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1. Electrochemical Detection of H2O2 Using Bi2O3/Bi2O2Se Nanocomposites

   https://doi.org/10.3390/nano14191592  

   Walimbe, Pooja D; Kumar, Rajeev; Shringi, Amit Kumar; Keelson, Obed; Ouma, Hazel Achieng; Yan, Fei (October 2024, Nanomaterials)

   The development of high-performance hydrogen peroxide (H2O2) sensors is critical for various applications, including environmental monitoring, industrial processes, and biomedical diagnostics. This study explores the development of efficient and selective H2O2 sensors based on bismuth oxide/bismuth oxyselenide (Bi2O3/Bi2O2Se) nanocomposites. The Bi2O3/Bi2O2Se nanocomposites were synthesized using a simple solution-processing method at room temperature, resulting in a unique heterostructure with remarkable electrochemical characteristics for H2O2 detection. Characterization techniques, including powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), confirmed the successful formation of the nanocomposites and their structural integrity. The synthesis time was varied to obtain the composites with different Se contents. The end goal was to obtain phase pure Bi2O2Se. Electrochemical measurements revealed that the Bi2O3/Bi2O2Se composite formed under optimal synthesis conditions displayed high sensitivity (75.7 µA µM−1 cm−2) and excellent selectivity towards H2O2 detection, along with a wide linear detection range (0–15 µM). The superior performance is attributed to the synergistic effect between Bi2O3 and Bi2O2Se, enhancing electron transfer and creating more active sites for H2O2 oxidation. These findings suggest that Bi2O3/Bi2O2Se nanocomposites hold great potential as advanced H2O2 sensors for practical applications. 

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2. Electrochemical Sensing of Hydrogen Peroxide Using Composite Bismuth Oxide/Bismuth Oxyselenide Nanostructures: Antagonistic Influence of Tungsten Doping

   https://doi.org/10.3390/electrochem5040030  

   Walimbe, Pooja D; Kumar, Rajeev; Shringi, Amit Kumar; Keelson, Obed; Ouma, Hazel Achieng; Yan, Fei (December 2024, Electrochem)

   This study investigates the underlying mechanisms of hydrogen peroxide (H₂O₂) sensing using a composite material of bismuth oxide and bismuth oxyselenide (Bi2OxSey). The antagonistic effect of tungsten (W)-doping on the electrochemical behavior was also examined. Undoped, 2 mol%, 4 mol%, and 6 mol% W-doped Bi2OxSey nanostructures were synthesized using a one-pot solution phase method involving selenium powder and hydrazine hydrate. W-doping induced a morphological transformation from nanosheets to spherical nanoparticles and amorphization of the bismuth oxyselenide phase. Electrochemical sensing measurements were conducted using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). H₂O₂ detection was achieved over a wide concentration range of 0.02 to 410 µM. In-depth CV analysis revealed the complex interplay of oxidation-reduction processes within the bismuth oxide and Bi2O2Se components of the composite material. W-doping exhibited an antagonistic effect, significantly reducing sensitivity. Among the studied samples, undoped Bi2OxSeγ demonstrated a high sensitivity of 83 μA μM⁻1 cm⁻2 for the CV oxidation peak at 0 V, while 6 mol% W-Bi2OxSey became completely insensitive to H2O2. Interestingly, DPV analysis showed a reversal of sensitivity trends with 2 and 4 mol% W-doping. The applicability of these samples for real-world analysis, including rainwater and urine, was also demonstrated. 

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3. Biomass-derived porous graphene for electrochemical sensing of dopamine

   https://doi.org/10.1039/D1RA00735A  

   Mahmood, Faisal; Sun, Yisheng; Wan, Caixia (April 2021, RSC Advances)

   null (Ed.)

   Cost-effective valorization of biomass into advanced carbon remains a challenge. Here we reported a facile and ultrafast laser writing technique to convert biomass into porous graphene for electrochemical sensing. Laser-induced graphene (LIG) was synthesized from a fully biomass-based film composed of kraft lignin (KL) and cellulose nanofibers (CNFs). The LIG-based electrode was applied to detect dopamine using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Dopamine with a concentration ranging from 5 to 40 μM was detected linearly, with a sensitivity of 4.39 μA μM −1 cm −2 . Our study eliminated the use of synthetic polymer for lignin-based film formation. It demonstrated the feasibility of using the film fully composed of biomass for LIG formation. Furthermore, derived LIG electrodes were shown to have high electrochemical sensing performance. 

