Anodized porous silicon films have been widely studied for biosensing applications, enabling label-free optical detection of numerous targets. Their appeal stems from the unique combination of tunable micro- and nanostructure with strong photonic properties, allowing precise control over pore size, layer thickness, and optical interference modes. Together with the large internal surface area, these attributes position PSi as a highly versatile optical transducer platform.
However, our work has shown that this same nanostructure also introduces a fundamental bottleneck: analyte delivery to reactive sites inside the porous matrix is strongly limited by mass transport. In PSi biosensors, target molecules must diffuse from the bulk solution to the sensor surface and then infiltrate the porous network, where transport is hindered by nanoscale confinement and coupled to surface binding kinetics. This leads to analyte depletion at pore entrances and along pore walls, effectively decoupling photonic sensitivity and surface area from molecular recognition, and imposing severe limits on detection performance at low analyte concentrations.
This talk will focus on integrated strategies to overcome these limitations by simultaneously engineering
mass transport and surface chemistry
in PSi optical biosensors for biomedical applications. We will present approaches developed by our group to enhance sensitivity using electrokinetic focusing for on-chip analyte pre-concentration, as well as microfluidic designs that promote convective transport and reduce diffusion boundary layers. In addition, we will discuss surface passivation strategies to minimize non-specific binding and the rational tailoring of capture probe conjugation to preserve accessibility and binding efficiency within the porous network. Together, these examples illustrate how aligning photonic design, mass transport, and surface chemistry enables porous silicon biosensors to move beyond diffusion-limited operation toward highly sensitive, application-relevant detection.
The integration of molecularly imprinted polymers (MIPs) onto silicon-based microfabricated electrodes represents a frontier in the development of selective, miniaturized, and intelligent electrochemical sensors. This approach merges the molecular recognition precision of synthetic polymers with the reproducibility and scalability of microfabrication technologies, opening new pathways toward compact, high-performance analytical platforms. In this work, nanocrystalline graphite (NCG) is employed as the primary electrode material owing to its exceptional conductivity, chemical stability, and compatibility with silicon processing. Its nanostructured surface promotes strong adhesion and uniform distribution of polymer films, while facilitating rapid electron transfer across the sensing interface.
To achieve molecular selectivity, MIP layers based on chitosan and polypyrrole (PPy) are electropolymerized on the NCG microelectrodes. Chitosan provides a biocompatible and chemically versatile scaffold capable of forming hydrogen bonds and coordinating with target analytes, whereas polypyrrole contributes high electrical conductivity and structural integrity to the recognition matrix. The imprinting process is designed for two environmentally critical pollutants: glyphosate, a widely used organophosphorus herbicide with potential carcinogenic effects, and bisphenol A (BPA), a known endocrine disruptor associated with plastic waste contamination. The accurate, on-site detection of these molecules is crucial for addressing global challenges related to environmental safety, food quality, and human health.
Beyond conventional MIP systems, this work introduces an advanced molecularly imprinted nanozyme (MINZ) architecture, achieved by integrating sulfur-doped graphene (S–Gr) into the polymer matrix. The incorporation of S–Gr significantly enhances the electron transfer kinetics and catalytic properties of the hybrid layer due to sulfur-induced defect sites that act as active catalytic centers. These heteroatom-doped graphene networks mimic natural enzyme-like behavior, providing peroxidase- and oxidase-like activity that amplifies electrochemical signals while preserving molecular recognition fidelity. The resulting MIP–S–Gr hybrid behaves as an artificial nanozyme layer capable of selective recognition and signal transduction, thus representing the next level of intelligent sensing interfaces.
The synergy between the silicon-based microelectrode platform, nanocrystalline graphite, biopolymer–conductive polymer hybrid MIPs, and sulfur-doped graphene nanozyme nanostructures establishes a multifunctional sensing interface that is selective, stable, and scalable. This architecture supports real-time and in situ monitoring of hazardous organic contaminants, with potential for integration into lab-on-chip and portable devices. Overall, this study demonstrates a promising strategy toward next-generation molecularly imprinted nanozyme electrochemical sensors, combining nanostructured materials, green polymer chemistry, and silicon microtechnology for advanced environmental and biomedical applications.
