Search for: All records

Abstract In fighting against infectious diseases such as COVID‐19, simple‐to‐use, sensitive, scalable, and rapid diagnostics are crucial for early disease diagnosis. In this regard, electrochemical biosensors are particularly attractive in developing point‐of‐need diagnostics. Importantly, by being compatible with nano‐ and microfabrication methods, they are amenable to miniaturization, which reduces background noise and the required sample volume. However, miniaturization also reduces the signal level, making it challenging to detect low virus counts. In this work, microfabricated electrochemical sensors with a dual signal amplification scheme based on evaporation‐enhanced redox cycling (E2RC) in a generator–collector configuration are developed. A scalable, nanolithography‐free fabrication method is proposed to achieve a controllable sub‐micrometer gap between three dimensional (3D) interdigitated microelectrodes by combining photolithography with template‐driven electrodeposition. Using the optimized electrodes, the sensors achieve rapid detection with a limit of quantification of ≈1.2 × 10³particles mL⁻¹through continuous measurement in evaporating droplets containing SARS‐CoV‐2 virion mimics. Investigating particle charge and size reveals the role of electrophoretic enrichment in the overall response. The sensor performance is also validated using heat‐inactivated SARS‐CoV‐2 virions, with selective response to SARS‐CoV‐2 against HCoV‐299E, SARS‐CoV S1, and MERS‐CoV S1 (captured using antibody‐functionalized magnetic nanoparticles). The proposed sensing method is sensitive, rapid, scalable, and can be extended to broader applications, including detection of bacteria, extracellular vesicles, and other viruses. 

Abstract Engineering superlattices (SLs)—which are spatially periodic potential landscapes for electrons—is an emerging approach for the realization of exotic properties, including superconductivity and correlated insulators, in two-dimensional materials. While moiré SL engineering has been a popular approach, nanopatterning is an attractive alternative offering control over the pattern and wavelength of the SL. However, the disorder arising in the system due to imperfect nanopatterning is seldom studied. Here, by creating a square lattice of nanoholes in the SiO₂dielectric layer using nanolithography, we study the SL potential and the disorder formed in hBN-graphene-hBN heterostructures. Specifically, we observe that while electrical transport shows distinct SL satellite peaks, the disorder of the device is significantly higher than graphene devices without any SL. We use finite-element simulations combined with a resistor network model to calculate the effects of this disorder on the transport properties of graphene. We consider three types of disorder: nanohole size variations, adjacent nanohole mergers, and nanohole vacancies. Comparing our experimental results with the model, we find that the disorder primarily originates from nanohole size variations rather than nanohole mergers in square SLs. We further confirm the validity of our model by comparing the results with quantum transport simulations. Our findings highlight the applicability of our simple framework to predict and engineer disorder in patterned SLs, specifically correlating variations in the resultant SL patterns to the observed disorder. Our combined experimental and theoretical results could serve as a valuable guide for optimizing nanofabrication processes to engineer disorder in nanopatterned SLs. 

Recent advances in graphene-based electroanalytical biodevices: different methods for graphene synthesis, functionalization, device fabrication, and transduction mechanisms are discussed for various healthcare applications. 

We present a scalable solution-processing method for fabricating high-quality graphene and graphene/1T-MoS 2 heterostructure films. The process begins with the synthesis of potassium-intercalated graphite (KC 8 ), which is exfoliated in tetrahydrofuran (THF) to produce stable dispersions of negatively charged (electron rich) graphene sheets. The graphene is subsequently transferred to water, forming a surfactant-free aqueous dispersion suitable for creating homogenous graphene films via vacuum filtration and stamping. Additionally, graphene is combined with 1T-MoS 2 nanosheets to fabricate graphene/1T-MoS 2 bulk heterostructure films. Comprehensive characterization, including X-ray diffraction (XRD), absorption spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy ( TEM), Raman spectroscopy, and X-ray photon emission spectroscopy (XPS), reveals that the heterostructure films exhibit enhanced optical and electronic properties, including improved light absorption, which could lead to novel photo-responsive devices. Raman spectroscopy shows significant changes in the graphene’s structural a nd electronic properties upon interaction with MoS 2 , indicating strong interlayer coupling and potential charge transfer between the layered components. The g raphene films demonstrate highly sensitive detection of dopamine (DA), while the graphene/1T-MoS 2 b ulk heterostructure films exhibit capacitance values up to 3 8.3 Fg − 1 at 5 mV/s in non-aqueous electrolytes. These results highlight the potential of these films for advanced applications in molecular sensing and energy storage.