Facile fabrication of laser induced versatile graphene-metal nanoparticles electrodes for the detection of hazardous molecules

Rocephin-graphene oxide-silver nanocomposites: A versatile platform for biomedical applications

For many years, the synthesis of graphene oxide (GO) had involved exfoliating graphite flakes, and the methods applied were expensive and time-consuming. Thus, an attempt had been made to create an inventive, less expensive method for the synthesis of GO using unrefined, raw carbon-containing material. Modified Hummer's method was used to prepare GO from banana peel. In addition, the metallic silver nanocomposite was also synthesized along with laoding of drug Rocephin where they interact with each other through electrostatic hydrogen bond interaction. The degree of crystallinity and the crystallite size were through x-ray diffraction (XRD) analysis and the crystallite size of AgNPs was found to be 40.40 nm. The scanning electron microscopy (SEM) analysis shows that the morphology of the GO gradually changes with the addition of AgNPs and Rocephin. A blue shift was seen in the absorbance maxima of the raw carbon upon the conjugation of Rocephin in UV analysis. The Fourier-transform infrared spectroscopy, and energy dispersive X-ray (EDX) spectroscopy were used to determine the chemical composition of the samples. Furthermore, a broad biological screening of the synthesized samples had been carried out following the total reducing power (TRP), total antioxidant capacity (TAC), antibacterial, antifungal, MTT (Cytotoxicity of biologically synthesized silver nanoparticles in MDA-MB-231 human breast cancer cells) cell viability, brine shrimp lethality, and hemolytic protocols. Significant results were obtained, and the Rocephin-GO-AgNPs had depicted promising activity as compared with their counterparts. RESEARCH HIGHLIGHTS: The GO was prepared from the raw carbon extracted from banana peels and was used as a substrate for the synthesis Graphene oxide silver nanoparticles (GO-AgNPs) and Rocephin-loaded graphene oxide silver nanoparticles (Rocephin-GO-AgNPs) The structural and compositional analysis of the nanomaterial was carried out, and they were screened for several biomedical applications. The Rocephin-GO-AgNPs exhibit the highest activity as compared with their counterparts.

Ti3C2Tx/laser-induced graphene-based micro-droplet electrochemical sensing platform for rapid and sensitive detection of benomyl

The design and fabrication of high-performance electrode devices are highly important for the practical application of electrochemical sensors. In this study, flexible three-dimensional porous graphene electrode devices were first facilely fabricated using common laser ablation technique at room temperature. After then, hydrophilic two-dimensional MXene (Ti3C2Tx) nanosheet was decorated on the surface of the laser-induced graphene (LIG), resulting in disposable Ti3C2Tx/LIG electrode devices. After introducing Ti3C2Tx nanosheet, the electrochemical active area, electron transfer ability of LIG electrode device and its adsorption efficiency toward organic pesticide benomyl was significantly boosted. As a result, the fabricated Ti3C2Tx/LIG electrode device exhibited significantly enhanced electrocatalytic activity toward benomyl oxidation. Based on this, a novel and ultra-sensitive electrochemical platform for micro-droplet detection of benomyl was achieved in the range of 10 nM-6000 nM with detection sensitivity of 169.9 μA μM-1 cm-2 and detection limit of 5.8 nM. Considering the low-cost Ti3C2Tx/LIG electrode devices are rarely used for electrochemical analysis, we believed this research work will contribute to exploring the broader application of MXene/LIG electrode devices in the field of electrochemical sensing.

Superlative and Selective Sensing of Serotonin in Undiluted Human Serum Using Novel Polystyrene Sulfonate Conductive Polymer

In the past 5 years, real-time health monitoring has become ubiquitous with the development of watches and rings that can measure and report on the physiological state. As an extension, real-time biomarker sensors, such as the continuous glucose monitor, are becoming popular for both health and performance monitoring. However, few real-time sensors for biomarkers have been made commercially available; this is primarily due to problems with cost, stability, sensitivity, selectivity, and reproducibility of biosensors. Therefore, simple, robust sensors are needed to expand the number of analytes that can be detected in emerging and existing wearable platforms. To address this need, we present a simple but novel sensing material. In short, we have modified the already popular PEDOT/PSS conductive polymer by completely removing the PEDOT component and thus have fabricated a polystyrene sulfonate (PSS) sensor electrodeposited on a glassy carbon (GC) base (GC-PSS). We demonstrate that coupling the GC-PSS sensor with differential pulse voltammetry creates a sensor capable of the selective and sensitive detection of serotonin. Notably, the GC-PSS sensor has a sensitivity of 179 μA μM-1 cm-2 which is 36x that of unmodified GC and an interferent-free detection limit of 10 nM, which is below the concentrations typically found in saliva, urine, and plasma. Notably, the redox potential of serotonin interfacing with the GC-PSS sensor is at -0.188 V versus Ag/AgCl, which is significantly distanced from peaks produced by common interferants found in biofluids, including serum. Therefore, this paper reports a novel, simple sensor and polymeric interface that is compatible with emerging wearable sensor platforms.

