Dopamine is a catecholamine neurotransmitter that sits at the center of the brain’s reward and motor control circuitry. Its dysregulation is implicated in Parkinson’s disease, hypertension, and a range of other neurological and cardiovascular conditions, which makes reliable, low-cost measurement of its concentration a longstanding goal in analytical chemistry. Because dopamine is electroactive, meaning it readily gives up electrons at an electrode surface, electrochemical sensors offer a direct route to detection without the enzymes, labels, or bulky optics that other approaches require. The challenge has always been sensitivity and selectivity at the vanishingly small concentrations relevant to real biological samples, and that is precisely where the new material makes its mark.

The synthesis itself is disarmingly simple. Rather than relying on ammonia, urea, or other industrial nitrogen sources commonly used to dope carbon materials, the team used hydrothermal carbonization of spinach leaf extract followed by annealing. Spinach is naturally rich in nitrogen-containing compounds, including amino acids, proteins, and chlorophyll, and during the hydrothermal step these molecules become incorporated into the developing carbon framework. Subsequent annealing consolidates the graphitic structure while preserving the nitrogen dopants. The result, which the authors call nitrogen-rich rGO-HCA, is a reduced graphene oxide lattice in which nitrogen atoms occupy a mixture of chemically distinct sites, all introduced without any synthetic nitrogen reagent at all.

Characterization confirmed that the material is exactly what the green recipe promised. X-ray diffraction and Raman spectroscopy revealed the restoration of the graphitic lattice after reduction of graphene oxide, while X-ray photoelectron spectroscopy identified the coexistence of pyridinic, pyrrolic, and graphitic nitrogen within the carbon framework. That distinction matters because each nitrogen configuration donates or withdraws electron density differently, altering the local electronic structure of neighboring carbon atoms. Fourier-transform infrared and UV-visible spectroscopy tracked the loss of oxygen functionalities during reduction, and scanning electron microscopy together with high-resolution transmission electron microscopy showed the characteristic wrinkled, few-layer morphology of reduced graphene oxide. Energy-dispersive spectroscopy verified the elemental composition, confirming that nitrogen had been successfully locked into the lattice.

Electrochemical testing told the more consequential story. Using cyclic voltammetry, the team demonstrated that the spinach-derived electrode responds linearly to dopamine across a concentration range of 0.8 to 50 micromolar, with the 3.66 microampere-per-micromolar-per-square-centimeter sensitivity and the 0.66 micromolar detection limit mentioned above. Electrochemical impedance spectroscopy showed that charge transfer at the electrode surface is fast, a direct consequence of the material’s high conductivity, while chronoamperometry confirmed a rapid, stable amperometric response. For a sensor built from a material that began its life as a bag of salad greens, the analytical figures of merit are competitive with, and in several respects superior to, those of sensors built from far more expensive engineered nanomaterials.

What elevates the study beyond a routine materials report is the theoretical layer. The authors ran density functional theory calculations on nitrogen-substituted graphene models and found that the band gap of the material depends strongly on where the nitrogen atom sits relative to the carbon lattice and its defects. Nitrogen substitution at an edge carbon site produced a band gap of 0.7 electron volts, while substitution at a carbon atom adjacent to an oxygen functionality narrowed the gap to 0.2 electron volts, and substitution at a central carbon atom yielded 0.3 electron volts. Because the bio-derived synthesis naturally distributes nitrogen across all of these configurations, the resulting material contains a mosaic of locally different electronic environments, some more conductive and some more catalytically active. The DFT results therefore connect the microscopic chemistry directly to the macroscopic electrochemical performance, providing a mechanistic rationale for why a heterogeneous, naturally doped carbon outperforms expectations.

Practical sensors live or die on their stability and their resistance to fouling, the gradual coating of the electrode surface by proteins and other biomolecules that degrades response over time. Here too the spinach-derived material performed admirably. The sensor showed good repeatability and reproducibility, with relative standard deviations of 1.59 percent and 1.828 percent respectively. It retained 88.92 percent of its initial response after fifteen days of storage, and it maintained stable electrochemical signals over forty successive measurement cycles, indicating genuine anti-fouling behavior rather than a fragile laboratory curiosity. Those numbers suggest a device that could survive the rigors of repeated use in a clinical or point-of-care setting.