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4. Advances and opportunities in point-of-care detection of toxic metals: a review of electrochemical and non-electrochemical approaches

   https://doi.org/10.1039/D6AN00248J  

   Udawaththa, Navoda; Zubak, Olga; Daninger, Ashley; Page, Ralph; Strini, Miriam; Romero, Brianna; Pathirathna, Pavithra (April 2026, The Analyst)

   Heavy metal contamination remains a persistent global threat to human health and the environment, driving the urgent need for rapid, portable, and sensitive detection technologies. Recent advances in point-of-care (POC) platforms have enabled real-time monitoring of toxic metals in diverse matrices, including soil, water, food, and biological fluids. Electrochemical approaches, particularly screen-printed electrode systems, have emerged as highly adaptable tools. These systems achieve ultralow detection limits through nanomaterial modifications and enable multiplexed detection using techniques such as square-wave anodic stripping voltammetry and differential pulse voltammetry. Complementary paper-based analytical devices provide low-cost, disposable, and environmentally friendly sensing formats. These platforms integrate electrochemical, fluorescent, and colorimetric strategies, often coupled with smartphone-based readouts for real-time field deployment. Smartphone-integrated systems further enhance accessibility by combining miniaturized sensing with wireless connectivity, cloud-based data sharing, and machine learning algorithms that improve signal analysis and enable predictive monitoring. Portable optical spectroscopy kits extend sensitivity to trace metals in clinical, environmental, and food matrices, while wearable sensors, including textiles, wristbands, patches, and gloves, allow for noninvasive, continuous assessment of biofluids and environmental exposures. Importantly, emerging ultrafast electrochemical techniques, such as fast-scan cyclic voltammetry at carbon fiber microelectrodes, hold the potential to detect metal speciation with unprecedented temporal resolution. When coupled with artificial intelligence (AI), these approaches can deconvolute overlapping signals, enhance selectivity, and provide actionable insights into exposure dynamics. Collectively, these POC platforms represent a trajectory toward miniaturized, intelligent, and multiplexed sensing systems, offering scalable, real-world solutions for environmental monitoring, occupational safety, and personalized healthcare. The integration of advanced electrochemical methods, wearable technologies, and AI-driven analytics highlights the transformative potential of next-generation POC devices for comprehensive heavy metal surveillance. 

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5. Laser-Trimmed, Surface-Functionalized Four-Bore CFMs Enable Co-Detection of Neurochemicals and Toxic Metal Ions

   https://doi.org/10.3390/chemosensors13120423  

   Udawaththa, Navoda; Daninger, Ashley; Manring, Noel; Guillen, Valentina; Koifman, Gene; Pathirathna, Pavithra (December 2025, Chemosensors)

   Simultaneous detection of multiple neurochemicals and toxic metal ions in real time remains a major analytical challenge in neurochemistry and environmental sensing. In this study, we present a novel, biocompatible, laser-trimmed four-bore carbon fiber microelectrode (CFM) platform capable of ultra-fast, multi-analyte detection using fast-scan cyclic voltammetry (FSCV). Each of the four carbon fibers, spaced nanometers apart within a glass housing, was independently functionalized and addressed with a distinct waveform, allowing the selective and concurrent detection of four analytes without electrical crosstalk. To validate the system, we developed two electrochemical detection paradigms: (1) selective electrodeposition of gold nanoparticles (AuNPs) on one fiber for enhanced detection of cadmium (Cd²⁺), alongside dopamine (DA), arsenic (As³⁺), and copper (Cu²⁺); and (2) Nafion-modification of two diagonally opposing fibers for discriminating DA and serotonin (5-HT) from their interferents, ascorbic acid (AA) and 5-hydroxyindoleacetic acid (5-HIAA), respectively. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis confirmed surface modifications and the spatial localization of electrodeposited materials. Electrochemical characterization in tris buffer, which mimics artificial cerebrospinal fluid, demonstrated enhanced analytical performance. Compared to single-bore CFMs, the four-bore design yielded a 28% increase in sensitivity for Cd²⁺ (147.62 to 190.02 nA µM⁻¹), 12% increase for DA (10.785 to 12.767 nA µM⁻¹), and enabled detection of As³⁺ with a sensitivity of 0.844 nA µM⁻¹, which was not possible with single-bore electrodes within the mixture of analytes. Limits of detection improved twofold for both DA (0.025 µM) and Cd²⁺ (0.005 µM), while As³⁺ was detectable down to 0.1 µM. In neurotransmitter-interference studies, sensitivity increased by 39% for DA and 33% for 5-HT with four-bore CFMs compared to single-bore CFMs, despite modest Nafion diffusion onto adjacent fibers. Overall, our four-bore CFM system enables rapid, selective, and multiplexed detection of chemically diverse analytes in a single scan, providing a highly promising platform for real-time neurochemical monitoring, envi-ronmental toxicology, and future integration with AI-based in vivo calibration models. 

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