Ali Ashraf

Moiré superlattices at two-dimensional (2D) material interfaces enable emergent electronic, electrical, and optical phenomena, yet their preparation remains constrained by complex fabrication and limited throughput. Here, we transform the preparation of hexagonal boron nitride (hBN) moiré homojunctions from a fabrication challenge into a classification problem by directly identifying parallel-stacked moiré samples with long wavelengths from spontaneously self-folded flakes following tape exfoliation. By exploiting the intrinsic cleavage behavior and wrinkle formation of layered materials, this strategy enables efficient screening and scalable batch production of these specific moiré structures. Correlative electrostatic force microscopy (EFM) and transmission electron microscopy (TEM) reveal that only parallel-stacked flakes exhibit electrostatic contrast associated with out-of-plane polarization. EFM, Kelvin probe force microscopy (KPFM), and Raman spectroscopy further identify AB/BA stacking domains and their transition regions. To accelerate and automate moiré identification, an XGBoost-based screening workflow achieves a mean test ROC-AUC of 0.78 ± 0.14. Compared with the conventional tear-and-stack approach, this method reduces moiré preparation time by at least 40% while eliminating manual stacking, providing a simple, scalable, and broadly applicable strategy for preparing high-quality interfacial moiré superlattices in 2D materials for next-generation moiré-based electronic and optoelectronic devices.

In this research, an interdigitated gear-shaped working electrode is presented for cortisol sensing. Overall, the sensor was designed in a three-electrode system and was fabricated using direct laser scribing. A synthesized conductive ink based on graphene and polyaniline was further employed to enhance the electrochemical performance of the sensor. Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were employed for physicochemical characterization of the laser-induced graphene (LIG) sensor. Cortisol, a biomarker essential in detecting stress, was detected both in phosphate-buffered saline (PBS, pH = 7.4) and human serum within a linear range of 100 ng/mL to 100 µg/mL. Ferri/ferrocyanide was employed as the redox probe to detect cortisol in PBS. The electrochemical performance of the developed sensor was assessed via differential pulse voltammetry (DPV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The electrochemical performance demonstrates high sensitivity and selectivity alongside strong repeatability (relative standard deviation (RSD) = 3.8%, n = 4) and reproducibility (RSD = 5.85%, n = 5). Overall, these results highlight the sensor’s reliability, high sensitivity, and repeatability and reproducibility in the detection of cortisol. The sensor successfully detected cortisol in the complex medium of human serum and effectively distinguished it in a ternary mixture containing cortisol and dopamine. Also, the use of direct laser writing on Kapton film makes the approach cost-effective and thus disposable, making it suitable for chronic stress diagnostics and neurological research applications.

A graphene nanoflake (GNF)‐enhanced elastomeric nanocomposite (G‐EMC) is fabricated following an innovative, cost‐effective, single‐step, in situ shear exfoliation (ISE) method from low‐cost bulk material, graphite, where uniform mixing happens simultaneously within the elastomer matrix. Electron microscopy, atomic force microscopy, and photo‐induced force microscopy results show good dispersion of GNFs with exfoliation to a few layers and uniform distribution in the elastomer matrix. X‐ray photoelectron spectroscopy analysis shows less than 1% oxygen‐containing functional groups/impurity, enhanced bonding through the formation of edge sites as fracture occurs across the GNF basal plane, and pi‐pi interactions with newly exfoliated planar basal plane surfaces of the GNFs. Raman spectroscopy results confirm the formation of GNFs with only a few layers of graphene formed by the ISE process. Fabricated 10 wt.% G‐EMC nanocomposites show a 400%–500% increase in strength and fracture toughness. And 35 wt.% G‐EMCs provide an electrical conductivity of 25.64 S m⁻¹ and a sensor gauge factor of 45. The resulting intrinsic piezo resistivity of the fabricated nanocomposite has been exploited to fabricate a multi‐functional wired and wireless sensor for detecting different body movements, speech, human vital functions, solvents, and biomolecules.