The most compelling demonstration came in real biological matrix. The team spiked dopamine into human serum samples supplied by the Interdisciplinary Brain Research Centre at Aligarh’s Jawaharlal Nehru Medical College and measured recovery using the same electrode. Recoveries were good across the tested concentrations, with relative standard deviations ranging from 2.58 to 5.5 percent. Detecting a neurotransmitter in the protein-rich, electrochemically crowded environment of blood serum, where ascorbic acid and uric acid typically interfere with dopamine measurements at bare carbon electrodes, is the standard acid test for any new dopamine sensor, and the nitrogen-rich rGO-HCA passed it with respectable precision.

The broader significance of the work lies in its convergence of two trends that have been moving in parallel for years. On one side, green synthesis of nanomaterials from sustainable precursors has been gaining momentum as researchers seek to reduce the environmental footprint and cost of sensor fabrication. On the other, computational methods such as density functional theory have become indispensable for understanding why doped carbons behave the way they do at electrode interfaces. By combining both in a single study, and by validating the theoretical predictions against a working device tested in human serum, the Aligarh and Jeddah team has produced a template that other laboratories can follow: derive your dopant from biomass, let nature distribute the nitrogen configurations for you, and use computation to explain what the resulting heterogeneity delivers.

There remain, of course, the usual caveats that separate a promising laboratory result from a bedside device. The linear range of 0.8 to 50 micromolar, while well matched to pharmacological and serum-spiked samples, would need to be extended and validated for the lower concentrations found in extracellular fluid in the brain. Long-term performance beyond fifteen days, mass production of the electrode, and regulatory-grade clinical validation all lie ahead. But the core demonstration stands: a leaf extract, a hydrothermal reactor, and an annealing furnace can produce a carbon electrode whose electronic structure is rich enough to demand quantum mechanical explanation and sensitive enough to detect one of biology’s most important messengers at sub-micromolar levels. In a field where the tools of neuroscience increasingly borrow from the kitchen, spinach has just earned a place on the periodic table of sensor materials.

Subject of Research: Bio-derived nitrogen-doped reduced graphene oxide electrochemical sensing of dopamine

Article Title: Bio-derived nitrogen rich reduced graphene oxide for high sensitivity dopamine sensing with DFT based mechanistic insights and validation

Article References: Agarwal, A., Waris, Hasan, S., Alkhtaby, L. A., Mujahid, M., & Khan, M. Z. (2026). Bio-derived nitrogen rich reduced graphene oxide for high sensitivity dopamine sensing with DFT based mechanistic insights and validation. Ionics. https://doi.org/10.1007/s11581-026-07565-1

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07565-1

Keywords: dopamine, reduced graphene oxide, spinach, green synthesis, electrochemical sensor, nitrogen doping, density functional theory, neurotransmitter detection, human serum, biosensor, Parkinson's disease, nanomaterials

Ticagrelor is a mainstay of modern cardiology. It works by reversibly blocking the platelet P2Y12 receptor, which prevents adenosine diphosphate from activating platelets and triggering the clotting cascade. Physicians prescribe it, often alongside aspirin, to patients with acute coronary syndrome or ST-segment elevation myocardial infarction to ward off further thrombotic events. Because the drug’s therapeutic effect depends on careful dosing and because patients differ widely in how they metabolize it, analytical methods that can measure ticagrelor quickly and accurately are clinically valuable. Until now, that job has mostly fallen to chromatography-based techniques such as high-performance liquid chromatography, liquid chromatography coupled with mass spectrometry, reverse-phase HPLC, and various spectrophotometric and bio-analytical approaches. These methods are accurate but typically require expensive instrumentation, trained operators, lengthy sample preparation, and centralized laboratory facilities.

Electrochemical sensing offers an appealing alternative. By translating molecular interactions at an electrode surface into an electrical current, such sensors can be fast, cheap, portable, and sensitive. The catch is that a bare electrode rarely provides enough signal for trace-level detection of a drug in a complex biological matrix. The standard remedy is to coat the electrode with a nanomaterial or nanocomposite that boosts conductivity, surface area, and catalytic activity. The Iranian-led team behind the new study chose an unusual pairing: carbon black, an abundant and highly conductive industrial carbon, and a silver-based metal-organic framework, a crystalline coordination network built from silver ions and the organic linker 1,3,5-benzenetricarboxylic acid.

