A nanofluidic sensing platform based on robust and flexible graphene oxide/chitosan nanochannel membranes for glucose and urea detection

Graphene oxide/DNA-aerogel pressure and acoustic sensor

The increasing demand for health monitoring, voice detection, electronic skins, and human-computer interaction has accelerated the development of highly sensitive, flexible, and miniaturized pressure and acoustic sensors. Among various sensing technologies, piezoresistive sensors offer advantages such as simple fabrication, low power consumption, and broad detection ranges, making them well-suited for detecting subtle vibrations and acoustic signals. However, traditional piezoresistive materials, including metals and semiconductors, are inherently stiff and brittle, limiting their integration into wearable electronics and bio-integrated devices. To overcome these challenges, we introduce a graphene oxide (GO)/deoxyribonucleic acid (DNA) aerogel, synthesized via a self-assembly approach using pre-formed hydrogel membranes. This biodegradable and biocompatible aerogel features tunable pore sizes, low density, and excellent mechanical resilience. Upon reduction, the GO/DNA aerogel exhibits high piezoresistive sensitivity (1.74 kPa-1) in the low-pressure range (0-130 Pa), surpassing conventional pressure sensors. Additionally, it detects acoustic signals, achieving a sensitivity of 74.4 kPa-1, outperforming existing acoustic sensors. These findings highlight the potential of rGO/DNA aerogels as materials for next-generation wearable electronics, biomedical diagnostics, and soft robotics.

Ultra-Tough Graphene Oxide/DNA 2D Hydrogel with Intrinsic Sensing and Actuation Functions

Hydrogel devices with mechanical toughness and tunable functionalities are highly desirable for practical long-term applications such as sensing and actuation elements for soft robotics. However, existing hydrogels have poor mechanical properties, slow rates of response, and low functionality. In this work, two-dimensional hydrogel actuators are proposed and formed on the self-assembly of graphene oxide (GO) and deoxynucleic acid (DNA). The self-assembly process is driven by the GO-induced transition of double stranded DNA (dsDNA) into single stranded DNA (ssDNA). Thus, the hydrogel's structural unit consists of two layers of GO covered by ssDNA and a layer of dsDNA in between. Such heterogeneous architectures stabilized by multiple hydrogen bondings have Young's modulus of up to 10 GPa and rapid swelling rates of 4.0 × 10-3 to 1.1 × 10-2 s-1, which surpasses most types of conventional hydrogels. It is demonstrated that the GO/DNA hydrogel actuators leverage the unique properties of these two materials, making them excellent candidates for various applications requiring sensing and actuation functions, such as artificial skin, wearable electronics, bioelectronics, and drug delivery systems.

Graphene/chitosan nanoreactors for ultrafast and precise recovery and catalytic conversion of gold from electronic waste

The extraction of gold (Au) from electronic waste (e-waste) has both environmental impact and inherent value. Improper e-waste disposal poses environmental and health risks, entailing substantial remediation and healthcare costs. Large efforts are applied for the recovery of Au from e-waste using complex processes which include the dissolution of Au, its adsorption in an ionic state and succeeding reduction to metallic Au. These processes themselves being complex and utilizing harsh chemicals contribute to the environmental impact of e-waste. Here, we present an approach for the simultaneous recovery and reduction of Au3+ and Au+ ions from e-waste to produce solid Au0 forms, thus skipping several technological steps. We develop a nanoscale cross-dimensional composite material via self-assembly of two-dimensional graphene oxide and one-dimensional chitosan macromolecules, capable of acting simultaneously as a scavenger of gold ions and as a reducing agent. Such multidimensional architecture doesn't require to apply any voltage for Au adsorption and reduction and solely relies on the chemisorption kinetics of Au ions in the heterogeneous GO/CS nanoconfinements and their chemical reduction on multiple binding sites. The cooperative phenomena in ionic absorption are responsible for the extremely high efficiency of gold extraction. The extraction capacity reaches 16.8 g/g for Au3+ and 6.2 g/g for Au+, which is ten times larger than any existing gold adsorbents can propose. The efficiency is above 99.5 wt.% (current limit is 75 wt.%) and extraction ability is down to very low concentrations of 3 ppm.