In this research, a novel interdigitated gear-shaped, graphene-based electrochemical biosensor was developed for the detection of dopamine (DA). The sensor’s innovative design improves the active surface area by 94.52% and 57% compared to commercially available Metrohm DropSens 110 screen-printed sensors and printed circular sensors, respectively. The screen-printed electrode was fabricated using laser processing and modified with graphene polyaniline conductive ink (G-PANI) to enhance its electrochemical properties. Fourier Transform Infrared (FTIR) Spectroscopy and X-ray diffraction (XRD) were employed to characterize the physiochemical properties of the sensor. Dopamine, a neurotransmitter crucial for several body functions, was detected within a linear range of 0.1–100 µM, with a Limit of Detection (LOD) of 0.043 µM (coefficient of determination, R² = 0.98) in phosphate-buffer saline (PBS) with ferri/ferrocyanide as the redox probe. The performance of the sensor was evaluated using cyclic voltammetry (CV) and Chronoamperometry, demonstrating high sensitivity and selectivity. The interdigitated gear-shaped design exhibited excellent repeatability, with a relative standard deviation (RSD) of 1.2% (n = 4) and reproducibility, with an RSD of 2.3% (n = 4). In addition to detecting dopamine in human serum, the sensor effectively distinguished dopamine in a ternary mixture containing uric acid (UA) and ascorbic acid (AA). Overall, this novel sensor design offers a reliable, disposable, and cost-effective solution for dopamine detection, with potential applications in medical diagnostics and neurological research.

In this research, a novel electrochemical biosensor is proposed based on inducing graphene formation on polyimide substrate via laser engraving. Graphene polyaniline (G-PANI) conductive ink was synthesized by planetary mixing and applied to the working zone of the developed sensor to effectively enhance the electrical signals. The laser-induced graphene (LIG) sensor was used to detect alpha-fetoprotein (AFP) and 17β-Estradiol (E2) in the phosphate buffer saline (PBS) buffer and human serum. The electrochemical performance of the biosensor in determining these biomarkers was investigated by differential pulse voltammetry (DPV) and chronoamperometry (CA). In a buffer environment, alpha-fetoprotein (AFP) and 17β-Estradiol detection range were 4–400 ng/mL and 20–400 pg/mL respectively. The experimental results showed a limit of detection (LOD) of 1.15 ng/mL and 0.96 pg/mL for AFP and estrogen, respectively, with an excellent linear range (R² = 0.98 and 0.99). In addition, the designed sensor was able to detect these two types of biomarkers in human serum successfully. The proposed sensor exhibited excellent reproducibility, repeatability, and good stability (relative standard deviation, RSD = 0.96%, 1.12%, 2.92%, respectively). The electrochemical biosensor proposed herein is easy to prepare and can be successfully used for low-cost, rapid detection of AFP and E2. This approach provides a promising platform for clinical detection and is advantageous to healthcare applications.

Novel and flexible disposable laser-induced graphene (LIG) sensors modified with graphene conductive inks have been developed for dopamine and interleukin-6 (IL-6) detection. The LIG sensors exhibit high reproducibility (relative standard deviation, RSD = 0.76%, N = 5) and stability (RSD = 4.39%, N = 15) after multiple bendings, making the sensors ideal for wearable and stretchable bioelectronics applications. We have developed electrode coatings based on graphene conductive inks, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (G-PEDOT:PSS) and polyaniline (G-PANI), for working electrode modification to improve the sensitivity and limit of detection (LOD). The selectivity of LIG sensors modified with the G-PANI ink is 41.47 times higher than that of the screen-printed electrode with the G-PANI ink modification. We have compared our fabricated bare laser-engraved Kapton sensor (LIG) with the LIG sensors modified with G-PEDOT (LIG/G-PEDOT) and G-PANI (LIG/G-PANI) conductive inks. We have further compared the performance of the fabricated electrodes with commercially available screen-printed electrodes (SPEs) and screen-printed electrodes modified with G-PEDOT:PSS (SPE/G-PEDOT:PSS) and G-PANI (SPE/G-PANI). SPE/G-PANI has a lower LOD of 0.632 μM compared to SPE/G-PEDOT:PSS (0.867 μM) and SPE/G-PANI (1.974 μM). The lowest LOD of the LIG/G-PANI sensor (0.4084 μM, S/N = 3) suggests that it can be a great alternative to measure dopamine levels in a physiological medium. Additionally, the LIG/G-PANI electrode has excellent LOD (2.6234 pg/mL) to detect IL-6. Also, the sensor is successfully able to detect ascorbic acid (AA), dopamine (DA), and uric acid (UA) in their ternary mixture. The differential pulse voltammetry (DPV) result shows peak potential separation of 229, 294, and 523 mV for AA-DA, DA-UA, and UA-AA, respectively.