Each component brings distinct strengths. Carbon black offers excellent porosity, high surface area, strong electrical conductivity, and a wide potential window, making it an ideal conductive backbone. Metal-organic frameworks, meanwhile, are prized for their enormous surface areas, tunable structures, and high porosity, all of which improve the interface between electrode and electrolyte. In this system, the silver framework performs three critical jobs: it supplies metal-based catalytic activity, it acts as an intrinsic electrochemical signal source through its own silver-related redox chemistry, and its tunable porosity facilitates molecular diffusion while enlarging the effective surface area available for recognition events. The researchers synthesized the framework by dissolving the organic linker and silver nitrate separately in methanol, combining the solutions, and heating the mixture at 120 degrees Celsius overnight, a straightforward and economical preparation.

Microscopy and spectroscopy confirmed that the marriage worked. Field-emission scanning electron microscopy showed carbon black forming a spherical film-like coating, while the silver framework appeared as sheet-like crystals with sharp, regular morphologies. In the composite, the two components merged into a porous, spongy, interconnected architecture with no phase separation, exactly the kind of structure that maximizes both conductivity and accessible surface area. Energy-dispersive X-ray analysis and elemental mapping verified that carbon, oxygen, nitrogen, and silver were uniformly distributed throughout the material. Fourier-transform infrared spectroscopy revealed characteristic bands from the aromatic linker and carboxylate groups, and X-ray diffraction showed that the framework’s crystalline structure survived composite formation intact, with no detectable separate crystalline silver oxide or metallic silver impurity phases.

Electrochemical tests then revealed why the composite outperforms its ingredients. Using cyclic voltammetry and electrochemical impedance spectroscopy with a ferricyanide redox probe, the team found that adding carbon black to a glassy carbon electrode increased current and lowered charge-transfer resistance from 687 ohms for the bare electrode to 344 ohms. The silver framework alone, hampered by its intrinsically low conductivity, actually raised resistance to 2016 ohms. But the combined composite slashed resistance to just 221 ohms, clear evidence of synergy. Calculations based on the Randles-Sevcik equation showed the composite electrode’s electrochemically active surface area reached 0.045 square centimeters, more than double the 0.021 square centimeters of the bare electrode.

Perhaps the most intriguing finding concerns how the sensor actually detects ticagrelor. Neither the bare electrode nor the carbon-black-modified electrode produced a distinct response to the drug. Instead, the signal originates from the silver-containing framework itself: the drug, with its sulfur-, nitrogen-, and oxygen-containing functional groups, accumulates on the electrode through affinity interactions with accessible silver sites and hydrogen bonding with the organic linker, thereby blocking the electroactive silver sites and suppressing the silver-related current. The result is an indirect, signal-off mechanism in which the drug’s presence is measured by how much it dampens the baseline signal. Carbon black amplifies this effect dramatically. The drug-induced current change was approximately 519 microamperes at the composite electrode versus 196 microamperes at the framework alone, a roughly 2.6-fold enhancement, because the conductive carbon network improves electron transfer between the electroactive silver sites and the underlying electrode while also dispersing the framework particles more effectively.

After optimizing the composite ratio, buffer pH, and salt concentration, the sensor delivered striking analytical performance. Differential pulse voltammetry yielded a linear response across an extraordinarily wide concentration range spanning 0.01 to 2500 nanomolar, with a correlation coefficient of 0.9983 and a calculated detection limit of 0.0033 nanomolar. For comparison, previously reported ticagrelor sensors based on carbon paste electrodes modified with multiwalled carbon nanotubes and titanium nanoparticles, zeolite-modified carbon paste, or solid gold electrodes achieved detection limits in the hundreds of nanomolar to micromolar range. The authors caution that such cross-study comparisons should be interpreted carefully, since electrode architectures, sample preparation, and detection-limit calculations differ, but the numbers nonetheless underline the platform’s analytical promise. Microscopy before and after testing also confirmed the composite’s structural stability under operating conditions.

The sensor proved robust in the ways that matter for real-world use. It tolerated high concentrations of structurally related drugs and common biological interferents, including ticlopidine, clopidogrel, warfarin, ascorbic acid, dopamine, uric acid, and glucose. Five identical electrodes produced responses with a relative standard deviation of just 2.5 percent, and five repeated measurements on a single electrode gave 3.1 percent. After fifteen days of storage at room temperature, the electrode retained 93 percent of its initial response, and fifty consecutive voltammetric cycles preserved 95.32 percent of the original signal. Most importantly, when the team spiked human serum samples with 50, 100, and 200 nanomolar ticagrelor after protein precipitation, the sensor recovered between 99.5 and 101.2 percent of the added drug with relative standard deviations below 2.8 percent, demonstrating that the platform can function in a genuine biological matrix rather than only in pristine buffer solutions.