Biomimetic laser-induced graphene fern leaf and enzymatic biosensor for pesticide spray collection and monitoring

Monitoring of pesticide concentration distribution across farm fields is crucial to ensure precise and efficient application while preventing overuse or untreated areas. Inspired by nature's wettability patterns, we developed a biomimetic fern leaf pesticide collection patch using laser-induced graphene (LIG) alongside an external electrochemical LIG biosensor. This "collect-and-sense" system allows for rapid pesticide spray monitoring in the farm field. The LIG is synthesized and patterned on polyimide through a high-throughput gantry-based CO2 laser process, making it amenable to scalable manufacturing. The resulting LIG-based leaf exhibits a remarkable water collection capacity, harvesting spray mist/fog at a rate approximately 11 times greater than a natural ostrich fern leaf when the collection is normalized to surface area. The developed three-electrode LIG pesticide biosensor, featuring a working electrode functionalized with electrodeposited platinum nanoparticles (PtNPs) and the enzyme glycine oxidase, displayed a linear range of 10-260 μM, a detection limit of 1.15 μM, and a sensitivity of 5.64 nA μM-1 for the widely used herbicide glyphosate. Also, a portable potentiostat with a user-friendly interface was developed for remote operation, achieving an accuracy of up to 97%, when compared to a standard commercial benchtop potentiostat. The LIG "collect-and-sense" system can consistently collect and monitor glyphosate spray after 24-48 hours of spraying, a time that corresponds to the restricted-entry interval required to enter most farm fields after pesticide spraying. Hence, this innovative "collect-and-sense" system not only advances precision agriculture by enabling monitoring and mapping of pesticide distribution but also holds the potential to significantly reduce environmental impact, enhance crop management practices, and contribute to the sustainable and efficient use of agrochemicals in modern agriculture.

Simple enzyme based fluorimetric biosensor for urea in human biofluids

As an important biomarker for renal related diseases, detection of urea is playing a vital role in human biofluids on clinical diagnosis concern. In this work, a synthetic salicyaldehyde based imine fluorophore was synthesized using sonication method and conjugated with urease which was used as fluorescent biosensor for the detection of urea in serum samples. This enzyme based biosensor has shown a good selectivity and sensitivity towards urea with the linear range from 2 to 80 mM and the detection limit of 73 µM. The sensing response obtain is highly agreeing with existing analytical technique for urea detection which strongly recommends this biosensor for clinical application.

"Clickable" graphene nanoribbons for biosensor interfaces

We report on the synthesis of "clickable" graphene nanoribbons (GNRs) and their application as a versatile interface for electrochemical biosensors. GNRs are successfully deposited on gold-coated working electrodes and serve as a platform for the covalent anchoring of a bioreceptor (i.e., a DNA aptamer), enabling selective and sensitive detection of Interleukin 6 (IL6). Moreover, when applied as the intermediate linker on reduced graphene oxide (rGO)-based field-effect transistors (FETs), the GNRs provide improved robustness compared to conventional aromatic bi-functional linker molecules. GNRs enable an orthogonal and covalent attachment of a recognition unit with a considerably higher probe density than previously established methods. Interestingly, we demonstrate that GNRs introduce photoluminescence (PL) when applied to rGO-based FETs, paving the way toward the simultaneous optical and electronic probing of the attached biointerface.

Bioinspired 2D nanofluidic membranes for energy applications

Bioinspired two-dimensional (2D) nanofluidic membranes have been explored for the creation of high-performance ion transport systems that can mimic the delicate transport functions of living organisms. Advanced energy devices made from these membranes show excellent energy storage and conversion capabilities. Further research and development in this area are essential to unlock the full potential of energy devices and facilitate the development of high-performance equipment toward real-world applications and a sustainable future. However, there has been minimal review and summarization of 2D nanofluidic membranes in recent years. Thus, it is necessary to carry out an extensive review to provide a survey library for researchers in related fields. In this review, the classification and the raw materials that are used to construct 2D nanofluidic membranes are first presented. Second, the top-down and bottom-up methods for constructing 2D membranes are introduced. Next, the applications of bioinspired 2D membranes in osmotic energy, hydraulic energy, mechanical energy, photoelectric conversion, lithium batteries, and flow batteries are discussed in detail. Finally, the opportunities and challenges that 2D nanofluidic membranes are likely to face in the future are envisioned. This review aims to provide a broad knowledge base for constructing high-performance bioinspired 2D nanofluidic membranes for advanced energy applications.