Figure 1
L. A. Dinu, C. Parvulescu, M. Aldrigo et al.· ECS Meeting Abstracts· 0 citations
Graphene is particularly well-suited for the fabrication of field-effect biosensors (bioGFETs) [1], due to its chemical stability in aqueous media and its reduced dimensionality resulting in an electrical conductivity highly sensitive to biochemical processes occurring at its surface. The selectivity of GFETs for specific molecular targets, however, must be engineered with the addition of biorecognition elements such as antibodies or nucleic acids. Immobilizing such bioreceptors hinges on introducing chemically addressable moieties on the graphene, without impeding the electrical sensitivity. In this talk, I will first present our work on optimizing the chemical functionalization of graphene to combine bioconjugation and electrical signals. I will describe our findings on controlling various functionalization routes, both covalent and non-covalent, with a particular focus on our recent advances in gate-controlled surface chemistry on graphene [2]. I will also describe our current efforts to develop parallelized instrumentation for high-throughput fabrication and characterization of on-chip biosensors [3]. Finally, I will outline our translational perspectives aimed at adapting nanocarbon-based bioFETs into lab-on-a-chip platforms for diagnostic applications.
[1] Béraud
et al
. Analyst, 146, 403 (2021)
[2] Bazán
et al
. Nano Letters 22, 2635 (2022)
[3] Bencherif
et al
. npj 2D materials and applications, 8, 53 (2024)
Organic electrochemical transistors (OECTs) are emerging as powerful biosensing platforms, offering high transduction efficiency, low‐voltage operation, and intrinsic compatibility with aqueous and physiological environments. Central to their recent progress is the strategic integration of biomaterials, which govern interfacial charge transfer, doping dynamics, and recognition specificity. A complete understanding of biomaterial‐enabled OECTs requires not only insights into intrinsic material chemistry but also interface engineering and device design principles that dictate signal transduction and reproducibility. In this review, we critically examine the full spectrum of biomaterials integrated into OECT biosensors (from natural macromolecules, such as proteins, nucleic acids, and polysaccharides to biocompatible polymers and synthetic engineered interfaces). Particular emphasis is placed on interfacial chemistries, including silanization and click reactions, that control receptor orientation, density, and long‐term stability. Beyond materials design, we discuss operating physics, signal transduction mechanisms, and device engineering strategies, thereby linking molecular‐scale chemistry with device‐level performance. By consolidating these interdisciplinary advances, we provide a timely roadmap for reproducible, scalable, and clinically relevant OECT biosensors. With growing demand for high‐performance and sustainable sensing platforms in precision medicine and environmental monitoring, this review highlights both key achievements and outstanding challenges that will shape the next generation of bioelectronic technologies.
A. Nawaz, L. Merces, Prashant Sonar· Advanced Functional Material...· 0 citations
As biosensing platforms based on solid-state electronics continue to evolve toward higher sensitivity, selectivity, and integration density, material-level innovation and surface functionalization have emerged as defining technological requirements. Until the early 2020s, carbon nanotubes (CNTs), graphene, nanomaterials, and metal nanoparticles have been extensively explored as promising signal and enzyme transducers due to their excellent electrical conductivity and large specific surface area. However, for practical biosensing applications, room-temperature process strategies that simultaneously enhance surface reactivity and enzyme loading while preserving or improving electrical transport properties remain insufficiently developed. In particular, CNT functionalization has often relied on high-temperature thermal treatments or high-energy chemical processes, resulting in limited efficiency relative to resource input and inherent constraints in improving loading capacity and sensing sensitivity.
Motivated by these limitations, our work began with the development of room-temperature CNT surface functionalization using low-power plasma processes compatible with semiconductor fabrication. By employing damage-free remote SF
6
plasma treatment, semi-permanent semi-ionic C–F bonds (physically adsorbed fluorine) were introduced onto CNT surfaces without degrading intrinsic conduction pathways. This approach enabled simultaneous enhancement of surface chemical reactivity and charge-transfer characteristics, without resorting to conventional high-temperature, high-energy, or acid-based treatments. As a result, plasma-functionalized CNTs exhibited a threefold increase in sensing sensitivity, a twofold reduction in charge-transfer resistance, and more than a sixfold enhancement in glucose oxidase (GOx) loading compared to pristine CNTs. These results quantitatively demonstrate how surface chemistry can alleviate charge-transport bottlenecks and how such correlations directly translate into amplified electrical signals in solid-state biosensors.