A NiO-nanostructure-based electrochemical sensor functionalized with supramolecular structures for the ultra-sensitive detection of the endocrine disruptor bisphenol S in an aquatic environment

Herein, NiO nanoparticles (NPs) functionalized with a para-hexanitrocalix[6]arene derivative (p-HNC6/NiO) were synthesized by using a facile method and applied as a selective electrochemical sensor for the determination of bisphenol S (BPS) in real samples. Moreover, the functional interactions, phase purities, surface morphologies and elemental compositions of the synthesized p-HNC6/NiO NPs were investigated via advanced analytical tools, such as Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Additionally, the synthesized p-HNC6/NiO NPs were cast on the surface of a bare glassy carbon electrode (GCE) via a drop casting method, which resulted in uniform deposition of p-HNC6/NiO/GCE over the surface of the GCE. Additionally, the developed p-HNC6/NiO/GCE sensor demonstrated an outstanding electrochemical response to BPS under optimized conditions, including a supporting electrolyte, a Briton-Robinson buffer electrolyte at pH 4, a scan rate of 110 mV s-1 and a potential window of between -0.2 and 1.0 V. The wide linear dynamic range was optimized to 0.8-70 μM to obtain a brilliant linear calibration curve for BPS. The limit of detection (LOD) and limit of quantification (LOQ) of the developed sensor were estimated to be 0.0059 and 0.019 μM, respectively, which are lower than those of reported sensors for BPS. The feasibility of the developed method was successfully assessed by analyzing the content of BPS in waste water samples, and good recoveries were achieved.

An electrochemical sensor for the determination of environmentally hazardous fungicide pyrimethanil in water and fruit samples

We developed a facile electroanalytical system for the rapid and sensitive detection of pyrimethanil through the modification of carbon paste electrode surface using the as-fabricated europium doped feather-type CuO nanoflowers (FT-Eu3+-CuO NF sensor). The peak current of pyrimethanil oxidation was elevated by the sensor due to the integration of appreciable electrochemical features of the modifier, which indicates the high ability of the modified electrode to enhance the sensitivity of pyrimethanil detection. The pyrimethanil sensor under the optimized setting had a broad linear dynamic range (0.001-800.0 μM) and a narrow limit of detection (0.18 nM). The practical applicability of the as-fabricated electrode was verified by sensing pyrimethanil in real samples; it also exhibited commendable specificity, stability and reproducibility.

Coupling metal organic frameworks nanozyme with carbon nanotubes on the gradient porous hollow fiber membrane for nonenzymatic electrochemical H2O2 detection

In this paper, we present a gradient porous hollow fiber structure integrated the signal transduction within a microspace, serving as a platform for cellular metabolism monitoring. We developed a nonenzymatic electrochemical electrode by coupling carbon nanotubes (CNT) and metal organic frameworks (MOF) nanozyme on three-dimensional (3D) gradient porous hollow fiber membrane (GPF) for in-situ detection of cell released hydrogen peroxide (H2O2). The GPF was used as a substrate for cell culture as well as the supporting matrix of the working electrode. The ultrasonically coupled CNT@MOF composite was immobilized on the outer surface of the GPF by means of pressure filtration. Notably, the MOF, acting as a peroxidase mimic, exhibits superior stability compared to traditional horseradish peroxidase. The incorporation of CNT not only provided sufficient specific surface area to improve the uniform distribution of MOF nanozyme, but also formed 3D conductive network. This network efficiently facilitates the electrons transfer during the catalytic process of the MOF, addressing the inherent poor conductivity of MOFs. The GPF-CNT@MOF nonenzymatic bioelectrode demonstrated excellent electrocatalytic performance including rapid response, satisfactory sensing selectivity, and attractive stability, which enabled the development of a robust in-situ cellular metabolic monitoring platform.

Smartphone-based wearable microfluidic electrochemical sensor for on-site monitoring of copper ions in sweat without external driving

The directional movement of liquid without exogenous drive can show great potential in portable electrochemical platforms. Herein, we developed a portable electrochemical platform that drove electrolyte flow by surface tension gradient, which can realize collection of electrolyte, flow preconcentration and electrochemical detection of Cu2+. The induced graphene electrodes (LIG) was fabricated using laser direct writing, and flower cluster shaped ZnO nanorods (FC-ZnONRs) were prepared and modified on LIG, which provided a large amount of space for electrolyte to shuttled between the holes of LIG and ZnO, and increased the electrochemical active sites and electrons transport ability. The effect of surface tension gradients driving fluid flow could accelerate preconcentration, shorten detection time (save 300 s of preconcentration time) and enhance electrochemical responses in synergy with the 3D FC-ZnONRs/LIG. The microfluidic system possessed excellent performance for detection of Cu2+ ranged from 1 μg L-1 to 2100 μg L-1 with a low detection limit (LOD) of 0.0368 μg L-1 and high sensitivity of 0.414 μA (μg L-1)-1 cm-2. Additionally, this portable microfluidic system was successfully worn on the skin for analysing Cu2+ in human sweat, and the results showed good consistency with inductively coupled plasma-mass spectrometry (ICP-MS). This novel sensing system provides a sample collection, rapid detection, low cost and easy-to-operate strategy for heavy metal ions analysis in real samples and shows huge application prospects in point-of-care testing.

Laser Scribing Turns Plastic Waste into a Biosensor via the Restructuration of Nanocarbon Composites for Noninvasive Dopamine Detection

The development of affordable and compact noninvasive point-of-care (POC) dopamine biosensors for the next generation is currently a major and challenging problem. In this context, a highly sensitive, selective, and low-cost sensing probe is developed by a simple one-step laser-scribing process of plastic waste. A flexible POC device is developed as a prototype and shows a highly specific response to dopamine in the real sample (urine) as low as 100 pmol/L in a broad linear range of 10-10-10-4 mol/L. The 3D topological feature, carrier kinetics, and surface chemistry are found to improve with the formation of high-density metal-embedded graphene-foam composite driven by laser irradiation on the plastic-waste surface. The development of various kinds of flexible and tunable biosensors by plastic waste is now possible thanks to the success of this simple, but effective, laser-scribing technique, which is capable of modifying the matrix's electronic and chemical composition.