a potential application as the transducer unit of oxidase-based biosensors with amperometric H₂O₂ readout.

Electrochemical Synthesis of Zinc Oxide Nanostructures on Flexible Substrate and Application as an Electrochemical Immunoglobulin-G Immunosensor

Immunoglobulin G (IgG), a type of antibody, represents approximately 75% of serum antibodies in humans, and is the most common type of antibody found in blood circulation. Consequently, the development of simple, fast and reliable systems for IgG detection, which can be achieved using electrochemical sandwich-type immunosensors, is of considerable interest. In this study we have developed an immunosensor for human (H)-IgG using an inexpensive and very simple fabrication method based on ZnO nanorods (NRs) obtained through the electrodeposition of ZnO. The ZnO NRs were treated by electrodepositing a layer of reduced graphene oxide (rGO) to ensure an easy immobilization of the antibodies. On Indium Tin Oxide supported on Polyethylene Terephthalate/ZnO NRs/rGO substrate, the sandwich configuration of the immunosensor was built through different incubation steps, which were all optimized. The immunosensor is electrochemically active thanks to the presence of gold nanoparticles tagging the secondary antibody. The immunosensor was used to measure the current density of the hydrogen development reaction which is indirectly linked to the concentration of H-IgG. In this way the calibration curve was constructed obtaining a logarithmic linear range of 10-1000 ng/mL with a detection limit of few ng/mL and good sensitivity.

Mechanochemical synthesis of an AIE-TICT-ESIPT active orange-emissive chemodosimeter for selective detection of hydrogen peroxide in aqueous media and living cells, and solid-phase quantitation using a smartphone

We report herein the design and mechanochemical synthesis of a chemodosimeter, benzothiazole-derived unsymmetrical azine protected by 4-bromomethylphenylboronic acid (BTPAB), an orange aggregation-induced emission (AIE), for the selective detection of H2O2 in a turn-on manner.

A smartphone-interfaced, low-cost colorimetry biosensor for selective detection of bronchiectasis via an artificial neural network

Exhaled breath (EB) contains several macromolecules that can be exploited as biomarkers to provide clinical information about various diseases. Hydrogen peroxide (H₂O₂) is a biomarker because it indicates bronchiectasis in humans. This paper presents a non-invasive, low-cost, and portable quantitative analysis for monitoring and quantifying H₂O₂ in EB. The sensing unit works on colorimetry by the synergetic effect of eosin blue, potassium permanganate, and starch-iodine (EPS) systems. Various sampling conditions like pH, response time, concentration, temperature and selectivity were examined. The UV-vis absorption study of the assay showed that the dye system could detect as low as ∼0.011 ppm levels of H₂O₂. A smart device-assisted detection unit that rapidly detects red, green and blue (RGB) values has been interfaced for practical and real-time application. The RGB value-based quantification of the H₂O₂ level was calibrated against NMR spectroscopy and exhibited a close correlation. Further, we adopted a machine learning approach to predict H₂O₂ concentration. For the evaluation, an artificial neural network (ANN) regression model returned 0.941 R² suggesting its great prospect for discrete level quantification of H₂O₂. The outcomes exemplified that the sensor could be used to detect bronchiectasis from exhaled breath.

Detection of bronchiectasis from exhaled breath.

A Label-Free Electrochemical Immunosensor for CEA Detection on a Novel Signal Amplification Platform of Cu2S/Pd/CuO Nanocomposites

Carcinoembryonic antigen (CEA) is regarded as one of the crucial tumor markers for colorectal cancer. In this study, we developed the snowflake Cu₂S/Pd/CuO nanocomposite to construct an original label-free electrochemical immunosensor for the ultrasensitive detection of CEA levels. The nanocomposite of cuprous sulfide (Cu₂S) with Pd nanoparticles (Pd NPs) was synthesized through an in situ formation of Pd NPs on the Cu₂S. Cuprous sulfide (Cu₂S) and CuO can not only be used as a carrier to increase the reaction area but also catalyze the substrate to generate current signal. Palladium nanoparticles (Pd NPs) have excellent catalytic properties and good biocompatibility, as well as the ability of excellent electron transfer. The immunosensor was designed using 5 mmol/L H₂O₂ as the active substrate by optimizing the conditions with a detection range from 100 fg/ml to 100 ng/ml and a minimum detection limit of 33.11 fg/ml. The human serum was detected by electrochemical immunoassay, and the results were consistent with those of the commercial electrochemical immunosensor. Therefore, the electrochemical immunosensor can be used for the detection of human serum samples and have potential value for clinical application.

Highly Sensitive Amperometric Detection of Hydrogen Peroxide in Saliva Based on N-Doped Graphene Nanoribbons and MnO2 Modified Carbon Paste Electrodes

Four different graphene-based nanomaterials (htGO, N-htGO, htGONR, and N-htGONR) were synthesized, characterized, and used as a modifier of carbon paste electrode (CPE) in order to produce a reliable, precise, and highly sensitive non-enzymatic amperometric hydrogen peroxide sensor for complex matrices. CPE, with their robustness, reliability, and ease of modification, present a convenient starting point for the development of new sensors. Modification of CPE was optimized by systematically changing the type and concentration of materials in the modifier and studying the prepared electrode surface by cyclic voltammetry. N-htGONR in combination with manganese dioxide (1:1 ratio) proved to be the most appropriate material for detection of hydrogen peroxide in pharmaceutical and saliva matrices. The developed sensor exhibited a wide linear range (1.0–300 µM) and an excellent limit of detection (0.08 µM) and reproducibility, as well as high sensitivity and stability. The sensor was successfully applied to real sample analysis, where the recovery values for a commercially obtained pharmaceutical product were between 94.3% and 98.0%. Saliva samples of a user of the pharmaceutical product were also successfully analyzed.

Nonenzymatic Hydrogen Peroxide Detection Using Surface-Enhanced Raman Scattering of Gold-Silver Core-Shell-Assembled Silica Nanostructures

Hydrogen peroxide (H₂O₂) plays important roles in cellular signaling and in industry. Thus, the accurate detection of H₂O₂ is critical for its application. Unfortunately, the direct detection of H₂O₂ by surface-enhanced Raman spectroscopy (SERS) is not possible because of its low Raman cross section. Therefore, the detection of H₂O₂ via the presence of an intermediary such as 3,3,5,5-tetramethylbenzidine (TMB) has recently been developed. In this study, the peroxidase-mimicking activity of gold–silver core–shell-assembled silica nanostructures (SiO₂@Au@Ag alloy NPs) in the presence of TMB was investigated using SERS for detecting H₂O₂. In the presence of H₂O₂, the SiO₂@Au@Ag alloy catalyzed the conversion of TMB to oxidized TMB, which was absorbed onto the surface of the SiO₂@Au@Ag alloy. The SERS characteristics of the alloy in the TMB–H₂O₂ mixture were investigated. The evaluation of the SERS band to determine the H₂O₂ level utilized the SERS intensity of oxidized TMB bands. Moreover, the optimal conditions for H₂O₂ detection using SiO₂@Au@Ag alloy included incubating 20 µg/mL SiO₂@Au@Ag alloy NPs with 0.8 mM TMB for 15 min and measuring the Raman signal at 400 µg/mL SiO₂@Au@Ag alloy NPs.