This surface chemistry–charge transport correlation–based strategy is not limited to CNTs and instead provides a conceptual foundation that can be naturally extended to two-dimensional (2D) materials, where more precise control of electronic and interfacial properties is possible. Owing to their atomic-scale thickness, high carrier mobility, and electrical and mechanical properties surpassing those of silicon, 2D materials (transition metal dichalcogenides (TMDs), graphene, boron nitride, etc.) have emerged as strong candidates for next-generation solid-state bio- and chemical sensing platforms. When combined with low-temperature, maskless laser and plasma-based surface engineering, these materials enable sensing functionalities that are intrinsically embedded within the channel.
In this context, laser-induced local oxidation and doping profile formation in TMDs such as WSe
2
produce pronounced electrical modulations, including threshold voltage (V
TH
) shifts, enhanced ambipolar behavior, and increased interfacial state density, thereby creating active domains that are highly sensitive to external chemical stimuli. In contrast, plasma treatments using nitrogen, oxygen, argon, or SF
6
introduce distinct defect states, adsorption sites, and charge-trapping characteristics, enabling process-dependent surface reactivity patterns even within a single 2D channel.
Device-level validation of these surface-engineered domains was achieved through droplet-based pH sensing experiments using sub-microliter volumes on fully fabricated field-effect transistor devices. Laser-oxidized regions exhibited clear and directional V
TH
shifts and drain current modulation in response to pH variations, whereas plasma-treated regions showed electrical responses with different magnitudes and polarities depending on the induced defect and adsorption characteristics. These observations directly reflect the distinct surface chemistry and interfacial charge dynamics introduced by each process and further indicate that sensitivity, linearity, and response speed can be selectively optimized through laser–plasma process combinations. By demonstrating reproducible electrical responses of laser-oxidized and plasma-functionalized 2D channels to external chemical stimuli such as pH and basic solutions, this research highlights a new direction for solid-state bio- and chemical sensing platforms enabled by the convergence of solid-state electronics with photonic and plasma-based surface engineering.
Structured boron‐doped diamond (BDD) electrodes have evolved beyond planar interfaces into a promising platform for electrochemical sensing. By introducing deliberately engineered micro‐ and nanostructures, the electrode–electrolyte interface can be tailored to enhance analytical performance while preserving the excellent properties of BDD, including wide potential window, chemical robustness, and resistance to fouling. Although the first sensing studies on structured BDD appeared in the late 2000s and the field has expanded markedly since then, no review has yet focused specifically on structured BDD for sensing and electroanalysis. This mini‐review fills that gap by summarizing the reported top‐down and bottom‐up fabrication strategies and the resulting architectures, including nanowires, nanograss, porous films, and template‐derived three‐dimensional structures. Their applications are discussed across major analyte classes, from neurotransmitters and other biologically relevant small molecules to biomacromolecules and toxic heavy metal ions. Particular emphasis is placed on emerging structure–property–performance relationships, showing that the benefits of structuring cannot be explained by surface area increase alone, but arise from the interplay of morphology, accessibility, mass transport, and local surface chemistry. Current challenges and future directions are also outlined, especially with respect to reproducibility, scalability, and device integration.
Ghazaleh Kholafazadehastamal, K. Schwarzová‐Pecková, S. Baluchová· Analysis & Sensing· 0 citations
Surface-enhanced Raman scattering (SERS) is a powerful analytical technique for label-free, ultrasensitive biochemical detection, offering broad potential for biomedical, environmental monitoring, and defense applications. However, conventional noble-metal SERS substrates remain limited by chemical instability, insufficient enhancement reproducibility, and slow analyte detection in dilute aqueous solutions. Recently, hybrid SERS platforms that integrate plasmonic nanostructures with functional material systems—such as semiconductors, two-dimensional materials, photonic crystals, and active robotic modules—have emerged as promising strategies to overcome these limitations. In this review, we examine recent advances in hybrid SERS platforms from the perspective of material systems. Their working principles can be broadly categorized into two types: functional materials that regulate interfacial electromagnetic and chemical enhancement, and robotized systems that promote targeted analyte access or active enrichment at sensing hotspots. By linking material properties, working mechanisms, and sensing performance, this review provides a materials-based perspective to guide the rational design of high-performance, application-oriented SERS platforms.
J. Bao, Bin Lian, H. Joh et al.· Materials and Interfaces· 0 citations