The broader significance of the work lies in its demonstration that cheap, readily available materials can be engineered into sensors rivaling far costlier analytical instruments. Carbon black costs pennies, the silver framework is synthesized in a single overnight reaction, and the entire electrode modification involves ultrasonicating the two powders in a drop of solvent and drying five microliters onto a glassy carbon electrode. A sensor built this way could, in principle, support point-of-care or bedside monitoring of ticagrelor, helping clinicians tailor antiplatelet therapy to individual patients and detect abnormal drug levels before they translate into bleeding or clotting complications. The signal-off design, in which the analyte suppresses a built-in silver redox signal, also offers a template that other researchers could adapt to different drug molecules capable of binding silver sites. While further validation in larger clinical studies would be needed before any diagnostic deployment, the study adds a compelling entry to the growing toolkit of metal-organic framework sensors and shows how the right nanoscale partnership can turn an ordinary electrode into an extraordinarily perceptive one.

Subject of Research: Electrochemical detection of the antithrombotic drug ticagrelor using a silver metal-organic framework and carbon black nanocomposite-modified electrode

Article Title: Electrochemical sensor based on Ag-metal organic framework/carbon black nanocomposite for the selective detection of Ticagrelor

Article References: Roushani, M., Karazan, Z. M., & Makki, I. S. (2026). Electrochemical sensor based on Ag-metal organic framework/carbon black nanocomposite for the selective detection of Ticagrelor. Results in Chemistry, 31, Article 103939. https://doi.org/10.1016/j.rechem.2026.103939

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103939

Keywords: ticagrelor, electrochemical sensor, metal-organic framework, carbon black, nanocomposite, glassy carbon electrode, antithrombotic drug, differential pulse voltammetry, human serum, detection limit, silver framework, P2Y12 receptor

The motivation for the work lies in the well-known weaknesses of enzyme-based glucose sensors, which dominate the commercial market but degrade when exposed to fluctuations in pH, temperature, or humidity. Enzymes are fragile biological molecules, and their activity drifts over time, complicating long-term monitoring. Nonenzymatic sensors replace the enzyme with an inorganic catalyst, trading some biochemical specificity for dramatically improved stability and shelf life. Among inorganic catalysts, nickel-based materials have long been favored because they are cheap, abundant, and highly active toward glucose oxidation in alkaline media, but their performance depends critically on how much catalytic surface area can be packed onto an electrode.

The Iranian team, led by Mohadeseh Haghkhah and Rahim Mohammad-Rezaei, addressed that surface-area problem with a two-step electrochemical strategy. First, they electrodeposited a nickel-copper alloy onto a flat graphitic electrode that had been coated with a composite of acid-treated carbon nanofibers and sulfur-nitrogen co-doped graphene quantum dots. The deposition was performed at minus 0.9 volts for 120 seconds in a solution containing nickel chloride, copper chloride, and boric acid. Then came the crucial dealloying step: applying a positive potential of 0.2 volts for 180 seconds selectively dissolves copper from the alloy while nickel, which rapidly forms a protective passive oxide layer, stays behind.

The choice of dealloying potential proved decisive. At 0.1 volts, substantial copper remained on the surface, confirmed by residual copper redox peaks in cyclic voltammetry. At 0.5 volts, the process became too aggressive and significant nickel leached away alongside the copper. Energy-dispersive X-ray spectroscopy and amperometric current-time traces both pointed to 0.2 volts as the sweet spot, where copper removal was nearly complete while nickel loss was minimized. Scanning electron microscopy revealed the dramatic morphological consequence: the spherical NiCu nanoparticles collapsed into needle-like nickel structures with vastly increased electroactive surface area, a transformation that simply did not occur when the dealloying step was skipped.

The underlying scaffold is just as important as the nanoneedles themselves. Carbon nanofibers, roughly 60 to 100 nanometers in diameter, were activated with a sulfuric and nitric acid treatment that replaced surface-bound oxides with hydroxyl groups, boosting hydrophilicity. The graphene quantum dots, synthesized hydrothermally from citric acid and thiourea, were confirmed by infrared spectroscopy and fluorescence measurements, showing characteristic blue emission at 443 nanometers. Raman spectroscopy tracked the whole transformation: copper oxide vibrational bands visible in the alloyed electrode vanished almost entirely after dealloying, while bands associated with nickel oxyhydroxide and hydroxide phases emerged, providing direct spectroscopic evidence that the copper had been stripped and the nickel converted to its active form.