Biosensing technology has advanced significantly in recent years because of its wide applications in healthcare and biomolecule detection. However, fabricating a biosensor that will be rapid, sensitive, inexpensive, simple, and selective can be challenging. In this study, we fabricated a paper-based biosensor using conductive polymers (CPs) and graphene to detect Interleukin-6 (IL-6) in human serum. Cross-sectional scanning electron microscopy (SEM) was carried out and the images indicated that flat graphene nanoflake (GNF) sheets are connected to the fibrous structure of cellulose. We used 20 μL of human serum and 2 μL of IL-6 antigen concentration to measure the electrical impedance spectroscopy (EIS) using Autolab potentiostat (PGSTAT302N). A typical three-electrode method was preferred over the two-electrode method for better accuracy, and the sensor was connected through an adapter to the potentiostat. The paper-based biosensor detected in the range of 2 pg/mL to 20 μg/mL (the solution was prepared by serial dilution method), and the charge transfer resistance (Rct) increases linearly with the concentration (899 Ω–964 Ω). The limit of detection (LOD) of IL-6 detection was ∼16 pg/mL for our biosensor. Thus, using a portable, simple, sensitive, and inexpensive paper-based biosensor can be a great platform to detect early-stage cancer biomarkers.

Paper-based biosensors are a potential paradigm of sensitivity achieved via microporous spreading/microfluidics, simplicity, and affordability. In this paper, we develop decorated paper with graphene and conductive polymer (herein referred to as graphene conductive polymer paper-based sensor or GCPPS) for sensitive detection of biomolecules. Planetary mixing resulted in uniformly dispersed graphene and conductive polymer ink, which was applied to laser-cut Whatman filter paper substrates. Scanning electron microscopy and Raman spectroscopy showed strong attachment of conductive polymer-functionalized graphene to cellulose fibers. The GCPPS detected dopamine and cytokines, such as tumor necrosis factor-alpha (TNF-α), and interleukin 6 (IL-6) in the ranges of 12.5–400 µM, 0.005–50 ng/mL, and 2 pg/mL–2 µg/mL, respectively, using a minute sample volume of 2 µL. The electrodes showed lower detection limits (LODs) of 3.4 µM, 5.97 pg/mL, and 9.55 pg/mL for dopamine, TNF-α, and IL-6 respectively, which are promising for rapid and easy analysis for biomarkers detection. Additionally, these paper-based biosensors were highly selective (no serpin A1 detection with IL-6 antibody) and were able to detect IL-6 antigen in human serum with high sensitivity and hence, the portable, adaptable, point-of-care, quick, minute sample requirement offered by our fabricated biosensor is advantageous to healthcare applications.

Graphene nanocomposites are a promising class of advanced materials for sensing applications; yet, their commercialization is hindered due to impurity incorporation during fabrication and high costs. The aim of this work is to prepare graphene–polysulfone (G−PSU) and graphene–polyvinylidene fluoride (G−PVDF) nanocomposites that perform as multifunctional sensors and are formed using a one-step, in situ exfoliation process whereby graphite is exfoliated into graphene nanoflakes (GNFs) directly within the polymer. This low-cost method creates a nanocomposite while avoiding impurity exposure since the raw materials used in the in situ shear exfoliation process are graphite and polymers. The morphology, structure, thermal properties, and flexural properties were determined for G−PSU and G−PVDF nanocomposites, as well as the electromechanical sensor capability during cyclic flexural loading, temperature sensor testing while heating and cooling, and electrochemical sensor capability to detect dopamine while sensing data wirelessly. G−PSU and G−PVDF nanocomposites show superior mechanical characteristics (gauge factor around 27 and significantly enhanced modulus), thermal characteristics (stability up to 500 °C and 170 °C for G−PSU and G−PVDF, respectively), electrical characteristics (0.1 S/m and 1 S/m conductivity for G−PSU and G−PVDF, respectively), and distinguished resonant peaks for wireless sensing (~212 MHz and ~429 MHz). These uniquely formed G−PMC nanocomposites are promising candidates as strain sensors for structural health monitoring, as temperature sensors for use in automobiles and aerospace applications, and as electrochemical sensors for health care and disease diagnostics.