Two Copper-Carbon Electrodes That Catch Pharmaceuticals in Water — and Show Their Work
The drugs we take don’t disappear — they end up in rivers, lakes and treated effluent at trace levels, and telling two of them apart in the same water sample used to mean a lab. Two electrodes change that.
Metformin is the world’s most-prescribed diabetes drug; acetaminophen (paracetamol) is in half the medicine cabinets on earth. Both pass through people and treatment plants and turn up in surface water, where they persist and accumulate. Monitoring them normally means chromatography — accurate, but slow, expensive and lab-bound. Electrochemistry offers the opposite: cheap, fast, portable, and — because different molecules oxidise at different potentials — inherently selective. The problem has always been building an electrode sensitive and selective enough for trace levels in real, messy water. Two 2025 papers from Yu-Jen Shih’s group at National Sun Yat-sen University do exactly that, with two different copper-carbon architectures — and, unusually, they prove the sensing mechanism by watching it happen.
The Obstacle
A trace electrochemical sensor for real water needs three things at once: a high electrochemical surface area (more active sites, bigger signal), redox-active sites that couple specifically to the target molecule (selectivity), and the ability to separate co-existing pollutants that might otherwise blur into one peak. Bare carbon gives surface area but little selectivity; a bare metal gives redox activity but fouls and lacks area. And even when a calibration curve works, you usually can’t say why one molecule is detected over another — which makes the method hard to trust and harder to transfer.
The Innovation
Both papers start from a metal-organic framework (MOF) built on copper and a benzene-tricarboxylate (trimesic acid, BTC) linker, then pyrolyse it so the organic scaffold collapses into a conductive carbon matrix studded with copper (and copper-oxide) nanoparticles. That gives the best of both worlds — carbon’s surface area and conductivity, plus copper’s redox chemistry — in one electrode. The two studies then diverge:
- Trimesic-acid-derived Cu in carbon nano-octahedrons (Carbon, 2025; DOI 10.1016/j.carbon.2025.120705). A CuBTC/PVP precursor pyrolyses into Cu nanoparticles in carbon nano-octahedrons (CuCNO), optimised at 400 °C. Target: trace metformin, single-analyte.
- Graphene-oxide-confined Cu-MOF (Chemical Engineering Journal 523, 2025, 168734; DOI 10.1016/j.cej.2025.168734). The Cu-BTC is grown confined in graphene oxide, then reduced to Cu carbon polyhedra in reduced graphene oxide (CuCP@rGO). Target: two drugs at once — acetaminophen and metformin — in one scan.
Key Results
Three results carry the story: reading two drugs in one scan, pushing a single drug to the nanogram level, and proving both mechanisms live with operando Raman.
Detecting Two Drugs in One Scan, by Potential
The CuCP@rGO electrode separates ACM and MTF because they stick to different sites by different chemistry: acetaminophen binds sp2 carbon through π–π stacking, while metformin coordinates directly to copper. Those chemistries oxidise at different potentials — ACM lower, metformin at +1.1 V (vs RHE) — so a single sweep reads both. In municipal wastewater, lake and river water the electrode quantified both across 0.5–300 µg/L with detection limits below 0.2 µg/L each.
Pushing a Single Drug to the Nanogram Level
Concentrating on metformin and tuning pyrolysis to 400 °C, CuCNO(400) reached its oxidation peak at just +0.85 V, with two linear ranges (0.5–50 and 50–300 µg/L) and a detection limit of 0.054 µg/L (LOQ 0.183 µg/L), validated in river, lake and wastewater. The key was a Cu(0)/Cu(I) mixed-valence state with oxygen defects plus bidentate chelation of metformin to copper at high pH.
Watching the Mechanism with Operando Raman
Recording spectra on the MRID at 785 nm while sweeping the potential, the team caught surface species appearing in step with the redox reactions: for acetaminophen, aromatic-ring bands at 450 and 650 cm-1 and the carbon D-band (1320) and G-band (1557 cm-1) rise as π–π stacking orders the surface; for metformin, amine and N–H bands (980 and 785 cm-1) appear only beyond +0.9 V. DFT then tied the selectivity to the different adsorption energies of the two oxidised products — a mechanism, not just a signal.
Why ProTrusTech Is Featuring This Research
The headline claim in both papers — that selectivity comes from two distinct surface chemistries switching with potential — is an operando-Raman result. Post-mortem spectroscopy could never show it; you have to record Raman inside the running electrochemical cell, potential by potential. That in-operando capability, at 785 nm on the MRID, is exactly the platform feature this cluster of work showcases. See the companion Tech Insights piece for how operando EC-Raman works.
Featured Instruments:
Why This Matters
Trace-drug monitoring is moving out of the central lab toward the water itself, and that shift needs sensors that are cheap, selective and explainable. These two electrodes show both ends of the design space — one prioritising multiplexed selectivity, the other single-analyte sensitivity — from one MOF-derived platform. And they are the detection chapter of a larger program from the same group that also recovers metal oxyanions and removes nitrate, all read by the same operando-Raman method.
What’s Next
- Field validation on continuously flowing water rather than grab samples.
- Extending the two-site trick (π–π vs Cu-coordination) to other co-occurring pollutant pairs.
- Miniaturisation toward a portable, screen-printed version of the CuCNO electrode.
Building electrochemical sensors or studying reaction mechanisms at an electrode surface — and need operando Raman to see what is happening under potential? Get in touch with our team.
Key Takeaways
- MOF-derived copper-carbon electrodes detect pharmaceutical pollutants in real water, selectively and at trace levels.
- CuCP@rGO: two drugs in one scan — acetaminophen (π–π on carbon) and metformin (Cu-coordination) separated by potential; LOD < 0.2 µg/L each.
- CuCNO: trace metformin down to 0.054 µg/L, via a Cu(0)/Cu(I) defect-rich carbon and bidentate chelation.
- Operando Raman (MRID, 785 nm) captured the potential-dependent surface species, turning a calibration into a proven mechanism.