Electrochemical impedance spectroscopy quantified the synergy between the components. The charge-transfer resistance of the full composite shrank progressively as carbon nanofibers and then quantum dots were added, and dropped again after copper removal. Cyclic voltammetry showed quasi-reversible nickel(II)/nickel(III) redox peaks at approximately 0.29 and 0.5 volts, and the electroactive surface area, calculated by charge integration, told a striking story: 0.146 square centimeters for nanoneedles on bare graphite, 2.49 square centimeters with carbon nanofibers, and 6.00 square centimeters with the full carbon nanofiber-quantum dot composite. In other words, the nanostructured scaffold multiplied the effective catalytic area more than fortyfold relative to the plain electrode.

Glucose oxidation on the finished electrode follows a well-understood electrochemical-chemical mechanism. In the anodic scan, surface nickel hydroxide is electrochemically oxidized to nickel oxyhydroxide, the true catalytic species. Glucose then reduces nickel oxyhydroxide back to nickel hydroxide while being converted to gluconolactone, and the regenerated nickel hydroxide is oxidized again, sustaining a continuous catalytic cycle that amplifies the anodic current. Scan-rate studies confirmed that peak currents scaled linearly with scan rate, consistent with this surface-confined redox cycle. Crucially, the un-dealloyed NiCu electrode showed essentially no sensitivity to glucose, demonstrating that residual copper participates in parasitic side reactions and disrupts the nickel redox kinetics that the sensing mechanism depends on.

The analytical figures of merit are impressive. Operating at 0.40 volts in 0.1 molar potassium hydroxide, the optimized sensor achieved a sensitivity of 2105.95 microamperes per millimolar per square centimeter, a linear range spanning 0.012 to 12 millimolar, and a detection limit of 3.13 micromolar, with a response time of about five seconds. That sensitivity represents a 240 percent improvement over electrodes lacking either the quantum dots or the dealloying treatment, and it compares favorably with recently reported nickel-based nonenzymatic sensors built on MoS2, MXenes, and layered double hydroxides. Selectivity tests showed that physiologically relevant concentrations of ascorbic acid, dopamine, citric acid, uric acid, and sodium chloride produced negligible signal changes, with interference fluctuations staying below five percent.

Reliability testing reinforced the platform’s practical credentials. Three independently fabricated electrodes gave responses with a relative standard deviation of just 3.5 percent, and repeated measurements on a single electrode yielded 4.15 percent. The amperometric signal remained stable for more than 1500 seconds of continuous operation, and the electrode retained its performance over four weeks of storage with only 3.19 percent variation. In real-world validation, the team deproteinized human serum with acetonitrile, added just 15 microliters of the treated serum to the micro-drop cell, and measured a glucose concentration of 4.90 millimolar using the standard addition method, with spike recoveries between 97.22 and 102.82 percent. Commercial glucometers read the same samples at 5.01 millimolar, a statistically indistinguishable result.

The micro-drop platform itself may prove as consequential as the nanomaterials. Built from air-dry modeling clay, epoxy resin, and flat graphitic electrodes arranged radially around a well of at most 800 microliters, it is inexpensive, reusable, and ideally suited to clinical samples where volume is scarce. Unlike disposable screen-printed electrodes, the flat platform can be regenerated and monitored over the long term. The authors suggest the combination of low cost, straightforward fabrication, micro-volume capability, and serum-level accuracy positions the sensor for point-of-care diagnostics and sample-limited biomedical assays, offering a glimpse of how rational nanoscale engineering, in this case the simple act of etching copper out of an alloy, can translate into clinically meaningful analytical performance.

Subject of Research: Nonenzymatic electrochemical glucose sensing using alloying-dealloying activated NiOOH nanoneedles on carbon nanofiber-graphene quantum dot composites

Article Title: Electrochemical alloying-dealloying driven activation of NiOOH nanoneedles on carbon nanofiber-graphene quantum dot composites for nonenzymatic glucose sensing on a micro-drop flat platform

Article References: Electrochemical alloying-dealloying driven activation of NiOOH nanoneedles on carbon nanofiber-graphene quantum dot composites for nonenzymatic glucose sensing on a micro-drop flat platform. (n.d.). https://doi.org/10.1016/j.rechem.2026.103905

Image Credits: AI Generated

DOI: 10.1016/j.rechem.2026.103905

Keywords: glucose sensor, nonenzymatic sensing, NiOOH nanoneedles, dealloying, carbon nanofibers, graphene quantum dots, electrodeposition, micro-drop electrode, electrocatalysis, human serum, point-of-care diagnostics, electrochemical biosensor